Battery cells, batteries, and electrical equipment

Abstract

Embodiments of the present application disclose a battery cell, a battery, and an electrical device. The battery cell includes an electrode assembly, the electrode assembly comprising a negative electrode piece, the negative electrode piece comprising a negative electrode active material capable of reversibly desorbing and inserting metal ions, the negative electrode active material comprising a silicon-based material, and a casing used to house the electrode assembly, the casing having a tensile strength of Rm at a temperature of 25°C in at least a portion of the casing, where Rm satisfies 250 MPa ≤ Rm ≤ 2000 MPa. The battery cell, battery, and electrical device according to embodiments of the present application can improve the reliability of the battery cell.

Description

[Technical Field]

[0001] This application relates to the field of batteries, and more specifically to battery cells, batteries, and electrical equipment. [Background technology]

[0002] Energy conservation and emission reduction are key to the sustainable development of the automotive industry. In this context, electric vehicles, with their energy-saving and environmentally friendly advantages, have become an important component of the sustainable development of the automotive industry. In the case of electric vehicles, battery technology is a crucial element related to their development.

[0003] In the development of battery technology, in addition to improving battery performance, safety issues have become an undeniable concern. If the safety of a battery cannot be guaranteed, it cannot be used. Therefore, how to improve battery performance while simultaneously guaranteeing battery safety has become a particularly important issue in the development of battery technology. [Overview of the project]

[0004] Embodiments of the present application provide a battery cell, a battery, and electrical equipment that can improve the reliability of the battery cell.

[0005] In a first embodiment, a battery cell is provided, the battery cell comprising: an electrode assembly, the electrode assembly comprising a negative electrode piece, the negative electrode piece comprising a negative electrode active material capable of reversibly desorbing and inserting metal ions, the negative electrode active material comprising a silicon-based material; and a casing used to house the electrode assembly, the casing having a tensile strength of Rm at a temperature of 25°C in at least a portion of the casing, where Rm satisfies 250 MPa ≤ Rm ≤ 2000 MPa.

[0006] Therefore, the battery cell according to the embodiments of the present application can accommodate more metal ions by disposing the silicon-based material on the negative electrode plate, which can effectively increase the energy density of the battery cell. In addition, when the negative electrode active material of the negative electrode plate includes the silicon-based material, the deformation amount of the electrode assembly inside the battery cell during use can also be increased. Particularly during the charging process of the battery cell, when metal ions are inserted into the silicon-based material of the negative electrode plate, volume expansion occurs in the electrode assembly, which further increases the pressure of the electrode assembly on the casing of the battery cell. Therefore, by increasing the tensile strength Rm of at least a partial region of the casing under the condition of normal temperature 25°C, the deformability of the casing can be improved, the casing is not easily damaged during the use of the battery cell, the structural stability of the battery cell is further improved, and the service life of the battery cell is further extended. However, in order to reduce the difficulty in material selection and processing of the casing, save costs, and facilitate processing, it is also undesirable that the tensile strength Rm of at least a partial region of the casing under the condition of normal temperature 25°C is excessively large.

[0007] In some embodiments, in the negative electrode active material, the mass proportion of the silicon-based material is g, the material of at least a partial region of the casing contains an iron element, and Rm and g satisfy 2%<g<40%, 300MPa<Rm<2000MPa.

[0008] In some embodiments, the material of at least a partial region of the casing includes carbon steel or stainless steel, and Rm and g satisfy 2.5%≦g≦15%, 315MPa≦Rm<800MPa.

[0009] In some embodiments, the material of at least a partial region of the casing includes carbon steel or stainless steel, and Rm and g satisfy 4.5%≦g≦40%, 380MPa≦Rm<2000MPa.

[0010] In some embodiments, Rm and g satisfy 8%≦g≦40%, 400MPa≦Rm<2000MPa.

[0011] In some examples, Rm and g satisfy the conditions 10% ≤ g ≤ 40% and 480 MPa ≤ Rm < 2000 MPa.

[0012] In several examples, Rm and g satisfy the conditions 15% ≤ g ≤ 40% and 520 MPa ≤ Rm < 2000 MPa.

[0013] In several examples, Rm and g satisfy the conditions 20% ≤ g ≤ 40% and 600 MPa ≤ Rm < 2000 MPa.

[0014] In some embodiments, the silicon-based material includes at least one of elemental silicon, silicon-oxygen compounds, silicon-carbon composites, silicon-nitrogen composites, silicon-containing alloys, or silicon-oxygen-carbon composite materials to facilitate implementation.

[0015] Each of the above materials is not only easy to process but can also meet design needs. Specifically, by adding a silicon-based material to the negative electrode active material of the negative electrode piece, the silicon-based material can accommodate more metal ions than other elements. For example, the capacity of silicon-based material is about 10 times that of graphite, so the energy density of the battery cell can be effectively improved. At the same time, it is undesirable to set the mass ratio g of the silicon-based material to be excessively large, otherwise it will increase the difficulty of processing the electrode assembly and the amount of deformation of the electrode assembly during use in the battery cell. In particular, during the charging process of the battery cell, metal ions are inserted into the silicon-based material of the negative electrode piece, causing volume expansion of the electrode assembly, further increasing the pressure of the electrode assembly on the battery cell casing, and further increasing the difficulty of processing the battery cell. Therefore, by rationally selecting the material, the tensile strength Rm at room temperature in at least a part of the casing can be appropriately increased, improving the deformation capacity of that part of the casing, thereby resisting the amount of expansion of the electrode assembly, preventing that part of the casing from easily breaking, and further improving the structural stability and service life of the battery cell. On the other hand, by controlling the tensile strength Rm of at least a portion of the casing at room temperature so that it is not too high, the difficulty of selecting and processing the material for the casing can be reduced, saving costs and making it easier to process.

[0016] In some embodiments, the casing includes a weld seam, and at least a partial region of the casing includes a region within a preset distance from the weld seam of the casing, the preset distance is L, and L satisfies L=10mm. When the negative electrode active material of the negative electrode sheet in the electrode assembly includes a silicon-based material, since the silicon-based material can accommodate more metal ions, the deformation amount of the electrode assembly in the battery cell during use increases, causing volume expansion of the electrode assembly, and further increasing the pressure of the electrode assembly on the casing of the battery cell. Under the same conditions, the structural strength of the region adjacent to the weld seam of the casing is relatively lower than the structural strength of other regions of the casing, so the region adjacent to the weld seam of the casing is more prone to damage during the use of the battery cell. Therefore, by setting the region within the preset distance L from the weld seam to meet the requirement of tensile strength Rm at normal temperature, the deformability of the region adjacent to the weld seam of the casing can be improved, the partial region of the casing will not be easily damaged, and the structural stability and service life of the battery cell are further improved.

[0017] In some embodiments, at least a partial region of the casing includes all walls of the casing. When the negative electrode active material of the negative electrode sheet of the electrode assembly includes a silicon-based material, since the silicon-based material can accommodate more metal ions, the deformation amount of the electrode assembly in the battery cell during use increases, causing volume expansion of the electrode assembly, and further increasing the pressure of the electrode assembly on the casing of the battery cell. Therefore, by arranging all regions of the casing to meet the requirement of tensile strength Rm at normal temperature, the deformability of the entire casing can be improved, the pressing force of the internal electrode assembly on the casing along each direction can be limited, the strength of each part of the casing is balanced, local weak regions will not be easily damaged, and the structural stability and service life of the battery cell are further improved.

[0018] In some embodiments, to facilitate processing, the casing has a cylindrical shape or a polygonal prism shape.

[0019] In some embodiments, the yield strength of at least a partial region of the casing at a temperature of 25°C is Re, wherein Re satisfies 140MPa≦Re≦1000MPa. By disposing a silicon-based material on the negative electrode tab, more metal ions can be accommodated, and the energy density of the battery cell can be effectively increased. In addition, when the negative electrode active material of the negative electrode tab contains the silicon-based material, the deformation amount of the electrode assembly in the battery cell during the use process can also be increased. Particularly during the charging process of the battery cell, when metal ions are intercalated into the silicon-based material of the negative electrode tab, volume expansion occurs in the electrode assembly, which further increases the pressure of the electrode assembly on the casing of the battery cell. Therefore, by increasing the yield strength Re of at least a partial region of the casing at normal temperature of 25°C, the deformability of the casing can be improved, the structural stability of the battery cell is further enhanced, and the service life of the battery cell is further prolonged. During the charging and discharging process of the battery cell, volume expansion and volume contraction occur repeatedly in the electrode assembly. By increasing the yield strength Re of at least a partial region of the casing at normal temperature, the maximum compressive force that the casing can bear can be improved. When the yield strength limit of the casing is not exceeded, the casing will not be easily damaged, the deformation of the casing is recoverable, and the service life of the casing is improved. However, in order to reduce the difficulty of material selection and processing of the casing, save cost and facilitate processing, it is also undesirable that the yield strength Re of at least a partial region of the casing under normal temperature conditions is too large.

[0020] In some embodiments, the electrode assembly further includes a positive electrode piece, the positive electrode piece containing a positive electrode active material capable of reversibly desorbing and inserting metal ions, the positive electrode active material containing a nickel-containing compound, and the melting point of at least a portion of the casing is p, where p satisfies 1200°C ≤ p ≤ 2000°C. When the positive electrode active material of the positive electrode piece contains a nickel-containing compound, it can effectively increase the energy density of the battery cell and improve its cycle life, but it also increases the amount of gas generated during the use of the battery cell, especially when thermal runaway occurs in the battery cell, causing the temperature inside the battery cell to rise rapidly and a large amount of gas to be generated. Therefore, by appropriately increasing the melting point p of at least a portion of the casing, the casing does not easily melt, reducing the possibility of the battery cell exploding, and further reducing the risk of thermal runaway occurring in adjacent battery cells, thereby improving the reliability of the battery. However, in order to reduce the difficulty of selecting and processing the casing material, save costs, and facilitate processing, it is undesirable for the melting point p of the casing to be too high.

[0021] In some embodiments, the electrode assembly further includes a positive electrode piece, the positive electrode piece containing a positive electrode active material capable of reversibly desorbing and inserting metal ions, the positive electrode active material containing a nickel-containing compound, and the tensile strength of at least a portion of the casing at a temperature of 500°C is Rn, where Rn satisfies 100MPa ≤ Rn ≤ 1200MPa. When the positive electrode active material of the positive electrode piece contains a nickel-containing compound, it can effectively increase the energy density of the battery cell and improve the cycle life, as well as increase the amount of gas generated during the use of the battery cell. In particular, when thermal runaway occurs in the battery cell, the temperature inside the battery cell rises rapidly and a large amount of gas is generated. Therefore, by appropriately improving the tensile strength Rn of at least a portion of the casing at a high temperature of 500°C, the deformation capability of that portion of the casing when the battery cell undergoes thermal runaway can be improved, preventing the casing from easily and quickly breaking or exploding, further reducing the risk of thermal runaway occurring in adjacent battery cells, thereby improving the reliability of the battery. However, in order to save costs and facilitate processing, it is also undesirable for the tensile strength Rn of at least some portion of the casing to be too high under high temperature conditions of 500°C.

[0022] In some embodiments, the casing includes at least a portion of a third casing wall, the average thickness of which is T, where T satisfies 0.05 mm ≤ T ≤ 0.5 mm and 60 mm MPa ≤ T × Rm ≤ 500 mm MPa. By increasing the tensile strength Rm at room temperature (25°C) in at least a portion of the casing, the deformation capacity of the casing can be improved, and the casing will not easily break during the use of the battery cell, further improving the structural stability and service life of the battery cell. However, in order to reduce the difficulty of selecting and processing the material for the casing, save costs, and facilitate processing, it is undesirable for the tensile strength Rm at room temperature in at least a portion of the casing to be too high. On the other hand, if the average thickness T of the third casing wall of the casing is relatively thin, the structural strength of the third casing wall can be increased by increasing the tensile strength Rm of the third casing wall at room temperature (25°C). In this way, not only can the energy density of the battery cell be improved, but the structural strength and stability of the battery cell can also be improved. Conversely, if the average thickness T of the third casing wall of the casing is relatively thick, the structural strength of the casing can be improved, and by appropriately reducing the tensile strength Rm of the third casing wall at room temperature, the difficulty of selecting the casing material can be reduced, and the difficulty and cost of processing the battery cell can be further reduced. Moreover, T × Rm indicates the rigidity of the third casing wall, and by limiting the rigidity of the third casing wall so that it is neither too low nor too high, the third casing wall can have relatively good deformation capacity, and the difficulty of processing can be reduced, as can the cost.

[0023] In some embodiments, the capacity of the battery cell is C, where C satisfies 25Ah ≤ C ≤ 550Ah. On the one hand, increasing the capacity C of a battery cell can improve the capacity density of a battery containing multiple such battery cells, or, if the total capacity of the battery does not change, increasing the capacity C of a single battery cell can reduce the number of battery cells installed, correspondingly reducing the number of electrical connections between multiple battery cells and lowering the probability of electrical connection failures, thus helping to improve the reliability of the battery. Furthermore, when the capacity C of a battery cell is relatively large, increasing the tensile strength Rm of at least a portion of the casing under normal temperature conditions of 25°C can satisfy the structural strength requirements for the casing of high-capacity battery cells, further improving the reliability and service life of the battery cell. On the other hand, when a battery cell has a relatively large capacity, the internal reaction becomes more vigorous, further increasing the requirements for the structural strength of the casing. Therefore, in order to limit the design requirements for the structural strength of the casing, it is undesirable for the capacity C of the battery cell to be too large, thereby reducing the difficulty of selecting and processing the battery cell, lowering costs, and improving processing efficiency.

[0024] In some embodiments, the casing has an opening, and the casing includes a first casing wall and at least two second casing walls installed opposite the opening, the first casing wall and the second casing walls are installed intersecting, and there is a transition region between two adjacent second casing walls in the at least two second casing walls, and the relationship between the maximum thickness T1 of the transition region and the maximum thickness T0 of the second casing wall with the maximum thickness in the two second casing walls satisfies T1 > T0.

[0025] In this embodiment, by providing a transition region between two adjacent second casing walls, stress concentration between the two adjacent second casing walls can be reduced, and the risk of structural failure caused by stress concentration can be lowered. Moreover, by setting the maximum thickness T1 of the transition region to be greater than the maximum thickness T0 of the second casing wall with the largest thickness among the two adjacent second casing walls, the thickened transition region can increase the structural strength of the casing, which is advantageous for solving the problem of casing deformation during the production and assembly process of battery cells, as well as the problem of casing deformation caused by gas generation and expansion during the use process of battery cells.

[0026] In some embodiments, the casing is an integrally formed structure, the casing has an opening, the casing includes a first casing wall disposed opposite to the opening and at least two second casing walls, the first casing wall and the second casing walls are arranged to intersect, two of the at least two second casing walls are connected by a first fillet, and the depth H of the casing and the inner diameter R1 of the first fillet satisfy 2.5mm≦R1≦20mm and 50mm<H≦250mm. Without affecting the energy density of the battery cell, the risk of cracking caused by force bearing during the integral forming process of the casing can be reduced as much as possible, and the forming difficulty of the casing is further reduced.

[0027] In some embodiments, the casing is an integrally formed structure, the casing has an opening, the casing includes a first casing wall disposed opposite to the opening and at least two second casing walls, the first casing wall and the second casing walls are arranged to intersect, two of the at least two second casing walls are connected by a first fillet, and the yield strength Re of the casing at a temperature of 25°C and the inner diameter R1 of the first fillet satisfy 140MPa≦Re≦1000MPa and 2.5mm≦R1≦20mm.

[0028] In this embodiment, by using a material with a yield strength Re satisfying 140MPa ≤ Re ≤ 1000MPa to manufacture the casing, the wall thickness of the casing can be reduced without reducing the strength of the casing, thereby increasing the capacity space of the battery cell. Furthermore, by setting the inner diameter R1 of the first fillet between adjacent second casing walls to satisfy 2.5mm ≤ R1 ≤ 20mm, the risk of cracking due to force bearing during the integral molding process of the casing is reduced as much as possible, thereby reducing the difficulty of molding the casing.

[0029] In some embodiments, the casing has an opening, and the casing includes a first casing wall and a second casing wall installed opposite the opening, the first casing wall and the second casing wall are installed intersecting, and the first casing wall and the second casing wall are connected by a second fillet, and the ratio between the inner diameter r1 of the second fillet and the minimum thickness T2 of the second casing wall having the minimum thickness among the at least two second casing walls satisfies 2.0 ≤ r1 / T2 ≤ 30. Setting the ratio of the inner diameter r1 of the second fillet between the first and second casing walls to the minimum thickness T2 of the second casing wall having the minimum wall thickness between [2.0, 30] helps to balance the difficulty of machining the casing with the spatial capacity and strength of the battery cell.

[0030] In some embodiments, the casing includes a first casing portion having an opening formed therein, which includes a first wall facing the opening and a second wall connected to the first wall, wherein the first wall and the second wall are integrally molded, and a second casing portion fixedly connected to the second wall, wherein at least a portion of the casing in the depth direction of the first casing portion is jointly formed by the first casing portion and the second casing portion. Compared to technical proposals for directly integrally molding the casing, the casing manufactured in this manner can reduce the risk of casing cracking during the integral deep drawing process.

[0031] In some embodiments, the battery cell is used in a battery, the electrode assembly includes a first tab and a second tab with opposite polarity, the casing includes a cylindrical body and a lid connected to the cylindrical body, the lid and the cylindrical body are integrally molded, the cylindrical body is installed surrounding the outer circumference of the electrode assembly, the lid is provided with electrode lead holes, at least a portion of the lid is used to electrically connect a first connecting component of the battery to the first tab, the battery cell further includes a second electrode terminal for electrically connecting a second connecting component of the battery to the second tab, the second electrode terminal is installed insulated from the lid and attached to the electrode lead holes, one of the lid and the second electrode terminal is the positive output electrode of the battery cell, and the other is the negative output electrode of the battery cell. By using the lid and the second electrode terminal as output electrodes, the structure of the battery cell can be simplified and the current passing capability of the battery cell can be guaranteed. By positioning the lid and the second electrode terminals at the same end of the battery cell, the first and second connecting components are assembled on the same side of the battery cell, thus simplifying the assembly process and improving the efficiency of assembling multiple battery cells into sets.

[0032] In some embodiments, the second tab is provided at one end of the electrode assembly facing the cover, and the first tab is provided at the other end of the electrode assembly away from the cover, and the cylinder is used to connect the first tab to the cover so that the first tab is electrically connected to the cover. By providing the first and second tabs at both ends of the electrode assembly, embodiments of the present application can reduce the risk of electrical contact between the first and second tabs and increase the current-passing area of ​​the first tab and the current-passing area of ​​the second tab.

[0033] In some embodiments, the electrode assembly includes a first tab, the casing includes a cylindrical body and a lid connected to the cylindrical body, the cylindrical body is installed surrounding the outer circumference of the electrode assembly, the lid includes the first electrode terminals, the first tab is electrically connected to the first electrode terminals by the cylindrical body, and the casing has a multilayer structure with different resistivity. The electrode assembly includes a first tab, the first tab is electrically connected to the first electrode terminals of the battery cell by the casing, and the casing has a multilayer structure with different resistivity. By electrically connecting the first tab to the first electrode terminals by the cylindrical body, the structure of the battery cell can be simplified, and by installing the casing in a multilayer structure with different resistivity, the current passability of the battery cell can be improved by a single layer with relatively low resistivity, and the structural strength of the casing can be improved by a single layer with relatively high resistivity, thereby improving the performance of the battery cell and further extending the service life of the battery cell.

[0034] In some embodiments, the casing has a multilayer structure, and the material of the outermost casing includes at least one of aluminum, aluminum alloy, copper, copper alloy, and chromium. When the outermost casing material includes aluminum, the aluminum is oxidized to dense aluminum oxide, making it corrosion-resistant. When the outermost casing material includes copper, the copper is oxidized to copper oxide, i.e., verdigris, making it corrosion-resistant. When the outermost casing material includes chromium, the chromium is oxidized to chromium oxide, also making it corrosion-resistant. Therefore, when the outermost casing material is made of one of the above corrosion-resistant materials, the outermost casing can protect other casing layers located inside it, improving the structural stability of the casing and extending its service life.

[0035] In a second embodiment, a battery is provided which includes a plurality of battery cells, wherein the battery cells are battery cells described in the first embodiment or any one embodiment of the first embodiment.

[0036] In a third aspect, the present invention provides an electrical device including a battery, wherein the battery includes a battery cell as described in the first aspect or any one embodiment of the first aspect, and the battery is used to supply power to the electrical device.

[0037] In some embodiments, the electrical equipment is a vehicle, a ship, or an aerospace aircraft. [Brief explanation of the drawing]

[0038] In drawings, the drawings are not drawn to actual scale. [Figure 1] This is a schematic diagram of a vehicle according to one embodiment of the present invention. [Figure 2] This is a schematic diagram of the disassembled structure of a battery according to one embodiment of the present invention. [Figure 3] This is a schematic diagram of the structure of a battery cell according to one embodiment of the present invention. [Figure 4] This is a schematic diagram of the disassembled structure of a battery cell according to one embodiment of the present invention. [Figure 5] This is a schematic cross-sectional view of an electrode assembly according to one embodiment of the present invention. [Figure 6] This is a schematic cross-sectional view of the negative electrode piece or positive electrode piece of an electrode assembly according to one embodiment of the present application. [Figure 7] This is a schematic diagram of the structure of a clamp for cycle charging fatigue testing according to one embodiment of the present invention. [Figure 8] This is a schematic diagram of the side structure of a battery cell casing according to one embodiment of the present invention. [Figure 9] This is a schematic diagram of the cross-sectional structure of a battery cell casing according to one embodiment of the present invention. [Figure 10] This is a schematic diagram of an exploded battery cell according to one embodiment of the present invention. [Figure 11] This is a cross-sectional view of a casing according to one embodiment of the present application. [Figure 12] This is a schematic diagram of the transition region of a casing according to one embodiment of the present invention. [Figure 13] This is a schematic diagram of another transition region of the casing according to one embodiment of the present application. [Figure 14] This is a schematic diagram of the material flow during the integral molding process of a casing according to one embodiment of the present invention. [Figure 15] This is a schematic diagram of a force bearing in the integral molding process of a casing according to one embodiment of the present invention. [Figure 16] This is another cross-sectional view of a casing according to one embodiment of the present application. [Figure 17] This is a schematic diagram showing a localized enlargement of section B in Figure 10. [Figure 18] This is a schematic diagram of an exploded view of a casing according to one embodiment of the present invention. [Figure 19] This is a schematic diagram of the structure of the second casing portion according to one embodiment of the present application. [Figure 20] This is another schematic diagram of the second casing portion according to one embodiment of the present application. [Figure 21] This is another exploded schematic diagram of a casing according to one embodiment of the present application. [Figure 22] This is an exemplary cross-sectional view of a casing according to one embodiment of the present application. [Figure 23] This is an enlarged view of the local structure of a casing according to one embodiment of the present invention. [Figure 24] This is a schematic cross-sectional view of the local structure of a battery according to another embodiment of the present application. [Figure 25] This is a schematic diagram of the disassembled structure of a battery cell according to another embodiment of the present invention. [Figure 26] This is a schematic diagram of the cross-sectional structure of a battery cell according to another embodiment of the present invention. [Figure 27] This is a schematic cross-sectional view of the local structure of a battery according to another embodiment of the present application. [Figure 28] This is a schematic cross-sectional view of another local structure of a battery according to another embodiment of the present application. [Modes for carrying out the invention]

[0039] The technical details of the embodiment of this application will be described below with reference to the drawings.

[0040] To further clarify the purpose, technical proposal, and advantages of the embodiments of this application, the technical proposal of the embodiments will be clearly described below in conjunction with the drawings of the embodiments of this application. However, it should be clear that the embodiments described are only a selection of embodiments of this application, not all of them. Based on the embodiments of this application, all other embodiments obtained without creative work by a person skilled in the art fall within the scope of protection of this application.

[0041] Unless otherwise defined, all technical and scientific terms used in this Application have the same meaning as those generally understood by those skilled in the art relating to the Application. The terms used in the Specification Filed in this Application are for the purpose of describing specific embodiments only and are not intended to limit this Application. The terms “includes” and “have,” and any variations thereof, in the Specification, Claims and Brief Description of the Drawings, are intended to cover non-exclusive inclusion. Terms such as “first,” “second,” etc., in the Specification and Claims or the Drawings are used to distinguish different subjects and are not used to indicate a particular order or priority.

[0042] The “Examples” as used herein mean that certain features, structures, or characteristics described in conjunction with the Examples may be included in at least one Example of this Application. Each occurrence of the “Examples” in the Specification does not necessarily refer to the same Example, nor do they represent mutually exclusive, independent, or substitutable Examples. Those skilled in the art will understand, both explicitly and implicitly, that the Examples described herein may be combined with other Examples.

[0043] In this description, unless otherwise specified or limited, the terms “attachment,” “connection,” “joining,” and “attaching” should be understood broadly to mean, for example, a fixed connection, a removable connection, an integral connection, a direct connection, an indirect connection via an intermediate medium, or internal communication between two elements. A person skilled in the art may understand the specific meaning of these terms in this application depending on the specific circumstances.

[0044] In this application, the term "and / or" simply describes a related relationship that explains the related objects, indicating that three types of relationships are possible. For example, A and / or B can represent three situations: A existing alone, A and B existing simultaneously, and B existing alone. In addition, the symbol " / " in this application generally indicates that the preceding and following related objects are in an "or" relationship.

[0045] In the embodiments of this application, the same drawing symbols represent the same components, and for the sake of brevity, detailed descriptions of the same components are omitted in different embodiments. It should be understood that the dimensions such as thickness, length, and width of various components in the embodiments of this application shown in the attached drawings, as well as the overall thickness, length, and width of the integrated device, are merely illustrative and should not constitute limitations of this application.

[0046] In this application, "multiple" refers to two or more (including two), similarly, "multiple sets" refers to two or more sets (including two sets), and "multiple sheets" refers to two or more sheets (including two sheets).

[0047] In the embodiments of the present invention, the battery cell may be a secondary battery, which refers to a battery cell that can be used continuously by activating the active material through charging after the battery cell has been discharged.

[0048] The battery cell may 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 these.

[0049] In some embodiments, the battery cell in the embodiment of the present application may be a metal battery, and specifically, such a metal battery may include lithium metal secondary batteries, sodium metal batteries, or magnesium metal batteries, and the embodiment of the present application is not limited to these.

[0050] A battery cell generally includes an electrode assembly. The electrode assembly includes a positive electrode, a negative electrode, and a separator. During the charging and discharging process of the battery cell, active ions (e.g., lithium ions) repeatedly insert into and remove from between the positive and negative electrodes. The separator is placed between the positive and negative electrodes and can prevent a short circuit between them while simultaneously allowing the passage of active ions.

[0051] In some embodiments, the positive electrode may be a positive electrode piece that includes a positive electrode current collector and a positive electrode active material placed on at least one surface of the positive electrode current collector.

[0052] For example, the positive electrode current collector has two opposing surfaces in its thickness direction, and the positive electrode active material is placed on one or both of the two opposing surfaces of the positive electrode current collector.

[0053] As an example, the positive electrode current collector can be a metal foil, foamed metal, or a composite current collector. For example, as a metal foil, silver-surface-treated aluminum or stainless steel, stainless steel, copper, aluminum, nickel, carbon electrodes, carbon, nickel, or titanium can be used. The foamed metal may be foamed nickel, foamed copper, foamed aluminum, foamed alloy, or foamed carbon. The composite current collector may include a polymer material base layer and a metal layer. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer material base (a base material such as polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.).

[0054] As an example, the positive electrode active material may include at least one of the following materials: lithium-containing phosphates, lithium transition metal oxides, and modified compounds thereof. However, the present invention is not limited to these materials, and other conventional materials that can be used as positive electrode active materials for batteries may be used. These positive electrode active materials may be used individually or in combination of two or more. Examples of lithium-containing phosphates may include, but are not limited to, at least one of lithium iron phosphate (e.g., LiFePO4 (which may be abbreviated as LFP)), composite materials of lithium iron phosphate and carbon, lithium manganese phosphate (e.g., LiMnPO4), composite materials of lithium manganese phosphate and carbon, lithium iron manganese phosphate, and composite materials of lithium iron manganese phosphate and carbon.

[0055] In some embodiments, the negative electrode may be a negative electrode piece, and the negative electrode piece may include a negative electrode current collector and a negative electrode active material placed on at least one surface of the negative electrode current collector.

[0056] For example, the negative electrode current collector has two opposing surfaces in its thickness direction, and the negative electrode active material is placed on one or both of the two opposing surfaces of the negative electrode current collector.

[0057] As an example, the negative electrode current collector can be a metal foil, foamed metal, or a composite current collector. For example, as the metal foil, aluminum or stainless steel with a silver surface treatment, stainless steel, copper, aluminum, nickel, carbon electrodes, carbon, nickel, or titanium can be used. The composite current collector may include a polymer material base layer and a metal layer. The foamed metal may be foamed nickel, foamed copper, foamed aluminum, foamed alloy, or foamed carbon. The composite current collector is formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer material base (a base material such as polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, or polyethylene).

[0058] In some embodiments, the electrode assembly further includes a separator placed between the positive and negative electrodes.

[0059] In some embodiments, the separator is a separator film. The present application does not impose any particular restrictions on the type of separator film, and any known porous separator film having good chemical and mechanical stability can be selected.

[0060] For example, the main material of the separator film may be at least one selected from glass fiber, nonwoven fabric, polyethylene, polypropylene, polyvinylidene fluoride, and ceramics.

[0061] In some embodiments, the separator is a solid electrolyte. The solid electrolyte is placed between the positive and negative electrodes and serves to transport ions and separate the positive and negative electrodes.

[0062] In some embodiments, the battery cell further includes an electrolyte that plays a role in conducting ions between the positive and negative electrodes. The present application does not specifically limit the type of electrolyte, which can be selected according to the needs. The electrolyte may be in a liquid state, a gel state, or a solid state.

[0063] In some embodiments, the electrode assembly is provided with tabs from which current can be drawn from the electrode assembly. The tabs include a positive electrode tab and a negative electrode tab.

