Battery cells, batteries and electrical equipment

Abstract

This application discloses a battery cell, a battery, and an electrical device. The battery cell includes: an electrode assembly comprising a positive electrode sheet, the positive electrode sheet comprising a positive electrode active material capable of reversibly extracting and inserting metal ions, the positive electrode active material comprising a nickel-containing compound; and a housing for housing the electrode assembly, wherein at least a portion of the housing has a melting point p, p satisfying: 1200℃ ≤ p ≤ 2000℃, and at least a portion of the housing has a tensile strength Rn at a temperature of 500℃, Rn satisfying: 100MPa ≤ Rn ≤ 1200MPa. The battery cell, battery, and electrical device of this application can improve the reliability of the battery cell.

Description

[0001] This application claims priority to PCT patent application PCT / CN2023 / 132468, filed on November 17, 2023, entitled “Battery Cell, Battery and Electrical Device”, the entire contents of which are incorporated herein by reference. Technical Field

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

[0003] Energy conservation and emission reduction are key to the sustainable development of the automotive industry. In this context, electric vehicles, due to their energy-saving and environmentally friendly advantages, have become an important component of the automotive industry's sustainable development. And for electric vehicles, battery technology is a crucial factor in their development.

[0004] In the development of battery technology, besides improving battery performance, safety is also a crucial issue that cannot be ignored. If battery safety cannot be guaranteed, then the battery is unusable. Therefore, how to improve battery performance while ensuring battery safety has become a particularly important issue in the development of battery technology. Summary of the Invention

[0005] This application provides a battery cell, a battery, and an electrical device that can improve the reliability of the battery cell.

[0006] In a first aspect, a battery cell is provided, the battery cell comprising: an electrode assembly including a positive electrode sheet, the positive electrode sheet including a positive active material capable of reversibly extracting and inserting metal ions, the positive active material including a nickel-containing compound; and a housing for housing the electrode assembly, wherein the melting point of at least a portion of the housing is p, p satisfying: 1200℃≤p≤2000℃, and the tensile strength of at least a portion of the housing at a temperature of 500℃ is Rn, Rn satisfying: 100MPa≤Rn≤1200MPa.

[0007] Therefore, in the battery cells of this application embodiment, when the positive electrode active material of the positive electrode sheet includes a nickel-containing compound, the energy density and cycle life of the battery cell can be effectively increased. However, this also increases the amount of gas generated during the use of the battery cell, especially in the event of thermal runaway, where 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 casing will make the casing less prone to melting, reducing the possibility of the battery cell exploding, and thus reducing the risk of thermal runaway in adjacent battery cells, thereby improving battery reliability. However, the melting point p of the casing should not be too high to reduce the difficulty of material selection and processing, save costs, and facilitate processing. In addition, appropriately increasing the tensile strength Rn of at least a portion of the casing at a high temperature of 500°C can improve the deformation ability of this portion of the casing when the battery cell experiences thermal runaway, making the casing less prone to rapid damage and explosion, thereby reducing the risk of thermal runaway in adjacent battery cells and improving battery reliability. However, the tensile strength Rn of at least a portion of the casing at a high temperature of 500°C should not be too high to save costs and facilitate processing.

[0008] In some embodiments, the nickel-containing compound comprises a layered lithium-containing transition metal oxide, wherein the molar amount of nickel in the layered lithium-containing transition metal oxide accounts for more than 50%, optionally more than 70%, optionally more than 80%, and optionally more than 90% of the total molar amount of transition metal elements in the layered lithium-containing transition metal oxide, thereby further improving the energy density of the battery cell.

[0009] In some embodiments, 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, in order to improve the energy density of the battery cell.

[0010] In some embodiments, at least a portion of the housing is made of at least one of the following materials: steel, copper alloy, titanium alloy, and nickel alloy. These materials have high melting points, meet the requirements of the housing, are easy to process, and are low in cost.

[0011] In some embodiments, at least a portion of the housing is made of steel with a temperature of 1300°C ≤ p ≤ 1800°C, which easily meets design requirements and improves the reliability of individual battery cells and the battery.

[0012] In some embodiments, at least a portion of the housing is made of at least one of the following materials: stainless steel and carbon steel. For example, if the housing is made of stainless steel, it is easy to meet the melting point requirement p. Furthermore, stainless steel is less prone to rusting, which improves the service life of the housing compared to other materials. If the housing is made of carbon steel, it is easy to meet the melting point requirement p.

[0013] In some embodiments, the mass content of chromium in the material of at least a portion of the housing is m, where m satisfies: 10% ≤ m ≤ 30%. Appropriately increasing the amount of chromium in the material of at least a portion of the housing can raise the melting point of the material, making it easier to meet the melting point p requirement. Furthermore, since chromium can react with oxygen to form a dense chromium oxide film, a corrosion-resistant protective film can be formed on the surface of the housing, improving its corrosion resistance.

[0014] In some embodiments, at least a portion of the housing includes all the sidewalls and the bottom wall of the housing. When the mass content d of nickel in the positive electrode of the electrode assembly is constant, if a single battery cell experiences thermal runaway, the internal temperature of the cell rapidly increases and a large amount of gas is generated. Since the entire area of ​​the housing meets the melting point p requirement, the overall deformability of the housing can be improved, making it less susceptible to damage or melting. This limits the high-temperature, high-pressure gas inside the housing, reducing its impact on connected battery cells and thus reducing the risk of thermal runaway in adjacent battery cells, thereby improving battery reliability.

[0015] In some embodiments, the housing is cylindrical or polygonal in shape to facilitate processing.

[0016] In some embodiments, the electrode assembly further includes a negative electrode sheet comprising a negative electrode active material capable of reversibly extracting and embedding metal ions, the negative electrode active material comprising a silicon-based material; the tensile strength Rm of at least a portion of the housing at a temperature of 25°C satisfies: 250MPa≤Rm≤2000MPa. The silicon-based material on the negative electrode sheet can accommodate more metal ions, effectively increasing the energy density of the battery cell. Furthermore, when the negative electrode active material of the negative electrode sheet is silicon-based, it also increases the deformation of the electrode assembly within the battery cell during use, especially during charging, where the embedding of metal ions into the silicon-based material of the negative electrode sheet causes volume expansion of the electrode assembly, thereby increasing the pressure exerted by the electrode assembly on the battery cell housing. Therefore, increasing the tensile strength Rm of at least a portion of the housing at room temperature (25°C) improves the housing's deformability, making the housing less prone to breakage during battery cell use, thereby improving the structural stability of the battery cell and ultimately extending its lifespan. However, the tensile strength Rm of at least some areas of the shell at room temperature (25°C) should not be too high, in order to reduce the difficulty of material selection and processing of the shell, save costs, and facilitate processing.

[0017] In some embodiments, the electrode assembly further includes a negative electrode sheet comprising a negative electrode active material capable of reversibly extracting and embedding metal ions, the negative electrode active material comprising a silicon-based material; the yield strength Re of at least a portion of the housing at a temperature of 25°C satisfies: 140MPa≤Re≤1000MPa. The silicon-based material on the negative electrode sheet can accommodate more metal ions, effectively increasing the energy density of the battery cell. Furthermore, when the negative electrode active material of the negative electrode sheet is silicon-based, it also increases the deformation of the electrode assembly within the battery cell during use, especially during charging, where the embedding of metal ions into the silicon-based material of the negative electrode sheet causes volume expansion of the electrode assembly, thereby increasing the pressure exerted by the electrode assembly on the battery cell housing. Therefore, increasing the yield strength Re of at least a portion of the housing at room temperature (25°C) can improve the deformation capacity of the housing, thereby improving the structural stability of the battery cell and ultimately extending its service life. During the charging and discharging of a single battery cell, the electrode assembly undergoes cyclic expansion and contraction. Increasing the room-temperature yield strength Re of at least a portion of the casing can improve the maximum compressive force the casing can withstand. Without exceeding the yield strength limit of the casing, the casing is less prone to damage, and its deformation can be recovered, thus extending its service life. However, the room-temperature yield strength Re of at least a portion of the casing should not be too high to reduce the difficulty of material selection and processing, saving costs and facilitating manufacturing.

[0018] In some embodiments, at least a portion of the housing has a tensile strength of Rm at a temperature of 25°C. The housing includes at least a third housing wall with an average thickness of T. Rm and T satisfy the following conditions: 250 MPa ≤ Rm ≤ 2000 MPa, 0.05 mm ≤ T ≤ 0.5 mm, and 60 mm·MPa ≤ T×Rm ≤ 500 mm·MPa. Increasing the tensile strength Rm of at least a portion of the housing at room temperature (25°C) improves the housing's deformability, making it less prone to breakage during battery cell use, thereby improving the structural stability and lifespan of the battery cell. However, the tensile strength Rm of at least a portion of the housing at room temperature should not be too high to reduce the difficulty of material selection and processing, save costs, and facilitate manufacturing. When the average thickness T of the third shell wall is relatively thin, the structural strength of the third shell wall can be increased by improving its tensile strength Rm at room temperature (25°C). This improves both the energy density and the structural strength and stability of the battery cell. Conversely, when the average thickness T of the third shell wall is relatively thick, the structural strength of the casing can be increased. Furthermore, by appropriately reducing the tensile strength Rm of the third shell wall at room temperature, the difficulty in selecting materials for the casing can be reduced, thereby lowering the processing difficulty and cost of the battery cell. T×Rm represents the stiffness of the third shell wall. Limiting the stiffness of the third shell wall to neither too small nor too large ensures good deformation capacity while reducing processing difficulty and cost.

[0019] In some embodiments, the capacity of the battery cell is C, and the tensile strength of at least a portion of the casing at a temperature of 25°C is Rm, where Rm and C satisfy: 250MPa≤Rm≤2000MPa, 25Ah≤C≤550Ah. On one hand, increasing the capacity C of the battery cell can increase the capacity density of a battery comprising multiple such cells. Alternatively, while maintaining the total battery capacity, increasing the capacity C of a single battery cell can reduce the number of battery cells required, correspondingly reducing the number of electrical connections between multiple battery cells, lowering the probability of electrical connection failures, and contributing to improved battery reliability. Furthermore, when the capacity C of the battery cell is large, the tensile strength Rm of at least a portion of the casing at room temperature (25°C) can be increased to meet the structural strength requirements of high-capacity battery cells, thereby improving the reliability and lifespan of the battery cell. On the other hand, if the battery cell has a large capacity, its internal reactions will intensify, thus increasing the requirements for the structural strength of the casing. Therefore, the capacity C of the battery cell should not be too large, so as to limit the design requirements for the structural strength of the casing, thereby reducing the difficulty of material selection and processing of the battery cell, reducing costs and improving processing efficiency.

[0020] In some embodiments, the housing has an opening, and the housing includes a first housing wall and at least two second housing walls disposed opposite to the opening, the first housing wall and the second housing walls being intersected; 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 satisfies the condition that T1 > T0 with respect to the maximum thickness T0 of the second housing wall with the largest thickness among the two second housing walls.

[0021] In this embodiment, by providing a transition region between two adjacent second shell walls, stress concentration between the two adjacent second shell walls can be reduced, thereby lowering the risk of structural failure caused by stress concentration. In addition, by setting the maximum thickness T1 of the transition region 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 region can enhance the structural strength of the shell, which is beneficial to solving the problem of shell deformation during the production and assembly of battery cells, as well as the problem of shell deformation caused by gas expansion during the use of battery cells.

[0022] 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. Two of the at least two second housing walls are connected by a first rounded corner. The depth H of the housing and the inner diameter R1 of the first rounded corner satisfy: 2.5 mm ≤ R1 ≤ 20 mm, 50 mm < H ≤ 250 mm. This 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.

[0023] 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. Two of the at least two second housing walls are connected by a first rounded corner. The yield strength Re of the housing at a temperature of 25 °C and the inner diameter R1 of the first rounded corner satisfy: 140 MPa ≤ Re ≤ 1000 Mpa, 2.5 mm ≤ R1 ≤ 20 mm.

[0024] 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 rounded corner between adjacent second housing walls to satisfy 2.5 mm ≤ R1 ≤ 20 mm, the cracking risk caused by stress during the integral forming process of the housing can be reduced as much as possible, and the forming difficulty of the housing can be reduced.

[0025] In some embodiments, the housing has an opening. The housing includes a first housing wall and a second housing wall disposed opposite to the opening. The first housing wall and the second housing wall intersect. The first housing wall and the second housing wall are connected by a second rounded corner. The inner diameter r1 of the second rounded corner and the minimum thickness T2 of the second housing wall with the smallest thickness among the at least two second housing walls satisfy: 2.0 ≤ r1 / T2 ≤ 30. By setting the ratio of the inner diameter r1 of the second rounded corner between the first housing wall and the second housing wall to the minimum thickness T2 of the second housing wall with the smallest thickness within [2.0, 30], it helps to balance the processing difficulty of the housing, the space capacity of the battery cell, and the strength.

[0026] In some embodiments, the housing includes: a first housing portion having a first opening, the first housing portion including 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; and a second housing portion fixedly connected to the second wall; wherein, in the depth direction of the first housing portion, at least a portion of the housing is formed jointly by the first housing portion and the second housing portion. Compared to techniques that directly integrally form the housing, the housing prepared in this manner reduces the risk of cracking during the integral deep drawing process.

[0027] In some embodiments, the battery cell is used as a battery, and the electrode assembly includes a first tab and a second tab with opposite polarities. The housing includes a cylindrical body and a cover connected to the cylindrical body, the cover and the cylindrical body being integrally formed. The cylindrical body is disposed around the outer periphery of the electrode assembly, and the cover has an electrode lead-out hole. At least a portion of the cover is used to electrically connect the first connecting member of the battery and the first tab. The battery cell further includes a second electrode terminal for electrically connecting the second connecting member of the battery and the second tab. The second electrode terminal is insulated from the cover and installed in the electrode lead-out hole. One of the cover and the second electrode terminal is the positive output terminal of the battery cell, and the other is the negative output terminal of the battery cell. By using the cover and the second electrode terminal as output terminals, the structure of the battery cell can be simplified, and the current carrying 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 simplifies the assembly process and improves the efficiency of assembling multiple battery cells into a group.

[0028] In some embodiments, the second tab is located at one end of the electrode assembly facing the cover, and the first tab is located at the other end of the electrode assembly away from the cover; the cylindrical body is used to connect the first tab and the cover, so that the first tab is electrically connected to the cover. By placing the first tab and the second tab at both ends of the electrode assembly in this embodiment, the risk of continuity between the first tab and the second tab can be reduced, and the current-carrying area of ​​the first tab and the second tab can be increased.

[0029] In some embodiments, the electrode assembly includes a first tab; the housing includes a cylindrical body and a cover connected to the cylindrical body, the cylindrical body surrounding the outer periphery of the electrode assembly, and the cover including the first electrode terminal. The first tab is electrically connected to the first electrode terminal through the cylindrical body. The housing has a multi-layer structure with different resistivities. The first tab, electrically connected to the first electrode terminal of the battery cell through the housing, simplifies the battery cell structure. The multi-layer structure with different resistivities allows for improved current carrying capacity of the battery cell through a lower resistivity layer and improved structural strength of the housing through a higher resistivity layer. This improves both the performance and structural strength of the battery cell, thereby increasing its lifespan.

[0030] In some embodiments, the housing has a multi-layer structure, and the outermost shell is made of at least one of the following materials: aluminum, aluminum alloy, copper, copper alloy, and chromium. When the outermost shell material contains aluminum, the aluminum is oxidized to dense alumina, which provides corrosion resistance; when the outermost shell material contains copper, the copper is oxidized to copper oxide, i.e., verdigris, which also provides corrosion resistance; when the outermost shell material contains chromium, the chromium is oxidized to chromium oxide, which also provides corrosion resistance. Therefore, when the outermost shell material is made of the aforementioned corrosion-resistant materials, it can protect the other shell layers located inside it, thereby improving both the structural stability and service life of the housing.

[0031] In a second aspect, a battery is provided, comprising: a plurality of battery cells, wherein the battery cells are those described in the first aspect or any embodiment of the first aspect.

[0032] Thirdly, an electrical device is provided, comprising: a battery, the battery including a battery cell as described in the first aspect or any embodiment of the first aspect, the battery being used to supply power to the electrical device.

[0033] In some embodiments, the electrical equipment is a vehicle, a ship, or a spacecraft. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of a vehicle according to one embodiment of this application;

[0035] Figure 2 This is an exploded structural diagram of a battery according to an embodiment of this application;

[0036] Figure 3 This is a schematic diagram of the structure of a battery cell according to an embodiment of this application;

[0037] Figure 4 This is an exploded structural diagram of a battery cell according to an embodiment of this application;

[0038] Figure 5 This is a cross-sectional schematic diagram of an electrode assembly according to an embodiment of this application;

[0039] Figure 6 This is a cross-sectional schematic diagram of the negative electrode or positive electrode of an electrode assembly according to an embodiment of this application;

[0040] Figure 7 This is a schematic diagram of the structure of a fixture for cyclic charging fatigue testing according to an embodiment of this application;

[0041] Figure 8 This is a side view of the casing of a battery cell according to one embodiment of this application;

[0042] Figure 9 This is a cross-sectional structural diagram of the casing of a battery cell according to an embodiment of this application;

[0043] Figure 10 This is an exploded structural diagram of a battery cell according to an embodiment of this application;

[0044] Figure 11 This is a cross-sectional view of the housing according to one embodiment of this application;

[0045] Figure 12 This is a schematic diagram of a transition region of the housing according to an embodiment of this application;

[0046] Figure 13 This is a schematic diagram of another transition region of the housing according to one embodiment of this application;

[0047] Figure 14 Another cross-sectional view of the housing according to one embodiment of this application;

[0048] Figure 15 for Figure 14 A magnified view of part B in the middle section;

[0049] Figure 16 This is an exploded view of the casing according to an embodiment of this application;

[0050] Figure 17 This is a schematic diagram of the structure of the second housing portion according to an embodiment of this application;

[0051] Figure 18 This is a schematic diagram of another structure of the second housing portion according to an embodiment of this application;

[0052] Figure 19 This is another exploded view of the housing according to an embodiment of this application;

[0053] Figure 20 This is a schematic cross-sectional view of the housing according to an embodiment of this application;

[0054] Figure 21 This is an enlarged view of a partial structure of the housing according to an embodiment of this application;

[0055] Figure 22 This is a schematic diagram of the structure of a battery cell according to another embodiment of this application;

[0056] Figure 23 This is an exploded structural diagram of a battery cell according to another embodiment of this application;

[0057] Figure 24 This is a schematic cross-sectional view of the casing structure of a battery cell according to another embodiment of this application;

[0058] Figure 25 This is a cross-sectional schematic diagram of a partial structure of a battery according to another embodiment of this application;

[0059] Figure 26 This is a cross-sectional schematic diagram of another partial structure of a battery according to another embodiment of this application.

[0060] The accompanying drawings are not drawn to scale. Detailed Implementation

[0061] The technical solutions in the embodiments of this application will now be described with reference to the accompanying drawings.

[0062] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0063] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used in the description of this application is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms "comprising" and "having," and any variations thereof, in the description, claims, and accompanying drawings of this application are intended to cover non-exclusive inclusion. The terms "first," "second," etc., in the description, claims, or accompanying drawings of this application are used to distinguish different objects, not to describe a specific order or hierarchy.

[0064] In this application, the reference to "embodiment" means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a mutually exclusive, independent, or alternative embodiment. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described in this application can be combined with other embodiments.

[0065] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," and "attachment" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0066] In this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. Additionally, in this application, the character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0067] In the embodiments of this application, the same reference numerals denote 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 this application shown in the accompanying drawings, as well as the overall thickness, length, width, and other dimensions of the integrated device, are merely illustrative and should not constitute any limitation on this application.

[0068] In this application, "multiple" refers to two or more (including two), similarly, "multiple sets" refers to two or more (including two sets), and "multiple pieces" refers to two or more (including two pieces).

[0069] In this embodiment of the application, the battery cell can be a secondary battery, which refers to a battery cell that can be recharged to activate the active materials and continue to be used after the battery cell has been discharged.

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

[0071] In some implementations, the battery cell in this application embodiment can be a metal battery. Specifically, the metal battery may include lithium metal secondary batteries, sodium metal batteries, or magnesium metal batteries, etc. This application embodiment does not limit this.

[0072] A single battery cell typically includes an electrode assembly. The electrode assembly includes a positive electrode, a negative electrode, and a separator. During the charging and discharging process of a single battery cell, active ions (such as lithium ions) repeatedly insert and extract between the positive and negative electrodes. The separator, positioned between the positive and negative electrodes, prevents short circuits while allowing active ions to pass through.

[0073] In some embodiments, the positive electrode may be a positive electrode sheet, which 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.

[0074] As an example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive active material is disposed on either or both of the two opposite surfaces of the positive current collector.

[0075] As an example, the positive electrode current collector can be a metal foil, a foamed metal, or a composite current collector. For example, as a metal foil, it can be silver-treated aluminum or stainless steel, stainless steel, copper, aluminum, nickel, carbon electrode, carbon, nickel, or titanium, etc. Foamed metal can be foamed nickel, foamed copper, foamed aluminum, foamed alloy, or foamed carbon, etc. Composite current collectors can include a polymer material base layer and a metal layer. Composite current collectors can 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.).

[0076] As an example, the positive electrode active material may include at least one of the following materials: lithium phosphate, lithium transition metal oxide, and their respective modified compounds. However, this application is not limited to these materials, and other conventional 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. Examples of lithium phosphate include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), lithium iron phosphate and carbon composites, lithium manganese phosphate (such as LiMnPO4), lithium manganese phosphate and carbon composites, lithium manganese iron phosphate, and lithium manganese iron phosphate and carbon composites.

[0077] In some embodiments, the negative electrode may be a negative electrode sheet, which 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.

[0078] As an example, the negative electrode current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode active material is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0079] As an example, the negative electrode current collector can be a metal foil, a foamed metal, or a composite current collector. For example, as a metal foil, it can be silver-treated aluminum or stainless steel, stainless steel, copper, aluminum, nickel, carbon electrodes, carbon, nickel, or titanium, etc. Composite current collectors can include a polymer material base layer and a metal layer. Foamed metal can be foamed nickel, foamed copper, foamed aluminum, foamed alloy, or foamed carbon, etc. Composite current collectors can 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.).

[0080] As an example, the negative electrode active material may be a negative electrode active material known in the art for use in battery cells. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate, etc.

[0081] In some embodiments, the electrode assembly further includes an isolator disposed between the positive and negative electrodes.

[0082] In some embodiments, the separator is a separator membrane. This application does not impose any particular limitation on the type of separator membrane; any known porous separator membrane with good chemical and mechanical stability can be selected.

[0083] As an example, the main material of the separator can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride, and ceramic.

[0084] In some embodiments, the separator is a solid electrolyte. The solid electrolyte is disposed between the positive and negative electrodes, serving both to transport ions and to isolate the positive and negative electrodes.

[0085] In some embodiments, the battery cell also includes an electrolyte, which acts as a conductor of ions between the positive and negative electrodes. This application does not impose specific limitations on the type of electrolyte; it can be selected according to requirements. The electrolyte can be liquid, gel, or solid.

[0086] In some embodiments, the electrode assembly is provided with tabs that allow current to be drawn from the electrode assembly. The tabs include a positive tab and a negative tab.

[0087] 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 made of steel, aluminum, plastic (such as polypropylene), composite metal (such as copper-aluminum composite), or aluminum-plastic film, etc. The housing includes a shell and a cover plate.

[0088] The battery mentioned in the embodiments of this application may be a single physical module comprising one or more battery cells to provide higher voltage and capacity. When there are multiple battery cells, the multiple battery cells are connected in series, parallel, or mixed via a busbar.

[0089] In some embodiments, the battery can be a battery pack, which includes a housing and individual battery cells, with the individual battery cells or battery modules housed within the housing.

[0090] In some embodiments, the housing may be part of the vehicle's chassis structure. For example, a portion of the housing may be at least a part of the vehicle's floor, or a portion of the housing may be at least a part of the vehicle's crossbeams and longitudinal beams.

[0091] In some embodiments, the battery may be located in an energy storage device. Energy storage devices include energy storage containers, energy storage cabinets, etc.

[0092] The development of battery technology must consider multiple design factors simultaneously, such as performance parameters like energy density, cycle life, discharge capacity, and charge / discharge rate. Additionally, battery safety and stability must also be considered. For example, by rationally selecting the positive active material of the positive electrode or the negative active material of the negative electrode in the electrode assembly, the energy of a single battery cell can be effectively improved, thereby increasing the overall battery energy. Taking the positive electrode as an example, appropriately adding nickel-containing compounds to the positive active material of the positive electrode can improve the energy of the single battery cell and extend its cycle life, but the internal reactions within the battery cell will also become more intense. Especially in the event of thermal runaway in a single battery cell, the runaway speed is faster, gas production is more intense, and the temperature rises significantly, typically exceeding 800°C to 900°C. If the battery cell's casing strength is insufficient, it is easily damaged or melted, leading to the thermal runaway affecting connected battery cells and causing heat diffusion.

[0093] Therefore, embodiments of this application provide a battery cell, a battery, and an electrical device that can solve the above-mentioned problems. The battery cell of this application includes: an electrode assembly and a housing for housing the electrode assembly. The electrode assembly includes a positive electrode sheet, which includes a positive electrode active material capable of reversibly extracting and inserting metal ions. The positive electrode active material includes a nickel-containing compound. The melting point of at least a portion of the housing is p, where p satisfies: 1200℃ ≤ p ≤ 2000℃. The tensile strength of at least a portion of the housing at a temperature of 500℃ is Rn, where Rn satisfies: 100MPa ≤ Rn ≤ 1200MPa. When the positive electrode active material of the positive electrode sheet includes a nickel-containing compound, the energy density and cycle life of the battery cell can be effectively increased. However, this also increases the amount of gas generated during the use of the battery cell, especially in the event of thermal runaway, where 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 casing will make the casing less prone to melting, reducing the possibility of the battery cell exploding, and thus reducing the risk of thermal runaway in adjacent battery cells, thereby improving battery reliability. However, the melting point p of the casing should not be too high, to reduce the difficulty of material selection and processing, save costs, and facilitate manufacturing. Furthermore, appropriately increasing the tensile strength Rn of at least a portion of the casing at a high temperature of 500°C can improve the deformation capacity of that portion of the casing in the event of thermal runaway in a battery cell, making the casing less prone to rapid damage and explosion, thereby reducing the risk of thermal runaway in adjacent battery cells and improving battery reliability. However, the tensile strength Rn of at least a portion of the casing at a high temperature of 500°C should not be too high, to save costs and facilitate manufacturing.

[0094] The technical solutions described in the embodiments of this application are applicable to various battery-powered electrical devices.

