Battery monomer, battery and electric equipment

Abstract

The invention discloses a battery monomer (10), a battery (100) and electric equipment. The battery monomer (10) comprises a shell (11), an end cover (12) and an electrode assembly (2), at least one end of the shell (11) along the first direction (Z) is provided with an opening, and the shell (11) comprises a first wall (111); the end cover (12) seals the opening, and the first wall (111) and the end cover (12) are welded to form a first connecting part (51); the electrode assembly (2) is at least partially accommodated in the shell (11), the electrode assembly (2) comprises a positive pole piece (22) and a negative pole piece (23), at least part of the positive pole piece (22) and at least part of the negative pole piece (23) are stacked along a second direction (Y), the second direction (Y) is parallel to the thickness direction of the first wall (111), and the first direction (Z) intersects with the second direction (Y); wherein the first wall (111) comprises a main body part (400), the main body part (400) is located on the side, away from the end cover (12), of the first connecting part (51) in the first direction (Z), the main body part (400) is provided with a buffer structure (410), and the buffer structure (410) and the first connecting part (51) are arranged in a spaced mode.

Description

Battery cell, battery and electric device TECHNICAL FIELD

[0001] The present application relates to the technical field of battery, in particular to a battery cell, a battery and an electric device. BACKGROUND

[0002] Energy saving and emission reduction is the key to the sustainable development of the automobile industry. Electric vehicles have become an important part of the sustainable development of the automobile industry due to their energy saving and environmental protection advantages. For electric vehicles, battery technology is an important factor for their development.

[0003] In the battery technology, the service life of the battery cell is a problem that cannot be ignored. Therefore, how to improve the service life of the battery cell is a technical problem that needs to be solved in the battery technology.

[0004] SUMMARY

[0005] In view of the above problems, the present application provides a battery cell, a battery and an electric device, which can effectively improve the service life of the battery cell.

[0006] In a first aspect, the embodiments of the present application provide a battery cell, which comprises a shell, an end cover and an electrode assembly; the shell has an opening at least at one end in a first direction, and the shell comprises a first wall; the end cover closes the opening, and the first wall and the end cover are welded to form a first connecting part; the electrode assembly is at least partially accommodated in the shell, and the electrode assembly comprises a positive electrode sheet and a negative electrode sheet, at least part of the positive electrode sheet and at least part of the negative electrode sheet are stacked in a second direction, the second direction is parallel to the thickness direction of the first wall, and the first direction intersects the second direction.

[0007] The first wall comprises a main body part, which is located on the side of the first connecting part away from the end cover in the first direction, and the main body part is provided with a buffer structure, which is spaced apart from the first connecting part.

[0008] 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 connecting part. Therefore, the buffer structure can reduce 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, thereby improving the service life of the battery cell.

[0009] In some embodiments, the buffer structure comprises a weak part provided on the main body part, and the minimum thickness of the weak part is smaller than the thickness of other parts of the main body part.

[0010] Therefore, compared with other parts of the main body, the weakened part can more effectively absorb the expansion force, thereby reducing the expansion force directly acting on the first connecting part. Therefore, the weakened part can reduce the risk of fatigue cracking of the region of the first wall near the first connecting part due to the expansion of the electrode assembly, thereby improving the service life of the battery cell.

[0011] In some embodiments, 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 weakened part is a region on the main body opposite to the notch of the groove.

[0012] Therefore, as a region opposite to the notch of the groove, the weakened part has better buffering performance and is easier to form, thereby reducing the manufacturing difficulty of the shell and further reducing the manufacturing cost of the shell.

[0013] In some embodiments, the groove includes a first side, a second side, and a bottom surface connected to the first side and the second side, and the weakened part includes a first weakened part opposite to the bottom surface, and the thickness of the first weakened part is less than the thickness of other parts of the main body.

[0014] Therefore, compared with other parts of the main body, the expansion force acting on the first weakened part is greater, and the first weakened part can more effectively absorb the expansion force, thereby reducing the expansion force directly acting on the first connecting part. Therefore, the first weakened part can reduce the risk of fatigue cracking of the region of the first wall near the first connecting part due to the expansion of the electrode assembly, thereby improving the service life of the battery cell.

[0015] In some embodiments, the weakened part further includes a second weakened part opposite to the first side and a third weakened part opposite to the second side, the first side is located on one side of the bottom surface close to the first connecting part, and the thickness of the second weakened part increases in the direction close to the first connecting part, the second side is located on one side of the bottom surface away from the first connecting part, and the thickness of the third weakened part increases in the direction away from the first connecting part.

[0016] Therefore, the non-equal thickness design of the second weakened part and the third weakened part makes the weakened part have a gradient strength, which helps to more effectively bear and disperse the expansion force from different directions, helps to guide the expansion force to pass along a specific path, reduces the direct impact on the first weakened part, and makes the weakened part not prone to functional failure while absorbing the expansion force; in addition, the weakened part with gradually changing thickness can also be easier to manufacture.

[0017] In some embodiments, the included angle between the first side and the bottom surface is greater than or equal to 135 degrees and less than 180 degrees; and / or the included angle between the second side and the bottom surface is greater than or equal to 135 degrees and less than 180 degrees.

[0018] Therefore, in the range of the included angles, the weak portion has a higher absorption capacity for the expansion force, thereby effectively reducing the risk of fatigue cracking of the region of the first wall near the first connecting portion due to the expansion of the electrode assembly, and thereby improving the service life of the battery cell.

[0019] In addition, the groove can generally be manufactured by a stamping process. The stamping process requires the use of a mold for processing, which generally includes an upper mold for stamping and a lower mold for supporting the shell. During the stamping process, the shell is fixed to the lower mold by a clamp or a fixed structure of the mold, and then the upper mold moves towards the shell and applies pressure, so that the region of the shell corresponding to the upper mold is deformed to form the groove.

[0020] When the angle is greater than or equal to 135 degrees and less than 180 degrees, the groove does not engage with the upper mold during demolding, thereby making it easier for the upper mold to separate from the groove after processing the groove. Therefore, by controlling the angle to be between 135 degrees and 180 degrees, the formation of the groove can be facilitated, the manufacturing difficulty of the shell can be reduced, and the processing precision of the shell and the service life of the mold can be improved.

[0021] In some embodiments, the buffer structure includes a first protruding portion and a first recessed portion, the first protruding portion is protruding from an outer surface of the main body portion, and the first recessed portion is recessed from an inner surface of the main body portion.

[0022] Therefore, the first protruding portion and the first recessed portion can form a local buffer region and increase the buffer path of the buffer structure to disperse the expansion force, thereby reducing the expansion force directly acting on the first connecting portion. Therefore, the first protruding portion and the first recessed portion can cooperate to reduce the risk of fatigue cracking of the region of the first wall near the first connecting portion due to the expansion of the electrode assembly, and thereby improve the service life of the battery cell.

[0023] In some embodiments, the number of first protruding portions is a plurality, and the number of first recessed portions is a plurality, and each first protruding portion corresponds to a first recessed portion.

[0024] Therefore, the plurality of first protruding portions and the corresponding first recessed portions can further increase the buffer path of the buffer structure and provide a plurality of regions for dispersing the expansion force, thereby achieving more effective absorption of the expansion force, and thereby effectively reducing the expansion force directly acting on the first connecting portion.

[0025] In some embodiments, the buffer structure includes a second protruding portion and a second recessed portion, the second protruding portion is protruding from an inner surface of the main body portion, and the second recessed portion is recessed from an outer surface of the main body portion.

[0026] In this way, the second protrusions and the second recesses can form a local buffer area, increase the buffer path of the buffer structure, and disperse the expansion force, thereby reducing the expansion force directly acting on the first connecting portion. Therefore, the second protrusions and the second recesses cooperating with each other can reduce the risk of fatigue cracking of the area of the first wall near the first connecting portion due to the expansion of the electrode assembly, thereby improving the service life of the battery cell.

[0027] In some embodiments, the number of the second protrusions is a plurality, and the number of the second recesses is a plurality, and each second protrusion is correspondingly provided with a second recess.

[0028] In this way, the plurality of second protrusions and the corresponding second recesses can further increase the buffer path of the buffer structure, provide a plurality of areas for dispersing the expansion force, thereby achieving more effective absorption of the expansion force, and effectively reducing the expansion force directly acting on the first connecting portion.

[0029] In some embodiments, along the first direction, the distance between the buffer structure and the edge of the first connecting portion is H, and H satisfies: 0.3mm≤H≤7mm, and optionally, 1.5mm≤H≤4mm.

[0030] In this way, within these numerical ranges, the buffer structure can effectively absorb the expansion force, thereby reducing the expansion force directly acting on the first connecting portion. The buffer structure will not fatigue and crack together with the first connecting portion because it is too close to the first connecting portion, nor will it fail to reduce the expansion force directly acting on the first connecting portion because it is too far from the first connecting portion.

[0031] In some embodiments, the electrode assembly further comprises a separator, and the separator is arranged between the positive electrode tab and the negative electrode tab.

[0032] The positive electrode tab comprises a positive electrode main area and a positive electrode tab protruding from the positive electrode main area, and the positive electrode main area has a positive electrode active material layer. The negative electrode tab comprises a negative electrode main area and a negative electrode tab protruding from the negative electrode main area, and the negative electrode main area has a negative electrode active material layer. Along the first direction, the positive electrode main area has a first end facing the end cover, the negative electrode main area has a second end facing the end cover, and the separator has a third end facing the end cover, and the third end is closer to the end cover than the first end and the second end.

[0033] In this way, the separator has a part beyond the first end and the second end, which enhances the insulation effect of the separator between the positive electrode tab and the negative electrode tab, and reduces the risk of the positive electrode tab and the negative electrode tab being overlapped.

[0034] In some embodiments, the separator comprises an overhanging area beyond the first end and the second end along the first direction, and in a projection plane perpendicular to the second direction, the orthographic projection of the overhanging area partially overlaps with the orthographic projection of the buffer structure.

[0035] In this way, the structure can increase the size of the buffer structure along the first direction, improve the ability of the buffer structure to absorb the expansion force, and further reduce the risk of fatigue cracking of the region of the first wall near the first connecting portion.

[0036] In some embodiments, a positive projection of the positive body region does not overlap with a positive projection of the buffer structure in a projection plane perpendicular to the second direction; and / or, a negative projection of the negative body region does not overlap with the positive projection of the buffer structure in the projection plane perpendicular to the second direction.

[0037] In this way, if the positive projection of the positive body region does not overlap with the positive 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, reduce the risk of the electrode assembly directly applying an expansion force to the buffer structure, reduce the deformation of the first wall, and further reduce the risk of fatigue cracking of the region of the first wall near the first connecting portion.

[0038] If the positive projection of the negative body region does not overlap with the positive 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, reduce the risk of the electrode assembly directly applying an expansion force to the buffer structure, reduce the deformation of the first wall, and further reduce the risk of fatigue cracking of the region of the first wall near the first connecting portion.

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

[0040] In this way, by disposing the negative active material layer on at least one side of the negative current collector, the content of active material in the battery cell can be increased, thereby improving the energy density of the battery.

[0041] In some embodiments, the negative active material layer includes a negative main portion and a negative thinning portion, and the negative main portion and the negative thinning portion are arranged along the first direction, and along the first direction, the negative main portion is provided with the negative thinning portion at one end close to the end cover.

[0042] In this way, the electrode assembly has a larger expansion gap in the region corresponding to the negative thinning portion, and the region of the electrode assembly corresponding to the negative thinning portion exerts a smaller force on the first wall after expansion, thereby reducing the risk of fatigue cracking of the region of the first wall near the first connecting portion.

[0043] In some embodiments, a positive projection of the negative thinning portion and a positive projection of the buffer structure are arranged apart along the first direction in a projection plane perpendicular to the second direction.

[0044] In this way, the influence of the negative thinning portion on the buffer structure and the first connecting portion is low, the risk of the electrode assembly expansion directly exerting expansion force on the buffer structure is reduced, and the risk of fatigue cracking of the region of the first wall near the first connecting portion is further reduced.

[0045] In some embodiments, in a projection plane perpendicular to the second direction, the interval size of the positive projection of the negative thinning portion and the positive projection of the buffer structure along the first direction is greater than or equal to 1 mm.

[0046] In this way, in a projection plane perpendicular to the second direction, the positive projection of the negative thinning portion and the positive projection of the buffer structure are farther apart along the first direction, further reducing the influence of the negative thinning portion on the buffer structure.

[0047] In some embodiments, the single-side coating weight of the negative active material layer is 90 mg / 1540 mm 2 ~ 170 mg / 1540 mm 2 .

[0048] The single-side coating weight of the negative active material layer is related to the expansion of the negative active material layer. Setting the single-side coating weight of the negative active material layer to 90 mg / 1540 mm 2 ~ 170 mg / 1540 mm 2 can to some extent balance the high energy density requirement of the battery monomer and the low expansion requirement of the negative electrode sheet, reduce the influence of the expansion of the negative electrode sheet on the first wall, and reduce the risk of fatigue cracking of the region of the first wall near the first connecting portion.

[0049] In some embodiments, the single-side coating weight of the negative active material layer is 110 mg / 1540 mm 2 ~ 150 mg / 1540 mm 2 .

[0050] In this way, this can further improve the energy density of the battery monomer and further slow down the expansion of the negative electrode sheet.

[0051] In some embodiments, the porosity of the negative electrode sheet is 27% ~ 40%.

[0052] In this way, this can provide space for impurities generated by the side reaction of the negative electrode sheet, slow down the expansion of the negative electrode sheet, and reduce the influence of the expansion of the negative electrode sheet on the first wall.

[0053] In some embodiments, the negative active material includes a silicon-based material, and the mass content of silicon in the negative active material is 0.3% ~ 10%.

[0054] Therefore, by controlling the content of silicon element in 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 the silicon-based material during charging and discharging can be reduced.

[0055] In some embodiments, the mass content of silicon element in the silicon-based material in the negative active material is 1% to 6%.

[0056] Therefore, by controlling the content of silicon element in the range of 1% to 6%, the cycle stability and energy density of the battery cell can be further balanced, and the volume expansion problem of the silicon-based material during charging and discharging can be further reduced.

[0057] In some embodiments, the size of the buffer structure along the third direction is greater 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 with each other.

[0058] Therefore, the size of the buffer structure along the third direction is larger, so that the buffer structure has stronger ability to absorb the expansion force, and the risk of fatigue cracking of the region of the first wall near the first connecting part is further reduced.

[0059] In some embodiments, the buffer structure passes through a middle cross section of the first wall, the middle cross section is perpendicular to the third direction, and the distance from the middle cross section to both ends of the first wall along the third direction is equal.

[0060] Therefore, when the first wall is subjected to the expansion force of the electrode assembly of the battery cell, the deformation of the middle region of the first wall along the third direction is larger, 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 middle cross section of the first wall, the expansion force received by at least the middle region of the first wall along the third direction is reduced, and the risk of fatigue cracking of the middle region of the first wall near the first connecting part along the third direction is reduced.

[0061] In some embodiments, the size of the buffer structure along the third direction is L1, the size of the first wall along the third direction is L, and 0.4≤L1 / L≤0.9.

[0062] Therefore, when 0.4≤L1 / L, the size of the buffer structure in the first wall along the third direction accounts for a larger proportion, which makes the expansion force received by the middle region of the first wall along the third direction smaller, and reduces the risk of fatigue cracking of the middle region of the first wall near the first connecting part along the third direction.

[0063] When L1 / L≤0.9, the size of the buffer structure in the first wall along the third direction accounts for a smaller proportion, which reduces the waste generated by manufacturing the buffer structure and reduces the production cost.

[0064] Therefore, the ratio of the size of the buffer structure along the third direction to the size of the first wall along the third direction is set to 0.4-0.9, which reduces the waste generated in manufacturing the buffer structure while ensuring that the buffer structure has sufficient capacity to absorb the expansion force, and balances the capacity requirement and economic requirement of the buffer structure to absorb the expansion force.

[0065] In some embodiments, the buffer structure has opposite fourth and fifth ends along the third direction, the first wall has opposite sixth and seventh ends along the third direction, the fourth end is close to the sixth end, the fifth end is close to the seventh end, the size 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.

[0066] In this way, if L2 / L≤0.3, the proportion of the minimum distance between the fourth end and the sixth end along the third direction in the size of the first wall along the third direction is reduced, so that the expansion force received by more areas of the fourth end along the third direction is reduced, further reducing the risk of fatigue cracking of the area of the first wall near the first connecting portion.

[0067] If L3 / L≤0.3, the proportion of the minimum distance between the fifth end and the seventh end along the third direction in the size of the first wall along the third direction is reduced, so that the expansion force received by more areas of the first wall along the third direction is reduced, further reducing the risk of fatigue cracking of the area of the first wall near the first connecting portion.

[0068] In some embodiments, 100mm≤L≤450mm.

[0069] In this way, within this numerical range, the first wall has a larger size along the third direction, which is conducive to the arrangement of the buffer structure, thereby facilitating the absorption of the expansion force by the buffer structure.

[0070] In some embodiments, the shell includes a corner wall, and the two ends of the first wall along the third direction are connected with the corner wall; and the at least one end of the buffer structure along the third direction is spaced apart from the corner wall.

[0071] In this way, since the at least one end of the buffer structure along the third direction is not in contact with the corner wall, this can reduce the waste generated in manufacturing the buffer structure, thereby reducing production costs.

[0072] In some embodiments, the main body portion 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.

[0073] In this way, the first area with a greater thickness can enhance the resistance of the first connecting portion to the expansion force, and the buffer structure can further reduce the risk of fatigue cracking of the region of the first wall near the first connecting portion due to the expansion of the electrode assembly, thereby improving the service life of the battery cell.

[0074] In some embodiments, the first area includes a first portion and a second portion arranged along the 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.

