Battery monomer, battery and electric equipment

Abstract

The embodiment of the invention discloses a battery monomer, a battery and electric equipment. The battery cell comprises: an electrode assembly comprising a first tab; a first electrode terminal; the shell comprises a cylinder body and a cover body connected to the cylinder body, the cylinder body is arranged around the periphery of the electrode assembly, the cover body comprises the first electrode terminal, the first tab is electrically connected with the first electrode terminal through the cylinder body, the shell is of a multi-layer structure, and the resistivity of the multi-layer structure is different. According to the battery monomer, the battery and the electric equipment provided by the embodiment of the invention, the reliability of the battery monomer can be improved.

Description

Technical Field

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

[0002] Energy conservation and emission reduction are the keys to the sustainable development of the automotive industry. In this context, electric vehicles have become an important part of the sustainable development of the automotive industry due to their advantages of energy conservation and environmental protection. For electric vehicles, battery technology is an important factor related to their development.

[0003] In the development of battery technology, in addition to improving the performance of the battery, safety issues are also a problem that cannot be ignored. If the safety of the battery cannot be guaranteed, the battery cannot be used. Therefore, how to improve the performance of the battery while ensuring the safety of the battery has become an extremely important issue in the development of battery technology. Summary of the Invention

[0004] Embodiments of the present application provide a battery cell, a battery, and an electrical device, which can improve the reliability of the battery cell.

[0005] In a first aspect, a battery cell is provided. The battery cell includes: an electrode assembly, the electrode assembly including a first tab; a first electrode terminal; a housing, the housing including a cylinder and a cover connected to the cylinder, the cylinder being disposed around the outer periphery of the electrode assembly, the cover including the first electrode terminal, the first tab being electrically connected to the first electrode terminal through the cylinder, the housing being a multi-layer structure, and the resistivity of the multi-layer structure being different.

[0006] Therefore, in the battery cell of the embodiments of the present application, the first tab is electrically connected to the first electrode terminal through the cylinder, which can simplify the structure of the battery cell; the housing is set as a multi-layer structure with different resistivities of the multi-layer structure, and the over-current capacity of the battery cell can be improved through the layer structure with a lower resistivity, and the structural strength of the housing can be improved through the layer structure with a higher resistivity, which can not only improve the performance of the battery cell, but also improve the structural strength of the battery cell, thereby increasing the service life of the battery cell.

[0007] In some embodiments, the housing includes a first housing layer, and the resistivity of the first housing layer is K1, where K1 satisfies: 1×10^-8 Ω·m ≤ K1 ≤ 6×10^-8 Ω·m. By setting the resistivity K1 of the first housing layer included in the housing to be small, the over-current capacity of the housing can be improved, and thus the performance of the battery cell can be improved.

[0008] In some embodiments, the average thickness of the first housing layer is T13, and the average thickness of the housing is T10. T13 and T10 satisfy: 0.15 ≤ T13 / T10 ≤ 0.85. If T13 / T10 is set too small, with a certain average thickness T10 of the housing, T13 will be too small, which will increase the processing difficulty and also cause the overcurrent heat to be too large, making thermal runaway likely to occur. Conversely, if T13 / T10 is set too large, with a certain average thickness T10 of the housing, T13 will be too large, and the thicknesses of other structural layers will be too small, which will affect the structural strength of the housing 211.

[0009] In some embodiments, the material of the first housing layer includes at least one of the following: silver, copper, aluminum, magnesium, and brass to meet the design requirements of the low resistivity K1 of the first housing layer.

[0010] In some embodiments, the housing includes a second housing layer. The tensile strength of the second housing layer at a temperature of 25°C is Rm2, and Rm2 satisfies: 250 MPa ≤ Rm2 ≤ 2000 MPa. By setting the tensile strength Rm2 of the second housing layer included in the housing to be relatively large at a temperature of 25°C, the structural strength and deformation ability of the housing can be improved, so that the housing is not easily damaged during the use of the battery cell, thereby improving the structural stability and service life of the battery cell. However, the tensile strength Rm2 of the second housing layer at room temperature of 25°C should not be too large to reduce the material selection difficulty and processing difficulty of the housing, save costs, and facilitate processing.

[0011] In some embodiments, the average thickness of the second housing layer is T14, and the average thickness of the housing is T10. T14 and T10 satisfy: 0.15 ≤ T14 / T10 ≤ 0.85. If T14 / T10 is set too small, with a certain average thickness T10 of the housing, T14 will be too small, which will affect the structural strength of the housing. Conversely, if T14 / T10 is set too large, with a certain average thickness T10 of the housing, it will be too large, and the thicknesses of other structural layers will be too small. For example, the thickness T13 of the first housing layer will be too small, thereby increasing the processing difficulty and also causing the overcurrent heat to be too large, making thermal runaway likely to occur.

[0012] In some embodiments, the resistivity of the second housing layer is K2, and K2 and K1 satisfy: 2 ≤ K2 / K1 ≤ 40 to limit the resistivity K1 of the first housing layer, thereby improving the overcurrent capacity of the housing.

[0013] In some embodiments, the material of the second housing layer includes at least one of the following: titanium, steel, silicon steel, and stainless steel to meet the strength design requirements of the second housing layer.

[0014] In some embodiments, the housing includes a plurality of the first housing layers and / or a plurality of the second housing layers to meet different application scenarios.

[0015] In some embodiments, the electrode assembly further includes a second tab. The second tab has a polarity opposite to that of the first tab. The first tab and the second tab are located on different end faces of the electrode assembly for ease of processing.

[0016] In some embodiments, the first tab and the second tab are respectively located on the oppositely arranged end faces of the electrode assembly for ease of processing.

[0017] In some embodiments, the battery cell includes: a second electrode terminal. The second electrode terminal is electrically connected to the second tab. The first electrode terminal and the second electrode terminal are located on the same wall of the battery cell to improve the integration of the battery cell, increase the space utilization rate of the battery cell in the battery, and facilitate processing and assembly.

[0018] In some embodiments, the cover body is the first electrode terminal. The cover body is provided with an electrode lead-out hole. The second electrode terminal is insulated and arranged on the cover body and installed in the electrode lead-out hole. One of the cover body and the second electrode terminal is the positive output pole of the battery cell, and the other is the negative output pole of the battery cell. At least part of the housing itself can be used as an output electrode of the battery cell, thus eliminating a traditional electrode terminal and simplifying the structure of the battery cell. When a plurality of battery cells are assembled into a group, the housing can be electrically connected to the busbar component. In this way, not only can the current-carrying area be increased, but also the structural design of the busbar component can be made more flexible.

[0019] In some embodiments, the cover body and the cylindrical body are integrally formed structures. This can eliminate the connection process between the cover body and the cylindrical body.

[0020] In some embodiments, the electrode assembly includes a negative electrode tab, the negative electrode tab 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 tensile strength of at least a part of the housing at a temperature of 25 °C is Rm, and Rm satisfies: 250 MPa ≤ Rm ≤ 2000 MPa. Arranging a silicon-based material on the negative electrode tab can accommodate more metal ions and can effectively increase the energy density of the battery cell. In addition, when the negative electrode active material of the negative electrode tab has a silicon-based material, the amount of deformation of the electrode assembly in the battery cell during use will also increase. Especially during the charging process of the battery cell, when metal ions intercalate into 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 tensile strength Rm of at least a part of the housing at room temperature of 25 °C can improve the deformation ability of the housing, making the housing not easily 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 tensile strength Rm of at least a part of the housing at room temperature of 25 °C should not be too large, so as to reduce the difficulty of material selection and processing of the housing, save costs, and facilitate processing.

[0021] In some embodiments, the electrode assembly includes a negative electrode tab, the negative electrode tab 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 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. Arranging a silicon-based material on the negative electrode tab can accommodate more metal ions and can effectively increase the energy density of the battery cell. In addition, when the negative electrode active material of the negative electrode tab has a silicon-based material, the amount of deformation of the electrode assembly in the battery cell during use will also increase. Especially during the charging process of the battery cell, when metal ions intercalate into 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 at room temperature of 25 °C 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 expands and contracts in volume cyclically, increasing the yield strength Re of at least a part of the housing at room temperature can increase the maximum extrusion force 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 room temperature conditions should not be too large, so as to reduce the difficulty of material selection and processing of the housing, save costs, and facilitate processing.

[0022] In some embodiments, the electrode assembly further includes a positive electrode tab, the positive electrode tab includes a positive electrode active material capable of reversibly deintercalating and intercalating 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. When the positive electrode active material of the positive electrode tab 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, making the housing not easily damaged and exploded quickly, thereby reducing the risk of adjacent battery cells undergoing thermal runaway and improving 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.

[0023] In some embodiments, the electrode assembly further includes a positive electrode tab, the positive electrode tab includes a positive electrode active material capable of reversibly deintercalating and intercalating 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. When the positive electrode active material of the positive electrode tab 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 adjacent battery cells undergoing thermal runaway 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.

[0024] In some embodiments, the electrode assembly includes a first tab; the housing includes a cylinder and a cover connected to the cylinder, the cylinder is disposed around the outer periphery of the electrode assembly, the cover includes a first electrode terminal, the first tab is electrically connected to the first electrode terminal through the cylinder, the housing is a multi-layer structure, and the resistivity of the multi-layer structure is different. The first tab is electrically connected to the first electrode terminal through the cylinder, which can simplify the structure of the battery cell; the housing is set as a multi-layer structure with different resistivities, and the over-current capacity of the battery cell can be improved through the layer structure with lower resistivity, and the structural strength of the housing can be improved through the layer structure with higher resistivity, which can not only improve the performance of the battery cell, but also improve the structural strength of the battery cell, thereby increasing the service life of the battery cell.

[0025] In some embodiments, the housing has an opening, the housing includes a first housing wall disposed opposite to the opening and at least two second housing walls, the first housing wall and the second housing walls intersect; there is a transition region between two adjacent second housing walls among the at least two second housing walls, and the maximum thickness T1 of the transition region and the maximum thickness T0 of the second housing wall with the largest thickness among the two second housing walls satisfy: T1 > T0.

[0026] In this embodiment, by providing a transition region between two adjacent second housing walls, the stress concentration between the two adjacent second housing walls can be reduced, and the risk of structural failure caused by stress concentration can be lowered; in addition, the maximum thickness T1 of the transition region is set to be greater than the maximum thickness T0 of the second housing wall with the largest thickness among the two adjacent second housing walls, and the thickened transition region can enhance the structural strength of the housing, which is beneficial to solving the problem of housing deformation during the production and assembly process of the battery cell, and the problem of housing deformation caused by gas production and expansion during the use of the battery cell.

[0027] In some embodiments, the housing is an integrally formed structure, the housing has an opening, the housing includes a first housing wall disposed opposite to the opening and at least two second housing walls, the first housing wall and the second housing walls intersect, and two of the at least two second housing walls are connected by a first fillet, and the depth H of the housing and the inner diameter R1 of the first fillet satisfy: 2.5 mm ≤ R1 ≤ 20 mm, 50 mm < H ≤ 250 mm, which can reduce the cracking risk caused by stress during the integral forming process of the housing as much as possible without affecting the energy density of the battery cell, thereby reducing the forming difficulty of the housing.

[0028] In some embodiments, the housing is an integrally formed structure. The housing has an opening and includes a first housing wall disposed opposite to the opening and at least two second housing walls. The first housing wall and the second housing walls intersect. Two of the at least two second housing walls are connected by a first rounded corner. The yield strength Re of the housing at a temperature of 25 °C and the inner diameter R1 of the first rounded corner satisfy: 140 MPa ≤ Re ≤ 1000 MPa, 2.5 mm ≤ R1 ≤ 20 mm.

[0029] In this embodiment, by using a material with a yield strength Re satisfying 140 MPa ≤ Re ≤ 1000 MPa to make the housing, it is possible to reduce the wall thickness of the housing without reducing the strength of the housing, thereby increasing the capacity space of the battery cell. In addition, by setting the inner diameter R1 of the first rounded corner between adjacent second housing walls to satisfy 2.5 mm ≤ R1 ≤ 20 mm, the cracking risk caused by stress during the integral forming process of the housing is reduced as much as possible, and the forming difficulty of the housing is reduced.

[0030] In some embodiments, the housing has an opening and includes a first housing wall and a second housing wall disposed opposite to the opening. The first housing wall and the second housing wall intersect. The first housing wall and the second housing wall are connected by a second rounded corner. The inner diameter r1 of the second rounded corner and the minimum thickness T2 of the second housing wall with the minimum thickness among the at least two second housing walls satisfy: 2.0 ≤ r1 / T2 ≤ 30. By setting the ratio of the inner diameter r1 of the second rounded corner between the first housing wall and the second housing wall to the minimum thickness T2 of the second housing wall with the minimum thickness within [2.0, 30], it helps to balance the processing difficulty of the housing, the space capacity of the battery cell, and the strength.

[0031] In some embodiments, the material of the outermost housing layer of the housing includes at least one of the following: aluminum, aluminum alloy, copper, copper alloy, and chromium. When the material of the outermost housing layer contains aluminum, the aluminum will be oxidized into dense aluminum oxide, which can prevent corrosion. When the material of the outermost housing layer contains copper, the copper will be oxidized into copper oxide, that is, verdigris, which can prevent corrosion. When the material of the outermost housing layer contains chromium, the chromium will be oxidized into chromium oxide, which can also prevent corrosion. Therefore, when the material of the outermost housing layer uses the above-mentioned corrosion-resistant materials, the other housing layers located inside it can be protected by the outermost housing layer, which can not only improve the structural stability of the housing but also extend the service life of the housing. Description of the Drawings

[0032] Figure 1 Schematic diagram of a vehicle according to an embodiment of the present application;

[0033] Figure 2 Exploded structural schematic diagram of a battery according to an embodiment of the present application;

[0034] Figure 3 Schematic structural diagram of a battery cell according to an embodiment of the present application;

[0035] Figure 4 Exploded structural diagram of a battery cell according to an embodiment of the present application;

[0036] Figure 5 Schematic cross-sectional structure diagram of a battery cell according to another embodiment of the present application;

[0037] Figure 6 Schematic cross-sectional view of a partial structure of a battery according to another embodiment of the present application;

[0038] Figure 7 Schematic cross-sectional view of another partial structure of a battery according to another embodiment of the present application;

[0039] Figure 8 Schematic cross-sectional view of a partial structure of a battery according to another embodiment of the present application;

[0040] Figure 9 Exploded structural diagram of a battery cell according to another embodiment of the present application;

[0041] Figure 10 Schematic cross-sectional view of an electrode assembly according to an embodiment of the present application;

[0042] Figure 11 Schematic cross-sectional view of a negative electrode tab or a positive electrode tab of an electrode assembly according to an embodiment of the present application;

[0043] Figure 12 Schematic structural diagram of a fixture for cyclic charge fatigue test according to an embodiment of the present application;

[0044] Figure 13 Schematic cross-sectional structure diagram of a housing of a battery cell according to an embodiment of the present application;

[0045] Figure 14 Schematic side view structure diagram of a housing of a battery cell according to an embodiment of the present application;

[0046] Figure 15 Explosion diagram of a battery cell according to an embodiment of the present application;

[0047] Figure 16 A cross-sectional view of a housing according to an embodiment of the present application;

[0048] Figure 17 Schematic diagram of a transition region of a housing according to an embodiment of the present application;

[0049] Figure 18Schematic diagram of another transition region of the housing according to an embodiment of the present application;

[0050] Figure 19 Schematic diagram of the material flow during the integral molding process of the housing according to an embodiment of the present application;

[0051] Figure 20 Schematic diagram of the force on the housing during the integral molding process according to an embodiment of the present application;

[0052] Figure 21 Another cross-sectional view of the housing according to an embodiment of the present application;

[0053] Figure r>Figure 22 is Figure 10 Partial enlarged schematic diagram of part B in

[0054] Figure 23 Exploded schematic diagram of the housing according to an embodiment of the present application;

[0055] Figure 24 Schematic diagram of a structure of the second housing part according to an embodiment of the present application;

[0056] Figure 25 Another schematic diagram of the structure of the second housing part according to an embodiment of the present application;

[0057] Figure 26 Another exploded schematic diagram of the housing according to an embodiment of the present application;

[0058] Figure 27 Schematic cross-sectional view of the housing according to an embodiment of the present application;

[0059] Figure 28 Partial enlarged view of the local structure of the housing according to an embodiment of the present application. Detailed implementation manners

[0060] Next, the technical solutions in the embodiments of the present application will be described with reference to the accompanying drawings.

[0061] 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 protection scope of the present application.

[0062] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by those skilled in the technical field to which this application belongs; the terms used in the description of this application in the specification are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in the specification and claims of this application and the above drawings are intended to cover non-exclusive inclusion. The terms "first", "second", etc. in the specification and claims of this application or the above drawings are used to distinguish different objects and are not used to describe a specific order or primary-secondary relationship.

[0063] Reference to "embodiment" in this application means that a specific feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of this application. The phrase appearing at various positions in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described in this application can be combined with other embodiments.

[0064] In the description of this application, it should be noted that unless otherwise clearly specified and limited, the terms "installed", "connected", "coupled", "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 internal communication of 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.

[0065] The term "and / or" in this application is only a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " in this application generally represents an "or" relationship between the associated objects before and after.

[0066] In the embodiments of this application, the same reference numerals represent the same components, and for the sake of brevity, 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.

[0067] The "plurality" mentioned in this application refers to two or more (including two). Similarly, "multiple groups" refers to two or more groups (including two groups), and "multiple pieces" refers to two or more pieces (including two pieces).