[0095] Electrical equipment can include vehicles, mobile phones, portable devices, laptops, ships, spacecraft, electric toys, and power tools, etc. Vehicles can be gasoline-powered cars, natural gas-powered cars, or new energy vehicles; new energy vehicles can be pure electric vehicles, hybrid electric vehicles, or range-extended electric vehicles, etc. Spacecraft include airplanes, rockets, space shuttles, and spacecraft, etc. Electric toys include stationary or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc. Power tools include metal cutting power tools, grinding power tools, assembly power tools, and railway power tools, such as electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact drills, concrete vibrators, and electric planers, etc. This application does not impose any special limitations on the above-mentioned electrical equipment.

[0096] For ease of explanation, the following embodiments use a vehicle as an example of electrical equipment.

[0097] For example, such as Figure 1 The diagram shown is a structural schematic of a vehicle 1 according to one embodiment of this application. Vehicle 1 can be a gasoline-powered vehicle, a natural gas-powered vehicle, or a new energy vehicle. New energy vehicles can be pure electric vehicles, hybrid electric vehicles, or range-extended electric vehicles, etc. A motor 80, a controller 70, and a battery 10 can be installed inside vehicle 1. The controller 70 controls the battery 10 to supply power to the motor 80. For example, the battery 10 can be installed at the bottom, front, or rear of vehicle 1. The battery 10 can be used to power vehicle 1; for example, it can serve as the operating power source for the vehicle 1's electrical system, such as for the power requirements of starting, navigation, and operation. In another embodiment of this application, the battery 10 can not only serve as the operating power source for vehicle 1 but also as the driving power source, replacing or partially replacing gasoline or natural gas to provide driving power to vehicle 1.

[0098] To meet diverse power demands, a battery can comprise multiple individual cells, which can be connected in series, parallel, or a combination of both. A battery can also be called a battery pack. For example, multiple individual cells can first be connected in series, parallel, or a combination of both to form a battery module, and then multiple battery modules can be connected in series, parallel, or a combination of both to form a battery. In other words, multiple individual cells can be directly assembled into a battery, or they can first be assembled into battery modules, and then the battery modules can be assembled into a battery.

[0099] Figure 2 The diagram illustrates the structure of a battery 10 according to one embodiment of this application. The battery 10 may include a plurality of battery cells 20. The battery 10 may also include a housing 11, which has a hollow interior structure, and the plurality of battery cells 20 are housed within the housing 11. Figure 2 This application illustrates one possible implementation of the housing 11, such as... Figure 2 As shown, the housing 11 may include two housing portions, referred to herein as a first housing portion 111 and a second housing portion 112, which are fastened together. The shapes of the first housing portion 111 and the second housing portion 112 can be determined according to the shape of the combination of multiple battery cells 20, and at least one of the first housing portion 111 and the second housing portion 112 has an opening. For example, as... Figure 2As shown, both the first housing portion 111 and the second housing portion 112 are hollow cuboids with only one open side. The openings of the first housing portion 111 and the second housing portion 112 are opposite to each other, and the first housing portion 111 and the second housing portion 112 are interlocked to form a housing 11 with a closed cavity. This cavity can accommodate multiple battery cells 20. The multiple battery cells 20 are connected in parallel, series, or mixed and placed inside the housing 11 formed by the interlocking of the first housing portion 111 and the second housing portion 112.

[0100] For example, unlike Figure 2 As shown, only one of the first box portion 111 and the second box portion 112 may be a hollow cuboid with an opening, while the other may be plate-shaped to cover the opening. For example, taking the second box portion 112 as a hollow cuboid with only one side being an opening, and the first box portion 111 as a plate-shaped example, then the first box portion 111 covers the opening of the second box portion 112 to form a box 11 with a closed cavity. The embodiments of this application are not limited to this.

[0101] Figure 3 A schematic diagram of the structure of a battery cell 20 according to an embodiment of this application is shown, for example, Figure 3 The battery cell 20 shown can be Figure 2 Any one of the battery cells 20 in the battery 10 shown; Figure 4 This illustration shows a partially exploded structural diagram of a battery cell 20 according to an embodiment of this application. For example, Figure 4 It can be Figure 3 The diagram shows a partial exploded structure of the battery cell 20.

[0102] In the embodiments of this application, such as Figure 3 and Figure 4 As shown, the battery cell 20 may include an electrode assembly 22 and a housing 211. Specifically, the electrode assembly 22 includes a positive electrode 223, which includes a positive active material capable of reversibly extracting and inserting metal ions, and the positive active material includes a nickel-containing compound; the housing 211 is used to house the electrode assembly 22, and at least a portion of the housing 211 has a melting point p, where p satisfies: 1200℃≤p≤2000℃.

[0103] like Figure 3 and Figure 4As shown, the battery cell 20 in this embodiment may include a housing 21. Specifically, the housing 21 may include a shell 211, which 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 a cover plate 212 for covering the opening of the shell 211, so that the electrode assembly 22 can be accommodated inside the housing 21.

[0104] It should be understood that the housing 211 in this embodiment is a component for accommodating the electrode assembly 22. The housing 211 can be a hollow structure with an opening at one or more ends. For example, if the housing 211 is a hollow structure with an opening at one end, a cover plate 212 can be provided accordingly; if the housing 211 is a hollow structure with openings at opposite ends, two cover plates 212 can be provided, with the two cover plates 212 respectively covering the openings at both ends of the housing 211.

[0105] It should be understood that the battery cell 20 in this application embodiment can be a cylindrical battery cell, a prismatic battery cell, a pouch battery, or a battery cell of other shapes. Among them, the prismatic battery cell can include a prismatic battery cell, a blade-shaped battery cell, or other multi-prismatic battery cells, such as a hexagonal prismatic battery cell or an octagonal prismatic battery cell, and this application embodiment is not limited to these.

[0106] Corresponding to different shapes of battery cells 20, the casing 211 of the battery cell 20 can be of various shapes, such as a cylinder or a polygonal prism. For example, as shown... Figure 3 and Figure 4 As shown, in this embodiment, the description mainly uses a hollow cuboid structure for the housing 211. Alternatively, this embodiment mainly uses a hollow structure with an opening at one end for the housing 211. However, the relevant descriptions of this embodiment are also applicable to battery cells 20 of other shapes; for the sake of brevity, they will not be elaborated upon here.

[0107] It should be understood that the cover plate 212 in this embodiment 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 has a cuboid structure, and the cover plate 212 has a rectangular plate structure that is adapted to the shell 211.

[0108] In this battery cell 20, the electrode assembly 22 is the component in which the electrochemical reaction occurs. Depending on actual usage requirements, the electrode assembly 22 within the casing 211 can be one or multiple. For example, as... Figure 3 and Figure 4As shown, two electrode assemblies 22 are provided inside the battery cell 20. The electrode assembly 22 can be a cylinder, a cuboid, 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 cuboid structure, the housing 211 can also be a cuboid structure.

[0109] It should be understood that, such as Figure 3 and Figure 4 As shown, the electrode assembly 22 in this embodiment may include tabs 222 and an electrode body 221. The tabs 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 the portions of the positive electrode sheet 223 that are not coated with positive active material, and the negative tab 222b may be formed by stacking the portions of the negative electrode sheet 224 that are not coated with negative active material. The electrode body 221 may be formed by stacking or winding the positive electrode sheet 223 and the negative electrode sheet 224 together.

[0110] The positive electrode 223 of this application embodiment is provided with a positive electrode active material that can reversibly extract and insert metal ions. This positive electrode active material can be flexibly configured according to actual applications. For example, the positive electrode active material may include a nickel-containing compound, which can effectively increase the energy density and cycle life of the battery cell 20, but will also increase the temperature and gas generated during the use of the battery cell 20. In particular, in the event of thermal runaway during the use of the battery cell 20, the internal temperature of the battery cell 20 will increase rapidly and a large amount of gas will be generated.

[0111] Therefore, appropriately increasing the melting point p of at least a portion of the casing 211 will make the casing 211 less prone to melting, reducing the possibility of the battery cell 20 exploding, and thus reducing the risk of thermal runaway in adjacent battery cells 20, thereby improving the reliability of the battery 10. However, the melting point p of at least a portion of the casing 211 should not be too high, in order to reduce the difficulty of material selection and processing of the casing 211, save costs, and facilitate processing. For example, the melting point p of at least a portion of the casing 211 can usually be set to satisfy 1200℃≤p≤2000℃.

[0112] It should be understood that the melting point p of at least a portion of the casing 211 in this embodiment can be adjusted according to actual application. For example, the melting point p of at least a portion of the casing 211 typically satisfies 1200℃≤p≤2000℃. Alternatively, the melting point p of at least a portion of the casing 211 can also satisfy 1300℃≤p≤1800℃. On the one hand, appropriately increasing the melting point p can improve the resistance of this portion of the casing 211 to melting during thermal runaway of the battery cell 20, making the casing 211 less prone to melting, thereby reducing the risk of thermal runaway of adjacent battery cells 20, i.e., reducing the risk of thermal diffusion, and improving the reliability of the battery 10. At the same time, the melting point p should not be too large, so as to facilitate the selection of suitable materials, reduce processing difficulty, and thus save costs and facilitate processing.

[0113] Furthermore, the melting point p of at least a portion of the casing 211 can be set to satisfy 1400℃≤p≤1600℃. This can improve the structural strength of the casing 211 in the event of thermal runaway of the battery cell 20, making the casing 211 less prone to melting, maintaining the structural integrity of that portion of the casing 211, and reducing the risk of thermal runaway of adjacent battery cells 20. It can also reduce processing difficulty and save costs.

[0114] In some embodiments, the melting point p of at least a portion of the housing 211 may be set to other values. For example, 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.

[0115] Figure 5 A cross-sectional schematic diagram of the electrode assembly 22 according to an embodiment of this application is shown. For example, the... Figure 5 The cross-sectional schematic diagram shown can be Figure 4 The diagram shows a cross-sectional view of the electrode assembly 22, which is perpendicular to the height direction Z of the battery cell 20. Figure 6 This illustration shows a partial cross-sectional view of the positive electrode 223 or the negative electrode 224 according to an embodiment of this application. For example, the... Figure 6 It can be expressed as follows Figure 5 The diagram shows a partial cross-sectional view of the negative electrode 224 of the electrode assembly 22 along its thickness direction, or it can also be represented as shown below. Figure 5 A partial cross-sectional schematic diagram of the positive electrode 223 of the electrode assembly 22 shown along its thickness direction.

[0116] like Figures 3 to 6As shown, the electrode assembly 22 of this embodiment includes a positive electrode 223 and a negative electrode 224. The electrode assembly 22 can be formed by stacking or winding the positive electrode 223 and the negative electrode 224. For example, the electrode assembly 22 may include a plurality of positive electrode 223 and a plurality of negative electrode 224; along the thickness direction of the electrode assembly 22, the plurality of positive electrode 223 and the plurality of negative electrode 224 are alternately stacked to form a stacked electrode assembly 22. As another example, the electrode assembly 22 may include a plurality of positive electrode 223, and the negative electrode 224 includes a plurality of interconnected and alternately arranged bent segments and a plurality of stacked segments. After the bent segments are bent, the plurality of positive electrode 223 and the plurality of stacked segments of the negative electrode 224 are alternately stacked to form a stacked electrode assembly 22. For example, the electrode assembly can also be formed by winding the positive electrode 223 and the negative electrode 224 together to form a wound electrode assembly 22. For ease of explanation, the wound electrode assembly 22 is used as an example in the accompanying drawings of the embodiments of this application, but the embodiments of this application are not limited thereto. Furthermore, the electrode assembly 22 may also include a spacer 225 for isolating the positive electrode 223 and the negative electrode 224.

[0117] In this embodiment, the positive electrode 223 includes a positive active material. For example, the positive active material coated on the positive electrode 223 can be used to form a positive active material layer 2231, which can be disposed on at least one side of the surface of the positive current collector 2232. For example, the positive active material layer 2231 can be disposed on both sides of the positive current collector 2232 perpendicular to its thickness direction, but this embodiment is not limited to this.

[0118] In some embodiments, the positive 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 polymeric material substrate and a metal material layer formed on at least one surface of the polymeric material substrate. As an example, the metal material may include one or more of aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. As an example, the polymeric material substrate may include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0119] It should be understood that the positive electrode active material in the embodiments of this application can be flexibly set according to actual applications. 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, wherein the molar amount of nickel in the layered lithium-containing transition metal oxide accounts for more than 50% of the total molar amount of transition metal elements in the layered lithium-containing transition metal oxide. Increasing the molar amount of nickel in the layered lithium-containing transition metal oxide to more than 50% can effectively improve the energy density and cycle life of the battery cell 20, but this proportion should not be set too high, otherwise it will increase the processing difficulty of the electrode assembly 22, and thus increase the processing cost of the battery cell 20.

[0120] Furthermore, the molar proportion of nickel in the layered lithium-containing transition metal oxide can be above 70%, or above 80%, or 90%. This effectively increases the energy density of the battery cell 20 while controlling the processing difficulty of the electrode assembly 22, thereby reducing the processing cost of the battery cell 20.

[0121] In some embodiments, the molar percentage of nickel in the layered lithium-containing transition metal oxide of this application can be set to other values. For example, the molar percentage of nickel in the layered lithium-containing transition metal oxide can be any one of the following values ​​or between any two of the following values: 50%, 53%, 55%, 58%, 60%, 63%, 65%, 68%, 70%, 73%, 75%, 78%, 80%, 83%, 85%, 88%, 90%, 92%, 94%, 96%, and 98%.

[0122] It should be understood that the testing methods for the molar amount of nickel and the total molar amount of transition metal elements in the layered lithium-containing transition metal oxides of this application embodiment can be selected according to actual applications and can be determined using instruments and methods known in the art. For example, the positive electrode active material can be laid and adhered to conductive adhesive to form a sample to be tested with a length × width of 6cm × 1.1cm; the particle morphology can be tested using a scanning electron microscope and energy dispersive spectroscopy (such as ZEISS Sigma 300). The test can refer to JY / T010-1996. To ensure the accuracy of the test results, 20 different regions can be randomly selected in the sample to be tested for scanning, and the content of layered lithium-containing transition metal oxides in each region can be statistically calculated at a certain magnification (e.g., above 1000x). For example, the average value of the test results of the 20 test regions can be taken as the amount of layered lithium-containing transition metal oxides in the positive electrode active material, thereby determining the molar amount of layered lithium-containing transition metal oxides; similarly, the molar amount of nickel in the layered lithium-containing transition metal oxides can also be determined by this method.

[0123] 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. The molar proportion b of nickel in the layered lithium-containing transition metal oxide is set to be 50% or more, i.e., this proportion 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.

[0124] As an example, layered lithium-containing transition metal oxides may include, but are 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.

[0125] In some embodiments, the positive electrode active material may also include other materials. For example, the positive electrode active material may also include a positive electrode conductive agent. This application does not impose any particular limitation 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.

[0126] In some embodiments, the positive electrode active material may further include a positive electrode binder. This application does not impose any particular limitation 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 fluorinated acrylate resins.

[0127] In some embodiments, the positive electrode 223 can be prepared by the following method: the positive electrode active material layer 2231 is typically formed by coating a positive electrode slurry onto a positive electrode current collector 2232, followed by drying and cold pressing. The positive electrode slurry is typically formed by dispersing positive electrode active materials, positive electrode binders, positive electrode conductive agents, etc., in a solvent and stirring them evenly. The solvent can be N-methylpyrrolidone (NMP) or deionized water, but the embodiments of this application are not limited to these.

[0128] The following comparative examples and embodiments provide a clear illustration. Specifically, the battery cell 20 in each of the following embodiments and comparative examples is as follows: Figure 3 and Figure 4 Taking the square-shell battery shown as an example, the casing 211 adopts a hollow structure with one end open.

[0129] In the following embodiments and comparative examples, the preparation methods of the positive electrode 223, negative electrode 224, electrolyte and separator 225 of the battery cell 20 are as follows.

[0130] 1. Preparation of positive electrode 223

[0131] LiNi, the positive electrode active material 0.95 Co 0.04 Mn 0.01 A positive electrode slurry is prepared in N-methylpyrrolidone (NMP) using O2, conductive agent Super P, and binder polyvinylidene fluoride (PVDF). The solid content of the positive electrode slurry is 50 wt%, and the solid component is LiNi. 0.95 Co 0.04 Mn 0.01 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. After cold pressing, the foil is trimmed, cut into sheets, and slit. Then, it is dried under vacuum at 85°C for 4 hours to produce the positive electrode sheet 223.

[0132] 2. Preparation of negative electrode 224

[0133] The negative electrode active material is mixed evenly with the conductive agent Super P, the thickener carboxymethyl cellulose (CMC), and the binder styrene-butadiene rubber (SBR) in deionized water to prepare a negative electrode slurry. 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 30 wt%, and the mass ratio of the negative electrode active material, Super P, CMC, and binder styrene-butadiene rubber (SBR) in the solid components is 88:7:3:2. The negative electrode slurry is coated on the upper and lower surfaces of the current collector copper foil and dried at 85°C. Then, it is cold-pressed, trimmed, cut into sheets, and slit. Finally, it is dried under vacuum at 120°C for 12 hours to prepare the negative electrode sheet 224.

[0134] 3. Preparation of electrolyte

[0135] In an argon atmosphere glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), the thoroughly 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 mixed evenly to obtain an electrolyte with a concentration of 1 mol / L.

[0136] 4. Preparation of the spacer 225

[0137] A 16μm polyethylene film is used as the separator 225.

[0138] 5. Preparation of lithium-ion battery cell 20

[0139] The positive electrode 223, the separator 225, and the negative electrode 224 are stacked in sequence, with the separator 225 positioned between the positive electrode 223 and the negative electrode 224 to isolate the positive and negative electrodes. The bare cell is then wound up, tabs are welded on, and the bare cell is placed in a shell of different materials. The electrolyte prepared above is injected into the dried cell, followed by encapsulation, settling, formation, shaping, and capacity testing to complete the preparation of the lithium-ion battery cell 20.

[0140] In the following embodiments and comparative examples, the melting point of the casing 211 of the battery cell 20 is p, and different materials are selected for the casing 211 to obtain different melting points; the capacity of the battery cell 20 is C; the wall thickness of the wall with the largest area of ​​the battery cell 20 is T. The specific parameter settings are shown in Table 1 below. In addition, in each embodiment and comparative example, the material of all areas of the casing 211 is the same. Furthermore, the battery cells 20 in the following embodiments and comparative examples are identical except for the parameter settings shown in Table 1. 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 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.

[0141] For each of the following comparative examples and embodiments, the battery cell 20 was tested according to the short-circuit test method in section 6.2.4 of "GBT31485-2015 Safety Requirements and Test Methods for Power Batteries for Electric Vehicles". After the test, the integrity of the casing 211 was observed, that is, whether the casing 211 melted.

[0142] Table 1

[0143]

[0144] Comparing the two comparative examples and the six embodiments in Table 1 above, it can be seen that different melting points p can be determined when the casing 211 is made of different materials. When the melting point p satisfies 1200℃≤p≤2000℃, for example, in Embodiments 1-6, the casing 211 of the battery cell 20 does not melt, thus meeting the design requirements of the battery cell 20. Furthermore, even when other parameters of the battery cell 20 fluctuate differently, such as different capacities C of the battery cell 20 or different thicknesses of the wall with the largest area of ​​the casing 211, the battery cell 20 does not melt, thus meeting the design requirements of the battery cell 20. However, when the melting point p does not satisfy 1200℃≤p≤2000℃, for example, in Comparative Examples 1-2, the casing 211 of the battery cell 20 melts, thus failing to meet the design requirements of the battery cell 20.

[0145] It should be understood that the battery cell 20 in this embodiment can also meet other design requirements. Specifically, at least a portion of the housing 211 has a tensile strength of Rn at a temperature of 500°C, where Rn satisfies: 100MPa≤Rn≤1200MPa.

[0146] The positive electrode 223 of this application embodiment is provided with a positive electrode active material that can reversibly extract and insert metal ions. This positive electrode active material can be flexibly configured according to actual applications. For example, the positive electrode active material may include a nickel-containing compound, which can effectively increase the energy density and cycle life of the battery cell 20, but will also increase the gas generated during the use of the battery cell 20. Especially in the event of thermal runaway during the use of the battery cell 20, the internal temperature of the battery cell 20 will increase rapidly and a large amount of gas will be generated.

[0147] Therefore, appropriately increasing the tensile strength Rn of at least a portion of the casing 211 at a high temperature of 500°C can improve the deformation capability of this portion of the casing 211 in the event of thermal runaway of the battery cell 20. This makes the casing 211 less prone to rapid damage and explosion, thereby reducing the risk of thermal runaway of adjacent battery cells 20 and improving the reliability of the battery 10. However, the tensile strength Rn of at least a portion of the casing 211 at high temperature should not be too high, otherwise it will increase the processing difficulty, such as easily scratching the mold and reducing the service life of the mold. Therefore, appropriately reducing the tensile strength Rn can save costs and facilitate processing. For example, the tensile strength Rn can usually be set to satisfy 100MPa≤Rn≤1200MPa.

[0148] It should be understood that the range of tensile strength Rn of at least a portion of the housing 211 in this embodiment at a high temperature of 500°C can be adjusted according to actual applications. For example, the value of the high-temperature tensile strength Rn can satisfy 100MPa≤Rn≤1200MPa. Another example is that 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 capability of this portion of the housing 211 when the battery cell 20 experiences thermal runaway, making the housing 211 less prone to rapid damage and explosion, thereby reducing the risk of thermal runaway in adjacent battery cells 20 and improving the reliability of the battery 10. Simultaneously, controlling the tensile strength Rn of at least a portion of the housing 211 under high-temperature conditions can reduce processing difficulty, thereby saving costs and facilitating processing.

[0149] Furthermore, the high-temperature tensile strength Rn can be set to satisfy 152MPa≤Rn≤480MPa. This can improve the deformation capability of this part of the casing 211 when the battery cell 20 experiences thermal runaway, increase the structural strength of the casing 211, and make the casing 211 less likely to be rapidly destroyed and explode, thereby reducing the risk of thermal runaway of adjacent battery cells 20 and improving the reliability of the battery 10. At the same time, it can also reduce the processing difficulty and save costs.

[0150] In some embodiments, the high-temperature tensile strength Rn of this application can also be set to other values. For example, the high-temperature tensile strength Rn can be any one 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. 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.

[0151] It should be understood that the tensile strength in the embodiments of this application refers to the maximum stress value that the material can withstand before breaking. The test method for the tensile strength Rn of at least a portion of the shell 211 in the embodiments of this application under high temperature conditions of 500°C can be selected according to actual application. For example, the national standard GB / T 228.1-2010 can be used to test the tensile strength Rn under high temperature conditions of 500°C.

[0152] The following comparative examples and embodiments provide a clear illustration. Specifically, the battery cell 20 in each of the following embodiments and comparative examples is as follows: Figure 3 and Figure 4 Taking the square-shell battery shown as an example, the casing 211 adopts a hollow structure with one end open.

[0153] In the following embodiments and comparative examples, the preparation methods of the positive electrode 223, negative electrode 224, electrolyte and separator 225 of the battery cell 20 are as follows.

[0154] 1. Preparation of positive electrode 223

[0155] LiNi, the positive electrode active material 0.95 Co 0.04 Mn 0.01 A positive electrode slurry is prepared in N-methylpyrrolidone (NMP) using O2, conductive agent Super P, and binder polyvinylidene fluoride (PVDF). The solid content of the positive electrode slurry is 50 wt%, and the solid component is LiNi. 0.95 Co 0.04 Mn 0.01The 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. After cold pressing, the foil is trimmed, cut into sheets, and slit. Then, it is dried under vacuum at 85°C for 4 hours to produce the positive electrode sheet 223.

[0156] 2. Preparation of negative electrode 224

[0157] The negative electrode active material is mixed evenly with the conductive agent Super P, the thickener carboxymethyl cellulose (CMC), and the binder styrene-butadiene rubber (SBR) in deionized water to prepare a negative electrode slurry. 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 30 wt%, and the mass ratio of the negative electrode active material, Super P, CMC, and binder styrene-butadiene rubber (SBR) in the solid components is 88:7:3:2. The negative electrode slurry is coated on the upper and lower surfaces of the current collector copper foil and dried at 85°C. Then, it is cold-pressed, trimmed, cut into sheets, and slit. Finally, it is dried under vacuum at 120°C for 12 hours to prepare the negative electrode sheet 224.

[0158] 3. Preparation of electrolyte

[0159] In an argon atmosphere glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), the thoroughly 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 mixed evenly to obtain an electrolyte with a concentration of 1 mol / L.

[0160] 4. Preparation of the spacer 225

[0161] A 16μm polyethylene film is used as the separator 225.

[0162] 5. Preparation of lithium-ion battery cell 20

[0163] The positive electrode 223, the separator 225, and the negative electrode 224 are stacked in sequence, with the separator 225 positioned between the positive electrode 223 and the negative electrode 224 to isolate the positive and negative electrodes. The bare cell is then wound up, tabs are welded on, and the bare cell is placed in a shell of different materials. The electrolyte prepared above is injected into the dried shell, and the process is followed by encapsulation, settling, formation, shaping, and capacity testing to complete the preparation of the lithium-ion battery cell 20.

[0164] In the following embodiments and comparative examples, the tensile strength of the casing 211 of the battery cell 20 at a temperature of 500°C is Rn, and different materials are selected for the casing 211 to obtain different tensile strengths Rn; the capacity of the battery cell 20 is C; and the wall thickness of the wall with the largest area of ​​the battery cell 20 is T. The specific parameter settings are shown in Table 2 below. Furthermore, in each embodiment and comparative example, the material of all areas of the casing 211 is the same, and the tensile strength Rn of the casing 211 at 500°C is measured using the method specified in GB / T 228.1-2010. Moreover, the battery cells 20 in the following embodiments and comparative examples are identical except for the parameter settings shown in Table 2. For example, in various embodiments, the positive electrode active material of the positive electrode 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.

[0165] For each of the following comparative examples and embodiments, the battery cell 20 was tested according to the short-circuit test method in section 6.2.4 of "GBT31485-2015 Safety Requirements and Test Methods for Power Batteries for Electric Vehicles". After the test, the integrity of the casing 211 was observed, that is, whether the casing 211 was cracked.

[0166] Table 2

[0167]

[0168] Comparing the two comparative examples and the six embodiments in Table 2 above, it can be seen that different tensile strengths Rn can be determined when the casing 211 is made of different materials. When the tensile strength Rn satisfies 100MPa≤Rn≤1200MPa, for example, in Embodiments 1-6, the casing 211 of the battery cell 20 does not crack, thus meeting the design requirements of the battery cell 20. Furthermore, even when other parameters of the battery cell 20 fluctuate, such as different capacities C or different thicknesses of the wall with the largest area of ​​the casing 211, the battery cell 20 does not crack, thus meeting the design requirements. However, when the tensile strength Rn does not satisfy 100MPa≤Rn≤1200MPa, for example, in Comparative Examples 1-2, the casing 211 of the battery cell 20 cracks, thus failing to meet the design requirements of the battery cell 20.

