Battery cell and electric device

Abstract

A battery cell and an electric device. The battery cell comprises a case and a pressure relief assembly, wherein the case is provided with an accommodating space and an electrolyte injection hole in communication with the accommodating space; and the pressure relief assembly covers the electrolyte injection hole, and the pressure relief assembly comprises an adapter, a sealing member and a pressure relief member, the case, the adapter, the sealing member and the pressure relief member being stacked in sequence in a first direction, the adapter comprising a first main body portion and a first weld mark portion, the first main body portion being provided with a first side wall arranged in a circumferential direction, and the first weld mark portion connecting the first side wall to the case. The safety of the battery cell is improved.

Description

Battery cells and electrical devices

[0001] This application claims priority to the Chinese patent application filed with the China Patent Office on January 29, 2024, with application number 202410121847.9 and invention name “Battery Cell and Electrical Device”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present application relates to the technical field of electric energy storage, and in particular to a battery cell and an electric device. Background Art

[0003] A battery cell is a device that converts external energy into electrical energy and stores it internally, thereby powering external electrical devices (such as portable electronic devices) when needed. In related technologies, a battery cell includes a housing with an injection hole, through which electrolyte is injected into the housing. The injection hole is then sealed with a pressure relief assembly. If the pressure relief assembly does not seal the injection hole well during assembly, the risk of leakage from the battery cell will be high, reducing the safety of the battery cell.

[0004] In summary, it is necessary to design a battery cell and an electrical device to solve the above technical problems. Summary of the Invention

[0005] Embodiments of the present application provide a battery cell and an electrical device, wherein the safety of the battery cell is improved.

[0006] In a first aspect, an embodiment of the present application provides a battery cell, comprising:

[0007] The shell has a receiving space and a liquid injection hole communicating with the receiving space;

[0008] The pressure relief assembly covers the liquid injection hole. The pressure relief assembly includes an adapter, a seal and a pressure relief assembly. The shell, the adapter, the seal and the pressure relief assembly are stacked in sequence along the first direction. The adapter includes a first main body and a first weld mark. The first main body has a first side wall arranged along the circumferential direction. The first weld mark connects the first side wall and the shell.

[0009] In some embodiments, a projection of the sealing component along the first direction on the adapter is a first projection, and the first projection is located in the first main body portion and is spaced apart from the first welding mark portion.

[0010] In some embodiments, the minimum spacing distance between the first projection and the first welding mark portion is d3, and d3 satisfies 0.02 mm to 0.5 mm.

[0011] In some embodiments, d3 satisfies 0.05 mm to 0.22 mm.

[0012] In some embodiments, the first welding mark is located at an edge of the adapter.

[0013] In some embodiments, the first weld mark portion has a width of the first weld mark portion along the second direction, the first weld mark portion has a first surface of the shell and a second surface facing the shell, the width of the first surface is d1, d1 satisfies 0.05mm~0.25mm, and the second direction is perpendicular to the first direction.

[0014] In some embodiments, the width of the second surface is d2, and d2 satisfies 0.02 mm to 0.15 mm.

[0015] In some embodiments, the shell includes a shell wall and a second weld mark portion, wherein the second weld mark portion is embedded in the shell wall and connected to the first weld mark portion.

[0016] In some embodiments, the length of the second welding mark portion along the first direction is H2, and H2 satisfies 0.01 mm to 0.06 mm.

[0017] In some embodiments, the adapter has a first through hole connected to the liquid injection hole, the sealing component has a second through hole connected to the liquid injection hole, and the pressure relief component covers the second through hole.

[0018] In some embodiments, a projection of the sealing member on the adapter along the first direction falls into the first through hole.

[0019] In some embodiments, the edge of the sealing member is located outside a projection of the pressure relief member on the sealing member along the first direction.

[0020] In some embodiments, a projection of the adapter on the housing along the first direction falls into the liquid injection hole.

[0021] In some embodiments, the seal comprises a first adhesive layer, a second adhesive layer, and a third adhesive layer sequentially arranged along a first direction, wherein the melting point of the second adhesive layer is greater than that of the first adhesive layer, and the melting point of the second adhesive layer is greater than that of the third adhesive layer.

[0022] In some embodiments, the maximum length of the housing along the second direction is greater than the maximum length of the pressure relief assembly along the third direction, and the maximum length of the housing along the first direction is greater than the maximum length of the pressure relief assembly along the third direction.

[0023] The maximum length of the pressure relief component along the second direction is greater than the maximum length of the pressure relief component along the third direction, and the first direction, the second direction and the third direction are perpendicular to each other.

[0024] In some embodiments, the length of the adapter along the third direction is L1, and L1 satisfies 1.0-6 mm.

[0025] In some embodiments, the first welding mark portion is a welding mark formed by swing welding.

[0026] In a second aspect, an embodiment of the present application further provides an electrical device, comprising a battery cell provided according to the second aspect, wherein the battery cell is used to provide electrical energy.

