Battery cells, batteries and electrical equipment

Abstract

The embodiments of the present application disclose a battery cell, a battery and an electrical device. The battery cell includes: an electrode assembly, the electrode assembly includes a negative electrode plate, the negative electrode plate includes a negative electrode active material that can reversibly release and embed metal ions, and the negative electrode active material includes a silicon-based material; a shell for accommodating the electrode assembly, the tensile strength of at least a part of the shell at a temperature of 25°C is Rm, and Rm satisfies: 250MPa≤Rm≤2000MPa, and the yield strength of at least a part of the shell at a temperature of 25°C is Re, and Re satisfies: 140MPa≤Re≤1000MPa. The battery cell, battery and electrical device of the embodiments of the present application can improve the reliability of the battery cell.

Description

[0001] This application claims priority to PCT patent application PCT / CN2023 / 132471 entitled “Battery Cells, Batteries and Electrical Devices” filed on November 17, 2023, the entire contents of which are incorporated herein by reference. Technical Field

[0002] The present application relates to the field of batteries, and more specifically, to a battery cell, a battery and an electrical device. Background Art

[0003] Energy conservation and emission reduction are the key to the sustainable development of the automobile industry. In this case, electric vehicles have become an important part of the sustainable development of the automobile industry due to their advantages of energy conservation and environmental protection. For electric vehicles, battery technology is an important factor in their development.

[0004] In the development of battery technology, in addition to improving battery performance, safety is also an issue that cannot be ignored. If the safety of the battery cannot be guaranteed, the battery cannot be used. Therefore, how to improve battery performance and ensure battery safety has become a particularly important issue in the development of battery technology. Summary of the invention

[0005] The embodiments of the present application provide a battery cell, a battery, and an electrical device, which can improve the reliability of the battery cell.

[0006] In a first aspect, a battery cell is provided, comprising: an electrode assembly, the electrode assembly comprising a negative electrode pole piece, the negative electrode pole piece comprising a negative electrode active material capable of reversibly extracting and embedding metal ions, the negative electrode active material comprising a silicon-based material; a shell for accommodating the electrode assembly, the tensile strength of at least a portion of the shell at a temperature of 25°C being Rm, and Rm satisfying: 250MPa≤Rm≤2000MPa, and the yield strength of at least a portion of the shell at a temperature of 25°C being Re, and Re satisfying: 140MPa≤Re≤1000MPa.

[0007] Therefore, the battery cell of the embodiment of the present application, by providing a silicon-based material on the negative electrode plate, can accommodate more metal ions, and can effectively increase the energy density of the battery cell. In addition, when the negative active material of the negative electrode plate has a silicon-based material, the deformation of the electrode assembly in the battery cell during use will also increase, especially during the charging process of the battery cell, the metal ions are embedded in the silicon-based material of the negative electrode plate, which will cause the volume expansion of the electrode assembly, thereby increasing the pressure of the electrode assembly on the shell of the battery cell. Therefore, increasing the tensile strength Rm of at least part of the shell at room temperature of 25°C can improve the deformation capacity of the shell, so that the shell is not easy to be damaged during the use of the battery cell, thereby improving the structural stability of the battery cell, and thereby improving the service life of the battery cell. However, the tensile strength Rm of at least part of the shell at room temperature of 25°C should not be too large, so as to reduce the difficulty of selecting and processing the material of the shell, save costs, and facilitate processing.

[0008] In addition, increasing the yield strength Re of at least part of the shell at room temperature of 25°C can improve the deformation capacity of the shell, thereby improving the structural stability of the battery cell, and thereby improving the service life of the battery cell. During the charge and discharge process of the battery cell, the electrode assembly will cyclically expand and shrink in volume. Increasing the room temperature yield strength Re of at least part of the shell can increase the maximum extrusion force that the shell can withstand. If the limit of the yield strength of the shell is not exceeded, the shell is not easily damaged, and the deformation of the shell can be restored, thereby increasing the service life of the shell. However, the yield strength Re of at least part of the shell at room temperature should not be too large, so as to reduce the difficulty of selecting the material and processing of the shell, save costs, and facilitate processing.

[0009] In some embodiments, in the negative electrode active material, the mass proportion of the silicon-based material is g, the material of at least a portion of the shell includes iron, Rm and g satisfy 2%≤g≤40%, and 300MPa<Rm<2000MPa.

[0010] In some embodiments, the material of at least a portion of the shell includes carbon steel or stainless steel, and Rm and g satisfy 2.5%≤g≤15%, 315MPa≤Rm<800MPa.

[0011] In some embodiments, the material of at least a portion of the shell includes carbon steel or stainless steel, and Rm and g satisfy 4.5%≤g≤40%, and 380MPa≤Rm<2000MPa.

[0012] In some embodiments, Rm and g satisfy 8%≤g≤40%, 400MPa≤Rm<2000MPa.

[0013] In some embodiments, Rm and g satisfy 10%≤g≤40%, 480MPa≤Rm<2000MPa.

[0014] In some embodiments, Rm and g satisfy 15%≤g≤40%, 520MPa≤Rm<2000MPa.

[0015] In some embodiments, Rm and g satisfy 20%≤g≤40%, 600MPa≤Rm<2000MPa.

[0016] In some embodiments, the silicon-based material includes at least one of elemental silicon, silicon-oxygen compounds, silicon-carbon composites, silicon-nitrogen composites, silicon-containing alloys, or silicon-oxygen-carbon composite materials for ease of implementation.

[0017] The above materials are easy to process and can meet the design requirements. Specifically, silicon-based materials are added to the negative active materials of the negative electrode plates. Since silicon-based materials can accommodate more metal ions than other elements, for example, the capacity of silicon-based materials is about ten times that of graphite, the energy density of the battery cell can be effectively improved. At the same time, the mass proportion g of the silicon-based material should not be set too large, otherwise it will increase the difficulty of processing the electrode assembly, and will also increase the deformation of the electrode assembly in the battery cell during use, especially during the charging process of the battery cell, the metal ions are embedded in the silicon-based material of the negative electrode plate, which will cause the volume expansion of the electrode assembly, thereby increasing the pressure of the electrode assembly on the shell of the battery cell, thereby increasing the difficulty of processing the battery cell. Therefore, by reasonably selecting materials, the tensile strength Rm of at least part of the shell under normal temperature conditions can be appropriately increased, and the deformation capacity of this part of the shell can be improved to resist the expansion of the electrode assembly, so that this part of the shell is not easily damaged, thereby improving the structural stability and service life of the battery cell. On the other hand, by controlling the tensile strength Rm of at least a portion of the shell at room temperature to not be too large, the difficulty of selecting and processing the material of the shell can be reduced, thus saving costs and facilitating processing.

[0018] In some embodiments, the shell includes a weld, and at least part of the shell includes an area of ​​the shell within a preset distance from the weld, and the preset distance is L, and L satisfies: L=10mm. In the case where the negative active material of the negative electrode plate of the electrode assembly includes a silicon-based material, since the silicon-based material can accommodate more metal ions, the deformation of the electrode assembly in the battery cell during use will increase, causing the volume expansion of the electrode assembly, thereby increasing the pressure of the electrode assembly on the shell of the battery cell. Under the same conditions, the structural strength of the area of ​​the shell near the weld is relatively small relative to the structural strength of other areas of the shell, so the area of ​​the shell near the weld is more likely to be damaged during the use of the battery cell. Therefore, setting the area within the preset distance L from the weld to meet the tensile strength Rm requirement under normal temperature conditions can improve the deformation capacity of the area of ​​the shell near the weld, so that this part of the shell is not easily damaged, thereby improving the structural stability and service life of the battery cell.

[0019] In some embodiments, at least a portion of the shell includes the entire wall of the shell. In the case where the negative active material of the negative electrode plate of the electrode assembly includes a silicon-based material, since the silicon-based material can accommodate more metal ions, the deformation of the electrode assembly in the battery cell during use will increase, causing the volume expansion of the electrode assembly, thereby increasing the pressure of the electrode assembly on the shell of the battery cell. Therefore, setting all areas of the shell to meet the requirements of the tensile strength Rm under normal temperature conditions can improve the overall deformation capacity of the shell, and can also limit the extrusion force of the internal electrode assembly on the shell in all directions, so that the strength of each part of the shell is balanced and it is not easy to be damaged in the local weak area, thereby improving the structural stability and service life of the battery cell.

[0020] In some embodiments, the shell is in a cylindrical or polygonal shape to facilitate processing.

[0021] In some embodiments, the electrode assembly further comprises a positive electrode plate, the positive electrode plate comprises a positive electrode active material capable of reversibly extracting and embedding metal ions, the positive electrode active material comprises a nickel-containing compound; the melting point of at least a portion of the shell is p, and p satisfies: 1200°C≤p≤2000°C. In the case where the positive electrode active material of the positive electrode plate comprises a nickel-containing 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 can also be increased, especially in the case of thermal runaway of the battery cell, the internal temperature of the battery cell increases rapidly and a large amount of gas is generated. Therefore, appropriately increasing the melting point p of at least a portion of the shell will make the shell less likely to be melted, reduce the possibility of explosion of the battery cell, and further reduce the risk of thermal runaway of adjacent battery cells, so as to improve the reliability of the battery. However, the melting point p of the shell should not be too large to reduce the difficulty of selecting and processing the material of the shell, save costs, and facilitate processing.

[0022] In some embodiments, the electrode assembly further comprises a positive electrode sheet, the positive electrode sheet comprises a positive electrode active material capable of reversibly extracting and embedding metal ions, 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: 100MPa≤Rn≤1200MPa. In the case where the positive electrode active material of the positive electrode sheet comprises a nickel-containing 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 can also be increased, especially when the battery cell has thermal runaway, the internal temperature of the battery cell increases rapidly and a large amount of gas is generated. Therefore, appropriately increasing the tensile strength Rn of at least a portion of the shell at a high temperature of 500°C can improve the deformation ability of the portion of the shell when the battery cell has thermal runaway, which will make the shell less likely to be quickly destroyed and exploded, thereby reducing the risk of thermal runaway of adjacent battery cells, so as to improve the reliability of the battery. However, the tensile strength Rn of at least a portion of the shell at a high temperature of 500°C should not be too large to save costs and facilitate processing.

[0023] In some embodiments, the shell at least partially includes a third shell wall, and the average thickness of the third shell wall is T, and T satisfies: 0.05mm≤T≤0.5mm, 60 mm·MPa≤T×Rm≤500 mm·MPa. Increasing the tensile strength Rm of at least part of the shell at room temperature of 25°C can improve the deformation capacity of the shell, making it less likely for the shell to be damaged during the use of the battery cell, thereby improving the structural stability and service life of the battery cell. However, the tensile strength Rm of at least part of the shell at room temperature should not be too large to reduce the difficulty of selecting and processing the material of the shell, save costs, and facilitate processing. When the average thickness T of the third shell wall of the shell is thin, the structural strength of the third shell wall can be increased by increasing the tensile strength Rm of the third shell wall of the shell at room temperature of 25°C, which can not only improve the energy density of the battery cell, but also improve the structural strength and stability of the battery cell; on the contrary, when the average thickness T of the third shell wall of the shell is thick, the structural strength of the shell can be improved, and the difficulty of selecting the material of the shell can be reduced by appropriately reducing the tensile strength Rm of the third shell wall of the shell at room temperature, thereby reducing the processing difficulty and processing cost of the battery cell. In addition, T×Rm represents the stiffness of the third shell wall, and the stiffness of the third shell wall should not be too small or too large, which can not only make the third shell wall have better deformation ability, but also reduce the processing difficulty and cost.

[0024] In some embodiments, the capacity of the battery cell is C, and C satisfies: 25Ah≤C≤550Ah. On the one hand, increasing the capacity C of the battery cell can increase the capacity density of the battery including multiple battery cells, or, if the total capacity of the battery remains unchanged, if the capacity C of a single battery cell is increased, the number of battery cells can be reduced, and the number of electrical connections between multiple battery cells can be reduced accordingly, reducing the probability of electrical connection failure, which helps to improve the reliability of the battery. In addition, when the capacity C of the battery cell is large, the tensile strength Rm of at least part of the shell at room temperature of 25°C can be increased to meet the requirements of the high-capacity battery cell for the structural strength of the shell, thereby improving the reliability and service life of the battery cell. On the other hand, if the battery cell has a large capacity, the reaction inside it will intensify, thereby increasing the requirements for the structural strength of the shell. Therefore, the capacity C of the battery cell should not be too large to limit the design requirements for the structural strength of the shell, which can reduce the difficulty of material selection and processing of the battery cell, reduce costs and improve processing efficiency.

[0025] In some embodiments, the housing has an opening, and the housing includes a first housing wall disposed opposite to the opening and at least two second housing walls, and 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, by setting the maximum thickness T1 of the transition region 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 can enhance the structural strength of the housing, which is beneficial to solving the problem of deformation of the housing during the production and assembly process of the battery cell, and the problem of deformation of the housing 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. 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, and thus reduce the forming difficulty of the housing.

[0028] 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. The yield strength Re of the housing under the condition of a temperature of 25 °C and the inner diameter R1 of the first fillet 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, the wall thickness of the housing can be thinned 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 fillet 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 can be reduced as much as possible, and the forming difficulty of the housing can be lowered.

[0030] In some embodiments, the shell has an opening, and the shell includes a first shell wall and a 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 two second shell walls satisfy: 2.0≤r1 / T2≤30. By setting the ratio of the inner diameter r1 of the second fillet between the first shell wall and the second shell wall to the minimum thickness T2 of the second shell wall with the smallest wall thickness between [2.0, 30], it helps to balance the processing difficulty of the shell with the space capacity and strength of the battery cell.

[0031] In some embodiments, the shell includes: a first shell portion, formed with a first opening portion, the first shell portion including a first wall opposite to the first opening portion and a second wall connected to the first wall, the first wall and the second wall being integrally formed; a second shell portion, fixedly connected to the second wall; wherein, in the depth direction of the first shell portion, at least a portion of the shell is formed by the first shell portion and the second shell portion. The shell prepared in this way can reduce the risk of shell cracking during the integral deep drawing process compared to the technical solution of directly integrally forming the shell.

[0032] In some embodiments, the battery cell is used for a battery, the electrode assembly includes a first pole ear and a second pole ear with opposite polarities; the shell includes a barrel and a cover connected to the barrel, the cover and the barrel are an integral structure, the barrel is arranged around the periphery of the electrode assembly, the cover is provided with an electrode lead-out hole, and at least a portion of the cover is used to electrically connect the first connecting member of the battery and the first pole ear; the battery cell also includes: a second electrode terminal, which is used to electrically connect the second connecting member of the battery and the second pole ear, the second electrode terminal is insulated and arranged on the cover and installed on the electrode lead-out hole, one of the cover 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. By using the cover and the second electrode terminal as the output pole, the structure of the battery cell can be simplified and the current capacity of the battery cell can be guaranteed. The cover and the second electrode terminal are located at the same end of the battery cell, so that the first connecting member and the second connecting member can be assembled to the same side of the battery cell, which can simplify the assembly process and improve the efficiency of assembling multiple battery cells into groups.

[0033] In some embodiments, the second pole tab is disposed at one end of the electrode assembly facing the cover, and the first pole tab is disposed at the other end of the electrode assembly away from the cover; the barrel is used to connect the first pole tab and the cover so that the first pole tab is electrically connected to the cover. In the embodiment of the present application, the first pole tab and the second pole tab are disposed at both ends of the electrode assembly, which can reduce the risk of the first pole tab and the second pole tab being conductive, and increase the flow area of ​​the first pole tab and the flow area of ​​the second pole tab.

[0034] In some embodiments, the electrode assembly includes a first pole ear; the shell includes a barrel and a cover connected to the barrel, the barrel is arranged around the periphery of the electrode assembly, the cover includes the first electrode terminal, the first pole ear is electrically connected to the first electrode terminal through the barrel, and the shell is a multi-layer structure, and the resistivity of the multi-layer structure is different. The electrode assembly includes a first pole ear, the first pole ear is electrically connected to the first electrode terminal of the battery cell through the shell, and the shell is a multi-layer structure, and the resistivity of the multi-layer structure is different. The first pole ear is electrically connected to the first electrode terminal through the barrel, which can simplify the structure of the battery cell; the shell is set to a multi-layer structure, and the resistivity of the multi-layer structure is different, and the current capacity of the battery cell can be improved by a layer structure with a lower resistivity, and the structural strength of the shell can be improved by a layer structure with a higher resistivity, which can improve the performance of the battery cell and the structural strength of the battery cell, thereby increasing the service life of the battery cell.

[0035] In some embodiments, the shell is a multi-layer structure, and the material of the outermost shell of the shell includes at least one of the following: aluminum, aluminum alloy, copper, copper alloy and chromium. When the material of the outermost shell contains aluminum, the aluminum will be oxidized into dense aluminum oxide, which can prevent corrosion; when the material of the outermost shell contains copper, the copper will be oxidized into copper oxide, that is, verdigris, which can prevent corrosion; when the material of the outermost shell contains chromium, the chromium will be oxidized into chromium oxide, which can also prevent corrosion. Therefore, when the material of the outermost shell is the above-mentioned anti-corrosion material, the outermost shell can protect other shell layers located inside it, which can not only improve the structural stability of the shell, but also improve the service life of the shell.

[0036] In a second aspect, a battery is provided, comprising: a plurality of battery cells, wherein the battery cells are the battery cells described in the first aspect or any one embodiment of the first aspect.

[0037] In a third aspect, an electrical device is provided, comprising: a battery, the battery comprising a battery cell as described in the first aspect or any one embodiment of the first aspect, the battery being used to supply power to the electrical device.

[0038] In some embodiments, the electrical equipment is a vehicle, a ship or a spacecraft. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 A schematic diagram of the structure of a vehicle according to an embodiment of the present application;

[0040] Figure 2 This is a schematic diagram of the exploded structure of a battery according to an embodiment of the present application;

[0041] Figure 3 A schematic diagram of the structure of a battery cell according to an embodiment of the present application;

[0042] Figure 4 A schematic diagram of a partial exploded structure of a battery cell according to an embodiment of the present application;

[0043] Figure 5 A cross-sectional schematic diagram of an electrode assembly according to an embodiment of the present application;

[0044] Figure 6 A partial cross-sectional schematic diagram of a negative electrode sheet or a positive electrode sheet of an electrode assembly according to an embodiment of the present application;

[0045] Figure 7 This is a schematic structural diagram of a fixture for cyclic charging fatigue testing according to an embodiment of the present application;

[0046] Figure 8 This is a schematic side structural diagram of a housing of a battery cell according to an embodiment of the present application;

[0047] Fig. 9 A schematic cross-sectional structure diagram of a battery cell housing according to an embodiment of the present application;

[0048] Fig.10 This is a schematic diagram of the exploded structure of a battery cell according to an embodiment of the present application;

[0049] Fig.11 A cross-sectional view of a housing according to an embodiment of the present application;

[0050] Fig.12 for Fig.11 A magnified view of part A;

[0051] Fig.13 A schematic diagram of a transition area of ​​a housing according to an embodiment of the present application;

[0052] Fig.14 A schematic diagram of another transition region of a housing according to an embodiment of the present application;

[0053] Fig.15 Another cross-sectional view of a housing according to an embodiment of the present application;

[0054] Fig.16 for Fig.15 A partial enlarged schematic diagram of part B;

[0055] Fig.17 for Fig.15 Another partial enlarged schematic diagram of part B;

[0056] Fig.18 An exploded schematic diagram of a housing according to an embodiment of the present application;

[0057] Fig.19 A schematic structural diagram of a second housing portion according to an embodiment of the present application;

[0058] Fig. 20 Another structural schematic diagram of the second housing portion of an embodiment of the present application;

[0059] Fig.21 Another exploded schematic diagram of a housing according to an embodiment of the present application;

[0060] Fig. 22 A schematic cross-sectional view of a housing according to an embodiment of the present application;

[0061] Fig.23 It is a schematic diagram of a partial structure of a housing according to an embodiment of the present application;

[0062] Fig.24 A schematic diagram of the structure of a battery cell according to another embodiment of the present application;

[0063] Fig.25 A schematic diagram of a partial exploded structure of a battery cell according to another embodiment of the present application;

[0064] Fig.26 A schematic cross-sectional structure diagram of a shell of a battery cell according to another embodiment of the present application;

[0065] Fig. 27 A schematic cross-sectional view of a partial structure of a battery according to another embodiment of the present application;

[0066] Fig.28 It is a cross-sectional schematic diagram of another partial structure of a battery according to another embodiment of the present application.

[0067] In the drawings, the drawings are not drawn to scale. DETAILED DESCRIPTION

[0068] The technical solutions in the embodiments of the present application will be described below in conjunction with the accompanying drawings.

[0069] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0070] Unless otherwise defined, all technical and scientific terms used in this application have the same meanings as those commonly understood by technicians in the technical field of this application; the terms used in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" in the specification and claims of this application and the above-mentioned drawings and any variations thereof are intended to cover non-exclusive inclusions. The terms "first", "second", etc. in the specification and claims of this application or the above-mentioned drawings are used to distinguish different objects, rather than to describe a specific order or a primary and secondary relationship.

[0071] Reference to "embodiments" in this application means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described in this application may be combined with other embodiments.

[0072] In the description of this application, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", and "attached" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be the internal communication of two elements. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0073] The term "and / or" in this application is only a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this application generally indicates that the associated objects before and after are in an "or" relationship.

[0074] In the embodiments of the present application, the same reference numerals represent the same components, and for the sake of brevity, detailed descriptions of the same components are omitted in different embodiments. It should be understood that the thickness, length, width and other dimensions of various components in the embodiments of the present application shown in the drawings, as well as the overall thickness, length, width and other dimensions of the integrated device are only exemplary descriptions and should not constitute any limitation to the present application.

[0075] The term "multiple" as used in the present application refers to more than two (including two). Similarly, "multiple groups" refers to more than two groups (including two groups), and "multiple sheets" refers to more than two sheets (including two sheets).

[0076] In the embodiment of the present application, the battery cell may be a secondary battery. A secondary battery refers to a battery cell that can be continuously used by activating active materials by charging after the battery cell is discharged.

[0077] The battery cell can be a lithium ion battery, a sodium ion battery, a sodium lithium ion battery, a lithium metal battery, a sodium metal battery, a lithium sulfur battery, a magnesium ion battery, a nickel hydrogen battery, a nickel cadmium battery, a lead storage battery, etc., which is not limited in the embodiments of the present application.

[0078] In some implementations, 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, or a magnesium metal battery, etc., which is not limited in the embodiments of the present application.

[0079] A battery cell generally includes an electrode assembly. The electrode assembly includes a positive electrode, a negative electrode, and a separator. During the charge and discharge process of the battery cell, active ions (such as lithium ions) are embedded and removed between the positive electrode and the negative electrode. The separator is set between the positive electrode and the negative electrode to prevent the positive and negative electrodes from short-circuiting, while allowing active ions to pass through.

[0080] 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.

[0081] As an example, the positive electrode current collector has two surfaces facing each other in its thickness direction, and the positive electrode active material is disposed on either or both of the two facing surfaces of the positive electrode current collector.

[0082] As an example, the positive electrode current collector may be a metal foil, a foamed metal or a composite current collector. For example, as the metal foil, aluminum or stainless steel treated with silver, stainless steel, copper, aluminum, nickel, carbon electrode, carbon, nickel or titanium, etc. may be used. The foamed metal may be foamed nickel, foamed copper, foamed aluminum, foamed alloy, or foamed carbon, etc. The composite current collector may include a polymer material base and a metal layer. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.).

[0083] As an example, the positive electrode active material may include at least one of the following materials: lithium-containing phosphates, lithium transition metal oxides, and their respective modified compounds. However, the present application is not limited to these materials, and other traditional materials that can be used as positive electrode active materials for batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more. Among them, examples of lithium-containing phosphates may include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO4), a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, and a composite material of lithium iron manganese phosphate and carbon.

[0084] 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.

[0085] As an example, the negative electrode current collector has two surfaces facing each other in its thickness direction, and the negative electrode active material is disposed on either or both of the two facing surfaces of the negative electrode current collector.

[0086] As an example, the negative electrode current collector may be a metal foil, a foamed metal or a composite current collector. For example, as the metal foil, aluminum or stainless steel treated with silver, stainless steel, copper, aluminum, nickel, carbon electrode, carbon, nickel or titanium, etc. may be used. The composite current collector may include a polymer material base layer and a metal layer. The foamed metal may be a foamed nickel, a foamed copper, a foamed aluminum, a foamed alloy, or a foamed carbon, etc. The composite current collector may be formed by forming a metal material (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.).

[0087] In some embodiments, the electrode assembly further includes a separator disposed between the positive electrode and the negative electrode.

[0088] In some embodiments, the separator is a separator. The present application has no particular limitation on the type of separator, and any known separator with a porous structure having good chemical stability and mechanical stability can be selected.

[0089] As an example, the main material of the isolation membrane can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, polyvinylidene fluoride, and ceramics.

[0090] In some embodiments, the separator is a solid electrolyte, which is disposed between the positive electrode and the negative electrode and serves to transmit ions and isolate the positive and negative electrodes.

[0091] In some embodiments, the battery cell further includes an electrolyte, which acts as a conductor of ions between the positive and negative electrodes. The present application has no specific restrictions on the type of electrolyte, which can be selected according to needs. The electrolyte can be liquid, gel or solid.

[0092] In some embodiments, the electrode assembly is provided with tabs, which can lead current out of the electrode assembly. The tabs include a positive tab and a negative tab.

[0093] In some embodiments, the battery cell may include a housing. The housing is used to encapsulate components such as electrode assemblies and electrolytes. The housing may be a steel housing, an aluminum housing, a plastic housing (such as polypropylene), a composite metal housing (such as a copper-aluminum composite housing), or an aluminum-plastic film. The housing includes a shell and a cover plate.

[0094] 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, in parallel or in mixed connection through a busbar component.

[0095] In some embodiments, the battery may be a battery pack, which includes a case and battery cells, wherein the battery cells or battery modules are accommodated in the case.

[0096] In some embodiments, the box body can be used as a part of the chassis structure of the vehicle. For example, part of the box body can become at least a part of the floor of the vehicle, or part of the box body can become at least a part of the cross beam and longitudinal beam of the vehicle.

[0097] In some embodiments, the battery may be located in an energy storage device, which includes an energy storage container, an energy storage cabinet, and the like.

[0098] The development of battery technology must consider many design factors at the same time, such as performance parameters such as energy density, cycle life, discharge capacity, charge and discharge rate, etc. In addition, the safety and stability of the battery also need to be considered. For example, by reasonably selecting the positive active material of the positive electrode sheet of the electrode assembly, or the negative active material of the negative electrode sheet, the energy of the battery cell can be effectively improved, thereby increasing the energy of the battery. Taking the negative active material of the negative electrode sheet of the electrode assembly as an example, adding silicon-based materials to the negative active material can increase the energy of the battery cell, but during the cycle charge and discharge of the battery cell, the expansion of the electrode assembly will also increase, which will easily increase the deformation of the battery cell shell. If the shell strength is insufficient, it may cause damage to the shell, affecting the life of the battery cell.

[0099] Therefore, the embodiments of the present application provide a battery cell, a battery and an electrical device that can solve the above problems. The battery cell of the embodiments of the present application includes: an electrode assembly and a shell for accommodating the electrode assembly, the electrode assembly includes a negative electrode plate, the negative electrode plate includes a negative electrode active material that can reversibly extract and embed metal ions, and the negative electrode active material includes a silicon-based material; the tensile strength of at least part of the shell under the condition of a temperature of 25°C is Rm, and Rm satisfies: 250MPa≤Rm≤2000MPa. Providing a silicon-based material on the negative electrode plate 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 plate has a silicon-based material, the deformation of the electrode assembly in the battery cell during use will also increase, especially during the charging process of the battery cell, the metal ions are embedded in the silicon-based material of the negative electrode plate, which will cause the volume expansion of the electrode assembly, thereby increasing the pressure of the electrode assembly on the shell of the battery cell. Therefore, increasing the tensile strength Rm of at least a portion of the shell at a normal temperature of 25°C can improve the deformation capacity of the shell, making it less likely for the shell to be damaged during the use of the battery cell, thereby improving the structural stability of the battery cell and thereby increasing the service life of the battery cell. However, the tensile strength Rm of at least a portion of the shell at a normal temperature of 25°C should not be too large, so as to reduce the difficulty of selecting the material and processing the shell, save costs, and facilitate processing.

