Battery monomer, battery and electric equipment

Abstract

The utility model discloses a battery monomer, a battery and electric equipment. The battery monomer comprises a shell, an end cover and an electrode assembly, at least one end of the shell in the first direction is provided with an opening, and the shell 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 shell; the first wall comprises a main body part, the main body part is located on the side, away from the end cover, of the first connecting part in the first direction, the main body part is provided with a buffering structure, and the buffering structure and the first connecting part are arranged at intervals. The buffer structure can absorb expansive force generated in the use process of the electrode assembly, so that the expansive force directly acting on the first connecting part is reduced. Therefore, the buffer structure can reduce the risk of fatigue cracking of the area, near the first connecting part, of the first wall due to the expansion of the electrode assembly, so that the service life of the battery monomer is prolonged.

Description

Technical Field

[0001] 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

[0002] 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.

[0003] 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. Utility Model Content

[0004] In view of the above problems, the present application provides a battery cell, a battery and an electrical device, which can effectively increase the service life of the battery cell.

[0005] In a first aspect, an embodiment of the present application provides a battery cell, comprising a housing, an end cap, and an electrode assembly; the housing has an opening at least at one end along a first direction, the housing comprising a first wall; the end cap closes the opening, and the first wall and the end cap are welded to form a first connection portion; the electrode assembly is at least partially housed within the housing, the electrode assembly comprising a positive electrode sheet and a negative electrode sheet, at least a portion of the positive electrode sheet and at least a portion of the negative electrode sheet being stacked along a second direction, the second direction being parallel to a thickness direction of the first wall, and the first direction intersecting the second direction;

[0006] The first wall includes a main body portion, which is located on a side of the first connecting portion away from the end cover along the first direction. The main body portion is provided with a buffer structure, which is spaced apart from the first connecting portion.

[0007] In the above technical solution, the buffer structure can absorb the expansion force generated during use of the electrode assembly, thereby reducing the expansion force directly acting on the first connecting portion. Therefore, the buffer structure can reduce the risk of fatigue cracking in the area of the first wall near the first connecting portion due to expansion of the electrode assembly, thereby extending the service life of the battery cell.

[0008] In some embodiments, the buffer structure includes a weakened portion disposed on the main body portion, and a minimum thickness of the weakened portion is smaller than a thickness of other portions of the main body portion.

[0009] As such, the weakened portion can more effectively absorb expansion forces than other portions of the main body, thereby reducing the expansion forces acting directly on the first connecting portion. Consequently, the weakened portion reduces the risk of fatigue cracking in the area of the first wall near the first connecting portion due to expansion of the electrode assembly, thereby increasing the service life of the battery cell.

[0010] In some embodiments, a groove is provided on the inner surface of the main body, and / or a groove is provided on the outer surface of the main body; the weak portion is an area on the main body opposite to the notch of the groove.

[0011] In this way, the weak portion, as the area opposite to the groove notch, has better buffering performance and makes it easier to form the weak portion, thereby reducing the manufacturing difficulty of the shell and further reducing the manufacturing cost of the shell.

[0012] In some embodiments, the groove includes a first side surface, a second side surface, and a bottom surface connected to the first side surface and the second side surface, and the weak portion includes a first weak portion arranged opposite to the bottom surface, and the thickness of the first weak portion is less than the thickness of other parts of the main body.

[0013] As a result, the expansion force acting on the first weak portion is greater than that on other parts of the main body, and the first weak portion can more effectively absorb the expansion force, thereby reducing the expansion force directly acting on the first connecting portion. Therefore, the first weak portion can reduce the risk of fatigue cracking in the area of the first wall near the first connecting portion due to expansion of the electrode assembly, thereby increasing the service life of the battery cell.

[0014] In some embodiments, the weak portion also includes a second weak portion arranged opposite to the first side surface and a third weak portion arranged opposite to the second side surface, the first side surface is located on the side of the bottom surface close to the first connecting portion, and the thickness of the second weak portion tends to increase in the direction close to the first connecting portion, the second side surface is located on the side of the bottom surface away from the first connecting portion, and the thickness of the third weak portion tends to increase in the direction away from the first connecting portion.

[0015] In this way, the non-uniform thickness design of the second weak portion and the third weak portion gives the weak portion a gradient strength, which helps to more effectively withstand and disperse the expansion force from different directions, helps to guide the expansion force along a specific path, and reduces the direct impact on the first weak portion, so that the weak portion can absorb the expansion force while being less likely to fail functionally; in addition, the weak portion with a gradual thickness change can also make the weak portion easier to manufacture.

[0016] In some embodiments, the angle between the first side surface and the bottom surface is greater than or equal to 135 degrees and less than 180 degrees; and / or the angle between the second side surface and the bottom surface is greater than or equal to 135 degrees and less than 180 degrees.

[0017] Thus, within these angle ranges, the weak portion has a higher ability to absorb expansion force, thereby effectively 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 increasing the service life of the battery cell.

[0018] In addition, the groove can generally be manufactured by a stamping process. When stamping, a mold is required for processing. The mold usually includes an upper die and a lower die. The upper die is used for stamping, and the lower die is used to support the housing. During the stamping process, the housing is fixed to the lower die through a fixture or a fixing structure of the mold, and then the upper die moves towards the housing and applies pressure, causing the area of the housing corresponding to the upper die to deform to form the groove.

[0019] When the angle is greater than or equal to 135 degrees and less than 180 degrees, the groove will not engage with the upper die during the demolding process, making it easier for the upper die to separate from the groove after processing the groove. Therefore, controlling the angle between 135 degrees and 180 degrees can facilitate the formation of the groove, reduce the manufacturing difficulty of the housing, and thus improve the processing accuracy of the housing and the service life of the mold.

[0020] In some embodiments, the buffer structure includes a first convex portion and a first concave portion. The first convex portion and the first concave portion are correspondingly arranged. The first convex portion protrudes from the outer surface of the main body portion, and the first concave portion recesses outward from the inner surface of the main body portion.

[0021] In this way, the first convex portion and the first concave portion can form a local buffer area, increasing the buffer path of the buffer structure to disperse the expansion force, thereby reducing the expansion force directly acting on the first connection portion. Therefore, the cooperation of the first convex portion and the first concave portion can reduce the risk of fatigue cracking in the area of the first wall near the first connection portion due to the expansion of the electrode assembly, and further improve the service life of the battery cell.

[0022] In some embodiments, the number of the first convex portions is multiple, and the number of the first concave portions is multiple. Each first convex portion is correspondingly provided with a first concave portion.

[0023] In this way, the multiple first convex portions and the corresponding first concave portions can further increase the buffer path of the buffer structure, providing multiple areas for dispersing the expansion force, so as to achieve more effective absorption of the expansion force, and further effectively reduce the expansion force directly acting on the first connection portion.

[0024] In some embodiments, the buffer structure includes a second convex portion and a second concave portion. The second convex portion and the second concave portion are correspondingly arranged. The second convex portion protrudes from the inner surface of the main body portion, and the second concave portion recesses inward from the outer surface of the main body portion.

[0025] In this way, the second convex portion and the second concave portion can form a local buffer area, increasing the buffer path of the buffer structure to disperse the expansion force, thereby reducing the expansion force directly acting on the first connection portion. Therefore, the cooperation of the second convex portion and the second concave portion can reduce the risk of fatigue cracking in the area of the first wall near the first connection portion due to the expansion of the electrode assembly, and further improve the service life of the battery cell.

[0026] In some embodiments, the number of the second convex portions is plural, the number of the second concave portions is plural, and each second convex portion is correspondingly provided with one second concave portion.

[0027] In this way, the plural second convex portions and the corresponding second concave portions can further increase the buffering paths of the buffering structure, provide plural regions for dispersing the expansion force, so as to more effectively absorb the expansion force, and further effectively reduce the expansion force directly acting on the first connecting portion.

[0028] In some embodiments, along the first direction, the distance between the buffering structure and the edge of the first connecting portion is H, and H satisfies: 0.3 mm ≤ H ≤ 7 mm. Optionally, 1.5 mm ≤ H ≤ 4 mm.

[0029] In this way, within these numerical ranges, the buffering structure can effectively absorb the expansion force, thereby reducing the expansion force directly acting on the first connecting portion. The buffering structure will not crack due to fatigue together with the first connecting portion because it is too close to the first connecting portion, nor will it be unable to reduce the expansion force directly acting on the first connecting portion because it is too far from the first connecting portion.

[0030] In some embodiments, the electrode assembly further includes a separator, and the separator is disposed between the positive electrode plate and the negative electrode plate;

[0031] The positive electrode plate 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 has a positive electrode active material layer. The negative electrode plate 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 has a negative electrode active material layer. Along the first direction, the positive electrode main body region has a first end facing the end cover, the negative electrode main body region has a second end facing the end cover, and the separator has a third end facing the end cover. The third end is closer to the end cover than the first end and the second end.

[0032] In this way, the separator has a portion exceeding the first end and the second end, enhancing the insulation effect of the separator between the positive electrode plate and the negative electrode plate, and reducing the risk of the positive electrode plate and the negative electrode plate overlapping.

[0033] In some embodiments, the separator includes an exceeding region exceeding the first end and the second end along the first direction. In the projection plane perpendicular to the second direction, the positive projection of the exceeding region partially overlaps with the positive projection of the buffering structure.

[0034] In this way, this structure can increase the size of the buffering structure along the first direction, improve the ability of the buffering structure to absorb the expansion force, and further reduce the risk of fatigue cracking in the region where the first wall is near the first connecting portion.

[0035] In some embodiments, in a projection plane perpendicular to the second direction, the orthographic projection of the positive electrode main body region does not overlap with the orthographic projection of the buffer structure; and / or, in a projection plane perpendicular to the second direction, the orthographic projection of the negative electrode main body region does not overlap with the orthographic projection of the buffer structure.

[0036] Thus, if in a projection plane perpendicular to the second direction, the orthographic projection of the positive electrode main body region does not overlap with the orthographic projection of the buffer structure, the housing can provide a larger expansion space for the electrode assembly, reducing the risk that the expansion of the electrode assembly directly applies an expansion force to the buffer, decreasing the deformation amount of the first wall, and further reducing the risk of fatigue cracking in the region of the first wall near the first connection portion.

[0037] If in a projection plane perpendicular to the second direction, the orthographic projection of the negative electrode main body region does not overlap with the orthographic projection of the buffer structure, the housing can provide a larger expansion space for the electrode assembly, reducing the risk that the expansion of the electrode assembly directly applies an expansion force to the buffer structure, decreasing the deformation amount of the first wall, and further reducing the risk of fatigue cracking in the region of the first wall near the first connection portion.

[0038] In some embodiments, the negative electrode tab includes a negative electrode current collector and a negative electrode active material layer provided on at least one side of the negative electrode current collector, and the negative electrode active material layer includes a negative electrode active material.

[0039] Thus, by providing a negative electrode active material layer on at least one side of the negative electrode current collector, the content of the active material in the battery cell can be increased, thereby improving the energy density of the battery.

[0040] In some embodiments, the negative electrode active material layer includes a negative electrode main body portion and a negative electrode thinning portion, the negative electrode main body portion and the negative electrode thinning portion are arranged along the first direction, and along the first direction, the negative electrode thinning portion is provided at one end of the negative electrode main body portion close to the end cap.

[0041] Thus, the electrode assembly has a larger expansion gap in the region corresponding to the negative electrode thinning portion, and the force exerted by the region of the electrode assembly corresponding to the negative electrode thinning portion on the first wall after expansion is smaller, which can reduce the risk of fatigue cracking in the region of the first wall near the first connection portion.

[0042] In some embodiments, in a projection plane perpendicular to the second direction, the orthographic projection of the negative electrode thinning portion and the orthographic projection of the buffer structure are arranged at intervals along the first direction.

[0043] Thus, the influence of the negative electrode thinning portion on the buffer structure and the first connection portion is relatively low, reducing the risk that the expansion of the electrode assembly directly applies an expansion force to the buffer structure, and further reducing the risk of fatigue cracking in the region of the first wall near the first connection portion.

[0044] In some embodiments, in a projection plane perpendicular to the second direction, the spacing dimension of the positive projection of the negative electrode thinning portion and the positive projection of the buffer structure along the first direction is greater than or equal to 1 mm.

[0045] In this way, in the projection plane perpendicular to the second direction, the positive projections of the negative electrode thinning portion and the buffer structure are farther apart along the first direction, further reducing the influence of the negative electrode thinning portion on the buffer structure.

[0046] In some embodiments, the single-sided coating weight of the negative electrode active material layer is 90 mg / 1540 mm 2 ~170 mg / 1540 mm 2 .

[0047] The single-sided coating weight of the negative electrode active material layer is related to the swelling of the negative electrode active material layer. By setting the single-sided coating weight of the negative electrode active material layer at 90 mg / 1540 mm 2 ~170 mg / 1540 mm 2 , it is possible to balance the requirements for high energy density of the battery cell and low swelling of the negative electrode sheet to a certain extent, so as to reduce the influence of the swelling of the negative electrode sheet on the first wall and reduce the risk of fatigue cracking in the area of the first wall near the first connection portion.

[0048] In some embodiments, the single-sided coating weight of the negative electrode active material layer is 110 mg / 1540 mm 2 ~150 mg / 1540 mm 2 .

[0049] In this way, this can further improve the energy density of the battery cell and further slow down the swelling of the negative electrode sheet.

[0050] In some embodiments, the porosity of the negative electrode sheet is 27% - 40%.

[0051] In this way, this can provide space for impurities generated by side reactions in the negative electrode sheet, slow down the swelling of the negative electrode sheet, and reduce the influence of the swelling of the negative electrode sheet on the first wall.

[0052] In some embodiments, the negative electrode active material includes a silicon-based material, and the mass content of silicon element in the silicon-based material in the negative electrode active material is 0.3% - 10%.

[0053] In this way, by controlling the content of silicon element within the range of 0.3% - 10%, the cycle stability and energy density of the battery cell can be balanced, and the volume expansion problem of the silicon-based material during charge and discharge can be reduced.

[0054] In some embodiments, the mass content of silicon element in the silicon-based material in the negative electrode active material is 1% - 6%.

[0055] Thus, by controlling the silicon element content within the range of 1% to 6%, the cycle stability and energy density of the battery cell can be further balanced, and the volume expansion problem of the silicon-based material during charge and discharge can be further reduced.

[0056] In some embodiments, the size of the buffer structure in the third direction is greater than the size of the buffer structure in the first direction, and the first direction, the second direction, and the third direction are non-coplanar and intersect pairwise.

[0057] Thus, the size of the buffer structure in the third direction is larger, so that the buffer structure has a stronger ability to absorb the expansion force, and further reduces the risk of fatigue cracking in the region of the first wall near the first connection portion.

[0058] In some embodiments, the buffer structure passes through the mid-section of the first wall. The mid-section is perpendicular to the third direction, and the distances from the mid-section to both ends of the first wall in the third direction are equal.

[0059] Thus, when the first wall is subjected to the expansion force of the battery cell electrode assembly, the deformation amount of the middle region of the first wall in the third direction is larger, and the middle region of the first wall in the third direction is more likely to suffer from fatigue cracking. Since the buffer structure passes through the mid-section of the first wall, the expansion force received by at least the middle region of the first wall in the third direction is reduced, and the risk of fatigue cracking in the middle region of the first wall in the third direction near the first connection portion is reduced.

[0060] In some embodiments, the size of the buffer structure in the third direction is L1, and the size of the first wall in the third direction is L, where 0.4 ≤ L1 / L ≤ 0.9.

[0061] [[ID=I9]]Thus, when 0.4 ≤ L1 / L, the proportion of the size of the buffer structure in the third direction in the first wall is relatively large, which makes the expansion force received by the middle region of the first wall in the third direction smaller, and reduces the risk of fatigue cracking in the middle region of the first wall in the third direction near the first connection portion.

[0062] When L1 / L ≤ 0.9, the proportion of the size of the buffer structure in the third direction in the first wall is relatively small, reducing the waste generated in manufacturing the buffer structure and lowering the production cost.

[0063] Therefore, setting the ratio of the size of the buffer structure in the third direction to the size of the first wall in the third direction to 0.4 to 0.9 can, while enabling the buffer structure to have sufficient ability to absorb the expansion force, reduce the waste generated in manufacturing the buffer structure, and take into account both the ability requirement for the buffer structure to absorb the expansion force and the economic requirement.

[0064] In some embodiments, the buffer structure has opposite fourth and fifth ends along a third direction, the first wall has opposite sixth and seventh ends along the third direction, the fourth end is close to the sixth end, the fifth end is close to the seventh end, the dimension of the first wall along the third direction is L, the minimum distance between the fourth end and the sixth end along the third direction is L2, and the minimum distance between the fifth end and the seventh end along the third direction is L3; L2 / L ≤ 0.3; and / or, L3 / L ≤ 0.3.

[0065] Thus, if L2 / L ≤ 0.3, the proportion of the minimum distance between the fourth end and the sixth end along the third direction in the dimension of the first wall along the third direction is reduced, such that more regions of the fourth end along the third direction are subject to reduced expansion force, further reducing the risk of fatigue cracking in the region of the first wall near the first connection portion.

[0066] If L3 / L ≤ 0.3, the proportion of the minimum distance between the fifth end and the seventh end along the third direction in the dimension of the first wall along the third direction is reduced, such that more regions of the first wall along the third direction are subject to reduced expansion force, further reducing the risk of fatigue cracking in the region of the first wall near the first connection portion.

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

[0068] Thus, within this numerical range, along the third direction, the first wall has a relatively large dimension, which helps with the arrangement of the buffer structure, thereby facilitating the buffer structure to absorb the expansion force.

[0069] In some embodiments, the housing includes corner walls, and both ends of the first wall along the third direction are connected to the corner walls; at least one end of the buffer structure along the third direction is spaced apart from the corner wall.

