Battery cell, battery device, and electric device

Abstract

The application provides a battery monomer, a battery device and a power utilization device, and belongs to the technical field of batteries. The battery monomer comprises a shell, an electrode assembly and a protective layer. The shell comprises a welding mark part and a transition part, the transition part is connected to the periphery of the welding mark part, the outer surface of the welding mark part is a welding surface, the outer surface of the transition part is a transition surface, at least part of the crystal grains in the transition part are first crystal grains, the longest line among multiple lines of any two points on the outer surface of the first crystal grains is a first line, the second line among the multiple lines of any two points on the outer surface of the first crystal grains comprises a second line perpendicular to the first line and passing through the midpoint of the first line, the length ratio of the first line to the second line is 1-5, and the number ratio of the first crystal grains in the transition part is greater than 50%. The electrode assembly is accommodated in the shell. The protective layer completely covers the welding surface and covers at least part of the transition surface, so that the adhesion of the protective layer arranged on the shell is improved, and the welding mark part and the transition part can be rust-proof protected.

Description

Technical Field

[0001] This application relates to the field of battery technology, and more specifically, to a battery cell, a battery device, and an electrical device. Background Technology

[0002] In recent years, new energy vehicles have experienced rapid development. In the field of electric vehicles, power batteries, as the power source, play an irreplaceable and crucial role. With the vigorous promotion of new energy vehicles, the demand for power battery products is also increasing day by day.

[0003] In battery technology, a battery cell in a battery device typically includes a casing and electrode components housed within the casing. However, the casing of existing battery cells is prone to rusting during use, which can affect the structural strength and sealing performance of the casing, leading to risks such as damage or leakage of the battery cell during use. This is detrimental to improving the service life and reliability of the battery cell. Utility Model Content

[0004] This application provides a battery cell, a battery device, and an electrical device, which can effectively improve the service life and reliability of the battery cell.

[0005] In a first aspect, embodiments of this application provide a battery cell, including a casing, an electrode assembly, and a protective layer; the casing is made of steel, and includes at least one solder mark and at least one transition portion, the transition portion being connected around the solder mark, the outer surface of the solder mark being a welding surface, the outer surface of the transition portion being a transition surface, the outer surface of the casing including the welding surface and the transition surface, the transition surface being connected to the welding surface and located on the outer periphery of the welding surface, at least some grains within the transition portion being first grains, the longest of a plurality of lines connecting any two points on the outer surface of the first grain being a first connecting line, and the plurality of lines connecting any two points on the outer surface of the first grain also including a second connecting line, the second connecting line being perpendicular to the first connecting line and passing through the midpoint of the first connecting line, the ratio of the length of the first connecting line to the length of the second connecting line being in the range of 1-5, the ratio of the number of the first grains to the number of all grains within the transition portion being greater than 50%; the electrode assembly is housed within the casing; the protective layer completely covers the welding surface, and the protective layer covers at least a portion of the transition surface.

[0006] In the above technical solution, at least one solder mark and at least one transition portion are formed on the outer casing. The transition portion is a structure connected to the periphery of the solder mark. The ratio of the length of the first connecting line to the length of the second connecting line of the first grains in the transition portion ranges from 1 to 5, and the number of first grains accounts for more than 50%, making most of the grains in the transition portion equiaxed. The transition portion is a heat-affected zone formed by the connection between the outer casing and the solder mark and the welding effect. By covering the welding surface of the solder mark with a protective layer, and the protective layer covering at least a portion of the transition surface of the transition portion, the battery cell with this structure, on the one hand, generates a large number of first grains due to the annealing effect of the welding temperature during the formation of the transition portion. This causes the first grains to form microscopic cracks or protrusions on the transition surface during the forming process, thereby increasing the roughness of the transition surface and making the protective layer and the The increased number of connection points between the outer surfaces of the casing enhances the adhesion of the protective layer, thereby improving its stability and firmness on the weld and transition surfaces. This helps reduce the likelihood of the protective layer detaching from the casing during use. Furthermore, the protective layer not only protects the area where the weld is formed but also provides some protection to the heat-affected zone surrounding the weld. This effectively mitigates the corrosion and rust that can easily occur in the weld area and surrounding heat-affected zone due to the high temperatures of welding, which can damage the structure and metallographic structure. This reduces the risk of decreased structural strength and sealing performance of the casing during use, ultimately lowering the risk of damage and leakage to individual battery cells and improving their lifespan and reliability.

[0007] In some embodiments, the protective layer completely covers the transition surface.

[0008] In the above technical solution, by setting the protective layer to completely cover the transition surface of the transition section, on the one hand, the connection area between the protective layer and the transition surface can be increased. This connection between the protective layer and the transition surface can further enhance the adhesion of the protective layer on the outer surface of the shell, thereby further improving the stability and firmness of the protective layer covering the welding surface and the transition surface. This further reduces the phenomenon of the protective layer falling off the shell during use. On the other hand, it can further enhance the protection effect on the heat-affected zone around the weld, thereby further mitigating the corrosion and rust phenomenon that easily occurs in the heat-affected zone around the weld due to the damage to the structure and metallographic structure caused by the high temperature of welding. This further reduces the risk of damage and leakage of battery cells during use, and is conducive to further improving the service life and reliability of battery cells.

[0009] In some embodiments, the welding surface is provided with a first groove, and a portion of the protective layer is accommodated within the first groove.

[0010] In the above technical solution, by setting a first groove on the welding surface and partially accommodating the protective layer within the first groove, the first groove can restrict the protective layer to a certain extent, thereby improving the stability and firmness of the protective layer covering the welding surface. This facilitates long-term protection of the weld area by the protective layer, thereby reducing the phenomenon of protective failure caused by the protective layer falling off the welding surface and transition surface in a short period of time. This further reduces the risk of corrosion and rust on the weld area and transition area of ​​the casing during use, which is beneficial to further improve the service life and reliability of the battery cell.

[0011] In some embodiments, the portion of the protective layer contained within the first groove is connected to the groove wall surface of the first groove.

[0012] In the above technical solution, by connecting the portion of the protective layer contained in the first groove with the groove wall surface of the first groove, it is beneficial to increase the contact area and connection area between the protective layer and the shell, so as to improve the adhesion of the protective layer on the welding surface and the transition surface, thereby further improving the stability and firmness of the protective layer covering the welding surface, and further reducing the phenomenon of the protective layer falling off the shell during use.

[0013] In some embodiments, the housing includes a shell and an end cap; the shell has an opening at at least one end in a first direction; the end cap corresponds to each opening and is disposed on the opening; wherein at least one of the soldering portions includes a first soldering portion, the first soldering portion connects the shell and the end cap, and both the shell and the end cap include the transition portion, the welding surface of the first soldering portion is a first welding surface, the outer surface of the shell and the outer surface of the end cap are both part of the outer surface of the shell, and both the outer surface of the shell and the outer surface of the end cap include the transition surface, and the first welding surface connects the outer surface of the shell and the outer surface of the end cap.

[0014] In the above technical solution, the first weld mark connects the housing and the end cap to achieve a stable connection between the housing and the end cap. By setting a first groove on the first welding surface of the first weld mark, and partially accommodating the protective layer within the first groove on the first welding surface, it is beneficial to improve the stability and firmness of the protective layer covering the first welding surface of the first weld mark and the transition surface connected to it. This facilitates long-term protection of the first weld mark by the protective layer, thereby reducing the phenomenon of protective failure caused by the protective layer falling off from the first welding surface and the transition surface connected to it in a short period of time. This also reduces the risk of corrosion and rust in the area where the housing and the end cap are welded together (the first weld mark) during use.

[0015] In some embodiments, the first welding surface is connected to the outer surface of the housing at a first edge, the first welding surface is connected to the outer surface of the end cap at a second edge, the first edge and the second edge are spaced apart along the first direction, and the first groove provided on the first welding surface extends to the first edge and the second edge.

[0016] In the above technical solution, by extending the first groove provided on the first welding surface to the first edge and the second edge of the first welding surface, it is beneficial to expand the span of the first groove in the first direction, so that more of the protective layer can be accommodated in the first groove, thereby further improving the stability and firmness of the protective layer covering the first welding surface of the first solder mark and the transition surface connected thereto, so as to further reduce the phenomenon of the protective layer falling off from the first welding surface and the transition surface connected thereto during use.

[0017] In some embodiments, the first welding surface is provided with a plurality of the first grooves, and the plurality of the first grooves provided on the first welding surface are spaced apart circumferentially along the opening.

[0018] In the above technical solution, by setting multiple first grooves on the first welding surface, and the multiple first grooves on the first welding surface are arranged circumferentially along the opening, the multiple first grooves can accommodate more of the protective layer, thereby further improving the stability and firmness of the protective layer covering the first welding surface of the first solder mark and the transition surface connected thereto, so as to further reduce the phenomenon of the protective layer falling off from the first welding surface and the transition surface connected thereto during use.

[0019] In some embodiments, the first groove disposed on the first welding surface extends circumferentially along the opening.

[0020] In the above technical solution, by setting the first groove on the first welding surface as a structure that extends circumferentially along the opening, on the one hand, the structure of the first groove is simple, the forming difficulty is low, and it is easy to manufacture; on the other hand, the size of the first groove in the circumferential direction of the opening is larger, which can reduce the number of first grooves set along the circumferential direction of the opening on the first welding surface, which is conducive to improving production efficiency.

[0021] In some embodiments, the first welding surface is provided with a plurality of the first grooves, and the plurality of the first grooves provided on the first welding surface are spaced apart along the first direction.

[0022] In the above technical solution, by providing a plurality of first grooves spaced apart along a first direction on the first welding surface, the plurality of first grooves can accommodate more of the protective layer, thereby further improving the stability and firmness of the protective layer covering the first welding surface of the first solder mark and the transition surface connected thereto, so as to further reduce the phenomenon of the protective layer falling off from the first welding surface and the transition surface connected thereto during use.

[0023] In some embodiments, the housing is cylindrical, the first direction is parallel to the axial direction of the housing, the first welding surface is provided with a plurality of first grooves, and the plurality of first grooves provided on the first welding surface are arranged at radial intervals along the housing.

[0024] In the above technical solution, by providing multiple first grooves arranged radially at intervals along the outer shell on the first welding surface, the multiple first grooves can accommodate more of the protective layer, thereby further improving the stability and firmness of the protective layer covering the first welding surface of the first solder mark and the transition surface connected thereto, so as to further reduce the phenomenon of the protective layer falling off from the first welding surface and the transition surface connected thereto during use.

[0025] In some embodiments, in a projection plane perpendicular to the first direction, the orthographic projection of the first groove disposed on the first welding surface extends along a planar spiral trajectory.

[0026] In the above technical solution, by setting the first groove on the first welding surface as a structure in which the orthographic projection in the projection plane perpendicular to the first direction extends along the plane spiral trajectory, on the one hand, the extension size of the first groove on the first welding surface can be increased so that more of the protective layer can be accommodated in the first groove, thereby further improving the stability and firmness of the protective layer covering the first welding surface of the first solder mark and the transition surface connected thereto. On the other hand, the processing difficulty of the first groove can be reduced and the number of processing times can be reduced, which is conducive to improving the processing efficiency of the first groove.

[0027] In some embodiments, the first groove disposed on the first welding surface extends along a spiral trajectory, and the central axis of the spiral extends along the first direction.

[0028] In the above technical solution, by setting the first groove on the first welding surface as a structure extending along a spiral trajectory, and the central axis of the spiral extending along the first direction, on the one hand, given that the axial dimension of the first groove along the outer shell is fixed, the extension dimension of the first groove can be effectively increased so that more of the protective layer can be accommodated in the first groove, thereby further improving the stability and firmness of the protective layer covering the first welding surface of the first solder mark and the transition surface connected thereto. On the other hand, it can reduce the processing difficulty of the first groove and reduce the number of processing steps, which is beneficial to improving the processing efficiency of the first groove.

[0029] In some embodiments, the outer surface of the housing includes a first outer peripheral surface, the first outer peripheral surface includes the transition surface, and the first outer peripheral surface is connected to the first welding surface; wherein, the first outer peripheral surface is provided with a second groove, at least a portion of the first outer peripheral surface is covered by the protective layer, and a portion of the protective layer is accommodated within the second groove.

[0030] In the above technical solution, at least a portion of the first outer peripheral surface of the shell is covered with a protective layer. This increases the connection area between the protective layer and the outer surface of the shell while also providing a certain degree of protection for the shell. This reduces the likelihood of the protective layer detaching during use and lowers the risk of corrosion and rust on the portion of the shell covered by the protective layer. Furthermore, a second groove is provided on the first outer peripheral surface, and a portion of the protective layer is accommodated within the second groove. This groove provides a certain degree of restraint for the protective layer, further enhancing its stability and firmness on the first outer peripheral surface. This ensures long-term protection of the covered area of ​​the shell and reduces the risk of the protective layer easily detaching from the first solder joint due to warping or detachment on the first outer peripheral surface. This improves the stability of the protective layer's protection of the first solder joint and transition areas.

[0031] In some embodiments, along the first direction, the outer surface of the end cap includes a first surface facing away from the electrode assembly, the first surface including the transition surface, and the first surface being connected to the first welding surface; wherein, the first surface is provided with a second groove, at least a portion of the first surface is covered by the protective layer, and a portion of the protective layer is accommodated within the second groove.

[0032] In the above technical solution, at least a portion of the first surface of the end cap is covered with a protective layer. This increases the connection area between the protective layer and the outer surface of the outer shell while also providing a certain degree of protection for the end cap. This reduces the likelihood of the protective layer detaching during use and lowers the risk of corrosion and rust on the portion of the end cap covered by the protective layer. Furthermore, a second groove is provided on the first surface, and a portion of the protective layer is accommodated within the second groove. This groove provides a certain degree of restraint for the protective layer, further enhancing its stability and firmness on the first surface. This ensures long-term protection of the area covered by the end cap and reduces the risk of the protective layer easily detaching from the first solder joint due to warping or detachment on the first surface of the end cap. This improves the stability of the protective layer's protection of the first solder joint and transition areas.

[0033] In some embodiments, the outer surface of the housing includes a first outer peripheral surface, and along the first direction, the outer surface of the end cap includes a first surface facing away from the electrode assembly. Both the first outer peripheral surface and the first surface include the transition surface, and the first welding surface connects the first surface and the first outer peripheral surface.

[0034] In the above technical solution, by setting the first welding surface as the structure connecting the first surface of the end cap and the first outer peripheral surface of the housing, the first solder mark is a structure extending to the first surface of the end cap away from the electrode assembly, thereby increasing the size of the first solder mark in the first direction, which is beneficial to improving the connection strength and connection stability of the end cap and the housing.

[0035] In some embodiments, the first welding surface includes a rounded corner area, which is connected to the first surface.

[0036] In the above technical solution, the rounded corner area in the first welding surface eliminates the sharp corners of the edge area of ​​the end cap, so that the material of the protective layer can better adhere to the rounded corner area of ​​the first welding surface during the process of forming and setting the protective layer on the first welding surface and the transition surface connected to it. This makes it easier for the protective layer to fall off the first welding surface under the action of gravity, thus reducing the difficulty of setting the protective layer on the first welding surface.

[0037] In some embodiments, along the first direction, the outer surface of the housing includes a first end face, the first end face being the end face of the housing near the end cap, the first end face being connected to the first welding surface, and each of the first end faces including the transition surface; wherein, the first end face is provided with a second groove, at least a portion of the first end face is covered by the protective layer, and a portion of the protective layer is accommodated within the second groove.

[0038] In the above technical solution, at least a portion of the first end face of the housing is covered with a protective layer. This increases the connection area between the protective layer and the outer surface of the housing while also providing protection for the end of the housing near the end cap. This reduces the risk of the protective layer detaching during use and also lowers the risk of corrosion and rust on the portion of the housing covered by the protective layer. Furthermore, a second groove is provided on the first end face, and a portion of the protective layer is accommodated within the second groove. This groove provides some restraint to the protective layer, further enhancing its stability and firmness on the first end face. This ensures long-term protection for the area covered by the protective layer and reduces the risk of the portion of the protective layer on the first solder joint easily detaching due to warping or detachment on the first end face. This improves the stability of the protective layer's protection of the first solder joint and transition areas.

[0039] In some embodiments, along the first direction, the outer surface of the end cap includes a first surface facing away from the electrode assembly, the outer surface of the housing includes a first end face, the first end face being the end face of the housing near the end cap, both the first surface and the first end face include the transition surface, and the first welding surface connects the first surface and the first end face.

[0040] In the above technical solution, by setting the first welding surface as a structure that connects the first surface of the end cap and the first end face of the shell, on the one hand, during the welding process of the end cap and the shell, the end cap and the shell can be welded together from the outside of the shell along the first direction to form the first weld mark. The welding method is simple and helps to reduce the assembly difficulty of the end cap and the shell. On the other hand, it can ensure that the first weld mark does not protrude from the outer peripheral surface (first outer peripheral surface) of the shell, which helps to reduce the influence of the first weld mark on the size of the battery cell in the direction perpendicular to the first direction.

[0041] In some embodiments, the first solder mark is an annular structure, the first solder mark extends circumferentially along the opening, and the transition portion is connected to both sides of the first solder mark.

[0042] In the above technical solution, by setting the first solder mark as an annular structure extending circumferentially along the opening, on the one hand, the contact area between the shell and the first solder mark and the end cap and the first solder mark can be increased, thereby improving the connection strength between the shell and the first solder mark and the end cap and the first solder mark, so as to improve the welding firmness between the shell and the end cap. On the other hand, the first solder mark can realize the sealed connection between the shell and the end cap, so as to reduce the leakage risk of the battery cell during use.

[0043] In some embodiments, the housing includes a housing body and a first anti-corrosion layer. The housing body is made of steel. The first anti-corrosion layer is disposed on the surface of the housing body. The outer surface of the first anti-corrosion layer is at least a portion of the outer surface of the housing. Both the housing body and the first anti-corrosion layer are connected to the first solder joint.

[0044] In the above technical solution, by setting the material of the shell body to include steel, it is beneficial to improve the overall structural strength of the shell, so as to reduce the risk of damage or deformation of the shell during use. The outer surface of the first anti-corrosion layer is at least a part of the outer surface of the shell, so that the first anti-corrosion layer is the surface layer of the shell. The first anti-corrosion layer has better corrosion resistance than the shell body, so that the first anti-corrosion layer can play a certain role in protecting and preventing rust on the steel shell body, so that the shell has good rust prevention ability.

[0045] In some embodiments, the first anti-corrosion layer includes a nickel layer.

[0046] In the above technical solution, the first anti-corrosion layer includes a nickel layer. Since the nickel layer has good corrosion resistance and high hardness, it can improve the corrosion resistance and wear resistance of the shell.

[0047] In some embodiments, a second groove is provided on the outer surface of the first anti-corrosion layer, at least a portion of the outer surface of the first anti-corrosion layer covers the protective layer, and a portion of the protective layer is accommodated within the second groove.

[0048] In the above technical solution, at least a portion of the outer surface of the first anti-corrosion layer is covered by a protective layer, so that the area where the protective layer overlaps with the first anti-corrosion layer can provide double protection for the shell body, thereby further reducing the risk of corrosion and rust on the shell body during use. Furthermore, a second groove is provided on the outer surface of the first anti-corrosion layer, and a portion of the protective layer is accommodated within the second groove. This allows the second groove to provide a certain degree of restraint on the protective layer, thereby further improving the stability and firmness of the protective layer on the first anti-corrosion layer of the shell. On the one hand, this enables the protective layer to provide long-term protection for the covered area of ​​the shell; on the other hand, it reduces the risk of the portion of the protective layer on the first weld mark easily detaching due to peeling or detachment of the portion of the protective layer on the first anti-corrosion layer of the shell. This improves the stability of the protective layer in protecting areas such as the first weld mark and transition areas.

[0049] In some embodiments, the depth of the second groove disposed on the outer surface of the first anti-corrosion layer is less than the thickness of the first anti-corrosion layer.

[0050] In the above technical solution, by setting the depth of the second groove on the outer surface of the first anti-corrosion layer to be less than the thickness of the first anti-corrosion layer, the second groove does not penetrate the first anti-corrosion layer in the thickness direction of the first anti-corrosion layer, thereby reducing the phenomenon of the shell body being exposed in the area where the second groove is provided in the first anti-corrosion layer, so that the area where the second groove is provided in the first anti-corrosion layer can still provide rust protection for the shell body.

[0051] In some embodiments, the end cap includes a cap body and a second anti-corrosion layer. The cap body is made of steel. The second anti-corrosion layer is disposed on the surface of the cap body. The outer surface of the second anti-corrosion layer is at least a portion of the outer surface of the end cap. Both the cap body and the second anti-corrosion layer are connected to the first solder mark portion.

[0052] In the above technical solution, by setting the material of the end cap body to include steel, it is beneficial to improve the overall structural strength of the end cap, so as to reduce the risk of damage or deformation of the end cap during use. The outer surface of the second anti-corrosion layer is at least a part of the outer surface of the end cap, so that the second anti-corrosion layer is the surface layer of the end cap. The second anti-corrosion layer has better corrosion resistance than the cap body, so that the second anti-corrosion layer can play a certain role in protecting and preventing rust on the steel cap body, so that the end cap has good rust prevention ability.

[0053] In some embodiments, the second anti-corrosion layer includes a nickel layer.

[0054] In the above technical solution, the second anti-corrosion layer includes a nickel layer. Since the nickel layer has good corrosion resistance and high hardness, it can improve the corrosion resistance and wear resistance of the end cap.

[0055] In some embodiments, a second groove is provided on the outer surface of the second anti-corrosion layer, at least a portion of the outer surface of the second anti-corrosion layer covers the protective layer, and a portion of the protective layer is accommodated within the second groove.

[0056] In the above technical solution, at least a portion of the outer surface of the second anti-corrosion layer is covered by a protective layer, so that the overlapping area of ​​the protective layer and the second anti-corrosion layer can provide double protection for the cover body, thereby further reducing the risk of corrosion and rust on the cover body during use. Furthermore, a second groove is provided on the outer surface of the second anti-corrosion layer, and a portion of the protective layer is accommodated within the second groove. This allows the second groove to provide a certain degree of restraint on the protective layer, thereby further improving the stability and firmness of the protective layer on the second anti-corrosion layer of the end cap. On the one hand, this enables the protective layer to provide long-term protection for the area covered by the end cap; on the other hand, it reduces the risk of the portion of the protective layer on the first weld mark easily detaching due to the lifting or detachment of the portion of the protective layer on the second anti-corrosion layer of the end cap. This improves the stability of the protective layer in protecting the first weld mark and transition areas.

[0057] In some embodiments, the depth of the second groove provided on the outer surface of the second anti-corrosion layer is less than the thickness of the second anti-corrosion layer.

[0058] In the above technical solution, by setting the depth of the second groove on the outer surface of the second anti-corrosion layer to be less than the thickness of the second anti-corrosion layer, the second groove does not penetrate the second anti-corrosion layer in the thickness direction of the second anti-corrosion layer, thereby reducing the phenomenon of the cover body being exposed in the area where the second groove is provided in the second anti-corrosion layer, so that the area where the second groove is provided in the second anti-corrosion layer can still provide rust protection for the cover body.

[0059] In some embodiments, the housing includes a wall portion disposed opposite to the electrode assembly along a first direction. The electrode assembly includes a main body portion and a first tab. The first tab is connected to one end of the main body portion facing the wall portion in the first direction. At least one solder mark portion includes a second solder mark portion disposed on the wall portion. The wall portion includes the transition portion. The welding surface of the second solder mark portion is a second welding surface. The outer surface of the wall portion is a part of the outer surface of the housing. The outer surface of the wall portion includes the transition surface. The second welding surface is connected to the outer surface of the wall portion. The second solder mark portion is connected to the first tab. Alternatively, the battery cell further includes a first current collector, which is connected to the first tab. The second solder mark portion is connected to the first current collector.

[0060] In the above technical solution, if the second solder mark is connected to the first tab and the wall, a stable connection between the first tab and the wall can be achieved, thus achieving stable overcurrent between the first tab and the wall; if the second solder mark is connected to the first current collector and the wall, a stable connection between the first current collector and the wall can be achieved, thus achieving stable overcurrent between the first current collector and the wall, and reducing the difficulty of electrical connection between the first tab and the wall. In this case, by setting a first groove on the second welding surface of the second solder mark, and partially accommodating the protective layer in the first groove on the second welding surface, it is beneficial to improve the stability and firmness of the protective layer covering the second welding surface of the second solder mark and the transition surface connected to it, so as to achieve long-term protection of the second solder mark by the protective layer, thereby reducing the phenomenon of protection failure caused by the protective layer falling off from the second welding surface and the transition surface connected to it in a short period of time, and reducing the risk of corrosion and rust in the area where the wall and the first current collector or the first tab are welded together (the second solder mark) during use.

[0061] In some embodiments, in a projection plane perpendicular to the first direction, the orthographic projection of the first groove disposed on the second welding surface extends along a planar spiral trajectory.

[0062] In the above technical solution, by setting the first groove on the second welding surface as a structure in which the orthographic projection in the projection plane perpendicular to the first direction extends along the plane spiral trajectory, on the one hand, the extension size of the first groove on the second welding surface can be increased so that more of the protective layer can be accommodated in the first groove, thereby further improving the stability and firmness of the protective layer covering the second welding surface of the second solder mark and the transition surface connected thereto. On the other hand, the processing difficulty of the first groove can be reduced and the number of processing times can be reduced, which is beneficial to improving the processing efficiency of the first groove.

[0063] In some embodiments, in a projection plane perpendicular to the first direction, the orthographic projection of the first groove disposed on the second welding surface extends circumferentially along the wall portion.

[0064] In the above technical solution, by setting the first groove on the second welding surface as a structure in which the orthographic projection in the projection plane perpendicular to the first direction extends circumferentially along the wall, on the one hand, the structure of the first groove is simple, the forming difficulty is low, and it is easy to manufacture; on the other hand, the size of the first groove in the circumferential direction of the wall is larger, which can reduce the number of first grooves set along the circumferential direction of the wall on the second welding surface, which is conducive to improving production efficiency.

[0065] In some embodiments, the housing is cylindrical, and the first direction is parallel to the axial direction of the housing; wherein, the second welding surface is provided with a plurality of the first grooves, and the plurality of the first grooves provided on the second welding surface are arranged at radial intervals along the housing.

[0066] In the above technical solution, by providing multiple first grooves arranged radially at intervals along the outer shell on the second welding surface, the multiple first grooves can accommodate more of the protective layer, thereby further improving the stability and firmness of the protective layer covering the first welding surface of the second soldering part and the transition surface connected thereto, so as to further reduce the phenomenon of the protective layer falling off from the second welding surface and the transition surface connected thereto during use.

[0067] In some embodiments, along the radial direction of the housing, the minimum distance between two adjacent first grooves disposed on the second welding surface is D1, satisfying 0.05mm≤D1≤0.1mm.

[0068] In the above technical solution, on the one hand, the minimum distance between two adjacent first grooves on the second welding surface is set to be greater than or equal to 0.05mm, so that the minimum distance between two adjacent first grooves on the second welding surface is not too small, which helps to reduce the risk of the part of the second solder mark located between two adjacent first grooves collapsing during processing, and also helps to reduce the forming difficulty of the first grooves. On the other hand, the minimum distance between two adjacent first grooves on the second welding surface is set to be less than or equal to 0.1mm, so that the minimum distance between two adjacent first grooves on the second welding surface is not too large, so that more first grooves can be set along the radial direction of the shell on the second welding surface of the second solder mark, which helps to increase the density of the first grooves, thereby increasing the surface roughness of the second solder mark, and further improving the adhesion effect of the protective layer on the second welding surface of the second solder mark.

[0069] In some embodiments, the second solder mark is an annular structure, the second solder mark extends circumferentially along the wall, and the transition portion is connected to both sides of the second solder mark.

[0070] In the above technical solution, by setting the second solder mark as a ring structure extending circumferentially along the wall, it is beneficial to increase the connection area between the second solder mark and the first current collector or the first electrode, so as to improve the connection reliability and flow area between the second solder mark and the first current collector or the first electrode.

[0071] In some embodiments, the wall portion is provided with a plurality of second solder marks, the plurality of second solder marks are spaced apart circumferentially along the wall portion, and each second solder mark is surrounded by a transition portion on its outer periphery.

[0072] In the above technical solution, the wall is provided with a plurality of second weld marks spaced apart circumferentially along the wall. This structure realizes discontinuous welding between the wall and the first electrode or the first current collector, thereby reducing the welding area of ​​the wall. On the one hand, it can reduce the total heat received by the wall during the welding process, which can reduce the area of ​​the heat-affected zone formed near the second weld marks and reduce the risk of deformation of the wall due to overheating during the welding process. On the other hand, it is easier to control the effective penetration depth of each second weld mark during the welding process, thereby reducing the risk of incomplete welding.

[0073] In some embodiments, the wall portion includes a wall body and a third anti-corrosion layer. The wall body is made of steel, and the third anti-corrosion layer is disposed on the surface of the wall body. The outer surface of the third anti-corrosion layer is at least a portion of the outer surface of the wall portion. Both the wall body and the third anti-corrosion layer are connected to the second weld mark portion.

[0074] In the above technical solution, by setting the material of the wall body to include steel, it is beneficial to improve the overall structural strength of the wall and reduce the risk of damage or deformation during use. The outer surface of the third anti-corrosion layer is at least a part of the outer surface of the wall, making the third anti-corrosion layer the surface layer of the wall. The third anti-corrosion layer has better corrosion resistance than the wall body, so that the third anti-corrosion layer can play a certain role in protecting and preventing rust on the steel wall body, thus giving the wall a good rust prevention ability.

[0075] In some embodiments, the third anti-corrosion layer includes a nickel layer.

[0076] In the above technical solution, the third anti-corrosion layer includes a nickel layer. Since the nickel layer has good corrosion resistance and high hardness, it can improve the corrosion resistance and wear resistance of the wall.

[0077] In some embodiments, the outer surface of the third anti-corrosion layer is provided with a second groove, at least a portion of the outer surface of the third anti-corrosion layer covers the protective layer, and a portion of the protective layer is accommodated within the second groove.

