A battery cell, a battery device, and an electrical device.

Abstract

This application provides a battery cell, a battery device, and an electrical device, belonging to the field of battery technology. The battery cell includes a housing, an electrode assembly, and an end cap. The housing has an opening at at least one end along a first direction and includes a first sidewall portion. The electrode assembly is at least partially housed within the housing and includes a positive electrode and a negative electrode. At least portions of the positive and negative electrode are stacked along a second direction, which is parallel to the thickness direction of the first sidewall portion. The first and second directions intersect. The end cap is used to close the opening, and the first sidewall portion is welded to the end cap to form a first connection portion. The first sidewall portion includes a first region and a second region arranged along the first direction. The first region is located between the first connection portion and the second region, and the hardness of the first region is lower than that of the second region. The expansion force of the electrode assembly is released through the lower-hardness first region to reduce the possibility of cracking of the first connection portion of the first sidewall portion.

Description

[0001] Cross-references to related applications

[0002] This application claims priority to the following patent applications: 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 which are incorporated herein by reference. Technical Field

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

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

[0005] In related technologies, an electrode assembly is installed inside the casing of a battery cell. During the charging and discharging process of the battery cell, the electrode assembly expands, which may cause the casing to crack. Summary of the Invention

[0006] In view of this, embodiments of this application aim to provide a battery cell, battery device, and power device that can reduce the possibility of casing cracking.

[0007] To achieve the above objectives, the technical solution of this application embodiment is implemented as follows:

[0008] One embodiment of this application discloses a single battery cell, including:

[0009] The housing has an opening at at least one end along a first direction, and the housing includes a first sidewall portion;

[0010] An electrode assembly is at least partially housed within a housing. The electrode assembly includes a positive electrode and a negative electrode. At least portions of the positive electrode and the negative electrode are stacked along a second direction, which is parallel to the thickness direction of the first sidewall portion. The first direction intersects the second direction.

[0011] An end cap is used to close the opening, and the first side wall portion is welded to the end cap to form a first connection portion;

[0012] The first sidewall portion includes a first region and a second region arranged along a first direction. The first region is located between the first connecting portion and the second region, and the hardness of the first region is lower than that of the second region.

[0013] By releasing the expansion force of the electrode assembly in the first region with lower hardness, the possibility of cracking in the first connection part is reduced.

[0014] 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.

[0015] Appropriate hardness can reduce cracking at the first connection and suppress cracking in the first region itself.

[0016] 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.

[0017] Appropriate hardness can reduce cracking at the first connection and suppress cracking in the first region itself.

[0018] In some embodiments, the hardness range of the second region is 40HV to 100HV, and the hardness range of the first region is 20HV to 55HV.

[0019] Appropriate hardness can reduce cracking at the first connection and suppress cracking in the first region itself.

[0020] In some embodiments, the size of the first region along the first direction ranges from 0.05 mm to 0.75 mm.

[0021] A suitable size range for the maximum dimension of the first region along the first direction can both reduce cracking of the first connection and prevent the first region from being too long and causing itself to crack.

[0022] In some embodiments, the size of the first region along the first direction ranges from 0.1 mm to 0.6 mm.

[0023] A suitable size range for the maximum dimension of the first region along the first direction can both reduce cracking of the first connection and prevent the first region from being too long and causing itself to crack.

[0024] In some embodiments, at least a portion of the grains in the first region are first grains, the ratio of the number of first grains in the first region to the total number of grains in the first region is greater than 50%, and the dimension of the first grain extending along the first direction is the first dimension, the maximum dimension of the first grain along the second direction is the second dimension, and the ratio of the first dimension to the second dimension ranges from 0.2 to 5.

[0025] The ratio of the first size to the second size is in the range of 0.2 to 5. This means that the proportion of the first grain is greater than 50%, which is beneficial to improving the toughness of the first region.

[0026] In some embodiments, the ratio of the first dimension to the second dimension ranges from 0.25 to 4.

[0027] The ratio of the first size to the second size is in the range of 0.25 to 4. This means that the proportion of the first grain is greater than 50%, which is beneficial to improving the toughness of the first region.

[0028] In some embodiments, the first size ranges from 5 μm to 500 μm, and the second size ranges from 5 μm to 500 μm.

[0029] When the ratio of the first size to the second size is within a certain 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.

[0030] In some embodiments, 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 total number of grains in the second region is greater than 50%, and the dimension of the second grain extending along the first direction is the third dimension, the maximum dimension of the second grain along the second direction is the fourth dimension, and the ratio of the third dimension to the fourth dimension ranges from 4 to 100.

[0031] The ratio of the third size to the fourth size ranges from 4 to 100. With such a proportion of second grains greater than 50%, it is beneficial to reduce the toughness of the second region and reduce the possibility of cracking of the second region itself under the action of expansion force.

[0032] In some embodiments, the ratio of the third dimension to the fourth dimension ranges from 4 to 50.

[0033] The ratio of the third size to the fourth size is in the range of 4 to 50. With such a proportion of second grains greater than 50%, it is beneficial to reduce the toughness of the second region and reduce the possibility of cracking of the second region itself under the action of expansion force.

[0034] In some embodiments, the third dimension ranges from 150 μm to 1000 μm, and the fourth dimension ranges from 5 μm to 120 μm.

[0035] When the ratio of the third dimension to the fourth dimension is within the appropriate range, a suitable range of the third and fourth dimensions is beneficial to reduce the toughness of the second zone and reduce the possibility of the second zone itself cracking under the action of expansion force.

[0036] In some embodiments, at least a portion of the grains in the first region are first grains, the ratio of the number of first grains in the first region to the total number of grains in the first region is greater than 50%, and the dimension of the first grain extending along the first direction is the first dimension, the maximum dimension of the first grain along the second direction is the second dimension, and the ratio of the first dimension to the second dimension ranges from 0.2 to 5.

[0037] 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 total number of grains in the second region is greater than 50%, and the dimension of the second grains extending along the first direction is the third dimension, the maximum dimension of the second grains along the second direction is the fourth dimension, and the ratio of the third dimension to the fourth dimension is in the range of 4 to 100.

[0038] The third dimension is larger than the first dimension.

[0039] Within the same dimension along the first direction, the first region has more grains that bear the expansion force, thus improving the toughness of the first region.

[0040] In some embodiments, the ratio of the third dimension to the first dimension ranges from 1.5 to 150, or the ratio of the third dimension to the first dimension ranges from 1.8 to 100.

[0041] In some embodiments, the first dimension ranges from 5 μm to 500 μm, and the third dimension ranges from 150 μm to 1000 μm.

[0042] In some embodiments, the maximum thickness of the first region is greater than the minimum thickness of the second region.

[0043] By increasing the thickness of the first zone, the possibility of cracking in the first zone is reduced.

[0044] 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 the direction from the end cap toward the electrode assembly, and the first outer surface and the second outer surface are sequentially connected along the direction from the end cap toward the electrode assembly. The first inner surface and the first outer surface are at least partially formed in a first region, and the second inner surface and the second outer surface are at least partially formed in a second region. The distance between the first inner surface and the first outer surface along a second direction is greater than the distance between the second inner surface and the second outer surface along a second direction.

[0045] The first sidewall portion reinforces the first region in the thicker part of the first inner surface, reducing the possibility of cracking in the first region.

[0046] In some embodiments, the first inner surface includes a first sub-surface and a second sub-surface sequentially connected along the direction from the end cap toward 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.

[0047] The first sidewall portion reinforces the first region in the area corresponding to the thicker first sub-surface, reducing the possibility of cracking in the first region.

[0048] 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 decreases along the direction from the end cap to the electrode assembly.

[0049] The first preset thickness decreases along the direction from the end cap to the electrode assembly, which helps to reduce the material cost of the first sidewall.

[0050] In some embodiments, a first sub-surface spans across a first region and a second region, and a first outer surface spans across a first region and a second region; or, a second sub-surface spans across a first region and a second region, and both first outer surfaces span across a first region and a second region.

[0051] The thicker portion of the first sidewall reinforces the junction between the first and second zones, reducing the likelihood of cracking at the junction.

[0052] In some embodiments, a first inner surface spans across a first region and a second region, and a first outer surface spans across a first region and a second region.

[0053] The thicker portion of the first sidewall on the first inner surface reinforces the junction between the first and second zones, reducing the likelihood of cracking at the junction.

[0054] In some embodiments, the dimension of the first inner surface along a third direction is greater than the dimension of the first inner surface along a first direction, and the first direction, the second direction, and the third direction are not coplanar and intersect each other.

[0055] The first sidewall portion is reinforced by the thicker portion along the third direction on the first inner surface and the longer region along the third direction, thereby reducing the possibility of cracking of the first sidewall portion.

[0056] In some embodiments, along the second direction, the projection of the first inner surface that coincides with the projection of the first region 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 each other.

[0057] The dimension of the first projection along the third direction is larger than the dimension of the first projection along the first direction. The portion of the first region that is reinforced along the third direction is longer, which helps to reduce the possibility of cracking in the first region.

[0058] In some embodiments, the first inner surface includes a first connecting surface that passes through the mid-section of the first sidewall portion, the mid-section being perpendicular to a third direction, and the mid-section being equidistant from both ends of the first sidewall portion along the third direction.

[0059] The first connecting surface passes through the mid-section of the first sidewall portion, reducing cracking at the mid-section.

[0060] In some embodiments, the first connecting surface is at least partially formed in the first region, and along the second direction, the projection of the first connecting surface that coincides with the projection of the first region is the second projection, which passes through the midsection of the first sidewall portion.

[0061] The second projection passes through the mid-section of the first sidewall, reinforcing the portion of the first region corresponding to the mid-section and reducing the possibility of cracking in the first region at the mid-section.

[0062] In some embodiments, 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 a third direction. The first connecting surface connects the second connecting surface and the third connecting surface. 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 less than the distance between the first connecting surface and the first outer surface.

[0063] The first sidewall is thicker in the portion corresponding to the first connecting surface, and thinner in the portions corresponding to the second and third connecting surfaces. This design can reduce shell cracking based on the distribution characteristics of expansion force, and also reduce costs.

[0064] In some embodiments, the first connecting surface, the second connecting surface, and the third connecting surface are all formed at least partially in the first region.

[0065] This helps reduce cracking in the first zone itself.

[0066] In some embodiments, 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 a 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 a second direction is a second preset thickness, and the second preset thickness increases along 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 a 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 a second direction is a third preset thickness, and the third preset thickness increases along the direction from the third connecting surface to the first connecting surface.

[0067] The transition is smoothed through a transition surface.

[0068] In some embodiments, a first transition surface is at least partially formed in a first region and / or a second transition surface is at least partially formed in the first region.

[0069] The first transition surface and / or the second transition surface increase the first zone, reducing the possibility of cracking in the first zone.

[0070] In some embodiments, the dimension of the first connecting surface along the third direction is L1, the dimension of the first sidewall portion along the third direction is L, and 0.2≤L1 / L≤0.6.

[0071] It can both reinforce more areas of the first sidewall in the third direction and increase costs to some extent.

[0072] In some embodiments, the first connecting surface has a first end and a second end opposite to each other along a third direction, the first sidewall portion has a third end and a fourth end opposite to each other along a 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 sidewall portion along a third direction is L, the minimum distance between the first end and the third end along a third direction is L2, the minimum distance between the second end and the fourth end along a third direction is L3; L2 / L≤0.3; and / or, L3 / L≤0.3.

[0073] It can both reinforce more areas of the first sidewall in the third direction and increase costs to some extent.

[0074] In some embodiments, 100mm ≤ L ≤ 450mm.

[0075] In some embodiments, the housing includes corner walls, and the first side wall is connected to both ends in a third direction.

[0076] At least one end of the first inner surface along the third direction does not contact the corner wall; or, the two ends of the first inner surface along the third direction extend to the two corner walls respectively.

[0077] In some embodiments, the electrode assembly further includes an isolation element, wherein an isolation element is disposed between the positive electrode and the negative electrode;

[0078] The positive electrode includes a positive electrode body region and a positive electrode tab protruding from the positive electrode body region. The positive electrode body region has a positive electrode active material layer. The negative electrode includes a negative electrode body region and a negative electrode tab protruding from the negative electrode body region. The negative electrode body region has a negative electrode active material layer. Along the first direction, the positive electrode body region has a fifth end facing the end cap, the negative electrode body 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 and sixth ends.

[0079] The separator has portions extending beyond the fifth and sixth terminals, enhancing its insulation effect between the positive and negative electrodes and reducing the risk of overlap between the positive and negative electrodes.

[0080] In some embodiments, the separator includes an overhang region extending beyond the fifth and sixth ends along a first direction, wherein the orthographic projection of the overhang region overlaps with the orthographic projection of the first inner surface in a projection plane perpendicular to the second direction.

[0081] The orthographic projection of the extended 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 capability of the first inner surface.

[0082] In some embodiments, the first inner surface protrudes beyond the second inner surface;

[0083] In a projection plane perpendicular to the second direction, the orthographic projection of the positive electrode main body 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 body area does not overlap with the orthographic projection of the first inner surface.

[0084] Reduce the degree of interference between the expanded electrode assembly and the first inner surface.

[0085] In some embodiments, the negative electrode sheet includes a negative current collector and a negative active material layer disposed on at least one side of the negative current collector, the negative active material layer including a negative active material.

[0086] In some embodiments, the negative electrode 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, a negative electrode thinning portion is provided at one end of the negative electrode main body near the end cap.

[0087] The thinning of the negative electrode section allows for a larger expansion gap in the electrode assembly, reducing the expansion force exerted by the electrode assembly on the first sidewall.

[0088] In some embodiments, in a projection plane perpendicular to the second direction, the orthographic projection of the negative electrode thinning portion and the orthographic projection of the first inner surface are spaced apart along the first direction.

[0089] Reduce the impact of the thinned negative electrode portion on the first inner surface and reduce the expansion force exerted by the electrode assembly on the first inner surface.

[0090] In some embodiments, in a projection plane perpendicular to the second direction, the distance between the orthographic projection of the negative electrode thinning portion and the orthographic projection of the first inner surface along the first direction is greater than or equal to 1 mm.

[0091] 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.

[0092] In some embodiments, the single-sided 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 110mg / 1540mm. 2 ~150mg / 1540mm 2 .

[0093] In some embodiments, the porosity of the negative electrode sheet is 27% to 40%.

[0094] In some embodiments, the negative electrode active material includes a silicon-based material, wherein the mass content of silicon element in the negative electrode active material is 0.3% to 10%, optionally 1% to 6%.

[0095] In some embodiments, the silicon-based material includes at least one of silicon oxides and silicon-carbon composites.

[0096] In some embodiments, the positive electrode sheet includes a positive current collector and a positive active material layer disposed on at least one side of the positive current collector, the positive active material layer including a positive active material.

[0097] In some embodiments, the positive electrode active material layer includes a positive electrode body portion and a positive electrode thinning portion, the positive electrode body portion and the positive electrode thinning portion are arranged along a first direction, and along the first direction, a positive electrode thinning portion is provided at one end of the positive electrode body portion near the end cap.

[0098] The setting of the positive electrode thinning section helps to increase the expansion gap of the electrode assembly and reduce the expansion force of the electrode assembly on the first sidewall.

[0099] In some embodiments, in a projection plane perpendicular to the second direction, the orthographic projection of the positive electrode thinning portion and the orthographic projection of the first inner surface are spaced apart along the first direction.

[0100] Reduce the impact of the thinned portion of the positive electrode on the first inner surface and reduce the expansion force exerted by the electrode assembly on the first inner surface.

[0101] In some embodiments, in a projection plane perpendicular to the second direction, the distance between the orthographic projection of the positive electrode thinning portion and the orthographic projection of the first inner surface along the first direction is greater than or equal to 1 mm.

[0102] The negative electrode thinning section is further away from the first inner surface, which helps to reduce the expansion force of the electrode assembly on the first inner surface.

[0103] 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 .

[0104] In some embodiments, the positive electrode active material is a lithium phosphate.

[0105] In some embodiments, the housing is made of steel;

[0106] The maximum distance between the second inner surface and the second outer surface along the second direction is D1, and the dimension of the shell along the second direction is D, 0.001≤D1 / D≤0.012.

[0107] With a high energy density, the shell has good strength.

[0108] In some embodiments, the housing is made of steel;

[0109] 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.

[0110] In some embodiments, the housing is made of aluminum alloy;

[0111] The maximum distance between the second inner surface and the second outer surface along the second direction is D1, and the dimension of the shell along the second direction is D, 0.005≤D1 / D≤0.065.

[0112] With a high energy density, the shell has good strength.

[0113] In some embodiments, the housing is made of aluminum alloy;

[0114] 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.

[0115] In some embodiments, the aluminum alloy comprises the following components in weight 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%.

[0116] In some embodiments, the first region is directly connected to the first connecting portion, and the first inner surface extends along a first direction to one end of the first region facing the connecting portion.

[0117] This is beneficial for strengthening the end of the first zone facing the first connecting part.

[0118] In some embodiments, the first sidewall portion further includes a first transition region, which is connected to the end of the first region away from the second region along a first direction. The first transition region is connected to the first connecting portion, and the connection position of the first transition region and the first connecting portion forms a first connecting interface. The first connecting interface has a first position closest to the first region along the first direction, and the first position is located at the end of the first region away from the second region along the first direction.

[0119] The first connection interface provides a larger contact area between the first transition zone and the first connection part, thereby improving the connection strength.

[0120] In some embodiments, at least a portion of the first connection interface extends at an angle relative to the second direction.

[0121] The tension force exerted by the contraction of the first connecting part on the first transition zone and the force exerted by the first sidewall part on the first transition zone are not on the same straight line, which reduces the possibility of fatigue cracking.

[0122] In some embodiments, the first connection interface includes a first interface that extends obliquely from a first position toward the end cap, and at least a portion of the first transition region is located between the first interface and the end cap along a second direction.

[0123] The first transition zone is protected by the stop of the first connection part, reducing the possibility of fatigue cracking in the first transition zone.

[0124] In some embodiments, the first interface is connected to the first outer surface at a first location, the first location being at least partially located in a first region.

[0125] The thickened portion of the first sidewall corresponding to the first outer surface is located as close as possible to the end of the first region facing the first connection portion, thereby reducing the possibility of fatigue cracking at the end of the first region facing the first connection portion.

[0126] In some embodiments, the first connection interface includes a second interface that extends obliquely from the first position toward the end cap, and at least a portion of the first transition area is located on the side of the second interface away from the end cap along the second direction.

[0127] The first transition zone blocks the first connecting part, reducing the possibility of the first connecting part detaching from the end cap.

[0128] In some embodiments, the second interface is connected to the first inner surface at a first location, the first location being at least partially located in a first region.

[0129] By bringing the thicker portion of the first sidewall closer to the first connecting portion on the first inner surface, it is beneficial to strengthen the end of the first region facing the first connecting portion and reduce the possibility of cracking at the end of the first region facing the first connecting portion.

[0130] In some embodiments, the hardness of the first transition zone is less than the hardness of the second zone; and / or, the hardness of the first transition zone is less than the hardness of the first connecting portion.

[0131] In some embodiments, the first connection interface is closer to the second region than the outer surface of the end cap.

[0132] The first connecting part can sink to a deeper position, which helps to improve the connection strength between the end cap and the first connecting part.

[0133] In some embodiments, the housing further includes a second sidewall and a corner wall, the first sidewall, the corner wall and the second sidewall are arranged circumferentially along the opening, and the corner wall connects the first sidewall and the second sidewall.

[0134] Reduce stress concentration by using corner walls.

[0135] In some embodiments, the corner wall is welded to the end cap to form a second connection portion;

[0136] The corner wall includes a third zone and a fourth zone arranged along the first direction. The hardness of the third zone is less than that of the fourth zone. The third zone is located between the fourth zone and the second connection.

[0137] The possibility of cracking in the second joint is reduced by using a third zone with lower hardness.

[0138] 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 sequentially in the direction from the end cap toward the electrode assembly. The third inner surface and the third outer surface are at least partially formed in a third region, and the fourth inner surface and the fourth outer surface are at least partially formed in a fourth region. 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.

[0139] The thicker portion of the corner wall on the third inner surface reinforces the third zone, reducing the possibility of fatigue cracking in the lower hardness third zone.

[0140] In some embodiments, the third region is directly connected to the first region, the third inner surface extends to the end of the third region facing the first region, and the first inner surface extends to the end of the first region facing the third region.

[0141] The thicker portion of the first sidewall corresponding to the first inner surface and the thicker portion of the corner wall corresponding to the third inner surface complement each other, which helps to reduce cracking in the first and third zones.

[0142] In some embodiments, the corner wall has a first connecting end and a second connecting end, a first side wall portion is connected to the first connecting end, a 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, the fourth preset thickness decreasing in the direction from the first connecting end to the second connecting end.

[0143] Reduce costs by reinforcing the third zone to decrease the likelihood of cracking in the third zone.

[0144] In some embodiments, the third region is directly connected to the second connecting portion, and the third inner surface extends to one end of the third region facing the second connecting portion.

[0145] The end of the third zone facing the second connection is reinforced to reduce the possibility of cracking at that end.

[0146] In some embodiments, the corner wall further includes a second transition zone, which is connected to the end of the third region away from the fourth region along a first direction. The second transition zone is connected to a second connecting portion, and the connection position of the second transition zone and the second connecting portion forms a second connecting interface. The second connecting interface has a second position that is closest to the third region along the first direction. The second position is located at the end of the third region away from the fourth region along the first direction.

[0147] The second connecting surface increases the contact area, reducing the possibility of cracking in the second transition zone and the second connecting part.

[0148] In some embodiments, at least a portion of the second connection interface extends obliquely relative to the thickness direction of the corner wall.

[0149] The forces exerted by the contraction of the second connecting part on the second transition zone and the forces exerted by the expansion deformation of the corner wall on the second transition zone are not on the same straight line, which reduces the possibility of fatigue cracking between the second transition zone and the second connecting part.

[0150] In some embodiments, the second connection interface includes a third interface that extends obliquely from the second position toward the end cap and along the thickness direction of the corner wall, with at least a portion of the second transition area located between the third interface and the end cap.

[0151] The second connection protects the second transition zone and reduces the possibility of fatigue cracking in the second transition zone.

[0152] In some embodiments, the third interface is connected to the third outer surface at a second location, which is located within the third region.

[0153] The thicker portion of the corner wall on the third outer surface is close to the second connection, which helps to reduce cracking in the third region towards the second connection.

[0154] In some embodiments, the second connection interface includes a fourth interface that extends obliquely from the second position toward the end cap and along the thickness direction of the corner wall, with at least a portion of the second transition area located on the side of the fourth interface away from the end cap.

[0155] The second transition zone protects the second connecting part and reduces the possibility of the second connecting part falling off.

[0156] In some embodiments, the fourth interface is connected to the third inner surface at a second location, which is located within the third region.

[0157] The thicker portion of the corner wall on the third inner surface is close to the second connection, which can reduce the possibility of cracking at the end of the third region facing the second connection.

[0158] In some embodiments, the hardness of the second transition zone is less than the hardness of the fourth zone; and / or, the hardness of the second transition zone is less than the hardness of the second connecting portion.

[0159] In some embodiments, the second connection interface is closer to the fourth region than the outer surface of the end cap.

[0160] This allows the second connecting part to sink deeper into the corner wall, improving the connection strength between the corner wall and the end cap.

[0161] In some embodiments, the hardness of the third region is lower than that of the second connecting portion.

[0162] In some embodiments, the housing includes two first sidewall portions and two second sidewall portions, the two first sidewall portions being disposed opposite each other along a second direction, and the two second sidewall portions being disposed opposite each other along a third direction, wherein the first direction, the second direction, and the third direction are perpendicular to each other.

[0163] In some embodiments, the first sidewall portion has a limiting surface facing the end cap, the limiting surface abutting against the end cap to restrict the end cap from moving toward the electrode assembly.

[0164] In the welding process, reducing the possibility of the end cap moving towards the electrode assembly improves welding quality and reduces welding difficulty.

[0165] In some embodiments, the first sidewall portion further includes a limiting area disposed on the limiting surface, the limiting area and the end cap being disposed opposite each other along the second direction, and the limiting area and the end cap being welded to form a first connecting portion.

[0166] This reduces the possibility of the end cap moving along the thickness direction of the first sidewall during welding, thereby improving welding quality and reducing welding difficulty.

[0167] In some embodiments, the electrode assembly is a stacked structure, and the electrode assembly includes a plurality of positive electrode sheets and a plurality of negative electrode sheets, which are stacked along a second direction.

[0168] 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.

[0169] In some embodiments, each negative electrode is provided with a negative electrode tab; and / or, each positive electrode is provided with a positive electrode tab.

[0170] 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 in the direction from the end cap toward the electrode assembly, and the first outer surface and the second outer surface are sequentially connected in the direction from the end cap toward the electrode assembly. The first inner surface and the first outer surface are at least partially formed in a first region, and the second inner surface and the second outer surface are at least partially formed in a second region. The distance between the first inner surface and the first outer surface in the second direction is greater than the distance between the second inner surface and the second outer surface in the second direction.

[0171] Along the third direction, the size of the first inner surface is larger than the size of the positive electrode and / or the size of the negative electrode, and the first direction, the second direction and the third direction are perpendicular to each other.

[0172] The thicker portion of the first sidewall corresponding to the first inner surface can enhance the entire positive electrode sheet along the third direction, which helps to reduce cracking of the first sidewall.

[0173] In some embodiments, the battery cell further includes two electrode terminals disposed on the end cap, the two electrode terminals having opposite polarities and both being electrically connected to the electrode assembly;

[0174] The end cap is provided with an outlet hole. The electrode terminal includes a terminal body, a first limiting part and a second limiting part. The terminal body is connected to the first limiting part and the second limiting part. The terminal body passes through the outlet hole. Along the first direction, the first limiting part is located on the side of the end cap away from the electrode assembly, and the second limiting part is located on the side of the end cap facing the electrode assembly.

[0175] The electrode terminals are riveted to the end cap, making installation easy.

[0176] In some embodiments, the electrode assembly has a flat region, and the portions of the positive electrode and the negative electrode located in the flat region are stacked along a second direction.

[0177] In some embodiments, the electrode assembly includes an adjacent fifth outer surface and a sixth outer surface, the fifth outer surface being perpendicular to the second direction, the area of ​​the fifth outer surface being larger than the area of ​​the sixth outer surface, and the fifth outer surface being disposed opposite to the first sidewall portion along the second direction.

[0178] The first zone releases expansion force in the direction of greater expansion force, and the first inner surface is reinforced in the direction of greater expansion force.

