Battery cell, battery apparatus and electrical apparatus

Abstract

A battery cell, a battery apparatus and an electrical apparatus. The battery cell comprises a housing (11), an electrode assembly (2) and an end cover (12), wherein at least one end of the housing (11) in a first direction is provided with an opening, and the housing (11) comprises a first side wall part (111). The electrode assembly (2) is at least partially accommodated in the housing (11). The electrode assembly (2) comprises a positive pole piece (22) and a negative pole piece (23). At least part of the positive pole piece (22) and at least part of the negative pole piece (23) are stacked in a second direction. The second direction is parallel to the thickness direction of the first side wall part (111). The first direction intersects with the second direction. The end cover (12) is used for sealing the opening, and the first side wall part (111) and the end cover (12) are welded to form a first connecting part (51). The first side wall part (111) comprises, arranged in a first direction, a first area (1111) and a second area (1112). The first area (1111) is located between the first connecting part (51) and the second area (1112). The hardness of the first area (1111) is less than the hardness of the second area (1112). The expansion force of the electrode assembly (2) is released by means of the first area (1111) having a lower hardness, so as to reduce the possibility of cracking of the first connecting part (51) of the first side wall part (111).

Description

Battery cell, battery device and power-consuming device

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to the following patent applications, including Chinese patent application No. 202410217408.8, filed on February 27, 2024, international patent application No. PCT / CN2024 / 113179, filed on August 19, 2024, international patent application No. PCT / CN2024 / 105243, filed on July 12, 2024, international patent application No. PCT / CN2024 / 089160, filed on April 22, 2024, international patent application No. PCT / CN2023 / 135607, filed on November 30, 2023, and international patent application No. PCT / CN2023 / 134129, filed on November 24, 2023. The entire contents of the above patent applications are hereby incorporated by reference into this application. Technical Field

[0003] The present application relates to the field of battery technology, and in particular to a battery cell, a battery device, and an electrical device. Background Art

[0004] Batteries are increasingly being used in everyday life and industry. They are not only used in energy storage systems like hydropower, thermal power, wind power, and solar power plants, but are also widely used in electric vehicles like electric bicycles, electric motorcycles, and electric cars.

[0005] In the related art, an electrode assembly is disposed in a shell of a battery cell. During the charge and discharge process of the battery cell, the electrode assembly expands, which may cause the shell to crack.

[0006] Summary of the Invention

[0007] In view of this, embodiments of the present application hope to provide a battery cell, a battery device, and an electrical device that can reduce the possibility of shell cracking.

[0008] In order to achieve the above-mentioned purpose, the technical solution of the embodiment of the present application is implemented as follows:

[0009] In one aspect, an embodiment of the present application discloses a battery cell, comprising:

[0010] The housing has an opening at at least one end along the first direction, and the housing includes a first side wall portion;

[0011] an electrode assembly at least partially contained within the housing, the electrode assembly comprising a positive electrode sheet and a negative electrode sheet, at least a portion of the positive electrode sheet and at least a portion of the negative electrode sheet being stacked along a second direction, the second direction being parallel to a thickness direction of the first sidewall portion, and the first direction intersecting the second direction;

[0012] An end cover is used to close the opening, and the first side wall portion and the end cover are welded to form a first connecting portion;

[0013] The first sidewall portion includes a first area and a second area arranged along a first direction, the first area is located between the first connecting portion and the second area, and the hardness of the first area is lower than that of the second area.

[0014] The expansion force of the electrode assembly is released by the first region with lower hardness, thereby reducing the possibility of cracking of the first connecting portion.

[0015] In some embodiments, the ratio of the hardness of the first region to the hardness of the second region is between 0.3 and 0.8.

[0016] Appropriate hardness can reduce the cracking of the first connecting portion and inhibit the cracking of the first region itself.

[0017] In some embodiments, the ratio of the hardness of the first region to the hardness of the second region is between 0.5 and 0.8.

[0018] Appropriate hardness can reduce the cracking of the first connecting portion and inhibit the cracking of the first region itself.

[0019] In some embodiments, the hardness of the second region ranges from 40 HV to 100 HV, and the hardness of the first region ranges from 20 HV to 55 HV.

[0020] Appropriate hardness can reduce the cracking of the first connecting portion and inhibit the cracking of the first region itself.

[0021] In some embodiments, a dimension of the first region along the first direction ranges from 0.05 mm to 0.75 mm.

[0022] The appropriate size range of the maximum size of the first region along the first direction can reduce the cracking of the first connecting portion and prevent the first region from being too long and causing itself to crack.

[0023] In some embodiments, a dimension of the first region along the first direction ranges from 0.1 mm to 0.6 mm.

[0024] The appropriate size range of the maximum size of the first region along the first direction can reduce the cracking of the first connecting portion and prevent the first region from being too long and causing itself to crack.

[0025] In some embodiments, at least some of the grains in the first zone are first grains, the ratio of the number of first grains in the first zone to the number of all grains in the first zone is greater than 50%, and the size of the first grain extending along the first direction is the first size, the maximum size of the first grain along the second direction is the second size, and the ratio of the first size to the second size ranges from 0.2 to 5.

[0026] The ratio of the first size to the second size ranges from 0.2 to 5. Such a ratio of the first grains is greater than 50%, which is beneficial to improving the toughness of the first zone.

[0027] In some embodiments, the ratio of the first size to the second size ranges from 0.25 to 4.

[0028] The ratio of the first size to the second size ranges from 0.25 to 4. Such a ratio of the first grains is greater than 50%, which is beneficial to improving the toughness of the first zone.

[0029] In some embodiments, the first size is in a range of 5 μm to 500 μm, and the second size is in a range of 5 μm to 500 μm.

[0030] When the ratio of the first size to the second size is within a corresponding range, the first grains corresponding to the appropriate range of the first size and the second size are beneficial to improving the toughness of the first region.

[0031] In some embodiments, at least some of the grains in the second zone are second grains, the ratio of the number of second grains in the second zone to the number of all grains in the second zone is greater than 50%, and the size of the second grains extending along the first direction is a third size, the maximum size of the second grains along the second direction is a fourth size, and the ratio of the third size to the fourth size ranges from 4 to 100.

[0032] The ratio of the third size to the fourth size ranges from 4 to 100. Such a ratio of the second grains is greater than 50%, which is beneficial to reducing the toughness of the second zone and reducing the possibility of the second zone itself cracking under the action of the expansion force.

[0033] In some embodiments, the ratio of the third dimension to the fourth dimension ranges from 4 to 50.

[0034] The ratio of the third size to the fourth size ranges from 4 to 50. Such a ratio of the second grains is greater than 50%, which is beneficial to reducing the toughness of the second zone and reducing the possibility of the second zone itself cracking under the action of the expansion force.

[0035] In some embodiments, the third dimension ranges from 150 μm to 1000 μm, and the fourth dimension ranges from 5 μm to 120 μm.

[0036] When the ratio of the third dimension to the fourth dimension is within a corresponding range, a suitable range of the third dimension and the fourth dimension is conducive to reducing the toughness of the second region and reducing the possibility of the second region itself cracking under the action of the expansion force.

[0037] In some embodiments, at least some of the grains in the first region are first grains, a ratio of the number of first grains in the first region to the number of all grains in the first region is greater than 50%, a dimension of the first grain extending along the first direction is a first dimension, a maximum dimension of the first grain along the second direction is a second dimension, and a ratio of the first dimension to the second dimension ranges from 0.2 to 5;

[0038] At least some of the grains in the second region are second grains, a ratio of the number of the second grains in the second region to the number of all the grains in the second region is greater than 50%, a dimension of the second grains extending along the first direction is a third dimension, a maximum dimension of the second grains along the second direction is a fourth dimension, and a ratio of the third dimension to the fourth dimension ranges from 4 to 100;

[0039] The third size is greater than the first size.

[0040] Within the same size along the first direction, more grains in the first region bear the expansion force, thereby improving the toughness of the first region.

[0041] In some embodiments, the ratio of the third size to the first size ranges from 1.5 to 150, or the ratio of the third size to the first size ranges from 1.8 to 100.

[0042] In some embodiments, the first dimension ranges from 5 μm to 500 μm, and the third dimension ranges from 150 μm to 1000 μm.

[0043] In some embodiments, the maximum thickness of the first region is greater than the minimum thickness of the second region.

[0044] The thicker thickness of the first region strengthens the first region, thereby reducing the possibility of cracking in the first region.

[0045] In some embodiments, the first sidewall portion has a first inner surface and a second inner surface facing the electrode assembly and a first outer surface and a second outer surface away from the electrode assembly, the first inner surface and the second inner surface are connected in sequence along the direction of the end cover pointing to the electrode assembly, the first outer surface and the second outer surface are connected in sequence along the direction of the end cover pointing to the electrode assembly, the first inner surface and the first outer surface are at least partially formed in the first zone, the second inner surface and the second outer surface are at least partially formed in the second zone, and the distance between the first inner surface and the first outer surface along the second direction is greater than the distance between the second inner surface and the second outer surface along the second direction.

[0046] The first sidewall portion reinforces the first region at a thicker portion of the first inner surface, thereby reducing the possibility of cracking in the first region.

[0047] In some embodiments, the first inner surface includes a first sub-surface and a second sub-surface connected in sequence along the direction of the end cap pointing to the electrode assembly, the first sub-surface is at least partially formed in the first region, and along the second direction, the first sub-surface is closer to the electrode assembly than the second sub-surface, and the distance between the first sub-surface and the first outer surface along the second direction is greater than the distance between the second sub-surface and the first outer surface along the second direction.

[0048] The first sidewall portion reinforces the first region at a portion corresponding to the thicker first sub-surface, thereby reducing the possibility of cracking of the first region.

[0049] In some embodiments, the distance between the second sub-surface and the first outer surface along the second direction is a first preset thickness, and the first preset thickness tends to decrease along the direction from the end cover to the electrode assembly.

[0050] The first preset thickness tends to decrease along the direction from the end cover to the electrode assembly, which is beneficial to reducing the material cost of the first side wall portion.

[0051] In some embodiments, the first sub-surface spans the first area and the second area, and the first outer surface spans the first area and the second area; or, the second sub-surface spans the first area and the second area, and the first outer surface spans both the first area and the second area.

[0052] The thicker portion of the first sidewall portion corresponding to the first sub-surface reinforces the junction between the first area and the second area, thereby reducing the possibility of cracking at the junction between the first area and the second area.

[0053] In some embodiments, the first inner surface spans the first region and the second region, and the first outer surface spans the first region and the second region.

[0054] The thicker portion of the first sidewall portion corresponding to the first inner surface reinforces the junction between the first area and the second area, thereby reducing the possibility of cracking at the junction between the first area and the second area.

[0055] In some embodiments, a dimension of the first inner surface along the third direction is greater than a dimension of the first inner surface along the first direction, and the first direction, the second direction, and the third direction are not coplanar and intersect with each other.

[0056] The first side wall portion is reinforced in an area where the portion of the first inner surface that is thicker along the third direction is longer along the third direction, thereby reducing the possibility of cracking of the first side wall portion.

[0057] In some embodiments, along the second direction, the projection of the first inner surface coincides with the projection of the first area and is the first projection. The size of the first projection along the third direction is greater than the size of the first projection along the first direction. The first direction, the second direction, and the third direction are not coplanar and intersect with each other.

[0058] The dimension of the first projection along the third direction is greater than the dimension of the first projection along the first direction. The portion of the first area reinforced along the third direction is longer, which is beneficial to reducing the possibility of cracking of the first area.

[0059] In some embodiments, the first inner surface includes a first connecting surface, which passes through a mid-section of the first side wall portion, the mid-section is perpendicular to the third direction, and the mid-section is equidistant from both ends of the first side wall portion along the third direction.

[0060] The first connecting surface passes through the middle section of the first side wall portion, reducing cracking at the middle section.

[0061] In some embodiments, the first connecting surface is at least partially formed in the first region. Along the second direction, a projection of the first connecting surface coincides with a projection of the first region as a second projection, and the second projection passes through a mid-section of the first sidewall portion.

[0062] The second projection passes through the middle section of the first side wall portion, thereby reinforcing a portion of the first area corresponding to the middle section and reducing the possibility of cracking of the first area at the middle section.

[0063] In some embodiments, the first inner surface also includes a second connecting surface and a third connecting surface, the second connecting surface, the first connecting surface and the third connecting surface are arranged along the third direction, the first connecting surface connects the second connecting surface and the third connecting surface, and along the second direction, the distance between the second connecting surface and the first outer surface and the distance between the third connecting surface and the first outer surface are both smaller than the distance between the first connecting surface and the first outer surface.

[0064] The first side wall portion is thicker at a portion corresponding to the first connection surface and thinner at portions corresponding to the second connection surface and the third connection surface, which can reduce cracking of the shell according to the distribution characteristics of the expansion force and reduce costs.

[0065] In some embodiments, the first connection surface, the second connection surface, and the third connection surface are all at least partially formed in the first region.

[0066] It is beneficial to reduce the cracking of the first zone itself.

[0067] In some embodiments, the first inner surface also includes a first transition surface, the first connecting surface, the first transition surface and the second connecting surface are arranged along the third direction, the first transition surface connects the second connecting surface and the first connecting surface, the distance between the first transition surface and the first outer surface along the second direction is a second preset thickness, and the second preset thickness tends to increase along the direction from the second connecting surface to the first connecting surface; and / or, the first inner surface also includes a second transition surface, the first connecting surface, the second transition surface and the third connecting surface are arranged along the third direction, the second transition surface connects the third connecting surface and the first connecting surface, the distance between the second transition surface and the first outer surface along the second direction is a third preset thickness, and the third preset thickness tends to increase along the direction from the third connecting surface to the first connecting surface.

[0068] Smooth transitions through transition surfaces.

[0069] In some embodiments, the first transition surface is at least partially formed in the first region and / or the second transition surface is at least partially formed in the first region.

[0070] The first transition surface and / or the second transition surface are increased toward the first region, thereby reducing the possibility of cracking in the first region.

[0071] In some embodiments, a dimension of the first connecting surface along the third direction is L1, a dimension of the first sidewall portion along the third direction is L, and 0.2≤L1 / L≤0.6.

[0072] This can not only strengthen more areas of the first side wall portion along the third direction, but also increase the cost to a certain extent.

[0073] In some embodiments, the first connecting surface has a first end and a second end relative to each other along the third direction, the first side wall portion has a third end and a fourth end relative to each other along the third direction, the first end is close to the third end, the second end is close to the fourth end, the dimension of the first side wall portion along the third direction is L, the minimum distance between the first end and the third end along the third direction is L2, and the minimum distance between the second end and the fourth end along the third direction is L3; L2 / L≤0.3; and / or, L3 / L≤0.3.

[0074] This can not only strengthen more areas of the first side wall portion along the third direction, but also increase the cost to a certain extent.

[0075] In some embodiments, 100 mm ≤ L ≤ 450 mm.

[0076] In some embodiments, the housing includes a corner wall, and both ends of the first side wall portion along the third direction are connected to the corner wall;

[0077] At least one end of the first inner surface along the third direction does not contact the corner wall; or, both ends of the first inner surface along the third direction extend to the two corner walls respectively.

[0078] In some embodiments, the electrode assembly further includes a separator, and the separator is disposed between the positive electrode sheet and the negative electrode sheet;

[0079] The positive electrode plate includes a positive electrode main area and a positive electrode tab protruding from the positive electrode main area, the positive electrode main area has a positive electrode active material layer, the negative electrode plate includes a negative electrode main area and a negative electrode tab protruding from the negative electrode main area, the negative electrode main area has a negative electrode active material layer, along the first direction, the positive electrode main area has a fifth end facing the end cover, the negative electrode main area has a sixth end facing the end cover, the insulating member has a seventh end facing the end cover, and the seventh end is closer to the end cover than the fifth and sixth ends.

[0080] The separator has a portion extending beyond the fifth end and the sixth end, thereby enhancing the insulating effect of the separator between the positive electrode sheet and the negative electrode sheet and reducing the risk of overlap between the positive electrode sheet and the negative electrode sheet.

[0081] In some embodiments, the spacer includes a protruding region extending beyond the fifth end and the sixth end along the first direction, and in a projection plane perpendicular to the second direction, an orthographic projection of the protruding region partially overlaps with an orthographic projection of the first inner surface.

[0082] The orthographic projection of the exceeding area partially overlaps with the orthographic projection of the first inner surface. This structure can increase the size of the first inner surface along the first direction and improve the reinforcement capacity of the first inner surface.

[0083] In some embodiments, the first inner surface is convex from the second inner surface;

[0084] In a projection plane perpendicular to the second direction, the orthographic projection of the positive electrode main area does not overlap with the orthographic projection of the first inner surface; and / or, in a projection plane perpendicular to the second direction, the orthographic projection of the negative electrode main area does not overlap with the orthographic projection of the first inner surface.

[0085] The degree of interference between the expanded electrode assembly and the first inner surface is reduced.

[0086] In some embodiments, the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer disposed on at least one side of the negative electrode current collector, and the negative electrode active material layer includes a negative electrode active material.

[0087] In some embodiments, the negative active material layer includes a negative electrode main body and a negative electrode thinning portion, which are arranged along a first direction. Along the first direction, the negative electrode main body is provided with a negative electrode thinning portion at one end close to the end cover.

[0088] The thinned portion of the negative electrode allows the electrode assembly to have a larger expansion gap, thereby reducing the expansion force of the electrode assembly on the first side wall.

[0089] In some embodiments, in a projection plane perpendicular to the second direction, an orthographic projection of the negative electrode thinned portion and an orthographic projection of the first inner surface are spaced apart along the first direction.

[0090] The influence of the thinned portion of the negative electrode on the first inner surface is reduced, and the expansion force exerted by the electrode assembly on the first inner surface is reduced.

[0091] In some embodiments, in a projection plane perpendicular to the second direction, a spacing between an orthographic projection of the negative electrode thinned portion and an orthographic projection of the first inner surface along the first direction is greater than or equal to 1 mm.

[0092] The first inner surface is further away from the first thinned portion, which helps to reduce the expansion force exerted by the electrode assembly on the first inner surface.

[0093] In some embodiments, the single-side coating weight of the negative electrode active material layer is 90 mg / 1540 mm 2 ~170mg / 1540mm 2 The single-sided coating weight of the negative electrode active material layer can be selected as 110 mg / 1540 mm 2 ~150mg / 1540mm 2 .

[0094] In some embodiments, the porosity of the negative electrode sheet is 27% to 40%.

[0095] In some embodiments, the negative electrode active material includes a silicon-based material, and the mass content of silicon in the silicon-based material is 0.3% to 10%, and can be optionally 1% to 6%.

[0096] In some embodiments, the silicon-based material includes at least one of a silicon-oxygen compound and a silicon-carbon composite.

[0097] In some embodiments, the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer disposed on at least one side of the positive electrode current collector, wherein the positive electrode active material layer includes a positive electrode active material.

[0098] In some embodiments, the positive active material layer includes a positive main body and a positive thinned portion, which are arranged along a first direction. Along the first direction, the positive thinned portion is provided at one end of the positive main body close to the end cover.

[0099] The provision of the positive electrode thinning portion is beneficial to increasing the expansion gap of the electrode assembly and reducing the expansion force of the electrode assembly on the first side wall portion.

[0100] In some embodiments, in a projection plane perpendicular to the second direction, an orthographic projection of the positive electrode thinned portion and an orthographic projection of the first inner surface are spaced apart along the first direction.

[0101] The influence of the thinned portion of the positive electrode on the first inner surface is reduced, and the expansion force exerted by the electrode assembly on the first inner surface is reduced.

[0102] In some embodiments, in a projection plane perpendicular to the second direction, a spacing dimension between an orthographic projection of the positive electrode thinned portion and an orthographic projection of the first inner surface along the first direction is greater than or equal to 1 mm.

[0103] The negative electrode thinning portion is farther away from the first inner surface, which is beneficial to reducing the expansion force of the electrode assembly on the first inner surface.

[0104] In some embodiments, the single-sided coating weight of the positive electrode active material layer is 200 mg / 1540 mm 2 ~370mg / 1540 / mm 2 The single-sided coating weight of the positive electrode active material layer can be selected as 240mg / 1540mm 2 ~330mg / 1540mm 2 .

[0105] In some embodiments, the positive electrode active material is a lithium-containing phosphate.

[0106] In some embodiments, the material of the housing includes steel;

[0107] The maximum distance between the second inner surface and the second outer surface along the second direction is D1, the dimension of the shell along the second direction is D, and 0.001≤D1 / D≤0.012.

[0108] With a higher energy density, the shell has better strength.

[0109] In some embodiments, the material of the housing includes steel;

[0110] The maximum distance between the second inner surface and the second outer surface along the second direction is D1, 0.08mm≤D1≤0.35mm; and / or the maximum distance between the first inner surface and the first outer surface along the second direction is D2, 0.1mm≤D2≤0.6mm.

[0111] In some embodiments, the material of the housing includes aluminum alloy;

[0112] The maximum distance between the second inner surface and the second outer surface along the second direction is D1, the dimension of the shell along the second direction is D, and 0.005≤D1 / D≤0.065.

[0113] With a higher energy density, the shell has better strength.

[0114] In some embodiments, the material of the housing includes aluminum alloy;

[0115] The maximum distance between the second inner surface and the second outer surface along the second direction is D1, 0.4mm≤D1≤0.8mm; and / or the maximum distance between the first inner surface and the first outer surface along the second direction is D2, 0.5mm≤D2≤1.5mm.

[0116] In some embodiments, the aluminum alloy includes the following components in mass percentage: aluminum ≥ 99.6%, copper ≤ 0.05%, iron ≤ 0.35%, magnesium ≤ 0.03%, manganese ≤ 0.03%, silicon ≤ 0.25%, titanium ≤ 0.03%, vanadium ≤ 0.05%, zinc ≤ 0.05%, and other individual elements ≤ 0.03%.

[0117] In some embodiments, the first region is directly connected to the first connecting portion, and the first inner surface extends along the first direction to an end of the first region facing the connecting portion.

[0118] This is beneficial for strengthening the end of the first region toward the first connecting portion.

[0119] In some embodiments, the first side wall portion also includes a first transition zone, the first transition zone is connected to one end of the first zone away from the second zone along the first direction, the first transition zone is connected to the first connecting portion, and the connection position between the first transition zone and the first connecting portion forms a first connecting interface, the first connecting interface has a first position closest to the first zone along the first direction, and the first position is located at one end of the first zone away from the second zone along the first direction.

[0120] The first connection interface allows the first transition zone and the first connection portion to have a larger contact area, thereby improving the connection firmness.

[0121] In some embodiments, at least a portion of the first connection interface extends obliquely relative to the second direction.

[0122] The tensile force exerted on the first transition zone by the contraction of the first connecting portion and the force exerted on the first transition zone by the first side wall portion are not in a straight line, thereby reducing the possibility of fatigue cracking.

[0123] In some embodiments, the first connection interface includes a first interface that extends obliquely from a first position toward the end cap, and along the second direction, at least a portion of the first transition zone is located between the first interface and the end cap.

[0124] The first transition zone is protected by the stopper of the first connecting portion, thereby reducing the possibility of fatigue cracking of the first transition zone.

[0125] In some embodiments, the first interface is connected to the first outer surface at a first location, and the first location is at least partially located in the first region.

[0126] The thickened portion of the first sidewall portion corresponding to the first outer surface is located as far as possible at the end of the first region facing the first connecting portion, thereby reducing the possibility of fatigue cracking at the end of the first region facing the first connecting portion.

[0127] In some embodiments, the first connection interface includes a second interface, the second interface extends obliquely from the first position toward a direction away from the end cap, and along the second direction, at least a portion of the first transition zone is located on a side of the second interface away from the end cap.

[0128] The first transition area blocks the first connecting portion, reducing the possibility of the first connecting portion being separated from the end cover.

[0129] In some embodiments, the second interface is connected to the first inner surface at a first location, and the first location is at least partially located in the first region.

[0130] Providing a thicker portion of the first sidewall corresponding to the first inner surface closer to the first connection portion is beneficial for strengthening the end of the first region toward the first connection portion and reducing the possibility of cracking of the end of the first region toward the first connection portion.

[0131] In some embodiments, the hardness of the first transition region is less than the hardness of the second region; and / or the hardness of the first transition region is less than the hardness of the first connecting portion.

[0132] In some embodiments, the first connection interface is closer to the second region than to the outer surface of the end cap.

[0133] The first connecting portion can sink to a deeper position, which is beneficial to improving the connection strength between the end cover and the first connecting portion.

[0134] In some embodiments, the shell further includes a second side wall portion and a corner wall, the first side wall portion, the corner wall and the second side wall portion are arranged along the circumference of the opening, and the corner wall connects the first side wall portion and the second side wall portion.

[0135] Reduce stress concentrations through corner walls.

[0136] In some embodiments, the corner wall and the end cover are welded to form a second connection portion;

[0137] The corner wall includes a third area and a fourth area arranged along the first direction, the hardness of the third area is smaller than the hardness of the fourth area, and the third area is located between the fourth area and the second connecting portion.

[0138] The third region with lower hardness reduces the possibility of cracking of the second connecting portion.

[0139] In some embodiments, the corner wall has a third inner surface and a fourth inner surface facing the electrode assembly and a third outer surface and a fourth outer surface facing away from the electrode assembly, the third inner surface and the fourth inner surface are connected in sequence along the direction of the end cover pointing to the electrode assembly, the third inner surface and the third outer surface are at least partially formed in the third zone, the fourth inner surface and the fourth outer surface are at least partially formed in the fourth zone, and the distance between the third inner surface and the third outer surface along the thickness direction of the corner wall is greater than the distance between the fourth inner surface and the fourth outer surface along the thickness direction of the corner wall.

[0140] The thicker portion of the corner wall corresponding to the third inner surface strengthens the third area, thereby reducing the possibility of fatigue cracking in the third area with lower hardness.

[0141] In some embodiments, the third region is directly connected to the first region, the third inner surface extends to one end of the third region facing the first region, and the first inner surface extends to one end of the first region facing the third region.

[0142] The thicker portion of the first side wall portion corresponding to the first inner surface and the thicker portion of the corner wall corresponding to the third inner surface promote each other, which is beneficial to reducing cracking in the first area and the third area.

[0143] In some embodiments, the corner wall has a first connecting end and a second connecting end, the first side wall portion is connected to the first connecting end, the second side wall portion is connected to the second connecting end, and the distance between the third inner surface and the third outer surface along the thickness direction of the corner wall is a fourth preset thickness, and the fourth preset thickness tends to decrease in the direction from the first connecting end to the second connecting end.

[0144] When the third zone is reinforced to reduce the possibility of cracking in the third zone, the cost is reduced.

[0145] In some embodiments, the third region is directly connected to the second connecting portion, and the third inner surface extends to an end of the third region facing the second connecting portion.

[0146] The end of the third region facing the second connecting portion is reinforced to reduce the possibility of cracking of the end of the third region facing the second connecting portion.

[0147] In some embodiments, the corner wall also includes a second transition zone, the second transition zone is connected to one end of the third zone along the first direction away from the fourth zone, the second transition zone is connected to the second connecting portion, and the connection position between the second transition zone and the second connecting portion forms a second connecting interface, the second connecting interface has a second position closest to the third zone along the first direction, and the second position is located at one end of the third zone along the first direction away from the fourth zone.

[0148] The second connecting surface increases the contact area and reduces the possibility of cracking between the second transition area and the second connecting portion.

[0149] In some embodiments, at least a portion of the second connection interface extends obliquely relative to a thickness direction of the corner wall.

[0150] The force exerted on the second transition zone by the contraction of the second connecting portion and the force exerted on the second transition zone by the deformation of the corner wall due to the expansion force are not in a straight line, thereby reducing the possibility of fatigue cracking of the second transition zone and the second connecting portion.

[0151] In some embodiments, the second connection interface includes a third interface, the third interface extends obliquely from the second position toward the end cap, and along the thickness direction of the corner wall, at least a portion of the second transition zone is located between the third interface and the end cap.

[0152] The second connecting portion protects the second transition zone, reducing the possibility of fatigue cracking in the second transition zone.

[0153] In some embodiments, the third interface is connected to the third outer surface at a second location, and the second location is located in the third region.

[0154] The thicker portion of the corner wall corresponding to the third outer surface is close to the second connecting portion, which is beneficial to reducing cracking of the third area toward the second connecting portion.

[0155] In some embodiments, the second connection interface includes a fourth interface, which extends obliquely from the second position away from the end cap, and along the thickness direction of the corner wall, at least a portion of the second transition zone is located on a side of the fourth interface away from the end cap.

[0156] The second transition zone protects the second connection portion, reducing the possibility of the second connection portion falling off.

[0157] In some embodiments, the fourth interface is connected to the third inner surface at a second location, and the second location is located in the third region.

[0158] The thicker portion of the corner wall corresponding to the third inner surface is close to the second connecting portion, which can reduce the possibility of cracking at the end of the third area facing the second connecting portion.

[0159] In some embodiments, the hardness of the second transition region is less than the hardness of the fourth region; and / or the hardness of the second transition region is less than the hardness of the second connecting portion.

[0160] In some embodiments, the second connection interface is closer to the fourth region than to the outer surface of the end cap.

[0161] The second connecting portion can be sunk to a deeper position of the corner wall, thereby improving the connection strength between the corner wall and the end cover.

[0162] In some embodiments, the hardness of the third region is lower than the hardness of the second connecting portion.

[0163] In some embodiments, the shell includes two first side wall portions and two second side wall portions, the two first side wall portions are arranged opposite to each other along the second direction, the two second side wall portions are arranged opposite to each other along the third direction, and the first direction, the second direction and the third direction are perpendicular to each other.

[0164] In some embodiments, the first side wall portion has a limiting surface facing the end cover, and the limiting surface abuts against the end cover to limit the end cover from moving in a direction close to the electrode assembly.

[0165] During the welding process, the possibility of the end cover moving toward the electrode assembly is reduced, the welding quality is improved, and the welding difficulty is reduced.

[0166] In some embodiments, the first side wall portion further includes a limiting area arranged on the limiting surface, the limiting area and the end cover are arranged opposite to each other along the second direction, and the limiting area and the end cover are welded to form a first connecting portion.

[0167] The possibility of the end cover moving along the thickness direction of the first side wall portion during the welding process is reduced, the welding quality is improved, and the welding difficulty is reduced.

[0168] In some embodiments, the electrode assembly is a laminate structure, and the electrode assembly includes a plurality of positive electrode sheets and a plurality of negative electrode sheets, and the plurality of positive electrode sheets and the plurality of negative electrode sheets are stacked along the second direction.

[0169] In some embodiments, the number of negative electrode plates is greater than the number of positive electrode plates, and a positive electrode plate is disposed between two adjacent negative electrode plates.

[0170] In some embodiments, each negative electrode plate is provided with a negative electrode tab; and / or each positive electrode plate is provided with a positive electrode tab.

[0171] In some embodiments, the first sidewall portion has a first inner surface and a second inner surface facing the electrode assembly and a first outer surface and a second outer surface facing away from the electrode assembly, the first inner surface and the second inner surface are sequentially connected along a direction from the end cap to the electrode assembly, the first outer surface and the second outer surface are sequentially connected along a direction from the end cap to the electrode assembly, the first inner surface and the first outer surface are at least partially formed in a first region, the second inner surface and the second outer surface are at least partially formed in a second region, and a distance between the first inner surface and the first outer surface along the second direction is greater than a distance between the second inner surface and the second outer surface along the second direction;

[0172] Along the third direction, the size of the first inner surface is larger than the size of the positive electrode sheet and / or the size of the negative electrode sheet, and the first direction, the second direction and the third direction are perpendicular to each other.

[0173] The thicker portion of the first side wall portion corresponding to the first inner surface can be strengthened within the range of the entire positive electrode sheet along the third direction, which is beneficial to reducing cracking of the first side wall portion.