[0078] In the above technical solution, at least a portion of the outer surface of the third anti-corrosion layer is covered by a protective layer, allowing the overlapping area of ​​the protective layer and the third anti-corrosion layer to provide double-layer protection for the wall body, thereby further reducing the risk of corrosion and rust on the wall body during use. Furthermore, a second groove is provided on the outer surface of the third anti-corrosion layer, and a portion of the protective layer is accommodated within the second groove. This allows the second groove to provide a certain degree of restraint on the protective layer, further enhancing the stability and firmness of the protective layer on the third anti-corrosion layer of the wall. On the one hand, this enables the protective layer to provide long-term protection to the covered area of ​​the wall; on the other hand, it reduces the risk of the protective layer easily detaching from the second weldment area due to peeling or detachment of the portion of the protective layer on the third anti-corrosion layer of the wall. This improves the stability of the protective layer in protecting the second weldment area and transition areas.

[0079] In some embodiments, the depth of the second groove disposed on the outer surface of the third anti-corrosion layer is less than the thickness of the third anti-corrosion layer.

[0080] In the above technical solution, by setting the depth of the second groove on the outer surface of the third anti-corrosion layer to be less than the thickness of the third anti-corrosion layer, the second groove does not penetrate the third anti-corrosion layer in the thickness direction of the third anti-corrosion layer. This reduces the phenomenon of the wall body being exposed in the area where the second groove is provided in the third anti-corrosion layer, so that the area where the second groove is provided in the third anti-corrosion layer can still provide rust protection for the wall body.

[0081] In some embodiments, along the first direction, the outer surface of the wall portion includes a second surface facing away from the electrode assembly, the wall portion is provided with a first recess, the first recess is recessed from the second surface toward the electrode assembly, and the wall surface of the first recess is a part of the outer surface of the wall portion; wherein, the wall surface of the first recess includes a first bottom surface, the first bottom surface includes the transition surface, and the second welding surface is connected to the first bottom surface, a portion of the second solder mark extends from the first bottom surface into the wall portion along the direction of the wall portion toward the electrode assembly, and at least a portion of the protective layer is accommodated within the first recess.

[0082] In the above technical solution, the wall portion is provided with a first recess, and a portion of the second solder mark extends from the first bottom surface of the first recess along the direction of the wall portion toward the electrode assembly into the wall portion. In this way, during welding, the wall portion and the first electrode tab or the first current collector can be welded and assembled from the outside of the housing, which facilitates the observation of the welding condition between the wall portion and the first electrode tab or the first current collector, and helps to improve the welding quality between the wall portion and the first electrode tab or the first current collector. After the wall portion and the first electrode tab or the first current collector are welded, the second solder mark may have a portion protruding from the first bottom surface. This portion can be accommodated in the first recess to reduce the phenomenon of the second solder mark protruding from the second surface, which helps to reduce the impact of the second solder mark on the flatness of the second surface. Furthermore, the portion of the protective layer located on the second welding surface of the second solder mark can be accommodated within the first recess, so that the first recess can provide a certain degree of protection for the protective layer, reducing wear or impact on the protective layer. This helps to reduce the risk of the protective layer failing to protect the second solder mark due to damage to the protective layer. In addition, the first recess can play a certain role in restricting the protective layer during the forming process, so that the protective layer can be set on the second welding surface of the second solder mark. For example, during the process of coating the outer surface of the shell with rust-preventive material to form a protective layer, the rust-preventive material can be sprayed into the first recess. The first recess restricts the rust-preventive material, making it difficult for the rust-preventive material to fall off the second welding surface, which is conducive to the adhesion of the rust-preventive material to the second solder mark.

[0083] In some embodiments, the first bottom surface is provided with a second groove, at least a portion of the first bottom surface is covered by the protective layer, and a portion of the protective layer is accommodated within the second groove.

[0084] In the above technical solution, at least a portion of the first bottom surface is covered with a protective layer. This increases the connection area between the protective layer and the outer surface of the shell while also providing a certain degree of protection for the first bottom surface. This reduces the likelihood of the protective layer detaching during use and lowers the risk of corrosion and rust on the portion of the wall covered by the protective layer. Furthermore, a second groove is provided on the first bottom surface, and a portion of the protective layer is accommodated within the second groove. This groove provides a certain degree of restraint for the protective layer, further enhancing its stability and firmness on the first bottom surface. This ensures long-term protection for the area covered by the protective layer on the first bottom surface and reduces the risk of the portion of the protective layer on the second solder joint easily detaching due to warping or peeling on the first bottom surface. This improves the stability of the protective layer's protection of the second solder joint and transition areas.

[0085] In some embodiments, along the first direction, the wall portion has a third surface disposed opposite to the second surface, the third surface facing the electrode assembly, and a first protrusion protruding from the third surface is formed in the area of ​​the wall portion corresponding to the first recess; wherein, the first protrusion abuts against the first tab, the second solder mark connects the first tab and the first protrusion, and the first protrusion includes the transition portion; or the battery cell further includes a first current collector, the first current collector is connected to the first tab, the first protrusion abuts against the first current collector, and the second solder mark connects the first current collector and the first protrusion, the first protrusion including the transition portion.

[0086] In the above technical solution, a first protrusion protrudes from the third surface in the area corresponding to the first recess. This wall structure allows the first protrusion to provide more recessed space for the first recess, increasing the recess depth and further reducing the risk of the second solder mark protruding from the second surface. This further reduces the impact of the second solder mark on the flatness of the second surface. Furthermore, compared to a structure where the first protrusion abuts against and connects with the first tab or the first current collector, a structure where the entire inner surface of the wall abuts against and connects with the first tab or the first current collector results in a smaller contact area between the wall and the first tab or the first current collector. This makes it easier to ensure the flatness of the surface of the first protrusion used for abutting against and connecting with the first tab or the first current collector, thereby improving the quality of the welded connection between the wall and the first tab or the first current collector to form the second solder mark and reducing the risk of incomplete soldering.

[0087] In some embodiments, the first recess is disposed around the outer side of the second surface, and the first protrusion is an annular structure; wherein, along the first direction, the surface of the first protrusion closest to the electrode assembly is a fourth surface, the fourth surface is provided with a flow guide groove, the flow guide groove penetrating the inner peripheral surface and the outer peripheral surface of the first protrusion.

[0088] In the above technical solution, the first concave portion is arranged around the outer side of the second surface, making the first convex portion an annular structure. By providing a guide groove on the fourth surface of the first convex portion, and the guide groove having a structure that penetrates the inner circumferential surface and the outer circumferential surface of the first convex portion, the guide groove can connect the space defined by the inner circumferential surface of the first convex portion and the space inside the shell used to accommodate the electrode assembly. This can improve the internal venting smoothness of the battery cell when thermal runaway occurs, thereby reducing the risk of the battery cell bursting or exploding due to local venting during thermal runaway, which is beneficial to improving the reliability of the battery cell.

[0089] In some embodiments, a second protrusion is formed in the area of ​​the wall portion corresponding to the flow channel, protruding from the first bottom surface; wherein, the outer surface of the second protrusion is a part of the outer surface of the wall portion, the outer surface of the second protrusion is provided with a second groove, at least a portion of the outer surface of the second protrusion is covered by the protective layer, and a portion of the protective layer is accommodated in the second groove.

[0090] In the above technical solution, a second protrusion is formed in the area corresponding to the flow channel on the wall, protruding from the first bottom surface. This wall structure allows the second protrusion to provide more recessed space for the flow channel, which helps to increase the depth of the flow channel and improve its air guiding capacity. Furthermore, by covering at least a portion of the outer surface of the second protrusion with a protective layer, the risk of corrosion and rust on the covered portion of the second protrusion during use can be reduced. Moreover, by providing a second groove on the outer surface of the second protrusion, a portion of the protective layer is accommodated within the second groove, allowing the second groove to provide a certain degree of restraint on the protective layer. This further enhances the stability and firmness of the protective layer on the wall. On the one hand, it enables long-term protection of the area covered by the second protrusion; on the other hand, it reduces the risk of the protective layer easily detaching from the second solder joint due to warping or peeling of the portion on the second protrusion. This improves the stability of the protective layer in protecting the second solder joint and transition areas.

[0091] In some embodiments, the first recess is disposed around the outer side of the second surface.

[0092] In the above technical solution, by setting the first recess as a structure surrounding the outer side of the second surface, the first recess is closer to the outer edge of the wall, which can realize the welding connection between the edge area of ​​the wall and the first electrode or the first current collector, which is beneficial to make better use of the central area of ​​the wall. For example, it is beneficial to set up a pressure relief component or other structure in the central area of ​​the wall.

[0093] In some embodiments, along the first direction, the outer surface of the wall portion includes a first surface facing away from the electrode assembly, the first surface being disposed around the outside of the first recess, and the wall surface of the first recess connecting the first surface and the second surface; wherein, along the first direction, the second surface is further away from the electrode assembly than the first surface.

[0094] In the above technical solution, by setting the second surface to be further away from the electrode assembly in the first direction than the first surface, the second surface can serve as a support surface for the battery cell, thereby improving the stability of the battery cell after it is placed on the external support.

[0095] In some embodiments, the second surface is disposed around the outside of the first recess.

[0096] In the above technical solution, by setting the second surface as a structure surrounding the outside of the first recess, the first recess is further away from the outer edge of the wall. On the one hand, this reduces the molding difficulty of the first recess, and on the other hand, it enables the central area of ​​the wall to be welded to the first electrode or the first current collector. This helps to reduce the circumferential extension dimension of the second solder mark on the wall, thereby reducing the difficulty of welding and assembling the wall with the first electrode or the first current collector.

[0097] In some embodiments, the wall portion is provided with a second recess, the second recess being recessed from the second surface toward the electrode assembly, the wall surface of the second recess being a part of the outer surface of the wall portion; wherein, along the first direction, the outer surface of the wall portion includes a first surface facing away from the electrode assembly, the second recess is disposed around the outside of the second surface, the first surface is disposed around the outside of the second recess, and the wall surface of the second recess connects the first surface and the second surface, and along the first direction, the second surface is further away from the electrode assembly than the first surface.

[0098] In the above technical solution, by configuring the second recess as a structure surrounding the outer side of the second surface, and configuring the first surface as a structure surrounding the outer side of the second recess, the wall of the second recess connects the first surface and the second surface. This allows the wall to have a certain buffering capacity in the area where the second recess is located. Therefore, when the second surface is subjected to external impact, the wall in the area where the second recess is located can act as a buffer, reducing the risk of damage to the wall. Furthermore, by configuring the second surface as a structure further away from the electrode assembly in the first direction than the first surface, the second surface can serve as a support surface for the battery cell, improving the stability of the battery cell when placed on the external support.

[0099] In some embodiments, along the first direction, the second surface is the surface of the wall furthest from the electrode assembly, and the protective layer does not contact the second surface.

[0100] In the above technical solution, the second surface is the surface of the wall furthest from the electrode assembly, so that the second surface can serve as the support surface of the battery cell. By setting the protective layer and the second surface to be non-contacting, the protective layer does not cover the second surface. On the one hand, it can reduce the interference effect of the protective layer on the second surface used for support, and on the other hand, it can reduce the risk of the protective layer rubbing off when the battery cell slides relative to the external support due to contact between the protective layer and the second surface.

[0101] In some embodiments, in a projection plane perpendicular to the first direction, the minimum distance between the orthographic projection of the protective layer and the orthographic projection of the second surface is D2, satisfying that D2≥0.8mm.

[0102] In the above technical solution, by setting the minimum distance between the protective layer and the second surface in the projection plane perpendicular to the first direction to be greater than or equal to 0.8 mm, it is beneficial to increase the distance between the protective layer and the second surface in the direction perpendicular to the first direction, thereby further reducing the risk of the protective layer and the second surface coming into contact with each other during the process of forming and setting the protective layer on the wall.

[0103] In some embodiments, the housing includes a shell and an end cap; the shell has an opening at at least one end in the first direction; the end cap corresponds to each opening and is disposed on the opening; wherein the end cap or the shell includes the wall portion.

[0104] In the above technical solution, by setting the wall portion of the outer casing as an end cap for sealing the opening of the casing, the battery cell with this structure can reduce the difficulty of welding the wall portion and the first tab or the first current collector to form the second solder mark, which helps to reduce the assembly difficulty of the battery cell and improve the production efficiency of the battery cell. By setting the wall portion of the outer casing as a wall of the casing, the wall of the outer casing with the second solder mark and connected to the first tab or the first current collector is far away from the end cap, thereby mitigating the force generated when the first tab or the first current collector pulls or twists on the wall portion and acts on the end cap, reducing the risk of connection failure between the end cap and the casing, and helping to reduce the risk of leakage or explosion of the battery cell during use.

[0105] In some embodiments, at least one of the soldering portions includes a first soldering portion, the end cap includes the wall portion, the first soldering portion connects the housing and the end cap, and both the housing and the end cap include the transition portion, the welding surface of the first soldering portion is a first welding surface, the outer surface of the housing and the outer surface of the end cap are both part of the outer surface of the outer shell, and both the outer surface of the housing and the outer surface of the end cap include the transition surface, the first welding surface connects the outer surface of the housing and the outer surface of the end cap; the protective layer includes a first protective layer and a second protective layer, the first protective layer completely covers the first welding surface and covers at least a portion of the transition surface of the transition portion connected to the first soldering portion, a portion of the first protective layer is accommodated in a first groove disposed on the first welding surface, the second protective layer completely covers the second welding surface and covers at least a portion of the transition surface of the transition portion connected to the second soldering portion, a portion of the second protective layer is accommodated in a first groove disposed on the second welding surface; wherein, the first protective layer and the second protective layer are integrally formed or spaced apart.

[0106] In the above technical solution, the first weld mark connects the housing and the end cap to achieve a stable connection between the housing and the end cap. The first protective layer completely covers the first welding surface and at least a portion of the transition surface of the transition portion connected to the first weld mark, so that the first protective layer can provide a certain degree of protection for the first weld mark connecting the housing and the end cap and the transition portion connected thereto. The first protective layer is partially accommodated in the first groove provided on the first welding surface, which helps to improve the firmness of the first protective layer on the first weld mark, so as to achieve long-term protection of the first weld mark by the first protective layer, thereby reducing the risk of corrosion and rust in the area where the housing and the end cap are welded together (the first weld mark) during use. Similarly, the second protective layer completely covers the second welding surface and at least a portion of the transition surface of the transition portion connected to the second solder mark, enabling the second protective layer to provide a certain degree of protection for the second solder mark and the transition portion connected thereto. The portion of the second protective layer is accommodated within the first groove on the second welding surface, which helps improve the firmness of the second protective layer on the second solder mark, achieving long-term protection and reducing the risk of corrosion and rust during use. Furthermore, if the first and second protective layers are integrally formed, the protective layer has good integrity, allowing it to cover more areas of the outer surface of the casing, thus increasing the protection range. If the first and second protective layers are spaced apart, on the one hand, the material required for the protective layer can be reduced, lowering the manufacturing cost of the battery cell; on the other hand, targeted protection can be provided for the first solder mark, the second solder mark, and the transition portion, reducing the difficulty of protecting these portions and simplifying the process of forming the protective layer on them.

[0107] In some embodiments, the minimum distance between the first solder mark and the second solder mark is D3, which satisfies that D3≥1.8mm.

[0108] In the above technical solution, by setting the minimum distance between the first solder mark and the second solder mark to be greater than or equal to 1.8 mm, a certain distance can be maintained between the first solder mark and the second solder mark, which helps to reduce the mutual influence between the first solder mark and the second solder mark, such as the heat influence or molten pool influence between the two during the welding process.

[0109] In some embodiments, the outer surface of the housing further includes a main body surface connected to the welding surface, the main body surface including the transition surface, the main body surface having a second groove, at least a portion of the main body surface being covered by the protective layer, and a portion of the protective layer being accommodated within the second groove.

[0110] In the above technical solution, at least a portion of the main body surface of the outer casing is covered with a protective layer. This increases the connection area between the protective layer and the outer surface of the outer casing while also providing a certain degree of protection for the main body surface of the outer casing. This reduces the likelihood of the protective layer detaching during use and lowers the risk of corrosion and rust on the portion of the outer casing covered by the protective layer. Furthermore, a second groove is provided on the main body surface, and a portion of the protective layer is accommodated within this groove. This second groove provides a certain degree of restraint for the protective layer, further enhancing its stability and firmness on the main body surface. On the one hand, this ensures long-term protection of the area covered by the protective layer on the main body surface; on the other hand, it reduces the risk of the protective layer easily detaching from the solder joint due to peeling or detachment of the portion on the main body surface. This improves the stability of the protective layer's protection of the solder joint and transition areas.

[0111] In some embodiments, the transition surface is provided with the second groove.

[0112] In the above technical solution, by setting a second groove on the transition surface and partially accommodating the protective layer within the second groove on the transition surface, the stability and firmness of the protective layer covering the transition surface can be improved, so as to achieve long-term protection of the transition part by the protective layer. This further reduces the phenomenon of protective failure caused by the protective layer falling off the transition surface in a short period of time, thereby further reducing the risk of corrosion and rust on the welded part and transition part of the casing during use, which is conducive to further improving the service life and reliability of the battery cell.

[0113] In some embodiments, the portion of the protective layer housed within the second groove is connected to the groove wall of the second groove.

[0114] In the above technical solution, by connecting the portion of the protective layer contained in the second groove with the groove wall surface of the second groove, it is beneficial to increase the contact area and connection area between the protective layer and the shell, so as to improve the adhesion of the protective layer on the main body surface, thereby further improving the stability and firmness of the protective layer covering the welding surface, and further reducing the phenomenon of the protective layer falling off the shell during use.

[0115] In some embodiments, at least one of the first grooves is in communication with at least one of the second grooves.

[0116] In the above technical solution, by setting at least one second groove and at least one first groove to be interconnected, the portion of the protective layer contained in the second groove and the portion of the protective layer contained in the first groove can be continuous and connected, thereby enabling more of the protective layer to be contained in the first groove and / or the second groove, which is beneficial to further improve the firmness and stability of the protective layer on the shell.

[0117] In some embodiments, the housing includes a shell and an end cap; the shell has an opening at at least one end in a first direction; the end cap corresponds to the opening one-to-one and is disposed on the opening; wherein the main body surface includes the outer surface of the shell and the outer surface of the end cap, at least one of the welding surfaces is connected to the outer surface of the shell, and the outer surface of the shell includes the transition surface, the outer surface of the shell is provided with a second groove, at least a portion of the outer surface of the shell is covered with a protective layer, and a portion of the protective layer is accommodated in the second groove.

[0118] In the above technical solution, at least a portion of the outer surface of the shell is covered with a protective layer. This increases the connection area between the protective layer and the outer surface of the shell while also providing a certain degree of protection for the shell. This reduces the likelihood of the protective layer detaching during use and lowers the risk of corrosion and rust on the portion of the shell covered by the protective layer. Furthermore, a second groove is provided on the outer surface of the shell, and a portion of the protective layer is accommodated within this groove. The second groove provides a certain degree of restraint for the protective layer, further enhancing its stability and firmness on the outer surface of the shell. This ensures long-term protection of the covered area of ​​the shell and reduces the risk of the protective layer detaching from the solder joint due to warping or peeling on the outer surface of the shell. This improves the stability of the protective layer's protection of the solder joint and transition areas.

[0119] In some embodiments, the housing includes a shell and an end cap; the shell has an opening at at least one end in a first direction; the end cap corresponds to each opening and is disposed on the opening; wherein the main body surface includes the outer surface of the shell and the outer surface of the end cap, at least one of the welding surfaces is connected to the outer surface of the end cap, and the outer surface of the end cap includes the transition surface, the outer surface of the end cap is provided with a second groove, at least a portion of the outer surface of the end cap is covered with a protective layer, and a portion of the protective layer is accommodated within the second groove.

[0120] In the above technical solution, at least a portion of the outer surface of the end cap is covered with a protective layer. This increases the connection area between the protective layer and the outer surface of the outer shell while also providing a certain degree of protection for the end cap. This reduces the likelihood of the protective layer detaching during use and lowers the risk of corrosion and rust on the portion of the end cap covered by the protective layer. Furthermore, a second groove is provided on the outer surface of the end cap, and a portion of the protective layer is accommodated within this groove. The second groove provides a certain degree of restraint for the protective layer, further enhancing its stability and firmness on the outer surface of the end cap. This ensures long-term protection of the area covered by the protective layer and reduces the risk of the portion of the protective layer on the solder joint easily detaching due to warping or detachment on the outer surface of the end cap. This improves the stability of the protective layer's protection of the solder joint and transition areas.

[0121] In some embodiments, the first groove includes a plurality of slots arranged along its extension direction, a portion of the protective layer is accommodated within the slots, and two adjacent slots are connected to each other and form a communication opening at the connection position.

[0122] In the above technical solution, the first groove includes a plurality of grooves arranged along its extension direction, and two adjacent grooves are connected to each other and a communication opening is formed at the connection position. The first groove with this structure can effectively reduce the flatness of the groove wall surface of the first groove, making the groove wall surface of the first groove rougher, thereby further improving the adhesion effect of the protective layer on the welding surface of the soldering part, so as to further reduce the risk of the protective layer falling off the soldering part of the shell during use.

[0123] In some embodiments, the area of ​​the communication opening is smaller than the area of ​​any cross-section of the groove, and the cross-section is perpendicular to the extending direction of the first groove.

[0124] In the above technical solution, by setting the area of ​​the connecting opening to be smaller than the area of ​​any cross-section of the groove, the first groove forms a necking structure at the connecting opening position, which can further improve the stability and reliability of the protective layer contained in the first groove, making it more difficult for the part of the protective layer contained in the first groove to detach from the first groove, which helps to further reduce the risk of the protective layer falling off the solder part of the shell during use.

[0125] In some embodiments, within the cross-section of the groove, the dimension of the groove in the width direction of the first groove gradually decreases along the depth direction of the first groove, and the cross-section is perpendicular to the extension direction of the first groove.

[0126] In the above technical solution, by setting the dimension of the groove in the width direction of the first groove to gradually decrease along the depth direction of the first groove, the material of the protective layer can more easily adhere to the groove wall surface during the process of forming and setting the protective layer on the outer surface of the shell. This helps to increase the contact area between the protective layer and the groove wall surface, thereby further improving the stability and firmness of the protective layer set on the welding surface of the shell.

[0127] In some embodiments, along the depth direction of the first groove, the maximum size of the communication opening is smaller than the maximum size of the groove portion.

[0128] In the above technical solution, by setting the maximum dimension of the connecting port along the depth direction of the first groove to be smaller than the maximum dimension of the groove along the depth direction of the first groove, it is beneficial to increase the area of ​​the groove wall surface of the groove, thereby effectively increasing the contact area between the protective layer and the groove wall surface of the groove, so as to further improve the stability and firmness of the protective layer set on the welding surface of the shell.

[0129] In some embodiments, along the width direction of the first groove, the maximum size of the communication opening is smaller than the maximum size of the groove portion.

[0130] In the above technical solution, by setting the maximum dimension of the connecting opening in the width direction of the first groove to be smaller than the maximum dimension of the groove in the width direction of the first groove, it is beneficial to increase the area of ​​the groove wall surface of the groove, thereby effectively increasing the contact area between the protective layer and the groove wall surface of the groove, so as to further improve the stability and firmness of the protective layer set on the welding surface of the shell.

[0131] In some embodiments, the maximum dimension of the groove is L along the extending direction of the first groove, and the maximum dimension of the groove is W along the width direction of the first groove, where 1.1 ≤ W / L ≤ 10.

[0132] In the above technical solution, by setting the ratio of the maximum dimension of the groove in the width direction of the first groove to the maximum dimension of the groove in the extension direction of the first groove to 1.1-10, the maximum dimension of the groove in the width direction of the first groove is larger than the maximum dimension of the groove in the extension direction of the first groove, thereby reducing the difficulty of the protective layer entering the first groove during the forming process on the outer surface of the shell.

[0133] In some embodiments, 70μm≤W≤90μm, 7μm≤L≤81μm.

[0134] In the above technical solution, the maximum dimension of the groove in the width direction of the first groove is set to 70μm-90μm, and the maximum dimension of the groove in the extension direction of the first groove is set to 7μm-81μm, so that the groove is a small groove with a smaller size, so as to accurately control the surface roughness of the soldering part of the shell, which is beneficial to improve the stability and firmness of the protective layer set on the welding surface of the shell.

[0135] In some embodiments, the maximum width of the first groove is W, where 70μm≤W≤90μm.

[0136] In the above technical solution, by setting the maximum width of the first groove to be greater than or equal to 70μm, the maximum width of the first groove is not too small. On the one hand, this reduces the processing difficulty of the first groove, and on the other hand, it reduces the difficulty of the protective layer entering the first groove during the forming process on the outer surface of the shell, thereby increasing the contact area between the protective layer and the groove wall. By setting the maximum width of the first groove to be less than or equal to 90μm, the maximum width of the first groove is not too large, thereby forming a narrower first groove on the welding surface of the soldering part of the shell. This allows for the placement of the first groove in more areas of the welding surface, which is beneficial to increasing the density of the first groove. This increases the surface roughness of the soldering part, thereby further improving the adhesion effect of the protective layer on the welding surface of the soldering part.

[0137] In some embodiments, the maximum depth of the first groove is H, where 5μm≤H≤20μm.

[0138] In the above technical solution, on the one hand, the maximum depth of the first groove is set to be greater than or equal to 5μm, so that the maximum depth of the first groove is not too small, so that the first groove can accommodate more of the protective layer, which is beneficial to improving the stability and firmness of the protective layer on the welding surface of the shell. On the other hand, the maximum depth of the first groove is set to be less than or equal to 20μm, so that the maximum depth of the first groove is not too large, which is beneficial to reducing the impact of the first groove on the structural strength of the shell.

[0139] In some embodiments, the first groove is a laser cleaning tank.

[0140] In the above technical solution, the first groove is a laser cleaning tank, which is formed on the welding surface by laser cleaning. On the one hand, during the process of forming the first groove, contaminants (oxide layer or dirt, etc.) on the welding surface can be cleaned away to reduce the risk of the contaminants forming a weak interface between the protective layer and the welding surface, which would reduce the adhesion of the protective layer. On the other hand, the groove wall surface of the first groove can be made into a relatively rough structure, which is beneficial to improving the connection effect between the protective layer and the groove wall surface of the first groove.

[0141] In some embodiments, the protective layer is a coating.

[0142] In the above technical solution, the protective layer is a coating, which can be formed by coating the outer surface of the shell with anti-rust material. On the one hand, the protective layer has good anti-corrosion performance and stability, and can improve the adhesion of the protective layer on the welding surface and transition surface. On the other hand, it can reduce the difficulty of forming and setting the protective layer on the welding surface and transition surface, thereby reducing the manufacturing difficulty of the battery cell.

[0143] In some embodiments, the housing is made of carbon steel.

[0144] In the above technical solution, by setting the material of the outer shell to include carbon steel, which has low cost and is easy to process, the overall structural strength of the outer shell can be improved while reducing the manufacturing difficulty and cost of the outer shell, thereby reducing the manufacturing cost of the battery cell.

[0145] In some embodiments, the battery cell is a cylindrical battery cell.

[0146] In the above technical solution, by setting the battery cell as a cylindrical battery cell, the battery cell has advantages such as high capacity, long cycle life, and wide operating temperature range.

[0147] Secondly, embodiments of this application also provide a battery device, including the aforementioned battery cell.

[0148] Thirdly, embodiments of this application also provide an electrical device, including the aforementioned battery cell, wherein the battery cell is used to provide electrical energy. Attached Figure Description

[0149] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0150] Figure 1 This application provides structural schematic diagrams of vehicles for some embodiments;

[0151] Figure 2 Exploded views of the structure of the battery device provided in some embodiments of this application;

[0152] Figure 3 Exploded views of the structure of a single battery cell provided in some embodiments of this application;

[0153] Figure 4 Cross-sectional views of a battery cell provided in some embodiments of this application;

[0154] Figure 5 for Figure 4 A magnified view of part A of the shown battery cell;

[0155] Figure 6 for Figure 4 A magnified view of part B of the shown battery cell;

[0156] Figure 7 A partial cross-sectional view of a battery cell provided for some embodiments of this application;

[0157] Figure 8 A partial structural schematic diagram of the casing of a battery cell provided in some embodiments of this application;

[0158] Figure 9 for Figure 8 A magnified view of a portion of the outer casing at point C;

[0159] Figure 10 A partial structural schematic diagram of the casing of a battery cell provided in some embodiments of this application in other embodiments;

[0160] Figure 11 A partial cross-sectional view of a battery cell provided in some embodiments of this application;

[0161] Figure 12 for Figure 11 A magnified view of part D of the battery cell shown;

[0162] Figure 13 A front view of the casing of a battery cell provided in some embodiments of this application, facing the end cap along a first direction;

[0163] Figure 14 The housing of the battery cell provided in some embodiments of this application is a front view of the end cap along a first direction in other embodiments;

[0164] Figure 15 Partial cross-sectional views of a battery cell provided for other embodiments of this application;

[0165] Figure 16 This is a partial structural diagram of the casing of a battery cell provided in other embodiments of this application;

[0166] Figure 17 A partial cross-sectional view of a battery cell provided in some further embodiments of this application;

[0167] Figure 18 A partial cross-sectional view of a battery cell provided for further embodiments of this application;

[0168] Figure 19 for Figure 18 A magnified view of part E of the shown battery cell;

[0169] Figure 20 A partial cross-sectional view of a battery cell provided for some other embodiments of this application;

[0170] Figure 21 A partial cross-sectional view of a battery cell provided for some other embodiments of this application;

[0171] Figure 22 for Figure 18 A magnified view of part F of the shown battery cell;

[0172] Figure 23 for Figure 22 A magnified view of point G on the battery cell shown.