[0064] In some embodiments, the battery cell may include an outer casing. The outer casing is used to enclose components such as the electrode assembly and electrolyte. The outer casing may be a steel shell, an aluminum casing, a plastic shell (e.g., polypropylene), a composite metal shell (e.g., copper-aluminum composite outer casing), or an aluminum-plastic film. The outer casing includes a casing and a cover plate.

[0065] The batteries referred to in the embodiments of this application may include one or more battery cells to provide a single physical module with higher voltage and capacity. If there are multiple battery cells, the multiple battery cells are connected in series, in parallel, or in series-parallel by a bus component.

[0066] In some embodiments, the battery may be a battery pack including a case and battery cells, where the battery cells or battery modules are housed within the case.

[0067] In some embodiments, the case may be part of the vehicle's chassis structure. For example, the case portion may be at least part of the vehicle's floor, or it may be at least part of the vehicle's cross members and side members.

[0068] In some embodiments, the battery may be placed within an energy storage device. The energy storage device includes energy storage containers, energy storage electrical cabinets, and the like.

[0069] The development of battery technology requires simultaneous consideration of various design elements, such as performance parameters including energy density, cycle life, discharge capacity, and charge / discharge rate, as well as battery safety and stability. For example, by rationally selecting the positive electrode active material for the positive electrode piece or the negative electrode active material for the negative electrode piece of the electrode assembly, the energy of the battery cell can be effectively improved, further enhancing the battery's energy output. Taking the negative electrode active material of the negative electrode piece of the electrode assembly as an example, adding a silicon-based material to the negative electrode active material can improve the energy of the battery cell. However, during the charge-discharge cycle of the battery cell, the expansion of the electrode assembly also increases, easily increasing the deformation of the battery cell casing. If the casing strength is insufficient, the casing may break, potentially affecting the battery cell's lifespan.

[0070] Accordingly, embodiments of the present application provide a battery cell, a battery, and an electrical device that can solve the above problems. The battery cell according to embodiments of the present application includes an electrode assembly and a casing used to house the electrode assembly, the electrode assembly including a negative electrode piece, the negative electrode piece including a reversibly detachable-insertable negative electrode active material, the negative electrode active material including a silicon-based material, and the tensile strength of at least a portion of the casing at a temperature of 25°C is Rm, where Rm satisfies 250 MPa ≤ Rm ≤ 2000 MPa. By installing a silicon-based material in the negative electrode piece, more metal ions can be accommodated, and the energy density of the battery cell can be effectively increased. Furthermore, when the negative electrode active material of the negative electrode piece is a silicon-based material, the amount of deformation of the electrode assembly in the battery cell during use can also be increased, and in particular, during the charging process of the battery cell, when metal ions are inserted into the silicon-based material of the negative electrode piece, volume expansion occurs in the electrode assembly, further increasing the pressure of the electrode assembly on the casing of the battery cell. Therefore, by increasing the tensile strength Rm at room temperature of 25°C in at least a portion of the casing, the deformation capacity of the casing can be improved, the casing will not easily break during the use of the battery cell, further improving the structural stability of the battery cell and extending the service life of the battery cell. However, in order to reduce the difficulty of selecting and processing the material for the casing, save costs, and facilitate processing, it is also undesirable for the tensile strength Rm at room temperature of 25°C in at least a portion of the casing to be too high.

[0071] All of the technical solutions described in the embodiments of this application are applicable to various electrical devices that use batteries.

[0072] Electrical equipment may include vehicles, mobile phones, portable devices, laptop computers, ships, aerospace vehicles, electric toys, and power tools. Vehicles may be fuel-powered vehicles, natural gas vehicles, or new energy vehicles, and new energy vehicles may include pure electric vehicles, hybrid vehicles, or range-extender vehicles. Aerospace vehicles may include airplanes, rockets, space shuttles, and spacecraft. Electric toys include stationary or mobile electric toys such as game consoles, electric car toys, electric boat toys, and electric airplane toys. Power tools include metal cutting power tools such as electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact drills, concrete vibrators, and electric planers, as well as grinding power tools, assembly power tools, and railway power tools. The embodiments of this application do not impose any special limitations on the above-mentioned electrical equipment.

[0073] The following examples will use a vehicle as an example for the sake of clarity.

[0074] As an example, Figure 1 is a schematic diagram of the structure of a vehicle 1 according to one embodiment of the present application, where the vehicle 1 may be a fuel vehicle, a gas vehicle, or a new energy vehicle, and the new energy vehicle may be a pure electric vehicle, a hybrid vehicle, or a range extender vehicle. A motor 80, a controller 70, and a battery 10 are installed inside the vehicle 1, and the controller 70 is used to control the battery 10 to supply power to the motor 80. For example, the battery 10 may be installed at the bottom of the vehicle 1 or at the front or rear of the vehicle. The battery 10 can be used to power the vehicle 1, for example, as an operating power source for the vehicle 1, it can be used for the operating power needs of the vehicle 1's circuit systems, such as starting the vehicle 1, navigation, and driving the vehicle 1. In another embodiment of the present application, the battery 10 can not only be an operating power source for the vehicle 1, but can also be a driving power source for the vehicle 1, providing driving force to the vehicle 1 by completely or partially replacing fuel or natural gas.

[0075] To meet different power consumption needs, a battery may contain multiple battery cells, which may be connected in series, in parallel, or in a series-parallel configuration, where series-parallel connection refers to a combination of series and parallel connections. A battery may also be called a battery pack. For example, multiple battery cells may be connected in series, in parallel, or in a series-parallel configuration to form a battery module, and multiple battery modules may be further connected in series, in parallel, or in a series-parallel configuration to form a battery. In other words, multiple battery cells may directly form a battery, or they may first form battery modules, and then further battery modules may be used to form a battery.

[0076] Figure 2 shows a schematic diagram of the structure of a battery 10 according to one embodiment of the present application, and the battery 10 may include a plurality of battery cells 20. The battery 10 may further include a case 11 which has a hollow internal structure, and the plurality of battery cells 20 are housed in the case 11. Figure 2 shows a possible embodiment of the case 11 according to an embodiment of the present application, and as shown in Figure 2, the case 11 may include two case parts called a first case part 111 and a second case part 112, respectively, and the first case part 111 and the second case part 112 are engaged. The shapes of the first case part 111 and the second case part 112 are determined by the combined shape of the plurality of battery cells 20, and at least one of the first case part 111 and the second case part 112 has one opening. For example, as shown in Figure 2, the first case portion 111 and the second case portion 112 may both be hollow rectangular parallelepipeds with only one open surface, the openings of the first case portion 111 and the second case portion 112 facing each other, and the first case portion 111 and the second case portion 112 engaging with each other to form a case 11 having a sealed cavity. This cavity may be used to house a plurality of battery cells 20. The plurality of battery cells 20 are connected in parallel, in series, or in series-parallel and then arranged in the case 11 formed by the engagement of the first case portion 111 and the second case portion 112.

[0077] Furthermore, unlike what is shown in Figure 2, for example, one of the first case portion 111 and the second case portion 112 may be a hollow rectangular parallelepiped with an opening, while the other is plate-shaped to cover the opening. For example, if the second case portion 112 is a hollow rectangular parallelepiped with only one side being an opening, and the first case portion 111 is plate-shaped, then the first case portion 111 would cover the opening of the second case portion 112 to form a case 11 having a sealed cavity, but the embodiments of the present application are not limited to these.

[0078] Figure 3 shows a schematic diagram of the structure of a battery cell 20 according to one embodiment of the present application. For example, the battery cell 20 shown in Figure 3 may be any battery cell 20 of the battery 10 shown in Figure 2. Figure 4 shows a schematic diagram of the partially disassembled structure of a battery cell 20 according to one embodiment of the present application. For example, Figure 4 may be a schematic diagram of the partially disassembled structure of the battery cell 20 shown in Figure 3.

[0079] In embodiments of the present application, as shown in Figures 3 and 4, the battery cell 20 may include an electrode assembly 22 and a casing 211. Specifically, the electrode assembly 22 includes a negative electrode piece 224, the negative electrode piece 224 includes a negative electrode active material capable of reversibly desorbing and inserting metal ions, the negative electrode active material includes a silicon-based material, and the tensile strength at a temperature of 25°C in at least a portion of the casing 211 used to house the electrode assembly 22 is Rm, where Rm satisfies 250 MPa ≤ Rm ≤ 2000 MPa.

[0080] As shown in Figures 3 and 4, the battery cell 20 according to the embodiment of the present application may include an outer casing 21. Specifically, the outer casing 21 may include a hollow casing 211 having at least one opening. Furthermore, the battery cell 20 may further include a cover plate 212, for example, the outer casing 21 may include a cover plate 212 for covering the opening of the casing 211 so that the electrode assembly 22 is housed inside the outer casing 21.

[0081] As can be understood, the casing 211 in the embodiment of the present application is a component for housing the electrode assembly 22, and the casing 211 may be a hollow structure with openings at one or more ends. For example, if the casing 211 is a hollow structure with an opening at one end, one cover plate 212 may be installed corresponding to it, and if the casing 211 is a hollow structure with openings at both opposing ends, two cover plates 212 may be installed, each covering the openings at both ends of the casing 211.

[0082] As should be understood, the battery cell 20 in the embodiments of the present application may be a cylindrical battery cell, a prismatic battery cell, a soft pack battery, or a battery cell of other shape. Among these, the prismatic battery cell may include a rectangular parallelepiped battery cell, a blade-shaped battery cell, or other polygonal prismatic battery cells such as a hexagonal or octagonal prismatic battery cell, but the embodiments of the present application are not limited to these.

[0083] In accordance with the different shapes of the battery cells 20, the casing 211 of the battery cell 20 may have various shapes, for example, the casing 211 may be cylindrical or polygonal prism-shaped. Exemplarily, as shown in Figures 3 and 4, the embodiments of this application will be described primarily as having a hollow rectangular parallelepiped structure for the casing 211. Furthermore, the embodiments of this application will primarily be described as having a hollow structure with an opening at one end. However, the explanations related to the embodiments of this application are similarly applicable to other shapes of battery cells 20, and for the sake of brevity, such explanations will be omitted here.

[0084] As can be understood, the cover plate 212 according to the embodiment of the present application is used as a member that covers the opening of the casing 211 in order to isolate the internal environment of the battery cell 20 from the external environment. The shape of the cover plate 212 may match the shape of the casing 211, as shown in Figures 3 and 4, the casing 211 has a rectangular parallelepiped structure, and the cover plate 212 has a rectangular plate-like structure that matches the casing 211.

[0085] In the battery cell 20, the electrode assembly 22 is a component that causes an electrochemical reaction within the battery cell 20. Depending on the needs of actual use, one electrode assembly 22 may be installed in the casing 211, or multiple electrode assemblies may be installed. For example, as shown in Figures 3 and 4, two electrode assemblies 22 are installed in the battery cell 20. The electrode assembly 22 may be cylindrical, a rectangular parallelepiped, or the like. If the electrode assembly 22 has a cylindrical structure, the casing 211 may also have a cylindrical structure. If the electrode assembly 22 has a rectangular parallelepiped structure, the casing 211 may also have a rectangular parallelepiped structure.

[0086] As can be understood, as shown in Figures 3 and 4, the electrode assembly 22 according to the embodiment of the present application may include tabs 222 and an electrode main body 221, of which the tabs 222 of the electrode assembly 22 may include a positive electrode tab 222a and a negative electrode tab 222b. The positive electrode tab 222a may be formed by laminating portions of a positive electrode piece 223 that are not coated with the positive electrode active material, the negative electrode tab 222b may be formed by laminating portions of a negative electrode piece 224 that are not coated with the negative electrode active material, and the electrode main body 221 may be formed by laminating the positive electrode piece 223 and the negative electrode piece 224 together or by winding them together.

[0087] The negative electrode active material contained in the negative electrode piece 224 according to the embodiment of the present invention can be flexibly configured according to the actual application. For example, the negative electrode active material may include a silicon-based material. When a silicon-based material is added to the negative electrode piece 224, the silicon-based material can accommodate more metal ions, effectively increasing the energy density of the battery cell 20, and increasing the amount of deformation of the electrode assembly 22 during use within the battery cell 20. In particular, during the charging process of the battery cell 20, metal ions are inserted into the silicon-based material of the negative electrode piece 224, causing volume expansion of the electrode assembly 22 and further increasing the pressure of the electrode assembly 22 on the casing 211 of the battery cell 20.

[0088] Therefore, by increasing the tensile strength Rm of at least a portion of the casing 211 under room temperature conditions of 25°C, the deformation capacity of that portion of the casing 211 can be improved, and that portion of the casing 211 will not easily break during the use of the battery cell 20, further improving the structural stability and service life of the battery cell 20. However, in order to reduce the difficulty of selecting and processing the material for the casing 211, save costs, and facilitate processing, it is also undesirable for the tensile strength Rm of at least a portion of the casing 211 under room temperature conditions to be too high. For example, the tensile strength Rm of at least a portion of the casing 211 under room temperature conditions may normally be set to satisfy 250 MPa ≤ Rm ≤ 2000 MPa.

[0089] As can be understood, the range of values ​​for the tensile strength Rm at room temperature conditions of 25°C in at least a portion of the casing 211 according to the embodiment of the present application can be adjusted according to the actual application. For example, the value of the tensile strength Rm at room temperature can satisfy 250 MPa ≤ Rm ≤ 2000 MPa. For example, the value of the tensile strength Rm at room temperature can further satisfy 400 MPa ≤ Rm ≤ 1200 MPa. On the one hand, by increasing the tensile strength Rm at room temperature conditions in at least a portion of the casing 211, the deformation capacity of that portion of the casing 211 can be improved to resist the expansion of the electrode assembly 22, and the portion of the casing 211 can not be easily broken, further improving the structural stability and service life of the battery cell 20. On the other hand, by controlling the tensile strength Rm at room temperature conditions in at least a portion of the casing 211 so that it is not too high, the difficulty of selecting and processing the material for the casing 211 can be reduced, saving costs and making processing easier.

[0090] Furthermore, the casing 211 may be configured such that the tensile strength Rm of at least a portion of the casing 211 at room temperature satisfies 450 MPa ≤ Rm ≤ 800 MPa. By ensuring that the tensile strength Rm of at least a portion of the casing 211 at room temperature is neither too high nor too low, the deformation capacity of that portion of the casing 211 can be improved to resist the expansion of the electrode assembly 22, and this can be easily implemented and cost-effective.

[0091] In some embodiments, the tensile strength Rm value at room temperature for at least a portion of the casing 211 according to the embodiments of the present application may also be set to other values. For example, the values ​​of the tensile strength Rm at room temperature may be 250 MPa, 280 MPa, 300 MPa, 330 MPa, 350 MPa, 380 MPa, 400 MPa, 450 MPa, 500 MPa, 550 MPa, 600 MPa, 650 MPa, 700 MPa, 750 MPa, 800 MPa, 850 MPa, 900 MPa, 950 MPa, 1000 MPa, 1050 MPa, 1100 MPa, and 1150 MPa. The value may be any one of the following values: Pa, 1200 MPa, 1250 MPa, 1300 MPa, 1350 MPa, 1400 MPa, 1450 MPa, 1500 MPa, 1550 MPa, 1600 MPa, 1650 MPa, 1700 MPa, 1750 MPa, 1800 MPa, 1850 MPa, 1900 MPa, 1950 MPa, and 2000 MPa, or it may be any two of these values.

[0092] As is to be understood, the tensile strength in the embodiments of this application refers to the maximum stress value that the material experiences before fracture. The test method for the tensile strength Rm at a temperature of 25°C in at least a portion of the casing 211 in the embodiments of this application can be selected according to the actual application. For example, the tensile strength Rm can be measured at room temperature conditions of 25°C by adopting the national standard GB / T 228.1-2010.

[0093] Figure 5 shows a schematic cross-sectional view of an electrode assembly 22 according to an embodiment of the present application. For example, the schematic cross-sectional view shown in Figure 5 may be a schematic cross-sectional view of the electrode assembly 22 shown in Figure 4, and the cross-section is perpendicular to the height direction Z of the battery cell 20. Figure 6 shows a schematic local cross-sectional view of a positive electrode piece 223 or a negative electrode piece 224 according to an embodiment of the present application. For example, Figure 6 may show a schematic local cross-sectional view of the negative electrode piece 224 of the electrode assembly 22 shown in Figure 5 along its thickness direction, or a schematic local cross-sectional view of the positive electrode piece 223 of the electrode assembly 22 shown in Figure 5 along its thickness direction.

[0094] As shown in Figures 3 to 6, the electrode assembly 22 according to the embodiment of the present application includes positive electrode pieces 223 and negative electrode pieces 224, and the electrode assembly 22 can be formed by stacking the positive electrode pieces 223 and negative electrode pieces 224 on each other or by winding them together. For example, the electrode assembly 22 may include a plurality of positive electrode pieces 223 and a plurality of negative electrode pieces 224. Along the thickness direction Y of the electrode assembly 22, the plurality of positive electrode pieces 223 and a plurality of negative electrode pieces 224 are stacked alternately on each other to form a laminated electrode assembly 22. Alternatively, for example, the electrode assembly 22 may include a plurality of positive electrode pieces 223, and the negative electrode pieces 224 include a plurality of bent sections and a plurality of stacked sections that are connected to each other and arranged alternately, and after the bent sections are bent, the plurality of stacked sections of the plurality of positive electrode pieces 223 and negative electrode pieces 224 are stacked alternately on each other to form a laminated electrode assembly 22. Alternatively, for example, the electrode assembly may be wound around each other by the positive electrode piece 223 and the negative electrode piece 224 to form a wound electrode assembly 22. For convenience of explanation, the drawings of the embodiments of the present application show a wound electrode assembly 22 as an example, but the embodiments of the present application are not limited to these. Furthermore, the electrode assembly 22 may further include a separator 225 used to separate the positive electrode piece 223 and the negative electrode piece 224.

[0095] In the embodiments of the present invention, the negative electrode piece 224 includes a negative electrode active material, and for example, the negative electrode active material coated on the negative electrode piece 224 may be used to form a negative electrode active material layer 2241, which may be installed on at least one surface of the negative electrode current collector 2242. For example, the negative electrode active material layer 2241 may be installed on both sides of the negative electrode current collector 2242 that are perpendicular to its thickness direction.

[0096] 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 material substrate and a metal material layer formed on at least one surface of the polymer material substrate. For example, the metal material may include one or more of copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. For example, the polymer material substrate may include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0097] As can be understood, the negative electrode active material according to the embodiments of the present application can be flexibly configured according to the actual application. Specifically, the negative electrode active material according to the embodiments of the present application can improve the energy density of the battery by including a silicon-based material. For example, the silicon-based material may include at least one of elemental silicon, silicon-oxygen compounds, silicon-carbon composites, silicon-nitrogen composites, silicon-containing alloys, or silicon-oxygen-carbon composite materials.

[0098] In some embodiments, the silicon-based material may contain silicon and one or more alkali metal elements and alkaline earth metal elements. For example, the alkali metal element may include Li. For example, the alkaline earth metal element may include Mg. For example, the silicon-based material may be a silicon-based material in which alkali metals and / or alkaline earth metals are pre-embedded, for example, a silicon-based material in which Li and / or Mg are pre-embedded.

[0099] As can be understood, the mass percentage g of the silicon-based material in the embodiment of the present application can be flexibly set according to the actual application.

[0100] For example, the silicon-based material may be set so that the range of the mass percentage g satisfies 2% ≤ g ≤ 40%. By adding a silicon-based material to the negative electrode active material of the negative electrode piece 224, the silicon-based material can accommodate more metal ions compared to other elements, for example, the capacity of the silicon-based material is about 10 times that of graphite, which can effectively improve the energy density of the battery cell 20. At the same time, it is undesirable to set the mass percentage g of the silicon-based material to be too large, otherwise it will increase the difficulty of processing the electrode assembly 22 and increase the amount of deformation of the electrode assembly 22 during use in the battery cell 20. In particular, during the charging process of the battery cell 20, metal ions are inserted into the silicon-based material of the negative electrode piece 224, causing volume expansion of the electrode assembly 22, further increasing the pressure of the electrode assembly 22 on the casing 211 of the battery cell 20, and further increasing the difficulty of processing the battery cell 20.

[0101] Furthermore, the mass percentage g of the silicon-based material may be set to satisfy the range of 8% ≤ g ≤ 40%. By appropriately reducing the mass percentage g of the silicon-based material, the difficulty of processing the electrode assembly 22 can be reduced, the amount of deformation of the electrode assembly 22 during the charging and discharging process of the battery cell 20 can be reduced, i.e., the amount of volume expansion of the electrode assembly 22 can be reduced, the pressure of the electrode assembly 22 on the casing 211 of the battery cell 20 can be further reduced, the requirements for the structural strength of the casing 211 can be reduced, processing can be made easier and costs can be reduced.

[0102] Furthermore, the mass percentage g of the silicon-based material may be set to satisfy the range of 10% ≤ g ≤ 30%. By rationally adjusting the mass percentage g of the silicon-based material, not only can the energy density of the battery cell 20 be effectively increased, but the difficulty of processing the electrode assembly 22 can also be reduced, and the amount of deformation of the electrode assembly 22 during the charging and discharging process of the battery cell 20 can also be effectively reduced, further reducing the requirements for the structural strength of the casing 211.

[0103] In some embodiments, the mass percentage g of the silicon-based material in the embodiments of the present application may also be set to other values. For example, the mass percentage g of the silicon-based material may be any one of the following values: 5%, 8%, 10%, 13%, 15%, 18%, 20%, 23%, 25%, 28%, 30%, 33%, 35%, 38%, 40%, 43%, 45%, 48%, and 50%, or it may be between any two of these values.

[0104] As can be understood, the mass percentage g of silicon-based material in the negative electrode active material according to the embodiment of the present application means that g is the ratio of the mass of silicon-based material in the negative electrode active material to the total mass of the negative electrode active material, and the test method for the mass percentage g of silicon-based material can be selected according to the actual application and can be measured by employing methods known in the art.

[0105] In the embodiments of the present application, the negative electrode active material may further contain other materials. For example, the negative electrode active material may further contain a negative electrode adhesive. For example, the negative electrode adhesive may contain one or more of the following: styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, aqueous acrylic resin (e.g., polyacrylate PAA, polymethacrylate PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS), but the embodiments of the present application are not limited to these.

[0106] In some embodiments, the negative electrode active material may further contain a negative electrode conductive agent. The present application is not particularly limited to the type of negative electrode conductive agent, and as an example, the negative electrode conductive agent may include one or more of the following: superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0107] In some embodiments, the negative electrode active material may further contain other auxiliary agents. For example, the other auxiliary agents may include thickeners such as sodium carboxymethylcellulose (CMC) or PTC thermistor material.

[0108] The negative electrode piece 224 does not exclude other additional functional layers other than the negative electrode active material layer 2241. For example, in some embodiments, the negative electrode piece 224 may further include a conductive primer layer (e.g., consisting of a conductive agent and an adhesive) sandwiched between the negative electrode current collector 2242 and the negative electrode active material layer 2241 and placed on the surface of the negative electrode current collector 2242. In some embodiments, the negative electrode piece 224 may further include a protective layer covering the surface of the negative electrode active material layer 2241.

[0109] In some embodiments, the negative electrode sheet 224 can be manufactured by the following method: a negative electrode active material, an optional negative electrode adhesive, an optional negative electrode conductive agent, and other optional auxiliaries are dispersed in a solvent, stirred uniformly to form a negative electrode slurry, the negative electrode slurry is applied onto the negative electrode current collector 2242, and processes such as drying and cold pressing are performed, after which the negative electrode sheet 224 is formed. The solvent may be N-methylpyrrolidone (NMP) or deionized water, but the embodiments of the present application are not limited thereto.

[0110] In the embodiments of the present application, the value of the mass proportion g of the silicon-based material and the value of the tensile strength Rm of at least a partial region of the casing 211 under the condition of 25°C can mutually restrict each other to balance the relationship between the energy density and the structural strength of the battery cell 20. For example, in the negative electrode active material, the mass proportion of the silicon-based material is g, the material of at least a partial region of the casing 211 contains an iron element, and Rm and g satisfy 2%<g<40% and 300MPa<Rm<2000MPa. The material of at least a partial region of the casing 211 contains the iron element, which can increase the structural strength of the material in the corresponding partial region of the casing 211, so as to meet the design requirements.

[0111] In some embodiments, the material of at least a partial region of the casing 211 includes carbon steel or stainless steel, and Rm and g satisfy 2.5%≦g≦15% and 315MPa≦Rm<800MPa. For example, the material of at least a partial region of the casing 211 may include Q195 carbon steel, which not only facilitates processing, but also can satisfy the value of the tensile strength Rm under the condition of 25°C.

[0112] In some embodiments, the material of at least a partial region of the casing 211 includes carbon steel or stainless steel, and Rm and g satisfy 4.5%≦g≦40% and 380MPa≦Rm<2000MPa. For example, the material of at least a partial region of the casing 211 may include SPCC carbon steel, which not only facilitates processing, but also can satisfy the value of the tensile strength Rm under the condition of 25°C.

[0113] 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 casing 211 may include modified stainless steel, which not only facilitates processing but also satisfies the tensile strength Rm value at 25°C.

[0114] In some embodiments, Rm and g satisfy 10% ≤ g ≤ 40% and 480 MPa ≤ Rm < 2000 MPa. For example, the material of at least a portion of the casing 211 may include 316 stainless steel, which not only facilitates processing but also satisfies the tensile strength Rm value at 25°C.

[0115] In some embodiments, Rm and g satisfy the conditions 15% ≤ g ≤ 40% and 520 MPa ≤ Rm < 2000 MPa. For example, the material of at least a portion of the casing 211 may include 304 stainless steel, which not only facilitates processing but also satisfies the tensile strength Rm value at 25°C.

[0116] In several examples, Rm and g satisfy the conditions 20% ≤ g ≤ 40% and 600 MPa ≤ Rm < 2000 MPa.

[0117] The following will be explained by comparing multiple comparative examples and multiple examples. Specifically, the battery cell 20 in each of the following examples and comparative examples is a rectangular parallelepiped type battery cell as shown in Figures 3 and 4, and among them, a hollow structure is adopted in which the casing 211 opens at one end.

[0118] In the following examples and comparative examples, the manufacturing methods for the positive electrode piece 223, negative electrode piece 224, electrolyte, and separator 225 of the battery cell 20 are as follows.

[0119] 1. Manufacturing of positive electrode piece 223 Positive electrode active material LiNi 0.95 Co 0.04Mn 0.01 O2, the conductive agent Super P, and the adhesive polyvinylidene fluoride (PVDF) were prepared as a positive electrode slurry in N-methylpyrrolidone (NMP), with a solid content of 50 wt% in the positive electrode slurry, and LiNi 0.7 Co 0.1 Mn 0.1 The mass ratio of O2, Super P, and PVDF was 8:1:1. The positive electrode slurry was applied to the upper and lower surfaces of the aluminum foil current collector, dried at 85°C, then cold-pressurized, edge-trimmed, cut, and slit, and finally dried under vacuum conditions at 85°C for 4 hours to produce the positive electrode piece 223.

[0120] 2. Manufacturing of the negative electrode piece 224 A negative electrode slurry was prepared by uniformly mixing a negative electrode active material, a conductive agent Super P, a thickener carboxymethylcellulose (CMC), and an adhesive styrene-butadiene rubber (SBR) in deionized water. The negative electrode active material contained graphite and a silicon-based material, and the silicon-based material was a silicon-oxygen compound. The solid content in the negative electrode slurry was 30 wt%, and the mass ratio of the negative electrode active material, silicon monoxide, Super P, CMC, and adhesive styrene-butadiene rubber (SBR) in the solid content was 88:7:3:2. The negative electrode slurry was applied to the upper and lower surfaces of a copper foil current collector and dried at 85°C. Then it was cold-pressed, edge-trimmed, cut, and slit, and then dried under vacuum conditions at 120°C for 12 hours to produce a negative electrode piece 224.

[0121] 3. Manufacturing of electrolyte In a glove box under an argon atmosphere (H2O < 0.1 ppm, O2 < 0.1 ppm), a thoroughly dried electrolyte salt, LiPF6, was dissolved in a mixed solvent (the mixed solvent contained ethylene carbonate (EC) and diethyl carbonate (DEC), and the ethylene carbonate (EC) and diethyl carbonate (DEC) were mixed in a 50:50 mass ratio). After homogeneous mixing, an electrolyte solution with a concentration of 1 mol / L was obtained.

[0122] 4. Manufacturing of separator 225 A 16 μm polyethylene film was used as separator 225.

[0123] 5. Manufacturing of lithium-ion battery cells 20 The positive electrode piece 223, separator 225, and negative electrode piece 224 are stacked in order, with the separator 225 positioned between the positive electrode piece 223 and the negative electrode piece 224 to isolate the positive and negative electrodes. The cells are then wound to obtain a bare cell, tabs are welded, the bare cell is placed in an outer casing made of a different material, the manufactured electrolyte is injected into the dried outer casing, and sealing, standing, chemical conversion, shaping, and capacity testing are performed to complete the manufacturing of the lithium-ion battery cell 20.

[0124] In each of the following examples and comparative examples, the tensile strength of the casing 211 of the battery cell 20 at a temperature of 25°C is Rm, and in order to obtain different tensile strengths Rm, different materials were correspondingly selected for the casing 211. The negative electrode active material of the negative electrode piece 224 of the electrode assembly 22 of the battery cell 20 contains a silicon-based material with a mass percentage of g, and the specific parameter settings are shown in Table 1 below. Furthermore, in each example 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 was measured using the method specified in GB / T 228.1-2010. In addition, the battery cell 20 in each of the following examples and comparative examples is the same in all other conditions except for the differences in the parameter settings shown in Table 1. 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 example, the capacity of the battery cell 20 in each embodiment is 350 Ah.