[0169] In some embodiments, the electrode assembly 22 further includes a negative electrode sheet 224, which comprises a negative electrode active material capable of reversibly extracting and inserting metal ions, the negative electrode active material comprising a silicon-based material; the tensile strength Rm of at least a portion of the housing 211 at a temperature of 25°C satisfies: 250MPa≤Rm≤2000MPa. Increasing the tensile strength Rm of at least a portion of the housing 211 at room temperature (25°C) can improve the deformability of this portion of the housing 211, making it less prone to breakage 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 room temperature should not be too large, in order to reduce the difficulty of material selection and processing of the housing 211, save costs, and facilitate processing. For example, the tensile strength Rm of at least a portion of the housing 211 at room temperature can typically be set to satisfy 250MPa≤Rm≤2000MPa.

[0170] It should be understood that the range of tensile strength Rm of at least a portion of the housing 211 in this embodiment at room temperature (25°C) can be adjusted according to actual application. For example, the room temperature tensile strength Rm can satisfy 250MPa≤Rm≤2000MPa. Alternatively, it can satisfy 400MPa≤Rm≤1200MPa. On the one hand, increasing the tensile strength Rm of at least a portion of the housing 211 at room temperature can improve the deformation capacity of that portion of the housing 211 to resist the expansion of the electrode assembly 22, making that portion of the housing 211 less prone to damage, thereby improving the structural stability and service life of the battery cell 20. On the other hand, controlling the tensile strength Rm of at least a portion of the housing 211 at room temperature to prevent it from becoming excessive can reduce the difficulty of material selection and processing for the housing 211, saving costs and facilitating processing.

[0171] Furthermore, the tensile strength Rm of at least a portion of the housing 211 under normal temperature conditions can be set to satisfy 450MPa≤Rm≤800MPa. The tensile strength Rm of at least a portion of the housing 211 under normal temperature conditions will not be too large or too small, which can improve the deformation capacity of this portion of the housing 211 to resist the expansion of the electrode assembly 22, while also being easy to implement and cost-effective.

[0172] In some embodiments, the tensile strength Rm of at least a portion of the shell 211 under normal temperature conditions in this application embodiment can also be set to other values. For example, the value of the room temperature tensile strength Rm can be any one 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, 1 000MPa, 1050MPa, 1100MPa, 1150MPa, 1200MPa, 1250MPa, 1300MPa, 1350MPa, 1400MPa, 1450MPa, 1500MPa, 1550MPa, 1600MPa, 1650MPa, 1700MPa, 1750MPa, 1800MPa, 1850MPa, 1900MPa, 1950MPa, and 2000MPa.

[0173] It should be understood that the tensile strength in the embodiments of this application refers to the maximum stress value that the material can withstand before breaking. The test method for the tensile strength Rm of at least a portion of the shell 211 in the embodiments of this 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 room temperature of 25°C.

[0174] In this embodiment, the negative electrode 224 includes a negative electrode active material. For example, the negative electrode active material coated on the negative electrode 224 can be used to form a negative electrode active material layer 2241, which can be disposed on at least one side of the surface 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 its thickness direction.

[0175] In some embodiments, the negative electrode current collector 2242 may be a metal foil or a composite current collector. Examples of metal foils include copper foil, copper alloy foil, aluminum foil, and aluminum alloy foil. The composite current collector may include a polymer substrate and a metal material layer formed on at least one surface of the polymer substrate. Examples of metal materials include one or more of copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. Examples of polymer substrates include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0176] It should be understood that the negative electrode active material in the embodiments of this application can be flexibly configured according to actual applications. Specifically, the negative electrode active material in the embodiments of this application may include silicon-based materials, thereby improving the energy density of the battery. For example, silicon-based materials may include at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, silicon-containing alloys, or silicon-oxygen-carbon composite materials.

[0177] In some embodiments, the silicon-based material may include silicon and one or more of alkali metals and alkaline earth metals. For example, the alkali metal may include Li. For example, the alkaline earth metal may include Mg. For example, the silicon-based material may be a silicon-based material pre-intercalated with alkali metals and / or alkaline earth metals, such as a silicon-based material pre-intercalated with Li and / or Mg.

[0178] It should be understood that the mass percentage g of the silicon-based material in the embodiments of this application can be flexibly set according to actual applications.

[0179] For example, the mass percentage g of the silicon-based material can be set to satisfy 2% ≤ g ≤ 40%. Adding silicon-based material to the negative electrode active material of the negative electrode sheet 224 can effectively improve the energy density of the battery cell 20 because 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. However, the mass percentage g of the silicon-based material should not be set too high, otherwise it will increase the processing difficulty of the electrode assembly 22 and also increase the deformation of the electrode assembly 22 within the battery cell 20 during use. Especially during the charging process of the battery cell 20, the embedding of metal ions into the silicon-based material of the negative electrode sheet 224 causes the electrode assembly 22 to expand in volume, thereby increasing the pressure of the electrode assembly 22 on the casing 211 of the battery cell 20, and further increasing the processing difficulty of the battery cell 20.

[0180] Furthermore, the mass percentage g of the silicon-based material can be set to satisfy 8% ≤ g ≤ 40%. Appropriately reducing the mass percentage g of the silicon-based material can reduce the processing difficulty of the electrode assembly 22, and also reduce the deformation of the electrode assembly 22 during the charging and discharging of the battery cell 20, that is, reduce the volume expansion of the electrode assembly 22. This reduces the pressure of the electrode assembly 22 on the casing 211 of the battery cell 20, lowers the structural strength requirements of the casing 211, facilitates processing, and reduces costs.

[0181] Furthermore, the mass percentage g of the silicon-based material can be set to satisfy 10% ≤ g ≤ 30%. By reasonably adjusting the mass percentage g of the silicon-based material, the energy density of the battery cell 20 can be effectively increased, the processing difficulty of the electrode assembly 22 can be reduced, and the deformation of the electrode assembly 22 during the charging and discharging process of the battery cell 20 can be effectively reduced, thereby reducing the structural strength requirements of the casing 211.

[0182] In some embodiments, the mass percentage g of the silicon-based material in this application embodiment can be set to other values. For example, the mass percentage g of the silicon-based material can be any one of the following values ​​or between any two of the following values: 5%, 8%, 10%, 13%, 15%, 18%, 20%, 23%, 25%, 28%, 30%, 33%, 35%, 38%, 40%, 43%, 45%, 48%, and 50%.

[0183] It should be understood that the mass percentage g of silicon-based material in the negative electrode active material of this application embodiment represents the ratio of the mass of silicon-based material to the total mass of the negative electrode active material. The test method for the mass percentage g of silicon-based material can be selected according to the actual application and can be tested using methods known in the art.

[0184] In the embodiments of this 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, waterborne acrylic resins (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 embodiments of this application are not limited thereto.

[0185] In some embodiments, the negative electrode active material may further include a negative electrode conductive agent. This application does not impose any particular limitation on the type of 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.

[0186] In some embodiments, the negative electrode active material may also include other additives. As an example, other additives may include thickeners, such as sodium carboxymethyl cellulose (CMC), PTC thermistor materials, etc.

[0187] The negative electrode 224 does not exclude other additional functional layers besides the negative electrode active material layer 2241. For example, in some embodiments, the negative electrode 224 may also include a conductive undercoating (e.g., composed of a conductive agent and an adhesive) 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 224 may also include a protective layer covering the surface of the negative electrode active material layer 2241.

[0188] In some embodiments, the negative electrode 224 can be prepared by dispersing the negative electrode active material, optional negative electrode binder, optional negative electrode conductive agent, and optional other additives in a solvent and stirring until homogeneous to form a negative electrode slurry; coating the negative electrode slurry onto the negative electrode current collector 2242, and after drying, cold pressing, and other processes, forming the negative electrode 224. The solvent can be N-methylpyrrolidone (NMP) or deionized water, but the embodiments of this application are not limited to these.

[0189] In this embodiment, the mass percentage (g) of the silicon-based material and the tensile strength (Rm) of at least a portion of the casing 211 at 25°C can be mutually constrained 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 percentage of the silicon-based material is g, and the material of at least a portion of the casing 211 includes iron. Rm and g satisfy 2% ≤ g ≤ 40%, and 300 MPa < Rm < 2000 MPa. The inclusion of iron in the material of at least a portion of the casing 211 can increase the structural strength of that portion of the casing 211 to meet design requirements.

[0190] In some embodiments, at least a portion of the housing 211 is made of carbon steel or stainless steel, with Rm and g satisfying 2.5% ≤ g ≤ 15% and 315 MPa ≤ Rm < 800 MPa. 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 tensile strength Rm value under 25°C conditions.

[0191] In some embodiments, at least a portion of the housing 211 is made of carbon steel or stainless steel, with Rm and g satisfying 4.5% ≤ g ≤ 40% and 380 MPa ≤ Rm < 2000 MPa. 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 tensile strength Rm value under 25°C conditions.

[0192] In some embodiments, Rm and g satisfy 8% ≤ g ≤ 40%, and 400 MPa ≤ Rm < 2000 MPa. For example, the material of at least a portion of the housing 211 may include modified stainless steel, which is easy to process and can meet the value of tensile strength Rm at 25°C.

[0193] In some embodiments, Rm and g satisfy 10%≤g≤40% and 480MPa≤Rm<2000MPa. For example, at least a portion of the material of the housing 211 may include 316 stainless steel, which is easy to process and can meet the value of tensile strength Rm under 25°C conditions.

[0194] In some embodiments, Rm and g satisfy 15%≤g≤40%, 520MPa≤Rm<2000MPa. For example, the material of at least a portion of the housing 211 may include 304 stainless steel, which is easy to process and can meet the value of tensile strength Rm under 25°C conditions.

[0195] In some embodiments, Rm and g satisfy 20%≤g≤40% and 600MPa≤Rm<2000MPa.

[0196] The following comparative examples and embodiments provide a clear illustration. Specifically, the battery cell 20 in each of the following embodiments and comparative examples is as follows: Figure 3 and Figure 4 Taking the square-shell battery shown as an example, the casing 211 adopts a hollow structure with one end open.

[0197] In the following embodiments and comparative examples, the preparation methods of the positive electrode 223, negative electrode 224, electrolyte and separator 225 of the battery cell 20 are as follows.

[0198] 1. Preparation of positive electrode 223

[0199] LiNi, the positive electrode active material 0.95 Co 0.04 Mn 0.01 A positive electrode slurry is prepared in N-methylpyrrolidone (NMP) using O2, conductive agent Super P, and binder polyvinylidene fluoride (PVDF). The solid content of the positive electrode slurry is 50 wt%, and the solid component is LiNi. 0.95 Co 0.04 Mn 0.01 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. After cold pressing, the foil is trimmed, cut into sheets, and slit. Then, it is dried under vacuum at 85°C for 4 hours to produce the positive electrode sheet 223.

[0200] 2. Preparation of negative electrode 224

[0201] The negative electrode active material is mixed evenly with the conductive agent Super P, the thickener carboxymethyl cellulose (CMC), and the binder styrene-butadiene rubber (SBR) in deionized water to prepare a negative electrode slurry. 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 30 wt%, and the mass ratio of the negative electrode active material, Super P, CMC, and binder styrene-butadiene rubber (SBR) in the solid components is 88:7:3:2. The negative electrode slurry is coated on the upper and lower surfaces of the current collector copper foil and dried at 85°C. Then, it is cold-pressed, trimmed, cut into sheets, and slit. Finally, it is dried under vacuum at 120°C for 12 hours to prepare the negative electrode sheet 224.

[0202] 3. Preparation of electrolyte

[0203] In an argon atmosphere glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), the thoroughly 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 mixed evenly to obtain an electrolyte with a concentration of 1 mol / L.

[0204] 4. Preparation of the spacer 225

[0205] A 16μm polyethylene film is used as the separator 225.

[0206] 5. Preparation of lithium-ion battery cell 20

[0207] The positive electrode 223, the separator 225, and the negative electrode 224 are stacked in sequence, with the separator 225 positioned between the positive electrode 223 and the negative electrode 224 to isolate the positive and negative electrodes. The bare cell is then wound up, tabs are welded on, and the bare cell is placed in a shell of different materials. The electrolyte prepared above is injected into the dried shell, and the process is followed by encapsulation, settling, formation, shaping, and capacity testing to complete the preparation of the lithium-ion battery cell 20.

[0208] In the following embodiments and comparative examples, the tensile strength Rm of the casing 211 of the battery cell 20 at a temperature of 25°C is used, and different materials are selected for the casing 211 to obtain different tensile strengths Rm. The negative electrode active material of the negative electrode plate 224 of the electrode assembly 22 of the battery cell 20 includes silicon-based material, and the mass percentage of silicon-based material is g. The specific parameter settings are shown in Table 3 below. In addition, in each embodiment and comparative example, the material of all areas of the casing 211 is the same, and the tensile strength Rm of the casing 211 at 25°C is measured using the method specified in GB / T 228.1-2010. Furthermore, the battery cells 20 in the following embodiments and comparative examples are the same except for the parameter settings shown in Table 3. For example, the wall thickness of each wall of the casing 211 of the battery cell 20 in each embodiment is 0.25 mm; and for another example, the capacity of the battery cell 20 in each embodiment is 350 Ah.

[0209] Cyclic charging fatigue tests were performed on the battery cells 20 in the following embodiments and comparative examples. Specifically, Figure 7 A schematic diagram of the structure of a fixture 700 for cyclic charging fatigue testing according to an embodiment of this application is shown. Figure 7 As shown, the clamp 700 comprises three 10mm thick steel plates, which completely cover the largest wall of the battery cell 20. For ease of explanation, the three clamping steel plates are sequentially defined as the first steel plate 710, the second steel plate 720, and the third steel plate 730. The first steel plate 710 and the third steel plate 730 are located at both ends of the clamp 700 and are fixed together by bolts. The second steel plate 720 in the middle is constrained by guide rails, allowing it to move only in a direction perpendicular to its large surface area. 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 in contact with 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 compressive 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.

[0210] Specifically, the battery cell 20 is clamped and fixed in the special fixture 700 to ensure that the two walls of the battery cell 20 with the largest relative area are clamped, and the initial pressure is set to 2000N. The electrode terminals 214 of the battery cell 20 are then connected to a special battery charging and discharging device.

[0211] The clamp 700 holding the battery cell 20 is placed in a constant temperature environment of 25±2℃, and the test is started after the battery cell 20 reaches temperature equilibrium.

[0212] The specific test procedures shall be performed in accordance with the "Standard Cycle Life" section 6.4 of "GBT31484-2015 Requirements and Test Methods for Cycle Life of Power Batteries for Electric Vehicles", and the test cycle cutoff condition shall be changed to "the test shall be stopped until the weld 2113 of the battery cell 20 is damaged".

[0213] For example, the test can be performed according to the following steps: Step a, discharge at 1I(A) to the discharge termination condition specified by the company; Step b, rest for not less than 30 minutes or the resting condition specified by the company; Step c, charge according to the method in 6.1.1.3; Step d, rest for not less than 30 minutes or the resting condition specified by the company; Step e, discharge at 1I1(A) to the discharge termination condition specified by the company; Step f, repeat steps b to e until the weld 2113 breaks and the test is stopped.

[0214] During the above testing process, the weld 2113 of the battery cell 20 was continuously observed until leakage occurred at the weld 2113. The number of cycles was recorded to obtain the condition of the housing 211 after 1000 cycles, as shown in Table 3 below. In the following embodiments and comparative examples, the weld 2113 refers to the weld between the housing 211 and the cover plate 212, that is, the weld 2113 surrounds the open end of the housing 211, and the housing 211 adopts an integral molding structure.

[0215] Table 3

[0216]

[0217] It should be understood that, in Table 3 above, the material of the shell 211 can be Q195 carbon steel, and the tensile strength Rm of Q195 carbon steel at room temperature of 25°C is usually at least 315MPa to 430MPa. The above embodiment only uses 328MPa as an example, but it 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 typically at least 380MPa to 430MPa, with 396MPa being used 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 typically at least 400MPa to 600MPa, with 421MPa being used 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 typically at least 450MPa, with 459MPa being used 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 typically at least 520MPa, with 533MPa and 625MPa being used as examples in the above embodiment.

[0218] Comparing the two comparative examples in Table 3 with the 12 embodiments, it can be seen that different tensile strengths Rm can be determined when the shell 211 is made of different materials. When the tensile strength Rm satisfies 250MPa≤Rm≤2000MPa, for example, in Embodiments 1-12, even if the mass percentage g of silicon-based material in the negative electrode 224 of the battery cell 20 is different, the failure fatigue cycles of the battery cell 20 can still reach over one thousand, thus meeting 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 percentage g of silicon-based material in the negative electrode 224 of the battery cell 20 is low, the failure fatigue cycles of the battery cell 20 do not reach one thousand, failing to meet the design requirements of the battery cell 20.

[0219] In some embodiments, the electrode assembly 22 further includes a negative electrode 224, which includes a negative electrode active material capable of reversibly extracting and embedding metal ions, the negative electrode active material including a silicon-based material; at least a portion of the housing 211 has a yield strength of Re at a temperature of 25°C, Re satisfying: 140MPa≤Re≤1000MPa.

[0220] Increasing the yield strength Re of at least a portion of the casing 211 at room temperature can improve the deformation capacity of the casing 211, thereby improving the structural stability and service life of the battery cell 20. During the charging and discharging process of the battery cell 20, when the electrode assembly 22 undergoes cyclic expansion and contraction, increasing the yield strength Re of at least a portion of the casing 211 at room temperature can increase the maximum compressive force that the casing 211 can withstand. Without exceeding the limit of the yield strength of the casing 211, the casing 211 is less likely to be damaged, and its deformation can be recovered, thus improving its service life. However, the yield strength Re of at least a portion of the casing 211 at room temperature should not be too large to reduce the difficulty of material selection and processing, saving costs and facilitating manufacturing. For example, the yield strength Re of at least a portion of the casing 211 at room temperature can typically be set to satisfy: 140MPa ≤ Re ≤ 1000MPa.

[0221] It should be understood that the range of yield strength Re of at least a portion of the housing 211 in this embodiment at room temperature (25°C) can be adjusted according to actual applications. For example, the room temperature yield strength Re can satisfy 140MPa≤Re≤1000MPa. Another example is that the room temperature yield strength Re can satisfy 180MPa≤Re≤600MPa. On the one hand, increasing the yield strength Re of at least a portion of the housing 211 at room temperature can improve the deformability of that portion of the housing 211 to resist the expansion of the electrode assembly 22, making that portion of the housing 211 less prone to damage. Furthermore, if the expansion of the electrode assembly 22 decreases without exceeding the limit of the yield strength of the housing 211, the deformation of the housing 211 can recover, 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 a portion of the housing 211 at room temperature will not be too large, which can reduce the difficulty of material selection and processing of the housing 211, saving costs and facilitating processing.

[0222] Furthermore, the yield strength Re of at least a portion of the housing 211 under normal temperature conditions can be set to satisfy 220MPa≤Re≤400MPa. The yield strength Re of at least a portion of the housing 211 under normal temperature conditions will not be too large or too small, which can improve the deformation capacity of this part of the housing 211 to resist the expansion of the electrode assembly 22, and is easy to implement and cost-effective.

[0223] In some embodiments, the yield strength Re of at least a portion of the shell 211 under normal temperature conditions can be set to other values. For example, the room temperature yield strength Re can be any one 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.

[0224] It should be understood that the yield strength in the embodiments of this application can be understood as the critical stress value at which the material yields. 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. Furthermore, the yield strength in the embodiments of this application generally refers to the upper yield strength, that is, the upper yield strength Re of at least a portion of the shell 211 at a temperature of 25°C.

[0225] The method for testing the yield strength Re of at least a portion of the housing 211 in this embodiment at a temperature of 25°C can be selected according to the actual application. For example, the yield strength Re can be tested at room temperature of 25°C using the national standard GB / T 228.1-2010.

[0226] In the embodiments of this application, the value of the mass ratio g of silicon-based material and the value of the yield strength Re of at least a portion of the casing 211 at a temperature of 25°C can be mutually restricted to improve the structural strength of the casing 211 while increasing the energy density of the battery cell 20, thereby improving the structural strength and service life of the battery cell 20.

[0227] For example, in the negative electrode active material, the mass percentage of silicon-based material is g, and g and Re satisfy: 2% ≤ g ≤ 40%, 140 MPa < Re < 600 MPa. Adding silicon-based material to the negative electrode active material of the negative electrode sheet 224 can effectively improve the energy density of the battery cell 20 because 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. However, the mass percentage g of this silicon-based material should not be set too high, otherwise it will increase the processing difficulty of the electrode assembly 22 and also increase the deformation of the electrode assembly 22 within the battery cell 20 during use. Especially during the charging process of the battery cell 20, the embedding of metal ions into the silicon-based material of the negative electrode sheet will cause the electrode assembly 22 to expand in volume, thereby increasing the pressure of the electrode assembly 22 on the casing 211 of the battery cell 20, and further increasing the processing difficulty of the battery cell 20. Therefore, the yield strength Re of at least a portion of the housing 211 under normal temperature conditions can be appropriately increased to improve the deformation capacity of this portion of the housing 211, thereby resisting the expansion of the electrode assembly 22 and making this portion of the housing 211 less prone to damage. Furthermore, if the expansion of the electrode assembly 22 decreases without exceeding the limit of the yield strength of the housing 211, the deformation of the housing 211 can recover, thus improving the structural stability and service life of the battery cell 20. In addition, controlling the yield strength Re of at least a portion of the housing 211 under normal temperature conditions should not be too large, which can reduce the difficulty of material selection and processing of the housing 211, saving costs and facilitating processing.

[0228] In some embodiments, at least a portion of the housing 211 is made of carbon steel or stainless steel, where g and Re satisfy 4.5% ≤ g ≤ 40% and 170 MPa ≤ Re < 600 MPa. For example, at least a portion of the housing 211 may be made of SPCC carbon steel, which is easy to process and meets the required yield strength Re at 25°C.

[0229] In some embodiments, g and Re satisfy 8% ≤ g ≤ 40%, and 180 MPa ≤ Re < 600 MPa. For example, the material of at least a portion of the housing 211 may include modified stainless steel, which is easy to process and meets the yield strength Re value at 25°C.

[0230] In some embodiments, g and Re satisfy 10% ≤ g ≤ 40% and 190 MPa ≤ Re < 600 MPa. For example, the material of at least a portion of the housing 211 may include 316 stainless steel, which is easy to process and meets the yield strength Re value under 25°C conditions.

[0231] In some embodiments, g and Re satisfy 15% ≤ g ≤ 40% and 200 MPa ≤ Re < 600 MPa. For example, the material of at least a portion of the housing 211 may include 304 stainless steel, which is easy to process and meets the yield strength Re value under 25°C conditions.

[0232] In some embodiments, g and Re satisfy 20%≤g≤40% and 210MPa≤Re<600MPa.

[0233] The following comparative examples and embodiments provide a clear illustration. Specifically, the battery cell 20 in each of the following embodiments and comparative examples is as follows: Figure 3 and Figure 4 Taking the square-shell battery shown as an example, the casing 211 adopts a hollow structure with one end open.

[0234] In the following embodiments and comparative examples, the preparation methods of the positive electrode 223, negative electrode 224, electrolyte and separator 225 of the battery cell 20 are as follows.

[0235] 1. Preparation of positive electrode 223

[0236] LiNi, the positive electrode active material 0.95 Co 0.04 Mn 0.01 A positive electrode slurry is prepared in N-methylpyrrolidone (NMP) using O2, conductive agent Super P, and binder polyvinylidene fluoride (PVDF). The solid content of the positive electrode slurry is 50 wt%, and the solid component is LiNi.0.95 Co 0.04 Mn 0.01 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. After cold pressing, the foil is trimmed, cut into sheets, and slit. Then, it is dried under vacuum at 85°C for 4 hours to produce the positive electrode sheet 223.

[0237] 2. Preparation of negative electrode 224

[0238] The negative electrode active material is mixed evenly with the conductive agent Super P, the thickener carboxymethyl cellulose (CMC), and the binder styrene-butadiene rubber (SBR) in deionized water to prepare a negative electrode slurry. 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 30 wt%, and the mass ratio of the negative electrode active material, Super P, CMC, and binder styrene-butadiene rubber (SBR) in the solid components is 88:7:3:2. The negative electrode slurry is coated on the upper and lower surfaces of the current collector copper foil and dried at 85°C. Then, it is cold-pressed, trimmed, cut into sheets, and slit. Finally, it is dried under vacuum at 120°C for 12 hours to prepare the negative electrode sheet 224.

[0239] 3. Preparation of electrolyte

[0240] In an argon atmosphere glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), the thoroughly 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 mixed evenly to obtain an electrolyte with a concentration of 1 mol / L.

[0241] 4. Preparation of the spacer 225

[0242] A 16μm polyethylene film is used as the separator 225.

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

[0244] The positive electrode 223, the separator 225, and the negative electrode 224 are stacked in sequence, with the separator 225 positioned between the positive electrode 223 and the negative electrode 224 to isolate the positive and negative electrodes. The bare cell is then wound up, tabs are welded on, and the bare cell is placed in a shell of different materials. The electrolyte prepared above is injected into the dried shell, and the process is followed by encapsulation, settling, formation, shaping, and capacity testing to complete the preparation of the lithium-ion battery cell 20.

[0245] In the following embodiments and comparative examples, the yield strength Re of the casing 211 of the battery cell 20 at a temperature of 25°C is denoted as Re, and different materials are selected for the casing 211 to obtain different yield strengths Re. The negative electrode active material of the negative electrode plate 224 of the electrode assembly 22 of the battery cell 20 includes silicon-based material, and the mass percentage of silicon-based material is g. The specific parameter settings are shown in Table 4 below. In addition, in each embodiment and comparative example, the material of all areas of the casing 211 is the same, and the yield strength Re of the casing 211 at 25°C is measured using the method specified in GB / T 228.1-2010. Furthermore, the battery cells 20 in the following embodiments and comparative examples are identical except for the parameter settings shown in Table 4. For example, the wall thickness of each wall of the casing 211 of the battery cell 20 in each embodiment is 0.25 mm; and for another example, the capacity of the battery cell 20 in each embodiment is 350 Ah.

[0246] Cyclic charging fatigue tests were performed on the battery cells 20 in the following embodiments and comparative examples. Specifically, methods such as... Figure 7 The fixture 700 shown is used for cyclic charging fatigue testing.