[0173] Figure 24 A front view of the casing of a battery cell facing the wall in a first direction, provided in some other embodiments of this application;

[0174] Figure 25 The casing of the battery cell provided in some other embodiments of this application is a front view of the wall portion along the first direction in other embodiments;

[0175] Figure 26 A front view of the casing of a battery cell facing the wall in a first direction, provided in some other embodiments of this application;

[0176] Figure 27 for Figure 26 A magnified view of part H of the battery cell shown;

[0177] Figure 28 A partial cross-sectional view of a battery cell provided for some other embodiments of this application;

[0178] Figure 29 This application also provides cross-sectional views of battery cells in some embodiments;

[0179] Figure 30 for Figure 29 A magnified view of part J of the shown battery cell;

[0180] Figure 31 for Figure 30 A magnified view of a portion of the battery cell at point K;

[0181] Figure 32 This application also provides structural schematic diagrams of the wall portion of the casing of a battery cell in some embodiments;

[0182] Figure 33 for Figure 32 The NN cross-sectional view of the wall shown;

[0183] Figure 34 Axonometric views of the wall portion of the housing of a battery cell are also provided for some embodiments of this application;

[0184] Figure 35 For some embodiments of this application, a front view of the casing of a battery cell facing the wall in a first direction is provided;

[0185] Figure 36 for Figure 30 A magnified view of the L-axis of the shown battery cell;

[0186] Figure 37 Cross-sectional views of a battery cell provided for other embodiments of this application;

[0187] Figure 38 for Figure 37 A magnified view of part M of the shown battery cell;

[0188] Figure 39 for Figure 38 A magnified view of point P of the shown battery cell;

[0189] Figure 40 A partially enlarged view of the casing of a battery cell provided in some embodiments of this application;

[0190] Figure 41 for Figure 40 The UU cross-sectional view of the casing is shown.

[0191] Icons: 1000 - Vehicle; 100 - Battery assembly; 10 - Housing; 11 - First housing body; 12 - Second housing body; 20 - Battery cell; 21 - Outer casing; 211 - Housing; 211a - Casing body; 211b - First anti-corrosion layer; 2111 - Opening; 2112 - First outer peripheral surface; 2113 - First end face; 212 - End cap; 212a - Cap body; 212b - Second anti-corrosion layer; 2121 - Second outer peripheral surface; 2122 - First surface ; 213- Solder stamp area; 213a- Welding surface; 2131- First solder stamp area; 21311- First welding surface; 21311a- Rounded corner area; 21311b- Connection area; 21311c- First edge; 21311d- Second edge; 21312- First interface; 21313- Second interface; 2132- Second solder stamp area; 21321- Second welding surface; 214- Transition area; 2141- Transition surface; 215- First groove; 2151 - Groove; 2152 Connecting opening; 216 Second groove; 217 Wall; 217a Wall body; 217b Third anti-corrosion layer; 2171 Second surface; 2172 First recess; 2172a First bottom surface; 2172b First side surface; 2173 Third surface; 2174 First protrusion; 2174a Fourth surface; 2174b Guide groove; 2175 Second protrusion; 2175a Fifth surface; 2175b First Connecting surface; 2176-Second recess; 2177-Third recess; 2178-Pressure relief groove; 2179-Third protrusion; 22-Electrode assembly; 221-Main body; 222-First electrode tab; 223-Second electrode tab; 23-Protective layer; 231-First protective layer; 232-Second protective layer; 24-Electrode terminal; 25-First current collector; 251-Abutting surface; 26-Second current collector; 200-Controller; 300-Motor; X-First direction. Detailed Implementation

[0192] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0193] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used in the description of this application is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms "comprising" and "having," and any variations thereof, in the description, claims, and accompanying drawings of this application are intended to cover non-exclusive inclusion. The terms "first," "second," etc., in the description, claims, or accompanying drawings of this application are used to distinguish different objects, not to describe a specific order or hierarchy.

[0194] In this application, the reference to "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment that is mutually exclusive with other embodiments.

[0195] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," and "attachment" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0196] In this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. Additionally, in this application, the character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0197] In the embodiments of this application, the same reference numerals denote the same components, and for the sake of brevity, detailed descriptions of the same components are omitted in different embodiments. It should be understood that the thickness, length, width, and other dimensions of various components in the embodiments of this application shown in the accompanying drawings, as well as the overall thickness, length, width, and other dimensions of the integrated device, are merely illustrative and should not constitute any limitation on this application.

[0198] In this application, "multiple" means two or more (including two).

[0199] In this embodiment of the application, the battery cell can be a secondary battery, which refers to a battery cell that can be recharged to activate the active materials and continue to be used after the battery cell has been discharged.

[0200] The battery cell can be a lithium-ion battery, sodium-ion battery, sodium-lithium-ion battery, lithium metal battery, sodium metal battery, lithium-sulfur battery, magnesium-ion battery, nickel-metal hydride battery, nickel-cadmium battery, lead-acid battery, etc., and the embodiments of this application are not limited to this.

[0201] A single battery cell typically includes an electrode assembly. The electrode assembly includes a positive electrode, a negative electrode, and a separator. During the charging and discharging process of a single battery cell, active ions (such as lithium ions) repeatedly insert and extract between the positive and negative electrodes. The separator, positioned between the positive and negative electrodes, helps prevent short circuits to some extent while allowing active ions to pass through.

[0202] In some embodiments, the positive electrode may be a positive electrode sheet, which may include a positive electrode current collector and a positive electrode active material disposed on at least one surface of the positive electrode current collector.

[0203] As an example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive active material is disposed on either or both of the two opposite surfaces of the positive current collector.

[0204] As an example, the positive electrode current collector can be a metal foil or a composite current collector. For example, as a metal foil, it can be aluminum with a silver-plated surface, stainless steel with a silver-plated surface, stainless steel, copper, aluminum, nickel, carbon electrode, carbon, or titanium, etc. Composite current collectors can include a polymer material base layer and a metal layer. Composite current collectors can be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.).

[0205] As an example, the positive electrode active material may include at least one of the following materials: lithium phosphate, lithium transition metal oxide, and their respective modified compounds. However, this application is not limited to these materials, and other conventional materials that can be used as battery positive electrode active materials may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium phosphate include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), lithium iron phosphate and carbon composites, lithium manganese phosphate (such as LiMnPO4), lithium manganese phosphate and carbon composites, lithium iron manganese phosphate, and lithium iron manganese phosphate and carbon composites. Examples of lithium transition metal oxides include, but are not limited to, lithium cobalt oxide (such as LiCoO2), lithium nickel oxide (such as LiNiO2), lithium manganese oxide (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, and lithium nickel cobalt manganese oxide (such as LiNi). 1 / 3 Co 1 / 3 Mn 1 / 3O2 (also known as NCM) 333 LiNi 0.5 Co 0.2 Mn 0.3 O2 (also known as NCM) 523 LiNi 0.5 Co 0.25 Mn 0.25 O2 (also known as NCM) 211 LiNi 0.6 Co 0.2 Mn 0.2 O2 (also known as NCM) 622 LiNi 0.8 Co 0.1 Mn 0.1 O2 (also known as NCM) 811 ), lithium nickel cobalt aluminum oxide (such as LiNi) 0.85 Co 0.15 Al 0.05 At least one of O2 and its modified compounds.

[0206] In some embodiments, the positive electrode can be a foamed metal. The foamed metal can be foamed nickel, foamed copper, foamed aluminum, foamed alloys, etc. When foamed metal is used as the positive electrode, the surface of the foamed metal may or may not contain a positive electrode active material. As an example, lithium source material, potassium metal, or sodium metal can also be filled and / or deposited within the foamed metal, where the lithium source material is lithium metal and / or a lithium-rich material.

[0207] In some embodiments, the negative electrode may be a negative electrode sheet, and the negative electrode sheet may include a negative electrode current collector.

[0208] As an example, the negative electrode current collector can be a metal foil, a foamed metal, or a composite current collector. For example, as a metal foil, it can be silver-treated aluminum or stainless steel, stainless steel, copper, aluminum, nickel, carbon electrodes, or titanium, etc. Foamed metal can be foamed nickel, foamed copper, foamed aluminum, foamed alloys, etc. Composite current collectors can include a polymer material base layer and a metal layer. Composite current collectors can be formed by forming a metal material (copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver and silver alloys, etc.) on a polymer material substrate (such as a substrate of polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.).

[0209] As an example, the negative electrode sheet may include a negative electrode current collector and a negative electrode active material disposed on at least one surface of the negative electrode current collector.

[0210] As an example, the negative electrode current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode active material is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0211] As an example, the negative electrode active material may be a negative electrode active material known in the art for use in battery cells. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate, etc. Silicon-based materials may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Tin-based materials may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. However, this application is not limited to these materials, and other conventional materials that can be used as battery negative electrode active materials may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0212] In some embodiments, the positive current collector can be made of aluminum, and the negative current collector can be made of copper.

[0213] In some embodiments, the electrode assembly further includes an isolator disposed between the positive and negative electrodes.

[0214] In some embodiments, the separator is a separator membrane. The separator membrane can be of various types, and any known porous separator membrane with good chemical and mechanical stability can be selected.

[0215] As an example, the material of the separator may include at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may be a single-layer film or a multi-layer composite film. When the separator is a multi-layer composite film, the materials of each layer may be the same or different. The separator may be a separate component located between the positive and negative electrodes, or it may be attached to the surfaces of the positive and negative electrodes.

[0216] In some embodiments, the separator is a solid electrolyte. The solid electrolyte is disposed between the positive and negative electrodes, serving both to transport ions and to isolate the positive and negative electrodes.

[0217] In some embodiments, the battery cell also includes an electrolyte, which acts as a conductor of ions between the positive and negative electrodes. The electrolyte can be liquid, gel-like, or solid. Liquid electrolytes include electrolyte salts and solvents.

[0218] In some embodiments, the electrolyte salt may include at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium dioxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate.

[0219] In some embodiments, the solvent may include at least one selected from ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butyl carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone. The solvent may also be an ether solvent. Ether solvents may include one or more selected from ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, 1,3-dioxolane, tetrahydrofuran, methyl tetrahydrofuran, diphenyl ether, and crown ethers.

[0220] Among them, the gel electrolyte includes a polymer as the electrolyte backbone network, combined with an ionic liquid - lithium salt.

[0221] Solid electrolytes include polymer solid electrolytes, inorganic solid electrolytes, and composite solid electrolytes.

[0222] As an example, polymer solid electrolytes can be polyether (polyoxyethylene), polysiloxane, polycarbonate, polyacrylonitrile, polyvinylidene fluoride, polymethyl methacrylate, monoionic polymers, polyionic liquids-lithium salts, cellulose, etc.

[0223] As an example, inorganic solid electrolytes may include one or more of the following: oxide solid electrolytes (crystalline perovskite, sodium superconducting ion conductor, garnet, amorphous LiPON thin film), sulfide solid electrolytes (crystalline lithium superconducting ion conductor (lithium germanium phosphate sulfide, silver sulfide germanium ore), amorphous sulfides), halide solid electrolytes, nitride solid electrolytes, and hydride solid electrolytes.

[0224] As an example, composite solid electrolytes are formed by adding inorganic solid electrolyte fillers to polymer solid electrolytes.

[0225] In some implementations, the electrode assembly has a wound structure. The positive and negative electrode sheets are wound into a wound structure.

[0226] In some implementations, the electrode assembly has a stacked structure.

[0227] As an example, multiple positive and negative electrodes can be set, and multiple positive and multiple negative electrodes can be stacked alternately.

[0228] As an example, multiple positive electrode plates can be provided, and negative electrode plates can be folded to form multiple stacked folded segments, with a positive electrode plate sandwiched between adjacent folded segments.

[0229] As an example, both the positive and negative electrode plates are folded to form multiple stacked folded segments.

[0230] As an example, multiple separators can be provided, each positioned between any adjacent positive or negative electrode plates.

[0231] As an example, the separators can be continuously arranged, either by folding or rolling between any adjacent positive or negative electrode plates.

[0232] In some embodiments, the electrode assembly can be cylindrical, flat, or polygonal, etc.

[0233] In some embodiments, the electrode assembly is provided with tabs that allow current to be drawn from the electrode assembly. The tabs include a positive tab and a negative tab.

[0234] In some implementations, a battery cell may include a housing. The housing is used to encapsulate components such as electrode assemblies and electrolytes.

[0235] As an example, a battery cell can be a cylindrical battery cell, a prismatic battery cell, or a battery cell of other shapes. Prismatic battery cells include, but are not limited to, square battery cells, blade-shaped battery cells, and multi-prismatic batteries, such as hexagonal prismatic batteries.

[0236] The battery device mentioned in the embodiments of this application may include one or more battery cell assemblies for providing voltage and capacity. A battery cell assembly may include multiple battery cells, which are connected in series, parallel, or mixed connections via a busbar.

[0237] In some embodiments, a battery cell assembly is typically formed by arranging multiple battery cells; as an example, a battery cell assembly can be a battery module, which is formed by arranging and fixing multiple battery cells into a single module. As an example, a battery module can be formed by bundling multiple battery cells together with cable ties.

[0238] In some embodiments, the battery device may be a battery pack, which includes a housing and one or more individual battery cell assemblies housed within the housing.

[0239] As an example, the battery cell assembly can be a battery module, which can be housed in a housing by fixing the battery module in the housing.

[0240] As an example, battery cell assemblies can also be housed in a housing by directly fixing multiple battery cells to the housing.

[0241] As an example, the enclosure may include a first enclosure body and a second enclosure body. The first enclosure body and the second enclosure body are fastened together to form a closed space inside the enclosure to house the individual battery cells. Here, "closed" refers to covering or closing, which can be either sealed or unsealed. The first enclosure body may be a top cover or a bottom plate.

[0242] As an example, the enclosure may include a top cover, a frame, and a bottom plate. The top cover and bottom plate are connected to the frame, creating an enclosed space inside the enclosure to house the individual battery cells.

[0243] As an example, the housing can be part of the vehicle's chassis structure. For instance, the housing's roof can be at least part of the vehicle's floor, or the housing's frame can be at least part of the vehicle's crossbeams and longitudinal beams.

[0244] In some embodiments, the battery device refers to an energy storage device, which includes a housing with a door on at least one side. Energy storage devices include energy storage containers, energy storage cabinets, etc.

[0245] Battery devices possess outstanding advantages such as high energy density, low environmental pollution, high power density, long service life, wide applicability, and low self-discharge coefficient, making them an important component of today's new energy development. The development of battery technology must simultaneously consider multiple design factors, such as performance parameters like energy density, cycle life, discharge capacity, and charge / discharge rate. Furthermore, the reliability of the battery device must also be taken into account.

[0246] For a typical battery cell, it includes a casing and an electrode assembly housed within the casing. The casing includes a housing and end caps, which are interconnected to form a sealed space for housing the electrode assembly. A current collector is typically located within the casing, connecting a tab to the casing and an electrode assembly to achieve electrical connection between them. In related technologies, to achieve rust prevention, especially in steel-cased battery cells, the casing is usually nickel-plated. However, to improve the connection reliability between the housing and end caps, and between the current collector and the housing, a welded connection is commonly used. The high temperatures generated during welding can cause… The nickel layer on the steel shell surface oxidizes rapidly, forming a loose and easily peeling oxide layer. This can even lead to the evaporation of some nickel layers, exposing the steel base layer of the shell. Similarly, the heat-affected zone (HAZ) adjacent to the solder mark is also affected by high temperatures, and the nickel layer is damaged to varying degrees. Even if the temperature is insufficient to cause oxidation or evaporation of the nickel layer, the rapid cooling during the welding process can easily lead to the formation of high-hardness but poorly corrosion-resistant metallic phases such as martensite in this area. This results in the formation of a HAZ with and adjacent to the solder mark on the shell, which is highly susceptible to corrosion and rust during use. This can severely affect the structural strength and sealing performance of the battery cell shell, posing a risk of damage or leakage to the battery cell during use, and hindering the improvement of the battery cell's service life and reliability.

[0247] Based on the above considerations, in order to solve the problems of low service life and low reliability of battery cells, this application provides a battery cell including a casing, an electrode assembly, and a protective layer. The casing is made of steel and includes at least one solder mark and at least one transition portion. The transition portion is connected around the solder mark. The outer surface of the solder mark is a welding surface, and the outer surface of the transition portion is a transition surface. The outer surface of the casing includes the welding surface and the transition surface. The transition surface is connected to the welding surface and located on the outer periphery of the welding surface. At least some of the grains in the transition portion are first grains. The longest line among multiple lines connecting any two points on the outer surface of the first grain is the first connecting line. The multiple lines connecting any two points on the outer surface of the first grain also include a second connecting line. The second connecting line is perpendicular to the first connecting line and passes through the midpoint of the first connecting line. The ratio of the length of the first connecting line to the length of the second connecting line is in the range of 1-5. The ratio of the number of first grains to the total number of grains in the transition portion is greater than 50%. The electrode assembly is housed within the casing. The protective layer completely covers the welding surface and covers at least a portion of the transition surface.

[0248] In this type of battery cell, at least one solder mark and at least one transition portion are formed on the outer casing. The transition portion is a structure connected to the area surrounding the solder mark. The ratio of the length of the first connecting line to the length of the second connecting line of the first grains within the transition portion ranges from 1 to 5, and the number of first grains accounts for more than 50%, making most of the grains within the transition portion equiaxed. The transition portion is a heat-affected zone formed by the connection between the outer casing and the solder mark and the welding process. By covering the welding surface of the solder mark with a protective layer that covers at least a portion of the transition surface of the transition portion, this battery cell structure, on the one hand, generates a higher content of first grains due to the annealing effect of the welding temperature during the formation of the transition portion. This causes the first grains to form microscopic cracks or protrusions on the transition surface during the forming process, thereby increasing the roughness of the transition surface and improving the protective layer... The increased number of connection points between the protective layer and the outer surface of the casing enhances the adhesion of the protective layer to the outer surface of the casing, thereby improving the stability and firmness of the protective layer covering the welding surface and transition surface. This helps reduce the phenomenon of the protective layer falling off the casing during use. On the other hand, the protective layer can protect not only the area where the weld is formed on the casing, but also the heat-affected zone around the weld. This effectively alleviates the corrosion and rust phenomenon that easily occurs in the area where the weld is formed on the casing and the heat-affected zone around the weld due to the damage to the structure and metallographic structure caused by the high temperature of welding. This reduces the decline in the structural strength and sealing performance of the casing during use, thereby effectively reducing the risk of damage and leakage of battery cells during use, and helping to improve the service life and reliability of battery cells.

[0249] The battery cells disclosed in this application can be used, but are not limited to, in electrical devices such as vehicles, ships, or aircraft. A power system for such an electrical device can be constructed using battery cells and battery devices disclosed in this application. This helps to alleviate the problem of rust on the casing of the battery cells during use, thereby improving the service life and reliability of the battery cells.

[0250] This application provides an electrical device that uses a single battery cell or battery assembly as a power source. The electrical device can be, but is not limited to, mobile phones, tablets, laptops, electric toys, power tools, electric vehicles, electric cars, ships, spacecraft, etc. Electric toys can include stationary or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc. Spacecraft can include airplanes, rockets, space shuttles, and spacecraft, etc.

[0251] For ease of explanation, the following embodiments will be described using a vehicle as an example of an electrical device according to an embodiment of this application.

[0252] Please refer to Figure 1 , Figure 1 This is a schematic diagram of the structure of a vehicle 1000 provided in some embodiments of this application. The vehicle 1000 can be a gasoline-powered vehicle, a natural gas-powered vehicle, or a new energy vehicle. New energy vehicles can be pure electric vehicles, hybrid electric vehicles, or range-extended electric vehicles, etc. A battery device 100 is installed inside the vehicle 1000. The battery device 100 can be located at the bottom, front, or rear of the vehicle 1000. The battery device 100 can be used to supply power to the vehicle 1000; for example, the battery device 100 can serve as the operating power source or general power source for the vehicle 1000. The vehicle 1000 may also include a controller 200 and a motor 300. The controller 200 controls the battery device 100 to supply power to the motor 300, for example, to meet the power needs of the vehicle 1000 during startup, navigation, and driving.

[0253] In some embodiments of this application, the battery device 100 can not only serve as the operating power or power source for the vehicle 1000, but also as the driving power source for the vehicle 1000, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle 1000.

[0254] Please refer to Figure 2 , Figure 2 This is an exploded view of the structure of a battery device 100 provided in some embodiments of this application. The battery device 100 includes a housing 10 and battery cells 20, the battery cells 20 being housed within the housing 10.

[0255] The housing 10 provides assembly space for the battery cell 20, and can adopt various structures. In some embodiments, the housing 10 may include a first housing body 11 and a second housing body 12, which overlap each other, and together define an assembly space for accommodating the battery cell 20. The second housing body 12 may be a hollow structure open at one end, and the first housing body 11 may be a plate-like structure, with the first housing body 11 covering the open side of the second housing body 12 so that the first housing body 11 and the second housing body 12 together define the assembly space; alternatively, the first housing body 11 and the second housing body 12 may both be hollow structures open on one side, with the open side of the first housing body 11 covering the open side of the second housing body 12.

[0256] Of course, the box 10 formed by the first box body 11 and the second box body 12 can be of various shapes, such as a cylinder, a cuboid, or a cube. For example, in... Figure 2 In the middle, the shape of box 10 is a cuboid.

[0257] In the battery device 100, there can be one or more battery cells 20 disposed within the housing 10. When there are multiple battery cells 20 disposed within the housing 10, they can be connected in series, in parallel, or in a mixed configuration. A mixed configuration means that multiple battery cells 20 are connected in both series and parallel configurations. Multiple battery cells 20 can be directly connected in series, in parallel, or in a mixed configuration, and then the entire assembly of the multiple battery cells 20 is housed within the housing 10. Alternatively, the battery device 100 can also consist of multiple battery cells 20 first connected in series, in parallel, or in a mixed configuration to form battery modules, and then multiple battery modules connected in series, in parallel, or in a mixed configuration to form a whole, which is then housed within the housing 10.

[0258] In some embodiments, the battery device 100 may also include other structures. For example, the battery device 100 may also include a busbar for connecting multiple battery cells 20 to achieve electrical connection between the multiple battery cells 20.

[0259] Each battery cell 20 can be a secondary battery or a primary battery; it can also be a lithium-sulfur battery, a sodium-ion battery, or a magnesium-ion battery, but is not limited to these. The battery cell 20 can be in the form of a cuboid, cylinder, prism, or other shapes. For example, in... Figure 2 In the middle, the battery cell 20 has a cylindrical structure.

[0260] According to some embodiments of this application, please refer to Figure 3 , Figure 4 , Figure 5 and Figure 6 As shown, Figure 3 This is an exploded view of the structure of a battery cell 20 provided in some embodiments of this application. Figure 4 This is a cross-sectional view of a battery cell 20 provided in some embodiments of this application. Figure 5 for Figure 4 A magnified view of part A of the battery cell 20 shown. Figure 6 for Figure 4The image shows a partial enlarged view of point B on the battery cell 20. This application provides a battery cell 20, which includes a housing 21, an electrode assembly 22, and a protective layer 23. The outer casing 21 is made of steel and includes at least one solder mark 213 and at least one transition portion 214. The transition portion 214 is connected around the solder mark 213. The outer surface of the solder mark 213 is a welding surface 213a, and the outer surface of the transition portion 214 is a transition surface 2141. The outer surface of the outer casing 21 includes the welding surface 213a and the transition surface 2141. The transition surface 2141 is connected to the welding surface 213a and located on the outer periphery of the welding surface 213a. At least some of the grains in the transition portion 214 are first grains. The longest line among multiple lines connecting any two points on the outer surface of the first grain is the first connecting line. The multiple lines connecting any two points on the outer surface of the first grain also include a second connecting line. The second connecting line is perpendicular to the first connecting line and passes through the midpoint of the first connecting line. The ratio of the length of the first connecting line to the length of the second connecting line is in the range of 1-5. The ratio of the number of first grains to the number of all grains in the transition portion 214 is greater than 50%. The electrode assembly 22 is housed within the outer casing 21. The protective layer 23 completely covers the weld surface 213a, and the protective layer 23 covers at least a portion of the transition surface 2141.

[0261] The outer casing 21 can be used to contain an electrolyte, such as an electrolyte solution. The outer casing 21 can have various structural forms, such as a cylinder or a cuboid. Similarly, the material of the outer casing 21 includes steel, which can include carbon steel or stainless steel. Carbon steel can be Q195 carbon steel, SPCC carbon steel, etc.; stainless steel can be SUS430 stainless steel, SUS304 stainless steel, SUS316 stainless steel, or modified stainless steel, etc. Exemplarily, in this embodiment, the material of the outer casing 21 includes carbon steel.

[0262] In some embodiments, the housing 21 may include a housing 211 and an end cap 212. The housing 211 has an internal cavity for accommodating the electrode assembly 22 and has an opening 2111. That is, the housing 211 is a hollow structure with an opening 2111 at one end. The end cap 212 covers the opening 2111 of the housing 211 and forms a sealed connection to form a closed space for accommodating the electrode assembly 22 and the electrolyte. Correspondingly, if the material of the housing 21 includes steel, that is, the material of the housing 211 includes steel and the material of the end cap 212 also includes steel.

[0263] The housing 211 includes an integrally formed side wall and a bottom wall. The side wall surrounds the bottom wall, one end of the side wall is connected to the bottom wall, and the other end forms an opening 2111. The bottom wall and the end cap 212 are arranged opposite to each other. The side wall and the bottom wall together define a receiving cavity, in which the electrode assembly 22 is received.

[0264] Optionally, the housing 211 can be of various shapes, such as a cylinder, cuboid, or prism. The shape of the housing 211 can be determined according to the specific shape of the electrode assembly 22. For example, if the electrode assembly 22 is a cylindrical structure, a cylindrical housing 211 can be used; if the electrode assembly 22 is a cuboid structure, a cuboid housing 211 can be used. Of course, the structure of the end cap 212 can also be various, such as a plate-like structure or a hollow structure with one end open. For example, in this embodiment, the outer shell 21 formed by the housing 211 and the end cap 212 has a cylindrical structure.

[0265] Of course, it is understandable that the outer casing 21 is not limited to the structure described above. The outer casing 21 can also be other structures. For example, the outer casing 21 can include a housing 211 and two end caps 212. The housing 211 is a hollow structure with openings 2111 formed on both opposite sides. One end cap 212 is fitted onto one opening 2111 of the housing 211 and forms a sealed connection to form a closed space for accommodating the electrode assembly 22 and the electrolyte. That is, the housing 211 has openings 2111 on both opposite sides, and the two end caps 212 are fitted onto both sides of the housing 211 to close the corresponding openings 2111.

[0266] In this embodiment, the electrode assembly 22 includes a main body 221, a first tab 222, and a second tab 223, both connected to the main body 221. The main body 221 is the primary component of the electrode assembly 22 for chemical reactions to occur inside the battery cell 20. The first tab 222 and the second tab 223 have opposite polarities; that is, if the first tab 222 is the positive tab of the electrode assembly 22, then the second tab 223 is the negative tab of the electrode assembly 22, and vice versa.

[0267] The main body 221 of the electrode assembly 22 includes a first electrode, a second electrode, and an isolator. The first and second electrodes have opposite polarities. That is, if the first electrode is the positive electrode of the electrode assembly 22, the second electrode is the negative electrode of the electrode assembly 22, and vice versa. Correspondingly, the first tab 222 is connected to the first electrode, and the second tab 223 is connected to the second electrode. Optionally, the structure of the main body 221 of the electrode assembly 22 can be various. The main body 221 of the electrode assembly 22 can be a wound structure formed by winding the first electrode, the second electrode, and the isolator, or it can be a stacked structure formed by alternatingly stacking the first electrode, the second electrode, and the isolator. The isolator is disposed between the first electrode and the second electrode to insulate and isolate the first electrode and the second electrode. In this embodiment of the application, the main body 221 of the electrode assembly 22 is a wound structure formed by winding the first electrode, the second electrode and the separator, and the main body 221 is cylindrical, with the central axis of the main body 221 extending along the first direction X.

[0268] The first tab 222 of the electrode assembly 22 is a multilayer metal foil structure connected to one end of the first electrode in the first direction X. Correspondingly, the second tab 223 of the electrode assembly 22 is a multilayer metal foil structure connected to one end of the second electrode in the first direction X. It should be noted that the first tab 222 and the first electrode can be separate structures. For example, the first tab 222 and the first current collector of the first electrode can be welded together. Of course, the first tab 222 and the first electrode can also be integrally formed. For example, the first tab 222 and the first current collector of the first electrode can be integrally formed by cutting the same metal foil to form the first tab 222 and the first current collector. Similarly, the second tab 223 and the second electrode can be separate structures. For example, the second tab 223 and the second current collector of the second electrode can be welded together. Of course, the second tab 223 and the second electrode can also be integrally formed. For example, the second tab 223 and the second current collector of the second electrode can be integrally formed by cutting the same metal foil to form the second tab 223 and the second current collector.

[0269] For example, the separator is a separator membrane, and the main material of the separator membrane can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride.

[0270] In some embodiments, the battery cell 20 may further include an electrode terminal 24, which is insulatedly mounted on the housing 21. The housing 21 has a wall portion 217. The first tab 222 of the electrode assembly 22 is electrically connected to the wall portion 217, and the second tab 223 of the electrode assembly 22 is electrically connected to the electrode terminal 24, so that the wall portion 217 of the housing 21 and the electrode terminal 24 can cooperate to input or output electrical energy of the battery cell 20.

[0271] The electrode terminal 24 is insulated and mounted on the housing 21, meaning that there is no electrical connection between the electrode terminal 24 and the housing 21.

[0272] For example, the electrode terminal 24 can be made of various materials, such as copper, iron, aluminum, steel or aluminum alloy.

[0273] It should be noted that the wall portion 217 for electrical connection with the first electrode 222 can be the end cap 212 of the housing 21, or it can be a wall of the housing 211 of the housing 21. For example, in... Figure 4 and Figure 5 In this embodiment, the wall portion 217 is the end cap 212. Of course, the structure of the battery cell 20 is not limited to this. In other embodiments, the wall portion 217 can also be the bottom wall of the housing 211 and the end cap 212 that are opposite to each other, or the wall portion 217 can also be the side wall of the housing 211 and the end cap 212 that are adjacent to each other and connected to each other.