[0100] The technical solutions described in the embodiments of the present application are applicable to various electrical devices using batteries.

[0101] Electrical equipment may be vehicles, mobile phones, portable devices, laptops, ships, spacecraft, electric toys, electric tools, and the like. Vehicles may be fuel vehicles, gas vehicles, or new energy vehicles, and new energy vehicles may be pure electric vehicles, hybrid vehicles, or extended-range vehicles, and the like; spacecraft include airplanes, rockets, space shuttles, and spacecraft, and the like; electric toys include fixed or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, and the like; electric tools include metal cutting electric tools, grinding electric tools, assembly electric tools, and railway electric tools, such as electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact drills, concrete vibrators, and electric planers, and the like. The embodiments of the present application do not impose any special restrictions on the above-mentioned electrical equipment.

[0102] For the convenience of description, the following embodiments are described by taking the electric device as a vehicle as an example.

[0103] For example, Figure 1 As shown, it is a structural schematic diagram of a vehicle 1 according to an embodiment of the present application. The vehicle 1 may be a fuel vehicle, a gas vehicle or a new energy vehicle. The new energy vehicle may be a pure electric vehicle, a hybrid vehicle or an extended-range vehicle, etc. A motor 80, a controller 70 and a battery 10 may be arranged inside the vehicle 1. The controller 70 is used to control the battery 10 to supply power to the motor 80. For example, a battery 10 may be arranged at the bottom, front or rear of the vehicle 1. The battery 10 may be used to supply power to the vehicle 1. For example, the battery 10 may be used as an operating power source for the vehicle 1, for the circuit system of the vehicle 1, for example, for the working power requirements during the start-up, navigation and operation of the vehicle 1. In another embodiment of the present application, the battery 10 may not only be used as an operating power source for the vehicle 1, but also as a driving power source for the vehicle 1, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle 1.

[0104] In order to meet different power requirements, a battery may include multiple battery cells, wherein multiple battery cells may be connected in series, in parallel, or in hybrid connection, where hybrid connection refers to a mixture of series and parallel connection. A battery may also be referred to as a battery pack. For example, multiple battery cells may be connected in series, in parallel, or in hybrid connection to form a battery module, and multiple battery modules may be connected in series, in parallel, or in hybrid connection to form a battery. In other words, multiple battery cells may be directly connected to form a battery, or they may be connected to form a battery module first, and then the battery module may be connected to form a battery.

[0105] Figure 2 The schematic diagram of the exploded structure of a battery 10 according to an embodiment of the present application is shown. The battery 10 may include a plurality of battery cells 20. The battery 10 may also include a box body 11. The box body 11 is a hollow structure, and the plurality of battery cells 20 are accommodated in the box body 11. Figure 2A possible implementation of the box 11 of the embodiment of the present application is shown, such as Figure 2 As shown, the box body 11 may include two box body parts, which are respectively referred to as the first box body part 111 and the second box body part 112, and the first box body part 111 and the second box body part 112 are buckled together. The shapes of the first box body part 111 and the second box body part 112 can be determined according to the shapes of the battery cells 20 after being combined, and at least one of the first box body part 111 and the second box body part 112 has an opening. For example, Figure 2 As shown, the first box body 111 and the second box body 112 can both be hollow cuboids and each has only one open face. The opening of the first box body 111 and the opening of the second box body 112 are arranged opposite to each other, and the first box body 111 and the second box body 112 are buckled together to form a box body 11 with a closed chamber. The chamber can be used to accommodate multiple battery cells 20. Multiple battery cells 20 are connected in parallel, in series, or in mixed combination and placed in the box body 11 formed by the buckling of the first box body 111 and the second box body 112.

[0106] For example, unlike Figure 2 As shown, only one of the first box body 111 and the second box body 112 may be a hollow cuboid with an opening, and the other may be a plate-shaped to cover the opening. For example, here, the second box body 112 is a hollow cuboid with only one face as an opening face, and the first box body 111 is a plate-shaped example, then the first box body 111 covers the opening of the second box body 112 to form a box body 11 with a closed chamber, but the embodiments of the present application are not limited thereto.

[0107] Figure 3 The structure diagram of a battery cell 20 according to an embodiment of the present application is shown, for example, Figure 3 The battery cell 20 shown may be Figure 2 Any battery cell 20 in the battery 10 shown; Figure 4 A partial exploded structural diagram of a battery cell 20 according to an embodiment of the present application is shown, for example, Figure 4 Can be Figure 3 The schematic diagram of the partial exploded structure of the battery cell 20 is shown.

[0108] In the embodiments of the present application, Figure 3 and Figure 4As shown, the battery cell 20 may include an electrode assembly 22 and a shell 211. Specifically, the electrode assembly 22 includes a negative electrode plate 224, the negative electrode plate 224 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 shell 211 is used to accommodate the electrode assembly 22, and the tensile strength of at least a part of the shell 211 under the condition of a temperature of 25°C is Rm, and Rm satisfies: 250MPa≤Rm≤2000MPa.

[0109] like Figure 3 and Figure 4 As shown, the battery cell 20 of the embodiment of the present application may include: a housing 21. Specifically, the housing 21 may include: a shell 211, and the shell 211 is a hollow structure with at least one opening. Further, the battery cell 20 may also include a cover plate 212, for example, the housing 21 includes the cover plate 212, and the cover plate 212 is used to cover the opening of the shell 211, so that the electrode assembly 22 can be accommodated in the housing 21.

[0110] It should be understood that the housing 211 of the embodiment of the present application is a component for accommodating the electrode assembly 22, and the housing 211 may be a hollow structure with one or more ends forming an opening. For example, if the housing 211 is a hollow structure with one end forming an opening, one cover plate 212 may be provided accordingly; if the housing 211 is a hollow structure with two opposite ends forming openings, two cover plates 212 may be provided, and the two cover plates 212 respectively cover the openings at the two ends of the housing 211.

[0111] It should be understood that the battery cell 20 of the embodiment of the present application can be a cylindrical battery cell, a prismatic battery cell, a soft-pack battery or a battery cell of other shapes. Among them, the prismatic battery cell can include a square-shell battery cell, a blade-shaped battery cell or other multi-prismatic battery cells, such as a hexagonal battery cell or an octagonal battery cell, and the embodiment of the present application is not limited thereto.

[0112] Corresponding to the battery cells 20 of different shapes, the housing 211 of the battery cells 20 may be in various shapes, for example, the housing 211 is cylindrical or polygonal. Figure 3 and Figure 4 As shown, in the embodiment of the present application, the shell 211 is mainly described as a hollow rectangular parallelepiped structure. In addition, the embodiment of the present application mainly takes the shell 211 as a hollow structure with an opening at one end as an example. However, the relevant description of the embodiment of the present application is also applicable to battery cells 20 of other shapes, and for the sake of brevity, they are not repeated here one by one.

[0113] It should be understood that the cover plate 212 of the embodiment of the present application is used to cover 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, such as Figure 3 and Figure 4 As shown, the shell 211 is a rectangular parallelepiped structure, and the cover plate 212 is a rectangular plate structure matched with the shell 211 .

[0114] In the battery cell 20, the electrode assembly 22 is a component in the battery cell 20 where an electrochemical reaction occurs. According to actual use requirements, the electrode assembly 22 in the housing 211 can be set to one or more. Figure 3 and Figure 4 As shown, two electrode assemblies 22 are arranged in the battery cell 20. The electrode assembly 22 can be cylindrical, rectangular, etc. If the electrode assembly 22 is a cylindrical structure, the housing 211 can also be a cylindrical structure. If the electrode assembly 22 is a rectangular structure, the housing 211 can also be a rectangular structure.

[0115] It should be understood that Figure 3 and Figure 4 As shown, the electrode assembly 22 of the embodiment of the present application may include a tab 222 and an electrode body 221, wherein 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 stacking a portion of the positive electrode sheet 223 that is not coated with a positive electrode active material, and the negative tab 222b may be formed by stacking a portion of the negative electrode sheet 224 that is not coated with a negative electrode active material; the electrode body 221 may be formed by stacking or winding a positive electrode sheet 223 and a negative electrode sheet 224.

[0116] The negative electrode active material included in the negative electrode plate 224 of the embodiment of the present application can be flexibly set according to the actual application. For example, the negative electrode active material may include a silicon-based material. In the case of adding a silicon-based material to the negative electrode plate 224, the silicon-based material can accommodate more metal ions, which can effectively increase the energy density of the battery cell 20; in addition, it will increase the deformation of the electrode assembly 22 in the battery cell 20 during use, especially during the charging process of the battery cell 20, the metal ions are embedded in the silicon-based material of the negative electrode plate 224, which will cause the volume expansion of the electrode assembly 22, thereby increasing the pressure of the electrode assembly 22 on the shell 211 of the battery cell 20.

[0117] Therefore, increasing the tensile strength Rm of at least a portion of the housing 211 at a normal temperature of 25°C can improve the deformation capacity of the portion of the housing 211, so that the portion of the housing 211 is not easily damaged during the use of the battery cell 20, thereby improving the structural stability and service life of the battery cell 20. However, the tensile strength Rm of at least a portion of the housing 211 at normal temperature should not be too large, so as to reduce the difficulty of selecting the material and processing the housing 211, save costs, and facilitate processing. For example, the tensile strength Rm of at least a portion of the housing 211 at normal temperature can usually be set to meet 250MPa≤Rm≤2000MPa.

[0118] It should be understood that the value range of the tensile strength Rm of at least part of the shell 211 of the embodiment of the present application at room temperature of 25°C can be adjusted according to the actual application. For example, the value of the tensile strength Rm at room temperature can satisfy 250MPa≤Rm≤2000MPa. For another example, the value of the tensile strength Rm at room temperature can also satisfy 400MPa≤Rm≤1200MPa. On the one hand, increasing the tensile strength Rm of at least part of the shell 211 at room temperature can improve the deformation capacity of the part of the shell 211 to resist the expansion of the electrode assembly 22, so that the part of the shell 211 is not easily damaged, thereby improving the structural stability and service life of the battery cell 20. On the other hand, controlling the tensile strength Rm of at least part of the shell 211 at room temperature will not be too large, which can reduce the difficulty of selecting and processing the material of the shell 211, save costs, and facilitate processing.

[0119] Furthermore, the tensile strength Rm of at least a portion of the shell 211 at room temperature may be set to satisfy 450MPa≤Rm≤800MPa. The tensile strength Rm of at least a portion of the shell 211 at room temperature is not too large or too small, which can improve the deformation capacity of the portion of the shell 211 to resist the expansion of the electrode assembly 22, and is easy to implement and saves costs.

[0120] In some embodiments, the tensile strength Rm of at least a portion of the housing 211 of the embodiment of the present application at room temperature can also be set to other values. For example, the tensile strength Rm at room temperature can be any of the following values ​​or between any two of the following values: 250MPa, 280MPa, 300MPa, 330MPa, 350MPa, 380MPa, 400MPa, 450MPa, 500MPa, 550MPa, 600MPa, 650MPa, 700MPa, 750MPa, 800MPa, 850MPa, 900MPa, 950MPa, 10 ... The abovementioned values ​​are as follows: 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.

[0121] It should be understood that the tensile strength of the embodiment of the present application refers to the maximum stress value that the material bears before breaking. The test method of the tensile strength Rm of at least a part of the housing 211 of the embodiment of the present application at a temperature of 25°C can be selected according to the actual application. For example, the national standard GB / T 228.1-2010 can be used to test the tensile strength Rm at a normal temperature of 25°C.

[0122] Figure 5 The cross-sectional schematic diagram of the electrode assembly 22 of the embodiment of the present application is shown. Figure 5 The cross-sectional diagram shown can be Figure 4 The schematic cross-sectional view of the electrode assembly 22 is shown, and the cross-section is perpendicular to the height direction Z of the battery cell 20 . Figure 6 The schematic diagram of the partial cross section of the positive electrode sheet 223 or the negative electrode sheet 224 of the embodiment of the present application is shown. Figure 6 It can be expressed as Figure 5 The schematic partial cross-sectional view of the negative electrode sheet 224 of the electrode assembly 22 along the thickness direction thereof, or it can also be represented as follows Figure 5 The schematic diagram of a partial cross section of the positive electrode sheet 223 of the electrode assembly 22 shown in FIG. 2 is shown along the thickness direction thereof.

[0123] like Figures 3 to 6As shown, the electrode assembly 22 of the embodiment of the present application includes a positive electrode sheet 223 and a negative electrode sheet 224, and the electrode assembly 22 can be formed by stacking or winding the positive electrode sheet 223 and the negative electrode sheet 224. For example, the electrode assembly 22 may include a plurality of positive electrode sheets 223 and a plurality of negative electrode sheets 224; along the thickness direction of the electrode assembly 22, the plurality of positive electrode sheets 223 and the plurality of negative electrode sheets 224 are alternately stacked to form a stacked electrode assembly 22. For another example, the electrode assembly 22 may include a plurality of positive electrode sheets 223, and the negative electrode sheet 224 includes a plurality of bending sections and a plurality of stacking sections that are connected to each other and alternately arranged. After the bending sections are bent, the plurality of positive electrode sheets 223 and the plurality of stacking sections of the negative electrode sheets 224 are alternately stacked to form a stacked electrode assembly 22. For another example, the electrode assembly can also be formed by winding the positive electrode sheet 223 and the negative electrode sheet 224 to form a wound electrode assembly 22. For ease 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 sheet 223 and the negative electrode sheet 224.

[0124] In the embodiment of the present application, the negative electrode plate 224 includes a negative electrode active material. For example, the negative electrode active material coated on the negative electrode plate 224 can be used to form a negative electrode active material layer 2241. The negative electrode active material layer 2241 can be disposed on the surface of at least one side of the negative electrode current collector 2242. For example, the negative electrode active material layer 2241 can be disposed on both sides of the negative electrode current collector 2242 perpendicular to the thickness direction thereof.

[0125] In some embodiments, the negative electrode current collector 2242 may be a metal foil or a composite current collector. As examples of metal foils, copper foil, copper alloy foil, aluminum foil, and aluminum alloy 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 copper, copper 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).

[0126] It should be understood that the negative electrode active material of the embodiment of the present application can be flexibly set according to the actual application. Specifically, the negative electrode active material of the embodiment of the present application may include a silicon-based material, thereby improving the energy density of the battery. For example, the silicon-based material may include at least one of elemental silicon, silicon-oxygen compounds, silicon-carbon composites, silicon-nitrogen composites, silicon-containing alloys, or silicon-oxygen-carbon composite materials.

[0127] In some embodiments, the silicon-based material may include silicon and one or more of an alkali metal element and an alkaline earth metal element. As an example, the alkali metal element may include Li. As an example, the alkaline earth metal element includes Mg. As an example, the silicon-based material may be a silicon-based material pre-embedded with an alkali metal and / or an alkaline earth metal, for example, a silicon-based material pre-embedded with Li and / or Mg.

[0128] It should be understood that the mass proportion g of the silicon-based material in the embodiment of the present application can be flexibly set according to actual applications.

[0129] For example, the value range of the mass proportion g of the silicon-based material can be set to satisfy 2%≤g≤40%. Silicon-based materials are added to the negative active material of the negative electrode plate 224. Since silicon-based materials can accommodate more metal ions than other elements, for example, the capacity of silicon-based materials is about ten times that of graphite, the energy density of the battery cell 20 can be effectively improved. At the same time, the mass proportion g of the silicon-based material should not be set too large, otherwise it will increase the difficulty of processing the electrode assembly 22, and it will also increase the deformation of the electrode assembly 22 in the battery cell 20 during use. In particular, during the charging process of the battery cell 20, metal ions are embedded in the silicon-based material of the negative electrode plate 224, which will cause the volume expansion of the electrode assembly 22, thereby increasing the pressure of the electrode assembly 22 on the shell 211 of the battery cell 20, thereby increasing the difficulty of processing the battery cell 20.

[0130] Furthermore, the value range of the mass proportion g of the silicon-based material can be set to meet 8%≤g≤40%. Appropriately reducing the mass proportion g of the silicon-based material can reduce the difficulty of processing the electrode assembly 22, and can also reduce the deformation of the electrode assembly 22 during the charging and discharging process of the battery cell 20, that is, reduce the volume expansion of the electrode assembly 22, thereby reducing the pressure of the electrode assembly 22 on the shell 211 of the battery cell 20, reducing the requirements for the structural strength of the shell 211, facilitating processing, and reducing costs.

[0131] Furthermore, the mass proportion g of the silicon-based material can be set to satisfy 10%≤g≤30%. Reasonable adjustment of the mass proportion g of the silicon-based material can effectively increase the energy density of the battery cell 20, reduce the processing difficulty of the electrode assembly 22, and effectively reduce the deformation of the electrode assembly 22 during the charging and discharging process of the battery cell 20, thereby reducing the requirements for the structural strength of the shell 211.

[0132] In some embodiments, the mass proportion g of the silicon-based material in the embodiment of the present application can also be set to other values. For example, the mass proportion g of the silicon-based material can be any 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%.

[0133] It should be understood that the mass proportion g of the silicon-based material in the negative electrode active material of the embodiment of the present application represents 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, and the test method for the mass proportion g of the silicon-based material can be selected according to the actual application, and can be tested by methods known in the art.

[0134] In the embodiment of the present application, the negative electrode active material may also include other materials. For example, the negative electrode active material may also 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 resin (e.g., 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 to this.

[0135] In some embodiments, the negative electrode active material may further include a negative electrode conductive agent. The present application has no particular restrictions 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.

[0136] In some embodiments, the negative electrode active material may further include other additives. As an example, the other additives may include a thickener, such as sodium carboxymethyl cellulose (CMC), a PTC thermistor material, and the like.

[0137] The negative electrode plate 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 plate 224 may also include a conductive primer layer (e.g., 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 plate 224 may also include a protective layer covering the surface of the negative electrode active material layer 2241.

[0138] In some embodiments, the negative electrode sheet 224 can be prepared as follows: the negative electrode active material, the optional negative electrode binder, the optional negative electrode conductive agent, and the optional other additives are dispersed in a solvent and stirred to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode current collector 2242, and after drying, cold pressing and other processes, 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.

[0139] In the embodiment of the present application, the value of the mass proportion g of the silicon-based material and the value of the tensile strength Rm of at least a portion of the shell 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 proportion of the silicon-based material is g, and the material of at least a portion of the shell 211 includes iron elements, and Rm and g satisfy 2%≤g≤40%, 300MPa<Rm<2000MPa. The inclusion of iron elements in the material of at least a portion of the shell 211 can increase the structural strength of the material of the portion of the shell 211 to meet the design requirements.

[0140] In some embodiments, the material of at least a portion of the housing 211 includes carbon steel or stainless steel, and Rm and g satisfy 2.5%≤g≤15%, 315MPa≤Rm<800MPa. For example, the material of at least a portion of the housing 211 may include Q195 carbon steel, which is easy to process and can meet the value of the tensile strength Rm under the condition of 25°C.

[0141] In some embodiments, the material of at least a portion of the housing 211 includes carbon steel or stainless steel, and Rm and g satisfy 4.5%≤g≤40%, 380MPa≤Rm<2000MPa. For example, the material of at least a portion of the housing 211 may include SPCC carbon steel, which is easy to process and can meet the value of the tensile strength Rm under the condition of 25°C.

[0142] In some embodiments, Rm and g satisfy 8%≤g≤40%, 400MPa≤Rm<2000MPa. For example, the material of at least part of the housing 211 may include modified stainless steel, which is easy to process and meets the tensile strength Rm value at 25°C.

[0143] In some embodiments, Rm and g satisfy 10%≤g≤40%, 480MPa≤Rm<2000MPa. For example, the material of at least part of the housing 211 may include 316 stainless steel, which is easy to process and meets the tensile strength Rm value at 25°C.

[0144] In some embodiments, Rm and g satisfy 15%≤g≤40%, 520MPa≤Rm<2000MPa. For example, the material of at least part of the housing 211 may include 304 stainless steel, which is easy to process and meets the tensile strength Rm value at 25°C.

[0145] In some embodiments, Rm and g satisfy 20%≤g≤40%, 600MPa≤Rm<2000MPa.

[0146] The following is a comparative explanation through a plurality of comparative examples and a plurality of embodiments. Specifically, the battery cells 20 in the following embodiments and comparative examples are as follows: Figure 3 and Figure 4 Taking the square shell battery shown as an example, the shell 211 adopts a hollow structure with one end open.

[0147] In the following embodiments and comparative examples, the preparation methods of the positive electrode sheet 223, the negative electrode sheet 224, the electrolyte and the separator 225 of the battery cell 20 are as follows.

[0148] 1. Preparation of positive electrode sheet 223

[0149] The positive electrode active material LiNi 0.95 Co 0.04 Mn 0.01 O2, conductive agent Super P, and binder polyvinylidene fluoride (PVDF) are used to prepare positive electrode slurry in N-methylpyrrolidone (NMP), wherein the solid content in the positive electrode slurry is 50wt%, and the solid content of LiNi 0.7 Co 0.1 Mn 0.1 The mass ratio of O2, 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 and dried at 85°C and then cold pressed. Then, it is trimmed, cut and stripped, and then dried at 85°C under vacuum conditions for 4 hours to form a positive electrode sheet 223.

[0150] 2. Preparation of negative electrode sheet 224

[0151] The negative electrode active material, the conductive agent Super P, the thickener carboxymethyl cellulose (CMC), and the adhesive styrene butadiene rubber (SBR) are mixed evenly in deionized water to form a negative electrode slurry, wherein the negative electrode active material includes graphite and silicon-based materials, and the silicon-based materials are silicon oxide compounds. The solid content in the negative electrode slurry is 30wt%, and the mass ratio of the negative electrode active material, silicon oxide, Super P, CMC and adhesive styrene butadiene rubber (SBR) in the solid component is 88:7:3:2. The negative electrode slurry is coated on the upper and lower surfaces of the current collector copper foil and dried at 85°C, and then cold pressed, trimmed, cut into pieces, and slit, and then dried at 120°C under vacuum conditions for 12 hours to form a negative electrode sheet 224.

[0152] 3. Preparation of electrolyte

[0153] In an argon atmosphere glove box (H2O<0.1ppm, O2<0.1ppm), fully dried electrolyte salt LiPF6 was dissolved in a mixed solvent (the mixed solvent included ethylene carbonate (EC) and diethyl carbonate (DEC), and ethylene carbonate (EC) and diethyl carbonate (DEC) were mixed in a mass ratio of 50:50), and after mixing evenly, an electrolyte with a concentration of 1 mol / L was obtained.

[0154] 4. Preparation of Isolation Component 225

[0155] A 16 μm polyethylene film was used as the separator 225 .

[0156] 5. Preparation of lithium-ion battery cell 20

[0157] The positive electrode sheet 223, the separator 225 and the negative electrode sheet 224 are stacked in order, and the separator 225 is located between the positive electrode sheet 223 and the negative electrode sheet 224 to isolate the positive and negative electrodes. The bare battery cell is wound and the pole ears are welded. The bare battery cell is placed in a shell made of different materials, and the prepared electrolyte is injected into the dried shell. The lithium-ion battery cell 20 is prepared by packaging, standing, forming, shaping, and capacity testing.

[0158] In the following embodiments and comparative examples, the tensile strength of the shell 211 of the battery cell 20 at a temperature of 25°C is Rm, and in order to obtain different tensile strengths Rm, different materials are selected for the shell 211; 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 proportion of the silicon-based material is g; the above specific parameter settings are shown in Table 1 below. In addition, in each embodiment and comparative example, the material of all areas of the shell 211 is the same, and the tensile strength Rm of the shell 211 at 25°C is measured using the method specified in GB / T 228.1-2010. In addition, the battery cells 20 in the following embodiments and comparative examples are the same except for the different parameter settings shown in Table 1. For example, the wall thickness of each wall of the shell 211 of the battery cell 20 in each embodiment is 0.25mm; for another example, the capacity of the battery cell 20 in each embodiment is 350Ah.

[0159] The battery cells 20 in the following embodiments and comparative examples were subjected to a cycle charging fatigue test. Specifically, Figure 7 FIG. 7 is a schematic diagram showing the structure of a fixture 700 for cyclic charging fatigue testing according to an embodiment of the present application. Figure 7 As shown, the fixture 700 includes three 10 mm steel plates, which completely cover the largest wall of the battery cell 20. For ease of explanation, the three fixture steel plates are defined as the first steel plate 710, the second steel plate 720 and the third steel plate 730 in sequence. The first steel plate 710 and the third steel plate 730 are located at both ends of the fixture 700 and are fixed by bolts. The second steel plate 720 in the middle is constrained by a guide rail so that the second steel plate 720 can only move in a direction perpendicular to the large surface of the second steel plate 720; the first steel plate 710 and the second steel plate 720 are used to clamp the battery cell 20, and the largest wall 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.

[0160] Specifically, the battery cell 20 is clamped and fixed in the dedicated fixture 700, ensuring that the two oppositely disposed walls with the largest area of ​​the battery cell 20 are clamped, and the initial pressure is set to 2000N, and the electrode terminal 214 of the battery cell 20 is connected to the dedicated battery charging and discharging equipment.

[0161] 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.

[0162] The specific test steps refer to Chapter 6.4 "Standard Cycle Life" of "GBT31484-2015 Requirements and Test Methods for Cycle Life of Power Batteries for Electric Vehicles", and the test cycle cutoff condition is changed to "stop testing until the weld 2113 of the battery cell 20 is damaged."

[0163] 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, leave it for not less than 30 minutes or the leaving condition specified by the enterprise; step c, charge according to the method of 6.1.1.3; step d, leave it for not less than 30 minutes or the leaving condition specified by the enterprise; step e, discharge at 1I1(A) to the discharge termination condition specified by the enterprise; step f, cycle from step b to step e until the weld 2113 is damaged and the test is stopped.

[0164] During the above test process, the weld 2113 of the battery cell 20 is continuously observed until the weld 2113 leaks, and the number of cycles is recorded to obtain the condition of the shell 211 at 1000 cycles as shown in Table 1 below. In the following embodiments and comparative examples, the weld 2113 refers to the weld between the shell 211 and the cover plate 212, that is, the weld 2113 surrounds the open end of the shell 211, and the shell 211 adopts an integrally formed structure.

[0165] Table 1

[0166]

[0167] It should be understood that in Table 1 above, the material of the shell 211 can be Q195 carbon steel, and the tensile strength Rm of Q195 carbon steel at room temperature 25°C is usually at least 315MPa to 430MPa. The above embodiment only takes 328MPa as an example, but is not limited to this. Similarly, the material of the shell 211 can be SPCC carbon steel, and the tensile strength Rm of SPCC carbon steel at room temperature 25°C is usually at least 380MPa to 430MPa, and only 396MPa is taken as an example in the above embodiment; the material of the shell 211 can be modified stainless steel, and the tensile strength Rm of modified stainless steel at room temperature 25°C is usually at least 400MPa to 600MPa, and only 421MPa is taken as an example in the above embodiment; the material of the shell 211 can be SUS430 stainless steel, and the tensile strength Rm of SUS430 stainless steel at room temperature 25°C is usually at least 450MPa, and only 459MPa is taken as an example in the above embodiment; the material of the shell 211 can be SUS304 stainless steel, and the tensile strength Rm of SUS304 stainless steel at room temperature 25°C is usually at least 520MPa, and only 533MPa and 625MPa are taken as examples in the above embodiment.