[0247] Specifically, the battery cell 20 is clamped and fixed in the special fixture 700 to ensure that the two walls of the battery cell 20 with the largest relative area are clamped, and the initial pressure is set to 2000N. The electrode terminals 214 of the battery cell 20 are then connected to a special battery charging and discharging device.

[0248] The clamp 700 holding the battery cell 20 is placed in a constant temperature environment of 25±2℃, and the test is started after the battery cell 20 reaches temperature equilibrium.

[0249] The specific test procedures shall be performed in accordance with the "Standard Cycle Life" section 6.4 of "GBT31484-2015 Requirements and Test Methods for Cycle Life of Power Batteries for Electric Vehicles", and the test cycle cutoff condition shall be changed to "the test shall be stopped until the weld 2113 of the battery cell 20 is damaged".

[0250] For example, the test can be performed according to the following steps: Step a, discharge at 1I(A) to the discharge termination condition specified by the company; Step b, rest for not less than 30 minutes or the resting condition specified by the company; Step c, charge according to the method in 6.1.1.3; Step d, rest for not less than 30 minutes or the resting condition specified by the company; Step e, discharge at 1I1(A) to the discharge termination condition specified by the company; Step f, repeat steps b to e until the weld 2113 breaks and the test is stopped.

[0251] During the above testing process, the weld 2113 of the battery cell 20 was continuously observed until leakage occurred at the weld 2113. The number of cycles was recorded to obtain the failure fatigue condition of the housing 211 after 1000 cycles, as shown in Table 4 below. In the following embodiments and comparative examples, the weld 2113 refers to the weld between the housing 211 and the cover plate 212, that is, the weld 2113 surrounds the open end of the housing 211, and the housing 211 adopts an integral molding structure.

[0252] Table 4

[0253]

[0254] It should be understood that, in Table 4 above, the material of the shell 211 can be modified stainless steel, and the yield strength Re of modified stainless steel at room temperature (25°C) is typically at least 140 MPa to 180 MPa. The above embodiments only use 145 MPa and 173 MPa as examples, but are not limited to these. 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 typically at least 177 MPa. The above embodiments only use 182 MPa and 193 MPa 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 typically at least 195 MPa. The above embodiments only use 203 MPa 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 typically at least 205 MPa. The above embodiments only use 212 MPa as an example.

[0255] Comparing the two comparative examples in Table 4 with the 12 embodiments, it can be seen that different yield strengths Re can be determined when the shell 211 is made of different materials. When the yield strength Re satisfies 140MPa≤Re≤1000MPa, for example, in Embodiments 1-12, even if the mass percentage g of silicon-based material in the negative electrode 224 of the battery cell 20 is different, the failure fatigue cycles of the battery cell 20 can still reach over one thousand, thus meeting 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 percentage g of silicon-based material in the negative electrode 224 of the battery cell 20 is low, the failure fatigue cycles of the battery cell 20 do not reach one thousand, failing to meet the design requirements of the battery cell 20.

[0256] It should be understood that at least a portion of the housing 211 in the embodiments of this application may include a local area of ​​the housing 211, or it may include the entire area of ​​the housing 211. In some embodiments, the housing 211 includes a weld 2113, and at least a portion of the housing 211 includes the area of ​​the housing 211 within a predetermined distance from the weld 2113, the predetermined distance being L, where L satisfies: L=10mm. When the negative electrode active material of the negative electrode sheet 224 of the electrode assembly 22 includes a silicon-based material, since the silicon-based material can accommodate more metal ions, it will increase the deformation of the electrode assembly 22 within the battery cell 20 during use, causing the electrode assembly 22 to expand in volume, thereby increasing the pressure of the electrode assembly 22 on the housing 211 of the battery cell 20. Under the same conditions, the structural strength of the area of ​​the housing 211 near the weld 2113 is relatively lower than the structural strength of other areas of the housing 211, so the area of ​​the housing 211 near the weld 2113 is more likely to break 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 near 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.

[0257] When the positive electrode active material of the positive electrode 223 of the electrode assembly 22 includes a nickel-containing compound, if the battery cell 20 experiences thermal runaway, the internal temperature of the battery cell 20 will increase rapidly and generate a large amount of gas. Under the same conditions, the structural strength of the area of ​​the casing 211 near the weld 2113 is relatively lower than that of other areas of the casing 211. Therefore, the casing 211 is prone to cracking in the area near the weld 2113, which may lead to thermal runaway of the connected battery cells 20, i.e., 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 casing 211, making this part less likely to be rapidly damaged or completely melted, reducing the risk of thermal diffusion or even explosion between multiple battery cells 20, thereby improving the reliability of the battery 10.

[0258] It should be understood that the weld 2113 included in the housing 211 of this application embodiment can include welds 2113 at any location on the housing 211. For example, the weld 2113 included in the housing 211 can include the weld between the housing 211 and the cover plate 212, that is, the area surrounding the open end of the housing 211 is the weld. As another example, the weld 2113 of the housing 211 can also include welds between different parts of the housing 211. For example, the housing 211 can include at least two parts, which are connected by welding to form the housing 211. Figure 4 Taking the casing 211 as an example, which comprises two parts along the height direction Z of the battery cell 20, a weld 2113 is provided between the upper and lower casing parts; or, unlike... Figure 4 As shown, other parts of the housing 211 may also be provided with welds 2113, but the embodiments of this application are not limited thereto.

[0259] In some embodiments, at least a portion of the housing 211 includes a surrounding region 2111 that surrounds the electrode assembly 22, and the surrounding region 2111 is at least a portion of the sidewall of the housing 211. Thus, when the negative electrode active material of the negative electrode sheet 224 of the electrode assembly 22 includes a silicon-based material, the silicon-based material can accommodate more metal ions, increasing the deformation of the electrode assembly 22 within the battery cell 20 during use, causing the electrode assembly 22 to expand in volume, thereby increasing the pressure exerted by the electrode assembly 22 on the housing 211 of the battery cell 20. Therefore, by providing a surrounding region 2111 that meets the requirements of tensile strength Rm or yield strength Re under normal temperature conditions, the deformation capacity of the housing 211 can be improved. Furthermore, the surrounding region 2111, which surrounds the electrode assembly 22, can limit the radial compressive force exerted by the internal electrode assembly 22 on the housing 211, making the housing 211 less prone to breakage, thereby improving the structural stability and service life of the battery cell 20.

[0260] If the positive electrode active material of the positive electrode 223 of the electrode assembly 22 includes a nickel-containing compound, and the battery cell 20 experiences thermal runaway, the internal temperature of the battery cell 20 will increase rapidly and generate a large amount of gas. If the surrounding region 2111 meets the requirements of tensile strength Rn or melting point p under high temperature conditions, the deformation capability of the surrounding region 2111 of the housing 211 can be improved, making the surrounding region 2111 less likely to be rapidly destroyed or completely melted. This can limit the excessive expansion of the electrode assembly 22 inside the housing 211 along its thickness direction, reduce the possibility of the battery cell 20 exploding, and thus reduce the risk of thermal runaway of adjacent battery cells 20, thereby improving the reliability of the battery 10.

[0261] It should be understood that the position and size of the surrounding region 2111 in this embodiment can be flexibly set according to actual applications. For example, along the height direction Z of the battery cell 20, the height of the surrounding region 2111 can be less than or equal to the height of the housing 211. Specifically, if the height of the surrounding region 2111 is less than the height of the housing 211 along the height direction Z of the battery cell 20, then the surrounding region 2111 can be located at any position of the housing 211 along the height direction Z of the battery cell 20. For example, the surrounding region 2111 can be located at the center of the housing 211 along the height direction Z of the battery cell 20 to limit the deformation of the corresponding center position of the electrode assembly 22.

[0262] If the height of the surrounding area 2111 is equal to the height of the housing 211 along the height direction Z of the battery cell 20, then the surrounding area 2111 includes all the sidewalls of the housing 211 and can wrap around the side of the electrode assembly 22, thereby improving the structural strength of the sidewalls of the housing 211 and reducing the risk of the battery cell 20 exploding and causing thermal diffusion due to the destruction of local weak areas of the sidewalls of the housing 211, thereby improving the reliability of the battery 10.

[0263] 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 this embodiment can refer to the entire area of ​​the housing 211. Thus, when the negative electrode active material of the negative electrode sheet 224 of the electrode assembly 22 includes a silicon-based material, the silicon-based material can accommodate more metal ions, increasing the deformation of the electrode assembly 22 within the battery cell 20 during use. This causes the electrode assembly 22 to expand in volume, thereby increasing the pressure exerted by the electrode assembly 22 on the housing 211 of the battery cell 20. Therefore, ensuring that all areas of the housing 211 meet the requirements for tensile strength Rm or yield strength Re under normal temperature conditions can improve the overall deformation capacity of the housing 211 and limit the compressive force exerted by the internal electrode assembly 22 on the housing 211 in all directions. This results in balanced strength across all parts of the housing 211, reducing the likelihood of breakage in locally weak areas, thereby improving the structural stability and service life of the battery cell 20.

[0264] When the positive electrode active material of the positive electrode 223 of the electrode assembly 22 includes a nickel-containing compound, if the battery cell 20 experiences thermal runaway, the internal temperature of the battery cell 20 will increase rapidly and a large amount of gas will be generated. However, if the entire area of ​​the casing 211 meets the requirements of tensile strength Rn or melting point p under high temperature conditions, the overall deformation capability of the casing 211 can be improved, making the casing 211 less likely to be damaged or melted. This can limit the high temperature and high pressure gas inside the casing 211, reduce the impact on the connected battery cells 20, and thus reduce the risk of thermal runaway of adjacent battery cells 20, thereby improving the reliability of the battery 10.

[0265] Furthermore, the cover plate 212 of this application embodiment may be made of the same material as at least a portion of the shell 211 of this application embodiment, 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 above requirements for tensile strength Rm and yield strength Re under normal temperature conditions, tensile strength Rn under high temperature conditions, and melting point p, so as to improve the structural strength of the cover plate 212 and thereby improve the structural stability of the battery cell 20, but this application embodiment is not limited to this.

[0266] In some embodiments, at least a portion of the housing 211 has a tensile strength of Rm at a temperature of 25°C, and at least a portion of the housing 211 includes a third housing wall 2112 with an average thickness of T. Rm and T satisfy: 250MPa≤Rm≤2000MPa, 0.05mm≤T≤0.5mm, and 60 mm·MPa≤T×Rm≤500 mm·MPa.

[0267] It should be understood that the third housing wall 2112 of the housing 211 in this embodiment can be any wall of the housing 211. Specifically, the battery cell 20 can be any polyhedral structure, the housing 211 can be a hollow structure with at least one open end, the housing 211 can include one or more walls, the third housing wall 2112 can be any wall of the housing 211, and the housing 211 can include one or more third housing walls 2112. For example, if the housing 211 is a polygonal prism, then the third housing wall 2112 can be any wall of the polygonal prism, and the surface of the third housing wall 2112 can be any polygon. For another example, such as... Figure 3 and Figure 4 As shown, if the housing 211 is a cuboid, then the third housing wall 2112 can be any wall of the housing 211, and the surface of the third housing wall 2112 is rectangular. For example, if the housing 211 is a cylinder, then the third housing wall 2112 can be the bottom surface of the cylinder or the side surface of the cylinder; this embodiment is not limited to these. Furthermore, if two adjacent walls of the housing 211 are connected by rounded corners, then when the third housing wall 2112 in this embodiment is any wall of the housing 211, the third housing wall 2112 does not include the rounded corner connection area between the wall and the adjacent wall.

[0268] In this embodiment, at least a portion of the housing 211 includes a third housing wall 2112, and the tensile strength of the third housing wall 2112 at room temperature (25°C) is Rm. Increasing the tensile strength Rm of at least a portion of the housing 211 at room temperature (25°C) can improve the deformability of the housing 211, making it less prone to breakage 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 room temperature should not be too large, in order to reduce the difficulty of material selection and processing of the housing 211, save costs, and facilitate processing.

[0269] When the average thickness T of the third shell wall 2112 of the shell 211 is relatively thin, the structural strength of the third shell wall 2112 can be increased by improving its tensile strength Rm at room temperature (25°C). This improves both the energy density and the structural strength and stability of the battery cell 20. Conversely, when the average thickness T of the third shell wall 2112 of the shell 211 is relatively thick, the structural strength of the shell 211 can be improved. Furthermore, by appropriately reducing the requirement for the tensile strength Rm of the third shell wall 2112 at room temperature, the material selection difficulty of the shell 211 can be reduced, thereby lowering the processing difficulty and cost of the battery cell 20. Moreover, T×Rm represents the stiffness of the third shell wall. Limiting the stiffness of the third shell wall to neither too small nor too large ensures good deformation capacity while reducing processing difficulty and cost.

[0270] It should be understood that the average thickness T of the third housing wall 2112 in this embodiment can also be flexibly set according to actual application. For example, the average thickness T of the third housing wall 2112 satisfies: 0.05mm ≤ T ≤ 0.5mm. Further, the average thickness T of the third housing wall 2112 satisfies: 0.1mm ≤ T ≤ 0.4mm. Appropriately thinning the average thickness T of the third housing wall 2112 can reduce the space occupied by the housing 211 inside the battery 10, thereby increasing the energy density of the battery 10. Furthermore, the structural strength requirements of the housing 211 can be compensated by increasing the tensile strength Rm of the third housing wall 2112 under normal temperature conditions, so as to maintain the stability of the housing 211. On the other hand, appropriately increasing the average thickness T of the third housing wall 2112 can also reduce the processing difficulty of the third housing wall 2112.

[0271] Furthermore, the average thickness T of the third housing wall 2112 satisfies: 0.1mm ≤ T ≤ 0.3mm. The average thickness T of the third housing wall 2112 is neither too large nor too small, which can improve the structural strength and stability of the housing 211, and reduce the space occupied by the housing 211 inside the battery 10, thereby improving the energy density of the battery 10.

[0272] In some embodiments of this application, the average thickness T of the third housing wall 2112 can be set to other values. For example, the average thickness T of the third housing wall 2112 can be any one of the following values ​​or between any two of the following values: 0.05mm, 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.

[0273] In some embodiments, the range of T×Rm can 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 appropriate materials, the tensile strength Rm of the third shell wall 2112 under normal temperature conditions can be improved, thereby reducing the average thickness T of the third shell wall 2112, so that the stiffness of the third shell wall 2112 meets the design requirements. This can improve both the structural strength and structural stability of the third shell wall 2112 of the shell 211, and also improve the energy density of the battery cell 20 and the battery 10.

[0274] Furthermore, the range of T×Rm can also be set as follows: Rm and T satisfy: 100 mm·MPa≤T×Rm≤300 mm·MPa, so that the stiffness of the third shell wall 2112 is more suitable, 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.

[0275] In some embodiments, the value of T×Rm in this application can also be set to other values. For example, the value of T×Rm can be any one of the following values ​​or between any two of the following values: 60 mm·MPa, 65 mm·MPa, 70 mm·MPa, 75 mm·MPa, 80 mm·MPa, 85 mm·MPa, 90 mm·MPa, 95 mm·MPa, 100 mm·MPa, 130 mm·MPa, 150 mm·MPa, 180 mm·MPa, 200 mm·MPa, 230 mm·MPa, 250 mm·MPa, 280 mm·MPa, 300 mm·MPa, 330 mm·MPa, 350 mm·MPa, 380 mm·MPa, 400 mm·MPa, 430 mm·MPa, 450 mm·MPa, 480 mm·MPa, and 500 mm·MPa.

[0276] In this embodiment, the mass percentage g of the silicon-based material and the average thickness T of the third shell wall 2112 can be mutually restricted, as can the tensile strength Rm of at least a portion of the shell 211 at a temperature of 25°C, 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 percentage of the silicon-based material is g, and g and T satisfy: 2% ≤ g ≤ 20%, 0.15 mm ≤ T ≤ 0.4 mm. When the mass percentage g of the silicon-based material is relatively small, the average thickness T of the third shell wall 2112 can be appropriately reduced to improve the space utilization of the shell 211. While increasing the energy density of the battery cell 20, the structural strength of the shell 211 can also be balanced.

[0277] In some embodiments, the mass percentage of silicon-based material in the negative electrode active material is g, and g, T, and Rm satisfy: 15% ≤ g ≤ 40%, 0.2 mm ≤ T ≤ 0.4 mm, and 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 can improve the structural strength and stability of the battery cell 20.

[0278] It should be understood that the average thickness T of the third housing wall 2112 in this application embodiment can refer to the average thickness of at least a portion of the third housing wall 2112. For example, the average thickness T of the third housing wall 2112 can refer to the average thickness T of the entire area of ​​the third housing wall 2112, especially when the third housing wall 2112 is relatively flat, that is, when the thickness of most areas of the third housing wall 2112 is substantially equal or the difference is small, or when the thickness of the entire area of ​​the third housing wall 2112 is substantially equal or the difference is small, then the average thickness of the entire area of ​​the third housing wall 2112 can be determined as T.

[0279] For example, the average thickness T of the third housing wall 2112 can also refer to the average thickness T of a local area of ​​the third housing wall 2112, that is, the average thickness T of the remaining area after excluding a certain area of ​​the third housing wall 2112. For example, if there are certain special areas in the third housing wall 2112 whose thickness differs significantly from other areas, such as having a protruding structure or a recessed area, making the thickness of the special area larger or smaller than other areas, then the special area can be excluded, and the average thickness T of the remaining area of ​​the third housing wall 2112 can be calculated.

[0280] In some embodiments, the third housing wall 2112 includes a functional region, and the average thickness T of the third housing wall 2112 is the average thickness of the region of the third housing wall 2112 excluding the functional region. The functional region includes at least one of the following regions: a pressure relief region, a region where the electrode terminal 214 is located, a liquid injection region, and a welding region. The thickness of the functional region is usually significantly different from the thickness of other regions of the third housing wall 2112. Therefore, calculating the average thickness T of the third housing wall 2112 without including the functional region allows the design of the third housing wall 2112 to better meet strength requirements, thereby improving the structural strength and stability of the battery cell 20.

[0281] Specifically, the functional area in this embodiment may include a region on the third housing wall 2112 that has a specific structure or a specific purpose. For example, the functional area may include a pressure relief region for providing a pressure relief mechanism, which is an element or component that is actuated to release internal pressure or temperature when the internal pressure or temperature of the battery cell 20 reaches a predetermined threshold. The predetermined threshold may be adjusted according to different design requirements. For example, the predetermined threshold may depend on one or more of the materials of the positive electrode, negative electrode, electrolyte, and separator in the battery cell 20.

[0282] The term "actuation" as used in this application refers to the pressure relief mechanism being activated or undergoing a certain state, thereby releasing the internal pressure and temperature of the battery cell 20. The actions of the pressure relief mechanism may include, but are not limited to, at least a portion of the pressure relief mechanism rupturing, breaking, tearing, or opening. When the pressure relief mechanism is actuated, the high-temperature, high-pressure substances inside the battery cell 20 are discharged outwards from the actuated portion as waste. This method allows for pressure and temperature relief of the battery cell 20 under controllable pressure or temperature conditions, thereby preventing potentially more serious accidents.

[0283] The emissions from the battery cell 20 mentioned in this application include, but are not limited to: electrolyte, dissolved or split positive and negative electrode plates, fragments of the separator, high-temperature and high-pressure gases generated by the reaction, flames, etc.

[0284] The pressure relief mechanism of this embodiment can be disposed on any wall of the battery cell 20. For example, the pressure relief mechanism can be disposed in the pressure relief area of ​​the third housing wall 2112 of the battery cell 20. The pressure relief mechanism can be a part of the third housing wall 2112; or it can be a separate structure from the third housing wall 2112 and fixed to the third housing wall 2112 by means of welding, for example. For example, when the pressure relief mechanism is a part of the third housing wall 2112, the pressure relief mechanism can be formed by setting a groove on the third housing wall 2112, that is, the third housing wall 2112 has a groove in the pressure relief area, and the thickness at the groove is significantly less than the thickness of other areas of the third housing wall 2112. Therefore, the average thickness T of the third housing wall 2112 can be disregarded in terms of the thickness at the groove. The groove is the weakest point of the pressure relief mechanism. When the battery cell 20 produces too much gas, causing the internal pressure to rise and reach a threshold, or when the internal reaction of the battery cell 20 generates heat, causing the internal temperature of the battery cell 20 to rise and reach a threshold, the pressure relief mechanism can rupture at the groove, causing the inside and outside of the battery cell 20 to communicate. The gas pressure and temperature are released to the outside through the rupture of the pressure relief mechanism, thereby preventing the battery cell 20 from exploding.

[0285] For example, the pressure relief mechanism can also be a separate structure from the third housing wall 2112. The pressure relief mechanism can take the form of an explosion-proof valve, a gas valve, a pressure relief valve, or a safety valve, and can specifically adopt pressure-sensitive or temperature-sensitive elements or structures. For example, the third housing wall 2112 is provided with a through hole in the pressure relief area, and the pressure relief mechanism is installed and fixed to the third housing wall 2112 through the through hole. After installation, the pressure relief mechanism may protrude or be recessed relative to other areas of the third housing wall 2112. Therefore, the average thickness T of the third housing 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.

[0286] In some embodiments, the functional area may further include the area where the electrode terminal 214 is located. Specifically, the electrode terminal 214 in this embodiment is used to electrically connect with the electrode assembly 22 inside the battery cell 20 to output the electrical energy of the battery cell 20. Furthermore, the battery cell 20 may include at least two electrode terminals 214, each including 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 may be a negative electrode terminal; or, the first electrode terminal 214a may be a negative electrode terminal, and the second electrode terminal 214b may be a positive electrode terminal. The positive electrode terminal is used to electrically connect with the positive electrode tab 222a of the electrode assembly 22, and the negative electrode terminal is used to electrically connect with the negative electrode tab 222b of the electrode assembly 22. The positive electrode terminal and the positive electrode tab 222a can be directly connected or indirectly connected, and the negative electrode terminal and the negative electrode tab 222b can be directly connected or indirectly connected. For example, the positive electrode terminal can be electrically connected to the positive electrode tab 222a through a current collector 23, and the negative electrode terminal can be electrically connected to the negative electrode tab 222b through a current collector 23.

[0287] It should be understood that each electrode terminal 214 in this embodiment can be disposed on any wall, and multiple electrode terminals 214 can be disposed on the same wall or different walls of the battery cell 20. For example, as Figure 3 and Figure 4 As shown, each battery cell 20 includes two electrode terminals 214, which are located on the same wall. For example, both electrode terminals 214 can be located on the cover plate 212.

[0288] For example, again taking the case where each battery cell 20 includes two electrode terminals 214, and these two electrode terminals 214 are located on the same wall, unlike... Figure 3 and Figure 4 As shown, the two electrode terminals 214 can also be located on the housing 211. For example, both electrode terminals 214 can be located on the third housing wall 2112 of the housing 211. When the electrode terminals 214 are located on the third housing wall 2112, the electrode terminals 214 typically protrude from other areas of the third housing wall 2112, meaning the thickness of the area where the electrode terminals 214 are located is much greater than the thickness of other areas of the third housing wall 2112. Therefore, the average thickness T of the third housing wall 2112 may not include the area where the electrode terminals 214 are located.

[0289] In some embodiments, the functional area may further include an injection area. For example, the injection area of ​​the third housing wall 2112 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 can be sealed by a sealant. Considering that the thickness of the injection area where the sealant is located is usually much greater than the thickness of other areas of the third housing wall 2112, the average thickness T of the third housing wall 2112 may not include the injection area.

[0290] In some embodiments, the functional area may further include a welding area. For example, the third housing wall 2112 may be fixed to other walls by welding, or the third housing wall 2112 itself needs to be formed by welding, in which case the third housing wall 2112 may include a welding area. For example, as... Figure 4 As shown, the housing 211 can be welded together, thus the housing 211 can have a weld seam 2113. Specifically, the housing 211 may include at least two parts, which are connected by welding to form the housing 211, wherein... Figure 4 Taking the casing 211 as an example, which comprises two parts along the height direction Z of the battery cell 20, a weld 2113 is provided between the upper and lower casing parts; or, unlike... Figure 4 As shown, other parts of the housing 211 may also be provided with welds 2113, but this application embodiment is not limited to this. The welding area of ​​the functional area in this application embodiment 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 housing wall 2112. Therefore, the average thickness T of the third housing wall 2112 may not include the welding area.

[0291] In this embodiment, the third housing wall 2112 of the housing 211 can be any wall of the housing 211. For example, the third housing wall 2112 can be the wall with the smallest thickness of the housing 211. That is, by limiting the thickness T of the wall with the smallest thickness of the housing 211, the thickness of the other walls of the housing 211 is limited, so that each wall of the housing 211 can meet the structural strength requirements, thereby improving the structural strength and stability of the battery cell 20.

[0292] In some embodiments, the third housing wall 2112 is the wall with the largest area of ​​the housing 211. Considering that multiple battery cells 20 are arranged inside the battery 10, and these multiple battery cells 20 are usually in contact with each other through the wall with the largest area of ​​the housing 211, the wall with the largest area is usually subjected to the greatest compressive force from the electrode assembly 22. Therefore, by limiting the average thickness T and the room temperature tensile strength Rm of the third housing wall 2112, the deformation capacity of the housing 211 can be effectively improved, thereby improving the structural strength and stability of the battery cells 20.

[0293] It should be understood that the position of the wall with the largest area of ​​the housing 211 in this application embodiment can be set according to 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. This application embodiment is not limited to this.

[0294] In some embodiments, the housing 211 includes an intersecting bottom wall and side walls, wherein the bottom wall supports the electrode assembly housed within the housing 211. Specifically, the housing 211 may be a hollow structure with an opening at at least one end, and the bottom wall and side walls of the housing 211 do not necessarily refer to the walls opposite and adjacent to the opening, respectively. The electrode assembly 22 is housed inside the housing 211. Considering that in practical applications, the orientation of the electrode assembly 22 may differ depending on the application scenario, the housing 211 may include walls for supporting the electrode assembly 22. Therefore, in this embodiment, the bottom wall of the housing 211 is the wall for supporting the electrode assembly 22, that is, the bottom wall of the housing 211 is used to bear the weight of the electrode assembly 22. Conversely, the wall of the housing 211 that directly intersects with the bottom wall is the side wall of the housing 211.

[0295] In some embodiments, the third housing wall 2112 is a side wall of the housing 211. Considering the different uses of the bottom wall and side walls of the housing 211, their design requirements may also differ. For example, the side walls of the housing 211 typically require higher deformability. Therefore, when the third housing wall 2112 is a side wall of the housing 211, by limiting the tensile strength Rm of the side wall under room temperature conditions and the average thickness T of the side wall, the deformability of the side wall of the housing 211 can be effectively improved, thereby enhancing the structural stability of the battery cell 20.

[0296] In some embodiments, the housing 211 includes a plurality of sidewalls of equal thickness to facilitate processing.

[0297] 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, so as to facilitate processing and optimize the space occupied by the housing 211.

