Shell, battery monomer, battery and electric device

Abstract

The embodiment of the invention provides a shell, a battery monomer, a battery and an electric device. The shell comprises a first shell part and a second shell part, an opening is formed in the first shell part, the first shell part comprises a first wall opposite to the opening and a second wall connected to the first wall, and the first wall and the second wall are integrally formed; the second shell part is fixedly connected to the second wall; wherein in the depth direction of the first shell part, at least partial area of the shell is jointly formed by the first shell part and the second shell part. According to the shell, the battery monomer, the battery and the power utilization device provided by the embodiment of the invention, the cracking risk of the shell can be reduced.

Description

Technical Field

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

[0002] Generally, the housing of a battery cell has a great influence on the performance of the battery cell itself. Therefore, how to improve the performance of the battery cell by improving the housing has been a problem under research. Summary of the Invention

[0003] In view of this, embodiments of this application provide a housing, a battery cell, a battery, and an electrical device, which can reduce the risk of housing cracking.

[0004] In a first aspect, a housing is provided, including: a first housing part, which forms an opening, the first housing part includes a first wall opposite to the opening and a second wall connected to the first wall, and the first wall and the second wall are integrally formed; a second housing part, fixedly connected to the second wall; wherein, in the depth direction of the first housing part, at least part of the area of the housing is formed by the first housing part and the second housing part together.

[0005] In this embodiment, the housing includes a first housing part and a second housing part. Among them, the first housing part has an opening, and includes a first wall opposite to the opening and a second wall connected to the first wall. The first wall and the second wall are integrally formed. In the depth direction of the first housing part, at least part of the area of the housing is formed by the first housing part and the second housing part together. The housing prepared in this way can reduce the risk of housing cracking during the integral drawing process compared with the technical solution of directly integrally forming the housing.

[0006] In a possible implementation manner, in the depth direction of the first housing part, the second housing part has two communicating openings.

[0007] In this embodiment, by setting the second housing part to have two communicating openings in the depth direction of the first housing part, the cover plate and the housing can be independently arranged, and components such as electrode terminals can be better arranged on the cover plate, making the preparation of the housing simpler.

[0008] In a possible implementation manner, the second housing part is an integrally formed structure.

[0009] In this embodiment, by setting the second housing part to be an integrally formed structure, the weld seams of the housing can be reduced, making the housing highly reliable and not easily at risk of deformation, cracking, or breakage.

[0010] In a possible implementation manner, the second housing part is formed by welding at least two parts together.

[0011] In this embodiment, the second housing part is arranged to be formed by welding at least two parts together, which is easy to process and the dimensions are easier to control, thereby improving the assembly accuracy of the housing.

[0012] In a possible implementation manner, the surface of the second wall facing away from the first wall is welded to the second housing part.

[0013] In this embodiment, welding the surface of the second wall facing away from the first wall to the second housing part can improve the space utilization rate of the housing.

[0014] In a possible implementation manner, the surface of the second wall perpendicular to the thickness direction of the second wall is welded to the second housing part.

[0015] In this embodiment, by welding the surface of the second wall perpendicular to the thickness direction of the second wall to the second housing part, it is beneficial to increase the welding area between the first housing part and the second housing part, thereby improving the welding strength between the two.

[0016] In a possible implementation manner, in the depth direction of the first housing part, the maximum dimension of the first housing part is h1, and the maximum dimension of the housing is H, and H and h1 satisfy: 3 ≤ H / h1 ≤ 80.

[0017] In this embodiment, setting the ratio of H to h1 within the range of [3, 80] will neither cause the welding position of the first housing part and the second housing part to be too close to the first housing part due to too large a ratio, resulting in excessive stress on the weld seam and easy cracking during the use of the battery cell, nor cause the housing to crack due to excessive stress during the drawing process due to too small a ratio, leading to great manufacturing difficulty of the first housing part.

[0018] In a possible implementation manner, h1 satisfies: 3mm ≤ h1 ≤ 50mm.

[0019] In this embodiment, by setting h1 within the range of [3mm, 50mm], it will neither cause the weld seam to be too close to the first housing part due to too small h1, resulting in a cracking risk during the charge and discharge process of the battery cell, nor cause the first housing part to crack during the integral drawing process due to too large h1, leading to great manufacturing difficulty of the first housing part.

[0020] In a possible implementation manner, the yield strength of the housing at a temperature of 25°C is Re, and Re satisfies: 125MPa ≤ Re ≤ 1000Mpa.

[0021] In this embodiment, by using a material with a yield strength c satisfying 125MPa ≤ Re ≤ 1000Mpa to make the first housing part, it is possible to reduce the wall thickness of the first housing part without reducing its strength, thereby increasing the capacity space of the battery cell.

[0022] In a possible implementation, the material of at least part of the housing includes at least one of the following: stainless steel and carbon steel.

[0023] In this embodiment, using stainless steel or carbon steel to prepare the housing can enhance the strength of the housing. Housing 40

[0024] In a possible implementation, the mass content of chromium element in the material of at least part of the housing is m, and m satisfies: 10% ≤ m ≤ 30%.

[0025] In this embodiment, appropriately increasing the chromium element in the material of at least part of the housing can improve the strength of the housing. In addition, since chromium element can react with oxygen to form a dense chromium oxide film, a corrosion-resistant protective film can also be formed on the surface of the housing, improving the corrosion resistance of the housing.

[0026] In a possible implementation, at least part of the housing includes all the walls of the housing.

[0027] In this embodiment, using carbon steel or stainless steel for all the walls of the housing, and / or appropriately increasing the chromium element in the material of all the walls of the housing can improve the strength of the housing.

[0028] In a second aspect, a battery cell is provided, including an electrode assembly and a housing as in the first aspect and any of its possible implementations, and the electrode assembly is accommodated in the housing.

[0029] In a possible implementation, the electrode assembly includes a negative electrode tab, the negative electrode tab includes a negative electrode active material capable of reversibly deintercalating / inserting metal ions, the negative electrode active material includes a silicon-based material; the tensile strength of at least part of the housing at a temperature of 25 °C is Rm, and Rm satisfies: 250 MPa ≤ Rm ≤ 2000 MPa.

[0030] In this embodiment, setting a silicon-based material on the negative electrode tab can accommodate more metal ions, effectively increasing the energy density of the battery cell. Additionally, when the negative electrode active material of the negative electrode tab includes a silicon-based material, the deformation amount of the electrode assembly within the battery cell during use will also increase. Especially during the charging process of the battery cell, when metal ions are embedded in the silicon-based material of the negative electrode tab, the electrode assembly will expand in volume, thereby increasing the pressure of the electrode assembly on the housing of the battery cell. Therefore, increasing the yield strength Rm of at least a part of the housing under the condition of 25°C at room temperature can improve the deformation ability of the housing, making it less likely to be damaged during the use of the battery cell, thereby improving the structural stability of the battery cell and further improving the service life of the battery cell. However, the yield strength Rm of at least a part of the housing under the condition of 25°C at room temperature should not be too large, so as to reduce the difficulty of material selection and processing of the housing, save costs, and facilitate processing.

[0031] In a possible implementation, the electrode assembly includes a negative electrode tab, the negative electrode tab includes a negative electrode active material capable of reversibly deintercalating-inserting metal ions, and the negative electrode active material includes a silicon-based material; the yield strength of at least a part of the housing at a temperature of 25°C is Re, and Re satisfies: 140 MPa ≤ Re ≤ 1000 MPa.

[0032] In this embodiment, setting a silicon-based material on the negative electrode tab can accommodate more metal ions, effectively increasing the energy density of the battery cell. Additionally, when the negative electrode active material of the negative electrode tab includes a silicon-based material, the deformation amount of the electrode assembly within the battery cell during use will also increase. Especially during the charging process of the battery cell, when metal ions are embedded in the silicon-based material of the negative electrode tab, the electrode assembly will expand in volume, thereby increasing the pressure of the electrode assembly on the housing of the battery cell. Therefore, increasing the yield strength Re of at least a part of the housing under the condition of 25°C at room temperature can improve the deformation ability of the housing, thereby improving the structural stability of the battery cell and further improving the service life of the battery cell. During the charge and discharge process of the battery cell, when the electrode assembly cyclically expands and contracts in volume, increasing the yield strength Re of at least a part of the housing at room temperature can increase the maximum extrusion pressure that the housing can withstand. Without exceeding the limit of the yield strength of the housing, the housing is not easily damaged, and the deformation of the housing can be restored, improving the service life of the housing. However, the yield strength Re of at least a part of the housing under the condition of room temperature should not be too large, so as to reduce the difficulty of material selection and processing of the housing, save costs, and facilitate processing.

[0033] In a possible implementation, the electrode assembly includes a positive electrode plate, the positive electrode plate includes a positive electrode active material capable of reversibly deintercalating / inserting metal ions, and the positive electrode active material includes a nickel-containing element compound; the melting point of at least a part of the housing is p, and p satisfies: 1200°C ≤ p ≤ 2000°C.

[0034] In this embodiment, when the positive electrode active material of the positive electrode plate includes a nickel-containing element compound, the energy density and long cycle life of the battery cell can be effectively increased, and the gas generated during the use of the battery cell will also increase. Especially when the battery cell undergoes thermal runaway, the internal temperature of the battery cell increases rapidly and a large amount of gas will be generated. Therefore, appropriately increasing the melting point p of at least a part of the housing will make the housing not easily melted, reduce the possibility of explosion of the battery cell, and further reduce the risk of thermal runaway of adjacent battery cells, so as to improve the reliability of the battery. However, the melting point p of the housing should not be too large to reduce the difficulty of material selection and processing of the housing, save costs, and facilitate processing.

[0035] In a possible implementation, the electrode assembly includes a positive electrode plate, the positive electrode plate includes a positive electrode active material capable of reversibly deintercalating / inserting metal ions, and the positive electrode active material includes a nickel-containing element compound; the tensile strength of at least a part of the housing at a temperature of 500°C is Rn, and Rn satisfies: 100 MPa ≤ Rn ≤ 1200 MPa.

[0036] In this embodiment, when the positive electrode active material of the positive electrode plate includes a nickel-containing element compound, the energy density and long cycle life of the battery cell can be effectively increased, and the gas generated during the use of the battery cell will also increase. Especially when the battery cell undergoes thermal runaway, the internal temperature of the battery cell increases rapidly and a large amount of gas will be generated. Therefore, appropriately increasing the tensile strength Rn of at least a part of the housing at a high temperature of 500°C can improve the deformation ability of this part of the housing when the battery cell undergoes thermal runaway, make the housing not easily be quickly damaged and exploded, and further reduce the risk of thermal runaway of adjacent battery cells, so as to improve the reliability of the battery. However, the tensile strength Rn of at least a part of the housing at a high temperature of 500°C should not be too large to save costs and facilitate processing.

[0037] In a third aspect, a battery is provided, which includes a plurality of battery cells as in the second aspect and any of its possible implementations.

[0038] In a fourth aspect, an electrical device is provided, which includes a battery, and the battery includes a plurality of battery cells as in the second aspect and any of its possible implementations. Description of the Drawings

[0039] To more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings required for use in the embodiments of the present application. Obviously, the following described drawings are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on the drawings.

[0040] Figure 1 It is a schematic structural diagram of a vehicle disclosed in an embodiment of the present application.

[0041] Figure 2 It is a schematic structural diagram of a battery disclosed in an embodiment of the present application.

[0042] Figure 3 It is a schematic structural diagram of a battery cell disclosed in an embodiment of the present application.

[0043] Figure 4 It is an exploded schematic diagram of a battery cell disclosed in an embodiment of the present application.

[0044] Figure 5 It shows an exploded schematic diagram of the housing in the embodiment of the present application.

[0045] Figure 6 It shows a schematic structural diagram of the second housing part in the embodiment of the present application.

[0046] Figure 7 It shows another schematic structural diagram of the second housing part in the embodiment of the present application.

[0047] Figure 8 It shows another exploded schematic diagram of the housing in the embodiment of the present application.

[0048] Figure 9 It shows a schematic cross-sectional view of the housing in the embodiment of the present application.

[0049] Figure 10 It is a schematic structural diagram of another battery cell disclosed in an embodiment of the present application.

[0050] Figure 11 It is an exploded schematic diagram of another battery cell disclosed in an embodiment of the present application.

[0051] Figure 12 It is a schematic cross-sectional view of the electrode assembly in an embodiment of the present application.

[0052] Figure 13 It is a schematic cross-sectional view of the negative electrode plate or the positive electrode plate of the electrode assembly in an embodiment of the present application.

[0053] Figure 14 It is a schematic structural diagram of the fixture for cyclic charge fatigue testing in an embodiment of the present application.

[0054] Figure 15 Shows a side view schematic diagram of the housing of the embodiment of the present application.

[0055] Figure 16 Is a top view schematic diagram of the housing of the embodiment of the present application.

[0056] Figure 17 Is an enlarged view of a partial structure of the housing of an embodiment of the present application.

[0057] Figure 18 Is a schematic cross-sectional view of a partial structure of a battery of another embodiment of the present application.

[0058] Figure 19 Is a schematic exploded view of a battery cell of another embodiment of the present application.

[0059] Figure 20 Is a schematic cross-sectional view of a battery cell of another embodiment of the present application.

[0060] Figure 21 Is a schematic cross-sectional view of a partial structure of a battery of another embodiment of the present application.

[0061] Figure 22 Is a schematic cross-sectional view of another partial structure of a battery of another embodiment of the present application. Detailed implementation manners

[0062] To make the objectives, 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 described below with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are some, but not all, of the embodiments of the present application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present application without creative efforts shall fall within the scope of protection of the present application.

[0063] Unless otherwise defined, all technical and scientific terms used in the present application have the same meaning as commonly understood by those skilled in the technical field to which the present application belongs; the terms used in the present application in the specification are only for the purpose of describing specific embodiments and are not intended to limit the present application; the terms "including" and "having" and any variations thereof in the specification and claims of the present application and the above drawings are intended to cover non-exclusive inclusion. The terms "first", "second", etc. in the specification and claims of the present application or the above drawings are used to distinguish different objects and are not used to describe a specific order or primary-secondary relationship.

[0064] References to "embodiments" in this application mean that specific features, structures, or characteristics described in connection with the embodiments can be included in at least one embodiment of this application. The phrase appears in various places in the specification and does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. Those skilled in the art will explicitly and implicitly understand that the embodiments described in this application can be combined with other embodiments.

[0065] 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 directly connected, or indirectly connected through an intermediate medium, and can be the communication inside two components. For those of ordinary skill in the art, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0066] 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 three situations: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " in this application generally represents an "or" relationship between the associated objects before and after.

[0067] In the embodiments of this application, the same reference numerals represent the same components. For the sake of simplicity, in different embodiments, the detailed description of the same components is omitted. It should be understood that the thickness, length, width, etc. of various components in the embodiments of this application shown in the drawings, as well as the overall thickness, length, width, etc. of the integrated device, are only for illustrative purposes and should not constitute any limitation to this application.

[0068] The term "a plurality of" appearing in this application refers to two or more (including two). Similarly, "a plurality of groups" refers to two or more groups (including two groups), and "a plurality of pieces" refers to two or more pieces (including two pieces).

[0069] In the embodiments of this application, the battery cell can be a secondary battery, which refers to a battery cell that can be activated by charging after discharging so as to continue to be used.

[0070] The battery cell can be a lithium-ion battery, a sodium-ion battery, a sodium-lithium-ion battery, a lithium metal battery, a sodium metal battery, a lithium-sulfur battery, a magnesium-ion battery, a nickel-metal hydride battery, a nickel-cadmium battery, a lead-acid battery, etc. The embodiments of this application are not limited thereto.

[0071] A battery cell generally includes an electrode assembly. The electrode assembly includes a positive electrode, a negative electrode, and a separator. During the charge and discharge process of the battery cell, active ions (such as lithium ions) are inserted into and extracted from between the positive electrode and the negative electrode back and forth. The separator is disposed between the positive electrode and the negative electrode, which can prevent the short circuit between the positive and negative electrodes and at the same time allow the active ions to pass through.

[0072] In some embodiments, the positive electrode can be a positive electrode sheet, and the positive electrode sheet can include a positive electrode current collector and a positive electrode active material disposed on at least one surface of the positive electrode current collector.

[0073] As an example, the positive electrode current collector has two surfaces opposite to each other in its own thickness direction, and the positive electrode active material is disposed on any one or both of the two opposite surfaces of the positive electrode current collector.

[0074] As an example, the positive electrode current collector can be a metal foil, a foam metal, or a composite current collector. For example, as the metal foil, aluminum or stainless steel with a silver surface treatment, stainless steel, copper, aluminum, nickel, carbon electrode, carbon, nickel, or titanium, etc. can be used. The foam metal can be foam nickel, foam copper, foam aluminum, foam alloy, or foam carbon, etc. The composite current collector can include a polymer material substrate layer and a metal layer. The composite current collector can be formed by forming a metal material (such as aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.).

[0075] As an example, the positive electrode active material can include at least one of the following materials: lithium-containing phosphate, lithium transition metal oxide, and their respective modified compounds. However, the present application is not limited to these materials, and other conventional materials that can be used as battery positive electrode active materials can also be used. These positive electrode active materials can be used alone or in combination of two or more. Among them, examples of the lithium-containing phosphate can include but are not limited to lithium iron phosphate (such as LiFePO 4 (which can also be abbreviated as LFP)), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO4), a composite material of lithium manganese phosphate and carbon, lithium manganese iron phosphate, and at least one of a composite material of lithium manganese iron phosphate and carbon.

[0076] In some embodiments, the negative electrode can be a negative electrode sheet, and the negative electrode sheet can include a negative electrode current collector and a negative electrode active material disposed on at least one surface of the negative electrode current collector.

[0077] As an example, the negative electrode current collector has two surfaces opposite to each other in its own thickness direction, and the negative electrode active material is disposed on any one or both of the two opposite surfaces of the negative electrode current collector.

[0078] As an example, the negative electrode current collector can be a metal foil, a foam metal, or a composite current collector. For example, as the metal foil, aluminum or stainless steel with a silver surface treatment, stainless steel, copper, aluminum, nickel, carbon electrodes, carbon, nickel, titanium, etc. can be used. The composite current collector can include a polymer material base layer and a metal layer. The foam metal can be foam nickel, foam copper, foam aluminum, foam alloy, or foam carbon, etc. The composite current collector can be formed by forming a metal material (such as copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer material substrate (such as substrates of polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.).

[0079] As an example, the negative electrode active material can be the negative electrode active material for battery monomers known in the art. As an example, the negative electrode active material can include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate, etc.

[0080] In some embodiments, the electrode assembly further includes a separator, and the separator is disposed between the positive electrode and the negative electrode.

[0081] In some embodiments, the separator is a separator membrane. The present application does not particularly limit the type of the separator membrane, and any known porous structure separator membrane with good chemical stability and mechanical stability can be selected.

[0082] As an example, the main material of the separator membrane can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, polyvinylidene fluoride, and ceramics.

[0083] In some embodiments, the separator is a solid electrolyte. The solid electrolyte is disposed between the positive electrode and the negative electrode, and simultaneously plays the role of transmitting ions and isolating the positive and negative electrodes.

[0084] In some embodiments, the battery monomer further includes an electrolyte, and the electrolyte plays the role of conducting ions between the positive and negative electrodes. The present application does not specifically limit the type of the electrolyte, and it can be selected according to requirements. The electrolyte can be liquid, gel-state, or solid-state.

[0085] In some embodiments, the electrode assembly is provided with tabs, and the tabs can lead the current out of the electrode assembly. The tabs include a positive tab and a negative tab.

[0086] In some embodiments, the battery monomer can include a housing. The housing is used to encapsulate components such as the electrode assembly and the electrolyte. The housing can be a steel shell, an aluminum shell, a plastic shell (such as polypropylene), a composite metal shell (such as a copper-aluminum composite shell), or an aluminum-plastic film, etc.

[0087] As an example, the battery cell can be a cylindrical battery cell, a prismatic battery cell, a pouch battery cell, or a battery cell of other shapes. The prismatic battery cell includes a square shell battery cell, a blade-shaped battery cell, a multi-prismatic battery, and the multi-prismatic battery is, for example, a hexagonal prism battery, etc. There is no special limitation in this application.

[0088] The battery mentioned in the embodiments of this application can include one or more battery cells to provide a single physical module with higher voltage and capacity. When there are multiple battery cells, the multiple battery cells are connected in series, parallel, or in a hybrid connection through a busbar component.

[0089] In some embodiments, the battery can be a battery module. When there are multiple battery cells, the multiple battery cells are arranged and fixed to form a battery module.

[0090] In some embodiments, the battery can be a battery pack. The battery pack includes a box body and battery cells, and the battery cells or battery modules are accommodated in the box body.

[0091] In some embodiments, the box body can be a part of the chassis structure of a vehicle. For example, a part of the box body can become at least a part of the floor of the vehicle, or a part of the box body can become at least a part of the crossbeam and longitudinal beam of the vehicle.

[0092] In some embodiments, the battery can be located in an energy storage device. The energy storage device includes an energy storage container, an energy storage cabinet, etc.

[0093] The development of battery technology needs to consider multiple design factors simultaneously. For example, performance parameters such as energy density, cycle life, discharge capacity, charge-discharge rate, etc. In addition, the influence of the housing on battery performance also needs to be considered. For example, the space utilization rate of the housing, the tensile capacity of the housing, and the manufacturability of the housing.

[0094] Therefore, the embodiments of this application provide a housing, which includes a first housing part and a second housing part. Among them, the first housing part has an opening, and includes a first wall opposite to the opening and a second wall connected to the first wall. The first wall and the second wall are integrally formed. The second housing part is fixedly connected to the second wall, and in the depth direction of the first housing part, at least part of the area of the housing is jointly formed by the first housing part and the second housing part. In this way, by dividing the housing into a first housing part and a second housing part, and the first housing part is an integrally formed structure, compared with the technical solution of directly integrally forming the housing, the risk of the housing cracking during the integral drawing process can be reduced.

[0095] The technical solutions described in the embodiments of this application are applicable to various electrical devices using batteries.

[0096] The electrical equipment can be a vehicle, a mobile phone, a portable device, a laptop computer, a ship, a spacecraft, an electric toy, an electric tool, etc. The vehicle can be a fuel vehicle, a gas vehicle or a new energy vehicle, and the new energy vehicle can be a pure electric vehicle, a hybrid vehicle or an extended-range vehicle, etc.; the spacecraft includes an airplane, a rocket, a space shuttle, a spaceship, etc.; the electric toy includes a stationary or mobile electric toy, for example, a game console, an electric vehicle toy, an electric ship toy, an electric airplane toy, etc.; the electric tool includes a metal cutting electric tool, a grinding electric tool, an assembly electric tool and a railway electric tool, for example, an electric drill, an electric grinding wheel, an electric wrench, an electric screwdriver, a hammer drill, an impact drill, a concrete vibrator, a planer, etc. The embodiments of the present application do not impose special restrictions on the above electrical equipment.

[0097] For example, as Figure 1 shown, it is a schematic structural diagram of a vehicle 1 according to an embodiment of the present application. The vehicle 1 can be a fuel vehicle, a gas vehicle or a new energy vehicle, and the new energy vehicle can be a pure electric vehicle, a hybrid vehicle or an extended-range vehicle, etc. A motor 80, a controller 60 and a battery 10 can be arranged inside the vehicle 1, and the controller 60 is used to control the power supply of the battery 10 to the motor 80. For example, the battery 10 can be arranged at the bottom, the front or the rear of the vehicle 1. The battery 10 can be used for the power supply of the vehicle 1. For example, the battery 10 can be used as the operating power supply of the vehicle 1 for the circuit system of the vehicle 1, for example, for the working power requirements during the start-up, navigation and operation of the vehicle 1. In another embodiment of the present application, the battery 10 can not only be used as the operating power supply of the vehicle 1, but also be used as the driving power supply of the vehicle 1 to replace or partially replace fuel or natural gas to provide driving power for the vehicle 1.

[0098] Figure 2 It shows a schematic structural diagram of a battery 10 according to an embodiment of the present application. The battery 10 can include a plurality of battery cells 20. The battery 10 can further include a box body 11, and the inside of the box body 11 is a hollow structure, and the plurality of battery cells 20 are accommodated in the box body 11. Figure 2 It shows a possible implementation manner of the box body 11 according to an embodiment of the present application. As Figure 2 shown, the box body 11 can include two parts, which are respectively referred to as a first box body part 111 and a second box body part 112 here, and the first box body part 111 and the second box body part 112 are buckled together. The shapes of the first box body part 111 and the second box body part 112 can be determined according to the shape of the combination of the plurality of battery cells 20, and at least one of the first box body part 111 and the second box body part 112 has an opening. For example, as Figure 2As shown, the first box body part 111 and the second box body part 112 can both be hollow cuboids and each has only one open face. The openings of the first box body part 111 and the second box body part 112 are arranged opposite to each other, and the first box body part 111 and the second box body part 112 are buckled with each other to form a box body 11 with a closed chamber. This closed chamber can be used to accommodate a plurality of battery cells 20. After a plurality of battery cells 20 are connected in parallel or in series or in a mixed connection combination, they are placed in the box body 11 formed by buckling the first box body part 111 and the second box body part 112.

[0099] For another example, different from Figure 2 As shown, only one of the first box body part 111 and the second box body part 112 can be a hollow cuboid with an opening, and the other can be a plate-shaped part to cover the opening. For example, taking the second box body part 112 as a hollow cuboid with only one open face and the first box body part 111 as a plate-shaped part as an example, then the first box body part 111 covers the opening of the second box body part 112 to form a box body 11 with a closed chamber. The embodiments of the present application are not limited to this.

[0100] Figure 3 The structural schematic diagram of the battery cell 20 according to an embodiment of the present application is shown. For example, Figure 3 The battery cell 20 shown can be Figure 2 any one of the battery cells 20 in the battery 10 shown; Figure 4 The partial exploded structural schematic diagram of a battery cell 20 according to an embodiment of the present application is shown. For example, Figure 4 The battery cell 20 described can be Figure 3 the battery cell 20 shown, or can also be Figure 2 any one of the battery cells 20 in the battery 10 shown.

[0101] As Figure 3 and Figure 4 shown, the battery cell 20 according to the embodiment of the present application can include: a housing 40 and an electrode assembly 22. The housing has a closed accommodation space, and the electrode assembly 22 is placed in the accommodation space inside the housing 21. The housing 40 can include a lower housing 45 and an upper housing 46. The lower housing 45 is a hollow structure with at least one opening; the upper housing 46 is used to buckle with the lower housing 45 to form a housing 40 with a closed accommodation space.

[0102] In some embodiments, as Figure 4 shown, one end of the lower housing 45 has an opening, and the upper housing 46 is a plate-shaped structure for covering the opening of the lower housing 45. In other embodiments, the structure of the upper housing 46 is similar to that of the lower housing 45, that is, both the upper housing 46 and the lower housing 45 are hollow structures with one opening, and the two openings are butted to form a housing 40 with a closed accommodation space.

[0103] It should be understood that if the upper housing 46 is a plate-like structure, the lower housing 45 can be a hollow structure with an opening formed at one end or multiple ends. For example, if the lower housing 45 is a hollow structure with an opening formed at one end, one upper housing 46 can be provided; if the lower housing 45 is a hollow structure with openings formed at opposite ends, two upper housings 46 can be provided, and the two upper housings 46 respectively cover the openings at both ends of the lower housing 45.

[0104] The housing 40 can be of various shapes, such as a cylinder, a cuboid, or other polyhedrons. Exemplarily, as Figure 3 and Figure 4 shown, in the embodiment of the present application, the housing 40 is mainly described by taking the cuboid structure as an example.

[0105] It should be understood that the upper housing 46 in the embodiment of the present application is used to cooperate with the lower housing 45 to isolate the internal environment of the battery cell 20 from the external environment. The shape of the upper housing 46 can be adapted to the shape of the lower housing 45. As Figure 4 shown, the lower housing 45 is a cuboid structure, and the upper housing 46 is a rectangular plate-like structure adapted to the lower housing 45.

[0106] It should be understood that the battery cell 20 further includes electrode terminals 214. The electrode terminals 214 in the embodiment of the present application are used to be electrically connected to the electrode assembly 22 inside the battery cell 20 to output the electric energy of the battery cell 20. As Figures 3 to 4 shown, the battery cell 20 can include at least two electrode terminals 214. The at least two electrode terminals 214 can include at least one positive electrode terminal 214a and at least one negative electrode terminal 214b. The positive electrode terminal 214a is used to be electrically connected to the positive electrode tab 222a of the electrode assembly 22, and the negative electrode terminal 214b is used to be electrically connected to the negative electrode tab 222b of the electrode assembly 22. The positive electrode terminal 214a and the positive electrode tab 222a can be directly connected or indirectly connected, and the negative electrode terminal 214b and the negative electrode tab 222b can be directly connected or indirectly connected. Exemplarily, the positive electrode terminal 214a can be electrically connected to the positive electrode tab 222a through a connecting member 23, and the negative electrode terminal 214b is electrically connected to the negative electrode tab 222b through a connecting member 23.