[0125] A cycle charge fatigue test was performed on the battery cells 20 in each of the embodiments and comparative examples described below. Specifically, Figure 7 shows a schematic diagram of the structure of the clamp 700 for cycle charge fatigue testing according to the embodiment of the present application. As shown in Figure 7, the clamp 700 includes three 10 mm steel plates, and the steel plates completely cover the walls of the maximum area of ​​the battery cell 20. For convenience of explanation, the three clamp steel plates are defined here as the first steel plate 710, the second steel plate 720, and the third steel plate 730, respectively. The first steel plate 710 and the third steel plate 730 are located at both ends of the clamp 700 and are connected and fixed by bolts. The central second steel plate 720 is constrained by guide rails so that it can translate only in a direction perpendicular to the large surface of the second steel plate 720, the space between the first steel plate 710 and the second steel plate 720 is used to clamp the battery cell 20, and the walls of the battery cell 20 with the largest surface area are bonded to the first steel plate 710 and the second steel plate 720, and a pressure sensor 740 is provided between the second steel plate 720 and the third steel plate 730. By adjusting the position of the second steel plate 720, it is possible to adjust the initial pressing force of the battery cell 20 on the second steel plate 720.

[0126] Specifically, the battery cell 20 is clamped and fixed within a dedicated clamp 700, ensuring that the two opposing walls of the maximum surface area of ​​the battery cell 20 are firmly held in place, and the initial pressure is set to 2000N. The electrode terminals 214 of the battery cell 20 are then connected to a dedicated battery charging and discharging device.

[0127] The clamp 700, which held the battery cell 20, was placed in a constant temperature environment of 25±2℃, and the test was started after the battery cell 20 reached temperature equilibrium.

[0128] The specific test steps were carried out by referring to Chapter 6.4, "Standard Cycle Life," of "GBT31484-2015 Cycle Life Requirements and Test Methods for Power Storage Batteries for Electric Vehicles," and the test cycle cutoff condition was changed to "Stop the test until the welded seam 2113 of the battery cell 20 is damaged."

[0129] For example, the test can be performed according to the following steps: step a, discharge at 1I(A) until the discharge stop condition specified by the company; step b, leave for 30 minutes or longer or until the leave condition specified by the company; step c, charge according to the method in 6.1.1.3; step d, leave for 30 minutes or longer or until the leave condition specified by the company; step e, discharge at 1I1(A) until the discharge stop condition specified by the company; and step f, cycle through steps b to e until the weld joint 2113 is damaged and the test is stopped.

[0130] During the above test process, the welded seam 2113 of the battery cell 20 was continuously observed and the number of cycles recorded until leakage occurred at the welded seam 2113, thereby obtaining the state of the casing 211 after 1000 cycles, as shown in Table 1 below. In each of the following examples and comparative examples, the welded seam 2113 refers to the welded seam between the casing 211 and the cover plate 212, that is, the welded seam 2113 surrounds the open end of the casing 211, while the casing 211 employs an integrally molded structure.

[0131] [Table 1]

[0132] As can be understood, in Table 1 above, the material of the casing 211 may be Q195 carbon steel, but the tensile strength Rm of Q195 carbon steel at room temperature of 25°C is typically at least 315 MPa to 430 MPa, and in the above example only 328 MPa is taken as an example, but it is not limited to this. Similarly, the material of the casing 211 may be SPCC carbon steel, but the tensile strength Rm of SPCC carbon steel at room temperature of 25°C is typically at least 380 MPa to 430 MPa, and in the above example only 396 MPa is taken as an example. The material of the casing 211 may also be modified stainless steel, but the tensile strength Rm of modified stainless steel at room temperature of 25°C is typically at least 400 MPa to 600 MPa, and in the above example only 421 MPa is taken as an example. The material of the casing 211 may be SUS430 stainless steel, but the tensile strength Rm of SUS430 stainless steel at room temperature of 25°C is usually at least 450 MPa, and in the above example only 459 MPa is taken as an example. The material of the casing 211 may also be SUS304 stainless steel, but the tensile strength Rm of SUS304 stainless steel at room temperature of 25°C is usually at least 520 MPa, and in the above example only 533 MPa and 625 MPa are taken as examples.

[0133] As can be seen by comparing the two comparative examples and the twelve examples in Table 1 above, when different materials are used for the casing 211, correspondingly different tensile strengths Rm can be determined. If the tensile strength Rm satisfies 250MPa ≤ Rm ≤ 2000MPa, for example, in Examples 1 to 12, even if the mass percentage g of silicon-based material in the negative electrode piece 224 of the battery cell 20 is different, the failure fatigue cycles of the battery cell 20 can reach more than 1,000, thereby meeting the design needs of the battery cell 20. However, if the tensile strength Rm does not satisfy 250MPa ≤ Rm ≤ 2000MPa, for example, in Comparative Examples 1 to 2, even if the mass percentage g of silicon-based material in the negative electrode piece 224 of the battery cell 20 is relatively low, the failure fatigue cycles of the battery cell 20 do not reach 1,000, and the design needs of the battery cell 20 cannot be met.

[0134] As can be understood, the battery cell 20 according to the embodiment of the present application can further satisfy other design needs. Specifically, the yield strength at a temperature of 25°C in at least a portion of the casing 211 is Re, where Re satisfies 140 MPa ≤ Re ≤ 1000 MPa.

[0135] By increasing the yield strength Re at room temperature in at least a portion of the casing 211, the deformation capacity of the casing 211 can be improved, further enhancing the structural stability and service life of the battery cell 20. During the charging and discharging process of the battery cell 20, the electrode assembly 22 undergoes repeated volume expansion and contraction. By increasing the yield strength Re at room temperature in at least a portion of the casing 211, the maximum compressive force that the casing 211 can withstand can be increased. If this does not exceed the limit of the yield strength of the casing 211, the casing 211 will not easily break, and the deformation of the casing 211 is recoverable, thus improving the service life of the casing 211. However, in order to reduce the difficulty of selecting and processing the material for the casing 211, save costs, and facilitate processing, it is undesirable for the yield strength Re at room temperature in at least a portion of the casing 211 to be too high. For example, the casing 211 may typically be installed such that the yield strength Re in at least a portion of the casing 211 under ambient temperature conditions satisfies 140 MPa ≤ Re ≤ 1000 MPa.

[0136] As can be understood, the range of yield strength Re values ​​at room temperature conditions of 25°C in at least a portion of the casing 211 according to the embodiment of the present application can be adjusted according to the actual application. For example, the yield strength Re value at room temperature can satisfy 140 MPa ≤ Re ≤ 1000 MPa. Alternatively, for example, the yield strength Re value at room temperature can satisfy 180 MPa ≤ Re ≤ 600 MPa. On the one hand, by increasing the yield strength Re at room temperature in at least a portion of the casing 211, the deformation capacity of that portion of the casing 211 can be improved to resist the expansion of the electrode assembly 22, and if that portion of the casing 211 is not easily broken and does not exceed the limit of the yield strength of the casing 211, then when the expansion of the electrode assembly 22 is reduced, the deformation of the casing 211 can also be recovered, further improving the structural stability and service life of the battery cell 20. On the other hand, by controlling the yield strength Re of at least a portion of the casing 211 at room temperature so that it is not too high, the difficulty of selecting and processing the material for the casing 211 can be reduced, costs can be saved, and processing can be made easier.

[0137] Furthermore, the casing 211 may be installed such that the yield strength Re in at least a portion of the casing 211 at room temperature satisfies 220 MPa ≤ Re ≤ 400 MPa. By ensuring that the yield strength Re in at least a portion of the casing 211 at room temperature is neither too high nor too low, the deformation capacity of that portion of the casing 211 can be improved to resist the expansion of the electrode assembly 22, and this can be easily implemented and cost-effective.

[0138] In some embodiments, the yield strength Re value at room temperature for at least a portion of the casing 211 according to the embodiment of the present application may also be set to other values. For example, the yield strength Re value at room temperature may be any one of the following values: 140MPa, 150MPa, 160MPa, 180MPa, 200MPa, 220MPa, 250MPa, 280MPa, 300MPa, 330MPa, 350MPa, 380MPa, 400MPa, 430MPa, 450MPa, 480MPa, 500MPa, 530MPa, 550MPa, 580MPa, 600MPa, 630MPa, 650MPa, 680MPa, 700MPa, 730MPa, 750MPa, 780MPa, 800MPa, 830MPa, 850MPa, 880MPa, 900MPa, 930MPa, 950MPa, 980MPa, and 1000MPa, or it may be between any two of these values.

[0139] As can be understood, the yield strength in the embodiments of the present application can be understood as the critical stress value for material yielding. Normally, after a material is subjected to stress, in addition to elastic deformation, plastic deformation may also occur as the stress increases. The point at which plastic deformation of the material occurs may 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 the present application usually refers to the upper yield strength, that is, the upper yield strength under the condition of a temperature of 25°C in at least a portion of the casing 211 is Re.

[0140] The test method for the yield strength Re of at least a portion of the casing 211 under a temperature of 25°C according to the embodiment of this application can be selected according to the actual application. For example, the yield strength Re can be measured under room temperature conditions of 25°C by adopting the national standard GB / T 228.1-2010.

[0141] In the embodiments of the present application, the value of the mass proportion g of the silicon-based material and the value of the yield strength Re of at least a partial region of the casing 211 under the condition of 25°C can be mutually restricted, so as to improve the energy density of the battery cell 20, improve the structural strength of the casing 211, and further improve the structural strength and service life of the battery cell 20.

[0142] For example, in the negative electrode active material, the mass proportion of the silicon-based material is g, and g and Re satisfy 2%<g<40% and 140MPa<Re<600MPa. By adding the silicon-based material to the negative electrode active material of the negative electrode piece 224, the silicon-based material can accommodate more metal ions compared with other elements. For example, since the capacity of the silicon-based material is about 10 times that of graphite, the energy density of the battery cell 20 can be effectively improved. At the same time, it is not desirable to set the mass proportion g of the silicon-based material to be excessively large, otherwise the processing difficulty of the electrode assembly 22 will be increased, and the deformation amount of the electrode assembly 22 in the battery cell 20 during the use process will also be increased. Especially during the charging process of the battery cell 20, metal ions are inserted into the silicon-based material of the negative electrode piece, which causes volume expansion of the electrode assembly 22, further increases the pressure of the electrode assembly 22 on the casing 211 of the battery cell 20, and further increases the processing difficulty of the battery cell 20. Therefore, by appropriately increasing the yield strength Re of at least a partial region of the casing 211 under normal temperature conditions, the deformability of the corresponding part of the casing 211 can be improved to resist the expansion amount of the electrode assembly 22. If the corresponding part of the casing 211 is not easily broken and does not exceed the limit of the yield strength of the casing 211, when the expansion amount of the electrode assembly 22 decreases, the deformation of the casing 211 can also be recovered, and the structural stability and service life of the battery cell 20 can be further improved. In addition, by controlling the yield strength Re of at least a partial region of the casing 211 under normal temperature conditions not to be excessively large, the difficulty of material selection and processing of the casing 211 can be reduced, costs can be saved, and processing can be facilitated.

[0143] In some embodiments, the material of at least a portion of the casing 211 includes carbon steel or stainless steel, and g and Re satisfy 4.5% ≤ g ≤ 40% and 170 MPa ≤ Re < 600 MPa. For example, the material of at least a portion of the casing 211 may include SPCC carbon steel, which not only facilitates processing but also satisfies the yield strength Re value at 25°C.

[0144] In some embodiments, g and Re satisfy the conditions 8% ≤ g ≤ 40% and 180 MPa ≤ Re < 600 MPa. For example, the material of at least a portion of the casing 211 may include modified stainless steel, which not only facilitates processing but also satisfies the yield strength Re value at 25°C.

[0145] In some embodiments, g and Re satisfy the conditions 10% ≤ g ≤ 40% and 190 MPa ≤ Re < 600 MPa. For example, the material of at least a portion of the casing 211 may include 316 stainless steel, which not only facilitates processing but also satisfies the yield strength Re value at 25°C.

[0146] In some embodiments, g and Re satisfy the conditions 15% ≤ g ≤ 40% and 200 MPa ≤ Re < 600 MPa. For example, the material of at least a portion of the casing 211 may include 304 stainless steel, which not only facilitates processing but also satisfies the yield strength Re value at 25°C.

[0147] In some examples, g and Re satisfy the conditions 20% ≤ g ≤ 40% and 210 MPa ≤ Re < 600 MPa.

[0148] The following will be explained by comparing multiple comparative examples and multiple examples. Specifically, the battery cell 20 in each of the following examples and comparative examples is a rectangular parallelepiped type battery cell as shown in Figures 3 and 4, and among them, a hollow structure is adopted in which the casing 211 opens at one end.

[0149] In each of the following Examples and Comparative Examples, the preparation methods for the positive electrode sheet 223, the negative electrode sheet 224, the electrolytic solution, and the separator 225 of the battery cell 20 are as follows.

[0150] 1. Preparation of positive electrode sheet 223 Positive active material LiNi 0.95 Co 0.04 Mn 0.01 O2, Super P as a conductive agent, and polyvinylidene fluoride (PVDF) as an adhesive were prepared into a positive electrode slurry in N-methylpyrrolidone (NMP), wherein the solid content in the positive electrode slurry was 50 wt%, and the mass ratio of LiNi in the solid components 0.7 Co 0.1 Mn 0.1 O2, Super P, and PVDF was 8:1:1. The positive electrode slurry was applied to the upper and lower surfaces of an aluminum foil serving as a current collector, dried at 85°C, then subjected to cold pressing, followed by edge trimming, cutting, and slitting, and then dried under vacuum at 85°C for 4 hours to produce the positive electrode sheet 223.

[0151] 2. Preparation of negative electrode sheet 224 A negative active material, Super P as a conductive agent, carboxymethyl cellulose (CMC) as a thickener, and styrene-butadiene rubber (SBR) as an adhesive were uniformly mixed in deionized water to prepare a negative electrode slurry. The negative active material included graphite and a silicon-based material, the silicon-based material being a silicon-oxygen compound, the solid content in the negative electrode slurry was 30 wt%, and the mass ratio of the negative active material, silicon monoxide, Super P, CMC, and styrene-butadiene rubber (SBR) as the adhesive in the solid components was 88:7:3:2. The negative electrode slurry was applied to the upper and lower surfaces of a copper foil serving as a current collector, dried at 85°C, then subjected to cold pressing, edge trimming, cutting, and slitting, and then dried under vacuum at 120°C for 12 hours to produce the negative electrode sheet 224.

[0152] 3. Preparation of electrolytic solution In a glove box under an argon atmosphere (H2O < 0.1 ppm, O2 < 0.1 ppm), a thoroughly dried electrolyte salt, LiPF6, was dissolved in a mixed solvent (the mixed solvent contained ethylene carbonate (EC) and diethyl carbonate (DEC), and the ethylene carbonate (EC) and diethyl carbonate (DEC) were mixed in a 50:50 mass ratio). After homogeneous mixing, an electrolyte solution with a concentration of 1 mol / L was obtained.

[0153] 4. Manufacturing of separator 225 A 16 μm polyethylene film was used as separator 225.

[0154] 5. Manufacturing of lithium-ion battery cells 20 The positive electrode piece 223, separator 225, and negative electrode piece 224 are stacked in order, with the separator 225 positioned between the positive electrode piece 223 and the negative electrode piece 224 to isolate the positive and negative electrodes. The cells are then wound to obtain a bare cell, tabs are welded, the bare cell is placed in an outer casing made of a different material, the manufactured electrolyte is injected into the dried outer casing, and sealing, standing, chemical conversion, shaping, and capacity testing are performed to complete the manufacturing of the lithium-ion battery cell 20.

[0155] In each of the following examples and comparative examples, the yield strength of the casing 211 of the battery cell 20 at a temperature of 25°C is Re, and to obtain different yield strengths Re, different materials are correspondingly selected for the casing 211. The negative electrode active material of the negative electrode piece 224 of the electrode assembly 22 of the battery cell 20 includes a silicon-based material with a mass percentage of g, and the specific parameter settings are shown in Table 2 below. In addition, in each example and comparative example, the material is the same for all areas of the casing 211, and the yield strength Re of the casing 211 at 25°C was measured using the method specified in GB / T 228.1-2010. Furthermore, in each of the following examples and comparative examples, the battery cell 20 is the same in all other conditions except for the parameter settings shown in Table 2. For example, the wall thickness of each wall of the casing 211 of the battery cell 20 in each example is 0.25 mm, and the capacity of the battery cell 20 in each example is 350 Ah.

[0156] A cycle charge fatigue test was performed on the battery cells 20 in each of the following examples and comparative examples. Specifically, the test can be performed using the cycle charge fatigue test clamp 700 shown in Figure 7.

[0157] Specifically, the battery cell 20 is clamped and fixed within a dedicated clamp 700, ensuring that the two opposing walls of the maximum surface area of ​​the battery cell 20 are firmly held in place, and the initial pressure is set to 2000N. The electrode terminals 214 of the battery cell 20 are then connected to a dedicated battery charging and discharging device.

[0158] The clamp 700, which held the battery cell 20, was placed in a constant temperature environment of 25±2℃, and the test was started after the battery cell 20 reached temperature equilibrium.

[0159] The specific test steps were carried out by referring to Chapter 6.4, "Standard Cycle Life," of "GBT31484-2015 Cycle Life Requirements and Test Methods for Power Storage Batteries for Electric Vehicles," and the test cycle cutoff condition was changed to "Stop the test until the welded seam 2113 of the battery cell 20 is damaged."

[0160] For example, the test can be performed according to the following steps: step a, discharge at 1I(A) until the discharge stop condition specified by the company; step b, leave for 30 minutes or longer or until the leave condition specified by the company; step c, charge according to the method in 6.1.1.3; step d, leave for 30 minutes or longer or until the leave condition specified by the company; step e, discharge at 1I1(A) until the discharge stop condition specified by the company; and step f, cycle through steps b to e until the weld joint 2113 is damaged and the test is stopped.

[0161] During the above test process, the welded seams 2113 of the battery cell 20 were continuously observed and the number of cycles recorded until leakage occurred at the welded seams 2113, thereby obtaining the failure fatigue state of the casing 211 after 1000 cycles, as shown in Table 2 below. In each of the following examples and comparative examples, the welded seam 2113 refers to the welded seam between the casing 211 and the cover plate 212, that is, the welded seam 2113 surrounds the open end of the casing 211, while the casing 211 employs an integrally molded structure.

[0162] [Table 2]

[0163] As can be understood, in Table 2 above, the material of the casing 211 may be modified stainless steel, but the yield strength Re of modified stainless steel at room temperature of 25°C is typically at least 140 MPa to 180 MPa, and in the above examples only 145 MPa and 173 MPa are taken as examples, but are not limited to these. Similarly, the material of the casing 211 may be SUS316 stainless steel, but the yield strength Re of SUS316 stainless steel at room temperature of 25°C is typically at least 177 MPa, and in the above examples only 182 MPa and 193 MPa are taken as examples. The material of the casing 211 may also be Q195 carbon steel, but the yield strength Re of Q195 carbon steel at room temperature of 25°C is typically at least 195 MPa, and in the above examples only 203 MPa is taken as an example. The material of the casing 211 may be SUS304 stainless steel, but the yield strength Re of SUS304 stainless steel at room temperature of 25°C is typically at least 205 MPa, and in the above example, only 212 MPa is used as an example.

[0164] As can be seen by comparing the two comparative examples and the twelve examples in Table 2 above, when different materials are used for the casing 211, correspondingly different yield strengths Re can be determined. If the yield strength Re satisfies 140 MPa ≤ Re ≤ 1000 MPa, for example, in Examples 1 to 12, even if the mass percentage g of silicon-based material in the negative electrode piece 224 of the battery cell 20 is different, the failure fatigue cycles of the battery cell 20 can reach more than 1000, thereby meeting the design needs of the battery cell 20. However, if the yield strength Re does not satisfy 140 MPa ≤ Re ≤ 1000 MPa, for example, in Comparative Examples 1 to 2, even if the mass percentage g of silicon-based material in the negative electrode piece 224 of the battery cell 20 is relatively low, the failure fatigue cycles of the battery cell 20 cannot reach 1000, and the design needs of the battery cell 20 cannot be met.

[0165] In some embodiments, the electrode assembly 22 further comprises a positive electrode piece 223, the positive electrode piece 223 comprising a positive electrode active material capable of reversibly desorbing and inserting metal ions, the positive electrode active material comprising a nickel-containing compound, and the melting point of at least a portion of the casing 211 is p, where p satisfies 1200°C ≤ p ≤ 2000°C.

[0166] The positive electrode piece 223 in the embodiment of the present invention is equipped with a positive electrode active material that can reversibly desorb and insert metal ions, and the positive electrode active material can be flexibly installed according to the actual application. For example, the positive electrode active material may contain a nickel element compound, which can effectively increase the energy density of the battery cell 20 and improve the cycle life, but at the same time, it also increases the temperature and gas generated during the use of the battery cell 20, and in particular, if thermal runaway occurs during the use of the battery cell 20, the internal temperature of the battery cell 20 rises rapidly and a large amount of gas is generated.

[0167] Therefore, by appropriately improving the melting point p of at least a portion of the casing 211, the casing 211 will not easily melt, reducing the possibility of the battery cell 20 exploding, and further reducing the risk of thermal runaway in adjacent battery cells 20, thereby improving the reliability of the battery 10. However, in order to reduce the difficulty of selecting and processing the material for the casing 211, save costs, and facilitate processing, it is also undesirable for the melting point p of at least a portion of the casing 211 to be too high. For example, the melting point p of at least a portion of the casing 211 may normally be set to satisfy 1200°C ≤ p ≤ 2000°C.

[0168] As can be understood, the range of the melting point p value for at least a portion of the casing 211 in the embodiment of the present application can be adjusted according to the actual application. For example, the melting point p of at least a portion of the casing 211 usually satisfies 1200°C ≤ p ≤ 2000°C. Alternatively, for example, the melting point p of at least a portion of the casing 211 may satisfy 1300°C ≤ p ≤ 1800°C. On the one hand, by appropriately increasing the value of the melting point p, the resistance of the casing 211 in that portion to melting when thermal runaway occurs in the battery cell 20 can be improved, the casing 211 will not melt easily, further reducing the risk of thermal runaway occurring in adjacent battery cells 20, i.e., reducing the risk of thermal diffusion, thereby improving the reliability of the battery 10. At the same time, the melting point p should not be too high in order to easily select a suitable material, reduce the difficulty of processing, save costs, and facilitate processing.

[0169] Furthermore, the melting point p of at least a portion of the casing 211 may be set to satisfy 1400°C ≤ p ≤ 1600°C. This improves the structural strength of the casing 211 when thermal runaway occurs in the battery cell 20, preventing the casing 211 from easily melting, maintaining the structural integrity of that portion of the casing 211, and reducing the risk of thermal runaway occurring in adjacent battery cells 20. At the same time, it can reduce the difficulty of processing and save costs.

[0170] In some embodiments, the range of the melting point p value for at least a portion of the casing 211 may be set to other values. For example, the melting point p value may be one 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, or it may be between any two of these values.

[0171] In the embodiments of the present application, the positive electrode piece 223 includes a positive electrode active material, and for example, the positive electrode active material coated on the positive electrode piece 223 may be used to form a positive electrode active material layer 2231, which may be installed on at least one surface of the positive electrode current collector 2232. For example, a positive electrode active material layer 2241 may be installed on both sides of the positive electrode current collector 2232 perpendicular to its thickness direction, but the embodiments of the present application are not limited to these.

[0172] In some embodiments, the positive electrode current collector 2232 may be a metal foil or a composite current collector. As an example of a metal foil, aluminum foil may be used. The composite current collector may include a polymer material substrate and a metal material layer formed on at least one surface of the polymer 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 polymer material substrate may include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0173] As can be understood, the cathode active material according to the embodiment of the present invention can be flexibly configured according to the actual application. For example, the cathode active material may contain a nickel element-containing compound. As an example, the nickel element-containing compound contains a layered lithium-containing transition metal oxide, and the molar amount of nickel element in the layered lithium-containing transition metal oxide accounts for 50% or more of the total molar amount of transition metal elements in the layered lithium-containing transition metal oxide. By increasing the proportion of nickel element in the layered lithium-containing transition metal oxide to 50% or more, the energy density of the battery cell 20 can be effectively improved and the cycle life can be improved. However, it is not desirable to set this proportion to be excessively large, otherwise it will increase the difficulty of processing the electrode assembly 22 and further increase the processing cost of the battery cell 20.

[0174] Furthermore, the molar proportion of nickel in the layered lithium-containing transition metal oxide may be 70% or more, 80% or more, or 90%. In this way, if the energy density of the battery cell 20 can be effectively improved, the difficulty of processing the electrode assembly 22 can be controlled, thereby reducing the processing cost of the battery cell 20.

[0175] In some embodiments, the molar percentage of nickel in the layered lithium-containing transition metal oxide according to the embodiments of the present application may also be set to other values. For example, the molar percentage of nickel in the layered lithium-containing transition metal oxide may be any one of 50%, 53%, 55%, 58%, 60%, 63%, 65%, 68%, 70%, 73%, 75%, 78%, 80%, 83%, 85%, 88%, 90%, 92%, 94%, 96%, and 98%, or it may be between any two of these values.

[0176] As can be appreciated, the test method for the molar amount of nickel element in the layered lithium-containing transition metal oxide and the total molar amount of transition metal elements in the layered lithium-containing transition metal oxide according to the embodiments of the present application may be selected according to practical applications, and may be measured using equipment and methods known in the art. For example, the positive electrode active material is laid and adhered on a conductive adhesive to prepare a sample to be measured with a length × width of 6 cm × 1.1 cm, and the particle morphology can be tested using a scanning electron microscope & energy dispersive X-ray spectrometer (e.g., ZEISS Sigma 300). The test may refer to JY / T010-1996. To ensure the accuracy of the test results, 20 different regions are randomly selected from the sample to be measured for scanning test, and the content of the layered lithium-containing transition metal oxide in each region can be statistically counted and calculated at a certain magnification (e.g., 1000 times or more). For example, the average value of the test results of 20 test regions is taken as the number of the layered lithium-containing transition metal oxide in the positive electrode active material, so that the molar amount of the layered lithium-containing transition metal oxide can be further determined. Similarly, the method can also be used to determine the molar amount of the nickel element in the layered lithium-containing transition metal oxide.

[0177] 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 LiaNibCocMdOeAf, where 0<a≤1.2, 0.5≤b<1, optionally 0.9≤b<1, 0<c<1, 0<d<1, 1≤e≤2, 0≤f≤1, M includes one or more of Mn, Al, Zr, Zn, Cu, Cr, Mg, Fe, V, Ti and B, but is not limited thereto, and A includes one or more of N, F, S and Cl, but is not limited thereto. Among them, the proportion b of the molar amount of nickel element in the layered lithium-containing transition metal oxide is set to 50% or more, that is, the proportion b satisfies 0.5≤b<1, and may further satisfy 0.8≤b<1, or 0.9≤b<1, whereby the energy density of the battery cell 20 can be further improved.

[0178] As an example, the layered lithium-containing transition metal oxide may contain one or more of the following: LiNi0.5 Co0.2 Mn0.3 O2 (abbreviated as NCM523), LiNi0.5 Co0.25 Mn0.25 O2 (abbreviated as NCM211), LiNi0.6 Co0.2 Mn0.2 O2 (abbreviated as NCM622), LiNi0.8 Co0.1 Mn0.1 O2 (abbreviated as NCM811), LiNi0.9 Co0.06 Mn0.04 O2, LiNi0.96 Co0.02 Mn0.02 O2, and LiNi0.85 Co0.15 Al0.05 O2, but is not limited to these.

[0179] In some embodiments, the positive electrode active material may further contain other materials. For example, the positive electrode active material may further contain a positive electrode conductive agent. The present application is not particularly limited to the type of positive electrode conductive agent. As an example, the positive electrode conductive agent may contain one or more of the following: superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0180] In some embodiments, the positive electrode active material may further include a positive electrode adhesive. The present application is not particularly limited to the type of positive electrode adhesive. For example, the positive electrode adhesive may include one or more of the following: polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylic resin.

[0181] In some embodiments, the positive electrode piece 223 can be manufactured by the following method: The positive electrode active material layer 2231 is usually formed by applying a positive electrode slurry to the positive electrode current collector 2232, drying, and cold pressing. The positive electrode slurry is usually formed by dispersing a positive electrode active material, a positive electrode adhesive, a positive electrode conductive agent, etc., in a solvent and stirring uniformly. The solvent may be N-methylpyrrolidone (NMP) or deionized water, but the embodiments of this application are not limited to these.

[0182] The following will be explained by comparing multiple comparative examples and multiple examples. Specifically, the battery cell 20 in each of the following examples and comparative examples is a rectangular parallelepiped type battery cell as shown in Figures 3 and 4, and among them, a hollow structure is adopted in which the casing 211 opens at one end.

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

[0184] 1. Manufacturing of positive electrode piece 223 Positive electrode active material LiNi 0.95 Co 0.04 Mn 0.01 O2, the conductive agent Super P, and the adhesive polyvinylidene fluoride (PVDF) were prepared as a positive electrode slurry in N-methylpyrrolidone (NMP), with a solid content of 50 wt% in the positive electrode slurry, and LiNi 0.7 Co 0.1 Mn 0.1 The mass ratio of O2, Super P, and PVDF was 8:1:1. The positive electrode slurry was applied to the upper and lower surfaces of the aluminum foil current collector, dried at 85°C, then cold-pressurized, edge-trimmed, cut, and slit, and finally dried under vacuum conditions at 85°C for 4 hours to produce the positive electrode piece 223.

[0185] 2. Manufacturing of the negative electrode piece 224 A negative electrode slurry was prepared by uniformly mixing a negative electrode active material, a conductive agent Super P, a thickener carboxymethylcellulose (CMC), and an adhesive styrene-butadiene rubber (SBR) in deionized water. The negative electrode active material contained graphite and a silicon-based material, and the silicon-based material was a silicon-oxygen compound. The solid content in the negative electrode slurry was 30 wt%, and the mass ratio of the negative electrode active material, silicon monoxide, Super P, CMC, and adhesive styrene-butadiene rubber (SBR) in the solid content was 88:7:3:2. The negative electrode slurry was applied to the upper and lower surfaces of a copper foil current collector and dried at 85°C. Then it was cold-pressed, edge-trimmed, cut, and slit, and then dried under vacuum conditions at 120°C for 12 hours to produce a negative electrode piece 224.