[0168] Comparing the two comparative examples in Table 1 above with the 12 embodiments, it can be seen that when the shell 211 is made of different materials, different tensile strengths Rm can be determined accordingly. When the tensile strength Rm satisfies 250MPa≤Rm≤2000MPa, for example, in embodiments 1-12, even if the mass proportion g of the silicon-based material in the material of the negative electrode plate 224 of the battery cell 20 is different, the number of failure fatigue times of the battery cell 20 can reach more than one thousand to meet the design requirements of the battery cell 20. However, when the tensile strength Rm does not satisfy 250MPa≤Rm≤2000MPa, for example, in comparative examples 1-2, even if the mass proportion g of the silicon-based material in the material of the negative electrode plate 224 of the battery cell 20 is low, the number of failure fatigue times of the battery cell 20 does not reach one thousand times, which cannot meet the design requirements of the battery cell 20.

[0169] It should be understood that the battery cell 20 of the embodiment of the present application can also meet other design requirements. Specifically, the yield strength of at least a portion of the housing 211 at a temperature of 25° C. is Re, and Re satisfies: 140 MPa≤Re≤1000 MPa.

[0170] Increasing the yield strength Re of at least a portion of the shell 211 at room temperature can improve the deformation ability of the shell 211, thereby improving the structural stability and service life of the battery cell 20. During the charge and discharge process of the battery cell 20, the electrode assembly 22 will cyclically expand and shrink in volume. Increasing the yield strength Re of at least a portion of the shell 211 at room temperature can increase the maximum extrusion force that the shell 211 can withstand. When the limit of the yield strength of the shell 211 is not exceeded, the shell 211 is not easily damaged, and the deformation of the shell 211 can be restored, thereby improving the service life of the shell 211. However, the yield strength Re of at least a portion of the shell 211 at room temperature should not be too large, so as to reduce the difficulty of selecting the material and processing difficulty of the shell 211, save costs, and facilitate processing. For example, it is usually possible to set the yield strength Re of at least a portion of the shell 211 at room temperature to meet: 140MPa≤Re≤1000MPa.

[0171] It should be understood that the value range of the yield strength Re of at least part of the shell 211 of the embodiment of the present application under normal temperature conditions of 25°C can be adjusted according to actual applications. For example, the value of the normal temperature yield strength Re can satisfy 140MPa≤Re≤1000MPa. For another example, the value of the normal temperature yield strength Re can satisfy 180MPa≤Re≤600MPa. On the one hand, increasing the yield strength Re of at least part of the shell 211 under normal temperature conditions can improve the deformation capacity of the part of the shell 211 to resist the expansion of the electrode assembly 22, so that the part of the shell 211 is not easily damaged; and, without exceeding the limit of the yield strength of the shell 211, if the expansion of the electrode assembly 22 is reduced, the deformation of the shell 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 shell 211 under normal temperature conditions will not be too large, which can reduce the difficulty of selecting and processing the material of the shell 211, save costs, and facilitate processing.

[0172] Furthermore, the yield strength Re of at least a portion of the shell 211 at room temperature may be set to satisfy 220MPa≤Re≤400MPa. The yield strength Re of at least a portion of the shell 211 at room temperature is not too large or too small, which can improve the deformation capacity of the portion of the shell 211 to resist the expansion of the electrode assembly 22, and is easy to implement and saves costs.

[0173] In some embodiments, the value of the yield strength Re of at least a portion 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 yield strength Re at normal temperature can be any of the following values ​​or between any two of the following values: 140MPa, 150MPa, 160MPa, 180MPa, 200MPa, 220MPa, 250MPa, 280MPa, 300MPa, 330MPa, 350MPa, 380MPa, 400MPa, 430MPa, 450MPa, 480MPa. a. 500MPa, 530MPa, 550MPa, 580MPa, 600MPa, 630MPa, 650MPa, 680MPa, 700MPa, 730MPa, 750 MPa, 780MPa, 800MPa, 830MPa, 850MPa, 880MPa, 900MPa, 930MPa, 950MPa, 980MPa and 1000MPa.

[0174] It should be understood that the yield strength of the embodiment of the present application can be understood as the critical stress value of the material yield. 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. In addition, the yield strength of the embodiment of the present application generally refers to the upper yield strength, that is, the upper yield strength of at least a portion of the shell 211 at a temperature of 25°C is Re.

[0175] The test method of the yield strength Re of at least a part of the housing 211 of the embodiment of the present application at a temperature of 25° C. can be selected according to the actual application. For example, the national standard GB / T 228.1-2010 can be used to test the yield strength Re at a normal temperature of 25° C.

[0176] In an embodiment of the present application, the value of the mass proportion g of the silicon-based material and the value of the yield strength Re of at least a portion of the shell 211 at a temperature of 25°C can be mutually restricted, so as to improve the structural strength of the shell 211 while increasing the energy density of the battery cell 20, thereby improving the structural strength and service life of the battery cell 20.

[0177] For example, in the negative electrode active material, the mass proportion of silicon-based material is g, and g and Re satisfy: 2%≤g≤40%, 140MPa<Re<600MPa. Silicon-based material is added to the negative electrode active material of the negative electrode plate 224. Since silicon-based material can accommodate more metal ions than other elements, for example, the capacity of silicon-based material is about ten times that of graphite, it can effectively improve the energy density of the battery cell 20. At the same time, the mass proportion g of the silicon-based material should not be set too large, otherwise it will increase the processing difficulty of the electrode assembly 22, and it will also increase the deformation of the electrode assembly 22 in the battery cell 20 during use, especially during the charging process of the battery cell 20, the metal ions are embedded in the silicon-based material of the negative electrode plate, which will cause the volume expansion of the electrode assembly 22, thereby increasing the pressure of the electrode assembly 22 on the shell 211 of the battery cell 20, thereby increasing the processing difficulty of the battery cell 20. Therefore, the yield strength Re of at least a portion of the housing 211 at room temperature can be appropriately increased to improve the deformation capacity of the portion of the housing 211 to resist the expansion of the electrode assembly 22, so that the portion of the housing 211 is not easily damaged; and, without exceeding the limit of the yield strength of the housing 211, if the expansion of the electrode assembly 22 is reduced, 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, the yield strength Re of at least a portion of the housing 211 at room temperature should not be too large, which can reduce the difficulty of selecting the material and processing of the housing 211, save costs, and facilitate processing.

[0178] In some embodiments, the material of at least a portion of the shell 211 includes carbon steel or stainless steel, and g and Re satisfy 4.5%≤g≤40%, 170MPa≤Re<600MPa. For example, the material of at least a portion of the shell 211 may include SPCC carbon steel, which is easy to process and can meet the value of the yield strength Re under the condition of 25°C.

[0179] In some embodiments, g and Re satisfy 8%≤g≤40%, 180MPa≤Re<600MPa. For example, the material of at least part of the housing 211 may include modified stainless steel, which is easy to process and can meet the yield strength Re value at 25°C.

[0180] In some embodiments, g and Re satisfy 10%≤g≤40%, 190MPa≤Re<600MPa. For example, the material of at least a part of the housing 211 may include 316 stainless steel, which is easy to process and can meet the yield strength Re value at 25°C.

[0181] In some embodiments, g and Re satisfy 15%≤g≤40%, 200MPa≤Re<600MPa. For example, the material of at least part of the housing 211 may include 304 stainless steel, which is easy to process and meets the yield strength Re value at 25°C.

[0182] In some embodiments, g and Re satisfy 20%≤g≤40%, 210MPa≤Re<600MPa.

[0183] The following is a comparative explanation through a plurality of comparative examples and a plurality of embodiments. Specifically, the battery cells 20 in the following embodiments and comparative examples are as follows: Figure 3 and Figure 4 Taking the square shell battery shown as an example, the shell 211 adopts a hollow structure with one end open.

[0184] In the following embodiments and comparative examples, the preparation methods of the positive electrode sheet 223, the negative electrode sheet 224, the electrolyte and the separator 225 of the battery cell 20 are as follows.

[0185] 1. Preparation of positive electrode sheet 223

[0186] The positive electrode active material LiNi 0.95 Co 0.04 Mn 0.01 O2, conductive agent Super P, and binder polyvinylidene fluoride (PVDF) are used to prepare positive electrode slurry in N-methylpyrrolidone (NMP), wherein the solid content in the positive electrode slurry is 50wt%, and the solid content of LiNi0.7 Co 0.1 Mn 0.1 The mass ratio of O2, 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 and dried at 85°C and then cold pressed. Then, it is trimmed, cut and stripped, and then dried at 85°C under vacuum conditions for 4 hours to form a positive electrode sheet 223.

[0187] 2. Preparation of negative electrode sheet 224

[0188] The negative electrode active material, the conductive agent Super P, the thickener carboxymethyl cellulose (CMC), and the adhesive styrene butadiene rubber (SBR) are mixed evenly in deionized water to form a negative electrode slurry, wherein the negative electrode active material includes graphite and silicon-based materials, and the silicon-based materials are silicon oxide compounds. The solid content in the negative electrode slurry is 30wt%, and the mass ratio of the negative electrode active material, silicon oxide, Super P, CMC and adhesive styrene butadiene rubber (SBR) in the solid component is 88:7:3:2. The negative electrode slurry is coated on the upper and lower surfaces of the current collector copper foil and dried at 85°C, and then cold pressed, trimmed, cut into pieces, and slit, and then dried at 120°C under vacuum conditions for 12 hours to form a negative electrode sheet 224.

[0189] 3. Preparation of electrolyte

[0190] In an argon atmosphere glove box (H2O<0.1ppm, O2<0.1ppm), fully dried electrolyte salt LiPF6 was dissolved in a mixed solvent (the mixed solvent included ethylene carbonate (EC) and diethyl carbonate (DEC), and ethylene carbonate (EC) and diethyl carbonate (DEC) were mixed in a mass ratio of 50:50), and after mixing evenly, an electrolyte with a concentration of 1 mol / L was obtained.

[0191] 4. Preparation of Isolation Component 225

[0192] A 16 μm polyethylene film was used as the separator 225 .

[0193] 5. Preparation of lithium-ion battery cell 20

[0194] The positive electrode sheet 223, the separator 225 and the negative electrode sheet 224 are stacked in order, and the separator 225 is located between the positive electrode sheet 223 and the negative electrode sheet 224 to isolate the positive and negative electrodes. The bare battery cell is wound and the pole ears are welded. The bare battery cell is placed in a shell made of different materials, and the prepared electrolyte is injected into the dried shell. The lithium-ion battery cell 20 is prepared by packaging, standing, forming, shaping, and capacity testing.

[0195] In the following embodiments and comparative examples, the yield strength of the shell 211 of the battery cell 20 at a temperature of 25°C is Re, and in order to obtain different yield strengths Re, different materials are selected for the shell 211; 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 proportion of the silicon-based material is g; the above specific parameter settings are shown in Table 2 below. In addition, in each embodiment and comparative example, the material of all areas of the shell 211 is the same, and the yield strength Re of the shell 211 at 25°C is measured using the method specified in GB / T 228.1-2010. In addition, the battery cells 20 in the following embodiments and comparative examples are the same except that the parameters shown in Table 2 are different. For example, the wall thickness of each wall of the shell 211 of the battery cell 20 in each embodiment is 0.25mm; for another example, the capacity of the battery cell 20 in each embodiment is 350Ah.

[0196] The battery cells 20 in the following embodiments and comparative examples are subjected to a cycle charging fatigue test. Figure 7 The fixture 700 shown is used for cyclic charging fatigue testing.

[0197] Specifically, the battery cell 20 is clamped and fixed in the dedicated fixture 700, ensuring that the two oppositely disposed walls with the largest area of ​​the battery cell 20 are clamped, and the initial pressure is set to 2000N, and the electrode terminal 214 of the battery cell 20 is connected to the dedicated battery charging and discharging equipment.

[0198] 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.

[0199] The specific test steps refer to Chapter 6.4 "Standard Cycle Life" of "GBT31484-2015 Requirements and Test Methods for Cycle Life of Power Batteries for Electric Vehicles", and the test cycle cutoff condition is changed to "stop testing until the weld 2113 of the battery cell 20 is damaged."

[0200] 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, leave it for not less than 30 minutes or the leaving condition specified by the enterprise; step c, charge according to the method of 6.1.1.3; step d, leave it for not less than 30 minutes or the leaving condition specified by the enterprise; step e, discharge at 1I1(A) to the discharge termination condition specified by the enterprise; step f, cycle from step b to step e until the weld 2113 is damaged and the test is stopped.

[0201] During the above test process, the weld 2113 of the battery cell 20 is continuously observed until the weld 2113 leaks, and the number of cycles is recorded to obtain the failure fatigue condition of the shell 211 at 1000 cycles as shown in Table 2 below. In the following embodiments and comparative examples, the weld 2113 refers to the weld between the shell 211 and the cover plate 212, that is, the weld 2113 surrounds the open end of the shell 211, and the shell 211 adopts an integrally formed structure.

[0202] Table 2

[0203]

[0204] It should be understood that in Table 2 above, the material of the shell 211 can be modified stainless steel, and the yield strength Re of the modified stainless steel at room temperature 25°C is generally at least 140MPa to 180MPa, and the above embodiment only takes 145MPa and 173MPa as examples, but is not limited thereto. Similarly, the material of the shell 211 can be SUS316 stainless steel, and the yield strength Re of SUS316 stainless steel at room temperature 25°C is generally at least 177MPa, and the above embodiment only takes 182MPa and 193MPa as examples; the material of the shell 211 can be Q195 carbon steel, and the yield strength Re of Q195 carbon steel at room temperature 25°C is generally at least 195MPa, and the above embodiment only takes 203MPa as an example; the material of the shell 211 can be SUS304 stainless steel, and the yield strength Re of SUS304 stainless steel at room temperature 25°C is generally at least 205MPa, and the above embodiment only takes 212MPa as an example.

[0205] Comparing the two comparative examples in Table 2 above with the 12 embodiments, it can be seen that when the shell 211 is made of different materials, different yield strengths Re can be determined accordingly. When the yield strength Re satisfies 140MPa≤Re≤1000MPa, for example, in embodiments 1-12, even if the mass proportion g of the silicon-based material in the material of the negative electrode plate 224 of the battery cell 20 is different, the number of failure fatigue times of the battery cell 20 can reach more than one thousand to meet the design requirements of the battery cell 20. However, when the yield strength Re does not satisfy 140MPa≤Re≤1000MPa, for example, in comparative examples 1-2, even if the mass proportion g of the silicon-based material in the material of the negative electrode plate 224 of the battery cell 20 is low, the number of failure fatigue times of the battery cell 20 does not reach one thousand times, and the design requirements of the battery cell 20 cannot be met.

[0206] In some embodiments, the electrode assembly 22 also includes a positive electrode plate 223, which includes a positive electrode active material that can reversibly extract and embed metal ions, and the positive electrode active material includes a nickel-containing compound; the melting point of at least a portion of the shell 211 is p, and p satisfies: 1200℃≤p≤2000℃.

[0207] The positive electrode plate 223 of the embodiment of the present application is provided with a positive electrode active material that can reversibly extract and embed metal ions, and the positive electrode active material can be flexibly set according to the actual application. For example, the positive electrode active material can include a nickel-containing 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 gas generated during the use of the battery cell 20, especially when the battery cell 20 is in thermal runaway, the internal temperature of the battery cell 20 will increase rapidly and a large amount of gas will be generated.

[0208] Therefore, appropriately increasing the melting point p of at least a portion of the shell 211 will make the shell 211 less likely to melt, reduce the possibility of the battery cell 20 exploding, and further reduce the risk of thermal runaway of adjacent battery cells 20, so as to improve the reliability of the battery 10. However, the melting point p of at least a portion of the shell 211 should not be too large, so as to reduce the difficulty of selecting the material and processing the shell 211, save costs, and facilitate processing. For example, the melting point p of at least a portion of the shell 211 can usually be set to meet 1200℃≤p≤2000℃.

[0209] It should be understood that the value range of the melting point p of at least part of the shell 211 of the embodiment of the present application can be adjusted according to the actual application. For example, the melting point p of at least part of the shell 211 usually satisfies 1200℃≤p≤2000℃. For another example, the melting point p of at least part of the shell 211 may also satisfy 1300℃≤p≤1800℃. On the one hand, appropriately increasing the value of the melting point p can improve the ability of the part of the shell 211 to resist melting when the battery cell 20 has thermal runaway, which will make the shell 211 less likely to be melted, thereby reducing the risk of thermal runaway of adjacent battery cells 20, that is, reducing the risk of heat 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 and reduce the difficulty of processing, thereby saving costs and facilitating processing.

[0210] Furthermore, the melting point p of at least a part of the shell 211 may be set to satisfy 1400°C≤p≤1600°C, so that when the battery cell 20 has thermal runaway, the structural strength of the shell 211 can be improved, the shell 211 is not easily melted, the structural integrity of the part of the shell 211 is maintained, and the risk of thermal runaway of the adjacent battery cell 20 is reduced. At the same time, the processing difficulty can be reduced and the cost can be saved.

[0211] In some embodiments, the value range of the melting point p of at least a portion of the housing 211 may also be set to other values. For example, the value of the melting point p may 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.

[0212] In the embodiment 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 the surface of at least one side of the positive electrode collector 2232. For example, the positive electrode active material layer 2231 can be disposed on both sides of the positive electrode collector 2232 perpendicular to the thickness direction thereof, but the embodiment of the present application is not limited thereto.

[0213] In some embodiments, the positive electrode current collector 2232 may be a metal foil or a composite current collector. As an example of a 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).

[0214] It should be understood that the positive electrode active material of the embodiment of the present application can be flexibly set according to the actual application. For example, the positive electrode active material may include a nickel-containing compound. As an example, the nickel-containing compound includes a layered lithium-containing transition metal oxide, and the molar amount of the nickel element in the layered lithium-containing transition metal oxide accounts for more than 50% of the total molar amount of the transition metal element in the layered lithium-containing transition metal oxide. Increasing the proportion of the molar amount of the 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, thereby increasing the processing cost of the battery cell 20.

[0215] Furthermore, the molar proportion of nickel in the layered lithium-containing transition metal oxide can be greater than 70%, or greater than 80%, or 90%. In this way, the energy density of the battery cell 20 can be effectively improved, and the processing difficulty of the electrode assembly 22 can be controlled to reduce the processing cost of the battery cell 20.

[0216] In some embodiments, the value of the molar ratio of the nickel element in the layered lithium-containing transition metal oxide of the embodiment of the present application can also be set to other values. For example, the value of the molar ratio of the nickel element in the layered lithium-containing transition metal oxide can be any 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%.

[0217] It should be understood that the test method for the molar amount of nickel in the layered lithium-containing transition metal oxide and the total molar amount of transition metal elements in the layered lithium-containing transition metal oxide in the embodiment of the present application can be selected according to the actual application, and can be measured using instruments and methods known in the art. For example, the positive electrode active material can be laid and adhered to the conductive glue to form a sample to be tested with a length × width of 6 cm × 1.1 cm; the particle morphology is tested using a scanning electron microscope & energy spectrometer (such as ZEISS Sigma300). The test can refer to JY / T010-1996. In order to ensure the accuracy of the test results, 20 different areas can be randomly selected from the sample to be tested for scanning testing, and at a certain magnification (for example, more than 1000 times), the content of the layered lithium-containing transition metal oxide in each area is counted and calculated. For example, the average value of the test results of 20 test areas can be taken as the number of layered lithium-containing transition metal oxides in the positive electrode active material, and then the molar amount of the layered lithium-containing transition metal oxide is determined; similarly, the molar amount of nickel in the layered lithium-containing transition metal oxide can also be determined by this method.

[0218] In some embodiments, the layered lithium-containing transition metal oxide may include one or more of lithium cobalt oxide and ternary materials. As an example, the layered lithium-containing transition metal oxide includes Li a Ni b Co c M d O e A f , wherein 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. Wherein, the molar ratio b of the nickel element in the layered lithium-containing transition metal oxide is set to be more than 50%, that is, the ratio b satisfies: 0.5≤b<1, and can further satisfy 0.8≤b<1, or 0.9≤b<1, thereby further improving the energy density of the battery cell 20.

[0219] As an example, the layered lithium-containing transition metal oxide may include but is not limited to LiNi 0.5 Co 0.2 Mn 0.3 O2 (abbreviated as NCM523), LiNi 0.5 Co 0.25 Mn 0.25 O2 (abbreviated as NCM211), LiNi 0.6 Co 0.2 Mn 0.2 O2 (abbreviated as NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O2 (abbreviated as NCM811), LiNi 0.9 Co 0.06 Mn 0.04 O2、LiNi 0.96 Co 0.02 Mn 0.02 O2、LiNi 0.85 Co 0.15 Al 0.05 One or more of O2.

[0220] 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 has no particular restrictions on the type of 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.

[0221] In some embodiments, the positive electrode active material may further include a positive electrode binder. The present application has no particular restrictions on the type of 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 fluorine-containing acrylic resin.

[0222] In some embodiments, the positive electrode sheet 223 can be prepared by the following method: the positive electrode active material layer 2231 is usually formed by coating the positive electrode slurry on the positive electrode current collector 2232, drying and cold pressing. The positive electrode slurry is usually formed by dispersing the positive electrode active material, positive electrode binder, positive electrode conductive agent, etc. in a solvent and stirring them evenly. The solvent can be N-methylpyrrolidone (NMP) or deionized water, but the embodiments of the present application are not limited thereto.

[0223] The following is a comparative explanation through a plurality of comparative examples and a plurality of embodiments. Specifically, the battery cells 20 in the following embodiments and comparative examples are as follows: Figure 3 and Figure 4 Taking the square shell battery shown as an example, the shell 211 adopts a hollow structure with one end open.

[0224] In the following embodiments and comparative examples, the preparation methods of the positive electrode sheet 223, the negative electrode sheet 224, the electrolyte and the separator 225 of the battery cell 20 are as follows.

[0225] 1. Preparation of positive electrode sheet 223

[0226] The positive electrode active material LiNi 0.95 Co 0.04 Mn 0.01 O2, conductive agent Super P, and binder polyvinylidene fluoride (PVDF) are used to prepare positive electrode slurry in N-methylpyrrolidone (NMP), wherein the solid content in the positive electrode slurry is 50wt%, and the solid content of LiNi 0.7 Co 0.1 Mn 0.1 The mass ratio of O2, 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 and dried at 85°C and then cold pressed. Then, it is trimmed, cut and stripped, and then dried at 85°C under vacuum conditions for 4 hours to form a positive electrode sheet 223.

[0227] 2. Preparation of negative electrode sheet 224

[0228] The negative electrode active material, the conductive agent Super P, the thickener carboxymethyl cellulose (CMC), and the adhesive styrene butadiene rubber (SBR) are mixed evenly in deionized water to form a negative electrode slurry, wherein the negative electrode active material includes graphite and silicon-based materials, and the silicon-based materials are silicon oxide compounds. The solid content in the negative electrode slurry is 30wt%, and the mass ratio of the negative electrode active material, silicon oxide, Super P, CMC and adhesive styrene butadiene rubber (SBR) in the solid component is 88:7:3:2. The negative electrode slurry is coated on the upper and lower surfaces of the current collector copper foil and dried at 85°C, and then cold pressed, trimmed, cut into pieces, and slit, and then dried at 120°C under vacuum conditions for 12 hours to form a negative electrode sheet 224.

[0229] 3. Preparation of electrolyte

[0230] In an argon atmosphere glove box (H2O<0.1ppm, O2<0.1ppm), fully dried electrolyte salt LiPF6 was dissolved in a mixed solvent (the mixed solvent included ethylene carbonate (EC) and diethyl carbonate (DEC), and ethylene carbonate (EC) and diethyl carbonate (DEC) were mixed in a mass ratio of 50:50), and after mixing evenly, an electrolyte with a concentration of 1 mol / L was obtained.

[0231] 4. Preparation of Isolation Component 225

[0232] A 16 μm polyethylene film was used as the separator 225 .

[0233] 5. Preparation of lithium-ion battery cell 20

[0234] The positive electrode sheet 223, the separator 225 and the negative electrode sheet 224 are stacked in order, and the separator 225 is located between the positive electrode sheet 223 and the negative electrode sheet 224 to isolate the positive and negative electrodes. The bare battery cell is wound and the pole ears are welded. The bare battery cell is placed in a shell made of different materials, and the prepared electrolyte is injected into the dried shell. The lithium-ion battery cell 20 is prepared by packaging, standing, forming, shaping, and capacity testing.

[0235] In the following embodiments and comparative examples, the melting point of the shell 211 of the battery cell 20 is p, and in order to obtain different melting points, different materials are selected for the shell 211; 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 above-mentioned specific parameter settings are shown in Table 3 below. In addition, in each embodiment and comparative example, the material of all areas of the shell 211 is the same. In addition, except for the different parameter settings shown in Table 3, the other setting conditions of the battery cells 20 in the following embodiments and comparative examples are the same. For example, in each embodiment, the positive active material of the positive electrode sheet 223 of the electrode assembly 22 of the battery cell 20 includes a nickel-containing compound, wherein the nickel-containing compound includes a layered lithium-containing transition metal oxide, and the molar amount of nickel 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.

[0236] The battery cells 20 in the following comparative examples and embodiments are tested by the short-circuit test method in Chapter 6.2.4 of GBT31485-2015 Safety requirements and test methods for power batteries for electric vehicles. After the test, the integrity of the shell 211 is observed, that is, whether the shell 211 is melted.

[0237] Table 3

[0238]

[0239] Comparing the two comparative examples in Table 3 above with the six embodiments, it can be seen that when the shell 211 is made of different materials, different melting points p can be determined accordingly. When the melting point p satisfies 1200℃≤p≤2000℃, for example, in embodiments 1-6, the shell 211 of the battery cell 20 does not melt, and the design requirements of the battery cell 20 can be met; and when other parameters of the battery cell 20 have different fluctuations, such as the different capacities C of the battery cell 20, or the different thicknesses of the walls with the largest area of ​​the shell 211, the battery cell 20 does not melt, and the design requirements of the battery cell 20 can be met. However, when the melting point p does not satisfy 1200℃≤p≤2000℃, for example, in comparative examples 1-2, the shell 211 of the battery cell 20 will melt, and the design requirements of the battery cell 20 cannot be met.

[0240] In some embodiments, the electrode assembly 22 also includes a positive electrode plate 223, which includes a positive electrode active material that can reversibly extract and embed metal ions, and the positive electrode active material includes a nickel-containing compound; the tensile strength of at least a portion of the shell 211 at a temperature of 500°C is Rn, and Rn satisfies: 100MPa≤Rn≤1200MPa.

[0241] The positive electrode active material may include a nickel-containing 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 will be generated.

[0242] Therefore, appropriately increasing the tensile strength Rn of at least part of the shell 211 under high temperature conditions of 500°C can improve the deformation ability of this part of the shell 211 when the battery cell 20 has thermal runaway, which will make the shell 211 less likely to be quickly destroyed and exploded, thereby reducing the risk of thermal runaway of adjacent battery cells 20, so as to improve the reliability of the battery 10. However, the tensile strength Rn of at least part of the shell 211 under high temperature conditions should not be too large, otherwise it will increase the difficulty of processing, 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, the tensile strength Rn can usually be set to meet 100MPa≤Rn≤1200MPa.

[0243] It should be understood that the value range of the tensile strength Rn of at least part of the shell 211 of the embodiment of the present application under high temperature conditions of 500°C can be adjusted according to the actual application. For example, the value of the high temperature tensile strength Rn can satisfy 100MPa≤Rn≤1200MPa. For another example, the value of the high temperature tensile strength Rn can also satisfy 112MPa≤Rn≤720MPa. On the one hand, appropriately increasing the value of the tensile strength Rn can improve the deformation ability of the part of the shell 211 when the battery cell 20 has thermal runaway, which will make the shell 211 less likely to be quickly destroyed and explode, thereby reducing the risk of thermal runaway of adjacent battery cells 20, so as to improve the reliability of the battery 10. At the same time, the tensile strength Rn of at least part of the shell 211 under high temperature conditions is controlled not to be too large to reduce the difficulty of processing, thereby saving costs and facilitating processing.