[0174] In some embodiments, the battery cell further includes two electrode terminals, which are disposed on the end caps, have opposite polarities, and are both electrically connected to the electrode assembly;

[0175] The end cover is provided with a lead-out hole, and the electrode terminal includes a terminal body, a first limiting portion and a second limiting portion. The terminal body is connected to the first limiting portion and the second limiting portion. The terminal body is passed through the lead-out hole. Along the first direction, the first limiting portion is located on the side of the end cover away from the electrode assembly, and the second limiting portion is located on the side of the end cover facing the electrode assembly.

[0176] The electrode terminal is installed on the end cover by riveting, which makes installation easy.

[0177] In some embodiments, the electrode assembly has a straight region, and a portion of the positive electrode sheet located in the straight region and a portion of the negative electrode sheet located in the straight region are stacked along the second direction.

[0178] In some embodiments, the electrode assembly includes adjacent fifth and sixth outer surfaces, the fifth outer surface is perpendicular to the second direction, the area of ​​the fifth outer surface is larger than the area of ​​the sixth outer surface, and the fifth outer surface is arranged opposite to the first side wall portion along the second direction.

[0179] The first area releases the expansion force in the direction of greater expansion force, and the first inner surface is reinforced in the direction of greater expansion force.

[0180] In some embodiments, the fifth outer surface is the largest surface among the outer surfaces of the electrode assembly.

[0181] In some embodiments, the electrode assembly has a wound structure, and the electrode assembly further has a corner region, and the corner region is provided at at least one end of the straight region along the third direction, and the first direction, the second direction, and the third direction are not coplanar and intersect with each other;

[0182] The outer surface of the straight area includes a fifth outer surface, and the outer surface of the corner area includes a sixth outer surface. At least a portion of the sixth outer surface is an arc surface.

[0183] In some embodiments, the electrode assembly is a laminated structure, the straight area includes multiple positive electrode sheets and multiple negative electrode sheets, the multiple positive electrode sheets and multiple negative electrode sheets are stacked along the second direction, and the fifth outer surface is perpendicular to the sixth outer surface.

[0184] The first area releases the expansion force in the direction of greater expansion force, and the first inner surface is reinforced in the direction of greater expansion force.

[0185] In some embodiments, the first side wall portion is a wall with the largest outer surface area in the housing.

[0186] In some embodiments, the shell includes two first side wall portions, which are arranged opposite to each other along the second direction, and the electrode assembly is located between the two first side wall portions.

[0187] In some embodiments, the hardness of the first region is lower than the hardness of the first connecting portion.

[0188] An embodiment of the present application provides a battery device including any of the above-mentioned battery cells.

[0189] In some embodiments, the number of the electrode assemblies is N1, each of the electrode assemblies further includes at least one separator, the number of the positive electrode sheet is at least one, the number of the negative electrode sheet is at least one, the positive electrode sheet, the negative electrode sheet, and the separator are stacked to form a flat region, and at least a portion of the positive electrode sheet, at least a portion of the negative electrode sheet, and at least a portion of the separator are stacked in the flat region along the second direction;

[0190] The number of layers of the positive electrode sheets stacked in the straight area of ​​each electrode assembly is N2, the straight area has an outer surface perpendicular to the second direction, and the area of ​​the outer surface is S, N1≥1, N2≥1, N1*N2≥50, and S≥8000mm 2 .

[0191] In the embodiment of the present application, the possibility of the first connecting portion of the first sidewall portion cracking under the action of a large expansion force is reduced by the first region with higher toughness.

[0192] In some embodiments, the negative electrode plate includes a negative electrode current collector and a negative electrode active material layer disposed on at least one side of the negative electrode current collector, wherein the negative electrode active material layer includes a negative electrode active material, and the discharge capacity per unit area of ​​the negative electrode active material layer is 2.0 mAh / cm 2 Up to 5.0 mAh / cm 2 .

[0193] In the embodiment of the present application, when the discharge capacity per unit area of ​​the negative electrode active material layer is within the above range, there are sufficient sites for lithium embedding in the negative electrode active material layer, which can reduce the risk of lithium plating; and it is conducive to fast charging, and the expansion force is not too large, reducing the possibility of the first connecting part cracking under the expansion shear of the electrode assembly.

[0194] In some embodiments, the thickness of the negative electrode active material layer is T1, and 9 μm≤T1≤75 μm.

[0195] In the embodiment of the present application, the thickness of the negative electrode active material layer is relatively large, and the expansion force is correspondingly relatively large. The possibility of the first connecting portion of the first side wall portion cracking under the action of the large expansion force is reduced by the first region with lower hardness.

[0196] An embodiment of the present application provides an electrical device, comprising any one of the above-mentioned battery cells, wherein the battery cell is used to provide electrical energy to the electrical device. BRIEF DESCRIPTION OF THE DRAWINGS

[0197] FIG1 is a schematic structural diagram of a vehicle provided in some embodiments of the present application;

[0198] FIG2 is an exploded view of a battery provided in some embodiments of the present application;

[0199] FIG3 is an exploded view of a battery cell provided in some embodiments of the present application;

[0200] FIG4 is an axonometric view of the battery cell shown in FIG3 ;

[0201] FIG5 is an AA cross-sectional view of the battery cell shown in FIG4 , wherein the cross section of the first side wall portion shown in the figure is a preset cross section;

[0202] FIG6 is a partial enlarged view of point B in FIG5 , and the cross section of the first side wall portion shown in the figure is the preset cross section;

[0203] FIG7 is an axonometric view of the housing shown in FIG5 ;

[0204] FIG8 is a partial enlarged view of point J in FIG7 , in which the dotted line is the boundary between the first area and the second area. One side of the dotted line along the first direction is the first area, and the other side of the dotted line along the first direction is the second area. The first sub-surface is shown as being arranged across the first and second areas.

[0205] FIG9 is a schematic metallographic diagram of a preset cross-section of a first sidewall portion provided by some embodiments of the present application. The diagram shows a first grain in a first zone, but does not show other grains in the first zone. The diagram shows a second grain in a second zone, but does not show other grains in the second zone. The diagram shows a dimension of the first grain in the first zone extending along the first direction and a maximum dimension along the second direction. The diagram shows a dimension of the second grain in the second zone extending along the first direction and a maximum dimension in the second direction. The dotted line in the diagram is the boundary between the first zone and the second zone. One side of the dotted line along the first direction is the first zone, and the other side of the dotted line along the first direction is the second zone. The shapes of the grains in the diagram are merely schematic and do not represent the actual shapes of the grains.

[0206] FIG10 is an axonometric view of an electrode assembly provided in some embodiments of the present application;

[0207] FIG11 is a schematic structural diagram of the electrode assembly shown in FIG10 ;

[0208] FIG12 is an axonometric view of electrode assemblies provided in some other embodiments of the present application;

[0209] FIG13 is a schematic structural diagram of the electrode assembly shown in FIG12 ;

[0210] FIG14 is a partial view of the first sidewall portion shown in FIG6 , wherein the dotted line in the figure is the boundary between the first area and the second area, the first sub-surface is arranged across the first area and the second area, and the first outer surface is arranged across the first area and the second area;

[0211] FIG15 is an axonometric view of a housing provided in some embodiments of the present application;

[0212] FIG16 is a top view of the housing shown in FIG15 ;

[0213] FIG17 is a partial enlarged view of point K in FIG15 , in which the dashed line is the boundary between the first zone and the second zone. The first zone and the second zone are located on opposite sides of the dashed line along the first direction, and the first inner surface spans the first zone and the second zone.

[0214] FIG18 is an axonometric view of a housing provided in some other embodiments of the present application;

[0215] FIG19 is a top view of the housing shown in FIG18 ;

[0216] FIG20 is a partial enlarged view of point M in FIG18 , in which the dotted line is the boundary between the first area and the second area. The first area and the second area are located on opposite sides of the dotted line along the first direction. The first connecting surface is provided across the first area and the second area, and the second connecting surface is provided across the first area and the second area.

[0217] FIG21 is a partial enlarged view of point N in FIG18 , in which the dashed line is the boundary between the first region and the second region. The first region and the second region are located on opposite sides of the dashed line along the first direction. The first connecting surface is provided across the first region and the second region, and the third connecting surface is provided across the first region and the second region.

[0218] FIG22 is an axonometric view of a housing provided in some other embodiments of the present application;

[0219] FIG23 is a top view of the housing shown in FIG17;

[0220] FIG24 is a partial enlarged view of point P in FIG22 , in which the dashed line is the boundary between the first zone and the second zone. The first zone and the second zone are located on opposite sides of the dashed line along the first direction. The first connecting surface spans the first zone and the second zone, the second connecting surface spans the first zone and the second zone, and the first transition surface spans the first zone and the second zone.

[0221] FIG25 is a partial enlarged view of point Q in FIG22 . The dashed line in the figure is the boundary between the first area and the second area. The first area and the second area are located on opposite sides of the dashed line along the first direction. The first connecting surface spans the first area and the second area. The third connecting surface spans the first area and the second area. The second transition surface spans the first area and the second area.

[0222] FIG26 is a partial view of a battery cell provided in some embodiments of the present application (showing the positive electrode sheet, negative electrode sheet, and separator of the electrode assembly);

[0223] FIG27 is a diagram showing the positional relationship among the positive electrode sheet, the negative electrode sheet, and the separator according to some embodiments of the present application;

[0224] FIG28 is a diagram showing the positional relationship among the positive electrode sheet, the negative electrode sheet, and the separator provided in other embodiments of the present application;

[0225] FIG29 is a partial view of a battery cell provided in some embodiments of the present application (showing a first side wall portion);

[0226] FIG30 is a partial view of the first sidewall portion shown in FIG29 , wherein the dashed line in the figure is the boundary between the first area and the second area, the first inner surface spans the first area and the second area, and the first outer surface spans the first area and the second area;

[0227] FIG31 is an axonometric view of the housing shown in FIG29;

[0228] FIG32 is a partial view of a battery cell provided in accordance with some other embodiments of the present application (showing the first side wall portion);

[0229] FIG33 is a partial enlarged view of point C in FIG32;

[0230] FIG34 is a partial view of a battery cell provided in accordance with yet other embodiments of the present application (showing the first side wall portion);

[0231] FIG35 is a partial enlarged view of point D in FIG34;

[0232] FIG36 is a partial view of a battery cell provided in some further embodiments of the present application (showing the first side wall portion);

[0233] FIG37 is a partial enlarged view of point E in FIG36;

[0234] FIG38 is an axonometric view of a housing according to some further embodiments of the present application;

[0235] Figure 39 is a partial enlarged view of point F in Figure 38 . The dashed line in the figure is both the boundary between the first and second areas, and the boundary between the third and fourth areas. The first and second areas are located on opposite sides of the dashed line along the first direction, and the third and fourth areas are located on opposite sides of the dashed line along the first direction. The first inner surface spans the first and second areas, and the third inner surface spans the third and fourth areas.

[0236] FIG40 is a partial view of a battery cell provided in some embodiments of the present application (showing a corner wall);

[0237] FIG41 is a schematic diagram of the structure of a corner wall provided in some embodiments of the present application. The dashed line in the figure is the boundary between the third zone and the fourth zone. The third inner surface is provided across the third zone and the fourth zone, and the third outer surface is provided across the third zone and the fourth zone.

[0238] FIG42 is a schematic structural diagram of a corner wall provided in other embodiments of the present application. The dashed line in the figure is the boundary between the third zone and the fourth zone. The third inner surface is provided across the third zone and the fourth zone, and the third outer surface is provided across the third zone and the fourth zone.

[0239] FIG43 is a partial view of a battery cell provided in accordance with some other embodiments of the present application (showing a corner wall);

[0240] FIG44 is a partial enlarged view of point G in FIG43;

[0241] FIG45 is a partial view of a battery cell provided in accordance with yet other embodiments of the present application (showing a corner wall);

[0242] FIG46 is a partial enlarged view of point H in FIG45;

[0243] FIG47 is a partial view of a battery cell provided in accordance with still other embodiments of the present application (showing a corner wall);

[0244] FIG48 is a partial enlarged view of point I in FIG47;

[0245] FIG49 is a diagram showing the positional relationship between the end cover and the side wall before welding in some embodiments of the present application;

[0246] Figure 50 is a schematic diagram of the connection between the end cap and the electrode terminal provided in some embodiments of the present application.

[0247] Figure numerals: 1, shell; 11, shell; 111, first side wall portion; 1111, first zone; 11111, first sub-surface; 11112, second sub-surface; 11113, first connecting surface; 11113a, first end; 11113b, second end; 11114, second connecting surface; 11115, third connecting surface; 11116, first transition surface; 11117, second transition surface; 1112, second zone; 1113, third end; 1114, fourth end; 1115, limiting surface; 1116, limiting zone; 1117, first transition zone; 112, second side wall portion; 113, corner wall; 1131, third zone; 1132, fourth 1133, first connection terminal; 1134, second connection terminal; 1135, second transition zone; 12, end cap; 121, outer surface of end cap; 2, electrode assembly; 21, tab; 21a, positive tab; 21b, negative tab; 22, positive electrode sheet; 221, positive electrode main body; 2211, fifth end; 222, positive electrode current collector; 223, positive electrode active material layer; 2231, positive electrode main body; 2232, positive electrode thinning portion; 224, insulating layer; 23, negative electrode sheet; 231, negative electrode main body; 2311, sixth end; 232, negative electrode current collector; 233, negative electrode active material layer; 2331, negative electrode main body; 2332, negative electrode thinning portion 1. Thin portion; 24. Isolator; 241. Seventh end; 242. Outer area; 25. Straight area; 26. Corner area; 27. Fifth outer surface; 28. Sixth outer surface; 3. Electrode terminal; 31. Terminal body; 32. First limiting portion; 33. Second limiting portion; 4. Pressure relief mechanism; 5. Connecting portion; 51. First connecting portion; 511. First connecting interface; 5111. First position; 5112. First interface; 5113. Second interface; 5114. Third position; 5115. Fourth position; 52. Second connecting portion; 521. Second connecting interface; 5211. Second position; 5212. Third interface; 5213. Fourth interface; 5214. Fifth position; 5215, sixth position; 6, first insulating member; 7, second insulating member; 10, battery cell; 20, casing; 201, first casing; 202, second casing; 100, battery device; 200, controller; 300, motor; 1000, vehicle; Z, first direction; Y, second direction; X, third direction; U, first interface; V, second interface; 800, first grain; 802, second grain; 804, first inner surface; 805, second inner surface; 806, first outer surface; 807, second outer surface; 810, third inner surface; 811, fourth inner surface; 812, third outer surface; 813, fourth outer surface. DETAILED DESCRIPTION

[0248] To make the purpose, technical solutions, and advantages of the embodiments of this application more clear, the technical solutions in the embodiments of this application will be clearly described below in conjunction with the drawings in the embodiments of this application. Obviously, the described embodiments are part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0249] Unless otherwise defined, all technical and scientific terms used in this application have the same meanings as commonly understood by those skilled in the art to which this application belongs. The terms used in the specification of this application are for the purpose of describing specific embodiments only and are not intended to limit this application. The terms "including" and "having" and any variations thereof in the specification and claims of this application and the above-mentioned drawings are intended to cover non-exclusive inclusions. The terms "first" and "second" in the specification and claims of this application or the above-mentioned drawings are used to distinguish different objects, rather than to describe a specific order or a primary-secondary relationship.

[0250] References to "embodiments" in this application mean that a particular feature, structure, or characteristic described in connection with the embodiment may be included in at least one embodiment of the application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive of other embodiments.

[0251] The term "and / or" in this application simply describes an association between related objects, indicating that three possible relationships exist. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " in this application generally indicates that the related objects are in an "or" relationship.

[0252] In the embodiments of this application, the same reference numerals represent the same components, and for the sake of brevity, detailed descriptions of the same components in different embodiments are omitted. It should be understood that the thickness, length, width, and other dimensions of the various components in the embodiments of this application, as well as the overall thickness, length, width, and other dimensions of the integrated device shown in the drawings are merely illustrative and should not constitute any limitation on this application.

[0253] The term "plurality" used in this application refers to two or more (including two).

[0254] In the embodiment of the present application, the battery cell may be a secondary battery. A secondary battery refers to a battery cell that can be continuously used by activating active materials by charging after the battery cell is discharged.

[0255] Battery cells include but are not limited to lithium-ion batteries, sodium-ion batteries, sodium-lithium-ion batteries, lithium metal batteries, sodium metal batteries, lithium-sulfur batteries, magnesium-ion batteries, nickel-hydrogen batteries, nickel-cadmium batteries, lead-acid batteries, etc.

[0256] It should be noted that the battery cells in the embodiments of the present application are the batteries in the prior application document with priority.

[0257] A battery cell 10 generally includes an electrode assembly 2. The electrode assembly 2 comprises a positive electrode, a negative electrode, and a separator 24. During the charge and discharge process of the battery cell 10, active ions (e.g., lithium ions) are intercalated and released between the positive and negative electrodes. Separator 24, positioned between the positive and negative electrodes, reduces the possibility of short circuits while allowing the active ions to pass through.

[0258] In some embodiments, the positive electrode may be a positive electrode sheet 22 , and the positive electrode sheet 22 may include a positive electrode current collector 222 and a positive electrode active material disposed on at least one surface of the positive electrode current collector 222 .

[0259] As an example, the positive electrode current collector 222 has two surfaces facing each other in its thickness direction, and the positive electrode active material is provided on either or both of the two facing surfaces of the positive electrode current collector 222 .

[0260] As an example, the positive electrode current collector 222 may be a metal foil or a composite current collector. For example, as the metal foil, aluminum with a silver-plated surface, stainless steel with a silver-plated surface, stainless steel, copper, aluminum, nickel, carbon electrode, carbon, nickel, or titanium may be used. The composite current collector may include a polymer material base layer and a metal layer. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.).

[0261] As an example, the positive electrode active material may include at least one of the following materials: lithium-containing phosphates, lithium transition metal oxides, and their respective modified compounds. However, the present application is not limited to these materials, and other traditional materials that can be used as positive electrode active materials for batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium-containing phosphates may include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO4), a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, and a composite material of lithium iron manganese phosphate and carbon. Examples of lithium transition metal oxides may include, but are not limited to, lithium cobalt oxide (such as LiCoO2), lithium nickel oxide (such as LiNiO2), lithium manganese oxide (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi1 / 3Co1 / 3Mn1 / 3O2 (also referred to as NCM333), LiNi0.5Co0.2Mn0.3O2 (also referred to as NCM523), LiNi0.5Co0.25Mn0.25O2 (also referred to as NCM211), LiNi0.6Co0.2Mn0.2O2 (also referred to as NCM622), LiNi0.8Co0.1Mn0.1O2 (also referred to as NCM811), lithium nickel cobalt aluminum oxide (such as LiNi0.85Co0.15Al0.05O2) and at least one of their modified compounds.

[0262] In some embodiments, a positive electrode may utilize a metal foam. The metal foam may include nickel foam, copper foam, aluminum foam, alloy foam, or the like. When a metal foam is used as the positive electrode, the surface of the metal foam may or may not include a positive electrode active material. For example, a lithium source material, potassium metal, or sodium metal may be filled or / and deposited within the metal foam, where the lithium source material is lithium metal and / or a lithium-rich material.

[0263] In some embodiments, the negative electrode may be a negative electrode sheet 23 , and the negative electrode sheet 23 may include a negative electrode current collector 232 .

[0264] As an example, the negative electrode current collector 232 may be a metal foil, a metal foam, or a composite current collector. For example, the metal foil may include aluminum with a silver-plated surface, stainless steel with a silver-plated surface, stainless steel, copper, aluminum, nickel, a carbon electrode, carbon, nickel, or titanium. The metal foam may be nickel foam, copper foam, aluminum foam, or an alloy foam. The composite current collector may include a polymer base layer and a metal layer. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, or silver alloy) on a polymer substrate (such as a substrate made of polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, or polyethylene).

[0265] As an example, the negative electrode sheet 23 may include a negative electrode current collector 232 and a negative electrode active material disposed on at least one surface of the negative electrode current collector 232 .

[0266] As an example, the negative electrode current collector 232 has two surfaces facing each other in its thickness direction, and the negative electrode active material is provided on either or both of the two facing surfaces of the negative electrode current collector 232 .

[0267] As an example, the negative electrode active material may adopt the negative electrode active material for the battery cell 10 that is well known in the art. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, etc. The silicon-based material can be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material can be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. However, the present application is not limited to these materials, and other traditional materials that can be used as battery negative electrode active materials can also be used. These negative electrode active materials can be used alone or in combination of two or more.

[0268] In some embodiments, the positive electrode current collector 222 may be made of aluminum, and the negative electrode current collector 232 may be made of copper.

[0269] In some embodiments, the separator 24 is a separator membrane, which can be any known porous separator membrane with good chemical and mechanical stability.

[0270] As an example, the separator can be made of at least one of fiberglass, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film. When the separator is a multi-layer composite film, the materials of each layer can be the same or different. The separator 24 can be a separate component positioned between the positive and negative electrodes, or it can be attached to the surfaces of the positive and negative electrodes.

[0271] In some embodiments, the separator 24 is a solid electrolyte. The solid electrolyte is disposed between the positive electrode and the negative electrode, and serves to transport ions and isolate the positive and negative electrodes.

[0272] In some embodiments, the battery cell 10 further includes an electrolyte, which acts as a conductor of ions between the positive and negative electrodes. The electrolyte may be liquid, gel, or solid. Liquid electrolytes include an electrolyte salt and a solvent.

[0273] In some embodiments, the electrolyte salt may include at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bisfluorosulfonyl imide, lithium bistrifluoromethanesulfonyl imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalatoborate, lithium bisoxalatoborate, lithium difluorodioxalatophosphate, and lithium tetrafluorooxalatophosphate.

[0274] In some embodiments, the solvent may include at least one of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methylpropyl carbonate, ethylpropyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclopentane, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone. The solvent may also be an ether solvent. The ether solvent may include one or more of ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, 1,3-dioxolane, tetrahydrofuran, methyltetrahydrofuran, diphenyl ether and crown ether.

[0275] Among them, the gel electrolyte includes a skeleton network with a polymer as the electrolyte, combined with an ionic liquid-lithium salt.

[0276] Among them, solid electrolytes include polymer solid electrolytes, inorganic solid electrolytes, and composite solid electrolytes.

[0277] As an example, the polymer solid electrolyte may be polyether (polyethylene oxide), polysiloxane, polycarbonate, polyacrylonitrile, polyvinylidene fluoride, polymethyl methacrylate, a single ion polymer, polyionic liquid-lithium salt, cellulose, or the like.

[0278] As an example, the inorganic solid electrolyte may include an oxide solid electrolyte (crystalline perovskite, sodium superconducting ion conductor, garnet, amorphous LiPON film), a sulfide solid electrolyte (crystalline lithium superion conductor (lithium germanium phosphosulfide, silver germanium sulfide), amorphous sulfide) and one or more of a halide solid electrolyte, a nitride solid electrolyte and a hydride solid electrolyte.

[0279] As an example, a composite solid electrolyte is formed by adding an inorganic solid electrolyte filler to a polymer solid electrolyte.

[0280] In some embodiments, the electrode assembly 2 is a wound structure, wherein the positive electrode sheet 22 and the negative electrode sheet 23 are wound into a wound structure.

[0281] In some embodiments, the electrode assembly 2 is a laminate structure.

[0282] As an example, a plurality of positive electrode sheets 22 and a plurality of negative electrode sheets 23 may be provided, and the plurality of positive electrode sheets 22 and the plurality of negative electrode sheets 23 may be alternately stacked.

[0283] As an example, a plurality of positive electrode sheets 22 may be provided, and the negative electrode sheet 23 may be folded to form a plurality of stacked folded segments, with one positive electrode sheet 22 being sandwiched between adjacent folded segments.

[0284] As an example, the positive electrode tab 22 and the negative electrode tab 23 are both folded to form a plurality of stacked folded segments.

[0285] As an example, a plurality of separators 24 may be provided, each of which is disposed between any adjacent positive electrode sheets 22 or negative electrode sheets 23 .

[0286] As an example, the separator 24 may be provided continuously, and may be provided between any adjacent positive electrode sheets 22 or negative electrode sheets 23 by folding or winding.

[0287] In some embodiments, the shape of the electrode assembly 2 can be cylindrical, flat, or polygonal.

[0288] In some embodiments, the electrode assembly 2 is provided with tabs 21, which can conduct current from the electrode assembly 2. The tabs 21 include a positive electrode tab 21a and a negative electrode tab 21b.

[0289] In some embodiments, the battery cell 10 may include a housing 1. The housing 1 is used to encapsulate components such as the electrode assembly 2 and the electrolyte. The housing 1 may be a steel shell, an aluminum shell, a plastic shell (such as polypropylene), a composite metal shell (such as a copper-aluminum composite housing 1), or an aluminum-plastic film.

[0290] As an example, the battery cell 10 can be a cylindrical battery cell 10, a prismatic battery cell 10, a soft-pack battery cell 10 or a battery cell 10 of other shapes. The prismatic battery cell 10 includes a square-shell battery cell 10, a blade-shaped battery cell 10, and a polygonal battery cell 10. The polygonal battery cell 10 is, for example, a hexagonal battery cell 10, etc.

[0291] The battery device 100 mentioned in the embodiments of the present application refers to a single physical module including one or more battery cells 10 to provide higher voltage and capacity.

[0292] In some embodiments, the battery device 100 may be a battery module. When there are multiple battery cells 10 , the multiple battery cells 10 are arranged and fixed to form a battery module.

[0293] In some embodiments, the battery device 100 may be a battery pack, which includes a case 20 and battery cells 10 . The battery cells 10 or battery modules are housed in the case 20 .

[0294] In some embodiments, the box 20 may serve as part of the chassis structure of the vehicle 1000. For example, a portion of the box 20 may form at least a portion of the floor of the vehicle 1000, or a portion of the box 20 may form at least a portion of the cross member and longitudinal member of the vehicle 1000.

[0295] In some embodiments, the battery device 100 may be an energy storage device, including an energy storage container, an energy storage cabinet, and the like.

[0296] In related art, a battery cell 10 generally includes an outer shell 1 and an electrode assembly 2. The outer shell 1 may include a shell 11 and an end cover 12. The shell 11 has an opening. After the electrode assembly 2 is installed in the shell 11, the opening of the shell 11 can be closed by the end cover 12 to form an enclosed space inside the outer shell 1 to accommodate the electrode assembly 2.

[0297] In order to achieve a stable connection between the end cap 12 and the shell 11, the end cap 12 and the shell 11 can be welded. After the end cap 12 and the shell 11 are welded, a connection portion 5 will be formed at the welding position of the end cap 12 and the shell 11, and the connection portion 5 has a relatively high hardness. During the charge and discharge process of the battery cell 10, due to the embedding and extraction of ions, the electrode assembly 2 will produce cyclic expansion and contraction, and the wall of the shell 11 will be deformed after being subjected to the expansion force of the electrode assembly 2. The force of the expansion and contraction of the electrode assembly 2 will be transmitted to the connection portion 5 at the opening of the shell 11 through this deformation of the shell 11. Since the connection portion 5 has a relatively high hardness and low toughness, it is difficult to withstand the force of the electrode assembly 2 during the expansion and contraction process, which may cause the shell 11 to crack at the connection portion 5 near the opening, affecting the service life of the battery cell 10.

[0298] Based on the above considerations, the embodiment of the present application sets a first area 1111 with lower hardness, and releases the expansion force of the electrode assembly 2 on the connecting part 5 through the deformation part of the first area 1111 with lower hardness, thereby reducing the possibility of cracking of the connecting part 5 at the opening of the shell 11 and improving the service life of the battery cell 10.

[0299] The battery cell 10 described in the embodiment of the present application is applicable to a battery device 100 and an electrical device using the battery cell 10 .

[0300] The electrical device can be a vehicle 1000, a mobile phone, a portable device, a laptop computer, a ship, a spacecraft, an electric toy, an electric tool, and the like. The vehicle 1000 can be a fuel vehicle, a gas vehicle, or a new energy vehicle. The new energy vehicle can be a pure electric vehicle, a hybrid vehicle, or an extended-range vehicle, and the like; the spacecraft includes airplanes, rockets, space shuttles, and spacecraft, and the like; the electric toys include fixed or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, and the like; the electric tools include metal cutting electric tools, grinding electric tools, assembly electric tools, and railway electric tools, such as electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact drills, concrete vibrators, and electric planers, and the like. The embodiments of the present application do not impose any special restrictions on the above-mentioned electrical devices.

[0301] For the convenience of description, the following embodiments are described by taking the electric device as a vehicle 1000 as an example.

[0302] Please refer to Figure 1, which is a schematic diagram of the structure of a vehicle 1000 provided in some embodiments of the present application. A battery device 100 is disposed within vehicle 1000. Battery device 100 can be located at the bottom, front, or rear of vehicle 1000. Battery device 100 can be used to power vehicle 1000. For example, battery device 100 can serve as the operating power source of vehicle 1000.

[0303] The vehicle 1000 may further include a controller 200 and a motor 300 . The controller 200 is used to control the battery device 100 to supply power to the motor 300 , for example, to meet the power requirements of the vehicle 1000 during startup, navigation, and driving.

[0304] In some embodiments of the present application, the battery device 100 can not only serve as the operating power source of the vehicle 1000, but also serve as the driving power source of the vehicle 1000, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle 1000.

[0305] Please refer to Figure 2, which is an exploded view of a battery device 100 provided in some embodiments of the present application. The battery device 100 may include a battery cell 10 and a housing 20, wherein the battery cell 10 is accommodated in the housing 20.

[0306] The housing 20 is a component that houses the battery cells 10 and provides a storage space for the battery cells 10. The housing 20 can have various structures. In some embodiments, the housing 20 can include a first housing 201 and a second housing 202. The first housing 201 and the second housing 202 cover each other to define a storage space for the battery cells 10. The first housing 201 and the second housing 202 can have various shapes, such as a rectangular parallelepiped or a cylindrical shape. The first housing 201 can be a hollow structure with an opening on one side, and the second housing 202 can be a hollow structure with an opening on one side. The open side of the second housing 202 covers the open side of the first housing 201, thereby forming the housing 20 with a storage space. Alternatively, the first housing 201 can be a hollow structure with an opening on one side, and the second housing 202 can be a plate-like structure. The second housing 202 covers the open side of the first housing 201, thereby forming the housing 20 with a storage space. The first box body 201 and the second box body 202 can be sealed by a sealing element, which can be a sealing ring, sealant, etc.

[0307] In the battery device 100, there can be one or more battery cells 10. If there are multiple battery cells 10, the multiple battery cells 10 can be connected in series, parallel, or in a hybrid connection. A hybrid connection refers to a combination of series and parallel connections among the multiple battery cells 10. Multiple battery cells 10 can be connected in series, parallel, or in a hybrid connection to form a battery module, which is then connected in series, parallel, or in a hybrid connection to form a whole and housed within the housing 20. Alternatively, all battery cells 10 can be directly connected in series, parallel, or in a hybrid connection, and then the whole battery module 10 can be housed within the housing 20.

[0308] 3 , 4 and 5 , the battery cell 10 may include a housing 1 and an electrode assembly 2 , wherein the electrode assembly 2 is accommodated in the housing 1 .

[0309] In some embodiments, the housing 1 may include a shell 11 and an end cover 12 . The shell 11 has an opening at at least one end along the first direction Z, and the end cover 12 closes the opening of the shell 11 .

[0310] The housing 11 is a component for accommodating the electrode assembly 2. The housing 11 can be a hollow structure with an opening at one end along the first direction Z, or it can be a hollow structure with openings at two opposite ends along the first direction Z. The housing 11 can have various shapes, such as a cylinder or a rectangular parallelepiped. The housing 11 can be made of various materials, such as copper, iron, aluminum, steel, and aluminum alloys. The electrode assembly 2 can be partially or completely located within the housing 11.