[0186] 3. Manufacturing of electrolyte In a glove box under an argon atmosphere (H2O < 0.1 ppm, O2 < 0.1 ppm), a thoroughly dried electrolyte salt, LiPF6, was dissolved in a mixed solvent (the mixed solvent contained ethylene carbonate (EC) and diethyl carbonate (DEC), and the ethylene carbonate (EC) and diethyl carbonate (DEC) were mixed in a 50:50 mass ratio). After homogeneous mixing, an electrolyte solution with a concentration of 1 mol / L was obtained.

[0187] 4. Manufacturing of separator 225 A 16 μm polyethylene film was used as separator 225.

[0188] 5. Manufacturing of lithium-ion battery cells 20 The positive electrode piece 223, separator 225, and negative electrode piece 224 are stacked in order, with the separator 225 positioned between the positive electrode piece 223 and the negative electrode piece 224 to isolate the positive and negative electrodes. The cells are then wound to obtain a bare cell, tabs are welded, the bare cell is placed in an outer casing made of a different material, the manufactured electrolyte is injected into the dried outer casing, and sealing, standing, chemical conversion, shaping, and capacity testing are performed to complete the manufacturing of the lithium-ion battery cell 20.

[0189] In each of the following examples and comparative examples, the melting point of the casing 211 of the battery cell 20 is p, and different materials are selected correspondingly for the casing 211 to obtain different melting points. The capacity of the battery cell 20 is C, and the wall thickness of the maximum area of ​​the battery cell 20 is T. The specific parameter settings are shown in Table 3 below. In addition, the material of all areas of the casing 211 is the same in each of the examples and comparative examples below. Furthermore, the battery cell 20 in each of the following examples and comparative examples is the same in all other conditions except for the parameter settings shown in Table 3. For example, in each example, the positive electrode active material of the positive electrode piece 223 of the electrode assembly 22 of the battery cell 20 contains a nickel element compound, of which the nickel element compound contains 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.

[0190] For each of the comparative examples and examples below, the battery cell 20 was tested by referring to the short-circuit test method in Chapter 6.2.4 of "GBT31485-2015 Safety Requirements and Test Methods for Power Storage Batteries for Electric Vehicles," and after the test, the integrity of the casing 211 was observed, i.e., whether or not the casing 211 had melted.

[0191] [Table 3]

[0192] As can be seen by comparing the two comparative examples and the six examples in Table 3 above, when different materials are used for the casing 211, correspondingly different melting points p can be determined. When the melting point p satisfies 1200℃ ≤ p ≤ 2000℃, for example in Examples 1 to 6, the design needs of the battery cell 20 can be met without melting of the casing 211 of the battery cell 20. Furthermore, when other parameters of the battery cell 20 have different variations, such as different capacities C of the battery cell 20 or different wall thicknesses of the maximum area of ​​the casing 211, the design requirements of the battery cell 20 can be met without melting of any of the battery cells 20. However, when the melting point p does not satisfy 1200℃ ≤ p ≤ 2000℃, for example in Comparative Examples 1 to 2, if the casing 211 of the battery cell 20 melts, the design needs of the battery cell 20 will no longer be met.

[0193] In some embodiments, the electrode assembly 22 further comprises a positive electrode piece 223, the positive electrode piece 223 comprising a positive electrode active material capable of reversibly desorbing and inserting metal ions, the positive electrode active material comprising a nickel-containing compound, and the tensile strength of at least a portion of the casing 211 at a temperature of 500°C is Rn, where Rn satisfies 100 MPa ≤ Rn ≤ 1200 MPa.

[0194] The positive electrode active material, by containing a nickel-containing compound, can effectively increase the energy density of the battery cell 20 and improve its cycle life, but it also increases the amount of gas generated during the use of the battery cell 20. In particular, if thermal runaway occurs during the use of the battery cell 20, the internal temperature of the battery cell 20 rises rapidly and a large amount of gas is generated.

[0195] Therefore, by appropriately improving the tensile strength Rn of at least a portion of the casing 211 under high-temperature conditions of 500°C, the deformation capacity of that portion of the casing 211 when thermal runaway occurs in the battery cell 20 can be improved, further reducing the risk of thermal runaway occurring in adjacent battery cells 20 without the casing 211 easily and quickly breaking or exploding, thereby improving the reliability of the battery 10. However, it is also undesirable for at least a portion of the casing 211 to have a tensile strength Rn that is too high under high-temperature conditions, otherwise it will be more prone to scratching of grinding tools, shortening the service life of the grinding tools and increasing the difficulty of processing. Therefore, by appropriately reducing the tensile strength Rn, costs can be saved and processing can be made easier. For example, the tensile strength Rn may normally be set to satisfy 100 MPa ≤ Rn ≤ 1200 MPa.

[0196] As can be understood, the range of values ​​for the tensile strength Rn at high temperature conditions of 500°C in at least a portion of the casing 211 according to the embodiment of the present application can be adjusted according to the actual application. For example, the value of the tensile strength Rn at high temperature can satisfy 100MPa ≤ Rn ≤ 1200MPa. Alternatively, for example, the value of the tensile strength Rn at high temperature can satisfy 112MPa ≤ Rn ≤ 720MPa. On the one hand, by appropriately increasing the value of the tensile strength Rn, the deformation capacity of the casing 211 in that portion when thermal runaway occurs in the battery cell 20 can be improved, further reducing the risk of thermal runaway occurring in adjacent battery cells 20 without the casing 211 easily and quickly breaking or exploding, thereby improving the reliability of the battery 10. At the same time, in order to reduce the difficulty of processing, further save costs, and facilitate processing, the tensile strength Rn at high temperature conditions in at least a portion of the casing 211 is controlled so as not to be too high.

[0197] Furthermore, the casing may be installed such that the tensile strength Rn value at high temperatures satisfies 152 MPa ≤ Rn ≤ 480 MPa, improving the deformation capacity of the casing 211 in that portion when thermal runaway occurs in the battery cell 20, thereby improving the structural strength of the casing 211. This further reduces the risk of thermal runaway occurring in adjacent battery cells 20 without the casing 211 easily and quickly breaking or exploding, thereby improving the reliability of the battery 10. At the same time, it is possible to reduce the difficulty of processing and save costs.

[0198] In some embodiments, the value of the high-temperature tensile strength Rn in the embodiments of the present application may also be set to other values. For example, the values ​​of the high-temperature tensile strength Rn may be 100MPa, 112MPa, 130MPa, 150MPa, 152MPa, 168MPa, 180MPa, 200MPa, 228MPa, 250MPa, 280MPa, 300MPa, 320MPa, 350MPa, 380MPa, 400MPa, 430MPa, 450MPa, 480MPa, 500MPa, 530MPa, 550MPa, 580MPa, and 600MPa. The value may be any one of the following values: Pa, 630MPa, 650MPa, 680MPa, 700MPa, 720MPa, 750MPa, 780MPa, 800MPa, 830MPa, 850MPa, 880MPa, 900MPa, 930MPa, 950MPa, 980MPa, 1000MPa, 1050MPa, 1100MPa, 1150MPa, and 1200MPa, or it may be any one of the two values.

[0199] To be understood, the tensile strength in the embodiments of this application refers to the maximum stress value that the material experiences before fracture. The test method for the tensile strength Rn at a high temperature of 500°C in at least a portion of the casing 211 in the embodiments of this application can be selected according to the actual application. For example, the tensile strength Rn at a high temperature of 500°C can be measured by adopting the national standard GB / T 228.1-2010.

[0200] The following will be explained by comparing multiple comparative examples and multiple examples. Specifically, the battery cell 20 in each of the following examples and comparative examples is a rectangular parallelepiped type battery cell as shown in Figures 3 and 4, and among them, a hollow structure is adopted in which the casing 211 opens at one end.

[0201] In the following examples and comparative examples, the manufacturing methods for the positive electrode piece 223, negative electrode piece 224, electrolyte, and separator 225 of the battery cell 20 are as follows.

[0202] 1. Manufacturing of positive electrode piece 223 Positive electrode active material LiNi 0.95 Co 0.04 Mn 0.01 O2, the conductive agent Super P, and the adhesive polyvinylidene fluoride (PVDF) were prepared as a positive electrode slurry in N-methylpyrrolidone (NMP), with a solid content of 50 wt% in the positive electrode slurry, and LiNi 0.7 Co 0.1 Mn 0.1 The mass ratio of O2, Super P, and PVDF was 8:1:1. The positive electrode slurry was applied to the upper and lower surfaces of the aluminum foil current collector, dried at 85°C, then cold-pressurized, edge-trimmed, cut, and slit, and finally dried under vacuum conditions at 85°C for 4 hours to produce the positive electrode piece 223.

[0203] 2. Manufacturing of the negative electrode piece 224 A negative electrode slurry was prepared by uniformly mixing a negative electrode active material, a conductive agent Super P, a thickener carboxymethylcellulose (CMC), and an adhesive styrene-butadiene rubber (SBR) in deionized water. The negative electrode active material contained graphite and a silicon-based material, and the silicon-based material was a silicon-oxygen compound. The solid content in the negative electrode slurry was 30 wt%, and the mass ratio of the negative electrode active material, silicon monoxide, Super P, CMC, and adhesive styrene-butadiene rubber (SBR) in the solid content was 88:7:3:2. The negative electrode slurry was applied to the upper and lower surfaces of a copper foil current collector and dried at 85°C. Then it was cold-pressed, edge-trimmed, cut, and slit, and then dried under vacuum conditions at 120°C for 12 hours to produce a negative electrode piece 224.

[0204] 3. Manufacturing of electrolyte In a glove box under an argon atmosphere (H2O < 0.1 ppm, O2 < 0.1 ppm), a thoroughly dried electrolyte salt, LiPF6, was dissolved in a mixed solvent (the mixed solvent contained ethylene carbonate (EC) and diethyl carbonate (DEC), and the ethylene carbonate (EC) and diethyl carbonate (DEC) were mixed in a 50:50 mass ratio). After homogeneous mixing, an electrolyte solution with a concentration of 1 mol / L was obtained.

[0205] 4. Manufacturing of separator 225 A 16 μm polyethylene film was used as separator 225.

[0206] 5. Manufacturing of lithium-ion battery cells 20 The positive electrode piece 223, separator 225, and negative electrode piece 224 are stacked in order, with the separator 225 positioned between the positive electrode piece 223 and the negative electrode piece 224 to isolate the positive and negative electrodes. The cells are then wound to obtain a bare cell, tabs are welded, the bare cell is placed in an outer casing made of a different material, the manufactured electrolyte is injected into the dried outer casing, and sealing, standing, chemical conversion, shaping, and capacity testing are performed to complete the manufacturing of the lithium-ion battery cell 20.

[0207] In each of the following examples 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 correspondingly 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 maximum area of ​​the battery cell 20 is T. The specific parameter settings are shown in Table 4 below. In each example 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. Furthermore, in each of the following examples and comparative examples, the battery cell 20 is the same in all other conditions except for the parameter settings shown in Table 4. For example, in each embodiment, the positive electrode active material of the positive electrode piece 223 of the electrode assembly 22 of the battery cell 20 contains a nickel element compound, of which the nickel element compound contains 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.

[0208] For each of the comparative examples and examples below, the battery cell 20 was tested by referring to the short-circuit test method in Chapter 6.2.4 of "GBT31485-2015 Safety Requirements and Test Methods for Power Storage Batteries for Electric Vehicles," and after the test, the integrity of the casing 211 was observed, i.e., whether or not the casing 211 had ruptured.

[0209] [Table 4]

[0210] As can be seen by comparing the two comparative examples and the six examples in Table 4 above, when different materials are used for the casing 211, correspondingly different tensile strengths Rn can be determined. When the tensile strength Rn satisfies 100MPa ≤ Rn ≤ 1200MPa, for example in Examples 1 to 6, the design requirements of the battery cell 20 can be met without cracking of the casing 211 of the battery cell 20. Furthermore, when other parameters of the battery cell 20 have different variations, such as different capacities C of the battery cell 20 or different wall thicknesses of the maximum area of ​​the casing 211, the design needs of the battery cell 20 can be met without cracking of any of the battery cells 20. However, when the tensile strength Rn does not satisfy 100MPa ≤ Rn ≤ 1200MPa, for example in Comparative Examples 1 to 2, if the casing 211 of the battery cell 20 cracks, the design needs of the battery cell 20 will no longer be met.

[0211] To be understood, at least a portion of the casing 211 in the embodiments of the present application may include a local area of ​​the casing 211, or it may include all of the casing 211. In some embodiments, the casing 211 includes a welded seam 2113, and at least a portion of the casing 211 includes an area of ​​the casing 211 within a predetermined distance from the welded seam 2113, where the predetermined distance is L, and L = 10 mm. If the negative electrode active material of the negative electrode piece 224 in the electrode assembly 22 contains a silicon-based material, the silicon-based material can accommodate more metal ions, which increases the amount of deformation of the electrode assembly 22 during use in the battery cell 20, causing volume expansion of the electrode assembly 22. Furthermore, this increases the pressure of the electrode assembly 22 on the casing 211 of the battery cell 20. Under the same conditions, the structural strength of the region of the casing 211 adjacent to the welded seam 2113 is relatively low compared to the structural strength of other regions of the casing 211, making the region of the casing 211 adjacent to the welded seam 2113 more easily damaged during use in the battery cell 20. Therefore, by setting the region within a predetermined distance L from the welded seam 2113 to meet the requirements of tensile strength Rm or yield strength Re at room temperature, the deformation capacity of the region of the casing 211 adjacent to the welded seam 2113 can be improved, further improving the structural stability and service life of the battery cell 20 without that portion of the casing 211 being easily damaged.

[0212] If the positive electrode active material of the positive electrode piece 223 of the electrode assembly 22 contains a nickel-containing compound, when thermal runaway occurs in the battery cell 20, the temperature inside the battery cell 20 rises rapidly and a large amount of gas is generated. On the other hand, under the same conditions, the structural strength of the region of the casing 211 adjacent to the welded seam 2113 is relatively low compared to the structural strength of other regions of the casing 211. Therefore, the casing 211 is prone to rupture in the region adjacent to the welded seam 2113, and furthermore, thermal runaway, i.e., thermal diffusion, can occur in the connected battery cells 20. Accordingly, by setting the region within a predetermined distance L from the welded seam 2113 to meet the requirements of tensile strength Rn or melting point p under high-temperature conditions, the deformability of that region of the casing 211 can be improved. This reduces the risk of thermal diffusion or explosion between multiple battery cells 20 without that region easily and rapidly breaking or completely melting, thereby improving the reliability of the battery 10.

[0213] As can be understood, the welded seams 2113 included in the casing 211 according to the embodiment of the present application may include welded seams 2113 at any position on the casing 211. For example, the welded seams 2113 included in the casing 211 may include the welded seam between the casing 211 and the cover plate 212, i.e., the region surrounding the open end of the casing 211 is a welded seam. Furthermore, for example, the welded seams 2113 of the casing 211 may further include welded seams between different parts of the casing 211, for example, the casing 211 may include at least two parts, the at least two parts being joined by welding to form the casing 211, of which Figure 4 shows an example in which the casing 211 includes two parts along the height Z direction of the battery cell 20, with a welded seam 2113 between the upper half casing and the lower half casing, or, contrary to what is shown in Figure 4, the welded seams 2113 may be located on other parts of the casing 211, and the embodiments of the present application are not limited thereto.

[0214] In some embodiments, at least a portion of the casing 211 includes a surrounding region 2111 of the casing 211, the surrounding region 2111 encloses the electrode assembly 22, and the surrounding region 2111 is at least a portion of the side wall of the casing 211. In this way, if the negative electrode active material of the negative electrode piece 224 of the electrode assembly 22 includes a silicon-based material, the silicon-based material can accommodate more metal ions, thereby increasing the amount of deformation of the electrode assembly 22 during use in the battery cell 20, causing volume expansion of the electrode assembly 22, and further increasing the pressure of the electrode assembly 22 on the casing 211 of the battery cell 20. Therefore, by positioning the surrounding region 2111 to satisfy the requirements of tensile strength Rm or yield strength Re under room temperature conditions, the deformation capacity of the casing 211 can be improved, and by positioning the surrounding region 2111 to surround the electrode assembly 22, the radial pressing force of the internal electrode assembly 22 on the casing 211 can be limited, thereby further improving the structural stability and service life of the battery cell 20 without the casing 211 being easily damaged.

[0215] If the positive electrode active material of the positive electrode piece 223 of the electrode assembly 22 contains a nickel-containing compound, when thermal runaway occurs in the battery cell 20, the internal temperature of the battery cell 20 rises rapidly and a large amount of gas is generated. On the other hand, if the surrounding region 2111 meets the requirements of tensile strength Rn or melting point p under high-temperature conditions, the deformation capacity of the surrounding region 2111 of the casing 211 can be improved, thereby limiting excessive expansion of the electrode assembly 22 inside the casing 211 along its thickness direction without the surrounding region 2111 easily and rapidly breaking or completely melting, reducing the possibility of the battery cell 20 exploding, further reducing the risk of thermal runaway occurring in adjacent battery cells 20, and thereby improving the reliability of the battery 10.

[0216] As can be understood, the position and dimensions of the surrounding region 2111 in the embodiments of the present application can be flexibly set according to the actual application. For example, the height of the surrounding region 2111 along the height direction Z of the battery cell 20 may be less than or equal to the height of the casing 211. Specifically, if the height of the surrounding region 2111 along the height direction Z of the battery cell 20 is less than the height of the casing 211, the surrounding region 2111 may be located at any position in the casing 211 along the height direction Z of the battery cell 20. For example, in order to limit deformation of the central position corresponding to the electrode assembly 22, the surrounding region 2111 may be located in the center of the casing 211 along the height direction Z of the battery cell 20.

[0217] If the height of the surrounding region 2111 is equal to the height of the casing 211 along the height direction Z of the battery cell 20, the surrounding region 2111 may include all the side walls of the casing 211 and may also wrap around the sides of the electrode assembly 22, further improving the structural strength of the side walls of the casing 211, thereby suppressing the explosion and thermal diffusive reaction of the battery cell 20 after thermal runaway due to the failure of a localized weak area of ​​the side wall of the casing 211, and further improving the reliability of the battery 10.

[0218] In some embodiments, at least a portion of the casing 211 includes all of its walls, i.e., at least a portion of the casing 211 in the embodiments of this application may refer to all of the casing 211. In this way, if the negative electrode active material of the negative electrode piece 224 of the electrode assembly 22 includes a silicon-based material, the silicon-based material can accommodate more metal ions, thereby increasing the amount of deformation of the electrode assembly 22 during use within the battery cell 20, causing volume expansion of the electrode assembly 22, and further increasing the pressure of the electrode assembly 22 on the casing 211 of the battery cell 20. Therefore, by positioning all of the casing 211 so that each satisfies the requirements of tensile strength Rm or yield strength Re at room temperature, the overall deformation capacity of the casing 211 can be improved, the pressing force of the internal electrode assembly 22 on the casing 211 along each direction can be limited, the strength of each part of the casing 211 can be balanced, and the structural stability and service life of the battery cell 20 can be further improved without easy breakage in localized weak areas.

[0219] If the positive electrode active material of the positive electrode piece 223 of the electrode assembly 22 contains a nickel-containing compound, when thermal runaway occurs in the battery cell 20, the temperature inside the battery cell 20 rises rapidly and a large amount of gas is generated. On the other hand, if all areas of the casing 211 meet the requirements of tensile strength Rn or melting point p under high-temperature conditions, the deformation capacity of the entire casing 211 can be improved, thereby limiting the high-temperature, high-pressure gas inside the casing 211 without the casing 211 easily breaking or melting, reducing the impact on the connected cell 20, further reducing the risk of thermal runaway occurring in adjacent battery cells 20, and thereby improving the reliability of the battery 10.

[0220] Furthermore, the cover plate 212 according to the embodiment of the present application may employ the same material as at least a portion of the casing 211 according to the embodiment of the present application, so that the structural strength of the cover plate 212 similarly meets the design needs. For example, the cover plate 212 may also satisfy at least one of the requirements of tensile strength Rm and yield strength Re at room temperature, tensile strength Rn and melting point p at high temperature, in order to improve the structural strength of the cover plate 212 and further improve the structural stability of the battery cell 20, but the embodiment of the present application is not limited to these.

[0221] In the embodiment of the present application, the casing 211 includes at least a portion of a third casing wall 2112, the average thickness of the third casing wall 2112 being T, where T satisfies 0.05 mm ≤ T ≤ 0.5 mm and 60 mm MPa ≤ T × Rm ≤ 500 mm MPa.

[0222] To be understood, the third casing wall 2112 of the casing 211 in the embodiment of the present application may be any one wall of the casing 211. Specifically, the battery cell 20 may be any polyhedral structure, the casing 211 may be a hollow structure with an opening at at least one end, the casing 211 may include one or more walls, the third casing wall 2112 may be any one wall of the casing 211, and the casing 211 may include one or more third casing walls 2112. For example, if the casing 211 is a polygonal prism, the third casing wall 2112 may be any one wall of the polygonal prism, and the surface of the third casing wall 2112 may be any polygon. Furthermore, for example, as shown in Figures 3 and 4, if the casing 211 is a rectangular parallelepiped, the third casing wall 2112 may be any one of the walls of the casing 211, and the surface of the third casing wall 2112 is rectangular. Also, for example, if the casing 211 is a cylindrical body, the third casing wall 2112 may be the bottom surface of the cylinder or a side surface of the cylinder, but the embodiments of the present application are not limited thereto. Furthermore, if two adjacent walls of the casing 211 are connected by a fillet, and the third casing wall 2112 in the embodiments of the present application is any one of the walls of the casing 211, the third casing wall 2112 does not include the connection area of ​​the fillet between the wall and the connecting wall.

[0223] In the embodiments of the present application, if at least a portion of the casing 211 includes a third casing wall 2112, the tensile strength of the third casing wall 2112 at room temperature conditions of 25°C is Rm. By increasing the tensile strength Rm at room temperature conditions of 25°C in at least a portion of the casing 211, the deformation capacity of the casing 211 can be improved, and the casing 211 will not easily break during the use of the battery cell 20, further improving the structural stability and service life of the battery cell 20. However, in order to reduce the difficulty of selecting and processing the material for the casing 211, save costs, and facilitate processing, it is also undesirable for the tensile strength Rm at room temperature in at least a portion of the casing 211 to be too large.

[0224] On the other hand, if the average thickness T of the third casing wall 2112 of the casing 211 is relatively thin, the structural strength of the third casing wall 2112 can be increased by increasing the tensile strength Rm of the third casing wall 2112 of the casing 211 at room temperature of 25°C. In this way, not only can the energy density of the battery cell 20 be improved, but the structural strength and stability of the battery cell 20 can also be improved. Conversely, if the average thickness T of the third casing wall 2112 of the casing 211 is relatively thick, the structural strength of the casing 211 can be improved, and the requirement for the tensile strength Rm of the third casing wall 2112 of the casing 211 at room temperature can be appropriately reduced, thereby reducing the difficulty of selecting the material for the casing 211 and further reducing the difficulty and cost of processing the battery cell 20. Furthermore, T×Rm indicates the rigidity of the third casing wall, and by limiting the rigidity of the third casing wall so that it is neither too low nor too high, the third casing wall not only has relatively good deformation capability, but the difficulty of processing can also be reduced and costs can be lowered.

[0225] As can be understood, the range of the average thickness T of the third casing wall 2112 in the embodiment of the present application can also be flexibly set according to the actual application. For example, the average thickness T of the third casing wall 2112 satisfies 0.05 mm ≤ T ≤ 0.5 mm. Furthermore, the average thickness T of the third casing wall 2112 satisfies 0.1 mm ≤ T ≤ 0.4 mm. By appropriately reducing the average thickness T of the third casing wall 2112, the space occupied by the casing 211 inside the battery 10 can be reduced, further improving the energy density of the battery 10. To maintain the stability of the casing 211, the tensile strength Rm of the third casing wall 2112 at room temperature can be improved to meet the structural strength requirements of the casing 211. On the other hand, by appropriately increasing the average thickness T of the third casing wall 2112, the difficulty of processing the third casing wall 2112 can also be reduced.

[0226] Furthermore, the average thickness T of the third casing wall 2112 satisfies the condition 0.1 mm ≤ T ≤ 0.3 mm. By ensuring that the average thickness T of the third casing wall 2112 is neither too large nor too small, it is possible to improve the structural strength and structural stability of the casing 211, as well as reduce the space occupied by the casing 211 inside the battery 10, thereby further improving the energy density of the battery 10.

[0227] In some embodiments, the average thickness T of the third casing wall 2112 according to the embodiments of the present application may also be set to other values. For example, the average thickness T of the third casing wall 2112 may be any one of the following values: 0.05 mm, 0.075 mm, 0.1 mm, 0.125 mm, 0.15 mm, 0.175 mm, 0.2 mm, 0.225 mm, 0.25 mm, 0.275 mm, 0.3 mm, 0.325 mm, 0.35 mm, 0.375 mm, 0.4 mm, 0.425 mm, 0.45 mm, 0.475 mm, and 0.5 mm, or it may be between any two of these values.

[0228] In some embodiments, the range of the T×Rm value can be adjusted according to the actual application. For example, Rm and T satisfy 60 mm MPa ≤ T×Rm ≤ 500 mm MPa. Furthermore, Rm and T can also satisfy 100 mm MPa ≤ T×Rm ≤ 500 mm MPa. By selecting an appropriate material, the tensile strength Rm of the third casing wall 2112 at room temperature can be improved, and the average thickness T of the third casing wall 2112 can be reduced, thereby meeting the design requirements for the stiffness value of the third casing wall 2112. This not only improves the structural strength and structural stability of the third casing wall 2112 of the casing 211, but also improves the energy density of the battery cell 20 and the battery 10.

[0229] Furthermore, the range of the T×Rm value may also be set such that Rm and T satisfy 100 mm MPa ≤ T×Rm ≤ 300 mm MPa. By making the rigidity value of the third casing wall 2112 more appropriate, the third casing wall 2112 can have good deformation capability to improve the service life of the battery cell 20, as well as reduce the difficulty of material selection, and further reduce the difficulty and cost of processing.

[0230] In some embodiments, the T×Rm value in the embodiments of the present application may also be set to other values. For example, the T×Rm value may be any one 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, or it may be between any two of these values.

[0231] In the examples of the present application, the value of the mass ratio g of the silicon-based material may mutually restrict the value of the average thickness T of the third casing wall 2112, and to balance the relationship between the energy density and the structural strength of the battery cell 20, it may also mutually restrict the value of the tensile strength Rm of at least a partial region of the casing 211 under the condition of 25°C. For example, in the negative electrode active material, the mass ratio of the silicon-based material is g, and g and T satisfy 2%<g<20% and 0.15mm≦T≦0.4mm. When the mass ratio g of the silicon-based material is relatively small, by appropriately reducing the average thickness T of the third casing wall 2112, the space utilization rate of the casing 211 can be improved, the energy density of the battery cell 20 is increased, and the structural strength of the casing 211 can also be balanced.

[0232] In some examples, the mass ratio of the silicon-based material in the negative electrode active material is g, and g, T and Rm satisfy 15%<g<40%, 0.2mm≦T≦0.4mm, and 100mm·MPa≦T×Rm≦500mm·MPa. By increasing the mass g of the silicon-based material, the energy density of the battery cell 20 can be effectively increased, and at the same time, by improving the thickness and rigidity T×Rm of the third casing wall 2112, the structural strength and stability of the battery cell 20 can be improved.

[0233] As can be understood, the average thickness T of the third casing wall 2112 according to the examples of the present application may refer to the average thickness of at least a partial region of the third casing wall 2112. For example, the average thickness T of the third casing wall 2112 may refer to the average thickness T of all regions of the third casing wall 2112, especially when the third casing wall 2112 is relatively flat, that is, the thickness of most regions of the third casing wall 2112 is basically equal or the difference is relatively small, or the thickness of all regions of the third casing wall 2112 is basically equal or the difference is relatively small, the average thickness of all regions of the third casing wall 2112 can be determined as T.

[0234] For example, the average thickness T of the third casing wall 2112 may also refer to the average thickness T of a local region of the third casing wall 2112, that is, the average thickness T of the remaining region after excluding a portion of the third casing wall 2112. For example, if a specific region exists in the third casing wall 2112, and the thickness of that specific region differs relatively significantly from that of other regions, for example, if a protruding structure or recessed region exists in that specific region, making the thickness of that specific region greater or smaller than that of other regions, then the average thickness T of the remaining region of the third casing wall 2112 can be calculated by excluding that specific region.

[0235] In some embodiments, the third casing wall 2112 includes a functional region, and the average thickness T of the third casing wall 2112 is the average thickness of the region of the third casing wall 2112 other than the functional region, the functional region including at least one of a pressure release region, a region where electrode terminals 214 are located, a fluid injection region, and a welding region. The difference between the thickness of the functional region and the thickness of the other regions of the third casing wall 2112 is usually relatively large, and therefore, if the average thickness T of the third casing wall 2112 is calculated so as not to include the functional region, the design of the third casing wall 2112 can better meet the strength needs, thereby improving the structural strength and stability of the battery cell 20.

[0236] Specifically, the functional region according to the embodiment of the present application may include a region having a specific structure or purpose installed on the third casing wall 2112. For example, the functional region may include a pressure relief region for installing a pressure relief mechanism used for an element or component that operates 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 design needs. For example, the predetermined threshold may depend on one or more materials among the positive electrode piece, negative electrode piece, electrolyte, and separator film in the battery cell 20.

[0237] As used in this application, "operation" refers to the release of pressure and temperature inside the battery cell 20 due to the pressure release mechanism acting or being activated to a certain state. The operation caused by the pressure release mechanism includes, but is not limited to, the rupture, shattering, tearing, or opening of at least a part of the pressure release mechanism. When the pressure release mechanism is operated, high-temperature, high-pressure material inside the battery cell 20 is discharged as waste from the point of operation to the outside. In this way, the pressure and temperature release of the battery cell 20 is made possible at a controllable pressure or temperature, thereby avoiding the occurrence of potentially more serious accidents.

[0238] The waste products from the battery cell 20 relating to this application include, but are not limited to, electrolyte, dissolved or fragmented positive and negative electrode pieces, fragments of separator film, high-temperature and high-pressure gases from the reaction, and flames.