[0298] In some embodiments, the third housing wall 2112 is perpendicular to the stacking direction of the electrodes of the electrode assembly 22. The stacking direction of the electrodes of the electrode assembly 22 is typically the thickness direction of the electrode assembly 22. Considering that the thickness direction of the electrode assembly 22 is prone to expansion during the cyclic charging and discharging of the battery cell 20, the deformation requirements of the corresponding housing wall 211 are relatively high. Therefore, by setting the third housing wall 2112 to be perpendicular to the stacking direction of the electrodes of the electrode assembly 22, or in other words, by arranging the third housing wall 2112 and the electrode assembly 22 along the stacking direction of the electrodes of the electrode assembly 22, the tensile strength Rm and average thickness T of the third housing wall 2112 under normal temperature conditions can be limited, thereby improving both the energy density of the battery cell 20 and the deformation capability of the third housing wall 2112, thus enhancing the structural stability of the battery cell 20.

[0299] It should be understood that the cover plate 212 in this embodiment of the application may adopt the same or different design as the third housing wall 2112. For example, the cover plate 212 may adopt the same design as the third housing wall 2112, that is, the average thickness of the cover plate 212 may be T, the room temperature tensile strength of the cover plate 212 may be b, and the design requirements of b and T mentioned above are met, so as to improve the deformation capacity of the cover plate 212, thereby improving the structural strength and stability of the battery cell 20.

[0300] In some embodiments, the ratio of the internal volume of the housing 211 to the external volume of the housing 211 is greater than or equal to 93%. That is, the housing 211 is thinner, so that the housing 211 itself occupies less space, thereby improving the space utilization and energy density of the battery 10.

[0301] It should be understood that the specific calculation methods for the internal volume of the housing 211 and the external volume of the housing 211 in the embodiments of this application are related to the shape of the housing 211. For example, the housing 211 is a cuboid. Figure 8 A side view of the housing 211 according to an embodiment of this application is shown. Figure 9 A top view of the housing 211 according to an embodiment of this application is shown. For example, the Figure 8 and Figure 9 The housing 211 shown can be as follows: Figure 3 and Figure 4 The casing 211 of the battery cell 20 shown.

[0302] like Figure 8 and Figure 9 As shown, a rectangular shell 211 is used as an example, and this shell 211 is a hollow rectangular shell open at one end. When calculating the volume of the internal space and the external volume of the shell 211, the fillet connections between adjacent walls of the shell 211 can be ignored. Figure 8 and Figure 9 As shown, since each wall of the housing 211 has a certain thickness, in the length direction Y, the internal length of the housing 211 is Y1, and the external length is Y2, where Y2 is greater than Y1; similarly, in the width direction X, the internal width of the housing 211 is X1, and the external width is X2, where X2 is greater than X1; in the height direction Z, the internal height of the housing 211 is Z1, and the external height is Z2, where Z2 is greater than Z1. Therefore, the volume of the internal space of the housing 211 is V1 = X1 × Y1 × Z1; the volume of the external space of the housing 211 is V2 = X2 × Y2 × Z2, and V1 / V2 is greater than or equal to 93%, thereby reducing the space occupied by the housing 211 itself and improving the space utilization and energy density of the battery 10.

[0303] The following comparative examples and embodiments provide a clear illustration. Specifically, the battery cell 20 in each of the following embodiments and comparative examples is as follows: Figure 3 and Figure 4 Taking the square-shell battery shown as an example, the casing 211 adopts a hollow structure with one end open.

[0304] In the following embodiments and comparative examples, the preparation methods of the positive electrode 223, negative electrode 224, electrolyte and separator 225 of the battery cell 20 are as follows.

[0305] 1. Preparation of positive electrode 223

[0306] LiNi, the positive electrode active material 0.95 Co 0.04 Mn 0.01A positive electrode slurry is prepared in N-methylpyrrolidone (NMP) using O2, conductive agent Super P, and binder polyvinylidene fluoride (PVDF). The solid content of the positive electrode slurry is 50 wt%, and the solid component is LiNi. 0.95 Co 0.04 Mn 0.01 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. After cold pressing, the foil is trimmed, cut into sheets, and slit. Then, it is dried under vacuum at 85°C for 4 hours to produce the positive electrode sheet 223.

[0307] 2. Preparation of negative electrode 224

[0308] The negative electrode active material is mixed evenly with the conductive agent Super P, the thickener carboxymethyl cellulose (CMC), and the binder styrene-butadiene rubber (SBR) in deionized water to prepare a negative electrode slurry. 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 30 wt%, and the mass ratio of the negative electrode active material, Super P, CMC, and binder styrene-butadiene rubber (SBR) in the solid components is 88:7:3:2. The negative electrode slurry is coated on the upper and lower surfaces of the current collector copper foil and dried at 85°C. Then, it is cold-pressed, trimmed, cut into sheets, and slit. Finally, it is dried under vacuum at 120°C for 12 hours to prepare the negative electrode sheet 224.

[0309] 3. Preparation of electrolyte

[0310] In an argon atmosphere glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), the thoroughly 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 mixed evenly to obtain an electrolyte with a concentration of 1 mol / L.

[0311] 4. Preparation of the spacer 225

[0312] A 16μm polyethylene film is used as the separator 225.

[0313] 5. Preparation of lithium-ion battery cell 20

[0314] The positive electrode 223, the separator 225, and the negative electrode 224 are stacked in sequence, with the separator 225 positioned between the positive electrode 223 and the negative electrode 224 to isolate the positive and negative electrodes. The bare cell is then wound up, tabs are welded on, and the bare cell is placed in a shell of different materials. The electrolyte prepared above is injected into the dried shell, and the process is followed by encapsulation, settling, formation, shaping, and capacity testing to complete the preparation of the lithium-ion battery cell 20.

[0315] In the following embodiments and comparative examples, the tensile strength of the casing 211 of the battery cell 20 at a temperature of 25°C is Rm, and different materials are selected for the casing 211 to obtain different tensile strengths Rm; the average thickness of the third casing wall 2112 of the casing 211 is T; the specific parameter settings are shown in Table 5 below. Furthermore, in each embodiment and comparative example, the material of all regions of the casing 211 is the same, and the tensile strength Rm of the casing 211 at 25°C is measured using the method specified in GB / T228.1-2010. Moreover, the battery cells 20 in the following embodiments and comparative examples are identical except for the parameter settings shown in Table 5. For example, the capacity of the battery cell 20 in each embodiment is 350Ah.

[0316] Cyclic charging fatigue tests were performed on the battery cells 20 in the following embodiments and comparative examples. Specifically, methods such as... Figure 7 The fixture 700 shown is used for cyclic charging fatigue testing.

[0317] Specifically, the battery cell 20 is clamped and fixed in the special fixture 700 to ensure that the two walls of the battery cell 20 with the largest relative area are clamped, and the initial pressure is set to 2000N. The electrode terminals 214 of the battery cell 20 are then connected to a special battery charging and discharging device.

[0318] The clamp 700 holding the battery cell 20 is placed in a constant temperature environment of 25±2℃, and the test is started after the battery cell 20 reaches temperature equilibrium.

[0319] The specific test procedures shall be performed in accordance with the "Standard Cycle Life" section 6.4 of "GBT31484-2015 Requirements and Test Methods for Cycle Life of Power Batteries for Electric Vehicles", and the test cycle cutoff condition shall be changed to "the test shall be stopped until the weld 2113 of the battery cell 20 is damaged".

[0320] For example, the test can be performed according to the following steps: Step a, discharge at 1I(A) to the discharge termination condition specified by the company; Step b, rest for not less than 30 minutes or the resting condition specified by the company; Step c, charge according to the method in 6.1.1.3; Step d, rest for not less than 30 minutes or the resting condition specified by the company; Step e, discharge at 1I1(A) to the discharge termination condition specified by the company; Step f, repeat steps b to e until the weld 2113 breaks and the test is stopped.

[0321] During the above testing process, the weld 2113 of the battery cell 20 was continuously observed until leakage occurred at the weld 2113. The number of cycles was recorded to obtain the condition of the housing 211 after 1000 cycles, as shown in Table 5 below. In the following embodiments and comparative examples, the weld 2113 refers to the weld between the housing 211 and the cover plate 212, that is, the weld 2113 surrounds the open end of the housing 211, and the housing 211 adopts an integrally formed structure.

[0322] Table 5

[0323]

[0324] 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 of 25°C is usually at least 315MPa to 430MPa. In the above embodiment, only 328MPa is used as an example, but it 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 of 25°C is typically at least 380MPa to 430MPa, with 396MPa being used 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 of 25°C is typically at least 450MPa, with 459MPa being used 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 of 25°C is typically at least 520MPa, with 533MPa, 625MPa, and 763MPa being used as examples in the above embodiment.

[0325] As shown in Table 5 above, in embodiments 1-12, the Rm and T of the third housing wall 2112 of the housing 211 satisfy the following conditions: 250MPa≤Rm≤2000MPa, 0.05mm≤T≤0.5mm, and 60 mm·MPa≤T×Rm≤500 mm·MPa. This allows the battery cell 20 to achieve a fatigue life of over one thousand cycles, meeting the design requirements of the battery cell 20. Furthermore, even with a smaller average thickness T of the third housing wall 2112, the battery cell 20 can still achieve a fatigue life of over one thousand cycles, and a smaller average thickness T can also increase the energy density of the battery 10. However, in the two comparative examples, the structural strength of the third housing wall 2112 is insufficient; Rm and T×Rm do not meet the above values. Even with a larger average thickness T of the third housing wall 2112, the battery cell 20 cannot achieve a fatigue life of one thousand cycles, failing to meet the design requirements of the battery cell 20.

[0326] In some embodiments, the capacity of the battery cell is C, and the tensile strength of at least a portion of the casing 211 at a temperature of 25°C is Rm, where Rm and C satisfy: 250MPa≤Rm≤2000MPa, 25Ah≤C≤550Ah. On one hand, increasing the capacity C of the battery cell 20 can increase the capacity density of the battery 10 comprising multiple battery cells 20. Alternatively, while keeping the total capacity of the battery 10 constant, increasing the capacity C of a single battery cell 20 can reduce the number of battery cells 20 required, correspondingly reducing the number of electrical connections between multiple battery cells 20, lowering the probability of electrical connection failures, and contributing to improved battery reliability. Furthermore, when the capacity C of the battery cell 20 is large, the tensile strength Rm of at least a portion of the casing 211 at room temperature (25°C) can be increased to meet the structural strength requirements of the high-capacity battery cell 20 on the casing 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 internal reaction will be intensified, which will increase the structural strength requirements of the casing 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 casing 211, which can reduce the difficulty of material selection and processing of the battery cell 20, reduce costs and improve processing efficiency.

[0327] It should be understood that the range of values ​​for the capacity C of the battery cell 20 in this application embodiment can be adjusted according to actual applications. For example, the capacity C of the battery cell 20 can be reasonably selected according to the actual needs of the battery 10. In some embodiments, the capacity C of the battery cell 20 can be set to further satisfy: 100Ah≤C≤300Ah. Appropriately increasing the capacity C of the battery cell 20 can increase the energy density of the battery 10; at the same time, the capacity C of the battery cell 20 should not be too large, so as to balance the relationship between the capacity C of the battery cell 20 and the structural strength of the casing 211, thereby improving the reliability and service life of the battery cell 20.

[0328] Furthermore, the capacity C of the battery cell 20 can 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 casing 211, thereby improving the reliability and service life of the battery cell 20 and the battery 10.

[0329] In some embodiments, the capacity C of the battery cell 20 in this application embodiment can also be set to other values. For example, 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.

[0330] It should be understood that the capacity C of the battery cell 20 in this application embodiment 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 testing method for 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 this application embodiment is not limited to this.

[0331] The following comparative examples and embodiments provide a clear illustration. Specifically, the battery cell 20 in each of the following embodiments and comparative examples is as follows: Figure 3 and Figure 4 Taking the square-shell battery shown as an example, the casing 211 adopts a hollow structure with one end open.

[0332] In the following embodiments and comparative examples, the preparation methods of the positive electrode 223, negative electrode 224, electrolyte and separator 225 of the battery cell 20 are as follows.

[0333] 1. Preparation of positive electrode 223

[0334] LiNi, the positive electrode active material 0.95 Co 0.04 Mn 0.01 A positive electrode slurry is prepared in N-methylpyrrolidone (NMP) using O2, conductive agent Super P, and binder polyvinylidene fluoride (PVDF). The solid content of the positive electrode slurry is 50 wt%, and the solid component is LiNi. 0.95 Co 0.04 Mn 0.01 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. After cold pressing, the foil is trimmed, cut into sheets, and slit. Then, it is dried under vacuum at 85°C for 4 hours to produce the positive electrode sheet 223.

[0335] 2. Preparation of negative electrode 224

[0336] The negative electrode active material is mixed evenly with the conductive agent Super P, the thickener carboxymethyl cellulose (CMC), and the binder styrene-butadiene rubber (SBR) in deionized water to prepare a negative electrode slurry. 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 30 wt%, and the mass ratio of the negative electrode active material, Super P, CMC, and binder styrene-butadiene rubber (SBR) in the solid components is 88:7:3:2. The negative electrode slurry is coated on the upper and lower surfaces of the current collector copper foil and dried at 85°C. Then, it is cold-pressed, trimmed, cut into sheets, and slit. Finally, it is dried under vacuum at 120°C for 12 hours to prepare the negative electrode sheet 224.

[0337] 3. Preparation of electrolyte

[0338] In an argon atmosphere glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), the thoroughly 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 mixed evenly to obtain an electrolyte with a concentration of 1 mol / L.

[0339] 4. Preparation of the spacer 225

[0340] A 16μm polyethylene film is used as the separator 225.

[0341] 5. Preparation of lithium-ion battery cell 20

[0342] The positive electrode 223, the separator 225, and the negative electrode 224 are stacked in sequence, with the separator 225 positioned between the positive electrode 223 and the negative electrode 224 to isolate the positive and negative electrodes. The bare cell is then wound up, tabs are welded on, and the bare cell is placed in a shell of different materials. The electrolyte prepared above is injected into the dried shell, and the process is followed by encapsulation, settling, formation, shaping, and capacity testing to complete the preparation of the lithium-ion battery cell 20.

[0343] In the following embodiments and comparative examples, the tensile strength of the casing 211 of the battery cell 20 at a temperature of 25°C is Rm, and different materials are selected for the casing 211 to obtain different tensile strengths Rm; the capacity of the battery cell 20 is C; the specific parameter settings are shown in Table 6 below. Furthermore, in each embodiment and comparative example, the material of all areas of the casing 211 is the same, and the tensile strength Rm of the casing 211 at 25°C is measured using the method specified in GB / T 228.1-2010. Moreover, the battery cells 20 in the following embodiments and comparative examples are identical except for the parameter settings shown in Table 6. For example, the wall thickness of the wall with the largest area of ​​the battery cell 20 in each embodiment is 0.15 mm; furthermore, the chemical system of the battery cells 20 in each embodiment is a nickel-cobalt-manganese ternary system.

[0344] Table 6

[0345]

[0346] Comparing the two comparative examples and the six embodiments in Table 6 above, it can be seen that different tensile strengths Rm can be determined when the casing 211 is made of different materials. 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 casing 211 of the battery cell 20 does not crack. Therefore, the structural strength of the casing 211 is sufficient for larger capacity battery cells 20, meeting 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 casing 211 of the battery cell 20 cracks, failing to meet the design requirements of the battery cell 20.

[0347] It should be understood that, in order to meet the above design requirements, the material of at least a portion of the housing 211 in this application embodiment can be flexibly selected according to the actual application.

[0348] In some embodiments, at least a portion of the housing 211 is made of at least one of the following materials: steel, copper alloy, titanium alloy, and nickel alloy. These materials have high strength, which meets the strength requirements of the housing 211, and are easy to process and have low cost.

[0349] In some embodiments, at least a portion of the housing 211 is made of at least one of the following materials: stainless steel, carbon steel, and high-strength alloy steel. For example, if the housing 211 is made of stainless steel, it has high structural strength and can generally 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 typically between 1400°C and 1500°C. Furthermore, the housing 211 is made of stainless steel, which is not prone to rust and can improve the service life of the housing 211 compared to other materials.

[0350] If the shell 211 is made of carbon steel, it has high structural strength and easily meets the requirements for 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 typically between 1425℃ and 1525℃. Furthermore, considering that carbon steel may be easily corroded during use, nickel can be plated on the outer surface of the carbon steel shell 211. For example, the thickness of the nickel plating layer is typically 1μm to 10μm to protect the surface of the shell 211 from oxidation and corrosion, thereby improving the service life of the shell 211.

[0351] 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 requirement of the shell 211 is high, high-strength alloy steel materials can be selected, which can easily meet the requirements of 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.

[0352] In some embodiments, where steel is used in at least a portion of the housing 211, 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 readily available, have sufficient strength to meet design requirements, and are relatively inexpensive. For example, approximate values ​​for 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.

[0353] Table 7

[0354]

[0355] It should be understood that the material of at least a portion of the shell 211 in this embodiment of the application may also be selected from other materials. For example, different materials may be reasonably selected based on the mass content of different elements in the material and the role played by those elements.

[0356] In some embodiments, the mass content of chromium in the material of at least a portion of the housing 211 is m, where m satisfies: 10% ≤ m ≤ 30%. Appropriately increasing the amount of chromium in the material of at least a portion of the housing 211 can improve the melting point and strength of the material, making it easier 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 embodiments of this application. Furthermore, 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 housing 211, improving the corrosion resistance of the housing 211.

[0357] In some embodiments, the mass content of nickel in the material of at least a portion of the housing 211 is n, where n satisfies 8% ≤ n ≤ 25%. Appropriately increasing the amount of nickel in the material of at least a portion of the housing 211 can improve the structural strength and plasticity of the housing 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 provide corrosion resistance to the material.

[0358] In some embodiments, taking the steel used for the housing 211 as an example, different types of steel contain different mass contents of different elements. For example, for stainless steel, iron is one of the basic elements of stainless steel, and its mass content is usually between 60% and 70%. As another example, Table 8 shows the mass contents of different elements in several types of steel. The values ​​in Table 8 are the maximum percentage of each element by mass in the material; that is, the percentage of each element by mass in the corresponding material is usually not greater than the values ​​shown in Table 8.

[0359] Table 8

[0360]

[0361] It should be understood that when at least a portion of the casing 211 is made of steel, increasing the carbon content in the steel can improve its strength and hardness. For example, generally, a higher carbon content results in higher hardness and strength in the steel, but may reduce its corrosion resistance.

[0362] Increasing the chromium content in steel can improve its corrosion resistance because chromium reacts with oxygen to form a dense chromium oxide film, creating a corrosion-resistant protective film on the steel surface.

[0363] Increasing the nickel content in steel can improve its corrosion resistance, strength, and plasticity.

[0364] Increasing the molybdenum content in steel can improve its corrosion resistance and strength, especially in corrosive media such as acids and salts.

[0365] Increasing the manganese content in steel can improve its toughness and fatigue resistance.

[0366] Increasing the silicon content in steel can improve the corrosion resistance and strength of stainless steel.

[0367] Reducing the mass content of phosphorus and sulfur in steel can reduce the negative impact of these two elements on the steel's corrosion resistance, plasticity, and toughness.

[0368] In addition, other elements can be added to steel. For example, steel can also include copper; the mass content of copper in Q195, Q215, and Q235 is generally no more than 0.3%, while that in modified stainless steel is generally no more than 2% to 3.5%. As another example, steel can also include nitrogen; the mass content of nitrogen in Q195, Q215, and Q235 is generally no more than 0.12%.

[0369] It should be understood that the testing methods for the mass content of each element in the steel described in the embodiments of this application can be set according to actual applications. For example, inductively coupled plasma atomic emission spectrometry (ICP) can be used for testing, but the embodiments of this application are not limited to this.

[0370] Figure 10 Another exploded structural diagram of the battery cell 20 according to an embodiment of this application is shown. Figure 11 A schematic cross-sectional view of the housing 211 according to an embodiment of this application is shown. It should be noted that... Figure 10 and Figure 11 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 In the battery cell 20 shown, and the Figure 10 and Figure 11 The housing 211 shown can be Figure 3 and Figure 4 The housing 211 shown above is applicable to the relevant descriptions above, and for the sake of brevity, it will not be described in detail here.

[0371] like Figure 10 and Figure 11As 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 disposed opposite to the opening 301, the first housing wall 31 and the second housing wall 32 being intersected.

[0372] like Figure 11 As shown in the enlarged view of part A, there is a transition region 33 between two adjacent second shell walls 32 of the shell 211. The maximum thickness of the transition region 33 is T1, and the maximum thickness of the second shell wall 32 with the largest thickness among the two adjacent second shell walls 32 is T0, wherein T1 is greater than T0.

[0373] In some embodiments, the second housing wall 32 may be perpendicular to the first housing wall 31.

[0374] In some embodiments, at least two second shell walls 32 can be connected end to end to 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.

[0375] In some embodiments, the housing 211 can be positioned as follows: Figure 10 As shown, the first housing wall 31 can be the bottom wall of the housing 211, used to support the electrode assembly 22, while the second housing wall 32 is the side wall of the housing 211, arranged around the electrode assembly 22.

[0376] Typically, the second shell wall 32 is not manufactured 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, meaning the shell 211 is a one-piece structure. For example, a plate-like structure can be stamped into a hollow structure with openings using a mold. The stamped shell 211 can have openings of various shapes; for example, the opening 301 can be circular, polygonal, or racetrack-shaped. Polygons can be square, pentagonal, hexagonal, or other irregular shapes.

[0377] 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 with the example of a uniform thickness.

[0378] from Figure 10As can be seen, the transition region 33 has two surfaces, namely an inner surface and an outer surface. In some embodiments, the inner and outer surfaces can be arc surfaces, and the inner and outer surfaces are coaxially arranged. The maximum thickness T1 of the transition region 33 can be defined as the length of the extension line connecting the center of the inner arc circle and the center of the outer arc circle in any cross section along a direction perpendicular to the axis of the inner and outer surfaces within the transition region 33. In other embodiments, the inner and outer surfaces can be planes, and the inner and outer surfaces are parallel, and the maximum thickness T1 of the transition region 33 can be defined as the vertical distance between the inner and outer surfaces. Similarly, the second housing wall 32 also has two surfaces, namely an inner surface and an outer surface, wherein the maximum value of the vertical distance between the inner and outer surfaces is the maximum thickness of a certain second housing wall 32.

[0379] 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 adjacent to a transition region 33 are not equal, then in this embodiment, T0 is the second shell wall 32 with the largest wall thickness among the two second shell walls 32 of the shell 211 adjacent to the transition region 33. Conversely, 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 adjacent to a transition region 33 are equal, then in this embodiment, T0 is the thickness of any second shell wall 32 of the shell 211.

[0380] It should be noted that if a second housing wall 32 includes a functional area, the maximum thickness of the second housing wall 32 actually refers to the maximum thickness of the area of ​​the second housing wall 32 other than the functional area. 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.

[0381] In this embodiment, by providing a transition region 33 between two adjacent second housing walls 32, stress concentration between the two adjacent second housing walls 32 can be reduced, thereby lowering the risk of structural failure due to stress concentration. In addition, by setting the maximum thickness T1 of the transition region 33 to be greater than the maximum thickness T0 of the second housing wall with the largest thickness among the two adjacent second housing walls, the thickened transition region 33 can enhance the structural strength of the housing 211, which is beneficial to solving the problem of housing 211 deformation during the production and assembly of the battery cell 20, as well as the problem of housing 211 deformation caused by gas expansion during the use of the battery cell 20.

[0382] 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 the two adjacent second shell walls 32 satisfy: 1.5≤T1 / T0≤7.

[0383] In this embodiment, by setting the ratio of the maximum thickness T1 of the transition region 33 to the maximum thickness T0 of the second shell wall 32 with the largest thickness among 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 the excessive thickness of the transition region 33 can be limited, thereby achieving a balance between the strength of the shell 211 and the manufacturing difficulty of the shell 211.

[0384] In practical applications, the ratio of T1 to T0 can be adjusted. For example, the maximum thickness T1 of the transition region 33 and the maximum thickness T0 of the second shell wall 32 with the largest thickness among the two adjacent second shell walls 32 can satisfy: 2≤T1 / T0≤4.

[0385] 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.

[0386] In this embodiment, by setting the ratio of the maximum thickness T1 of the transition region 33 to the maximum thickness T0 of the second shell wall 32 with the largest thickness among the two adjacent second shell walls 32 between [2, 4], the strength of the shell 211 and the manufacturing difficulty of the shell 211 can be maximized and balanced.

[0387] Optionally, such as Figure 11 and Figure 12 As shown, two adjacent second shell walls 32 are connected by a first fillet 331, and the transition region 33 includes the first fillet 331. That is, the transition region 33 is achieved by fillets.

[0388] In this embodiment, the transition area 33 between two adjacent second shell walls 32 is achieved by rounding the corners, which makes the shell 211 easier to form and has a better surface finish. At the same time, when affected by gas generation inside the battery cell 20, the risk of shell 211 cracking due to stress concentration at the sharp point can be reduced.

[0389] like Figure 12 As shown, the inner diameter of the first fillet 331 is R1, and the outer diameter of the first fillet 331 is R2.

[0390] In some embodiments, the first fillet 331 has an inner surface and an outer surface, and both the inner and outer surfaces are arc surfaces. The inner diameter R1 of the first fillet 331 can be understood as the radius of the circle containing the inner arc of the first fillet 331, while the outer diameter R2 of the first fillet 331 can be understood as the radius of the circle containing the outer arc of the first fillet 331.

[0391] 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.

[0392] In this embodiment, the inner diameter of the first fillet 331 between two adjacent second shell walls 32 is set between [2mm, 4mm]. On the one hand, the inner diameter will not occupy the internal space of the shell 211 due to being too large, which would increase the gas generation pressure inside the shell 211; on the other hand, the inner diameter will not be too small, which would result in insufficient wall thickness increment of the first fillet 331 and thus insufficient strength of the shell 211. This allows a balance to be achieved between the internal space utilization rate of the shell 211 and the strength of the shell 211.

[0393] In some embodiments, the outer diameter R2 of the first fillet 331 satisfies: 1.5mm ≤ R2 ≤ 3.5mm. For example, R2 = 1.5mm, 2mm, 2.5mm, 3.0mm, 3.5mm, etc.

[0394] 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 fillet 331 between two adjacent second housing walls 32, the more difficult it is to control the welding quality and the more likely it is to have a false weld; while the smaller the outer diameter R2 of the first fillet 331, the more difficult it is to form the housing 211. Therefore, by controlling the outer diameter R2 of the first fillet 331 within the range of [1.5mm, 3.5mm], a balance can be achieved between the welding quality and the difficulty of forming the housing.