[0311] The end cap 12 is a component that closes the opening of the shell 11 to isolate the internal environment of the battery cell 10 from the external environment. The end cap 12 and the shell 11 together define a receiving space for accommodating the electrode assembly 2, electrolyte and other components. The end cap 12 can be connected to the shell 11 by welding or rolling to close the opening of the shell 11. The shape of the end cap 12 can be adapted to the shape of the shell 11. For example, the shell 11 is a rectangular parallelepiped structure, and the end cap 12 is a rectangular plate structure adapted to the shell 11. For another example, the shell 11 is a cylindrical structure, and the end cap 12 is a circular plate structure adapted to the shell 11. The material of the end cap 12 can also be a variety of materials, such as copper, iron, aluminum, steel, aluminum alloy, etc. The material of the end cap 12 and the shell 11 can be the same or different.

[0312] In an embodiment where the housing 11 is open at one end, one end cap 12 may be provided. In an embodiment where the housing 11 is open at two opposite ends, two end caps 12 may be provided, each of which closes the two openings of the housing 11, and the two end caps 12 and the housing 11 together define a receiving space.

[0313] In some embodiments, the battery cell 10 may further include an electrode terminal 3, which is disposed on the outer casing 1. The electrode terminal 3 is used to electrically connect to the tab 21 of the electrode assembly 2 to input or output electrical energy from the battery cell 10. The electrode terminal 3 may be disposed on the shell 11 of the outer casing 1 or on the end cap 12 of the outer casing 1. The electrode terminal 3 and the tab 21 may be directly connected, for example, by welding the electrode terminal 3 to the tab 21. The electrode terminal 3 and the tab 21 may also be indirectly connected, for example, by indirectly connecting the electrode terminal 3 and the tab 21 through a current collecting member. The current collecting member may be a metal conductor, such as copper, iron, aluminum, steel, or an aluminum alloy.

[0314] In some embodiments, the battery cell 10 may further include a pressure relief mechanism 4, which may be provided on the end cover 12, or the pressure relief mechanism 4 may be provided on the housing 11. The pressure relief mechanism 4 may be a pressure relief component installed on the housing 11 or the end cover 12, such as an explosion-proof disc, a safety valve, etc. The pressure relief mechanism 4 may also be integrally formed with the end cover 12 or the housing 11. The pressure relief mechanism 4 may be provided with a pressure relief groove, so as to crack along the pressure relief groove when the battery cell 10 is depressurized. The pressure relief groove may be a groove extending along a closed trajectory, which may be a circular trajectory, a rectangular trajectory, etc.; the pressure relief groove may also be a groove extending along a non-closed trajectory, which may be an H-shaped trajectory, a Y-shaped trajectory, a V-shaped trajectory, a U-shaped trajectory, etc.

[0315] As an example, as shown in Figures 3, 4, and 5, an opening is formed at one end of the housing 11, and there is only one end cap 12 in the outer shell 1, and each end cap 12 closes the opening of the housing 11. The end cap 12 is provided with a pressure relief mechanism 4, and two electrode terminals 3 are provided on the end cap 12, respectively a positive electrode terminal 3 and a negative electrode terminal 3. A positive electrode tab 21a and a negative electrode tab 21b are formed on the end of the electrode assembly 2 facing the end cap 12, and the positive electrode terminal 3 is electrically connected to the positive electrode tab 21a, and the negative electrode terminal 3 is electrically connected to the negative electrode tab 21b.

[0316] Referring to Figures 6 to 9 , the battery cell 10 of the embodiment of the present application comprises a housing 11, an electrode assembly 2, and an end cap 12. The housing 11 has an opening at at least one end along a first direction Z. The housing 11 includes a first sidewall 111. The electrode assembly 2 is at least partially housed within the housing 11. The electrode assembly 2 includes a positive electrode sheet 22 and a negative electrode sheet 23. At least portions of the positive electrode sheet 22 and at least portions of the negative electrode sheet 23 are stacked along a second direction Y. The second direction Y is parallel to the thickness of the first sidewall 111, and the first direction Z intersects the second direction Y. The end cap 12 is used to seal the opening. The first sidewall 111 is welded to the end cap 12 to form a first connecting portion 51. The first sidewall 111 includes a first region 1111 and a second region 1112 arranged along the first direction Z. The first region 1111 is located between the first connecting portion 51 and the second region 1112. The hardness of the first region 1111 is lower than that of the second region 1112.

[0317] The shell 11 may have an opening formed at only one end along the first direction Z, and only one end cover 12 is provided correspondingly.

[0318] The housing 11 may have openings at both opposite ends along the first direction Z, and two end covers 12 may be provided accordingly.

[0319] The housing 11 may be in various shapes, such as cylindrical, prism, etc. The prism may be a triangular prism, a quadrangular prism, a pentagonal prism, a hexagonal prism, etc. The quadrangular prism may be a cuboid, a cube, etc.

[0320] The first direction Z is parallel to the direction of the opening of the housing 11. In embodiments where the housing 11 is cylindrical, the first direction Z may be parallel to the axial direction of the housing 11; in embodiments where the housing 11 is prismatic, the first direction Z may be parallel to the extending direction of the side edges of the housing 11.

[0321] The second direction Y is parallel to the thickness direction of the first sidewall portion 111. In embodiments where the housing 11 is cylindrical, the first sidewall portion 111 is cylindrical, and the radial direction of the housing 11 is the thickness direction of the first sidewall portion 111. The second direction Y is parallel to the radial direction of the housing 11. In embodiments where the housing 11 is prismatic, the first sidewall portion 111 may be a rectangular plate-like structure. The first direction Z and the second direction Y may form an acute angle, a right angle, or an obtuse angle.

[0322] The end cap 12 can be welded to the housing 11. The welding of the end cap 12 and the housing 11 can form a connecting portion 5, which can extend along the circumference of the opening of the housing 11. The end cap 12 and the housing 11 are connected and fixed by the connecting portion 5 to achieve a seal between the end cap 12 and the housing 11. The connecting portion 5 is the portion where the weld mark is formed after the end cap 12 and the housing 11 are welded together. The connecting portion 5 can be the portion where the end cap 12 and the housing 11 are welded and fused together.

[0323] The first side wall portion 111 in the shell 11 can be one or more. The first connection portion 51 can correspond to the first side wall portion 111 one by one. The first connection portion 51 is the portion with a weld mark formed after the end cover 12 and the first side wall portion 111 are welded together. The first connection portion 51 can be the portion where the end cover 12 and the first side wall portion 111 are welded and fused together. A portion of the first connection portion 51 is formed on the end cover 12, and another portion of the first connection portion 51 is formed on the first side wall portion 111. The first side wall portion 111 and the end cover 12 can form the first connection portion 51 by seam welding or by penetration welding. The first connection portion 51 can be a portion of the connection portion 5 or the entire connection portion 5. In an embodiment in which the shell 11 is cylindrical, there is only one first side wall portion 111 in the shell 11, the first side wall portion 111 is cylindrical, and the first connecting portion 51 is the connecting portion 5; in an embodiment in which the shell 11 is prismatic, the shell 11 may include multiple side walls, and the multiple side walls are arranged along the opening of the shell 11, and at least one of the two side walls arranged opposite to each other along the second direction Y may be the first side wall portion 111, and the first connecting portion 51 is a part of the connecting portion 5.

[0324] The first side wall portion 111 may be the wall with the largest outer surface area in the shell 11, or the first side wall portion 111 may not be the wall with the largest outer surface area in the shell 11. Taking the shell 11 as a rectangular parallelepiped as an example, the shell 11 may include two first side wall portions 111 and two second side wall portions 112, the two first side wall portions 111 being arranged opposite to each other along the second direction Y, and the two second side wall portions 112 being arranged opposite to each other along the third direction X, with the first direction Z, the second direction Y, and the third direction X being perpendicular to each other. The first side wall portion 111 may be the wall with the largest outer surface area in the shell 11, such that the outer surface area of ​​the first side wall portion 111 is larger than the outer surface area of ​​the second side wall portion 112, or the second side wall portion 112 may be the wall with the largest outer surface area in the shell 11, such that the outer surface area of ​​the second side wall portion 112 is larger than the outer surface area of ​​the first side wall portion 111.

[0325] The first region 1111 may be a region of the first sidewall portion 111 with lower hardness. The hardness of the first region 1111 is lower than that of the second region 1112. The second region 1112 may be a portion of the first sidewall portion 111 located along the first direction Z on the side of the first region 1111 facing away from the first connection portion 51. The first region 1111 and the first connection portion 51 may be directly connected; the first region 1111 and the second region 1112 may be directly or indirectly connected. The maximum hardness of the first region 1111 may be lower than the minimum hardness of the second region 1112, thereby achieving a lower hardness of the first region 1111 than the second region 1112.

[0326] The electrode assembly 2 is located within the housing 11 and the end cap 12. The electrode assembly 2 may be a laminated structure or a wound structure. There may be one or more electrode assemblies 2 in the housing 11. If there are multiple electrode assemblies 2, the multiple electrode assemblies 2 may be stacked, for example, along the second direction Y.

[0327] As an example, the hardness of the first region 1111 and the hardness of the second region 1112 may be measured by a known hardness meter.

[0328] As an example, the first region 1111 extends along the third direction X to opposite ends of the first sidewall portion 111 .

[0329] The method for forming the first region 1111 with lower hardness is not limited. As an example, the shell 11 can be heated and softened by laser to obtain the first region 1111 with lower hardness. As an example, a portion of the shell 11 can be annealed to obtain the first region 1111 with lower hardness.

[0330] As an example, the power used in welding the shell 11 and the end cap 12 can be controlled to reduce the hardness of the area on one side of the weld mark along the first direction, that is, the hardness of the area on one side of the connecting portion 5 along the first direction is reduced, thereby forming a first area 1111 with lower hardness. It is understood that, if the power used in welding the shell 11 and the end cap 12 is not greater than the maximum allowable power, appropriately increasing the welding power can increase the size of the first area 1111 with lower hardness along the first direction, thereby reducing cracking of the first connecting portion 51.

[0331] In the embodiment of the present application, at least a portion of the positive electrode sheet 22 and at least a portion of the negative electrode sheet 23 are stacked along the second direction Y. The electrode assembly 2 will expand along the second direction Y during the cycle, and the first side wall portion 111 is affected by the expansion force of the electrode assembly 2. Since the hardness of the first area 1111 is lower than the hardness of the second area 1112, the first area 1111 has higher toughness relative to the second area 1112. By setting the first area 1111 with lower hardness on the first side wall portion 111, the toughness of the first area 1111 is higher, thereby releasing part of the expansion force of the electrode assembly 2, reducing the influence of the expansion force of the electrode assembly 2 on the first connecting portion 51, and reducing the possibility of cracking of the first connecting portion 51 at the opening of the shell 11, thereby improving the service life of the battery cell 10.

[0332] In some embodiments, referring to FIG. 6 to FIG. 9 , a ratio of the hardness of the first region 1111 to the hardness of the second region 1112 is between 0.3 and 0.8.

[0333] It should be explained that the type of hardness of the first area 1111 is the same as the type of hardness of the second area 1112 .

[0334] As an example, the hardness of the first region 1111 and the hardness of the second region 1112 may both be Vickers hardness.

[0335] As an example, the hardness of the first region 1111 and the hardness of the second region 1112 may both be Brinell hardness.

[0336] The type of hardness of the first area 1111 and the type of hardness of the second area 1112 may also be other known hardness types, as long as the type of hardness of the first area 1111 and the type of hardness of the second area 1112 are the same.

[0337] As an example, the ratio of the hardness of the first area 1111 to the hardness of the second area 1112 is any one of 0.3, 0.35, 0.4, 0.45, 0.5, 0.6, 0.7, 0.8, etc., or a range of values ​​between any two of them.

[0338] In the embodiment of the present application, the ratio of the hardness of the first zone 1111 to the hardness of the second zone 1112 is between 0.3 and 0.8, so that the ratio of the hardness of the first zone 1111 to the hardness of the second zone 1112 is within a relatively appropriate range, so that the first zone 1111 with lower hardness can not only reduce the possibility of cracking of the first connecting part 51, but also to a certain extent suppress the cracking of the first zone 1111 under the action of the larger expansion force of the electrode assembly 2.

[0339] It is understood that the ratio of the hardness of the first region 1111 to the hardness of the second region 1112 is not limited, as long as the hardness of the first region 1111 is lower than the hardness of the second region 1112. As an example, the ratio of the hardness of the first region 1111 to the hardness of the second region 1112 may be less than 0.3, or the ratio of the hardness of the first region 1111 to the hardness of the second region 1112 may be greater than 0.8 and less than 1.

[0340] In some embodiments, referring to FIG. 6 to FIG. 9 , a ratio of the hardness of the first region 1111 to the hardness of the second region 1112 is between 0.5 and 0.8.

[0341] As an example, the ratio of the hardness of the first area 1111 to the hardness of the second area 1112 is any one of 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, etc., or a range of values ​​between any two of them.

[0342] In the embodiment of the present application, the ratio of the hardness of the first zone 1111 to the hardness of the second zone 1112 is between 0.3 and 0.8, so that the ratio of the hardness of the first zone 1111 to the hardness of the second zone 1112 is within a relatively appropriate range, so that the first zone 1111 with lower hardness can not only reduce the possibility of cracking of the first connecting part 51, but also to a certain extent suppress the cracking of the first zone 1111 under the action of the larger expansion force of the electrode assembly 2.

[0343] It is understood that the ratio of the hardness of the first region 1111 to the hardness of the second region 1112 is not limited, as long as the hardness of the first region 1111 is lower than the hardness of the second region 1112. As an example, the ratio of the hardness of the first region 1111 to the hardness of the second region 1112 can be less than 0.5 as appropriate.

[0344] In some embodiments, referring to FIG. 6 to FIG. 9 , the hardness of the second region 1112 ranges from 40 HV to 100 HV, and the hardness of the first region 1111 ranges from 20 HV to 55 HV.

[0345] It should be noted that "HV" is a unit of Vickers hardness.

[0346] As an example, the hardness of the second region 1112 ranges from any one of 40 HV, 45 HV, 50 HV, 60 HV, 70 HV, 80 HV, 90 HV, 100 HV, etc., or ranges between any two of the values.

[0347] As an example, the hardness of the first region 1111 is in the range of any one of 20 HV, 25 HV, 30 HV, 35 HV, 40 HV, 45 HV, 50 HV, 55 HV, etc., or in the range between any two of them.

[0348] In the embodiment of the present application, the hardness range of the second zone 1112 is relatively appropriate, which is beneficial to protecting the electrode assembly 2 in the shell 11, reducing the impact of the external environment on the electrode assembly 2 in the shell 11, and realizing the basic protection of the electrode assembly 2 by the shell 11. The hardness range of the first zone 1111 is relatively appropriate. The lower hardness of the first zone 1111 enables the first zone 1111 to reduce the possibility of cracking of the first connecting part 51, and to a certain extent inhibit the first zone 1111 from cracking under the action of the larger expansion force of the electrode assembly 2.

[0349] It is understood that the hardness ranges of the first region 1111 and the second region 1112 are not limited, as long as the hardness of the first region 1111 is lower than the hardness of the second region 1112. As an example, the hardness of the second region 1112 may be less than 40 HV or greater than 100 HV, and the hardness of the first region 1111 may be less than 20 HV or greater than 55 HV.

[0350] In some embodiments, referring to FIG. 6 , FIG. 26 , FIG. 29 , FIG. 32 , FIG. 34 and FIG. 36 , a size of the first region 1111 along the first direction Z ranges from 0.05 mm to 0.75 mm.

[0351] As an example, the size of the first region 1111 along the first direction Z is D 10 , 0.05mm≤D 10 ≤0.75mm.

[0352] As an example, the size of the first zone 1111 along the first direction Z is any point value among 0.05mm, 0.1mm, 0.15mm, 0.2mm, 0.25mm, 0.3mm, 0.4mm, 0.5mm, 0.6mm, 0.7mm, 0.75mm, etc., or a range value between any two of them.

[0353] As an example, the size of the first area 1111 along the first direction Z can be measured by a vernier caliper or a micrometer.

[0354] In the embodiment of the present application, the size range of the first zone 1111 along the first direction Z is relatively appropriate, and the first zone 1111 with lower hardness is formed within an appropriate size range. On the one hand, it reduces the possibility of cracking of the first connecting portion 51, and on the other hand, it is conducive to suppressing the first zone 1111 with lower hardness from cracking due to excessive length under the influence of the expansion force of the electrode assembly 2.

[0355] It is understood that the size of the first region 1111 along the first direction Z is not limited. As an example, the size of the first region 1111 along the first direction Z may be less than 0.05 mm or greater than 0.75 mm.

[0356] In some embodiments, referring to FIG. 6 , FIG. 26 , FIG. 29 , FIG. 32 , FIG. 34 and FIG. 36 , a size of the first region 1111 along the first direction Z ranges from 0.1 mm to 0.6 mm.

[0357] As an example, the size of the first zone 1111 along the first direction Z is any point value among 0.1mm, 0.15mm, 0.2mm, 0.25mm, 0.3mm, 0.35mm, 0.4mm, 0.45mm, 0.5mm, 0.55mm, 0.6mm, etc., or a range value between any two of them.

[0358] In the embodiment of the present application, the size range of the first zone 1111 along the first direction Z is relatively appropriate, and the first zone 1111 with lower hardness is formed within an appropriate size range. On the one hand, the expansion force of the electrode assembly 2 is released through the first zone 1111 by deformation of the first zone 1111 with lower hardness, thereby reducing the possibility of cracking of the first connecting portion 51. On the other hand, it is beneficial to suppress the cracking of the first zone 1111 with lower hardness due to the influence of the expansion force of the electrode assembly 2 due to excessive length.

[0359] It is understood that the size of the first area 1111 along the first direction Z is not limited. As an example, the size of the first area 1111 along the first direction Z may be less than 0.1 mm or greater than 0.6 mm.

[0360] In some embodiments, referring to FIG. 9 , at least some of the grains in the first region 1111 are first grains 800, a ratio of the number of first grains 800 in the first region 1111 to the number of all grains in the first region 1111 is greater than 50%, a dimension of the first grain 800 extending along the first direction Z is a first dimension, a maximum dimension of the first grain 800 along the second direction Y is a second dimension, and a ratio of the first dimension to the second dimension ranges from 0.2 to 5.

[0361] As an example, referring to Figures 4 to 6, 9, and 14, the cross-sections of the first sidewall portion 111 shown in the figures are predetermined cross-sections, which are substantially parallel to the first direction Z and the second direction Y. The predetermined cross-sections intersect with the first region 1111 to form a first cross-section.

[0362] As an example, the first crystal grain 800 is an equiaxed crystal.

[0363] The step of measuring the grains in the first region includes sample cutting, sample processing and grain measurement.

[0364] The sample cutting steps specifically include:

[0365] The shell 11 is connected to an end cap 12 at the first end along the first direction Z, and the second end of the shell 11 along the first direction Z is arranged opposite to the first end of the shell 11. The shell 11 is cut along the circumference of the shell 11 at 30 mm away from the second end of the shell 11 along the first direction Z, and the electrode assembly 2 and the electrolyte in the shell 11 are separated from the shell 11. The shell 11 with the first end after cutting is cleaned, and the side wall of the cleaned shell 11 is restored to flatness. The shell 11 with the flattened side wall is arranged downwardly at the first end along the first direction Z so that the end cap 12 at the first end is located below the shell 11. Crystal glue is poured into the space enclosed by the shell 11 and the end cap 12 below the shell 11 so that the height of the crystal glue in the space enclosed by the end cap 12 and the shell 11 is greater than or equal to a preset height, and the preset height is half the height of the shell 11 with the first end after cutting. Cut the first sidewall 111 of the housing 11 filled with crystal glue to obtain the desired sample for measurement. The cutting plane of the housing 11 is approximately perpendicular to the reference plane, and the reference plane is parallel to the first direction Z and the second direction Y. For example, the angle between the cutting plane of the housing 11 and the reference plane is 80° to 95°. Cut as far as possible from the top of the housing 11 filled with crystal glue downward to the end cap 12 below the housing 11 filled with crystal glue.

[0366] Sample processing specifically includes:

[0367] After the first side wall portion 111 of the shell 11 filled with crystal glue is cut to obtain the required sample for measurement, the cross-section of the sample for measurement that is roughly parallel to the first direction Z and the second direction Y is the preset cross-section of the first side wall portion 111, and the cut preset cross-section is polished with sandpaper, and the mesh number of the sandpaper used to polish the preset cross-section is greater than or equal to 1600 mesh. The polished preset cross-section is cleaned and corroded to obtain a sample to be measured that can be observed under an optical microscope, and the corroded sample to be measured is placed under an optical microscope to observe the preset cross-section of the sample to be measured.

[0368] An Olympus BX53M optical microscope can be used to measure grains in a predetermined cross-section. By selecting a rough area to be measured using a relatively low magnification optical microscope, and then increasing the magnification of the optical microscope to observe the selected rough area, the measurement position can be determined. It is understood that the number of first grains 800 in the first region 1111 accounts for greater than 50%, and the number of second grains 802 in the second region 1112 accounts for greater than 50%, resulting in a significant difference in the grains between the two regions. The grains observed under the optical microscope can be used to identify the approximate area to be measured.

[0369] The grains displayed under an optical microscope of model BX53M can be measured using corresponding software from Olympus, for example, software Capture 2.2.1.

[0370] The grain measurement steps specifically include:

[0371] The software Capture 2.2.1 is used to display and measure the grains under an optical microscope of model BX53M. A 0.1 mm*0.2 mm rectangular frame is drawn in the first area 1111. The sides of the rectangular frame with a side length of 0.2 mm are parallel to the second direction Y. The grains completely within the rectangular frame and the grains intersecting with the sides of the rectangular frame are all grains within the rectangular frame.

[0372] Measure the size of each grain within the 0.1mm*0.2mm rectangular frame along the first direction Z. Specifically, project each grain within the rectangular frame along the second direction Y to obtain a corresponding projection line extending along the first direction Z. The size of this projection line along the first direction Z corresponds to the size of the corresponding grain along the first direction Z. The size of each grain along the first direction is the size at the system scale of the Capture 2.2.1 software, that is, the actual size without optical microscope magnification. This size value does not change with changes in the magnification of the optical microscope.

[0373] It should be noted that a 0.1mm*0.2mm rectangular frame means that the two sides of the rectangular frame that are opposite each other along the first direction Z are 0.2mm long, the 0.2mm side is parallel to the second direction Y, and the two sides of the rectangular frame that are opposite each other along the second direction Y are 0.1mm long. The dimensions of the rectangular frame are based on the system scale of the Capture 2.2.1 software, that is, the actual dimensions when not magnified by an optical microscope. These dimensions do not change with changes in the magnification of the optical microscope.

[0374] Measure the maximum dimension of each grain along the second direction Y within the 0.1mm*0.2mm rectangular frame. Specifically, draw multiple transversal lines parallel to the second direction Y for each grain. The distance between two intercept points along the second direction Y formed by the intersection of the transversal lines with the corresponding grain is the intercept of the transversal line on the corresponding grain. Among the intercepts of the multiple transversal lines parallel to the second direction Y for each grain, the largest intercept is the maximum dimension of the grain along the second direction Y. The maximum dimension of each grain along the second direction Y is the dimension at the system scale corresponding to the Capture 2.2.1 software, that is, the actual dimension when not magnified by an optical microscope. This dimension value does not change with changes in the magnification of the optical microscope.

[0375] The grains are screened based on the size of each grain extending along the first direction Z and the maximum size of each grain along the second direction Y within the 0.1mm*0.2mm rectangular frame. When the ratio of the size of a grain extending along the first direction Z to the maximum size along the second direction Y within the 0.1mm*0.2mm rectangular frame is within a range of 0.2 to 5, the grain is identified as a first grain 800. In this manner, the first grains 800 within the 0.1mm*0.2mm rectangular frame are screened. The ratio of the number of first grains 800 within the 0.1mm*0.2mm rectangular frame to the number of all grains within the 0.1mm*0.2mm rectangular frame is greater than 50%, indicating that the number of first grains 800 within the first cross-section and the number of all grains within the first cross-section are greater than 50%, thereby confirming that the number of first grains 800 within the first region 1111 and the number of all grains within the first region 1111 are greater than 50%.

[0376] As an example, referring to FIG. 9 , the first dimension is D3 , the second dimension is D4 , and 0.2≤D3 / D4≤5.

[0377] As an example, the ratio of the first size to the second size can be any one of 0.2, 0.3, 0.5, 0.8, 1, 2, 2.5, 3, 3.5, 4, 5, etc., or a range of values ​​between any two of them.

[0378] In the embodiment of the present application, the ratio of the first size to the second size ranges from 0.2 to 5, the size of the first grain 800 extending in the first direction Z is relatively close to the maximum size of the first grain 800 in the second direction Y, and the first grain 800 has a relatively uniform structure in the first direction Z and the second direction Y, which is conducive to improving toughness. The ratio of the number of first grains 800 in the first zone 1111 to the number of all grains in the first zone 1111 is greater than 50%, so that the first zone 1111 can have better toughness to release the expansion force of the electrode assembly 2 and reduce the possibility of cracking of the first connecting part 51.

[0379] It is understandable that the specific metallographic structure of the first region 1111 is not limited, as long as the hardness of the first region 1111 is lower than the hardness of the second region 1112 .

[0380] In some embodiments, referring to FIG. 9 , the ratio of the first size to the second size ranges from 0.25 to 4.

[0381] As an example, the ratio of the first size to the second size can be any one of 0.25, 0.5, 0.7, 0.9, 1, 2, 2.1, 2.4, 2.5, 2.7, 2.8, 3, 3.5, 4, etc., or a range of values ​​between any two of them.

[0382] In the embodiment of the present application, the ratio of the first size to the second size ranges from 0.25 to 4, so that the size of the first grain 800 extending in the first direction Z and the maximum size in the second direction Y are relatively close. Such first grains 800 are conducive to improving toughness, so that the first zone 1111 where the number of first grains 800 accounts for a relatively large proportion has higher toughness.

[0383] It is understood that the ratio range of the first size to the second size is not limited to 0.25 to 4. As an example, the ratio range of the first size to the second size may be greater than 4 and less than or equal to 5.

[0384] In some embodiments, referring to FIG. 9 , the first size ranges from 5 μm to 500 μm, and the second size ranges from 5 μm to 500 μm.

[0385] As an example, referring to FIG. 9 , the first dimension is D3 , 5 μm ≤ D3 ≤ 500 μm.

[0386] As an example, the first size may be any one of 5 μm, 10 μm, 20 μm, 30 μm, 40 μm, 55 μm, 100 μm, 200 μm, 300 μm, 400 μm, 500 μm, etc., or a range of values ​​between any two of them.

[0387] As an example, referring to FIG. 9 , the second dimension D4 is 5 μm≤D4≤500 μm.

[0388] As an example, the first size may be any one of 5 μm, 10 μm, 20 μm, 30 μm, 40 μm, 55 μm, 100 μm, 200 μm, 300 μm, 400 μm, 500 μm, etc., or a range of values ​​between any two of them.

[0389] In the embodiment of the present application, the range of the first size and the range of the second size are roughly close, and accordingly the first size and the second size are relatively close. The corresponding first grains 800 are conducive to improving toughness, so that the first area 1111 where the number of first grains 800 accounts for a relatively large proportion has better toughness to release the expansion force of the electrode assembly 2 and reduce the possibility of cracking of the first connecting part 51.

[0390] It can be understood that the range of the first size and the range of the second size are not limited, as long as the ratio of the first size to the second size is within the corresponding ratio range.

[0391] In some embodiments, referring to FIG. 9 , at least some of the grains in the second region 1112 are second grains 802, a ratio of the number of second grains 802 in the second region 1112 to the number of all grains in the second region 1112 is greater than 50%, a dimension of the second grain 802 extending along the first direction Z is a third dimension, a maximum dimension of the second grain 802 along the second direction Y is a fourth dimension, and a ratio of the third dimension to the fourth dimension ranges from 4 to 100.

[0392] As an example, referring to Figures 4 to 6, 9, and 14, the cross-sections of the first sidewall portion 111 shown in the figures are predetermined cross-sections, which are substantially parallel to the first direction Z and the second direction Y. The predetermined cross-sections intersect with the second region 1112 to form a second cross-section.

[0393] As an example, the second crystal grains 802 are ribbon crystals.

[0394] The step of measuring the grains in the second region includes sample cutting, sample processing, and grain measurement.

[0395] The sample cutting steps specifically include:

[0396] The shell 11 is connected to an end cap 12 at the first end along the first direction Z, and the second end of the shell 11 along the first direction Z is arranged opposite to the first end of the shell 11. The shell 11 is cut along the circumference of the shell 11 at 30 mm away from the second end of the shell 11 along the first direction Z, and the electrode assembly 2 and the electrolyte in the shell 11 are separated from the shell 11. The shell 11 with the first end after cutting is cleaned, and the side wall of the cleaned shell 11 is restored to flatness. The shell 11 with the flattened side wall is arranged downwardly at the first end along the first direction Z so that the end cap 12 at the first end is located below the shell 11. Crystal glue is poured into the space enclosed by the shell 11 and the end cap 12 below the shell 11 so that the height of the crystal glue in the space enclosed by the end cap 12 and the shell 11 is greater than or equal to a preset height, and the preset height is half the height of the shell 11 with the first end after cutting. Cut the first sidewall 111 of the housing 11 filled with crystal glue to obtain the desired sample for measurement. The cutting plane of the housing 11 is approximately perpendicular to the reference plane, and the reference plane is parallel to the first direction Z and the second direction Y. For example, the angle between the cutting plane of the housing 11 and the reference plane is 80° to 95°. Cut as far as possible from the top of the housing 11 filled with crystal glue downward to the end cap 12 below the housing 11 filled with crystal glue.

[0397] Sample processing specifically includes:

[0398] After the first side wall portion 111 of the shell 11 filled with crystal glue is cut to obtain the required sample for measurement, the cross-section of the sample for measurement that is roughly parallel to the first direction Z and the second direction Y is the preset cross-section of the first side wall portion 111, and the cut preset cross-section is polished with sandpaper, and the mesh number of the sandpaper used to polish the preset cross-section is greater than or equal to 1600 mesh. The polished preset cross-section is cleaned and corroded to obtain a sample to be measured that can be observed under an optical microscope, and the corroded sample to be measured is placed under an optical microscope to observe the preset cross-section of the sample to be measured.

[0399] An Olympus BX53M optical microscope can be used to measure grains in a predetermined cross-section. By selecting a rough area to be measured using a relatively low magnification optical microscope, and then increasing the magnification of the optical microscope to observe the selected rough area, the measurement position can be determined. It is understood that the number of first grains 800 in the first region 1111 accounts for greater than 50%, and the number of second grains 802 in the second region 1112 accounts for greater than 50%, resulting in a significant difference in the grains between the two regions. The grains observed under the optical microscope can be used to identify the approximate area to be measured.

[0400] The grains displayed under an optical microscope of model BX53M can be measured using corresponding software from Olympus, for example, software Capture 2.2.1.

[0401] The grain measurement steps specifically include:

[0402] The software Capture 2.2.1 is used to display and measure the grains under an optical microscope of model BX53M. A 5 mm*0.3 mm rectangular frame is drawn in the second area 1112. The sides of the rectangular frame with a side length of 0.3 mm are parallel to the second direction Y. The grains completely within the rectangular frame and the grains intersecting with the sides of the rectangular frame are all grains within the rectangular frame.

[0403] Measure the size of each grain within the 5mm*0.3mm rectangular frame along the first direction Z. Specifically, project each grain within the rectangular frame along the second direction Y to obtain a corresponding projection line extending along the first direction Z. The size of this projection line along the first direction Z corresponds to the size of the corresponding grain along the first direction Z. The size of each grain along the first direction is the size at the system scale of the Capture 2.2.1 software, that is, the actual size without optical microscope magnification. This size value does not change with changes in the magnification of the optical microscope.

[0404] It should be noted that a 5mm*0.3mm rectangular frame means that the length of two sides of the rectangular frame opposite each other along the first direction Z is 0.3mm, the 0.3mm side is parallel to the second direction Y, and the length of two sides of the rectangular frame opposite each other along the second direction Y is 5mm. The size of the rectangular frame is the size at the system scale corresponding to the Capture 2.2.1 software, that is, the actual size when not magnified by an optical microscope. This size value does not change with changes in the magnification of the optical microscope.