[0239] The pressure relief mechanism according to the embodiment of the present application may be installed on any one wall of the battery cell 20. For example, the pressure relief mechanism may be installed in the pressure relief region of the third casing wall 2112 of the battery cell 20. The pressure relief mechanism may be part of the third casing wall 2112, or it may be a separate structure and fixed to the third casing wall 2112, for example, by welding. For example, if the pressure relief mechanism is part of the third casing wall 2112, the pressure relief mechanism may be formed by installing a notch in the third casing wall 2112, i.e., the third casing wall 2112 has a notch installed in the pressure relief region, and the thickness of the notched area is clearly smaller than the thickness of other areas of the third casing wall 2112. Therefore, the average thickness T of the third casing wall 2112 does not need to be calculated based on the thickness of the notched area. The notched area is the most vulnerable location of the pressure relief mechanism. When the internal pressure of the battery cell 20 rises to a threshold due to excessive gas generation, or when the internal temperature of the battery cell 20 rises to a threshold due to heat generated by the internal reaction of the battery cell 20, the pressure release mechanism ruptures at the notch, creating communication between the inside and outside of the battery elevator 20. The gas pressure and temperature are released to the outside by the rupture of the pressure release mechanism, further preventing the explosion of the battery cell 20.

[0240] For example, the pressure relief mechanism may also be a separate structure from the third casing wall 2112, and the pressure relief mechanism may take the form of an explosion-proof valve, a gas valve, a pressure relief valve, or a safety valve, and more specifically, it may take the form of a pressure-sensitive element or pressure-sensitive structure or a temperature-sensitive element or temperature-sensitive structure. For example, the third casing wall 2112 may have a communication hole in the pressure relief region, and the pressure relief mechanism may be attached and fixed to the third casing wall 2112 through the communication hole, and after attachment, the pressure relief mechanism may protrude or recess relative to other areas of the third casing wall 2112, and therefore the calculation of the average thickness T of the third casing wall 2112 may not include the pressure relief region in which 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 is activated, or a vulnerable structure provided within the pressure relief mechanism is destroyed, thereby forming an opening or passage for releasing the internal pressure or temperature.

[0241] In some embodiments, the functional region may further include the region in which the electrode terminals 214 are located. Specifically, the electrode terminals 214 in the embodiments of the present application are used to be electrically connected to an electrode assembly 22 inside the battery cell 20 so as to output electrical energy from 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 polarity of the first electrode terminal 214a and the second electrode terminal 214b are opposite. For example, if the first electrode terminal 214a is a positive electrode terminal, the second electrode terminal 214b may be a negative electrode terminal, or if the first electrode terminal 214a is a negative electrode terminal, the second electrode terminal 214b may be a positive electrode terminal. Of these, the positive electrode terminal is used to be electrically connected to the positive electrode tab 222a of the electrode assembly 22, and the negative electrode terminal is used to be connected to the negative electrode tab 222b of the electrode assembly 22. The positive electrode terminal and the positive electrode tab 222a may be directly connected or indirectly connected, and the negative electrode terminal and the negative electrode tab 222b may be directly connected or indirectly connected. Exemplaryly, the positive electrode terminal may be electrically connected to the positive electrode tab 222a via one connecting component 23, and the negative electrode terminal may be electrically connected to the negative electrode tab 222b via one connecting component 23.

[0242] As can be understood, each electrode terminal 214 in the embodiments of the present application may be installed on any one wall, and multiple electrode terminals 214 may be installed on the same wall or different walls of the battery cell 20. For example, taking as shown in Figures 3 and 4, if each battery cell 20 includes two electrode terminals 214 located on the same wall, then, for example, both electrode terminals 214 may be located on the cover plate 212.

[0243] For example, if each battery cell 20 includes two electrode terminals 214 located on the same wall, then, unlike what is shown in Figures 3 and 4, the two electrode terminals 214 may also be located on the casing 211, for example, both electrode terminals 214 may be located on a third casing wall 2112 of the casing 211. If the electrode terminals 214 are located on the third casing wall 2112, they usually protrude into other areas of the third casing wall 2112, i.e., the thickness of the area where the electrode terminals 214 are located is much greater than the thickness of other areas of the third casing wall 2112. Therefore, the calculation of the average thickness T of the third casing wall 2112 does not need to include the area where the electrode terminals 214 are located.

[0244] In some embodiments, the functional region may further include an electrolyte injection region. For example, an electrolyte injection hole may be provided in the electrolyte injection region of the third casing wall 2112, and the electrolyte is injected into the interior of the casing 211 through the electrolyte injection hole. After the electrolyte injection is complete, the electrolyte injection hole may be sealed with a sealing member. Considering that the thickness of the electrolyte injection region where the sealing member is located is usually much greater than the thickness of other regions of the third casing wall 2112, the calculation of the average thickness T of the third casing wall 2112 does not need to include the electrolyte injection region.

[0245] In some embodiments, the functional area may further include a welded area. For example, the third casing wall 2112 may be fixed to another wall by welding, or if the third casing wall 2112 itself needs to be fabricated by welding, the third casing wall 2112 may include a welded area. For example, as shown in Figure 4, the casing 211 may be welded by splicing, and the casing 211 may have a welded seam 2113. Specifically, the casing 211 may include at least two parts, which are joined by welding to form the casing 211, and taking Figure 4 as an example, the casing 211 includes two parts along the height direction Z of the battery cell 20, with a welded seam 2113 between the upper and lower casings, or, contrary to what is shown in Figure 4, the welded seam 2113 may be located in other parts of the casing 211, and the embodiments of the present application are not limited to these. The welded area of ​​the functional region according to the embodiments of the present application may further include the welded seam 2113. Due to the manufacturing process, the thickness of the welded area is usually greater than the thickness of other areas of the third casing wall 2112, and therefore the calculation of the average thickness T of the third casing wall 2112 does not need to include the welded area.

[0246] In the embodiment of the present invention, the third casing wall 2112 of the casing 211 may be any one of the walls of the casing 211. For example, the third casing wall 2112 is the wall with the minimum thickness in the casing 211. That is, by limiting the thickness T of the wall with the minimum thickness in the casing 211, the thickness of the other walls of the casing 211 is limited, thereby ensuring that each wall of the casing 211 meets the structural strength requirements, further improving the structural strength and stability of the battery cell 20.

[0247] In some embodiments, the third casing wall 2112 is the wall with the largest surface area of ​​the casing 211. When multiple battery cells 20 are arranged within the battery 10, the multiple battery cells 20 are usually in contact with each other by the wall with the largest surface area of ​​the casing 211, and therefore, this wall with the largest surface area is usually subjected to the greatest pressing force from the electrode assembly 22. By limiting the average thickness T and tensile strength Rm at room temperature of the third casing wall 2112, the deformation capacity of the casing 211 can be effectively improved, further enhancing the structural strength and stability of the battery cells 20.

[0248] As can be understood, the location of the wall with the largest area of ​​the casing 211 in the embodiments of the present application can be set according to the actual application. For example, the battery 10 may include a plurality of battery cells 20, and the arrangement direction of the plurality of battery cells 20 may be perpendicular or parallel to the wall with the largest area of ​​the casing 211, and the embodiments of the present application are not limited to these.

[0249] In some embodiments, the casing 211 includes intersecting bottom and side walls, the bottom wall of which is used to support the electrode assembly housed within the casing 211. Specifically, the casing 211 may be a hollow structure with at least one end open, and the bottom and side walls of the casing 211 do not necessarily refer to walls opposite or adjacent to the opening, respectively. The electrode assembly 22 is housed inside the casing 211, and in actual applications, considering different application scenarios, the orientation of the electrode assembly 22 may differ, and the casing 211 may include walls to support the electrode assembly 22. Therefore, the bottom wall of the casing 211 in the embodiments of the present application is a wall for supporting the electrode assembly 22, that is, the bottom wall of the casing 211 is used to withstand the gravitational force of the electrode assembly 22, while the wall of the casing 211 that directly intersects the bottom wall is a side wall of the casing 211.

[0250] In some embodiments, the third casing wall 2112 is a side wall of the casing 211. Considering that the bottom wall and the side wall of the casing 211 have different uses, the design requirements for the bottom wall and the side wall may also differ. For example, the side wall of the casing 211 usually has higher requirements for deformation capability. When the third casing wall 2112 is the side wall of the casing 211, by limiting the tensile strength Rm of the side wall of the casing 211 under normal temperature conditions and the average thickness T of the side wall, the deformation capability of the side wall of the casing 211 can be effectively improved, and the structural stability of the battery cell 20 is further enhanced.

[0251] In some embodiments, to facilitate processing, the casing 211 includes a plurality of side walls with equal thickness.

[0252] In some embodiments, to facilitate processing and optimize the space occupied by the casing 211, the thickness of the bottom wall of the casing 211 is equal to the thickness of the side wall of the casing 211.

[0253] In some embodiments, the third casing wall 2112 is perpendicular to the stacking direction of the pole pieces of the electrode assembly 22. The stacking direction of the pole pieces of the electrode assembly 22 is usually the thickness direction of the electrode assembly 22. Considering that the thickness direction of the electrode assembly 22 is prone to expansion during the use of the charge-discharge cycle of the battery cell 20, the corresponding requirement for the deformation of the wall of the casing 211 is relatively high. Therefore, the third casing wall 2112 is arranged as a wall perpendicular to the stacking direction of the pole pieces of the electrode assembly 22, or the third casing wall 2112 and the electrode assembly 22 are arranged along the stacking direction of the pole pieces of the electrode assembly 22. By limiting the tensile strength Rm and the average thickness T of the third casing wall 2112 under normal temperature conditions, not only the energy density of the battery cell 20 is improved, but also the deformation capability of the third casing wall 2112 is effectively enhanced, and the structural stability of the battery cell 20 can be further improved.

[0254] As can be appreciated, the cover plate 212 according to the embodiments of the present application may adopt the same or different design as the third casing wall 2112. For example, the cover plate 212 may adopt the same design as the third casing wall 2112, that is, the average thickness of the cover plate 212 may be T, the tensile strength of the cover plate 212 at normal temperature may be b, and the above design requirements for b and T are satisfied, thereby improving the deformation capability of the cover plate 212, and further enhancing the structural strength and stability of the battery cell 20.

[0255] In some embodiments, the ratio of the volume of the inner space of the casing 211 to the outer volume of the casing 211 is 93% or more. That is, in order to make the space occupied by the casing 211 itself relatively small, the thickness of the casing 211 is made relatively thin, so as to further improve the space utilization rate and energy density of the battery 10.

[0256] As can be appreciated, the specific calculation method for the volume of the inner space of the casing 211 and the outer volume of the casing 211 according to the embodiments of the present application is related to the shape of the casing 211. For example, taking that the casing 211 is a rectangular parallelepiped as an example. FIG. 8 shows a schematic side view of the casing 211 according to the embodiments of the present application, and FIG. 9 shows a schematic top view of the casing 211 according to the embodiments of the present application. For example, the casing 211 shown in FIG. 8 and FIG. 9 may be the casing 211 of the battery cell 20 shown in FIG. 3 and FIG. 4.

[0257] As shown in Figures 8 and 9, taking a rectangular casing 211 as an example, the casing 211 is a hollow rectangular casing with an opening at one end. When calculating the internal volume of the casing 211 and the external volume of the casing 211, fillet connections between adjacent walls of the casing 211 can be ignored. As shown in Figures 8 and 9, each wall of the casing 211 has a constant thickness, so in the length direction Y, the internal length of the casing 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 casing 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 casing 211 is Z1 and the external height is Z2, where Z2 is greater than Z1. Therefore, the volume of the internal space of the casing 211 is V1 = X1 × Y1 × Z1, the volume of the external space of the casing 211 is V2 = X2 × Y2 × Z2, and V1 / V2 is 93% or more, thereby reducing the space occupied by the casing 211 itself and further improving the space utilization rate and energy density of the battery 10.

[0258] The following will be explained by comparing multiple comparative examples and multiple examples. Specifically, the battery cell 20 in each of the following examples and comparative examples is a rectangular parallelepiped type battery cell as shown in Figures 3 and 4, and among them, a hollow structure is adopted in which the casing 211 opens at one end.

[0259] In the following examples and comparative examples, the manufacturing methods for the positive electrode piece 223, negative electrode piece 224, electrolyte, and separator 225 of the battery cell 20 are as follows.

[0260] 1. Manufacturing of positive electrode piece 223 Positive electrode active material LiNi 0.95 Co 0.04 Mn 0.01 O2, the conductive agent Super P, and the adhesive polyvinylidene fluoride (PVDF) were prepared as a positive electrode slurry in N-methylpyrrolidone (NMP), with a solid content of 50 wt% in the positive electrode slurry, and LiNi 0.7 Co 0.1Mn 0.1 The mass ratio of O2, Super P, and PVDF was 8:1:1. The positive electrode slurry was applied to the upper and lower surfaces of the aluminum foil current collector, dried at 85°C, then cold-pressurized, edge-trimmed, cut, and slit, and finally dried under vacuum conditions at 85°C for 4 hours to produce the positive electrode piece 223.

[0261] 2. Manufacturing of the negative electrode piece 224 A negative electrode slurry was prepared by uniformly mixing a negative electrode active material, a conductive agent Super P, a thickener carboxymethylcellulose (CMC), and an adhesive styrene-butadiene rubber (SBR) in deionized water. The negative electrode active material contained graphite and a silicon-based material, and the silicon-based material was a silicon-oxygen compound. The solid content in the negative electrode slurry was 30 wt%, and the mass ratio of the negative electrode active material, silicon monoxide, Super P, CMC, and adhesive styrene-butadiene rubber (SBR) in the solid content was 88:7:3:2. The negative electrode slurry was applied to the upper and lower surfaces of a copper foil current collector and dried at 85°C. Then it was cold-pressed, edge-trimmed, cut, and slit, and then dried under vacuum conditions at 120°C for 12 hours to produce a negative electrode piece 224.

[0262] 3. Manufacturing of electrolyte In a glove box under an argon atmosphere (H2O < 0.1 ppm, O2 < 0.1 ppm), a thoroughly dried electrolyte salt, LiPF6, was dissolved in a mixed solvent (the mixed solvent contained ethylene carbonate (EC) and diethyl carbonate (DEC), and the ethylene carbonate (EC) and diethyl carbonate (DEC) were mixed in a 50:50 mass ratio). After homogeneous mixing, an electrolyte solution with a concentration of 1 mol / L was obtained.

[0263] 4. Manufacturing of separator 225 A 16 μm polyethylene film was used as separator 225.

[0264] 5. Manufacturing of lithium-ion battery cells 20 The positive electrode piece 223, separator 225, and negative electrode piece 224 are stacked in order, with the separator 225 positioned between the positive electrode piece 223 and the negative electrode piece 224 to isolate the positive and negative electrodes. The cells are then wound to obtain a bare cell, tabs are welded, the bare cell is placed in an outer casing made of a different material, the manufactured electrolyte is injected into the dried outer casing, and sealing, standing, chemical conversion, shaping, and capacity testing are performed to complete the manufacturing of the lithium-ion battery cell 20.

[0265] In each of the following examples 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 correspondingly 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, and the specific parameter settings are shown in Table 5 below. In addition, in each example and comparative example, the material is the same for all areas of the casing 211, and the tensile strength Rm of the casing 211 at 25°C was measured using the method specified in GB / T 228.1-2010. Furthermore, in each of the following examples and comparative examples, the battery cell 20 is the same in all other installation conditions except for the differences in the parameter settings shown in Table 5. For example, the capacity of the battery cell 20 in each example is 350Ah.

[0266] A cycle charge fatigue test was performed on the battery cells 20 in each of the following examples and comparative examples. Specifically, the test can be performed using the cycle charge fatigue test clamp 700 shown in Figure 7.

[0267] Specifically, the battery cell 20 is clamped and fixed within a dedicated clamp 700, ensuring that the two opposing walls of the maximum surface area of ​​the battery cell 20 are firmly held in place, and the initial pressure is set to 2000N. The electrode terminals 214 of the battery cell 20 are then connected to a dedicated battery charging and discharging device.

[0268] The clamp 700, which held the battery cell 20, was placed in a constant temperature environment of 25±2℃, and the test was started after the battery cell 20 reached temperature equilibrium.

[0269] The specific test steps were carried out by referring to Chapter 6.4, "Standard Cycle Life," of "GBT31484-2015 Cycle Life Requirements and Test Methods for Power Storage Batteries for Electric Vehicles," and the test cycle cutoff condition was changed to "Stop the test until the welded seam 2113 of the battery cell 20 is damaged."

[0270] For example, the test can be performed according to the following steps: step a, discharge at 1I(A) until the discharge stop condition specified by the company; step b, leave for 30 minutes or longer or until the leave condition specified by the company; step c, charge according to the method in 6.1.1.3; step d, leave for 30 minutes or longer or until the leave condition specified by the company; step e, discharge at 1I1(A) until the discharge stop condition specified by the company; and step f, cycle through steps b to e until the weld joint 2113 is damaged and the test is stopped.

[0271] During the above test process, the welded seam 2113 of the battery cell 20 was continuously observed and the number of cycles recorded until leakage occurred at the welded seam 2113, thereby obtaining the state of the casing 211 after 1000 cycles, as shown in Table 5 below. In each of the following examples and comparative examples, the welded seam 2113 refers to the welded seam between the casing 211 and the cover plate 212, that is, the welded seam 2113 surrounds the open end of the casing 211, while the casing 211 employs an integrally molded structure.

[0272] [Table 5]

[0273] As can be appreciated, in the above Table 5, the material of the casing 211 may be Q195 carbon steel, and the tensile strength Rm of Q195 carbon steel at a normal temperature of 25°C is typically at least 315MPa to 430MPa, and only 328MPa is taken as an example in the above embodiments, which is not limited thereto. Similarly, the material of the casing 211 may be SPCC carbon steel, and the tensile strength Rm of SPCC carbon steel at a normal temperature of 25°C is typically at least 380MPa to 430MPa, and only 396MPa is taken as an example in the above embodiments. The material of the casing 211 may be SUS430 stainless steel, and the tensile strength Rm of SUS430 stainless steel at a normal temperature of 25°C is typically at least 450MPa, and only 459MPa is taken as an example in the above embodiments. The material of the casing 211 may be SUS304 stainless steel, and the tensile strength Rm of SUS304 stainless steel at a normal temperature of 25°C is typically at least 520MPa, and only 533MPa, 625MPa and 763MPa are taken as examples in the above embodiments.

[0274] As can be seen from the above Table 5, in the above Examples 1 to 12, Rm and T of the third casing wall 2112 of the casing 211 satisfy 250MPa≦Rm≦2000MPa, 0.05mm≦T≦0.5mm and 60mm·MPa≦T×Rm≦500mm·MPa. To meet the design requirements of the battery cell 20, the number of failure fatigue cycles of the battery cell 20 can reach more than one thousand, and even if the average thickness T of the third casing wall 2112 is set to be relatively small, the number of failure fatigue cycles of the battery cell 20 can still reach more than one thousand. By setting the average thickness T of the third casing wall 2112 to be relatively small, the energy density of the battery 10 can also be increased. However, in the two comparative examples, the structural strength of the third casing wall 2112 is insufficient, neither Rm nor T×Rm meets the above values, and even if the average thickness T of the third casing wall 2112 is relatively large, the number of failure fatigue cycles of the battery cell 20 cannot reach one thousand, which cannot meet the design requirements of the battery cell 20.

[0275] In some embodiments, the capacity of the battery cell is C, where C satisfies 25Ah ≤ C ≤ 550Ah. On the one hand, increasing the capacity C of a battery cell 20 can improve the capacity density of a battery 10 containing multiple such battery cells 20. Alternatively, if the total capacity of the battery 10 does not change, increasing the capacity C of a single battery cell 20 can reduce the number of battery cells 20 installed, correspondingly reducing the number of electrical connections between multiple battery cells 20 and lowering the probability of electrical connection failures, thereby improving the reliability of the battery. Furthermore, when the capacity C of a battery cell 20 is relatively large, increasing the tensile strength Rm of at least a portion of the casing 211 under normal temperature conditions of 25°C can satisfy the structural strength requirements of the casing 211 for high-capacity battery cells 20, further improving the reliability and service life of the battery cell 20. On the other hand, when a battery cell 20 has a relatively large capacity, the internal reaction becomes more vigorous, further increasing the structural strength requirements of the casing 211. Therefore, in order to limit the design requirements for the structural strength of the casing 211, it is undesirable for the capacity C of the battery cell 20 to be too large, thereby reducing the difficulty of selecting and processing the battery cell 20, reducing costs, and improving processing efficiency.

[0276] As can be understood, the range of the capacity C value of the battery cell 20 in the embodiments of the present application can be adjusted according to the actual application. For example, the capacity C of the battery cell 20 can be reasonably selected according to the actual needs of the battery 10. In some embodiments, the capacity C of the battery cell 20 may be set to further satisfy 100Ah ≤ C ≤ 300Ah. By appropriately increasing the capacity C of the battery cell 20, the energy density of the battery 10 can be improved. At the same time, it is undesirable for the capacity C of the battery cell 20 to be too large in order to balance the relationship between the capacity C of the battery cell 20 and the structural strength of the casing 211 and to improve the reliability and service life of the battery cell 20.

[0277] Furthermore, the capacity C of the battery cell 20 can further satisfy the condition 150Ah ≤ C ≤ 250Ah. By further limiting the capacity C of the battery cell 20, not only can the energy density of the battery 10 be improved, but the structural strength of the casing 211 can also be improved, further enhancing the reliability and service life of the battery cell 20 and the battery 10.

[0278] In some embodiments, the value of the capacity C of the battery cell 20 according to the embodiment of the present application may also be set to other values. For example, the capacity C of the battery cell 20 may be any one 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, or it may be between any two of these values.

[0279] To ensure understanding, the capacity C of the battery cell 20 in the embodiment of the present application represents the amount of electricity output when the battery cell 20 is fully charged and discharged to the cutoff voltage under predetermined discharge conditions. The test method for the capacity C of the battery cell 20 can be selected according to the actual application. For example, the capacity C of the battery cell 20 may be determined by performing a discharge test using GB / T 31467.1, but the embodiments of the present application are not limited to these.

[0280] The following will be explained by comparing multiple comparative examples and multiple examples. Specifically, the battery cell 20 in each of the following examples and comparative examples is a rectangular parallelepiped type battery cell as shown in Figures 3 and 4, and among them, a hollow structure is adopted in which the casing 211 opens at one end.

[0281] In the following examples and comparative examples, the manufacturing methods for the positive electrode piece 223, negative electrode piece 224, electrolyte, and separator 225 of the battery cell 20 are as follows.

[0282] 1. Manufacturing of positive electrode piece 223 Positive electrode active material LiNi 0.95 Co 0.04 Mn 0.01 O2, the conductive agent Super P, and the adhesive polyvinylidene fluoride (PVDF) were prepared as a positive electrode slurry in N-methylpyrrolidone (NMP), with a solid content of 50 wt% in the positive electrode slurry, and LiNi 0.7 Co 0.1 Mn 0.1 The mass ratio of O2, Super P, and PVDF was 8:1:1. The positive electrode slurry was applied to the upper and lower surfaces of the aluminum foil current collector, dried at 85°C, then cold-pressurized, edge-trimmed, cut, and slit, and finally dried under vacuum conditions at 85°C for 4 hours to produce the positive electrode piece 223.

[0283] 2. Manufacturing of the negative electrode piece 224 A negative electrode slurry was prepared by uniformly mixing a negative electrode active material, a conductive agent Super P, a thickener carboxymethylcellulose (CMC), and an adhesive styrene-butadiene rubber (SBR) in deionized water. The negative electrode active material contained graphite and a silicon-based material, and the silicon-based material was a silicon-oxygen compound. The solid content in the negative electrode slurry was 30 wt%, and the mass ratio of the negative electrode active material, silicon monoxide, Super P, CMC, and adhesive styrene-butadiene rubber (SBR) in the solid content was 88:7:3:2. The negative electrode slurry was applied to the upper and lower surfaces of a copper foil current collector and dried at 85°C. Then it was cold-pressed, edge-trimmed, cut, and slit, and then dried under vacuum conditions at 120°C for 12 hours to produce a negative electrode piece 224.

[0284] 3. Manufacturing of electrolyte In a glove box under an argon atmosphere (H2O < 0.1 ppm, O2 < 0.1 ppm), a thoroughly dried electrolyte salt, LiPF6, was dissolved in a mixed solvent (the mixed solvent contained ethylene carbonate (EC) and diethyl carbonate (DEC), and the ethylene carbonate (EC) and diethyl carbonate (DEC) were mixed in a 50:50 mass ratio). After homogeneous mixing, an electrolyte solution with a concentration of 1 mol / L was obtained.

[0285] 4. Manufacturing of separator 225 A 16 μm polyethylene film was used as separator 225.

[0286] 5. Manufacturing of lithium-ion battery cells 20 The positive electrode piece 223, separator 225, and negative electrode piece 224 are stacked in order, with the separator 225 positioned between the positive electrode piece 223 and the negative electrode piece 224 to isolate the positive and negative electrodes. The cells are then wound to obtain a bare cell, tabs are welded, the bare cell is placed in an outer casing made of a different material, the manufactured electrolyte is injected into the dried outer casing, and sealing, standing, chemical conversion, shaping, and capacity testing are performed to complete the manufacturing of the lithium-ion battery cell 20.

[0287] In each of the following examples 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 correspondingly for the casing 211 to obtain different tensile strengths Rm, the capacity of the battery cell 20 is C, and the specific parameter settings are shown in Table 6 below. In addition, in each example 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 was measured using the method specified in GB / T 228.1-2010. Furthermore, in each of the following examples and comparative examples, the battery cell 20 is the same in all other installation conditions except for the parameter settings shown in Table 6. For example, the wall thickness of the maximum area of ​​the battery cell 20 in each example is 0.15 mm, and for example, the chemical system of the battery cell 20 in each example is nickel-cobalt-manganese ternary.

[0288] [Table 6]

[0289] As can be seen by comparing the two comparative examples and the six examples in Table 6 above, when different materials are used for the casing 211, correspondingly different tensile strengths Rm can be determined. If the tensile strength Rm satisfies 250MPa ≤ Rm ≤ 2000MPa and the capacity C of the battery cell 20 satisfies 25Ah ≤ C ≤ 550Ah, for example, in Examples 1 to 6, if no cracks occur in the casing 211 of the battery cell 20, the structural strength of the casing 211 can be used for battery cells 20 with relatively large capacities, and the design needs of the battery cell 20 can be met. However, if the tensile strength Rm does not satisfy 250MPa ≤ Rm ≤ 2000MPa, for example, in Comparative Examples 1 to 2, if the casing 211 of the battery cell 20 cracks, the design needs of the battery cell 20 cannot be met.

[0290] As can be understood, in order to meet the above design needs, the material of at least a portion of the casing 211 in the embodiment of the present application can be flexibly selected according to the actual application.

[0291] In some embodiments, the material of at least a portion of the casing 211 includes at least one of steel, copper alloy, titanium alloy, and nickel alloy. These materials have relatively high strength, so they can meet the strength requirements of the casing 211, and are easy to process and relatively inexpensive.

[0292] In some embodiments, the material of at least a portion of the casing 211 includes at least one of stainless steel, carbon steel, and high-strength alloy steel. For example, when the casing 211 is made of stainless steel, its structural strength is relatively high and can usually satisfy the requirements of tensile strength Rm at room temperature, yield strength Re at room temperature, tensile strength Rn at high temperature, and melting point p. For example, the melting point of stainless steel is usually between 1400°C and 1500°C. Furthermore, when the casing 211 is made of stainless steel, it becomes less susceptible to rust, which can improve the service life of the casing 211 compared to other materials.

[0293] When carbon steel is used for the casing 211, its structural strength is high, and it 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 usually between 1425°C and 1525°C. Furthermore, considering that carbon steel is susceptible to corrosion during use, nickel plating can be applied to the outer surface of the carbon steel casing 211. For example, the thickness of the nickel plating layer is usually between 1 μm and 10 μm to protect the surface of the casing 211 from corrosion due to oxidation and to improve the service life of the casing 211.

[0294] To effectively improve the structural strength of the casing 211, other high-strength alloy steel materials may be used. For example, if the requirements for the structural strength of the casing 211 are relatively high, a high-strength alloy steel material can be selected, which easily satisfies the above-mentioned requirements for tensile strength Rm at room temperature, yield strength Re at room temperature, tensile strength Rn at high temperature, and melting point p.

[0295] In some embodiments, when at least a portion of the casing 211 is made of steel, the steel type may include at least one of SPCC, Q195, Q215, Q235, SUS304, SUS316, and other modified stainless steels. These steels are readily available, their strength can meet design needs, and their cost is relatively low. For example, approximate values ​​of the tensile strength Rm, yield strength Re, tensile strength Rn, and melting point p of different steels at room temperature (25°C), room temperature (25°C), and high temperature (500°C) can be found in Table 7 below.

[0296] [Table 7]

[0297] As can be understood, the material of at least a portion of the casing 211 according to the embodiment of the present application may also be made of other materials. For example, different materials can be reasonably selected based on the mass content of different elements in the material and the function that those elements perform.

[0298] In some embodiments, the mass content of chromium in the material of at least a portion of the casing 211 is m, where m satisfies 10% ≤ m ≤ 30%. By increasing the amount of chromium in the material of at least a portion of the casing 211, the melting point and strength of the material can be improved, easily satisfying 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 reacts with oxygen to form an even denser chromium oxide film, a corrosion-resistant protective film can be formed on the surface of the casing 211, improving the corrosion resistance of the casing 211.

[0299] In some embodiments, the mass content of nickel in the material of at least a portion of the casing 211 is n, where n satisfies 8% ≤ n ≤ 25%. By increasing the nickel content in the material of at least a portion of the casing 211 by an appropriate amount, the structural strength and plasticity of the casing 211 can be improved, for example, the tensile strength Rm at room temperature, the yield strength Re at room temperature, and the tensile strength Rn at high temperature can be improved, and the corrosion resistance of the material can also be provided.

[0300] In some embodiments, taking steel as an example, the mass content of different elements in different types of steel varies. For example, in the case of stainless steel, iron is one of the basic elements of stainless steel, and its mass content is usually 60% to 70%. For example, Table 8 shows the mass content of different elements in several types of steel, and the values ​​in Table 8 are the maximum mass percentages of each element in that material; that is, the mass percentages of each element in the corresponding applications are usually less than or equal to the values ​​shown in Table 8.