[0395] In other embodiments, such as Figure 13 As shown, two adjacent second shell walls 32 are connected by a C-angle. For example, the included angle between the C-angle and the two adjacent second shell walls 32 is 45°.

[0396] In one embodiment, the housing 211 can be a one-piece molded structure, such as... Figure 10As shown, the depth of the housing 211 is H. Among them, the depth H of the housing 211 and the inner diameter R1 of the first rounded corner 331 satisfy: 2.5mm ≤ R1 ≤ 20mm, 50mm < H ≤ 250mm.

[0397] In the embodiment of the present application, the depth can be understood as the distance from the opening to the bottom inward. For example, the depth H of the housing 211 can be understood as the distance from the opening 301 to the first housing wall 31.

[0398] 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 2.5mm ≤ R1 ≤ 20mm, 50mm < H ≤ 250mm, it is possible to reduce the cracking risk caused by stress during the integral molding process of the housing 211 as much as possible without affecting the energy density of the battery cell 20, and thus reduce the molding difficulty of the housing 211.

[0399] For example, R1 = 2.5mm, 5mm, 7.5mm, 10mm, 12.5mm, 15mm, 17.5mm, 20mm; and / or, H = 50mm, 100mm, 150mm, 200mm, 250mm.

[0400] In some embodiments, H and R1 satisfy: 75mm ≤ H ≤ 180mm, 4mm ≤ R1 ≤ 15mm.

[0401] For example, H = 75mm, 100mm, 125mm, 150mm, 175mm, 180mm. For example: R1 = 4mm, 6mm, 8mm, 10mm, 12mm, 14mm, 15mm.

[0402] 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 too small H or too large R, and on the other hand, the housing 211 will not be prone to material accumulation during the molding process due to too large H or too small R, thereby causing the situation that the housing 211 is overstressed and cracked.

[0403] In other embodiments, H and R1 satisfy: 5mm ≤ R1 ≤ 10mm, 90mm ≤ H ≤ 14mm. For example, R1 = 5mm, 6mm, 7mm, 8mm, 9mm, 10mm. For another example, H = 90mm, 100mm, 110mm, 120mm, 130mm, 140mm.

[0404] In other embodiments, the housing 211 is an integrally formed structure, and the yield strength of the housing 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 the following: 140MPa≤Re≤1000MPa, 2.5mm≤R1≤20mm.

[0405] 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.

[0406] For example, R1 = 2.5mm, 5mm, 7.5mm, 10mm, 12.5mm, 15mm, 17.5mm, 20mm.

[0407] Yield strength can be understood as the critical stress value at which a material yields. 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 plastic deformation occurs is 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 in this embodiment at a temperature of 25°C can be selected according to the actual application. For example, the yield strength Re can be tested at room temperature (25°C) using GB / T228.1-2010.

[0408] To address the issue of material buildup at the first fillet 331 during the integral molding of the shell 211, leading to high friction between the shell 211 and the mold and making the shell 211 prone to cracking, this application provides another solution. 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. This ensures that R1 is not too small, reducing the molding difficulty of the shell 211, and that R1 is not too large, reducing the stress deformation of the shell 211.

[0409] 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 reduced 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 stress during the integral molding process is reduced as much as possible, and the molding difficulty of the shell 211 is reduced.

[0410] In some embodiments, the yield strengths Re and R1 of the housing 211 can satisfy: 150MPa≤Re≤400MPa, 4mm≤R1≤15mm.

[0411] For example, Re = 150MPa, 170MPa, 190MPa, 210MPa, 230MPa, 260MPa, 290MPa, 310MPa, 330MPa, 370MPa, 390MPa, 400MPa.

[0412] For example, R1 = 4mm, 6mm, 8mm, 10mm, 12mm, 14mm, 15mm.

[0413] In this embodiment, by limiting 150MPa≤Re≤400MPa and 4mm≤R1≤15mm, a balance is achieved between the molding difficulty and the degree of deformation of the shell 211.

[0414] In some embodiments, the yield strengths Re and R1 of the housing 211 can satisfy: 160MPa≤Re≤300MPa, 5mm≤R1≤10mm.

[0415] For example, Re = 160MPa, 170MPa, 180MPa, 190MPa, 200MPa, 210MPa, 220MPa, 230MPa, 240MPa, 250MPa, 260MPa, 270MPa, 280MPa, 290MPa, 300MPa.

[0416] For example, R1 = 5mm, 6mm, 7mm, 8mm, 9mm, 10mm.

[0417] 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 molding difficulty of the shell 211.

[0418] In some embodiments, the tensile strength of the housing 211 at a temperature of 25°C is Rm, and Rm and R1 satisfy: 250MPa≤Rm≤2000MPa, 2.5mm≤R1≤20mm.

[0419] Tensile strength can be understood as the maximum stress a material can withstand before it breaks. The test method for the tensile strength Rm of the shell 211 in this embodiment at a temperature of 25°C can be selected according to the actual application. For example, the tensile strength Rm can be tested at room temperature (25°C) using ISO 6892-2:2018.

[0420] 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.

[0421] In this embodiment, by setting 250MPa≤Rm≤1000MPa and 2.5mm≤R1≤20mm, the stress on the mold during the manufacturing process of the shell 211 can be reduced as much as possible without affecting the strength of the shell 211, thereby ensuring that the size or surface of the shell 211 is not affected.

[0422] In some embodiments, Rm and R1 satisfy: 280MPa≤Rm≤800MPa, 4mm≤R1≤15mm.

[0423] For example, Rm=280MPa, 310MPa, 340MPa, 370MPa, 390MPa, 430MPa, 470MPa, 510MPa, 540MPa, 580MPa, 610MPa, 630MPa, 660MPa, 690MPa, 720MPa, 740MPa, 780MPa, 800MPa.

[0424] In other embodiments, Rm and R1 satisfy: 380MPa≤Rm≤600MPa, 5mm≤R1≤10mm.

[0425] For example, Rm = 380MPa, 390MPa, 410MPa, 440MPa, 480MPa, 520MPa, 535MPa, 570MPa, 596MPa, 600MPa.

[0426] In some embodiments, the maximum wall thickness of at least two second housing walls 32 of housing 211 is equal.

[0427] 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 is equal.

[0428] 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 shell 211 can be reduced, and on the other hand, setting at least two second shell walls 32 to the minimum processing wall thickness can help to fully improve the space utilization of shell 211.

[0429] In other embodiments, there is a transition region 33 between any two adjacent second shell walls 32 of at least two second shell walls 32, and the maximum thickness of the at least two transition regions 33 corresponding to the at least two second shell walls 32 is equal.

[0430] In this embodiment, by setting the maximum thickness of at least two transition regions 33 between at least two second housing walls 32 of housing 211 to be equal, it helps to prepare housing 211 as a symmetrical structure, which is easy to process, and there is no need to worry about incorrect assembly when assembling housing 211 and cover plate 212, thus having a foolproof function.

[0431] Figure 14 Another schematic cross-sectional view of the housing 211 according to an embodiment of this application is shown. Figure 14 As shown in the enlarged view of part B, the first housing wall 31 and the second housing wall 32 are connected by a second fillet 34, as... Figure 14 As shown in the enlarged schematic diagram of part B, 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. 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 the following condition: 2.0≤r1 / T2≤30.

[0432] It should be understood that each of the first housing walls 31 is connected to at least two second housing walls 32. Optionally, any one of the second housing walls 32 is connected to the first housing wall 31 via a means such as... Figure 14 The second fillet 34 shown is connected. Furthermore, the second fillet 34 here is connected to... Figure 12The first fillet 331 is implemented similarly, that is, the second fillet 34 has an inner surface and an outer surface, and both the inner and outer surfaces are circular arc surfaces. The inner diameter r1 of the second fillet 34 can be understood as the radius of the circle containing the inner arc.

[0433] It should be noted that if each second shell wall 32 is a wall of uniform thickness, then the minimum thickness T2 of the second shell wall 32 can 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 not uniform, then the minimum thickness T2 of the second shell wall 32 can refer to the thickness of the thinnest region among all the second shell walls 32.

[0434] It should also be noted that if a second housing wall 32 includes a functional area, the minimum thickness of the second housing wall 32 actually refers to the minimum thickness of the area of ​​the second housing wall 32 other than the functional area. 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.

[0435] In this embodiment, by setting the ratio of the inner diameter r1 of the second fillet 34 between the first housing wall 31 and the second housing wall 32 to the minimum thickness T2 of the second housing wall 32 with the smallest thickness between [2.0, 30], it helps to balance the processing difficulty of the housing 211 with the space capacity and strength of the battery cell 20.

[0436] In some embodiments, the inner diameter r1 of the second fillet 34 satisfies the condition that the minimum thickness T2 of the second housing wall 32 with the smallest thickness among the at least two second housing walls 32 is 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.

[0437] Optionally, the inner diameter r1 of the second fillet 34 can satisfy: 0.8mm≤r1≤1.5mm. For example, r1=0.8mm,0.9mm,1.0mm,1.1mm,1.2mm,1.3mm,1.4mm,1.5mm.

[0438] In this embodiment, by setting the inner diameter r1 of the second fillet 34 within [0.8mm, 1.5mm], on the one hand, the manufacturing difficulty of the housing 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 reduce the height of the electrode assembly 22 and sacrifice the capacity of the electrode assembly 22 to meet the assembly of the housing 211 and the electrode assembly 22. In addition, if r1 is too large, the housing 211 is also prone to deformation.

[0439] Figure 15 It shows Figure 14 Another enlarged view of part B in the diagram. (See attached image.) Figure 15 As shown, the outer diameter of the second fillet 34 is r2, where 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.

[0440] 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 containing the outer arc of the second fillet 34.

[0441] In this embodiment, by setting the outer diameter r2 of the second fillet 34 within [1.0mm, 2.5mm], on the one hand, the insulation film on the outside of the battery cell 20 will not be punctured by the sharp point due to r2 being too small, thus causing insulation failure; on the other hand, the thickness of the second fillet 34 will not be too thin due to r2 being too large, affecting the strength of the casing 211.

[0442] In some embodiments, H and T2 satisfy the condition: 300 ≤ H / T2 ≤ 800. For example, H / T2 = 300, 350, 400, 450, 500, 550, 600, 650, 700, 750, 800, etc.

[0443] 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], the volume utilization rate and strength of the battery cell 20 can be balanced.

[0444] like Figure 15 As shown, the maximum thickness of the second fillet 34 is T3, where the ratio of T3 to T2 satisfies: 0.8 ≤ T3 / T2 ≤ 2. For example, T3 / T2 = 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0.

[0445] The thickness of the second fillet 34 can be uniform or non-uniform. The following will define the maximum thickness T3 of the second fillet 34 as an example of a uniform thickness. In some embodiments, the maximum thickness T3 of the second fillet 34 can be defined as the length of the extension line connecting the center of the inner arc circle and the center of the outer arc circle in any cross section along the axis perpendicular to the inner and outer surfaces in the second fillet 34.

[0446] 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 (which has the smallest thickness) in the range of [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 too weak due to excessive thinning of the second fillet 34, nor will the shell 211 be difficult to manufacture due to insufficient thinning of the second fillet 34.

[0447] In some embodiments, the wall thickness of the housing 211 is uniform, that is, all walls of the housing 211 have the same wall thickness.

[0448] In this embodiment, by setting the wall thickness of the housing 211 to be uniform, on the one hand, the processing difficulty of the housing 211 can be reduced, and on the other hand, each wall of the housing 211 can be set to the minimum processing wall thickness, which helps to fully improve the space utilization of the housing 211.

[0449] In some embodiments, the battery cell 20 further includes a cover plate 212 for covering the opening 301 of the housing 211 to enclose the electrode assembly 22 within the cavity of the housing 211.

[0450] In this embodiment, by setting the inner diameter R1 of the first fillet between the depth H of the housing and the second housing wall to satisfy 2.5mm≤R1≤20mm and 50mm≤H≤250mm, the risk of cracking caused by stress during the integral molding process of the housing can be reduced as much as possible without affecting the energy density of the battery cell, thereby reducing the molding difficulty of the housing.

[0451] In some embodiments, the battery cell 20 is generally rectangular in shape; for example, the battery cell 20 is a rectangular parallelepiped battery cell. As another example, the battery cell 20 is a racetrack-shaped battery cell with a thickness of D1, where H, R1, and D1 satisfy: 0.15mm ≤ R1*D1 / H ≤ 36mm.

[0452] 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.

[0453] In some embodiments, D2 may be the dimension of the battery cell 20 in the expansion direction of the electrode assembly 22.

[0454] In this embodiment, by setting 0.15mm≤R1*D1 / H≤36mm, the risk of the casing 211 cracking due to excessive stress caused by the small value of R1*D1 / H during the molding process can be reduced. Moreover, the impact on the energy density of the battery cell 20 caused by the large value of R1*D1 / H can be reduced.

[0455] 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.

[0456] In this embodiment, H and R1 satisfy: 50mm≤H≤250mm, 2.5mm≤R1≤20mm.

[0457] In some embodiments, H, R1, and D1 satisfy: 0.34mm ≤ R1*D1 / H ≤ 18mm.

[0458] In this embodiment, by setting 0.34mm≤R1*D1 / H≤18mm, a balance can be achieved between the molding difficulty and energy density of the housing 211.

[0459] For example, R1*D1 / H=0.34, 0.5, 1, 3, 5, 8, 11, 13, 16, 18.

[0460] Similarly, in this embodiment, D1 satisfies: 15mm≤D1≤90mm.

[0461] In this embodiment, H and R1 satisfy: 75mm≤H≤180mm, 4mm≤R1≤15mm.

[0462] In some embodiments, H, R1, and D1 satisfy: 0.9mm ≤ R*D / H ≤ 6.6mm.

[0463] 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.

[0464] 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.

[0465] Furthermore, in this embodiment, H and R1 satisfy: 90mm≤H≤140mm, 3mm≤R≤10mm.

[0466] It should be noted that the value ranges of R1, H, D1, and R1*D1 / H can be interrelated. For example, under the conditions of 15mm≤D1≤90mm, 50mm≤H≤250mm, and 2.5mm≤R1≤20mm, 0.15mm≤R1*D1 / H≤36mm. Another example is under the conditions of 15mm≤D1≤90mm, 75mm≤H≤180mm, and 4mm≤R1≤15mm, 0.34mm≤R*D / H≤18mm. Yet another example is under the conditions of 25mm≤D1≤60mm, 90mm≤H≤140mm, and 3mm≤R1≤10mm, 0.9mm≤R1*D1 / H≤6.6mm.

[0467] In some embodiments, the thickness of the electrode assembly 22 is D2, and R1 and D2 satisfy: 0.125≤R1 / D2≤0.45.

[0468] 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.

[0469] Optionally, D2 can be the dimension of the electrode assembly 22 in the expansion direction.

[0470] In this embodiment, by setting 0.125≤R1 / D2≤0.45, on the one hand, it will not interfere with the electrode assembly 22 or have insufficient residual space inside the battery cell 20 due to excessively large R1, thereby affecting the performance of the battery cell 20; on the other hand, it will not cause difficulties in forming the casing 211 due to excessively small R1.

[0471] Figure 16 An exploded schematic diagram of the housing 211 according to an embodiment of this application is shown. Figure 17 A schematic diagram of the structure of the second housing portion 42 according to an embodiment of this application is shown. Figure 18 This paper shows another structural schematic diagram of the second housing portion 42 according to an embodiment of the present application. Figure 19Another exploded view of the housing 211 according to an embodiment of this application is shown. It should be noted that this housing 211 can be applied to the battery cell 20. For example, as... Figures 16 to 19 The housing 211 shown can be applied to Figure 3 and Figure 4 In the battery cell 20 shown, and as Figures 16 to 19 The housing 211 shown may include only Figure 4 The housing 211 shown may also include both Figure 4 The housing 211 shown also includes Figure 4 The cover plate 212 is shown. Alternatively, the housing 211 can also be placed as follows... Figure 3 or Figure 4 As shown.

[0472] like Figure 16 As shown, the housing 211 includes a first housing portion 41 with a first opening 401. The first housing portion 41 includes a first wall 411 opposite to the first opening 401 and a second wall 412 connected to the first wall 411. The first wall 411 and the second wall 412 are integrally formed. A second housing portion 42 is fixedly connected to the second wall 412. At least a portion of the housing 211 is formed by the first housing portion 41 and the second housing portion 42 along its depth direction. For ease of explanation, the depth direction of the first housing portion 41 is taken as the height direction Z of the battery cell 20 as an example below.

[0473] It should be explained that the first wall 411 and the second wall 412 in the first housing part 41 are integrally formed structures, which means that the first housing part 41 is made by an integral deep drawing process. For example, the first housing 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 housing design and process requirements. The die is usually made of die steel, carbon steel, or cemented carbide, and includes components such as punch, die, and blank holder; 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, causing it to deform and fill the shape of the die; Step 5: Control the speed and pressure of the punch to ensure that the steel deforms uniformly during the deep drawing process, drawing it to a certain depth and obtaining the required shape; Step 6: Perform auxiliary operations such as piercing, trimming, and marking during the deep drawing process as needed; Step 7: After the deep drawing is completed, remove the product from the die and perform necessary processing, such as cleaning and deburring, to obtain the first housing part 41.

[0474] Since the first housing portion 41 is integrally drawn, it typically has a first opening 401. The first opening 401 can be circular, polygonal, or racetrack-shaped. Polygons can be, for example, square, pentagonal, hexagonal, or other irregular shapes.

[0475] The first housing portion 41 is a hollow structure formed by a first wall 411 and a second wall 412 opposite to the first opening portion 401, wherein the second wall 412 intersects with the first wall 411. For example, the first wall 411 and the second wall 412 are arranged perpendicularly. In some embodiments, the first housing portion 41 includes a second wall 412, which is connected end to end and together with the first wall 411 forms a cylindrical hollow structure. In other embodiments, the first housing portion 41 includes four second walls 412, which are arranged in pairs opposite to each other, and adjacent two second walls 412 intersect perpendicularly. Therefore, the four second walls 412 and the first wall 411 together form a square columnar hollow structure.

[0476] Since the first wall 411 and the first opening 401 of the first housing portion 41 are disposed opposite to each other, the depth direction Z of the first housing portion 41 can be understood as the direction perpendicular to the first wall 411, and the distance between the first opening 401 and the first wall 411 of the first housing portion 41 is the depth of the first housing portion 41.

[0477] In this embodiment, the second housing portion 42 is fixedly connected to the second wall 412, and does not include a second housing portion 42 being a flat plate structure and fitting into the first opening 401 of the first housing portion 41. In other words, in this embodiment, 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 Figure 17 The second opening 402 shown is disposed opposite to the first opening 401 of the first housing portion 41, and the second wall 412 and the third wall 421 are fixedly connected such 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 portion 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. Here, the depth H of the housing 211 can be understood as the dimension of the housing 211 along the depth direction of the first housing portion 41. Normally, the wall of the housing 211 has a certain thickness, but here, the wall thickness of the housing 211 can be ignored.

[0478] In this embodiment, the housing 211 includes a first housing portion 41 and a second housing portion 42. The first housing portion 41 has a first opening 401 and includes a first wall 411 opposite to the first opening 401 and a second wall 412 connected to the first wall 411. The first wall 411 and the second wall 412 are integrally formed. In the depth direction 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. Compared with the technical solution of directly integrally forming the housing 211, the housing 211 prepared in this way can reduce the risk of cracking of the housing 211 during the integral deep drawing process.

[0479] In some embodiments, the dimensions of the second wall 412 are uniform along the depth direction Z of the first housing portion 41. Similarly, the dimensions of the third wall 421 are uniform along the depth direction Z of the first housing portion 41. Thus, the entire area of ​​the housing 211 along the depth direction Z of the first housing portion 41 is formed by the first housing portion 41 and the second housing portion 42.

[0480] In other embodiments, the dimensions of the second wall 412 are not entirely equal in the depth direction Z of the first housing portion 41. For example, the unfolded second wall 412 may be semi-circular or triangular. Similarly, the dimensions of the third wall 421 are not entirely equal in the depth direction Z of the first housing portion 41. For example, the unfolded third wall 421 may be semi-circular or triangular. Therefore, in the depth direction Z of the first housing portion 41, a portion of the housing 211 may be formed jointly by the first housing portion 41 and the second housing portion 42.

[0481] In one embodiment, the first housing part 41 and the second housing part 42 are fixedly connected by welding. Thus, the housing 211 prepared in the manner described in this application embodiment is less prone to cracking and damage than a housing formed by welding a flat structure and a tubular structure with an opening.

[0482] Optionally, in the depth direction Z of the first housing portion 41, the second housing portion 42 has two communicating openings. For example, the second housing portion 42 includes, for example, Figure 17 The second opening 402 and the third opening 403 are shown, and the second opening 402 and the third opening 403 are disposed opposite each other in the depth direction Z along the first housing portion 41.

[0483] In this embodiment, by setting the second housing portion 42 to have two interconnected openings in the depth direction Z of the first housing portion 41, the cover plate and the housing 211 can be set independently, thereby allowing for better placement of components such as electrode terminals on the cover plate, and making the fabrication of the housing 211 simpler.

[0484] In other embodiments, the second housing portion 42 may have only one opening. For example, the second housing portion 42, similar to the first housing portion 41, is also manufactured by an integral deep drawing process. In this process, in addition to the third wall 421 mentioned above, the second housing portion 42 also includes a wall that intersects with the third wall 421 and is opposite to the opening of the second housing portion 42, such as a cover plate.

[0485] In one embodiment, the second housing portion 42 is an integrally formed structure.

[0486] In this embodiment, by setting the second housing part 42 as an integrally formed structure, the welds of the housing 211 can be reduced, making the housing 211 highly reliable and less prone to deformation, cracking and damage.

[0487] In another embodiment, where the second housing portion 42 has only one opening, the second housing portion 42 may be formed by welding together at least two parts.

[0488] It should be noted that when the second housing portion 42 is formed by welding together at least two parts, the weld seam of the second housing portion 42 should not be on the edge, that is, on the right-angle edge. For example, as Figure 18 As shown, the second housing portion 42 includes four third walls 421, namely 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 each other, and the sixth wall 4213 and the seventh wall 4214 are arranged opposite each other. The sixth wall 4213 includes a first sub-wall 4213a and a second sub-wall 4213b, which are symmetrical about a first center line 4251. The seventh wall 4214 includes a third sub-wall 4214a and a fourth sub-wall 4214b, which are symmetrical about a second center line 4261. The second housing portion 42 is formed by welding together a first portion 423 and a second portion 424. The first part 423 includes a first sub-wall 4213a, a fourth wall 4211 and a third sub-wall 4214a, the second part 424 includes a second sub-wall 4213b, a fifth wall 4212 and a fourth sub-wall 4214b, and the first center line 4251 and the second center line 4261 are the weld seams of the second housing part 42.

[0489] In this embodiment, the second housing part 42 is configured to be formed by welding together at least two parts, which is easy to process and easier to control in size, thereby improving the assembly accuracy of the housing 211.

[0490] 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, where the wall thickness of the housing 211 should be taken into account. 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 joined to form a plane.

[0491] 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.

[0492] In this embodiment, welding the surface 4121 of the second wall 412 that faces away from the first wall 411 to the second housing portion 42 can improve the space utilization of the housing 211.

[0493] In other embodiments, the surface of the second wall 412 perpendicular to the thickness direction of the second wall 412 is welded to the second housing portion 42. For example, as... Figure 19 As shown, the inner surface 4122 of the second wall 412 is welded to the outer surface 4215 of the third wall 421 of the second housing part 42 at the first opening 401 of the first housing part 41.

[0494] 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 housing portion 42, it is beneficial to increase the welding area of ​​the first housing portion 41 and the second housing portion 42, thereby improving the welding strength between them.

[0495] Figure 20 A schematic cross-sectional view of the housing 211 according to an embodiment of this application is shown. Figure 20 As shown, in the depth direction Z of the first housing part 41, the maximum dimension of the first housing part 41 is h1, and the maximum dimension of the housing 211 is H, wherein H and h1 satisfy: 3≤H / h1≤80.

[0496] It should be explained that, without considering wall thickness, the dimensions of the first housing portion 41 in the depth direction Z can be non-uniform. The maximum dimension h1 of the first housing portion 41 can refer to the maximum distance between the end of the second wall 412 furthest from the first wall 411 and the first wall 411. Similarly, without considering wall thickness, the dimensions of the housing 211 in the depth direction Z of the first housing portion 41 can also be non-uniform. The maximum dimension H of the housing 211 can refer to the maximum distance between the end of the second housing portion 42 furthest from the first wall 411 and the first wall 411.

[0497] In some embodiments, the dimensions of the first housing portion 41 are uniform in the depth direction Z, and the dimensions of the housing 211 are also uniform.

[0498] For example, H / h1=3, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80.

[0499] In this embodiment, the ratio of H to h1 is set within the range of [3, 80]. This ensures that the welding positions of the first housing part 41 and the second housing part 42 are not too close to the first housing part 41 due to an excessively large ratio, which could cause the weld to crack due to excessive stress during the use of the battery cell; and that the ratio is not too small, which could cause the housing 211 to crack due to excessive stress during the deep drawing process, thus making the manufacturing of the first housing part 41 difficult.

[0500] Alternatively, 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.

[0501] In some embodiments, h1 satisfies: 3mm≤h1≤50mm.

[0502] For example, h1 = 3mm, 5mm, 10mm, 15mm, 20mm, 25mm, 30mm, 35mm, 40mm, 45mm, 50mm.

[0503] In this embodiment, by setting h1 within the range of [3mm, 50mm], it is possible to avoid the weld seam being too close to the first housing part 41 due to h1 being too small, which would pose a risk of cracking of the battery cell during charging and discharging; and to avoid the first housing part 41 cracking during the integral drawing process due to h1 being too large, which would make the manufacturing of the first housing part 41 difficult.

[0504] Alternatively, h1 can satisfy: 5mm≤h1≤30mm.

[0505] It should be noted that, provided h1 satisfies the above conditions, H can also satisfy the condition that H is greater than or equal to 100 mm. For example, H equals 400 mm.

[0506] In some embodiments, the yield strength of the shell 211 at a temperature of 25°C is Re, where Re satisfies: 125MPa≤Re≤1000MPa.

[0507] Yield strength can be understood as the critical stress value at which a material yields. 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 plastic deformation occurs is 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 in this embodiment at a temperature of 25°C can be selected according to the actual application. For example, the yield strength Re can be tested at room temperature (25°C) using GB / T228.1-2010.

[0508] 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, 980 MPa, 1000 MPa.

[0509] In this embodiment, by using a material with a yield strength Re satisfying 125MPa≤Re≤1000MPa to make the first housing part, the wall thickness of the first housing part can be reduced without reducing the strength of the first housing part, thereby increasing the capacity space of the battery cell.