[0244] Furthermore, the value of the high temperature tensile strength Rn can be set to satisfy 152MPa≤Rn≤480MPa, which can improve the deformation ability of the part of the shell 211 when the battery cell 20 has thermal runaway, improve the structural strength of the shell 211, make the shell 211 not easily destroyed and exploded, and further reduce the risk of thermal runaway of the adjacent battery cell 20, so as to improve the reliability of the battery 10. At the same time, it can also reduce the difficulty of processing and save costs.

[0245] In some embodiments, the value of the high temperature tensile strength Rn of the embodiment 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 of the following values ​​or between any two of the following values: 100MPa, 112MPa, 130MPa, 150MPa, 152MPa, 168MPa, 180MPa, 200MPa, 228MPa, 250MPa, 280MPa, 300MPa, 320MPa, 350MPa, 380MPa, 400MPa, 430MPa, 450MPa, 480MPa, 500MPa, 600MPa, 700MPa, 800MPa, 900MPa, 1000MPa, 1100MPa, 1200MPa, 1300MPa, 1500MPa, 152MPa, 168MPa, 180MPa, 200MPa, 228MPa, 250MPa, 280MPa, 300MPa, 320MPa, 350MPa, 380MPa, 400MPa, 430MPa, 450MPa, 480MPa, 500MPa, 600MPa, 700MPa, 8 ... Pa, 530MPa, 550MPa, 580MPa, 600MPa, 630MPa, 650MPa, 680MPa, 700MPa, 720MPa, 750MPa, 780MPa, 800MPa, 8 30MPa, 850MPa, 880MPa, 900MPa, 930MPa, 950MPa, 980MPa, 1000MPa, 1050MPa, 1100MPa, 1150MPa and 1200MPa.

[0246] It should be understood that the tensile strength of the embodiment of the present application refers to the maximum stress value that the material withstands before breaking. The test method of the tensile strength Rn of at least a part of the housing 211 of the embodiment of the present application under the high temperature condition of 500°C can be selected according to the actual application. For example, the national standard GB / T 228.1-2010 can be adopted to test the tensile strength Rn under the high temperature condition of 500°C.

[0247] The following is a comparative explanation through a plurality of comparative examples and a plurality of embodiments. Specifically, the battery cells 20 in the following embodiments and comparative examples are as follows: Figure 3 and Figure 4 Taking the square shell battery shown as an example, the shell 211 adopts a hollow structure with one end open.

[0248] In the following embodiments and comparative examples, the preparation methods of the positive electrode sheet 223, the negative electrode sheet 224, the electrolyte and the separator 225 of the battery cell 20 are as follows.

[0249] 1. Preparation of positive electrode sheet 223

[0250] The positive electrode active material LiNi 0.95 Co 0.04 Mn 0.01 O2, conductive agent Super P, and binder polyvinylidene fluoride (PVDF) are used to prepare positive electrode slurry in N-methylpyrrolidone (NMP), wherein the solid content in the positive electrode slurry is 50wt%, and the solid content of LiNi 0.7 Co 0.1 Mn 0.1 The mass ratio of O2, 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 and dried at 85°C and then cold pressed. Then, it is trimmed, cut and stripped, and then dried at 85°C under vacuum conditions for 4 hours to form a positive electrode sheet 223.

[0251] 2. Preparation of negative electrode sheet 224

[0252] The negative electrode active material, the conductive agent Super P, the thickener carboxymethyl cellulose (CMC), and the adhesive styrene butadiene rubber (SBR) are mixed evenly in deionized water to form a negative electrode slurry, wherein the negative electrode active material includes graphite and silicon-based materials, and the silicon-based materials are silicon oxide compounds. The solid content in the negative electrode slurry is 30wt%, and the mass ratio of the negative electrode active material, silicon oxide, Super P, CMC and adhesive styrene butadiene rubber (SBR) in the solid component is 88:7:3:2. The negative electrode slurry is coated on the upper and lower surfaces of the current collector copper foil and dried at 85°C, and then cold pressed, trimmed, cut into pieces, and slit, and then dried at 120°C under vacuum conditions for 12 hours to form a negative electrode sheet 224.

[0253] 3. Preparation of electrolyte

[0254] In an argon atmosphere glove box (H2O<0.1ppm, O2<0.1ppm), fully dried electrolyte salt LiPF6 was dissolved in a mixed solvent (the mixed solvent included ethylene carbonate (EC) and diethyl carbonate (DEC), and ethylene carbonate (EC) and diethyl carbonate (DEC) were mixed in a mass ratio of 50:50), and after mixing evenly, an electrolyte with a concentration of 1 mol / L was obtained.

[0255] 4. Preparation of Isolation Component 225

[0256] A 16 μm polyethylene film was used as the separator 225 .

[0257] 5. Preparation of lithium-ion battery cell 20

[0258] The positive electrode sheet 223, the separator 225 and the negative electrode sheet 224 are stacked in order, and the separator 225 is located between the positive electrode sheet 223 and the negative electrode sheet 224 to isolate the positive and negative electrodes. The bare battery cell is wound and the pole ears are welded. The bare battery cell is placed in a shell made of different materials, and the prepared electrolyte is injected into the dried shell. The lithium-ion battery cell 20 is prepared by packaging, standing, forming, shaping, and capacity testing.

[0259] In the following embodiments and comparative examples, the tensile strength of the shell 211 of the battery cell 20 at a temperature of 500°C is Rn, and different materials are selected for the shell 211 to obtain different tensile strengths Rn; the capacity of the battery cell 20 is C; the wall thickness of the largest wall of the battery cell 20 is T, and the above specific parameter settings are shown in Table 4 below. In addition, in each embodiment and comparative example, the material of the entire area of ​​the shell 211 is the same, and the tensile strength Rn of the shell 211 at 500°C is measured using the method specified in GB / T 228.1-2010. In addition, except for the different parameter settings shown in Table 4, the battery cells 20 in the following embodiments and comparative examples have the same setting conditions. 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 compound, wherein the nickel-containing compound includes a layered lithium-containing transition metal oxide, and the molar amount of the nickel element in the layered lithium-containing transition metal oxide accounts for 95% of the total molar amount of the transition metal element in the layered lithium-containing transition metal oxide.

[0260] The battery cells 20 in the following comparative examples and embodiments are tested by referring to the short-circuit test method in Chapter 6.2.4 of "GBT31485-2015 Safety requirements and test methods for power batteries for electric vehicles". After the test, the integrity of the shell 211 is observed, that is, whether the shell 211 is broken.

[0261] Table 4

[0262]

[0263] Comparing the two comparative examples in Table 4 above with the six embodiments, it can be seen that when the shell 211 is made of different materials, different tensile strengths Rn can be determined accordingly. When the tensile strength Rn satisfies 100MPa≤Rn≤1200MPa, for example, in embodiments 1-6, the shell 211 of the battery cell 20 does not crack, and the design requirements of the battery cell 20 can be met; and when other parameters of the battery cell 20 have different fluctuations, such as the capacity C of the battery cell 20 is different, or the thickness of the wall with the largest area of ​​the shell 211 is different, the battery cell 20 does not crack, and the design requirements of the battery cell 20 can be met. However, when the tensile strength Rn does not satisfy 100MPa≤Rn≤1200MPa, for example, in comparative examples 1-2, the shell 211 of the battery cell 20 cracks, and the design requirements of the battery cell 20 cannot be met.

[0264] It should be understood that at least a portion of the area of ​​the shell 211 in the embodiment of the present application may include a partial area of ​​the shell 211, and may also include the entire area of ​​the shell 211. In some embodiments, the shell 211 includes a weld 2113, and at least a portion of the area of ​​the shell 211 includes an area of ​​the shell 211 within a preset distance from the weld 2113, and the preset distance is L, and L satisfies: L=10mm. In the case where the negative active material of the negative electrode plate 224 of the electrode assembly 22 includes a silicon-based material, since the silicon-based material can accommodate more metal ions, the deformation of the electrode assembly 22 in the battery cell 20 during use will be increased, causing the volume of the electrode assembly 22 to expand, thereby increasing the pressure of the electrode assembly 22 on the shell 211 of the battery cell 20, and under the same conditions, the structural strength of the area of ​​the shell 211 near the weld 2113 is smaller than the structural strength of other areas of the shell 211, so the area of ​​the shell 211 near the weld 2113 is more likely to be damaged during the use of the battery cell 20. Therefore, setting the area within a preset distance L from the weld 2113 to meet the requirements of tensile strength Rm or yield strength Re under normal temperature conditions can improve the deformation capacity of the area of ​​the shell 211 close to the weld 2113, making this part of the shell 211 less prone to damage, thereby improving the structural stability and service life of the battery cell 20.

[0265] In the case where the positive electrode active material of the positive electrode plate 223 of the electrode assembly 22 includes a nickel-containing compound, if the battery cell 20 has thermal runaway, the internal temperature of the battery cell 20 will increase rapidly and a large amount of gas will be generated. Under the same conditions, the structural strength of the area near the weld 2113 of the shell 211 is relatively small compared to the structural strength of other areas of the shell 211, so the shell 211 is prone to rupture in the area near the weld 2113, which may cause the connected battery cell 20 to have thermal runaway, that is, cause thermal diffusion. Therefore, setting the area within a preset distance L from the weld 2113 to meet the requirements of tensile strength Rn or melting point p under high temperature conditions can improve the deformation capacity of this part of the shell 211, so that this part of the area is not easily destroyed or completely melted, reducing the risk of thermal diffusion or even explosion between multiple battery cells 20, so as to improve the reliability of the battery 10.

[0266] It should be understood that the weld 2113 included in the shell 211 of the embodiment of the present application may include a weld 2113 at any position of the shell 211. For example, the weld 2113 included in the shell 211 may include a weld between the shell 211 and the cover plate 212, that is, the area around the open end of the shell 211 is a weld. For another example, the weld 2113 of the shell 211 may also include a weld between different parts of the shell 211. For example, the shell 211 may include at least two parts, and the at least two parts are connected by welding to form the shell 211, wherein, Figure 4 For example, the shell 211 includes two parts along the height direction Z of the battery cell 20, and there is a weld 2113 between the upper shell and the lower shell; or, different from Figure 4 As shown, other parts of the shell 211 may also be provided with welds 2113, but the embodiments of the present application are not limited thereto.

[0267] In some embodiments, at least a portion of the housing 211 includes a surrounding area 2111 of the housing 211, the surrounding area 2111 surrounds the electrode assembly 22, and the surrounding area 2111 is at least a portion of the side wall of the housing 211. In this way, when the negative active material of the negative electrode plate 224 of the electrode assembly 22 includes a silicon-based material, since the silicon-based material can accommodate more metal ions, the deformation of the electrode assembly 22 in the battery cell 20 during use will increase, causing the volume expansion of the electrode assembly 22, thereby increasing the pressure of the electrode assembly 22 on the housing 211 of the battery cell 20. Therefore, the surrounding area 2111 is provided to meet the requirements of the tensile strength Rm or the yield strength Re under normal temperature conditions, which can improve the deformation capacity of the housing 211, and the surrounding area 2111 is provided around the electrode assembly 22, which can limit the extrusion force of the internal electrode assembly 22 on the housing 211 in the radial direction, so that the housing 211 is not easily damaged, thereby improving the structural stability and service life of the battery cell 20.

[0268] When the positive active material of the positive electrode plate 223 of the electrode assembly 22 includes a nickel-containing compound, if the battery cell 20 has thermal runaway, the internal temperature of the battery cell 20 will increase rapidly and a large amount of gas will be generated; and the surrounding area 2111 meets the requirements of tensile strength Rn or melting point p under high temperature conditions, then the deformation ability of the surrounding area 2111 of the shell 211 can be improved, which will make the surrounding area 2111 not easily destroyed or completely melted, and can limit the excessive expansion of the electrode assembly 22 inside the shell 211 along its thickness direction, thereby reducing the possibility of explosion of the battery cell 20, and further reducing the risk of thermal runaway of adjacent battery cells 20, so as to improve the reliability of the battery 10.

[0269] It should be understood that the position and size of the surrounding area 2111 of the embodiment of the present application can be flexibly set according to the actual application. For example, along the height direction Z of the battery cell 20, the height of the surrounding area 2111 can be less than or equal to the height of the shell 211. Specifically, if the height of the surrounding area 2111 is less than the height of the shell 211 along the height direction Z of the battery cell 20, the surrounding area 2111 can be located at any position of the shell 211 along the height direction Z of the battery cell 20. For example, the surrounding area 2111 can be located in the middle of the shell 211 along the height direction Z of the battery cell 20 to limit the deformation of the corresponding middle position of the electrode assembly 22.

[0270] If along the height direction Z of the battery cell 20, the height of the surrounding area 2111 is equal to the height of the shell 211, then the surrounding area 2111 includes all the side walls of the shell 211 and can wrap the sides of the electrode assembly 22, thereby improving the structural strength of the side walls of the shell 211 and reducing the risk of explosion and heat diffusion of the battery cell 20 after thermal runaway due to damage to the local weak areas of the side walls of the shell 211, thereby improving the reliability of the battery 10.

[0271] In some embodiments, at least a portion of the housing 211 includes the entire wall of the housing 211, that is, at least a portion of the housing 211 in the embodiments of the present application may refer to the entire area of ​​the housing 211. In this way, when the negative active material of the negative electrode plate 224 of the electrode assembly 22 includes a silicon-based material, since the silicon-based material can accommodate more metal ions, the deformation of the electrode assembly 22 in the battery cell 20 during use will increase, causing the volume expansion of the electrode assembly 22, thereby increasing the pressure of the electrode assembly 22 on the housing 211 of the battery cell 20. Therefore, setting the entire area of ​​the housing 211 to meet the requirements of the tensile strength Rm or the yield strength Re under normal temperature conditions can improve the overall deformation capacity of the housing 211, and can also limit the extrusion force of the internal electrode assembly 22 on the housing 211 in all directions, so that the strength of each part of the housing 211 is balanced, and it is not easy to be damaged in the local weak area, thereby improving the structural stability and service life of the battery cell 20.

[0272] In the case where the positive active material of the positive electrode plate 223 of the electrode assembly 22 includes a nickel-containing compound, if the battery cell 20 undergoes thermal runaway, the internal temperature of the battery cell 20 will increase rapidly and a large amount of gas will be generated; and the entire area of ​​the shell 211 meets the requirements of the tensile strength Rn or the melting point p under high temperature conditions, then the overall deformation capacity of the shell 211 can be improved, making the shell 211 less likely to be damaged or melted, and being able to limit the high-temperature and high-pressure gas inside the shell 211, reducing the impact on the connected battery cells 20, and thereby reducing the risk of thermal runaway of adjacent battery cells 20, thereby improving the reliability of the battery 10.

[0273] Furthermore, the cover plate 212 of the embodiment of the present application may be made of the same material as at least a portion 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 may also meet at least one of the requirements of the tensile strength Rm and yield strength Re under normal temperature conditions, the tensile strength Rn and melting point p under high temperature conditions, so as to improve the structural strength of the cover plate 212, and further improve the structural stability of the battery cell 20, but the embodiment of the present application is not limited thereto.

[0274] In the embodiment of the present application, the shell 211 at least partially includes a third shell wall 2112 , and the average thickness of the third shell wall 2112 is T, where T satisfies: 0.05 mm≤T≤0.5 mm, 60 mm·MPa≤T×Rm≤500 mm·MPa.

[0275] It should be understood that the third shell wall 2112 of the shell 211 of the embodiment of the present application can be any wall of the shell 211. Specifically, the battery cell 20 can be any polyhedral structure, the shell 211 can be a hollow structure with at least one end open, the shell 211 can include one or more walls, the third shell wall 2112 can be any wall of the shell 211, and the shell 211 can include one or more third shell walls 2112. For example, if the shell 211 is a polygonal column, the third shell wall 2112 can be any wall of the polygonal column, and the surface of the third shell wall 2112 can be any polygon. For another example, Figure 3 and Figure 4 As shown, if the shell 211 is a rectangular parallelepiped, the third shell wall 2112 can be any wall of the shell 211, and the surface of the third shell wall 2112 is rectangular. For another example, if the shell 211 is a cylinder, the third shell wall 2112 can be the bottom surface of the cylinder or the side surface of the cylinder, and the embodiments of the present application are not limited thereto. In addition, if two adjacent walls of the shell 211 are connected by fillets, then when the third shell wall 2112 of the embodiment of the present application is any wall of the shell 211, the third shell wall 2112 does not include the fillet connection area between the wall and the connected wall.

[0276] In the embodiment of the present application, at least part of the area of ​​the shell 211 includes a third shell wall 2112, and the tensile strength of the third shell wall 2112 at a normal temperature of 25°C is Rm. Increasing the tensile strength Rm of at least part of the area of ​​the shell 211 at a normal temperature of 25°C can improve the deformation ability of the shell 211, so that the shell 211 is not easily damaged during the use of the battery cell 20, thereby improving the structural stability and service life of the battery cell 20. However, the tensile strength Rm of at least part of the area of ​​the shell 211 at normal temperature should not be too large, so as to reduce the difficulty of selecting the material and processing of the shell 211, save costs, and facilitate processing.

[0277] In the case where the average thickness T of the third shell wall 2112 of the shell 211 is thin, the structural strength of the third shell wall 2112 can be increased by increasing the tensile strength Rm of the third shell wall 2112 of the shell 211 at a normal temperature of 25°C, so that the energy density of the battery cell 20 can be increased, and the structural strength and stability of the battery cell 20 can be increased; on the contrary, in the case where the average thickness T of the third shell wall 2112 of the shell 211 is thick, the structural strength of the shell 211 can be increased, and the difficulty of selecting the material of the shell 211 can be reduced by appropriately reducing the requirement for the tensile strength Rm of the third shell wall 2112 of the shell 211 at a normal temperature, thereby reducing the processing difficulty and processing cost of the battery cell 20. In addition, T×Rm represents the stiffness of the third shell wall, and the stiffness of the third shell wall should not be too small or too large, so that the third shell wall has a better deformation ability, and the processing difficulty and cost can be reduced.

[0278] It should be understood that the value range of the average thickness T of the third shell wall 2112 of the embodiment of the present application can also be flexibly set according to the actual application. For example, the average thickness T of the third shell wall 2112 satisfies: 0.05mm≤T≤0.5mm. Further, the average thickness T of the third shell wall 2112 satisfies: 0.1mm≤T≤0.4mm. Appropriately thinning the average thickness T of the third shell wall 2112 can reduce the space occupied by the shell 211 inside the battery 10, thereby improving the energy density of the battery 10, and can compensate for the structural strength requirement of the shell 211 by increasing the tensile strength Rm of the third shell wall 2112 at room temperature to maintain the stability of the shell 211; and appropriately increasing the average thickness T of the third shell wall 2112 can also reduce the difficulty of processing the third shell wall 2112.

[0279] Furthermore, the average thickness T of the third shell wall 2112 satisfies: 0.1 mm ≤ T ≤ 0.3 mm. The average thickness T of the third shell wall 2112 is neither too large nor too small, which can improve the structural strength and structural stability of the shell 211 and reduce the space occupied by the shell 211 inside the battery 10, thereby improving the energy density of the battery 10.

[0280] In some embodiments, the average thickness T of the third shell wall 2112 of the embodiment of the present application can also be set to other values. For example, the average thickness T of the third shell wall 2112 can be any one of the following values ​​or between any two of the following values: 0.05mm, 0.075mm, 0.1mm, 0.125mm, 0.15mm, 0.175mm, 0.2mm, 0.225mm, 0.25mm, 0.275mm, 0.3mm, 0.325mm, 0.35mm, 0.375mm, 0.4mm, 0.425mm, 0.45mm, 0.475mm and 0.5mm.

[0281] In some embodiments, the value range of T×Rm can also be adjusted according to the actual application. 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 shell wall 2112 at room temperature can be improved, thereby reducing the average thickness T of the third shell wall 2112, so that the stiffness value of the third shell wall 2112 meets the design requirements, which can not only improve the structural strength and structural stability of the third shell wall 2112 of the shell 211, but also improve the energy density of the battery cell 20 and the battery 10.

[0282] Furthermore, 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 shell wall 2112 is more appropriate, which can not only make the third shell wall 2112 have good deformation ability to improve the service life of the battery cell 20, but also reduce the difficulty of material selection, thereby reducing the processing difficulty and processing cost.

[0283] In some embodiments, the value of T×Rm in the embodiment of the present application can also be set to other values. For example, the value of T×Rm can be any 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.

[0284] In the embodiment of the present application, the value of the mass proportion g of the silicon-based material and the value of the average thickness T of the third shell wall 2112 can be mutually restricted, and the value of the tensile strength Rm of at least a part of the shell 211 at a temperature of 25°C can also be mutually restricted to balance the relationship between the energy density and structural strength of the battery cell 20. For example, in the negative electrode active material, the mass proportion of the silicon-based material is g, and g and T satisfy: 2%≤g≤20%, 0.15mm≤T≤0.4mm. When the mass proportion g of the silicon-based material is small, the average thickness T of the third shell wall 2112 can be appropriately reduced to improve the space utilization of the shell 211, increase the energy density of the battery cell 20, and balance the structural strength of the shell 211.

[0285] In some embodiments, the mass proportion of the silicon-based material in the negative electrode active material is g, and g, T and Rm satisfy: 15%≤g≤40%, 0.2mm≤T≤0.4mm, 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, while increasing the thickness and stiffness T×Rm of the third shell wall 2112, which can improve the structural strength and stability of the battery cell 20.

[0286] It should be understood that the average thickness T of the third shell wall 2112 in the embodiment of the present application may refer to the average thickness of at least a portion of the third shell wall 2112. For example, the average thickness T of the third shell wall 2112 may refer to the average thickness T of the entire area of ​​the third shell wall 2112, especially when the third shell wall 2112 is relatively flat, that is, the thickness of most areas of the third shell wall 2112 is substantially equal or has a small difference, or the thickness of all areas of the third shell wall 2112 is substantially equal or has a small difference, then the average thickness of the entire area of ​​the third shell wall 2112 can be determined to be T.

[0287] For another example, the average thickness T of the third shell wall 2112 may also refer to the average thickness T of a local area of ​​the third shell wall 2112, that is, the average thickness T of the remaining area after excluding the partial area of ​​the third shell wall 2112. For example, if there are some special areas in the third shell wall 2112, and the thickness of the special areas is greatly different from that of other areas, for example, there are protruding structures or recessed areas in the special areas, so that the thickness of the special areas is larger or smaller than that of other areas, then the special areas may be excluded to calculate the average thickness T of the remaining areas of the third shell wall 2112.

[0288] In some embodiments, the third shell wall 2112 includes a functional area, and the average thickness T of the third shell wall 2112 is the average thickness of the area other than the functional area of ​​the third shell wall 2112, and the functional area includes at least one of the following areas: a pressure relief area, an area where the electrode terminal 214 is located, a liquid injection area, and a welding area. The thickness of the functional area is usually different from the thickness of other areas of the third shell wall 2112. Therefore, when the average thickness T of the third shell wall 2112 is calculated without excluding the functional area, the design of the third shell wall 2112 can be made to better meet the strength requirements, so as to improve the structural strength and stability of the battery cell 20.

[0289] Specifically, the functional area of ​​the embodiment of the present application may include an area on the third shell wall 2112 that is provided with a specific structure or has a specific purpose. For example, the functional area may include a pressure relief area, which is used to set a pressure relief mechanism, and the pressure relief mechanism is used to actuate when the internal pressure or temperature of the battery cell 20 reaches a predetermined threshold to release the internal pressure or temperature of the element or component. The predetermined threshold can be adjusted according to different design requirements. For example, the predetermined threshold may depend on one or more materials of the positive electrode plate, the negative electrode plate, the electrolyte and the separator in the battery cell 20.

[0290] The "actuation" mentioned in this application means that the pressure relief mechanism is in action or activated to a certain state, so that the internal pressure and temperature of the battery cell 20 can be released. The action produced by the pressure relief mechanism may include but is not limited to: at least a part of the pressure relief mechanism is ruptured, broken, torn or opened, etc. When the pressure relief mechanism is actuated, the high-temperature and high-pressure substances inside the battery cell 20 will be discharged from the actuated part as emissions. In this way, the battery cell 20 can be depressurized and cooled under controllable pressure or temperature, thereby avoiding potential more serious accidents.

[0291] The emissions from the battery cells 20 mentioned in the present application include, but are not limited to: electrolyte, dissolved or split positive and negative electrode plates, fragments of the isolation membrane, high-temperature and high-pressure gas generated by the reaction, flames, and the like.

[0292] 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 shell wall 2112 of the battery cell 20. The pressure relief mechanism can be a part of the third shell wall 2112; or, it can also be a separate structure from the third shell wall 2112 and fixed to the third shell wall 2112 by, for example, welding. For example, when the pressure relief mechanism is a part of the third shell wall 2112, for example, the pressure relief mechanism can be formed by providing a notch on the third shell wall 2112, that is, the third shell 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 shell wall 2112. Therefore, the average thickness T of the third shell wall 2112 can exclude the thickness at the notch. The notch is the weakest position of the pressure relief mechanism. When the battery cell 20 generates too much gas so that the internal pressure increases and reaches a threshold value, or the internal reaction of the battery cell 20 generates heat, causing the internal temperature of the battery cell 20 to increase and reach a threshold value, the pressure relief mechanism can rupture at the notch, causing the inside and outside of the battery elevator 20 to be connected, and the gas pressure and temperature are released outward through the rupture of the pressure relief mechanism, thereby preventing the battery cell 20 from exploding.

[0293] For another example, the pressure relief mechanism may also be a separate structure from the third shell wall 2112. The pressure relief mechanism may be in the form of an explosion-proof valve, an air valve, a pressure relief valve or a safety valve, and may specifically be a pressure-sensitive or temperature-sensitive element or structure. For example, the third shell wall 2112 is provided with a through hole at the pressure relief area, and the pressure relief mechanism is mutually mounted and fixed with the third shell wall 2112 through the through hole. The installed pressure relief mechanism may protrude or be recessed relative to other areas of the third shell wall 2112. Therefore, the calculation of the average thickness T of the third shell wall 2112 may 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 the weak structure provided in the pressure relief mechanism is destroyed, thereby forming an opening or channel for the internal pressure or temperature to be released.

[0294] In some embodiments, the functional area may also include an area where the electrode terminal 214 is located. Specifically, the electrode terminal 214 of the embodiment of the present application is used to electrically connect to the electrode assembly 22 inside the battery cell 20 to output the electrical energy of the battery cell 20. In addition, 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, and the second electrode terminal 214b is a negative electrode terminal; or, the first electrode terminal 214a may be a negative electrode terminal, and the second electrode terminal 214b is a positive electrode terminal. Among them, the positive electrode terminal is used to electrically connect to the positive pole ear 222a of the electrode assembly 22, and the negative electrode terminal is used to electrically connect to the negative pole ear 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 current collecting member 23, and the negative electrode terminal may be electrically connected to the negative electrode tab 222b through a current collecting member 23.

[0295] It should be understood that each electrode terminal 214 of the embodiment of the present application can be disposed on any wall, and multiple electrode terminals 214 can be disposed on the same wall or on different walls of the battery cell 20. Figure 3 and Figure 4 As shown, it is taken as an example that each battery cell 20 includes two electrode terminals 214 , and the two electrode terminals 214 are located on the same wall. For example, the two electrode terminals 214 may both be located on the cover plate 212 .

[0296] For another example, each battery cell 20 includes two electrode terminals 214, and the two electrode terminals 214 are located on the same wall. Figure 3 and Figure 4 As shown, the two electrode terminals 214 may also be located in the housing 211, for example, the two electrode terminals 214 may both be located in the third housing wall 2112 of the housing 211. When the electrode terminal 214 is located in the third housing wall 2112, the electrode terminal 214 usually 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, the calculation of the average thickness T of the third housing wall 2112 may not include the area where the electrode terminal 214 is located.