[0301] [Table 8]

[0302] As can be understood, if at least a portion of the casing 211 is made of steel, increasing the mass content of carbon in the steel can improve the strength and hardness of the steel. For example, generally, the higher the carbon content, the higher the hardness and strength of the steel, but the lower the corrosion resistance may be.

[0303] Increasing the mass content of chromium in steel allows the chromium to react with oxygen to form a denser chromium oxide film, creating a corrosion-resistant protective film on the surface of the steel, thereby improving the corrosion resistance of the steel.

[0304] Increasing the mass content of nickel in steel materials can improve the corrosion resistance, strength, and plasticity of the steel.

[0305] Increasing the molybdenum content in steel materials can improve their corrosion resistance and strength, which is particularly noticeable in corrosive media such as acids and salts.

[0306] Increasing the mass content of manganese in steel materials can increase the toughness and fatigue resistance of the steel.

[0307] Increasing the mass content of silicon in steel materials can increase the corrosion resistance and strength of stainless steel.

[0308] Reducing the mass content of phosphorus and sulfur in steel materials can mitigate the adverse effects of these two elements on the corrosion resistance, plasticity, and toughness of the steel.

[0309] Furthermore, other elements may be incorporated into the steel material. For example, the steel material may further contain copper, and in Q195, Q215, and Q235, for example, the mass content of copper is generally 0.3% or less, while in modified stainless steel it is generally 2% to 3.5% or less. Also, for example, the steel material may further contain nitrogen, and in Q195, Q215, and Q235, for example, the mass content of nitrogen is generally 0.12% or less.

[0310] As can be understood, in the embodiments of this application, the test method for determining the mass content of each element in the steel material can be adapted to the actual application. For example, the test can be performed using inductively coupled plasma atomic emission spectroscopy, i.e., inductively coupled plasma (ICP) technology, but the embodiments of this application are not limited thereto.

[0311] Figure 10 shows a schematic diagram of another exploded structure of the battery cell 20 according to an embodiment of the present application, and Figure 11 shows an exemplary cross-sectional view of the casing 30 according to an embodiment of the present application. For the purposes of explanation, the casing 30 shown in Figures 10 and 11 may be applied to the battery cell 20, for example, the casing 30 may be applied to the battery cell 20 shown in Figures 3 and 4, and the casing 30 shown in Figures 10 and 11 may also be the casing 211 shown in Figures 3 and 4, which are applicable to the relevant explanations above and are omitted here for brevity.

[0312] As shown in Figures 10 and 11, the casing 30 has an opening 301, and the casing 30 includes a first casing wall 31 and at least two second casing walls 32 installed opposite the opening 301, the first casing wall 31 and the second casing walls 32 being installed intersecting each other.

[0313] As shown in the localized enlarged view of portion A in Figure 11, the casing 30 has a transition region 33 between two adjacent second casing walls 32, where T1 is the maximum thickness of the second casing wall 32 with the maximum thickness among the two adjacent second casing walls 32, and T0 is the maximum thickness of the second casing wall 32, of which T1 is greater than T0.

[0314] In some embodiments, the second casing wall 32 and the first casing wall 31 may be perpendicular to each other.

[0315] In some embodiments, at least two second casing walls 32 can be connected end to end to form a hollow structure that is enclosed and open at both ends, of which the first casing wall 31 covers the opening at one end of the hollow structure.

[0316] In some embodiments, the arrangement of the casing 30 is as shown in Figure 10, where the first casing wall 31 may be the bottom wall of the casing 30 for supporting the electrode assembly 22, and in this case, the second casing wall 32 is the side wall of the casing 30 installed surrounding the electrode assembly 22.

[0317] Typically, the second casing wall 32 is not manufactured independently; that is, the at least two second casing walls 32 may be integrally molded. In some other embodiments, the at least two second casing walls 32 and the first casing wall 31 are integrally molded, i.e., the casing 30 is an integrally molded structure. For example, a plate-like structure is stamped using a mold into a hollow structure with an opening, and the stamped casing 30 can have openings of various shapes, for example, the opening 301 may be circular, polygonal, or racetrack-shaped. The polygons may be, for example, square, pentagonal, hexagonal, or other irregular shapes.

[0318] In some embodiments, the thickness of the transition region 33 may be uniform or non-uniform. Hereinafter, we define the maximum thickness T1 of the transition region 33, taking the case where the thickness of the transition region 33 is uniform as an example.

[0319] As can be seen from Figure 10, the transition region 33 has two surfaces, namely an inner surface and an outer surface. In some embodiments, the inner and outer surfaces may be arcuate surfaces, and the inner and outer surfaces are coaxially positioned. The maximum thickness T1 of the transition region 33 can be defined as the length of the extension of the connecting line between the center of the circle on which the inner arc is located and the center of the circle on which the outer arc is located, in any cross section along a direction perpendicular to the axes of the inner and outer surfaces. In some other embodiments, the inner and outer surfaces may be planar, and the inner and outer surfaces are parallel, and the maximum thickness T1 of the transition region 33 can be defined as the perpendicular distance between the inner and outer surfaces. Similarly, the second casing wall 32 also has two surfaces, namely an inner surface and an outer surface, of which the maximum perpendicular distance between the inner and outer surfaces is the maximum thickness of a given second casing wall 32.

[0320] If the thicknesses of at least two second casing walls 32 of the casing 30 are not equal, for example, if they are not equal to the thicknesses of two second casing walls 32 adjacent to one transition region 33, then in an embodiment of the present application, T0 is the second casing wall 32 with the maximum thickness of the two second casing walls 32 adjacent to the transition region 33 in the casing 30. On the other hand, if the thicknesses of at least two second casing walls 32 of the casing 30 are equal, for example, if they are equal to the thicknesses of two second casing walls 32 of one transition region 33, then in an embodiment of the present application, T0 is the thickness of any one of the second casing walls 32 of the casing 30.

[0321] It should be explained that, if a second casing wall 32 includes a functional area, the maximum thickness of the second casing wall 32 actually refers to the maximum thickness of the area of ​​the second casing wall 32 other than the functional area, and the functional area includes at least one of a pressure release area, an area where electrode terminals are located, a fluid injection area, and a welding area.

[0322] In this embodiment, by installing a transition region 33 between two adjacent second casing walls 32, stress concentration between the two adjacent second casing walls 32 can be reduced, thereby lowering the risk of structural failure due to stress concentration. Furthermore, by setting the maximum thickness T1 of the transition region 33 to be greater than the maximum thickness T0 of the second casing wall with the greatest thickness among the two adjacent second casing walls, the thicker transition region 33 can increase the structural strength of the casing 30, which is advantageous in solving the problems of deformation of the casing 30 during the production and assembly process of the battery cell 20, as well as the problems of deformation of the casing 30 due to gas generation and expansion during the use of the battery cell 20.

[0323] In some embodiments, the maximum thickness T1 of the transition region 33 and the maximum thickness T0 of the second casing wall 32, which is the maximum thickness of the two adjacent second casing walls 32, satisfy 1.5 ≤ T1 / T0 ≤ 7.

[0324] 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 casing wall 32, which is the thickest of the two adjacent second casing walls 32, between [1.5, 7], the strength of the casing can be increased by the relatively thick transition region 33, while the difficulty in manufacturing the casing 30 due to the transition region 33 being too thick can be limited, thereby balancing the strength of the casing 30 with the difficulty of manufacturing the casing 30.

[0325] In actual 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 casing wall 32, which is the maximum thickness in the two adjacent second casing walls 32, can satisfy 2 ≤ T1 / T0 ≤ 4.

[0326] For example, T1 / T0 may 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.

[0327] 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 casing wall 32, which is the maximum thickness of the two adjacent second casing walls 32, between [2,4], the strength of the casing 30 and the difficulty of manufacturing the casing 30 can be balanced to the greatest extent possible.

[0328] Selectively, as shown in Figures 11 and 12, the space between two adjacent second casing walls 32 is connected by a first fillet 331, and the transition region 33 includes the first fillet 331. That is, the transition region 33 is realized by the fillet.

[0329] In this embodiment, by creating a transition region 33 between two adjacent second casing walls 32 using fillets, the casing 30 can be formed more easily, has better surface smoothness, and at the same time reduces the risk of cracking of the casing 30 due to stress concentration at the cusp when affected by internal gas generation in the battery cell 20.

[0330] As shown in Figure 12, the inner diameter of the first fillet 331 is R1, and the outer diameter of the first fillet 331 is R2.

[0331] In some embodiments, the first fillet 331 has an inner surface and an outer surface, both of which are arcuate surfaces. The inner diameter R1 of the first fillet 331 can be understood as the radius of the circle in which the inner arc of the first fillet 331 is located, while the outer diameter R2 of the first fillet 331 can be understood as the radius of the circle in which the outer arc of the first fillet 331 is located.

[0332] In several embodiments, the inner diameter R1 of the first fillet 331 satisfies the condition 2 mm ≤ R1 ≤ 4 mm. For example, R1 = 2 mm, 2.1 mm, 2.2 mm, 2.3 mm, 2.4 mm, 2.5 mm, 2.6 mm, 2.7 mm, 2.8 mm, 2.9 mm, 3.0 mm, 3.1 mm, 3.2 mm, 3.3 mm, 3.4 mm, 3.5 mm, 3.6 mm, 3.7 mm, 3.8 mm, 3.9 mm, 4.0 mm, etc.

[0333] In this embodiment, by setting the inner diameter of the first fillet 331 between two adjacent second casing walls 32 to be between [2 mm, 4 mm], on the one hand, the inner diameter is not too large and occupies too much of the internal space of the casing 30, thus preventing an increase in the pressure of gas generation inside the casing 30. On the other hand, the inner diameter is not too small, so that the increase in the wall thickness of the first fillet 331 is insufficient, and furthermore, the strength of the casing 30 is not insufficient. Thus, the utilization rate of the internal space of the casing 30 and the strength of the casing 30 can be balanced.

[0334] In several embodiments, the outer diameter R2 of the first fillet 331 satisfies the condition 1.5 mm ≤ R2 ≤ 3.5 mm. For example, R2 = 1.5 mm, 2 mm, 2.5 mm, 3.0 mm, 3.5 mm, etc.

[0335] In this embodiment, when the cover plate 40 and the casing 30 are fixedly connected by a side welding method, the larger the outer diameter R2 of the first fillet 331 between two adjacent second casing walls 32, the more difficult it becomes to control the welding quality and the more likely cold solder joints are to occur. On the other hand, the smaller the outer diameter R2 of the first fillet 331, the more difficult it becomes to form the casing 30. Therefore, by controlling the outer diameter R2 of the first fillet 331 within the range of [1.5 mm, 3.5 mm], it is possible to balance the welding quality and the difficulty of forming the casing.

[0336] In some other embodiments, as shown in Figure 13, two adjacent second casing walls 32 are connected by a chamfer, for example, the angles between the chamfer and the two adjacent second casing walls 32 are both 45°.

[0337] In one embodiment, the casing 30 may be an integrally formed structure. As shown in Figure 10, the depth of the casing 30 is H, where the depth H of the casing 30 and the inner diameter R1 of the first fillet 331 satisfy 2.5mm≦R1≦20mm and 50mm<H≦250mm.

[0338] In the embodiments of the present application, the depth can be understood as the distance from the opening inward to the bottom. For example, the depth H of the casing 30 can be understood as the distance from the opening 301 to the first casing wall 31.

[0339] Figure 14 shows a schematic diagram of material flow during the integral forming process of the casing 30. Figure 15 shows a schematic diagram of force bearing during the integral forming process of the casing 30. As can be seen from Figure 14 and Figure 15, when the casing 30 is formed, the material of the casing 30 tends to accumulate at the position of the first fillet 331, so the frictional force between the casing 30 and the mold increases, and the casing 30 is prone to cracking. Therefore, in this embodiment, by setting the depth H of the casing 30 and the inner diameter R1 of the first fillet 331 to satisfy 2.5mm≦R1≦20mm and 50mm<H≦250mm, without affecting the energy density of the battery cell 20, the risk of cracking caused by force bearing during the integral forming process of the casing 30 can be reduced as much as possible, and the forming difficulty of the casing 30 is further lowered.

[0340] By way of example, R1 is 2.5mm, 5mm, 7.5mm, 10mm, 12.5mm, 15mm, 17.5mm, 20mm, and / or H is 50mm, 100mm, 150mm, 200mm, 250mm.

[0341] In some embodiments, H and R1 satisfy the conditions 75mm ≤ H ≤ 180mm and 4mm ≤ R1 ≤ 15mm.

[0342] For example, H = 75mm, 100mm, 125mm, 150mm, 175mm, 180mm. For example, R1 = 4mm, 6mm, 8mm, 10mm, 12mm, 14mm, 15mm.

[0343] In this embodiment, by setting H and R1 to satisfy 4mm ≤ R1 ≤ 15mm and 75mm ≤ H ≤ 180mm, on the one hand, the energy density of the battery cell 20 is not reduced due to H being too small or R being too large, and on the other hand, the casing 30 is not prone to deposition during the molding process due to H being too large or R being too small, and furthermore, the casing 30 does not crack due to excessive force bearing.

[0344] In some other embodiments, H and R1 satisfy 5mm ≤ R1 ≤ 10mm and 90mm ≤ H ≤ 140mm, for example, R1 = 5mm, 6mm, 7mm, 8mm, 9mm, 10mm. Also, for example, H = 90mm, 100mm, 110mm, 120mm, 130mm, 140mm.

[0345] In some other embodiments, the casing 30 is a single-piece molded structure, and the yield strength of the casing 30 at a temperature of 25°C is Re, where the relationship between the yield strength Re and the inner diameter R1 of the first fillet 331 satisfies 140 MPa ≤ Re ≤ 1000 MPa and 2.5 mm ≤ R1 ≤ 20 mm.

[0346] 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.

[0347] For example, R1 can be 2.5mm, 5mm, 7.5mm, 10mm, 12.5mm, 15mm, 17.5mm, or 20mm.

[0348] Yield strength can be understood as the critical stress value at which a material yields. Normally, after a material is subjected to stress, in addition to elastic deformation, plastic deformation may also occur as the stress increases. The point at which plastic deformation occurs in a material may be called the yield point, and the strength corresponding to the yield point is called the yield strength. The test method for the yield strength Re of the casing 30 at a temperature of 25°C according to the embodiment of this application can be selected according to the actual application. For example, GB / T 228.1-2010 can be used to measure the yield strength Re at room temperature conditions of 25°C.

[0349] When integrally molding the casing 30, the material accumulates on the first fillet 331, increasing the frictional force between the casing 30 and the mold, which makes the casing 30 prone to cracking. To address this problem, the embodiment of the present application further provides another solution: for a casing 30 satisfying a yield strength Re of 140 MPa ≤ Re ≤ 1000 MPa, the inner diameter R1 of the first fillet 331 is set to 2.5 mm ≤ R1 ≤ 20 mm. This reduces the difficulty of molding the casing 30 without R1 being too small, and reduces deformation of the casing 30 due to force bearing without R1 being too large.

[0350] In this embodiment, by using a material with a yield strength Re satisfying 140MPa ≤ Re ≤ 1000MPa to manufacture the casing 30, the wall thickness of the casing can be reduced without reducing the strength of the casing 30, thereby increasing the capacity space of the battery cell 20. Furthermore, by setting the inner diameter R1 of the first fillet 331 between adjacent second casing walls 32 to satisfy 2.5mm ≤ R1 ≤ 20mm, the risk of cracking due to force bearing during the integral molding process of the casing 30 is reduced as much as possible, thereby reducing the difficulty of molding the casing 30.

[0351] In some embodiments, the yield strengths Re and R1 of the casing 30 can satisfy 150 MPa ≤ Re ≤ 400 MPa and 4 mm ≤ R1 ≤ 15 mm.

[0352] For example, Re = 150MPa, 170MPa, 190MPa, 210MPa, 230MPa, 260MPa, 290MPa, 310MPa, 330MPa, 370MPa, 390MPa, 400MPa.

[0353] For example, R1 can be 4mm, 6mm, 8mm, 10mm, 12mm, 14mm, or 15mm.

[0354] In this embodiment, limiting the ranges to 150MPa ≤ Re ≤ 400MPa and 4mm ≤ R1 ≤ 15mm helps to balance the difficulty of molding the casing 30 with the degree of deformation.

[0355] In some embodiments, the yield strengths Re and R1 of the casing 30 can satisfy 160MPa ≤ Re ≤ 300MPa and 5mm ≤ R1 ≤ 10mm.

[0356] For example, Re = 160MPa, 170MPa, 180MPa, 190MPa, 200MPa, 210MPa, 220MPa, 230MPa, 240MPa, 250MPa, 260MPa, 270MPa, 280MPa, 290MPa, 300MPa.

[0357] For example, R1 = 5mm, 6mm, 7mm, 8mm, 9mm, 10mm.

[0358] In this embodiment, by limiting the ranges to 160MPa≦Re≦300MPa and 5mm≦R1≦10mm, deformation due to force bearing during use of the casing 30 can be reduced as much as possible, provided that it does not affect the difficulty of molding the casing 30.

[0359] In several examples, the tensile strength of the casing 30 at a temperature of 25°C is Rm, and Rm and R1 satisfy the conditions 250 MPa ≤ Rm ≤ 2000 MPa and 2.5 mm ≤ R1 ≤ 20 mm.

[0360] Tensile strength can be understood as the maximum stress value experienced by a material during fracture. The test method for the tensile strength Rm of the casing 30 at a temperature of 25°C according to the embodiment of this application can be selected according to the actual application. For example, the tensile strength Rm can be measured at room temperature conditions of 25°C by adopting ISO 6892-2:2018.

[0361] 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.

[0362] In this embodiment, by setting 250MPa≦Rm≦1000MPa and 2.5mm≦R1≦20mm, if the strength of the casing 30 is not affected, the force bearing of the mold during the manufacturing process of the casing 30 can be reduced as much as possible, and furthermore, the dimensions or surface of the casing 30 can not be affected.

[0363] In some embodiments, Rm and R1 satisfy the conditions 280 MPa ≤ Rm ≤ 800 MPa and 4 mm ≤ R1 ≤ 15 mm.

[0364] For example, Rm = 280MPa, 310MPa, 340MPa, 370MPa, 390MPa, 430MPa, 470MPa, 510MPa, 540MPa, 580MPa, 610MPa, 630MPa, 660MPa, 690MPa, 720MPa, 740MPa, 780MPa, 800MPa.

[0365] In several other embodiments, Rm and R1 satisfy the conditions 380 MPa ≤ Rm ≤ 600 MPa and 5 mm ≤ R1 ≤ 10 mm.

[0366] For example, Rm = 380 MPa, 390 MPa, 410 MPa, 440 MPa, 480 MPa, 520 MPa, 535 MPa, 570 MPa, 596 MPa, and 600 MPa.

[0367] In some embodiments, the maximum wall thickness of at least two second casing walls 32 of the casing 30 is equal.

[0368] More selectively, the thickness of each of the at least two second casing walls 32 of the casing 30 is uniform, and the thickness of all at least two second casing walls 32 is equal.

[0369] In this embodiment, by setting the thickness of at least two second casing walls 32 to be equal, the difficulty of processing the casing 30 can be reduced, and at least two second casing walls 32 can both be set to the minimum processing thickness, which helps to significantly improve the space utilization rate of the casing 30.

[0370] In some other embodiments, there is a transition region 33 between any two adjacent second casing walls 32 in at least two second casing walls 32, and the maximum thickness of at least two transition regions 33 corresponding to at least two second casing walls 32 is equal.

[0371] In this embodiment, by setting the maximum thickness of at least two transition regions 33 between at least two second casing walls 32 of the casing 30 to be equal, it is possible to manufacture the casing 30 as a symmetrical structure, making it easy to process, and eliminating the worry of incorrectly installing the casing 30 and cover plate 40 when assembling them, thus providing a poka-yoke prevention function.

[0372] Figure 16 shows another exemplary cross-sectional view of a casing 30 according to an embodiment of the present application. As shown in the local enlarged view of portion B of Figure 16, the first casing wall 31 and the second casing wall 32 are connected by a second fillet 34, and as shown in the enlarged schematic view of portion B of Figure 16, the inner diameter of the second fillet 34 is r1, and the minimum thickness of the second casing wall 32 having the minimum thickness in at least two of the second casing walls 32 is T2, where the relationship between the inner diameter r1 of the second fillet 34 and the minimum thickness T2 of the second casing wall 32 having the minimum thickness in at least two of the second casing walls 32 satisfies 2.0 ≤ r1 / T2 ≤ 30.

[0373] As can be understood, each of the first casing walls 31 is connected to at least two second casing walls 32, and selectively, one of the second casing walls 32 is connected to the first casing wall 31 by a second fillet 34 shown in Figure 16. Furthermore, the second fillet 34 here is realized similarly to the first fillet 331 in Figure 12, i.e., the second fillet 34 has an inner surface and an outer surface, both of which are arcuate surfaces. The inner diameter r1 of the second fillet 34 can be understood as the radius of the circle in which the inner arc is located.

[0374] For the purposes of explanation, if each second casing wall 32 is of uniform thickness, the minimum thickness T2 of the second casing wall 32 may refer to the thickness of the thinnest second casing wall 32 in at least two of the second casing walls 32. If the thickness of each second casing wall 32 is non-uniform, the minimum thickness T2 of the second casing wall 32 may refer to the thickness of the thinnest region in all of the second casing walls 32.

[0375] Furthermore, it should be explained that if a second casing wall 32 includes a functional area, the minimum thickness of the second casing wall 32 refers to the minimum thickness of the area of ​​the second casing wall 32 other than the functional area, and the functional area includes at least one of a pressure release area, an area where electrode terminals are located, a fluid injection area, and a welding area.

[0376] In this embodiment, by setting the ratio of the inner diameter r1 of the second fillet 34 between the first casing wall 31 and the second casing wall 32 to the minimum thickness T2 of the second casing wall 32, which has the minimum thickness, to between [2.0, 30], it is possible to balance the difficulty of processing the casing 30 with the spatial capacity and strength of the battery cell 20.

[0377] In several embodiments, the inner diameter r1 of the second fillet 34 and the minimum thickness T2 of the second casing wall 32, which is the minimum thickness in at least two of the second casing walls 32, satisfy 2.5 ≤ r1 / T2 ≤ 10. For example, r1 / T2 = 2.5, 3.0, 3.5, 4.0, 4.5, 5.0, 5.5, 6.0, 6.5, 7.0, 7.5, 8.0, 8.5, 9.0, 9.5, 10, etc.

[0378] Selectively, the inner diameter r1 of the second fillet 34 can satisfy 0.8 mm ≤ r1 ≤ 1.5 mm. For example, r1 = 0.8 mm, 0.9 mm, 1.0 mm, 1.1 mm, 1.2 mm, 1.3 mm, 1.4 mm, 1.5 mm.

[0379] In this embodiment, by setting the inner diameter r1 of the second fillet 34 to [0.8 mm, 1.5 mm], on the one hand, if r1 is too small, it does not increase the difficulty of manufacturing the casing 30, and on the other hand, if r1 is too large, it does not reduce the interference between the electrode assembly 22 and the second fillet 34, that is, by lowering the height of the electrode assembly 22, it is not necessary to sacrifice the capacity of the electrode assembly 22 to satisfy the assembly of the casing 30 and the electrode assembly 22, and on the other hand, if r1 is too large, the casing 30 is prone to deformation.

[0380] Figure 17 shows another localized schematic view of section B in Figure 16. As shown in Figure 17, the outer diameter of the second fillet 34 is r2, where r2 satisfies the condition 1 mm ≤ r2 ≤ 2.5 mm. For example, r2 = 1.0 mm, 1.1 mm, 1.2 mm, 1.3 mm, 1.4 mm, 1.5 mm, 1.6 mm, 1.7 mm, 1.8 mm, 1.9 mm, 2.0 mm, 2.1 mm, 2.2 mm, 2.3 mm, 2.4 mm, 2.5 mm.

[0381] 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 on which the outer arc of the second fillet 34 is located.

[0382] In this embodiment, by setting the outer diameter r2 of the second fillet 34 to [1.0 mm, 2.5 mm], on the one hand, r2 is not too small, so the insulating film on the outside of the battery cell 20 does not break through at the sharp point and cause an insulation failure, and on the other hand, r2 is not too large, so the thickness of the second fillet 34 does not become too thin and affect the strength of the casing 30.

[0383] In some embodiments, the relationship between H and T2 satisfies 300 ≤ H / T2 ≤ 800. For example, H / T2 = 300, 350, 400, 450, 500, 550, 600, 650, 700, 750, 800, etc.

[0384] In this embodiment, by setting the ratio between the depth H of the casing 30 and the minimum thickness T2 of the second casing wall 32, which has the minimum thickness, to be between [300, 800], it is possible to achieve both the volume utilization rate and strength of the battery cell 20.

[0385] As shown in Figure 17, the maximum thickness of the second fillet 34 is T3, and 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.

[0386] The thickness of the second fillet 34 may be uniform or non-uniform. Hereinafter, the maximum thickness T3 of the second fillet 34 is defined as an example where the thickness of the second fillet 34 is uniform. In some embodiments, the maximum thickness T3 of the second fillet 34 can be defined as the length of the extension of the connecting line between the center of the circle on which the inner arc of the second fillet 34 is located and the center of the circle on which the outer arc is located, in any one cross section along a direction perpendicular to the axes of the inner and outer surfaces.

[0387] 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 casing wall 32, which has the minimum thickness, to [0.8,2], the strength and manufacturability of the casing 30 can be balanced. That is, the strength of the casing 30 is not compromised by making the second fillet 34 excessively thin, nor is the manufacturing of the casing 30 difficult by making the second fillet 34 insufficiently thin.

[0388] In some embodiments, the wall thickness of the casing 30 is uniform, that is, the wall thickness of all walls of the casing 30 is equal.

[0389] In this embodiment, by setting the wall thickness of the casing 30 to be uniform, on the one hand, the difficulty of processing the casing 30 can be reduced, and on the other hand, each wall of the casing 30 can be set to the minimum processing thickness, which helps to significantly improve the space utilization rate of the casing 30.

[0390] In some embodiments, the battery cell 20 further includes a cover plate 40 to cover an opening 301 of the casing 30 in order to seal the electrode assembly 22 within the cavity of the casing 30.

[0391] In this embodiment, by setting the inner diameter R1 of the first fillet between the depth H of the casing and the second casing wall to satisfy 2.5 mm ≤ R1 ≤ 20 mm and 50 mm ≤ H ≤ 250 mm, the risk of cracking due to force bearing during the integral molding process of the casing is reduced as much as possible without affecting the energy density of the battery cell, and the difficulty of molding the casing is further reduced.

[0392] In some embodiments, the shape of the battery cell 20 is approximately a rectangular parallelepiped; for example, the battery cell 20 is a rectangular parallelepiped battery cell. Alternatively, for example, the battery cell 20 is a racetrack-shaped battery cell, and the thickness of the battery cell 20 is D1, where H, R1, and D1 satisfy the condition 0.15 mm ≤ R1 * D1 / H ≤ 36 mm.

[0393] 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.

[0394] In some embodiments, D2 may be the dimension of the electrode assembly 22 of the battery cell 20 in the expansion direction.

[0395] In this embodiment, by setting 0.15 mm ≤ R1*D1 / H ≤ 36 mm, the risk of the casing 30 easily accumulating during the molding process due to the R1*D1 / H value being too small, and the risk of the casing 30 cracking due to excessive force bearing, can be reduced. Furthermore, the impact on the energy density of the battery cell 20 can be reduced because the R1*D1 / H value is not too large.

[0396] In this embodiment, D1 satisfies the condition 15mm ≤ D1 ≤ 90mm. For example, D1 = 15mm, 20mm, 25mm, 30mm, 35mm, 40mm, 45mm, 50mm, 55mm, 60mm, 65mm, 70mm, 75mm, 80mm, 85mm, 90mm.

[0397] In this embodiment, H and R1 satisfy the conditions 50mm ≤ H ≤ 250mm and 2.5mm ≤ R1 ≤ 20mm.

[0398] In some embodiments, H, R1, and D1 satisfy the condition 0.34 mm ≤ R1 * D1 / H ≤ 18 mm.

[0399] In this embodiment, by setting 0.34 mm ≤ R1 * D1 / H ≤ 18 mm, the difficulty of molding the casing 30 and its energy density can be balanced.

[0400] For example, R1*D1 / H = 0.34, 0.5, 1, 3, 5, 8, 11, 13, 16, 18.

[0401] Similarly, in this embodiment, D1 satisfies the condition 15 mm ≤ D1 ≤ 90 mm.

[0402] In this embodiment, H and R1 satisfy the conditions 75mm ≤ H ≤ 180mm and 4mm ≤ R1 ≤ 15mm.

[0403] In some embodiments, H, R1, and D1 satisfy the condition 0.9 mm ≤ R*D / H ≤ 6.6 mm.

[0404] 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.

[0405] In this embodiment, D1 satisfies the condition 25mm ≤ D1 ≤ 60mm. For example, D1 = 25mm, 28mm, 31mm, 34mm, 37mm, 39mm, 41mm, 43mm, 46mm, 49mm, 51mm, 54mm, 58mm, 50mm.

[0406] Furthermore, in this embodiment, H and R1 satisfy the conditions 90mm ≤ H ≤ 140mm and 3mm ≤ R ≤ 10mm.

[0407] It should be explained that the ranges of values ​​for R1, H, D1, and R1*D1 / H can be related to each other. For example, if 15mm≦D1≦90mm, 50mm≦H≦250mm, and 2.5mm≦R1≦20mm, then 0.15mm≦R1*D1 / H≦36mm. Also, for example, if 15mm≦D1≦90mm, 75mm≦H≦180mm, and 4mm≦R1≦15mm, then 0.34mm≦R*D / H≦18mm. Furthermore, for example, if 25mm≦D1≦60mm, 90mm≦H≦140mm, and 3mm≦R1≦10mm, then 0.9mm≦R1*D1 / H≦6.6mm.

[0408] In some embodiments, the thickness of the electrode assembly 22 is D2, and R1 and D2 satisfy 0.125 ≤ R1 / D2 ≤ 0.45.