[0510] Figure 21 A partial structural schematic diagram of the housing 211 according to an embodiment of this application is shown. For example, the Figure 21 It can be Figure 9 A magnified view of a portion of region A' shown. (See attached image.) Figure 21 As shown, the housing 211 in this embodiment of the application has a multi-layer structure, and the material of the outermost housing 2117 of the housing 211 includes at least one of the following: aluminum, aluminum alloy, copper, copper alloy and chromium.

[0511] It should be understood that the shell 211 in this embodiment is a multi-layer structure, meaning that for any wall of the shell 211, multiple layers are stacked along the thickness direction of that wall to make the shell 211 a multi-layer structure. Furthermore, the installation method between the multi-layer structures of the shell 211 can be flexibly configured according to actual applications. For example, multiple single-layer shell structures of different sizes but basically the same shape can be processed first, for example, each single-layer shell structure is a hollow structure with an opening; then, the larger shell structure among the multiple single-layer shell structures is sequentially nested on the outside of the smaller shell structure, so that the multiple single-layer shell structures can be combined into a multi-layer shell 211. As another example, an approximately plate-like structure with a multi-layer structure can also be processed first; then, multiple such plate-like structures can be spliced ​​together to form a multi-layer shell 211, but this embodiment is not limited to this.

[0512] It should be understood that the outermost shell 2117 of the shell 211 in this embodiment 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.

[0513] In this embodiment, the material of the outermost shell 2117 of the housing 211 may include at least one of the following: aluminum, aluminum alloy, copper, copper alloy, and chromium. When the material of the outermost shell 2117 contains aluminum, the aluminum will be oxidized into dense alumina, which provides corrosion resistance; when the material of the outermost shell 2117 contains copper, the copper will be oxidized into copper oxide, i.e., verdigris, which also provides corrosion resistance; when the material of the outermost shell 2117 contains chromium, the chromium will be oxidized into chromium oxide, which also provides corrosion resistance. Therefore, when the material of the outermost shell 2117 is a corrosion-resistant material as described above, the outermost shell 2117 can protect the other shell layers located inside it, which can improve both the structural stability and service life of the housing 211.

[0514] It should be understood that the specific thickness of the outermost shell 2117 in this embodiment can also be flexibly set according to actual applications. For example, the thickness of the outermost shell 2117 can be set according to a certain proportion based on the thickness of the shell 211.

[0515] In some embodiments, the average thickness of the outermost shell 2117 is T11, and the average thickness of the shell 211 is T10, where T11 and T10 satisfy: 0.15 ≤ T11 / T10 ≤ 0.5. If the ratio T11 / T10 is set too small, the average thickness T11 of the outermost shell 2117 will be very small due to the limited average thickness T10 of the shell 211. This will increase the processing difficulty and reduce the corrosion resistance of the outermost shell 2117, thus affecting the structural reliability of the shell 211. Conversely, if the ratio T11 / T10 is set too large, the average thickness T11 of the outermost shell 2117 will be very large, while the thickness of the other shell layers of the shell 211 will be very small. However, the structural strength of the outermost shell 2117 may be insufficient, especially after oxidation, its deformation capacity is poor, and a large average thickness T11 will affect the overall structural strength of the shell 211, thus reducing the stability of the shell 211.

[0516] Furthermore, T11 and T10 satisfy: 0.15 ≤ T11 / T10 ≤ 0.4. Appropriately reducing the maximum value of the ratio T11 / T10 and increasing the minimum value of the ratio T11 / T10 can limit the average thickness T11 of the outermost shell 2117 to be neither too large nor too small, which can improve the corrosion resistance and the structural strength and stability of the shell 211.

[0517] Furthermore, T11 and T10 satisfy: 0.2≤T11 / T10≤0.3, in order to better improve the corrosion resistance and enhance the stability and reliability of the shell 211.

[0518] In some embodiments, the ratio T11 / T10 of the average thickness T11 of the outermost shell 2117 to the average thickness T10 of the shell 211 can be set to other values. For example, the ratio T11 / T10 can be any one of the following values ​​or between any two of the following values: 0.15, 0.18, 0.2, 0.23, 0.25, 0.28, 0.3, 0.33, 0.35, 0.38, 0.4, 0.43, 0.45, 0.48, and 0.5.

[0519] It should be understood that the average thickness T10 of the housing 211 in this embodiment can also be flexibly set according to actual application. For example, the average thickness T10 of the housing 211 satisfies: 0.05mm ≤ T10 ≤ 0.5mm. The average thickness T10 of the housing 211 should not be too small to reduce the processing difficulty of the multi-layer housing 211 and improve the structural strength of the housing 211. For example, the housing 211 is not easy to break, thereby improving the service life of the housing 211. Conversely, the average thickness T10 of the housing 211 should not be too large to reduce the space occupied by the housing 211, improve the space utilization of the battery cell 20, and thus improve the energy density of the battery 10 with multiple battery cells 20.

[0520] Furthermore, the average thickness T10 of the housing 211 satisfies: 0.075mm≤T10≤0.4mm. Appropriately reducing the average thickness T10 of the housing 211 can reduce the space occupied by the housing 211 inside the battery 10, thereby increasing the energy density of the battery 10; while appropriately increasing the average thickness T10 of the housing 211 can also reduce the processing difficulty of the housing 211.

[0521] Furthermore, the average thickness T10 of the housing 211 satisfies: 0.1mm ≤ T10 ≤ 0.3mm. The average thickness T10 of the housing 211 is neither too large nor too small, which can improve the structural strength and stability of the housing 211, and reduce the space occupied by the housing 211 inside the battery 10, thereby improving the energy density of the battery 10.

[0522] In some embodiments of this application, the average thickness T10 of the housing 211 can be set to other values. For example, the average thickness T10 of the housing 211 can be any one of the following values ​​or between any two of the following values: 0.05mm, 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.

[0523] It should be understood that the average thickness T11 of the outermost shell 2117 in this embodiment can also be flexibly set according to actual applications. 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 processing difficulty, improve the corrosion resistance of the outermost shell 2117, and thus improve the structural reliability of the shell 211. Conversely, the average thickness T11 of the outermost shell 2117 should not be too large either. Considering that the outermost shell 2117 has poor deformation ability after oxidation, if its average thickness T11 is too large, it will affect the overall deformation ability of the shell 211, thereby reducing the reliability and stability of the shell 211.

[0524] Furthermore, the average thickness T11 of the outermost shell 2117 can also satisfy: 0.05mm ≤ T11 ≤ 0.2mm. Appropriately increasing the minimum value of the average thickness T11 of the outermost shell 2117 can improve its corrosion resistance; appropriately decreasing the maximum value of the average thickness T11 of the outermost shell 2117 can improve the overall structural deformation capacity of the shell 211, thereby improving the reliability and stability of the shell 211.

[0525] Furthermore, the average thickness T11 of the outermost shell 2117 can also satisfy: 0.075mm≤T11≤0.15mm. This can improve the corrosion resistance 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.

[0526] In some embodiments of this application, the average thickness T11 of the outermost shell 2117 may 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.

[0527] It should be understood that the thickness of the inner shell 2118 of the shell 211 in this embodiment can also be flexibly set according to actual applications. The inner shell 2118 can be any shell layer of the shell 211 other than the outermost shell 2117. Furthermore, the shell 211 may include one or more inner shells 2118. When the shell 211 includes multiple inner shells 2118, the thickness of these multiple inner shells 2118 can be the same to facilitate processing, or they can be different to flexibly adjust the thickness of the inner shells 2118 at different positions according to actual applications. For example, as... Figure 21 As shown, taking a three-layer shell structure as an example, the shell 211 includes an outermost shell 2117 and two inner shells 2118. 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 both 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. The embodiments of this application are not limited to this.

[0528] It should be understood that the average thickness T10 of the shell 211 in this embodiment can refer to the average thickness of at least a portion of the shell 211. The average thickness T11 of the outermost shell 2117 of the shell 211 can also refer to the average thickness of at least a portion of the outermost shell 2117. The average thickness T12 of the inner shell 2118 of the shell 211 can also refer to the average thickness of at least a portion of the inner shell 2118. Furthermore, the calculation area for the average thickness T10 of the shell 211 is generally consistent with the calculation area for the average thickness T11 of the outermost shell 2117 and also with the calculation area for the average thickness T12 of the inner shell 2118. For example, if some areas are 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 and the calculation of the average thickness T12 of the inner shell 2118 also require excluding the same areas. For ease of explanation, the following description takes the calculation of the average thickness T10 of the shell 211 as an example. However, the same description applies to determining the average thickness T11 of the outermost shell 2117 and the average thickness T12 of the inner shell 2118, and will not be repeated here.

[0529] For example, the average thickness T10 of the housing 211 can refer to the average thickness T10 of the entire area of ​​the housing 211. Especially when the entire surface of the housing 211 is relatively flat, that is, when the thickness of most areas of the housing 211 is basically equal or the difference is small, or when the thickness of the entire area of ​​the housing 211 is basically equal or the difference is small, the average thickness of the entire area of ​​the housing 211 can be determined as T10.

[0530] For example, the average thickness T10 of the housing 211 can also refer to the average thickness T10 of a local area of ​​the housing 211, that is, the average thickness T10 of the remaining area after excluding a certain area of ​​the housing 211. For example, if there are certain special areas in the housing 211 whose thickness differs significantly from other areas, such as if these special areas have protruding structures or recessed areas along the thickness direction, making their thickness larger or smaller than other areas, then these special areas can be excluded, and the average thickness T10 of the remaining area of ​​the housing 211 can be calculated.

[0531] In some embodiments, the housing 211 may include functional regions, and the average thickness T10 of the housing 211 is the average thickness of the regions of the housing 211 other than the functional regions. For example, the functional regions include at least one of the following regions: a pressure relief region, a region where the electrode terminals 214 are located, a liquid injection region, and a welding region. The thickness of the functional regions is usually significantly different from the thickness of other regions of the housing 211. Therefore, calculating the average thickness T10 of the housing 211 without including the functional regions allows the design of the housing 211 to better meet strength requirements, thereby improving the structural strength and stability of the battery cell 20.

[0532] It should be understood that the functional areas of this application embodiment may include areas on the housing 211 that have specific structures or specific uses, and are applicable to the "functional areas" described above. For the sake of brevity, they will not be described in detail here. For example, the functional area may include a pressure relief area, which is used to install a pressure relief mechanism. The pressure relief mechanism of this application embodiment can be installed on any wall of the battery cell 20. For example, the pressure relief mechanism can be installed in the pressure relief area of ​​the housing 211 of the battery cell 20. The pressure relief mechanism can be part of the housing 211; or it can be a separate structure from the housing 211 and fixed to the housing 211 by means of, for example, welding. For example, when the pressure relief mechanism is part of the housing 211, for example, the pressure relief mechanism can be formed by setting a groove on the housing 211, that is, the housing 211 has a groove in the pressure relief area, and the thickness at the groove is significantly less than the thickness of other areas of the housing 211. Therefore, the average thickness T10 of the housing 211 can be disregarded by calculating the thickness at the groove. The groove is the weakest point of the pressure relief mechanism. When the battery cell 20 produces too much gas, causing the internal pressure to rise and reach a threshold, or when the internal reaction of the battery cell 20 generates heat, causing the internal temperature of the battery cell 20 to rise and reach a threshold, the pressure relief mechanism can rupture at the groove, causing the inside and outside of the battery cell 20 to communicate. The gas pressure and temperature are released to the outside through the rupture of the pressure relief mechanism, thereby preventing the battery cell 20 from exploding.

[0533] For example, the pressure relief mechanism can also be a separate structure from the housing 211. The pressure relief mechanism can take the form of an explosion-proof valve, gas valve, pressure relief valve, or safety valve, and can specifically employ pressure-sensitive or temperature-sensitive elements or structures. For instance, the housing 211 has a through hole in the pressure relief area, and the pressure relief mechanism is installed and fixed to the housing 211 through the through hole. After installation, the pressure relief mechanism may protrude or be recessed relative to other areas of the housing 211. Therefore, the average thickness T10 of the housing 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 activates or a weak structure within the pressure relief mechanism is damaged, thereby forming an opening or channel for the release of internal pressure or temperature.

[0534] In some embodiments, the functional area may further include the area where the electrode terminals 214 are located. Each electrode terminal 214 in this application embodiment can be disposed on any wall, and multiple electrode terminals 214 can be disposed on the same wall or different walls of the battery cell 20. For example, as... Figures 3 to 4 As shown, each battery cell 20 includes two electrode terminals 214, which are located on the same wall. For example, both electrode terminals 214 can be located on the cover plate 212.

[0535] For example, again taking the case where each battery cell 20 includes two electrode terminals 214, and these two electrode terminals 214 are located on the same wall, unlike... Figures 3 to 4 As shown, the two electrode terminals 214 can also be located on any wall of the housing 211. For example, both electrode terminals 214 can be located on the wall with the smallest area of ​​the housing 211. When one or more electrode terminals 214 are located on the housing 211, each electrode terminal 214 typically protrudes from other areas of the housing 211, meaning 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 average thickness T10 of the housing 211 may not include the area where all the electrode terminals 214 are located.

[0536] In some embodiments, the functional area may further include a liquid injection area. For example, the liquid injection area of ​​the housing 211 may be provided with a liquid injection hole through which electrolyte is injected into the housing 211. After the electrolyte injection is completed, the liquid injection hole can be sealed by a sealant. Considering that the thickness of the liquid injection area where the sealant 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 liquid injection area.

[0537] In some embodiments, the functional area may further include a welding area. For example, the housing 211 and the cover plate 212 may be fixed by welding, or the housing 211 itself needs to be formed by welding. For example, any two walls of the housing 211 may be welded together, or the housing 211 may be formed by splicing at least two parts together, in which case the housing 211 may include a welding area. For example, the housing 211 may be welded by splicing, in which case the housing 211 may have a weld seam 2113. Specifically, the housing 211 may include at least two parts, which are connected by welding to form the housing 211. In this embodiment, the housing 211 mainly includes two parts along the height direction Z of the battery cell 20 as an example, with a weld seam 2113 between the upper half and the lower half of the housing; or, different from Figure 4 As shown, other parts of the housing 211 may also be provided with welds 2113, but this application embodiment is not limited to this. The welding area of ​​the functional area in this application embodiment 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 housing 211. Therefore, the average thickness T10 of the housing 211 may not include the welding area.

[0538] It should be understood that, in order to further improve the structural strength and reliability of the housing 211, the inner housing 2118 of the housing 211 can be configured according to actual applications. In some embodiments, the tensile strength of the inner housing 2118 of the housing 211 at 25°C is Rm1, where Rm1 satisfies: 250MPa≤Rm1≤2000MPa. By increasing the tensile strength Rm1 of the inner housing 2118 at room temperature (25°C), the overall structural strength and stability of the housing 211 are increased; however, the tensile strength Rm1 of the inner housing 2118 at room temperature should not be too large, so as to reduce the difficulty of material selection for the inner housing 2118, thereby reducing the processing difficulty and processing cost of the battery cell 20.

[0539] It should be understood that the range of tensile strength Rm1 of the inner shell 2118 at room temperature (25°C) in this embodiment can be adjusted according to actual application. For example, the value of the room temperature tensile strength Rm1 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 its deformation capacity to resist the expansion of the electrode assembly 22, making the inner shell 2118 less prone to damage, 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 to avoid it being too large can reduce the difficulty of material selection and processing of the inner shell 2118, save costs, and facilitate processing.

[0540] Furthermore, the tensile strength Rm1 of the inner shell 2118 under normal temperature conditions can be set to satisfy 450MPa≤Rm1≤800MPa. The tensile strength Rm1 of the inner shell 2118 under normal temperature conditions will not be 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 cost-effective.

[0541] In some embodiments, the tensile strength Rm1 of the inner shell 2118 under normal temperature conditions in this application embodiment can also be set to other values. For example, the value of the room temperature tensile strength Rm1 can be any one of the following values ​​or between any two of the following values: 250MPa, 280MPa, 300MPa, 330MPa, 350MPa, 380MPa, 400MPa, 450MPa, 500MPa, 550MPa, 600MPa, 650MPa, 700MPa, 750MPa, 800MPa, 850MPa, 900MPa, 950MPa, 1 000MPa, 1050MPa, 1100MPa, 1150MPa, 1200MPa, 1250MPa, 1300MPa, 1350MPa, 1400MPa, 1450MPa, 1500MPa, 1550MPa, 1600MPa, 1650MPa, 1700MPa, 1750MPa, 1800MPa, 1850MPa, 1900MPa, 1950MPa, and 2000MPa.

[0542] It should be understood that the tensile strength in this application embodiment refers to the maximum stress value that the material can withstand before breaking. The test method for the tensile strength Rm1 of the inner shell 2118 in this application embodiment 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 room temperature of 25°C.

[0543] The preceding text primarily used a rectangular battery cell 20 as an example for description. The following text, in conjunction with the accompanying drawings, will use a cylindrical battery cell 20 as an example for description. The cylindrical battery cell 20 of this embodiment is identical to the rectangular battery cell 20 described above, except for their shape; therefore, further details will not be repeated here.

[0544] Figure 22 A schematic diagram of the structure of a battery cell 20 according to an embodiment of this application is shown, for example, Figure 3 The battery cell 20 shown can be any one of the battery cells 20 in the battery 10; Figure 23 This illustration shows a partially exploded structural diagram of a battery cell 20 according to an embodiment of this application. For example, Figure 23 It can be Figure 22 The diagram shows a partial exploded structure of the battery cell 20. Figure 24 This paper shows a cross-sectional schematic diagram of the casing 211 of a battery cell 20 according to one embodiment of this application. For example, Figure 24 It can be Figure 22 and Figure 23 The diagram shows a cross-sectional view of the housing 211 of the battery cell 20.

[0545] In the embodiments of this application, such as Figures 22 to 24 As shown, the battery cell 20 includes: an electrode assembly 22, which includes a first tab 2221; a first electrode terminal 214a; and a housing 211, which includes a cylindrical body 211b and a cover 211a connected to the cylindrical body 211b. The cylindrical body 211b is disposed around the outer periphery of the electrode assembly 22, and the cover 211a includes the first electrode terminal 214a. The first tab 2221 is electrically connected to the first electrode terminal 214a through the cylindrical body 211b. The housing 211 has a multi-layer structure with different resistivities.

[0546] The shell 211 can be of various shapes, such as a cylinder, a cuboid, or other polyhedrons. For example, ... Figures 22 to 24 As shown, the shell 211 is described here as a hollow cylindrical structure. Furthermore, this embodiment mainly uses a hollow structure with an opening at one end as an example, with the cover plate 212 being a circular plate structure adapted to fit the shell 211. For the cylindrical shell 211, correspondingly, the cylinder 211b is a cylinder, and the cover 211a is a circular plate structure.

[0547] The electrode assembly 22 in this embodiment may include a first tab 2221, which can be electrically connected to a first electrode terminal 214a through the cylindrical body 211b of the housing 211, thus simplifying the structure of the battery cell 20. The housing 211 is configured as a multi-layer structure with different resistivities. The current carrying capacity of the battery cell 20 can be improved by using a layer with lower resistivity, and the structural strength of the housing 211 can be improved by using a layer with higher resistivity. This can improve both the performance and structural strength of the battery cell 20, thereby increasing the service life of the battery cell 20.

[0548] In this embodiment, the electrode assembly 22 further includes a second tab 2222, which has the opposite polarity to the first tab 2221. Specifically, from the external shape of the electrode assembly 22, the electrode assembly 22 includes an electrode body 221 and tabs 222. The tabs 222 include a first tab 2221 and a second tab 2222, which protrude from the electrode body 221. The first tab 2221 is the portion of the first electrode sheet without an active material layer, and the second tab 2222 is the portion of the second electrode sheet without an active material layer. The first tab 2221 and the second tab 2222 are used to draw current from the electrode body 221.

[0549] The first tab 2221 and the second tab 2222 can extend from the same side of the electrode body 221, meaning that the first tab 2221 and the second tab are located on the same end face of the electrode assembly 22. Alternatively, the first tab 2221 and the second tab 2222 can also extend from different sides of the electrode body 221, meaning that the first tab 2221 and the second tab are located on different end faces of the electrode assembly 22. For example, the first tab 2221 and the second tab 2222 can also extend from opposite sides, meaning that the first tab 2221 and the second tab 2222 are located on opposite end faces of the electrode assembly 22, for ease of processing. Figures 22 to 24 As shown, the first tab 2221 and the second tab 2222 can be respectively disposed on both sides of the electrode body 221 along the first direction Z. In other words, the first tab 2221 and the second tab 2222 are respectively disposed at both ends of the electrode assembly 22 along the first direction Z. The first direction Z can be the height direction Z of the electrode assembly 22.

[0550] It should be understood that the electrode assembly 22 includes a first electrode, a second electrode, and a separator, the separator being used to separate the first electrode and the second electrode. The first electrode and the second electrode have opposite polarities; in other words, one of the first electrode and the second electrode is the positive electrode 223, and the other of the first electrode and the second electrode is the negative electrode 224.

[0551] The first electrode, the second electrode, and the separator are all strip-shaped structures, and are wound together to form a wound structure. The wound structure can be cylindrical, flat, or other shapes.

[0552] Optionally, the first tab 2221 is wound multiple times around the central axis of the electrode assembly 22, and the first tab 2221 includes multiple tab layers. After winding, the first tab 2221 is generally cylindrical, with gaps between adjacent tab layers. In this embodiment, the first tab 2221 can be processed to reduce the gaps between tab layers, facilitating connection between the first tab 2221 and other conductive structures. For example, in this embodiment, the first tab 2221 can be flattened to gather and aggregate the end regions of the first tab 2221 away from the electrode body 221; the flattening process forms a dense end face at the end of the first tab 2221 away from the electrode body 221, reducing the gaps between tab layers and facilitating connection between the first tab 2221 and other conductive structures. Alternatively, in this embodiment, conductive material can be filled between adjacent tab layers to reduce the gaps between tab layers.

[0553] Optionally, the second tab 2222 is wound around the central axis of the electrode assembly 22 multiple times, and the second tab 2222 includes multiple tab layers. Exemplarily, the second tab 2222 is also flattened to reduce the gaps between the tab layers of the second tab 2222.

[0554] In this embodiment of the application, the battery cell 20 further includes a second electrode terminal 214b, which is electrically connected to the second tab 2222. The first electrode terminal 214a and the second electrode terminal 214b are located on the same wall of the battery cell 20, so as to improve the integration of the battery cell 20, improve the space utilization of the battery cell 20 in the battery 10, and facilitate processing and assembly.

[0555] It should be understood that the cover 211a in this embodiment includes a first electrode terminal 214a. For example, the first electrode terminal 214a can be disposed on the cover 211a, or the cover 211a can be directly used as the first electrode terminal 214a.

[0556] In some embodiments, the cover 211a serves as the first electrode terminal 214a, and the cover 211a has an electrode lead-out hole 211c. The second electrode terminal 214b is insulated from the cover 211a and mounted in the electrode lead-out hole 211c. One of the cover 211a and the second electrode terminal 214b is the positive output terminal of the battery cell, and the other is the negative output terminal of the battery cell. At least a portion of the housing 211 itself can serve as the output electrode of one of the battery cells 20, thereby eliminating a traditional electrode terminal and simplifying the structure of the battery cell 20. When multiple battery cells 20 are assembled into a group, the housing 211 can be electrically connected to a busbar component, which increases the current-carrying area and allows for more flexible structural design of the busbar component.

[0557] For ease of description, the following mainly uses the cover 211a as an example of the first electrode terminal 214a, but the embodiments of this application are not limited to this.

[0558] Figure 25 This is a partial cross-sectional schematic diagram of a battery 10 provided in some embodiments of this application. The battery 10 may include a plurality of battery cells 20. Figure 26 This is another partial cross-sectional schematic diagram of the battery 10 provided in some embodiments of this application, for example, the Figure 26 It can be Figure 25 The diagram shows an enlarged view of battery 10 at region B'.

[0559] like Figures 22 to 26As shown, the cover 211a is provided with an electrode lead-out hole 211c. At least a portion of the cover 211a is used to electrically connect the first connecting member 81 and the first electrode tab 2221 of the battery 10. The second electrode terminal 214b is used to electrically connect the second connecting member 82 and the second electrode tab 2222 of the battery 10. The second electrode terminal 214b is insulated from the cover 211a and installed in the electrode lead-out hole 211c. One of the cover 211a and the second electrode terminal 214b is the positive output terminal of the battery cell 20, and the other is the negative output terminal of the battery cell 20.

[0560] The cover 211a is electrically connected to the cylinder 211b, and the cover 211a and the cylinder 211b may have the same polarity.

[0561] It should be understood that the cover 211a and the cylinder 211b in this embodiment can be integrally formed, that is, the shell 211 is an integrally formed component. This eliminates the need for the connection process between the cover 211a and the cylinder 211b. For example, the shell 211 can be formed by a stretching process. Of course, the cover 211a and the cylinder 211b can also be two separate components, which are then connected together by welding, riveting, bonding, or other methods. This embodiment mainly uses the example of the cover 211a and the cylinder 211b being integrally formed.

[0562] The housing 211 in this embodiment can be a hollow structure with an opening at one end. Specifically, the cylindrical body 211b has a cylindrical opening 211d at the end opposite to the cover 211a. The battery cell 20 also includes a cover plate 212, which covers the cylindrical opening 211d to close it. The cover plate 212 can have various structures; for example, it can be a plate-like structure.

[0563] 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 a region for welding with the first connecting member 81, that is, the cover 211a can be welded to the first connecting member 81 to form a first welded portion W1. Exemplarily, during welding, a laser acts on the surface of the first connecting member 81 opposite to 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 welded portion W1.

[0564] Electrode lead-out hole 211c extends through cover 211a to allow electrical energy in electrode assembly 22 to be led out to the outside of housing 211. Exemplarily, electrode lead-out hole 211c extends through cover 211a along a first direction Z.

[0565] In this embodiment, the electrode lead-out hole 211c is formed after the housing 211 is stretched and formed. For example, in this embodiment, an electrode lead-out hole 211c for mounting the second electrode terminal 214b is formed on the cover 211a using an opening process, so that the positive output electrode and the negative output electrode are located at the end of the battery cell 20 away from the opening of the housing 211. The cover 211a is formed during the molding process of the housing 211, and the flatness can be ensured after opening the electrode lead-out hole 211c, thus ensuring 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 carrying capacity of the battery cell 20.

[0566] In some embodiments, the cylinder 211b is cylindrical, the electrode lead-out hole 211c is a circular hole, and the central axis of the cylinder 211b and the central axis of the electrode lead-out hole 211c are coincidentally arranged. "Coincidentally arranged" does not require that the central axis of the cylinder 211b and the central axis of the electrode lead-out hole 211c be absolutely and completely coincident, and there may be process-permissible deviations.