[0274] For example, in the embodiments of this application, the first electrode 222 and the second electrode 223 are respectively connected to the two ends of the main body 221 in the first direction X. Correspondingly, the first electrode 222 is located between the wall portion 217 and the main body 221 in the first direction X, and the electrode terminal 24 is disposed on the end of the outer shell 21 away from the wall portion 217 in the first direction X.

[0275] In some embodiments, see Figure 3 , Figure 4 and Figure 5 As shown, the battery cell 20 may also include a first current collector 25, which is disposed between the wall portion 217 and the main body portion 221 in the first direction X, and the first current collector 25 connects the wall portion 217 and the first tab 222 to electrically connect the electrode assembly 22 and the wall portion 217.

[0276] For example, the material of the first current collector 25 can be various, such as copper, iron, aluminum, steel or aluminum alloy.

[0277] It should be noted that in other embodiments, the first current collector 25 may not be provided in the battery cell 20. Correspondingly, the first tab 222 is directly connected to the wall 217 of the outer casing 21 to electrically connect the electrode assembly 22 and the outer casing 21.

[0278] In some embodiments, see Figure 3 and Figure 4 As shown, the battery cell 20 may also include a second current collector 26, which is disposed between the electrode terminal 24 and the main body 221 in the first direction X, and the second current collector 26 connects the electrode terminal 24 and the second tab 223 to electrically connect the electrode assembly 22 and the electrode terminal 24.

[0279] For example, the material of the second current collector 26 can be various, such as copper, iron, aluminum, steel or aluminum alloy.

[0280] It should be noted that in other embodiments, the second current collector 26 may not be provided in the battery cell 20. Correspondingly, the second tab 223 is directly connected to the electrode terminal 24 to electrically connect the electrode assembly 22 and the electrode terminal 24.

[0281] In this embodiment, the outer casing 21 includes at least one solder mark 213, that is, a portion of the outer casing 21 is formed by welding during the assembly process. Correspondingly, the outer surface of the solder mark 213 facing away from the electrode assembly 22 is the welding surface 213a of the solder mark 213, and the welding surface 213a is a part of the outer surface of the outer casing 21.

[0282] In one embodiment, at least one solder mark 213 includes a first solder mark 2131. In an embodiment where the housing 21 includes a housing 211 and an end cap 212, the housing 211 and the end cap 212 are welded together to form the first solder mark 2131, that is, the first solder mark 2131 connects the housing 211 and the end cap 212. Correspondingly, the outer surface of the first solder mark 2131 facing away from the electrode assembly 22 is the first welding surface 21311, and the first welding surface 21311 is a part of the outer surface of the housing 21. In this embodiment, the first solder mark 2131 is the area where the housing 211 and the end cap 212 are welded together to form a fused area or a solder mark area.

[0283] At least one solder mark 213 further includes a second solder mark 2132. In an embodiment where the battery cell 20 includes a first current collector 25, and the first current collector 25 is connected to the first tab 222 and the wall portion 217, the first current collector 25 is connected to the first tab 222, and the first current collector 25 is welded to the wall portion 217 to form the second solder mark 2132. That is, the second solder mark 2132 is disposed on the wall portion 217 and connected to the first current collector 25. Correspondingly, the second solder mark 2132 facing away from the outer surface of the electrode assembly 22 is the second welding surface 21321, and the second welding surface 21321 is part of the outer surface of the housing 21. In this embodiment, the second solder mark 2132 is the first current collector. The component 25 and the wall portion 217 are welded together to form a region that is mutually fused or a region that is welded to form a solder mark. In the embodiment where the first electrode tab 222 and the wall portion 217 are directly connected, the first electrode tab 222 is welded to the wall portion 217 to form a second solder mark 2132. That is, the second solder mark 2132 is disposed on the wall portion 217 and connected to the first electrode tab 222. Correspondingly, the second solder mark 2132 is the second welding surface 21321 away from the outer surface of the electrode assembly 22, and the second welding surface 21321 is part of the outer surface of the outer shell 21. In this embodiment, the second solder mark 2132 is the region where the first electrode tab 222 and the wall portion 217 are welded together to form a region that is mutually fused or a region that is welded to form a solder mark.

[0284] The outer casing 21 also includes at least one transition portion 214, which is connected around the soldering portion 213. That is, the transition portion 214 is the part of the outer casing 21 that is adjacent to and connected to the soldering portion 213. It should be noted that if the soldering portion 213 is a block-shaped or strip-shaped structure that is not connected end to end, then the transition portion 214 is an annular structure that surrounds the outside of the soldering portion 213. Correspondingly, each soldering portion 213 is surrounded by one transition portion 214. If the soldering portion 213 is an annular structure, then both sides of the soldering portion 213 are connected to the transition portion 214. Correspondingly, each soldering portion 213 is correspondingly provided and connected to two transition portions 214, so that the soldering portion 213 is a structure that is connected to other parts of the outer casing 21 through the transition portion 214.

[0285] The transition portion 214 is separated from the outer surface of the electrode assembly 22 by a transition surface 2141, and the transition surface 2141 is a part of the outer surface of the outer shell 21. Correspondingly, the welding surface 213a of the soldering portion 213 is directly connected to the transition surface 2141, and the welding surface 213a of the soldering portion 213 is connected to other areas of the outer surface of the outer shell 21 through the transition surface 2141. It should be noted that in the embodiment where the outer casing 21 includes an end cap 212 and a housing 211, if the end cap 212 is connected to a solder mark 213, then the outer surface of the end cap 212 includes at least one transition surface 2141, that is, the transition surface 2141 is a part of the outer surface of the end cap 212, and the area where the outer surface of the end cap 212 is connected to the solder mark 213a is the transition surface 2141. Similarly, if the housing 211 is connected to a solder mark 213, then the outer surface of the housing 211 includes at least one transition surface 2141, that is, the transition surface 2141 is a part of the outer surface of the housing 211, and the area where the outer surface of the housing 211 is connected to the solder mark 213a is the transition surface 2141. Correspondingly, the outer surface of the housing 21 includes the outer surface of the housing 211, the outer surface of the end cap 212, and the welding surface 213a. The outer surface of the housing 211 and / or the outer surface of the end cap 212 includes a transition surface 2141. The welding surface 213a can connect the transition surface 2141 of the outer surface of the housing 211 and / or the transition surface 2141 of the outer surface of the end cap 212. The outer surface of the housing 211 is the surface of the housing 211 exposed to the outside of the housing 21, the outer surface of the end cap 212 is the surface of the end cap 212 exposed to the outside of the housing 21, and the welding surface 213a is the surface of the solder mark 213 exposed to the outside of the housing 21.

[0286] In this embodiment of the application, at least a portion of the grains in the transition portion 214 are first grains, and the ratio of the number of first grains to the total number of grains in the transition portion 214 is greater than 50%. That is, the proportion of the number of first grains in the transition portion 214 is greater than 50%, meaning that more than half of the grains in the transition portion 214 are first grains.

[0287] The longest line among the multiple lines connecting any two points on the outer surface of the first grain is the first line, that is, the first line is the longest straight line among the multiple straight lines formed by connecting any two points on the outer surface of the first grain.

[0288] The line connecting any two points on the outer surface of the first grain also includes a second line. The second line is perpendicular to the first line and passes through the midpoint of the first line. In other words, the second line is a straight line that is perpendicular to the first line and passes through the midpoint of the first line among the multiple straight lines formed by connecting any two points on the outer surface of the first grain.

[0289] The ratio of the length of the first connecting line to the length of the second connecting line is in the range of 1-5, that is, the difference between the length of the first connecting line and the length of the second connecting line is small. In other words, the first grain is an equiaxed grain. Correspondingly, the proportion of equiaxed grains in the transition portion 214 is greater than 50%. That is, the transition portion 214 is the heat-affected zone in the outer shell 21 that is adjacent to the soldering portion 213 and is affected by the welding temperature during the formation of the soldering portion 213. It should be noted that before the formation of the soldering portion 213, most of the grains in the outer shell 21 are banded grains. During the formation of the soldering portion 213, the part of the outer shell 21 located around the soldering portion 213 will be affected by welding and undergo annealing, causing most of the grains to change from banded grains to equiaxed grains. As a result, the transition portion 214 will be formed around the soldering portion 213.

[0290] In this embodiment of the application, the step of measuring the grains in the transition section 214 includes sample cutting, sample processing and grain measurement. The sample is a cylindrical battery cell 20. The outer shell 21 of the battery cell 20 includes a housing 211 and an end cap 212. The housing 211 is a hollow structure with an opening 2111 at only one end in the first direction X. The end cap 212 is welded to the housing 211 to form a first solder mark 2131 and the end cap 212 closes the opening 2111. The first tab 222 of the electrode assembly 22 is welded to the end cap 212 through a first current collector 25 to form a second solder mark 2132.

[0291] The sample cutting steps specifically include:

[0292] The sidewall of the housing 211 is cut along its circumference in the first direction X, 30 mm from the bottom wall of the housing 211. The electrode assembly 22 and electrolyte inside the housing 21 are separated from the housing 21. The housing 21 with the first solder mark 2131 and the second solder mark 2132 after cutting is cleaned, and the sidewall of the housing 211 after cleaning is restored to flatness. Crystal glue is poured into the space formed by the sidewall and the end cap 212, and the height of the crystal glue in the space formed by the sidewall and the end cap 212 in the first direction X exceeds the first solder mark 2131. Then the sidewall and the end cap 212 are cut again, with the cutting surface parallel to the first direction X and passing through the first solder mark 2131 and the second solder mark 2132, to obtain the test sample.

[0293] Sample processing specifically includes:

[0294] The cut surface of the test sample is polished with sandpaper with a grit greater than or equal to 1600. The polished cut surface is then cleaned and etched to obtain a test sample that can be observed under an optical microscope. The etched test sample is then placed under an optical microscope to observe the cut surface of the test sample.

[0295] The grains on the cut surface of the sample to be tested can be measured using an Olympus BX53M optical microscope. By selecting a general area to be measured at a lower magnification using the optical microscope, and then increasing the magnification to observe this area, the measurement location can be determined. It is understood that the proportion of the first grains within the transition section 214 is greater than 50%, making the grain differences between the transition section 214 and other areas of the outer shell 21 quite significant. The approximate area to be measured can be identified by observing the grains under the optical microscope.

[0296] The grains displayed under an optical microscope on the BX53M model can be measured using Olympus's corresponding software, such as Capture 2.2.1.

[0297] The specific steps for measuring grains within the transition section 214 include:

[0298] The software Capture 2.2.1 is used to display and measure the grains under an optical microscope of model BX53M. The length of the longest first line connecting any two points of the outer contour of each grain in the area surrounding the first solder mark 2131 and the second solder mark 2132, as well as the length of the second line perpendicular to the first line and passing through the midpoint of the first line, are measured. The first grains that satisfy the length ratio of 1 to 5 and other grains that do not satisfy the length ratio of 1 to 5 are marked. Then, the area in which the number of first grains accounts for more than or equal to 50% is the transition area 214.

[0299] It should be noted that the lengths of the first and second connections for each grain are the dimensions under the system scale corresponding to the Capture2.2.1 software, that is, the actual dimensions without being magnified by an optical microscope. These dimensions will not change with the magnification of the optical microscope.

[0300] For example, the ratio of the length of the first connection to the length of the second connection can be 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2, 2.1, 2.2, 2.4, 2.5, 2.6, 2.8, 3, 3.1, 3.3, 3.5, 3.7, 4, 4.2, 4.5, 4.7, 4.8, 4.9, or 5, etc.

[0301] In this embodiment, the protective layer 23 is a structure disposed on the outer surface of the housing 21 to protect the outer surface of the housing 21. The protective layer 23 completely covers the welding surface 213a, that is, the first welding surface 21311 and the second welding surface 21321 are both entirely covered by the protective layer 23. Optionally, the protective layer 23 may also be a structure partially disposed on the outer surface of the housing 211 and the outer surface of the end cap 212.

[0302] Among them, see Figure 5 and Figure 6 As shown, the protective layer 23 covers at least a portion of the transition surface 2141, meaning that the edge of the protective layer 23 extends beyond the edge of the welding surface 213a and covers at least a portion of the transition surface 2141 connected to the welding surface 213a. Optionally, the protective layer 23 can be a structure that covers a portion of the transition surface 2141 or a structure that completely covers the transition surface 2141. The protective layer 23 is used to prevent media in the external environment from contacting the welding surface 213a and the portion of the transition surface 2141 covered by the protective layer 23, thereby achieving a rust-proof effect. Therefore, the protective layer 23 can also be called a rust-proof layer.

[0303] For example, the protective layer 23 may be an insulating material, such as an adhesive layer, coating, tape, or insulating film.

[0304] It should be noted that even in embodiments where both the housing 211 and end cap 212 of the outer casing 21 have anti-corrosion layers, the high welding temperature during welding of the housing 211 and / or end cap 212 can cause the surface anti-corrosion layer to oxidize, forming a loose and easily peeling oxide layer, or even causing part of the anti-corrosion layer to evaporate, exposing the steel substrate in the welded area and making the welded area of ​​the outer casing 21 prone to rusting. In other words, in related technologies, even if both the housing 211 and end cap 212 of the outer casing 21 have anti-corrosion layers, the outer casing 21 is still prone to rusting in the welded area. Therefore, in this embodiment, by covering the welded surface 213a and at least a portion of the transition surface 2141 with a protective layer 23, the risk of corrosion and rusting in the welded area of ​​the outer casing 21 and the surrounding heat-affected zone during use can be effectively reduced.

[0305] In some embodiments, the battery cell 20 may further include a pressure relief component disposed on the housing 21, which is used to release the internal pressure of the battery cell 20 when the internal pressure or temperature of the battery cell 20 reaches a predetermined value.

[0306] Optionally, the pressure relief component can be disposed on the end cap 212 of the outer casing 21 or on the housing 211 of the outer casing 21. Similarly, the pressure relief component and the outer casing 21 can be integrally formed or separately disposed. If the pressure relief component and the outer casing 21 are integrally formed, the pressure relief component is an area on the outer casing 21 with a weak structure, such as an area on the outer casing 21 with a groove. If the pressure relief component and the outer casing 21 are separately disposed, the pressure relief component can be connected to the outer casing 21 by welding or other means. Correspondingly, the pressure relief component can be a component such as an explosion-proof valve, an explosion-proof disc, a gas valve, a pressure relief valve, or a safety valve.

[0307] In this embodiment, at least one solder mark 213 and at least one transition portion 214 are formed on the outer casing 21. The transition portion 214 is a structure connected to the periphery of the solder mark 213. The ratio of the length of the first connecting line to the length of the second connecting line of the first grains in the transition portion 214 is in the range of 1-5, and the number of first grains accounts for more than 50%, making most of the grains in the transition portion 214 equiaxed. The transition portion 214 is a heat-affected zone formed by the connection between the outer casing 21 and the solder mark 213 and the welding effect. By covering the welding surface 213a of the solder mark 213 with a protective layer 23, and the protective layer 23 covering at least a portion of the transition surface 2141 of the transition portion 214, the battery cell 20 with this structure, on the one hand, generates a large amount of first grains due to the annealing effect of the welding temperature during the formation of the transition portion 214. This causes the first grains to form microscopic cracks or protrusions on the transition surface 2141 during the forming process, thereby increasing the roughness of the transition surface 2141. The increased number of connection points between the protective layer 23 and the outer surface of the outer shell 21 enhances the adhesion of the protective layer 23 to the outer surface of the outer shell 21, thereby improving the stability and firmness of the protective layer 23 covering the welding surface 213a and the transition surface 2141. This helps reduce the phenomenon of the protective layer 23 detaching from the outer shell 21 during use. On the other hand, the protective layer 23 can protect not only the area where the weld mark 213 is formed on the outer shell 21, but also the heat-affected zone around the weld mark 213. This effectively alleviates the corrosion and rust phenomenon that easily occurs in the area where the weld mark 213 is formed on the outer shell 21 and the heat-affected zone around the weld mark 213 after the structure and metallographic structure are damaged due to the high temperature of welding. This reduces the decrease in the structural strength and sealing performance of the outer shell 21 during use, thereby effectively reducing the risk of damage and leakage of the battery cell 20 during use, and helping to improve the service life and reliability of the battery cell 20.

[0308] In some embodiments, see Figure 5 and Figure 6As shown, the protective layer 23 completely covers the transition surface 2141. That is, the entire transition surface 2141 of the transition portion 214 is covered by the protective layer 23, so that the heat-affected zone around the solder mark portion 213 is completely covered by the protective layer 23.

[0309] It should be noted that in the embodiment where the soldering part 213 includes a first soldering part 2131 and a second soldering part 2132, the transition surface 2141 of the transition part 214 connected to the first soldering part 2131 is entirely covered by the protective layer 23, and the transition surface 2141 of the transition part 214 connected to the second soldering part 213 is also entirely covered by the protective layer 23.

[0310] In this embodiment, by setting the protective layer 23 to completely cover the transition surface 2141 of the transition portion 214, the connection area between the protective layer 23 and the transition surface 2141 can be increased. This connection between the protective layer 23 and the transition surface 2141 can further enhance the adhesion of the protective layer 23 to the outer surface of the outer shell 21, thereby improving the stability and firmness of the protective layer 23 covering the welding surface 213a and the transition surface 2141. This further reduces the phenomenon of the protective layer 23 falling off the outer shell 21 during use. On the other hand, it can further enhance the protection effect on the heat-affected zone around the solder portion 213, thereby further mitigating the corrosion and rust phenomenon that easily occurs in the heat-affected zone around the solder portion 213 of the outer shell 21 after the structure and metallographic structure are damaged due to the high temperature of welding. This further reduces the risk of damage and leakage of the battery cell 20 during use, and is conducive to further improving the service life and reliability of the battery cell 20.

[0311] According to some embodiments of this application, refer to Figure 7 , Figure 8 and Figure 9 As shown, Figure 7 This is a partial cross-sectional view of a battery cell 20 provided in some embodiments of this application. Figure 8 This is a partial structural diagram of the casing 21 of the battery cell 20 provided in some embodiments of this application. Figure 9 for Figure 8 The enlarged view of part C of the outer casing 21 is shown. The welding surface 213a is provided with a first groove 215, and part of the protective layer 23 is accommodated within the first groove 215.

[0312] The welding surface 213a is provided with a first groove 215, which is recessed from the welding surface 213a into the interior of the solder area 213. The opening of the first groove 215 is formed on the welding surface 213a. The number of first grooves 215 on the welding surface 213a can be one or more.

[0313] It should be noted that the groove (first groove 215) may be provided only on the welding surface 213a, or the groove (first groove 215) may be provided on the welding surface 213a, and at least one of the outer surface of the housing 211 and the outer surface of the end cap 212 may also be provided with a groove. Of course, the groove may also be provided on the transition surface 2141.

[0314] Optionally, the first groove 215 can be formed on the welding surface 213a by laser cleaning, stamping, milling, or other methods. Similarly, the cross-section of the first groove 215 can be rectangular, V-shaped, semi-circular, etc., and the cross-section of the first groove 215 is perpendicular to its extension direction. Likewise, the extension trajectory of the first groove 215 can be a straight line, an arc, a circular line, a planar spiral, a helix, etc.

[0315] A portion of the protective layer 23 is accommodated within the first groove 215, meaning the protective layer 23 has a portion covering the welding surface 213a and the transition surface 2141, and a portion accommodated within the first groove 215. Optionally, the portion of the protective layer 23 accommodated within the first groove 215 may completely fill the first groove 215, or it may not occupy the entire space of the first groove 215. Similarly, the portion of the protective layer 23 accommodated within the first groove 215 may be connected to the groove wall of the first groove 215. Of course, the portion of the protective layer 23 accommodated within the first groove 215 may also not be connected to the groove wall of the first groove 215. For example, the portion of the protective layer 23 accommodated within the first groove 215 may be inserted into the first groove 215, such that the portion of the protective layer 23 accommodated within the first groove 215 only maintains contact with the groove wall of the first groove 215.

[0316] In this embodiment, by providing a first groove 215 on the welding surface 213a, and partially accommodating the protective layer 23 within the first groove 215, the first groove 215 can provide a certain degree of restriction on the protective layer 23, thereby improving the stability and firmness of the protective layer 23 covering the welding surface 213a. This facilitates long-term protection of the solder joint 213 by the protective layer 23, thereby reducing the phenomenon of protective failure caused by the protective layer 23 falling off the welding surface 213a and the transition surface 2141 in a short period of time. This further reduces the risk of corrosion and rust on the solder joint 213 and the transition surface 214 of the outer casing 21 during use, which is beneficial to further improve the service life and reliability of the battery cell 20.

[0317] In some embodiments, see Figure 7 As shown, the portion of the protective layer 23 contained within the first groove 215 is connected to the groove wall of the first groove 215.

[0318] The portion of the protective layer 23 contained within the first groove 215 is connected to the groove wall of the first groove 215, thereby creating a certain adhesion between the portion of the protective layer 23 contained within the first groove 215 and the groove wall of the first groove 215.

[0319] Optionally, the portion of the protective layer 23 contained within the first groove 215 may cover only a portion of the groove wall of the first groove 215, or it may cover the entire groove wall of the first groove 215. It is understood that if the portion of the protective layer 23 contained within the first groove 215 completely fills the first groove 215, then the portion of the protective layer 23 contained within the first groove 215 covers the entire groove wall of the first groove 215.

[0320] The groove wall of the first groove 215 defines the internal space of the first groove 215. Taking the cross-section of the first groove 215 as rectangular as an example, the groove wall of the first groove 215 may include the groove side and the groove bottom. The groove bottom is disposed opposite to the groove opening of the first groove 215. The portion of the protective layer 23 accommodated in the first groove 215 may be connected to the groove side and / or the groove bottom of the first groove 215.

[0321] In this embodiment, by connecting the portion of the protective layer 23 contained in the first groove 215 with the groove wall of the first groove 215, it is beneficial to increase the contact area and connection area between the protective layer 23 and the outer shell 21, thereby improving the adhesion of the protective layer 23 on the welding surface 213a and the transition surface 2141. This further enhances the stability and firmness of the protective layer 23 covering the welding surface 213a, thereby further reducing the phenomenon of the protective layer 23 falling off the outer shell 21 during use.

[0322] According to some embodiments of this application, see Figure 3 and Figure 6 as well as Figure 7 As shown, the outer casing 21 may include a housing 211 and an end cap 212. The housing 211 has an opening 2111 at at least one end in the first direction X. The end cap 212 corresponds one-to-one with the opening 2111 and covers the opening 2111. At least one solder mark 213 includes a first solder mark 2131, which connects the housing 211 and the end cap 212. Both the housing 211 and the end cap 212 include a transition portion 214. The welding surface 213a of the first solder mark 2131 is the first welding surface 21311. The outer surface of the housing 211 and the outer surface of the end cap 212 are both part of the outer surface of the outer casing 21, and both the outer surface of the housing 211 and the outer surface of the end cap 212 include a transition surface 2141. The first welding surface 21311 connects the outer surface of the housing 211 and the outer surface of the end cap 212.

[0323] Wherein, the housing 211 has an opening 2111 at least one end in the first direction X. This opening 2111 can be formed at only one end of the housing 211 in the first direction X, or it can be formed at both ends. For example, in... Figure 3 In the case, the housing 211 has an opening 2111 at only one end in the first direction X. Correspondingly, the end cap 212 is connected to the housing 211 through the first solder part 2131 and covers the opening 2111 to close the opening 2111.

[0324] In all the solder marks 213 of the outer casing 21, at least one solder mark 213 is a first solder mark 2131. The first solder mark 2131 is the solder mark 213 that connects the casing 211 and the end cap 212. That is, the welding area formed by welding the casing 211 and the end cap 212 is the first solder mark 2131, so that both the end cap 212 and the casing 211 are connected to the first solder mark 2131. Correspondingly, both the end cap 212 and the casing 211 include at least one transition part 214. The transition part 214 in the end cap 212 is connected to the first solder mark 2131, and the transition part 214 in the casing 211 is also connected to the first solder mark 2131, so that the outer surface of the end cap 212 and the outer surface of the casing 211 both include at least one transition surface 2141.

[0325] Optionally, the number of first solder marks 2131 can be one or more. Similarly, the housing 21 may only have the first solder mark 2131, or the housing 21 may have other solder marks 213 in addition to the first solder mark 2131.

[0326] The first welding surface 21311 is the outer surface of the first solder mark 2131 facing away from the electrode assembly 22. Correspondingly, the first welding surface 21311 is provided with a first groove 215, and a part of the protective layer 23 is accommodated in the first groove 215 provided in the first welding surface 21311. The protective layer 23 covers the entire first welding surface 21311 (the protective layer 23 completely covers the first welding surface 21311). Correspondingly, the transition surface 2141 of the outer surface of the housing 211 transitions to the transition surface 2141 of the outer surface of the end cap 212 through the first welding surface 21311, and the protective layer 23 covers at least a portion of the transition surface 2141 of the outer surface of the housing 211 and at least a portion of the transition surface 2141 of the outer surface of the end cap 212.

[0327] In this embodiment, the first solder mark 2131 connects the housing 211 and the end cap 212 to achieve a stable connection between the housing 211 and the end cap 212. By providing a first groove 215 on the first welding surface 21311 of the first solder mark 2131, and partially accommodating the protective layer 23 within the first groove 215 on the first welding surface 21311, it is beneficial to improve the stability and firmness of the protective layer 23 covering the first welding surface 21311 of the first solder mark 2131 and the transition surface 2141 connected thereto. This facilitates long-term protection of the first solder mark 2131 by the protective layer 23, thereby reducing the phenomenon of protective failure caused by the protective layer 23 falling off the first welding surface 21311 and the transition surface 2141 connected thereto in a short period of time. This reduces the risk of corrosion and rust in the area where the housing 211 and the end cap 212 are welded together (the first solder mark 2131) during use.

[0328] According to some embodiments of this application, see Figure 7 , Figure 8 and Figure 9 As shown, the first welding surface 21311 is connected to the outer surface of the housing 211 at the first edge 21311c, and the first welding surface 21311 is connected to the outer surface of the end cap 212 at the second edge 21311d. The first edge 21311c and the second edge 21311d are spaced apart along the first direction X. The first groove 215 provided on the first welding surface 21311 extends to the first edge 21311c and the second edge 21311d.

[0329] Wherein, the first edge 21311c is the intersection line of the connection position between the first welding surface 21311 and the transition surface 2141 of the outer surface of the housing 211, and the second edge 21311d is the intersection line of the connection position between the first welding surface 21311 and the transition surface 2141 of the outer surface of the end cap 212. The first edge 21311c and the second edge 21311d can extend circumferentially along the opening 2111 of the housing 211. The first groove 215 provided on the first welding surface 21311 extends to the first edge 21311c and the second edge 21311d, that is, one end of the first groove 215 provided on the first welding surface 21311 is located at the first edge 21311c, and the other end is located at the second edge 21311d.

[0330] Optionally, the first groove 215 provided on the first welding surface 21311 can be a groove structure extending along a straight trajectory. For example, the first groove 215 provided on the first welding surface 21311 can extend along the first direction X, or the first groove 215 provided on the first welding surface 21311 can extend to the two ends of the first edge 21311c and the second edge 21311d, which are at a distance in the circumferential direction of the opening 2111 of the housing 211. Of course, the first groove 215 provided on the first welding surface 21311 can also be a groove structure extending along a curved trajectory.

[0331] In this embodiment, by extending the first groove 215 provided on the first welding surface 21311 to the first edge 21311c and the second edge 21311d of the first welding surface 21311, it is beneficial to expand the span of the first groove 215 in the first direction X, so that more of the protective layer 23 can be accommodated in the first groove 215. This can further improve the stability and firmness of the protective layer 23 covering the first welding surface 21311 of the first solder mark portion 2131 and the transition surface 2141 connected thereto, so as to further reduce the phenomenon of the protective layer 23 falling off from the first welding surface 21311 and the transition surface 2141 connected thereto during use.

[0332] In some embodiments, see Figure 8 and Figure 9 As shown, the first welding surface 21311 is provided with a plurality of first grooves 215, and the plurality of first grooves 215 provided on the first welding surface 21311 are spaced apart along the circumferential direction of the opening 2111.

[0333] The number of first grooves 215 on the first welding surface 21311 can be one, two, three, four, five, six or more.

[0334] Among the plurality of first grooves 215 provided on the first welding surface 21311, two adjacent first grooves 215 may be arranged in parallel or at a non-zero included angle.

[0335] For example, the first welding surface 21311 connects the transition surface 2141 of the outer peripheral surface of the housing 211 and the transition surface 2141 of the outer peripheral surface of the end cap 212. The outer peripheral surface of the housing 211 is the first outer peripheral surface 2112, which is a part of the outer surface of the housing 211 and includes the transition surface 2141. The outer peripheral surface of the end cap 212 is the second outer peripheral surface 2121, which is a part of the outer surface of the end cap 212 and includes the transition surface 2141. Both the first outer peripheral surface 2112 and the second outer peripheral surface 2121 are provided with a second groove 216. Both the first outer peripheral surface 2112 and the second outer peripheral surface 2121 are covered with a protective layer 23. For example, the transition surface 2141 of the first outer peripheral surface 2112 and the transition surface 2141 of the second outer peripheral surface 2121 are both covered with a protective layer 23, and a part of the protective layer 23 is accommodated in the second groove 216. Two adjacent first grooves 215 provided on the first welding surface 21311 are arranged at a non-zero included angle. Among the three adjacent first grooves 215 provided on the first welding surface 21311, the first first groove 215, a second groove 216 provided on the first outer peripheral surface 2112, the second first groove 215, a second groove 216 provided on the second outer peripheral surface 2121, and the third first groove 215 are connected in sequence to form an N-shaped structure. The first outer peripheral surface 2112 of the housing 211 surrounds the opening 2111 of the housing 211 in the circumferential direction and extends in the first direction X; the second outer peripheral surface 2121 of the end cap 212 surrounds the opening 2111 of the housing 211 in the circumferential direction and extends in the first direction X.