[0068] In the embodiments of the present application, the battery cell may be a secondary battery, which refers to a battery cell that can be activated by charging after discharging and can be used continuously.

[0069] The battery cell may 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., and the embodiments of the present application are not limited thereto.

[0070] In some implementation manners, the battery cell in the embodiments of the present application may be a metal battery. Specifically, the metal battery may include a lithium-metal secondary battery, a sodium-metal battery, a magnesium-metal battery, etc., and the embodiments of the present application are not limited thereto.

[0071] The battery cell generally includes an electrode assembly. The electrode assembly includes a positive electrode, a negative electrode, and a separator. During the charging and discharging process of the battery cell, active ions (such as lithium ions) are embedded and extracted back and forth between the positive electrode and the negative electrode. 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 allow the active ions to pass through at the same time.

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

[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 may 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. may be used. The foam metal may be foam nickel, foam copper, foam aluminum, foam alloy, or foam carbon, etc. The composite current collector may include a polymer material substrate and a metal layer. The composite current collector may 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 may 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 may also be used. These positive electrode active materials may be used alone or in combination of two or more. Among them, examples of the lithium-containing phosphate may include, but are not limited to, lithium iron phosphate (such as LiFePO 4(which may also be abbreviated as LFP)), at least one of 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 a composite material of lithium manganese iron phosphate and carbon.

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

[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 may 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. may be used. The composite current collector may include a polymer material substrate and a metal layer. The foam metal may be foam nickel, foam copper, foam aluminum, foam alloy, or foam carbon, etc. The composite current collector may 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 a substrate of polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.).

[0079] In some embodiments, the electrode assembly further includes a separator disposed between the positive electrode and the negative electrode.

[0080] In some embodiments, the separator is a separator membrane. The present application does not particularly limit the type of the separator membrane, and any well-known porous structure separator membrane with good chemical stability and mechanical stability can be selected.

[0081] As an example, the main material of the separator membrane may be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, polyvinylidene fluoride, and ceramics.

[0082] In some embodiments, the separator is a solid electrolyte. The solid electrolyte is disposed between the positive electrode and the negative electrode, and simultaneously functions to transport ions and isolate the positive and negative electrodes.

[0083] In some embodiments, the battery cell further includes an electrolyte, and the electrolyte functions to conduct 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-like, or solid.

[0084] In some embodiments, the electrode assembly is provided with tabs, and the tabs can lead out the current from the electrode assembly. The tabs include a positive tab and a negative tab.

[0085] In some embodiments, a battery cell may include a housing. The housing is used to encapsulate components such as an electrode assembly and an 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 housing), or an aluminum plastic film, etc. The housing includes a case and a cover plate.

[0086] The battery mentioned in the embodiments of the present application may 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.

[0087] In some embodiments, the battery may be a battery pack, and the battery pack includes a box body and battery cells, and the battery cells or battery modules are accommodated in the box body.

[0088] In some embodiments, the box body can be 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.

[0089] In some embodiments, the battery may be located in an energy storage device. The energy storage device includes an energy storage container, an energy storage cabinet, etc.

[0090] The development of battery technology needs to consider various design factors simultaneously. For example, performance parameters such as energy density, cycle life, discharge capacity, charge-discharge rate, etc. For the case where the two tabs of the electrode assembly are arranged oppositely, usually one end of the tab can be electrically connected to the housing, and the housing is directly used to pass current during the use of the battery cell to form an electrical circuit. In this way, when the two tabs of the electrode assembly are arranged oppositely, the positive and negative terminals of the battery cell can be arranged on the same side. In addition, to further increase the capacity of the battery cell, a common method is to reduce the wall thickness of the housing. However, after the wall thickness is reduced, the strength of the housing is insufficient, and the overcurrent resistance will also increase. Large deformation or excessive heating of the battery cell during use will result in poor performance of the battery cell.

[0091] Therefore, the embodiments of the present application provide a battery cell, a battery and an electrical device, which can solve the above problems. The battery cell of the embodiments of the present application includes: an electrode assembly, a first electrode terminal and a housing. Wherein, the electrode assembly includes a first tab; the housing includes a cylinder body and a cover body connected to the cylinder body, the cylinder body is disposed around the outer periphery of the electrode assembly, the cover body includes the first electrode terminal, the first tab is electrically connected to the first electrode terminal through the cylinder body, the housing is a multi-layer structure, and the resistivity of the multi-layer structure is different. The first tab is electrically connected to the first electrode terminal through the cylinder body, which can simplify the structure of the battery cell; the housing is set as a multi-layer structure with different resistivity, and the over-current capacity of the battery cell can be improved through the layer structure with lower resistivity, and the structural strength of the housing can be improved through the layer structure with higher resistivity, which can not only improve the performance of the battery cell, but also improve the structural strength of the battery cell, thereby increasing the service life of the battery cell.

[0092] The technical solutions described in the embodiments of the present application are applicable to various electrical devices using batteries.

[0093] The electrical device can be a vehicle, a mobile phone, a portable device, a laptop computer, a ship, a spacecraft, an electric toy and 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 and a spaceship, etc.; the electric toy includes a fixed or mobile electric toy, for example, a game console, an electric vehicle toy, an electric ship toy and an electric airplane toy, etc.; the electric tool includes a metal cutting electric tool, a grinding electric tool, an 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 electric drill, a concrete vibrator and a planer, etc. The embodiments of the present application do not make special restrictions on the above electrical devices.

[0094] For the convenience of description, the following embodiments take the electrical device as a vehicle as an example for description.

[0095] For example, as Figure 1As shown in the figure, 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. The new energy vehicle can be a pure electric vehicle, a hybrid vehicle, an extended-range vehicle, etc. A motor 80, a controller 70, and a battery 10 can be arranged inside the vehicle 1. The controller 70 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 end, or the rear end 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 source of the vehicle 1 and used for the circuit system of the vehicle 1, such as the working power requirements for starting, navigation, and running of the vehicle 1. In another embodiment of the present application, the battery 10 can not only be used as the operating power source of the vehicle 1 but also be used as the driving power source of the vehicle 1, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle 1.

[0096] To meet different power usage requirements, the battery can include a plurality of battery cells. Among them, the plurality of battery cells can be connected in series, in parallel, or in a series-parallel combination. The series-parallel combination means a combination of series and parallel connections. The battery can also be referred to as a battery pack. For example, a plurality of battery cells can first be connected in series, in parallel, or in a series-parallel combination to form a battery module, and then a plurality of battery modules are connected in series, in parallel, or in a series-parallel combination to form a battery. That is to say, a plurality of battery cells can directly form a battery, or they can first form a battery module, and then the battery module forms a battery.

[0097] Figure 2 The figure 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. The inside of the box body 11 is a hollow structure, and a plurality of battery cells 20 are accommodated in the box body 11. Figure 2 The figure 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. The first box body part 111 and the second box body part 112 are snapped 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 combined plurality of battery cells 20. At least one of the first box body part 111 and the second box body part 112 has an opening. For example, as Figure 2 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 surface 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 embodiment of the present application is not limited to this.

[0098] For another example, different from 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 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] Figure 3 FIG. shows a schematic structural diagram of a battery cell 20 according to an embodiment of the present application. 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 FIG. shows a partial exploded structural diagram of a battery cell 20 according to an embodiment of the present application. For example, Figure 4 it can be Figure 3 the partial exploded structural diagram of the battery cell 20 shown. Figure 5 FIG. shows a cross-sectional schematic diagram of a housing 211 of a battery cell 20 according to an embodiment of the present application. For example, Figure 5 it can be Figure 3 and Figure 4 the cross-sectional view of the housing 211 of the battery cell 20 shown. This cross-section is the cross-section of the housing 211.

[0100] In the embodiment of the present application, as Figures 3 to 5 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 cylinder 211b and a cover body 211a connected to the cylinder 211b. The cylinder 211b is arranged 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 cylinder 211b. The housing 211 is a multi-layer structure, and the resistivity of the multi-layer structure is different.

[0101] As Figures 3 to 5 shown, the battery cell 20 of the embodiment of the present application can include: a housing. Specifically, the housing can include: a housing 211, and the housing 211 is a hollow structure with at least one opening. Further, the battery cell 20 can further include a cover plate 212. For example, the housing includes a cover plate 212, and the cover plate 212 is used to cover the opening of the housing 211 so that the electrode assembly 22 can be accommodated in the housing.

[0102] It should be understood that the housing 211 in the embodiments of the present application is a component for accommodating the electrode assembly 22, and the housing 211 may be a hollow structure with an opening formed at one end or multiple ends. For example, if the housing 211 is a hollow structure with an opening formed at one end, the cover plate 212 may be correspondingly provided as one; if the housing 211 is a hollow structure with openings formed at opposite ends, the cover plate 212 may be provided as two, and the two cover plates 212 respectively cover the openings at both ends of the housing 211.

[0103] The housing 211 can be of various shapes, such as a cylinder, a cuboid, or other polyhedrons. Exemplarily, as Figures 3 to 5 shown, here the housing 211 is described as an example of a hollow cylinder structure. Additionally, in the embodiments of the present application, the housing 211 is mainly taken as an example of a hollow structure with an opening formed at one end.

[0104] It should be understood that the cover plate 212 in the embodiments of the present application is a component for covering the opening of the housing 211 to isolate the internal environment of the battery cell 20 from the external environment. The shape of the cover plate 212 can be adapted to the shape of the housing 211. As Figures 3 to 5 shown, if the housing 211 is a cylinder structure, the cover plate 212 is a circular plate-like structure adapted to the housing 211. Or, if the housing 211 is a cuboid structure, the cover plate 212 is a rectangular plate-like structure adapted to the housing 211.

[0105] In the battery cell 20, the electrode assembly 22 is a component in which an electrochemical reaction occurs in the battery cell 20. According to actual usage requirements, the electrode assembly 22 in the housing 211 can be set to one or multiple. For example, as Figures 3 to 5 shown, there is 1 electrode assembly 22 provided in the battery cell 20. The electrode assembly 22 can be a cylinder, a cuboid, etc. If the electrode assembly 22 is a cylinder structure, the housing 211 can also be a cylinder structure or a cuboid structure. For example, for the cylindrical housing 211, correspondingly, the cylindrical body 211b is a cylinder, and the cover body 211a is a circular plate-like structure. Or, if the electrode assembly 22 is a cuboid structure, the housing 211 is usually a cuboid structure.

[0106] The electrode assembly 22 in the embodiments of the present application may 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 provided 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 the layer structure with a lower resistivity, and the structural strength of the housing 211 can be improved through the layer structure with a higher resistivity. This 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.

[0107] In an embodiment of the present application, the electrode assembly 22 further includes a second tab 2222, and the second tab 2222 has a polarity opposite to that of the first tab 2221. Specifically, from the perspective of 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, and the first tab 2221 and the second tab 2222 protrude from the main body portion 221. The first tab 2221 is the portion of the first electrode plate where the active material layer is not coated, and the second tab 2222 is the portion of the second electrode plate 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.

[0108] The first tab 2221 and the second tab 2222 can extend from the same side of the main body portion 221, that is, the first tab 2221 and the second tab are located on the same end face of the electrode assembly 22. Alternatively, the first tab 2221 and the second tab 2222 can also extend from different sides of the main body portion 221, that is, the first tab 2221 and the second tab are located on different end faces of the electrode assembly 22. For example, the first tab 2221 and the second tab 2222 can also extend from opposite sides respectively, that is, the first tab 2221 and the second tab 2222 are respectively located on the end faces of the electrode assembly 22 that are oppositely arranged, so as to facilitate processing. As Figures 3 to 5 shown, the first tab 2221 and the second tab 2222 can be respectively arranged on both sides of the main body portion 221 along the first direction Z. In other words, the first tab 2221 and the second tab 2222 are respectively arranged at both ends of the electrode assembly 22 along the first direction Z. Wherein, the first direction Z can be the height direction Z of the electrode assembly 22.

[0109] It should be understood that the electrode assembly 22 includes a first electrode plate, a second electrode plate and a separator. The separator is used to separate the first electrode plate and the second electrode plate. The first electrode plate and the second electrode plate have opposite polarities. In other words, one of the first electrode plate and the second electrode plate is the positive electrode plate 223, and the other of the first electrode plate and the second electrode plate is the negative electrode plate 224.

[0110] The first electrode plate, the second electrode plate and the separator are all in a strip structure, and the first electrode plate, the second electrode plate and the separator are wound together to form a wound structure. The wound structure can be a cylindrical structure, a flat structure or a structure of other shapes.

[0111] 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 can 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 can 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 can also fill the conductive material between two adjacent turns of pole lug layers to reduce the gap between the pole lug layers.

[0112] Optionally, the second pole tab 2222 is wound around the central axis of the electrode assembly 22 for multiple turns, and the second pole tab 2222 includes multiple turns of pole tab layers. Exemplarily, the second pole tab 2222 is also flattened to reduce the gap between the pole tab layers of the second pole tab 2222.

[0113] In the embodiment of the present application, the battery cell 20 further includes: a second electrode terminal 214b, the second electrode terminal 214b is electrically connected to the second pole ear 2222, and the first electrode terminal 214a and the second electrode terminal 214b are located on the same wall of the battery cell 20, so as to improve the integration of the battery cell 20, improve the space utilization of the battery cell 20 in the battery 10, and facilitate processing and assembly.

[0114] 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.

[0115] 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 arranged 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 electrode of the battery cell, and the other is the negative output electrode of the battery cell. At least part of the shell 211 itself can be used as an output electrode of the battery cell 20, thereby 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 shell 211 can be electrically connected to the confluence component, which can not only increase the flow area, but also make the structural design of the confluence component more flexible.

[0116] For ease of description, the following mainly takes the cover body 211a as an example of the first electrode terminal 214a, but the embodiments of the present application are not limited thereto.

[0117] Figures 3 to 5 A partial cross-sectional schematic diagram of the battery 10 provided by some embodiments of the present application. The battery 10 may include a plurality of battery cells 20; Figure 6 Another partial cross-sectional schematic diagram of the battery 10 provided by some embodiments of the present application. For example, the Figure 7 may be Figure 7 An enlarged schematic diagram of the battery 10 shown in region B'.

[0118] As Figure 6 shown, the cover body 211a is provided with an electrode lead-out hole 211c. 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 pole of the battery cell 20, and the other is the negative output pole of the battery cell 20.

[0119] 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.

[0120] It should be understood that the cover body 211a and the cylindrical body 211b of the embodiments 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 embodiments of the present application mainly take the cover body 211a and the cylindrical body 211b as an integrally formed structure as an example.

[0121] The housing 211 of the embodiments of the present application may 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.

[0122] In some embodiments, the cover body 211a is provided with an electrode lead-out hole 211c. 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 portion 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 portion W1.

[0123] 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.

[0124] The electrode lead-out hole 211c of the embodiment of the present application is formed after the housing 211 is stretch-formed. For example, in this embodiment, an opening process is used to form the electrode lead-out hole 211c for installing the second electrode terminal 214b on the cover body 211a, so as to arrange the positive output electrode and the negative output electrode at one end of the battery cell 20 facing away from the opening of the housing 211; the cover body 211a is formed during the forming process of the housing 211, and the flatness can still be guaranteed after the electrode lead-out hole 211c is opened, ensuring the connection strength between the cover body 211a and the first connection member 81. At the same time, the flatness of the cover body 211a is not restricted by its own size, so the cover body 211a can have a larger size, thereby improving the over-current capacity of the battery cell 20.

[0125] In some embodiments, the cylindrical body 211b is cylindrical, the electrode lead-out hole 211c is a circular hole, and the central axis of the cylindrical body 211b and the central axis of the electrode lead-out hole 211c are arranged to coincide. "Arranged to coincide" does not require the central axis of the cylindrical body 211b and the central axis of the electrode lead-out hole 211c to be absolutely completely coincident, and there can be deviations allowed by the process.

[0126] 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 arranged to coincide with the central axis of the cylindrical body 211b, so that at least part of the second electrode terminal 214b can be located at the central position of the cover body 211a. In this way, when multiple battery cells 20 are assembled into a group, the requirement for the position accuracy of the second electrode terminal 214b can be reduced, the assembly process can be simplified, and the assembly efficiency can be improved.

[0127] 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 arranged to be offset from the electrode lead-out hole 211c, and this embodiment does not limit this.

[0128] The first tab 2221 is electrically connected to the cover 211a. The first tab 2221 can be directly electrically connected to the cover 211a, or can be indirectly electrically connected to the cover 211a through other conductive structures. For example, the first tab 2221 can be electrically connected to the cover 211a through the cylinder 211b.

[0129] The second tab 2222 is electrically connected to the second electrode terminal 214b. The second tab 2222 can be directly electrically connected to the second electrode terminal 214b, or can be indirectly electrically connected to the second electrode terminal 214b through other conductive structures. For example, the second tab 2222 can be electrically connected to the second electrode terminal 214b through the current collector member 23.

[0130] The second electrode terminal 214b is insulated from 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.

[0131] The second electrode terminal 214b is fixed to the cover 211a. The second electrode terminal 214b can be integrally fixed on the outside of the cover 211a, or can extend into the interior of the housing 211 through the electrode lead hole 211c.

[0132] When the first tab 2221 is a negative tab and the second tab 2222 is a positive 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 tab and the second tab 2222 is a negative 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.

[0133] In the battery 10, a plurality of battery cells 20 are electrically connected through a bus bar component. The bus bar component includes a first connection member 81 and a second connection member 82. The first connection member 81 is used to connect to the cover 211a of the battery cell 20, and the second connection member 82 is used to connect to the second electrode terminal 214b of the battery cell 20.