[0179] In some embodiments, the fifth outer surface is the surface with the largest area among the outer surfaces of the electrode assembly.

[0180] In some embodiments, the electrode assembly is a wound structure, and the electrode assembly further has a corner region. The straight region is provided with a corner region at at least one end along a third direction, and the first direction, the second direction and the third direction are not coplanar and intersect each other.

[0181] 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 which is a circular arc surface.

[0182] In some embodiments, the electrode assembly is a stacked structure, the flat region includes a plurality of positive electrode sheets and a plurality of negative electrode sheets, the plurality of positive electrode sheets and the plurality of negative electrode sheets are stacked along a second direction, and the fifth outer surface is perpendicular to the sixth outer surface.

[0183] The first zone releases expansion force in the direction of greater expansion force, and the first inner surface is reinforced in the direction of greater expansion force.

[0184] In some embodiments, the first sidewall portion is the wall with the largest outer surface area in the housing.

[0185] In some embodiments, the housing includes two first sidewall portions disposed opposite each other along a second direction, and the electrode assembly is located between the two first sidewall portions.

[0186] In some embodiments, the hardness of the first region is lower than the hardness of the first connecting portion.

[0187] This application provides a battery device including any of the above-described battery cells.

[0188] In some embodiments, the number of electrode assemblies is N1, each electrode assembly further includes at least one separator, the number of positive electrode plates is at least one, the number of 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 portion of the positive electrode plates, at least a portion of the negative electrode plates and at least a portion of the separator are stacked in the flat region along the second direction;

[0189] Each electrode assembly has N2 layers of positive electrode sheets stacked in the flat region, the flat region having an outer surface perpendicular to the second direction, the area of ​​the outer surface being S, where N1≥1, N2≥1, N1*N2≥50, and S≥8000mm². 2 .

[0190] In this embodiment, the possibility of cracking of the first connecting part of the first sidewall portion under the action of a large expansion force is reduced by the first region with higher toughness.

[0191] In some embodiments, the negative electrode includes a negative current collector and a negative active material layer disposed on at least one side of the negative current collector. The negative active material layer includes a negative active material, and the discharge capacity per unit area of ​​the negative active material layer is 2.0 mAh / cm². 2 Up to 5.0mAh / cm 2 .

[0192] In this embodiment, when the discharge capacity of the negative electrode active material layer per unit area is within the above range, there are sufficient sites in the negative electrode active material layer for lithium insertion, which can reduce the risk of lithium plating; and it is conducive to fast charging, so that the expansion force is not too large, reducing the possibility of the first connection part cracking under the expansion chopping action of the electrode assembly.

[0193] In some embodiments, the thickness of the negative electrode active material layer is T1, where 9 μm ≤ T1 ≤ 75 μm.

[0194] In this embodiment, the negative electrode active material layer is thicker, resulting in a larger expansion force. The lower hardness of the first region reduces the possibility of cracking of the first connecting part of the first sidewall under the action of the larger expansion force.

[0195] This application provides an electrical device including any of the above-described battery cells, which are used to provide electrical energy to the electrical device. Attached Figure Description

[0196] Figure 1 This application provides structural schematic diagrams of vehicles for some embodiments;

[0197] Figure 2 Exploded views of batteries provided for some embodiments of this application;

[0198] Figure 3 Exploded views of a single battery cell provided in some embodiments of this application;

[0199] Figure 4 for Figure 3 The image shows an isometric view of a single battery cell.

[0200] Figure 5 for Figure 4 The AA cross-sectional view of the battery cell shown in the figure is the preset cross-section of the first side wall portion shown in the figure.

[0201] Figure 6 for Figure 5 A magnified view of a portion of point B in the middle; the cross-section of the first sidewall shown in the figure is the preset cross-section.

[0202] Figure 7 for Figure 5 The isometric view of the shell shown;

[0203] Figure 8 for Figure 7 The enlarged view of part J in the figure shows that the dashed line is the boundary line between the first region and the second region. The first region is on one side of the dashed line along the first direction, and the second region is on the other side of the dashed line along the first direction. The first sub-surface is shown to span the first region and the second region.

[0204] Figure 9 This is a simplified metallographic diagram of a predetermined cross-section of the first sidewall portion provided in some embodiments of this application. The diagram shows the first grain in the first region, but not the other grains in the first region. The diagram shows the second grain in the second region, but not the other grains in the second region. The diagram shows the dimension of the first grain in the first region extending along the first direction and the maximum dimension along the second direction. The diagram shows the dimension of the second grain in the second region extending along the first direction and the maximum dimension along the second direction. The dashed line in the diagram is the boundary line between the first region and the second region. The side of the dashed line along the first direction is the first region, and the other side of the dashed line along the first direction is the second region. The shape of the grain in the diagram is only schematic and does not represent the actual shape of the grain.

[0205] Figure 10Axonometric views of electrode assemblies provided in some embodiments of this application;

[0206] Figure 11 for Figure 10 The diagram shows the structure of the electrode assembly.

[0207] Figure 12 Axonometric views of electrode assemblies provided for other embodiments of this application;

[0208] Figure 13 for Figure 12 The diagram shows the structure of the electrode assembly.

[0209] Figure 14 for Figure 6 The figure shows a partial view of the first sidewall portion. The dashed line in the figure is the dividing line between the first region and the second region. The first sub-surface spans the first region and the second region, and the first outer surface spans the first region and the second region.

[0210] Figure 15 Axonometric views of the housing provided for some embodiments of this application;

[0211] Figure 16 for Figure 15 The top view of the casing shown;

[0212] Figure 17 for Figure 15 A magnified view of a portion of point K in the figure. The dashed line in the figure is the boundary line 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 inner surface spans across the first region and the second region.

[0213] Figure 18 Axonometric views of the housing provided for other embodiments of this application;

[0214] Figure 19 for Figure 18 The top view of the casing shown;

[0215] Figure 20 for Figure 18 A magnified view of part M in the middle. The dashed line in the figure is the dividing line 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 spans the first region and the second region. The second connecting surface spans the first region and the second region.

[0216] Figure 21 for Figure 18 The enlarged view at point N shows that the dashed line is the boundary between the first and second regions. The first and second regions are located on opposite sides of the dashed line along the first direction. The first connecting surface spans the first and second regions, and the third connecting surface spans the first and second regions.

[0217] Figure 22 Axonometric views of the housing provided for some embodiments of this application;

[0218] Figure 23 for Figure 17 The top view of the casing shown;

[0219] Figure 24 for Figure 22 A magnified view of part P in the middle. The dashed line in the figure is the dividing line 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 spans the first region and the second region, the second connecting surface spans the first region and the second region, and the first transition surface spans the first region and the second region.

[0220] Figure 25 for Figure 22 A magnified view of part Q in the figure. The dashed line in the figure is the dividing line 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 spans the first region and the second region. The third connecting surface spans the first region and the second region. The second transition surface spans the first region and the second region.

[0221] Figure 26 Partial view of a battery cell provided for some embodiments of this application (showing the positive electrode, negative electrode, and separator of the electrode assembly);

[0222] Figure 27 This application provides a diagram showing the positional relationship between the positive electrode, negative electrode, and insulating element in some embodiments.

[0223] Figure 28 This is a diagram showing the positional relationship between the positive electrode, negative electrode, and separator provided in other embodiments of this application;

[0224] Figure 29 A partial view of a battery cell provided for some embodiments of this application (showing the first sidewall portion);

[0225] Figure 30 for Figure 29 The figure shows a partial view of the first sidewall portion. The dashed line in the figure is the dividing line between the first region and the second region. 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.

[0226] Figure 31 for Figure 29 The isometric view of the shell shown;

[0227] Figure 32 A partial view of a battery cell provided for other embodiments of this application (showing the first sidewall portion);

[0228] Figure 33 for Figure 32A magnified view of a section at point C;

[0229] Figure 34 A partial view of a battery cell provided for some embodiments of this application (showing the first sidewall portion);

[0230] Figure 35 for Figure 34 A magnified view of a section at point D;

[0231] Figure 36 A partial view of a battery cell provided for some embodiments of this application (showing the first sidewall portion);

[0232] Figure 37 for Figure 36 A magnified view of a section at point E in the middle;

[0233] Figure 38 Axonometric views of the housing are provided for further embodiments of this application;

[0234] Figure 39 for Figure 38 The enlarged view at point F shows that the dashed line is the boundary between the first and second zones, as well as the boundary between the third and fourth zones. The first and second zones are located on opposite sides of the dashed line along the first direction, and the third and fourth zones are located on opposite sides of the dashed line along the first direction. The first inner surface spans the first and second zones, and the third inner surface spans the third and fourth zones.

[0235] Figure 40 A partial view of a battery cell provided for some embodiments of this application (showing a corner wall);

[0236] Figure 41 The diagram shows the structure of a corner wall provided in some embodiments of this application. The dashed line in the diagram is the boundary line between the third and fourth regions. The third inner surface spans the third and fourth regions, and the third outer surface spans the third and fourth regions.

[0237] Figure 42 The diagram shows the structure of a corner wall provided in some other embodiments of this application. The dashed line in the diagram is the boundary line between the third and fourth regions. The third inner surface spans the third and fourth regions, and the third outer surface spans the third and fourth regions.

[0238] Figure 43 Partial view of a battery cell provided for other embodiments of this application (showing a corner wall);

[0239] Figure 44 for Figure 43 A magnified view of a section at point G in the middle;

[0240] Figure 45A partial view of a battery cell provided for some embodiments of this application (showing a corner wall);

[0241] Figure 46 for Figure 45 A magnified view of a section at point H in the middle;

[0242] Figure 47 A partial view of a battery cell provided for some embodiments of this application (showing a corner wall);

[0243] Figure 48 for Figure 47 A magnified view of a section at point I;

[0244] Figure 49 This is a diagram showing the positional relationship between the end cap and the sidewall before welding in some embodiments of this application;

[0245] Figure 50 This is a schematic diagram showing the connection between the end cap and the electrode terminal provided in some embodiments of this application.

[0246] Reference numerals: 1. Outer shell; 11. Shell; 111. First sidewall portion; 1111. First region; 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 region; 1113. Third end; 1114. Fourth end; 1115. Limiting surface; 1116. Limiting area; 1117. First transition area; 112. Second sidewall portion; 113. Corner wall; 1131. Third region; 1132. Fourth… 1133, First connecting end; 1134, Second connecting end; 1135, Second transition region; 12, End cap; 121, Outer surface of end cap; 2, Electrode assembly; 21, Tab; 21a, Positive electrode tab; 21b, Negative electrode tab; 22, Positive electrode sheet; 221, Positive electrode body region; 2211, Fifth end; 222, Positive electrode current collector; 223, Positive electrode active material layer; 2231, Positive electrode body portion; 2232, Positive electrode thinning portion; 224, Insulating layer; 23, Negative electrode sheet; 231, Negative electrode body region; 2311, Sixth end; 232, Negative electrode current collector; 233, Negative electrode active material layer; 2331, Negative electrode body portion; 2332, Negative electrode thinning portion; 24. Thin section; 241. Isolator; 242. Seventh end; 243. Extended area; 244. Straight area; 25. Corner area; 26. Fifth outer surface; 27. Sixth outer surface; 28. Electrode terminal; 39. Terminal body; 30. First limiting part; 31. Second limiting part; 4. Pressure relief mechanism; 50. Connecting part; 51. First connecting part; 511. First connecting interface; 5111. First position; 5112. First interface; 5113. Second interface; 5114. Third position; 5115. Fourth position; 52. Second connecting part; 521. Second connecting interface; 5211. Second position; 5212. Third interface; 5213. Fourth interface; 5214. Fifth position; 5215, Sixth position; 6, First insulating component; 7, Second insulating component; 10, Battery cell; 20, Housing; 201, First housing; 202, Second housing; 100, Battery assembly; 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 Implementation

[0247] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0248] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used in the description of this application is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms "comprising" and "having," and any variations thereof, in the description, claims, and accompanying drawings of this application are intended to cover non-exclusive inclusion. The terms "first," "second," etc., in the description, claims, or accompanying drawings of this application are used to distinguish different objects, not to describe a specific order or hierarchy.

[0249] In this application, the reference to "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment that is mutually exclusive with other embodiments.

[0250] In this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. Additionally, in this application, the character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0251] In the embodiments of this application, the same reference numerals denote the same components, and for the sake of brevity, detailed descriptions of the same components are omitted in different embodiments. It should be understood that the thickness, length, width, and other dimensions of various components in the embodiments of this application shown in the accompanying drawings, as well as the overall thickness, length, width, and other dimensions of the integrated device, are merely illustrative and should not constitute any limitation on this application.

[0252] In this application, "multiple" means two or more (including two).

[0253] In this embodiment of the application, the battery cell can be a secondary battery, which refers to a battery cell that can be recharged to activate the active materials and continue to be used after the battery cell has been discharged.

[0254] 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-metal hydride batteries, nickel-cadmium batteries, lead-acid batteries, etc.

[0255] It should be noted that the battery cell in this application embodiment is the same battery as the one in the prior art application.

[0256] A battery cell 10 typically includes an electrode assembly 2. The electrode assembly 2 includes a positive electrode, a negative electrode, and a separator 24. During the charging and discharging process of the battery cell 10, active ions (such as lithium ions) repeatedly insert and extract between the positive and negative electrodes. The separator 24 is disposed between the positive and negative electrodes, which can reduce the possibility of short circuit between the positive and negative electrodes, while allowing active ions to pass through.

[0257] In some embodiments, the positive electrode may be a positive electrode sheet 22, which may include a positive current collector 222 and a positive active material disposed on at least one surface of the positive current collector 222.

[0258] As an example, the positive current collector 222 has two surfaces opposite each other in its own thickness direction, and the positive active material is disposed on either or both of the two opposite surfaces of the positive current collector 222.

[0259] As an example, the positive current collector 222 can be a metal foil or a composite current collector. For example, as a metal foil, it can be aluminum with a silver-plated surface, stainless steel with a silver-plated surface, stainless steel, copper, aluminum, nickel, carbon electrode, carbon, nickel, or titanium, etc. The composite current collector may include a polymer material base layer and a metal layer. The composite current collector can 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.).

[0260] As an example, the positive electrode active material may include at least one of the following materials: lithium phosphate, lithium transition metal oxide, and their respective modified compounds. However, this application is not limited to these materials, and other conventional 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 phosphate include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), lithium iron phosphate and carbon composites, lithium manganese phosphate (such as LiMnPO4), lithium manganese phosphate and carbon composites, lithium manganese iron phosphate, and lithium manganese iron phosphate and carbon composites. Examples of lithium transition metal oxides may include, but are not limited to, at least one of lithium cobalt oxides (such as LiCoO2), lithium nickel oxides (such as LiNiO2), lithium manganese oxides (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, lithium nickel cobalt manganese oxides (such as LiNi1 / 3Co1 / 3Mn1 / 3O2 (also abbreviated as NCM333), LiNi0.5Co0.2Mn0.3O2 (also abbreviated as NCM523), LiNi0.5Co0.25Mn0.25O2 (also abbreviated as NCM211), LiNi0.6Co0.2Mn0.2O2 (also abbreviated as NCM622), LiNi0.8Co0.1Mn0.1O2 (also abbreviated as NCM811), lithium nickel cobalt aluminum oxides (such as LiNi0.85Co0.15Al0.05O2) and their modified compounds.

[0261] In some embodiments, the positive electrode can be a foamed metal. The foamed metal can be foamed nickel, foamed copper, foamed aluminum, foamed alloys, etc. When foamed metal is used as the positive electrode, the surface of the foamed metal may or may not contain a positive electrode active material. As an example, lithium source material, potassium metal, or sodium metal can also be filled and / or deposited within the foamed metal, where the lithium source material is lithium metal and / or a lithium-rich material.

[0262] In some embodiments, the negative electrode can be a negative electrode plate 23, and the negative electrode plate 23 can include a negative electrode current collector 232.

[0263] As an example, the negative electrode current collector 232 can be a metal foil, a foamed metal, or a composite current collector. For example, as a metal foil, it can be aluminum with a silver-plated surface, stainless steel with a silver-plated surface, stainless steel, copper, aluminum, nickel, carbon electrode, carbon, nickel, or titanium, etc. The foamed metal can be foamed nickel, foamed copper, foamed aluminum, foamed alloy, etc. The composite current collector can include a polymer material base layer and a metal layer. The composite current collector can be formed by forming a metal material (copper, copper 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.).

[0264] As an example, the negative electrode 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.

[0265] As an example, the negative electrode current collector 232 has two surfaces opposite each other in its own thickness direction, and the negative electrode active material is disposed on either or both of the two opposite surfaces of the negative electrode current collector 232.

[0266] As an example, the negative electrode active material may be a negative electrode active material known in the art for use in battery cell 10. 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, and lithium titanate, etc. Silicon-based materials may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Tin-based materials may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. However, this application is not limited to these materials, and other conventional materials that can be used as battery negative electrode active materials may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0267] In some embodiments, the positive current collector 222 may be made of aluminum, and the negative current collector 232 may be made of copper.

[0268] In some embodiments, the separator 24 is a separator membrane. The separator membrane can be any known porous separator membrane with good chemical and mechanical stability.

[0269] As an example, the material of the separator may include at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may 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 may be the same or different. The separator 24 may be a separate component located between the positive and negative electrodes, or it may be attached to the surfaces of the positive and negative electrodes.

[0270] In some embodiments, the separator 24 is a solid electrolyte. The solid electrolyte is disposed between the positive and negative electrodes, serving both to transport ions and to isolate the positive and negative electrodes.

[0271] 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 can be liquid, gel-like, or solid. Liquid electrolytes include electrolyte salts and solvents.

[0272] In some embodiments, the electrolyte salt may include at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium dioxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate.

[0273] In some embodiments, the solvent may include at least one selected from ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butyl carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone. The solvent may also be an ether solvent. Ether solvents may include one or more selected from ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, 1,3-dioxolane, tetrahydrofuran, methyl tetrahydrofuran, diphenyl ether, and crown ethers.

[0274] Among them, the gel electrolyte includes a polymer as the electrolyte backbone network, combined with an ionic liquid - lithium salt.

[0275] Solid electrolytes include polymer solid electrolytes, inorganic solid electrolytes, and composite solid electrolytes.

[0276] As an example, polymer solid electrolytes can be polyether (polyoxyethylene), polysiloxane, polycarbonate, polyacrylonitrile, polyvinylidene fluoride, polymethyl methacrylate, monoionic polymers, polyionic liquids-lithium salts, cellulose, etc.

[0277] As an example, inorganic solid electrolytes may include one or more of the following: oxide solid electrolytes (crystalline perovskite, sodium superconducting ion conductor, garnet, amorphous LiPON thin film), sulfide solid electrolytes (crystalline lithium superconducting ion conductor (lithium germanium phosphate sulfide, silver sulfide germanium ore), amorphous sulfides), halide solid electrolytes, nitride solid electrolytes, and hydride solid electrolytes.

[0278] As an example, composite solid electrolytes are formed by adding inorganic solid electrolyte fillers to polymer solid electrolytes.

[0279] In some embodiments, the electrode assembly 2 is a wound structure. The positive electrode 22 and the negative electrode 23 are wound into a wound structure.

[0280] In some embodiments, the electrode assembly 2 has a stacked structure.

[0281] As an example, multiple positive electrode plates 22 and multiple negative electrode plates 23 can be set, and multiple positive electrode plates 22 and multiple negative electrode plates 23 can be stacked alternately.

[0282] As an example, multiple positive electrode plates 22 can be provided, and multiple negative electrode plates 23 can be folded to form multiple stacked folded segments, with a positive electrode plate 22 sandwiched between adjacent folded segments.

[0283] As an example, both the positive electrode 22 and the negative electrode 23 are folded to form multiple stacked folded segments.

[0284] As an example, multiple separators 24 can be provided, respectively disposed between any adjacent positive electrode 22 or negative electrode 23.

[0285] As an example, the separator 24 can be continuously arranged between any adjacent positive electrode 22 or negative electrode 23 by folding or rolling.

[0286] In some embodiments, the electrode assembly 2 may be cylindrical, flat, or polygonal, etc.

[0287] 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 tab 21a and a negative tab 21b.

[0288] In some embodiments, the battery cell 10 may include a housing 1. The housing 1 is used to encapsulate the electrode assembly 2 and components such as the electrolyte. The housing 1 may be a steel housing, an aluminum housing, a plastic housing (such as polypropylene), a composite metal housing (such as a copper-aluminum composite housing 1), or an aluminum-plastic film, etc.

[0289] As an example, the battery cell 10 can be a cylindrical battery cell 10, a prismatic battery cell 10, a pouch battery cell 10, or a battery cell 10 of other shapes. The prismatic battery cell 10 includes a square battery cell 10, a blade-shaped battery cell 10, and a multi-prismatic battery cell 10, such as a hexagonal prismatic battery cell 10.

[0290] The battery device 100 mentioned in the embodiments of this application refers to a single physical module that includes one or more battery cells 10 to provide higher voltage and capacity.

[0291] In some embodiments, the battery device 100 can 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.

[0292] In some embodiments, the battery device 100 may be a battery pack, which includes a housing 20 and battery cells 10, wherein the battery cells 10 or battery modules are housed in the housing 20.

[0293] In some embodiments, the housing 20 may be part of the chassis structure of the vehicle 1000. For example, a portion of the housing 20 may be at least a portion of the floor of the vehicle 1000, or a portion of the housing 20 may be at least a portion of the crossbeams and longitudinal beams of the vehicle 1000.

[0294] In some embodiments, the battery device 100 may be an energy storage device. Energy storage devices include energy storage containers, energy storage cabinets, etc.

[0295] In related technologies, a battery cell 10 generally includes a housing 1 and an electrode assembly 2. The housing 1 may include a shell 11 and an end cap 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 cap 12 to form a sealed space inside the shell 1 to accommodate the electrode assembly 2.

[0296] To achieve a stable connection between the end cap 12 and the housing 11, the end cap 12 and the housing 11 can be welded. After welding, a connection portion 5 will be formed at the weld position of the end cap 12 and the housing 11. The connection portion 5 has a relatively high hardness. During the charging and discharging process of the battery cell 10, due to the insertion and extraction of ions, the electrode assembly 2 will undergo cyclic expansion and contraction. The wall of the housing 11 will deform under 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 housing 11 through this deformation. Because the connection portion 5 has a high hardness and low toughness, it is difficult to withstand the force during the expansion and contraction of the electrode assembly 2, which may cause the housing 11 to crack at the connection portion 5 near the opening, affecting the service life of the battery cell 10.

[0297] Based on the above considerations, this application embodiment sets a first region 1111 with lower hardness. The expansion force of the electrode assembly 2 acting on the connection part 5 is released by the deformation part of the first region 1111 with lower hardness, thereby reducing the possibility of cracking of the connection part 5 at the opening of the housing 11 and improving the service life of the battery cell 10.

[0298] The battery cell 10 described in this application is applicable to battery device 100 and electrical device using battery cell 10.

[0299] Electrical devices can include vehicles 1000, mobile phones, portable devices, laptops, ships, spacecraft, electric toys, and power tools, etc. Vehicles 1000 can be gasoline-powered cars, natural gas-powered cars, or new energy vehicles; new energy vehicles can be pure electric vehicles, hybrid electric vehicles, or range-extended electric vehicles, etc. Spacecraft include airplanes, rockets, space shuttles, and spacecraft, etc. Electric toys include stationary or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc. Power tools include metal cutting power tools, grinding power tools, assembly power tools, and railway power tools, such as electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact drills, concrete vibrators, and electric planers, etc. This application does not impose special limitations on the above-mentioned electrical devices.

[0300] For ease of explanation, the following embodiments will be described using a vehicle 1000 as an example of an electrical device.

[0301] Please refer to Figure 1 The figure is a schematic diagram of the structure of a vehicle 1000 provided in some embodiments of this application. A battery device 100 is disposed inside the vehicle 1000, and the battery device 100 may be located at the bottom, front, or rear of the vehicle 1000. The battery device 100 can be used to power the vehicle 1000; for example, the battery device 100 can serve as the operating power source for the vehicle 1000.

[0302] The vehicle 1000 may also 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, for the power needs of the vehicle 1000 during startup, navigation and driving.

[0303] In some embodiments of this application, the battery device 100 can not only serve as the operating power source for the vehicle 1000, but also as the driving power source for the vehicle 1000, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle 1000.

[0304] Please refer to Figure 2 , Figure 2 This is an exploded view of a battery device 100 provided in some embodiments of this application. The battery device 100 may include a battery cell 10 and a housing 20, wherein the battery cell 10 is housed within the housing 20.

[0305] The housing 20 is a component that houses the battery cell 10, providing a space for the battery cell 10. The housing 20 can adopt various structures. In some embodiments, the housing 20 may include a first housing 201 and a second housing 202, which overlap each other to define a space for accommodating the battery cell 10. The first housing 201 and the second housing 202 can have various shapes, such as cuboid or cylindrical. The first housing 201 can be a hollow structure with an opening on one side, and the second housing 202 can also be a hollow structure with an opening on one side. The opening side of the second housing 202 overlaps the opening side of the first housing 201, thus forming a housing 20 with a accommodating 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, overlapping the opening side of the first housing 201, thus forming a housing 20 with a accommodating space. The first housing 201 and the second housing 202 can be sealed by a sealing element, such as a sealing ring or sealant.

[0306] In the battery device 100, there can be one or more battery cells 10. If there are multiple battery cells 10, they can be connected in series, in parallel, or in a mixed configuration. A mixed configuration means that multiple battery cells 10 are connected in both series and parallel. Alternatively, multiple battery cells 10 can be first connected in series, in parallel, or in a mixed configuration to form a battery module, and then multiple battery modules can be connected in series, in parallel, or in a mixed configuration to form a whole, which is then housed within the housing 20. Another option is that all battery cells 10 can be directly connected in series, in parallel, or in a mixed configuration, and then the whole consisting of all battery cells 10 is housed within the housing 20.

[0307] Please refer to Figure 3 , Figure 4 and Figure 5 The battery cell 10 may include a housing 1 and an electrode assembly 2, with the electrode assembly 2 housed within the housing 1.

[0308] In some embodiments, the housing 1 may include a housing 11 and an end cap 12, wherein the housing 11 has an opening at at least one end along a first direction Z, and the end cap 12 closes the opening of the housing 11.

[0309] The housing 11 is a component used to house 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 opposite ends along the first direction Z. The housing 11 can have various shapes, such as cylindrical or cuboid. The housing 11 can be made of various materials, such as copper, iron, aluminum, steel, or aluminum alloy. The electrode assembly 2 can be partially or completely located within the housing 11.