[0107] In this battery cell 20, the electrode assembly 22 is the component in the battery cell 20 where the electrochemical reaction occurs. According to actual usage requirements, the electrode assembly 22 in the housing 40 can be provided as one or multiple. For example, as Figure 4As shown, there are two electrode assemblies 22 disposed within the battery cell 20. The electrode assemblies 22 can be in the shape of a cylinder, a cuboid, etc. If the electrode assembly 22 is in a cylindrical structure, the housing 40 can also be in a cylindrical structure; if the electrode assembly 22 is in a cuboid structure, the housing 40 can also be in a cuboid structure.

[0108] It should be understood that, as Figure 3 and Figure 4 shown, the electrode assembly 22 includes a tab 222 and an electrode main body portion 221. Among them, the tab 222 of the electrode assembly 22 can include a positive tab 222a and a negative tab 222b. The positive tab 222a can be formed by laminating the portion of the positive electrode tab that is not coated with the positive active material layer, and the negative tab 222b can be formed by laminating the portion of the negative electrode tab that is not coated with the negative active material layer; the electrode main body portion 221 can be formed by laminating or winding the positive electrode tab and the negative electrode tab with each other.

[0109] Figure 5 Fig. shows an exploded view of a housing 40 according to an embodiment of the present application. Figure 6 Fig. shows a schematic structural view of a second housing portion 42 according to an embodiment of the present application. Figure 7 Fig. shows another schematic structural view of the second housing portion 42 according to an embodiment of the present application. Figure 8 Fig. shows another exploded view of the housing 40 according to an embodiment of the present application. It should be noted that the housing 40 can be applied to a battery cell. For example, the housing 40 can be applied to Figure 3 and Figure 4 the battery cell 20 shown, and the housing 40 can include only Figure 4 the lower housing 45 shown, or can include both Figure 4 the lower housing 45 shown and also include Figure 4 the upper housing 46 shown. Additionally, the placement manner of the housing 40 can also be as Figure 3 or Figure 4 shown.

[0110] As Figure 5 shown, the housing 40 includes a first housing portion 41, which forms an opening 401. The first housing portion 41 includes a first wall 411 opposite to the opening 401 and a second wall 412 connected to the first wall 411, and the first wall 411 and the second wall 412 are integrally formed; a second housing portion 42, fixedly connected to the second wall 412. Among them, in the depth direction X of the first housing portion 41, at least part of the region of the housing 40 is formed by the first housing portion 41 and the second housing portion 42 together.

[0111] It should be noted that the first wall 411 and the second wall 412 in the first housing part 41 are of an integrally formed structure, which may mean that the first housing part 41 is made by an integral drawing process. For example, the first housing part 41 can be prepared through the following steps: Step 1, select steel suitable for drawing; Step 2, prepare a suitable stamping die according to the housing design and process requirements. The die is usually made of die steel, carbon steel, or cemented carbide, and includes components such as a punch, a die, and a blank holder; Step 3, fix the steel between the fixture and the die to ensure the stability of the steel during the drawing process; Step 4, move the punch downward into the die to apply a tensile stress to the steel, causing it to deform and fill the shape of the die; Step 5, control the speed and pressure of the punch to ensure uniform deformation of the steel during the drawing process, so that it is drawn to a certain depth and the required shape is obtained; Step 6, perform auxiliary operations such as punching, trimming, and marking during the drawing process as needed; Step 7, after completing the drawing, remove the product from the die and perform necessary treatments such as cleaning and deburring to obtain the first housing part 41.

[0112] Since the first housing part 41 is integrally drawn, it usually has an opening 401. The opening 401 can be circular, polygonal, or racetrack-shaped. The polygon is, for example, square, pentagonal, hexagonal, or other irregular shapes.

[0113] The first housing part 41 is a hollow structure formed by enclosing the first wall 411 and the second wall 412 opposite to the opening 401, wherein the second wall 412 intersects with the first wall 411. For example, the first wall 411 and the second wall 412 are perpendicularly arranged. In some embodiments, the first housing part 41 includes one second wall 412, and the head and tail of the second wall 412 are joined end to end and together with the first wall 411 enclose a cylindrical hollow structure. In other embodiments, the first housing part 41 includes four second walls 412, and the four second walls 412 are arranged in pairs opposite to each other, and two adjacent second walls 412 intersect perpendicularly. Therefore, the four second walls 412 and the first wall 411 together enclose a square-columnar hollow structure.

[0114] Since the first wall 411 is arranged opposite to the opening 401 of the first housing part 41, the depth direction X of the first housing part 41 can be understood as the direction perpendicular to the first wall 411, and the distance between the opening 401 of the first housing part 41 and the first wall 411 is the depth of the first housing part 41.

[0115] In the embodiments of the present application, the second housing part 42 is fixedly connected to the second wall 412, and does not include the case where the second housing part 42 is in a flat plate structure and the second housing part 42 is fitted at the opening 401 of the first housing part 41. In other words, in the embodiments of the present application, the second housing part 42 includes at least one third wall 421, wherein the at least one third wall 421 jointly encloses a hollow structure having at least one opening. For example, the second housing part 42 at least includes Figure 6 the opening 402 shown, and the opening 402 of the second housing part 42 is disposed opposite to the opening 401 of the first housing part 41, and the second wall 412 and the third wall 421 are fixedly connected, so that in the depth direction X of the first housing part 41, the second wall 412 and the third wall 421 jointly form at least part of the housing 40, that is, the depth H of the housing 40 is at least greater than the depth of the first housing part 41. Wherein, the depth H of the housing 40 can be understood as the dimension of the housing 40 in the depth direction of the first housing part 41. Generally, the wall of the housing 40 has a certain thickness, but here, the wall thickness of the housing 40 can be ignored.

[0116] In this embodiment, the housing 40 includes a first housing part 41 and a second housing part 42, wherein the first housing part 41 has an opening 401, and includes a first wall 411 opposite to the opening 401 and a second wall 412 connected to the first wall 411. The first wall 411 and the second wall 412 are integrally formed. In the depth direction X of the first housing part 41, at least part of the housing 40 is jointly formed by the first housing part 41 and the second housing part 42. The housing 40 prepared in this way can reduce the risk of cracking of the housing 40 during the integral drawing process compared with the technical solution of directly integrally forming the housing 40.

[0117] In some embodiments, in the depth direction X of the first housing part 41, the dimensions of the second wall 412 are equal everywhere. Similarly, in the depth direction X of the first housing part 41, the dimensions of the third wall 421 are equal everywhere. Then in the depth direction X of the first housing part 41, the entire area of the housing 40 is jointly formed by the first housing part 41 and the second housing part 42.

[0118] In other embodiments, in the depth direction X of the first housing part 41, the dimensions of the second wall 412 are not completely equal. For example, the unfolded second wall 412 can be semicircular or triangular. Similarly, in the depth direction X of the first housing part 41, the dimensions of the third wall 421 are not completely equal. For example, the unfolded third wall 421 can be semicircular or triangular. Then, in the depth direction X of the first housing part 41, part of the area of the housing 40 can be jointly formed by the first housing part 41 and the second housing part 42.

[0119] In one embodiment, the first housing portion 41 and the second housing portion 42 are fixedly connected by welding. In this way, for the housing 40 prepared by the method of the embodiment of the present application, compared with the housing formed by welding a flat structure and a tubular structure with an opening, the weld seam is not at the right-angle edge, and the housing 40 is not likely to crack or break.

[0120] Optionally, in the depth direction X of the first housing portion 41, the second housing portion 42 has two communicating openings. For example, the second housing portion 42 includes the Figure 6 shown openings 402 and 403, and the openings 402 and 403 are oppositely arranged in the depth direction X of the first housing portion 41.

[0121] In this embodiment, by setting the second housing portion 42 to have two communicating openings in the depth direction X of the first housing portion 41, the cover plate and the housing 40 can be independently arranged, and then components such as electrode terminals can be better arranged on the cover plate, making the preparation of the housing 40 simpler.

[0122] In other embodiments, the second housing portion 42 may have only one opening. For example, the second housing portion 42 is also prepared by an integral drawing process similar to the first housing portion 41. Among them, in addition to the above-mentioned third wall 421, the second housing portion 42 further includes a wall intersecting with the third wall 421 and opposite to the opening of the second housing portion 42, for example, a cover plate.

[0123] In one embodiment, the second housing portion 42 is an integrally formed structure.

[0124] In this embodiment, by setting the second housing portion 42 to be an integrally formed structure, the weld seams of the housing 40 can be reduced, making the housing 40 highly reliable and not likely to be deformed, cracked or broken.

[0125] In another embodiment, when the second housing portion 42 has only one opening, the second housing portion 42 may be formed by welding at least two parts.

[0126] It should be noted that when the second housing portion 42 is formed by welding at least two parts, the weld seam of the second housing portion 42 should not be at the edge, that is, the so-called right-angle edge. For example, as Figure 7As shown, the second housing portion 42 includes four third walls 421, which respectively include a fourth wall 4211, a fifth wall 4212, a sixth wall 4213, and a seventh wall 4214. Among them, the fourth wall 4211 and the fifth wall 4212 are arranged oppositely, the sixth wall 4213 and the seventh wall 4214 are arranged oppositely, and the sixth wall 4213 includes a first sub-wall 4213a and a second sub-wall 4213b, and the first sub-wall 4213a and the second sub-wall 4213b are symmetric with respect to the first center line 4251. The seventh wall 4214 includes a third sub-wall 4214a and a fourth sub-wall 4214b, and the third sub-wall 4214a and the fourth sub-wall 4214b are symmetric with respect to the second center line 4261. The second housing portion 42 is formed by welding a first part 423 and a second part 424. Among them, the first part 423 includes the first sub-wall 4213a, the fourth wall 4211, and the third sub-wall 4214a, and the second part 424 includes the second sub-wall 4213b, the fifth wall 4212, and the fourth sub-wall 4214b. The first center line 4251 and the second center line 4261 are the weld seams of the second housing portion 42.

[0127] In this embodiment, the second housing portion 42 is arranged to be formed by welding at least two parts, which is easy to process, the size is easier to control, and the assembly accuracy of the housing 40 can be improved.

[0128] In some embodiments, the surface 4121 of the second wall 412 facing away from the first wall 411 is welded to the second housing portion 42, and the wall thickness of the housing 40 should be considered here. It can be understood that the second wall 412 is welded to the third wall 421, and the inner surface of the second wall 412 and the inner surface of the third wall 421 are spliced to form a plane.

[0129] In other words, the depth of the housing 40 is equal to the sum of the depth of the first housing portion 41 and the depth of the second housing portion 42.

[0130] In this embodiment, welding the surface 4121 of the second wall 412 facing away from the first wall 411 to the second housing portion 42 can improve the space utilization rate of the housing 40.

[0131] In other embodiments, the surface of the second wall 412 perpendicular to the thickness direction Y of the second wall 412 is welded to the second housing portion 42. For example, as Figure 8 shown, the inner surface 4122 of the second wall 412 is welded to the second housing portion 42 at the outer surface 4215 of the third wall 421 of the second housing portion 42 at the opening 401 of the first housing portion 41.

[0132] In this embodiment, by welding the surface of the second wall 412 perpendicular to the thickness direction Y of the second wall 412 to the second housing portion 42, it is beneficial to increase the welding area between the first housing portion 41 and the second housing portion 42, thereby improving the welding strength between the two.

[0133] Figure 9 shows a schematic cross-sectional view of the housing 40 according to an embodiment of the present application. As Figure 9 shown, in the depth direction X of the first housing portion 41, the maximum dimension of the first housing portion 41 is h1, and the maximum dimension of the housing 40 is H, where H and h1 satisfy: 3 ≤ H / h1 ≤ 80.

[0134] It should be noted that, without considering the wall thickness, in the depth direction X of the first housing portion 41, the dimensions of the first housing portion 41 may not be uniform, and the maximum dimension h1 of the first housing portion 41 may refer to the maximum distance between the end of the second wall 412 away from the first wall 411 and the first wall 411. Similarly, without considering the wall thickness, in the depth direction X of the first housing portion 41, the dimensions of the housing 40 may also not be uniform, and the maximum dimension H of the housing 40 may refer to the maximum distance between the end of the second housing portion 42 away from the first wall 411 and the first wall 411.

[0135] In some embodiments, in the depth direction X of the first housing portion 41, the dimensions of the first housing portion 41 are uniform and the dimensions of the housing 40 are also uniform.

[0136] For example, H / h1 = 3, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80.

[0137] In this embodiment, setting the ratio of H to h1 within the range of [3, 80] will neither cause the welding position of the first housing portion 41 and the second housing portion 42 to be too close to the first housing portion 41 due to an overly large ratio, resulting in excessive stress on the weld seam and easy cracking during the use of the battery cell, nor cause excessive stress on the housing 40 during the drawing process and cracking due to an overly small ratio, thus leading to a large manufacturing difficulty for the first housing portion 41.

[0138] Further optionally, H and h1 satisfy: 5 ≤ H / h1 ≤ 20. For example, H / h1 = 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20.

[0139] In some embodiments, h1 satisfies: 3 mm ≤ h1 ≤ 50 mm.

[0140] For example, h1 = 3 mm, 5 mm, 10 mm, 15 mm, 20 mm, 25 mm, 30 mm, 35 mm, 40 mm, 45 mm, 50 mm.

[0141] In this embodiment, by setting h1 within the range of [3 mm, 50 mm], neither will the weld be too close to the first housing part 41 due to too small h1, resulting in a risk of cracking of the battery cell during charge and discharge; nor will the first housing part 41 crack during the integral drawing process due to too large h1, leading to a great manufacturing difficulty of the first housing part 41.

[0142] Further optionally, h1 satisfies: 5 mm ≤ h1 ≤ 30 mm.

[0143] It should be noted that when h1 satisfies the above conditions, H can satisfy: H is greater than or equal to 100 mm. For example, H is equal to 400 mm.

[0144] In some embodiments, the yield strength of the housing 40 at a temperature of 25 °C is Re, and Re satisfies: 125 MPa ≤ Re ≤ 1000 Mpa.

[0145] The yield strength can be understood as the critical stress value at which the material yields. Generally, after the material is stressed, as the stress increases, in addition to elastic deformation, plastic deformation may also occur. The point at which the material undergoes plastic deformation can be called the yield point, and the strength corresponding to the yield point is called the yield strength. The test method for the yield strength Re of the housing 40 in the embodiment of the present application at a temperature of 25 °C can be selected according to actual applications. For example, the yield strength Re can be tested under the normal temperature condition of 25 °C by using GB / T228.1-2010.

[0146] For example, Re = 125 MPa, 130 MPa, 150 MPa, 180 MPa, 200 MPa, 230 MPa, 250 MPa, 280 MPa, 300 MPa, 320 MPa, 350 MPa, 380 MPa, 400 MPa, 430 MPa, 450 MPa, 480 MPa, 500 MPa, 530 MPa, 550 MPa, 570 MPa, 600 Mpa, 610 Mpa, 640 Mpa, 680 Mpa, 700 Mpa, 720 Mpa, 750 Mpa, 780 Mpa, 800 Mpa, 830 Mpa, 850 Mpa, 880 Mpa, 900 Mpa, 920 Mpa, 950 Mpa, 980 Mpa, 1000 Mpa.

[0147] In this embodiment, by using a material with a yield strength Re satisfying 125 MPa ≤ Re ≤ 1000 Mpa to make the first housing part, the wall thickness of the first housing part can be thinned without reducing the strength of the first housing part, thereby increasing the capacity space of the battery cell.

[0148] Such as Figure 10 and Figure 11As shown in the figure, the embodiment of the present application further provides a battery cell 20, which includes an electrode assembly 22 and a housing 211, and the electrode assembly 22 is accommodated in the housing 211. It should be noted that the housing 211 can be the housing 40 in the above various embodiments.

[0149] In some embodiments, the battery cell 20 further includes: a cover plate 212, which is used to cover the opening of the housing 211 to enclose the electrode assembly 22 in the cavity of the housing 211.

[0150] In the embodiment of the present application, the electrode assembly 22 includes a negative electrode tab 224, and the negative electrode tab 224 includes a negative electrode active material capable of reversibly deintercalating and intercalating metal ions, and the negative electrode active material includes a silicon-based material; the housing 211 is used to accommodate the electrode assembly 22, and the tensile strength of at least a part of the housing 211 at a temperature of 25 °C is Rm, and Rm satisfies: 250 MPa ≤ Rm ≤ 2000 MPa.

[0151] It should be understood that, as Figure 10 and Figure 11 shown in the figure, the electrode assembly 22 of the embodiment of the present application may include tabs 222 and an electrode main body portion 221. Among them, the tabs 222 of the electrode assembly 22 may include a positive electrode tab 222a and a negative electrode tab 222b. The positive electrode tab 222a may be formed by laminating a part of the positive electrode tab 223 that is not coated with the positive electrode active material, and the negative electrode tab 222b may be formed by laminating a part of the negative electrode tab 224 that is not coated with the negative electrode active material; the electrode main body portion 221 may be formed by laminating or winding the positive electrode tab 223 and the negative electrode tab 224 with each other.

[0152] The negative electrode active material included in the negative electrode tab 224 of the embodiment of the present application can be flexibly set according to actual applications. For example, the negative electrode active material may include a silicon-based material. When a silicon-based material is added to the negative electrode tab 224, the silicon-based material can accommodate more metal ions, which can effectively increase the energy density of the battery cell 20; in addition, it will also increase the deformation amount of the electrode assembly 22 in the battery cell 20 during use. Especially during the charging process of the battery cell 20, when metal ions are embedded in the silicon-based material of the negative electrode tab 224, the electrode assembly 22 will expand in volume, thereby increasing the pressure of the electrode assembly 22 on the housing 211 of the battery cell 20.

[0153] Therefore, increasing the tensile strength Rm of at least part of the housing 211 under the normal temperature condition of 25°C can improve the deformation ability of this part of the housing 211, making this part of the housing 211 not easily damaged during the use of the battery cell 20, thereby improving the structural stability and service life of the battery cell 20. However, the tensile strength Rm of at least part of the housing 211 under normal temperature conditions should not be too large, so as to reduce the difficulty of material selection and processing of the housing 211, save costs, and facilitate processing. For example, generally, it can be set that the tensile strength Rm of at least part of the housing 211 under normal temperature conditions satisfies 250 MPa ≤ Rm ≤ 2000 MPa.

[0154] It should be understood that the value range of the tensile strength Rm of at least part of the housing 211 of the embodiment of the present application under the normal temperature condition of 25°C can be adjusted according to actual applications. For example, the value of the normal temperature tensile strength Rm can satisfy 250 MPa ≤ Rm ≤ 2000 MPa. For another example, the value of the normal temperature tensile strength Rm can also satisfy 400 MPa ≤ Rm ≤ 1200 MPa. On the one hand, increasing the tensile strength Rm of at least part of the housing 211 under normal temperature conditions can improve the deformation ability of this part of the housing 211 to resist the expansion amount of the electrode assembly 22, making this part of the housing 211 not easily damaged, thereby improving the structural stability and service life of the battery cell 20. On the other hand, controlling the tensile strength Rm of at least part of the housing 211 under normal temperature conditions not to be too large can reduce the difficulty of material selection and processing of the housing 211, save costs, and facilitate processing.

[0155] Furthermore, it can also be set that the tensile strength Rm of at least part of the housing 211 under normal temperature conditions satisfies 450 MPa ≤ Rm ≤ 800 MPa. The tensile strength Rm of at least part of the housing 211 under normal temperature conditions is neither too large nor too small, which can not only improve the deformation ability of this part of the housing 211 to resist the expansion amount of the electrode assembly 22, but also be easy to implement and save costs.

[0156] In some embodiments, the value of the tensile strength Rm of at least a part of the housing 211 of the embodiments of the present application under normal temperature conditions can also be set to other values. For example, the value of the tensile strength Rm at normal temperature can be any one of the following values or between any two of the following values: 250 MPa, 280 MPa, 300 MPa, 330 MPa, 350 MPa, 380 MPa, 400 MPa, 450 MPa, 500 MPa, 550 MPa, 600 MPa, 650 MPa, 700 MPa, 750 MPa, 800 MPa, 850 MPa, 900 MPa, 950 MPa, 1000 MPa, 1050 MPa, 1100 MPa, 1150 MPa, 1200 MPa, 1250 MPa, 1300 MPa, 1350 MPa, 1400 MPa, 1450 MPa, 1500 MPa, 1550 MPa, 1600 MPa, 1650 MPa, 1700 MPa, 1750 MPa, 1800 MPa, 1850 MPa, 1900 MPa, 1950 MPa, and 2000 MPa.

[0157] It should be understood that the tensile strength of the embodiments of the present application refers to the maximum stress value that the material can withstand before being broken. The test method for the tensile strength Rm of at least a part of the housing 211 of the embodiments of the present application under the condition that the temperature is 25 °C can be selected according to the actual application. For example, the national standard GB / T 228.1-2010 can be used to test the tensile strength Rm under the normal temperature condition of 25 °C.

[0158] Figure 12 shows a cross-sectional schematic diagram of the electrode assembly 22 of the embodiments of the present application. For example, the Figure 12 shown cross-sectional schematic diagram can be Figure 10 the cross-sectional schematic diagram of the electrode assembly 22 shown, and this cross-section is perpendicular to the height direction Z of the battery cell 20. Figure 13 shows a partial cross-sectional schematic diagram of the positive electrode tab 223 or the negative electrode tab 224 of the embodiments of the present application. For example, the Figure 13 can represent Figure 12 the partial cross-sectional schematic diagram of the negative electrode tab 224 of the electrode assembly 22 shown along its thickness direction, or can also represent Figure 12 the partial cross-sectional schematic diagram of the positive electrode tab 223 of the electrode assembly 22 shown along its thickness direction.

[0159] Such as Figures 10 to 13As shown, the electrode assembly 22 of the embodiment of the present application includes a positive electrode tab 223 and a negative electrode tab 224. The electrode assembly 22 can be formed by laminating or winding the positive electrode tab 223 and the negative electrode tab 224 with each other. For example, the electrode assembly 22 can include a plurality of positive electrode tabs 223 and a plurality of negative electrode tabs 224; along the thickness direction Y of the electrode assembly 22, the plurality of positive electrode tabs 223 and the plurality of negative electrode tabs 224 are alternately laminated with each other to form a laminated electrode assembly 22. For another example, the electrode assembly 22 can include a plurality of positive electrode tabs 223. The negative electrode tab 224 includes a plurality of bent segments and a plurality of laminated segments that are connected to each other and alternately arranged. After the bent segments are bent, the plurality of positive electrode tabs 223 and the plurality of laminated segments of the negative electrode tab 224 are alternately laminated with each other to form a laminated electrode assembly 22. For another example, the electrode assembly can also be formed by winding the positive electrode tab 223 and the negative electrode tab 224 with each other to form a wound electrode assembly 22. For the convenience of description, the wound electrode assembly 22 is taken as an example in the drawings of the embodiment of the present application, but the embodiment of the present application is not limited thereto. Further, the electrode assembly 22 can further include a separator 225 for isolating the positive electrode tab 223 and the negative electrode tab 224.

[0160] In the embodiment of the present application, the negative electrode tab 224 includes a negative active material. For example, the negative active material coated on the negative electrode tab 224 can be used to form a negative active material layer 2241, and the negative active material layer 2241 can be disposed on at least one surface of the negative current collector 2242. For example, the negative active material layers 2241 can be disposed on both sides of the negative current collector 2242 perpendicular to its thickness direction.

[0161] In some embodiments, the negative current collector 2242 can be a metal foil or a composite current collector. As an example of the metal foil, copper foil, copper alloy foil, aluminum foil, or aluminum alloy foil can be used. The composite current collector can include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. As an example, the metal material can include one or more of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. As an example, the polymer material base layer can include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0162] It should be understood that the negative active material of the embodiment of the present application can be flexibly set according to actual applications. Specifically, the negative active material of the embodiment of the present application can include a silicon-based material, whereby the energy density of the battery can be improved. For example, the silicon-based material can include at least one of elemental silicon, silicon oxide compound, silicon-carbon composite, silicon-nitrogen composite, silicon-containing alloy, or silicon-oxy-carbon composite material.

[0163] In some embodiments, the silicon-based material may include silicon element and one or more of alkali metal elements and alkaline earth metal elements. Among them, as an example, the alkali metal element may include Li. As an example, the alkaline earth metal element includes Mg. As an example, the silicon-based material may be a silicon-based material pre-embedded with alkali metal and / or alkaline earth metal, for example, a silicon-based material pre-embedded with Li and / or Mg.

[0164] It should be understood that the mass fraction g of the silicon-based material in the embodiments of the present application can be flexibly set according to actual applications.

[0165] For example, the value range of the mass fraction g of the silicon-based material can be set to satisfy 2% ≤ g ≤ 40%. Adding the silicon-based material to the negative active material of the negative electrode sheet 224 can effectively improve the energy density of the battery cell 20 because the silicon-based material can accommodate more metal ions than other elements. For example, the capacity of the silicon-based material is about ten times that of graphite. At the same time, the mass fraction g of the silicon-based material should not be set too large, otherwise it will increase the processing difficulty of the electrode assembly 22. In addition, it will also increase the deformation amount of the electrode assembly 22 in the battery cell 20 during use. Especially during the charging process of the battery cell 20, when metal ions are embedded in the silicon-based material of the negative electrode sheet 224, the electrode assembly 22 will expand in volume, thereby increasing the pressure of the electrode assembly 22 on the housing 211 of the battery cell 20, and further increasing the processing difficulty of the battery cell 20.

[0166] Furthermore, the value range of the mass fraction g of the silicon-based material can be set to satisfy 8% ≤ g ≤ 40%. Appropriately reducing the mass fraction g of the silicon-based material can reduce the processing difficulty of the electrode assembly 22 and also reduce the deformation amount of the electrode assembly 22 during the charge and discharge process of the battery cell 20, that is, reduce the volume expansion amount of the electrode assembly 22, thereby reducing the pressure of the electrode assembly 22 on the housing 211 of the battery cell 20 and reducing the requirement for the structural strength of the housing 211, facilitating processing and reducing costs.

[0167] Furthermore, the value range of the mass fraction g of the silicon-based material can be set to satisfy 10% ≤ g ≤ 30%. Reasonably adjusting the mass fraction g of the silicon-based material can not only effectively increase the energy density of the battery cell 20, but also reduce the processing difficulty of the electrode assembly 22 and effectively reduce the deformation amount of the electrode assembly 22 during the charge and discharge process of the battery cell 20, thereby reducing the requirement for the structural strength of the housing 211.

[0168] In some embodiments, the value of the mass fraction g of the silicon-based material in the embodiment of the present application can also be set to other values. For example, the value of the mass fraction g of the silicon-based material can be any one of the following values or between any two of the following values: 5%, 8%, 10%, 13%, 15%, 18%, 20%, 23%, 25%, 28%, 30%, 33%, 35%, 38%, 40%, 43%, 45%, 48%, and 50%.

[0169] It should be understood that the mass fraction g of the silicon-based material in the negative electrode active material in the embodiment of the present application means that the ratio of the mass of the silicon-based material in the negative electrode active material to the total mass of the negative electrode active material is g. The test method of the mass fraction g of the silicon-based material can be selected according to actual applications and can be tested by methods known in the art.

[0170] In the embodiment of the present application, the negative electrode active material may further include other materials. For example, the negative electrode active material may further include a negative electrode binder. For example, the negative electrode binder may include one or more of styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, water-based acrylic resins (such as polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS), and the embodiment of the present application is not limited thereto.

[0171] In some embodiments, the negative electrode active material may further include a negative electrode conductive agent. The present application has no particular limitation on the type of the negative electrode conductive agent. As an example, the negative electrode conductive agent may include one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0172] In some embodiments, the negative electrode active material may further include other additives. As an example, the other additives may include thickeners, such as sodium carboxymethyl cellulose (CMC), PTC thermistor materials, etc.

[0173] The negative electrode sheet 224 does not exclude other additional functional layers other than the negative electrode active material layer 2241. For example, in some embodiments, the negative electrode sheet 224 may further include a conductive bottom coating (for example, composed of a conductive agent and a binder) sandwiched between the negative electrode current collector 2242 and the negative electrode active material layer 2241 and disposed on the surface of the negative electrode current collector 2242; in some embodiments, the negative electrode sheet 224 may further include a protective layer covering the surface of the negative electrode active material layer 2241.

[0174] In some embodiments, the negative electrode sheet 224 can be prepared as follows: Dispersing the negative electrode active material, optional negative electrode binder, optional negative electrode conductive agent, and optional other additives in a solvent and stirring evenly to form a negative electrode slurry; Coating the negative electrode slurry on the negative electrode current collector 2242, and after processes such as drying and cold pressing, the negative electrode sheet 224 is formed. The solvent can be N-methylpyrrolidone (NMP) or deionized water, but the embodiments of the present application are not limited thereto.