[0070] Thus, since at least one end of the buffer structure along the third direction is not in contact with the corner wall, this can reduce the waste generated during the manufacture of the buffer structure and lower the production cost.

[0071] In some embodiments, the main body portion includes a first region and a second region arranged along a first direction, the thickness of the first region is greater than the thickness of the second region, and the buffer structure is located between the first region and the second region.

[0072] Thus, the first region with a larger thickness can enhance the resistance of the first connection portion to the expansion force. In combination with the buffer structure, it can further reduce the risk of fatigue cracking in the region of the first wall near the first connection portion due to the expansion of the electrode assembly, thereby improving the service life of the battery cell.

[0073] In some embodiments, the first region includes a first part and a second part arranged along the first direction, the second part is located between the first part and the buffer structure, and the thickness of the first part is greater than the thickness of the second part.

[0074] Thus, in the first region near the first connection portion, it is easier to form a heat affected zone, and this region is more prone to fatigue cracking. However, since the second portion connects the first portion and the buffer structure, and the thickness of the first portion is greater than that of the second portion, the thicker first portion in the first region is closer to the first connection portion, which can effectively weaken the influence of the heat affected zone on the first region and reduce the risk of fatigue cracking in the region of the first wall near the first connection portion. In addition, since the thickness of the second portion is less than that of the first portion, the material used in the first region can be reduced, thereby reducing the production cost.

[0075] In some embodiments, the thickness of the second portion decreases in the direction from the end cap to the electrode assembly.

[0076] Thus, on the one hand, this can reduce the influence of the second portion on the electrode assembly and reduce the risk of interference between the second portion and the electrode assembly.

[0077] On the other hand, this makes the strengthening effect of the second portion increase in the direction from the electrode assembly to the end cap, so that the region of the second portion near the first portion has a good strengthening effect even under the influence of the first connection portion, reducing the risk of fatigue cracking of the first wall in the second portion.

[0078] On the other hand, through the second portion, the transition between the first portion and the second region can be realized, reducing stress concentration.

[0079] In some embodiments, the Vickers hardness of at least part of the first region is less than that of the second region.

[0080] It can be understood that when the first wall is subjected to the expansion force, the first region with lower hardness may first respond to the overload through plastic deformation, while the second region with higher hardness may first develop cracks. Therefore, the risk of fatigue cracking in the first region is lower.

[0081] In some embodiments, the electrode assembly has a flat region, and 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 are stacked along the second direction.

[0082] Thus, the second direction is the same as the stacking direction of 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. During the cycling process, the electrode assembly expands more along the second direction, and the first wall is more affected by the expansion of the electrode assembly. However, since the buffer structure can absorb the expansion force, the expansion force on the region of the first wall near the first connection portion is reduced, reducing the risk of fatigue cracking of the first wall near the first connection portion due to the expansion of the electrode assembly.

[0083] In some embodiments, the electrode assembly includes adjacent first and second surfaces. The first surface is perpendicular to the second direction, the area of the first surface is larger than that of the second surface, and the first surface and the first wall are disposed opposite to each other along the second direction.

[0084] In this way, the area of the first surface is larger than that of the second surface, so that the first wall disposed opposite to the first surface in the housing receives a greater expansion force. Since the buffer structure can absorb the expansion force, the expansion force received by the area of the first wall near the first connection portion is reduced, and the risk of fatigue cracking of the first wall near the first connection portion due to the expansion of the electrode assembly is reduced.

[0085] In some embodiments, the first surface is the surface with the largest area among the outer surfaces of the electrode assembly.

[0086] In this way, the first wall disposed opposite to the first surface in the housing receives the greatest expansion force. Since the buffer structure can absorb the expansion force, the expansion force received by the area of the first wall near the first connection portion is reduced, and the risk of fatigue cracking of the first wall near the first connection portion due to the expansion of the electrode assembly is reduced.

[0087] In some embodiments, the electrode assembly is a wound structure. The electrode assembly further has a corner region. The corner region is provided at at least one end of the flat region along the third direction. The first, second, and third directions are non-coplanar and intersect pairwise;

[0088] The outer surface of the flat region includes the first surface, and the outer surface of the corner region includes the second surface. At least a part of the second surface is an arc surface.

[0089] In this way, for the wound electrode assembly, the expansion amount of the flat region in the second direction is greater. Since the buffer structure can absorb the expansion force, the expansion force received by the area of the first wall near the first connection portion is reduced, and the risk of fatigue cracking of the first wall near the first connection portion due to the expansion of the electrode assembly is reduced.

[0090] In some embodiments, the electrode assembly is a laminated structure. The flat region includes a plurality of positive electrode plates and a plurality of negative electrode plates. The plurality of positive electrode plates and the plurality of negative electrode plates are stacked along the second direction, and the first surface is perpendicular to the second surface.

[0091] In this way, for the laminated electrode assembly, the expansion amount of the electrode assembly in the stacking direction of the positive electrode plates and the negative electrode plates is greater. Since the buffer structure can absorb the expansion force, the expansion force received by the area of the first wall near the first connection portion is reduced, and the risk of fatigue cracking of the first wall near the first connection portion due to the expansion of the electrode assembly is reduced.

[0092] In some embodiments, the first wall is the wall with the largest outer surface area in the housing.

[0093] In this way, the wall with the largest outer surface area in the housing is more likely to deform after being 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 first wall near the first connection portion due to the expansion of the electrode assembly is relatively low.

[0094] In some embodiments, the housing 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.

[0095] In this way, this reduces the risk of fatigue cracking of the two first walls near the first connection portion due to the expansion of the electrode assembly.

[0096] In some embodiments, the first wall further includes a transition region, which is located between the main body portion and the first connection portion along the first direction. The transition region is connected to the first connection portion, and the connection position between the transition region and the first connection portion forms a connection interface. The connection interface has a connection position closest to the main body portion along the first direction, and the connection position is located at one end of the main body portion close to the opening along the first direction.

[0097] In this way, the transition region is connected to the first connection portion to form a connection interface, so that the transition region and the first connection portion have a sufficiently large contact area, improving the firmness after the first wall and the end cap are welded.

[0098] In some embodiments, at least a part of the connection interface extends obliquely with respect to the second direction.

[0099] In this way, 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 transition region. When the first wall is subjected to the expansion force of the electrode assembly, the first wall will deform, and the transition region will generate tensile stress on the first connection portion. Since at least a part of the connection interface extends obliquely with respect to the second direction, near the part where the connection interface extends obliquely with respect to the second direction, the tensile stress generated by the contraction of the first connection portion on the transition region and the tensile stress generated by the deformation of the first wall on the first connection portion by the transition region are not on the same straight line, reducing the risk of fatigue cracking of the region of the transition region near the connection interface.

[0100] In some embodiments, the connection interface includes a first interface, which extends obliquely from the connection position towards the end cap. Along the second direction, at least a part of the transition region is located between the first interface and the end cap.

[0101] In this way, the first connection portion plays a protective role for the transition region. When the first wall is subjected to the expansion force of the electrode assembly, the deformation of the transition region during the force application process is blocked by the first connection portion, reducing the risk of fatigue cracking of the region of the transition region near the first interface.

[0102] In some embodiments, the first interface is connected to the outer surface of the main body at a connection position.

[0103] In this way, since the first interface is in a direct connection state with the main body, the main body and the first connection part are closer along the first direction, further reducing the risk of fatigue cracking of the area of the first wall near the first connection part due to expansion of the electrode assembly.

[0104] In some embodiments, the connection interface includes a second interface that extends obliquely from the connection position away from the end cap, and along the second direction, at least a portion of the transition zone is located on a side of the second interface away from the end cap.

[0105] In this way, the transition zone restricts the first connection portion, reducing the risk of the first connection portion falling off.

[0106] In some embodiments, the second interface is connected to the inner surface of the main body at a connection position.

[0107] In this way, the main body and the first connecting part are in a directly connected state, so that the main body and the first connecting part are closer along the first direction, further reducing the risk of fatigue cracking of the area of the first wall near the first connecting part due to expansion of the electrode assembly.

[0108] In some embodiments, the Vickers hardness of the transition region is less than the Vickers hardness of the main body; and / or the Vickers hardness of the transition region is less than the Vickers hardness of the first connecting portion.

[0109] Thus, if the Vickers hardness of the transition zone is lower than that of the main body, the transition zone with the 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, thereby reducing the risk of separation between the first wall and the first connecting portion. If the Vickers hardness of the transition zone is lower than that of the first connecting portion, the transition zone is more susceptible to deformation 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, thereby reducing the risk of separation between the first wall and the first connecting portion.

[0110] In some embodiments, the electrode assembly is a laminate structure, and the electrode assembly includes a plurality of positive electrode sheets and a plurality of negative electrode sheets, and the plurality of positive electrode sheets and the plurality of negative electrode sheets are stacked along the second direction.

[0111] In this way, the laminated electrode assembly structure is more compact and has stronger anti-extrusion ability.

[0112] 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.

[0113] In this way, by arranging the positive electrode sheet between adjacent negative electrode sheets, the transmission distance of lithium ions inside the battery cell can be reduced, and more lithium ion transmission paths can be provided, thereby improving the charge and discharge efficiency of the battery cell.

[0114] 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.

[0115] In this way, the tabs can simplify the electrical connection between the battery cell and the external circuit.

[0116] In some embodiments, along the third direction, the size of the buffer structure 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.

[0117] In this way, the buffer structure has a larger size along the third direction, so that the expansion force on more areas of the first wall along the third direction is reduced, further reducing the risk of fatigue cracking in the area of the first wall near the first connecting portion.

[0118] In some embodiments, the battery cell further includes two electrode terminals, which are disposed on the end caps, have opposite polarities, and are both electrically connected to the electrode assembly;

[0119] The end cover is provided with a lead-out hole, and the electrode terminal includes a terminal body, a first limiting portion and a second limiting portion. The terminal body is connected to the first limiting portion and the second limiting portion. The terminal body is passed through the lead-out hole. Along the first direction, the first limiting portion is located on the side of the end cover away from the electrode assembly, and the second limiting portion is located on the side of the end cover facing the electrode assembly.

[0120] In this way, the electrode terminal of this structure can be installed on the end cover by riveting, which has low installation difficulty and better economy.

[0121] In a second aspect, an embodiment of the present application provides a battery, which includes a battery cell provided by any embodiment of the first aspect.

[0122] Thus, since the battery includes the above-mentioned battery cells, the battery at least includes all the beneficial effects of the above-mentioned battery cells, which will not be described in detail here.

[0123] In a third aspect, an embodiment of the present application provides an electrical device, which includes a battery cell provided by any embodiment of the first aspect, and the battery cell is used to provide electrical energy to the electrical device.

[0124] Thus, since the electrical equipment includes the above-mentioned battery cell, the electrical equipment at least includes all the beneficial effects of the above-mentioned battery cell, which will not be described in detail here.

[0125] The above description is only an overview of the technical solution of this application. In order to understand the technical means of this application more clearly, it can be implemented according to the content of the specification. And in order to make the above and other purposes, features and advantages of this application more obvious and understandable, the following specifically gives the specific implementation manners of this application. BRIEF DESCRIPTION OF THE DRAWINGS

[0126] By reading the following detailed description of the preferred embodiments, various other advantages and benefits will become clear to those of ordinary skill in the art. The drawings are only for the purpose of showing the preferred embodiments and are not considered to be a limitation of this application. And in all the drawings, the same reference numerals are used to represent the same components. In the drawings:

[0127] Figure 1 is a schematic structural diagram of a vehicle provided by some embodiments of this application;

[0128] Figure 2 is an exploded view of a battery provided by some embodiments of this application;

[0129] Figure 3 is an exploded view of a battery cell provided by some embodiments of this application;

[0130] Figure 4 is Figure 3 a schematic structural diagram of the battery cell shown;

[0131] Figure 5 is Figure 4 a sectional view of the battery cell in the A-A direction;

[0132] Figure 6 is Figure 5 an enlarged view of part B of the battery cell in ;

[0133] Figure 7 is a partial schematic diagram of a battery cell provided by some embodiments of this application;

[0134] Figure 8 is a partial schematic diagram of a battery cell provided by some other embodiments of this application;

[0135] Figure 9 is a schematic diagram of an electrode assembly provided by some embodiments of this application;

[0136] Figure 10 is a partial schematic diagram of a battery cell provided by some other embodiments of this application;

[0137] Figure 11 is a partial schematic diagram of an electrode assembly provided by some embodiments of this application;

[0138] Figure 12 is a partial schematic diagram of an electrode assembly provided by some other embodiments of this application;

[0139] Figure 13 is a schematic structural diagram of a housing provided by some embodiments of the present application;

[0140] Figure 14 is a schematic structural diagram of a housing provided by other embodiments of the present application;

[0141] Figure 15 is a schematic structural diagram of a battery cell provided by still other embodiments of the present application;

[0142] Figure 16 is a schematic diagram of an electrode assembly provided by other embodiments of the present application;

[0143] Figure 17 is a schematic structural diagram of an electrode assembly provided by some embodiments of the present application;

[0144] Figure 18 is a schematic structural diagram of an electrode assembly provided by other embodiments of the present application;

[0145] Figure 19 is a partial schematic diagram of a battery cell provided by still other embodiments of the present application;

[0146] Figure 20 is Figure 19 an enlarged view of part C of the battery cell;

[0147] Figure 21 is a partial schematic diagram of a battery cell provided by still other embodiments of the present application;

[0148] Figure 22 is Figure 21 an enlarged view of part D of the battery cell;

[0149] Figure 23 is a schematic connection diagram of an end cap and an electrode terminal provided by some embodiments of the present application.

[0150] Explanation of reference numerals in the drawings:

[0151] 1 - Outer shell; 11 - Housing; 111 - First wall; 112 - Second wall; 12 - End cap; 4 - Pressure relief mechanism; 5 - Connecting part; 51 - First connecting part; 52 - Second connecting part; 2 - Electrode assembly; 22 - Positive electrode plate; 23 - Negative electrode plate; 400 - Main body part; 410 - Buffer structure; 411 - Weak part; 412 - Groove; 4120 - First side; 4121 - Second side; 4122 - Bottom surface; 4110 - First weak part; 4111 - Second weak part; 4112 - Third weak part; 413 - First convex part; 414 - First concave part; 420 - Outer surface of the main body part; 430 - Inner surface of the main body part; 417 - Second convex part; 418 - Second concave part; 24 - Separator; 221 - Positive electrode main area; 2231 - Positive electrode main body part; 2232 - Positive electrode thinning part; 21 - Tab; 21a - Positive electrode tab; 222 - Positive electrode current collector; 223 - Positive electrode active material layer; 224 - Insulating layer; 231 - Negative electrode main area; 21b - Negative electrode tab; 233 - Negative electrode active material layer; 2211 - First end; 2311 - Second end; 241 - Third end; 242 - Extended area; 232 - Negative electrode current collector; 2331 - Negative electrode main body part; 2332 - Negative electrode thinning part; 11113a - Fourth end; 11113b - Fifth end; 1113 - Sixth end; 1114 - Seventh end; 113 - Corner wall; 440 - First area; 450 - Second area; 441 - First part; 442 - Second part; 25 - Straight area; 26 - Corner area; 27 - First surface; 28 - Second surface; 1117 - Transition area; 511 - Connection interface; 5111 - Connection position; 5112 - First interface; 5113 - Second interface; 3 - Electrode terminal; 31 - Terminal main body; 32 - First limiting part; 33 - Second limiting part; 6 - First insulating part; 7 - Second insulating part; 10 - Battery cell; 20 - Box body; 201 - First box body; 202 - Second box body; 100 - Battery; 200 - Controller; 300 - Motor; 1000 - Vehicle; Z - First direction; Y - Second direction; X - Third direction; U - Interface. Detailed implementation manners

[0152] The embodiments of the technical solutions of the present application will be described in detail below with reference to the accompanying drawings. The following embodiments are only used to illustrate the technical solutions of the present application more clearly, so they are only examples and cannot be used to limit the protection scope of the present application.

[0153] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the technical field to which this application belongs; the terms used herein 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 description of the specification, claims and above drawings of this application are intended to cover non-exclusive inclusion.

[0154] In the description of the embodiments of this application, technical terms such as "first" and "second" are only used to distinguish different objects and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity, specific order or primary-secondary relationship of the indicated technical features. In the description of the embodiments of this application, the meaning of "a plurality" is more than two, unless otherwise specifically defined.

[0155] Reference to "an embodiment" herein means that a particular feature, structure or characteristic described in connection with the embodiment can be included in at least one embodiment of this application. The phrase appears in various places in the specification and does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. Those skilled in the art will explicitly and implicitly understand that the embodiments described herein can be combined with other embodiments.

[0156] In the description of the embodiments of this application, the term "and / or" is merely a description of the association relationship of associated objects, indicating that three relationships can exist. For example, A and / or B can represent three situations: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " herein generally represents an "or" relationship between the associated objects before and after.

[0157] In the description of the embodiments of this application, the term "a plurality" refers to more than two (including two). Similarly, "a plurality of groups" refers to more than two groups (including two groups), and "a plurality of pieces" refers to more than two pieces (including two pieces).

[0158] In the description of the embodiments of this application, the orientation or positional relationship indicated by technical terms such as "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the embodiments of this application and simplifying the description, rather than indicating or implying that the indicated device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the embodiments of this application.

[0159] In the description of the embodiments of the present application, unless otherwise clearly specified or limited, technical terms such as "installation", "connection", "connection", "fixation" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral body; it can also be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two components or the interaction relationship between two components. For those of ordinary skill in the art, the specific meanings of the above terms in the embodiments of the present application can be understood according to specific circumstances.

[0160] In the embodiments of the present application, "a plurality" means two or more (including two).