[0297] In some embodiments, the functional area may also include an injection area. For example, the injection area of ​​the third shell wall 2112 may be provided with an injection hole, through which electrolyte is injected into the shell 211. After the electrolyte is injected, the injection hole may be sealed by a seal. Considering that the thickness of the injection area where the seal is located is usually much greater than the thickness of other areas of the third shell wall 2112, the average thickness T of the third shell wall 2112 may not include the injection area.

[0298] In some embodiments, the functional area may also include a welding area. For example, the third shell wall 2112 may be fixed to other walls by welding, or the third shell wall 2112 itself needs to be processed and formed by welding, then the third shell wall 2112 may include a welding area. Figure 4 As shown, the shell 211 can be welded by splicing, and the shell 211 can have a weld 2113. Specifically, the shell 211 can include at least two parts, and the at least two parts are connected by welding to form the shell 211, wherein: Figure 4 For example, the shell 211 includes two parts along the height direction Z of the battery cell 20, and there is a weld 2113 between the upper shell and the lower shell; or, different from Figure 4 As shown, other parts of the shell 211 may also be provided with welds 2113, but the embodiment of the present application is not limited thereto. The welding area of ​​the functional area of ​​the embodiment of the present application may also include the weld 2113. Due to the processing technology, the thickness of the welding area is usually greater than the thickness of other areas of the third shell wall 2112. Therefore, the calculation of the average thickness T of the third shell wall 2112 may not include the welding area.

[0299] In the embodiment of the present application, the third shell wall 2112 of the shell 211 can be any wall of the shell 211. For example, the third shell wall 2112 is the wall with the smallest thickness of the shell 211. That is, by limiting the thickness T of the wall with the smallest thickness of the shell 211, the thickness of other walls of the shell 211 is limited, so that each wall of the shell 211 can meet the structural strength requirements, thereby improving the structural strength and stability of the battery cell 20.

[0300] In some embodiments, the third shell wall 2112 is the wall with the largest area of ​​the shell 211. Considering that when a plurality of battery cells 20 are arranged in the battery 10, the plurality of battery cells 20 are usually abutted against each other through the wall with the largest area of ​​the shell 211, and therefore, the wall with the largest area is usually subjected to the greatest extrusion force from the electrode assembly 22, by limiting the average thickness T and room temperature tensile strength Rm of the third shell wall 2112, the deformation capacity of the shell 211 can be effectively improved, thereby improving the structural strength and stability of the battery cells 20.

[0301] It should be understood that the position of the wall with the largest area of ​​the housing 211 of the embodiment of the present application can be set according to the actual application. For example, the battery 10 may include a plurality of battery cells 20, and the arrangement direction of the plurality of battery cells 20 may be perpendicular or parallel to the wall with the largest area of ​​the housing 211, and the embodiment of the present application is not limited thereto.

[0302] In some embodiments, the shell 211 includes a bottom wall and a side wall intersecting each other, wherein the bottom wall is used to support the electrode assembly contained in the shell 211. Specifically, the shell 211 may be a hollow structure with at least one end open, and the bottom wall and the side wall of the shell 211 do not necessarily refer to the walls opposite to and adjacent to the opening, respectively. The electrode assembly 22 is contained inside the shell 211. Considering that in actual applications, the electrode assembly 22 may be arranged in different directions in different application scenarios, and the shell 211 may include a wall for supporting the electrode assembly 22. Therefore, the bottom wall of the shell 211 of the embodiment of the present application is a wall for supporting the electrode assembly 22, that is, the bottom wall of the shell 211 is used to bear the gravity of the electrode assembly 22, and relatively, the wall of the shell 211 that directly intersects with the bottom wall is the side wall of the shell 211.

[0303] In some embodiments, the third shell wall 2112 is the side wall of the shell 211. Considering the different uses of the bottom wall and the side wall of the shell 211, the design requirements of the bottom wall and the side wall may also be different. For example, the side wall of the shell 211 usually has a higher requirement for deformation ability. In the case where the third shell wall 2112 is the side wall of the shell 211, by limiting the tensile strength Rm of the side wall of the shell 211 at room temperature and the average thickness T of the side wall, the deformation ability of the side wall of the shell 211 can be effectively improved, thereby improving the structural stability of the battery cell 20.

[0304] In some embodiments, the housing 211 includes a plurality of side walls having equal thickness to facilitate processing.

[0305] In some embodiments, the thickness of the bottom wall of the housing 211 is equal to the thickness of the side wall of the housing 211 to facilitate processing and optimize the space occupied by the housing 211 .

[0306] In some embodiments, the third shell wall 2112 is perpendicular to the stacking direction of the pole pieces of the electrode assembly 22. The stacking direction of the pole pieces of the electrode assembly 22 is usually the thickness direction of the electrode assembly 22. Considering that the electrode assembly 22 is prone to expand in the thickness direction during the cyclic charge and discharge of the battery cell 20, the deformation requirements of the corresponding shell 211 wall are relatively high. Therefore, the third shell wall 2112 is set to be a wall perpendicular to the stacking direction of the pole pieces of the electrode assembly 22, or the third shell wall 2112 and the electrode assembly 22 are arranged along the stacking direction of the pole pieces of the electrode assembly 22. By limiting the tensile strength Rm and the average thickness T of the third shell wall 2112 under normal temperature conditions, the energy density of the battery cell 20 can be improved, and the deformation capacity of the third shell wall 2112 can be effectively improved, thereby improving the structural stability of the battery cell 20.

[0307] It should be understood that the cover plate 212 of the embodiment of the present application can adopt the same or different design as the third shell wall 2112. For example, the cover plate 212 can adopt the same design as the third shell 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 met to improve the deformation ability of the cover plate 212, thereby improving the structural strength and stability of the battery cell 20.

[0308] In some embodiments, the ratio of the volume of the internal space of the housing 211 to the outer volume of the housing 211 is greater than or equal to 93%. That is, the thickness of the housing 211 is relatively thin, so that the housing 211 itself occupies less space, thereby improving the space utilization and energy density of the battery 10.

[0309] It should be understood that the specific calculation method of the volume of the internal space of the housing 211 and the external volume of the housing 211 in the embodiment of the present application is related to the shape of the housing 211. For example, the housing 211 is a rectangular parallelepiped. Figure 8 2 shows a schematic side view of the structure of the housing 211 of the battery cell of the embodiment of the present application. Fig. 9 The cross-sectional structure diagram of the housing 211 of the embodiment of the present application is shown. Figure 8 and Fig. 9 The housing 211 shown may be Figure 3 and Figure 4 The housing 211 of the battery cell 20 is shown.

[0310] like Figure 8 and Fig. 9 As shown, a rectangular shell 211 is taken as an example, and the shell 211 is a hollow rectangular shell with one end open. When calculating the volume of the internal space of the shell 211 and the outer volume of the shell 211, the fillet connection between adjacent walls of the shell 211 can be ignored. Figure 8 and Fig. 9 As shown, since each wall of the shell 211 has a certain thickness, in the length direction Y, the inner length of the shell 211 is Y1, and the outer length is Y2, and Y2 is greater than Y1; similarly, in the width direction X, the inner width of the shell 211 is X1, and the outer width is X2, and X2 is greater than X1; in the height direction Z, the inner height of the shell 211 is Z1, and the outer height is Z2, and Z2 is greater than Z1. Therefore, the volume V1 of the inner space of the shell 211 = X1×Y1×Z1; the volume V2 of the outer space of the shell 211 = X2×Y2×Z2, and V1 / V2 is greater than or equal to 93%, so as to reduce the space occupied by the shell 211 itself, thereby improving the space utilization and energy density of the battery 10.

[0311] The following is a comparative explanation through a plurality of comparative examples and a plurality of embodiments. Specifically, the battery cells 20 in the following embodiments and comparative examples are as follows: Figure 3 and Figure 4 Taking the square shell battery shown as an example, the shell 211 adopts a hollow structure with one end open.

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

[0313] 1. Preparation of positive electrode sheet 223

[0314] The positive electrode active material LiNi 0.95 Co 0.04 Mn 0.01O2, conductive agent Super P, and binder polyvinylidene fluoride (PVDF) are used to prepare positive electrode slurry in N-methylpyrrolidone (NMP), wherein the solid content in the positive electrode slurry is 50wt%, and the solid content of LiNi 0.7 Co 0.1 Mn 0.1 The mass ratio of O2, 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 and dried at 85°C and then cold pressed. Then, it is trimmed, cut and stripped, and then dried at 85°C under vacuum conditions for 4 hours to form a positive electrode sheet 223.

[0315] 2. Preparation of negative electrode sheet 224

[0316] The negative electrode active material, the conductive agent Super P, the thickener carboxymethyl cellulose (CMC), and the adhesive styrene butadiene rubber (SBR) are mixed evenly in deionized water to form a negative electrode slurry, wherein the negative electrode active material includes graphite and silicon-based materials, and the silicon-based materials are silicon oxide compounds. The solid content in the negative electrode slurry is 30wt%, and the mass ratio of the negative electrode active material, silicon oxide, Super P, CMC and adhesive styrene butadiene rubber (SBR) in the solid component is 88:7:3:2. The negative electrode slurry is coated on the upper and lower surfaces of the current collector copper foil and dried at 85°C, and then cold pressed, trimmed, cut into pieces, and slit, and then dried at 120°C under vacuum conditions for 12 hours to form a negative electrode sheet 224.

[0317] 3. Preparation of electrolyte

[0318] In an argon atmosphere glove box (H2O<0.1ppm, O2<0.1ppm), fully dried electrolyte salt LiPF6 was dissolved in a mixed solvent (the mixed solvent included ethylene carbonate (EC) and diethyl carbonate (DEC), and ethylene carbonate (EC) and diethyl carbonate (DEC) were mixed in a mass ratio of 50:50), and after mixing evenly, an electrolyte with a concentration of 1 mol / L was obtained.

[0319] 4. Preparation of Isolation Component 225

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

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

[0322] The positive electrode sheet 223, the separator 225 and the negative electrode sheet 224 are stacked in order, and the separator 225 is located between the positive electrode sheet 223 and the negative electrode sheet 224 to isolate the positive and negative electrodes. The bare battery cell is wound and the pole ears are welded. The bare battery cell is placed in a shell made of different materials, and the prepared electrolyte is injected into the dried shell. The lithium-ion battery cell 20 is prepared by packaging, standing, forming, shaping, and capacity testing.

[0323] In the following embodiments and comparative examples, the tensile strength of the shell 211 of the battery cell 20 at a temperature of 25°C is Rm, and in order to obtain different tensile strengths Rm, different materials are selected for the shell 211; the average thickness of the third shell wall 2112 of the shell 211 is T; the above specific parameter settings are shown in Table 5 below. In addition, in each embodiment and comparative example, the material of all areas of the shell 211 is the same, and the tensile strength Rm of the shell 211 at 25°C is measured using the method specified in GB / T228.1-2010. In addition, the battery cells 20 in the following embodiments and comparative examples have the same setting conditions except for the different parameter settings shown in Table 5. For example, the capacity of the battery cell 20 in each embodiment is 350Ah.

[0324] The battery cells 20 in the following embodiments and comparative examples are subjected to a cycle charging fatigue test. Figure 7 The fixture 700 shown is used for cyclic charging fatigue testing.

[0325] Specifically, the battery cell 20 is clamped and fixed in the dedicated fixture 700, ensuring that the two oppositely disposed walls with the largest area of ​​the battery cell 20 are clamped, and the initial pressure is set to 2000N, and the electrode terminal 214 of the battery cell 20 is connected to the dedicated battery charging and discharging equipment.

[0326] 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.

[0327] The specific test steps refer to Chapter 6.4 "Standard Cycle Life" of "GBT31484-2015 Requirements and Test Methods for Cycle Life of Power Batteries for Electric Vehicles", and the test cycle cutoff condition is changed to "stop testing until the weld 2113 of the battery cell 20 is damaged."

[0328] 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, leave it for not less than 30 minutes or the leaving condition specified by the enterprise; step c, charge according to the method of 6.1.1.3; step d, leave it for not less than 30 minutes or the leaving condition specified by the enterprise; step e, discharge at 1I1(A) to the discharge termination condition specified by the enterprise; step f, cycle from step b to step e until the weld 2113 is damaged and the test is stopped.

[0329] During the above test process, the weld 2113 of the battery cell 20 is continuously observed until the weld 2113 leaks, and the number of cycles is recorded to obtain the condition of the shell 211 at 1000 cycles as shown in Table 5 below. In the following embodiments and comparative examples, the weld 2113 refers to the weld between the shell 211 and the cover plate 212, that is, the weld 2113 surrounds the open end of the shell 211, and the shell 211 adopts an integrally formed structure.

[0330] Table 5

[0331]

[0332] It should be understood that in Table 5 above, the material of the shell 211 can be Q195 carbon steel, and the tensile strength Rm of Q195 carbon steel at room temperature 25°C is usually at least 315MPa to 430MPa. The above embodiment only takes 328MPa as an example, but is not limited to this. Similarly, the material of the shell 211 can be SPCC carbon steel, and the tensile strength Rm of SPCC carbon steel at room temperature 25°C is usually at least 380MPa to 430MPa, and only 396MPa is taken as an example in the above embodiment; the material of the shell 211 can be SUS430 stainless steel, and the tensile strength Rm of SUS430 stainless steel at room temperature 25°C is usually at least 450MPa, and only 459MPa is taken as an example in the above embodiment; the material of the shell 211 can be SUS304 stainless steel, and the tensile strength Rm of SUS304 stainless steel at room temperature 25°C is usually at least 520MPa, and only 533MPa, 625MPa and 763MPa are taken as examples in the above embodiment.

[0333] According to Table 5 above, in the above embodiments 1-12, Rm and T of the third shell wall 2112 of the shell 211 meet the following conditions: 250MPa≤Rm≤2000MPa, 0.05mm≤T≤0.5mm, and 60 mm·MPa≤T×Rm≤500 mm·MPa, and the number of failure fatigue times of the battery cell 20 can reach more than one thousand times, so as to meet the design requirements of the battery cell 20, and even if the average thickness T of the third shell wall 2112 is set to be small, the number of failure fatigue times of the battery cell 20 can reach more than one thousand times, and the average thickness T of the third shell wall 2112 can also increase the energy density of the battery 10. However, in the two comparative examples, the structural strength of the third shell wall 2112 is insufficient, and Rm and T×Rm do not meet the above values. Even if the average thickness T of the third shell wall 2112 is large, the number of failure fatigue times of the battery cell 20 does not reach one thousand times, and the design requirements of the battery cell 20 cannot be met.

[0334] In some embodiments, the capacity of the battery cell is C, and C satisfies: 25Ah≤C≤550Ah. On the one hand, increasing the capacity C of the battery cell 20 can increase the capacity density of the battery 10 including multiple battery cells 20, or, if 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 can be reduced, and the number of electrical connections between multiple battery cells 20 can be reduced accordingly, reducing the probability of electrical connection failure, which helps to improve the reliability of the battery. In addition, when the capacity C of the battery cell 20 is large, the tensile strength Rm of at least part of the shell 211 at room temperature of 25°C can be increased to meet the requirements of the high-capacity battery cell 20 for the structural strength of the shell 211, thereby improving the reliability and service life of the battery cell 20. On the other hand, if the battery cell 20 has a large capacity, the reaction inside it will be intensified, thereby increasing the requirements for the structural strength of the shell 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 shell 211, which can reduce the difficulty of material selection and processing of the battery cell 20, reduce costs and improve processing efficiency.

[0335] It should be understood that the value range of the capacity C of the battery cell 20 of the embodiment of the present application can be adjusted according to the actual application. For example, the capacity C of the battery cell 20 can be reasonably selected according to the actual needs of the battery 10. In some embodiments, the capacity C of the battery cell 20 can be set to further meet: 100Ah≤C≤300Ah. Properly 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 shell 211, thereby improving the reliability and service life of the battery cell 20.

[0336] Furthermore, the capacity C of the battery cell 20 may also satisfy: 150Ah≤C≤250Ah. Further limiting the capacity C of the battery cell 20 can both increase the energy density of the battery 10 and improve the structural strength of the housing 211, thereby improving the reliability and service life of the battery cell 20 and the battery 10.

[0337] In some embodiments, the value of the capacity C of the battery cell 20 of the embodiment 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: 25Ah, 30Ah, 35Ah, 40Ah, 45Ah, 50Ah, 55Ah, 60Ah, 65Ah, 70Ah, 75Ah, 80Ah, 85Ah, 90Ah, 95Ah, 100Ah, 130Ah, 150Ah, 180Ah, 200Ah, 230Ah, 250Ah, 280Ah, 300Ah, 330Ah, 350Ah, 380Ah, 400Ah, 430Ah, 450Ah, 480Ah, 500Ah, 530Ah and 550Ah.

[0338] It should be understood that the capacity C of the battery cell 20 of the embodiment of the present application represents the amount of electricity output when the battery cell 20 is fully charged and discharged to the termination voltage under specified discharge conditions. The test method of the capacity C of the battery cell 20 can be selected according to the actual application. For example, GB / T 31467.1 can be used for discharge testing to determine the capacity C of the battery cell 20, but the embodiment of the present application is not limited thereto.

[0339] The following is a comparative explanation through a plurality of comparative examples and a plurality of embodiments. Specifically, the battery cells 20 in the following embodiments and comparative examples are as follows: Figure 3 and Figure 4 Taking the square shell battery shown as an example, the shell 211 adopts a hollow structure with one end open.

[0340] In the following embodiments and comparative examples, the preparation methods of the positive electrode sheet 223, the negative electrode sheet 224, the electrolyte and the separator 225 of the battery cell 20 are as follows.

[0341] 1. Preparation of positive electrode sheet 223

[0342] The positive electrode active material LiNi 0.95 Co 0.04 Mn 0.01 O2, conductive agent Super P, and binder polyvinylidene fluoride (PVDF) are used to prepare positive electrode slurry in N-methylpyrrolidone (NMP), wherein the solid content in the positive electrode slurry is 50wt%, and the solid content of LiNi0.7 Co 0.1 Mn 0.1 The mass ratio of O2, 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 and dried at 85°C and then cold pressed. Then, it is trimmed, cut and stripped, and then dried at 85°C under vacuum conditions for 4 hours to form a positive electrode sheet 223.

[0343] 2. Preparation of negative electrode sheet 224

[0344] The negative electrode active material, the conductive agent Super P, the thickener carboxymethyl cellulose (CMC), and the adhesive styrene butadiene rubber (SBR) are mixed evenly in deionized water to form a negative electrode slurry, wherein the negative electrode active material includes graphite and silicon-based materials, and the silicon-based materials are silicon oxide compounds. The solid content in the negative electrode slurry is 30wt%, and the mass ratio of the negative electrode active material, silicon oxide, Super P, CMC and adhesive styrene butadiene rubber (SBR) in the solid component is 88:7:3:2. The negative electrode slurry is coated on the upper and lower surfaces of the current collector copper foil and dried at 85°C, and then cold pressed, trimmed, cut into pieces, and slit, and then dried at 120°C under vacuum conditions for 12 hours to form a negative electrode sheet 224.

[0345] 3. Preparation of electrolyte

[0346] In an argon atmosphere glove box (H2O<0.1ppm, O2<0.1ppm), fully dried electrolyte salt LiPF6 was dissolved in a mixed solvent (the mixed solvent included ethylene carbonate (EC) and diethyl carbonate (DEC), and ethylene carbonate (EC) and diethyl carbonate (DEC) were mixed in a mass ratio of 50:50), and after mixing evenly, an electrolyte with a concentration of 1 mol / L was obtained.

[0347] 4. Preparation of Isolation Component 225

[0348] A 16 μm polyethylene film was used as the separator 225 .

[0349] 5. Preparation of lithium-ion battery cell 20

[0350] The positive electrode sheet 223, the separator 225 and the negative electrode sheet 224 are stacked in order, and the separator 225 is located between the positive electrode sheet 223 and the negative electrode sheet 224 to isolate the positive and negative electrodes. The bare battery cell is wound and the pole ears are welded. The bare battery cell is placed in a shell made of different materials, and the prepared electrolyte is injected into the dried shell. The lithium-ion battery cell 20 is prepared by packaging, standing, forming, shaping, and capacity testing.

[0351] In the following embodiments and comparative examples, the tensile strength of the shell 211 of the battery cell 20 at a temperature of 25°C is Rm, and in order to obtain different tensile strengths Rm, different materials are selected for the shell 211; the capacity of the battery cell 20 is C; the above specific parameter settings are shown in Table 6 below. In addition, in each embodiment and comparative example, the material of the entire area of ​​the shell 211 is the same, and the tensile strength Rm of the shell 211 at 25°C is measured using the method specified in GB / T 228.1-2010. In addition, the battery cells 20 in the following embodiments and comparative examples have the same setting conditions except for the different parameter settings shown in Table 6. For example, the wall thickness of the largest wall 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.

[0352] Table 6

[0353]

[0354] Comparing the two comparative examples in Table 6 above with the six embodiments, it can be seen that when the shell 211 is made of different materials, different tensile strengths Rm can be determined accordingly. When the tensile strength Rm satisfies 250MPa≤Rm≤2000MPa and the capacity C of the battery cell 20 satisfies 25Ah≤C≤550Ah, for example, in embodiments 1-6, the shell 211 of the battery cell 20 does not crack, then the structural strength of the shell 211 can be used for battery cells 20 with larger capacity, and can meet the design requirements of the battery cell 20. However, when the tensile strength Rm does not satisfy 250MPa≤Rm≤2000MPa, for example, in comparative examples 1-2, the shell 211 of the battery cell 20 cracks, and the design requirements of the battery cell 20 cannot be met.

[0355] It should be understood that in order to meet the above-mentioned design requirements, the material of at least a part of the area of ​​the shell 211 in the embodiment of the present application can be flexibly selected according to the actual application.

[0356] In some embodiments, the material of at least a part 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 cost.

[0357] In some embodiments, the material of at least a 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, its structural strength is relatively large, and it can usually meet the requirements of tensile strength Rm at room temperature, yield strength Re at room temperature, tensile strength Rn at high temperature, and melting point p. For example, the melting point of stainless steel is usually between 1400°C and 1500°C. In addition, the housing 211 is made of stainless steel, which is not easy to rust, and can increase the service life of the housing 211 compared with other materials.

[0358] If the shell 211 is made of carbon steel, it has a high structural strength and is easy to meet the requirements of tensile strength Rm at room temperature, yield strength Re at room temperature, tensile strength Rn at high temperature and melting point p. For example, the melting point of carbon steel is usually between 1425° C. and 1525° C. In addition, considering that the carbon steel material may be easily corroded during use, the outer surface of the carbon steel shell 211 may be nickel plated. For example, the thickness of the nickel plated layer is usually 1 μm to 10 μm, so as to protect the surface of the shell 211 from being oxidized and corroded, thereby improving the service life of the shell 211.

[0359] The shell 211 can also be made of other high-strength alloy steel materials to effectively improve the structural strength of the shell 211. For example, when the structural strength requirements of the shell 211 are high, a high-strength alloy steel material can be selected, which is easy to meet the above-mentioned tensile strength Rm under normal temperature conditions, yield strength Re under normal temperature conditions, tensile strength Rn under high temperature conditions and melting point p requirements.

[0360] In some embodiments, when at least part of the housing 211 is made of steel, the type of the steel may include at least one of the following: SPCC, Q195, Q215, Q235, SUS 304, SUS 316 and other modified stainless steels. These steels are easy to obtain, have strengths that meet design requirements, and are low in cost. For example, the approximate values ​​of the tensile strength Rm at room temperature 25°C, the yield strength Re at room temperature 25°C, the tensile strength Rn at high temperature 500°C, and the melting point p of different steels can be found in Table 7 below.

[0361] Table 7

[0362]

[0363] It should be understood that the material of at least a part of the housing 211 in the embodiment of the present application may also be other materials. For example, different materials may be reasonably selected according to the mass content of different elements in the material and the role played by the elements.

[0364] In some embodiments, the mass content of chromium in the material of at least a portion of the shell 211 is m, and m satisfies: 10%≤m≤30%. Adding a proper amount of chromium to the material of at least a portion of the shell 211 can increase the melting point and strength of the material, making it easy to meet the requirements of tensile strength Rm at room temperature, yield strength Re at room temperature, tensile strength Rn at high temperature, and melting point p in the embodiment of the present application. In addition, since chromium 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 shell 211, thereby improving the corrosion resistance of the shell 211.

[0365] In some embodiments, the mass content of nickel in the material of at least a portion of the shell 211 is n, and n satisfies 8%≤n≤25%. Adding a proper amount of nickel to the material of at least a portion of the shell 211 can improve the structural strength and plasticity of the shell 211, for example, it can improve the tensile strength Rm at room temperature, the yield strength Re at room temperature, and the tensile strength Rn at high temperature, and can also improve the corrosion resistance of the material.

[0366] In some embodiments, taking the steel material used for the shell 211 as an example, different types of steel materials contain different mass contents of different elements. For example, for stainless steel materials, the mass content of iron is one of the basic elements of stainless steel, and its mass content is usually 60% to 70%. For another example, Table 8 shows the mass content of different elements in several steel materials, wherein the values ​​in Table 8 are the maximum values ​​of the mass percentages of each element in the material, i.e., the mass percentage of each element in the corresponding material is usually not greater than the values ​​shown in Table 8.

[0367] Table 8

[0368]

[0369] It should be understood that when at least part of the housing 211 is made of steel, increasing the mass content of carbon in the steel can improve the strength and hardness of the steel. For example, generally, the higher the carbon content, the higher the hardness and strength of the steel, but the corrosion resistance may be reduced.

[0370] If the mass content of chromium in steel is increased, the corrosion resistance of the steel can be improved because chromium can react with oxygen to form a dense chromium oxide film, which forms a corrosion-resistant protective film on the surface of the steel.

[0371] Increasing the mass content of nickel in steel can improve the corrosion resistance, strength and plasticity of the steel.

[0372] Increasing the mass content of molybdenum in steel can improve the corrosion resistance and strength of the steel, especially in corrosive media such as acids and salts.

[0373] Increasing the mass content of manganese in steel can increase the toughness and fatigue resistance of the steel.

[0374] Increasing the mass content of silicon in steel can increase the corrosion resistance and strength of stainless steel.

[0375] If the mass content of phosphorus and sulfur in steel is reduced, the negative impact of these two elements on the corrosion resistance, plasticity and toughness of the steel can be reduced.

[0376] In addition, other elements may also be provided in the steel. For example, the steel may also include copper, such as the mass content of copper in Q195, Q215 and Q235 is generally not more than 0.3%, and the modified stainless steel is generally not more than 2% to 3.5%. For another example, the steel may also include nitrogen, such as the mass content of nitrogen in Q195, Q215 and Q235 is generally not more than 0.12%.

[0377] It should be understood that the test method for the mass content of each element of the steel in the embodiment of the present application can be set according to the actual application. For example, inductively coupled plasma atomic emission spectrometry, i.e., inductively coupled plasma (ICP) testing can be used, but the embodiment of the present application is not limited thereto.

[0378] Fig.10 Another exploded structural diagram of the battery cell 20 according to an embodiment of the present application is shown. Fig.11 A cross-sectional view of the housing 211 of the embodiment of the present application is shown. Fig.12 for Fig.11 It should be noted that the Figures 10 to 12 The housing 211 shown can be applied to the battery cell 20. For example, the housing 211 can be applied to Figure 3 and Figure 4 The battery cell 20 shown in FIG. Figures 10 to 12 The housing 211 shown may be Figure 3 and Figure 4 The housing 211 shown is applicable to the relevant descriptions above, and for the sake of brevity, they will not be described in detail here.

[0379] like Figures 10 to 12 As shown, the housing 211 has an opening 301 , and the housing 211 includes a first housing wall 31 and at least two second housing walls 32 arranged opposite to the opening 301 , and the first housing wall 31 and the second housing wall 32 are arranged to intersect with each other.

[0380] A transition region 33 is provided between two adjacent second shell walls 32 of the shell 211 . The maximum thickness of the transition region 33 is T1 . The maximum thickness of the thickest second shell wall 32 of the two adjacent second shell walls 32 is T0 , wherein T1 is greater than T0 .