[0310] End cap 12 is a component that closes the opening of housing 11 to isolate the internal environment of battery cell 10 from the external environment. End cap 12 and housing 11 together define a storage space for accommodating electrode assembly 2, electrolyte, and other components. End cap 12 can be connected to housing 11 by welding or roll sealing to close the opening of housing 11. The shape of end cap 12 can be adapted to the shape of housing 11. For example, if housing 11 is a cuboid structure, end cap 12 can be a rectangular plate structure adapted to housing 11; or if housing 11 is a cylindrical structure, end cap 12 can be a circular plate structure adapted to housing 11. The material of end cap 12 can also be various, such as copper, iron, aluminum, steel, aluminum alloy, etc. The materials of end cap 12 and housing 11 can be the same or different.

[0311] In an embodiment where the housing 11 has an opening at one end, one end cap 12 may be provided accordingly. In an embodiment where the housing 11 has openings at both opposite ends, two end caps 12 may be provided accordingly. The two end caps 12 respectively close the two openings of the housing 11, and the two end caps 12 and the housing 11 together define the receiving space.

[0312] In some embodiments, the battery cell 10 may further include electrode terminals 3, which are disposed on the housing 1 and are used for electrical connection with the tabs 21 of the electrode assembly 2 to input or output electrical energy of the battery cell 10. The electrode terminals 3 may be disposed on the housing 11 of the housing 1 or on the end cap 12 of the housing 1. The electrode terminals 3 and the tabs 21 may be directly connected, for example, by welding. Alternatively, the electrode terminals 3 and the tabs 21 may be indirectly connected, for example, through a current collector. The current collector may be a metallic conductor, such as copper, iron, aluminum, steel, or aluminum alloy.

[0313] In some embodiments, the battery cell 10 may further include a pressure relief mechanism 4, which may be disposed on the end cap 12 or the housing 11. The pressure relief mechanism 4 may be a pressure relief component installed on the housing 11 or the end cap 12, such as an explosion-proof plate or a safety valve. The pressure relief mechanism 4 may also be integrally formed with the end cap 12 or the housing 11. The pressure relief mechanism 4 may be provided with a pressure relief groove to split 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.

[0314] As an example, such as Figure 3 , Figure 4 and Figure 5As shown, one end of the housing 11 forms an opening, and there is one end cap 12 in the housing 1, which closes one 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, namely a positive electrode terminal 3 and a negative electrode terminal 3. The end of the electrode assembly 2 facing the end cap 12 has a positive electrode tab 21a and a negative electrode tab 21b. 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.

[0315] For the battery cell 10 in this embodiment, please refer to [link / reference]. Figures 6-9 The battery cell 10 includes 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, and includes a first sidewall portion 111. The electrode assembly 2 is at least partially housed within the housing 11. The electrode assembly 2 includes a positive electrode 22 and a negative electrode 23. At least portions of the positive electrode 22 and the negative electrode 23 are stacked along a second direction Y, which is parallel to the thickness direction of the first sidewall portion 111. The first direction Z intersects the second direction Y. The end cap 12 is used to close the opening. The first sidewall portion 111 is welded to the end cap 12 to form a first connection portion 51. The first sidewall portion 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 connection portion 51 and the second region 1112, and the hardness of the first region 1111 is lower than the hardness of the second region 1112.

[0316] The housing 11 may have an opening at only one end along the first direction Z, and the end cap 12 may be configured as one.

[0317] The housing 11 may have openings at both ends opposite each other along the first direction Z, and the end caps 12 may be configured as two.

[0318] The shell 11 can be in various shapes, such as cylindrical, prismatic, etc. The prismatic shape can be triangular, quadrangular, pentagonal, hexagonal, etc. The quadrangular prism can be cuboid, cube, etc.

[0319] The first direction Z is parallel to the orientation of the opening of the housing 11. In an embodiment where the housing 11 is cylindrical, the first direction Z may be parallel to the axial direction of the housing 11; in an embodiment where the housing 11 is prismatic, the first direction Z may be parallel to the extension direction of the side edge of the housing 11.

[0320] The second direction Y is parallel to the thickness direction of the first sidewall portion 111. In an embodiment where the housing 11 is cylindrical, the first sidewall portion 111 is cylindrical, the radial direction of the housing 11 is the thickness direction of the first sidewall portion 111, and the second direction Y is parallel to the radial direction of the housing 11. In an embodiment where the housing 11 is prismatic, the first sidewall portion 111 can be a rectangular plate structure. The first direction Z and the second direction Y can be set at an acute angle, a right angle, or an obtuse angle.

[0321] The end cap 12 can be welded to the housing 11, and the welding of the end cap 12 and the housing 11 forms a connecting part 5, which can extend circumferentially along the opening of the housing 11. The end cap 12 and the housing 11 are connected and fixed through the connecting part 5 to achieve a seal between the end cap 12 and the housing 11. The connecting part 5 is the part with weld marks formed after the end cap 12 and the housing 11 are welded together; the connecting part 5 can be the part where the end cap 12 and the housing 11 are welded together.

[0322] The first sidewall portion 111 in the housing 11 can be one or more. The first connecting portion 51 can correspond one-to-one with the first sidewall portion 111. The first connecting portion 51 is the part with a weld mark formed after the end cap 12 is welded to the first sidewall portion 111; it can be the part where the end cap 12 and the first sidewall portion 111 are welded together. A portion of the first connecting portion 51 is formed on the end cap 12, and another portion is formed on the first sidewall portion 111. The first sidewall portion 111 and the end cap 12 can form the first connecting portion 51 by seam welding or by through welding. The first connecting portion 51 can be a part of the connecting portion 5 or the entire connecting portion 5. In an embodiment where the housing 11 is cylindrical, there is only one first sidewall portion 111 in the housing 11, and the first sidewall portion 111 is cylindrical, and the first connecting portion 51 is the connecting portion 5; in an embodiment where the housing 11 is prismatic, the housing 11 may include multiple sidewalls, which are arranged along the opening of the housing 11, and at least one of the two sidewalls arranged opposite each other in the second direction Y may be the first sidewall portion 111, and the first connecting portion 51 is a part of the connecting portion 5.

[0323] The first sidewall portion 111 may be the wall with the largest outer surface area in the shell 11, or it may not be the wall with the largest outer surface area in the shell 11. Taking the shell 11 as a cuboid as an example, the shell 11 may include two first sidewall portions 111 and two second sidewall portions 112. The two first sidewall portions 111 are arranged opposite each other along the second direction Y, and the two second sidewall portions 112 are arranged opposite 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 sidewall 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 sidewall portion 111 is greater than the outer surface area of ​​the second sidewall portion 112. Alternatively, the second sidewall 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 sidewall portion 112 is greater than the outer surface area of ​​the first sidewall portion 111.

[0324] The first region 1111 can be a region with lower hardness than the first sidewall portion 111. The hardness of the first region 1111 is lower than that of the second region 1112. The second region 1112 can be the portion of the first sidewall portion 111 located along the first direction Z on the side of the first region 1111 opposite to the first connecting portion 51. The first region 1111 and the first connecting portion 51 can be directly connected; the first region 1111 and the second region 1112 can be directly connected or indirectly connected. The maximum hardness of the first region 1111 can be less than the minimum hardness of the second region 1112, so that the hardness of the first region 1111 is lower than that of the second region 1112.

[0325] The electrode assembly 2 is located within the receiving space defined by the housing 11 and the end cap 12. The electrode assembly 2 can be a stacked structure or a wound structure. There can be one or more electrode assemblies 2 in the housing 11. If there are multiple electrode assemblies 2, they can be stacked, for example, multiple electrode assemblies 2 can be stacked along the second direction Y.

[0326] As an example, the hardness of zone 1111 and the hardness of zone 1112 can be measured using a known hardness tester.

[0327] As an example, the first region 1111 extends along the third direction X to the opposite ends of the first sidewall portion 111.

[0328] The formation method of the first region 1111 with lower hardness is not limited. As an example, the first region 1111 with lower hardness can be obtained by heating and softening the shell 11 with a laser. As an example, a portion of the shell 11 can be annealed to obtain the first region 1111 with lower hardness.

[0329] As an example, the hardness of the area along the first direction of the weld is reduced by controlling the welding power of the housing 11 and the end cap 12, that is, the hardness of the area along the first direction of the connecting part 5 is reduced, thereby forming a first region 1111 with lower hardness. It is understood that, when the welding power of the housing 11 and the end cap 12 is not greater than the maximum allowable power, appropriately increasing the welding power can make the dimension of the first region 1111 with lower hardness larger along the first direction, which is beneficial to reducing cracking of the first connecting part 51.

[0330] In this embodiment, at least a portion of the positive electrode 22 and at least a portion of the negative electrode 23 are stacked along the second direction Y. During cycling, the electrode assembly 2 expands along the second direction Y. The first sidewall portion 111 is subjected to the expansion force of the electrode assembly 2. Since the hardness of the first region 1111 is lower than that of the second region 1112, the first region 1111 has higher toughness than the second region 1112. By setting the first region 1111 with lower hardness in the first sidewall portion 111, the first region 1111 has higher toughness, thereby releasing part of the expansion force of the electrode assembly 2, reducing the impact of the expansion force of the electrode assembly 2 on the first connection portion 51, reducing the possibility of cracking of the first connection portion 51 at the opening of the housing 11, and thus improving the service life of the battery cell 10.

[0331] In some embodiments, please refer to Figures 6-9 The ratio of the hardness of Zone 1111 to the hardness of Zone 2112 is between 0.3 and 0.8.

[0332] It should be explained that the hardness type of Zone 1111 is the same as that of Zone 2112.

[0333] As an example, the hardness of zone 1111 and the hardness of zone 1112 can both be Vickers hardness.

[0334] As an example, the hardness of the first zone 1111 and the hardness of the second zone 1112 can both be Brinell hardness.

[0335] The hardness type of Zone 1111 and the hardness type of Zone 1112 can also be other known hardness types, as long as the hardness type of Zone 1111 and the hardness type of Zone 1112 are the same.

[0336] As an example, the ratio of the hardness of the first zone 1111 to the hardness of the second zone 1112 is any one of the point values ​​or any range between the two, such as 0.3, 0.35, 0.4, 0.45, 0.5, 0.6, 0.7, 0.8.

[0337] In this embodiment, the ratio of the hardness of the first region 1111 to the hardness of the second region 1112 is between 0.3 and 0.8, which makes the ratio of the hardness of the first region 1111 to the hardness of the second region 1112 within a suitable range. This allows the lower hardness of the first region 1111 to reduce the possibility of cracking of the first connecting part 51 and to a certain extent suppress cracking of the first region 1111 under the large expansion force of the electrode assembly 2.

[0338] Understandably, the ratio of the hardness of Zone 1111 to the hardness of Zone 1112 is not limited, as long as the hardness of Zone 1111 is lower than that of Zone 1112. For example, the ratio of the hardness of Zone 1111 to the hardness of Zone 1112 can be less than 0.3, or the ratio can be greater than 0.8 and less than 1.

[0339] In some embodiments, please refer to Figures 6-9 The ratio of the hardness of Zone 1111 to the hardness of Zone 2112 is between 0.5 and 0.8.

[0340] As an example, the ratio of the hardness of the first zone 1111 to the hardness of the second zone 1112 is any one of the following point values ​​or any range between the two: 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8.

[0341] In this embodiment, the ratio of the hardness of the first region 1111 to the hardness of the second region 1112 is between 0.3 and 0.8, which makes the ratio of the hardness of the first region 1111 to the hardness of the second region 1112 within a suitable range. This allows the lower hardness of the first region 1111 to reduce the possibility of cracking of the first connecting part 51 and to a certain extent suppress cracking of the first region 1111 under the large expansion force of the electrode assembly 2.

[0342] It is understandable that the ratio of the hardness of Zone 1111 to the hardness of Zone 1112 is not limited, as long as the hardness of Zone 1111 is lower than that of Zone 1112. As an example, the ratio of the hardness of Zone 1111 to the hardness of Zone 1112 can be less than 0.5 depending on the circumstances.

[0343] In some embodiments, please refer to Figures 6-9 The hardness range of Zone 2 1112 is 40HV to 100HV, and the hardness range of Zone 1 1111 is 20HV to 55HV.

[0344] It should be noted that "HV" is the unit of Vickers hardness.

[0345] As an example, the hardness range of Zone 1112 is any one of the following values ​​or any range between two: 40HV, 45HV, 50HV, 60HV, 70HV, 80HV, 90HV, 100HV.

[0346] As an example, the hardness range of Zone 1111 is any one of the following values ​​or any range between two: 20HV, 25HV, 30HV, 35HV, 40HV, 45HV, 50HV, 55HV.

[0347] In this embodiment, the hardness range of the second region 1112 is suitable, which is beneficial to protect the electrode assembly 2 inside the housing 11, reduce the impact of the external environment on the electrode assembly 2 inside the housing 11, and realize the basic protection of the electrode assembly 2 by the housing 11. The hardness range of the first region 1111 is also suitable. The lower hardness of the first region 1111 allows the first region 1111 to reduce the possibility of cracking of the first connection 51, and to a certain extent suppress the cracking of the first region 1111 under the action of the large expansion force of the electrode assembly 2.

[0348] It is understandable that the hardness range of Zone 1111 and the hardness range of Zone 1112 are not limited, as long as the hardness of Zone 1111 is lower than that of Zone 1112. As an example, the hardness range of Zone 1112 can be less than 40 HV or greater than 100 HV, and the hardness range of Zone 1111 can be less than 20 HV or greater than 55 HV.

[0349] In some embodiments, please refer to Figure 6 , Figure 26 , Figure 29 , Figure 32 , Figure 34 and, Figure 36 The dimension of the first zone 1111 along the first direction Z ranges from 0.05mm to 0.75mm.

[0350] As an example, the dimension of the first region 1111 along the first direction Z is D. 10 , 0.05mm≤D 10 ≤0.75mm.

[0351] As an example, the dimension of the first region 1111 along the first direction Z is any one of the following point values ​​or any range between two: 0.05mm, 0.1mm, 0.15mm, 0.2mm, 0.25mm, 0.3mm, 0.4mm, 0.5mm, 0.6mm, 0.7mm, 0.75mm.

[0352] As an example, the dimension of the first zone 1111 along the first direction Z can be measured using a vernier caliper or micrometer.

[0353] In this embodiment, the size range of the first region 1111 along the first direction Z is more suitable. The first region 1111 with lower hardness is formed within the appropriate size range. On the one hand, this reduces the possibility of cracking of the first connection part 51. On the other hand, it helps to suppress the cracking of the first region 1111 with lower hardness due to excessive length under the influence of the expansion force of the electrode assembly 2.

[0354] 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 can be less than 0.05 mm or greater than 0.75 mm.

[0355] See some implementation columns. Figure 6 , Figure 26 , Figure 29 , Figure 32 , Figure 34 and, Figure 36 The dimension of the first zone 1111 along the first direction Z ranges from 0.1mm to 0.6mm.

[0356] As an example, the dimension of the first region 1111 along the first direction Z is any one of the following point values ​​or any range between two: 0.1mm, 0.15mm, 0.2mm, 0.25mm, 0.3mm, 0.35mm, 0.4mm, 0.45mm, 0.5mm, 0.55mm, 0.6mm.

[0357] In this embodiment, the size range of the first region 1111 along the first direction Z is more suitable. The first region 1111 with lower hardness is formed within the appropriate size range. On the one hand, the expansion force of the electrode assembly 2 is released through the first region 1111 by the deformation of the first region 1111 with lower hardness, reducing the possibility of cracking of the first connection part 51. On the other hand, it is beneficial to suppress the cracking of the first region 1111 with lower hardness due to excessive length under the influence of the expansion force of the electrode assembly 2.

[0358] 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 can be less than 0.1 mm or greater than 0.6 mm.

[0359] In some embodiments, please refer to Figure 9At least some of the grains in the first region 1111 are first grains 800, the 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%, and the dimension of the first grain 800 extending along the first direction Z is the first dimension, the maximum dimension of the first grain 800 along the second direction Y is the second dimension, and the ratio of the first dimension to the second dimension is in the range of 0.2 to 5.

[0360] For example, please refer to Figures 4-6 ,as well as Figure 9 and Figure 14 The cross-section of the first sidewall portion 111 shown in the figure is a preset cross-section, which is approximately parallel to the first direction Z and the second direction Y. The preset cross-section intersects with the first region 1111 to form the first cross-section.

[0361] As an example, the first grain 800 is an equiaxed crystal.

[0362] The steps for measuring the grains in the first region include sample cutting, sample processing, and grain measurement.

[0363] The sample cutting steps specifically include:

[0364] The housing 11 is connected to an end cap 12 at its first end along the first direction Z. The second end of the housing 11 along the first direction Z is arranged opposite to the first end of the housing 11. The housing 11 is cut along its circumference at a distance of 30 mm from the second end along the first direction Z, separating the electrode assembly 2 and electrolyte inside the housing 11 from the housing 11. The cut housing 11 with the first end is cleaned, and the sidewall of the cleaned housing 11 is restored to a flat surface. The housing 11 with the sidewall restored to a flat surface is arranged with the first end facing down along the first direction Z so that the end cap 12 of the first end is located below the housing 11. Crystal glue is poured into the space enclosed by the housing 11 and the end cap 12 below the housing 11 so that the height of the crystal glue in the space enclosed by the end cap 12 and the housing 11 is greater than or equal to a preset height, which is half the height of the cut housing 11 with the first end. The first sidewall 111 of the housing 11 containing the crystal resin is cut to obtain the sample to be measured. The cutting plane of the housing 11 is approximately perpendicular to the reference plane, which is parallel to the first direction Z and the second direction Y, respectively. For example, the angle between the cutting plane of the housing 11 and the reference plane is 80° to 95°. The cutting is made as far as possible from the top of the housing 11 containing the crystal resin downwards to the end cap 12 below the housing 11 containing the crystal resin.

[0365] Sample processing specifically includes:

[0366] After cutting the first sidewall portion 111 of the shell 11 containing the crystal glue to obtain the sample to be measured, the cross section of the sample to be measured, which is approximately parallel to the first direction Z and the second direction Y, is the preset cross section of the first sidewall portion 111. The preset cross section is polished with sandpaper with a grit greater than or equal to 1600 grit. The polished preset cross section is cleaned and etched to obtain the test sample that can be observed under an optical microscope. The etched test sample is placed under an optical microscope to observe the preset cross section of the test sample.

[0367] An Olympus BX53M optical microscope can be used to measure the grains in a preset cross-section. By selecting a general area to be measured at a lower magnification using the optical microscope, and then increasing the magnification to observe this area, the measurement location can be determined. It is understood that the first grain 800 in region 1111 accounts for more than 50% of the total grains, and the second grain 802 in region 1112 accounts for more than 50%, making the grain differences between the two regions quite obvious. The approximate area to be measured can be identified by observing the grains under the optical microscope.

[0368] The grains displayed under an optical microscope on the BX53M model can be measured using Olympus's corresponding software, such as Capture 2.2.1.

[0369] The specific steps for grain measurement include:

[0370] The crystals under the optical microscope of model BX53M were displayed and measured using the software Capture2.2.1. A 0.1mm*0.2mm rectangle was drawn in the first region 1111. The side of the rectangle with a side length of 0.2mm was parallel to the second direction Y. The crystals completely inside the rectangle and the crystals intersecting the side of the rectangle were all considered to be within the rectangle.

[0371] The dimension of each grain extending along the first direction Z within the 0.1mm*0.2mm rectangular frame is measured. Specifically, each grain within the rectangular frame is projected along the second direction Y to obtain a corresponding projection line extending along the first direction Z. The dimension of this projection line extending along the first direction Z is the dimension of the corresponding grain extending along the first direction Z. The dimension of each grain extending along the first direction is the dimension under the system scale corresponding to the software Capture2.2.1, that is, the actual dimension without being magnified by an optical microscope. This dimension value will not change with the magnification of the optical microscope.

[0372] It should be noted that the 0.1mm*0.2mm rectangle refers to the rectangle having two opposite sides arranged along the first direction Z with a side length of 0.2mm, and these 0.2mm sides being parallel to the second direction Y. The rectangle also has two opposite sides arranged along the second direction Y with a side length of 0.1mm. The dimensions of the rectangle are those under the system scale corresponding to the Capture 2.2.1 software, representing the actual dimensions without magnification by an optical microscope. This dimension will not change with variations in the magnification of the optical microscope.

[0373] The maximum dimension along the second direction Y is measured for each grain within the 0.1mm*0.2mm rectangular frame. Specifically, multiple intercepts parallel to the second direction Y are drawn for each grain. The distance between the two intercept points along the second direction Y formed by the intersection of these intercepts with the corresponding grain is the intercept of the intercept on the corresponding grain. Among the intercepts of the multiple intercepts parallel to the second direction Y for each grain, the largest intercept is the maximum dimension of that grain along the second direction Y. The maximum dimension of each grain along the second direction Y is the dimension under the system scale corresponding to the Capture2.2.1 software, that is, the actual dimension without magnification by an optical microscope. This dimension value will not change with the magnification of the optical microscope.

[0374] The grains are screened by measuring the dimension of each grain extending along the first direction Z within the 0.1mm*0.2mm rectangular frame and the maximum dimension of each grain along the second direction Y. If the ratio of the dimension extending along the first direction Z to the maximum dimension along the second direction Y within the 0.1mm*0.2mm rectangular frame is in the range of 0.2 to 5, then the grain is identified as the first grain 800. The first grains 800 within the 0.1mm*0.2mm rectangular frame are selected in this way. If the ratio of the number of first grains 800 within the 0.1mm*0.2mm rectangular frame to the total number of grains within the 0.1mm*0.2mm rectangular frame is greater than 50%, then the number of first grains 800 within the first cross-section and the total number of grains within the first cross-section are both greater than 50%, thus determining that the number of first grains 800 within the first region 1111 and the total number of grains within the first region 1111 are both greater than 50%.

[0375] For example, please refer to Figure 9 The first dimension is D3, the second dimension is D4, and 0.2≤D3 / D4≤5.

[0376] As an example, the ratio of the first dimension to the second dimension can be any point value or a range between any two of the following: 0.2, 0.3, 0.5, 0.8, 1, 2, 2.5, 3, 3.5, 4, 5.

[0377] In this embodiment, the ratio of the first dimension to the second dimension ranges from 0.2 to 5. The dimension of the first grain 800 extending in the first direction Z is relatively close to the maximum dimension of the first grain 800 in the second direction Y. The structure of the first grain 800 in the first direction Z and the second direction Y is relatively uniform, which is beneficial to improving toughness. The ratio of the number of the first grain 800 in the first region 1111 to the number of all grains in the first region 1111 is greater than 50%, which enables the first region 1111 to have good toughness to release the expansion force of the electrode assembly 2 and reduce the possibility of cracking of the first connection 51.

[0378] It is understandable that the specific metallographic structure of Zone 1111 is not limited, as long as the hardness of Zone 1111 is lower than that of Zone 2112.

[0379] In some embodiments, please refer to Figure 9 The ratio of the first dimension to the second dimension ranges from 0.25 to 4.

[0380] As an example, the ratio of the first dimension to the second dimension can be any one of the following point values ​​or any range between the two: 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.

[0381] In this embodiment, the ratio of the first size to the second size is in the range of 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 a first grain 800 is beneficial to improving toughness, and the first region 1111 with a large proportion of first grains 800 has higher toughness.

[0382] It is understood that the ratio of the first dimension to the second dimension is not limited to the range of 0.25 to 4. As an example, the ratio of the first dimension to the second dimension can be greater than 4 and less than or equal to 5.

[0383] In some embodiments, please refer to Figure 9 The first size ranges from 5μm to 500μm, and the second size ranges from 5μm to 500μm.

[0384] For example, please refer to Figure 9 The first dimension is D3, where 5μm≤D3≤500μm.

[0385] As an example, the first dimension can be any point value or a range of any two of the following: 5μm, 10μm, 20μm, 30μm, 40μm, 55μm, 100μm, 200μm, 300μm, 400μm, 500μm.

[0386] For example, please refer to Figure 9 The second dimension, D4, is 5μm ≤ D4 ≤ 500μm.

[0387] As an example, the first dimension can be any point value or a range of any two of the following: 5μm, 10μm, 20μm, 30μm, 40μm, 55μm, 100μm, 200μm, 300μm, 400μm, 500μm.

[0388] In this embodiment, the range of the first size and the range of the second size are approximately similar. Accordingly, the first size and the second size are relatively close, and the corresponding first grains 800 are beneficial to improving toughness. This makes the first region 1111, which has a larger proportion of first grains 800, have better toughness to release the expansion force of the electrode assembly 2 and reduce the possibility of cracking of the first connection 51.

[0389] It is understandable that the range of the first dimension and the range of the second dimension are not limited, as long as the ratio of the first dimension and the second dimension is within the corresponding ratio range.

[0390] In some embodiments, please refer to Figure 9 At least some of the grains in the second region 1112 are second grains 802, the 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%, and the dimension of the second grains 802 extending along the first direction Z is the third dimension, the maximum dimension of the second grains 802 along the second direction Y is the fourth dimension, and the ratio of the third dimension to the fourth dimension is in the range of 4 to 100.

[0391] For example, please refer to Figures 4-6 ,as well as Figure 9 and Figure 14 The cross-section of the first sidewall portion 111 shown in the figure is a preset cross-section, which is approximately parallel to the first direction Z and the second direction Y. The preset cross-section intersects with the second region 1112 to form a second cross-section.

[0392] As an example, the second grain 802 is a banded crystal.

[0393] The steps for measuring the grains in the second region include sample cutting, sample processing, and grain measurement.

[0394] The sample cutting steps specifically include:

[0395] The housing 11 is connected to an end cap 12 at its first end along the first direction Z. The second end of the housing 11 along the first direction Z is arranged opposite to the first end of the housing 11. The housing 11 is cut along its circumference at a distance of 30 mm from the second end along the first direction Z, separating the electrode assembly 2 and electrolyte inside the housing 11 from the housing 11. The cut housing 11 with the first end is cleaned, and the sidewall of the cleaned housing 11 is restored to a flat surface. The housing 11 with the sidewall restored to a flat surface is arranged with the first end facing down along the first direction Z so that the end cap 12 of the first end is located below the housing 11. Crystal glue is poured into the space enclosed by the housing 11 and the end cap 12 below the housing 11 so that the height of the crystal glue in the space enclosed by the end cap 12 and the housing 11 is greater than or equal to a preset height, which is half the height of the cut housing 11 with the first end. The first sidewall 111 of the housing 11 containing the crystal resin is cut to obtain the sample to be measured. The cutting plane of the housing 11 is approximately perpendicular to the reference plane, which is parallel to the first direction Z and the second direction Y, respectively. For example, the angle between the cutting plane of the housing 11 and the reference plane is 80° to 95°. The cutting is made as far as possible from the top of the housing 11 containing the crystal resin downwards to the end cap 12 below the housing 11 containing the crystal resin.