[0336] In this embodiment, by setting multiple first grooves 215 on the first welding surface 21311, and the multiple first grooves 215 on the first welding surface 21311 being arranged circumferentially spaced along the opening 2111, the multiple first grooves 215 can accommodate more of the protective layer 23, thereby further improving the stability and firmness of the protective layer 23 covering the first welding surface 21311 of the first solder mark portion 2131 and the transition surface 2141 connected thereto, so as to further reduce the phenomenon of the protective layer 23 falling off from the first welding surface 21311 and the transition surface 2141 connected thereto during use.

[0337] According to some embodiments of this application, refer to Figure 10 As shown, Figure 10 This is a partial structural diagram of the casing 21 of the battery cell 20 provided in some embodiments of this application in other embodiments. A first groove 215 provided on the first welding surface 21311 extends circumferentially along the opening 2111.

[0338] The first groove 215 provided on the first welding surface 21311 can extend around the circumference of the opening 2111 of the housing 211. For example, the first groove 215 provided on the first welding surface 21311 can be an annular groove extending around the opening 2111 of the housing 211. Of course, the first groove 215 provided on the first welding surface 21311 can also extend around the opening 2111 of the housing 211 and have a distance between the two ends of the opening 2111 of the housing 211, that is, the first groove 215 provided on the first welding surface 21311 is not connected to each other at the two ends of the opening 2111 of the housing 211.

[0339] In this embodiment, by setting the first groove 215 on the first welding surface 21311 as a structure extending circumferentially along the opening 2111, on the one hand, the structure of the first groove 215 is simple, the molding difficulty is low, and it is easy to manufacture; on the other hand, the size of the first groove 215 in the circumferential direction of the opening 2111 is larger, which can reduce the number of first grooves 215 set along the circumferential direction of the opening 2111 on the first welding surface 21311, which is beneficial to improving production efficiency.

[0340] In some embodiments, please continue to see Figure 10 As shown, the first welding surface 21311 is provided with a plurality of first grooves 215, and the plurality of first grooves 215 provided on the first welding surface 21311 are spaced apart along the first direction X.

[0341] The plurality of first grooves 215 disposed on the first welding surface 21311 can be a structure with varying spacing along the first direction X, or a structure with equal spacing along the first direction X.

[0342] The number of first grooves 215 on the first welding surface 21311 can be one, two, three, four, five, six or more. As an example, the number of first grooves 215 on the first welding surface 21311 is four or more (including four).

[0343] In this embodiment, by providing a plurality of first grooves 215 spaced apart along the first direction X on the first welding surface 21311, the plurality of first grooves 215 can accommodate more of the protective layer 23, thereby further improving the stability and firmness of the protective layer 23 covering the first welding surface 21311 of the first solder mark portion 2131 and the transition surface 2141 connected thereto, so as to further reduce the phenomenon of the protective layer 23 falling off from the first welding surface 21311 and the transition surface 2141 connected thereto during use.

[0344] According to some embodiments of this application, refer to Figure 11 , Figure 12 and Figure 13 As shown, Figure 11 This is a partial cross-sectional view of a battery cell 20 provided in some embodiments of this application. Figure 12 for Figure 11 A magnified view of part D of the battery cell 20 shown. Figure 13 This is a front view of the casing 21 of the battery cell 20 provided in some embodiments of this application, facing the end cap 212 along the first direction X. The casing 21 is cylindrical, and the first direction X is parallel to the axial direction of the casing 21. A plurality of first grooves 215 are provided on the first welding surface 21311, and the plurality of first grooves 215 provided on the first welding surface 21311 are arranged at radial intervals along the casing 21.

[0345] The first groove 215 provided on the first welding surface 21311 is a structure that extends circumferentially along the opening 2111 of the housing 211.

[0346] The number of first grooves 215 provided on the first welding surface 21311 can be two, three, four, five, six or more. As an example, the number of first grooves 215 provided on the first welding surface 21311 is four or more (including four).

[0347] As an example, along the first direction X, the first welding surface 21311 faces the outer side of the housing 21, the outer surface of the end cap 212 includes a first surface 2122 facing away from the electrode assembly 22, the outer surface of the housing 211 includes a first end face 2113, the end face of the housing 211 near the end cap 212 is the first end face 2113, the first end face 2113 is connected to the first outer peripheral surface 2112 of the housing 211, the first end face 2113 and the first surface 2122 both include a transition surface 2141, and the first welding surface 21311 connects the transition surface 2141 of the first surface 2122 and the transition surface 2141 of the first end face 2113, and the first groove 215 provided on the first welding surface 21311 is an annular groove extending circumferentially along the opening 2111 of the housing 211.

[0348] In this embodiment, by providing a plurality of first grooves 215 arranged radially at intervals along the outer shell 21 on the first welding surface 21311, the plurality of first grooves 215 can accommodate more of the protective layer 23, thereby further improving the stability and firmness of the protective layer 23 covering the first welding surface 21311 of the first solder mark portion 2131 and the transition surface 2141 connected thereto, so as to further reduce the phenomenon of the protective layer 23 falling off from the first welding surface 21311 and the transition surface 2141 connected thereto during use.

[0349] According to some embodiments of this application, refer to Figure 14 As shown, Figure 14The housing 21 of the battery cell 20 provided in some embodiments of this application is a front view of the end cap 212 along the first direction X in other embodiments. In the projection plane perpendicular to the first direction X, the orthographic projection of the first groove 215 provided on the first welding surface 21311 extends along a planar spiral trajectory.

[0350] Among them, the planar spiral can be an Archimedean spiral or a logarithmic spiral, etc.

[0351] It should be noted that, in the embodiments of this application, the orthographic projection of the groove refers to the orthographic projection of the groove wall surface. It can be understood that, in the projection plane perpendicular to the first direction X, the orthographic projection of the first groove 215 disposed on the first welding surface 21311 is the orthographic projection of the groove wall surface of the first groove 215.

[0352] In this embodiment, by setting the first groove 215 on the first welding surface 21311 as a structure in which the orthographic projection in the projection plane perpendicular to the first direction X extends along a planar spiral trajectory, on the one hand, the extension dimension of the first groove 215 on the first welding surface 21311 can be increased so that more of the protective layer 23 can be accommodated in the first groove 215, thereby further improving the stability and firmness of the protective layer 23 covering the first welding surface 21311 of the first solder mark 2131 and the transition surface 2141 connected thereto. On the other hand, the processing difficulty of the first groove 215 can be reduced and the number of processing times can be reduced, which is beneficial to improving the processing efficiency of the first groove 215.

[0353] According to some embodiments of this application, refer to Figure 15 and Figure 16 As shown, Figure 15 This is a partial cross-sectional view of a battery cell 20 provided in other embodiments of this application. Figure 16 This is a partial structural diagram of the casing 21 of the battery cell 20 provided in other embodiments of this application. The first groove 215 provided on the first welding surface 21311 extends along a spiral trajectory, and the central axis of the spiral extends along the first direction X.

[0354] It should be noted that when a moving point rotates around the central axis and simultaneously moves along the extension direction of the central axis, the trajectory of this combined motion of the moving point is a spiral, and the central axis is the central axis of the spiral.

[0355] As an example, the outer shell 21 is cylindrical, and the first groove 215 provided on the first welding surface 21311 extends along a cylindrical helical trajectory. The first welding surface 21311 is located on the outer periphery of the outer shell 21. The first outer peripheral surface 2112 of the shell 211 and the second outer peripheral surface 2121 of the end cap 212 both include a transition surface 2141. The first welding surface 21311 connects the transition surface 2141 of the first outer peripheral surface 2112 of the shell 211 and the transition surface 2141 of the second outer peripheral surface 2121 of the end cap 212. The first welding surface 21311 is connected to the first outer peripheral surface 2112 of the shell 211 at the first edge 21311c, and the first welding surface 21311 is connected to the second outer peripheral surface 2121 of the end cap 212 at the second edge 21311d. The first groove 215 provided on the first welding surface 21311 is connected to the first edge 21311c and the second edge 21311d at its two ends in its helical extension direction, respectively. It should be noted that in the embodiment where both the first outer peripheral surface 2112 and the second outer peripheral surface 2121 are provided with a second groove 216, the second groove 216 provided on the first outer peripheral surface 2112 and the second outer peripheral surface 2121 are also structures that extend along a cylindrical helical trajectory. The second groove 216 provided on the first outer peripheral surface 2112, the first groove 215 provided on the first welding surface 21311, and the second groove 216 provided on the second outer peripheral surface 2121 can be a continuous structure. The first groove 215 provided on the first welding surface 21311 connects the second groove 216 provided on the first outer peripheral surface 2112 and the second groove 216 provided on the second outer peripheral surface 2121, so that the first groove 215 provided on the first welding surface 21311 communicates with the second groove 216 provided on the first outer peripheral surface 2112 and the second groove 216 provided on the second outer peripheral surface 2121.

[0356] In this embodiment, by setting the first groove 215 on the first welding surface 21311 as a structure extending along a spiral trajectory, and the central axis of the spiral extending along the first direction X, on the one hand, given that the axial dimension of the first groove 215 along the outer shell 21 is fixed, the extension dimension of the first groove 215 can be effectively increased, so that more of the protective layer 23 can be accommodated in the first groove 215, thereby further improving the stability and firmness of the protective layer 23 covering the first welding surface 21311 of the first solder mark portion 2131 and the transition surface 2141 connected thereto. On the other hand, it can reduce the processing difficulty of the first groove 215 and reduce the number of processing steps, which is beneficial to improving the processing efficiency of the first groove 215.

[0357] According to some embodiments of this application, refer to Figure 17 As shown, Figure 17This is a partial cross-sectional view of a battery cell 20 provided in some embodiments of this application. The outer surface of the housing 211 includes a first outer peripheral surface 2112, which includes a transition surface 2141 and is connected to a first welding surface 21311. The first outer peripheral surface 2112 is provided with a second groove 216, and at least a portion of the first outer peripheral surface 2112 is covered with a protective layer 23, with a portion of the protective layer 23 accommodated within the second groove 216.

[0358] The area where the first outer peripheral surface 2112 is connected to the first welding surface 21311 is the transition surface 2141 of the first outer peripheral surface 2112, and the first outer peripheral surface 2112 is at least a part of the outer surface of the shell 211. The first outer peripheral surface 2112 surrounds the opening 2111 of the shell 211 circumferentially.

[0359] At least a portion of the first outer peripheral surface 2112 is covered by the protective layer 23, that is, the protective layer 23 covers at least a portion of the first outer peripheral surface 2112. The protective layer 23 can cover a portion of the first outer peripheral surface 2112, for example, the protective layer 23 covers the transition surface 2141 of the first outer peripheral surface 2112, or it can cover the entire first outer peripheral surface 2112 (the protective layer 23 completely covers the first outer peripheral surface 2112).

[0360] The first outer peripheral surface 2112 is provided with a second groove 216, such that the second groove 216 is recessed from the first outer peripheral surface 2112 into the interior of the housing 211. The opening of the second groove 216 is formed on the first outer peripheral surface 2112. Correspondingly, a portion of the protective layer 23 is accommodated in the second groove 216. It can be a structure in which the portion of the protective layer 23 accommodated in the second groove 216 is connected to the groove wall of the second groove 216, or it can be a structure in which the portion of the protective layer 23 accommodated in the second groove 216 is not connected to the groove wall of the second groove 216. For example, the portion of the protective layer 23 accommodated in the second groove 216 is inserted into the second groove 216, such that the portion of the protective layer 23 accommodated in the second groove 216 only maintains contact with the groove wall of the second groove 216.

[0361] Optionally, the second groove 216 provided on the first outer peripheral surface 2112 can be a groove structure extending circumferentially along the opening 2111 of the housing 211, or it can be a groove structure extending along a spiral trajectory.

[0362] It should be noted that when the first outer peripheral surface 2112 is connected to the first welding surface 21311, the first welding surface 21311 can be connected to the second outer peripheral surface 2121 of the end cap 212, or the first welding surface 21311 can be connected to the first surface 2122 of the end cap 212. Figure 17 In the illustrated embodiment, the second welding surface 21321 connects the first outer peripheral surface 2112 and the second outer peripheral surface 2121.

[0363] In this embodiment, at least a portion of the first outer peripheral surface 2112 of the housing 211 is covered with a protective layer 23, which not only further increases the connection area between the protective layer 23 and the outer surface of the housing 21, but also enables the protective layer 23 to provide a certain degree of protection for the housing 211. This reduces the phenomenon of the protective layer 23 falling off during use, and also reduces the risk of corrosion and rust on the part of the housing 211 covered by the protective layer 23 during use. Furthermore, the first outer peripheral surface 2112 is provided with a second groove 216, and part of the protective layer 23 is accommodated in the second groove 216, so that the second groove 216 can play a certain restrictive role on the protective layer 23, thereby further improving the stability and firmness of the protective layer 23 on the first outer peripheral surface 2112. On the one hand, it can realize the long-term protection of the area covered by the protective layer 23 on the shell 211. On the other hand, it can reduce the risk that the part of the protective layer 23 on the first solder mark 2131 may fall off due to the part of the protective layer 23 on the first outer peripheral surface 2112 of the shell 211 lifting or falling off, thereby improving the stability of the protective layer 23 in protecting the first solder mark 2131 and the transition part 214 and other areas.

[0364] According to some embodiments of this application, refer to Figure 18 and Figure 19 As shown, Figure 18 A partial cross-sectional view of the battery cell 20 provided in some further embodiments of this application. Figure 19 for Figure 18 The diagram shows a partial enlarged view of point E of the battery cell 20. Along the first direction X, the outer surface of the end cap 212 includes a first surface 2122 facing away from the electrode assembly 22. The first surface 2122 includes a transition surface 2141 and is connected to a first welding surface 21311. The first surface 2122 is provided with a second groove 216, and at least a portion of the first surface 2122 is covered by a protective layer 23, with a portion of the protective layer 23 accommodated within the second groove 216.

[0365] Along the first direction X, the first surface 2122 of the end cap 212 faces the outer side of the outer shell 21. Optionally, along the first direction X, the first surface 2122 can be the surface of the end cap 212 furthest from the electrode assembly 22, that is, the first surface 2122 is the surface of the end cap 212 that is furthest from the electrode assembly 22. For example, the end cap 2122 is a flat plate structure, the first surface 2122 is the surface of the end cap 212 facing away from the electrode assembly 22, and the first surface 2122 is a plane. The first surface 2122 is the surface of the end cap 212 furthest from the electrode assembly 22. Of course, along the first direction X, the first surface 2122 may not be the surface of the end cap 212 furthest from the electrode assembly 22. For example, the first surface 2122 is located in the edge region of the end cap 212, and the surface of the end cap 212 furthest from the electrode assembly 22 is located in the central region of the end cap 212. The first surface 2122 is closer to the electrode assembly 22 than the surface of the end cap 212 furthest from the electrode assembly 22.

[0366] At least a portion of the first surface 2122 is covered by a protective layer 23, meaning the protective layer 23 covers at least a portion of the first surface 2122. The protective layer 23 may cover a portion of the first surface 2122, for example, the protective layer 23 may cover the transition surface 2141 of the first surface 2122, or it may cover the entire first surface 2122 (the protective layer 23 completely covers the first surface 2122). The first surface 2122 is provided with a second groove 216, such that the second groove 216 is recessed from the first surface 2122 toward the interior of the end cap 212, and the opening of the second groove 216 is formed on the first surface 2122.

[0367] The second groove 216 provided on the first surface 2122 can be a groove structure extending circumferentially along the opening 2111 of the housing 211, or it can be a groove structure extending along a planar spiral trajectory.

[0368] In this embodiment, at least a portion of the first surface 2122 of the end cap 212 is covered with a protective layer 23, which not only further increases the connection area between the protective layer 23 and the outer surface of the outer shell 21, but also enables the protective layer 23 to provide a certain degree of protection for the end cap 212. This reduces the phenomenon of the protective layer 23 falling off during use, and also reduces the risk of corrosion and rust on the part of the end cap 212 covered by the protective layer 23 during use. Furthermore, the first surface 2122 is provided with a second groove 216, and a portion of the protective layer 23 is accommodated within the second groove 216. This allows the second groove 216 to provide a certain degree of restriction on the protective layer 23, thereby further enhancing the stability and firmness of the protective layer 23 on the first surface 2122. On the one hand, this enables the protective layer 23 to provide long-term protection for the area covered by the end cap 212. On the other hand, it reduces the risk that the portion of the protective layer 23 located on the first solder mark 2131 may easily fall off due to the portion of the protective layer 23 on the first surface 2122 of the end cap 212 lifting or falling off. This enhances the stability of the protective layer 23 in protecting the first solder mark 2131 and the transition portion 214.

[0369] According to some embodiments of this application, please refer to Figure 18 and Figure 19 As shown, the outer surface of the housing 211 includes a first outer peripheral surface 2112. Along the first direction X, the outer surface of the end cap 212 includes a first surface 2122 that is away from the electrode assembly 22. Both the first outer peripheral surface 2112 and the first surface 2122 include a transition surface 2141, and the first welding surface 21311 connects the first surface 2122 and the first outer peripheral surface 2112.

[0370] As an example, the first solder mark 2131 is located on the outer periphery of the end cap 212 and is located at one end of the housing 211 near the end cap 212 in the first direction X.

[0371] In this embodiment, the first welding surface 21311 is configured as the first surface 2122 of the end cap 212 and the first outer peripheral surface 2112 of the housing 211, so that the first solder mark 2131 extends to the first surface 2122 of the end cap 212 away from the electrode assembly 22. This increases the size of the first solder mark 2131 in the first direction X, which is beneficial to improving the connection strength and connection stability of the end cap 212 and the housing 211.

[0372] In some embodiments, see Figure 19 As shown, the first welding surface 21311 includes a rounded corner area 21311a, which is connected to the first surface 2122.

[0373] The first welding surface 21311 can be entirely composed of rounded corner areas 21311a, or a portion of the first welding surface 21311 adjacent to the transition surface 2141 of the first surface 2122 can be a rounded corner area 21311a. The cross-section of the rounded corner area 21311a parallel to the first direction X is approximately arc-shaped. Correspondingly, the protective layer 23 covers the entire rounded corner area 21311a.

[0374] In the embodiments of this application, see Figure 19 As shown, a portion of the first welding surface 21311 adjacent to the transition surface 2141 of the first surface 2122 is a rounded corner area 21311a. Correspondingly, the first welding surface 21311 may also include a connecting area 21311b. The connecting area 21311b is connected to the transition surface 2141 of the first outer peripheral surface 2112 of the housing 211. The connecting area 21311b transitions to the transition surface 2141 of the first surface 2122 through the rounded corner area 21311a.

[0375] The connecting area 21311b can smoothly transition to the transition surface 2141 of the first outer peripheral surface 2112 of the housing 211, and the rounded corner area 21311a can smoothly transition to the transition surface 2141 of the first surface 2122. Correspondingly, the protective layer 23 covers the entire connecting area 21311b.

[0376] For the first groove 215 disposed on the first welding surface 21311, the first groove 215 may have a portion located in the rounded corner area 21311a and / or the connecting area 21311b. Alternatively, a portion of the first groove 215 may be disposed in the connecting area 21311b, and a portion of the protective layer 23 may be accommodated in the portion of the first groove 215 located in the connecting area 21311b. Another portion of the first groove 215 may be disposed in the rounded corner area 21311a, and a portion of the protective layer 23 may be accommodated in the portion of the first groove 215 located in the rounded corner area 21311a.

[0377] There may be multiple first grooves 215 provided on the first welding surface 21311, with first grooves 215 provided in both the rounded corner area 21311a and the connecting area 21311b. A portion of the first grooves 215 may be provided in the connecting area 21311b, with a portion of the protective layer 23 accommodated within the first groove 215 in the connecting area 21311b; another portion of the first grooves 215 may be provided in the rounded corner area 21311a, with a portion of the protective layer 23 accommodated within the first groove 215 in the rounded corner area 21311a.

[0378] For example, in Figure 19In the housing 211, both the rounded corner area 21311a and the connecting area 21311b are provided with multiple first grooves 215. The first grooves 215 in both areas are annular grooves extending circumferentially along the opening 2111 of the housing 211. The protective layer 23 covers the entire first welding surface 21311 and at least a portion of the transition surface 2141 of the first surface 2122 and at least a portion of the transition surface 2141 of the first outer peripheral surface 2112 of the housing 211. Both the first surface 2122 of the end cap 212 and the first outer peripheral surface 2112 of the housing 211 are provided with second grooves 216. The second grooves 216 on the first outer peripheral surface 2112 are annular grooves extending circumferentially along the opening 2111 of the housing 211. In a projection plane perpendicular to the first direction X, the orthographic projection of the second grooves 216 on the first surface 2122 extends along a planar spiral trajectory. Of course, in other embodiments, the rounded corner area 21311a may be provided with a plurality of first grooves 215, and the first grooves 215 provided in the rounded corner area 21311a may be annular grooves extending circumferentially along the opening 2111 of the housing 211, while the connecting area 21311b may not be provided with first grooves 215. Alternatively, the connecting area 21311b may be provided with a plurality of first grooves 215, and the first grooves 215 provided in the connecting area 21311b may be annular grooves extending circumferentially along the opening 2111 of the housing 211, while the rounded corner area 21311a may not be provided with first grooves 215. Similarly, a portion of the first grooves 215 provided on the first welding surface 21311 may be located in the rounded corner area 21311a, and another portion may be located in the connecting area 21311b.

[0379] As an example, the first groove 215 provided on the first welding surface 21311 has a portion located in the rounded corner area 21311a, and a portion of the protective layer 23 is accommodated in the portion of the first groove 215 located in the rounded corner area 21311a.

[0380] In this embodiment, the rounded corner area 21311a in the first welding surface 21311 eliminates the sharp corners of the edge area of ​​the end cap 212. This allows the material of the protective layer 23 to better adhere to the rounded corner area 21311a of the first welding surface 21311 during the process of forming and setting the protective layer 23 on the first welding surface 21311 and the transition surface 2141 connected thereto. This makes it less likely for the protective layer 23 to fall off the first welding surface 21311 under the action of gravity, thus facilitating the forming of the protective layer 23 on the first welding surface 21311 and reducing the difficulty of setting the protective layer 23 on the first welding surface 21311.

[0381] According to some embodiments of this application, refer to Figure 20 As shown, Figure 20This is a partial cross-sectional view of a battery cell 20 provided in some other embodiments of this application. Along the first direction X, the outer surface of the housing 211 includes a first end face 2113, which is the end face of the housing 211 near the end cap 212. The first end face 2113 is connected to a first welding surface 21311, and each of the first end faces 2113 includes a transition surface 2141. The first end face 2113 is provided with a second groove 216, and at least a portion of the first end face 2113 is covered by a protective layer 23, with a portion of the protective layer 23 accommodated within the second groove 216.

[0382] The first end face 2113 is part of the outer surface of the housing 211, and the end of the housing 211 near the end cap 212 is the end of the housing 211 with the opening 2111. At least a portion of the first end face 2113 is covered by a protective layer 23, that is, the protective layer 23 covers at least a portion of the first end face 2113. The protective layer 23 can cover a portion of the first end face 2113, for example, the protective layer 23 covers the transition surface 2141 of the first end face 2113, or it can cover the entire first end face 2113 (the protective layer 23 completely covers the first end face 2113). The first end face 2113 is provided with a second groove 216, such that the second groove 216 is recessed from the first end face 2113 into the interior of the housing 211, and the opening of the second groove 216 is formed on the first end face 2113.

[0383] The second groove 216 provided on the first end face 2113 can be a groove extending circumferentially along the opening 2111 of the housing 211, or it can be a groove extending along a planar spiral trajectory.

[0384] When the first end face 2113 is connected to the first welding surface 21311, the first welding surface 21311 is connected to the transition surface 2141 of the first end face 2113. Correspondingly, the first welding surface 21311 can be connected to the second outer peripheral surface 2121 of the end cover 212, that is, the first welding surface 21311 connects the first end face 2113 and the second outer peripheral surface 2121. Alternatively, the first welding surface 21311 can be connected to the first surface 2122 of the end cover 212, that is, the first welding surface 21311 connects the first end face 2113 and the first surface 2122.

[0385] In this embodiment, at least a portion of the first end face 2113 of the housing 211 is covered with a protective layer 23, which not only further increases the connection area between the protective layer 23 and the outer surface of the housing 21, but also enables the protective layer 23 to provide a certain degree of protection to the end of the housing 211 near the end cap 212. This reduces the phenomenon of the protective layer 23 falling off during use and also reduces the risk of corrosion and rust on the part of the housing 211 covered by the protective layer 23 during use. Furthermore, the first end face 2113 is provided with a second groove 216, and part of the protective layer 23 is accommodated in the second groove 216, so that the second groove 216 can play a certain restrictive role on the protective layer 23, thereby further improving the stability and firmness of the protective layer 23 on the first end face 2113. On the one hand, it can realize the long-term protection of the area covered by the protective layer 23 on the shell 211. On the other hand, it can reduce the risk that the part of the protective layer 23 on the first solder mark 2131 may fall off due to the part of the protective layer 23 on the first end face 2113 of the shell 211 lifting or falling off, thereby improving the stability of the protective layer 23 in protecting the first solder mark 2131 and the transition part 214 and other areas.

[0386] In some embodiments, please continue to see Figure 20 As shown, along the first direction X, the outer surface of the end cap 212 includes a first surface 2122 facing away from the electrode assembly 22, and the outer surface of the housing 211 includes a first end face 2113. The first end face 2113 is the end face of the housing 211 near the end cap 212. Both the first surface 2122 and the first end face 2113 include a transition surface 2141, and the first welding surface 21311 connects the first surface 2122 and the first end face 2113.

[0387] The first welding surface 21311 is a structure that connects the transition surface 2141 of the first surface 2122 and the transition surface 2141 of the first end surface 2113. Optionally, the first surface 2122 may be flush with the first end surface 2113, or the first surface 2122 may be closer to or farther away from the electrode assembly 22 along the first direction X than the first end surface 2113.

[0388] As an example, the first end face 2113 is connected to the first outer peripheral surface 2112 of the housing 211. The first end face 2113 is flush with the first surface 2122, and the first solder mark 2131 partially protrudes from the first end face 2113 and the first surface 2122. In a projection plane perpendicular to the first direction X, the orthographic projection of the first groove 215 provided on the first welding surface 21311 extends along a planar spiral trajectory, the orthographic projection of the second groove 216 provided on the first surface 2122 extends along a planar spiral trajectory, and the orthographic projection of the second groove 216 provided on the first end face 2113 extends along a planar spiral trajectory. The first groove 215 provided on the first welding surface 21311 connects the second groove 216 provided on the first surface 2122 and the second groove 216 provided on the first end face 2113, so that the first groove 215 provided on the first welding surface 21311 communicates with the second groove 216 provided on the first surface 2122 and the second groove 216 provided on the first end face 2113. The protective layer 23 covers the entire first welding surface 21311 and at least a portion of the transition surface 2141 of the first surface 2122 and at least a portion of the transition surface 2141 of the first end face 2113. The protective layer 23 does not cover the first outer peripheral surface 2112. A portion of the protective layer 23 is accommodated in a first groove 215 disposed on the first welding surface 21311 and is connected to the groove wall of the first groove 215 disposed on the first welding surface 21311; a portion of the protective layer 23 is accommodated in a second groove 216 disposed on the transition surface 2141 of the first surface 2122 and is connected to the groove wall of the second groove 216 disposed on the transition surface 2141 of the first surface 2122; a portion of the protective layer 23 is accommodated in a second groove 216 disposed on the transition surface 2141 of the first end face 2113 and is connected to the groove wall of the second groove 216 disposed on the transition surface 2141 of the first end face 2113.

[0389] In this embodiment, by setting the first welding surface 21311 as the structure connecting the first surface 2122 of the end cap 212 and the first end face 2113 of the housing 211, on the one hand, during the welding process of the end cap 212 and the housing 211, the end cap 212 and the housing 211 can be welded together from the outside of the housing 21 along the first direction X to form the first weld mark 2131. The welding method is simple and helps to reduce the assembly difficulty of the end cap 212 and the housing 211. On the other hand, it can ensure that the first weld mark 2131 does not protrude from the outer peripheral surface (first outer peripheral surface 2112) of the housing 211, which helps to reduce the influence of the first weld mark 2131 on the size of the battery cell 20 in the direction perpendicular to the first direction X.

[0390] According to some embodiments of this application, see Figures 5-20As shown, the first solder mark 2131 has a ring structure, the first solder mark 2131 extends circumferentially along the opening 2111, and transition portions 214 are connected to both sides of the first solder mark 2131.

[0391] The first solder mark 2131 has a ring-shaped structure and extends circumferentially along the opening 2111. In other words, the extension trajectory of the first solder mark 2131 is a closed trajectory extending circumferentially along the opening 2111, allowing the two ends of the first solder mark 2131 to connect to each other circumferentially around the opening 2111. If the first solder mark 2131 is a rectangular ring, its extension trajectory is rectangular; if the first solder mark 2131 is a circular ring, its extension trajectory is circular.

[0392] When welding the housing 211 and the end cap 212, welding can be performed continuously along the circumference of the opening 2111 of the housing 211 to form a first weld mark 2131 with an annular structure.

[0393] As an example, see Figure 17 , Figure 19 and Figure 20 As shown, the surface of the first solder mark 2131 includes a first interface 21312, a second interface 21313, and a first welding surface 21311. The first interface 21312, the second interface 21313, and the first welding surface 21311 are all annular structures extending circumferentially along the opening 2111 of the housing 211. The first interface 21312 is connected to the transition portion 214 of the housing 211 and is covered by the transition portion 214 of the housing 211. The second interface 21313 is connected to the transition portion 214 of the end cap 212 and is covered by the transition portion 214 of the end cap 212. The first welding surface 21311 is exposed on the outside of the housing 21 and is not covered by the transition portion 214 of the housing 211 and the transition portion 214 of the end cap 212. Within the cross-section of the first solder mark 2131 parallel to the first direction X, the first interface 21312, the second interface 21313, and the first welding surface 21311 are connected end to end.