[0381] In some embodiments, the second housing wall 32 may be perpendicular to the first housing wall 31 .

[0382] In some embodiments, at least two second shell walls 32 may be connected end to end to enclose and form a hollow structure with openings at both ends, wherein the first shell wall 31 covers the opening at one end of the hollow structure.

[0383] In some embodiments, the housing 211 may be placed as follows: Fig.10 As shown, the first shell wall 31 may be the bottom wall of the shell 211 for supporting the electrode assembly 22 , while the second shell wall 32 may be the side wall of the shell 211 and disposed around the electrode assembly 22 .

[0384] Generally, the second shell wall 32 is not prepared independently, that is, the at least two second shell walls 32 can be integrally formed. In other embodiments, the at least two second shell walls 32 and the first shell wall 31 are integrally formed, that is, the shell 211 is an integrally formed structure. For example, a plate-like structure is punched into a hollow structure with an opening by a mold, and the shell 211 after punching can have openings of various shapes, for example, the opening 301 can be circular, polygonal or track-shaped. The polygon is, for example, a square, pentagon, hexagon or other irregular shapes.

[0385] In some embodiments, the thickness of the transition region 33 may be uniform or non-uniform. The maximum thickness T1 of the transition region 33 will be defined below by taking the uniform thickness of the transition region 33 as an example.

[0386] from Fig.10 It can be seen that the transition area 33 has two surfaces, namely the inner surface and the outer surface. In some embodiments, the inner surface and the outer surface can be arc surfaces, and the inner surface and the outer surface are coaxially arranged. The maximum thickness T1 of the transition area 33 can be defined as the length of the extended line of the line between the center of the circle where the inner arc is located and the center of the circle where the outer arc is located in any cross section in the direction perpendicular to the axis of the inner surface and the outer surface in the transition area 33. In other embodiments, the inner surface and the outer surface can be planes, and the inner surface and the outer surface are parallel, and the maximum thickness T1 of the transition area 33 can be defined as the vertical distance between the inner surface and the outer surface. Similarly, the second shell wall 32 also has two surfaces, namely the inner surface and the outer surface, wherein the maximum value of the vertical distance between the inner surface and the outer surface is the maximum thickness of the second shell wall 32.

[0387] If at least two second shell walls 32 of the shell 211 have unequal wall thicknesses, for example, the wall thicknesses of the two second shell walls 32 of a transition region 33 are unequal, then in the embodiment of the present application, T0 is the second shell wall 32 with the largest wall thickness among the two second shell walls 32 adjacent to the transition region 33 in the shell 211. If at least two second shell walls 32 of the shell 211 have equal wall thicknesses, for example, the wall thicknesses of the two second shell walls 32 of a transition region 33 are equal, then in the embodiment of the present application, T0 is the thickness of any second shell wall 32 of the shell 211.

[0388] It should be noted that if a second shell wall 32 includes a functional area, the maximum thickness of the second shell wall 32 actually refers to the maximum thickness of the area of ​​the second shell 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 the electrode terminals are located, a liquid injection area, and a welding area.

[0389] In this embodiment, by setting a transition area 33 between two adjacent second shell walls 32, the stress concentration between the two adjacent second shell walls 32 can be reduced, and the risk of structural failure caused by stress concentration can be reduced; in addition, the maximum thickness T1 of the transition area 33 is set to be greater than the maximum thickness T0 of the second shell wall with the largest thickness among the two adjacent second shell walls. The thickened transition area 33 can enhance the structural strength of the shell 211, which is conducive to solving the problem of deformation of the shell 211 during the production and assembly process of the battery cell 20, and the problem of deformation of the shell 211 caused by gas production and expansion of the battery cell 20 during use.

[0390] In some embodiments, the maximum thickness T1 of the transition region 33 and the maximum thickness T0 of the second shell wall 32 with the largest thickness among two adjacent second shell walls 32 satisfy the following: 1.5≤T1 / T0≤7.

[0391] In this embodiment, by setting the ratio of the maximum thickness T1 of the transition region 33 to the maximum thickness T0 of the thickest second shell wall 32 of the two adjacent second shell walls 32 between [1.5, 7], on the one hand, the strength of the shell can be enhanced by the thicker transition region 33, and on the other hand, the difficulty in manufacturing the shell 211 due to excessive thickening of the transition region 33 can be limited, thereby achieving a balance between the strength of the shell 211 and the difficulty of manufacturing the shell 211.

[0392] 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 thickest second shell wall 32 of two adjacent second shell walls 32 can satisfy: 2≤T1 / T0≤4.

[0393] 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.

[0394] In this embodiment, by setting the ratio of the maximum thickness T1 of the transition area 33 to the maximum thickness T0 of the thickest second shell wall 32 of the two adjacent second shell walls 32 between [2, 4], the strength of the shell 211 and the difficulty of manufacturing the shell 211 can be maximized. Balance.

[0395] Alternatively, if Figures 11 to 13 As shown, two adjacent second housing walls 32 are connected via a first rounded corner 331, and the transition region 33 includes the first rounded corner 331. In other words, the transition region 33 is implemented via a rounded corner.

[0396] In this embodiment, the transition area 33 between two adjacent second shell walls 32 is realized by rounding the corners, which can make the shell 211 easier to form and have a better surface finish. At the same time, when affected by gas production inside the battery cell 20, the risk of cracking of the shell 211 due to sharp point stress concentration can be reduced.

[0397] like Fig.13 As shown, the inner diameter of the first fillet 331 is R1, and the outer diameter of the first fillet 331 is R2.

[0398] 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.

[0399] In some embodiments, the inner diameter R1 of the first fillet 331 satisfies: 2mm≤R1≤4mm. For example, R1=2mm, 2.1mm, 2.2mm, 2.3mm, 2.4mm, 2.5mm, 2.6mm, 2.7mm, 2.8mm, 2.9mm, 3.0mm, 3.1mm, 3.2mm, 3.3mm, 3.4mm, 3.5mm, 3.6mm, 3.7mm, 3.8mm, 3.9mm, 4.0mm, etc.

[0400] 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 211 due to too large an inner diameter, resulting in an increase in the gas production pressure inside the housing 211. On the other hand, it will not lead to insufficient wall thickness increment of the first rounded corner 331 due to too small an inner diameter, and then lead to insufficient strength of the housing 211, so that a balance can be achieved between the internal space utilization rate of the housing 211 and the strength of the housing 211.

[0401] 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.

[0402] In this embodiment, when the cover plate 212 is fixedly connected to the housing 211 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 it is easy to have false welding; while the smaller the outer diameter R2 of the first rounded corner 331, the more difficult it is for the housing 211 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.

[0403] In some other embodiments, as Fig.14 shown, two adjacent second housing walls 32 are connected by a C corner. For example, the angle between the C corner and the two adjacent second housing walls 32 is 45°.

[0404] In one embodiment, the housing 211 can be an integrally formed structure, as Fig.10 shown, the depth of the housing 211 is H, where the depth H of the housing 211 and the inner diameter R1 of the first rounded corner 331 satisfy: 2.5 mm ≤ R1 ≤ 20 mm, 50 mm < H ≤ 250 mm.

[0405] In the embodiment of the present application, the depth can be understood as the distance from the opening inward to the bottom. For example, the depth H of the housing 211 can be understood as the distance from the opening 301 to the first housing wall 31.

[0406] When the housing 211 is formed, the material of the housing 211 is likely to accumulate at the position of the first rounded corner 331, resulting in a large frictional force between the housing 211 and the mold, and the housing 211 is likely to crack. Therefore, in this embodiment, by setting the depth H of the housing 211 and the inner diameter R1 of the first rounded corner 331 to satisfy 2.5 mm ≤ R1 ≤ 20 mm, 50 mm < H ≤ 250 mm, the risk of cracking of the housing 211 caused by stress during the integral forming process can be reduced as much as possible without affecting the energy density of the battery cell 20, and thus the forming difficulty of the housing 211 is reduced.

[0407] For example, R1=2.5mm, 5mm, 7.5mm, 10mm, 12.5mm, 15mm, 17.5mm, 20mm; and / or, H=50mm, 100mm, 150mm, 200mm, 250mm.

[0408] In some embodiments, H and R1 satisfy: 75 mm ≤ H ≤ 180 mm, 4 mm ≤ R1 ≤ 15 mm.

[0409] For example, H=75mm, 100mm, 125mm, 150mm, 175mm, 180mm. For example: R1=4mm, 6mm, 8mm,10mm, 12mm, 14mm, 15mm.

[0410] In this embodiment, by setting H and R1 to satisfy: 4mm≤R1≤15mm, 75mm≤H≤180mm, on the one hand, the energy density of the battery cell 20 will not be reduced due to H being too small or R being too large, and on the other hand, the shell 211 will not be easily piled up during the molding process due to H being too large or R being too small, thereby causing the shell 211 to be subjected to excessive force and crack.

[0411] In some other embodiments, H and R1 satisfy: 5mm≤R1≤10mm, 90mm≤H≤140mm, for example, R1=5mm, 6mm, 7mm, 8mm, 9mm, 10mm. For another example, H=90mm, 100mm, 110mm, 120mm, 130mm, 140mm.

[0412] In other embodiments, the shell 211 is an integrally formed structure, and the yield strength of the shell 211 at a temperature of 25° C. is Re, wherein the yield strength Re and the inner diameter R1 of the first fillet 331 satisfy: 140MPa≤Re≤1000Mpa, 2.5mm≤R1≤20mm.

[0413] For example, Re=140MPa, 180MPa, 200MPa, 230MPa, 250MPa, 280MPa, 300MPa, 320MPa, 350MPa, 380MPa, 400MPa, 430MPa, 450MPa, 480MPa, 500MPa, 550MPa, 600MPa, 650MPa, 700MPa, 750MPa, 800MPa, 850MPa, 900MPa, 950MPa, 1000MPa.

[0414] For example, R1=2.5mm, 5mm, 7.5mm, 10mm, 12.5mm, 15mm, 17.5mm, 20mm.

[0415] Yield strength can be understood as the critical stress value of material yield. Generally, after a 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 shell 211 of the embodiment of the present application at a temperature of 25°C can be selected according to the actual application. For example, GB / T228.1-2010 can be used to test the yield strength Re at a normal temperature of 25°C.

[0416] In order to solve the problem that when the shell 211 is integrally formed, the material is easily piled up at the first fillet 331, which leads to large friction between the shell 211 and the mold and the shell 211 is easy to crack, the embodiment of the present application also provides another solution, that is, for the shell 211 with a yield strength Re satisfying 140MPa≤Re≤1000Mpa, the inner diameter R1 of the first fillet 331 is set to 2.5mm≤R1≤20mm, so that R1 cannot be too small, thereby reducing the difficulty of forming the shell 211, and R1 cannot be too large, thereby reducing the stress deformation of the shell 211.

[0417] In this embodiment, by using a material with a yield strength Re satisfying 140MPa≤Re≤1000Mpa to make the shell 211, the wall thickness of the shell can be thinned without reducing the strength of the shell 211, 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 shell walls 32 to satisfy 2.5mm≤R1≤20mm, the risk of cracking of the shell 211 due to force during the one-piece molding process is reduced as much as possible, and the molding difficulty of the shell 211 is reduced.

[0418] In some embodiments, the yield strength Re and R1 of the shell 211 may satisfy: 150 MPa≤Re≤400 MPa, 4 mm≤R1≤15 mm.

[0419] For example, Re=150MPa, 170MPa, 190MPa, 210MPa, 230MPa, 260MPa, 290MPa,310MPa, 330MPa, 370MPa, 390MPa, 400Mpa.

[0420] For example, R1=4mm, 6mm, 8mm, 10mm, 12mm, 14mm, 15mm.

[0421] In this embodiment, by defining 150MPa≤Re≤400Mpa and 4mm≤R1≤15mm, it is helpful to achieve a balance between the molding difficulty and the deformation degree of the shell 211.

[0422] In some embodiments, the yield strength Re and R1 of the shell 211 may satisfy: 160 MPa≤Re≤300 MPa, 5 mm≤R1≤10 mm.

[0423] For example, Re=160MPa, 170MPa, 180MPa, 190MPa, 200MPa, 210MPa, 220MPa,230MPa, 240MPa, 250MPa, 260MPa, 270MPa, 280MPa, 290MPa, 300Mpa.

[0424] For example, R1=5mm, 6mm, 7mm, 8mm, 9mm, 10mm.

[0425] In this embodiment, by limiting 160MPa≤Re≤300Mpa and 5mm≤R1≤10mm, the stress deformation of the shell 211 during use can be reduced as much as possible without affecting the difficulty of forming the shell 211.

[0426] In some embodiments, the tensile strength of the shell 211 at a temperature of 25° C. is Rm, and Rm and R1 satisfy: 250 MPa≤Rm≤2000 MPa, 2.5 mm≤R1≤20 mm.

[0427] The tensile strength can be understood as the maximum stress value that a material can withstand before breaking. The test method for the tensile strength Rm of the housing 211 of the embodiment of the present application at a temperature of 25°C can be selected according to the actual application. For example, ISO 6892-2:2018 can be used to test the tensile strength Rm at a room temperature of 25°C.

[0428] For example, Rm=250MPa, 300MPa, 350MPa, 400MPa, 450MPa, 500MPa, 550MPa,600MPa, 650MPa, 700MPa, 750MPa, 800MPa, 850MPa, 900MPa, 950MPa, 1000MPa, 1100Mpa, 1200MPa, 1300MPa, 1400MPa, 1500MPa, 1600MPa, 1700MPa, 1800MPa, 1900MPa, 2000MPa.

[0429] In this embodiment, by setting 250MPa≤Rm≤1000MPa and 2.5mm≤R1≤20mm, the force on the mold can be reduced as much as possible during the manufacturing process of the shell 211 without affecting the strength of the shell 211, so that the size or surface of the shell 211 is not affected.

[0430] In some embodiments, Rm and R1 satisfy: 280MPa≤Rm≤800MPa, 4mm≤R1≤15mm.

[0431] For example, Rm=280MPa, 310MPa, 340MPa, 370MPa, 390MPa, 430MPa, 470MPa, 510MPa, 540MPa, 580MPa, 610MPa, 630MPa, 660MPa, 690MPa, 720MPa, 740MPa, 780MPa, 800MPa.

[0432] In other embodiments, Rm and R1 satisfy: 380MPa≤Rm≤600MPa, 5mm≤R1≤10mm.

[0433] For example, Rm=380MPa, 390MPa, 410MPa,440MPa, 480MPa, 520MPa, 535MPa,570MPa, 596MPa, 600MPa.

[0434] In some embodiments, the maximum wall thicknesses of at least two second housing walls 32 of the housing 211 are equal.

[0435] Further optionally, the wall thickness of each of the at least two second shell walls 32 of the shell 211 is uniform, and the wall thickness of the at least two second shell walls 32 are equal.

[0436] In this embodiment, by setting the wall thickness of at least two second shell walls 32 to be equal, on the one hand, the processing difficulty of the shell 211 can be reduced, and on the other hand, at least two second shell walls 32 can also be set to the minimum processing wall thickness, which helps to fully improve the space utilization of the shell 211.

[0437] In some other embodiments, a transition region 33 is provided between any two adjacent second shell walls 32 of the at least two second shell walls 32 , and the maximum thicknesses of the at least two transition regions 33 corresponding to the at least two second shell walls 32 are equal.

[0438] In this embodiment, by setting the maximum thickness of at least two transition areas 33 between at least two second shell walls 32 of the shell 211 to be equal, it is helpful to prepare the shell 211 into a symmetrical structure, which is easy to process, and there is no need to worry about reverse installation when assembling the shell 211 and the cover plate 212, which has an anti-foolproof function.

[0439] Fig.15 Another cross-sectional view of the housing 211 of the embodiment of the present application is shown; Fig.16 for Fig.15 A partial enlarged schematic diagram of part B in FIG. Fig.16 As shown, the first housing wall 31 and the second housing wall 32 are connected via a second fillet 34. Fig.16 As shown, the inner diameter of the second fillet 34 is r1, and the minimum thickness of the second shell wall 32 with the smallest thickness among the at least two second shell walls 32 is T2, wherein the inner diameter r1 of the second fillet 34 and the minimum thickness T2 of the second shell wall 32 with the smallest thickness among the at least two second shell walls 32 satisfy: 2.0≤r1 / T2≤30.

[0440] It should be understood that the first shell wall 31 is connected to at least two second shell walls 32. Optionally, any second shell wall 32 is connected to the first shell wall 31 through the following Fig.15 The second fillet 34 shown is connected. In addition, the second fillet 34 here is connected to Fig.13 The first fillet 331 in the embodiment is implemented similarly, 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.

[0441] It should be noted that, if each second shell wall 32 is a wall with uniform thickness, the minimum thickness T2 of the second shell wall 32 may refer to the thickness of the thinnest second shell wall 32 among at least two second shell walls 32. If the thickness of each second shell wall 32 is uneven, the minimum thickness T2 of the second shell wall 32 may refer to the thickness of the thinnest region among all the second shell walls 32.

[0442] It should also be noted that if a second shell wall 32 includes a functional area, the minimum thickness of the second shell wall 32 actually refers to the minimum thickness of the area of ​​the second shell 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 the electrode terminals are located, a liquid injection area, and a welding area.

[0443] In this embodiment, by setting the ratio of the inner diameter r1 of the second fillet 34 between the first shell wall 31 and the second shell wall 32 to the minimum thickness T2 of the second shell wall 32 with the smallest thickness between [2.0, 30], it helps to balance the processing difficulty of the shell 211 with the space capacity and strength of the battery cell 20.

[0444] In some embodiments, the inner diameter r1 of the second fillet 34 and the minimum thickness T2 of the second shell wall 32 with the smallest thickness among the at least two second shell 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.

[0445] 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.

[0446] In this embodiment, by setting the inner diameter r1 of the second fillet 34 within [0.8mm, 1.5mm], on the one hand, the difficulty of manufacturing the shell 211 will not be increased due to r1 being too small, and on the other hand, the interference between the electrode assembly 22 and the second fillet 34 will not be reduced due to r1 being too large, that is, there is no need to lower the height of the electrode assembly 22 and sacrifice the capacity of the electrode assembly 22 to meet the assembly of the shell 211 and the electrode assembly 22. In addition, if r1 is too large, the shell 211 is also prone to deformation.

[0447] Fig.17 Shows Fig.16 Another partial enlarged schematic diagram of part B in FIG. Fig.17 As shown, the outer diameter of the second fillet 34 is r2, wherein r2 satisfies: 1mm≤r2≤2.5mm. For example, r2=1.0mm, 1.1mm, 1.2mm, 1.3mm, 1.4mm, 1.5mm, 1.6mm, 1.7mm, 1.8mm, 1.9mm, 2.0mm, 2.1mm, 2.2mm, 2.3mm, 2.4mm, 2.5mm.

[0448] Similar to the definition of the inner diameter r1 of the second fillet 34 , the outer diameter r2 of the second fillet 34 can be understood as the radius of the circle where the outer arc of the second fillet 34 is located.

[0449] In this embodiment, by setting the outer diameter r2 of the second fillet 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 r2 being too small, thereby causing insulation failure; on the other hand, r2 will not be too large, causing the thickness of the second fillet 34 to be too thin to affect the strength of the shell 211.

[0450] 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.

[0451] In this embodiment, by setting the ratio between the depth H of the housing 211 and the minimum thickness T2 of the second housing wall 32 with the smallest thickness between [300, 800], both the volume utilization and the strength of the battery cell 20 can be taken into consideration.

[0452] like Fig.17 As shown, the maximum thickness of the second fillet 34 is T3, wherein 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.

[0453] The thickness of the second fillet 34 may be uniform or non-uniform. The maximum thickness T3 of the second fillet 34 will be defined below by taking the uniform thickness of the second fillet 34 as an example. In some embodiments, the maximum thickness T3 of the second fillet 34 may be defined as the length of the extension line of the line between the center of the circle where the inner arc is located and the center of the circle where the outer arc is located in any cross section in the direction perpendicular to the axis of the inner surface and the outer surface at the second fillet 34.

[0454] In this embodiment, by setting the ratio between the maximum thickness T3 of the second fillet 34 and the minimum thickness T2 of the second shell wall 32 with the smallest thickness at [0.8, 2], a balance can be achieved between the strength and manufacturability of the shell 211. That is, the shell 211 will not be insufficient in strength due to excessive thinning of the second fillet 34, nor will the shell 211 be difficult to manufacture due to excessive thinning of the second fillet 34.

[0455] In some embodiments, the wall thickness of the shell 211 is uniform, that is, all walls of the shell 211 have the same wall thickness.

[0456] In this embodiment, by setting the wall thickness of the shell 211 to be uniform, on the one hand, the processing difficulty of the shell 211 can be reduced, and on the other hand, each wall of the shell 211 can be set to the minimum processing wall thickness, which helps to fully improve the space utilization of the shell 211.

[0457] In some embodiments, the battery cell 20 further includes a cover plate 212 for covering the opening 301 of the shell 211 to enclose the electrode assembly 22 in the cavity of the shell 211 .

[0458] In this embodiment, by setting the inner diameter R1 of the first fillet between the depth H of the shell and the second shell wall to satisfy 2.5mm≤R1≤20mm, 50mm≤H≤250mm, the risk of cracking of the shell caused by stress during the one-piece molding process can be reduced as much as possible without affecting the energy density of the battery cell, thereby reducing the difficulty of molding the shell.

[0459] In some embodiments, the battery cell 20 is roughly rectangular, for example, the battery cell 20 is a rectangular battery cell. For another example, the battery cell 20 is a track-shaped battery cell, and the thickness of the battery cell 20 is D1, wherein H, R1 and D1 satisfy: 0.15mm≤R1*D1 / H≤36mm.

[0460] 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.

[0461] In some embodiments, D2 may be a dimension of the battery cell 20 in an expansion direction of the electrode assembly 22 .

[0462] In this embodiment, by setting 0.15mm≤R1*D1 / H≤36mm, the risk of easy accumulation of materials during the molding process of the shell 211 due to the small value of R1*D1 / H, which may cause the shell 211 to be subjected to excessive force and crack, can be reduced, and the impact of the excessively large value of R1*D1 / H on the energy density of the battery cell 20 can be reduced.

[0463] In this embodiment, D1 satisfies: 15mm≤D1≤90mm. For example, D1=15mm, 20mm, 25mm, 30mm, 35mm, 40mm, 45mm, 50mm, 55mm, 60mm, 65mm, 70mm, 75mm, 80mm, 85mm, 90mm.

[0464] In this embodiment, H and R1 satisfy: 50 mm ≤ H ≤ 250 mm, 2.5 mm ≤ R1 ≤ 20 mm.

[0465] In some embodiments, H, R1, and D1 satisfy: 0.34 mm ≤ R1*D1 / H ≤ 18 mm.

[0466] In this embodiment, by setting 0.34 mm ≤ R1 * D1 / H ≤ 18 mm, a balance can be achieved between the molding difficulty of the shell 211 and the energy density.

[0467] For example, R1*D1 / H=0.34, 0.5, 1, 3, 5, 8, 11, 13, 16, 18.

[0468] Similarly, in this embodiment, D1 satisfies: 15 mm ≤ D1 ≤ 90 mm.

[0469] In this embodiment, H and R1 satisfy: 75 mm ≤ H ≤ 180 mm, 4 mm ≤ R1 ≤ 15 mm.

[0470] In some embodiments, H, R1, and D1 satisfy: 0.9 mm ≤ R*D / H ≤ 6.6 mm.

[0471] 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.

[0472] In this embodiment, D1 satisfies: 25mm≤D1≤60mm. For example, D1=25mm, 28mm, 31mm, 34mm, 37mm, 39mm, 41mm, 43mm, 46mm, 49mm, 51mm, 54mm, 58mm, 50mm.

[0473] And in this embodiment, H and R1 satisfy: 90mm≤H≤140mm, 3mm≤R≤10mm.

[0474] It should be noted that the value range of R1, the value range of H, the value range of D1 and the value range of R1*D1 / H can be related to each other. For example, when 15mm≤D1≤90mm, 50mm≤H≤250mm, and 2.5mm≤R1≤20mm, 0.15mm≤R1*D1 / H≤36mm. For another example, when 15mm≤D1≤90mm, 75mm≤H≤180mm, and 4mm≤R1≤15mm, 0.34mm≤R*D / H≤18mm. For another example, when 25mm≤D1≤60mm, 90mm≤H≤140mm, and 3mm≤R1≤10mm, 0.9mm≤R1*D1 / H≤6.6mm.

[0475] In some embodiments, the thickness of the electrode assembly 22 is D2, and R1 and D2 satisfy: 0.125≤R1 / D2≤0.45.

[0476] 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.

[0477] Alternatively, D2 may be the dimension of the electrode assembly 22 in the expansion direction.

[0478] In this embodiment, by setting 0.125≤R1 / D2≤0.45, on the one hand, R1 will not interfere with the electrode assembly 22 or the residual space inside the battery cell 20 will not be insufficient due to R1 being too large, thereby affecting the performance of the battery cell 20; on the other hand, R1 will not be too small, resulting in difficulty in molding the shell 211.

[0479] Fig.18 An exploded schematic diagram of the housing 211 of the embodiment of the present application is shown. Fig.19 A structural schematic diagram of the second shell portion 42 of an embodiment of the present application is shown. Fig. 20 Another structural schematic diagram of the second shell portion 42 of an embodiment of the present application is shown. Fig.21 Another exploded schematic diagram of the housing 211 of the embodiment of the present application is shown. It should be noted that the housing 211 can be applied to the battery cell 20. For example, Figures 18 to 21 The housing 211 shown can be applied to Figure 3 and Figure 4 In the battery cell 20 shown, the housing 211 may only include Figure 4 The housing 211 shown may also include Figure 4 The housing 211 shown also includes Figure 4In addition, the housing 211 may also be placed as follows: Figure 3 or Figure 4 shown.

[0480] like Fig.18 As shown, the housing 211 includes a first housing portion 41, which is formed with a first opening portion 401. The first housing portion 41 includes a first wall 411 opposite to the first opening portion 401 and a second wall 412 connected to the first wall 411, and the first wall 411 and the second wall 412 are integrally formed; the second housing portion 42 is fixedly connected to the second wall 412. In the depth direction of the first housing portion 41, at least part of the housing 211 is formed by the first housing portion 41 and the second housing portion 42. For ease of explanation, the depth direction of the first housing portion 41 is taken as an example below as the height direction Z of the battery cell 20.

[0481] It should be explained that the first wall 411 and the second wall 412 in the first shell portion 41 are an integrally formed structure, which may mean that the first shell portion 41 is made by an integral deep drawing process. For example, the first shell part 41 can be prepared by the following steps: Step 1, select steel suitable for deep drawing; Step 2, prepare a suitable stamping die according to the shell 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 clamp; Step 3, fix the steel between the fixture and the die to ensure that the steel remains stable during the deep drawing process; Step 4, move the punch downward into the die to apply tensile stress to the steel to deform it and fill the shape of the die; Step 5, control the speed and pressure of the punch to ensure that the steel is uniformly deformed during the deep drawing process, so that it is drawn to a certain depth and obtains the desired shape; Step 6, as needed, perform auxiliary operations such as perforation, trimming, and marking during the deep drawing process; Step 7, after completing the deep drawing, remove the product from the die and perform necessary treatments such as cleaning and deburring, so as to obtain the first shell part 41.

[0482] Since the first housing portion 41 is formed by deep drawing as an integral body, it generally has a first opening portion 401. The first opening portion 401 may be circular, polygonal or track-shaped. The polygonal shape may be, for example, a square, a pentagon, a hexagon or other irregular shapes.

[0483] The first shell portion 41 is a hollow structure formed by a first wall 411 and a second wall 412 that are opposite to the first opening portion 401, wherein the second wall 412 is arranged to intersect with the first wall 411. For example, the first wall 411 and the second wall 412 are arranged vertically. In some embodiments, the first shell portion 41 includes a second wall 412, which is connected end to end and together with the first wall 411, encloses a cylindrical hollow structure. In other embodiments, the first shell portion 41 includes four second walls 412, which are arranged opposite to each other in pairs, and two adjacent second walls 412 intersect vertically, so that the four second walls 412 and the first wall 411 together enclose a square columnar hollow structure.