[0075] In this way, the region of the first area near the first connecting portion is more likely to form a heat-affected zone, which is more likely to fatigue crack. However, since the second portion connects the first portion and the buffer structure, and the thickness of the first portion is greater than the thickness of the second portion, the first portion with a greater thickness in the first area is closer to the first connecting portion, which can effectively weaken the influence of the heat-affected zone on the first area, thereby reducing the risk of fatigue cracking of the region of the first wall near the first connecting portion. In addition, since the thickness of the second portion is less than the thickness of the first portion, the material of the first area can be reduced, thereby reducing the production cost.

[0076] In some embodiments, the thickness of the second portion decreases in a direction in which the end cover points to the electrode assembly.

[0077] In this way, on the one hand, this can reduce the influence of the second portion on the electrode assembly, thereby reducing the risk of interference between the second portion and the electrode assembly.

[0078] On the other hand, this makes the reinforcing effect of the second portion increase in a direction in which the electrode assembly points to the end cover, so that the region of the second portion near the first portion has a good reinforcing effect even if it is affected by the first connecting portion, thereby reducing the risk of fatigue cracking of the first wall in the second portion.

[0079] On the other hand, by the second portion, the transition between the first portion and the second area can be realized, thereby reducing stress concentration.

[0080] In some embodiments, at least part of the first area has a Vickers hardness less than that of the second area.

[0081] It can be understood that when the first wall is subjected to the expansion force, the first area with a lower hardness may first respond to the overload by plastic deformation, and the second area with a higher hardness may first crack, so the risk of fatigue cracking of the first area is lower.

[0082] In some embodiments, the electrode assembly has a flat area, and the portion of the positive electrode tab located in the flat area and the portion of the negative electrode tab located in the flat area are arranged in a stacked manner along the second direction.

[0083] Thus, the stacking direction of the second direction and the part of the flat area where the positive electrode tab is located and the part of the flat area where the negative electrode tab is located is the same, the expansion amount of the electrode assembly expanding in the second direction during the cycle process is larger, and the first wall is more affected by the expansion of the electrode assembly. However, since the buffer structure can absorb the expansion force, the expansion force on the area of the first wall near the first connecting portion is reduced, and the risk of fatigue cracking of the first wall near the first connecting portion due to the expansion of the electrode assembly is reduced.

[0084] In some embodiments, the electrode assembly includes adjacent first and second surfaces, the first surface is perpendicular to the second direction, the area of the first surface is larger than the area of the second surface, and the first surface is arranged opposite to the first wall along the second direction.

[0085] Thus, the area of the first surface is larger than the area of the second surface, so that the first wall opposite to the first surface in the shell receives a larger expansion force. Since the buffer structure can absorb the expansion force, the expansion force on the area of the first wall near the first connecting portion is reduced, and the risk of fatigue cracking of the first wall near the first connecting portion due to the expansion of the electrode assembly is reduced.

[0086] In some embodiments, the first surface is the surface with the largest area among the outer surfaces of the electrode assembly.

[0087] Thus, the first wall opposite to the first surface in the shell receives the largest expansion force. Since the buffer structure can absorb the expansion force, the expansion force on the area of the first wall near the first connecting portion is reduced, and the risk of fatigue cracking of the first wall near the first connecting portion due to the expansion of the electrode assembly is reduced.

[0088] In some embodiments, the electrode assembly is a jelly-roll structure, the electrode assembly further has a corner area, the corner area is arranged at at least one end of the flat area along a third direction, and the first direction, the second direction and the third direction are not coplanar and intersect with each other.

[0089] The outer surface of the flat area includes the first surface, and the outer surface of the corner area includes the second surface, at least part of the second surface is a circular arc surface.

[0090] Thus, for the jelly-roll electrode assembly, the expansion amount of the flat area expanding in the second direction is larger. Since the buffer structure can absorb the expansion force, the expansion force on the area of the first wall near the first connecting portion is reduced, and the risk of fatigue cracking of the first wall near the first connecting portion due to the expansion of the electrode assembly is reduced.

[0091] In some embodiments, the electrode assembly is a jelly-roll structure, the electrode assembly further has a corner area, the corner area is arranged at at least one end of the flat area along a third direction, and the first direction, the second direction and the third direction are not coplanar and intersect with each other.

[0092] Thus, for the laminated electrode assembly, the expansion amount of the electrode assembly in the stacking direction of the positive electrode tab and the negative electrode tab is larger. Since the buffer structure can absorb the expansion force, the expansion force on the region where the first wall is located near the first connecting portion is reduced, and the risk of fatigue cracking of the first wall near the first connecting portion due to the expansion of the electrode assembly is reduced.

[0093] In some embodiments, the first wall is the wall with the largest outer surface area in the housing.

[0094] Thus, the wall with the largest outer surface area in the housing is more likely to deform after being subjected to the expansion force of the electrode assembly, and since the first wall is the wall with the largest outer surface area in the housing, the risk of fatigue cracking of the first wall near the first connecting portion due to the expansion of the electrode assembly is lower.

[0095] In some embodiments, the housing includes two first walls, and the two first walls are oppositely arranged along the second direction, and the electrode assembly is located between the two first walls.

[0096] Thus, this reduces the risk of fatigue cracking of the two first walls near the first connecting portion due to the expansion of the electrode assembly.

[0097] In some embodiments, the first wall further includes a transition region, the transition region is located between the main body portion and the first connecting portion along the first direction, the transition region is connected to the first connecting portion, a connection position of the transition region and the first connecting portion forms a connection interface, the connection interface has a connection position closest to the main body portion along the first direction, and the connection position is located at one end of the main body portion close to the opening along the first direction.

[0098] Thus, the transition region and the first connecting portion form a connection interface, so that the transition region and the first connecting portion have a large enough contact area, improving the firmness of the first wall after welding with the end cover.

[0099] In some embodiments, at least part of the connection interface extends obliquely relative to the second direction.

[0100] Thus, after the end cover and the first wall are welded, the first connecting portion will shrink as it solidifies, and the first connecting portion will generate a tensile stress on the transition region. When the first wall is subjected to the expansion force of the electrode assembly, the first wall will deform, and the transition region will generate a tensile stress on the first connecting portion. Since the connection interface at least partially extends obliquely relative to the second direction, near the part of the connection interface that extends obliquely relative to the second direction, the tensile stress on the transition region due to the shrinkage of the first connecting portion and the tensile stress on the first connecting portion due to the deformation of the first wall are not on the same straight line, reducing the risk of fatigue cracking of the region near the connection interface of the transition region.

[0101] In some embodiments, the connecting interface comprises a first interface, the first interface extending obliquely from the connecting position towards the end cover in the first direction, at least part of the transition region being located between the first interface and the end cover in the second direction.

[0102] In this way, the first connecting portion protects the transition region, and when the first wall is subjected to the expansion force of the electrode assembly, the deformation of the transition region during the force is blocked by the first connecting portion, reducing the risk of fatigue cracking of the region of the transition region near the first interface.

[0103] In some embodiments, the first interface is connected to the outer surface of the main body portion at the connecting position.

[0104] In this way, since the first interface is directly connected to the main body portion, the main body portion and the first connecting portion are closer in the first direction, further reducing the risk of fatigue cracking of the region of the first wall near the first connecting portion due to the expansion of the electrode assembly.

[0105] In some embodiments, the connecting interface comprises a second interface, the second interface extending obliquely from the connecting position away from the end cover in the first direction, at least part of the transition region being located on the side of the second interface away from the end cover in the second direction.

[0106] In this way, the transition region limits the first connecting portion, reducing the risk of the first connecting portion falling off.

[0107] In some embodiments, the second interface is connected to the inner surface of the main body portion at the connecting position.

[0108] In this way, the main body portion and the first connecting portion are directly connected, so that the main body portion and the first connecting portion are closer in the first direction, further reducing the risk of fatigue cracking of the region of the first wall near the first connecting portion due to the expansion of the electrode assembly.

[0109] In some embodiments, the Vickers hardness of the transition region is less than the Vickers hardness of the main body portion; and / or, the Vickers hardness of the transition region is less than the Vickers hardness of the first connecting portion.

[0110] In this way, if the Vickers hardness of the transition region is less than the Vickers hardness of the main body portion, the transition region with lower Vickers hardness is connected to the first connecting portion, which can alleviate the rigid pulling between the first wall and the first connecting portion when the first wall deforms, reducing the risk of the first wall separating from the first connecting portion. If the Vickers hardness of the transition region is less than the Vickers hardness of the first connecting portion, the transition region is more likely to deform than the first connecting portion, which can alleviate the rigid pulling between the first wall and the first connecting portion when the first wall deforms, reducing the risk of the first wall separating from the first connecting portion.

[0111] In some embodiments, the electrode assembly is a laminated structure, and the electrode assembly includes a plurality of positive electrode laminates and a plurality of negative electrode laminates, the plurality of positive electrode laminates and the plurality of negative electrode laminates are arranged in a stacking manner along a second direction.

[0112] In this way, the laminated electrode assembly structure is more compact and has stronger extrusion resistance.

[0113] In some embodiments, the number of negative electrode laminates is greater than the number of positive electrode laminates, and one positive electrode laminate is arranged between two adjacent negative electrode laminates.

[0114] In this way, arranging a positive electrode laminate between adjacent negative electrode laminates can reduce the transmission distance of lithium ions inside the battery cell and provide more lithium ion transmission paths, thereby improving the charge and discharge efficiency of the battery cell.

[0115] In some embodiments, each negative electrode laminate is provided with a negative electrode tab; and / or, each positive electrode laminate is provided with a positive electrode tab.

[0116] In this way, the tabs can simplify the electrical connection between the battery cell and the external circuit.

[0117] In some embodiments, along a third direction, the size of the buffer structure is greater than the size of the positive electrode laminates and / or the size of the negative electrode laminates, and the first direction, the second direction and the third direction are perpendicular to each other.

[0118] In this way, the larger size of the buffer structure along the third direction reduces the expansion force on the area of the first wall along the third direction, further reducing the risk of fatigue cracking of the area of the first wall near the first connecting portion.

[0119] In some embodiments, the battery cell further includes two electrode terminals, the two electrode terminals are arranged on the end cover, the two electrode terminals are opposite in polarity and are electrically connected to the electrode assembly.

[0120] The end cover is provided with a lead-out hole, the electrode terminal includes a terminal body, a first limiting portion and a second limiting portion, the terminal body connects the first limiting portion and the second limiting portion, the terminal body is arranged in the lead-out hole, along the first direction, the first limiting portion is located on the side of the end cover away from the electrode assembly, and the second limiting portion is located on the side of the end cover facing the electrode assembly.

[0121] In this way, the electrode terminal of this structure can be installed on the end cover by riveting, which has low installation difficulty and better economy.

[0122] In a second aspect, the embodiments of the present application provide a battery, which includes the battery cell provided by any one of the embodiments of the first aspect.

[0123] Therefore, the battery at least has all the advantages of the battery monomer, which will not be repeated here.

[0124] In a third aspect, the embodiments of the present application provide a power consuming device, which comprises the battery monomer provided by any one of the embodiments of the first aspect, and the battery monomer is used to provide electric energy for the power consuming device.

[0125] Therefore, the power consuming device at least has all the advantages of the battery monomer, which will not be repeated here.

[0126] The above description is only a summary of the technical solutions of the present application. In order to make the technical means of the present application more clear and understandable, and to enable the above and other purposes, characteristics and advantages of the present application to be more obvious and easy to understand, the following specific embodiments of the present application are described in detail. BRIEF DESCRIPTION OF DRAWINGS

[0127] Various other advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiments. The accompanying drawings are included to provide a description of the preferred embodiments and are not meant to limit the present application. Furthermore, the same reference numerals are used throughout the several views that follow. In the drawings:

[0128] FIG. 1 is a structural schematic diagram of a vehicle provided by some embodiments of the present application;

[0129] FIG. 2 is an exploded view of a battery provided by some embodiments of the present application;

[0130] FIG. 3 is an exploded view of a battery monomer provided by some embodiments of the present application;

[0131] FIG. 4 is a structural schematic diagram of the battery monomer shown in FIG. 3;

[0132] FIG. 5 is a sectional view of the battery monomer of FIG. 4 in the A-A direction;

[0133] FIG. 6 is an enlarged view of the battery monomer in FIG. 5 at B;

[0134] FIG. 7 is a partial schematic diagram of a battery monomer provided by some embodiments of the present application;

[0135] FIG. 8 is a partial schematic diagram of a battery monomer provided by some other embodiments of the present application;

[0136] FIG. 9 is a schematic diagram of an electrode assembly provided by some embodiments of the present application;

[0137] FIG. 10 is a partial schematic diagram of a battery monomer provided by some other embodiments of the present application;

[0138] Fig. 11 is a partial schematic view of an electrode assembly according to some embodiments of the present application;

[0139] Fig. 12 is a partial schematic view of an electrode assembly according to some other embodiments of the present application;

[0140] Fig. 13 is a structural schematic view of a housing according to some embodiments of the present application;

[0141] Fig. 14 is a structural schematic view of a housing according to some other embodiments of the present application;

[0142] Fig. 15 is a structural schematic view of a battery cell according to some further embodiments of the present application;

[0143] Fig. 16 is a schematic view of an electrode assembly according to some other embodiments of the present application;

[0144] Fig. 17 is a structural schematic view of an electrode assembly according to some embodiments of the present application;

[0145] Fig. 18 is a structural schematic view of an electrode assembly according to some other embodiments of the present application;

[0146] Fig. 19 is a partial schematic view of a battery cell according to some further embodiments of the present application;

[0147] Fig. 20 is an enlarged view of portion C of the battery cell of Fig. 19;

[0148] Fig. 21 is a partial schematic view of a battery cell according to some further embodiments of the present application;

[0149] Fig. 22 is an enlarged view of portion D of the battery cell of Fig. 21;

[0150] Fig. 23 is a schematic view of the connection between an end cap and an electrode terminal according to some embodiments of the present application.

[0151] BRIEF DESCRIPTION OF THE DRAWINGS

[0152] 1-outer shell; 11-housing; 111-first wall; 112-second wall; 12-end cover; 4-pressure relief mechanism; 5-connection part; 51-first connection part; 52-second connection part; 2-electrode assembly; 22-positive electrode tab; 23-negative electrode tab; 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 protrusion; 414-first recess; 420-outer surface of main body; 430-inner surface of main body; 417-second protrusion; 418-second recess; 24-separator; 221-positive main area; 2231-positive main part; 2232-positive thinning part; 21-tab; 21a-positive tab; 222-positive current collector; 223-positive active material layer; 224-insulating layer; 231-negative main area; 21b-negative tab; 233-negative active material layer; 2211-first end; 2311-second end; 241-third end; 242-excess area; 232-negative current collector; 2331-negative main part; 2332-negative thinning part; 11113a-fourth end; 11113b-fifth end; 1113-sixth end; 1114-seventh end; 113-corner wall; 440-first area; 450-second area; 441-first part; 442-second part; 25-flat area; 26-corner area; 27-first surface; 28-second surface; 1117-transition area; 511-connection interface; 5111-connection position; 5112-first interface; 5113-second interface; 3-electrode terminal; 31-terminal main body; 32-first limiting part; 33-second limiting part; 6-first insulating member; 7-second insulating member; 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 DESCRIPTION

[0153] The embodiments of the technical solution of the present application will be described in detail below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present application, and therefore only serve as examples, and cannot limit the protection scope of the present application.

[0154] 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 belongs; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of this application; the use of the terms "including," "comprising," or "having" and variations thereof herein is intended to be broad and encompass the terms "consisting of" and "consisting essentially of" and variations thereof. Unless otherwise noted, the terms "including" and "comprising" are open-ended and do not exclude the presence of unrecited elements or limitations.

[0155] In the description of the embodiments of the present application, the technical terms "first", "second", etc. are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features. In the description of the embodiments of the present application, the meaning of "a plurality of" is two or more, unless otherwise explicitly and specifically limited.

[0156] Reference herein to "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the application. The appearance of the phrase in various places in the specification does not necessarily all refer to the same embodiment, nor is it necessarily independent or alternative embodiments to each other. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0157] In the description of the embodiments of the present application, the term "and / or" is only a description of the association relationship of the associated objects, which means that there can be three relationships, for example, A and / or B, which can represent the three cases of A alone, A and B together, and B alone. In addition, the character " / " in this paper generally represents that the front and rear associated objects are a "or" relationship.

[0158] In the description of the embodiments of the present application, the term "a plurality of" refers to two or more (including two), and similarly, "a plurality of groups" refers to two or more groups (including two groups), and "a plurality of pieces" refers to two or more pieces (including two pieces).

[0159] In the description of the embodiments of the present application, the technical terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the embodiments of the present application and simplifying the description, and therefore cannot be understood as limiting the embodiments of the present application. The orientation or position of the device or element indicated, and therefore cannot be understood as limiting the embodiments of the present application.

[0160] In the description of the embodiments of the present application, unless otherwise explicitly specified and limited, the technical terms "mount", "connect", "connect", "fix", and other terms should be understood in a broad sense, for example, can be fixedly connected, or can be detachably connected, or can be integrated; can be mechanically connected, or can be electrically connected; can be directly connected, or can be indirectly connected through an intermediate medium, can be the internal communication of two elements or the interaction relationship between two elements. For those skilled in the art, the specific meaning of the above terms in the embodiments of the present application can be understood according to the specific circumstances.

[0161] In the embodiments of the present application, "a plurality of" refers to more than two (including two).

[0162] In the embodiments of the present application, the battery cell can be a secondary battery, which refers to a battery cell that can be activated by charging after discharging.

[0163] The battery cell includes but is not limited to lithium ion battery, sodium ion battery, sodium lithium ion battery, lithium metal battery, sodium metal battery, lithium sulfur battery, magnesium ion battery, nickel hydrogen battery, nickel cadmium battery, lead-acid battery, etc.

[0164] The battery cell generally includes an electrode assembly. The electrode assembly includes a positive electrode, a negative electrode, and a separator. During the charging and discharging process of the battery cell, active ions (such as lithium ions) are inserted and extracted between the positive electrode and the negative electrode. The separator is arranged between the positive electrode and the negative electrode, which can reduce the risk of short circuit of the positive and negative electrodes, and at the same time allow the active ions to pass through.