[0027] Compared with the related art, in the battery cell and the electrical device provided in the embodiment of the present application, the first weld mark portion and the shell are welded to each other, so that the connection between the shell and the adapter is stable, and the electrolyte is prevented from flowing out of the shell from between the shell and the first weld mark portion; the sealing member is stacked between the first main body and the pressure relief member, so that the connection between the adapter and the pressure relief member is stable, and the electrolyte is prevented from flowing out of the shell from between the adapter and the pressure relief member; the first weld mark portion is connected to the first side wall by providing a connection between the first weld mark portion and the shell, thereby reducing the size of the adapter and miniaturizing the pressure relief assembly, and the first weld mark portion is connected to the first side wall, thereby increasing the spacing distance between the first weld mark portion and the sealing member, avoiding the processing steps of forming the first weld mark portion affecting the structure of the sealing member, reducing or avoiding battery cell leakage to a certain extent, and improving the safety of the battery cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following briefly introduces the drawings required for use in the embodiments of the present application. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0029] FIG1 is a schematic diagram of the three-dimensional structure of a battery cell provided in one embodiment of the present application;

[0030] FIG2 is a schematic diagram of the disassembled structure of a battery cell provided in one embodiment of the present application;

[0031] FIG3 is a schematic diagram of a partial cross-sectional structure of a battery cell provided in one embodiment of the present application;

[0032] FIG4 is a schematic diagram of a partial cross-sectional structure of a battery cell provided in one embodiment of the present application;

[0033] FIG5 is a schematic diagram of a partial cross-sectional structure of a battery cell provided in a first ratio of related art;

[0034] FIG6 is a schematic diagram of a partial cross-sectional structure of a battery cell provided in one embodiment of the present application;

[0035] FIG7 is a schematic diagram of a partial cross-sectional structure of a sealing member provided in one embodiment of the present application;

[0036] FIG8 is a schematic diagram of a planar structure of a battery cell provided in one embodiment of the present application;

[0037] FIG9 is a schematic diagram of the three-dimensional structure of a battery cell provided in one embodiment of the present application;

[0038] FIG10 is an enlarged structural diagram of portion A shown in FIG9 ;

[0039] FIG11 is an electron microscope image of a partial cross-sectional structure of a battery cell provided in one embodiment of the present application.

[0040] In the accompanying drawings: 1. Shell; 11. Liquid injection hole; 12. Shell wall; 13. Second weld mark portion; 14. Accommodation space; 15. Upper cover; 16. Lower cover; 17. Recessed portion; 2. Pressure relief assembly; 21. Adapter; 211. First main body portion; 212. First weld mark portion; 213. First side wall; 214. First through hole; 22. Sealing member; 221. Second through hole; 224. First adhesive layer; 222. Second adhesive layer; 223. Third adhesive layer; 23. Pressure relief member; X, first direction; Y, second direction; Z, third direction. DETAILED DESCRIPTION

[0041] The features and exemplary embodiments of various aspects of the present application will be described in detail below. In the detailed description below, many specific details are proposed to provide a comprehensive understanding of the present application. However, it will be apparent to those skilled in the art that the present application can be implemented without the need for some of these specific details. The following description of the embodiments is merely intended to provide a better understanding of the present application by illustrating the examples of the present application.

[0042] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The embodiments will be described in detail below with reference to the accompanying drawings.

[0043] In one aspect, the present application provides a battery cell. In order to better understand the technical solution and technical effects of the present application, specific embodiments will be described in detail below with reference to the accompanying drawings.

[0044] Please refer to Figures 1, 2, 3 and 4. A battery cell includes a shell 1 and a pressure relief assembly 2. The shell 1 has a receiving space 14 and a liquid injection hole 11 connected to the receiving space 14; the pressure relief assembly 2 covers the liquid injection hole 11, and the pressure relief assembly 2 includes an adapter 21, a seal 22 and a pressure relief member 23. The shell 1, the adapter 21, the seal 22 and the pressure relief member 23 are stacked in sequence along the first direction X. The adapter 21 includes a first main body 211 and a first weld mark 212. The first weld mark 212 surrounds the first main body 211. The first main body 211 has a first side wall 213 arranged along the circumferential direction. The first weld mark 212 connects the first side wall 213 and the shell 1.

[0045] The battery cells provided in this application may specifically be lithium-ion secondary battery cells, lithium-ion primary battery cells, lithium-sulfur battery cells, sodium-lithium-ion battery cells, sodium-ion battery cells or magnesium-ion battery cells, etc., and the embodiments of this application are not limited to this.

[0046] The housing 1 has an upper cover 15 and a lower cover 16, which together form a receiving space 14 of the housing 1. A battery cell can be placed in the receiving space 14. The battery cell includes a positive electrode sheet, a negative electrode sheet, and a separator. The portion of the battery cell containing active material constitutes the positive and negative electrode sheets of the battery cell, and the portion without active material constitutes the tab. Electrolyte can also be injected into the receiving space 14 through the injection hole 11, and the positive electrode sheet, negative electrode sheet, and separator are immersed in the electrolyte. In some embodiments, the positive electrode sheet, negative electrode sheet, and separator are wound to form a wound structure. In other embodiments, the positive electrode sheet, separator, and negative electrode sheet are stacked in sequence to form a laminated structure. Those skilled in the art can select a suitable battery cell as needed. During the charge and discharge process of the battery cell, the positive electrode active material and the negative electrode active material react with the electrolyte. The tab is used to connect the electrode terminal to form a current circuit, and the electrode terminal is led out from one end of the housing 1.

[0047] The housing 1 may include a top wall and a bottom wall arranged along a thickness direction Z, and a side wall connecting the top wall and the bottom wall. The injection hole 11 may be arranged on the side wall. The first direction X may be a length direction or a width direction of the housing 1.

[0048] The pressure relief assembly 2 is welded to the housing 1 via the adapter 21, allowing the pressure relief assembly 2 to seal the injection hole 11 and prevent leakage of the electrolyte in the housing 1. The seal 22 is made of a material with a preset melting point, which can be lower than the melting point of the adapter 21 and / or lower than the melting point of the pressure relief member 23. When the battery cell is in a thermal runaway state, the temperature of the seal 22 reaches the preset melting point, the seal 22 melts, and a pressure relief channel is formed between the adapter 21 and the pressure relief member 23. The pressure in the housing 1 is relieved through the pressure relief channel, thereby preventing or reducing the risk of battery cell explosion.