[0396] Sample processing specifically includes:

[0397] After cutting the first sidewall portion 111 of the shell 11 containing the crystal glue to obtain the sample to be measured, the cross section of the sample to be measured, which is approximately parallel to the first direction Z and the second direction Y, is the preset cross section of the first sidewall portion 111. The preset cross section is polished with sandpaper with a grit greater than or equal to 1600 grit. The polished preset cross section is cleaned and etched to obtain the test sample that can be observed under an optical microscope. The etched test sample is placed under an optical microscope to observe the preset cross section of the test sample.

[0398] An Olympus BX53M optical microscope can be used to measure the grains in a preset cross-section. By selecting a general area to be measured at a lower magnification using the optical microscope, and then increasing the magnification to observe this area, the measurement location can be determined. It is understood that the first grain 800 in region 1111 accounts for more than 50% of the total grains, and the second grain 802 in region 1112 accounts for more than 50%, making the grain differences between the two regions quite obvious. The approximate area to be measured can be identified by observing the grains under the optical microscope.

[0399] The grains displayed under an optical microscope on the BX53M model can be measured using Olympus's corresponding software, such as Capture 2.2.1.

[0400] The specific steps for grain measurement include:

[0401] The crystals under the optical microscope of model BX53M were displayed and measured using the software Capture2.2.1. A 5mm*0.3mm rectangle was drawn in the second region 1112. The side of the rectangle with a side length of 0.3mm is parallel to the second direction Y. The crystals completely inside the rectangle and the crystals intersecting the side of the rectangle are all considered to be within the rectangle.

[0402] The dimension of each grain within the 5mm*0.3mm rectangular frame extended along the first direction Z is measured. Specifically, each grain within the rectangular frame is projected along the second direction Y to obtain a corresponding projection line extending along the first direction Z. The dimension of this projection line extending along the first direction Z is the dimension of the corresponding grain extending along the first direction Z. The dimension of each grain extending along the first direction is the dimension under the system scale corresponding to the software Capture2.2.1, that is, the actual dimension without being magnified by an optical microscope. This dimension value will not change with the magnification of the optical microscope.

[0403] It should be noted that the 5mm*0.3mm rectangle refers to the rectangle having two opposite sides with a length of 0.3mm along the first direction Z, and these 0.3mm sides being parallel to the second direction Y. The rectangle also has two opposite sides with a length of 5mm along the second direction Y. The dimensions of the rectangle are those under the system scale of the Capture 2.2.1 software, representing its actual dimensions without magnification by an optical microscope. These dimensions will not change with variations in the magnification of the optical microscope.

[0404] The maximum dimension along the second direction Y is measured for each grain within the 5mm*0.3mm rectangular frame. Specifically, multiple intercepts parallel to the second direction Y are drawn for each grain. The distance between the two intercept points formed by the intersection of these intercepts with the corresponding grain along the second direction Y is the intercept of the intercept on the corresponding grain. Among the intercepts of the multiple intercepts parallel to the second direction Y for each grain, the largest intercept is the maximum dimension of that grain along the second direction Y. The maximum dimension of each grain along the second direction Y is the dimension under the system scale corresponding to the Capture2.2.1 software, that is, the actual dimension without magnification by an optical microscope. This dimension value will not change with the magnification of the optical microscope.

[0405] The grains are screened by measuring the dimension of each grain extending along the first direction Z within the 5mm*0.3mm rectangular frame and the maximum dimension of each grain along the second direction Y. If the ratio of the dimension extending along the first direction Z to the maximum dimension along the second direction Y within the 5mm*0.3mm rectangular frame is in the range of 4 to 100, then the grain is identified as the second grain 802. The second grains 802 within the 5mm*0.3mm rectangular frame are screened in this way. If the ratio of the number of second grains 802 within the 5mm*0.3mm rectangular frame to the total number of 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 total number of grains within the second cross-section are both greater than 50%, thus confirming that the number of second grains 802 within the second region 1112 and the total number of grains within the second region 1112 are both greater than 50%.

[0406] For example, please refer to Figure 9 The third dimension is D5, the fourth dimension is D6, and 4≤D5 / D6≤100.

[0407] As an example, the ratio of the third dimension to the fourth dimension can be any point value or a range between any two of the following: 4, 5, 6, 10, 30, 40, 50, 60, 70, 80, 90, 100.

[0408] In this embodiment, the ratio of the third dimension to the fourth dimension ranges from 4 to 100. The dimension of the second grain 802 extending in the first direction Z is larger than the maximum dimension of the second grain 802 in the second direction Y by a certain extent. Such a second grain 802 is beneficial to reduce toughness. The 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%, which makes the toughness of the second region 1112 smaller. Under the action of the expansion force of the electrode assembly 2, it is beneficial to reduce the cracking of the second region 1112 itself.

[0409] It is understandable that the metallographic structure of the second zone 1112 is not limited, as long as the hardness of the first zone 1111 is lower than that of the second zone 1112.

[0410] In some embodiments, please refer to Figure 9 The ratio of the third dimension to the fourth dimension ranges from 4 to 50.

[0411] As an example, the ratio of the third dimension to the fourth dimension can be any point value or a range between any two of the following: 4, 5, 6, 7, 8, 10, 15, 20, 25, 30, 35, 40, 45, 50.

[0412] In this embodiment, the ratio of the third dimension to the fourth dimension is in the range of 4 to 50, which makes the maximum size deviation of the second grain 802 in the first direction Z and the second direction Y larger. Such a second grain 802 reduces toughness, and the second region with a large proportion of second grains has lower toughness. Under the action of the expansion force of the electrode assembly 2, it is beneficial to reduce the cracking of the second region 1112 itself.

[0413] It is understandable that the ratio of the third dimension to the fourth dimension is not limited to 4–50. As an example, the ratio of the third dimension to the fourth dimension can be greater than 50, or the ratio of the third dimension to the fourth dimension can be greater than 100.

[0414] In some embodiments, please refer to Figure 9 The third size ranges from 150μm to 1000μm, and the fourth size ranges from 5μm to 120μm.

[0415] For example, please refer to Figure 9 The third dimension is D5, where 150μm≤D5≤1000μm.

[0416] For example, please refer to Figure 9 The third dimension can be any point value or a range between any two of the following: 150μm, 170μm, 200μm, 300μm, 400μm, 500μm, 600μm, 700μm, 800μm, 900μm, 950μm, 1000μm.

[0417] For example, please refer to Figure 9 The fourth dimension, D6, is 5μm ≤ D6 ≤ 120μm.

[0418] For example, please refer to Figure 9 The fourth dimension can be any one of the following values ​​or a range between any two: 5μm, 10μm, 15μm, 20μm, 30μm, 40μm, 50μm, 60μm, 70μm, 80μm, 90μm, 100μm, 110μm, 120μm.

[0419] In this embodiment, the lower limit of the third dimension's size range of 150μm is greater than the upper limit of the fourth dimension's size range of 120μm. The maximum size deviation of the second grain 802 in the first direction Z and the second direction Y is relatively large. The second grain 802 in the corresponding size range is conducive to reducing toughness, so that the second region with a large proportion of second grains has lower toughness. Under the expansion force of the electrode assembly 2, it is conducive to reducing the cracking of the second region 1112 itself.

[0420] It is understandable that the range of the third and fourth dimensions is not limited, as long as the ratio of the third and fourth dimensions is within the corresponding range.

[0421] In some embodiments, please refer to Figure 9 At least some of the grains in the first region 1111 are first grains 800. The ratio of the number of first grains 800 in the first region 1111 to the total number of grains in the first region 1111 is greater than 50%. The dimension of the first grain 800 extending along the first direction Z is the first dimension, and the maximum dimension of the first grain 800 along the second direction Y is the second dimension. The ratio of the first dimension to the second dimension ranges from 0.2 to 5. At least some of the grains in the second region 1112 are second grains 802. The ratio of the number of second grains 802 in the second region 1112 to the total number of grains in the second region 1112 is greater than 50%. The dimension of the second grain 802 extending along the first direction Z is the third dimension, and the maximum dimension of the second grain 802 along the second direction Y is the fourth dimension. The ratio of the third dimension to the fourth dimension ranges from 4 to 100. The third dimension is larger than the first dimension.

[0422] In this embodiment, the third dimension of the second grain 802 is larger than the first dimension of the first grain 800. The maximum dimension of the second grain 802 in the first direction Z is larger than the maximum dimension of the first grain 800 in the first direction Z. Therefore, within the same dimension along the first direction Z, the number of first grains 800 is greater than the number of second grains 802. Since the proportion of the number of first grains 800 in the first region 1111 is greater than 50%, and the proportion of the number of second grains 802 in the second region 1112 is greater than 50%, the first region 1111 has more first grains 800, while the second region 1112 is dominated by second grains 802. Within the same dimension along the first direction, the first region 1111 can have more grains to share the expansion force, so that the first region 1111 near the first connection portion 51 has better toughness to release the expansion force of the electrode assembly 2, thereby reducing the possibility of cracking of the first connection portion 51.

[0423] In some embodiments, please refer to Figure 9 The ratio of the third dimension to the first dimension ranges from 1.5 to 150.

[0424] For example, please refer to Figure 9 The third dimension is D5, the first dimension is D3, and 1.5≤D3 / D5≤150.

[0425] For example, please refer to Figure 9The ratio of the third dimension to the first dimension can be any one of the following values ​​or any range between the two: 1.5, 2, 2.5, 3, 4, 5, 5.5, 6, 7, 8, 9, 10, 20, 40, 50, 70, 90, 120, 130, 150.

[0426] In this embodiment, the ratio of the third dimension to the first dimension is within a suitable range, making the toughness of the first region 1111 more suitable than that of the second region. This reduces the possibility of cracking of the first connection 51 and helps to suppress cracking of the first region 1111 itself.

[0427] In some embodiments, please refer to Figure 9 The ratio of the third dimension to the first dimension ranges from 1.8 to 100.

[0428] In some embodiments, please refer to Figure 9 The first size ranges from 5μm to 500μm, and the third size ranges from 150μm to 1000μm.

[0429] In some embodiments, the hardness of the first region 1111 is lower than the hardness of the first connecting portion 51.

[0430] It should be noted that the hardness of the first zone 1111 is lower than that of the second zone 1112. The first zone 1111 has better toughness than the second zone 1112. During the cyclic charging and discharging of the battery cell 10, the electrode assembly 2 repeatedly expands and contracts, generating periodic expansion forces that act on the first sidewall portion 111. This causes the first sidewall portion 1111 to undergo periodic deformation and release the expansion forces mainly in the tougher first zone 1111, which may cause fatigue cracking of the tougher first zone 1111 itself.

[0431] Therefore, in some embodiments, please refer to Figure 6 and Figure 14 The maximum thickness of the first zone 1111 is greater than the minimum thickness of the second zone 1112.

[0432] 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.

[0433] As an example, the first zone 1111 can be a structure of equal thickness or a structure of unequal thickness.

[0434] As an example, the second zone 1112 can be a structure of equal thickness or a structure of unequal thickness.

[0435] In this embodiment, the maximum thickness of the first region 1111 is greater than the minimum thickness of the second region 1112, so that at least a portion of the first region 1111 with higher toughness is thicker than at least a portion of the second region 1112 with lower toughness. The first region 1111 with higher toughness is strengthened in the corresponding thicker portion, which can suppress the possibility of fatigue cracking of the first region 1111 itself to a certain extent.

[0436] It is understood that the relationship between the thickness of the first zone 1111 and the thickness of the second zone 1112 is not limited. As an example, the maximum thickness of the first zone 1111 can be less than or equal to the minimum thickness of the second zone 1112, or the minimum thickness of the first zone 1111 can be greater than the maximum thickness of the second zone 1112. As an example, the thickness of some locations in the first zone 1111 is greater than the thickness of some locations in the second zone 1112, and the thickness of some locations in the first zone 1111 is less than the thickness of some locations in the second zone 1112. As an example, the thickness of the first zone 1111 and the thickness of the second zone 1112 can be equal, and the first zone 1111 and the second zone 1112 have an equal thickness structure.

[0437] In one embodiment, please refer to Figure 6 , Figure 8 , Figure 14 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 connected sequentially along the direction of the end cap 12 pointing towards the electrode assembly 2. The first outer surface 806 and the second outer surface 807 are connected sequentially along the direction of the end cap 12 pointing towards 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. 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.

[0438] For example, please refer to Figure 29 and Figure 30 The first inner surface 804 and the second inner surface 805 can be in the same plane.

[0439] For example, please refer to Figure 6 , Figures 14-16 ,as well as Figure 18 , Figure 19 , Figure 22 , Figure 23 and Figure 26 The first inner surface 804 can be closer to the electrode assembly 2 along the second direction Y relative to the second inner surface 805.

[0440] For example, please refer to Figure 6 , Figures 14-16 ,as well as Figure 18 , Figure 19 , Figure 22 , Figure 23 and Figure 26 The first outer surface 806 and the second outer surface 807 can be in the same plane.

[0441] For example, please refer to Figure 29 and Figure 30 The first outer surface 806 can be further away from the electrode assembly 2 along the second direction Y relative to the second outer surface 807.

[0442] For example, please refer to Figure 29 and Figure 30 When the first inner surface 804 and the second inner surface 805 are in a plane, the first outer surface 806 can be further away from the electrode assembly 2 along the second direction Y relative to the second outer surface 807.

[0443] For example, please refer to Figure 6 , Figures 14-16 ,as well as Figure 18 , Figure 19 , Figure 22 , Figure 23 and Figure 26 When the first outer surface 806 and the second outer surface 807 are in a plane, the first inner surface 804 can be closer to the electrode assembly 2 along the second direction Y relative to the second inner surface 805.

[0444] As an example, the first outer surface 806 may be further away from the electrode assembly 2 along the second direction Y relative to the second outer surface 807. The first inner surface 804 may be closer to the electrode assembly 2 along the second direction Y relative to the second inner surface 805.

[0445] As an example, the distance from each position of the first inner surface 804 to the first outer surface 806 can be equal, that is, the area between the first inner surface 804 and the first outer surface 806 is a structure of equal thickness.

[0446] As an example, the distances from various positions on the first inner surface 804 to the first outer surface 806 may not be equal, that is, the area between the first inner surface 804 and the first outer surface 806 may be a structure of unequal thickness.

[0447] As an example, the distances from each position of the second inner surface 805 to the second outer surface 807 can be equal, that is, the area between the second inner surface 805 and the second outer surface 807 is a structure of equal thickness.

[0448] As an example, the distances from various positions on the second inner surface 805 to the second outer surface 807 may not be equal, that is, the area between the second inner surface 805 and the second outer surface 807 may be a structure of unequal thickness.

[0449] In this embodiment, 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 first region 1111 is better strengthened by the thicker 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 region 1111 itself.

[0450] It is understood that the relationship between the first inner surface 804, the second inner surface 805, the first outer surface 806, and the second outer surface 807 is not limited. As an example, the first inner surface 804 and the second inner surface 805 may be spaced apart, and the first outer surface 806 and the second outer surface 807 may be spaced apart.

[0451] In some embodiments, please refer to Figure 14 The first inner surface 804 includes a first sub-surface 11111 and a second sub-surface 11112 connected sequentially along the direction from the end cap 12 toward the electrode assembly 2. The first sub-surface 11111 is at least partially formed in the first region 1111. Along the second direction Y, the first sub-surface 11111 is closer to the electrode assembly 2 than the second sub-surface 11112. 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.

[0452] 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 region between the first sub-surface 11111 and the first outer surface 806 along the second direction Y is thicker, while the region between the second sub-surface 11112 and the first outer surface 806 along the second direction Y is thinner.

[0453] The first sub-surface 11111 transitions to the second inner surface 805 via the second sub-surface 11112.

[0454] As an example, the distance from each position on the first sub-face 11111 to the first outer surface 806 can be equal, and the area between the first sub-face 11111 and the first outer surface 806 is a structure of equal thickness.

[0455] As an example, the distances from various positions on the first sub-face 11111 to the second outer surface 807 may not be equal, and the region between the first sub-face 11111 and the first outer surface 806 is a non-uniform thickness structure.

[0456] As an example, the distances from each position on the second sub-face 11112 to the second outer surface 807 can be equal, and the area between the second sub-face 11112 and the second outer surface 807 is a structure of equal thickness.

[0457] As an example, the distances from various positions on the second sub-face 11112 to the second outer surface 807 may not be equal, and the region between the second sub-face 11112 and the second outer surface 807 is a non-uniform thickness structure.

[0458] As an example, the minimum distance between the first sub-face 11111 along the second direction Y and the first outer surface 806 may be greater than the maximum distance between the second sub-face 11112 along the second direction Y and the first outer surface 806.

[0459] In this embodiment, since the distance between the first sub-surface 11111 and the first outer surface 806 along the second direction Y is large, the corresponding thickness is relatively large. The first sub-surface 11111 is at least partially formed in the first region 1111, making the first region 1111 thicker, which is beneficial to strengthen the first region 1111 and thus suppress the fatigue cracking of the first region 1111 itself.

[0460] 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 along the second direction Y and the first outer surface 806 may be less than or equal to the distance between the second sub-surface 11112 and the first outer surface 806.

[0461] In some embodiments, please refer to Figure 14 The distance between the second sub-surface 11112 and the first outer surface 806 along the second direction Y is the first preset thickness, and the first preset thickness decreases along the direction from the end cap 12 to the electrode assembly 2.

[0462] 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.

[0463] For example, please refer to Figure 14 The distances between the various positions on the second sub-surface 11112 and the second outer surface 807 are not equal. The first preset thickness decreases along the direction from the end cap 12 to the electrode assembly 2. The second sub-surface 11112 can be an inclined surface.

[0464] For example, please refer to Figure 14The distances between each position on the first sub-surface 11111 and the first outer surface 806 are equal, and the distances between the second inner surface 805 and the second outer surface 807 are equal. The first sub-surface 11111 is parallel to the first outer surface 806, and the second inner surface 805 is parallel to the second outer surface 807. The first outer surface 806 and the second outer surface 807 are coplanar. The first sub-surface 11111 is closer to the electrode assembly 2 along the second direction Y than the second sub-surface 11112, and the second sub-surface 11112 is closer to the electrode assembly 2 along the second direction Y than the second inner surface 805. The second sub-surface 11112 connects to the first sub-surface 11111 and the second inner surface 805.

[0465] In this embodiment, the first preset thickness decreases along the direction from the end cap 12 toward the electrode assembly 2. This allows for a smoother 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 minimizing the possibility of interference between them. Furthermore, the reinforcement effect of the first sidewall portion 111 on the portion corresponding to the second sub-surface 11112 increases along the direction from the electrode assembly 2 toward the end cap 12, resulting in better reinforcement of the portion of the second sub-surface 11112 near the first sub-surface 11111, reducing the possibility of fatigue cracking in the first region 1111. Moreover, the smoother transition between the first sub-surface and the second inner surface 805 helps reduce stress concentration.

[0466] It is understood that the embodiments of this application are not limited to the first preset thickness decreasing in the direction from the end cover 12 toward the electrode assembly 2. As an example, the first preset thickness in the direction from the end cover 12 toward the electrode assembly 2 may remain unchanged.

[0467] See some implementation columns. Figure 14 The first sub-surface 11111 spans across the first region 1111 and the second region 1112, and the first outer surface 806 spans across the first region 1111 and the second region 1112.

[0468] The first sub-face 11111 spans across the first region 1111 and the second region 1112, meaning that the first sub-face 11111 is partially formed in the first region 1111 and partially formed in the second region 1112.

[0469] The first outer surface 806 spans across the first region 1111 and the second region 1112, meaning that the first outer surface 806 is partially formed in the first region 1111 and partially formed in the second region 1112.

[0470] In this embodiment, 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 sidewall portion 111 is thicker in the portion corresponding to the first sub-surface 11111. The first sub-surface 11111 spans across the first region 1111 and the second region 1112, so that the thicker portion of the first sidewall portion 1111 spans across the first region 1111 and the second region 1112, thereby strengthening the junction of the first region 1111 and the second region 1112 with different toughnesses, which is beneficial to suppressing cracking at the junction of the first region 1111 and the second region 1112 with different toughnesses.

[0471] In some embodiments, the second sub-surface 11112 spans across the first region 1111 and the second region 1112, and the first outer surface 806 spans across the first region 1111 and the second region 1112.

[0472] The second sub-face 11112 spans across the first region 1111 and the second region 1112, meaning that the second sub-face 11112 is partially formed in the first region 1111 and partially formed in the second region 1112.

[0473] The first outer surface 806 spans across the first region 1111 and the second region 1112, meaning that the first outer surface 806 is partially formed in the first region 1111 and partially formed in the second region 1112.

[0474] In this embodiment, 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 sidewall portion 111 corresponding to the second sub-surface 11112 is thicker than the portion of the first sidewall portion 111 corresponding to the second inner surface 805. The second sub-surface 11112 spans across the first region 1111 and the second region 1112, so that the thicker portion of the first sidewall portion 111 spans across the first region 1111 and the second region 1112, thereby strengthening the junction of the first region 1111 and the second region 1112 with different toughnesses, which is beneficial to suppressing cracking at the junction of the first region 1111 and the second region 1112 with different toughnesses.

[0475] It is understood that in the embodiments of this application, the relationship between the first sub-surface 11111, the second sub-surface 11112, the first region 1111, and the second region 1112 is not limited. As an example, the first sub-surface 11111 and the second sub-surface 11112 may both be located in the first region 1111.

[0476] In some embodiments, please refer to Figure 6 , Figure 8 , Figure 14 , Figure 17 , Figure 20 , Figure 21 , Figure 24 , Figure 25 , Figure 26 , Figure 29 and Figure 30 The first inner surface 804 spans across the first region 1111 and the second region 1112, and the first outer surface 806 spans across the first region 1111 and the second region 1112.

[0477] The first inner surface 804 spanning the first region 1111 and the second region 1112 means that the first inner surface 804 is partially formed in the first region 1111 and partially formed in the second region 1112.

[0478] The first outer surface 806 spanning the first region 1111 and the second region 1112 means that the first outer surface 806 is partially formed in the first region 1111 and partially formed in the second region 1112.

[0479] As an example, the first sub-face 11111 is located in the first zone 1111, the second sub-face 11112 is located in the second zone 1112, and the boundary between the first sub-face 11111 and the second sub-face 11112 is exactly located at the boundary between the first zone 1111 and the second zone 1112.

[0480] As an example, the first sub-face 11111 is partially formed in the first region 1111, and the first sub-face 11111 is partially formed in the second region 1112. The second sub-face 11112 is located in the second region 1112.

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

[0482] In this embodiment, 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 sidewall portion 111 corresponding to the first inner surface 804 is thicker than the portion of the first sidewall portion 111 corresponding to the second inner surface 805. The first inner surface 804 spans the first region 1111 and the second region 1112, and the first outer surface 806 spans the first region 1111 and the second region 1112. This allows the thicker portion of the first sidewall portion 111 to span the first region 1111 and the second region 1112, thereby strengthening the junction between the first region 1111 and the second region 1112, which have different toughnesses. This helps to suppress cracking at the junction between the first region 1111 and the second region 1112, which have different toughnesses.

[0483] It is understood that the relationship between the first inner surface 804, the first outer surface 806, the first region 1111, and the second region 1112 is not limited. As an example, the first inner surface 804 and the first outer surface 806 are both located in the first region 1111, the second inner surface 805 and the second outer surface 807 are both located in the second region 1112, the boundary between the first inner surface 804 and the second inner surface 805 is exactly at the boundary between the first region 1111 and the second region 1112, and the boundary between the first outer surface 806 and the second outer surface 807 is exactly at the boundary between the first region 1111 and the second region 1112.

[0484] In some embodiments, please refer to Figure 7 , Figure 15 , Figure 16 , Figure 18 , Figure 19 , Figure 22 and Figure 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. The first direction Z, the second direction Y and the third direction X are not coplanar and intersect each other.

[0485] 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, such that the portion of the first sidewall 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.

[0486] As an example, the housing 11 is cuboid in shape and includes two first sidewall portions 111 and two second sidewall portions 112. The two first sidewall portions 111 are arranged opposite each other along the second direction Y, and the two second sidewall portions 112 are arranged opposite 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 housing 11, the second direction Y is parallel to the width direction of the housing 11, and the third direction X is parallel to the length direction of the housing 11.

[0487] For example, please refer to Figure 38 and Figure 39 The first zone 1111 extends along the third direction X to the opposite ends of the first sidewall portion 111.

[0488] 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, making the dimension of the first inner surface 804 along the third direction X larger. More areas of the first sidewall portion 111 along the third direction X are reinforced by the thicker portion corresponding to the first inner surface 804, which helps to prevent the shell 11 from cracking.

[0489] It is understood that there are no specific restrictions 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.

[0490] Please refer to the figure for some implementation columns. Figures 15-25 Along the second direction Y, the projection of the first inner surface 804 that coincides with the projection of the first region 1111 is the first projection. 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 first direction Z, the second direction Y and the third direction X are not coplanar and intersect each other.

[0491] The position corresponding to the first projection is precisely the position where the thickened portion of the first inner surface 804 reinforces the first region 1111.

[0492] As an example, the first direction Z, the second direction Y, and the third direction X are perpendicular to each other.

[0493] In this embodiment, since the size of the first projection along the third direction X is larger than the size of the first projection along the first direction Z, the portion of the first inner surface 804 that reinforces the first region 1111 has a larger size in the third direction X. This results in the first region 1111, which has higher toughness, having more areas reinforced along the third direction X, further reducing the possibility of fatigue cracking in the first region 1111 itself.

[0494] It is understandable that the 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 is not limited. 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.

[0495] In some embodiments, please refer to the figure. Figures 15-25 The first inner surface 804 includes a first connecting surface 11113, which passes through the middle section of the first side wall portion 111. The middle section is perpendicular to the third direction X, and the distance from the middle section to both ends of the first side wall portion 111 along the third direction X is equal.

[0496] The first connecting surface 11113 may be a part of the first inner surface 804, or the first connecting surface 11113 may be the same as the first inner surface 804. The distances between the first connecting surface 11113 and the first outer surface 806 at various locations are equal or unequal. The first connecting surface 11113 has two opposite ends along a third direction X, and the first connecting surface 11113 passes through the mid-section of the first sidewall portion 111, such that the mid-section of the first sidewall 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 can 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 sidewall portion 111 are equal, the first connecting surface 11113 may be a symmetrical structure symmetrically arranged about the mid-section of the first sidewall portion 111. It should be noted that the mid-section of the first sidewall portion 111 is a virtual plane and is not shown in the figure.