[0134] The first connection member 81 can be connected to the cover 211a by welding, bonding or other means to achieve the electrical connection between the first connection member 81 and the cover 211a. The second connection 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 connection member 82 and the second electrode terminal 214b.

[0135] Exemplarily, the first connection member 81 connects the cover 211a of one battery cell 20 and the second electrode terminal 214b of another battery cell 20, while the second connection 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 connection member 81 and the second connection member 82 connect three battery cells 20 in series.

[0136] 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 connection member 81 and the second connection 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 multiple battery cells 20 into a group.

[0137] It should be understood that as Figures 3 to 7 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 211a by riveting. For example, at least a part of the terminal body 2141 is located within the electrode lead-out hole 211c, and both ends of the terminal body 2141 are riveted to the electrode lead-out hole 211c.

[0138] In some embodiments, the terminal body 2141 can be provided with a recess that depresses from the outer surface of the terminal body 2141 in the direction facing the electrode assembly 22. The bottom of the recess is used for welding to the current collector member 23.

[0139] 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 211a, an external welding device can weld the bottom of the recess and the current collector member 23 from the side of the bottom of the recess facing away from the current collector member 23.

[0140] In this embodiment, by providing the recess, the thickness of the terminal body 2141 is reduced, which can reduce the welding power required for welding the bottom of the recess to the current collector member 23, reduce heat generation, and reduce the risk of other components (such as the first insulating member 61 and the second insulating member 60) being burned.

[0141] In some embodiments, the second electrode terminal 214b further includes a sealing plate 2142 for closing the opening of the recess. The sealing plate 2142 may 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 damage to the bottom of the recess by external impurities, and improve the sealing performance of the battery cell 20.

[0142] 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 overcurrent capacity.

[0143] In some embodiments, at least a part 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, first attach the second connecting member 82 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 weld the second connecting member 82 and the sealing plate 2142. At least a part 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, and ensure close attachment of the second connecting member 82 and the sealing plate 2142.

[0144] In the embodiments of the present application, the battery cell 20 further includes: a first insulating member 61 for insulating at least a part of the second electrode terminal 214b from the cover body 211a. Exemplarily, at least a part 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 and reduce the risk of short circuit.

[0145] In the embodiments 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, reduce the risk of contact conduction between the electrode assembly 22 and the cover body 211a when the battery cell 20 vibrates, and improve the safety performance.

[0146] 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, which is 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.

[0147] In some embodiments, the second pole tab 2222 is disposed at one end of the electrode assembly 22 facing the cover 211a, and the first pole tab 2221 is disposed at the other end of the electrode assembly 22 away from the cover 211a. The barrel 211b is used to connect the first pole tab 2221 and the cover 211a so that the first pole tab 2221 is electrically connected to the cover 211a.

[0148] The barrel 211b can be directly electrically connected to the first pole lug 2221, or can be electrically connected to the first pole lug 2221 through other components. For example, the first pole lug 2221 is electrically connected to the barrel 211b through the cover plate 212.

[0149] In the embodiment of the present application, the first pole tab 2221 and the second pole tab 2222 are arranged at both ends of the electrode assembly 22, which can reduce the risk of the first pole tab 2221 and the second pole tab 2222 being conductive, and increase the flow area of ​​the first pole tab 2221 and the flow area of ​​the second pole tab 2222.

[0150] In some embodiments, the first pole tab 2221 is a negative pole tab, and the base material of the shell 211 is steel. The shell 211 is electrically connected to the negative pole tab, that is, the shell 211 is in a low potential state. The steel shell 211 is not easily corroded by the electrolyte in a low potential state, thereby reducing safety risks.

[0151] In some embodiments, the battery cell 20 further includes a current collecting member 23 for connecting the second pole tab 2222 and the second electrode terminal 214b. The current collecting member 23 can be connected to the second pole tab 2222 by welding, abutting, or bonding, and connected to the second electrode terminal 214b by welding, abutting, bonding, riveting, etc., so as to achieve electrical connection between the second pole tab 2222 and the second electrode terminal 214b.

[0152] In the first direction Z, the second electrode terminal 214b is arranged opposite to the middle area of ​​the second pole ear 2222. If the second electrode terminal 214b and the second pole ear 2222 are directly connected, the conductive path between the edge area of ​​the second pole ear 2222 and the second electrode terminal 214b will be too long, resulting in uneven current density of the second pole piece of the electrode assembly 22, increasing the internal resistance, and affecting the current capacity and charging efficiency of the battery cell 20.

[0153] In the embodiment of the present application, there can be a relatively large connection area between the current collector member 23 and the second tab 2222. The current of the second tab 2222 can flow into the second electrode terminal 214b via the current collector member 23. In this way, the current collector member 23 can reduce the difference in the conduction paths 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 overcurrent capacity and charging efficiency of the battery cell 20.

[0154] 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.

[0155] 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, where K1 satisfies: 1×10^-8 Ω·m ≤ K1 ≤ 6×10^-8 Ω·m. Among them, the first housing layer 2115 is any one of the multi-layer housing 211. For example, Figures 3 to 7 taking the innermost housing as the first housing layer 2115 as an example, but the embodiment of the present application is not limited thereto. By setting the resistivity K1 of the first housing layer 2115 included in the housing 211 to be relatively small, the overcurrent capacity of the housing 211 can be improved, and thus the performance of the battery cell 20 can be improved.

[0156] In some embodiments, the resistivity K1 of the first housing layer 2115 can also satisfy 1×10^-8 Ω·m ≤ K1 ≤ 2.8×10^-8 Ω·m. This can not only improve the overcurrent capacity and performance of the housing 211 but also facilitate implementation. In some embodiments, the value of the resistivity K1 of the first housing layer 2115 can also be set to other values. For example, the value of the resistivity K1 of the first housing layer 2115 can be any one of the following values or between any two of the following values: 1×10^-8 Ω·m, 1.3×10^-8 Ω·m, 1.5×10^-8 Ω·m, 1.8×10^-8 Ω·m, 2×10^-8 Ω·m, 2.3×10^-8 Ω·m, 2.5×10^-8 Ω·m, 2.8×10^-8 Ω·m, 3×10^-8 Ω·m, 3.3×10^-8 Ω·m, 3.5×10^-8 Ω·m, 3.8×10^-8 Ω·m, 4×10^-8 Ω·m, 4.3×10^-8 Ω·m, 4.5×10^-8 Ω·m, 4.8×10^-8 Ω·m, 5×10^-8 Ω·m, 5.3×10^-8 Ω·m, 5.5×10^-8 Ω·m, 5.8 and 6×10^-8 Ω·m.

[0157] It should be understood that the specific thickness of the first housing 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 housing layer 2115 can be set according to a certain ratio based on the thickness of the housing 211.

[0158] In some embodiments, the average thickness of the first housing layer 2115 is T13, and the average thickness of the housing 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 housing 211 is fixed, T13 will be too small, which will increase the processing difficulty and also cause the over-current heat to be too large, easily leading to thermal runaway. On the contrary, if T13 / T10 is set too large, when the average thickness T10 of the housing 211 is fixed, T13 will be too large, and the thickness of other structural layers will be too small, which will affect the structural strength of the housing 211.

[0159] Furthermore, T13 and T10 satisfy: 0.2 ≤ T13 / T10 ≤ 0.6. This can not only improve the over-current 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.

[0160] 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 less, 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.

[0161] Furthermore, the average thickness T10 of the housing 211 satisfies: 0.075 mm ≤ T10 ≤ 0.4 mm. Appropriately reducing 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.

[0162] 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.

[0163] 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.

[0164] 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, so as to meet the design requirements of the resistivity K1 of the first housing layer 2115.

[0165] In the embodiments of the present application, the housing 211 includes a second housing layer 2116. 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 housing layers of the housing 211. For example, Figure 5 taking the outermost housing layer 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, so as to reduce the difficulty of material selection and processing of the housing 211, save costs, and facilitate processing.

[0166] It should be understood that the value range of the tensile strength Rm2 of the second housing layer 211 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 211 under normal temperature conditions can improve the deformation ability of this part of the second housing layer 211 to resist the expansion amount of the electrode assembly 22, making the second housing layer 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 Rm2 of the second housing layer 211 under normal temperature conditions not to be too large can reduce the difficulty of material selection and processing of the second housing layer 211, save costs, and facilitate processing.

[0167] Furthermore, it can also be set that the tensile strength Rm2 of the second housing layer 211 under normal temperature conditions satisfies 450 MPa ≤ Rm2 ≤ 800 MPa. The tensile strength Rm2 of the second housing layer 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.

[0168] In some embodiments, the value of the tensile strength Rm2 of the second housing layer 211 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.

[0169] 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 can be selected according to actual applications. For example, the national standard GB / T 228.1-2010 can be adopted to test the tensile strength Rm2 under the normal temperature condition of 25°C.

[0170] In the embodiments 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, with a certain average thickness T10 of the housing 211, 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, with a certain average thickness T10 of the housing 211, T14 will be too large, and 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 over-current heat too large, easily resulting in thermal runaway.

[0171] Furthermore, T14 and T10 satisfy: 0.2 ≤ T14 / T10 ≤ 0.6. This can not only improve the over-current 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.

[0172] Moreover, the average thickness T14 of the second housing layer 2116 and the average thickness T13 of the first housing layer 2115 in the embodiments of the present application can be the same or different to meet different design requirements.

[0173] 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 2115, 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 from the calculation of the average thickness T10 of the housing 211, correspondingly, the same areas need to be excluded from the calculation of the average thickness T13 of the first housing layer 2115, and the same areas also need to be excluded from the calculation of 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, and will not be elaborated here one by one.

[0174] 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.

[0175] 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 area of the housing 211 as T10.

[0176] 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.

[0177] 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.

[0178] As used in this 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 breaks, shatters, is torn, or opens, etc. When the pressure relief mechanism actuates, the high-temperature and high-pressure substances inside the battery cell 20 are discharged outwards 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.

[0179] The emissions from the battery cell 20 mentioned in this 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 reactions, flames, etc.

[0180] 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 means 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 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 avoiding the explosion of the battery cell 20.

[0181] 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 explosion-proof valves, gas valves, pressure relief valves or safety valves, and can specifically adopt pressure-sensitive or temperature-sensitive elements or structures. 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 channel for discharging the internal pressure or temperature.

[0182] 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 with the electrode assembly 22 inside the battery cell 20 to output the electric 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 with the positive electrode tab of the electrode assembly 22, and the negative electrode terminal is used to electrically connect with 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, then the negative electrode terminal is the second electrode terminal 214b, or the positive electrode terminal may be the second electrode terminal 214b, then the negative electrode terminal is the first electrode terminal 214a.

[0183] It should be understood that each electrode terminal 214 in the embodiment of the present application may be disposed on any one 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 3 to 7 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 body 211a. However, in the embodiment of the present application, if the cover body 211a is the first electrode terminal 214a, then among the two electrode terminals 214 included in the battery cell 20, there is still one electrode terminal 214 protruding from other regions of the cover body 211a of the housing 211, 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.

[0184] 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.

[0185] In some embodiments, the functional region may further include a welding region. 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 region. 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 4 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 region of the functional region in the embodiments of the present application may also include the weld 2113. Due to processing technology reasons, the thickness of the welding region is usually greater than the thickness of other regions of the housing 211. Therefore, when calculating the average thickness T10 of the housing 211, the welding region may not be included.

[0186] 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 over-current capacity of the housing 211.

[0187] 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 strength design requirements of the second housing layer 2116.

[0188] 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 1 to meet the design requirements.

[0189] Table 1

[0190]

[0191]

[0192] It should be understood that the housing 211 of the embodiment 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.

[0193] In some embodiments, the housing 211 may include a plurality of first housing layers 2115 and one 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 one 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. 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.

[0194] 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.

[0195] It should be understood that the battery cell 20 of the embodiment of the present application may also meet other design requirements. For the convenience of description, the "housing 211" in the following text may include a multi-layer structure. For example, the housing 211 may at least include a first housing layer 2115 and a second housing layer 2116, which will not be elaborated herein.

[0196] The cylindrical battery cell 20 is mainly described as an example in the above text. In the following text, the battery cell 20 in the shape of a cuboid will be described with reference to the drawings. Except for the different shapes, the descriptions of the rectangular battery cell 20 and the cylindrical battery cell 20 in the above text are mutually applicable, and will not be elaborated one by one herein.

[0197] br>Figure 8 The structural schematic diagram of the battery cell 20 according to an embodiment of the present application is shown. For example, Figure 3The battery cell 20 shown can be any battery cell 20 in the battery 10; Figure 9 FIG. 2 shows a partial exploded structural schematic diagram of a battery cell 20 according to an embodiment of the present application. For example, Figure 9 it can be Figure 8 the partial exploded structural schematic diagram of the battery cell 20 shown.

[0198] Exemplarily, such as Figure 8 and Figure 9 shown, in the embodiment of the present application, the case 211 is taken as an example of a hollow cuboid structure for description. In addition, the embodiment of the present application mainly takes the case 211 as an example of a hollow structure with an opening at one end. However, the relevant descriptions of the embodiment of the present application are equally applicable to battery cells 20 of other shapes. For the sake of brevity, they will not be elaborated one by one here.

[0199] It should be understood that the cover plate 212 in the embodiment of the present application is a component for covering the opening of the case 211 to isolate the internal environment of the battery cell 20 from the external environment. The shape of the cover plate 212 can be adapted to the shape of the case 211. Such as Figure 8 and Figure 9 shown, the case 211 is a cuboid structure, and the cover plate 212 is a rectangular plate-like structure adapted to the case 211.

[0200] Specifically, the battery cell 20 in the embodiment of the present application may further include an electrode assembly 22, and the electrode assembly 22 is accommodated in the case 211. In this battery cell 20, the electrode assembly 22 is a component in which an electrochemical reaction occurs in the battery cell 20. According to actual use requirements, the electrode assembly 22 in the case 211 can be set to one or multiple. For example, such as Figure 8 and Figure 9 shown, there are 2 electrode assemblies 22 provided in the battery cell 20. The electrode assembly 22 can be a cylinder, a cuboid, etc. If the electrode assembly 22 is a cylinder structure, the case 211 can also be a cylinder structure. If the electrode assembly 22 is a cuboid structure, the case 211 can also be a cuboid structure.

[0201] It should be understood that, such as Figure 8 and Figure 9 shown, the electrode assembly 22 in the embodiment of the present application may include a tab 222 and an electrode main body part 221. Among them, the tab 222 of the electrode assembly 22 may include a positive tab 222a and a negative tab 222b. The positive tab 222a may be formed by laminating a part of the positive electrode plate 223 that is not coated with the positive electrode active material, and the negative tab 222b may be formed by laminating a part of the negative electrode plate 224 that is not coated with the negative electrode active material; the electrode main body part 221 may be formed by laminating or winding the positive electrode plate 223 and the negative electrode plate 224 with each other.

[0202] In some embodiments, the electrode assembly 22 includes a negative electrode tab 224, 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 yield strength of at least a part of the housing 211 at a temperature of 25 °C is Re, and Re satisfies: 125 MPa ≤ Re ≤ 1000 MPa.

[0203] The negative electrode active material included in the negative electrode tab 224 of the embodiments 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, effectively increasing 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 intercalated into 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.

[0204] Therefore, increasing the tensile strength Rm of at least a part of the housing 211 at room temperature 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 a part of the housing 211 at room temperature should not be too large, so as to reduce the material selection difficulty and processing difficulty of the housing 211, save costs, and facilitate processing. For example, generally, the tensile strength Rm of at least a part of the housing 211 at room temperature can be set to satisfy 250 MPa ≤ Rm ≤ 2000 MPa.

[0205] It should be understood that the value range of the tensile strength Rm of at least a part of the housing 211 of the embodiments 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 tensile strength Rm can satisfy 250 MPa ≤ Rm ≤ 2000 MPa. For another example, the value of the room temperature tensile strength Rm can also satisfy 400 MPa ≤ Rm ≤ 1200 MPa. On the one hand, increasing the tensile strength Rm of at least a 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, 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 a part of the housing 211 at room temperature not to be too large can reduce the material selection difficulty and processing difficulty of the housing 211, save costs, and facilitate processing.

[0206] Further, at least part of the housing 211 can be set such that the tensile strength Rm 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 facilitate implementation and save costs.

[0207] In some embodiments, the value of the tensile strength Rm of at least part of the housing 211 of the embodiment of the present application under normal temperature conditions can also be set to other values. For example, the value of the normal temperature tensile strength Rm 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.

[0208] It should be understood that the tensile strength in the embodiment of the present application refers to the maximum stress value that the material can withstand before being pulled apart. The test method for the tensile strength Rm of at least part of the housing 211 of the embodiment 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 Rm under normal temperature conditions of 25 °C.

[0209] Figure 10 shows a cross-sectional schematic diagram of the electrode assembly 22 of the embodiment of the present application. For example, the Figure 10 shown cross-sectional schematic diagram can be Figure 9 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 11 shows a partial cross-sectional schematic diagram of the positive electrode plate 223 or the negative electrode plate 224 of the embodiment of the present application. For example, the Figure 11 can represent the Figure 10 partial cross-sectional schematic diagram of the negative electrode plate 223 of the electrode assembly 22 shown along its thickness direction, or can also represent the Figure 10Partial cross-sectional schematic view of the positive electrode tab 224 of the electrode assembly 22 shown along its thickness direction.