[0049] The adapter 21 can be in the shape of a metal plate to facilitate welding of the adapter and the housing 1. The adapter 21 can be a nickel sheet with a passivation layer, and the passivation layer is chromium oxide. The pressure relief member 23 can also be in the shape of a metal plate to facilitate the sealing member 22 to connect the adapter 21 and the pressure relief member 23. The pressure relief member 23 can be a nickel sheet with a passivation layer, and the passivation layer is chromium oxide. The nickel sheet after cleaning the surface can be immersed in a chromate solution to form a passivation layer of chromium oxide on the surface of the nickel sheet. Optionally, the thickness of the passivation layer is 10nm to 150nm. The passivation layer can reduce or prevent the electrolyte from corroding the adapter 21 and the pressure relief member 23. The adapter 21 and the pressure relief member 23 can be made of different materials so that the adapter 21 and the pressure relief member 23 have different physical and chemical properties. The adapter 21 and the pressure relief member 23 can also be made of the same material to simplify the preparation steps.

[0050] When preparing a battery cell, the adapter 21, the seal 22 and the pressure relief component 23 can be stacked in sequence to pre-assemble the pressure relief assembly 2, and then the assembled pressure relief assembly 2 can be welded to the shell 1, and the pressure relief assembly 2 can seal the injection hole 11. The adapter 21 and the shell 1 can be connected by welding. When welding the adapter 21 and the shell 1, the welding gun acts on the edge of the adapter 21 to melt the edge of the adapter 21 and the area corresponding to the edge in the shell 1, and the two solidify to form a first weld mark 212. The first weld mark 212 is located at the edge of the adapter 21. Since the first weld mark 212 is a weld mark formed by welding, the crystal structure of the first weld mark 212 and the crystal structure of the first main body 211 are different, forming an interface. The first side wall 213 is located at this interface.

[0051] Please refer to Figure 5, which is a schematic diagram of the cross-sectional structure of the pressure relief assembly of the comparative example in the related art. In the pressure relief assembly of the comparative example, the adapter 21b, the seal 22b and the pressure relief member 23b are stacked in sequence. When welding the adapter 21 and the shell 1, the welding gun acts on the connection between the main body 211b and the edge 212c of the adapter 21b, and the material corresponding to the connection melts to form a weld mark portion 212b. The adapter 21b after welding has a main body 211b, a weld mark portion 212b and an edge portion 212c connected in sequence, and the weld mark portion 212b is not located at the edge of the adapter 21. When the adapter 21 in this embodiment and the adapter 21b in the comparative example maintain the same size, the distance between the first weld mark portion 212 and the seal 22 is greater than the distance between the weld mark portion 212b and the seal 22b, so that during the assembly of the pressure relief assembly 2 and the shell 1, the structural damage to the seal 22 is avoided or reduced.

[0052] In this embodiment, by setting the first weld mark 212 and welding it to the shell 1, the connection between the shell 1 and the adapter 21 is stable, and the electrolyte is prevented from flowing out of the shell 1 from between the shell 1 and the first weld mark 212; by setting the sealing member 22 to be stacked between the first main body 211 and the pressure relief member 23, the connection between the adapter 21 and the pressure relief member 23 is stable, and the electrolyte is prevented from flowing out of the shell 1 from between the adapter 21 and the pressure relief member 23; by setting the first weld mark 212 to connect the first side wall 213 and the shell 1, the size of the adapter 21 is reduced to miniaturize the pressure relief assembly 2, and the first weld mark 212 is connected to the first side wall 213, thereby increasing the spacing distance between the first weld mark 212 and the sealing member 22, avoiding the processing step of forming the first weld mark 212 affecting the structure of the sealing member 22, reducing or preventing battery cell leakage to a certain extent, and improving the safety of the battery cell.

[0053] Referring to FIG. 4 , in some embodiments, a projection of the sealing member 22 along the first direction X on the adapter 21 is a first projection. The first projection is located within the first main body portion 211 and spaced apart from the first welding mark portion 212 .

[0054] The projection of the sealing member 22 along the first direction X on the adapter 21 is arranged to be located within the first main body portion 211 and spaced apart from the first welding mark portion 212, so that when welding the first welding mark portion 212 and the shell 1, the welding area is spaced apart from the sealing member 22 by a certain distance, which can avoid or reduce the impact of the welding operation on the connection between the sealing member 22 and the adapter 21 and the pressure relief member 23 when welding the first welding mark portion 212 and the shell 1, avoid or reduce damage to the pressure relief assembly 2, thereby improving the safety of the prepared battery cell.

[0055] In some embodiments, the minimum spacing distance d3 between the first projection and the first welding mark portion 212 is 0.02 mm to 0.5 mm.

[0056] If d3 is too narrow, the heat generated by welding during the process of forming the first weld mark 212 will be easily transferred to the seal 22, reducing the reliability of the seal 22. If d3 is too wide, the adapter 21 will be too large or the seal 22 will be too small. If the adapter 21 is too large, it will be not conducive to the miniaturization of the battery cell. If the seal 22 is too small, the pressure relief channel formed by the melted seal 22 will have insufficient pressure reduction capacity in the event of electrical runaway. Set d3 to 0.02mm~0.5mm to reduce or avoid the heat generated during the welding process affecting the reliability of the sealing layer. The size of the adapter 21 and the size of the seal 22 are appropriate. Optionally, d3 is 0.05mm~0.22mm, which further ensures the miniaturization of the battery while improving the reliability of the sealing layer.