[0161] In the embodiments of the present application, the battery cell can be a secondary battery, which refers to a battery cell that can activate the active material and continue to be used by charging after discharging the battery cell.

[0162] The battery cell includes, but is not limited to, lithium-ion batteries, sodium-ion batteries, sodium-lithium-ion batteries, lithium-metal batteries, sodium-metal batteries, lithium-sulfur batteries, magnesium-ion batteries, nickel-metal hydride batteries, nickel-cadmium batteries, lead-acid batteries, etc.

[0163] The battery cell generally includes an electrode assembly. The electrode assembly includes a positive electrode, a negative electrode, and a separator. During the charge and discharge process of the battery cell, active ions (such as lithium ions) are embedded and extracted back and forth between the positive electrode and the negative electrode. The separator is arranged between the positive electrode and the negative electrode, which can reduce the risk of short circuit between the positive and negative electrodes and at the same time allow active ions to pass through.

[0164] In some embodiments, the positive electrode can be a positive electrode plate, and the positive electrode plate can include a positive electrode current collector and a positive electrode active material provided on at least one surface of the positive electrode current collector.

[0165] As an example, the positive electrode current collector has two surfaces opposite to each other in its own thickness direction, and the positive electrode active material is provided on any one or both of the two opposite surfaces of the positive electrode current collector.

[0166] As an example, the positive electrode current collector can be a metal foil or a composite current collector. For example, as a metal foil, aluminum with silver plating on the surface, stainless steel with silver plating on the surface, stainless steel, copper, aluminum, nickel, carbon electrode, carbon, nickel, or titanium, etc. can be used. The composite current collector can include a polymer material base layer and a metal layer. The composite current collector can be formed by forming a metal material (such as 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.).

[0167] 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 conventional materials that can be used as the positive electrode active material of the battery may also be used. These positive electrode active materials may be used alone or in combination of two or more. Among them, examples of the lithium-containing phosphate may include, but are not limited to, lithium iron phosphate (such as LiFePO4 (which may also be abbreviated 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 manganese iron phosphate, and at least one of a composite material of lithium manganese iron phosphate and carbon. Examples of the lithium transition metal oxide 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 / 3 O2, which may also be abbreviated as NCM 333 )、LiNi 0.5 Co 0.2 Mn 0.3 O2 (which may also be abbreviated as NCM 523 )、LiNi 0.5 Co 0.25 Mn 0.25 O2 (which may also be abbreviated as NCM 211 )、LiNi 0.6 Co 0.2 Mn 0.2 O2 (which may also be abbreviated as NCM 622 )、LiNi 0.8 Co 0.1 Mn 0.1 O2 (which may also be abbreviated as NCM 811 )、lithium nickel cobalt aluminum oxide (such as LiNi 0.85 Co 0.15 Al 0.05 O2) and their modified compounds, etc.

[0168] In some embodiments, the positive electrode may employ a foam metal. The foam metal may be foam nickel, foam copper, foam aluminum, foam alloy, etc. When the foam metal is used as the positive electrode, the positive electrode active material may not be provided on the surface of the foam metal, and of course, the positive electrode active material may also be provided. As an example, a lithium source material, potassium metal, or sodium metal may be filled and / or deposited in the foam metal, and the lithium source material is lithium metal and / or a lithium-rich material.

[0169] In some embodiments, the negative electrode may be a negative electrode plate, and the negative electrode plate may include a negative electrode current collector.

[0170] As an example, the negative electrode current collector can be a metal foil, a foam metal, 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 electrodes, carbon, nickel, or titanium, etc. can be used. The foam metal can be foam nickel, foam copper, foam aluminum, foam alloy, etc. The composite current collector can include a polymer material base layer and a metal layer. The composite current collector can be formed by forming a metal material (such as copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.).

[0171] As an example, the negative electrode sheet can include a negative electrode current collector and a negative electrode active material provided on at least one surface of the negative electrode current collector.

[0172] As an example, the negative electrode current collector has two surfaces opposite to each other in its own thickness direction, and the negative electrode active material is provided on either one or both of the two opposite surfaces of the negative electrode current collector.

[0173] As an example, the negative electrode active material can be a negative electrode active material for battery cells known in the art. As an example, the negative electrode active material can include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate, etc. The silicon-based materials can be selected from at least one of elemental silicon, silicon oxides, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based materials can be selected from at least one of elemental tin, tin oxides, and tin alloys. However, the present application is not limited to these materials, and other conventional materials that can be used as battery negative electrode active materials can also be used. These negative electrode active materials can be used alone or in combination of two or more.

[0174] In some embodiments, the material of the positive electrode current collector can be aluminum, and the material of the negative electrode current collector can be copper.

[0175] In some embodiments, the separator is a separator membrane. The separator membrane can be any known porous structure separator membrane with good chemical stability and mechanical stability.

[0176] As an example, the material of the separator membrane can include at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator membrane can be a single-layer film or a multi-layer composite film. When the separator membrane is a multi-layer composite film, the materials of each layer can be the same or different. The separator can be a single component located between the positive and negative electrodes, or can be attached to the surfaces of the positive and negative electrodes.

[0177] In some embodiments, the separator is a solid electrolyte. The solid electrolyte is disposed between the positive electrode and the negative electrode, and functions to transport ions and isolate the positive and negative electrodes simultaneously.

[0178] In some embodiments, the battery cell further includes an electrolyte, which functions to conduct ions between the positive and negative electrodes. The electrolyte can be liquid, gel or solid. Among them, the liquid electrolyte includes an electrolyte salt and a solvent.

[0179] In some embodiments, the electrolyte salt may include at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluoro(oxalato)borate, lithium bis(oxalato)borate, lithium difluoro bis(oxalato)phosphate, and lithium tetrafluoro(oxalato)phosphate.

[0180] In some embodiments, the solvent may include at least one of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone. The solvent can 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.

[0181] Among them, the gel electrolyte includes a polymer as the backbone network of the electrolyte, combined with an ionic liquid-lithium salt.

[0182] Among them, the solid electrolyte includes a polymer solid electrolyte, an inorganic solid electrolyte, and a composite solid electrolyte.

[0183] As an example, the polymer solid electrolyte can be polyether (polyethylene oxide), polysiloxane, polycarbonate, polyacrylonitrile, polyvinylidene fluoride, polymethyl methacrylate, single-ion polymer, poly(ionic liquid)-lithium salt, cellulose, etc.

[0184] As an example, the inorganic solid electrolyte may include an oxide solid electrolyte (crystalline perovskite, sodium superionic conductor, garnet, amorphous LiPON film), a sulfide solid electrolyte (crystalline lithium superionic conductor (lithium germanium phosphorus sulfur, argyrodite), amorphous sulfide), and one or more of a halide solid electrolyte, a nitride solid electrolyte, and a hydride solid electrolyte.

[0185] As an example, the composite solid electrolyte is formed by adding an inorganic solid electrolyte filler to a polymer solid electrolyte.

[0186] In some embodiments, the electrode assembly has a wound structure. The positive electrode sheet and the negative electrode sheet are wound into a wound structure.

[0187] In some embodiments, the electrode assembly has a stacked structure.

[0188] 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 are alternately stacked.

[0189] As an example, multiple positive electrode sheets can be provided, and the negative electrode sheet is folded to form multiple stacked folding segments, and a positive electrode sheet is clamped between adjacent folding segments.

[0190] As an example, both the positive electrode sheet and the negative electrode sheet are folded to form multiple stacked folding segments.

[0191] As an example, multiple separators can be provided and are respectively disposed between any adjacent positive electrode sheets or negative electrode sheets.

[0192] As an example, the separator can be continuously provided and is disposed between any adjacent positive electrode sheets or negative electrode sheets by folding or winding.

[0193] In some embodiments, the shape of the electrode assembly can be cylindrical, flat, prismatic, etc.

[0194] In some embodiments, the electrode assembly is provided with tabs, and the tabs can conduct current out of the electrode assembly. The tabs include a positive tab and a negative tab.

[0195] In some embodiments, the battery cell can include a housing. The housing is used to encapsulate components such as the electrode assembly and the electrolyte. The housing can be a steel shell, an aluminum shell, a plastic shell (such as polypropylene), a composite metal shell (such as a copper-aluminum composite shell), or an aluminum plastic film, etc.

[0196] As an example, the battery cell can be a cylindrical battery cell, a prismatic battery cell, a soft-pack battery cell, or a battery cell of other shapes. The prismatic battery cell includes a square shell battery cell, a blade-shaped battery cell, a multi-prismatic battery cell, and the multi-prismatic battery cell is, for example, a hexagonal prism battery cell, etc.

[0197] The battery mentioned in the embodiments of the present application refers to a single physical module including one or more battery cells to provide a higher voltage and capacity.

[0198] In some embodiments, the battery can be a battery module. When there are multiple battery cells, the multiple battery cells are arranged and fixed to form a battery module.

[0199] 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.

[0200] 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.

[0201] In some embodiments, the battery may be an energy storage device, including an energy storage container, an energy storage cabinet, and the like.

[0202] 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.

[0203] 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. 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.

[0204] 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.

[0205] Based on the above considerations, in order to alleviate the problem that the area of the shell wall near the connection part is prone to fatigue cracking, an embodiment of the present application provides a battery cell, the battery cell includes a shell, an end cover and an electrode assembly; the shell has an opening at at least one end along the first direction, and 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 part; 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 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; wherein the first wall includes a main body, and along the first direction, the main body is located on the side of the first connection part away from the end cover, and the main body is provided with a buffer structure, and the buffer structure is spaced apart from the first connection part.

[0206] In such a battery cell, the buffer structure can absorb the expansion force generated during the use of the electrode assembly, thereby reducing the expansion force directly acting on the first connection portion. Therefore, the buffer structure can reduce the risk of fatigue cracking of the region of the first wall near the first connection portion due to the expansion of the electrode assembly, and thus improve the service life of the battery cell.

[0207] The battery cell described in the embodiments of the present application is applicable to batteries and electrical devices using the battery cell.

[0208] The electrical device can be a vehicle, a mobile phone, a portable device, a laptop computer, a ship, a spacecraft, an electric toy, an electric tool, etc. The vehicle can be a fuel vehicle, a gas vehicle or a new energy vehicle, and the new energy vehicle can be a pure electric vehicle, a hybrid electric vehicle or an extended-range electric vehicle, etc.; the spacecraft includes an airplane, a rocket, a space shuttle, a spaceship, etc.; the electric toy includes a fixed or mobile electric toy, for example, a game console, an electric vehicle toy, an electric ship toy, an electric airplane toy, etc.; the electric tool includes a metal cutting electric tool, a grinding electric tool, an assembly electric tool and a railway electric tool, for example, an electric drill, an electric grinder, an electric wrench, an electric screwdriver, a hammer drill, an impact drill, a concrete vibrator, a planer, etc. The embodiments of the present application do not impose special restrictions on the above electrical devices.

[0209] For the convenience of description in the following embodiments, the electrical device is taken as an example of a vehicle for illustration.

[0210] Please refer to Figure 1 , Figure 1 , which is a schematic structural diagram of a vehicle 1000 provided by some embodiments of the present application. A battery 100 is disposed inside the vehicle 1000, and the battery 100 can be disposed at the bottom, head or tail of the vehicle 1000. The battery 100 can be used for power supply of the vehicle 1000. For example, the battery 100 can be used as the operating power source of the vehicle 1000.

[0211] 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, for the working power requirements during the start, navigation and driving of the vehicle 1000.

[0212] In some embodiments of the present application, the battery 100 can not only be used as the operating power source of the vehicle 1000, but also be used 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.

[0213] Please refer to Figure 2 , Figure 2It is an exploded view of the battery 100 provided by some embodiments of the present application. The battery 100 may include battery cells 10 and a housing 20, and the battery cells 10 are accommodated in the housing 20.

[0214] Among them, the housing 20 is a component for accommodating the battery cells 10, the housing 20 provides an accommodation space for the battery cells 10, and the housing 20 can adopt various structures.

[0215] In some embodiments, the housing 20 may include a first housing 201 and a second housing 202, and the first housing 201 and the second housing 202 cover each other to define an accommodation space for accommodating the battery cells 10.

[0216] The first housing 201 and the second housing 202 can be of various shapes, for example, rectangular parallelepiped shape, cylindrical shape, etc. The first housing 201 may be a hollow structure with an opening on one side, and the second housing 202 may also be a hollow structure with an opening on one side. The opening side of the second housing 202 covers the opening side of the first housing 201, then the housing 20 with an accommodation space is formed. It can also be that the first housing 201 is a hollow structure with an opening on one side, and the second housing 202 is a plate-like structure. The second housing 202 covers the opening side of the first housing 201, then the housing 20 with an accommodation space is formed. The first housing 201 and the second housing 202 can be sealed by a sealing element, and the sealing element can be a sealing ring, sealant, etc.

[0217] In the battery 100, the number of battery cells 10 can be one or more. If there are multiple battery cells 10, the multiple battery cells 10 can be connected in series, parallel or in a mixed connection. A mixed connection means that there are both series and parallel connections among the multiple battery cells 10. It can be that multiple battery cells 10 are first connected in series, parallel or in a mixed connection to form a battery module, and then multiple battery modules are connected in series, parallel or in a mixed connection to form a whole and are accommodated in the housing 20. It can also be that all the battery cells 10 are directly connected in series, parallel or in a mixed connection together, and then the whole formed by all the battery cells 10 is accommodated in the housing 20.

[0218] Please refer to Figure 3 and Figure 4 , Figure 3 is an exploded view of the battery cell 10 provided by some embodiments of the present application; Figure 4 is Figure 3 a schematic structural view of the battery cell 10 shown. The battery cell 10 may include a housing 1 and an electrode assembly 2, and the electrode assembly 2 is accommodated in the housing 1.

[0219] In some embodiments, the housing 1 may include a housing body 11 and an end cap 12. The housing body 11 has an opening, and the end cap 12 closes the opening of the housing body 11.

[0220] The housing 11 is a component for accommodating the electrode assembly 2. The housing 11 can be a hollow structure with an opening formed at one end, or a hollow structure with openings formed at opposite ends. The housing 11 can be of various shapes, such as cylindrical, cuboid, etc. The material of the housing 11 can be various, such as copper, iron, aluminum, steel, aluminum alloy, etc. The electrode assembly 2 can be partially located inside the housing 11 or entirely located inside the housing 11.

[0221] The end cap 12 is a component for closing the opening of the housing 11 to isolate the internal environment of the battery cell 10 from the external environment. The end cap 12 and the housing 11 together define a receiving space for accommodating the electrode assembly 2, the electrolyte, and other components. The end cap 12 can be connected to the housing 11 by welding or crimping to close the opening of the housing 11. The shape of the end cap 12 can be adapted to the shape of the housing 11. For example, when the housing 11 is a cuboid structure, the end cap 12 is a rectangular plate-like structure adapted to the housing 11. Another example is that when the housing 11 is a cylindrical structure, the end cap 12 is a circular plate-like structure adapted to the housing 11. The material of the end cap 12 can also be various, such as copper, iron, aluminum, steel, aluminum alloy, etc. The material of the end cap 12 and the housing 11 can be the same or different.

[0222] In an embodiment where the housing 11 has an opening formed at one end, one end cap 12 can be correspondingly provided. In an embodiment where the housing 11 has openings formed at opposite ends, two end caps 12 can be correspondingly provided. The two end caps 12 respectively close the two openings of the housing 11, and the two end caps 12 and the housing 11 together define a receiving space.

[0223] In some embodiments, the battery cell 10 may further include electrode terminals 3. The electrode terminals 3 are provided on the outer shell 1 and are used for electrically connecting to the tabs 21 of the electrode assembly 2 to input or output the electrical energy of the battery cell 10. The electrode terminals 3 can be provided on the housing 11 of the outer shell 1 or on the end cap 12 of the outer shell 1. The electrode terminals 3 and the tabs 21 can be directly connected. For example, the electrode terminals 3 are welded to the tabs 21. The electrode terminals 3 and the tabs 21 can also be indirectly connected. For example, the electrode terminals 3 and the tabs 21 are indirectly connected through a current collecting member. The current collecting member can be a metal conductor, such as copper, iron, aluminum, steel, aluminum alloy, etc.

[0224] 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.

[0225] As an example, Figure 3 and Figure 4 As shown, an opening is formed at one end of the housing 11, and there is only one end cap 12 in the housing 1, and each end cap 12 closes one opening of the housing 11. The end cap 12 is provided with a pressure relief mechanism 4, and two electrode terminals 3 are provided on the end cap 12, 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, and 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.

[0226] Please refer to Figure 5 and Figure 6 , Figure 5 yes Figure 4 A cross-sectional view of the battery cell 10 taken along the AA direction; Figure 6 yes Figure 5 An enlarged view of a battery cell 10 at point B in FIG. The present embodiment 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, and the housing 11 comprises a first wall 111. The end cap 12 closes the opening, and the first wall 111 and the end cap 12 are welded to form a first connecting portion 51. The electrode assembly 2 is at least partially housed within the housing 11, and comprises 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, and the second direction Y is parallel to the thickness direction of the first wall 111. The first direction Z intersects with the second direction Y.

[0227] The first wall 111 includes a main body 400 . Along the first direction Z, the main body 400 is located on a side of the first connecting portion 51 away from the end cover 12 . The main body 400 is provided with a buffer structure 410 , which is spaced apart from the first connecting portion 51 .

[0228] Specifically, the housing 11 may have an opening formed only at one end along the first direction Z, and correspondingly, there is one end cover 12; or the housing 11 may have openings formed at both opposite ends along the first direction Z, and correspondingly, there are two end covers 12.