[0210] As Figure 10 to Figure 11< \br>Figure 8 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. As another example, the electrode assembly 22 can include a plurality of positive electrode tabs 223, and 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. As yet 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 also include a separator 225 for isolating the positive electrode tab 223 and the negative electrode tab 224.

[0211] 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 layer 2241 can be disposed on both sides of the negative current collector 2242 perpendicular to its thickness direction.

[0212] 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).

[0213] It should be understood that the negative electrode active material of the embodiments of the present application can be flexibly set according to actual applications. Specifically, the negative electrode active material of the embodiments of the present application can include silicon-based materials, thereby improving the energy density of the battery. For example, the silicon-based materials can include at least one of elemental silicon, silicon oxides, silicon-carbon composites, silicon-nitrogen composites, silicon-containing alloys, or silicon-oxy-carbon composites.

[0214] In some embodiments, the silicon-based materials can include silicon elements and one or more of alkali metal elements and alkaline earth metal elements. Among them, as an example, the alkali metal elements can include Li. As an example, the alkaline earth metal elements include Mg. As an example, the silicon-based materials can be silicon-based materials pre-embedded with alkali metals and / or alkaline earth metals, such as silicon-based materials pre-embedded with Li and / or Mg.

[0215] It should be understood that the mass ratio g of the silicon-based materials of the embodiments of the present application can be flexibly set according to actual applications.

[0216] For example, the value range of the mass ratio g of the silicon-based materials can be set to satisfy 2% ≤ g ≤ 40%. Adding silicon-based materials to the negative electrode active material of the negative electrode sheet 224 can effectively improve the energy density of the battery cell 20 because the silicon-based materials can accommodate more metal ions compared with other elements. For example, the capacity of the silicon-based materials is about ten times that of graphite. At the same time, the mass ratio g of the silicon-based materials 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 materials 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.

[0217] Furthermore, the value range of the mass ratio g of the silicon-based materials can be set to satisfy 8% ≤ g ≤ 40%. Appropriately reducing the mass ratio g of the silicon-based materials can reduce the processing difficulty of the electrode assembly 22, and can 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.

[0218] 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 can also 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.

[0219] 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%.

[0220] It should be understood that the mass fraction g of the silicon-based material in the negative electrode active material of 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, and 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.

[0221] 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 (for example, 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.

[0222] 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.

[0223] 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.

[0224] The negative electrode sheet 224 does not exclude other additional functional layers in addition to 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.

[0225] In some embodiments, the negative electrode sheet 224 can be prepared by the following method: dispersing a negative electrode active material, an optional negative electrode binder, an optional negative electrode conductive agent, and an optional other auxiliary agent 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.

[0226] In the embodiments of the present application, the value of the mass ratio 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 ratio of the silicon-based material is g, and the material of at least a part of the housing 211 includes iron element, and Rm and g satisfy 2% < g < 40%, 300 MPa < Rm < 2000 MPa. The material of at least a part of the housing 211 including iron element can increase the structural strength of the material of this part of the housing 211 to meet the design requirements.

[0227] In some embodiments, the material of at least a part 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, the material of at least a part of the housing 211 may include Q195 carbon steel, which is convenient for processing and can also meet the value of the tensile strength Rm at 25 °C.

[0228] In some embodiments, the material of at least a part 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, the material of at least a part of the housing 211 may include SPCC carbon steel, which is convenient for processing and can also meet the value of the tensile strength Rm at 25 °C.

[0229] In some embodiments, Rm and g satisfy 8% ≤ g ≤ 40%, 400 MPa ≤ Rm < 2000 MPa. For example, the material of at least part of the housing 211 may include modified stainless steel, which is convenient for processing and can meet the value of the tensile strength Rm at 25°C.

[0230] In some embodiments, Rm and g satisfy 10% ≤ g ≤ 40%, 480 MPa ≤ Rm < 2000 MPa. For example, the material of at least part of the housing 211 may include 316 stainless steel, which is convenient for processing and can meet the value of the tensile strength Rm at 25°C.

[0231] 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 at 25°C.

[0232] In some embodiments, Rm and g satisfy 20% ≤ g ≤ 40%, 600 MPa ≤ Rm < 2000 MPa.

[0233] 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 9 and Figure 12 shown square shell batteries, where the housing 211 has a hollow structure with one end open.

[0234] 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.

[0235] 1. Preparation of the positive electrode plate 223

[0236] 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, 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.

[0237] 2. Preparation of the negative electrode plate 224

[0238] Mix the negative electrode active material, conductive agent Super P, thickening agent carboxymethyl cellulose (CMC), and binder styrene-butadiene rubber (SBR) evenly 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. The solid content in the negative electrode slurry is 30 wt%. The mass ratio of the negative electrode active material, silicon monoxide, Super P, CMC, and binder styrene-butadiene rubber (SBR) in the solid components is 88:7:3:2. Coat the negative electrode slurry on the upper and lower surfaces of the current collector copper foil and dry it at 85 °C, then perform cold pressing, edge trimming, slicing, and strip cutting, and finally dry it in a vacuum at 120 °C for 12 h to prepare the negative electrode plate 224.

[0239] 3. Preparation of the electrolyte

[0240] In an argon atmosphere glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), dissolve the fully dried electrolyte salt LiPF6 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, obtain an electrolyte with a concentration of 1 mol / L.

[0241] 4. Preparation of the separator 225

[0242] Use a 16-μm polyethylene film as the separator 225.

[0243] 5. Preparation of the lithium-ion battery single cell 20

[0244] Stack the positive electrode plate 223, separator 225, and negative electrode plate 224 in sequence, with the separator 225 in the middle of the positive electrode plate 223 and the negative electrode plate 224 to isolate the positive and negative electrodes, wind to obtain a bare battery core, weld the electrode tabs, place the bare battery core 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 single cell 20.

[0245] 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 plate 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 2 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 2. 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.

[0246] A cyclic charge fatigue test is performed on the battery cell 20 in the following embodiments and comparative examples. Specifically, Figure 12 FIG. shows a schematic structural diagram of a fixture 700 for cyclic charge fatigue testing according to an embodiment of the present application. As Rm (MPa) 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.

[0247] 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.

[0248] 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.

[0249] For the specific test steps, refer to 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 change the test cycle cut-off condition to "stop the test until the weld 2113 of battery cell 20 is damaged".

[0250] For example, the test can be carried out according to the following steps: Step a, discharge at 1I (A) until the discharge cut-off 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) until the discharge cut-off condition specified by the enterprise; Step f, cycle according to Steps b to e until the weld 2113 is damaged and stop the test.

[0251] During the above test process, continuously observe the weld 2113 of battery cell 20 until the weld 2113 leaks, record the number of cycles, so as to obtain the 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.

[0252] Table 2

[0253] Shell material g Shell condition after 1000 cycles Comparative Example 1 Aluminum 178 0.03 Shell cracked at 656 times Comparative Example 2 Aluminum 189 0.05 Shell cracked at 437 times Example 1 Not cracked 328 0.025 Q195 Example 2 Not cracked 328 0.15 Q195 Example 3 SPCC 396 0.045 Not cracked Example 4 SPCC 396 0.4 Not cracked Example 5 Modified stainless steel 421 0.08 Not cracked Example 6 Modified stainless steel 421 0.4 Not cracked Example 7 SUS430 459 0.1 Not cracked Example 8 SUS430<\br >Uncracked 459 0.4 Example 9 SUS304 Uncracked 533 0.15 Example 10 SUS304 Uncracked 533 0.4 Example 11 SUS304 Uncracked 625 0.2 Example 12 SUS304 Uncracked 625 0.4 Figure 8 Figure 9

[0254] It should be understood that in Table 2 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.

[0255] Comparing the two comparative examples and the twelve examples in Table 2 above, it can be seen that when different materials are used for the housing 211, different tensile strengths Rm can be correspondingly determined. When the tensile strength Rm satisfies 250 MPa ≤ Rm ≤ 2000 MPa, for example, in Examples 1-12, even if the mass fraction 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, so as 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 fraction 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.

[0256] 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 part of the housing 211 at a temperature of 25 °C is Re, and Re satisfies: 140 MPa ≤ Re ≤ 1000 MPa.

[0257] 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, and further improve 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 room temperature yield strength Re of at least part of the housing 211 can increase the maximum extrusion force borne by the housing 211. Without exceeding the limit of the yield strength 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, the yield strength Re of at least part of the housing 211 at room temperature can be set to satisfy: 140 MPa ≤ Re ≤ 1000 MPa.

[0258] It should be understood that the value range of the yield strength Re of at least part 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 yield strength Re at normal temperature can satisfy 140 MPa ≤ Re ≤ 1000 MPa. For another example, the value of the yield strength Re at normal temperature can satisfy 180 MPa ≤ Re ≤ 600 MPa. On the one hand, increasing the yield strength Re 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, 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. On the other hand, controlling the yield strength Re 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.

[0259] Further, it can also be set that the yield strength Re of at least part of the housing 211 under normal temperature conditions satisfies 220 MPa ≤ Re ≤ 400 MPa. The yield strength Re 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.

[0260] In some embodiments, the value of the yield strength Re of at least part 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 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.

[0261] It should be understood that the yield strength in 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 in 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 region of the housing 211 at a temperature of 25°C is Re.

[0262] The test method for the yield strength Re of at least part of the region of the housing 211 in 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 adopted to test the yield strength Re under normal temperature conditions of 25°C.

[0263] 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 region of the housing 211 at a temperature of 25°C can be mutually restricted, 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.

[0264] 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. 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, 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 region 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 region 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.

[0265] In some embodiments, the material of at least a portion of the housing 211 includes carbon steel or stainless steel, and g and Re satisfy 4.5% ≤ g ≤ 40% and 170 MPa ≤ Re < 600 MPa. For example, the material of at least a portion of the housing 211 may include SPCC carbon steel, which is convenient for processing and can meet the value of the yield strength Re under the condition of 25°C.

[0266] In some embodiments, g and Re satisfy 8% ≤ g ≤ 40% and 180 MPa ≤ Re < 600 MPa. For example, the material of at least a portion of the housing 211 may include modified stainless steel, which is convenient for processing and can meet the value of the yield strength Re under the condition of 25°C.

[0267] In some embodiments, g and Re satisfy 10% ≤ g ≤ 40% and 190 MPa ≤ Re < 600 MPa. For example, the material of at least a portion of the housing 211 may include 316 stainless steel, which is convenient for processing and can meet the value of the yield strength Re under the condition of 25°C.

[0268] In some embodiments, g and Re satisfy 15% ≤ g ≤ 40% and 200 MPa ≤ Re < 600 MPa. For example, the material of at least a portion 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.

[0269] In some embodiments, g and Re satisfy 20% ≤ g ≤ 40% and 210 MPa ≤ Re < 600 MPa.

[0270] 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 12 and Figure 8 shown square shell batteries, where the housing 211 has a hollow structure with one end open.

[0271] 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.

[0272] 1. Preparation of the positive electrode sheet 223

[0273] Mix the positive active material LiNi 0.95 Co 0.04 Mn 0.01 O 2, the conductive agent Super P and the 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 and dried at 85°C, followed by cold pressing. Then, after trimming, slicing, and striping, it is dried in a vacuum at 85°C for 4 h to make the positive electrode plate 223.

[0274] 2. Preparation of the negative electrode plate 224

[0275] 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 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%. 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 paste is coated on the upper and lower surfaces of the current collector copper foil and dried at 85°C, followed by cold pressing, trimming, slicing, and striping. Then, it is dried in a vacuum at 120°C for 12 h to make the negative electrode plate 224.

[0276] 3. Preparation of the electrolyte

[0277] 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.

[0278] 4. Preparation of the separator 225

[0279] A 16-μm polyethylene film is used as the separator 225.

[0280] 5. Preparation of the lithium-ion battery monomer 20

[0281] 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 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.

[0282] In the following respective embodiments and comparative examples, the yield strength of the housing 211 of the battery monomer 20 at a temperature of 25 °C is Re, and to obtain different yield strengths Re, different materials are correspondingly selected for the housing 211; the negative electrode active material of the negative electrode plate 224 of the electrode assembly 22 of the battery monomer 20 includes a silicon-based material, and the mass ratio of the silicon-based material is g; the specific parameter settings are as shown in Table 3 below. Additionally, in each embodiment and comparative example, the material of the entire area 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 monomers 20 in the following respective embodiments and comparative examples have the same other setting conditions except for the different parameter settings shown in Table 3. For example, the wall thickness of each wall of the housing 211 of the battery monomer 20 in each embodiment is 0.25 mm; for another example, the capacity of the battery monomer 20 in each embodiment is 350 Ah.

[0283] Perform a cyclic charge fatigue test on the battery monomers 20 in the following respective embodiments and comparative examples. Specifically, it can be carried out using a fixture 700 for cyclic charge fatigue test as Figure 9 shown.

[0284] Specifically, clamp and fix the battery monomer 20 into the special fixture 700, ensure that the two relatively largest-area walls of the battery monomer 20 are clamped, set the initial pressure to 2000 N, and connect the electrode terminals 214 of the battery monomer 20 to a special battery charge and discharge device.

[0285] Place the fixture 700 holding the battery monomer 20 in a constant temperature environment of 25 ± 2 °C, and start the test after the battery monomer 20 reaches temperature equilibrium.

[0286] 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 change the test cycle cut-off condition to "stop the test until the weld 2113 of the battery monomer 20 is damaged".

[0287] 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 under 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 under the idle condition specified by the enterprise; Step e, discharge at 1I1(A) until the discharge termination condition specified by the enterprise; Step f, repeat the cycle from Step b to Step e until the weld 2113 is damaged and stop the test.

[0288] 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 3 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.

[0289] Table 3

[0290]

[0291]

[0292] It should be understood that in Table 3 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. Only 145 MPa and 173 MPa are taken as examples in the above embodiments, but it is not limited thereto. Similarly, the material of the housing 211 can be SUS316 stainless steel, and the yield strength Re of the SUS316 stainless steel at room temperature of 25°C is usually at least 177 MPa. Only 182 MPa and 193 MPa are taken as examples in the above embodiments; the material of the housing 211 can be Q195 carbon steel, and the yield strength Re of the Q195 carbon steel at room temperature of 25°C is usually at least 195 MPa. Only 203 MPa is taken as an example in the above embodiments; the material of the housing 211 can be SUS304 stainless steel, and the yield strength Re of the SUS304 stainless steel at room temperature of 25°C is usually at least 205 MPa. Only 212 MPa is taken as an example in the above embodiments.

[0293] Comparing the 2 comparative examples and the 12 examples in Table 3 above, it can be seen that when the housing 211 uses different materials, different yield strengths Re can be correspondingly determined. When the yield strength Re satisfies 140 MPa ≤ Re ≤ 1000 MPa, for example, in Examples 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 number of 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 number of failure fatigue times of the battery cell 20 cannot reach one thousand times and cannot meet the design requirements of the battery cell 20.

[0294] In some embodiments, the electrode assembly 22 further includes a positive electrode tab 223, the positive electrode tab 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.

[0295] The positive electrode tab 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 can 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.

[0296] 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 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 to reduce the material selection difficulty and processing difficulty 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.

[0297] It should be understood that the value range of the melting point p of at least part of the housing 211 in the embodiments of the present application can be adjusted according to actual applications. For example, the melting point p of at least part of the housing 211 generally satisfies 1200°C ≤ p ≤ 2000°C. For another example, the melting point p of at least 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 the battery cell 20 undergoes thermal runaway, making the housing 211 not easily melted, thereby reducing the risk of adjacent battery cells 20 undergoing thermal runaway, that is, reducing 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 thus save costs and facilitate processing.

[0298] Furthermore, it can also be set that the melting point p of at least part of the housing 211 satisfies 1400°C ≤ p ≤ 1600°C. When the battery cell 20 undergoes thermal runaway, it can improve the structural strength of the housing 211, make the housing 211 not easily melted, maintain the structural integrity of this part of the housing 211, and reduce the risk of adjacent battery cells 20 undergoing thermal runaway. At the same time, it can also reduce the processing difficulty and save costs.

[0299] In some embodiments, the value range of the melting point p of at least part of the housing 211 can also be set to other values. For example, the value of the melting point p can be any one of the following values or 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.

[0300] In the embodiments of the present application, the positive electrode plate 223 includes a positive electrode active material. For example, the positive electrode active material coated on the positive electrode plate 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, 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.

[0301] In some embodiments, the positive electrode current collector 2232 may be a metal foil or a composite current collector. As an example of the metal foil, aluminum foil may be used. The composite current collector may 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 may 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 may include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0302] 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 may 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 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.

[0303] Furthermore, the proportion of the molar amount of nickel element in the layered lithium-containing transition metal oxide may 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.

[0304] In some embodiments, the value of 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 value of 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%.

[0305] It should be understood that the test method for the molar amount of nickel element in the layered lithium-containing transition metal oxide of the embodiments of the present application and the total molar amount of transition metal elements in the layered lithium-containing transition metal oxide can be selected according to actual applications, and can be determined by instruments and methods known 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.

[0306] In some embodiments, the layered lithium-containing transition metal oxide may 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 be 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, whereby the energy density of the battery cell 20 can be further improved.

[0307] 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, LiNi0.85Co0.15Al0.05O2.

[0308] 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.

[0309] 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 resin.

[0310] In some embodiments, the positive electrode plate 223 may be prepared by the following method: The positive electrode active material layer 2231 is usually 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 usually formed by dispersing the positive electrode active material, the positive electrode binder, the 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.