[0165] In some embodiments, the positive electrode can be a positive electrode tab, which can include a positive electrode current collector and a positive electrode active material arranged on at least one surface of the positive electrode current collector.

[0166] As an example, the positive electrode current collector has two opposite surfaces in its own thickness direction, and the positive electrode active material is arranged on any one or both of the two opposite surfaces of the positive electrode current collector.

[0167] As an example, the positive electrode current collector can adopt a metal foil or a composite current collector. For example, as a metal foil, aluminum with silver plating treatment on the surface, stainless steel with silver plating treatment on the surface, stainless steel, copper, aluminum, nickel, carbon electrode, carbon, nickel or titanium, etc. can be used. The composite current collector can include a high polymer material base layer and a metal layer. The composite current collector can be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a high polymer material base material (such as a base material of polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.).

[0168] As an example, the positive active material can include at least one of a lithium-containing phosphate, a lithium transition metal oxide, and a modified compound of each thereof. However, the present application is not limited to these materials, and other conventional materials that can be used as a battery positive active material can also be used. These positive active materials can be used alone only one or two or more can be used in combination. Among them, examples of the lithium-containing phosphate can include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO4 (which can also be referred to as LFP)), a composite of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO4), a composite of lithium manganese phosphate and carbon, lithium manganese iron phosphate, and a composite of lithium manganese iron phosphate and carbon. Examples of the lithium transition metal oxide can include, but are not limited to, at least one of lithium cobalt oxide (such as LiCoO2), lithium nickel oxide (such as LiNiO2), lithium manganese oxide (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, which can also be referred to as NCM 333 ), LiNi 0.5 Co 0.2 Mn 0.3 O2, which can also be referred to as NCM 523 ), LiNi 0.5 Co 0.25 Mn 0.25 O2, which can also be referred to as NCM 211 ), LiNi 0.6 Co 0.2 Mn 0.2 O2, which can also be referred to as NCM 622 ), LiNi 0.8 Co 0.1 Mn 0.1 O2, which can also be referred to as NCM 811 ), lithium nickel cobalt aluminum oxide (such as LiNi 0.85 Co 0.15 Al 0.05 O2), and modified compounds thereof.

[0169] In some embodiments, the positive electrode can employ a foam metal. The foam metal can be a foam nickel, a foam copper, a foam aluminum, a foam alloy, etc. When the foam metal is used as the positive electrode, the surface of the foam metal can not be provided with a positive active material, or of course can be provided with a positive active material. As an example, the foam metal can also be filled or / and deposited with a lithium source material, a potassium metal, or a sodium metal, the lithium source material being a lithium metal and / or a lithium-rich material.

[0170] In some embodiments, the negative electrode can be a negative electrode tab, and the negative electrode tab can include a negative current collector.

[0171] As an example, the negative current collector can employ a metal foil, a foam metal, or a composite current collector. For example, as the metal foil, aluminum plated with silver on the surface, stainless steel plated with silver on the surface, stainless steel, copper, aluminum, nickel, a carbon electrode, carbon, nickel, or titanium, etc. can be employed. The foam metal can be a foam nickel, a foam copper, a foam aluminum, a foam alloy, etc. The composite current collector can include a polymer material base layer and a metal layer. The composite current collector can be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer material base material (such as a base material of polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.).

[0172] As an example, the negative electrode tab can include a negative current collector and a negative active material disposed on at least one surface of the negative current collector.

[0173] As an example, the negative current collector has two surfaces opposite in the thickness direction thereof, and the negative active material is disposed on either one or both of the two opposite surfaces of the negative current collector.

[0174] As an example, the negative active material can employ a negative active material for a battery cell known in the art. As an example, the negative active material can include at least one of artificial graphite, natural graphite, soft carbon, hard carbon, a silicon-based material, a tin-based material, and lithium titanate, etc. The silicon-based material can be selected from at least one of elemental silicon, a silicon oxide compound, a silicon-carbon composite, a silicon-nitrogen composite, and a silicon alloy. The tin-based material can be selected from at least one of elemental tin, a tin oxide compound, and a tin alloy. However, the present application is not limited to these materials, and other conventional materials that can be used as a battery negative active material can also be used. These negative active materials can be used alone only one or in combination of two or more.

[0175] In some embodiments, the material of the positive current collector can be aluminum, and the material of the negative current collector can be copper.

[0176] In some embodiments, the separator is a separator film. The separator film can be any known porous structure separator film having good chemical stability and mechanical stability.

[0177] As an example, the material of the separator film can include at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator film can be a single layer film or a multi-layer composite film. When the separator film is a multi-layer composite film, the materials of the respective layers can be the same or different. The separator can be a separate component located between the positive and negative electrodes, or can be attached to the surface of the positive and negative electrodes.

[0178] In some embodiments, the separator is a solid-state electrolyte. The solid-state electrolyte is disposed between the positive electrode and the negative electrode, and functions to transport ions and to separate the positive electrode and the negative electrode.

[0179] In some embodiments, the battery cell further includes an electrolyte that functions to conduct ions between the positive electrode and the negative electrode. The electrolyte can be liquid, gel, or solid. In some embodiments, the liquid electrolyte includes an electrolyte salt and a solvent.

[0180] In some embodiments, the electrolyte salt can include at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bisfluorosulfonylimide, lithium bis-trifluoromethanesulfonylimide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluoro oxalate borate, lithium bis-oxalate borate, lithium difluoro bis-oxalate phosphate, and lithium tetrafluoro oxalate phosphate.

[0181] In some embodiments, the solvent can include at least one of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, butyrosulfone, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone. The solvent can also be an ether solvent. The ether solvent can include one or more of ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, 1,3-dioxolane, tetrahydrofuran, methyl tetrahydrofuran, diphenyl ether, and crown ether.

[0182] In some embodiments, the gel electrolyte includes a polymer as a backbone network of the electrolyte, in combination with an ionic liquid-lithium salt.

[0183] In some embodiments, the solid-state electrolyte includes a polymer solid-state electrolyte, an inorganic solid-state electrolyte, a composite solid-state electrolyte.

[0184] As an example, the polymer solid-state electrolyte can be polyether (polyethylene oxide), polysiloxane, polycarbonate, polyacrylonitrile, polyvinylidene fluoride, polymethyl methacrylate, a single-ion polymer, a polyionic liquid-lithium salt, cellulose, etc.

[0185] As an example, the inorganic solid-state electrolyte can include one or more of an oxide solid-state electrolyte (crystalline perovskite, sodium superionic conductor, garnet, amorphous LiPON thin film), a sulfide solid-state electrolyte (crystalline lithium superionic conductor (lithium germanium phosphorous sulfide, argyrodite), amorphous sulfide), a halide solid-state electrolyte, a nitride solid-state electrolyte, and a hydride solid-state electrolyte.

[0186] As an example, the composite solid-state electrolyte is formed by adding inorganic solid-state electrolyte fillers in a polymer solid-state electrolyte.

[0187] In some embodiments, the electrode assembly is in a jelly-roll structure. The positive electrode sheet and the negative electrode sheet are wound into the jelly-roll structure.

[0188] In some embodiments, the electrode assembly is in a stack structure.

[0189] As an example, a plurality of positive electrode sheets and a plurality of negative electrode sheets can be provided respectively and are alternately stacked.

[0190] As an example, a plurality of positive electrode sheets can be provided, and the negative electrode sheet is folded to form a plurality of folded segments which are stacked. One positive electrode sheet is clamped between adjacent folded segments.

[0191] As an example, the positive electrode sheet and the negative electrode sheet are both folded to form a plurality of folded segments which are stacked.

[0192] As an example, a plurality of separators can be provided, and each of the separators is provided between any adjacent positive electrode sheet or negative electrode sheet.

[0193] As an example, the separators can be provided continuously and are provided between any adjacent positive electrode sheet or negative electrode sheet by folding or winding.

[0194] In some embodiments, the electrode assembly can have a cylindrical shape, a flat shape, or a multi-prism shape, etc.

[0195] In some embodiments, the electrode assembly is provided with tabs. The tabs can guide the current out of the electrode assembly. The tabs include positive electrode tabs and negative electrode tabs.

[0196] In some embodiments, the battery cell can include a housing. The housing is used to encapsulate the electrode assembly and other components such as the electrolyte. The housing can be a steel shell, an aluminum shell, a plastic shell (such as polypropylene), a composite metal shell (such as a copper-aluminum composite shell), or an aluminum-plastic film, etc.

[0197] As an example, the battery cell can be a cylindrical battery cell, a prismatic battery cell, a pouch battery cell, or a battery cell of other shapes. The prismatic battery cell includes a square battery cell, a blade-shaped battery cell, and a multi-prismatic battery cell, such as a hexagonal battery cell, etc.

[0198] The battery referred to in the embodiments of the present application refers to a single physical module including one or more battery cells to provide higher voltage and capacity.

[0199] In some embodiments, the battery can be a battery module. When there are multiple battery cells, the multiple battery cells are arranged and fixed to form a battery module.

[0200] In some embodiments, the battery can be a battery pack, the battery comprising a box body and battery cells, the battery cells or battery modules being accommodated in the box body.

[0201] In some embodiments, the box body can be part of a chassis structure of a vehicle. For example, part of the box body can be at least part of a floor of the vehicle, or part of the box body can be at least part of a cross beam and a longitudinal beam of the vehicle.

[0202] In some embodiments, the battery can be an energy storage device. The energy storage device can include an energy storage container, an energy storage cabinet, etc.

[0203] In the related art, a battery cell generally comprises a shell and an electrode assembly, the shell can comprise a casing and an end cover, the casing has an opening, and the electrode assembly, after being accommodated in the casing, can close the opening of the casing by the end cover to form a sealed space inside the shell to accommodate the electrode assembly.

[0204] To realize stable connection of the end cover and the casing, the end cover and the casing can be welded. After the end cover and the casing are welded, a connection portion will be formed at the welding position of the end cover and the casing, and the area near the connection portion of the wall of the casing will form a heat-affected zone due to high temperature of welding, and the strength of the part of the wall of the casing in the heat-affected zone will be reduced.

[0205] During the charging and discharging cycle of the battery cell, the electrode assembly will expand, and the wall of the casing will be deformed by the expansion force of the electrode assembly, which will easily lead to fatigue cracking of the area near the connection portion (heat-affected zone) of the wall of the casing over a long period of time, affecting the service life of the battery cell.

[0206] Based on the above considerations, to alleviate the problem that the area near the connection portion of the wall of the casing is prone to fatigue cracking, the embodiments of the present application provide a battery cell, the battery cell comprising a casing, an end cover and an electrode assembly; the casing has an opening at least at one end in a first direction, the casing comprising a first wall; the end cover closes the opening, and the first wall and the end cover are welded to form a first connection portion; the electrode assembly is at least partially accommodated in the casing, the electrode assembly comprising a positive electrode sheet and a negative electrode sheet, at least part of the positive electrode sheet and at least part of the negative electrode sheet being stacked in a second direction, the second direction being parallel to the thickness direction of the first wall, and the first direction intersecting the second direction; wherein the first wall comprises a main body portion, the main body portion being located on the side of the first connection portion away from the end cover in the first direction, the main body portion being provided with a buffer structure, and the buffer structure being spaced apart from the first connection portion.

[0207] In the battery cell, the buffer structure can absorb the expansion force generated during use of the electrode assembly, thereby reducing the expansion force directly acting on the first connecting portion. Therefore, the buffer structure can reduce the risk of fatigue cracking of the region of the first wall near the first connecting portion due to the expansion of the electrode assembly, thereby improving the service life of the battery cell.

[0208] The battery cell described in the embodiments of the present application is suitable for a battery and a power consumption device using the battery cell.

[0209] The power consumption device can be a vehicle, a mobile phone, a portable device, a notebook computer, a ship, a spacecraft, an electric toy, and an electric tool, etc. The vehicle can be a fuel automobile, a gas automobile, or a new energy automobile, and the new energy automobile can be a pure electric automobile, a hybrid electric automobile, or a range extended automobile, etc. The spacecraft includes an airplane, a rocket, a space shuttle, and a spacecraft, etc. The electric toy includes a fixed or mobile electric toy, for example, a game machine, an electric automobile toy, an electric ship toy, and an electric airplane toy, etc. The electric tool includes a metal cutting electric tool, a grinding electric tool, an assembling electric tool, and a railway electric tool, for example, an electric drill, an electric grinder, an electric wrench, an electric screwdriver, an electric hammer, an impact electric drill, a concrete vibrator, and an electric planer, etc. The embodiments of the present application do not specially limit the above power consumption devices.

[0210] The following embodiments take the vehicle as an example for convenience of description.

[0211] Please refer to FIG. 1, which is a structural schematic diagram of a vehicle 1000 provided by some embodiments of the present application. The vehicle 1000 is internally provided with a battery 100, which can be arranged at the bottom, the head, or the tail of the vehicle 1000. The battery 100 can be used for power supply of the vehicle 1000, for example, the battery 100 can be used as an operating power source of the vehicle 1000.

[0212] The vehicle 1000 can further include a controller 200 and a motor 300, and the controller 200 is used to control the battery 100 to supply power to the motor 300, for example, to meet the working power demand of the vehicle 1000 during starting, navigation, and driving.

[0213] In some embodiments of the present application, the battery 100 can not only be used as an operating power source of the vehicle 1000, but also be used as a driving power source of the vehicle 1000, to replace or partially replace fuel or natural gas to provide driving power for the vehicle 1000.

[0214] Please refer to FIG. 2, which is an exploded view of the battery 100 provided by some embodiments of the present application. The battery 100 can include a battery cell 10 and a box 20, and the battery cell 10 is contained in the box 20.

[0215] The battery 100 can include a plurality of battery cells 10, a plurality of battery modules, and a battery case 20.

[0216] In some embodiments, the battery case 20 can include a first case 201 and a second case 202. The first case 201 and the second case 202 are coupled to each other to define a space for accommodating the battery cells 10.

[0217] The first case 201 and the second case 202 can have various shapes, such as a cuboid shape, a cylindrical shape, etc. The first case 201 can be a hollow structure having an opening at one side, and the second case 202 can also be a hollow structure having an opening at one side. The opening of the second case 202 can be coupled to the opening of the first case 201 to form the battery case 20 having the space for accommodating the battery cells 10. Alternatively, the first case 201 can be a hollow structure having an opening at one side, and the second case 202 can be a plate structure. The second case 202 can be coupled to the opening of the first case 201 to form the battery case 20 having the space for accommodating the battery cells 10. The first case 201 and the second case 202 can be sealed by a sealing element, such as a sealing ring, sealing glue, etc.

[0218] In the battery 100, the battery cells 10 can be one or a plurality of battery cells. If the battery cells 10 are a plurality of battery cells, the plurality of battery cells 10 can be connected in series, in parallel, or in a mixed connection. The mixed connection means that the plurality of battery cells 10 are connected in series and in parallel. The plurality of battery cells 10 can be connected in series, in parallel, or in a mixed connection to form a battery module, and the plurality of battery modules can be connected in series, in parallel, or in a mixed connection to form a whole, which is accommodated in the battery case 20. Alternatively, the plurality of battery cells 10 can be directly connected in series, in parallel, or in a mixed connection, and the whole formed by the plurality of battery cells 10 can be accommodated in the battery case 20.

[0219] Please refer to FIG. 3 and FIG. 4. FIG. 3 is an exploded view of the battery cell 10 according to some embodiments of the present application. FIG. 4 is a structural schematic view of the battery cell 10 shown in FIG. 3. The battery cell 10 can include a housing 1 and an electrode assembly 2. The electrode assembly 2 is accommodated in the housing 1.

[0220] In some embodiments, the housing 1 can include a shell 11 and an end cover 12. The shell 11 has an opening, and the end cover 12 closes the opening of the shell 11.

[0221] The shell 11 is a component for accommodating the electrode assembly 2. The shell 11 can be a hollow structure having an opening at one end, or a hollow structure having openings at opposite ends. The shell 11 can have various shapes, such as a cylindrical shape, a cuboid shape, etc. The shell 11 can be made of various materials, such as copper, iron, aluminum, steel, aluminum alloy, etc. The electrode assembly 2 can be partially located in the shell 11, or entirely located in the shell 11.

[0222] The end cover 12 is a component that closes the opening of the shell 11 to isolate the internal environment of the battery cell 10 from the external environment. The end cover 12 cooperates with the shell 11 to define a receiving space for accommodating the electrode assembly 2, the electrolyte, and other components. The end cover 12 can be connected to the shell 11 by welding or crimping to close the opening of the shell 11. The shape of the end cover 12 can be adapted to the shape of the shell 11, for example, the shell 11 is a cuboid structure, and the end cover 12 is a rectangular plate structure adapted to the shell 11, or the shell 11 is a cylindrical structure, and the end cover 12 is a circular plate structure adapted to the shell 11. The material of the end cover 12 can also be various, such as copper, iron, aluminum, steel, aluminum alloy, etc. The material of the end cover 12 and the shell 11 can be the same or different.

[0223] In the embodiment in which the shell 11 has an opening formed at one end, one end cover 12 can be correspondingly provided. In the embodiment in which the shell 11 has openings formed at opposite ends, two end covers 12 can be correspondingly provided, and the two end covers 12 respectively close the two openings of the shell 11, and the two end covers 12 cooperates with the shell 11 to define a receiving space.

[0224] In some embodiments, the battery cell 10 can further include an electrode terminal 3 provided on the shell 1, and the electrode terminal 3 is used to electrically connect with the tab 21 of the electrode assembly 2 to input or output the electric energy of the battery cell 10. The electrode terminal 3 can be provided on the shell 11 of the shell 1, or can be provided on the end cover 12 of the shell 1. The electrode terminal 3 and the tab 21 can be directly connected, for example, the electrode terminal 3 is welded with the tab 21. The electrode terminal 3 and the tab 21 can also be indirectly connected, for example, the electrode terminal 3 is indirectly connected with the tab 21 through a current collecting member. The current collecting member can be a metal conductor, such as copper, iron, aluminum, steel, aluminum alloy, etc.

