Battery cells, batteries and electrical equipment

Abstract

This application discloses a battery cell, a battery, and an electrical device. The battery cell includes a housing, an end cap, and an electrode assembly. The housing has an opening at at least one end along a first direction and includes a first wall. The end cap closes the opening, and the first wall is welded to the end cap to form a first connection portion. A portion of the first connection portion is formed on the end cap, and another portion is formed on the first wall. The electrode assembly is at least partially housed within the housing. The first wall includes a main body portion located along the first direction on the side of the first connection portion away from the end cap. The main body portion has a buffer structure, which is spaced apart from the first connection portion. 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 area of ​​the first wall near the first connection portion due to electrode assembly expansion, thereby improving the service life of the battery cell.

Description

[0001] Priority information

[0002] This application claims priority and benefit to patent application No. PCT / CN2024 / 113184, filed with the China National Intellectual Property Administration on August 19, 2024, the entire contents of which are incorporated herein by reference. Technical Field

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

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

[0005] In battery technology, the lifespan of individual battery cells is a crucial issue. Therefore, improving the lifespan of individual battery cells is a pressing technical problem that needs to be solved. Utility Model Content

[0006] In view of the above problems, this application provides a battery cell, a battery, and an electrical device that can effectively improve the service life of the battery cell.

[0007] In a first aspect, embodiments of this application provide a battery cell, which includes a housing, an end cap, and an electrode assembly. The housing has an opening at at least one end along a first direction and includes a first wall. The end cap closes the opening, and the first wall is welded to the end cap to form a first connection portion. A portion of the first connection portion is formed on the end cap, and another portion of the first connection portion is on the first wall. The electrode assembly is at least partially housed within the housing, and the electrode assembly includes a positive electrode and a negative electrode. At least portions of the positive electrode and the negative electrode are stacked along a second direction, which is parallel to the thickness direction of the first wall, and the first direction intersects the second direction.

[0008] The first wall includes a main body portion. Along the first direction, the main body portion is located on the side of the first connecting portion away from the end cover. The main body portion is provided with a buffer structure, which is spaced apart from the first connecting portion.

[0009] In the above technical solution, 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 area 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.

[0010] In some embodiments, the buffer structure includes a weak portion disposed on the main body, the minimum thickness of which is less than the thickness of other portions of the main body.

[0011] Thus, compared to other parts of the main body, the weaker portion can more effectively absorb expansion forces, thereby reducing the expansion forces acting directly on the first connection portion. Therefore, the weaker portion reduces the risk of fatigue cracking of the area of ​​the first wall near the first connection portion due to electrode assembly expansion, thereby improving the service life of the battery cell.

[0012] 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 part is the area on the main body opposite to the groove opening.

[0013] In this way, the weak part, as the area opposite to the groove opening, has better buffering performance and makes it easier to form the weak part, reducing the manufacturing difficulty of the shell and thus reducing the manufacturing cost of the shell.

[0014] 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. The weak portion includes a first weak portion disposed 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.

[0015] Thus, compared to other parts of the main body, the expansion force acting on the first weak part is greater. The first weak part can more effectively absorb the expansion force, thereby reducing the expansion force directly acting on the first connection part. Therefore, the first weak part can reduce the risk of fatigue cracking of the area of ​​the first wall near the first connection part due to the expansion of the electrode assembly, thereby improving the service life of the battery cell.

[0016] In some embodiments, the weak portion further includes a second weak portion disposed opposite to the first side and a third weak portion disposed opposite to the second side. The first side is located on the bottom surface near 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 is located on 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.

[0017] Thus, the non-uniform thickness design of the second and third weak parts gives the weak parts a gradient strength, which helps to more effectively withstand and disperse expansion forces from different directions, helps to guide the expansion forces along a specific path, and reduces the direct impact on the first weak part. This makes the weak parts less prone to functional failure while absorbing expansion forces. In addition, the gradually changing thickness of the weak parts also makes them easier to manufacture and form.

[0018] 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.

[0019] Thus, within these included angle ranges, the weaker portion has a higher capacity to absorb expansion forces, thereby effectively reducing the risk of fatigue cracking of the area of ​​the first wall near the first connection due to the expansion of the electrode assembly, and thus improving the service life of the battery cell.

[0020] Furthermore, grooves can generally be manufactured using a stamping process. Stamping requires the use of a die, which typically consists of an upper die and a lower die. The upper die is used for stamping, and the lower die supports the housing. During the stamping process, the housing is fixed to the lower die using a fixture or die fixing structure. Then, the upper die moves towards the housing and applies pressure, causing the area of ​​the housing corresponding to the upper die to deform, thus forming a groove.

[0021] When the angle is greater than or equal to 135 degrees and less than 180 degrees, the groove and the upper mold will not get stuck during demolding, making it easier for the upper mold to separate from the groove after it has been machined. Therefore, controlling the angle between 135 degrees and 180 degrees facilitates the formation of the groove, reduces the manufacturing difficulty of the shell, and thus improves the machining accuracy of the shell and the service life of the mold.

[0022] In some embodiments, the buffer structure includes a first protrusion and a first recess, the first protrusion and the first recess being disposed correspondingly, the first protrusion protruding from the outer surface of the main body, and the first recess being recessed from the inner surface of the main body outward.

[0023] In this way, the first protrusion and the first recess can form a local buffer area, increasing the buffer path of the buffer structure to disperse the expansion force, thereby reducing the expansion force acting directly on the first connection. Therefore, the cooperation between the first protrusion and the first recess can reduce the risk of fatigue cracking of the area of ​​the first wall near the first connection due to the expansion of the electrode assembly, thereby improving the service life of the battery cell.

[0024] In some embodiments, there are multiple first protrusions and multiple first recesses, with each first protrusion corresponding to a first recess.

[0025] Thus, the multiple first protrusions and corresponding first recesses can further increase the buffer path of the buffer structure, providing multiple areas for dispersing the expansion force, thereby achieving more effective absorption of the expansion force and effectively reducing the expansion force acting directly on the first connecting part.

[0026] 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 being disposed correspondingly, the second convex portion protruding from the inner surface of the main body portion, and the second concave portion being recessed from the outer surface of the main body portion inward.

[0027] Thus, the second convex and the second concave can form a local buffer area, increasing the buffer path of the buffer structure to disperse the expansion force, thereby reducing the expansion force acting directly on the first connection. Therefore, the cooperation between the second convex and the second concave can reduce the risk of fatigue cracking of the area of ​​the first wall near the first connection due to the expansion of the electrode assembly, thereby improving the service life of the battery cell.

[0028] In some embodiments, there are multiple second protrusions and multiple second recesses, with each second protrusion corresponding to a second recess.

[0029] Thus, multiple second protrusions and corresponding second concave portions can further increase the buffer path of the buffer structure, providing multiple areas for dispersing expansion force, thereby achieving more effective absorption of expansion force and effectively reducing the expansion force acting directly on the first connecting portion.

[0030] In some embodiments, the distance between the buffer structure and the edge of the first connection portion along the first direction is H, where H satisfies: 0.3mm≤H≤7mm, and optionally, 1.5mm≤H≤4mm.

[0031] Thus, within these numerical ranges, the buffer structure can effectively absorb the expansion force, thereby reducing the expansion force acting directly on the first connection. The buffer structure will not fatigue and crack along with the first connection due to its proximity to the first connection, nor will it fail to reduce the expansion force acting directly on the first connection due to its distance from the first connection.

[0032] In some embodiments, the electrode assembly further includes an isolation element, wherein an isolation element is disposed between the positive electrode and the negative electrode;

[0033] The positive electrode includes a positive electrode body region and a positive electrode tab protruding from the positive electrode body region. The positive electrode body region has a positive electrode active material layer. The negative electrode includes a negative electrode body region and a negative electrode tab protruding from the negative electrode body region. The negative electrode body region has a negative electrode active material layer. Along a first direction, the positive electrode body region has a first end facing the end cap, the negative electrode 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.

[0034] Thus, the insulating element has a portion extending beyond the first and second ends, enhancing the insulation effect between the positive and negative electrode plates and reducing the risk of overlap between the positive and negative electrode plates.

[0035] In some embodiments, the separator includes an overhang region extending beyond the first end and the second end along a first direction, wherein the orthographic projection of the overhang region overlaps with the orthographic projection portion of the buffer structure in a projection plane perpendicular to the second direction.

[0036] Thus, this structure can increase the size of the buffer structure along the first direction, improve the ability of the buffer structure to absorb expansion force, and further reduce the risk of fatigue cracking in the area of ​​the first wall near the first connection.

[0037] In some embodiments, the orthographic projection of the positive electrode main body region and the orthographic projection of the buffer structure do not overlap in a projection plane perpendicular to the second direction; and / or, the orthographic projection of the negative electrode main body region and the orthographic projection of the buffer structure do not overlap in a projection plane perpendicular to the second direction.

[0038] Thus, if the orthographic projection of the positive electrode main body area and the orthographic projection of the buffer structure do not overlap in the projection plane perpendicular to the second direction, the shell can provide a larger expansion space for the electrode assembly, reducing the risk that the expansion of the electrode assembly will directly apply expansion force to the buffer, reducing the deformation of the first wall, and further reducing the risk of fatigue cracking in the area of ​​the first wall near the first connection.

[0039] If the orthographic projection of the negative electrode main body area does not overlap with the orthographic projection of the buffer structure in the projection plane perpendicular to the second direction, the shell can provide a larger expansion space for the electrode assembly, reducing the risk that the expansion of the electrode assembly will directly exert an expansion force on the buffer structure, reducing the deformation of the first wall, and further reducing the risk of fatigue cracking in the area of ​​the first wall near the first connection.

[0040] In some embodiments, the orthographic projection of the positive electrode main body region overlaps with the orthographic projection of the buffer structure in a projection plane perpendicular to the second direction; and / or, the orthographic projection of the negative electrode main body region overlaps with the orthographic projection of the buffer structure in a projection plane perpendicular to the second direction.

[0041] Thus, if the orthographic projection of the positive electrode main body area overlaps with the orthographic projection of the buffer structure in the projection plane perpendicular to the second direction, the buffer structure has a larger design width, which can enhance the ability of the buffer structure to absorb expansion force, thereby reducing the risk of fatigue cracking in the area of ​​the first wall near the first connection.

[0042] If the orthographic projection of the negative electrode main body area overlaps with the orthographic projection of the buffer structure in the projection plane perpendicular to the second direction, the buffer structure has a larger design width, which can enhance the ability of the buffer structure to absorb expansion force, thereby reducing the risk of fatigue cracking in the area of ​​the first wall near the first connection.

[0043] In some embodiments, in a projection plane perpendicular to the second direction, at least a portion of the orthogonal projection of the buffer structure is located between the orthogonal projection of the first connecting portion and the orthogonal projection of the positive electrode main body region; and / or, in a projection plane perpendicular to the second direction, at least a portion of the orthogonal projection of the buffer structure is located between the orthogonal projection of the first connecting portion and the orthogonal projection of the negative electrode main body region.

[0044] Thus, if at least part of the orthographic projection of the buffer structure is located between the orthographic projection of the first connection part and the orthographic projection of the positive electrode main body in the projection plane perpendicular to the second direction, this reduces the probability that the expansion force of the electrode assembly will directly act on the buffer structure, reduces the deformation of the first wall, and further reduces the risk of fatigue cracking in the area of ​​the first wall near the first connection part.

[0045] If at least part of the orthographic projection of the buffer structure is located between the orthographic projection of the first connection part and the orthographic projection of the negative electrode main body area, this reduces the probability that the expansion force of the electrode assembly will directly act on the buffer structure, reduces the deformation of the first wall, and further reduces the risk of fatigue cracking in the area of ​​the first wall near the first connection part.

[0046] In some embodiments, in a projection plane perpendicular to the second direction, the orthographic projection of the main body region away from the first connection portion in the positive electrode main body region and the negative electrode main body region is the first orthographic projection, and the orthographic projection of the lowest residual thickness of the buffer structure is located between the orthographic projection of the first connection portion and the first orthographic projection.

[0047] Thus, during the charging process of a single battery cell, ions in the positive electrode are deintercalated and inserted into the electrolyte, while electrons are released and flow to the negative electrode through the external circuit. This process is accompanied by the expansion of the negative electrode volume in the corresponding area of ​​the positive electrode. Therefore, placing the orthographic projection of the lowest point of the residual thickness of the buffer structure between the orthographic projection of the first connection and the first orthographic projection reduces the probability that the expansion force generated when the negative electrode expands will directly act on the lowest point of the residual thickness of the buffer structure, thereby preventing the buffer structure from breaking directly and causing functional failure. At the same time, the buffer structure can maintain a large width, which enhances its ability to absorb expansion force, thereby reducing the risk of fatigue cracking in the area of ​​the first wall near the first connection.

[0048] In some embodiments, the negative electrode includes a negative current collector and a negative active material layer disposed on at least one side of the negative current collector, the negative active material layer comprising a negative active material; the positive electrode includes a positive current collector and a positive active material layer disposed on at least one side of the positive current collector, the positive active material layer comprising a positive active material.

[0049] Thus, by providing a negative electrode active material layer on at least one side of the negative electrode current collector, the content of active material in the battery cell can be increased, thereby improving the energy density of the battery. Similarly, by providing a positive electrode active material layer on at least one side of the positive electrode current collector, the content of active material in the battery cell can be increased, thereby improving the energy density of the battery.

[0050] In some embodiments, the negative electrode active material layer includes a negative electrode main body and a negative electrode thinning portion, the negative electrode main body and the negative electrode thinning portion are arranged along a first direction, and the negative electrode thinning portion is provided at one end of the negative electrode main body near the end cap along the first direction; the positive electrode active material layer includes a positive electrode main body and a positive electrode thinning portion, the positive electrode main body and the positive electrode thinning portion are arranged along a first direction, and the positive electrode thinning portion is provided at one end of the positive electrode main body near the end cap along the first direction.

[0051] Thus, the electrode assembly has a larger expansion gap in the region corresponding to the thinned negative electrode portion, and the region of the electrode assembly corresponding to the thinned negative electrode portion exerts less force on the first wall after expansion, which can reduce the risk of fatigue cracking in the region of the first wall near the first connection portion.

[0052] A positive electrode thinning section is provided at one end of the positive electrode body near the end cap. The electrode assembly has a larger expansion gap in the area corresponding to the positive electrode thinning section. After expansion, the area of ​​the electrode assembly corresponding to the positive electrode thinning section exerts less force on the first wall, which can reduce the risk of fatigue cracking in the area of ​​the first wall near the first connection.

[0053] In some embodiments, in a projection plane perpendicular to the second direction, the orthographic projection of the main body portion of the positive electrode main body portion and the negative electrode main body portion that is far from the first connecting portion is the second orthographic projection, and the orthographic projection of the lowest residual thickness of the buffer structure is located between the orthographic projection of the first connecting portion and the second orthographic projection.

[0054] Thus, ion deintercalation and deintercalation of the positive electrode mainly occur in the positive electrode body, resulting in less volume expansion of the negative electrode in the region corresponding to the thinned positive electrode portion. Therefore, placing the orthographic projection of the lowest point of the remaining thickness of the buffer structure between the orthographic projection of the first connection portion and the second orthographic projection reduces the probability that the expansion force generated when the negative electrode in the region corresponding to the positive electrode body directly acts on the lowest point of the remaining thickness of the buffer structure, thereby preventing direct breakage of the buffer structure and functional failure. Furthermore, this arrangement allows for a larger design width in the buffer structure, enhancing its ability to absorb expansion forces and reducing the risk of fatigue cracking in the area of ​​the first wall near the first connection portion.

[0055] 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 spaced apart along the first direction.

[0056] Thus, the negative electrode thinning section has a lower impact on the buffer structure and the first connection section, reducing the risk that the expansion of the electrode assembly will directly exert an expansion force on the buffer structure, and further reducing the risk of fatigue cracking in the area of ​​the first wall near the first connection section.

[0057] In some embodiments, in a projection plane perpendicular to the second direction, the distance between the orthographic projection of the negative electrode thinning portion and the orthographic projection of the buffer structure along the first direction is greater than or equal to 1 mm.

[0058] Thus, in the projection plane perpendicular to the second direction, the orthographic projection of the negative electrode thinning part and the orthographic projection of the buffer structure are further apart along the first direction, which further reduces the influence of the negative electrode thinning part on the buffer structure.

[0059] In some embodiments, the single-sided coating weight of the negative electrode active material layer is 90 mg / 1540 mm2 to 170 mg / 1540 mm2.

[0060] The single-sided coating weight of the negative electrode active material layer is related to the expansion of the negative electrode active material layer. Setting the single-sided coating weight of the negative electrode active material layer to 90mg / 1540mm2~170mg / 1540mm2 can, to a certain extent, take into account both the high energy density requirements of the battery cell and the low expansion requirements of the negative electrode sheet, so as to reduce the impact of the expansion of the negative electrode sheet on the first wall and reduce the risk of fatigue cracking in the area of ​​the first wall near the first connection part.

[0061] In some embodiments, the single-sided coating weight of the negative electrode active material layer is 110 mg / 1540 mm2 to 150 mg / 1540 mm2.

[0062] This can further increase the energy density of the battery cells and further reduce the expansion of the negative electrode.

[0063] In some embodiments, the porosity of the negative electrode sheet is 27% to 40%.

[0064] This provides space for impurities generated by side reactions in the negative electrode, slows down the expansion of the negative electrode, and reduces the impact of the expansion of the negative electrode on the first wall.

[0065] In some embodiments, the negative electrode active material includes a silicon-based material, wherein the mass content of silicon in the silicon-based material is 0.3% to 10%.

[0066] Thus, by controlling the silicon content within the range of 0.3% to 10%, the cycle stability and energy density of the battery cell can be balanced, and the volume expansion problem of silicon-based materials during charging and discharging can be reduced.

[0067] In some embodiments, the mass content of silicon in the negative electrode active material is 1% to 6%.

[0068] Thus, by controlling the silicon 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 silicon-based materials during charging and discharging can be further reduced.

[0069] In some embodiments, the size of the buffer structure along the third direction is larger than the size of the buffer structure along the first direction, and the first direction, the second direction and the third direction are not coplanar and intersect each other.

[0070] Thus, the buffer structure has a larger dimension along the third direction, which makes the buffer structure more capable of absorbing expansion force and further reduces the risk of fatigue cracking in the area of ​​the first wall near the first connection.

[0071] In some embodiments, the buffer structure passes through the middle section of the first wall, the middle section is perpendicular to the third direction, and the distance from the middle section to both ends of the first wall along the third direction is equal.

[0072] Thus, when the first wall is subjected to the expansion force of the battery cell electrode assembly, the deformation of the middle region of the first wall along the third direction is greater, and the middle region of the first wall along the third direction is more prone to fatigue cracking. Since the buffer structure passes through the mid-section of the first wall, the expansion force on the middle region of the first wall along the third direction is reduced, thereby reducing the risk of fatigue cracking of the middle region of the first wall along the third direction near the first connection.

[0073] In some embodiments, the dimension of the buffer structure along the third direction is L1, the dimension of the first wall along the third direction is L, and 0.4≤L1 / L≤0.9.

[0074] Thus, when 0.4≤L1 / L, the buffer structure has a larger proportion of size along the third direction in the first wall, which makes the expansion force on the middle area of ​​the first wall along the third direction smaller, reducing the risk of fatigue cracking in the middle area of ​​the first wall along the third direction near the first connection.

[0075] When L1 / L≤0.9, the size of the buffer structure in the third direction of the first wall is relatively small, which reduces the waste generated in manufacturing the buffer structure and lowers the production cost.

[0076] Therefore, setting the ratio of the dimension of the buffer structure along the third direction to the dimension of the first wall along the third direction to 0.4 to 0.9 ensures that the buffer structure has sufficient capacity to absorb expansion force while reducing the waste generated in manufacturing the buffer structure, thus balancing the requirements of the buffer structure's capacity to absorb expansion force and its economic efficiency.