[0497] For example, please refer to Figures 15-17 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. 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.

[0498] Taking the shell 11 as a cuboid as an example, the distance from the mid-section of the first side wall portion 111 to both ends of the first side wall portion 111 along the third direction X is equal, that is, the distance from the mid-section of the first side wall portion 111 to the two second side wall portions 112 that are arranged opposite each other along the third direction X of the shell 11 is equal.

[0499] It should be noted that, along the third direction X, the distance from the mid-section of the first sidewall portion 111 to both ends of the first sidewall portion 111 is approximately equal, which should also be understood as the distance from the mid-section to both ends of the first sidewall portion 111 being equal.

[0500] In this embodiment, when the first sidewall portion 111 is subjected to the expansion force of the electrode assembly 2 of the battery cell 10, the middle region of the first sidewall 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 sidewall portion 111, the first sidewall portion 111 has a large thickness at the middle section position, which makes the first sidewall portion 111 reinforced 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 region of the first sidewall portion 111 along the third direction X.

[0501] It is understood that the positions of the first connecting surface 11113 and the mid-section of the first sidewall portion 111 are 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 may be located on one side of the mid-section of the first sidewall portion 111 along the third direction X.

[0502] In some embodiments, please refer to Figure 16 , Figure 17 , Figure 19 , Figure 20 , Figure 21 , Figure 23 , Figure 24 and Figure 25 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 that coincides with the projection of the first region 1111 is the second projection. The second projection passes through the mid-section of the first sidewall portion 111.

[0503] The first connecting surface 11113 is a part of the first inner surface 804, or the first connecting surface 11113 is the same as the first inner surface 804.

[0504] 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 will at least partially overlap. The position corresponding to the overlapping second projection is the position where the first sidewall portion 111 reinforces the first region 1111 in the thicker portion corresponding to the first connecting surface 11113.

[0505] In this embodiment, since the second projection passes through the mid-section of the first sidewall portion 111, the correspondingly tougher first region 1111 also passes through the mid-section. The tougher first region 1111 can release the expansion force of the electrode assembly 2 at the mid-section to a certain extent, which helps to reduce the cracking of the first connecting 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 connecting surface 11113 can be at least partially located at the position of the mid-section corresponding to the first region 1111, which helps to suppress the fatigue cracking of the tougher first region 1111 at the mid-section of the first sidewall.

[0506] It is understood 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 along the third direction X can be located on one side of the mid-section of the first sidewall portion 111.

[0507] In some embodiments, please refer to Figures 18-25The 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 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.

[0508] The first connecting surface 11113 is a segment of the first inner surface 804 passing through the mid-section of the first sidewall portion 111. The second connecting surface 11114 and the third connecting surface 11115 are two segments of the first inner surface 804 located at two ends along the third direction X, respectively. The second connecting surface 11114 and the first connecting surface 11113 can be directly connected or indirectly connected, and the third connecting surface 11115 and the first connecting surface 11113 can be directly connected or indirectly connected.

[0509] The distances between various locations on the first connecting surface 11113 and the first outer surface 806 can be equal or unequal. The distances between various locations on the second connecting surface 11114 and the first outer surface 806 can be equal or unequal. The distances between various locations on the third connecting surface 11115 and the first outer surface 806 can be equal or unequal. If the distances between 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 can be less than or equal to the minimum distance between the first connecting surface 11113 and the first outer surface 806, so 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 may be less than or equal to the minimum distance between the first connecting surface 11113 and the first outer surface 806, so 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.

[0510] The dimensions of the second connecting surface 11114 along the third direction X and the dimensions of the third connecting surface 11115 along the third direction X can be equal or unequal. If the dimensions of the second connecting surface 11114 along the third direction X and the dimensions of the third connecting surface 11115 along the third direction X are equal, the second connecting surface 11114 and the third connecting surface 11115 can be symmetrically arranged about the mid-section of the first sidewall portion 111.

[0511] It is understood that in embodiments where the first inner surface 804 includes a first sub-surface and a 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.

[0512] The second connecting surface 11114 may be partially closer to the electrode assembly 2 relative to 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 relative to 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 relative to 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.

[0513] For example, please refer to Figures 18-25 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 to the second connecting surface 11114, and the distance between the third connecting surface 11115 and the first outer surface 806 also gradually decreases along the direction from the second connecting surface 11114 to 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 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 plane.

[0514] In this embodiment, when the first sidewall portion 111 is subjected to the expansion force of the electrode assembly 2, the electrode assembly 2 expands to a greater extent in the region near the middle along the third direction X of the first sidewall portion 111, and expands to a relatively smaller extent in the regions near both ends along the third direction X of the first sidewall portion 111. The expansion forces of the electrode assembly 2 at both ends and in the middle of the first sidewall portion 111 along the third direction X are different. The distances between the second connecting surface 11114 and the first outer surface 806 and 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 sidewall portion 111 is significantly strengthened in the region near the center corresponding to the first connecting surface 11113, which is beneficial for bearing the large expansion force exerted by the electrode assembly 2 on the first sidewall portion 111 in the third direction X near the center. The regions near the two ends corresponding to the second connecting surface 11114 and the third connecting surface 11115 are strengthened to a certain extent, which can bear the expansion force exerted by the two ends of the electrode assembly 2 in the third direction X on the first sidewall portion 111. Furthermore, the thickness of the first sidewall portion 111 in the regions near the two ends corresponding to the second connecting surface 11114 and the third connecting surface 11115 is small, which is beneficial for reducing costs.

[0515] It is understood that the relationships between the distances between the second connecting surface 11114 and the first outer surface 806, the distances between the third connecting surface 11115 and the first outer surface 806, and the distances between the first connecting surface 11113 and the first outer surface 806 are not limited. As an example, the distance between the second connecting surface 11114 and the first outer surface 806 may 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 may be greater than or equal to the distance between the first connecting surface 11113 and the first outer surface 806.

[0516] In some embodiments, please refer to Figure 20 , Figure 21 , Figure 24 and Figure 25 The first connecting surface 11113, the second connecting surface 11114 and the third connecting surface 11115 are all formed at least partially in the first region 1111.

[0517] For example, please refer to Figure 20 , Figure 21 , Figure 24 and Figure 25 The first connecting surface 11113 is partially formed in the first region 1111, the second connecting surface 11114 is partially formed in the first region 1111, and the third connecting surface 11115 is partially formed in the first region 1111.

[0518] For example, please refer to Figure 20 , Figure 21 , Figure 24 and Figure 25 The first connecting surface 11113 spans across the first zone 1111 and the second zone 1112, the second connecting surface 11114 spans across the first zone 1111 and the second zone 1112, and the third connecting surface 11115 spans across the first zone 1111 and the second zone 1112.

[0519] The first connecting surface 11113 spans across the first region 1111 and the second region 1112, meaning that the first connecting surface 11113 is partially formed in the first region 1111 and partially formed in the second region 1112.

[0520] The second connecting surface 11114 spans across the first region 1111 and the second region 1112, meaning that the second connecting surface 11114 is partially formed in the first region 1111 and partially formed in the second region 1112.

[0521] The third connecting surface 11115 spans across the first region 1111 and the second region 1112, meaning that the third connecting surface 11115 is partially formed in the first region 1111 and partially formed in the second region 1112.

[0522] In this embodiment, the first region 1111 located at the position corresponding to the first connecting surface 11113 partially releases the expansion force of the electrode assembly 2 at the first connecting surface 11113, which helps to reduce the cracking of the first connecting part 51 at the first connecting surface 11113. The periodic expansion force of the electrode assembly 2 repeatedly expanding on the first region 1111 located at the position corresponding to the first connecting surface 11113 is relatively large. 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 allows the thicker part of the first sidewall portion 111 at the first connecting surface 11113 to better reinforce the first region 1111, which helps to suppress the possibility of fatigue cracking of the first region 1111 located at the position corresponding to the first connecting surface 11113. The expansion force of the partial release electrode assembly 2 in the first region 1111, located at the corresponding position on the second connecting surface 11114, at the second connecting surface 11114, helps to reduce the cracking of the first connecting portion 51 at the second connecting surface 11114. Similarly, the expansion force of the partial release electrode assembly 2 in the first region 1111, located at the corresponding position on the third connecting surface 11115, at the third connecting surface 11115, helps to reduce the cracking of the first connecting portion 51 at the third connecting surface 11115. Because the periodic expansion force of the electrode assembly 2 on the first sidewall portion 111 at the corresponding positions of the second connecting surface 11114 and the third connecting surface 11115 is 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 suppress fatigue cracking of the first region 1111 at the corresponding positions of the second connecting surface 11114 and the third connecting surface 11115, and also reduce the material used in the first sidewall at the corresponding positions of the second connecting surface 11114 and the third connecting surface 11115, which is beneficial for saving costs.

[0523] It is understood that the relationship between the first connecting surface 11113, the second connecting surface 11114, and the third connecting surface 11115 and the first region 1111 is not limited. As an example, one of the first connecting surface 11113, the second connecting surface 11114, and the third connecting surface 11115 may be at least partially formed in the first region 1111, while the remaining two may not be formed in the first region 1111. As an example, two of the first connecting surface 11113, the second connecting surface 11114, and the third connecting surface 11115 may be at least partially formed in the first region 1111, while the remaining one may not be formed in the first region 1111.

[0524] In some embodiments, please refer to Figures 22-25The first inner surface 804 also includes a first transition surface 11116, a first connecting surface 11113, a first transition surface 11116, and a second connecting surface 11114 arranged along a third direction X. The first transition surface 11116 connects the second connecting surface 11114 and the first connecting surface 11113. The distance between the first transition surface 11116 and the first outer surface 806 along the second direction Y is a second preset thickness. The second preset thickness increases along the direction from the second connecting surface 11114 to the first connecting surface 11113. / 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, 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 increases along the direction from the third connecting surface 11115 to the first connecting surface 11113.

[0525] The distances between the first transition surface 11116 and the first outer surface 806 are not equal at various locations. As an example, the second preset thickness gradually increases along the direction from the second connecting surface 11114 to the first connecting surface 11113. The distances between the second transition surface 11117 and the first outer surface 806 are also not equal. As an example, the third preset thickness gradually increases along the direction from the third connecting surface 11115 to the first connecting surface 11113.

[0526] 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 dimensions of the first transition surface 11116 along the third direction X and the dimensions of the second transition surface 11117 along the third direction X can be equal or unequal. If the dimensions of the first transition surface 11116 along the third direction X and the dimensions of the second transition surface 11117 along the third direction X are equal, the first transition surface 11116 and the second transition surface 11117 can be symmetrically arranged about the mid-section of the first sidewall portion 111.

[0527] It is 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 further 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 further away from the electrode assembly 2 relative to the second outer surface 807 along the second direction Y.

[0528] For example, please refer to Figures 22-25 The second connecting surface 11114 is indirectly connected to the first connecting surface 11113 via the first transition surface 11116, and the third connecting surface 11115 is indirectly connected to the first connecting surface 11113 via the second transition surface 11117. The second preset thickness gradually increases along the direction from the second connecting surface 11114 to the first connecting surface 11113, and the third preset thickness gradually increases along the direction from the third connecting surface 11115 to the first connecting surface 11113. A portion of the second connecting surface 11114, a portion of the first connecting surface 11113, a portion of the third connecting surface 11115, a portion of the first transition surface 11116, and a portion of the second transition surface 11117 are all closer to the electrode assembly 2 relative to the second inner surface 805 along the second direction Y. The first transition surface 11116 connects the first connecting surface 11113 and the second connecting surface 11114, and the second transition surface 11117 connects the first connecting surface 11113 and the third connecting surface 11115. The first outer surface 806 is a plane.

[0529] In this embodiment, if the second connecting surface 11114 and the first connecting surface 11113 are connected by the first transition surface 11116, and the second preset 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, reducing stress concentration. If the third connecting surface 11115 and the first connecting surface 11113 are connected by the second transition surface 11117, and the third preset 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, reducing stress concentration.

[0530] In some embodiments, please refer to Figure 24 and Figure 25The 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.

[0531] In this embodiment, 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 position of the first region 1111. The thicker second transition surface 11117 can also reinforce the corresponding first region 1111, thereby suppressing fatigue cracking at the corresponding position of the first region 1111.

[0532] It is understood that the positional relationship between the first transition surface 11116 and the second transition surface 11117 and the first region 1111 is not limited. As an example, the first transition surface 11116 is outside the first region 1111 and / or the second transition surface 11117 is outside the first region 1111.

[0533] In some embodiments, please refer to Figure 16 , Figure 19 and Figure 23 The dimension of the first connecting surface 11113 along the third direction X is L1, and the dimension of the first sidewall portion 111 along the third direction X is L, 0.2≤L1 / L≤0.6.

[0534] 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.

[0535] L1 / L can take any one of the following point values ​​or a range between any two: 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.

[0536] In this embodiment, L1 / L≥0.2 increases the size proportion of the first connecting surface 11113 in the third direction X of the first sidewall portion 111, so that the middle area of ​​the first sidewall portion 111 in the third direction X is reinforced over a larger range, thereby improving the strength of the middle area of ​​the first sidewall portion 111 in the third direction X; L1 / L≤0.6 decreases the size proportion of the first connecting surface 11113 in the third direction X of the first sidewall portion 111, thereby reducing the material used in the part of the first sidewall portion 111 corresponding to the first connecting surface 11113 and reducing production costs. Therefore, the ratio of the dimension of the first connecting surface 11113 along the third direction X to the dimension of the first sidewall portion 111 along the third direction X is set to 0.2 to 0.6. This ensures that the first sidewall portion 111 has sufficient reinforcing capacity at the position corresponding to the first connecting surface 11113, while reducing the material usage of the first sidewall portion 111 at the first connecting surface 11113, thus balancing the requirements for reinforcing capacity and economy of the first sidewall portion 111 at the first connecting surface 11113.

[0537] In some embodiments, please refer to Figure 16 , Figure 19 and Figure 23 The first connecting surface 11113 has a first end 11113a and a second end 11113b along the third direction X. The first sidewall portion 111 has a third end 1113 and a fourth end 1114 along the third direction X. The first end 11113a is close to the third end 1113, and the second end 11113b is close to the fourth end 1114. The dimension of the first sidewall 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.

[0538] It is understandable 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.

[0539] It can be L2 = L3; or it can be L2 > L3 or L2 < L3.

[0540] L2 / L can take any one of the following values ​​or a range between any two: 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.

[0541] L3 / L can take any one of the following values ​​or a range between any two: 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.

[0542] In this embodiment, if L2 / L≤0.3, the proportion of the minimum distance between the first end 11113a and the third end 1113 along the third direction X is reduced in the dimension of the first sidewall portion 111 along the third direction X, thereby strengthening the first sidewall portion 111 in a larger area along the third direction X. If L3 / L≤0.3, the proportion of the minimum distance between the second end 11113b and the fourth end 1114 along the third direction X is reduced in the dimension of the first sidewall portion 111 along the third direction X, thereby strengthening the first sidewall portion 111 in a larger area along the third direction X.

[0543] In some embodiments, please refer to Figure 16 , Figure 19 and Figure 23 , 100mm≤L≤450mm.

[0544] L can be any one of the following values ​​or a range between any two: 100mm, 120mm, 150mm, 180mm, 200mm, 220mm, 250mm, 260mm, 280mm, 300mm, 310mm, 320mm, 350mm, 390mm, 400mm, 410mm, 420mm, 430mm, 440mm, 450mm.

[0545] In some embodiments, please refer to Figure 15 , Figure 18 and Figure 22 The housing 11 includes a corner wall 113, and the first side wall portion 111 is connected to both ends of the corner wall 113 along the third direction X.

[0546] At least one end of the first inner surface 804 along the third direction X does not contact the corner wall 113; or, the two ends of the first inner surface 804 along the third direction X extend to the two corner walls 113 respectively.

[0547] 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 a corner wall 113 while the other end does not extend to another corner wall 113. Alternatively, neither end of the first inner surface 804 may extend to the corner wall 113, so that at least one end of the first inner surface 804 along the third direction X does not contact the corner wall 113.

[0548] For example, please refer to Figure 15 and Figure 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.

[0549] In this embodiment, 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 for the first side wall portion 111 in the corresponding part of the first inner surface 804 can be reduced, thus lowering 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, improving the reinforcing ability of the first side wall portion 111 in the corresponding part of the first inner surface 804, thereby strengthening more areas of the first side wall portion 111 along the third direction X.

[0550] See some implementation columns. Figure 26 , Figure 27 and Figure 28 The electrode assembly 2 also includes a separator 24, which is disposed between the positive electrode 22 and the negative electrode 23. The positive electrode 22 includes a positive electrode body region 221 and a positive electrode tab 21a protruding from the positive electrode body region 221. The positive electrode body region 221 has a positive electrode active material layer 223. The negative electrode 23 includes a negative electrode body region 231 and a negative electrode tab 21b protruding from the negative electrode body region 231. The negative electrode body region 231 has a negative electrode active material layer 233. Along the first direction Z, the positive electrode body region 221 has a fifth end 2211 facing the end cap 12, and the negative electrode body 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.

[0551] As an example, electrode assembly 2 can be a wound structure or a stacked structure.

[0552] The positive electrode 22 may include a positive current collector 222 and a positive active material layer 223, wherein the positive current collector 222 has the positive active material layer 223 disposed on one or both surfaces in its thickness direction. (See also...) Figure 26 , Figure 27 and Figure 28 The positive electrode 22 also includes an insulating layer 224. The positive current collector 222 has insulating layers 224 on both opposite surfaces in the thickness direction. The insulating layers 224 and the positive active material layer 223 are arranged along the first direction Z. The insulating layers 224 are located at the ends of the positive active material layer 223. The portion of the positive electrode 22 that corresponds to the positive active material layer 223 and the insulating layer 224 as a whole is the positive electrode body region 221. The end of the insulating layer 224 near the end cap 12 forms the fifth end 2211 of the positive electrode body region 221. The portion of the positive current collector 222 extending beyond the insulating layer 224 forms the positive electrode tab 21a. Please refer to [link to relevant documentation]. Figure 26 , Figure 27 and Figure 28 The positive electrode 22 does not have an insulating layer 224. The part of the positive electrode 22 corresponding to the positive active material layer 223 is the positive electrode main body region 221. The end of the positive active material layer 223 near the end cap 12 forms the fifth end 2211 of the positive electrode main body region 221. The part of the positive current collector 222 that extends beyond the positive active material layer 223 forms the positive electrode tab 21a.

[0553] The negative electrode sheet 23 may include a negative electrode current collector 232 and a negative electrode active material layer 233. The negative electrode current collector 232 has the negative electrode active material layer 233 disposed on one or both surfaces in its thickness direction. The portion of the negative electrode sheet 23 corresponding to the negative electrode active material layer 233 is the negative electrode main body 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 body 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.

[0554] The fifth end 2211 and the sixth end 2311 can be flush. Please refer to [link / reference]. Figure 26 , Figure 27 and Figure 28 Alternatively, the fifth end 2211 could be closer to the end cap 12 than the sixth end 2311. Please refer to [link / reference]. Figure 26 , Figure 27 and Figure 28 Alternatively, the sixth end 2311 may be closer to the end cap 12 than the fifth end 2211.

[0555] In this embodiment, the seventh end 241 of the insulating member 24 is closer to the end cap 12 than the fifth end 2211 of the positive electrode main body region 221 and the sixth end 2311 of the negative electrode main body region 231. This makes the insulating member 24 have a portion that extends beyond the fifth end 2211 and the sixth end 2311, thereby enhancing the insulation effect of the insulating member 24 between the positive electrode plate 22 and the negative electrode plate 23 and reducing the possibility of overlap between the positive electrode plate 22 and the negative electrode plate 23.

[0556] In some embodiments, please refer to Figure 26 , Figure 27 and Figure 28 The isolation member 24 includes an extension region 242 extending beyond the fifth end 2211 and the sixth end 2311 along the first direction Z. In a projection plane perpendicular to the second direction Y, the orthographic projection of the extension region 242 partially overlaps with the orthographic projection of the first inner surface 804.

[0557] The extended region 242 is the portion of the separator 24 that extends beyond both the fifth end 2211 of the positive electrode main body region 221 and the sixth end 2311 of the negative electrode main body region 231. It is understood that, referring to the figures, 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 extending beyond the fifth end 2211 is the extended region 242. Referring to the figures, 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 extending beyond the sixth end 2311 is the extended region 242.

[0558] For example, please refer to Figure 11 In electrode assembly 2, the positive electrode 22, the negative electrode 23, and the separator 24 are stacked along the second direction Y in the flat region 25.

[0559] In this embodiment of the application, in the projection plane perpendicular to the second direction Y, the orthographic projection of the area 242 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 capability of the first sidewall portion 111 in the corresponding part of the first inner surface 804, and make more areas of the first sidewall portion 111 along the first direction Z reinforced.

[0560] See some implementation columns. Figure 26 The first inner surface 804 protrudes from the second inner surface 805. In the projection plane perpendicular to the second direction Y, the orthographic projection of the positive electrode main body region 221 does not overlap with the orthographic projection of the first inner surface 804; and / or, in the projection plane perpendicular to the second direction Y, the orthographic projection of the negative electrode main body region 231 does not overlap with the orthographic projection of the first inner surface 804.

[0561] 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 relative to the second inner surface 805.

[0562] The first inner surface 804 can extend to the first connecting portion 51, so that the first inner surface 804 is directly connected to the first connecting portion 51.

[0563] It is understood that in embodiments where the first inner surface 804 includes a first sub-surface 11111 and a second sub-surface 11112 arranged along a first direction Z, both 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 a second direction Y. In embodiments where the first inner surface 804 includes a second connecting surface 11114, a first connecting surface 11113, and a third connecting surface 11115 arranged along a third direction X, all three connecting surfaces are closer to the electrode assembly 2 relative to the second inner surface 805 along a second direction Y.

[0564] For example, please refer to Figure 26 In the projection plane perpendicular to the second direction Y, the positive electrode main body area 221 and the orthographic projection of the first inner surface 804 do not overlap, and the negative electrode main body area 231 and the orthographic projection of the first inner surface 804 do not overlap.

[0565] In this embodiment, if the orthographic projection of the positive electrode main body region 221 does not overlap with the orthographic projection of the first inner surface 804 in the projection plane perpendicular to the second direction Y, the housing 11 can provide a larger expansion space for the electrode assembly 2, reducing the expansion force exerted directly on the first sidewall portion 111 on the portion corresponding to the first inner surface 804, and reducing the deformation of the first sidewall portion 111. Similarly, if the orthographic projection of the negative electrode main body region 231 does not overlap with the orthographic projection of the first inner surface 804 in the projection plane perpendicular to the second direction Y, the housing 11 can provide a larger expansion space for the electrode assembly 2, reducing the expansion force exerted directly on the first sidewall portion 111 on the portion corresponding to the first inner surface 804, and reducing the deformation of the first sidewall portion 111.

[0566] In some embodiments, please refer to Figure 27 and Figure 28 The negative electrode 23 includes a negative current collector 232 and a negative active material layer 233 disposed on at least one side of the negative current collector 232, the negative active material layer 233 including a negative active material.

[0567] The negative electrode current collector 232 may have a negative electrode active material layer 233 on only one side, that is, the negative electrode current collector 232 may have a negative electrode active material layer 233 on only one surface along the thickness direction; or the negative electrode current collector 232 may have a negative electrode active material layer 233 on both opposite sides, that is, the negative electrode current collector 232 may have a negative electrode active material layer 233 on both opposite surfaces along the thickness direction.

[0568] 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, and lithium titanate, etc.

[0569] In some embodiments, please refer to Figure 27 and Figure 28 The negative electrode active material layer 233 includes a negative electrode main body 2331 and a negative electrode thinning part 2332. The negative electrode main body 2331 and the negative electrode thinning part 2332 are arranged along the first direction Z. Along the first direction Z, the negative electrode main body 2331 is provided with a negative electrode thinning part 2332 at one end near the end cap 12.

[0570] 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 along the first direction Z, near the end cap 12, or it 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 uniform thickness or non-uniform thickness, and the negative electrode thinning portion 2332 may also be of uniform thickness or non-uniform thickness. If at least one of the negative electrode main body 2331 and the negative electrode thinning portion 2332 is of non-uniform thickness, 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, thereby achieving a thickness greater than that of the negative electrode main body 2331.

[0571] As an example, the negative electrode main body 2331 has a uniform thickness structure, and the thickness of the negative electrode thinning part 2332 decreases along the direction from the negative electrode main body 2331 to the negative electrode thinning part 2332.

[0572] In this embodiment, a negative electrode thinning portion 2332 is provided at one end of the negative electrode main body 2331 near the end cap 12. The electrode assembly 2 has a larger expansion gap in the area corresponding to the negative electrode thinning portion 2332. After expansion, the area of ​​the electrode assembly 2 corresponding to the negative electrode thinning portion 2332 exerts less force on the first sidewall portion 111, which is beneficial to reduce the cracking of the housing 11.

[0573] In some embodiments, please refer to Figures 26-28 In the projection plane perpendicular to the second direction Y, the orthographic projection of the negative electrode thinning portion 2332 and the orthographic projection of the first inner surface 804 are spaced apart along the first direction Z.

[0574] It is understandable that, in the projection plane perpendicular to the second direction Y, the orthographic projection of the negative electrode thinning portion 2332 located at the end of the negative electrode main body portion 2331 near the end cap 12 does not overlap with the orthographic projection of the first inner surface 804.

[0575] In this embodiment, in a projection plane perpendicular to the second direction Y, the orthographic projection of the negative electrode thinning portion 2332 located at one end of the negative electrode main body 2331 near the end cap 12 and the orthographic projection of the first inner surface 804 are spaced apart along the first direction Z. This can reduce the influence of the negative electrode thinning portion 2332 on the corresponding portion of the first sidewall portion 111 at the first inner surface 804, reduce the expansion force exerted directly on the corresponding portion of the first sidewall portion 111 at the first inner surface 804 by the expansion of the electrode assembly 2, and further reduce the possibility of cracking of the first sidewall portion 111 of the housing 11.

[0576] In some embodiments, please refer to Figures 26-28 In the projection plane perpendicular to the second direction Y, the distance between the orthographic projection of the negative electrode thinning 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.

[0577] In a projection plane perpendicular to the second direction Y, the distance between the orthographic projection of the negative electrode thinning 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 distance is the minimum distance between the orthographic projections of the negative electrode thinning portion 2332 and the first inner surface 804 along the first direction Z in a projection plane perpendicular to the second direction Y. W1 can be any point value or a range between any two of the following: 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.