[0225] In some embodiments, the battery cell 10 can further include a pressure relief mechanism 4, which can be provided on the end cover 12 or the shell 11. The pressure relief mechanism 4 can be a pressure relief component mounted on the shell 11 or the end cover 12, such as a rupture disc, a safety valve, etc. The pressure relief mechanism 4 can also be integrally formed with the end cover 12 or the shell 11. The pressure relief mechanism 4 can be provided with a pressure relief groove to be cracked along the pressure relief groove when the battery cell 10 is relieved. The pressure relief groove can be a groove extending along a closed trajectory, and the closed trajectory can be a circular trajectory, a rectangular trajectory, etc. The pressure relief groove can also be a groove extending along a non-closed trajectory, and the non-closed trajectory can be an H-shaped trajectory, a Y-shaped trajectory, a V-shaped trajectory, a U-shaped trajectory, etc.

[0226] As shown in FIGS. 3 and 4, for example, the shell 11 has an opening formed at one end thereof, and the battery 1 has one end cover 12, which closes one opening of the shell 11. The end cover 12 is provided with the pressure relief mechanism 4, and two electrode terminals 3 are provided on the end cover 12, which are a positive electrode terminal and a negative electrode terminal, respectively. The electrode assembly 2 has a positive tab 21a and a negative tab 21b formed at one end thereof facing the end cover 12, and the positive electrode terminal is electrically connected to the positive tab 21a, and the negative electrode terminal is electrically connected to the negative tab 21b.

[0227] Please refer to FIGS. 5 and 6, FIG. 5 is a sectional view of the battery monomer 10 of FIG. 4 in the direction of A-A; and FIG. 6 is an enlarged view of B in the battery monomer 10 of FIG. 5. The embodiment of the present application provides a battery monomer 10, which comprises a shell 11, an end cover 12 and an electrode assembly 2; the shell 11 has an opening at at least one end thereof along a first direction Z, and the shell 11 comprises a first wall 111; the end cover 12 closes the opening, and the first wall 111 is welded with the end cover 12 to form a first connecting part 51; and the electrode assembly 2 is at least partially accommodated in the shell 11, and the electrode assembly 2 comprises a positive tab 22 and a negative tab 23, at least part of the positive tab 22 and at least part of the negative tab 23 are arranged in a stacking manner along a second direction Y, the second direction Y is parallel to the thickness direction of the first wall 111, and the first direction Z intersects with the second direction Y.

[0228] The first wall 111 comprises a main body part 400, which is located at the side of the first connecting part 51 away from the end cover 12 along the first direction Z, and the main body part 400 is provided with a buffer structure 410, which is arranged in a spaced manner with the first connecting part 51.

[0229] Specifically, the shell 11 can have an opening formed at only one end thereof along the first direction Z, and the end cover 12 is correspondingly provided as one; or the shell 11 can have openings formed at opposite ends thereof along the first direction Z, and the end cover 12 is correspondingly provided as two.

[0230] The shell 11 can have various shapes, such as a cylindrical shape, a prismatic shape, etc., and the prismatic shape can be a triangular prism, a quadrangular prism, a pentagonal prism, a hexagonal prism, etc., and the quadrangular prism can be a cuboid, a cube, etc. The first direction Z is parallel to the direction of the opening of the shell 11.

[0231] In the embodiment where the shell 11 is cylindrical, the first direction Z can be parallel to the axial direction of the shell 11; in the embodiment where the shell 11 is prismatic, the first direction Z can be parallel to the extension direction of the side edge of the shell 11. The second direction Y is parallel to the thickness direction of the first wall 111. In the embodiment where the shell 11 is cylindrical, the first wall 111 is cylindrical, the radial direction of the shell 11 is the thickness direction of the first wall 111, and the second direction Y is parallel to the radial direction of the shell 11. In the embodiment where the shell 11 is prismatic, the first wall 111 can be a rectangular plate structure. The first direction Z and the second direction Y can be arranged at an acute angle, a right angle, or an obtuse angle.

[0232] The end cover 12 can be welded to the shell 11, and the welding of the end cover 12 to the shell 11 can form a connecting portion 5. The connecting portion 5 can extend along the circumferential direction of the opening of the shell 11. The end cover 12 and the shell 11 are connected and fixed by the connecting portion 5 to achieve the sealing of the end cover 12 and the shell 11. The connecting portion 5 is the portion where the end cover 12 and the shell 11 are welded to form a welding mark. The portion where the end cover 12 and the shell 11 are welded and fused together can be the connecting portion 5.

[0233] The first wall 111 in the shell 11 can be one or multiple. The first connecting portion 51 can correspond to the first wall 111 one by one. The first connecting portion 51 is the portion where the end cover 12 and the first wall 111 are welded to form a welding mark. The portion where the end cover 12 and the first wall 111 are welded and fused together can be the first connecting portion 51.

[0234] Part of the first connecting portion 51 is formed on the end cover 12, and another part of the first connecting portion 51 is formed on the first wall 111. The first wall 111 and the end cover 12 can form the first connecting portion 51 by means of stitch welding, or can form the first connecting portion 51 by means of penetration welding.

[0235] The first connecting portion 51 can be part of the connecting portion 5, or can be the entire connecting portion 5. In the embodiment where the shell 11 is cylindrical, the first wall 111 in the shell 11 is only one, the first wall 111 is cylindrical, and the first connecting portion 51 is the connecting portion 5; in the embodiment where the shell 11 is prismatic, the shell 11 can include multiple side walls arranged along the opening of the shell 11. At least one of the two side walls arranged opposite to each other along the second direction Y can be the first wall 111, and the first connecting portion 51 is part of the connecting portion 5.

[0236] The first wall 111 can be the wall with the largest outer surface area in the shell 11, or can not be the wall with the largest outer surface area in the shell 11. For example, the shell 11 is cuboid, the shell 11 can include two first walls 111 and two second walls 112, the two first walls 111 are oppositely arranged along the second direction Y, the two second walls 112 are oppositely arranged along the third direction X, the first direction Z, the second direction Y and the third direction X are perpendicular to each other, the first wall 111 can be the wall with the largest outer surface area in the shell 11, so that the outer surface area of the first wall 111 is larger than that of the second wall 112, or the second wall 112 can be the wall with the largest outer surface area in the shell 11, so that the outer surface area of the second wall 112 is larger than that of the first wall 111.

[0237] The electrode assembly 2 is located in the accommodation space defined by the shell 11 and the end cover 12. The electrode assembly 2 can be a laminated structure or a wound structure. The electrode assembly 2 in the shell 11 can be one or multiple. If the electrode assembly 2 is multiple, the multiple electrode assemblies 2 can be stacked, for example, the multiple electrode assemblies 2 are stacked along the second direction Y.

[0238] At least part of the positive electrode sheet 22 and at least part of the negative electrode sheet 23 are stacked along the second direction Y, the electrode assembly 2 will expand along the second direction Y during the cycle process, and the first wall 111 will deform under the expansion force of the electrode assembly 2, which is easy to cause fatigue cracking of the area of the first wall 111 near the first connecting part 51.

[0239] The buffer structure 410 can absorb deformation, which can be an area with reduced strength, for example, reduced thickness or reduced hardness, or a bending structure. After the first wall 111 is subjected to the expansion force, the expansion force acting on the first connecting part 51 is smaller due to the buffer structure 410 which can absorb deformation.

[0240] 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 acting directly on the first connecting part 51. Therefore, the buffer structure 410 can reduce 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, thereby prolonging the service life of the battery monomer 10.

[0241] Please refer to FIG. 6, in some embodiments, the buffer structure 410 includes a weak part 411 arranged on the main body part 400, the minimum thickness of the weak part 411 is smaller than the thickness of other parts of the main body part 400.

[0242] Specifically, the weakened portion 411 can be a blind hole or a groove on the main body portion 400. The weakened portion 411 can be continuous or discontinuous. For example, the weakened portion 411 can include a plurality of weakened regions arranged on the main body portion 400 at intervals along the first direction Z.

[0243] In this way, the weakened portion 411 can more effectively absorb the expansion force than other portions of the main body portion 400, thereby reducing the expansion force acting directly on the first connecting portion 51. Therefore, the weakened portion 411 reduces the risk of fatigue cracking of the region 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.

[0244] In some embodiments, the inner surface 430 of the main body portion 400 is provided with the groove 412.

[0245] In some embodiments, the outer surface 420 of the main body portion 400 is provided with the groove 412.

[0246] In some embodiments, the inner surface 430 and the outer surface of the main body portion 400 are both provided with the groove 412.

[0247] The weakened portion 411 is a region on the main body portion 400 opposite the notch of the groove 412.

[0248] Specifically, the groove 412 can be circular, rectangular, oval, or the like in shape, and the size and shape can be adjusted as needed. By providing the groove 412, the corresponding region of the inner surface 430 of the main body portion 400 or the outer surface 420 of the main body portion 400 is more likely to deform when the electrode assembly 2 expands, thereby absorbing the expansion force.

[0249] In this way, the weakened portion 411, as a region opposite the notch of the groove, has better buffering performance and makes it easier to form the weakened portion 411, thereby reducing the manufacturing difficulty of the shell 11 and further reducing the manufacturing cost of the shell 11.

[0250] Please refer to FIG. 7, which is a partial schematic view of the battery cell 10 according to some embodiments of the present application. In some embodiments, the groove 412 includes a first side surface 4120, a second side surface 4121, and a bottom surface 4122 connected to the first side surface 4120 and the second side surface 4121, and the weakened portion 411 includes a first weakened portion 4110 arranged opposite the bottom surface 4122, the thickness of the first weakened portion 4110 being less than the thickness of other portions of the main body portion 400.

[0251] Specifically, the first weakened portion 4110 can be continuous or discontinuous. For example, the first weakened portion 4110 extends along the first direction Z and connects the first side surface 4120 and the second side surface 4121; the first weakened portion 4110 can also include a plurality of first weakened regions arranged at intervals along the first direction Z in a region opposite the bottom surface 4122 of the first weakened portion 4110.

[0252] The first side surface 4120, the second side surface 4121, and the bottom surface 4122 can be surfaces forming a shape profile of the groove 412. The first side surface 4120, the second side surface 4121, and the bottom surface 4122 can be coplanar or not coplanar.

[0253] In this way, compared with other parts of the body portion 400, the expansion force acting on the first weakened portion 4110 is greater, and the first weakened portion 4110 can more effectively absorb the expansion force, thereby reducing the expansion force directly acting on the first connecting portion 51. Therefore, the first weakened portion 4110 can reduce the risk of fatigue cracking of the region 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.

[0254] Please refer to FIG. 7, in some embodiments, the weakened portion 411 further includes a second weakened portion 4111 disposed opposite the first side surface 4120 and a third weakened portion 4112 disposed opposite the second side surface 4121, the first side surface 4120 is located on a side of the bottom surface 4122 close to the first connecting portion 51, and the thickness of the second weakened portion 4111 has a trend of increasing along the direction close to the first connecting portion 51, the second side surface 4121 is located on a side of the bottom surface 4122 away from the first connecting portion 51, and the thickness of the third weakened portion 4112 has a trend of increasing along the direction away from the first connecting portion 51.

[0255] Specifically, the direction close to the first connecting portion 51 and the direction away from the first connecting portion 51 can be different parts in the first direction Z. Along the first direction Z, the second weakened portion 4111 and the third weakened portion 4112 can be located on the two sides of the first weakened portion 4110, respectively. The second weakened portion 4111 can be connected or spaced apart from the first weakened portion 4110. The third weakened portion 4112 can be connected or spaced apart from the first weakened portion 4110.

[0256] The second weakened portion 4111 can be continuous or discontinuous. For example, the second weakened portion 4111 extends along the first direction Z and connects the first weakened portion 4110; the second weakened portion 4111 can also include a plurality of second weakened regions arranged at intervals along the first direction Z in a region opposite the first side surface 4120 of the second weakened portion 4111.

[0257] The third weak portion 4112 can be continuous or discontinuous. For example, the third weak portion 4112 extends along the first direction Z and connects the first weak portion 4110; the third weak portion 4112 can also include a plurality of third weak regions arranged at intervals along the first direction Z in the region opposite the second side surface 4121 of the third weak portion 4112.

[0258] The thickness of the second weak portion 4111 can be gradually increased or segmentedly increased along the direction close to the first connecting portion 51. For the convenience of manufacturing, the thickness of the second weak portion 4111 can be gradually increased along the direction close to the first connecting portion 51.

[0259] The thickness of the third weak portion 4112 can be gradually increased or segmentedly increased along the direction away from the first connecting portion 51. For the convenience of manufacturing, the thickness of the third weak portion 4112 can be gradually increased along the direction away from the first connecting portion 51.

[0260] In this way, the non-equal thickness design of the second weak portion 4111 and the third weak portion 4112 makes the weak portion 411 have a gradient strength, which helps to more effectively bear and disperse the expansion force from different directions, helps to guide the expansion force to pass along a specific path, reduces the direct impact on the first weak portion 4110, which makes the weak portion 411 able to absorb the expansion force without being prone to functional failure; in addition, the weak portion 411 with gradually changing thickness can also make the weak portion 411 more easily manufactured and formed.

[0261] Please refer to FIG. 7, in some embodiments, the 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.

[0262] Please refer to FIG. 7, in some embodiments, the 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.

[0263] Please refer to FIG. 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.

[0264] The angle between the first side surface 4120 and the bottom surface 4122 can be 135 degrees, 140 degrees, 145 degrees, 150 degrees, 155 degrees, 160 degrees, 165 degrees, 170 degrees, 175 degrees, etc. Any one point value or a range value between any two of them.

[0265] The included angle between the second side surface 4121 and the bottom surface 4122 can be any one of 135 degrees, 140 degrees, 145 degrees, 150 degrees, 155 degrees, 160 degrees, 165 degrees, 170 degrees, 175 degrees, etc., or a range value between any two of them.

[0266] Specifically, the included angle between the first side surface 4120 and the bottom surface 4122 is denoted as a first included angle a1, and the included angle between the second side surface 4121 and the bottom surface 4122 is denoted as a second included angle a2. The first included angle a1 and the second included angle a2 can be the same or different.

[0267] In this way, within these included angle ranges, the weak portion 411 has a higher absorption capacity for expansion force, thereby effectively reducing the risk of fatigue cracking of the region of the first wall 111 near the first connecting portion 51 due to the expansion of the electrode assembly 2, and further improving the service life of the battery monomer 10.

[0268] In addition, the groove 412 can generally be manufactured by a stamping forming process. When stamping forming, a mold needs to be used for processing, and the mold generally includes two parts of an upper mold and a lower mold, the upper mold is used for stamping, and the lower mold is used for supporting the shell 11. In the process of stamping, the shell 11 is fixed to the lower mold through a clamp or a fixed structure of the mold, and then the upper mold moves to the shell 11 and applies pressure, so that the region of the shell 11 corresponding to the upper mold is deformed to form the groove 412.

[0269] When the angle is greater than or equal to 135 degrees and less than 180 degrees, the groove 412 will not be clamped with the upper mold during demolding, so that the upper mold is easier to separate from the groove 412 after processing the groove 412. Therefore, by controlling the angle to be between 135 degrees and 180 degrees, the formation of the groove 412 can be facilitated, the manufacturing difficulty of the shell 11 is reduced, and thus the processing precision of the shell 11 and the service life of the mold are improved.

[0270] Please refer to FIG. 8, which is a partial schematic view of a battery monomer 10 provided by some embodiments of the present application. In some embodiments, the buffer structure 410 includes a first protruding portion 413 and a first recessed portion 414, the first protruding portion 413 is arranged correspondingly to the first recessed portion 414, the first protruding portion 413 protrudes from the outer surface 420 of the main body portion 400, and the first recessed portion 414 is recessed outwardly from the inner surface 430 of the main body portion 400.

[0271] Specifically, the first protruding portion 413 and the first recessed portion 414 can be arranged along a first direction Z. Along the first direction Z, one end of the first protruding portion 413 can be connected to one end of the first recessed portion 414. The first protruding portion 413 and the first recessed portion 414 can form a curved structure. For example, the first protruding portion 413 and the first recessed portion 414 can form an “S” shape structure.

[0272] In this way, the first protrusions 413 and the first recesses 414 can form a local buffer area, increase the buffer path of the buffer structure 410, and disperse the expansion force, thereby reducing the expansion force directly acting on the first connecting portion 51. Therefore, the first protrusions 413 and the first recesses 414 cooperating with each other 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.

[0273] In some embodiments, the number of the first protrusions 413 is a plurality, and the number of the first recesses 414 is a plurality, and each of the first protrusions 413 is provided with one of the first recesses 414.

[0274] Specifically, the number of the first protrusions 413 can be two, three, four, or even more. The number of the first recesses 414 can be two, three, four, or even more.

[0275] For example, the first protrusions 413 can include a first sub-protrusion, a second sub-protrusion, and a third sub-protrusion. The first recesses 414 can include a first sub-recess, a second sub-recess, and a third sub-recess. Along the first direction Z, the first sub-protrusion, the first sub-recess, the second sub-protrusion, the second sub-recess, the third sub-protrusion, and the third sub-recess are sequentially connected.

[0276] In this way, the plurality of first protrusions 413 and the corresponding first recesses 414 can further increase the buffer path of the buffer structure 410, provide a plurality of areas for dispersing the expansion force, thereby achieving more effective absorption of the expansion force, and effectively reducing the expansion force directly acting on the first connecting portion 51.

[0277] Please refer to FIG. 8, in some embodiments, the buffer structure 410 includes a second protrusion 417 and a second recess 418, the second protrusion 417 is provided corresponding to the second recess 418, the second protrusion 417 protrudes from the inner surface 430 of the main body portion 400, and the second recess 418 is recessed inward from the outer surface 420 of the main body portion 400.