[0311] 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 br>T(mm) and C(Ah) shown square shell batteries, where the housing 211 has a hollow structure with one end open.

[0312] In the following embodiments and comparative examples, the preparation methods of the positive electrode plate 223, the negative electrode plate 224, the electrolyte, and the separator 225 of the battery cell 20 are as follows.

[0313] 1. Preparation of the positive electrode plate 223

[0314] The positive electrode active material LiNi 0.95 Co 0.04 Mn 0.01 O 2 , the conductive agent Super P, and the binder polyvinylidene fluoride (PVDF) are made into a positive electrode slurry in N-methylpyrrolidone (NMP), where the solid content in the positive electrode slurry is 50 wt%, and in the solid components, LiNi 0.7 Co 0.1 Mn 0.1 O 2, the 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 produce the positive electrode plate 223.

[0315] 2. Preparation of the negative electrode plate 224

[0316] 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 produce 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 produce the negative electrode plate 224.

[0317] 3. Preparation of the electrolyte

[0318] 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.

[0319] 4. Preparation of the separator 225

[0320] A 16-μm polyethylene film is used as the separator 225.

[0321] 5. Preparation of the lithium-ion battery single cell 20

[0322] 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 electrode tabs are welded, the bare battery core is placed in a housing made of different materials, and the above-prepared electrolyte 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.

[0323] In the following embodiments and comparative examples, the melting point of the housing 211 of the battery cell 20 is p, and different materials are selected for the housing 211 to obtain different melting points; the capacity of the battery cell 20 is C; the wall thickness of the wall with the largest area of the battery cell 20 is T, and the specific parameter settings are shown in Table 4 below. In addition, in each embodiment and comparative example, the material of all regions of the housing 211 is the same. 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 4. For example, in each embodiment, the positive electrode active material of the positive electrode tab 223 of the electrode assembly 22 of the battery cell 20 includes a nickel-containing element compound, wherein the nickel-containing element 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 transition metal elements in the layered lithium-containing transition metal oxide.

[0324] For the battery cells 20 in the following comparative examples and embodiments, 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.

[0325] Table 4

[0326] p(℃) Shell material Test results Comparative example 1 Aluminum Shell melting 660 0.7 350 Comparative example 2 Aluminum Shell melting 660 0.15 72 Example 1 High carbon ferromanganese Shell intact 1250 0.15 350 Example 2 High carbon ferromanganese Shell intact 1250 0.15 72 Example 3 Low carbon steel br>Shell integrity 1425 0.15 350 Example 4 Low carbon steel Shell integrity 1425 0.15 72 Example 5 Stainless steel Shell integrity 1510 0.15 350 Example 6 Stainless steel Shell integrity 1510 0.15 72 Figure 8 Figure 9

[0327] Comparing the two comparative examples and six embodiments in Table 4 above, it can be seen that when different materials are used for the housing 211, different melting points p can be determined correspondingly. When the melting point p satisfies 1200°C ≤ p ≤ 2000°C, for example, in Embodiments 1-6, the housing 211 of the battery cell 20 does not melt and can meet the design requirements of the battery cell 20; and, when other parameters of the battery cell 20 fluctuate differently, such as different capacities C of the battery cell 20 or different thicknesses of the wall with the largest area of the housing 211, the battery cell 20 does not melt and can meet the design requirements of the battery 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 cell 20 will melt and cannot meet the design requirements of the battery cell 20.

[0328] In some embodiments, the electrode assembly 22 further includes a positive electrode tab 223, the positive electrode tab 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 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.

[0329] 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.

[0330] Therefore, appropriately increasing the tensile strength Rn of at least part of the housing 211 under the high-temperature condition 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 the housing 211 not easily damaged and exploded quickly, thereby reducing the risk of thermal runaway of adjacent battery cells 20 and improving the reliability of the battery 10. However, the tensile strength Rn of at least part of the housing 211 under the high-temperature condition 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.

[0331] It should be understood that the value range of the tensile strength Rn of at least part of the housing 211 of the embodiment of the present application under the high-temperature condition 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 the housing 211 not easily damaged and exploded quickly, thereby reducing the risk of thermal runaway of adjacent battery cells 20 and improving the reliability of the battery 10. At the same time, it is controlled that the tensile strength Rn of at least part of the housing 211 under the high-temperature condition cannot be too large to reduce the processing difficulty, and thus the cost can be saved and the processing is facilitated.

[0332] Furthermore, 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 this part of the housing 211 when thermal runaway occurs in the battery cell 20, improve the structural strength of the housing 211, make the housing 211 not easily damaged and exploded quickly, thereby reducing the risk of thermal runaway of adjacent battery cells 20 and improving the reliability of the battery 10. At the same time, the processing difficulty can also be reduced and the cost can be saved.

[0333] In some embodiments, the value of the high-temperature tensile strength Rn of 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.

[0334] 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 Rn of at least part of the housing 211 of the embodiments of the present application under the high-temperature condition of 500 °C can be selected according to actual applications. For example, the national standard GB / T228.1-2010 can be used to test the tensile strength Rn under the high-temperature condition of 500 °C.

[0335] 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 Rn(MPa) and T(mm) shown square shell batteries as an example, where the housing 211 has a hollow structure with one end open.

[0336] 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.

[0337] 1. Preparation of the positive electrode sheet 223

[0338] 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, LiNi 0.7 Co 0.1 Mn0.1 O 2 The mass ratio of O, 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, 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.

[0339] 2. Preparation of the negative electrode plate 224

[0340] 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 the negative electrode slurry. The negative electrode active material includes graphite and silicon-based material, and the silicon-based material is silicon oxide. 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, 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.

[0341] 3. Preparation of the electrolyte

[0342] 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.

[0343] 4. Preparation of the separator 225

[0344] A 16-μm polyethylene film is used as the separator 225.

[0345] 5. Preparation of the lithium-ion battery single cell 20

[0346] The positive electrode plate 223, separator 225, and 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, and the bare battery core is placed in a casing made of different materials. The above-prepared electrolyte is injected into the dried casing, and then it is encapsulated, left standing, formed, shaped, and capacity tested, etc., to complete the preparation of the lithium-ion battery single cell 20.

[0347] In the following embodiments and comparative examples, the tensile strength of the housing 211 of the battery cell 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 cell 20 is C; the wall thickness of the wall with the largest area of the battery cell 20 is T, and 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 Rn of the housing 211 at 500 °C is measured by the method specified in GB / T 228.1-2010. And, except for the different parameter settings shown in Table 5, the other setting conditions of the battery cell 20 in the following embodiments and comparative examples are the same. For example, in each embodiment, the positive electrode active material of the positive electrode plate 223 of the electrode assembly 22 of the battery cell 20 includes a nickel-containing element compound, wherein the nickel-containing element 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.

[0348] For the battery cell 20 in the following comparative examples and embodiments, 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.

[0349] Table 5

[0350] C(Ah) Shell material Test results Comparative example 1 Aluminum Shell cracking 13 0.7 350 Comparative example 2 Aluminum Shell cracking 12 0.15 72 Example 1 Low carbon steel Shell integrity 115 0.15 350 Example 2 Low carbon steel Shell integrity 113 0.15 72 Example 3 Low carbon steel Shell integrity 129 0.15 350 Example 4 Stainless steel Shell integrity 194 0.15 350 Example 5<\br >Stainless steel Complete shell Example 6 191 0.15 72 Stainless steel Complete shell Figure 8 234 0.15 350 Figure 9 Figure 8

[0351] Comparing the two comparative examples and six embodiments in Table 5 above, it can be seen that when different materials are used for the housing 211, different tensile strengths Rn can be determined accordingly. When the tensile strength Rn satisfies 100 MPa ≤ Rn ≤ 1200 MPa, for example, in Embodiments 1-6, the housing 211 of the battery cell 20 does not crack and can meet the design requirements of the battery cell 20; and, when other parameters of the battery cell 20 fluctuate differently, such as the capacity C of the battery cell 20 is different, or the thickness of the wall with the largest area of the housing 211 is different, the battery cell 20 does not crack and can 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 cracks and cannot meet the design requirements of the battery cell 20.

[0352] In an embodiment of the present application, the housing 211 at least partially includes a third housing wall 2112, and an average thickness of the third housing wall 2112 is T, where T satisfies: 0.05 mm ≤ T ≤ 0.5 mm, 60 mm·MPa ≤ T×Rm ≤ 500 mm·MPa.

[0353] 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 open end, 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 a surface of the third housing wall 2112 can be any polygon. For another example, as Figure 9 and Figure 8 shown, if the housing 211 is a cuboid, the third housing wall 2112 can be any wall of the housing 211, and a 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 a bottom surface of the cylinder or a side surface of the cylinder, and the embodiment of the present application is not limited thereto. Additionally, if 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 a connection area of the fillet between the wall and the adjacent wall.

[0354] In the embodiment of the present application, at least a part of the housing 211 includes the third housing wall 2112, and a tensile strength of the third housing wall 2112 under normal temperature conditions of 25°C is Rm. Increasing the tensile strength Rm of at least a part of the housing 211 under normal temperature conditions of 25°C can improve a deformation ability of the housing 211, so that the housing 211 is not easily damaged during use of the battery cell 20, thereby improving a structural stability and a 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 a material selection difficulty and a processing difficulty of the housing 211, save costs, and facilitate processing.

[0355] 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. This can not only increase the energy density of the battery cell 20, but also improve the structural strength and stability of the battery cell 20. 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 increased, and the difficulty of material selection for 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.

[0356] 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 increasing 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.

[0357] 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 increasing the energy density of the battery 10.

[0358] 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.

[0359] 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 increased, 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.

[0360] 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.

[0361] 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.

[0362] In the embodiments of the present application, the value of the mass ratio g of the silicon-based material and the value of the average thickness T of the third housing wall 2112 can limit each other, and can also limit each other 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 ratio 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 ratio g of the silicon-based material is 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.

[0363] In some embodiments, the mass ratio 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.

[0364] 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 thicknesses of most regions of the third housing wall 2112 are basically equal or have a small difference, or the thicknesses of all regions of the third housing wall 2112 are basically equal or have a small difference, then the average thickness of all regions of the third housing wall 2112 can be determined as T.

[0365] 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 this part of the special region is quite different from that of other regions. For example, there are convex structures or concave regions in this part of the special region, making the thickness of this part of the special region larger or smaller than that of other regions, then this part of the special region can be excluded to calculate the average thickness of the remaining region of the third housing wall 2112 as T.

[0366] 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.

[0367] 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, and the pressure relief region is used to provide a pressure relief mechanism, and 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 membrane in the battery cell 20.

[0368] As used in this 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.

[0369] The emissions from the battery cell 20 mentioned in this application include, but are not limited to: electrolyte, dissolved or fragmented positive and negative electrode plates, fragments of the separator membrane, high-temperature and high-pressure gases generated by the reaction, flames, etc.

[0370] The pressure relief mechanism of the embodiment of the present application can be arranged on any wall of the battery cell 20. For example, the pressure relief mechanism can be arranged 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 setting 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 smaller 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 value, or when 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 value, 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.

[0371] For another example, the pressure relief mechanism can also be a split structure with the third housing wall 2112. The pressure relief mechanism can adopt forms such as explosion-proof valves, air valves, pressure relief valves or safety valves, and can specifically adopt pressure-sensitive or temperature-sensitive elements or structures. 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, calculating 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 value, 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.

[0372] 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 electric 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 first electrode terminal 214a and at least one second electrode terminal 214b, wherein the first electrode terminal 214a and the second electrode terminal 214b have opposite polarities. For example, the first electrode terminal 214a may be a positive electrode terminal, then the second electrode terminal 214b is a negative electrode terminal; or, the first electrode terminal 214a may be a negative electrode terminal, then the second electrode terminal 214b is a positive electrode terminal. Among them, the positive electrode terminal is used to be electrically connected to the positive electrode tab 222a of the electrode assembly 22, and the negative electrode terminal is used to be electrically connected to the negative electrode tab 222b of the electrode assembly 22. The positive electrode terminal and the positive electrode tab 222a may be directly connected or indirectly connected, and the negative electrode terminal and the negative electrode tab 222b may be directly connected or indirectly connected. Exemplarily, the positive electrode terminal may be electrically connected to the positive electrode tab 222a through a connecting member 23, and the negative electrode terminal is electrically connected to the negative electrode tab 222b through a connecting member 23.

[0373] It should be understood that each electrode terminal 214 in the embodiment of the present application may be disposed on any 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 9 and Figure 9 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.

[0374] For another example, still 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 9 and Figure 13 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.

[0375] 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 third housing wall 2112, 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, the average thickness T of the third housing wall 2112 may not include this liquid injection region when calculated.

[0376] 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 14 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 13 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 14 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 region of the functional region in the embodiments of the present application may further include this 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, the average thickness T of the third housing wall 2112 may not include this welding region when calculated.

[0377] 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.

[0378] In some embodiments, the third housing wall 2112 is the wall with the largest area of the housing 211. Considering that multiple battery cells 20 are 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.

[0379] 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.

[0380] 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 and adjacent to the opening respectively. When the electrode assembly 22 is accommodated inside the housing 211, considering that in actual applications, the application scenarios are different, 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.

[0381] In some embodiments, the third housing wall 2112 is the side wall of the housing 211. Considering the different uses of the bottom wall and side walls of the housing 211, 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.

[0382] In some embodiments, the housing 211 includes multiple side walls with equal thicknesses for easy processing.

[0383] 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.

[0384] 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 during the cyclic charge and discharge of the battery cell 20, the thickness direction of the electrode assembly 22 is prone to expansion, relatively high 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 room temperature, both 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.

[0385] 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 room temperature tensile strength 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.

[0386] 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 housing 211 has a relatively thin thickness, 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.

[0387] 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 8 The side view schematic diagram of the housing 211 of the embodiment of the present application is shown, Figure 9 The top view schematic diagram of the housing 211 of the embodiment of the present application is shown. For example, the Figure 13< \br>Figure 14 and Figure 13 The shown housing 211 can be the housing 211 of the battery cell 20 as shown in Figure 14 and Figure 8 shown.

[0388] Such as Figure 9 and Figure 12As shown, here, the rectangular parallelepiped housing 211 is taken as an example, and the housing 211 is a hollow rectangular parallelepiped 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 fillet connection between the adjacent walls of the housing 211 can be ignored. As Figure 8 and Figure 9 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, the external length is Y2, and Y2 is greater than Y1; similarly, in the width direction X, the internal width of the housing 211 is X1, the external width is X2, and X2 is greater than X1; in the height direction Z, the internal height of the housing 211 is Z1, the external height is Z2, and 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.

[0389] 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 taken as the square shell batteries as shown in Rm(MPa) and C(Ah) shown, wherein the housing 211 adopts a hollow structure with one end open.

[0390] 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.

[0391] 1. Preparation of the positive electrode plate 223

[0392] 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. Then, after trimming, slicing, and slitting, it is dried in a vacuum at 85°C for 4 h to make the positive electrode plate 223.

[0393] 2. Preparation of the negative electrode plate 224

[0394] 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 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%. 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 paste 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 prepare the negative electrode plate 224.

[0395] 3. Preparation of the electrolyte

[0396] 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 with a concentration of 1 mol / L is obtained.

[0397] 4. Preparation of the separator 225

[0398] A 16-μm polyethylene film is used as the separator 225.

[0399] 5. Preparation of the lithium-ion battery cell 20

[0400] 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 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 cell. The electrode tabs are welded, the bare battery cell is placed in a housing made of different materials, and the above-prepared electrolyte 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.

[0401] 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 6 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 other setting conditions except for the different parameter settings shown in Table 6. For example, the capacity of the battery cell 20 in each embodiment is 350 Ah.

[0402] A cyclic charge fatigue test was carried out on the battery cell 20 in the following embodiments and comparative examples. Specifically, it can be tested using the fixture 700 for cyclic charge fatigue test as shown in Shell Material Figure.

[0403] Specifically, the battery cell 20 was clamped and fixed in the special fixture 700, ensuring that the two walls with the largest relative setting 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 the special battery charge and discharge equipment.

[0404] 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.

[0405] The specific test steps refer to Section 6.4 "Standard Cycle Life" in "GBT31484-2015 Requirements and Test Methods for the 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".

[0406] 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 not 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 not 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.

[0407] During the above-mentioned 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 at 1000 cycles as shown in Table 6 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.

[0408] Table 6

[0409]

[0410]

[0411] It should be understood that in Table 6 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.

[0412] According to Table 6 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, so as 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, 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.

[0413] 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, and correspondingly, the number of electrical connections between the plurality of battery cells 20 can also be reduced, reducing the probability of electrical connection failures and helping to improve the reliability of the battery. Moreover, 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 further 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, further 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, which can also reduce the material selection difficulty and processing difficulty of the battery cell 20, reduce costs and improve processing efficiency.

[0414] 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.

[0415] 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.

[0416] In some embodiments, the value of the capacity C of the battery cell 20 in 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.

[0417] It should be understood that the capacity C of the battery cell 20 in 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.

[0418] 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 Test Results and Comparative Example 1 shown rectangular shell batteries, where the housing 211 has a hollow structure with one end open.

[0419] 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.

[0420] 1. Preparation of the positive electrode plate 223

[0421] 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), where the solid content in the positive electrode slurry 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. After that, it is dried under vacuum at 85°C for 4 h to make the positive electrode plate 223.

[0422] 2. Preparation of the negative electrode plate 224

[0423] 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 make 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 and dried at 85°C, then cold-pressed, trimmed, sliced, and slit. After that, it is dried under vacuum at 120°C for 12 h to make the negative electrode plate 224.

