Battery cell, battery, and electrical device

Abstract

The present application provides a battery cell, a battery, and an electrical device. The battery cell comprises a housing, an end cover and an electrode assembly. At least one end of the housing in a first direction is provided with an opening. The housing comprises a first wall. The end cover seals the opening. The first wall and the end cover are welded to form a first connecting part. The electrode assembly is at least partially accommodated in the housing. The electrode assembly comprises a positive pole piece and a negative pole piece. At least part of the positive pole piece and at least part of the negative pole piece are stacked in a second direction. The second direction is parallel to the thickness direction of the first wall, and the first direction intersects with the second direction. The first wall comprises a first area and a second area which are arranged in the first direction. The thickness of the first area is larger than the thickness of the second area. The first area is located between the first connecting part and the second area. The solution reduces the risk of fatigue cracking of the first wall at the area located near the first connecting part caused by the expansion of the electrode assembly, and prolongs the service life of the battery cell.

Description

Battery cells, batteries and electrical equipment

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to international patent application No. PCT / CN2024 / 089160 filed on April 22, 2024, entitled “A battery cell, a battery and an electrical device”, international patent application No. PCT / CN2023 / 135607 filed on November 30, 2023, entitled “Battery cell, a battery, an electrical equipment and an energy storage device”, and international patent application No. PCT / CN2023 / 134129 filed on November 24, 2023, entitled “Casing, battery cell, battery and an electrical device”, the entire contents of which are incorporated herein by reference. Technical Field

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

[0004] Energy conservation and emission reduction are key to the sustainable development of the automotive industry. Electric vehicles, due to their energy-saving and environmentally friendly advantages, have become an important component of the sustainable development of the automotive industry. For electric vehicles, battery technology is a key factor in their development.

[0005] In battery technology, the service life of battery cells is an issue that cannot be ignored. Therefore, how to improve the service life of battery cells is a technical problem that needs to be solved urgently in battery technology.

[0006] Summary of the Invention

[0007] The embodiments of the present application provide a battery cell, a battery, and an electrical device, which can effectively increase the service life of the battery cell.

[0008] In a first aspect, an embodiment of the present application provides a battery cell, the battery cell comprising a shell, an end cover and an electrode assembly; the shell has an opening at at least one end along a first direction, and the shell comprises a first wall; the end cover closes the opening, and the first wall and the end cover are welded to form a first connecting portion; the electrode assembly is at least partially accommodated in the shell, the electrode assembly comprises a positive electrode sheet and a negative electrode sheet, at least a portion of the positive electrode sheet and at least a portion of the negative electrode sheet are stacked along a second direction, the second direction is parallel to the thickness direction of the first wall, and the first direction intersects with the second direction; the first wall comprises a first area and a second area arranged along the first direction, the thickness of the first area is greater than the thickness of the second area, and the first area is located between the first connecting portion and the second area.

[0009] In the above technical solution, the thickness of the first zone is greater than that of the second zone, and the first zone is located between the first connecting portion and the second zone, so that the first zone with a larger thickness is closer to the first connecting portion than the second zone. The first zone strengthens the area of ​​the first wall near the first connecting portion, reducing the risk of fatigue cracking of the area of ​​the first wall near the first connecting portion due to expansion of the electrode assembly, thereby improving the service life of the battery cell.

[0010] In some embodiments, the electrode assembly has a flat region, with the portion of the positive electrode tab located in the flat region and the portion of the negative electrode tab located in the flat region stacked along a second direction. The second direction is the direction in which the portions of the positive electrode tab located in the flat region and the portions of the negative electrode tab located in the flat region are stacked. During cycling, the electrode assembly expands more significantly along the second direction, and the first wall is more affected by the electrode assembly expansion. However, because the first region reinforces the area of ​​the first wall near the first connection, the risk of fatigue cracking of the first wall near the first connection due to electrode assembly expansion is reduced.

[0011] In some embodiments, the electrode assembly includes a first surface and a second surface adjacent to each other, the first surface being perpendicular to a second direction, the first surface having an area greater than that of the second surface, and the first surface and the first wall being arranged opposite each other along the second direction. The larger area of ​​the first surface relative to the second surface causes a greater expansion force to be applied to the first wall of the housing opposite the first surface. Because the first region reinforces the area of ​​the first wall near the first connection portion, the risk of fatigue cracking of the first wall near the first connection portion due to expansion of the electrode assembly is reduced.

[0012] In some embodiments, the first surface is the largest surface area of ​​the outer surface of the electrode assembly. This maximizes the expansion force on the first wall of the housing, which is located opposite the first surface. Because the first region reinforces the area of ​​the first wall near the first connection, the risk of fatigue cracking of the first wall near the first connection due to expansion of the electrode assembly is reduced.

[0013] In some embodiments, the electrode assembly has a wound structure and further includes a corner region. The straight region is provided with a corner region at at least one end along the third direction. The first, second, and third directions are non-coplanar and intersect with each other. The outer surface of the straight region includes a first surface, and the outer surface of the corner region includes a second surface, at least part of which is an arc surface. For a wound electrode assembly, the straight region expands more significantly in the second direction. Because the first region reinforces the area of ​​the first wall near the first connection portion, the risk of fatigue cracking of the first wall near the first connection portion due to expansion of the electrode assembly can be effectively reduced.

[0014] In some embodiments, the electrode assembly has a laminated structure, and the flat region includes multiple positive electrode sheets and multiple negative electrode sheets, which are stacked along the second direction, with the first surface perpendicular to the second surface. For a laminated electrode assembly, the electrode assembly expands more in the direction of stacking the positive and negative electrode sheets. Because the first region reinforces the area of ​​the first wall near the first connection, the risk of fatigue cracking of the first wall near the first connection due to expansion of the electrode assembly can be effectively reduced.

[0015] In some embodiments, the first wall is the wall with the largest outer surface area in the housing. The wall with the largest outer surface area in the housing is more likely to deform when subjected to the expansion force of the electrode assembly. Since the first wall is the wall with the largest outer surface area in the housing, the risk of fatigue cracking of the wall with the largest outer surface area in the housing near the first connection portion due to expansion of the electrode assembly is reduced.

[0016] In some embodiments, the housing includes two first walls that are disposed opposite each other along the second direction, with the electrode assembly located between the two first walls. This reduces the risk of fatigue cracking of the two first walls near the first connection portion due to expansion of the electrode assembly.

[0017] In some embodiments, the first zone includes a first portion and a second portion arranged along a first direction, the second portion connects the first portion and the second zone, and the thickness of the first portion is greater than the thickness of the second portion. The area of ​​the first zone near the first connecting portion is more likely to form a heat-affected zone, which is more prone to fatigue cracking. However, since the second portion connects the first portion and the second zone, and the thickness of the first portion is greater than the thickness of the second portion, the thicker first portion in the first zone is closer to the first connecting portion, which can effectively weaken the impact of the heat-affected zone on the first zone and reduce the risk of fatigue cracking in the area of ​​the first wall near the first connecting portion. In addition, since the thickness of the second portion is less than the thickness of the first portion, the material used in the first zone can be reduced, reducing production costs.

[0018] In some embodiments, the thickness of the second portion decreases along the direction from the end cap to the electrode assembly. This reduces the impact of the second portion on the electrode assembly, lowering the risk of interference between the second portion and the electrode assembly. Furthermore, the reinforcing effect of the second portion increases along the direction from the electrode assembly to the end cap, effectively reinforcing the area of ​​the second portion near the first portion even when affected by the first connection, thereby reducing the risk of fatigue cracking of the first wall in the second portion. Furthermore, the second portion provides a transition between the first portion and the second region, reducing stress concentration.

[0019] In some embodiments, the dimension of the first region along the third direction is larger than the dimension of the first region along the first direction, and the first, second, and third directions are not coplanar and intersect with each other. The larger dimension of the first region along the third direction increases the strength of the first wall over a larger area along the third direction, further reducing the risk of fatigue cracking in the area of ​​the first wall near the first connection portion.

[0020] In some embodiments, the first region includes a first connecting segment that passes through a mid-section of the first wall. The mid-section is perpendicular to the third direction and is equidistant from both ends of the first wall along the third direction. When the first wall is subjected to the expansion force of the battery cell electrode assembly, the mid-section of the first wall along the third direction deforms more significantly, making it more susceptible to fatigue cracking. Because the first connecting segment of the first region passes through the mid-section of the first wall, the strength of at least the mid-section of the first wall along the third direction is enhanced, reducing the risk of fatigue cracking in the mid-section of the first wall along the third direction near the first connecting portion.

[0021] In some embodiments, the first region further includes a second connecting segment and a third connecting segment, the second connecting segment, the first connecting segment, and the third connecting segment being arranged along a third direction, the first connecting segment connecting the second connecting segment and the third connecting segment, and the thickness of the first connecting segment being greater than the thickness of the second connecting segment and the thickness of the third connecting segment. When the first wall is subjected to the expansion force of the electrode assembly, the deformation of the first wall gradually decreases from the middle to the ends along the third direction. By dividing the first region into a multi-segment structure, and setting the thickness of the first connecting segment located in the middle region to be larger, and setting the thickness of the second connecting segment and the third connecting segment located at the ends of the first connecting segment to be smaller, the first region is designed according to the different deformation amounts of different regions of the first wall along the third direction, thereby specifically improving the strength of different regions of the first wall along the third direction. While ensuring sufficient strength in the region of the first wall near the first connecting portion, the material used in the first region is reduced, thereby reducing production costs.

[0022] In some embodiments, the first region further comprises a first transition section, the first connecting section, the first transition section, and the second connecting section are arranged along a third direction, the first transition section connects the second connecting section and the first connecting section, and the thickness of the first transition section increases in the direction from the second connecting section to the first connecting section; and / or, the first region further comprises a second transition section, the first connecting section, the second transition section, and the third connecting section are arranged along the third direction, the second transition section connects the third connecting section and the first connecting section, and the thickness of the second transition section increases in the direction from the third connecting section to the first connecting section. If the second connecting section and the first connecting section are connected by the first transition section, and the thickness of the first transition section increases in the direction from the second connecting section to the first connecting section, the first transition section can achieve a transition between the second connecting section and the first connecting section, thereby reducing stress concentration. If the third connecting section and the first connecting section are connected by the second transition section, and the thickness of the second transition section increases in the direction from the third connecting section to the first connecting section, the second transition section can achieve a transition between the third connecting section and the first connecting section, thereby reducing stress concentration.

[0023] In some embodiments, the dimension of the first connecting segment along the third direction is L1, and the dimension of the first wall along the third direction is L, and 0.2 ≤ L1 / L ≤ 0.6. L1 / L ≥ 0.2 increases the proportion of the first connecting segment's dimension in the first wall along the third direction, thereby strengthening a wider area of ​​the first wall's central region along the third direction and improving the strength of the central region of the first wall along the third direction. L1 / L ≤ 0.6 decreases the proportion of the first connecting segment's dimension in the first wall along the third direction, reducing material usage for the first connecting segment and lowering production costs. Therefore, setting the ratio of the first connecting segment's dimension along the third direction to the first wall's dimension along the third direction to 0.2 to 0.6 reduces material usage for the first connecting segment while ensuring sufficient reinforcement for the first connecting segment, thus achieving both reinforcement and economic efficiency.

[0024] In some embodiments, the first connecting segment has a first end and a second end opposite each other along the third direction, and the first wall has a third end and a fourth end opposite each other along the third direction, with the first end being closer to the third end and the second end being closer to the fourth end. The first wall has a dimension L along the third direction, a minimum distance L2 between the first end and the third end along the third direction, and a minimum distance L3 between the second end and the fourth end along the third direction; L2 / L ≤ 0.3; and / or L3 / L ≤ 0.3. If L2 / L ≤ 0.3, the proportion of the minimum distance between the first end and the third end along the third direction to the dimension of the first wall along the third direction is reduced, thereby increasing the strength of the first wall in a larger area along the third direction, further reducing the risk of fatigue cracking in the area of ​​the first wall near the first connecting portion. If L3 / L ≤ 0.3, the proportion of the minimum distance between the second end and the fourth end along the third direction to the dimension of the first wall along the third direction is reduced, thereby increasing the strength of the first wall in a larger area along the third direction, further reducing the risk of fatigue cracking in the area of ​​the first wall near the first connecting portion.

[0025] In some embodiments, 100 mm ≤ L ≤ 450 mm.

[0026] In some embodiments, the housing includes corner walls, with both ends of the first wall along the third direction connected to the corner walls; at least one end of the first region along the third direction does not contact the corner wall; or, the first region extends to both ends of the first region along the third direction. If at least one end of the first region along the third direction does not contact the corner wall, the material used in the first region can be reduced, lowering production costs. If both ends of the first region along the third direction extend to both corner walls, the length of the first region is increased, improving the reinforcement capacity of the first region, thereby strengthening more areas of the first wall along the third direction and further reducing the risk of fatigue cracking in the area of ​​the first wall near the first connection portion.

[0027] In some embodiments, the electrode assembly further includes a separator disposed between the positive electrode sheet and the negative electrode sheet. The positive electrode sheet includes a positive electrode main body region and a positive electrode tab protruding from the positive electrode main body region, the positive electrode main body region having a positive electrode active material layer. The negative electrode sheet includes a negative electrode main body region and a negative electrode tab protruding from the negative electrode main body region, the negative electrode main body region having a negative electrode active material layer. Along a first direction, the positive electrode main body region has a fifth end facing the end cap, the negative electrode main body region has a sixth end facing the end cap, and the separator has a seventh end facing the end cap, the seventh end being closer to the end cap than the fifth and sixth ends. The separator has a portion extending beyond the fifth and sixth ends, thereby enhancing the insulation effect of the separator between the positive and negative electrode sheets and reducing the risk of overlap between the positive and negative electrode sheets.

[0028] In some embodiments, the spacer includes a protruding region extending beyond the fifth and sixth ends along the first direction. In a projection plane perpendicular to the second direction, the orthographic projection of the protruding region partially overlaps with the orthographic projection of the first region. This structure can increase the size of the first region along the first direction, improving the reinforcement capacity of the first region. This strengthens more areas of the first wall along the first direction, further reducing the risk of fatigue cracking in the area of ​​the first wall near the first connection portion.

[0029] In some embodiments, the second region has a first inner surface facing the interior space of the housing, and the first region includes a first protrusion protruding from the first inner surface. In a projection plane perpendicular to the second direction, the orthographic projection of the positive electrode main region does not overlap with the orthographic projection of the first protrusion; and / or, in a projection plane perpendicular to the second direction, the orthographic projection of the negative electrode main region does not overlap with the orthographic projection of the first protrusion. If the orthographic projection of the positive electrode main region does not overlap with the orthographic projection of the first protrusion in a projection plane perpendicular to the second direction, the housing can provide more space for expansion of the electrode assembly, reducing the risk of expansion of the electrode assembly directly applying expansion force to the first protrusion, reducing deformation of the first wall, and further reducing the risk of fatigue cracking in the area of ​​the first wall near the first connection. If the orthographic projection of the negative electrode main region does not overlap with the orthographic projection of the first protrusion in a projection plane perpendicular to the second direction, the housing can provide more space for expansion of the electrode assembly, reducing the risk of expansion of the electrode assembly directly applying expansion force to the first protrusion, reducing deformation of the first wall, and further reducing the risk of fatigue cracking in the area of ​​the first wall near the first connection.

[0030] In some embodiments, the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer disposed on at least one side of the negative electrode current collector, and the negative electrode active material layer includes a negative electrode active material.

[0031] In some embodiments, the negative electrode active material layer includes a negative electrode main body and a negative electrode thinning portion, which are arranged along a first direction. The negative electrode thinning portion is provided at one end of the negative electrode main body near the end cap along the first direction. The electrode assembly has a larger expansion gap in the region corresponding to the negative electrode thinning portion. This region of the electrode assembly corresponding to the negative electrode thinning portion exerts less force on the first wall after expansion, thereby reducing the risk of fatigue cracking in the region of the first wall near the first connection portion.

[0032] In some embodiments, within a projection plane perpendicular to the second direction, the orthographic projection of the negative electrode thinning portion is spaced apart from the orthographic projection of the first region along the first direction. This can reduce the impact of the negative electrode thinning portion on the first region, reduce the risk of the electrode assembly expanding and directly applying expansion force to the first region, and further reduce the risk of fatigue cracking in the area of ​​the first wall near the first connecting portion.

[0033] In some embodiments, in a projection plane perpendicular to the second direction, the spacing between the orthogonal projection of the negative electrode thinned portion and the orthogonal projection of the first region along the first direction is greater than or equal to 1 mm. This allows the orthogonal projection of the negative electrode thinned portion to be further away from the orthogonal projection of the first region along the first direction in the projection plane perpendicular to the second direction, further reducing the impact of the negative electrode thinned portion on the first region.

[0034] In some embodiments, the single-side coating weight of the negative electrode active material layer is 90 mg / 1540 mm 2 ~170mg / 1540mm 2 The coating weight of the negative electrode active material layer on one side is related to the expansion of the negative electrode active material layer. The coating weight of the negative electrode active material layer on one side is set at 90 mg / 1540 mm 2 ~170mg / 1540mm 2 , which can, to a certain extent, take into account the high energy density requirements of the battery cell and the low expansion requirements of the negative electrode sheet, so as to reduce the impact of the expansion of the negative electrode sheet on the first wall, and can reduce the risk of fatigue cracking in the area of ​​the first wall near the first connecting portion.

[0035] In some embodiments, the single-side coating weight of the negative electrode active material layer is 110 mg / 1540 mm 2 ~150mg / 1540mm 2 It can further increase the energy density requirements of battery cells and further slow down the expansion of negative electrode sheets.

[0036] In some embodiments, the porosity of the negative electrode plate is 27% to 40%, which can provide space for impurities generated by side reactions in the negative electrode plate, slow down the expansion of the negative electrode plate, and reduce the impact of the expansion of the negative electrode plate on the first wall.

[0037] In some embodiments, the negative electrode active material includes a silicon-based material, and the mass content of silicon in the silicon-based material is 0.3% to 10%, and can be optionally 1% to 6%.

[0038] In some embodiments, the silicon-based material includes at least one of a silicon-oxygen compound and a silicon-carbon composite.

[0039] In some embodiments, the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer disposed on at least one side of the positive electrode current collector, wherein the positive electrode active material layer includes a positive electrode active material.

[0040] In some embodiments, the positive electrode active material layer includes a positive electrode main body and a positive electrode thinning portion, which are arranged along a first direction. The positive electrode thinning portion is provided at one end of the positive electrode main body near the end cap along the first direction. The electrode assembly has a larger expansion gap in the region corresponding to the positive electrode thinning portion. This region of the electrode assembly corresponding to the positive electrode thinning portion exerts less force on the first wall after expansion, thereby reducing the risk of fatigue cracking in the region of the first wall near the first connection portion.

[0041] In some embodiments, within a projection plane perpendicular to the second direction, the orthographic projection of the positive electrode thinning portion is spaced apart from the orthographic projection of the first region along the first direction. This can reduce the impact of the positive electrode thinning portion on the first region, reduce the risk of the electrode assembly expanding and directly applying expansion force to the first region, and further reduce the risk of fatigue cracking in the area of ​​the first wall near the first connecting portion.

[0042] In some embodiments, in a projection plane perpendicular to the second direction, the distance between the orthographic projection of the positive electrode thinned portion and the orthographic projection of the first region along the first direction is greater than or equal to 1 mm. This allows the orthographic projection of the positive electrode thinned portion to be further away from the orthographic projection of the first region along the first direction in the projection plane perpendicular to the second direction, further reducing the impact of the positive electrode thinned portion on the first region.

[0043] In some embodiments, the single-sided coating weight of the positive electrode active material layer is 200 mg / 1540 mm 2 ~370mg / 1540 / mm 2 The single-sided coating weight of the positive electrode active material layer is related to the expansion of the positive electrode active material layer. The single-sided coating weight of the positive electrode active material layer is set at 200 mg / 1540 mm 2 ~370mg / 1540 / mm 2 , which can, to a certain extent, take into account the high energy density requirements of the battery cell and the low expansion requirements of the positive electrode sheet, so as to reduce the impact of the expansion of the positive electrode sheet on the first wall, and can reduce the risk of fatigue cracking in the area of ​​the first wall near the first connecting portion.

[0044] In some embodiments, the single-side coating weight of the positive electrode active material layer is 240 mg / 1540 mm 2 ~330mg / 1540mm 2 It can further increase the energy density requirements of battery cells and further slow down the expansion of the positive electrode sheets.

[0045] In some embodiments, the positive electrode active material is a lithium-containing phosphate.

[0046] In some embodiments, the housing is made of steel; the maximum thickness of the second region is D1, and the dimension of the housing along the second direction is D, where 0.001 ≤ D1 / D ≤ 0.012. For a steel housing, D1 / D ≥ 0.001 increases the thickness ratio of the second region within the housing, ensuring sufficient strength to meet the strength requirements of the housing. D1 / D ≤ 0.012 reduces the thickness ratio of the second region within the housing. Given a given volume, this increases the internal space of the housing, freeing up more space for the electrode assembly to meet the volumetric energy density requirements of the battery cells.

[0047] In some embodiments, the housing is made of steel; the maximum thickness of the second zone is D1, 0.08mm≤D1≤0.35mm; and / or the maximum thickness of the first zone is D2, 0.1mm≤D2≤0.6mm. For a housing made of steel, setting the maximum thickness of the second zone to 0.08mm to 0.35mm can meet both the strength requirements of the second zone and the volumetric energy density requirements of the battery cell. Setting the maximum thickness of the first zone to 0.1mm to 0.6mm provides sufficient strength in the first zone to enhance the strength of the area of ​​the first wall near the first connection portion.

[0048] In some embodiments, the shell is made of aluminum alloy; the maximum thickness of the second region is D1, and the dimension of the shell along the second direction is D, with 0.005 ≤ D1 / D ≤ 0.065. For a shell made of aluminum alloy, D1 / D ≥ 0.005 increases the thickness ratio of the second region within the shell, ensuring sufficient strength to meet the shell's strength requirements; D1 / D ≤ 0.065 reduces the thickness ratio of the second region within the shell. Given a given shell volume, this increases the internal space of the shell, freeing up more space for the electrode assembly to meet the volumetric energy density requirements of the battery cells.

[0049] In some embodiments, the housing is made of aluminum alloy; the maximum thickness of the second zone is D1, 0.4 mm ≤ D1 ≤ 0.8 mm; and / or the maximum thickness of the first zone is D2, 0.5 mm ≤ D2 ≤ 1.5 mm. For a housing made of aluminum alloy, setting the maximum thickness of the second zone to 0.4 mm to 0.8 mm can meet both the strength requirements of the second zone and the volumetric energy density requirements of the battery cell. Setting the maximum thickness of the first zone to 0.5 mm to 1.5 mm provides sufficient strength in the first zone to enhance the strength of the area of ​​the first wall near the first connection portion.

[0050] In some embodiments, the aluminum alloy includes the following composition by weight: aluminum ≥ 99.6%, copper ≤ 0.05%, iron ≤ 0.35%, magnesium ≤ 0.03%, manganese ≤ 0.03%, silicon ≤ 0.25%, titanium ≤ 0.03%, vanadium ≤ 0.05%, zinc ≤ 0.05%, and other individual elements ≤ 0.03%. This aluminum alloy has good processability and facilitates shell molding.

[0051] In some embodiments, the first region is directly connected to the first connecting portion, which brings the first region closer to the first connecting portion along the first direction and places the first region near the first connecting portion, further reducing the risk of fatigue cracking of the area of ​​the first wall near the first connecting portion due to expansion of the electrode assembly.

[0052] In some embodiments, the first wall further comprises a first transition region, the first transition region being connected to an end of the first region distal from the second region along the first direction, the first transition region being connected to the first connecting portion, the connection between the first transition region and the first connecting portion forming a first connecting interface, the first connecting interface having a first position closest to the first region along the first direction, the first position being located at an end of the first region distal from the second region along the first direction. The first transition region and the first connecting portion are connected to form the first connecting interface, providing a sufficiently large contact area between the first transition region and the first connecting portion, thereby improving the securement of the first wall and the end cap after welding.

[0053] In some embodiments, at least a portion of the first connection interface extends obliquely relative to the second direction. After the end cap and the first wall are welded, the first connection portion will shrink as it solidifies, and the first connection portion will generate tensile stress on the first transition zone. When the first wall is subjected to the expansion force of the electrode assembly, the first wall will deform, and the first transition zone will generate tensile stress on the first connection portion. Since at least a portion of the first connection interface extends obliquely relative to the second direction, near the portion of the first connection interface that extends obliquely relative to the second direction, the tensile stress generated by the first connection portion on the first transition zone due to shrinkage and the tensile stress generated by the first transition zone due to deformation of the first wall are not on the same straight line, thereby reducing the risk of fatigue cracking in the area of ​​the first transition zone near the first connection interface.

[0054] In some embodiments, the first connection interface includes a first interface that extends obliquely from a first position toward the end cap, and along a second direction, at least a portion of the first transition region is located between the first interface and the end cap. The first connection portion protects the first transition region. When the first wall is subjected to an expansion force of the electrode assembly, deformation of the first transition region during the force application is blocked by the first connection portion, thereby reducing the risk of fatigue cracking in the first transition region near the first interface.

