Cases, battery cells, batteries and electrical devices

Abstract

Embodiments of this application provide a case, a battery cell, a battery, and an electrical device. The case has an opening and is a one-piece molded structure, including a first wall and at least two second walls facing the opening, the first and second walls intersecting, two of the at least two second walls being connected by a first fillet, the inner diameter of the first fillet being R1, and the yield strength of the case at a temperature of 25°C being Re, where Re and R1 satisfy 140MPa ≤ Re ≤ 1000MPa and 2.5mm ≤ R1 ≤ 20mm. The case, battery cell, battery, and electrical device according to embodiments of this application can reduce the problem of wrinkles and cracks occurring in the case due to material deposition at the fillet during the one-piece molding of the case.

Description

[Technical Field]

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

[0002] Typically, the casing of a battery cell significantly impacts the performance of the battery cell itself. Therefore, improving the performance of battery cells through casing modifications has been a long-standing research topic. [Overview of the Initiative]

[0003] In view of this, the embodiments of this application provide a case, a battery cell, a battery, and an electrical device, which can reduce the problem of wrinkles and cracks occurring in the case due to material deposition in the fillet during integral molding of the case.

[0004] In the first embodiment, a case is provided having an opening, being a integrally molded structure, and including a first wall and at least two second walls provided opposite the opening, wherein the first wall and the second walls are provided to intersect, and two of the at least two second walls are connected by a first fillet, the inner diameter of the first fillet is R1, and the yield strength of the case at a temperature of 25°C is Re, where Re and R1 satisfy 140MPa ≤ Re ≤ 1000MPa and 2.5mm ≤ R1 ≤ 20mm.

[0005] In this embodiment, by manufacturing the case with a material whose yield strength Re satisfies 140MPa ≤ Re ≤ 1000MPa, the case thickness can be reduced without reducing the strength of the case, thereby increasing the space for housing the battery cells. Furthermore, by setting the inner diameter R1 of the first fillet between the two second walls to satisfy 2.5mm ≤ R1 ≤ 20mm, the problem of case cracking due to force bearing during the integral molding process of the highest possible strength material is solved, and the difficulty of molding the case is reduced.

[0006] In one possible embodiment, Re and R1 satisfy 150 MPa ≤ Re ≤ 400 MPa and 4 mm ≤ R1 ≤ 15 mm.

[0007] In this embodiment, by limiting to 150 MPa ≤ Re ≤ 400 MPa and 4 mm ≤ R1 ≤ 15 mm, it helps to balance the forming difficulty of the case and the degree of deformation.

[0008] In one possible embodiment, the depth of the case is H, and H satisfies 50 mm < H ≤ 250 mm.

[0009] In this embodiment, by having the depth H of the case satisfy 50 mm < H ≤ 250 mm, without affecting the energy density of the battery cell, it can reduce the problem of case cracking due to the force received during the integral forming process of the highest-strength material as much as possible, and further reduce the forming difficulty of the case.

[0010] In one possible embodiment, the tensile strength of the case at 25°C is Rm, and Rm satisfies 250 MPa ≤ Rm ≤ 2000 MPa.

[0011] In this embodiment, by setting 250 MPa ≤ Rm ≤ 2000 MPa and 2.5 mm ≤ R1 ≤ 20 mm, without affecting the case strength, it can reduce the force received by the mold during the manufacturing process of the case as much as possible, and further ensure that the dimensions or surface of the case are not affected.

[0012] In one possible embodiment, the two second walls are two adjacent second walls, and the maximum thickness T1 of the first fillet and the maximum thickness T0 of the thickest second wall among the two second walls satisfy T1 > T0.

[0013] In this embodiment, by providing a first fillet between two adjacent second walls and making the maximum thickness T1 of the first fillet greater than the maximum thickness T0 of the thickest second wall among the two second walls, it helps to solve the problem of case deformation during the production and installation process of the battery cell, and the problem of case deformation caused by expansion due to gas generation during the use of the battery cell.