[0175] In the embodiments of the present application, the value of the mass percentage g of the silicon-based material and the value of the tensile strength Rm of at least a part of the housing 211 at a temperature of 25 °C can be mutually restricted to balance the relationship between the energy density and the structural strength of the battery cell 20. For example, in the negative electrode active material, the mass percentage of the silicon-based material is g, and at least a part of the material of the housing 211 includes iron element, and Rm and g satisfy 2% < g < 40%, 300 MPa < Rm < 2000 MPa. That at least a part of the material of the housing 211 includes iron element can increase the structural strength of the material of this part of the housing 211 to meet the design requirements.

[0176] In some embodiments, at least a part of the material of the housing 211 includes carbon steel or stainless steel, and Rm and g satisfy 2.5% ≤ g ≤ 15%, 315 MPa ≤ Rm < 800 MPa. For example, at least a part of the material of the housing 211 can include Q195 carbon steel, which is convenient for processing and can also meet the value of the tensile strength Rm at 25 °C.

[0177] In some embodiments, at least a part of the material of the housing 211 includes carbon steel or stainless steel, and Rm and g satisfy 4.5% ≤ g ≤ 40%, 380 MPa ≤ Rm < 2000 MPa. For example, at least a part of the material of the housing 211 can include SPCC carbon steel, which is convenient for processing and can also meet the value of the tensile strength Rm at 25 °C.

[0178] In some embodiments, Rm and g satisfy 8% ≤ g ≤ 40%, 400 MPa ≤ Rm < 2000 MPa. For example, at least a part of the material of the housing 211 can include modified stainless steel, which is convenient for processing and can also meet the value of the tensile strength Rm at 25 °C.

[0179] In some embodiments, Rm and g satisfy 10% ≤ g ≤ 40%, 480 MPa ≤ Rm < 2000 MPa. For example, at least a part of the material of the housing 211 can include 316 stainless steel, which is convenient for processing and can also meet the value of the tensile strength Rm at 25 °C.

[0180] In some embodiments, Rm and g satisfy 15% ≤ g ≤ 40%, 520 MPa ≤ Rm < 2000 MPa. For example, the material of at least part of the housing 211 may include 304 stainless steel, which is convenient for processing and can meet the value of the tensile strength Rm under the condition of 25 °C.

[0181] In some embodiments, Rm and g satisfy 20% ≤ g ≤ 40%, 600 MPa ≤ Rm < 2000 MPa.

[0182] The following is a comparative description through multiple comparative examples and multiple embodiments. Specifically, the battery cells 20 in the following embodiments and comparative examples are all in the form of Figure 10 and Figure 11 shown square shell batteries, where the housing 211 has a hollow structure with one end open.

[0183] In the following embodiments and comparative examples, the preparation methods of the positive electrode sheet 223, negative electrode sheet 224, electrolyte, and separator 225 of the battery cell 20 are as follows.

[0184] 1. Preparation of the positive electrode sheet 223

[0185] The positive electrode active material LiNi 0.95 Co 0.04 Mn 0.01 O 2 , conductive agent Super P, and binder polyvinylidene fluoride (PVDF) are made into a positive electrode slurry in N-methylpyrrolidone (NMP). The solid content in the positive electrode slurry is 50 wt%, and the mass ratio of LiNi 0.7 Co 0.1 Mn 0.1 O 2 , Super P, and PVDF is 8:1:1. The positive electrode slurry is coated on the upper and lower surfaces of the current collector aluminum foil, dried at 85 °C, and then cold-pressed. After that, it is trimmed, sliced, and slit, and then dried in a vacuum at 85 °C for 4 h to make the positive electrode sheet 223.

[0186] 2. Preparation of the negative electrode sheet 224

[0187] The negative electrode active material is mixed evenly with conductive agent Super P, thickening agent carboxymethyl cellulose (CMC), and binder styrene-butadiene rubber (SBR) in deionized water to prepare a negative electrode slurry. The negative electrode active material includes graphite and a silicon-based material, and the silicon-based material is a silicon oxide compound. The solid content in the negative electrode slurry is 30 wt%. The mass ratio of the negative electrode active material, silicon suboxide, Super P, CMC, and binder styrene-butadiene rubber (SBR) in the solid components is 88:7:3:2. The negative electrode slurry is coated on the upper and lower surfaces of the current collector copper foil and dried at 85°C, and then after cold pressing, edge trimming, slicing, and slitting, it is dried in a vacuum at 120°C for 12 h to prepare the negative electrode plate 224.

[0188] 3. Preparation of the electrolyte

[0189] In an argon atmosphere glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), the fully dried electrolyte salt LiPF6 is dissolved in a mixed solvent (the mixed solvent includes ethylene carbonate (EC) and diethyl carbonate (DEC), and ethylene carbonate (EC) and diethyl carbonate (DEC) are mixed in a mass ratio of 50:50), and after mixing evenly, an electrolyte solution with a concentration of 1 mol / L is obtained.

[0190] 4. Preparation of the separator 225

[0191] A 16-μm polyethylene film is used as the separator 225.

[0192] 5. Preparation of the lithium-ion battery single cell 20

[0193] The positive electrode plate 223, separator 225, and negative electrode plate 224 are stacked in sequence, with the separator 225 placed in the middle between the positive electrode plate 223 and the negative electrode plate 224 to isolate the positive and negative electrodes, and then wound to obtain a bare battery core. The electrode tabs are welded, the bare battery core is placed in a housing made of different materials, and the above-prepared electrolyte solution is injected into the dried housing, followed by encapsulation, standing, formation, shaping, capacity testing, etc., to complete the preparation of the lithium-ion battery single cell 20.

[0194] In the following embodiments and comparative examples, the tensile strength of the housing 211 of the battery cell 20 at a temperature of 25°C is Rm, and different materials are selected for the housing 211 to obtain different tensile strengths Rm; the negative electrode active material of the negative electrode tab 224 of the electrode assembly 22 of the battery cell 20 includes a silicon-based material, and the mass ratio of the silicon-based material is g; the specific parameter settings are shown in Table 1 below. In addition, in each embodiment and comparative example, the material of all regions of the housing 211 is the same, and the tensile strength Rm of the housing 211 at 25°C is measured by the method specified in GB / T 228.1-2010. Moreover, the battery cells 20 in the following embodiments and comparative examples are the same in all settings except for the different parameter settings shown in Table 1. For example, the wall thickness of each wall of the housing 211 of the battery cell 20 in each embodiment is 0.25 mm; for another example, the capacity of the battery cell 20 in each embodiment is 350 Ah.

[0195] A cyclic charge fatigue test is performed on the battery cells 20 in the following embodiments and comparative examples. Specifically, Figure 14 FIG. shows a schematic structural diagram of a fixture 700 for cyclic charge fatigue testing according to an embodiment of the present application. As Figure 14 shown, the fixture 700 includes three steel plates with a thickness of 10 mm, and the steel plates completely cover the wall with the largest area of the battery cell 20. For the convenience of description, the three fixture steel plates are sequentially defined as the first steel plate 710, the second steel plate 720, and the third steel plate 730 here. The first steel plate 710 and the third steel plate 730 are located at both ends of the fixture 700 and are fixedly connected by bolts. The middle second steel plate 720 is constrained by a guide rail so that the second steel plate 720 can only translate in a direction perpendicular to the large surface of the second steel plate 720; the battery cell 20 is clamped between the first steel plate 710 and the second steel plate 720, and the wall with the largest area of the battery cell 20 is attached to the first steel plate 710 and the second steel plate 720; a pressure sensor 740 is provided between the second steel plate 720 and the third steel plate 730. The initial extrusion force of the second steel plate 720 on the battery cell 20 can be adjusted by adjusting the position of the second steel plate 720.

[0196] Specifically, the battery cell 20 is clamped and fixed in the special fixture 700 to ensure that the two opposite walls with the largest area of the battery cell 20 are clamped, and the initial pressure is set to 2000 N, and the electrode terminals 214 of the battery cell 20 are connected to a special battery charge and discharge device.

[0197] The fixture 700 holding the battery cell 20 is placed in a constant temperature environment of 25 ± 2°C, and the test is started after the battery cell 20 reaches temperature equilibrium.

[0198] The specific test steps shall be carried out in accordance with the "Standard Cycle Life" in Section 6.4 of "GBT31484-2015 Requirements and Test Methods for Cycle Life of Power Batteries for Electric Vehicles", and the test cycle cut-off condition shall be changed to "stop the test until the weld 2113 of battery cell 20 is damaged".

[0199] For example, the test can be carried out according to the following steps: Step a, discharge at 1I (A) until the discharge termination condition specified by the enterprise; Step b, leave it idle for no less than 30 min or the idle condition specified by the enterprise; Step c, charge according to the method in 6.1.1.3; Step d, leave it idle for no less than 30 min or the idle condition specified by the enterprise; Step e, discharge at 1I1 (A) until the discharge termination condition specified by the enterprise; Step f, cycle according to Steps b to e until the weld 2113 is damaged and stop the test.

[0200] During the above test process, continuously observe the weld 2113 of battery cell 20 until the weld 2113 leaks liquid, record the number of cycles, so as to obtain the situation of the housing 211 at 1000 cycles as shown in Table 1 below. Among them, in the following embodiments and comparative examples, the weld 2113 refers to the weld between the housing 211 and the cover plate 212, that is, the weld 2113 surrounds the open end of the housing 211, and the housing 211 adopts an integrally formed structure.

[0201] Table 1

[0202]

[0203]

[0204] It should be understood that in Table 1 above, the material of the housing 211 can be Q195 carbon steel, and the tensile strength Rm of Q195 carbon steel at room temperature of 25°C is usually at least 315 MPa to 430 MPa. In the above embodiments, only 328 MPa is taken as an example, but it is not limited thereto. Similarly, the material of the housing 211 can be SPCC carbon steel, and the tensile strength Rm of SPCC carbon steel at room temperature of 25°C is usually at least 380 MPa to 430 MPa. In the above embodiments, only 396 MPa is taken as an example; the material of the housing 211 can be modified stainless steel, and the tensile strength Rm of modified stainless steel at room temperature of 25°C is usually at least 400 MPa to 600 MPa. In the above embodiments, only 421 MPa is taken as an example; the material of the housing 211 can be SUS430 stainless steel, and the tensile strength Rm of SUS430 stainless steel at room temperature of 25°C is usually at least 450 MPa. In the above embodiments, only 459 MPa is taken as an example; the material of the housing 211 can be SUS304 stainless steel, and the tensile strength Rm of SUS304 stainless steel at room temperature of 25°C is usually at least 520 MPa. In the above embodiments, only 533 MPa and 625 MPa are taken as examples.

[0205] Comparing the 2 comparative examples with the 12 embodiments in Table 1 above, it can be seen that when different materials are used for the housing 211, different tensile strengths Rm can be determined accordingly. When the tensile strength Rm satisfies 250 MPa ≤ Rm ≤ 2000 MPa, for example, in Embodiments 1-12, even if the mass ratio g of the silicon-based material in the negative electrode tab 224 of the battery cell 20 is different, the failure fatigue times of the battery cell 20 can all reach more than one thousand to meet the design requirements of the battery cell 20. However, when the tensile strength Rm does not satisfy 250 MPa ≤ Rm ≤ 2000 MPa, for example, in Comparative Examples 1-2, even if the mass ratio g of the silicon-based material in the negative electrode tab 224 of the battery cell 20 is low, the failure fatigue times of the battery cell 20 cannot reach one thousand times and cannot meet the design requirements of the battery cell 20.

[0206] It should be understood that the battery cell 20 of the embodiment of the present application can also meet other design requirements. Specifically, the yield strength of at least a part of the housing 211 at a temperature of 25°C is Re, and Re satisfies: 140 MPa ≤ Re ≤ 1000 MPa.

[0207] Increasing the yield strength Re of at least part of the housing 211 at room temperature can improve the deformation ability of the housing 211, thereby enhancing the structural stability and service life of the battery cell 20. During the charge and discharge process of the battery cell 20, when the electrode assembly 22 cyclically expands and contracts in volume, increasing the yield strength Re of at least part of the housing 211 at room temperature can increase the maximum extrusion force borne by the housing 211. Without exceeding the yield strength limit of the housing 211, the housing 211 is not easily damaged, and the deformation of the housing 211 can be restored, improving the service life of the housing 211. However, the yield strength Re of at least part of the housing 211 at room temperature should not be too large, so as to reduce the difficulty of material selection and processing of the housing 211, save costs, and facilitate processing. For example, generally, it can be set that the yield strength Re of at least part of the housing 211 at room temperature satisfies: 140 MPa ≤ Re ≤ 1000 MPa.

[0208] It should be understood that the value range of the yield strength Re of at least part of the housing 211 of the embodiment of the present application at room temperature of 25 °C can be adjusted according to actual applications. For example, the value of the room temperature yield strength Re can satisfy 140 MPa ≤ Re ≤ 1000 MPa. For another example, the value of the room temperature yield strength Re can satisfy 180 MPa ≤ Re ≤ 600 MPa. On the one hand, increasing the yield strength Re of at least part of the housing 211 at room temperature can improve the deformation ability of this part of the housing 211 to resist the expansion amount of the electrode assembly 22, making this part of the housing 211 not easily damaged; and, without exceeding the yield strength limit of the housing 211, if the expansion amount of the electrode assembly 22 shrinks, the deformation of the housing 211 can also be restored, thereby enhancing the structural stability and service life of the battery cell 20. On the other hand, controlling the yield strength Re of at least part of the housing 211 at room temperature not to be too large can reduce the difficulty of material selection and processing of the housing 211, save costs, and facilitate processing.

[0209] Furthermore, it can also be set that the yield strength Re of at least part of the housing 211 at room temperature satisfies 220 MPa ≤ Re ≤ 400 MPa. The yield strength Re of at least part of the housing 211 at room temperature is neither too large nor too small, which can not only improve the deformation ability of this part of the housing 211 to resist the expansion amount of the electrode assembly 22, but also be easy to implement and save costs.

[0210] In some embodiments, the yield strength Re of at least part of the housing 211 of the embodiments of the present application at normal temperature can also be set to other values. For example, the value of the yield strength Re at normal temperature can be any one of the following values or between any two of the following values: 140 MPa, 150 MPa, 160 MPa, 180 MPa, 200 MPa, 220 MPa, 250 MPa, 280 MPa, 300 MPa, 330 MPa, 350 MPa, 380 MPa, 400 MPa, 430 MPa, 450 MPa, 480 MPa, 500 MPa, 530 MPa, 550 MPa, 580 MPa, 600 MPa, 630 MPa, 650 MPa, 680 MPa, 700 MPa, 730 MPa, 750 MPa, 780 MPa, 800 MPa, 830 MPa, 850 MPa, 880 MPa, 900 MPa, 930 MPa, 950 MPa, 980 MPa, and 1000 MPa.

[0211] It should be understood that the yield strength of the embodiments of the present application can be understood as the critical stress value at which the material yields. Generally, after the material is stressed, as the stress increases, in addition to elastic deformation, plastic deformation may also occur. The point at which the material undergoes plastic deformation can be called the yield point, and the strength corresponding to the yield point is called the yield strength. In addition, the yield strength of the embodiments of the present application generally refers to the upper yield strength, that is, the upper yield strength of at least part of the housing 211 at a temperature of 25°C is Re.

[0212] The test method for the yield strength Re of at least part of the housing 211 of the embodiments of the present application at a temperature of 25°C can be selected according to actual applications. For example, the national standard GB / T228.1-2010 can be used to test the yield strength Re at a normal temperature of 25°C.

[0213] In the embodiments of the present application, the value of the mass ratio g of the silicon-based material and the value of the yield strength Re of at least part of the housing 211 at a temperature of 25°C can be restricted from each other, so as to improve the structural strength of the housing 211 while increasing the energy density of the battery cell 20, thereby improving the structural strength and service life of the battery cell 20.

[0214] For example, in the negative electrode active material, the mass ratio of the silicon-based material is g, and g and Re satisfy: 2% < g < 40%, 140 MPa < Re < 600 MPa. Adding a silicon-based material to the negative electrode active material of the negative electrode sheet 224 can effectively increase the energy density of the battery cell 20 because the silicon-based material can accommodate more metal ions than other elements. For example, the capacity of the silicon-based material is about ten times that of graphite. At the same time, the mass ratio g of the silicon-based material should not be set too large, otherwise it will increase the processing difficulty of the electrode assembly 22 and also increase the deformation amount of the electrode assembly 22 in the battery cell 20 during use. Especially during the charging process of the battery cell 20, when metal ions are embedded in the silicon-based material of the negative electrode sheet, the electrode assembly 22 will expand in volume, thereby increasing the pressure of the electrode assembly 22 on the housing 211 of the battery cell 20 and further increasing the processing difficulty of the battery cell 20. Therefore, the yield strength Re of at least part of the housing 211 under normal temperature conditions can be appropriately increased to improve the deformation ability of this part of the housing 211 to resist the expansion amount of the electrode assembly 22, so that this part of the housing 211 is not easily damaged; and, without exceeding the limit of the yield strength of the housing 211, if the expansion amount of the electrode assembly 22 shrinks, the deformation of the housing 211 can also be restored, thereby improving the structural stability and service life of the battery cell 20. In addition, controlling the yield strength Re of at least part of the housing 211 under normal temperature conditions should not be too large, which can reduce the material selection difficulty and processing difficulty of the housing 211, save costs, and facilitate processing.

[0215] In some embodiments, the material of at least part of the housing 211 includes carbon steel or stainless steel, and g and Re satisfy 4.5% ≤ g ≤ 40%, 170 MPa ≤ Re < 600 MPa. For example, the material of at least part of the housing 211 can include SPCC carbon steel, which is not only easy to process but also can meet the value of the yield strength Re under the condition of 25°C.

[0216] In some embodiments, g and Re satisfy 8% ≤ g ≤ 40%, 180 MPa ≤ Re < 600 MPa. For example, the material of at least part of the housing 211 can include modified stainless steel, which is not only easy to process but also can meet the value of the yield strength Re under the condition of 25°C.

[0217] In some embodiments, g and Re satisfy 10% ≤ g ≤ 40%, 190 MPa ≤ Re < 600 MPa. For example, the material of at least part of the housing 211 can include 316 stainless steel, which is not only easy to process but also can meet the value of the yield strength Re under the condition of 25°C.

[0218] In some embodiments, g and Re satisfy 15% ≤ g ≤ 40% and 200 MPa ≤ Re < 600 MPa. For example, the material of at least part of the housing 211 may include 304 stainless steel, which is convenient for processing and can meet the value of the yield strength Re under the condition of 25°C.

[0219] In some embodiments, g and Re satisfy 20% ≤ g ≤ 40% and 210 MPa ≤ Re < 600 MPa.

[0220] The following is a comparative description through multiple comparative examples and multiple embodiments. Specifically, the battery cells 20 in the following embodiments and comparative examples are all in the form of Figure 10 and Figure 11 shown square shell batteries for example, wherein the housing 211 adopts a hollow structure with one end open.

[0221] In the following embodiments and comparative examples, the preparation methods of the positive electrode plate 223, negative electrode plate 224, electrolyte and separator 225 of the battery cell 20 are as follows.

[0222] 1. Preparation of the positive electrode plate 223

[0223] The positive electrode active material LiNi 0.95 Co 0.04 Mn 0.01 O 2 , conductive agent Super P, and binder polyvinylidene fluoride (PVDF) are made into a positive electrode paste in N-methylpyrrolidone (NMP). The solid content in the positive electrode paste is 50 wt%. In the solid components, the mass ratio of LiNi 0.7 Co 0.1 Mn 0.1 O 2 , Super P, and PVDF is 8:1:1. The positive electrode paste is coated on the upper and lower surfaces of the current collector aluminum foil, dried at 85°C, and then cold-pressed. After trimming, slicing, and slitting, it is dried in a vacuum at 85°C for 4 h to make the positive electrode plate 223.

[0224] 2. Preparation of the negative electrode plate 224

[0225] The negative electrode active material is mixed evenly with conductive agent Super P, thickening agent carboxymethyl cellulose (CMC), and binder styrene-butadiene rubber (SBR) in deionized water to make a negative electrode slurry. The negative electrode active material includes graphite and a silicon-based material, and the silicon-based material is a silicon oxide compound. The solid content in the negative electrode slurry is 30 wt%. The mass ratio of the negative electrode active material, silicon suboxide, Super P, CMC, and binder styrene-butadiene rubber (SBR) in the solid components is 88:7:3:2. The negative electrode slurry is coated on the upper and lower surfaces of the current collector copper foil and dried at 85°C, and then after cold pressing, edge trimming, slicing, and strip cutting, it is dried in a vacuum at 120°C for 12 h to make the negative electrode plate 224.

[0226] 3. Preparation of the electrolyte

[0227] In an argon atmosphere glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), the fully dried electrolyte salt LiPF6 is dissolved in a mixed solvent (the mixed solvent includes ethylene carbonate (EC) and diethyl carbonate (DEC), and ethylene carbonate (EC) and diethyl carbonate (DEC) are mixed in a mass ratio of 50:50), and after mixing evenly, an electrolyte solution with a concentration of 1 mol / L is obtained.

[0228] 4. Preparation of the separator 225

[0229] A 16-μm polyethylene film is used as the separator 225.

[0230] 5. Preparation of the lithium-ion battery single cell 20

[0231] The positive electrode plate 223, the separator 225, and the negative electrode plate 224 are stacked in sequence, with the separator 225 placed in the middle of the positive electrode plate 223 and the negative electrode plate 224 to play the role of isolating the positive and negative electrodes. After winding, a bare battery core is obtained, the electrode tabs are welded, the bare battery core is placed in a housing made of different materials, and the above-prepared electrolyte solution is injected into the dried housing, followed by encapsulation, standing, formation, shaping, capacity testing, etc. to complete the preparation of the lithium-ion battery single cell 20.

[0232] In the following embodiments and comparative examples, the yield strength of the housing 211 of the battery cell 20 at a temperature of 25°C is Re, and different materials are selected for the housing 211 to obtain different yield strengths Re; the negative electrode active material of the negative electrode tab 224 of the electrode assembly 22 of the battery cell 20 includes a silicon-based material, and the mass ratio of the silicon-based material is g; the specific parameter settings are shown in Table 1 below. In addition, in each embodiment and comparative example, the material of all regions of the housing 211 is the same, and the yield strength Re of the housing 211 at 25°C is measured by the method specified in GB / T 228.1-2010. Moreover, the battery cells 20 in the following embodiments and comparative examples are the same in all other settings except for the different parameter settings shown in Table 1. For example, the wall thickness of each wall of the housing 211 of the battery cell 20 in each embodiment is 0.25 mm; for another example, the capacity of the battery cell 20 in each embodiment is 350 Ah.

[0233] A cyclic charge fatigue test is performed on the battery cell 20 in the following embodiments and comparative examples. Specifically, a fixture 700 for cyclic charge fatigue test as shown in the figure can be used for the test.

[0234] Specifically, the battery cell 20 is clamped and fixed in a special fixture 700, ensuring that the two relatively largest-area walls of the battery cell 20 are clamped, and the initial pressure is set to 2000 N, and the electrode terminals 214 of the battery cell 20 are connected to a special battery charge and discharge device.

[0235] The fixture 700 holding the battery cell 20 is placed in a constant temperature environment of 25 ± 2°C, and the test is started after the battery cell 20 reaches temperature equilibrium.

[0236] The specific test steps are carried out in accordance with Section 6.4 "Standard Cycle Life" of "GBT31484-2015 Requirements and Test Methods for Cycle Life of Power Batteries for Electric Vehicles", and the test cycle cut-off condition is changed to "stop the test until the weld 2113 of the battery cell 20 is damaged".

[0237] For example, the test can be carried out according to the following steps: Step a, discharge at 1I (A) to the discharge termination condition specified by the enterprise; Step b, set aside for no less than 30 min or the set-aside condition specified by the enterprise; Step c, charge according to the method in 6.1.1.3; Step d, set aside for no less than 30 min or the set-aside condition specified by the enterprise; Step e, discharge at 1I1 (A) to the discharge termination condition specified by the enterprise; Step f, cycle according to Steps b to e until the weld 2113 is damaged and stop the test.

[0238] During the above test process, continuously observe the weld 2113 of the battery cell 20 until the weld 2113 leaks liquid, record the number of cycles, so as to obtain the failure fatigue situation of the housing 211 at 1000 cycles as shown in Table 2 below. Among them, in the following embodiments and comparative examples, the weld 2113 refers to the weld between the housing 211 and the cover plate 212, that is, the weld 2113 surrounds the open end of the housing 211, and the housing 211 adopts an integrally formed structure.

[0239] Table 2

[0240]

[0241] It should be understood that in Table 2 above, the material of the housing 211 can be modified stainless steel, and the yield strength Re of the modified stainless steel at room temperature of 25°C is usually at least 140 MPa to 180 MPa. In the above embodiments, only 145 MPa and 173 MPa are taken as examples, but it is not limited thereto. Similarly, the material of the housing 211 can be SUS316 stainless steel, and the yield strength Re of SUS316 stainless steel at room temperature of 25°C is usually at least 177 MPa. In the above embodiments, only 182 MPa and 193 MPa are taken as examples; the material of the housing 211 can be Q195 carbon steel, and the yield strength Re of Q195 carbon steel at room temperature of 25°C is usually at least 195 MPa. In the above embodiments, only 203 MPa is taken as an example; the material of the housing 211 can be SUS304 stainless steel, and the yield strength Re of SUS304 stainless steel at room temperature of 25°C is usually at least 205 MPa. In the above embodiments, only 212 MPa is taken as an example.

[0242] Comparing the 2 comparative examples and 12 embodiments in Table 2 above, it can be seen that when the housing 211 uses different materials, different yield strengths Re can be determined accordingly. When the yield strength Re satisfies 140 MPa ≤ Re ≤ 1000 MPa, for example, in Embodiments 1-12, even if the mass ratio g of the silicon-based material in the material of the negative electrode tab 224 of the battery cell 20 is different, the failure fatigue times of the battery cell 20 can all reach more than one thousand to meet the design requirements of the battery cell 20. However, when the yield strength Re does not satisfy 140 MPa ≤ Re ≤ 1000 MPa, for example, in Comparative Examples 1-2, even if the mass ratio g of the silicon-based material in the material of the negative electrode tab 224 of the battery cell 20 is low, the failure fatigue times of the battery cell 20 cannot reach one thousand times and cannot meet the design requirements of the battery cell 20.

[0243] In some embodiments, the electrode assembly 22 further includes a positive electrode plate 223, the positive electrode plate 223 includes a positive electrode active material capable of reversibly deintercalating-inserting metal ions, and the positive electrode active material includes a nickel-containing element compound; the melting point of at least a part of the housing 211 is p, and p satisfies: 1200°C ≤ p ≤ 2000°C.

[0244] The positive electrode plate 223 of the embodiment of the present application is provided with a positive electrode active material capable of reversibly deintercalating-inserting metal ions, and the positive electrode active material can be flexibly set according to actual applications. For example, the positive electrode active material may include a nickel-containing element compound, which can effectively increase the energy density and long cycle life of the battery cell 20, but at the same time, it will also increase the temperature and the generated gas during the use of the battery cell 20. Especially when thermal runaway occurs during the use of the battery cell 20, the internal temperature of the battery cell 20 will increase rapidly and a large amount of gas will be generated.

[0245] Therefore, appropriately increasing the melting point p of at least a part of the housing 211 will make the housing 211 not easily melted, reduce the possibility of explosion of the battery cell 20, and further reduce the risk of thermal runaway of adjacent battery cells 20, so as to improve the reliability of the battery 10. However, the melting point p of at least a part of the housing 211 should not be too large, so as to reduce the difficulty of material selection and processing of the housing 211, save costs, and facilitate processing. For example, generally, the melting point p of at least a part of the housing 211 can be set to satisfy 1200°C ≤ p ≤ 2000°C.

[0246] It should be understood that the value range of the melting point p of at least a part of the housing 211 in the embodiment of the present application can be adjusted according to actual applications. For example, the melting point p of at least a part of the housing 211 generally satisfies 1200°C ≤ p ≤ 2000°C. For another example, the melting point p of at least a part of the housing 211 can also satisfy 1300°C ≤ p ≤ 1800°C. On the one hand, appropriately increasing the value of the melting point p can improve the anti-melting ability of this part of the housing 211 when thermal runaway occurs in the battery cell 20, make the housing 211 not easily melted, and further reduce the risk of thermal runaway of adjacent battery cells 20, that is, reduce the risk of thermal diffusion, so as to improve the reliability of the battery 10. At the same time, the melting point p cannot be too large, so as to facilitate the selection of suitable materials, reduce the processing difficulty, and further save costs and facilitate processing.