[0057] In some embodiments, the first weld mark portion 212 is the width of the first weld mark portion 212 along the second direction Y, the first weld mark portion 212 has a first surface facing away from the shell 1 and a second surface facing the shell 1, the width of the first surface is d1, d1 satisfies 0.05mm~0.25mm, and the second direction Y is perpendicular to the first direction X.

[0058] In the case where the adapter 21 is in the shape of a circular ring, the second direction Y can be the radial direction of the adapter 21. If d1 is too narrow, it will affect the first weld mark 212 from conducting heat energy to the second weld mark 13, and affect the connection area between the first weld mark 212 and the second weld mark 13. If d1 is too wide, it will affect the spacing distance between the first weld mark 212 and the sealing member 22, and the structure of the sealing member 22 may be affected during the formation of the first weld mark 212. d1 is set to 0.05mm~0.25mm to ensure that the connection between the first weld mark 212 and the second weld mark 13 formed during the welding process is stable, and the spacing distance between the first weld mark 212 and the sealing member 22 is large enough to avoid or reduce the impact of the welding operation on the sealing member 22. Optionally, d1 is 90um~120um.

[0059] In some embodiments, the width of the second surface is d2, and d2 satisfies 0.02 mm to 0.15 mm.

[0060] If d2 is too narrow, it will affect the stability of the connection between the first weld mark 212 and the shell 1. If d2 is too wide, during the formation of the first weld mark 212, a large amount of heat energy generated by welding will be transferred to the shell, which will easily affect the electrolyte in the shell 1 and the quality of the battery cell. Set d2 to 0.02mm~0.15mm to ensure that the first weld mark 212 formed during the welding process is stably connected to the shell 1, and avoid or reduce the heat energy generated by welding affecting the electrolyte and battery cells. When the welding gun acts on the surface of the adapter 21 away from the shell 1 to form the first weld mark 212, the working parameters of the welding gun are controlled so that d1 is greater than d2, or d1 and d2 are the same.

[0061] In some embodiments, the housing 1 includes a housing wall 12 and a second welding mark portion 13 . The second welding mark portion 13 is embedded in the housing wall 12 and connected to the first welding mark portion 212 .

[0062] When the welding torch is applied to adapter 21, high temperature is transferred through adapter 21 to housing 1, causing some of the housing 1 material to melt, forming a second weld mark 13 connected to first weld mark 212. The welding torch parameters are controlled so that the formed second weld mark 13 is embedded in housing wall 12, but does not penetrate through it. This prevents over-welding and prevents the welding operation from affecting the electrolyte, battery cells, etc. within housing 1.

[0063] Please refer to FIG. 6 . In some embodiments, the length of the second welding mark portion 13 along the first direction X is H2 , and H2 satisfies 0.01 mm to 0.06 mm.

[0064] The length of the first weld mark 212 along the first direction X is H1. Since the first weld mark 212 passes through the first main body 211, H1 can be equal to the length of the adapter 21 along the first direction X. The second weld mark 13 is embedded in the shell 1 to form the shell wall 12 of the liquid injection hole 11, so that the length H2 of the second weld mark 13 along the first direction X is less than the length H3 of the shell wall 12 along the first direction X. If H2 is too small, it will affect the stability of the connection between the shell 1 and the second weld mark 13. If H2 is too large, the second weld mark 13 will be too deep, resulting in over-welding. H2 is set to 0.01mm~0.06mm to ensure that the connection between the first weld mark 212 and the second weld mark 13 formed during the welding process is stable, and the size of the second weld mark 13 is small enough to avoid or reduce the formation of the second weld mark 13 affecting the electrolyte and battery cells.

[0065] In some embodiments, the adapter 21 has a first through hole 214 communicating with the liquid injection hole 11 , the sealing member 22 has a second through hole 221 communicating with the liquid injection hole 11 , and the pressure relief member 23 covers the second through hole 221 .

[0066] The injection hole 11, first through hole 214, and second through hole 221 can be coaxially arranged. The receiving space 14, injection hole 11, first through hole 214, and second through hole 221 are sequentially connected. The diameter of the injection hole 11 can be greater than or equal to the diameter of the first through hole 214, and the diameter of the first through hole 214 can be greater than the diameter of the second through hole 221. In the event of thermal runaway of the battery cell, the pressure relief channel formed by the melting of the seal 22 communicates with the second through hole 221, allowing the pressure relief channel to exhaust the high-pressure gas in the receiving space 14.

[0067] In some embodiments, a projection of the sealing member 22 on the adapter 21 along the first direction X falls into the first through hole 214 .

[0068] The seal 22 and adapter 21 can be annular. The outer diameter Φ1 of the adapter 21 is greater than the outer diameter Φ2 of the seal 22. That is, the projection of the outer edge of the seal 22 along the first direction X is located inward of the outer edge of the adapter 21. This allows the first projection of the seal 22 stacked on the adapter 21 to be spaced apart from the first weld mark 212. The inner diameter ψ1 of the adapter 21 is greater than the inner diameter ψ1 of the seal 22. This allows the projection of the seal 22 along the first direction X onto the adapter 21 to partially fall into the first through-hole 214, thereby improving the sealing performance of the seal 22 between the adapter 21 and the pressure relief member 23.

[0069] In some embodiments, an edge of the sealing member 22 is located outside a projection of the pressure relief member 23 along the first direction X onto the sealing member 22 .