[0405] Measure the maximum dimension of each grain along the second direction Y within the 5mm*0.3mm rectangular frame. Specifically, draw multiple transversal lines parallel to the second direction Y for each grain. The distance between two intercepts along the second direction Y formed by the intersection of the transversal lines with the corresponding grain is the intercept of the transversal line on the corresponding grain. Among the intercepts of the multiple transversal lines parallel to the second direction Y for each grain, the largest intercept is the maximum dimension of the grain along the second direction Y. The maximum dimension of each grain along the second direction Y is the dimension at the system scale of the Capture 2.2.1 software, that is, the actual dimension when not magnified by an optical microscope. This dimension value does not change with changes in the magnification of the optical microscope.

[0406] The grains are screened based on the size of each grain extending along the first direction Z and the maximum size of each grain along the second direction Y within the 5mm*0.3mm rectangular frame. When the ratio of the size of a grain extending along the first direction Z to the maximum size along the second direction Y within the 5mm*0.3mm rectangular frame is within a range of 4 to 100, the grain is identified as a second grain 802. Second grains 802 within the 5mm*0.3mm rectangular frame are screened in this manner. If the ratio of the number of second grains 802 within the 5mm*0.3mm rectangular frame to the number of all grains within the 5mm*0.3mm rectangular frame is greater than 50%, then the number of second grains 802 within the second cross-section and the number of all grains within the second cross-section are greater than 50%, thereby confirming that the number of second grains 802 within the second region 1112 and the number of all grains within the second region 1112 are greater than 50%.

[0407] As an example, referring to FIG. 9 , the third dimension is D5 , the fourth dimension is D6 , and 4≤D5 / D6≤100.

[0408] As an example, the ratio of the third size to the fourth size can be any one of 4, 5, 6, 10, 30, 40, 50, 60, 70, 80, 90, 100, etc., or a range of values ​​between any two of them.

[0409] In the embodiment of the present application, the ratio of the third size to the fourth size ranges from 4 to 100, and the size of the second grain 802 extending in the first direction Z is larger than the maximum size of the second grain 802 in the second direction Y to a certain extent. Such second grains 802 are conducive to reducing toughness. The ratio of the number of second grains 802 in the second zone 1112 to the number of all grains in the second zone 1112 is greater than 50%, so that the toughness of the second zone 1112 is relatively small, which is conducive to reducing the cracking of the second zone 1112 itself under the action of the expansion force of the electrode assembly 2.

[0410] It is understandable that the metallographic structure of the second region 1112 is not limited, as long as the hardness of the first region 1111 is lower than the hardness of the second region 1112 .

[0411] In some embodiments, referring to FIG. 9 , the ratio of the third size to the fourth size ranges from 4 to 50.

[0412] As an example, the ratio of the third size to the fourth size can be any one of 4, 5, 6, 7, 8, 10, 15, 20, 25, 30, 35, 40, 45, 50, etc., or a range of values ​​between any two of them.

[0413] In the embodiment of the present application, the ratio of the third size to the fourth size ranges from 4 to 50, so that the maximum size deviation of the second grain 802 in the first direction Z and the second direction Y is relatively large. Such second grains 802 have reduced toughness, so that the toughness of the second zone where the number of second grains accounts for a relatively large proportion is lower, which is beneficial to reducing the cracking of the second zone 1112 itself under the action of the expansion force of the electrode assembly 2.

[0414] It is understood that the ratio of the third dimension to the fourth dimension is not limited to 4 to 50. As an example, the ratio of the third dimension to the fourth dimension may be greater than 50, or the ratio of the third dimension to the fourth dimension may be greater than 100.

[0415] In some embodiments, referring to FIG. 9 , the third dimension ranges from 150 μm to 1000 μm, and the fourth dimension ranges from 5 μm to 120 μm.

[0416] As an example, referring to FIG. 9 , the third dimension is D5, and 150 μm ≤ D5 ≤ 1000 μm.

[0417] As an example, referring to FIG9 , the third size may be any point value among 150 μm, 170 μm, 200 μm, 300 μm, 400 μm, 500 μm, 600 μm, 700 μm, 800 μm, 900 μm, 950 μm, 1000 μm, etc., or a range value between any two of them.

[0418] As an example, referring to FIG. 9 , the fourth dimension D6 is 5 μm≤D6≤120 μm.

[0419] As an example, referring to FIG9 , the fourth size can be any point value among 5μm, 10μm, 15μm, 20μm, 30μm, 40μm, 50μm, 60μm, 70μm, 80μm, 90μm, 100μm, 110μm, 120μm, etc., or a range value between any two of them.

[0420] In the embodiment of the present application, the lower limit of the size range of the third size 150μm is greater than the upper limit of the fourth size 120μm, and the maximum size deviation of the second grain 802 in the first direction Z and the second direction Y is relatively large. The second grains 802 in the corresponding size range are conducive to reducing toughness, so that the toughness of the second zone where the number of second grains accounts for a relatively large proportion is lower, which is conducive to reducing the cracking of the second zone 1112 itself under the action of the expansion force of the electrode assembly 2.

[0421] It can be understood that the range of the third dimension and the range of the fourth dimension are not limited, as long as the ratio of the third dimension to the fourth dimension is within the corresponding ratio range.

[0422] In some embodiments, referring to FIG. 9 , at least some of the grains within the first region 1111 are first grains 800, the ratio of the number of first grains 800 within the first region 1111 to the number of all grains within the first region 1111 is greater than 50%, the dimension of the first grains 800 extending along the first direction Z is a first dimension, the maximum dimension of the first grains 800 along the second direction Y is a second dimension, and the ratio of the first dimension to the second dimension ranges from 0.2 to 5. At least some of the grains within the second region 1112 are second grains 802, the ratio of the number of second grains 802 within the second region 1112 to the number of all grains within the second region 1112 is greater than 50%, the dimension of the second grains 802 extending along the first direction Z is a third dimension, the maximum dimension of the second grains 802 along the second direction Y is a fourth dimension, and the ratio of the third dimension to the fourth dimension ranges from 4 to 100. The third dimension is greater than the first dimension.

[0423] In the embodiment of the present application, the third size of the second grain 802 is larger than the first size of the first grain 800, and the maximum size of the second grain 802 in the first direction Z is larger than the maximum size of the first grain 800 in the first direction Z. Therefore, within the same size along the first direction Z, the number of first grains 800 is greater than the number of second grains 802. Since the number of first grains 800 in the first zone 1111 accounts for more than 50%, and the number of second grains 802 in the second zone 1112 accounts for more than 50%, there are more first grains 800 in the first zone 1111, and the second zone 1112 is mainly composed of second grains 802. Within the approximately same size along the first direction, the first zone 1111 can have more grains to share the expansion force, so that the first zone 1111 close to the first connecting portion 51 has better toughness to release the expansion force of the electrode assembly 2, thereby reducing the possibility of cracking of the first connecting portion 51.

[0424] In some embodiments, referring to FIG. 9 , a ratio of the third size to the first size ranges from 1.5 to 150.

[0425] As an example, referring to FIG. 9 , the third dimension is D5 , the first dimension is D3 , and 1.5≤D3 / D5≤150.

[0426] As an example, referring to FIG9 , the ratio of the third size to the first size can be any one of 1.5, 2, 2.5, 3, 4, 5, 5.5, 6, 7, 8, 9, 10, 20, 40, 50, 70, 90, 120, 130, 150, etc., or a range of values ​​between any two of them.

[0427] In the embodiment of the present application, the ratio of the third dimension to the first dimension is within a relatively appropriate range, so that the toughness of the first zone 1111 is relatively appropriate relative to the toughness of the second zone, which is beneficial to suppressing the cracking of the first zone 1111 itself while reducing the possibility of cracking of the first connecting portion 51.

[0428] In some embodiments, referring to FIG. 9 , a ratio of the third size to the first size ranges from 1.8 to 100.

[0429] In some embodiments, referring to FIG. 9 , the first dimension ranges from 5 μm to 500 μm, and the third dimension ranges from 150 μm to 1000 μm.

[0430] In some embodiments, the hardness of the first region 1111 is lower than the hardness of the first connecting portion 51 .

[0431] It should be noted that the hardness of the first area 1111 is lower than that of the second area 1112, and the toughness of the first area 1111 is better than that of the second area 1112. During the cyclic charge and discharge process of the battery cell 10, the electrode assembly 2 repeatedly expands and contracts to generate periodic expansion force acting on the first side wall portion 111, causing the first side wall portion 1111 to periodically deform and release the expansion force mainly in the first area 1111 with higher toughness, which may cause fatigue cracking of the first area 1111 with higher toughness itself.

[0432] In view of this, in some embodiments, referring to FIG. 6 and FIG. 14 , the maximum thickness of the first region 1111 is greater than the minimum thickness of the second region 1112 .

[0433] The maximum thickness of the first region 1111 is the maximum dimension of the first region 1111 along the second direction Y. The minimum thickness of the second region 1112 is the minimum dimension of the first region 1111 along the second direction Y.

[0434] As an example, the first region 1111 may be a structure of uniform thickness or a structure of unequal thickness.

[0435] As an example, the second region 1112 may be a structure of uniform thickness or a structure of unequal thickness.

[0436] In the embodiment of the present application, the maximum thickness of the first zone 1111 is greater than the minimum thickness of the second zone 1112, so that at least a portion of the first zone 1111 with higher toughness is thicker than at least a portion of the second zone 1112 with lower toughness. The first zone 1111 with higher toughness is strengthened in the portion with corresponding larger thickness, which can suppress the possibility of fatigue cracking of the first zone 1111 itself to a certain extent.

[0437] It is understood that the relationship between the thickness of the first region 1111 and the thickness of the second region 1112 is not limited. As an example, the maximum thickness of the first region 1111 can be less than or equal to the minimum thickness of the second region 1112, or the minimum thickness of the first region 1111 can be greater than the maximum thickness of the second region 1112. As an example, the thickness of the first region 1111 can be greater than the thickness of the second region 1112 at some locations, and the thickness of the first region 1111 can be less than the thickness of the second region 1112 at some locations. As an example, the thickness of the first region 1111 and the thickness of the second region 1112 can be equal, and the first region 1111 and the second region 1112 can have equal thickness structures.

[0438] In one embodiment, referring to Figures 6, 8, and 14, the first side wall portion 111 has a first inner surface 804 and a second inner surface 805 facing the electrode assembly 2, and a first outer surface 806 and a second outer surface 807 away from the electrode assembly 2. The first inner surface 804 and the second inner surface 805 are connected in sequence along the direction of the end cover 12 pointing to the electrode assembly 2, and the first outer surface 806 and the second outer surface 807 are connected in sequence along the direction of the end cover 12 pointing to the electrode assembly 2. The first inner surface 804 and the first outer surface 806 are at least partially formed in the first area 1111, and the second inner surface 805 and the second outer surface 807 are at least partially formed in the second area 1112. The distance between the first inner surface 804 and the first outer surface 806 along the second direction Y is greater than the distance between the second inner surface 805 and the second outer surface 807 along the second direction Y.

[0439] As an example, referring to FIG. 29 and FIG. 30 , the first inner surface 804 and the second inner surface 805 may be in a single plane.

[0440] As an example, referring to FIG. 6 , FIG. 14 to FIG. 16 , and FIG. 18 , FIG. 19 , FIG. 22 , FIG. 23 and FIG. 26 , the first inner surface 804 may be closer to the electrode assembly 2 along the second direction Y than the second inner surface 805 .

[0441] As an example, referring to FIG. 6 , FIG. 14 to FIG. 16 , and FIG. 18 , FIG. 19 , FIG. 22 , FIG. 23 and FIG. 26 , the first outer surface 806 and the second outer surface 807 may be in the same plane.

[0442] As an example, referring to FIG. 29 and FIG. 30 , the first outer surface 806 may be further away from the electrode assembly 2 along the second direction Y than the second outer surface 807 .

[0443] As an example, referring to FIG. 29 and FIG. 30 , when the first inner surface 804 and the second inner surface 805 are in the same plane, the first outer surface 806 may be further away from the electrode assembly 2 along the second direction Y than the second outer surface 807 .

[0444] As an example, referring to Figures 6, 14 to 16, and 18, 19, 22, 23 and 26, when the first outer surface 806 and the second outer surface 807 are in the same plane, the first inner surface 804 can be closer to the electrode assembly 2 relative to the second inner surface 805 along the second direction Y.

[0445] As an example, the first outer surface 806 may be farther from the electrode assembly 2 along the second direction Y than the second outer surface 807. The first inner surface 804 may be closer to the electrode assembly 2 along the second direction Y than the second inner surface 805.

[0446] As an example, the distances from various positions of the first inner surface 804 to the first outer surface 806 may be equal, that is, the area between the first inner surface 804 and the first outer surface 806 is a structure of equal thickness.

[0447] As an example, the distances from various positions of the first inner surface 804 to the first outer surface 806 may be unequal, that is, the area between the first inner surface 804 and the first outer surface 806 may be a structure of unequal thickness.

[0448] As an example, the distances from various positions of the second inner surface 805 to the second outer surface 807 may be equal, that is, the area between the second inner surface 805 and the second outer surface 807 is a structure of equal thickness.

[0449] As an example, the distances from various positions of the second inner surface 805 to the second outer surface 807 may be unequal, that is, the area between the second inner surface 805 and the second outer surface 807 may be structures of unequal thickness.

[0450] In the embodiment of the present application, the first inner surface 804 and the first outer surface 806 are at least partially formed in the first zone 1111, and the second inner surface 805 and the second outer surface 807 are at least partially formed in the second zone 1112. The first zone 1111 is better strengthened by the larger thickness portions corresponding to the first inner surface 804 and the first outer surface 806, which helps to reduce the possibility of fatigue cracking in the first zone 1111 itself.

[0451] It is understood that there is no limitation on the relationship between the first inner surface 804, the second inner surface 805, the first outer surface 806, and the second outer surface 807. As an example, the first inner surface 804 and the second inner surface 805 can be spaced apart, and the first outer surface 806 and the second outer surface 807 can be spaced apart.

[0452] In some embodiments, referring to Figure 14, the first inner surface 804 includes a first sub-surface 11111 and a second sub-surface 11112 connected in sequence along the direction of the end cap 12 pointing to the electrode assembly 2, the first sub-surface 11111 is at least partially formed in the first area 1111, along the second direction Y, the first sub-surface 11111 is closer to the electrode assembly 2 than the second sub-surface 11112, and the distance between the first sub-surface 11111 and the first outer surface 806 along the second direction Y is greater than the distance between the second sub-surface 11112 and the first outer surface 806 along the second direction Y.

[0453] The distance between the first sub-surface 11111 and the first outer surface 806 along the second direction Y is greater than the distance between the second sub-surface 11112 and the first outer surface 806 along the second direction Y. The area between the first sub-surface 11111 and the first outer surface 806 along the second direction Y is thicker, and the area between the second sub-surface 11112 and the first outer surface 806 along the second direction Y is thinner.

[0454] The first sub-surface 11111 transitions to the second inner surface 805 via the second sub-surface 11112 .

[0455] As an example, the distances from various positions on the first sub-surface 11111 to the first outer surface 806 may be equal, and the area between the first sub-surface 11111 and the first outer surface 806 is a structure of equal thickness.

[0456] As an example, the distances from various positions on the first sub-surface 11111 to the second outer surface 807 may be unequal, and the area between the first sub-surface 11111 and the first outer surface 806 is a non-uniform thickness structure.

[0457] As an example, the distances from various positions on the second sub-surface 11112 to the second outer surface 807 may be equal, and the area between the second sub-surface 11112 and the second outer surface 807 is a structure of equal thickness.

[0458] As an example, the distances from various positions on the second sub-surface 11112 to the second outer surface 807 may be unequal, and the area between the second sub-surface 11112 and the second outer surface 807 is a non-uniform thickness structure.

[0459] As an example, the minimum distance between the first sub-surface 11111 and the first outer surface 806 along the second direction Y may be greater than the maximum distance between the second sub-surface 11112 and the first outer surface 806 along the second direction Y.

[0460] In the embodiment of the present application, since the distance between the first sub-surface 11111 and the first outer surface 806 along the second direction Y is large and the corresponding thickness is thicker, the first sub-surface 11111 is at least partially formed in the first zone 1111, so that the thickness of the first zone 1111 is thicker, which is beneficial to strengthening the first zone 1111, thereby suppressing fatigue cracking of the first zone 1111 itself.

[0461] It is understood that the relationship between the first sub-surface, the second sub-surface, and the first outer surface 806 is not limited. As an example, the distance between the first sub-surface 11111 and the first outer surface 806 along the second direction Y can be less than or equal to the distance between the second sub-surface 11112 and the first outer surface 806.

[0462] In some embodiments, referring to FIG. 14 , the distance between the second sub-surface 11112 and the first outer surface 806 along the second direction Y is a first preset thickness, and the first preset thickness decreases along the direction from the end cap 12 to the electrode assembly 2 .

[0463] It should be noted that the direction in which the end cap 12 points to the electrode assembly 2 is consistent with the direction in which the first sub-surface 11111 points to the second sub-surface 11112 along the first direction Z.

[0464] As an example, referring to FIG14 , the distances between various positions on the second sub-surface 11112 and the second outer surface 807 are not equal, and the first preset thickness tends to decrease along the direction from the end cover 12 to the electrode assembly 2 , and the second sub-surface 11112 may be a slope.

[0465] As an example, referring to FIG. 14 , the distances between each location on first sub-surface 11111 and first outer surface 806 are equal, and the distances between second inner surface 805 and second outer surface 807 are equal. First sub-surface 11111 is parallel to first outer surface 806, and second inner surface 805 is parallel to second outer surface 807. First outer surface 806 and second outer surface 807 are coplanar. First sub-surface 11111 is closer to electrode assembly 2 along second direction Y than second sub-surface 11112. Second sub-surface 11112 is closer to electrode assembly 2 along second direction Y than second inner surface 805. Second sub-surface 11112 connects first sub-surface 11111 and second inner surface 805, respectively.

[0466] In the embodiment of the present application, the first preset thickness tends to decrease along the direction from the end cap 12 to the electrode assembly 2. On the one hand, this allows for a relatively smooth transition between the first sub-surface and the second inner surface 805, reducing the impact of the second sub-surface 11112 on the electrode assembly 2 and reducing the possibility of interference between the second sub-surface 11112 and the electrode assembly 2. On the other hand, the reinforcement effect of the portion of the first sidewall portion 1111 corresponding to the second sub-surface 11112 tends to increase along the direction from the electrode assembly 2 to the end cap 12, resulting in a better reinforcement effect on the portion of the second sub-surface 11112 of the first sidewall portion 111 close to the first sub-surface 11111, reducing the possibility of fatigue cracking in the first area 1111. Furthermore, the relatively smooth transition between the first sub-surface and the second inner surface 805 is beneficial for reducing stress concentration.

[0467] It is understood that the embodiment of the present application is not limited to the first preset thickness decreasing along the direction from the end cap 12 to the electrode assembly 2. As an example, the first preset thickness may remain constant along the direction from the end cap 12 to the electrode assembly 2.

[0468] In some embodiments, referring to FIG. 14 , the first sub-surface 11111 is disposed across the first region 1111 and the second region 1112 , and the first outer surface 806 is disposed across the first region 1111 and the second region 1112 .

[0469] The first sub-surface 11111 is arranged across the first area 1111 and the second area 1112 , which means that the first sub-surface 11111 is partially formed in the first area 1111 and the first sub-surface 11111 is partially formed in the second area 1112 .

[0470] The first outer surface 806 is arranged across the first area 1111 and the second area 1112 , which means that the first outer surface 806 is partially formed in the first area 1111 and partially formed in the second area 1112 .

[0471] In the embodiment of the present application, since the distance between the first sub-surface 11111 and the first outer surface 806 is greater than the distance between the second inner surface 805 and the second outer surface 807, and the distance between the first sub-surface 11111 and the first outer surface 806 is greater than the distance between the second sub-surface 11112 and the first outer surface 806, the first side wall portion 111 is thicker at a portion corresponding to the first sub-surface 11111, and the first sub-surface 11111 spans the first zone 1111 and the second zone 1112, so that the thicker portion of the first side wall portion 111 spans the first zone 1111 and the second zone 1112, thereby strengthening the junction of the first zone 1111 and the second zone 1112 with different toughness, which is beneficial to suppressing cracking at the junction of the first zone 1111 and the second zone 1112 with different toughness.

[0472] In some embodiments, the second sub-surface 11112 spans the first area 1111 and the second area 1112 , and the first outer surface 806 spans the first area 1111 and the second area 1112 .

[0473] The second sub-surface 11112 is arranged across the first area 1111 and the second area 1112 , which means that the second sub-surface 11112 is partially formed in the first area 1111 and partially formed in the second area 1112 .

[0474] The first outer surface 806 is arranged across the first area 1111 and the second area 1112 , which means that the first outer surface 806 is partially formed in the first area 1111 and partially formed in the second area 1112 .

[0475] In the embodiment of the present application, since the distance between the second sub-surface 11112 and the first outer surface 806 is greater than the distance between the second inner surface 805 and the second outer surface 807, the portion of the first side wall portion 111 corresponding to the second sub-surface 11112 is thicker than the portion of the first side wall portion 111 corresponding to the second inner surface 805. The second sub-surface 11112 spans the first zone 1111 and the second zone 1112, so that the thicker portion of the first side wall portion 111 spans the first zone 1111 and the second zone 1112, thereby strengthening the junction of the first zone 1111 and the second zone 1112 with different toughness, which is beneficial to suppressing cracking at the junction of the first zone 1111 and the second zone 1112 with different toughness.

[0476] It is understood that in the embodiment of the present application, the relationship between the first sub-surface 11111, the second sub-surface 11112, the first area 1111, and the second area 1112 is not limited. As an example, the first sub-surface 11111 and the second sub-surface 11112 can both be located in the first area 1111.

[0477] In some embodiments, referring to Figures 6, 8, 14, 17, 20, 21, 24, 25, 26, 29 and 30, the first inner surface 804 spans the first area 1111 and the second area 1112, and the first outer surface 806 spans the first area 1111 and the second area 1112.

[0478] The first inner surface 804 is provided across the first area 1111 and the second area 1112 , which means that the first inner surface 804 is partially formed in the first area 1111 , and the first inner surface 804 is partially formed in the second area 1112 .

[0479] The first outer surface 806 is arranged across the first area 1111 and the second area 1112 , which means that the first outer surface 806 is partially formed in the first area 1111 and partially formed in the second area 1112 .

[0480] As an example, the first sub-surface 11111 is located in the first area 1111, the second sub-surface 11112 is located in the second area 1112, and the junction between the first sub-surface 11111 and the second sub-surface 11112 is exactly located at the junction of the first area 1111 and the second area 1112.

[0481] As an example, the first sub-surface 11111 is partially formed in the first area 1111 , and the first sub-surface 11111 is partially formed in the second area 1112 . The second sub-surface 11112 is located in the second area 1112 .

[0482] As an example, the second sub-surface 11112 is partially formed in the first area 1111 , and the second sub-surface 11112 is partially formed in the second area 1112 . The first sub-surface 11111 is located in the first area 1111 .

[0483] In the embodiment of the present application, since the distance between the first inner surface 804 and the first outer surface 806 is greater than the distance between the second inner surface 805 and the second outer surface 807, the portion of the first side wall portion 111 corresponding to the first inner surface 804 is thicker than the portion of the first side wall portion 111 corresponding to the second inner surface 805. The first inner surface 804 spans the first zone 1111 and the second zone 1112, and the first outer surface 806 spans the first zone 1111 and the second zone 1112, so that the thicker portion of the first side wall portion 111 spans the first zone 1111 and the second zone 1112, so that the junction of the first zone 1111 and the second zone 1112 with different toughness is strengthened, which is beneficial to suppress cracking at the junction of the first zone 1111 and the second zone 1112 with different toughness.

[0484] It is understood that the relationship between the first inner surface 804, the first outer surface 806, the first zone 1111, and the second zone 1112 is not limited. As an example, the first inner surface 804 and the first outer surface 806 are both located in the first zone 1111, the second inner surface 805 and the second outer surface 807 are both located in the second zone 1112, the intersection of the first inner surface 804 and the second inner surface 805 is exactly at the intersection of the first zone 1111 and the second zone 1112, and the intersection of the first outer surface 806 and the second outer surface 807 is exactly at the intersection of the first zone 1111 and the second zone 1112.

[0485] In some embodiments, referring to Figures 7, 15, 16, 18, 19, 22 and 23, the dimension of the first inner surface 804 along the third direction X is greater than the dimension of the first inner surface 804 along the first direction Z, and the first direction Z, the second direction Y and the third direction X are not coplanar and intersect each other.

[0486] The dimension of the first inner surface 804 along the third direction X is the length of the first inner surface 804, and the dimension of the first inner surface 804 along the first direction Z is the width of the first inner surface 804. The length of the first inner surface 804 is greater than the width of the first inner surface 804, so that the part of the first side wall portion 111 between the first inner surface 804 and the first outer surface 806 is a long strip structure extending along the third direction X.

[0487] As an example, the shell 11 is in the shape of a rectangular parallelepiped, and the shell 11 includes two first side wall portions 111 and two second side wall portions 112. The two first side wall portions 111 are arranged opposite to each other along the second direction Y, and the two second side wall portions 112 are arranged opposite to each other along the third direction X. The first direction Z, the second direction Y and the third direction X are perpendicular to each other. The first direction Z is parallel to the height direction of the shell 11, the second direction Y is parallel to the width direction of the shell 11, and the third direction X is parallel to the length direction of the shell 11.

[0488] As an example, referring to FIG. 38 and FIG. 39 , the first region 1111 extends along the third direction X to opposite ends of the first sidewall portion 111 .

[0489] In this embodiment, the dimension of the first inner surface 804 along the third direction X is greater than the dimension of the first inner surface 804 along the first direction Z, so that the dimension of the first inner surface 804 along the third direction X is larger, and more areas of the first side wall portion 111 along the third direction X are reinforced by the thicker parts corresponding to the first inner surface 804, which is beneficial to prevent the shell 11 from cracking.

[0490] It is understood that there is no specific limitation on the relationship between the size of the first inner surface 804 along the third direction X and the size of the first inner surface 804 along the first direction Z. As an example, the size of the first inner surface 804 along the third direction X can be less than or equal to the size of the first inner surface 804 along the first direction Z.

[0491] In some embodiments, referring to Figures 15 to 25 , along the second direction Y, a projection of the first inner surface 804 that overlaps with a projection of the first region 1111 is a first projection. A dimension of the first projection along the third direction X is greater than a dimension of the first projection along the first direction Z. The first direction Z, the second direction Y, and the third direction X are non-coplanar and intersect with each other.

[0492] The position corresponding to the first projection is exactly the position where the thickened portion corresponding to the first inner surface 804 reinforces the first area 1111 .

[0493] As an example, the first direction Z, the second direction Y, and the third direction X are perpendicular to each other.

[0494] In the embodiment of the present application, since the size of the first projection along the third direction X is greater than the size of the first projection along the first direction Z, the portion of the first inner surface 804 corresponding to the reinforcement of the first area 1111 is larger in the third direction X, so that the first area 1111 with higher toughness has more areas reinforced along the third direction X, further reducing the possibility of fatigue cracking of the first area 1111 itself.

[0495] It is understandable that there is no limitation on the size relationship between the size of the first projection along the third direction X and the size of the first projection along the first direction Z. As an example, the size of the first projection along the third direction X is less than or equal to the size of the first projection along the first direction Z.

[0496] In some embodiments, referring to Figures 15 to 25, the first inner surface 804 includes a first connecting surface 11113, which passes through a mid-section of the first side wall portion 111, the mid-section is perpendicular to the third direction X, and the distances from the mid-section to both ends of the first side wall portion 111 along the third direction X are equal.

[0497] The first connecting surface 11113 may be a portion of the first inner surface 804, or the first connecting surface 11113 may be the first inner surface 804. The distances between various locations on the first connecting surface 11113 and the first outer surface 806 are equal or unequal. The first connecting surface 11113 has two opposite ends along the third direction X. The first connecting surface 11113 passes through the mid-section of the first side wall portion 111, so that the mid-section of the first side wall portion 111 is located between the two opposite ends of the first connecting surface 11113 along the third direction X. The distances from the two opposite ends of the first connecting surface 11113 along the third direction X to the mid-section may be equal or unequal. If the distances from the two opposite ends of the first connecting surface 11113 along the third direction X to the mid-section of the first side wall portion 111 are equal, the first connecting surface 11113 may be a symmetrical structure symmetrically arranged about the mid-section of the first side wall portion 111. It should be noted that the mid-section of the first side wall portion 111 is a virtual plane and is not shown in the figure.

[0498] As an example, please refer to Figures 15 to 17. The first connecting surface 11113 is the first inner surface 804. The distance between each position on the first connecting surface 11113 and the first outer surface 806 is equal, and the distance from the two opposite ends of the first connecting surface 11113 along the third direction X to the middle section of the first side wall portion 111 is equal.

[0499] Taking the shell 11 as a rectangular parallelepiped as an example, the distances from the mid-section of the first side wall portion 111 to the two ends of the first side wall portion 111 along the third direction X are equal, that is, the distances from the mid-section of the first side wall portion 111 to the two second side wall portions 112 of the shell 11 that are oppositely arranged along the third direction X are equal.

[0500] It should be noted that, along the third direction X, the distances from the middle section of the first side wall portion 111 to both ends of the first side wall portion 111 are substantially equal, which should also be understood as the distances from the middle section to both ends of the first side wall portion 111 are equal.

[0501] In the embodiment of the present application, when the first side wall portion 111 is subjected to the expansion force of the electrode assembly 2 of the battery cell 10, the middle area of ​​the first side wall portion 111 along the third direction X is greatly affected by the expansion force of the electrode assembly 2. Since the first connecting surface 11113 passes through the middle section of the first side wall portion 111, the thickness of the first side wall portion 111 at the middle section position is relatively large, so that the first side wall portion 111 is strengthened to a certain extent at the middle section, which is beneficial to reducing the influence of the expansion force of the electrode assembly 2 on the middle area of ​​the first side wall portion 111 along the third direction X.

[0502] It is understood that the position of the first connecting surface 11113 and the mid-section of the first sidewall portion 111 is not limited. As an example, the first connecting surface 11113 may not pass through the mid-section. As an example, the first connecting surface 11113 is located on one side of the mid-section of the first sidewall portion 111 along the third direction X.

[0503] In some embodiments, referring to Figures 16, 17, 19, 20, 21, 23, 24 and 25, the first connecting surface 11113 is at least partially formed in the first area 1111, and along the second direction Y, the projection of the first connecting surface 11113 coincides with the projection of the first area 1111, which is the second projection, and the second projection passes through the mid-section of the first side wall portion 111.

[0504] The first connecting surface 11113 is a portion of the first inner surface 804 , or the first connecting surface 11113 is the first inner surface 804 .

[0505] The first connecting surface 11113 is at least partially formed in the first region 1111. Along the second direction Y, the projection of the first connecting surface 11113 and the projection of the first region 1111 at least partially overlap. The location corresponding to the overlapping second projection is where the first sidewall portion 111 reinforces the first region 1111 at the thicker portion corresponding to the first connecting surface 11113.

[0506] In the embodiment of the present application, since the second projection passes through the mid-section of the first sidewall portion 111, the correspondingly more ductile first region 1111 passes through the mid-section. The more ductile first region 1111 can, to a certain extent, release the expansion force of the electrode assembly 2 at the mid-section, thereby facilitating the reduction of cracking of the first connection portion 51 at the mid-section of the first sidewall portion 111. Since the second projection passes through the mid-section of the first sidewall portion 111, the thicker portion of the first sidewall portion 111 corresponding to the first connection surface 11113 can be at least partially located at the mid-section corresponding to the first region 1111, thereby facilitating the suppression of fatigue cracking of the more ductile first region 1111 at the mid-section of the first sidewall.