[0247] Furthermore, the melting point p of at least a part of the housing 211 can be set to satisfy 1400°C ≤ p ≤ 1600°C, which can improve the structural strength of the housing 211 when thermal runaway occurs in the battery cell 20, make the housing 211 not easily melted, maintain the structural integrity of this part of the housing 211, and reduce the risk of thermal runaway of adjacent battery cells 20. At the same time, it can also reduce the processing difficulty and save costs.

[0248] In some embodiments, the melting point p of at least a partial region of the housing 211 may also be set to other values. For example, the melting point p may take any one of the following values or be between any two of the following values: 1200 °C, 1250 °C, 1300 °C, 1350 °C, 1400 °C, 1450 °C, 1500 °C, 1550 °C, 1600 °C, 1650 °C, 1700 °C, 1750 °C, 1800 °C, 1850 °C, 1900 °C, 1950 °C, and 2000 °C.

[0249] In the embodiments of the present application, the positive electrode tab 223 includes a positive electrode active material. For example, the positive electrode active material coated on the positive electrode tab 223 can be used to form a positive electrode active material layer 2231, and the positive electrode active material layer 2231 can be disposed on at least one side surface of the positive electrode current collector 2232. For example, the positive electrode active material layers 2241 can be disposed on both sides of the positive electrode current collector 2232 perpendicular to its thickness direction, but the embodiments of the present application are not limited thereto.

[0250] In some embodiments, the positive electrode current collector 2232 can be a metal foil or a composite current collector. As an example of the metal foil, aluminum foil can be used. The composite current collector can include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. As an example, the metal material can include one or more of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. As an example, the polymer material base layer can include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0251] It should be understood that the positive electrode active material of the embodiments of the present application can be flexibly set according to actual applications. For example, the positive electrode active material can include a nickel element-containing compound. As an example, the nickel element-containing compound includes a layered lithium-containing transition metal oxide, and the molar amount of nickel element in the layered lithium-containing transition metal oxide accounts for more than 50% of the total molar amount of the transition metal elements in the layered lithium-containing transition metal oxide. Increasing the proportion of the molar amount of nickel element in the layered lithium-containing transition metal oxide to more than 50% can effectively improve the energy density and long cycle life of the battery cell 20, but the proportion should not be set too large, otherwise it will increase the processing difficulty of the electrode assembly 22, and further increase the processing cost of the battery cell 20.

[0252] Furthermore, the proportion of the molar amount of nickel element in the layered lithium-containing transition metal oxide can also be more than 70%, or more than 80%, or 90%. In this way, while effectively improving the energy density of the battery cell 20, the processing difficulty of the electrode assembly 22 can also be controlled to reduce the processing cost of the battery cell 20.

[0253] In some embodiments, the proportion of the molar amount of nickel element in the layered lithium-containing transition metal oxide of the embodiments of the present application can also be set to other values. For example, the proportion of the molar amount of nickel element in the layered lithium-containing transition metal oxide can be any one of the following values or between any two of the following values: 50%, 53%, 55%, 58%, 60%, 63%, 65%, 68%, 70%, 73%, 75%, 78%, 80%, 83%, 85%, 88%, 90%, 92%, 94%, 96%, and 98%.

[0254] It should be understood that the test method for the molar amount of nickel element in the layered lithium-containing transition metal oxide and the total molar amount of transition metal elements in the layered lithium-containing transition metal oxide of the embodiments of the present application can be selected according to actual applications and can be determined by known instruments and methods in the art. For example, the positive electrode active material can be laid and adhered to the conductive adhesive to make a test sample with a length × width of 6 cm × 1.1 cm; a scanning electron microscope & energy spectrometer (such as ZEISS Sigma300) can be used to test the particle morphology. The test can refer to JY / T 010-1996. To ensure the accuracy of the test results, 20 different regions can be randomly selected in the test sample for scanning test, and at a certain magnification (for example, more than 1000 times), the content of the layered lithium-containing transition metal oxide in each region can be statistically calculated. For example, the average value of the test results of 20 test regions can be taken as the quantity of the layered lithium-containing transition metal oxide in the positive electrode active material, and then the molar amount of the layered lithium-containing transition metal oxide can be determined; similarly, the molar amount of nickel element in the layered lithium-containing transition metal oxide can also be determined by this method.

[0255] In some embodiments, the layered lithium-containing transition metal oxide can include one or more of lithium cobaltate and ternary materials. As an example, the layered lithium-containing transition metal oxide includes LiaNibCocMdOeAf, where 0 < a ≤ 1.2, 0.5 ≤ b < 1, optionally, 0.9 ≤ b < 1; 0 < c < 1; 0 < d < 1; 1 ≤ e ≤ 2; 0 ≤ f ≤ 1, M includes but is not limited to one or more of Mn, Al, Zr, Zn, Cu, Cr, Mg, Fe, V, Ti, and B, and A includes but is not limited to one or more of N, F, S, and Cl. Among them, the proportion b of the molar amount of nickel element in the layered lithium-containing transition metal oxide is set to more than 50%, that is, the proportion b satisfies: 0.5 ≤ b < 1, and further can satisfy 0.8 ≤ b < 1, or 0.9 ≤ b < 1, thereby further improving the energy density of the battery cell 20.

[0256] As an example, the layered lithium-containing transition metal oxide may include, but is not limited to, one or more of LiNi0.5Co0.2Mn0.3O2 (abbreviated as NCM523), LiNi0.5Co0.25Mn0.25O2 (abbreviated as NCM211), LiNi0.6Co0.2Mn0.2O2 (abbreviated as NCM622), LiNi0.8Co0.1Mn0.1O2 (abbreviated as NCM811), LiNi0.9Co0.06Mn0.04O2, LiNi0.96Co0.02Mn0.02O2, and LiNi0.85Co0.15Al0.05O2.

[0257] In some embodiments, the positive electrode active material may further include other materials. For example, the positive electrode active material may further include a positive electrode conductive agent. The present application does not particularly limit the type of the positive electrode conductive agent. As an example, the positive electrode conductive agent may include one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0258] In some embodiments, the positive electrode active material may further include a positive electrode binder. The present application does not particularly limit the type of the positive electrode binder. As an example, the positive electrode binder may include one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resins.

[0259] In some embodiments, the positive electrode sheet 223 may be prepared by the following method: The positive electrode active material layer 2231 is generally formed by coating a positive electrode slurry on a positive electrode current collector 2232 and then drying and cold pressing. The positive electrode slurry is generally formed by dispersing a positive electrode active material, a positive electrode binder, a positive electrode conductive agent, etc. in a solvent and stirring evenly. The solvent may be N-methylpyrrolidone (NMP) or deionized water, but the embodiments of the present application are not limited thereto.

[0260] The following is a comparative description through multiple comparative examples and multiple embodiments. Specifically, the battery cells 20 in the following embodiments and comparative examples are all in the form of Figure 10 and Figure 11 shown square shell batteries, where the housing 211 has a hollow structure with one end open.

[0261] In the following embodiments and comparative examples, the preparation methods of the positive electrode sheet 223, the negative electrode sheet 224, the electrolyte, and the separator 225 of the battery cell 20 are as follows.

[0262] 1. Preparation of the positive electrode sheet 223

[0263] The positive electrode active material LiNi 0.95 Co 0.04 Mn 0.01 O 2 、conductive agent Super P, and binder polyvinylidene fluoride (PVDF) are made into a positive electrode paste in N-methylpyrrolidone (NMP). The solid content in the positive electrode paste is 50 wt%, and in the solid components, the mass ratio of LiNi 0.7 Co 0.1 Mn 0.1 O 2 、Super P, and PVDF is 8:1:1. The positive electrode paste is coated on the upper and lower surfaces of the current collector aluminum foil, dried at 85°C, cold-pressed, then trimmed, sliced, and slit, and finally dried in a vacuum at 85°C for 4 h to make the positive electrode plate 223.

[0264] 2. Preparation of the negative electrode plate 224

[0265] The negative electrode active material, conductive agent Super P, thickening agent carboxymethyl cellulose (CMC), and binder styrene-butadiene rubber (SBR) are mixed evenly in deionized water to make a negative electrode paste. The negative electrode active material includes graphite and a silicon-based material, and the silicon-based material is a silicon oxide compound. The solid content in the negative electrode paste is 30 wt%, and in the solid components, the mass ratio of the negative electrode active material, silicon suboxide, Super P, CMC, and binder styrene-butadiene rubber (SBR) is 88:7:3:2. The negative electrode paste is coated on the upper and lower surfaces of the current collector copper foil, dried at 85°C, then cold-pressed, trimmed, sliced, and slit, and finally dried in a vacuum at 120°C for 12 h to make the negative electrode plate 224.

[0266] 3. Preparation of the electrolyte

[0267] In a glove box under an argon atmosphere (H2O < 0.1 ppm, O2 < 0.1 ppm), the fully dried electrolyte salt LiPF6 is dissolved in a mixed solvent (the mixed solvent includes ethylene carbonate (EC) and diethyl carbonate (DEC), and ethylene carbonate (EC) and diethyl carbonate (DEC) are mixed in a mass ratio of 50:50). After mixing evenly, an electrolyte with a concentration of 1 mol / L is obtained.

[0268] 4. Preparation of the separator 225

[0269] A 16-μm polyethylene film is used as the separator 225.

[0270] 5. Preparation of the lithium-ion battery monomer 20

[0271] Stack the positive electrode plate 223, the separator 225, and the negative electrode plate 224 in sequence, with the separator 225 placed between the positive electrode plate 223 and the negative electrode plate 224 to isolate the positive and negative electrodes, wind to obtain a bare battery cell, weld the electrode tabs, place the bare battery cell in a housing made of different materials, inject the above-prepared electrolyte into the dried housing, perform encapsulation, standing, formation, shaping, capacity testing, etc. to complete the preparation of the lithium-ion battery single cell 20.

[0272] In the following examples and comparative examples, the melting point of the housing 211 of the battery single cell 20 is p, and to obtain different melting points, different materials are correspondingly selected for the housing 211; the capacity of the battery single cell 20 is C; the wall thickness of the wall with the largest area of the battery single cell 20 is T, and the specific parameter settings are shown in Table 3 below. In addition, in each example and comparative example, the material of all regions of the housing 211 is the same. And, except for the different parameter settings shown in Table 3, the other setting conditions of the battery single cell 20 in the following examples and comparative examples are the same. For example, in each example, the positive electrode active material of the positive electrode plate 223 of the electrode assembly 22 of the battery single cell 20 includes a nickel-containing compound, wherein the nickel-containing compound includes a layered lithium-containing transition metal oxide, and the molar amount of nickel element in the layered lithium-containing transition metal oxide accounts for 95% of the total molar amount of the transition metal elements in the layered lithium-containing transition metal oxide.

[0273] For the battery single cell 20 in the following comparative examples and examples, refer to the short-circuit test method in Section 6.2.4 of "GBT31485-2015 Safety Requirements and Test Methods for Power Batteries for Electric Vehicles" to test the single battery, and observe the integrity of the housing 211 after the test, that is, observe whether the housing 211 melts.

[0274] Table 3

[0275] p(℃) T (mm) C (Ah) Housing material Test results Comparative example 1 660 0.7 350 Aluminum Housing melted Comparative example 2 660 0.15 72 Aluminum Housing melted Example 1 1250 0.15 350 Ferromanganese Housing intact Example 2 1250 0.15 72 Ferromanganese Housing intact Example 3 1425 0.15 350 Low-carbon steel Housing intact Example 4 1425 0.15 72 Low-carbon steel Housing intact Example 5 1510 0.15 350 Stainless steel Housing intact Example 6 1510 0.15 72 Stainless steel Housing intact

[0276] Comparing the two comparative examples and six examples in Table 3 above, it can be seen that when different materials are used for the housing 211, different melting points p can be correspondingly determined. When the melting point p satisfies 1200°C ≤ p ≤ 2000°C, for example, in Examples 1-6, the housing 211 of the battery single cell 20 does not melt and can meet the design requirements of the battery single cell 20; and, when other parameters of the battery single cell 20 fluctuate differently, such as different capacities C of the battery single cell 20 or different thicknesses of the wall with the largest area of the housing 211, the battery single cell 20 does not melt and can meet the design requirements of the battery single cell 20. However, when the melting point p does not satisfy 1200°C ≤ p ≤ 2000°C, for example, in Comparative Examples 1-2, the housing 211 of the battery single cell 20 will melt and cannot meet the design requirements of the battery single cell 20.

[0277] In some embodiments, the electrode assembly 22 further includes a positive electrode plate 223. The positive electrode plate 223 includes a positive electrode active material capable of reversibly deintercalating and intercalating metal ions. The positive electrode active material includes a nickel-containing element compound. The tensile strength of at least a part of the housing 211 at a temperature of 500 °C is Rn, and Rn satisfies: 100 MPa ≤ Rn ≤ 1200 MPa.

[0278] The positive electrode active material may include a nickel-containing element compound, which can effectively increase the energy density and long cycle life of the battery cell 20, but also increase the gas generated during the use of the battery cell 20. Especially when thermal runaway occurs during the use of the battery cell 20, the internal temperature of the battery cell 20 increases rapidly and a large amount of gas is generated.

[0279] Therefore, appropriately increasing the tensile strength Rn of at least a part of the housing 211 at a high temperature of 500 °C can improve the deformation ability of this part of the housing 211 when thermal runaway occurs in the battery cell 20, making it less likely for the housing 211 to be quickly damaged and explode, thereby reducing the risk of thermal runaway in adjacent battery cells 20 and improving the reliability of the battery 10. However, the tensile strength Rn of at least a part of the housing 211 at high temperature should not be too large, otherwise it will increase the processing difficulty, such as easily scratching the mold and reducing the service life of the mold. Therefore, appropriately reducing the tensile strength Rn can save costs and facilitate processing. For example, generally, the tensile strength Rn can be set to satisfy 100 MPa ≤ Rn ≤ 1200 MPa.

[0280] It should be understood that the value range of the tensile strength Rn of at least a part of the housing 211 in the embodiment of the present application at a high temperature of 500 °C can be adjusted according to actual applications. For example, the value of the high-temperature tensile strength Rn can satisfy 100 MPa ≤ Rn ≤ 1200 MPa. For another example, the value of the high-temperature tensile strength Rn can also satisfy 112 MPa ≤ Rn ≤ 720 MPa. On the one hand, appropriately increasing the value of the tensile strength Rn can improve the deformation ability of this part of the housing 211 when thermal runaway occurs in the battery cell 20, making it less likely for the housing 211 to be quickly damaged and explode, thereby reducing the risk of thermal runaway in adjacent battery cells 20 and improving the reliability of the battery 10. At the same time, it is necessary to control that the tensile strength Rn of at least a part of the housing 211 at high temperature is not too large to reduce the processing difficulty, and thus can save costs and facilitate processing.

[0281] Further, the value of the high-temperature tensile strength Rn can be set to satisfy 152 MPa ≤ Rn ≤ 480 MPa, which can improve the deformation ability of the part of the housing 211 when the battery cell 20 undergoes thermal runaway, enhance the structural strength of the housing 211, make the housing 211 not easily be quickly damaged and explode, thereby reducing the risk of adjacent battery cells 20 undergoing thermal runaway, so as to improve the reliability of the battery 10. At the same time, the processing difficulty can also be reduced and the cost can be saved.

[0282] In some embodiments, the value of the high-temperature tensile strength Rn in the embodiments of the present application can also be set to other values. For example, the value of the high-temperature tensile strength Rn can be any one of the following values or between any two of the following values: 100 MPa, 112 MPa, 130 MPa, 150 MPa, 152 MPa, 168 MPa, 180 MPa, 200 MPa, 228 MPa, 250 MPa, 280 MPa, 300 MPa, 320 MPa, 350 MPa, 380 MPa, 400 MPa, 430 MPa, 450 MPa, 480 MPa, 500 MPa, 530 MPa, 550 MPa, 580 MPa, 600 MPa, 630 MPa, 650 MPa, 680 MPa, 700 MPa, 720 MPa, 750 MPa, 780 MPa, 800 MPa, 830 MPa, 850 MPa, 880 MPa, 900 MPa, 930 MPa, 950 MPa, 980 MPa, 1000 MPa, 1050 MPa, 1100 MPa, 1150 MPa, and 1200 MPa.

[0283] It should be understood that the tensile strength in the embodiments of the present application refers to the maximum stress value that the material can withstand before being broken. The test method for the tensile strength Rn of at least part of the area of the housing 211 in the embodiments of the present application at a high temperature of 500 °C can be selected according to actual applications. For example, the national standard GB / T228.1-2010 can be adopted to test the tensile strength Rn at a high temperature of 500 °C.

[0284] The following is a comparative description through multiple comparative examples and multiple embodiments. Specifically, the battery cells 20 in the following embodiments and comparative examples are all square shell batteries as shown in Figure 10 and Figure 11 wherein, the housing 211 adopts a hollow structure with one end open.

[0285] In the following embodiments and comparative examples, the preparation methods of the positive electrode plate 223, negative electrode plate 224, electrolyte, and separator 225 of the battery cell 20 are as follows.

[0286] 1. Preparation of the positive electrode plate 223

[0287] The positive electrode active material LiNi 0.95 Co 0.04 Mn 0.01 O 2 、conductive agent Super P, and binder polyvinylidene fluoride (PVDF) are made into a positive electrode slurry in N-methylpyrrolidone (NMP). The solid content in the positive electrode slurry is 50 wt%, and in the solid components, the mass ratio of LiNi 0.7 Co 0.1 Mn 0.1 O 2 、Super P, and PVDF is 8:1:1. The positive electrode slurry is coated on the upper and lower surfaces of the current collector aluminum foil, dried at 85°C, then cold-pressed, and then trimmed, sliced, and slit. After that, it is dried in a vacuum at 85°C for 4 h to make the positive electrode plate 223.

[0288] 2. Preparation of the negative electrode plate 224

[0289] The negative electrode active material, conductive agent Super P, thickening agent carboxymethyl cellulose (CMC), and binder styrene-butadiene rubber (SBR) are mixed evenly in deionized water to make a negative electrode slurry. The negative electrode active material includes graphite and a silicon-based material, and the silicon-based material is a silicon oxide compound. The solid content in the negative electrode slurry is 30 wt%. In the solid components, the mass ratio of the negative electrode active material, silicon monoxide, Super P, CMC, and binder styrene-butadiene rubber (SBR) is 88:7:3:2. The negative electrode slurry is coated on the upper and lower surfaces of the current collector copper foil, dried at 85°C, then cold-pressed, trimmed, sliced, and slit. After that, it is dried in a vacuum at 120°C for 12 h to make the negative electrode plate 224.

[0290] 3. Preparation of the electrolyte

[0291] In an argon atmosphere glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), the fully dried electrolyte salt LiPF6 is dissolved in a mixed solvent (the mixed solvent includes ethylene carbonate (EC) and diethyl carbonate (DEC), and ethylene carbonate (EC) and diethyl carbonate (DEC) are mixed in a mass ratio of 50:50). After mixing evenly, an electrolyte with a concentration of 1 mol / L is obtained.

[0292] 4. Preparation of the separator 225

[0293] A 16-μm polyethylene film is used as the separator 225.

[0294] 5. Preparation of the lithium-ion battery monomer 20

[0295] Stack the positive electrode plate 223, the separator 225, and the negative electrode plate 224 in sequence, with the separator 225 placed between the positive electrode plate 223 and the negative electrode plate 224 to isolate the positive and negative electrodes, wind to obtain a bare battery cell, weld the electrode tabs, place the bare battery cell in a housing made of different materials, inject the above-prepared electrolyte into the dried housing, and perform encapsulation, standing, formation, shaping, capacity testing, etc. to complete the preparation of the lithium-ion battery monomer 20.

[0296] In the following examples and comparative examples, the tensile strength of the housing 211 of the battery monomer 20 at a temperature of 500 °C is Rn, and different materials are selected for the housing 211 to obtain different tensile strengths Rn; the capacity of the battery monomer 20 is C; the wall thickness of the wall with the largest area of the battery monomer 20 is T. The specific parameter settings are shown in Table 4 below. In addition, in each example and comparative example, the material of the entire area of the housing 211 is the same, and the tensile strength Rn of the housing 211 at 500 °C is measured by the method specified in GB / T 228.1-2010. Moreover, except for the different parameter settings shown in Table 4 for the battery monomer 20 in the following examples and comparative examples, the remaining setting conditions are the same. For example, in each example, the positive electrode active material of the positive electrode plate 223 of the electrode assembly 22 of the battery monomer 20 includes a nickel element-containing compound. Among them, the nickel element-containing compound includes a layered lithium-containing transition metal oxide, and the molar amount of nickel element in the layered lithium-containing transition metal oxide accounts for 95% of the total molar amount of the transition metal elements in the layered lithium-containing transition metal oxide.

[0297] For the battery monomer 20 in the following comparative examples and examples, refer to the short-circuit test method in Section 6.2.4 of "GBT31485-2015 Safety Requirements and Test Methods for Power Batteries for Electric Vehicles" to test the single battery, and observe the integrity of the housing 211 after the test, that is, observe whether the housing 211 is cracked.

[0298] Table 4

[0299] Rn (MPa) T (mm) C (Ah) Housing material Test results Comparative example 1 13 0.7 350 Aluminum Housing cracked Comparative example 2 12 0.15 72 Aluminum Housing cracked Example 1 115 0.15 350 Low-carbon steel Housing intact Example 2 113 0.15 72 Low-carbon steel Housing intact Example 3 129 0.15 350 Low-carbon steel Housing intact Example 4 194 0.15 350 Stainless steel Housing intact Example 5 191 0.15 72 Stainless steel Housing intact Example 6 234 0.15 350 Stainless steel Housing intact

[0300] Comparing the two comparative examples and the six examples in Table 4 above, it can be seen that when the housing 211 uses different materials, different tensile strengths Rn can be determined accordingly. When the tensile strength Rn satisfies 100 MPa ≤ Rn ≤ 1200 MPa, for example, in Examples 1-6, the housing 211 of the battery cell 20 did not crack and could meet the design requirements of the battery cell 20; moreover, when other parameters of the battery cell 20 fluctuated differently, such as the capacity C of the battery cell 20 was different, or the thickness of the wall with the largest area of the housing 211 was different, the battery cell 20 did not crack and could meet the design requirements of the battery cell 20. However, when the tensile strength Rn does not satisfy 100 MPa ≤ Rn ≤ 1200 MPa, for example, in Comparative Examples 1-2, the housing 211 of the battery cell 20 cracked and could not meet the design requirements of the battery cell 20.

[0301] It should be understood that at least part of the area of the housing 211 in the embodiments of the present application may include a partial area of the housing 211 and may also include the entire area of the housing 211. In some embodiments, the housing 211 includes a weld 2113, and at least part of the area of the housing 211 includes the area within a preset distance from the weld 2113 of the housing 211, and the preset distance is L, and L satisfies: L = 10 mm. When the negative active material of the negative electrode tab 224 of the electrode assembly 22 includes a silicon-based material, since the silicon-based material can accommodate more metal ions, it will increase the deformation amount of the electrode assembly 22 in the battery cell 20 during use, causing the electrode assembly 22 to expand in volume, and further increasing the pressure of the electrode assembly 22 on the housing 211 of the battery cell 20. Under the same conditions, the structural strength of the area of the housing 211 near the weld 2113 is smaller than that of other areas of the housing 211. Therefore, the area of the housing 211 near the weld 2113 is more likely to be damaged during the use of the battery cell 20. Therefore, setting the area within the preset distance L from the weld 2113 to meet the requirements of the tensile strength Rm or the yield strength Re under normal temperature conditions can improve the deformation ability of the area of the housing 211 near the weld 2113, making this part of the area of the housing 211 not easily damaged, and further improving the structural stability and service life of the battery cell 20.

[0302] When the positive electrode active material of the positive electrode plate 223 of the electrode assembly 22 includes a nickel element-containing compound, if the battery cell 20 undergoes thermal runaway, the internal temperature of the battery cell 20 will increase rapidly and a large amount of gas will be generated. Under the same conditions, the structural strength of the region of the housing 211 near the weld 2113 is smaller than that of other regions of the housing 211. Therefore, the housing 211 is likely to rupture in the region near the weld 2113, which may trigger thermal runaway of the connected battery cells 20, that is, cause thermal diffusion. Therefore, setting the region within a preset distance L from the weld 2113 to meet the requirements of the tensile strength Rn or the melting point p under high temperature conditions can improve the deformation ability of this part of the housing 211, making this part of the region not easily damaged quickly or completely melted, reducing the risk of thermal diffusion or even explosion between multiple battery cells 20, so as to improve the reliability of the battery 10.

[0303] It should be understood that the weld 2113 included in the housing 211 of the embodiment of the present application may include the weld 2113 at any position of the housing 211. For example, the weld 2113 included in the housing 211 may include the weld between the housing 211 and the cover plate 212, that is, the region around the open end of the housing 211 is the weld. For another example, the weld 2113 of the housing 211 may also include the weld between different parts of the housing 211. For example, the housing 211 may include at least two parts, and the at least two parts are connected by welding to form the housing 211, where Figure 11 Taking the housing 211 including two parts along the height direction Z of the battery cell 20 as an example, there is a weld 2113 between the upper half housing and the lower half housing; or, different from Figure 11 as shown, the other parts of the housing 211 may also be provided with a weld 2113, and the embodiment of the present application is not limited thereto.

[0304] In some embodiments, at least a part of the housing 211 includes a surrounding area 2111 of the housing 211. The surrounding area 2111 surrounds the electrode assembly 22, and the surrounding area 2111 is at least a part of the side wall of the housing 211. In this way, when the negative active material of the negative electrode tab 224 of the electrode assembly 22 includes a silicon-based material, since the silicon-based material can accommodate more metal ions, the amount of deformation of the electrode assembly 22 in the battery cell 20 during use will increase, causing the electrode assembly 22 to expand in volume, thereby increasing the pressure of the electrode assembly 22 on the housing 211 of the battery cell 20. Therefore, setting the surrounding area 2111 to meet the requirements of the tensile strength Rm or the yield strength Re under normal temperature conditions can improve the deformation ability of the housing 211. Moreover, since the surrounding area 2111 is arranged to surround the electrode assembly 22, it can limit the extrusion force of the internal electrode assembly 22 on the housing 211 in the radial direction, making the housing 211 not easily damaged, thereby improving the structural stability and service life of the battery cell 20.

[0305] When the positive active material of the positive electrode tab 223 of the electrode assembly 22 includes a nickel-containing compound, if the battery cell 20 undergoes thermal runaway, the temperature inside the battery cell 20 will increase rapidly and a large amount of gas will be generated. If the surrounding area 2111 meets the requirements of the tensile strength Rn or the melting point p under high temperature conditions, then the deformation ability of the surrounding area 2111 of the housing 211 can be improved, making the surrounding area 2111 not easily be damaged rapidly or completely melted, capable of restricting the excessive expansion of the internal electrode assembly 22 of the housing 211 in its thickness direction, reducing the possibility of the battery cell 20 exploding, and further reducing the risk of adjacent battery cells 20 undergoing thermal runaway, so as to improve the reliability of the battery 10.

[0306] It should be understood that the position and size of the surrounding area 2111 in the embodiments of the present application can be flexibly set according to actual applications. For example, along the height direction Z of the battery cell 20, the height of the surrounding area 2111 can be less than or equal to the height of the housing 211. Specifically, if along the height direction Z of the battery cell 20, the height of the surrounding area 2111 is less than the height of the housing 211, then the surrounding area 2111 can be located at any position of the housing 211 along the height direction Z of the battery cell 20. For example, the surrounding area 2111 can be located in the middle of the housing 211 along the height direction Z of the battery cell 20 to limit the deformation of the corresponding middle position of the electrode assembly 22.

[0307] If, along the height direction Z of the battery cell 20, the height of the surrounding area 2111 is equal to the height of the housing 211, then the surrounding area 2111 includes all the side walls of the housing 211 and can wrap the side surface of the electrode assembly 22, thereby improving the structural strength of the side walls of the housing 211 and reducing the risk of explosion and heat diffusion caused by the damage of the local weak area of the side walls of the housing 211 after the thermal runaway of the battery cell 20, and thus improving the reliability of the battery 10.

[0308] In some embodiments, at least part of the housing 211 includes all the walls of the housing 211, that is, at least part of the housing 211 in the embodiments of the present application may refer to all areas of the housing 211. In this way, when the negative active material of the negative electrode tab 224 of the electrode assembly 22 includes a silicon-based material, since the silicon-based material can accommodate more metal ions, the deformation amount of the electrode assembly 22 in the battery cell 20 during use will increase, causing the electrode assembly 22 to expand in volume, and thus increasing the pressure of the electrode assembly 22 on the housing 211 of the battery cell 20. Therefore, setting all areas of the housing 211 to meet the requirements of the tensile strength Rm or the yield strength Re at normal temperature can improve the overall deformation ability of the housing 211, and can also limit the extrusion force of the internal electrode assembly 22 on the housing 211 in all directions, making the strength of each part of the housing 211 balanced and not easily damaged in the local weak area, thereby improving the structural stability and service life of the battery cell 20.

