Battery cell, manufacturing method thereof and electric equipment

Abstract

The embodiment of the invention provides a battery cell, a manufacturing method thereof and electric equipment. The battery cell comprises a shell and an electrode assembly. The first electrode assembly and the second electrode assembly are arranged in a stacked mode in the first direction, the length of the second electrode assembly is larger than that of the first electrode assembly in the second direction, and a first step is formed by the side wall, close to the non-overlapping area, of the first electrode assembly in the second direction and the surface of the non-overlapping area; the shell forms a second step corresponding to the first step, a containing space is formed between the first step and the second step, the second electrode assembly is provided with a first area, and the first area comprises an area overlapped with the containing space in the first direction; wherein in the first area, the difference value of the bonding force between any two second negative pole pieces and the second diaphragm connected with the second negative pole pieces is smaller than or equal to 2N / m, and the bonding force between any second negative pole piece and the second diaphragm connected with the second negative pole piece is larger than or equal to 5N / m. According to the technical scheme, the safety and reliability of the battery cell can be improved.

Description

Technical Field

[0001] The present application relates to the field of battery cell technology, and more specifically, to a battery cell and a manufacturing method thereof, and electrical equipment. Background Art

[0002] In recent years, with the rapid development of new energy technologies, batteries have been widely used in electronic equipment, electric vehicles, electric two-wheelers, power tools and other electrical equipment.

[0003] As the application scenarios of battery cells increase, the shape of the battery cells also changes to meet different setting environments. In the same battery cell, multiple electrode assemblies of different sizes are set, so that two adjacent electrode assemblies form steps. However, in the non-overlapping areas between electrode assemblies of different sizes, due to the different stresses on the overlapping areas and non-overlapping areas, the non-overlapping areas will warp, causing the diaphragm to separate, resulting in a poor electrode interface in the non-overlapping areas. During the charge and discharge cycle, black spots and the risk of metal lithium precipitation may form, resulting in reduced safety and reliability of the battery cell. Summary of the invention

[0004] The present application provides a battery cell and a manufacturing method thereof, and electrical equipment, which can improve the safety and reliability of the battery cell.

[0005] This application is achieved through the following technical solutions:

[0006] In a first aspect, an embodiment of the present application provides a battery cell, which includes a shell and an electrode assembly, wherein the electrode assembly is accommodated in the shell. The electrode assembly includes a first electrode assembly and a second electrode assembly, wherein the first electrode assembly and the second electrode assembly are stacked along a first direction, wherein the length of the second electrode assembly is greater than the length of the first electrode assembly along a second direction, wherein the second electrode assembly has a first surface facing the first electrode assembly and a second surface facing away from the first electrode assembly, wherein the second electrode assembly has an overlapping region overlapping with the first electrode assembly and a non-overlapping region not overlapping with the first electrode assembly along the first direction, wherein the side wall of the first electrode assembly close to the non-overlapping region in the second direction and the first surface of the non-overlapping region form a first step, and the second direction is perpendicular to the first direction; the shell corresponds to the first electrode assembly. A step forms a second step, and a holding space is formed between the first step and the second step. The second electrode assembly has a first area, and the first area includes an area overlapping with the holding space along a first direction, and the first area extends from the first surface to the second surface; wherein the second electrode assembly includes a second positive electrode sheet, a second negative electrode sheet and a second diaphragm, and the second diaphragm is arranged between the second positive electrode sheet and the second negative electrode sheet. In the first area, the difference in bonding strength between any two second negative electrode sheets and the connected second diaphragms is less than or equal to 2N / m; in the first area, the bonding strength between any second negative electrode sheet and the connected second diaphragm is greater than or equal to 5N / m.

[0007] According to the battery cell of the embodiment of the present application, the first electrode assembly and the second electrode assembly form a first step, and the shell forms a second step corresponding to the first step, so as to facilitate the assembly of the electrode assembly and the shell, so that the battery cell is a stepped structure, so that the battery cell can adapt to different application scenarios. During the assembly process of the electrode assembly and the shell, a storage space is formed between the first step of the electrode assembly and the second step of the shell, and the electrolyte can be contained in the storage space, which is conducive to the charge and discharge cycle of the battery cell. When the first electrode assembly and the second electrode assembly are pressurized, the non-overlapping area of ​​the second electrode assembly will be warped toward the first electrode assembly, which is easy to cause the bonding force between the second negative electrode sheet close to the first electrode assembly in the non-overlapping area and the second diaphragm connected to be reduced, especially the second negative electrode sheet closest to the first electrode assembly in the non-overlapping area is debonded from the second diaphragm connected, resulting in a large difference between the maximum and minimum values ​​of the bonding force between all the second negative electrode sheets and the second diaphragm connected in the first area, so that black spots and metal lithium are generated on the surface of the second negative electrode sheet, resulting in low safety and reliability of the battery cell. Since the positive electrode plate is oily, the positive active material contains polyvinylidene fluoride adhesive, and the second diaphragm also contains polyvinylidene fluoride adhesive, the bonding between the second diaphragm and the second positive electrode plate is relatively strong, and the second negative electrode plate and the second diaphragm are more likely to debond. Therefore, the bonding between the second negative electrode plate and the second diaphragm is used to reflect the change in the bonding between the warping electrode plate and the second diaphragm in the non-overlapping area. In the present application, in the first region, the difference in bonding strength between any two second negative electrode sheets and the second diaphragm connected thereto is less than or equal to 2 N / m, the smaller the difference in bonding strength between any two second negative electrode sheets and the second diaphragm connected thereto is, the better the bonding consistency between all second negative electrode sheets in the first region and the second diaphragm connected thereto is. At the same time, in the first region, the bonding strength between any second negative electrode sheet and the second diaphragm connected thereto is greater than or equal to 5 N / m, and all second negative electrode sheets and the second diaphragm connected thereto are less affected by the warping of the non-overlapping region of the second electrode assembly, indicating that the better the bonding effect between the second negative electrode sheet in the first region and the second diaphragm connected thereto is, the consistency of bonding strength between the second negative electrode sheet in the first region and other regions of the second electrode assembly and the second diaphragm connected thereto can be ensured, the bonding strength between the second negative electrode sheet and the second diaphragm connected thereto is greater, the problem of black spots formed on the surface of the second negative electrode sheet and the precipitation of metallic lithium can be improved, the risk of short circuit between the positive and negative electrodes can be reduced, and the safety and reliability of the battery cell can be improved.

[0008] In one or more optional embodiments above, in the first region, the difference in bonding force between any two second negative electrode sheets and the second separator connected thereto is less than or equal to 1.8 N / m.

[0009] The difference in bonding strength between any two second negative electrode sheets and the connected second separators is less than or equal to 1.8 N / m, further improving the safety performance of the battery cell.

[0010] In one or more of the above optional embodiments, the second electrode assembly further has a second region, and along the first direction, the second region overlaps with the first electrode assembly, and the second region extends from the first surface to the second surface; in the first region, the bonding force between any second negative electrode plate and the second connected diaphragm is F1; in the second region, the bonding force between any second negative electrode plate and the second connected diaphragm is F2; ​​satisfying, 0≤F2-F1≤3N / m.

[0011] The difference between the bonding force between any second negative electrode sheet in the second region and the connected second diaphragm and the bonding force between any second negative electrode sheet in the first region and the connected second diaphragm satisfies the above relationship, so that the bonding force consistency between the second region and the first region of the second electrode assembly is good, the warping of the non-overlapping area of ​​the second electrode assembly has little effect on the bonding force between the second negative electrode sheet in the first region and the connected second diaphragm, and the bonding force between the second negative electrode sheets in different areas of the second electrode assembly and the connected second diaphragm is large, which can improve the problem of black spots and precipitation of metallic lithium on the surface of the second negative electrode sheet, can reduce the risk of short circuit between the positive and negative electrodes, and can improve the safety and reliability of the battery cell.

[0012] In one or more of the above optional embodiments, 0≤F2-F1≤2.5N / m.

[0013] When 0≤F2-F1≤2.5N / m, the difference between the bonding force between any second negative electrode sheet in the first region and the connected second diaphragm and the bonding force between any second negative electrode sheet in the second region and the connected second diaphragm is small, further making the warping of the non-overlapping area of ​​the second electrode assembly have less influence on the bonding force between the second negative electrode sheet in the first region and the connected second diaphragm, further improving the problem of black spots and precipitation of metallic lithium on the surface of the second negative electrode sheet.

[0014] In one or more optional embodiments above, in the first region, the bonding force between any second negative electrode plate and the connected second separator is greater than or equal to 10 N / m.

[0015] When the bonding strength between any second negative electrode plate in the first region and the connected second diaphragm is greater than or equal to 10 N / m, the warping of the non-overlapping area of ​​the second electrode assembly has less influence on the bonding strength between the second negative electrode plate in the first region and the connected second diaphragm, which can effectively improve the problem of black spots and metal lithium precipitation on the surface of the second negative electrode plate.

[0016] In one or more of the above optional embodiments, along the first direction, the minimum distance between the electrode assembly and the housing is H, satisfying 0≤H≤5mm.

[0017] The shell has a certain elasticity. By setting the distance between the electrode assembly and the shell along the first direction to be greater than or equal to 0 and less than or equal to 5 mm, the pressure on the shell is facilitated to be transmitted to the electrode assembly along the first direction.

[0018] In one or more of the above optional embodiments, 0.4 mm ≤ H ≤ 3.5 mm.

[0019] When H≥0.4mm, it is easy to assemble the electrode assembly and the shell, and can adapt to processing errors; when H≤3.5mm, the distance between the shell and the electrode assembly is small, which is further conducive to transferring the pressure on the shell to the electrode assembly.

[0020] In one or more of the above optional embodiments, the outer shell includes a first wall and a second wall arranged opposite to each other along a first direction, the first wall has a main body wall and a step wall, along the second direction, the step wall is located at at least one end of the main body wall, the step wall is recessed relative to the main body wall in the direction of the second wall, and the step wall and the main body wall are connected by a connecting wall to form a second step; the second electrode assembly is arranged between the step wall and the second wall, the first electrode assembly is arranged between the main body wall and the second electrode assembly, and the first electrode assembly, the second electrode assembly, the connecting wall and the main body wall form a accommodating space.

[0021] The first wall can be formed into a second step by stamping or injection molding, which is convenient for processing and manufacturing, and the first wall has a high overall strength. The second electrode assembly is arranged between the step wall and the second wall, and the first electrode assembly is arranged between the main body wall and the second electrode assembly, so that the outer shell and the electrode assembly contour match, the outer shell is convenient for protecting the electrode assembly, and the risk of damage to the electrode assembly is reduced.

[0022] In one or more of the above optional embodiments, along the first direction, the first region has a first overlapping region overlapping with the first positive electrode plate, and a second overlapping region overlapping with the step wall.

[0023] The first region extends in the second direction to the region overlapping with the first positive electrode plate and the region overlapping with the step wall. The first region has a larger area, so that the bonding force between the second negative electrode plate near the overlapping region of the second electrode assembly and the first electrode assembly and the connected second diaphragm is larger, which facilitates reducing the risk of black spots forming on the surface of the second negative electrode plate and the precipitation of metallic lithium.

[0024] In one or more optional embodiments above, along the second direction, the distance between the first positive electrode plate and the step wall is L1, the length of the first overlapping area is L2, and the length of the second overlapping area is L3, satisfying L2 / L1≤0.3, L3 / L1≤0.3.

[0025] By setting L2 / L1 to be less than or equal to 0.3, and setting L3 / L1 to be less than or equal to 0.3, the first region and the first positive electrode plate have a certain overlapping area, and the first region and the step wall have a certain overlapping area, so that the bonding force between the second negative electrode plate and the connected second diaphragm is greater, which is beneficial to reduce the risk of black spots forming on the surface of the second negative electrode plate and the precipitation of metallic lithium.

[0026] In one or more optional embodiments above, along the first direction, the projection area of ​​the first region is S1, and the projection area of ​​the second electrode assembly is S2, satisfying 0.001≤S1 / S2≤0.2.

[0027] If the ratio of the projected area of ​​the first region to the projected area of ​​the second electrode assembly is too small, the volume of the accommodating space is too small, and the electrode assembly is likely to cause interference when it is installed in the outer shell, which is not conducive to the assembly of the electrode assembly and the outer shell; if the ratio of the projected area of ​​the first region to the projected area of ​​the second electrode assembly is too large, the volume of the accommodating space is too large, the utilization rate of the internal space of the outer shell is low, and the energy density of the battery cell is low.

[0028] The first region corresponds to the boundary region between the second electrode assembly and the first electrode assembly. By setting the ratio of the projected area of ​​the first region to the projected area of ​​the second electrode assembly to be greater than or equal to 0.001 and less than or equal to 0.2, on the one hand, it is convenient to assemble metallic lithium between the electrode assembly and the outer shell; on the other hand, the internal space utilization rate of the outer shell is higher, and the battery cell has a higher energy density.

[0029] In one or more optional embodiments above, along the first direction, the projection area of ​​the first electrode assembly is S3, and the projection area of ​​the second electrode assembly is S2, satisfying 0.2≤S3 / S2≤0.9.