[0077] In some embodiments, the buffer structure has a fourth end and a fifth end opposite to each other along a third direction, and the first wall has a sixth end and a seventh end opposite to each other along a third direction, with the fourth end close to the sixth end and the fifth end 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.

[0078] Thus, if L2 / L≤0.3, the proportion of the minimum distance between the fourth and sixth ends along the third direction in the dimension of the first wall along the third direction is reduced, resulting in a larger area of ​​the fourth end along the third direction experiencing reduced expansion force, further reducing the risk of fatigue cracking in the area of ​​the first wall near the first connection.

[0079] If L3 / L≤0.3, the proportion of the minimum distance between the fifth and seventh ends along the third direction in the dimension of the first wall along the third direction is reduced, resulting in a reduction in the expansion force on a larger area of ​​the first wall along the third direction, further reducing the risk of fatigue cracking in the area of ​​the first wall near the first connection.

[0080] In some embodiments, 100mm ≤ L ≤ 450mm.

[0081] Thus, within this numerical range, the first wall has a larger size along the third direction, which helps in setting up the buffer structure and thus facilitates the absorption of expansion forces by the buffer structure.

[0082] In some embodiments, the housing includes corner walls, and the first wall is connected to both ends of the corner walls along the third direction; the buffer structure is spaced apart from the corner walls at at least one end along the third direction.

[0083] Thus, since at least one end of the buffer structure along the third direction does not contact the corner wall, this can reduce the waste generated during the manufacture of the buffer structure and lower production costs.

[0084] In some embodiments, the main body includes a first region and a second region arranged along a first direction, the thickness of the first region being greater than the thickness of the second region, and a buffer structure located between the first region and the second region.

[0085] Thus, the thicker first region can enhance the resistance of the first connection to expansion forces. Combined with the buffer structure, it can further reduce the risk of fatigue cracking of the area of ​​the first wall near the first connection due to the expansion of the electrode assembly, thereby improving the service life of the battery cell.

[0086] In some embodiments, the width of the first region is K1; K1 satisfies: 1.8mm≤K1≤15mm, and optionally, 2mm≤K1≤10mm.

[0087] Thus, if 1.8mm≤K1≤15mm, the first region can enhance the resistance of the first connection part to expansion force. Combined with the buffer structure, it can further reduce the risk of fatigue cracking of the area of ​​the first wall near the first connection part due to the expansion of the electrode assembly, thereby improving the service life of the battery cell.

[0088] If 2mm≤K1≤10mm, the first region can more effectively enhance the resistance of the first connection to expansion force. Combined with the buffer structure, it can further reduce the risk of fatigue cracking of the area of ​​the first wall near the first connection due to the expansion of the electrode assembly, thereby improving the service life of the battery cell.

[0089] In some embodiments, the first region includes a first portion and a second portion arranged along a first direction, the second portion being located between the first portion and the buffer structure, and the thickness of the first portion being greater than the thickness of the second portion.

[0090] Thus, the area of ​​the first region near the first connection is more prone to heat-affected zone formation, which is more susceptible to fatigue cracking. However, since the second part connects the first part and the buffer structure, and the thickness of the first part is greater than that of the second part, the thicker first part in the first region is closer to the first connection, effectively reducing the impact of the heat-affected zone on the first region and lowering the risk of fatigue cracking in the area of ​​the first wall near the first connection. Furthermore, because the thickness of the second part is less than that of the first part, less material is needed in the first region, reducing production costs.

[0091] In some embodiments, the width of the first part is K2; K2 satisfies: 1mm≤K2≤10mm, and optionally, 1.5≤K2≤5mm.

[0092] Thus, if 1mm≤K2≤10mm, the first part has a larger width, which enables the first part to effectively weaken the influence of the heat-affected zone on the first region and reduce the risk of fatigue cracking in the area of ​​the first wall near the first connection.

[0093] If 1.5 ≤ K2 ≤ 5 mm, the first part has a larger width, which allows it to more effectively weaken the influence of the heat-affected zone on the first region, reducing the risk of fatigue cracking in the area of ​​the first wall near the first connection. Furthermore, the manufacturing cost of the first part is lower.

[0094] In some embodiments, the thickness of the second portion decreases along the direction from the end cap toward the electrode assembly.

[0095] In this way, on the one hand, this can reduce the impact of the second part on the electrode assembly and reduce the risk of interference between the second part and the electrode assembly.

[0096] On the other hand, this makes the strengthening effect of the second part increase along the direction of the electrode assembly toward the end cap, so that the area of ​​the second part close to the first part has a good strengthening effect even if it is affected by the first connection, reducing the risk of fatigue cracking of the first wall in the second part.

[0097] On the other hand, the second part can facilitate the transition between the first part and the second zone, reducing stress concentration.

[0098] In some embodiments, at least a portion of the Vickers hardness of the first region is less than the Vickers hardness of the second region.

[0099] It is understandable that when the first wall is subjected to expansion force, the first zone with lower hardness may respond to the overload first through plastic deformation, while the second zone with higher hardness may crack first. Therefore, the risk of fatigue cracking in the first zone is lower.

[0100] In some embodiments, the electrode assembly has a flat region, and the portions of the positive electrode and the negative electrode located in the flat region are stacked along a second direction.

[0101] Thus, the second direction and the stacking direction of the positive electrode portion and the negative electrode portion in the flat region are the same. During cycling, the electrode assembly expands more along the second direction, and the first wall is more significantly affected by this expansion. However, because the buffer structure can absorb the expansion force, the expansion force on the area of ​​the first wall near the first connection is reduced, lowering the risk of fatigue cracking of the first wall near the first connection due to electrode assembly expansion.

[0102] In some embodiments, the electrode assembly includes an adjacent first surface and a second surface, the first surface being perpendicular to a second direction, the area of ​​the first surface being larger than the area of ​​the second surface, and the first surface and the first wall being disposed opposite each other along the second direction.

[0103] Thus, the area of ​​the first surface is larger than that of the second surface, resulting in a greater expansion force on the first wall in the housing, which is positioned opposite the first surface. Because the buffer structure can absorb the expansion force, the expansion force on the area of ​​the first wall near the first connection is reduced, lowering the risk of fatigue cracking of the first wall near the first connection due to the expansion of the electrode assembly.

[0104] In some embodiments, the first surface is the surface with the largest area among the outer surfaces of the electrode assembly.

[0105] Thus, the first wall, which is positioned opposite the first surface in the housing, experiences the greatest expansion force. Because the buffer structure absorbs the expansion force, the expansion force on the area of ​​the first wall near the first connection is reduced, lowering the risk of fatigue cracking of the first wall near the first connection due to the expansion of the electrode assembly.

[0106] In some embodiments, the electrode assembly is a wound structure, and the electrode assembly further has a corner region. The straight region is provided with a corner region at at least one end along a third direction, and the first direction, the second direction and the third direction are not coplanar and intersect each other.

[0107] The outer surface of the straight area includes a first surface, and the outer surface of the corner area includes a second surface, at least a portion of which is an arc surface.

[0108] Thus, for the wound electrode assembly, the flat area expands more in the second direction. Because the buffer structure can absorb the expansion force, the expansion force on the area of ​​the first wall near the first connection is reduced, thereby reducing the risk of fatigue cracking of the first wall near the first connection due to the expansion of the electrode assembly.

[0109] In some embodiments, the electrode assembly is a stacked structure, and the flat region includes a plurality of positive electrode sheets and a plurality of negative electrode sheets. The plurality of positive electrode sheets and the plurality of negative electrode sheets are stacked along a second direction, and the first surface is perpendicular to the second surface.

[0110] Thus, for stacked electrode assemblies, the expansion of the electrode assembly is greater in the stacking direction of the positive and negative electrode sheets. Since the buffer structure can absorb the expansion force, the expansion force on the area of ​​the first wall near the first connection is reduced, thereby reducing the risk of fatigue cracking of the first wall near the first connection due to the expansion of the electrode assembly.

[0111] In some embodiments, the first wall is the wall with the largest outer surface area in the housing.

[0112] Thus, the wall with the largest outer surface area in the housing is more likely to deform under the expansion force of the electrode assembly. Since the first wall has the largest outer surface area in the housing, the risk of fatigue cracking of the first wall near the first connection due to the expansion of the electrode assembly is low.

[0113] In some embodiments, the housing includes two first walls disposed opposite each other along a second direction, and the electrode assembly is located between the two first walls.

[0114] This reduces the risk of fatigue cracking of the two first walls near the first connection due to the expansion of the electrode assembly.

[0115] In some embodiments, the first wall further includes a transition zone located between the main body and the first connecting portion along a first direction. The transition zone is connected to the first connecting portion, and the connection position between the transition zone and the first connecting portion forms a connection interface. The connection interface has a connection position closest to the main body along the first direction, and the connection position is located at the end of the main body that is closest to the opening along the first direction.

[0116] In this way, the transition zone and the first connecting part are connected to form a connection interface, so that the transition zone and the first connecting part have a sufficiently large contact area, which improves the firmness of the first wall and the end cap after welding.

[0117] In some embodiments, at least a portion of the connection interface extends at an angle relative to the second direction.

[0118] Thus, after the end cap and the first wall are welded, the first connection will shrink as it solidifies, generating tensile stress in the transition zone. When the first wall is subjected to the expansion force of the electrode assembly, it will deform, generating tensile stress in the transition zone on the first connection. Since the connection interface extends at least partially at an angle relative to the second direction, the tensile stress generated by the shrinkage of the first connection on the transition zone near the portion of the connection interface that extends at an angle relative to the second direction is not on the same straight line as the tensile stress generated by the deformation of the first wall on the first connection in the transition zone. This reduces the risk of fatigue cracking in the area of ​​the transition zone near the connection interface.

[0119] In some embodiments, the connection interface includes a first interface that extends obliquely from the connection location toward the end cap, and at least a portion of the transition area is located between the first interface and the end cap along a second direction.

[0120] Thus, the first connecting part protects the transition zone. When the first wall is subjected to the expansion force of the electrode assembly, the deformation of the transition zone during the stress process is blocked by the first connecting part, reducing the risk of fatigue cracking in the area of ​​the transition zone near the first interface.

[0121] In some embodiments, the first interface is connected to the outer surface of the main body at a connection position.

[0122] Thus, since the first interface is directly connected to the main body, 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 the expansion of the electrode assembly.

[0123] In some embodiments, the connection interface includes a second interface that extends obliquely from the connection location toward the end cap, and along the second direction, at least a portion of the transition area is located on the side of the second interface away from the end cap.

[0124] In this way, the transition zone restricts the first connecting part, reducing the risk of the first connecting part falling off.

[0125] In some embodiments, the second interface is connected to the inner surface of the main body at a connection position.

[0126] In this way, the main body and the first connecting part are in a direct connection state, which makes the main body and the first connecting part 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 the expansion of the electrode assembly.

[0127] In some embodiments, the Vickers hardness of the transition zone is less than that of the main body; and / or, the Vickers hardness of the transition zone is less than that of the first connecting portion.

[0128] Thus, if the Vickers hardness of the transition zone is lower than that of the main body, allowing the transition zone with lower Vickers hardness to connect with the first connecting part, it can alleviate the rigid tension between the first wall and the first connecting part when the first wall deforms, reducing the risk of the first wall separating from the first connecting part. Conversely, if the Vickers hardness of the transition zone is lower than that of the first connecting part, making the transition zone more prone to deformation than the first connecting part, it can also alleviate the rigid tension between the first wall and the first connecting part when the first wall deforms, reducing the risk of the first wall separating from the first connecting part.

[0129] In some embodiments, the electrode assembly is a stacked structure, and the electrode assembly includes a plurality of positive electrode sheets and a plurality of negative electrode sheets, which are stacked along a second direction.

[0130] Thus, the stacked electrode assembly has a more compact structure and stronger resistance to compression.

[0131] 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.

[0132] Thus, by placing positive electrode plates between adjacent negative electrode plates, the transport distance of lithium ions within the battery cell can be reduced, and more lithium ion transport paths can be provided, thereby improving the charging and discharging efficiency of the battery cell.

[0133] In some embodiments, each negative electrode is provided with a negative electrode tab; and / or, each positive electrode is provided with a positive electrode tab.

[0134] In this way, the tabs can simplify the electrical connection between the battery cell and the external circuit.

[0135] In some embodiments, along the third direction, the size of the buffer structure is larger than the size of the positive electrode and / or the size of the negative electrode, and the first direction, the second direction and the third direction are perpendicular to each other.

[0136] Thus, the buffer structure has a larger dimension along the third direction, which reduces the expansion force on more areas of the first wall along the third direction, further reducing the risk of fatigue cracking in the area of ​​the first wall near the first connection.

[0137] In some embodiments, the battery cell further includes two electrode terminals disposed on the end cap, the two electrode terminals having opposite polarities and both being electrically connected to the electrode assembly;

[0138] The end cap is provided with an outlet hole. The electrode terminal includes a terminal body, a first limiting part and a second limiting part. The terminal body is connected to the first limiting part and the second limiting part. The terminal body passes through the outlet hole. Along the first direction, the first limiting part is located on the side of the end cap away from the electrode assembly, and the second limiting part is located on the side of the end cap facing the electrode assembly.

[0139] Thus, the electrode terminals of this structure can be installed on the end cap by riveting, which is easy to install and more economical.

[0140] In some embodiments, the thickness at the lowest point of the residual thickness of the buffer structure is T, where T satisfies: 0.1mm≤T≤1mm, and optionally, 0.2mm≤T≤0.5mm.

[0141] Thus, if 0.1mm≤T≤1mm, the buffer structure can not only effectively absorb the expansion force, but also avoid functional failure due to breakage.

[0142] If 0.2mm≤T≤0.5mm, the buffer structure has a better ability to absorb expansion force and is more likely to avoid functional failure due to breakage.

[0143] In some embodiments, the width of the buffer structure is K3, where K3 satisfies: 0.1mm≤K3≤20mm, and optionally, 0.15mm≤K3≤10mm.

[0144] Thus, if 0.1mm≤K3≤20mm, the buffer structure can effectively absorb the expansion force and reduce manufacturing costs.

[0145] If 0.15mm≤K3≤10mm, the buffer structure has a better ability to absorb expansion force and a lower manufacturing cost.

[0146] In some embodiments, the distance between the buffer structure and the upper edge of the end cap is J, where J satisfies: 1mm≤J≤20mm, and optionally, 1.5mm≤J≤10mm.

[0147] Thus, if 1mm≤J≤20mm, the buffer structure is far from the heat-affected zone, which can enhance the buffer structure's ability to absorb expansion force, thereby reducing the risk of fatigue cracking in the area of ​​the first wall near the first connection.

[0148] If 1.5mm≤J≤10mm, the buffer structure is far from the heat-affected zone, which can enhance the ability of the buffer structure to absorb expansion force, thereby reducing the risk of fatigue cracking in the area of ​​the first wall near the first connection.

[0149] Secondly, embodiments of this application provide a battery, which includes the battery cell provided in any one of the embodiments of the first aspect.

[0150] Since the battery includes the aforementioned battery cells, it includes at least all the beneficial effects of the aforementioned battery cells, which will not be elaborated here.

[0151] Thirdly, embodiments of this application provide an electrical device, which includes a battery cell provided in any of the embodiments of the first aspect, the battery cell being used to provide electrical energy to the electrical device.

[0152] Since the electrical equipment includes the aforementioned battery cells, the electrical equipment includes at least all the beneficial effects of the aforementioned battery cells, which will not be elaborated here.

[0153] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, specific embodiments of this application are given below. Attached Figure Description

[0154] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiments below. The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of this application. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0155] Figure 1 These are schematic diagrams of the vehicle structure provided in some embodiments of this application;

[0156] Figure 2 These are exploded views of batteries provided in some embodiments of this application;

[0157] Figure 3 These are exploded views of a single battery cell provided in some embodiments of this application;

[0158] Figure 4 yes Figure 3 The diagram shows the structure of a single battery cell;

[0159] Figure 5 yes Figure 4 A cross-sectional view of the battery cell along the AA direction;

[0160] Figure 6 yes Figure 5 A magnified view of point B in the battery cell;

[0161] Figure 7 This is a partial schematic diagram of a battery cell provided in some embodiments of this application;

[0162] Figure 8 This is a partial schematic diagram of a battery cell provided in other embodiments of this application;

[0163] Figure 9 This is a schematic diagram of an electrode assembly provided in some embodiments of this application;

[0164] Figure 10 This is a partial schematic diagram of a battery cell provided in some embodiments of this application;

[0165] Figure 11 This is a partial schematic diagram of an electrode assembly provided in some embodiments of this application;

[0166] Figure 12 This is a partial schematic diagram of an electrode assembly provided in other embodiments of this application;

[0167] Figure 13 These are schematic diagrams of the structure of a battery cell provided in other embodiments of this application;

[0168] Figure 14 yes Figure 13 A cross-sectional view of the battery cell along the BB direction;

[0169] Figure 15 yes Figure 14 A magnified view of point P of a single battery cell;

[0170] Figure 16 This is a partial schematic diagram of a battery cell provided in some embodiments of this application;

[0171] Figure 17 These are schematic diagrams of the shell structure provided in some embodiments of this application;

[0172] Figure 18 These are schematic diagrams of the housing structure provided in other embodiments of this application;

[0173] Figure 19 These are schematic diagrams of the structure of a battery cell provided in some embodiments of this application;

[0174] Figure 20 This is a partial schematic diagram of a battery cell provided in some embodiments of this application;

[0175] Figure 21 These are schematic diagrams of electrode assemblies provided in other embodiments of this application;

[0176] Figure 22 This is a schematic diagram of the structure of an electrode assembly provided in some embodiments of this application;

[0177] Figure 23 These are schematic diagrams of the electrode assemblies provided in other embodiments of this application;

[0178] Figure 24 This is a partial schematic diagram of a battery cell provided in some embodiments of this application;

[0179] Figure 25 yes Figure 24 Enlarged view of part C of a single battery cell;

[0180] Figure 26 This is a partial schematic diagram of a battery cell provided in some embodiments of this application;

[0181] Figure 27 yes Figure 26 Enlarged view of part D of a single battery cell;

[0182] Figure 28 This is a schematic diagram showing the connection between the end cap and the electrode terminal provided in some embodiments of this application.

[0183] Explanation of icon numbers:

[0184] 1-Outer shell; 11-Housing shell; 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; 23-Negative electrode; 400-Main body; 410-Buffer structure; 411-Weak part; 412-Groove; 4120-First side surface; 4121-Second side surface; 4122-Bottom surface; 4110-First weak part; 4111-Second weak part; 4112-Third weak part ; 413-First convex portion; 414-First concave portion; 420-Outer surface of the main body portion; 430-Inner surface of the main body portion; 417-Second convex portion; 418-Second concave portion; 24-Separator; 221-Positive electrode main body region; 2231-Positive electrode main body portion; 2232-Positive electrode thinning portion; 21-Taper; 21a-Positive electrode tab; 222-Positive electrode current collector; 223-Positive electrode active material layer; 224-Insulating layer; 231-Negative electrode main body region; 21b-Negative electrode tab; 233-Negative electrode active material layer; 2211 - First end; 2311- Second end; 241- Third end; 242- Exceeding region; 232- Negative electrode current collector; 2331- Negative electrode main body; 2332- Negative electrode thinning section; 11113a- Fourth end; 11113b- Fifth end; 1113- Sixth end; 1114- Seventh end; 113- Corner wall; 440- First region; 450- Second region; 441- First part; 442- Second part; 25- Straight region; 26- Corner region; 27- First surface; 28- Second surface; 1117- Through 511-Connection interface; 5111-Connection position; 5112-First interface; 5113-Second interface; 3-Electrode terminal; 31-Terminal body; 32-First limiting part; 33-Second limiting part; 6-First insulating component; 7-Second insulating component; 10-Battery cell; 20-Box; 201-First box; 202-Second box; 100-Battery; 200-Controller; 300-Motor; 1000-Vehicle; Z-First direction; Y-Second direction; X-Third direction; U-Interface. Detailed Implementation

[0185] The embodiments of the technical solution of this application will now be described in detail with reference to the accompanying drawings. These embodiments are only used to more clearly illustrate the technical solution of this application and are therefore merely examples, and should not be used to limit the scope of protection of this application.

