Battery cells, battery devices, and electrical devices

Abstract

A battery cell, a battery device, and an electrical device belonging to the field of battery technology, wherein the battery cell includes a casing, an electrode assembly, and an end cover, the casing having an opening at least one end along a first direction, and the casing includes a first side wall. At least a portion of the electrode assembly is housed within the casing, and the electrode assembly includes a positive electrode plate and a negative electrode plate, the positive electrode plate and the negative electrode plate being stacked along a second direction, the second direction being parallel to the thickness direction of the first side wall, and the first direction intersecting the second direction. The end cover is used to seal the opening, and the first side wall is welded to the end cover to form a first connection. Here, the first side wall includes a first region and a second region arranged along the first direction, the first region being located between the first connection and the second region, and the hardness of the first region being lower than that of the second region.

Description

[Technical Field]

[0001] Cross-citation of related applications This application is a Chinese patent application with application number 202410217408.8 and filing date February 27, 2024, an international patent application with application number PCT / CN2024 / 113179 and filing date August 19, 2024, an international patent application with application number PCT / CN2024 / 105243 and filing date July 12, 2024, and application number PCT / CN2024 / 089160. This application claims priority to an international patent application filed on April 22, 2024, an international patent application with application number PCT / CN2023 / 135607 filed on November 30, 2023, and an international patent application with application number PCT / CN2023 / 134129 filed on November 24, 2023, and all contents of the above patent applications are incorporated herein by reference.

[0002] This application relates to the battery technology field, and more particularly to battery cells, battery devices, and electrical devices. [Background technology]

[0003] Batteries are being used more and more widely in daily life and industry. They are used in energy storage systems such as hydroelectric, thermal, wind, and solar power plants, and are also widely used in electric transportation tools such as electric bicycles, electric motorcycles, and electric vehicles.

[0004] In related technologies, the electrode assembly is installed inside the battery cell casing, and during the charging and discharging process of the battery cell, expansion of the electrode assembly may occur, potentially causing the casing to rupture. [Overview of the project] [Means for solving the problem]

[0005] In light of this, the embodiments of this application are expected to provide a battery cell, battery device, and electrical device that can reduce the possibility of casing rupture.

[0006] To achieve the above objective, the technical solution of the embodiment of this application is realized as follows.

[0007] In one embodiment of this application, a battery cell is disclosed, and this battery cell is, A casing having an opening at least at one end along the first direction, including a first side wall portion, An electrode assembly comprising a positive electrode plate and a negative electrode plate, wherein at least a portion of the positive electrode plate and at least a portion of the negative electrode plate are stacked along a second direction, the second direction is parallel to the thickness direction of the first side wall, and the first direction intersects the second direction. An end cover for sealing an opening, comprising an end cover whose first side wall portion is welded to the end cover to form a first connection portion, Here, the first sidewall includes a first region and a second region arranged along a first direction, the first region being located between the first connection and the second region, and the hardness of the first region being lower than that of the second region.

[0008] The first region, which has relatively low hardness, releases the expansion force of the electrode assembly, reducing the possibility of cracking at the first connection.

[0009] 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.

[0010] Appropriate hardness can reduce cracking of the first connection and also suppress cracking of the first region itself.

[0011] 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.

[0012] Appropriate hardness can reduce cracking of the first connection and also suppress cracking of the first region itself.

[0013] In some examples, the hardness range of the second region is 40HV to 100HV, and the hardness range of the first region is 20HV to 55HV.

[0014] Appropriate hardness can reduce cracking of the first connection and also suppress cracking of the first region itself.

[0015] In some embodiments, the size range along the first direction of the first region is 0.05 mm to 0.75 mm.

[0016] An appropriate size range for the maximum size along the first direction of the first region can reduce cracking of the first connection and also prevent the first region from being too long, which can cause self-cracking.

[0017] In some embodiments, the size range along the first direction of the first region is 0.1 mm to 0.6 mm.

[0018] An appropriate size range for the maximum size along the first direction of the first region can reduce cracking of the first connection and also prevent the first region from being too long, which can cause self-cracking.

[0019] In some embodiments, at least a portion of the crystal grains within a first region are first crystal grains, the ratio of the number of first crystal grains within the first region to the total number of crystal grains within the first region is greater than 50%, the size of the first crystal grain stretched along a first direction is a first size, the maximum size of the first crystal grain along a second direction is a second size, and the ratio of the first size to the second size is in the range of 0.2 to 5.

[0020] The ratio of the first size to the second size is in the range of 0.2 to 5, and the occupancy rate of the first crystal grain is greater than 50%, which is advantageous for improving the toughness of the first region.

[0021] In some embodiments, the ratio of the first size to the second size ranges from 0.25 to 4.

[0022] The ratio of the first size to the second size is in the range of 0.25 to 4, and the occupancy rate of the first crystal grain is greater than 50%, which is advantageous for improving the toughness of the first region.

[0023] In some embodiments, the first size range is 5 μm to 500 μm, and the second size range is 5 μm to 500 μm.

[0024] When the ratio of the first size to the second size falls within the appropriate range, the first crystal grains corresponding to the appropriate range of first and second sizes are advantageous for improving the toughness of the first region.

[0025] In some embodiments, at least a portion of the crystal grains within a second region are second crystal grains, the ratio of the number of second crystal grains within the second region to the total number of crystal grains within the second region is greater than 50%, the size of the second crystal grains stretched along a first direction is a third size, the maximum size of the second crystal grains along a second direction is a fourth size, and the ratio of the third size to the fourth size is in the range of 4 to 100.

[0026] The ratio of the third size to the fourth size is in the range of 4 to 100, and such a second grain occupancy rate is greater than 50%, which is advantageous in reducing the toughness of the second region and reducing the possibility of the second region itself cracking under the action of expansion forces.

[0027] In some embodiments, the ratio of the third size to the fourth size is in the range of 4 to 50.

[0028] The ratio of the third size to the fourth size is in the range of 4 to 50. When the occupancy rate of such second crystal grains is greater than 50%, it is advantageous in reducing the toughness of the second region and decreasing the possibility of the second region itself cracking due to the action of expansion forces.

[0029] In some examples, the third size range is 150 μm to 1000 μm, and the fourth size range is 5 μm to 120 μm.

[0030] When the ratio of the third size to the fourth size falls within the appropriate range, an appropriate range of third and fourth sizes is advantageous in reducing the toughness of the second region and reducing the likelihood of the second region itself rupturing under the action of expansion forces.

[0031] In some embodiments, at least a portion of the crystal grains within a first region are first crystal grains, the ratio of the number of first crystal grains within the first region to the total number of crystal grains within the first region is greater than 50%, the size of the first crystal grains stretched along a first direction is a first size, the maximum size of the first crystal grains along a second direction is a second size, and the ratio of the first size to the second size is in the range of 0.2 to 5. At least a portion of the crystal grains within the second region are second crystal grains, the ratio of the number of second crystal grains within the second region to the total number of crystal grains within the second region is greater than 50%, the size of the second crystal grains stretched along the first direction is the third size, the maximum size of the second crystal grains stretched along the second direction is the fourth size, and the ratio of the third size to the fourth size is in the range of 4 to 100. Here, the third size is larger than the first size.

[0032] Along the first direction, at the same size, the first region has more crystal grains subjected to expansion forces, improving the toughness of the first region.

[0033] In some embodiments, the ratio range of the third size to the first size is 1.5 to 150, or the ratio range of the third size to the first size is 1.8 to 100.

[0034] In some examples, the first size range is 5 μm to 500 μm, and the third size range is 150 μm to 1000 μm.

[0035] In some embodiments, the maximum thickness of the first region is greater than the minimum thickness of the second region.

[0036] The relatively thick first region reinforces the first region, reducing the possibility of cracking in the first region.

[0037] In some embodiments, the first sidewall has a first inner surface and a second inner surface facing the electrode assembly and a first outer surface and a second outer surface away from the electrode assembly, the first inner surface and the second inner surface being connected sequentially along the direction of the end cover facing the electrode assembly, the first outer surface and the second outer surface being connected sequentially along the direction of the end cover facing the electrode assembly, the first inner surface and the first outer surface being at least partially formed in a first region, the second inner surface and the second outer surface being at least partially formed in a second region, and the distance between the first inner surface and the first outer surface along the second direction is greater than the distance between the second inner surface and the second outer surface along the second direction.

[0038] The first sidewall reinforces the first region with a relatively thick portion of the first inner surface, reducing the possibility of cracking in the first region.

[0039] In some embodiments, the first inner surface includes a first sub-surface and a second sub-surface connected in sequence along a direction toward the electrode assembly of the end cover, wherein the first sub-surface is at least partially formed in a first region, and along a second direction, the first sub-surface is closer to the electrode assembly than the second sub-surface, and the distance between the first sub-surface and the first outer surface along the second direction is greater than the distance between the second sub-surface and the first outer surface along the second direction.

[0040] The first sidewall reinforces the first region in the portion corresponding to the relatively thick first subsurface, thereby reducing the possibility of cracking in the first region.

[0041] In some embodiments, the distance along the second direction between the second subsurface and the first outer surface is a first predetermined thickness, and the first predetermined thickness tends to decrease along the direction toward the electrode assembly of the end cover.

[0042] The first predetermined thickness tends to decrease along the direction of the end cover facing the electrode assembly, which is advantageous in reducing the material cost of the first side wall.

[0043] In some embodiments, the first sub-surface spans the first and second regions, and the first outer surface spans the first and second regions; or the second sub-surface spans the first and second regions, and the first outer surface spans the first and second regions.

[0044] The first sidewall portion is a relatively thick section corresponding to the first sub-surface, reinforcing the boundary between the first and second regions and reducing the possibility of cracking at the boundary between the first and second regions.

[0045] In some embodiments, the first inner surface spans the first and second regions, and the first outer surface spans the first and second regions.

[0046] The first sidewall portion, being a relatively thick portion corresponding to the first inner surface, reinforces the boundary between the first and second regions, reducing the possibility of cracking at the boundary between the first and second regions.

[0047] In some embodiments, the size of the first inner surface along the third direction is larger than the size of the first inner surface along the first direction, and the first, second, and third directions are not located on the same plane but intersect in pairs.

[0048] The first sidewall portion is a relatively thick portion along the third direction of the first inner surface, reinforcing the first sidewall portion along a region where the third direction is relatively long, thereby reducing the possibility of cracking of the first sidewall portion.

[0049] In some embodiments, along the second direction, the overlapping projection of the first inner surface and 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, and the first, second, and third directions do not lie on the same plane and intersect in pairs.

[0050] The size of the first projection along the third direction is larger than the size of the first projection along the first direction, and the portion reinforced along the third direction within the first region is relatively long, which is advantageous in reducing the possibility of cracking in the first region.

[0051] In some embodiments, the first inner surface includes a first connecting surface, the first connecting surface passes through the intermediate cross-section of the first sidewall, the intermediate cross-section is perpendicular to the third direction, and the distance from the intermediate cross-section to both ends of the first sidewall is equal along the third direction.

[0052] The first connecting surface passes through the intermediate cross-section of the first side wall, reducing cracking in the intermediate cross-section.

[0053] In some embodiments, the first connecting surface is formed at least partially in the first region, and along the second direction, the overlapping projection of the projection of the first connecting surface and the projection of the first region is the second projection, and the second projection passes through the middle cross-section of the first side wall.

[0054] The second projection passes through the intermediate section of the first side wall, reinforcing the first region in the portion corresponding to the intermediate section and reducing the possibility of the first region cracking in the intermediate section.

[0055] 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 being arranged along a third direction, the first connecting surface connecting the second connecting surface and the third connecting surface, and along the second direction, the distance between the second connecting surface and the first outer surface and the distance between the third connecting surface and the first outer surface are both smaller than the distance between the first connecting surface and the first outer surface.

[0056] The first sidewall is relatively thick in the portion corresponding to the first connection surface and relatively thin in the portions corresponding to the second and third connection surfaces. Based on the distribution characteristics of the expansion force, casing cracking can be reduced, and costs can also be reduced.

[0057] 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.

[0058] This is advantageous in reducing the cracking of the first region itself.

[0059] 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 the second direction is a second predetermined thickness, the second predetermined thickness tends to increase along the direction of the second connecting surface toward 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 the second direction is a third predetermined thickness, the third predetermined thickness tends to increase along the direction of the third connecting surface toward the first connecting surface.

[0060] The transition is smooth via the transition surface.

[0061] In some embodiments, a first transition plane is formed at least partially in a first region and / or a second transition plane is formed at least partially in a first region.

[0062] The first transition surface and / or the second transition surface increase the first region and reduce the possibility of cleavage in the first region.

[0063] In some embodiments, the size of the first connecting surface along the third direction is L1, the size of the first side wall along the third direction is L, and 0.2 ≤ L1 / L ≤ 0.6.

[0064] This allows for reinforcement of a larger area along the third direction of the first side wall, which can increase costs to a certain extent.

[0065] In some embodiments, the first connecting surface has a first end and a second end facing each other along the third direction, the first sidewall has a third end and a fourth end facing each other along the third direction, the first end is close to the third end, the second end is close to the fourth end, the size of the first sidewall along the third direction is L, the minimum distance along the third direction between the first end and the third end is L2, the minimum distance along the third direction between the second end and the fourth end is L3, and L2 / L ≤ 0.3 and / or L3 / L ≤ 0.3.

[0066] This allows for reinforcement of a larger area along the third direction of the first side wall, which can increase costs to a certain extent.

[0067] In some embodiments, 100mm ≤ L ≤ 450mm.

[0068] In some embodiments, the casing includes corner walls, with corner walls connected to both ends of the first side wall portion along the third direction. At least one end of the first inner surface along the third direction 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.

[0069] In some embodiments, the electrode assembly further includes a separator, which is placed between the positive electrode plate and the negative electrode plate. The positive electrode plate includes a positive electrode body region and a positive electrode tab protruding from the positive electrode body region, the positive electrode body region having a positive electrode active material layer; the negative electrode plate includes a negative electrode body region and a negative electrode tab protruding from the negative electrode body region, the negative electrode body region having a negative electrode active material layer; along a first direction, the positive electrode body region has a fifth end facing the end cover, the negative electrode body region has a sixth end facing the end cover, the separator has a seventh end facing the end cover, the seventh end is closer to the end cover than the fifth and sixth ends.

[0070] The separator has portions that protrude beyond the fifth and sixth ends, reinforcing the insulating effect between the positive and negative electrode plates of the separator and reducing the risk of contact between the positive and negative electrode plates.

[0071] In some embodiments, the separator includes protruding regions that extend beyond the fifth and sixth ends along the first direction, and in a projection plane perpendicular to the second direction, the orthographic projection of the protruding regions partially overlaps with the orthographic projection of the first inner surface.

[0072] The orthographic projection of the protruding region partially overlaps with the orthographic projection of the first inner surface, and such a structure can increase the size of the first inner surface along the first direction, thereby improving the reinforcing capacity of the first inner surface.

[0073] In some embodiments, 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 body region 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 body region does not overlap with the orthographic projection of the first inner surface.

[0074] This reduces the degree of interference between the expanding electrode assembly and the first inner surface.

[0075] In some embodiments, the negative electrode plate includes a negative electrode current collector and a negative electrode active material layer installed on at least one side of the negative electrode current collector, the negative electrode active material layer includes a negative electrode active material.

[0076] In some embodiments, the negative electrode active material layer includes a negative electrode body portion and a negative electrode thinning portion, which are arranged along a first direction, and the negative electrode thinning portion is located at the end of the negative electrode body portion adjacent to the end cover along the first direction.

[0077] The thinned negative electrode section provides a relatively large expansion gap in the electrode assembly, reducing the expansion force on the first side wall of the electrode assembly.

[0078] In some embodiments, 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 in a projection plane perpendicular to the second direction.

[0079] This reduces the impact on the first inner surface of the thinned negative electrode section and decreases the expansion force applied to the first inner surface by the electrode assembly.

[0080] In some embodiments, the spacing size along the first direction between the orthographic projection of the negative electrode thinning portion and the orthographic projection of the first inner surface in a projection plane perpendicular to the second direction is 1 mm or more.

[0081] The greater the distance between the first inner surface and the first thinned portion, the more advantageous it is for reducing the expansion force applied to the first inner surface by the electrode assembly.

[0082] In some embodiments, the coating weight of the negative electrode active material layer on one side was 90 mg / 1540 mm². 2 ~170mg / 1540mg 2 Therefore, the coating weight on one side of the negative electrode active material layer is selectively 110 mg / 1540 mm 2 ~150mg / 1540mg 2 That is the case.

[0083] In some embodiments, the porosity of the negative electrode plate is 27% to 40%.

[0084] In some embodiments, the negative electrode active material includes a silicone-based material, and the mass content of silicon element in the negative electrode active material of the silicone-based material is 0.3% to 10%, and selectively 1% to 6%.

[0085] In some embodiments, the silicone-based material includes at least one of a silicone oxide and a silicone-carbon composite.

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

[0087] In some embodiments, the positive electrode active material layer includes a positive electrode body portion and a positive electrode thinning portion, which are arranged along a first direction, and the positive electrode thinning portion is located at the end of the positive electrode body portion adjacent to the end cover along the first direction.

[0088] The installation of a thinned positive electrode section is advantageous in improving the expansion gap of the electrode assembly and reducing the expansion force on the first side wall of the electrode assembly.

[0089] In some embodiments, 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 in a projection plane perpendicular to the second direction.

[0090] This reduces the impact on the first inner surface of the thinned positive electrode section and decreases the expansion force applied to the first inner surface by the electrode assembly.

[0091] In some embodiments, the spacing size along the first direction between the orthographic projection of the positive electrode thinning portion and the orthographic projection of the first inner surface in a projection plane perpendicular to the second direction is 1 mm or more.

[0092] The thinned portion of the negative electrode is further away from the first inner surface, which is advantageous in reducing the expansion force on the first inner surface of the electrode assembly.

[0093] In some embodiments, the coating weight of the positive electrode active material layer on one side was 200 mg / 1540 mm². 2 ~370mg / 1540 / mm 2 Therefore, the coating weight on one side of the positive electrode active material layer is selectively 240 mg / 1540 mm 2 ~330mg / 1540mg 2 That is the case.

[0094] In some embodiments, the positive electrode active material is a lithium-containing phosphate.

[0095] In some embodiments, the casing material includes steel. The maximum distance along the second direction between the second inner surface and the second outer surface is D1, the size of the casing along the second direction is D, and 0.001 ≤ D1 / D ≤ 0.012.

[0096] The casing is designed to have relatively good strength when the energy density is relatively high.

[0097] In some embodiments, the casing material includes steel. The maximum distance along the second direction between the second inner surface and the second outer surface is D1, where 0.08 mm ≤ D1 ≤ 0.35 mm, and / or the maximum distance along the second direction between the first inner surface and the first outer surface is D2, where 0.1 mm ≤ D2 ≤ 0.6 mm.

[0098] In some embodiments, the casing material includes an aluminum alloy. The maximum distance along the second direction between the second inner surface and the second outer surface is D1, the size of the casing along the second direction is D, and 0.005 ≤ D1 / D ≤ 0.065.

[0099] The casing is designed to have relatively good strength when the energy density is relatively high.

[0100] In some embodiments, the casing material includes an aluminum alloy. The maximum distance along the second direction between the second inner surface and the second outer surface is D1, where 0.4 mm ≤ D1 ≤ 0.8 mm, and / or the maximum distance along the second direction between the first inner surface and the first outer surface is D2, where 0.5 mm ≤ D2 ≤ 1.5 mm.

[0101] In some embodiments, the aluminum alloy contains the following mass% components: aluminum ≥ 99.6%, copper ≤ 0.05%, iron ≤ 0.35%, magnesium ≤ 0.03%, manganese ≤ 0.03%, silicon ≤ 0.25%, titanium ≤ 0.03%, vanadium ≤ 0.05%, zinc ≤ 0.05%, and other single elements ≤ 0.03%.

[0102] In some embodiments, the first region is directly connected to the first connection, and the first inner surface extends along the first direction to the end of the first region facing the connection.

[0103] This is advantageous for reinforcing the end facing the first connection point of the first region.

[0104] In some embodiments, the first sidewall further includes a first transition region, the first transition region being connected to an end of the first region away from the second region along a first direction, the first transition region being connected to a first connection, a first connection interface being formed at the connection point between the first transition region and the first connection, the first connection interface having a first position closest to the first region along a first direction, the first position being located at the end of the first region away from the second region along a first direction.

[0105] A relatively large contact area is provided between the first transition region and the first connection portion via the first connection interface, thereby improving the robustness of the connection.

[0106] In some embodiments, at least a portion of the first connecting interface extends at an angle compared to the second direction.

[0107] The contraction of the first connection point causes the tensile force on the first transition region and the force acting on the first sidewall portion of the first transition region to not be located on the same straight line, thereby reducing the possibility of fatigue cracking.

[0108] In some embodiments, the first connecting interface includes a first interface which extends inclined toward the end cover from a first position, and along a second direction, at least a portion of the first transition region is located between the first interface and the end cover.

[0109] The first transition region is stopped and protected by the first connection, reducing the possibility of fatigue cracking in the first transition region.

[0110] In some embodiments, the first interface and the first outer surface are connected at a first position, the first position being at least partially located in a first region.

[0111] The thickened portion corresponding to the first outer surface of the first side wall is positioned as far as possible towards the first connection point of the first region, thereby reducing the possibility of fatigue cracking at the end facing the first connection point of the first region.

[0112] In some embodiments, the first connecting interface includes a second interface, which extends inclined away from the end cover from the first position, and along the second direction, at least a portion of the first transition region is located on the side of the second interface away from the end cover.

[0113] The first transition region blocks the first connection point, reducing the possibility of the first connection point detaching from the end cover.

[0114] In some embodiments, the second interface and the first inner surface are connected at a first position, the first position being at least partially located within a first region.

[0115] This approach is advantageous in bringing the first sidewall closer to the first connection point in a relatively thick portion corresponding to the first inner surface, reinforcing the end of the first region facing the first connection point, and reducing the possibility of cracking at the end of the first region facing the first connection point.

[0116] In some embodiments, the hardness of the first transition region is less than the hardness of the second region, and / or the hardness of the first transition region is less than the hardness of the first connection.

[0117] In some embodiments, the first connection interface is closer to the second region than to the outer surface of the end cover.

[0118] The first connection can be recessed to a deeper position, which is advantageous in improving the connection strength between the end cover and the first connection.

[0119] In some embodiments, the casing further includes a second side wall and a corner wall, the first side wall, the corner wall and the second side wall being arranged along the circumferential direction of the opening, and the corner wall connecting the first side wall and the second side wall.

[0120] The corner walls reduce stress concentration.

[0121] In some embodiments, the corner wall is welded to the end cover to form a second connection. The corner wall includes a third region and a fourth region aligned along a first direction, the hardness of the third region being less than that of the fourth region, and the third region being located between the fourth region and the second connection.

[0122] The relatively low hardness of the third region reduces the possibility of cracking at the second connection point.

[0123] 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 away from the electrode assembly, the third inner surface and the fourth inner surface being connected in order along the direction of the end cover facing the electrode assembly, the third inner surface and the third outer surface being at least partially formed in the third region, the fourth inner surface and the fourth outer surface being at least partially formed in the fourth region, and the distance along the thickness direction of the corner wall between the third inner surface and the third outer surface is greater than the distance along the thickness direction of the corner wall between the fourth inner surface and the fourth outer surface.

[0124] The corner walls reinforce the third region with a relatively thick portion corresponding to the third inner surface, reducing the possibility of fatigue cracking in the third region, which has relatively low hardness.

[0125] 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.

[0126] The relatively thick portion corresponding to the first inner surface of the first side wall and the relatively thick portion corresponding to the third inner surface of the corner wall mutually promote each other, which is advantageous in reducing cracking between the first and third regions.

[0127] In some embodiments, the corner wall has a first connecting end and a second connecting end, the first side wall portion is connected to the first connecting end, the second side wall portion is connected to the second connecting end, and the distance along the thickness direction of the corner wall between the third inner surface and the third outer surface is a fourth predetermined thickness, the fourth predetermined thickness tends to decrease along the direction of the first connecting end toward the second connecting end.

[0128] Reinforcing the third region reduces the possibility of cracking in the third region, thereby reducing costs.

[0129] In some embodiments, the third region is directly connected to the second connection, and the third inner surface extends to the end of the third region facing the second connection.

[0130] The end of the third region facing the second connection is reinforced, reducing the possibility of cracking at the end of the third region facing the second connection.

[0131] In some embodiments, the corner wall further includes a second transition region, the second transition region being connected to the end of the third region moving away from the fourth region along a first direction, the second transition region being connected to a second connection, a second connection interface being formed at the connection point between the second transition region and the second connection, the second connection interface having a second position closest to the third region along a first direction, the second position being located at the end of the third region moving away from the fourth region along a first direction.

[0132] The second connecting surface increases the contact area and reduces the possibility of cracking between the second transition region and the second connecting portion.

[0133] In some embodiments, at least a portion of the second connecting interface extends at an angle relative to the thickness direction of the corner wall.

[0134] The force acting on the second transition region due to the contraction of the second connection and the force acting on the second transition region due to the deformation of the corner wall due to expansion do not exist on the same straight line, thus reducing the possibility of fatigue cracking between the second transition region and the second connection.

[0135] In some embodiments, the second connecting interface includes a third interface, which extends inclined toward the end cover from the second position, and along the thickness direction of the corner wall, at least a portion of the second transition region is located between the third interface and the end cover.

[0136] The second connection protects the second transition region and reduces the possibility of fatigue cracking in the second transition region.

[0137] In some embodiments, the third interface and the third outer surface are connected at a second position, and the second position is located within the third region.

[0138] The corner wall is relatively thick in the portion corresponding to the third outer surface and is close to the second connection, which is advantageous in reducing cracking at the end of the third region facing the second connection.

[0139] In some embodiments, the second connecting interface includes a fourth interface, which extends inclined away from the end cover from the second position, and along the thickness direction of the corner wall, at least a portion of the second transition region is located on the side of the fourth interface away from the end cover.

[0140] The second transition region protects the second connection and reduces the possibility of the second connection becoming detached.

[0141] In some embodiments, the fourth interface and the third inner surface are connected at a second position, and the second position is located within the third region.

[0142] The corner wall is relatively thick in the portion corresponding to the third inner surface and is close to the second connection, which can reduce the possibility of cracking at the end of the third region facing the second connection.

[0143] In some embodiments, the hardness of the second transition region is less than the hardness of the fourth region, and / or the hardness of the second transition region is less than the hardness of the second connection.

[0144] In some embodiments, the second connection interface is closer to the fourth region than to the outer surface of the end cover.

[0145] The second connection point is designed to sink deeper into the corner wall, improving the connection strength between the corner wall and the end cover.

[0146] In some embodiments, the hardness of the third region is lower than that of the second connection.

[0147] In some embodiments, the casing includes two first sidewalls and two second sidewalls, the two first sidewalls facing each other along a second direction, and the two second sidewalls facing each other along a third direction, with the first, second, and third directions being two perpendicular to each other.

[0148] In some embodiments, the first side wall portion has a stopper surface facing the end cover, which abuts against the end cover and restricts the end cover's movement toward the electrode assembly.

[0149] In the welding process, this reduces the possibility of the end cover moving to the electrode assembly, improving weld quality and reducing welding difficulty.

[0150] In some embodiments, the first side wall further includes a stopper region installed on the stopper surface, the stopper region and the end cover are installed facing each other along a second direction, and the stopper region is welded to the end cover to form a first connection.

[0151] This reduces the possibility of the end cover moving along the thickness direction of the first side wall during the welding process, thereby improving welding quality and reducing welding difficulty.

[0152] In some embodiments, the electrode assembly is a laminated structure, and the electrode assembly includes a plurality of positive electrode plates and a plurality of negative electrode plates, which are stacked along a second direction.

[0153] In some embodiments, the number of negative electrodes is greater than the number of positive electrodes, and one positive electrode is placed between two adjacent negative electrodes.

[0154] In some embodiments, a negative electrode tab is provided on each negative electrode plate and / or a positive electrode tab is provided on each positive electrode plate.

[0155] In some embodiments, the first sidewall has a first inner surface and a second inner surface facing the electrode assembly and a first outer surface and a second outer surface away from the electrode assembly, the first inner surface and the second inner surface are connected sequentially along the direction of the end cover facing the electrode assembly, the first outer surface and the second outer surface are connected sequentially along the direction of the end cover facing the electrode assembly, the first inner surface and the first outer surface are formed at least partially in a first region, the second inner surface and the second outer surface are formed at least partially in a second region, the distance between the first inner surface and the first outer surface along the second direction is greater than the distance between the second inner surface and the second outer surface along the second direction. Along the third direction, the size of the first inner surface is greater than the size of the positive electrode plate and / or the size of the negative electrode plate, and the first, second, and third directions are perpendicular to each other in pairs.

[0156] The first sidewall can be reinforced in a relatively thick portion corresponding to the first inner surface, extending along the third direction of the entire positive electrode plate, which is advantageous in reducing cracking of the first sidewall.