[0309] When the positive active material of the positive electrode tab 223 of the electrode assembly 22 includes a nickel-containing compound, if the battery cell 20 undergoes thermal runaway, the internal temperature of the battery cell 20 will increase rapidly and a large amount of gas will be generated; and if all areas of the housing 211 meet the requirements of the tensile strength Rn or the melting point p at high temperature, then the overall deformation ability of the housing 211 can be improved, making the housing 211 not easily damaged or melted, capable of restricting the high-temperature and high-pressure gas inside the housing 211, reducing the impact on the connected battery cell 20, and thus reducing the risk of thermal runaway of adjacent battery cells 20 to improve the reliability of the battery 10.

[0310] Further, the cover plate 212 in the embodiments of the present application can be made of the same material as at least part of the housing 211 in the embodiments of the present application, so that the structural strength of the cover plate 212 also meets the design requirements. For example, the cover plate 212 can also meet at least one of the above requirements of the tensile strength Rm and the yield strength Re at normal temperature, the tensile strength Rn at high temperature, and the melting point p, so as to improve the structural strength of the cover plate 212 and thus improve the structural stability of the battery cell 20, but the embodiments of the present application are not limited thereto.

[0311] In an embodiment of the present application, the housing 211 at least partially includes a third housing wall 2112, and the average thickness of the third housing wall 2112 is T, where T satisfies: 0.05 mm ≤ T ≤ 0.5 mm, and 60 mm·MPa ≤ T×Rm ≤ 500 mm·MPa.

[0312] It should be understood that the third housing wall 2112 of the housing 211 in the embodiment of the present application can be any wall of the housing 211. Specifically, the battery cell 20 can be any polyhedron structure, the housing 211 can be a hollow structure with at least one end open, the housing 211 can include one or more walls, the third housing wall 2112 is any wall of the housing 211, and the housing 211 can include one or more third housing walls 2112. For example, if the housing 211 is a prism, the third housing wall 2112 can be any wall of the prism, and the surface of the third housing wall 2112 can be any polygon. For another example, as Figure 10 and Figure 11 shown, if the housing 211 is a cuboid, the third housing wall 2112 can be any wall of the housing 211, and the surface of the third housing wall 2112 is a rectangle. For another example, if the housing 211 is a cylinder, the third housing wall 2112 can be the bottom surface of the cylinder or the side surface of the cylinder, and the embodiment of the present application is not limited thereto. In addition, if the adjacent two walls of the housing 211 are connected by a fillet, when the third housing wall 2112 of the housing 211 in the embodiment of the present application is any wall of the housing 211, the third housing wall 2112 does not include the connection area of the fillet between this wall and the adjacent wall.

[0313] In an embodiment of the present application, at least a part of the housing 211 includes the third housing wall 2112, and the tensile strength of the third housing wall 2112 at a normal temperature of 25°C is Rm. Increasing the tensile strength Rm of at least a part of the housing 211 under the condition of normal temperature of 25°C can improve the deformation ability of the housing 211, so that the housing 211 is not easily damaged during the use of the battery cell 20, thereby improving the structural stability and service life of the battery cell 20. However, the tensile strength Rm of at least a part of the housing 211 under normal temperature conditions should not be too large, so as to reduce the difficulty of material selection and processing of the housing 211, save costs, and facilitate processing.

[0314] When the average thickness T of the third housing wall 2112 of the housing 211 is relatively thin, the structural strength of the third housing wall 2112 can be increased by increasing the tensile strength Rm of the third housing wall 2112 of the housing 211 at room temperature of 25°C. In this way, both the energy density of the battery cell 20 and the structural strength and stability of the battery cell 20 can be improved. On the contrary, when the average thickness T of the third housing wall 2112 of the housing 211 is relatively thick, the structural strength of the housing 211 can be improved, and the difficulty of selecting the material of the housing 211 can be reduced by appropriately reducing the requirement for the tensile strength Rm of the third housing wall 2112 of the housing 211 at room temperature, thereby reducing the processing difficulty and processing cost of the battery cell 20. Moreover, T×Rm represents the stiffness of the third housing wall, and it is restricted that the stiffness of the third housing wall should not be too small or too large, which can not only enable the third housing wall to have good deformation ability, but also reduce the processing difficulty and cost.

[0315] It should be understood that the value range of the average thickness T of the third housing wall 2112 in the embodiment of the present application can also be flexibly set according to actual applications. For example, the average thickness T of the third housing wall 2112 satisfies: 0.05 mm ≤ T ≤ 0.5 mm. Further, the average thickness T of the third housing wall 2112 satisfies: 0.1 mm ≤ T ≤ 0.4 mm. Appropriately thinning the average thickness T of the third housing wall 2112 can reduce the space occupied by the housing 211 inside the battery 10, thereby improving the energy density of the battery 10, and the requirement for the structural strength of the housing 211 can be compensated by increasing the tensile strength Rm of the third housing wall 2112 at room temperature to maintain the stability of the housing 211; while appropriately increasing the average thickness T of the third housing wall 2112 can also reduce the processing difficulty of the third housing wall 2112.

[0316] Further, the average thickness T of the third housing wall 2112 satisfies: 0.1 mm ≤ T ≤ 0.3 mm. The average thickness T of the third housing wall 2112 is neither too large nor too small, which can not only improve the structural strength and structural stability of the housing 211, but also reduce the space occupied by the housing 211 inside the battery 10, thereby improving the energy density of the battery 10.

[0317] In some embodiments, the value of the average thickness T of the third housing wall 2112 of the embodiments of the present application can also be set to other values. For example, the value of the average thickness T of the third housing wall 2112 can be any one of the following values or between any two of the following values: 0.05 mm, 0.075 mm, 0.1 mm, 0.125 mm, 0.15 mm, 0.175 mm, 0.2 mm, 0.225 mm, 0.25 mm, 0.275 mm, 0.3 mm, 0.325 mm, 0.35 mm, 0.375 mm, 0.4 mm, 0.425 mm, 0.45 mm, 0.475 mm, and 0.5 mm.

[0318] In some embodiments, the value range of T×Rm can also be adjusted according to actual applications. For example, Rm and T satisfy: 60 mm·MPa ≤ T×Rm ≤ 500 mm·MPa; further, Rm and T can also satisfy: 100 mm·MPa ≤ T×Rm ≤ 500 mm·MPa. By selecting a suitable material, the tensile strength Rm of the third housing wall 2112 at room temperature can be improved, and then the average thickness T of the third housing wall 2112 can be reduced, so that the stiffness value of the third housing wall 2112 meets the design requirements, which can not only improve the structural strength and structural stability of the third housing wall 2112 of the housing 211, but also improve the energy density of the battery cell 20 and the battery 10.

[0319] Further, the value range of T×Rm can also be set to: Rm and T satisfy: 100 mm·MPa ≤ T×Rm ≤ 300 mm·MPa, so that the stiffness value of the third housing wall 2112 is more suitable, which can not only enable the third housing wall 2112 to have good deformation ability to improve the service life of the battery cell 20, but also reduce the difficulty of material selection, and then reduce the processing difficulty and processing cost.

[0320] In some embodiments, the value of T×Rm of the embodiments of the present application can also be set to other values. For example, the value of T×Rm can be any one of the following values or between any two of the following values: 60 mm·MPa, 65 mm·MPa, 70 mm·MPa, 75 mm·MPa, 80 mm·MPa, 85 mm·MPa, 90 mm·MPa, 95 mm·MPa, 100 mm·MPa, 130 mm·MPa, 150 mm·MPa, 180 mm·MPa, 200 mm·MPa, 230 mm·MPa, 250 mm·MPa, 280 mm·MPa, 300 mm·MPa, 330 mm·MPa, 350 mm·MPa, 380 mm·MPa, 400 mm·MPa, 430 mm·MPa, 450 mm·MPa, 480 mm·MPa, and 500 mm·MPa.

[0321] In the embodiments of the present application, the value of the mass fraction g of the silicon-based material and the value of the average thickness T of the third housing wall 2112 can be mutually restricted, and can also be mutually restricted with the value of the tensile strength Rm of at least a part of the housing 211 under the condition that the temperature is 25 °C, so as to balance the relationship between the energy density and the structural strength of the battery cell 20. For example, in the negative electrode active material, the mass fraction of the silicon-based material is g, and g and T satisfy: 2% < g < 20%, 0.15 mm ≤ T ≤ 0.4 mm. When the mass fraction g of the silicon-based material is relatively small, the average thickness T of the third housing wall 2112 can be appropriately reduced to improve the space utilization rate of the housing 211. When the energy density of the battery cell 20 is increased, the structural strength of the housing 211 can also be balanced.

[0322] In some embodiments, the mass fraction of the silicon-based material in the negative electrode active material is g, and g, T, and Rm satisfy: 15% < g < 40%, 0.2 mm ≤ T ≤ 0.4 mm, 100 mm·MPa ≤ T×Rm ≤ 500 mm·MPa. Increasing the mass g of the silicon-based material can effectively increase the energy density of the battery cell 20. At the same time, increasing the thickness and stiffness T×Rm of the third housing wall 2112 can improve the structural strength and stability of the battery cell 20.

[0323] It should be understood that the average thickness T of the third housing wall 2112 in the embodiments of the present application may refer to the average thickness of at least a part of the third housing wall 2112. For example, the average thickness T of the third housing wall 2112 may refer to the average thickness T of all regions of the third housing wall 2112, especially when the third housing wall 2112 is relatively flat, that is, the thickness of most regions of the third housing wall 2112 is basically equal or differs little, or the thickness of all regions of the third housing wall 2112 is basically equal or differs little, then the average thickness of all regions of the third housing wall 2112 can be determined as T.

[0324] For another example, the average thickness T of the third housing wall 2112 may also refer to the average thickness T of a local region of the third housing wall 2112, that is, the average thickness T of the remaining region after excluding a part of the third housing wall 2112. For example, if there are some special regions in the third housing wall 2112, and the thickness of these special regions is quite different from that of other regions. For example, there are convex structures or concave regions in these special regions, making the thickness of these special regions larger or smaller than that of other regions, then these special regions can be excluded to calculate the average thickness of the remaining regions of the third housing wall 2112 as T.

[0325] In some embodiments, the third housing wall 2112 includes a functional region, and the average thickness T of the third housing wall 2112 is the average thickness of the region of the third housing wall 2112 other than the functional region. The functional region includes at least one of the following regions: a pressure relief region, the region where the electrode terminal 214 is located, a liquid injection region, and a welding region. The thickness of the functional region usually varies significantly compared to the thickness of other regions of the third housing wall 2112. Therefore, when calculating the average thickness T of the third housing wall 2112 without including the functional region, the design of the third housing wall 2112 can better meet the strength requirements, thereby improving the structural strength and stability of the battery cell 20.

[0326] Specifically, the functional region in the embodiments of the present application may include a region on the third housing wall 2112 where a specific structure is provided or which has a specific use. For example, the functional region may include a pressure relief region for setting a pressure relief mechanism, and the pressure relief mechanism is an element or component that is actuated to release the internal pressure or temperature when the internal pressure or temperature of the battery cell 20 reaches a predetermined threshold. The predetermined threshold can be adjusted according to different design requirements. For example, the predetermined threshold may depend on one or several of the materials of the positive electrode sheet, negative electrode sheet, electrolyte, and separator in the battery cell 20.

[0327] As used in the present application, "actuate" means that the pressure relief mechanism generates an action or is activated to a certain state, so that the internal pressure and temperature of the battery cell 20 can be released. The actions generated by the pressure relief mechanism may include, but are not limited to: at least a part of the pressure relief mechanism rupturing, breaking, being torn, or opening, etc. When the pressure relief mechanism is actuated, the high-temperature and high-pressure substances inside the battery cell 20 are discharged outward from the actuated part as emissions. In this way, the battery cell 20 can be depressurized and cooled under controlled pressure or temperature, thereby avoiding potential more serious accidents.

[0328] The emissions from the battery cell 20 mentioned in the present application include, but are not limited to: electrolyte, dissolved or fragmented positive and negative electrode sheets, fragments of the separator, high-temperature and high-pressure gases generated by the reaction, flames, etc.

[0329] The pressure relief mechanism of the embodiment of the present application can be disposed on any wall of the battery cell 20. For example, the pressure relief mechanism can be disposed in the pressure relief area of the third housing wall 2112 of the battery cell 20. The pressure relief mechanism can be a part of the third housing wall 2112; or, it can also be a split structure with the third housing wall 2112 and is fixed on the third housing wall 2112 by means such as welding. For example, when the pressure relief mechanism is a part of the third housing wall 2112, for example, the pressure relief mechanism can be formed by making a notch on the third housing wall 2112, that is, the third housing wall 2112 is provided with a notch in the pressure relief area, and the thickness at the notch is significantly less than the thickness of other areas of the third housing wall 2112. Therefore, the average thickness T of the third housing wall 2112 can not calculate the thickness at the notch. The notch is the weakest position of the pressure relief mechanism. When too much gas is generated in the battery cell 20 causing the internal pressure to rise and reach the threshold or the internal reaction in the battery cell 20 generates heat causing the internal temperature of the battery cell 20 to rise and reach the threshold, the pressure relief mechanism can rupture at the notch, resulting in the internal and external communication of the battery cell 20, and the gas pressure and temperature are released outward through the crack of the pressure relief mechanism, thereby preventing the battery cell 20 from exploding.

[0330] For another example, the pressure relief mechanism can also be a split structure with the third housing wall 2112. The pressure relief mechanism can be in the form of, for example, an explosion-proof valve, a gas valve, a pressure relief valve or a safety valve, and can specifically adopt a pressure-sensitive or temperature-sensitive element or structure. For example, the third housing wall 2112 is provided with a through hole in the pressure relief area, and the pressure relief mechanism is installed and fixed to the third housing wall 2112 through the through hole. After installation, the pressure relief mechanism may protrude or recess relative to other areas of the third housing wall 2112. Therefore, the average thickness T of the third housing wall 2112 can not include the pressure relief area where the pressure relief mechanism is located. When the internal pressure or temperature of the battery cell 20 reaches a predetermined threshold, the pressure relief mechanism performs an action or a weak structure provided in the pressure relief mechanism is damaged, thereby forming an opening or a channel for discharging the internal pressure or temperature.

[0331] In some embodiments, the functional area may further include the area where the electrode terminal 214 is located. Specifically, the electrode terminal 214 in the embodiment of the present application is used to be electrically connected to the electrode assembly 22 inside the battery cell 20 to output the electrical energy of the battery cell 20. Moreover, the battery cell 20 may include at least two electrode terminals 214, and the at least two electrode terminals 214 respectively include at least one positive electrode terminal 214a and at least one negative electrode terminal 214b. The positive electrode terminal 214a is used to be electrically connected to the positive electrode tab 222a of the electrode assembly 22, and the negative electrode terminal 214b is used to be electrically connected to the negative electrode tab 222b of the electrode assembly 22. The positive electrode terminal 214a and the positive electrode tab 222a may be directly connected or indirectly connected, and the negative electrode terminal 214b and the negative electrode tab 222b may be directly connected or indirectly connected. Exemplarily, the positive electrode terminal 214a may be electrically connected to the positive electrode tab 222a through a connecting member 23, and the negative electrode terminal 214b is electrically connected to the negative electrode tab 222b through a connecting member 23.

[0332] It should be understood that each electrode terminal 214 in the embodiment of the present application may be disposed on any one wall, and a plurality of electrode terminals 214 may be disposed on the same wall or different walls of the battery cell 20. For example, as Figure 10 and Figure 11 shown, taking each battery cell 20 including two electrode terminals 214 and the two electrode terminals 214 being located on the same wall as an example, for example, the two electrode terminals 214 may both be located on the cover plate 212.

[0333] For another example, also taking each battery cell 20 including two electrode terminals 214 and the two electrode terminals 214 being located on the same wall as an example, different from Figure 10 and Figure 11 shown, the two electrode terminals 214 may also be located on the housing 211. For example, the two electrode terminals 214 may both be located on the third housing wall 2112 of the housing 211. When the electrode terminal 214 is located on the third housing wall 2112, the electrode terminal 214 generally protrudes from other areas of the third housing wall 2112, that is, the thickness of the area where the electrode terminal 214 is located is much greater than the thickness of other areas of the third housing wall 2112. Therefore, calculating the average thickness T of the third housing wall 2112 may not include the area where the electrode terminal 214 is located.

[0334] In some embodiments, the functional region may further include a liquid injection region. For example, the liquid injection region of the third housing wall 2112 may be provided with a liquid injection hole, and electrolyte is injected into the housing 211 through the liquid injection hole. After the electrolyte injection is completed, the liquid injection hole may be sealed by a seal. Considering that the thickness of the liquid injection region where the seal is located is generally much greater than the thickness of other regions of the third housing wall 2112, therefore, when calculating the average thickness T of the third housing wall 2112, the liquid injection region may not be included.

[0335] In some embodiments, the functional region may further include a welding region. For example, the third housing wall 2112 may be fixed to other walls by welding, or the third housing wall 2112 itself needs to be processed and formed by welding, then the third housing wall 2112 may include a welding region. For example, as Figure 11 shown, the housing 211 may be welded in a splicing manner, then the housing 211 may have a weld 2113. Specifically, the housing 211 may include at least two parts, and the at least two parts are connected by welding to form the housing 211, where Figure 11 taking the housing 211 including two parts along the height direction Z of the battery cell 20 as an example, there is a weld 2113 between the upper half housing and the lower half housing; or, different from Figure 11 shown, the other parts of the housing 211 may also be provided with a weld 2113, and the embodiments of the present application are not limited thereto. The welding region of the functional region of the embodiments of the present application may further include the weld 2113. Due to process reasons, the thickness of the welding region is generally greater than the thickness of other regions of the third housing wall 2112, therefore, when calculating the average thickness T of the third housing wall 2112, the welding region may not be included.

[0336] In the embodiments of the present application, the third housing wall 2112 of the housing 211 may be any wall of the housing 211. For example, the third housing wall 2112 is the wall with the smallest thickness of the housing 211. That is, by restricting the thickness T of the wall with the smallest thickness of the housing 211 to restrict the thickness of other walls of the housing 211, so that each wall of the housing 211 can meet the structural strength requirements, thereby improving the structural strength and stability of the battery cell 20.

[0337] In some embodiments, the third housing wall 2112 is the wall with the largest area of the housing 211. Considering that there are multiple battery cells 20 arranged in the battery 10, the multiple battery cells 20 usually abut against each other through the wall with the largest area of the housing 211. Therefore, the wall with the largest area usually receives the greatest extrusion force from the electrode assembly 22. By restricting the average thickness T and the room-temperature tensile strength Rm of the third housing wall 2112, the deformation ability of the housing 211 can be effectively improved, thereby improving the structural strength and stability of the battery cell 20.

[0338] It should be understood that the position of the wall with the largest area of the housing 211 in the embodiments of the present application can be set according to actual applications. For example, the battery 10 may include multiple battery cells 20, and the arrangement direction of the multiple battery cells 20 may be perpendicular or parallel to the wall with the largest area of the housing 211. The embodiments of the present application are not limited thereto.

[0339] In some embodiments, the housing 211 includes an intersecting bottom wall and side walls, wherein the bottom wall is used to support the electrode assembly accommodated in the housing 211. Specifically, the housing 211 may be a hollow structure with at least one open end, and the bottom wall and side walls of the housing 211 do not necessarily refer to the walls opposite to and adjacent to the opening respectively. When the electrode assembly 22 is accommodated inside the housing 211, considering that in actual applications, due to different application scenarios, the setting direction of the electrode assembly 22 may be different, and the housing 211 may include walls for supporting the electrode assembly 22. Therefore, the bottom wall of the housing 211 in the embodiments of the present application is the wall for supporting the electrode assembly 22, that is, the bottom wall of the housing 211 is used to bear the gravity of the electrode assembly 22. Relatively, the wall of the housing 211 that directly intersects with the bottom wall is the side wall of the housing 211.

[0340] In some embodiments, the third housing wall 2112 is the side wall of the housing 211. Considering that the uses of the bottom wall and side walls of the housing 211 are different, the design requirements for the bottom wall and side walls may also be different. For example, the side walls of the housing 211 usually have higher requirements for deformation ability. In the case where the third housing wall 2112 is the side wall of the housing 211, by restricting the room-temperature tensile strength Rm of the side wall of the housing 211 and the average thickness T of the side wall, the deformation ability of the side wall of the housing 211 can be effectively improved, thereby improving the structural stability of the battery cell 20.

[0341] In some embodiments, the housing 211 includes multiple side walls with equal thicknesses for easy processing.

[0342] In some embodiments, the thickness of the bottom wall of the housing 211 is equal to the thickness of the side walls of the housing 211 for easy processing and optimizing the space occupied by the housing 211.

[0343] In some embodiments, the third housing wall 2112 is perpendicular to the stacking direction of the electrode sheets of the electrode assembly 22. The stacking direction of the electrode sheets of the electrode assembly 22 is generally the thickness direction of the electrode assembly 22. Considering that the thickness direction of the electrode assembly 22 is prone to expansion during the cyclic charge and discharge of the battery cell 20, higher requirements are imposed on the deformation of the corresponding wall of the housing 211. Therefore, by setting the third housing wall 2112 as the wall perpendicular to the stacking direction of the electrode sheets of the electrode assembly 22, or in other words, arranging the third housing wall 2112 along the stacking direction of the electrode sheets of the electrode assembly 22, by restricting the tensile strength Rm and the average thickness T of the third housing wall 2112 at normal temperature, the energy density of the battery cell 20 can be increased, and the deformation ability of the third housing wall 2112 can be effectively improved, thereby improving the structural stability of the battery cell 20.

[0344] It should be understood that the cover plate 212 of the embodiment of the present application can adopt the same or different designs from the third housing wall 2112. For example, the cover plate 212 can adopt the same design as the third housing wall 2112, that is, the average thickness of the cover plate 212 can be T, the tensile strength at normal temperature of the cover plate 212 can be b, and the design requirements of b and T are satisfied above, so as to improve the deformation ability of the cover plate 212, thereby improving the structural strength and stability of the battery cell 20.

[0345] In some embodiments, the ratio of the volume of the internal space of the housing 211 to the outer shape volume of the housing 211 is greater than or equal to 93%. That is, the thickness of the housing 211 is relatively thin, so that the space occupied by the housing 211 itself is small, thereby improving the space utilization rate and energy density of the battery 10.

[0346] It should be understood that the specific calculation methods of the volume of the internal space of the housing 211 and the outer shape volume of the housing 211 in the embodiment of the present application are related to the shape of the housing 211. For example, taking the housing 211 as a cuboid as an example. Figure 15 The side view schematic diagram of the housing 211 of the embodiment of the present application is shown, Figure 16 The top view schematic diagram of the housing 211 of the embodiment of the present application is shown. For example, the Figure 15 and Figure 16 The shown housing 211 can be the housing 211 of the battery cell 20 as shown in Figure 10 and Figure 11 shown.

[0347] Such as Figure 15 and Figure 16As shown, here, the housing 211 of a cuboid is taken as an example, and the housing 211 is a hollow cuboid with one end open. When calculating the volume of the internal space of the housing 211 and the external volume of the housing 211, the rounded connection between adjacent walls of the housing 211 can be ignored. As Figure 15 and Figure 16 shown, since each wall of the housing 211 has a certain thickness, in the length direction Y, the internal length of the housing 211 is Y1, and the external length is Y2, where Y2 is greater than Y1; similarly, in the width direction X, the internal width of the housing 211 is X1, and the external width is X2, where X2 is greater than X1; in the height direction Z, the internal height of the housing 211 is Z1, and the external height is Z2, where Z2 is greater than Z1. Therefore, the volume V1 of the internal space of the housing 211 = X1 × Y1 × Z1; the volume V2 of the external space of the housing 211 = X2 × Y2 × Z2, and V1 / V2 is greater than or equal to 93%, so as to reduce the space occupied by the housing 211 itself, thereby improving the space utilization rate and energy density of the battery 10.

[0348] The following is a comparative description through multiple comparative examples and multiple implementation examples. Specifically, the battery cells 20 in the following implementation examples and comparative examples are all taken as the square shell battery as shown in Figure 10 and Figure 11 shown, where the housing 211 adopts a hollow structure with one end open.

[0349] In the following implementation examples and comparative examples, the preparation methods of the positive electrode plate 223, negative electrode plate 224, electrolyte, and separator 225 of the battery cell 20 are as follows.

[0350] 1. Preparation of the positive electrode plate 223

[0351] The positive electrode active material LiNi 0.95 Co 0.04 Mn 0.01 O 2 , conductive agent Super P, and binder polyvinylidene fluoride (PVDF) are made into a positive electrode slurry in N-methylpyrrolidone (NMP). The solid content in the positive electrode slurry is 50 wt%, and the mass ratio of LiNi 0.7 Co 0.1 Mn 0.1 O 2 , Super P, and PVDF in the solid components is 8:1:1. The positive electrode slurry is coated on the upper and lower surfaces of the current collector aluminum foil, dried at 85°C, then cold-pressed, and then trimmed, sliced, and slit, and finally dried in a vacuum at 85°C for 4 h to make the positive electrode plate 223.

[0352] 2. Preparation of the negative electrode plate 224

[0353] The negative electrode active material is mixed evenly with conductive agent Super P, thickening agent carboxymethyl cellulose (CMC), and binder styrene butadiene rubber (SBR) in deionized water to form a negative electrode slurry. The negative electrode active material includes graphite and a silicon-based material, and the silicon-based material is a silicon oxide compound. The solid content in the negative electrode slurry is 30 wt%. The mass ratio of the negative electrode active material, silicon suboxide, Super P, CMC, and binder styrene butadiene rubber (SBR) in the solid components is 88:7:3:2. The negative electrode slurry is coated on the upper and lower surfaces of the current collector copper foil and dried at 85°C, and then after cold pressing, edge trimming, slicing, and slitting, it is dried in a vacuum at 120°C for 12 h to make the negative electrode plate 224.

[0354] 3. Preparation of the electrolyte

[0355] In an argon atmosphere glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), the fully dried electrolyte salt LiPF6 is dissolved in a mixed solvent (the mixed solvent includes ethylene carbonate (EC) and diethyl carbonate (DEC), and ethylene carbonate (EC) and diethyl carbonate (DEC) are mixed in a mass ratio of 50:50), and after mixing evenly, an electrolyte solution with a concentration of 1 mol / L is obtained.

[0356] 4. Preparation of the separator 225

[0357] A 16-μm polyethylene film is used as the separator 225.

[0358] 5. Preparation of the lithium-ion battery cell 20

[0359] The positive electrode plate 223, the separator 225, and the negative electrode plate 224 are stacked in sequence, with the separator 225 placed in the middle of the positive electrode plate 223 and the negative electrode plate 224 to isolate the positive and negative electrodes, and then wound to obtain a bare battery cell. The electrode tabs are welded, the bare battery cell is placed in a housing made of different materials, and the above-prepared electrolyte solution is injected into the dried housing, followed by encapsulation, standing, formation, shaping, capacity testing, etc., to complete the preparation of the lithium-ion battery cell 20.

[0360] In the following embodiments and comparative examples, the tensile strength of the housing 211 of the battery cell 20 at a temperature of 25 °C is Rm, and different materials are selected for the housing 211 to obtain different tensile strengths Rm; the average thickness of the third housing wall 2112 of the housing 211 is T; the specific parameter settings are shown in Table 5 below. In addition, in each embodiment and comparative example, the material of all regions of the housing 211 is the same, and the tensile strength Rm of the housing 211 at 25 °C is measured by the method specified in GB / T 228.1-2010. Moreover, the battery cells 20 in the following embodiments and comparative examples have the same settings except for the different parameter settings shown in Table 5. For example, the capacity of the battery cell 20 in each embodiment is 350 Ah.

[0361] A cyclic charge fatigue test was performed on the battery cells 20 in the following embodiments and comparative examples. Specifically, a fixture 700 for cyclic charge fatigue test as shown in Figure 14 could be used for the test.

[0362] Specifically, the battery cell 20 was clamped and fixed in the special fixture 700 to ensure that the two walls with the largest relative area of the battery cell 20 were clamped, and the initial pressure was set to 2000 N, and the electrode terminals 214 of the battery cell 20 were connected to a special battery charge and discharge device.

[0363] The fixture 700 holding the battery cell 20 was placed in a constant temperature environment of 25 ± 2 °C, and the test was started after the battery cell 20 reached temperature equilibrium.

[0364] The specific test steps refer to Section 6.4 "Standard Cycle Life" in "GBT31484-2015 Requirements and Test Methods for Cycle Life of Power Batteries for Electric Vehicles", and the test cycle cut-off condition was changed to "stop the test until the weld 2113 of the battery cell 20 is damaged".