[0030] If the ratio of the projected area of ​​the first electrode assembly to the projected area of ​​the second electrode assembly is too large, the difference between the size of the first electrode assembly and the size of the second electrode assembly is too small, and the processing and manufacturing are difficult; if the ratio of the projected area of ​​the first electrode assembly to the projected area of ​​the second electrode assembly is too small, the difference between the size of the first electrode assembly and the size of the second electrode assembly is too large, which is not conducive to the design purpose of increasing the energy density of the battery cell by flexible use of space, and if the difference between the size of the first electrode assembly and the size of the second electrode assembly is too large, the area of ​​the junction area between the first electrode assembly and the second electrode assembly, that is, the first area, will be larger, and the problem of uneven force will be more serious.

[0031] By setting the ratio of the projected area of ​​the first electrode assembly to the projected area of ​​the second electrode assembly to be greater than or equal to 0.2 and less than or equal to 0.9, on the one hand, the processing and manufacturing difficulty is lower; on the other hand, the battery cell has a higher energy density, reducing the uneven force in the interface area between the first electrode assembly and the second electrode assembly.

[0032] In a second aspect, an embodiment of the present application further provides an electrical device, which includes a battery cell provided according to any of the above embodiments.

[0033] In a third aspect, an embodiment of the present application further provides a method for manufacturing a battery cell, which is used to manufacture a battery cell provided according to any of the above embodiments, and the method for manufacturing the battery cell comprises: stacking a first electrode assembly and a second electrode assembly along a first direction, wherein the first electrode assembly and the second electrode assembly are both of a laminated structure, and along a second direction, the length of the second electrode assembly is greater than the length of the first electrode assembly, the second direction is perpendicular to the first direction, and a first step is formed at at least one end of the electrode assembly along the second direction; in a hot pressing composite process, pressure is applied to the first electrode assembly by a first pressing block on a side of the first electrode assembly facing away from the second electrode assembly, and pressure is applied to the second electrode assembly by a second pressing block on a side of the second electrode assembly facing away from the first electrode assembly, wherein along the second direction, the second pressing block does not extend beyond the first electrode assembly. In the hot pressing composite process, along the second direction, the first pressing block exceeds the first electrode assembly, and the second pressing block does not exceed the first electrode assembly. When the first pressing block and the second pressing block cooperate to apply pressure to the electrode assembly, the force on the second pressing block acts on the area corresponding to the second electrode assembly and the first electrode assembly. The stress at the junction of the second electrode assembly and the first electrode assembly is balanced, which effectively ensures the consistency of the interface bonding force at the junction of the second electrode assembly and the first electrode assembly. The interface bonding force between the second negative electrode sheet in the first area and the connected second diaphragm is good. In the first area, any two second negative electrode sheets can be realized. The difference in bonding strength with the connected second diaphragm is less than or equal to 2N / m, and the bonding strength between any second negative electrode plate and the connected second diaphragm can be greater than or equal to 5N / m. The smaller the difference in bonding strength between any two second negative electrode plates and the connected second diaphragms is, the less impact of the warping of the non-overlapping areas of the second electrode assembly will be on all second negative electrode plates and the connected second diaphragms. The better the bonding effect between the second negative electrode plate in the first area and the connected second diaphragm, the problem of black spots and metal lithium precipitation on the surface of the second negative electrode plate can be significantly improved, which is beneficial to improving the performance of the battery cell.

[0034] In one or more optional embodiments above, along the second direction, the second pressing block does not exceed the first electrode assembly; along the first direction, the projection area of ​​the first electrode assembly is S3, and the projection area of ​​the second pressing block is S4, satisfying 0.8≤S4 / S3≤1.

[0035] The ratio of the projected area of ​​the second pressing block along the first direction to the projected area of ​​the first electrode assembly along the first direction is set to be greater than or equal to 0.8 and less than or equal to 1. Under the cooperation of the pressure applied by the first pressing block to the first electrode assembly and the pressure applied by the second pressing block to the second electrode assembly, the first electrode assembly and the second electrode assembly are subjected to balanced force, so as to ensure the force consistency between the first area and other areas of the second electrode assembly.

[0036] In one or more of the above optional embodiments, the Shore hardness of the second pressing block is 30HA-90HA.

[0037] The Shore hardness of the second pressing block is set to be greater than or equal to 30HA and less than or equal to 90HA, so as to facilitate uniform pressure transmission and ensure balanced force on the second electrode assembly.

[0038] In one or more of the above optional embodiments, the method for manufacturing a battery cell further includes: in a formation process, pressure is applied to the first electrode assembly by a third pressing block on a side of the first electrode assembly facing away from the second electrode assembly, the third pressing block does not extend beyond the first electrode assembly along the second direction, pressure is applied to the second electrode assembly by a fourth pressing block on a side of the second electrode assembly facing away from the first electrode assembly, and pressure is applied to a portion of the second electrode assembly that exceeds the first electrode assembly on the side of the first electrode assembly along the second direction by a fifth pressing block.

[0039] In the formation process, along the second direction, the third pressing block does not exceed the first electrode assembly, the fourth pressing block exceeds the first electrode assembly, and the fifth pressing block is located on the side of the first electrode assembly along the second direction. When the third pressing block, the fifth pressing block and the fourth pressing block cooperate to apply pressure to the electrode assembly, the force on the third pressing block directly acts on the first electrode assembly, and the first electrode assembly is evenly stressed. The fifth pressing block acts on the area of ​​the second electrode assembly that exceeds the first electrode assembly, and the stress at the junction of the second electrode assembly and the first electrode assembly is balanced, which effectively ensures the consistency of the interface bonding force at the junction of the second electrode assembly and the first electrode assembly. The interface of the second negative electrode plate in the first area and the connected second diaphragm The bonding force is good. In the first area, the difference in bonding force between any two second negative electrode sheets and the second diaphragm connected thereto can be less than or equal to 2N / m, and the bonding force between any second negative electrode sheets and the second diaphragm connected thereto can be greater than or equal to 5N / m. The smaller the difference in bonding force between any two second negative electrode sheets and the second diaphragm connected thereto is, the less influence of the warping of the non-overlapping area of ​​the second electrode assembly on all second negative electrode sheets and the second diaphragm connected thereto is, and the better the bonding effect between the second negative electrode sheets and the second diaphragm connected thereto in the first area, the problem of black spots formed on the surface of the second negative electrode sheets and the precipitation of metallic lithium can be significantly improved, which is beneficial to improving the performance of the battery cell.

[0040] In one or more optional embodiments above, along the second direction, the third pressing block does not exceed the first electrode assembly; along the first direction, the projection area of ​​the first electrode assembly is S3, and the projection area of ​​the third pressing block is S5, satisfying 0.75≤S5 / S3≤0.95.

[0041] The ratio of the projected area of ​​the third pressing block along the first direction to the projected area of ​​the first electrode assembly along the first direction is set to be greater than or equal to 0.75 and less than or equal to 0.95. With the cooperation of the third pressing block, the fifth pressing block and the fourth pressing block, the first electrode assembly and the second electrode assembly are subjected to balanced force, thereby ensuring the force consistency between the first area and other areas of the second electrode assembly.

[0042] In one or more optional embodiments above, in the formation process, pressure is applied to the first electrode assembly by a third pressing block on a side of the first electrode assembly facing away from the second electrode assembly, and the third pressing block does not exceed the first electrode assembly along the second direction; pressure is applied to the second electrode assembly by a fourth pressing block on a side of the second electrode assembly facing away from the first electrode assembly, and before pressure is applied to a portion of the second electrode assembly that exceeds the first electrode assembly by a fifth pressing block on the side of the first electrode assembly along the second direction, the method for manufacturing the battery cell further includes: placing the first electrode assembly and the second electrode assembly in a casing.

[0043] Before the chemical formation process, the first electrode assembly and the second electrode assembly after hot pressing and compounding are placed in a shell to protect the electrode assembly and inject electrolyte into the shell to facilitate the chemical formation operation.

[0044] In one or more optional embodiments above, the housing includes a first wall and a second wall arranged opposite to each other along a first direction, the first wall includes a main body wall and a step wall, along the second direction, the step wall is located at at least one end of the main body wall, the step wall is recessed relative to the main body wall toward the second wall, the step wall and the main body wall are connected by a connecting wall to form a second step, the second electrode assembly is arranged between the step wall and the second wall, and the first electrode assembly is arranged between the main body wall and the second electrode assembly;

[0045] Along the second direction, the first pressing block does not exceed the first electrode assembly;

[0046] In the formation process, on the side of the first electrode assembly facing away from the second electrode assembly, a pressure is applied to the first electrode assembly through a third pressing block, and along the second direction, the third pressing block does not exceed the first electrode assembly; on the side of the second electrode assembly facing away from the first electrode assembly, a pressure is applied to the second electrode assembly through a fourth pressing block, and on the side of the first electrode assembly along the second direction, a pressure is applied to the portion of the second electrode assembly exceeding the first electrode assembly through a fifth pressing block, including:

[0047] During the formation process, on the side of the first electrode assembly facing away from the second electrode assembly, the third pressing block is pressed against the main wall to apply pressure to the first electrode assembly, and along the second direction, the third pressing block does not exceed the first electrode assembly; on the side of the second electrode assembly facing away from the first electrode assembly, the fourth pressing block is pressed against the second wall to apply pressure to the second electrode assembly; and on the side of the first electrode assembly along the second direction, the fifth pressing block is pressed against the step wall to apply pressure to the portion of the second electrode assembly that exceeds the first electrode assembly.

[0048] The third pressing block and the fifth pressing block are separately arranged, and the third pressing block is used to press the main body wall to apply pressure to the first electrode assembly. Combined with the fifth pressing block pressing the step wall to apply pressure to the portion of the second electrode assembly that exceeds the first electrode assembly, the consistency of the interfacial bonding force at the junction of the second electrode assembly and the first electrode assembly can be effectively guaranteed, so that the internal interface of the electrode assembly of the battery cell is effectively bonded, which significantly improves the problem of black spots and metal lithium precipitation on the surface of the second negative electrode plate, and is beneficial to improving the performance of the battery cell.

[0049] In one or more optional embodiments above, along the first direction, the projection area of ​​the fifth pressing block is S6, and the projection area of ​​the portion of the second electrode assembly exceeding the first electrode assembly is S7, satisfying 0.8≤S6 / S7≤1.

[0050] The ratio of the projected area of ​​the fifth pressing block along the first direction to the projected area of ​​the portion of the second electrode assembly extending beyond the first electrode assembly is set to be greater than or equal to 0.8 and less than or equal to 1, so that the first electrode assembly and the second electrode assembly are subjected to balanced force, thereby ensuring the consistency of force between the first area and other areas of the second electrode assembly.

[0051] In one or more of the above optional embodiments, the Shore hardness of the fifth pressing block is 30HA-90HA.

[0052] The Shore hardness of the fifth pressing block is set to be greater than or equal to 30HA and less than or equal to 90HA, so as to facilitate uniform pressure transmission and balance the force on the second electrode assembly. In one or more optional embodiments above, the material of any one of the second pressing block, the third pressing block and the fifth pressing block is at least one of polyurethane, silicone rubber, ethylene propylene rubber, butyl rubber, chloroprene rubber, nitrile rubber, styrene butadiene rubber, fluororubber, nylon 6, nylon 66, polyethylene, polypropylene, polyethylene terephthalate, polybutylene terephthalate, polycarbonate or polystyrene.

[0053] The material of the second pressing block, the third pressing block or the fifth pressing block is at least one of the above materials, which has a good supporting effect and is conducive to uniform pressure transmission.

[0054] In one or more of the above optional embodiments, the method for manufacturing a battery cell further includes:

[0055] In the formation process, pressure is applied to the first electrode assembly through a third pressing block on a side of the first electrode assembly facing away from the second electrode assembly. The third pressing block is divided into a first part and a second part along a second direction. Along the first direction, the first part overlaps with the first electrode assembly, and the second part does not overlap with the first electrode assembly. The thickness of the second part is greater than that of the first part. The second part applies pressure to the second electrode assembly. The Shore hardness of the third pressing block is 30HA to 90HA. The thickness of the second part exceeding the first part along the first direction is greater than the thickness of the first electrode assembly.

[0056] The third pressing block may be a special-shaped pressing block, and the Shore hardness of the third pressing block is 30HA to 90HA. Since the size of the first electrode assembly in the second direction is smaller than that of the second electrode assembly, there is a space in the thickness direction in the non-overlapping area of ​​the first electrode assembly and the second electrode assembly. When the third pressing block is made into a special-shaped pressing block, the third pressing block is divided into a first part and a second part along the second direction. When observed along the first direction, the first part overlaps with the first electrode assembly, and the second part does not overlap with the first electrode assembly. The thickness of the second part is large, and pressure can be applied to the second electrode assembly. However, when the material of the third pressing block is relatively hard and the Shore hardness is greater than 90HA, it is difficult to strictly control the size of the battery cell during the process. The shrinkage of the battery cell and the deviation of the process operation may cause errors. Therefore, if the Shore hardness of the third pressing block is high, one of the electrode assemblies will have a poor pressure effect. The Shore hardness of the third pressing block is made low, and the thickness of the second part minus the thickness of the first part is greater than the thickness of the first electrode assembly. It can be ensured that when the second electrode assembly is pressed, the first electrode assembly can also be pressed by relying on the elasticity of the third pressing block. If the Shore hardness is too low, it may lead to poor pressure transmission.