[0229] The housing 11 can be of various shapes, such as cylindrical, prismatic, etc. The prism can be a triangular prism, a quadrangular prism, a pentagonal prism, a hexagonal prism, etc. The quadrangular prism can be a cuboid, a cube, etc. The first direction Z is parallel to the orientation of the opening of the housing 11.

[0230] In an embodiment where the housing 11 is cylindrical, the first direction Z can be parallel to the axial direction of the housing 11; in an embodiment where the housing 11 is prismatic, the first direction Z can be parallel to the extending direction of the side edges of the housing 11. The second direction Y is parallel to the thickness direction of the first wall 111. In an embodiment where the housing 11 is cylindrical, the first wall 111 is a cylindrical shape, and the radial direction of the housing 11 is the thickness direction of the first wall 111, and the second direction Y is parallel to the radial direction of the housing 11. In an embodiment where the housing 11 is prismatic, the first wall 111 can be a rectangular plate-like structure. The first direction Z and the second direction Y can be set at an acute angle, a right angle, or an obtuse angle.

[0231] The end cover 12 can be welded to the housing 11. The welding of the end cover 12 and the housing 11 can form a connecting portion 5, and the connecting portion 5 can extend along the circumferential direction of the opening of the housing 11. The end cover 12 and the housing 11 are connected and fixed through the connecting portion 5 to achieve the sealing between the end cover 12 and the housing 11. The connecting portion 5 is the part where there is a weld mark after the end cover 12 and the housing 11 are welded, and the part where the end cover 12 and the housing 11 are welded and fused together can be the connecting portion 5.

[0232] The first wall 111 in the housing 11 can be one or multiple. The first connecting portion 51 can correspond to the first wall 111 one by one. The first connecting portion 51 is the part where there is a weld mark after the end cover 12 and the first wall 111 are welded, and the part where the end cover 12 and the first wall 111 are welded and fused together can be the first connecting portion 51.

[0233] One part of the first connecting portion 51 is formed on the end cover 12, and the other part of the first connecting portion 51 is formed on the first wall 111. The first wall 111 and the end cover 12 can form the first connecting portion 51 by means of stitch welding or penetration welding.

[0234] The first connection part 51 can be a part of the connection part 5 or the whole of the connection part 5. In an embodiment where the housing 11 is cylindrical, there is only one first wall 111 in the housing 11, the first wall 111 is cylindrical, and the first connection part 51 is the connection part 5; in an embodiment where the housing 11 is prismatic, the housing 11 can include a plurality of side walls, the plurality of side walls are arranged along the opening of the housing 11, and at least one of the two side walls arranged opposite to each other along the second direction Y can be the first wall 111, and the first connection part 51 is a part of the connection part 5.

[0235] The first wall 111 can be the wall with the largest outer surface area in the housing 11, or the first wall 111 can also not be the wall with the largest outer surface area in the housing 11. Taking the housing 11 as a cuboid as an example, the housing 11 can include 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 in pairs. It can be that the first wall 111 is the wall with the largest outer surface area in the housing 11, so that the outer surface area of the first wall 111 is larger than the outer surface area of the second wall 112, or it can be that the second wall 112 is the wall with the largest outer surface area in the housing 11, so that the outer surface area of the second wall 112 is larger than the outer surface area of the first wall 111.

[0236] The electrode assembly 2 is located in the accommodation space jointly defined by the housing 11 and the end cover 12. The electrode assembly 2 can be a laminated structure or a wound structure. The number of electrode assemblies 2 in the housing 11 can be one or multiple. If there are multiple electrode assemblies 2, the multiple electrode assemblies 2 can be stacked, for example, the multiple electrode assemblies 2 are stacked along the second direction Y.

[0237] At least part of the positive electrode plate 22 and at least part of the negative electrode plate 23 are stacked along the second direction Y. The electrode assembly 2 will expand along the second direction Y during cycling. After the first wall 111 is subjected to the expansion force of the electrode assembly 2, it will deform, and it is easy to cause fatigue cracking in the area of the first wall 111 near the first connection part 51.

[0238] The buffer structure 410 is an area that can absorb deformation. It can be an area with reduced strength, such as reduced thickness or reduced hardness, etc., or it can be a bending structure. After the first wall 111 is subjected to the expansion force, since the buffer structure 410 can absorb deformation, the expansion force received by the first connection part 51 is smaller.

[0239] In the above technical solution, the buffer structure 410 can absorb the expansion force generated during the use of the electrode assembly 2, thereby reducing the expansion force directly acting on the first connection portion 51. Therefore, the buffer structure 410 can reduce the risk of fatigue cracking in the region of the first wall 111 near the first connection portion 51 due to the expansion of the electrode assembly 2, and thus improve the service life of the battery cell 10.

[0240] Please refer to Figure 6 , in some embodiments, the buffer structure 410 includes a weak portion 411 provided on the main body portion 400, and the minimum thickness of the weak portion 411 is less than the thickness of other portions of the main body portion 400.

[0241] Specifically, the weak portion 411 can be provided as a blind hole or a groove on the main body portion 400. The weak portion 411 can be continuous or discontinuous. For example, the weak portion 411 can include a plurality of weak regions, and the plurality of weak regions are arranged at intervals along the first direction Z on the main body portion 400.

[0242] In this way, compared with other portions of the main body portion 400, the weak portion 411 can more effectively absorb the expansion force, thereby reducing the expansion force directly acting on the first connection portion 51. Therefore, the weak portion 411 reduces the risk of fatigue cracking in the region of the first wall 111 near the first connection portion 51 due to the expansion of the electrode assembly 2, and thus improves the service life of the battery cell 10.

[0243] In some embodiments, a groove 412 is provided on the inner surface 430 of the main body portion 400.

[0244] In some embodiments, a groove 412 is provided on the outer surface 420 of the main body portion 400.

[0245] In some embodiments, grooves 412 are provided on both the inner surface 430 and the outer surface of the main body portion 400.

[0246] Wherein, the weak portion 411 is the region on the main body portion 400 opposite to the notch of the groove 412.

[0247] Specifically, the groove 412 can be circular, rectangular, oval, etc. in shape, and the size and shape can be adjusted as needed. By providing the groove 412, the corresponding region of the inner surface 430 of the main body portion 400 or the outer surface 420 of the main body portion 400 is more likely to deform when the electrode assembly 2 expands, so as to absorb the expansion force.

[0248] In this way, the weak portion 411, as the region opposite to the notch of the groove, has better buffering performance and makes the weak portion 411 easier to form, reducing the manufacturing difficulty of the housing 11 and thus reducing the manufacturing cost of the housing 11.

[0249] Please refer to Figure 7 ,Figure 7 FIG. Figure 7 is a partial schematic view of the battery cell 10 provided by some embodiments of the present application. In some embodiments, the groove 412 includes a first side surface 4120, a second side surface 4121, and a bottom surface 4122 connecting the first side surface 4120 and the second side surface 4121. The weak part 411 includes a first weak part 4110 disposed opposite to the bottom surface 4122, and the thickness of the first weak part 4110 is smaller than the thickness of other parts of the main body part 400.

[0250] Specifically, the first weak part 4110 may be continuous or discontinuous. For example, the first weak part 4110 extends along the first direction Z and connects the first side surface 4120 and the second side surface 4121; the first weak part 4110 may also include a plurality of first weak areas, and the plurality of first weak areas are arranged at intervals along the first direction Z in the area where the first weak part 4110 is opposite to the bottom surface 4122.

[0251] The first side surface 4120, the second side surface 4121, and the bottom surface 4122 may be surfaces forming the shape profile of the groove 412. The first side surface 4120, the second side surface 4121, and the bottom surface 4122 may be coplanar or non-coplanar.

[0252] In this way, compared with other parts of the main body part 400, the expansion force acting on the first weak part 4110 is greater, and the first weak part 4110 can absorb the expansion force more effectively, thereby reducing the expansion force directly acting on the first connection part 51. Therefore, the first weak part 4110 can reduce the risk of fatigue cracking of the area where the first wall 111 is near the first connection part 51 due to the expansion of the electrode assembly 2, and further improves the service life of the battery cell 10.

[0253] Please refer to Figure 7 , in some embodiments, the weak part 411 further includes a second weak part 4111 disposed opposite to the first side surface 4120 and a third weak part 4112 disposed opposite to the second side surface 4121. The first side surface 4120 is located on the side of the bottom surface 4122 close to the first connection part 51, and the thickness of the second weak part 4111 shows an increasing trend along the direction close to the first connection part 51. The second side surface 4121 is located on the side of the bottom surface 4122 away from the first connection part 51, and the thickness of the third weak part 4112 shows an increasing trend along the direction away from the first connection part 51.

[0254] Specifically, the direction close to the first connection part 51 and the direction away from the first connection part 51 may be different parts in the first direction Z. Along the first direction Z, the second weak part 4111 and the third weak part 4112 may be respectively located on both sides of the first weak part 4110. The second weak part 4111 may be connected to or spaced from the first weak part 4110. The third weak part 4112 may be connected to or spaced from the first weak part 4110.

[0255] The second weak part 4111 may be continuous or discontinuous. For example, the second weak part 4111 extends along the first direction Z and connects to the first weak part 4110; the second weak part 4111 may also include a plurality of second weak areas, and the plurality of second weak areas are arranged at intervals along the first direction Z in the area of the second weak part 4111 opposite to the first side surface 4120.

[0256] The third weak part 4112 may be continuous or discontinuous. For example, the third weak part 4112 extends along the first direction Z and connects to the first weak part 4110; the third weak part 4112 may also include a plurality of third weak areas, and the plurality of third weak areas are arranged at intervals along the first direction Z in the area of the third weak part 4112 opposite to the second side surface 4121.

[0257] The thickness of the second weak part 4111 may increase in a stepped manner or gradually along the direction close to the first connecting part 51. For the convenience of manufacturing, the thickness of the second weak part 4111 may increase gradually along the direction close to the first connecting part 51.

[0258] The thickness of the third weak part 4112 may increase in a stepped manner or gradually along the direction away from the first connecting part 51. For the convenience of manufacturing, the thickness of the third weak part 4112 may increase gradually along the direction away from the first connecting part 51.

[0259] In this way, the non-uniform thickness design of the second weak part 4111 and the third weak part 4112 enables the weak part 411 to have a gradient strength, which helps to more effectively withstand and disperse the expansion forces from different directions, helps to guide the expansion forces to be transmitted along a specific path, reduces the direct impact on the first weak part 4110, so that the weak part 411 can absorb the expansion forces and is not prone to functional failure; in addition, the weak part 411 with a gradually changing thickness can also make the weak part 411 easier to manufacture and form.

[0260] Please refer to Figure 7 , in some embodiments, the included angle between the first side surface 4120 and the bottom surface 4122 is greater than or equal to 135 degrees and less than 180 degrees.

[0261] Please refer to Figure 7 , in some embodiments, the included angle between the second side surface 4121 and the bottom surface 4122 is greater than or equal to 135 degrees and less than 180 degrees.

[0262] Please refer to Figure 7 , in some embodiments, both the included angle between the first side surface 4120 and the bottom surface 4122 and the included angle between the second side surface 4121 and the bottom surface 4122 are greater than or equal to 135 degrees and less than 180 degrees.

[0263] Among them, the included angle between the first side surface 4120 and the bottom surface 4122 can be any one of the point values such as 135 degrees, 140 degrees, 145 degrees, 150 degrees, 155 degrees, 160 degrees, 165 degrees, 170 degrees, 175 degrees, etc., or the range value between any two of them.

[0264] The included angle between the second side surface 4121 and the bottom surface 4122 can be any one of the point values such as 135 degrees, 140 degrees, 145 degrees, 150 degrees, 155 degrees, 160 degrees, 165 degrees, 170 degrees, 175 degrees, etc., or the range value between any two of them.

[0265] Specifically, the included angle between the first side surface 4120 and the bottom surface 4122 is denoted as the first included angle a1, and the included angle between the second side surface 4121 and the bottom surface 4122 is denoted as the second included angle a2. The first included angle a1 and the second included angle a2 can be the same or different.

[0266] In this way, within these included angle ranges, the weak part 411 has a relatively high absorption capacity for the expansion force, thereby effectively reducing the risk of fatigue cracking in the area where the first wall 111 is near the first connection part 51 due to the expansion of the electrode assembly 2, and further improving the service life of the battery cell 10.

[0267] In addition, the groove 412 can generally be manufactured by a stamping process. When stamping, a mold is required for processing. The mold usually includes two parts: an upper mold and a lower mold. The upper mold is used for stamping, and the lower mold is used to support the housing 11. During the stamping process, the housing 11 is fixed to the lower mold through a fixture or the fixing structure of the mold, and then the upper mold moves towards the housing 11 and applies pressure, so that the area of the housing 11 corresponding to the upper mold deforms to form the groove 412.

[0268] When the angle is greater than or equal to 135 degrees and less than 180 degrees, the groove 412 and the upper mold will not be stuck during the demolding process, so that the upper mold is more likely to separate from the groove 412 after processing the groove 412. Therefore, controlling the angle between 135 degrees and 180 degrees can facilitate the formation of the groove 412, reduce the manufacturing difficulty of the housing 11, and thus improve the processing accuracy of the housing 11 and the service life of the mold.

[0269] Please refer to Figure 8 , Figure 8 is a partial schematic diagram of the battery cell 10 provided by some other embodiments of the present application. In some embodiments, the buffer structure 410 includes a first convex portion 413 and a first concave portion 414. The first convex portion 413 and the first concave portion 414 are correspondingly arranged. The first convex portion 413 protrudes from the outer surface 420 of the main body portion 400, and the first concave portion 414 depresses outward from the inner surface 430 of the main body portion 400.

[0270] Specifically, the first convex portion 413 and the first concave portion 414 can be arranged along the first direction Z. Along the first direction Z, one end of the first convex portion 413 can be connected to one end of the first concave portion 414. The first convex portion 413 and the first concave portion 414 can form a curved structure. For example, the first convex portion 413 and the first concave portion 414 can form an "S" - shaped structure.

[0271] In this way, the first convex portion 413 and the first concave portion 414 can form a local buffer area, increasing the buffer path of the buffer structure 410 to disperse the expansion force, thereby reducing the expansion force directly acting on the first connecting portion 51. Therefore, the cooperation between the first convex portion 413 and the first concave portion 414 can reduce 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, and further improve the service life of the battery cell 10.

[0272] In some embodiments, the number of the first convex portions 413 is multiple, the number of the first concave portions 414 is multiple, and each first convex portion 413 is correspondingly provided with a first concave portion 414.

[0273] Specifically, the number of the first convex portions 413 can be two, three, four or even more. The number of the first concave portions 414 can be two, three, four or even more.

[0274] As an example, the first convex portion 413 can include a first sub - convex portion, a second sub - convex portion and a third sub - convex portion. The first concave portion 414 can include a first sub - concave portion, a second sub - concave portion and a third sub - concave portion. Along the first direction Z, the first sub - convex portion, the first sub - concave portion, the second sub - convex portion, the second sub - concave portion, the third sub - convex portion and the third sub - concave portion are connected in sequence.

[0275] In this way, the multiple first convex portions 413 and the corresponding first concave portions 414 can further increase the buffer path of the buffer structure 410, providing multiple areas for dispersing the expansion force, so as to achieve a more effective absorption of the expansion force, and further effectively reduce the expansion force directly acting on the first connecting portion 51.

[0276] Please refer to Figure 8 , in some embodiments, the buffer structure 410 includes a second convex portion 417 and a second concave portion 418. The second convex portion 417 and the second concave portion 418 are correspondingly arranged. The second convex portion 417 protrudes from the inner surface 430 of the main body portion 400, and the second concave portion 418 depresses inward from the outer surface 420 of the main body portion 400.

[0277] Specifically, the second convex portion 417 and the second concave portion 418 may be arranged along the second direction Y. Along the second direction Y, one end of the second convex portion 417 may be connected to one end of the second concave portion 418. The second convex portion 417 and the second concave portion 418 may form a curved structure. For example, the second convex portion 417 and the second concave portion 418 may form an "S" shaped structure.

[0278] In this way, the second convex portion 417 and the second concave portion 418 may form a local buffer area, increasing the buffer path of the buffer structure 410 to disperse the expansion force, thereby reducing the expansion force directly acting on the first connection portion 51. Therefore, the cooperation between the second convex portion 417 and the second concave portion 418 can reduce the risk of fatigue cracking in the area of the first wall 111 near the first connection portion 51 due to the expansion of the electrode assembly 2, and further improve the service life of the battery cell 10.

[0279] In some embodiments, the number of the second convex portions 417 is plural, the number of the second concave portions 418 is plural, and one second concave portion 418 is correspondingly arranged for each second convex portion 417.

[0280] Specifically, the number of the second convex portions 417 may be two, three, four or even more. The number of the second concave portions 418 may be two, three, four or even more.

[0281] As an example, the second convex portion 417 may include a fourth sub-convex portion, a fifth sub-convex portion and a sixth sub-convex portion. The second concave portion 418 may include a fourth sub-concave portion, a fifth sub-concave portion and a sixth sub-concave portion. Along the first direction Z, the fourth sub-convex portion, the fourth sub-concave portion, the fifth sub-convex portion, the fifth sub-concave portion, the sixth sub-convex portion and the sixth sub-concave portion are connected in sequence.

[0282] In this way, the plurality of second convex portions 417 and the corresponding second concave portions 418 may further increase the buffer path of the buffer structure 410, providing a plurality of areas for dispersing the expansion force, so as to achieve a more effective absorption of the expansion force, and further effectively reduce the expansion force directly acting on the first connection portion 51.

[0283] Please refer to Figure 6 , in some embodiments, along the first direction Z, the distance between the buffer structure 410 and the edge of the first connection portion 51 is H, and H satisfies: 0.3 mm ≤ H ≤ 7 mm. H may take any one of the point values such as 0.3 mm, 1.5 mm, 2 mm, 3 mm, 4 mm, 5.5 mm, 7 mm or the range value between any two of them.