[0365] For example, the test could be performed according to the following steps: Step a, discharge at 1I (A) to the discharge termination condition specified by the enterprise; Step b, set aside for no less than 30 min or the set-aside condition specified by the enterprise; Step c, charge according to the method in 6.1.1.3; Step d, set aside for no less than 30 min or the set-aside condition specified by the enterprise; Step e, discharge at 1I1 (A) to the discharge termination condition specified by the enterprise; Step f, repeat Steps b to e until the weld 2113 is damaged and stop the test.

[0366] During the above test process, continuously observe the weld 2113 of the battery cell 20 until the weld 2113 leaks liquid, record the number of cycles, so as to obtain the situation of the housing 211 when cycling 1000 times as shown in Table 5 below. Among them, in the following embodiments and comparative examples, the weld 2113 refers to the weld between the housing 211 and the cover plate 212, that is, the weld 2113 surrounds the open end of the housing 211, and the housing 211 adopts an integrally formed structure.

[0367] Table 5

[0368]

[0369]

[0370] It should be understood that in Table 5 above, the material of the housing 211 can be Q195 carbon steel, and the tensile strength Rm of Q195 carbon steel at room temperature of 25°C is usually at least 315 MPa to 430 MPa. In the above embodiments, only 328 MPa is taken as an example, but it is not limited thereto. Similarly, the material of the housing 211 can be SPCC carbon steel, and the tensile strength Rm of SPCC carbon steel at room temperature of 25°C is usually at least 380 MPa to 430 MPa. In the above embodiments, only 396 MPa is taken as an example; the material of the housing 211 can be SUS430 stainless steel, and the tensile strength Rm of SUS430 stainless steel at room temperature of 25°C is usually at least 450 MPa. In the above embodiments, only 459 MPa is taken as an example; the material of the housing 211 can be SUS304 stainless steel, and the tensile strength Rm of SUS304 stainless steel at room temperature of 25°C is usually at least 520 MPa. In the above embodiments, only 533 MPa, 625 MPa and 763 MPa are taken as examples.

[0371] According to Table 5 above, in the above Embodiments 1-12, the Rm and T of the third housing wall 2112 of the housing 211 satisfy: 250 MPa ≤ Rm ≤ 2000 Mpa, 0.05 mm ≤ T ≤ 0.5 mm, and 60 mm·MPa ≤ T×Rm ≤ 500 mm·MPa. The failure fatigue life of the battery cell 20 can reach more than one thousand times to meet the design requirements of the battery cell 20. Moreover, even if the average thickness T of the third housing wall 2112 is set to be small, the failure fatigue life of the battery cell 20 can also reach more than one thousand times. And setting the average thickness T of the third housing wall 2112 to be small can also increase the energy density of the battery 10. However, in the two comparative examples, the structural strength of the third housing wall 2112 is insufficient, and both Rm and T×Rm do not meet the above values. Even if the average thickness T of the third housing wall 2112 is large, the failure fatigue life of the battery cell 20 cannot reach one thousand times and cannot meet the design requirements of the battery cell 20.

[0372] In some embodiments, the capacity of the battery cell is C, and C satisfies: 25 Ah ≤ C ≤ 550 Ah. On the one hand, increasing the capacity C of the battery cell 20 can increase the capacity density of the battery 10 including a plurality of such battery cells 20. Or, when the total capacity of the battery 10 remains unchanged, if the capacity C of a single battery cell 20 is increased, the number of battery cells 20 provided can be reduced. Correspondingly, the number of electrical connections between the plurality of battery cells 20 can also be reduced, and the probability of electrical connection failure can be reduced, which helps to improve the reliability of the battery. And, when the capacity C of the battery cell 20 is relatively large, the tensile strength Rm of at least part of the housing 211 can be increased under the condition of normal temperature of 25 °C to meet the requirements of the high-capacity battery cell 20 for the structural strength of the housing 211, thereby improving the reliability and service life of the battery cell 20. On the other hand, if the battery cell 20 has a large capacity, the reaction inside it will intensify, thereby increasing the requirements for the structural strength of the housing 211. Therefore, the capacity C of the battery cell 20 should not be too large to limit the design requirements for the structural strength of the housing 211, and thus the material selection difficulty and processing difficulty of the battery cell 20 can be reduced, the cost can be reduced, and the processing efficiency can be improved.

[0373] It should be understood that the value range of the capacity C of the battery cell 20 in the embodiments of the present application can be adjusted according to actual applications. For example, the capacity C of the battery cell 20 can be reasonably selected according to the actual requirements of the battery 10. In some embodiments, the capacity C of the battery cell 20 can be further set to satisfy: 100 Ah ≤ C ≤ 300 Ah. Appropriately increasing the capacity C of the battery cell 20 can increase the energy density of the battery 10; at the same time, the capacity C of the battery cell 20 should not be too large to balance the relationship between the capacity C of the battery cell 20 and the structural strength of the housing 211, and improve the reliability and service life of the battery cell 20.

[0374] Furthermore, the capacity C of the battery cell 20 can also satisfy: 150 Ah ≤ C ≤ 250 Ah. Further restricting the capacity C of the battery cell 20 can not only increase the energy density of the battery 10, but also increase the structural strength of the housing 211, thereby improving the reliability and service life of the battery cell 20 and the battery 10.

[0375] In some embodiments, the value of the capacity C of the battery cell 20 according to the embodiments of the present application can also be set to other values. For example, the value of the capacity C of the battery cell 20 can be any one of the following values or between any two of the following values: 25 Ah, 30 Ah, 35 Ah, 40 Ah, 45 Ah, 50 Ah, 55 Ah, 60 Ah, 65 Ah, 70 Ah, 75 Ah, 80 Ah, 85 Ah, 90 Ah, 95 Ah, 100 Ah, 130 Ah, 150 Ah, 180 Ah, 200 Ah, 230 Ah, 250 Ah, 280 Ah, 300 Ah, 330 Ah, 350 Ah, 380 Ah, 400 Ah, 430 Ah, 450 Ah, 480 Ah, 500 Ah, 530 Ah, and 550 Ah.

[0376] It should be understood that the capacity C of the battery cell 20 according to the embodiments of the present application represents the amount of electricity output when the battery cell 20 is fully charged and discharged to the cut-off voltage under specified discharge conditions. The test method for the capacity C of the battery cell 20 can be selected according to actual applications. For example, GB / T 31467.1 can be used for the discharge test to determine the capacity C of the battery cell 20, but the embodiments of the present application are not limited thereto.

[0377] The following is a comparative description through multiple comparative examples and multiple embodiments. Specifically, the battery cells 20 in the following embodiments and comparative examples are all in the form of Figure 10 and Figure 11 shown square shell batteries, where the housing 211 has a hollow structure with one end open.

[0378] In the following embodiments and comparative examples, the preparation methods of the positive electrode plate 223, negative electrode plate 224, electrolyte, and separator 225 of the battery cell 20 are as follows.

[0379] 1. Preparation of the positive electrode plate 223

[0380] The positive electrode active material LiNi 0.95 Co 0.04 Mn 0.01 O 2 , conductive agent Super P, and binder polyvinylidene fluoride (PVDF) are made into a positive electrode paste in N-methylpyrrolidone (NMP). The solid content in the positive electrode paste is 50 wt%, and in the solid components, LiNi 0.7 Co 0.1 Mn 0.1 O 2The mass ratio of Super P, PVDF is 8:1:1. The positive electrode slurry is coated on the upper and lower surfaces of the current collector aluminum foil, dried at 85°C, cold-pressed, then trimmed, sliced, and slit, and finally dried in a vacuum at 85°C for 4 h to obtain the positive electrode plate 223.

[0381] 2. Preparation of the negative electrode plate 224

[0382] The negative electrode active material is mixed evenly with the conductive agent Super P, the thickening agent carboxymethyl cellulose (CMC), and the binder styrene-butadiene rubber (SBR) in deionized water to prepare the negative electrode slurry. The negative electrode active material includes graphite and a silicon-based material, and the silicon-based material is a silicon oxide compound. The solid content in the negative electrode slurry is 30 wt%. The mass ratio of the negative electrode active material, silicon suboxide, Super P, CMC, and the binder styrene-butadiene rubber (SBR) in the solid components is 88:7:3:2. The negative electrode slurry is coated on the upper and lower surfaces of the current collector copper foil, dried at 85°C, then cold-pressed, trimmed, sliced, and slit, and finally dried in a vacuum at 120°C for 12 h to obtain the negative electrode plate 224.

[0383] 3. Preparation of the electrolyte

[0384] In a glove box under an argon atmosphere (H2O < 0.1 ppm, O2 < 0.1 ppm), the fully dried electrolyte salt LiPF6 is dissolved in a mixed solvent (the mixed solvent includes ethylene carbonate (EC) and diethyl carbonate (DEC), and ethylene carbonate (EC) and diethyl carbonate (DEC) are mixed in a mass ratio of 50:50). After mixing evenly, an electrolyte with a concentration of 1 mol / L is obtained.

[0385] 4. Preparation of the separator 225

[0386] A 16-μm polyethylene film is used as the separator 225.

[0387] 5. Preparation of the lithium-ion battery monomer 20

[0388] The positive electrode plate 223, the separator 225, and the negative electrode plate 224 are stacked in sequence, with the separator 225 placed between the positive electrode plate 223 and the negative electrode plate 224 to isolate the positive and negative electrodes. After winding, a bare battery core is obtained, the tabs are welded, the bare battery core is placed in a casing made of different materials, and the above-prepared electrolyte is injected into the dried casing. Then, processes such as encapsulation, standing, formation, shaping, and capacity testing are carried out to complete the preparation of the lithium-ion battery monomer 20.

[0389] In the following examples and comparative examples, the tensile strength of the housing 211 of the battery cell 20 at a temperature of 25°C is Rm, and different materials are selected for the housing 211 to obtain different tensile strengths Rm; the capacity of the battery cell 20 is C; the specific parameter settings are shown in Table 6 below. In addition, in each example and comparative example, the material of all regions of the housing 211 is the same, and the tensile strength Rm of the housing 211 at 25°C is measured by the method specified in GB / T 228.1-2010. Moreover, the battery cells 20 in the following examples and comparative examples have the same other setting conditions except for the different parameter settings shown in Table 6. For example, the wall thickness of the wall with the largest area of the battery cell 20 in each example is 0.15 mm; for another example, the chemical system of the battery cell 20 in each example is a nickel-cobalt-manganese ternary system.

[0390] Table 6

[0391] Rm (MPa) C (Ah) Housing material Test results Comparative example 1 177 500 Aluminum Housing cracked Comparative example 2 190 100 Aluminum Housing cracked Example 1 393 500 Low-carbon steel Housing intact Example 2 394 300 Low-carbon steel Housing intact Example 3 390 100 Low-carbon steel Housing intact Example 4 851 500 Stainless steel Housing intact Example 5 854 300 Stainless steel Housing intact Example 6 845 100 Stainless steel Housing intact

[0392] Comparing the two comparative examples and the six examples in Table 6 above, it can be seen that different tensile strengths Rm can be determined corresponding to different materials used for the housing 211. When the tensile strength Rm satisfies 250 MPa ≤ Rm ≤ 2000 MPa and the capacity C of the battery cell 20 satisfies 25 Ah ≤ C ≤ 550 Ah, for example, in Examples 1-6, the housing 211 of the battery cell 20 does not crack, so the structural strength of the housing 211 can be used for battery cells 20 with a larger capacity and can meet the design requirements of the battery cell 20. However, when the tensile strength Rm does not satisfy 250 MPa ≤ Rm ≤ 2000 MPa, for example, in Comparative Examples 1-2, the housing 211 of the battery cell 20 cracks, and thus the design requirements of the battery cell 20 cannot be met.

[0393] It should be understood that in order to meet the above design requirements, the material of at least part of the region of the housing 211 in the embodiments of the present application can be flexibly selected according to actual applications.

[0394] In some embodiments, the material of at least part of the region of the housing 211 includes at least one of the following: steel, copper alloy, titanium alloy, and nickel alloy. These materials have relatively high strength, can meet the strength requirements of the housing 211, are easy to process, and have low costs.

[0395] In some embodiments, the material of at least part of the housing 211 includes at least one of the following: stainless steel, carbon steel, and high-strength alloy steel. For example, if the housing 211 is made of stainless steel, it has relatively high structural strength and can generally meet the requirements for the tensile strength Rm at normal temperature, the yield strength Re at normal temperature, the tensile strength Rn at high temperature, and the melting point p. For example, the melting point of stainless steel is usually between 1400°C and 1500°C. Moreover, when the housing 211 is made of stainless steel, it is not easy to rust, and compared with other materials, it can extend the service life of the housing 211.

[0396] If the housing 211 is made of carbon steel, it has high structural strength and is easy to meet the requirements for the tensile strength Rm at normal temperature, the yield strength Re at normal temperature, the tensile strength Rn at high temperature, and the melting point p. For example, the melting point of carbon steel is usually between 1425°C and 1525°C. In addition, considering that carbon steel may be easily corroded during use, nickel can be plated on the outer surface of the carbon steel housing 211. For example, the thickness of the nickel plating layer is usually 1 μm to 10 μm to protect the surface of the housing 211 from oxidation and corrosion, and to extend the service life of the housing 211.

[0397] The housing 211 can also be made of other high-strength alloy steel materials to effectively improve the structural strength of the housing 211. For example, when the requirement for the structural strength of the housing 211 is relatively high, high-strength alloy steel materials can be selected, which are easy to meet the requirements for the tensile strength Rm at normal temperature, the yield strength Re at normal temperature, the tensile strength Rn at high temperature, and the melting point p.

[0398] In some embodiments, when steel is used in at least part of the housing 211, the types of the steel can include at least one of the following: SPCC, Q195, Q215, Q235, SUS 304, SUS 316, and other modified stainless steels. These steels are easy to obtain, their strength can meet the design requirements, and the cost is relatively low. For example, the approximate values of the tensile strength Rm at normal temperature of 25°C, the yield strength Re at normal temperature of 25°C, the tensile strength Rn at high temperature of 500°C, and the melting point p of different steels can be seen in Table 7 below.

[0399] Table 7

[0400]

[0401]

[0402] It should be understood that other materials can also be selected for the material of at least part of the housing 211 in the embodiments of the present application. For example, different materials can be reasonably selected according to the mass content of different elements in the material and the role played by the element.

[0403] In some embodiments, the mass content of chromium element in the material of at least part of the housing 211 is m, and m satisfies: 10% ≤ m ≤ 30%. Appropriately increasing the chromium element in the material of at least part of the housing 211 can increase the melting point and strength of the material, making it easy to meet the requirements of the tensile strength Rm at normal temperature, the yield strength Re at normal temperature, the tensile strength Rn at high temperature, and the melting point p in the embodiments of the present application. In addition, since chromium element can react with oxygen to form a dense chromium oxide film, a corrosion-resistant protective film can also be formed on the surface of the housing 211, improving the corrosion resistance of the housing 211.

[0404] In some embodiments, the mass content of nickel element in the material of at least part of the housing 211 is n, and n satisfies 8% ≤ n ≤ 25%. Appropriately increasing the nickel element in the material of at least part of the housing 211 can increase the structural strength and plasticity of the housing 211. For example, it can increase the tensile strength Rm at normal temperature, the yield strength Re at normal temperature, and the tensile strength Rn at high temperature, and can also provide the corrosion resistance of the material.

[0405] In some embodiments, taking the housing 211 made of steel as an example, the mass contents of different elements in different types of steel are different. For example, for stainless steel materials, the mass content of iron element is one of the basic elements of stainless steel, and its mass content is usually between 60% and 70%. For another example, Table 8 shows the mass contents of different elements in several types of steel. Among them, the values in Table 8 are the maximum values of the mass percentages of each element in the material, that is, the mass percentages of each element in the corresponding application are usually not greater than the values shown in Table 8.

[0406] Table 8

[0407]

[0408]

[0409] It should be understood that when at least part of the housing 211 is made of steel, if the mass content of carbon element in the steel is increased, the strength and hardness of the steel can be improved. For example, generally, the higher the carbon content, the higher the hardness and strength of the steel, but the corrosion resistance may be reduced.

[0410] If the mass content of chromium element in the steel is increased, since chromium element can react with oxygen to form a dense chromium oxide film, forming a corrosion-resistant protective film on the surface of the steel, the corrosion resistance of the steel can be improved.

[0411] If the mass content of nickel element in the steel is increased, the corrosion resistance, strength, and plasticity of the steel can be improved.

[0412] If the mass content of molybdenum element in the steel is increased, the corrosion resistance and strength of the steel can be improved, especially in corrosive media such as acids and salts.

[0413] If the mass content of manganese element in the steel is increased, the toughness and fatigue resistance of the steel can be increased.

[0414] If the mass content of silicon element in the steel is increased, the corrosion resistance and strength of the stainless steel can be increased.

[0415] If the mass content of phosphorus element and sulfur element in the steel is reduced, the negative impacts of these two elements on the corrosion resistance, plasticity and toughness of the steel can be reduced.

[0416] In addition, other elements can also be provided in the steel. For example, the steel can also include copper element. For example, the mass content of copper element in Q195, Q215 and Q235 is generally not more than 0.3%, while that in modified stainless steel is generally not more than 2% to 3.5%. For another example, the steel can also include nitrogen element. For example, the mass content of nitrogen element in Q195, Q215 and Q235 is generally not more than 0.12%.

[0417] It should be understood that the test method for the mass content of each element of the above steel in the embodiments of the present application can be set according to actual applications. For example, inductively coupled plasma atomic emission spectrometry, that is, inductively coupled plasma technology (ICP) can be used for testing, but the embodiments of the present application are not limited thereto.

[0418] Figure 17 The partial structural schematic diagram of the housing 211 in the embodiments of the present application is shown. For example, this Figure 17 can be Figure 16 the partial enlarged view of the area A' shown. As Figure 17 shown, the housing 211 in the embodiments of the present application is a multi-layer structure, and the material of the outermost housing 2117 of the housing 211 includes at least one of the following: aluminum, aluminum alloy, copper, copper alloy and chromium.

[0419] It should be understood that the housing 211 of the embodiment of the present application is a multi-layer structure, that is, for any wall of the housing 211, a multi-layer structure is stacked in the thickness direction of the wall, so that the housing 211 is a multi-layer structure. Moreover, the installation manner between the multi-layer structures of the housing 211 can be flexibly set according to actual applications. For example, multiple single-layer housing structures with different sizes but basically the same shape can be processed first. For example, each single-layer housing structure is a hollow structure with an opening; then the housing structures with relatively larger sizes among the multiple single-layer housing structures are sequentially sleeved outside the housing structures with relatively smaller sizes, so that the multiple single-layer housing structures can be combined into a multi-layer housing 211. For another example, an approximately plate-shaped structure with a multi-layer structure can also be processed first; then multiple such plate-shaped structures are spliced and combined with each other, and a multi-layer housing 211 can also be formed, but the embodiment of the present application is not limited thereto.

[0420] It should be understood that the outermost housing 2117 of the housing 211 in the embodiment of the present application includes the outermost structure of each wall of the housing 211, that is, the outermost housing 2117 is a layer of housing structure including the outer surface of the housing 211.

[0421] In the embodiment of the present application, the material of the outermost housing 2117 of the housing 211 may include at least one of the following: aluminum, aluminum alloy, copper, copper alloy, and chromium. Among them, when the material of the outermost housing 2117 contains aluminum, the aluminum will be oxidized into dense aluminum oxide, which can prevent corrosion; when the material of the outermost housing 2117 contains copper, the copper will be oxidized into copper oxide, that is, verdigris, which can prevent corrosion; when the material of the outermost housing 2117 contains chromium, the chromium will be oxidized into chromium oxide, which can also prevent corrosion. Therefore, when the material of the outermost housing 2117 adopts the above-mentioned corrosion-preventive materials, the other housing layers located inside it can be protected by the outermost housing 2117, which can not only improve the structural stability of the housing 211, but also improve the service life of the housing 211.

[0422] It should be understood that the specific thickness of the outermost housing 2117 in the embodiment of the present application can also be flexibly set according to actual applications. For example, the thickness of the outermost housing 2117 can be set according to a certain ratio based on the thickness of the housing 211.

[0423] In some embodiments, the average thickness of the outermost shell 2117 is T11, and the average thickness of the shell 211 is T10. T11 and T10 satisfy: 0.15 ≤ T11 / T10 ≤ 0.5. If the ratio T11 / T10 is set too small, since the average thickness T10 of the shell 211 is limited, the average thickness T11 of the outermost shell 2117 will be very small. On the one hand, it will increase the processing difficulty, and on the other hand, it will also reduce the anti-corrosion effect of the outermost shell 2117, thereby affecting the structural reliability of the shell 211. Conversely, if the ratio T11 / T10 is set too large, the average thickness T11 of the outermost shell 2117 will be very large, while the thickness of the other layers of the shell 211 except the outermost shell 2117 will be very small. However, the structural strength of the outermost shell 2117 may be insufficient. Especially after it is oxidized, its deformation ability is poor. In the case where its average thickness T11 is large, it will affect the overall structural strength of the shell 211, thereby reducing the stability of the shell 211.

[0424] Further, T11 and T10 satisfy: 0.15 ≤ T11 / T10 ≤ 0.4. Appropriately reducing the maximum value of the ratio T11 / T10 and increasing the minimum value of the ratio T11 / T10 can limit the average thickness T11 of the outermost shell 2117 from being too large or too small, which can not only improve the anti-corrosion effect, but also improve the structural strength and structural stability of the shell 211.

[0425] Further, T11 and T10 satisfy: 0.2 ≤ T11 / T10 ≤ 0.3, so as to better improve the anti-corrosion effect, as well as the stability and reliability of the shell 211.

[0426] In some embodiments, the value of the ratio T11 / T10 of the average thickness T11 of the outermost shell 2117 to the average thickness T10 of the shell 211 in the embodiments of the present application can also be set to other values. For example, the value of the ratio T11 / T10 can be any one of the following values or between any two of the following values: 0.15, 0.18, 0.2, 0.23, 0.25, 0.28, 0.3, 0.33, 0.35, 0.38, 0.4, 0.43, 0.45, 0.48, and 0.5.

[0427] It should be understood that the value range of the average thickness T10 of the housing 211 in the embodiments of the present application can also be flexibly set according to actual applications. For example, the average thickness T10 of the housing 211 satisfies: 0.05 mm ≤ T10 ≤ 0.5 mm. The value of the average thickness T10 of the housing 211 should not be too small to reduce the processing difficulty of the multi-layer housing 211 and improve the structural strength of the housing 211. For example, the housing 211 is not easily broken, thereby improving the service life of the housing 211. On the contrary, the value of the average thickness T10 of the housing 211 should not be too large to make the space occupied by the housing 211 smaller, improve the space utilization rate of the battery cell 20, and thereby improve the energy density of the battery 10 provided with a plurality of battery cells 20.

[0428] Further, the average thickness T10 of the housing 211 satisfies: 0.075 mm ≤ T10 ≤ 0.4 mm. Appropriately thinning the average thickness T10 of the housing 211 can reduce the space occupied by the housing 211 inside the battery 10, and thereby improve the energy density of the battery 10; while appropriately increasing the average thickness T10 of the housing 211 can also reduce the processing difficulty of the housing 211.

[0429] Further, the average thickness T10 of the housing 211 satisfies: 0.1 mm ≤ T10 ≤ 0.3 mm. The average thickness T10 of the housing 211 is neither too large nor too small, which can not only improve the structural strength and structural stability of the housing 211, but also reduce the space occupied by the housing 211 inside the battery 10, and thereby improve the energy density of the battery 10.

[0430] In some embodiments, the value of the average thickness T10 of the housing 211 in the embodiments of the present application can also be set to other values. For example, the value of the average thickness T10 of the housing 211 can be any one of the following values or between any two of the following values: 0.05 mm, 0.075 mm, 0.1 mm, 0.125 mm, 0.15 mm, 0.175 mm, 0.2 mm, 0.225 mm, 0.25 mm, 0.275 mm, 0.3 mm, 0.325 mm, 0.35 mm, 0.375 mm, 0.4 mm, 0.425 mm, 0.45 mm, 0.475 mm, and 0.5 mm.

[0431] It should be understood that the value range of the average thickness T11 of the outermost shell 2117 in the embodiments of the present application can also be flexibly set according to actual applications. For example, T11 satisfies: 0.015 mm ≤ T11 ≤ 0.25 mm. The average thickness T11 of the outermost shell 2117 should not be too small to reduce the processing difficulty, improve the anti-corrosion effect of the outermost shell 2117, and thus improve the structural reliability of the shell 211. On the contrary, the average thickness T11 of the outermost shell 2117 should not be too large. Considering that after the outermost shell 2117 is oxidized, its deformation ability is poor. When its average thickness T11 is too large, it will affect the deformation ability of the overall structure of the shell 211, and thus reduce the reliability and stability of the shell 211.

[0432] Furthermore, the average thickness T11 of the outermost shell 2117 can also satisfy: 0.05 mm ≤ T11 ≤ 0.2 mm. Appropriately increasing the minimum value of the average thickness T11 of the outermost shell 2117 can improve the anti-corrosion effect of the outermost shell 2117; appropriately reducing the maximum value of the average thickness T11 of the outermost shell 2117 can improve the deformation ability of the overall structure of the shell 211, and thus improve the reliability and stability of the shell 211.

[0433] Furthermore, the average thickness T11 of the outermost shell 2117 can also satisfy: 0.075 mm ≤ T11 ≤ 0.15 mm. It can not only improve the anti-corrosion effect of the outermost shell 2117, but also improve the deformation ability of the overall structure of the shell 211, thereby improving the reliability and stability of the shell 211.

[0434] In some embodiments, the value of the average thickness T11 of the outermost shell 2117 in the embodiments of the present application can also be set to other values. For example, the value of the average thickness T11 of the outermost shell 2117 can be any one of the following values or between any two of the following values: 0.015 mm, 0.02 mm, 0.025 mm, 0.03 mm, 0.035 mm, 0.04 mm, 0.045 mm, 0.05 mm, 0.055 mm, 0.06 mm, 0.065 mm, 0.07 mm, 0.075 mm, 0.08 mm, 0.085 mm, 0.09 mm, 0.095 mm, 0.1 mm, 0.11 mm, 0.12 mm, 0.13 mm, 0.14 mm, 0.15 mm, 0.16 mm, 0.17 mm, 0.18 mm, 0.19 mm, 0.2 mm, 0.21 mm, 0.22 mm, 0.23 mm, 0.24 mm, and 0.25 mm.

[0435] It should be understood that the thickness of the inner shell 2118 of the shell 211 in the embodiments of the present application can also be flexibly set according to actual applications. Here, the inner shell 2118 is any layer of the shell 211 other than the outermost shell 2117. And, the shell 211 can include one or more inner shells 2118. In the case where the shell 211 includes multiple inner shells 2118, the thicknesses of the multiple inner shells 2118 can be the same for easy processing, or can also be different to flexibly adjust the thicknesses of the inner shells 2118 at different positions according to actual applications. For example, as Figure 17 shown, here, taking the shell 211 including a three-layer shell structure as an example, the three-layer shell structure includes the outermost shell 2117 located on the outermost side and two inner shells 2118 located inside. The two inner shells 2118 include the innermost shell 2118b and the intermediate shell 2118a. The average thickness of the innermost shell 2118b and the average thickness of the intermediate shell 2118a can be the same or different. For example, the average thickness of the innermost shell 2118b and the average thickness of the intermediate shell 2118a can both be set to T12, and the value of T12 can be set according to the application. For example, T12 can be greater than or equal to or less than T11. The embodiments of the present application are not limited thereto.

[0436] It should be understood that the average thickness T10 of the shell 211 in the embodiments of the present application can refer to the average thickness of at least part of the area of the shell 211. The average thickness T11 of the outermost shell 2117 of the shell 211 can also refer to the average thickness of at least part of the area of the outermost shell 2117. The average thickness T12 of the inner shell 2118 of the shell 211 can also refer to the average thickness of at least part of the area of the inner shell 2118. And, the calculation area of the average thickness T10 of the shell 211 is usually the same as the calculation area of the average thickness T11 of the outermost shell 2117, and is also the same as the calculation area of the average thickness T12 of the inner shell 2118. For example, if part of the area is excluded from the calculation of the average thickness T10 of the shell 211, correspondingly, the same area needs to be excluded from the calculation of the average thickness T11 of the outermost shell 2117, and the same area also needs to be excluded from the calculation of the average thickness T12 of the inner shell 2118. For the sake of convenience of description, the following takes the calculation of the average thickness T10 of the shell 211 as an example for description, but the relevant description is equally applicable to determining the average thickness T11 of the outermost shell 2117 and the average thickness T12 of the inner shell 2118, and will not be elaborated herein one by one.

[0437] For example, the average thickness T10 of the housing 211 may refer to the average thickness T10 of all regions of the housing 211. In particular, when the entire surface of the housing 211 is relatively flat, that is, the thicknesses of most regions of the housing 211 are substantially equal or have a small difference, or the thicknesses of all regions of the housing 211 are substantially equal or have a small difference, then the average thickness of all regions of the housing 211 can be determined to be T10.