[0057] In one or more of the above optional embodiments, the material of the second pressing block or the third pressing block is at least one of polyurethane, silicone rubber, ethylene propylene rubber, butyl rubber, chloroprene rubber, nitrile rubber, styrene butadiene rubber, fluororubber, nylon 6, nylon 66, polyethylene, polypropylene, polyethylene terephthalate, polybutylene terephthalate, polycarbonate or polystyrene.

[0058] The material of the second pressing block or the third pressing block is at least one of the above materials, which has a good supporting effect and is conducive to uniform pressure transmission.

[0059] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become apparent from the description below, or will be learned through the practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0061] Figure 1 A three-dimensional diagram of a battery cell provided in some embodiments of the present application;

[0062] Figure 2 A three-dimensional diagram of an electrode assembly provided for some embodiments of the present application;

[0063] Figure 3 A schematic diagram of the structure of an electrode assembly provided in some embodiments of the present application;

[0064] Figure 4 A schematic diagram of a partial structure of a battery cell provided in some embodiments of the present application;

[0065] Figure 5 A schematic diagram of a process for manufacturing a battery cell provided in some embodiments of the present application;

[0066] Figure 6 A schematic diagram of the composite state of the electrode assembly in the hot pressing composite process provided in some embodiments of the present application;

[0067] Figure 7 A schematic diagram of the composite state of the electrode assembly in the hot pressing composite process provided in some other embodiments of the present application;

[0068] Figure 8 A schematic diagram of a pressurized state of a battery cell in a formation process provided in some embodiments of the present application;

[0069] Fig. 9 A schematic diagram of a process for manufacturing a battery cell provided in some other embodiments of the present application;

[0070] Fig.10 A schematic flow chart of a method for manufacturing a battery cell provided in some embodiments of the present application;

[0071] Fig.11 Schematic diagram of the pressurized state of the battery cell during the formation process.

[0072] Icon: 100-battery cell; 1-housing; 11-second step; 12-first wall; 121-main body wall; 122-step wall; 123-connecting wall; 124-straight section; 125-arc section; 13-second wall; 14-third wall; 15-fourth wall; 16-fifth wall; 2-electrode assembly; 2a-first electrode assembly; 21a-first positive electrode sheet; 22a-first negative electrode sheet; 23a-first diaphragm; 2b-first Two electrode assemblies; 21-first surface; 22-second surface; 23-first step; 24-first area; 241-first end; 242-second end; 25-second area; 26-third area; 3-accommodating space; 4-upper pressing block; 41-first pressing block; 42-third pressing block; 43-fifth pressing block; 5-lower pressing block; 51-second pressing block; 52-fourth pressing block; X-third direction; Y-second direction; Z-first direction. DETAILED DESCRIPTION

[0073] In order to make the purpose, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments.

[0074] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as those commonly understood by technicians in the technical field of this application; the terms used in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" in the specification and claims of this application and the above-mentioned drawings and any variations thereof are intended to cover non-exclusive inclusions. The terms "first", "second", etc. in the specification and claims of this application or the above-mentioned drawings are used to distinguish different objects, rather than to describe a specific order or a primary and secondary relationship.

[0075] Reference to "embodiments" in this application means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described in this application may be combined with other embodiments.

[0076] In the description of this application, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", and "attached" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be the internal communication of two elements. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0077] The term "and / or" in this application is only a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this application generally indicates that the associated objects before and after are in an "or" relationship.

[0078] The term "multiple" as used in this application refers to more than two (including two). Similarly, "multiple groups" refers to more than two groups (including two groups), and "multiple sheets" refers to more than two sheets (including two sheets).

[0079] At present, judging from the development of the market situation, the application of battery cells is becoming more and more extensive. Battery cells are widely used in electric vehicles such as electric bicycles, electric motorcycles, electric vehicles, as well as in many fields such as electric tools, mobile phones, tablets, drones, energy storage equipment, etc. With the increase in the application scenarios of battery cells, in order to meet different setting environments, the shape of the battery cells has also changed. For example, the battery cell is stepped. In the same battery cell, multiple electrode assemblies of different sizes are set, so that two adjacent electrode assemblies form steps. For example, the first step is formed at the junction of the large and small electrode assemblies. Due to the large hardness of the outer shell, in order to assemble the electrode assembly with the outer shell, the outer shell forms a second step corresponding to the first step, so that the contour of the outer shell matches the contour of the electrode assembly. However, during the manufacturing process of the battery cell, pressure is applied to the battery cell. For example, before the electrode assembly is installed in the casing, the electrode assembly is hot-pressed and composited. Usually, two parallel pressing blocks of equal length are used to pressurize the electrode assembly. For example, the upper pressing block acts on the small electrode assembly, and the lower pressing block acts on the large electrode assembly. In the direction in which the large electrode assembly exceeds the small electrode assembly, the upper pressing block extends out of the small electrode assembly. The force application position of the upper pressing block is in the middle of the upper pressing block, and the electrode assembly has a stepped structure. Since the portion of the large electrode assembly exceeding the small electrode assembly is not constrained by the upper pressing block, the junction between the large electrode assembly and the small electrode assembly is not subjected to force as other areas of the large electrode assembly The portion of the large electrode assembly that extends beyond the small electrode assembly is lifted toward the small battery cell due to the pressure transmitted by the pressing block, which makes the bonding force between the interface between the large electrode assembly and the small electrode assembly and other areas of the large electrode assembly inconsistent, especially the bonding force between the electrode piece closest to the small electrode assembly at the interface between the large electrode assembly and the small electrode assembly and the connected diaphragm is most affected, making the difference between the maximum and minimum values ​​of the bonding force between the electrode piece and the diaphragm at the interface between the large electrode assembly and the small electrode assembly large, resulting in the weakening of the bonding force between the electrode piece and the diaphragm at the interface, and the electrode piece closest to the small electrode assembly at the interface between the large electrode assembly and the small electrode assembly is easy to debond from the diaphragm. Because the positive electrode sheet is oily, the positive active material contains polyvinylidene fluoride adhesive, and the diaphragm also contains polyvinylidene fluoride adhesive, the adhesion between the diaphragm and the positive electrode sheet is relatively strong. When the non-overlapping area of ​​the large electrode assembly is warped, the adhesion between the negative electrode sheet and the diaphragm is lost faster, and the negative electrode sheet is more likely to debond from the diaphragm. Therefore, the adhesion between the negative electrode sheet and the diaphragm is used to reflect the effect of the warping in the non-overlapping area on the adhesion between the electrode sheet and the diaphragm. Furthermore, due to the weakening of the adhesion between the negative electrode sheet and the diaphragm, or even the debonding of the negative electrode sheet and the diaphragm, during the charge and discharge cycle, the surface of the negative electrode sheet at the junction of the large electrode assembly and the small electrode assembly is prone to form black spots and metal lithium precipitation, resulting in low safety and reliability of the battery cell; therefore, the size of the adhesion between the negative electrode sheet and the diaphragm affects the safety and reliability of the battery cell.Although a special-shaped upper pressing block is used in the formation process, the height of the special-shaped upper pressing block and the large electrode assembly exceeding the corresponding area of ​​the small electrode assembly is basically equal to the thickness of the small electrode assembly, and there is a height difference between the special-shaped upper pressing block. However, since the special-shaped upper pressing block is an integrated structure and the pressing block adopts a metal pressing block with higher hardness, it is difficult to strictly control the size of the battery cell 100 when applying pressure during the process. The special-shaped upper pressing block cannot simultaneously apply appropriate force to the large electrode assembly and the small electrode assembly, and the special-shaped upper pressing block cannot act on the area where the large electrode assembly overlaps with the accommodating space, which still causes uneven force on the junction part of the large electrode assembly and the small electrode assembly and other areas of the large electrode assembly, causing the area where the large electrode assembly overlaps with the accommodating space to warp toward the small electrode assembly, resulting in weakening the bonding force between the negative electrode sheet and the diaphragm in this area, especially the bonding force between the negative electrode sheet closest to the small electrode assembly in this area and the diaphragm is the smallest. During the charge and discharge cycle, black spots and metallic lithium precipitation may appear on the surface of the negative electrode sheet in this area, resulting in low safety and reliability of the battery cell.

[0080] Based on the above considerations, in order to solve the problem of low safety and reliability of the battery cell due to black spots and metal lithium precipitation at the combined interface between electrode assemblies of different sizes, an embodiment of the present application provides a battery cell, which includes a shell and an electrode assembly, and the electrode assembly is accommodated in the shell. The electrode assembly includes a first electrode assembly and a second electrode assembly, the first electrode assembly and the second electrode assembly are stacked along a first direction, along the second direction, the length of the second electrode assembly is greater than the length of the first electrode assembly, the second electrode assembly has a first surface facing the first electrode assembly and a second surface away from the first electrode assembly, along the first direction, the second electrode assembly has an overlapping area overlapping with the first electrode assembly, and a non-overlapping area that does not overlap with the first electrode assembly, the side wall of the first electrode assembly close to the non-overlapping area in the second direction and the first surface of the non-overlapping area form a first step, and the second direction is perpendicular to the first direction; the shell corresponds to the first electrode assembly. A step forms a second step, and a holding space is formed between the first step and the second step. The second electrode assembly has a first area, and the first area includes an area overlapping with the holding space along a first direction, and the first area extends from the first surface to the second surface; wherein the second electrode assembly includes a second positive electrode sheet, a second negative electrode sheet and a second diaphragm, and the second diaphragm is arranged between the second positive electrode sheet and the second negative electrode sheet. In the first area, the difference in bonding strength between any two second negative electrode sheets and the connected second diaphragms is less than or equal to 2N / m; in the first area, the bonding strength between any second negative electrode sheet and the connected second diaphragm is greater than or equal to 5N / m.

[0081] In the above-mentioned battery cell, the first electrode assembly and the second electrode assembly form a first step, and the shell forms a second step corresponding to the first step, so as to facilitate the assembly of the electrode assembly and the shell, so that the battery cell has a stepped structure, so that the battery cell can adapt to different application scenarios. During the assembly process of the electrode assembly and the shell, a storage space is formed between the first step of the electrode assembly and the second step of the shell, and the storage space can accommodate electrolyte, which is conducive to the charge and discharge cycle of the battery cell. In the first region, the difference in adhesion between any two second negative electrode sheets and the second diaphragm connected thereto is less than or equal to 2 N / m, the smaller the difference in adhesion between any two adhesive forces, the better the adhesion consistency between all second negative electrode sheets and the second diaphragm connected thereto in the first region; at the same time, in the first region, the adhesion between any second negative electrode sheet and the second diaphragm connected thereto is greater than or equal to 5 N / m, and all second negative electrode sheets and the second diaphragm connected thereto in the first region are less affected by the warping of the non-overlapping region, indicating that the better the adhesion effect between the second negative electrode sheet in the first region and the second diaphragm connected thereto, the adhesion consistency between the first region and other regions of the second electrode assembly can be ensured, the second negative electrode sheet and the second diaphragm connected thereto have greater adhesion, which can improve the problem of black spots formed on the surface of the second negative electrode sheet and the precipitation of metallic lithium, can reduce the risk of short circuit between the positive and negative electrodes, and can improve the safety and reliability of the battery cell.

[0082] The battery cell disclosed in the embodiments of the present application can be used in, but not limited to, electric two-wheeled vehicles, electronic equipment, electric tools, drones, energy storage equipment and other electrical equipment. The battery cell disclosed in the present application can also be used as a power supply system for electrical equipment, which is conducive to improving the safety performance of the battery cell.

[0083] The present application provides an electric device using a battery cell as a power source, and the electric device may be, but is not limited to, electronic equipment, electric tools, electric vehicles, drones, and energy storage devices. Among them, electronic equipment may include mobile phones, tablets, laptops, etc., electric tools may include electric drills, electric saws, etc., and electric vehicles may include electric cars, electric motorcycles, electric bicycles, etc.

[0084] The structure of the battery cell provided in the embodiments of the present application will be described below with reference to the accompanying drawings.

[0085] Please refer to Figures 1 to 4 An embodiment of the present application provides a battery cell 100 , which includes a housing 1 and an electrode assembly 2 , wherein the electrode assembly 2 is accommodated in the housing 1 .

[0086] The housing 1 has a space for accommodating the electrode assembly 2, and the electrode assembly 2 and the electrolyte are accommodated in the space. The housing 1 can be a hard shell, for example, the housing 1 can be a steel shell, an aluminum shell, a hard plastic shell, etc., and the battery cell 100 is a hard shell battery cell 100.

[0087] The electrode assembly 2 includes a positive electrode sheet, a negative electrode sheet and a separator, and the separator is disposed between the positive electrode sheet and the negative electrode sheet to insulate and separate the positive electrode sheet and the negative electrode sheet, thereby reducing the risk of short circuit of the battery cell 100. The separator may be made of polypropylene or polyethylene.