[0284] In some embodiments, along the first direction Z, H satisfies: 1.5 mm ≤ H ≤ 4 mm. H may take any one of the point values such as 1.5 mm, 2.5 mm, 3.5 mm, 3.6 mm, 3.7 mm, 3.8 mm, 4 mm or the range value between any two of them.

[0285] Thus, within these numerical ranges, the buffer structure 410 can effectively absorb the expansion force, thereby reducing the expansion force directly acting on the first connection portion 51. The buffer structure 410 will not fatigue and crack together with the first connection portion 51 due to being close to the first connection portion 51, nor will it be unable to reduce the expansion force directly acting on the first connection portion 51 due to being far from the first connection portion 51.

[0286] Please refer to Figure 9 , Figure 9 is a schematic diagram of the electrode assembly 2 provided in some embodiments of the present application. In some embodiments, the electrode assembly 2 further includes a separator 24, and a separator 24 is disposed between the positive electrode plate 22 and the negative electrode plate 23;

[0287] The positive electrode plate 22 includes a positive electrode main body region 221 and a positive electrode tab 21a protruding from the positive electrode main body region 221. The positive electrode main body region 221 has a positive electrode active material layer 223. The negative electrode plate 23 includes a negative electrode main body region 231 and a negative electrode tab 21b protruding from the negative electrode main body region 231. The negative electrode main body region 231 has a negative electrode active material layer 233. Along the first direction Z, the positive electrode main body region 221 has a first end 2211 facing the end cover 12, the negative electrode main body region 231 has a second end 2311 facing the end cover 12, and the separator 24 has a third end 241 facing the end cover 12. The third end 241 is closer to the end cover 12 than the first end 2211 and the second end 2311.

[0288] Specifically, in this embodiment, the electrode assembly 22 can be a wound structure or a stacked structure.

[0289] The positive electrode plate 22 may include a positive electrode current collector 222 and a positive electrode active material layer 223. The positive electrode active material layer 223 is disposed on one or both surfaces of the positive electrode current collector 222 in its thickness direction.

[0290] Please refer to Figure 10 , Figure 11 and Figure 12 , Figure 10 is a partial schematic diagram of the battery cell 10 provided in some other embodiments of the present application, Figure 11 is a partial schematic diagram of the electrode assembly 2 provided in some embodiments of the present application, Figure 12FIG. 0 is a partial schematic view of the electrode assembly 2 provided by some other embodiments of the present application. The positive electrode tab 22 further includes an insulating layer 224. Insulating layers 224 are provided on both surfaces of the positive current collector 222 that are opposite to each other in the thickness direction. The insulating layer 224 and the positive active material layer 223 are arranged along the first direction Z. The insulating layer 224 is provided at the end of the positive active material layer 223. The part of the positive electrode tab 22 corresponding to the overall positive active material layer 223 and the insulating layer 224 is the positive electrode main body region 221. One end of the insulating layer 224 close to the end cap 12 forms the first end 2211 of the positive electrode main body region 221. The part of the positive current collector 222 that extends beyond the insulating layer 224 forms the positive electrode tab 21a.

[0291] In Figure 12 the illustrated embodiment, the positive electrode tab 22 is not provided with the insulating layer 224. The part of the positive electrode tab 22 corresponding to the positive active material layer 223 is the positive electrode main body region 221. One end of the positive active material layer 223 close to the end cap 12 forms the first end 2211 of the positive electrode main body region 221. The part of the positive current collector 222 that extends beyond the positive active material layer 223 forms the positive electrode tab 21a.

[0292] The negative electrode tab 23 may include a negative current collector 232 and a negative active material layer 233. The negative active material layer 233 is provided on one or both surfaces of the negative current collector 232 in its thickness direction. The part of the negative electrode tab 23 corresponding to the negative active material layer 233 is the negative electrode main body region 231. One end of the negative active material layer 233 close to the end cap 12 forms the second end 2311 of the negative electrode main body region 231. The part of the negative current collector 232 that extends beyond the negative active material layer 233 forms the negative electrode tab 21b.

[0293] It may be that the first end 2211 is flush with the second end 2311; as Figure 11 shown, it may also be that the first end 2211 is closer to the end cap 12 than the second end 2311 ( Figure 10 shown in); as Figure 12 shown, it may also be that the second end 2311 is closer to the end cap 12 than the first end 2211 ( Figure 10 shown in).

[0294] In this way, the separator 24 has a part that extends beyond the first end 2211 and the second end 2311, enhancing the insulation effect of the separator 24 between the positive electrode tab 22 and the negative electrode tab 23 and reducing the risk of the positive electrode tab 22 and the negative electrode tab 23 overlapping.

[0295] Please refer to Figure 10, in some embodiments, the separator 24 includes an overhanging region 242 that extends beyond the first end 2211 and the second end 2311 along the first direction Z. In the projection plane perpendicular to the second direction Y, the orthographic projection of the overhanging region 242 partially overlaps with the orthographic projection of the buffer structure 410.

[0296] Specifically, the overhanging region 242 is the part of the separator 24 that extends beyond both the first end 2211 of the positive electrode main body region 221 and the second end 2311 of the negative electrode main body region 231. It can be understood that, as Figure 11 shown, in the embodiment where the first end 2211 is closer to the end cap 12 than the second end 2311, the part of the separator 24 that extends beyond the first end 2211 is the overhanging region 242; as Figure 12 shown, in the embodiment where the second end 2311 is closer to the end cap 12 than the first end 2211, the part of the separator 24 that extends beyond the second end 2311 is the overhanging region 242.

[0297] As an example, in Figures 10 - 12 , the parts of the positive electrode tab 22, the negative electrode tab 23, and the separator 24 in the electrode assembly 2 that are located in the flat region 25 ( Figures 10 - 12 not shown) are stacked along the second direction Y.

[0298] In this way, this structure can increase the size of the buffer structure 410 along the first direction Z, improve the ability of the buffer structure 410 to absorb the swelling force, and further reduce the risk of fatigue cracking in the region of the first wall 111 near the first connection portion 51.

[0299] Please refer to Figure 10 , in some embodiments, in the projection plane perpendicular to the second direction Y, the orthographic projection of the positive electrode main body region 221 does not overlap with the orthographic projection of the buffer structure 410.

[0300] Please refer to Figure 10 , in some embodiments, in the projection plane perpendicular to the second direction Y, the orthographic projection of the negative electrode main body region 231 does not overlap with the orthographic projection of the buffer structure 410.

[0301] Please refer to Figure 10 , in some embodiments, in the projection plane perpendicular to the second direction Y, both the orthographic projection of the positive electrode main body region 221 and the orthographic projection of the negative electrode main body region 231 do not overlap with the orthographic projection of the buffer structure 410.

[0302] As an example, in the embodiment of Figures 10 - 12 , in the projection plane perpendicular to the second direction Y, the orthographic projection of the positive electrode main body region 221 does not overlap with the orthographic projection of the buffer structure 410, and the orthographic projection of the negative electrode main body region 23 does not overlap with the orthographic projection of the buffer structure 410.

[0303] Thus, if in the projection plane perpendicular to the second direction Y, the positive projection of the positive electrode main body region 221 does not overlap with the positive projection of the buffer structure 410, the housing 11 can provide a larger expansion space for the electrode assembly 2, reducing the risk that the expansion of the electrode assembly 2 directly applies an expansion force to the buffer, decreasing the deformation amount of the first wall 111, and further reducing the risk of fatigue cracking in the region of the first wall 111 near the first connection portion 51.

[0304] If in the projection plane perpendicular to the second direction Y, the positive projection of the negative electrode main body region 231 does not overlap with the positive projection of the buffer structure 410, the housing 11 can provide a larger expansion space for the electrode assembly 2, reducing the risk that the expansion of the electrode assembly 2 directly applies an expansion force to the buffer structure 410, decreasing the deformation amount of the first wall 111, and further reducing the risk of fatigue cracking in the region of the first wall 111 near the first connection portion 51.

[0305] Please refer to Figure 11 and Figure 12 , in some embodiments, the negative electrode tab 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, and the negative electrode active material layer 233 includes a negative electrode active material.

[0306] Specifically, the negative electrode active material layer 233 can be disposed on only one side of the negative electrode current collector 232, that is, the negative electrode active material layer 233 is disposed on only one surface of the negative electrode current collector 232 in the thickness direction; or the negative electrode active material layer 233 can be disposed on both opposite sides of the negative electrode current collector 232, that is, the negative electrode active material layer 233 is disposed on both opposite surfaces of the negative electrode current collector 232 in the thickness direction.

[0307] The negative electrode active material can include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate, etc.

[0308] Thus, by disposing the negative electrode active material layer 233 on at least one side of the negative electrode current collector 232, the content of the active material in the battery cell 10 can be increased, thereby improving the energy density of the battery.

[0309] Please refer to Figure 11 and Figure 12 , in some embodiments, the negative electrode active material layer 233 includes a negative electrode main body portion 2331 and a negative electrode thinning portion 2332, the negative electrode main body portion 2331 and the negative electrode thinning portion 2332 are arranged along the first direction Z, and along the first direction Z, the negative electrode thinning portion 2332 is disposed at one end of the negative electrode main body portion 2331 close to the end cap 12.

[0310] Specifically, the thickness of the negative electrode main body portion 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 portion 2331 close to the end cap 12 along the first direction Z, or the negative electrode thinning portions 2332 may be provided at both ends of the negative electrode main body portion 2331 along the first direction Z. The negative electrode main body portion 2331 may be a structure with uniform thickness or a non-uniform thickness structure, and the negative electrode thinning portion 2332 may be a structure with uniform thickness or a non-uniform thickness structure. If at least one of the negative electrode main body portion 2331 and the negative electrode thinning portion 2332 is 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 portion 2331, so as to achieve that the thickness of the negative electrode main body portion 2331 is greater than the thickness of the negative electrode thinning portion 2332.

[0311] As an example, the negative electrode main body portion 2331 is a structure with uniform thickness, and the thickness of the negative electrode thinning portion 2332 decreases along the direction from the negative electrode main body portion 2331 to the negative electrode thinning portion 2332.

[0312] In this way, the electrode assembly 2 has a larger expansion gap in the area corresponding to the negative electrode thinning portion 2332, and the force exerted on the first wall 111 by the area of the electrode assembly 2 corresponding to the negative electrode thinning portion 2332 after expansion is smaller, which can reduce the risk of fatigue cracking in the area of the first wall 111 near the first connection portion 51.

[0313] In some embodiments, in the projection plane perpendicular to the second direction Y, the positive projection of the negative electrode thinning portion 2332 and the positive projection of the buffer structure 410 are spaced apart along the first direction Z.

[0314] Specifically, it can be understood that 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 portion 2331 close to the end cap 12 does not overlap with the positive projection of the buffer structure 410.

[0315] In this way, the influence of the negative electrode thinning portion 2332 on the buffer structure 410 and the first connection portion 51 is relatively low, reducing the risk that the expansion of the electrode assembly 2 directly applies an expansion force to the buffer structure 410, and further reducing the risk of fatigue cracking in the area of the first wall 111 near the first connection portion 51.

[0316] In some embodiments, in the projection plane perpendicular to the second direction Y, the spacing dimension between the positive projection of the negative electrode thinning portion 2332 and the positive projection of the buffer structure 410 along the first direction Z is greater than or equal to 1 mm.

[0317] Specifically, 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 buffer structure 410 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 buffer structure 410 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.

[0318] Thus, in the projection plane perpendicular to the second direction Y, the orthographic projection of the negative electrode thinned portion 2332 is further away from the orthographic projection of the buffer structure 410 along the first direction Z, further reducing the impact of the negative electrode thinned portion 2332 on the buffer structure 410 .

[0319] 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 .

[0320] Specifically, the coating weight of the negative electrode active material layer 233233 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.

[0321] 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.

[0322] The single-sided coating weight of the negative electrode active material layer 233 is related to the swelling of the negative electrode active material layer 233. The single-sided coating weight of the negative electrode active material layer 233 is set at 90 mg / 1540 mm 2 ~170 mg / 1540 mm 2 , which can balance the requirements for high energy density of the battery cell 10 and the low swelling requirements of the negative electrode plate 23 to a certain extent, reduce the influence of the swelling of the negative electrode plate 23 on the first wall 111, and reduce the risk of fatigue cracking in the area of the first wall 111 near the first connection portion 51.

[0323] In some embodiments, the single-sided coating weight of the negative electrode active material layer 233 is 110 mg / 1540 mm 2 ~150 mg / 1540 mm 2 .

[0324] Specifically, the single-sided coating weight of the negative electrode active material layer 233 can take any one point value or the range value between any two of 110 mg / 1540 mm 2 , 115 mg / 1540 mm 2 , 120 mg / 1540 mm 2 , 125 mg / 1540 mm 2 , 130 mg / 1540 mm 2 , 135 mg / 1540 mm 2 , 140 mg / 1540 mm 2 , 145 mg / 1540 mm 2 , 150 mg / 1540 mm 2 etc.

[0325] In this way, this can further improve the energy density of the battery cell 10 and further slow down the swelling of the negative electrode plate 23.

[0326] In some embodiments, the porosity of the negative electrode plate 23 is 27% - 40%.

[0327] Specifically, the porosity of the negative electrode plate 23 can take any one point value or the range value between any two of 27%, 28%, 29%, 30%, 31%, 32%, 33%, x34%, 35%, 36%, 37%, 38%, 39%, 40%, etc.

[0328] The porosity of the negative electrode plate 23 can be the percentage of the pore volume in the negative electrode plate 23 to the total volume of the negative electrode plate 23. As an example, when the battery cell 10 is in the 0% state of charge, a double-sided coated negative electrode plate 23 is taken; the AccuPyc II 1340 true density meter is used to measure the porosity of the negative electrode plate 23 in accordance with the national standard GB / T 24586-2009.

[0329] In this way, it can provide space for the impurities generated by the side reactions of the negative electrode plate 23, slow down the swelling of the negative electrode plate 23, and reduce the impact of the swelling of the negative electrode plate 23 on the first wall 111.

[0330] In some embodiments, the negative electrode active material includes a silicon-based material, and the mass content of silicon element in the silicon-based material in the negative electrode active material is 0.3% to 10%.

[0331] In some embodiments, the mass content of silicon element in the silicon-based material in the negative electrode active material is 1% to 6%.

[0332] Specifically, the mass content of silicon element in the silicon-based material in the negative electrode active material can take any one of the point values such as 0.3%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10% or the range values between any two of them.

[0333] In this way, by controlling the content of silicon element within the range of 0.3% to 10%, the cycle stability and energy density of the battery cell 10 can be balanced, and the volume expansion problem of the silicon-based material during charge and discharge can be reduced.

[0334] By controlling the content of silicon element within the range of 1% to 6%, the cycle stability and energy density of the battery cell 10 can be further balanced, and the volume expansion problem of the silicon-based material during charge and discharge can be further reduced.

[0335] Please refer to Figure 11 and Figure 12 , in some embodiments, the positive electrode active material layer 223 includes a positive electrode main body portion 2231 and a positive electrode thinning portion 2232. The positive electrode main body portion 2231 and the positive electrode thinning portion 2232 are arranged along the first direction Z. Along the first direction Z, the positive electrode thinning portion 2232 is provided at one end of the positive electrode main body portion 2231 close to the end cover 12.

[0336] The thickness of the positive electrode main body portion 2231 is greater than that of the positive electrode thinned portion 2232. The positive electrode thinned portion 2232 may be provided only at one end of the positive electrode main body portion 2231 close to the end cap 12 along the first direction Z, or there may be positive electrode thinned portions 2232 at both ends of the positive electrode main body portion 2231 along the first direction Z. The positive electrode main body portion 2231 may be a structure with equal thickness or a non-uniform thickness structure, and the positive electrode thinned portion 2232 may be a structure with equal thickness or a non-uniform thickness structure. If at least one of the positive electrode main body portion 2231 and the positive electrode thinned portion 2232 is a non-uniform thickness structure, the maximum thickness of the positive electrode thinned portion 2232 may be less than or equal to the minimum thickness of the positive electrode main body portion 2231, so as to achieve that the thickness of the positive electrode main body portion 2231 is greater than that of the positive electrode thinned portion 2232.

[0337] As an example, the positive electrode main body portion 2231 has an equal-thickness structure, and the thickness of the positive electrode thinned portion 2232 decreases along the direction from the positive electrode main body portion 2231 to the positive electrode thinned portion 2232.

[0338] In this embodiment, a positive electrode thinned portion 2232 is provided at one end of the positive electrode main body portion 2231 close to the end cap 12, and the electrode assembly 2 has a larger expansion gap in the area corresponding to the positive electrode thinned portion 2232. The force exerted on the first wall 111 by the area of the electrode assembly 2 corresponding to the positive electrode thinned portion 2232 after expansion is smaller, which can reduce the risk of fatigue cracking in the area of the first wall 111 near the first connection portion 51.

[0339] Please refer to Figure 13 , Figure 13 which is a schematic structural diagram of the housing 11 provided in some embodiments of the present application. In some embodiments, the dimension of the buffer structure 410 along the third direction X is greater than the dimension of the buffer structure 410 along the first direction Z, and the first direction Z, the second direction Y, and the third direction X are non-coplanar and intersect pairwise.

[0340] Specifically, the dimension of the buffer structure 410 along the third direction X is the length of the buffer structure 410, the dimension of the buffer structure 410 along the first direction Z is the width of the buffer structure 410, and the length of the buffer structure 410 is greater than the width of the buffer structure 410, so that the buffer structure 410 is a long strip-shaped structure extending along the third direction X.

[0341] In this way, the dimension of the buffer structure 410 along the third direction X is larger, so that the buffer structure 410 has a stronger ability to absorb the expansion force, further reducing the risk of fatigue cracking in the area of the first wall 111 near the first connection portion 51.