[0438] For another example, the average thickness T10 of the housing 211 may also refer to the average thickness T10 of a partial region of the housing 211, that is, the average thickness T10 of the remaining region after excluding a partial region of the housing 211. For example, if there are some special regions in the housing 211 and the thicknesses of these special regions are significantly different from those of other regions. For example, there are raised structures or recessed regions in these special regions along the thickness direction, making the thicknesses of these special regions larger or smaller than those of other regions, then these special regions can be excluded to calculate the average thickness of the remaining regions of the housing 211 as T10.

[0439] In some embodiments, the housing 211 may include functional regions, and the average thickness T10 of the housing 211 is the average thickness of the regions of the housing 211 other than the functional regions. For example, the functional regions include at least one of the following regions: a pressure relief region, the region where the electrode terminal 214 is located, a liquid injection region, and a welding region. The thicknesses of the functional regions are usually significantly different from those of other regions of the housing 211. Therefore, when calculating the average thickness T10 of the housing 211 without including the functional regions, the design of the housing 211 can better meet the strength requirements, thereby improving the structural strength and stability of the battery cell 20.

[0440] It should be understood that the functional regions in the embodiments of the present application may include regions on the housing 211 provided with specific structures or having specific uses, and are applicable to the "functional regions" described above. For the sake of brevity, they will not be elaborated one by one here. For example, the functional region may include a pressure relief region for setting a pressure relief mechanism. The pressure relief mechanism in the embodiments of the present application may be provided on any wall of the battery cell 20. For example, the pressure relief mechanism may be provided in the pressure relief region of the housing 211 of the battery cell 20. The pressure relief mechanism may be a part of the housing 211; or, it may also be a split structure with the housing 211 and is fixed to the housing 211 by means such as welding. For example, when the pressure relief mechanism is a part of the housing 211, for example, the pressure relief mechanism may be formed by setting a notch on the housing 211, that is, the housing 211 is provided with a notch in the pressure relief region, and the thickness at the notch is significantly smaller than the thickness of other regions of the housing 211. Therefore, the average thickness T10 of the housing 211 may not calculate the thickness at the notch. The notch is the weakest position of the pressure relief mechanism. When the gas generated by the battery cell 20 is too much, causing the internal pressure to rise and reach the threshold, or the internal reaction of the battery cell 20 generates heat, causing the internal temperature of the battery cell 20 to rise and reach the threshold, the pressure relief mechanism may rupture at the notch, resulting in the internal and external communication of the battery cell 20, and the gas pressure and temperature are released outward through the crack of the pressure relief mechanism, thereby avoiding the explosion of the battery cell 20.

[0441] For another example, the pressure relief mechanism may also be a split structure with the housing 211. The pressure relief mechanism may be in the form of, for example, an explosion-proof valve, a gas valve, a pressure relief valve or a safety valve, and may specifically adopt a pressure-sensitive or temperature-sensitive element or structure. For example, the housing 211 is provided with a through hole in the pressure relief region, and the pressure relief mechanism is installed and fixed to the housing 211 through the through hole. After installation, the pressure relief mechanism may protrude or recess relative to other regions of the housing 211. Therefore, the average thickness T10 of the housing 211 may not include the pressure relief region where the pressure relief mechanism is located. When the internal pressure or temperature of the battery cell 20 reaches a predetermined threshold, the pressure relief mechanism performs an action or a weak structure provided in the pressure relief mechanism is damaged, thereby forming an opening or channel for discharging the internal pressure or temperature.

[0442] In some embodiments, the functional region may further include the region where the electrode terminal 214 is located. Each electrode terminal 214 in the embodiments of the present application may be provided on any wall, and a plurality of electrode terminals 214 may be provided on the same wall or different walls of the battery cell 20. For example, as Figures 3 to 4 shown, taking each battery cell 20 including two electrode terminals 214 and the two electrode terminals 214 being located on the same wall as an example, for example, the two electrode terminals 214 may both be located on the cover plate 212.

[0443] For another example, taking the case where each battery cell 20 includes two electrode terminals 214 and the two electrode terminals 214 are located on the same wall as an example, different from Figures 3 to 4 as shown, the two electrode terminals 214 may also be located on any wall of the housing 211. For example, the two electrode terminals 214 may both be located on the wall with the smallest area of the housing 211. When one or more electrode terminals 214 are located on the housing 211, each electrode terminal 214 generally protrudes from other areas of the housing 211, that is, the thickness of the area where the electrode terminal 214 is located is much greater than the thickness of other areas of the housing 211. Therefore, when calculating the average thickness T10 of the housing 211, the areas where all the electrode terminals 214 are located may not be included.

[0444] In some embodiments, the functional area may further include a liquid injection area. For example, a liquid injection hole may be provided in the liquid injection area of the housing 211, and electrolyte is injected into the housing 211 through the liquid injection hole. After the electrolyte injection is completed, the liquid injection hole may be sealed by a seal. Considering that the thickness of the liquid injection area where the seal is located is generally much greater than the thickness of other areas of the housing 211, therefore, when calculating the average thickness T10 of the housing 211, the liquid injection area may not be included.

[0445] In some embodiments, the functional area may further include a welding area. For example, the housing 211 and the cover plate 212 may be fixed by welding, or the housing 211 itself needs to be processed and formed by welding. For example, any two walls of the housing 211 may be welded, or the housing 211 is formed by splicing at least two parts, then the housing 211 may include a welding area. For example, the housing 211 may be welded by splicing, then the housing 211 may have a weld 2113. Specifically, the housing 211 may include at least two parts, and the at least two parts are connected by welding to form the housing 211. Among them, in the embodiments of the present application, mainly taking the case where the housing 211 includes two parts along the height direction Z of the battery cell 20 as an example, there is a weld 2113 between the upper half housing and the lower half housing; or, different from Figure 4 as shown, welds 2113 may also be provided in other parts of the housing 211, and the embodiments of the present application are not limited thereto. The welding area of the functional area in the embodiments of the present application may further include the weld 2113. Due to processing technology reasons, the thickness of the welding area is generally greater than the thickness of other areas of the housing 211. Therefore, when calculating the average thickness T10 of the housing 211, the welding area may not be included.

[0446] It should be understood that in order to further improve the structural strength and reliability of the housing 211, the inner housing 2118 of the housing 211 can be set according to actual applications. In some embodiments, the tensile strength of the inner housing 2118 of the housing 211 at 25°C is Rm1, and Rm1 satisfies: 250 MPa ≤ Rm1 ≤ 2000 MPa. By increasing the tensile strength Rm1 of the inner housing 2118 of the housing 211 at room temperature (25°C), the overall structural strength and stability of the housing 211 are increased; however, the tensile strength Rm1 of the inner housing 2118 at room temperature should not be too large, so as to reduce the difficulty of selecting the material of the inner housing 2118, and further reduce the processing difficulty and processing cost of the battery cell 20.

[0447] It should be understood that the value range of the tensile strength Rm1 of the inner housing 2118 in the embodiment of the present application at room temperature (25°C) can be adjusted according to actual applications. For example, the value of the room temperature tensile strength Rm1 can also satisfy 400 MPa ≤ Rm1 ≤ 1200 MPa. On the one hand, increasing the tensile strength Rm1 of the inner housing 2118 at room temperature can improve the deformation ability of the inner housing 2118 to resist the expansion amount of the electrode assembly 22, so that the inner housing 2118 is not easily damaged, and further improve the structural stability and service life of the housing 211 and the battery cell 20. On the other hand, controlling the tensile strength Rm1 of the inner housing 2118 at room temperature not to be too large can reduce the difficulty of selecting the material and the processing difficulty of the inner housing 2118, save costs, and facilitate processing.

[0448] Furthermore, it can be set that the tensile strength Rm1 of the inner housing 2118 at room temperature satisfies 450 MPa ≤ Rm1 ≤ 800 MPa. The tensile strength Rm1 of the inner housing 2118 at room temperature is neither too large nor too small, which can not only improve the deformation ability of the inner housing 2118 to resist the expansion amount of the electrode assembly 22, but also be easy to implement and save costs.

[0449] In some embodiments, the value of the tensile strength Rm1 of the inner housing 2118 of the embodiments of the present application at room temperature can also be set to other values. For example, the value of the room temperature tensile strength Rm1 can be any one of the following values or between any two of the following values: 250 MPa, 280 MPa, 300 MPa, 330 MPa, 350 MPa, 380 MPa, 400 MPa, 450 MPa, 500 MPa, 550 MPa, 600 MPa, 650 MPa, 700 MPa, 750 MPa, 800 MPa, 850 MPa, 900 MPa, 950 MPa, 1000 MPa, 1050 MPa, 1100 MPa, 1150 MPa, 1200 MPa, 1250 MPa, 1300 MPa, 1350 MPa, 1400 MPa, 1450 MPa, 1500 MPa, 1550 MPa, 1600 MPa, 1650 MPa, 1700 MPa, 1750 MPa, 1800 MPa, 1850 MPa, 1900 MPa, 1950 MPa, and 2000 MPa.

[0450] It should be understood that the tensile strength in the embodiments of the present application refers to the maximum stress value that the material can withstand before being broken. The test method for the tensile strength Rm1 of the inner housing 2118 of the embodiments of the present application at a temperature of 25 °C can be selected according to actual applications. For example, the national standard GB / T 228.1-2010 can be used to test the tensile strength Rm1 at room temperature of 25 °C.

[0451] In the above text, the battery cell 20 in the shape of a cuboid is mainly described as an example. In the following text, the cylindrical battery cell 20 will be described with reference to the accompanying drawings. The cylindrical battery cell 20 of the embodiments of the present application is applicable to the rest of the description except for the different shape from the rectangular battery cell 20 described above, and will not be elaborated here one by one.

[0452] Figure 18 The structural schematic diagram of the battery cell 20 according to an embodiment of the present application is shown. For example, Figure 3 The shown battery cell 20 can be any battery cell 20 in the battery 10; Figure 19 The partial exploded structural schematic diagram of a battery cell 20 according to an embodiment of the present application is shown. For example, Figure 19 can be Figure 18 The partial exploded structural schematic diagram of the shown battery cell 20. Figure 20 The cross-sectional schematic diagram of the housing 211 of a battery cell 20 according to an embodiment of the present application is shown. For example, Figure 20 can be Figure 18 and Figure 19 The cross-sectional view of the housing 211 of the shown battery cell 20, and this cross-section is the cross-section of the housing 211.

[0453] In an embodiment of the present application, as Figures 18 to 20 shown, the battery cell 20 includes: an electrode assembly 22, and the electrode assembly 22 includes a first tab 2221; a first electrode terminal 214a; a housing 211, and the housing 211 includes a cylindrical body 211b and a cover body 211a connected to the cylindrical body 211b. The cylindrical body 211b is disposed around the outer periphery of the electrode assembly 22. The cover body 211a includes the first electrode terminal 214a. The first tab 2221 is electrically connected to the first electrode terminal 214a through the cylindrical body 211b. The housing 211 is a multi-layer structure, and the resistivity of the multi-layer structure is different.

[0454] The housing 211 can be in various shapes, for example, a cylinder, a cuboid, or other polyhedrons. Exemplarily, as Figures 18 to 20 shown, here the housing 211 is taken as a hollow cylindrical structure for description. In addition, in the embodiment of the present application, the housing 211 is mainly taken as a hollow structure with an opening formed at one end, and correspondingly, the cover plate 212 is a circular plate-like structure adapted to the housing 211. For the cylindrical housing 211, correspondingly, the cylindrical body 211b is a cylinder, and the cover body 211a is a circular plate-like structure.

[0455] The electrode assembly 22 in the embodiment of the present application can include a first tab 2221, and the first tab 2221 can be electrically connected to the first electrode terminal 214a through the cylindrical body 211b of the housing 211, which can simplify the structure of the battery cell 20; the housing 211 is set as a multi-layer structure, and the resistivity of the multi-layer structure is different. The over-current capacity of the battery cell 20 can be improved through a layer structure with a lower resistivity, and the structural strength of the housing 211 can be improved through a layer structure with a higher resistivity, which can not only improve the performance of the battery cell 20 but also improve the structural strength of the battery cell 20, thereby increasing the service life of the battery cell 20.

[0456] In an embodiment of the present application, the electrode assembly 22 further includes a second tab 2222, and the second tab 2222 and the first tab 2221 have opposite polarities. Specifically, from the outer shape of the electrode assembly 22, the electrode assembly 22 includes a main body portion 221 and tabs 222. The tabs 222 include a first tab 2221 and a second tab 2222. The first tab 2221 and the second tab 2222 protrude from the main body portion 221. The first tab 2221 is a portion of the first electrode sheet where the active material layer is not coated, and the second tab 2222 is a portion of the second electrode sheet where the active material layer is not coated. The first tab 2221 and the second tab 2222 are used to lead out the current in the main body portion 221.

[0457] The first pole lug 2221 and the second pole lug 2222 may extend from the same side of the main body 221, that is, the first pole lug 2221 and the second pole lug are located at the same end surface of the electrode assembly 22. Alternatively, the first pole lug 2221 and the second pole lug 2222 may extend from different sides of the main body 221, that is, the first pole lug 2221 and the second pole lug are located at different end surfaces of the electrode assembly 22. For example, the first pole lug 2221 and the second pole lug 2222 may also extend from opposite sides, that is, the first pole lug 2221 and the second pole lug 2222 are located at opposite end surfaces of the electrode assembly 22, for easy processing. Figures 18 to 20 As shown in FIG. 1 , the first pole tab 2221 and the second pole tab 2222 may be respectively disposed on both sides of the main body 221 along the first direction Z. In other words, the first pole tab 2221 and the second pole tab 2222 are respectively disposed at both ends of the electrode assembly 22 along the first direction Z. The first direction Z may be the height direction Z of the electrode assembly 22.

[0458] It should be understood that the electrode assembly 22 includes a first electrode sheet, a second electrode sheet and a separator, and the separator is used to separate the first electrode sheet from the second electrode sheet. The polarities of the first electrode sheet and the second electrode sheet are opposite. In other words, one of the first electrode sheet and the second electrode sheet is a positive electrode sheet 223, and the other of the first electrode sheet and the second electrode sheet is a negative electrode sheet 224.

[0459] The first pole piece, the second pole piece and the separator are all strip-shaped structures, and the first pole piece, the second pole piece and the separator are wound together to form a winding structure. The winding structure can be a cylindrical structure, a flat structure or a structure of other shapes.

[0460] Optionally, the first pole lug 2221 is wound around the central axis of the electrode assembly 22 for multiple turns, and the first pole lug 2221 includes multiple turns of pole lug layers. After the winding is completed, the first pole lug 2221 is generally cylindrical, and a gap is left between two adjacent turns of pole lug layers. The embodiment of the present application may process the first pole lug 2221 to reduce the gap between the pole lug layers, so as to facilitate the connection of the first pole lug 2221 with other conductive structures. For example, the embodiment of the present application may flatten the first pole lug 2221 so that the end area of ​​the first pole lug 2221 away from the main body 221 is gathered and gathered together; the flattening process forms a dense end face at the end of the first pole lug 2221 away from the main body 221, reduces the gap between the pole lug layers, and facilitates the connection of the first pole lug 2221 with other conductive structures. Alternatively, the embodiment of the present application may also fill the conductive material between two adjacent turns of pole lug layers to reduce the gap between the pole lug layers.

[0461] ​​​Optionally, the second tab 2222 is wound around the central axis of the electrode assembly 22 for multiple turns, and the second tab 2222 includes multiple tab layers. Exemplarily, the second tab 2222 has also been flattened to reduce the gap between the tab layers of the second tab 2222.

[0462] In the embodiment of the present application, the battery cell 20 further includes: a second electrode terminal 214b, which is electrically connected to the second tab 2222, and the first electrode terminal 214a and the second electrode terminal 214b are located on the same wall of the battery cell 20 to improve the integration of the battery cell 20, improve the space utilization rate of the battery cell 20 in the battery 10, and facilitate processing and assembly.

[0463] It should be understood that the cover 211a of the embodiment of the present application includes the first electrode terminal 214a. For example, the first electrode terminal 214a can be disposed on the cover 211a, or the cover 211a can also directly serve as the first electrode terminal 214a.

[0464] In some embodiments, the cover 211a is the first electrode terminal 214a. The cover 211a is provided with an electrode lead-out hole 211c. The second electrode terminal 214b is insulated and disposed on the cover 211a and installed in the electrode lead-out hole 211c. One of the cover 211a and the second electrode terminal 214b is the positive output pole of the battery cell, and the other is the negative output pole of the battery cell. At least a part of the housing 211 itself can be used as an output electrode of the battery cell 20, thus eliminating a traditional electrode terminal and simplifying the structure of the battery cell 20. When multiple battery cells 20 are assembled into a group, the housing 211 can be electrically connected to the busbar component, which can not only increase the current-carrying area but also make the structural design of the busbar component more flexible.

[0465] For the sake of convenience of description, hereinafter, the cover 211a is taken as an example of the first electrode terminal 214a, but the embodiment of the present application is not limited thereto.

[0466] Figure 21 FIG. is a partial cross-sectional schematic diagram of the battery 10 provided by some embodiments of the present application. The battery 10 may include multiple battery cells 20; Figure 22 FIG. is another partial cross-sectional schematic diagram of the battery 10 provided by some embodiments of the present application. For example, the Figure 22 may be Figure 21 an enlarged schematic diagram of the battery 10 shown in FIG. at region B'.

[0467] As Figures 18 to 22As shown, the cover body 211a is provided with an electrode lead-out hole 211c, and at least a part of the cover body 211a is used for electrically connecting the first connection member 81 and the first tab 2221 of the battery 10; the second electrode terminal 214b is used for electrically connecting the second connection member 82 and the second tab 2222 of the battery 10. The second electrode terminal 214b is insulated and arranged on the cover body 211a and installed in the electrode lead-out hole 211c. One of the cover body 211a and the second electrode terminal 214b is the positive output electrode of the battery cell 20, and the other is the negative output electrode of the battery cell 20.

[0468] The cover body 211a is electrically connected to the cylindrical body 211b, and the cover body 211a and the cylindrical body 211b may have the same polarity.

[0469] It should be understood that the cover body 211a and the cylindrical body 211b of the embodiment of the present application may be an integrally formed structure, that is, the housing 211 is an integrally formed member. In this way, the connection process between the cover body 211a and the cylindrical body 211b can be omitted. For example, the housing 211 can be formed by a stretching process. Of course, the cover body 211a and the cylindrical body 211b can also be two separately provided members, and then connected together by welding, riveting, bonding, etc. The embodiment of the present application mainly takes the cover body 211a and the cylindrical body 211b as an integrally formed structure as an example.

[0470] The housing 211 of the embodiment of the present application can be a hollow structure with one end open. Specifically, the cylindrical body 211b has an opening 211d at the end facing away from the cover body 211a. The battery cell 20 further includes a cover plate 212, and the cover plate 212 covers the opening 211d of the cylindrical body 211b to close the opening 211d of the cylindrical body 211b. The cover plate 212 can be of various structures. For example, the cover plate 212 is a plate-like structure.

[0471] In some embodiments, the cover body 211a is provided with an electrode lead-out hole 211c, and the area of the cover body 211a other than the electrode lead-out hole 211c includes an area for welding with the first connection member 81, that is, the cover body 211a can be welded to the first connection member 81 to form a first welding part W1. Exemplarily, during welding, the laser acts on the surface of the first connection member 81 facing away from the cover body 211a, and the laser melts and connects a part of the first connection member 81 and a part of the cover body 211a to form the first welding part W1.

[0472] The electrode lead-out hole 211c penetrates through the cover body 211a to facilitate the extraction of electrical energy in the electrode assembly 22 to the outside of the housing 211. Exemplarily, the electrode lead-out hole 211c penetrates through the cover body 211a along the first direction Z.

[0473] The electrode lead-out hole 211c of the embodiment of the present application is formed after the shell 211 is stretched and formed. For example, the present embodiment uses a hole-opening process to form an electrode lead-out hole 211c for installing the second electrode terminal 214b on the cover 211a, so that the positive output electrode and the negative output electrode are arranged at the end of the battery cell 20 that is away from the opening of the shell 211; the cover 211a is formed during the molding process of the shell 211, and the flatness can be ensured after the electrode lead-out hole 211c is opened, and the connection strength between the cover 211a and the first connecting member 81 is ensured. At the same time, the flatness of the cover 211a is not constrained by its own size, so the cover 211a can have a larger size, thereby improving the current-carrying capacity of the battery cell 20.

[0474] In some embodiments, the barrel 211b is cylindrical, the electrode lead-out hole 211c is a circular hole, and the central axis of the barrel 211b and the central axis of the electrode lead-out hole 211c are arranged to coincide with each other. "Coincidence arrangement" does not require that the central axis of the barrel 211b and the central axis of the electrode lead-out hole 211c absolutely and completely coincide with each other, and there may be deviations allowed by the process.

[0475] The electrode lead-out hole 211c can be used to define the position of the second electrode terminal 214b. In this embodiment, the central axis of the electrode lead-out hole 211c is overlapped with the central axis of the cylinder 211b, so that at least part of the second electrode terminal 214b is located at the center of the cover 211a. In this way, when multiple battery cells 20 are assembled into a group, the position accuracy requirements of the second electrode terminal 214b can be reduced, the assembly process can be simplified, and the assembly efficiency can be improved.

[0476] The central axis of the electrode assembly 22 is a virtual straight line, which is parallel to the first direction Z. The central axis of the electrode assembly 22 can pass through the electrode lead-out hole 211c, or can be staggered with the electrode lead-out hole 211c, which is not limited in this embodiment.

[0477] The first pole tab 2221 is electrically connected to the cover 211a. The first pole tab 2221 can be directly electrically connected to the cover 211a, or indirectly electrically connected to the cover 211a through other conductive structures. For example, the first pole tab 2221 can be electrically connected to the cover 211a through the barrel 211b.

[0478] The second electrode tab 2222 is electrically connected to the second electrode terminal 214b. The second electrode tab 2222 may be directly electrically connected to the second electrode terminal 214b, or may be indirectly electrically connected to the second electrode terminal 214b through other conductive structures. For example, the second electrode tab 2222 may be electrically connected to the second electrode terminal 214b through the current collecting member 23.

[0479] The second electrode terminal 214b is insulated and disposed on the cover 211a. Therefore, the second electrode terminal 214b and the cover 211a can have different polarities, and the second electrode terminal 214b and the cover 211a can serve as different output poles.

[0480] The second electrode terminal 214b is fixed to the cover 211a. The second electrode terminal 214b can be integrally fixed on the outer side of the cover 211a, or can extend into the interior of the housing 211 through the electrode lead-out hole 211c.

[0481] When the first tab 2221 is a negative electrode tab and the second tab 2222 is a positive electrode tab, the cover 211a is the negative output pole of the battery cell 20, and the second electrode terminal 214b is the positive output pole of the battery cell 20. When the first tab 2221 is a positive electrode tab and the second tab 2222 is a negative electrode tab, the cover 211a is the positive output pole of the battery cell 20, and the second electrode terminal 214b is the negative output pole of the battery cell 20.

[0482] In the battery 10, a plurality of battery cells 20 are electrically connected through a current collecting member. The current collecting member includes a first connecting member 81 and a second connecting member 82. The first connecting member 81 is used to connect to the cover 211a of the battery cell 20, and the second connecting member 82 is used to connect to the second electrode terminal 214b of the battery cell 20.

[0483] The first connecting member 81 can be connected to the cover 211a by welding, bonding or other means to achieve the electrical connection between the first connecting member 81 and the cover 211a. The second connecting member 82 can be connected to the second electrode terminal 214b by welding, bonding, riveting or other means to achieve the electrical connection between the second connecting member 82 and the second electrode terminal 214b.

[0484] Exemplarily, the first connecting member 81 connects the cover 211a of one battery cell 20 and the second electrode terminal 214b of another battery cell 20, and the second connecting member 82 connects the second electrode terminal 214b of this one battery cell 20 and the cover 211a of yet another battery cell 20. In this way, the first connecting member 81 and the second connecting member 82 connect three battery cells 20 in series.

[0485] In this embodiment, by using the cover 211a and the second electrode terminal 214b as output poles, the structure of the battery cell 20 can be simplified, and the over-current capacity of the battery cell 20 can be ensured. The cover 211a and the second electrode terminal 214b are located at the same end of the battery cell 20. In this way, the first connecting member 81 and the second connecting member 82 can be assembled on the same side of the battery cell 20, which can simplify the assembly process and improve the efficiency of assembling a plurality of battery cells 20 into a group.

[0486] It should be understood that, as Figures 18 to 22 shown, the second electrode terminal 214b of the embodiment of the present application includes a terminal body 2141. Further, the terminal body 2141 can be fixed to the cover body 211a by riveting. For example, at least a part of the terminal body 2141 is located in the electrode lead-out hole 211c, and both ends of the terminal body 2141 are riveted to the electrode lead-out hole 211c.

[0487] In some embodiments, the terminal body 2141 can be provided with a recess, which recess depresses from the outer surface of the terminal body 2141 in a direction facing the electrode assembly 22. The bottom of the recess is used for welding to the current collector member 23.

[0488] When the electrode assembly 22 and the current collector member 23 are installed into the housing 211 through the opening 211d of the cylindrical body 211b and the current collector member 23 abuts against the cover body 211a, an external welding device can weld the bottom of the recess and the current collector member 23 from a side of the bottom of the recess facing away from the current collector member 23.

[0489] In this embodiment, by providing the recess, the thickness of the terminal body 2141 is reduced, so that the welding power required for welding the bottom of the recess to the current collector member 23 can be reduced, heat generation can be reduced, and the risk of other components (such as the first insulating member 61 and the second insulating member 60) being burned can be reduced.

[0490] In some embodiments, the second electrode terminal 214b further includes a sealing plate 2142, and the sealing plate 2142 is used to close the opening of the recess. The sealing plate 2142 can be entirely located outside the recess or partially received in the recess, as long as the sealing plate 2142 can close the opening of the recess. The sealing plate 2142 can protect the recess from the outside, reduce external impurities entering the recess, reduce the risk of the bottom of the recess being damaged by external impurities, and improve the sealing performance of the battery cell 20.

[0491] In some embodiments, the sealing plate 2142 is used to be welded to the second connecting member 82 to form a second welding portion W2. The second welding portion W2 can reduce the contact resistance between the sealing plate 2142 and the second connecting member 82 and improve the over-current capacity.

[0492] In some embodiments, at least a portion of the sealing plate 2142 protrudes from the outer surface of the terminal body 2141. When welding the second connecting member 82 and the sealing plate 2142 is required, first, the second connecting member 82 is attached to the upper surface of the sealing plate 2142 (i.e., the surface of the sealing plate 2142 facing away from the recess), and then the second connecting member 82 and the sealing plate 2142 are welded. At least a portion of the sealing plate 2142 protrudes from the outer surface of the terminal body 2141 to prevent the outer surface of the terminal body 2141 from interfering with the attachment of the sealing plate 2142 and the second connecting member 82, ensuring a tight fit between the second connecting member 82 and the sealing plate 2142.

[0493] In an embodiment of the present application, the battery cell 20 further includes: a first insulating member 61 for insulating at least a portion of the second electrode terminal 214b from the cover body 211a. Exemplarily, at least a portion of the first insulating member 61 is clamped between the cover body 211a and the second electrode terminal 214b to insulate the cover body 211a and the second electrode terminal 214b from each other, reducing the risk of short circuit.

[0494] In an embodiment of the present application, the battery cell 20 further includes a second insulating member 60 located between the cover body 211a and the electrode assembly 22. Specifically, the second insulating member 60 can separate the electrode assembly 22 from the cover body 211a, reducing the risk of contact conduction between the electrode assembly 22 and the cover body 211a when the battery cell 20 vibrates, and improving the safety performance.

[0495] In some embodiments, at least one of the first insulating member 61 and the second insulating member 60 can be used to seal the electrode lead-out hole 211c. In other embodiments, the battery cell 20 further includes a sealing ring 62 sleeved on the second electrode terminal 214b and used to seal the electrode lead-out hole 211c. Optionally, a portion of the sealing ring 62 extends into the electrode lead-out hole 211c to separate the hole wall of the electrode lead-out hole 211c from the second electrode terminal 214b.

[0496] In some embodiments, the second tab 2222 is provided at one end of the electrode assembly 22 facing the cover body 211a, and the first tab 2221 is provided at the other end of the electrode assembly 22 facing away from the cover body 211a. The cylindrical body 211b is used to connect the first tab 2221 and the cover body 211a so that the first tab 2221 is electrically connected to the cover body 211a.

[0497] The cylindrical body 211b can be directly electrically connected to the first tab 2221 or can be electrically connected to the first tab 2221 through other components. For example, the first tab 2221 is electrically connected to the cylindrical body 211b through the cover plate 212.