[0394] In this embodiment, by setting the first solder mark 2131 as an annular structure extending circumferentially along the opening 2111, the contact area between the housing 211 and the first solder mark 2131, and between the end cap 212 and the first solder mark 2131, can be increased, thereby improving the connection strength between the housing 211 and the first solder mark 2131, and between the end cap 212 and the first solder mark 2131, so as to improve the welding firmness between the housing 211 and the end cap 212. On the other hand, the first solder mark 2131 can realize the sealed connection between the housing 211 and the end cap 212, so as to reduce the leakage risk of the battery cell 20 during use.

[0395] According to some embodiments of this application, refer to Figure 21 As shown, Figure 21 This is a partial cross-sectional view of a battery cell 20 provided in some other embodiments of this application. The housing 211 may include a housing body 211a and a first anti-corrosion layer 211b. The housing body 211a is made of steel. The first anti-corrosion layer 211b is disposed on the surface of the housing body 211a. The outer surface of the first anti-corrosion layer 211b is at least a part of the outer surface of the housing 211. Both the housing body 211a and the first anti-corrosion layer 211b are connected to the first solder joint 2131.

[0396] The shell body 211a is the base material of the shell 211. The shell body 211a can be made of steel, including carbon steel or stainless steel. Carbon steel can be Q195 carbon steel, SPCC carbon steel, etc.; stainless steel can be SUS430 stainless steel, SUS304 stainless steel, SUS316 stainless steel, or modified stainless steel, etc. In this embodiment, the shell body 211a is made of carbon steel. The first anti-corrosion layer 211b is the surface layer of the shell 211, and its thickness is less than that of the shell body 211a. The first anti-corrosion layer 211b can be a plating layer applied to the surface of the shell body 211a. The material of the first anti-corrosion layer 211b can include at least one of nickel, aluminum, zinc, etc.

[0397] The outer surface of the first anti-corrosion layer 211b can be the outer surface of the shell 211, or the outer surface of the first anti-corrosion layer 211b can be a part of the outer surface of the shell 211. In an embodiment where the outer surface of the shell 211 includes a first outer peripheral surface 2112, the first outer peripheral surface 2112 can be a part of the outer surface of the first anti-corrosion layer 211b; in an embodiment where the outer surface of the shell 211 includes a first end face 2113, the first end face 2113 can be a part of the outer surface of the first anti-corrosion layer 211b.

[0398] As an example, the shell body 211a and the first anti-corrosion layer 211b are both connected to the first interface 21312 of the first solder joint 2131. The outer surface of the first anti-corrosion layer 211b is the outer surface of the shell 211, and the first outer peripheral surface 2112 is a part of the outer surface of the first anti-corrosion layer 211b.

[0399] It should be noted that a portion of the transition portion 214 connecting the shell 211 and the first solder mark 2131 is located inside the shell body 211a, and another portion is located inside the first anti-corrosion layer 211b. Correspondingly, the outer surface of the portion of the transition portion 214 connecting the shell 211 and the first solder mark 2131 located inside the first anti-corrosion layer 211b is the transition surface 2141 on the outer surface of the shell 211 that connects with the first welding surface 21311.

[0400] In this embodiment, by setting the material of the shell body 211a of the shell 211 to include steel, it is beneficial to improve the overall structural strength of the shell 211, thereby reducing the risk of damage or deformation of the shell 211 during use. The outer surface of the first anti-corrosion layer 211b is at least a part of the outer surface of the shell 211, making the first anti-corrosion layer 211b the surface layer of the shell 211. The first anti-corrosion layer 211b has better corrosion resistance than the shell body 211a, so that the first anti-corrosion layer 211b can play a certain role in protecting and preventing rust on the steel shell body 211a, thereby giving the shell 211 good rust prevention ability.

[0401] In some embodiments, the first anti-corrosion layer 211b includes a nickel layer.

[0402] For example, a portion of the first anti-corrosion layer 211b may be a nickel layer, or the entire first anti-corrosion layer 211b may be a nickel layer.

[0403] In this embodiment, the first anti-corrosion layer 211b includes a nickel layer. Since the nickel layer has good corrosion resistance and high hardness, it can improve the corrosion resistance and wear resistance of the shell 211.

[0404] In some embodiments, please continue to see Figure 21 As shown, the outer surface of the first anti-corrosion layer 211b is provided with a second groove 216, at least a portion of the outer surface of the first anti-corrosion layer 211b is covered with a protective layer 23, and a portion of the protective layer 23 is accommodated within the second groove 216.

[0405] At least a portion of the outer surface of the first anti-corrosion layer 211b is covered by the protective layer 23. Specifically, the protective layer 23 covers at least a portion of the outer surface of the first anti-corrosion layer 211b. The protective layer 23 can cover a portion of the outer surface of the first anti-corrosion layer 211b, for example, covering the portion of the transition portion 214 located within the first anti-corrosion layer 211b, or it can cover the entire outer surface of the first anti-corrosion layer 211b. A second groove 216 is provided on the outer surface of the first anti-corrosion layer 211b, such that the second groove 216 is recessed from the outer surface of the first anti-corrosion layer 211b into the interior of the housing 211. The opening of the second groove 216 is formed on the outer surface of the first anti-corrosion layer 211b.

[0406] Optionally, the depth of the second groove 216 provided on the outer surface of the first anti-corrosion layer 211b can be less than or equal to the thickness of the first anti-corrosion layer 211b. Of course, the depth of the second groove 216 provided on the outer surface of the first anti-corrosion layer 211b can also be greater than the thickness of the first anti-corrosion layer 211b, so that the second groove 216 penetrates the first anti-corrosion layer 211b along the depth direction and extends into the shell body 211a.

[0407] It is understood that in the embodiment where the first welding surface 21311 is connected to the first end face 2113, the second groove 216 provided on the outer surface of the first anti-corrosion layer 211b can be provided on the first end face 2113; in the embodiment where the first welding surface 21311 is connected to the first outer peripheral surface 2112, the second groove 216 provided on the outer surface of the first anti-corrosion layer 211b can be provided on the first outer peripheral surface 2112.

[0408] For example, in Figure 21 In the first welding surface 21311, the first groove 215 is connected to the second groove 216 on the first anti-corrosion layer 211b.

[0409] In this embodiment, at least a portion of the outer surface of the first anti-corrosion layer 211b is covered by a protective layer 23, so that the area where the protective layer 23 overlaps with the first anti-corrosion layer 211b can provide double-layer protection for the shell body 211a, thereby further reducing the risk of corrosion and rust on the shell body 211a during use. Furthermore, a second groove 216 is provided on the outer surface of the first anti-corrosion layer 211b, and a portion of the protective layer 23 is accommodated within the second groove 216. This allows the second groove 216 to provide a certain degree of constraint on the protective layer 23, thereby further improving the stability and firmness of the protective layer 23 on the first anti-corrosion layer 211b of the shell 211. On the one hand, this enables the protective layer 23 to provide long-term protection for the covered area of ​​the shell 211; on the other hand, it reduces the risk of the portion of the protective layer 23 on the first solder mark 2131 easily detaching due to the lifting or detachment of the portion of the protective layer 23 on the first anti-corrosion layer 211b of the shell 211. This improves the stability of the protective layer 23 in protecting areas such as the first solder mark 2131 and the transition portion 214.

[0410] In some embodiments, please continue to see Figure 21 As shown, the depth of the second groove 216 provided on the outer surface of the first anti-corrosion layer 211b is less than the thickness of the first anti-corrosion layer 211b. That is to say, the second groove 216 provided on the outer surface of the first anti-corrosion layer 211b does not penetrate the first anti-corrosion layer 211b in the depth direction.

[0411] As an example, the depth of the second groove 216 provided on the outer surface of the first anti-corrosion layer 211b is less than or equal to 0.7 times the thickness of the first anti-corrosion layer 211b.

[0412] In this embodiment, by setting the depth of the second groove 216 on the outer surface of the first anti-corrosion layer 211b to be less than the thickness of the first anti-corrosion layer 211b, the second groove 216 does not penetrate the first anti-corrosion layer 211b in the thickness direction. This reduces the phenomenon of the shell body 211a being exposed in the area of ​​the first anti-corrosion layer 211b where the second groove 216 is provided, so that the area of ​​the first anti-corrosion layer 211b where the second groove 216 is provided can still provide rust protection for the shell body 211a.

[0413] According to some embodiments of this application, refer to Figure 21 As shown, the end cap 212 may include a cap body 212a and a second anti-corrosion layer 212b. The material of the cap body 212a includes steel. The second anti-corrosion layer 212b is disposed on the surface of the cap body 212a. The outer surface of the second anti-corrosion layer 212b is at least a part of the outer surface of the end cap 212. Both the cap body 212a and the second anti-corrosion layer 212b are connected to the first solder mark 2131.

[0414] The cover body 212a is the base material of the end cap 212. The cover body 212a can be made of steel, including carbon steel or stainless steel. Carbon steel can be Q195 carbon steel, SPCC carbon steel, etc.; stainless steel can be SUS430 stainless steel, SUS304 stainless steel, SUS316 stainless steel, or modified stainless steel, etc. In this embodiment, the material of the cover body 212a includes carbon steel. The second anti-corrosion layer 212b is the surface layer of the end cap 212, and the thickness of the second anti-corrosion layer 212b is less than the thickness of the cover body 212a. The second anti-corrosion layer 212b can be a plating layer disposed on the surface of the cover body 212a. The material of the second anti-corrosion layer 212b can include at least one of nickel, aluminum, zinc, etc.

[0415] The outer surface of the second anti-corrosion layer 212b can be the outer surface of the end cap 212, or the outer surface of the second anti-corrosion layer 212b can be a part of the outer surface of the end cap 212. In embodiments where the outer surface of the end cap 212 includes the first surface 2122, the first surface 2122 can be a part of the outer surface of the second anti-corrosion layer 212b.

[0416] As an example, both the cover body 212a and the second anti-corrosion layer 212b are connected to the second interface 21313 of the first solder joint 2131. The outer surface of the second anti-corrosion layer 212b is the outer surface of the end cap 212, and the first surface 2122 is a part of the outer surface of the second anti-corrosion layer 212b.

[0417] It should be noted that a portion of the transition portion 214 connecting the end cap 212 and the first solder mark portion 2131 is located inside the cap body 212a, and another portion is located inside the second anti-corrosion layer 212b. Correspondingly, the outer surface of the portion of the transition portion 214 connecting the end cap 212 and the first solder mark portion 2131 located inside the second anti-corrosion layer 212b is the transition surface 2141 of the outer surface of the end cap 212 that connects with the first welding surface 21311.

[0418] In this embodiment, by setting the material of the cover body 212a of the end cap 212 to include steel, it is beneficial to improve the overall structural strength of the end cap 212, thereby reducing the risk of damage or deformation of the end cap 212 during use. The outer surface of the second anti-corrosion layer 212b is at least a part of the outer surface of the end cap 212, making the second anti-corrosion layer 212b the surface layer of the end cap 212. The second anti-corrosion layer 212b has better corrosion resistance than the cover body 212a, so that the second anti-corrosion layer 212b can play a certain role in protecting and preventing rust on the steel cover body 212a, thereby giving the end cap 212 good rust prevention ability.

[0419] In some embodiments, the second anti-corrosion layer 212b includes a nickel layer.

[0420] For example, a portion of the second anti-corrosion layer 212b may be a nickel layer, or the entire second anti-corrosion layer 212b may be a nickel layer.

[0421] In this embodiment, the second anti-corrosion layer 212b includes a nickel layer. Since the nickel layer has good corrosion resistance and high hardness, it can improve the corrosion resistance and wear resistance of the end cap 212.

[0422] In some embodiments, please continue to see Figure 21 As shown, the outer surface of the second anti-corrosion layer 212b is provided with a second groove 216, at least a portion of the outer surface of the second anti-corrosion layer 212b is covered by a protective layer 23, and a portion of the protective layer 23 is accommodated within the second groove 216.

[0423] At least a portion of the outer surface of the second anti-corrosion layer 212b is covered by the protective layer 23. Specifically, the protective layer 23 covers at least a portion of the outer surface of the second anti-corrosion layer 212b. The protective layer 23 may cover only a portion of the outer surface of the second anti-corrosion layer 212b; for example, it may cover the portion of the transition portion 214 located within the second anti-corrosion layer 212b, or it may cover the entire outer surface of the second anti-corrosion layer 212b. A second groove 216 is provided on the outer surface of the second anti-corrosion layer 212b, such that the second groove 216 is recessed from the outer surface of the second anti-corrosion layer 212b into the interior of the end cap 212. The opening of the second groove 216 is formed on the outer surface of the second anti-corrosion layer 212b.

[0424] Optionally, the depth of the second groove 216 provided on the outer surface of the second anti-corrosion layer 212b can be less than or equal to the thickness of the second anti-corrosion layer 212b. Of course, the depth of the second groove 216 provided on the outer surface of the second anti-corrosion layer 212b can also be greater than the thickness of the second anti-corrosion layer 212b, so that the second groove 216 penetrates the second anti-corrosion layer 212b along the depth direction and extends into the cover body 212a.

[0425] It is understood that in the embodiment where the first welding surface 21311 is connected to the first surface 2122, the second groove 216 provided on the outer surface of the second anti-corrosion layer 212b can be provided on the first surface 2122; in the embodiment where the first welding surface 21311 is connected to the second outer peripheral surface 2121, the second groove 216 provided on the outer surface of the second anti-corrosion layer 212b can be provided on the second outer peripheral surface 2121.

[0426] As an example, see Figure 21 As shown, the first surface 2122 is the outer surface of the second anti-corrosion layer 212b, the first outer peripheral surface 2112 is a part of the outer surface of the first anti-corrosion layer 211b, the first welding surface 21311 connects the transition surface 2141 of the first surface 2122 and the transition surface 2141 of the first outer peripheral surface 2112, and the first groove 215 provided in the first welding surface 21311 is... Figure 9 The structure shown has a portion of the first groove 215 on the first welding surface 21311 located in the rounded corner area 21311a, and another portion located in the connecting area 21311b. The first welding surface 21311 is connected to the first surface 2122 of the end cap 212 at the second edge 21311d. Figure 9 As shown in the diagram, the first welding surface 21311 is connected to the first outer peripheral surface 2112 of the housing 211 at the first edge 21311c. Figure 9 As shown in the diagram, a first groove 215 disposed on the first welding surface 21311 extends to the first edge 21311c and the second edge 21311d. A plurality of first grooves 215 disposed on the first welding surface 21311 are spaced circumferentially along the opening 2111 of the housing 211. A protective layer 23 covers the entire first welding surface 21311 and also covers the transition surface 2141 of the first surface 2122 of the end cap 212 and the transition surface 2141 of the first outer peripheral surface 2112 of the housing 211. Both the first surface 2122 of the end cap 212 and the first outer peripheral surface 2112 of the housing 211 are provided with second grooves 216. The second grooves 216 disposed on the first outer peripheral surface 2112 of the housing 211 connect to two adjacent first grooves 215 disposed on the first welding surface 21311. In a projection plane perpendicular to the first direction X, the orthographic projection of the second grooves 216 disposed on the first surface 2122 extends along a planar spiral trajectory.

[0427] In this embodiment, at least a portion of the outer surface of the second anti-corrosion layer 212b is covered with a protective layer 23, so that the area where the protective layer 23 overlaps with the second anti-corrosion layer 212b can provide double protection for the cover body 212a, thereby further reducing the risk of corrosion and rust on the cover body 212a during use. Furthermore, a second groove 216 is provided on the outer surface of the second anti-corrosion layer 212b, and a portion of the protective layer 23 is accommodated within the second groove 216. This allows the second groove 216 to provide a certain degree of restriction on the protective layer 23, thereby further enhancing the stability and firmness of the protective layer 23 on the second anti-corrosion layer 212b of the end cap 212. On the one hand, this enables the protective layer 23 to provide long-term protection for the area covered by the end cap 212. On the other hand, it reduces the risk that the portion of the protective layer 23 on the first solder mark 2131 may easily fall off due to the portion of the protective layer 23 on the second anti-corrosion layer 212b of the end cap 212 lifting or falling off. This improves the stability of the protective layer 23 in protecting the first solder mark 2131 and the transition portion 214.

[0428] In some embodiments, please continue to see Figure 21 As shown, the depth of the second groove 216 provided on the outer surface of the second anti-corrosion layer 212b is less than the thickness of the second anti-corrosion layer 212b. That is to say, the second groove 216 provided on the outer surface of the second anti-corrosion layer 212b does not penetrate the second anti-corrosion layer 212b in the depth direction.

[0429] As an example, the depth of the second groove 216 provided on the outer surface of the second anti-corrosion layer 212b is less than or equal to 0.7 times the thickness of the second anti-corrosion layer 212b.

[0430] In this embodiment, by setting the depth of the second groove 216 on the outer surface of the second anti-corrosion layer 212b to be less than the thickness of the second anti-corrosion layer 212b, the second groove 216 does not penetrate the second anti-corrosion layer 212b in the thickness direction. This reduces the phenomenon of the cover body 212a being exposed in the area of ​​the second anti-corrosion layer 212b where the second groove 216 is provided, so that the area of ​​the second anti-corrosion layer 212b where the second groove 216 is provided can still provide rust protection for the cover body 212a.

[0431] According to some embodiments of this application, refer to Figure 3 , Figure 4 and Figure 5 as well as Figure 18 Please refer to further details. Figure 22 and Figure 23 As shown, Figure 22 for Figure 18 The image shows a partial enlarged view of point F of the battery cell 20. Figure 23 for Figure 22 The diagram shows a partial enlarged view of point G on the battery cell 20. The housing 21 includes a wall portion 217, which is disposed opposite to the electrode assembly 22 along a first direction X. The electrode assembly 22 includes a main body portion 221 and a first tab 222. The first tab 222 is connected to the end of the main body portion 221 facing the wall portion 217 in the first direction X. At least one solder mark portion 213 includes a second solder mark portion 2132, which is disposed on the wall portion 217. The wall portion 217 includes a transition portion 214. The welding surface 213a of the second solder mark portion 2132 is the second welding surface 21321. The outer surface of the wall portion 217 is part of the outer surface of the housing 21, and the outer surface of the wall portion 217 includes a transition surface 2141. The second welding surface 21321 is connected to the outer surface of the wall portion 217. The second solder mark 2132 is connected to the first tab 222; or the battery cell 20 further includes a first current collector 25, which is connected to the first tab 222, and the second solder mark 2132 is connected to the first current collector 25.

[0432] The electrode assembly 22 further includes a second tab 223. The second tab 223 and the first tab 222 are respectively connected to two pairs of the main body 221 in the first direction X. The first tab 222 is connected to the end of the main body 221 facing the wall portion 217 in the first direction X. The first tab 222 is electrically connected to the wall portion 217. The second tab 223 is electrically connected to the electrode terminal 24 disposed on the housing 21, so as to input or output the electrical energy of the battery cell 20 through the wall portion 217 and the electrode terminal 24.

[0433] It should be noted that the wall portion 217 with the second solder mark 2132 can be the end cap 212 of the outer casing 21, or it can be a wall of the housing 211 of the outer casing 21. For example, in... Figure 4 and Figure 5 In this embodiment, the wall portion 217 is the end cap 212. Of course, the structure of the battery cell 20 is not limited to this. In other embodiments, the wall portion 217 can also be the bottom wall of the housing 211 and the end cap 212 that are opposite to each other, or the wall portion 217 can also be the side wall of the housing 211 and the end cap 212 that are adjacent to each other and connected to each other.

[0434] Of all the solder marks 213 on the outer casing 21, at least one solder mark 213 is a second solder mark 2132. The second solder mark 2132 can be directly connected to the wall portion 217 and the first electrode tab 222, that is, the second solder mark 213 is a solder mark 213 formed by welding the wall portion 217 and the first electrode tab 222 together. Alternatively, the second solder mark 2132 can be directly connected to the wall portion 217 and the first current collector 25, that is, the second solder mark 2132 is a solder mark 213 formed by welding the wall portion 217 and the first current collector 25 together. Exemplarily, in an embodiment of this application, see... Figure 22As shown, the second solder mark 2132 is directly connected to the wall portion 217 and the first current collector 25, and the first current collector 25 is connected to the first electrode 222 to electrically connect the first electrode 222 and the wall portion 217. That is, the wall portion 217 and the first current collector 25 are welded together to form the second solder mark 2132. Correspondingly, a transition portion 214 is connected around the second solder mark 2132. That is, the second solder mark 2132 is a structure that is connected to other parts of the wall portion 217 through the transition portion 214, and the second welding surface 21321 is a structure that is connected to the transition surface 2141 of the outer surface of the wall portion 217.

[0435] The number of second solder marks 2132 can be one or more. The outer casing 21 may only have the second solder mark 2132, or the outer casing 21 may have other solder marks 213 in addition to the second solder mark 2132, such as the first solder mark 2131 in the aforementioned embodiment.

[0436] See Figure 22 and Figure 23 As shown, the second welding surface 21321 is the outer surface of the second solder mark 2132 facing away from the electrode assembly 22. The second welding surface 21321 is provided with a first groove 215. A portion of the protective layer 23 is accommodated in the first groove 215 provided in the second welding surface 21321, and the protective layer 23 covers the entire second welding surface 21321 (the protective layer 23 completely covers the second welding surface 21321). In the embodiment where the end cap 212 includes a wall portion 217, if the first surface 2122 of the end cap 212 is connected to the second welding surface 21321, the first groove 215 provided in the second welding surface 21321 can be connected to or spaced apart from the second groove 216 provided in the first surface 2122.

[0437] The second welding surface 21321 may be located in the central region of the outer surface of the wall portion 217 and connected to the outer surface of the wall portion 217. For example, the second welding surface 21321 may be a circular region, and the outer surface of the wall portion 217 may be an annular region surrounding the outer side of the second welding surface 21321. Correspondingly, the transition surface 2141 on the outer surface of the wall portion 217 that is connected to the second welding surface 21321 may be an annular structure. The second welding surface 21321 can also be an annular region. The second welding surface 21321 is disposed around the outer side of a portion of the outer surface of the wall portion 217, and another portion of the outer surface of the wall portion 217 is disposed around the outer side of the second welding surface 21321. The second welding surface 21321 connects the portion of the outer surface of the wall portion 217 located inside the second welding surface 21321 and the portion of the outer surface of the wall portion 217 located outside the second welding surface 21321. Correspondingly, the inner and outer sides of the second welding surface 21321 are connected to the transition surface 2141. That is, the portion of the outer surface of the wall portion 217 located inside the second welding surface 21321 includes the transition surface 2141 connected to the second welding surface 21321, and the portion of the outer surface of the wall portion 217 located outside the second welding surface 21321 also includes the transition surface 2141 connected to the second welding surface 21321.

[0438] In this embodiment, if the second solder mark 2132 connects the first tab 222 and the wall portion 217, a stable connection between the first tab 222 and the wall portion 217 can be achieved, thereby realizing stable overcurrent between the first tab 222 and the wall portion 217; if the second solder mark 2132 connects the first current collector 25 and the wall portion 217, a stable connection between the first current collector 25 and the wall portion 217 can be achieved, thereby realizing stable overcurrent between the first current collector 25 and the wall portion 217, and reducing the difficulty of electrical connection between the first tab 222 and the wall portion 217. This is achieved by providing a first groove 215 on the second welding surface 21321 of the second solder mark 2132, and a protective layer... The portion 23 is accommodated in the first groove 215 provided on the second welding surface 21321, which helps to improve the stability and firmness of the protective layer 23 covering the second welding surface 21321 of the second welded portion 2132 and the transition surface 2141 connected thereto. This facilitates the long-term protection of the second welded portion 2132 by the protective layer 23, thereby reducing the phenomenon of protection failure caused by the protective layer 23 falling off the second welding surface 21321 and the transition surface 2141 connected thereto in a short period of time. This also reduces the risk of corrosion and rust in the area where the wall portion 217 is welded to the first current collector 25 or the first electrode tab 222 (the second welded portion 2132) during use.

[0439] According to some embodiments of this application, refer to Figure 24 As shown, Figure 24This is a front view of the casing 21 of the battery cell 20 provided in some other embodiments of this application, facing the wall portion 217 along the first direction X. In the projection plane perpendicular to the first direction X, the orthographic projection of the first groove 215 provided on the second welding surface 21321 extends along a planar spiral trajectory.

[0440] Among them, the planar spiral can be an Archimedean spiral or a logarithmic spiral, etc.

[0441] In this embodiment, by setting the first groove 215 on the second welding surface 21321 as a structure in which the orthographic projection in the projection plane perpendicular to the first direction X extends along a planar spiral trajectory, on the one hand, the extension size of the first groove 215 on the second welding surface 21321 can be increased so that more of the protective layer 23 can be accommodated in the first groove 215, thereby further improving the stability and firmness of the protective layer 23 covering the second welding surface 21321 of the second solder mark 2132 and the transition surface 2141 connected thereto. On the other hand, it can reduce the processing difficulty of the first groove 215 and reduce the number of processing times, which is beneficial to improving the processing efficiency of the first groove 215.

[0442] According to some embodiments of this application, refer to Figure 25 and Figure 26 As shown, Figure 25 The casing 21 of the battery cell 20 provided in other embodiments of this application is a front view of the wall portion 217 along the first direction X in other embodiments. Figure 26 This is a front view of the casing 21 of the battery cell 20 provided in some other embodiments of this application, facing the wall portion 217 along the first direction X. In a projection plane perpendicular to the first direction X, the orthographic projection of the first groove 215 provided on the second welding surface 21321 extends circumferentially along the wall portion 217.

[0443] In the projection plane perpendicular to the first direction X, the orthographic projection of the first groove 215 on the second welding surface 21321 can be a ring structure extending around the circumference of the wall portion 217, or the orthographic projection of the first groove 215 on the second welding surface 21321 can be a structure with a distance between the two ends of the wall portion 217 in the circumferential direction, that is, the two ends of the orthographic projection of the first groove 215 on the second welding surface 21321 in the circumferential direction of the wall portion 217 are not connected to each other.

[0444] Optionally, the number of first grooves 215 provided on the second welding surface 21321 can be one or more.

[0445] exist Figure 25In the illustrated embodiment, in the projection plane perpendicular to the first direction X, the orthographic projection of the second solder mark 2132 is annular, and the orthographic projection of the first groove 215 provided on the second welding surface 21321 is also annular, so that the orthographic projection of the first groove 215 provided on the second welding surface 21321 is an annular structure extending circumferentially along the wall portion 217.

[0446] exist Figure 26 In the illustrated embodiment, the orthographic projection of the second solder mark 2132 is arc-shaped in the projection plane perpendicular to the first direction X, and the orthographic projection of the first groove 215 provided on the second welding surface 21321 is also arc-shaped, so that the orthographic projection of the first groove 215 provided on the second welding surface 21321 is a structure in which there is a distance between the two ends in the circumferential direction of the wall portion 217.

[0447] In this embodiment, by setting the first groove 215 on the second welding surface 21321 as a structure in which the orthographic projection in the projection plane perpendicular to the first direction X extends circumferentially along the wall portion 217, on the one hand, the structure of the first groove 215 is simple, the molding difficulty is low, and it is easy to manufacture; on the other hand, the size of the first groove 215 in the circumferential direction of the wall portion 217 is larger, which can reduce the number of first grooves 215 set along the circumferential direction of the wall portion 217 on the second welding surface 21321, which is beneficial to improving production efficiency.

[0448] In some embodiments, refer to Figure 25 and Figure 26 Please refer to further details. Figure 27 As shown, Figure 27 for Figure 26 The image shows a partial enlarged view of the battery cell 20 at point H. The outer casing 21 is cylindrical, with the first direction X parallel to the axial direction of the outer casing 21. The second welding surface 21321 is provided with a plurality of first grooves 215, which are arranged at radial intervals along the outer casing 21.

[0449] For example, the number of first grooves 215 provided on the second welding surface 21321 can be two, three, four, five or more.

[0450] In this embodiment, by providing a plurality of first grooves 215 arranged radially at intervals along the outer shell 21 on the second welding surface 21321, the plurality of first grooves 215 can accommodate more of the protective layer 23, thereby further improving the stability and firmness of the protective layer 23 covering the first welding surface 21311 of the second solder mark portion 2132 and the transition surface 2141 connected thereto, so as to further reduce the phenomenon of the protective layer 23 falling off from the second welding surface 21321 and the transition surface 2141 connected thereto during use.

[0451] In some embodiments, see Figure 26 and Figure 27 As shown, along the radial direction of the outer shell 21, the minimum distance between two adjacent first grooves 215 located on the second welding surface 21321 is D1, which satisfies 0.05mm≤D1≤0.1mm.

[0452] Wherein, D1 is the minimum distance between two adjacent first grooves 215 located on the second welding surface 21321. For example, D1 can be any one of 0.05mm, 0.06mm, 0.07mm, 0.08mm, 0.09mm or 0.1mm or any range between two.

[0453] In this embodiment, on the one hand, the minimum distance between two adjacent first grooves 215 on the second welding surface 21321 is set to be greater than or equal to 0.05mm, so that the minimum distance between two adjacent first grooves 215 on the second welding surface 21321 is not too small. This helps to reduce the risk of the portion of the second solder mark 2132 located between two adjacent first grooves 215 during processing, and also helps to reduce the forming difficulty of the first grooves 215. On the other hand, the minimum distance between two adjacent first grooves 215 on the second welding surface 21321 is set to be greater than or equal to 0.05mm. The minimum distance between the grooves 215 is set to be less than or equal to 0.1 mm, so that the minimum distance between two adjacent first grooves 215 on the second welding surface 21321 is not too large. This allows for more first grooves 215 to be provided on the second welding surface 21321 of the second soldering portion 2132 along the radial direction of the outer shell 21, which helps to increase the density of the first grooves 215. This increases the surface roughness of the second soldering portion 2132, thereby further improving the adhesion effect of the protective layer 23 on the second welding surface 21321 of the second soldering portion 2132.

[0454] According to some embodiments of this application, see Figure 24 as well as Figure 25 As shown, the second solder mark 2132 has a ring structure, the second solder mark 2132 extends circumferentially along the wall 217, and transition portions 214 are connected to both sides of the second solder mark 2132.