[0342] Please refer to Figure 14 , Figure 14It is a schematic structural diagram of the housing 11 provided by other embodiments of the present application. In some embodiments, the buffer structure 410 passes through the middle section of the first wall 111, the middle section is perpendicular to the third direction X, and the distances from the middle section along the third direction X to both ends of the first wall 111 are equal.

[0343] Specifically, the buffer structure 410 has opposite ends along the third direction X. The buffer structure 410 passes through the middle section of the first wall 111, so that the middle section of the first wall 111 is located between the opposite ends of the buffer structure 410 along the third direction X. The distances from the opposite ends of the buffer structure 410 along the third direction X to the middle section may be equal or unequal. If the distances from the opposite ends of the buffer structure 410 along the third direction X to the middle section of the first wall 111 are equal, it indicates that the buffer structure 410 is a symmetric structure symmetrically arranged with respect to the middle section of the first wall 111. It should be noted that the middle section of the first wall 111 is a virtual plane and is not shown in the figure.

[0344] As an example, in Figure 14 the illustrated embodiment, the distances from the opposite ends of the buffer structure 410 along the third direction X to the middle section of the first wall 111 are equal.

[0345] In this way, when the first wall 111 is subjected to the expansion force of the electrode assembly 2 of the battery cell 10, the deformation amount of the middle region of the first wall 111 along the third direction X is larger, and the middle region of the first wall 111 along the third direction X is more likely to fatigue and crack. Since the buffer structure 410 passes through the middle section of the first wall 111, the expansion force received by at least the middle region of the first wall 111 along the third direction X is reduced, reducing the risk of fatigue cracking of the middle region of the first wall 111 near the first connection portion 51 along the third direction X.

[0346] Please refer to Figure 14 , in some embodiments, the dimension of the buffer structure 410 along the third direction X is L1, and the dimension of the first wall 111 along the third direction X is L, and 0.4 ≤ L1 / L ≤ 0.9.

[0347] Specifically, L1 / L can take any one of the point values such as 0.4, 0.42, 0.45, 0.48, 0.5, 0.52, 0.55, 0.58, 0.6, 0.7, 0.5, 0.8, 0.85, 0.9 or the range value between any two of them.

[0348] In this way, when 0.4 ≤ L1 / L, the proportion of the dimension of the buffer structure 410 in the first wall 111 along the third direction X is relatively large, which makes the expansion force received by the middle region of the first wall 111 along the third direction X smaller, reducing the risk of fatigue cracking of the middle region of the first wall 111 near the first connection portion 51 along the third direction X.

[0349] When L1 / L ≤ 0.9, the dimension of the buffer structure 410 along the third direction X in the first wall 111 accounts for a relatively small proportion, reducing the waste generated in manufacturing the buffer structure 410 and lowering the production cost.

[0350] Therefore, the ratio of the dimension of the buffer structure 410 along the third direction X to the dimension of the first wall 111 along the third direction X is set to 0.4 - 0.9. While enabling the buffer structure 410 to have sufficient ability to absorb the expansion force, it reduces the waste generated in manufacturing the buffer structure 410, taking into account both the requirement for the buffer structure 410's ability to absorb the expansion force and the economic requirement.

[0351] Please refer to Figure 14 , in some embodiments, the buffer structure 410 has opposite fourth ends 11113a and fifth ends 11113b along the third direction X, the first wall 111 has opposite sixth ends 1113 and seventh ends 1114 along the third direction X, the fourth end 11113a is close to the sixth end 1113, the fifth end 11113b is close to the seventh end 1114, the dimension of the first wall 111 along the third direction X is L, the minimum distance between the fourth end 11113a and the sixth end 1113 along the third direction X is L2, and the minimum distance between the fifth end 11113b and the seventh end 1114 along the third direction X is L3; L2 / L ≤ 0.3; and / or, L3 / L ≤ 0.3.

[0352] Specifically, it can be understood that along the third direction X, the sixth end 1113a is closer to the fourth end 11113a than the seventh end 1114b, and the seventh end 1114b is closer to the fifth end 11113b than the sixth end 1113a.

[0353] It can be L2 = L3; it can also be L2 > L3 or L2 < L3.

[0354] L2 / L can take any one of the point values such as 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 the range values between any two of them.

[0355] L3 / L can take any one of the point values such as 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 the range value between any two of them.

[0356] Thus, if L2 / L ≤ 0.3, the proportion of the minimum distance between the fourth end 11113a and the sixth end 1113 in the dimension of the first wall 111 along the third direction X is reduced, so that more regions of the fourth end 11113a along the third direction X are subjected to reduced expansion force, further reducing the risk of fatigue cracking in the region of the first wall 111 near the first connection portion 51.

[0357] If L3 / L ≤ 0.3, the proportion of the minimum distance between the fifth end 11113b and the seventh end 1114 in the dimension of the first wall 111 along the third direction X is reduced, so that more regions of the first wall 111 along the third direction X are subjected to reduced expansion force, further reducing the risk of fatigue cracking in the region of the first wall 111 near the first connection portion 51.

[0358] In some embodiments, 100 mm ≤ L ≤ 450 mm.

[0359] Specifically, L can take any one of the point values such as 100 mm, 120 mm, 150 mm, 180 mm, 200 mm, 220 mm, 250 mm, 260 mm, 280 mm, 300 mm, 310 mm, 320 mm, 350 mm, 390 mm, 400 mm, 410 mm, 420 mm, 430 mm, 440 mm, 450 mm, etc., or the range value between any two of them.

[0360] Thus, within this numerical range, along the third direction X, the first wall 111 has a relatively large dimension, which helps the buffer structure 410 to be arranged, thereby facilitating the buffer structure 410 to absorb the expansion force.

[0361] Please refer to Figure 13 and Figure 14 , in some embodiments, the housing 11 includes a corner wall 113, and both ends of the first wall 111 along the third direction X are connected to the corner wall 113; at least one end of the buffer structure 410 along the third direction X is spaced apart from the corner wall 113.

[0362] Specifically, along the third direction X, the buffer structure 410 has opposite ends. One end of the buffer structure 410 may extend to a corner wall 113, while the other end does not extend to another corner wall 113. Alternatively, neither end of the buffer structure 410 extends to the corner wall 113, so that at least one end of the buffer structure 410 along the third direction X does not contact the corner wall 113.

[0363] As an example, in Figures 13 - 14 the illustrated embodiment, along the third direction X, one end of the buffer structure 410 does not contact the corner wall 113 at one end of the first wall 111, and the other end of the buffer structure 410 does not contact the corner wall 113 at the other end of the first wall 111.

[0364] Thus, since at least one end of the buffer structure 410 along the third direction X does not contact the corner wall 113, this can reduce the waste generated during the manufacture of the buffer structure 410 and lower the production cost.

[0365] Please refer to Figure 15 , Figure 15 which is a schematic structural diagram of the battery cell 10 provided in some other embodiments of the present application. In some embodiments, the corner wall 113 is welded to the end cap 12 to form a second connection portion 52.

[0366] The second connection portions 52 may correspond to the corner walls 113 one by one. The second connection portion 52 is the part with a welding mark formed after the end cap 12 and the corner wall 113 are welded, and may be the part where the end cap 12 and the corner wall 113 are welded and fused together as the second connection portion 52. A part of the second connection portion 52 is formed on the end cap 12, and another part of the second connection portion 52 is formed on the corner wall 113. The corner wall 113 and the end cap 12 may form the second connection portion 52 by seam welding or by penetration welding. Both the second connection portion 52 and the first connection portion 51 are parts of the connection portion 5.

[0367] Please refer to Figure 10 , in some embodiments, the main body portion 400 includes a first region 440 and a second region 450 arranged along the first direction Z. The thickness of the first region 440 is greater than the thickness of the second region 450, and the buffer structure 410 is located between the first region 440 and the second region 450.

[0368] Specifically, the first region 440 may be a region where the thickness of the first wall 111 is thickened. The first region 440 is thicker than the second region 450. The second region 450 may be a part of the first wall 111 along the first direction Z on the side of the first region 440 away from the first connection portion 51. The first region 440 and the first connection portion 51 may be directly connected or indirectly connected; the first region 440 and the buffer structure 410 may be directly connected or indirectly connected.

[0369] The first area 440 may be a structure with uniform thickness or a non-uniform thickness structure; the second area 450 may be a structure with uniform thickness or a non-uniform thickness structure. If at least one of the first area 440 and the second area 450 is a non-uniform thickness structure, the maximum thickness of the second area 450 may be less than or equal to the minimum thickness of the first area 440, so that the thickness of the first area 440 is greater than the thickness of the second area 450.

[0370] Along the first direction Z, the buffer structure 410 may include opposite ends, one of which may be connected to the first area 440 and the other may be connected to the second area 450.

[0371] In this way, the first area 440 with a larger thickness can enhance the resistance of the first connecting portion 51 to the expansion force. Cooperating with the buffer structure 410 can further reduce 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, thereby improving the service life of the battery cell 10.

[0372] Please refer to Figure 10 , in some embodiments, the first area 440 includes a first portion 441 and a second portion 442 arranged along the first direction Z. The second portion 442 is located between the first portion 441 and the buffer structure 410, and the thickness of the first portion 441 is greater than the thickness of the second portion 442.

[0373] Specifically, the first portion 441, the second portion 442 and the buffer structure 410 are arranged in sequence along the first direction Z, and the first portion 441 transitions to the buffer structure 410 through the second portion 442. The first portion 441 may be a structure with uniform thickness or a non-uniform thickness structure; the second portion 442 may be a structure with uniform thickness or a non-uniform thickness structure.

[0374] If at least one of the first portion 441 and the second portion 442 is a non-uniform thickness structure, the maximum thickness of the second portion 442 may be less than or equal to the minimum thickness of the first portion 441, so that the thickness of the first portion 441 is greater than the thickness of the second portion 442.

[0375] In this way, the area of the first area 440 close to the first connecting portion 51 is more likely to form a heat affected zone, and this area is more likely to have fatigue cracking. However, since the second portion 442 connects the first portion 441 and the buffer structure 410, and the thickness of the first portion 441 is greater than the thickness of the second portion 442, the thicker first portion 441 in the first area 440 is closer to the first connecting portion 51, which can effectively weaken the influence of the heat affected zone on the first area 440 and reduce the risk of fatigue cracking in the area of the first wall 111 near the first connecting portion 51. In addition, since the thickness of the second portion 442 is less than the thickness of the first portion 441, the material used in the first area 440 can be reduced, and the production cost is lowered.

[0376] Please refer to Figure 10 , in some embodiments, the thickness of the second portion 442 decreases along the direction from the end cap 12 towards the electrode assembly 2.

[0377] Specifically, the direction from the end cap 12 towards the electrode assembly 2 is consistent with the direction in which the first portion 441 points along the first direction Z towards the buffer structure 410.

[0378] The thickness of the second portion 442 can decrease in a segmented manner or gradually along the direction from the end cap 12 towards the electrode assembly 2. In order to reduce the manufacturing cost of the second portion 442, the thickness of the second portion 442 can decrease gradually along the direction from the end cap 12 towards the electrode assembly 2.

[0379] It can be understood that the second portion 442 has a non-uniform thickness structure. As an example, the thickness of the second portion 442 gradually decreases along the direction from the end cap 12 towards the electrode assembly 2. It can be that at least one of the inner surface and the outer surface of the second portion 442 is an inclined surface to achieve the gradual decrease of the thickness of the second portion 442 along the direction from the end cap 12 towards the electrode assembly 2.

[0380] As an example, in Figure 10 the illustrated embodiment, the first portion 441 has a uniform thickness structure, and the inner surface and the outer surface of the first portion 441 are parallel. The outer surface of the second portion 442 is coplanar with the outer surface of the first portion 441, and the inner surface of the second portion 442 is connected to the inner surface of the first portion 441.

[0381] In this way, on the one hand, this can reduce the influence of the second portion 442 on the electrode assembly 2 and reduce the risk of interference between the second portion 442 and the electrode assembly 2.

[0382] On the other hand, this makes the strengthening effect of the second portion 442 increase along the direction from the electrode assembly 2 towards the end cap 12, so that the area of the second portion 442 close to the first portion 441 has a good strengthening effect even under the influence of the first connecting portion 51, and reduces the risk of fatigue cracking of the first wall 111 in the second portion 442.

[0383] On the other hand, through the second portion 442, the transition between the first portion 441 and the second region 450 can be achieved, reducing stress concentration.

[0384] In some embodiments, the Vickers hardness of at least part of the first region 440 is less than the Vickers hardness of the second region 450.

[0385] Specifically, it can be that the Vickers hardness of the region of the first region 440 close to the first connecting portion 51 is less than the Vickers hardness of the second region 450.

[0386] It can be understood that when the first wall 111 is subjected to the expansion force, the first region 440 with a lower hardness may first respond to the overload through plastic deformation, while the second region 450 with a higher hardness may first develop cracks. Therefore, the risk of fatigue cracking in the first region 440 is relatively low.

[0387] Please refer to Figure 9 and Figure 16 , Figure 16 FIG. [FIG. ID] is a schematic diagram of the electrode assembly 2 provided in some other embodiments of the present application. In some embodiments, the electrode assembly 2 has a flat region 25, and 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 are stacked along the second direction Y.

[0388] Specifically, the flat region 25 is the flat part of the electrode assembly 2. The portion of the positive electrode tab 22 located in the flat region 25 is substantially flat, and the portion of the negative electrode tab 23 located in the flat region 25 is substantially flat. As an example, both 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 are in a flat plate structure.

[0389] Please refer to Figure 17 , Figure 17 FIG. [FIG. ID] is a schematic structural diagram of the electrode assembly 2 provided in some embodiments of the present application. If the electrode assembly 2 is a wound structure, the electrode assembly 2 is a wound electrode assembly 2, and a part of the electrode assembly 2 can be the flat region 25.

[0390] Please refer to Figure 18 , Figure 18 FIG. [FIG. ID] is a schematic structural diagram of the electrode assembly 2 provided in some other embodiments of the present application. If the electrode assembly 2 is a stacked structure, the electrode assembly 2 is a stacked electrode assembly 2, and the entire electrode assembly 2 can be the flat region 25. 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.

[0391] In this way, the second direction Y is the same as 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. The expansion amount of the electrode assembly 2 expanding along the second direction Y during cycling is larger, and the first wall 111 is more affected by the expansion of the electrode assembly 2. However, since the buffer structure 410 can absorb the expansion force, the expansion force on the region of the first wall 111 near the first connection portion 51 is reduced, and the risk of fatigue cracking of the first wall 111 near the first connection portion 51 due to the expansion of the electrode assembly 2 is reduced.

[0392] Please refer to Figure 17 and Figure 18, in some embodiments, the electrode assembly 2 includes adjacent first surface 27 and second surface 28. The first surface 27 is perpendicular to the second direction Y, the area of the first surface 27 is larger than that of the second surface 28, and the first surface 27 and the first wall 111 are oppositely arranged along the second direction Y.

[0393] Specifically, 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 adjacent to the first surface 27. The first surface 27 faces the first wall 111 along the second direction Y. The first surface 27 can be a flat surface. The first surface 27 can be the surface with the largest area among the outer surfaces of the electrode assembly 2, or it can not be the surface with the largest area among the outer surfaces of the electrode assembly 2. The second surface 28 can be a flat surface or at least partially an arc surface. It should be noted that the first surface 27 is substantially perpendicular to the second direction Y, and it should also be understood that the first surface 27 is perpendicular to the second direction Y.

[0394] As an example, both the first surface 27 and the second surface 28 are two. The two first surfaces 27 are oppositely arranged along the second direction Y, the two second surfaces 28 are oppositely arranged along the third direction X. The positive electrode tab 21a and the negative electrode tab 21b protrude from the surface of the electrode assembly 2 along the first direction Z. The outermost part of the electrode assembly 2 along the second direction Y is the separator 24. The first surface 27 is formed on the separator 24. The first direction Z, the second direction Y, and the third direction X are perpendicular to each other pairwise.

[0395] In this way, the area of the first surface 27 is larger than that of the second surface 28, so that the first wall 111 in the housing 11 that is oppositely arranged with the first surface 27 receives a greater expansion force. Since the buffer structure 410 can absorb the expansion force, the expansion force received by the area of the first wall 111 near the first connecting portion 51 is reduced, and the risk of fatigue cracking of the first wall 111 near the first connecting portion 51 due to the expansion of the electrode assembly 2 is reduced.

[0396] Please refer to Figure 17 and Figure 18 , in some embodiments, the first surface 27 is the surface with the largest area among the outer surfaces of the electrode assembly 2.

[0397] Specifically, 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 that there is only one first surface 27 in the electrode assembly 2. It can be understood that the first surface 27 of the electrode assembly 2 can be one or two.

[0398] As an example, in Figure 17In the illustrated embodiment, the electrode assembly 2 has a wound structure, the electrode assembly 2 is flat, the electrode assembly 2 includes six surfaces, and among the six surfaces, the two surfaces oppositely arranged along the second direction Y have the largest areas, and both of these two surfaces are the first surfaces 27.

[0399] In Figure 18 In the illustrated embodiment, the electrode assembly 2 has a stacked structure, the electrode assembly 2 is generally cuboid-shaped, the electrode assembly 2 includes six surfaces, and among the six surfaces, the two surfaces oppositely arranged along the second direction Y have the largest areas, and both of these two surfaces are the first surfaces 27.

[0400] Thus, the first wall 111 disposed opposite to the first surface 27 in the housing 11 is subjected to the greatest expansion force. Since the buffer structure 410 can absorb the expansion force, the expansion force on the region of the first wall 111 near the first connecting portion 51 is reduced, and the risk of fatigue cracking of the first wall 111 near the first connecting portion 51 due to the expansion of the electrode assembly 2 is reduced.