[0578] In this embodiment, W1≥1mm makes the orthographic projection of the negative electrode thinning portion 2332 and the orthographic projection of the first inner surface 804 further apart along the first direction Z in the projection plane perpendicular to the second direction Y, thereby further reducing the influence of the negative electrode thinning portion 2332 on the corresponding portion of the first sidewall portion 111 at the first inner surface 804.

[0579] In some embodiments, the single-sided coating weight of the negative electrode active material layer 233 is 90 mg / 1540 mm. 2 ~170mg / 1540mm 2 .

[0580] The single-sided coating weight of the negative electrode active material layer 233 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 The value of any one of them or the range between any two.

[0581] When measuring the single-sided coating weight of the negative electrode active material layer 233, a single-sided coated negative electrode sheet 23 (if it is a double-sided coated negative electrode sheet 23, the negative electrode active material layer 233 on one side can be wiped off first), is cut into a small circular piece with an area of ​​S1, and its weight is recorded as M1. Then, the negative electrode active material layer 233 of the weighed negative electrode sheet 23 is wiped off, and the weight of the negative electrode current collector 232 is measured and recorded as M2. The single-sided coating weight of the negative electrode active material layer 233 = (M1-M2) / S1.

[0582] The single-sided coating weight of the negative electrode active material layer 233 is related to the expansion of the negative electrode active material layer 233. The single-sided coating weight of the negative electrode active material layer 233 is set at 90 mg / 1540 mm². 2 ~170mg / 1540mm 2 It can, to a certain extent, balance the high energy density requirements of the battery cell 10 and the low expansion requirements of the negative electrode 23, so as to reduce the impact of the expansion of the negative electrode 23 on the first side wall portion 111 and reduce the possibility of cracking of the first side wall portion 111 of the casing 11.

[0583] In some embodiments, the single-sided coating weight of the negative electrode active material layer 233 is 110 mg / 1540 mm. 2 ~150mg / 1540mm 2 .

[0584] In this embodiment, the single-sided coating weight of the negative electrode active material layer 233 can be 110 mg / 1540 mm. 2 115mg / 1540mm 2 120mg / 1540mm 2 125mg / 1540mm 2 130mg / 1540mm 2 135mg / 1540mm 2 140mg / 1540mm 2145mg / 1540mm 2 150mg / 1540mm 2 The value of any one of them or the range between any two.

[0585] In this embodiment, the single-sided coating weight of the negative electrode active material layer 233 is 110 mg / 1540 mm. 2 ~150mg / 1540mm 2 This can further improve the energy density requirements of the battery cell 10 and further reduce the expansion of the negative electrode 23.

[0586] In some embodiments, the porosity of the negative electrode 23 is 27% to 40%.

[0587] The porosity of the negative electrode 23 can be any one of the following values ​​or a range between any two: 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%.

[0588] The porosity of the negative electrode 23 can be defined as the percentage of the pore volume within the negative electrode 23 to the total volume of the negative electrode 23. As an example, when the battery cell 10 is at 0% state of charge, a negative electrode 23 with double-sided coating is taken; the porosity of the negative electrode 23 is measured using a true density meter AccuPyc II 1340 according to the national standard GB / T 24586-2009.

[0589] In this embodiment, the porosity of the negative electrode 23 is 27% to 40%, which provides space for impurities generated by the side reactions of the negative electrode 23, slows down the expansion of the negative electrode 23, and reduces the impact of the expansion of the negative electrode 23 on the first sidewall portion 111.

[0590] In some embodiments, the negative electrode active material includes a silicon-based material, wherein the mass content of silicon element in the negative electrode active material is 0.3% to 10%, optionally 1% to 6%.

[0591] In silicon-based materials, the mass content of silicon in the negative electrode active material can be any one of the following values ​​or any range between two: 0.3%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%.

[0592] In some embodiments, the silicon-based material includes at least one of silicon oxides and silicon-carbon composites.

[0593] In some embodiments, please refer to Figure 27 and Figure 28The positive electrode 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 including a positive active material.

[0594] The positive electrode current collector 222 may have a positive electrode active material layer 223 on only one side, that is, the positive electrode current collector 222 may have a positive electrode active material layer 223 on only one surface along the thickness direction; or the positive electrode current collector 222 may have a positive electrode active material layer 223 on both opposite sides, that is, the positive electrode current collector 222 may have a positive electrode active material layer 223 on both opposite surfaces along the thickness direction.

[0595] The positive electrode active material may include at least one of the following materials: lithium phosphate, lithium transition metal oxide and their respective modified compounds.

[0596] In some embodiments, please refer to Figure 27 and Figure 28 The positive electrode active material layer 223 includes a positive electrode main body 2231 and a positive electrode thinning part 2232. The positive electrode main body 2231 and the positive electrode thinning part 2232 are arranged along the first direction Z. Along the first direction Z, the positive electrode main body 2231 is provided with the positive electrode thinning part 2232 at one end near the end cap 12.

[0597] 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 near the end cap 12 along the first direction Z, or it 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 uniform thickness or of non-uniform thickness, and the positive electrode thinning portion 2232 may also be of uniform thickness or of non-uniform thickness. If at least one of the positive electrode main body 2231 and the positive electrode thinning portion 2232 is of non-uniform thickness, 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, thereby achieving a thickness of the positive electrode main body 2231 greater than the thickness of the positive electrode thinning portion 2232.

[0598] As an example, the positive electrode main body 2231 has a uniform thickness structure, and the thickness of the positive electrode thinning part 2232 decreases along the direction from the positive electrode main body 2231 to the positive electrode thinning part 2232.

[0599] In this embodiment, a positive electrode thinning portion 2232 is provided at one end of the positive electrode main body 2231 near the end cap 12. The electrode assembly 2 has a larger expansion gap in the area corresponding to the positive electrode thinning portion 2232. After expansion, the area of ​​the electrode assembly 2 corresponding to the positive electrode thinning portion 2232 exerts less force on the first sidewall portion 111, which can reduce the possibility of cracking of the first sidewall portion 111 of the housing 11.

[0600] In some embodiments, please refer to Figures 26-28 In the projection plane perpendicular to the second direction Y, the orthographic projection of the positive electrode thinning portion 2232 and the orthographic projection of the first inner surface 804 are spaced apart along the first direction Z.

[0601] It is understandable that, in the projection plane perpendicular to the second direction Y, the orthographic projection of the positive electrode thinning portion 2232 located at the end of the positive electrode main body 2231 near the end cap 12 does not overlap with the orthographic projection of the first inner surface 804.

[0602] In a 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 near the end cap 12 and the orthographic projection of the first inner surface 804 are spaced apart along the first direction Z. This can reduce the influence of the positive electrode thinning portion 2232 on the corresponding part of the first sidewall portion 111 on the first inner surface 804, reduce the expansion force exerted directly on the corresponding part of the first sidewall portion 111 on the first inner surface 804 by the expansion of the electrode assembly 2, and reduce the possibility of cracking of the first sidewall portion 111 of the housing 11.

[0603] In some embodiments, please refer to Figures 26-28 In the projection plane perpendicular to the second direction Y, the distance between the orthographic projection of the positive electrode thinning 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.

[0604] In a projection plane perpendicular to the second direction Y, the distance between the orthographic projection of the positive electrode thinning 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 thinning portion 2232 and the first inner surface 804 along the first direction Z in a projection plane perpendicular to the second direction Y. W2 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, and 20 mm, or any value between two of these values.

[0605] In this embodiment, W2≥1mm, so that in the projection plane perpendicular to the second direction Y, the orthographic projection of the positive electrode thinning portion 2232 and the orthographic projection of the first inner surface 804 are further apart along the first direction Z, thereby further reducing the influence of the positive electrode thinning portion 2232 on the first inner surface 804.

[0606] In some embodiments, the single-sided coating weight of the positive electrode active material layer 223 is 200 mg / 1540 mm.2 ~370mg / 1540 / mm 2 .

[0607] The single-sided coating weight of the positive electrode active material layer 223 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 The value of any one of them or the range between any two.

[0608] When measuring the weight of a single-sided coating of the positive electrode active material layer 223, a single-sided coated positive electrode sheet 22 (if it is a double-sided coated positive electrode sheet 22, the positive electrode active material layer 223 on one side can be wiped off first) can be cut into a small circular piece with an area of ​​S2, and its weight recorded as M3. Then, the positive electrode active material layer 223 of the weighed positive electrode sheet 22 can be wiped off, and the weight of the positive electrode current collector 222 can be measured and recorded as M4. The weight of a single-sided coating of the positive electrode active material layer 223 = (M3-M4) / S2.

[0609] The single-sided coating weight of the positive electrode active material layer 223 is related to the expansion of the positive electrode active material layer 223. The single-sided coating weight of the positive electrode active material layer 223 is set at 200 mg / 1540 mm². 2 ~370mg / 1540 / mm 2 It can, to a certain extent, balance the high energy density requirements of the battery cell 10 and the low expansion requirements of the positive electrode 22, so as to reduce the impact of the expansion of the positive electrode 22 on the first side wall portion 111 and reduce the possibility of cracking of the first side wall portion 111 of the casing 11.

[0610] In some embodiments, the single-sided coating weight of the positive electrode active material layer 223 is 240 mg / 1540 mm. 2 ~330mg / 1540mm 2 .

[0611] The single-sided coating weight of the positive electrode active material layer 223 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 The value of any one of them or the range between any two.

[0612] In this embodiment, the single-sided coating weight of the positive electrode active material layer 223 is 240 mg / 1540 mm. 2 ~330mg / 1540mm 2 This can further improve the energy density requirements of the battery cell 10 and further reduce the expansion of the positive electrode 22.

[0613] In some embodiments, the positive electrode active material is a lithium phosphate.

[0614] See some implementation columns. Figure 14 , Figure 30 and Figure 31The material of the housing 11 includes steel. The maximum distance between the second inner surface 805 and the second outer surface 807 along the second direction Y is D1, and the dimension of the housing 11 along the second direction Y is D, where 0.001≤D1 / D≤0.012.

[0615] As an example, the distance between the second inner surface 805 and the second outer surface 807 along the second direction Y at each position can be equal, and the distance between the second inner surface 805 and the second outer surface 807 along the second direction Y at any position can be taken as the maximum distance between the second inner surface 805 and the second outer surface 807 along the second direction Y.

[0616] 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 not be equal.

[0617] In this embodiment, the first inner surface 804 may be partially closer to the electrode assembly 2 relative to the second inner surface 805 along the second direction Y, or the first outer surface 806 may be partially further away from the electrode assembly 2 relative to the second outer surface 807 along the second direction Y. For example, please refer to... Figure 29 and Figure 30 The first outer surface 806 may be partially further away from the electrode assembly 2 along the second direction Y relative to the second outer surface 807, and the first inner surface 804 and the second inner surface 805 are coplanar.

[0618] The maximum distance between the 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 is understood 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.

[0619] For the steel shell 11, D1 / D can take any one of the following point values ​​or any range between two values: 0.001, 0.002, 0.003, 0.004, 0.005, 0.006, 0.007, 0.008, 0.009, 0.01, 0.011, 0.012.

[0620] For the steel casing 11, D1 / D≥0.001 increases the proportion of the distance between the second inner surface 805 along the second direction Y and the second outer surface 807 in the thickness of the casing 11, so that the part of the first sidewall portion 111 corresponding to the second inner surface 805 has sufficient strength to meet the strength requirements of the casing 11; D1 / D≤0.012 decreases the proportion of the distance between the second inner surface 805 along the second direction Y and the second outer surface 807 in the thickness of the casing 11. With a fixed volume of the casing 11, the internal space of the casing 11 can be increased, thereby freeing up more space for the electrode assembly 2 to meet the volumetric energy density requirements of the battery cell 10.

[0621] In this embodiment of the application, for the steel casing 11, in order to meet the volumetric energy density requirements of the battery cell 10, D1 / D needs to be controlled below 0.012. The first sidewall portion 111 is reinforced by the thicker portion corresponding to the first inner surface 804, thereby reducing the possibility of cracking of the first sidewall portion 111 of the casing 11.

[0622] In some embodiments, please refer to Figure 14 and Figure 30 The material of the housing 11 includes steel. The maximum distance between the second inner surface 805 and the second outer surface 807 along the second direction Y is D1, 0.08mm≤D1≤0.35mm; and / or, the maximum distance between the first inner surface 804 and the first outer surface 806 along the second direction Y is D2, 0.1mm≤D2≤0.6mm.

[0623] It is understandable that the maximum distance between the second inner surface 805 and the second outer surface 807 is less 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 less than the maximum distance between the first inner surface 804 and the first outer surface 806. That is, D1 < D2.

[0624] For the steel shell 11, D1 can be any one of the following values ​​or a range between any two: 0.08mm, 0.1mm, 0.12mm, 0.15mm, 0.18mm, 0.2mm, 0.22mm, 0.25mm, 0.28mm, 0.3mm, 0.32mm, 0.35mm; D2 can be any one of the following values ​​or a range between any two: 0.1mm, 0.15mm, 0.2mm, 0.25mm, 0.3mm, 0.35mm, 0.4mm, 0.45mm, 0.5mm, 0.55mm, 0.6mm.

[0625] In this embodiment, for the steel casing 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 0.08mm to 0.35mm, it can satisfy both the strength requirements of the first sidewall portion 111 corresponding to the second inner surface 805 and 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 0.1mm to 0.6mm, the portion of the first sidewall portion 111 corresponding to the first inner surface 804 is strengthened.

[0626] In some embodiments, please refer to Figure 14 , Figure 30 and Figure 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, and the dimension of the housing 11 along the second direction Y is D, where 0.005≤D1 / D≤0.065.

[0627] For the aluminum alloy housing 11, D1 / D can be any one of the following values ​​or a range between any two: 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.

[0628] For the aluminum alloy casing 11, D1 / D≥0.005 increases the proportion of the distance between the second inner surface 805 and the second outer surface 807 in the thickness of the casing 11, so that the part of the first sidewall portion 111 corresponding to the second inner surface 805 has sufficient strength to meet the strength requirements of the casing 11; D1 / D≤0.065 decreases the proportion of the distance between the second inner surface 805 and the second outer surface 807 in the thickness of the casing 11. With a fixed volume of the casing 11, the internal space of the casing 11 can be increased, thereby freeing up more space for the electrode assembly 2 to meet the volumetric energy density requirements of the battery cell 10.

[0629] For the aluminum alloy casing 11, in order to meet the volumetric energy density requirements of the battery cell 10, D1 / D needs to be controlled below 0.065. The first sidewall portion 111 is reinforced by the thicker portion of the first inner wall portion, thereby reducing the possibility of cracking of the casing 11.

[0630] In some embodiments, please refer to Figure 14 and Figure 30The 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, 0.4mm≤D1≤0.8mm; and / or, the maximum distance between the first inner surface 804 and the first outer surface 806 along the second direction Y is D2, 0.5mm≤D2≤1.5mm.

[0631] For the aluminum alloy shell 11, D1 can be any one of the following values ​​or a range between any two: 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; D2 can be any one of the following values ​​or a range between any two: 0.5mm, 0.6mm, 0.7mm, 0.8mm, 0.9mm, 1mm, 1.1mm, 1.2mm, 1.3mm, 1.4mm, 1.5mm.

[0632] For the aluminum alloy casing 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 0.4mm to 0.8mm, it can satisfy both the strength requirements of the portion of the first sidewall 111 corresponding to the second inner surface 805 and 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 0.5mm to 1.5mm, the portion of the first sidewall 111 corresponding to the first inner surface 804 will have sufficient strength.

[0633] In some embodiments, the aluminum alloy comprises the following components by weight 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%. This aluminum alloy has good processing and forming properties, facilitating the forming of the shell 11.

[0634] In some embodiments, the aluminum alloy comprises the following components by mass percentage: aluminum ≥ 96.7%, copper ≤ 0.05% ≤ 0.2%, iron ≤ 0.7%, manganese ≤ 1.5%, silicon ≤ 0.6%, zinc ≤ 0.1%, other individual element components ≤ 0.05%, and other element total components ≤ 0.15%. This aluminum alloy exhibits good processing and forming properties and corrosion resistance.

[0635] In some embodiments, please refer to Figure 6 , Figure 26 , Figure 29 , Figure 32 , Figure 34 , Figure 36 The first region 1111 is directly connected to the first connecting part 51, and the first inner surface 804 extends along the first direction Z to the end of the first region 1111 facing the connecting part 5.

[0636] The first zone 1111 and the first connecting part 51 can be in point contact, line contact or surface contact to achieve direct connection between the two.

[0637] In this embodiment, the first region 1111 is directly connected to the first connecting part 51, making the first region 1111 and the first connecting part 51 closer along the first direction Z. By releasing the expansion force of the electrode assembly 2 through the first region 1111 which is close to the first connecting part 51, it is beneficial to reduce the possibility of cracking of the first connecting part 51.

[0638] In some embodiments, please refer to Figures 32-37 The first sidewall portion 111 also includes a first transition region 1117. The first transition region 1117 is connected to the end of the first region 1111 that is away from the second region 1112 along the first direction Z. The first transition region 1117 is connected to the first connecting portion 51. The connection position of the first transition region 1117 and the first connecting portion 51 forms a first connecting interface 511. The first connecting interface 511 has a first position 5111 that is closest to the first region 1111 along the first direction Z. The first position 5111 is located at the end of the first region 1111 that is away from the second region 1112 along the first direction Z.

[0639] The first transition region 1117 may be the portion of the first sidewall portion 111 connecting the first connecting portion 51 and the first region 1111. The first transition region 1117 may be a structure of uniform thickness or a structure of non-uniform thickness. The thickness of the first transition region 1117 may be less than the thickness of the first region 1111. For example, please refer to... Figures 32-37 Along the direction from the second zone 1112 to the first zone 1111, the thickness of the first transition zone 1117 gradually decreases.

[0640] The first connection interface 511 is formed at the connection position between the first transition region 1117 and the first connection part 51, and the first transition region 1117 and the first connection part 51 are separated by the first connection interface 511. The first connection interface 511 can be a plane or a curved surface.

[0641] The first zone 1111 and the first transition zone 1117 are separated by the first interface U, which is a virtual plane. The first interface U passes through the first position 5111 and is perpendicular to the first direction Z. The first transition zone 1117 and the first connecting part 51 are located above the first interface U, and the first zone 1111 is located below the first interface U.

[0642] In this embodiment, the first transition region 1117 is connected to the first connecting portion 51 to form a first connecting interface 511, so that the first transition region 1117 and the first connecting portion 51 have a sufficiently large contact area, which improves the firmness of the first side wall portion 111 and the end cap 12 after welding.

[0643] In some embodiments, please refer to Figures 32-37 At least a portion of the first connection interface 511 extends at an angle relative to the second direction Y.

[0644] The first connection interface 511 can extend at an overall angle relative to the second direction Y, or the first connection interface 511 can extend at a partial angle relative to the second direction Y.

[0645] It is understandable that the extension direction of the portion of the first connecting interface 511 that extends at an angle relative to the second direction Y is not parallel to the second direction Y.

[0646] After the end cap 12 and the first sidewall portion 111 are welded, the first connecting portion 51 shrinks as it solidifies, generating tensile stress on the first transition region 1117. When the first sidewall portion 111 is subjected to the expansion force of the electrode assembly 2, it deforms, and the first transition region 1117 generates tensile stress on the first connecting portion 51. Since the first connecting interface 511 extends at least partially at an angle relative to the second direction Y, the tensile stress generated by the first connecting portion 51 due to shrinkage on the first transition region 1117 near the portion of the first connecting interface 511 that extends at an angle relative to the second direction Y is not on the same straight line as the tensile stress generated by the first transition region 1117 due to deformation of the first sidewall portion 111 on the first connecting portion 51, reducing the risk of fatigue cracking in the area of ​​the first transition region 1117 near the first connecting interface 511.

[0647] In some embodiments, please refer to Figures 32-37 The first connection interface 511 includes a first interface 5112, which extends obliquely from the first position 5111 toward the end cap 12 along the second direction Y. At least a portion of the first transition area 1117 is located between the first interface 5112 and the end cap 12.

[0648] It is understandable that the first interface 5112 extends at an angle relative to the second direction Y. The first interface 5112 can be a plane or a curved surface.

[0649] The first position 5111 is the lowest position of the first interface 5112 (the position closest to the first area 1111). The first interface 5112 extends obliquely from the first position 5111 towards the end cover 12, that is, the first interface 5112 extends obliquely upward from the first position 5111 towards the end cover 12.

[0650] Along the second direction Y, the first transition region 1117 can be entirely located between the first interface 5112 and the end cap 12, or only a portion of the first transition region 1117 can be located between the first interface 5112 and the end cap 12.

[0651] In this embodiment, at least a portion of the first transition region 1117 is located between the first interface 5112 and the end cap 12 along the second direction Y. In this way, the first connecting portion 51 protects the first transition region 1117. When the first sidewall portion 111 is subjected to the expansion force of the electrode assembly 2, the deformation of the first transition region 1117 during the stress process is blocked by the first connecting portion 51, reducing the possibility of fatigue cracking in the area of ​​the first transition region 1117 near the first interface 5112.

[0652] In some embodiments, please refer to Figures 32-37 The first interface 5112 is connected to the first outer surface 806 at the first position 5111, and the first position 5111 is at least partially located in the first region 1111.

[0653] As an example, the first interface 5112 intersects the first outer surface 806 at a first straight line, which extends along a third direction X, and the location of the first straight line is the 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 a first direction Z. The third position 5114 is farther away from the first region 1111 than the first position 5111. The first transition region 1117 is approximately triangular in shape.

[0654] 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 region 1111, such that the first outer surface 806 extends to one end of the first region 1111 along the first direction Z toward the first connecting portion 51, and the portion of the first sidewall portion 111 corresponding to the first outer surface 806 can better strengthen the end of the first region 1111 toward the first connecting portion 51, reducing the possibility of fatigue cracking at the end of the first region 1111 toward the first connecting portion 51.

[0655] In some embodiments, please refer to Figures 32-37 The first connection interface 511 includes a second interface 5113, which extends obliquely from the first position 5111 in a direction away from the end cap 12 along the second direction Y. At least a portion of the first transition area 1117 is located on the side of the second interface 5113 away from the end cap 12.

[0656] Understandably, the second interface 5113 extends at an angle relative to the second direction Y. The second interface 5113 can be planar or curved. 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 cap 12.

[0657] The first position 5111 is the lowest position of the second interface 5113 (the position closest to the first area 1111). 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.

[0658] Along the second direction Y, the first transition region 1117 can be entirely located on the side of the second interface 5113 away from the end cover 12, or the first transition region 1117 can be only partially located on the side of the second interface 5113 away from the end cover 12.

[0659] In this embodiment, at least a portion of the first transition region 1117 is located on the side of the second interface 5113 away from the end cap 12 along the second direction Y, so that the first transition region 1117 restricts the first connecting portion 51 and reduces the possibility of the first connecting portion 51 falling off.

[0660] In some embodiments, please refer to Figures 32-37 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 region 1111.

[0661] As an example, the second interface 5113 intersects the first inner surface 804 at a first straight line, which extends along a third direction X, and the location of the first straight line is the 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 a first direction Z. The fourth position 5115 is farther away from the first region 1111 than the first position 5111. The first transition region 1117 is approximately triangular in shape.

[0662] 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 region 1111, such that the first inner surface 804 extends to one end of the first region 1111 facing the first connecting portion 51 along the first direction Z. The portion of the first sidewall portion 111 corresponding to the first inner surface 804 can better strengthen the end of the first region 1111 facing the first connecting portion 51, reducing the possibility of fatigue cracking at the end of the first region 1111 facing the first connecting portion 51.

[0663] In some embodiments, please refer to Figures 32-37The 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 end cap 12, and the second interface 5113 extends obliquely from the first position 5111 toward the end cap 12. Along the second direction Y, a portion of the first transition region 1117 is located between the first interface 5112 and the end cap 12, and another portion of the first transition region 1117 is located on the side of the second interface 5113 away from the end cap 12.

[0664] As an example, the first interface 5112 is connected to the inner surface of the first transition zone 1117 at the third position 5114, and the second interface 5113 is connected to the outer surface of the first transition zone 1117 at the fourth position 5115.

[0665] 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.

[0666] As an example, the hardness of the second zone 1112 is less than the hardness of the first connecting part 51.

[0667] As an example, the hardness type of the first transition zone 1117, the hardness type of the first zone 1111, the hardness type of the second zone 1112, and the hardness type of the first connecting part 51 are all Vickers hardness.

[0668] If the hardness of the first transition zone 1117 is less than the hardness of the second zone 1112, the lower-hardness first transition zone 1117 connects to the first connecting portion 51, which can alleviate the rigid tension between the first sidewall portion 111 and the first connecting portion 51 when the first sidewall portion 111 deforms, reducing the possibility of separation between the first sidewall portion 111 and the first connecting portion 51. If the hardness of the first transition zone 1117 is less than the hardness of the first connecting portion 51, the first transition zone 1117 is more prone to deformation than the first connecting portion 51, which can alleviate the rigid tension between the first sidewall portion 111 and the first connecting portion 51 when the first sidewall portion 111 deforms, reducing the possibility of separation between the first sidewall portion 111 and the first connecting portion 51.

[0669] In some embodiments, please refer to Figures 32-37 The first connection interface 511 is closer to the second region 1112 than the outer surface 121 of the end cap.

[0670] Along the first direction Z, the surface of the end cap 12 that is away from the electrode assembly 2 is the outer surface 121 of the end cap.

[0671] Please see Figures 32-37 Along the first direction Z, both the third position 5114 and the first position 5111 are closer to the second region 1112 than the outer surface 121 of the end cap.

[0672] Please see Figures 32-37 Along the first direction Z, both the fourth position 5115 and the first position 5111 are closer to the second region 1112 than the outer surface 121 of the end cap.

[0673] Please see Figures 32-37 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 the outer surface 121 of the end cap.

[0674] In this embodiment, the first connection interface 511 is closer to the second region 1112 along the first direction Z than the outer surface 121 of the end cap, so that the first connection portion 51 can sink to a deeper position in the first side wall portion 111, which can effectively improve the connection strength between the first side wall portion 111 and the end cap 12.

[0675] In some embodiments, please refer to Figure 7 , Figure 15 , Figure 16 , Figure 18 , Figure 19 , Figure 22 , Figure 23 , Figure 31 , Figure 38 and Figure 39 The housing 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 circumferentially along the opening, and the corner wall 113 connects the first side wall portion 111 and the second side wall portion 112.