[0157] In some embodiments, the battery cell further includes two electrode terminals, the two electrode terminals being mounted on an end cover, the two electrode terminals having opposite polarities, and both being electrically connected to an electrode assembly. An end cover is provided with a pull-out hole, and the electrode terminal includes a terminal body, a first stopper portion, and a second stopper portion. The terminal body connects the first stopper portion and the second stopper portion, and the terminal body is inserted through the pull-out hole. Along the first direction, the first stopper portion is located on the side away from the electrode assembly of the end cover, and the second stopper portion is located on the side facing the electrode assembly of the end cover.

[0158] The electrode terminals are attached to the end cover by riveting, making installation easy.

[0159] In some embodiments, 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 a second direction.

[0160] In some embodiments, the electrode assembly includes adjacent fifth and sixth outer surfaces, 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 and the first side wall being positioned opposite each other along the second direction.

[0161] The first region releases the expansion force in the direction where the expansion force is relatively large, while the first inner surface reinforces it in the direction where the expansion force is relatively large.

[0162] In some embodiments, the fifth outer surface is the surface with the largest area among the outer surfaces of the electrode assembly.

[0163] In some embodiments, the electrode assembly is a wound structure, and the electrode assembly further has a corner region, the corner region is located at at least one end along a third direction of the flat region, and the first, second, and third directions are not located on the same plane and intersect in pairs. The outer surface of the flat region includes the fifth outer surface, and the outer surface of the corner region includes the sixth outer surface, and at least a portion of the sixth outer surface is an arcuate surface.

[0164] In some embodiments, the electrode assembly is a laminated structure, where a flat region includes a plurality of positive electrode plates and a plurality of negative electrode plates, the plurality of positive electrode plates and the plurality of negative electrode plates are stacked along a second direction, and the fifth outer surface is perpendicular to the sixth outer surface.

[0165] The first region releases the expansion force in the direction where the expansion force is relatively large, while the first inner surface reinforces it in the direction where the expansion force is relatively large.

[0166] In some embodiments, the first side wall is the wall with the largest outer surface area in the casing.

[0167] In some embodiments, the casing includes two first sidewalls, which are positioned opposite each other along a second direction, and the electrode assembly is located between the two first sidewalls.

[0168] In some embodiments, the hardness of the first region is lower than the hardness of the first connection portion.

[0169] Embodiments of the present application provide a battery device including any one of the above battery cells.

[0170] In some embodiments, the number of the electrode assemblies is N1, each of the electrode assemblies further includes at least one separator, the number of the positive electrode plates is at least one, the number of the negative electrode plates is at least one, the positive electrode plates, the negative electrode plates and the separators are stacked to form a flat region, and at least a part of the positive electrode plates, at least a part of the negative electrode plates and at least a part of the separators are stacked and installed along the second direction in the flat region. For each of the electrode assemblies, the number of layers of the positive electrode plates deposited in the flat region is N2, the flat region has an outer surface perpendicular to the second direction, the area of the outer surface is S, N1≧1, N2≧1, N1×N2≧50, S≧8000mm 2 is satisfied.

[0171] In embodiments of the present application, the first connection portion of the first side wall portion is reduced in the possibility of cracking under the action of a relatively large expansion force by the first region having relatively high toughness.

[0172] In some embodiments, the negative electrode plate includes a negative electrode current collector and a negative electrode active material layer disposed on at least one side of the negative electrode current collector, the negative electrode active material layer includes a negative electrode active material, and the discharge capacity per unit area of the negative electrode active material layer is 2.0mAh / cm 2 to 5.0mAh / cm 2 is satisfied.

[0173] In embodiments of the present application, when the discharge capacity per unit area of the negative electrode active material layer is within the above range, there are sufficient sites for lithium storage in the negative electrode active material layer, the risk of lithium precipitation can be reduced, it is advantageous for rapid charging, the expansion force is not too large, and the possibility of the first connection portion cracking under the action of the expansion force of the electrode assembly is reduced.

[0174] In some embodiments, the thickness of the negative electrode active material layer is T1, where 9 μm ≤ T1 ≤ 75 μm.

[0175] In the embodiments of this application, the thickness of the negative electrode active material layer is relatively large, and accordingly the expansion force is relatively large, and the possibility of the first connection portion of the first side wall cracking due to the action of a relatively large expansion force is reduced by the first region with relatively low hardness.

[0176] Embodiments of this application provide an electrical device including any one of the above-mentioned battery cells used to provide electrical energy to an electrical device. [Brief explanation of the drawing]

[0177] [Figure 1] These are schematic diagrams of the structure of a vehicle according to some embodiments of this application. [Figure 2] This is an exploded view of a battery according to some embodiments of this application. [Figure 3] This is an exploded view of a battery cell according to some embodiments of this application. [Figure 4] Figure 3 is a perspective view of the battery cell. [Figure 5] Figure 4 is a cross-sectional view AA of the battery cell, and the cross-section of the first side wall shown in the figure is a predetermined cross-section. [Figure 6] Figure 5 shows a localized enlarged view of B, and the cross-section of the first side wall shown in the figure is a predetermined cross-section. [Figure 7] Figure 5 is a perspective view of the casing. [Figure 8] Figure 7 is a localized enlarged view of J, where the dotted line shown in the figure is the boundary line between the first region and the second region, with one side along the first direction of the dotted line being the first region and the other side along the first direction of the dotted line being the second region, and the first sub-surface shown in the figure spanning both the first and second regions. [Figure 9]The diagrams show schematic metallographic structures in a predetermined cross-section of a first sidewall according to several embodiments of this application. The diagrams show a first crystal grain in a first region, with other crystal grains in the first region not shown. The diagrams show a second crystal grain in a second region, with other crystal grains in the second region not shown. The diagrams show the size of the first crystal grain in the first region stretching along a first direction and its maximum size along a second direction. The diagrams show the size of the second crystal grain in the second region stretching along a first direction and its maximum size in a second direction. The dotted lines shown in the diagrams are the boundary lines between the first and second regions, with one side of the dotted line along the first direction being the first region and the other side of the dotted line along the first direction being the second region. The shapes of the crystal grains in the diagrams are illustrative and do not represent the actual shapes of the crystal grains. [Figure 10] This is a perspective view of an electrode assembly according to some embodiments of this application. [Figure 11] Figure 10 is a schematic diagram of the electrode assembly structure. [Figure 12] This is a perspective view of an electrode assembly according to some other embodiments of this application. [Figure 13] Figure 12 is a schematic diagram of the electrode assembly structure. [Figure 14] Figure 6 is a partial view of the first side wall, where the dotted line in the figure represents the boundary between the first and second regions, the first sub-surface spans both the first and second regions, and the first outer surface spans both the first and second regions. [Figure 15] This is a perspective view of a casing according to some embodiments of this application. [Figure 16] Figure 15 is a top view of the casing. [Figure 17] Figure 15 is a localized enlarged view of K, where the dotted line shown in the figure is the boundary line between the first region and the second region, and the first and second regions are located on opposite sides of the dotted line along the first direction, with the first inner surface spanning both the first and second regions. [Figure 18] This is a perspective view of a casing according to some other embodiments of the present application. [Figure 19] Figure 18 is a top view of the casing. [Figure 20] Figure 18 is a localized enlarged view of M, where the dotted line shown in the figure is the boundary line between the first region and the second region. The first and second regions are located on opposite sides of the dotted line along the first direction, the first connecting surface spans both the first and second regions, and the second connecting surface spans both the first and second regions. [Figure 21] Figure 18 is a localized enlarged view of N, where the dotted line shown in the figure is the boundary line between the first region and the second region. The first and second regions are located on opposite sides of the dotted line along the first direction, the first connecting surface spans both the first and second regions, and the third connecting surface spans both the first and second regions. [Figure 22] This is a perspective view of a casing according to some other embodiments of this application. [Figure 23] Figure 17 is a top view of the casing. [Figure 24] Figure 22 is a local enlargement view of P, where the dotted line shown 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 dotted 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. [Figure 25] Figure 22 is a localized enlarged view of Q, where the dotted line shown in the figure is the boundary line between the first region and the second region. The first and second regions are located on opposite sides of the dotted line along the first direction, the first connecting surface spans the first and second regions, the third connecting surface spans the first and second regions, and the second transition surface spans the first and second regions. [Figure 26] This is a partial diagram of a battery cell according to some embodiments of this application (showing the positive electrode plate, negative electrode plate, and separator of the electrode assembly). [Figure 27] This diagram shows the relative positions of the positive electrode plate, negative electrode plate, and separator according to some embodiments of this application. [Figure 28] This diagram shows the relative positions of the positive electrode plate, negative electrode plate, and separator according to some other embodiments of this application. [Figure 29] This is a partial view of a battery cell according to some embodiments of this application (showing the first side wall). [Figure 30] Figure 29 is a partial view of the first side wall, where the dotted line in the figure represents the boundary between the first and second regions, the first inner surface spans both the first and second regions, and the first outer surface spans both the first and second regions. [Figure 31] Figure 29 is a perspective view of the casing. [Figure 32] This is a partial view of a battery cell according to some other embodiments of the present application (showing the first side wall). [Figure 33] Figure 32 shows a localized enlarged view of point C. [Figure 34] This is a partial view of a battery cell according to some other embodiments of the present application (showing the first side wall). [Figure 35] Figure 34 shows a localized enlarged view of D. [Figure 36] This is a partial view of a battery cell according to some further embodiments of the present application (showing the first side wall). [Figure 37] Figure 36 is a localized enlarged view of point E. [Figure 38] This is a perspective view of a casing according to some further embodiments of the present application. [Figure 39] Figure 38 is a localized enlarged view of F, where the dotted lines shown in the figure represent the boundary between the first and second regions, and also the boundary between the third and fourth regions. The first and second regions are located on opposite sides of the dotted line along the first direction, and the third and fourth regions are located on opposite sides of the dotted line along the first direction. The first inner surface spans the first and second regions, and the third inner surface spans the third and fourth regions. [Figure 40] This is a partial view of a battery cell according to some embodiments of this application (showing the corner wall). [Figure 41]This is a schematic diagram of the structure of a corner wall according to some embodiments of the present application. The dotted line shown in the figure is the boundary line between the third region and the fourth region. The third inner surface spans both the third and fourth regions, and the third outer surface spans both the third and fourth regions. [Figure 42] This is a schematic diagram of the structure of a corner wall according to some other embodiments of the present application, where the dotted line shown in the figure is the boundary line between the third region and the fourth region, the third inner surface is provided spanning the third region and the fourth region, and the third outer surface is provided spanning the third region and the fourth region. [Figure 43] This is a partial view of a battery cell according to some other embodiments of this application (showing a corner wall). [Figure 44] Figure 43 is a localized magnified view of G. [Figure 45] This is a partial view of a battery cell according to some other embodiments of this application (showing a corner wall). [Figure 46] Figure 45 is a localized magnified view of point H. [Figure 47] This is a partial view of a battery cell according to some further embodiments of the present application (showing a corner wall). [Figure 48] Figure 47 shows a localized enlarged view of I. [Figure 49] This diagram shows the positional relationship between the end cover and the side wall before welding in some embodiments of this application. [Figure 50] This is a schematic diagram of the connection between the end cover and the electrode terminal according to some embodiments of this application.

[0178] 1. Housing, 11. Casing, 111. First side wall, 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. Stopper surface, 1116. Stopper region, 1117. First transition region, 112. Second side wall, 113. Corner wall, 1131. Third region, 11 32, 4th region, 1133, 1st connection terminal, 1134, 2nd connection terminal, 1135, 2nd transition region, 12, end cover, 121, outer surface of end cover, 2, electrode assembly, 21, tab, 21a, positive electrode tab, 21b, negative electrode tab, 22, positive electrode plate, 221, positive electrode body region, 2211, 5th terminal, 222, positive electrode current collector, 223, positive electrode active material layer, 2231, positive electrode body part, 2232, positive electrode thinning part, 224, insulating layer, 23, negative electrode plate, 231, negative electrode body region, 2311, 6th terminal, 232, negative electrode current collector, 233, negative electrode active material layer, 2331, negative electrode body part 2332, Negative electrode thinning section, 24, Separator, 241, 7th end, 242, Protruding region, 25, Flat region, 26, Corner region, 27, 5th outer surface, 28, 6th outer surface, 3, Electrode terminal, 31, Terminal body, 32, 1st stopper section, 33, 2nd stopper section, 4, Pressure reduction mechanism, 5, Connection section, 51, 1st connection section, 511, 1st connection interface, 5111, 1st position, 5112, 1st interface, 5113, 2nd interface, 5114, 3rd position, 5115, 4th position, 52, 2nd connection section, 521, 2nd connection interface, 5211, 2nd position, 5212, 3rd interface, 5213, 4 interface, 5214, fifth position, 5215, sixth position, 6, first insulating member, 7, second insulating member, 10, battery cell, 20, housing, 201, first housing, 202, second housing, 100, battery device, 200, controller, 300, motor, 1000, vehicle, Z, first direction, Y, second direction, X, third direction, U, first interface, V, second interface, 800, first crystal grain, 802, second crystal 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. [Modes for carrying out the invention]

[0179] To further clarify the purpose, technical aspects, and advantages of the embodiments of this application, the technical aspects of the embodiments of this application will be clearly described below with reference to the drawings of the embodiments of this application, although it is clear that the embodiments described are only some of the embodiments of this application, not all of them. All other embodiments that can be obtained by a person skilled in the art without creative labor based on the embodiments of this application are all within the scope of protection of this application.

[0180] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as that ordinarily understood by a person skilled in the art. In this application, terms used in the specification are for the sole purpose of describing specific embodiments and are not intended to limit this application. The terms “includes” and “have,” and any variations thereof, in the description of the specification, claims, and drawings of this application are intended to cover non-exclusive “inclusion.” Terms such as “first,” “second,” etc., in the specification, claims, or drawings of this application are for the purpose of distinguishing different subjects and are not intended to describe a particular order or hierarchical relationship.

[0181] As used in this application, “Examples” means that certain features, structures, or properties described with reference to the Examples are encompassed in at least one Example of this application. The term, appearing in various parts of the Specification, does not necessarily refer to the same Example, nor does it mean that any of the Examples are exclusive, independent, or alternative to each other.

[0182] In this application, the terms "and / or" are merely used to describe the relationship between related objects, indicating that three types of relationships are possible. For example, A and / or B can represent three situations: A existing alone, A and B existing simultaneously, and B existing alone. In addition, the symbol " / " in this application generally indicates that the related objects before and after it have an "or" relationship.

[0183] In the embodiments of this application, the same reference numerals represent the same components, and for the sake of brevity, detailed descriptions of the same components in different embodiments are omitted. The thickness, length, width, and other dimensions of the various components in the embodiments of this application shown in the drawings, as well as the overall thickness, length, width, and other dimensions of the integrating device, are for illustrative purposes only and should be understood as not limiting this application in any way.

[0184] In this application, "multiple" means two or more (including two).

[0185] In the embodiments of this application, the battery cell may be a secondary battery, and a secondary battery refers to a battery cell that can be continuously used by activating the active material by charging after the battery cell has been discharged.

[0186] 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, and lead-acid batteries.

[0187] It should be explained that the battery cell in the embodiment of this application is the battery in the priority application.

[0188] The battery cell 10 generally 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 (e.g., lithium ions) reciprocate between the positive and negative electrodes, undergoing intercalation and deintercalation. The separator 24 is provided between the positive and negative electrodes and can reduce the possibility of a short circuit between the positive and negative electrodes while allowing active ions to pass through.

[0189] In some embodiments, the positive electrode may be a positive electrode plate 22, which may include a positive electrode current collector 222 and a positive electrode active material provided on at least one surface of the positive electrode current collector 222.

[0190] As an example, the positive electrode current collector 222 has two opposing surfaces in the thickness direction of itself, and the positive electrode active material is provided on one or both of the two opposing surfaces of the positive electrode current collector 222.

[0191] As an example, the positive electrode current collector 222 may be a metal foil sheet or a composite current collector. For example, as the metal foil sheet, silver-plated aluminum, silver-plated stainless steel, stainless steel, copper, aluminum, nickel, carbide-finished electrodes, carbon, nickel, or titanium may be used. The composite current collector may include a polymer material base layer and a metal layer. The composite current collector can be formed by forming a metal material (such as aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy) on a polymer material substrate (for example, a substrate such as polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, or polyethylene).

[0192] As an example, the positive electrode active material may include at least one of lithium-containing phosphates, lithium transition metal oxides, and modified compounds thereof. 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 be used. These positive electrode active materials may be used individually or in combination of two or more. Here, examples of lithium-containing phosphates may include, but are not limited to, at least one of lithium iron phosphate (e.g., LiFePO4 (which can also be abbreviated as LFP)), composite materials of lithium iron phosphate and carbon, lithium manganese phosphate (e.g., LiMnPO4), composite materials of lithium manganese phosphate and carbon, lithium iron manganese phosphate, and composite materials of lithium iron manganese phosphate and carbon. Examples of lithium transition metal oxides include lithium cobalt oxide (e.g., LiCoO2), lithium nickel oxide (e.g., LiNiO2), lithium manganese oxide (e.g., LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (e.g., LiNi1 / 3Co1 / 3Mn1 / 3O2 (can also be abbreviated as NCM333), LiNi0.5Co0.2Mn0.3O2 (NCM It may include, but is not limited to, at least one of the following: LiNi0.5Co0.25Mn0.25O2 (which can also be abbreviated as NCM211), LiNi0.6Co0.2Mn0.2O2 (which can also be abbreviated as NCM622), LiNi0.8Co0.1Mn0.1O2 (which can also be abbreviated as NCM811), lithium nickel cobalt aluminum oxide (e.g., LiNi0.85Co0.15Al0.05O2) and its modified compounds.

[0193] In some embodiments, a foamed metal can be used as the positive electrode. The foamed metal may be foamed nickel, foamed copper, foamed aluminum, or a foamed alloy. When a foamed metal is used as the positive electrode, a positive electrode active material may or may not be provided on the surface of the foamed metal. For example, a lithium source material, potassium metal, or sodium metal may be filled and / or deposited within the foamed metal, and the lithium source material is lithium metal and / or a lithium-rich material.

[0194] In some embodiments, the negative electrode may be a negative electrode plate 23, and the negative electrode plate 23 may include a negative electrode current collector 232.

[0195] As an example, the negative electrode current collector 232 may be a metal foil sheet, a foamed metal, or a composite current collector. For example, the metal foil sheet may be silver-plated aluminum, silver-plated stainless steel, stainless steel, copper, aluminum, nickel, carbide-finished electrodes, carbon, nickel, or titanium. The foamed metal may be foamed nickel, foamed copper, foamed aluminum, or foamed alloy. The composite current collector may include a polymer base layer and a metal layer. The composite current collector can be formed by forming a metal material (such as copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys) on a polymer material substrate (for example, a substrate such as polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, or polyethylene).

[0196] As an example, the negative electrode plate 23 may include a negative electrode current collector 232 and a negative electrode active material provided on at least one surface of the negative electrode current collector 232.

[0197] As an example, the negative electrode current collector 232 has two opposing surfaces in its own thickness direction, and the negative electrode active material is provided on one or both of the two opposing surfaces of the negative electrode current collector 232.

[0198] As an example, the negative electrode active material may be a negative electrode active material used in a battery cell 10 known in the art. For example, the negative electrode active material may include at least one of artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate. The silicon-based material may be at least one selected from elemental silicon, silicon-oxygen compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be at least one selected from elemental tin, tin-oxy compounds, and tin alloys. However, this application is not limited to these materials, and other conventional materials that can be used as negative electrode active materials for batteries may be used. These negative electrode active materials may be used individually or in combination of two or more.

[0199] In some embodiments, the material of the positive electrode current collector 222 may be aluminum, and the material of the negative electrode current collector 232 may be copper.

[0200] In some embodiments, the separator 24 is a separator film. The type of separator film can be selected from any known porous structure separator film that has good chemical stability and mechanical stability.

[0201] As an example, the material of the separator film may include at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator film may be a single-layer film or a multi-layer composite film. If the separator film is a multi-layer composite film, the materials of each layer may be the same or different. The separator 24 may be a single component located between the positive and negative electrodes, or it may be attached to the surfaces of the positive and negative electrodes.

[0202] In some embodiments, the separator 24 is a solid electrolyte. The solid electrolyte is placed between the positive electrode and the negative electrode and simultaneously performs the functions of ion transport and separation of the positive and negative electrodes.

[0203] In some embodiments, the battery cell 10 further contains an electrolyte, which acts as a conductor of ions between the positive and negative electrodes. The electrolyte may be liquid, gel-like, or solid. Here, the liquid electrolyte comprises an electrolyte salt and a solvent.

[0204] 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 difluoro(oxalato)borate, lithium bis(oxalato)borate, lithium difluorobis(oxalato)phosphate, and lithium tetrafluoro(oxalato)phosphate.

[0205] In some embodiments, the solvent may include at least one of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, ethyl methyl sulfone, and diethyl sulfone. The solvent may also be an ether-based solvent. The ether-based solvent may include one or more of ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, 1,3-dioxolane, tetrahydrofuran, methyltetrahydrofuran, diphenyl ether, and crown ether.

[0206] Here, the gel-like electrolyte contains a polymer backbone network as the electrolyte and is compounded with an ionic liquid-lithium salt.

[0207] Here, the solid electrolyte includes polymer solid electrolytes, inorganic solid electrolytes, and composite solid electrolytes.

[0208] Examples of polymer solid electrolytes include polyethers (polyethylene oxide), polysiloxanes, polycarbonates, polyacrylonitriles, polyvinylidene fluoride, polymethyl methacrylate, monoionic polymers, polyionic liquid lithium salts, and cellulose.

[0209] 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 film), sulfide solid electrolytes (crystalline lithium superionic conductor (lithium germanium phosphate sulfur, argyrodite), amorphous sulfide), halide solid electrolytes, nitride solid electrolytes, and hydride solid electrolytes.

[0210] As an example, a composite solid electrolyte is formed by adding an inorganic solid electrolyte filler to a polymer solid electrolyte.

[0211] In some embodiments, the electrode assembly 2 has a wound structure. The positive electrode plate 22 and the negative electrode plate 23 are wound in the wound structure.

[0212] In some embodiments, the electrode assembly 2 has a stacked structure.

[0213] As an example, there may be multiple positive electrode plates 22 and multiple negative electrode plates 23, and the multiple positive electrode plates 22 and multiple negative electrode plates 23 may be arranged in an alternating stacking configuration.

[0214] As an example, a plurality of positive electrode plates 22 may be provided. The negative electrode plate 23 is folded to form a plurality of stacked and arranged folding segments, and one positive electrode plate 22 is sandwiched between adjacent folding segments.

[0215] As an example, both the positive electrode plate 22 and the negative electrode plate 23 are folded to form a plurality of stacked and arranged folding segments.

[0216] As an example, a plurality of separators 24 may be provided, and each is provided between any adjacent positive electrode plate 22 or negative electrode plate 23.

[0217] As an example, the separator 24 may be provided continuously and is provided between any adjacent positive electrode plate 22 or negative electrode plate 23 in a folded or wound form.

[0218] In some embodiments, the shape of the electrode assembly 2 may be cylindrical, flat, polygonal columnar, or the like.

[0219] In some embodiments, a tab 21 is provided on the electrode assembly 2, and the tab 21 can conduct current from the electrode assembly 2. The tab 21 includes a positive tab 21a and a negative tab 21b.

[0220] In some embodiments, the battery cell 10 may include a housing 1. The housing 1 is used to enclose members such as the electrode assembly 2 and the electrolyte. The housing 1 may be a steel housing, an aluminum housing, a plastic housing (e.g., polypropylene), a composite metal housing (e.g., a copper-aluminum composite housing 1), or an aluminum plastic film, or the like.

[0221] As an example, the battery cell 10 may be a cylindrical battery cell 10, a prismatic battery cell 10, a pouch battery cell 10, or a battery cell 10 of another shape. The prismatic battery cell 10 includes a battery cell 10 with a square housing, a blade-shaped battery cell 10, and a polygonal prismatic battery cell 10, for example, a hexagonal prismatic battery cell 10.

[0222] The battery device 100 referred to in the embodiments of this application refers to a single physical module that provides higher voltage and capacity by including one or more battery cells 10.

[0223] In some embodiments, the battery device 100 may be a battery module, and if there are multiple battery cells 10, the multiple battery cells 10 are arranged and fixed together to form a single battery module.

[0224] In some embodiments, the battery device 100 may be a battery pack, which includes a housing 20 and battery cells 10, and the battery cells 10 or battery modules are housed in the housing 20.

[0225] In some embodiments, the housing 20 may be used as part of the chassis structure of the vehicle 1000. For example, a portion of the housing 20 may become at least a portion of the floor of the vehicle 1000, and a portion of the housing 20 may become at least a portion of the crossbeams and longitudinal beams of the vehicle 1000.

[0226] In some embodiments, the battery device 100 may be an energy storage device. The energy storage device includes an energy storage collection container, an energy storage cabinet, and the like.

[0227] In related technologies, a battery cell 10 generally includes a housing 1 and an electrode assembly 2, and the housing 1 may include a casing 11 and an end cover 12, the casing 11 having an opening, and after the electrode assembly 2 is assembled into the casing 11, the opening of the casing 11 can be sealed by the end cover 12 to form a sealed space inside the housing 1 that accommodates the electrode assembly 2.

[0228] To ensure a stable connection between the end cover 12 and the casing 11, the end cover 12 may be welded to the casing 11. After the end cover 12 is welded to the casing 11, a connection portion 5 is formed at the welding location between the end cover 12 and the casing 11, and the hardness of the connection portion 5 is relatively high. During the charging and discharging process of the battery cell 10, the electrode assembly 2 undergoes cyclical expansion and contraction due to ion absorption and desorption. The walls of the casing 11 deform after being subjected to the expansion force of the electrode assembly 2, and the expansion and contraction forces of the electrode assembly 2 are transmitted to the connection portion 5 at the opening of the casing 11 via the deformation of this part of the casing 11. Because the hardness of the connection portion 5 is relatively high and its toughness is relatively low, it is difficult for it to withstand the forces during the expansion and contraction process of the electrode assembly 2, which may cause the connection portion 5 near the opening of the casing 11 to crack, affecting the service life of the battery cell 10.

[0229] Based on the above considerations, the embodiment of this application provides a first region 1111 with relatively low hardness, and by releasing the expansion force acting on the connection portion 5 by the electrode assembly 2 through the deformable portion of the first region 1111 with relatively low hardness, the possibility of cracking of the connection portion 5 at the opening of the casing 11 is reduced, thereby improving the service life of the battery cell 10.

[0230] The battery cell 10 described in the embodiment of this application is applicable to a battery device 100 and an electrical device that uses the battery cell 10.

[0231] Electrical devices may include vehicles 1000, mobile phones, portable devices, laptop computers, steamships, aerospace equipment, electric toys, and power tools. Vehicle 1000 may be a fuel-fueled vehicle, a gas vehicle, or a new energy vehicle, and a new energy vehicle may be an electric vehicle (BEV), a hybrid vehicle, or a range extender vehicle, etc. Aerospace equipment includes airplanes, rockets, space shuttles, and spacecraft, etc. Electric toys include stationary or mobile electric toys, such as game consoles, electric vehicle toys, electric steamship toys, and electric airplane toys, etc. Power tools include metal cutting power tools, polishing power tools, assembly power tools, and railway power tools, such as electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact driver drills, concrete vibrators, and electric planers, etc. Embodiments of this application are not particularly limited to the electrical equipment described above.

[0232] In the following embodiments, for the sake of explanation, the electrical device will be described as a vehicle 1000.

[0233] Please refer to Figure 1. Figure 1 is a schematic diagram of the structure of a vehicle 1000 according to some embodiments of this application. A battery device 100 is provided inside the vehicle 1000, and the battery device 100 may be located at the bottom, top, or rear of the vehicle 1000. The battery device 100 may be used to power the vehicle 1000, for example, the battery device 100 may be used as the operating power source for the vehicle 1000.

[0234] The vehicle 1000 may further include a controller 200 and a motor 300, the controller 200 being used to control the power supply to the motor 300 by the battery device 100, for example, to meet the operating power consumption needs of the vehicle 1000 during startup, navigation, and driving.

[0235] In some embodiments of this application, the battery device 100 is used not only as an operating power source for the vehicle 1000, but also as a power source for driving the vehicle 1000, and can provide driving power to the vehicle 1000 as a substitute or partial substitute for gasoline or natural gas.

[0236] Please refer to Figure 2. Figure 2 is an exploded view of a battery device 100 according to some embodiments of the present application. The battery device 100 may include a battery cell 10 and a housing 20, the battery cell 10 being housed within the housing 20.