[0055] In some embodiments, the first interface is connected to the outer surface of the first region at a first position, so that the first region and the first connecting portion are in direct connection, bringing the first region and the first connecting portion closer together along the first direction, and further reducing the risk of fatigue cracking of the area of ​​the first wall near the first connecting portion due to expansion of the electrode assembly.

[0056] In some embodiments, the first connection interface includes a second interface that extends obliquely from the first position toward a direction away from the end cap. Along the second direction, at least a portion of the first transition zone is located on a side of the second interface that is away from the end cap. This allows the first transition zone to restrain the first connection portion, reducing the risk of the first connection portion falling off.

[0057] In some embodiments, the second interface is connected to the inner surface of the first region at a first position, so that the first region and the first connecting portion are in direct connection, bringing the first region and the first connecting portion closer together along the first direction, further reducing the risk of fatigue cracking of the area of ​​the first wall near the first connecting portion due to expansion of the electrode assembly.

[0058] In some embodiments, the Vickers hardness of the first transition zone is less than the Vickers hardness of the second zone; and / or the Vickers hardness of the first transition zone is less than the Vickers hardness of the first connecting portion. If the Vickers hardness of the first transition zone is less than the Vickers hardness of the second zone, the first transition zone with a lower Vickers hardness is connected to the first connecting portion, which can alleviate the rigid pull between the first wall and the first connecting portion when the first wall deforms, reducing the risk of separation between the first wall and the first connecting portion. If the Vickers hardness of the first transition zone is less than the Vickers hardness of the first connecting portion, the first transition zone is more easily deformed than the first connecting portion, which can alleviate the rigid pull between the first wall and the first connecting portion when the first wall deforms, reducing the risk of separation between the first wall and the first connecting portion.

[0059] In some embodiments, along the first direction, the first connection interface is closer to the second region than the outer surface of the end cap, so that the first connection portion can sink deeper into the first wall, which can effectively improve the connection strength between the first wall and the end cap.

[0060] In some embodiments, the housing further includes a second wall and a corner wall, wherein the first wall, the corner wall, and the second wall are arranged along the circumference of the opening, and the corner wall connects the first wall and the second wall. This allows the first wall to transition to the second wall through the corner wall, effectively reducing the risk of stress concentration at the corner of the housing.

[0061] In some embodiments, the corner wall is welded to the end cap to form a second connecting portion. The corner wall includes a third region and a fourth region arranged along the first direction. The third region is thicker than the fourth region and is located between the fourth region and the second connecting portion. The third region is thicker than the fourth region and is located between the second connecting portion and the fourth region. This places the thicker third region closer to the second connecting portion than the fourth region. The third region reinforces the area of ​​the corner wall near the second connecting portion, reducing the risk of fatigue cracking in the area near the second connecting portion, thereby increasing the service life of the battery cell.

[0062] In some embodiments, the third area is directly connected to the first area. Directly connecting the third area to the first area connects the first area and the third area into a whole. The third area and the first area promote each other, thereby enhancing the reinforcement effect of the first area on the first wall and the reinforcement effect of the second area on the corner wall.

[0063] In some embodiments, along the circumference of the opening, the corner wall has a first connection end and a second connection end, the first wall is connected to the first connection end, the second wall is connected to the second connection end, and the thickness of the third region decreases in the direction from the first connection end to the second connection end. When the first wall is subjected to the expansion force of the electrode assembly in the second direction, the deformation of the first wall may cause the corner wall to deform as well. The closer the corner wall is to the first wall along the circumference of the opening, the greater the impact of the first wall on the corner wall is, and the greater the deformation of the area closer to the first wall. The thickness of the third region decreases in the direction from the first connection end to the second connection end, making the third region stronger in the area near the first wall along the circumference of the opening, thereby reducing the impact of the deformation of the first wall on the corner wall. While ensuring that the area near the second connection portion of the corner wall has sufficient strength, the material used in the third region is reduced, thereby reducing production costs.

[0064] In some embodiments, the third area is directly connected to the second connection portion, so that the third area is closer to the second connection portion along the first direction and the third area is located near the second connection portion, further reducing the risk of fatigue cracking in the area of ​​the corner wall near the second connection portion.

[0065] In some embodiments, the corner wall further includes a second transition region connected to an end of the third region distal from the fourth region along the first direction. The second transition region is connected to the second connecting portion. The connection between the second transition region and the second connecting portion forms a second connecting interface. The second connecting interface has a second position closest to the third region along the first direction, and the second position is located at an end of the third region distal from the fourth region along the first direction. The second transition region and the second connecting portion form the second connecting interface, providing a sufficiently large contact area between the second transition region and the second connecting portion, thereby improving the securement of the corner wall and the end cap after welding.

[0066] In some embodiments, at least a portion of the second connection interface extends obliquely relative to the thickness direction of the corner wall. Near the portion of the second connection interface that extends obliquely relative to the thickness direction of the corner wall, the tensile stress in the second transition zone caused by shrinkage of the second connection portion and the tensile stress in the second transition zone caused by deformation of the corner wall are not aligned, thereby reducing the risk of fatigue cracking in the second transition zone near the second connection interface.

[0067] In some embodiments, the second connection interface includes a third interface. The third interface extends obliquely from the second position toward the end cap. Along the thickness direction of the corner wall, at least a portion of the second transition zone is located between the third interface and the end cap. The second connection portion protects the second transition zone. Outward deformation of the second transition zone is blocked by the second connection portion, thereby reducing the risk of fatigue cracking in the second transition zone near the third interface.

[0068] In some embodiments, the third interface is connected to the outer surface of the third region at a second position, so that the third region is directly connected to the second connecting portion, bringing the third region and the second connecting portion closer together along the first direction, further reducing the risk of fatigue cracking in the corner wall near the second connecting portion.

[0069] In some embodiments, the second connection interface includes a fourth interface that extends obliquely from the second position away from the end cap. Along the thickness direction of the corner wall, at least a portion of the second transition zone is located on a side of the fourth interface that is away from the end cap. This allows the second transition zone to restrain the second connection portion, reducing the risk of the second connection portion falling off.

[0070] In some embodiments, the fourth interface is connected to the inner surface of the third region at a second position, so that the third region and the second connecting portion are directly connected, bringing the third region and the second connecting portion closer together along the first direction, further reducing the risk of fatigue cracking in the corner wall near the second connecting portion.

[0071] In some embodiments, the Vickers hardness of the second transition zone is less than the Vickers hardness of the fourth zone; and / or, the Vickers hardness of the second transition zone is less than the Vickers hardness of the second connecting portion. If the Vickers hardness of the second transition zone is less than the Vickers hardness of the fourth zone, the second transition zone with a lower Vickers hardness is connected to the second connecting portion, which can alleviate the rigid pull between the corner wall and the second connecting portion when it deforms, reducing the risk of the corner wall separating from the second connecting portion. If the Vickers hardness of the second transition zone is less than the Vickers hardness of the second connecting portion, the second transition zone is more easily deformed than the second connecting portion, which can alleviate the rigid pull between the corner wall and the second connecting portion when it deforms, reducing the risk of the corner wall separating from the second connecting portion.

[0072] In some embodiments, along the first direction, the second connection interface is closer to the fourth region than the outer surface of the end cap, so that the second connection portion can sink deeper into the corner wall, which can effectively improve the connection strength between the corner wall and the end cap.

[0073] In some embodiments, the housing includes two first walls and two second walls, the two first walls being arranged opposite each other along the second direction, the two second walls being arranged opposite each other along the third direction, and the first direction, the second direction, and the third direction being perpendicular to each other. This allows the housing to be roughly rectangular, allowing for a larger housing size, which is advantageous for meeting the large capacity requirements of the battery cells.

[0074] In some embodiments, at least a portion of the first region has a lower Vickers hardness than the second region. When the second region is deformed by the expansion force of the electrode assembly, the region of the first region having a lower Vickers hardness than the second region can reduce the impact of the deformation of the second region on the region of the first wall near the first connection portion, thereby reducing the risk of fatigue cracking in the region of the first wall near the first connection portion due to expansion of the electrode assembly.

[0075] In some embodiments, the first wall has a limiting surface facing the end cap along the first direction. The limiting surface abuts the end cap to limit movement of the end cap toward the electrode assembly. The limiting surface acts as a limiter for the end cap, reducing the risk of the end cap moving toward the electrode assembly during welding to the housing, effectively improving the weld quality between the end cap and the housing and reducing the difficulty of welding the end cap and the housing.

[0076] In some embodiments, the first wall further includes a limiting region disposed on the limiting surface, the limiting region and the end cap being disposed opposite each other along the second direction, and the limiting region and the end cap being welded to form a first connection portion. The limiting region also serves to limit the end cap, reducing the risk of movement along the thickness direction of the first wall during welding of the end cap to the shell, further improving the welding quality of the end cap and the shell, and reducing the difficulty of welding the end cap and the shell.

[0077] In some embodiments, the electrode assembly is a laminated structure, comprising a plurality of positive electrode sheets and a plurality of negative electrode sheets, wherein the plurality of positive electrode sheets and the plurality of negative electrode sheets are stacked along the second direction. The laminated electrode assembly is more compact and has greater compression resistance.

[0078] In some embodiments, the number of negative electrode plates is greater than the number of positive electrode plates, and a positive electrode plate is disposed between two adjacent negative electrode plates.

[0079] In some embodiments, each negative electrode plate is provided with a negative electrode tab; and / or each positive electrode plate is provided with a positive electrode tab.

[0080] In some embodiments, along the third direction, the first region is larger than the positive electrode tab and / or the negative electrode tab, and the first, second, and third directions are perpendicular to each other. This increases the size of the first region along the third direction, thereby enhancing the strength of the first wall over a wider area along the third direction and further reducing the risk of fatigue cracking in the area of ​​the first wall near the first connection portion.

[0081] In some embodiments, the battery cell further includes two electrode terminals, disposed on an end cap. The two electrode terminals have opposite polarities and are both electrically connected to the electrode assembly. The end cap is provided with an extraction hole. The electrode terminal comprises a terminal body, a first stopper, and a second stopper. The terminal body connects the first and second stoppers and extends through the extraction hole. Along a first direction, the first stopper is located on the side of the end cap facing away from the electrode assembly, and the second stopper is located on the side of the end cap facing the electrode assembly. This electrode terminal structure can be riveted to the end cap, which reduces installation complexity and offers improved cost-effectiveness.

[0082] In a second aspect, an embodiment of the present application provides a battery, comprising a battery cell provided by any embodiment of the first aspect.

[0083] In a third aspect, an embodiment of the present application provides an electrical device, including a battery cell provided by any embodiment of the first aspect, wherein the battery cell is used to provide electrical energy to the electrical device. BRIEF DESCRIPTION OF THE DRAWINGS

[0084] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without creative work.

[0085] FIG1 is a schematic structural diagram of a vehicle provided in some embodiments of the present application;

[0086] FIG2 is an exploded view of a battery provided in some embodiments of the present application;

[0087] FIG3 is an exploded view of a battery cell provided in some embodiments of the present application;

[0088] FIG4 is an axonometric view of the battery cell shown in FIG3 ;

[0089] FIG5 is an AA cross-sectional view of the battery cell shown in FIG4 ;

[0090] FIG6 is a partial enlarged view of point B in FIG5 ;

[0091] FIG7 is an axonometric view of the housing shown in FIG5 ;

[0092] FIG8 is an axonometric view of an electrode assembly provided in some embodiments of the present application;

[0093] FIG9 is a schematic structural diagram of the electrode assembly shown in FIG8 ;

[0094] FIG10 is an axonometric view of electrode assemblies provided in some other embodiments of the present application;

[0095] FIG11 is a schematic structural diagram of the electrode assembly shown in FIG10 ;

[0096] FIG12 is a partial view of the first wall shown in FIG6;

[0097] FIG13 is an axonometric view of a housing provided in some embodiments of the present application;

[0098] FIG14 is a top view of the housing shown in FIG13 ;

[0099] FIG15 is an axonometric view of a housing provided in some other embodiments of the present application;

[0100] FIG16 is a top view of the housing shown in FIG15 ;

[0101] FIG17 is an axonometric view of a housing provided in some other embodiments of the present application;

[0102] FIG18 is a top view of the housing shown in FIG17 ;

[0103] FIG19 is a partial view of a battery cell provided in some embodiments of the present application (showing a positive electrode sheet, a negative electrode sheet, and a separator of an electrode assembly);

[0104] FIG20 is a diagram showing the positional relationship between the positive electrode sheet, the negative electrode sheet, and the separator according to some embodiments of the present application;

[0105] FIG21 is a diagram showing the positional relationship among the positive electrode sheet, the negative electrode sheet, and the separator provided in some other embodiments of the present application;

[0106] FIG22 is a partial view of a battery cell provided in some embodiments of the present application (showing the first wall);

[0107] FIG23 is a partial view of the first wall shown in FIG22;

[0108] FIG24 is an axonometric view of the housing shown in FIG22 ;

[0109] FIG25 is a partial view of a battery cell provided in accordance with some other embodiments of the present application (showing the first wall);

[0110] FIG26 is a partial enlarged view of point C in FIG25;

[0111] FIG27 is a partial view of a battery cell provided in accordance with yet other embodiments of the present application (showing the first wall);

[0112] FIG28 is a partial enlarged view of point D in FIG27;

[0113] FIG29 is a partial view of a battery cell provided in some further embodiments of the present application (showing the first wall);

[0114] FIG30 is a partial enlarged view of point E in FIG29;

[0115] FIG31 is an axonometric view of a housing according to some further embodiments of the present application;

[0116] FIG32 is a partial enlarged view of point F in FIG31;

[0117] FIG33 is a partial view of a battery cell provided in some embodiments of the present application (showing a corner wall);

[0118] FIG34 is a schematic structural diagram of a corner wall provided in some embodiments of the present application;

[0119] FIG35 is a schematic structural diagram of corner walls provided in other embodiments of the present application;

[0120] FIG36 is a partial view of a battery cell provided in accordance with some other embodiments of the present application (showing a corner wall);

[0121] FIG37 is a partial enlarged view of point G in FIG36;

[0122] FIG38 is a partial view of a battery cell provided in accordance with yet other embodiments of the present application (showing a corner wall);

[0123] FIG39 is a partial enlarged view of point H in FIG38;

[0124] FIG40 is a partial view of a battery cell provided in accordance with still other embodiments of the present application (showing a corner wall);

[0125] FIG41 is a partial enlarged view of point I in FIG40;

[0126] FIG42 is a diagram showing the positional relationship between the end cover and the side wall before welding in some embodiments of the present application;

[0127] Figure 43 is a schematic diagram of the connection between the end cap and the electrode terminal provided in some embodiments of the present application.

[0128] Icons: 1-shell; 11-shell; 111-first wall; 1111-first zone; 11111-first part; 11112-second part; 11113-first connecting section; 11113a-first end; 11113b-second end; 11114-second connecting section; 11115-third connecting section; 11116-first transition section; 11117-second transition section; 11118-first protrusion; 1112-second zone; 11121-first inner surface; 11122-first outer surface; 1113-third end; 1114-fourth end; 1115-limiting surface; 1116-limiting zone; 1 117 - first transition zone; 112 - second wall; 113 - corner wall; 1131 - third zone; 1132 - fourth zone; 11321 - second inner surface; 11322 - second outer surface; 1133 - first connection terminal; 1134 - second connection terminal; 1135 - second transition zone; 12 - end cap; 121 - outer surface of end cap; 2 - electrode assembly; 21 - tab; 21a - positive electrode tab; 21b - negative electrode tab; 22 - positive electrode sheet; 221 - positive electrode main body; 2211 - fifth end; 222 - positive electrode current collector; 223 - positive electrode active material layer; 2231 - positive electrode main body; 2232 - positive electrode thinning 224-insulating layer; 23-negative electrode sheet; 231-negative electrode main body; 2311-sixth end; 232-negative electrode current collector; 233-negative electrode active material layer; 2331-negative electrode main body; 2332-negative electrode thinning portion; 24-separator; 241-seventh end; 242-excess area; 25-straight area; 26-corner area; 27-first surface; 28-second surface; 3-electrode terminal; 31-terminal body; 32-first limiting portion; 33-second limiting portion; 4-pressure relief mechanism; 5-connecting portion; 51-first connecting portion; 511-first connecting interface; 5111-first position; 5112-first Interface; 5113-second interface; 5114-third position; 5115-fourth position; 52-second connection part; 521-second connection interface; 5211-second position; 5212-third interface; 5213-fourth interface; 5214-fifth position; 5215-sixth position; 6-first insulating member; 7-second insulating member; 10-battery cell; 20-housing; 201-first housing; 202-second housing; 100-battery; 200-controller; 300-motor; 1000-vehicle; Z-first direction; Y-second direction; X-third direction; U-first dividing interface; V-second dividing interface. DETAILED DESCRIPTION

[0129] To make the purpose, technical solutions, and advantages of the embodiments of this application more clear, the technical solutions in the embodiments of this application will be clearly described below in conjunction with the drawings in the embodiments of this application. Obviously, the described embodiments are part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0130] Unless otherwise defined, all technical and scientific terms used in this application have the same meanings as commonly understood by those skilled in the art to which this application belongs. The terms used in the specification of this application are for the purpose of describing specific embodiments only and are not intended to limit this application. The terms "including" and "having" and any variations thereof in the specification and claims of this application and the above-mentioned drawings are intended to cover non-exclusive inclusions. The terms "first" and "second" in the specification and claims of this application or the above-mentioned drawings are used to distinguish different objects, rather than to describe a specific order or a primary-secondary relationship.

[0131] References to "embodiments" in this application mean that a particular feature, structure, or characteristic described in connection with the embodiment may be included in at least one embodiment of the application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive of other embodiments.

[0132] The term "and / or" in this application simply describes an association between related objects, indicating that three possible relationships exist. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " in this application generally indicates that the related objects are in an "or" relationship.

[0133] In the embodiments of this application, the same reference numerals represent the same components, and for the sake of brevity, detailed descriptions of the same components in different embodiments are omitted. It should be understood that the thickness, length, width, and other dimensions of the various components in the embodiments of this application, as well as the overall thickness, length, width, and other dimensions of the integrated device shown in the drawings are merely illustrative and should not constitute any limitation on this application.

[0134] The term "plurality" used in this application refers to two or more (including two).

[0135] In the embodiment of the present application, the battery cell may be a secondary battery. A secondary battery refers to a battery cell that can be continuously used by activating active materials by charging after the battery cell is discharged.

[0136] Battery cells include but are not limited to lithium-ion batteries, sodium-ion batteries, sodium-lithium-ion batteries, lithium metal batteries, sodium metal batteries, lithium-sulfur batteries, magnesium-ion batteries, nickel-hydrogen batteries, nickel-cadmium batteries, lead-acid batteries, etc.

[0137] A battery cell typically includes an electrode assembly. This assembly includes a positive electrode, a negative electrode, and a separator. During the charge and discharge process, active ions (such as lithium ions) move back and forth between the positive and negative electrodes. A separator, placed between the positive and negative electrodes, reduces the risk of short circuits while allowing active ions to pass through.

[0138] In some embodiments, the positive electrode may be a positive electrode sheet, which may include a positive electrode current collector and a positive electrode active material disposed on at least one surface of the positive electrode current collector.

[0139] As an example, the positive electrode current collector has two surfaces facing each other in its thickness direction, and the positive electrode active material is provided on either or both of the two facing surfaces of the positive electrode current collector.

[0140] As an example, the positive electrode current collector may be a metal foil or a composite current collector. For example, as the metal foil, aluminum with a silver-plated surface, stainless steel with a silver-plated surface, stainless steel, copper, aluminum, nickel, carbon electrode, carbon, nickel or titanium, etc. may be used. The composite current collector may include a polymer material base layer and a metal layer. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.).

[0141] As an example, the positive electrode active material may include at least one of the following materials: lithium-containing phosphates, lithium transition metal oxides and their respective modified compounds. However, the present application is not limited to these materials, and other traditional materials that can be used as positive electrode active materials for batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more. Among them, examples of lithium-containing phosphates may include but are not limited to at least one of lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO4), a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, and a composite material of lithium iron manganese phosphate and carbon. Examples of lithium transition metal oxides may include but are not limited to lithium cobalt oxide (such as LiCoO2), lithium nickel oxide (such as LiNiO2), lithium manganese oxide (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi 1 / 3 Co 1 / 3 Mn 1 / 3O2 (also referred to as NCM 333 ), LiNi 0.5 Co 0.2 Mn 0.3 O2 (also referred to as NCM 523 ), LiNi 0.5 Co 0.25 Mn 0.25 O2 (also referred to as NCM 211 ), LiNi 0.6 Co 0.2 Mn 0.2 O2 (also referred to as NCM 622 ), LiNi 0.8 Co 0.1 Mn 0.1 O2 (also referred to as NCM 811 ), lithium nickel cobalt aluminum oxide (such as LiNi 0.85 Co 0.15 Al 0.05 O2) and at least one of its modified compounds, etc.

[0142] In some embodiments, a positive electrode may utilize a metal foam. The metal foam may include nickel foam, copper foam, aluminum foam, alloy foam, or the like. When a metal foam is used as the positive electrode, the surface of the metal foam may or may not include a positive electrode active material. For example, a lithium source material, potassium metal, or sodium metal may be filled or / and deposited within the metal foam, where the lithium source material is lithium metal and / or a lithium-rich material.

[0143] In some embodiments, the negative electrode may be a negative electrode sheet, and the negative electrode sheet may include a negative electrode current collector.

[0144] As an example, the negative electrode current collector may be a metal foil, a metal foam, or a composite current collector. For example, the metal foil may include aluminum with a silver coating on the surface, stainless steel with a silver coating on the surface, stainless steel, copper, aluminum, nickel, a carbon electrode, carbon, nickel, or titanium. The metal foam may be nickel foam, copper foam, aluminum foam, or an alloy foam. The composite current collector may include a polymer base layer and a metal layer. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, or silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.).

[0145] As an example, the negative electrode sheet may include a negative electrode current collector and a negative electrode active material disposed on at least one surface of the negative electrode current collector.

[0146] As an example, the negative electrode current collector has two surfaces facing each other in its thickness direction, and the negative electrode active material is provided on either or both of the two facing surfaces of the negative electrode current collector.

[0147] As an example, the negative electrode active material may adopt the negative electrode active material for battery cells that is well known in the art. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, etc. The silicon-based material may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. However, the present application is not limited to these materials, and other traditional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0148] In some embodiments, the material of the positive electrode current collector may be aluminum, and the material of the negative electrode current collector may be copper.

[0149] In some embodiments, the separator is a separator membrane, which can be any known porous separator membrane with good chemical and mechanical stability.

[0150] As an example, the separator can be made of at least one of fiberglass, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film. In the case of a multi-layer composite film, the materials of each layer can be the same or different. The separator can be a separate component positioned between the positive and negative electrodes, or it can be attached to the surfaces of the positive and negative electrodes.

[0151] In some embodiments, the separator is a solid electrolyte, which is disposed between the positive electrode and the negative electrode and serves to transport ions and isolate the positive and negative electrodes.

[0152] In some embodiments, the battery cell further includes an electrolyte, which acts as a conductor of ions between the positive and negative electrodes. The electrolyte can be liquid, gel, or solid. Liquid electrolytes include an electrolyte salt and a solvent.

[0153] In some embodiments, the electrolyte salt may include at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bisfluorosulfonyl imide, lithium bistrifluoromethanesulfonyl imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalatoborate, lithium bisoxalatoborate, lithium difluorodioxalatophosphate, and lithium tetrafluorooxalatophosphate.

[0154] In some embodiments, the solvent may include at least one of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methylpropyl carbonate, ethylpropyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclopentane, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone. The solvent may also be an ether solvent. The ether solvent may include one or more of ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, 1,3-dioxolane, tetrahydrofuran, methyltetrahydrofuran, diphenyl ether and crown ether.

[0155] Among them, the gel electrolyte includes a skeleton network with a polymer as the electrolyte, combined with an ionic liquid-lithium salt.

[0156] Among them, solid electrolytes include polymer solid electrolytes, inorganic solid electrolytes, and composite solid electrolytes.

[0157] As an example, the polymer solid electrolyte may be polyether (polyethylene oxide), polysiloxane, polycarbonate, polyacrylonitrile, polyvinylidene fluoride, polymethyl methacrylate, a single ion polymer, polyionic liquid-lithium salt, cellulose, or the like.

[0158] As an example, the inorganic solid electrolyte may include an oxide solid electrolyte (crystalline perovskite, sodium superconducting ion conductor, garnet, amorphous LiPON film), a sulfide solid electrolyte (crystalline lithium superion conductor (lithium germanium phosphosulfide, silver germanium sulfide), amorphous sulfide) and one or more of a halide solid electrolyte, a nitride solid electrolyte and a hydride solid electrolyte.

[0159] As an example, a composite solid electrolyte is formed by adding an inorganic solid electrolyte filler to a polymer solid electrolyte.

[0160] In some embodiments, the electrode assembly is a wound structure, wherein the positive electrode sheet and the negative electrode sheet are wound into a wound structure.

[0161] In some embodiments, the electrode assembly is a laminate structure.

[0162] As an example, multiple positive electrode sheets and multiple negative electrode sheets can be provided respectively, and the multiple positive electrode sheets and the multiple negative electrode sheets can be alternately stacked.