[0088] The electrode assembly 2 is a laminated structure, in which the positive electrode sheet, the separator and the negative electrode sheet are laminated in a certain order.

[0089] Please refer to Figure 2 and Figure 3 The electrode assembly 2 includes a first electrode assembly 2a and a second electrode assembly 2b, which are stacked along a first direction Z, and the first direction Z may be parallel to the thickness direction of the battery cell 100. The first electrode assembly 2a includes a first positive electrode sheet 21a, a first negative electrode sheet 22a, and a first separator 23a, which are stacked along the first direction Z, and the first separator 23a is disposed between the first positive electrode sheet 21a and the first negative electrode sheet 22a. The second electrode assembly 2b includes a second positive electrode sheet, a second negative electrode sheet, and a second separator, which are stacked along the first direction Z, and the second separator is disposed between the second positive electrode sheet and the second negative electrode sheet.

[0090] Along the second direction Y, the length of the second electrode assembly 2b is greater than the length of the first electrode assembly 2a, and at least one end of the second electrode assembly 2b exceeds the first electrode assembly 2a. The second electrode assembly 2b can be called a large electrode assembly, and the first electrode assembly 2a can be called a small electrode assembly. The second direction Y is perpendicular to the first direction Z, and the second direction Y can be parallel to the length direction of the battery cell 100, or the second direction Y can be parallel to the width direction of the battery cell 100.

[0091] Please refer to Figure 2 and Figure 3 The second electrode assembly 2b has a first surface 21 facing the first electrode assembly 2a and a second surface 22 facing away from the first electrode assembly 2a. Along the first direction Z, the second electrode assembly 2b has an overlapping region overlapping with the first electrode assembly 2a and a non-overlapping region not overlapping with the first electrode assembly 2a. The side wall of the first electrode assembly 2a near the non-overlapping region and the first surface 21 of the non-overlapping region in the second direction Y form a first step 23. The first surface 21 and the second surface 22 are parallel to each other, and the first surface 21 and the second surface 22 are both arranged perpendicular to the first direction Z. The first step 23 can be located at one end of the electrode assembly 2 in the second direction Y, or at both ends of the electrode assembly 2 in the second direction Y.

[0092] Please refer to Figure 1 and Figure 4The outer shell 1 corresponds to the shape of the electrode assembly 2, and the outer shell 1 forms a second step 11 corresponding to the first step 23, and a receiving space 3 is formed between the first step 23 and the second step 11. The surface of the second step 11 facing the inside of the battery cell 100, the first step 23, and other wall portions of the outer shell 1 enclose the receiving space 3.

[0093] The outer shell 1 is a hard shell, and the second step 11 is provided so that the contour of the outer shell 1 matches the contour of the electrode assembly 2 , so as to facilitate the assembly of the electrode assembly 2 and the outer shell 1 .

[0094] When the shell 1 is a hard shell, it is more difficult for the pressure from the outside to pass through the shell 1 and be applied to the electrode assembly 2 than the soft pack. In some embodiments, along the first direction Z, the minimum distance between the electrode assembly 2 and the shell 1 is H, satisfying 0≤H≤5mm.

[0095] When the outer shell 1 is a hard shell, if the distance between the electrode assembly 2 and the outer shell 1 along the first direction Z is too large, the pressure on the outer shell 1 cannot be transmitted to the electrode assembly 2 .

[0096] The shell 1 has a certain elasticity. By setting the distance between the electrode assembly 2 and the shell 1 along the first direction Z to be greater than or equal to 0 and less than or equal to 5 mm, the pressure on the shell 1 is facilitated to be transmitted to the electrode assembly 2 along the first direction Z.

[0097] Exemplarily, H may be, but is not limited to, 0, 0.2 mm, 0.4 mm, 0.6 mm, 0.8 mm, 1 mm, 1.2 mm, 1.4 mm, 1.6 mm, 1.8 mm, 2 mm, 2.2 mm, 2.4 mm, 2.6 mm, 2.8 mm, 3 mm, 3.5 mm, 4 mm, 4.5 mm, 5 mm, etc.

[0098] In some embodiments, 0.4 mm ≤ H ≤ 3.5 mm. When H ≥ 0.4 mm, it is easy to assemble the electrode assembly 2 and the housing 1 and can adapt to processing errors; when H ≤ 3.5 mm, the distance between the housing 1 and the electrode assembly 2 is small, which is further conducive to transmitting the pressure on the housing 1 to the electrode assembly 2.

[0099] The second electrode assembly 2b has a first region 24, the first region 24 includes a region overlapping with the accommodation space 3 along the first direction Z, and the first region 24 extends from the first surface 21 to the second surface 22. Along the first direction Z, at least a portion of the first region 24 overlaps with the accommodation space 3, for example, the entire first region 24 may overlap with the accommodation space 3, or a portion of the first region 24 may overlap with the accommodation space 3, and another portion of the first region 24 may not overlap with the accommodation space 3.

[0100] In the first region 24, the difference in the adhesive force between any two second negative electrode sheets and the second separator connected thereto is less than or equal to 2 N / m. The battery cell 100 is disassembled, and the first region 24 is sampled using a sampler. Each second negative electrode sheet and the second separator connected thereto constitute a sample. The adhesive force between the second negative electrode sheet and the second separator connected thereto is tested for all samples, and the maximum and minimum values ​​are selected from all test results.

[0101] When the electrode assembly 2 is subjected to pressure, the non-overlapping area of ​​the second electrode assembly 2b will warp toward the first electrode assembly 2a, which will easily lead to a reduction in the bonding force between the second negative electrode plate near the first electrode assembly 2a and the second diaphragm connected thereto in the non-overlapping area. In particular, the second negative electrode plate near the first electrode assembly 2a and the second diaphragm connected thereto in the non-overlapping area are prone to debonding. Therefore, the difference between the maximum and minimum values ​​of the bonding force between the second negative electrode plate and the second diaphragm connected thereto in the non-overlapping area will become larger.

[0102] In one or more optional embodiments above, in the first region 24 , the bonding force between any second negative electrode plate and the connected second separator is greater than or equal to 5 N / m.

[0103] The bonding force between any second negative electrode plate in the first region 24 and the second diaphragm connected thereto is greater than or equal to 5 N / m, the bonding force between any second negative electrode plate in the first region 24 and the second diaphragm connected thereto is relatively large, and the warping of the non-overlapping region of the second electrode assembly 2b has little effect on the bonding force between the second negative electrode plate in the first region 24 and the second diaphragm connected thereto, which can improve the problem of black spots formed on the surface of the second negative electrode plate and the precipitation of metallic lithium.

[0104] In the first region 24, the difference in bonding strength between any two second negative electrode sheets and the second diaphragm connected thereto reflects the bonding condition of the second negative electrode sheets and the second diaphragm connected thereto in the first region 24. The smaller the difference in bonding strength between any two second negative electrode sheets and the second diaphragm connected thereto is, the less the impact of the warping of the non-overlapping areas on all the second negative electrode sheets and the second diaphragms connected thereto is, indicating that the bonding effect between the second negative electrode sheets and the second diaphragms connected thereto is better. In the present application, in the first region 24, the difference in bonding strength between any two second negative electrode sheets and the second diaphragms connected thereto is less than or equal to 2 N / m, and the bonding strength consistency between the second negative electrode sheets and the second diaphragms connected thereto in the first region 24 and other regions of the second electrode assembly 2b is good, which can effectively ensure the consistency of the interfacial bonding strength at the junction of the second electrode assembly 2b and the first electrode assembly 2a.

[0105] Illustratively, in the first region 24 , the difference in bonding strength between any two second negative electrode sheets and the connected second separator may be 2 N / m, 1.8 N / m, 1.5 N / m, 1.2 N / m, 1 N / m, 0.8 N / m, 0.5 N / m, 0, etc.

[0106] According to the battery cell 100 of the embodiment of the present application, the first electrode assembly 2a and the second electrode assembly 2b form a first step 23, and the housing 1 forms a second step 11 corresponding to the first step 23, so as to facilitate the assembly of the electrode assembly 2 and the housing 1, so that the battery cell 100 has a stepped structure, so that the battery cell 100 can adapt to different application scenarios. During the assembly process of the electrode assembly 2 and the housing 1, a receiving space 3 is formed between the first step 23 of the electrode assembly 2 and the second step 11 of the housing 1, and the receiving space 3 can accommodate electrolyte, which is beneficial to the charge and discharge cycle of the battery cell 100. In the first region 24, the difference in adhesion between any two second negative electrode sheets and the second diaphragm connected thereto is less than or equal to 2 N / m, and the adhesion consistency between all second negative electrode sheets and the second diaphragm connected thereto in the first region 24 is good. At the same time, in the first region 24, the adhesion between any second negative electrode sheet and the second diaphragm connected thereto is greater than or equal to 5 N / m, and all second negative electrode sheets and the second diaphragm connected thereto are less affected by the warping of the non-overlapping areas of the second electrode assembly 2b, thereby ensuring the adhesion consistency between the first region 24 and other areas of the second electrode assembly 2b. The adhesion between the second negative electrode sheet and the second diaphragm connected thereto is relatively large, thereby improving the problem of black spots and precipitation of metallic lithium on the surface of the second negative electrode sheet, thereby reducing the risk of short circuit between the positive and negative electrodes, and thereby improving the safety and reliability of the battery cell 100.

[0107] In one or more optional embodiments above, in the first region 24 , the difference in bonding force between any two second negative electrode sheets and the second separator connected thereto is less than or equal to 1.8 N / m.

[0108] The second negative electrode plate and the connected second diaphragm are taken as a unit, and the bonding strength between the second negative electrode plate and the second diaphragm of the unit is measured to obtain a bonding strength value. In the first area 24, the bonding strength values ​​of any two units are compared to obtain a difference, which is less than or equal to 1.8N / m.

[0109] The difference in bonding strength between any two second negative electrode sheets and the connected second separators is less than or equal to 1.8 N / m, which further improves the safety performance of the battery cell 100 .

[0110] In one or more optional embodiments above, the second electrode assembly 2b further has a second region 25, and along the first direction Z, the second region 25 overlaps with the first electrode assembly 2a, and the second region 25 extends from the first surface 21 to the second surface 22; in the first region 24, the bonding force between any second negative electrode plate and the second connected diaphragm is F1; in the second region 25, the bonding force between any second negative electrode plate and the second connected diaphragm is F2; ​​satisfying, 0≤F2-F1≤3N / m.

[0111] The difference between the bonding force between any second negative electrode sheet in the second region 25 and the second diaphragm connected thereto and the bonding force between any second negative electrode sheet in the first region 24 and the second diaphragm connected thereto satisfies the above relationship, so that the bonding force consistency between the second region 25 and the first region 24 of the second electrode assembly 2b is good, the warping of the non-overlapping region of the second electrode assembly 2b has little effect on the bonding force between the second negative electrode sheet in the first region 24 and the second diaphragm connected thereto, the bonding force between the second negative electrode sheets in different regions of the second electrode assembly 2b and the second diaphragm connected thereto is large, which can improve the problem of black spots formed on the surface of the second negative electrode sheet and the precipitation of metallic lithium, can reduce the risk of short circuit between the positive and negative electrodes, and can improve the safety and reliability of the battery cell.

[0112] In one or more of the above optional embodiments, 0≤F2-F1≤2.5N / m.

[0113] When 0≤F2-F1≤2.5N / m, the difference between the bonding force between any second negative electrode sheet in the first region 24 and the second diaphragm connected thereto and the bonding force between any second negative electrode sheet in the second region 25 and the second diaphragm connected thereto is relatively small, further making the warping of the non-overlapping area of ​​the second electrode assembly 2b have less influence on the bonding force between the second negative electrode sheet in the first region 24 and the second diaphragm connected thereto, further improving the problem of black spots and precipitation of metallic lithium on the surface of the second negative electrode sheet.

[0114] In one or more optional embodiments above, in the first region 24 , the bonding force between any second negative electrode plate and the connected second separator is greater than or equal to 10 N / m.

[0115] When the bonding strength between any second negative electrode plate in the first region 24 and the second diaphragm connected thereto is greater than or equal to 10 N / m, the warping of the non-overlapping region of the second electrode assembly 2b has less influence on the bonding strength between the second negative electrode plate in the first region 24 and the second diaphragm connected thereto, and can effectively improve the problem of black spots and metal lithium precipitation on the surface of the second negative electrode plate.

[0116] Please refer to Figure 1 and Figure 4In one or more of the above optional embodiments, the housing 1 includes a first wall 12 and a second wall 13 arranged opposite to each other along a first direction Z, the first wall 12 has a main wall 121 and a step wall 122, along the second direction Y, the step wall 122 is located at at least one end of the main wall 121, the step wall 122 is recessed relative to the main wall 121 toward the direction of the second wall 13, and the step wall 122 is connected to the main wall 121 by a connecting wall 123 to form a second step 11.

[0117] The step wall 122 corresponds to the portion of the second electrode assembly 2b that exceeds the first electrode assembly 2a along the second direction Y. When one end of the second electrode assembly 2b along the second direction Y exceeds the first electrode assembly 2a, the step wall 122 is located at one end of the main wall 121 along the second direction Y; or, when both ends of the second electrode assembly 2b along the second direction Y exceed the first electrode assembly 2a, the step wall 122 is located at both ends of the main wall 121 along the second direction Y.