[0237] Here, the housing 20 is a component that houses the battery cell 10, and the housing 20 provides a housing space for the battery cell 10, and the housing 20 can employ multiple types of structures. In some embodiments, the housing 20 may include a first housing 201 and a second housing 202, and the first housing 201 and the second housing 202 close each other's lids to define a housing space for housing the battery cell 10. The first housing 201 and the second housing 202 may have multiple shapes, such as a rectangular parallelepiped or a cylindrical shape. The first housing 201 may have a hollow structure with one side open, and the second housing 202 may also have a hollow structure with one side open, and when the open side of the second housing 202 is closed to the open side of the first housing 201, a housing 20 having a housing space is formed. The first housing 201 may have a hollow structure with one side open, and the second housing 202 may have a plate-like structure, such that when the second housing 202 is closed on the open side of the first housing 201, a box body 20 with a storage space is formed. The first housing 201 and the second housing 202 can be sealed by a sealing element, which may be a sealing ring, sealant, or the like.

[0238] In the battery device 100, there may be one or more battery cells 10. If there are multiple battery cells 10, the multiple battery cells 10 may be connected in series, in parallel, or in a double row. A double row connection means that there are not only series connections but also parallel connections among the multiple battery cells 10. Multiple battery cells 10 may be connected in series, in parallel, or in a double row to form a battery module, and multiple battery modules may be further connected in series, in parallel, or in a double row to form a single whole, which may be housed in the housing 20. All the battery cells 10 may be directly connected in series, in parallel, or in a double row, and the whole composed of all the battery cells 10 may be housed in the housing 20.

[0239] Please refer to FIGS. 3, 4 and 5. The battery cell 10 may include a housing 1 and an electrode assembly 2, and the electrode assembly 2 is housed within the housing 1.

[0240] In some embodiments, the housing 1 may include a casing 11 and an end cover 12. The casing 11 has an opening at at least one end along the first direction Z, and the end cover 12 seals the opening of the casing 11.

[0241] The casing 11 is a member for housing the electrode assembly 2. The casing 11 may be a hollow structure forming an opening at one end along the first direction Z, or may be a hollow structure forming openings at both opposite ends along the first direction Z. The casing 11 may have various shapes such as a cylindrical shape or a rectangular parallelepiped shape. The material of the casing 11 may be a plurality of types such as copper, iron, aluminum, steel, aluminum alloy, etc. A part of the electrode assembly 2 may be located within the casing 11, or all of it may be located within the casing 11.

[0242] The end cover 12 is a member that seals the opening of the casing 11 to block the internal environment of the battery cell 10 from the external environment. The end cover 12, together with the casing 11, defines a housing space for housing the electrode assembly 2, the electrolyte and other members. The end cover 12 can be connected to the casing 11 by welding or winding to seal the opening of the casing 11. The shape of the end cover 12 can match the shape of the casing 11. For example, if the casing 11 has a rectangular parallelepiped structure, the end cover 12 has a rectangular plate-like structure that matches the casing 11. Also, for example, if the casing 11 has a cylindrical structure, the end cover 12 has a circular plate-like structure that matches the casing 11. The material of the end cover 12 may be a plurality of types such as copper, iron, aluminum, steel, aluminum alloy, plastic, etc. The materials of the end cover 12 and the casing 11 may be the same or different.

[0243] In an embodiment where the casing 11 has an opening at one end, one end cover 12 may be provided. In an embodiment where the casing 11 has openings at both opposing ends, two end covers 12 may be provided, each sealing two openings in the casing 11, and the two end covers 12 together with the casing 11 define the housing space.

[0244] In some embodiments, the battery cell 10 may further include electrode terminals 3, which are provided on the housing 1 and are electrically connected to tabs 21 of the electrode assembly 2 to be used for inputting and outputting electrical energy to the battery cell 10. The electrode terminals 3 may be provided on the casing 11 of the housing 1 or on the end cover 12 of the housing 1. The electrode terminals 3 and tabs 21 may be directly connected, for example, by welding. The electrode terminals 3 and tabs 21 may be indirectly connected, for example, by a current collector. The current collector may be a metal conductor such as copper, iron, aluminum, steel, or an aluminum alloy.

[0245] In some embodiments, the battery cell 10 may further include a pressure reduction mechanism 4, which may be installed on an end cover 12 or on a casing 11. The pressure reduction mechanism 4 may be a pressure reduction member attached to the casing 11 or end cover 12, such as a rupture disc or a safety valve. The pressure reduction mechanism 4 may be integrally molded with the end cover 12 or casing 11. A pressure reduction groove may be provided in the pressure reduction mechanism 4, so that when the battery cell 10 is depressurized, it ruptures along the groove. The pressure reduction groove may be a groove extending along a sealed trajectory, which may be a circular trajectory, a rectangular trajectory, etc. The pressure reduction groove may be a groove extending along an unsealed trajectory, which may be an H-shaped trajectory, a Y-shaped trajectory, a V-shaped trajectory, a U-shaped trajectory, etc.

[0246] For example, as shown in Figures 3, 4, and 5, one end of the casing 11 is formed as an opening, and there is one end cover 12 in the housing 1, which seals one of the openings in the casing 11. A pressure reducing mechanism 4 is installed on the end cover 12, and two electrode terminals 3 are installed on the end cover 12, the two electrode terminals 3 being a positive electrode terminal 3 and a negative electrode terminal 3 respectively, and a positive electrode tab 21a and a negative electrode tab 21b are formed on the end of the electrode assembly 2 facing the end cover 12, 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.

[0247] Please refer to Figures 6 to 9 for the battery cell 10 of the embodiment of this application. The battery cell 10 includes a casing 11, an electrode assembly 2, and an end cover 12. At least one end of the casing 11 along a first direction Z has an opening, and the casing 11 includes a first side wall portion 111. At least a portion of the electrode assembly 2 is housed within the casing 11, and the electrode assembly 2 includes a positive electrode plate 22 and a negative electrode plate 23, with at least a portion of the positive electrode plate 22 and at least a portion of the negative electrode plate 23 stacked along a second direction Y, the second direction Y being parallel to the thickness direction of the first side wall portion 111, and the first direction Z intersecting the second direction Y. The end cover 12 is used to seal the opening, and the first side wall portion 111 is welded to the end cover 12 to form a first connection portion 51. Here, the first side wall portion 111 includes a first region 1111 and a second region 1112 arranged along a first direction Z, the first region 1111 is located between the first connecting portion 51 and the second region 1112, and the hardness of the first region 1111 is lower than that of the second region 1112.

[0248] The casing 11 may be formed as an opening only at one end along the first direction Z, and one end cover 12 may be installed accordingly.

[0249] Both opposing ends of the casing 11 along the first direction Z may be formed as openings, and two end covers 12 are installed accordingly.

[0250] The casing 11 may have various shapes, such as cylindrical or prismatic, and the prismatic may be triangular, square, pentagonal, or hexagonal, and the square prismatic may be a rectangular prism or a perfect prism.

[0251] The first direction Z is parallel to the direction of the opening of the casing 11. In embodiments where the casing 11 is cylindrical, the first direction Z may be parallel to the axial direction of the casing 11, and in embodiments where the casing 11 is prismatic, the first direction Z may be parallel to the direction of extension of the side edges of the casing 11.

[0252] The second direction Y is parallel to the thickness direction of the first side wall portion 111. In embodiments where the casing 11 is cylindrical, the first side wall portion 111 is cylindrical, the radial direction of the casing 11 is the thickness direction of the first side wall portion 111, and the second direction Y is parallel to the radial direction of the casing 11. In embodiments where the casing 11 is prismatic, the first side wall portion 111 may be a rectangular plate structure. The first direction Z and the second direction Y may be set at an acute angle, a right angle, or an obtuse angle.

[0253] The end cover 12 may be connected to the casing 11 by welding, and the end cover 12 can be welded to the casing 11 to form a connection portion 5, which can extend along the circumferential direction of the opening of the casing 11. The end cover 12 is connected and fixed to the casing 11 via the connection portion 5 to achieve a seal between the end cover 12 and the casing 11. The connection portion 5 is the portion where a weld mark is formed after the end cover 12 is welded to the casing 11, and the portion where the end cover 12 is welded to the casing 11 and fused together may be the connection portion 5.

[0254] The first side wall portion 111 in the casing 11 may be one or multiple. The first connecting portion 51 may correspond one-to-one with the first side wall portion 111, and the first connecting portion 51 is the portion where a weld mark is formed after the end cover 12 is welded to the first side wall portion 111, and the portion where the end cover 12 is welded to the first side wall portion 111 and fuses together may be the first connecting portion 51. A part of the first connecting portion 51 is formed on the end cover 12, and another part of the first connecting portion 51 is formed on the first side wall portion 111. The first side wall portion 111 and the end cover 12 may form the first connecting portion 51 by stitching welding or by through welding. The first connecting portion 51 may be a part of the connecting portion 5 or all of the connecting portion 5. In embodiments where the casing 11 is cylindrical, there is only one first side wall portion 111 in the casing 11, the first side wall portion 111 is cylindrical, and the first connecting portion 51 is the connecting portion 5. In embodiments where the casing 11 is prismatic, the casing 11 may include a plurality of side walls, the plurality of side walls are installed along the opening of the casing 11, and at least one of the two side walls installed opposite each other along the second direction Y may be the first side wall portion 111, and the first connecting portion 51 is part of the connecting portion 5.

[0255] The first side wall portion 111 may be the wall with the largest outer surface area in the casing 11, or it may not be the wall with the largest outer surface area in the casing 11. Taking the casing 11 as an example, the casing 11 may include two first side walls 111 and two second side walls 112, the two first side walls 111 being installed opposite each other along a second direction Y, and the two second side walls 112 being installed opposite each other along a third direction X, the first direction Z, the second direction Y, and the third direction X being perpendicular in pairs, the first side wall 111 being the wall with the largest outer surface area in the casing 11, thereby the outer surface area of ​​the first side wall 111 being larger than the outer surface area of ​​the second side wall 112, the second side wall 112 being the wall with the largest outer surface area in the casing 11, and the outer surface area of ​​the second side wall 112 being larger than the outer surface area of ​​the first side wall 111.

[0256] The first region 1111 may be a region of the first side wall 111 with relatively low hardness, and the hardness of the first region 1111 is relatively low compared to the hardness of the second region 1112. The second region 1112 may be a portion of the first region 1111 located away from the first connection portion 51 along the first direction Z of the first side wall 111. The first region 1111 may be directly connected to the first connection portion 51, and the first region 1111 may be directly connected to the second region 1112, or indirectly connected. The maximum hardness of the first region 1111 may be less than the minimum hardness of the second region 1112, thereby achieving that the hardness of the first region 1111 is lower than that of the second region 1112.

[0257] The electrode assembly 2 is located within a housing space defined by the casing 11 and the end cover 12. The electrode assembly 2 may be a stacked structure or a wound structure. There may be one electrode assembly 2 in the casing 11 or multiple electrode assemblies 2. If there are multiple electrode assemblies 2, the multiple electrode assemblies 2 may be stacked, for example, stacked along the second direction Y.

[0258] For example, the hardness of the first region 1111 and the hardness of the second region 1112 can be measured with a known hardness tester.

[0259] For example, the first region 1111 extends along the third direction X to the opposing ends of the first side wall portion 111.

[0260] The method for forming the first region 1111, which has relatively low hardness, is not limited. For example, the casing 11 can be heated and softened with a laser to obtain the first region 1111, which has relatively low hardness. For example, a portion of the casing 11 can be subjected to an annealing treatment to obtain the first region 1111, which has relatively low hardness.

[0261] For example, by controlling the power used to weld the casing 11 and the end cover 12, the hardness of the region of the weld along the first direction can be reduced, that is, the hardness of the region of the connection 5 along the first direction becomes smaller, thereby forming a first region 1111 with relatively low hardness. As can be seen, when the power used to weld the casing 11 and the end cover 12 is below the maximum allowable power, by appropriately increasing the welding power, the size of the first region 1111 along the first direction with relatively low hardness can be made relatively larger, which is advantageous in reducing cracking of the first connection 51.

[0262] In the embodiments of this application, at least a portion of the positive electrode plate 22 and at least a portion of the negative electrode plate 23 are stacked along the second direction Y, the electrode assembly 2 expands along the second direction Y during the cycle process, and the first sidewall portion 111 is subjected to the expansion force of the electrode assembly 2, and 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, and by providing the first region 1111, which has relatively low hardness, in the first sidewall portion 111, the toughness of the first region 1111 becomes relatively high, thereby releasing a portion of the expansion force of the electrode assembly 2, reducing the influence of the expansion force of the electrode assembly 2 on the first connection portion 51, reducing the possibility of the first connection portion 51 cracking at the opening of the casing 11, and further improving the service life of the battery cell 10.

[0263] For some embodiments, please refer to Figures 6 to 9. 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.

[0264] The interpretation is that the hardness type of the first domain 1111 is the same as the hardness type of the second domain 1112.

[0265] For example, the hardness of the first region 1111 and the hardness of the second region 1112 may both be measured in Vickers hardness.

[0266] For example, the hardness of the first region 1111 and the hardness of the second region 1112 may both be Brinell hardness.

[0267] The hardness types of the first region 1111 and the second region 1112 may be other known hardness types, and the hardness type of the first region 1111 may be the same as the hardness type of the second region 1112.

[0268] For example, the ratio of the hardness of the first region 1111 to the hardness of the second region 1112 is one point value or a range value between any two of the following: 0.3, 0.35, 0.4, 0.45, 0.5, 0.6, 0.7, 0.8, etc.

[0269] In the embodiments of this application, 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. Since the ratio of the hardness of the first region 1111 to the hardness of the second region 1112 is within a relatively appropriate range, the first region 1111, which has relatively low hardness, can reduce the possibility of cracking of the first connection portion 51, and can also suppress cracking of the first region 1111 due to the action of the relatively large expansion force of the electrode assembly 2 to a certain extent.

[0270] To make it easier to understand, the ratio of the hardness of the first region 1111 to the hardness of the second region 1112 is not limited, and it is sufficient that the hardness of the first region 1111 is lower than the hardness of the second region 1112. For example, the ratio of the hardness of the first region 1111 to the hardness of the second region 1112 may be less than 0.3 in some cases, or the ratio may be greater than 0.8 and less than 1 in some cases.

[0271] For some embodiments, please refer to Figures 6 to 9. The ratio of the hardness of the first region 1111 to the hardness of the second region 1112 is between 0.5 and 0.8.

[0272] For example, the ratio of the hardness of the first region 1111 to the hardness of the second region 1112 is one point value or a range value between any two of the following: 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, etc.

[0273] In the embodiments of this application, 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. Since the ratio of the hardness of the first region 1111 to the hardness of the second region 1112 is within a relatively appropriate range, the first region 1111, which has relatively low hardness, can reduce the possibility of cracking of the first connection portion 51, and can also suppress cracking of the first region 1111 due to the action of the relatively large expansion force of the electrode assembly 2 to a certain extent.

[0274] To make it easier to understand, the ratio of the hardness of the first region 1111 to the hardness of the second region 1112 is not limited; it is sufficient that the hardness of the first region 1111 is lower than the hardness of the second region 1112. For example, the ratio of the hardness of the first region 1111 to the hardness of the second region 1112 may be less than 0.5 in some cases.

[0275] For some examples, please refer to Figures 6 to 9. The hardness range of the second region 1112 is 40 HV to 100 HV, and the hardness range of the first region 1111 is 20 HV to 55 HV.

[0276] It should be explained that "HV" is the unit of Vickers hardness.

[0277] For example, the hardness range of the second region 1112 is one point value or a range value between any two of the following: 40HV, 45HV, 50HV, 60HV, 70HV, 80HV, 90HV, 100HV, etc.

[0278] For example, the hardness range of the first region 1111 is one point value or a range value between any two of the following: 20HV, 25HV, 30HV, 35HV, 40HV, 45HV, 50HV, 55HV, etc.

[0279] In the embodiments of this application, the hardness range of the second region 1112 is relatively appropriate and advantageous for protecting the electrode assembly 2 within the casing 11, reducing the impact of the external environment on the electrode assembly 2 within the casing 11 and achieving basic protection of the casing 11 to the electrode assembly 2. The hardness range of the first region 1111 is also relatively appropriate, and the relatively low hardness of the first region 1111 reduces the possibility of cracking of the first connection 51, and to a certain extent can also suppress cracking of the first region 1111 due to the action of the relatively large expansion force of the electrode assembly 2.

[0280] To make it easier to understand, the hardness ranges of the first region 1111 and the second region 1112 are not limited; it is sufficient that the hardness of the first region 1111 is lower than the hardness of the second region 1112. For example, the hardness range of the second region 1112 may be less than 40 HV or greater than 100 HV, and the hardness range of the first region 1111 may be less than 20 HV or greater than 55 HV.

[0281] For some embodiments, please refer to Figures 6, 26, 29, 32, 34, and 36. The size range of the first region 1111 along the first direction Z is 0.05 mm to 0.75 mm.

[0282] For example, the size of the first region 1111 along the first direction Z is D 10 Therefore, 0.05mm≦D 10 The value is ≤0.75mm.

[0283] For example, the size along the first direction Z of the first region 1111 is one point value or a range value between any two of the following: 0.05 mm, 0.1 mm, 0.15 mm, 0.2 mm, 0.25 mm, 0.3 mm, 0.4 mm, 0.5 mm, 0.6 mm, 0.7 mm, 0.75 mm, etc.

[0284] For example, the size of the first region 1111 along the first direction Z can be measured with a caliper or micrometer.

[0285] In the embodiments of this application, the size range of the first region 1111 along the first direction Z is relatively appropriate, and within an appropriate size range, the first region 1111 is formed with relatively low hardness, which is advantageous in reducing the possibility of cracking of the first connection portion 51, and on the other hand in suppressing cracking due to the influence of the expansion force of the electrode assembly 2 caused by the first region 1111 being too long and having relatively low hardness.

[0286] To ensure clarity, the size range along the first direction Z of the first region 1111 is not limited. For example, the size range along the first direction Z of the first region 1111 may be less than 0.05 mm or greater than 0.75 mm.

[0287] For some embodiments, please refer to Figures 6, 26, 29, 32, 34, and 36. The size range of the first region 1111 along the first direction Z is 0.1 mm to 0.6 mm.

[0288] For example, the size along the first direction Z of the first region 1111 is one point value or a range value between any two of the following: 0.1 mm, 0.15 mm, 0.2 mm, 0.25 mm, 0.3 mm, 0.35 mm, 0.4 mm, 0.45 mm, 0.5 mm, 0.55 mm, 0.6 mm, etc.

[0289] In the embodiments of this application, the size range of the first region 1111 along the first direction Z is relatively appropriate, forming a first region 1111 with relatively low hardness within an appropriate size range. On the one hand, the deformation of the first region 1111 with relatively low hardness releases the expansion force of the electrode assembly 2 by the first region 1111, reducing the possibility of cracking of the first connection 51. On the other hand, it is advantageous in suppressing cracking due to the influence of the expansion force of the electrode assembly 2 caused by the first region 1111 being too long with relatively low hardness.

[0290] To ensure clarity, the size range along the first direction Z of the first region 1111 is not limited. For example, the size range along the first direction Z of the first region 1111 may be less than 0.1 mm or greater than 0.6 mm.

[0291] For some embodiments, please refer to Figure 9. At least a portion of the crystal grains in the first region 1111 are first crystal grains 800, the ratio of the number of first crystal grains 800 in the first region 1111 to the total number of crystal grains in the first region 1111 is greater than 50%, the size of the first crystal grains 800 stretched along the first direction Z is the first size, the maximum size of the first crystal grains 800 along the second direction Y is the second size, and the ratio of the first size to the second size is in the range of 0.2 to 5.

[0292] For example, please refer to Figures 4 to 6, and Figures 9 and 14. The cross-section of the first side wall portion 111 shown in the figures is a predetermined cross-section, which is substantially parallel to the first direction Z and the second direction Y, respectively. The predetermined cross-section intersects with the first region 1111 to form the first cross-section.

[0293] For example, the first crystal grain 800 is equiaxial.

[0294] The step of measuring the crystal grains in the first region includes sample cutting, sample processing, and crystal grain measurement.

[0295] The sample cutting step specifically includes the following:

[0296] An end cover 12 is connected to the first end of the casing 11 along the first direction Z, and the second end of the casing 11 along the first direction Z is positioned opposite the first end of the casing 11. The casing 11 is separated along the circumferential direction of the casing 11 at a position 30 mm from the second end of the casing 11 along the first direction Z, the electrode assembly 2 and electrolyte inside the casing 11 are separated from the casing 11, the casing 11 with the first end attached after being cut is cleaned, and the casing 11 after being cleaned The side walls are restored to a flat state, and the first end of the casing 11, whose side walls have been restored to a flat state, is positioned downward along the first direction Z so that the end cover 12 at the first end is located below the casing 11. Transparent resin is injected into the space enclosed by the casing 11 and the lower end cover 12 of the casing 11 so that the height of the transparent resin in the space enclosed by the end cover 12 and the casing 11 is equal to or greater than a predetermined height, which is half the height of the casing 11 with the first end attached after it has been cut. The first side wall portion 111 of the casing 11 into which the transparent resin has been placed is cut to obtain the necessary sample for measurement, the cutting plane of the casing 11 is approximately perpendicular to the reference plane, the reference plane is parallel to the first direction Z and the second direction Y, respectively, and for example, the angle between the cutting plane of the casing 11 and the reference plane is 80° to 95°. The casing 11 into which the transparent resin has been placed is cut as far as possible from the top downwards to the lower end cover 12 of the casing 11 into which the transparent resin has been placed.

[0297] Sample preparation specifically includes the following:

[0298] After obtaining the necessary sample for measurement by cutting the first side wall portion 111 of the casing 11 containing transparent resin, the cross-section of the sample for measurement that is approximately parallel to the first direction Z and the second direction Y is a predetermined cross-section of the first side wall portion 111. The predetermined cross-section is polished with a file, the mesh count of the file used to polish the predetermined cross-section is 1600 mesh or more. The predetermined cross-section after polishing is cleaned and corroded to obtain a sample to be measured that can be observed with an optical microscope, and the sample to be measured after corrosion is placed under an optical microscope to observe the predetermined cross-section of the sample to be measured.

[0299] An optical microscope, model BX53M, manufactured by Olympus, may be used to measure the crystal grains in a predetermined cross-section. The measurement position is determined by first selecting a rough measurement area with a relatively low magnification of the optical microscope, and then observing the selected rough measurement area by increasing the magnification of the optical microscope. As can be seen, the occupancy rate of the first crystal grain 800 in the first region 1111 is greater than 50%, and the occupancy rate of the second crystal grain 802 in the second region 1112 is also greater than 50%, so the difference in crystal grains between the two regions is relatively clear, and the rough area to be measured can be identified by the crystal grains observed with the optical microscope.

[0300] The relevant software from Olympus allows for the measurement of crystal grains displayed on the optical microscope model BX53M; for example, software Capture 2.2.1 can be used.

[0301] The steps for grain measurement specifically include the following:

[0302] The software Capture2.2.1 displays and measures crystal grains in an optical microscope with model number BX53M. A rectangular frame of 0.1 mm × 0.2 mm is drawn within the first region 1111. The side of this rectangular frame with a side length of 0.2 mm is parallel to the second direction Y. Crystal grains that are completely within the rectangular frame and crystal grains that intersect the side of the rectangular frame all belong to the crystal grains within this rectangular frame.

[0303] The size of each crystal grain stretched along the first direction Z within this 0.1 mm × 0.2 mm rectangular frame is measured. Specifically, each crystal grain within this rectangular frame is projected along the second direction Y to obtain a projection line stretching along the corresponding first direction Z, and the size of this projection line stretched along the first direction Z corresponds to the size of the crystal grain stretched along the first direction Z. The size of each crystal grain stretched along the first direction is the size at the system scale corresponding to the software Capture 2.2.1, i.e., the actual size when not magnified by the optical microscope, and this size value does not change with changes in the magnification of the optical microscope.

[0304] What needs to be explained is that a 0.1mm x 0.2mm rectangular frame means that two sides facing each other along the first direction Z of the rectangular frame have a side length of 0.2mm, and two sides with a side length of 0.2mm are parallel to the second direction Y, and the two sides facing each other along the second direction Y of the rectangular frame have a side length of 0.1mm. The size of the rectangular frame is the size at the system scale corresponding to the software Capture 2.2.1, that is, the actual size when not magnified by the optical microscope, and this size value does not change with changes in the magnification of the optical microscope.

[0305] The maximum size of each crystal grain along the second direction Y within this 0.1 mm × 0.2 mm rectangular frame is measured. Specifically, multiple cutting lines parallel to the second direction Y are drawn corresponding to each crystal grain, and the distance between two cutting points aligned along the second direction Y, formed when these cutting lines intersect the corresponding crystal grain, is the intercept of the cutting line in the corresponding crystal grain. Of the intercepts of the multiple cutting lines parallel to the second direction Y corresponding to each crystal grain, the largest intercept is the maximum size of that crystal grain along the second direction Y. The maximum size of each crystal grain along the second direction Y is the size at the system scale corresponding to the software Capture 2.2.1, i.e., the actual size when not magnified by the optical microscope, and this size value does not change with changes in the magnification of the optical microscope.

[0306] Crystal grains are screened based on the size of each crystal grain stretched along the first direction Z and the maximum size of each crystal grain along the second direction Y within this 0.1 mm × 0.2 mm rectangular frame. If the ratio of the size of each crystal grain stretched along the first direction Z to the maximum size along the second direction Y within the 0.1 mm × 0.2 mm rectangular frame is within the range of 0.2 to 5, then this crystal grain is the first crystal grain 800. The first crystal grain 800 within the 0.1 mm × 0.2 mm rectangular frame is screened using this method. The ratio of the number of first crystal grains 800 in a 0.1 mm × 0.2 mm rectangular frame to the total number of crystal grains in the 0.1 mm × 0.2 mm rectangular frame is greater than 50%. This means that the number of first crystal grains 800 in the first cross section and the total number of crystal grains in the first cross section are both greater than 50%, and thus the number of first crystal grains 800 in the first region 1111 and the total number of crystal grains in the first region 1111 are both greater than 50%.

[0307] For example, please refer to Figure 9. The first size is D3, the second size is D4, and 0.2 ≤ D3 / D4 ≤ 5.

[0308] For example, the ratio of the first size to the second size may be any single point value or a range value between any two of the following: 0.2, 0.3, 0.5, 0.8, 1, 2, 2.5, 3, 3.5, 4, 5, etc.

[0309] In the embodiments of this application, the ratio of the first size to the second size is in the range of 0.2 to 5, the size of the first crystal grain 800 stretched in the first direction Z is close to the maximum size of the first crystal grain 800 in the second direction Y, the structure of the first crystal grain 800 in the first direction Z and the second direction Y is relatively uniform, which is advantageous for improving toughness, and the ratio of the number of first crystal grains 800 in the first region 1111 to the number of crystal grains in the first region 1111 is greater than 50%, thereby allowing the first region 1111 to have relatively good toughness to release the expansion force of the electrode assembly 2 and reduce the possibility of cracking of the first connection 51.

[0310] To make it easier to understand, the specific metallic structure of the first region 1111 is not limited; it is sufficient that the hardness of the first region 1111 is lower than the hardness of the second region 1112.

[0311] For some examples, please refer to Figure 9. The ratio of the first size to the second size is in the range of 0.25 to 4.

[0312] For example, the ratio of the first size to the second size may be any one point value or a range value between any two of the following: 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.

[0313] In the embodiments of this application, the ratio of the first size to the second size is in the range of 0.25 to 4. Therefore, the size of the first crystal grain 800 stretched in the first direction Z is relatively close to the maximum size in the second direction Y. Since such first crystal grains 800 are advantageous for improving toughness, the toughness of the first region 1111, where the number of first crystal grains 800 occupies a relatively large proportion, is relatively high.

[0314] To ensure clarity, the range of the ratio between the first and second sizes is not limited to 0.25 to 4. For example, the range of the ratio between the first and second sizes may be greater than 4 and less than or equal to 5.

[0315] For some examples, please refer to Figure 9. The first size range is 5 μm to 500 μm, and the second size range is 5 μm to 500 μm.

[0316] For example, please refer to Figure 9. The first size is D3, and 5μm ≤ D3 ≤ 500μm.

[0317] For example, the first size may be any one point value or a range value between any two of the following: 5 μm, 10 μm, 20 μm, 30 μm, 40 μm, 55 μm, 100 μm, 200 μm, 300 μm, 400 μm, 500 μm, etc.

[0318] For example, please refer to Figure 9. The second size is D4, where 5μm ≤ D4 ≤ 500μm.

[0319] For example, the first size may be any one point value or a range value between any two of the following: 5 μm, 10 μm, 20 μm, 30 μm, 40 μm, 55 μm, 100 μm, 200 μm, 300 μm, 400 μm, 500 μm, etc.

[0320] In the embodiments of this application, the range of the first size is substantially close to the range of the second size, and accordingly the first size is relatively close to the second size, and the corresponding first crystal grains 800 are advantageous in improving toughness, so the first region 1111, in which the number occupancy rate of the first crystal grains 800 is relatively large, has relatively good toughness, releases the expansion force of the electrode assembly 2, and reduces the possibility of cracking of the first connection portion 51.