[0014] In one possible implementation, the two second walls are two second walls provided opposite to each other.

[0015] In this embodiment, by providing a first fillet between two second walls provided opposite to each other, it is advantageous to reduce the risk of case cracking due to force reception during the integral molding process of the high-strength material by increasing the inner diameter R1 of the first fillet.

[0016] In one possible implementation, the first wall and the second wall are connected by a second fillet, and the inner diameter r1 of the second fillet and the minimum thickness T2 of the thinnest second wall among at least two second walls satisfy 2.0 ≤ r1 / T2 ≤ 30.

[0017] In this embodiment, by setting the ratio between the inner diameter r1 of the second fillet between the first wall and the second wall and the minimum thickness T2 of the thinnest second wall within [2.0, 30], it helps to balance the processing difficulty of the case, the space capacity of the battery cell, and the strength.

[0018] In one possible implementation, the thickness of the case is uniform.

[0019] In this embodiment, by making the thickness of the case uniform, the processing difficulty of the case can be reduced. On the other hand, each wall of the case can also be made to have the minimum processing thickness, which helps to sufficiently increase the space utilization rate of the case.

[0020] A second embodiment provides a battery cell comprising an electrode assembly and a case as described in the first embodiment and any one possible embodiment thereof, wherein the electrode assembly is housed within the case.

[0021] In one possible implementation, let D1 be the thickness of the battery cell, where H, R1, and D1 satisfy the condition 0.15 mm ≤ R1 * D1 / H ≤ 36 mm.

[0022] In this embodiment, by setting R1*D1 / H to 0.15mm ≤ R1*D1 / H ≤ 36mm, it is possible to reduce the risk of material deposition during the case molding process and the case cracking due to excessive force caused by an R1*D1 / H value that is too small, and to mitigate the impact on the energy density of the battery cell caused by an R1*D1 / H value that is too large.

[0023] In one possible implementation, H, R1, and D1 satisfy 0.34 mm ≤ R1 * D1 / H ≤ 18 mm.

[0024] In this embodiment, by setting 0.34 mm ≤ R1 * D1 / H ≤ 18 mm, a balance can be struck between the difficulty of molding the case and its energy density.

[0025] In one possible implementation, let D2 be the thickness of the electrode assembly, and R1 and D2 satisfy 0.125 ≤ R1 / D2 ≤ 0.45.

[0026] In this embodiment, by setting R1 / D2 to 0.125 ≤ R1 / D2 ≤ 0.45, interference with the electrode assembly or insufficient residual space inside the battery cell due to R1 being too large will not occur, nor will the performance of the battery cell be affected. On the other hand, difficulty in molding the case due to R1 being too small will not occur.

[0027] In one possible embodiment, the electrode assembly includes a negative electrode sheet, the negative electrode sheet 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 of at least a portion of the case under temperature conditions of 25°C is Rm, where Rm satisfies 250 MPa ≤ Rm ≤ 2000 MPa.

[0028] In this embodiment, providing a silicon-based material in the negative electrode sheet allows for the accommodation of more metal ions, effectively increasing the energy density of the battery cell. Furthermore, when the negative electrode active material of the negative electrode sheet contains a silicon-based material, the amount of deformation of the electrode assembly in the battery cell during use increases. In particular, during charging of the battery cell, metal ions are inserted into the silicon-based material of the negative electrode sheet, causing the volume of the electrode assembly to expand and increasing the pressure of the electrode assembly on the battery cell case. Therefore, increasing the tensile strength Rm of at least a portion of the case under normal temperature conditions of 25°C can enhance the deformation capacity of the case, thereby making the case less likely to break during use of the battery cell, further improving the structural stability of the battery cell, and further increasing the service life of the battery cell. However, in order to reduce the difficulty of material selection and processing of the case, reduce costs, and facilitate processing, the tensile strength Rm of at least a portion of the case under normal temperature conditions of 25°C should not be excessive.