[0484] Since the first wall 411 is arranged opposite to the first opening portion 401 of the first shell portion 41, the depth direction Z of the first shell portion 41 can be understood as a direction perpendicular to the first wall 411, and the distance from the first opening portion 401 to the first wall 411 of the first shell portion 41 is the depth of the first shell portion 41.

[0485] In the embodiment of the present application, the second housing portion 42 is fixedly connected to the second wall 412, and the second housing portion 42 is not a flat plate structure and the second housing portion 42 is embedded in the first opening portion 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 includes at least Fig.19 The second opening portion 402 of the second housing portion 42 is arranged opposite to the first opening portion 401 of the first housing portion 41, and the second wall 412 is fixedly connected to the third wall 421, so that in the depth direction Z of the first housing portion 41, the second wall 412 and the third wall 421 together form at least a partial area of ​​the housing 211, that is, the depth H of the housing 211 is at least greater than the depth of the first housing portion 41. The depth H of the housing 211 can be understood as the size of the housing 211 along the depth direction of the first housing portion 41. Generally, the wall of the housing 211 has a certain thickness, but here, the wall thickness of the housing 211 can be ignored.

[0486] In this embodiment, the housing 211 includes a first housing portion 41 and a second housing portion 42, wherein the first housing portion 41 has a first opening portion 401, and includes a first wall 411 opposite to the first opening portion 401 and a second wall 412 connected to the first wall 411, the first wall 411 and the second wall 412 are integrally formed, and in the depth direction Z of the first housing portion 41, at least a portion of the housing 211 is formed by the first housing portion 41 and the second housing portion 42. The housing 211 prepared in this way can reduce the risk of cracking of the housing 211 during the integral deep drawing process, compared with the technical solution of directly integrally forming the housing 211.

[0487] In some embodiments, the size of the second wall 412 is equal everywhere in the depth direction Z of the first housing portion 41. Similarly, the size of the third wall 421 is equal everywhere in the depth direction Z of the first housing portion 41. Then, in the depth direction Z of the first housing portion 41, the entire area of ​​the housing 211 is formed by the first housing portion 41 and the second housing portion 42.

[0488] In other embodiments, in the depth direction Z of the first housing portion 41, the sizes of the second wall 412 are not completely equal. For example, the second wall 412 after unfolding may be semicircular or triangular. Similarly, in the depth direction Z of the first housing portion 41, the sizes of the third wall 421 are not completely equal. For example, the third wall 421 after unfolding may be semicircular or triangular. Then, in the depth direction Z of the first housing portion 41, a partial area of ​​the housing 211 may be formed by the first housing portion 41 and the second housing portion 42.

[0489] In one embodiment, the first shell portion 41 and the second shell portion 42 are fixedly connected by welding. Thus, compared with a shell formed by welding a flat plate structure and a tubular structure with an opening, the shell 211 prepared by the method of the embodiment of the present application has a weld that is not at a right-angle edge, and the shell 211 is not prone to cracking and damage.

[0490] Optionally, in the depth direction Z of the first housing portion 41, the second housing portion 42 has two openings that are connected. For example, the second housing portion 42 includes: Fig.19 The second opening portion 402 and the third opening portion 403 are shown, and the second opening portion 402 and the third opening portion 403 are arranged opposite to each other in the depth direction Z along the first shell portion 41 .

[0491] In this embodiment, by setting the second shell portion 42 to have two connected openings in the depth direction Z of the first shell portion 41, the cover plate and the shell 211 can be set independently, so that components such as electrode terminals can be better set on the cover plate, making the preparation of the shell 211 simpler.

[0492] In other embodiments, the second housing portion 42 may have only one opening. For example, the second housing portion 42 is similar to the first housing portion 41 and is also prepared by an integral deep drawing process, wherein the second housing portion 42 includes, in addition to the third wall 421, a wall intersecting the third wall 421 and opposite to the opening of the second housing portion 42, such as a cover plate.

[0493] In one embodiment, the second housing portion 42 is an integrally formed structure.

[0494] In this embodiment, by configuring the second shell portion 42 as an integrally formed structure, the welds of the shell 211 can be reduced, so that the reliability of the shell 211 is high and the risk of deformation, cracking and damage of the shell 211 is not easily incurred.

[0495] In another embodiment, when the second shell portion 42 has only one opening, the second shell portion 42 may be formed by butt-welding at least two parts.

[0496] It should be noted that when the second housing portion 42 is formed by welding at least two parts, the weld of the second housing portion 42 should not be on the edge, that is, the so-called right angle edge. Fig. 20 As shown, the second housing portion 42 includes four third walls 421, including a fourth wall 4211, a fifth wall 4212, a sixth wall 4213 and a seventh wall 4214. The fourth wall 4211 and the fifth wall 4212 are arranged opposite to each other, the sixth wall 4213 and the seventh wall 4214 are arranged opposite to each other, and the sixth wall 4213 includes a first sub-wall 4213a and a second sub-wall 4213b, the first sub-wall 4213a and the second sub-wall 4213b are symmetrical with respect to the first center line 4251, and the seventh wall 4214 includes a third sub-wall 4214a and a fourth sub-wall 4214b, the third sub-wall 4214a and the fourth sub-wall 4214b are symmetrical with respect to the second center line 4261. The second housing portion 42 is formed by welding the first part 423 and the second part 424. Among them, the first part 423 includes the first sub-wall 4213a, the fourth wall 4211 and the third sub-wall 4214a, the second part 424 includes the second sub-wall 4213b, the fifth wall 4212 and the fourth sub-wall 4214b, and the first center line 4251 and the second center line 4261 are the welds of the second shell part 42.

[0497] In this embodiment, the second shell portion 42 is configured to be formed by welding at least two parts, which is easy to process and has a more controllable size, thereby improving the assembly accuracy of the shell 211 .

[0498] In some embodiments, the surface 4121 of the second wall 412 facing away from the first wall 411 is welded to the second housing portion 42, and the wall thickness of the housing 211 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.

[0499] In other words, the depth of the housing 211 is equal to the sum of the depth of the first housing portion 41 and the depth of the second housing portion 42 .

[0500] In this embodiment, the surface 4121 of the second wall 412 facing away from the first wall 411 is welded to the second shell portion 42 , so that the space utilization rate of the shell 211 can be improved.

[0501] In other embodiments, a surface of the second wall 412 perpendicular to the thickness direction of the second wall 412 is welded to the second housing portion 42. Fig.21 As shown, the inner surface 4122 of the second wall 412 and the second housing portion 42 are welded to the outer surface 4215 of the third wall 421 of the second housing portion 42 at the first opening 401 of the first housing portion 41 .

[0502] In this embodiment, by welding the surface of the second wall 412 perpendicular to the thickness direction of the second wall 412 to the second shell portion 42, it is beneficial to increase the welding area of ​​the first shell portion 41 and the second shell portion 42, thereby improving the welding strength therebetween.

[0503] Fig. 22 FIG. 2 shows a schematic cross-sectional view of the housing 211 of an embodiment of the present application. Fig. 22 As shown, in the depth direction Z of the first shell portion 41 , the maximum dimension of the first shell portion 41 is h1 , and the maximum dimension of the shell 211 is H, wherein H and h1 satisfy: 3≤H / h1≤80.

[0504] It should be explained that, without considering the wall thickness, the size of the first housing portion 41 may be uneven in the depth direction Z of the first housing portion 41, and the maximum size 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, the size of the housing 211 may be uneven in the depth direction Z of the first housing portion 41, and the maximum size H of the housing 211 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.

[0505] In some embodiments, in the depth direction Z of the first housing portion 41 , the size of the first housing portion 41 is uniform and the size of the housing 211 is also uniform.

[0506] For example, H / h1=3, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70,75, 80.

[0507] In this embodiment, the ratio of H to h1 is set in the range of [3, 80]. This will neither cause the welding position of the first shell part 41 and the second shell part 42 to be too close to the first shell part 41 due to the ratio being too large, causing the weld to be subjected to excessive stress and easy to crack during the use of the battery cell; nor will it cause the shell 211 to be subjected to excessive stress and crack during the drawing process due to the ratio being too small, thereby making the first shell part 41 difficult to manufacture.

[0508] 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.

[0509] In some embodiments, h1 satisfies: 3mm≤h1≤50mm.

[0510] For example, h1=3mm, 5mm, 10mm, 15mm, 20mm, 25mm, 30mm, 35mm, 40mm, 45mm,50mm.

[0511] In this embodiment, by setting h1 within the range of [3mm, 50mm], the weld will not be too close to the first shell portion 41 due to h1 being too small, which will cause the battery cell to crack during the charging and discharging process; nor will h1 be too large, which will cause the first shell portion 41 to crack during the integrated drawing process, making the manufacturing of the first shell portion 41 difficult.

[0512] Further optionally, h1 satisfies: 5mm≤h1≤30mm.

[0513] It should be noted that, when h1 satisfies the above conditions, H may satisfy: H is greater than or equal to 100 mm. For example, H is equal to 400 mm.

[0514] In some embodiments, the yield strength of the shell 211 at a temperature of 25° C. is Re, and Re satisfies: 125 MPa≤Re≤1000 MPa.

[0515] Yield strength can be understood as the critical stress value of material yield. Generally, after a 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 shell 211 of the embodiment of the present application at a temperature of 25°C can be selected according to the actual application. For example, GB / T228.1-2010 can be used to test the yield strength Re at a normal temperature of 25°C.

[0516] 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.

[0517] In this embodiment, by using a material with a yield strength Re satisfying 125MPa≤Re≤1000MPa to make the first shell portion, the wall thickness of the first shell portion can be reduced without reducing the strength of the first shell portion, thereby increasing the capacity space of the battery cell.

[0518] Fig.23 A partial structural diagram of the housing 211 of the embodiment of the present application is shown. Fig.23 Can be Fig. 9 A partial enlarged view of the area A' shown in FIG. Fig.23 As shown, the shell 211 of the embodiment of the present application is a multi-layer structure, and the material of the outermost shell 2117 of the shell 211 includes at least one of the following: aluminum, aluminum alloy, copper, copper alloy and chromium.

[0519] It should be understood that the shell 211 of the embodiment of the present application is a multi-layer structure, that is, for any wall of the shell 211, a multi-layer structure is stacked along the thickness direction of the wall, so that the shell 211 is a multi-layer structure. In addition, the installation method between the multi-layer structures of the shell 211 can be flexibly set according to the actual application. For example, a plurality of single-layer shell structures of different sizes but basically the same shape can be first processed, for example, each single-layer shell structure is a hollow structure with an opening; then the shell structures with relatively larger sizes among the multiple single-layer shell structures are sequentially sleeved on the outside of the shell structures with relatively smaller sizes, so that the multiple single-layer shell structures can be combined into a multi-layer shell 211. For another example, it is also possible to first process an approximately plate-like structure with a multi-layer structure; then multiple of the plate-like structures are spliced ​​and combined with each other, and a multi-layer shell 211 can also be formed, but the embodiment of the present application is not limited to this.

[0520] It should be understood that the outermost shell 2117 of the shell 211 of the embodiment of the present application includes the outermost structure of each wall of the shell 211 , that is, the outermost shell 2117 is a shell structure including the outer surface of the shell 211 .

[0521] In the embodiment of the present application, the material of the outermost shell 2117 of the shell 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 shell 2117 contains aluminum, the aluminum will be oxidized into dense aluminum oxide, which can prevent corrosion; when the material of the outermost shell 2117 contains copper, the copper will be oxidized into copper oxide, that is, verdigris, which can prevent corrosion; when the material of the outermost shell 2117 contains chromium, the chromium will be oxidized into chromium oxide, which can also prevent corrosion. Therefore, when the material of the outermost shell 2117 adopts the above-mentioned anti-corrosion material, the outermost shell 2117 can protect other shell layers located inside it, which can not only improve the structural stability of the shell 211, but also improve the service life of the shell 211.

[0522] It should be understood that the specific thickness of the outermost shell 2117 of the embodiment of the present application can also be flexibly set according to the actual application. For example, the thickness of the outermost shell 2117 can be set according to a certain ratio based on the thickness of the shell 211.

[0523] In some embodiments, the average thickness of the outermost shell 2117 is T11, and the average thickness of the shell 211 is T10, and T11 and T10 satisfy: 0.15≤T11 / T10≤0.5. If the ratio T11 / T10 is set too small, due to the limited average thickness T10 of the shell 211, the average thickness T11 of the outermost shell 2117 will be very small, which will increase the difficulty of processing on the one hand, and reduce the anti-corrosion effect of the outermost shell 2117 on the other hand, thereby affecting the structural reliability of the shell 211. On the contrary, if the ratio T11 / T10 is set too large, the average thickness T11 of the outermost shell 2117 will be very large, and the thickness of the other shells of the shell 211 except the outermost shell 2117 will be very small. However, the structural strength of the outermost shell 2117 may be insufficient, especially after it is oxidized, the deformation ability is poor. When the average thickness T11 is large, it will affect the overall structural strength of the shell 211, thereby reducing the stability of the shell 211.

[0524] Furthermore, T11 and T10 satisfy: 0.15≤T11 / T10≤0.4. By appropriately reducing the maximum value of the ratio T11 / T10 and increasing the minimum value of the ratio T11 / T10, the average thickness T11 of the outermost shell 2117 can be limited to be neither too large nor too small, which can improve the anti-corrosion effect and the structural strength and stability of the shell 211.

[0525] Furthermore, T11 and T10 satisfy: 0.2≤T11 / T10≤0.3, so as to better improve the anti-corrosion effect and improve the stability and reliability of the housing 211.

[0526] In some embodiments, the value of the ratio T11 / T10 of the average thickness T11 of the outermost shell 2117 of the embodiment of the present application to the average thickness T10 of the shell 211 can also be set to other values. For example, the value of the ratio T11 / T10 can be any of the following values ​​or between any two of the following values: 0.15, 0.18, 0.2, 0.23, 0.25, 0.28, 0.3, 0.33, 0.35, 0.38, 0.4, 0.43, 0.45, 0.48 and 0.5.

[0527] It should be understood that the value range of the average thickness T10 of the shell 211 of the embodiment of the present application can also be flexibly set according to the actual application. For example, the average thickness T10 of the shell 211 satisfies: 0.05mm≤T10≤0.5mm. The average thickness T10 of the shell 211 should not be too small to reduce the processing difficulty of the multi-layer shell 211 and improve the structural strength of the shell 211. For example, the shell 211 is not easy to break, thereby increasing the service life of the shell 211. On the contrary, the average thickness T10 of the shell 211 should not be too large, so that the shell 211 occupies less space, improves the space utilization of the battery cell 20, and thereby increases the energy density of the battery 10 provided with multiple battery cells 20.

[0528] Furthermore, the average thickness T10 of the shell 211 satisfies: 0.075 mm ≤ T10 ≤ 0.4 mm. Appropriately reducing the average thickness T10 of the shell 211 can reduce the space occupied by the shell 211 inside the battery 10, thereby increasing the energy density of the battery 10; and appropriately increasing the average thickness T10 of the shell 211 can also reduce the difficulty of processing the shell 211.

[0529] Furthermore, the average thickness T10 of the shell 211 satisfies: 0.1 mm ≤ T10 ≤ 0.3 mm. The average thickness T10 of the shell 211 is neither too large nor too small, which can improve the structural strength and stability of the shell 211 and reduce the space occupied by the shell 211 inside the battery 10, thereby improving the energy density of the battery 10.

[0530] In some embodiments, the average thickness T10 of the shell 211 of the embodiment of the present application can also be set to other values. For example, the average thickness T10 of the shell 211 can be any of the following values ​​or between any two of the following values: 0.05mm, 0.075mm, 0.1mm, 0.125mm, 0.15mm, 0.175mm, 0.2mm, 0.225mm, 0.25mm, 0.275mm, 0.3mm, 0.325mm, 0.35mm, 0.375mm, 0.4mm, 0.425mm, 0.45mm, 0.475mm and 0.5mm.

[0531] It should be understood that the value range of the average thickness T11 of the outermost shell 2117 of the embodiment of the present application can also be flexibly set according to the actual application. For example, T11 satisfies: 0.015mm≤T11≤0.25mm. The average thickness T11 of the outermost shell 2117 should not be too small to reduce the difficulty of processing, improve the anti-corrosion effect of the outermost shell 2117, and thus improve the structural reliability of the shell 211. On the contrary, the average thickness T11 of the outermost shell 2117 should not be too large. Considering that the outermost shell 2117 has poor deformation ability after being oxidized, if its average thickness T11 is too large, it will affect the deformation ability of the overall structure of the shell 211, thereby reducing the reliability and stability of the shell 211.

[0532] Furthermore, the average thickness T11 of the outermost shell 2117 can also satisfy: 0.05mm≤T11≤0.2mm. Properly increasing the minimum value of the average thickness T11 of the outermost shell 2117 can improve the anti-corrosion effect of the outermost shell 2117; properly reducing the maximum value of the average thickness T11 of the outermost shell 2117 can improve the deformation capacity of the overall structure of the shell 211, thereby improving the reliability and stability of the shell 211.

[0533] Furthermore, the average thickness T11 of the outermost shell 2117 may also satisfy: 0.075 mm ≤ T11 ≤ 0.15 mm, which can improve the anti-corrosion effect of the outermost shell 2117 and the deformation capacity of the overall structure of the shell 211, thereby improving the reliability and stability of the shell 211.

[0534] In some embodiments, the average thickness T11 of the outermost shell 2117 of the embodiment of the present application can also be set to other values. For example, the average thickness T11 of the outermost shell 2117 can be any one of the following values ​​or between any two of the following values: 0.015mm, 0.02mm, 0.025mm, 0.03mm, 0.035mm, 0.04mm, 0.045mm, 0.05mm, 0.055mm, 0.06mm, 0.065mm, 0.07mm, 0.075mm, 0.08mm, 0.085mm, 0.09mm, 0.095mm, 0.1mm, 0.11mm, 0.12mm, 0.13mm, 0.14mm, 0.15mm, 0.16mm, 0.17mm, 0.18mm, 0.19mm, 0.2mm, 0.21mm, 0.22mm, 0.23mm, 0.24mm and 0.25mm.

[0535] It should be understood that the thickness of the inner shell 2118 of the shell 211 of the embodiment of the present application can also be flexibly set according to the actual application, wherein the inner shell 2118 is any shell layer of the shell 211 except the outermost shell 2117. In addition, the shell 211 may include one or more layers of the inner shell 2118. When the shell 211 includes multiple layers of the inner shell 2118, the thickness of the multiple layers of the inner shell 2118 may be the same for easy processing, or may be different to flexibly adjust the thickness of the inner shell 2118 at different positions according to the actual application. For example, Fig.23 As shown, here, the shell 211 includes a three-layer shell structure as an example, the three-layer shell structure includes an outermost shell 2117 located at the outermost side and two inner shells 2118 located inside, and the two inner shells 2118 include an innermost shell 2118b and an intermediate shell 2118a. The average thickness of the innermost shell 2118b and the average thickness of the intermediate shell 2118a can be the same or different. For example, the average thickness of the innermost shell 2118b and the average thickness of the intermediate shell 2118a can be set to T12, and the value of T12 can be set according to the application. For example, T12 can be greater than, equal to, or less than T11, and the embodiment of the present application is not limited thereto.

[0536] It should be understood that the average thickness T10 of the shell 211 of the embodiment of the present application may refer to the average thickness of at least a part of the area of ​​the shell 211. The average thickness T11 of the outermost shell 2117 of the shell 211 may also refer to the average thickness of at least a part of the area of ​​the outermost shell 2117. The average thickness T12 of the inner shell 2118 of the shell 211 may also refer to the average thickness of at least a part of the area of ​​the inner shell 2118. In addition, the calculation area of ​​the average thickness T10 of the shell 211 is usually consistent with the calculation area of ​​the average thickness T11 of the outermost shell 2117, and is also consistent with the calculation area of ​​the average thickness T12 of the inner shell 2118. For example, if part of the area is excluded from the calculation of the average thickness T10 of the shell 211, then correspondingly, the calculation of the average thickness T11 of the outermost shell 2117 also needs to exclude the same area from the calculation, and the calculation of the average thickness T12 of the inner shell 2118 also needs to exclude the same area from the calculation. For ease of explanation, the following description is made by taking the calculation of the average thickness T10 of the shell 211 as an example, but the relevant description is also applicable to determining the average thickness T11 of the outermost shell 2117 and the average thickness T12 of the inner shell 2118, which will not be repeated here.

[0537] For example, the average thickness T10 of the shell 211 may refer to the average thickness T10 of the entire area of ​​the shell 211, especially when the overall surface of the shell 211 is relatively flat, that is, the thicknesses of most areas of the shell 211 are basically equal or have a small difference, or the thicknesses of all areas of the shell 211 are basically equal or have a small difference, then the average thickness of the entire area of ​​the shell 211 can be determined to be T10.

[0538] For another example, the average thickness T10 of the shell 211 may also refer to the average thickness T10 of a local area of ​​the shell 211, that is, the average thickness T10 of the remaining area after excluding the partial area of ​​the shell 211. For example, if there are some special areas in the shell 211, and the thickness of the special areas is greatly different from that of other areas, for example, there are convex structures or concave areas in the thickness direction of the special areas, so that the thickness of the special areas is larger or smaller than that of other areas, then the special areas can be excluded to calculate the average thickness of the remaining areas of the shell 211 as T10.

[0539] In some embodiments, the shell 211 may include a functional area, and the average thickness T10 of the shell 211 is the average thickness of the area of ​​the shell 211 other than the functional area. For example, the functional area includes at least one of the following areas: a pressure relief area, an area where the electrode terminal 214 is located, a liquid injection area, and a welding area. The thickness of the functional area is generally different from the thickness of other areas of the shell 211. Therefore, when the average thickness T10 of the shell 211 is calculated without including the functional area, the design of the shell 211 can be made to better meet the strength requirements, so as to improve the structural strength and stability of the battery cell 20.

[0540] It should be understood that the functional area of ​​the embodiment of the present application may include an area on the shell 211 that is provided with a specific structure or has a specific purpose, and is applicable to the "functional area" described above. For the sake of brevity, it will not be repeated here one by one. For example, the functional area may include a pressure relief area, which is used to set a pressure relief mechanism. The pressure relief mechanism of the embodiment of the present application can be set on any wall of the battery cell 20, for example, the pressure relief mechanism can be set in the pressure relief area of ​​the shell 211 of the battery cell 20. The pressure relief mechanism can be a part of the shell 211; or, it can also be a separate structure with the shell 211, and fixed to the shell 211 by, for example, welding. For example, when the pressure relief mechanism is a part of the shell 211, for example, the pressure relief mechanism can be formed by providing a notch on the shell 211, that is, the shell 211 is provided with a notch in the pressure relief area, and the thickness at the notch is significantly less than the thickness of other areas of the shell 211. Therefore, the average thickness T10 of the shell 211 can not calculate the thickness at the notch. The notch is the weakest position of the pressure relief mechanism. When the battery cell 20 generates too much gas so that the internal pressure increases and reaches a threshold value, or the internal reaction of the battery cell 20 generates heat, causing the internal temperature of the battery cell 20 to increase and reach a threshold value, the pressure relief mechanism can rupture at the notch, causing the inside and outside of the battery elevator 20 to be connected, and the gas pressure and temperature are released outward through the rupture of the pressure relief mechanism, thereby preventing the battery cell 20 from exploding.

[0541] For another example, the pressure relief mechanism may also be a separate structure from the shell 211. The pressure relief mechanism may take the form of an explosion-proof valve, an air valve, a pressure relief valve or a safety valve, and may specifically adopt a pressure-sensitive or temperature-sensitive element or structure. For example, the shell 211 is provided with a through hole at the pressure relief area, and the pressure relief mechanism is mutually installed and fixed with the shell 211 through the through hole. The installed pressure relief mechanism may protrude or be recessed relative to other areas of the shell 211. Therefore, the calculation of the average thickness T10 of the shell 211 may 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 the weak structure provided in the pressure relief mechanism is destroyed, thereby forming an opening or channel for the internal pressure or temperature to be released.

[0542] In some embodiments, the functional area may also include an area where the electrode terminal 214 is located. Each electrode terminal 214 of the embodiment of the present application may be disposed on any wall, and multiple electrode terminals 214 may be disposed on the same wall or on different walls of the battery cell 20. For example, Figure 3 to Figure 4 As shown, it is taken as an example that each battery cell 20 includes two electrode terminals 214 , and the two electrode terminals 214 are located on the same wall. For example, the two electrode terminals 214 may both be located on the cover plate 212 .

[0543] For another example, each battery cell 20 includes two electrode terminals 214, and the two electrode terminals 214 are located on the same wall. Figure 3 to Figure 4 As shown, the two electrode terminals 214 may also be located on any wall of the housing 211, for example, the two electrode terminals 214 may both be located on the wall with the smallest area of ​​the housing 211. When one or more electrode terminals 214 are located in the housing 211, each electrode terminal 214 usually protrudes from other areas of the housing 211, that is, the thickness of the area where the electrode terminal 214 is located is much greater than the thickness of other areas of the housing 211. Therefore, the calculation of the average thickness T10 of the housing 211 may not include the area where all the electrode terminals 214 are located.

[0544] In some embodiments, the functional area may also include an injection area. For example, the injection area of ​​the housing 211 may be provided with an injection hole, through which electrolyte is injected into the housing 211. After the electrolyte injection is completed, the injection hole may be sealed by a seal. Considering that the thickness of the injection area where the seal is located is usually much greater than the thickness of other areas of the housing 211, the average thickness T10 of the housing 211 may not include the injection area.

[0545] In some embodiments, the functional area may also include a welding area. For example, the shell 211 and the cover plate 212 may be fixed by welding, or the shell 211 itself needs to be processed and formed by welding. For example, any two walls of the shell 211 may be welded, or the shell 211 is formed by splicing at least two parts together, then the shell 211 may include a welding area. For example, the shell 211 can be welded by splicing, then the shell 211 may have a weld 2113. Specifically, the shell 211 may include at least two parts, and the at least two parts are connected by welding to form the shell 211, wherein the embodiment of the present application mainly takes the shell 211 as an example including two parts along the height direction Z of the battery cell 20, and there is a weld 2113 between the upper half of the shell and the lower half of the shell; or, different from Figure 4 As shown, other parts of the shell 211 may also be provided with welds 2113, but the embodiment of the present application is not limited thereto. The welding area of ​​the functional area of ​​the embodiment of the present application may also include the weld 2113. Due to the processing technology, the thickness of the welding area is usually greater than the thickness of other areas of the shell 211. Therefore, the calculation of the average thickness T10 of the shell 211 may not include the welding area.

[0546] It should be understood that in order to further improve the structural strength and reliability of the shell 211, the inner shell 2118 of the shell 211 can be set according to the actual application. In some embodiments, the tensile strength of the inner shell 2118 of the shell 211 at 25°C is Rm1, and Rm1 satisfies: 250MPa≤Rm1≤2000MPa. By increasing the tensile strength Rm1 of the inner shell 2118 of the shell 211 at room temperature of 25°C, the overall structural strength and stability of the shell 211 are increased; however, the tensile strength Rm1 of the inner shell 2118 at room temperature should not be too large, so as to reduce the difficulty of selecting the material of the inner shell 2118, thereby reducing the processing difficulty and processing cost of the battery cell 20.

[0547] It should be understood that the value range of the tensile strength Rm1 of the inner shell 2118 at room temperature of 25°C in the embodiment of the present application can be adjusted according to the actual application. For example, the value of the tensile strength Rm1 at room temperature can also satisfy 400MPa≤Rm1≤1200MPa. On the one hand, increasing the tensile strength Rm1 of the inner shell 2118 at room temperature can improve the deformation capacity of the inner shell 2118 to resist the expansion of the electrode assembly 22, so that the inner shell 2118 is not easily damaged, thereby improving the structural stability and service life of the shell 211 and the battery cell 20. On the other hand, controlling the tensile strength Rm1 of the inner shell 2118 at room temperature will not be too large, which can reduce the difficulty of selecting and processing the material of the inner shell 2118, save costs, and facilitate processing.