[0321] To make it easier to understand, the ranges of the first size and the second size are not limited; the ratio between the first size and the second size simply needs to be within the range of the corresponding ratio.

[0322] For some embodiments, please refer to Figure 9. At least a portion of the crystal grains in the second region 1112 are second crystal grains 802, the ratio of the number of second crystal grains 802 in the second region 1112 to the total number of crystal grains in the second region 1112 is greater than 50%, the size of the second crystal grains 802 stretched along the first direction Z is the third size, the maximum size of the second crystal grains 802 along the second direction Y is the fourth size, and the ratio of the third size to the fourth size is in the range of 4 to 100.

[0323] For example, please refer to Figures 4 to 6, and Figures 9 and 14. The cross-section of the first side wall portion 111 shown in the figures is a predetermined cross-section, which is substantially parallel to the first direction Z and the second direction Y, respectively. The predetermined cross-section intersects with the second region 1112 to form a second cross-section.

[0324] For example, the second crystal grain 802 is a band-shaped crystal grain.

[0325] The step of measuring the crystal grains in the second region includes sample cutting, sample processing, and crystal grain measurement.

[0326] The sample cutting step specifically includes the following:

[0327] An end cover 12 is connected to the first end of the casing 11 along the first direction Z, and the second end of the casing 11 along the first direction Z is positioned opposite the first end of the casing 11. The casing 11 is separated along the circumferential direction of the casing 11 at a position 30 mm from the second end of the casing 11 along the first direction Z, the electrode assembly 2 and electrolyte inside the casing 11 are separated from the casing 11, the casing 11 with the first end attached after being cut is cleaned, and the casing 11 after being cleaned The side wall is restored to a flat state, and the first end of the casing 11, whose side wall has been restored to a flat state, is positioned downward along the first direction Z so that the end cover 12 at the first end is located below the casing 11. Transparent resin is injected into the space enclosed by the casing 11 and the lower end cover 12 of the casing 11 so that the height of the transparent resin in the space enclosed by the end cover 12 and the casing 11 is equal to or greater than a predetermined height, which is half the height of the casing 11 with the first end attached after it has been cut. The first side wall portion 111 of the casing 11 into which the transparent resin has been poured is cut to obtain the necessary sample for measurement, the cutting plane of the casing 11 is approximately perpendicular to the reference plane, the reference plane is parallel to the first direction Z and the second direction Y, for example, the angle between the cutting plane of the casing 11 and the reference plane is 80 ° ~95 ° Therefore, cut from the top of the casing 11 containing the transparent resin downwards to the end cover 12 at the bottom of the casing 11 containing the transparent resin.

[0328] Sample preparation specifically includes the following:

[0329] After obtaining the necessary sample for measurement by cutting the first side wall portion 111 of the casing 11 containing transparent resin, the cross-section of the sample for measurement that is approximately parallel to the first direction Z and the second direction Y is a predetermined cross-section of the first side wall portion 111. The predetermined cross-section is polished with a file, the mesh count of the file used to polish the predetermined cross-section is 1600 mesh or more. The predetermined cross-section after polishing is cleaned and corroded to obtain a sample to be measured that can be observed with an optical microscope, and the sample to be measured after corrosion is placed under an optical microscope to observe the predetermined cross-section of the sample to be measured.

[0330] An optical microscope, model BX53M, manufactured by Olympus, may be used to measure the crystal grains in a predetermined cross-section. The measurement position is determined by first selecting a rough measurement area with a relatively low magnification of the optical microscope, and then observing the selected rough measurement area by increasing the magnification of the optical microscope. As can be seen, the occupancy rate of the first crystal grain 800 in the first region 1111 is greater than 50%, and the occupancy rate of the second crystal grain 802 in the second region 1112 is also greater than 50%, so the difference in crystal grains between the two regions is relatively clear, and the rough area to be measured can be identified by the crystal grains observed with the optical microscope.

[0331] The relevant software from Olympus allows for the measurement of crystal grains displayed on the optical microscope model BX53M; for example, software Capture 2.2.1 can be used.

[0332] The steps for grain measurement specifically include the following:

[0333] The software Capture2.2.1 displays and measures crystal grains in an optical microscope with model number BX53M. A rectangular frame of 5 mm × 0.3 mm is drawn within the second region 1112. The side of this rectangular frame with a side length of 0.3 mm is parallel to the second direction Y. Crystal grains that are completely within the rectangular frame and crystal grains that intersect the side of the rectangular frame all belong to the crystal grains within this rectangular frame.

[0334] The size of each crystal grain stretched along the first direction Z within this 5mm x 0.3mm rectangular frame is measured. Specifically, each crystal grain within this rectangular frame is projected along the second direction Y to obtain a projection line stretching along the corresponding first direction Z, and the size of this projection line stretched along the first direction Z corresponds to the size of the crystal grain stretched along the first direction Z. The size of each crystal grain stretched along the first direction is the size at the system scale corresponding to the software Capture2.2.1, i.e., the actual size when not magnified by the optical microscope, and this size value does not change with changes in the magnification of the optical microscope.

[0335] What needs to be explained is that a 5mm x 0.3mm rectangular frame means that two sides facing each other along the first direction Z of the rectangular frame have a side length of 0.3mm, and two sides with a side length of 0.3mm are parallel to the second direction Y, and the side length of two sides facing each other along the second direction Y of the rectangular frame has a side length of 5mm. The size of the rectangular frame is the size at the system scale corresponding to the software Capture 2.2.1, that is, the actual size when not magnified by the optical microscope, and this size value does not change with changes in the magnification of the optical microscope.

[0336] The maximum size of each crystal grain along the second direction Y within this 5mm x 0.3mm rectangular frame is measured. Specifically, multiple cutting lines parallel to the second direction Y are drawn corresponding to each crystal grain, and the distance between two cutting points aligned along the second direction Y, formed when these cutting lines intersect the corresponding crystal grain, is the intercept of the cutting line in the corresponding crystal grain. Of the intercepts of the multiple cutting lines parallel to the second direction Y corresponding to each crystal grain, the largest intercept is the maximum size of that crystal grain along the second direction Y. The maximum size of each crystal grain along the second direction Y is the size at the system scale corresponding to the software Capture2.2.1, i.e., the actual size when not magnified by the optical microscope, and this size value does not change with changes in the magnification of the optical microscope.

[0337] Crystal grains are screened based on the size of each crystal grain stretched along the first direction Z and the maximum size of each crystal grain along the second direction Y within this 5mm × 0.3mm rectangular frame. If the ratio of the size of each crystal grain stretched along the first direction Z to the maximum size along the second direction Y within the 5mm × 0.3mm rectangular frame is within the range of 4 to 100, then this crystal grain is the second crystal grain 802. The second crystal grain 802 within the 5mm × 0.3mm rectangular frame is screened using this method. The ratio of the number of second crystal grains 802 within the 5mm × 0.3mm rectangular frame to the total number of crystal grains within the 5mm × 0.3mm rectangular frame is greater than 50%, meaning that the number of second crystal grains 802 within the second cross section and the total number of crystal grains within the second cross section are both greater than 50%. This determines that the number of second crystal grains 802 within the second region 1112 and the total number of crystal grains within the second region 1112 are both greater than 50%.

[0338] For example, please refer to Figure 9. The third size is D5, the fourth size is D6, and 4 ≤ D5 / D6 ≤ 100.

[0339] For example, the ratio of the third size to the fourth size may be any one point value or a range value between any two of the following: 4, 5, 6, 10, 30, 40, 50, 60, 70, 80, 90, 100, etc.

[0340] In the embodiments of this application, the ratio of the third size to the fourth size is in the range of 4 to 100, and the size of the second crystal grain 802 stretched in the first direction Z is to a certain extent larger than the maximum size of the second crystal grain 802 in the second direction Y, which is advantageous for reducing toughness, and the ratio of the number of second crystal grains 802 in the second region 1112 to the number of crystal grains in the second region 1112 is greater than 50%, thereby the toughness of the second region 1112 is relatively low, which is advantageous for reducing cracking of the second region 1112 itself due to the action of the expansion force of the electrode assembly 2.

[0341] To make it easier to understand, the metallic structure of the second region 1112 is not limited; it is sufficient that the hardness of the first region 1111 is lower than the hardness of the second region 1112.

[0342] For some examples, please refer to Figure 9. The ratio of the third size to the fourth size ranges from 4 to 50.

[0343] For example, the ratio of the third size to the fourth size may be any one point value or a range value between any two of the following: 4, 5, 6, 7, 8, 10, 15, 20, 25, 30, 35, 40, 45, 50, etc.

[0344] In the embodiments of this application, the ratio of the third size to the fourth size is in the range of 4 to 50. As a result, the maximum size deviation of the second crystal grain 802 in the first direction Z and the second direction Y is relatively large. Such second crystal grains 802 have reduced toughness, and the toughness of the second region, where the number of second crystal grains occupies a relatively large proportion, is relatively low. This is advantageous in reducing the cracking of the second region 1112 itself due to the action of the expansion force of the electrode assembly 2.

[0345] To ensure clarity, the range of the ratio between the third and fourth sizes is not limited to 4-50. For example, the ratio between the third and fourth sizes may be greater than 50, or greater than 100.

[0346] For some examples, please refer to Figure 9. The third size range is 150 μm to 1000 μm, and the fourth size range is 5 μm to 120 μm.

[0347] For example, please refer to Figure 9. The third size is D5, where 150 μm ≤ D5 ≤ 1000 μm.

[0348] For example, please refer to Figure 9. The third size may be any one point value or a range value between any two of the following: 150 μm, 170 μm, 200 μm, 300 μm, 400 μm, 500 μm, 600 μm, 700 μm, 800 μm, 900 μm, 950 μm, 1000 μm, etc.

[0349] For example, please refer to Figure 9. The fourth size is D6, where 5μm ≤ D6 ≤ 120μm.

[0350] For example, please refer to Figure 9. The fourth size may be any one point value or a range value between any two of the following: 5 μm, 10 μm, 15 μm, 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm, 110 μm, 120 μm, etc.

[0351] In the embodiments of this application, the lower limit of the size range of the third size, 150 μm, is greater than the upper limit of the fourth size, 120 μm. The maximum size deviation of the second crystal grain 802 in the first direction Z and the second direction Y is relatively large. The second crystal grain 802 in the corresponding size range is advantageous for reducing toughness. Therefore, the toughness of the second region, where the number of second crystal grains occupies a relatively large proportion, is relatively low, which is advantageous for reducing cracking of the second region 1112 itself due to the action of the expansion force of the electrode assembly 2.

[0352] To make it easier to understand, the ranges of the third and fourth sizes are not limited; the ratio between the third and fourth sizes simply needs to fall within the range of the corresponding ratio.

[0353] For some embodiments, please refer to Figure 9. At least a portion of the crystal grains in the first region 1111 are first crystal grains 800, the ratio of the number of first crystal grains 800 in the first region 1111 to the total number of crystal grains in the first region 1111 is greater than 50%, the size of the first crystal grains 800 stretched along the first direction Z is the first size, the maximum size of the first crystal grains 800 along the second direction Y is the second size, and the ratio of the first size to the second size is in the range of 0.2 to 5. At least a portion of the crystal grains within the second region 1112 are second crystal grains 802, the ratio of the number of second crystal grains 802 in the second region 1112 to the total number of crystal grains in the second region 1112 is greater than 50%, the size of the second crystal grains 802 stretched along the first direction Z is the third size, the maximum size of the second crystal grains 802 along the second direction Y is the fourth size, and the ratio of the third size to the fourth size is in the range of 4 to 100. Here, the third size is greater than the first size.

[0354] In the embodiments of this application, the third size of the second crystal grain 802 is larger than the first size of the first crystal grain 800, and the maximum size of the second crystal grain 802 in the first direction Z is larger than the maximum size of the first crystal grain 800 in the first direction Z. Therefore, the number of first crystal grains 800 along the first direction Z for the same size is greater than the number of second crystal grains 802, the occupancy rate of the number of first crystal grains 800 in the first region 1111 is greater than 50%, and the occupancy rate of the number of second crystal grains 802 in the second region 1112 is greater than 50%. Because the prevalence is greater than 50%, there are more first crystal grains 800 in the first region 1111 and more second crystal grains 802 in the second region 1112, and in approximately the same size along the first direction, the first region 1111 may have more crystal grains to share the expansion force, thereby the first region 1111 adjacent to the first connection 51 has relatively good toughness and releases the expansion force of the electrode assembly 2, thereby reducing the possibility of cracking of the first connection 51.

[0355] For some examples, please refer to Figure 9. The ratio of the third size to the first size ranges from 1.5 to 150.

[0356] For example, please refer to Figure 9. The third size is D5, the first size is D3, and 1.5 ≤ D3 / D5 ≤ 150.

[0357] For example, please refer to Figure 9. The ratio of the third size to the first size may be any one point value or a range value between any two of the following: 1.5, 2, 2.5, 3, 4, 5, 5.5, 6, 7, 8, 9, 10, 20, 40, 50, 70, 90, 120, 130, 150, etc.

[0358] In the embodiments of this application, the ratio of the third size to the first size is within a relatively appropriate range, so the toughness of the first region 1111 is more appropriate than that of the second region, which is advantageous in suppressing cracking of the first region 1111 itself when the possibility of cracking of the first connection portion 51 is reduced.

[0359] For some examples, please refer to Figure 9. The ratio of the third size to the first size ranges from 1.8 to 100.

[0360] For some examples, please refer to Figure 9. The first size range is 5 μm to 500 μm, and the third size range is 150 μm to 1000 μm.

[0361] In some examples, the hardness of the first region 1111 is lower than the hardness of the first connection portion 51.

[0362] What needs to be explained is that the hardness of the first region 1111 is lower than that of the second region 1112, and the toughness of the first region 1111 is better than that of the second region 1112. In the process of cycle charging and discharging of the battery cell 10, the electrode assembly 2 repeatedly expands and contracts, generating periodic expansion forces acting on the first sidewall portion 111. As a result, the first sidewall portion 1111 releases the expansion forces by undergoing periodic deformation mainly in the first region 1111, which has relatively high toughness, and there is a risk of fatigue cracking of the first region 1111 itself, which has relatively high toughness.

[0363] In light of this point, please refer to Figures 6 and 14 for some embodiments. The maximum thickness of the first region 1111 is greater than the minimum thickness of the second region 1112.

[0364] The maximum thickness of the first region 1111 is the maximum size along the second direction Y of the first region 1111. The minimum thickness of the second region 1112 is the minimum size along the second direction Y of the first region 1111.

[0365] For example, the first region 1111 may have a uniform thickness structure or a unequal thickness structure.

[0366] For example, the second region 1112 may have a uniform thickness structure or a unequal thickness structure.

[0367] In the embodiments of this application, 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, which has relatively high toughness, is thicker than at least a portion of the second region 1112, which has relatively low toughness, and the first region 1111, which has relatively high toughness, is reinforced in the portion with a corresponding relatively large thickness, thereby suppressing to a certain extent the possibility of fatigue cracking of the first region 1111 itself.

[0368] To ensure understanding, the relationship between the thickness of the first region 1111 and the thickness of the second region 1112 is not limited. For example, the maximum thickness of the first region 1111 may be less than or equal to the minimum thickness of the second region 1112, or the minimum thickness of the first region 1111 may be greater than the maximum thickness of the second region 1112. For example, the thickness at some locations in the first region 1111 may be greater than the thickness at some locations in the second region 1112, and the thickness at some locations in the first region 1111 may be less than the thickness at some locations in the second region 1112. For example, the thickness of the first region 1111 and the thickness of the second region 1112 may be equal, and the first region 1111 and the second region 1112 have an equal-thickness structure.

[0369] In one embodiment, please refer to Figures 6, 8, and 14. The first side wall portion 111 has a first inner surface 804 and a second inner surface 805 facing the electrode assembly 2, and a first outer surface 806 and a second outer surface 807 away from the electrode assembly 2, wherein the first inner surface 804 and the second inner surface 805 are connected in order along the direction of the end cover 12 toward the electrode assembly 2, and the first outer surface 806 and the second outer surface 807 are connected in order along the direction of the end cover 12 toward 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, and 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.

[0370] For example, please refer to Figures 29 and 30. The first inner surface 804 and the second inner surface 805 may be located within the same plane.

[0371] For example, see Figures 6, 14-16, and 18, 19, 22, 23, and 26. The first inner surface 804 may be closer to the electrode assembly 2 than the second inner surface 805 along the second direction Y.

[0372] For example, please refer to Figures 6, 14-16, and 18, 19, 22, 23, and 26. The first outer surface 806 and the second outer surface 807 may lie within a single plane.

[0373] For example, see Figures 29 and 30. The first outer surface 806 may be further away from the electrode assembly 2 than the second outer surface 807 along the second direction Y.

[0374] For example, see Figures 29 and 30. When the first inner surface 804 and the second inner surface 805 are in the same plane, the first outer surface 806 may be further away from the electrode assembly 2 than the second outer surface 807 along the second direction Y.

[0375] For example, see Figures 6, 14-16, and 18, 19, 22, 23, and 26. When the first outer surface 806 and the second outer surface 807 are in the same plane, the first inner surface 804 may be closer to the electrode assembly 2 than the second inner surface 805 along the second direction Y.

[0376] For example, the first outer surface 806 may be further away from the electrode assembly 2 than the second outer surface 807 along the second direction Y. The first inner surface 804 may be closer to the electrode assembly 2 than the second inner surface 805 along the second direction Y.

[0377] For example, the distance from each position on the first inner surface 804 to the first outer surface 806 may be equal, that is, the region between the first inner surface 804 and the first outer surface 806 has a uniform thickness structure.

[0378] For example, the distances from each position on the first inner surface 804 to the first outer surface 806 do not have to be equal; that is, the region between the first inner surface 804 and the first outer surface 806 may have an uneven thickness structure.

[0379] For example, the distance from each position on the second inner surface 805 to the second outer surface 807 may be equal, that is, the region between the second inner surface 805 and the second outer surface 807 has a uniform thickness structure.

[0380] For example, the distances from each position on the second inner surface 805 to the second outer surface 807 do not have to be equal; that is, the region between the second inner surface 805 and the second outer surface 807 may have an uneven thickness structure.

[0381] In the embodiments of this application, the first inner surface 804 and the first outer surface 806 are formed at least partially on the first region 1111, and the second inner surface 805 and the second outer surface 807 are formed at least partially on the second region 1112, and the relatively large thickness portions corresponding to the first inner surface 804 and the first outer surface 806 relatively suitably reinforce the first region 1111, which is advantageous in reducing the possibility of fatigue cracking occurring in the first region 1111 itself.

[0382] To ensure understanding, the relationship between the first inner surface 804, the second inner surface 805, and the first outer surface 806 and the second outer surface 807 is not limited. For 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.

[0383] For 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 in sequence along the direction toward the electrode assembly 2 of the end cover 12, wherein the first sub-surface 11111 is at least partially formed in the first region 1111, and along the second direction Y, the first sub-surface 11111 is closer to the electrode assembly 2 than the second sub-surface 11112, and the distance along the second direction Y between the first sub-surface 11111 and the first outer surface 806 is greater than the distance along the second direction Y between the second sub-surface 11112 and the first outer surface 806.

[0384] The distance along the second direction Y between the first sub-surface 11111 and the first outer surface 806 is greater than the distance along the second direction Y between the second sub-surface 11112 and the first outer surface 806. The region along the second direction Y between the first sub-surface 11111 and the first outer surface 806 is thicker, while the region along the second direction Y between the second sub-surface 11112 and the first outer surface 806 is relatively thin.

[0385] The first sub-surface 11111 transitions to the second inner surface 805 via the second sub-surface 11112.

[0386] For example, the distance from each position on the first sub-surface 11111 to the first outer surface 806 may be equal, and the region between the first sub-surface 11111 and the first outer surface 806 has a uniform thickness structure.

[0387] For example, the distances from each position on the first sub-surface 11111 to the second outer surface 807 do not have to be equal, and the region between the first sub-surface 11111 and the first outer surface 806 has a non-uniform thickness structure.

[0388] For example, the distance from each position on the second sub-surface 11112 to the second outer surface 807 may be equal, and the region between the second sub-surface 11112 and the second outer surface 807 has a uniform thickness structure.

[0389] For example, the distances from each position on the second sub-surface 11112 to the second outer surface 807 do not have to be equal, and the region between the second sub-surface 11112 and the second outer surface 807 has a non-uniform thickness structure.

[0390] For example, the minimum distance along the second direction Y between the first sub-surface 11111 and the first outer surface 806 may be greater than the maximum distance along the second direction Y between the second sub-surface 11112 and the first outer surface 806.

[0391] In the embodiments of this application, the distance along the second direction Y between the first subsurface 11111 and the first outer surface 806 is relatively large, and the corresponding thickness is relatively thick. Therefore, the first subsurface 11111 is formed at least partially on the first region 1111, thereby increasing the thickness of the first region 1111, which is advantageous for reinforcing the first region 1111 and thus suppressing fatigue cracking of the first region 1111 itself.

[0392] To ensure understanding, the relationship between the first subsurface, the second subsurface, and the first outer surface 806 is not limited. For example, the distance between the first subsurface 11111 and the first outer surface 806 along the second direction Y may be less than or equal to the distance between the second subsurface 11112 and the first outer surface 806.

[0393] For some embodiments, please refer to Figure 14. The distance along the second direction Y between the second subsurface 11112 and the first outer surface 806 is a first predetermined thickness, and the first predetermined thickness tends to decrease along the direction of the end cover 12 toward the electrode assembly 2.

[0394] What needs to be explained is that the direction of the end cover 12 toward the electrode assembly 2 coincides with the direction of the first sub-surface 11111 toward the second sub-surface 11112 along the first direction Z.

[0395] For example, see Figure 14. The distances between each position on the second sub-surface 11112 and the second outer surface 807 are not equal, the first predetermined thickness tends to decrease along the direction of the end cover 12 toward the electrode assembly 2, and the second sub-surface 11112 may be a slope.

[0396] For example, see Figure 14. The distance between each position on the first sub-surface 11111 and the first outer surface 806 is equal, and the distance between the second inner surface 805 and the second outer surface 807 is 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 located in the same plane. The first sub-surface 11111 is closer to the electrode assembly 2 than the second sub-surface 11112 along the second direction Y, the second sub-surface 11112 is closer to the electrode assembly 2 than the second inner surface 805 along the second direction Y, and the second sub-surface 11112 is connected to the first sub-surface 11111 and the second inner surface 805, respectively.

[0397] In the embodiments of this application, the first predetermined thickness tends to decrease along the direction of the end cover 12 toward the electrode assembly 2. On the other hand, the transition between the first sub-surface and the second inner surface 805 can be relatively gradual, reducing the influence of the second sub-surface 11112 on the electrode assembly 2 and reducing the possibility of interference between the second sub-surface 11112 and the electrode assembly 2. On the other hand, the reinforcing effect in the portion of the first sidewall portion 111 corresponding to the second sub-surface 11112 tends to increase along the direction of the electrode assembly 2 toward the end cover 12. Therefore, the portion of the second sub-surface 11112 of the first sidewall portion 111 adjacent to the first sub-surface 11111 has a relatively good reinforcing effect, reducing the possibility of fatigue cracking of the first region 1111. In addition, the transition between the first sub-surface and the second inner surface 805 can be relatively gradual, which is advantageous in reducing stress concentration.

[0398] To ensure understanding, the embodiments of this application are not limited to the first predetermined thickness tending to decrease along the direction of the end cover 12 toward the electrode assembly 2. For example, the first predetermined thickness does not have to change along the direction of the end cover 12 toward the electrode assembly 2.

[0399] For some embodiments, please refer to Figure 14. The first sub-surface 11111 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.

[0400] The provision of the first sub-surface 11111 spanning the first region 1111 and the second region 1112 means that the first sub-surface 11111 is partially formed in the first region 1111 and the first sub-surface 11111 is partially formed in the second region 1112.

[0401] The provision of 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 the first outer surface 806 is partially formed in the second region 1112.

[0402] In the embodiments of this application, 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. Therefore, the first sidewall portion 111 is relatively thick in the portion corresponding to the first sub-surface 11111, and the first sub-surface 11111 spans the first region 1111 and the second region 1112. This is advantageous in reinforcing the boundary between the first region 1111 and the second region 1112, which have different toughnesses, and in suppressing cracking at the boundary between the first region 1111 and the second region 1112, which have different toughnesses.

[0403] In some embodiments, the second sub-surface 11112 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.

[0404] The provision of the second sub-surface 11112 spanning the first region 1111 and the second region 1112 means that the second sub-surface 11112 is partially formed in the first region 1111, and the second sub-surface 11112 is partially formed in the second region 1112.

[0405] The provision of 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 the first outer surface 806 is partially formed in the second region 1112.

[0406] In the embodiments of this application, 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. Therefore, 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 both the first region 1111 and the second region 1112. This allows the relatively thick portion of the first sidewall portion 111 to span both the first region 1111 and the second region 1112, which is advantageous for reinforcing the boundary between the first region 1111 and the second region 1112, which have different toughnesses, and for suppressing cracking at the boundary between the first region 1111 and the second region 1112, which have different toughnesses.

[0407] To ensure clarity, the relationships between the first sub-surface 11111, the second sub-surface 11112, and the first region 1111 and the second region 1112 in the embodiments of this application are not limited. For example, both the first sub-surface 11111 and the second sub-surface 11112 may be located within the first region 1111.

[0408] For some embodiments, please refer to Figures 6, 8, 14, 17, 20, 21, 24, 25, 26, 29, and 30. 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.

[0409] The provision of 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.

[0410] The provision of 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 the first outer surface 806 is partially formed in the second region 1112.

[0411] For example, the first sub-surface 11111 is located in the first region 1111, the second sub-surface 11112 is located in the second region 1112, and the boundary between the first sub-surface 11111 and the second sub-surface 11112 is exactly at the boundary between the first region 1111 and the second region 1112.

[0412] For example, the first sub-surface 11111 is partially formed in the first region 1111, and the first sub-surface 11111 is partially formed in the second region 1112. The second sub-surface 11112 is located in the second region 1112.

[0413] For example, the second sub-surface 11112 is partially formed in the first region 1111, and the second sub-surface 11112 is partially formed in the second region 1112. The first sub-surface 11111 is located in the first region 1111.

[0414] In the embodiments of this application, 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. Therefore, 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 relatively thick portion of the first sidewall portion 111 to span the first region 1111 and the second region 1112, which is advantageous for reinforcing the boundary between the first region 1111 and the second region 1112, which have different toughnesses, and for suppressing cracking at the boundary between the first region 1111 and the second region 1112, which have different toughnesses.

[0415] To ensure understanding, the relationship between the first inner surface 804, the first outer surface 806, and the first region 1111 and the second region 1112 is not limited. For example, both the first inner surface 804 and the first outer surface 806 are located in the first region 1111, both the second inner surface 805 and the second outer surface 807 are 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.

[0416] For some embodiments, please refer to Figures 7, 15, 16, 18, 19, 22, and 23. The size of the first inner surface 804 along the third direction X is greater than the size of the first inner surface 804 along the first direction Z, and the first direction Z, the second direction Y, and the third direction X are not located on the same plane and intersect in pairs.

[0417] The size of the first inner surface 804 along the third direction X is the length of the first inner surface 804, and the size 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, and as a result, the portion of the first side wall 111 between the first inner surface 804 and the first outer surface 806 has an elongated structure that extends along the third direction X.

[0418] For example, the casing 11 is rectangular parallelepiped and includes two first sidewalls 111 and two second sidewalls 112, the two first sidewalls 111 being positioned opposite each other along a second direction Y, and the two second sidewalls 112 being positioned opposite each other along a third direction X, the first direction Z, the second direction Y, and the third direction X being perpendicular in pairs, the first direction Z being parallel to the height direction of the casing 11, the second direction Y being parallel to the width direction of the casing 11, and the third direction X being parallel to the longitudinal direction of the casing 11.

[0419] For example, see Figures 38 and 39. The first region 1111 extends along the third direction X to the opposing ends of the first side wall portion 111.

[0420] In this embodiment, the size of the first inner surface 804 along the third direction X is larger than the size of the first inner surface 804 along the first direction Z, and as a result the size of the first inner surface 804 along the third direction X is larger, a larger area of ​​the first side wall portion 111 along the third direction X is reinforced by the relatively thick portion corresponding to the first inner surface 804, which is advantageous in preventing cracking of the casing 11.

[0421] To ensure clarity, the size 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 is not specifically limited. For example, the size of the first inner surface 804 along the third direction X may be less than or equal to the size of the first inner surface 804 along the first direction Z.

[0422] For some embodiments, please refer to Figures 15 to 25. Along the second direction Y, the overlapping projection of the first inner surface 804 and the projection of the first region 1111 is the first projection, and 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, and the first direction Z, the second direction Y, and the third direction X do not lie on the same plane and intersect in pairs.

[0423] The position corresponding to the first projection is precisely the position reinforced by the thickened portion corresponding to the first inner surface 804 of the first region 1111.

[0424] For example, the first direction Z, the second direction Y, and the third direction X are perpendicular to each other.