[0507] It is understandable that the positional relationship between the second projection and the mid-section of the first sidewall portion 111 is not limited. For example, the second projection may be located on one side of the mid-section of the first sidewall portion 111 along the third direction X.

[0508] In some embodiments, referring to Figures 18 to 25, the first inner surface 804 also includes a second connecting surface 11114 and a third connecting surface 11115. The second connecting surface 11114, the first connecting surface 11113 and the third connecting segment surface are arranged along the third direction X. The first connecting surface 11113 connects the second connecting surface 11114 and the third connecting surface 11115. Along the second direction Y, the distance between the second connecting surface 11114 and the first outer surface 806 and the distance between the third connecting surface 11115 and the first outer surface 806 are both smaller than the distance between the first connecting surface 11113 and the first outer surface 806.

[0509] The first connecting surface 11113 is a section of the first inner surface 804 that passes through the mid-section of the first sidewall portion 111. The second connecting surface 11114 and the third connecting surface 11115 are two sections of the first inner surface 804 located at the two ends along the third direction X. The second connecting surface 11114 and the first connecting surface 11113 can be directly or indirectly connected, and the third connecting surface 11115 and the first connecting surface 11113 can be directly or indirectly connected.

[0510] The distances between various positions on the first connecting surface 11113 and the first outer surface 806 may be equal or unequal. The distances between various positions on the second connecting surface 11114 and the first outer surface 806 may be equal or unequal. The distances between various positions on the third connecting surface 11115 and the first outer surface 806 may be equal or unequal. If the distances between various positions on at least one of the first connecting surface 11113 and the second connecting surface 11114 and the first outer surface 806 are unequal, the maximum distance between the second connecting surface 11114 and the first outer surface 806 may be less than or equal to the minimum distance between the first connecting surface 11113 and the first outer surface 806, so as to achieve that the distance between the second connecting surface 11114 and the first outer surface 806 is less than the distance between the first connecting surface 11113 and the first outer surface 806. If the distances between each position of at least one of the third connecting surface 11115 and the first connecting surface 11113 and the first outer surface 806 are not equal, the maximum distance between the third connecting surface 11115 and the first outer surface 806 can be less than or equal to the minimum distance between the first connecting surface 11113 and the first outer surface 806, so as to achieve that the distance between the third connecting surface 11115 and the first outer surface 806 is less than the distance between the first connecting surface 11113 and the first outer surface 806.

[0511] The size of the second connecting surface 11114 along the third direction X may be equal to or different from the size of the third connecting surface 11115 along the third direction X. If the size of the second connecting surface 11114 along the third direction X is equal to the size of the third connecting surface 11115 along the third direction X, the second connecting surface 11114 and the third connecting surface 11115 may be symmetrically arranged about the mid-section of the first sidewall portion 111.

[0512] It can be understood that in the embodiment where the first inner surface 804 includes the first sub-surface and the second sub-surface 11112, at least one of the first connecting surface 11113, the second connecting surface 11114, and the third connecting surface 11115 may include the first sub-surface 11111 and the second sub-surface 11112 arranged along the first direction Z.

[0513] The second connecting surface 11114 may be partially closer to the electrode assembly 2 than the second inner surface 805 along the second direction Y and / or the first outer surface 806 may be partially farther away from the electrode assembly 2 relative to the second outer surface 807 along the second direction Y, the first connecting surface 11113 may be partially closer to the electrode assembly 2 than the second inner surface 805 along the second direction Y and / or the first outer surface 806 may be partially farther away from the electrode assembly 2 relative to the second outer surface 807 along the second direction Y, the third connecting surface 11115 may be partially closer to the electrode assembly 2 than the second inner surface 805 along the second direction Y and / or the first outer surface 806 may be partially farther away from the electrode assembly 2 relative to the second outer surface 807 along the second direction Y.

[0514] As an example, referring to Figures 18 to 25 , both the second connecting surface 11114 and the third connecting surface 11115 are directly connected to the first connecting surface 11113. The distance between the second connecting surface 11114 and the first outer surface 806 gradually decreases along the direction from the third connecting surface 11115 toward the second connecting surface 11114, and the distance between the third connecting surface 11115 and the first outer surface 806 gradually decreases along the direction from the second connecting surface 11114 toward the third connecting surface 11115. A portion of the second connecting surface 11114, a portion of the first connecting surface 11113, and a portion of the third connecting surface 11115 are all located closer to the electrode assembly 2 relative to the second inner surface 805 along the second direction Y. The second connecting surface 11114 connects the first connecting surface 11113 and the second inner surface 805, and the third connecting surface 11115 connects the inner surface of the first connecting surface 11113 and the second inner surface 805. The first outer surface 806 is a planar surface.

[0515] In the embodiment of the present application, when the first side wall portion 111 is subjected to the expansion force of the electrode assembly 2, the electrode assembly 2 expands to a greater extent in the middle area of ​​the first side wall portion 111 along the third direction X, and the electrode assembly 2 expands to a relatively smaller extent in the areas near the two ends of the first side wall portion 111 along the third direction X. The expansion forces of the electrode assembly 2 at the two ends and the middle of the first side wall portion 111 along the third direction X are different. The distance between the second connecting surface 11114 and the first outer surface 806 and the distance between the third connecting surface 11115 and the first outer surface 806 are both smaller than the distance between the first connecting surface 11113 and the first outer surface 806. The first side wall portion 111 is strengthened to a great extent in the area near the middle corresponding to the first connecting surface 11113, which is beneficial to bearing the large expansion force of the electrode assembly 2 acting on the first side wall portion 111 near the middle part along the third direction X. The first side wall portion 111 is strengthened to a certain extent in the areas near the two ends corresponding to the second connecting surface 11114 and the third connecting surface 11115, which can bear the expansion force of the electrode assembly 2 acting on the first side wall portion 111 at both ends along the third direction X, and the thickness of the first side wall portion 111 in the areas near the two ends corresponding to the second connecting surface 11114 and the third connecting surface 11115 is relatively small, which is beneficial to reducing costs.

[0516] It is understood that the relationship between the distance between the second connecting surface 11114 and the first outer surface 806, the distance between the third connecting surface 11115 and the first outer surface 806, and the distance between the first connecting surface 11113 and the first outer surface 806 is not limited. As an example, the distance between the second connecting surface 11114 and the first outer surface 806 can be greater than or equal to the distance between the first connecting surface 11113 and the first outer surface 806, and the distance between the third connecting surface 11115 and the first outer surface 806 can be greater than or equal to the distance between the first connecting surface 11113 and the first outer surface 806.

[0517] In some embodiments, referring to FIG. 20 , FIG. 21 , FIG. 24 and FIG. 25 , the first connection surface 11113 , the second connection surface 11114 and the third connection surface 11115 are all at least partially formed in the first region 1111 .

[0518] As an example, referring to Figures 20, 21, 24 and 25, the first connection surface 11113 is partially formed in the first area 1111, the second connection surface 11114 is partially formed in the first area 1111, and the third connection surface 11115 is partially formed in the first area 1111.

[0519] As an example, referring to Figures 20, 21, 24 and 25, the first connecting surface 11113 is arranged across the first area 1111 and the second area 1112, the second connecting surface 11114 is arranged across the first area 1111 and the second area 1112, and the third connecting surface 11115 is arranged across the first area 1111 and the second area 1112.

[0520] The first connection surface 11113 is arranged across the first area 1111 and the second area 1112 , which means that the first connection surface 11113 is partially formed in the first area 1111 and partially formed in the second area 1112 .

[0521] The second connection surface 11114 is arranged across the first area 1111 and the second area 1112 , which means that the second connection surface 11114 is partially formed in the first area 1111 and partially formed in the second area 1112 .

[0522] The third connection surface 11115 is arranged across the first area 1111 and the second area 1112 , which means that the third connection surface 11115 is partially formed in the first area 1111 and partially formed in the second area 1112 .

[0523] In the embodiment of the present application, part of the first zone 1111 located at the corresponding position of the first connecting surface 11113 releases the expansion force of the electrode assembly 2 at the first connecting surface 11113, which is beneficial to reducing the cracking of the first connecting portion 51 at the first connecting surface 11113. The part of the first zone 1111 located at the corresponding position of the first connecting surface 11113 is subjected to a large periodic expansion force caused by the repeated expansion of the electrode assembly 2. The distance between the second connecting surface 11114 and the first outer surface 806 and the distance between the third connecting surface 11115 and the first outer surface 806 are both smaller than the distance between the first connecting surface 11113 and the first outer surface 806, so that the thicker part of the first side wall portion 1111 at the first connecting surface 11113 can better reinforce the first zone 1111, which is beneficial to suppressing the possibility of fatigue cracking of part of the first zone 1111 located at the corresponding position of the first connecting surface 11113. The expansion force of the electrode assembly 2 at the second connecting surface 11114 is partially released in the first area 1111 at the corresponding position of the second connecting surface 11114, which helps to reduce cracking of the first connecting portion 51 at the second connecting surface 11114. The expansion force of the electrode assembly 2 at the third connecting surface 11115 is partially released in the first area 1111 at the corresponding position of the third connecting surface 11115, which helps to reduce cracking of the first connecting portion 51 at the third connecting surface 11115. Since the periodic expansion force of the electrode assembly 2 on the first side wall portion 111 at the corresponding positions of the second connecting surface 11114 and the third connecting surface 11115 is relatively small, the distance between the second connecting surface 11114 and the first outer surface 806 and the distance between the third connecting surface 11115 and the first outer surface 806 are both smaller than the distance between the first connecting surface 11113 and the first outer surface 806. This can not only suppress fatigue cracking of the first zone 1111 at the portion corresponding to the second connecting surface 11114 and the portion corresponding to the third connecting surface 11115, but also reduce the material usage of the first side wall at the positions corresponding to the second connecting surface 11114 and the third connecting surface 11115, thereby saving costs.

[0524] It is understood that the relationship between the first connection surface 11113, the second connection surface 11114, and the third connection surface 11115 and the first area 1111 is not limited. As an example, one of the first connection surface 11113, the second connection surface 11114, and the third connection surface 11115 is at least partially formed in the first area 1111, and the remaining two may not be formed in the first area 1111. As an example, two of the first connection surface 11113, the second connection surface 11114, and the third connection surface 11115 are at least partially formed in the first area 1111, and the remaining one may not be formed in the first area 1111.

[0525] In some embodiments, referring to Figures 22 to 25, the first inner surface 804 further includes a first transition surface 11116, the first connecting surface 11113, the first transition surface 11116 and the second connecting surface 11114 are arranged along the third direction X, the first transition surface 11116 connects the second connecting surface 11114 and the first connecting surface 11113, and the distance between the first transition surface 11116 and the first outer surface 806 along the second direction Y is a second preset thickness, and the second preset thickness is along the second connecting surface 11114 pointing to the first connecting surface 11113. direction tends to increase; and / or, the first inner surface 804 also includes a second transition surface 11117, the first connecting surface 11113, the second transition surface 11117 and the third connecting surface 11115 are arranged along the third direction X, the second transition surface 11117 connects the third connecting surface 11115 and the first connecting surface 11113, and the distance between the second transition surface 11117 and the first outer surface 806 along the second direction Y is a third preset thickness, and the third preset thickness tends to increase along the direction from the third connecting surface 11115 to the first connecting surface 11113.

[0526] The distances between various locations on the first transition surface 11116 and the first outer surface 806 are not equal. As an example, the second predetermined thickness gradually increases along the direction from the second connecting surface 11114 to the first connecting surface 11113. The distances between various locations on the second transition surface 11117 and the first outer surface 806 are not equal. As an example, the third predetermined thickness gradually increases along the direction from the third connecting surface 11115 to the first connecting surface 11113.

[0527] If a first transition surface 11116 is provided between the second connecting surface 11114 and the first connecting surface 11113, and a second transition surface 11117 is provided between the third connecting surface 11115 and the first connecting surface 11113, the dimension of the first transition surface 11116 along the third direction X may be equal to or different from the dimension of the second transition surface 11117 along the third direction X. If the dimension of the first transition surface 11116 along the third direction X is equal to the dimension of the second transition surface 11117 along the third direction X, the first transition surface 11116 and the second transition surface 11117 may be symmetrically arranged about the mid-section of the first sidewall portion 111.

[0528] It can be understood that if a first transition surface 11116 is provided between the second connecting surface 11114 and the first connecting surface 11113, the first transition surface 11116 can be closer to the electrode assembly 2 relative to the second inner surface 805 along the second direction Y and / or the portion of the first outer surface 806 corresponding to the first transition surface 11116 can be farther away from the electrode assembly 2 relative to the second outer surface 807 along the second direction Y; if a second transition surface 11117 is provided between the third connecting surface 11115 and the first connecting surface 11113, the second transition surface 11117 can be closer to the electrode assembly 2 relative to the second inner surface 805 along the second direction Y and / or the portion of the first outer surface 806 corresponding to the second transition surface 11117 can be farther away from the electrode assembly 2 relative to the second outer surface 807 along the second direction Y.

[0529] As an example, referring to Figures 22 to 25, second connecting surface 11114 is indirectly connected to first connecting surface 11113 via first transition surface 11116, and third connecting surface 11115 is indirectly connected to first connecting surface 11113 via second transition surface 11117. The second predetermined thickness gradually increases along the direction from second connecting surface 11114 toward first connecting surface 11113, and the third predetermined thickness gradually increases along the direction from third connecting surface 11115 toward first connecting surface 11113. A portion of second connecting surface 11114, a portion of first connecting surface 11113, a portion of third connecting surface 11115, a portion of first transition surface 11116, and a portion of second transition surface 11117 are all closer to electrode assembly 2 relative to second inner surface 805 along second direction Y. The first transition surface 11116 connects the first connection surface 11113 and the second connection surface 11114 , the second transition surface 11117 connects the first connection surface 11113 and the third connection surface 11115 , and the first outer surface 806 is a plane.

[0530] In the embodiment of the present application, if the second connecting surface 11114 and the first connecting surface 11113 are connected via a first transition surface 11116, and the second predetermined thickness increases along the direction from the second connecting surface 11114 to the first connecting surface 11113, the first transition surface 11116 can achieve a transition between the second connecting surface 11114 and the first connecting surface 11113, thereby reducing stress concentration. If the third connecting surface 11115 and the first connecting surface 11113 are connected via a second transition surface 11117, and the third predetermined thickness increases along the direction from the third connecting surface 11115 to the first connecting surface 11113, the second transition surface 11117 can achieve a transition between the third connecting surface 11115 and the first connecting surface 11113, thereby reducing stress concentration.

[0531] In some embodiments, referring to FIG. 24 and FIG. 25 , the first transition surface 11116 is at least partially formed in the first region 1111 and / or the second transition surface 11117 is at least partially formed in the first region 1111 .

[0532] In the embodiment of the present application, the portion of the first sidewall portion 111 corresponding to the first transition surface 11116 and the second transition surface 11117 is thicker than the portion of the first sidewall portion 111 corresponding to the second inner surface 805. The thicker first transition surface 11116 can reinforce the corresponding first region 1111, thereby suppressing fatigue cracking at the corresponding location of the first region 1111. The thicker second transition surface 11117 can reinforce the corresponding first region 1111, thereby suppressing fatigue cracking at the corresponding location of the first region 1111.

[0533] It is understood that the positional relationship between the first transition surface 11116 and the second transition surface 11117 and the first zone 1111 is not limited. As an example, the first transition surface 11116 is outside the first zone 1111 and / or the second transition surface 11117 is outside the first zone 1111.

[0534] In some embodiments, referring to FIG. 16 , FIG. 19 and FIG. 23 , a dimension of the first connection surface 11113 along the third direction X is L1 , a dimension of the first sidewall portion 111 along the third direction X is L, and 0.2≤L1 / L≤0.6.

[0535] The dimension of the first connecting surface 11113 along the third direction X is the length of the first connecting surface 11113, the dimension of the first side wall portion 111 along the third direction X is the length of the first side wall portion 111, the dimension of the first side wall portion 111 along the second direction Y is the thickness of the first side wall portion 111, and the dimension of the first side wall portion 111 along the first direction Z is the width of the first side wall portion 111.

[0536] L1 / L can be any point value among 0.2, 0.22, 0.25, 0.28, 0.3, 0.32, 0.35, 0.38, 0.4, 0.42, 0.45, 0.48, 0.5, 0.52, 0.55, 0.58, 0.6, etc., or a range of values ​​between any two of them.

[0537] In the embodiment of the present application, L1 / L≥0.2, which increases the dimensional proportion of the first connecting surface 11113 in the first side wall portion 111 along the third direction X, so that the middle area of ​​the first side wall portion 111 along the third direction X is strengthened to a larger extent, thereby improving the strength of the middle area of ​​the first side wall portion 111 along the third direction X; L1 / L≤0.6, which reduces the dimensional proportion of the first connecting surface 11113 in the first side wall portion 111 along the third direction X, reduces the material used in the part of the first side wall portion 111 corresponding to the first connecting surface 11113, and reduces the production cost. Therefore, the ratio of the dimension of the first connecting surface 11113 along the third direction X to the dimension of the first side wall portion 111 along the third direction X is set to 0.2~0.6. While ensuring that the first side wall portion 111 has sufficient reinforcement capacity at the position corresponding to the first connecting surface 11113, the material used for the first side wall portion 111 at the first connecting surface 11113 is reduced, taking into account both the reinforcement capacity requirements and the economic requirements of the first side wall portion 111 at the first connecting surface 11113.

[0538] In some embodiments, referring to Figures 16, 19 and 23, the first connecting surface 11113 has a first end 11113a and a second end 11113b relative to each other along the third direction X, the first side wall portion 111 has a third end 1113 and a fourth end 1114 relative to each other along the third direction X, the first end 11113a is close to the third end 1113, the second end 11113b is close to the fourth end 1114, the dimension of the first side wall portion 111 along the third direction X is L, the minimum distance between the first end 11113a and the third end 1113 along the third direction X is L2, and the minimum distance between the second end 11113b and the fourth end 1114 along the third direction X is L3; L2 / L≤0.3; and / or, L3 / L≤0.3.

[0539] It can be understood that, along the third direction X, the first end 11113a is closer to the third end 1113 than the second end 11113b, and the second end 11113b is closer to the fourth end 1114 than the first end 11113a.

[0540] It can be L2=L3; it can also be L2>L3 or L2<L3.

[0541] L2 / L can be any point value among 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.11, 0.12, 0.13, 0.14, 0.15, 0.16, 0.17, 0.18, 0.19, 0.2, 0.21, 0.22, 0.23, 0.24, 0.25, 0.26, 0.27, 0.28, 0.29, 0.3, etc., or a range between any two of them.

[0542] L3 / L can be any point value among 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.11, 0.12, 0.13, 0.14, 0.15, 0.16, 0.17, 0.18, 0.19, 0.2, 0.21, 0.22, 0.23, 0.24, 0.25, 0.26, 0.27, 0.28, 0.29, 0.3, etc., or a range between any two of them.

[0543] In the embodiment of the present application, if L2 / L ≤ 0.3, the ratio of the minimum distance between the first end 11113a and the third end 1113 along the third direction X to the dimension of the first side wall portion 111 along the third direction X is reduced, thereby increasing the strength of the first side wall portion 111 along the third direction X. If L3 / L ≤ 0.3, the ratio of the minimum distance between the second end 11113b and the fourth end 1114 along the third direction X to the dimension of the first side wall portion 111 along the third direction X is reduced, thereby increasing the strength of the first side wall portion 111 along the third direction X.

[0544] In some embodiments, referring to FIG. 16 , FIG. 19 and FIG. 23 , 100 mm ≤ L ≤ 450 mm.

[0545] L can be any point value among 100mm, 120mm, 150mm, 180mm, 200mm, 220mm, 250mm, 260mm, 280mm, 300mm, 310mm, 320mm, 350mm, 390mm, 400mm, 410mm, 420mm, 430mm, 440mm, 450mm, etc., or a range value between any two of them.

[0546] In some embodiments, referring to FIG. 15 , FIG. 18 and FIG. 22 , the housing 11 includes a corner wall 113 , and both ends of the first side wall portion 111 along the third direction X are connected to the corner wall 113 ;

[0547] At least one end of the first inner surface 804 along the third direction X does not contact the corner wall 113 ; or, both ends of the first inner surface 804 along the third direction X extend to the two corner walls 113 .

[0548] Along the third direction X, the first inner surface 804 has two opposite ends. One end of the first inner surface 804 may extend to one corner wall 113, and the other end may not extend to the other corner wall 113, or both ends of the first inner surface 804 may not extend to the corner wall 113, so as to achieve that at least one end of the first inner surface 804 along the third direction X does not contact the corner wall 113.

[0549] As an example, referring to Figures 15 and 16, along the third direction X, one end of the first inner surface 804 does not contact the corner wall 113 at one end of the first side wall portion 111, and the other end of the first inner surface 804 does not contact the corner wall 113 at the other end of the first side wall portion 111.

[0550] In the embodiment of the present application, if at least one end of the first inner surface 804 along the third direction X does not contact the corner wall 113, the material used in the portion of the first side wall portion 111 corresponding to the first inner surface 804 can be reduced, thereby reducing production costs. If the first inner surface 804 extends to the two corner walls 113 at both ends along the third direction X, the length of the first inner surface 804 is increased, and the reinforcement capability of the first side wall portion 111 in the portion corresponding to the first inner surface 804 is enhanced, thereby strengthening more areas of the first side wall portion 111 along the third direction X.

[0551] In some embodiments, referring to Figures 26, 27, and 28, the electrode assembly 2 further includes a separator 24 disposed between the positive electrode sheet 22 and the negative electrode sheet 23. The positive electrode sheet 22 includes a positive electrode main region 221 and a positive electrode tab 21a protruding from the positive electrode main region 221. The positive electrode main region 221 has a positive electrode active material layer 223. The negative electrode sheet 23 includes a negative electrode main region 231 and a negative electrode tab 21b protruding from the negative electrode main region 231. The negative electrode main region 231 has a negative electrode active material layer 233. Along the first direction Z, the positive electrode main region 221 has a fifth end 2211 facing the end cap 12, and the negative electrode main region 231 has a sixth end 2311 facing the end cap 12. The separator 24 has a seventh end 241 facing the end cap 12. The seventh end 241 is closer to the end cap 12 than the fifth end 2211 and the sixth end 2311.

[0552] As an example, the electrode assembly 2 may be a wound structure or a laminated structure.

[0553] The positive electrode sheet 22 may include a positive electrode current collector 222 and a positive electrode active material layer 223. The positive electrode current collector 222 is provided with the positive electrode active material layer 223 on one or both surfaces in the thickness direction. Referring to Figures 26, 27, and 28, the positive electrode sheet 22 also includes an insulating layer 224. The insulating layer 224 is provided on both opposing surfaces in the thickness direction of the positive electrode current collector 222. The insulating layer 224 and the positive electrode active material layer 223 are arranged along a first direction Z. The insulating layer 224 is provided at the end of the positive electrode active material layer 223. The portion of the positive electrode sheet 22 corresponding to the entirety of the positive electrode active material layer 223 and the insulating layer 224 is the positive electrode main region 221. The end of the insulating layer 224 near the end cap 12 forms the fifth end 2211 of the positive electrode main region 221. The portion of the positive electrode current collector 222 that extends beyond the insulating layer 224 forms the positive electrode tab 21a. Please refer to Figures 26, 27 and 28. The positive electrode sheet 22 is not provided with an insulating layer 224. The portion of the positive electrode sheet 22 corresponding to the positive active material layer 223 is the positive electrode main area 221. The end of the positive active material layer 223 close to the end cover 12 forms the fifth end 2211 of the positive electrode main area 221. The portion of the positive current collector 222 that extends beyond the positive active material layer 223 forms the positive electrode tab 21a.

[0554] The negative electrode sheet 23 may include a negative electrode current collector 232 and a negative electrode active material layer 233. The negative electrode active material layer 233 is provided on one or both surfaces of the negative electrode current collector 232 in the thickness direction. The portion of the negative electrode sheet 23 corresponding to the negative electrode active material layer 233 is the negative electrode main region 231. The end of the negative electrode active material layer 233 near the end cap 12 forms the sixth end 2311 of the negative electrode main region 231. The portion of the negative electrode current collector 232 that extends beyond the negative electrode active material layer 233 forms the negative electrode tab 21b.

[0555] The fifth end 2211 may be flush with the sixth end 2311. Refer to Figures 26, 27, and 28. Alternatively, the fifth end 2211 may be closer to the end cap 12 than the sixth end 2311. Refer to Figures 26, 27, and 28. Alternatively, the sixth end 2311 may be closer to the end cap 12 than the fifth end 2211.

[0556] In the embodiment of the present application, the seventh end 241 of the isolation member 24 is closer to the end cover 12 than the fifth end 2211 of the positive electrode main area 221 and the sixth end 2311 of the negative electrode main area 231, so that the isolation member 24 has a portion that exceeds the fifth end 2211 and the sixth end 2311, thereby enhancing the insulation effect of the isolation member 24 between the positive electrode sheet 22 and the negative electrode sheet 23, and reducing the possibility of overlap between the positive electrode sheet 22 and the negative electrode sheet 23.

[0557] In some embodiments, referring to Figures 26, 27 and 28, the isolation member 24 includes a protruding area 242 extending beyond the fifth end 2211 and the sixth end 2311 along the first direction Z, and in a projection plane perpendicular to the second direction Y, the orthographic projection of the protruding area 242 partially overlaps with the orthographic projection of the first inner surface 804.

[0558] The protruding region 242 is the portion of the separator 24 that extends beyond both the fifth end 2211 of the positive electrode main region 221 and the sixth end 2311 of the negative electrode main region 231. As will be understood, referring to the figure, in embodiments where the fifth end 2211 is closer to the end cap 12 than the sixth end 2311, the portion of the separator 24 that extends beyond the fifth end 2211 is the protruding region 242. Also referring to the figure, in embodiments where the sixth end 2311 is closer to the end cap 12 than the fifth end 2211, the portion of the separator 24 that extends beyond the sixth end 2311 is the protruding region 242.

[0559] As an example, referring to FIG. 11 , the positive electrode sheet 22 , the negative electrode sheet 23 and the separator 24 in the electrode assembly 2 are stacked along the second direction Y in the flat region 25 .

[0560] In the embodiment of the present application, in the projection plane perpendicular to the second direction Y, the orthographic projection of the excess area 242 partially overlaps with the orthographic projection of the first inner surface 804. This structure can increase the size of the first inner surface 804 along the first direction Z, improve the reinforcement ability of the first side wall portion 111 at the corresponding portion of the first inner surface 804, and thus strengthen more areas of the first side wall portion 111 along the first direction Z.

[0561] In some embodiments, referring to FIG. 26 , the first inner surface 804 protrudes from the second inner surface 805. Within a projection plane perpendicular to the second direction Y, the orthographic projection of the positive electrode body region 221 does not overlap with the orthographic projection of the first inner surface 804; and / or, within a projection plane perpendicular to the second direction Y, the orthographic projection of the negative electrode body region 231 does not overlap with the orthographic projection of the first inner surface 804.

[0562] It should be explained that the first inner surface 804 protrudes from the second inner surface 805 , that is, the first inner surface 804 is closer to the electrode assembly 2 along the second direction Y than the second inner surface 805 .

[0563] The first inner surface 804 may extend to the first connecting portion 51 , such that the first inner surface 804 is directly connected to the first connecting portion 51 .

[0564] It can be understood that, in the embodiment where the first inner surface 804 includes the first sub-surface 11111 and the second sub-surface 11112 arranged along the first direction Z, the first sub-surface 11111 and the second sub-surface 11112 may be closer to the electrode assembly 2 relative to the second inner surface 805 along the second direction Y. In the embodiment where the first inner surface 804 includes the second connecting surface 11114, the first connecting surface 11113, and the third connecting surface 11115 arranged along the third direction X, the second connecting surface 11114, the first connecting surface 11113, and the third connecting surface 11115 may be closer to the electrode assembly 2 relative to the second inner surface 805 along the second direction Y.

[0565] As an example, referring to FIG. 26 , in a projection plane perpendicular to the second direction Y, the positive electrode main region 221 does not overlap with the orthographic projection of the first inner surface 804 , and the negative electrode main region 231 does not overlap with the orthographic projection of the first inner surface 804 .

[0566] In the embodiment of the present application, if the orthographic projection of the positive electrode main region 221 does not overlap with the orthographic projection of the first inner surface 804 within a projection plane perpendicular to the second direction Y, the housing 11 can provide greater expansion space for the electrode assembly 2, reducing the expansion force directly exerted by the electrode assembly 2 on the portion of the first side wall portion 111 corresponding to the first inner surface 804, thereby reducing the deformation of the first side wall portion 111. If the orthographic projection of the negative electrode main region 231 does not overlap with the orthographic projection of the first inner surface 804 within a projection plane perpendicular to the second direction Y, the housing 11 can provide greater expansion space for the electrode assembly 2, reducing the expansion force directly exerted by the electrode assembly 2 on the portion of the first side wall portion 111 corresponding to the first inner surface 804, thereby reducing the deformation of the first side wall portion 111.

[0567] In some embodiments, referring to FIG. 27 and FIG. 28 , the negative electrode sheet 23 includes a negative electrode current collector 232 and a negative electrode active material layer 233 disposed on at least one side of the negative electrode current collector 232 . The negative electrode active material layer 233 includes a negative electrode active material.

[0568] The negative electrode active material layer 233 may be provided on only one side of the negative electrode current collector 232, that is, the negative electrode active material layer 233 may be provided on only one surface of the negative electrode current collector 232 along the thickness direction; or the negative electrode active material layer 233 may be provided on both opposite sides of the negative electrode current collector 232, that is, the negative electrode active material layer 233 may be provided on both opposite surfaces of the negative electrode current collector 232 along the thickness direction.

[0569] The negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, and the like.

[0570] In some embodiments, referring to Figures 27 and 28, the negative electrode active material layer 233 includes a negative electrode main body 2331 and a negative electrode thinning portion 2332. The negative electrode main body 2331 and the negative electrode thinning portion 2332 are arranged along a first direction Z. Along the first direction Z, the negative electrode main body 2331 is provided with a negative electrode thinning portion 2332 at one end close to the end cover 12.

[0571] The thickness of the negative electrode main body 2331 is greater than the thickness of the negative electrode thinning portion 2332. The negative electrode thinning portion 2332 may be provided only at one end of the negative electrode main body 2331 close to the end cap 12 along the first direction Z, or the negative electrode thinning portion 2332 may be provided at both ends of the negative electrode main body 2331 along the first direction Z. The negative electrode main body 2331 may be of a uniform thickness structure or a non-uniform thickness structure, and the negative electrode thinning portion 2332 may be of a uniform thickness structure or a non-uniform thickness structure. If at least one of the negative electrode main body 2331 and the negative electrode thinning portion 2332 is of a non-uniform thickness structure, the maximum thickness of the negative electrode thinning portion 2332 may be less than or equal to the minimum thickness of the negative electrode main body 2331, so that the thickness of the negative electrode main body 2331 is greater than the thickness of the negative electrode thinning portion 2332.

[0572] As an example, the negative electrode main body 2331 has a uniform thickness structure, and the thickness of the negative electrode thinned portion 2332 decreases along the direction from the negative electrode main body 2331 to the negative electrode thinned portion 2332 .

[0573] In this embodiment, a negative electrode thinning portion 2332 is provided at one end of the negative electrode main body 2331 close to the end cover 12, and the electrode assembly 2 has a larger expansion gap in the area corresponding to the negative electrode thinning portion 2332. The area of ​​the electrode assembly 2 corresponding to the negative electrode thinning portion 2332 exerts a smaller force on the first side wall portion 111 after expansion, which is beneficial to reducing cracking of the shell 11.

[0574] In some embodiments, referring to FIG. 26 to FIG. 28 , in a projection plane perpendicular to the second direction Y, the orthographic projection of the negative electrode thinned portion 2332 and the orthographic projection of the first inner surface 804 are spaced apart along the first direction Z.

[0575] It is understandable that, in the projection plane perpendicular to the second direction Y, the orthographic projection of the negative electrode thinned portion 2332 located at one end of the negative electrode main body 2331 close to the end cover 12 does not overlap with the orthographic projection of the first inner surface 804 .