[0029] In one possible embodiment, the electrode assembly includes a negative electrode sheet, the negative electrode sheet 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 yield strength of at least a portion of the case under temperature conditions of 25°C is denoted as Re, where Re satisfies 140 MPa ≤ Re ≤ 1000 MPa.

[0030] In this embodiment, by providing a silicon-based material in the negative electrode sheet, more metal ions can be accommodated, effectively increasing the energy density of the battery cell. Furthermore, when the negative electrode active material of the negative electrode sheet contains a silicon-based material, the amount of deformation of the electrode assembly in the battery cell during use increases. In particular, during charging of the battery cell, metal ions are inserted into the silicon-based material of the negative electrode sheet, causing the volume of the electrode assembly to expand and increasing the pressure of the electrode assembly on the battery cell case. Therefore, by increasing the yield strength Re at room temperature (25°C) in at least a portion of the case, the deformation capacity of the case can be enhanced, further improving the structural stability of the battery cell and increasing the service life of the battery cell. When the electrode assembly undergoes repeated volume expansion and contraction during charging and discharging of the battery cell, increasing the yield strength Re at room temperature in at least a portion of the case increases the maximum compressive force that the case can withstand. As long as the limit of the yield strength of the case is not exceeded, the case is less likely to break, the deformation of the case can be recovered, and the service life of the case is increased. However, in order to reduce the difficulty of material selection and processing in the case, reduce costs, and facilitate processing, the yield strength Re under room temperature conditions in at least some areas of the case should not be excessive.

[0031] In one possible embodiment, the electrode assembly includes a positive electrode sheet, the positive electrode sheet includes a positive electrode active material capable of reversibly desorbing and inserting metal ions, the positive electrode active material includes a nickel-containing compound, and the melting point of at least a portion of the case is p, where p satisfies 1200°C ≤ p ≤ 2000°C.

[0032] In this embodiment, when the positive electrode active material of the positive electrode sheet contains a nickel-containing compound, the energy density and cycle life of the battery cell can be effectively increased. However, the amount of gas generated during use of the battery cell also increases, and in particular, if thermal runaway occurs in the battery cell, the internal temperature of the battery cell rises rapidly, generating a large amount of gas. For this reason, moderately increasing the melting point p of at least a portion of the case makes the case less likely to melt, reducing the possibility of the battery cell exploding, further reducing the risk of thermal runaway occurring in adjacent battery cells, and improving the reliability of the battery. However, in order to reduce the difficulty of material selection and processing of the case, reduce costs, and facilitate processing, the melting point p of the case should not be excessively high.

[0033] In one possible embodiment, the electrode assembly includes a positive electrode sheet, the positive electrode sheet includes a positive electrode active material capable of reversibly desorbing and inserting metal ions, the positive electrode active material includes a nickel-containing compound, and the tensile strength of at least a portion of the case under temperature conditions of 500°C is Rn, where Rn satisfies 100 MPa ≤ Rn ≤ 1200 MPa.

[0034] In this embodiment, when the positive electrode active material of the positive electrode sheet contains a nickel-containing compound, the energy density and cycle life of the battery cell can be effectively increased. However, the amount of gas generated during use of the battery cell also increases, and in particular, when thermal runaway occurs in the battery cell, the internal temperature of the battery cell rises rapidly, generating a large amount of gas. For this reason, moderately increasing the tensile strength Rn under high temperature conditions of 500°C in at least a portion of the case can enhance the deformation capacity of that portion of the case during thermal runaway of the battery cell, thereby making rapid fracture and explosion of the case less likely, further reducing the risk of thermal runaway occurring in adjacent battery cells, and improving the reliability of the battery. However, in order to reduce costs and facilitate processing, the tensile strength Rn under high temperature conditions of 500°C in at least a portion of the case should not be excessively high.