[0409] 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.

[0410] Selectively, D2 may be a dimension in the expansion direction of the electrode assembly 22.

[0411] In this embodiment, by setting 0.125 ≤ R1 / D2 ≤ 0.45, on the one hand, R1 is not too large, which would interfere with the electrode assembly 22 or leave insufficient space inside the battery cell 20, thus not affecting the performance of the battery cell 20. On the other hand, R1 is not too small, which would not make it difficult to mold the casing 30.

[0412] Figure 18 shows an exploded schematic diagram of the casing 40 according to an embodiment of the present application. Figure 19 shows a schematic diagram of the structure of the second casing part 42 according to an embodiment of the present application. Figure 20 shows another schematic diagram of the structure of the second casing part 42 according to an embodiment of the present application. Figure 21 shows another exploded schematic diagram of the casing 40 according to an embodiment of the present application. It should be noted that the casing 40 may be applied to a battery cell 20. For example, the casing 40 shown in Figures 18 to 21 may be applied to the battery cell 20 shown in Figures 3 and 4, and the casing 40 may include only the casing 211 shown in Figure 4, or it may include the casing 211 shown in Figure 4 and further include the cover plate 212 shown in Figure 4. Also, the arrangement method of the casing 40 may be shown in Figure 3 or Figure 4.

[0413] As shown in Figure 18, the casing 40 includes a first casing portion 41 having an opening 401 formed therein, which includes a first wall 411 facing the opening 401 and a second wall 412 connected to the first wall 411, with the first wall 411 and the second wall 412 integrally molded, and a second casing portion 42 fixedly connected to the second wall 412. Of these, in the depth direction X of the first casing portion 41, at least a portion of the casing 40 is jointly formed by the first casing portion 41 and the second casing portion 42.

[0414] It should be interpreted that the fact that the first wall 411 and the second wall 412 in the first casing portion 41 are integrally molded structures may also mean that the first casing portion 41 is manufactured by an integral deep drawing process. For example, the first casing 41 can be manufactured by the following steps: step 1: selecting a steel material suitable for deep drawing; step 2: preparing a suitable stamping die, usually made from die steel, carbon steel, or hard alloy, including components such as a punch, die, and blank holder, according to the casing design and process requirements; step 3: fixing the steel material between the clamp and the die to ensure the stability of the steel material during the deep drawing process; step 4: applying tensile stress to the steel material by moving the punch downward into the die, thereby deforming it and filling the shape of the die; step 5: controlling the speed and pressure of the punch to ensure that the steel material deforms uniformly during the deep drawing process, is drawn to a predetermined depth, and obtains the required shape; step 6: performing auxiliary operations such as drilling, trimming, and marking during the deep drawing process as needed; step 7: removing the product from the die after the deep drawing is complete and performing necessary processing such as cleaning and deburring; thereby obtaining the first casing 41.

[0415] Since the first casing portion 41 is integrally deep-drawn, it usually has an opening 401. The opening 401 may be circular, polygonal, or racetrack-shaped. The polygon may be, for example, a square, pentagon, hexagon, or other irregular shape.

[0416] The first casing section 41 is a hollow structure formed by a first wall 411 and a second wall 412 surrounding the opening 401, wherein the second wall 412 and the first wall 411 are installed intersecting. For example, the first wall 411 and the second wall 412 are installed perpendicularly. In some embodiments, the first casing section 41 includes a second wall 412 that is connected from end to end and jointly surrounds a cylindrical hollow structure together with the first wall 411. In some other embodiments, the first casing section 41 includes four second walls 412 that are installed in pairs facing each other, and two adjacent second walls 412 intersect perpendicularly, so that the four second walls 412 and the first wall 411 jointly surround a rectangular columnar hollow structure.

[0417] Since the first wall 411 is installed facing the opening 401 of the first casing portion 41, the depth direction X of the first casing portion 41 can be understood as the distance between the opening 401 of the first casing portion 41 and the first wall 411 in the direction perpendicular to the first wall 411.

[0418] In the embodiments of the present application, the second casing portion 42 is fixedly connected to the second wall 412, the second casing portion 42 is a flat plate structure, and the second casing portion 42 does not fit into the opening 401 of the first casing portion 41. In other words, in the embodiments of the present application, the second casing portion 42 includes at least one third wall 421, of which at least one third wall 421 jointly surrounds and forms a hollow structure having at least one opening. For example, the second casing portion 42 includes at least the opening 402 shown in Figure 19, and the opening 402 of the second casing portion 42 is positioned opposite the opening 401 of the first casing portion 41, and the second wall 412 and the third wall 421 are fixedly connected, so that in the depth direction X of the first casing portion 41, the second wall 412 and the third wall 421 jointly form at least a portion of the casing 40, i.e., the depth H of the casing 40 is at least greater than the depth of the first casing portion 41. Of these, the depth H of the casing 40 can be understood as the dimension of the casing 40 along the depth direction of the first casing portion 41. Normally, the walls of the casing 40 have a predetermined thickness, but the wall thickness of the casing 40 can be ignored here.

[0419] In this embodiment, the casing 40 includes a first casing portion 41 and a second casing portion 42, of which the first casing portion 41 has an opening 401 and includes a first wall 411 facing the opening 401 and a second wall 412 connected to the first wall 411, the first wall 411 and the second wall 412 are integrally molded, and in the depth direction X of the first casing portion 41, at least a portion of the casing 40 is jointly formed by the first casing portion 41 and the second casing portion 42. Compared to the technical method of directly integrally molding the casing 40, the casing 40 manufactured in this manner can reduce the risk of cracking of the casing 40 during the integral deep drawing process.

[0420] In some embodiments, the dimensions of the second wall 412 are equal at all points in the depth direction X of the first casing portion 41. Similarly, the dimensions of the third wall 421 are equal at all points in the depth direction X of the first casing portion 41. Thus, in the depth direction X of the first casing portion 41, all areas of the casing 40 are jointly formed by the first casing portion 41 and the second casing portion 42.

[0421] In some other embodiments, the dimensions of the second wall 412 are not exactly equal in the depth direction X of the first casing portion 41. For example, the second wall 412 after unfolding may be semicircular or triangular. Similarly, the dimensions of the third wall 421 are not exactly equal in the depth direction X of the first casing portion 41. For example, the third wall 421 after unfolding may be semicircular or triangular. In this case, a portion of the casing 40 may be jointly formed by the first casing portion 41 and the second casing portion 42 in the depth direction X of the first casing portion 41.

[0422] In one embodiment, the first casing portion 41 and the second casing portion 42 are fixedly connected by welding. In this way, the casing 40 manufactured by employing the method according to the embodiment of the present application has no welded seams located at right-angle edges, and is less prone to cracking or damage compared to a casing formed by butt welding a flat plate-shaped structure and a tubular structure having an opening.

[0423] Selectively, the second casing portion 42 has two communicating openings in the depth direction X of the first casing portion 41. For example, the second casing portion 42 has openings 402 and 403 as shown in Figure 19, and openings 402 and 403 are positioned opposite each other in the depth direction X of the first casing portion 41.

[0424] In this embodiment, by installing the second casing portion 42 having two openings that communicate with the first casing portion 41 in the depth direction X, the cover plate and the casing 40 can be installed independently, and an assembly such as electrode terminals can be more suitably installed on the cover plate, thereby simplifying the manufacturing of the casing 40.

[0425] In other embodiments, the second casing portion 42 may have only one opening. For example, the second casing portion 42 is manufactured by a deep drawing process similar to that of the first casing portion 41, and the second casing portion 42 further includes a wall, such as a cover plate, that intersects with the third wall 421 and faces the opening of the second casing portion 42, in addition to including the third wall 421.

[0426] In one embodiment, the second casing portion 42 is an integrally molded structure.

[0427] In this embodiment, by installing the second casing portion 42 in an integrally molded structure, the number of welded seams in the casing 40 can be reduced, thereby increasing the reliability of the casing 40 and reducing the risk of deformation, cracking, or breakage of the casing 40.

[0428] In another embodiment, if the second casing portion 42 has only one opening, the second casing portion 42 is formed by butt welding of at least two parts.

[0429] It should be explained that if the second casing portion 42 is formed by butt welding of at least two parts, the welded seams of the second casing portion 42 must not be on the edges, so-called right-angle sides. For example, as shown in Figure 20, the second casing portion 42 includes four third walls 421, each including a fourth wall 4211, a fifth wall 4212, a sixth wall 4213, and a seventh wall 4214. Of these, the fourth wall 4211 is installed opposite the fifth wall 4212, the sixth wall 4213 is installed opposite the seventh wall 4214, and the sixth wall 4213 includes the first sub-wall 4213a and the second sub-wall 4213b, the first sub-wall 4213a and the second sub-wall 4213b are symmetrical with respect to the first centerline 4251, and the seventh wall 4214 includes the third sub-wall 4214a and the fourth sub-wall 4214b, the third sub-wall 4214a and the fourth sub-wall 4214b are symmetrical with respect to the second centerline 4261. The second casing portion 42 is formed by butt welding of the first portion 423 and the second portion 424. Of these, the first portion 423 includes a first sub-wall 4213a, a fourth wall 4211, and a third sub-wall 4214a, the second portion 424 includes a second sub-wall 4213b, a fifth wall 4212, and a fourth sub-wall 4214b, and the first centerline 4251 and the second centerline 4261 are welded joints of the second casing portion 42.

[0430] In this embodiment, by installing the second casing portion 42 such that at least two parts are formed by butt welding, processing can be facilitated, dimensions can be controlled more easily, and the assembly accuracy of the casing 40 can be improved.

[0431] In some embodiments, the surface 4121 of the second wall 412 that separates from the first wall 411 is welded to the second casing portion 42, where the thickness of the casing 40 is taken into consideration. As can be understood, the second wall 412 is welded to the third wall 421, and the inner surface of the second wall 412 and the inner surface of the third wall 421 are spliced ​​to form a single plane.

[0432] In other words, the depth of the casing 40 is equal to the sum of the depth of the first casing section 41 and the depth of the second casing section 42.

[0433] In this embodiment, the space utilization rate of the casing 40 can be improved by welding the surface 4121 of the second wall 412 that separates from the first wall 411 to the second casing portion 42.

[0434] In some other embodiments, the surface of the second wall 412 perpendicular to the thickness direction Y of the second wall 412 is welded to the second casing portion 42. For example, as shown in Figure 21, the inner surface 4122 of the second wall 412 and the second casing portion 42 are welded to the outer surface 4215 of the third wall 421 of the second casing portion 42 at the opening 401 of the first casing portion 41.

[0435] In this embodiment, welding the surface of the second wall 412 perpendicular to the thickness direction Y of the second wall 412 to the second casing portion 42 is advantageous in increasing the welding area between the first casing portion 41 and the second casing portion 42, thereby improving the welding strength between them.

[0436] Figure 22 shows an exemplary cross-sectional view of a casing 40 according to an embodiment of the present application. As shown in Figure 22, in the depth direction X of the first casing portion 41, the maximum dimension of the first casing portion 41 is h1, and the maximum dimension of the casing 40 is H, where H and h1 satisfy 3 ≤ H / h1 ≤ 80.

[0437] As an interpretation, if wall thickness is not considered, the dimensions of the first casing portion 41 do not have to be uniform in the depth direction X of the first casing portion 41, and the maximum dimension h1 of the first casing portion 41 may refer to the maximum distance between one end of the second wall 412 away from the first wall 411 and the first wall 411. Similarly, if wall thickness is not considered, the dimensions of the casing 40 do not have to be uniform in the depth direction X of the first casing portion 41, and the maximum dimension H of the casing 40 may refer to the maximum distance between one end of the second casing portion 42 away from the first wall 411 and the first wall 411.

[0438] In some embodiments, the dimensions of the first casing portion 41 are uniform in the depth direction X of the first casing portion 41, and the dimensions of the casing 40 are also uniform.

[0439] For example, H / h1 = 3, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80.

[0440] In this embodiment, by setting the ratio of H to h1 within the range of [3,80], the ratio is not too large, so the welding position between the first casing portion 41 and the second casing portion 42 is not too close to the first casing portion 41, and the battery cell will not be prone to cracking due to excessive force bearing at the weld joint during use. On the other hand, if the ratio is too small, the casing 40 will not crack due to excessive force bearing during the deep drawing process, and this will not increase the difficulty of manufacturing the first casing portion 41.

[0441] Furthermore, selectively, 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.

[0442] In some embodiments, h1 satisfies the condition 3 mm ≤ h1 ≤ 50 mm.

[0443] For example, h1 = 3mm, 5mm, 10mm, 15mm, 20mm, 25mm, 30mm, 35mm, 40mm, 45mm, 50mm.

[0444] In this embodiment, by setting h1 within the range of [3mm, 50mm], if h1 is too small, the welded seam will be too close to the first casing portion 41, and there will be no risk of the battery cell cracking during the charging and discharging process. Conversely, if h1 is too large, cracking will occur in the first casing portion 41 during the integral deep drawing process, thereby not increasing the manufacturing difficulty of the first casing portion 41.

[0445] More selectively, h1 satisfies the condition 5mm ≤ h1 ≤ 30mm.

[0446] To explain, if h1 satisfies the above conditions, then H can satisfy the condition of being 100 mm or more. For example, H is equal to 400 mm.

[0447] In several embodiments, the yield strength of the casing 40 at a temperature of 25°C is Re, where Re satisfies 125 MPa ≤ Re ≤ 1000 MPa.

[0448] Yield strength can be understood as the critical stress value at which a material yields. Normally, after a material is subjected to stress, in addition to elastic deformation, plastic deformation may also occur as the stress increases. The point at which plastic deformation occurs in a material may be called the yield point, and the strength corresponding to the yield point is called the yield strength. The test method for the yield strength Re of the casing 40 at a temperature of 25°C according to the embodiment of this application can be selected according to the actual application. For example, GB / T 228.1-2010 can be used to measure the yield strength Re at room temperature conditions of 25°C.

[0449] For example, Re = 125MPa, 130MPa, 150MPa, 180MPa, 200MPa, 230MPa, 250MPa, 280MPa, 300MPa, 320MPa, 350MPa, 380MPa, 400MPa, 430MPa, 450MPa, 480MPa, 500MPa, 530MPa, 550MPa, 570MPa, 600MPa, 610MPa, 640MPa, 680MPa, 700MPa, 720MPa, 750MPa, 780MPa, 800MPa, 830MPa, 850MPa, 880MPa, 900MPa, 920MPa, 950MPa, 980MPa, 1000MPa.

[0450] In this embodiment, by using a material that satisfies a yield strength Re of 125 MPa ≤ Re ≤ 1000 MPa to manufacture the first casing, the wall thickness of the first casing can be reduced without reducing the strength of the first casing, thereby improving the capacity space of the battery cell.

[0451] Figure 23 shows a schematic diagram of the local structure of the casing 211 according to an embodiment of the present application, which may be, for example, a magnified view of region A' shown in Figure 9. As shown in Figure 23, the casing 211 according to an embodiment of the present application has a multilayer structure, and the material of the outermost casing 2117 of the casing 211 includes at least one of aluminum, aluminum alloy, copper, copper alloy, and chromium.

[0452] As can be understood, the casing 211 according to the embodiment of the present application has a multilayer structure, that is, for any one wall of the casing 211, the multilayer structure is stacked along the thickness direction of the wall in order to make the casing 211 a multilayer structure. Furthermore, the method of mounting between the multilayer structures of the casing 211 can be flexibly installed according to the actual application. For example, first, multiple single-layer casing structures that have different dimensions but are basically the same shape can be obtained by processing, for example, hollow structures in which each single-layer casing structure has an opening, and then the casing structures with relatively larger dimensions among the multiple single-layer casing structures can be fitted sequentially onto the outside of the casing structures with relatively smaller dimensions to combine the multiple single-layer casing structures into a multilayer casing 211. Alternatively, for example, a substantially plate-like structure having a multilayer structure can be obtained by processing, and then multiple such plate-like structures can be spliced ​​together to form a multilayer casing 211 in the same way, but the embodiment of the present application is not limited to these.

[0453] As can be understood, the outermost casing 2117 of the casing 211 according to the embodiment of the present application includes the outermost structure of each wall of the casing 211, that is, the outermost casing 2117 is a single casing structure including the outer surface of the casing 211.

[0454] In the embodiments of the present invention, the material of the outermost casing 2117 of the casing 211 may include at least one of aluminum, aluminum alloy, copper, copper alloy, and chromium. Of these, if the material of the outermost casing 2117 includes aluminum, the aluminum is oxidized to dense aluminum oxide, making corrosion protection possible. If the material of the outermost casing 2117 includes copper, the copper is oxidized to copper oxide, i.e., verdigris, making corrosion protection possible. If the material of the outermost casing 2117 includes chromium, the chromium is oxidized to chromium oxide, also making corrosion protection possible. Therefore, if the material of the outermost casing 2117 is one of the above corrosion-resistant materials, the outermost casing 2117 can protect other casing layers located inside it, improving the structural stability of the casing 211 and extending the service life of the casing 211.

[0455] As can be understood, the specific thickness of the outermost casing 2117 in the embodiments of the present application can be flexibly set according to the actual application. For example, the thickness of the outermost casing 2117 can be set according to a certain ratio depending on the thickness of the casing 211.

[0456] In some embodiments, the average thickness of the outermost casing 2117 is T11, and the average thickness of the casing 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 T10 of the casing 211 is limited, resulting in a very small average thickness T11 of the outermost casing 2117. On the one hand, this increases the difficulty of processing, on the other hand, it reduces the corrosion protection effect of the outermost casing 2117 and further affects the structural reliability of the casing 211. Conversely, if the ratio T11 / T10 is set too large, the average thickness T11 of the outermost casing 2117 becomes very large, while the thickness of the other layers of the casing 211 other than the outermost casing 2117 becomes very small. However, the structural strength of the outermost casing 2117 may be insufficient, and especially after oxidation, if its deformation capacity is relatively low and its average thickness T11 is relatively large, it will affect the overall structural strength of the casing 211 and further reduce the stability of the casing 211.

[0457] Furthermore, T11 and T10 satisfy the condition 0.15 ≤ T11 / T10 ≤ 0.4. By appropriately reducing the maximum value of the ratio T11 / T10 and increasing the minimum value of the ratio T11 / T10, the average thickness T11 of the outermost casing 2117 can be limited to not being too large or too small, thereby improving the corrosion protection effect, as well as improving the structural strength and structural stability of the casing 211.

[0458] Furthermore, in order to further improve the corrosion protection effect and enhance the stability and reliability of the casing 211, T11 and T10 satisfy the condition 0.2 ≤ T11 / T10 ≤ 0.3.

[0459] In some embodiments, the ratio T11 / T10 of the average thickness T11 of the outermost casing 2117 to the average thickness T10 of the casing 211 according to the embodiments of the present application may also be set to other values. For example, the value of the ratio T11 / T10 may be any one of 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, or it may be between any two of these values.

[0460] As can be understood, the range of the average thickness T10 of the casing 211 in the embodiment of the present application can be flexibly set according to the actual application, for example, the average thickness T10 of the casing 211 satisfies 0.05 mm ≤ T10 ≤ 0.5 mm. In order to reduce the difficulty of processing the multilayer casing 211 and improve the structural strength of the casing 211, for example, in order to further improve the service life of the casing 211 without the casing 211 easily rupturing, it is undesirable for the average thickness T10 of the casing 211 to be too small. Conversely, in order to relatively reduce the space occupied by the casing 211, improve the space utilization rate of the battery cells 20, and further improve the energy density of the battery 10 in which multiple battery cells 20 are installed, it is also undesirable for the average thickness T10 of the casing 211 to be too large.

[0461] Furthermore, the average thickness T10 of the casing 211 satisfies the condition 0.075 mm ≤ T10 ≤ 0.4 mm. By appropriately reducing the average thickness T10 of the casing 211, the space occupied by the casing 211 inside the battery 10 can be reduced, thereby further improving the energy density of the battery 10. On the other hand, by appropriately increasing the average thickness T10 of the casing 211, the difficulty of processing the casing 211 can also be reduced.

[0462] Furthermore, the average thickness T10 of the casing 211 satisfies the condition 0.1 mm ≤ T10 ≤ 0.3 mm. By ensuring that the average thickness T10 of the casing 211 is neither too large nor too small, not only can the structural strength and structural stability of the casing 211 be improved, but the space occupied by the casing 211 inside the battery 10 can also be reduced, further improving the energy density of the battery 10.

[0463] In some embodiments, the average thickness T10 of the casing 211 according to the embodiments of the present application may also be set to other values. For example, the average thickness T10 of the casing 211 may be any one of the following values: 0.05 mm, 0.075 mm, 0.1 mm, 0.125 mm, 0.15 mm, 0.175 mm, 0.2 mm, 0.225 mm, 0.25 mm, 0.275 mm, 0.3 mm, 0.325 mm, 0.35 mm, 0.375 mm, 0.4 mm, 0.425 mm, 0.45 mm, 0.475 mm, and 0.5 mm, or it may be between any two of these values.

[0464] As can be understood, the range of the average thickness T11 of the outermost casing 2117 in the embodiments of this application can be flexibly set according to the actual application, for example, T11 satisfies 0.015 mm ≤ T11 ≤ 0.25 mm. It is undesirable for the average thickness T11 of the outermost casing 2117 to be too small in order to reduce the difficulty of processing, improve the corrosion protection effect of the outermost casing 2117, and further improve the structural reliability of the casing 211. Conversely, it is also undesirable for the average thickness T11 of the outermost casing 2117 to be too large, considering that if the deformation capacity of the outermost casing 2117 is relatively low after oxidation and its average thickness T11 is too large, it will affect the deformation capacity of the overall structure of the casing 211 and further reduce the reliability and stability of the casing 211.

[0465] Furthermore, the average thickness T11 of the outermost casing 2117 can further satisfy the condition 0.05 mm ≤ T11 ≤ 0.2 mm. By appropriately improving the minimum value of the average thickness T11 of the outermost casing 2117, the corrosion protection effect of the outermost casing 2117 can be improved. By appropriately decreasing the maximum value of the average thickness T11 of the outermost casing 2117, the deformation capacity of the overall structure of the casing 211 can be improved, further enhancing the reliability and stability of the casing 211.

[0466] Furthermore, the average thickness T11 of the outermost casing 2117 can further satisfy the condition 0.075 mm ≤ T11 ≤ 0.15 mm. This not only improves the corrosion protection effect of the outermost casing 2117, but also improves the deformation capacity of the overall structure of the casing 211, thereby improving the reliability and stability of the casing 211.

[0467] In some embodiments, the average thickness T11 of the outermost casing 2117 according to the embodiments of the present application may also be set to other values. For example, the average thickness T11 of the outermost casing 2117 may be any one 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, or it may be between any two of these values.

[0468] As can be understood, the thickness of the inner casing 2118 of the casing 211 according to the embodiment of the present application can be flexibly set according to the actual application, and the inner casing 2118 is any single layer of casing other than the outermost casing 2117 of the casing 211. Furthermore, the casing 211 may include one or more layers of inner casing 2118, and if the casing 211 includes multiple layers of inner casing 2118, the thicknesses of the multiple layers of inner casing 2118 may be the same to facilitate processing, or they may be different to flexibly adjust the thickness of the inner casing 2118 at different positions according to the actual application. For example, as shown in Figure 23, taking the example that the casing 211 includes a three-layer casing structure, the three-layer casing structure includes the outermost outermost casing 2117 and two inner layers casings 2118 located inside, the two inner layers casings 2118 including the innermost casing 2118b and the intermediate casing 2118a. The average thickness of the innermost casing 2118b and the average thickness of the intermediate casing 2118a may be the same or different. For example, both the average thickness of the innermost casing 2118b and the average thickness of the intermediate casing 2118a may be set to T12, and the value of T12 may be set according to the application, for example, T12 may be greater than, less than, or equal to T11, but the embodiments of the present application are not limited to these.

[0469] As can be understood, the average thickness T10 of the casing 211 in the embodiments of the present application may refer to the average thickness of at least a portion of the casing 211. The average thickness T11 of the outermost casing 2117 of the casing 211 may also refer to the average thickness of at least a portion of the outermost casing 2117. The average thickness T12 of the inner casing 2118 of the casing 211 may also refer to the average thickness of at least a portion of the inner casing 2118. Furthermore, the calculation domain for the average thickness T10 of the casing 211 usually coincides with the calculation domain for the average thickness T11 of the outermost casing 2117 and also coincides with the calculation domain for the average thickness T12 of the inner casing 2118. For example, when calculating the average thickness T10 of the casing 211, if a certain area is excluded from the calculation, then correspondingly, the calculation of the average thickness T11 of the outermost casing 2117 must also exclude the same area, and the calculation of the average thickness T12 of the inner casing 2118 must also exclude the same area. For the sake of explanation, the calculation of the average thickness T10 of the casing 211 will be used as an example below, but the relevant explanations apply similarly to determining the average thickness T11 of the outermost casing 2117 and the average thickness T12 of the inner casing 2118, and those explanations will be omitted here.

[0470] For example, the average thickness T10 of the casing 211 may refer to the average thickness T10 of all areas of the casing 211, and in particular, if the entire surface of the casing 211 is relatively flat, that is, if the thickness of most areas of the casing 211 is basically equal or the difference is relatively small, or if the thickness of all areas of the casing 211 is basically equal or the difference is relatively small, then the average thickness of all areas of the casing 211 can be determined as T10.

[0471] Furthermore, for example, the average thickness T10 of the casing 211 may also refer to the average thickness T10 of a localized area of ​​the casing 211, that is, the average thickness T10 of the remaining area after excluding a portion of the casing 211. For example, if a specific area exists in the casing 211, and the thickness of that specific area differs relatively significantly from that of other areas, for example, if a protruding structure or recessed area exists in that specific area along the thickness direction, and the thickness of that specific area is greater or smaller than that of other areas, then the average thickness of the remaining area of ​​the casing 211 can be calculated as T10 by excluding that specific area.

[0472] In some embodiments, the casing 211 may include a functional region, and the average thickness T10 of the casing 211 is the average thickness of the region of the casing 211 other than the functional region, for example, the functional region includes at least one of a pressure release region, a region where electrode terminals 214 are located, a fluid injection region, and a welding region. The difference between the thickness of the functional region and the thickness of the other regions of the casing 211 is usually relatively large, and therefore, if the average thickness T10 of the casing 211 is calculated so as not to include the functional region, the design of the casing 211 can better meet the strength needs, thereby improving the structural strength and stability of the battery cell 20.

[0473] To ensure clarity, the functional area in the embodiment of the present application may include an area in the casing 211 where a specific structure is installed or which has a specific purpose, and is applicable to the “functional area” described above, and for brevity, its description is omitted here. For example, the functional area may include a pressure relief area for installing a pressure relief mechanism. The pressure relief mechanism in the embodiment of the present application may be installed on any one wall of the battery cell 20, for example, the pressure relief mechanism may be installed in the pressure relief area of ​​the casing 211 of the battery cell 20. The pressure relief mechanism may be part of the casing 211, or it may be a separate structure from the casing 211, and may be fixed to the casing 211, for example, by welding. For example, if the pressure release mechanism is part of the casing 211, the pressure release mechanism may be formed by installing a notch in the casing 211, i.e., the casing 211 has a notch installed in the pressure release region, and the thickness of the notched area is clearly smaller than the thickness of other areas of the casing 211, so the average thickness T10 of the casing 211 does not need to be calculated from the thickness of the notched area. The notched area is the most vulnerable location of the pressure release mechanism. When the internal pressure rises to a threshold due to too much gas generated from the battery cell 20, or when the internal temperature of the battery cell 20 rises to a threshold due to heat generated in the internal reaction of the battery cell 20, the pressure release mechanism ruptures at the notch, creating communication between the inside and outside of the battery elevator 20, releasing the gas pressure and temperature to the outside through the rupture of the pressure release mechanism, and further preventing the explosion of the battery cell 20.

[0474] For example, the pressure relief mechanism may be a separate structure from the casing 211, and 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 may specifically employ a pressure-sensitive or temperature-sensitive element or structure. For example, the casing 211 may have a communication hole in the pressure relief region, and the pressure relief mechanism may be attached and fixed to the casing 211 via the communication hole, and the attached pressure relief mechanism may protrude or recess relative to other areas of the casing 211, so that the calculation of the average thickness T10 of the casing 211 does not have to include the pressure relief region where the pressure relief mechanism is located. When the internal pressure or temperature of the battery cell 20 reaches a predetermined threshold, the pressure relief mechanism is activated, or a vulnerable structure provided within the pressure relief mechanism is destroyed, thereby forming an opening or passage for releasing the internal pressure or temperature.

[0475] In some embodiments, the functional region may further include the region in which the electrode terminals 214 are located. Each electrode terminal 214 in the embodiments of the present application may be installed on any one wall, and multiple electrode terminals 214 may be installed on the same wall or different walls of the battery cell 20. For example, as shown in Figures 3 and 4, if each battery cell 20 includes two electrode terminals 214 located on the same wall, then, for example, both electrode terminals 214 may be located on the cover plate 212.

[0476] For example, if each battery cell 20 includes two electrode terminals 214 located on the same wall, then, unlike what is shown in Figures 3 and 4, the two electrode terminals 214 may be located on any one wall of the casing 211, for example, both electrode terminals 214 may be located on the wall with the smallest area of ​​the casing 211. When one or more electrode terminals 214 are located on the casing 211, each electrode terminal 214 usually protrudes into other areas of the casing 211, i.e., the thickness of the area where the electrode terminal 214 is located is much greater than the thickness of other areas of the casing 211. Therefore, the calculation of the average thickness T10 of the casing 211 does not need to include the area where all electrode terminals 214 are located.

[0477] In some embodiments, the functional region may further include an electrolyte injection region. For example, an electrolyte injection hole may be provided in the electrolyte injection region of the casing 211, and the electrolyte is injected into the interior of the casing 211 through the electrolyte injection hole. After the electrolyte injection is complete, the electrolyte injection hole may be sealed with a sealing member. Considering that the thickness of the electrolyte injection region where the sealing member is located is usually much greater than the thickness of other regions of the casing 211, the calculation of the average thickness T10 of the casing 211 does not need to include the electrolyte injection region.