[0070] The outer diameter Φ3 of the pressure relief member 23 is smaller than the outer diameter Φ2 of the sealing member 22, so that the edge of the sealing member 22 is located outside the projection of the pressure relief member 23 on the sealing member 22 along the first direction X. The pressure relief member 23 can be stacked on the sealing member 22, ensuring an effective seal between the sealing member 22 and the pressure relief member 23. The outer diameter Φ3 of the pressure relief member 23 is larger than the inner diameter ψ1 of the sealing member 22, so that the pressure relief member 23 can cover the second through hole 221 along the first direction X, thereby sealing the liquid injection hole 11.

[0071] In some embodiments, a projection of the adapter 21 on the housing 1 along the first direction X falls into the liquid injection hole 11 .

[0072] The outer diameter Φ1 of the adapter 21 is larger than the diameter r1 of the liquid injection hole 11, allowing the adapter 21 to cover one side of the liquid injection hole 11. The inner diameter ψ1 of the adapter 21 is smaller than the diameter r1 of the liquid injection hole 11, allowing the projection of the adapter 21 on the housing 1 along the first direction X to fall into the liquid injection hole 11. This increases the diameter of the liquid injection hole 11, facilitates liquid injection into the receiving space 14 through the liquid injection hole 11, reduces the diameter of the first through hole 214, reduces the diameter of the second through hole 221, and reduces the size of the pressure relief member 23, thereby improving the sealing performance between the adapter and the seal 22, and between the seal 22 and the pressure relief member 23.

[0073] The diameter D1 of the liquid injection hole 11 may be 0.5-3 mm to ensure the efficiency of liquid injection through the liquid injection hole 11 .

[0074] In some embodiments, the outer diameter Φ1 of the adapter 21 is 3 to 4 mm, the inner diameter ψ1 of the adapter 21 is 0.5 to 2 mm, and the thickness of the adapter 21 along the first direction X is 0.05 to 1.5 mm. The inner diameter ψ1 of the adapter 21 is the diameter of the first through hole 214. If the inner diameter ψ1 of the adapter 21 is too large, the area required for the adapter 21 to connect with the housing 1 increases, which is not conducive to sealing the adapter 21 and the housing 1. If the inner diameter ψ1 of the adapter 21 is too small, the diameter of the first through hole 214 is reduced, which is not conducive to pressure relief through the first through hole 214 in the event of thermal runaway.

[0075] In one embodiment, the initial outer diameter of the seal 22 before the adapter 21 and the pressure relief member 23 are bonded is 2 to 4 mm, the initial inner diameter of the seal 22 is 0.8 to 1.9 mm, and the initial thickness of the seal 22 along the first direction X is 0.05 to 1.5 mm. The seal 22 is hot-pressed to connect the adapter 21 and the pressure relief member 23. After the hot-pressing, the outer diameter Φ2 of the seal 22 is 2.5 to 3.0 mm, the inner diameter ψ2 of the seal 22 is 0.6 to 1.0 mm, and the thickness of the seal 22 along the first direction X is 0.03 to 0.07 mm. The inner diameter ψ2 of the seal 22 is the aperture of the second through hole 221. If the inner diameter ψ2 of the seal 22 is too large, the connection area between the seal 22 and the pressure relief component 23 will be reduced, which is not conducive to the sealing between the seal 22 and the pressure relief component 23; if the inner diameter ψ2 of the seal 22 is too small, the aperture of the second through hole 221 will be reduced, and the seal 22 after melting will easily overflow excessively, which is not conducive to forming a pressure relief channel and not conducive to pressure relief in the case of thermal runaway.

[0076] In one embodiment, the outer diameter Φ3 of the pressure relief member 23 is 2 to 3 mm, and the thickness of the pressure relief member 23 along the first direction X is 0.1 to 0.2 mm. If the outer diameter Φ3 of the pressure relief member 23 is too large, it is not conducive to forming a pressure relief channel in the melted seal 22, which is not conducive to pressure relief in the event of thermal runaway. If the outer diameter Φ3 of the pressure relief member 23 is too small, the area of ​​the pressure relief member 23 available for connection with the seal 22 is reduced, which is not conducive to the sealing between the seal 22 and the pressure relief member 23.

[0077] Optionally, the outer diameter Φ1 of the adapter 21 is 3.4 mm, the inner diameter ψ1 of the adapter 21 is 1 mm, and the thickness of the adapter 21 along the first direction X is 0.08 mm. The outer diameter Φ3 of the pressure relief member 23 is 2.5 mm, and the thickness of the pressure relief member 23 along the first direction X is 0.08 mm. The diameter D1 of the injection hole 11 is 1-2 mm. The initial outer diameter of the sealing member 22 before the adapter 21 and the pressure relief member 23 are bonded is 2.2 mm, the initial inner diameter of the sealing member 22 is 1.2 mm, and the initial thickness of the sealing member 22 along the first direction X is 0.08 mm.

[0078] The seal 22 can be single-layer or multi-layer. A single-layer seal 22 is made of the same material so that the melting point of the seal 22 is consistent. A multi-layer seal 22 is made of different materials so that different layers have different melting points.

[0079] In some embodiments, the sealant 22 is a single layer, and the melting point of the sealant 22 is 123±5°C.

[0080] 7 , in some embodiments, the seal 22 is double-layered, including a first adhesive layer 224 and a second adhesive layer 222 . The first adhesive layer 224 is located on a side of the second adhesive layer 222 close to the adapter 21 . The melting point of the first adhesive layer 224 is 123±5° C.

[0081] In some embodiments, the seal 22 includes a first adhesive layer 224 , a second adhesive layer 222 , and a third adhesive layer 223 sequentially arranged along the first direction X. The melting point of the second adhesive layer 222 is greater than that of the first adhesive layer 224 , and the melting point of the second adhesive layer 222 is greater than that of the third adhesive layer 223 .