[0163] As an example, multiple positive electrode sheets may be provided, and the negative electrode sheet is folded to form multiple stacked folded segments, with a positive electrode sheet sandwiched between adjacent folded segments.

[0164] As an example, both the positive electrode sheet and the negative electrode sheet are folded to form a plurality of stacked folded segments.

[0165] As an example, multiple separators may be provided, each of which is provided between any adjacent positive electrode sheets or negative electrode sheets.

[0166] As an example, the separator may be provided continuously, and may be provided between any adjacent positive electrode sheets or negative electrode sheets by folding or winding.

[0167] In some embodiments, the shape of the electrode assembly can be cylindrical, flat, or polygonal.

[0168] In some embodiments, the electrode assembly is provided with tabs that can conduct current from the electrode assembly. The tabs include a positive electrode tab and a negative electrode tab.

[0169] In some embodiments, a battery cell may include a housing. The housing is used to encapsulate components such as the electrode assembly and the electrolyte. The housing 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), or an aluminum-plastic film.

[0170] As an example, the battery cell may be a cylindrical battery cell, a prismatic battery cell, a soft-pack battery cell or a battery cell of other shapes. Prismatic battery cells include square-shell battery cells, blade-shaped battery cells, and polygonal battery cells. Polygonal battery cells are, for example, hexagonal battery cells.

[0171] The battery mentioned in the embodiments of the present application refers to a single physical module including one or more battery cells to provide higher voltage and capacity.

[0172] In some embodiments, the battery may be a battery module. When there are multiple battery cells, the multiple battery cells are arranged and fixed to form a battery module.

[0173] In some embodiments, the battery may be a battery pack, which includes a case and battery cells, wherein the battery cells or battery modules are housed in the case.

[0174] In some embodiments, the box body can be used as a part of the chassis structure of the vehicle. For example, part of the box body can become at least a part of the floor of the vehicle, or part of the box body can become at least a part of the cross beam and longitudinal beam of the vehicle.

[0175] In some embodiments, the battery may be an energy storage device, including an energy storage container, an energy storage cabinet, and the like.

[0176] In related technologies, a battery cell generally includes an outer shell and an electrode assembly. The outer shell may include a shell and an end cover. The shell has an opening. After the electrode assembly is installed in the shell, the opening of the shell can be closed by the end cover to form an enclosed space inside the shell to accommodate the electrode assembly.

[0177] To achieve a stable connection between the end cap and the shell, the two can be welded. After welding, a joint is formed at the weld point between the end cap and the shell. The high welding temperature causes a heat-affected zone (HAZ) to form on the shell wall near the joint, reducing the strength of the shell wall in this heat-affected zone.

[0178] During the charge and discharge cycle of the battery cell, the electrode assembly will expand, and the wall of the shell will be deformed after being subjected to the expansion force of the electrode assembly. If this continues for a long time, it will easily cause fatigue cracking in the area near the connection part of the shell wall (heat-affected zone), affecting the service life of the battery cell.

[0179] Based on the above considerations, in order to alleviate the problem that the area of ​​the shell wall near the connection portion is prone to fatigue cracking, an embodiment of the present application provides a battery cell, which includes a shell, an end cover and an electrode assembly. The shell has an opening at at least one end along the first direction, the shell includes a first wall, the end cover closes the opening, and the first wall and the end cover are welded to form a first connection portion. The electrode assembly is at least partially accommodated in the shell, and the electrode assembly includes a positive electrode sheet and a negative electrode sheet. At least part of the positive electrode sheet and at least part of the negative electrode sheet are stacked along the second direction. The second direction is parallel to the thickness direction of the first wall, and the first direction intersects with the second direction. The first wall includes a first area and a second area arranged along the first direction. The thickness of the first area is greater than the thickness of the second area. The first area is located between the first connection portion and the second area.

[0180] In such a battery cell, the thickness of the first zone is greater than that of the second zone, and the first zone is located between the first connecting portion and the second zone, so that the first zone with a larger thickness is closer to the first connecting portion than the second zone. The first zone strengthens the area of ​​the first wall near the first connecting portion, reducing the risk of fatigue cracking of the area of ​​the first wall near the first connecting portion due to expansion of the electrode assembly, thereby improving the service life of the battery cell.

[0181] The battery cells described in the embodiments of the present application are suitable for batteries and electrical equipment using the battery cells.

[0182] Electrical equipment can be vehicles, mobile phones, portable devices, laptops, ships, spacecraft, electric toys, and electric tools, etc. Vehicles can be fuel vehicles, gas vehicles, or new energy vehicles. New energy vehicles can be pure electric vehicles, hybrid vehicles, or extended-range vehicles, etc. Spacecraft include airplanes, rockets, space shuttles, and spacecraft, etc. Electric toys include fixed or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc. Electric tools include metal cutting electric tools, grinding electric tools, assembly electric tools, and railway electric tools, such as electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact drills, concrete vibrators, and electric planers, etc. The embodiments of the present application do not impose any special restrictions on the above-mentioned electrical equipment.

[0183] For the convenience of description, the following embodiments are described by taking a vehicle as an example of an electrical device.

[0184] Please refer to Figure 1, which is a schematic diagram of the structure of a vehicle 1000 provided in some embodiments of the present application. A battery 100 is disposed within vehicle 1000. Battery 100 can be located at the bottom, front, or rear of vehicle 1000. Battery 100 can be used to power vehicle 1000, for example, as an operating power source for vehicle 1000.

[0185] The vehicle 1000 may further include a controller 200 and a motor 300 . The controller 200 is used to control the battery 100 to supply power to the motor 300 , for example, to meet the power requirements of the vehicle 1000 during startup, navigation, and driving.

[0186] In some embodiments of the present application, the battery 100 can not only serve as the operating power source of the vehicle 1000, but also serve as the driving power source of the vehicle 1000, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle 1000.

[0187] Please refer to Figure 2, which is an exploded view of a battery 100 provided in some embodiments of the present application. The battery 100 may include a battery cell 10 and a housing 20, wherein the battery cell 10 is accommodated in the housing 20.

[0188] The housing 20 is a component that houses the battery cells 10 and provides a storage space for the battery cells 10. The housing 20 can have various structures. In some embodiments, the housing 20 can include a first housing 201 and a second housing 202. The first housing 201 and the second housing 202 cover each other to define a storage space for the battery cells 10. The first housing 201 and the second housing 202 can have various shapes, such as a rectangular parallelepiped or a cylindrical shape. The first housing 201 can be a hollow structure with an opening on one side, and the second housing 202 can be a hollow structure with an opening on one side. The open side of the second housing 202 covers the open side of the first housing 201, thereby forming the housing 20 with a storage space. Alternatively, the first housing 201 can be a hollow structure with an opening on one side, and the second housing 202 can be a plate-like structure. The second housing 202 covers the open side of the first housing 201, thereby forming the housing 20 with a storage space. The first box body 201 and the second box body 202 can be sealed by a sealing element, which can be a sealing ring, sealant, etc.

[0189] In the battery 100, there can be one or more battery cells 10. If there are multiple battery cells 10, the multiple battery cells 10 can be connected in series, parallel, or in a hybrid connection. A hybrid connection refers to a combination of series and parallel connections among the multiple battery cells 10. Multiple battery cells 10 can be connected in series, parallel, or in a hybrid connection to form a battery module, which can then be connected in series, parallel, or in a hybrid connection to form a single unit and housed within the housing 20. Alternatively, all battery cells 10 can be directly connected in series, parallel, or in a hybrid connection, and then the entire unit formed by all battery cells 10 can be housed within the housing 20.

[0190] 3 and 4 , FIG3 is an exploded view of a battery cell 10 provided in some embodiments of the present application; FIG4 is an isometric view of the battery cell 10 shown in FIG3 . The battery cell 10 may include a housing 1 and an electrode assembly 2 , wherein the electrode assembly 2 is accommodated in the housing 1 .

[0191] In some embodiments, the housing 1 may include a shell 11 and an end cover 12 , wherein the shell 11 has an opening and the end cover 12 closes the opening of the shell 11 .

[0192] The housing 11 is a component for accommodating the electrode assembly 2. The housing 11 can be a hollow structure with an opening at one end, or it can be a hollow structure with openings at opposite ends. The housing 11 can have various shapes, such as a cylinder or a rectangular parallelepiped. The housing 11 can be made of various materials, such as copper, iron, aluminum, steel, and aluminum alloys. The electrode assembly 2 can be partially or completely located within the housing 11.

[0193] The end cap 12 is a component that closes the opening of the shell 11 to isolate the internal environment of the battery cell 10 from the external environment. The end cap 12 and the shell 11 together define a receiving space for accommodating the electrode assembly 2, electrolyte and other components. The end cap 12 can be connected to the shell 11 by welding or rolling to close the opening of the shell 11. The shape of the end cap 12 can be adapted to the shape of the shell 11. For example, the shell 11 is a rectangular parallelepiped structure, and the end cap 12 is a rectangular plate structure adapted to the shell 11. For another example, the shell 11 is a cylindrical structure, and the end cap 12 is a circular plate structure adapted to the shell 11. The material of the end cap 12 can also be a variety of materials, such as copper, iron, aluminum, steel, aluminum alloy, etc. The material of the end cap 12 and the shell 11 can be the same or different.

[0194] In an embodiment where the housing 11 is open at one end, one end cap 12 may be provided. In an embodiment where the housing 11 is open at two opposite ends, two end caps 12 may be provided, each of which closes the two openings of the housing 11, and the two end caps 12 and the housing 11 together define a receiving space.

[0195] In some embodiments, the battery cell 10 may further include an electrode terminal 3, which is disposed on the outer casing 1. The electrode terminal 3 is used to electrically connect to the tab 21 of the electrode assembly 2 to input or output electrical energy from the battery cell 10. The electrode terminal 3 may be disposed on the shell 11 of the outer casing 1 or on the end cap 12 of the outer casing 1. The electrode terminal 3 and the tab 21 may be directly connected, for example, by welding the electrode terminal 3 to the tab 21. The electrode terminal 3 and the tab 21 may also be indirectly connected, for example, by indirectly connecting the electrode terminal 3 and the tab 21 through a current collecting member. The current collecting member may be a metal conductor, such as copper, iron, aluminum, steel, or an aluminum alloy.

[0196] In some embodiments, the battery cell 10 may further include a pressure relief mechanism 4, which may be provided on the end cover 12, or the pressure relief mechanism 4 may be provided on the housing 11. The pressure relief mechanism 4 may be a pressure relief component installed on the housing 11 or the end cover 12, such as an explosion-proof disc, a safety valve, etc. The pressure relief mechanism 4 may also be integrally formed with the end cover 12 or the housing 11. The pressure relief mechanism 4 may be provided with a pressure relief groove, so as to crack along the pressure relief groove when the battery cell 10 is depressurized. The pressure relief groove may be a groove extending along a closed trajectory, which may be a circular trajectory, a rectangular trajectory, etc.; the pressure relief groove may also be a groove extending along a non-closed trajectory, which may be an H-shaped trajectory, a Y-shaped trajectory, a V-shaped trajectory, a U-shaped trajectory, etc.

[0197] As an example, as shown in Figures 3 and 4, an opening is formed at one end of the shell 11, and there is only one end cap 12 in the outer shell 1, and each end cap 12 closes the opening of the shell 11. The end cap 12 is provided with a pressure relief mechanism 4, and two electrode terminals 3 are provided on the end cap 12, which are respectively a positive electrode terminal and a negative electrode terminal. A positive electrode tab 21a and a negative electrode tab 21b are formed on the end of the electrode assembly 2 facing the end cap 12. The positive electrode terminal is electrically connected to the positive electrode tab 21a, and the negative electrode terminal is electrically connected to the negative electrode tab 21b.

[0198] Please refer to Figures 5-7. Figure 5 is a cross-sectional view taken along line AA of the battery cell 10 shown in Figure 4; Figure 6 is a partially enlarged view of point B in Figure 5; and Figure 7 is an isometric view of the housing 11 shown in Figure 5. An embodiment of the present application provides a battery cell 10, comprising a housing 11, an end cap 12, and an electrode assembly 2. The housing 11 has an opening at at least one end along a first direction Z. The housing 11 includes a first wall 111. The end cap 12 closes the opening. The first wall 111 and the end cap 12 are welded to form a first connection portion 51. The electrode assembly 2 is at least partially housed within the housing 11. The electrode assembly 2 includes a positive electrode sheet 22 and a negative electrode sheet 23. At least a portion of the positive electrode sheet 22 and at least a portion of the negative electrode sheet 23 are stacked along a second direction Y. The second direction Y is parallel to the thickness direction of the first wall 111, and the first direction Z intersects the second direction Y. The first wall 111 includes a first area 1111 and a second area 1112 arranged along the first direction Z. The thickness of the first area 1111 is greater than that of the second area 1112 . The first area 1111 is located between the first connecting portion 51 and the second area 1112 .

[0199] The shell 11 may have an opening formed at only one end along the first direction Z, and one end cap 12 may be provided accordingly; or the shell 11 may have openings formed at both opposite ends along the first direction Z, and two end caps 12 may be provided accordingly. The shell 11 may have various shapes, such as cylindrical, prismatic, etc. The prism may be a triangular prism, a quadrangular prism, a pentagonal prism, a hexagonal prism, etc. The quadrangular prism may be a cuboid, a cube, etc. The first direction Z is parallel to the direction of the opening of the shell 11. In an embodiment where the shell 11 is cylindrical, the first direction Z may be parallel to the axial direction of the shell 11; in an embodiment where the shell 11 is prismatic, the first direction Z may be parallel to the extension direction of the side edges of the shell 11. The second direction Y is parallel to the thickness direction of the first wall 111. In an embodiment where the shell 11 is cylindrical, the first wall 111 is cylindrical, the radial direction of the shell 11 is the thickness direction of the first wall 111, and the second direction Y is parallel to the radial direction of the shell 11. In the embodiment where the housing 11 is prismatic, the first wall 111 may be a rectangular plate-shaped structure. The first direction Z and the second direction Y may be arranged at an acute angle, a right angle, or an obtuse angle.

[0200] The end cap 12 can be welded to the housing 11. The welding of the end cap 12 and the housing 11 can form a connecting portion 5, which can extend along the circumference of the opening of the housing 11. The end cap 12 and the housing 11 are connected and fixed by the connecting portion 5 to achieve a seal between the end cap 12 and the housing 11. The connecting portion 5 is the portion where the weld mark is formed after the end cap 12 and the housing 11 are welded together. The connecting portion 5 can be the portion where the end cap 12 and the housing 11 are welded and fused together.

[0201] The first wall 111 in the shell 11 can be one or more. The first connection portion 51 can correspond to the first wall 111 one-to-one. The first connection portion 51 is the portion with a weld mark formed after the end cover 12 and the first wall 111 are welded together. The first connection portion 51 can be the portion where the end cover 12 and the first wall 111 are welded and fused together. A portion of the first connection portion 51 is formed on the end cover 12, and another portion of the first connection portion 51 is formed on the first wall 111. The first wall 111 and the end cover 12 can form the first connection portion 51 by seam welding or by penetration welding. The first connection portion 51 can be a portion of the connection portion 5 or the entire connection portion 5. In an embodiment where the shell 11 is cylindrical, there is only one first wall 111 in the shell 11, the first wall 111 is cylindrical, and the first connecting portion 51 is the connecting portion 5; in an embodiment where the shell 11 is prismatic, the shell 11 may include multiple side walls, and the multiple side walls are arranged along the opening of the shell 11, and at least one of the two side walls arranged opposite to each other along the second direction Y may be the first wall 111, and the first connecting portion 51 is a part of the connecting portion 5.

[0202] The first wall 111 may be the wall with the largest outer surface area in the shell 11, or the first wall 111 may not be the wall with the largest outer surface area in the shell 11. Taking the shell 11 as a rectangular parallelepiped as an example, the shell 11 may include two first walls 111 and two second walls 112, the two first walls 111 being arranged opposite each other along the second direction Y, and the two second walls 112 being arranged opposite each other along the third direction X. The first direction Z, the second direction Y, and the third direction X are perpendicular to each other. The first wall 111 may be the wall with the largest outer surface area in the shell 11, such that the outer surface area of ​​the first wall 111 is larger than the outer surface area of ​​the second wall 112, or the second wall 112 may be the wall with the largest outer surface area in the shell 11, such that the outer surface area of ​​the second wall 112 is larger than the outer surface area of ​​the first wall 111.

[0203] The first region 1111 may be a region where the thickness of the first wall 111 is thickened. The first region 1111 is thicker than the second region 1112. The second region 1112 may be a portion of the first wall 111 located along the first direction Z on the side of the first region 1111 away from the first connection portion 51. The first region 1111 and the first connection portion 51 may be directly or indirectly connected; the first region 1111 and the second region 1112 may be directly or indirectly connected. The first region 1111 may be a structure of uniform thickness or a structure of unequal thickness; the second region 1112 may be a structure of uniform thickness or a structure of unequal thickness. If at least one of the first region 1111 and the second region 1112 is a structure of unequal thickness, the maximum thickness of the second region 1112 may be less than or equal to the minimum thickness of the first region 1111, so that the thickness of the first region 1111 is greater than the thickness of the second region 1112.

[0204] The second region 1112 has a first inner surface 11121 facing the interior space of the housing 11 and a first outer surface 11122 facing away from the interior space of the housing 11. The first region 1111 may partially protrude from the first inner surface 11121 and / or the first outer surface 11122. As an example, in the embodiment shown in FIG6 , a portion of the first region 1111 protrudes from the first inner surface 11121, and the outer surface of the first region 1111 is coplanar with the first outer surface 11122.

[0205] The electrode assembly 2 is located within the housing 11 and the end cap 12. The electrode assembly 2 may be a laminated structure or a wound structure. There may be one or more electrode assemblies 2 in the housing 11. If there are multiple electrode assemblies 2, the multiple electrode assemblies 2 may be stacked, for example, along the second direction Y.

[0206] At least a portion of the positive electrode sheet 22 and at least a portion of the negative electrode sheet 23 are stacked along the second direction Y. During cycling, the electrode assembly 2 will expand along the second direction Y. The first wall 111 will deform under the expansion force of the electrode assembly 2, which can easily cause fatigue cracking in the area of ​​the first wall 111 near the first connection portion 51. In the present application, the thickness of the first region 1111 is set to be greater than the thickness of the second region 1112, and the first region 1111 is positioned between the first connection portion 51 and the second region 1112. This allows the thicker first region 1111 to be closer to the first connection portion 51 than the second region 1112. The first region 1111 strengthens the area of ​​the first wall 111 near the first connection portion 51, reducing the risk of fatigue cracking in the area of ​​the first wall 111 near the first connection portion 51 due to expansion of the electrode assembly 2, thereby increasing the service life of the battery cell 10.

[0207] In some embodiments, referring to Figures 8-11, Figure 8 is an isometric view of an electrode assembly 2 provided in some embodiments of the present application; Figure 9 is a schematic structural diagram of the electrode assembly 2 shown in Figure 8; Figure 10 is an isometric view of an electrode assembly 2 provided in other embodiments of the present application; and Figure 11 is a schematic structural diagram of the electrode assembly 2 shown in Figure 10. The electrode assembly 2 has a straight region 25, and the portion of the positive electrode sheet 22 located in the straight region 25 and the portion of the negative electrode sheet 23 located in the straight region 25 are stacked along the second direction Y.

[0208] The flat region 25 is the flat portion of the electrode assembly 2. The portion of the positive electrode sheet 22 located in the flat region 25 is generally flat, and the portion of the negative electrode sheet 23 located in the flat region 25 is generally flat. As an example, the portion of the positive electrode sheet 22 located in the flat region 25 and the portion of the negative electrode sheet 23 located in the flat region 25 are both flat plate structures. If the electrode assembly 2 has a wound structure, the electrode assembly 2 is a wound electrode assembly, and a portion of the electrode assembly 2 may be the flat region 25. If the electrode assembly 2 has a laminated structure, the electrode assembly 2 is a wound electrode assembly, and the entire electrode assembly 2 may be the flat region 25. The second direction Y is the stacking direction of the portion of the positive electrode sheet 22 located in the flat region 25 and the portion of the negative electrode sheet 23 located in the flat region 25.

[0209] As an example, the electrode assembly 2 may further include a separator 24, which is provided between the positive electrode sheet 22 and the negative electrode sheet 23. The separator 24 is used to separate the positive electrode sheet 22 from the negative electrode sheet 23. The portion of the positive electrode sheet 22 located in the straight region 25, the portion of the negative electrode sheet 23 located in the straight region 25, and the portion of the separator 24 located in the straight region 25 are stacked along the second direction Y.

[0210] The second direction Y is the stacking direction of the portion of the positive electrode tab 22 located in the flat region 25 and the portion of the negative electrode tab 23 located in the flat region 25. During cycling, the electrode assembly 2 expands more significantly along the second direction Y, and the first wall 111 is more affected by the expansion of the electrode assembly 2. However, because the first region 1111 reinforces the area of ​​the first wall 111 near the first connecting portion 51, the risk of fatigue cracking of the first wall 111 near the first connecting portion 51 due to expansion of the electrode assembly 2 is reduced.

[0211] In some embodiments, please continue to refer to Figures 8-11, the electrode assembly 2 includes adjacent first surfaces 27 and second surfaces 28, the first surface 27 is perpendicular to the second direction Y, the area of ​​the first surface 27 is larger than the area of ​​the second surface 28, and the first surface 27 and the first wall 111 are arranged opposite to each other along the second direction Y.

[0212] The first surface 27 is the surface of the outer surface of the electrode assembly 2 that is perpendicular to the second direction Y, and the second surface 28 is the surface of the outer surface of the electrode assembly 2 that is adjacent to the first surface 27. The first surface 27 is arranged facing the first wall 111 along the second direction Y. The first surface 27 can be a plane. The first surface 27 can be the surface with the largest area among the outer surfaces of the electrode assembly 2, or it can be other than the surface with the largest area among the outer surfaces of the electrode assembly 2. The second surface 28 can be a plane, or it can be at least partially an arc surface. It should be noted that the first surface 27 is approximately perpendicular to the second direction Y, which should also be understood as the first surface 27 being perpendicular to the second direction Y.

[0213] As an example, there are two first surfaces 27 and two second surfaces 28, the two first surfaces 27 are arranged opposite to each other along the second direction Y, and the two second surfaces 28 are arranged opposite to each other along the third direction X. The positive electrode tab 21a and the negative electrode tab 21b protrude from the surface of the electrode assembly 2 along the first direction Z. The outermost part of the electrode assembly 2 along the second direction Y is the insulating member 24, and the first surface 27 is formed on the insulating member 24. The first direction Z, the second direction Y and the third direction X are perpendicular to each other.

[0214] In this embodiment, the area of ​​the first surface 27 is larger than that of the second surface 28, so that the first wall 111 of the housing 11, which is disposed opposite the first surface 27, is subjected to a greater expansion force. Because the first region 1111 strengthens the area of ​​the first wall 111 near the first connecting portion 51, the risk of fatigue cracking of the first wall 111 near the first connecting portion 51 due to expansion of the electrode assembly 2 is reduced.

[0215] In some embodiments, the first surface 27 is the surface with the largest area among the outer surfaces of the electrode assembly 2 .

[0216] It should be noted that the first surface 27 is the largest surface among the outer surfaces of the electrode assembly 2, which does not limit the electrode assembly 2 to having only one first surface 27. It is understandable that the electrode assembly 2 can have one or two first surfaces 27.

[0217] As an example, in the embodiment shown in FIG8 , the electrode assembly 2 has a wound structure, is flat, and includes six surfaces. Of the six surfaces, two surfaces disposed opposite each other along the second direction Y have the largest areas, and both surfaces are first surfaces 27. In the embodiment shown in FIG10 , the electrode assembly 2 has a laminated structure, is roughly rectangular, and includes six surfaces. Of the six surfaces, two surfaces disposed opposite each other along the second direction Y have the largest areas, and both surfaces are first surfaces 27.

[0218] In this embodiment, the first surface 27 is the largest surface area of ​​the outer surface of the electrode assembly 2, so that the first wall 111 of the housing 11, which is located opposite the first surface 27, is subjected to the greatest expansion force. Because the first region 1111 strengthens the area of ​​the first wall 111 near the first connection portion 51, the risk of fatigue cracking of the first wall 111 near the first connection portion 51 due to expansion of the electrode assembly 2 is reduced.

[0219] In some embodiments, referring again to Figures 8 and 9 , the electrode assembly 2 has a wound structure and further includes a corner region 26 . The straight region 25 is provided with a corner region 26 at at least one end along the third direction X. The first direction Z, the second direction Y, and the third direction X are not coplanar and intersect with each other. The outer surface of the straight region 25 includes a first surface 27 , and the outer surface of the corner region 26 includes a second surface 28 , at least a portion of which is an arcuate surface.

[0220] The straight region 25 may be provided with a corner region 26 at only one end along the third direction X, or at both opposite ends along the third direction X. The first direction Z, the second direction Y, and the third direction X are not coplanar, and any two of the first direction Z, the second direction Y, and the third direction X may form an acute angle, a right angle, or an obtuse angle. The first surface 27 may be a portion of the outer surface of the straight region 25, and the second surface 28 may be a portion of the outer surface of the corner region 26. The second surface 28 may be an entirely arcuate surface, or only a portion thereof.