[0676] The second sidewall portion 112 and the end cap 12 can be welded to form a third connecting portion 5, where both the first connecting portion 51 and the third connecting portion 5 are part of the connecting portion 5. The second sidewall portion 112 can be of uniform thickness or of non-uniform thickness.

[0677] The first side wall portion 111 and the second side wall portion 112 in the housing 11 are indirectly connected by a corner wall 113, and the sum of the number of the first side wall portion 111 and the second side wall portion 112 is equal to the number of corner walls 113.

[0678] As an example, the first sidewall portion 111, the second sidewall portion 112, and the corner wall 113 are integrally formed. The cross-section of the outer surface and / or inner surface of the corner wall 113 may be arc-shaped, and the cross-section is perpendicular to the first direction Z.

[0679] In this embodiment, the first sidewall portion 111 and the second sidewall portion 112 are connected by a corner wall 113, which allows the first sidewall portion 111 to transition to the second sidewall portion 112 through the corner wall 113, effectively reducing the risk of stress concentration in the housing 11 at the corner position.

[0680] In some embodiments, please refer to Figures 38-42 The corner wall 113 is welded to the end cap 12 to form a second connecting part 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 part 52.

[0681] The third zone 1131 is located between the fourth zone 1132 and the second connecting part 52. The third zone 1131, which has lower hardness, is closer to the second connecting part 52 than the fourth zone 1132.

[0682] The third zone 1131 and the second connecting part 52 can be directly connected.

[0683] Zone 3 (1131) and Zone 4 (1132) can be directly connected or indirectly connected.

[0684] The second connecting portion 52 can correspond one-to-one with the corner wall 113. The second connecting portion 52 is the part with weld marks formed after the end cap 12 and the corner wall 113 are welded together. The part where the end cap 12 and the corner wall 113 are welded together can be the second connecting portion 52. A part of the second connecting portion 52 is formed on the end cap 12, and another part of the second connecting portion 52 is formed on the corner wall 113. The corner wall 113 and the end cap 12 can form the second connecting portion 52 by seam welding or by through welding. The second connecting portion 52 and the first connecting portion 51 are both part of the connecting portion 5.

[0685] As an example, the hardness of the third zone and the hardness of the fourth zone are both Vickers hardness.

[0686] As an example, the hardness type of the second connection is Vickers hardness.

[0687] In this embodiment, the third region 1131 has a lower hardness, which makes the third region 1131 more tough. The third region 1131 with higher toughness releases part of the expansion force of the electrode assembly 2 on the corner wall 113, which helps to reduce the possibility of cracking of the second connection portion 52 of the second side wall portion 112 of the corner wall 113.

[0688] It should be noted that the third zone 1131 has a lower hardness, which gives it higher toughness. The high toughness of the third zone 1131 may lead to fatigue cracking under the periodic expansion force of the electrode assembly 2.

[0689] In some embodiments, please refer to Figures 38-42The 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 facing away from the electrode assembly 2. The third inner surface 810 and the fourth inner surface 811 are connected sequentially along the direction of the end cap 12 pointing towards the electrode assembly 2. The third inner surface 810 and the third outer surface 812 are at least partially formed in the third region 1131, and the fourth inner surface 811 and the fourth outer surface 813 are at least partially formed in the fourth region 1132. 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.

[0690] 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 can be equal or unequal. 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 can be equal or unequal. When the distances between the positions on the third inner surface 810 along the thickness direction of the corner wall 113 and the third outer surface 812 are not equal, or the distances between the positions on the fourth inner surface 811 along the thickness direction of the corner wall 113 and the third outer surface 812 are not equal, the minimum distance between the third inner surface 810 along the thickness direction of the corner wall 113 and the third outer surface 812 is greater than the maximum distance between the fourth inner surface 811 along the thickness direction of the corner wall 113 and the fourth outer surface 813, so as to achieve that the distance between the third inner surface 810 along the thickness direction of the corner wall 113 and the third outer surface 812 is greater than the distance between the fourth inner surface 811 along the thickness direction of the corner wall 113 and the fourth outer surface 813.

[0691] The third inner surface 810 is closer to the electrode assembly 2 along the thickness direction of the corner wall 113 relative to the fourth inner surface 811, and / or the third outer surface 812 is farther away from the electrode assembly 2 along the thickness direction of the corner wall 113 relative to the fourth outer surface 813. See also... Figures 38-41 The third inner surface 810 is closer to the electrode assembly 2 along the thickness direction of the corner wall 113 relative to the fourth inner surface 811, and the third outer surface 812 and the fourth outer surface 813 are coplanar. Referring to the figure, the third outer surface 812 is further away from the electrode assembly 2 along the thickness direction of the corner wall 113 relative to the fourth outer surface 813, and the third inner surface 810 and the fourth inner surface 811 are coplanar.

[0692] For example, please refer to Figure 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, where D8 > D9.

[0693] In this embodiment, 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. The third inner surface 810 and the third outer surface 812 are at least partially formed in the third region 1131, so that the portion of the corner wall 113 with a larger thickness corresponding to the third inner surface 810 can strengthen the third region 1131 with higher toughness, which is beneficial to suppressing fatigue cracking of the third region 1131 and improving the service life of the battery cell 10.

[0694] In some embodiments, please refer to Figure 38 and Figure 39 The third region 1131 is directly connected to the first region 1111. The third inner surface 810 extends to the end of the third region 1131 facing the first region 1111, and the first inner surface 804 extends to the end of the first region 1111 facing the third region 1131.

[0695] As an example, the third zone 1131 is integrally formed with the first zone 1111, and the first zone 1111 is connected to the third zone 1131 at both ends along the third direction X.

[0696] In this embodiment, the third inner surface 810 extends to the end of the third region 1131 facing the first region 1111, and the first inner surface 804 extends to the end of the first region 1111 facing the third region 1131. The portion of the first sidewall 111 on the first inner surface 804 and the portion of the corner wall 113 on the third inner surface 810 are connected to form a whole. The portion of the first sidewall 111 on the first inner surface 804 and the portion of the corner wall 113 on the third inner surface 810 have a mutually reinforcing effect, so that the portion of the first sidewall 111 on the first inner surface 804 and the portion of the corner wall 113 on the third inner surface 810 are both well reinforced, reducing the possibility of the shell 11 cracking. Since the first inner surface 804 and the first outer surface 806 are at least partially formed in the first region 1111, and the third inner surface 810 and the third outer surface 812 are at least partially formed in the third region 1131, the first sidewall portion 111 in the portion of the first inner surface 804 and the corner wall 113 in the portion of the third inner surface 810 have a mutually reinforcing effect, which can also affect the first region 1111 and the third region 1131, thereby strengthening the first region 1111 and the third region 1131 and reducing the possibility of fatigue cracking in the first region 1111 and the third region 1131.

[0697] In some embodiments, please refer to Figure 38 and Figure 39The corner wall 113 has a first connecting end 1133 and a second connecting end 1134. The first side wall portion 111 is connected to the first connecting end 1133, and the second side wall portion 112 is connected to the second connecting end 1134. The distance between the third inner surface 810 along the thickness direction of the corner wall 113 and the third outer surface 812 is a fourth preset thickness. The fourth preset thickness decreases along the direction from the first connecting end 1133 to the second connecting end 1134.

[0698] As an example, the fourth preset thickness gradually decreases along the direction from the first connecting end 1133 to the second connecting end 1134, the second sidewall portion 112 has a uniform thickness structure, the third inner surface 810 connects the first inner surface 804 and the inner surface of the second sidewall portion 112, and the third outer surface 812 connects the first outer surface 806 and the outer surface of the second sidewall portion 112.

[0699] When the first sidewall portion 111 is subjected to the expansion force of the electrode assembly 2 in the second direction Y, the deformation of the first sidewall portion 111 may cause the corner wall 113 to deform. Along the circumference of the opening, the corner wall 113 is more affected by the first sidewall portion 111 the closer it is to the first sidewall portion 111, resulting in greater deformation in the area of ​​the corner wall 113 closer to the first sidewall portion 111. The fourth preset thickness decreases along the direction from the first connecting end 1133 to the second connecting end 1134, making the area of ​​the third region 1131 closer to the first sidewall portion 111 along the circumference of the opening stronger, reducing the possibility of cracking at the end of the third region 1131 with lower hardness towards the first sidewall portion 111. With the reinforcement of the tougher third region 1131, the material used in the portion of the corner wall 113 corresponding to the third inner surface 810 is reduced, lowering production costs.

[0700] In some embodiments, please refer to Figures 38-40 ,as well as Figure 44 , Figure 46 and Figure 48 The third region 1131 is directly connected to the second connecting part 52, and the third inner surface 810 extends to the end of the third region 1131 facing the second connecting part 52.

[0701] The third zone 1131 and the second connecting part 52 can be in point contact, line contact, or surface contact to achieve direct connection between the two.

[0702] In this embodiment, the third region 1131 is directly connected to the second connecting portion 52, and the third inner surface 810 extends to the end of the third region 1131 facing the second connecting portion 52, so that the end of the third region 1131 facing the second connecting portion 52 with higher toughness is better strengthened, which helps to reduce the possibility of fatigue cracking at the end of the third region 1131 facing the second connecting portion 52.

[0703] See some implementation columns. Figures 43-48 The corner wall 113 also includes a second transition zone 1135, which is connected to the end of the third zone 1131 away from the fourth zone 1132 along the first direction Z. The second transition zone 1135 is connected to the second connecting part 52. The connection position of the second transition zone 1135 and the second connecting part 52 forms a second connecting interface 521. The second connecting interface 521 has a second position 5211 that is closest to the third zone 1131 along the first direction Z. The second position 5211 is located at the end of the third zone 1131 away from the fourth zone 1132 along the first direction Z.

[0704] The second transition region 1135 may be the portion of the corner wall 113 connecting the second connecting portion 52 and the third region 1131. The second transition region 1135 may be a structure of uniform thickness or a structure of non-uniform thickness. The thickness of the second transition region 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 Figures 43-48 In the illustrated embodiment, the thickness of the second transition region 1135 gradually decreases along the direction from the fourth region 1132 to the third region 1131.

[0705] The second connection interface 521 is formed at the connection position between the second transition region 1135 and the second connection portion 52, and the second transition region 1135 and the second connection portion 52 are separated by the second connection interface 521. The second connection interface 521 can be a plane or a curved surface.

[0706] The third zone 1131 and the second transition zone 1135 are separated by the second interface V, which is a virtual plane. The second interface V passes through the second position 5211 and is perpendicular to the first direction Z. The second transition zone 1135 and the second connecting part 52 are located above the second interface V, and the third zone 1131 is located below the second interface V.

[0707] In this embodiment, the second transition area 1135 is connected to the second connecting part 52 to form a second connecting interface 521, so that the second transition area 1135 and the second connecting part 52 have a sufficiently large contact area, which improves the firmness of the corner wall 113 and the end cap 12 after welding.

[0708] In some embodiments, please refer to Figures 43-48 At least a portion of the second connection interface 521 extends obliquely relative to the thickness direction of the corner wall 113.

[0709] The second connection interface 521 can extend at an angle relative to the thickness direction of the corner wall 113 as a whole, or it can extend at an angle relative to the thickness direction of the corner wall 113 locally.

[0710] Near the portion of the second connection interface 521 that extends obliquely relative to 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 is not on the same straight line as the tensile stress generated by the second transition zone 1135 on the second connection portion 52 due to the deformation of the corner wall 113. This reduces the risk of fatigue cracking in the area of ​​the second transition zone 1135 near the second connection interface 521.

[0711] In some embodiments, please refer to Figures 43-48 The second connection interface 521 includes a third interface 5212, which extends obliquely from the second position 5211 toward the end cap 12. Along the thickness direction of the corner wall 113, at least a portion of the second transition area 1135 is located between the third interface 5212 and the end cap 12.

[0712] It is understandable that the third interface 5212 extends at an angle relative to the thickness direction of the corner wall 113. The third interface 5212 can be a plane or a curved surface.

[0713] The second position 5211 is the lowest position of the third interface 5212 (the position closest to the third area 1131). The third interface 5212 extends obliquely from the second position 5211 toward the end cover 12, that is, the third interface 5212 extends obliquely upward from the second position 5211 toward the end cover 12.

[0714] Along the thickness direction of the corner wall 113, the second transition zone 1135 can be entirely located between the third interface 5212 and the end cap 12, or only a portion of the second transition zone 1135 can be located between the third interface 5212 and the end cap 12.

[0715] In this embodiment, at least a portion of the second transition region 1135 is located between the third interface 5212 and the end cap 12 along the thickness direction of the corner wall 113. The second connecting portion 52 protects the second transition region 1135. When the second transition region 1135 deforms outward, it will be blocked by the second connecting portion 52, reducing the risk of fatigue cracking in the area of ​​the second transition region 1135 near the third interface 5212.

[0716] In some embodiments, please refer to Figures 43-48 The third interface 5212 is connected to the third outer surface 812 at the second position 5211, which is located within the third region 1131.

[0717] As an example, the third interface 5212 intersects the third outer surface 812 at a second straight line, which extends along the third direction X, and the location of the second straight line is the second position 5211. The third interface 5212 is connected 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 farther away from the third region 1131 than the second position 5211. The second transition region 1135 is approximately triangular.

[0718] 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 within the third region 1131, such that the third outer surface 812 extends to one end of the third region 1131 facing the second connecting portion 52 along the first direction Z. The corner wall 113 at the portion corresponding to the third outer surface 812 can better strengthen the end of the third region 1131 facing the second connecting portion 52, reducing the possibility of fatigue cracking at the end of the third region 1131 facing the second connecting portion 52 due to its lower hardness.

[0719] In some embodiments, please refer to Figures 43-48 The second connection interface 521 includes a fourth interface 5213, which extends obliquely from the second position 5211 toward the end cap 12. Along the thickness direction of the corner wall 113, at least a portion of the second transition region 1135 is located on the side of the fourth interface 5213 away from the end cap 12.

[0720] Understandably, the fourth interface 5213 extends obliquely relative to the thickness direction of the corner wall 113. The fourth interface 5213 can be planar or curved. 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.

[0721] The second position 5211 is the lowest position of the fourth interface 5213 (the position closest to the first area 1111). The fourth interface 5213 extends obliquely from the second position 5211 in a direction away from the end cover 12, that is, the fourth interface 5213 extends obliquely upward from the second position 5211 in a direction away from the end cover 12.

[0722] Along the thickness direction of the corner wall 113, the second transition zone 1135 can be entirely located on the side of the fourth interface 5213 away from the end cap 12, or the second transition zone 1135 can be only partially located on the side of the fourth interface 5213 away from the end cap 12.

[0723] In this embodiment, at least a portion of the second transition region 1135 is located on the side of the fourth interface 5213 away from the end cap 12 along the thickness direction of the corner wall 113, so that the second transition region 1135 restricts the second connection portion 52 and reduces the risk of the second connection portion 52 falling off.

[0724] In some embodiments, please refer to Figures 43-48 The fourth interface 5213 is connected to the third inner surface 810 at the second position 5211, which is located within the third region 1131.

[0725] As an example, the fourth interface 5213 intersects the third inner surface 810 at a second straight line, which extends along the third direction X, and the location of the second straight line is the 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 farther away from the third region 1131 than the second position 5211. The second transition region 1135 is approximately triangular.

[0726] 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 within the third region 1131, such that the third inner surface 810 extends to one end of the third region 1131 facing the second connecting portion 52 along the first direction Z. The corner wall 113 at the portion corresponding to the third inner surface 810 can better strengthen the end of the third region 1131 facing the second connecting portion 52, reducing the possibility of fatigue cracking at the end of the third region 1131 facing the second connecting portion 52 due to its lower hardness.

[0727] 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 end cap 12, and the fourth interface 5213 extends obliquely from the second position 5211 toward the end cap 12. Along the thickness direction of the corner wall 113, a portion of the second transition region 1135 is located between the third interface 5212 and the end cap 12, and another portion of the second transition region 1135 is located on the side of the fourth interface 5213 away from the end cap 12.

[0728] As an example, the third interface 5212 is connected to the inner surface of the second transition region 1135 at the fifth position 5214, and the fourth interface 5213 is connected to the outer surface of the second transition region 1135 at the sixth position 5215.

[0729] 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.

[0730] As an example, the hardness of the fourth zone 1132 is less than the hardness of the second connecting part 52.

[0731] If the hardness of the second transition zone 1135 is less than the hardness of the fourth zone 1132, the lower-hardness second transition zone 1135 connects to the second connecting portion 52, which can alleviate the rigid tension between the corner wall 113 and the second connecting portion 52 when the corner wall 113 deforms, reducing the possibility of separation between the corner wall 113 and the second connecting portion 52. If the hardness of the second transition zone 1135 is less than the hardness of the second connecting portion 52, the second transition zone 1135 is more prone to deformation than the second connecting portion 52, which can alleviate the rigid tension between the corner wall 113 and the second connecting portion 52 when the corner wall 113 deforms, reducing the possibility of separation between the corner wall 113 and the second connecting portion 52.

[0732] In some embodiments, please refer to Figures 43-48 The second connection interface 521 is closer to the fourth region 1132 than the outer surface 121 of the end cap.

[0733] exist Figures 43-48 In the illustrated embodiment, along the first direction Z, both the fifth position 5214 and the second position 5211 are closer to the fourth region 1132 than the outer surface 121 of the end cap.

[0734] exist Figures 43-48 In the illustrated embodiment, along the first direction Z, the sixth position 5215 and the second position 5211 are both closer to the fourth region 1132 than the outer surface 121 of the end cap.

[0735] exist Figures 43-48 In the illustrated embodiment, 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 the outer surface 121 of the end cap.

[0736] In this embodiment, the second connection interface 521 is closer to the fourth region 1132 along the first direction Z than the outer surface 121 of the end cap, so that the second connection part 52 can sink to a deeper position in the corner wall 113, which can effectively improve the connection strength between the corner wall 113 and the end cap 12.

[0737] In some embodiments, the hardness of the third region 1131 is lower than the hardness of the second connecting portion 52.

[0738] In some embodiments, please refer to Figure 7 , Figure 16 , Figure 19 and Figure 23 The housing 11 includes two first sidewall portions 111 and two second sidewall portions 112. The two first sidewall portions 111 are arranged opposite each other along the second direction Y, and the two second sidewall portions 112 are arranged opposite 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.

[0739] The first sidewall portion 111 has corner walls 113 at both ends along the third direction X, and the second sidewall portion 112 has corner walls 113 at both ends along the second direction Y. It can be understood that there are four corner walls 113 in the housing 11.

[0740] In this embodiment, the housing 11 is generally rectangular, and the size of the housing 11 can be made larger, which is beneficial to meet the large capacity requirements of the battery cell 10.

[0741] In some embodiments, please refer to Figure 49 The first sidewall portion 111 has a limiting surface 1115 facing the end cap 12, the limiting surface 1115 abutting against the end cap 12 to restrict the end cap 12 from moving toward the electrode assembly 2.

[0742] The limiting surface 1115 can be perpendicular to the first direction Z. The limiting surface 1115 can be the end face of the first side wall portion 111 located at the opening of the housing 11. The limiting surface 1115 can also be a step surface on the first side wall portion 111. The step surface is a certain distance away from the end face of the first side wall portion 111 located at the opening of the housing 11.

[0743] The limiting surface 1115 limits the end cap 12, reducing the risk of the end cap 12 moving towards the electrode assembly 2 when it is welded to the housing 11. This can effectively improve the welding quality of the end cap 12 and the housing 11 and reduce the welding difficulty of the end cap 12 and the housing 11.

[0744] In some embodiments, please refer to Figure 49 The first sidewall portion 111 also includes a limiting area 1116 disposed on the limiting surface 1115. The limiting area 1116 and the end cap 12 are disposed opposite to each other along the second direction Y. The limiting area 1116 and the end cap 12 are welded to form a first connecting portion 51.

[0745] As an example, the end cap 12 is at least partially housed within the housing 11, such that the limiting region 1116 is disposed opposite to the end cap 12 along the second direction Y.

[0746] After the limiting region 1116 is welded to the end cap 12, a portion of the limiting region 1116 and a portion of the end cap 12 can be fused together to form the first connecting portion 51, and the remaining portion of the limiting region 1116 can form at least a portion of the first transition region 1117.

[0747] The limiting area 1116 can also limit the end cap 12, reducing the risk of the end cap 12 moving along the thickness direction of the first side wall portion 111 when welding the end cap 12 and the housing 11, further improving the welding quality of the end cap 12 and the housing 11, and reducing the welding difficulty of the end cap 12 and the housing 11.

[0748] In some embodiments, Figure 7 , Figure 16 , Figure 19 and Figure 23 In one embodiment, the second sidewall portion 112 has a uniform thickness. In other embodiments, the second sidewall portion 112 may also have a non-uniform thickness structure, and its structure may be the same as that of the first sidewall portion 111. For example, the second sidewall portion 112 may include a fifth region and a sixth region arranged along the first direction Z, with the hardness of the fifth region being lower than that of the sixth region. The fifth region is located between the third connecting portion 5 and the sixth region, which 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 may be the same as that of the first region 1111, and the structure of the sixth region may be the same as that of the second region 1112.

[0749] In some embodiments, the hardness of the fifth region is lower than that of the third connecting portion 5.

[0750] In some embodiments, the second sidewall 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.

[0751] In some embodiments, where the 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.

[0752] In some embodiments, please refer to Figure 12 and Figure 13 The electrode assembly 2 has a stacked structure, and includes multiple positive electrode plates 22 and multiple negative electrode plates 23, which are stacked along the second direction Y.

[0753] As an example, the positive electrode 22 and the negative electrode tab 21b in the electrode assembly 2 are arranged alternately along the second direction Y, and an isolation member 24 is provided between the positive electrode 22 and the negative electrode 23.

[0754] In this embodiment, the electrode assembly 2 has a stacked structure, which is more compact and has stronger resistance to compression.

[0755] In some embodiments, please refer to Figure 12 and Figure 13 The number of negative electrode plates 23 is greater than the number of positive electrode plates 22, and a positive electrode plate 22 is set between two adjacent negative electrode plates 23.

[0756] As an example, the negative electrode 23 has one more electrode than the positive electrode 22.

[0757] In some embodiments, please refer to Figure 12 and Figure 13 Each negative electrode 23 is provided with a negative electrode tab 21b; and / or each positive electrode 22 is provided with a positive electrode tab 21a.

[0758] 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 of the end cap 12 pointing towards the electrode assembly 2, and the first outer surface 806 and the second outer surface 807 are sequentially connected along the direction of the end cap 12 pointing towards 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 size of the first inner surface 804 is greater than the size of the positive electrode 22 and / or the size of the negative electrode 23. The first direction Z, the second direction Y, and the third direction X are perpendicular to each other.

[0759] If along the third direction X, the size of the first inner surface 804 is larger than the size of the positive electrode 22, and the first inner surface 804 extends beyond at least one end of the positive electrode 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 23, and the first inner surface 804 extends beyond at least one end of the negative electrode 23 along the third direction X.

[0760] As an example, along the third direction X, the size of the projection of the first inner surface 804 along the second direction Y and the first region 1111 is larger than the size of the positive electrode 22 and / or the negative electrode 23.

[0761] 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 22 and / or the size of the negative electrode 23, making the size of the first inner surface 804 larger along the third direction X. This strengthens the first sidewall portion 111 by increasing the strength of a larger area along the third direction X, which helps to reduce the possibility of cracking of the shell 11.

[0762] In some embodiments, please refer to Figure 50The battery cell 10 also includes two electrode terminals 3, which are disposed on the end cover 12. The two electrode terminals 3 have opposite polarities and are both electrically connected to the electrode assembly 2. The end cover 12 is provided with a lead-out hole. The electrode terminal 3 includes a terminal body 31, a first limiting part 32, and a second limiting part 33. The terminal body 31 is connected to the first limiting part 32 and the second limiting part 33. The terminal body 31 passes through the lead-out hole. Along the first direction Z, the first limiting part 32 is located on the side of the end cover 12 away from the electrode assembly 2, and the second limiting part 33 is located on the side of the end cover 12 facing the electrode assembly 2.

[0763] The first limiting part 32 and the second limiting part 33 have a limiting function. The first limiting part 32 and the second limiting part 33 are respectively connected to both ends of the terminal body 31. The first limiting part 32 and the second limiting part 33 cooperate to prevent the terminal body 31 from disengaging from the lead-out hole. Along the first direction Z, the projected area of ​​the first limiting part 32 and the projected area of ​​the second limiting part 33 are both larger than the projected area of ​​the terminal body 31. Alternatively, the projected area of ​​the first limiting part 32 can be larger than the projected area of ​​the second limiting part 33, or the projected area of ​​the second limiting part 33 can be larger than the projected area of ​​the first limiting part 32. The first limiting part 32, the second limiting part 33 and the terminal body 31 can be integrally formed, or one of the first limiting part 32 and the second limiting part 33 can be integrally formed with the terminal body 31, while the other is separately provided and connected to the terminal body 31.

[0764] 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 is at least partially disposed between the electrode terminal 3 and the end cap 12 to insulate and isolate the electrode terminal 3 and the end cap 12. The second insulating member 7 is disposed on the side of the end cap 12 facing the electrode assembly 2 to insulate and isolate the electrode assembly 2 and the end cap 12.

[0765] In this embodiment, the electrode terminal 3 can be installed on the end cap 12 by riveting, which is easy to install and more economical.

[0766] In some embodiments, please refer to Figure 10 and Figure 11 The electrode assembly 2 has a flat region 25, and the portion of the positive electrode 22 located in the flat region 25 and the portion of the negative electrode 23 located in the flat region 25 are stacked along the second direction Y.

[0767] The flat region 25 is the flat portion of the electrode assembly 2. The portion of the positive electrode 22 located in the flat region 25 is approximately flat, and the portion of the negative electrode 23 located in the flat region 25 is also approximately flat. As an example, both the portions of the positive electrode 22 and the negative electrode 23 located in the flat region 25 are flat plate structures. If the electrode assembly 2 is a wound structure, then the flat region 25 can be a portion of the electrode assembly 2; if the electrode assembly 2 is a stacked structure, then the entire electrode assembly 2 can be the flat region 25. The second direction Y is the stacking direction of the portions of the positive electrode 22 and the negative electrode 23 located in the flat region 25.

[0768] As an example, the electrode assembly 2 may also include a separator 24, which is disposed between the positive electrode 22 and the negative electrode 23, and serves to separate the positive electrode 22 and the negative electrode 23. The portion of the positive electrode 22 located in the flat region 25, the portion of the negative electrode 23 located in the flat region 25, and the portion of the separator 24 located in the flat region 25 are stacked along the second direction Y.