[0118] The step wall 122 is recessed relative to the main body wall 121 toward the direction of the second wall 13, and the step wall 122 is connected to the main body wall 121 through the connecting wall 123, and the first wall 12 can be an integrally formed structure. For example, the step wall 122 is recessed relative to the main body wall 121 toward the direction of the second wall 13, and the housing 1 can be formed by stamping during the manufacturing process. Alternatively, the first wall 12 can be an integrally injection molded structure.

[0119] The first wall 12 can be formed into the second step 11 by stamping or injection molding, which is easy to process and manufacture, and the first wall 12 has a high overall strength.

[0120] Please refer to Figure 1 The housing 1 may further include a third wall 14, a fourth wall 15 and two fifth walls 16, the third wall 14 and the fourth wall 15 are arranged opposite to each other along the second direction Y, the third wall 14 connects the main wall 121 and the second wall 13, the fourth wall 15 connects the step wall 122 and the second wall 13, and the two fifth walls 16 are arranged opposite to each other along the third direction X, one end of the fifth wall 16 is connected to the second wall 13, and the other end of the fifth wall 16 is connected to the main wall 121, the step wall 122 and the connecting wall 123. The third direction X, the second direction Y and the first direction Z are perpendicular to each other.

[0121] The second electrode assembly 2b is disposed between the step wall 122 and the second wall 13 , and the first electrode assembly 2a is disposed between the main body wall 121 and the second electrode assembly 2b . The first electrode assembly 2a , the second electrode assembly 2b , the connecting wall 123 and the main body wall 121 form a receiving space 3 .

[0122] The first wall 12 and the second wall 13 are spaced apart along the first direction Z. After the electrode assembly 2 is assembled with the outer shell 1, along the first direction Z, the second electrode assembly 2b is arranged between the step wall 122 and the second wall 13, that is, the second electrode assembly 2b is located between the second wall 13 and the first wall 12; along the first direction Z, the first electrode assembly 2a is arranged between the main wall 121 and the second electrode assembly 2b.

[0123] The second electrode assembly 2b is arranged between the step wall 122 and the second wall 13, and the first electrode assembly 2a is arranged between the main wall 121 and the second electrode assembly 2b, so that the outer shell 1 matches the contour of the electrode assembly 2, the outer shell 1 protects the electrode assembly 2, and reduces the risk of damage to the electrode assembly 2.

[0124] In some embodiments, the connecting wall 123 includes a straight section 124 and two arc sections 125 , one end of the straight section 124 is connected to the main wall 121 through one arc section 125 , and the other end of the straight section 124 is connected to the step wall 122 through another arc section 125 .

[0125] In some embodiments, the body wall 121 and the step wall 122 may be parallel to each other.

[0126] In some embodiments, the straight section 124 may be arranged parallel to the first direction Z, or the straight section 124 may be arranged obliquely relative to the first direction Z, that is, the straight section 124 may be arranged at an angle to the first direction Z.

[0127] Please refer to Figure 4 In one or more of the above optional embodiments, along the second direction Y, the first region 24 has a first end 241 and a second end 242 that are relatively arranged, the first end 241 is closer to the first electrode assembly 2a relative to the second end 242, and the second end 242 is farther away from the first electrode assembly 2a relative to the first end 241.

[0128] The first end 241 is an end of the first region 24 close to the first electrode assembly 2a in the second direction Y, and the second end 242 is an end of the first region 24 away from the first electrode assembly 2a in the second direction Y. The second end 242 is closer to the step wall 122 than the first end 241.

[0129] Along the first direction Z, the first region 24 has a first overlapping region overlapping a portion of the first positive electrode tab 21 a , and a second overlapping region overlapping a portion of the step wall 122 .

[0130] Along the second direction Y, the first end 241 extends to a region of the second electrode assembly 2 b corresponding to the first positive electrode tab 21 a of the first electrode assembly 2 a , and the second end 242 extends to a region of the second electrode assembly 2 b corresponding to the step wall 122 .

[0131] The first region 24 extends in the second direction Y to the region overlapping with the first positive electrode plate 21a and the region overlapping with the step wall 122. The first region 24 has a large area, so that the bonding force between the second negative electrode plate near the overlapping region between the second electrode assembly 2b and the first electrode assembly 2a and the connected second diaphragm is relatively large, which facilitates reducing the risk of black spots forming on the surface of the second negative electrode plate and the precipitation of metallic lithium.

[0132] In one or more optional embodiments above, along the second direction Y, the distance between the first positive electrode plate 21a and the step wall 122 is L1, the length of the first overlapping area is L2, and the length of the second overlapping area is L3, satisfying L2 / L1≤0.3, L3 / L1≤0.3.

[0133] By setting L2 / L1 to be less than or equal to 0.3, and setting L3 / L1 to be less than or equal to 0.3, the first region 24 and the first positive electrode plate 21a have a certain overlapping area, and the first region 24 and the step wall 122 have a certain overlapping area, so that the bonding force between the second negative electrode plate and the connected second diaphragm is greater, which helps to reduce the risk of black spots forming on the surface of the second negative electrode plate and the precipitation of metallic lithium.

[0134] In one or more optional embodiments above, along the first direction Z, the projection area of ​​the first region 24 is S1, and the projection area of ​​the second electrode assembly 2b is S2, satisfying 0.001≤S1 / S2≤0.2.

[0135] Taking the first direction Z as the projection direction, on the projection plane perpendicular to the first direction Z, the area of ​​the orthographic projection of the first region 24 is S1, and the area of ​​the orthographic projection of the second electrode assembly 2b is S2.

[0136] If the ratio of the projection area of ​​the first region 24 to the projection area of ​​the second electrode assembly 2b is too small, the volume of the accommodating space 3 is too small, which is not conducive to the assembly of the electrode assembly 2 and the outer shell 1; if the ratio of the projection area of ​​the first region 24 to the projection area of ​​the second electrode assembly 2b is too large, the volume of the accommodating space 3 is too large, the internal space utilization rate of the outer shell 1 is low, and the energy density of the battery cell 100 is low.

[0137] The first region 24 corresponds to the boundary region between the second electrode assembly 2b and the first electrode assembly 2a. By setting the ratio of the projected area of ​​the first region 24 to the projected area of ​​the second electrode assembly 2b to be greater than or equal to 0.001 and less than or equal to 0.2, on the one hand, it is convenient to assemble metallic lithium between the electrode assembly 2 and the outer shell 1; on the other hand, the internal space utilization rate of the outer shell 1 is higher, and the battery cell 100 has a higher energy density.

[0138] Illustratively, the ratio of the projected area of ​​the first region 24 to the projected area of ​​the second electrode assembly 2 b may be, but is not limited to, 0.001, 0.005, 0.01, 0.05, 0.1, 0.15, 0.2, or the like.

[0139] Exemplarily, 0.01≤S1 / S2≤0.15. S1 / S2≥0.01 further facilitates the assembly of metallic lithium between the electrode assembly 2 and the housing 1; S1 / S2≤0.15 further increases the utilization rate of the internal space of the housing 1, and the battery cell 100 has a higher energy density.

[0140] In some embodiments, please refer to Figure 4 The second electrode assembly 2b also includes a third region 26. The second region 25, the first region 24 and the third region 26 are distributed along the second direction Y, and the first region 24 connects the second region 25 and the third region 26. Along the first direction Z, the projection of the second region 25 partially overlaps with the main wall 121, and the projection of the third region 26 at least partially overlaps with the step wall 122.

[0141] In one or more optional embodiments above, along the first direction Z, the projection area of ​​the first electrode assembly 2a is S3, and the projection area of ​​the second electrode assembly 2b is S2, satisfying 0.2≤S3 / S2≤0.9.

[0142] Taking the first direction Z as the projection direction, the area of ​​the orthographic projection of the first electrode assembly 2a is S3, and the area of ​​the orthographic projection of the second electrode assembly 2b is S2.

[0143] If the ratio of the projected area of ​​the first electrode assembly 2a to the projected area of ​​the second electrode assembly 2b is too large, the difference between the size of the first electrode assembly 2a and the size of the second electrode assembly 2b is too small, and the processing and manufacturing difficulty is relatively high; if the ratio of the projected area of ​​the first electrode assembly 2a to the projected area of ​​the second electrode assembly 2b is too small, the difference between the size of the first electrode assembly 2a and the size of the second electrode assembly 2b is too large, which is not conducive to the design purpose of increasing the energy density of the battery cell 100 by flexibly utilizing space, and if the difference between the size of the first electrode assembly 2a and the size of the second electrode assembly 2b is large, the area of ​​the boundary area of ​​the first electrode assembly 2a and the second electrode assembly 2b, that is, the first area 24, will be larger, and the problem of uneven force will be more serious.

[0144] By setting the ratio of the projected area of ​​the first electrode assembly 2a to the projected area of ​​the second electrode assembly 2b to be greater than or equal to 0.2 and less than or equal to 0.9, on the one hand, the processing and manufacturing difficulty is lower; on the other hand, the battery cell 100 has a higher energy density, reducing the uneven force in the interface area between the first electrode assembly 2a and the second electrode assembly 2b.

[0145] Illustratively, the ratio of the projected area of ​​the first electrode assembly 2a to the projected area of ​​the second electrode assembly 2b may be, but is not limited to, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, etc.

[0146] For example, 0.3≤S3 / S2≤0.8. S3 / S2≥0.3 further reduces the difficulty of processing and manufacturing; S3 / S2≤0.8 further enables the battery cell 100 to have a higher energy density.

[0147] In one or more optional embodiments above, the housing 1 is a hard housing, and the battery cell 100 is a hard housing battery cell 100. For example, the housing 1 can be a steel housing, an aluminum housing, a hard plastic housing, or the like.

[0148] Based on the above-mentioned battery cell 100, an embodiment of the present application further provides an electrical device, which includes the battery cell 100 provided according to any of the above-mentioned embodiments.

[0149] The battery cell 100 described above has high safety and reliability, so that the electrical equipment formed by the battery cell 100 has high safety and reliability.

[0150] When the first electrode assembly 2a and the second electrode assembly 2b are stacked along the first direction Z, the first direction Z may be a height direction, and the first electrode assembly 2a may be located above the second electrode assembly 2b.

[0151] During the preparation of the battery cell 100, there are at least two stations for applying pressure to the battery cell 100, such as a hot pressing station and a formation station. For example, after the first electrode assembly 2a and the second electrode assembly 2b are stacked, in the hot pressing process, the upper pressing block and the lower pressing block cooperate to apply pressure to the electrode assembly 2 to ensure effective bonding of the internal interface of the electrode assembly 2. For another example, after the electrode assembly 2 is loaded into the housing 1, in the formation process, the upper pressing block and the lower pressing block cooperate to apply pressure to the battery cell 100 to ensure effective bonding of the internal interface of the electrode assembly 2.

[0152] Please refer to Figure 5 and Figure 6 The present application also provides a method for manufacturing a battery cell 100, which is used to manufacture the battery cell 100 provided according to any of the above embodiments. The method for manufacturing the battery cell 100 includes:

[0153] S100, stacking the first electrode assembly 2a and the second electrode assembly 2b along the first direction Z, wherein the first electrode assembly 2a and the second electrode assembly 2b are both laminated structures, the first electrode assembly 2a is located above the second electrode assembly 2b, along the second direction Y, the length of the second electrode assembly 2b is greater than the length of the first electrode assembly 2a, the second direction Y is perpendicular to the first direction Z, and a first step 23 is formed at least at one end of the electrode assembly 2 along the second direction Y;

[0154] S200, in the hot pressing composite process, pressure is applied to the first electrode assembly 2a by the first pressing block 41 on the side of the first electrode assembly 2a facing away from the second electrode assembly 2b, and pressure is applied to the second electrode assembly 2b by the second pressing block 51 on the side of the second electrode assembly 2b facing away from the first electrode assembly 2a, wherein along the second direction Y, the second pressing block 51 does not extend beyond the first electrode assembly 2a.

[0155] In the hot pressing composite process, when pressure is applied to the battery cell 100, the first pressing block 41 is on the side of the first electrode assembly 2a away from the second electrode assembly 2b, and applies a force to the first electrode assembly 2a toward the second electrode assembly 2b, and the second pressing block 51 is on the side of the second electrode assembly 2b away from the first electrode assembly 2a, and applies a force to the second electrode assembly 2b toward the first electrode assembly 2a.