[0278] Specifically, the second protrusions 417 and the second recesses 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” shape structure.

[0279] In this way, the second protrusions 417 and the second recesses 418 can form a local buffer area, increase the buffer path of the buffer structure 410, and disperse the expansion force, thereby reducing the expansion force directly acting on the first connecting portion 51. Therefore, the second protrusions 417 and the second recesses 418 cooperating with each other 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.

[0280] In some embodiments, the number of the second protrusions 417 is a plurality, and the number of the second recesses 418 is a plurality, and each second protrusion 417 is provided with a second recess 418.

[0281] Specifically, the number of the second protrusions 417 can be two, three, four, or even more. The number of the second recesses 418 can be two, three, four, or even more.

[0282] As an example, the second protrusions 417 can include a fourth sub-protrusion, a fifth sub-protrusion, and a sixth sub-protrusion. The second recesses 418 can 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 sequentially connected.

[0283] In this way, the plurality of second protrusions 417 and the corresponding second recesses 418 can further increase the buffer path of the buffer structure 410, provide a plurality of areas for dispersing the expansion force, thereby achieving more effective absorption of the expansion force, and effectively reducing the expansion force directly acting on the first connecting portion 51.

[0284] Please refer to FIG. 6. In some embodiments, along the first direction Z, the distance between the buffer structure 410 and the edge of the first connecting portion 51 is H, and H satisfies: 0.3mm≤H≤7mm. H can take any one of 0.3mm, 1.5mm, 2mm, 3mm, 4mm, 5.5mm, 7mm, or a range value between any two of them.

[0285] In some embodiments, along the first direction Z, H satisfies: 1.5mm≤H≤4mm. H can take any one of 1.5mm, 2.5mm, 3.5mm, 3.6mm, 3.7mm, 3.8mm, 4mm, or a range value between any two of them.

[0286] In this way, 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 fatigue and crack together with the first connecting portion 51 because it is too close to the first connecting portion 51, nor will it be unable to reduce the expansion force directly acting on the first connecting portion 51 because it is too far from the first connecting portion 51.

[0287] Please refer to FIG. 9, which is a schematic diagram of the electrode assembly 2 according to some embodiments of the present application. In some embodiments, the electrode assembly 2 further comprises a separator 24, which is arranged between the positive electrode tab 22 and the negative electrode tab 23.

[0288] The positive electrode tab 22 comprises a positive electrode body region 221 and a positive electrode lug 21a protruding from the positive electrode body region 221, and the positive electrode body region 221 has a positive electrode active material layer 223. The negative electrode tab 23 comprises a negative electrode body region 231 and a negative electrode lug 21b protruding from the negative electrode body region 231, and the negative electrode body region 231 has a negative electrode active material layer 233. In the first direction Z, the positive electrode body region 221 has a first end 2211 facing the end cover 12, the negative electrode body region 231 has a second end 2311 facing the end cover 12, and the separator 24 has a third end 241 facing the end cover 12, and the third end 241 is closer to the end cover 12 than the first end 2211 and the second end 2311.

[0289] Specifically, in the present embodiment, the electrode assembly 22 can be a wound structure or a stacked structure.

[0290] The positive electrode tab 22 can comprise a positive electrode current collector 222 and a positive electrode active material layer 223, and the positive electrode current collector 222 is provided with the positive electrode active material layer 223 on one or both surfaces in the thickness direction thereof.

[0291] Please refer to FIG. 10, FIG. 11 and FIG. 12, FIG. 10 is a partial schematic diagram of the battery cell 10 according to some other embodiments of the present application, FIG. 11 is a partial schematic diagram of the electrode assembly 2 according to some embodiments of the present application, and FIG. 12 is a partial schematic diagram of the electrode assembly 2 according to some other embodiments of the present application. The positive electrode tab 22 further comprises an insulating layer 224, and the positive electrode current collector 222 is provided with the insulating layer 224 on both opposite surfaces in the thickness direction thereof. The insulating layer 224 is arranged along the first direction Z with the positive electrode active material layer 223, and the insulating layer 224 is arranged at the end of the positive electrode active material layer 223. The part of the positive electrode tab 22 corresponding to the positive electrode active material layer 223 and the insulating layer 224 as a whole is the positive electrode body region 221, and the end of the insulating layer 224 close to the end cover 12 forms the first end 2211 of the positive electrode body region 221, and the part of the positive electrode current collector 222 beyond the insulating layer 224 forms the positive electrode lug 21a.

[0292] In the embodiment shown in FIG. 12, the positive electrode tab 22 is not provided with the insulating layer 224, and the part of the positive electrode tab 22 corresponding to the positive electrode active material layer 223 is the positive electrode body region 221, and the end of the positive electrode active material layer 223 close to the end cover 12 forms the first end 2211 of the positive electrode body region 221, and the part of the positive electrode current collector 222 beyond the positive electrode active material layer 223 forms the positive electrode lug 21a.

[0293] The negative electrode tab 23 can include a negative current collector 232 and a negative active material layer 233, and the negative current collector 232 is provided with the negative active material layer 233 on one or both surfaces in the thickness direction of the negative current collector 232. The part of the negative electrode tab 23 corresponding to the negative active material layer 233 is the negative main body area 231, the part of the negative active material layer 233 close to one end of the end cover 12 forms the second end 2311 of the negative main body area 231, and the part of the negative current collector 232 beyond the negative active material layer 233 forms the negative tab 21b.

[0294] The first end 2211 can be flush with the second end 2311; as shown in FIG. 11, the first end 2211 can be closer to the end cover 12 (shown in FIG. 10) than the second end 2311; as shown in FIG. 12, the second end 2311 can be closer to the end cover 12 (shown in FIG. 10) than the first end 2211.

[0295] In this way, the spacer 24 has a part beyond the first end 2211 and the second end 2311, which enhances the insulation effect of the spacer 24 between the positive electrode tab 22 and the negative electrode tab 23, and reduces the risk of the positive electrode tab 22 and the negative electrode tab 23 being overlapped.

[0296] Referring to FIG. 10, in some embodiments, the spacer 24 includes an overhanging area 242 beyond the first end 2211 and the second end 2311 along the first direction Z, and the orthographic projection of the overhanging area 242 partially overlaps with the orthographic projection of the buffer structure 410 in the projection plane perpendicular to the second direction Y.

[0297] Specifically, the overhanging area 242 is the part of the spacer 24 beyond both the first end 2211 of the positive main body area 221 and the second end 2311 of the negative main body area 231. As shown in FIG. 11, in the embodiment where the first end 2211 is closer to the end cover 12 than the second end 2311, the part of the spacer 24 beyond the first end 2211 is the overhanging area 242; as shown in FIG. 12, in the embodiment where the second end 2311 is closer to the end cover 12 than the first end 2211, the part of the spacer 24 beyond the second end 2311 is the overhanging area 242.

[0298] As an example, in FIGS. 10-12, the positive electrode tab 22, the negative electrode tab 23 and the spacer 24 in the electrode assembly 2 are arranged in layers along the second direction Y in the part of the flat area 25 (not shown in FIGS. 10-12).

[0299] In this way, this structure can increase the size of the buffer structure 410 along the first direction Z, improve the ability of the buffer structure 410 to absorb expansion force, and further reduce the risk of fatigue cracking of the area of the first wall 111 near the first connecting part 51.

[0300] Referring to FIG. 10, in some embodiments, a projection of the positive body region 221 in a projection plane perpendicular to the second direction Y does not overlap with a projection of the buffer structure 410.

[0301] Referring to FIG. 10, in some embodiments, a projection of the negative body region 231 in a projection plane perpendicular to the second direction Y does not overlap with a projection of the buffer structure 410.

[0302] Referring to FIG. 10, in some embodiments, a projection of the positive body region 221 and a projection of the negative body region 231 in a projection plane perpendicular to the second direction Y do not overlap with a projection of the buffer structure 410.

[0303] As an example, in the embodiments of FIGS. 10-12, a projection of the positive body region 221 and a projection of the negative body region 231 in a projection plane perpendicular to the second direction Y do not overlap with a projection of the buffer structure 410.

[0304] In this way, if a projection of the positive body region 221 in a projection plane perpendicular to the second direction Y does not overlap with a projection of the buffer structure 410, the shell 11 can provide a larger expansion space for the electrode assembly 2, reducing the risk of the electrode assembly 2 expanding directly to the buffer to apply expansion force, reducing the deformation of the first wall 111, and further reducing the risk of fatigue cracking of the area of the first wall 111 near the first connecting portion 51.

[0305] If a projection of the negative body region 231 in a projection plane perpendicular to the second direction Y does not overlap with a projection of the buffer structure 410, the shell 11 can provide a larger expansion space for the electrode assembly 2, reducing the risk of the electrode assembly 2 expanding directly to the buffer structure 410 to apply expansion force, reducing the deformation of the first wall 111, and further reducing the risk of fatigue cracking of the area of the first wall 111 near the first connecting portion 51.

[0306] Referring to FIGS. 11 and 12, in some embodiments, the negative electrode tab 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, and the negative active material layer 233 includes a negative active material.

[0307] Specifically, the negative active material layer 233 can be disposed on only one side of the negative current collector 232, i.e., the negative active material layer 233 is disposed on only one surface of the negative current collector 232 along the thickness direction; or the negative active material layer 233 can be disposed on both opposite sides of the negative current collector 232, i.e., the negative active material layer 233 is disposed on both opposite surfaces of the negative current collector 232 along the thickness direction.

[0308] The negative active material can include at least one of artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based material, tin-based material, and lithium titanate, etc.

[0309] In this way, by arranging the negative active material layer 233 on at least one side of the negative current collector 232, the content of active material in the battery monomer 10 can be increased, thereby improving the energy density of the battery.

[0310] Referring to FIGS. 11 and 12, in some embodiments, the negative active material layer 233 includes a negative main body part 2331 and a negative thinning part 2332, and the negative main body part 2331 and the negative thinning part 2332 are arranged along the first direction Z. Along the first direction Z, the negative main body part 2331 is provided with the negative thinning part 2332 at one end close to the end cover 12.

[0311] Specifically, the thickness of the negative main body part 2331 is greater than the thickness of the negative thinning part 2332. It can be that the negative main body part 2331 is provided with the negative thinning part 2332 only at one end close to the end cover 12 along the first direction Z, or that the negative main body part 2331 has the negative thinning part 2332 at both ends along the first direction Z. The negative main body part 2331 can be an equal-thickness structure or a non-equal-thickness structure, and the negative thinning part 2332 can be an equal-thickness structure or a non-equal-thickness structure. If at least one of the negative main body part 2331 and the negative thinning part 2332 is a non-equal-thickness structure, the maximum thickness of the negative thinning part 2332 can be less than or equal to the minimum thickness of the negative main body part 2331, so as to realize that the thickness of the negative main body part 2331 is greater than the thickness of the negative thinning part 2332.

[0312] As an example, the negative main body part 2331 is an equal-thickness structure, and the thickness of the negative thinning part 2332 decreases in a direction in which the negative main body part 2331 points to the negative thinning part 2332.

[0313] In this way, the electrode assembly 2 has a larger expansion gap in the area corresponding to the negative thinning part 2332, and the area of the electrode assembly 2 corresponding to the negative thinning part 2332 exerts a smaller force on the first wall 111 after expansion, thereby reducing the risk of fatigue cracking of the area of the first wall 111 near the first connecting part 51.

[0314] In some embodiments, in a projection plane perpendicular to the second direction Y, the orthographic projection of the negative thinning part 2332 and the orthographic projection of the buffer structure 410 are arranged apart along the first direction Z.

[0315] Specifically, it can be understood that, in the projection plane perpendicular to the second direction Y, the orthographic projection of the negative thinning part 2332 at one end of the negative main body part 2331 close to the end cover 12 and the orthographic projection of the buffer structure 410 do not overlap.

[0316] In this way, the influence of the negative electrode thinning portion 2332 on the buffer structure 410 and the first connecting portion 51 is low, the risk of the electrode assembly 2 expansion directly applying expansion force to the buffer structure 410 is reduced, and the risk of fatigue cracking of the region of the first wall 111 near the first connecting portion 51 is further reduced.

[0317] In some embodiments, in a projection plane perpendicular to the second direction Y, the interval size of the positive projection of the negative electrode thinning portion 2332 and the positive projection of the buffer structure 410 along the first direction Z is greater than or equal to 1 mm.

[0318] Specifically, in a projection plane perpendicular to the second direction Y, the interval size of the positive projection of the negative electrode thinning portion 2332 located at one end of the negative electrode main body portion 2331 near the end cover 12 and the positive projection of the buffer structure 410 along the first direction Z is W1, W1≥1 mm, which is the minimum distance between the positive 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 take any one of 1 mm, 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, 10 mm, 11 mm, 12 mm, 13 mm, 14 mm, 15 mm, 16 mm, 17 mm, 18 mm, 19 mm, 20 mm, etc. or a range value between any two of them.

[0319] In this way, in a projection plane perpendicular to the second direction Y, the positive projection of the negative electrode thinning portion 2332 and the positive projection of the buffer structure 410 are farther apart along the first direction Z, further reducing the influence of the negative electrode thinning portion 2332 on the buffer structure 410.

[0320] In some embodiments, the single-sided coating weight of the negative electrode active material layer 233 is 90 mg / 1540 mm 2 ~ 170 mg / 1540 mm 2 .

[0321] Specifically, the single-sided coating weight of the negative electrode active material layer 233 can take any one of 90 mg / 1540 mm 2 , 100 mg / 1540 mm 2 , 110 mg / 1540 mm 2 , 120 mg / 1540 mm 2 , 130 mg / 1540 mm 2 , 140 mg / 1540 mm 2 , 150 mg / 1540 mm 2 , 160 mg / 1540 mm 2 , 170 mg / 1540 mm 2 , etc. or a range value between any two of them.

[0322] When measuring the single-sided coating weight of the negative electrode active material layer 233, the 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 of one side can be wiped off first) can be punched into a small round piece with an area of S1, weighed, and recorded as M1. Then the negative electrode active material layer 233 of the above weighed negative electrode sheet 23 is wiped off, the weight of the negative electrode current collector 232 is weighed, and recorded as M2. The single-sided coating weight of the negative electrode active material layer 233 = (M1-M2) / S1.

[0323] The single-sided coating weight of the negative electrode active material layer 233 is related to the expansion of the negative electrode active material layer 233. The single-sided coating weight of the negative electrode active material layer 233 is set to 90 mg / 1540 mm 2 ~ 170 mg / 1540 mm 2 , which can balance the high energy density requirement of the battery monomer 10 and the low expansion requirement of the negative electrode sheet 23 to a certain extent, reduce the influence of the expansion of the negative electrode sheet 23 on the first wall 111, and reduce the risk of fatigue cracking of the area where the first wall 111 is located near the first connecting part 51.

[0324] In some embodiments, the single-sided coating weight of the negative electrode active material layer 233 is 110 mg / 1540 mm 2 ~ 150 mg / 1540 mm 2 .

[0325] Specifically, the single-sided coating weight of the negative electrode active material layer 233 can be any one of 110 mg / 1540 mm 2 , 115 mg / 1540 mm 2 , 120 mg / 1540 mm 2 , 125 mg / 1540 mm 2 , 130 mg / 1540 mm 2 , 135 mg / 1540 mm 2 , 140 mg / 1540 mm 2 , 145 mg / 1540 mm 2 , 150 mg / 1540 mm 2 , etc. or a range value between any two of them.

[0326] In this way, it can further improve the energy density of the battery monomer 10 and further slow down the expansion of the negative electrode sheet 23.

[0327] In some embodiments, the porosity of the negative electrode sheet 23 is 27%~40%.

[0328] Specifically, the porosity of the negative electrode tab 2323 can take any one of 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, etc. or a range value between any two of them.

[0329] The porosity of the negative electrode tab 23 can be the percentage of the pore volume in the negative electrode tab 23 to the total volume of the negative electrode tab 23. As an example, at 0% state of charge of the battery cell 10, the negative electrode tab 23 is taken as a double-sided coated negative electrode tab 23; the porosity of the negative electrode tab 23 is measured by the true density instrument AccuPyc II 1340 according to the national standard GB / T 24586-2009.

[0330] In this way, space can be provided for impurities generated by the negative electrode tab 23 due to side reactions, slowing down the expansion of the negative electrode tab 23 and reducing the impact of the expansion of the negative electrode tab 23 on the first wall 111.

[0331] In some embodiments, the silicon-based material is included in the negative active material, and the mass content of silicon in the silicon-based material in the negative active material is 0.3% to 10%.

[0332] In some embodiments, the mass content of silicon in the silicon-based material in the negative active material is 1% to 6%.

[0333] Specifically, the mass content of silicon in the silicon-based material in the negative active material can take any one of 0.3%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, etc. or a range value between any two of them.

[0334] In this way, by controlling the content of silicon to be within the range of 0.3% to 10%, the cycle stability and energy density of the battery cell 10 can be balanced, and the volume expansion problem of the silicon-based material during charging and discharging can be reduced.

[0335] By controlling the content of silicon to be within the range of 1% to 6%, the cycle stability and energy density of the battery cell 10 can be further balanced, and the volume expansion problem of the silicon-based material during charging and discharging can be further reduced.

[0336] Please refer to FIG. 11 and FIG. 12, in some embodiments, the positive active material layer 223 includes a positive main part 2231 and a positive thinning part 2232, the positive main part 2231 and the positive thinning part 2232 are arranged along the first direction Z, and along the first direction Z, the positive main part 2231 is provided with the positive thinning part 2232 at one end close to the end cover 12.