[0082] The first adhesive layer 224 and the third adhesive layer 223 can be made of the same material. Optionally, the melting point of the first adhesive layer 224 and the third adhesive layer 223 is 123±5°C. The melting point of the second adhesive layer 222 is 145±10°C. In the event of thermal runaway, the first adhesive layer 224 and the third adhesive layer 223 melt before the second adhesive layer 222, so that the second adhesive layer 222 can support the first adhesive layer 224 and the third adhesive layer 223. The first adhesive layer 224 melts, forming a pressure relief channel between the second adhesive layer 222 and the adapter 21; the third adhesive layer 223 melts, forming a pressure relief channel between the second adhesive layer 222 and the pressure relief member 23.

[0083] 8 and 9 , in some embodiments, the maximum length of the housing 1 along the second direction Y is greater than the maximum length of the pressure relief assembly along the third direction Z, and the maximum length of the housing 1 along the first direction X is greater than the maximum length of the pressure relief assembly along the third direction Z.

[0084] The maximum length L2 of the pressure relief assembly 2 along the second direction Y is greater than the maximum length L1 of the pressure relief assembly 2 along the third direction Z. The first direction X, the second direction Y and the third direction Z are perpendicular to each other.

[0085] The reference plane of the second direction Y and the third direction Z can be parallel to the shell wall 12 forming the injection hole 11. The pressure relief assembly 2 can be rectangular, the first direction X and the second direction Y can be the length and width directions of the shell 1, respectively, and the third direction Z can be the thickness direction of the battery cell.

[0086] The pressure relief assembly 2 is set so that its maximum length L2 along the second direction Y is greater than its maximum length L1 along the third direction Z, so as to increase the contact area between the pressure relief assembly 2 and the shell 1. If the size of the adapter 21 is too small, the size of the liquid injection hole 11 will be reduced, affecting the liquid injection efficiency; if the size of the adapter 21 is too large, the occupancy rate of the adapter 21 on the surface of the shell 1 will increase, which is not conducive to the arrangement of other structures on the shell 1. The length of the adapter 21 in the third direction Z is L1, and L1 can be 1.0 to 6 mm. Optionally, the length of the adapter 21 in the third direction Z is 1.0 mm to 3.5 mm. The length of the shell 1 along the third direction Z can be 1.1 mm to 5 mm, and the thickness of the shell wall 12 along the first direction X is 0.075 to 0.20 mm.

[0087] Please refer to Figure 10. In some embodiments, the shell 1 has a recess 17, which is recessed relative to the outer surface of the shell 1 in a direction closer to the battery cell. The liquid injection hole 11 is opened in the recess 17, and the pressure relief assembly 2 is arranged in the recess 17. The surface of the pressure relief member 23 facing away from the adapter is coplanar with the outer surface of the shell 1, or the surface of the pressure relief member 23 facing away from the adapter is located on the side of the outer surface of the shell 1 close to the battery cell.

[0088] In some embodiments, the first welding mark portion 212 is a welding mark formed by swing welding.

[0089] The adapter 21 and the housing 1 can be welded using oscillatory welding. During welding, the welding torch can be moved relative to the adapter 21 in a first welding direction, thereby forming a first weld mark 212 on the adapter 21 extending along the first welding direction. Simultaneously, the welding torch also reciprocates in a second welding direction, resulting in a wave-like movement path. This ensures good fusion of the first weld mark 212 formed on the adapter 21, improving weld quality, enhancing the stability of the weld between the first weld mark 212 and the housing 1, and improving the airtightness between the adapter 21 and the housing 1. The first and second welding directions intersect.

[0090] Exemplarily, when preparing a battery cell, the adapter 21, the seal 22 and the pressure relief member 23 are stacked in sequence to pre-assemble the pressure relief assembly 2; the battery cell is placed in the shell 1, and the electrolyte is injected into the shell 1 through the injection hole 11; an image showing the injection hole 11 is obtained, the injection hole 11 in the image is identified, and the first coordinate information of the injection hole 11 is obtained, and the second coordinate information is obtained based on the preset offset coordinate and the first coordinate information; according to the second coordinate information, the pre-assembled pressure relief assembly 2 is controlled to be located on one side of the injection hole 11 so that the pressure relief assembly 2 covers the injection hole 11; an image showing the adapter 21 is obtained, the adapter 21 in the image is identified, and the third coordinate information of the welding is obtained; the carrier carrying the shell 1 is moved to be opposite to the laser galvanometer, and the welding gun is controlled to shoot the laser to the position corresponding to the first weld mark 212 in the adapter 21 according to the third coordinate information to weld to form the first weld mark 212 welded to the shell 1. During the welding process, the welding gun will swing at a preset frequency to form a first welding mark portion 212 stably connected to the housing 1 .

[0091] By arranging the swing welding to form the first welding mark portion 212 , the stability of the connection between the adapter 21 and the housing 1 is improved, and the leakage of the battery cell is reduced or avoided to a certain extent, thereby improving the safety of the battery cell.

[0092] In a second aspect, the present application further provides an electrical device, which includes the battery cell provided in the first aspect, and the battery cell is used to provide electrical energy.

[0093] There can be multiple battery cells, which can be connected in series, in parallel, or in hybrid connection to form a whole, through which charging and discharging are carried out. Hybrid connection means that multiple battery cells are connected in both series and in parallel.

[0094] Specific product types of electrical devices include but are not limited to mobile terminals, smart wearables, power tools, electric vehicles, mobile power supplies, etc.

[0095] Since the battery cell has the aforementioned beneficial effects, the electrical device is safe and reliable to use.