[0401] Please refer to Figure 9 and Figure 17 , in some embodiments, the electrode assembly 2 has a wound structure, the electrode assembly 2 further has a corner region 26, the corner region 26 is provided at at least one end of the straight region 25 along the third direction X, and the first direction Z, the second direction Y, and the third direction X are not coplanar and intersect pairwise;

[0402] The outer surface of the straight region 25 includes the first surface 27, the outer surface of the corner region 26 includes the second surface 28, and at least a part of the second surface 28 is an arc surface.

[0403] Specifically, the corner region 26 may be provided at only one end of the straight region 25 along the third direction X, or may be provided at both opposite ends of the straight region 25 along the third direction X. The first direction Z, the second direction Y, and the third direction X are not coplanar, and any two of the first direction Z, the second direction Y, and the third direction X may be provided at an acute angle, a right angle, or an obtuse angle. The first surface 27 may be a part of the outer surface of the straight region 25, the second surface 28 may be a part of the outer surface of the corner region 26, the second surface 28 may be an integral arc surface, or only a part thereof may be an arc surface.

[0404] As an example, the positive electrode plate 22, the separator 24, and the negative electrode plate 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 pairwise, and the corner regions 26 are provided at both ends of the straight region 25 along the third direction X.

[0405] The portions of the positive electrode tab 22, the negative electrode tab 23, and the separator 24 located in the corner region 26 are in a bent state. The portion of the positive electrode tab 22 located in the corner region 26 can be at least partially arc-shaped, the portion of the negative electrode tab 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.

[0406] Along the winding direction of the electrode assembly 2, the outermost layer of the electrode assembly 2 is the separator 24. Both the first surface 27 and the second surface 28 are parts of the outer surface of the outermost layer of the electrode assembly 2. The first surface 27 is a flat surface, and the second surface 28 is an arc surface. The axis of the arc surface extends along the first direction Z.

[0407] Along the second direction Y, the surfaces on both sides of the flat region 25 are both the first surface 27; along the third direction X, the surface on one side of one corner region 26 facing away from the other corner region 26 is one second surface 28, and the surface on one side of the other corner region 26 facing away from one corner region 26 is the other second surface 28.

[0408] Thus, for the wound electrode assembly 2, the expansion amount of the flat region 25 expanding in the second direction Y is larger. Since the buffer structure 410 can absorb the expansion force, the expansion force received by the region of the first wall 111 near the first connection portion 51 is reduced, and the risk of fatigue cracking of the first wall 111 near the first connection portion 51 due to the expansion of the electrode assembly 2 is reduced.

[0409] Please refer to Figure 16 and Figure 18 , in some embodiments, the electrode assembly 2 is a stacked structure. The flat region 25 includes a plurality of positive electrode tabs 22 and a plurality of negative electrode tabs 23. The plurality of positive electrode tabs 22 and the plurality of negative electrode tabs 23 are stacked along the second direction Y, and the first surface 27 is perpendicular to the second surface 28.

[0410] Specifically, as an example, a plurality of positive electrode tabs 22, a plurality of negative electrode tabs 23, and a plurality of separators 24 are stacked along the second direction Y to form a stacked structure. The positive electrode tabs 22 and the negative electrode tabs 23 are completely located in the flat region 25. A separator 24 is provided between adjacent positive electrode tabs 22 and negative electrode tabs 23. The separator 24 extends beyond the two ends of the positive electrode tab 22 and the two ends of the negative electrode tab 23 along the third direction X. The extended portions of the plurality of separators 24 are connected to form an integral portion, and the second surface 28 is formed on this integral portion. Along the second direction Y, all the positive electrode tabs 22 and all the negative electrode tabs 23 are between the two outermost separators 24, and the outer surfaces of these two separators 24 are both the first surface 27.

[0411] It should be noted that the first surface 27 is substantially perpendicular to the second surface 28, which should also be understood as the first surface 27 being perpendicular to the second surface 28. For example, the angle formed by the first surface 27 and the second surface 28 within the range of 85° to 95° can be understood as the first surface 27 being perpendicular to the second surface 28.

[0412] Thus, for the stacked electrode assembly 2, the expansion amount of the electrode assembly 2 in the stacking direction of the positive electrode sheet 22 and the negative electrode sheet 23 is larger. Since the buffer structure 410 can absorb the expansion force, the expansion force received by the area of the first wall 111 near the first connection portion 51 is reduced, and the risk of fatigue cracking of the first wall 111 near the first connection portion 51 due to the expansion of the electrode assembly 2 is lowered.

[0413] Please refer to Figure 13 , in some embodiments, the first wall 111 is the wall with the largest outer surface area in the housing 11.

[0414] Specifically, it should be noted that the first wall 111 being the wall with the largest outer surface area in the housing 11 does not limit the first wall 111 in the housing 11 to be only one. It can be understood that the wall with the largest outer surface area in the housing 11 can be one or two.

[0415] Thus, the wall with the largest outer surface area in the housing 11 is more likely to deform after receiving the expansion force of the electrode assembly 2. Since the first wall 111 is the wall with the largest outer surface area in the housing 11, the risk of fatigue cracking of the first wall 111 near the first connection portion 51 due to the expansion of the electrode assembly 2 is relatively low.

[0416] Please refer to Figure 3 and Figure 13 , in some embodiments, the housing 11 includes two first walls 111. Along the second direction Y, the two first walls 111 are arranged oppositely, and the electrode assembly 2 is located between the two first walls 111.

[0417] Specifically, as an example, in the Figure 13 illustrated embodiment, the housing 11 is in the shape of a cuboid. The housing 11 may include two first walls 111 and two second walls 112. The two first walls 111 are arranged oppositely along the second direction Y, and the two second walls 112 are arranged oppositely along the third direction X. The outer surface area of the first wall 111 is larger 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.

[0418] Thus, this reduces the risk of fatigue cracking of the two first walls 111 near the first connection portion 51 due to the expansion of the electrode assembly 2.

[0419] Please refer toFigure 19 and Figure 20 , Figure 19 FIG. Figure 19 is a partial schematic view of the battery cell 10 provided in some embodiments of the present application, Figure 20 and Figure 19 FIG. Figure 19 is an enlarged view of part C of the battery cell 10. In some embodiments, the first wall 111 further includes a transition region 1117. The transition region 1117 is located between the main body portion 400 and the first connection portion 51 along the first direction Z. The transition region 1117 is connected to the first connection portion 51. A connection interface 511 is formed at the connection position between the transition region 1117 and the first connection portion 51. The connection interface 511 has a connection position 5111 closest to the main body portion 400 along the first direction Z. The connection position 5111 is located at one end of the main body portion 400 close to the opening along the first direction Z.

[0420] Specifically, the transition region 1117 may be a portion of the first wall 111 connected between the first connection portion 51 and the main body portion 400. The transition region 1117 may be a structure with a uniform thickness or a non-uniform thickness structure. As an example, in the embodiments shown in Figure 19 and Figure 20 FIG. Figure 20 , the thickness of the transition region 1117 gradually decreases along the direction from the second region 450 to the first region 440.

[0421] The connection interface 511 is formed at the connection position between the transition region 1117 and the first connection portion 51. The transition region 1117 and the first connection portion 51 are demarcated at the connection interface 511. The connection interface 511 may be a plane or a curved surface.

[0422] The main body portion 400 and the transition region 1117 are demarcated by a demarcation surface U. The demarcation surface U is a virtual plane. The demarcation surface U passes through the connection position 5111. The demarcation surface U is perpendicular to the first direction Z. The transition region 1117 and the first connection portion 51 are located above the demarcation surface U, and the main body portion 400 is located below the demarcation surface U.

[0423] In this way, the transition region 1117 is connected to the first connection portion 51 to form the connection interface 511, so that the transition region 1117 and the first connection portion 51 have a sufficiently large contact area, improving the firmness after welding the first wall 111 and the end cover 12.

[0424] Please refer to Figure 20 , in some embodiments, at least a part of the connection interface 511 extends obliquely with respect to the second direction Y.

[0425] Specifically, the connection interface 511 may extend obliquely as a whole with respect to the second direction Y, or a part of the connection interface 511 may extend obliquely with respect to the second direction Y.

[0426] It can be understood that the extending direction of the connecting interface 511 in the part extending obliquely with respect to the second direction Y is not parallel to the second direction Y.

[0427] In this way, after the end cap 12 and the first wall 111 are welded, the first connecting portion 51 will shrink during solidification, and the first connecting portion 51 will generate tensile stress on the transition region 1117. When the first wall 111 is subjected to the expansion force of the electrode assembly 2, the first wall 111 will deform, and the transition region 1117 will generate tensile stress on the first connecting portion 51. Since the connecting interface 511 extends obliquely at least partially with respect to the second direction Y, near the part where the connecting interface 511 extends obliquely with respect to the second direction Y, the tensile stress generated by the shrinkage of the first connecting portion 51 on the transition region 1117 and the tensile stress generated by the deformation of the first wall 111 on the first connecting portion 51 are not on the same straight line, reducing the risk of fatigue cracking in the region of the transition region 1117 near the connecting interface 511.

[0428] Please refer to Figure 20 , in some embodiments, the connecting interface 511 includes a first interface 5112, and the first interface 5112 extends obliquely from the connecting position 5111 in the direction close to the end cap 12. Along the second direction Y, at least part of the transition region 1117 is located between the first interface 5112 and the end cap 12.

[0429] Specifically, it can be understood that the first interface 5112 extends obliquely with respect to the second direction Y. The first interface 5112 can be a plane or a curved surface.

[0430] The connecting position 5111 is the lowest position (the position closest to the main body portion 400) of the first interface 5112, and the first interface 5112 extends obliquely from the connecting position 5111 in the direction close to the end cap 12, that is, the first interface 5112 extends obliquely upward from the connecting position 5111 in the direction close to the end cap 12.

[0431] Along the second direction Y, the transition region 1117 can be entirely located between the first interface 5112 and the end cap 12, or only a part of the transition region 1117 can be located between the first interface 5112 and the end cap 12.

[0432] In this way, the first connecting portion 51 plays a protective role on the transition region 1117. When the first wall 111 is subjected to the expansion force of the electrode assembly 2, the deformation of the transition region 1117 during the force application process is blocked by the first connecting portion 51, reducing the risk of fatigue cracking in the region of the transition region 1117 near the first interface 5112.

[0433] Please refer to Figure 20 , in some embodiments, the first interface 5112 is connected to the outer surface 420 of the main body portion 400 at the connecting position 5111.

[0434] Specifically, as an example, the first interface 5112 intersects the outer surface 420 of the main body 400 at a first straight line that extends along the third direction X, and the position where the first straight line is located is the connection position 5111. The transition region 1117 is generally triangular.

[0435] Thus, since the first interface 5112 is in a directly connected state with the main body 400, the main body 400 and the first connection portion 51 are closer along the first direction Z, further reducing the risk of fatigue cracking in the region of the first wall 111 near the first connection portion 51 due to the expansion of the electrode assembly 2.

[0436] Please refer to Figure 21 and Figure 22 , Figure 21 which is a partial schematic view of the battery cell 10 provided in some other embodiments of the present application, Figure 22 and Figure 21 is an enlarged view of part D of the battery cell 10. In some embodiments, the connection interface 511 includes a second interface 5113 that extends obliquely away from the end cap 12 from the connection position 5111. Along the second direction Y, at least a part of the transition region 1117 is located on the side of the second interface 5113 facing away from the end cap 12.

[0437] Specifically, it can be understood that the second interface 5113 extends obliquely with respect 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 part of the first connection portion 51 is located between the second interface 5113 and the end cap 12.

[0438] The connection position 5111 is the lowest position (the position closest to the main body 400) of the second interface 5113, and the second interface 5113 extends obliquely away from the end cap 12 from the connection position 5111, that is, the second interface 5113 extends obliquely upward away from the end cap 12 from the connection position 5111.

[0439] Along the second direction Y, the entire transition region 1117 can be located on the side of the second interface 5X13 facing away from the end cap 12, or only a part of the transition region 1117 can be located on the side of the second interface 5113 facing away from the end cap 12.

[0440] Thus, the transition region 1117 restricts the first connection portion 51, reducing the risk of the first connection portion 51 falling off.

[0441] Please refer to Figure 22 . In some embodiments, the second interface 5113 is connected to the inner surface 430 of the main body 400 at the connection position 5111.

[0442] Specifically, as an example, the second interface 5113 intersects the inner surface 430 of the main body 400 at a first straight line, which extends along the third direction X. The first straight line is located at the connection position 5111. The transition area 1117 is substantially triangular.

[0443] In this way, the main body 400 and the first connecting part 51 are in a directly connected state, so that the main body 400 and the first connecting part 51 are closer along the first direction Z, further reducing the risk of fatigue cracking of the area of the first wall 111 near the first connecting part 51 due to expansion of the electrode assembly 2.

[0444] In some embodiments, the Vickers hardness of the transition region 1117 is less than the Vickers hardness of the main body portion 400 .

[0445] In some embodiments, the Vickers hardness of the transition region 1117 is less than the Vickers hardness of the first connecting portion 51 .

[0446] In some embodiments, the Vickers hardness of the transition region 1117 is less than the Vickers hardness of the main body 400 , and the Vickers hardness of the transition region 1117 is less than the Vickers hardness of the first connection portion 51 .

[0447] As an example, the Vickers hardness of the main body portion 400 is smaller than the Vickers hardness of the first connection portion 51 .

[0448] Thus, if the Vickers hardness of the transition region 1117 is lower than the Vickers hardness of the main body 400, the transition region 1117 with the lower Vickers hardness is connected to the first connecting portion 51. This can alleviate the rigid pulling 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 transition region 1117 is lower than the Vickers hardness of the first connecting portion 51, the transition region 1117 is more easily deformed than the first connecting portion 51, thereby alleviating the rigid pulling 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.

[0449] Please refer to Figure 16 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.

[0450] 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 .

[0451] In this way, the laminated electrode assembly 2 has a more compact structure and a stronger ability to resist extrusion.

[0452] Please refer toFigure 16 , in some embodiments, the number of negative electrode plates 23 is greater than the number of positive electrode plates 22, and one positive electrode plate 22 is arranged between two adjacent negative electrode plates 23.

[0453] As an example, there is one more negative electrode plate 23 than positive electrode plate 22.

[0454] In this way, by arranging the positive electrode plate 22 between adjacent negative electrode plates 23, the transmission distance of lithium ions inside the battery cell 10 can be reduced, and more lithium ion transmission paths can be provided, thereby improving the charge and discharge efficiency of the battery cell 10.

[0455] In some embodiments, each negative electrode plate 23 is provided with a negative electrode tab 21b.

[0456] In some embodiments, each positive electrode plate 22 is provided with a positive electrode tab 21a.

[0457] In some embodiments, each negative electrode plate 23 is provided with a negative electrode tab 21b, and each positive electrode plate 22 is provided with a positive electrode tab 21a.

[0458] Specifically, the number of negative electrode tabs 21b can be one or more. When the number of negative electrode tabs 21b is multiple, the multiple negative electrode tabs 21b can be located on the same side of the negative electrode plate 23 or on different sides of the negative electrode plate 23. The number of positive electrode tabs 21a can be one or more. When the number of positive electrode tabs 21a is multiple, the multiple positive electrode tabs 21a can be located on the same side of the positive electrode plate 22 or on different sides of the positive electrode plate 22.

[0459] In this way, the tabs 21 can simplify the electrical connection between the battery cell 10 and the external circuit.

[0460] Please refer to Figure 3 , in some embodiments, along the third direction X, the size of the buffer structure 410 is greater than the size of the positive electrode plate 22 and / or the size of the negative electrode plate 23, and the first direction Z, the second direction Y, and the third direction X are perpendicular to each other in pairs.

[0461] Specifically, if along the third direction X, the size of the buffer structure 410 is greater than the size of the positive electrode plate 22, the buffer structure 410 extends beyond at least one end of the positive electrode plate 22 along the third direction X; if along the third direction X, the size of the buffer structure 410 is greater than the size of the negative electrode plate 23, the buffer structure 410 extends beyond at least one end of the negative electrode plate 23 along the third direction X.

[0462] In this way, the size of the buffer structure 410 along the third direction X is larger, so that more regions of the first wall 111 along the third direction X are subjected to reduced expansion force, further reducing the risk of fatigue cracking in the region of the first wall 111 near the first connection portion 51.

[0463] Please refer to Figure 3 and Figure 23 , Figure 23 Schematic diagram of the connection between the end cap 12 and the electrode terminal 3 provided in some embodiments of the present application. In some embodiments, the battery cell 10 further includes two electrode terminals 3, which are disposed on the end cap 12, have opposite polarities, and are both electrically connected to the electrode assembly 2;

[0464] The end cover 12 is provided with a lead-out hole, and 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 passed through the lead-out hole. Along the first direction Z, the first limiting portion 32 is located on the side of the end cover 12 away from the electrode assembly 2, and the second limiting portion 33 is located on the side of the end cover 12 facing the electrode assembly 2.

[0465] Specifically, the first limiting portion 32 and the second limiting portion 33 have limiting functions. 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 escaping from the lead-out hole.

[0466] Along the first direction Z, the projection area of the first limiting portion 32 and the projection area of the second limiting portion 33 are both larger than the projection area of the terminal body 31. The projection area of the first limiting portion 32 can be larger than the projection area of the second limiting portion 33, or the projection area of the second limiting portion 33 can be larger than the projection area of the first limiting portion 32.

[0467] The first limiting portion 32 , the second limiting portion 33 and the terminal body 31 may be integrally formed, or one of the first limiting portion 32 and the second limiting portion 33 may be integrally formed with the terminal body 31 , and the other may be separately provided and connected to the terminal body 31 .