[0337] The thickness of the positive electrode main part 2231 is greater than the thickness of the positive electrode thinning part 2232. The positive electrode main part 2231 can be provided with the positive electrode thinning part 2232 only at one end close to the end cover 12 along the first direction Z, or the positive electrode main part 2231 can be provided with the positive electrode thinning part 2232 at both ends along the first direction Z. The positive electrode main part 2231 can be an equal-thickness structure or a non-equal-thickness structure, and the positive electrode thinning part 2232 can be an equal-thickness structure or a non-equal-thickness structure. If at least one of the positive electrode main part 2231 and the positive electrode thinning part 2232 is a non-equal-thickness structure, the maximum thickness of the positive electrode thinning part 2232 can be less than or equal to the minimum thickness of the positive electrode main part 2231, so that the thickness of the positive electrode main part 2231 is greater than the thickness of the positive electrode thinning part 2232.

[0338] For example, the positive electrode main part 2231 is an equal-thickness structure, and the thickness of the positive electrode thinning part 2232 decreases along the direction of the positive electrode main part 2231 pointing to the positive electrode thinning part 2232.

[0339] In this embodiment, the positive electrode main part 2231 is provided with the positive electrode thinning part 2232 at one end close to the end cover 12, the electrode assembly 2 has a larger expansion gap in the area corresponding to the positive electrode thinning part 2232, and the area of the electrode assembly 2 corresponding to the positive electrode thinning part 2232 exerts a smaller force on the first wall 111 after expansion, thereby reducing the risk of fatigue cracking of the area of the first wall 111 near the first connecting part 51.

[0340] Please refer to FIG. 13, which is a structural schematic diagram of the shell 11 provided by some embodiments of the present application. In some embodiments, the size of the buffer structure 410 along the third direction X is greater than the size 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 with each other.

[0341] Specifically, the size of the buffer structure 410 along the third direction X is the length of the buffer structure 410, the size of the buffer structure 410 along the first direction Z is the width of the buffer structure 410, and the length of the buffer structure 410 is greater than the width of the buffer structure 410, so that the buffer structure 410 is a long strip structure extending along the third direction X.

[0342] In this way, the size of the buffer structure 410 along the third direction X is greater, so that the buffer structure 410 has stronger ability to absorb the expansion force, further reducing the risk of fatigue cracking of the area of the first wall 111 near the first connecting part 51.

[0343] Please refer to FIG. 14, which is a structural schematic diagram of the shell 11 provided by some other embodiments of the present application. In some embodiments, the buffer structure 410 passes through the middle section of the first wall 111, the middle section is perpendicular to the third direction X, and the distance from the middle section to both ends of the first wall 111 along the third direction X is equal.

[0344] Specifically, the buffer structure 410 has opposite ends along the third direction X, and the buffer structure 410 passes through the middle section of the first wall 111, such that the middle section of the first wall 111 is located between the opposite ends of the buffer structure 410 along the third direction X. The distances from the opposite ends of the buffer structure 410 along the third direction X to the middle section of the first wall 111 can be equal or not equal. If the distances from the opposite ends of the buffer structure 410 along the third direction X to the middle section of the first wall 111 are equal, it indicates that the buffer structure 410 is a symmetric structure symmetrically arranged about the middle section of the first wall 111. It should be noted that the middle section of the first wall 111 is a virtual plane, which is not shown in the figure.

[0345] As an example, in the embodiment shown in FIG. 14, the distances from the opposite ends of the buffer structure 410 along the third direction X to the middle section of the first wall 111 are equal.

[0346] In this way, when the first wall 111 is subjected to the expansion force of the electrode assembly 2 of the battery cell 10, the middle region of the first wall 111 along the third direction X deforms more, 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 received by at least the middle region of the first wall 111 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 connecting portion 51.

[0347] Please refer to FIG. 14, in some embodiments, the size of the buffer structure 410 along the third direction X is L1, and the size of the first wall 111 along the third direction X is L, 0.4≤L1 / L≤0.9.

[0348] Specifically, L1 / L can take any one of 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, etc. as a point value or a range value between any two of them.

[0349] In this way, when 0.4≤L1 / L, the size of the buffer structure 410 in the first wall 111 along the third direction X accounts for a larger proportion, which makes the expansion force received by the middle region of the first wall 111 along the third direction X smaller, thereby reducing the risk of fatigue cracking of the middle region of the first wall 111 along the third direction X near the first connecting portion 51.

[0350] When L1 / L≤0.9, the size of the buffer structure 410 in the first wall 111 along the third direction X accounts for a smaller proportion, which reduces the waste generated by manufacturing the buffer structure 410 and reduces the production cost.

[0351] Therefore, the ratio of the size of the buffer structure 410 along the third direction X to the size of the first wall 111 along the third direction X is set to 0.4-0.9, which reduces the waste generated in manufacturing the buffer structure 410 while ensuring that the buffer structure 410 has sufficient capacity to absorb the expansion force, and balances the capacity requirement and the economic requirement of the buffer structure 410.

[0352] Referring to FIG. 14, in some embodiments, the buffer structure 410 has opposite fourth and fifth ends 11113a and 11113b along the third direction X, the first wall 111 has opposite sixth and seventh ends 1113 and 1114 along the third direction X, the fourth end 11113a is closer to the sixth end 1113, the fifth end 11113b is closer to the seventh end 1114, the size 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.

[0353] 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.

[0354] L2 can be equal to L3; or L2>L3 or L2

[0355] L2 / L can take any one of the following values: 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.11, 0.12, 0.13, 0.14, 0.15, 0.16, 0.17, 0.18, 0.19, 0.2, 0.21, 0.22, 0.23, 0.24, 0.25, 0.26, 0.27, 0.28, 0.29, 0.3, etc., or a range value between any two of them.

[0356] L3 / L can take any one of the following values: 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.11, 0.12, 0.13, 0.14, 0.15, 0.16, 0.17, 0.18, 0.19, 0.2, 0.21, 0.22, 0.23, 0.24, 0.25, 0.26, 0.27, 0.28, 0.29, 0.3, etc., or a range value between any two of them.

[0357] Thus, if L2 / L≤0.3, the ratio of the minimum distance between the fourth end 11113a and the sixth end 1113 along the third direction X to the size of the first wall 111 along the third direction X is reduced, so that the fourth end 11113a has more area along the third direction X that is subjected to reduced expansion force, further reducing the risk of fatigue cracking of the area of the first wall 111 near the first connecting portion 51.

[0358] If L3 / L≤0.3, the ratio of the minimum distance between the fifth end 11113b and the seventh end 1114 along the third direction X to the size of the first wall 111 along the third direction X is reduced, so that the first wall 111 has more area along the third direction X that is subjected to reduced expansion force, further reducing the risk of fatigue cracking of the area of the first wall 111 near the first connecting portion 51.

[0359] In some embodiments, 100mm≤L≤450mm.

[0360] Specifically, L can take any one of 100mm, 120mm, 150mm, 180mm, 200mm, 220mm, 250mm, 260mm, 280mm, 300mm, 310mm, 320mm, 350mm, 390mm, 400mm, 410mm, 420mm, 430mm, 440mm, 450mm, etc. or a range value between any two of them.

[0361] Thus, within this numerical range, the first wall 111 has a larger size along the third direction X, which helps to set the buffer structure 410, thereby facilitating the buffer structure 410 to absorb the expansion force.

[0362] Please refer to FIG. 13 and FIG. 14, in some embodiments, the shell 11 includes a corner wall 113, and the first wall 111 is connected with 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.

[0363] Specifically, along the third direction X, the buffer structure 410 has opposite two ends, which can be that one end of the buffer structure 410 extends to one corner wall 113 and the other end does not extend to the other corner wall 113, or both ends of the buffer structure 410 do not extend to the corner wall 113, so as to achieve that at least one end of the buffer structure 410 along the third direction X does not contact the corner wall 113.

[0364] As an example, in the embodiments shown in FIG. 13-FIG. 14, 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.

[0365] Thus, since the buffer structure 410 is not in contact with the corner wall 113 at at least one end thereof along the third direction X, the waste generated when manufacturing the buffer structure 410 can be reduced, and the production cost can be lowered.

[0366] Please refer to FIG. 15, which is a structural schematic diagram of the battery cell 10 according to some embodiments of the present application. In some embodiments, the corner wall 113 and the end cover 12 are welded to form the second connection part 52.

[0367] The second connection part 52 can correspond to the corner wall 113 one by one. The second connection part 52 is a part of the end cover 12 and the corner wall 113 after welding, which can be a part of the end cover 12 and the corner wall 113 welded and fused together. Part of the second connection part 52 is formed on the end cover 12, and the other part of the second connection part 52 is formed on the corner wall 113. The corner wall 113 and the end cover 12 can form the second connection part 52 by means of stitch welding, or can form the second connection part 52 by means of penetration welding. The second connection part 52 and the first connection part 51 are both part of the connection part 5.

[0368] Please refer to FIG. 10. In some embodiments, the main body part 400 includes a first area 440 and a second area 450 arranged along the first direction Z. The thickness of the first area 440 is greater than the thickness of the second area 450, and the buffer structure 410 is located between the first area 440 and the second area 450.

[0369] Specifically, the first area 440 can be a region where the thickness of the first wall 111 is thickened. The first area 440 is thicker than the second area 450, and the second area 450 can be a part of the first wall 111 located on the side of the first area 440 away from the first connection part 51 along the first direction Z. The first area 440 can be directly connected to the first connection part 51, or indirectly connected to the first connection part 51. The first area 440 can be directly connected to the buffer structure 410, or indirectly connected to the buffer structure 410.

[0370] The first area 440 can be an equal-thickness structure, or a non-equal-thickness structure. The second area 450 can be an equal-thickness structure, or a non-equal-thickness structure. If at least one of the first area 440 and the second area 450 is a non-equal-thickness structure, the maximum thickness of the second area 450 can be less than or equal to the minimum thickness of the first area 440, so that the thickness of the first area 440 is greater than the thickness of the second area 450.

[0371] Along the first direction Z, the buffer structure 410 can include opposite two ends, one of which can be connected to the first area 440, and the other of which can be connected to the second area 450.

[0372] In this way, the first region 440 with a greater thickness can enhance the resistance of the first connecting portion 51 to the expansion force, and the buffer structure 410 can further reduce the risk of fatigue cracking of the region 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.

[0373] Referring to FIG. 10, in some embodiments, the first region 440 includes a first portion 441 and a second portion 442 arranged along the 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.

[0374] Specifically, the first portion 441, the second portion 442, and the buffer structure 410 are arranged along the first direction Z in sequence, and the first portion 441 transitions to the buffer structure 410 through the second portion 442. The first portion 441 can be an equal-thickness structure or a non-equal-thickness structure, and the second portion 442 can be an equal-thickness structure or a non-equal-thickness structure.

[0375] If at least one of the first portion 441 and the second portion 442 is a non-equal-thickness structure, the maximum thickness of the second portion 442 can be less than or equal to the minimum thickness of the first portion 441, so that the thickness of the first portion 441 is greater than the thickness of the second portion 442.

[0376] In this way, the region of the first region 440 near the first connecting portion 51 is more likely to form a heat-affected zone, which is more likely to fatigue crack. 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 first portion 441 with a greater thickness in the first region 440 is closer to the first connecting portion 51, which can effectively weaken the influence of the heat-affected zone on the first region 440, thereby reducing the risk of fatigue cracking of the region of the first wall 111 near the first connecting portion 51. In addition, since the thickness of the second portion 442 is less than the thickness of the first portion 441, the material of the first region 440 can be reduced, thereby reducing the production cost.

[0377] Referring to FIG. 10, in some embodiments, the thickness of the second portion 442 decreases in a direction in which the end cover 12 points to the electrode assembly 2.

[0378] Specifically, the direction in which the end cover 12 points to the electrode assembly 2 is consistent with the direction in which the first portion 441 points to the buffer structure 410 along the first direction Z.

[0379] The thickness of the second portion 442 can gradually decrease or decrease in sections in a direction of the end cover 12 pointing to the electrode assembly 2. In order to reduce the manufacturing cost of the second portion 442, the thickness of the second portion 442 can gradually decrease in a direction of the end cover 12 pointing to the electrode assembly 2.

[0380] It can be understood that the second portion 442 is a non-uniform thickness structure. As an example, the thickness of the second portion 442 gradually decreases in a direction of the end cover 12 pointing to the electrode assembly 2. At least one of the inner surface and the outer surface of the second portion 442 can be beveled to achieve the gradual decrease of the thickness of the second portion 442 in the direction of the end cover 12 pointing to the electrode assembly 2.

[0381] As an example, in the embodiment shown in FIG. 10, the first portion 441 is a uniform thickness structure, and the inner surface and the outer surface of the first portion 441 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.

[0382] In this way, on the one hand, it can reduce the influence of the second portion 442 on the electrode assembly 2 and reduce the risk of interference between the second portion 442 and the electrode assembly 2.

[0383] On the other hand, it makes the reinforcing effect of the second portion 442 increase in a direction of the electrode assembly 2 pointing to the end cover 12, so that the area of the second portion 442 close to the first portion 441 has good reinforcing effect even if it is affected by the first connecting portion 51, thereby reducing the risk of fatigue cracking of the second portion 442.

[0384] On the other hand, by the second portion 442, the transition between the first portion 441 and the second region 450 can be achieved, and stress concentration can be reduced.

[0385] In some embodiments, the Vickers hardness of at least part of the first region 440 is less than the Vickers hardness of the second region 450.

[0386] Specifically, the Vickers hardness of the area of the first region 440 close to the first connecting portion 51 can be less than the Vickers hardness of the second region 450.

[0387] It can be understood that when the first wall 111 is subjected to the expansion force, the first region 440 with lower hardness can first respond to the overload by plastic deformation, and the second region 450 with higher hardness can first appear cracks, so the risk of fatigue cracking of the first region 440 is lower.

[0388] Please refer to FIG. 9 and FIG. 16, FIG. 16 is a schematic diagram of the electrode assembly 2 provided by some embodiments of the present application. In some embodiments, the electrode assembly 2 has a flat area 25, and the positive electrode tab 22 is located in a portion of the flat area 25 and the negative electrode tab 23 is located in a portion of the flat area 25, which are arranged in a stacking manner along the second direction Y.

[0389] Specifically, the flat area 25 is a flat part of the electrode assembly 2, and the positive electrode tab 22 located in the flat area 25 is in a substantially flat state, and the negative electrode tab 23 located in the flat area 25 is in a substantially flat state. As an example, the positive electrode tab 22 located in the flat area 25 and the negative electrode tab 23 located in the flat area 25 are both in a flat plate structure.

[0390] Please refer to FIG. 17, FIG. 17 is a structural schematic diagram of the electrode assembly 2 provided by some embodiments of the present application. If the electrode assembly 2 is a winding structure, the electrode assembly 2 is a winding electrode assembly 2, and a part of the electrode assembly 2 can be the flat area 25.

[0391] Please refer to FIG. 18, FIG. 18 is a structural schematic diagram of the electrode assembly 2 provided by some embodiments of the present application. If the electrode assembly 2 is a stacking structure, the electrode assembly 2 is a stacking electrode assembly 2, and the entire electrode assembly 2 can be the flat area 25. The second direction Y is the stacking direction of the positive electrode tab 22 located in the flat area 25 and the negative electrode tab 23 located in the flat area 25.

[0392] In this way, the second direction Y is the same as the stacking direction of the positive electrode tab 22 located in the flat area 25 and the negative electrode tab 23 located in the flat area 25, the electrode assembly 2 has a larger expansion amount in the second direction Y during the cycle process, and the first wall 111 is more affected by the expansion of the electrode assembly 2. However, since the buffer structure 410 can absorb the expansion force, the expansion force on the area of the first wall 111 near the first connecting part 51 is reduced, and the risk of fatigue cracking of the first wall 111 near the first connecting part 51 due to the expansion of the electrode assembly 2 is reduced.

[0393] Please refer to FIG. 17 and FIG. 18, in some embodiments, the electrode assembly 2 includes adjacent first and second surfaces 27 and 28, the first surface 27 is perpendicular to the second direction Y, the area of the first surface 27 is larger than the area of the second surface 28, and the first surface 27 is arranged opposite to the first wall 111 along the second direction Y.

[0394] Specifically, the first surface 27 is a surface of the outer surface of the electrode assembly 2 that is perpendicular to the second direction Y, and the second surface 28 is a surface of the outer surface of the electrode assembly 2 that is adjacent to the first surface 27. The first surface 27 is disposed facing the first wall 111 along the second direction Y. The first surface 27 can be a plane, and the first surface 27 can be the largest surface of the outer surface of the electrode assembly 2 or can not be the largest surface of the outer surface of the electrode assembly 2. The second surface 28 can be a plane or at least partially a circular arc surface. It should be noted that the first surface 27 is substantially perpendicular to the second direction Y, and it should also be understood that the first surface 27 is perpendicular to the second direction Y.

[0395] As an example, the first surface 27 and the second surface 28 are both two, the two first surfaces 27 are oppositely disposed along the second direction Y, the two second surfaces 28 are oppositely disposed 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 part of the electrode assembly 2 that is located at the outermost side along the second direction Y is the separator 24, the first surface 27 is formed on the separator 24, and the first direction Z, the second direction Y, and the third direction X are perpendicular to each other.

[0396] In this way, the area of the first surface 27 is larger than the area of the second surface 28, so that the first wall 111 oppositely disposed to the first surface 27 in the shell 11 receives a larger expansion force. Since the buffer structure 410 can absorb the expansion force, the expansion force received by the area of the first wall 111 near the first connecting portion 51 is reduced, thereby reducing the risk of fatigue cracking of the first wall 111 near the first connecting portion 51 due to the expansion of the electrode assembly 2.

[0397] Please refer to FIG. 17 and FIG. 18, in some embodiments, the first surface 27 is the largest surface of the outer surface of the electrode assembly 2.

[0398] Specifically, it should be noted that the first surface 27 is the largest surface of the outer surface of the electrode assembly 2, which does not limit that there is only one first surface 27 in the electrode assembly 2. It can be understood that the first surface 27 of the electrode assembly 2 can be one or two.