[0186] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0187] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0188] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0189] In the description of the embodiments in this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0190] In the description of the embodiments of this application, the term "multiple" refers to two or more (including two), similarly, "multiple sets" refers to two or more (including two sets), and "multiple pieces" refers to two or more (including two pieces).

[0191] In the description of the embodiments of this application, the technical terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the embodiments of this application and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of this application.

[0192] In the description of the embodiments of this application, unless otherwise expressly specified and limited, technical terms such as "installation," "connection," "joining," and "fixing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. For those skilled in the art, the specific meaning of the above terms in the embodiments of this application can be understood according to the specific circumstances.

[0193] In this application embodiment, "multiple" refers to two or more (including two).

[0194] In this embodiment of the application, the battery cell can be a secondary battery, which refers to a battery cell that can be recharged to activate the active materials and continue to be used after the battery cell has been discharged.

[0195] Battery cells include, but are not limited to, lithium-ion batteries, sodium-ion batteries, sodium-lithium-ion batteries, lithium metal batteries, sodium metal batteries, lithium-sulfur batteries, magnesium-ion batteries, nickel-metal hydride batteries, nickel-cadmium batteries, lead-acid batteries, etc.

[0196] A single battery cell typically includes an electrode assembly. The electrode assembly includes a positive electrode, a negative electrode, and a separator. During the charging and discharging process of a single battery cell, active ions (such as lithium ions) repeatedly insert and extract between the positive and negative electrodes. The separator, positioned between the positive and negative electrodes, reduces the risk of short circuits while allowing active ions to pass through.

[0197] In some embodiments, the positive electrode can be a positive electrode sheet, which may include a positive current collector and a positive active material disposed on at least one surface of the positive current collector.

[0198] As an example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive active material is disposed on either or both of the two opposite surfaces of the positive current collector.

[0199] As an example, the positive electrode current collector can be a metal foil or a composite current collector. For example, as a metal foil, it can be aluminum with a silver-plated surface, stainless steel with a silver-plated surface, stainless steel, copper, aluminum, nickel, carbon electrode, carbon, nickel, or titanium, etc. Composite current collectors can include a polymer material base layer and a metal layer. Composite current collectors can be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.).

[0200] As an example, the positive electrode active material may include at least one of the following materials: lithium phosphate, lithium transition metal oxide, and their respective modified compounds. However, this application is not limited to these materials, and other conventional materials that can be used as positive electrode active materials for batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium phosphate include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), lithium iron phosphate and carbon composites, lithium manganese phosphate (such as LiMnPO4), lithium manganese phosphate and carbon composites, lithium manganese iron phosphate, and lithium manganese iron phosphate and carbon composites. Examples of lithium transition metal oxides may include, but are not limited to, at least one of lithium cobalt oxides (such as LiCoO2), lithium nickel oxides (such as LiNiO2), lithium manganese oxides (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, lithium nickel cobalt manganese oxides (such as LiNi1 / 3Co1 / 3Mn1 / 3O2, also referred to as NCM333), LiNi0.5Co0.2Mn0.3O2 (also referred to as NCM523), LiNi0.5Co0.25Mn0.25O2 (also referred to as NCM211), LiNi0.6Co0.2Mn0.2O2 (also referred to as NCM622), LiNi0.8Co0.1Mn0.1O2 (also referred to as NCM811), lithium nickel cobalt aluminum oxides (such as LiNi0.85Co0.15Al0.05O2), and their modified compounds.

[0201] In some embodiments, the positive electrode can be a foamed metal. The foamed metal can be foamed nickel, foamed copper, foamed aluminum, foamed alloys, etc. When foamed metal is used as the positive electrode, the surface of the foamed metal may or may not contain a positive electrode active material. As an example, lithium source material, potassium metal, or sodium metal can also be filled and / or deposited within the foamed metal, where the lithium source material is lithium metal and / or a lithium-rich material.

[0202] In some embodiments, the negative electrode can be a negative electrode sheet, and the negative electrode sheet can include a negative current collector.

[0203] As an example, the negative electrode current collector can be a metal foil, a foamed metal, or a composite current collector. For example, as a metal foil, it can be aluminum with a silver-plated surface, stainless steel with a silver-plated surface, stainless steel, copper, aluminum, nickel, carbon electrode, carbon, nickel, or titanium, etc. Foamed metal can be nickel foam, copper foam, aluminum foam, foam alloy, etc. Composite current collectors can include a polymer material base layer and a metal layer. Composite current collectors can be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.).

[0204] As an example, the negative electrode sheet may include a negative current collector and a negative active material disposed on at least one surface of the negative current collector.

[0205] As an example, the negative electrode current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode active material is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0206] As an example, the negative electrode active material may be a negative electrode active material known in the art for use in battery cells. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate, etc. Silicon-based materials may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Tin-based materials may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. However, this application is not limited to these materials, and other conventional materials that can be used as battery negative electrode active materials may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0207] In some embodiments, the positive current collector can be made of aluminum, and the negative current collector can be made of copper.

[0208] In some embodiments, the separator is a separator membrane. The separator membrane can be any known porous structure separator membrane with good chemical and mechanical stability.

[0209] As an example, the material of the separator may include at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may be a single-layer film or a multi-layer composite film. When the separator is a multi-layer composite film, the materials of each layer may be the same or different. The separator may be a separate component located between the positive and negative electrodes, or it may be attached to the surfaces of the positive and negative electrodes.

[0210] In some embodiments, the separator is a solid electrolyte. The solid electrolyte is disposed between the positive and negative electrodes, serving both to transport ions and to isolate the positive and negative electrodes.

[0211] In some embodiments, the battery cell also includes an electrolyte, which acts as a conductor of ions between the positive and negative electrodes. The electrolyte can be liquid, gel-like, or solid. Liquid electrolytes include electrolyte salts and solvents.

[0212] In some embodiments, the electrolyte salt may include at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium dioxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate.

[0213] In some embodiments, the solvent may include at least one selected from ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butyl carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone. The solvent may also be an ether solvent. Ether solvents may include one or more selected from ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, 1,3-dioxolane, tetrahydrofuran, methyl tetrahydrofuran, diphenyl ether, and crown ethers.

[0214] Among them, the gel electrolyte includes a polymer as the electrolyte backbone network, combined with an ionic liquid - lithium salt.

[0215] Solid electrolytes include polymer solid electrolytes, inorganic solid electrolytes, and composite solid electrolytes.

[0216] As an example, polymer solid electrolytes can be polyether (polyoxyethylene), polysiloxane, polycarbonate, polyacrylonitrile, polyvinylidene fluoride, polymethyl methacrylate, monoionic polymers, polyionic liquids-lithium salts, cellulose, etc.

[0217] As an example, inorganic solid electrolytes may include one or more of the following: oxide solid electrolytes (crystalline perovskite, sodium superconducting ion conductor, garnet, amorphous LiPON thin film), sulfide solid electrolytes (crystalline lithium superconducting ion conductor (lithium germanium phosphate sulfide, silver sulfide germanium ore), amorphous sulfides), halide solid electrolytes, nitride solid electrolytes, and hydride solid electrolytes.

[0218] As an example, composite solid electrolytes are formed by adding inorganic solid electrolyte fillers to polymer solid electrolytes.

[0219] In some embodiments, the electrode assembly is a wound structure. The positive electrode and the negative electrode are wound into a wound structure.

[0220] In some implementations, the electrode assembly is a stacked structure.

[0221] As an example, multiple positive and negative electrode plates can be set, and multiple positive and multiple negative electrode plates can be stacked alternately.

[0222] As an example, multiple positive electrode sheets can be set, and negative electrode sheets are folded to form multiple stacked folded segments, with a positive electrode sheet sandwiched between adjacent folded segments.

[0223] As an example, both the positive and negative electrode sheets are folded to form multiple stacked folded segments.

[0224] As an example, multiple separators can be provided, each positioned between any adjacent positive or negative electrode plates.

[0225] As an example, the separator can be continuously arranged between any adjacent positive or negative electrode plates by folding or rolling.

[0226] In some embodiments, the electrode assembly can be cylindrical, flat, or polygonal, etc.

[0227] In some embodiments, the electrode assembly is provided with tabs that allow current to be drawn from the electrode assembly. The tabs include a positive tab and a negative tab.

[0228] In some embodiments, the battery cell may include a housing. The housing is used to encapsulate components such as electrode assemblies and electrolytes. The housing may be made of steel, aluminum, plastic (such as polypropylene), composite metal (such as copper-aluminum composite), or aluminum-plastic film, etc.

[0229] As an example, a battery cell can be a cylindrical battery cell, a prismatic battery cell, a pouch battery cell, or a battery cell of other shapes. Prismatic battery cells include prismatic battery cells, blade-shaped battery cells, and multi-prismatic battery cells, such as hexagonal prismatic battery cells.

[0230] The battery mentioned in the embodiments of this application refers to a single physical module comprising one or more battery cells to provide higher voltage and capacity.

[0231] In some embodiments, the battery can be a battery module, and when there are multiple battery cells, the multiple battery cells are arranged and fixed to form a battery module.

[0232] In some embodiments, the battery can be a battery pack, which includes a housing and individual battery cells, with the individual battery cells or battery modules housed within the housing.

[0233] In some embodiments, the housing may be part of the vehicle's chassis structure. For example, a portion of the housing may be at least a part of the vehicle's floor, or a portion of the housing may be at least a part of the vehicle's crossbeams and longitudinal beams.

[0234] In some embodiments, the battery can be an energy storage device. Energy storage devices include energy storage containers, energy storage cabinets, etc.

[0235] In related technologies, a battery cell generally includes a casing and an electrode assembly. The casing may include a housing and an end cap. The housing has an opening. After the electrode assembly is installed inside the housing, the opening of the housing can be closed by the end cap to form a sealed space inside the housing to accommodate the electrode assembly.

[0236] To achieve a stable connection between the end cap and the housing, the end cap and the housing can be welded. After welding, the welded area between the end cap and the housing will form a connection part. The area of ​​the housing wall near the connection part will form a heat-affected zone due to the high temperature of welding, and the strength of the portion of the housing wall in the heat-affected zone will be reduced.

[0237] During the charge and discharge cycle of a battery cell, the electrode assembly expands. The wall of the casing is deformed by the expansion force of the electrode assembly. Over time, this can easily lead to fatigue cracking in the area of ​​the casing wall near the connection (heat-affected zone), affecting the service life of the battery cell.

[0238] Based on the above considerations, in order to alleviate the problem of fatigue cracking in the area of ​​the casing wall near the connection portion, this application provides a battery cell, which includes a casing, an end cap, and an electrode assembly; the casing has an opening at at least one end along a first direction, and the casing includes a first wall; the end cap closes the opening, and the first wall is welded to the end cap to form a first connection portion; the electrode assembly is at least partially housed in the casing, and the electrode assembly includes a positive electrode and a negative electrode, at least a portion of the positive electrode and at least a portion of the negative electrode are stacked along a second direction, the second direction is parallel to the thickness direction of the first wall, and the first direction intersects the second direction; wherein, the first wall includes a main body portion, along the first direction, the main body portion is located on the side of the first connection portion away from the end cap, the main body portion is provided with a buffer structure, and the buffer structure is spaced apart from the first connection portion.

[0239] 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 acting directly on the first connection portion. Therefore, the buffer structure can reduce the risk of fatigue cracking of the area of ​​the first wall near the first connection portion due to electrode assembly expansion, thus improving the service life of the battery cell.

[0240] The battery cells described in the embodiments of this application are applicable to batteries and electrical devices that use battery cells.

[0241] Electrical equipment can include vehicles, mobile phones, portable devices, laptops, ships, spacecraft, electric toys, and power tools, etc. Vehicles can be gasoline-powered cars, natural gas-powered cars, or new energy vehicles; new energy vehicles can be pure electric vehicles, hybrid electric vehicles, or range-extended electric vehicles, etc. Spacecraft include airplanes, rockets, space shuttles, and spacecraft, etc. Electric toys include stationary or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc. Power tools include metal cutting power tools, grinding power tools, assembly power tools, and railway power tools, such as electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact drills, concrete vibrators, and electric planers, etc. This application does not impose any special limitations on the above-mentioned electrical equipment.

[0242] For ease of explanation, the following embodiments use a vehicle as an example of electrical equipment.

[0243] Please refer to Figure 1 , Figure 1 This is a structural schematic diagram of a vehicle 1000 provided in some embodiments of this application. A battery 100 is disposed inside the vehicle 1000, and the battery 100 may be located at the bottom, front, or rear of the vehicle 1000. The battery 100 can be used to power the vehicle 1000; for example, the battery 100 can serve as the operating power source for the vehicle 1000.

[0244] The vehicle 1000 may also 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 power needs of the vehicle 1000 during startup, navigation and driving.

[0245] In some embodiments of this application, the battery 100 can not only serve as the operating power source for the vehicle 1000, but also as the driving power source for the vehicle 1000, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle 1000.

[0246] Please refer to Figure 2 , Figure 2This is an exploded view of a battery 100 provided in some embodiments of this application. The battery 100 may include a battery cell 10 and a housing 20, with the battery cell 10 housed within the housing 20.

[0247] The housing 20 is a component that houses the battery cell 10. The housing 20 provides space for the battery cell 10 and can adopt various structures.

[0248] In some embodiments, the housing 20 may include a first housing 201 and a second housing 202, which cover each other to define a receiving space for accommodating the battery cell 10.

[0249] The first box 201 and the second box 202 can have various shapes, such as cuboids or cylinders. The first box 201 can be a hollow structure with an opening on one side, and the second box 202 can also be a hollow structure with an opening on one side. The opening side of the second box 202 covers the opening side of the first box 201, thus forming a box 20 with a storage space. Alternatively, the first box 201 can be a hollow structure with an opening on one side, and the second box 202 can be a plate-like structure, with the second box 202 covering the opening side of the first box 201, thus forming a box 20 with a storage space. The first box 201 and the second box 202 can be sealed using a sealing element, such as a sealing ring or sealant.

[0250] In battery 100, there can be one or more battery cells 10. If there are multiple battery cells 10, they can be connected in series, parallel, or in a mixed manner. A mixed connection means that multiple battery cells 10 are connected in both series and parallel. Alternatively, multiple battery cells 10 can be first connected in series, parallel, or in a mixed manner to form a battery module, and then multiple battery modules can be connected in series, parallel, or in a mixed manner to form a whole, which is then housed within the housing 20. Another option is that all battery cells 10 can be directly connected in series, parallel, or in a mixed manner, and then the whole consisting of all battery cells 10 is housed within the housing 20.

[0251] Please refer to Figure 3 and Figure 4 , Figure 3 This is an exploded view of a battery cell 10 provided in some embodiments of this application; Figure 4 yes Figure 3 The diagram shows the structure of a single battery cell 10. The single battery cell 10 may include a housing 1 and an electrode assembly 2, with the electrode assembly 2 housed within the housing 1.

[0252] In some embodiments, the housing 1 may include a housing 11 and an end cap 12, the housing 11 having an opening and the end cap 12 closing the opening of the housing 11.

[0253] The housing 11 is a component used to house the electrode assembly 2. The housing 11 can be a hollow structure with an opening at one end, or it can be a hollow structure with openings at both opposite ends. The housing 11 can have various shapes, such as cylindrical or cuboid. The housing 11 can be made of various materials, such as copper, iron, aluminum, steel, or aluminum alloy. The electrode assembly 2 can be partially or completely housed within the housing 11.

[0254] End cap 12 is a component that closes the opening of housing 11 to isolate the internal environment of battery cell 10 from the external environment. End cap 12 and housing 11 together define a storage space for accommodating electrode assembly 2, electrolyte, and other components. End cap 12 can be connected to housing 11 by welding or roll sealing to close the opening of housing 11. The shape of end cap 12 can be adapted to the shape of housing 11. For example, if housing 11 is a cuboid structure, end cap 12 can be a rectangular plate structure adapted to housing 11; or if housing 11 is a cylindrical structure, end cap 12 can be a circular plate structure adapted to housing 11. The material of end cap 12 can also be various, such as copper, iron, aluminum, steel, aluminum alloy, etc. The materials of end cap 12 and housing 11 can be the same or different.

[0255] In an embodiment where the housing 11 has an opening at one end, one end cap 12 may be provided accordingly. In an embodiment where the housing 11 has openings at both opposite ends, two end caps 12 may be provided accordingly. The two end caps 12 respectively close the two openings of the housing 11, and the two end caps 12 and the housing 11 together define the receiving space.

[0256] In some embodiments, the battery cell 10 may further include electrode terminals 3, which are disposed on the housing 1 and are used for electrical connection with the tabs 21 of the electrode assembly 2 to input or output electrical energy of the battery cell 10. The electrode terminals 3 may be disposed on the housing 11 of the housing 1 or on the end cap 12 of the housing 1. The electrode terminals 3 and the tabs 21 may be directly connected, for example, by welding. Alternatively, the electrode terminals 3 and the tabs 21 may be indirectly connected, for example, through a current collector. The current collector may be a metallic conductor, such as copper, iron, aluminum, steel, or aluminum alloy.

[0257] In some embodiments, the battery cell 10 may further include a pressure relief mechanism 4, which may be disposed on the end cap 12 or the housing 11. The pressure relief mechanism 4 may be a pressure relief component installed on the housing 11 or the end cap 12, such as an explosion-proof plate or a safety valve. The pressure relief mechanism 4 may also be integrally formed with the end cap 12 or the housing 11. The pressure relief mechanism 4 may be provided with a pressure relief groove to split along the pressure relief groove when the battery cell 10 is depressurized. The pressure relief groove may be a groove extending along a closed trajectory, which may be a circular trajectory, a rectangular trajectory, etc.; the pressure relief groove may also be a groove extending along a non-closed trajectory, which may be an H-shaped trajectory, a Y-shaped trajectory, a V-shaped trajectory, a U-shaped trajectory, etc.

[0258] As an example, such as Figure 3 and Figure 4 As shown, one end of the housing 11 forms an opening, and there is one end cap 12 in the housing 1, which closes one opening of the housing 11. The end cap 12 is provided with a pressure relief mechanism 4, and two electrode terminals 3 are provided on the end cap 12. The two electrode terminals 3 are a positive electrode terminal and a negative electrode terminal, respectively. The end of the electrode assembly 2 facing the end cap 12 has a positive electrode tab 21a and a negative electrode tab 21b. The positive electrode terminal is electrically connected to the positive electrode tab 21a, and the negative electrode terminal is electrically connected to the negative electrode tab 21b.

[0259] Please refer to Figure 5 and Figure 6 , Figure 5 yes Figure 4 A cross-sectional view of the battery cell 10 along the AA direction; Figure 6 yes Figure 5 The image shows an enlarged view of point B of the battery cell 10. This application provides a battery cell 10, which includes a housing 11, an end cap 12, and an electrode assembly 2. The housing 11 has an opening at at least one end along a first direction Z, and includes a first wall 111. The end cap 12 closes the opening. The first wall 111 is welded to the end cap 12 to form a first connection portion 51. A portion of the first connection portion 51 is formed on the end cap 12, and another portion of the first connection portion 51 is formed on the first wall 111. The electrode assembly 2 is at least partially housed within the housing 11. The electrode assembly 2 includes a positive electrode 22 and a negative electrode 23. At least portions of the positive electrode 22 and at least portions of the negative electrode 23 are stacked along a second direction Y, which is parallel to the thickness direction of the first wall 111. The first direction Z intersects the second direction Y.