[0424] 3. Preparation of the electrolyte

[0425] 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 according to a mass ratio of 50:50). After mixing evenly, an electrolyte with a concentration of 1 mol / L is obtained.

[0426] 4. Preparation of the separator 225

[0427] A 16-μm polyethylene film is used as the separator 225.

[0428] 5. Preparation of the lithium-ion battery monomer 20

[0429] 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 housing made of different materials, and the above-prepared electrolyte is injected into the dried housing. 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.

[0430] 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 capacity of the battery cell 20 is C; the specific parameter settings are shown in Table 7 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 7. For example, the wall thickness of the wall with the largest area of the battery cell 20 in each embodiment is 0.15 mm; for another example, the chemical system of the battery cell 20 in each embodiment is a nickel-cobalt-manganese ternary system.

[0431] Table 7

[0432] Aluminum Shell cracking Comparative Example 2 Aluminum Shell cracking 177 500 Example 1 Low carbon steel Shell intact 190 100 Example 2 Low carbon steel Shell intact 393 500 Example 3 Low carbon steel Shell intact 394 300 Example 4 Stainless steel Shell intact 390 100 Example 5 Stainless steel Shell intact 851 500 Example 6 Stainless steel Shell intact 854 300 Figure 15 r>Figure 16 Figure 15 845 100 Figure 16 Figure 8

[0433] Comparing the two comparative examples and the six embodiments in Table 7 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 Embodiments 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 cannot meet the design requirements of the battery cell 20.

[0434] In some embodiments, the housing 211 of the embodiment of the present application can be a multi-layer structure, and at least part of the region of the housing 211 can include at least one housing structure of the housing 211. In this way, when increasing the capacity C of the battery cell 20, the internal reaction of the battery cell 20 will intensify, and thus the pressure on the housing 211 will increase. Therefore, when the capacity C of the battery cell 20 is constant, setting at least one housing structure to meet the tensile strength Rm under normal temperature conditions can at least improve the deformation ability of this part of the housing, can limit the extrusion force of the internal electrode assembly 22, make the housing 211 not easily damaged, and thus improve the structural stability and service life of the battery cell 20.

[0435] 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 at least one layer of the housing structure to meet the requirements of the tensile strength Rm or the yield strength Re at room temperature can at least improve the deformation ability of this part of the housing structure, limit the extrusion force of the internal electrode assembly 22, make the housing 211 not easily damaged, and thereby improve the structural stability and service life of the battery cell 20.

[0436] When the positive active material of the positive electrode tab 223 of the electrode assembly 22 includes a nickel-containing element 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 setting at least one layer of the housing structure to meet the requirements of the tensile strength Rn or the melting point p at high temperature, then the deformation ability of this part of the housing structure can be at least improved, and at least this part of the housing structure will not be easily damaged or completely melted, which can limit the excessive expansion of the internal electrode assembly 22 in the housing 211, reduce the possibility of the battery cell 20 exploding, and thereby reduce the risk of adjacent battery cells 20 undergoing thermal runaway, so as to improve the reliability of the battery 10.

[0437] 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 regions of the housing 211. In this way, when increasing the capacity C of the battery cell 20, the internal reaction of the battery cell 20 will intensify, thereby increasing the pressure on the housing 211. Therefore, when increasing the capacity C of the battery cell 20, setting all regions of the housing 211 to meet the requirements of the tensile strength Rm at room temperature as described above 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.

[0438] 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 all regions of the housing 211 to meet the requirements of the tensile strength Rm or the yield strength Re at room 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 local weak areas, thereby improving the structural stability and service life of the battery cell 20.

[0439] 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; and if all regions 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 thereby reducing the risk of thermal runaway of adjacent battery cells 20 to improve the reliability of the battery 10.

[0440] Furthermore, the cover plate 212 of the embodiment of the present application can be made of the same material as at least part of the region of the housing 211 of the embodiment 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 requirements of the tensile strength Rm and the yield strength Re at room 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 thereby improve the structural stability of the battery cell 20, but the embodiment of the present application is not limited thereto.

[0441] 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 of the embodiment of the present application can be flexibly selected according to actual applications.

[0442] 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 high strength, can meet the strength requirements of the housing 211, are easy to process, and have low costs.

[0443] 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, the housing 211 made of stainless steel is not easily rusted, and compared with other materials, it can extend the service life of the housing 211.

[0444] 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. Additionally, 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, thereby extending the service life of the housing 211.

[0445] 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.

[0446] In some embodiments, when steel is used in at least part of the housing 211, the steel types can include at least one of the following: SPCC, Q195, Q215, Q235, SUS 304, SUS 316, and other modified stainless steels. These steels are easily obtainable, 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 8 below.

[0447] Table 8

[0448]

[0449] 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.

[0450] 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.

[0451] 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.

[0452] In some embodiments, taking the housing 211 made of steel as an example, the mass contents of different elements included 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 9 shows the mass contents of different elements of several types of steel, where the values in Table 9 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 9.

[0453] Table 9

[0454]

[0455] 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.

[0456] 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, a corrosion-resistant protective film is formed on the surface of the steel, so the corrosion resistance of the steel can be improved.

[0457] If the mass content of nickel element in the steel is increased, the corrosion resistance, strength, and plasticity of the steel can be improved.

[0458] 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.

[0459] If the mass content of manganese element in the steel is increased, the toughness and fatigue resistance of the steel can be increased.

[0460] If the mass content of silicon element in the steel is increased, the corrosion resistance and strength of the stainless steel can be increased.

[0461] 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.

[0462] 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%.

[0463] 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.

[0464] Figure 9 Another exploded structure diagram of the battery cell 20 according to the embodiment of the present application is shown. Figure 15 A schematic cross-sectional view of the housing 30 according to the embodiment of the present application is shown. It should be noted that the Figure 16 and Figure 8 The shown housing 30 can be applied to the battery cell 20. For example, the housing 30 can be applied to the Figure 9 and Figure 15 shown battery cell 20, and the Figure 16 and Figure 15 shown housing 30 can be the Figure 16 and Figure 17 shown housing 211, which is applicable to the relevant descriptions above. For the sake of brevity, it will not be repeated here one by one.

[0465] As Figure 17 and Figure 18 shown, the housing 30 has an opening 301. The housing 30 includes a first housing wall 31 opposite to the opening 301 and at least two second housing walls 32. The first housing wall 31 and the second housing walls 32 intersect.

[0466] As Figure 15As shown in the enlarged partial view of part A, there is a transition region 33 between two adjacent second housing walls 32 among at least two second housing walls 32 of the housing 30. The maximum thickness of the transition region 33 is T1, and the maximum thickness of the second housing wall 32 with the largest thickness among the two adjacent second housing walls 32 is T0, where T1 is greater than T0.

[0467] In some embodiments, the second housing wall 32 may be perpendicular to the first housing wall 31.

[0468] In some embodiments, at least two second housing walls 32 may be connected end to end to enclose a hollow structure with two open ends, where the first housing wall 31 covers the opening at one end of the hollow structure.

[0469] In some embodiments, the placement manner of the housing 30 may be as Figure 19<\br >Figure 20 shown. Then, the first housing wall 31 may be the bottom wall of the housing 30 for supporting the electrode assembly 22, and the second housing walls 32 are the side walls of the housing 30 disposed around the electrode assembly 22.

[0470] Generally, the second housing walls 32 are not prepared independently, that is, the at least two second housing walls 32 may be integrally formed. In other embodiments, the at least two second housing walls 32 and the first housing wall 31 are integrally formed, that is, the housing 30 is an integrally formed structure. For example, a plate-like structure is stamped into a hollow structure with an opening by using a mold, and the housing 30 after stamping may have openings of various shapes. For example, the opening 301 may be circular, polygonal or racetrack-shaped. The polygon is, for example, square, pentagonal, hexagonal or other irregular shapes.

[0471] In some embodiments, the thickness of the transition region 33 may be uniform or non-uniform. Hereinafter, the maximum thickness T1 of the transition region 33 will be defined by taking the thickness of the transition region 33 as uniform as an example.

[0472] From Figure 19As can be seen, the transition region 33 has two surfaces, namely an inner surface and an outer surface. In some embodiments, the inner surface and the outer surface may be arc surfaces, and the inner surface and the outer surface are coaxially arranged. The maximum thickness T1 of the transition region 33 can be defined as the length of the extension line of the connection line between the centers of the inner arc circle and the outer arc circle in the transition region 33 in any cross-section along the direction perpendicular to the axis of the inner surface and the outer surface. In other embodiments, the inner surface and the outer surface may be planes, and the inner surface and the outer surface are parallel, and the maximum thickness T1 of the transition region 33 can be defined as the vertical distance between the inner surface and the outer surface. Similarly, the second housing wall 32 also has two surfaces, namely an inner surface and an outer surface, wherein the maximum value of the vertical distance between the inner surface and the outer surface is the maximum thickness of a certain second housing wall 32.

[0473] If at least two second housing walls 32 of the housing 30 have unequal wall thicknesses, for example, the wall thicknesses of the two second housing walls 32 adjacent to a transition region 33 are not equal, then in the embodiments of the present application, T0 is the second housing wall 32 with the largest wall thickness among the two second housing walls 32 adjacent to the transition region 33 in the housing 30. And if at least two second housing walls 32 of the housing 30 have equal wall thicknesses, for example, the wall thicknesses of the two second housing walls 32 adjacent to a transition region 33 are equal, then in the embodiments of the present application, T0 is the thickness of any second housing wall 32 of the housing 30.

[0474] It should be noted that if a certain second housing wall 32 includes a functional region, the maximum thickness of the second housing wall 32 actually refers to the maximum thickness of the region of the second housing wall 32 other than the functional region, and the functional region includes at least one of the following regions: a pressure relief region, a region where an electrode terminal is located, a liquid injection region, and a welding region.

[0475] In this embodiment, by providing a transition region 33 between two adjacent second housing walls 32, the stress concentration between the two adjacent second housing walls 32 can be reduced, and the risk of structural failure caused by stress concentration can be lowered; in addition, by setting the maximum thickness T1 of the transition region 33 to be greater than the maximum thickness T0 of the second housing wall with the largest thickness among the two adjacent second housing walls, the thickened transition region 33 can enhance the structural strength of the housing 30, which is beneficial to solving the problem of deformation of the housing 30 during the production and assembly process of the battery cell 20, and the problem of deformation of the housing 30 caused by gas production and expansion during the use of the battery cell 20.

[0476] In some embodiments, the maximum thickness T1 of the transition region 33 and the maximum thickness T0 of the second housing wall 32 with the largest thickness among the two adjacent second housing walls 32 satisfy: 1.5 ≤ T1 / T0 ≤ 7.

[0477] In this embodiment, by setting the ratio of the maximum thickness T1 of the transition region 33 to the maximum thickness T0 of the second housing wall 32 with the largest thickness among the two adjacent second housing walls 32 within the range of [1.5, 7], on the one hand, the strength of the housing can be enhanced by the relatively thick transition region 33, and on the other hand, the difficulty in manufacturing the housing 30 due to excessive thickening of the transition region 33 can be restricted, so that a balance can be achieved between the strength of the housing 30 and the manufacturing difficulty of the housing 30.

[0478] In practical applications, the ratio of T1 to T0 can be adjusted. For example, the maximum thickness T1 of the transition region 33 and the maximum thickness T0 of the second housing wall 32 with the largest thickness among the two adjacent second housing walls 32 can satisfy: 2 ≤ T1 / T0 ≤ 4.

[0479] For example, T1 / T0 can be equal to 2, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3.0, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4.0, etc.

[0480] In this embodiment, by setting the ratio of the maximum thickness T1 of the transition region 33 to the maximum thickness T0 of the second housing wall 32 with the largest thickness among the two adjacent second housing walls 32 within the range of [2, 4], the maximum balance can be achieved between the strength of the housing 30 and the manufacturing difficulty of the housing 30.

[0481] Optionally, as Figure 20 and Figure 21 shown, the two adjacent second housing walls 32 are connected by a first fillet 331, and the transition region 33 includes this first fillet 331. That is to say, the transition region 33 is realized by a fillet.

[0482] In this embodiment, the transition region 33 between the two adjacent second housing walls 32 is realized by a fillet, which can make the housing 30 easier to form and have a better surface finish. At the same time, when affected by the gas generation inside the battery cell 20, the risk of cracking of the housing 30 caused by stress concentration at the sharp points can be reduced.

[0483] As Figure 21 shown, the inner diameter of the first fillet 331 is R1, and the outer diameter of the first fillet 331 is R2.

[0484] In some embodiments, the first fillet 331 has an inner surface and an outer surface, and both the inner surface and the outer surface are arc surfaces. The inner diameter R1 of the first fillet 331 can be understood as the radius of the circle where the inner arc of the first fillet 331 is located, and the outer diameter R2 of the first fillet 331 can be understood as the radius of the circle where the outer arc of the first fillet 331 is located.

[0485] In some embodiments, the inner diameter R1 of the first rounded corner 331 satisfies: 2 mm ≤ R1 ≤ 4 mm. For example, R1 = 2 mm, 2.1 mm, 2.2 mm, 2.3 mm, 2.4 mm, 2.5 mm, 2.6 mm, 2.7 mm, 2.8 mm, 2.9 mm, 3.0 mm, 3.1 mm, 3.2 mm, 3.3 mm, 3.4 mm, 3.5 mm, 3.6 mm, 3.7 mm, 3.8 mm, 3.9 mm, 4.0 mm, etc.

[0486] In this embodiment, the inner diameter of the first rounded corner 331 between two adjacent second housing walls 32 is set between [2 mm, 4 mm]. On the one hand, it will not occupy the internal space of the housing 30 due to too large an inner diameter, causing the gas production pressure inside the housing 30 to increase; on the other hand, it will not cause insufficient wall thickness increment of the first rounded corner 331 due to too small an inner diameter, resulting in insufficient strength of the housing 30. Therefore, a balance can be achieved between the internal space utilization rate of the housing 30 and the strength of the housing 30.

[0487] In some embodiments, the outer diameter R2 of the first rounded corner 331 satisfies: 1.5 mm ≤ R2 ≤ 3.5 mm. For example, R2 = 1.5 mm, 2 mm, 2.5 mm, 3.0 mm, 3.5 mm, etc.

[0488] In this embodiment, when the cover plate 40 is fixedly connected to the housing 30 by side welding, the larger the outer diameter R2 of the first rounded corner 331 between two adjacent second housing walls 32, the more difficult it is to control the welding quality and easy to have false welding; and the smaller the outer diameter R2 of the first rounded corner 331, the more difficult it is for the housing 30 to be formed. Therefore, controlling the outer diameter R2 of the first rounded corner 331 within the range of [1.5 mm, 3.5 mm] can balance the welding quality and the forming difficulty of the housing.

[0489] In other embodiments, as Figure 21 shown, two adjacent second housing walls 32 are connected by a C angle. For example, the angle between the C angle and two adjacent second housing walls 32 is 45°.

[0490] In one embodiment, the housing 30 can be an integrally formed structure, as Figure 17 shown, the depth of the housing 30 is H, where the depth H of the housing 30 and the inner diameter R1 of the first rounded corner 331 satisfy: 2.5 mm ≤ R1 ≤ 20 mm, 50 mm < H ≤ 250 mm.

[0491] In the embodiments of the present application, the depth can be understood as the distance from the opening to the bottom inward. For example, the depth H of the housing 30 can be understood as the distance from the opening 301 to the first housing wall 31.

[0492] Figure 22 Shows a schematic diagram of the material flow of the housing 30 during the one-piece molding process. Figure 21 Shows a schematic diagram of the force on the housing 30 during the one-piece molding process. From Figure 22 and Figure 22 it can be seen that when the housing 30 is molded, the material of the housing 30 is likely to accumulate at the position of the first fillet 331, resulting in a large frictional force between the housing 30 and the mold, and the housing 30 is prone to cracking. Therefore, in this embodiment, by setting the depth H of the housing 30 and the inner diameter R1 of the first fillet 331 to satisfy 2.5 mm ≤ R1 ≤ 20 mm and 50 mm < H ≤ 250 mm, it is possible to reduce the cracking risk caused by the force during the one-piece molding process of the housing 30 as much as possible without affecting the energy density of the battery cell 20, thereby reducing the molding difficulty of the housing 30.

[0493] For example, R1 = 2.5 mm, 5 mm, 7.5 mm, 10 mm, 12.5 mm, 15 mm, 17.5 mm, 20 mm; and / or, H = 50 mm, 100 mm, 150 mm, 200 mm, 250 mm.

[0494] In some embodiments, H and R1 satisfy: 75 mm ≤ H ≤ 180 mm, 4 mm ≤ R1 ≤ 15 mm.

[0495] For example, H = 75 mm, 100 mm, 125 mm, 150 mm, 175 mm, 180 mm. For example: R1 = 4 mm, 6 mm, 8 mm, 10 mm, 12 mm, 14 mm, 15 mm.

[0496] In this embodiment, by setting H and R1 to satisfy: 4 mm ≤ R1 ≤ 15 mm, 75 mm ≤ H ≤ 180 mm, on the one hand, the energy density of the battery cell 20 will not be reduced due to too small H or too large R, and on the other hand, the housing 30 will not be prone to material accumulation during the molding process due to too large H or too small R, thereby preventing the situation where the housing 30 is overstressed and cracked.