[0035] In the third embodiment, a battery is provided that includes a plurality of battery cells described in the second embodiment and any one of its possible embodiments.

[0036] In the fourth aspect, an electrical device is provided that includes a battery comprising a plurality of battery cells as described in the second aspect and any one of the possible embodiments thereof. [Brief explanation of the drawing]

[0037] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments of this application are briefly described below. The drawings described below are merely examples of some embodiments of this application, and it will be apparent that those skilled in the art can conceive of other drawings based on these drawings without any creative effort.

[0038] [Figure 1] This is a schematic diagram of the structure of a vehicle disclosed in one embodiment of this application. [Figure 2] This is a schematic diagram of the structure of a battery disclosed in one embodiment of this application. [Figure 3] This is a schematic diagram of the structure of a battery cell disclosed in one embodiment of this application. [Figure 4] This is an exploded schematic diagram of a battery cell disclosed in one embodiment of this application. [Figure 5] This is a structural diagram of the case disclosed in the embodiments of this application. [Figure 6] This is a cross-sectional view of the case disclosed in the embodiments of this application. [Figure 7] This is a localized, enlarged schematic diagram of area A in Figure 6. [Figure 8] This diagram shows a schematic representation of material flow during the integral molding process of the case. [Figure 9] This diagram shows a schematic representation of the force distribution during the integral molding process of the case. [Figure 10] This is another cross-sectional view of the case disclosed in the embodiments of this application. [Figure 11] This is a localized, enlarged schematic diagram of section B in Figure 10. [Figure 12] This is a schematic diagram of the structure of another battery cell disclosed in one embodiment of this application. [Figure 13] This is an exploded schematic diagram of another battery cell disclosed in one embodiment of this application. [Figure 14] This is a schematic cross-sectional view of an electrode assembly according to one embodiment of the present application. [Figure 15] This is a schematic cross-sectional view of the negative electrode sheet or positive electrode sheet of an electrode assembly according to one embodiment of this application. [Figure 16] This is a schematic diagram of the structure of a jig for fatigue testing by cyclic charging in one embodiment of the present application. [Figure 17] A schematic side view of the case of the embodiment of this application is shown. [Figure 18] This is a schematic plan view of the case of the embodiment of this application. [Figure 19] This is a local structure enlargement view of one embodiment of the present application. [Figure 20] This is a schematic cross-sectional view of the local structure of a battery according to another embodiment of this application. [Figure 21] This is a schematic diagram of the exploded structure of a battery cell according to another embodiment of this application. [Figure 22] This is a schematic diagram of the cross-sectional structure of a battery cell according to another embodiment of this application. [Figure 23] This is a schematic cross-sectional view of the local structure of a battery according to another embodiment of this application. [Figure 24] This is a schematic cross-sectional view of another local structure of a battery according to another embodiment of this application. [Modes for carrying out the invention]

[0039] To further clarify the purpose, technical solutions, and advantages of the embodiments of this application, the technical solutions of the embodiments of this application will be clearly explained below with reference to the drawings of the embodiments of this application. Naturally, the embodiments described are only a part of the embodiments of this application, not all of them. All other embodiments that a person skilled in the art could obtain without creative work based on the embodiments of this application are all included within the scope of protection of this application.

[0040] Unless otherwise defined, all technical and specialized terms used in this application have the same meaning as those generally understood by those skilled in the art. Terms used in the specification of this application are for illustrative purposes only and are not intended to limit this application. The terms “includes,” “equipped,” and variations thereof in the specification and claims of this application, and in the brief description of the drawings above, are intended to include non-exclusive inclusion. Terms such as “first,” “second,” etc., in the specification and claims of this application, or in the accompanying drawings above, are used to distinguish different subjects, not to indicate a specific order or hierarchical relationship.