[0096] The above-mentioned beneficial effects are further illustrated below through examples and comparative examples.

[0097] Examples 1-26

[0098] Battery cells were prepared using the parameters listed in Tables 1-3. Unless otherwise specified, the adapter, seal, and pressure relief member of Examples 1-26 were identical and coaxially arranged. The width of the first surface was d1, the minimum separation distance between the first projection and the first weld mark 212 was d3, and the width of the second surface was d2.

[0099] The prepared battery cells were subjected to bonding strength testing. With the housing 1 fixed, a pin, compatible with the injection port 11, was used to apply varying thrusts F1 to the adapter 21. The bonding strength between the adapter 21 and the housing 1 was measured. With the housing 1 and adapter 21 fixed, a pin, compatible with the injection port 11, was used to apply thrusts F2 to the pressure relief member 23. The bonding strength between the seal 22 and the adapter 21 and the pressure relief member 23 was measured. For each embodiment or comparative example, 100 repetitions were performed. The average bonding strength of the battery cells in the same group was calculated and recorded as the bonding strength for that embodiment or comparative example.

[0100] The prepared battery cells were subjected to a high-temperature, high-humidity test. The fully charged battery cells were placed in an open circuit at (65±2)°C and 90-95% humidity for 42 days. The cells were removed every 7 days and inspected for leakage. If no leakage was observed, the fully charged battery cells were recorded as having passed the test. For each embodiment or comparative example, 100 groups were repeated. The probability of battery cells in the same group passing the test was calculated as the high-temperature, high-humidity test pass rate.

[0101] Table 1

[0102] F2 represents the bonding strength between the seal 22, adapter 21, and pressure relief member 23. Examples 1-14 show that, while d1 remains constant, increasing d3 also increases F2. This indicates that a greater distance between the seal 22 and the first weld mark 212 improves the bonding strength between the seal 22, adapter 21, and pressure relief member 23, and thus increases the structural stability of the pressure relief assembly 2. As d3 increases, the leakage test pass rate of the battery cells in high-temperature and high-humidity environments increases, indicating improved battery cell safety.

[0103] In Example 15, d3 is 0, and the adapter 21 and housing 1 are welded along the edge of the seal 22, resulting in a first weld mark 212 positioned along the edge of the seal 22. A comparison of Example 15 and Example 1 shows that when the first weld mark 212 is not spaced from the first projection of the seal 22, F2 is small, resulting in a low leakage test pass rate. This indicates that the formation of the first weld mark 212 affects the seal 22, resulting in poor bonding strength between the seal 22, the adapter 21, and the pressure relief member 23, and low battery cell safety.

[0104] By comparing Example 1 and Example 16, it can be seen that when d3 is less than 20um, F2 decreases, indicating that the welding process affects the structure of the seal 22. The battery cell has a leakage test pass rate of less than 90% under a high temperature and high humidity environment, and its safety is poor. By comparing Example 8 and Example 9, it can be seen that when d3 is greater than 220um, F2 remains unchanged. The battery cell has a leakage test pass rate that remains unchanged under a high temperature and high humidity environment, indicating that after d3 is greater than 220um, the increase in d3 has no effect on F2 and the leakage test pass rate. The larger the value of d1+d3, the larger the outer diameter of the adapter 21, which is not conducive to the miniaturization of the pressure relief assembly. Therefore, 50-220um is preferred.

[0105] Table 2

[0106] F1 represents the bonding strength between adapter 21 and housing 1. Examples 4 and 18-25 show that, while d3 and d4 remain constant, increasing d1 also increases F1. This indicates that a wider width of second surface 2122 improves the bonding strength between adapter 21 and housing 1, and a more stable connection between pressure relief assembly 2 and housing 1. As d1 increases, the leakage test pass rate of battery cells in high-temperature and high-humidity environments increases, indicating improved battery cell safety.

[0107] By comparing Example 24 with Example 23, it can be seen that when d1 is greater than 250um, F1 continues to increase, and the leakage test pass rate of the battery cell remains unchanged in a high temperature and high humidity environment, indicating that after d1 is greater than 250um, the increase in d3 has little effect on the leakage test pass rate. The larger the value of d1+d3, the larger the outer diameter of the adapter 21, which is not conducive to the miniaturization of the pressure relief assembly. By comparing Example 25 with Example 18, it can be seen that when d1 is less than 50um, F1 decreases, and the leakage test pass rate of the battery cell in a high temperature and high humidity environment is less than 90%, and the safety of the battery cell is poor.

[0108] Table 3

[0109] It can be seen from Examples 26-33 that when d1 remains unchanged, d2 increases, and F1 increases, indicating that the width of the first surface increases, the bonding strength between the adapter 21 and the shell 1 is better, and the connection between the pressure relief assembly 2 and the shell 1 is more stable. It can be seen from Examples 26-29 that when d2 is between 20um and 100um, the increase of d2 and the higher the pass rate of the leakage test of the battery cell in a high temperature and high humidity environment are, the better the safety of the battery cell is. It can be seen from Examples 29-32 that when d2 is between 100um and 160um, the increase of d2 and the lower the pass rate of the leakage test of the battery cell in a high temperature and high humidity environment are, the worse the safety of the battery cell is, indicating that when d2 is greater than a certain threshold, the welding process affects the structure of the seal 22, affecting the safety of the battery cell in a high temperature and high humidity environment.

[0110] It can be seen from Example 33 and Example 32 that when d2 is less than 20um or d2 is greater than 150um, the leakage test pass rate of the battery cell in a high temperature and high humidity environment is less than 90%, and the safety of the battery cell is poor.