[0399] As an example, in the embodiment shown in FIG. 17, the electrode assembly 2 is a winding structure, the electrode assembly 2 is in a flat state, the electrode assembly 2 includes six surfaces, and two surfaces of the six surfaces oppositely disposed along the second direction Y are the largest, both of which are the first surface 27.

[0400] In the embodiment shown in FIG. 18, the electrode assembly 2 is a laminated structure, the electrode assembly 2 is substantially in a cuboid shape, the electrode assembly 2 includes six surfaces, and two surfaces of the six surfaces oppositely disposed along the second direction Y are the largest, both of which are the first surface 27.

[0401] In this way, the first wall 111 opposite to the first surface 27 in the shell 11 is subjected to the largest expansion force. Since the buffer structure 410 can absorb the expansion force, the expansion force on the region of the first wall 111 near the first connecting portion 51 is reduced, and the risk of fatigue cracking of the first wall 111 near the first connecting portion 51 due to the expansion of the electrode assembly 2 is reduced.

[0402] Please refer to FIG. 9 and FIG. 17. In some embodiments, the electrode assembly 2 has a winding structure, and the electrode assembly 2 further has a corner region 26. The corner region 26 is arranged at at least one end of the flat region 25 along the third direction X. The first direction Z, the second direction Y and the third direction X are not coplanar and intersect with each other.

[0403] The outer surface of the flat region 25 includes the first surface 27, and the outer surface of the corner region 26 includes the second surface 28. At least part of the second surface 28 is a circular arc surface.

[0404] Specifically, the flat region 25 can be provided with the corner region 26 at only one end along the third direction X, or can be provided with the corner region 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 can be arranged at an acute angle, a right angle or an obtuse angle. The first surface 27 can be part of the outer surface of the flat region 25, and the second surface 28 can be part of the outer surface of the corner region 26. The second surface 28 can be a circular arc surface as a whole, or only part of the second surface 28 can be a circular arc surface.

[0405] As an example, the positive electrode tab 22, the separator 24 and the negative electrode tab 23 are stacked and wound to form a winding structure. The first direction Z, the second direction Y and the third direction X are perpendicular to each other. The flat region 25 is provided with the corner region 26 at both ends along the third direction X.

[0406] The parts of the positive electrode tab 22, the negative electrode tab 23 and the separator 24 located in the corner region 26 are in a curved state. The part of the positive electrode tab 22 located in the corner region 26 can be at least partially in a circular arc shape. The part of the negative electrode tab 23 located in the corner region 26 can be at least partially in a circular arc shape. The part of the separator 24 located in the corner region 26 can be at least partially in a circular arc shape.

[0407] In the winding direction of the electrode assembly 2, the outermost circle of the electrode assembly 2 is the separator 24. The first surface 27 and the second surface 28 are part of the outer surface of the outermost circle of the electrode assembly 2. The first surface 27 is a plane, and the second surface 28 is a circular arc surface. The axis of the circular arc surface extends along the first direction Z.

[0408] Along the second direction Y, the surfaces on both sides of the flat area 25 are the first surfaces 27; along the third direction X, the surface on one side of one corner area 26 away from the other corner area 26 is one second surface 28, and the surface on one side of the other corner area 26 away from the one corner area 26 is the other second surface 28.

[0409] In this way, for the winding electrode assembly 2, the expansion amount of the flat area 25 in the second direction Y is larger. Since the buffer structure 410 can absorb the expansion force, the expansion force received by the area where the first wall 111 is located near the first connecting part 51 is reduced, and the risk of fatigue cracking of the first wall 111 near the first connecting part 51 due to the expansion of the electrode assembly 2 is reduced.

[0410] Please refer to FIG. 16 and FIG. 18, in some embodiments, the electrode assembly 2 is a laminated structure, the flat area 25 includes a plurality of positive electrode sheets 22 and a plurality of negative electrode sheets 23, the plurality of positive electrode sheets 22 and the plurality of negative electrode sheets 23 are stacked along the second direction Y, and the first surface 27 is perpendicular to the second surface 28.

[0411] Specifically, as an example, the plurality of positive electrode sheets 22, the plurality of negative electrode sheets 23, and the plurality of separators 24 are stacked along the second direction Y to form a laminated structure. The positive electrode sheets 22 and the negative electrode sheets 23 are completely located in the flat area 25, the adjacent positive electrode sheet 22 and the negative electrode sheet 23 are provided with a separator 24, the separator 24 extends beyond the two ends of the positive electrode sheet 22 and the two ends of the negative electrode sheet 23 along the third direction X, and the extended part of the plurality of separators 24 is connected to form an integral part, and the second surface 28 is formed on the integral part. Along the second direction Y, all the positive electrode sheets 22 and all the negative electrode sheets 23 are between the two outermost separators 24, and the outer surfaces of the two separators 24 are the first surfaces 27.

[0412] It should be noted that the first surface 27 is substantially perpendicular to the second surface 28, and it should also be understood that the first surface 27 is perpendicular to the second surface 28. For example, the angle between the first surface 27 and the second surface 28 in the range of 85°-95° can be understood as the first surface 27 being perpendicular to the second surface 28.

[0413] In this way, for the laminated electrode assembly 2, the expansion amount of the electrode assembly 2 in the stacking direction of the positive electrode sheet 22 and the negative electrode sheet 23 is larger. Since the buffer structure 410 can absorb the expansion force, the expansion force received by the area where the first wall 111 is located near the first connecting part 51 is reduced, and the risk of fatigue cracking of the first wall 111 near the first connecting part 51 due to the expansion of the electrode assembly 2 is reduced.

[0414] Please refer to FIG. 13, in some embodiments, the first wall 111 is the wall with the largest outer surface area in the shell 11.

[0415] Specifically, it is to be noted that the first wall 111 is the wall with the largest outer surface area in the housing 11, which does not limit the first wall 111 in the housing 11 to only one. It can be understood that the wall with the largest outer surface area in the housing 11 can be one or two.

[0416] In this way, 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, and 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 connecting portion 51 due to the expansion of the electrode assembly 2 is lower.

[0417] Please refer to FIG. 3 and FIG. 13, in some embodiments, the housing 11 includes two first walls 111, which are oppositely arranged along the second direction Y, and the electrode assembly 2 is located between the two first walls 111.

[0418] Specifically, as an example, in the embodiment shown in FIG. 13, the housing 11 is in the shape of a cuboid, and the housing 11 can include two first walls 111 and two second walls 112, the two first walls 111 are oppositely arranged along the second direction Y, and the two second walls 112 are oppositely arranged along the third direction X, the outer surface area of the first wall 111 is larger than that of the second wall 112. The first direction Z is parallel to the height direction of the housing 11, the second direction Y is parallel to the width direction of the housing 11, and the third direction X is parallel to the length direction of the housing 11.

[0419] In this way, this reduces the risk of fatigue cracking of the two first walls 111 near the first connecting portion 51 due to the expansion of the electrode assembly 2.

[0420] Please refer to FIG. 19 and FIG. 20, FIG. 19 is a partial schematic view of a battery monomer 10 provided in some embodiments of the present application, and FIG. 20 is an enlarged view of part C of the battery monomer 10 in FIG. 19. In some embodiments, the first wall 111 further includes a transition zone 1117, which is located between the main body portion 400 and the first connecting portion 51 along the first direction Z, and the transition zone 1117 is connected to the first connecting portion 51. The connection position of the transition zone 1117 and the first connecting portion 51 forms a connection interface 511, and the connection interface 511 has a connection position 5111 closest to the main body portion 400 along the first direction Z, and the connection position 5111 is located at the end of the main body portion 400 close to the opening along the first direction Z.

[0421] Specifically, the transition zone 1117 can be the part of the first wall 111 connected between the first connecting portion 51 and the main body portion 400. The transition zone 1117 can be an equal-thickness structure or a non-equal-thickness structure. As an example, in the embodiment shown in FIG. 19 and FIG. 20, the thickness of the transition zone 1117 gradually decreases in the direction from the second zone 450 to the first zone 440.

[0422] The connecting interface 511 is formed at the connecting position of the transition region 1117 and the first connecting portion 51, and the transition region 1117 and the first connecting portion 51 are divided by the connecting interface 511. The connecting interface 511 can be a plane or a curved surface.

[0423] The main body portion 400 and the transition region 1117 are divided by a dividing surface U, the dividing surface U is a virtual plane, the dividing surface U passes through the connecting position 5111, the dividing surface U is perpendicular to the first direction Z, the transition region 1117 and the first connecting portion 51 are located above the dividing surface U, and the main body portion 400 is located below the dividing surface U.

[0424] In this way, the transition region 1117 and the first connecting portion 51 are connected to form the connecting interface 511, so that the transition region 1117 and the first connecting portion 51 have a large enough contact area, and the firmness of the first wall 111 after welding with the end cover 12 is improved.

[0425] Please refer to FIG. 20, in some embodiments, at least part of the connecting interface 511 extends obliquely compared to the second direction Y.

[0426] Specifically, the connecting interface 511 can extend obliquely compared to the second direction Y as a whole, or the connecting interface 511 can extend obliquely compared to the second direction Y locally.

[0427] It can be understood that the extension direction of the part of the connecting interface 511 extending obliquely compared to the second direction Y is not parallel to the second direction Y.

[0428] In this way, after the end cover 12 and the first wall 111 are welded, the first connecting portion 51 will shrink with solidification, and the first connecting portion 51 will generate a 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 a tensile stress on the first connecting portion 51. Since at least part of the connecting interface 511 extends obliquely compared to the second direction Y, near the part of the connecting interface 511 extending obliquely compared to the second direction Y, the tensile stress on the transition region 1117 caused by the shrinkage of the first connecting portion 51 and the tensile stress on the first connecting portion 51 caused by the deformation of the first wall 111 are not on the same straight line, which reduces the risk of fatigue cracking of the region of the transition region 1117 near the connecting interface 511.

[0429] Please refer to FIG. 20, in some embodiments, the connecting interface 511 includes a first interface 5112, the first interface 5112 extends obliquely from the connecting position 5111 to the direction close to the end cover 12, and at least part of the transition region 1117 is located between the first interface 5112 and the end cover 12 along the second direction Y.

[0430] Specifically, it can be understood that the first interface 5112 extends obliquely compared to the second direction Y. The first interface 5112 can be a flat surface or a curved surface.

[0431] The connection position 5111 is the lowest position (the position closest to the body portion 400) of the first interface 5112, and the first interface 5112 extends obliquely from the connection position 5111 to the direction close to the end cover 12, i.e., the first interface 5112 extends obliquely upward from the connection position 5111 to the direction close to the end cover 12.

[0432] Along the second direction Y, the transition zone 1117 can be located entirely between the first interface 5112 and the end cover 12, or only a part of the transition zone 1117 can be located between the first interface 5112 and the end cover 12.

[0433] In this way, the first connecting portion 51 plays a protective role on the transition zone 1117, and 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 force process is blocked by the first connecting portion 51, thereby reducing the risk of fatigue cracking of the area of the transition zone 1117 near the first interface 5112.

[0434] Please refer to FIG. 20, in some embodiments, the first interface 5112 is connected to the outer surface 420 of the body portion 400 at the connection position 5111.

[0435] Specifically, as an example, the first interface 5112 intersects the outer surface 420 of the body portion 400 at a first straight line, the first straight line extends along the third direction X, and the position where the first straight line is located is the connection position 5111. The transition zone 1117 is approximately triangular.

[0436] In this way, since the first interface 5112 is in a direct connection state with the body portion 400, the body portion 400 and the first connecting portion 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 portion 51 due to the expansion of the electrode assembly 2.

[0437] Please refer to FIG. 21 and FIG. 22, FIG. 21 is a partial schematic view of a battery monomer 10 provided in some embodiments of the present application, and FIG. 22 is an enlarged view of part D of the battery monomer 10 of FIG. 21. In some embodiments, the connection interface 511 includes a second interface 5113, the second interface 5113 extends obliquely from the connection position 5111 to the direction away from the end cover 12, and at least a part of the transition zone 1117 is located on the side of the second interface 5113 away from the end cover 12 along the second direction Y.

[0438] Specifically, it can be understood that the second interface 5113 extends obliquely compared to the second direction Y. The second interface 5113 can be a flat surface or a curved surface. Along the second direction Y, at least part of the first connecting portion 51 is located between the second interface 5113 and the end cover 12.

[0439] The connection position 5111 is the lowest position (the position closest to the main body portion 400) of the second interface 5113, and the second interface 5113 extends obliquely from the connection position 5111 in a direction away from the end cover 12, i.e., the second interface 5113 extends obliquely upward from the connection position 5111 in a direction away from the end cover 12.

[0440] Along the second direction Y, the transition region 1117 can be located entirely on the side of the second interface 5113 away from the end cover 12, or the transition region 1117 can be located only partially on the side of the second interface 5113 away from the end cover 12.

[0441] In this way, the transition region 1117 plays a limiting role on the first connecting portion 51, reducing the risk of the first connecting portion 51 falling off.

[0442] Referring to FIG. 22, in some embodiments, the second interface 5113 is connected to the inner surface 430 of the main body portion 400 at the connection position 5111.

[0443] Specifically, as an example, the second interface 5113 intersects the inner surface 430 of the main body portion 400 at a first straight line, the first straight line extends along the third direction X, and the position where the first straight line is located is the connection position 5111. The transition region 1117 is approximately triangular.

[0444] In this way, the main body portion 400 and the first connecting portion 51 are in a direct connection state, so that the main body portion 400 and the first connecting portion 51 are closer along the first direction Z, further reducing the risk of fatigue cracking of the area near the first connecting portion 51 due to the expansion of the electrode assembly 2.

[0445] In some embodiments, the Vickers hardness of the transition region 1117 is less than the Vickers hardness of the main body portion 400.

[0446] In some embodiments, the Vickers hardness of the transition region 1117 is less than the Vickers hardness of the first connecting portion 51.

[0447] In some embodiments, the Vickers hardness of the transition region 1117 is less than the Vickers hardness of the main body portion 400, and the Vickers hardness of the transition region 1117 is less than the Vickers hardness of the first connecting portion 51.

[0448] As an example, the Vickers hardness of the main body portion 400 is less than the Vickers hardness of the first connecting portion 51.

[0449] In this way, if the Vickers hardness of the transition region 1117 is less than the Vickers hardness of the main body 400, the transition region 1117 with the lower Vickers hardness is connected to the first connecting portion 51, which can alleviate the rigid pulling between the first wall 111 and the first connecting portion 51 when the first wall 111 is deformed, and reduce the risk of separation of the first wall 111 and the first connecting portion 51. If the Vickers hardness of the transition region 1117 is less than the Vickers hardness of the first connecting portion 51, the transition region 1117 is more likely to deform than the first connecting portion 51, which can alleviate the rigid pulling between the first wall 111 and the first connecting portion 51 when the first wall 111 is deformed, and reduce the risk of separation of the first wall 111 and the first connecting portion 51.

[0450] Referring to FIG. 16, in some embodiments, the electrode assembly 2 is a laminated structure, and the electrode assembly 2 includes a plurality of positive electrode sheets 22 and a plurality of negative electrode sheets 23, which are arranged in layers along the second direction Y.

[0451] For example, the positive electrode sheets 22 and the negative electrode sheets 23 in the electrode assembly 2 are arranged alternately along the second direction Y, and a separator 24 is arranged between the positive electrode sheets 22 and the negative electrode sheets 23.

[0452] In this way, the laminated electrode assembly 2 has a more compact structure and stronger resistance to extrusion.

[0453] Referring to FIG. 16, in some embodiments, the number of negative electrode sheets 23 is greater than the number of positive electrode sheets 22, and one positive electrode sheet 22 is arranged between two adjacent negative electrode sheets 23.

[0454] For example, the number of negative electrode sheets 23 is one more than the number of positive electrode sheets 22.

[0455] In this way, arranging a positive electrode sheet 22 between adjacent negative electrode sheets 23 can reduce the transmission distance of lithium ions inside the battery monomer 10, and can provide more lithium ion transmission paths, thereby improving the charge and discharge efficiency of the battery monomer 10.

[0456] In some embodiments, each negative electrode sheet 23 is provided with a negative electrode tab 21b.

[0457] In some embodiments, each positive electrode sheet 22 is provided with a positive electrode tab 21a.

[0458] In some embodiments, each negative electrode sheet 23 is provided with a negative electrode tab 21b, and each positive electrode sheet 22 is provided with a positive electrode tab 21a.

[0459] Specifically, the number of the negative tab 21b can be one or more. When the number of the negative tab 21b is more than one, the plurality of negative tabs 21b can be located on the same side of the negative tab 23, or can be located on different sides of the negative tab 23. The number of the positive tab 21a can be one or more. When the number of the positive tab 21a is more than one, the plurality of positive tabs 21a can be located on the same side of the positive tab 22, or can be located on different sides of the positive tab 22.

[0460] In this way, the tab 21 can simplify the electrical connection between the battery monomer 10 and the external circuit.

[0461] Referring to FIG. 3, in some embodiments, along the third direction X, the size of the buffer structure 410 is greater than the size of the positive tab 22 and / or the size of the negative tab 23, and the first direction Z, the second direction Y and the third direction X are perpendicular to each other.

[0462] Specifically, if along the third direction X, the size of the buffer structure 410 is greater than the size of the positive tab 22, the buffer structure 410 exceeds at least one end of the positive tab 22 along the third direction X; if along the third direction X, the size of the buffer structure 410 is greater than the size of the negative tab 23, the buffer structure 410 exceeds at least one end of the negative tab 23 along the third direction X.

[0463] In this way, the size of the buffer structure 410 along the third direction X is larger, so that the first wall 111 has more area along the third direction X to reduce the expansion force, further reducing the risk of fatigue cracking of the area of the first wall 111 near the first connecting part 51.