[0576] In this embodiment, in the projection plane perpendicular to the second direction Y, the positive projection of the negative electrode thinning portion 2332 located at one end of the negative electrode main body 2331 close to the end cover 12 and the positive projection of the first inner surface 804 are spaced apart along the first direction Z, which can reduce the influence of the negative electrode thinning portion 2332 on the corresponding portion of the first side wall portion 111 at the first inner surface 804, reduce the expansion force directly applied by the expansion of the electrode assembly 2 to the corresponding portion of the first side wall portion 111 at the first inner surface 804, and further reduce the possibility of cracking of the first side wall portion 111 of the shell 11.

[0577] In some embodiments, referring to FIG. 26 to FIG. 28 , in a projection plane perpendicular to the second direction Y, a spacing dimension between the orthographic projection of the negative electrode thinned portion 2332 and the orthographic projection of the first inner surface 804 along the first direction Z is greater than or equal to 1 mm.

[0578] In a projection plane perpendicular to the second direction Y, the spacing between the orthographic projection of the negative electrode thinned portion 2332 located at the end of the negative electrode main body 2331 near the end cap 12 and the orthographic projection of the first inner surface 804 along the first direction Z is W1, where W1 ≥ 1 mm. This spacing is the minimum distance between the orthographic projections of the negative electrode thinned portion 2332 and the first inner surface 804 along the first direction Z in the projection plane perpendicular to the second direction Y. W1 can be any value among 1 mm, 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, 10 mm, 11 mm, 12 mm, 13 mm, 14 mm, 15 mm, 16 mm, 17 mm, 18 mm, 19 mm, 20 mm, or a range between any two values.

[0579] In this embodiment, W1≥1mm makes the positive projection of the negative electrode thinning portion 2332 and the positive projection of the first inner surface 804 along the first direction Z farther apart in the projection plane perpendicular to the second direction Y, further reducing the influence of the negative electrode thinning portion 2332 on the corresponding portion of the first side wall portion 111 at the first inner surface 804.

[0580] In some embodiments, the coating weight of the negative electrode active material layer 233 on one side is 90 mg / 1540 mm 2 ~170mg / 1540mm 2 .

[0581] The coating weight of the negative electrode active material layer 233 on one side can be 90 mg / 1540 mm 2 、100mg / 1540mm 2 、110mg / 1540mm 2 、120mg / 1540mm 2 、130mg / 1540mm 2、140mg / 1540mm 2 、150mg / 1540mm 2 、160mg / 1540mm 2 、170mg / 1540mm 2 Any point value or any range of values ​​between the two.

[0582] To measure the coating weight of the negative electrode active material layer 233 on one side, take a negative electrode sheet 23 coated on one side (if it is coated on both sides, wipe off the negative electrode active material layer 233 on one side first), punch it out into small discs with an area of ​​S1, weigh them, and record their weight as M1. Then, wipe off the negative electrode active material layer 233 from the weighed negative electrode sheet 23, and weigh the negative electrode current collector 232, recording its weight as M2. The coating weight of the negative electrode active material layer 233 on one side = (M1 - M2) / S1.

[0583] The coating weight of the negative electrode active material layer 233 on one side is related to the expansion of the negative electrode active material layer 233. The coating weight of the negative electrode active material layer 233 on one side is set at 90 mg / 1540 mm. 2 ~170mg / 1540mm 2 , which can, to a certain extent, take into account the high energy density requirements of the battery cell 10 and the low expansion requirements of the negative electrode sheet 23, thereby reducing the impact of the expansion of the negative electrode sheet 23 on the first side wall portion 111 and the possibility of cracking the first side wall portion 111 of the shell 11.

[0584] In some embodiments, the coating weight of the negative electrode active material layer 233 on one side is 110 mg / 1540 mm 2 ~150mg / 1540mm 2 .

[0585] In this embodiment, the coating weight of the negative electrode active material layer 233 on one side can be 110 mg / 1540 mm 2 、115mg / 1540mm 2 、120mg / 1540mm 2 、125mg / 1540mm 2 、130mg / 1540mm 2 、135mg / 1540mm 2 、140mg / 1540mm 2 、145mg / 1540mm 2 、150mg / 1540mm 2 Any point value or any range of values ​​between the two.

[0586] In this embodiment, the coating weight of the negative electrode active material layer 233 on one side is 110 mg / 1540 mm 2 ~150mg / 1540mm 2 , which can further improve the energy density requirement of the battery cell 10 and further slow down the expansion of the negative electrode sheet 23.

[0587] In some embodiments, the porosity of the negative electrode sheet 23 is 27% to 40%.

[0588] The porosity of the negative electrode sheet 23 can be any point value among 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, etc., or a range of values ​​between any two points.

[0589] The porosity of the negative electrode sheet 23 can be defined as the percentage of the pore volume within the negative electrode sheet 23 to the total volume of the negative electrode sheet 23. As an example, when the battery cell 10 is at a 0% state of charge, a double-sided coated negative electrode sheet 23 is taken and the porosity of the negative electrode sheet 23 is measured using an AccuPyc II 1340 density meter in accordance with the national standard GB / T 24586-2009.

[0590] In this embodiment, the porosity of the negative electrode sheet 23 is 27% to 40%, which can provide space for impurities generated by side reactions in the negative electrode sheet 23, slow down the expansion of the negative electrode sheet 23, and reduce the impact of the expansion of the negative electrode sheet 23 on the first side wall portion 111.

[0591] In some embodiments, the negative electrode active material includes a silicon-based material, and the mass content of silicon in the silicon-based material is 0.3% to 10%, and can be optionally 1% to 6%.

[0592] The mass content of silicon element in the negative electrode active material in the silicon-based material can be any point value among 0.3%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, etc., or a range value between any two points.

[0593] In some embodiments, the silicon-based material includes at least one of a silicon-oxygen compound and a silicon-carbon composite.

[0594] In some embodiments, referring to FIG. 27 and FIG. 28 , the positive electrode sheet 22 includes a positive current collector 222 and a positive active material layer 223 disposed on at least one side of the positive current collector 222 . The positive active material layer 223 includes a positive active material.

[0595] The positive electrode active material layer 223 may be provided on only one side of the positive electrode current collector 222, that is, the positive electrode active material layer 223 may be provided on only one surface of the positive electrode current collector 222 along the thickness direction; or the positive electrode active material layer 223 may be provided on both opposite sides of the positive electrode current collector 222, that is, the positive electrode active material layer 223 may be provided on both opposite surfaces of the positive electrode current collector 222 along the thickness direction.

[0596] The positive electrode active material may include at least one of the following materials: a lithium-containing phosphate, a lithium transition metal oxide, and modified compounds thereof.

[0597] In some embodiments, referring to Figures 27 and 28, the positive electrode active material layer 223 includes a positive electrode main body 2231 and a positive electrode thinning portion 2232. The positive electrode main body 2231 and the positive electrode thinning portion 2232 are arranged along a first direction Z. Along the first direction Z, the positive electrode main body 2231 is provided with a positive electrode thinning portion 2232 at one end close to the end cover 12.

[0598] The thickness of the positive electrode main body 2231 is greater than the thickness of the positive electrode thinning portion 2232. The positive electrode thinning portion 2232 may be provided only at one end of the positive electrode main body 2231 close to the end cap 12 along the first direction Z, or the positive electrode thinning portion 2232 may be provided at both ends of the positive electrode main body 2231 along the first direction Z. The positive electrode main body 2231 may be of a uniform thickness structure or a non-uniform thickness structure, and the positive electrode thinning portion 2232 may be of a uniform thickness structure or a non-uniform thickness structure. If at least one of the positive electrode main body 2231 and the positive electrode thinning portion 2232 is of a non-uniform thickness structure, the maximum thickness of the positive electrode thinning portion 2232 may be less than or equal to the minimum thickness of the positive electrode main body 2231, so that the thickness of the positive electrode main body 2231 is greater than the thickness of the positive electrode thinning portion 2232.

[0599] As an example, the positive electrode main body 2231 has a uniform thickness structure, and the thickness of the positive electrode thinned portion 2232 decreases along the direction from the positive electrode main body 2231 to the positive electrode thinned portion 2232 .

[0600] In this embodiment, a positive electrode thinning portion 2232 is provided at one end of the positive electrode main body 2231 close to the end cover 12, and the electrode assembly 2 has a larger expansion gap in the area corresponding to the positive electrode thinning portion 2232. The area of ​​the electrode assembly 2 corresponding to the positive electrode thinning portion 2232 exerts a smaller force on the first side wall portion 111 after expansion, which can reduce the possibility of cracking of the first side wall portion 111 of the shell 11.

[0601] In some embodiments, referring to FIG. 26 to FIG. 28 , in a projection plane perpendicular to the second direction Y, the orthographic projection of the positive electrode thinned portion 2232 and the orthographic projection of the first inner surface 804 are spaced apart along the first direction Z.

[0602] It is understandable that, in the projection plane perpendicular to the second direction Y, the orthographic projection of the positive electrode thinned portion 2232 located at one end of the positive electrode main body 2231 close to the end cover 12 does not overlap with the orthographic projection of the first inner surface 804 .

[0603] In the projection plane perpendicular to the second direction Y, the orthographic projection of the positive electrode thinning portion 2232 located at one end of the positive electrode main body 2231 close to the end cover 12 and the orthographic projection of the first inner surface 804 are spaced apart along the first direction Z, which can reduce the influence of the positive electrode thinning portion 2232 on the corresponding portion of the first side wall portion 111 on the first inner surface 804, reduce the expansion force directly applied by the expansion of the electrode assembly 2 to the corresponding portion of the first side wall portion 111 on the first inner surface 804, and reduce the possibility of cracking of the first side wall portion 111 of the shell 11.

[0604] In some embodiments, referring to FIG. 26 to FIG. 28 , in a projection plane perpendicular to the second direction Y, a spacing dimension between the orthographic projection of the positive electrode thinned portion 2232 and the orthographic projection of the first inner surface 804 along the first direction Z is greater than or equal to 1 mm.

[0605] In a projection plane perpendicular to the second direction Y, the distance between the orthographic projection of the positive electrode thinned portion 2232 located at the end of the positive electrode main body 2231 near the end cap 12 and the orthographic projection of the first inner surface 804 along the first direction Z is W2, where W2 ≥ 1 mm. This distance is the minimum distance between the orthographic projections of the positive electrode thinned portion 2232 and the first inner surface 804 along the first direction Z in a projection plane perpendicular to the second direction Y. W1 may be W2, W1 ≤ W2, or W1 ≥ W2. W2 may be any value among 1 mm, 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, 10 mm, 11 mm, 12 mm, 13 mm, 14 mm, 15 mm, 16 mm, 17 mm, 18 mm, 19 mm, 20 mm, or any range therebetween.

[0606] In this embodiment, W2 ≥ 1 mm, so that in the projection plane perpendicular to the second direction Y, the orthographic projection of the positive electrode thinning portion 2232 is farther away from the orthographic projection of the first inner surface 804 along the first direction Z, further reducing the influence of the positive electrode thinning portion 2232 on the first inner surface 804.

[0607] In some embodiments, the coating weight of the positive electrode active material layer 223 on one side is 200 mg / 1540 mm 2 ~370mg / 1540 / mm 2 .

[0608] The coating weight of the positive electrode active material layer 223 on one side can be 200 mg / 1540 mm 2、210mg / 1540mm 2 , 220mg / 1540mm 2 、230mg / 1540mm 2 , 240mg / 1540mm 2 , 250mg / 1540mm 2 、260mg / 1540mm 2 、270mg / 1540mm 2 、280mg / 1540mm 2 、290mg / 1540mm 2 、300mg / 1540mm 2 、310mg / 1540mm 2 、320mg / 1540mm 2 、330mg / 1540mm 2 、340mg / 1540mm 2 、350mg / 1540mm 2 、360mg / 1540mm 2 、370mg / 1540mm 2 Any point value or any range of values ​​between the two.

[0609] To measure the coating weight of the positive electrode active material layer 223 on one side, take a single-sided coated positive electrode sheet 22 (if a double-sided coated positive electrode sheet 22 is used, wipe off the positive electrode active material layer 223 on one side first), punch it out into small discs with an area of ​​S2, weigh them, and record their weight as M3. Then, wipe off the positive electrode active material layer 223 from the weighed positive electrode sheet 22, and weigh the positive electrode current collector 222, recording its weight as M4. The coating weight of the positive electrode active material layer 223 on one side = (M3 - M4) / S2.

[0610] The coating weight of the positive electrode active material layer 223 on one side is related to the expansion of the positive electrode active material layer 223. The coating weight of the positive electrode active material layer 223 on one side is set at 200 mg / 1540 mm 2 ~370mg / 1540 / mm 2 , which can, to a certain extent, take into account the high energy density requirements of the battery cell 10 and the low expansion requirements of the positive electrode sheet 22, thereby reducing the impact of the expansion of the positive electrode sheet 22 on the first side wall portion 111, and can reduce the possibility of cracking of the first side wall portion 111 of the shell 11.

[0611] In some embodiments, the coating weight of the positive electrode active material layer 223 on one side is 240 mg / 1540 mm 2 ~330mg / 1540mm 2 .

[0612] The coating weight of the positive electrode active material layer 223 on one side can be 240 mg / 1540 mm 2 、 245mg / 1540mm 2 , 250mg / 1540mm 2 、255mg / 1540mm 2 、260mg / 1540mm 2 、265mg / 1540mm 2 、270mg / 1540mm 2 、275mg / 1540mm 2 、280mg / 1540mm 2 、285mg / 1540mm 2 、290mg / 1540mm 2 、295mg / 1540mm 2 、300mg / 1540mm 2 、305mg / 1540mm 2 、310mg / 1540mm 2 、315mg / 1540mm 2 、320mg / 1540mm 2 、325mg / 1540mm 2 、330mg / 1540mm 2 Any point value or any range of values ​​between the two.

[0613] In this embodiment, the coating weight of the positive electrode active material layer 223 on one side is 240 mg / 1540 mm 2 ~330mg / 1540mm 2 , which can further improve the energy density requirement of the battery cell 10 and further slow down the expansion of the positive electrode sheet 22.

[0614] In some embodiments, the positive electrode active material is a lithium-containing phosphate.

[0615] In some embodiments, referring to Figures 14, 30, and 31, the housing 11 is made of steel. The maximum distance between the second inner surface 805 and the second outer surface 807 along the second direction Y is D1. The dimension of the housing 11 along the second direction Y is D, and 0.001≤D1 / D≤0.012.

[0616] As an example, the distance between the second inner surface 805 and the second outer surface 807 at each position along the second direction Y can be equal, and the distance between the second inner surface 805 and the second outer surface 807 at any position along the second direction Y can be used as the maximum distance between the second inner surface 805 and the second outer surface 807 along the second direction Y.

[0617] As an example, the distances between the second inner surface 805 and the second outer surface 807 along the second direction Y at various locations may be unequal.

[0618] In this embodiment, a portion of the first inner surface 804 may be closer to the electrode assembly 2 relative to the second inner surface 805 along the second direction Y, or a portion of the first outer surface 806 may be farther away from the electrode assembly 2 relative to the second outer surface 807 along the second direction Y. As an example, referring to Figures 29 and 30, a portion of the first outer surface 806 may be farther away from the electrode assembly 2 relative to the second outer surface 807 along the second direction Y, and the first inner surface 804 and the second inner surface 805 are coplanar.

[0619] The maximum distance between the corresponding second outer surfaces 807 of the two opposing first sidewall portions 111 of the housing 11 is the dimension of the housing 11 along the second direction Y. It will be appreciated that when measuring the dimension of the housing 11 along the second direction Y, the measurement reference is the second outer surface 807 of the first sidewall portion 111. As an example, the second outer surfaces 807 of the two opposing first sidewall portions 111 are arranged in parallel.

[0620] For the shell 11 made of steel, D1 / D can be any point value among 0.001, 0.002, 0.003, 0.004, 0.005, 0.006, 0.007, 0.008, 0.009, 0.01, 0.011, 0.012, etc., or a range of values ​​between any two points.

[0621] For the shell 11 made of steel, D1 / D≥0.001, which increases the ratio of the distance between the second inner surface 805 and the second outer surface 807 along the second direction Y to the thickness of the shell 11, so that the part of the first side wall portion 111 corresponding to the second inner surface 805 has sufficient strength to meet the strength requirements of the shell 11; D1 / D≤0.012, which reduces the ratio of the distance between the second inner surface 805 and the second outer surface 807 along the second direction Y to the thickness of the shell 11. When the volume of the shell 11 is constant, the internal space of the shell 11 can be increased, thereby freeing up more space for the electrode assembly 2 to meet the volume energy density requirements of the battery cell 10.

[0622] In the embodiment of the present application, for the shell 11 made of steel, in order to meet the volume energy density requirement of the battery cell 10, D1 / D needs to be controlled below 0.012. The first side wall portion 111 is reinforced by the thicker portion corresponding to the first inner surface 804 of the first side wall portion 111 to reduce the possibility of cracking of the first side wall portion 111 of the shell 11.

[0623] In some embodiments, referring to Figures 14 and 30 , the housing 11 is made of steel. A maximum distance D1 between the second inner surface 805 and the second outer surface 807 along the second direction Y is defined as 0.08 mm ≤ D1 ≤ 0.35 mm. Furthermore, a maximum distance D2 between the first inner surface 804 and the first outer surface 806 along the second direction Y is defined as 0.1 mm ≤ D2 ≤ 0.6 mm.

[0624] It is understood that the maximum distance between the second inner surface 805 and the second outer surface 807 is smaller than the minimum distance between the first inner surface 804 and the first outer surface 806. Therefore, the maximum distance between the second inner surface 805 and the second outer surface 807 is smaller than the maximum distance between the first inner surface 804 and the first outer surface 806. That is, D1 < D2.

[0625] For the shell 11 made of steel, D1 can take any point value among 0.08mm, 0.1mm, 0.12mm, 0.15mm, 0.18mm, 0.2mm, 0.22mm, 0.25mm, 0.28mm, 0.3mm, 0.32mm, 0.35mm, etc., or a range value between any two of them; D2 can take any point value among 0.1mm, 0.15mm, 0.2mm, 0.25mm, 0.3mm, 0.35mm, 0.4mm, 0.45mm, 0.5mm, 0.55mm, 0.6mm, etc., or a range value between any two of them.

[0626] In the embodiment of the present application, for the steel housing 11, if the maximum distance between the second inner surface 805 and the second outer surface 807 along the second direction Y is set to 0.08 mm to 0.35 mm, the strength requirements of the portion of the first side wall 111 corresponding to the second inner surface 805 can be met while also meeting the volumetric energy density requirements of the battery cell 10. If the maximum distance between the first inner surface 804 and the first outer surface 806 along the second direction Y is set to 0.1 mm to 0.6 mm, the portion of the first side wall 111 corresponding to the first inner surface 804 can be strengthened.

[0627] In some embodiments, referring to Figures 14, 30, and 31, the housing 11 is made of aluminum alloy. The maximum distance between the second inner surface 805 and the second outer surface 807 along the second direction Y is D1. The dimension of the housing 11 along the second direction Y is D, and 0.005≤D1 / D≤0.065.

[0628] For the shell 11 made of aluminum alloy, D1 / D can be any point value among 0.005, 0.01, 0.015, 0.02, 0.025, 0.03, 0.035, 0.04, 0.045, 0.05, 0.055, 0.06, 0.65, etc., or a range of values ​​between any two of them.

[0629] For the shell 11 made of aluminum alloy, D1 / D≥0.005, which increases the ratio of the distance between the second inner surface 805 and the second outer surface 807 to the thickness of the shell 11, so that the part of the first side wall portion 111 corresponding to the second inner surface 805 has sufficient strength to meet the strength requirement of the shell 11; D1 / D≤0.065, which reduces the ratio of the distance between the second inner surface 805 and the second outer surface 807 to the thickness of the shell 11. When the volume of the shell 11 is constant, the internal space of the shell 11 can be increased, thereby freeing up more space for the electrode assembly 2 to meet the volume energy density requirement of the battery cell 10.

[0630] For the shell 11 made of aluminum alloy, in order to meet the volume energy density requirement of the battery cell 10, D1 / D needs to be controlled below 0.065. The first side wall portion 111 of the shell 11 is strengthened by the thicker part of the first side wall portion 111 in the first inner wall portion to reduce the possibility of cracking of the shell 11.

[0631] In some embodiments, referring to Figures 14 and 30 , the housing 11 is made of aluminum alloy. The maximum distance D1 between the second inner surface 805 and the second outer surface 807 along the second direction Y is 0.4 mm ≤ D1 ≤ 0.8 mm; and / or the maximum distance D2 between the first inner surface 804 and the first outer surface 806 along the second direction Y is 0.5 mm ≤ D2 ≤ 1.5 mm.

[0632] For the shell 11 made of aluminum alloy, D1 can take any point value among 0.4mm, 0.42mm, 0.45mm, 0.48mm, 0.5mm, 0.52mm, 0.55mm, 0.58mm, 0.6mm, 0.62mm, 0.65mm, 0.68mm, 0.7mm, 0.72mm, 0.75mm, 0.78mm, 0.8mm, etc., or a range value between any two of them; D2 can take any point value among 0.5mm, 0.6mm, 0.7mm, 0.8mm, 0.9mm, 1mm, 1.1mm, 1.2mm, 1.3mm, 1.4mm, 1.5mm, etc., or a range value between any two of them.

[0633] For the aluminum alloy housing 11, if the maximum distance between the second inner surface 805 and the second outer surface 807 along the second direction Y is set to 0.4 mm to 0.8 mm, the strength requirements of the portion of the first side wall 111 corresponding to the second inner surface 805 can be met while also meeting the volumetric energy density requirements of the battery cell 10. If the maximum distance between the first inner surface 804 and the first outer surface 806 along the second direction Y is set to 0.5 mm to 1.5 mm, the portion of the first side wall 111 corresponding to the first inner surface 804 has sufficient strength.

[0634] In some embodiments, the aluminum alloy includes the following composition by weight: aluminum ≥ 99.6%, copper ≤ 0.05%, iron ≤ 0.35%, magnesium ≤ 0.03%, manganese ≤ 0.03%, silicon ≤ 0.25%, titanium ≤ 0.03%, vanadium ≤ 0.05%, zinc ≤ 0.05%, and other individual elements ≤ 0.03%. This aluminum alloy has good processing and forming properties, facilitating the molding of the housing 11.

[0635] In some embodiments, the aluminum alloy comprises the following composition by weight: aluminum ≥ 96.7%, copper ≤ 0.2%, iron ≤ 0.7%, manganese ≤ 1.5%, silicon ≤ 0.6%, zinc ≤ 0.1%, other individual elements ≤ 0.05%, and other elements total ≤ 0.15%. This aluminum alloy has good machinability and corrosion resistance.

[0636] In some embodiments, referring to Figures 6, 26, 29, 32, 34, and 36, the first region 1111 is directly connected to the first connecting portion 51, and the first inner surface 804 extends along the first direction Z to one end of the first region 1111 facing the connecting portion 5.

[0637] The first region 1111 and the first connection portion 51 may be in point contact, line contact, or surface contact to achieve direct connection between the two.

[0638] In this embodiment, the first zone 1111 is directly connected to the first connecting part 51, so that the first zone 1111 is closer to the first connecting part 51 along the first direction Z. By releasing the expansion force of the electrode assembly 2 through the first zone 1111 close to the first connecting part 51, the possibility of cracking of the first connecting part 51 is reduced.

[0639] In some embodiments, referring to Figures 32 to 37, the first side wall portion 111 also includes a first transition zone 1117, the first transition zone 1117 is connected to the end of the first zone 1111 along the first direction Z away from the second zone 1112, the first transition zone 1117 is connected to the first connection portion 51, and the connection position between the first transition zone 1117 and the first connection portion 51 forms a first connection interface 511, the first connection interface 511 has a first position 5111 that is closest to the first zone 1111 along the first direction Z, and the first position 5111 is located at the end of the first zone 1111 along the first direction Z away from the second zone 1112.

[0640] The first transition region 1117 may be the portion of the first sidewall portion 111 where the first connecting portion 51 and the first region 1111 are connected. The first transition region 1117 may have a uniform thickness or a non-uniform thickness. The thickness of the first transition region 1117 may be less than that of the first region 1111. For example, referring to Figures 32 to 37 , the thickness of the first transition region 1117 gradually decreases as it moves from the second region 1112 toward the first region 1111.

[0641] The first connection interface 511 is formed at the connection position between the first transition area 1117 and the first connection portion 51. The first transition area 1117 and the first connection portion 51 are separated by the first connection interface 511. The first connection interface 511 can be a plane or a curved surface.

[0642] The first zone 1111 and the first transition zone 1117 are separated by a first interface U. The first interface U is a virtual plane. The first interface U passes through the first position 5111. The first interface U is perpendicular to the first direction Z. The first transition zone 1117 and the first connecting portion 51 are located above the first interface U, and the first zone 1111 is located below the first interface U.

[0643] In this embodiment, the first transition zone 1117 is connected to the first connection portion 51 to form a first connection interface 511, so that the first transition zone 1117 and the first connection portion 51 have a sufficiently large contact area, thereby improving the firmness of the first side wall portion 111 and the end cover 12 after welding.

[0644] In some embodiments, referring to FIG. 32 to FIG. 37 , at least a portion of the first connection interface 511 extends obliquely relative to the second direction Y.

[0645] The first connection interface 511 may extend obliquely relative to the second direction Y as a whole, and the first connection interface 511 may also extend obliquely relative to the second direction Y in part.

[0646] It can be understood that the extending direction of the portion of the first connection interface 511 that extends obliquely relative to the second direction Y is not parallel to the second direction Y.

[0647] After welding the end cap 12 to the first sidewall portion 111, the first connection portion 51 shrinks as it solidifies, generating tensile stress in the first transition region 1117. When the first sidewall portion 111 is subjected to the expansion force of the electrode assembly 2, the first sidewall portion 111 deforms, generating tensile stress in the first transition region 1117. Because at least a portion of the first connection interface 511 extends obliquely relative to the second direction Y, the tensile stress generated in the first transition region 1117 by the shrinkage of the first connection portion 51 and the tensile stress generated in the first transition region 1117 by the deformation of the first sidewall portion 111 are not aligned in the same straight line near the portion of the first connection interface 511 extending obliquely relative to the second direction Y. This reduces the risk of fatigue cracking in the first transition region 1117 near the first connection interface 511.

[0648] In some embodiments, referring to Figures 32 to 37, the first connection interface 511 includes a first interface 5112, and the first interface 5112 extends obliquely from the first position 5111 toward the direction close to the end cover 12. Along the second direction Y, at least a portion of the first transition zone 1117 is located between the first interface 5112 and the end cover 12.

[0649] It is understandable that the first interface 5112 extends obliquely relative to the second direction Y. The first interface 5112 can be a plane or a curved surface.

[0650] The first position 5111 is the lowest position of the first interface 5112 (the position closest to the first zone 1111), and the first interface 5112 extends obliquely from the first position 5111 toward the direction close to the end cover 12, that is, the first interface 5112 extends obliquely upward from the first position 5111 toward the direction close to the end cover 12.

[0651] Along the second direction Y, the first transition zone 1117 may be entirely located between the first interface 5112 and the end cover 12 , or only a portion of the first transition zone 1117 may be located between the first interface 5112 and the end cover 12 .

[0652] In this embodiment, along the second direction Y, at least part of the first transition zone 1117 is located between the first interface 5112 and the end cover 12, so that the first connecting portion 51 protects the first transition zone 1117. When the first side wall portion 111 is subjected to the expansion force of the electrode assembly 2, the first transition zone 1117 is deformed during the force process and is blocked by the first connecting portion 51, thereby reducing the possibility of fatigue cracking in the area of ​​the first transition zone 1117 near the first interface 5112.

[0653] In some embodiments, referring to FIG. 32 to FIG. 37 , the first interface 5112 is connected to the first outer surface 806 at a first position 5111 , and the first position 5111 is at least partially located in the first area 1111 .

[0654] As an example, the first interface 5112 intersects the first outer surface 806 at a first straight line extending along the third direction X. The first straight line is located at a first position 5111. The first interface 5112 is connected to the inner surface of the first transition region 1117 at a third position 5114. Along the first direction Z, the third position 5114 is farther from the first region 1111 than the first position 5111. The first transition region 1117 is generally triangular in shape.

[0655] In this embodiment, the first interface 5112 is connected to the first outer surface 806 at the first position 5111, and the first position 5111 is located in the first zone 1111, so that the first outer surface 806 extends to the first zone 1111 along the first direction Z toward one end of the first connection portion 51, and the portion of the first side wall portion 111 corresponding to the first outer surface 806 can better reinforce the end of the first zone 1111 toward the first connection portion 51, thereby reducing the possibility of fatigue cracking at the end of the first zone 1111 toward the first connection portion 51.

[0656] In some embodiments, referring to Figures 32 to 37, the first connection interface 511 includes a second interface 5113, and the second interface 5113 extends obliquely from the first position 5111 in a direction away from the end cover 12. Along the second direction Y, at least a portion of the first transition zone 1117 is located on the side of the second interface 5113 away from the end cover 12.

[0657] It is understandable that the second interface 5113 extends obliquely relative to the second direction Y. The second interface 5113 can be a plane or a curved surface. Along the second direction Y, at least a portion of the first connecting portion 51 is located between the second interface 5113 and the end cover 12 .

[0658] The first position 5111 is the lowest position of the second interface 5113 (the position closest to the first zone 1111), and the second interface 5113 extends obliquely from the first position 5111 in a direction away from the end cover 12, that is, the second interface 5113 extends obliquely upward from the first position 5111 in a direction away from the end cover 12.

[0659] Along the second direction Y, the first transition zone 1117 may be entirely located on the side of the second interface 5113 away from the end cover 12 , or only a portion of the first transition zone 1117 may be located on the side of the second interface 5113 away from the end cover 12 .

[0660] In this embodiment, along the second direction Y, at least a portion of the first transition zone 1117 is located on the side of the second interface 5113 away from the end cover 12, so that the first transition zone 1117 has a restrictive effect on the first connecting portion 51, reducing the possibility of the first connecting portion 51 falling off.

[0661] In some embodiments, referring to FIG. 32 to FIG. 37 , the second interface 5113 is connected to the first inner surface 804 at a first position 5111 , and the first position 5111 is at least partially located in the first area 1111 .

[0662] As an example, the second interface 5113 intersects the first inner surface 804 at a first straight line extending along the third direction X. The first straight line is located at a first position 5111. The second interface 5113 is connected to the outer surface of the first transition region 1117 at a fourth position 5115. Along the first direction Z, the fourth position 5115 is farther from the first region 1111 than the first position 5111. The first transition region 1117 is generally triangular in shape.

[0663] In this embodiment, the second interface 5113 is connected to the first inner surface 804 at the first position 5111, and the first position 5111 is at least partially located in the first zone 1111, so that the first inner surface 804 extends to the first zone 1111 along the first direction Z toward one end of the first connection portion 51, and the portion of the first side wall portion 111 corresponding to the first inner surface 804 can better reinforce the end of the first zone 1111 toward the first connection portion 51, thereby reducing the possibility of fatigue cracking at the end of the first zone 1111 toward the first connection portion 51.

[0664] In some embodiments, referring to Figures 32 to 37, the first connection interface 511 includes a first interface 5112 and a second interface 5113. The first interface 5112 extends obliquely from the first position 5111 toward the direction close to the end cover 12, and the second interface 5113 extends obliquely from the first position 5111 toward the direction away from the end cover 12. Along the second direction Y, a portion of the first transition zone 1117 is located between the first interface 5112 and the end cover 12, and another portion of the first transition zone 1117 is located on the side of the second interface 5113 away from the end cover 12.

[0665] As an example, the first interface 5112 is connected to the inner surface of the first transition region 1117 at a third position 5114 , and the second interface 5113 is connected to the outer surface of the first transition region 1117 at a fourth position 5115 .