[0260] The first wall 111 includes a main body 400. Along the first direction Z, the main body 400 is located on the side of the first connecting part 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 part 51.

[0261] Specifically, the housing 11 may have an opening at only one end along the first direction Z, and the end cap 12 may be configured as one; or the housing 11 may have openings at both opposite ends along the first direction Z, and the end cap 12 may be configured as two.

[0262] The shell 11 can be of various shapes, such as cylindrical, prismatic, etc. The prism can be a triangular prism, a square prism, a pentagonal prism, a hexagonal prism, etc. The square prism can be a cuboid, a cube, etc. The first direction Z is parallel to the orientation of the opening of the shell 11.

[0263] In embodiments where the housing 11 is cylindrical, the first direction Z can be parallel to the axial direction of the housing 11; in embodiments where the housing 11 is prismatic, the first direction Z can be parallel to the extension 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 embodiments where the housing 11 is cylindrical, the first wall 111 is cylindrical, 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 embodiments where the housing 11 is prismatic, the first wall 111 can be a rectangular plate structure. The first direction Z and the second direction Y can be set at an acute angle, a right angle, or an obtuse angle.

[0264] The end cap 12 can be welded to the housing 11, and the welding of the end cap 12 and the housing 11 forms a connecting part 5, which can extend circumferentially along the opening of the housing 11. The end cap 12 and the housing 11 are connected and fixed through the connecting part 5 to achieve a seal between the end cap 12 and the housing 11. The connecting part 5 is the part with weld marks formed after the end cap 12 and the housing 11 are welded together; the connecting part 5 can be the part where the end cap 12 and the housing 11 are welded together.

[0265] There may be one or more first walls 111 in the housing 11. The first connecting part 51 may correspond one-to-one with the first wall 111. The first connecting part 51 is the part with a weld mark formed after the end cap 12 is welded to the first wall 111. The part where the end cap 12 and the first wall 111 are welded together may be the first connecting part 51.

[0266] A portion of the first connecting part 51 is formed on the end cap 12, and another portion of the first connecting part 51 is formed on the first wall 111. The first wall 111 and the end cap 12 can be formed by seam welding or by through welding to form the first connecting part 51.

[0267] The first connecting portion 51 can be a part of or the entirety of the connecting portion 5. In an embodiment where the housing 11 is cylindrical, there is only one first wall 111 in the housing 11, and the first wall 111 is cylindrical, and the first connecting portion 51 is the connecting portion 5; in an embodiment where the housing 11 is prismatic, the housing 11 can include multiple side walls, which are arranged along the opening of the housing 11, and at least one of the two side walls arranged opposite each other in the second direction Y can be the first wall 111, and the first connecting portion 51 is a part of the connecting portion 5.

[0268] The first wall 111 can be the wall with the largest outer surface area in the shell 11, or it can be other than the wall with the largest outer surface area in the shell 11. Taking the shell 11 as a cuboid as an example, the shell 11 can include two first walls 111 and two second walls 112. The two first walls 111 are arranged opposite each other along the second direction Y, and the two second walls 112 are arranged opposite each other along the third direction X. The first direction Z, the second direction Y, and the third direction X are all perpendicular to each other. The first wall 111 can be the wall with the largest outer surface area in the shell 11, such that the outer surface area of ​​the first wall 111 is greater than the outer surface area of ​​the second wall 112, or the second wall 112 can be the wall with the largest outer surface area in the shell 11, such that the outer surface area of ​​the second wall 112 is greater than the outer surface area of ​​the first wall 111.

[0269] The electrode assembly 2 is located within the receiving space defined by the housing 11 and the end cap 12. The electrode assembly 2 can be a stacked structure or a wound structure. There can be one or more electrode assemblies 2 in the housing 11. If there are multiple electrode assemblies 2, they can be stacked, for example, multiple electrode assemblies 2 can be stacked along the second direction Y.

[0270] At least a portion of the positive electrode 22 and at least a portion of the negative electrode 23 are stacked along the second direction Y. During the cycle, the electrode assembly 2 will expand along the second direction Y. The first wall 111 will deform after being subjected to the expansion force of the electrode assembly 2, which can easily cause fatigue cracking in the area of ​​the first wall 111 near the first connection 51.

[0271] The buffer structure 410 is a region that can absorb deformation. It can be a region with reduced strength, such as a decrease in thickness or hardness, or it can be a bending structure. After the first wall 111 is subjected to expansion force, the expansion force on the first connecting part 51 is relatively small because the buffer structure 410 can absorb the deformation.

[0272] 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 of the area of ​​the first wall 111 near the first connection portion 51 due to the expansion of the electrode assembly 2, thereby improving the service life of the battery cell 10.

[0273] Please refer to Figure 6 In some embodiments, the buffer structure 410 includes a weak portion 411 disposed on the main body 400, the minimum thickness of the weak portion 411 being less than the thickness of other portions of the main body 400.

[0274] Specifically, the weak portion 411 may be provided as a blind hole or groove on the main body 400. The weak portion 411 may be continuous or discontinuous. For example, the weak portion 411 may include multiple weak areas, which are arranged at intervals along the first direction Z on the main body 400.

[0275] Thus, compared to other parts of the main body 400, the weak portion 411 can more effectively absorb expansion force, thereby reducing the expansion force acting directly on the first connection portion 51. Therefore, the weak portion 411 reduces the risk of fatigue cracking of the area of ​​the first wall 111 near the first connection portion 51 due to the expansion of the electrode assembly 2, thereby improving the service life of the battery cell 10.

[0276] In some embodiments, a groove 412 is provided on the inner surface 430 of the main body 400.

[0277] In some embodiments, a groove 412 is provided on the outer surface 420 of the main body 400.

[0278] In some embodiments, grooves 412 are provided on both the inner surface 430 and the outer surface of the main body 400.

[0279] The weak part 411 is the area on the main body 400 that is opposite to the groove of the recess 412.

[0280] Specifically, the groove 412 can be circular, rectangular, elliptical, or other shapes, and its size and shape can be adjusted as needed. By providing the groove 412, the area corresponding to the inner surface 430 or the outer surface 420 of the main body 400 is more likely to deform when the electrode assembly 2 expands, thus absorbing the expansion force.

[0281] Thus, the weak part 411, as the area opposite to the groove opening, has better buffering performance and makes the weak part 411 easier to form, reducing the manufacturing difficulty of the shell 11 and thus reducing the manufacturing cost of the shell 11.

[0282] Please refer to Figure 7 , Figure 7 This is a partial schematic diagram of a battery cell 10 provided in some embodiments of this application. In some embodiments, the groove 412 includes a first side surface 4120, a second side surface 4121, and a bottom surface 4122 connected to the first side surface 4120 and the second side surface 4121. The weak portion 411 includes a first weak portion 4110 disposed opposite to the bottom surface 4122. The thickness of the first weak portion 4110 is less than the thickness of other portions of the main body 400.

[0283] Specifically, the first weak portion 4110 may be continuous or discontinuous. For example, the first weak portion 4110 extends along the first direction Z and connects the first side surface 4120 and the second side surface 4121; the first weak portion 4110 may also include a plurality of first weak regions, which are arranged at intervals along the first direction Z in the region of the first weak portion 4110 opposite to the bottom surface 4122.

[0284] The first side surface 4120, the second side surface 4121, and the bottom surface 4122 can be surfaces that form the shape and outline of the groove 412. The first side surface 4120, the second side surface 4121, and the bottom surface 4122 can be coplanar or non-coplanar.

[0285] Thus, compared to other parts of the main body 400, the expansion force acting on the first weak portion 4110 is greater. The first weak portion 4110 can absorb the expansion force more effectively, thereby reducing the expansion force acting directly on the first connecting portion 51. Therefore, the first weak portion 4110 can reduce the risk of fatigue cracking of 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.

[0286] Please refer to Figure 7 In some embodiments, the weak portion 411 further includes a second weak portion 4111 disposed opposite to the first side surface 4120 and a third weak portion 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 portion 51, and the thickness of the second weak portion 4111 increases in the direction close to the first connecting portion 51. The second side surface 4121 is located on the side of the bottom surface 4122 away from the first connecting portion 51, and the thickness of the third weak portion 4112 increases in the direction away from the first connecting portion 51.

[0287] Specifically, the direction near the first connecting portion 51 and the direction away from the first connecting portion 51 can be different parts facing the first direction Z. Along the first direction Z, the second weak portion 4111 and the third weak portion 4112 can be located on both sides of the first weak portion 4110, respectively. The second weak portion 4111 can be connected to or spaced apart from the first weak portion 4110. The third weak portion 4112 can be connected to or spaced apart from the first weak portion 4110.

[0288] The second weak portion 4111 can be continuous or discontinuous. For example, the second weak portion 4111 extends along the first direction Z and connects to the first weak portion 4110; the second weak portion 4111 may also include a plurality of second weak regions, which are arranged at intervals along the first direction Z in the region of the second weak portion 4111 opposite to the first side surface 4120.

[0289] The third weak portion 4112 may be continuous or discontinuous. For example, the third weak portion 4112 extends along the first direction Z and connects to the first weak portion 4110; the third weak portion 4112 may also include a plurality of third weak regions, which are arranged at intervals along the first direction Z in the region opposite to the second side surface 4121.

[0290] The thickness of the second weak portion 4111 can increase in segments or gradually along the direction close to the first connecting portion 51. For ease of manufacturing, the thickness of the second weak portion 4111 can gradually increase along the direction close to the first connecting portion 51.

[0291] The thickness of the third weak portion 4112 can increase in segments or gradually in the direction away from the first connecting portion 51. For ease of manufacturing, the thickness of the third weak portion 4112 can gradually increase in the direction away from the first connecting portion 51.

[0292] Thus, the non-uniform thickness design of the second weak portion 4111 and the third weak portion 4112 gives the weak portion 411 a gradient strength, which helps to more effectively withstand and disperse expansion forces from different directions, helps to guide the expansion forces along a specific path, and reduces the direct impact on the first weak portion 4110. This makes the weak portion 411 less prone to functional failure while absorbing expansion forces. In addition, the gradually changing thickness of the weak portion 411 also makes it easier to manufacture and form the weak portion 411.

[0293] 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.

[0294] 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.

[0295] Please refer to Figure 7 In some embodiments, the angle between the first side surface 4120 and the bottom surface 4122, and the angle between the second side surface 4121 and the bottom surface 4122 are both greater than or equal to 135 degrees and less than 180 degrees.

[0296] The included angle between the first side surface 4120 and the bottom surface 4122 can be any one of the following values: 135 degrees, 140 degrees, 145 degrees, 150 degrees, 155 degrees, 160 degrees, 165 degrees, 170 degrees, 175 degrees, etc., or a range between any two.

[0297] The included angle between the second side surface 4121 and the bottom surface 4122 can be any one of the following values: 135 degrees, 140 degrees, 145 degrees, 150 degrees, 155 degrees, 160 degrees, 165 degrees, 170 degrees, 175 degrees, etc., or any range between the two.

[0298] Specifically, the angle between the first side surface 4120 and the bottom surface 4122 is denoted as the first included angle a1, and the 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.

[0299] Thus, within these included angle ranges, the weak portion 411 has a high capacity to absorb expansion forces, thereby effectively reducing the risk of fatigue cracking of the area of ​​the first wall 111 near the first connection portion 51 due to the expansion of the electrode assembly 2, thereby improving the service life of the battery cell 10.

[0300] Furthermore, the groove 412 can generally be manufactured using a stamping process. Stamping requires the use of a die, which typically consists of an upper die and a lower die. The upper die is used for stamping, and the lower die supports the housing 11. During the stamping process, the housing 11 is fixed to the lower die using a fixture or die fixing structure. Then, the upper die moves towards the housing 11 and applies pressure, causing the area of ​​the housing 11 corresponding to the upper die to deform, thereby forming the groove 412.

[0301] When the angle is greater than or equal to 135 degrees and less than 180 degrees, the groove 412 will not get stuck with the upper mold during demolding, making it easier for the upper mold to separate from the groove 412 after it has been machined. Therefore, controlling the angle between 135 degrees and 180 degrees facilitates the formation of the groove 412, reduces the manufacturing difficulty of the housing 11, and thus improves the machining accuracy of the housing 11 and the service life of the mold.

[0302] Please refer to Figure 8 , Figure 8 This is a partial schematic diagram of a battery cell 10 provided in other embodiments of this application. In some embodiments, the buffer structure 410 includes a first protrusion 413 and a first recess 414, the first protrusion 413 and the first recess 414 are correspondingly disposed, the first protrusion 413 protrudes from the outer surface 420 of the main body 400, and the first recess 414 is recessed outward from the inner surface 430 of the main body 400.

[0303] Specifically, the first protrusion 413 and the first recess 414 can be arranged along the first direction Z. Along the first direction Z, one end of the first protrusion 413 can be connected to one end of the first recess 414. The first protrusion 413 and the first recess 414 can form a curved structure. For example, the first protrusion 413 and the first recess 414 can form an "S" shaped structure.

[0304] Thus, the first protrusion 413 and the first recess 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 protrusion 413 and the first recess 414 can reduce the risk of fatigue cracking of 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.

[0305] In some embodiments, there are multiple first protrusions 413 and multiple first recesses 414, with each first protrusion 413 corresponding to one first recess 414.

[0306] Specifically, the number of first protrusions 413 can be two, three, four, or even more. The number of first recesses 414 can be two, three, four, or even more.

[0307] As an example, the first convex portion 413 may include a first sub-convex portion, a second sub-convex portion and a third sub-convex portion. The first recess 414 may include first, second and third sub-recesses. Along the first direction Z, the first sub-convex part, the first sub-recessed part, the second sub-convex part, the second sub-recessed part, the third sub-convex part and the third sub-recessed part are connected in sequence.

[0308] Thus, the multiple first protrusions 413 and the corresponding first recesses 414 can further increase the buffer path of the buffer structure 410, providing multiple areas for dispersing the expansion force, thereby achieving more effective absorption of the expansion force and effectively reducing the expansion force acting directly on the first connecting part 51.

[0309] Please refer to Figure 8 In some embodiments, the buffer structure 410 includes a second protrusion 417 and a second recess 418, with the second protrusion 417 and the second recess 418 correspondingly disposed. The second protrusion 417 protrudes from the inner surface 430 of the main body 400, and the second recess 418 is recessed inward from the outer surface 420 of the main body 400.

[0310] Specifically, the second protrusion 417 and the second recess 418 can be arranged along the second direction Y. Along the second direction Y, one end of the second protrusion 417 can be connected to one end of the second recess 418. The second protrusion 417 and the second recess 418 can form a curved structure. For example, the second protrusion 417 and the second recess 418 can form an "S" shaped structure.

[0311] Thus, the second protrusion 417 and the second recess 418 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 of the second protrusion 417 and the second recess 418 can reduce the risk of fatigue cracking of 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.

[0312] In some embodiments, there are multiple second protrusions 417 and multiple second recesses 418, with each second protrusion 417 corresponding to one second recess 418.

[0313] Specifically, the number of second protrusions 417 can be two, three, four, or even more. The number of second recesses 418 can be two, three, four, or even more.

[0314] As an example, the second protrusion 417 may include a fourth sub-protrusion, a fifth sub-protrusion, and a sixth sub-protrusion. The second recess 418 may include a fourth sub-recess, a fifth sub-recess, and a sixth sub-recess. Along the first direction Z, the fourth sub-protrusion, the fourth sub-recess, the fifth sub-protrusion, the fifth sub-recess, the sixth sub-protrusion, and the sixth sub-recess are connected sequentially.

[0315] Thus, the multiple second protrusions 417 and the corresponding second recesses 418 can further increase the buffer path of the buffer structure 410, providing multiple areas for dispersing the expansion force, thereby achieving more effective absorption of the expansion force and effectively reducing the expansion force acting directly on the first connecting part 51.

[0316] Please refer to Figure 6 In some embodiments, along the first direction Z, the distance between the edge of the buffer structure 410 and the edge of the first connecting portion 51 is H, where H satisfies: 0.3mm ≤ H ≤ 7mm. H can be any one of 0.3mm, 1.5mm, 2mm, 3mm, 4mm, 5.5mm, 7mm, or any range between two values.

[0317] In some embodiments, along the first direction Z, H satisfies: 1.5mm ≤ H ≤ 4mm. H can take any point value or a range between any two of 1.5mm, 2.5mm, 3.5mm, 3.6mm, 3.7mm, 3.8mm, 4mm, etc.

[0318] 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 connecting portion 51. The buffer structure 410 will not suffer fatigue cracking along with the first connecting portion 51 due to its proximity to the first connecting portion 51, nor will it fail to reduce the expansion force directly acting on the first connecting portion 51 due to its distance from the first connecting portion 51.

[0319] Please refer to Figure 9 , Figure 9 This is a schematic diagram of an electrode assembly 2 provided in some embodiments of this application. In some embodiments, the electrode assembly 2 further includes a separator 24, which is disposed between the positive electrode 22 and the negative electrode 23;

[0320] The positive electrode 22 includes a positive electrode body region 221 and a positive electrode tab 21a protruding from the positive electrode body region 221. The positive electrode body region 221 has a positive electrode active material layer 223. The negative electrode 23 includes a negative electrode body region 231 and a negative electrode tab 21b protruding from the negative electrode body region 231. The negative electrode body region 231 has a negative electrode active material layer 233. Along the first direction Z, the positive electrode body region 221 has a first end 2211 facing the end cap 12, the negative electrode body region 231 has a second end 2311 facing the end cap 12, and the separator 24 has a third end 241 facing the end cap 12. The third end 241 is closer to the end cap 12 than the first end 2211 and the second end 2311.

[0321] Specifically, in this embodiment, the electrode assembly 22 can be a wound structure or a stacked structure.

[0322] The positive electrode 22 may include a positive current collector 222 and a positive active material layer 223. The positive current collector 222 has a positive active material layer 223 disposed on one or two surfaces in its thickness direction.

[0323] Please refer to Figure 10 , Figure 11 and Figure 12 , Figure 10 This is a partial schematic diagram of a battery cell 10 provided in some embodiments of this application. Figure 11 This is a partial schematic diagram of the electrode assembly 2 provided in some embodiments of this application. Figure 12This is a partial schematic diagram of the electrode assembly 2 provided in other embodiments of this application. The positive electrode 22 also includes an insulating layer 224. The positive current collector 222 has an insulating layer 224 on both opposite surfaces 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 disposed at the end of the positive active material layer 223. The portion of the positive electrode 22 that corresponds to the positive active material layer 223 and the insulating layer 224 as a whole is the positive electrode body region 221. The end of the insulating layer 224 near the end cap 12 forms the first end 2211 of the positive electrode body region 221. The portion of the positive current collector 222 that extends beyond the insulating layer 224 forms the positive electrode tab 21a.

[0324] exist Figure 12 In the illustrated embodiment, the positive electrode 22 does not have an insulating layer 224. The portion of the positive electrode 22 corresponding to the positive active material layer 223 is the positive electrode body region 221. The end of the positive active material layer 223 near the end cap 12 forms the first end 2211 of the positive electrode body region 221. The portion of the positive current collector 222 that extends beyond the positive active material layer 223 forms the positive electrode tab 21a.

[0325] The negative electrode sheet 23 may include a negative electrode current collector 232 and a negative electrode active material layer 233. The negative electrode current collector 232 has the negative electrode active material layer 233 disposed on one or both surfaces in its thickness direction. The portion of the negative electrode sheet 23 corresponding to the negative electrode active material layer 233 is the negative electrode main body region 231. The end of the negative electrode active material layer 233 near the end cap 12 forms the second end 2311 of the negative electrode main body region 231. The portion of the negative electrode current collector 232 that extends beyond the negative electrode active material layer 233 forms the negative electrode tab 21b.