[0221] As an example, the positive electrode sheet 22, the separator 24, and the negative electrode sheet 23 are stacked and wound to form a wound structure. The first direction Z, the second direction Y, and the third direction X are perpendicular to each other, and a corner region 26 is provided at both ends of the straight region 25 along the third direction X. The portions of the positive electrode sheet 22, the negative electrode sheet 23, and the separator 24 located in the corner region 26 are in a curved state. The portion of the positive electrode sheet 22 located in the corner region 26 can be at least partially arc-shaped, the portion of the negative electrode sheet 23 located in the corner region 26 can be at least partially arc-shaped, and the portion of the separator 24 located in the corner region 26 can be at least partially arc-shaped. Along the winding direction of the electrode assembly 2, the outermost ring of the electrode assembly 2 is the separator 24. The first surface 27 and the second surface 28 are both portions of the outer surface of the outermost ring of the electrode assembly 2. The first surface 27 is a plane, and the second surface 28 is an arc surface. The axis of the arc surface extends along the first direction Z. Along the second direction Y, the surfaces on both sides of the straight area 25 are both first surfaces 27; along the third direction X, the surface of one corner area 26 facing away from the other corner area 26 is a second surface 28, and the surface of the other corner area 26 facing away from the one corner area 26 is another second surface 28.

[0222] For a wound electrode assembly, the straight region 25 expands more significantly in the second direction Y. Because the first region 1111 strengthens the area of ​​the first wall 111 near the first connecting portion 51, the risk of fatigue cracking of the first wall 111 near the first connecting portion 51 due to expansion of the electrode assembly 2 can be effectively reduced.

[0223] In some embodiments, please continue to refer to Figures 10 and 11. The electrode assembly 2 is a laminated structure, and the straight area 25 includes multiple positive electrode sheets 22 and multiple negative electrode sheets 23. The multiple positive electrode sheets 22 and the multiple negative electrode sheets 23 are stacked along the second direction Y, and the first surface 27 is perpendicular to the second surface 28.

[0224] As an example, multiple positive electrode sheets 22, multiple negative electrode sheets 23, and multiple separators 24 are stacked along the second direction Y to form a laminate structure. The positive electrode sheets 22 and negative electrode sheets 23 are completely located in the flat region 25. Separators 24 are provided between adjacent positive electrode sheets 22 and negative electrode sheets 23. The separators 24 extend beyond both ends of the positive electrode sheet 22 and the negative electrode sheet 23 along the third direction X. The extending portions of the multiple separators 24 are connected to form an integral portion, and the second surface 28 is formed in the integral portion. Along the second direction Y, all positive electrode sheets 22 and all negative electrode sheets 23 are located between the two outermost separators 24, and the outer surfaces of the two separators 24 are both the first surface 27.

[0225] It should be noted that the first surface 27 and the second surface 28 are substantially perpendicular, which should also be understood as the first surface 27 being perpendicular to the second surface 28. For example, if the angle between the first surface 27 and the second surface 28 is in the range of 85° to 95°, it can be understood that the first surface 27 and the second surface 28 are perpendicular.

[0226] For a wound electrode assembly, the electrode assembly 2 expands more in the stacking direction of the positive electrode sheets 22 and the negative electrode sheets 23. Because the first region 1111 reinforces the area of ​​the first wall 111 near the first connection portion 51, the risk of fatigue cracking of the first wall 111 near the first connection portion 51 due to expansion of the electrode assembly 2 can be effectively reduced.

[0227] In some embodiments, please continue to refer to FIG. 7 , the first wall 111 is the wall with the largest outer surface area in the housing 11 .

[0228] It should be noted that the first wall 111 is the wall with the largest outer surface area in the housing 11, which does not limit the housing 11 to having only one first wall 111. It is understandable that the housing 11 may have one or two walls with the largest outer surface area.

[0229] The wall with the largest outer surface area in the shell 11 is more likely to deform after being subjected to the expansion force of the electrode assembly 2. Since the first wall 111 is the wall with the largest outer surface area in the shell 11, the risk of fatigue cracking of the wall with the largest outer surface area in the shell 11 near the first connecting part 51 due to the expansion of the electrode assembly 2 is reduced.

[0230] In some embodiments, the housing 11 includes two first walls 111 . The two first walls 111 are oppositely disposed along the second direction Y, and the electrode assembly 2 (shown in FIG. 5 ) is located between the two first walls 111 .

[0231] As an example, in the embodiment shown in FIG7 , the housing 11 is in the shape of a rectangular parallelepiped and may include two first walls 111 and two second walls 112. The two first walls 111 are arranged opposite each other along a second direction Y, and the two second walls 112 are arranged opposite each other along a third direction X. The outer surface area of ​​the first wall 111 is greater than the outer surface area of ​​the second wall 112. The first direction Z is parallel to the height direction of the housing 11, the second direction Y is parallel to the width direction of the housing 11, and the third direction X is parallel to the length direction of the housing 11.

[0232] In this embodiment, the housing 11 includes two first walls 111 , which reduces the risk of fatigue cracking of the two first walls 111 near the first connecting portion 51 due to expansion of the electrode assembly 2 .

[0233] In some embodiments, please refer to Figure 12, which is a partial view of the first wall 111 shown in Figure 6. The first region 1111 includes a first portion 11111 and a second portion 11112 arranged along a first direction Z. The second portion 11112 connects the first portion 11111 and the second region 1112. The thickness of the first portion 11111 is greater than the thickness of the second portion 11112.

[0234] The first portion 11111, the second portion 11112, and the second region 1112 are arranged sequentially along the first direction Z, with the first portion 11111 transitioning to the second region 1112 through the second portion 11112. The first portion 11111 can have a uniform thickness or a non-uniform thickness structure; the second portion 11112 can have a uniform thickness or a non-uniform thickness structure. If at least one of the first portion 11111 and the second portion 11112 has a non-uniform thickness structure, the maximum thickness of the second portion 11112 can be less than or equal to the minimum thickness of the first portion 11111, such that the thickness of the first portion 11111 is greater than the thickness of the second portion 11112.

[0235] The first portion 11111 may partially protrude from the first inner surface 11121 and / or the first outer surface 11122 , and the second portion 11112 may also protrude from the first inner surface 11121 and / or the first outer surface 11122 .

[0236] The area of ​​the first region 1111 near the first connection portion 51 is more likely to form a heat-affected zone, making this area more susceptible to fatigue cracking. However, because the second portion 11112 connects the first portion 11111 and the second region 1112, and the thickness of the first portion 11111 is greater than that of the second portion 11112, the thicker first portion 11111 in the first region 1111 is closer to the first connection portion 51. This effectively weakens the effect of the heat-affected zone on the first region 1111, reducing the risk of fatigue cracking in the area of ​​the first wall 111 near the first connection portion 51. Furthermore, because the thickness of the second portion 11112 is less than that of the first portion 11111, the material used in the first region 1111 can be reduced, thereby lowering production costs.

[0237] In some embodiments, the thickness of the second portion 11112 decreases in a direction from the end cap 12 (not shown in FIG. 12 ) to the electrode assembly 2 (not shown in FIG. 12 ).

[0238] The direction in which the end cap 12 points toward the electrode assembly 2 is consistent with the direction in which the first portion 11111 points toward the second region 1112 along the first direction Z.

[0239] It is understood that the second portion 11112 has a non-uniform thickness structure. As an example, the thickness of the second portion 11112 gradually decreases along the direction from the end cap 12 to the electrode assembly 2. At least one of the inner surface and the outer surface of the second portion 11112 may be an inclined surface to achieve the gradual decrease in thickness of the second portion 11112 along the direction from the end cap 12 to the electrode assembly 2.

[0240] As an example, in the embodiment shown in FIG12 , the first portion 11111 and the second region 1112 are both structures of equal thickness. The inner and outer surfaces of the first portion 11111 are arranged in parallel, and the first inner surface 11121 and the first outer surface 11122 of the second region 1112 are arranged in parallel. The outer surface of the second portion 11112, the outer surface of the first portion 11111, and the first outer surface 11122 are coplanar. A portion of the first portion 11111 and a portion of the second portion 11112 both protrude from the first inner surface 11121. The inner surface of the second portion 11112 connects the first inner surface 11121 and the inner surface of the first portion 11111.

[0241] In this embodiment, the thickness of the second part 11112 tends to decrease along the direction of the end cover 12 pointing to the electrode assembly 2. On the one hand, it can reduce the influence of the second part 11112 on the electrode assembly 2 and reduce the risk of interference between the second part 11112 and the electrode assembly 2; on the other hand, the reinforcing effect of the second part 11112 tends to increase along the direction of the electrode assembly 2 pointing to the end cover 12, so that the area of ​​the second part 11112 close to the first part 11111 has a good reinforcing effect even if it is affected by the first connecting part 51, thereby reducing the risk of fatigue cracking of the first wall 11112 in the second part 11112; on the other hand, the transition between the first part 11111 and the second area 1112 can be achieved through the second part 11112, thereby reducing stress concentration.

[0242] In some embodiments, referring to Figures 13 and 14, Figure 13 is an isometric view of the housing 11 provided in some embodiments of the present application; Figure 14 is a top view of the housing 11 shown in Figure 13. The dimension of the first region 1111 along the third direction X is greater than the dimension of the first region 1111 along the first direction Z. The first direction Z, the second direction Y, and the third direction X are non-coplanar and intersect with each other.

[0243] The dimension of the first region 1111 along the third direction X is the length of the first region 1111 , and the dimension of the first region 1111 along the first direction Z is the width of the first region 1111 . The length of the first region 1111 is greater than the width of the first region 1111 , so that the first region 1111 is a long strip structure extending along the third direction X.

[0244] As an example, the shell 11 is in the shape of a rectangular parallelepiped, and the shell 11 includes two first walls 111 and two second walls 112. The two first walls 111 are arranged opposite to each other along the second direction Y, and the two second walls 112 are arranged opposite to each other along the third direction X. The first direction Z, the second direction Y and the third direction X are perpendicular to each other. The first direction Z is parallel to the height direction of the shell 11, the second direction Y is parallel to the width direction of the shell 11, and the third direction X is parallel to the length direction of the shell 11.

[0245] In this embodiment, the size of the first area 1111 along the third direction X is larger than the size of the first area 1111 along the first direction Z, so that the size of the first area 1111 along the third direction X is larger, so that the strength of more areas of the first wall 111 along the third direction X is enhanced, further reducing the risk of fatigue cracking in the area of ​​the first wall 111 near the first connecting portion 51.

[0246] In some embodiments, the first region 1111 includes a first connecting segment 11113 , which passes through a midsection of the first wall 111 , the midsection being perpendicular to the third direction X, and the midsection being equidistant from both ends of the first wall 111 along the third direction X.

[0247] The first connecting section 11113 may be a part of the first area 1111, or the first connecting section 11113 may be the first area 1111. The first connecting section 11113 may be a structure of equal thickness or a structure of unequal thickness; the first connecting section 11113 has two opposite ends along the third direction X, and the first connecting section 11113 passes through the mid-section of the first wall 111, so that the mid-section of the first wall 1111 is located between the two opposite ends of the first connecting section 11113 along the third direction X. The distances from the two opposite ends of the first connecting section 11113 along the third direction X to the mid-section may be equal or unequal. If the distances from the two opposite ends of the first connecting section 11113 along the third direction X to the mid-section of the first wall 111 are equal, the first connecting section 11113 may be a symmetrical structure symmetrically arranged about the mid-section of the first wall 111. It should be noted that the mid-section of the first wall 111 is a virtual plane and is not shown in the figure.

[0248] As an example, in the embodiments shown in Figures 13 and 14, the first connecting section 11113 is the first zone 1111, the first connecting section 11113 is an equal-thickness structure, and the distances from the two opposite ends of the first connecting section 11113 along the third direction X to the mid-section of the first wall 111 are equal.

[0249] Taking the shell 11 as a rectangular parallelepiped as an example, the distances from the mid-section of the first wall 111 to the two ends of the first wall 111 along the third direction X are equal, that is, the distances from the mid-section of the first wall 111 to the two second walls 112 of the shell 11 arranged opposite to each other along the third direction X are equal.

[0250] It should be noted that, along the third direction X, the distances from the middle section of the first wall 111 to both ends of the first wall 111 are substantially equal, which should also be understood as the distances from the middle section to both ends of the first wall 111 are equal.

[0251] When the first wall 111 is subjected to the expansion force of the electrode assembly 2 of the battery cell 10, the deformation of the middle region of the first wall 111 along the third direction X is greater, making the middle region of the first wall 111 along the third direction X more susceptible to fatigue cracking. Because the first connecting segment 11113 of the first region 1111 passes through the mid-section of the first wall 111, the strength of at least the middle region of the first wall 111 along the third direction X is enhanced, reducing the risk of fatigue cracking in the middle region of the first wall 111 along the third direction X near the first connecting portion 51.

[0252] In some embodiments, Figure 15 is an isometric view of the housing 11 provided in other embodiments of the present application; Figure 16 is a top view of the housing 11 shown in Figure 15. The first region 1111 further includes a second connecting segment 11114 and a third connecting segment 11115. The second connecting segment 11114, the first connecting segment 11113, and the third connecting segment 11115 are arranged along the third direction X. The first connecting segment 11113 connects the second connecting segment 11114 and the third connecting segment 11115. The thickness of the first connecting segment 11113 is greater than the thickness of the second connecting segment 11114 and the thickness of the third connecting segment 11115.

[0253] The first connecting segment 11113 is a segment of the first area 1111 that passes through the mid-section of the first wall 111. The second connecting segment 11114 and the third connecting segment 11115 are two segments located at the two ends of the first area 1111 along the third direction X. The second connecting segment 11114 and the first connecting segment 11113 can be directly or indirectly connected, and the third connecting segment 11115 and the first connecting segment 11113 can be directly or indirectly connected.

[0254] The first connecting segment 11113 can be a structure of uniform thickness or a structure of unequal thickness; the second connecting segment 11114 can be a structure of uniform thickness or a structure of unequal thickness; and the third connecting segment 11115 can be a structure of uniform thickness or a structure of unequal thickness. If at least one of the first connecting segment 11113 and the second connecting segment 11114 is a structure of unequal thickness, the maximum thickness of the second connecting segment 11114 can be less than or equal to the minimum thickness of the first connecting segment 11113, so that the thickness of the first connecting segment 11113 is greater than the thickness of the second connecting segment 11114. If at least one of the third connecting segment 11115 and the first connecting segment 11113 is a structure of unequal thickness, the maximum thickness of the third connecting segment 11115 can be less than or equal to the minimum thickness of the first connecting segment 11113, so that the thickness of the first connecting segment 11113 is greater than the thickness of the third connecting segment 11115.

[0255] The dimension of the second connecting segment 11114 along the third direction X may be equal to or different from the dimension of the third connecting segment 11115 along the third direction X. If the dimension of the second connecting segment 11114 along the third direction X is equal to the dimension of the third connecting segment 11115 along the third direction X, the second connecting segment 11114 and the third connecting segment 11115 may be symmetrically arranged about the mid-section of the first wall 111.

[0256] It can be understood that in the embodiment where the first zone 1111 includes the first part 11111 and the second part 11112, at least one of the first connecting segment 11113, the second connecting segment 11114, and the third connecting segment 11115 may include the first part 11111 and the second part 11112 arranged along the first direction Z.

[0257] The second connecting segment 11114 may partially protrude from the first inner surface 11121 (not shown in Figures 15 and 16) and / or the first outer surface 11122 (not shown in Figures 15 and 16), the first connecting segment 11113 may partially protrude from the first inner surface 11121 and / or the first outer surface 11122, and the third connecting segment 11115 may partially protrude from the first inner surface 11121 and / or the first outer surface 11122.

[0258] As an example, in the embodiment shown in FIG16 , second connecting segment 11114 and third connecting segment 11115 are both directly connected to first connecting segment 11113. The thickness of second connecting segment 11114 gradually decreases along the direction from third connecting segment 11115 toward second connecting segment 11114, and the thickness of third connecting segment 11115 gradually decreases along the direction from second connecting segment 11114 toward third connecting segment 11115. A portion of second connecting segment 11114, a portion of first connecting segment 11113, and a portion of third connecting segment 11115 all protrude from first inner surface 11121 of second region 1112. The inner surface of the second connecting segment 11114 connects the inner surface of the first connecting segment 11113 and the first inner surface 11121, and the inner surface of the third connecting segment 11115 connects the inner surface of the first connecting segment 11113 and the first inner surface 11121. The outer surface of the second connecting segment 11114, the outer surface of the first connecting segment 11113 and the outer surface of the third connecting segment 11115 are coplanar.

[0259] When the first wall 111 is subjected to the expansion force of the electrode assembly 2, the deformation of the first wall 111 gradually decreases from the middle to the ends along the third direction X. By dividing the first region 1111 into multiple sections, with the first connecting section 11113 located in the middle region having a greater thickness, and the second connecting section 11114 and the third connecting section 11115 located at the ends of the first connecting section 11113 having smaller thicknesses, the first region 1111 is designed specifically according to the different deformation amounts of different regions of the first wall 1111 along the third direction X. This improves the strength of different regions of the first wall 1111 along the third direction X. While ensuring sufficient strength in the region of the first wall 1111 near the first connecting portion 51, the material used in the first region 1111 is reduced, thereby lowering production costs.

[0260] In some embodiments, please refer to Figures 17 and 18. Figure 17 is an axonometric view of the shell 11 provided in some embodiments of the present application; Figure 18 is a top view of the shell 11 shown in Figure 17. The first zone 1111 also includes a first transition section 11116, the first connecting section 11113, the first transition section 11116 and the second connecting section 11114 are arranged along the third direction X, the first transition section 11116 connects the second connecting section 11114 and the first connecting section 11113, and the thickness of the first transition section 11116 tends to increase along the direction from the second connecting section 11114 to the first connecting section 11113; and / or, the first zone 1111 also includes a second transition section 11117, the first connecting section 11113, the second transition section 11117 and the third connecting section 11115 are arranged along the third direction X, the second transition section 11117 connects the third connecting section 11115 and the first connecting section 11113, and the thickness of the second transition section 11117 tends to increase along the direction from the third connecting section 11115 to the first connecting section 11113.

[0261] First transition section 11116 has a non-uniform thickness structure. For example, the thickness of first transition section 11116 gradually increases along the direction from second connecting section 11114 to first connecting section 11113. Second transition section 11117 has a non-uniform thickness structure. For example, the thickness of second transition section 11117 gradually increases along the direction from third connecting section 11115 to first connecting section 11113.

[0262] If a first transition section 11116 is provided between the second connecting section 11114 and the first connecting section 11113, and a second transition section 11117 is provided between the third connecting section 11115 and the first connecting section 11113, the dimension of the first transition section 11116 along the third direction X may be equal to or different from the dimension of the second transition section 11117 along the third direction X. If the dimension of the first transition section 11116 along the third direction X is equal to the dimension of the second transition section 11117 along the third direction X, the first transition section 11116 and the second transition section 11117 may be symmetrically arranged about the mid-section of the first wall 111.

[0263] It can be understood that if a first transition section 11116 is provided between the second connecting section 11114 and the first connecting section 11113, the first transition section 11116 may partially protrude from the first inner surface 11121 (not shown in Figures 17 and 18) and / or the first outer surface 11122 (not shown in Figures 17 and 18) of the second zone 1112; if a second transition section 11117 is provided between the third connecting section 11115 and the first connecting section 11113, the second transition section 11117 may partially protrude from the first inner surface 11121 and / or the first outer surface 11122 of the second zone 1112.

[0264] As an example, in the embodiment shown in FIG18 , second connecting segment 11114 is indirectly connected to first connecting segment 11113 via first transition segment 11116, and third connecting segment 11115 is indirectly connected to first connecting segment 11113 via second transition segment 11117. The thickness of first transition segment 11116 gradually increases along the direction from second connecting segment 11114 to first connecting segment 11113, and the thickness of second transition segment 11117 gradually increases along the direction from third connecting segment 11115 to first connecting segment 11113. A portion of second connecting segment 11114, a portion of first connecting segment 11113, a portion of third connecting segment 11115, a portion of first transition segment 11116, and a portion of second transition segment 11117 all protrude from first inner surface 11121. The inner surface of the first transition section 11116 connects the inner surface of the first connecting section 11113 and the inner surface of the second connecting section 11114, the inner surface of the second transition section 11117 connects the inner surface of the first connecting section 11113 and the inner surface of the third connecting section 11115, and the outer surface of the second connecting section 11114, the outer surface of the first connecting section 11113, the outer surface of the third connecting section 11115, the outer surface of the first transition section 11116, and the outer surface of the second transition section 11117 are coplanar.

[0265] In this embodiment, if the second connecting segment 11114 and the first connecting segment 11113 are connected by the first transition segment 11116, and the thickness of the first transition segment 11116 increases along the direction from the second connecting segment 11114 to the first connecting segment 11113, the first transition segment 11116 can achieve a transition between the second connecting segment 11114 and the first connecting segment 11113, thereby reducing stress concentration. If the third connecting segment 11115 and the first connecting segment 11113 are connected by the second transition segment 11117, and the thickness of the second transition segment 11117 increases along the direction from the third connecting segment 11115 to the first connecting segment 11113, the second transition segment 11117 can achieve a transition between the third connecting segment 11115 and the first connecting segment 11113, thereby reducing stress concentration.

[0266] In some embodiments, referring to FIG. 14 , FIG. 16 and FIG. 18 , the dimension of the first connecting segment 11113 along the third direction X is L1 , the dimension of the first wall 111 along the third direction X is L, and 0.2≤L1 / L≤0.6.

[0267] The dimension of the first connecting section 11113 along the third direction X is the length of the first connecting section 11113, the dimension of the first wall 111 along the third direction X is the length of the first wall 111, the dimension of the first wall 111 along the second direction Y is the thickness of the first wall 111, and the dimension of the first wall 111 along the first direction Z is the width of the first wall 111.

[0268] L1 / L can be any point value among 0.2, 0.22, 0.25, 0.28, 0.3, 0.32, 0.35, 0.38, 0.4, 0.42, 0.45, 0.48, 0.5, 0.52, 0.55, 0.58, 0.6, etc., or a range of values ​​between any two of them.

[0269] L1 / L ≥ 0.2 increases the proportion of the first connecting segment 11113 in the first wall 111 along the third direction X, thereby strengthening a wider area of ​​the middle region of the first wall 111 along the third direction X and improving the strength of the middle region of the first wall 111 along the third direction X. L1 / L ≤ 0.6 reduces the proportion of the first connecting segment 11113 in the first wall 111 along the third direction X, reducing the material used for the first connecting segment 11113 and lowering production costs. Therefore, setting the ratio of the dimension of the first connecting segment 11113 along the third direction X to the dimension of the first wall 1111 along the third direction X to 0.2 to 0.6 ensures sufficient reinforcement for the first connecting segment 11113 while reducing the material used for the first connecting segment 11113, thus achieving both the required reinforcement and economic efficiency for the first connecting segment 11113.

[0270] In some embodiments, please continue to refer to Figures 14, 16 and 18, the first connecting section 11113 has a first end 11113a and a second end 11113b opposite to each other along the third direction X, the first wall 111 has a third end 1113 and a fourth end 1114 opposite to each other along the third direction X, the first end 11113a is close to the third end 1113, the second end 11113b is close to the fourth end 1114, the dimension of the first wall 111 along the third direction X is L, the minimum distance between the first end 11113a and the third end 1113 along the third direction X is L2, and the minimum distance between the second end 11113b and the fourth end 1114 along the third direction X is L3; L2 / L≤0.3; and / or, L3 / L≤0.3.

[0271] It can be understood that, along the third direction X, the first end 11113a is closer to the third end 1113 than the second end 11113b, and the second end 11113b is closer to the fourth end 1114 than the first end 11113a.

[0272] It can be L2=L3; it can also be L2>L3 or L2<L3.

[0273] L2 / L can be any point value among 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.11, 0.12, 0.13, 0.14, 0.15, 0.16, 0.17, 0.18, 0.19, 0.2, 0.21, 0.22, 0.23, 0.24, 0.25, 0.26, 0.27, 0.28, 0.29, 0.3, etc., or a range between any two of them.

[0274] L3 / L can be any point value among 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.11, 0.12, 0.13, 0.14, 0.15, 0.16, 0.17, 0.18, 0.19, 0.2, 0.21, 0.22, 0.23, 0.24, 0.25, 0.26, 0.27, 0.28, 0.29, 0.3, etc., or a range between any two of them.

[0275] If L2 / L ≤ 0.3, the ratio of the minimum distance between the first end 11113a and the third end 1113 along the third direction X to the dimension of the first wall 111 along the third direction X is reduced, thereby increasing the strength of more areas of the first wall 111 along the third direction X, further reducing the risk of fatigue cracking in the area of ​​the first wall 111 near the first connection portion 51. If L3 / L ≤ 0.3, the ratio of the minimum distance between the second end 11113b and the fourth end 1114 along the third direction X to the dimension of the first wall 111 along the third direction X is reduced, thereby increasing the strength of more areas of the first wall 111 along the third direction X, further reducing the risk of fatigue cracking in the area of ​​the first wall 111 near the first connection portion 51.

[0276] In some embodiments, 100 mm ≤ L ≤ 450 mm.