[0548] Furthermore, the tensile strength Rm1 of the inner shell 2118 at room temperature can be set to meet 450MPa≤Rm1≤800MPa. The tensile strength Rm1 of the inner shell 2118 at room temperature is not too large or too small, which can improve the deformation capacity of the inner shell 2118 to resist the expansion of the electrode assembly 22, and is easy to implement and save costs.

[0549] In some embodiments, the tensile strength Rm1 of the inner shell 2118 of the embodiment of the present application at room temperature can also be set to other values. For example, the value of the tensile strength Rm1 at room temperature can be any of the following values ​​or between any two of the following values: 250MPa, 280MPa, 300MPa, 330MPa, 350MPa, 380MPa, 400MPa, 450MPa, 500MPa, 550MPa, 600MPa, 650MPa, 700MPa, 750MPa, 800MPa, 850MPa, 900MPa, 950MPa, 10 ... The abovementioned values ​​are as follows: 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.

[0550] It should be understood that the tensile strength of the embodiment of the present application refers to the maximum stress value that the material bears before breaking. The test method of the tensile strength Rm1 of the inner shell 2118 of the embodiment of the present application at a temperature of 25°C can be selected according to the actual application. For example, the national standard GB / T 228.1-2010 can be used to test the tensile strength Rm1 at a normal temperature of 25°C.

[0551] The above mainly describes a rectangular battery cell 20 as an example. The following will be described with reference to the accompanying drawings and take a cylindrical battery cell 20 as an example. The cylindrical battery cell 20 of the embodiment of the present application and the rectangular battery cell 20 described above are mutually applicable except for the difference in shape, and will not be repeated here one by one.

[0552] Fig.24 The structure diagram of a battery cell 20 according to an embodiment of the present application is shown, for example, Figure 3 The battery cell 20 shown may be any battery cell 20 in the battery 10 ; Fig.25 A partial exploded structural diagram of a battery cell 20 according to an embodiment of the present application is shown, for example, Fig.25 Can be Fig.24 The schematic diagram of the partial exploded structure of the battery cell 20 is shown. Fig.26 A schematic cross-sectional structure diagram of a housing 211 of a battery cell 20 according to an embodiment of the present application is shown. For example, Fig.26 Can be Fig.24 and Fig.25 The illustrated schematic is a sectional view of a housing 211 of a battery cell 20 , wherein the sectional view is a cross section of the housing 211 .

[0553] In the embodiments of the present application, Figure 24 to Figure 26 As shown, the battery cell 20 includes: an electrode assembly 22, the electrode assembly 22 includes a first pole ear 2221; a first electrode terminal 214a; a shell 211, the shell 211 includes a barrel 211b and a cover 211a connected to the barrel 211b, the barrel 211b is arranged around the periphery of the electrode assembly 22, the cover 211a includes the first electrode terminal 214a, the first pole ear 2221 is electrically connected to the first electrode terminal 214a through the barrel 211b, and the shell 211 is a multi-layer structure with different resistivities.

[0554] The housing 211 may be in various shapes, such as a cylinder, a cuboid, or other polyhedrons. Figure 24 to Figure 26 As shown, the shell 211 is described as a hollow cylindrical structure. In addition, the embodiment of the present application mainly takes the shell 211 as a hollow structure with an opening at one end as an example, and the corresponding cover plate 212 is a circular plate structure adapted to the shell 211. For the cylindrical shell 211, correspondingly, the barrel 211b is a cylinder, and the cover 211a is a circular plate structure.

[0555] The electrode assembly 22 of the embodiment of the present application may include a first pole ear 2221, which can be electrically connected to the first electrode terminal 214a through the barrel 211b of the shell 211, which can simplify the structure of the battery cell 20; the shell 211 is set to a multi-layer structure with different resistivities, and the current carrying capacity of the battery cell 20 can be improved by a layer of structure with lower resistivity, and the structural strength of the shell 211 can be improved by a layer of structure with higher resistivity, which can improve the performance of the battery cell 20, and improve the structural strength of the battery cell 20, thereby increasing the service life of the battery cell 20.

[0556] In the embodiment of the present application, the electrode assembly 22 further includes a second pole ear 2222, and the second pole ear 2222 has opposite polarity to the first pole ear 2221. Specifically, from the appearance of the electrode assembly 22, the electrode assembly 22 includes an electrode body 221 and a pole ear 222, and the pole ear 222 includes a first pole ear 2221 and a second pole ear 2222, and the first pole ear 2221 and the second pole ear 2222 protrude from the electrode body 221. The first pole ear 2221 is a portion of the first pole piece that is not coated with an active material layer, and the second pole ear 2222 is a portion of the second pole piece that is not coated with an active material layer. The first pole ear 2221 and the second pole ear 2222 are used to draw out the current in the electrode body 221.

[0557] The first pole lug 2221 and the second pole lug 2222 may extend from the same side of the electrode body 221, that is, the first pole lug 2221 and the second pole lug are located at the same end surface of the electrode assembly 22. Alternatively, the first pole lug 2221 and the second pole lug 2222 may extend from different sides of the electrode body 221, that is, the first pole lug 2221 and the second pole lug are located at different end surfaces of the electrode assembly 22. For example, the first pole lug 2221 and the second pole lug 2222 may also extend from opposite sides, that is, the first pole lug 2221 and the second pole lug 2222 are located at opposite end surfaces of the electrode assembly 22, for ease of processing. Figure 24 to Figure 26 As shown, the first pole tab 2221 and the second pole tab 2222 may be respectively disposed on both sides of the electrode body 221 along the first direction Z. In other words, the first pole tab 2221 and the second pole tab 2222 are respectively disposed at both ends of the electrode assembly 22 along the first direction Z. The first direction Z may be a height direction Z of the electrode assembly 22.

[0558] It should be understood that the electrode assembly 22 includes a first electrode sheet, a second electrode sheet and a separator, and the separator is used to separate the first electrode sheet from the second electrode sheet. The polarity of the first electrode sheet and the second electrode sheet are opposite, in other words, one of the first electrode sheet and the second electrode sheet is a positive electrode sheet 223, and the other of the first electrode sheet and the second electrode sheet is a negative electrode sheet 224.

[0559] The first pole piece, the second pole piece and the separator are all strip-shaped structures, and the first pole piece, the second pole piece and the separator are wound together to form a wound structure. The wound structure can be a cylindrical structure, a flat structure or a structure of other shapes.

[0560] Optionally, the first pole ear 2221 is wound around the central axis of the electrode assembly 22 for multiple turns, and the first pole ear 2221 includes multiple turns of pole ear layers. After the winding is completed, the first pole ear 2221 is generally cylindrical, and a gap is left between two adjacent turns of pole ear layers. The embodiment of the present application can process the first pole ear 2221 to reduce the gap between the pole ear layers, so as to facilitate the connection of the first pole ear 2221 with other conductive structures. For example, the embodiment of the present application can flatten the first pole ear 2221 so that the end area of ​​the first pole ear 2221 away from the electrode main body 221 is gathered and gathered together; the flattening process forms a dense end face at one end of the first pole ear 2221 away from the electrode main body 221, reduces the gap between the pole ear layers, and facilitates the connection of the first pole ear 2221 with other conductive structures. Alternatively, the embodiment of the present application can also fill the conductive material between two adjacent turns of pole ear layers to reduce the gap between the pole ear layers.

[0561] Optionally, the second pole tab 2222 is wound multiple times around the central axis of the electrode assembly 22, 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.

[0562] In the embodiment of the present application, the battery cell 20 also includes: a second electrode terminal 214b, which is electrically connected to the second electrode tab 2222, and the first electrode terminal 214a and the second electrode terminal 214b are located on the same wall of the battery cell 20 to improve the integration of the battery cell 20, improve the space utilization of the battery cell 20 in the battery 10, and facilitate processing and assembly.

[0563] It should be understood that the cover 211 a of the embodiment of the present application includes the first electrode terminal 214 a . For example, the first electrode terminal 214 a may be disposed on the cover 211 a , or the cover 211 a may directly serve as the first electrode terminal 214 a .

[0564] 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 on 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 housing 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 a plurality of battery cells 20 are assembled into a group, the housing 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.

[0565] For the convenience of description, the following mainly takes the cover body 211 a as the first electrode terminal 214 a as an example, but the embodiments of the present application are not limited thereto.

[0566] Fig. 27 A schematic cross-sectional view of a partial structure of a battery 10 provided in some embodiments of the present application, wherein the battery 10 may include a plurality of battery cells 20; Fig.28 A schematic cross-sectional view of another partial structure of a battery 10 provided in some embodiments of the present application, for example, Fig.28 Can be Fig. 27 The battery 10 is shown in an enlarged schematic diagram at area B'.

[0567] like Figure 24 to Figure 28As shown, the cover body 211a is provided with an electrode lead-out hole 211c, and at least a portion of the cover body 211a is used to electrically connect the first connecting member 81 and the first pole ear 2221 of the battery 10; the second electrode terminal 214b is used to electrically connect the second connecting member 82 and the second pole ear 2222 of the battery 10, and the second electrode terminal 214b is insulated and arranged on the cover body 211a and installed in the electrode lead-out hole 211c, and 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.

[0568] The cover 211 a is electrically connected to the barrel 211 b , and the cover 211 a and the barrel 211 b may have the same polarity.

[0569] It should be understood that the cover 211a and the barrel 211b of the embodiment of the present application can be an integrally formed structure, that is, the shell 211 is an integrally formed component. In this way, the connection process of the cover 211a and the barrel 211b can be omitted. For example, the shell 211 can be formed by a stretching process. Of course, the cover 211a and the barrel 211b can also be two components provided separately, and then connected together by welding, riveting, bonding, etc. The embodiment of the present application mainly takes the cover 211a and the barrel 211b as an example of an integrally formed structure.

[0570] The housing 211 of the embodiment of the present application may be a hollow structure with one end open. Specifically, the barrel 211b has a barrel opening 211d at one end away from the cover 211a. The battery cell 20 further includes a cover plate 212, which covers the barrel opening 211d to close the barrel opening 211d. The cover plate 212 may be of various structures, for example, the cover plate 212 is a plate-like structure.

[0571] In some embodiments, the cover 211a is provided with an electrode lead-out hole 211c, and the area of ​​the cover 211a other than the electrode lead-out hole 211c includes an area for welding with the first connecting member 81, that is, the cover 211a can be welded with the first connecting member 81 to form a first welding portion W1. Exemplarily, during welding, the laser acts on the surface of the first connecting member 81 away from the cover 211a, and the laser melts and connects a portion of the first connecting member 81 and a portion of the cover 211a to form the first welding portion W1.

[0572] The electrode lead-out hole 211c passes through the cover 211a, so as to facilitate the electrical energy in the electrode assembly 22 to be led out of the shell 211. Exemplarily, the electrode lead-out hole 211c passes through the cover 211a along the first direction Z.

[0573] The electrode lead-out hole 211c of the embodiment of the present application is formed after the shell 211 is stretched and formed. For example, the electrode lead-out hole 211c for installing the second electrode terminal 214b is formed on the cover 211a by using the hole-opening process in the present embodiment, so as to set the positive output electrode and the negative output electrode at the end of the battery cell 20 away from the opening of the shell 211; the cover 211a is formed during the molding process of the shell 211, and the flatness can be ensured after the electrode lead-out hole 211c is opened, so as to ensure the connection strength between the cover 211a and the first connecting member 81. At the same time, the flatness of the cover 211a is not constrained by its own size, so the cover 211a can have a larger size, thereby improving the current capacity of the battery cell 20.

[0574] In some embodiments, the barrel 211b is cylindrical, the electrode lead-out hole 211c is a circular hole, and the central axis of the barrel 211b and the central axis of the electrode lead-out hole 211c are arranged to coincide with each other. "Coincidence arrangement" does not require that the central axis of the barrel 211b and the central axis of the electrode lead-out hole 211c absolutely and completely coincide with each other, and there may be deviations allowed by the process.

[0575] 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 cylinder 211b, so that at least part of the second electrode terminal 214b can be located at the center of the cover 211a. In this way, when multiple battery cells 20 are assembled into a group, the position accuracy requirements of the second electrode terminal 214b can be reduced, the assembly process can be simplified, and the assembly efficiency can be improved.

[0576] 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 may pass through the electrode lead-out hole 211 c or may be staggered with the electrode lead-out hole 211 c, which is not limited in this embodiment.

[0577] The first electrode tab 2221 is electrically connected to the cover 211a. The first electrode tab 2221 can be directly electrically connected to the cover 211a, or indirectly electrically connected to the cover 211a through other conductive structures. For example, the first electrode tab 2221 can be electrically connected to the cover 211a through the cylinder 211b.

[0578] The second electrode tab 2222 is electrically connected to the second electrode terminal 214b. The second electrode tab 2222 may be directly electrically connected to the second electrode terminal 214b, or may be indirectly electrically connected to the second electrode terminal 214b through other conductive structures. For example, the second electrode tab 2222 may be electrically connected to the second electrode terminal 214b through the current collecting member 23.

[0579] The second electrode terminal 214 b is insulated from the cover 211 a , so the second electrode terminal 214 b and the cover 211 a may have different polarities, and the second electrode terminal 214 b and the cover 211 a may serve as different output poles.

[0580] The second electrode terminal 214b is fixed to the cover 211a. The second electrode terminal 214b can be fixed as a whole to the outside of the cover 211a, or can extend into the interior of the housing 211 through the electrode lead-out hole 211c.

[0581] When the first pole tab 2221 is a negative pole tab and the second pole tab 2222 is a positive pole 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 pole tab 2221 is a positive pole tab and the second pole tab 2222 is a negative pole 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.

[0582] In the battery 10, a plurality of battery cells 20 are electrically connected by a busbar. The busbar includes a first connection member 81 for connecting to the cover 211a of the battery cell 20 and a second connection member 82 for connecting to the second electrode terminal 214b of the battery cell 20.

[0583] The first connection member 81 can be connected to the cover 211a by welding, bonding or other methods to achieve 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 methods to achieve electrical connection between the second connection member 82 and the second electrode terminal 214b.

[0584] Exemplarily, the first connecting member 81 connects the cover 211a of one battery cell 20 and the second electrode terminal 214b of another battery cell 20, and the second connecting member 82 connects the second electrode terminal 214b of the one battery cell 20 and the cover 211a of yet another battery cell 20, so that the first connecting member 81 and the second connecting member 82 connect the three battery cells 20 in series.

[0585] In this embodiment, by using the cover 211a and the second electrode terminal 214b as the output pole, the structure of the battery cell 20 can be simplified and the current capacity of the battery cell 20 can be guaranteed. The cover 211a and the second electrode terminal 214b are located at the same end of the battery cell 20, so that the first connecting member 81 and the second connecting member 82 can be assembled to 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 groups.

[0586] It should be understood that Figure 24 to Figure 28 As shown, the second electrode terminal 214b of the embodiment of the present application includes a terminal body 2141. Further, the terminal body 2141 can be fixed to the cover body 211a by riveting. For example, at least a portion of the terminal body 2141 is located in the electrode lead-out hole 211c, and both ends of the terminal body 2141 are riveted to the electrode lead-out hole 211c.

[0587] In some embodiments, the terminal body 2141 may be provided with a recessed portion that is recessed from the outer surface of the terminal body 2141 in a direction facing the electrode assembly 22. The bottom of the recessed portion is used for welding to the current collecting member 23.

[0588] When the electrode assembly 22 and the current collecting member 23 are installed in the shell 211 through the barrel opening 211d and the current collecting member 23 is pressed against the cover 211a, the external welding equipment can weld the bottom of the recess and the current collecting member 23 from the side of the bottom of the recess away from the current collecting member 23.

[0589] In this embodiment, the thickness of the terminal body 2141 is reduced by providing a recess, which can reduce the welding power required for welding the bottom of the recess to the current collecting member 23, reduce heat generation, and reduce the risk of burning other components (such as the first insulating member 61 and the second insulating member 60).

[0590] In some embodiments, the second electrode terminal 214b further includes a sealing plate 2142, which is used to seal the opening of the recess. The sealing plate 2142 can be located entirely outside the recess, or partially contained in the recess, as long as the sealing plate 2142 can seal the opening of the recess. The sealing plate 2142 can protect the recess from the outside, reduce external impurities entering the recess, reduce the risk of the bottom of the recess being damaged by external impurities, and improve the sealing performance of the battery cell 20.

[0591] In some embodiments, the sealing plate 2142 is used to be welded with 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 current carrying capacity.

[0592] In some embodiments, at least a portion of the sealing plate 2142 protrudes from the outer surface of the terminal body 2141. When the second connecting member 82 and the sealing plate 2142 need to be welded, the second connecting member 82 is first attached to the upper surface of the sealing plate 2142 (i.e., the surface of the sealing plate 2142 that is away from the recess), and then the second connecting member 82 and the sealing plate 2142 are welded. At least a portion of the sealing plate 2142 protrudes from the outer surface of the terminal body 2141 to avoid the outer surface of the terminal body 2141 interfering with the attachment of the sealing plate 2142 and the second connecting member 82, thereby ensuring that the second connecting member 82 and the sealing plate 2142 are tightly attached.

[0593] In the embodiment of the present application, the battery cell 20 further includes: a first insulating member 61, which is used to insulate at least a portion of the second electrode terminal 214b from the cover 211a. Exemplarily, at least a portion of the first insulating member 61 is clamped between the cover 211a and the second electrode terminal 214b to insulate the cover 211a and the second electrode terminal 214b, thereby reducing the risk of short circuit.

[0594] In the embodiment of the present application, the battery cell 20 further includes a second insulating member 60, which is located between the cover 211a and the electrode assembly 22. Specifically, the second insulating member 60 can separate the electrode assembly 22 from the cover 211a, reduce the risk of contact and conduction between the electrode assembly 22 and the cover 211a when the battery cell 20 vibrates, and improve safety performance.

[0595] 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 is 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.

[0596] In some embodiments, the second tab 2222 is disposed at one end of the electrode assembly 22 facing the cover 211a, and the first 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 tab 2221 and the cover 211a so that the first tab 2221 is electrically connected to the cover 211a.

[0597] The barrel 211b may be directly electrically connected to the first pole tab 2221, or may be electrically connected to the first pole tab 2221 through other components. For example, the first pole tab 2221 is electrically connected to the barrel 211b through the cover plate 212.

[0598] In the embodiment of the present application, the first pole ear 2221 and the second pole ear 2222 are arranged at both ends of the electrode assembly 22, which can reduce the risk of conduction between the first pole ear 2221 and the second pole ear 2222 and increase the flow area of ​​the first pole ear 2221 and the flow area of ​​the second pole ear 2222.

[0599] 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, so as to reduce safety risks.

[0600] 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.

[0601] In the first direction Z, the second electrode terminal 214b is arranged opposite to the middle area of ​​the second pole tab 2222. If the second electrode terminal 214b and the second pole tab 2222 are directly connected, the conductive path between the edge area of ​​the second pole tab 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.

[0602] The current collecting component 23 of the embodiment of the present application and the second pole lug 2222 may have a larger connection area, and the current of the second pole lug 2222 may be connected to the second electrode terminal 214b via the current collecting component 23. In this way, the current collecting component 23 may reduce the difference in the conductive path between different areas of the second pole lug 2222 and the second electrode terminal 214b, improve the uniformity of the current density of the second pole sheet, reduce the internal resistance, and improve the current flow capacity and charging efficiency of the battery cell 20.

[0603] It should be understood that the housing 211 of the embodiment of the present application is a multi-layer structure, that is, the barrel 211b and the cover 211a of the housing 211 are both multi-layer structures. For ease of description, the housing 211 hereinafter includes the barrel 211b and the cover 211a.

[0604] In the embodiment of the present application, the shell 211 includes a first shell layer 2115, and the resistivity of the first shell layer 2115 is K1, and K1 satisfies: 1×10^-8 Ω·m≤K1≤6×10^-8 Ω·m. The first shell layer 2115 is any shell layer in the multi-layer shell 211, for example, Fig.26The innermost shell is the first shell layer 2115 as an example, but the present application is not limited thereto. By setting the first shell layer 2115 of the shell 211 to have a smaller resistivity K1, the current carrying capacity of the shell 211 can be improved, thereby improving the performance of the battery cell 20.

[0605] In some embodiments, the resistivity K1 of the first shell layer 2115 can also satisfy 1×10^-8 Ω·m≤K1≤2.8×10^-8 Ω·m. This can improve the flow capacity and performance of the shell 211 and facilitate implementation. In some embodiments, the resistivity K1 of the first shell layer 2115 can also be set to other values. For example, the resistivity K1 of the first shell layer 2115 can be any one of the following values ​​or between any two of the following values: 1×10^-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^-8Ω·m, 5.8 and 6×10^-8 Ω·m.

[0606] It should be understood that the specific thickness of the first shell layer 2115 of the embodiment of the present application can also be flexibly set according to actual applications. For example, the thickness of the first shell layer 2115 can be set according to a certain ratio according to the thickness of the shell 211.

[0607] In some embodiments, the average thickness of the first shell layer 2115 is T13, the average thickness of the shell 211 is T10, and T13 and T10 satisfy: 0.15≤T13 / T10≤0.85. If T13 / T10 is set too small, when the average thickness T10 of the shell 211 is constant, T13 will be too small, which will increase the difficulty of processing, and will also cause the overcurrent heat to be too large, which will easily cause thermal runaway. On the contrary, if T13 / T10 is set too large, when the average thickness T10 of the shell 211 is constant, T13 will be too large, and the thickness of other structural layers will be too small, which will affect the structural strength of the shell 211.

[0608] Further, T13 and T10 satisfy: 0.2≤T13 / T10≤0.6. This can improve the flow capacity of the housing 211 and 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 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.

[0609] It should be understood that the value range of the average thickness T10 of the shell 211 of the embodiment of the present application can also be flexibly set according to the actual application. For example, the average thickness T10 of the shell 211 satisfies: 0.05mm≤T10≤0.5mm. The average thickness T10 of the shell 211 should not be too small to reduce the processing difficulty of the multi-layer shell 211 and improve the structural strength...

Claims

1. A battery cell, characterized in that: include: An electrode assembly, the electrode assembly comprising a negative electrode plate, the negative electrode plate comprising a negative electrode active material capable of reversibly extracting and inserting metal ions, the negative electrode active material comprising a silicon-based material; A shell for accommodating the electrode assembly, wherein the inner surface of the shell is in contact with the electrolyte, the tensile strength of at least a portion of the shell at a temperature of 25° C. is Rm, and Rm satisfies: 250 MPa≤Rm≤1200 MPa, and the yield strength of at least a portion of the shell at a temperature of 25° C. is Re, and Re satisfies: 140 MPa≤Re≤600 MPa; The material of at least a part of the housing includes stainless steel; At least a portion of the shell includes a third shell wall, the third shell wall has an average thickness of T, and T satisfies: 0.05 mm ≤ T ≤ 0.5 mm, 60 mm·MPa ≤ T×Rm ≤ 500 mm·MPa; 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.

2. The battery cell according to claim 1, characterized in that: In the negative electrode active material, the mass proportion of the silicon-based material is g, the material of at least a part of the shell includes iron, Rm and g satisfy 2%≤g≤40%, and 300MPa<Rm≤1200MPa.

3. The battery cell according to claim 2, characterized in that: Rm and g satisfy 2.5%≤g≤15%, 315MPa≤Rm<800MPa.

4. The battery cell according to claim 2, characterized in that: Rm and g satisfy 4.5%≤g≤40%, 380MPa≤Rm≤1200MPa.

5. The battery cell according to claim 4, characterized in that: Rm and g satisfy 8%≤g≤40%, 400MPa≤Rm≤1200MPa.

6. The battery cell according to claim 5, characterized in that: Rm and g satisfy 10%≤g≤40%, 480MPa≤Rm≤1200MPa.

7. The battery cell according to claim 6, characterized in that: Rm and g satisfy 15%≤g≤40%, 520MPa≤Rm≤1200MPa.

8. The battery cell according to claim 7, characterized in that: Rm and g satisfy 20%≤g≤40%, 600MPa≤Rm≤1200MPa.

9. The battery cell according to any one of claims 1 to 7, characterized in that: The silicon-based material includes at least one of elemental silicon, silicon-oxygen compounds, silicon-carbon composites, silicon-nitrogen composites, silicon-containing alloys or silicon-oxygen-carbon composite materials.

10. The battery cell according to any one of claims 1 to 7, characterized in that: The shell includes a weld, and at least a portion of the shell includes an area of ​​the shell within a preset distance from the weld, where the preset distance is L, and L satisfies: L=10 mm.

11. The battery cell according to any one of claims 1 to 7, characterized in that: At least a partial area of ​​the housing includes the entire wall of the housing.

12. The battery cell according to any one of claims 1 to 7, characterized in that: The shell is in a cylindrical or polygonal shape.

13. The battery cell according to any one of claims 1 to 7, 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.

14. The battery cell according to any one of claims 1 to 7, characterized in that: The capacity of the battery cell is C, and C satisfies: 25Ah≤C≤550Ah.

15. The battery cell according to any one of claims 1 to 7, 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.

16. The battery cell according to any one of claims 1 to 7, 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。 17. The battery cell according to any one of claims 1 to 7, 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 inner diameter R1 of the first fillet satisfies: 2.5mm≤R1≤20mm.

18. The battery cell according to any one of claims 1 to 7, 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.

19. The battery cell according to any one of claims 1 to 7, characterized in that: The housing comprises: A first housing portion having a first opening formed therein, the first housing portion comprising a first wall opposite to the first opening and a second wall connected to the first wall, the first wall and the second wall being integrally formed; A second housing portion, fixedly connected to the second wall; Wherein, in the depth direction of the first shell part, at least a partial area of ​​the shell is formed by the first shell part and the second shell part.

20. The battery cell according to any one of claims 1 to 7, characterized in that: The battery cell is used in a battery, and the electrode assembly includes a first pole lug and a second pole lug with opposite polarities; The shell comprises a barrel and a cover connected to the barrel, the cover and the barrel are integrally formed, the barrel is arranged around the outer circumference of the electrode assembly, the cover is provided with an electrode lead-out hole, and at least a portion of the cover is used to electrically connect the first connecting member of the battery and the first electrode tab; The battery cell further comprises: The second electrode terminal is used to electrically connect the second connecting member and the second electrode ear of the battery. 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 electrode of the battery cell, and the other is the negative output electrode of the battery cell.

21. The battery cell according to claim 20, characterized in that: The second electrode tab is arranged at one end of the electrode assembly facing the cover body, and the first electrode tab is arranged at the other end of the electrode assembly away from the cover body; The barrel is used to connect the first electrode tab and the cover body so that the first electrode tab is electrically connected to the cover body.

22. The battery cell according to any one of claims 1 to 7, 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.

23. The battery cell according to any one of claims 1 to 7, characterized in that: The shell is a multi-layer structure, and 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. The battery cell according to any one of claims 1 to 7, characterized in that: T and Rm satisfy: 0.1 mm ≤ T ≤ 0.4 mm, and / or, 100 mm·MPa ≤ T×Rm ≤ 500 mm·MPa.

25. The battery cell according to any one of claims 1 to 7, characterized in that: T and Rm satisfy: 0.1 mm ≤ T ≤ 0.3 mm, and / or, 100 mm·MPa ≤ T×Rm ≤ 300 mm·MPa.

26. The battery cell according to any one of claims 1 to 7, characterized in that: The stainless steel includes at least one of the following: SUS430, SUS304 and SUS316.

27. 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 26.

28. An electrical equipment, characterized in that: include: A battery, comprising a battery cell as claimed in any one of claims 1 to 26, wherein the battery is used to supply power to the electrical device.

Images