[0156] By ensuring that the second pressing block 51 does not exceed the first electrode assembly 2a along the second direction Y, when the first pressing block 41 and the second pressing block 51 cooperate to apply pressure to the electrode assembly 2, the force of the second pressing block 51 acts on the area corresponding to the second electrode assembly 2b and the first electrode assembly 2a, and the stress at the junction of the second electrode assembly 2b and the first electrode assembly 2a is balanced, which effectively ensures the consistency of the interface bonding force at the junction of the second electrode assembly 2b and the first electrode assembly 2a, and the interface bonding force between the second negative electrode sheet in the first area 24 and the connected second diaphragm is good. In the first area 24, any two second negative electrodes can be connected. The difference in bonding strength between the second negative electrode sheet and the second diaphragm connected thereto is less than or equal to 2 N / m, and the bonding strength between any second negative electrode sheet and the second diaphragm connected thereto can be greater than or equal to 5 N / m. The smaller the difference in bonding strength between any two second negative electrode sheets and the second diaphragms connected thereto is, the less influence of the warping of the non-overlapping areas of the second electrode assembly 2b on all second negative electrode sheets and the second diaphragms connected thereto is, indicating that the bonding effect between the second negative electrode sheet in the first area 24 and the second diaphragm connected thereto is better, which can significantly improve the problems of black spots formed on the surface of the second negative electrode sheet and the precipitation of metallic lithium, and is beneficial to improving the performance of the battery cell 100.

[0157] In one or more optional embodiments above, along the second direction Y, the second pressing block 51 does not exceed the first electrode assembly 2a; along the first direction Z, the projection area of ​​the first electrode assembly 2a is S3, and the projection area of ​​the second pressing block 51 is S4, satisfying 0.8≤S4 / S3≤1.

[0158] Taking the first direction Z as the projection direction, the area of ​​the orthographic projection of the first electrode assembly 2a is S3, the area of ​​the orthographic projection of the second pressing block 51 is S4, and the orthographic projection of the second pressing block falls within the orthographic projection of the first electrode assembly 2a.

[0159] The ratio of the projected area of ​​the second pressing block 51 along the first direction Z to the projected area of ​​the first electrode assembly 2a along the first direction Z is set to be greater than or equal to 0.8 and less than or equal to 1. Under the pressure applied by the first pressing block 41 to the first electrode assembly 2a and the pressure applied by the second pressing block 51 to the second electrode assembly 2b, the first electrode assembly 2a and the second electrode assembly 2b are subjected to balanced force, thereby ensuring the force consistency between the first area 24 and other areas of the second electrode assembly 2b.

[0160] Exemplarily, S4 / S3 may be, but is not limited to, 0.8, 0.85, 0.9, 0.95, 1, etc.

[0161] Exemplarily, 0.85≤S4 / S3≤0.95.

[0162] In one or more of the above optional embodiments, the first pressing block 41 can be an elastic member, which can absorb the force acting on the first electrode assembly 2a on the first pressing block 41, thereby providing uniform pressure to the first electrode assembly 2a and the second electrode assembly 2b, and facilitating effective bonding of the internal interface of the electrode assembly 2.

[0163] In some embodiments, the second pressing block 51 can be an elastic member that can absorb the force exerted by the second electrode assembly 2b on the second pressing block 51, thereby providing uniform pressure to the first electrode assembly 2a and the second electrode assembly 2b, and facilitating effective bonding of the internal interface of the electrode assembly 2.

[0164] In some embodiments, the first pressing block 41 and the second pressing block 51 are both elastic parts, which can absorb the force acting on the first electrode assembly 2a on the first pressing block 41, and absorb the force acting on the second electrode assembly 2b on the second pressing block 51, so as to provide uniform pressure on the first electrode assembly 2a and the second electrode assembly 2b, and facilitate effective bonding of the internal interface of the electrode assembly 2.

[0165] Please refer to Figure 7 and Figure 8 In one or more of the above optional embodiments, the method for manufacturing the battery cell 100 further includes:

[0166] S300, in the formation process, on the side of the first electrode assembly 2a facing away from the second electrode assembly 2b, pressure is applied to the first electrode assembly 2a by the third pressing block 42, and along the second direction Y, the third pressing block 42 does not exceed the first electrode assembly 2a, and on the side of the first electrode assembly 2a along the second direction Y, pressure is applied to the second electrode assembly 2b by the fourth pressing block 52. On the side of the first electrode assembly 2a along the second direction Y, pressure is applied to the portion of the second electrode assembly 2b that exceeds the first electrode assembly 2a by the fifth pressing block 43.

[0167] For example, please refer to Figure 7 , the manufacturing method of the battery cell 100 includes:

[0168] S100, stacking the first electrode assembly 2a and the second electrode assembly 2b along the first direction Z, wherein the first electrode assembly 2a and the second electrode assembly 2b are both laminated structures, the first electrode assembly 2a is located above the second electrode assembly 2b, along the second direction Y, the length of the second electrode assembly 2b is greater than the length of the first electrode assembly 2a, the second direction Y is perpendicular to the first direction Z, and a first step 23 is formed at least at one end of the electrode assembly 2 along the second direction Y;

[0169] S200, in the hot pressing composite process, at a side of the first electrode assembly 2a facing away from the second electrode assembly 2b, a pressure is applied to the first electrode assembly 2a by the first pressing block 41, and at a side of the second electrode assembly 2b facing away from the first electrode assembly 2a, a pressure is applied to the second electrode assembly 2b by the second pressing block 51, wherein along the second direction Y, the second pressing block 51 does not extend beyond the first electrode assembly 2a;

[0170] S300, in the formation process, on the side of the first electrode assembly 2a facing away from the second electrode assembly 2b, pressure is applied to the first electrode assembly 2a by the third pressing block 42, and along the second direction Y, the third pressing block 42 does not exceed the first electrode assembly 2a, and on the side of the first electrode assembly 2a along the second direction Y, pressure is applied to the second electrode assembly 2b by the fourth pressing block 52. On the side of the first electrode assembly 2a along the second direction Y, pressure is applied to the portion of the second electrode assembly 2b that exceeds the first electrode assembly 2a by the fifth pressing block 43.

[0171] In the formation process, along the second direction Y, the third pressing block 42 does not exceed the first electrode assembly 2a, the fourth pressing block 52 exceeds the first electrode assembly 2a, and the fifth pressing block 43 is located on the side of the first electrode assembly 2a along the second direction Y. When the third pressing block 42 and the fifth pressing block 43 cooperate with the fourth pressing block 52 to apply pressure to the electrode assembly 2, the force on the third pressing block 42 directly acts on the first electrode assembly 2a, and the first electrode assembly 2a is evenly stressed. The fifth pressing block 43 acts on the area of ​​the second electrode assembly 2b that exceeds the first electrode assembly 2a. The stress at the junction of the second electrode assembly 2b and the first electrode assembly 2a is balanced, which effectively ensures the consistency of the interface bonding force at the junction of the second electrode assembly 2b and the first electrode assembly 2a. The interface bonding force between the two negative electrode sheets and the second diaphragm connected thereto is good. In the first region 24, the difference in bonding force between any two second negative electrode sheets and the second diaphragm connected thereto can be less than or equal to 2N / m, and the bonding force between any second negative electrode sheets and the second diaphragm connected thereto can be greater than or equal to 5N / m. The smaller the difference in bonding force between any two second negative electrode sheets and the second diaphragm connected thereto is, the less impact of the warping of the non-overlapping area of ​​the second electrode assembly 2b will be on all the second negative electrode sheets and the second diaphragm connected thereto. The better the bonding effect between the second negative electrode sheet and the second diaphragm connected thereto in the first region 24, the problem of black spots formed on the surface of the second negative electrode sheet and the precipitation of metallic lithium can be significantly improved, which is beneficial to improving the performance of the battery cell 100.

[0172] In one or more optional embodiments above, along the second direction Y, the third pressing block 42 does not exceed the first electrode assembly 2a; along the first direction Z, the projection area of ​​the first electrode assembly 2a is S3, and the projection area of ​​the third pressing block 42 is S5, satisfying 0.75≤S5 / S3≤0.95.

[0173] Taking the first direction Z as the projection direction, the area of ​​the orthographic projection of the first electrode assembly 2a is S3, the area of ​​the orthographic projection of the third pressing block 42 is S5, and the orthographic projection of the third pressing block 42 falls within the orthographic projection of the first electrode assembly 2a.

[0174] The ratio of the projected area of ​​the third pressing block 42 along the first direction Z to the projected area of ​​the first electrode assembly 2a along the first direction Z is set to be greater than or equal to 0.75 and less than or equal to 0.95. With the cooperation of the third pressing block 42, the fifth pressing block 43 and the fourth pressing block 52, the first electrode assembly 2a and the second electrode assembly 2b are subjected to balanced force, thereby ensuring the force consistency between the first area 24 and other areas of the second electrode assembly 2b.

[0175] Exemplarily, S5 / S3 may be, but is not limited to, 0.75, 0.8, 0.85, 0.9, 0.95, etc.

[0176] Exemplarily, 0.8≤S5 / S3≤0.9.

[0177] In one or more optional embodiments above, in the formation process, on the side of the first electrode assembly 2a away from the second electrode assembly 2b, pressure is applied to the first electrode assembly 2a by the third pressing block 42, and along the second direction Y, the third pressing block 42 does not exceed the first electrode assembly 2a, and on the side of the second electrode assembly 2b away from the first electrode assembly 2a, pressure is applied to the second electrode assembly 2b by the fourth pressing block 52, and on the side of the first electrode assembly 2a along the second direction Y, pressure is applied to the portion of the second electrode assembly 2b exceeding the first electrode assembly 2a by the fifth pressing block 43, the manufacturing method of the battery cell 100 further includes:

[0178] S400 , placing the first electrode assembly 2 a and the second electrode assembly 2 b in the housing 1 .

[0179] For example, please refer to Fig. 9 , the manufacturing method of the battery cell 100 includes:

[0180] S100, stacking the first electrode assembly 2a and the second electrode assembly 2b along the first direction Z, wherein the first electrode assembly 2a and the second electrode assembly 2b are both laminated structures, the first electrode assembly 2a is located above the second electrode assembly 2b, along the second direction Y, the length of the second electrode assembly 2b is greater than the length of the first electrode assembly 2a, the second direction Y is perpendicular to the first direction Z, and a first step 23 is formed at least at one end of the electrode assembly 2 along the second direction Y;

[0181] S200, in the hot pressing composite process, at a side of the first electrode assembly 2a facing away from the second electrode assembly 2b, a pressure is applied to the first electrode assembly 2a by the first pressing block 41, and at a side of the second electrode assembly 2b facing away from the first electrode assembly 2a, a pressure is applied to the second electrode assembly 2b by the second pressing block 51, wherein along the second direction Y, the second pressing block 51 does not extend beyond the first electrode assembly 2a;

[0182] S400, placing the first electrode assembly 2a and the second electrode assembly 2b in the housing 1;

[0183] S300, in the formation process, on the side of the first electrode assembly 2a facing away from the second electrode assembly 2b, pressure is applied to the first electrode assembly 2a by the third pressing block 42, and along the second direction Y, the third pressing block 42 does not exceed the first electrode assembly 2a, and on the side of the first electrode assembly 2a along the second direction Y, pressure is applied to the second electrode assembly 2b by the fourth pressing block 52. On the side of the first electrode assembly 2a along the second direction Y, pressure is applied to the portion of the second electrode assembly 2b that exceeds the first electrode assembly 2a by the fifth pressing block 43.

[0184] In the hot pressing and compounding process, the first pressing block 41 and the second pressing block 51 are abutted against the electrode assembly 2, so that the first electrode assembly 2a and the second electrode assembly 2b are compounded to form a stepped electrode assembly 2. After the electrode assembly 2 is compounded, the composite structure of the first electrode assembly 2a and the second electrode assembly 2b is placed in the housing 1 to complete the assembly of the electrode assembly 2 and the housing 1. Before the formation process, the first electrode assembly 2a and the second electrode assembly 2b after hot pressing and compounding are placed in the housing 1 to protect the electrode assembly 2 and to inject electrolyte into the housing 1 for the formation operation.

[0185] In some embodiments, after the electrode assembly 2 is placed in the housing 1 and before the formation process, the method for manufacturing the battery cell 100 further includes:

[0186] S500 , injecting electrolyte into the housing 1 , and sealing the housing 1 .

[0187] For example, please refer to Fig.10 , the manufacturing method of the battery cell 100 includes:

[0188] S100, stacking the first electrode assembly 2a and the second electrode assembly 2b along the first direction Z, wherein the first electrode assembly 2a and the second electrode assembly 2b are both laminated structures, the first electrode assembly 2a is located above the second electrode assembly 2b, along the second direction Y, the length of the second electrode assembly 2b is greater than the length of the first electrode assembly 2a, the second direction Y is perpendicular to the first direction Z, and a first step 23 is formed at least at one end of the electrode assembly 2 along the second direction Y;

[0189] S200, in the hot pressing composite process, at a side of the first electrode assembly 2a facing away from the second electrode assembly 2b, a pressure is applied to the first electrode assembly 2a by the first pressing block 41, and at a side of the second electrode assembly 2b facing away from the first electrode assembly 2a, a pressure is applied to the second electrode assembly 2b by the second pressing block 51, wherein along the second direction Y, the second pressing block 51 does not extend beyond the first electrode assembly 2a;

[0190] S400, placing the first electrode assembly 2a and the second electrode assembly 2b in the housing 1;

[0191] S500, injecting electrolyte into the housing 1 and sealing the housing 1;

[0192] S300, in the formation process, on the side of the first electrode assembly 2a facing away from the second electrode assembly 2b, pressure is applied to the first electrode assembly 2a by the third pressing block 42, and along the second direction Y, the third pressing block 42 does not exceed the first electrode assembly 2a, and on the side of the first electrode assembly 2a along the second direction Y, pressure is applied to the second electrode assembly 2b by the fourth pressing block 52. On the side of the first electrode assembly 2a along the second direction Y, pressure is applied to the portion of the second electrode assembly 2b that exceeds the first electrode assembly 2a by the fifth pressing block 43.