[0111] Examples 34 and 35

[0112] Example 34 and Example 35 use the same preparation method to prepare battery cells. The difference is that Example 34 uses swing welding to weld the adapter and the shell to form a first weld mark at the edge of the adapter, while Example 35 uses a welding gun moving in a single direction to form a weld mark connected to the shell at the edge of the adapter.

[0113] Please refer to Figure 11, which is an electron microscope image of a partial cross-section of a battery cell. Figures 11(a) and 11(b) respectively illustrate the formation of a first weld mark 212 on the edge of adapter 21 using a welding torch in Example 1. As can be seen from Figure 11, swing welding can form the first weld mark 212 on the edge of adapter 21 and the second weld mark 13 in housing 1.

[0114] Experiments were conducted to determine the sealing efficiency of the pressure relief assembly for the liquid injection hole in Examples 34 and 35. The experimental results showed that the sealing efficiency of the battery cell provided in Example 34 was 100%, while that of the battery cell provided in Example 35 was 54%. This indicates that both oscillating welding and direct laser welding can achieve the connection between the first weld mark 212 and the housing 1. Furthermore, the first weld mark formed along the edge of the adapter through oscillating welding can improve the stability of the connection between the first weld mark 212 and the housing 1, thereby increasing the production yield of the battery cells.

[0115] In this document, the term "and / or" simply describes a relationship between related objects, indicating that three possible relationships exist. For example, "A and / or B" can represent: A exists alone, A and B exist simultaneously, or B exists alone. Furthermore, the character " / " in this document generally indicates that the related objects are in an "or" relationship.

[0116] It should be understood that in the embodiments of the present application, "B corresponding to A" means that B is associated with A and B can be determined based on A. However, it should also be understood that determining B based on A does not mean determining B based solely on A, but B can also be determined based on A and / or other information.

[0117] The above are only specific embodiments of the present application, but the scope of protection of the present application is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in this application, and such modifications or substitutions should be included in the scope of protection of this application. Therefore, the scope of protection of this application should be based on the scope of protection of the claims.

Claims

1. A battery cell, characterized in that: include: A shell having a receiving space and a liquid injection hole communicating with the receiving space; A pressure relief assembly covers the liquid injection hole, and the pressure relief assembly includes an adapter, a seal and a pressure relief piece. The shell, the adapter, the seal and the pressure relief piece are stacked in sequence along a first direction. The adapter includes a first main body and a first weld mark portion. The first main body has a first side wall arranged along the circumferential direction. The first weld mark portion connects the first side wall and the shell.

2. The battery cell according to claim 1, wherein: The projection of the sealing component on the adapter along the first direction is a first projection, and the first projection is located in the first main body portion and is spaced apart from the first welding mark portion.

3. The battery cell according to claim 2, characterized in that: The minimum spacing distance between the first projection and the first welding mark is d3, and d3 satisfies 0.02 mm to 0.5 mm.

4. The battery cell according to claim 3, characterized in that d3 meets 0.05mm~0.22mm.

5. The battery cell according to claim 1, characterized in that The first weld mark portion has a width along the second direction of the first weld mark portion, and the first weld mark portion has a first surface facing away from the shell and a second surface facing the shell. The width of the first surface is d1, and d1 satisfies 0.05mm~0.25mm. The second direction is perpendicular to the first direction.

6. The battery cell according to claim 5, characterized in that The width of the second surface is d2, and d2 satisfies 0.02 mm to 0.15 mm.

7. The battery cell according to claim 1, characterized in that The shell includes a shell wall and a second welding mark portion, wherein the second welding mark portion is embedded in the shell wall and connected to the first welding mark portion.

8. The battery cell according to claim 7, characterized in that The length of the second welding mark along the first direction is H2, and H2 satisfies 0.01 mm to 0.06 mm.

9. The battery cell according to any one of claims 1 to 8, characterized in that: The adapter has a first through hole connected to the liquid injection hole, the sealing component has a second through hole connected to the liquid injection hole, and the pressure relief component covers the second through hole.

10. The battery cell according to claim 9, characterized in that: A projection of the sealing member on the adapter along the first direction falls into the first through hole.

11. The battery cell according to any one of claims 1 to 8, characterized in that: The edge of the sealing member is located outside a projection of the pressure relief member on the sealing member along the first direction.

12. The battery cell according to any one of claims 1 to 8, characterized in that: A projection of the adapter on the housing along the first direction falls into the liquid injection hole.

13. The battery cell according to any one of claims 1 to 8, characterized in that: The sealing member includes a first adhesive layer, a second adhesive layer and a third adhesive layer sequentially arranged along the first direction, the melting point of the second adhesive layer is greater than that of the first adhesive layer, and the melting point of the second adhesive layer is greater than that of the third adhesive layer.

14. The battery cell according to any one of claims 1 to 8, characterized in that: The maximum length of the housing along the second direction is greater than the maximum length of the pressure relief assembly along the third direction, and the maximum length of the housing along the first direction is greater than the maximum length of the pressure relief assembly along the third direction. The maximum length of the pressure relief assembly along the second direction is greater than the maximum length of the pressure relief assembly along the third direction, and the first direction, the second direction and the third direction are perpendicular to each other.

15. The battery cell according to claim 14, characterized in that The length of the adapter along the third direction is L1, and L1 satisfies 1.0-6 mm.

16. The battery cell according to any one of claims 1 to 8, characterized in that: The first welding mark portion is a welding mark formed by swing welding.

17. An electrical device, characterized in that: The invention comprises a battery cell according to any one of claims 1 to 16, wherein the battery cell is used to provide electric energy.

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