[0277] L can be any point value among 100mm, 120mm, 150mm, 180mm, 200mm, 220mm, 250mm, 260mm, 280mm, 300mm, 310mm, 320mm, 350mm, 390mm, 400mm, 410mm, 420mm, 430mm, 440mm, 450mm, etc., or a range value between any two of them.

[0278] In some embodiments, please continue to refer to Figures 13 to 18, the shell 11 includes a corner wall 113, and the first wall 111 is connected to the corner wall 113 at both ends along the third direction X; at least one end of the first area 1111 along the third direction X is not in contact with the corner wall 113; or, the first area 1111 extends to two corner walls 113 at both ends along the third direction X.

[0279] Along the third direction X, the first area 1111 has two opposite ends. One end of the first area 1111 may extend to one corner wall 113, and the other end may not extend to the other corner wall 113, or both ends of the first area 1111 may not extend to the corner wall 113, so as to achieve that at least one end of the first area 1111 along the third direction X does not contact the corner wall 113.

[0280] As an example, in the embodiments shown in Figures 13 to 18, along the third direction X, one end of the first zone 1111 does not contact the corner wall 113 at one end of the first wall 111, and the other end of the first zone 1111 does not contact the corner wall 113 at the other end of the first wall 111.

[0281] If at least one end of the first region 1111 along the third direction X does not contact the corner wall 113, the material used in the first region 1111 can be reduced, thereby lowering production costs. If both ends of the first region 1111 along the third direction X extend to the two corner walls 113, the length of the first region 1111 is increased, and the reinforcement capacity of the first region 1111 is improved, so that more areas of the first wall 111 along the third direction X are strengthened, further reducing the risk of fatigue cracking in the area of ​​the first wall 111 near the first connecting portion 51.

[0282] In some embodiments, please refer to Figures 19 to 21. Figure 19 is a partial view of a battery cell 10 provided in some embodiments of the present application (showing the positive electrode sheet 22, the negative electrode sheet 23 and the separator 24 of the electrode assembly 2); Figure 20 is a positional relationship diagram of the positive electrode sheet 22, the negative electrode sheet 23 and the separator 24 provided in some embodiments of the present application; and Figure 21 is a positional relationship diagram of the positive electrode sheet 22, the negative electrode sheet 23 and the separator 24 provided in other embodiments of the present application. The electrode assembly 2 also includes a separator 24, and the separator 24 is provided between the positive electrode sheet 22 and the negative electrode sheet 23. The positive electrode sheet 22 includes a positive electrode main body area 221 and a positive electrode tab 21a protruding from the positive electrode main body area 221. The positive electrode main body area 221 has a positive electrode active material layer 223. The negative electrode tab 23 includes a negative electrode main region 231 and a negative electrode tab 21b protruding from the negative electrode main region 231. The negative electrode main region 231 has a negative electrode active material layer 233. Along the first direction Z, the positive electrode main region 221 has a fifth end 2211 facing the end cap 12, the negative electrode main region 231 has a sixth end 2311 facing the end cap 12, and the separator 24 has a seventh end 241 facing the end cap 12. The seventh end 241 is closer to the end cap 12 than the fifth end 2211 and the sixth end 2311.

[0283] In this embodiment, the electrode assembly 2 may be a wound structure or a laminated structure.

[0284] The positive electrode sheet 22 may include a positive electrode current collector 222 and a positive electrode active material layer 223. The positive electrode current collector 222 is provided with the positive electrode active material layer 223 on one or both surfaces in the thickness direction. In the embodiment shown in FIG20 , the positive electrode sheet 22 also includes an insulating layer 224. The insulating layer 224 is provided on both opposing surfaces in the thickness direction of the positive electrode current collector 222. The insulating layer 224 and the positive electrode active material layer 223 are arranged along the first direction Z. The insulating layer 224 is provided at the end of the positive electrode active material layer 223. The portion of the positive electrode sheet 22 corresponding to the entire positive electrode active material layer 223 and the insulating layer 224 is the positive electrode main region 221. The end of the insulating layer 224 near the end cap 12 forms the fifth end 2211 of the positive electrode main region 221. The portion of the positive electrode current collector 222 that extends beyond the insulating layer 224 forms the positive electrode tab 21a. In the embodiment shown in FIG21 , the positive electrode plate 22 is not provided with an insulating layer 224, and the portion of the positive electrode plate 22 corresponding to the positive electrode active material layer 223 is the positive electrode main area 221. The end of the positive electrode active material layer 223 close to the end cover 12 forms the fifth end 2211 of the positive electrode main area 221, and the portion of the positive current collector 222 extending beyond the positive electrode active material layer 223 forms the positive electrode tab 21a.

[0285] The negative electrode sheet 23 may include a negative electrode current collector 232 and a negative electrode active material layer 233. The negative electrode active material layer 233 is provided on one or both surfaces of the negative electrode current collector 232 in the thickness direction. The portion of the negative electrode sheet 23 corresponding to the negative electrode active material layer 233 is the negative electrode main region 231. The end of the negative electrode active material layer 233 near the end cap 12 forms the sixth end 2311 of the negative electrode main region 231. The portion of the negative electrode current collector 232 that extends beyond the negative electrode active material layer 233 forms the negative electrode tab 21b.

[0286] The fifth end 2211 may be flush with the sixth end 2311; as shown in FIG. 20 , the fifth end 2211 may be closer to the end cover 12 (shown in FIG. 19 ) than the sixth end 2311; as shown in FIG. 21 , the sixth end 2311 may be closer to the end cover 12 (shown in FIG. 19 ) than the fifth end 2211.

[0287] In this embodiment, the seventh end 241 of the isolation member 24 is closer to the end cover 12 than the fifth end 2211 of the positive electrode main area 221 and the sixth end 2311 of the negative electrode main area 231, so that the isolation member 24 has a portion that exceeds the fifth end 2211 and the sixth end 2311, thereby enhancing the insulation effect of the isolation member 24 between the positive electrode sheet 22 and the negative electrode sheet 23, and reducing the risk of overlap between the positive electrode sheet 22 and the negative electrode sheet 23.

[0288] In some embodiments, please continue to refer to Figures 19-21, the isolation member 24 includes a protruding area 242 that extends beyond the fifth end 2211 and the sixth end 2311 along the first direction Z. In the projection plane perpendicular to the second direction Y, the orthographic projection of the protruding area 242 partially overlaps with the orthographic projection of the first area 1111.

[0289] The protruding region 242 is the portion of the separator 24 that extends beyond both the fifth end 2211 of the positive electrode main region 221 and the sixth end 2311 of the negative electrode main region 231. It will be appreciated that, as shown in FIG20 , in an embodiment where the fifth end 2211 is closer to the end cap 12 than the sixth end 2311, the portion of the separator 24 that extends beyond the fifth end 2211 is the protruding region 242; and as shown in FIG21 , in an embodiment where the sixth end 2311 is closer to the end cap 12 than the fifth end 2211, the portion of the separator 24 that extends beyond the sixth end 2311 is the protruding region 242.

[0290] As an example, in Figures 19-21, the positive electrode sheet 22, the negative electrode sheet 23 and the separator 24 in the electrode assembly 2 are stacked along the second direction Y in the straight area 25 (not shown in Figures 19-21).

[0291] In this embodiment, in the projection plane perpendicular to the second direction Y, the orthographic projection of the excess area 242 partially overlaps with the orthographic projection of the first area 1111. This structure can increase the size of the first area 1111 along the first direction Z, improve the reinforcement capacity of the first area 1111, so that more areas of the first wall 111 along the first direction Z are strengthened, further reducing the risk of fatigue cracking in the area of ​​the first wall 111 near the first connection portion 51.

[0292] 19-21 , in some embodiments, the second region 1112 has a first inner surface 11121 facing the interior space of the housing 11, and the first region 1111 includes a first protrusion 11118 protruding from the first inner surface 11121. Within a projection plane perpendicular to the second direction Y, the orthographic projection of the positive electrode main region 221 does not overlap with the orthographic projection of the first protrusion 11118; and / or, within a projection plane perpendicular to the second direction Y, the orthographic projection of the negative electrode main region 231 does not overlap with the orthographic projection of the first protrusion 11118.

[0293] The first protrusion 11118 is the portion of the first region 1111 that protrudes from the first inner surface 11121 of the second region 1112. The first protrusion 11118 can have a uniform thickness or a non-uniform thickness. Along the first direction Z, the first protrusion 11118 can extend to the first connecting portion 51, directly connecting the first protrusion 11118 to the first connecting portion 51.

[0294] It can be understood that, in an embodiment where the first region 1111 includes a first portion 11111 and a second portion 11112 arranged along the first direction Z, a portion of the first protrusion 11118 may be located in the first portion 11111, and another portion may be located in the second portion 11112. In an embodiment where the first region 1111 includes a first connecting segment 11113, a second connecting segment 11114, and a third connecting segment 11115 arranged along the third direction X, a portion of the first protrusion 11118 may be located in the first connecting segment 11113, another portion of the first protrusion 11118 may be located in the second connecting segment 11114, and yet another portion of the first protrusion 11118 may be located in the third connecting segment 11115.

[0295] As an example, in the embodiments of Figures 19-21, in the projection plane perpendicular to the second direction Y, the positive main area 221 does not overlap with the orthographic projection of the first protrusion 11118, and the negative main area 231 does not overlap with the orthographic projection of the first protrusion 11118.

[0296] If, in a projection plane perpendicular to the second direction Y, the orthographic projection of the positive electrode main region 221 does not overlap with the orthographic projection of the first protrusion 11118, the housing 11 can provide greater expansion space for the electrode assembly 2, reducing the risk of the electrode assembly 2 directly applying an expansion force to the first protrusion 11118 due to expansion, reducing the deformation of the first wall 111, and further reducing the risk of fatigue cracking in the area of ​​the first wall 111 near the first connection portion 51. If, in a projection plane perpendicular to the second direction Y, the orthographic projection of the negative electrode main region 231 does not overlap with the orthographic projection of the first protrusion 11118, the housing 11 can provide greater expansion space for the electrode assembly 2, reducing the risk of the electrode assembly 2 directly applying an expansion force to the first protrusion 11118 due to expansion, reducing the deformation of the first wall 111, and further reducing the risk of fatigue cracking in the area of ​​the first wall 111 near the first connection portion 51.

[0297] In some embodiments, referring to FIG. 19 to FIG. 21 , the negative electrode sheet 23 includes a negative electrode current collector 232 and a negative electrode active material layer 233 disposed on at least one side of the negative electrode current collector 232 . The negative electrode active material layer 233 includes a negative electrode active material.

[0298] The negative electrode active material layer 233 may be provided on only one side of the negative electrode current collector 232, that is, the negative electrode active material layer 233 may be provided on only one surface of the negative electrode current collector 232 along the thickness direction; or the negative electrode active material layer 233 may be provided on both opposite sides of the negative electrode current collector 232, that is, the negative electrode active material layer 233 may be provided on both opposite surfaces of the negative electrode current collector 232 along the thickness direction.

[0299] The negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, and the like.

[0300] In some embodiments, the negative electrode active material layer 233 includes a negative electrode main body 2331 and a negative electrode thinning portion 2332. The negative electrode main body 2331 and the negative electrode thinning portion 2332 are arranged along a first direction Z. Along the first direction Z, the negative electrode main body 2331 is provided with a negative electrode thinning portion 2332 at one end close to the end cover 12.

[0301] The thickness of the negative electrode main body 2331 is greater than the thickness of the negative electrode thinning portion 2332. The negative electrode thinning portion 2332 may be provided only at one end of the negative electrode main body 2331 close to the end cap 12 along the first direction Z, or the negative electrode thinning portion 2332 may be provided at both ends of the negative electrode main body 2331 along the first direction Z. The negative electrode main body 2331 may be of a uniform thickness structure or a non-uniform thickness structure, and the negative electrode thinning portion 2332 may be of a uniform thickness structure or a non-uniform thickness structure. If at least one of the negative electrode main body 2331 and the negative electrode thinning portion 2332 is of a non-uniform thickness structure, the maximum thickness of the negative electrode thinning portion 2332 may be less than or equal to the minimum thickness of the negative electrode main body 2331, so that the thickness of the negative electrode main body 2331 is greater than the thickness of the negative electrode thinning portion 2332.

[0302] As an example, the negative electrode main body 2331 has a uniform thickness structure, and the thickness of the negative electrode thinned portion 2332 decreases along the direction from the negative electrode main body 2331 to the negative electrode thinned portion 2332 .

[0303] In this embodiment, a negative electrode thinning portion 2332 is provided at one end of the negative electrode main body 2331 close to the end cover 12, and the electrode assembly 2 has a larger expansion gap in the area corresponding to the negative electrode thinning portion 2332. The area of ​​the electrode assembly 2 corresponding to the negative electrode thinning portion 2332 exerts a smaller force on the first wall 111 after expansion, which can reduce the risk of fatigue cracking in the area of ​​the first wall 111 near the first connecting portion 51.

[0304] In some embodiments, in a projection plane perpendicular to the second direction Y, the orthographic projection of the negative electrode thinned portion 2332 located at one end of the negative electrode main body 2331 close to the end cover 12 is spaced apart from the orthographic projection of the first region 1111 along the first direction Z.

[0305] It is understandable that, in a projection plane perpendicular to the second direction Y, the orthographic projection of the negative electrode thinned portion 2332 located at one end of the negative electrode main body 2331 close to the end cover 12 does not overlap with the orthographic projection of the first area 1111 .

[0306] In this embodiment, in the projection plane perpendicular to the second direction Y, the positive projection of the negative electrode thinning portion 2332 located at one end of the negative electrode main body 2331 close to the end cover 12 is spaced apart from the positive projection of the first zone 1111 along the first direction Z, which can reduce the impact of the negative electrode thinning portion 2332 on the first zone 1111, reduce the risk of the electrode assembly 2 expanding and directly applying expansion force to the first zone 1111, and further reduce the risk of fatigue cracking in the area of ​​the first wall 111 near the first connecting portion 51.

[0307] In some embodiments, in a projection plane perpendicular to the second direction Y, the spacing between the orthographic projection of the negative electrode thinning portion 2332 located at one end of the negative electrode main body 2331 close to the end cover 12 and the orthographic projection of the first area 1111 along the first direction Z is greater than or equal to 1 mm.

[0308] In a projection plane perpendicular to the second direction Y, the spacing between the orthographic projection of the negative electrode thinned portion 2332 located at the end of the negative electrode main body 2331 near the end cap 12 and the orthographic projection of the first region 1111 along the first direction Z is W1, where W1 ≥ 1 mm. This spacing is the minimum distance between the orthographic projections of the negative electrode thinned portion 2332 and the first region 1111 along the first direction Z in the projection plane perpendicular to the second direction Y. W1 can be any value among 1 mm, 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, 10 mm, 11 mm, 12 mm, 13 mm, 14 mm, 15 mm, 16 mm, 17 mm, 18 mm, 19 mm, 20 mm, or a range between any two values.

[0309] In this embodiment, W1≥1mm makes the positive projection of the negative electrode thinning portion 2332 and the positive projection of the first area 1111 in the projection plane perpendicular to the second direction Y farther apart along the first direction Z, further reducing the influence of the negative electrode thinning portion 2332 on the first area 1111.

[0310] In some embodiments, the coating weight of the negative electrode active material layer 233 on one side is 90 mg / 1540 mm 2 ~170mg / 1540mm 2 .

[0311] The coating weight of the negative electrode active material layer 233 on one side can be 90 mg / 1540 mm 2 、100mg / 1540mm 2 、110mg / 1540mm 2 、120mg / 1540mm 2 、130mg / 1540mm 2 、140mg / 1540mm 2 、150mg / 1540mm 2 、160mg / 1540mm 2 、170mg / 1540mm 2 Any point value or any range of values ​​between the two.

[0312] To measure the coating weight of the negative electrode active material layer 233 on one side, take a negative electrode sheet 23 coated on one side (if it is coated on both sides, wipe off the negative electrode active material layer 233 on one side first), punch it out into small discs with an area of ​​S1, weigh them, and record their weight as M1. Then, wipe off the negative electrode active material layer 233 from the weighed negative electrode sheet 23, and weigh the negative electrode current collector 232, recording its weight as M2. The coating weight of the negative electrode active material layer 233 on one side = (M1 - M2) / S1.

[0313] The coating weight of the negative electrode active material layer 233 on one side is related to the expansion of the negative electrode active material layer 233. The coating weight of the negative electrode active material layer 233 on one side is set at 90 mg / 1540 mm. 2 ~170mg / 1540mm 2 , which can, to a certain extent, take into account the high energy density requirements of the battery cell 10 and the low expansion requirements of the negative electrode tab 23, thereby reducing the impact of the expansion of the negative electrode tab 23 on the first wall 111, and can reduce the risk of fatigue cracking in the area of ​​the first wall 111 near the first connecting portion 51.

[0314] In some embodiments, the coating weight of the negative electrode active material layer 233 on one side is 110 mg / 1540 mm 2 ~150mg / 1540mm 2 .

[0315] In this embodiment, the coating weight of the negative electrode active material layer 233 on one side can be 110 mg / 1540 mm 2 、115mg / 1540mm 2 、120mg / 1540mm 2 、125mg / 1540mm 2 、130mg / 1540mm 2 、135mg / 1540mm 2 、140mg / 1540mm 2 、145mg / 1540mm 2 、150mg / 1540mm 2 Any point value or any range of values ​​between the two.

[0316] In this embodiment, the coating weight of the negative electrode active material layer 233 on one side is 110 mg / 1540 mm 2 ~150mg / 1540mm 2 , which can further improve the energy density requirement of the battery cell 10 and further slow down the expansion of the negative electrode sheet 23.

[0317] In some embodiments, the porosity of the negative electrode sheet 23 is 27% to 40%.

[0318] The porosity of the negative electrode sheet 23 can be any point value among 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, etc., or a range of values ​​between any two points.

[0319] The porosity of the negative electrode sheet 23 can be defined as the percentage of the pore volume within the negative electrode sheet 23 to the total volume of the negative electrode sheet 23. As an example, when the battery cell 10 is at a 0% state of charge, a double-sided coated negative electrode sheet 23 is taken and the porosity of the negative electrode sheet 23 is measured using an AccuPyc II 1340 density meter in accordance with the national standard GB / T 24586-2009.

[0320] In this embodiment, the porosity of the negative electrode sheet 23 is 27% to 40%, which can provide space for impurities generated by side reactions in the negative electrode sheet 23, slow down the expansion of the negative electrode sheet 23, and reduce the impact of the expansion of the negative electrode sheet 23 on the first wall 111.

[0321] In some embodiments, the negative electrode active material includes a silicon-based material, and the mass content of silicon in the silicon-based material is 0.3% to 10%, and can be optionally 1% to 6%.

[0322] The mass content of silicon element in the negative electrode active material in the silicon-based material can be any point value among 0.3%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, etc., or a range value between any two points.

[0323] In some embodiments, the silicon-based material includes at least one of a silicon-oxygen compound and a silicon-carbon composite.

[0324] In some embodiments, referring to FIG. 19 to FIG. 21 , the positive electrode sheet 22 includes a positive electrode current collector 222 and a positive electrode active material layer 223 disposed on at least one side of the positive electrode current collector 222 . The positive electrode active material layer 223 includes a positive electrode active material.

[0325] The positive electrode active material layer 223 may be provided on only one side of the positive electrode current collector 222, that is, the positive electrode active material layer 223 may be provided on only one surface of the positive electrode current collector 222 along the thickness direction; or the positive electrode active material layer 223 may be provided on both opposite sides of the positive electrode current collector 222, that is, the positive electrode active material layer 223 may be provided on both opposite surfaces of the positive electrode current collector 222 along the thickness direction.

[0326] The positive electrode active material may include at least one of the following materials: a lithium-containing phosphate, a lithium transition metal oxide, and modified compounds thereof.

[0327] In some embodiments, the positive electrode active material layer 223 includes a positive electrode main body 2231 and a positive electrode thinning portion 2232. The positive electrode main body 2231 and the positive electrode thinning portion 2232 are arranged along a first direction Z. Along the first direction Z, the positive electrode main body 2231 is provided with a positive electrode thinning portion 2232 at one end close to the end cover 12.

[0328] The thickness of the positive electrode main body 2231 is greater than the thickness of the positive electrode thinning portion 2232. The positive electrode thinning portion 2232 may be provided only at one end of the positive electrode main body 2231 close to the end cap 12 along the first direction Z, or the positive electrode thinning portion 2232 may be provided at both ends of the positive electrode main body 2231 along the first direction Z. The positive electrode main body 2231 may be of a uniform thickness structure or a non-uniform thickness structure, and the positive electrode thinning portion 2232 may be of a uniform thickness structure or a non-uniform thickness structure. If at least one of the positive electrode main body 2231 and the positive electrode thinning portion 2232 is of a non-uniform thickness structure, the maximum thickness of the positive electrode thinning portion 2232 may be less than or equal to the minimum thickness of the positive electrode main body 2231, so that the thickness of the positive electrode main body 2231 is greater than the thickness of the positive electrode thinning portion 2232.

[0329] As an example, the positive electrode main body 2231 has a uniform thickness structure, and the thickness of the positive electrode thinned portion 2232 decreases along the direction from the positive electrode main body 2231 to the positive electrode thinned portion 2232 .

[0330] In this embodiment, a positive electrode thinning portion 2232 is provided at one end of the positive electrode main body 2231 close to the end cover 12, and the electrode assembly 2 has a larger expansion gap in the area corresponding to the positive electrode thinning portion 2232. The area of ​​the electrode assembly 2 corresponding to the positive electrode thinning portion 2232 exerts a smaller force on the first wall 111 after expansion, which can reduce the risk of fatigue cracking in the area of ​​the first wall 111 near the first connecting portion 51.

[0331] In some embodiments, in a projection plane perpendicular to the second direction Y, the orthographic projection of the positive electrode thinned portion 2232 located at one end of the positive electrode main body 2231 close to the end cover 12 is spaced apart from the orthographic projection of the first area 1111 along the first direction Z.

[0332] It can be understood that, in the projection plane perpendicular to the second direction Y, the orthographic projection of the positive electrode thinned portion 2232 located at one end of the positive electrode main body 2231 close to the end cover 12 does not overlap with the orthographic projection of the first area 1111 .

[0333] In the projection plane perpendicular to the second direction Y, the orthographic projection of the positive electrode thinning portion 2232 located at one end of the positive electrode main body 2231 close to the end cover 12 is spaced apart from the orthographic projection of the first zone 1111 along the first direction Z, which can reduce the impact of the positive electrode thinning portion 2232 on the first zone 1111, reduce the risk of the electrode assembly 2 expanding and directly applying expansion force to the first zone 1111, and further reduce the risk of fatigue cracking in the area of ​​the first wall 111 near the first connecting portion 51.

[0334] In some embodiments, in a projection plane perpendicular to the second direction Y, the spacing between the orthographic projection of the positive electrode thinning portion 2232 located at one end of the positive electrode main body 2231 close to the end cover 12 and the orthographic projection of the first area 1111 along the first direction Z is greater than or equal to 1 mm.

[0335] In a projection plane perpendicular to the second direction Y, the spacing between the orthographic projection of the positive electrode thinned portion 2232 located at the end of the positive electrode main body 2231 near the end cap 12 and the orthographic projection of the first region 1111 along the first direction Z is W2, where W2 ≥ 1 mm. This spacing is the minimum distance between the orthographic projections of the positive electrode thinned portion 2232 and the first region 1111 along the first direction Z in a projection plane perpendicular to the second direction Y. W1 may be W2, W1 ≤ W2, or W1 ≥ W2. W2 may be any value among 1 mm, 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, 10 mm, 11 mm, 12 mm, 13 mm, 14 mm, 15 mm, 16 mm, 17 mm, 18 mm, 19 mm, 20 mm, or any range between any two values.

[0336] In this embodiment, W2 ≥ 1 mm, so that in the projection plane perpendicular to the second direction Y, the orthographic projection of the positive electrode thinning portion 2232 is farther away from the orthographic projection of the first zone 1111 along the first direction Z, further reducing the influence of the positive electrode thinning portion 2232 on the first zone 1111.

[0337] In some embodiments, the coating weight of the positive electrode active material layer 223 on one side is 200 mg / 1540 mm 2 ~370mg / 1540 / mm 2 .

[0338] The coating weight of the positive electrode active material layer 223 on one side can be 200 mg / 1540 mm 2 、210mg / 1540mm 2 , 220mg / 1540mm 2 、230mg / 1540mm 2 , 240mg / 1540mm 2, 250mg / 1540mm 2 、260mg / 1540mm 2 、270mg / 1540mm 2 、280mg / 1540mm 2 、290mg / 1540mm 2 、300mg / 1540mm 2 、310mg / 1540mm 2 、320mg / 1540mm 2 、330mg / 1540mm 2 、340mg / 1540mm 2 、350mg / 1540mm 2 、360mg / 1540mm 2 、370mg / 1540mm 2 Any point value or any range of values ​​between the two.

[0339] To measure the coating weight of the positive electrode active material layer 223 on one side, take a single-sided coated positive electrode sheet 22 (if a double-sided coated positive electrode sheet 22 is used, wipe off the positive electrode active material layer 223 on one side first), punch it out into small discs with an area of ​​S2, weigh them, and record their weight as M3. Then, wipe off the positive electrode active material layer 223 from the weighed positive electrode sheet 22, and weigh the positive electrode current collector 222, recording its weight as M4. The coating weight of the positive electrode active material layer 223 on one side = (M3 - M4) / S2.