[0425] In the embodiments of this application, the size along the third direction X of the first projection is larger than the size along the first direction Z of the first projection. Therefore, the portion reinforcing the first region 1111 corresponding to the first inner surface 804 is relatively large in the third direction X, and as a result, the first region 1111, which has relatively high toughness, is reinforced over a larger area along the third direction X, further reducing the possibility of fatigue cracking of the first region 1111 itself.

[0426] To ensure understanding, the size relationship between the size of the first projection along the third direction X and the size of the first projection along the first direction Z is not limited. For 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.

[0427] For some embodiments, please refer to Figures 15 to 25. The first inner surface 804 includes a first connecting surface 11113, the first connecting surface 11113 passing through the middle section of the first side wall 111, the middle section being perpendicular to the third direction X, and the distance of the middle section to both ends of the first side wall 111 being equal along the third direction X.

[0428] The first connecting surface 11113 may be a part of the first inner surface 804, or it may be the first inner surface 804. The distance between each position on the first connecting surface 11113 and the first outer surface 806 may be equal or unequal. The first connecting surface 11113 has opposing ends along the third direction X, and the first connecting surface 11113 passes through the middle section of the first side wall 111, so that the middle section of the first side wall 111 is located between the opposing ends of the first connecting surface 11113 along the third direction X. The distance from the opposing ends of the first connecting surface 11113 along the third direction X to the middle section may be equal or unequal. If the distance from the opposing ends of the first connecting surface 11113 along the third direction X to the middle section of the first side wall 111 is equal, the first connecting surface 11113 may be a symmetrical structure installed symmetrically with respect to the middle section of the first side wall 111. It should be explained that the intermediate cross-section of the first side wall portion 111 is a virtual plane and is not shown in the diagram.

[0429] For example, please refer to Figures 15 to 17. The first connecting surface 11113 is the first inner surface 804, the distance between each position on the first connecting surface 11113 and the first outer surface 806 is equal, and the distance from both opposing ends of the first connecting surface 11113 along the third direction X to the middle section of the first side wall portion 111 is equal.

[0430] Taking the case where the casing 11 is rectangular parallelepiped, the distance from the middle cross-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 middle cross-section of the first side wall portion 111 to the two second side wall portions 112 installed opposite each other along the third direction X of the casing 11 is equal.

[0431] What needs to be explained is that, along the third direction X, the distance from the middle section of the first side wall 111 to both ends of the first side wall 111 is approximately equal, and what needs to be understood is that the distance from the middle section to both ends of the first side wall 111 is equal.

[0432] In the embodiments of this application, when the first sidewall portion 111 is subjected to the expansion force of the electrode assembly 2 of the battery cell 10, the influence of the expansion force of the electrode assembly 2 on the intermediate region of the first sidewall portion 111 along the third direction X is relatively large. Since the first connecting surface 11113 passes through the middle cross section of the first sidewall portion 111 and the thickness at the middle cross section of the first sidewall portion 111 is relatively large, the first sidewall portion 111 is reinforced to a certain extent in the middle cross section, which is advantageous in reducing the influence of the expansion force of the electrode assembly 2 on the intermediate region of the first sidewall portion 111 along the third direction X.

[0433] To ensure clarity, the positions of the first connecting surface 11113 and the intermediate section of the first side wall 111 are not limited. For example, the first connecting surface 11113 does not have to pass through the intermediate section. For example, the first connecting surface 11113 is located on one side of the intermediate section of the first side wall 111 along the third direction X.

[0434] For some embodiments, please refer to Figures 16, 17, 19, 20, 21, 23, 24, and 25. The first connecting surface 11113 is formed at least partially on the first region 1111, and the overlapping projection of the projection of the first connecting surface 11113 and the projection of the first region 1111 along the second direction Y is the second projection, and the second projection passes through the middle section of the first side wall 111.

[0435] The first connecting surface 11113 is part of the first inner surface 804, or the first connecting surface 11113 is the first inner surface 804.

[0436] The first connecting surface 11113 is formed at least partially on the first region 1111, and along the second direction Y, the projection of the first connecting surface 11113 at least partially overlaps with the projection of the first region 1111. The position corresponding to the overlapping second projection is where the first side wall portion 111 reinforces the first region 1111 with a relatively thick portion corresponding to the first connecting surface 11113.

[0437] In the embodiments of this application, since the second projection passes through the middle section of the first sidewall portion 111, the first region 1111, which has relatively high toughness, passes through the middle section and can release the expansion force in the middle section of the electrode assembly 2 to a certain extent, which is advantageous in reducing cracking in the middle section of the first sidewall portion 111 of the first connection portion 51. Since the second projection passes through the middle section of the first sidewall portion 111, the relatively thick portion of the first sidewall portion 111 corresponding to the first connection surface 11113 can be at least partially located at the position of the interrupted surface corresponding to the first region 1111, which is advantageous in suppressing fatigue cracking in the middle section of the first side wall of the first region 1111, which has relatively high toughness.

[0438] To ensure clarity, the positional relationship between the second projection and the midsection of the first side wall 111 is not limited. For example, the second projection may be located on one side of the midsection of the first side wall 111 along the third direction X.

[0439] For some embodiments, please refer to Figures 18 to 25. The first inner surface 804 further 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 a third direction X, the first connecting surface 11113 connects the second connecting surface 11114 and the third connecting surface 11115, and 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.

[0440] The first connecting surface 11113 is a segment that passes through the middle section of the first side wall portion 111 in the first inner surface 804, and the second connecting surface 11114 and the third connecting surface 11115 are two segments located at two ends, respectively, along the third direction X of the first inner surface 804. The second connecting surface 11114 may be directly connected to the first connecting surface 11113 or indirectly connected, and the third connecting surface 11115 may be directly connected to the first connecting surface 11113 or indirectly connected.

[0441] The distance between each position on the first connecting surface 11113 and the first outer surface 806 may be equal or unequal. The distance between each position on the second connecting surface 11114 and the first outer surface 806 may be equal or unequal. The distance between each position on the third connecting surface 11115 and the first outer surface 806 may be equal or unequal. If the distance between at least one position on either the first connecting surface 11113 or the second connecting surface 11114 and the first outer surface 806 is not equal, the maximum distance between the second connecting surface 11114 and the first outer surface 806 may be less than or equal to the minimum distance between the first connecting surface 11113 and the first outer surface 806, thereby achieving the condition that the distance between the second connecting surface 11114 and the first outer surface 806 is smaller than the distance between the first connecting surface 11113 and the first outer surface 806. If the distance between at least one position on the third connecting surface 11115 and the first connecting surface 11113 and the first outer surface 806 is 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, thereby achieving the condition that the distance between the third connecting surface 11115 and the first outer surface 806 is smaller than the distance between the first connecting surface 11113 and the first outer surface 806.

[0442] The size of the second connecting surface 11114 along the third direction X may or may not be equal to the size of the third connecting surface 11115 along the third direction X. If the size of the second connecting surface 11114 along the third direction X is equal to the size of the third connecting surface 11115 along the third direction X, the second connecting surface 11114 and the third connecting surface 11115 may be installed symmetrically with respect to the middle cross-section of the first side wall portion 111.

[0443] To make it clear, in embodiments in which 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, which are arranged along the first direction Z.

[0444] The second connection surface 11114 may be partially closer to the electrode assembly 2 than the second inner surface 805 along the second direction Y and / or the first outer surface 806 may be partially further away from the electrode assembly 2 than the second outer surface 807 along the second direction Y, the first connection surface 11113 may be partially closer to the electrode assembly 2 than the second inner surface 805 along the second direction Y and / or the first outer surface 806 may be partially further away from the electrode assembly 2 than the second outer surface 807 along the second direction Y, the third connection surface 11115 may be partially closer to the electrode assembly 2 than the second inner surface 805 along the second direction Y and / or the first outer surface 806 may be partially further away from the electrode assembly 2 than the second outer surface 807 along the second direction Y.

[0445] For example, please refer to Figures 18 to 25. The second connection surface 11114 and the third connection surface 11115 are both directly connected to the first connection surface 11113. The distance between the second connection surface 11114 and the first outer surface 806 gradually decreases along the direction of the third connection surface 11115 toward the second connection surface 11114, and the distance between the third connection surface 11115 and the first outer surface 806 gradually decreases along the direction of the second connection surface 11114 toward the third connection surface 11115. Parts of the second connection surface 11114, part of the first connection surface 11113, and part of the third connection surface 11115 are all closer to the electrode assembly 2 than 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, and the first outer surface 806 is a plane.

[0446] In the embodiments of this application, when the first sidewall portion 111 is subjected to the expansion force of the electrode assembly 2, the electrode assembly 2 expands relatively large in the region of the first sidewall portion 111 that is close to the middle along the third direction X, and expands relatively small in the region of the first sidewall portion 111 that is close to both ends along the third direction X, and the expansion force of the electrode assembly 2 differs between the ends and the middle along the third direction X of the first sidewall portion 111. The distance between the second connecting surface 11114 and the first outer surface 806 and the distance between the third connecting surface 11115 and the first outer surface 806 are both smaller than the distance between the first connecting surface 11113 and the first outer surface 806, the first sidewall portion 111 is reinforced to a relatively large extent in the region of the first sidewall portion 11113 that is close to the middle, and the electrode assembly 2 is subjected to a relatively large expansion force acting on the portion of the first sidewall portion 111 that is close to the middle along the third direction X. This is advantageous because the first side wall portion 111 is reinforced to a certain extent in the regions adjacent to both ends corresponding to the second connection surface 11114 and the third connection surface 11115, and the expansion force acting on the first side wall portion 111 from both ends along the third direction X of the electrode assembly 2 can be carried by it, and the thickness of the first side wall portion 111 in the regions adjacent to both ends corresponding to the second connection surface 11114 and the third connection surface 11115 is relatively small, which is advantageous for reducing costs.

[0447] To ensure understanding, the relationships between the distances between the second connecting surface 11114 and the first outer surface 806, the distance between the third connecting surface 11115 and the first outer surface 806, and the distance between the first connecting surface 11113 and the first outer surface 806 are not limited. For 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.

[0448] For some embodiments, please refer to Figures 20, 21, 24, and 25. The first connecting surface 11113, the second connecting surface 11114, and the third connecting surface 11115 are all formed at least partially on the first region 1111.

[0449] For example, see Figures 20, 21, 24, and 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.

[0450] For example, see Figures 20, 21, 24, and 25. The first connecting surface 11113 spans the first region 1111 and the second region 1112, the second connecting surface 11114 spans the first region 1111 and the second region 1112, and the third connecting surface 11115 spans the first region 1111 and the second region 1112.

[0451] The provision of the first connecting surface 11113 spanning the first region 1111 and the second region 1112 means that the first connecting surface 11113 is partially formed in the first region 1111 and the first connecting surface 11113 is partially formed in the second region 1112.

[0452] The provision of the second connecting surface 11114 spanning the first region 1111 and the second region 1112 means that the second connecting surface 11114 is partially formed in the first region 1111 and the second connecting surface 11114 is partially formed in the second region 1112.

[0453] The provision of the third connecting surface 11115 spanning the first region 1111 and the second region 1112 means that the third connecting surface 11115 is partially formed in the first region 1111 and the third connecting surface 11115 is partially formed in the second region 1112.

[0454] In the embodiments of this application, the portion of the first region 1111 located at the corresponding position of the first connection surface 11113 is advantageous in releasing the expansion force at the first connection surface 11113 of the electrode assembly 2 and reducing cracking at the first connection surface 11113 of the first connection portion 51. The periodic expansion force that the electrode assembly 2 receives from the portion of the first region 1111 located at the corresponding position of the first connection surface 11113 is relatively large, and the second connection surface 11114 The distance between the first outer surface 806 and 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 first sidewall portion 111 to relatively favorably reinforce the first region 1111 with the relatively thick portion of the first connecting surface 11113, which is advantageous in reducing the possibility of fatigue cracking in the portion of the first region 1111 located at the corresponding position of the first connecting surface 11113. The portion of the first region 1111 located at the corresponding position of the second connecting surface 11114 is advantageous in releasing the expansion force at the second connecting surface 11114 of the electrode assembly 2 and reducing cracking at the second connecting surface 11114 of the first connecting portion 51. The portion of the first region 1111 located at the corresponding position of the third connection surface 11115 is advantageous in releasing the expansion force at the third connection surface 11115 of the electrode assembly 2 and reducing cracking at the third connection surface 11115 of the first connection portion 51. Because the periodic expansion force on the first sidewall portion 111 at the corresponding positions of the second connection surface 11114 and the third connection surface 11115 of the electrode assembly 2 is relatively small, the distance between the second connection surface 11114 and the first outer surface 806 and the distance between the third connection surface 11115 and the first outer surface 806 are both smaller than the distance between the first connection surface 11113 and the first outer surface 806. This suppresses fatigue cracking in the portion of the first region 1111 corresponding to the second connection surface 11114 and the portion corresponding to the third connection surface 11115, and also reduces the amount of material used at the positions of the first sidewall corresponding to the second connection surface 11114 and the third connection surface 11115, which is advantageous for saving costs.

[0455] To ensure understanding, the relationship between the first connecting surface 11113, the second connecting surface 11114, the third connecting surface 11115, and the first region 1111 is not limited. For 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 other two may not be formed in the first region 1111. For 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.

[0456] For some embodiments, please refer to Figures 22 to 25. The first inner surface 804 further includes a first transition surface 11116, the first connecting surface 11113, the first transition surface 11116 and the second connecting surface 11114 are arranged along a third direction X, the first transition surface 11116 connects the second connecting surface 11114 and the first connecting surface 11113, the distance along the second direction Y between the first transition surface 11116 and the first outer surface 806 is a second predetermined thickness, the second predetermined thickness tends to increase along the direction of the second connecting surface 11114 toward the first connecting surface 11113, and / Alternatively, the first inner surface 804 further 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 a 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 predetermined thickness, and the third predetermined thickness tends to increase along the direction of the third connecting surface 11115 toward the first connecting surface 11113.

[0457] The distances between each position on the first transition surface 11116 and the first outer surface 806 are not equal. For example, the second predetermined thickness gradually increases along the direction of the second connecting surface 11114 toward the first connecting surface 11113. The distances between each position on the second transition surface 11117 and the first outer surface 806 are not equal. For example, the third predetermined thickness gradually increases along the direction of the third connecting surface 11115 toward the first connecting surface 11113.

[0458] If a first transition surface 11116 is installed between the second connection surface 11114 and the first connection surface 11113, and a second transition surface 11117 is installed between the third connection surface 11115 and the first connection surface 11113, then the size of the first transition surface 11116 along the third direction X may or may not be equal to the size of the second transition surface 11117 along the third direction X. If the size of the first transition surface 11116 along the third direction X is equal to the size of the second transition surface 11117 along the third direction X, then the first transition surface 11116 and the second transition surface 11117 may be installed symmetrically with respect to the middle cross-section of the first side wall portion 111.

[0459] To make it understandable, if a first transition surface 11116 is placed between the second connection surface 11114 and the first connection surface 11113, the first transition surface 11116 may be closer to the electrode assembly 2 than 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 may be further away from the electrode assembly 2 than the second outer surface 807 along the second direction Y. If a second transition surface 11117 is placed between the third connection surface 11115 and the first connection surface 11113, the second transition surface 11117 may be closer to the electrode assembly 2 than 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 may be further away from the electrode assembly 2 than the second outer surface 807 along the second direction Y.

[0460] For example, see Figures 22 to 25. The second connection surface 11114 and the first connection surface 11113 are indirectly connected via the first transition surface 11116, and the third connection surface 11115 and the first connection surface 11113 are indirectly connected via the second transition surface 11117. The second predetermined thickness gradually increases along the direction of the second connection surface 11114 toward the first connection surface 11113, and the third predetermined thickness gradually increases along the direction of the third connection surface 11115 toward the first connection surface 11113. Parts of the second connection surface 11114, part of the first connection surface 11113, part of the third connection surface 11115, part of the first transition surface 11116, and part of the second transition surface 11117 are all closer to the electrode assembly 2 than the second inner surface 805 along the second direction Y. The first transition surface 11116 connects the first connection surface 11113 and the second connection surface 11114, the second transition surface 11117 connects the first connection surface 11113 and the third connection surface 11115, and the first outer surface 806 is a plane.

[0461] In the embodiments of this application, if the second connecting surface 11114 and the first connecting surface 11113 are connected via the first transition surface 11116, and the second predetermined thickness tends to increase along the direction of the second connecting surface 11114 toward the first connecting surface 11113, then the first transition surface 11116 can realize a transition between the second connecting surface 11114 and the first connecting surface 11113, thereby reducing stress concentration. If the third connecting surface 11115 and the first connecting surface 11113 are connected via the second transition surface 11117, and the third predetermined thickness tends to increase along the direction of the third connecting surface 11115 toward the first connecting surface 11113, then the second transition surface 11117 can realize a transition between the third connecting surface 11115 and the first connecting surface 11113, thereby reducing stress concentration.

[0462] For some embodiments, please refer to Figures 24 and 25. The first transition surface 11116 is at least partially formed in the first region 1111 and / or the second transition surface 11117 is at least partially formed in the first region 1111.

[0463] In the embodiments of this application, the portions of the first sidewall portion 111 corresponding to the first transition surface 11116 and the second transition surface 11117 are thicker than the portion of the first sidewall portion 111 corresponding to the second inner surface 805. The relatively thick first transition surface 11116 can reinforce the corresponding first region 1111 and suppress fatigue cracking at the corresponding location in the first region 1111. The relatively thick second transition surface 11117 can reinforce the corresponding first region 1111 and suppress fatigue cracking at the corresponding location in the first region 1111.

[0464] To ensure understanding, the positional relationship between the first transition surface 11116, the second transition surface 11117, and the first region 1111 is not limited. For 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.

[0465] For some embodiments, please refer to Figures 16, 19, and 23. The size of the first connecting surface 11113 along the third direction X is L1, and the size of the first side wall portion 111 along the third direction X is L, where 0.2 ≤ L1 / L ≤ 0.6.

[0466] The size of the first connecting surface 11113 along the third direction X is the length of the first connecting surface 11113, the size of the first side wall portion 111 along the third direction X is the length of the first side wall portion 111, the size of the first side wall portion 111 along the second direction Y is the thickness of the first side wall portion 111, and the size of the first side wall portion 111 along the first direction Z is the width of the first side wall portion 111.

[0467] L1 / L can take any one point value or a range value between any two of the following: 0.2, 0.22, 0.25, 0.28, 0.3, 0.32, 0.35, 0.38, 0.4, 0.42, 0.45, 0.48, 0.5, 0.52, 0.55, 0.58, 0.6, etc.

[0468] In the embodiments of this application, when L1 / L≧0.2, the size occupancy ratio of the first side wall portion 111 of the first connecting surface 11113 along the third direction X is increased, thereby increasing the reinforced area of ​​the intermediate region of the first side wall portion 111 along the third direction X and improving the strength of the intermediate region of the first side wall portion 111 along the third direction X. When L1 / L≦0.6, the size occupancy ratio of the first side wall portion 111 of the first connecting surface 11113 along the third direction X is decreased, thereby reducing the amount of material used in the portion of the first side wall portion 111 corresponding to the first connecting surface 11113 and lowering production costs. Therefore, the ratio of the size of the first connecting surface 11113 along the third direction X to the size of the first side wall portion 111 along the third direction X is set to 0.2 to 0.6, thereby providing the first side wall portion 111 with sufficient reinforcing capacity at the position corresponding to the first connecting surface 11113, while simultaneously reducing the amount of material used at the first connecting surface 11113 of the first side wall portion 111, thus achieving both the requirement for reinforcing capacity and economic efficiency at the first connecting surface 11113 of the first side wall portion 111.

[0469] For some examples, please refer to Figures 16, 19, and 23. The first connecting surface 11113 has a first end 11113a and a second end 11113b facing each other along the third direction X, and the first side wall portion 111 has a third end 1113 and a fourth end 1114 facing each other along the third direction X, the first end 11113a is close to the third end 1113, the second end 11113b is close to the fourth end 1114, the size of the first side wall portion 111 along the third direction X is L, the minimum distance along the third direction X between the first end 11113a and the third end 1113 is L2, the minimum distance along the third direction X between the second end 11113b and the fourth end 1114 is L3, L2 / L ≤ 0.3, and / or L3 / L ≤ 0.3.

[0470] To make it clear, 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.

[0471] L2 = L3 is also acceptable, and L2 > L3 or L2 <L3であってもよい。

[0472] L2 / L can take any one point value or a range value between any two of the following: 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.11, 0.12, 0.13, 0.14, 0.15, 0.16, 0.17, 0.18, 0.19, 0.2, 0.21, 0.22, 0.23, 0.24, 0.25, 0.26, 0.27, 0.28, 0.29, 0.3, etc.

[0473] L3 / L can take any one point value or a range value between any two of the following: 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.11, 0.12, 0.13, 0.14, 0.15, 0.16, 0.17, 0.18, 0.19, 0.2, 0.21, 0.22, 0.23, 0.24, 0.25, 0.26, 0.27, 0.28, 0.29, 0.3, etc.

[0474] In the embodiments of this application, if L2 / L ≤ 0.3, the first sidewall portion 111 is reinforced in a larger area along the third direction X by reducing the occupancy rate of the first sidewall portion 111 in the size along the third direction X at the minimum distance between the first end 11113a and the third end 1113. If L3 / L ≤ 0.3, the first sidewall portion 111 is reinforced in a larger area along the third direction X by reducing the occupancy rate of the first sidewall portion 111 in the size along the third direction X at the minimum distance between the second end 11113b and the fourth end 1114.

[0475] For some embodiments, please refer to Figures 16, 19, and 23. The interval is 100mm ≤ L ≤ 450mm.

[0476] L can take any one point value or a range value between any two of the following: 100mm, 120mm, 150mm, 180mm, 200mm, 220mm, 250mm, 260mm, 280mm, 300mm, 310mm, 320mm, 350mm, 390mm, 400mm, 410mm, 420mm, 430mm, 440mm, 450mm, etc.

[0477] In some embodiments, please refer to Figures 15, 18 and 22. The casing 11 includes corner walls 113, with the corner walls 113 connected to both ends of the first side wall portion 111 along the third direction X. At least one end of the first inner surface 804 along the third direction X does not contact the corner wall 113, or both ends of the first inner surface 804 along the third direction X extend to the two corner walls 113.

[0478] Along the third direction X, the first inner surface 804 has opposing ends, and one end of the first inner surface 804 does not have to extend to one corner wall 113 and the other end to another corner wall 113, and neither end of the first inner surface 804 has to extend to a corner wall 113, thereby ensuring that at least one end of the first inner surface 804 along the third direction X does not come into contact with the corner wall 113.

[0479] For example, see Figures 15 and 16. Along the third direction X, one end of the first inner surface 804 does not contact the corner wall 113 at one end of the first side wall portion 111, and the other end of the first inner surface 804 does not contact the corner wall 113 at the other end of the first side wall portion 111.

[0480] In the embodiments of this application, if at least one end of the first inner surface 804 along the third direction X does not contact the corner wall 113, the amount of material used in the corresponding portion of the first inner surface 804 of the first side wall 111 can be reduced, thereby lowering production costs. If both ends of the first inner surface 804 along the third direction X extend to the two corner walls 113, the length of the first inner surface 804 can be increased, improving the reinforcing capacity of the corresponding portion of the first inner surface 804 of the first side wall 111, thereby reinforcing a larger area of ​​the first side wall 111 along the third direction X.

[0481] In some embodiments, please refer to Figures 26, 27, and 28. The electrode assembly 2 further includes a separator 24, which is placed between the positive electrode plate 22 and the negative electrode plate 23. The positive electrode plate 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 having a positive electrode active material layer 223; the negative electrode plate 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 having 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 cover 12, the negative electrode body region 231 has a sixth end 2311 facing the end cover 12; the separator 24 has a seventh end 241 facing the end cover 12, the seventh end 241 is closer to the end cover 12 than the fifth end 2211 and the sixth end 2311.

[0482] For example, electrode assembly 2 may have a wound structure or a laminated structure.

[0483] The positive electrode plate 22 may include a positive electrode current collector 222 and a positive electrode active material layer 223, wherein the positive electrode active material layer 223 is provided on one or two surfaces of the positive electrode current collector 222 in its thickness direction. See Figures 26, 27, and 28. The positive electrode plate 22 further includes an insulating layer 224, and the insulating layer 224 is provided on both of the two opposing surfaces in the thickness direction of the positive electrode current collector 222. The insulating layer 224 and the positive electrode active material layer 223 are arranged along the first direction Z, and the insulating layer 224 is provided at the end of the positive electrode active material layer 223. The portion of the positive electrode plate 22 corresponding to the entire positive electrode active material layer 223 and insulating layer 224 is the positive electrode body region 221, and the end of the insulating layer 224 adjacent to the end cover 12 forms the fifth end 2211 of the positive electrode body region 221. The portion of the positive electrode current collector 222 protruding from the insulating layer 224 forms the positive electrode tab 21a. See Figures 26, 27, and 28. An insulating layer 224 is not installed on the positive electrode plate 22. The portion of the positive electrode plate 22 corresponding to the positive electrode active material layer 223 is the positive electrode body region 221. The end of the positive electrode active material layer 223 adjacent to the end cover 12 forms the fifth end 2211 of the positive electrode body region 221, and the portion of the positive electrode current collector 222 protruding from the positive electrode active material layer 223 forms the positive electrode tab 21a.

[0484] The negative electrode plate 23 may include a negative electrode current collector 232 and a negative electrode active material layer 233, wherein the negative electrode active material layer 233 is provided on one or two surfaces of the negative electrode current collector 232 in its thickness direction. The portion of the negative electrode plate 23 corresponding to the negative electrode active material layer 233 is the negative electrode body region 231, the end of the negative electrode active material layer 233 adjacent to the end cover 12 forms the sixth end 2311 of the negative electrode body region 231, and the portion of the negative electrode current collector 232 protruding from the negative electrode active material layer 233 forms the negative electrode tab 21b.

[0485] The fifth end 2211 may be flush with the sixth end 2311. See Figures 26, 27, and 28. The fifth end 2211 may be closer to the end cover 12 than the sixth end 2311. See Figures 26, 27, and 28. The sixth end 2311 may be closer to the end cover 12 than the fifth end 2211.

[0486] In the embodiments of this application, the seventh end 241 of the separator 24 is closer to the end cover 12 than the fifth end 2211 of the positive electrode body region 221 and the sixth end 2311 of the negative electrode body region 231, so that the separator 24 has a portion that protrudes more than the fifth end 2211 and the sixth end 2311, reinforcing the insulating effect between the positive electrode plate 22 and the negative electrode plate 23 of the separator 24 and reducing the possibility of contact between the positive electrode plate 22 and the negative electrode plate 23.

[0487] In some embodiments, please refer to Figures 26, 27, and 28. The separator 24 includes a protruding region 242 that extends beyond the fifth end 2211 and the sixth end 2311 along the first direction Z, and in a projection plane perpendicular to the second direction Y, the orthographic projection of the protruding region 242 partially overlaps with the orthographic projection of the first inner surface 804.

[0488] The protruding region 242 is the portion of the separator 24 that protrudes beyond the fifth end 2211 of the positive electrode body region 221 and the sixth end 2311 of the negative electrode body region 231. To make it clear, referring to the figure, in an embodiment where the fifth end 2211 is closer to the end cover 12 than the sixth end 2311, the portion of the separator 24 that protrudes beyond the fifth end 2211 is the protruding region 242. Please refer to the figure. In an embodiment where the sixth end 2311 is closer to the end cover 12 than the fifth end 2211, the portion of the separator 24 that protrudes beyond the sixth end 2311 is the protruding region 242.

[0489] For example, please refer to Figure 11. The portions located in the three flat regions 25 of the electrode assembly 2, namely the positive electrode plate 22, the negative electrode plate 23, and the separator 24, are stacked along the second direction Y.

[0490] In the embodiments of this application, the orthographic projection of the protruding region 242 partially overlaps with the orthographic projection of the first inner surface 804 in a projection plane perpendicular to the second direction Y, and such a structure can increase the size of the first inner surface 804 along the first direction Z, thereby improving the reinforcing capacity of the first sidewall 111 in the corresponding portion of the first inner surface 804, and thus the first sidewall 111 is reinforced over a larger area along the first direction Z.

[0491] For some embodiments, please refer to Figure 26. The first inner surface 804 protrudes from the second inner surface 805. In a projection plane perpendicular to the second direction Y, the orthographic projection of the positive electrode body region 221 does not overlap with the orthographic projection of the first inner surface 804, and / or, in a projection plane perpendicular to the second direction Y, the orthographic projection of the negative electrode body region 231 does not overlap with the orthographic projection of the first inner surface 804.

[0492] The interpretation is 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 than the second inner surface 805 along the second direction Y.

[0493] The first inner surface 804 can extend to the first connecting portion 51, thereby directly connecting the first inner surface 804 to the first connecting portion 51.