[0498] In the embodiment of the present application, the first tab 2221 and the second tab 2222 are arranged at both ends of the electrode assembly 22, which can reduce the risk of conduction between the first tab 2221 and the second tab 2222, and increase the current-carrying area of the first tab 2221 and the current-carrying area of the second tab 2222.

[0499] In some embodiments, the first tab 2221 is a negative tab, and the base material of the housing 211 is steel. The housing 211 is electrically connected to the negative tab, that is, the housing 211 is in a low-potential state. The steel housing 211 is not easily corroded by the electrolyte in the low-potential state, so as to reduce the safety risk.

[0500] In some embodiments, the battery cell 20 further includes a current collector member 23 for connecting the second tab 2222 and the second electrode terminal 214b. The current collector member 23 can be connected to the second tab 2222 by means of welding, abutting or bonding, and connected to the second electrode terminal 214b by means of welding, abutting, bonding, riveting, etc., so as to realize the electrical connection between the second tab 2222 and the second electrode terminal 214b.

[0501] In the first direction Z, the second electrode terminal 214b is disposed opposite to the middle region of the second tab 2222. If the second electrode terminal 214b and the second tab 2222 are directly connected, the conduction path between the edge region of the second tab 2222 and the second electrode terminal 214b will be too long, resulting in uneven current density of the second electrode plate of the electrode assembly 22, increasing the internal resistance, and affecting the over-current capacity and charging efficiency of the battery cell 20.

[0502] The current collector member 23 in the embodiment of the present application can have a large connection area with the second tab 2222, and the current of the second tab 2222 can flow into the second electrode terminal 214b through the current collector member 23. In this way, the current collector member 23 can reduce the difference in the conduction path between different regions of the second tab 2222 and the second electrode terminal 214b, improve the uniformity of the current density of the second electrode plate, reduce the internal resistance, and improve the over-current capacity and charging efficiency of the battery cell 20.

[0503] It should be understood that the housing 211 in the embodiment of the present application is a multi-layer structure, that is, both the cylinder 211b and the cover 211a of the housing 211 are multi-layer structures. For the convenience of description, the housing 211 in the following text includes both the cylinder 211b and the cover 211a.

[0504] In the embodiment of the present application, the housing 211 includes a first housing layer 2115, and the resistivity of the first housing layer 2115 is K1, and K1 satisfies: 1×10^-8Ω·m ≤ K1 ≤ 6×10^-8Ω·m. Wherein, the first housing layer 2115 is any one layer of the multi-layer housing 211. For example, Figure 20Taking the innermost shell as the first shell layer 2115 as an example, but the embodiments of the present application are not limited thereto. By setting the resistivity K1 of the first shell layer 2115 included in the shell 211 to be small, the overcurrent capacity of the shell 211 can be improved, and thus the performance of the battery cell 20 can be improved.

[0505] In some embodiments, the resistivity K1 of the first shell layer 2115 can also satisfy 1×10^-8Ω·m ≤ K1 ≤ 2.8×10^-8Ω·m. This can not only improve the overcurrent capacity and performance of the shell 211, but also facilitate implementation. In some embodiments, the value of the resistivity K1 of the first shell layer 2115 can also be set to other values. For example, the value of the resistivity K1 of the first shell layer 2115 can be any one of the following values or between any two of the following values: 1×10^-8Ω·m, 1.3×10^-8Ω·m, 1.5×10^-8Ω·m, 1.8×10^-8Ω·m, 2×10^-8Ω·m, 2.3×10^-8Ω·m, 2.5×10^-8Ω·m, 2.8×10^-8Ω·m, 3×10^-8Ω·m, 3.3×10^-8Ω·m, 3.5×10^-8Ω·m, 3.8×10^-8Ω·m, 4×10^-8Ω·m, 4.3×10^-8Ω·m, 4.5×10^-8Ω·m, 4.8×10^-8Ω·m, 5×10^-8Ω·m, 5.3×10^-8Ω·m, 5.5×10^-8Ω·m, 5.8 and 6×10^-8Ω·m.

[0506] It should be understood that the specific thickness of the first shell layer 2115 in the embodiments of the present application can also be flexibly set according to actual applications. For example, the thickness of the first shell layer 2115 can be set according to a certain proportion based on the thickness of the shell 211.

[0507] In some embodiments, the average thickness of the first shell layer 2115 is T13, and the average thickness of the shell 211 is T10. T13 and T10 satisfy: 0.15 ≤ T13 / T10 ≤ 0.85. If T13 / T10 is set too small, when the average thickness T10 of the shell 211 is fixed, T13 will be too small, which will increase the processing difficulty and also make the overcurrent heat too large, easily leading to thermal runaway. On the contrary, if T13 / T10 is set too large, when the average thickness T10 of the shell 211 is fixed, T13 will be too large, and the thicknesses of other structural layers will be too small, which will affect the structural strength of the shell 211.

[0508] Further, T13 and T10 satisfy: 0.2 ≤ T13 / T10 ≤ 0.6. This can not only improve the current-carrying capacity of the housing 211, but also improve the structural strength of the housing 211. In some embodiments, the value of the ratio T13 / T10 can also be set to other values. For example, the value of the ratio T13 / T10 can be any one of the following values or between any two of the following values: 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, and 0.85.

[0509] It should be understood that the value range of the average thickness T10 of the housing 211 in the embodiments of the present application can also be flexibly set according to actual applications. For example, the average thickness T10 of the housing 211 satisfies: 0.05 mm ≤ T10 ≤ 0.5 mm. The value of the average thickness T10 of the housing 211 should not be too small to reduce the processing difficulty of the multi-layer housing 211 and improve the structural strength of the housing 211. For example, the housing 211 is not easily broken, thereby improving the service life of the housing 211. On the contrary, the value of the average thickness T10 of the housing 211 should not be too large so that the space occupied by the housing 211 is less, the space utilization rate of the battery cell 20 is improved, and thus the energy density of the battery 10 provided with a plurality of battery cells 20 is improved.

[0510] Further, the average thickness T10 of the housing 211 satisfies: 0.075 mm ≤ T10 ≤ 0.4 mm. Appropriately thinning the average thickness T10 of the housing 211 can reduce the space occupied by the housing 211 inside the battery 10, thereby improving the energy density of the battery 10; while appropriately increasing the average thickness T10 of the housing 211 can also reduce the processing difficulty of the housing 211.

[0511] Further, the average thickness T10 of the housing 211 satisfies: 0.1 mm ≤ T10 ≤ 0.3 mm. The average thickness T10 of the housing 211 is neither too large nor too small, which can not only improve the structural strength and structural stability of the housing 211, but also reduce the space occupied by the housing 211 inside the battery 10, thereby improving the energy density of the battery 10.

[0512] In some embodiments, the value of the average thickness T10 of the housing 211 of the embodiments of the present application can also be set to other values. For example, the value of the average thickness T10 of the housing 211 can be any one of the following values or between any two of the following values: 0.05 mm, 0.075 mm, 0.1 mm, 0.125 mm, 0.15 mm, 0.175 mm, 0.2 mm, 0.225 mm, 0.25 mm, 0.275 mm, 0.3 mm, 0.325 mm, 0.35 mm, 0.375 mm, 0.4 mm, 0.425 mm, 0.45 mm, 0.475 mm, and 0.5 mm.

[0513] In the embodiments of the present application, the material of the first housing layer 2115 can be flexibly set according to actual applications. For example, the material of the first housing layer 2115 includes at least one of the following: silver, copper, aluminum, magnesium, and brass to meet the design requirements of the resistivity K1 of the first housing layer 2115.

[0514] In the embodiments of the present application, the housing 211 includes a second housing layer 2116, and the tensile strength of the second housing layer 2116 at a temperature of 25°C is Rm2, and Rm2 satisfies: 250 MPa ≤ Rm2 ≤ 2000 MPa. Among them, the second housing layer 2116 is any one of the multiple layers of the housing 211. For example, Figure 20 taking the outermost housing as the second housing layer 2116 as an example, but the embodiments of the present application are not limited thereto. By setting the tensile strength Rm2 of the second housing layer 2116 included in the housing 211 at a temperature of 25°C to be relatively large, the structural strength and deformation ability of the housing 211 can be improved, so that the housing 211 is not easily damaged during the use of the battery cell 20, thereby improving the structural stability and service life of the battery cell 20. However, the tensile strength Rm2 of the second housing layer 2116 at room temperature of 25°C should not be too large to reduce the difficulty of material selection and processing of the housing 211, save costs, and facilitate processing.

[0515] It should be understood that the value range of the tensile strength Rm2 of the second housing layer 2116 of the housing 211 in the embodiments of the present application under normal temperature conditions of 25 °C can be adjusted according to actual applications. For example, the value of the tensile strength Rm2 at normal temperature can also satisfy 400 MPa ≤ Rm2 ≤ 1200 MPa. On the one hand, increasing the tensile strength Rm2 of the second housing layer 2116 under normal temperature conditions can improve the deformation ability of this part of the second housing layer 2116 to resist the expansion amount of the electrode assembly 22, making the second housing layer 2116 not easily damaged, thereby improving the structural stability and service life of the battery cell 20. On the other hand, controlling the tensile strength Rm2 of the second housing layer 2116 under normal temperature conditions not to be too large can reduce the difficulty of material selection and processing of the second housing layer 2116, save costs, and facilitate processing.

[0516] Furthermore, it can also be set that the tensile strength Rm2 of the second housing layer 2116 under normal temperature conditions satisfies 450 MPa ≤ Rm2 ≤ 800 MPa. The tensile strength Rm2 of the second housing layer 2116 under normal temperature conditions is neither too large nor too small, which can not only improve the deformation ability of this part of the housing 211 to resist the expansion amount of the electrode assembly 22, but also facilitate implementation and save costs.

[0517] In some embodiments, the value of the tensile strength Rm2 of the second housing layer 2116 of the housing 211 in the embodiments of the present application under normal temperature conditions can also be set to other values. For example, the value of the tensile strength Rm2 at normal temperature can be any one of the following values or between any two of the following values: 250 MPa, 280 MPa, 300 MPa, 330 MPa, 350 MPa, 380 MPa, 400 MPa, 450 MPa, 500 MPa, 550 MPa, 600 MPa, 650 MPa, 700 MPa, 750 MPa, 800 MPa, 850 MPa, 900 MPa, 950 MPa, 1000 MPa, 1050 MPa, 1100 MPa, 1150 MPa, 1200 MPa, 1250 MPa, 1300 MPa, 1350 MPa, 1400 MPa, 1450 MPa, 1500 MPa, 1550 MPa, 1600 MPa, 1650 MPa, 1700 MPa, 1750 MPa, 1800 MPa, 1850 MPa, 1900 MPa, 1950 MPa, and 2000 MPa.

[0518] It should be understood that the tensile strength in the embodiments of the present application refers to the maximum stress value that the material can withstand before being broken. The test method for the tensile strength Rm2 of the second housing layer 2116 of the housing 211 in the embodiments of the present application under the condition of 25 °C can be selected according to actual applications. For example, the national standard GB / T can be adopted.

[0519] Test the tensile strength Rm2 under the normal temperature condition of 25°C according to GB / T 228.1-2010.

[0520] In the embodiment of the present application, the average thickness of the second housing layer 2116 is T14, and the average thickness of the housing 211 is T10. T14 and T10 satisfy: 0.15 ≤ T14 / T10 ≤ 0.85. If T14 / T10 is set too small, when the average thickness T10 of the housing 211 is certain, T14 will be too small, which will affect the structural strength of the housing 211. On the contrary, if T14 / T10 is set too large, when the average thickness T10 of the housing 211 is certain, T14 will be too large, then the thickness of other structural layers will be too small. For example, the thickness T13 of the first housing layer 2115 will be too small, which will increase the processing difficulty and also make the overcurrent heat too large, and it is easy to occur thermal runaway.

[0521] Furthermore, T14 and T10 satisfy: 0.2 ≤ T14 / T10 ≤ 0.6. It can not only improve the overcurrent capacity of the housing 211, but also improve the structural strength of the housing 211. In some embodiments, the value of the ratio T14 / T10 can also be set to other values. For example, the value of the ratio T14 / T10 can be any one of the following values or between any two of the following values: 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, and 0.85.

[0522] Moreover, the average thickness T14 of the second housing layer 2116 and the average thickness T13 of the first housing layer 2115 in the embodiment of the present application can be the same or different to meet different design requirements.

[0523] It should be understood that the average thickness T10 of the housing 211 in the embodiments of the present application may refer to the average thickness of at least a part of the housing 211. The average thickness T13 of the first housing layer 2115 of the housing 211 may also refer to the average thickness of at least a part of the first housing layer 2115. The average thickness T14 of the second housing layer 2116 of the housing 211 may also refer to the average thickness of at least a part of the second housing layer 2116. Moreover, the calculation area of the average thickness T10 of the housing 211 is generally consistent with the calculation area of the average thickness T13 of the first housing layer 2111 and is also consistent with the calculation area of the average thickness T14 of the second housing layer 2116. For example, if some areas are excluded when calculating the average thickness T10 of the housing 211, correspondingly, the same areas need to be excluded when calculating the average thickness T13 of the first housing layer 2115, and the same areas also need to be excluded when calculating the average thickness T14 of the second housing layer 2116. For the sake of convenience of description, the following takes the calculation of the average thickness T10 of the housing 211 as an example for description, but the relevant description is equally applicable to determining the average thickness T13 of the first housing layer 2115 and the average thickness T14 of the second housing layer 2116, which will not be elaborated here one by one.

[0524] For example, the average thickness T10 of the housing 211 may refer to the average thickness T10 of all areas of the housing 211, especially when the overall surface of the housing 211 is relatively flat, that is, when the thicknesses of most areas of the housing 211 are basically equal or have a small difference, or when the thicknesses of all areas of the housing 211 are basically equal or have a small difference, the average thickness of all areas of the housing 211 can be determined to be T10.

[0525] For another example, the average thickness T10 of the housing 211 may also refer to the average thickness T10 of a local area of the housing 211, that is, the average thickness T10 of the remaining area after excluding some areas of the housing 211. For example, if there are some special areas in the housing 211 and the thicknesses of these special areas are quite different from those of other areas. For example, there are convex structures or concave areas in these special areas along the thickness direction, making the thicknesses of these special areas larger or smaller than those of other areas, then these special areas can be excluded to calculate the average thickness of the remaining areas of the housing 211 as T10.

[0526] In some embodiments, the housing 211 may include functional regions, and the average thickness T10 of the housing 211 is the average thickness of the regions of the housing 211 other than the functional regions. For example, the functional regions include at least one of the following regions: a pressure relief region, the region where the electrode terminal 214 is located, a liquid injection region, and a welding region. The thickness of the functional regions usually varies significantly compared to the thickness of other regions of the housing 211. Therefore, when calculating the average thickness T10 of the housing 211 without including the functional regions, the design of the housing 211 can better meet the strength requirements, thereby improving the structural strength and stability of the battery cell 20.

[0527] Specifically, the functional regions of the embodiments of the present application may include regions on the housing 211 that are provided with specific structures or have specific uses. For example, the functional regions may include a pressure relief region, which is used to provide a pressure relief mechanism. The pressure relief mechanism is an element or component that actuates to release the internal pressure or temperature when the internal pressure or temperature of the battery cell 20 reaches a predetermined threshold. The predetermined threshold can be adjusted according to different design requirements. For example, the predetermined threshold may depend on one or several of the materials of the positive electrode plate, negative electrode plate, electrolyte, and separator in the battery cell 20.

[0528] As used in the present application, "actuate" means that the pressure relief mechanism generates an action or is activated to a certain state, so that the internal pressure and temperature of the battery cell 20 can be released. The actions generated by the pressure relief mechanism may include, but are not limited to: at least a part of the pressure relief mechanism rupturing, breaking, being torn, or opening, etc. When the pressure relief mechanism actuates, the high-temperature and high-pressure substances inside the battery cell 20 will be discharged outward from the actuated part as emissions. In this way, the battery cell 20 can be depressurized and cooled under controlled pressure or temperature, thereby avoiding potential more serious accidents.

[0529] The emissions from the battery cell 20 mentioned in the present application include, but are not limited to: electrolyte, dissolved or fragmented positive and negative electrode plates, fragments of the separator, high-temperature and high-pressure gases generated by the reaction, flames, etc.

[0530] The pressure relief mechanism of the embodiment of the present application can be disposed on any wall of the battery cell 20. For example, the pressure relief mechanism can be disposed in the pressure relief area of the housing 211 of the battery cell 20. The pressure relief mechanism can be a part of the housing 211; or, it can also be a split structure with the housing 211 and is fixed on the housing 211 by a method such as welding. For example, when the pressure relief mechanism is a part of the housing 211, for example, the pressure relief mechanism can be formed by setting a notch on the housing 211, that is, the housing 211 is provided with a notch in the pressure relief area, and the thickness at the notch is significantly smaller than the thickness of other areas of the housing 211. Therefore, the average thickness T10 of the housing 211 can not calculate the thickness at the notch. The notch is the weakest position of the pressure relief mechanism. When the gas generated by the battery cell 20 is too much so that the internal pressure rises and reaches the threshold or the internal reaction of the battery cell 20 generates heat causing the internal temperature of the battery cell 20 to rise and reach the threshold, the pressure relief mechanism can rupture at the notch, resulting in the internal and external communication of the battery cell 20, and the gas pressure and temperature are released outward through the crack of the pressure relief mechanism, thereby avoiding the explosion of the battery cell 20.

[0531] For another example, the pressure relief mechanism can also be a split structure with the housing 211. The pressure relief mechanism can adopt forms such as an explosion-proof valve, a gas valve, a pressure relief valve or a safety valve, and can specifically adopt a pressure-sensitive or temperature-sensitive element or structure. For example, the housing 211 is provided with a through hole in the pressure relief area, and the pressure relief mechanism is installed and fixed to the housing 211 through the through hole. After installation, the pressure relief mechanism may protrude or recess relative to other areas of the housing 211. Therefore, the average thickness T10 of the housing 211 can not include the pressure relief area where the pressure relief mechanism is located. When the internal pressure or temperature of the battery cell 20 reaches a predetermined threshold, the pressure relief mechanism performs an action or a weak structure provided in the pressure relief mechanism is damaged, thereby forming an opening or a channel for discharging the internal pressure or temperature.

[0532] In some embodiments, the functional region may further include the region where the electrode terminal 214 is located. Specifically, the electrode terminal 214 in the embodiment of the present application is used to electrically connect to the electrode assembly 22 inside the battery cell 20 to output the electrical energy of the battery cell 20. Moreover, the battery cell 20 may include at least two electrode terminals 214, and the at least two electrode terminals 214 respectively include at least one positive electrode terminal and at least one negative electrode terminal. The positive electrode terminal is used to electrically connect to the positive electrode tab of the electrode assembly 22, and the negative electrode terminal is used to electrically connect to the negative electrode tab of the electrode assembly 22. The positive electrode terminal and the positive electrode tab may be directly connected or indirectly connected, and the negative electrode terminal and the negative electrode tab may be directly connected or indirectly connected. Exemplarily, in the embodiment of the present application, the positive electrode terminal may be the first electrode terminal 214a, and the negative electrode terminal is the second electrode terminal 214b. Or, the positive electrode terminal may be the second electrode terminal 214b, and the negative electrode terminal is the first electrode terminal 214a.

[0533] It should be understood that each electrode terminal 214 in the embodiment of the present application may be disposed on any wall, and multiple electrode terminals 214 may be disposed on the same wall or different walls of the battery cell 20. For example, as Figures 18 to 22 shown, taking each battery cell 20 including two electrode terminals 214 and the two electrode terminals 214 being located on the same wall as an example. For example, the two electrode terminals 214 may both be located on the cover 211a. However, in the embodiment of the present application, if the cover 23 is the first electrode terminal 214a, then there is still one electrode terminal 214 protruding from other regions of the cover 211a of the housing 211 among the two electrode terminals 214 included in the battery cell 20, that is, the thickness of the region where the second electrode terminal 214b is located is much greater than the thickness of other regions of the housing 211. Therefore, the average thickness T10 of the housing 211 may not include the region where the second electrode terminal 214b is located.

[0534] In some embodiments, the functional region may further include a liquid injection region. For example, a liquid injection hole may be provided in the liquid injection region of the housing 211, and electrolyte is injected into the housing 211 through the liquid injection hole. After the electrolyte injection is completed, the liquid injection hole may be sealed by a seal. Considering that the thickness of the liquid injection region where the seal is located is usually much greater than the thickness of other regions of the housing 211, therefore, the average thickness T10 of the housing 211 may not include the liquid injection region.

[0535] In some embodiments, the functional area may further include a welding area. For example, the housing 211 and the cover plate 212 may be fixed by welding, or the housing 211 itself needs to be processed and formed by welding. For example, any two walls of the housing 211 may be welded, or the housing 211 is formed by splicing at least two parts, then the housing 211 may include a welding area. For example, the housing 211 may be welded in a splicing manner, then the housing 211 may have a weld 2113. Specifically, the housing 211 may include at least two parts, and the at least two parts are connected by welding to form the housing 211. Among them, in the embodiments of the present application, mainly taking the housing 211 including two parts along the height direction Z of the battery cell 20 as an example, there is a weld 2113 between the upper half housing and the lower half housing; or, different from Figure 19 As shown, the other parts of the housing 211 may also be provided with a weld 2113, which is not limited in the embodiments of the present application. The welding area of the functional area in the embodiments of the present application may also include the weld 2113. Due to processing technology reasons, the thickness of the welding area is usually greater than the thickness of other areas of the housing 211. Therefore, when calculating the average thickness T10 of the housing 211, the welding area may not be included.

[0536] In some embodiments, the resistivity of the second housing layer 2116 is K2, and K2 and K1 satisfy: 2 ≤ K2 / K1 ≤ 40. Further, it may also satisfy: 2 ≤ K2 / K1 ≤ 20, so as to limit the resistivity K1 of the first housing layer 2115, and further improve the overcurrent capacity of the housing 211.

[0537] In the embodiments of the present application, the material of the second housing layer 2116 can be flexibly set according to actual applications. For example, the material of the second housing layer 2116 includes at least one of the following: titanium, steel, silicon steel, and stainless steel, so as to meet the design requirements of the second housing layer 2116.

[0538] In some embodiments, the materials of the first housing layer 2115 and the second housing layer 2116 can be selected from the various materials shown in Table 9 to meet the design requirements.

[0539] Table 9

[0540] Serial number Material Resistivity (Ω·m) Tensile strength (MPa) 1 Silver 1.59×10^-8 160-420 2 Copper 1.68×10^-8 210-270 3 Aluminum 2.65×10^-8 120-160 4 Magnesium 4.45×10^-8 120-220 5 Brass 6×10^-8 330-550 6 Titanium 4.2×10^-7 280-550 7 Steel 1.35×10^-7 370-2000 8 Silicon steel 5×10^-7 1,000-1,300 9 Stainless steel 6.9×10^-7 500-1,000

[0541] It should be understood that the housing 211 in the embodiments of the present application is a multi-layer structure, and the number of layers of the housing 211 can be set according to actual applications. For example, the housing 211 includes a plurality of the first housing layers 2115 and / or a plurality of the second housing layers 2116, and the positions of different first housing layers 2115 and second housing layers 2116 can be flexibly set according to actual applications to meet different application scenarios.

[0542] In some embodiments, the housing 211 may include a plurality of first housing layers 2115 and a second housing layer 2116, and the second housing layer 2116 may be located in the middle or on one side of the plurality of first housing layers 2115. Similarly, the housing 211 may include a first housing layer 2115 and a plurality of second housing layers 2116, and the first housing layer 2115 may be located in the middle or on one side of the plurality of second housing layers 2116. For another example, the housing 211 may include a plurality of first housing layers 2115 and a plurality of second housing layers 2116, and the plurality of first housing layers 2115 and the plurality of second housing layers 2116 may be arranged at intervals, or the plurality of first housing layers 2115 may be arranged on one side of the plurality of second housing layers 2116. The embodiments of the present application are not limited thereto.

[0543] In some embodiments, if the housing 211 includes a plurality of first housing layers 2115 that meet the above design requirements, the materials of the plurality of first housing layers 2115 may be the same or different, the resistivity K1 may be the same or different, and the thickness T13 may be the same or different, so as to increase the design flexibility. Similarly, if the housing 211 includes a plurality of second housing layers 2116 that meet the above design requirements, the materials of the plurality of second housing layers 2116 may be the same or different, the tensile strength Rm2 under normal temperature conditions may be the same or different, and the thickness T14 may be the same or different, so as to increase the design flexibility.

[0544] The embodiments of the present application further provide a battery, which includes the battery cells 20 of the above various embodiments.

[0545] The embodiments of the present application further provide an electrical device, including a battery, which includes the battery cells 20 of the above various embodiments and is used to provide electrical energy for the electrical device.

[0546] The electrical device may be a vehicle as shown in Figure 1 or any device using a battery.

[0547] Although the present application has been described with reference to the preferred embodiments, various improvements can be made to it and components therein can be replaced with equivalents without departing from the scope of the present application. In particular, as long as there is no structural conflict, the technical features mentioned in each embodiment can be combined in any way. The present application is not limited to the specific embodiments disclosed in the text, but includes all technical solutions falling within the scope of the claims.

Claims

1. A housing, characterized in that: include: A first housing portion is formed with an opening, the first housing portion comprises a first wall opposite to the opening and a second wall connected to the first wall, the first wall and the second wall are integrally formed; A second housing portion, fixedly connected to the second wall; Wherein, in the depth direction of the first shell part, at least a partial area of ​​the shell is formed by the first shell part and the second shell part.

2. The housing according to claim 1, characterized in that The second housing portion has two communicating openings in the depth direction of the first housing portion.

3. The housing according to claim 2, characterized in that: The second housing portion is an integrally formed structure.

4. The housing according to claim 2, characterized in that: The second shell portion is formed by butt welding at least two parts.

5. The housing according to any one of claims 1 to 4, characterized in that A surface of the second wall facing away from the first wall is welded to the second housing portion.

6. The housing according to any one of claims 1 to 4, characterized in that A surface of the second wall perpendicular to a thickness direction of the second wall is welded to the second case portion.

7. The housing according to any one of claims 1 to 6, characterized in that In the depth direction of the first shell part, the maximum dimension of the first shell part is h1, the maximum dimension of the shell is H, and H and h1 satisfy: 3≤H / h1≤80.

8. The housing according to claim 7, characterized in that h1 satisfies: 3mm≤h1≤50mm.

9. The housing according to any one of claims 1 to 8, characterized in that The yield strength of the shell at a temperature of 25° C. is Re, and Re satisfies: 125MPa≤Re≤1000Mpa.

10. The housing according to any one of claims 1 to 9, characterized in that The material of at least a part of the shell includes at least one of the following: stainless steel and carbon steel.

11. The housing according to any one of claims 1 to 10, characterized in that The mass content of chromium in the material of at least a partial area of ​​the shell is m, and m satisfies: 10%≤m≤30%.

12. The housing according to claim 10 or 11, characterized in that: At least a partial area of ​​the housing includes the entire wall of the housing.

13. A battery cell, characterized in that: The invention comprises an electrode assembly and a casing according to any one of claims 1 to 12, wherein the electrode assembly is accommodated in the casing.

14. The battery cell according to claim 13, characterized in that: The electrode assembly includes a negative electrode plate, the negative electrode plate includes a negative electrode active material capable of reversibly extracting and inserting metal ions, and the negative electrode active material includes a silicon-based material; The tensile strength of at least a portion of the shell at a temperature of 25° C. is Rm, and Rm satisfies: 250 MPa≤Rm≤2000 MPa.

15. The battery cell according to claim 13 or 14, characterized in that: The electrode assembly includes a negative electrode plate, the negative electrode plate includes a negative electrode active material capable of reversibly extracting and inserting metal ions, and the negative electrode active material includes a silicon-based material; The yield strength of at least a part of the shell at a temperature of 25° C. is Re, and Re satisfies: 140 MPa≤Re≤1000 MPa.

16. The battery cell according to any one of claims 13 to 15, characterized in that: The electrode assembly includes a positive electrode plate, the positive electrode plate includes a positive electrode active material capable of reversibly extracting and inserting metal ions, and the positive electrode active material includes a nickel-containing compound; The melting point of at least a part of the shell is p, and p satisfies: 1200°C≤p≤2000°C.

17. The battery cell according to any one of claims 13 to 16, characterized in that: The electrode assembly includes a positive electrode plate, the positive electrode plate includes a positive electrode active material capable of reversibly extracting and inserting metal ions, and the positive electrode active material includes a nickel-containing compound; The tensile strength of at least a portion of the shell at a temperature of 500° C. is Rn, and Rn satisfies: 100 MPa≤Rn≤1200 MPa.

18. A battery, characterized in that: include: A plurality of battery cells, wherein the battery cells are the battery cells according to any one of claims 13 to 17.

19. An electrical device, characterized in that: include: A battery, comprising the battery cell according to any one of claims 13 to 17, wherein the battery is used to supply power to the electrical device.

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