[0340] The coating weight of the positive electrode active material layer 223 on one side is related to the expansion of the positive electrode active material layer 223. The coating weight of the positive electrode active material layer 223 on one side is set at 200 mg / 1540 mm 2 ~370mg / 1540 / mm 2 , which can, to a certain extent, take into account the high energy density requirements of the battery cell 10 and the low expansion requirements of the positive electrode sheet 22, thereby reducing the impact of the expansion of the positive electrode sheet 22 on the first wall 111, and can reduce the risk of fatigue cracking in the area of ​​the first wall 111 near the first connecting portion 51.

[0341] In some embodiments, the coating weight of the positive electrode active material layer 223 on one side is 240 mg / 1540 mm 2 ~330mg / 1540mm 2 .

[0342] The coating weight of the positive electrode active material layer 223 on one side can be 240 mg / 1540 mm 2 , 245mg / 1540mm 2 , 250mg / 1540mm2 、255mg / 1540mm 2 、260mg / 1540mm 2 、265mg / 1540mm 2 、270mg / 1540mm 2 、275mg / 1540mm 2 、280mg / 1540mm 2 、285mg / 1540mm 2 、290mg / 1540mm 2 、295mg / 1540mm 2 、300mg / 1540mm 2 、305mg / 1540mm 2 、310mg / 1540mm 2 、315mg / 1540mm 2 、320mg / 1540mm 2 、325mg / 1540mm 2 、330mg / 1540mm 2 Any point value or any range of values ​​between the two.

[0343] In this embodiment, the coating weight of the positive electrode active material layer 223 on one side is 240 mg / 1540 mm 2 ~330mg / 1540mm 2 , which can further improve the energy density requirement of the battery cell 10 and further slow down the expansion of the positive electrode sheet 22.

[0344] In some embodiments, the positive electrode active material is a lithium-containing phosphate.

[0345] In some embodiments, please refer to Figures 22-24. Figure 22 is a partial view of a battery cell 10 (showing the first wall 111) provided in some embodiments of the present application; Figure 23 is a partial view of the first wall 111 shown in Figure 22; and Figure 24 is an isometric view of the housing 11 shown in Figure 22. The housing 11 is made of steel. The maximum thickness of the second region 1112 is D1. The dimension of the housing 11 along the second direction Y is D, and 0.001≤D1 / D≤0.012.

[0346] The thickness at the thickest position of the second region 1112 is the maximum thickness of the second region 1112. As an example, the second region 1112 is a uniform thickness structure, and the thickness at any position of the second region 1112 can be regarded as the maximum thickness of the second region 1112.

[0347] In this embodiment, a portion of the first region 1111 may protrude from the first inner surface 11121 and / or the first outer surface 11122. As an example, in the embodiments shown in Figures 22 to 24 , a portion of the first region 1111 protrudes from the first outer surface 11122, and the inner surface of the first region 1111 is coplanar with the first inner surface 11121.

[0348] The maximum distance between the first outer surfaces 11122 of the second sections 1112 of the two opposing first walls 111 of the housing 11 is the dimension of the housing 11 along the second direction Y. It should be understood that when measuring the dimension of the housing 11 along the second direction Y, the measurement reference is the first outer surface 11122 of the second section 1112. As an example, the first outer surfaces 11122 of the second sections 1112 of the two opposing first walls 111 are arranged in parallel.

[0349] For the shell 11 made of steel, D1 / D can be any point value among 0.001, 0.002, 0.003, 0.004, 0.005, 0.006, 0.007, 0.008, 0.009, 0.01, 0.011, 0.012, etc., or a range of values ​​between any two points.

[0350] For the shell 11 made of steel, D1 / D≥0.001, which increases the thickness ratio of the second zone 1112 in the shell 11, so that the second zone 1112 has sufficient strength to meet the strength requirements of the shell 11; D1 / D≤0.012, which reduces the thickness ratio of the second zone 1112 in the shell 11. When the volume of the shell 11 is constant, the internal space of the shell 11 can be increased, thereby freeing up more space for the electrode assembly 2 to meet the volume energy density requirements of the battery cell 10.

[0351] For the steel casing 11, D1 / D must be controlled below 0.012 to meet the volumetric energy density requirements of the battery cell 10. If the entire thickness of the first wall 111 were the same as that of the second region 1112, the first wall 111 would be susceptible to deformation due to the expansion force of the electrode assembly 2. This could lead to fatigue cracking in the area of ​​the first wall 111 near the first connection portion 51 over time. Therefore, a thicker first region 1111 is provided in the first wall 111 to enhance the strength of the area of ​​the first wall 111 near the first connection portion 51, reducing the risk of fatigue cracking.

[0352] In some embodiments, the material of the housing 11 includes steel. The maximum thickness of the second region 1112 is D1, 0.08 mm ≤ D1 ≤ 0.35 mm; and / or the maximum thickness of the first region 1111 is D2, 0.1 mm ≤ D2 ≤ 0.6 mm.

[0353] The thickness at the thickest point of the second region 1112 is the maximum thickness of the second region 1112. The thickness at the thickest point of the first region 1111 is the maximum thickness of the first region 1111. It is understood that the maximum thickness of the second region 1112 is less than the maximum thickness of the first region 1111, that is, D1 < D2.

[0354] For the shell 11 made of steel, D1 can take any point value among 0.08mm, 0.1mm, 0.12mm, 0.15mm, 0.18mm, 0.2mm, 0.22mm, 0.25mm, 0.28mm, 0.3mm, 0.32mm, 0.35mm, etc., or a range value between any two of them; D2 can take any point value among 0.1mm, 0.15mm, 0.2mm, 0.25mm, 0.3mm, 0.35mm, 0.4mm, 0.45mm, 0.5mm, 0.55mm, 0.6mm, etc., or a range value between any two of them.

[0355] For the steel housing 11, setting the maximum thickness of the second region 1112 to 0.08 mm to 0.35 mm can meet both the strength requirements of the second region 1112 and the volumetric energy density requirements of the battery cell 10. Setting the maximum thickness of the first region 1111 to 0.1 mm to 0.6 mm provides sufficient strength for the first region 1111 to enhance the strength of the area of ​​the first wall 111 near the first connection portion 51.

[0356] In some embodiments, the material of the housing 11 includes aluminum alloy. The maximum thickness of the second region 1112 is D1, and the dimension of the housing 11 along the second direction Y is D, and 0.005≤D1 / D≤0.065.

[0357] For the shell 11 made of aluminum alloy, D1 / D can be any point value among 0.005, 0.01, 0.015, 0.02, 0.025, 0.03, 0.035, 0.04, 0.045, 0.05, 0.055, 0.06, 0.65, etc., or a range of values ​​between any two of them.

[0358] For the shell 11 made of aluminum alloy, D1 / D≥0.005, which increases the thickness ratio of the second zone 1112 in the shell 11, so that the second zone 1112 has sufficient strength to meet the strength requirements of the shell 11; D1 / D≤0.065, which reduces the thickness ratio of the second zone 1112 in the shell 11. When the volume of the shell 11 is constant, the internal space of the shell 11 can be increased, thereby freeing up more space for the electrode assembly 2 to meet the volume energy density requirements of the battery cell 10.

[0359] For the aluminum alloy housing 11, D1 / D must be controlled below 0.065 to meet the volumetric energy density requirements of the battery cell 10. If the entire thickness of the first wall 111 were the same as that of the second region 1112, the first wall 111 would be susceptible to deformation due to the expansion force of the electrode assembly 2. This could lead to fatigue cracking in the area of ​​the first wall 111 near the first connection portion 51 over time. Therefore, a thicker first region 1111 is provided in the first wall 111 to enhance the strength of the area of ​​the first wall 111 near the first connection portion 51, reducing the risk of fatigue cracking.

[0360] In some embodiments, the material of the housing 11 includes aluminum alloy. The maximum thickness of the second region 1112 is D1, 0.4 mm ≤ D1 ≤ 0.8 mm; and / or the maximum thickness of the first region 1111 is D2, 0.5 mm ≤ D2 ≤ 1.5 mm.

[0361] For the shell 11 made of aluminum alloy, D1 can take any point value among 0.4mm, 0.42mm, 0.45mm, 0.48mm, 0.5mm, 0.52mm, 0.55mm, 0.58mm, 0.6mm, 0.62mm, 0.65mm, 0.68mm, 0.7mm, 0.72mm, 0.75mm, 0.78mm, 0.8mm, etc., or a range value between any two of them; D2 can take any point value among 0.5mm, 0.6mm, 0.7mm, 0.8mm, 0.9mm, 1mm, 1.1mm, 1.2mm, 1.3mm, 1.4mm, 1.5mm, etc., or a range value between any two of them.

[0362] For the aluminum alloy housing 11, setting the maximum thickness of the second region 1112 to 0.4 mm to 0.8 mm can meet both the strength requirements of the second region 1112 and the volumetric energy density requirements of the battery cell 10. Setting the maximum thickness of the first region 1111 to 0.5 mm to 1.5 mm provides sufficient strength for enhancing the strength of the area of ​​the first wall 111 near the first connection portion 51.

[0363] In some embodiments, the aluminum alloy includes the following composition by weight: aluminum ≥ 99.6%, copper ≤ 0.05%, iron ≤ 0.35%, magnesium ≤ 0.03%, manganese ≤ 0.03%, silicon ≤ 0.25%, titanium ≤ 0.03%, vanadium ≤ 0.05%, zinc ≤ 0.05%, and other individual elements ≤ 0.03%. This aluminum alloy has good processing and forming properties, facilitating the molding of the housing 11.

[0364] In some embodiments, the aluminum alloy comprises the following composition by weight: aluminum ≥ 96.7%, copper ≤ 0.2%, iron ≤ 0.7%, manganese ≤ 1.5%, silicon ≤ 0.6%, zinc ≤ 0.1%, other individual elements ≤ 0.05%, and other elements total ≤ 0.15%. This aluminum alloy has good machinability and corrosion resistance.

[0365] 25 and 26 , FIG25 is a partial view of a battery cell 10 according to another embodiment of the present application (showing the first wall 111 ), and FIG26 is a partial enlarged view of point C in FIG25 . The first region 1111 is directly connected to the first connecting portion 51 .

[0366] The first region 1111 and the first connection portion 51 may be in point contact, line contact, or surface contact to achieve direct connection between the two.

[0367] In this embodiment, the first zone 1111 is directly connected to the first connecting portion 51, so that the first zone 1111 is closer to the first connecting portion 51 along the first direction Z, so that the first zone 1111 is located near the first connecting portion 51, further reducing the risk of fatigue cracking in the area of ​​the first wall 111 near the first connecting portion 51 due to the expansion of the electrode assembly 2.

[0368] In some embodiments, the first wall 111 also includes a first transition zone 1117, which is connected to one end of the first zone 1111 along the first direction Z away from the second zone 1112, and the first transition zone 1117 is connected to the first connecting portion 51. The connection position between the first transition zone 1117 and the first connecting portion 51 forms a first connection interface 511, and the first connection interface 511 has a first position 5111 that is closest to the first zone 1111 along the first direction Z. The first position 5111 is located at one end of the first zone 1111 along the first direction Z away from the second zone 1112.

[0369] The first transition region 1117 may be the portion of the first wall 111 connecting the first connecting portion 51 and the first region 1111. The first transition region 1117 may have a uniform thickness or a non-uniform thickness. The thickness of the first transition region 1117 may be less than that of the first region 1111. As an example, in the embodiment shown in Figures 25 and 26, the thickness of the first transition region 1117 gradually decreases along the direction from the second region 1112 to the first region 1111.

[0370] The first connection interface 511 is formed at the connection position between the first transition area 1117 and the first connection portion 51. The first transition area 1117 and the first connection portion 51 are separated by the first connection interface 511. The first connection interface 511 can be a plane or a curved surface.

[0371] The first zone 1111 and the first transition zone 1117 are separated by a first interface U. The first interface U is a virtual plane. The first interface U passes through the first position 5111. The first interface U is perpendicular to the first direction Z. The first transition zone 1117 and the first connecting portion 51 are located above the first interface U, and the first zone 1111 is located below the first interface U.

[0372] In this embodiment, the first transition zone 1117 is connected to the first connection portion 51 to form a first connection interface 511, so that the first transition zone 1117 and the first connection portion 51 have a sufficiently large contact area, thereby improving the firmness of the first wall 111 and the end cover 12 after welding.

[0373] In some embodiments, at least a portion of the first connection interface 511 extends obliquely relative to the second direction Y.

[0374] The first connection interface 511 may extend obliquely relative to the second direction Y as a whole, and the first connection interface 511 may also extend obliquely relative to the second direction Y in part.

[0375] It can be understood that the extending direction of the portion of the first connection interface 511 that extends obliquely relative to the second direction Y is not parallel to the second direction Y.

[0376] After the end cap 12 and the first wall 111 are welded, the first connection portion 51 shrinks as it solidifies, generating tensile stress in the first transition region 1117. When the first wall 111 is subjected to the expansion force of the electrode assembly 2, the first wall 111 deforms, generating tensile stress in the first transition region 1117. Because at least a portion of the first connection interface 511 extends obliquely relative to the second direction Y, the tensile stress generated in the first transition region 1117 by the shrinkage of the first connection portion 51 and the tensile stress generated in the first transition region 1117 by the deformation of the first wall 111 are not aligned in the same straight line near the portion of the first connection interface 511 extending obliquely relative to the second direction Y. This reduces the risk of fatigue cracking in the first transition region 1117 near the first connection interface 511.

[0377] In some embodiments, please continue to refer to Figure 26, the first connection interface 511 includes a first interface 5112, the first interface 5112 extends obliquely from the first position 5111 toward the direction close to the end cover 12, and along the second direction Y, at least a portion of the first transition zone 1117 is located between the first interface 5112 and the end cover 12.

[0378] It is understandable that the first interface 5112 extends obliquely relative to the second direction Y. The first interface 5112 can be a plane or a curved surface.

[0379] The first position 5111 is the lowest position of the first interface 5112 (the position closest to the first zone 1111), and the first interface 5112 extends obliquely from the first position 5111 toward the direction close to the end cover 12, that is, the first interface 5112 extends obliquely upward from the first position 5111 toward the direction close to the end cover 12.

[0380] Along the second direction Y, the first transition zone 1117 may be entirely located between the first interface 5112 and the end cover 12 , or only a portion of the first transition zone 1117 may be located between the first interface 5112 and the end cover 12 .

[0381] In this embodiment, along the second direction Y, at least part of the first transition zone 1117 is located between the first interface 5112 and the end cover 12, so that the first connecting portion 51 protects the first transition zone 1117. When the first wall 111 is subjected to the expansion force of the electrode assembly 2, the first transition zone 1117 is deformed during the force process and is blocked by the first connecting portion 51, thereby reducing the risk of fatigue cracking in the area of ​​the first transition zone 1117 near the first interface 5112.

[0382] In some embodiments, referring again to FIG. 26 , the first interface 5112 is connected to the outer surface of the first region 1111 at the first position 5111 .

[0383] As an example, the first interface 5112 intersects the outer surface of the first region 1111 at a first straight line, which extends along the third direction X. The first straight line is located at a first position 5111. The first interface 5112 is connected to the inner surface of the first transition region 1117 at a third position 5114. Along the first direction Z, the third position 5114 is farther from the first region 1111 than the first position 5111. The first transition region 1117 is generally triangular in shape.

[0384] In this embodiment, the first interface 5112 is connected to the outer surface of the first zone 1111 at the first position 5111, so that the first zone 1111 and the first connecting portion 51 are in a direct connection state, so that the first zone 1111 and the first connecting portion 51 are closer along the first direction Z, further reducing the risk of fatigue cracking in the area of ​​the first wall 111 near the first connecting portion 51 due to the expansion of the electrode assembly 2.

[0385] In some embodiments, referring to Figures 27 and 28 , Figure 27 is a partial view of a battery cell 10 (showing the first wall 111) provided in yet other embodiments of the present application; Figure 28 is a partial, enlarged view of point D in Figure 27 . The first connection interface 511 includes a second interface 5113 , which extends obliquely from the first position 5111 away from the end cap 12 . 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 facing away from the end cap 12 .

[0386] It is understandable that the second interface 5113 extends obliquely relative to the second direction Y. The second interface 5113 can be a plane or a curved surface. Along the second direction Y, at least a portion of the first connecting portion 51 is located between the second interface 5113 and the end cover 12 .

[0387] The first position 5111 is the lowest position of the second interface 5113 (the position closest to the first zone 1111), and the second interface 5113 extends obliquely from the first position 5111 in a direction away from the end cover 12, that is, the second interface 5113 extends obliquely upward from the first position 5111 in a direction away from the end cover 12.

[0388] Along the second direction Y, the first transition zone 1117 may be entirely located on the side of the second interface 5113 away from the end cover 12 , or only a portion of the first transition zone 1117 may be located on the side of the second interface 5113 away from the end cover 12 .

[0389] In this embodiment, along the second direction Y, at least part of the first transition zone 1117 is located on the side of the second interface 5113 away from the end cover 12, so that the first transition zone 1117 has a restrictive effect on the first connection part 51, reducing the risk of the first connection part 51 falling off.

[0390] In some embodiments, referring again to FIG. 28 , the second interface 5113 is connected to the inner surface of the first region 1111 at the first position 5111 .

[0391] As an example, the second interface 5113 intersects the inner surface of the first region 1111 at a first straight line extending along the third direction X. The first straight line is located at a first position 5111. The second interface 5113 is connected to the outer surface of the first transition region 1117 at a fourth position 5115. Along the first direction Z, the fourth position 5115 is further away from the first region 1111 than the first position 5111. The first transition region 1117 is generally triangular in shape.

[0392] In this embodiment, the second interface 5113 is connected to the inner surface of the first zone 1111 at the first position 5111, so that the first zone 1111 and the first connecting portion 51 are in a direct connection state, so that the first zone 1111 and the first connecting portion 51 are closer along the first direction Z, further reducing the risk of fatigue cracking in the area of ​​the first wall 111 near the first connecting portion 51 due to the expansion of the electrode assembly 2.

[0393] In some embodiments, please refer to Figures 29 and 30. Figure 29 is a partial view of a battery cell 10 provided in some further embodiments of the present application (showing the first wall 111); Figure 30 is a partial enlarged view of point E in Figure 29. The first connection interface 511 includes a first interface 5112 and a second interface 5113. The first interface 5112 extends obliquely from the first position 5111 toward the end cap 12, and the second interface 5113 extends obliquely from the first position 5111 toward the end cap 12. Along the second direction Y, a portion of the first transition region 1117 is located between the first interface 5112 and the end cap 12, and another portion of the first transition region 1117 is located on the side of the second interface 5113 facing away from the end cap 12.

[0394] As an example, the first interface 5112 is connected to the inner surface of the first transition region 1117 at a third position 5114 , and the second interface 5113 is connected to the outer surface of the first transition region 1117 at a fourth position 5115 .

[0395] In some embodiments, the Vickers hardness of the first transition region 1117 is less than the Vickers hardness of the second region 1112 ; and / or the Vickers hardness of the first transition region 1117 is less than the Vickers hardness of the first connecting portion 51 .

[0396] As an example, the Vickers hardness of the second region 1112 is smaller than the Vickers hardness of the first connection portion 51 .

[0397] If the Vickers hardness of the first transition region 1117 is lower than the Vickers hardness of the second region 1112, the first transition region 1117 with the lower Vickers hardness is connected to the first connecting portion 51. This can alleviate the rigid pull between the first wall 111 and the first connecting portion 51 when the first wall 111 deforms, thereby reducing the risk of separation between the first wall 111 and the first connecting portion 51. If the Vickers hardness of the first transition region 1117 is lower than the Vickers hardness of the first connecting portion 51, the first transition region 1117 is more easily deformed than the first connecting portion 51. This can alleviate the rigid pull between the first wall 111 and the first connecting portion 51 when the first wall 111 deforms, thereby reducing the risk of separation between the first wall 111 and the first connecting portion 51.

[0398] In some embodiments, please continue to refer to FIG. 25 to FIG. 30 , along the first direction Z, the first connection interface 511 is closer to the second area 1112 than the outer surface 121 of the end cover.

[0399] Along the first direction Z, the surface of the end cover 12 facing away from the electrode assembly 2 is the outer surface 121 of the end cover.

[0400] In the embodiment shown in FIG. 25 and FIG. 26 , along the first direction Z, the third position 5114 and the first position 5111 are both closer to the second region 1112 than to the outer surface 121 of the end cap.

[0401] In the embodiment shown in FIG. 27 and FIG. 28 , along the first direction Z, the fourth position 5115 and the first position 5111 are both closer to the second region 1112 than to the outer surface 121 of the end cap.

[0402] In the embodiment shown in FIG. 29 and FIG. 30 , 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 cap.

[0403] In this embodiment, the first connection interface 511 is closer to the second area 1112 along the first direction Z than the outer surface 121 of the end cover, so that the first connection part 51 can sink to a deeper position of the first wall 111, which can effectively improve the connection strength between the first wall 111 and the end cover 12.

[0404] In some embodiments, please refer to Figures 31 and 32. Figure 31 is an isometric view of the housing 11 in some further embodiments of the present application; Figure 32 is a partial enlarged view of point F in Figure 31. The housing 11 further includes a second wall 112 and a corner wall 113. The first wall 111, the corner wall 113, and the second wall 112 are arranged along the circumference of the opening, and the corner wall 113 connects the first wall 111 and the second wall 112.

[0405] The second wall 112 and the end cover 12 can be welded to form the third connecting portion 5, and the first connecting portion 51 and the third connecting portion 5 are both part of the connecting portion 5. The second wall 112 can be a uniform thickness structure or a non-uniform thickness structure.

[0406] In the embodiments of Figures 31 and 32 , the second wall 112 has a uniform thickness structure. In other embodiments, the second wall 112 may have a non-uniform thickness structure. The structure of the second wall 112 may be the same as that of the first wall 111. For example, the second wall 112 includes a fifth region and a sixth region arranged along the first direction Z. The thickness of the fifth region is greater than that of the sixth region. The fifth region is located between the third connecting portion 5 and the sixth region. This reduces the risk of fatigue cracking in the area of ​​the second wall 112 near the third connecting portion 5. 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.

[0407] The first wall 111 and the second wall 112 in the housing 11 are indirectly connected via the corner walls 113 , and the sum of the number of the first walls 111 and the number of the second walls 112 is equal to the number of the corner walls 113 .

[0408] As an example, the first wall 111, the second wall 112 and the corner wall 113 are integrally formed. The cross section of the outer surface and / or the inner surface of the corner wall 113 may be arc-shaped, and the cross section is perpendicular to the first direction Z.

[0409] In this embodiment, the first wall 111 and the second wall 112 are connected by a corner wall 113 , so that the first wall 111 can transition to the second wall 112 through the corner wall 113 , which can effectively reduce the risk of stress concentration at the corner position of the shell 11 .

[0410] In some embodiments, please refer to Figures 33 to 35. Figure 33 is a partial view of the battery cell 10 provided in some embodiments of the present application (showing the corner wall 113); Figure 34 is a structural schematic diagram of the corner wall 113 provided in some embodiments of the present application; Figure 35 is a structural schematic diagram of the corner wall 113 provided in other embodiments of the present application. The corner wall 113 is welded to the end cover 12 to form the second connecting portion 52. The corner wall 113 includes a third area 1131 and a fourth area 1132 arranged along the first direction Z. The thickness of the third area 1131 is greater than the thickness of the fourth area 1132. The third area 1131 is located between the fourth area 1132 and the second connecting portion 52.

[0411] The third region 1131 may be a region where the thickness of the corner wall 113 is thickened. The third region 1131 is thicker than the fourth region 1132. The fourth region 1132 may be a portion of the corner wall 113 located along the first direction Z on the side of the third region 1131 away from the second connection portion 52. The third region 1131 and the second connection portion 52 may be directly or indirectly connected; the third region 1131 and the fourth region 1132 may be directly or indirectly connected. The third region 1131 may have a uniform thickness structure or a non-uniform thickness structure; the fourth region 1132 may have a uniform thickness structure or a non-uniform thickness structure. If at least one of the third region 1131 and the fourth region 1132 has a non-uniform thickness structure, the maximum thickness of the fourth region 1132 may be less than or equal to the minimum thickness of the fourth region 1132, so that the thickness of the third region 1131 is greater than the thickness of the fourth region 1132.

[0412] The fourth region 1132 has a second inner surface 11321 facing the interior space of the housing 11 and a second outer surface 11322 facing away from the interior space of the housing 11. The third region 1131 may partially protrude from the second inner surface 11321 and / or the second outer surface 11322. As an example, in the embodiments shown in Figures 33 and 34 , a portion of the third region 1131 protrudes from the second inner surface 11321, and the outer surface of the third region 1131 is coplanar with the second outer surface 11322. In the embodiment shown in Figure 35 , a portion of the third region 1131 protrudes from the second outer surface 11322, and the inner surface of the third region 1131 is coplanar with the second inner surface 11321.