[0494] To make it clear, in an embodiment in which the first inner surface 804 includes a first sub-surface 11111 and a second sub-surface 11112 positioned 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 than the second inner surface 805 along a second direction Y. In an embodiment in which the first inner surface 804 includes a second connecting surface 11114 positioned along a third direction X, and a first connecting surface 11113 and a third connecting surface 11115, both the second connecting surface 11114, the first connecting surface 11113 and the third connecting surface 11115 are closer to the electrode assembly 2 than the second inner surface 805 along a second direction Y.

[0495] For example, please refer to Figure 26. In the projection plane perpendicular to the second direction Y, the positive electrode body region 221 does not overlap with the orthographic projection of the first inner surface 804, and the negative electrode body region 231 does not overlap with the orthographic projection of the first inner surface 804.

[0496] In the embodiments of this application, if the orthographic projection of the positive electrode body region 221 does not overlap with the orthographic projection of the first inner surface 804 in a projection plane perpendicular to the second direction Y, the casing 11 can provide a larger expansion space for the electrode assembly 2, reducing the expansion force that the electrode assembly 2 expands and directly applies to the portion of the first sidewall 111 corresponding to the first inner surface 804, thereby reducing the amount of deformation of the first sidewall 111. If the orthographic projection of the negative electrode body region 231 does not overlap with the orthographic projection of the first inner surface 804 in a projection plane perpendicular to the second direction Y, the casing 11 can provide a larger expansion space for the electrode assembly 2, reducing the expansion force that the electrode assembly 2 expands and directly applies to the portion of the first sidewall 111 corresponding to the first inner surface 804, thereby reducing the amount of deformation of the first sidewall 111.

[0497] For some embodiments, please refer to Figures 27 and 28. The negative electrode plate 23 includes a negative electrode current collector 232 and a negative electrode active material layer 233 installed on at least one side of the negative electrode current collector 232, the negative electrode active material layer 233 comprising a negative electrode active material.

[0498] The negative electrode active material layer 233 may be installed on only one side of the negative electrode current collector 232, that is, on only one surface along the thickness direction of the negative electrode current collector 232, or the negative electrode active material layer 233 may be installed on both opposing sides of the negative electrode current collector 232, that is, on both opposing surfaces along the thickness direction of the negative electrode current collector 232.

[0499] The negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicone-based materials, tin-based materials, and lithium titanate.

[0500] In some embodiments, please refer to Figures 27 and 28. The negative electrode active material layer 233 includes a negative electrode body portion 2331 and a negative electrode thinning portion 2332, which are arranged along a first direction Z, and the negative electrode thinning portion 2332 is located at the end of the negative electrode body portion 2331 adjacent to the end cover 12 along the first direction Z.

[0501] The thickness of the negative electrode body portion 2331 is greater than the thickness of the negative electrode thinning portion 2332. The negative electrode thinning portion 2332 may be installed only at the end of the negative electrode body portion 2331 that is close to the end cover 12 along the first direction Z, or the negative electrode thinning portion 2332 may be present at both ends of the negative electrode body portion 2331 along the first direction Z. The negative electrode body portion 2331 may have a uniform thickness structure or a non-uniform thickness structure, and the negative electrode thinning portion 2332 may have a uniform thickness structure or a non-uniform thickness structure. If at least one of the negative electrode body portion 2331 and the negative electrode thinning portion 2332 has a non-uniform thickness structure, the maximum thickness of the negative electrode thinning portion 2332 may be less than or equal to the minimum thickness of the negative electrode body portion 2331, thereby achieving that the thickness of the negative electrode body portion 2331 is greater than the thickness of the negative electrode thinning portion 2332.

[0502] For example, the negative electrode body portion 2331 has a uniform thickness structure, and the thickness of the negative electrode thinning portion 2332 tends to decrease along the direction of the negative electrode body portion 2331 toward the negative electrode thinning portion 2332.

[0503] In this embodiment, a negative electrode thinning portion 2332 is installed at the end of the negative electrode body portion 2331 adjacent to the end cover 12, and the electrode assembly 2 has a larger expansion gap in the region corresponding to the negative electrode thinning portion 2332. The region of the electrode assembly 2 corresponding to the negative electrode thinning portion 2332 has a smaller force applied to the first side wall portion 111 after expansion, which is advantageous in reducing cracking of the casing 11.

[0504] For some embodiments, please refer to Figures 26 to 28. In a 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.

[0505] To make it clear, in a projection plane perpendicular to the second direction Y, the orthographic projection of the thinned negative electrode portion 2332 located at the end of the negative electrode body portion 2331 adjacent to the end cover 12 does not overlap with the orthographic projection of the first inner surface 804.

[0506] In this embodiment, in a projection plane perpendicular to the second direction Y, the orthographic projection of the thinned negative electrode portion 2332 located at the end of the negative electrode body portion 2331 adjacent to the end cover 12 and the orthographic projection of the first inner surface 804 are spaced apart along the first direction Z. This reduces the influence on the corresponding portion of the first inner surface 804 of the first side wall portion 111 of the thinned negative electrode portion 2332, reduces the expansion force that the electrode assembly 2 expands and directly applies to the corresponding portion of the first inner surface 804 of the first side wall portion 111, and further reduces the possibility of cracking of the first side wall portion 111 of the casing 11.

[0507] For some embodiments, please refer to Figures 26 to 28. In a projection plane perpendicular to the second direction Y, the spacing size along the first direction Z between the orthographic projection of the negative electrode thinning portion 2332 and the orthographic projection of the first inner surface 804 is 1 mm or more.

[0508] In a projection plane perpendicular to the second direction Y, the spacing size along the first direction Z between the orthographic projection of the thinned negative electrode portion 2332 located at the end of the negative electrode body portion 2331 adjacent to the end cover 12 and the orthographic projection of the first inner surface 804 is W1, where W1 ≥ 1 mm. This spacing size is the minimum distance along the first direction Z of the orthographic projections of both the thinned negative electrode portion 2332 and the first inner surface 804 in a projection plane perpendicular to the second direction Y. W1 can take any one point value or a range value 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, etc.

[0509] In this embodiment, since W1 ≥ 1 mm, the distance along the first direction Z between the orthographic projection of the negative electrode thinning portion 2332 and the orthographic projection of the first inner surface 804 in the projection plane perpendicular to the second direction Y is greater, further reducing the influence on the corresponding portion of the first inner surface 804 of the first side wall portion 111 of the negative electrode thinning portion 2332.

[0510] In some embodiments, the single-sided coating weight of the negative electrode active material layer 233 is 90 mg / 1540 mm². 2~170mg / 1540mg 2 That is the case.

[0511] The coating weight on one side of the negative electrode active material layer 233 is 90 mg / 1540 mm². 2 , 100mg / 1540mg 2 , 110mg / 1540mg 2 , 120mg / 1540mg 2 , 130mg / 1540mg 2 , 140mg / 1540mg 2 , 150mg / 1540mg 2 , 160mg / 1540mg 2 , 170mg / 1540mg 2 It can take any one of these point values ​​or a range value between any two of them.

[0512] When measuring the weight of the single-sided coating of the negative electrode active material layer 233, one can take a single-sided coated negative electrode plate 23 (or, if it is a double-sided coated negative electrode plate 23, one side of the negative electrode active material layer 233 may be wiped off first), punch it into a small disk with an area of ​​S1, weigh it, and record it as M1. Then, the negative electrode active material layer 233 is wiped off the weighed negative electrode plate 23, and the weight of the negative electrode current collector 232 is weighed and recorded as M2. The single-sided coating weight of the negative electrode active material layer 233 = (M1 - M2) / S1.

[0513] 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, and the single-sided coating weight of the negative electrode active material layer 233 is 90 mg / 1540 mm 2 ~170mg / 1540mg 2 By setting it to such a value, it is possible to achieve both the high energy density requirement of the battery cell 10 and the low expansion requirement of the negative electrode plate 23 to a certain extent, thereby reducing the impact of the expansion of the negative electrode plate 23 on the first side wall portion 111 and reducing the possibility of cracking of the first side wall portion 111 of the casing 11.

[0514] In some embodiments, the single-sided coating weight of the negative electrode active material layer 233 is 110 mg / 1540 mm². 2 ~150mg / 1540mg 2That is the case.

[0515] In this embodiment, the single-sided coating weight of the negative electrode active material layer 233 is 110 mg / 1540 mm². 2 , 115mg / 1540mg 2 , 120mg / 1540mg 2 , 125mg / 1540mg 2 , 130mg / 1540mg 2 , 135mg / 1540mg 2 , 140mg / 1540mg 2 , 145mg / 1540mg 2 , 150mg / 1540mg 2 It can take any one of these point values ​​or a range value between any two of them.

[0516] In this embodiment, the single-sided coating weight of the negative electrode active material layer 233 is 110 mg / 1540 mm². 2 ~150mg / 1540mg 2 This further improves the energy density requirements of the battery cell 10 and also reduces the expansion of the negative electrode plate 23.

[0517] In some embodiments, the porosity of the negative electrode plate 23 is 27% to 40%.

[0518] The porosity of the negative electrode plate 23 is 27%, 28%, 29%, or 30%, and can take any one point value or a range value between any two of the following: 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, or 40%.

[0519] The porosity of the negative electrode plate 23 may be the percentage of the volume of holes within the negative electrode plate 23 that occupies the total volume of the negative electrode plate 23. For example, when the battery cell 10 is in a 0% charged state, the porosity of the negative electrode plate 23 is measured by taking a double-sided coated negative electrode plate 23 and performing a true density meter AccuPyc II 1340 in accordance with the Chinese national standard GB / T 24586-2009.

[0520] In this embodiment, the porosity of the negative electrode plate 23 is 27% to 40%, which provides space for impurities resulting from side reactions of the negative electrode plate 23, thereby slowing the expansion of the negative electrode plate 23 and reducing the influence of the expansion of the negative electrode plate 23 on the first side wall portion 111.

[0521] In some embodiments, the negative electrode active material includes a silicone-based material, and the mass content of silicon element in the negative electrode active material of the silicone-based material is 0.3% to 10%, and selectively 1% to 6%.

[0522] The mass content of silicon element in the negative electrode active material of silicone-based materials can be any one point value or a range value between any two of the following: 0.3%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%.

[0523] In some embodiments, the silicone-based material includes at least one of a silicone oxide and a silicone-carbon composite.

[0524] For some embodiments, please refer to Figures 27 and 28. The positive electrode plate 22 includes a positive electrode current collector 222 and a positive electrode active material layer 223 installed on at least one side of the positive electrode current collector 222, the positive electrode active material layer 223 comprising positive electrode active material.

[0525] The positive electrode active material layer 223 may be installed on only one side of the positive electrode current collector 222, that is, on only one surface along the thickness direction of the positive electrode current collector 222, or the positive electrode active material layer 223 may be installed on both opposing sides of the positive electrode current collector 222, that is, on both opposing surfaces along the thickness direction of the positive electrode current collector 222.

[0526] The positive electrode active material may contain at least one of lithium-containing phosphates, lithium transition metal oxides, and their respective reformed compounds.

[0527] For some embodiments, please refer to Figures 27 and 28. The positive electrode active material layer 223 includes a positive electrode body portion 2231 and a positive electrode thinning portion 2232, which are arranged along a first direction Z, and the positive electrode thinning portion 2232 is located at the end of the positive electrode body portion 2231 adjacent to the end cover 12 along the first direction Z.

[0528] The thickness of the positive electrode body portion 2231 is greater than the thickness of the positive electrode thinning portion 2232. The positive electrode thinning portion 2232 may be installed only at the end of the positive electrode body portion 2231 that is close to the end cover 12 along the first direction Z, or the positive electrode thinning portion 2232 may be present at both ends of the positive electrode body portion 2231 along the first direction Z. The positive electrode body portion 2231 may have a uniform thickness structure or a non-uniform thickness structure, and the positive electrode thinning portion 2232 may have a uniform thickness structure or a non-uniform thickness structure. If at least one of the positive electrode body portion 2231 and the positive electrode thinning portion 2232 has a non-uniform thickness structure, the maximum thickness of the positive electrode thinning portion 2232 may be less than or equal to the minimum thickness of the positive electrode body portion 2231, thereby achieving that the thickness of the positive electrode body portion 2231 is greater than the thickness of the positive electrode thinning portion 2232.

[0529] For example, the positive electrode body portion 2231 has a uniform thickness structure, and the thickness of the positive electrode thinning portion 2232 tends to decrease along the direction of the positive electrode body portion 2231 toward the positive electrode thinning portion 2232.

[0530] In this embodiment, a positive electrode thinning portion 2232 is installed at the end of the positive electrode body portion 2231 adjacent to the end cover 12, and the electrode assembly 2 has a larger expansion gap in the region corresponding to the positive electrode thinning portion 2232. As a result, the force applied to the first side wall portion 111 in the region of the electrode assembly 2 corresponding to the positive electrode thinning portion 2232 after expansion is reduced, thereby reducing the possibility of cracking of the first side wall portion 111 of the casing 11.

[0531] For some embodiments, please refer to Figures 26 to 28. In a 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.

[0532] To make it clear, in a 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 body portion 2231 adjacent to the end cover 12 does not overlap with the orthographic projection of the first inner surface 804.

[0533] In a 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 body portion 2231 adjacent to the end cover 12 and the orthographic projection of the first inner surface 804 are spaced apart along the first direction Z, thereby reducing the influence on the corresponding portion of the first inner surface 804 of the first side wall portion 111 of the positive electrode thinning portion 2232, reducing the expansion force that the electrode assembly 2 expands and directly applies to the corresponding portion of the first inner surface 804 of the first side wall portion 111, and reducing the possibility of cracking of the first side wall portion 111 of the casing 11.

[0534] For some embodiments, please refer to Figures 26 to 28. In a projection plane perpendicular to the second direction Y, the spacing size along the first direction Z between the orthographic projection of the positive electrode thinning portion 2232 and the orthographic projection of the first inner surface 804 is 1 mm or more.

[0535] In a projection plane perpendicular to the second direction Y, the spacing size along the first direction Z between the orthographic projection of the positive electrode thinning portion 2232 located at the end of the positive electrode body portion 2231 adjacent to the end cover 12 and the orthographic projection of the first inner surface 804 is W2, where W2 ≥ 1 mm. This spacing size is the minimum distance along the first direction Z of the orthographic projections of both the positive electrode thinning portion 2232 and the first inner surface 804 in a projection plane perpendicular to the second direction Y. Here, W1 = W2, W1 ≤ W2, and W1 ≥ W2. W2 can take any one point value or a range value 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, etc.

[0536] In this embodiment, since W2 ≥ 1 mm, the distance along the first direction Z between the orthographic projection of the positive electrode thinning portion 2232 and the orthographic projection of the first inner surface 804 in the projection plane perpendicular to the second direction Y is greater, further reducing the influence of the positive electrode thinning portion 2232 on the first inner surface 804.

[0537] In some embodiments, the single-sided coating weight of the positive electrode active material layer 223 is 200 mg / 1540 mm². 2 ~370mg / 1540 / mm 2 That is the case.

[0538] The coating weight on one side of the positive electrode active material layer 223 is 200 mg / 1540 mm². 2 , 210mg / 1540mg 2 , 220mg / 1540mg 2 230mg / 1540mg 2 240mg / 1540mg 2 , 250mg / 1540mm 2 , 260mg / 1540mg 2 270mg / 1540mg 2 280mg / 1540mg 2 290mg / 1540mg 2 300mg / 1540mg 2 310mg / 1540mg2 320mg / 1540mg 2 330mg / 1540mg 2 340mg / 1540mg 2 350mg / 1540mg 2 360mg / 1540mg 2 370mg / 1540mg 2 It can take any one of these point values ​​or a range value between any two of them.

[0539] When measuring the weight of the positive electrode active material layer 223 coated on one side, one can take a positive electrode plate 22 coated on one side (if the positive electrode plate 22 is coated on both sides, one can first wipe off the positive electrode active material layer 223 from one side), punch it into a small disk with an area of ​​S2, weigh it, and record it as M3. Then, wipe off the positive electrode active material layer 223 from the weighed positive electrode plate 22, weigh the positive electrode current collector 222, and record it as M4. The weight of the positive electrode active material layer 223 coated on one side = (M3 - M4) / S2.

[0540] 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, and the single-sided coating weight of the positive electrode active material layer 223 is 200 mg / 1540 mm 2 ~370mg / 1540 / mm 2 By setting it to such a value, it is possible to achieve both the high energy density requirement of the battery cell 10 and the low expansion requirement of the positive electrode plate 22 to a certain extent, thereby reducing the impact of the expansion of the positive electrode plate 22 on the first side wall portion 111 and reducing the possibility of cracking of the first side wall portion 111 of the casing 11.

[0541] In some embodiments, the single-sided coating weight of the positive electrode active material layer 223 is 240 mg / 1540 mm². 2 ~330mg / 1540mg 2 That is the case.

[0542] The coating weight on one side of the positive electrode active material layer 223 is 240 mg / 1540 mm². 2 , 245mg / 1540mg 2 , 250mg / 1540mm 2, 255mg / 1540mg 2 , 260mg / 1540mg 2 265mg / 1540mg 2 270mg / 1540mg 2 , 275mg / 1540mg 2 280mg / 1540mg 2 , 285mg / 1540mg 2 290mg / 1540mg 2 295mg / 1540mg 2 300mg / 1540mg 2 305mg / 1540mg 2 310mg / 1540mg 2 315mg / 1540mg 2 320mg / 1540mg 2 325mg / 1540mg 2 330mg / 1540mg 2 It can take any one of these point values ​​or a range value between any two of them.

[0543] In this embodiment, the single-sided coating weight of the positive electrode active material layer 223 is 240 mg / 1540 mm². 2 ~330mg / 1540mg 2 This further improves the energy density requirements of the battery cell 10 and also reduces the expansion of the positive electrode plate 22.

[0544] In some embodiments, the positive electrode active material is a lithium-containing phosphate.

[0545] For some embodiments, please refer to Figures 14, 30, and 31. The material of the casing 11 includes steel. The maximum distance along the second direction Y between the second inner surface 805 and the second outer surface 807 is D1, and the size of the casing 11 along the second direction Y is D, where 0.001 ≤ D1 / D ≤ 0.012.

[0546] For example, the distance along the second direction Y between each position on the second inner surface 805 and the second outer surface 807 may be equal, and the distance along the second direction Y between any position on the second inner surface 805 and the second outer surface 807 may be the maximum distance along the second direction Y between the second inner surface 805 and the second outer surface 807.

[0547] For example, the distances along the second direction Y between each position on the second inner surface 805 and the second outer surface 807 do not have to be equal.

[0548] In this embodiment, a portion of the first inner surface 804 may be closer to the electrode assembly 2 than the second inner surface 805 along the second direction Y, or a portion of the first outer surface 806 may be further away from the electrode assembly 2 than the second outer surface 807 along the second direction Y. See Figures 29 and 30 for an example. A portion of the first outer surface 806 may be further away from the electrode assembly 2 than the second outer surface 807 along the second direction Y, and the first inner surface 804 and the second inner surface 805 are located on the same plane.

[0549] The maximum distance between the second outer surfaces 807 corresponding to the two opposing first sidewalls 111 of the casing 11 is the size along the second direction Y of the casing 11. To make it clear, when measuring the size along the second direction Y of the casing 11, the measurement reference is the second outer surface 807 of the first sidewalls 111. For example, the second outer surfaces 807 of the two opposing first sidewalls 111 are installed parallel to each other.

[0550] For the steel casing 11, D1 / D can take any one point value or a range value between any two of the following: 0.001, 0.002, 0.003, 0.004, 0.005, 0.006, 0.007, 0.008, 0.009, 0.01, 0.011, 0.012, etc.

[0551] For the steel casing 11, if D1 / D ≥ 0.001, increasing the thickness occupancy ratio in the casing 11 along the second direction Y between the second inner surface 805 and the second outer surface 807 allows the portion of the first side wall 111 corresponding to the second inner surface 805 to have sufficient strength, satisfying the strength requirements of the casing 11. If D1 / D ≤ 0.012, decreasing the thickness occupancy ratio in the casing 11 along the second direction Y between the second inner surface 805 and the second outer surface 807 allows the internal space of the casing 11 to be increased when the volume of the casing 11 is constant, further leaving more space for the electrode assembly 2, satisfying the volumetric energy density requirements of the battery cell 10.

[0552] In the embodiments of this application, for the steel casing 11, in order to satisfy the requirements for the volumetric energy density of the battery cell 10, the D1 / D must be controlled to 0.012 or less. Therefore, the first sidewall 111 is reinforced by a relatively thick portion corresponding to the first inner surface 804 of the first sidewall 111, thereby reducing the possibility of cracking of the first sidewall 111 of the casing 11.

[0553] For some embodiments, please refer to Figures 14 and 30. The material of the casing 11 includes steel. The maximum distance along the second direction Y between the second inner surface 805 and the second outer surface 807 is D1, where 0.08 mm ≤ D1 ≤ 0.35 mm, and / or the maximum distance along the second direction Y between the first inner surface 804 and the first outer surface 806 is D2, where 0.1 mm ≤ D2 ≤ 0.6 mm.

[0554] To make it clear, the maximum distance between the second inner surface 805 and the second outer surface 807 is smaller than the minimum distance between the first inner surface 804 and the first outer surface 806. Therefore, the maximum distance between the second inner surface 805 and the second outer surface 807 is smaller than the maximum distance between the first inner surface 804 and the first outer surface 806. That is, D1 <D2である。

[0555] For the steel casing 11, D1 can take any one point value or a range value between any two of the following: 0.08 mm, 0.1 mm, 0.12 mm, 0.15 mm, 0.18 mm, 0.2 mm, 0.22 mm, 0.25 mm, 0.28 mm, 0.3 mm, 0.32 mm, 0.35 mm, etc., and D2 can take any one point value or a range value between any two of the following: 0.1 mm, 0.15 mm, 0.2 mm, 0.25 mm, 0.3 mm, 0.35 mm, 0.4 mm, 0.45 mm, 0.5 mm, 0.55 mm, 0.6 mm, etc.

[0556] In the embodiments of this application, if the maximum distance along the second direction Y between the second inner surface 805 and the second outer surface 807 of the steel casing 11 is set to 0.08 mm to 0.35 mm, the strength requirements of the portion of the first side wall 111 corresponding to the second inner surface 805 can be met, and the requirements for the volumetric energy density of the battery cell 10 can also be met. If the maximum distance along the second direction Y between the first inner surface 804 and the first outer surface 806 is set to 0.1 mm to 0.6 mm, the portion of the first side wall 111 corresponding to the first inner surface 804 is reinforced.

[0557] For some embodiments, please refer to Figures 14, 30, and 31. The material of the casing 11 includes an aluminum alloy. The maximum distance along the second direction Y between the second inner surface 805 and the second outer surface 807 is D1, and the size of the casing 11 along the second direction Y is D, where 0.005 ≤ D1 / D ≤ 0.065.

[0558] For the aluminum alloy casing 11, D1 / D can take any one point value or a range value between any two of the following: 0.005, 0.01, 0.015, 0.02, 0.025, 0.03, 0.035, 0.04, 0.045, 0.05, 0.055, 0.06, 0.65, etc.

[0559] For the aluminum alloy casing 11, if D1 / D ≥ 0.005, increasing the thickness occupancy ratio in the casing 11 at the distance between the second inner surface 805 and the second outer surface 807 allows the portion of the first side wall 111 corresponding to the second inner surface 805 to have sufficient strength, satisfying the strength requirements of the casing 11. If D1 / D ≤ 0.065, decreasing the thickness occupancy ratio in the casing 11 at the distance between the second inner surface 805 and the second outer surface 807 allows the internal space of the casing 11 to be increased when the volume of the casing 11 is constant, further leaving more space for the electrode assembly 2, and satisfying the volumetric energy density requirements of the battery cell 10.

[0560] For the aluminum alloy casing 11, in order to meet the requirements for the volumetric energy density of the battery cell 10, it is necessary to control D1 / D to 0.065 or less. Therefore, the first side wall portion 111 of the casing 11 is reinforced by a relatively thick portion of the first inner wall portion of the first side wall portion 111, thereby reducing the possibility of cracking of the casing 11.

[0561] For some embodiments, please refer to Figures 14 and 30. The material of the casing 11 includes an aluminum alloy. The maximum distance along the second direction Y between the second inner surface 805 and the second outer surface 807 is D1, where 0.4 mm ≤ D1 ≤ 0.8 mm, and / or the maximum distance along the second direction Y between the first inner surface 804 and the first outer surface 806 is D2, where 0.5 mm ≤ D2 ≤ 1.5 mm.

[0562] For the aluminum alloy casing 11, D1 can take any one point value or a range value between any two of the following: 0.4mm, 0.42mm, 0.45mm, 0.48mm, 0.5mm, 0.52mm, 0.55mm, 0.58mm, 0.6mm, 0.62mm, 0.65mm, 0.68mm, 0.7mm, 0.72mm, 0.75mm, 0.78mm, 0.8mm, etc., and D2 can take any one point value or a range value between any two of the following: 0.5mm, 0.6mm, 0.7mm, 0.8mm, 0.9mm, 1mm, 1.1mm, 1.2mm, 1.3mm, 1.4mm, 1.5mm, etc.

[0563] If the maximum distance along the second direction Y between the second inner surface 805 and the second outer surface 807 of the aluminum alloy casing 11 is set to 0.4 mm to 0.8 mm, the strength requirements for the portion of the first side wall 111 corresponding to the second inner surface 805 can be met, and the volumetric energy density requirements for the battery cell 10 can also be met. If the maximum distance along the second direction Y between the first inner surface 804 and the first outer surface 806 is set to 0.5 mm to 1.5 mm, the portion of the first side wall 111 corresponding to the first inner surface 804 will have sufficient strength.

[0564] In some embodiments, the aluminum alloy contains the following mass% components: aluminum ≥ 99.6%, copper ≤ 0.05%, iron ≤ 0.35%, magnesium ≤ 0.03%, manganese ≤ 0.03%, silicon ≤ 0.25%, titanium ≤ 0.03%, vanadium ≤ 0.05%, zinc ≤ 0.05%, and other single elements ≤ 0.03%. Such an aluminum alloy has good workability and the casing 11 is easy to form.

[0565] In some embodiments, the aluminum alloy contains the following mass% components: aluminum ≥ 96.7%, copper ≤ 0.2%, iron ≤ 0.7%, manganese ≤ 1.5%, silicon ≤ 0.6%, zinc ≤ 0.1%, other single element components ≤ 0.05%, and the total components of other elements ≤ 0.15%. Such aluminum alloys have good workability and corrosion resistance.

[0566] For some embodiments, please refer to Figures 6, 26, 29, 32, 34, and 36. The first region 1111 is directly connected to the first connection 51, and the first inner surface 804 extends along the first direction Z to the end of the first region 1111 facing the connection 5.

[0567] The first region 1111 and the first connecting portion 51 may be in point contact, line contact, or surface contact, thereby achieving direct connection between the two.

[0568] In this embodiment, the first region 1111 is directly connected to the first connection portion 51, thereby the first region 1111 is closer to the first connection portion 51 along the first direction Z, which is advantageous in releasing the expansion force of the electrode assembly 2 by the first region 1111 being close to the first connection portion 51 and reducing the possibility of cracking of the first connection portion 51.

[0569] For some embodiments, please refer to Figures 32 to 37. The first sidewall 111 further includes a first transition region 1117, which is connected to the end of the first region 1111 away from the second region 1112 along a first direction Z, and the first transition region 1117 is connected to a first connection portion 51, where a first connection interface 511 is formed at the connection position between the first transition region 1117 and the first connection portion 51, and the first connection interface 511 has a first position 5111 that is closest to the first region 1111 along a first direction Z, and the first position 5111 is located at the end of the first region 1111 away from the second region 1112 along a first direction Z.

[0570] The first transition region 1117 may be the portion connected between the first connection portion 51 of the first side wall portion 111 and the first region 1111. The first transition region 1117 may have an equal thickness structure or an uneven thickness structure. The thickness of the first transition region 1117 may be less than the thickness of the first region 1111. See Figures 32 to 37 for an example. Along the direction of the second region 1112 toward the first region 1111, the thickness of the first transition region 1117 gradually decreases.

[0571] The first connection interface 511 is formed at the connection position between the first transition region 1117 and the first connection portion 51, and the first transition region 1117 and the first connection portion 51 are bounded by the first connection interface 511. The first connection interface 511 may be a plane or a curved surface.

[0572] The first region 1111 and the first transition region 1117 are separated by a first boundary surface U, which is a virtual plane, passes through the first position 5111, is perpendicular to the first direction Z, the first transition region 1117 and the first connection 51 are located above the first boundary surface U, and the first region 1111 is located below the first boundary surface U.

[0573] In this embodiment, the first transition region 1117 connects with the first connecting portion 51 to form a first connection interface 511, thereby providing a sufficiently large contact area between the first transition region 1117 and the first connecting portion 51, and improving the rigidity after welding the first side wall portion 111 and the end cover 12.