[0468] 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.

[0469] In this way, the electrode terminal 3 of this structure can be installed on the end cover 12 by riveting, which has low installation difficulty and better economy.

[0470] In a specific embodiment, a battery cell 10 is also provided in the embodiment of the present application. The battery cell 10 includes a shell 11, an end cover 12 and an electrode assembly 2. The shell 11 forms an opening at one end along the first direction Z. The end cover 12 is welded to the shell 11 and closes the opening of the shell 11. The electrode assembly 2 is at least partially accommodated in the shell 11.

[0471] The shell 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 shell 11. Adjacent first walls 111 and second walls 112 are connected by a corner wall 113. 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.

[0472] 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.

[0473] The positive electrode plate 22 includes a positive electrode main area 221 and a positive electrode tab 21a protruding from the positive electrode main area 221, and the positive electrode main area 221 has a positive electrode active material layer 223. The negative electrode plate 23 includes a negative electrode main area 231 and a negative electrode tab 21b protruding from the negative electrode main area 231, and the negative electrode main area 231 has a negative electrode active material layer 233. Along the first direction Z, the positive electrode main area 221 has a first end 2211 facing the end cover 12, the negative electrode main area 231 has a second end 2311 facing the end cover 12, and the isolation member 24 has a third end 241 facing the end cover 12, and the third end 241 is closer to the end cover 12 than the first end 2211 and the second end 2311.

[0474] The first wall 111 and the end cover 12 are welded to form a first connecting portion 51 . The first wall 111 includes a main body 400 . Along the first direction Z, the main body 400 is located on a side of the first connecting portion 51 away from the end cover 12 .

[0475] The main body 400 is provided with a buffer structure 410, and the buffer structure 410 is arranged at an interval from the first connecting portion 51. Along the first direction Z, the distance between the buffer structure 410 and the edge of the first connecting portion 51 is 2 mm. The dimension of the buffer structure 410 along the third direction X is L1, and the dimension of the first wall 111 along the third direction X is L, and L1 / L = 0.5. The buffer structure 410 has opposite fourth ends 11113a and fifth ends 11113b along the third direction X, the first wall 111 has opposite sixth ends 1113 and seventh ends 1114 along the third direction X, the fourth end 11113a is close to the sixth end 1113, the fifth end 11113b is close to the seventh end 1114, the dimension of the first wall 111 along the third direction X is L, the minimum distance between the fourth end 11113a and the sixth end 1113 along the third direction X is L2, and the minimum distance between the fifth end 11113b and the seventh end 1114 along the third direction X is L3. L2 / L = 0.3, and L3 / L = 0.3. Along the third direction X, the dimension of the buffer structure 410 is greater than the dimension of the positive electrode plate 22 and / or the dimension of the negative electrode plate 23.

[0476] The main body 400 further includes a first region 440 and a second region 450 arranged along the first direction Z. The thickness of the first region 440 is greater than the thickness of the second region 450, and the buffer structure 410 is located between the first region 440 and the second region 450. The first region 440 includes a first part 441 and a second part 442 arranged along the first direction Z. The second part 442 is located between the first part 441 and the buffer structure 410, and the thickness of the first part 441 is greater than the thickness of the second part 442. The thickness of the second part 442 shows a decreasing trend in the direction from the end cover 12 to the electrode assembly 2.

[0477] Among them, the buffer structure 410 includes a weak part 411 provided on the main body 400, and the minimum thickness of the weak part 411 is less than the thickness of other parts of the main body 400.

[0478] Both the inner surface 430 and the outer surface 420 of the main body 400 are provided with grooves 412. The grooves 412 are arranged opposite to the weak part 411. The grooves 412 include a first side surface 4120, a second side surface 4121, and a bottom surface 4122 connecting the first side surface 4120 and the second side surface 4121.

[0479] The weak part 411 includes a first weak part 4110 disposed opposite to the bottom surface 4122. The thickness of the first weak part 4110 is smaller than the thickness of other parts of the main body part 400. The weak part 411 further includes a second weak part 4111 disposed opposite to the first side surface 4120 and a third weak part 4112 disposed opposite to the second side surface 4121. The first side surface 4120 is located on the side of the bottom surface 4122 close to the first connecting part 51, and the thickness of the second weak part 4111 gradually increases in the direction close to the first connecting part 51. The second side surface 4121 is located on the side of the bottom surface 4122 away from the first connecting part 51, and the thickness of the third weak part 4112 gradually increases in the direction away from the first connecting part 51. Among them, the included angle between the first side surface 4120 and the bottom surface 4122 is 150 degrees, and the included angle between the second side surface 4121 and the bottom surface 4122 is 150 degrees.

[0480] The electrode assembly 2 further includes a separator 24, and the separator 24 is disposed between the positive electrode plate 22 and the negative electrode plate 23. The separator 24 includes an extending area 242 extending beyond the first end 2211 and the second end 2311 along the first direction Z. In the projection plane perpendicular to the second direction Y, the positive projection of the extending area 242 partially overlaps with the positive projection of the buffer structure 410. In the projection plane perpendicular to the second direction Y, the positive projection of the positive electrode main body area 221 does not overlap with the positive projection of the buffer structure 410, and the positive projection of the negative electrode main body area 231 does not overlap with the positive projection of the buffer structure 410.

[0481] The first wall 111 further includes a transition area 1117. The transition area 1117 is located between the main body part 400 and the first connecting part 51 along the first direction Z. The transition area 1117 is connected to the first connecting part 51, and the connection position between the transition area 1117 and the first connecting part 51 forms a connection interface 511. The connection interface 511 has a connection position 5111 closest to the main body part 400 along the first direction Z, and the connection position 5111 is located at one end of the main body part 400 close to the opening along the first direction Z. At least part of the connection interface 511 extends obliquely with respect to the second direction Y.

[0482] The connection interface 511 includes a first interface 5112. The first interface 5112 extends obliquely from the connection position 5111 in the direction close to the end cover 12. Along the second direction Y, at least part of the transition area 1117 is located between the first interface 5112 and the end cover 12. The first interface 5112 is connected to the outer surface 420 of the main body part 400 at the connection position 5111. The connection interface 511 includes a second interface 5113. The second interface 5113 extends obliquely from the connection position 5111 in the direction away from the end cover 12. Along the second direction Y, at least part of the transition area 1117 is located on the side of the second interface 5113 away from the end cover 12. The second interface 5113 is connected to the inner surface 430 of the main body part 400 at the connection position 5111.

[0483] Among them, the Vickers hardness of the transition region 1117 is less than that of the main body 400, and the Vickers hardness of the transition region 1117 is less than that of the first connecting portion 51.

[0484] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present application, and they should all be covered by the scope of the claims and the specification of the present application. In particular, as long as there is no structural conflict, the technical features mentioned in each embodiment can be combined in any way. The present application is not limited to the specific embodiments disclosed in the text, but includes all technical solutions falling within the scope of the claims.

Claims

1. A battery cell, wherein, The battery cell comprises: 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 housed within the housing, the electrode assembly comprising a positive electrode sheet and a negative electrode sheet, at least a portion of the positive electrode sheet and at least a portion of the negative electrode sheet being stacked along a second direction, the second direction being parallel to a thickness direction of the first wall, and the first direction intersecting the second direction; The first wall includes a main body portion, which is located on a side of the first connecting portion away from the end cover along the first direction. The main body portion is provided with a buffer structure, which is spaced apart from the first connecting portion.

2. The battery cell according to claim 1, wherein The buffer structure includes a weak portion provided on the main body, and a minimum thickness of the weak portion is smaller than a thickness of other portions of the main body.

3. The battery cell according to claim 2, wherein, The inner surface of the main body is provided with a groove, and / or the outer surface of the main body is provided with a groove; the weak portion is an area on the main body opposite to the notch of the groove.

4. The battery cell according to claim 3, wherein The groove includes a first side surface, a second side surface and a bottom surface connected to the first side surface and the second side surface. The weak portion includes a first weak portion arranged opposite to the bottom surface. The thickness of the first weak portion is less than the thickness of other parts of the main body.

5. The battery cell according to claim 4, wherein, The weak portion also includes a second weak portion arranged opposite to the first side surface and a third weak portion arranged opposite to the second side surface, the first side surface is located on the side of the bottom surface close to the first connecting portion, and the thickness of the second weak portion tends to increase in the direction close to the first connecting portion, the second side surface is located on the side of the bottom surface away from the first connecting portion, and the thickness of the third weak portion tends to increase in the direction away from the first connecting portion.

6. The battery cell according to claim 4 or 5, wherein, The included angle between the first side surface and the bottom surface is greater than or equal to 135 degrees and less than 180 degrees; and / or the included angle between the second side surface and the bottom surface is greater than or equal to 135 degrees and less than 180 degrees.

7. The battery cell according to claim 1, wherein, The buffer structure includes a first convex portion and a first concave portion, wherein the first convex portion and the first concave portion are arranged correspondingly, the first convex portion protrudes from the outer surface of the main body portion, and the first concave portion is recessed outward from the inner surface of the main body portion.

8. The battery cell according to claim 7, wherein, There are multiple first convex portions, and there are multiple first concave portions. One first concave portion is corresponding to each first convex portion.

9. The battery cell according to claim 1, wherein, The buffer structure includes a second convex portion and a second concave portion, the second convex portion and the second concave portion are arranged correspondingly, the second convex portion protrudes from the inner surface of the main body, and the second concave portion is recessed inward from the outer surface of the main body.

10. The battery cell according to claim 9, wherein, There are multiple second convex portions, and there are multiple second concave portions. One second concave portion is corresponding to each second convex portion.

11. The battery cell according to claim 1, wherein, Along the first direction, a distance between the buffer structure and an edge of the first connecting portion is H, where H satisfies: 0.3 mm ≤ H ≤ 7 mm, optionally, 1.5 mm ≤ H ≤ 4 mm.

12. The battery cell according to claim 1, wherein, The electrode assembly further includes a separator disposed between the positive electrode plate and the negative electrode plate; The positive electrode plate 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 has a positive electrode active material layer. The negative electrode plate 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 has a negative electrode active material layer. Along the first direction, the positive electrode main body region has a first end facing the end cap, the negative electrode main body region has a second end facing the end cap, and the separator has a third end facing the end cap. The third end is closer to the end cap than the first end and the second end.

13. The battery cell according to claim 12, wherein, The separator includes an overhanging region that extends beyond the first end and the second end along the first direction. In a projection plane perpendicular to the second direction, the positive projection of the overhanging region overlaps with the positive projection of the buffer structure partially.

14. The battery cell according to claim 12 or 13, wherein, In a projection plane perpendicular to the second direction, the positive projection of the positive electrode main body region does not overlap with the positive projection of the buffer structure; and / or, in a projection plane perpendicular to the second direction, the positive projection of the negative electrode main body region does not overlap with the positive projection of the buffer structure.

15. The battery cell according to claim 1, wherein, The negative electrode plate includes a negative electrode current collector and a negative electrode active material layer disposed on at least one side of the negative electrode current collector. The negative electrode active material layer includes a negative electrode active material.

16. The battery cell according to claim 15, wherein, The negative electrode active material layer includes a negative electrode main body portion and a negative electrode thinning portion. The negative electrode main body portion and the negative electrode thinning portion are arranged along the first direction. Along the first direction, the negative electrode thinning portion is provided at one end of the negative electrode main body portion close to the end cap.

17. The battery cell according to claim 16, wherein, In a projection plane perpendicular to the second direction, the positive projection of the negative electrode thinning portion and the positive projection of the buffer structure are spaced apart along the first direction.

18. The battery cell according to claim 17, wherein, In a projection plane perpendicular to the second direction, the spacing dimension between the positive projection of the negative electrode thinning portion and the positive projection of the buffer structure along the first direction is greater than or equal to 1 mm.

19. The battery cell according to claim 15, wherein, The single-sided coating weight of the negative electrode active material layer is 90 mg / 1540 mm 2 to 170 mg / 1540 mm 2 , and can be optionally 110 mg / 1540 mm 2 to 150 mg / 1540 mm 2 .

20. The battery cell according to claim 15, wherein, The porosity of the negative electrode plate is 27% - 40%.

21. The battery cell according to claim 15, wherein, The negative electrode active material includes a silicon-based material. The mass content of silicon element in the silicon-based material in the negative electrode active material is 0.3% - 10%, and can be optionally 1% - 6%.

22. The battery cell according to claim 1, wherein, The dimension of the buffer structure along the third direction is greater than the dimension of the buffer structure along the first direction. The first direction, the second direction, and the third direction are not coplanar and intersect pairwise.

23. The battery cell according to claim 22, wherein, The buffer structure passes through the mid-section of the first wall. The mid-section is perpendicular to the third direction, and the distances from the mid-section to the two ends of the first wall along the third direction are equal.

24. The battery cell according to claim 22 or 23, wherein, The dimension of the buffer structure along the third direction is L1, and the dimension of the first wall along the third direction is L. 0.4 ≤ L1 / L ≤ 0.

9.

25. The battery cell according to claim 22 or 23, wherein The buffer structure has opposite fourth and fifth ends along the third direction, the first wall has opposite sixth and seventh ends along the third direction, the fourth end is close to the sixth end, the fifth end is close to the seventh end, the dimension of the first wall along the third direction is L, the minimum distance between the fourth end and the sixth end along the third direction is L2, and the minimum distance between the fifth end and the seventh end along the third direction is L3; L2 / L ≤ 0.3; and / or, L3 / L ≤ 0.

3.

26. The battery cell according to claim 24, wherein, 100mm ≤ L ≤ 450mm.

27. The battery cell according to claim 22, wherein, The housing includes corner walls, and the corner walls are connected to both ends of the first wall along the third direction; At least one end of the buffer structure along the third direction is spaced from the corner wall.

28. The battery cell according to claim 1, wherein, The main body portion includes a first area and a second area arranged along the first direction, the thickness of the first area is greater than that of the second area, and the buffer structure is located between the first area and the second area.

29. The battery cell according to claim 28, wherein, The first area includes a first part and a second part arranged along the first direction, the second part is located between the first part and the buffer structure, and the thickness of the first part is greater than that of the second part.

30. The battery cell according to claim 29, wherein, The thickness of the second part decreases in the direction from the end cap to the electrode assembly.

31. The battery cell according to claim 28, wherein, The Vickers hardness of at least part of the first area is less than that of the second area.

32. The battery cell according to claim 1, wherein, The electrode assembly has a flat area, and the part of the positive electrode tab located in the flat area and the part of the negative electrode tab located in the flat area are stacked along the second direction.

33. The battery cell according to claim 32, wherein, The electrode assembly includes adjacent first and second surfaces, the first surface is perpendicular to the second direction, the area of the first surface is greater than that of the second surface, and the first surface is arranged opposite to the first wall along the second direction.

34. The battery cell according to claim 33, wherein, The first surface is the surface with the largest area among the outer surfaces of the electrode assembly.

35. The battery cell according to claim 33 or 34, wherein, The electrode assembly is a wound structure, and the electrode assembly further has a corner area, and the corner area is provided at at least one end of the flat area along the third direction, and the first direction, the second direction and the third direction are not coplanar and intersect pairwise; The outer surface of the flat area includes the first surface, the outer surface of the corner area includes the second surface, and at least part of the second surface is an arc surface.

36. The battery cell according to claim 33 or 34, wherein, The electrode assembly is a stacked structure, the flat area includes a plurality of positive electrode tabs and a plurality of negative electrode tabs, the plurality of positive electrode tabs and the plurality of negative electrode tabs are stacked along the second direction, and the first surface is perpendicular to the second surface.

37. The battery cell according to claim 32, wherein, Along the third direction, the dimension of the buffer structure is greater than the part of the positive electrode tab located in the flat area and / or the part of the negative electrode tab located in the flat area, and the first direction, the second direction and the third direction are perpendicular to each other pairwise.

38. The battery cell according to claim 1, wherein, The first wall is the wall with the largest outer surface area in the housing.

39. The battery cell according to claim 1, wherein, The housing includes two first walls, and the two first walls are arranged opposite to each other along the second direction, and the electrode assembly is located between the two first walls.

40. The battery cell according to claim 1, wherein, The first wall also includes a transition zone, which is located between the main body and the first connecting portion along the first direction, and the transition zone is connected to the first connecting portion. The connection position of the transition zone and the first connecting portion forms a connection interface, and the connection interface has a connection position closest to the main body along the first direction, and the connection position is located at one end of the main body close to the opening along the first direction.

41. The battery cell according to claim 40, wherein, At least a portion of the connection interface extends obliquely relative to the second direction.

42. The battery cell according to claim 41, wherein, The connection interface includes a first interface, which extends obliquely from the connection position toward the end cover. Along the second direction, at least a portion of the transition zone is located between the first interface and the end cover.

43. The battery cell according to claim 42, wherein, The first interface is connected to the outer surface of the main body at the connection position.

44. The battery cell according to claim 41, wherein, The connection interface includes a second interface, which extends obliquely from the connection position in a direction away from the end cover. Along the second direction, at least a portion of the transition zone is located on a side of the second interface away from the end cover.

45. The battery cell according to claim 44, wherein, The second interface is connected to the inner surface of the main body at the connection position.

46. The battery cell according to claim 40, wherein, The Vickers hardness of the transition zone is smaller than the Vickers hardness of the main body; and / or the Vickers hardness of the transition zone is smaller than the Vickers hardness of the first connecting portion.

47. The battery cell according to claim 1, wherein, 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.

48. The battery cell according to claim 47, 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.

49. The battery cell according to claim 47 or 48, 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.

50. The battery cell according to claim 1, 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.

51. A battery comprising the battery cell according to any one of claims 1 to 50.

52. An electrical device comprising the battery cell according to any one of claims 1 to 50, wherein the battery cell is used to provide electrical energy to the electrical device.

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