[0497] In other embodiments, H and R1 satisfy: 5 mm ≤ R1 ≤ 10 mm, 90 mm ≤ H ≤ 140 mm. For example, R1 = 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, 10 mm. Again, for example, H = 90 mm, 100 mm, 110 mm, 120 mm, 130 mm, 140 mm.

[0498] In some other embodiments, the housing 30 is an integrally formed structure, and the yield strength of the housing 30 at a temperature of 25 °C is Re. Among them, the following relationship is satisfied between the yield strength Re and the inner diameter R1 of the first rounded corner 331: 140 MPa ≤ Re ≤ 1000 MPa, 2.5 mm ≤ R1 ≤ 20 mm.

[0499] For example, Re = 140 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, 550 MPa, 600 MPa, 650 MPa, 700 MPa, 750 MPa, 800 MPa, 850 MPa, 900 MPa, 950 MPa, 1000 MPa.

[0500] For example, R1 = 2.5 mm, 5 mm, 7.5 mm, 10 mm, 12.5 mm, 15 mm, 17.5 mm, 20 mm.

[0501] 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 30 in the embodiments of the present application at a temperature of 25 °C can be selected according to actual applications. For example, GB / T 228.1-2010 can be used to test the yield strength Re under normal temperature conditions of 25 °C.

[0502] In order to solve the problem that when the housing 30 is integrally formed, the material is likely to accumulate at the first rounded corner 331, resulting in a large frictional force between the housing 30 and the mold and the housing 30 being prone to cracking, the embodiments of the present application also provide another solution, that is, for the housing 30 with a yield strength Re satisfying 140 MPa ≤ Re ≤ 1000 MPa, the inner diameter R1 of the first rounded corner 331 is set to 2.5 mm ≤ R1 ≤ 20 mm, so that R1 cannot be too small to reduce the difficulty of forming the housing 30, and R1 cannot be too large to reduce the stress deformation of the housing 30.

[0503] In this embodiment, by using a material with a yield strength Re satisfying 140 MPa ≤ Re ≤ 1000 MPa to fabricate the housing 30, the wall thickness of the housing can be thinned without reducing the strength of the housing 30, thereby increasing the capacity space of the battery cell 20. In addition, by setting the inner diameter R1 of the first fillet 331 between adjacent second housing walls 32 to satisfy 2.5 mm ≤ R1 ≤ 20 mm, the risk of cracking of the housing 30 caused by stress during the integral molding process is minimized, and the molding difficulty of the housing 30 is reduced.

[0504] In some embodiments, the yield strength Re and R1 of the housing 30 may satisfy: 150 MPa ≤ Re ≤ 400 MPa, 4 mm ≤ R1 ≤ 15 mm.

[0505] For example, Re = 150 MPa, 170 MPa, 190 MPa, 210 MPa, 230 MPa, 260 MPa, 290 MPa, 310 MPa, 330 MPa, 370 MPa, 390 MPa, 400 MPa.

[0506] For example, R1 = 4 mm, 6 mm, 8 mm, 10 mm, 12 mm, 14 mm, 15 mm.

[0507] In this embodiment, by defining 150 MPa ≤ Re ≤ 400 MPa, 4 mm ≤ R1 ≤ 15 mm, it helps to achieve a balance between the molding difficulty and the degree of deformation of the housing 30.

[0508] In some embodiments, the yield strength Re and R1 of the housing 30 may satisfy: 160 MPa ≤ Re ≤ 300 MPa, 5 mm ≤ R1 ≤ 10 mm.

[0509] For example, Re = 160 MPa, 170 MPa, 180 MPa, 190 MPa, 200 MPa, 210 MPa, 220 MPa, 230 MPa, 240 MPa, 250 MPa, 260 MPa, 270 MPa, 280 MPa, 290 MPa, 300 MPa.

[0510] For example, R1 = 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, 10 mm.

[0511] In this embodiment, by defining 160 MPa ≤ Re ≤ 300 MPa, 5 mm ≤ R1 ≤ 10 mm, it is possible to minimize the stress deformation of the housing 30 during use without affecting the molding difficulty of the housing 30.

[0512] In some embodiments, the tensile strength of the housing 30 at a temperature of 25 °C is Rm, and Rm and R1 satisfy: 250 MPa ≤ Rm ≤ 2000 MPa, 2.5 mm ≤ R1 ≤ 20 mm.

[0513] The tensile strength can be understood as the maximum stress value that the material can withstand before being broken. The test method for the tensile strength Rm of the housing 30 in the embodiments of the present application at a temperature of 25 °C can be selected according to actual applications. For example, ISO 6892-2:2018 can be used to test the tensile strength Rm at a normal temperature of 25 °C.

[0514] For example, Rm = 250 MPa, 300 MPa, 350 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, 1100 Mpa, 1200 MPa, 1300 MPa, 1400 MPa, 1500 MPa, 1600 MPa, 1700 MPa, 1800 MPa, 1900 MPa, 2000 MPa.

[0515] In this embodiment, by setting 250 MPa ≤ Rm ≤ 1000 MPa, 2.5 mm ≤ R1 ≤ 20 mm, it is possible to minimize the force on the mold during the manufacturing process of the housing 30 without affecting the strength of the housing 30, and thus the size or surface of the housing 30 can be unaffected.

[0516] In some embodiments, Rm and R1 satisfy: 280 MPa ≤ Rm ≤ 800 MPa, 4 mm ≤ R1 ≤ 15 mm.

[0517] For example, Rm = 280 MPa, 310 MPa, 340 MPa, 370 MPa, 390 MPa, 430 MPa, 470 MPa, 510 MPa, 540 MPa, 580 MPa, 610 MPa, 630 MPa, 660 MPa, 690 MPa, 720 MPa, 740 MPa, 780 MPa, 800 MPa.

[0518] In other embodiments, Rm and R1 satisfy: 380 MPa ≤ Rm ≤ 600 MPa, 5 mm ≤ R1 ≤ 10 mm.

[0519] For example, Rm = 380 MPa, 390 MPa, 410 MPa, 440 MPa, 480 MPa, 520 MPa, 535 MPa, 570 MPa, 596 MPa, 600 MPa.

[0520] In some embodiments, the maximum wall thicknesses of at least two second housing walls 32 of the housing 30 are equal.

[0521] Further optionally, the wall thickness of each of the at least two second housing walls 32 of the housing 30 is uniform, and the wall thicknesses of the at least two second housing walls 32 are all equal.

[0522] In this embodiment, by setting the wall thicknesses of at least two second housing walls 32 to be equal, on the one hand, the processing difficulty of the housing 30 can be reduced, and on the other hand, at least two second housing walls 32 can be set to the minimum processing wall thickness, which helps to fully improve the space utilization rate of the housing 30.

[0523] In some other embodiments, there is a transition region 33 between any two adjacent second housing walls 32 among the at least two second housing walls 32, and the maximum thicknesses of the at least two transition regions 33 corresponding to the at least two second housing walls 32 are equal.

[0524] In this embodiment, by setting the maximum thicknesses of the at least two transition regions 33 between the at least two second housing walls 32 of the housing 30 to be equal, it helps to prepare the housing 30 into a symmetric structure, which is easy to process, and there is no need to worry about incorrect assembly when assembling the housing 30 with the cover plate 40, having an anti-fooling function.

[0525] Figure 23 Another schematic cross-sectional view of the housing 30 according to an embodiment of the present application is shown. As Figure 24 shown in the partial enlarged view of part B, the first housing wall 31 and the second housing wall 32 are connected by a second fillet 34. As Figure 25 shown in the enlarged schematic view of part B, the inner diameter of the second fillet 34 is r1, and the minimum thickness of the second housing wall 32 with the smallest thickness among the at least two second housing walls 32 is T2. Among them, the inner diameter r1 of the second fillet 34 and the minimum thickness T2 of the second housing wall 32 with the smallest thickness among the at least two second housing walls 32 satisfy: 2.0 ≤ r1 / T2 ≤ 30.

[0526] It should be understood that the first housing wall 31 is connected to all of the at least two second housing walls 32. Optionally, any second housing wall 32 and the first housing wall 31 are connected by a second fillet 34 as Figure 26 shown. In addition, the second fillet 34 here is similar to the first fillet 331 in Figures 23 to 24 , that is, the second fillet 34 has an inner surface and an outer surface, and both the inner surface and the outer surface are arc surfaces. The inner diameter r1 of the second fillet 34 can be understood as the radius of the circle where the inner arc is located.

[0527] It should be noted that if each second housing wall 32 is a wall with a uniform thickness, the minimum thickness T2 of the second housing wall 32 may refer to the thickness of the second housing wall 32 with the thinnest thickness among at least two second housing walls 32. If the thickness of each second housing wall 32 is non-uniform, the minimum thickness T2 of the second housing wall 32 may refer to the thickness of the thinnest region among all second housing walls 32.

[0528] It should also be noted that if a certain second housing wall 32 includes a functional area, the minimum thickness of this second housing wall 32 actually refers to the minimum thickness of the area of this second housing wall 32 other than the functional area, and the functional area includes at least one of the following areas: a pressure relief area, an area where an electrode terminal is located, a liquid injection area, and a welding area.

[0529] In this embodiment, by setting the ratio of the inner diameter r1 of the second fillet 34 between the first housing wall 31 and the second housing wall 32 to the minimum thickness T2 of the second housing wall 32 with the smallest thickness within [2.0, 30], it helps to balance the processing difficulty of the housing 30, the space capacity of the battery cell 20, and the strength.

[0530] In some embodiments, the inner diameter r1 of the second fillet 34 and the minimum thickness T2 of the second housing wall 32 with the smallest thickness among at least two second housing walls 32 satisfy: 2.5 ≤ r1 / T2 ≤ 10. For example, r1 / T2 = 2.5, 3.0, 3.5, 4.0, 4.5, 5.0, 5.5, 6.0, 6.5, 7.0, 7.5, 8.0, 8.5, 9.0, 9.5, 10, etc.

[0531] Optionally, the inner diameter r1 of the second fillet 34 may satisfy: 0.8 mm ≤ r1 ≤ 1.5 mm. For example, r1 = 0.8 mm, 0.9 mm, 1.0 mm, 1.1 mm, 1.2 mm, 1.3 mm, 1.4 mm, 1.5 mm.

[0532] In this embodiment, by setting the inner diameter r1 of the second fillet 34 within [0.8 mm, 1.5 mm], on the one hand, it will not increase the manufacturing difficulty of the housing 30 due to too small r1, and on the other hand, it will not reduce the interference between the electrode assembly 22 and the second fillet 34, that is, there is no need to sacrifice the capacity of the electrode assembly 22 by reducing the height of the electrode assembly 22 to meet the assembly of the housing 30 and the electrode assembly 22. In addition, if r1 is too large, the housing 30 is also prone to deformation.

[0533] Figure 8 Shows Figure 9 Another partial enlarged schematic diagram of part B in. As Figure 9 As shown, the outer diameter of the second rounded corner 34 is r2, where r2 satisfies: 1 mm ≤ r2 ≤ 2.5 mm. For example, r2 = 1.0 mm, 1.1 mm, 1.2 mm, 1.3 mm, 1.4 mm, 1.5 mm, 1.6 mm, 1.7 mm, 1.8 mm, 1.9 mm, 2.0 mm, 2.1 mm, 2.2 mm, 2.3 mm, 2.4 mm, 2.5 mm.

[0534] Similar to the definition of the inner diameter r1 of the second rounded corner 34, the outer diameter r2 of the second rounded corner 34 can be understood as the radius of the circle where the outer arc of the second rounded corner 34 is located.

[0535] In this embodiment, by setting the outer diameter r2 of the second rounded corner 34 within [1.0 mm, 2.5 mm], on the one hand, the insulating film outside the battery cell 20 will not be punctured by sharp points due to too small r2, resulting in insulation failure; on the other hand, the thickness of the second rounded corner 34 will not be too thin due to too large r2, affecting the strength of the housing 30.

[0536] In some embodiments, H and T2 satisfy: 300 ≤ H / T2 ≤ 800. For example, H / T2 = 300, 350, 400, 450, 500, 550, 600, 650, 700, 750, 800, etc.

[0537] In this embodiment, by setting the ratio between the depth H of the housing 30 and the minimum thickness T2 of the second housing wall 32 with the smallest thickness within [300, 800], the volume utilization rate and strength of the battery cell 20 can be taken into account.

[0538] As Figure 9 shown, the maximum thickness of the second rounded corner 34 is T3, where the ratio of T3 to T2 satisfies: 0.8 ≤ T3 / T2 ≤ 2. For example, T3 / T2 = 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0.

[0539] The thickness of the second rounded corner 34 can be uniform or non-uniform. Hereinafter, the maximum thickness T3 of the second rounded corner 34 will be defined with the thickness of the second rounded corner 34 being uniform as an example. In some embodiments, the maximum thickness T3 of the second rounded corner 34 can be defined as the length of the extension line of the connection line between the centers of the inner arc circle and the outer arc circle in any cross-section along the axis perpendicular to the inner surface and the outer surface in the second rounded corner 34.

[0540] In this embodiment, by setting the ratio between the maximum thickness T3 of the second rounded corner 34 and the minimum thickness T2 of the second housing wall 32 with the minimum thickness within the range of [0.8, 2], the strength and manufacturability of the housing 30 can be balanced. That is, the strength of the housing 30 will not be insufficient due to excessive thinning of the second rounded corner 34, nor will the housing 30 be difficult to manufacture due to insufficient thinning of the second rounded corner 34.

[0541] In some embodiments, the wall thickness of the housing 30 is uniform, that is, all walls of the housing 30 have the same wall thickness.

[0542] In this embodiment, by setting the wall thickness of the housing 30 to be uniform, on the one hand, the processing difficulty of the housing 30 can be reduced, and on the other hand, each wall of the housing 30 can be set to the minimum processing wall thickness, which helps to fully improve the space utilization rate of the housing 30.

[0543] In some embodiments, the battery cell 20 further includes: a cover plate 40 for covering the opening 301 of the housing 30 to enclose the electrode assembly 22 in the cavity of the housing 30.

[0544] In this embodiment, by setting the depth H of the housing and the inner diameter R1 of the first rounded corner between the second housing walls to satisfy 2.5 mm ≤ R1 ≤ 20 mm and 50 mm ≤ H ≤ 250 mm, the risk of cracking caused by the force during the integral molding process of the housing can be reduced as much as possible without affecting the energy density of the battery cell, thereby reducing the molding difficulty of the housing.

[0545] In some embodiments, the shape of the battery cell 20 is generally a cuboid. For example, the battery cell 20 is a cuboid battery cell. For another example, the battery cell 20 is a runway-shaped battery cell, and the thickness of the battery cell 20 is D1, where H, R1, and D1 satisfy: 0.15 mm ≤ R1 * D1 / H ≤ 36 mm.

[0546] For example, R1 * D1 / H = 0.15, 0.5, 1, 5, 10, 15, 17.5, 20, 22.5, 25, 27.5, 30, 32.5, 35, 36.

[0547] In some embodiments, D2 can be the dimension of the battery cell 20 in the expansion direction of the electrode assembly 22.

[0548] In this embodiment, by setting 0.15 mm ≤ R1 * D1 / H ≤ 36 mm, the risk of material accumulation during the molding process of the housing 30 caused by too small a value of R1 * D1 / H can be reduced, thereby reducing the risk of cracking due to excessive force on the housing 30, and the influence on the energy density of the battery cell 20 caused by too large a value of R1 * D1 / H can be reduced.

[0549] In this embodiment, D1 satisfies: 15 mm ≤ D1 ≤ 90 mm. For example, D1 = 15 mm, 20 mm, 25 mm, 30 mm, 35 mm, 40 mm, 45 mm, 50 mm, 55 mm, 60 mm, 65 mm, 70 mm, 75 mm, 80 mm, 85 mm, 90 mm.

[0550] In this embodiment, H and R1 satisfy: 50 mm ≤ H ≤ 250 mm, 2.5 mm ≤ R1 ≤ 20 mm.

[0551] In some embodiments, H, R1, and D1 satisfy: 0.34 mm ≤ R1 * D1 / H ≤ 18 mm.

[0552] In this embodiment, by setting 0.34 mm ≤ R1 * D1 / H ≤ 18 mm, a balance can be achieved between the forming difficulty and the energy density of the housing 30.

[0553] For example, R1 * D1 / H = 0.34, 0.5, 1, 3, 5, 8, 11, 13, 16, 18.

[0554] Similarly, in this embodiment, D1 satisfies: 15 mm ≤ D1 ≤ 90 mm.

[0555] In this embodiment, H and R1 satisfy: 75 mm ≤ H ≤ 180 mm, 4 mm ≤ R1 ≤ 15 mm.

[0556] In some embodiments, H, R1, and D1 satisfy: 0.9 mm ≤ R * D / H ≤ 6.6 mm.

[0557] For example, R1 * D1 / H = 0.9, 1, 1.3, 1.5, 1.8, 2.0, 2.3, 2.6, 2.8, 3.0, 3.3, 3.5, 3.8, 4.0, 4.3, 4.5, 4.7, 4.9, 5.1, 5.4, 5.7, 6.0, 6.2, 6.5, 6.6.

[0558] In this embodiment, D1 satisfies: 25 mm ≤ D1 ≤ 60 mm. For example, D1 = 25 mm, 28 mm, 31 mm, 34 mm, 37 mm, 39 mm, 41 mm, 43 mm, 46 mm, 49 mm, 51 mm, 54 mm, 58 mm, 50 mm.

[0559] And in this embodiment, H and R1 satisfy: 90 mm ≤ H ≤ 140 mm, 3 mm ≤ R ≤ 10 mm.