[0413] The second connecting portion 52 can correspond one-to-one with the corner wall 113. The second connecting portion 52 is the portion where the weld mark is formed after the end cover 12 and the corner wall 113 are welded together. The second connecting portion 52 can be formed by a portion formed on the end cover 12 and another portion formed on the corner wall 113. The corner wall 113 and the end cover 12 can be formed by a saddle weld or a penetration weld to form the second connecting portion 52. The second connecting portion 52 and the first connecting portion 51 are both part of the connecting portion 5.

[0414] The thickness of the third region 1131 is greater than that of the fourth region 1132, and the third region 1131 is located between the second connecting portion 52 and the fourth region 1132, so that the third region 1131 with a larger thickness is closer to the second connecting portion 52 than the fourth region 1132. The third region 1131 strengthens the area of ​​the corner wall 113 near the second connecting portion 52, reducing the risk of fatigue cracking in the area of ​​the corner wall 113 near the second connecting portion 52, thereby improving the service life of the battery cell 10.

[0415] In some embodiments, referring still to FIG. 32 , the third region 1131 is directly connected to the first region 1111 .

[0416] As an example, the third area 1131 and the first area 1111 are integrally formed, and both ends of the first area 1111 along the third direction X are connected to the third area 1131 .

[0417] In an embodiment where the second wall 112 includes a fifth region and a sixth region, the third region 1131 may connect the first region 1111 and the fifth region, and the fourth region 1132 may connect the second region 1112 and the sixth region.

[0418] The third area 1131 is directly connected to the first area 1111, so that the first area 1111 and the third area 1131 are connected into a whole. The third area 1131 and the first area 1111 promote each other, thereby enhancing the reinforcing effect of the first area 1111 on the first wall 111 and the reinforcing effect of the second area 1112 on the corner wall 113.

[0419] In some embodiments, please continue to refer to Figure 32. Along the circumference of the opening, the corner wall 113 has a first connection end 1133 and a second connection end 1134. The first wall 111 is connected to the first connection end 1133, and the second wall 112 is connected to the second connection end 1134. The thickness of the third area 1131 tends to decrease in the direction from the first connection end 1133 to the second connection end 1134.

[0420] As an example, the thickness of the third zone 1131 gradually decreases in the direction from the first connection end 1133 to the second connection end 1134, the second wall 112 is a structure of equal thickness, the inner surface of the third zone 1131 is connected to the inner surface of the first zone 1111 and the inner surface of the second wall 112, and the outer surface of the third zone 1131 is connected to the outer surface of the first zone 1111 and the outer surface of the second wall 112.

[0421] When the first wall 111 is subjected to the expansion force of the electrode assembly 2 in the second direction Y, deformation of the first wall 111 may cause deformation of the corner wall 113. Along the circumference of the opening, the closer the corner wall 113 is to the first wall 111, the greater the impact of the first wall 111 is on the corner wall 113. The area closer to the first wall 111, the greater the deformation of the corner wall 113. The thickness of the third region 1131 decreases from the first connection end 1133 to the second connection end 1134. This increases the strength of the third region 1131 in the area near the first wall 111 along the circumference of the opening. This reduces the impact of deformation of the first wall 111 on the corner wall 113. While ensuring sufficient strength in the area near the second connection portion 52, the material used in the third region 1131 is reduced, thereby reducing production costs.

[0422] In some embodiments, referring to Figures 36 and 37 , Figure 36 is a partial view of a battery cell 10 (showing the corner wall 113 ) provided in other embodiments of the present application; and Figure 37 is a partial enlarged view of point G in Figure 36 . The third region 1131 is directly connected to the second connection portion 52 .

[0423] The third region 1131 and the second connection portion 52 may be in point contact, line contact, or surface contact to achieve direct connection between the two.

[0424] In this embodiment, the third zone 1131 is directly connected to the second connection portion 52, so that the third zone 1131 is closer to the second connection portion 52 along the first direction Z, so that the third zone 1131 is located near the second connection portion 52, further reducing the risk of fatigue cracking in the area of ​​the corner wall 113 near the second connection portion 52.

[0425] In some embodiments, the corner wall 113 also includes a second transition zone 1135, which is connected to the end of the third zone 1131 along the first direction Z away from the fourth zone 1132, and the second transition zone 1135 is connected to the second connecting portion 52. The connection position between the second transition zone 1135 and the second connecting portion 52 forms a second connection interface 521, and the second connection interface 521 has a second position 5211 that is closest to the third zone 1131 along the first direction Z, and the second position 5211 is located at the end of the third zone 1131 along the first direction Z away from the fourth zone 1132.

[0426] The second transition region 1135 may be the portion of the corner wall 113 where the second connecting portion 52 and the third region 1131 are connected. The second transition region 1135 may have a uniform thickness or a non-uniform thickness. The thickness of the second transition region 1135 may be less than that of the third region 1131. As an example, in the embodiment shown in Figures 36 and 37, the thickness of the second transition region 1135 gradually decreases along the direction from the fourth region 1132 to the third region 1131.

[0427] The second connection interface 521 is formed at the connection position between the second transition area 1135 and the second connection portion 52. The second transition area 1135 and the second connection portion 52 are separated at the second connection interface 521. The second connection interface 521 can be a plane or a curved surface.

[0428] The third region 1131 and the second transition region 1135 are separated by a second boundary surface V. The second boundary surface V is a virtual plane. The second boundary surface V passes through the second position 5211. The second boundary surface V is perpendicular to the first direction Z. The second transition region 1135 and the second connecting portion 52 are located above the second boundary surface V, and the third region 1131 is located below the second boundary surface V.

[0429] In this embodiment, the second transition zone 1135 is connected to the second connection portion 52 to form a second connection interface 521, so that the second transition zone 1135 and the second connection portion 52 have a sufficiently large contact area, thereby improving the firmness of the corner wall 113 and the end cover 12 after welding.

[0430] In some embodiments, at least a portion of the second connection interface 521 extends obliquely relative to the thickness direction of the corner wall 113 .

[0431] The second connection interface 521 may extend obliquely as a whole compared to the thickness direction of the corner wall 113 , or the second connection interface 521 may extend obliquely as a part compared to the thickness direction of the corner wall 113 .

[0432] Near the portion of the second connection interface 521 that extends obliquely in the thickness direction of the corner wall 113, the tensile stress generated by the second connection portion 52 on the second transition zone 1135 due to contraction and the tensile stress generated by the second transition zone 1135 on the second connection portion 52 due to deformation of the corner wall 113 are not on the same straight line, thereby reducing the risk of fatigue cracking in the area of ​​the second transition zone 1135 near the second connection interface 521.

[0433] In some embodiments, please continue to refer to Figure 37, the second connection interface 521 includes a third interface 5212, the third interface 5212 extends obliquely from the second position 5211 toward the direction close to the end cover 12, and along the thickness direction of the corner wall 113, at least part of the second transition zone 1135 is located between the third interface 5212 and the end cover 12.

[0434] It is understandable that the third interface 5212 extends obliquely relative to the thickness direction of the corner wall 113. The third interface 5212 can be a plane or a curved surface.

[0435] The second position 5211 is the lowest position of the third interface 5212 (the position closest to the third zone 1131), and the third interface 5212 extends obliquely from the second position 5211 toward the direction close to the end cover 12, that is, the third interface 5212 extends obliquely upward from the second position 5211 toward the direction close to the end cover 12.

[0436] Along the thickness direction of the corner wall 113 , the second transition zone 1135 may be entirely located between the third interface 5212 and the end cover 12 , or only a portion of the second transition zone 1135 may be located between the third interface 5212 and the end cover 12 .

[0437] In this embodiment, along the thickness direction of the corner wall 113, at least a portion of the second transition zone 1135 is located between the third interface 5212 and the end cover 12, and the second connecting portion 52 protects the second transition zone 1135. When the second transition zone 1135 deforms outward, it will be blocked by the second connecting portion 52, thereby reducing the risk of fatigue cracking in the area of ​​the second transition zone 1135 near the third interface 5212.

[0438] In some embodiments, referring again to FIG. 37 , the third interface 5212 is connected to the outer surface of the third region 1131 at the second position 5211 .

[0439] As an example, the third interface 5212 intersects the outer surface of the third region 1131 at a second straight line extending along the third direction X. The second straight line is located at a second position 5211. The third interface 5212 connects to the inner surface of the second transition region 1135 at a fifth position 5214. Along the first direction Z, the fifth position 5214 is further from the third region 1131 than the second position 5211. The second transition region 1135 is generally triangular in shape.

[0440] In this embodiment, the third interface 5212 is connected to the outer surface of the third zone 1131 at the second position 5211, so that the third zone 1131 and the second connecting portion 52 are in a direct connection state, so that the third zone 1131 and the second connecting portion 52 are closer along the first direction Z, further reducing the risk of fatigue cracking in the area of ​​the corner wall 113 near the second connecting portion 52.

[0441] In some embodiments, referring to Figures 38 and 39 , Figure 38 is a partial view of a battery cell 10 (illustrating the corner wall 113 ) provided in yet other embodiments of the present application; Figure 39 is a partial, enlarged view of point H in Figure 38 . The second connection interface 521 includes a fourth interface 5213 , which extends obliquely from the second position 5211 away from the end cap 12 . Along the thickness direction of the corner wall 113 , at least a portion of the second transition region 1135 is located on the side of the fourth interface 5213 facing away from the end cap 12 .

[0442] It is understood that the fourth interface 5213 extends obliquely relative to the second direction Y. The fourth interface 5213 can be a flat surface or a curved surface. Along the thickness direction of the corner wall 113, at least a portion of the second connecting portion 52 is located between the fourth interface 5213 and the end cover 12.

[0443] The second position 5211 is the lowest position of the fourth interface 5213 (the position closest to the first zone 1111), and the fourth interface 5213 extends obliquely from the second position 5211 in the direction away from the end cover 12, that is, the fourth interface 5213 extends obliquely upward from the second position 5211 in the direction away from the end cover 12.

[0444] Along the thickness direction of the corner wall 113 , the second transition zone 1135 may be entirely located on the side of the fourth interface 5213 away from the end cover 12 , or only partially located on the side of the fourth interface 5213 away from the end cover 12 .

[0445] In this embodiment, along the thickness direction of the corner wall 113, at least a portion of the second transition zone 1135 is located on the side of the fourth interface 5213 away from the end cover 12, so that the second transition zone 1135 has a restrictive effect on the second connecting portion 52, thereby reducing the risk of the second connecting portion 52 falling off.

[0446] In some embodiments, the fourth interface 5213 is connected to the inner surface of the third region 1131 at the second position 5211 .

[0447] As an example, the fourth interface 5213 intersects the inner surface of the third region 1131 at a second straight line extending along the third direction X. The second straight line is located at a second position 5211. The fourth interface 5213 connects to the outer surface of the second transition region 1135 at a sixth position 5215. Along the first direction Z, the sixth position 5215 is further from the third region 1131 than the second position 5211. The second transition region 1135 is generally triangular in shape.

[0448] In this embodiment, the fourth interface 5213 is connected to the inner surface of the third zone 1131 at the second position 5211, so that the third zone 1131 and the second connecting portion 52 are in a direct connection state, so that the third zone 1131 and the second connecting portion 52 are closer along the first direction Z, further reducing the risk of fatigue cracking in the area of ​​the corner wall 113 near the second connecting portion 52.

[0449] In some embodiments, please refer to Figures 40 and 41. Figure 40 is a partial view of a battery cell 10 provided in some further embodiments of the present application (illustrating the corner wall 113); Figure 41 is a partial enlarged view of point I in Figure 40. The second connection interface 521 includes a third interface 5212 and a fourth interface 5213. The third interface 5212 extends obliquely from the second position 5211 toward the end cap 12, and the fourth interface 5213 extends obliquely from the second position 5211 toward the end cap 12. Along the thickness direction of the corner wall 113, a portion of the second transition region 1135 is located between the third interface 5212 and the end cap 12, and another portion of the second transition region 1135 is located on the side of the fourth interface 5213 facing away from the end cap 12.

[0450] As an example, the third interface 5212 is connected to the inner surface of the second transition region 1135 at a fifth position 5214 , and the fourth interface 5213 is connected to the outer surface of the second transition region 1135 at a sixth position 5215 .

[0451] In some embodiments, the Vickers hardness of the second transition region 1135 is less than the Vickers hardness of the fourth region 1132 ; and / or the Vickers hardness of the second transition region 1135 is less than the Vickers hardness of the second connecting portion 52 .

[0452] As an example, the Vickers hardness of the fourth region 1132 is lower than the Vickers hardness of the second connecting portion 52 .

[0453] If the Vickers hardness of the second transition region 1135 is lower than the Vickers hardness of the fourth region 1132, the second transition region 1135 with the lower Vickers hardness is connected to the second connecting portion 52. This can alleviate the rigid pulling between the corner wall 113 and the second connecting portion 52 when it deforms, thereby reducing the risk of separation between the corner wall 113 and the second connecting portion 52. If the Vickers hardness of the second transition region 1135 is lower than the Vickers hardness of the second connecting portion 52, the second transition region 1135 is more easily deformed than the second connecting portion 52. This can alleviate the rigid pulling between the corner wall 113 and the second connecting portion 52 when it deforms, thereby reducing the risk of separation between the corner wall 113 and the second connecting portion 52.

[0454] In some embodiments, referring to FIG. 36 to FIG. 41 , along the first direction Z, the second connection interface 521 is closer to the fourth region 1132 than the outer surface 121 of the end cap.

[0455] In the embodiment shown in FIG. 36 and FIG. 37 , along the first direction Z, the fifth position 5214 and the second position 5211 are both closer to the fourth region 1132 than to the outer surface 121 of the end cap.

[0456] In the embodiment shown in FIG. 38 and FIG. 39 , along the first direction Z, the sixth position 5215 and the second position 5211 are both closer to the second region 1112 than to the outer surface 121 of the end cap.

[0457] In the embodiment shown in FIG. 40 and FIG. 41 , along the first direction Z, the fifth position 5214 , the sixth position 5215 , and the second position 5211 are all closer to the second region 1112 than to the outer surface 121 of the end cap.

[0458] In this embodiment, the second connection interface 521 is closer to the fourth area 1132 along the first direction Z than the outer surface 121 of the end cover, so that the second connection part 52 can sink to a deeper position of the corner wall 113, which can effectively improve the connection strength between the corner wall 113 and the end cover 12.

[0459] In some embodiments, please continue to refer to Figure 31, the shell 11 includes two first walls 111 and two second walls 112, the two first walls 111 are arranged opposite to each other along the second direction Y, and the two second walls 112 are arranged opposite to each other along the third direction X, and the first direction Z, the second direction Y and the third direction X are perpendicular to each other.

[0460] Corner walls 113 are provided at both ends of the first wall 111 along the third direction X, and corner walls 113 are provided at both ends of the second wall 112 along the second direction Y. It is understandable that there are four corner walls 113 in the housing 11 .

[0461] In this embodiment, the housing 11 is substantially in the shape of a rectangular parallelepiped. The size of the housing 11 can be made larger, which is conducive to meeting the large capacity requirement of the battery cell 10.

[0462] In some embodiments, the Vickers hardness of at least a portion of the first region 1111 is less than the Vickers hardness of the second region 1112 .

[0463] The Vickers hardness of the entire first region 1111 may be lower than the Vickers hardness of the second region 1112 , or the Vickers hardness of only a portion of the first region 1111 may be lower than the Vickers hardness of the second region 1112 .

[0464] As an example, the Vickers hardness of a portion of the first zone 1111 is less than the Vickers hardness of the second zone 1112, the Vickers hardness of another portion of the first zone 1111 is equal to the Vickers hardness of the second zone 1112, and the portion of the first zone 1111 having the same Vickers hardness as the second zone 1112 is directly connected to the second zone 1112.

[0465] When the second zone 1112 is deformed by the expansion force of the electrode assembly 2, the area in the first zone 1111 with a smaller Vickers hardness than the second zone 1112 can reduce the impact of the deformation of the second zone 1112 on the area of ​​the first wall 111 located near the first connecting portion 51, thereby reducing the risk of fatigue cracking in the area of ​​the first wall 111 located near the first connecting portion 51 due to the expansion of the electrode assembly 2.

[0466] In some embodiments, please refer to FIG. 42 , which illustrates the positional relationship between the end cap 12 and the side wall before welding in some embodiments of the present application. Along a first direction Z, the first wall 111 has a limiting surface 1115 facing the end cap 12 . The limiting surface 1115 abuts against the end cap 12 to restrict movement of the end cap 12 toward the electrode assembly 2 .

[0467] The limiting surface 1115 can be perpendicular to the first direction Z. The limiting surface 1115 can be the end surface of the first wall 111 at one end of the opening of the shell 11. The limiting surface 1115 can also be a step surface on the first wall 111, and the step surface is a certain distance away from the end surface of the first wall 111 at one end of the opening of the shell 11.

[0468] The limiting surface 1115 limits the end cover 12, reducing the risk of the end cover 12 moving toward the electrode assembly 2 when welded to the shell 11, which can effectively improve the welding quality of the end cover 12 and the shell 11 and reduce the difficulty of welding the end cover 12 and the shell 11.

[0469] In some embodiments, the first wall 111 further includes a limiting area 1116 disposed on the limiting surface 1115 . The limiting area 1116 and the end cover 12 are disposed opposite to each other along the second direction Y. The limiting area 1116 and the end cover 12 are welded to form a first connecting portion 51 .

[0470] As an example, the end cover 12 is at least partially accommodated in the housing 11 , so that the limiting area 1116 and the end cover 12 are arranged opposite to each other along the second direction Y.

[0471] After the limiting area 1116 is welded to the end cover 12, a portion of the limiting area 1116 and a portion of the end cover 12 may be fused together to form a first connecting portion 51, and the remaining portion of the limiting area 1116 may form at least a portion of the first transition area 1117 (not shown in FIG. 42 ).

[0472] The limiting area 1116 can also limit the end cover 12, reducing the risk of the end cover 12 moving along the thickness direction of the first wall 111 when welding the end cover 12 to the shell 11, further improving the welding quality of the end cover 12 and the shell 11, and reducing the difficulty of welding the end cover 12 and the shell 11.

[0473] In some embodiments, the electrode assembly 2 is a laminated structure, and the electrode assembly 2 includes a plurality of positive electrode sheets 22 and a plurality of negative electrode sheets 23 , and the plurality of positive electrode sheets 22 and the plurality of negative electrode sheets 23 are stacked along the second direction Y.

[0474] As an example, the positive electrode sheets 22 and the negative electrode tabs 21 b in the electrode assembly 2 are alternately arranged along the second direction Y, and a separator 24 is provided between the positive electrode sheet 22 and the negative electrode sheet 23 .

[0475] In this embodiment, the electrode assembly 2 is a wound electrode assembly, which has a more compact structure and a stronger anti-extrusion capability.

[0476] In some embodiments, the number of negative electrode sheets 23 is greater than the number of positive electrode sheets 22 , and one positive electrode sheet 22 is disposed between two adjacent negative electrode sheets 23 .

[0477] As an example, there is one more negative electrode tab 23 than positive electrode tab 22 .

[0478] In some embodiments, each negative electrode plate 23 is provided with a negative electrode tab 21 b ; and / or each positive electrode plate 22 is provided with a positive electrode tab 21 a .

[0479] In some embodiments, along the third direction X, the size of the first region 1111 is larger than the size of the positive electrode sheet 22 and / or the size of the negative electrode sheet 23 , and the first direction Z, the second direction Y and the third direction X are perpendicular to each other.

[0480] If along the third direction X, the size of the first region 1111 is larger than the size of the positive electrode sheet 22, the first region 1111 extends beyond at least one end of the positive electrode sheet 22 along the third direction X; if along the third direction X, the size of the first region 1111 is larger than the size of the negative electrode sheet 23, the first region 1111 extends beyond at least one end of the negative electrode sheet 23 along the third direction X.

[0481] In this embodiment, along the third direction X, the size of the first area 1111 is larger than the size of the positive electrode sheet 22 and / or the size of the negative electrode sheet 23, so that the size of the first area 1111 along the third direction X is larger, so that the strength of more areas of the first wall 111 along the third direction X is enhanced, further reducing the risk of fatigue cracking in the area of ​​the first wall 111 near the first connecting portion 51.

[0482] In some embodiments, please refer to FIG43, which is a schematic diagram of the connection between the end cap 12 and the electrode terminal 3 provided in some embodiments of the present application. The battery cell 10 also includes two electrode terminals 3, which are provided on the end cap 12. The two electrode terminals 3 have opposite polarities and are both electrically connected to the electrode assembly 2. The end cap 12 is provided with an extraction hole. The electrode terminal 3 includes a terminal body 31, a first limiting portion 32, and a second limiting portion 33. The terminal body 31 connects the first limiting portion 32 and the second limiting portion 33. The terminal body 31 is provided through the extraction hole. Along the first direction Z, the first limiting portion 32 is located on the side of the end cap 12 away from the electrode assembly 2, and the second limiting portion 33 is located on the side of the end cap 12 facing the electrode assembly 2.

[0483] The first limiting portion 32 and the second limiting portion 33 have a limiting function. The first limiting portion 32 and the second limiting portion 33 are respectively connected to the two ends of the terminal body 31. The first limiting portion 32 and the second limiting portion 33 cooperate to limit the terminal body 31 from being separated from the lead-out hole. Along the first direction Z, the projected area of ​​the first limiting portion 32 and the projected area of ​​the second limiting portion 33 are both larger than the projected area of ​​the terminal body 31. The projected area of ​​the first limiting portion 32 can be larger than the projected area of ​​the second limiting portion 33, or the projected area of ​​the second limiting portion 33 can be larger than the projected area of ​​the first limiting portion 32. The first limiting portion 32, the second limiting portion 33, and the terminal body 31 can be integrally formed, or one of the first limiting portion 32 and the second limiting portion 33 can be integrally formed with the terminal body 31, while the other is separately provided and connected to the terminal body 31.

[0484] As an example, the battery cell 10 may also include a first insulating member 6 and a second insulating member 7, the first insulating member 6 being at least partially disposed between the electrode terminal 3 and the end cover 12 to insulate and isolate the electrode terminal 3 and the end cover 12, and the second insulating member 7 being disposed on the side of the end cover 12 facing the electrode assembly 2 to insulate and isolate the electrode assembly 2 and the end cover 12.

[0485] In this embodiment, the electrode terminal 3 can be installed on the end cover 12 by riveting, which has low installation difficulty and better economy.

[0486] An embodiment of the present application provides a battery 100 , comprising the battery cell 10 provided in any one of the above embodiments.

[0487] An embodiment of the present application provides an electrical device, including a battery cell 10 provided in any one of the above embodiments, and the battery cell 10 is used to provide electrical energy to the electrical device.

[0488] The embodiment of the present application also provides a battery cell 10, which includes a housing 11, an end cap 12, and an electrode assembly 2. The housing 11 has an opening formed at one end along a first direction Z. The end cap 12 is welded to the housing 11 and closes the opening of the housing 11. The electrode assembly 2 is at least partially accommodated within the housing 11. The housing 11 is in the shape of a rectangular parallelepiped and includes two first walls 111, two second walls 112, and four corner walls 113. The first wall 111 is the wall with the largest outer surface area in the housing 11. Adjacent first walls 111 and second walls 112 are connected by a corner wall 113. The two first walls 111 are arranged opposite each other along a second direction Y, and the two second walls 112 are arranged opposite each other along a third direction X. The first direction Z, the second direction Y, and the third direction X are perpendicular to each other. The electrode assembly 2 includes a positive electrode sheet 22, a negative electrode sheet 23, and a separator 24. The separator 24 is disposed between the positive electrode sheet 22 and the negative electrode sheet 23. The electrode assembly 2 has a flat region 25. The portion of the positive electrode sheet 22 located in the flat region 25, the portion of the negative electrode sheet 23 located in the flat region 25, and the portion of the separator 24 located in the flat region 25 are stacked along the second direction Y. The electrode assembly 2 includes a first surface 27 perpendicular to the second direction Y. The first surface 27 is the largest surface of the outer surface of the electrode assembly 2. The first wall 111 is disposed opposite the first surface 27 along the second direction Y.

[0489] The first wall 111 is welded to the end cap 12 to form the first connecting portion 51. The first wall 111 includes a first region 1111 and a second region 1112 arranged along the first direction Z. The thickness of the first region 1111 is greater than that of the second region 1112. The first region 1111 is located between the first connecting portion 51 and the second region 1112. The housing 11 is made of aluminum alloy. The maximum thickness of the second region 1112 is D1, and the maximum thickness of the first region 1111 is D2. The dimension D of the housing 11 along the second direction Y is 0.005≤D1 / D≤0.065, 0.4mm≤D1≤0.8mm, and 0.5mm≤D2≤1.5mm. Corner wall 113 is welded to end cap 12 to form second connecting portion 52. Corner wall 113 includes a third region 1131 and a fourth region 1132 arranged along the first direction Z. The thickness of third region 1131 is greater than that of fourth region 1132 and is located between fourth region 1132 and second connecting portion 52. The dimension of first region 1111 along third direction X is greater than that of second region 1112 along first direction Z. Both ends of first region 1111 along third direction X are directly connected to third regions 1131 of two corner walls 113, respectively. Along the circumference of the opening, corner wall 113 has a first connecting end 1133 and a second connecting end 1134. The first wall 111 is connected to first connecting end 1133, and the second wall 112 is connected to second connecting end 1134. The thickness of third region 1131 decreases from first connecting end 1133 toward second connecting end 1134. The first zone 1111 includes a first part 11111 and a second part 11112 arranged along the first direction Z, the second part 11112 connects the first part 11111 and the second zone 1112, the thickness of the first part 11111 is greater than the thickness of the second part 11112, and the thickness of the second part 11112 tends to decrease along the direction of the end cover 12 pointing to the electrode assembly 2.