[0455] The second solder mark 2132 is an annular structure that extends circumferentially along the wall 217. That is, the second solder mark 2132 is an annular structure that extends circumferentially along the wall 217 and is connected end to end. Correspondingly, the inner and outer sides of the second solder mark 2132 are connected by transition portions 214, so that the inner and outer circumferential surfaces of the second solder mark 2132 are connected to other parts of the wall 217 through two transition portions 214 respectively. The transition portion 214 connected to the inner side of the second solder mark 2132 and the transition portion 214 connected to the outer side of the second solder mark 2132 are both annular structures that extend circumferentially along the wall 217.

[0456] The second solder mark 2132 has an annular structure, making its extension trajectory a closed trajectory. If the second solder mark 2132 is a rectangular ring, its extension trajectory is rectangular; if the second solder mark 2132 is a circular ring, its extension trajectory is circular. It should be noted that when welding the wall portion 217 and the first electrode lug 222 or welding the wall portion 217 and the first current collector 25, welding can be performed continuously along the circumference of the wall portion 217 to form the second solder mark 2132 with an annular structure.

[0457] Optionally, the number of second solder marks 2132 can be one or more. If the number of second solder marks 2132 is multiple, the multiple second solder marks 2132 can be coaxially arranged and radially spaced along the wall portion 217. Similarly, the number of first grooves 215 provided on the second welding surface 21321 of the second solder mark 2132 can be one or more.

[0458] exist Figure 24 In the illustrated embodiment, the projection of the wall portion 217 along the first direction X is circular, the number of the second solder mark portion 2132 is one, and the second solder mark portion 2132 is a ring structure. The second welding surface 21321 is provided with only one first groove 215. In the projection plane perpendicular to the first direction X, the orthographic projection of the first groove 215 provided on the second welding surface 21321 extends along a planar spiral trajectory.

[0459] exist Figure 25 In the illustrated embodiment, the projection of the wall portion 217 along the first direction X is circular, the number of the second solder mark portion 2132 is one, and the second solder mark portion 2132 is a ring structure. The second welding surface 21321 is provided with a plurality of first grooves 215. In the projection plane perpendicular to the first direction X, the orthographic projection of the first groove 215 provided on the second welding surface 21321 extends along the circumference of the wall portion 217, and the plurality of first grooves 215 are arranged at radial intervals along the wall portion 217.

[0460] In this embodiment, by setting the second solder mark 2132 as an annular structure extending circumferentially along the wall 217, it is beneficial to increase the connection area between the second solder mark 2132 and the first current collector 25 or the first electrode 222, thereby improving the connection reliability and flow area between the second solder mark 2132 and the first current collector 25 or the first electrode 222.

[0461] According to some embodiments of this application, see Figure 26 As shown, the wall portion 217 is provided with a plurality of second solder marks 2132, which are spaced apart along the circumference of the wall portion 217, and each second solder mark 2132 is surrounded by a transition portion 214 on its outer periphery.

[0462] The number of second solder marks 2132 can be two, three, four, five or more. The number of first grooves 215 provided on the second welding surface 21321 of the second solder mark 2132 can be one or more.

[0463] exist Figure 26 In the illustrated embodiment, the projection of the wall portion 217 along the first direction X is circular, and there are four second solder marks 2132. The four second solder marks 2132 are arranged at intervals along the circumference of the wall portion 217. Each second solder mark 2132 has a plurality of first grooves 215 on its second welding surface 21321. The plurality of first grooves 215 on the second welding surface 21321 are arranged at intervals along the radial direction of the outer shell 21, and the extension direction of the first grooves 215 on the second welding surface 21321 is consistent with the extension direction of the corresponding second solder mark 2132. Both extend circumferentially along the wall portion 217.

[0464] In this embodiment, the wall portion 217 is provided with a plurality of second solder marks 2132 spaced apart circumferentially along the wall portion 217. This structure enables discontinuous welding of the wall portion 217 with the first electrode tab 222 or the first current collector 25, thereby reducing the welding surface area 213a of the wall portion 217. On the one hand, it can reduce the total heat received by the wall portion 217 during the welding process, which can reduce the area of ​​the heat-affected zone formed near the second solder marks 2132 of the wall portion 217, and reduce the risk of deformation of the wall portion 217 due to overheating during the welding process. On the other hand, it is easier to control the effective penetration depth of each second solder mark 2132 during the welding process, thereby reducing the risk of incomplete welding.

[0465] According to some embodiments of this application, refer to Figure 28 As shown, Figure 28This is a partial cross-sectional view of a battery cell 20 provided in some other embodiments of this application. The wall portion 217 may include a wall body 217a and a third anti-corrosion layer 217b. The wall body 217a is made of steel. The third anti-corrosion layer 217b is disposed on the surface of the wall body 217a. The outer surface of the third anti-corrosion layer 217b is at least a portion of the outer surface of the wall portion 217. Both the wall body 217a and the third anti-corrosion layer 217b are connected to the second solder mark portion 2132.

[0466] The wall body 217a is the base material of the wall portion 217. The wall body 217a can be made of steel, including carbon steel or stainless steel. Carbon steel can be Q195 carbon steel, SPCC carbon steel, etc.; stainless steel can be SUS430 stainless steel, SUS304 stainless steel, SUS316 stainless steel, or modified stainless steel, etc. In this embodiment, the wall body 217a is made of carbon steel. The third anti-corrosion layer 217b is the surface layer of the wall portion 217, and its thickness is less than that of the wall body 217a. The third anti-corrosion layer 217b can be a plating layer applied to the surface of the wall body 217a. The material of the third anti-corrosion layer 217b can include at least one of nickel, aluminum, zinc, etc.

[0467] The outer surface of the third anti-corrosion layer 217b can be the outer surface of the wall portion 217, or the outer surface of the third anti-corrosion layer 217b can be a part of the outer surface of the wall portion 217.

[0468] It is understood that, in embodiments where the end cap 212 includes the wall portion 217, the third anti-corrosion layer 217b may be the second anti-corrosion layer 212b of the end cap 212, and the wall body 217a may be the cap body 212a of the end cap 212; in embodiments where the housing 211 includes the wall portion 217, the third anti-corrosion layer 217b may be a part of the first anti-corrosion layer 211b of the housing 211, and the wall body 217a may be a part of the shell body 211a of the housing 211. Figure 28 In the illustrated embodiment, the end cap 212 is the wall portion 217, and correspondingly, the third anti-corrosion layer 217b is the second anti-corrosion layer 212b, and the wall body 217a is the cap body 212a.

[0469] It should be noted that a portion of the transition portion 214 connecting the wall portion 217 and the second solder mark portion 2132 is located within the wall body 217a, and another portion is located within the third anti-corrosion layer 217b. Correspondingly, the outer surface of the portion of the transition portion 214 connecting the wall portion 217 and the second solder mark portion 2132 located within the third anti-corrosion layer 217b is the transition surface 2141 of the outer surface of the wall portion 217 that connects with the second welding surface 21321.

[0470] In this embodiment, by setting the material of the wall body 217a of the wall portion 217 to include steel, it is beneficial to improve the overall structural strength of the wall portion 217, thereby reducing the risk of damage or deformation of the wall portion 217 during use. The outer surface of the third anti-corrosion layer 217b is at least a part of the outer surface of the wall portion 217, making the third anti-corrosion layer 217b the surface layer of the wall portion 217. The third anti-corrosion layer 217b has better corrosion resistance than the wall body 217a, so that the third anti-corrosion layer 217b can play a certain role in protecting and preventing rust on the steel wall body 217a, thereby giving the wall portion 217 good rust prevention ability.

[0471] In some embodiments, the third anti-corrosion layer 217b includes a nickel layer.

[0472] For example, a portion of the third anti-corrosion layer 217b may be a nickel layer, or the entire third anti-corrosion layer 217b may be a nickel layer.

[0473] In this embodiment, the third anti-corrosion layer 217b includes a nickel layer. Since the nickel layer has good corrosion resistance and high hardness, it can improve the corrosion resistance and wear resistance of the wall 217.

[0474] In some embodiments, please continue to see Figure 28 As shown, the outer surface of the third anti-corrosion layer 217b is provided with a second groove 216, at least a portion of the outer surface of the third anti-corrosion layer 217b is covered by a protective layer 23, and a portion of the protective layer 23 is accommodated within the second groove 216.

[0475] At least a portion of the outer surface of the third anti-corrosion layer 217b is covered by the protective layer 23. Specifically, the protective layer 23 covers at least a portion of the outer surface of the third anti-corrosion layer 217b. The protective layer 23 may cover only a portion of the outer surface of the third anti-corrosion layer 217b; for example, it may cover the outer surface of the portion of the transition portion 214 located within the third anti-corrosion layer 217b, or it may cover the entire outer surface of the third anti-corrosion layer 217b. A second groove 216 is provided on the outer surface of the third anti-corrosion layer 217b, such that the second groove 216 is recessed from the outer surface of the third anti-corrosion layer 217b into the interior of the wall portion 217. The opening of the second groove 216 is formed on the outer surface of the third anti-corrosion layer 217b.

[0476] Optionally, the depth of the second groove 216 provided on the outer surface of the third anti-corrosion layer 217b can be less than or equal to the thickness of the third anti-corrosion layer 217b. Of course, the depth of the second groove 216 provided on the outer surface of the third anti-corrosion layer 217b can also be greater than the thickness of the third anti-corrosion layer 217b, so that the second groove 216 penetrates the third anti-corrosion layer 217b along the depth direction and extends into the wall body 217a.

[0477] In this embodiment, at least a portion of the outer surface of the third anti-corrosion layer 217b is covered with a protective layer 23, so that the area where the protective layer 23 overlaps with the third anti-corrosion layer 217b can provide double protection for the wall body 217a, thereby further reducing the risk of corrosion and rust on the wall body 217a during use. Furthermore, a second groove 216 is provided on the outer surface of the third anti-corrosion layer 217b, and part of the protective layer 23 is accommodated in the second groove 216. This allows the second groove 216 to restrict the protective layer 23 to a certain extent, thereby further improving the stability and firmness of the protective layer 23 on the third anti-corrosion layer 217b of the wall portion 217. On the one hand, it enables the protective layer 23 to provide long-term protection for the area covered by the wall portion 217. On the other hand, it reduces the risk that the part of the protective layer 23 on the second solder mark portion 2132 may easily fall off due to the lifting or falling off of the part of the third anti-corrosion layer 217b on the wall portion 217. This improves the stability of the protective layer 23 in protecting the second solder mark portion 2132 and the transition portion 214.

[0478] In some embodiments, please continue to see Figure 28 As shown, the depth of the second groove 216 provided on the outer surface of the third anti-corrosion layer 217b is less than the thickness of the third anti-corrosion layer 217b. That is to say, the second groove 216 provided on the outer surface of the third anti-corrosion layer 217b does not penetrate the third anti-corrosion layer 217b in the depth direction.

[0479] As an example, the depth of the second groove 216 provided on the outer surface of the third anti-corrosion layer 217b is less than or equal to 0.7 times the thickness of the third anti-corrosion layer 217b.

[0480] In this embodiment, by setting the depth of the second groove 216 on the outer surface of the third anti-corrosion layer 217b to be less than the thickness of the third anti-corrosion layer 217b, the second groove 216 does not penetrate the third anti-corrosion layer 217b in the thickness direction. This reduces the phenomenon of the wall body 217a being exposed in the area of ​​the third anti-corrosion layer 217b where the second groove 216 is provided, so that the area of ​​the third anti-corrosion layer 217b where the second groove 216 is provided can still provide rust protection for the wall body 217a.

[0481] According to some embodiments of this application, please refer to Figure 29 and Figure 30 As shown, Figure 29 This application also provides cross-sectional views of the battery cell 20 in some embodiments. Figure 30 for Figure 29The diagram shows a partial enlarged view of cell J of the battery cell 20. Along the first direction X, the outer surface of the wall portion 217 includes a second surface 2171 facing away from the electrode assembly 22. The wall portion 217 is provided with a first recess 2172, which is recessed from the second surface 2171 towards the electrode assembly 22. The wall surface of the first recess 2172 is a portion of the outer surface of the wall portion 217. The wall surface of the first recess 2172 includes a first bottom surface 2172a, which includes a transition surface 2141. A second solder surface 21321 is connected to the first bottom surface 2172a. A portion of the second solder mark 2132 extends from the first bottom surface 2172a into the wall portion 217 along the direction from the wall portion 217 towards the electrode assembly 22. At least a portion of the protective layer 23 is accommodated within the first recess 2172.

[0482] The second surface 2171 can be the surface of the wall portion 217 furthest from the electrode assembly 22, or it can be closer to the electrode assembly 22 than the surface of the wall portion 217 furthest from the electrode assembly 22. The first recess 2172 is recessed from the second surface 2171 toward the electrode assembly 22. The first recess 2172 can be a structure surrounding the outside of the second surface 2171, or the second surface 2171 can surround the outside of the first recess 2172.

[0483] It is understood that the wall surface of the first recess 2172 and the second surface 2171 are both part of the outer surface of the housing 21. The wall surface of the first recess 2172 defines the internal space of the first recess 2172. The wall surface of the first recess 2172 may also include a first side surface 2172b connected to the first bottom surface 2172a, and the first bottom surface 2172a and the first side surface 2172b together define the internal space of the first recess 2172. Along the first direction X, the wall portion 217 has a third surface 2173 disposed opposite to the second surface 2171. The third surface 2173 faces the electrode assembly 22, and the first bottom surface 2172a may be closer to the electrode assembly 22 than the third surface 2173, or the first bottom surface 2172a may be farther away from the electrode assembly 22 than the third surface 2173. In embodiments where the wall portion 217 has a third anti-corrosion layer 217b, the walls of the second surface 2171 and the first recess 2172 are both part of the outer surface of the third anti-corrosion layer 217b.

[0484] The first bottom surface 2172a includes a transition surface 2141, and the second welding surface 21321 is connected to the first bottom surface 2172a. That is, the bottom wall of the first recess 2172 is welded to the first current collector 25 or the first electrode 222 to form a second solder mark 2132. Correspondingly, the bottom wall of the first recess 2172 forms a transition portion 214 around the second solder mark 2132, and the second welding surface 21321 of the second solder mark 2132 is connected to the transition surface 2141 of the first bottom surface 2172a.

[0485] A portion of the second solder mark 2132 extends from the first bottom surface 2172a into the wall portion 217 along the direction of the wall portion 217 toward the electrode assembly 22. This can be achieved by a portion of the second solder mark 2132 extending from the first bottom surface 2172a into the wall portion 217 along the direction of the wall portion 217 toward the electrode assembly 22, and another portion of the second solder mark 2132 protruding from the first bottom surface 2172a. Alternatively, the second solder surface 21321 can be flush with the first bottom surface 2172a, such that the second solder mark 2132 extends from the first bottom surface 2172a into the wall portion 217 along the direction of the wall portion 217 toward the electrode assembly 22. In an embodiment where the second solder mark 2132 connects the wall portion 217 and the first electrode tab 222, the second solder mark 2132 may also extend into the first electrode tab 222; in an embodiment where the second solder mark 2132 connects the wall portion 217 and the first current collector 25, the second solder mark 2132 may also extend into the first current collector 25.

[0486] At least a portion of the protective layer 23 is accommodated within the first recess 2172. This can be a partial or complete accommodating portion of the protective layer 23 within the first recess 2172. The portion of the protective layer 23 accommodated within the first recess 2172 covers the entire second welding surface 21321. Alternatively, the protective layer 23 may only cover the second welding surface 21321; or it may cover both the second welding surface 21321 and the outer surface of the wall portion 217, for example, the protective layer 23 may cover both the second welding surface 21321 and the first bottom surface 2172a.

[0487] In this embodiment, the wall portion 217 is provided with a first recess 2172, and a portion of the second solder mark portion 2132 extends from the first bottom surface 2172a of the first recess 2172 along the direction of the wall portion 217 toward the electrode assembly 22 into the wall portion 217. This allows the wall portion 217 to be soldered and assembled with the first tab 222 or the first current collector 25 from the outside of the housing 21 during soldering, facilitating observation of the soldering process between the wall portion 217 and the first tab 222 or the first current collector 25. This is beneficial to improving the welding quality of the wall portion 217 and the first electrode ear 222 or the first current collector 25. After the wall portion 217 is welded to the first electrode ear 222 or the first current collector 25, the second solder mark portion 2132 may have a portion protruding from the first bottom surface 2172a. This portion can be accommodated in the first recess 2172 to reduce the phenomenon of the second solder mark portion 2132 protruding from the second surface 2171, which is beneficial to reducing the impact of the second solder mark portion 2132 on the flatness of the second surface 2171. Furthermore, the portion of the protective layer 23 disposed on the second welding surface 21321 of the second solder mark portion 2132 can be accommodated within the first recess 2172, so that the first recess 2172 can provide a certain degree of protection for the protective layer 23, thereby reducing wear or impact on the protective layer 23. This helps to reduce the risk of the protective layer 23 failing to protect the second solder mark portion 2132 due to damage to the protective layer 23. Moreover, the first recess 2172 can play a certain restrictive role in the forming process of the protective layer 23, so that the protective layer 23 can be disposed on the second welding surface 21321 of the second solder mark portion 2132. For example, during the process of coating the outer surface of the outer shell 21 with rust-preventive material to form the protective layer 23, the rust-preventive material can be sprayed into the first recess 2172. The first recess 2172 restricts the rust-preventive material, making it difficult for the rust-preventive material to fall off from the second welding surface 21321, which is conducive to the adhesion of the rust-preventive material to the second solder mark portion 2132.

[0488] In some embodiments, refer to Figure 31 As shown, Figure 31 for Figure 30 The image shows a partial enlarged view of point K of the battery cell 20. A second groove 216 is provided on the first bottom surface 2172a, at least a portion of the first bottom surface 2172a is covered by a protective layer 23, and a portion of the protective layer 23 is accommodated within the second groove 216.

[0489] At least a portion of the first bottom surface 2172a is covered by a protective layer 23, meaning the protective layer 23 covers at least a portion of the first bottom surface 2172a. The protective layer 23 may cover a portion of the first bottom surface 2172a or it may cover the entire first bottom surface 2172a (the protective layer 23 completely covers the first bottom surface 2172a). The first bottom surface 2172a is provided with a second groove 216, such that the second groove 216 is recessed from the first bottom surface 2172a toward the interior of the wall portion 217, and the opening of the second groove 216 is formed on the first bottom surface 2172a.

[0490] Optionally, the portion of the protective layer 23 housed within the second groove 216 disposed on the first bottom surface 2172a may be connected to the groove wall of the second groove 216 disposed on the first bottom surface 2172a, or it may not be connected. The second groove 216 disposed on the first bottom surface 2172a may be a groove structure extending circumferentially along the opening 2111 of the housing 211, or it may be a groove structure extending along a planar helical trajectory. Similarly, the second groove 216 disposed on the first bottom surface 2172a and the first groove 215 disposed on the second welding surface 21321 may be interconnected, allowing them to communicate. Of course, the second groove 216 disposed on the first bottom surface 2172a and the first groove 215 disposed on the second welding surface 21321 may also be spaced apart.

[0491] In this embodiment, at least a portion of the first bottom surface 2172a is covered with a protective layer 23, which not only further increases the connection area between the protective layer 23 and the outer surface of the outer shell 21, but also enables the protective layer 23 to provide a certain degree of protection for the first bottom surface 2172a. This reduces the phenomenon of the protective layer 23 falling off during use and also reduces the risk of corrosion and rust on the part of the wall 217 covered by the protective layer 23 during use. Furthermore, the first bottom surface 2172a is provided with a second groove 216, and part of the protective layer 23 is accommodated in the second groove 216. This allows the second groove 216 to provide a certain degree of restriction on the protective layer 23, thereby further improving the stability and firmness of the protective layer 23 on the first bottom surface 2172a. On the one hand, it enables the protective layer 23 to provide long-term protection for the area covered by the first bottom surface 2172a. On the other hand, it reduces the risk that the part of the protective layer 23 on the second solder mark 2132 may easily fall off due to the part of the protective layer 23 on the first bottom surface 2172a lifting or falling off. This improves the stability of the protective layer 23 in protecting the second solder mark 2132 and the transition part 214.

[0492] According to some embodiments of this application, refer to Figure 30 and Figure 31 Please refer to further details. Figure 32 , Figure 33 and Figure 34 As shown, Figure 32 This application also provides structural schematic diagrams of the wall portion 217 of the outer casing 21 of the battery cell 20 according to some embodiments. Figure 33 for Figure 32 The NN cross-sectional view of the wall portion 217 shown. Figure 34 The following is an axial view of the wall portion 217 of the housing 21 of the battery cell 20 provided in some embodiments of this application. Along the first direction X, the wall portion 217 has a third surface 2173 disposed opposite to the second surface 2171, the third surface 2173 facing the electrode assembly 22. A first protrusion 2174 protruding from the third surface 2173 is formed in the area of ​​the wall portion 217 corresponding to the first recess 2172. The first protrusion 2174 abuts against the first tab 222, and a second solder mark 2132 connects the first tab 222 and the first protrusion 2174. The first protrusion 2174 includes a transition portion 214; or the battery cell 20 further includes a first current collector 25 connected to the first tab 222, the first protrusion 2174 abutting against the first current collector 25, and the second solder mark 2132 connecting the first current collector 25 and the first protrusion 2174. The first protrusion 2174 includes a transition portion 214.

[0493] The first protrusion 2174 can be a structure that is directly connected to the first electrode 222 through the second solder mark 2132, that is, the first protrusion 2174 and the first electrode 222 are welded together to form the second solder mark 2132. Of course, the first protrusion 2174 can also be a structure that is directly connected to the first current collector 25 through the second solder mark 2132, and the first current collector 25 is connected to the first electrode 222, that is, the first protrusion 2174 and the first current collector 25 are welded together to form the second solder mark 2132. It should be noted that the bottom wall of the groove of the first recess 2172 is a part of the first protrusion 2174.

[0494] It is understood that in the embodiment where the second solder mark 2132 is directly connected to the wall portion 217 and the first tab 222, the first protrusion 2174 abuts against the first tab 222, the second solder mark 2132 connects the first tab 222 and the first protrusion 2174 together, and at least a portion of the second solder mark 2132 extends from the first bottom surface 2172a along the direction of the wall portion 217 toward the electrode assembly 22 into the first tab 222; in the embodiment where the second solder mark 2132 is directly connected to the wall portion 217 and the first current collector 25, the first protrusion 2174 abuts against the first current collector 25, the second solder mark 2132 connects the first current collector 25 and the first protrusion 2174 together, and at least a portion of the second solder mark 2132 extends from the first bottom surface 2172a along the direction of the wall portion 217 toward the electrode assembly 22 into the first current collector 25.

[0495] For example, in Figure 30 and Figure 31 In the process, the battery cell 20 may also include a first current collector 25, and the first protrusion 2174 is welded to the first current collector 25 to form a second solder mark 2132.

[0496] As an example, see Figure 30 and Figure 31 As shown, along the first direction X, the first current collector 25 has a contact surface 251 facing away from the electrode assembly 22, the first protrusion 2174 abuts against the contact surface 251, the third surface 2173 is spaced apart from the contact surface 251, and the first bottom surface 2172a is closer to the electrode assembly 22 than the third surface 2173.

[0497] In this embodiment, a first protrusion 2174 protruding from the third surface 2173 is formed in the area corresponding to the first recess 2172 of the wall portion 217. The wall portion 217 with this structure allows the first protrusion 2174 to provide more recessed space for the first recess 2172, which is beneficial to increase the recessed depth of the first recess 2172, thereby further reducing the risk of the second solder mark 2132 protruding from the second surface 2171, and thus further reducing the impact of the second solder mark 2132 on the flatness of the second surface 2171. Furthermore, compared to the structure in which the first protrusion 2174 abuts and connects with the first tab 222 or the first current collector 25, the structure in which the wall portion 217 abuts and connects with the first tab 222 or the first current collector 25 through the first protrusion 2174 abuts and connects with the first tab 222 or the first current collector 25 has a smaller contact area. This makes it easier to ensure the flatness of the surface of the first protrusion 2174 that abuts and connects with the first tab 222 or the first current collector 25, thereby improving the quality of the welding connection between the wall portion 217 and the first tab 222 or the first current collector 25 to form the second solder mark 2132, which helps to reduce the risk of poor soldering.

[0498] According to some embodiments of this application, see Figure 30 , Figure 32 , Figure 33 and Figure 34 As shown, the first recess 2172 is disposed around the outer side of the second surface 2171, and the first protrusion 2174 has an annular structure. Along the first direction X, the surface of the first protrusion 2174 closest to the electrode assembly 22 is the fourth surface 2174a, and the fourth surface 2174a is provided with a flow guide groove 2174b, which penetrates the inner peripheral surface and the outer peripheral surface of the first protrusion 2174.

[0499] In the embodiment where the second solder mark 2132 is directly connected to the wall portion 217 and the first electrode tab 222, the fourth surface 2174a abuts against the first electrode tab 222; in the embodiment where the second solder mark 2132 is directly connected to the wall portion 217 and the first current collector 25, the fourth surface 2174a abuts against the abutting surface 251 of the first current collector 25. As an example, along the first direction X, the fourth surface 2174a is the surface of the wall portion 217 closest to the electrode assembly 22.

[0500] The flow guide groove 2174b penetrates both the inner and outer peripheral surfaces of the first protrusion 2174, meaning that both ends of the flow guide groove 2174b extend to the inner and outer peripheral surfaces of the first protrusion 2174, respectively. There can be one or more flow guide grooves 2174b. If there are multiple flow guide grooves 2174b, they can be spaced apart circumferentially along the wall portion 217. In embodiments where the outer casing 21 is cylindrical, the flow guide groove 2174b can extend radially along the outer casing 21.

[0501] Optionally, the wall portion 217 may be provided with a pressure relief component, with a first recess 2172 and a first protrusion 2174 surrounding the outer side of the pressure relief component. The pressure relief component and the wall portion 217 may be integrally formed or separately configured.

[0502] In this embodiment, the first recess 2172 is disposed around the outer side of the second surface 2171, making the first protrusion 2174 annular. By providing a guide groove 2174b on the fourth surface 2174a of the first protrusion 2174, and the guide groove 2174b having a structure that penetrates the inner circumferential surface and the outer circumferential surface of the first protrusion 2174, the guide groove 2174b can connect the space defined by the inner circumferential surface of the first protrusion 2174 and the space inside the outer casing 21 used to accommodate the electrode assembly 22. This can improve the internal venting smoothness of the battery cell 20 when thermal runaway occurs, thereby reducing the risk of the battery cell 20 bursting or exploding due to local venting during thermal runaway, which is beneficial to improving the reliability of the battery cell 20.

[0503] In some embodiments, refer to Figure 30 , Figure 31 , Figure 32 , Figure 33 and Figure 34 Please refer to further details. Figure 35 As shown, Figure 35This application also provides a front view of the casing 21 of the battery cell 20 along the first direction X facing the wall portion 217 in some embodiments. A second protrusion 2175 is formed in the area of ​​the wall portion 217 corresponding to the guide groove 2174b, protruding from the first bottom surface 2172a. The outer surface of the second protrusion 2175 is a part of the outer surface of the wall portion 217, and a second groove 216 is provided on the outer surface of the second protrusion 2175. Figure 31 As shown in the figure, at least a portion of the outer surface of the second protrusion 2175 is covered with a protective layer 23. Figure 30 (as shown in the figure), and a portion of the protective layer 23 is accommodated within the second groove 216.

[0504] At least a portion of the outer surface of the second protrusion 2175 is covered by a protective layer 23. Specifically, the protective layer 23 covers at least a portion of the outer surface of the second protrusion 2175. The protective layer 23 may cover a portion of the outer surface of the second protrusion 2175 or it may cover the entire outer surface of the second protrusion 2175 (the protective layer 23 completely covers the outer surface of the second protrusion 2175). A second groove 216 is provided on the outer surface of the second protrusion 2175, such that the second groove 216 is recessed from the outer surface of the second protrusion 2175 into the interior of the second protrusion 2175, and the opening of the second groove 216 is formed on the outer surface of the second protrusion 2175.

[0505] The portion of the protective layer 23 housed within the second groove 216 disposed on the outer surface of the second protrusion 2175 may be connected to the groove wall of the second groove 216 disposed on the outer surface of the second protrusion 2175, or it may not be connected.

[0506] Optionally, there may be one or more second protrusions 2175 in the wall portion 217, and the second protrusions 2175 and the guide grooves 2174b are respectively set in the first direction X.

[0507] As an example, there are multiple second protrusions 2175 in the wall portion 217, and the multiple second protrusions 2175 are arranged at intervals along the circumference of the wall portion 217. There are also multiple second solder marks 2132, and the second protrusions 2175 and the second solder marks 2132 are arranged alternately along the circumference of the wall portion 217. The outer surface of the second protrusion 2175 includes a fifth surface 2175a and a first connecting surface 2175b. The fifth surface 2175a is the end face of the second protrusion 2175 away from the first bottom surface 2172a along the first direction X. The first connecting surface 2175b is connected to both ends of the fifth surface 2175a along the circumferential direction of the wall portion 217. The first connecting surface 2175b connects the fifth surface 2175a and the first bottom surface 2172a. Along the first direction X, the fifth surface 2175a is closer to the electrode assembly 22 than the first surface 2122, and the fifth surface 2175a is also closer to the electrode assembly 22 than the second surface 2171. Both the fifth surface 2175a and the first connecting surface 2175b are provided with a second groove 216. In the circumferential direction of the wall portion 217, at least one first groove 215 provided on the second welding surface 21321, at least one second groove 216 provided on the first bottom surface 2172a, at least one second groove 216 provided on the first connecting surface 2175b, and at least one second groove 216 provided on the fifth surface 2175a are sequentially connected.