[0464] Referring to FIG. 3 and FIG. 23, FIG. 23 is a schematic diagram of the connection between the end cover 12 and the electrode terminal 3 according to some embodiments of the present application. In some embodiments, the battery monomer 10 further comprises two electrode terminals 3, the two electrode terminals 3 are arranged on the end cover 12, the two electrode terminals 3 are opposite in polarity, and both are electrically connected with the electrode assembly 2;

[0465] The end cover 12 is provided with a lead-out hole, and the electrode terminal 3 comprises a terminal body 31, a first limiting part 32 and a second limiting part 33, the terminal body 31 connects the first limiting part 32 and the second limiting part 33, the terminal body 31 is arranged in the lead-out hole, along the first direction Z, the first limiting part 32 is located on the side of the end cover 12 away from the electrode assembly 2, and the second limiting part 33 is located on the side of the end cover 12 facing the electrode assembly 2.

[0466] 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 with the two ends of the terminal body 31, and the first limiting part 32 and the second limiting part 33 cooperate to limit the terminal body 31 from leaving the lead-out hole.

[0467] In the first direction Z, the projection area of the first limiting part 32 and the projection area of the second limiting part 33 are both greater than the projection area of the terminal body 31, which can be that the projection area of the first limiting part 32 is greater than the projection area of the second limiting part 33, or that the projection area of the second limiting part 33 is greater than the projection area of the first limiting part 32.

[0468] 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, and the other can be separately provided and connected with the terminal body 31.

[0469] As an example, the battery monomer 10 can further include a first insulating piece 6 and a second insulating piece 7, the first insulating piece 6 is at least partially arranged between the electrode terminal 3 and the end cover 12 to insulate and separate the electrode terminal 3 and the end cover 12, and the second insulating piece 7 is arranged on the side of the end cover 12 facing the electrode assembly 2 to insulate and separate the electrode assembly 2 and the end cover 12.

[0470] In this way, the electrode terminal 3 of this structure can be installed on the end cover 12 by riveting, which has low installation difficulty and better economy.

[0471] In a specific embodiment, the battery monomer 10 provided in the embodiments of the present application further includes a shell 11, an end cover 12 and an electrode assembly 2, the shell 11 has an opening at one end in a first direction Z, the end cover 12 is welded and connected with the shell 11 and closes the opening of the shell 11, and the electrode assembly 2 is at least partially accommodated in the shell 11.

[0472] The shell 11 is in the shape of a rectangular parallelepiped, the shell 11 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 through a corner wall 113, the two first walls 111 are oppositely arranged along a second direction Y, the two second walls 112 are oppositely arranged along a third direction X, and the first direction Z, the second direction Y and the third direction X are perpendicular to each other.

[0473] The electrode assembly 2 includes a positive electrode tab 22, a negative electrode tab 23 and a separator 24, the separator 24 is arranged between the positive electrode tab 22 and the negative electrode tab 23, the electrode assembly 2 has a flat area 25, the part of the positive electrode tab 22 located in the flat area 25, the part of the negative electrode tab 23 located in the flat area 25 and the part of the separator 24 located in the flat area 25 are stacked along the second direction Y. The electrode assembly 2 includes a first surface 27 perpendicular to the second direction Y, the first surface 27 is the surface with the largest area among the outer surfaces of the electrode assembly 2, and the first wall 111 is oppositely arranged with the first surface 27 along the second direction Y.

[0474] The positive electrode tab 22 includes a positive electrode body area 221 and a positive electrode tab 21a protruding from the positive electrode body area 221, and the positive electrode body area 221 has a positive electrode active material layer 223. The negative electrode tab 23 includes a negative electrode body area 231 and a negative electrode tab 21b protruding from the negative electrode body area 231, and the negative electrode body area 231 has a negative electrode active material layer 233. Along the first direction Z, the positive electrode body area 221 has a first end 2211 facing the end cover 12, the negative electrode body area 231 has a second end 2311 facing the end cover 12, and the separator 24 has a third end 241 facing the end cover 12, and the third end 241 is closer to the end cover 12 than the first end 2211 and the second end 2311.

[0475] The first wall 111 is welded to the end cover 12 to form a first connecting part 51, and the first wall 111 includes a main body part 400. Along the first direction Z, the main body part 400 is located on the side of the first connecting part 51 away from the end cover 12.

[0476] The main body part 400 is provided with a buffer structure 410, and the buffer structure 410 is arranged apart from the first connecting part 51. Along the first direction Z, the distance between the buffer structure 410 and the edge of the first connecting part 51 is 2 mm. The size of the buffer structure 410 along the third direction X is L1, and the size of the first wall 111 along the third direction X is L, and L1 / L = 0.5. The buffer structure 410 has opposite fourth and fifth ends 11113a and 11113b along the third direction X, and the first wall 111 has opposite sixth and seventh ends 1113 and 1114 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 size of the first wall 111 along the third direction X is L, the minimum distance between the fourth end 11113a and the sixth end 1113 along the third direction X is L2, and the minimum distance between the fifth end 11113b and the seventh end 1114 along the third direction X is L3. L2 / L = 0.3, and L3 / L = 0.3. Along the third direction X, the size of the buffer structure 410 is greater than the size of the positive electrode tab 22 and / or the size of the negative electrode tab 23.

[0477] The main body part 400 further includes a first area 440 and a second area 450 arranged along the first direction Z, and the thickness of the first area 440 is greater than the thickness of the second area 450. The buffer structure 410 is located between the first area 440 and the second area 450. The first area 440 includes a first part 441 and a second part 442 arranged along the first direction Z, and the second part 442 is located between the first part 441 and the buffer structure 410. The thickness of the first part 441 is greater than the thickness of the second part 442. The thickness of the second part 442 decreases in the direction of the end cover 12 pointing to the electrode assembly 2.

[0478] The buffer structure 410 includes a weak portion 411 disposed on the main body portion 400, and the minimum thickness of the weak portion 411 is smaller than the thickness of other portions of the main body portion 400.

[0479] The inner surface 430 of the main body portion 400 and the outer surface 420 of the main body portion 400 are both provided with a groove 412. The groove 412 is disposed opposite the weak portion 411. 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.

[0480] The weak portion 411 includes a first weak portion 4110 disposed opposite the bottom surface 4122. The thickness of the first weak portion 4110 is smaller than the thickness of other portions of the main body portion 400. The weak portion 411 further includes a second weak portion 4111 disposed opposite the first side surface 4120 and a third weak portion 4112 disposed opposite 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 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 included angle between the first side surface 4120 and the bottom surface 4122 is 150 degrees, and the included angle between the second side surface 4121 and the bottom surface 4122 is 150 degrees.

[0481] The electrode assembly 2 further includes a separator 24 disposed between the positive electrode tab 22 and the negative electrode tab 23. The separator 24 includes an overhanging region 242 that overhangs the first end 2211 and the second end 2311 in the first direction Z, and in a projection plane perpendicular to the second direction Y, the orthographic projection of the overhanging region 242 partially overlaps 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 the orthographic projection of the buffer structure 410, and the orthographic projection of the negative electrode main body region 231 does not overlap the orthographic projection of the buffer structure 410.

[0482] The first wall 111 further includes a transition region 1117. The transition region 1117 is located between the main body portion 400 and the first connecting portion 51 in the first direction Z, and the transition region 1117 is connected to the first connecting portion 51. The connection position of 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 in the first direction Z, and the connection position 5111 is located at the end of the main body portion 400 close to the opening in the first direction Z. At least part of the connection interface 511 extends obliquely compared to the second direction Y.

[0483] The connecting interface 511 includes a first interface 5112. The first interface 5112 extends obliquely from the connecting position 5111 toward the direction close to the end cover 12. Along the second direction Y, at least part of the transition region 1117 is located between the first interface 5112 and the end cover 12. The first interface 5112 is connected to the outer surface 420 of the main body portion 400 at the connecting position 5111. The connecting interface 511 includes a second interface 5113. The second interface 5113 extends obliquely from the connecting position 5111 toward the direction away from the end cover 12. Along the second direction Y, at least part of the transition region 1117 is located on the side of the second interface 5113 away from the end cover 12. The second interface 5113 is connected to the inner surface 430 of the main body portion 400 at the connecting position 5111.

[0484] The Vickers hardness of the transition region 1117 is less than the Vickers hardness of the main body portion 400, and the Vickers hardness of the transition region 1117 is less than the Vickers hardness of the first connecting portion 51.

[0485] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, and are not intended to limit the same; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacements for part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application, and they should be covered in the scope of the claims and the specification of the present application. In particular, as long as there is no structural conflict, each technical feature mentioned in each embodiment can be combined in any way. The present 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 comprises: a shell having an opening at at least one end in a first direction, the shell comprising a first wall; an end cover closing the opening, the first wall and the end cover being welded to form a first connecting portion; an electrode assembly at least partially accommodated in the shell, the electrode assembly comprising a positive electrode tab and a negative electrode tab, at least part of the positive electrode tab and at least part of the negative electrode tab being arranged in a stacking manner in a second direction, the second direction being parallel to a thickness direction of the first wall, the first direction intersecting the second direction; wherein the first wall comprises a main body portion, in the first direction, the main body portion being located on a side of the first connecting portion away from the end cover, the main body portion being provided with a buffer structure, the buffer structure being arranged in a spaced manner with the first connecting portion.

2. The battery cell of claim 1, wherein, The buffer structure comprises a weak portion arranged on the main body portion, a minimum thickness of the weak portion being less than a thickness of other portions of the main body portion.

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

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

5. The battery cell of claim 4, wherein, The weak portion further comprises a second weak portion arranged opposite to the first side and a third weak portion arranged opposite to the second side, the first side being located on a side of the bottom surface close to the first connecting portion, and the thickness of the second weak portion has a trend of increasing in a direction close to the first connecting portion, the second side being located on a side of the bottom surface away from the first connecting portion, and the thickness of the third weak portion has a trend of increasing in a direction away from the first connecting portion.

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

7. The battery cell of any one of claims 1-6, wherein, The buffer structure comprises a first protruding portion and a first recessed portion, the first protruding portion and the first recessed portion are arranged correspondingly, the first protruding portion protrudes out of an outer surface of the main body portion, and the first recessed portion is recessed outwards from an inner surface of the main body portion.

8. The battery cell of claim 7, wherein, The number of the first protruding portions is plural, and the number of the first recessed portions is plural, each first protruding portion corresponds to one first recessed portion.

9. The battery cell of any one of claims 1-8, wherein, The buffer structure comprises a second protruding portion and a second recessed portion, the second protruding portion and the second recessed portion are arranged correspondingly, the second protruding portion protrudes out of an inner surface of the main body portion, and the second recessed portion is recessed inwards from an outer surface of the main body portion.

10. The battery cell of claim 9, wherein, The number of the second protruding portions is plural, and the number of the second recessed portions is plural, each second protruding portion corresponds to one second recessed portion.

11. The battery cell of any one of claims 1-10, wherein, In the first direction, a distance between the buffer structure and an edge of the first connecting portion is H, H satisfies: 0.3mm≤H≤7mm, and optionally, 1.5mm≤H≤4mm.

12. The battery cell of any one of claims 1-11, wherein, The electrode assembly further comprises a separator, the separator is arranged between the positive electrode tab and the negative electrode tab; The positive electrode tab comprises 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 tab comprises 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 cover, the negative electrode body region has a second end facing the end cover, the separator has a third end facing the end cover, and the third end is closer to the end cover than the first end and the second end.

13. The battery cell of claim 12, wherein, The separator comprises an overhanging region beyond the first end and the second end along the first direction, and a normal projection of the overhanging region partially overlaps a normal projection of the buffer structure in a projection plane perpendicular to the second direction.

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

15. The battery cell of any one of claims 1-14, wherein, The negative electrode tab comprises a negative electrode current collector and a negative electrode active material layer arranged on at least one side of the negative electrode current collector, and the negative electrode active material layer comprises a negative electrode active material.

16. The battery cell of claim 15, wherein, The negative electrode active material layer comprises a negative electrode main part and a negative electrode thinning part, the negative electrode main part and the negative electrode thinning part are arranged along the first direction, and along the first direction, one end of the negative electrode main part close to the end cover is provided with the negative electrode thinning part.

17. The battery cell of claim 16, wherein, In a projection plane perpendicular to the second direction, a normal projection of the negative electrode thinning part is arranged apart from a normal projection of the buffer structure along the first direction.

18. The battery cell of claim 17, wherein, In a projection plane perpendicular to the second direction, the interval size of the normal projection of the negative electrode thinning part and the normal projection of the buffer structure along the first direction is greater than or equal to 1 mm.

19. The battery cell of any one of claims 15-18, wherein, The single-sided coating weight of the negative electrode active material layer is 90 mg / 1540 mm 2 ~ 170 mg / 1540 mm 2 , optionally 110 mg / 1540 mm 2 ~ 150 mg / 1540 mm 2 .

20. The battery cell of any one of claims 15-19, wherein, The porosity of the negative electrode tab is 27% to 40%.

21. The battery cell of any one of claims 15-20, wherein, The negative electrode active material comprises a silicon-based material, and the mass content of silicon in the negative electrode active material is 0.3% to 10%, and optionally 1% to 6%.

22. The battery cell of any one of claims 1-21, wherein, The size of the buffer structure along the third direction is greater 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 with each other.

23. The battery cell of claim 22, wherein, The buffer structure passes through a middle cross section of the first wall, the middle cross section is perpendicular to the third direction, and the distance from the middle cross section to the two ends of the first wall along the third direction is equal.

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

9.

25. The battery cell of any one of claims 22-24, wherein, The buffer structure has opposite fourth and fifth ends along the third direction, the first wall has opposite sixth and seventh ends along the third direction, the fourth end is close to the sixth end, the fifth end is close to the seventh end, the size of the first wall along the third direction is L, the minimum distance between the fourth end and the sixth end along the third direction is L2, and the minimum distance between the fifth end and the seventh end along the third direction is L3; L2 / L≤0.3; and / or, L3 / L≤0.

3.

26. The battery cell of claim 24 or 25, wherein, 100mm≤L≤450mm.

27. The battery cell of any one of claims 22-26, wherein, The shell comprises a corner wall, and the two ends of the first wall along the third direction are connected with the corner wall. The buffer structure is spaced apart from the corner wall at least at one end along the third direction.

28. The battery cell of any one of claims 1-27, wherein, The main body part comprises a first area and a second area arranged along the first direction, the thickness of the first area is greater than the thickness of the second area, and the buffer structure is located between the first area and the second area.

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

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

31. The battery cell of any one of claims 28-30, wherein, The Vickers hardness of at least part of the first area is less than the Vickers hardness of the second area.

32. The battery cell of any one of claims 1-31, wherein, The electrode assembly has a flat area, and the part of the positive electrode tab located in the flat area and the part of the negative electrode tab located in the flat area are stacked along the second direction.

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

34. The battery cell of claim 33, wherein, The first surface is the largest surface in the outer surface of the electrode assembly.

35. The battery cell of claim 33 or 34, wherein, The electrode assembly is in a wound structure, and the electrode assembly further has a corner area, at least one end of the flat area along a third direction is provided with the corner area, and the first direction, the second direction and the third direction are not coplanar and intersect with each other. The outer surface of the flat area comprises the first surface, and the outer surface of the corner area comprises the second surface, at least part of the second surface is a circular arc surface.

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

37. The battery cell of any one of claims 32-36, wherein, Along the third direction, the size of the buffer structure is greater than the part of the positive electrode tab located in the flat area and / or the part of the negative electrode tab located in the flat area, and the first direction, the second direction and the third direction are perpendicular to each other.

38. The battery cell of any one of claims 1-37, wherein, The first wall is the wall with the largest outer surface area in the shell.

39. The battery cell of any one of claims 1-38, wherein, The shell comprises two first walls, and the two first walls are arranged opposite to each other along the second direction, and the electrode assembly is located between the two first walls.

40. The battery cell of any one of claims 1-39, wherein, The first wall further comprises a transition region located between the main body portion and the first connecting portion along the first direction, the transition region is connected with the first connecting portion, a connection interface is formed between the transition region and the first connecting portion, the connection interface has a connection position closest to the main body portion along the first direction, and the connection position is located at one end of the main body portion close to the opening along the first direction.

41. The battery cell of claim 40, wherein, At least part of the connection interface extends obliquely compared with the second direction.

42. The battery cell of claim 41, wherein, The connection interface comprises a first interface extending obliquely from the connection position to the direction close to the end cover, and at least part of the transition region is located between the first interface and the end cover along the second direction.

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

44. The battery cell of any one of claims 41-43, wherein, The connection interface comprises a second interface extending obliquely from the connection position to the direction away from the end cover, and at least part of the transition region is located on the side of the second interface away from the end cover along the second direction.

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

46. The battery cell of any one of claims 40-45, wherein, The Vickers hardness of the transition region is less than the Vickers hardness of the main body portion; and / or, the Vickers hardness of the transition region is less than the Vickers hardness of the first connecting portion.

47. The battery cell of any one of claims 1-46, wherein, The electrode assembly is a laminated structure, and the electrode assembly comprises a plurality of positive electrode laminates and a plurality of negative electrode laminates, the plurality of positive electrode laminates and the plurality of negative electrode laminates are arranged in a stacked manner along the second direction.

48. The battery cell of claim 47, wherein, The number of negative electrode laminates is greater than the number of positive electrode laminates, and one positive electrode laminate is arranged between two adjacent negative electrode laminates.

49. The battery cell of claim 47 or 48, wherein, Each negative electrode laminate is provided with a negative electrode tab; and / or, each positive electrode laminate is provided with a positive electrode tab.

50. The battery cell of any one of claims 1-49, wherein, The battery monomer further comprises two electrode terminals, the two electrode terminals are arranged on the end cover, the two electrode terminals are opposite in polarity, and are electrically connected with the electrode assembly; The end cover is provided with a lead-out hole, the electrode terminal comprises a terminal body, a first limiting portion and a second limiting portion, the terminal body is connected with the first limiting portion and the second limiting portion, the terminal body is arranged in the lead-out hole, along the first direction, the first limiting portion is located on the side of the end cover away from the electrode assembly, and the second limiting portion is located on the side of the end cover facing the electrode assembly.

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

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

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