[0666] In some embodiments, the hardness of the first transition region 1117 is less than the hardness of the second region 1112 ; and / or the hardness of the first transition region 1117 is less than the hardness of the first connecting portion 51 .

[0667] As an example, the hardness of the second region 1112 is less than the hardness of the first connection portion 51 .

[0668] As an example, the type of hardness of the first transition region 1117 , the type of hardness of the first region 1111 , the type of hardness of the second region 1112 , and the type of hardness of the first connecting portion 51 are all Vickers hardness.

[0669] If the hardness of the first transition region 1117 is lower than the hardness of the second region 1112, the first transition region 1117 with lower hardness is connected to the first connecting portion 51. This can alleviate the rigid pulling between the first side wall portion 111 and the first connecting portion 51 when the first side wall portion 111 is deformed, thereby reducing the possibility of the first side wall portion 111 and the first connecting portion 51 separating. If the hardness of the first transition region 1117 is lower than the hardness of the first connecting portion 51, the first transition region 1117 is more easily deformed than the first connecting portion 51, thereby alleviating the rigid pulling between the first side wall portion 111 and the first connecting portion 51 when the first side wall portion 111 is deformed, thereby reducing the possibility of the first side wall portion 111 and the first connecting portion 51 separating.

[0670] In some embodiments, referring to FIG. 32 to FIG. 37 , the first connection interface 511 is closer to the second region 1112 than the outer surface 121 of the end cover.

[0671] Along the first direction Z, the surface of the end cover 12 facing away from the electrode assembly 2 is the outer surface 121 of the end cover.

[0672] 32 to 37 , along the first direction Z, the third position 5114 and the first position 5111 are both closer to the second region 1112 than to the outer surface 121 of the end cover.

[0673] 32 to 37 , along the first direction Z, the fourth position 5115 and the first position 5111 are both closer to the second region 1112 than to the outer surface 121 of the end cover.

[0674] 32 to 37 , along the first direction Z, the third position 5114 , the fourth position 5115 , and the first position 5111 are all closer to the second region 1112 than to the outer surface 121 of the end cover.

[0675] In this embodiment, the first connection interface 511 is closer to the second area 1112 along the first direction Z than the outer surface 121 of the end cover, so that the first connection portion 51 can sink to a deeper position of the first side wall portion 111, which can effectively improve the connection strength between the first side wall portion 111 and the end cover 12.

[0676] In some embodiments, referring to Figures 7, 15, 16, 18, 19, 22, 23, 31, 38 and 39, the shell 11 also includes a second side wall portion 112 and a corner wall 113. The first side wall portion 111, the corner wall 113 and the second side wall portion 112 are arranged along the circumference of the opening, and the corner wall 113 connects the first side wall portion 111 and the second side wall portion 112.

[0677] The second side wall portion 112 and the end cover 12 can be welded to form the third connecting portion 5, and the first connecting portion 51 and the third connecting portion 5 are both part of the connecting portion 5. The second side wall portion 112 can be a uniform thickness structure or a non-uniform thickness structure.

[0678] The first side wall portions 111 and the second side wall portions 112 in the housing 11 are indirectly connected via the corner walls 113 , and the sum of the number of the first side wall portions 111 and the number of the second side wall portions 112 is equal to the number of the corner walls 113 .

[0679] As an example, the first side wall portion 111, the second side wall portion 112 and the corner wall 113 are integrally formed. The cross section of the outer surface and / or the inner surface of the corner wall 113 may be arc-shaped, and the cross section is perpendicular to the first direction Z.

[0680] In this embodiment, the first side wall portion 111 and the second side wall portion 112 are connected by a corner wall 113, so that the first side wall portion 111 can transition to the second side wall portion 112 through the corner wall 113, which can effectively reduce the risk of stress concentration at the corner position of the shell 11.

[0681] In some embodiments, referring to Figures 38 to 42 , the corner wall 113 is welded to the end cap 12 to form the second connecting portion 52. The corner wall 113 includes a third region 1131 and a fourth region 1132 arranged along the first direction Z. The hardness of the third region 1131 is less than that of the fourth region 1132. The third region 1131 is located between the fourth region 1132 and the second connecting portion 52.

[0682] The third region 1131 is located between the fourth region 1132 and the second connection portion 52 . The third region 1131 with lower hardness is closer to the second connection portion 52 than the fourth region 1132 .

[0683] The third region 1131 and the second connection portion 52 may be directly connected.

[0684] The third region 1131 and the fourth region 1132 may be directly connected or indirectly connected.

[0685] The second connecting portion 52 can correspond one-to-one with the corner wall 113. The second connecting portion 52 is the portion where the weld mark is formed after the end cover 12 and the corner wall 113 are welded together. The second connecting portion 52 can be formed by a portion formed on the end cover 12 and another portion formed on the corner wall 113. The corner wall 113 and the end cover 12 can be formed by a saddle weld or a penetration weld to form the second connecting portion 52. The second connecting portion 52 and the first connecting portion 51 are both part of the connecting portion 5.

[0686] As an example, the hardness of the third region and the hardness of the fourth region are both of the Vickers hardness type.

[0687] As an example, the type of hardness of the second connection portion is Vickers hardness.

[0688] In the embodiment of the present application, the hardness of the third region 1131 is relatively low, so that the third region 1131 has relatively high toughness. The third region 1131 with relatively high toughness releases part of the expansion force of the electrode assembly 2 on the corner wall 113, which is beneficial to reducing the possibility of the corner wall 113 cracking in the second connecting portion 52 of the second side wall portion 112.

[0689] It should be noted that the third region 1131 has a lower hardness, which makes the third region 1131 have higher toughness. The third region 1131 with higher toughness may produce fatigue cracks under the action of the periodic expansion force of the repeated expansion and contraction of the electrode assembly 2.

[0690] In some embodiments, referring to Figures 38 to 42, the corner wall 113 has a third inner surface 810 and a fourth inner surface 811 facing the electrode assembly 2 and a third outer surface 812 and a fourth outer surface 813 away from the electrode assembly 2, the third inner surface 810 and the fourth inner surface 811 are connected in sequence along the direction of the end cover 12 pointing to the electrode assembly 2, the third inner surface 810 and the third outer surface 812 are at least partially formed in the third area 1131, the fourth inner surface 811 and the fourth outer surface 813 are at least partially formed in the fourth area 1132, and the distance between the third inner surface 810 and the third outer surface 812 along the thickness direction of the corner wall 113 is greater than the distance between the fourth inner surface 811 and the fourth outer surface 813 along the thickness direction of the corner wall 113.

[0691] The distances between the third outer surface 812 and each position on the third inner surface 810 along the thickness direction of the corner wall 113 can be equal or unequal. The distances between the third outer surface 812 and each position on the fourth inner surface 811 along the thickness direction of the corner wall 113 can be equal or unequal. When the distances between each position on the third inner surface 810 and the third outer surface 812 along the thickness direction of the corner wall 113 are not equal, or the distances between each position on the fourth inner surface 811 and the third outer surface 812 along the thickness direction of the corner wall 113 are not equal, the minimum distance between the third inner surface 810 and the third outer surface 812 along the thickness direction of the corner wall 113 is greater than the maximum distance between the fourth inner surface 811 and the fourth outer surface 813 along the thickness direction of the corner wall 113, so as to achieve that the distance between the third inner surface 810 and the third outer surface 812 along the thickness direction of the corner wall 113 is greater than the distance between the fourth inner surface 811 and the fourth outer surface 813 along the thickness direction of the corner wall 113.

[0692] The third inner surface 810 is closer to the electrode assembly 2 relative to the fourth inner surface 811 along the thickness direction of the corner wall 113, and / or the third outer surface 812 is farther away from the electrode assembly 2 relative to the fourth outer surface 813 along the thickness direction of the corner wall 113. Referring to Figures 38 to 41, the third inner surface 810 is closer to the electrode assembly 2 relative to the fourth inner surface 811 along the thickness direction of the corner wall 113, and the third outer surface 812 and the fourth outer surface 813 are coplanar. Referring to the figures, the third outer surface 812 is farther away from the electrode assembly 2 relative to the fourth outer surface 813 along the thickness direction of the corner wall 113, and the third inner surface 810 and the fourth inner surface 811 are coplanar.

[0693] As an example, referring to FIG. 42 , the distance between the third inner surface 810 and the third outer surface 812 along the thickness direction of the corner wall 113 is D8, and the distance between the fourth inner surface 811 and the fourth outer surface 813 along the thickness direction of the corner wall 113 is D9, and D8>D9.

[0694] In the embodiment of the present application, the distance between the third inner surface 810 and the third outer surface 812 along the thickness direction of the corner wall 113 is greater than the distance between the fourth inner surface 811 and the fourth outer surface 813 along the thickness direction of the corner wall 113. The thickness of the portion of the corner wall 113 corresponding to the third inner surface 810 is larger, and the third inner surface 810 and the third outer surface 812 are at least partially formed in the third area 1131, so that the portion of the corner wall 113 with a larger thickness corresponding to the third inner surface 810 can reinforce the third area 1131 with higher toughness, which is beneficial to suppress fatigue cracking of the third area 1131 and improve the service life of the battery cell 10.

[0695] 38 and 39 , the third region 1131 is directly connected to the first region 1111 , the third inner surface 810 extends to one end of the third region 1131 facing the first region 1111 , and the first inner surface 804 extends to one end of the first region 1111 facing the third region 1131 .

[0696] As an example, the third area 1131 and the first area 1111 are integrally formed, and both ends of the first area 1111 along the third direction X are connected to the third area 1131 .

[0697] In the embodiment of the present application, the third inner surface 810 extends to one end of the third zone 1131 toward the first zone 1111, the first inner surface 804 extends to one end of the first zone 1111 toward the third zone 1131, the first side wall portion 111 at the first inner surface 804 and the corner wall 113 at the third inner surface 810 are connected into a whole, and the first side wall portion 111 at the first inner surface 804 and the corner wall 113 at the third inner surface 810 have a mutually promoting effect, so that the first side wall portion 111 at the first inner surface 804 and the corner wall 113 at the third inner surface 810 are both well reinforced, thereby reducing the possibility of cracking of the shell 11. Since the first inner surface 804 and the first outer surface 806 are at least partially formed in the first zone 1111, and the third inner surface 810 and the third outer surface 812 are at least partially formed in the third zone 1131, the first side wall portion 111 in the first inner surface 804 and the corner wall 113 in the third inner surface 810 have a mutually promoting effect and can also affect the first zone 1111 and the third zone 1131, thereby strengthening the first zone 1111 and the third zone 1131 and reducing the possibility of fatigue cracking in the first zone 1111 and the third zone 1131.

[0698] In some embodiments, referring to Figures 38 and 39, the corner wall 113 has a first connection end 1133 and a second connection end 1134, the first side wall portion 111 is connected to the first connection end 1133, the second side wall portion 112 is connected to the second connection end 1134, and the distance between the third inner surface 810 and the third outer surface 812 along the thickness direction of the corner wall 113 is a fourth preset thickness, and the fourth preset thickness tends to decrease along the direction from the first connection end 1133 to the second connection end 1134.

[0699] As an example, the fourth preset thickness gradually decreases in the direction from the first connection end 1133 to the second connection end 1134, the second side wall portion 112 is an equal thickness structure, the third inner surface 810 connects the first inner surface 804 and the inner surface of the second side wall portion 112, and the third outer surface 812 connects the first outer surface 806 and the outer surface of the second side wall portion 112.

[0700] When first sidewall portion 111 is subjected to the expansion force of electrode assembly 2 in the second direction Y, deformation of first sidewall portion 111 may cause deformation of corner wall 113 as well. Along the circumference of the opening, the closer corner wall 113 is to first sidewall portion 111, the greater the impact of first sidewall portion 111 is on corner wall 113. The area closer to first sidewall portion 111 experiences greater deformation. The fourth predetermined thickness decreases in the direction from first connection end 1133 to second connection end 1134, increasing the strength of third region 1131 near first sidewall portion 111 along the circumference of the opening. This reduces the likelihood of cracking in third region 1131, which has lower hardness, towards the end of first sidewall portion 111. By strengthening third region 1131, which has higher toughness, the material used in the portion of corner wall 113 corresponding to third inner surface 810 is reduced, thereby reducing production costs.

[0701] In some embodiments, referring to Figures 38 to 40 , as well as Figures 44 , 46 and 48 , the third region 1131 is directly connected to the second connection portion 52 , and the third inner surface 810 extends to one end of the third region 1131 facing the second connection portion 52 .

[0702] The third region 1131 and the second connection portion 52 may be in point contact, line contact, or surface contact to achieve direct connection between the two.

[0703] In this embodiment, the third zone 1131 is directly connected to the second connection part 52, and the third inner surface 810 extends to the end of the third zone 1131 facing the second connection part 52, so that the end of the third zone 1131 with higher toughness facing the second connection part 52 is better strengthened, which is beneficial to reducing the possibility of fatigue cracking at the end of the third zone 1131 facing the second connection part 52.

[0704] In some embodiments, please refer to Figures 43 to 48, the corner wall 113 also includes a second transition zone 1135, the second transition zone 1135 is connected to the end of the third zone 1131 along the first direction Z away from the fourth zone 1132, the second transition zone 1135 is connected to the second connecting portion 52, and the connection position between the second transition zone 1135 and the second connecting portion 52 forms a second connection interface 521, the second connection interface 521 has a second position 5211 that is closest to the third zone 1131 along the first direction Z, and the second position 5211 is located at the end of the third zone 1131 along the first direction Z away from the fourth zone 1132.

[0705] The second transition zone 1135 may be the portion of the corner wall 113 connecting the second connecting portion 52 and the third zone 1131. The second transition zone 1135 may have a uniform thickness or a non-uniform thickness. The thickness of the second transition zone 1135 may be less than the distance between the third inner surface 810 and the third outer surface 812 along the thickness direction of the corner wall 113. As an example, in the embodiments shown in Figures 43 to 48, the thickness of the second transition zone 1135 gradually decreases along the direction from the fourth zone 1132 to the third zone 1131.

[0706] The second connection interface 521 is formed at the connection position between the second transition area 1135 and the second connection portion 52. The second transition area 1135 and the second connection portion 52 are separated at the second connection interface 521. The second connection interface 521 can be a plane or a curved surface.

[0707] The third region 1131 and the second transition region 1135 are separated by a second boundary surface V. The second boundary surface V is a virtual plane. The second boundary surface V passes through the second position 5211. The second boundary surface V is perpendicular to the first direction Z. The second transition region 1135 and the second connecting portion 52 are located above the second boundary surface V, and the third region 1131 is located below the second boundary surface V.

[0708] In this embodiment, the second transition zone 1135 is connected to the second connection portion 52 to form a second connection interface 521, so that the second transition zone 1135 and the second connection portion 52 have a sufficiently large contact area, thereby improving the firmness of the corner wall 113 and the end cover 12 after welding.

[0709] In some embodiments, referring to FIG. 43 to FIG. 48 , at least a portion of the second connection interface 521 extends obliquely relative to the thickness direction of the corner wall 113 .

[0710] The second connection interface 521 may extend obliquely as a whole compared to the thickness direction of the corner wall 113 , or the second connection interface 521 may extend obliquely as a part compared to the thickness direction of the corner wall 113 .

[0711] Near the portion of the second connection interface 521 that extends obliquely in the thickness direction of the corner wall 113, the tensile stress generated by the second connection portion 52 on the second transition zone 1135 due to contraction and the tensile stress generated by the second transition zone 1135 on the second connection portion 52 due to deformation of the corner wall 113 are not on the same straight line, thereby reducing the risk of fatigue cracking in the area of ​​the second transition zone 1135 near the second connection interface 521.

[0712] In some embodiments, referring to Figures 43 to 48, the second connection interface 521 includes a third interface 5212, and the third interface 5212 extends obliquely from the second position 5211 toward the direction close to the end cover 12. Along the thickness direction of the corner wall 113, at least a portion of the second transition zone 1135 is located between the third interface 5212 and the end cover 12.

[0713] It is understandable that the third interface 5212 extends obliquely relative to the thickness direction of the corner wall 113. The third interface 5212 can be a plane or a curved surface.

[0714] The second position 5211 is the lowest position of the third interface 5212 (the position closest to the third zone 1131), and the third interface 5212 extends obliquely from the second position 5211 toward the direction close to the end cover 12, that is, the third interface 5212 extends obliquely upward from the second position 5211 toward the direction close to the end cover 12.

[0715] Along the thickness direction of the corner wall 113 , the second transition zone 1135 may be entirely located between the third interface 5212 and the end cover 12 , or only a portion of the second transition zone 1135 may be located between the third interface 5212 and the end cover 12 .

[0716] In this embodiment, along the thickness direction of the corner wall 113, at least a portion of the second transition zone 1135 is located between the third interface 5212 and the end cover 12, and the second connecting portion 52 protects the second transition zone 1135. When the second transition zone 1135 deforms outward, it will be blocked by the second connecting portion 52, thereby reducing the risk of fatigue cracking in the area of ​​the second transition zone 1135 near the third interface 5212.

[0717] In some embodiments, referring to FIG. 43 to FIG. 48 , the third interface 5212 is connected to the third outer surface 812 at the second position 5211 , and the second position 5211 is located in the third area 1131 .

[0718] As an example, the third interface 5212 intersects the third outer surface 812 at a second straight line extending along the third direction X. The second straight line is located at a second position 5211. The third interface 5212 connects to the inner surface of the second transition region 1135 at a fifth position 5214. Along the first direction Z, the fifth position 5214 is further from the third region 1131 than the second position 5211. The second transition region 1135 is generally triangular in shape.

[0719] In this embodiment, the third interface 5212 is connected to the third outer surface 812 at the second position 5211, and the second position 5211 is located in the third zone 1131, so that the third outer surface 812 extends to the end of the third zone 1131 along the first direction Z toward the second connection portion 52. The portion of the corner wall 113 corresponding to the third outer surface 812 can better reinforce the end of the third zone 1131 toward the second connection portion 52, thereby reducing the possibility of fatigue cracking at the end of the third zone 1131 with lower hardness toward the second connection portion 52.

[0720] In some embodiments, referring to Figures 43 to 48, the second connection interface 521 includes a fourth interface 5213, and the fourth interface 5213 extends obliquely from the second position 5211 in a direction away from the end cover 12. Along the thickness direction of the corner wall 113, at least a portion of the second transition zone 1135 is located on the side of the fourth interface 5213 away from the end cover 12.

[0721] It is understood that the fourth interface 5213 extends obliquely relative to the thickness direction of the corner wall 113. The fourth interface 5213 can be a flat surface or a curved surface. Along the thickness direction of the corner wall 113, at least a portion of the second connecting portion 52 is located between the fourth interface 5213 and the end cap 12.

[0722] The second position 5211 is the lowest position of the fourth interface 5213 (the position closest to the first zone 1111), and the fourth interface 5213 extends obliquely from the second position 5211 in the direction away from the end cover 12, that is, the fourth interface 5213 extends obliquely upward from the second position 5211 in the direction away from the end cover 12.

[0723] Along the thickness direction of the corner wall 113 , the second transition zone 1135 may be entirely located on the side of the fourth interface 5213 away from the end cover 12 , or only partially located on the side of the fourth interface 5213 away from the end cover 12 .

[0724] In this embodiment, along the thickness direction of the corner wall 113, at least a portion of the second transition zone 1135 is located on the side of the fourth interface 5213 away from the end cover 12, so that the second transition zone 1135 has a restrictive effect on the second connecting portion 52, thereby reducing the risk of the second connecting portion 52 falling off.

[0725] In some embodiments, referring to FIG. 43 to FIG. 48 , the fourth interface 5213 is connected to the third inner surface 810 at the second position 5211 , and the second position 5211 is located in the third area 1131 .

[0726] As an example, the fourth interface 5213 intersects the third inner surface 810 at a second straight line extending along the third direction X. The second straight line is located at a second position 5211. The fourth interface 5213 is connected to the outer surface of the second transition region 1135 at a sixth position 5215. Along the first direction Z, the sixth position 5215 is further away from the third region 1131 than the second position 5211. The second transition region 1135 is generally triangular in shape.

[0727] In this embodiment, the fourth interface 5213 is connected to the third inner surface 810 at the second position 5211, and the second position 5211 is located in the third zone 1131, so that the third inner surface 810 extends to the end of the third zone 1131 along the first direction Z toward the second connection portion 52. The portion of the corner wall 113 corresponding to the third inner surface 810 can better strengthen the end of the third zone 1131 toward the second connection portion 52, thereby reducing the possibility of fatigue cracking at the end of the third zone 1131 with lower hardness toward the second connection portion 52.

[0728] In some embodiments, the second connection interface 521 includes a third interface 5212 and a fourth interface 5213, the third interface 5212 extends obliquely from the second position 5211 toward the direction close to the end cover 12, and the fourth interface 5213 extends obliquely from the second position 5211 toward the direction away from the end cover 12. Along the thickness direction of the corner wall 113, a portion of the second transition zone 1135 is located between the third interface 5212 and the end cover 12, and another portion of the second transition zone 1135 is located on the side of the fourth interface 5213 away from the end cover 12.

[0729] As an example, the third interface 5212 is connected to the inner surface of the second transition region 1135 at a fifth position 5214 , and the fourth interface 5213 is connected to the outer surface of the second transition region 1135 at a sixth position 5215 .

[0730] In some embodiments, the hardness of the second transition region 1135 is less than the hardness of the fourth region 1132 ; and / or the hardness of the second transition region 1135 is less than the hardness of the second connecting portion 52 .

[0731] As an example, the hardness of the fourth region 1132 is less than the hardness of the second connection portion 52 .

[0732] If the hardness of the second transition region 1135 is less than that of the fourth region 1132, the second transition region 1135 with a lower hardness is connected to the second connecting portion 52. This can alleviate the rigid pulling between the corner wall 113 and the second connecting portion 52 when it deforms, thereby reducing the possibility of the corner wall 113 and the second connecting portion 52 separating. If the hardness of the second transition region 1135 is less than that of the second connecting portion 52, the second transition region 1135 is more susceptible to deformation than the second connecting portion 52. This can alleviate the rigid pulling between the corner wall 113 and the second connecting portion 52 when it deforms, thereby reducing the possibility of the corner wall 113 and the second connecting portion 52 separating.

[0733] In some embodiments, referring to FIG. 43 to FIG. 48 , the second connection interface 521 is closer to the fourth region 1132 than the outer surface 121 of the end cover.

[0734] In the embodiments shown in FIG. 43 to FIG. 48 , along the first direction Z, the fifth position 5214 and the second position 5211 are both closer to the fourth region 1132 than to the outer surface 121 of the end cover.

[0735] In the embodiments shown in FIG. 43 to FIG. 48 , along the first direction Z, the sixth position 5215 and the second position 5211 are both closer to the fourth region 1132 than to the outer surface 121 of the end cover.

[0736] In the embodiments shown in FIG. 43 to FIG. 48 , along the first direction Z, the fifth position 5214 , the sixth position 5215 , and the second position 5211 are all closer to the fourth region 1132 than to the outer surface 121 of the end cover.

[0737] In this embodiment, the second connection interface 521 is closer to the fourth area 1132 along the first direction Z than the outer surface 121 of the end cover, so that the second connection part 52 can sink to a deeper position of the corner wall 113, which can effectively improve the connection strength between the corner wall 113 and the end cover 12.

[0738] In some embodiments, the hardness of the third region 1131 is lower than the hardness of the second connection portion 52 .

[0739] In some embodiments, referring to Figures 7, 16, 19 and 23, the shell 11 includes two first side wall portions 111 and two second side wall portions 112. The two first side wall portions 111 are arranged opposite to each other along the second direction Y, and the two second side wall portions 112 are arranged opposite to each other along the third direction X. The first direction Z, the second direction Y and the third direction X are perpendicular to each other.

[0740] Corner walls 113 are provided at both ends of the first side wall portion 111 along the third direction X, and corner walls 113 are provided at both ends of the second side wall portion 112 along the second direction Y. It is understandable that there are four corner walls 113 in the housing 11 .

[0741] In this embodiment, the housing 11 is substantially in the shape of a rectangular parallelepiped. The size of the housing 11 can be made larger, which is conducive to meeting the large capacity requirement of the battery cell 10.

[0742] In some embodiments, referring to FIG. 49 , the first sidewall portion 111 has a limiting surface 1115 facing the end cover 12 , and the limiting surface 1115 abuts against the end cover 12 to limit the end cover 12 from moving toward the electrode assembly 2 .

[0743] The limiting surface 1115 can be perpendicular to the first direction Z. The limiting surface 1115 can be the end surface of the first side wall portion 111 at one end of the opening of the shell 11. The limiting surface 1115 can also be a step surface on the first side wall portion 111, and the step surface is a certain distance away from the end surface of the first side wall portion 111 at one end of the opening of the shell 11.

[0744] The limiting surface 1115 limits the end cover 12, reducing the risk of the end cover 12 moving toward the electrode assembly 2 when welded to the shell 11, which can effectively improve the welding quality of the end cover 12 and the shell 11 and reduce the difficulty of welding the end cover 12 and the shell 11.

[0745] In some embodiments, referring to FIG. 49 , the first side wall portion 111 further includes a limiting area 1116 disposed on the limiting surface 1115 . The limiting area 1116 and the end cover 12 are disposed opposite to each other along the second direction Y. The limiting area 1116 and the end cover 12 are welded to form a first connecting portion 51 .

[0746] As an example, the end cover 12 is at least partially accommodated in the housing 11 , so that the limiting area 1116 and the end cover 12 are arranged opposite to each other along the second direction Y.

[0747] After the limiting area 1116 is welded to the end cover 12, a portion of the limiting area 1116 and a portion of the end cover 12 may be fused together to form a first connecting portion 51, and the remaining portion of the limiting area 1116 may form at least a portion of the first transition area 1117.

[0748] The limiting area 1116 can also limit the end cover 12, reducing the risk of the end cover 12 moving along the thickness direction of the first side wall portion 111 when welding the end cover 12 to the shell 11, further improving the welding quality of the end cover 12 and the shell 11, and reducing the difficulty of welding the end cover 12 and the shell 11.

[0749] In some embodiments, in the embodiments of Figures 7, 16, 19, and 23, the second sidewall portion 112 has a uniform thickness structure. In other embodiments, the second sidewall portion 112 may also have a non-uniform thickness structure. The structure of the second sidewall portion 112 may be the same as that of the first sidewall portion 111. For example, the second sidewall portion 112 includes a fifth region and a sixth region arranged along the first direction Z. The hardness of the fifth region is lower than that of the sixth region. The fifth region is located between the third connecting portion 5 and the sixth region. This can reduce the possibility of cracking of the third connecting portion 5 corresponding to the second sidewall portion 112. The structure of the fifth region can be the same as that of the first region 1111, and the structure of the sixth region can be the same as that of the second region 1112.

[0750] In some embodiments, the hardness of the fifth region is lower than the hardness of the third connecting portion 5 .

[0751] In some embodiments, the second side wall portion 112 has a fifth inner surface and a sixth inner surface facing the electrode assembly 2 and a seventh outer surface and an eighth outer surface facing away from the electrode assembly 2, the fifth inner surface has the same structure as the first inner surface 804, the seventh outer surface has the same structure as the first outer surface 806, the sixth inner surface has the same structure as the second inner surface 805, and the eighth outer surface has the same structure as the second outer surface 807.

[0752] In some embodiments, in an embodiment where the first sidewall portion includes a fifth region and a sixth region, the third region 1131 may connect the first region 1111 and the fifth region, and the fourth region 1132 may connect the second region 1112 and the sixth region.

[0753] In some embodiments, referring to FIG. 12 and FIG. 13 , the electrode assembly 2 is a laminated structure, and the electrode assembly 2 includes a plurality of positive electrode sheets 22 and a plurality of negative electrode sheets 23 , and the plurality of positive electrode sheets 22 and the plurality of negative electrode sheets 23 are stacked along the second direction Y.

[0754] As an example, the positive electrode sheets 22 and the negative electrode tabs 21 b in the electrode assembly 2 are alternately arranged along the second direction Y, and a separator 24 is provided between the positive electrode sheet 22 and the negative electrode sheet 23 .

[0755] In this embodiment, the electrode assembly 2 is a laminated structure, which is more compact and has a stronger anti-extrusion capability.

[0756] In some embodiments, referring to FIG. 12 and FIG. 13 , the number of negative electrode sheets 23 is greater than the number of positive electrode sheets 22 , and one positive electrode sheet 22 is disposed between two adjacent negative electrode sheets 23 .

[0757] As an example, there is one more negative electrode tab 23 than positive electrode tab 22 .

[0758] In some embodiments, referring to FIG. 12 and FIG. 13 , each negative electrode plate 23 is provided with a negative electrode tab 21 b ; and / or each positive electrode plate 22 is provided with a positive electrode tab 21 a .

[0759] In some embodiments, the first sidewall portion 111 has a first inner surface 804 and a second inner surface 805 facing the electrode assembly 2, and a first outer surface 806 and a second outer surface 807 facing away from the electrode assembly 2. The first inner surface 804 and the second inner surface 805 are sequentially connected along the direction from the end cap 12 to the electrode assembly 2, and the first outer surface 806 and the second outer surface 807 are sequentially connected along the direction from the end cap 12 to the electrode assembly 2. The first inner surface 804 and the first outer surface 806 are at least partially formed in the first region 1111, and the second inner surface 805 and the second outer surface 807 are at least partially formed in the second region 1112. The distance between the first inner surface 804 and the first outer surface 806 along the second direction Y is greater than the distance between the second inner surface 805 and the second outer surface 807 along the second direction Y. Along the third direction X, the dimension of the first inner surface 804 is greater than the dimension of the positive electrode tab 22 and / or the dimension of the negative electrode tab 23. The first direction Z, the second direction Y, and the third direction X are perpendicular to each other.

[0760] If along the third direction X, the size of the first inner surface 804 is larger than the size of the positive electrode sheet 22, the first inner surface 804 extends beyond at least one end of the positive electrode sheet 22 along the third direction X; if along the third direction X, the size of the first inner surface 804 is larger than the size of the negative electrode sheet 23, the first inner surface 804 extends beyond at least one end of the negative electrode sheet 23 along the third direction X.

[0761] As an example, along the third direction X, the size of the projection of the first inner surface 804 overlapping the first region 1111 along the second direction Y is larger than the size of the positive electrode tab 22 and / or the negative electrode tab 23 .

[0762] In this embodiment, along the third direction X, the size of the first inner surface 804 is larger than the size of the positive electrode sheet 22 and / or the size of the negative electrode sheet 23, so that the size of the first inner surface 804 along the third direction X is larger, so that the strength of the first side wall portion 111 in more areas along the third direction X is enhanced, which is beneficial to reducing the possibility of cracking of the shell 11.

[0763] In some embodiments, referring to FIG. 50 , the battery cell 10 further includes two electrode terminals 3 disposed on the end cap 12. The two electrode terminals 3 have opposite polarities and are both electrically connected to the electrode assembly 2. The end cap 12 is provided with an extraction hole. The electrode terminal 3 includes a terminal body 31, a first stopper 32, and a second stopper 33. The terminal body 31 connects the first stopper 32 and the second stopper 33. The terminal body 31 passes through the extraction hole. Along the first direction Z, the first stopper 32 is located on the side of the end cap 12 facing away from the electrode assembly 2, and the second stopper 33 is located on the side of the end cap 12 facing the electrode assembly 2.

[0764] The first limiting portion 32 and the second limiting portion 33 have a limiting function. The first limiting portion 32 and the second limiting portion 33 are respectively connected to the two ends of the terminal body 31. The first limiting portion 32 and the second limiting portion 33 cooperate to limit the terminal body 31 from being separated from the lead-out hole. Along the first direction Z, the projected area of ​​the first limiting portion 32 and the projected area of ​​the second limiting portion 33 are both larger than the projected area of ​​the terminal body 31. The projected area of ​​the first limiting portion 32 can be larger than the projected area of ​​the second limiting portion 33, or the projected area of ​​the second limiting portion 33 can be larger than the projected area of ​​the first limiting portion 32. The first limiting portion 32, the second limiting portion 33, and the terminal body 31 can be integrally formed, or one of the first limiting portion 32 and the second limiting portion 33 can be integrally formed with the terminal body 31, while the other is separately provided and connected to the terminal body 31.