[0574] For some embodiments, please refer to Figures 32 to 37. At least a portion of the first connection interface 511 extends at an angle with respect to the second direction Y.

[0575] The first connecting interface 511 may be extended at an inclination with respect to the second direction Y overall, or it may be extended at an inclination with respect to the second direction Y locally.

[0576] To make it clear, the extension direction of the portion of the first connection interface 511 that extends at an angle compared to the second direction Y is not parallel to the second direction Y.

[0577] After the end cover 12 is welded to the first sidewall portion 111, the first connection 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, the first sidewall portion 111 deforms, generating tensile stress on the first transition region 1117 on the first connection portion 51. Because at least a portion of the first connection interface 511 stretches at an inclination relative to the second direction Y, the tensile stress on the first transition region 1117 due to the shrinkage of the first connection portion 51 near the portion of the first connection interface 511 that stretches at an inclination relative to the second direction Y does not lie on the same straight line as the tensile stress on the first connection portion 51 due to the deformation of the first sidewall portion 111 in the first transition region 1117, thereby reducing the risk of fatigue cracking in the region of the first transition region 1117 located near the first connection interface 511.

[0578] For some embodiments, please refer to Figures 32 to 37. The first connecting interface 511 includes a first interface 5112, which extends inclined toward the end cover 12 from the first position 5111, and along the second direction Y, at least a portion of the first transition region 1117 is located between the first interface 5112 and the end cover 12.

[0579] To make it easier to understand, the first interface 5112 extends at an inclination relative to the second direction Y. The first interface 5112 may be a plane or a curved surface.

[0580] The first position 5111 is the lowest position of the first interface 5112 (the position closest to the first region 1111), and the first interface 5112 extends inclined from the first position 5111 toward the end cover 12, that is, the first interface 5112 extends upward inclined from the first position 5111 toward the end cover 12.

[0581] Along the second direction Y, the first transition region 1117 may be entirely located between the first interface 5112 and the end cover 12, or only a portion of the first transition region 1117 may be located between the first interface 5112 and the end cover 12.

[0582] In this embodiment, along the second direction Y, at least a portion of the first transition region 1117 is located between the first interface 5112 and the end cover 12, and in this way the first connection portion 51 provides protection to the first transition region 1117, and when the first side wall portion 111 is subjected to the expansion force of the electrode assembly 2, deformation in the process of the first transition region 1117 being subjected to force is prevented by the first connection portion 51, thereby reducing the possibility of fatigue cracking in the region of the first transition region 1117 located near the first interface 5112.

[0583] For some embodiments, please refer to Figures 32 to 37. The first interface 5112 and the first outer surface 806 are connected at a first position 5111, which is at least partially located in the first region 1111.

[0584] For example, the first interface 5112 intersects the first outer surface 806 with a first straight line, the first straight line extends along a third direction X, and the position of the first straight line is the first position 5111. The first interface 5112 and the inner surface of the first transition region 1117 are connected at the third position 5114, and along the first direction Z, the third position 5114 is further from the first region 1111 than the first position 5111. The first transition region 1117 is approximately triangular.

[0585] In this embodiment, the first interface 5112 and the first outer surface 806 are connected at a first position 5111, and the first position 5111 is located in the first region 1111. As a result, the first outer surface 806 extends along the first direction Z of the first region 1111 toward the end facing the first connection portion 51, and the portion of the first side wall portion 111 corresponding to the first outer surface 806 can relatively suitably reinforce the end of the first region 1111 toward the first connection portion 51, thereby reducing the possibility of fatigue cracking at the end of the first region 1111 toward the first connection portion 51.

[0586] For some embodiments, please refer to Figures 32 to 37. The first connecting interface 511 includes a second interface 5113, which extends inclined toward the direction away from the end cover 12 from the first position 5111, and along the second direction Y, at least a portion of the first transition region 1117 is located on the side of the second interface 5113 away from the end cover 12.

[0587] To make it clear, the second interface 5113 extends at an angle relative to the second direction Y. The second interface 5113 may be a plane or a curved surface. Along the second direction Y, at least a portion of the first connection 51 is located between the second interface 5113 and the end cover 12.

[0588] The first position 5111 is the lowest position of the second interface 5113 (the position closest to the first region 1111), and the second interface 5113 extends inclined away from the first position 5111 in a direction away from the end cover 12, that is, the second interface 5113 extends upward inclined away from the first position 5111 in a direction away from the end cover 12.

[0589] Along the second direction Y, the first transition region 1117 may be entirely located on the side away from the end cover 12 of the second interface 5113, or only a portion of the first transition region 1117 may be located on the side away from the end cover 12 of the second interface 5113.

[0590] In this embodiment, along the second direction Y, at least a portion of the first transition region 1117 is located away from the end cover 12 of the second interface 5113, thereby the first transition region 1117 acts as a limiting force on the first connection portion 51, reducing the possibility of the first connection portion 51 falling off.

[0591] For some embodiments, please refer to Figures 32 to 37. The second interface 5113 and the first inner surface 804 are connected at a first position 5111, which is at least partially located in the first region 1111.

[0592] For example, the second interface 5113 intersects the first inner surface 804 with a first straight line, the first straight line extends along the third direction X, and the position of the first straight line is the first position 5111. The second interface 5113 and the outer surface of the first transition region 1117 are connected at the fourth position 5115, and along the first direction Z, the fourth position 5115 is further from the first region 1111 than the first position 5111. The first transition region 1117 is approximately triangular.

[0593] In this embodiment, the second interface 5113 and the first inner surface 804 are connected at a first position 5111, and the first position 5111 is located at least partially in the first region 1111. As a result, the first inner surface 804 extends along the first direction Z of the first region 1111 toward the end facing the first connection portion 51, and the portion of the first side wall portion 111 corresponding to the first inner surface 804 can relatively suitably reinforce the end of the first region 1111 toward the first connection portion 51, thereby reducing the possibility of fatigue cracking at the end of the first region 1111 toward the first connection portion 51.

[0594] For some embodiments, please refer to Figures 32 to 37. The first connecting interface 511 includes a first interface 5112 and a second interface 5113, the first interface 5112 extending inclined toward the end cover 12 from the first position 5111, and the second interface 5113 extending inclined toward the end cover 12 from the first position 5111, and along the second direction Y, a portion of the first transition region 1117 is located between the first interface 5112 and the end cover 12, and another portion of the first transition region 1117 is located on the side of the second interface 5113 away from the end cover 12.

[0595] For example, the first interface 5112 and the inner surface of the first transition region 1117 are connected at the third position 5114, and the second interface 5113 and the outer surface of the first transition region 1117 are connected at the fourth position 5115.

[0596] 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 connection portion 51.

[0597] For example, the hardness of the second region 1112 is less than the hardness of the first connection portion 51.

[0598] For example, the hardness type of the first transition region 1117, the hardness type of the first region 1111, the hardness type of the second region 1112, and the hardness type of the first connection portion 51 are all Vickers hardness.

[0599] If the hardness of the first transition region 1117 is less than that of the second region 1112, the less hard first transition region 1117 will connect with the first connection portion 51, mitigating the rigid tension between the first side wall portion 111 and the first connection portion 51 during deformation, thereby reducing the possibility of separation between the first side wall portion 111 and the first connection portion 51. If the hardness of the first transition region 1117 is less than that of the first connection portion 51, the first transition region 1117 will deform more easily than the first connection portion 51, mitigating the rigid tension between the first side wall portion 111 and the first connection portion 51 during deformation, thereby reducing the possibility of separation between the first side wall portion 111 and the first connection portion 51.

[0600] For some embodiments, please refer to Figures 32 to 37. The first connection interface 511 is closer to the second region 1112 than to the outer surface 121 of the end cover.

[0601] Along the first direction Z, the surface of the end cover 12 away from the electrode assembly 2 is the outer surface 121 of the end cover.

[0602] Please refer to Figures 32 to 37. Along the first direction Z, both the third position 5114 and the first position 5111 are closer to the second region 1112 than to the outer surface 121 of the end cover.

[0603] Please refer to Figures 32 to 37. Along the first direction Z, both the fourth position 5115 and the first position 5111 are closer to the second region 1112 than to the outer surface 121 of the end cover.

[0604] Please refer to Figures 32 to 37. Along the first direction Z, the third position 5114, the fourth position 5115, and the first position 5111 are all closer to the second region 1112 than to the outer surface 121 of the end cover.

[0605] In this embodiment, the first connection interface 511 is closer to the second region 1112 along the first direction Z compared to the outer surface 121 of the end cover. This allows the first connection portion 51 to sink into a deeper position within the first side wall portion 111, effectively improving the connection strength between the first side wall portion 111 and the end cover 12.

[0606] For some embodiments, please refer to Figures 7, 15, 16, 18, 19, 22, 23, 31, 38, and 39. The casing 11 further includes a second side wall 112 and a corner wall 113, the first side wall 111, the corner wall 113, and the second side wall 112 are arranged along the circumferential direction of the opening, and the corner wall 113 connects the first side wall 111 and the second side wall 112.

[0607] The second side wall portion 112 can be welded to the end cover 12 to form the third connection portion 5, and both the first connection portion 51 and the third connection portion 5 are part of the connection portion 5. The second side wall portion 112 may have a uniform thickness structure or a non-uniform thickness structure.

[0608] The first side wall portion 111 in the casing 11 is indirectly connected to the second side wall portion 112 via the corner wall 113, and the sum of the number of both the first side wall portion 111 and the second side wall portion 112 is equal to the number of corner walls 113.

[0609] For example, the first side wall portion 111, the second side wall portion 112, and the corner wall 113 are integrally molded. The cross-section of the outer and / or inner surface of the corner wall 113 may be arc-shaped, and this cross-section is perpendicular to the first direction Z.

[0610] In this embodiment, the first side wall portion 111 is connected to the second side wall portion 112 via the corner wall portion 113. In this way, the first side wall portion 111 can transition to the second side wall portion 112 via the corner wall portion 113, effectively reducing the risk of stress concentration occurring at the corner position of the casing 11.

[0611] For some embodiments, please refer to Figures 38 to 42. The corner wall 113 is welded to the end cover 12 to form a second connection 52. The corner wall 113 includes a third region 1131 and a fourth region 1132 arranged along a first direction Z, the hardness of the third region 1131 being less than that of the fourth region 1132, and the third region 1131 is located between the fourth region 1132 and the second connection 52.

[0612] The third region 1131 is located between the fourth region 1132 and the second connecting portion 52, and the third region 1131, which has relatively low hardness, is closer to the second connecting portion 52 than to the fourth region 1132.

[0613] The third region 1131 may be directly connected to the second connection portion 52.

[0614] The third region 1131 may be directly connected to the fourth region 1132, or it may be connected indirectly.

[0615] The second connection portion 52 may correspond one-to-one with the corner wall 113, and the second connection portion 52 is the portion where a weld mark is formed after the end cover 12 is welded to the corner wall 113, and the portion where the end cover 12 is welded to the corner wall 113 and fuses together may be the second connection portion 52. A part of the second connection portion 52 is formed on the end cover 12, and another part of the second connection portion 52 is formed on the corner wall 113. The corner wall 113 and the end cover 12 may form the second connection portion 52 by stitching welding, or by through welding. Both the second connection portion 52 and the first connection portion 51 are part of the connection portion 5.

[0616] For example, the hardness types in the third and fourth regions are both Vickers hardness.

[0617] For example, the hardness type of the second connection is Vickers hardness.

[0618] In the embodiments of this application, the hardness of the third region 1131 is relatively low, which gives the third region 1131 relatively high toughness. The relatively high toughness of the third region 1131 is advantageous in that it releases some of the expansion force on the corner wall 113 of the electrode assembly 2, thereby reducing the possibility of the corner wall 113 cracking at the second connection portion 52 of the second side wall portion 112.

[0619] What needs to be explained is that the hardness of the third region 1131 is relatively low, and the third region 1131 has relatively high toughness. However, the relatively high toughness of the third region 1131 means that fatigue cracking may occur due to the action of periodic expansion forces as the electrode assembly 2 repeatedly expands and contracts.

[0620] For some embodiments, please refer to Figures 38 to 42. The corner wall 113 has a third inner surface 810 and a fourth inner surface 811 facing the electrode assembly 2 and a third outer surface 812 and a fourth outer surface 813 away from the electrode assembly 2, the third inner surface 810 and the fourth inner surface 811 are connected in order along the direction of the end cover 12 facing 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, the fourth inner surface 811 and the fourth outer surface 813 are at least partially formed in the fourth region 1132, and the distance along the thickness direction of the corner wall 113 between the third inner surface 810 and the third outer surface 812 is greater than the distance along the thickness direction of the corner wall 113 between the fourth inner surface 811 and the fourth outer surface 813.

[0621] The distance along the thickness direction of the corner wall 113 between each position on the third inner surface 810 and the third outer surface 812 may be equal or unequal. The distance along the thickness direction of the corner wall 113 between each position on the fourth inner surface 811 and the third outer surface 812 may be equal or unequal. If the distances along the thickness direction of the corner wall 113 between each position on the third inner surface 810 and the third outer surface 812 are not equal, or if the distances along the thickness direction of the corner wall 113 between each position on the fourth inner surface 811 and the third outer surface 812 are not equal, then the minimum distance along the thickness direction of the corner wall 113 between the third inner surface 810 and the third outer surface 812 is greater than the maximum distance along the thickness direction of the corner wall 113 between the fourth inner surface 811 and the fourth outer surface 813, thereby ensuring that the distance along the thickness direction of the corner wall 113 between the third inner surface 810 and the third outer surface 812 is greater than the distance along the thickness direction of the corner wall 113 between the fourth inner surface 811 and the fourth outer surface 813.

[0622] The third inner surface 810 is closer to the electrode assembly 2 than the fourth inner surface 811 along the thickness direction of the corner wall 113, and / or the third outer surface 812 is further away from the electrode assembly 2 than the fourth outer surface 813 along the thickness direction of the corner wall 113. See Figures 38 to 41. The third inner surface 810 is closer to the electrode assembly 2 than the fourth inner surface 811 along the thickness direction of the corner wall 113, and the third outer surface 812 and the fourth outer surface 813 are located in the same plane. See Figure. The third outer surface 812 is further away from the electrode assembly 2 than the fourth outer surface 813 along the thickness direction of the corner wall 113, and the third inner surface 810 and the fourth inner surface 811 are located in the same plane.

[0623] For example, please refer to Figure 42. The distance along the thickness direction of the corner wall 113 between the third inner surface 810 and the third outer surface 812 is D8, and the distance along the thickness direction of the corner wall 113 between the fourth inner surface 811 and the fourth outer surface 813 is D9, and D8 > D9.

[0624] In the embodiments of this application, the distance along the thickness direction of the corner wall 113 between the third inner surface 810 and the third outer surface 812 is greater than the distance along the thickness direction of the corner wall 113 between the fourth inner surface 811 and the fourth outer surface 813, the thickness of the portion of the corner wall 113 corresponding to the third inner surface 810 is relatively large, the third inner surface 810 and the third outer surface 812 are formed at least partially in the third region 1131, and thereby the portion of the corner wall 113 with a relatively large thickness corresponding to the third inner surface 810 can reinforce the third region 1131 which has relatively high toughness, which is advantageous in suppressing fatigue cracking of the third region 1131 and improving the service life of the battery cell 10.

[0625] For some embodiments, please refer to Figures 38 and 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.

[0626] For example, the third region 1131 and the first region 1111 are integrally molded, and the third region 1131 is connected to both ends of the first region 1111 along the third direction X.

[0627] In the embodiments of this application, 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 side wall portion 111 at the first inner surface 804 is integrally connected to the portion of the corner wall 113 at the third inner surface 810. The portion of the first side wall portion 111 at the first inner surface 804 and the portion of the corner wall 113 at the third inner surface 810 have a mutually reinforcing effect, thereby relatively favorably reinforcing both the portion of the first side wall portion 111 at the first inner surface 804 and the portion of the corner wall 113 at the third inner surface 810, thereby reducing the possibility of cracking of the casing 11. Since the first inner surface 804 and the first outer surface 806 are formed at least partially in the first region 1111, and the third inner surface 810 and the third outer surface 812 are formed at least partially in the third region 1131, the portion of the first side wall portion 111 on the first inner surface 804 and the portion of the corner wall portion 113 on the third inner surface 810 have a mutually reinforcing effect and can influence the first region 1111 and the third region 1131, thereby reinforcing the first region 1111 and the third region 1131 and reducing the possibility of fatigue cracking between the first region 1111 and the third region 1131.

[0628] For some embodiments, please refer to Figures 38 and 39. The 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, the second side wall portion 112 is connected to the second connecting end 1134, and the distance along the thickness direction of the corner wall 113 between the third inner surface 810 and the third outer surface 812 is a fourth predetermined thickness, and the fourth predetermined thickness tends to decrease along the direction of the first connecting end 1133 toward the second connecting end 1134.

[0629] For example, the fourth predetermined thickness gradually decreases along the direction of the first connecting end 1133 toward the second connecting end 1134, the second side wall 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 side wall portion 112, and the third outer surface 812 connects the first outer surface 806 and the outer surface of the second side wall portion 112.

[0630] When the first side wall portion 111 is subjected to the expansion force of the electrode assembly 2 in the second direction Y, the first side wall portion 111 may deform and move the corner wall 113 to deform. Along the circumferential direction of the opening, the corner wall 113 is more affected by the first side wall portion 111 as it approaches it, and the amount of deformation of the corner wall 113 increases as it approaches the region of the first side wall portion 111. Since the fourth predetermined thickness tends to decrease along the direction of the first connecting end 1133 toward the second connecting end 1134, the third region 1131 has greater strength in the region adjacent to the first side wall portion 111 along the circumferential direction of the opening, reducing the possibility of cracking at the end of the third region 1131 facing the first side wall portion 111, which has relatively lower hardness. When the third region 1131, which has relatively high toughness, is reinforced, the amount of material used in the portion corresponding to the third inner surface 810 of the corner wall 113 is reduced, thereby lowering production costs.

[0631] For some embodiments, please refer to Figures 38 to 40, and Figures 44, 46, and 48. The third region 1131 is directly connected to the second connection 52, and the third inner surface 810 extends to the end of the third region 1131 facing the second connection 52.

[0632] The third region 1131 and the second connection portion 52 may be in point contact, line contact, or surface contact, thereby achieving direct connection between the two.

[0633] In this embodiment, the third region 1131 is directly connected to the second connection portion 52, and the third inner surface 810 extends to the end of the third region 1131 facing the second connection portion 52. This allows the end of the third region 1131 facing the second connection portion 52, which has relatively high toughness, to be reinforced relatively well, which is advantageous in reducing the possibility of fatigue cracking at the end of the third region 1131 facing the second connection portion 52.

[0634] For some embodiments, please refer to Figures 43 to 48. The corner wall 113 further includes a second transition region 1135, which is connected to the end of the third region 1131 away from the fourth region 1132 along a first direction Z, and the second transition region 1135 is connected to a second connection 52, where a second connection interface 521 is formed at the connection point between the second transition region 1135 and the second connection 52, and the second connection interface 521 has a second position 5211 that is closest to the third region 1131 along a first direction Z, and the second position 5211 is located at the end of the third region 1131 away from the fourth region 1132 along a first direction Z.

[0635] The second transition region 1135 may be the portion connected between the second connection portion 52 of the corner wall 113 and the third region 1131. The second transition region 1135 may have a uniform thickness structure or a non-uniform thickness structure. The thickness of the second transition region 1135 may be less than the distance along the thickness direction of the corner wall 113 between the third inner surface 810 and the third outer surface 812. For example, in the embodiment shown in Figures 43 to 48, the thickness of the second transition region 1135 gradually decreases along the direction of the fourth region 1132 toward the third region 1131.

[0636] 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 bounded by the second connection interface 521. The second connection interface 521 may be a plane or a curved surface.

[0637] The third region 1131 and the second transition region 1135 are separated by a second boundary surface V, which is a virtual plane, passes through the second position 5211, and is perpendicular to the first direction Z. The second transition region 1135 and the second connection 52 are located above the second boundary surface V, while the third region 1131 is located below the second boundary surface V.

[0638] In this embodiment, the second transition region 1135 connects with the second connection portion 52 to form a second connection interface 521, thereby providing a sufficiently large contact area between the second transition region 1135 and the second connection portion 52, and improving the rigidity after welding the corner wall 113 and the end cover 12.

[0639] For some embodiments, please refer to Figures 43 to 48. At least a portion of the second connecting interface 521 extends at an angle relative to the thickness direction of the corner wall 113.

[0640] The second connecting interface 521 may extend in an inclination relative to the thickness direction of the corner wall 113 overall, or it may extend in an inclination relative to the thickness direction of the corner wall 113 locally.

[0641] Near the portion of the second connection interface 521 that extends at an inclination compared to the thickness direction of the corner wall 113, the tensile stress on the second transition region 1135 due to the contraction of the second connection portion 52 does not lie on the same straight line as the tensile stress on the second connection portion 52 due to the deformation of the corner wall 113 of the second transition region 1135, thereby reducing the risk of fatigue cracking in the region located near the second connection interface 521 of the second transition region 1135.

[0642] For some embodiments, please refer to Figures 43 to 48. The second connecting interface 521 includes a third interface 5212, which extends inclined toward the end cover 12 from the second position 5211, and along the thickness direction of the corner wall 113, at least a portion of the second transition region 1135 is located between the third interface 5212 and the end cover 12.

[0643] To make it easier to understand, the third interface 5212 extends at an angle relative to the thickness direction of the corner wall 113. The third interface 5212 may be a plane or a curved surface.

[0644] The second position 5211 is the lowest position of the third interface 5212 (the position closest to the third region 1131), and the third interface 5212 extends inclined from the second position 5211 toward the end cover 12, that is, the third interface 5212 extends upward inclined from the second position 5211 toward the end cover 12.

[0645] Along the thickness direction of the corner wall 113, the second transition region 1135 may be entirely located between the third interface 5212 and the end cover 12, or only a portion of the second transition region 1135 may be located between the third interface 5212 and the end cover 12.

[0646] In this embodiment, along the thickness direction of the corner wall 113, at least a portion of the second transition region 1135 is located between the third interface 5212 and the end cover 12, and the second connection portion 52 provides protection to the second transition region 1135, preventing outward deformation of the second transition region 1135 and reducing the risk of fatigue cracking in the region of the second transition region 1135 located near the third interface 5212.

[0647] For some embodiments, please refer to Figures 43 to 48. The third interface 5212 and the third outer surface 812 are connected at the second position 5211, which is located within the third region 1131.

[0648] For example, the third interface 5212 intersects the third outer surface 812 with a second straight line, the second straight line extends along the third direction X, and the position of the second straight line is the second position 5211. The third interface 5212 and the inner surface of the second transition region 1135 are connected at the fifth position 5214, and along the first direction Z, the fifth position 5214 is further from the third region 1131 than the second position 5211. The second transition region 1135 is approximately triangular.

[0649] In this embodiment, the third interface 5212 and the third outer surface 812 are connected at the second position 5211, and the second position 5211 is located within the third region 1131. As a result, the third outer surface 812 extends along the first direction Z of the third region 1131 toward the end facing the second connection portion 52. The portion of the corner wall 113 corresponding to the third outer surface 812 can relatively suitably reinforce the end of the third region 1131 toward the second connection portion 52, thereby reducing the possibility of fatigue cracking at the end of the third region 1131 toward the second connection portion 52, which has relatively low hardness.

[0650] For some embodiments, please refer to Figures 43 to 48. The second connecting interface 521 includes a fourth interface 5213, which extends inclined toward the end cover 12 from the second position 5211, and 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 cover 12.

[0651] To make it clear, the fourth interface 5213 extends at an angle relative to the thickness direction of the corner wall 113. The fourth interface 5213 may be planar or curved. Along the thickness direction of the corner wall 113, at least a portion of the second connection 52 is located between the fourth interface 5213 and the end cover 12.

[0652] The second position 5211 is the lowest position of the fourth interface 5213 (the position closest to the first region 1111), and the fourth interface 5213 extends inclined away from the end cover 12 from the second position 5211, that is, the fourth interface 5213 extends upward inclined away from the end cover 12 from the second position 5211.

[0653] Along the thickness direction of the corner wall 113, the second transition region 1135 may be entirely located on the side away from the end cover 12 of the fourth interface 5213, or only a portion of the second transition region 1135 may be located on the side away from the end cover 12 of the fourth interface 5213.

[0654] In this embodiment, at least a portion of the second transition region 1135 is located on the side away from the end cover 12 of the fourth interface 5213 along the thickness direction of the corner wall 113, thereby the second transition region 1135 acts as a limiting force on the second connection portion 52, reducing the risk of the second connection portion 52 falling off.

[0655] For some embodiments, please refer to Figures 43 to 48. Here, the fourth interface 5213 and the third inner surface 810 are connected at the second position 5211, and the second position 5211 is located within the third region 1131.

[0656] For example, the fourth interface 5213 intersects the third inner surface 810 with a second straight line, the second straight line extends along the third direction X, and the position of the second straight line is the second position 5211. The fourth interface 5213 and the outer surface of the second transition region 1135 are connected at the sixth position 5215, and along the first direction Z, the sixth position 5215 is further from the third region 1131 than the second position 5211. The second transition region 1135 is approximately triangular.

[0657] In this embodiment, the fourth interface 5213 and the third inner surface 810 are connected at the second position 5211, and the second position 5211 is located within the third region 1131. As a result, the third inner surface 810 extends along the first direction Z of the third region 1131 toward the end facing the second connection portion 52, and the portion of the corner wall 113 corresponding to the third inner surface 810 can relatively suitably reinforce the end of the third region 1131 toward the second connection portion 52, thereby reducing the possibility of fatigue cracking at the end of the third region 1131 toward the second connection portion 52, which has relatively low hardness.

[0658] In some embodiments, the second connecting interface 521 includes a third interface 5212 and a fourth interface 5213, the third interface 5212 extending inclined toward the end cover 12 from the second position 5211, and the fourth interface 5213 extending inclined toward the end cover 12 from the second position 5211, and 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 cover 12, and another portion of the second transition region 1135 is located on the side of the fourth interface 5213 away from the end cover 12.

[0659] For example, the third interface 5212 and the inner surface of the second transition region 1135 are connected at the fifth position 5214, and the fourth interface 5213 and the outer surface of the second transition region 1135 are connected at the sixth position 5215.

[0660] 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 connection 52.

[0661] For example, the hardness of the fourth region 1132 is less than the hardness of the second connection portion 52.

[0662] If the hardness of the second transition region 1135 is less than that of the fourth region 1132, the less hard second transition region 1135 will connect with the second connection 52, mitigating the rigid tension between the corner wall 113 and the second connection 52 during deformation, and reducing the possibility of separation between the corner wall 113 and the second connection 52. If the hardness of the second transition region 1135 is less than that of the second connection 52, the second transition region 1135 will deform more easily than the second connection 52, mitigating the rigid tension between the corner wall 113 and the second connection 52 during deformation, and reducing the possibility of separation between the corner wall 113 and the second connection 52.

[0663] In some embodiments, please refer to Figures 43 to 48. The second connection interface 521 is closer to the fourth region 1132 than to the outer surface 121 of the end cover.

[0664] In the embodiments shown in Figures 43 to 48, along the first direction Z, both the fifth position 5214 and the second position 5211 are closer to the fourth region 1132 than to the outer surface 121 of the end cover.

[0665] In the embodiments shown in Figures 43 to 48, along the first direction Z, both the sixth position 5215 and the second position 5211 are closer to the fourth region 1132 than to the outer surface 121 of the end cover.

[0666] In the embodiments shown in Figures 43 to 48, along the first direction Z, the fifth position 5214, the sixth position 5215, and the second position 5211 are all closer to the fourth region 1132 than to the outer surface 121 of the end cover.

[0667] In this embodiment, the second connection interface 521 is closer to the fourth region 1132 along the first direction Z compared to the outer surface 121 of the end cover. This allows the second connection portion 52 to sink deeper into the corner wall 113, effectively improving the connection strength between the corner wall 113 and the end cover 12.

[0668] In some embodiments, the hardness of the third region 1131 is lower than that of the second connection portion 52.

[0669] For some embodiments, please refer to Figures 7, 16, 19, and 23. The casing 11 includes two first sidewalls 111 and two second sidewalls 112, the two first sidewalls 111 being positioned opposite each other along a second direction Y, and the two second sidewalls 112 being positioned opposite each other along a third direction X, with the first direction Z, the second direction Y, and the third direction X being perpendicular in pairs.

[0670] Corner walls 113 are installed at both ends of the first side wall portion 111 along the third direction X, and corner walls 113 are installed at both ends of the second side wall portion 112 along the second direction Y. To make it clear, there are four corner walls 113 in the casing 11.

[0671] In this embodiment, the casing 11 is substantially rectangular, and the size of the casing 11 may be manufactured to be larger, which is advantageous in meeting the large capacitance requirement of the battery cell 10.

[0672] For some embodiments, please refer to Figure 49. The first side wall portion 111 has a stopper surface 1115 facing the end cover 12, the stopper surface 1115 abutting against the end cover 12 and restricting the movement of the end cover 12 in the direction toward the electrode assembly 2.