[0193] The fifth pressing block 43 and the third pressing block 42 are independent of each other, and the force applied by the third pressing block 42 and the force applied by the fifth pressing block 43 may be the same or different.

[0194] In one or more of the above optional embodiments, the housing 1 includes a first wall 12 and a second wall 13 arranged opposite to each other along a first direction Z, the first wall 12 has a main wall 121 and a step wall 122, along the second direction Y, the step wall 122 is located at at least one end of the main wall 121, the step wall 122 is recessed relative to the main wall 121 toward the second wall 13, the step wall 122 is connected to the main wall 121 by a connecting wall 123 to form a second step 11, the second electrode assembly 2b is arranged between the step wall 122 and the second wall 13, and the first electrode assembly 2a is arranged between the main wall 121 and the second electrode assembly 2b; along the second direction Y, the first pressing block 41 does not exceed the first electrode assembly 2a.

[0195] The step “S300, in the formation process, on the side of the first electrode assembly 2a away from the second electrode assembly 2b, pressure is applied to the first electrode assembly 2a by the third pressing block 42, and along the second direction Y, the third pressing block 42 does not exceed the first electrode assembly 2a; on the side of the second electrode assembly 2b away from the first electrode assembly 2a, pressure is applied to the second electrode assembly 2b by the fourth pressing block 52, and on the side of the first electrode assembly 2a along the second direction Y, pressure is applied to the portion of the second electrode assembly 2b that exceeds the first electrode assembly 2a by the fifth pressing block 43”, includes:

[0196] S310, in the formation process, on the side of the first electrode assembly 2a facing away from the second electrode assembly 2b, the third pressing block 42 is pressed against the main wall 121 to apply pressure to the first electrode assembly 2a, and along the second direction Y, the third pressing block 42 does not exceed the first electrode assembly 2a; on the side of the second electrode assembly 2b facing away from the first electrode assembly 2a, the fourth pressing block 52 is pressed against the second wall 13 to apply pressure to the second electrode assembly 2b; on the side of the first electrode assembly 2a along the second direction Y, the fifth pressing block 43 is pressed against the step wall 122 to apply pressure to the portion of the second electrode assembly 2b that exceeds the first electrode assembly 2a.

[0197] Exemplarily, the method for manufacturing the battery cell 100 includes:

[0198] S100, stacking the first electrode assembly 2a and the second electrode assembly 2b along the first direction Z, wherein the first electrode assembly 2a and the second electrode assembly 2b are both laminated structures, the first electrode assembly 2a is located above the second electrode assembly 2b, along the second direction Y, the length of the second electrode assembly 2b is greater than the length of the first electrode assembly 2a, the second direction Y is perpendicular to the first direction Z, and a first step 23 is formed at least at one end of the electrode assembly 2 along the second direction Y;

[0199] S200, in the hot pressing composite process, at a side of the first electrode assembly 2a facing away from the second electrode assembly 2b, a pressure is applied to the first electrode assembly 2a by the first pressing block 41, and at a side of the second electrode assembly 2b facing away from the first electrode assembly 2a, a pressure is applied to the second electrode assembly 2b by the second pressing block 51, wherein along the second direction Y, the second pressing block 51 does not extend beyond the first electrode assembly 2a;

[0200] S400, placing the first electrode assembly 2a and the second electrode assembly 2b in the housing 1;

[0201] S500, injecting electrolyte into the housing 1 and sealing the housing 1;

[0202] S310, in the formation process, on the side of the first electrode assembly 2a facing away from the second electrode assembly 2b, the third pressing block 42 is pressed against the main wall 121 to apply pressure to the first electrode assembly 2a, and along the second direction Y, the third pressing block 42 does not exceed the first electrode assembly 2a; on the side of the second electrode assembly 2b facing away from the first electrode assembly 2a, the fourth pressing block 52 is pressed against the second wall 13 to apply pressure to the second electrode assembly 2b; on the side of the first electrode assembly 2a along the second direction Y, the fifth pressing block 43 is pressed against the step wall 122 to apply pressure to the portion of the second electrode assembly 2b that exceeds the first electrode assembly 2a.

[0203] By adopting the above-mentioned method for manufacturing the battery cell 100, the third pressing block 42 and the fifth pressing block 43 are separately arranged, and the third pressing block 42 is pressed against the main wall 121 to apply pressure to the first electrode assembly 2a, combined with the fifth pressing block 43 pressing against the step wall 122 to apply pressure to the portion of the second electrode assembly 2b that exceeds the first electrode assembly 2a, which can effectively ensure the consistency of the interfacial bonding force at the junction of the second electrode assembly 2b and the first electrode assembly 2a, so that the internal interface of the electrode assembly 2 of the battery cell 100 is effectively bonded, significantly improving the problem of black spots formed on the surface of the second negative electrode plate and the precipitation of metallic lithium, which is beneficial to improving the performance of the battery cell 100.

[0204] In one or more of the above optional embodiments, the method for manufacturing the battery cell 100 further includes:

[0205] In the formation process, at the side of the first electrode assembly 2a facing away from the second electrode assembly 2b, pressure is applied to the first electrode assembly 2a by the third pressing block 42. The third pressing block 42 is divided into a first part and a second part along the second direction Y. Along the first direction Z, the first part overlaps with the first electrode assembly 2a, and the second part does not overlap with the first electrode assembly 2a. The thickness of the second part is greater than that of the first part. The second part applies pressure to the second electrode assembly 2b. The Shore hardness of the third pressing block 42 is 30HA to 90HA. The thickness of the second part exceeding the first part along the first direction Z is greater than the thickness of the first electrode assembly 2a. At the side of the second electrode assembly 2b facing away from the first electrode assembly 2a, pressure is applied to the second electrode assembly 2b by the fourth pressing block 52.

[0206] For example, Fig.11 As shown, the first portion presses against the main body wall 121 , the second portion presses against the step wall 122 , and the fourth pressing block 52 presses against the second wall 13 . The battery cell 100 is clamped by the cooperation between the third pressing block 42 and the fourth pressing block 52 .

[0207] In some embodiments, the third pressing block 42 may be a special-shaped pressing block, and the Shore hardness of the third pressing block 42 is 30HA to 90HA. Fig.11 As shown, the size of the first electrode assembly 2a in the second direction Y is smaller than that of the second electrode assembly 2b, so there is a thickness space in the non-overlapping area of ​​the first electrode assembly 2a and the second electrode assembly 2b. When the third pressing block 42 is made into a special-shaped pressing block, along the second direction Y, the third pressing block 42 is divided into a first part and a second part. Observing along the first direction Z, the first part overlaps with the first electrode assembly 2a, and the second part does not overlap with the first electrode assembly 2a. The second part is thicker and can apply pressure to the second electrode assembly 2b. However, when the material of the third pressing block 42 is harder and the Shore hardness is greater than 90HA, it is difficult to strictly control the size of the battery cell 100 during the process. The shrinkage of the battery cell 100 and the deviation of the process operation may cause errors. Therefore, if the Shore hardness of the third pressing block 42 is higher, the pressure effect of one of the electrode assemblies will be poor. Therefore, the Shore hardness of the third pressing block 42 is made lower, and the thickness of the second part minus the thickness of the first part is greater than the thickness of the first electrode assembly, which can ensure that when the second electrode assembly 2b is pressed, the first electrode assembly can also be pressed by relying on the elasticity of the third pressing block 42. If the Shore hardness is too low, the pressure transmission may be poor.

[0208] In one or more optional embodiments above, along the first direction Z, the projection area of ​​the fifth pressing block 43 is S6, and the projection area of ​​the portion of the second electrode assembly 2b that exceeds the first electrode assembly 2a is S7, satisfying 0.8≤S6 / S7≤1.

[0209] Taking the first direction Z as the projection direction, the area of ​​the orthographic projection of the fifth pressing block 43 is S6, and the area of ​​the orthographic projection of the portion of the second electrode assembly 2b that exceeds the first electrode assembly 2a is S7.

[0210] The ratio of the projected area of ​​the fifth pressing block 43 along the first direction Z to the projected area of ​​the portion of the second electrode assembly 2b that extends beyond the first electrode assembly 2a is set to be greater than or equal to 0.8 and less than or equal to 1, so that the first electrode assembly 2a and the second electrode assembly 2b are subjected to balanced force, thereby ensuring the consistency of force between the first region 24 and other regions of the second electrode assembly 2b.

[0211] Exemplarily, S6 / S7 may be, but is not limited to, 0.8, 0.85, 0.9, 0.95, 1, etc.

[0212] Exemplarily, 0.85≤S6 / S7≤0.95.

[0213] In one or more of the above optional embodiments, the Shore hardness of the fifth pressing block 43 is 30HA~90HA. The Shore hardness of the fifth pressing block 43 is 30HA~90HA, which can absorb the force of the second electrode assembly 2b acting on the fifth pressing block 43, facilitate the provision of uniform pressure to the second electrode assembly 2b, and facilitate the effective bonding of the internal interface of the electrode assembly 2.

[0214] In one or more optional embodiments above, at least one of the second pressing block 51, the third pressing block 42, the fourth pressing block 52 and the fifth pressing block 43 is made of at least one of polyurethane, silicone rubber, ethylene propylene rubber, butyl rubber, chloroprene rubber, nitrile rubber, styrene butadiene rubber, fluororubber, nylon 6, nylon 66, polyethylene, polypropylene, polyethylene terephthalate, polybutylene terephthalate, polycarbonate or polystyrene.

[0215] The second pressing block 51 , the third pressing block 42 , the fourth pressing block 53 and the fifth pressing block 43 are made of at least one of the above materials, which has a good supporting effect and is conducive to uniform pressure transmission.

[0216] In one or more of the above optional embodiments, the Shore hardness of the second pressing block 51 is 30HA-90HA.

[0217] The Shore hardness of the second pressing block 51 is set to be greater than or equal to 30HA and less than or equal to 90HA, so as to facilitate uniform pressure transmission and ensure balanced force on the second electrode assembly 2b.

[0218] In the above manufacturing method of the battery cell 100, the first direction Z can be parallel to the direction of gravity, the first electrode assembly 2a can be located above the second electrode assembly 2b, the first pressing block 41, the third pressing block 42 and the fifth pressing block 43 can be the upper pressing block 4, and the second pressing block 51 can be the lower pressing block 5.

[0219] The features and performance of the battery cell 100 of the present application are further described in detail below in conjunction with the embodiments.

[0220] The battery cells 100 in each embodiment and comparative example are prepared and tested according to the following directions.

[0221] 1. Preparation of battery cell 100

[0222] The active material lithium cobalt oxide, the conductive agent (conductive carbon (super P)), and the binder (polyvinylidene fluoride (PVDF)) are fully stirred and mixed in an N-methylpyrrolidone solvent system at a weight ratio of 94:3:3, and then coated on an aluminum foil, dried, and cold pressed to obtain a positive electrode sheet.

[0223] Active material artificial graphite, conductive agent (conductive carbon (super P)), adhesive (styrene-butadiene rubber (SBR)), thickener (sodium carbon methyl cellulose (CMC)) are fully stirred and mixed in a deionized water solvent system at a weight ratio of 97:1:1.5:0.5, and then coated on copper foil, dried, and cold pressed to obtain a negative electrode sheet.

[0224] The positive electrode sheet, the separator, and the negative electrode sheet are stacked in order, with the separator being placed between the positive electrode sheet and the negative electrode sheet to play an isolating role, to obtain a first electrode assembly 2a and a second electrode assembly 2b, the first electrode assembly 2a and the second electrode assembly 2b are hot-pressed and composited to form a stepped electrode assembly 2 structure, the electrode assembly 2 is placed in a steel shell, the electrolyte is injected and packaged, and after chemical formation, the final battery cell 100 is made.

[0225] 2. Test methods

[0226] 2.1 Adhesion test between the second negative electrode plate and the second separator

[0227] Take the finished battery cell 100 after formation, discharge it at a low rate of 0.5C to 3.0V, and then use a sampler to take out the composite of the second negative electrode sheet and the second diaphragm connected to it from the top layer (first layer) to the bottom layer of the first region 24. Each layer of the composite of the second negative electrode sheet and the second diaphragm connected to it is made into a spline with a length and width of 100mm*15mm. Both sides of the thickness direction of each second negative electrode sheet are connected to the second diaphragm. In order from top to bottom, the test position The second diaphragm on the lower surface of the second negative electrode plate (either the upper surface or the lower surface is acceptable, this is an example), clamp one end of the second diaphragm on the lower surface of the second negative electrode plate to the upper clamp of the high-speed rail tensile machine, and clamp one end of the second negative electrode plate to the lower clamp of the high-speed rail tensile machine. The stretching speed is 50mm / min. The adhesion of each layer of the second negative electrode plate and the second diaphragm is tested 5 times and the average value is taken. The average value is recorded as the adhesion F, which is the adhesion between a group of second negative electrode plates and the second diaphragm. Among the multiple layers of plates from top to bottom, take the group with the largest adhesion and the group with the smallest adhesion. The adhesion difference F0 is calculated as follows: the group with the largest adhesion between the second negative electrode plate and the second diaphragm is F max The group with the smallest bonding force between the second negative electrode plate and the second separator is F min , F0=F max -F min .