[0765] As an example, the battery cell 10 may also include a first insulating member 6 and a second insulating member 7, the first insulating member 6 being at least partially disposed between the electrode terminal 3 and the end cover 12 to insulate and isolate the electrode terminal 3 and the end cover 12, and the second insulating member 7 being disposed on the side of the end cover 12 facing the electrode assembly 2 to insulate and isolate the electrode assembly 2 and the end cover 12.

[0766] In this embodiment, the electrode terminal 3 can be installed on the end cover 12 by riveting, which has low installation difficulty and better economy.

[0767] In some embodiments, referring to FIG. 10 and FIG. 11 , the electrode assembly 2 has a straight region 25 , and the portion of the positive electrode sheet 22 located in the straight region 25 and the portion of the negative electrode sheet 23 located in the straight region 25 are stacked along the second direction Y.

[0768] The straight region 25 is the straight portion of the electrode assembly 2. The portion of the positive electrode sheet 22 located in the straight region 25 is generally straight, and the portion of the negative electrode sheet 23 located in the straight region 25 is generally straight. As an example, the portion of the positive electrode sheet 22 located in the straight region 25 and the portion of the negative electrode sheet 23 located in the straight region 25 are both flat plate structures. If the electrode assembly 2 has a wound structure, the electrode assembly 2 is a wound electrode assembly 2, and a portion of the electrode assembly 2 may be the straight region 25. If the electrode assembly 2 has a laminated structure, the electrode assembly 2 is a laminated electrode assembly 2, and the entire electrode assembly 2 may be the straight region 25. The second direction Y is the stacking direction of the portion of the positive electrode sheet 22 located in the straight region 25 and the portion of the negative electrode sheet 23 located in the straight region 25.

[0769] As an example, the electrode assembly 2 may further include a separator 24, which is provided between the positive electrode sheet 22 and the negative electrode sheet 23. The separator 24 is used to separate the positive electrode sheet 22 from the negative electrode sheet 23. The portion of the positive electrode sheet 22 located in the straight region 25, the portion of the negative electrode sheet 23 located in the straight region 25, and the portion of the separator 24 located in the straight region 25 are stacked along the second direction Y.

[0770] The second direction Y is the stacking direction of the positive electrode tabs 22 and the negative electrode tabs 23 located in the straight region 25. During cycling, the electrode assembly 2 expands more significantly along the second direction Y, and the first sidewall 111 is more significantly affected by the expansion of the electrode assembly 2. However, the higher toughness of the first region 1111 relieves the expansion force of the electrode assembly 2 on the first sidewall 111, thereby reducing the possibility of cracking in the first connecting portion 51 of the first sidewall 111.

[0771] As an example, when the first inner surface 804 and the first outer surface 806 are at least partially formed in the first zone 1111, the thicker portion of the first side wall portion 111 corresponding to the first inner surface 804 can reinforce the first zone 1111 with lower hardness and reduce the possibility of fatigue cracking of the first zone 1111 with higher toughness itself.

[0772] In some embodiments, referring to Figures 10 to 13, the electrode assembly 2 includes an adjacent fifth outer surface 27 and a sixth outer surface, the fifth outer surface 27 is perpendicular to the second direction Y, the area of ​​the fifth outer surface 27 is larger than the area of ​​the sixth outer surface, and the fifth outer surface 27 is arranged opposite to the first side wall portion 111 along the second direction Y.

[0773] The fifth outer surface 27 is the surface of the outer surface of the electrode assembly 2 that is perpendicular to the second direction Y, and the sixth outer surface is the surface of the outer surface of the electrode assembly 2 that is adjacent to the fifth outer surface 27. The fifth outer surface 27 is arranged along the second direction Y facing the first side wall portion 111. The fifth outer surface 27 can be a plane. The fifth outer surface 27 can be the surface with the largest area among the outer surfaces of the electrode assembly 2, or it can be other than the surface with the largest area among the outer surfaces of the electrode assembly 2. The sixth outer surface can be a plane or can be at least partially an arc surface. It should be noted that the fifth outer surface 27 is approximately perpendicular to the second direction Y, which should also be understood as the fifth outer surface 27 being perpendicular to the second direction Y.

[0774] As an example, there are two fifth outer surfaces 27 and two sixth outer surfaces, the two fifth outer surfaces 27 are arranged opposite to each other along the second direction Y, and the two sixth outer surfaces are arranged opposite to each other along the third direction X. The positive electrode tab 21a and the negative electrode tab 21b protrude from the surface of the electrode assembly 2 along the first direction Z. The outermost part of the electrode assembly 2 along the second direction Y is the insulating member 24. The fifth outer surface 27 is formed on the insulating member 24. The first direction Z, the second direction Y and the third direction X are perpendicular to each other.

[0775] In this embodiment, the area of ​​the fifth outer surface 27 is larger than that of the sixth outer surface, resulting in a greater expansion force being applied to the first sidewall portion 111 of the housing 11, which is located opposite the fifth outer surface 27. The higher toughness of the first region 1111 relieves the expansion force exerted by the electrode assembly 2 on the first sidewall portion 111, thereby reducing the possibility of cracking in the first connecting portion 51 of the first sidewall portion 111.

[0776] As an example, when the first inner surface 804 and the first outer surface 806 are at least partially formed in the first zone 1111, the thicker portion of the first side wall portion 111 corresponding to the first inner surface 804 can reinforce the first zone 1111 with higher toughness, and can reduce the possibility of fatigue cracking of the first zone 1111 with higher toughness itself.

[0777] In some embodiments, referring to FIG. 10 to FIG. 13 , the fifth outer surface 27 is the surface with the largest area among the outer surfaces of the electrode assembly 2 .

[0778] It should be noted that the fifth outer surface 27 is the largest outer surface of the electrode assembly 2, which does not limit the electrode assembly 2 to having only one fifth outer surface 27. It is understandable that the electrode assembly 2 may have one or two fifth outer surfaces 27.

[0779] As an ...

Claims

1. A battery cell, comprising: a housing having an opening at at least one end along a first direction, the housing including a first sidewall portion; an electrode assembly at least partially received in the housing, the electrode assembly including a positive electrode tab and a negative electrode tab, at least a part of the positive electrode tab and at least a part of the negative electrode tab being stacked along a second direction, the second direction being parallel to the thickness direction of the first sidewall portion, the first direction intersecting the second direction; an end cap for closing the opening, the first sidewall portion and the end cap being welded to form a first connection portion; wherein the first sidewall portion includes a first region and a second region arranged along the first direction, the first region being located between the first connection portion and the second region, and the hardness of the first region is lower than the hardness of the second region.

2. The battery cell according to claim 1, wherein The ratio of the hardness of the first region to the hardness of the second region is between 0.3 and 0.

8.

3. The battery cell according to claim 2, wherein, The ratio of the hardness of the first region to the hardness of the second region is between 0.5 and 0.

8.

4. The battery cell according to any one of claims 1 to 3, wherein, The hardness of the second region ranges from 40 HV to 100 HV, and the hardness of the first region ranges from 20 HV to 55 HV.

5. The battery cell according to any one of claims 1 to 4, wherein, The dimension of the first region along the first direction ranges from 0.05 mm to 0.75 mm.

6. The battery cell according to claim 5, wherein, The dimension of the first region along the first direction ranges from 0.1 mm to 0.6 mm.

7. The battery cell according to any one of claims 1 to 6, wherein, At least some of the grains in the first region are first grains, the ratio of the number of first grains in the first region to the number of all grains in the first region is greater than 50%, and the dimension of the first grains extending along the first direction is a first dimension, the maximum dimension of the first grains along the second direction is a second dimension, and the ratio range of the first dimension to the second dimension is 0.2 to 5.

8. The battery cell according to claim 7, wherein, The ratio range of the first dimension to the second dimension is 0.25 to 4.

9. The battery cell according to claim 7 or 8, wherein, The first dimension ranges from 5 μm to 500 μm, and the second dimension ranges from 5 μm to 500 μm.

10. The battery cell according to any one of claims 1 to 9, wherein, At least some of the grains in the second region are second grains, the ratio of the number of second grains in the second region to the number of all grains in the second region is greater than 50%, and the dimension of the second grains extending along the first direction is a third dimension, the maximum dimension of the second grains along the second direction is a fourth dimension, and the ratio range of the third dimension to the fourth dimension is 4 to 100.

11. The battery cell according to claim 10, wherein, The ratio range of the third dimension to the fourth dimension is 4 to 50.

12. The battery cell according to claim 10 or 11, wherein, The third dimension ranges from 150 μm to 1000 μm, and the fourth dimension ranges from 5 μm to 120 μm.

13. The battery cell according to any one of claims 1 to 12, wherein, At least some of the grains in the first region are first grains, the ratio of the number of first grains in the first region to the number of all grains in the first region is greater than 50%, and the dimension of the first grains extending along the first direction is a first dimension, the maximum dimension of the first grains along the second direction is a second dimension, and the ratio range of the first dimension to the second dimension is 0.2 to 5; At least some of the grains in the second region are second grains, and the ratio of the number of second grains in the second region to the number of all grains in the second region is greater than 50%. The size of the second grains extending in the first direction is the third size, and the maximum size of the second grains in the second direction is the fourth size. The ratio range of the third size to the fourth size is 4 to 100; Wherein, the third size is greater than the first size.

14. The battery cell according to claim 13, wherein, The ratio range of the third size to the first size is 1.5 to 150, or, the ratio range of the third size to the first size is 1.8 to 100.

15. The battery cell according to claim 13 or 14, wherein, The range of the first size is 5 μm to 500 μm, and the range of the third size is 150 μm to 1000 μm.

16. The battery cell according to any one of claims 1 to 15, wherein, The maximum thickness of the first region is greater than the minimum thickness of the second region.

17. The battery cell according to claim 16, wherein, The first sidewall portion has a first inner surface and a second inner surface facing the electrode assembly, and a first outer surface and a second outer surface facing away from the electrode assembly. The first inner surface and the second inner surface are sequentially connected along the direction from the end cap to the electrode assembly. The first outer surface and the second outer surface are sequentially connected along the direction from the end cap to the electrode assembly. At least part of the first inner surface and the first outer surface are formed in the first region, and at least part of the second inner surface and the second outer surface are formed in the second region. The distance between the first inner surface and the first outer surface along the second direction is greater than the distance between the second inner surface and the second outer surface along the second direction.

18. The battery cell according to claim 17, wherein, The first inner surface includes a first sub-surface and a second sub-surface that are sequentially connected along the direction from the end cap to the electrode assembly. The first sub-surface is at least partially formed in the first region. Along the second direction, the first sub-surface is closer to the electrode assembly than the second sub-surface. The distance between the first sub-surface and the first outer surface along the second direction is greater than the distance between the second sub-surface and the first outer surface along the second direction.

19. The battery cell according to claim 18, wherein The distance between the second sub-surface and the first outer surface along the second direction is the first preset thickness, and the first preset thickness shows a decreasing trend along the direction from the end cap to the electrode assembly.

20. The battery cell according to claim 18 or 19, wherein The first sub-surface straddles the first region and the second region, and the first outer surface straddles the first region and the second region; or, the second sub-surface straddles the first region and the second region, and the first outer surface straddles the first region and the second region.

21. The battery cell according to any one of claims 17 to 20, wherein, The first inner surface straddles the first region and the second region, and the first outer surface straddles the first region and the second region.

22. The battery cell according to any one of claims 17 to 21, wherein, The size of the first inner surface along the third direction is greater than the size of the first inner surface along the first direction. The first direction, the second direction, and the third direction are non-coplanar and intersect pairwise.

23. The battery cell according to any one of claims 17 to 22, wherein, Along the second direction, the projection where the projection of the first inner surface coincides with the projection of the first region is the first projection. The dimension of the first projection along the third direction is greater than the dimension of the first projection along the first direction. The first direction, the second direction, and the third direction are non-coplanar and intersect pairwise.

24. The battery cell according to claim 22 or 23, wherein, The first inner surface includes a first connecting surface that passes through the mid-section of the first side wall portion. The mid-section is perpendicular to the third direction, and the distances from the mid-section along the third direction to both ends of the first side wall portion are equal.

25. The battery cell according to claim 24, wherein, At least part of the first connecting surface is formed in the first region. Along the second direction, the projection where the projection of the first connecting surface coincides with the projection of the first region is the second projection, and the second projection passes through the mid-section of the first side wall portion.

26. The battery cell according to claim 24 or 25, wherein, The first inner surface further includes a second connecting surface and a third connecting surface. The second connecting surface, the first connecting surface, and the third connecting surface are arranged along the third direction, with the first connecting surface located between the second connecting surface and the third connecting surface. Along the second direction, the distances between the second connecting surface and the first outer surface and between the third connecting surface and the first outer surface are both smaller than the distance between the first connecting surface and the first outer surface.

27. The battery cell according to claim 26, wherein, The first connecting surface, the second connecting surface, and the third connecting surface are all at least partially formed in the first region.

28. The battery cell according to claim 26 or 27, wherein, The first inner surface further includes a first transition surface. The first connecting surface, the first transition surface, and the second connecting surface are arranged along the third direction. The first transition surface connects the second connecting surface and the first connecting surface. The distance between the first transition surface and the first outer surface along the second direction is a second preset thickness, and the second preset thickness increases in the direction from the second connecting surface to the first connecting surface; and / or, the first inner surface further includes a second transition surface. The first connecting surface, the second transition surface, and the third connecting surface are arranged along the third direction. The second transition surface connects the third connecting surface and the first connecting surface. The distance between the second transition surface and the first outer surface along the second direction is a third preset thickness, and the third preset thickness increases in the direction from the third connecting surface to the first connecting surface.

29. The battery cell according to claim 28, wherein, The first transition surface is at least partially formed in the first region and / or the second transition surface is at least partially formed in the first region.

30. The battery cell according to any one of claims 24 to 29, wherein, The dimension of the first connecting surface along the third direction is L1, and the dimension of the first side wall portion along the third direction is L, where 0.2 ≤ L1 / L ≤ 0.

6.

31. The battery cell according to any one of claims 24 to 30, wherein, The first connection surface has opposite first and second ends along the third direction. The first side wall portion has opposite third and fourth ends along the third direction. The first end is close to the third end, and the second end is close to the fourth end. The dimension of the first side wall portion along the third direction is L. The minimum distance between the first end and the third end along the third direction is L2, and the minimum distance between the second end and the fourth end along the third direction is L3; L2 / L ≤ 0.3; and / or, L3 / L ≤ 0.

3.

32. The battery cell according to claim 30 or 31, wherein, 100mm ≤ L ≤ 450mm.

33. The battery cell according to any one of claims 22 to 32, wherein, The housing includes corner walls, and the corner walls are connected to both ends of the first side wall portion along the third direction. At least one end of the first inner surface along the third direction is not in contact with the corner wall; or, both ends of the first inner surface along the third direction extend to the two corner walls respectively.

34. The battery cell according to any one of claims 17 to 33, wherein, The electrode assembly further includes a separator, and the separator is disposed between the positive electrode plate and the negative electrode plate. The positive electrode plate includes a positive electrode main region and a positive electrode tab protruding from the positive electrode main region. The positive electrode main region has a positive electrode active material layer. The negative electrode plate includes a negative electrode main region and a negative electrode tab protruding from the negative electrode main region. The negative electrode main region has a negative electrode active material layer. Along the first direction, the positive electrode main region has a fifth end facing the end cap, the negative electrode main region has a sixth end facing the end cap, and the separator has a seventh end facing the end cap. The seventh end is closer to the end cap than the fifth end and the sixth end.

35. The battery cell according to claim 34, wherein, The separator includes an overhanging region that extends beyond the fifth end and the sixth end along the first direction. In the projection plane perpendicular to the second direction, the positive projection of the overhanging region overlaps with the positive projection of the first inner surface partially.

36. The battery cell according to claim 34 or 35, wherein, The first inner surface protrudes from the second inner surface. In the projection plane perpendicular to the second direction, the positive projection of the positive electrode main region does not overlap with the positive projection of the first inner surface; and / or, in the projection plane perpendicular to the second direction, the positive projection of the negative electrode main region does not overlap with the positive projection of the first inner surface.

37. The battery cell according to any one of claims 17 to 36, wherein, The negative electrode plate includes a negative electrode current collector and a negative electrode active material layer disposed on at least one side of the negative electrode current collector. The negative electrode active material layer includes a negative electrode active material.

38. The battery cell according to claim 37, wherein, The negative electrode active material layer includes a negative electrode main portion and a negative electrode thinning portion. The negative electrode main portion and the negative electrode thinning portion are arranged along the first direction. Along the first direction, the negative electrode thinning portion is provided at one end of the negative electrode main portion close to the end cap.

39. The battery cell according to claim 38, wherein, In the projection plane perpendicular to the second direction, the positive projection of the negative electrode thinning portion and the positive projection of the first inner surface are spaced apart along the first direction.

40. The battery cell according to claim 39, wherein, In the projection plane perpendicular to the second direction, the spacing dimension between the positive projection of the negative electrode thinning portion and the positive projection of the first inner surface along the first direction is greater than or equal to 1mm.

41. The battery cell according to any one of claims 37 to 40, wherein, The single-sided coating weight of the negative electrode active material layer is 90 mg / 1540 mm 2 ~170 mg / 1540 mm 2 , and it can be optionally 110 mg / 1540 mm 2 ~150 mg / 1540 mm 2 .

42. The battery cell according to any one of claims 37 to 41, wherein, The porosity of the negative electrode plate is 27% - 40%.

43. The battery cell according to any one of claims 37 to 42, wherein, The negative electrode active material includes a silicon-based material, and the mass content of silicon element in the silicon-based material in the negative electrode active material is 0.3% to 10%, and may be optionally 1% to 6%.

44. The battery cell according to claim 43, wherein, The silicon-based material includes at least one of silicon oxide and silicon-carbon composite.

45. The battery cell according to any one of claims 17 to 44, wherein, The positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer provided on at least one side of the positive electrode current collector, and the positive electrode active material layer includes a positive electrode active material.

46. The battery cell according to claim 45, wherein, The positive electrode active material layer includes a positive electrode main body portion and a positive electrode thinning portion, the positive electrode main body portion and the positive electrode thinning portion are arranged along the first direction, and along the first direction, the positive electrode thinning portion is provided at one end of the positive electrode main body portion close to the end cover.

47. The battery cell according to claim 46, wherein, In the projection plane perpendicular to the second direction, the positive projection of the positive electrode thinning portion and the positive projection of the first inner surface are spaced apart along the first direction.

48. The battery cell according to claim 47, wherein, In the projection plane perpendicular to the second direction, the spacing dimension between the positive projection of the positive electrode thinning portion and the positive projection of the first inner surface along the first direction is greater than or equal to 1 mm.

49. The battery cell according to any one of claims 45 to 48, wherein, The single-sided coating weight of the positive electrode active material layer is 200 mg / 1540 mm 2 to 370 mg / 1540 / mm 2 ; optionally 240 mg / 1540 mm 2 to 330 mg / 1540 mm 2 .

50. The battery cell according to any one of claims 45 to 49, wherein, The positive electrode active material is a lithium-containing phosphate.

51. The battery cell according to any one of claims 17 to 50, wherein, The material of the housing includes steel; The maximum distance between the second inner surface and the second outer surface along the second direction is D1, the dimension of the housing along the second direction is D, and 0.001 ≤ D1 / D ≤ 0.

012.

52. The battery cell according to any one of claims 17 to 51, wherein, The material of the housing includes steel; The maximum distance between the second inner surface and the second outer surface along the second direction is D1, 0.08 mm ≤ D1 ≤ 0.35 mm; and / or, the maximum distance between the first inner surface and the first outer surface along the second direction is D2, 0.1 mm ≤ D2 ≤ 0.6 mm.

53. The battery cell according to any one of claims 17 to 50, wherein, The material of the housing includes aluminum alloy; The maximum distance between the second inner surface and the second outer surface along the second direction is D1, the dimension of the housing along the second direction is D, and 0.005 ≤ D1 / D ≤ 0.

065.

54. The battery cell according to any one of claims 17 to 50 or claim 53, wherein, The material of the housing includes aluminum alloy; The maximum distance between the second inner surface and the second outer surface along the second direction is D1, 0.4 mm ≤ D1 ≤ 0.8 mm; and / or, the maximum distance between the first inner surface and the first outer surface along the second direction is D2, 0.5 mm ≤ D2 ≤ 1.5 mm.

55. The battery cell according to claim 53 or 54, wherein, The aluminum alloy includes components with the following mass percentages: aluminum ≥ 99.6%, copper ≤ 0.05%, iron ≤ 0.35%, magnesium ≤ 0.03%, manganese ≤ 0.03%, silicon ≤ 0.25%, titanium ≤ 0.03%, vanadium ≤ 0.05%, zinc ≤ 0.05%, and other single elements ≤ 0.03%.

56. The battery cell according to any one of claims 17 to 55, wherein, The first region is directly connected to the first connecting portion, and the first inner surface extends along the first direction to one end of the first region facing the connecting portion.

57. The battery cell according to any one of claims 17 to 56, wherein, The first side wall portion further includes a first transition region, the first transition region being connected to an end of the first region away from the second region along the first direction, the first transition region being connected to the first connection portion, a connection position between the first transition region and the first connection portion forming a first connection interface, the first connection interface having a first position closest to the first region along the first direction, the first position being located at an end of the first region away from the second region along the first direction.

58. The battery cell according to claim 57, wherein, At least a portion of the first connection interface extends obliquely with respect to the second direction.

59. The battery cell according to claim 58, wherein, The first connection interface includes a first interface, the first interface extending obliquely from the first position towards the end cap, along the second direction, at least a portion of the first transition region being located between the first interface and the end cap.

60. The battery cell according to claim 59, wherein, The first interface is connected to the first outer surface at the first position, the first position being at least partially located in the first region.

61. The battery cell according to any one of claims 58 to 60, wherein, The first connection interface includes a second interface, the second interface extending obliquely from the first position away from the end cap, along the second direction, at least a portion of the first transition region being located on a side of the second interface away from the end cap.

62. The battery cell according to claim 61, wherein, The second interface is connected to the first inner surface at the first position, the first position being at least partially located in the first region.

63. The battery cell according to any one of claims 57 to 62, wherein, The hardness of the first transition region is less than the hardness of the second region; and / or, the hardness of the first transition region is less than the hardness of the first connection portion.

64. The battery cell according to any one of claims 57 to 63, wherein, The first connection interface is closer to the second region than the outer surface of the end cap.

65. The battery cell according to any one of claims 17 to 64, wherein, The housing further includes a second side wall portion and a corner wall, the first side wall portion, the corner wall and the second side wall portion being arranged circumferentially along the opening, the corner wall connecting the first side wall portion and the second side wall portion.

66. The battery cell according to claim 65, wherein, The corner wall is welded to the end cap to form a second connection portion; The corner wall includes a third region and a fourth region arranged along the first direction, the hardness of the third region being less than the hardness of the fourth region, the third region being located between the fourth region and the second connection portion.

67. The battery cell according to claim 66, wherein, The corner wall has a third inner surface and a fourth inner surface facing the electrode assembly and a third outer surface and a fourth outer surface facing away from the electrode assembly, the third inner surface and the fourth inner surface being sequentially connected along the direction from the end cap to the electrode assembly, at least a portion of the third inner surface and the third outer surface being formed in the third region, at least a portion of the fourth inner surface and the fourth outer surface being formed in the fourth region, a distance between the third inner surface and the third outer surface along the thickness direction of the corner wall being greater than a distance between the fourth inner surface and the fourth outer surface along the thickness direction of the corner wall.

68. The battery cell according to claim 67, wherein, The third region is directly connected to the first region, the third inner surface extending to an end of the third region facing the first region, the first inner surface extending to an end of the first region facing the third region.

69. The battery cell according to claim 68, wherein, The corner wall has a first connecting end and a second connecting end, the first side wall portion is connected to the first connecting end, the second side wall portion is connected to the second connecting end, and the distance between the third inner surface and the third outer surface along the thickness direction of the corner wall is a fourth preset thickness, and the fourth preset thickness tends to decrease along the direction from the first connecting end to the second connecting end.

70. The battery cell according to any one of claims 67 to 69, wherein, The third area is directly connected to the second connecting portion, and the third inner surface extends to an end of the third area facing the second connecting portion.

71. The battery cell according to any one of claims 67 to 70, wherein, The corner wall also includes a second transition zone, which is connected to an end of the third zone along the first direction away from the fourth zone, and the second transition zone is connected to the second connecting portion. The connecting position of the second transition zone and the second connecting portion forms a second connecting interface, and the second connecting interface has a second position closest to the third zone along the first direction, and the second position is located at an end of the third zone along the first direction away from the fourth zone.

72. The battery cell according to claim 71, wherein, At least a portion of the second connection interface extends obliquely relative to a thickness direction of the corner wall.

73. The battery cell according to claim 72, wherein, The second connection interface includes a third interface, and the third interface extends obliquely from the second position toward the end cover. Along the thickness direction of the corner wall, at least a part of the second transition zone is located between the third interface and the end cover.

74. The battery cell according to claim 73, wherein, The third interface is connected to the third outer surface at the second position, and the second position is located in the third area.

75. The battery cell according to any one of claims 72 to 74, wherein, The second connection interface includes a fourth interface, which extends obliquely from the second position away from the end cover, and along the thickness direction of the corner wall, at least part of the second transition zone is located on a side of the fourth interface away from the end cover.

76. The battery cell according to claim 75, wherein, The fourth interface is connected to the third inner surface at the second position, and the second position is located in the third area.

77. The battery cell according to any one of claims 71 to 76, wherein, The hardness of the second transition zone is smaller than the hardness of the fourth zone; and / or the hardness of the second transition zone is smaller than the hardness of the second connecting portion.

78. The battery cell according to any one of claims 71 to 77, wherein, The second connection interface is closer to the fourth region than the outer surface of the end cover.

79. The battery cell according to any one of claims 66 to 78, wherein, The hardness of the third region is lower than the hardness of the second connecting portion.

80. The battery cell according to any one of claims 65 to 79, wherein, The shell includes two first side wall portions and two second side wall portions, the two first side wall portions are arranged opposite to each other along the second direction, the two second side wall portions are arranged opposite to each other along the third direction, and the first direction, the second direction and the third direction are perpendicular to each other.

81. The battery cell according to any one of claims 1 to 80, wherein, The first side wall portion has a limiting surface facing the end cover, and the limiting surface abuts against the end cover to limit the end cover from moving in a direction close to the electrode assembly.

82. The battery cell according to claim 81, wherein, The first side wall portion further includes a limiting area disposed on the limiting surface, the limiting area and the end cover are disposed opposite to each other along the second direction, and the limiting area and the end cover are welded to form the first connecting portion.

83. The battery cell according to any one of claims 1 to 82, wherein, The electrode assembly is a laminated structure, and includes a plurality of positive electrode sheets and a plurality of negative electrode sheets, and the plurality of positive electrode sheets and the plurality of negative electrode sheets are stacked along the second direction.

84. The battery cell according to claim 83, wherein, The number of the negative electrode plates is greater than that of the positive electrode plates, and one positive electrode plate is disposed between two adjacent negative electrode plates.

85. The battery cell according to claim 83 or 84, wherein, Each negative electrode plate is provided with a negative electrode tab; and / or each positive electrode plate is provided with a positive electrode tab.

86. The battery cell according to any one of claims 83 to 85, wherein, The first side wall portion has a first inner surface and a second inner surface facing the electrode assembly, and a first outer surface and a second outer surface facing away from the electrode assembly. The first inner surface and the second inner surface are sequentially connected along the direction from the end cover to the electrode assembly, and the first outer surface and the second outer surface are sequentially connected along the direction from the end cover to the electrode assembly. At least a part of the first inner surface and the first outer surface is formed in the first region, and at least a part of the second inner surface and the second outer surface is formed in the second region. The distance between the first inner surface and the first outer surface along the second direction is greater than the distance between the second inner surface and the second outer surface along the second direction. Along the third direction, the size of the first inner surface is greater than the size of the positive electrode plate and / or the size of the negative electrode plate, and the first direction, the second direction and the third direction are perpendicular to each other in pairs.

87. The battery cell according to any one of claims 1 to 86, wherein, The battery cell further includes two electrode terminals, the two electrode terminals are disposed on the end cover, the two electrode terminals have opposite polarities and are both electrically connected to the electrode assembly. The end cover is provided with a lead-out hole. The electrode terminal includes a terminal body, a first limiting portion and a second limiting portion. The terminal body connects the first limiting portion and the second limiting portion. The terminal body passes through the lead-out hole. Along the first direction, the first limiting portion is located on the side of the end cover facing away from the electrode assembly, and the second limiting portion is located on the side of the end cover facing the electrode assembly.

88. The battery cell according to any one of claims 1 to 87, wherein, The electrode assembly has a flat region, and the portions of the positive electrode plate and the negative electrode plate located in the flat region are stacked along the second direction.

89. The battery cell according to claim 88, wherein, The electrode assembly includes an adjacent fifth outer surface and sixth outer surface. The fifth outer surface is perpendicular to the second direction, and the area of the fifth outer surface is greater than that of the sixth outer surface. The fifth outer surface and the first side wall portion are disposed opposite to each other along the second direction.

90. The battery cell according to claim 89, wherein, The fifth outer surface is the surface with the largest area among the outer surfaces of the electrode assembly.

91. The battery cell according to claim 89 or 90, wherein The electrode assembly is a wound structure, and the electrode assembly further has a corner region. The corner region is disposed at at least one end of the flat region along the third direction. The first direction, the second direction and the third direction are not coplanar and intersect in pairs. The outer surface of the flat region includes the fifth outer surface, and the outer surface of the corner region includes the sixth outer surface. At least a part of the sixth outer surface is an arc surface.

92. The battery cell according to claim 89 or 90, wherein, The electrode assembly is a stacked structure. The flat region includes a plurality of positive electrode plates and a plurality of negative electrode plates. The plurality of positive electrode plates and the plurality of negative electrode plates are stacked along the second direction. The fifth outer surface is perpendicular to the sixth outer surface.

93. The battery cell according to any one of claims 1 to 92, wherein, The first side wall portion is the wall with the largest outer surface area in the housing.

94. The battery cell according to any one of claims 1 to 93, wherein, The housing includes two of the first side wall portions, and the two first side wall portions are disposed opposite to each other along the second direction, and the electrode assembly is located between the two first side wall portions.

95. The battery cell according to any one of claims 1 to 94, wherein, The hardness of the first region is lower than the hardness of the first connecting portion.

96. The battery cell according to any one of claims 1 to 95, wherein, The number of the electrode assemblies is N1, and each electrode assembly further includes at least one separator. The number of the positive electrode plates is at least one, and the number of the negative electrode plates is at least one. The positive electrode plates, the negative electrode plates, and the separator are stacked to form a flat region, and at least a part of the positive electrode plates, at least a part of the negative electrode plates, and at least a part of the separator are stacked in the flat region along the second direction; The number of layers of the positive electrode plates stacked in the flat region for each electrode assembly is N2. The flat region has an outer surface perpendicular to the second direction, the area of the outer surface is S, N1≥1, N2≥1, N1*N2≥50, S≥8000mm 2 .

97. The battery cell according to any one of claims 1 to 96, wherein, The negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer provided on at least one side of the negative electrode current collector. The negative electrode active material layer includes a negative electrode active material, and the discharge capacity of the negative electrode active material layer per unit area is 2.0 mAh / cm 2 to 5.0 mAh / cm 2 .

98. The battery cell according to claim 96, wherein, The thickness of the negative electrode active material layer is T1, and 9 μm ≤ T1 ≤ 75 μm.

99. A battery device, comprising the battery cell according to any one of claims 1 to 98.

100. An electrical device, comprising the battery cell according to any one of claims 1 to 98, and the battery cell is used to supply electrical energy to the electrical device.

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