[0560] It should be noted that the value ranges of R1, H, D1, and R1*D1 / H can be interrelated. For example, when 15 mm ≤ D1 ≤ 90 mm, 50 mm ≤ H ≤ 250 mm, and 2.5 mm ≤ R1 ≤ 20 mm, 0.15 mm ≤ R1*D1 / H ≤ 36 mm. Another example, when 15 mm ≤ D1 ≤ 90 mm, 75 mm ≤ H ≤ 180 mm, and 4 mm ≤ R1 ≤ 15 mm, 0.34 mm ≤ R*D / H ≤ 18 mm. Another example, when 25 mm ≤ D1 ≤ 60 mm, 90 mm ≤ H ≤ 140 mm, and 3 mm ≤ R1 ≤ 10 mm, 0.9 mm ≤ R1*D1 / H ≤ 6.6 mm.

[0561] In some embodiments, the thickness of the electrode assembly 22 is D2, and R1 and D2 satisfy: 0.125 ≤ R1 / D2 ≤ 0.45.

[0562] For example, R1 / D2 = 0.125, 0.15, 0.175, 0.2, 0.225, 0.25, 0.275, 0.3, 0.325, 0.35, 0.375, 0.4, 0.425, 0.45.

[0563] Optionally, D2 may be the dimension of the electrode assembly 22 in the expansion direction.

[0564] In this embodiment, by setting 0.125 ≤ R1 / D2 ≤ 0.45, on the one hand, it will not interfere with the electrode assembly 22 or cause insufficient residual space inside the battery cell 20 due to too large R1, thus affecting the performance of the battery cell 20; on the other hand, it will not cause difficulty in forming the housing 30 due to too small R1.

[0565] Figure 9 Shows an exploded schematic view of a housing 40 according to an embodiment of the present application. Figure 8 Shows a schematic structural view of a second housing part 42 according to an embodiment of the present application. Figure 9 Shows another schematic structural view of the second housing part 42 according to an embodiment of the present application. Figure 23 Shows another exploded schematic view of the housing 40 according to an embodiment of the present application. It should be noted that this housing 40 can be applied to the battery cell 20. For example, the housing 40 shown as Figure 24 can be applied to the battery cell 20 shown as Figure 24 and Figure 25 , and this housing 40 may only include the housing 211 shown as Figure 26 , or may include both the housing 211 shown as Figure 27 and also include the cover plate 212 shown as Figure 27 . In addition, the placement manner of this housing 40 can also be as shown in Figure 28 orFigure 28 as shown

[0566] as Figure 13 As shown, the housing 40 includes a first housing portion 41 formed with 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. The first wall 411 and the second wall 412 are integrally formed; a second housing portion 42 fixedly connected to the second wall 412. Wherein, in the depth direction X of the first housing portion 41, at least part of the area of the housing 40 is jointly formed by the first housing portion 41 and the second housing portion 42.

[0567] It should be noted that the first wall 411 and the second wall 412 in the first housing portion 41 being an integrally formed structure may mean that the first housing portion 41 is made by an integral drawing process. For example, the first housing portion 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 desired shape is obtained; Step 6, perform auxiliary operations such as perforation, 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 portion 41.

[0568] Since the first housing portion 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.

[0569] The first housing portion 41 is a hollow structure surrounded by 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 portion 41 includes one second wall 412 whose head and tail are connected and jointly enclose a cylindrical hollow structure with the first wall 411. In other embodiments, the first housing portion 41 includes four second walls 412 which 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 jointly enclose a square-columnar hollow structure.

[0570] Since the first wall 411 is disposed opposite to the opening 401 of the first housing portion 41, the depth direction X of the first housing portion 41 can be understood as the direction perpendicular to the first wall 411, and the distance between the opening 401 and the first wall 411 of the first housing portion 41 is the depth of the first housing portion 41.

[0571] In the embodiment of the present application, the second housing portion 42 is fixedly connected to the second wall 412, and does not include the second housing portion 42 being a flat plate structure and the second housing portion 42 being fitted at the opening 401 of the first housing portion 41. In other words, in the embodiment of the present application, the second housing portion 42 includes at least one third wall 421, wherein the at least one third wall 421 together encloses a hollow structure having at least one opening. For example, the second housing portion 42 at least includes Figure 28 the opening 402 shown, and the opening 402 of the second housing portion 42 is disposed opposite to the opening 401 of the first housing portion 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 portion 41, the second wall 412 and the third wall 421 together form at least a 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 portion 41. Wherein, the depth H of the housing 40 can be understood as the size of the housing 40 in the depth direction of the first housing portion 41. Generally, the wall of the housing 40 has a certain thickness, but here, the wall thickness of the housing 40 can be ignored.

[0572] In this embodiment, the housing 40 includes a first housing portion 41 and a second housing portion 42, wherein the first housing portion 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 portion 41, at least a part of the housing 40 is formed by the first housing portion 41 and the second housing portion 42 together. 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.

[0573] In some embodiments, in the depth direction X of the first housing portion 41, the size of the second wall 412 is equal everywhere. Similarly, in the depth direction X of the first housing portion 41, the size of the third wall 421 is equal everywhere. Then in the depth direction X of the first housing portion 41, the entire area of the housing 40 is formed by the first housing portion 41 and the second housing portion 42 together.

[0574] In some other embodiments, in the depth direction X of the first housing part 41, the sizes of the second wall 412 are not completely equal. For example, after unfolding, the second wall 412 can be semi-circular or triangular. Similarly, in the depth direction X of the first housing part 41, the sizes of the third wall 421 are not completely equal. For example, after unfolding, the third wall 421 can be semi-circular or triangular. Then, in the depth direction X of the first housing part 41, a partial area of the housing 40 can be jointly formed by the first housing part 41 and the second housing part 42.

[0575] In one embodiment, the first housing part 41 and the second housing part 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 plate structure and a tubular structure with an opening, the weld seam is not at the right-angle edge, and the housing 40 is not prone to cracking and breakage.

[0576] Optionally, in the depth direction X of the first housing part 41, the second housing part 42 has two communicating openings. For example, the second housing part 42 includes the Figure 28 shown openings 402 and 403, and the openings 402 and 403 are oppositely arranged in the depth direction X of the first housing part 41.

[0577] In this embodiment, by setting the second housing part 42 to have two communicating openings in the depth direction X of the first housing part 41, the cover plate and the housing 40 can be independently arranged. Furthermore, components such as electrode terminals can be better arranged on the cover plate, making the preparation of the housing 40 simpler.

[0578] In other embodiments, the second housing part 42 can have only one opening. For example, the second housing part 42 is also prepared by an integral drawing process similar to the first housing part 41. Among them, in addition to the above-mentioned third wall 421, the second housing part 42 further includes a wall that intersects with the third wall 421 and is opposite to the opening of the second housing part 42, for example, a cover plate.

[0579] In one embodiment, the second housing part 42 is an integrally formed structure.

[0580] In this embodiment, by setting the second housing part 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 prone to the risk of deformation, cracking, and breakage.

[0581] In another embodiment, when the second housing part 42 has only one opening, the second housing part 42 can be formed by welding at least two parts.

[0582] It should be noted that when the second housing part 42 is formed by welding at least two parts together, the weld seam of the second housing part 42 should not be on the edge, that is, the so-called right-angle side. For example, as Figure 8 to Figure 9 shown, the second housing part 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 part 42 is formed by welding a first part 423 and a second part 424 together. 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 seam positions of the second housing part 42.

[0583] In this embodiment, the second housing part 42 is set to be formed by welding at least two parts together, which is easy to process, the size is easier to control, and the assembly accuracy of the housing 40 can be improved.

[0584] In some embodiments, the surface 4121 of the second wall 412 facing away from the first wall 411 is welded to the second housing part 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.

[0585] In other words, the depth of the housing 40 is equal to the sum of the depths of the first housing part 41 and the second housing part 42.

[0586] In this embodiment, welding the surface 4121 of the second wall 412 facing away from the first wall 411 to the second housing part 42 can improve the space utilization rate of the housing 40.

[0587] 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 part 42. For example, as Figure 8 to Figure 9 shown, the inner surface 4122 of the second wall 412 is welded to the second housing part 42 at the opening 401 of the first housing part 41 and the outer surface 4215 of the third wall 421 of the second housing part 42.

[0588] 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 therebetween.

[0589] Figure 1 FIG. 4 shows a schematic cross-sectional view of a housing 40 according to an embodiment of the present application. As ​ 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.

[0590] 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.

[0591] 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.

[0592] For example, H / h1 = 3, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80.

[0593] In this embodiment, setting the ratio of H to h1 within the range of [3, 80] will neither cause the welding position between 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 the housing 40 to crack due to excessive stress during the drawing process due to an overly small ratio, thereby making the manufacturing of the first housing portion 41 difficult.

[0594] 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.

[0595] In some embodiments, h1 satisfies: 3 mm ≤ h1 ≤ 50 mm.

[0596] For example, h1 = 3mm, 5mm, 10mm, 15mm, 20mm, 25mm, 30mm, 35mm, 40mm, 45mm, 50mm.

[0597] In this embodiment, by setting h1 within the range of [3mm, 50mm], neither will the weld seam be too close to the first housing portion 41 due to too small h1, resulting in a cracking risk during the charge and discharge process of the battery cell; nor will the first housing portion 41 crack during the integral drawing process due to too large h1, leading to a high manufacturing difficulty of the first housing portion 41.

[0598] Further optionally, h1 satisfies: 5mm ≤ h1 ≤ 30mm.

[0599] It should be noted that when h1 satisfies the above conditions, H can satisfy: H is greater than or equal to 100mm. For example, H is equal to 400mm.

[0600] In some embodiments, the yield strength of the housing 40 at a temperature of 25 °C is Re, and Re satisfies: 125MPa ≤ Re ≤ 1000Mpa.

[0601] The yield strength can be understood as the critical stress value at which the material yields. Generally, after the material is subjected to stress, 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, GB / T228.1 - 2010 can be used to test the yield strength Re at room temperature of 25 °C.

[0602] For example, Re = 125MPa, 130MPa, 150MPa, 180MPa, 200MPa, 230MPa, 250MPa, 280MPa, 300MPa, 320MPa, 350MPa, 380MPa, 400MPa, 430MPa, 450MPa, 480MPa, 500MPa, 530MPa, 550MPa, 570MPa, 600Mpa, 610Mpa, 640Mpa, 680Mpa, 700Mpa, 720Mpa, 750Mpa, 780Mpa, 800Mpa, 830Mpa, 850Mpa, 880Mpa, 900Mpa, 920Mpa, 950Mpa, 980Mpa, 1000Mpa.

[0603] In this embodiment, by using a material with a yield strength Re satisfying 125 MPa ≤ Re ≤ 1000 MPa to fabricate the first housing portion, the wall thickness of the first housing portion can be thinned without reducing the strength of the first housing portion, thereby increasing the capacity space of the battery cell.

[0604] ​ FIG. 4 shows a partial structural schematic diagram of the housing 211 according to an embodiment of the present application. For example, this ​ may be ​ a partial enlarged view of the region A' shown in FIG. As ​ shown, the housing 211 according to an embodiment 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.

[0605] It should be understood that the housing 211 according to an 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 along 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-like structure with a multi-layer structure can also be processed first; then multiple such plate-like structures are spliced and combined with each other, and a multi-layer housing 211 can also be formed, but the embodiments of the present application are not limited thereto.

[0606] It should be understood that the outermost housing 2117 of the housing 211 according to an 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.

[0607] 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...

Claims

1. A battery cell, characterized in that: include: An electrode assembly, the electrode assembly comprising a first electrode tab; a first electrode terminal; The shell comprises a cylinder and a cover connected to the cylinder, the cylinder is arranged around the periphery of the electrode assembly, the cover comprises the first electrode terminal, the first electrode tab is electrically connected to the first electrode terminal through the cylinder, and the shell is a multi-layer structure with different resistivities.

2. The battery cell according to claim 1, characterized in that: The shell includes a first shell layer, the resistivity of the first shell layer is K1, and K1 satisfies: 1×10^-8Ω·m≤K1≤6×10^-8Ω·m.

3. The battery cell according to claim 2, characterized in that: The average thickness of the first shell layer is T13, the average thickness of the shell is T10, and T13 and T10 satisfy: 0.15≤T13 / T10≤0.

85.

4. The battery cell according to claim 2 or 3, characterized in that: The material of the first shell layer includes at least one of the following: silver, copper, aluminum, magnesium and brass.

5. The battery cell according to any one of claims 2 to 4, characterized in that: The shell includes a second shell layer, and the tensile strength of the second shell layer at a temperature of 25° C. is Rm2, and Rm2 satisfies: 250MPa≤Rm2≤2000MPa.

6. The battery cell according to claim 5, characterized in that: The average thickness of the second shell layer is T14, the average thickness of the shell is T10, and T14 and T10 satisfy: 0.15≤T14 / T10≤0.

85.

7. The battery cell according to claim 5 or 6, characterized in that: The resistivity of the second shell layer is K2, and K2 and K1 satisfy: 2≤K2 / K1≤40.

8. The battery cell according to any one of claims 5 to 7, characterized in that: The material of the second shell layer includes at least one of the following: titanium, steel, silicon steel and stainless steel.

9. The battery cell according to any one of claims 5 to 8, characterized in that: The housing includes a plurality of the first housing layers and / or a plurality of the second housing layers.

10. The battery cell according to any one of claims 1 to 9, characterized in that: The electrode assembly further includes a second electrode tab, the second electrode tab has opposite polarity to the first electrode tab, and the first electrode tab and the second electrode tab are located at different end surfaces of the electrode assembly.

11. The battery cell according to claim 10, characterized in that: The first electrode tab and the second electrode tab are respectively located on opposite end surfaces of the electrode assembly.

12. The battery cell according to claim 10 or 11, characterized in that: The battery cell comprises: The second electrode terminal is electrically connected to the second electrode tab, and the first electrode terminal and the second electrode terminal are located on the same wall of the battery cell.

13. The battery cell according to claim 12, characterized in that: The cover body is the first electrode terminal, the cover body is provided with an electrode lead-out hole, the second electrode terminal is insulated and arranged on the cover body and installed in the electrode lead-out hole, one of the cover body and the second electrode terminal is the positive output pole of the battery cell, and the other is the negative output pole of the battery cell.

14. The battery cell according to any one of claims 1 to 13, characterized in that: The cover body and the cylinder body are integrally formed.

15. The battery cell according to any one of claims 1 to 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 1 to 15, characterized in that: The electrode assembly further comprises a positive electrode plate, wherein the positive electrode plate comprises a positive electrode active material capable of reversibly extracting and inserting metal ions, wherein the positive electrode active material comprises 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.

17. The battery cell according to any one of claims 1 to 16, characterized in that: The electrode assembly further comprises a positive electrode plate, wherein the positive electrode plate comprises a positive electrode active material capable of reversibly extracting and inserting metal ions, wherein the positive electrode active material comprises 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.

18. The battery cell according to any one of claims 1 to 17, characterized in that: The electrode assembly includes a first electrode tab; the shell includes a cylinder and a cover connected to the cylinder, the cylinder is arranged around the periphery of the electrode assembly, the cover includes a first electrode terminal, the first electrode tab is electrically connected to the first electrode terminal through the cylinder, and the shell is a multi-layer structure with different resistivities.

19. The battery cell according to any one of claims 1 to 18, characterized in that: The shell has an opening, and the shell includes a first shell wall and at least two second shell walls arranged opposite to the opening, wherein the first shell wall and the second shell wall are arranged to intersect; A transition region is provided between two adjacent second shell walls of the at least two second shell walls, and a maximum thickness T1 of the transition region and a maximum thickness T0 of the thickest second shell wall of the two second shell walls satisfy the following relationship: T1>T0.

20. The battery cell according to any one of claims 1 to 19, characterized in that: The shell is an integrally formed structure, the shell has an opening, the shell includes a first shell wall and at least two second shell walls arranged opposite to the opening, the first shell wall and the second shell wall are arranged to intersect, two of the at least two second shell walls are connected by a first fillet, and the depth H of the shell and the inner diameter R1 of the first fillet satisfy: 2.5mm≤R1≤20mm, 50mm <H≤250mm。 21. The battery cell according to any one of claims 1 to 20, characterized in that: The shell is an integrally formed structure, the shell has an opening, the shell includes a first shell wall and at least two second shell walls arranged opposite to the opening, the first shell wall and the second shell wall are arranged to intersect, two of the at least two second shell walls are connected by a first fillet, and the yield strength Re of the shell at a temperature of 25°C and the inner diameter R1 of the first fillet satisfy the following conditions: 140MPa≤Re≤1000Mpa, 2.5mm≤R1≤20mm.

22. The battery cell according to any one of claims 1 to 21, characterized in that: The shell has an opening, and the shell includes a first shell wall and at least one second shell wall arranged opposite to the opening, the first shell wall and the second shell wall are arranged to intersect, the first shell wall and the second shell wall are connected by a second fillet, and the inner diameter r1 of the second fillet and the minimum thickness T2 of the second shell wall with the smallest thickness among the at least one second shell wall satisfy the following relationship: 2.0≤r1 / T2≤30.

23. The battery cell according to any one of claims 1 to 22, characterized in that: The material of the outermost shell of the shell includes at least one of the following: aluminum, aluminum alloy, copper, copper alloy and chromium.

24. 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 1 to 23.

25. An electrical equipment, characterized in that: include: A battery, comprising a battery cell as claimed in any one of claims 1 to 23, wherein the battery is used to supply power to the electrical device.

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