[0326] The first end 2211 and the second end 2311 can be flush; for example Figure 11 As shown, the first end 2211 can also be closer to the end cap 12 than the second end 2311. Figure 10 (as shown in the image); Figure 12 As shown, the second end 2311 can also be closer to the end cap 12 than the first end 2211. Figure 10 (as shown in the image).

[0327] Thus, the insulating member 24 has a portion that extends beyond the first end 2211 and the second end 2311, which enhances the insulation effect of the insulating member 24 between the positive electrode 22 and the negative electrode 23 and reduces the risk of the positive electrode 22 and the negative electrode 23 overlapping.

[0328] Please refer to Figure 10In some embodiments, the isolation member 24 includes an extension region 242 extending beyond the first end 2211 and the second end 2311 along the first direction Z. In a projection plane perpendicular to the second direction Y, the orthographic projection of the extension region 242 overlaps with the orthographic projection of the buffer structure 410.

[0329] Specifically, the extended area 242 is the portion of the isolation element 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 As shown, in the embodiment where the first end 2211 is closer to the end cap 12 than the second end 2311, the portion of the spacer 24 extending beyond the first end 2211 is the extended area 242; as Figure 12 As shown, in an embodiment where the second end 2311 is closer to the end cap 12 than the first end 2211, the portion of the spacer 24 that extends beyond the second end 2311 is the extended area 242.

[0330] As an example, in Figures 10-12 In the electrode assembly 2, the positive electrode 22, the negative electrode 23, and the separator 24 are located in the flat region 25. Figures 10-12 (Not shown) portions are stacked along the second direction Y.

[0331] Thus, 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 expansion force, and further reduce the risk of fatigue cracking in the area of ​​the first wall 111 near the first connection 51.

[0332] Please refer to Figure 10 In some embodiments, the orthographic projection of the positive electrode main body region 221 and the orthographic projection of the buffer structure 410 do not overlap in the projection plane perpendicular to the second direction Y.

[0333] Please refer to Figure 10 In some embodiments, the orthographic projection of the negative electrode main body region 231 and the orthographic projection of the buffer structure 410 do not overlap in the projection plane perpendicular to the second direction Y.

[0334] Please refer to Figure 10 In some embodiments, in a projection plane perpendicular to the second direction Y, the orthogonal projections of the positive electrode main body region 221 and the negative electrode main body region 231 do not overlap with the orthogonal projection of the buffer structure 410.

[0335] As an example, in Figures 10-12 In the embodiment, in the projection plane perpendicular to the second direction Y, the positive electrode main body region 221 and the positive projection of the buffer structure 410 do not overlap, and the negative electrode main body region 231 and the positive projection of the buffer structure 410 do not overlap.

[0336] Thus, if the orthographic projection of the positive electrode main body region 221 and the orthographic projection of the buffer structure 410 do not overlap in the projection plane perpendicular to the second direction Y, the housing 11 can provide a larger expansion space for the electrode assembly 2, reducing the risk that the expansion of the electrode assembly 2 will directly apply expansion force to the buffer, reducing the deformation of the first wall 111, and further reducing the risk of fatigue cracking in the area of ​​the first wall 111 near the first connection part 51.

[0337] If the orthographic projection of the negative electrode main body region 231 and the orthographic projection of the buffer structure 410 do not overlap in the projection plane perpendicular to the second direction Y, the housing 11 can provide a larger expansion space for the electrode assembly 2, reducing the risk that the expansion of the electrode assembly 2 will directly apply expansion force to the buffer structure 410, reducing the deformation of the first wall 111, and further reducing the risk of fatigue cracking in the area of ​​the first wall 111 near the first connection part 51.

[0338] In some embodiments, the orthographic projection of the positive electrode main body region 221 overlaps with the orthographic projection of the buffer structure 410 in a projection plane perpendicular to the second direction.

[0339] In some embodiments, the orthographic projection of the negative electrode main body region 231 overlaps with the orthographic projection of the buffer structure 410 in a projection plane perpendicular to the second direction.

[0340] Please refer to Figure 13 , Figure 14 and Figure 15 , Figure 13 This is a schematic diagram of the structure of a battery cell 10 provided in other embodiments of this application; Figure 14 yes Figure 13 A cross-sectional view of the battery cell 10 along the BB direction; is Figure 14 An enlarged view of point P of the battery cell 10. In some embodiments, in a projection plane perpendicular to the second direction, the orthographic projections of the positive electrode main body region 221 and the negative electrode main body region 231 both overlap with the orthographic projection of the buffer structure 410.

[0341] As an example, in Figure 15 In one embodiment, in a projection plane perpendicular to the second direction, the positive electrode main body region 221 overlaps with the orthogonal projection of the buffer structure 410, and the negative electrode main body region 231 overlaps with the orthogonal projection of the buffer structure 410.

[0342] Thus, if the orthographic projection of the positive electrode main body region 221 overlaps with the orthographic projection of the buffer structure 410 in the projection plane perpendicular to the second direction, the buffer structure 410 has a larger design width, which can enhance the ability of the buffer structure 410 to absorb expansion force, thereby reducing the risk of fatigue cracking in the area of ​​the first wall 111 near the first connection part 51.

[0343] If the orthographic projection of the negative electrode main body area 231 overlaps with the orthographic projection of the buffer structure 410 in the projection plane perpendicular to the second direction, the buffer structure 410 has a larger design width, which can enhance the ability of the buffer structure 410 to absorb expansion force, thereby reducing the risk of fatigue cracking in the area of ​​the first wall 111 near the first connection part 51.

[0344] In some embodiments, in a projection plane perpendicular to the second direction, at least a portion of the orthographic projection of the buffer structure 410 is located between the orthographic projection of the first connecting portion 51 and the orthographic projection of the positive electrode main body region 221.

[0345] In some embodiments, in a projection plane perpendicular to the second direction, at least a portion of the orthographic projection of the buffer structure 410 is located between the orthographic projection of the first connecting portion 51 and the orthographic projection of the negative electrode main body region 231.

[0346] In some embodiments, in a projection plane perpendicular to the second direction, at least a portion of the orthographic projection of the buffer structure 410 is located between the orthographic projection of the first connecting portion 51 and the orthographic projection of the positive electrode main body region 221, and at least a portion of the orthographic projection of the buffer structure 410 is located between the orthographic projection of the first connecting portion 51 and the orthographic projection of the negative electrode main body region 231.

[0347] As an example, in Figure 15 In one embodiment, in a projection plane perpendicular to the second direction, at least a portion of the orthographic projection of the buffer structure 410 is located between the orthographic projection of the first connecting portion 51 and the orthographic projection of the positive electrode main body region 221, and at least a portion of the orthographic projection of the buffer structure 410 is located between the orthographic projection of the first connecting portion 51 and the orthographic projection of the negative electrode main body region 231.

[0348] Thus, if at least part of the orthographic projection of the buffer structure 410 is located between the orthographic projection of the first connecting part 51 and the orthographic projection of the positive electrode main body region 221 in the projection plane perpendicular to the second direction, this reduces the probability that the expansion force of the electrode assembly 2 will directly act on the buffer structure 410, reduces the deformation of the first wall 111, and further reduces the risk of fatigue cracking in the area of ​​the first wall 111 near the first connecting part 51.

[0349] If at least part of the orthographic projection of the buffer structure 410 is located between the orthographic projection of the first connecting portion 51 and the orthographic projection of the negative electrode main body region 231, this reduces the probability that the expansion force of the electrode assembly 2 will directly act on the buffer structure 410, reduces the deformation of the first wall 111, and further reduces the risk of fatigue cracking in the area of ​​the first wall 111 near the first connecting portion 51.

[0350] In some embodiments, in a projection plane perpendicular to the second direction, the orthographic projection of the main body region away from the first connecting portion 51 in the positive electrode main body region 221 and the negative electrode main body region 231 is the first orthographic projection, and the orthographic projection of the lowest residual thickness of the buffer structure 410 is located between the orthographic projection of the first connecting portion 51 and the first orthographic projection.

[0351] Specifically, when the remaining thickness of the buffer structure 410 gradually decreases from both ends to the middle, and there is a region with the same remaining thickness in the middle, the lowest point of the remaining thickness of the buffer structure 410 is the thickness of the region with the same remaining thickness. When the buffer structure 410 is a symmetrical structure and the remaining thickness gradually decreases from both ends to the middle, the lowest point of the remaining thickness of the buffer structure 410 is located at the center line of the buffer structure 410. Of course, the buffer structure 410 can also be an asymmetrical structure.

[0352] As an example, in Figure 15 In the embodiment, the positive electrode main body region 221 is far away from the first connecting part 51 relative to the negative electrode main body region 231, the buffer structure 410 is a symmetrical structure and the residual thickness gradually decreases from both ends to the middle, and the distance F1 between the lowest point of the residual thickness of the buffer structure 410 and the positive electrode main body region 221 is greater than 0.

[0353] Thus, during the charging process of the battery cell 10, ions in the positive electrode 22 are deintercalated and enter the electrolyte, while electrons are released and flow through the external circuit to the negative electrode 23. This process is accompanied by the expansion of the volume of the negative electrode 23 in the corresponding area of ​​the positive electrode 22. Therefore, placing the orthographic projection of the lowest point of the residual thickness of the buffer structure 410 between the orthographic projection of the first connecting portion 51 and the first orthographic projection reduces the probability that the expansion force generated when the negative electrode 23 expands will directly act on the lowest point of the residual thickness of the buffer structure 410, thereby avoiding direct breakage of the buffer structure 410 and resulting in functional failure. At the same time, the buffer structure 410 can maintain a large width, which enhances its ability to absorb expansion force, thereby reducing the risk of fatigue cracking in the area of ​​the first wall 111 near the first connecting portion 51.

[0354] Please refer to Figure 11 and Figure 12 In some embodiments, the negative electrode 23 includes a negative current collector 232 and a negative active material layer 233 disposed on at least one side of the negative current collector 232, the negative active material layer 233 including a negative active material; the positive electrode 22 includes a positive current collector 222 and a positive active material layer 223 disposed on at least one side of the positive current collector, the positive active material layer 223 including a positive active material.

[0355] Specifically, the negative electrode active material layer 233 can be provided on only one side of the negative electrode current collector 232, that is, the negative electrode active material layer 233 is provided on only one surface of the negative electrode current collector 232 along the thickness direction; or the negative electrode active material layer 233 can be provided on both opposite sides of the negative electrode current collector 232, that is, the negative electrode active material layer 233 is provided on both opposite surfaces of the negative electrode current collector 232 along the thickness direction.

[0356] The negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate, etc.

[0357] The positive electrode active material layer 223 can be provided on only one side of the positive electrode current collector 222, that is, the positive electrode active material layer 223 is provided on only one surface of the positive electrode current collector 222 along the thickness direction; or the positive electrode active material layer 223 can be provided on both opposite sides of the positive electrode current collector 222, that is, the positive electrode active material layer 223 is provided on both opposite surfaces of the positive electrode current collector 222 along the thickness direction.

[0358] Thus, by providing a negative electrode active material layer 233 on at least one side of the negative electrode current collector 232, the content of active material in the battery cell 10 can be increased, thereby improving the energy density of the battery; by providing a positive electrode active material layer 223 on at least one side of the positive electrode current collector 222, the content of active material in the battery cell 10 can be increased, thereby improving the energy density of the battery 100.

[0359] 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, which are arranged along a first direction Z. Along the first direction Z, the negative electrode main body portion 2331 is provided with a negative electrode thinning portion 2332 at one end near the end cap 12. The positive electrode active material layer 223 includes a positive electrode main body portion 2231 and a positive electrode thinning portion 2232, which are arranged along a first direction Z. Along the first direction Z, the positive electrode main body portion 2231 is provided with a positive electrode thinning portion 2232 at one end near the end cap 12.

[0360] Specifically, the thickness of the negative electrode main body 2331 is greater than the thickness of the negative electrode thinning portion 2332. The negative electrode thinning portion 2332 can be provided only at one end of the negative electrode main body 2331 along the first direction Z, near the end cap 12, or it can be provided at both ends of the negative electrode main body 2331 along the first direction Z. The negative electrode main body 2331 can be of uniform thickness or non-uniform thickness, and the negative electrode thinning portion 2332 can also be of uniform thickness or non-uniform thickness. If at least one of the negative electrode main body 2331 and the negative electrode thinning portion 2332 is non-uniform thickness, the maximum thickness of the negative electrode thinning portion 2332 can be less than or equal to the minimum thickness of the negative electrode main body 2331, thereby achieving a thickness greater than that of the negative electrode main body 2331.

[0361] As an example, the negative electrode main body 2331 has a uniform thickness structure, and the thickness of the negative electrode thinning part 2332 decreases along the direction from the negative electrode main body 2331 to the negative electrode thinning part 2332.

[0362] The thickness of the positive electrode main body 2231 is greater than the thickness of the positive electrode thinning portion 2232. The positive electrode thinning portion 2232 may be provided only at one end of the positive electrode main body 2231 near the end cap 12 along the first direction Z, or it may be provided at both ends of the positive electrode main body 2231 along the first direction Z. The positive electrode main body 2231 may be of uniform thickness or non-uniform thickness, and the positive electrode thinning portion 2232 may also be of uniform thickness or non-uniform thickness. If at least one of the positive electrode main body 2231 and the positive electrode thinning portion 2232 is of non-uniform thickness, the maximum thickness of the positive electrode thinning portion 2232 may be less than or equal to the minimum thickness of the positive electrode main body 2231, thereby achieving a thickness greater than that of the positive electrode thinning portion 2232.

[0363] As an example, the positive electrode main body 2231 has a uniform thickness structure, and the thickness of the positive electrode thinning part 2232 decreases along the direction from the positive electrode main body 2231 to the positive electrode thinning part 2232.

[0364] Thus, the electrode assembly 2 has a larger expansion gap in the region corresponding to the negative electrode thinning portion 2332, and the region of the electrode assembly 2 corresponding to the negative electrode thinning portion 2332 exerts less force on the first wall 111 after expansion, which can reduce the risk of fatigue cracking in the region of the first wall 111 near the first connection portion 51.

[0365] A positive electrode thinning portion 2232 is provided at one end of the positive electrode body 2231 near the end cap 12. The electrode assembly 2 has a larger expansion gap in the area corresponding to the positive electrode thinning portion 2232. After expansion, the area of ​​the electrode assembly 2 corresponding to the positive electrode thinning portion 2232 exerts less force on the first wall 111, which can reduce the risk of fatigue cracking in the area of ​​the first wall 111 near the first connection portion 51.

[0366] Please refer to Figure 16 , Figure 16 This is a partial schematic diagram of a battery cell 10 provided in some embodiments of this application. In some embodiments, in a projection plane perpendicular to the second direction, the orthographic projection of the main body portion of the positive electrode main body portion 2231 and the negative electrode main body portion 2331 that is far from the first connecting portion 51 is the second orthographic projection, and the orthographic projection of the lowest residual thickness of the buffer structure 410 is located between the orthographic projection of the first connecting portion 51 and the second orthographic projection.

[0367] As an example, in Figure 16 In the embodiment, the positive electrode main body 2231 is far away from the first connecting part 51 relative to the negative electrode main body 2331, the buffer structure 410 is a symmetrical structure and the residual thickness gradually decreases from both ends to the middle, and the distance F2 between the lowest point of the residual thickness of the buffer structure 410 and the positive electrode main body 2231 is greater than 0.

[0368] Thus, the ion deintercalation / intercalation of the positive electrode 22 mainly occurs in the positive electrode body 2231, resulting in less volume expansion of the negative electrode 23 in the region corresponding to the positive electrode thinning portion 2232. Therefore, by placing the orthographic projection of the lowest remaining thickness of the buffer structure 410 between the orthographic projection of the first connecting portion 51 and the second orthographic projection, the probability of the expansion force generated when the negative electrode 23 in the region corresponding to the positive electrode body 2231 expands directly acting on the lowest remaining thickness of the buffer structure 410 is reduced, thereby preventing the buffer structure 410 from directly breaking and causing functional failure. Furthermore, this arrangement allows the buffer structure 410 to have a larger design width, which enhances its ability to absorb expansion forces, thereby reducing the risk of fatigue cracking in the region of the first wall 111 near the first connecting portion 51.

[0369] In some embodiments, in a projection plane perpendicular to the second direction Y, the orthogonal projection of the negative electrode thinning portion 2332 and the orthogonal projection of the buffer structure 410 are spaced apart along the first direction Z.

[0370] Specifically, it can be understood that in the projection plane perpendicular to the second direction Y, the orthographic projection of the negative electrode thinning portion 2332 located at the end of the negative electrode main body portion 2331 near the end cap 12 does not overlap with the orthographic projection of the buffer structure 410.

[0371] Thus, the negative electrode thinning portion 2332 has a lower impact on the buffer structure 410 and the first connection portion 51, reducing the risk that the expansion of the electrode assembly 2 will directly exert an expansion force on 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.

[0372] In some embodiments, in a projection plane perpendicular to the second direction Y, the distance between the orthogonal projection of the negative electrode thinning portion 2332 and the orthogonal projection of the buffer structure 410 along the first direction Z is greater than or equal to 1 mm.

[0373] Specifically, in the projection plane perpendicular to the second direction Y, the distance between the orthographic projection of the negative electrode thinning portion 2332 located at the end of the negative electrode main body 2331 near the end cap 12 and the orthographic projection of the buffer structure 410 along the first direction Z is W1, where W1 ≥ 1 mm. This distance is the minimum distance between the orthographic projections of the negative electrode thinning portion 2332 and the buffer structure 410 along the first direction Z in the projection plane perpendicular to the second direction Y. W1 can be any point value or a range between any two of the following: 1 mm, 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, 10 mm, 11 mm, 12 mm, 13 mm, 14 mm, 15 mm, 16 mm, 17 mm, 18 mm, 19 mm, 20 mm.

[0374] Thus, in the projection plane perpendicular to the second direction Y, the orthographic projection of the negative electrode thinning portion 2332 and the orthographic projection of the buffer structure 410 are further apart along the first direction Z, further reducing the influence of the negative electrode thinning portion 2332 on the buffer structure 410.

[0375] In some embodiments, the single-sided coating weight of the negative electrode active material layer 233 is 90 mg / 1540 mm2 to 170 mg / 1540 mm2.

[0376] Specifically, the coating weight of the negative electrode active material layer 233233 on one side can be any one of the following values ​​or a range between any two: 90mg / 1540mm2, 100mg / 1540mm2, 110mg / 1540mm2, 120mg / 1540mm2, 130mg / 1540mm2, 140mg / 1540mm2, 150mg / 1540mm2, 160mg / 1540mm2, 170mg / 1540mm2.

[0377] When measuring the single-sided coating weight of the negative electrode active material layer 233, a single-sided coated negative electrode sheet 23 (if it is a double-sided coated negative electrode sheet 23, the negative electrode active material layer 233 on one side can be wiped off first), is cut into a small circular piece with an area of ​​S1, and its weight is recorded as M1. Then, the negative electrode active material layer 233 of the weighed negative electrode sheet 23 is wiped off, and the weight of the negative electrode current collector 232 is measured and recorded as M2. The single-sided coating weight of the negative electrode active material layer 233 = (M1-M2) / S1.

[0378] The single-sided coating weight of the negative electrode active material layer 233 is related to the expansion of the negative electrode active material layer 233. Setting the single-sided coating weight of the negative electrode active material layer 233 to 90mg / 1540mm2 to 170mg / 1540mm2 can, to a certain extent, take into account both the high energy density requirements of the battery cell 10 and the low expansion requirements of the negative electrode sheet 23, so as to reduce the impact of the expansion of the negative electrode sheet 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.