[0673] The stopper surface 1115 may be perpendicular to the first direction Z, the stopper surface 1115 may be an end face located at one end of the opening of the casing 11 of the first side wall portion 111, the stopper surface 1115 may be a stepped surface on the first side wall portion 111, and there is a certain distance between the stepped surface and the end face located at one end of the opening of the casing 11 of the first side wall portion 111.

[0674] The stopper surface 1115 acts as a stopper for the end cover 12, reducing the risk of the end cover 12 moving toward the electrode assembly 2 when it is welded to the casing 11, thereby effectively improving the welding quality between the end cover 12 and the casing 11 and reducing the difficulty of welding the end cover 12 and the casing 11.

[0675] For some embodiments, please refer to Figure 49. The first side wall portion 111 further includes a stopper region 1116 installed on the stopper surface 1115, the stopper region 1116 and the end cover 12 are installed facing each other along a second direction Y, and the stopper region 1116 is welded to the end cover 12 to form a first connection portion 51.

[0676] For example, at least a portion of the end cover 12 is housed within the casing 11, thereby positioning the stopper region 1116 and the end cover 12 opposite each other along the second direction Y.

[0677] After the stopper region 1116 is welded to the end cover 12, a portion of the stopper region 1116 may be fused integrally with a portion of the end cover 12 to form the first connection portion 51, and the remaining portion of the stopper region 1116 may form at least a portion of the first transition region 1117.

[0678] The stopper region 1116 can also act as a stopper for the end cover 12, reducing the risk of the end cover 12 moving along the thickness direction of the first side wall portion 111 when it is welded to the casing 11, further improving the welding quality between the end cover 12 and the casing 11, and reducing the difficulty of welding the end cover 12 and the casing 11.

[0679] In some embodiments, as shown in Figures 7, 16, 19, and 23, the second sidewall 112 has a uniform thickness structure. In other embodiments, the second sidewall 112 may have a non-uniform thickness structure, and the structure of the second sidewall 112 may be the same as the structure of the first sidewall 111. For example, the second sidewall 112 includes a fifth region and a sixth region arranged along a first direction Z, the hardness of the fifth region being lower than that of the sixth region, and the fifth region being located between the third connection 5 and the sixth region, thus reducing the possibility of cracking of the third connection 5 corresponding to the second sidewall 112. Here, 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.

[0680] In some embodiments, the hardness of the fifth region is lower than that of the third connection portion 5.

[0681] In some embodiments, the second side wall portion 112 has a fifth inner surface and a sixth inner surface facing the electrode assembly 2, and a seventh outer surface and an eighth outer surface away from the electrode assembly 2, wherein 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.

[0682] In some embodiments, in which the second side wall includes a fifth region and a sixth region, the third region 1131 can connect the first region 1111 and the fifth region, and the fourth region 1132 can connect the second region 1112 and the sixth region.

[0683] In some embodiments, please refer to Figures 12 and 13. The electrode assembly 2 is a laminated structure and includes a plurality of positive electrode plates 22 and a plurality of negative electrode plates 23, which are stacked along a second direction Y.

[0684] For example, in electrode assembly 2, the positive electrode plate 22 and the negative electrode tab 21b are arranged alternately along the second direction Y, and a separator 24 is placed between the positive electrode plate 22 and the negative electrode plate 23.

[0685] In this embodiment, the electrode assembly 2 has a layered structure, which makes the structure more compact and provides relatively strong resistance to crushing.

[0686] In some embodiments, please refer to Figures 12 and 13. The number of negative electrode plates 23 is greater than the number of positive electrode plates 22, and one positive electrode plate 22 is placed between two adjacent negative electrode plates 23.

[0687] For example, there is one more negative electrode plate 23 than positive electrode plates 22.

[0688] For some embodiments, please refer to Figures 12 and 13. A negative electrode tab 21b is provided on each negative electrode plate 23, and / or a positive electrode tab 21a is provided on each positive electrode plate 22.

[0689] 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 away from the electrode assembly 2, wherein the first inner surface 804 and the second inner surface 805 are connected in order along the direction of the end cover 12 toward the electrode assembly 2, the first outer surface 806 and the second outer surface 807 are connected in order along the direction of the end cover 12 toward 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, and 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 larger than the size of the positive electrode plate 22 and / or the negative electrode plate 23, and the first direction Z, the second direction Y, and the third direction X are perpendicular to each other in pairs.

[0690] If the size of the first inner surface 804 is larger than the size of the positive electrode plate 22 along the third direction X, the first inner surface 804 protrudes beyond at least one end of the positive electrode plate 22 along the third direction X, and if the size of the first inner surface 804 is larger than the size of the negative electrode plate 23 along the third direction X, the first inner surface 804 protrudes beyond at least one end of the negative electrode plate 23 along the third direction X.

[0691] For example, the size of the projection that overlaps the first region 1111 along the second direction Y of the first inner surface 804 along the third direction X is larger than the size of the positive electrode plate 22 and / or the negative electrode plate 23.

[0692] 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 plate 22 and / or the negative electrode plate 23, thereby the size of the first inner surface 804 along the third direction X is larger, thereby the first sidewall portion 111 is reinforced in a larger area along the third direction X, which is advantageous in reducing the possibility of cracking of the casing 11.

[0693] Refer to Figure 50 for some embodiments. The battery cell 10 further includes two electrode terminals 3, which are mounted on an end cover 12, and the two electrode terminals 3 have opposite polarities and are both electrically connected to an electrode assembly 2. A pull-out hole is provided in the end cover 12, and the electrode terminal 3 includes a terminal body 31 and a first stopper portion 32 and a second stopper portion 33, the terminal body 31 connecting the first stopper portion 32 and the second stopper portion 33, the terminal body 31 is mounted through the pull-out hole, and along a first direction Z, the first stopper portion 32 is located on the side of the end cover 12 away from the electrode assembly 2, and the second stopper portion 33 is located on the side of the end cover 12 facing the electrode assembly 2.

[0694] The first stopper portion 32 and the second stopper portion 33 have a stopper function, and the first stopper portion 32 and the second stopper portion 33 are each connected to both ends of the terminal body 31, and together the first stopper portion 32 and the second stopper portion 33 restrict the terminal body 31 from coming out of the pull-out hole. Along the first direction Z, the projected area of ​​the first stopper portion 32 and the projected area of ​​the second stopper portion 33 are both larger than the projected area of ​​the terminal body 31, and the projected area of ​​the first stopper portion 32 may be larger than the projected area of ​​the second stopper portion 33, and the projected area of ​​the second stopper portion 33 may be larger than the projected area of ​​the first stopper portion 32. The first stopper portion 32, the second stopper portion 33 and the terminal body 31 may be integrally molded, or one of the first stopper portion 32 and the second stopper portion 33 may be integrally molded with the terminal body 31, and the other may be installed separately from the terminal body 31 and connected.

[0695] For example, the battery cell 10 may further include a first insulating member 6 and a second insulating member 7, where at least a portion of the first insulating member 6 is installed between the electrode terminals 3 and the end cover 12 to insulate and isolate the electrode terminals 3 and the end cover 12, and the second insulating member 7 is installed on the side of the end cover 12 facing the electrode assembly 2 to insulate and isolate the electrode assembly 2 and the end cover 12.

[0696] In this embodiment, the electrode terminal 3 may be attached to the end cover 12 by riveting, which is easier to install and offers better cost-effectiveness.

[0697] In some embodiments, please refer to Figures 10 and 11. The electrode assembly 2 has a flat region 25, and the portion of the positive electrode plate 22 located in the flat region 25 and the portion of the negative electrode plate 23 located in the flat region 25 are stacked along the second direction Y.

[0698] The flat region 25 is the flat portion of the electrode assembly 2, and the portion of the positive electrode plate 22 located in the flat region 25 is in a nearly flat state, and the portion of the negative electrode plate 23 located in the flat region 25 is also in a nearly flat state. For example, both the portion of the positive electrode plate 22 located in the flat region 25 and the portion of the negative electrode plate 23 located in the flat region 25 are flat plate structures. If the electrode assembly 2 has a wound structure, then the electrode assembly 2 is a wound-type electrode assembly 2, and a part of the electrode assembly 2 may be the flat region 25, and if the electrode assembly 2 has a laminated structure, then the electrode assembly 2 is a laminated-type electrode...

Claims

1. It is a battery cell, A casing having an opening at least at one end along the first direction, including a first side wall portion, An electrode assembly comprising a positive electrode plate and a negative electrode plate, wherein at least a portion of the positive electrode plate and at least a portion of the negative electrode plate are stacked along a second direction, the second direction being parallel to the thickness direction of the first side wall, and the first direction intersecting the second direction, An end cover for sealing the opening, the end cover having a first side wall portion welded to the end cover to form a first connection portion, Herein, the first side wall 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, in a battery cell.

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

8.

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

8.

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

5. The battery cell according to any one of claims 1 to 4, wherein the size range along the first direction of the first region is 0.05 mm to 0.75 mm.

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

7. A battery cell according to any one of claims 1 to 6, wherein at least a portion of the crystal grains in the first region are first crystal grains, the ratio of the number of first crystal grains in the first region to the total number of crystal grains in the first region is greater than 50%, the size of the first crystal grains stretched along the first direction is a first size, the maximum size of the first crystal grains along the second direction is a second size, and the range of the ratio of the first size to the second size is 0.2 to 5.

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

9. The battery cell according to claim 7 or 8, wherein the first size range is 5 μm to 500 μm, and the second size range is 5 μm to 500 μm.

10. A battery cell according to any one of claims 1 to 9, wherein at least a portion of the crystal grains in the second region are second crystal grains, the ratio of the number of second crystal grains in the second region to the total number of crystal grains in the second region is greater than 50%, the size of the second crystal grains stretched along the first direction is the third size, the maximum size of the second crystal grains along the second direction is the fourth size, and the ratio of the third size to the fourth size is in the range of 4 to 100.

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

12. The battery cell according to claim 10 or 11, wherein the third size range is 150 μm to 1000 μm, and the fourth size range is 5 μm to 120 μm.

13. At least a portion of the crystal grains within the first region are first crystal grains, the ratio of the number of first crystal grains within the first region to the total number of crystal grains within the first region is greater than 50%, the size of the first crystal grains stretched along the first direction is the first size, the maximum size of the first crystal grains along the second direction is the second size, and the ratio of the first size to the second size is in the range of 0.2 to 5. At least a portion of the crystal grains within the second region are second crystal grains, the ratio of the number of second crystal grains within the second region to the total number of crystal grains within the second region is greater than 50%, the size of the second crystal grains stretched along the first direction is the third size, the maximum size of the second crystal grains along the second direction is the fourth size, and the ratio of the third size to the fourth size is in the range of 4 to 100. Here, the third size is larger than the first size, as described in any one of claims 1 to 12.

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

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

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

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

18. The battery cell according to claim 17, wherein the first inner surface includes a first sub-surface and a second sub-surface connected in sequence along the direction of the end cover toward the electrode assembly, the first sub-surface being at least partially formed in the first region, and along the second direction, the first sub-surface being closer to the electrode assembly than the second sub-surface, and the distance between the first sub-surface and the first outer surface along the second direction is greater than the distance between the second sub-surface and the first outer surface along the second direction.

19. The battery cell according to claim 18, wherein the distance between the second sub-surface and the first outer surface along the second direction is a first predetermined thickness, and the first predetermined thickness tends to decrease along the direction of the end cover toward the electrode assembly.

20. The battery cell according to claim 18 or 19, 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 according to any one of claims 17 to 20, 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 according to any one of claims 17 to 21, wherein the size of the first inner surface along the third direction is larger than the size of the first inner surface along the first direction, and the first, second, and third directions are not located on the same plane and intersect in pairs.

23. The battery cell according to any one of claims 17 to 22, wherein, along the second direction, the overlapping projection of the projection of the first inner surface and the projection of the first region is a 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, and the first, second, and third directions are not located on the same plane and intersect two at a time.

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

25. The battery cell according to claim 24, wherein the first connecting surface is at least partially formed in the first region, and along the second direction, the overlapping projection of the projection of the first connecting surface and the projection of the first region is a second projection, and the second projection passes through the middle cross section of the first side wall.

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

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

28. The battery cell according to claim 26 or 27, wherein the first inner surface further includes a first transition surface, the first connecting surface, the first transition surface and the second connecting surface are arranged along the third direction, the first transition surface connects the second connecting surface and the first connecting surface, the distance between the first transition surface and the first outer surface along the second direction is a second predetermined thickness, the second predetermined thickness tends to increase along the direction of the second connecting surface toward 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 predetermined thickness, the third predetermined thickness tends to increase along the direction of the third connecting surface toward the first connecting surface.

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

30. The size of the first connecting surface along the third direction is L １ The size of the first side wall portion along the third direction is L, and 0.2 ≤ L １ A battery cell according to any one of claims 24 to 29, wherein / L ≤ 0.

6.

31. The first connecting surface has a first end and a second end facing each other along the third direction, the first side wall portion has a third end and a fourth end facing each other along the third direction, the first end is close to the third end, the second end is close to the fourth end, the size of the first side wall portion along the third direction is L, and the minimum distance between the first end and the third end along the third direction is L ２ The minimum distance between the second end and the fourth end along the third direction is L ３ And L ２ / L ≤ 0.3, and / or L ３ A battery cell according to any one of claims 24 to 30, wherein / L ≤ 0.

3.

32. A battery cell according to claim 30 or 31, wherein 100 mm ≤ L ≤ 450 mm.

33. The casing includes a corner wall, and the corner wall is connected to both ends of the first side wall portion along the third direction. The battery cell according to any one of claims 22 to 32, wherein 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 each extend to the two corner walls.

34. The electrode assembly further includes a separator, the separator being placed between the positive electrode plate and the negative electrode plate. The battery cell according to any one of claims 17 to 33, wherein the positive electrode plate includes a positive electrode body region and a positive electrode tab protruding from the positive electrode body region, the positive electrode body region having a positive electrode active material layer, the negative electrode plate includes a negative electrode body region and a negative electrode tab protruding from the negative electrode body region, the negative electrode body region having a negative electrode active material layer, and along the first direction, the positive electrode body region has a fifth end facing the end cover, the negative electrode body region has a sixth end facing the end cover, the separator has a seventh end facing the end cover, the seventh end being closer to the end cover than the fifth and sixth ends.

35. The battery cell according to claim 34, wherein the separator includes protruding regions that protrude 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 protruding regions partially overlaps with the orthographic projection of the first inner surface.

36. The first inner surface protrudes from the second inner surface, The battery cell according to claim 34 or 35, wherein, in a projection plane perpendicular to the second direction, the orthographic projection of the positive electrode body region 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 body region does not overlap with the orthographic projection of the first inner surface.

37. The battery cell according to any one of claims 17 to 36, wherein the negative electrode plate includes a negative electrode current collector and a negative electrode active material layer installed on at least one side of the negative electrode current collector, and the negative electrode active material layer includes a negative electrode active material.

38. The battery cell according to claim 37, wherein the negative electrode active material layer includes a negative electrode main body and a negative electrode thinning portion, the negative electrode main body and the negative electrode thinning portion are arranged along the first direction, and the negative electrode thinning portion is installed along the first direction at the end of the negative electrode main body adjacent to the end cover.

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

40. The battery cell according to claim 39, wherein, in a projection plane perpendicular to the second direction, the spacing size along the first direction between the orthographic projection of the negative electrode thinning portion and the orthographic projection of the first inner surface is 1 mm or more.

41. The one-sided coating weight of the negative electrode active material layer is 90 mg / 1540 mm ２ to 170 mg / 1540 mm ２ and selectively 110 mg / 1540 mm ２ to 150 mg / 1540 mm ２ The battery cell according to any one of claims 37 to 40, which is such.

42. The battery cell according to any one of claims 37 to 41, wherein the porosity of the negative electrode plate is 27% to 40%.

43. The battery cell according to any one of claims 37 to 42, wherein the negative electrode active material includes a silicone-based material, and the mass content of silicon element in the silicone-based material in the negative electrode active material is 0.3% to 10%, and selectively 1% to 6%.

44. The battery cell according to claim 43, wherein the silicone-based material comprises at least one of a silicone oxide and a silicone carbon composite.

45. The battery cell according to any one of claims 17 to 44, wherein the positive electrode plate includes a positive electrode current collector and a positive electrode active material layer installed on at least one side of the positive electrode current collector, and the positive electrode active material layer includes a positive electrode active material.

46. The battery cell according to claim 45, wherein the positive electrode active material layer includes a positive electrode main body and a positive electrode thinning portion, the positive electrode main body and the positive electrode thinning portion are arranged along the first direction, and the positive electrode thinning portion is installed along the first direction at the end of the positive electrode main body adjacent to the end cover.

47. The battery cell according to 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 according to claim 47, wherein, in a projection plane perpendicular to the second direction, the spacing size along the first direction between the orthographic projection of the positive electrode thinning portion and the orthographic projection of the first inner surface is 1 mm or more.

49. The coating weight on one side of the positive electrode active material layer is 200 mg / 1540 mm². ２ ~370mg / 1540 / mm ２ Therefore, selectively 240 mg / 1540 mg ２ ~330mg / 1540mm ２ The battery cell according to any one of claims 45 to 48.

50. The battery cell according to any one of claims 45 to 49, wherein the positive electrode active material is a lithium-containing phosphate.

51. The material of the casing includes steel, The maximum distance along the second direction between the second inner surface and the second outer surface is D １ The size of the casing along the second direction is D, and 0.001 ≤ D １ A battery cell according to any one of claims 17 to 50, wherein / D ≤ 0.

012.

52. The material of the casing includes steel, The maximum distance along the second direction between the second inner surface and the second outer surface is D １ Therefore, 0.08 mm ≤ D １ ≤0.35 mm, and / or the maximum distance along the second direction between the first inner surface and the first outer surface is D ２ Therefore, 0.1 mm ≤ D ２ A battery cell according to any one of claims 17 to 51, wherein the diameter is ≤0.6 mm.

53. The material of the casing includes an aluminum alloy. The maximum distance along the second direction between the second inner surface and the second outer surface is D １ The size of the casing along the second direction is D, and 0.005 ≤ D １ A battery cell according to any one of claims 17 to 50, wherein / D ≤ 0.

065.

54. The material of the casing includes an aluminum alloy. The maximum distance along the second direction between the second inner surface and the second outer surface is D １ Therefore, 0.4 mm ≤ D １ ≤0.8 mm, and / or the maximum distance along the second direction between the first inner surface and the first outer surface is D ２ Therefore, 0.5 mm ≤ D ２ A battery cell according to any one of claims 17 to 50 or 53, wherein the diameter is ≤ 1.5 mm.

55. The battery cell according to claim 53 or 54, wherein the aluminum alloy comprises the following mass percent components: aluminum ≥ 99.6%, copper ≤ 0.05%, iron ≤ 0.35%, magnesium ≤ 0.03%, manganese ≤ 0.03%, silicon ≤ 0.25%, titanium ≤ 0.03%, vanadium ≤ 0.05%, zinc ≤ 0.05%, and other single elements ≤ 0.03%.

56. The battery cell according to any one of claims 17 to 55, wherein the first region is directly connected to the first connection portion, and the first inner surface extends along the first direction to the end of the first region facing the connection portion.

57. The battery cell according to any one of claims 17 to 56, wherein the first sidewall further includes a first transition region, the first transition region is connected to an end of the first region away from the second region along a first direction, the first transition region is connected to a first connection portion, a first connection interface is formed at the connection position between the first transition region and the first connection portion, the first connection interface has a first position closest to the first region along a first direction, and the first position is located at an end of the first region away from the second region along a first direction.

58. The battery cell according to claim 57, wherein at least a portion of the first connection interface extends at an angle with respect to the second direction.

59. The battery cell according to claim 58, wherein the first connection interface includes a first interface, the first interface extends inclined toward the end cover from the first position, and at least a portion of the first transition region is located between the first interface and the end cover along the second direction.

60. The battery cell according to claim 59, wherein the first interface and the first outer surface are connected at a first position, and the first position is at least partially located in the first region.

61. The battery cell according to any one of claims 58 to 60, wherein the first connection interface includes a second interface, the second interface extends inclined toward a direction away from the first position toward the end cover, and along the second direction, at least a portion of the first transition region is located on the side of the second interface away from the end cover.

62. The battery cell according to claim 61, wherein the second interface and the first inner surface are connected at the first position, and the first position is at least partially located in the first region.

63. The battery cell according to any one of claims 57 to 62, wherein the hardness of the first transition region is less than the hardness of the second region, and / or the hardness of the first transition region is less than the hardness of the first connection portion.

64. The battery cell according to any one of claims 57 to 63, wherein the first connection interface is closer to the second region than to the outer surface of the end cover.

65. The battery cell according to any one of claims 17 to 64, wherein the casing further includes a second side wall and a corner wall, the first side wall, the corner wall and the second side wall are arranged along the circumferential direction of the opening, and the corner wall connects the first side wall and the second side wall.

66. The aforementioned corner wall is welded to the end cover to form a second connection portion. The battery cell according to claim 65, wherein the corner wall includes a third region and a fourth region arranged along the first direction, the hardness of the third region is less than that of the fourth region, and the third region is located between the fourth region and the second connection portion.

67. The battery cell according to claim 66, wherein the corner wall has a third inner surface and a fourth inner surface facing the electrode assembly and a third outer surface and a fourth outer surface away from the electrode assembly, the third inner surface and the fourth inner surface are connected in order along the direction of the end cover facing the electrode assembly, the third inner surface and the third outer surface are at least partially formed in the third region, the fourth inner surface and the fourth outer surface are at least partially formed in the fourth region, and the distance between the third inner surface and the third outer surface along the thickness direction of the corner wall is greater than the distance between the fourth inner surface and the fourth outer surface along the thickness direction of the corner wall.

68. The battery cell according to 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 according to claim 68, wherein the corner wall has a first connecting end and a second connecting end, the first side wall portion is connected to the first connecting end, the second side wall portion is connected to the second connecting end, and the distance along the thickness direction of the corner wall between the third inner surface and the third outer surface is a fourth predetermined thickness, and the fourth predetermined thickness tends to decrease along the direction of the first connecting end toward the second connecting end.

70. The battery cell according to any one of claims 67 to 69, wherein the third region is directly connected to the second connection portion, and the third inner surface extends to the end of the third region facing the second connection portion.

71. The battery cell according to any one of claims 67 to 70, wherein the corner wall further includes a second transition region, the second transition region is connected to the end of the third region away from the fourth region along the first direction, the second transition region is connected to the second connection portion, a second connection interface is formed at the connection position between the second transition region and the second connection portion, the second connection interface has a second position closest to the third region along the first direction, and the second position is located at the end of the third region away from the fourth region along the first direction.

72. The battery cell according to claim 71, wherein at least a portion of the second connection interface extends at an inclination relative to the thickness direction of the corner wall.

73. The battery cell according to claim 72, wherein the second connection interface includes a third interface, the third interface extends inclined toward the end cover from the second position, and at least a portion of the second transition region is located between the third interface and the end cover along the thickness direction of the corner wall.

74. The battery cell according to claim 73, wherein the third interface and the third outer surface are connected at the second position, and the second position is located within the third region.

75. The battery cell according to any one of claims 72 to 74, wherein the second connection interface includes a fourth interface, the fourth interface extends inclined toward away from the second position toward the end cover, and at least a portion of the second transition region is located toward the side of the fourth interface away from the end cover along the thickness direction of the corner wall.

76. The battery cell according to claim 75, wherein the fourth interface and the third inner surface are connected at the second position, and the second position is located within the third region.

77. The battery cell according to any one of claims 71 to 76, wherein the hardness of the second transition region is less than the hardness of the fourth region, and / or the hardness of the second transition region is less than the hardness of the second connection portion.

78. The battery cell according to any one of claims 71 to 77, wherein the second connection interface is closer to the fourth region than to the outer surface of the end cover.

79. The battery cell according to any one of claims 66 to 78, wherein the hardness of the third region is lower than the hardness of the second connection portion.

80. The battery cell according to any one of claims 65 to 79, wherein the casing includes two first sidewalls and two second sidewalls, the two first sidewalls being positioned opposite each other along the second direction, the two second sidewalls being positioned opposite each other along the third direction, and the first, second, and third directions being perpendicular in pairs.

81. The battery cell according to any one of claims 1 to 80, wherein the first side wall portion has a stopper surface facing the end cover, and the stopper surface abuts against the end cover to restrict the movement of the end cover in the direction approaching the electrode assembly.

82. The battery cell according to claim 81, wherein the first side wall portion further includes a stopper region installed on the stopper surface, the stopper region and the end cover are installed facing each other along the second direction, and the stopper region is welded to the end cover to form the first connection portion.

83. The battery cell according to any one of claims 1 to 82, wherein the electrode assembly has a laminated structure, and the electrode assembly includes a plurality of positive electrode plates and a plurality of negative electrode plates, and the plurality of positive electrode plates and a plurality of negative electrode plates are stacked and installed along the second direction.

84. The battery cell according to claim 83, wherein the number of negative electrode plates is greater than the number of positive electrode plates, and one positive electrode plate is installed between two adjacent negative electrode plates.

85. The battery cell according to claim 83 or 84, wherein a negative electrode tab is provided on each of the negative electrode plates and / or a positive electrode tab is provided on each of the positive electrode plates.

86. The first side wall portion has a first inner surface and a second inner surface facing the electrode assembly and a first outer surface and a second outer surface away from the electrode assembly, the first inner surface and the second inner surface are connected in order along the direction of the end cover facing the electrode assembly, the first outer surface and the second outer surface are connected in order along the direction of the end cover facing 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. The battery cell according to any one of claims 83 to 85, wherein, along the third direction, the size of the first inner surface is greater than the size of the positive electrode plate and / or the size of the negative electrode plate, and the first direction, the second direction and the third direction are perpendicular to each other in pairs.

87. The battery cell further includes two electrode terminals, the two electrode terminals being mounted on the end cover, the two electrode terminals having opposite polarities, and both being electrically connected to the electrode assembly. A battery cell according to any one of claims 1 to 86, wherein the end cover is provided with a pull-out hole, the electrode terminal includes a terminal body, a first stopper portion and a second stopper portion, the terminal body connects the first stopper portion and the second stopper portion, the terminal body is inserted through the pull-out hole, and along the first direction, the first stopper portion is located on the side of the end cover away from the electrode assembly, and the second stopper portion is located on the side of the end cover facing the electrode assembly.

88. The battery cell according to any one of claims 1 to 87, wherein the electrode assembly has a flat region, and the 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 and installed along the second direction.

89. The battery cell according to claim 88, wherein the electrode assembly includes adjacent fifth and sixth outer surfaces, 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 and the first side wall being positioned opposite each other along the second direction.

90. The battery cell according to claim 89, wherein the fifth outer surface is the surface with the largest area among the outer surfaces of the electrode assembly.

91. The electrode assembly has a wound structure, and the electrode assembly further has a corner region, the corner region is located at at least one end along the third direction of the flat region, and the first, second and third directions are not located on the same plane and intersect in pairs. The battery cell according to claim 89 or 90, wherein the outer surface of the flat region includes the fifth outer surface, and the outer surface of the corner region includes the sixth outer surface, and at least a portion of the sixth outer surface is an arcuate surface.

92. The battery cell according to claim 89 or 90, wherein the electrode assembly has a laminated structure, the flat region includes a plurality of positive electrode plates and a plurality of negative electrode plates, the plurality of positive electrode plates and the plurality of negative electrode plates are stacked along the second direction, and the fifth outer surface is perpendicular to the sixth outer surface.

93. The battery cell according to any one of claims 1 to 92, wherein the first side wall portion is the wall with the largest outer surface area in the casing.

94. The battery cell according to any one of claims 1 to 93, wherein the casing includes two first sidewalls, the two first sidewalls are positioned opposite each other along the second direction, and the electrode assembly is located between the two first sidewalls.

95. The battery cell according to any one of claims 1 to 94, wherein the hardness of the first region is lower than the hardness of the first connection portion.

96. 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 separators are stacked and 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 separators are stacked in the flat region along the second direction. Each electrode assembly has N2 layers of positive electrode plates deposited in the flat region, the flat region has an outer surface perpendicular to the second direction, the area of ​​the outer surface is S, and N1 ≥ 1, N2 ≥ 1, N1 × N2 ≥ 50, S ≥ 8000 mm². ２ The battery cell according to any one of claims 1 to 95.

97. The negative electrode plate includes a negative electrode current collector and a negative electrode active material layer installed on at least one side of the negative electrode current collector, the negative electrode active material layer includes a negative electrode active material, and the discharge capacity per unit area of ​​the negative electrode active material layer is 2.0 mAh / cm². ２ ~5.0mAh / cm ２ The battery cell according to any one of claims 1 to 96.

98. The battery cell according to claim 96, wherein the thickness of the negative electrode active material layer is T1, and 9 μm ≤ T1 ≤ 75 μm.

99. A battery device comprising a battery cell according to any one of claims 1 to 98.

100. An electrical device comprising 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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