[0508] In this embodiment, a second protrusion 2175 protruding from the first bottom surface 2172a is formed in the area of ​​the wall portion 217 corresponding to the flow channel 2174b. The wall portion 217 with this structure allows the second protrusion 2175 to provide more recessed space for the flow channel 2174b, which is beneficial to increase the depth of the flow channel 2174b and improve the air guiding capacity of the flow channel 2174b. Furthermore, by covering at least a portion of the outer surface of the second protrusion 2175 with a protective layer 23, the risk of corrosion and rust on the portion of the outer surface of the second protrusion 2175 covered by the protective layer 23 during use can be reduced. Moreover, by providing a second groove 216 on the outer surface of the second protrusion 2175, a portion of the protective layer 23 is accommodated within the second groove 216, which allows the second groove 216 to provide a certain degree of restriction on the protective layer 23. This further enhances the stability and firmness of the protective layer 23 on the wall portion 217. On the one hand, it enables the protective layer 23 to provide long-term protection to the area covered by the second protrusion 2175. On the other hand, it reduces the risk that the portion of the protective layer 23 on the second solder mark portion 2132 may easily fall off due to the lifting or falling off of the portion of the protective layer 23 on the second protrusion 2175. This improves the stability of the protective layer 23 in protecting the second solder mark portion 2132 and the transition portion 214.

[0509] According to some embodiments of this application, see Figure 30 , Figure 32 and Figure 33 As shown, the first recess 2172 is disposed around the outside of the second surface 2171, that is, the first recess 2172 is an annular groove structure, and correspondingly, the first protrusion 2174 is an annular protrusion structure disposed corresponding to the first recess 2172.

[0510] In this embodiment, by setting the first recess 2172 as a structure surrounding the outer side of the second surface 2171, the first recess 2172 is closer to the outer edge of the wall portion 217. This allows the edge region of the wall portion 217 to be welded to the first electrode tab 222 or the first current collector 25, which is beneficial for better utilization of the central region of the wall portion 217. For example, it is beneficial for setting up structures such as pressure relief components in the central region of the wall portion 217.

[0511] In some embodiments, refer to Figure 30 , Figure 32 and Figure 33 Please refer to further details. Figure 36 As shown, Figure 36 for Figure 30 The diagram shows a partial enlarged view of the battery cell 20 at point L. Along the first direction X, the outer surface of the wall portion 217 includes a first surface 2122 facing away from the electrode assembly 22. The first surface 2122 surrounds the outer side of the first recess 2172, and the wall surface of the first recess 2172 connects the first surface 2122 and the second surface 2171. Along the first direction X, the second surface 2171 is further away from the electrode assembly 22 than the first surface 2122.

[0512] In one embodiment where the wall portion 217 has a third anti-corrosion layer 217b, both the first surface 2122 and the second surface 2171 can be part of the outer surface of the third anti-corrosion layer 217b.

[0513] exist Figure 32 , Figure 33 and Figure 36In the middle, the projection of the wall portion 217 along the first direction X is circular. The wall portion 217 is an end cap 212. The end cap 212 is connected to the housing 211 through the first solder mark portion 2131. The first solder surface 21311 connects the first surface 2122 and the first outer peripheral surface 2112 of the housing 211. The wall surface of the first recess 2172 includes a first bottom surface 2172a and two first side surfaces 2172b. The first bottom surface 2172a connects to the two first side surfaces 2172b, and the two first side surfaces 2172b are arranged radially upward on the wall portion 217. One first side surface 2172b is located inside the other first side surface 2172b. Both first side surfaces 2172b are connected to the first bottom surface 2172a through rounded corners. The inner first side surface 2172b is connected to the second surface 2171 through rounded corners, and the outer first side surface 2172b is connected to the first surface 2122 through rounded corners. The rounded corners are part of the wall surface of the first recess 2172. The protective layer 23 covers the entire second welding surface 21321, the entire first bottom surface 2172a, the entire outer surface of the second protrusion 2175, the entire first side surface 2172b connecting the first bottom surface 2172a and the first surface 2122, the entire rounded corner surface connecting the first bottom surface 2172a and the outermost of the two first side surfaces 2172b, the entire first surface 2122, the entire rounded corner surface connecting the first surface 2122 and the first side surface 2172b, the entire first welding surface 21311, and a portion of the first outer peripheral surface 2112 of the housing 211. The first welding surface 21311 is connected to the first surface 2122 at the second edge 21311d. Figure 9 As shown in the diagram, the first welding surface 21311 is connected to the first outer peripheral surface 2112 of the housing 211 at the first edge 21311c. Figure 9 As shown in the diagram, a first groove 215 provided on the first welding surface 21311 extends to a first edge 21311c and a second edge 21311d. A plurality of first grooves 215 provided on the first welding surface 21311 are spaced circumferentially along the opening 2111 of the housing 211. A second groove 216 is provided on both the first surface 2122 of the wall portion 217 and the first outer peripheral surface 2112 of the housing 211. The second groove 216 on the first outer peripheral surface 2112 of the housing 211 connects to two adjacent first grooves 215 provided on the first welding surface 21311. In a projection plane perpendicular to the first direction X, the orthographic projection of the second groove 216 on the first surface 2122 extends along a planar spiral trajectory.

[0514] In some embodiments, see Figure 33As shown, the wall portion 217 is also provided with a third recess 2177 and a pressure relief groove 2178. The third recess 2177 is recessed from the second surface 2171 toward the direction close to the electrode assembly 22. The second surface 2171 is disposed around the outside of the third recess 2177. In the projection plane perpendicular to the first direction X, the orthographic projection of the pressure relief groove 2178 is located in the orthographic projection of the bottom surface of the third recess 2177. The wall portion 217 forms a weak part in the area where the pressure relief groove 2178 is provided. The weak part can be destroyed when the internal pressure of the battery cell 20 reaches a threshold, so as to release the internal pressure of the battery cell 20. Correspondingly, the area of ​​the wall portion 217 where the pressure relief groove 2178 is provided is a pressure relief component, that is, the pressure relief component is integrally formed with the wall portion 217. For example, the pressure relief groove 2178 is an annular groove structure.

[0515] In this embodiment, by setting the second surface 2171 to be further away from the electrode assembly 22 in the first direction X than the first surface 2122, the second surface 2171 can serve as a support surface for the battery cell 20, thereby improving the stability of the battery cell 20 after it is placed on the external support.

[0516] According to some embodiments of this application, please refer to Figure 37 and Figure 38 , Figure 37 This is a cross-sectional view of a battery cell 20 provided in some other embodiments of this application. Figure 38 for Figure 37 A partially enlarged view of point M of the battery cell 20 shown. The second surface 2171 is disposed around the outside of the first recess 2172.

[0517] As an example, the projection of the wall portion 217 along the first direction X is circular, the second surface 2171 is an annular surface, and the first recess 2172 is located in the central region of the wall portion 217. The wall surface of the first recess 2172 may include a first bottom surface 2172a and a first side surface 2172b. The first side surface 2172b surrounds the first bottom surface 2172a, that is, the first side surface 2172b has an annular structure. The first bottom surface 2172a and the first side surface 2172b are connected by a rounded corner surface, and the first side surface 2172b is connected to the second surface 2171 by a rounded corner surface. The rounded corner surface is part of the wall surface of the first recess 2172.

[0518] In this embodiment, by setting the second surface 2171 to a structure surrounding the outside of the first recess 2172, the first recess 2172 is further away from the outer edge of the wall portion 217. On the one hand, this reduces the molding difficulty of the first recess 2172, and on the other hand, it enables the central region of the wall portion 217 to be welded to the first tab 222 or the first current collector 25. This helps to reduce the circumferential extension dimension of the second solder mark 2132 in the wall portion 217, thereby reducing the difficulty of welding and assembling the wall portion 217 with the first tab 222 or the first current collector 25.

[0519] In some embodiments, refer to Figure 37 and Figure 38 Please refer to further details. Figure 39 As shown, Figure 39 for Figure 38 The diagram shows a partial enlarged view of point P of the battery cell 20. The wall portion 217 is provided with a second recess 2176, which is recessed from the second surface 2171 towards the electrode assembly 22. The wall surface of the second recess 2176 is part of the outer surface of the wall portion 217. Along the first direction X, the outer surface of the wall portion 217 includes a first surface 2122 facing away from the electrode assembly 22. The second recess 2176 is disposed around the outside of the second surface 2171, and the first surface 2122 is disposed around the outside of the second recess 2176. The wall surface of the second recess 2176 connects the first surface 2122 and the second surface 2171. Along the first direction X, the second surface 2171 is further away from the electrode assembly 22 than the first surface 2122.

[0520] In one embodiment where the wall portion 217 has a third anti-corrosion layer 217b, the first surface 2122, the second surface 2171, the wall surface of the first recess 2172, and the wall surface of the second recess 2176 can all be part of the outer surface of the third anti-corrosion layer 217b.

[0521] As an example, the second recess 2176 is an annular groove structure. Along the first direction X, the wall portion 217 has a third surface 2173 disposed opposite to the second surface 2171. The third surface 2173 faces the electrode assembly 22. A third protrusion 2179 protruding from the third surface 2173 is formed in the area of ​​the wall portion 217 corresponding to the second recess 2176. The projection of the wall portion 217 along the first direction X is circular. The wall portion 217 is an end cap 212, which is connected to the housing 211 through a first solder joint 2131. Along the first direction X, the end face of the housing 211 near the end cap 212 is a first end face 2113. The first end face 2113 is flush with the first surface 2122. Both the first surface 2122 and the first end face 2113 include a transition surface 2141. The first solder joint 21311 connects the transition surface 2141 of the first surface 2122 and the transition surface 2141 of the first end face 2113. In a projection plane perpendicular to the first direction X, the orthographic projection of the first groove 215 on the first welding surface 21311 extends along a planar spiral trajectory; the orthographic projection of the second groove 216 on the first surface 2122 extends along a planar spiral trajectory; the orthographic projection of the second groove 216 on the first end face 2113 extends along a planar spiral trajectory; the first groove 215 on the first welding surface 21311 connects the second groove 216 on the first surface 2122 and the second groove 216 on the first end face 2113. The protective layer 23 covers the entire first welding surface 21311, and also covers the entire first surface 2122 and the entire first end face 2113. A portion of the protective layer 23 is accommodated in a first groove 215 disposed on the first welding surface 21311 and is connected to the groove wall of the first groove 215 disposed on the first welding surface 21311; a portion of the protective layer 23 is accommodated in a second groove 216 disposed on the first surface 2122 and is connected to the groove wall of the second groove 216 disposed on the first surface 2122; a portion of the protective layer 23 is accommodated in a second groove 216 disposed on the first end face 2113 and is connected to the groove wall of the second groove 216 disposed on the first end face 2113.

[0522] In this embodiment, by configuring the second recess 2176 to surround the outside of the second surface 2171, and configuring the first surface 2122 to surround the outside of the second recess 2176, the wall of the second recess 2176 connects the first surface 2122 and the second surface 2171. This allows the wall 217 to have a certain buffering capacity in the area where the second recess 2176 is located. Therefore, when the second surface 2171 is subjected to external impact, the wall 217 can act as a buffer in the area where the second recess 2176 is located, reducing the risk of damage to the wall 217. Furthermore, by configuring the second surface 2171 to be further away from the electrode assembly 22 in the first direction X compared to the first surface 2122, the second surface 2171 can serve as a support surface for the battery cell 20, improving the stability of the battery cell 20 when placed on the external support.

[0523] According to some embodiments of this application, please refer to Figure 30 and Figure 38 As shown, along the first direction X, the second surface 2171 is the surface of the wall portion 217 furthest from the electrode assembly 22, and the protective layer 23 does not contact the second surface 2171.

[0524] The second surface 2171 is the surface of the wall portion 217 furthest from the electrode assembly 22, so that the second surface 2171 can serve as a supporting surface for the outer casing 21 of the battery cell 20, and the protective layer 23 does not have a portion covering the second surface 2171. As an example, along the direction from the electrode assembly 22 to the wall portion 217, the protective layer 23 does not extend beyond the second surface 2171.

[0525] In this embodiment, the second surface 2171 is the surface of th...

Claims

1. A battery cell, characterized in that, include: The outer casing, made of steel, includes at least one solder mark and at least one transition portion, the transition portion being connected around the solder mark. The outer surface of the solder mark is a welding surface, and the outer surface of the transition portion is a transition surface. The outer surface of the outer casing includes the welding surface and the transition surface. The transition surface is connected to the welding surface and located on the outer periphery of the welding surface. At least some grains within the transition portion are first grains. The longest line among multiple lines connecting any two points on the outer surface of the first grain is the first connecting line. The multiple lines connecting any two points on the outer surface of the first grain also include a second connecting line. The second connecting line is perpendicular to the first connecting line and passes through the midpoint of the first connecting line. The ratio of the length of the first connecting line to the length of the second connecting line is in the range of 1-5. The ratio of the number of first grains to the number of all grains within the transition portion is greater than 50%. Electrode assembly, housed within the housing; as well as A protective layer completely covers the weld surface, and the protective layer covers at least a portion of the transition surface.

2. The battery cell according to claim 1, characterized in that, The protective layer completely covers the transition surface.

3. The battery cell according to claim 1, characterized in that, The welding surface is provided with a first groove, and a portion of the protective layer is accommodated within the first groove.

4. The battery cell according to claim 3, characterized in that, The portion of the protective layer contained within the first groove is connected to the groove wall surface of the first groove.

5. The battery cell according to claim 3, characterized in that, The outer casing includes: The housing has an opening at at least one end in a first direction; An end cap, corresponding one-to-one with the opening, is provided on the opening; Wherein, at least one of the soldering portions includes a first soldering portion, the first soldering portion connects the housing and the end cap, and both the housing and the end cap include the transition portion, the welding surface of the first soldering portion is the first welding surface, the outer surface of the housing and the outer surface of the end cap are both part of the outer surface of the outer shell, and both the outer surface of the housing and the outer surface of the end cap include the transition surface, and the first welding surface connects the outer surface of the housing and the outer surface of the end cap.

6. The battery cell according to claim 5, characterized in that, The first welding surface is connected to the outer surface of the housing at a first edge, and the first welding surface is connected to the outer surface of the end cap at a second edge. The first edge and the second edge are spaced apart along the first direction, and the first groove provided on the first welding surface extends to the first edge and the second edge.

7. The battery cell according to claim 6, characterized in that, The first welding surface is provided with a plurality of first grooves, and the plurality of first grooves provided on the first welding surface are spaced apart circumferentially along the opening.

8. The battery cell according to claim 5, characterized in that, The first groove disposed on the first welding surface extends circumferentially along the opening.

9. The battery cell according to claim 8, characterized in that, The first welding surface is provided with a plurality of first grooves, and the plurality of first grooves provided on the first welding surface are spaced apart along the first direction.

10. The battery cell according to claim 8, characterized in that, The outer shell is cylindrical, the first direction is parallel to the axial direction of the outer shell, and the first welding surface is provided with a plurality of first grooves, which are arranged at radial intervals along the outer shell.

11. The battery cell according to claim 5, characterized in that, In a projection plane perpendicular to the first direction, the orthographic projection of the first groove on the first welding surface extends along a planar spiral trajectory.

12. The battery cell according to claim 5, characterized in that, The first groove disposed on the first welding surface extends along a spiral trajectory, and the central axis of the spiral extends along the first direction.

13. The battery cell according to claim 5, characterized in that, The outer surface of the housing includes a first outer peripheral surface, the first outer peripheral surface includes the transition surface, and the first outer peripheral surface is connected to the first welding surface; The first outer peripheral surface is provided with a second groove, at least a portion of the first outer peripheral surface is covered by the protective layer, and a portion of the protective layer is accommodated within the second groove.

14. The battery cell according to claim 5, characterized in that, Along the first direction, the outer surface of the end cap includes a first surface facing away from the electrode assembly, the first surface including the transition surface, and the first surface being connected to the first welding surface; The first surface is provided with a second groove, at least a portion of the first surface is covered by the protective layer, and a portion of the protective layer is accommodated within the second groove.

15. The battery cell according to claim 5, characterized in that, The outer surface of the housing includes a first outer peripheral surface. Along the first direction, the outer surface of the end cap includes a first surface facing away from the electrode assembly. Both the first outer peripheral surface and the first surface include the transition surface, and the first welding surface connects the first surface and the first outer peripheral surface.

16. The battery cell according to claim 15, characterized in that, The first welding surface includes a rounded corner area, which is connected to the first surface.

17. The battery cell according to claim 5, characterized in that, Along the first direction, the outer surface of the housing includes a first end face, which is the end face of the housing near the end cap. The first end face is connected to the first welding surface, and each of the first end faces includes the transition surface. The first end face is provided with a second groove, at least a portion of the first end face is covered by the protective layer, and a portion of the protective layer is accommodated within the second groove.

18. The battery cell according to claim 5, characterized in that, Along the first direction, the outer surface of the end cap includes a first surface facing away from the electrode assembly, the outer surface of the housing includes a first end face, the first end face is the end face of the housing near the end cap, both the first surface and the first end face include the transition surface, and the first welding surface connects the first surface and the first end face.

19. The battery cell according to claim 5, characterized in that, The first solder mark is an annular structure, extending circumferentially along the opening, and the transition portion is connected to both sides of the first solder mark.

20. The battery cell according to claim 5, characterized in that, The shell includes a shell body and a first anti-corrosion layer. The shell body is made of steel. The first anti-corrosion layer is disposed on the surface of the shell body. The outer surface of the first anti-corrosion layer is at least a part of the outer surface of the shell. Both the shell body and the first anti-corrosion layer are connected to the first weld mark.

21. The battery cell according to claim 20, characterized in that, The first anti-corrosion layer includes a nickel layer.

22. The battery cell according to claim 20, characterized in that, The outer surface of the first anti-corrosion layer is provided with a second groove, at least a portion of the outer surface of the first anti-corrosion layer is covered by the protective layer, and a portion of the protective layer is accommodated within the second groove.

23. The battery cell according to claim 22, characterized in that, The depth of the second groove provided on the outer surface of the first anti-corrosion layer is less than the thickness of the first anti-corrosion layer.

24. The battery cell according to claim 5, characterized in that, The end cap includes a cap body and a second anti-corrosion layer. The cap body is made of steel. The second anti-corrosion layer is disposed on the surface of the cap body. The outer surface of the second anti-corrosion layer is at least a part of the outer surface of the end cap. Both the cap body and the second anti-corrosion layer are connected to the first solder mark.

25. The battery cell according to claim 24, characterized in that, The second anti-corrosion layer includes a nickel layer.

26. The battery cell according to claim 24, characterized in that, The outer surface of the second anti-corrosion layer is provided with a second groove, at least a portion of the outer surface of the second anti-corrosion layer is covered by the protective layer, and a portion of the protective layer is accommodated within the second groove.

27. The battery cell according to claim 26, characterized in that, The depth of the second groove provided on the outer surface of the second anti-corrosion layer is less than the thickness of the second anti-corrosion layer.

28. The battery cell according to claim 3, characterized in that, The housing includes a wall portion, which is disposed opposite to the electrode assembly along a first direction. The electrode assembly includes a main body portion and a first electrode tab, which is connected to one end of the main body portion facing the wall portion in the first direction. At least one of the soldering portions includes a second soldering portion, which is disposed on the wall portion. The wall portion includes the transition portion, and the welding surface of the second soldering portion is a second welding surface. The outer surface of the wall portion is a part of the outer surface of the housing, and the outer surface of the wall portion includes the transition surface. The second welding surface is connected to the outer surface of the wall portion. Wherein, the second solder mark is connected to the first tab; or the battery cell further includes a first current collector, the first current collector is connected to the first tab, and the second solder mark is connected to the first current collector.

29. The battery cell according to claim 28, characterized in that, In a projection plane perpendicular to the first direction, the orthographic projection of the first groove disposed on the second welding surface extends along a planar spiral trajectory.

30. The battery cell according to claim 28, characterized in that, In a projection plane perpendicular to the first direction, the orthographic projection of the first groove disposed on the second welding surface extends circumferentially along the wall portion.

31. The battery cell according to claim 30, characterized in that, The outer shell is cylindrical, and the first direction is parallel to the axial direction of the outer shell; The second welding surface is provided with a plurality of the first grooves, and the plurality of the first grooves provided on the second welding surface are arranged at radial intervals along the outer shell.

32. The battery cell according to claim 31, characterized in that, Along the radial direction of the outer shell, the minimum distance between two adjacent first grooves on the second welding surface is D1, which satisfies 0.05mm≤D1≤0.1mm.

33. The battery cell according to claim 28, characterized in that, The second solder mark is a ring structure, extending circumferentially along the wall, and the transition portion is connected to both sides of the second solder mark.

34. The battery cell according to claim 28, characterized in that, The wall portion is provided with a plurality of second solder marks, which are spaced apart circumferentially along the wall portion, and each second solder mark is surrounded by a transition portion on its outer periphery.

35. The battery cell according to claim 28, characterized in that, The wall portion includes a wall body and a third anti-corrosion layer. The wall body is made of steel. The third anti-corrosion layer is disposed on the surface of the wall body. The outer surface of the third anti-corrosion layer is at least a part of the outer surface of the wall portion. Both the wall body and the third anti-corrosion layer are connected to the second weld mark portion.

36. The battery cell according to claim 35, characterized in that, The third anti-corrosion layer includes a nickel layer.

37. The battery cell according to claim 35, characterized in that, The outer surface of the third anti-corrosion layer is provided with a second groove, at least a portion of the outer surface of the third anti-corrosion layer is covered by the protective layer, and a portion of the protective layer is accommodated within the second groove.

38. The battery cell according to claim 37, characterized in that, The depth of the second groove provided on the outer surface of the third anti-corrosion layer is less than the thickness of the third anti-corrosion layer.

39. The battery cell according to claim 28, characterized in that, Along the first direction, the outer surface of the wall portion includes a second surface facing away from the electrode assembly, the wall portion is provided with a first recess, the first recess is recessed from the second surface toward the electrode assembly, and the wall surface of the first recess is a part of the outer surface of the wall portion; The wall of the first recess includes a first bottom surface, the first bottom surface includes the transition surface, and the second welding surface is connected to the first bottom surface. A portion of the second solder mark extends from the first bottom surface along the wall in a direction pointing towards the electrode assembly into the wall. At least a portion of the protective layer is accommodated within the first recess.

40. The battery cell according to claim 39, characterized in that, The first bottom surface is provided with a second groove, at least a portion of the first bottom surface is covered by the protective layer, and a portion of the protective layer is accommodated within the second groove.

41. The battery cell according to claim 39, characterized in that, Along the first direction, the wall portion has a third surface disposed opposite to the second surface, the third surface being disposed facing the electrode assembly, and a first protrusion protruding from the third surface is formed in the area of ​​the wall portion corresponding to the first recess. Wherein, the first protrusion abuts against the first tab, the second solder mark connects the first tab and the first protrusion, and the first protrusion includes the transition portion; or the battery cell further includes a first current collector, the first current collector is connected to the first tab, the first protrusion abuts against the first current collector, and the second solder mark connects the first current collector and the first protrusion, and the first protrusion includes the transition portion.

42. The battery cell according to claim 41, characterized in that, The first recess is disposed around the outer side of the second surface, and the first protrusion is an annular structure; Wherein, along the first direction, the surface of the first protrusion closest to the electrode assembly is the fourth surface, and the fourth surface is provided with a flow guide groove, which penetrates the inner peripheral surface and the outer peripheral surface of the first protrusion.

43. The battery cell according to claim 42, characterized in that, The area of ​​the wall corresponding to the flow channel has a second protrusion that protrudes from the first bottom surface; Wherein, the outer surface of the second protrusion is a part of the outer surface of the wall portion, the outer surface of the second protrusion is provided with a second groove, at least a portion of the outer surface of the second protrusion is covered by the protective layer, and a portion of the protective layer is accommodated in the second groove.

44. The battery cell according to claim 39, characterized in that, The first recess is disposed around the outer side of the second surface.

45. The battery cell according to claim 44, characterized in that, Along the first direction, the outer surface of the wall portion includes a first surface facing away from the electrode assembly, the first surface being disposed around the outside of the first recess, and the wall surface of the first recess connecting the first surface and the second surface; Along the first direction, the second surface is further away from the electrode assembly than the first surface.

46. ​​The battery cell according to claim 39, characterized in that, The second surface is disposed around the outside of the first recess.

47. The battery cell according to claim 46, characterized in that, The wall portion is provided with a second recess, which is recessed from the second surface toward the electrode assembly, and the wall surface of the second recess is a part of the outer surface of the wall portion; Wherein, along the first direction, the outer surface of the wall portion includes a first surface facing away from the electrode assembly, the second recess is disposed around the outside of the second surface, the first surface is disposed around the outside of the second recess, and the wall surface of the second recess connects the first surface and the second surface, and along the first direction, the second surface is further away from the electrode assembly than the first surface.

48. The battery cell according to claim 39, characterized in that, Along the first direction, the second surface is the surface of the wall portion furthest from the electrode assembly, and the protective layer does not contact the second surface.

49. The battery cell according to claim 48, characterized in that, In a projection plane perpendicular to the first direction, the minimum distance between the orthographic projection of the protective layer and the orthographic projection of the second surface is D2, which satisfies D2≥0.8mm.

50. The battery cell according to claim 28, characterized in that, The outer casing includes: The housing has an opening at at least one end in the first direction; An end cap, corresponding one-to-one with the opening, is provided on the opening; The end cap or the housing includes the wall portion.

51. The battery cell according to claim 50, characterized in that, At least one of the soldering portions includes a first soldering portion, the end cap includes the wall portion, the first soldering portion connects the housing and the end cap, and both the housing and the end cap include the transition portion, the welding surface of the first soldering portion is a first welding surface, the outer surface of the housing and the outer surface of the end cap are both part of the outer surface of the outer shell, and both the outer surface of the housing and the outer surface of the end cap include the transition surface, and the first welding surface connects the outer surface of the housing and the outer surface of the end cap; The protective layer includes a first protective layer and a second protective layer. The first protective layer completely covers the first welding surface and covers at least a portion of the transition surface of the transition portion connected to the first solder mark. A portion of the first protective layer is accommodated in the first groove disposed on the first welding surface. The second protective layer completely covers the second welding surface and covers at least a portion of the transition surface of the transition portion connected to the second solder mark. A portion of the second protective layer is accommodated in the first groove disposed on the second welding surface. The first protective layer and the second protective layer are integrally formed or spaced apart.

52. The battery cell according to claim 51, characterized in that, The minimum distance between the first solder mark and the second solder mark is D3, which satisfies that D3≥1.8mm.

53. The battery cell according to claim 3, characterized in that, The outer surface of the housing also includes a main body surface connected to the welding surface. The main body surface includes the transition surface. The main body surface is provided with a second groove. At least a portion of the main body surface is covered by the protective layer, and a portion of the protective layer is accommodated within the second groove.

54. The battery cell according to claim 53, characterized in that, The transition surface is provided with the second groove.

55. The battery cell according to claim 53, characterized in that, The portion of the protective layer contained within the second groove is connected to the groove wall of the second groove.

56. The battery cell according to claim 53, characterized in that, At least one of the first grooves is in communication with at least one of the second grooves.

57. The battery cell according to claim 53, characterized in that, The outer casing includes: The housing has an opening at at least one end in a first direction; An end cap, corresponding one-to-one with the opening, is provided on the opening; The main body surface includes the outer surface of the housing and the outer surface of the end cap. At least one of the welding surfaces is connected to the outer surface of the housing, and the outer surface of the housing includes the transition surface. The outer surface of the housing is provided with a second groove. At least a portion of the outer surface of the housing is covered with a protective layer, and a portion of the protective layer is accommodated within the second groove.

58. The battery cell according to claim 53, characterized in that, The outer casing includes: The housing has an opening at at least one end in a first direction; An end cap, corresponding one-to-one with the opening, is provided on the opening; The main body surface includes the outer surface of the housing and the outer surface of the end cap. At least one of the welding surfaces is connected to the outer surface of the end cap, and the outer surface of the end cap includes the transition surface. The outer surface of the end cap is provided with a second groove. At least a portion of the outer surface of the end cap is covered with a protective layer, and a portion of the protective layer is accommodated within the second groove.

59. The battery cell according to any one of claims 3-58, characterized in that, The first groove includes a plurality of slots arranged along its extension direction, a portion of the protective layer is accommodated within the slots, and two adjacent slots are connected to each other and form a communication opening at the connection position.

60. The battery cell according to claim 59, characterized in that, The area of ​​the connecting opening is smaller than the area of ​​any cross-section of the groove, and the cross-section is perpendicular to the extension direction of the first groove.

61. The battery cell according to claim 59, characterized in that, Within the cross-section of the groove, the dimension of the groove in the width direction of the first groove gradually decreases along the depth direction of the first groove, and the cross-section is perpendicular to the extension direction of the first groove.

62. The battery cell according to claim 59, characterized in that, Along the depth direction of the first groove, the maximum size of the connecting opening is smaller than the maximum size of the groove portion.

63. The battery cell according to claim 59, characterized in that, Along the width direction of the first groove, the maximum size of the connecting opening is smaller than the maximum size of the groove portion.

64. The battery cell according to claim 59, characterized in that, Along the extension direction of the first groove, the maximum dimension of the groove is L, and along the width direction of the first groove, the maximum dimension of the groove is W, where 1.1 ≤ W / L ≤ 10.

65. The battery cell according to claim 64, characterized in that, 70μm≤W≤90μm, 7μm≤L≤81μm.

66. The battery cell according to any one of claims 3-58, characterized in that, The maximum width of the first groove is W, where 70μm≤W≤90μm.

67. The battery cell according to any one of claims 3-58, characterized in that, The maximum depth of the first groove is H, where 5μm≤H≤20μm.

68. The battery cell according to any one of claims 3-58, characterized in that, The first groove is a laser cleaning tank.

69. The battery cell according to any one of claims 1-58, characterized in that, The protective layer is a coating.

70. The battery cell according to any one of claims 1-58, characterized in that, The outer casing is made of carbon steel.

71. The battery cell according to any one of claims 1-58, characterized in that, The battery cell is a cylindrical battery cell.

72. A battery device, characterized in that, Includes the battery cell as described in any one of claims 1-71.

73. An electrical device, characterized in that, Includes a battery cell as described in any one of claims 1-71, the battery cell being used to provide electrical energy.

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