[0379] In some embodiments, the single-sided coating weight of the negative electrode active material layer 233 is 110 mg / 1540 mm2 to 150 mg / 1540 mm2.

[0380] Specifically, the coating weight of the negative electrode active material layer 233 on one side can be any one of the following values ​​or a range between any two: 110mg / 1540mm2, 115mg / 1540mm2, 120mg / 1540mm2, 125mg / 1540mm2, 130mg / 1540mm2, 135mg / 1540mm2, 140mg / 1540mm2, 145mg / 1540mm2, 150mg / 1540mm2.

[0381] This can further increase the energy density of the battery cell 10 and further reduce the expansion of the negative electrode 23.

[0382] In some embodiments, the porosity of the negative electrode 23 is 27% to 40%.

[0383] Specifically, the porosity of the negative electrode 2323 can be any one of the following values ​​or a range between any two: 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%.

[0384] The porosity of the negative electrode 23 can be defined as the percentage of the pore volume within the negative electrode 23 to the total volume of the negative electrode 23. As an example, when the battery cell 10 is at 0% state of charge, a negative electrode 23 with double-sided coating is taken; the porosity of the negative electrode 23 is measured using a true density meter AccuPyc II 1340 according to the national standard GB / T 24586-2009.

[0385] In this way, space can be provided for impurities generated by side reactions in the negative electrode 23, the expansion of the negative electrode 23 can be slowed down, and the impact of the expansion of the negative electrode 23 on the first wall 111 can be reduced.

[0386] In some embodiments, the negative electrode active material includes a silicon-based material, wherein the mass content of silicon in the silicon-based material is 0.3% to 10%.

[0387] In some embodiments, the mass content of silicon in the negative electrode active material is 1% to 6%.

[0388] Specifically, the mass content of silicon in the negative electrode active material of the silicon-based material can be any one of the following values ​​or any range between two: 0.3%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%.

[0389] Thus, by controlling the silicon content 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 silicon-based materials during charging and discharging can be reduced.

[0390] By controlling the silicon content 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 silicon-based materials during charging and discharging can be further reduced.

[0391] Please refer to Figure 17 , Figure 17 This is a schematic diagram of the structure of the housing 11 provided in some embodiments of this application. In some embodiments, the dimension of the buffer structure 410 along the third direction X is larger 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 not coplanar and intersect each other.

[0392] Specifically, the dimension of the buffer structure 410 along the third direction X is the length of the buffer structure 410, and the dimension of the buffer structure 410 along the first direction Z is the width of the buffer structure 410. 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 structure extending along the third direction X.

[0393] Thus, the buffer structure 410 has a larger dimension along the third direction X, making the buffer structure 410 more capable of absorbing expansion force, and further reducing the risk of fatigue cracking in the area of ​​the first wall 111 near the first connection 51.

[0394] Please refer to Figure 18 , Figure 18 This is a schematic diagram of the structure of the housing 11 provided in other embodiments of this 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 distance from the middle section to both ends of the first wall 111 along the third direction X is equal.

[0395] Specifically, the buffer structure 410 has two opposite ends along the third direction X. The buffer structure 410 passes through the mid-section of the first wall 111, such that the mid-section of the first wall 111 is located between the two opposite ends of the buffer structure 410 along the third direction X. The distances from the two opposite ends of the buffer structure 410 along the third direction X to the mid-section can be equal or unequal. If the distances from the two opposite ends of the buffer structure 410 along the third direction X to the mid-section of the first wall 111 are equal, it indicates that the buffer structure 410 is a symmetrical structure symmetrically arranged about the mid-section of the first wall 111. It should be noted that the mid-section of the first wall 111 is a virtual plane and is not shown in the figure.

[0396] As an example, in Figure 18 In the illustrated embodiment, the distances from the two opposite ends of the buffer structure 410 along the third direction X to the mid-section of the first wall 111111 are equal.

[0397] Thus, when the first wall 111 is subjected to the expansion force of the electrode assembly 2 of the battery cell 10, the deformation of the middle region of the first wall 111 along the third direction X is greater, and the middle region of the first wall 111 along the third direction X is more prone to fatigue cracking. Since the buffer structure 410 passes through the middle section of the first wall 111, the expansion force on the first wall 111 at least in the middle region along the third direction X is reduced, thereby reducing the risk of fatigue cracking of the middle region of the first wall 111 along the third direction X near the first connection 51.

[0398] Please refer to Figure 18 In some embodiments, the buffer structure 410 has a dimension of L1 along the third direction X, and the first wall 111 has a dimension of L along the third direction X, where 0.4 ≤ L1 / L ≤ 0.9.

[0399] Specifically, L1 / L can take any one of the following point values ​​or any range between two values: 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.

[0400] Thus, when 0.4≤L1 / L, the buffer structure 410 has a larger proportion of the size along the third direction X in the first wall 111, which makes the expansion force on the middle area of ​​the first wall 111 along the third direction X smaller, reducing the risk of fatigue cracking of the middle area of ​​the first wall 111 along the third direction X near the first connection 51.

[0401] When L1 / L≤0.9, the size of the buffer structure 410 in the third direction X of the first wall 111 is relatively small, which reduces the waste generated in manufacturing the buffer structure 410 and lowers the production cost.

[0402] 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 to 0.9. This ensures that the buffer structure 410 has sufficient capacity to absorb expansion force while reducing the waste generated in manufacturing the buffer structure 410, thus balancing the requirements for the buffer structure 410's capacity to absorb expansion force and its economic efficiency.

[0403] Please refer to Figure 18 In some embodiments, the buffer structure 410 has a fourth end 11113a and a fifth end 11113b opposite each other along the third direction X, and the first wall 111 has a sixth end 1113 and a seventh end 1114 opposite each other along the third direction X. The fourth end 11113a is close to the sixth end 1113, and 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.

[0404] 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.

[0405] It can be L2 = L3; or it can be L2 > L3 or L2 < L3.

[0406] L2 / L can take any one of the following values ​​or a range between any two: 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.11, 0.12, 0.13, 0.14, 0.15, 0.16, 0.17, 0.18, 0.19, 0.2, 0.21, 0.22, 0.23, 0.24, 0.25, 0.26, 0.27, 0.28, 0.29, 0.3.

[0407] L3 / L can take any one of the following values ​​or a range between any two: 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.11, 0.12, 0.13, 0.14, 0.15, 0.16, 0.17, 0.18, 0.19, 0.2, 0.21, 0.22, 0.23, 0.24, 0.25, 0.26, 0.27, 0.28, 0.29, 0.3.

[0408] Thus, if L2 / L≤0.3, the proportion of the minimum distance between the fourth end 11113a and the sixth end 1113 along the third direction X in the dimension of the first wall 111 along the third direction X is reduced, so that the fourth end 11113a has a larger area along the third direction X where the expansion force is reduced, further reducing the risk of fatigue cracking in the area of ​​the first wall 111 near the first connection 51.

[0409] If L3 / L≤0.3, the proportion of the minimum distance between the fifth end 11113b and the seventh end 1114 along the third direction X in the dimension of the first wall 111 along the third direction X is reduced, so that the expansion force on the first wall 111 along the third direction X is reduced in more areas, further reducing the risk of fatigue cracking in the area of ​​the first wall 111 near the first connection 51.

[0410] In some embodiments, 100mm ≤ L ≤ 450mm.

[0411] Specifically, L can be any point value or a range of any two of the following: 100mm, 120mm, 150mm, 180mm, 200mm, 220mm, 250mm, 260mm, 280mm, 300mm, 310mm, 320mm, 350mm, 390mm, 400mm, 410mm, 420mm, 430mm, 440mm, 450mm.

[0412] Thus, within this numerical range, the first wall 111 has a larger size along the third direction X, which helps to set up the buffer structure 410, thereby facilitating the absorption of expansion force by the buffer structure 410.

[0413] Please refer to Figure 17 and Figure 18 In some embodiments, the housing 11 includes a corner wall 113, and the first wall 111 is connected to the corner wall 113 at both ends along the third direction X; the buffer structure 410 is spaced apart from the corner wall 113 at at least one end along the third direction X.

[0414] Specifically, along the third direction X, the buffer structure 410 has two 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 may extend 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.

[0415] As an example, in Figures 17-18In 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.

[0416] 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 reduce production costs.

[0417] Please refer to Figure 19 , Figure 19 This is a schematic diagram of the structure of a battery cell 10 provided in some embodiments of this application. In some embodiments, the corner wall 113 is welded to the end cap 12 to form a second connection portion 52.

[0418] The second connecting portion 52 can correspond one-to-one with the corner wall 113. The second connecting portion 52 is the part with weld marks formed after the end cap 12 and the corner wall 113 are welded together. The part where the end cap 12 and the corner wall 113 are welded together can be the second connecting portion 52. A part of the second connecting portion 52 is formed on the end cap 12, and another part of the second connecting portion 52 is formed on the corner wall 113. The corner wall 113 and the end cap 12 can form the second connecting portion 52 by seam welding or by through welding. The second connecting portion 52 and the first connecting portion 51 are both part of the connecting portion 5.

[0419] Please refer to Figure 10 In some embodiments, the main body 400 includes a first region 440 and a second region 450 arranged along a 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.

[0420] Specifically, the first region 440 can be a region where the thickness of the first wall 111 is increased, and the first region 440 is thicker than the second region 450. The second region 450 can be a portion of the first wall 111 along the first direction Z located on the side of the first region 440 opposite to the first connecting portion 51. The first region 440 and the first connecting portion 51 can be directly connected or indirectly connected; the first region 440 and the buffer structure 410 can be directly connected or indirectly connected.

[0421] The first zone 440 can be a structure of equal thickness or a structure of non-equal thickness; the second zone 450 can be a structure of equal thickness or a structure of non-equal thickness. If at least one of the first zone 440 and the second zone 450 is a structure of non-equal thickness, the maximum thickness of the second zone 450 can be less than or equal to the minimum thickness of the first zone 440, so that the thickness of the first zone 440 is greater than the thickness of the second zone 450.

[0422] Along the first direction Z, the buffer structure 410 may include two opposite ends, one of which may be connected to the first region 440 and the other end may be connected to the second region 450.

[0423] Thus, the thicker first region 440 can enhance the resistance of the first connection portion 51 to expansion force. Combined with the buffer structure 410, it can further reduce the risk of fatigue cracking of the area of ​​the first wall 111 near the first connection portion 51 due to the expansion of the electrode assembly 2, thereby improving the service life of the battery cell 10.

[0424] Please refer to Figure 20 , Figure 20 This is a schematic diagram of the structure of a battery cell 1010 provided in some embodiments of this application. In some embodiments, the width of the first region 440 is K1; K1 satisfies: 1.8mm≤K1≤15mm, optionally, 2mm≤K1≤10mm.

[0425] Specifically, K1 can be any one of the following values: 1.8mm, 2mm, 3mm, 4mm, 5mm, 6mm, 7mm, 8mm, 9mm, 10mm, 11mm, 12mm, 13mm, 14mm, 15mm, or any range between two of them.

[0426] Thus, if 1.8mm≤K1≤15mm, the first region 440 can enhance the resistance of the first connection 51 to expansion force. Combined with the buffer structure 410, it can further reduce the risk of fatigue cracking of the area of ​​the first wall 111 near the first connection 51 due to the expansion of the electrode assembly 2, thereby improving the service life of the battery cell 10.

[0427] If 2mm≤K1≤10mm, the first region 440 can more effectively enhance the resistance of the first connection part 51 to expansion force. Combined with the buffer structure 410, it can further reduce the risk of fatigue cracking of the area of ​​the first wall 111 near the first connection part 51 due to the expansion of the electrode assembly 2, thereby improving the service life of the battery cell 10.

[0428] Please refer to Figure 10 In some embodiments, the first region 440 includes a first portion 441 and a second portion 442 arranged along a first direction Z, the second portion 442 being located between the first portion 441 and the buffer structure 410, and the thickness of the first portion 441 being greater than the thickness of the second portion 442.

[0429] Specifically, the first part 441, the second part 442, and the buffer structure 410 are arranged sequentially along the first direction Z, with the first part 441 transitioning to the buffer structure 410 through the second part 442. The first part 441 can be a structure of equal thickness or a structure of non-equal thickness; the second part 442 can be a structure of equal thickness or a structure of non-equal thickness.

[0430] If at least one of the first part 441 and the second part 442 is a non-equal thickness structure, the maximum thickness of the second part 442 may be less than or equal to the minimum thickness of the first part 441, so that the thickness of the first part 441 is greater than the thickness of the second part 442.

[0431] Thus, the area of ​​the first region 440 near the first connection portion 51 is more prone to heat-affected zone formation, which is more susceptible to 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 region 440 is closer to the first connection portion 51, effectively weakening the impact of the heat-affected zone on the first region 440 and reducing the risk of fatigue cracking in the area of ​​the first wall 111 near the first connection portion 51. Furthermore, since the thickness of the second portion 442 is less than the thickness of the first portion 441, the material used in the first region 440 can be reduced, lowering production costs.

[0432] Please refer to Figure 20 In some embodiments, the width of the first portion 441 is K2; K2 satisfies: 1mm≤K2≤10mm, and optionally, 1.5≤K2≤5mm.

[0433] Specifically, K2 can be any one of the following values: 1mm, 1.5mm, 2mm, 3mm, 4mm, 5mm, 6mm, 7mm, 8mm, 9mm, 10mm, or any range between two values.

[0434] Thus, if 1mm≤K2≤10mm, the first part 441 has a large width, which enables the first part 441 to effectively weaken the influence of the heat-affected zone on the first region 440 and reduce the risk of fatigue cracking in the area of ​​the first wall 111 near the first connection 51.

[0435] If 1.5 ≤ K2 ≤ 5 mm, the first portion 441 has a larger width, which allows it to more effectively weaken the influence of the heat-affected zone on the first region 440, reducing the risk of fatigue cracking in the area of ​​the first wall 111 near the first connection 51. Furthermore, the manufacturing cost of the first portion 441 is lower.

[0436] Please refer to Figure 10In some embodiments, the thickness of the second portion 442 decreases along the direction from the end cap 12 toward the electrode assembly 2.

[0437] Specifically, the direction in which the end cap 12 points to the electrode assembly 2 is consistent with the direction in which the first part 441 points to the buffer structure 410 along the first direction Z.

[0438] The thickness of the second part 442 can be reduced in segments or gradually along the direction from the end cap 12 toward the electrode assembly 2. In order to reduce the manufacturing cost of the second part 442, the thickness of the second part 442 can be reduced gradually along the direction from the end cap 12 toward the electrode assembly 2.

[0439] It is understood that the second part 442 is a non-uniform thickness structure. As an example, the thickness of the second part 442 gradually decreases along the direction from the end cap 12 toward the electrode assembly 2. At least one of the inner and outer surfaces of the second part 442 may be a slope to achieve the gradual decrease in thickness of the second part 442 along the direction from the end cap 12 toward the electrode assembly 2.

[0440] As an example, in Figure 10 In the illustrated embodiment, the first portion 441 has a uniform thickness, and its inner and outer surfaces are arranged in 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.

[0441] In this way, on the one hand, this can reduce the impact of the second part 442 on the electrode assembly 2 and reduce the risk of interference between the second part 442 and the electrode assembly 2.

[0442] On the other hand, this makes the reinforcing effect of the second part 442 increase along the direction from the electrode assembly 2 to the end cap 12, so that the area of ​​the second part 442 close to the first part 441 has a good reinforcing effect even if it is affected by the first connecting part 51, reducing the risk of fatigue cracking of the first wall 111 in the second part 442.

[0443] On the other hand, the transition between the first part 441 and the second zone 450 can be achieved through the second part 442, reducing stress concentration.

[0444] In some embodiments, at least a portion of the Vickers hardness of the first region 440 is less than the Vickers hardness of the second region 450.

[0445] Specifically, the Vickers hardness of the region of the first zone 440 near the first connecting portion 51 may be less than the Vickers hardness of the second zone 450.

[0446] It is understandable that when the first wall 111 is subjected to expansion force, the first zone 440 with lower hardness may respond to the overload first through plastic deformation, while the second zone 450 with higher hardness may crack first. Therefore, the risk of fatigue cracking in the first zone 440 is lower.

[0447] Please refer to Figure 9 and Figure 21 , Figure 21 This is a schematic diagram of an electrode assembly 2 provided in other embodiments of this application. In some embodiments, the electrode assembly 2 has a flat region 25, and the portion of the positive electrode 22 located in the flat region 25 and the portion of the negative electrode 23 located in the flat region 25 are stacked along the second direction Y.

[0448] Specifically, the flat region 25 is the flat portion of the electrode assembly 2. The portion of the positive electrode 22 located in the flat region 25 is roughly flat, and the portion of the negative electrode 23 located in the flat region 25 is roughly flat. As an example, both the portions of the positive electrode 22 and the negative electrode 23 located in the flat region 25 are flat plate structures.

[0449] Please refer to Figure 22 , Figure 22 This is a schematic diagram of the structure of the electrode assembly 2 provided in some embodiments of this application. If the electrode assembly 2 is a wound structure, the electrode assembly 2 is a wound electrode assembly 2, and a portion of the electrode assembly 2 may be a flat region 25.

[0450] Please refer to Figure 23 , Figure 23 This is a schematic diagram of the structure of the electrode assembly 2 provided in some other embodiments of this 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 a flat region 25. The second direction Y is the stacking direction of the portion of the positive electrode 22 located in the flat region 25 and the portion of the negative electrode 23 located in the flat region 25.

[0451] Thus, the second direction Y and the stacking direction of the positive electrode 22 in the flat region 25 are the same as those of the negative electrode 23 in the flat region 25. During cycling, the electrode assembly 2 expands more along the second direction Y, and the first wall 111 is more significantly affected by the expansion of the electrode assembly 2. However, because the buffer structure 410 can absorb the expansion force, the expansion force on the area of ​​the first wall 111 near the first connection portion 51 is reduced, lowering 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.

[0452] Please refer to Figure 22 and Figure 23In some embodiments, the electrode assembly 2 includes an adjacent first surface 27 and a second surface 28. The first surface 27 is perpendicular to the second direction Y, and the area of ​​the first surface 27 is larger than the area of ​​the second surface 28. The first surface 27 and the first wall 111 are disposed opposite each other along the second direction Y.

[0453] Specifically, the first surface 27 is the outer surface of the electrode assembly 2 that is perpendicular to the second direction Y, and the second surface 28 is the outer surface of the electrode assembly 2 that is adjacent to the first surface 27. The first surface 27 is disposed on the first wall 111 along the second direction Y. The first surface 27 can be a plane, and it can be the surface with the largest area on the outer surface of the electrode assembly 2, or it can be not the surface with the largest area on the outer surface of the electrode assembly 2. The second surface 28 can be a plane, or it can be at least partially an arc surface. It should be noted that the first surface 27 is approximately perpendicular to the second direction Y, which should also be understood as the first surface 27 being perpendicular to the second direction Y.

[0454] As an example, there are two first surfaces 27 and two second surfaces 28. The two first surfaces 27 are arranged opposite each other along the second direction Y, and the two second surfaces 28 are arranged opposite each other along the third direction X. The positive electrode tab 21a and the negative electrode tab 21b protrude from the surface of the electrode assembly 2 along the first direction Z. The outermost part of the electrode assembly 2 along the second direction Y is the separator 24. The 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.

[0455] Thus, the area of ​​the first surface 27 is larger than that of the second surface 28, resulting in a greater expansion force on the first wall 111, which is disposed opposite to the first surface 27 in the housing 11. Since the buffer structure 410 can absorb the expansion force, the expansion force on the area of ​​the first wall 111 near the first connection 51 is reduced, thereby reducing the risk of fatigue cracking of the first wall 111 near the first connection 51 due to the expansion of the electrode assembly 2.