[0769] The second direction Y is the stacking direction of the portion of the positive electrode 22 located in the flat region 25 and the portion of the negative electrode 23 located in the flat region 25. During cycling, the electrode assembly 2 expands more along the second direction Y, and the first sidewall portion 111 is more affected by the expansion of the electrode assembly 2. However, because the first region 1111 has high toughness, it releases the expansion force of the electrode assembly 2 on the first sidewall portion 111, which helps to reduce the possibility of cracking of the first connection portion 51 of the first sidewall portion 111.

[0770] As an example, when the first inner surface 804 and the first outer surface 806 are at least partially formed in the first region 1111, the thicker portion of the first sidewall portion 111 corresponding to the first inner surface 804 can reinforce the first region 1111, which has lower hardness, and can reduce the possibility of fatigue cracking of the first region 1111 itself, which has higher toughness.

[0771] In some embodiments, please refer to Figures 10-13 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. The fifth outer surface 27 is disposed opposite to the first sidewall portion 111 along the second direction Y.

[0772] The fifth outer surface 27 is the outer surface of the electrode assembly 2 that is perpendicular to the second direction Y, and the sixth outer surface is the outer surface of the electrode assembly 2 that is adjacent to the fifth outer surface 27. The fifth outer surface 27 is disposed along the second direction Y towards the first sidewall portion 111. The fifth outer surface 27 can be a plane, and it can be the surface with the largest area among the outer surfaces of the electrode assembly 2, or it can not be the surface with the largest area among the outer surfaces of the electrode assembly 2. The sixth outer surface can be a plane, or it 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.

[0773] As an example, there are two fifth outer surfaces 27 and two sixth outer surfaces. The two fifth outer surfaces 27 are arranged opposite each other along the second direction Y, and the two sixth outer surfaces are arranged opposite 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 separator 24. The fifth outer surface 27 is formed on the separator 24. The first direction Z, the second direction Y and the third direction X are perpendicular to each other.

[0774] 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 on the first sidewall portion 111 in the housing 11 that is disposed opposite to the fifth outer surface 27. Since the first region 1111 has high toughness, it releases the expansion force of the electrode assembly 2 on the first sidewall portion 111, which helps to reduce the possibility of cracking of the first connection portion 51 of the first sidewall portion 111.

[0775] As an example, when the first inner surface 804 and the first outer surface 806 are at least partially formed in the first region 1111, the thicker portion of the first sidewall portion 111 corresponding to the first inner surface 804 can reinforce the tougher first region 1111, thereby reducing the possibility of fatigue cracking of the tougher first region 1111 itself.

[0776] In some embodiments, please refer to Figures 10-13 The fifth outer surface 27 is the surface with the largest area among the outer surfaces of the electrode assembly 2.

[0777] It should be noted that the fifth outer surface 27 is the largest surface among the outer surfaces of the electrode assembly 2, but this does not limit the fifth outer surface 27 in the electrode assembly 2 to only one. It is understood that the fifth outer surface 27 of the electrode assembly 2 can be one or two.

[0778] As an example, in the illustrated embodiment, the electrode assembly 2 has a wound structure and is flat. The electrode assembly 2 includes six surfaces, of which two surfaces arranged opposite each other along the second direction Y have the largest area, and these two surfaces are both the fifth outer surface 27. In the illustrated embodiment, the electrode assembly 2 has a stacked structure and is generally cuboid in shape. The electrode assembly 2 includes six surfaces, of which two surfaces arranged opposite each other along the second direction Y have the largest area, and these two surfaces are both the fifth outer surface 27.

[0779] In this embodiment, the fifth outer surface 27 is the surface with the largest area among the outer surfaces of the electrode assembly 2, so that the first sidewall portion 111, which is disposed opposite to the fifth outer surface 27 in the housing 11, is subjected to the greatest expansion force. Since the first region 1111 has high toughness, it releases the expansion force of the electrode assembly 2 on the first sidewall portion 111, which helps to reduce the possibility of cracking of the first connection portion 51 of the first sidewall portion 111.

[0780] As an example, when the first inner surface 804 and the first outer surface 806 are at least partially formed in the first region 1111, the thicker portion of the first sidewall portion 111 corresponding to the first inner surface 804 can reinforce the tougher first region 1111, thereby reducing the possibility of fatigue cracking of the tougher first region 1111 itself.

[0781] In some embodiments, please refer to Figure 10 and Figure 11 The electrode assembly 2 has a wound structure and also has a corner region 26. The straight region 25 has a corner region 26 at at least one end along the third direction X. The first direction Z, the second direction Y, and the third direction X are not coplanar and intersect each other. The outer surface of the straight region 25 includes a fifth outer surface 27, and the outer surface of the corner region 26 includes a sixth outer surface. At least a portion of the sixth outer surface is an arc surface.

[0782] The straight section 25 may have a corner section 26 at only one end along the third direction X, or it may have corner sections 26 at both opposite ends along the third direction X. The first direction Z, the second direction Y, and the third direction X are not coplanar, and any two of the first direction Z, the second direction Y, and the third direction X may be set at acute, right, or obtuse angles. The fifth outer surface 27 may be part of the outer surface of the straight section 25, and the sixth outer surface may be part of the outer surface of the corner section 26. The sixth outer surface may be entirely an arc surface, or only part of it may be an arc surface.

[0783] As an example, the positive electrode 22, the separator 24, and the negative electrode 23 are stacked and wound to form a wound structure. The first direction Z, the second direction Y, and the third direction X are perpendicular to each other, and the straight region 25 has corner regions 26 at both ends along the third direction X. The portions of the positive electrode 22, the negative electrode 23, and the separator 24 located in the corner regions 26 are in a bent state. The portion of the positive electrode 22 located in the corner region 26 can be at least partially arc-shaped, the portion of the negative electrode 23 located in the corner region 26 can be at least partially arc-shaped, and the portion of the separator 24 located in the corner region 26 can be at least partially arc-shaped. Along the winding direction of the electrode assembly 2, the outermost ring of the electrode assembly 2 is the separator 24, and the fifth outer surface 27 and the sixth outer surface are both parts of the outermost ring of the electrode assembly 2. The fifth outer surface 27 is a plane, and the sixth outer surface is an arc surface, with the axis of the arc surface extending along the first direction Z. Along the second direction Y, the surfaces on both sides of the straight area 25 are the fifth outer surface 27; along the third direction X, the surface of one corner area 26 facing away from the other corner area 26 is a sixth outer surface, and the surface of the other corner area 26 facing away from the corner area 26 is another sixth outer surface.

[0784] For the wound electrode assembly 2, the flat region 25 expands more in the second direction Y. Since the first region 1111 has high toughness, it releases the expansion force of the electrode assembly 2 on the first sidewall portion 111, which helps to reduce the possibility of cracking of the first connection portion 51 of the first sidewall portion 111.

[0785] As an example, when the first inner surface 804 and the first outer surface 806 are at least partially formed in the first region 1111, the thicker portion of the first sidewall portion 111 corresponding to the first inner surface 804 can reinforce the tougher first region 1111, thereby reducing the possibility of fatigue cracking of the tougher first region 1111 itself.

[0786] In some embodiments, please refer to Figure 12 and Figure 13 The electrode assembly 2 has a stacked structure. The flat region 25 includes multiple positive electrode plates 22 and multiple negative electrode plates 23. The multiple positive electrode plates 22 and multiple negative electrode plates 23 are stacked along the second direction Y. The fifth outer surface 27 is perpendicular to the sixth outer surface.

[0787] As an example, multiple positive electrode plates 22, multiple negative electrode plates 23, and multiple separators 24 are stacked along the second direction Y to form a laminated structure. The positive electrode plates 22 and negative electrode plates 23 are completely located in the flat region 25. Separators 24 are disposed between adjacent positive electrode plates 22 and negative electrode plates 23. The separators 24 extend beyond the two ends of the positive electrode plates 22 and the two ends of the negative electrode plates 23 along the third direction X. The extended portions of multiple separators 24 are connected to form a whole portion, and a sixth outer surface is formed in this whole portion. Along the second direction Y, all positive electrode plates 22 and all negative electrode plates 23 are between the two outermost separators 24, and the outer surfaces of the two separator...

Claims

1. A battery cell, characterized by, include: The housing has an opening at at least one end along a first direction, and the housing includes a first sidewall portion; An electrode assembly, at least partially housed within a housing, includes a positive electrode and a negative electrode, at least portions of the positive electrode and the negative electrode being stacked along a second direction parallel to the thickness direction of the first sidewall portion, and the first direction intersecting the second direction. An end cap for closing the opening, wherein the first sidewall portion is welded to the end cap to form a first connection portion; The first sidewall portion includes a first region and a second region arranged along the first direction. The first region is located between the first connecting portion and the second region, and the hardness of the first region is lower than that of the second region.

2. The battery cell of 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 of 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, characterized in that The hardness range of the second zone is 40HV to 100HV, and the hardness range of the first zone is 20HV to 55HV.

5. The battery cell according to any one of claims 1 to 3, characterized in that The size of the first region along the first direction ranges from 0.05 mm to 0.75 mm.

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

7. The battery cell of any one of claims 1-3, 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 total number of grains in the first region is greater than 50%, and the dimension of the first grain extending along the first direction is the first dimension, the maximum dimension of the first grain along the second direction is the second dimension, and the ratio of the first dimension to the second dimension is in the range of 0.2 to 5.

8. The battery cell of claim 7, wherein, The ratio of the first dimension to the second dimension ranges from 0.25 to 4.

9. The battery cell of claim 7, wherein, The first size ranges from 5μm to 500μm, and the second size ranges from 5μm to 500μm.

10. The battery cell of any one of claims 1-3, 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 total number of grains in the second region is greater than 50%, and the dimension of the second grain extending along the first direction is a third dimension, the maximum dimension of the second grain along the second direction is a fourth dimension, and the ratio of the third dimension to the fourth dimension is in the range of 4 to 100.

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

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

13. The battery cell of any one of claims 1-3, 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 total number of grains in the first region is greater than 50%, and the dimension of the first grain extending along the first direction is the first dimension, the maximum dimension of the first grain along the second direction is the second dimension, and the ratio of the first dimension to the second dimension is in the range of 0.2 to 5. 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 total number of grains in the second region is greater than 50%, and the dimension of the second grain extending along the first direction is a third dimension, the maximum dimension of the second grain along the second direction is a fourth dimension, and the ratio of the third dimension to the fourth dimension is in the range of 4 to 100. The third dimension is larger than the first dimension.

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

15. The battery cell of claim 13, wherein, The first size ranges from 5 μm to 500 μm, and the third size ranges from 150 μm to 1000 μm.

16. The battery cell of any one of claims 1-3, wherein, The maximum thickness of the first region is greater than the minimum thickness of the second region.

17. The battery cell of 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 of the end cap pointing towards the electrode assembly. The first outer surface and the second outer surface are sequentially connected along the direction of the end cap pointing towards the electrode assembly. The first inner surface and the first outer surface are at least partially formed in the first region. The second inner surface and the second outer surface are at least partially 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 of claim 17, wherein, The first inner surface includes a first sub-surface and a second sub-surface connected sequentially along the direction from the end cap toward 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 of claim 18, wherein, 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 decreases along the direction from the end cap to the electrode assembly.

20. The battery cell of claim 18, wherein, The first sub-surface spans the first region and the second region, and the first outer surface spans the first region and the second region; or, the second sub-surface spans the first region and the second region, and the first outer surface spans the first region and the second region.

21. The battery cell of claim 17, wherein, 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.

22. The battery cell of claim 17, wherein, The dimension of the first inner surface along the third direction is greater than the 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 each other.

23. The battery cell of claim 17, wherein, Along the second direction, the projection of the first inner surface that coincides with the projection of the first region 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 each other.

24. The battery cell of claim 22, wherein, The first inner surface includes a first connecting surface, which passes through the mid-section of the first sidewall portion. The mid-section is perpendicular to the third direction, and the distance from the mid-section to both ends of the first sidewall portion along the third direction is equal.

25. The battery cell of claim 24, wherein, The first connecting surface is at least partially formed in the first region. Along the second direction, the projection of the first connecting surface that coincides with the projection of the first region is the second projection. The second projection passes through the midsection of the first sidewall portion.

26. The battery cell of claim 24, 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. The first connecting surface is located between the second connecting surface and the third connecting surface. 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 less than the distance between the first connecting surface and the first outer surface.

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

28. The battery cell of claim 26, 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 along 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 along the direction from the third connecting surface to the first connecting surface.

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

30. The battery cell of claim 24, wherein, The dimension of the first connecting surface along the third direction is L1, and the dimension of the first sidewall portion along the third direction is L, where 0.2≤L1 / L≤0.

6.

31. The battery cell of claim 24, wherein, The first connecting surface has a first end and a second end opposite to each other along the third direction, and the first sidewall portion has a third end and a fourth end opposite to each other along the third direction, with the first end close to the third end and the second end close to the fourth end. The dimension of the first sidewall 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 of claim 30, wherein, 100mm≤L≤450mm.

33. The battery cell of claim 22, wherein, The housing includes corner walls, and the first side wall is connected to both ends of the corner walls in the third direction; 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.

34. The battery cell of claim 17, wherein, The electrode assembly further includes an insulating element, which is disposed between the positive electrode and the negative electrode. The positive electrode includes a positive electrode body region and a positive electrode tab protruding from the positive electrode body region. The positive electrode body region has a positive electrode active material layer. The negative electrode includes a negative electrode body region and a negative electrode tab protruding from the negative electrode body region. The negative electrode body region has a negative electrode active material layer. Along the first direction, the positive electrode body region has a fifth end facing the end cap, the negative electrode body 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 of claim 34, wherein, The separator includes an extension region extending beyond the fifth and sixth ends along a first direction, and in a projection plane perpendicular to the second direction, the orthographic projection of the extension region partially overlaps with the orthographic projection of the first inner surface.

36. The battery cell of claim 34, wherein, The first inner surface protrudes from the second inner surface; In a projection plane perpendicular to the second direction, the orthographic projection of the positive electrode main body 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 body area does not overlap with the orthographic projection of the first inner surface.

37. The battery cell of claim 17, wherein, The negative electrode sheet includes a negative current collector and a negative active material layer disposed on at least one side of the negative current collector, wherein the negative active material layer includes a negative active material.

38. The battery cell of claim 37, wherein, The negative electrode active material layer includes a negative electrode main body and a negative electrode thinning part. The negative electrode main body and the negative electrode thinning part are arranged along the first direction. Along the first direction, the negative electrode thinning part is provided at one end of the negative electrode main body near the end cap.

39. The battery cell of claim 38, wherein, In a projection plane perpendicular to the second direction, the orthographic projection of the negative electrode thinning portion and the orthographic projection of the first inner surface are spaced apart along the first direction.

40. The battery cell of claim 39, wherein, In the projection plane perpendicular to the second direction, the distance between the orthographic projection of the negative electrode thinning portion and the orthographic projection of the first inner surface along the first direction is greater than or equal to 1 mm.

41. The battery cell of claim 37, wherein, The single-sided coating weight of the negative electrode active material layer is 90 mg / 1540 mm 2 170 mg / 1540 mm 2 , optionally 110 mg / 1540 mm 2 150 mg / 1540 mm 2 .

42. The battery cell of claim 37, wherein, The porosity of the negative electrode sheet is 27%~40%.

43. The battery cell of claim 37, wherein, The negative electrode active material includes a silicon-based material, wherein the mass content of silicon element in the negative electrode active material is 0.3% to 10%, and can be selected as 1% to 6%.

44. The battery cell of claim 43, wherein, The silicon-based material includes at least one of silicon oxide compounds and silicon-carbon composites.

45. The battery cell of claim 17, wherein, The positive electrode includes a positive current collector and a positive active material layer disposed on at least one side of the positive current collector, the positive active material layer including a positive active material.

46. The battery cell of claim 45, wherein, The positive electrode active material layer includes a positive electrode body portion and a positive electrode thinning portion. The positive electrode body portion and the positive electrode thinning portion are arranged along the first direction. Along the first direction, the positive electrode thinning portion is provided at one end of the positive electrode body portion near the end cap.

47. The battery cell of claim 46, wherein, In a projection plane perpendicular to the second direction, the orthographic projection of the positive electrode thinning portion and the orthographic projection of the first inner surface are spaced apart along the first direction.

48. The battery cell of claim 47, wherein, In a projection plane perpendicular to the second direction, the distance between the orthographic projection of the positive electrode thinning portion and the orthographic projection of the first inner surface along the first direction is greater than or equal to 1 mm.

49. The battery cell of claim 45, wherein, The single-sided coating weight of the positive electrode active material layer is 200 mg / 1540 mm 2 370 mg / 1540 / mm 2 ; optionally 240 mg / 1540 mm 2 330 mg / 1540 mm 2 .

50. The battery cell of claim 45, wherein, The positive electrode active material is a lithium phosphate.

51. The battery cell of claim 17, wherein, The shell is made of steel; The maximum distance between the second inner surface and the second outer surface along the second direction is D1, and the dimension of the housing along the second direction is D, 0.001≤D1 / D≤0.

012.

52. The battery cell of claim 17, wherein, The shell is made of steel; 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.

53. The battery cell of claim 17, wherein, The housing is made of aluminum alloy; The maximum distance between the second inner surface and the second outer surface along the second direction is D1, and the dimension of the housing along the second direction is D, 0.005≤D1 / D≤0.

065.

54. The battery cell of claim 17, wherein, The housing is made of aluminum alloy; 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.

55. The battery cell of claim 53, wherein, The aluminum alloy comprises the following components by 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%, and zinc ≤ 0.05%.

56. The battery cell of claim 17, 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 of claim 17, wherein, The first sidewall portion further includes a first transition region, which is connected to the end of the first region away from the second region along the first direction. The first transition region is connected to the first connecting portion, and the connection position of the first transition region and the first connecting portion forms a first connecting interface. The first connecting interface has a first position closest to the first region along the first direction, and the first position is located at the end of the first region away from the second region along the first direction.

58. The battery cell of claim 57, wherein, At least a portion of the first connection interface extends at an angle relative to the second direction.

59. The battery cell of claim 58, wherein, The first connection interface includes a first interface that extends obliquely from the first position toward the end cap. Along the second direction, at least a portion of the first transition area is located between the first interface and the end cap.

60. The battery cell of claim 59, wherein, The first interface is connected to the first outer surface at the first position, and the first position is at least partially located in the first region.

61. The battery cell of claim 58, wherein, The first connection interface includes a second interface that extends obliquely from the first position toward the end cap. Along the second direction, at least a portion of the first transition area is located on the side of the second interface opposite to the end cap.

62. The battery cell of claim 61, wherein, The second interface is connected to the first inner surface at the first position, and the first position is at least partially located in the first region.

63. The battery cell of claim 57, wherein, The hardness of the first transition zone is less than the hardness of the second zone; and / or, the hardness of the first transition zone is less than the hardness of the first connecting portion.

64. The battery cell of claim 57, wherein, The first connection interface is closer to the second region than the outer surface of the end cap.

65. The battery cell of claim 17, wherein, The housing further includes a second sidewall and a corner wall, the first sidewall, the corner wall and the second sidewall are arranged circumferentially along the opening, and the corner wall connects the first sidewall and the second sidewall.

66. The battery cell of claim 65, wherein, The corner wall is welded to the end cap to form a second connection part; The corner wall includes a third zone and a fourth zone arranged along the first direction. The hardness of the third zone is less than that of the fourth zone. The third zone is located between the fourth zone and the second connecting portion.

67. The battery cell of 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 are connected sequentially along the direction of the end cap toward the electrode assembly. The third inner surface and the third outer surface are at least partially formed in the third region, and the fourth inner surface and the fourth outer surface are at least partially formed in the fourth region. 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.

68. The battery cell of claim 67, wherein, The third region is directly connected to the first region, the third inner surface extends to the end of the third region facing the first region, and the first inner surface extends to the end of the first region facing the third region.

69. The battery cell of 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, and the second side wall portion is connected to the second connecting end. 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. The fourth preset thickness decreases along the direction from the first connecting end to the second connecting end.

70. The battery cell of claim 67, wherein, The third region is directly connected to the second connecting portion, and the third inner surface extends to one end of the third region facing the second connecting portion.

71. The battery cell of claim 67, wherein, The corner wall further includes a second transition zone, which is connected to the end of the third zone away from the fourth zone along the first direction. The second transition zone is connected to the second connecting part, and the connection position of the second transition zone and the second connecting part forms a second connecting interface. The second connecting interface has a second position that is closest to the third zone along the first direction. The second position is located at the end of the third zone away from the fourth zone along the first direction.

72. The battery cell of claim 71, wherein, At least a portion of the second connection interface extends obliquely relative to the thickness direction of the corner wall.

73. The battery cell of claim 72, wherein, The second connection interface includes a third interface that extends obliquely from the second position toward the end cap along the thickness direction of the corner wall, and at least a portion of the second transition area is located between the third interface and the end cap.

74. The battery cell of claim 73, wherein, The third interface is connected to the third outer surface at the second position, and the second position is located within the third region.

75. The battery cell of claim 72, wherein, The second connection interface includes a fourth interface that extends obliquely from the second position toward the end cap along the thickness direction of the corner wall, and at least a portion of the second transition area is located on the side of the fourth interface away from the end cap.

76. The battery cell of claim 75, wherein, The fourth interface is connected to the third inner surface at the second position, and the second position is located within the third region.

77. The battery cell of claim 71, wherein, The hardness of the second transition zone is less than the hardness of the fourth zone; and / or, the hardness of the second transition zone is less than the hardness of the second connecting portion.

78. The battery cell of claim 71, wherein, The second connection interface is closer to the fourth region than the outer surface of the end cap.

79. The battery cell of claim 66, wherein, The hardness of the third region is lower than that of the second connecting part.

80. The battery cell of claim 65, wherein, The housing includes two first sidewall portions and two second sidewall portions. The two first sidewall portions are arranged opposite each other along the second direction, and the two second sidewall portions are arranged opposite each other along the third direction. The first direction, the second direction, and the third direction are perpendicular to each other.

81. The battery cell of any one of claims 1-3, wherein, The first sidewall portion has a limiting surface facing the end cap, the limiting surface abutting against the end cap to restrict the end cap from moving toward the electrode assembly.

82. The battery cell of claim 81, wherein, The first sidewall portion further includes a limiting area disposed on the limiting surface, the limiting area and the end cap being disposed opposite to each other along the second direction, and the limiting area and the end cap being welded to form the first connecting portion.

83. The battery cell of any one of claims 1-3, wherein, The electrode assembly is a stacked structure, comprising a plurality of positive electrode plates and a plurality of negative electrode plates, which are stacked along the second direction.

84. The battery cell of claim 83, wherein, 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.

85. The battery cell of claim 83, wherein, Each of the negative electrode plates is provided with a negative electrode tab; and / or, each of the positive electrode plates is provided with a positive electrode tab.

86. The battery cell of claim 83, 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 of the end cap pointing towards the electrode assembly. The first outer surface and the second outer surface are sequentially connected along the direction of the end cap pointing towards the electrode assembly. The first inner surface and the first outer surface are at least partially formed in the first region. The second inner surface and the second outer surface are at least partially 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 larger than the size of the positive electrode and / or the size of the negative electrode, and the first direction, the second direction and the third direction are perpendicular to each other.

87. The battery cell of any one of claims 1-3, wherein, The battery cell also includes two electrode terminals, which are disposed on the end cap. The two electrode terminals have opposite polarities and are both electrically connected to the electrode assembly. The end cap is provided with an outlet hole. The electrode terminal includes a terminal body, a first limiting part and a second limiting part. The terminal body is connected to the first limiting part and the second limiting part. The terminal body passes through the outlet hole. Along the first direction, the first limiting part is located on the side of the end cap away from the electrode assembly, and the second limiting part is located on the side of the end cap facing the electrode assembly.

88. The battery cell of any one of claims 1-3, wherein, The electrode assembly has a flat region, and the portion of the positive electrode plate located in the flat region and the portion of the negative electrode plate located in the flat region are stacked along the second direction.

89. The battery cell of claim 88, wherein, The electrode assembly includes an adjacent fifth outer surface and a sixth outer surface. The fifth outer surface is perpendicular to the second direction, and the area of ​​the fifth outer surface is larger than the area of ​​the sixth outer surface. The fifth outer surface and the first sidewall portion are disposed opposite to each other along the second direction.

90. The battery cell of 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 of claim 89, wherein, The electrode assembly is a wound structure, and the electrode assembly also has a corner area. The corner area is provided at least one end of the straight area along a third direction. The first direction, the second direction and the third direction are not coplanar and intersect each other. The outer surface of the straight area includes the fifth outer surface, and the outer surface of the corner area includes the sixth outer surface, at least a portion of which is an arc surface.

92. The battery cell of claim 89, wherein, The electrode assembly is a stacked structure, and the flat region includes multiple positive electrode plates and multiple negative electrode plates. The multiple positive electrode plates and the multiple negative electrode plates are stacked along the second direction, and the fifth outer surface is perpendicular to the sixth outer surface.

93. The battery cell of any one of claims 1-3, wherein, The first sidewall portion is the wall with the largest outer surface area in the housing.

94. The battery cell of any one of claims 1-3, wherein, The housing includes two first sidewall portions disposed opposite each other along the second direction, and the electrode assembly is located between the two first sidewall portions.

95. The battery cell of any one of claims 1-3, wherein, The hardness of the first zone is lower than that of the first connecting part.

96. The battery cell of any one of claims 1-3, wherein, The number of electrode assemblies is N1, and each electrode assembly further includes at least one separator. The number of positive electrode plates is at least one, and the number of 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. At least a portion of the positive electrode plates, at least a portion of the negative electrode plates, and at least a portion of the separator are stacked in the flat region along the second direction. Each of the electrode assemblies has N2 layers of positive electrode sheets stacked in the flat region, the flat region having an outer surface perpendicular to the second direction, the area of ​​the outer surface being S, N1≥1, N2≥1, N1*N2≥50, S≥8000mm².

97. The battery cell of any one of claims 1-3, wherein, The negative electrode includes a negative current collector and a negative active material layer disposed on at least one side of the negative current collector. The negative active material layer includes a negative active material, and the discharge capacity per unit area of ​​the negative active material layer is 2.0 mAh / cm². 2 Up to 5.0mAh / cm 2 .

98. The battery cell of claim 96, wherein, The thickness of the negative electrode active material layer is T1, where 9μm≤T1≤75μm.

99. A battery device, characterized by Includes the battery cell according to any one of claims 1 to 98.

100. An electrical device, comprising: Includes a battery cell according to any one of claims 1 to 98, wherein the battery cell is used to provide electrical energy to the electrical device.

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