[0478] In some embodiments, the functional area may further include a welded area. For example, the casing 211 and the cover plate 212 may be fixed together by welding, or the casing 211 itself may include a welded area if it is necessary to process and form the casing 211 by welding, for example, if any two walls of the casing 211 are welded together, or if the casing 211 is formed by splicing at least two parts together. For example, the casing 211 may be welded by splicing, and the casing 211 may have a welded seam 2113. Specifically, the casing 211 may include at least two parts, which are joined by welding to form the casing 211, and in the embodiments of the present application, taking as an example that the casing 211 mainly includes two parts along the height direction Z of the battery cell 20, there is a welded seam 2113 between the upper half casing and the lower half casing, or, contrary to what is shown in Figure 4, the welded seam 2113 may be located in other parts of the casing 211, and the embodiments of the present application are not limited to these. The welded area of ​​the functional area according to the embodiments of the present application may further include the welded seam 2113. Due to the manufacturing process, the thickness of the welded area is usually greater than the thickness of other areas of the casing 211, and therefore the calculation of the average thickness T10 of the casing 211 does not need to include the welded area.

[0479] As can be understood, in order to further improve the structural strength and reliability of the casing 211, the inner casing 2118 of the casing 211 can be installed according to the actual application. In some embodiments, the tensile strength of the inner casing 2118 of the casing 211 at 25°C is Rm1, and Rm1 satisfies 250MPa ≤ Rm1 ≤ 2000MPa. Increasing the tensile strength Rm1 of the inner casing 2118 of the casing 211 at room temperature (25°C) improves the overall structural strength and stability of the casing 211. However, it is also undesirable for the tensile strength Rm1 of the inner casing 2118 at room temperature to be too high in order to reduce the difficulty of selecting the material for the inner casing 2118 and to reduce the difficulty and cost of processing the battery cell 20.

[0480] As can be understood, the range of values ​​for the tensile strength Rm1 of the inner casing 2118 at room temperature conditions of 25°C according to the embodiment of the present application can be adjusted according to the actual application. For example, the value of the tensile strength Rm1 at room temperature can further satisfy 400 MPa ≤ Rm1 ≤ 1200 MPa. On the one hand, by increasing the tensile strength Rm1 of the inner casing 2118 at room temperature conditions, the deformation capacity of the inner casing 2118 can be improved to resist the expansion of the electrode assembly 22, and the inner casing 2118 will not easily break, further improving the structural stability and service life of the casing 211 and the battery cell 20. On the other hand, by controlling the tensile strength Rm1 of the inner casing 2118 at room temperature conditions so that it is not too large, the difficulty of material selection and processing of the inner casing 2118 can be reduced, costs can be saved, and processing can be made easier.

[0481] Furthermore, the inner casing 2118 may be installed such that its tensile strength Rm1 at room temperature satisfies 450 MPa ≤ Rm1 ≤ 800 MPa. By ensuring that the tensile strength Rm1 of the inner casing 2118 at room temperature is neither too high nor too low, the deformation capacity of the inner casing 2118 can be improved to resist the expansion of the electrode assembly 22, and this can be easily implemented while saving costs.

[0482] In some embodiments, the value of the tensile strength Rm1 of the inner casing 2118 according to the embodiments of the present application at room temperature may also be set to other values. For example, the values ​​of the tensile strength Rm1 at room temperature may be 250 MPa, 280 MPa, 300 MPa, 330 MPa, 350 MPa, 380 MPa, 400 MPa, 450 MPa, 500 MPa, 550 MPa, 600 MPa, 650 MPa, 700 MPa, 750 MPa, 800 MPa, 850 MPa, 900 MPa, 950 MPa, 1000 MPa, 1050 MPa, 1100 MPa, 1150 MPa The value may be any one of the following numbers: MPa, 1200MPa, 1250MPa, 1300MPa, 1350MPa, 1400MPa, 1450MPa, 1500MPa, 1550MPa, 1600MPa, 1650MPa, 1700MPa, 1750MPa, 1800MPa, 1850MPa, 1900MPa, 1950MPa, and 2000MPa, or it may be any two of these numbers.

[0483] To be understood, the tensile strength in the embodiments of this application refers to the maximum stress value that the material experiences before fracture. The test method for the tensile strength Rm1 of the inner casing 2118 at a temperature of 25°C in the embodiments of this application can be selected according to the actual application. For example, the tensile strength Rm1 can be measured at room temperature conditions of 25°C by adopting the national standard GB / T 228.1-2010.

[0484] The above explanation mainly uses a rectangular battery cell 20 as an example. Below, the explanation will use a cylindrical battery cell 20 as an example, as shown in the drawings. The cylindrical battery cell 20 according to the embodiment of this application and the rectangular battery cell 20 described above are mutually applicable except for their shapes, and the explanation of these differences will be omitted here.

[0485] Figure 24 shows a schematic diagram of the structure of a battery cell 20 according to one embodiment of the present application. For example, the battery cell 20 shown in Figure 3 may be any one of the battery cells 20 in the battery 10. Figure 25 shows a schematic diagram of the partially disassembled structure of a battery cell 20 according to one embodiment of the present application. For example, Figure 25 may be a schematic diagram of the partially disassembled structure of the battery cell 20 shown in Figure 24. Figure 26 shows a schematic cross-sectional view of the casing 211 of a battery cell 20 according to one embodiment of the present application. For example, Figure 26 may be a cross-sectional view of the casing 211 of the battery cell 20 shown in Figures 24 and 25, and the cross-section is a cross-section of the casing 211.

[0486] In the embodiment of the present application, as shown in Figures 24 to 26, the battery cell 20 includes an electrode assembly 22 including a first tab 2221, a first electrode terminal 214a, and a casing 211 including a cylindrical body 211b and a cover 211a connected to the cylindrical body 211b, wherein the cylindrical body 211b is installed surrounding the outer circumference of the electrode assembly 22, the cover 211a includes the first electrode terminal 214a, the first tab 2221 is electrically connected to the first electrode terminal 214a by the cylindrical body 211b, and the casing 211 has a multilayer structure with different resistivity.

[0487] The casing 211 may have various shapes, such as a cylinder, a rectangular parallelepiped, or other polyhedron. For illustrative purposes, as shown in Figures 24 to 26, the casing 211 is described here as a hollow cylindrical structure. Furthermore, in the embodiments of this application, if the casing 211 is a hollow structure with an opening at one end, the cover plate 212 is a corresponding circular plate structure that matches the casing 211. In the case of a cylindrical casing 211, the cylindrical body 211b is a cylinder, and the lid 211a is a circular plate structure.

[0488] The electrode assembly 22 according to the embodiment of the present application may include a first tab 2221, which may be electrically connected to the first electrode terminal 214a by the cylindrical body 211b of the casing 211, thereby simplifying the structure of the battery cell 20. By arranging the casing 211 in a multilayer structure with different resistivity, the current passability of the battery cell 20 can be improved by a single layer structure having a relatively low resistivity, while the structural strength of the casing 211 can be improved by a single layer structure having a relatively high resistivity. This not only improves the performance of the battery cell 20 but also improves the structural strength of the battery cell 20, further extending its service life.

[0489] In the embodiment of the present application, the electrode assembly 22 further includes a second tab 2222, the polarity of the second tab 2222 and the first tab 2221 being opposite. Specifically, in terms of external appearance, the electrode assembly 22 includes a main body 221 and a tab 222 protruding from the main body 221, the tab 2221 including the first tab 2221 and the second tab 2222. The first tab 2221 is the portion of the first electrode piece that is not coated with the active material layer, and the second tab 2222 is the portion of the second electrode piece that is not coated with the active material layer. The first tab 2221 and the second tab 2222 are used to draw current from within the main body 221.

[0490] The first tab 2221 and the second tab 2222 may extend from the same side of the main body 221, i.e., the first tab 2221 and the second tab may be located on the same end face of the electrode assembly 22. Alternatively, the first tab 2221 and the second tab 2222 may extend from different sides of the main body 221, i.e., the first tab 2221 and the second tab may be located on different end faces of the electrode assembly 22. For example, to facilitate machining, the first tab 2221 and the second tab 2222 may extend from opposite sides, i.e., the first tab 2221 and the second tab 2222 may be located on opposing end faces of the electrode assembly 22. As shown in Figures 24 to 26, the first tab 2221 and the second tab 2222 may be provided on both sides of the main body 221 along the first direction Z, in other words, the first tab 2221 and the second tab 2222 may be provided at both ends of the electrode assembly 22 along the first direction Z. Of these, the first direction Z may be the height direction Z of the electrode assembly 22.

[0491] As can be understood, the electrode assembly 22 includes a first electrode piece, a second electrode piece, and a separator for separating the first electrode piece and the second electrode piece. The polarities of the first and second electrode pieces are opposite; in other words, one of the first and second electrode pieces is the positive electrode piece 223, and the other of the first and second electrode pieces is the negative electrode piece 224.

[0492] The first pole piece, the second pole piece, and the separator are all strip-shaped structures, and the first pole piece, the second pole piece, and the separator are wound together to form a wound structure. The wound structure may be cylindrical, flattened, or of other shapes.

[0493] Selectively, 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 is complete, the first tab 2221 is substantially columnar, with slits remaining between two adjacent tab layers. Embodiments of the present application can reduce the slits between the tab layers by processing the first tab 2221, which facilitates connection between the first tab 2221 and other conductive structures. For example, embodiments of the present application can perform a kneading treatment on the first tab 2221, thereby converging and gathering the end region of the first tab 2221 away from the main body 221. The kneading treatment forms a dense end face at one end of the first tab 2221 away from the main body 221, reducing the slits between the tab layers and facilitating connection between the first tab 2221 and other conductive structures. Alternatively, embodiments of the present invention may fill the space between two adjacent tab layers with conductive material to reduce the slit between the tab layers.

[0494] Selectively, the second tab 2222 is wound multiple times around the central axis of the electrode assembly 22, and the second tab 2222 includes multiple tab layers. Exemplarily, the second tab 2222 is also kneaded to reduce the slits between the tab layers of the second tab 2222.

[0495] In the embodiment of the present application, the battery cell 20 further includes a second electrode terminal 214b electrically connected to the second tab 2222, and the first electrode terminal 214a and the second electrode terminal 214b are located on the same wall of the battery cell 20, thereby improving the integration density of the battery cell 20, improving the space utilization rate of the battery cell 20 within the battery 10, and facilitating processing and assembly.

[0496] As can be understood, the cover 211a in the embodiment of the present application includes a first electrode terminal 214a, for example, the first electrode terminal 214a may be installed on the cover 211a, or the cover 211a may be the first electrode terminal 214a directly.

[0497] In some embodiments, the cover 211a is the first electrode terminal 214a, the cover 211a is provided with an electrode lead-out hole 211c, and the second electrode terminal 214b is installed insulated from the cover 211a and attached to the electrode lead-out hole 211c, with one of the cover 211a and the second electrode terminal 214b being the positive output electrode of the battery cell and the other being the negative output electrode of the battery cell. By making at least a portion of the casing 211 itself one output electrode of the battery cell 20, one conventional electrode terminal can be omitted, and the structure of the battery cell 20 can be simplified. When assembling multiple battery cells 20 into a set, the casing 211 can be electrically connected to a bus member, which not only increases the current passage area but also allows for greater flexibility in the structural design of the bus member.

[0498] For the sake of explanation, the following examples will mainly use the cover 211a as the first electrode terminal 214a, but the embodiments of this application are not limited to this.

[0499] Figure 27 is a schematic local cross-sectional view of a battery 10 provided in some embodiments of the present application, which may include a plurality of battery cells 20. Figure 28 is another schematic local cross-sectional view of a battery 10 provided in some embodiments of the present application, which may be, for example, an enlarged schematic view of region B' of the battery 10 shown in Figure 27.

[0500] As shown in Figures 24 to 28, the cover 211a is provided with an electrode lead-out hole 211c, and at least a portion of the cover 211a is used to electrically connect to the first connecting component 81 and the first tab 2221 of the battery 10, and the second electrode terminal 214b is used to electrically connect to the second connecting component 82 and the second tab 2222 of the battery 10, and the second electrode terminal 214b is installed insulated from the cover 211a and attached to the electrode lead-out hole 211c, and one of the cover 211a and the second electrode terminal 214b is the positive output electrode of the battery cell 20 and the other is the negative output electrode of the battery cell 20.

[0501] The lid 211a is electrically connected to the cylinder 211b, and the lid 211a and the cylinder 211b may have the same polarity.

[0502] As can be understood, the lid 211a and the cylinder 211b in the embodiments of the present application may be integrally molded, that is, the casing 211 is an integrally molded part. In this way, the process of connecting the lid 211a and the cylinder 211b can be omitted. For example, the casing 211 may be formed by a tensile process. Of course, the lid 211a and the cylinder 211b may be two separate parts that are then connected by welding, riveting, bonding, etc. The embodiments of the present application mainly take the example of the lid 211a and the cylinder 211b being integrally molded.

[0503] The casing 211 according to the embodiment of the present application may be a hollow structure with an opening at one end. Specifically, it has an opening 211d at one end of the cylindrical body 211b that is separated from the lid 211a. The battery cell 20 further includes a cover plate 212 that covers the opening 211d of the cylindrical body 211b in order to seal the opening 211d of the cylindrical body 211b. The cover plate 212 may have various structures; for example, the cover plate 212 may have a plate-like structure.

[0504] In some embodiments, an electrode extraction hole 211c is provided in the lid 211a, and the area of ​​the lid 211a other than the electrode extraction hole 211c includes an area for welding to the first connecting component 81, that is, the lid 211a may be welded to the first connecting component 81 to form a first welded portion W1. Exemplarily, during welding, the laser acts on the surface of the first connecting component 81 that is separated from the lid 211a, and the laser melts and connects a part of the first connecting component 81 and a part of the lid 211a, forming a first welded portion W1.

[0505] The electrode extraction holes 211c penetrate the cover 211a, facilitating the discharge of electrical energy within the electrode assembly 22 to the outside of the casing 211. Exemplarily, the electrode extraction holes 211c penetrate the cover 211a along a first direction Z.

[0506] The electrode lead-out holes 211c in the embodiment of the present application are manufactured after the casing 211 has been tensile-formed. For example, in this embodiment, the positive and negative output electrodes are positioned at one end of the battery cell 20 away from the opening of the casing 211 by forming the electrode lead-out holes 211c in the lid 211a using a perforation process for attaching the second electrode terminal 214b. The lid 211a is formed during the molding process of the casing 211 and ensures flatness even after the electrode lead-out holes 211c are opened, thereby ensuring the connection strength between the lid 211a and the first connecting component 81. At the same time, since the flatness of the lid 211a is not limited by its own dimensions, the lid 211a can have relatively large dimensions, thereby improving the current passability of the battery cell 20.

[0507] In some embodiments, the cylindrical body 211b is cylindrical, the electrode extraction hole 211c is a circular hole, and the central axis of the cylindrical body 211b and the central axis of the electrode extraction hole 211c are set to overlap. "Set to overlap" does not require that the central axis of the cylindrical body 211b and the central axis of the electrode extraction hole 211c absolutely and perfectly overlap, and there may be a process-acceptable deviation.

[0508] The electrode extraction hole 211c may be used to limit the position of the second electrode terminal 214b. In this embodiment, by aligning the central axis of the electrode extraction hole 211c with the central axis of the cylindrical body 211b, at least a portion of the second electrode terminal 214b can be positioned at the center of the cover 211a. In this way, when assembling multiple battery cells 20 into a set, the requirements for positional accuracy of the second electrode terminal 214b can be reduced, the assembly process can be simplified, and assembly efficiency can be improved.

[0509] 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 may pass through the electrode extraction hole 211c, or it may be offset from the electrode extraction hole 211c, and this embodiment is not limited to these.

[0510] The first tab 2221 is electrically connected to the lid 211a. The first tab 2221 may be directly electrically connected to the lid 211a, or it may be indirectly electrically connected to the lid 211a by another conductive structure. For example, the first tab 2221 may be electrically connected to the lid 211a by the cylinder 211b.

[0511] The second tab 2222 is electrically connected to the second electrode terminal 214b. The second tab 2222 may be directly electrically connected to the second electrode terminal 214b, or it may be indirectly electrically connected to the second electrode terminal 214b by other conductive structures. For example, the second tab 2222 may be electrically connected to the second electrode terminal 214b by the current collector component 23.

[0512] The second electrode terminal 214b is installed insulated from the cover 211a, and therefore the second electrode terminal 214b and the cover 211a may have different polarities, and the second electrode terminal 214b and the cover 211a may be different output poles.

[0513] The second electrode terminal 214b is fixed to the cover 211a. The second electrode terminal 214b may be fixed entirely to the outside of the cover 211a, or it may extend into the interior of the casing 211 through the electrode lead-out hole 211c.

[0514] When the first tab 2221 is the negative electrode tab and the second tab 2222 is the positive electrode tab, the cover 211a is the negative output electrode of the battery cell 20, while the second electrode terminal 214b is the positive output electrode of the battery cell 20. When the first tab 2221 is the positive electrode tab and the second tab 2222 is the negative electrode tab, the cover 211a is the positive output electrode of the battery cell 20, while the second electrode terminal 214b is the negative output electrode of the battery cell 20.

[0515] In the battery 10, a plurality of battery cells 20 are electrically connected by a bus member. The bus member includes a first connecting component 81 for connecting to the cover 211a of the battery cell 20 and a second connecting component 82 for connecting to the second electrode terminal 214b of the battery cell 20.

[0516] The first connecting component 81 can be connected to the cover 211a by welding, bonding, or other means to achieve an electrical connection between the first connecting component 81 and the cover 211a. The second connecting component 82 can be connected to the second electrode terminal 214b by welding, bonding, riveting, or other means to achieve an electrical connection between the second connecting component 82 and the second electrode terminal 214b.

[0517] For example, the first connecting component 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 component 82 connects the second electrode terminal 214b of the first battery cell 20 to the cover 211a of the other battery cell 20, so that the first connecting component 81 and the second connecting component 82 connect the three battery cells 20 in series.

[0518] In this embodiment, by using the cover 211a and the second electrode terminal 214b as output electrodes, the structure of the battery cell 20 can be simplified while ensuring the current passing capability 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, and in this way the first connecting component 81 and the second connecting component 82 are assembled on the same side of the battery cell 20, thus simplifying the assembly process and improving the efficiency of assembling multiple battery cells 20 into sets.

[0519] As can be understood, as shown in Figures 24 to 28, the second electrode terminal 214b according to the embodiment of the present application includes a terminal body 2141. Furthermore, the terminal body 2141 may 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 hole 211c, and both ends of the terminal body 2141 are riveted to the electrode lead hole 211c.

[0520] In some embodiments, the terminal body 2141 may be provided with a recess extending in the direction toward the electrode assembly 22 from the outer surface of the terminal body 2141. The bottom of the recess is used for welding to the current collector component 23.

[0521] The electrode assembly 22 and the current collector component 23 are mounted inside the casing 211 through the opening 211d of the cylindrical body 211b, and after the current collector component 23 is brought into contact with the cover 211a, an external welding device can weld the bottom of the recess to the current collector component 23 from the side away from the current collector component 23 at the bottom of the recess.

[0522] In this embodiment, the thickness of the terminal body 2141 is reduced by providing a recess, thereby reducing the welding power required to weld the bottom of the recess to the current collector component 23, reducing the heat generated, and thus reducing the risk of other components (for example, the first insulating component 61 and the second insulating component 60) being burned.

[0523] In some embodiments, the second electrode terminal 214b further includes a seal plate 2142 for sealing the opening of the recess. The seal plate 2142 may be located entirely outside the recess, or a portion thereof may be housed inside the recess, as long as it can seal the opening of the recess. The seal plate 2142 can protect the recess from the outside, reduce external impurities entering the recess, reduce the risk of the bottom of the recess being damaged by external impurities, and improve the sealing performance of the battery cell 20.

[0524] In some embodiments, the seal plate 2142 is used to weld to the second connecting component 82 to form a second weld W2. The second weld W2 can reduce the contact resistance between the seal plate 2142 and the second connecting component 82 and improve the current transmission capability.

[0525] In some embodiments, at least a portion of the seal plate 2142 protrudes from the outer surface of the terminal body 2141. When it is necessary to weld the second connector 82 to the seal plate 2142, the second connector 82 is first bonded to the upper surface of the seal plate 2142 (i.e., the surface away from the recess of the seal plate 2142), and then the second connector 82 and the seal plate 2142 are welded together. At least a portion of the seal plate 2142 protrudes from the outer surface of the terminal body 2141, thereby preventing the outer surface of the terminal body 2141 from interfering with the bonding of the seal plate 2142 to the second connector 82, and ensuring a tight bond between the second connector 82 and the seal plate 2142.

[0526] In embodiments of the present invention, the battery cell 20 further includes a first insulating component 61 for insulating at least a portion of the second electrode terminal 214b from the cover 211a. Exemplarily, at least a portion of the first insulating component 61 is sandwiched between the cover 211a and the second electrode terminal 214b, thereby insulating the cover 211a from the second electrode terminal 214b and reducing the risk of short circuits.

[0527] In the embodiment of the present invention, the battery cell 20 further includes a second insulating component 60 located between the cover 211a and the electrode assembly 22. Specifically, the second insulating component 60 separates the electrode assembly 22 from the cover 211a, reducing the risk of the electrode assembly 22 coming into contact with the cover 211a and becoming electrically conductive during vibration of the battery cell 20, thereby improving safety performance.

[0528] In some embodiments, at least one of the first insulating component 61 and the second insulating component 60 may be used to seal the electrode lead hole 211c. In some other embodiments, the battery cell 20 further includes a seal ring 62 which is fitted onto the second electrode terminal 214b and used to seal the electrode lead hole 211c. Selectively, a portion of the seal ring 62 extends into the electrode lead hole 211c to separate the hole wall of the electrode lead hole 211c from the second electrode terminal 214b.

[0529] In some embodiments, the second tab 2222 is provided at one end of the electrode assembly 22 facing the cover 211a, and the first tab 2221 is provided 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 to the cover 211a so that the first tab 2221 is electrically connected to the cover 211a.

[0530] The cylindrical body 211b may be electrically connected directly to the first tab 2221, or it may be electrically connected to the first tab 2221 by other components. For example, the first tab 2221 may be electrically connected to the cylindrical body 211b by the cover plate 212.

[0531] In the embo...

Claims

1. It is a battery cell, An electrode assembly comprising a negative electrode piece, the negative electrode piece comprising a negative electrode active material capable of reversibly desorbing and inserting metal ions, the negative electrode active material comprising a silicon-based material, and A casing used to house the electrode assembly, wherein the tensile strength of at least a portion of the casing at a temperature of 25°C is Rm, and Rm satisfies 250 MPa ≤ Rm ≤ 2000 MPa, characterized in that it includes Battery cell.

2. In the aforementioned negative electrode active material, the mass percentage of the silicon-based material is g, the material in at least a portion of the casing contains iron, and Rm and g satisfy 2% < g < 40% and 300 MPa < Rm < 2000 MPa. The battery cell according to claim 1.

3. The material of at least a portion of the casing is carbon steel or stainless steel, and Rm and g are 2.5% ≤ g ≤ 15%, and the pressure satisfies 315 MPa ≤ Rm < 800 MPa. The battery cell according to claim 2.

4. The material of at least a portion of the casing is carbon steel or stainless steel, and Rm and g are 4.5% ≤ g ≤ 40%, and the pressure is 380 MPa ≤ Rm < 2000 MPa. The battery cell according to claim 2.

5. Rm and g are characterized by satisfying the conditions 8% ≤ g ≤ 40% and 400 MPa ≤ Rm < 2000 MPa. The battery cell according to claim 4.

6. Rm and g are characterized by satisfying the conditions 10% ≤ g ≤ 40% and 480 MPa ≤ Rm < 2000 MPa. The battery cell according to claim 5.

7. Rm and g are characterized by satisfying the conditions 15% ≤ g ≤ 40% and 520 MPa ≤ Rm < 2000 MPa. The battery cell according to claim 6.

8. Rm and g are characterized by satisfying 20% ​​≤ g ≤ 40% and 600 MPa ≤ Rm < 2000 MPa. The battery cell according to claim 7.

9. The silicon-based material is characterized by comprising at least one of elemental silicon, silicon oxygen compounds, silicon carbon composites, silicon nitrogen composites, silicon-containing alloys, or silicon oxygen carbon composite materials. A battery cell according to any one of claims 1 to 8.

10. The casing includes a welded seam, and at least a portion of the casing includes an area within a predetermined distance from the casing to the welded seam, wherein the predetermined distance is L, and L = 10 mm. A battery cell according to any one of claims 1 to 9.

11. At least a portion of the casing is characterized in that it includes all of the walls of the casing. A battery cell according to any one of claims 1 to 10.

12. The casing is characterized by having a cylindrical or polygonal prism shape. A battery cell according to any one of claims 1 to 11.

13. The yield strength of at least a portion of the casing at a temperature of 25°C is Re, and Re satisfies the condition 140 MPa ≤ Re ≤ 1000 MPa. A battery cell according to any one of claims 1 to 12.

14. The electrode assembly further comprises a positive electrode piece, the positive electrode piece comprising a positive electrode active material capable of reversibly desorbing and inserting metal ions, the positive electrode active material comprising a nickel element-containing compound, The melting point of at least a portion of the casing is p, and p satisfies the condition 1200°C ≤ p ≤ 2000°C. A battery cell according to any one of claims 1 to 13.

15. The electrode assembly further comprises a positive electrode piece, the positive electrode piece comprising a positive electrode active material capable of reversibly desorbing and inserting metal ions, the positive electrode active material comprising a nickel element-containing compound, The tensile strength of at least a portion of the casing at a temperature of 500°C is Rn, and Rn is characterized in that 100 MPa ≤ Rn ≤ 1200 MPa. A battery cell according to any one of claims 1 to 14.

16. The casing comprises at least a portion of a third casing wall, the average thickness of the third casing wall being T, and T satisfying the following conditions: 0.05 mm ≤ T ≤ 0.5 mm and 60 mm MPa ≤ T × Rm ≤ 500 mm MPa. A battery cell according to any one of claims 1 to 15.

17. The capacity of the aforementioned battery cell is C, and C is characterized in that 25Ah ≤ C ≤ 550Ah. A battery cell according to any one of claims 1 to 16.

18. The casing has an opening, and the casing includes a first casing wall and at least two second casing walls installed opposite the opening, the first casing walls and the second casing walls are installed intersecting each other, The present invention is characterized in that there is a transition region between two adjacent second casing walls in at least two second casing walls, and the maximum thickness T1 of the transition region and the maximum thickness T0 of the second casing wall with the maximum thickness among the two second casing walls satisfy T1 > T0. A battery cell according to any one of claims 1 to 17.

19. The casing is a one-piece molded structure, has an opening, includes a first casing wall and at least two second casing walls positioned opposite the opening, the first and second casing walls are positioned intersecting, two of the at least two second casing walls are connected by a first fillet, and the distance between the depth H of the casing and the inner diameter R1 of the first fillet satisfies 2.5 mm ≤ R1 ≤ 20 mm and 50 mm < H ≤ 250 mm. A battery cell according to any one of claims 1 to 18.

20. The casing is a one-piece molded structure, has an opening, includes a first casing wall and at least two second casing walls positioned opposite the opening, the first and second casing walls are positioned intersecting, two of the at least two second casing walls are connected by a first fillet, and the yield strength Re of the casing at a temperature of 25°C satisfies the following conditions: 140 MPa ≤ Re ≤ 1000 MPa and 2.5 mm ≤ R1 ≤ 20 mm. A battery cell according to any one of claims 1 to 19.

21. The casing has an opening, and the casing includes a first casing wall and at least one second casing wall installed opposite the opening, the first casing wall and the second casing wall are installed intersecting, the first casing wall and the second casing wall are connected by a second fillet, and the relationship between the inner diameter r1 of the second fillet and the minimum thickness T2 of the second casing wall, which is the minimum thickness of the at least one second casing wall, is such that 2.0 ≤ r1 / T2 ≤ 30. A battery cell according to any one of claims 1 to 20.

22. The aforementioned casing is A first casing portion includes an opening formed therein, a first wall facing the opening, and a second wall connected to the first wall, the first wall being integrally molded with the second wall, The present invention includes a second casing portion fixedly connected to the second wall, In the depth direction of the first casing portion, at least a portion of the casing is jointly formed by the first casing portion and the second casing portion. A battery cell according to any one of claims 1 to 21.

23. The battery cell is used in a battery, and the electrode assembly includes a first tab and a second tab with opposite polarity. The casing includes a cylindrical body and a lid connected to the cylindrical body, the lid and the cylindrical body being integrally formed, the cylindrical body being installed surrounding the outer circumference of the electrode assembly, the lid being provided with electrode extraction holes, and at least a portion of the lid being used to electrically connect the first connecting component of the battery to the first tab. The aforementioned battery cell is A second electrode terminal used to electrically connect a second connecting component of the battery to the second tab, wherein the second electrode terminal is installed insulated from the cover and attached to the electrode lead hole, and one of the cover and the second electrode terminal is the positive output electrode of the battery cell and the other is the negative output electrode of the battery cell, further comprising the second electrode terminal. A battery cell according to any one of claims 1 to 22.

24. The second tab is provided at one end of the electrode assembly facing the cover, and the first tab is provided at the other end of the electrode assembly away from the cover. The cylindrical body is used to connect the first tab and the lid, thereby electrically connecting the first tab to the lid. The battery cell according to claim 23.

25. The electrode assembly includes a first tab, the casing includes a cylindrical body positioned to surround the outer circumference of the electrode assembly, and a lid connected to the cylindrical body and including a first electrode terminal, the first tab is electrically connected to the first electrode terminal via the cylindrical body, and the casing is characterized by having a multilayer structure with different resistivity. A battery cell according to any one of claims 1 to 24.

26. The casing has a multilayer structure, and the material of the outermost casing of the casing is characterized by containing at least one of aluminum, aluminum alloy, copper, copper alloy, and chromium. A battery cell according to any one of claims 1 to 25.

27. It is a battery, The invention comprises a plurality of battery cells, wherein each battery cell is a battery cell according to any one of claims 1 to 26. battery.

28. Electrical equipment, The invention is characterized by including a battery, which includes a battery cell according to any one of claims 1 to 26, used to supply power to the aforementioned electrical equipment. Electrical equipment.

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