[0456] Please refer to Figure 22 and Figure 23 In some embodiments, the first surface 27 is the surface with the largest area among the outer surfaces of the electrode assembly 2.

[0457] Specifically, it should be noted that the first surface 27 is the largest surface among the outer surfaces of the electrode assembly 2, but this does not limit the first surface 27 in the electrode assembly 2 to only one. It can be understood that the first surface 27 of the electrode assembly 2 can be one or two.

[0458] As an example, in Figure 22In the illustrated embodiment, the electrode assembly 2 has a wound structure and is flat. The electrode assembly 2 includes six surfaces, of which two surfaces arranged opposite each other along the second direction Y have the largest area. These two surfaces are both first surfaces 27.

[0459] exist Figure 23 In the illustrated embodiment, the electrode assembly 2 is a stacked structure, and the electrode assembly 2 is generally cuboid in shape. The electrode assembly 2 includes six surfaces, among which the two surfaces arranged opposite each other along the second direction Y have the largest areas. These two surfaces are both first surfaces 27.

[0460] Thus, the first wall 111, which is 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 area of ​​the first wall 111 near the first connection 51 is reduced, thereby reducing the risk of fatigue cracking of the first wall 111 near the first connection 51 due to the expansion of the electrode assembly 2.

[0461] Please refer to Figure 9 and Figure 22 In some embodiments, the electrode assembly 2 is a wound structure, and the electrode assembly 2 also has a corner area 26. The straight area 25 is provided with a corner area 26 at at least one end along the third direction X. The first direction Z, the second direction Y and the third direction X are not coplanar and intersect each other.

[0462] The outer surface of the straight area 25 includes a first surface 27, and the outer surface of the corner area 26 includes a second surface 28, at least a portion of which is an arc surface.

[0463] Specifically, the straight area 25 may have a corner area 26 at only one end along the third direction X, or it may have corner areas 26 at both opposite ends along the third direction X. The first direction Z, the second direction Y, and the third direction X are not coplanar, and any two of the first direction Z, the second direction Y, and the third direction X may be set at acute, right, or obtuse angles. The first surface 27 may be part of the outer surface of the straight area 25, and the second surface 28 may be part of the outer surface of the corner area 26. The second surface 28 may be entirely an arc surface, or only part of it may be an arc surface.

[0464] As an example, the positive electrode 22, the separator 24, and the negative electrode 23 are stacked and wound to form a wound structure. The first direction Z, the second direction Y, and the third direction X are perpendicular to each other, and the straight region 25 has corner regions 26 at both ends along the third direction X.

[0465] The positive electrode 22, the negative electrode 23, and the separator 24 are in a bent state in the corner area 26. The part of the positive electrode 22 in the corner area 26 can be at least partially arc-shaped, the part of the negative electrode 23 in the corner area 26 can be at least partially arc-shaped, and the part of the separator 24 in the corner area 26 can be at least partially arc-shaped.

[0466] Along the winding direction of the electrode assembly 2, the outermost ring of the electrode assembly 2 is the separator 24. The first surface 27 and the second surface 28 are both part of the outer surface of the outermost ring of the electrode assembly 2. The first surface 27 is a plane and the second surface 28 is an arc surface. The axis of the arc surface extends along the first direction Z.

[0467] Along the second direction Y, the surfaces on both sides of the straight area 25 are both first surfaces 27; along the third direction X, the surface of one corner area 26 facing away from the other corner area 26 is a second surface 28, and the surface of the other corner area 26 facing away from one corner area 26 is another second surface 28.

[0468] Thus, for the wound electrode assembly 2, the flat region 25 expands more in the second direction Y. Since the buffer structure 410 can absorb the expansion force, the expansion force on the area of ​​the first wall 111 near the first connection 51 is reduced, thereby reducing the risk of fatigue cracking of the first wall 111 near the first connection 51 due to the expansion of the electrode assembly 2.

[0469] Please refer to Figure 21 and Figure 23 In some embodiments, the electrode assembly 2 is a stacked structure, and the flat region 25 includes a plurality of positive electrode plates 22 and a plurality of negative electrode plates 23. The plurality of positive electrode plates 22 and the plurality of negative electrode plates 23 are stacked along the second direction Y, and the first surface 27 is perpendicular to the second surface 28.

[0470] Specifically, as an example, multiple positive electrode plates 22, multiple negative electrode plates 23, and multiple separators 24 are stacked along the second direction Y to form a laminated structure. The positive electrode plates 22 and negative electrode plates 23 are entirely located in the flat region 25. Separators 24 are disposed between adjacent positive electrode plates 22 and negative electrode plates 23. The separators 24 extend beyond both ends of the positive electrode plates 22 and the negative electrode plates 23 along the third direction X. The extended portions of the multiple separators 24 are connected to form a single integral part, and a second surface 28 is formed on this integral part. Along the second direction Y, all positive electrode plates 22 and all negative electrode plates 23 are located between the two outermost separators 24, and the outer surfaces of these two separators 24 are both first surfaces 27.

[0471] It should be noted that the fact that the first surface 27 is approximately perpendicular to the second surface 28 should also be understood as the first surface 27 being perpendicular to the second surface 28. For example, if the angle between the first surface 27 and the second surface 28 is in the range of 85° to 95°, it can be understood that the first surface 27 is perpendicular to the second surface 28.

[0472] Thus, for the stacked electrode assembly 2, the expansion amount of the electrode assembly 2 in the stacking direction of the positive electrode 22 and the negative electrode 23 is greater. Since the buffer structure 410 can absorb the expansion force, the expansion force on the area of ​​the first wall 111 near the first connection portion 51 is reduced, thereby reducing 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.

[0473] Please refer to Figure 17 In some embodiments, the first wall 111 is the wall with the largest outer surface area in the housing 11.

[0474] Specifically, it should be noted that the first wall 111 is the wall with the largest outer surface area in the shell 11, but this does not limit the first wall 111 in the shell 11 to only one. It can be understood that there can be one or two walls with the largest outer surface area in the shell 11.

[0475] Thus, the wall with the largest outer surface area in the housing 11 is more likely to deform under 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 51 due to the expansion of the electrode assembly 2 is low.

[0476] Please refer to Figure 3 and Figure 17 In some embodiments, the housing 11 includes two first walls 111 along the second direction Y, the two first walls 111 being disposed opposite to each other, and the electrode assembly 2 being located between the two first walls 111.

[0477] Specifically, as an example, in Figure 17 In the illustrated embodiment, the housing 11 is cuboid in shape and may include two first walls 111 and two second walls 112. The two first walls 111 are arranged opposite each other along a second direction Y, and the two second walls 112 are arranged opposite each other along a third direction X. The outer surface area of ​​the first walls 111 is larger than the outer surface area of ​​the second walls 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.

[0478] This reduces the risk of fatigue cracking of the two first walls 111 near the first connection 51 due to the expansion of the electrode assembly 2.

[0479] Please refer to Figure 24 and Figure 25 , Figure 24 This is a partial schematic diagram of a battery cell 10 provided in some embodiments of this application. Figure 25 yes Figure 24 An enlarged view of portion C of the battery cell 10. In some embodiments, the first wall 111 further includes a transition region 1117, which is located between the main body portion 400 and the first connecting portion 51 along the first direction Z. The transition region 1117 is connected to the first connecting portion 51, and the connection position between the transition region 1117 and the first connecting portion 51 forms a connection interface 511. 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 the end of the main body portion 400 near the opening along the first direction Z.

[0480] Specifically, the transition zone 1117 may be the portion of the first wall 111 connecting the first connecting portion 51 and the main body portion 400. The transition zone 1117 may be a structure of uniform thickness or a structure of non-uniform thickness. As an example, in Figure 24 and Figure 25 In the illustrated embodiment, the thickness of the transition region 1117 gradually decreases along the direction from the second region 450 to the first region 440.

[0481] The connection interface 511 is formed at the connection position between the transition area 1117 and the first connection part 51, and the transition area 1117 and the first connection part 51 are separated at the connection interface 511. The connection interface 511 can be a plane or a curved surface.

[0482] The main body 400 and the transition area 1117 are separated by the interface U, which is a virtual plane. The interface U passes through the connection position 5111 and is perpendicular to the first direction Z. The transition area 1117 and the first connection part 51 are located above the interface U, and the main body 400 is located below the interface U.

[0483] Thus, the transition zone 1117 is connected to the first connecting part 51 to form a connecting interface 511, which makes the transition zone 1117 and the first connecting part 51 have a sufficiently large contact area, improving the firmness of the first wall 111 and the end cap 12 after welding.

[0484] Please refer to Figure 25 In some embodiments, at least a portion of the connection interface 511 extends at an angle relative to the second direction Y.

[0485] Specifically, the connection interface 511 can extend at an overall angle relative to the second direction Y, or the connection interface 511 can extend at a partial angle relative to the second direction Y.

[0486] It is understandable that the extension direction of the portion of the connection interface 511 that is inclined relative to the second direction Y is not parallel to the second direction Y.

[0487] Thus, after the end cap 12 and the first wall 111 are welded, the first connecting portion 51 will shrink as it solidifies, generating 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 at least partially at an angle relative to the second direction Y, the tensile stress generated by the first connecting portion 51 on the transition region 1117 due to shrinkage near the portion of the connecting interface 511 that extends at an angle relative to the second direction Y is not on the same straight line as the tensile stress generated by the transition region 1117 on the first connecting portion 51 due to the deformation of the first wall 111, reducing the risk of fatigue cracking in the area of ​​the transition region 1117 near the connecting interface 511.

[0488] Please refer to Figure 25 In some embodiments, the connection interface 511 includes a first interface 5112 that extends obliquely from the connection position 5111 toward the end cap 12 along the second direction Y, and at least a portion of the transition region 1117 is located between the first interface 5112 and the end cap 12.

[0489] Specifically, it can be understood that the first interface 5112 extends at an angle relative to the second direction Y. The first interface 5112 can be a plane or a curved surface.

[0490] The connection position 5111 is the lowest position of the first interface 5112 (the position closest to the main body 400). The first interface 5112 extends obliquely from the connection position 5111 towards the end cover 12, that is, the first interface 5112 extends obliquely upward from the connection position 5111 towards the end cover 12.

[0491] Along the second direction Y, the transition zone 1117 can be entirely located between the first interface 5112 and the end cap 12, or the transition zone 1117 can be only partially located between the first interface 5112 and the end cap 12.

[0492] Thus, the first connecting part 51 protects the transition zone 1117. When the first wall 111 is subjected to the expansion force of the electrode assembly 2, the deformation of the transition zone 1117 during the stress process is blocked by the first connecting part 51, reducing the risk of fatigue cracking in the area of ​​the transition zone 1117 near the first interface 5112.

[0493] Please refer to Figure 25 In some embodiments, the first interface 5112 is connected to the outer surface 420 of the main body 400 at the connection position 5111.

[0494] Specifically, as an example, the first interface 5112 intersects the outer surface 420 of the main body 400 at a first straight line, which extends along a third direction X, and the location of the first straight line is the connection position 5111. The transition area 1117 is roughly triangular.

[0495] Thus, since the first interface 5112 is in a direct connection with the main body 400, 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 the expansion of the electrode assembly 2.

[0496] Please refer to Figure 26 and Figure 27 , Figure 26 This is a partial schematic diagram of a battery cell 10 provided in some embodiments of this application. Figure 27 yes Figure 26 Enlarged view of portion D of the battery cell 10. In some embodiments, the connection interface 511 includes a second interface 5113 that extends obliquely from the connection position 5111 in a direction away from the end cap 12 along the second direction Y, and at least a portion of the transition region 1117 is located on the side of the second interface 5113 opposite to the end cap 12.

[0497] Specifically, it can be understood that the second interface 5113 extends at an angle relative to the second direction Y. The second interface 5113 can be a plane or a curved surface. Along the second direction Y, at least a portion of the first connecting portion 51 is located between the second interface 5113 and the end cap 12.

[0498] The connection position 5111 is the lowest position of the second interface 5113 (the position closest to the main body 400). The second interface 5113 extends obliquely from the connection position 5111 in a direction away from the end cover 12, that is, the second interface 5113 extends obliquely upward from the connection position 5111 in a direction away from the end cover 12.

[0499] Along the second direction Y, the transition region 1117 can be entirely located on the side of the second interface 5113 away from the end cover 12, or the transition region 1117 can be only partially located on the side of the second interface 5113 away from the end cover 12.

[0500] Thus, the transition zone 1117 restricts the first connecting part 51, reducing the risk of the first connecting part 51 falling off.

[0501] Please refer to Figure 27 In some embodiments, the second interface 5113 is connected to the inner surface 430 of the main body 400 at the connection position 5111.

[0502] 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 in the third direction X, and the location of the first straight line is the connection position 5111. The transition area 1117 is roughly triangular.

[0503] Thus, the main body 400 and the first connecting part 51 are in a direct connection state, making the main body 400 and the first connecting part 51 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 the expansion of the electrode assembly 2.

[0504] In some embodiments, the Vickers hardness of the transition region 1117 is less than the Vickers hardness of the main body 400.

[0505] In some embodiments, the Vickers hardness of the transition region 1117 is less than the Vickers hardness of the first connecting portion 51.

[0506] 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 connecting portion 51.

[0507] As an example, the Vickers hardness of the main body 400 is less than that of the first connecting part 51.

[0508] Thus, if the Vickers hardness of the transition zone 1117 is less than that of the main body 400, the transition zone 1117, with its lower Vickers hardness, connects with the first connecting portion 51. This can alleviate the rigid tension between the first wall 111 and the first connecting portion 51 when the first wall 111 deforms, reducing the risk of separation between the first wall 111 and the first connecting portion 51. If the Vickers hardness of the transition zone 1117 is less than that of the first connecting portion 51, the transition zone 1117 is more prone to deformation than the first connecting portion 51. This can also alleviate the rigid tension between the first wall 111 and the first connecting portion 51 when the first wall 111 deforms, reducing the risk of separation between the first wall 111 and the first connecting portion 51.

[0509] Please refer to Figure 21 In some embodiments, the electrode assembly 2 is a stacked structure, and the electrode assembly 2 includes a plurality of positive electrode plates 22 and a plurality of negative electrode plates 23, which are stacked along the second direction Y.

[0510] As an example, the positive electrode 22 and the negative electrode tab 21b in the electrode assembly 2 are arranged alternately along the second direction Y, and an isolation member 24 is provided between the positive electrode 22 and the negative electrode 23.

[0511] Thus, the stacked electrode assembly 2 has a more compact structure and stronger resistance to compression.

[0512] Please refer to Figure 21 In some embodiments, the number of negative electrode plates 23 is greater than the number of positive electrode plates 22, and a positive electrode plate 22 is disposed between two adjacent negative electrode plates 23.

[0513] As an example, the negative electrode 23 has one more electrode than the positive electrode 22.

[0514] Thus, by placing a positive electrode 22 between adjacent negative electrode 23, the transport distance of lithium ions inside the battery cell 10 can be reduced, and more lithium ion transport paths can be provided, thereby improving the charging and discharging efficiency of the battery cell 10.

[0515] In some embodiments, each negative electrode 23 is provided with a negative electrode tab 21b.

[0516] In some embodiments, each positive electrode 22 is provided with a positive electrode tab 21a.

[0517] In some embodiments, each negative electrode 23 is provided with a negative electrode tab 21b, and each positive electrode 22 is provided with a positive electrode tab 21a.

[0518] Specifically, the number of negative electrode tabs 21b can be one or more. When there are multiple negative electrode tabs 21b, they 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 also be one or more. When there are multiple positive electrode tabs 21a, they can be located on the same side of the positive electrode plate 22 or on different sides of the positive electrode plate 22.

[0519] In this way, the tab 21 can simplify the electrical connection between the battery cell 10 and the external circuit.

[0520] Please refer to Figure 3 In some embodiments, along the third direction X, the size of the buffer structure 410 is larger than the size of the positive electrode 22 and / or the size of the negative electrode 23, and the first direction Z, the second direction Y and the third direction X are perpendicular to each other.

[0521] Specifically, if along the third direction X, the size of the buffer structure 410 is larger than the size of the positive electrode 22, and the buffer structure 410 extends beyond at least one end of the positive electrode 22 along the third direction X; if along the third direction X, the size of the buffer structure 410 is larger than the size of the negative electrode 23, and the buffer structure 410 extends beyond at least one end of the negative electrode 23 along the third direction X.

[0522] Thus, the buffer structure 410 has a larger dimension along the third direction X, which reduces the expansion force on more areas of the first wall 111 along the third direction X, further reducing the risk of fatigue cracking in the area of ​​the first wall 111 near the first connection 51.

[0523] Please refer to Figure 3 and Figure 28 , Figure 28 This is a schematic diagram showing the connection between the end cap 12 and the electrode terminals 3 according to some embodiments of this application. In some embodiments, the battery cell 10 further includes two electrode terminals 3, which are disposed on the end cap 12. The two electrode terminals 3 have opposite polarities and are both electrically connected to the electrode assembly 2.

[0524] The end cap 12 is provided with an outlet hole. The electrode terminal 3 includes a terminal body 31, a first limiting part 32 and a second limiting part 33. The terminal body 31 is connected to the first limiting part 32 and the second limiting part 33. The terminal body 31 passes through the outlet hole. Along the first direction Z, the first limiting part 32 is located on the side of the end cap 12 away from the electrode assembly 2, and the second limiting part 33 is located on the side of the end cap 12 facing the electrode assembly 2.

[0525] Specifically, the first limiting part 32 and the second limiting part 33 have a limiting function. The first limiting part 32 and the second limiting part 33 are respectively connected to the two ends of the terminal body 31. The first limiting part 32 and the second limiting part 33 cooperate to restrict the terminal body 31 from disengaging from the lead-out hole.

[0526] Along the first direction Z, the projected area of ​​the first limiting part 32 and the projected area of ​​the second limiting part 33 are both greater than the projected area of ​​the terminal body 31. It is possible that the projected area of ​​the first limiting part 32 is greater than the projected area of ​​the second limiting part 33, or that the projected area of ​​the second limiting part 33 is greater than the projected area of ​​the first limiting part 32.

[0527] The first limiting part 32, the second limiting part 33 and the terminal body 31 can be integrally formed, or one of the first limiting part 32 and the second limiting part 33 can be integrally formed with the terminal body 31, while the other is separately set and connected to the terminal body 31.

[0528] As an example, the battery cell 10 may also include a first insulating member 6 and a second insulating member 7. The first insulating member 6 is at least partially disposed between the electrode terminal 3 and the end cap 12 to insulate and isolate the electrode terminal 3 and the end cap 12. The second insulating member 7 is disposed on the side of the end cap 12 facing the electrode assembly 2 to insulate and isolate the electrode assembly 2 and the end cap 12.

[0529] Thus, the electrode terminal 3 of this structure can be installed on the end cap 12 by riveting, which is easy to install and more economical.

[0530] Please refer to Figure 20 In some embodiments, the thickness of the lowest residual thickness of the buffer structure 410 is T, where T satisfies: 0.1mm≤T≤1mm, and optionally, 0.2mm≤T≤0.5mm.

[0531] Specifically, T can be any point value or a range between any two of the following: 0.1mm, 0.2mm, 0.3mm, 0.4mm, 0.5mm, 0.6mm, 0.7mm, 0.8mm, 0.9mm, 1mm.

[0532] Thus, if 0.1mm≤T≤1mm, the buffer structure 410 can not only effectively absorb the expansion force, but also avoid functional failure due to breakage.

[0533] If 0.2mm≤T≤0.5mm, the buffer structure 410 has a better ability to absorb expansion force and is more able to avoid functional failure due to breakage.

[0534] Please refer to Figure 20 In some embodiments, the width of the buffer structure 410 is K3, where K3 satisfies: 0.1mm≤K3≤20mm, and optionally, 0.15mm≤K3≤10mm.