[0228] 2.2 Hardness test

[0229] Take a cylindrical sample with a thickness of 10 mm and a diameter of 10 mm, and use a Shore hardness tester to test the hardness of the sample. Test three times and take the average value, which is recorded as the hardness.

[0230] 2.3 Battery Cell 100 Interface Test

[0231] The finished battery cell 100 after being formed was taken and disassembled after being fully charged at 0.5C. The black spots and lithium precipitation on the interface of the second negative electrode plate were visually observed and recorded with a camera.

[0232] Please refer to Table 1 for the test results.

[0233] Table 1

[0234]

[0235] It can be seen from Table 1 that the difference between the maximum and minimum values ​​of the bonding strength between the multi-layer second negative electrode plates and the connected second diaphragm is greater than 2N / m, that is, the difference in bonding strength between any two second negative electrode plates and the connected second diaphragm is greater than 2N / m, or, the bonding strength between the second negative electrode plates and the connected second diaphragm is less than 5N / m, resulting in the precipitation of metallic lithium on the surface of the second negative electrode plates and obvious black spots or purple spots on the interface of the second negative electrode plates.

[0236] When the difference in bonding strength between any two second negative electrode plates and the connected second diaphragms is less than 2 N / m and the bonding strength between the second negative electrode plates and the connected second diaphragms is greater than 5 N / m, the plate interface is significantly improved.

[0237] When the difference in bonding strength between any two second negative electrode plates and the connected second separator is less than 1.8 N / m, and the bonding strength between the second negative electrode plates and the connected second separator is greater than 5 N / m, there are only slight black spots or purple spots on the interface of the second negative electrode plates.

[0238] When the bonding force between the second negative electrode plate and the connected second separator is greater than 10 N / m, and the difference in bonding force between any two second negative electrode plates and the connected second separators is less than 2 N / m, there are only slight black spots or purple spots on the interface of the second negative electrode plate.

[0239] When the difference in bonding strength between any two second negative electrode plates and the connected second diaphragm is less than 1.8 N / m, and the bonding strength between the second negative electrode plates and the connected second diaphragm is greater than 10 N / m, there are no black spots or purple spots.

[0240] Although the present application has been described with reference to preferred embodiments, various modifications may be made thereto and parts thereof may be replaced with equivalents without departing from the scope of the present application. In particular, the various technical features mentioned in the various embodiments may be combined in any manner as long as there are no structural conflicts. The present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A battery cell, characterized in that: It comprises a housing and an electrode assembly, wherein the electrode assembly is accommodated in the housing; The electrode assembly comprises a first electrode assembly and a second electrode assembly, the first electrode assembly and the second electrode assembly are stacked along a first direction, along the second direction, the length of the second electrode assembly is greater than the length of the first electrode assembly, the second electrode assembly has a first surface facing the first electrode assembly and a second surface away from the first electrode assembly, observed along the first direction, the second electrode assembly has an overlapping region overlapping with the first electrode assembly, and a non-overlapping region not overlapping with the first electrode assembly, a side wall of the first electrode assembly close to the non-overlapping region in the second direction and the first surface of the non-overlapping region form a first step, and the second direction is perpendicular to the first direction; The housing forms a second step corresponding to the first step, a receiving space is formed between the first step and the second step, the second electrode assembly has a first region, the first region includes a region overlapping with the receiving space along the first direction, and the first region extends from the first surface to the second surface; The second electrode assembly includes a second positive electrode sheet, a second negative electrode sheet and a second separator, the second separator is arranged between the second positive electrode sheet and the second negative electrode sheet, and in the first region, the difference in bonding force between any two of the second negative electrode sheets and the connected second separators is less than or equal to 2N / m; In the first region, the bonding force between any second negative electrode sheet and the connected second separator is greater than or equal to 5 N / m.

2. The battery cell according to claim 1, characterized in that: In the first region, the difference in bonding strength between any two of the second negative electrode sheets and the second separator connected thereto is less than or equal to 1.8 N / m.

3. The battery cell according to claim 1, characterized in that: The second electrode assembly further has a second region, the second region overlaps with the first electrode assembly along the first direction, and the second region extends from the first surface to the second surface; In the first region, the bonding force between any second negative electrode sheet and the connected second separator is F1; In the second region, the bonding force between any second negative electrode sheet and the connected second separator is F2; Satisfies, 0≤F2-F1≤3N / m.

4. The battery cell according to claim 3, characterized in that: 0≤F2-F1≤2.5N / m.

5. The battery cell according to claim 1, characterized in that: In the first region, the bonding force between any second negative electrode sheet and the connected second separator is greater than or equal to 10 N / m.

6. The battery cell according to claim 1, characterized in that: Along the first direction, the minimum distance between the electrode assembly and the housing is H, satisfying 0≤H≤5mm.

7. The battery cell according to claim 6, characterized in that: 0.4mm≤H≤3.5mm.

8. The battery cell according to claim 1, characterized in that: The housing comprises a first wall and a second wall arranged opposite to each other along the first direction, the first wall comprises a main body wall and a step wall, the step wall is located at at least one end of the main body wall along the second direction, the step wall is recessed relative to the main body wall toward the direction of the second wall, and the step wall is connected to the main body wall via a connecting wall to form the second step; The second electrode assembly is disposed between the step wall and the second wall, the first electrode assembly is disposed between the main body wall and the second electrode assembly, and the first electrode assembly, the second electrode assembly, the connecting wall and the main body wall enclose the accommodating space.

9. The battery cell according to claim 8, characterized in that: The first electrode assembly includes a first positive electrode plate; Along the first direction, the first region has a first overlapping region overlapping with a portion of the first positive electrode sheet, and a second overlapping region overlapping with a portion of the step wall.

10. The battery cell according to claim 9, characterized in that: Along the second direction, the distance between the first positive electrode plate and the step wall is L1, the length of the first overlapping area is L2, and the length of the second overlapping area is L3, satisfying L2 / L1≤0.3, L3 / L1≤0.

3.

11. The battery cell according to claim 1, characterized in that: Along the first direction, the projection area of ​​the first region is S1, and the projection area of ​​the second electrode assembly is S2, satisfying 0.001≤S1 / S2≤0.

2.

12. The battery cell according to claim 1, characterized in that: Along the first direction, the projection area of ​​the first electrode assembly is S3, and the projection area of ​​the second electrode assembly is S2, satisfying 0.2≤S3 / S2≤0.

9.

13. An electrical equipment, characterized in that: The invention comprises a battery cell as claimed in any one of claims 1 to 12.

14. A method for manufacturing a battery cell, used for manufacturing the battery cell according to any one of claims 1 to 13, characterized in that: The manufacturing method of the battery core comprises: The first electrode assembly and the second electrode assembly are stacked along a first direction, the first electrode assembly and the second electrode assembly are both laminated structures, along a second direction, the length of the second electrode assembly is greater than the length of the first electrode assembly, the second direction is perpendicular to the first direction, and at least one end of the electrode assembly along the second direction forms a first step; In the hot pressing composite process, pressure is applied to the first electrode assembly by a first pressing block on a side of the first electrode assembly facing away from the second electrode assembly, and pressure is applied to the second electrode assembly by a second pressing block on a side of the second electrode assembly facing away from the first electrode assembly, wherein along the second direction, the second pressing block does not extend beyond the first electrode assembly.

15. The method for manufacturing a battery cell according to claim 14, characterized in that: Along the second direction, the second pressing block does not exceed the first electrode assembly; Along the first direction, the projection area of ​​the first electrode assembly is S3, and the projection area of ​​the second pressing block is S4, satisfying 0.8≤S4 / S3≤1.

16. The method for manufacturing a battery cell according to claim 15, characterized in that: The Shore hardness of the second pressing block is 30HA to 90HA.

17. The method for manufacturing a battery cell according to claim 14, characterized in that: The manufacturing method of the battery cell also includes: During the formation process, pressure is applied to the first electrode assembly by a third pressing block on a side of the first electrode assembly facing away from the second electrode assembly, and the third pressing block does not exceed the first electrode assembly along the second direction. Pressure is applied to the second electrode assembly by a fourth pressing block on a side of the second electrode assembly facing away from the first electrode assembly, and pressure is applied to a portion of the second electrode assembly that exceeds the first electrode assembly on the side of the first electrode assembly along the second direction by a fifth pressing block.

18. The method for manufacturing a battery cell according to claim 17, characterized in that: Along the second direction, the third pressing block does not exceed the first electrode assembly; Along the first direction, the projection area of ​​the first electrode assembly is S3, and the projection area of ​​the third pressing block is S5, satisfying 0.75≤S5 / S3≤0.

95.

19. The method for manufacturing a battery cell according to claim 17, characterized in that: In the formation process, on the side of the first electrode assembly facing away from the second electrode assembly, the third pressing block applies pressure to the first electrode assembly, and along the second direction, the third pressing block does not exceed the first electrode assembly, on the side of the second electrode assembly facing away from the first electrode assembly, the fourth pressing block applies pressure to the second electrode assembly, and on the side of the first electrode assembly along the second direction, the fifth pressing block applies pressure to the portion of the second electrode assembly exceeding the first electrode assembly, the method for manufacturing the battery cell further includes: The first electrode assembly and the second electrode assembly are placed in a housing.

20. The method for manufacturing a battery cell according to claim 19, characterized in that: The housing comprises a first wall and a second wall arranged opposite to each other along the first direction, the first wall having a main body wall and a step wall, the step wall being located at at least one end of the main body wall along the second direction, the step wall being recessed relative to the main body wall toward the direction of the second wall, the step wall being connected to the main body wall through a connecting wall to form the second step, the second electrode assembly being arranged between the step wall and the second wall, and the first electrode assembly being arranged between the main body wall and the second electrode assembly; Along the second direction, the first pressing block does not exceed the first electrode assembly; In the formation process, a pressure is applied to the first electrode assembly by a third pressing block on a side of the first electrode assembly facing away from the second electrode assembly, and the third pressing block does not exceed the first electrode assembly along the second direction; On a side of the second electrode assembly facing away from the first electrode assembly, a fourth pressing block applies pressure to the second electrode assembly, and on a side of the first electrode assembly along the second direction, a fifth pressing block applies pressure to a portion of the second electrode assembly that exceeds the first electrode assembly, including: In the formation process, on the side of the first electrode assembly facing away from the second electrode assembly, a third pressing block abuts against the main body wall to apply pressure to the first electrode assembly, and along the second direction, the third pressing block does not exceed the first electrode assembly; On the side of the second electrode assembly facing away from the first electrode assembly, the fourth pressing block is pressed against the second wall to apply pressure to the second electrode assembly; on the side of the first electrode assembly along the second direction, the fifth pressing block is pressed against the step wall to apply pressure to the portion of the second electrode assembly that exceeds the first electrode assembly.

21. The method for manufacturing a battery cell according to claim 20, characterized in that: Along the first direction, the projection area of ​​the fifth pressing block is S6, and the projection area of ​​the portion of the second electrode assembly that exceeds the first electrode assembly is S7, satisfying 0.8≤S6 / S7≤1.

22. The method for manufacturing a battery cell according to claim 20, characterized in that: The Shore hardness of the fifth pressing block is 30HA-90HA.

23. The method for manufacturing a battery cell according to claim 17 or 22, characterized in that: The material of any one of the second pressing block, the third pressing block and the fifth pressing block is at least one of polyurethane, silicone rubber, ethylene propylene rubber, butyl rubber, chloroprene rubber, nitrile butadiene rubber, styrene butadiene rubber, fluororubber, nylon 6, nylon 66, polyethylene, polypropylene, polyethylene terephthalate, polybutylene terephthalate, polycarbonate or polystyrene.

24. The method for manufacturing a battery cell according to claim 14, characterized in that: The manufacturing method of the battery cell also includes: In the formation process, on the side of the first electrode assembly facing away from the second electrode assembly, pressure is applied to the first electrode assembly through a third pressing block, the third pressing block is divided into a first part and a second part along the second direction, along the first direction, the first part overlaps with the first electrode assembly, the second part does not overlap with the first electrode assembly, the thickness of the second part is greater than the first part, the second part applies pressure to the second electrode assembly, the Shore hardness of the third pressing block is 30HA to 90HA, and the thickness of the second part exceeding the first part along the first direction is greater than the thickness of the first electrode assembly.

25. The method for manufacturing a battery cell according to claim 24, characterized in that: The material of the second pressing block or the third pressing block is at least one of polyurethane, silicone rubber, ethylene propylene rubber, butyl rubber, chloroprene rubber, nitrile butadiene rubber, styrene butadiene rubber, fluororubber, nylon 6, nylon 66, polyethylene, polypropylene, polyethylene terephthalate, polybutylene terephthalate, polycarbonate or polystyrene.

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