[0490] The positive electrode tab 22 includes a positive electrode main region 221 and a positive electrode tab 21a protruding from the positive electrode main region 221. The negative electrode tab 23 includes a negative electrode main region 231 and a negative electrode tab 21b protruding from the negative electrode main region 231. Along the first direction Z, the positive electrode main region 221 has a fifth end 2211 facing the end cap 12, and the negative electrode main region 231 has a sixth end 2311 facing the end cap 12. The separator 24 has a seventh end 241 facing the end cap 12, and the seventh end 241 is closer to the end cap 12 than the fifth end 2211 and the sixth end 2311. 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. In a projection plane perpendicular to the second direction Y, the protruding region 242 partially overlaps with the orthographic projection of the first region 1111. The first region 1111 includes a first protrusion 11118 protruding from the first inner surface 11121; in the projection plane perpendicular to the second direction Y, the positive electrode main region 221 and the orthographic projection of the first protrusion 11118 do not overlap; in the projection plane perpendicular to the second direction Y, the negative electrode main region 231 and the orthographic projection of the first protrusion 11118 do not overlap.

[0491] The first wall 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 the first direction Z. The first transition region 1117 is connected to the first connecting portion 51. The connection between the first transition region 1117 and the first connecting portion 51 forms a first connecting interface 511. The first connecting interface 511 has a first position 5111 closest to the first region 1111 along the first direction Z. The first position 5111 is located at the end of the first region 1111 away from the second region 1112 along the first direction Z. The first connecting interface 511 includes a second interface 5113, which extends obliquely from the first position 5111 in a direction away from the end cap 12. Along the second direction Y, a portion of the first connecting portion 51 is located between the second interface 5113 and the end cap 12. The second interface 5113 is connected to the inner surface of the first region 1111 at the first position 5111.

[0492] The corner wall 113 also includes a second transition region 1135, which is connected to the end of the third region 1131 that is distal to the fourth region 1132 along the first direction Z. The second transition region 1135 is connected to the second connecting portion 52. The connection between the second transition region 1135 and the second connecting portion 52 forms a second connecting interface 521. The second connecting interface 521 has a second position 5211 that is closest to the third region 1131 along the first direction Z. The second position 5211 is located at the end of the third region 1131 that is distal to the fourth region 1132 along the first direction Z. The second connecting interface 521 includes a fourth interface 5213, which extends obliquely from the second position 5211 in a direction away from the end cap 12. Along the thickness direction of the corner wall 113, a portion of the second connecting portion 52 is located between the fourth interface 5213 and the end cap 12. The fourth interface 5213 is connected to the inner surface of the third region 1131 at the second position 5211.

[0493] The embodiment of the present application also provides a battery cell 10, which includes a housing 11, an end cap 12, and an electrode assembly 2. The housing 11 has an opening formed at one end along a first direction Z. The end cap 12 is welded to the housing 11 and closes the opening of the housing 11. The electrode assembly 2 is at least partially accommodated within the housing 11. The housing 11 is in the shape of a rectangular parallelepiped and includes two first walls 111, two second walls 112, and four corner walls 113. The first wall 111 is the wall with the largest outer surface area in the housing 11. Adjacent first walls 111 and second walls 112 are connected by a corner wall 113. The two first walls 111 are arranged opposite each other along a second direction Y, and the two second walls 112 are arranged opposite each other along a third direction X. The first direction Z, the second direction Y, and the third direction X are perpendicular to each other. The electrode assembly 2 includes a positive electrode sheet 22, a negative electrode sheet 23, and a separator 24. The separator 24 is disposed between the positive electrode sheet 22 and the negative electrode sheet 23. The electrode assembly 2 has a flat region 25. The portion of the positive electrode sheet 22 located in the flat region 25, the portion of the negative electrode sheet 23 located in the flat region 25, and the portion of the separator 24 located in the flat region 25 are stacked along the second direction Y. The electrode assembly 2 includes a first surface 27 perpendicular to the second direction Y. The first surface 27 is the largest surface of the outer surface of the electrode assembly 2. The first wall 111 is disposed opposite the first surface 27 along the second direction Y.

[0494] The first wall 111 is welded to the end cap 12 to form the first connecting portion 51. The first wall 111 includes a first region 1111 and a second region 1112 arranged along the first direction Z. The thickness of the first region 1111 is greater than that of the second region 1112. The first region 1111 is located between the first connecting portion 51 and the second region 1112. The housing 11 is made of aluminum alloy. The maximum thickness of the second region 1112 is D1, and the maximum thickness of the first region 1111 is D2. The dimension D of the housing 11 along the second direction Y is 0.005≤D1 / D≤0.065, 0.4mm≤D1≤0.8mm, and 0.5mm≤D2≤1.5mm.

[0495] The dimension of the first region 1111 along the third direction X is greater than the dimension of the first region 1111 along the first direction Z. The first region 1111 includes a first portion 11111 and a second portion 11112 arranged along the first direction Z. The second portion 11112 connects the first portion 11111 and the second region 1112. The thickness of the first portion 11111 is greater than the thickness of the second portion 11112. The thickness of the second portion 11112 decreases in a direction from the end cap 12 to the electrode assembly 2.

[0496] Both ends of the first region 1111 along the third direction X do not contact the corner wall 113. The first region 1111 includes a second connecting segment 11114, a first connecting segment 11113, and a third connecting segment 11115 arranged along the third direction X. The first connecting segment 11113 passes through a mid-section, and the thickness of the first connecting segment 11113 is greater than that of both the second connecting segment 11114 and the third connecting segment 11115. The first connecting segment 11113 connects the second connecting segment 11114 and the third connecting segment 11115. The dimension of the first connecting segment 11113 along the third direction X is L1. The dimension of the first wall 1111 along the third direction X is L, and 0.2≤L1 / L≤0.6. The first connecting section 11113 has a first end 11113a and a second end 11113b opposite to each other along the third direction X. The first wall 111 has a third end 1113 and a fourth end 1114 opposite to each other along the third direction X. The first end 11113a is close to the third end 1113, and the second end 11113b is close to the fourth end 1114. The dimension of the first wall 1111 along the third direction X is L. The minimum distance between the first end 11113a and the third end 1113 along the third direction X is L2. The minimum distance between the second end 11113b and the fourth end 1114 along the third direction X is L3. L2 / L≤0.3, L3 / L≤0.3, 100mm≤L≤450mm.

[0497] The positive electrode tab 22 includes a positive electrode main region 221 and a positive electrode tab 21a protruding from the positive electrode main region 221. The negative electrode tab 23 includes a negative electrode main region 231 and a negative electrode tab 21b protruding from the negative electrode main region 231. Along the first direction Z, the positive electrode main region 221 has a fifth end 2211 facing the end cap 12, and the negative electrode main region 231 has a sixth end 2311 facing the end cap 12. The separator 24 has a seventh end 241 facing the end cap 12, and the seventh end 241 is closer to the end cap 12 than the fifth end 2211 and the sixth end 2311. 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. In a projection plane perpendicular to the second direction Y, the protruding region 242 partially overlaps with the orthographic projection of the first region 1111. The first region 1111 includes a first protrusion 11118 protruding from the first inner surface 11121; in the projection plane perpendicular to the second direction Y, the positive electrode main region 221 and the orthographic projection of the first protrusion 11118 do not overlap; in the projection plane perpendicular to the second direction Y, the negative electrode main region 231 and the orthographic projection of the first protrusion 11118 do not overlap.

[0498] The first wall 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 the first direction Z. The first transition region 1117 is connected to the first connecting portion 51. The connection between the first transition region 1117 and the first connecting portion 51 forms a first connecting interface 511. The first connecting interface 511 has a first position 5111 closest to the first region 1111 along the first direction Z. The first position 5111 is located at the end of the first region 1111 away from the second region 1112 along the first direction Z. The first connecting interface 511 includes a second interface 5113, which extends obliquely from the first position 5111 in a direction away from the end cap 12. Along the second direction Y, a portion of the first connecting portion 51 is located between the second interface 5113 and the end cap 12. The second interface 5113 is connected to the inner surface of the first region 1111 at the first position 5111.

[0499] It should be noted that, unless there is any conflict, the embodiments and features in the embodiments of this application can be combined with each other.

[0500] The above embodiments are intended only to illustrate the technical solutions of this application and are not intended to limit this application. Those skilled in the art will appreciate that various modifications and variations are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of this application are intended to be within the scope of protection of this application.

Claims

1. A battery cell, comprising: A housing having an opening at at least one end along a first direction, the housing comprising a first wall; An end cover, closing the opening, wherein the first wall and the end cover are welded to form a first connecting portion; an electrode assembly, at least partially contained in the housing, the electrode assembly comprising a positive electrode sheet and a negative electrode sheet, at least a portion of the positive electrode sheet and at least a portion of the negative electrode sheet being stacked along a second direction, the second direction being parallel to a thickness direction of the first wall, and the first direction intersecting the second direction; The first wall includes a first area and a second area arranged along the first direction, the thickness of the first area is greater than the thickness of the second area, and the first area is located between the first connecting portion and the second area.

2. The battery cell according to claim 1, wherein: The electrode assembly has a straight area, and a portion of the positive electrode sheet located in the straight area and a portion of the negative electrode sheet located in the straight area are stacked along the second direction.

3. The battery cell according to claim 2, wherein: The electrode assembly includes a first surface and a second surface adjacent to each other, the first surface is perpendicular to the second direction, an area of ​​the first surface is larger than an area of ​​the second surface, and the first surface is arranged opposite to the first wall along the second direction.

4. The battery cell according to claim 3, wherein: The first surface is a surface with the largest area among the outer surfaces of the electrode assembly.

5. The battery cell according to claim 3 or 4, wherein: The electrode assembly is a winding structure, and the electrode assembly further has a corner area, and the corner area is provided at least at one end of the straight area along the third direction, and the first direction, the second direction and the third direction are not coplanar and intersect each other; The outer surface of the straight area includes the first surface, and the outer surface of the corner area includes the second surface, and at least a part of the second surface is an arc surface.

6. The battery cell according to claim 3 or 4, wherein: The electrode assembly is a laminated structure, the straight area includes a plurality of positive electrode sheets and a plurality of negative electrode sheets, the plurality of positive electrode sheets and the plurality of negative electrode sheets are stacked along the second direction, and the first surface is perpendicular to the second surface.

7. The battery cell according to any one of claims 1 to 6, wherein: The first wall is a wall with the largest outer surface area in the shell.

8. The battery cell according to any one of claims 1 to 7, wherein: The shell includes two first walls, which are arranged opposite to each other along the second direction, and the electrode assembly is located between the two first walls.

9. The battery cell according to any one of claims 1 to 8, wherein: The first region includes a first portion and a second portion arranged along the first direction, the second portion connects the first portion and the second region, and a thickness of the first portion is greater than a thickness of the second portion.

10. The battery cell according to claim 9, wherein: The thickness of the second portion decreases along a direction from the end cover to the electrode assembly.

11. The battery cell according to any one of claims 1 to 10, wherein: A size of the first region along the third direction is greater than a size of the first region along the first direction, and the first direction, the second direction, and the third direction are not coplanar and intersect each other.

12. The battery cell according to claim 11, wherein: The first area includes a first connecting segment, the first connecting segment passes through a middle section of the first wall, the middle section is perpendicular to the third direction, and the distances from the middle section to both ends of the first wall along the third direction are equal.

13. The battery cell according to claim 12, wherein: The first zone also includes a second connecting segment and a third connecting segment, the second connecting segment, the first connecting segment and the third connecting segment are arranged along the third direction, the first connecting segment connects the second connecting segment and the third connecting segment, and the thickness of the first connecting segment is greater than the thickness of the second connecting segment and the thickness of the third connecting segment.

14. The battery cell according to claim 13, wherein: The first zone also includes a first transition section, the first connecting section, the first transition section and the second connecting section are arranged along the third direction, the first transition section connects the second connecting section and the first connecting section, and the thickness of the first transition section increases along the direction from the second connecting section to the first connecting section; and / or, the first zone also includes a second transition section, the first connecting section, the second transition section and the third connecting section are arranged along the third direction, the second transition section connects the third connecting section and the first connecting section, and the thickness of the second transition section increases along the direction from the third connecting section to the first connecting section.

15. The battery cell according to any one of claims 12 to 14, wherein: A dimension of the first connecting section along the third direction is L1, a dimension of the first wall along the third direction is L, and 0.2≤L1 / L≤0.

6.

16. The battery cell according to any one of claims 12 to 15, wherein: The first connecting section has a first end and a second end relative to each other along the third direction, the first wall has a third end and a fourth end relative to each other along the third direction, the first end is close to the third end, the second end is close to the fourth end, the dimension of the first wall along the third direction is L, the minimum distance between the first end and the third end along the third direction is L2, and the minimum distance between the second end and the fourth end along the third direction is L3; L2 / L≤0.3; and / or, L3 / L≤0.

3.

17. The battery cell according to claim 15 or 16, wherein: 100mm≤L≤450mm.

18. The battery cell according to any one of claims 11 to 17, wherein: The shell comprises a corner wall, and both ends of the first wall along the third direction are connected to the corner wall; At least one end of the first area along the third direction is not in contact with the corner wall; or, both ends of the first area along the third direction extend to the two corner walls respectively.

19. The battery cell according to any one of claims 1 to 18, wherein: The electrode assembly further includes a separator, which is disposed between the positive electrode sheet and the negative electrode sheet; The positive electrode sheet includes a positive electrode main area and a positive electrode tab protruding from the positive electrode main area, wherein the positive electrode main area has a positive electrode active material layer, and the negative electrode sheet includes a negative electrode main area and a negative electrode tab protruding from the negative electrode main area, wherein the negative electrode main area has a negative electrode active material layer. In one direction, the positive electrode main region has a fifth end facing the end cap, the negative electrode main region has a sixth end facing the end cap, and the separator has a seventh end facing the end cap, and the seventh end is closer to the end cap than the fifth end and the sixth end.

20. The battery cell according to claim 19, wherein: The isolation member includes a protruding area that protrudes beyond the fifth end and the sixth end along the first direction, and in a projection plane perpendicular to the second direction, an orthographic projection of the protruding area partially overlaps with an orthographic projection of the first area.

21. The battery cell according to claim 19 or 20, wherein: The second region has a first inner surface facing the inner space of the housing, and the first region includes a first protrusion protruding from the first inner surface; In a projection plane perpendicular to the second direction, the orthographic projection of the positive electrode main area does not overlap with the orthographic projection of the first protrusion; and / or, in a projection plane perpendicular to the second direction, the orthographic projection of the negative electrode main area does not overlap with the orthographic projection of the first protrusion.

22. The battery cell according to any one of claims 1 to 21, wherein: The negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer disposed on at least one side of the negative electrode current collector, and the negative electrode active material layer includes a negative electrode active material.

23. The battery cell according to claim 22, 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 provided at one end of the negative electrode main body close to the end cover along the first direction.

24. The battery cell according to claim 23, wherein: In a projection plane perpendicular to the second direction, an orthographic projection of the negative electrode thinned portion and an orthographic projection of the first region are spaced apart along the first direction.

25. The battery cell according to claim 24, wherein: In a projection plane perpendicular to the second direction, a spacing dimension between an orthographic projection of the negative electrode thinned portion and an orthographic projection of the first region along the first direction is greater than or equal to 1 mm.

26. The battery cell according to any one of claims 22 to 25, wherein: The single-sided coating weight of the negative electrode active material layer is 90 mg / 1540 mm 2 ~170mg / 1540mm 2 , optional 110mg / 1540mm 2 ~150mg / 1540mm 2 .

27. The battery cell according to any one of claims 22 to 26, wherein: The porosity of the negative electrode plate is 27% to 40%.

28. The battery cell according to any one of claims 22 to 27, wherein: The negative electrode active material comprises a silicon-based material, and the mass content of silicon in the silicon-based material is 0.3% to 10%, and can be optionally 1% to 6%.

29. The battery cell according to claim 28, wherein: The silicon-based material includes at least one of a silicon-oxygen compound and a silicon-carbon composite.

30. The battery cell according to any one of claims 1 to 29, wherein: The positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer disposed on at least one side of the positive electrode current collector, wherein the positive electrode active material layer includes a positive electrode active material.

31. The battery cell according to claim 30, 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 provided at one end of the positive electrode main body close to the end cover along the first direction.

32. The battery cell according to claim 31, wherein: In a projection plane perpendicular to the second direction, an orthographic projection of the positive electrode thinned portion and an orthographic projection of the first region are spaced apart along the first direction.

33. The battery cell according to claim 32, wherein: In a projection plane perpendicular to the second direction, a spacing dimension between an orthographic projection of the positive electrode thinned portion and an orthographic projection of the first region along the first direction is greater than or equal to 1 mm.

34. The battery cell according to any one of claims 30 to 33, wherein: The single-sided coating weight of the positive electrode active material layer is 200 mg / 1540 mm 2 ~370mg / 1540 / mm 2 ; Optional: 240mg / 1540mm 2 ~330mg / 1540mm 2 .

35. The battery cell according to any one of claims 30 to 34, wherein: The positive electrode active material is a lithium-containing phosphate.

36. The battery cell according to any one of claims 1 to 35, wherein: The material of the shell includes steel; The maximum thickness of the second zone is D1, the dimension of the shell along the second direction is D, and 0.001≤D1 / D≤0.

012.

37. The battery cell according to any one of claims 1 to 36, wherein: The material of the shell includes steel; The maximum thickness of the second region is D1, 0.08 mm ≤ D1 ≤ 0.35 mm; and / or the maximum thickness of the first region is D2, 0.1 mm ≤ D2 ≤ 0.6 mm.

38. The battery cell according to any one of claims 1 to 35, wherein: The material of the shell includes aluminum alloy; The maximum thickness of the second zone is D1, the dimension of the shell along the second direction is D, and 0.005≤D1 / D≤0.

065.

39. The battery cell according to any one of claims 1 to 35 and 38, wherein: The material of the shell includes aluminum alloy; The maximum thickness of the second region is D1, 0.4 mm ≤ D1 ≤ 0.8 mm; and / or the maximum thickness of the first region is D2, 0.5 mm ≤ D2 ≤ 1.5 mm.

40. The battery cell according to claim 38 or 39, wherein: The aluminum alloy includes the following components in percentage by mass: 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%.

41. The battery cell according to any one of claims 1 to 40, wherein: The first region is directly connected to the first connecting portion.

42. The battery cell according to any one of claims 1 to 41, wherein: The first wall also includes a first transition zone, which is connected to one end of the first zone away from the second zone along the first direction, and the first transition zone is connected to the first connecting portion. The connecting position of the first transition zone and the first connecting portion forms a first connecting interface, and the first connecting interface has a first position closest to the first zone along the first direction, and the first position is located at one end of the first zone away from the second zone along the first direction.

43. The battery cell according to claim 42, wherein: At least a portion of the first connection interface extends obliquely relative to the second direction.

44. The battery cell according to claim 43, wherein: The first connection interface includes a first interface, the first interface extends obliquely from the first position toward the end cover, and along the second direction, at least a portion of the first transition zone is located between the first interface and the end cover.

45. The battery cell according to claim 44, wherein: The first interface is connected to the outer surface of the first region at the first location.

46. ​​The battery cell according to any one of claims 43 to 45, wherein: The first connection interface includes a second interface, the second interface extends obliquely from the first position in a direction away from the end cover, and along the second direction, at least a portion of the first transition zone is located on a side of the second interface away from the end cover.

47. The battery cell according to claim 46, wherein: The second interface is connected to the inner surface of the first region at the first position.

48. The battery cell according to any one of claims 42 to 47, wherein: The Vickers hardness of the first transition zone is smaller than the Vickers hardness of the second zone; and / or the Vickers hardness of the first transition zone is smaller than the Vickers hardness of the first connecting portion.

49. The battery cell according to any one of claims 42 to 48, wherein: Along the first direction, the first connection interface is closer to the second region than to the outer surface of the end cover.

50. The battery cell according to any one of claims 1 to 49, wherein: The housing further includes a second wall and a corner wall. The first wall, the corner wall and the second wall are arranged along the circumference of the opening. The corner wall connects the first wall and the second wall.

51. The battery cell according to claim 50, wherein: The corner wall and the end cover are welded to form a second connection portion; The corner wall includes a third area and a fourth area arranged along the first direction, the thickness of the third area is greater than the thickness of the fourth area, and the third area is located between the fourth area and the second connecting portion.

52. The battery cell according to claim 51, wherein: The third region is directly connected to the first region.

53. The battery cell according to claim 52, wherein: Along the circumference of the opening, the corner wall has a first connecting end and a second connecting end, the first wall is connected to the first connecting end, the second wall is connected to the second connecting end, and the thickness of the third zone tends to decrease in the direction from the first connecting end to the second connecting end.

54. The battery cell according to any one of claims 51 to 53, wherein: The third region is directly connected to the second connecting portion.

55. The battery cell according to any one of claims 51 to 54, wherein: The corner wall also includes a second transition zone, which is connected to an end of the third zone along the first direction away from the fourth zone, and the second transition zone is connected to the second connecting portion. The connecting position of the second transition zone and the second connecting portion forms a second connecting interface, and the second connecting interface has a second position closest to the third zone along the first direction, and the second position is located at an end of the third zone along the first direction away from the fourth zone.

56. The battery cell according to claim 55, wherein: At least a portion of the second connection interface extends obliquely relative to a thickness direction of the corner wall.

57. The battery cell according to claim 56, wherein: The second connection interface includes a third interface, and the third interface extends obliquely from the second position toward the end cover. Along the thickness direction of the corner wall, at least a part of the second transition zone is located between the third interface and the end cover.

58. The battery cell according to claim 57, wherein: The third interface is connected to the outer surface of the third region at the second position.

59. The battery cell according to any one of claims 56 to 58, wherein: The second connection interface includes a fourth interface, which extends obliquely from the second position away from the end cover, and along the thickness direction of the corner wall, at least part of the second transition zone is located on a side of the fourth interface away from the end cover.

60. The battery cell according to claim 59, wherein: The fourth interface is connected to the inner surface of the third region at the second position.

61. The battery cell according to any one of claims 55 to 60, wherein: The Vickers hardness of the second transition zone is smaller than the Vickers hardness of the fourth zone; and / or the Vickers hardness of the second transition zone is smaller than the Vickers hardness of the second connecting portion.

62. The battery cell according to any one of claims 55 to 61, wherein: Along the first direction, the second connection interface is closer to the fourth region than to the outer surface of the end cover.

63. The battery cell according to any one of claims 50 to 62, wherein: The shell includes two first walls and two second walls, the two first walls are arranged opposite to each other along the second direction, the two second walls are arranged opposite to each other along the third direction, and the first direction, the second direction and the third direction are perpendicular to each other.

64. The battery cell according to any one of claims 1 to 63, wherein: The Vickers hardness of at least a portion of the first region is less than the Vickers hardness of the second region.

65. The battery cell according to any one of claims 1 to 64, wherein: Along the first direction, the first wall has a limiting surface facing the end cover, and the limiting surface abuts against the end cover to limit the end cover from moving in a direction close to the electrode assembly.

66. The battery cell of claim 65, wherein: The first wall further includes a limiting area arranged on the limiting surface, the limiting area and the end cover are arranged opposite to each other along the second direction, and the limiting area and the end cover are welded to form the first connecting portion.

67. The battery cell according to any one of claims 1 to 66, wherein: The electrode assembly is a laminated structure, and includes a plurality of positive electrode sheets and a plurality of negative electrode sheets, and the plurality of positive electrode sheets and the plurality of negative electrode sheets are stacked along the second direction.

68. The battery cell according to claim 67, wherein: The number of the negative electrode sheets is greater than the number of the positive electrode sheets, and one positive electrode sheet is arranged between two adjacent negative electrode sheets.

69. The battery cell according to claim 67 or 68, wherein: Each of the negative electrode plates is provided with a negative electrode tab; and / or each of the positive electrode plates is provided with a positive electrode tab.

70. The battery cell according to any one of claims 67 to 69, wherein: Along the third direction, the size of the first region is larger than the size of the positive electrode sheet and / or the size of the negative electrode sheet, and the first direction, the second direction and the third direction are perpendicular to each other.

71. The battery cell according to any one of claims 1 to 70, wherein: The battery cell further includes two electrode terminals, which are disposed on the end cap, have opposite polarities, and are both electrically connected to the electrode assembly; The end cover is provided with a lead-out hole, and the electrode terminal includes a terminal body, a first limiting portion and a second limiting portion, the terminal body connects the first limiting portion and the second limiting portion, and the terminal body is passed through the lead-out hole. Along the first direction, the first limiting portion is located on the side of the end cover away from the electrode assembly, and the second limiting portion is located on the side of the end cover facing the electrode assembly.

72. A battery comprising the battery cell according to any one of claims 1 to 71.

73. An electrical device, comprising a battery cell as described in any one of claims 1 to 71, wherein the battery cell is used to provide electrical energy to the electrical device.

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