[0535] Specifically, K3 can be any one of the following point values: 0.1mm, 0.15mm, 0.5mm, 1mm, 5mm, 10mm, 15mm, 20mm, or any range between two of them.

[0536] Thus, if 0.1mm≤K3≤20mm, the buffer structure 410 can effectively absorb the expansion force and reduce manufacturing costs.

[0537] If 0.15mm≤K3≤10mm, the buffer structure 410 has a better ability to absorb expansion force and a lower manufacturing cost.

[0538] Please refer to Figure 20 In some embodiments, the distance between the buffer structure 410 and the upper edge of the end cap 12 is J, where J satisfies: 1mm≤J≤20mm, and optionally, 1.5mm≤J≤10mm.

[0539] Specifically, J can be any one of the following values: 1mm, 1.5mm, 2mm, 3mm, 5mm, 10mm, 15mm, 20mm, or any range between two values.

[0540] Thus, if 1mm≤J≤20mm, the buffer structure 410 is far from the heat-affected zone, which can enhance the ability of the buffer structure 410 to absorb expansion force, thereby reducing the risk of fatigue cracking in the area of ​​the first wall 111 near the first connection 51.

[0541] If 1.5mm≤J≤10mm, the buffer structure 410 is far from the heat-affected zone, which can enhance the ability of the buffer structure 410 to absorb expansion force, thereby reducing the risk of fatigue cracking in the area of ​​the first wall 111 near the first connection 51.

[0542] In one specific embodiment, this application also provides a battery cell 10, which includes a housing 11, an end cap 12, and an electrode assembly 2. The housing 11 has an opening at one end along a first direction Z, and the end cap 12 is welded to the housing 11 and closes the opening of the housing 11. The electrode assembly 2 is at least partially housed within the housing 11.

[0543] The shell 11 is rectangular 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 each other along the second direction Y, and the two second walls 112 are arranged opposite each other along the third direction X. The first direction Z, the second direction Y and the third direction X are perpendicular to each other.

[0544] Electrode assembly 2 includes a positive electrode 22, a negative electrode 23, and a separator 24. The separator 24 is disposed between the positive electrode 22 and the negative electrode 23. Electrode assembly 2 has a flat region 25. The portions of the positive electrode 22, the negative electrode 23, and the separator 24 located in the flat region 25 are stacked along the second direction Y. Electrode assembly 2 includes a first surface 27 perpendicular to the second direction Y. The first surface 27 is the surface with the largest area among the outer surfaces of electrode assembly 2. A first wall 111 is disposed opposite to the first surface 27 along the second direction Y.

[0545] The positive electrode 22 includes a positive electrode body region 221 and a positive electrode tab 21a protruding from the positive electrode body region 221. The positive electrode body region 221 has a positive electrode active material layer 223. The negative electrode 23 includes a negative electrode body region 231 and a negative electrode tab 21b protruding from the negative electrode body region 231. The negative electrode body region 231 has a negative electrode active material layer 233. Along the first direction Z, the positive electrode body region 221 has a first end 2211 facing the end cap 12, the negative electrode body region 231 has a second end 2311 facing the end cap 12, and the separator 24 has a third end 241 facing the end cap 12. The third end 241 is closer to the end cap 12 than the first end 2211 and the second end 2311.

[0546] The first wall 111 is welded to the end cap 12 to form a first connecting portion 51. The first wall 111 includes a main body 400, which is located on the side of the first connecting portion 51 away from the end cap 12 along the first direction Z.

[0547] The main body 400 is provided with a buffer structure 410, which is spaced apart from the first connecting part 51. Along the first direction Z, the distance between the edges of the buffer structure 410 and the first connecting part 51 is 2 mm. The buffer structure 410 has a dimension L1 along the third direction X, and the first wall 111 has a dimension L along the third direction X, where L1 / L = 0.5. The buffer structure 410 has opposing fourth ends 11113a and fifth ends 11113b along the third direction X, and the first wall 111 has opposing sixth ends 1113 and seventh ends 1114 along the third direction X. The fourth end 11113a is closer to the sixth end 1113, and the fifth end 11113b is closer to the seventh end 1114. The first wall 111 has a dimension L along the third direction X, 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 size of the buffer structure 410 is larger than the size of the positive electrode 22 and / or the size of the negative electrode 23.

[0548] The positive electrode main body 2231 is located away from the first connecting part 51 relative to the negative electrode main body 2331. In a projection plane perpendicular to the second direction, the orthographic projection of the lowest point of the residual thickness of the buffer structure 410 lies between the orthographic projection of the first connecting part 51 and the orthographic projection of the positive electrode main body 2231. The thickness of the lowest point of the residual thickness of the buffer structure 410 is T. T is 0.5 mm. The width of the buffer structure 410 is K3. K3 is 10 mm. The distance between the buffer structure 410 and the upper edge of the end cap 12 is J. J is 5 mm.

[0549] The main body 400 also 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. A buffer structure 410 is located between the first region 440 and the second region 450. The first region 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. The thickness of the first portion 441 is greater than the thickness of the second portion 442. The thickness of the second portion 442 decreases along the direction from the end cap 12 toward the electrode assembly 2.

[0550] The buffer structure 410 includes a weak portion 411 disposed on the main body 400, the minimum thickness of which is less than the thickness of other parts of the main body 400. The width of the first region 440 is K1, which is 5 mm. The width of the first portion 441 is K2, which is 3 mm.

[0551] Both the inner surface 430 and the outer surface 420 of the main body 400 are provided with grooves 412. The grooves 412 are disposed 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.

[0552] The weak portion 411 includes a first weak portion 4110 disposed opposite to the bottom surface 4122. The thickness of the first weak portion 4110 is less than the thickness of other parts of the main body 400. The weak portion 411 also includes a second weak portion 4111 disposed opposite to the first side surface 4120 and a third weak portion 4112 disposed opposite to the second side surface 4121. The first side surface 4120 is located on the side of the bottom surface 4122 near the first connecting portion 51, and the thickness of the second weak portion 4111 gradually increases in the direction close to the first connecting portion 51. The second side surface 4121 is located on the side of the bottom surface 4122 away from the first connecting portion 51, and the thickness of the third weak portion 4112 gradually increases in the direction away from the first connecting portion 51. The angle between the first side surface 4120 and the bottom surface 4122 is 150 degrees, and the angle between the second side surface 4121 and the bottom surface 4122 is 150 degrees.

[0553] The electrode assembly 2 also includes a spacer 24 disposed between the positive electrode 22 and the negative electrode 23. The spacer 24 includes an extension region 242 extending beyond the first end 2211 and the second end 2311 along a first direction Z. In a projection plane perpendicular to the second direction Y, the orthographic projection of the extension region 242 partially overlaps with the orthographic projection of the buffer structure 410. 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 231 does not overlap with the orthographic projection of the buffer structure 410.

[0554] The first wall 111 also includes a transition region 1117. The transition region 1117 is located between the main body 400 and the first connecting portion 51 along the first direction Z. The transition region 1117 is connected to the first connecting portion 51, and the connection point between the transition region 1117 and the first connecting portion 51 forms a connection interface 511. The connection interface 511 has a connection position 5111 closest to the main body 400 along the first direction Z, located at the end of the main body 400 near the opening along the first direction Z. At least a portion of the connection interface 511 extends obliquely relative to the second direction Y.

[0555] The connection interface 511 includes a first interface 5112. The first interface 5112 extends obliquely from the connection position 5111 toward the end cap 12. Along the second direction Y, at least a portion of the transition region 1117 is located between the first interface 5112 and the end cap 12. The first interface 5112 is connected to the outer surface 420 of the main body 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 toward the end cap 12. Along the second direction Y, at least a portion of the transition region 1117 is located on the side of the second interface 5113 opposite to the end cap 12. The second interface 5113 is connected to the inner surface 430 of the main body 400 at the connection position 5111.

[0556] The Vickers hardness of the transition zone 1117 is less than that of the main body 400, and the Vickers hardness of the transition zone 1117 is less than that of the first connecting part 51.

[0557] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and not to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application, and they should all be covered within the scope of the claims and specification of this application. In particular, as long as there is no structural conflict, the various technical features mentioned in the embodiments can be combined in any way. This application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A battery cell, wherein, The battery cell includes: The housing has an opening at at least one end along a first direction, and the housing includes a first wall; An end cap is provided to close the opening. The first wall is welded to the end cap to form a first connecting portion. A portion of the first connecting portion is formed on the end cap, and another portion of the first connecting portion is formed on the first wall. An electrode assembly, at least partially housed within the housing, includes a positive electrode and a negative electrode, at least portions of the positive electrode and the negative electrode being stacked along a second direction parallel to the thickness direction of the first wall, and the first direction intersecting the second direction. The first wall includes a main body portion. Along the first direction, the main body portion is located on the side of the first connecting portion away from the end cap. The main body portion is provided with a buffer structure, which is spaced apart from the first connecting portion.

2. The battery cell of claim 1, wherein, The buffer structure includes a weak portion disposed on the main body, the minimum thickness of which is less than the thickness of other parts of the main body.

3. The battery cell of 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 part is the area on the main body that is opposite to the groove opening.

4. The battery cell of 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 part includes a first weak part disposed opposite to the bottom surface, and the thickness of the first weak part is less than the thickness of other parts of the main body.

5. The battery cell of claim 4, wherein, The weak portion further includes a second weak portion disposed opposite to the first side and a third weak portion disposed opposite to the second side. The first side is located on the bottom surface near the first connecting portion, and the thickness of the second weak portion increases in the direction close to the first connecting portion. The second side is located on the bottom surface away from the first connecting portion, and the thickness of the third weak portion increases in the direction away from the first connecting portion.

6. The battery cell according to claim 4 or 5, wherein, 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.

7. The battery cell according to any one of claims 1-5, wherein, The buffer structure includes a first protrusion and a first recess, the first protrusion and the first recess are correspondingly disposed, the first protrusion protrudes from the outer surface of the main body, and the first recess is recessed from the inner surface of the main body outward.

8. The battery cell according to claim 7, wherein, There are multiple first protrusions and multiple first recesses, with each first protrusion corresponding to one first recess.

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 being correspondingly disposed, the second convex portion protruding from the inner surface of the main body portion, and the second concave portion being recessed from the outer surface of the main body portion inward.

10. The battery cell according to claim 9, wherein, There are multiple second protrusions and multiple second recesses, with each second protrusion corresponding to one second recess.

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

12. The battery cell according to claim 11, wherein, 1.5mm≤H≤4mm.

13. The battery cell according to claim 1, wherein, The electrode assembly further includes an insulating element, which is disposed between the positive electrode and the negative electrode. The positive electrode includes a positive electrode body region and a positive electrode tab protruding from the positive electrode body region. The positive electrode body region has a positive electrode active material layer. The negative electrode includes a negative electrode body region and a negative electrode tab protruding from the negative electrode body region. The negative electrode body region has a negative electrode active material layer. Along the first direction, the positive electrode body region has a first end facing the end cap, the negative electrode 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.

14. The battery cell according to claim 13, wherein, The isolation member includes an extension area extending beyond the first end and the second end along a first direction. In a projection plane perpendicular to the second direction, the orthographic projection of the extension area overlaps with the orthographic projection of the buffer structure.

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

16. The battery cell according to claim 13 or 14, wherein, In a projection plane perpendicular to the second direction, the orthographic projection of the positive electrode main body region overlaps 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 overlaps with the orthographic projection of the buffer structure.

17. The battery cell according to claim 13 or 14, wherein, In a projection plane perpendicular to the second direction, at least a portion of the orthographic projection of the buffer structure lies between the orthographic projection of the first connecting portion and the orthographic projection of the positive electrode main body area; and / or, in a projection plane perpendicular to the second direction, at least a portion of the orthographic projection of the buffer structure lies between the orthographic projection of the first connecting portion and the orthographic projection of the negative electrode main body area.

18. The battery cell according to claim 13 or 14, wherein, In the projection plane perpendicular to the second direction, the orthographic projection of the main body area of ​​the positive electrode main body area and the negative electrode main body area that is far away from the first connecting part is the first orthographic projection, and the orthographic projection of the lowest residual thickness of the buffer structure is located between the orthographic projection of the first connecting part and the first orthographic projection.

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

20. The battery cell according to claim 19, wherein, The negative electrode active material layer includes a negative electrode main body and a negative electrode thinning portion, the negative electrode main body and the negative electrode thinning portion are arranged along the first direction, and the negative electrode thinning portion is provided at one end of the negative electrode main body near the end cap along the first direction; the positive electrode active material layer includes a positive electrode main body and a positive electrode thinning portion, the positive electrode main body and the positive electrode thinning portion are arranged along the first direction, and the positive electrode thinning portion is provided at one end of the positive electrode main body near the end cap along the first direction.

21. The battery cell according to claim 20, wherein, In the projection plane perpendicular to the second direction, the orthographic projection of the main body portion of the positive electrode and the negative electrode that is far from the first connecting portion is the second orthographic projection, and the orthographic projection of the lowest residual thickness of the buffer structure is located between the orthographic projection of the first connecting portion and the second orthographic projection.

22. The battery cell according to claim 20, wherein, In a projection plane perpendicular to the second direction, the orthographic projection of the negative electrode thinning portion and the orthographic projection of the buffer structure are spaced apart along the first direction.

23. The battery cell according to claim 22, wherein, In the projection plane perpendicular to the second direction, the distance between the orthographic projection of the negative electrode thinning portion and the orthographic projection of the buffer structure along the first direction is greater than or equal to 1 mm.

24. The battery cell according to any one of claims 19-23, wherein, The single-sided coating weight of the negative electrode active material layer is 90mg / 1540mm2~170mg / 1540mm2.

25. The battery cell according to claim 24, wherein, The single-sided coating weight of the negative electrode active material layer is 110mg / 1540mm2~150mg / 1540mm2.

26. The battery cell according to claim 20, wherein, The porosity of the negative electrode sheet is 27%~40%.

27. 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, and the first direction, the second direction and the third direction are not coplanar and intersect each other.

28. The battery cell according to claim 27, wherein, The buffer structure passes through the mid-section of the first wall, the mid-section is perpendicular to the third direction, and the mid-section is equidistant from both ends of the first wall along the third direction.

29. The battery cell according to claim 27 or 28, wherein, The buffer structure has a dimension of L1 along the third direction, and the first wall has a dimension of L along the third direction, where 0.4 ≤ L1 / L ≤ 0.

9.

30. The battery cell according to any one of claims 27-28, wherein, The buffer structure has a fourth end and a fifth end opposite each other along the third direction, and the first wall has a sixth end and a seventh end opposite each other along the third direction, with the fourth end close to the sixth end and the fifth end 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.

31. The battery cell according to claim 29, wherein, 100mm≤L≤450mm.

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

33. The battery cell according to claim 1, wherein, The main body includes a first region and a second region arranged along the 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.

34. The battery cell according to claim 33, wherein, The width of the first region is K1; K1 satisfies: 1.8mm≤G2≤15mm.

35. The battery cell according to claim 34, wherein, 2mm≤K1≤10mm.

36. The battery cell according to claim 34, wherein, The first region includes a first part and a second part arranged along the first direction, the second part being located between the first part and the buffer structure, and the thickness of the first part being greater than the thickness of the second part.

37. The battery cell according to claim 36, wherein, The width of the first part is K2; K2 satisfies: 1mm≤K2≤10mm.

38. The battery cell according to claim 37, wherein, 1.5≤K2≤5mm.

39. The battery cell according to claim 37, wherein, The thickness of the second part decreases along the direction from the end cap toward the electrode assembly.

40. The battery cell according to any one of claims 33-39, wherein, At least a portion of the Vickers hardness in the first region is less than that in the second region.

41. The battery cell according to claim 1, wherein, The electrode assembly has a flat region, and the portion of the positive electrode plate located in the flat region and the portion of the negative electrode plate located in the flat region are stacked along the second direction.

42. The battery cell according to claim 41, wherein, The electrode assembly includes an adjacent first surface and a second surface, the first surface being perpendicular to the second direction, the area of ​​the first surface being larger than the area of ​​the second surface, and the first surface and the first wall being disposed opposite each other along the second direction.

43. The battery cell according to claim 42, wherein, The first surface is the surface with the largest area among the outer surfaces of the electrode assembly.

44. The battery cell according to claim 42, wherein, The electrode assembly is a wound structure, and the electrode assembly also has a corner area. The corner area is provided at least one end of the straight area along a third direction. The first direction, the second direction and the third direction are not coplanar and intersect each other. The outer surface of the straight area includes the first surface, and the outer surface of the corner area includes the second surface, at least a portion of which is an arc surface.

45. The battery cell according to claim 42, wherein, The electrode assembly is a stacked structure, and 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.

46. ​​The battery cell according to any one of claims 41-43, wherein, Along the third direction, the size of the buffer structure is larger than the portion of the positive electrode sheet located in the flat region and / or the portion of the negative electrode sheet located in the flat region, and the first direction, the second direction and the third direction are perpendicular to each other.

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

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

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

50. The battery cell according to claim 49, wherein, At least a portion of the connection interface extends at an angle relative to the second direction.

51. The battery cell according to claim 50, wherein, The connection interface includes a first interface that extends obliquely from the connection position toward the end cap. Along the second direction, at least a portion of the transition area is located between the first interface and the end cap.

52. The battery cell according to claim 51, wherein, The first interface is connected to the outer surface of the main body at the connection position.

53. The battery cell according to any one of claims 49-52, wherein, The connection interface includes a second interface that extends obliquely from the connection position toward the end cap. Along the second direction, at least a portion of the transition area is located on the side of the second interface opposite to the end cap.

54. The battery cell according to claim 53, wherein, The second interface is connected to the inner surface of the main body at the connection position.

55. The battery cell according to claim 49, wherein, The Vickers hardness of the transition zone is less than that of the main body; and / or, the Vickers hardness of the transition zone is less than that of the first connecting portion.

56. The battery cell according to claim 1, wherein, The electrode assembly is a stacked structure, comprising a plurality of positive electrode plates and a plurality of negative electrode plates, which are stacked along the second direction.

57. The battery cell according to claim 56, wherein, The number of negative electrode plates is greater than the number of positive electrode plates, and a positive electrode plate is disposed between two adjacent negative electrode plates.

58. The battery cell according to claim 56 or 57, 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.

59. The battery cell according to claim 1, wherein, The battery cell also includes two electrode terminals, which are disposed on the end cap. The two electrode terminals have opposite polarities and are both electrically connected to the electrode assembly. The end cap is provided with a lead-out hole. The electrode terminal includes a terminal body, a first limiting part and a second limiting part. The terminal body is connected to the first limiting part and the second limiting part. The terminal body passes through the lead-out hole. Along the first direction, the first limiting part is located on the side of the end cap away from the electrode assembly, and the second limiting part is located on the side of the end cap facing the electrode assembly.

60. The battery cell according to claim 1, wherein, The thickness of the lowest residual thickness of the buffer structure is T, and T satisfies: 0.1mm≤T≤1mm.

61. The battery cell according to claim 60, wherein, 0.2mm≤T≤0.5mm.

62. The battery cell according to claim 1, wherein, The width of the buffer structure is K3, and K3 satisfies: 0.1mm≤K3≤20mm.

63. The battery cell according to claim 62, wherein, 0.15mm≤K3≤10mm.

64. The battery cell according to claim 1, wherein, The distance between the buffer structure and the upper edge of the end cap is J, where J satisfies: 1mm≤J≤20mm.

65. The battery cell according to claim 64, wherein, 1.5mm≤J≤10mm.

66. A battery comprising a battery cell as claimed in any one of claims 1-65.

67. An electrical device comprising a battery cell as claimed in any one of claims 1-65, the battery cell being used to provide electrical energy to the electrical device.

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