[0567] 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 aligned with the central axis of the cylindrical body 211b, so that at least a portion of the second electrode terminal 214b is located at the center of the cover 211a. In this way, when multiple battery cells 20 are assembled into a group, the positional accuracy requirement of the second electrode terminal 214b can be reduced, the assembly process can be simplified, and the assembly efficiency can be improved.

[0568] The central axis of the electrode assembly 22 is a virtual straight line parallel to the first direction Z. The central axis of the electrode assembly 22 can pass through the electrode lead-out hole 211c or be offset from the electrode lead-out hole 211c; this embodiment does not limit this.

[0569] The first tab 2221 is electrically connected to the cover 211a. The first tab 2221 can be directly electrically connected to the cover 211a, or it can be indirectly electrically connected to the cover 211a through other conductive structures. For example, the first tab 2221 can be electrically connected to the cover 211a through the cylinder 211b.

[0570] The second tab 2222 is electrically connected to the second electrode terminal 214b. The second tab 2222 can be directly electrically connected to the second electrode terminal 214b, or it can be indirectly electrically connected to the second electrode terminal 214b through other conductive structures. For example, the second tab 2222 can be electrically connected to the second electrode terminal 214b through the current collector 23.

[0571] The second electrode terminal 214b is insulated from the cover 211a. Therefore, the second electrode terminal 214b and the cover 211a can have different polarities and can serve as different output terminals.

[0572] 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 it can extend into the inside of the housing 211 through the electrode lead-out hole 211c.

[0573] When the first electrode tab 2221 is the negative electrode tab and the second electrode tab 2222 is the positive electrode tab, the cover 211a is the negative output terminal of the battery cell 20, and the second electrode terminal 214b is the positive output terminal of the battery cell 20.

[0574] In battery 10, multiple battery cells 20 are electrically connected via a busbar. The busbar includes a first connecting member 81 and a second connecting member 82. The first connecting member 81 is used to connect to the cover 211a of the battery cell 20, while the second connecting member 82 is used to connect to the second electrode terminal 214b of the battery cell 20.

[0575] The first connecting member 81 can be connected to the cover 211a by welding, bonding or other means to achieve electrical connection between the first connecting member 81 and the cover 211a. The second connecting member 82 can be connected to the second electrode terminal 214b by welding, bonding, riveting or other means to achieve electrical connection between the second connecting member 82 and the second electrode terminal 214b.

[0576] For example, the first connecting member 81 connects the cover 211a of one battery cell 20 to the second electrode terminal 214b of another battery cell 20, while the second connecting member 82 connects the second electrode terminal 214b of the one battery cell 20 to the cover 211a of yet another battery cell 20. In this way, the first connecting member 81 and the second connecting member 82 connect the three battery cells 20 in series.

[0577] In this embodiment, by using the cover 211a and the second electrode terminal 214b as the output terminals, the structure of the battery cell 20 can be simplified while ensuring the overcurrent capacity of the battery cell 20. The cover 211a and the second electrode terminal 214b are located at the same end of the battery cell 20, allowing the first connecting member 81 and the second connecting member 82 to be assembled onto the same side of the battery cell 20. This simplifies the assembly process and improves the efficiency of assembling multiple battery cells 20 into a group.

[0578] It should be understood that, such as Figures 22 to 26 As shown, the second electrode terminal 214b in this embodiment includes a terminal body 2141. Further, the terminal body 2141 can be fixed to the cover 211a by riveting. For example, at least a portion of the terminal body 2141 is located within the electrode lead-out hole 211c, and both ends of the terminal body 2141 are riveted to the electrode lead-out hole 211c.

[0579] In some embodiments, the terminal body 2141 may have a recess that is recessed from the outer surface of the terminal body 2141 in a direction facing the electrode assembly 22. The bottom of the recess is used for welding to the current collector 23.

[0580] When the electrode assembly 22 and the current collector 23 are installed into the housing 211 through the cylinder opening 211d, and the current collector 23 is pressed against the cover 211a, the external welding equipment can weld the bottom of the recess and the current collector 23 from the side of the bottom of the recess away from the current collector 23.

[0581] This embodiment reduces the thickness of the terminal body 2141 by providing a recess, which reduces the welding power required to weld the bottom of the recess to the current collector 23, reduces heat generation, and lowers the risk of other components (such as the first insulating component 61 and the second insulating component 60) being burned.

[0582] In some embodiments, the second electrode terminal 214b further includes a sealing plate 2142 for closing the opening of the recess. The sealing plate 2142 may be entirely located outside the recess or partially accommodated within the recess, as long as the sealing plate 2142 can close the opening of the recess. The sealing plate 2142 can protect the recess from the outside, reduce the entry of external impurities into the recess, reduce the risk of damage to the bottom of the recess by external impurities, and improve the sealing performance of the battery cell 20.

[0583] In some embodiments, the sealing plate 2142 is used to weld to the second connecting member 82 to form a second weld portion W2. The second weld portion W2 can reduce the contact resistance between the sealing plate 2142 and the second connecting member 82, thereby improving the current carrying capacity.

[0584] In some embodiments, at least a portion of the sealing plate 2142 protrudes from the outer surface of the terminal body 2141. When it is necessary to weld the second connecting member 82 and the sealing plate 2142, 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 facing away from the recess), and then the second connecting member 82 and the sealing plate 2142 are welded. At least a portion of the sealing plate 2142 protrudes from the outer surface of the terminal body 2141 to avoid the outer surface of the terminal body 2141 interfering with the contact between the sealing plate 2142 and the second connecting member 82, ensuring a tight contact between the second connecting member 82 and the sealing plate 2142.

[0585] In this embodiment, 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 sandwiched 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.

[0586] In this embodiment, 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, reducing the risk of contact and conduction between the electrode assembly 22 and the cover 211a when the battery cell 20 vibrates, thereby improving safety performance.

[0587] In some embodiments, at least one of the first insulating member 61 and the second insulating member 60 may 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 fitted onto the second electrode terminal 214b and used to seal the electrode lead-out hole 211c. Optionally, a portion of the sealing ring 62 extends into the electrode lead-out hole 211c to separate the hole wall of the electrode lead-out hole 211c from the second electrode terminal 214b.

[0588] In some embodiments, a second tab 2222 is disposed at one end of the electrode assembly 22 facing the cover 211a, and a first tab 2221 is disposed at the other end of the electrode assembly 22 away from the cover 211a. The cylindrical body 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.

[0589] The cylinder 211b can be directly electrically connected to the first electrode 2221, or it can be electrically connected to the first electrode 2221 through other components. For example, the first electrode 2221 is electrically connected to the cylinder 211b through the cover plate 212.

[0590] In this embodiment, the first tab 2221 and the second tab 2222 are disposed at both ends of the electrode assembly 22, which can reduce the risk of the first tab 2221 and the second tab 2222 being connected, and increase the current-carrying area of ​​the first tab 2221 and the current-carrying area of ​​the second tab 2222.

[0591] In some embodiments, the first tab 2221 is the negative tab, and the base material of the housing 211 is steel. The housing 211 is electrically connected to the negative tab, meaning that the housing 211 is in a low potential state. The steel housing 211 is less susceptible to corrosion by the electrolyte in a low potential state, thus reducing safety risks.

[0592] In some embodiments, the battery cell 20 further includes a current collector 23 for connecting the second tab 2222 and the second electrode terminal 214b. The current collector 23 can be connected to the second tab 2222 by welding, abutting, or bonding, and connected to the second electrode terminal 214b by welding, abutting, bonding, riveting, etc., thereby realizing the electrical connection between the second tab 2222 and the second electrode terminal 214b.

[0593] In the first direction Z, the second electrode terminal 214b is positioned opposite to the middle region of the second tab 2222. If the second electrode terminal 214b and the second tab 2222 are directly connected, the conductive path between the edge region of the second tab 2222 and the second electrode terminal 214b will be too long, resulting in uneven current density in the second electrode of the electrode assembly 22, increasing internal resistance, and affecting the overcurrent capability and charging efficiency of the battery cell 20.

[0594] In this embodiment, the current collector 23 and the second tab 2222 can have a large connection area. The current of the second tab 2222 can be channeled into the second electrode terminal 214b via the current collector 23. In this way, the current collector 23 can reduce the difference in the conductive path between different areas of the second tab 2222 and the second electrode terminal 214b, improve the uniformity of the current density of the second electrode, reduce the internal resistance, and improve the overcurrent capacity and charging efficiency of the battery cell 20.

[0595] It should be understood that the shell 211 in this embodiment of the application has a multi-layer structure, that is, both the cylindrical body 211b and the cover 211a of the shell 211 have multi-layer structures. For ease of description, the shell 211 mentioned below includes both the cylindrical body 211b and the cover 211a.

[0596] In this embodiment, the housing 211 includes a first housing layer 2115, the resistivity of which is K1, satisfying: 1×10⁻⁸ Ω·m ≤ K1 ≤ 6×10⁻⁸ Ω·m. The first housing layer 2115 can be any layer in a multi-layered housing 211, for example... Figure 24Taking the innermost shell as the first shell layer 2115 as an example, the embodiments of this application are not limited to this. By setting the resistivity K1 of the first shell layer 2115 included in the shell 211 to be relatively small, the current carrying capacity of the shell 211 can be improved, thereby improving the performance of the battery cell 20.

[0597] In some embodiments, the resistivity K1 of the first housing layer 2115 can also satisfy 1×10^-8 Ω·m≤K1≤2.8×10^-8 Ω·m. This can improve the current carrying capacity and performance of the housing 211 and is easy to implement. In some embodiments, the resistivity K1 of the first housing 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.

[0598] It should be understood that the specific thickness of the first shell layer 2115 in this embodiment can also be flexibly set according to actual applications. For example, the thickness of the first shell layer 2115 can be set according to a certain proportion based on the thickness of the shell 211.

[0599] In some embodiments, the average thickness of the first shell layer 2115 is T13, and the average thickness of the shell 211 is T10, where T13 and T10 satisfy: 0.15 ≤ T13 / T10 ≤ 0.85. If T13 / T10 is set too small, with a fixed average thickness T10 of the shell 211, T13 will be too small, increasing processing difficulty and causing excessive heat generation, which may lead to thermal runaway. Conversely, if T13 / T10 is set too large, with a fixed average thickness T10 of the shell 211, T13 will be too large, resulting in insufficient thickness of other structural layers, which will affect the structural strength of the shell 211.

[0600] Furthermore, T13 and T10 satisfy: 0.2 ≤ T13 / T10 ≤ 0.6. This improves both the current-carrying capacity and the structural strength of the housing 211. In some embodiments, the ratio T13 / T10 can also be set to other values. For example, the ratio T13 / T10 can be any one of the following values ​​or between any two of the following values: 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, and 0.85.

[0601] It should be understood that the average thickness T10 of the housing 211 in this embodiment can also be flexibly set according to actual application. For example, the average thickness T10 of the housing 211 satisfies: 0.05mm ≤ T10 ≤ 0.5mm. The average thickness T10 of the housing 211 should not be too small to reduce the processing difficulty of the multi-layer housing 211 and improve the structural strength of the housing 211. For example, the housing 211 is not easy to break, thereby improving the service life of the housing 211. Conversely, the average thickness T10 of the housing 211 should not be too large to reduce the space occupied by the housing 211, improve the space utilization of the battery cell 20, and thus improve the energy density of the battery 10 with multiple battery cells 20.

[0602] Furthermore, the average thickness T10 of the housing 211 satisfies: 0.075mm≤T10≤0.4mm. Appropriately reducing the average thickness T10 of the housing 211 can reduce the space occupied by the housing 211 inside the battery 10, thereby increasing the energy density of the battery 10; while appropriately increasing the average thickness T10 of the housing 211 can also reduce the processing difficulty of the housing 211.

[0603] Furthermore, the average thickness T10 of the housing 211 satisfies: 0.1mm ≤ T10 ≤ 0.3mm. The average thickness T10 of the housing 211 is neither too large nor too small, which can improve the structural strength and stability of the housing 211, and reduce the space occupied by the housing 211 inside the battery 10, thereby improving the energy density of the battery 10.

[0604] In some embodiments of this application, the average thickness T10 of the housing 211 can be set to other values. For example, the average thickness T10 of the housing 211 can be any one of the following values ​​or between any two of the following values: 0.05mm, 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.

[0605] In this embodiment, the material of the first housing layer 2115 can be flexibly set according to the actual application. For example, the material of the first housing layer 2115 includes at least one of the following: silver, copper, aluminum, magnesium and brass, to meet the design requirements of the resistivity K1 of the first housing layer 2115.

[0606] In this embodiment, the housing 211 includes a second housing layer 2116. The tensile strength of the second housing layer 2116 at a temperature of 25°C is Rm2, where Rm2 satisfies: 250MPa≤Rm2≤2000MPa. The second housing layer 2116 can be any layer in a multi-layered housing 211, for example... Figure 24 Taking the outermost shell as the second shell layer 2116 as an example, the embodiments of this application are not limited to this. By setting the tensile strength Rm2 of the second shell layer 2116 included in the shell 211 to be relatively large at a temperature of 25°C, the structural strength and deformation capacity of the shell 211 can be improved, making the shell 211 less prone to damage during the use of the battery cell 20, thereby improving the structural stability and service life of the battery cell 20. However, the tensile strength Rm2 of the second shell layer 2116 at room temperature of 25°C should not be too large, so as to reduce the difficulty of material selection and processing of the shell 211, save costs, and facilitate processing.

[0607] It should be understood that the range of tensile strength Rm2 of the second shell layer 2116 of the shell 211 in this embodiment of the application at room temperature (25°C) can be adjusted according to actual applications. For example, the value of the room temperature tensile strength Rm2 can also satisfy 400MPa≤Rm2≤1200MPa. On the one hand, increasing the tensile strength Rm2 of the second shell layer 2116 at room temperature can improve the deformation capacity of this part of the second shell layer 2116 to resist the expansion of the electrode assembly 22, making the second shell layer 2116 less prone to damage, thereby improving the structural stability and service life of the battery cell 20. On the other hand, controlling the tensile strength Rm2 of the second shell layer 2116 at room temperature to not be too large can reduce the difficulty of material selection and processing of the second shell layer 2116, save costs, and facilitate processing.

[0608] Furthermore, the tensile strength Rm2 of the second shell layer 2116 under normal temperature conditions can be set to satisfy 450MPa≤Rm2≤800MPa. The tensile strength Rm2 of the second shell layer 2116 under normal temperature conditions will not be too large or too small, which can improve the deformation capacity of this part of the shell 211 to resist the expansion of the electrode assembly 22, and is easy to implement and cost-effective.

[0609] In some embodiments, the tensile strength Rm2 of the second shell layer 2116 of the shell 211 in this application embodiment under normal temperature conditions can also be set to other values. For example, the value of the room temperature tensile strength Rm2 can be any one 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, 1 000MPa, 1050MPa, 1100MPa, 1150MPa, 1200MPa, 1250MPa, 1300MPa, 1350MPa, 1400MPa, 1450MPa, 1500MPa, 1550MPa, 1600MPa, 1650MPa, 1700MPa, 1750MPa, 1800MPa, 1850MPa, 1900MPa, 1950MPa, and 2000MPa.

[0610] It should be understood that the tensile strength in this application embodiment refers to the maximum stress value that the material can withstand before breaking. The test method for the tensile strength Rm2 of the second shell layer 2116 of the shell 211 in this application embodiment 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 Rm2 at room temperature of 25°C.

[0611] In this embodiment, the average thickness of the second shell layer 2116 is T14, and the average thickness of the shell 211 is T10. T14 and T10 satisfy: 0.15 ≤ T14 / T10 ≤ 0.85. If T14 / T10 is set too small, with a fixed average thickness T10 of the shell 211, T14 will be too small, affecting the structural strength of the shell 211. Conversely, if T14 / T10 is set too large, with a fixed average thickness T10 of the shell 211, T14 will be too large, resulting in insufficient thickness of other structural layers. For example, the thickness T13 of the first shell layer 2115 will be too small, increasing processing difficulty and causing excessive heat generation, which can easily lead to thermal runaway.

[0612] Furthermore, T14 and T10 satisfy the condition: 0.2 ≤ T14 / T10 ≤ 0.6. This improves both the current-carrying capacity and the structural strength of the housing 211. In some embodiments, the ratio T14 / T10 can also be set to other values. For example, the ratio T14 / T10 can be any one of the following values ​​or between any two of the following values: 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, and 0.85.

[0613] Furthermore, the average thickness T14 of the second shell layer 2116 in this embodiment can be the same as or different from the average thickness T13 of the first shell layer 2115 to meet different design requirements.

[0614] It should be understood that the average thickness T10 of the shell 211 in this embodiment can refer to the average thickness of at least a portion of the shell 211. The average thickness T13 of the first shell layer 2115 of the shell 211 can also refer to the average thickness of at least a portion of the first shell layer 2115. The average thickness T14 of the second shell layer 2116 of the shell 211 can also refer to the average thickness of at least a portion of the second shell layer 2116. Furthermore, the calculation area for the average thickness T10 of the shell 211 is generally consistent with the calculation area for the average thickness T13 of the first shell layer 2115 and the calculation area for the average thickness T14 of the second shell layer 2116. For example, if some areas are excluded from the calculation of the average thickness T10 of the shell 211, then correspondingly, the calculation of the average thickness T13 of the first shell layer 2115 also requires excluding the same areas, and the calculation of the average thickness T14 of the second shell layer 2116 also requires excluding the same areas. For ease of explanation, the following description takes the calculation of the average thickness T10 of the shell 211 as an example. However, the same description applies to determining the average thickness T13 of the first shell layer 2115 and the average thickness T14 of the second shell layer 2116. They will not be repeated here.

[0615] For example, the average thickness T10 of the housing 211 can refer to the average thickness T10 of the entire area of ​​the housing 211. Especially when the entire surface of the housing 211 is relatively flat, that is, when the thickness of most areas of the housing 211 is basically equal or the difference is small, or when the thickness of the entire area of ​​the housing 211 is basically equal or the difference is small, the average thickness of the entire area of ​​the housing 211 can be determined as T10.

[0616] For example, the average thickness T10 of the housing 211 can also refer to the average thickness T10 of a local area of ​​the housing 211, that is, the average thickness T10 of the remaining area after excluding a certain area of ​​the housing 211. For example, if there are certain special areas in the housing 211 whose thickness differs significantly from other areas, such as if these special areas have protruding structures or recessed areas along the thickness direction, making their thickness larger or smaller than other areas, then these special areas can be excluded, and the average thickness T10 of the remaining area of ​​the housing 211 can be calculated.

[0617] In some embodiments, the housing 211 may include functional regions, and the average thickness T10 of the housing 211 is the average thickness of the regions of the housing 211 other than the functional regions. For example, the functional regions include at least one of the following regions: a pressure relief region, a region where the electrode terminals 214 are located, a liquid injection region, and a welding region. The thickness of the functional regions is usually significantly different from the thickness of other regions of the housing 211. Therefore, calculating the average thickness T10 of the housing 211 without including the functional regions allows the design of the housing 211 to better meet strength requirements, thereby improving the structural strength and stability of the battery cell 20.

[0618] Specifically, the functional areas in this application embodiment may include areas on the housing 211 that have specific structures or specific uses. For example, the functional area may include a pressure relief area for providing a pressure relief mechanism, which is an element or component that is actuated to release internal pressure or temperature when the internal pressure or temperature of the battery cell 20 reaches a predetermined threshold. The predetermined threshold can be adjusted according to different design requirements. For example, the predetermined threshold may depend on one or more of the materials of the positive electrode, negative electrode, electrolyte, and separator in the battery cell 20.

[0619] The term "actuation" as used in this application refers to the pressure relief mechanism being activated or undergoing a certain state, thereby releasing the internal pressure and temperature of the battery cell 20. The actions of the pressure relief mechanism may include, but are not limited...

Claims

1. A battery cell, characterized in that, include: An electrode assembly, the electrode assembly including a positive electrode sheet, the positive electrode sheet including a positive electrode active material capable of reversibly extracting and inserting metal ions, the positive electrode active material including a nickel-containing compound; A housing for accommodating the electrode assembly, wherein at least a portion of the housing has a melting point p, p satisfying: 1200℃≤p≤2000℃; the tensile strength of at least a portion of the housing at a temperature of 500℃ is Rn, Rn satisfying: 100MPa≤Rn≤1200MPa; the tensile strength of at least a portion of the housing at a temperature of 25℃ is Rm, and at least a portion of the housing includes a third housing wall with an average thickness T, Rm and T satisfying: 250MPa≤Rm≤2000MPa, 0.05mm≤T≤0.5mm, and 60 mm·MPa≤T×Rm≤500 mm·MPa.

2. The battery cell according to claim 1, characterized in that, The nickel-containing compound includes layered lithium-containing transition metal oxides, wherein the molar amount of nickel in the layered lithium-containing transition metal oxides accounts for more than 50% of the total molar amount of transition metal elements in the layered lithium-containing transition metal oxides.

3. The battery cell according to claim 2, characterized in that, 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; 0 < c < 1; 0 < d < 1; 1 ≤ e ≤ 2; 0 ≤ f ≤ 1, M includes one or more of Mn, Al, Zr, Zn, Cu, Cr, Mg, Fe, V, Ti and B, and A includes one or more of N, F, S and Cl.

4. The battery cell according to any one of claims 1 to 3, characterized in that, The material of at least a portion of the housing includes at least one of the following: steel, copper alloy, titanium alloy, and nickel alloy.

5. The battery cell according to claim 4, characterized in that, The material of at least a portion of the housing comprises steel, with a temperature of 1300°C ≤ p ≤ 1800°C.

6. The battery cell according to claim 4, characterized in that, The material of at least a portion of the housing includes at least one of the following: stainless steel and carbon steel.

7. The battery cell according to claim 4, characterized in that, The mass content of chromium in the material of at least a portion of the shell is m, where m satisfies: 10% ≤ m ≤ 30%.

8. The battery cell according to any one of claims 1 to 3, characterized in that, At least a portion of the housing includes all of the housing's walls.

9. The battery cell according to any one of claims 1 to 3, characterized in that, The shell is cylindrical or polygonal.

10. The battery cell according to any one of claims 1 to 3, characterized in that, The electrode assembly further includes a negative electrode sheet, which includes a negative electrode active material capable of reversibly extracting and inserting metal ions, and the negative electrode active material includes a silicon-based material. The tensile strength of at least a portion of the shell at a temperature of 25°C is Rm, where Rm satisfies: 250MPa≤Rm≤2000MPa.

11. The battery cell according to any one of claims 1 to 3, characterized in that, The electrode assembly further includes a negative electrode sheet, which includes a negative electrode active material capable of reversibly extracting and inserting metal ions, and the negative electrode active material includes a silicon-based material. The yield strength of at least a portion of the shell at a temperature of 25°C is Re, where Re satisfies: 140MPa≤Re≤1000MPa.

12. The battery cell according to any one of claims 1 to 3, characterized in that, The capacity of the battery cell is C, and the tensile strength of at least a portion of the casing at a temperature of 25°C is Rm. Rm and C satisfy: 250MPa≤Rm≤2000MPa, 25Ah≤C≤550Ah.

13. The battery cell according to any one of claims 1 to 3, characterized in that, The housing has an opening, and the housing includes a first housing wall and at least two second housing walls disposed opposite to the opening, wherein the first housing wall and the second housing walls are intersecting. There is a transition region between two adjacent second shell walls of the at least two second shell walls, and the maximum thickness T1 of the transition region satisfies the condition that T1 > T0 with respect to the maximum thickness T0 of the second shell wall with the largest thickness among the two second shell walls.

14. The battery cell according to any one of claims 1 to 3, characterized in that, The housing is a one-piece molded structure with an opening. The housing includes a first housing wall and at least two second housing walls opposite to the opening. The first and second housing walls intersect. 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 the following condition: 2.5mm ≤ R1 ≤ 20mm, 50mm. <H≤250mm。 15. The battery cell according to any one of claims 1 to 3, characterized in that, The shell is a one-piece molded structure with an opening. The shell includes a first shell wall and at least two second shell walls disposed opposite to the opening. The first shell wall and the second shell walls intersect each other. Two of the at least two second shell walls are connected by a first fillet. The yield strength Re of the shell at a temperature of 25°C satisfies the following relationship with the inner diameter R1 of the first fillet: 140MPa≤Re≤1000MPa, 2.5mm≤R1≤20mm.

16. The battery cell according to any one of claims 1 to 3, characterized in that, The housing has an opening, and the housing includes a first housing wall and at least one second housing wall disposed opposite to the opening. The first housing wall and the second housing wall are intersecting and are connected by a second fillet. The inner diameter r1 of the second fillet satisfies the following condition with respect to the minimum thickness T2 of the second housing wall with the smallest thickness: 2.0 ≤ r1 / T2 ≤ 30.

17. The battery cell according to any one of claims 1 to 3, characterized in that, The housing includes: A first housing portion is formed with a first opening portion. The first housing portion includes 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 are integrally formed. The second housing portion is fixedly connected to the second wall; Wherein, in the depth direction of the first housing portion, at least a portion of the housing is formed by the first housing portion and the second housing portion together.

18. The battery cell according to any one of claims 1 to 3, characterized in that, The battery cell is used in the battery, and the electrode assembly includes a first tab and a second tab with opposite polarities. The housing includes a cylindrical body and a cover connected to the cylindrical body. The cover and the cylindrical body are integrally formed. The cylindrical body is arranged around the outer periphery of the electrode assembly. The cover is provided with an electrode lead-out hole. 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 also includes: The second electrode terminal is used to electrically connect the second connecting member and the second tab of the battery. The second electrode terminal is insulated from the cover and installed in the electrode lead hole. One of the cover and the second electrode terminal is the positive output terminal of the battery cell, and the other is the negative output terminal of the battery cell.

19. The battery cell according to claim 18, characterized in that, The second electrode tab is located at one end of the electrode assembly facing the cover, and the first electrode tab is located at the other end of the electrode assembly away from the cover; The cylindrical body 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.

20. The battery cell according to any one of claims 1 to 3, characterized in that, The electrode assembly includes a first tab; the housing includes a cylindrical body and a cover connected to the cylindrical body, the cylindrical body is arranged around the outer periphery of the electrode assembly, the cover includes a first electrode terminal, the first tab is electrically connected to the first electrode terminal through the cylindrical body, and the housing has a multi-layer structure with different resistivities.

21. The battery cell according to any one of claims 1 to 3, characterized in that, The shell has a multi-layer structure, and the material of the outermost shell includes at least one of the following: aluminum, aluminum alloy, copper, copper alloy and chromium.

22. A battery, characterized in that, include: Multiple battery cells, wherein the battery cells are battery cells as described in any one of claims 1 to 21.

23. An electrical appliance, characterized in that, include: A battery comprising a battery cell as described in any one of claims 1 to 21, the battery being used to power the electrical device.

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