[0041] Where the “Examples” are referred to in this application, it means that certain features, structures, or properties described in conjunction with the Examples may be included in at least one Example of this application. The phrase “Examples” appearing in different parts of the specification does not necessarily refer to the same Example, nor does it refer to an Example that is exclusively independent or alternative to another Example. It will be understood, expressly or implicitly, by those skilled in the art that the Examples described in this application may be combined with other Examples.

[0042] In the description of this application, unless otherwise explicitly stated and limited, the terms “attachment,” “connection,” “connection,” and “mounting” should be understood in a broad sense, including, for example, fixed connections, removable connections, integral connections, direct connections, indirect connections via an intermediate medium, or internal connections between two elements. Those skilled in the art may understand the specific meaning of these terms in this application on a case-by-case basis.

[0043] In this application, the term "and / or" simply describes the relationship between related objects and indicates that three relationships may exist. For example, A and / or B may indicate that there are three situations: A exists alone, A and B exist simultaneously, or B exists alone. In this application, the symbol " / " generally indicates that the preceding and following related objects are in an "or" relationship.

[0044] In the embodiments of this application, the same reference numerals indicate the same components, and for the sake of brevity, detailed descriptions of the same components are omitted in different embodiments. The dimensions such as thickness, length, and width of various components in the embodiments of this application shown in the accompanying drawings, as well as the dimensions such as thickness, length, and width of the overall integrated device, are for illustrative purposes only and should be understood not as limiting to this application.

[0045] 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).

[0046] In the embodiments of this application, the battery cell may be a secondary battery, which is a battery cell that can be reused by recharging after discharge to activate the active material.

[0047] 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 thereto.

[0048] A battery cell generally includes an electrode assembly. The electrode assembly includes a positive electrode, a negative electrode, and a separator. During charging and discharging of the battery cell, active ions (e.g., lithium ions) are inserted and removed by moving back and forth between the positive and negative electrodes. The separator is placed between the positive and negative electrodes and serves to prevent short circuits between them while also allowing active ions to pass through.

[0049] In some embodiments, the positive electrode may be a positive electrode sheet, and the positive electrode sheet may include a positive electrode current collector and a positive electrode active material provided on at least one of the surfaces of the positive electrode current collector.

[0050] For example, a positive electrode current collector has two opposing surfaces in its own thickness direction, and the positive electrode active material is provided on one or both of the two opposing surfaces of the positive electrode current collector.

[0051] As an example, a positive electrode current collector can be a metal foil, a 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, calcined 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 substrate layer and a metal layer. The composite current collector can be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer material substrate (for example, a substrate such as polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, or polyethylene).

[0052] For example, the positive electrode active material may include at least one of lithium-containing phosphates, lithium transition metal oxides, and modified compounds thereof. However, this application is not limited to these materials, and other conventional materials usable 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. Here, examples of lithium-containing phosphates may include, but are not limited to, at least one of lithium iron phosphate (e.g., LiFePO4 (also abbreviated as LFP)), lithium iron phosphate and carbon composites, lithium manganese phosphate (e.g., LiMnPO4), lithium manganese phosphate and carbon composites, lithium iron manganese phosphate, and lithium iron manganese phosphate and carbon composites.

[0053] In some embodiments, the negative electrode may be a negative electrode sheet, and the negative electrode sheet may include a negative electrode current collector and a negative electrode active material provided on at least one of the surfaces of the negative electrode current collector.

[0054] For example, the negative electrode current collector has two opposing surfaces in its thickness direction, and the negative electrode active material is provided on one or both of the two opposing surfaces of the negative electrode current collector.

[0055] As an example, a negative 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, calcined carbon electrodes, carbon, nickel, or titanium can be used. A composite current collector may include a polymer material substrate layer and a metal layer. The foamed metal may be foamed nickel, foamed copper, foamed aluminum, foamed alloy, or foamed carbon. A composite current collector can be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer material substrate (for example, a substrate such as polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, or polyethylene).

[0056] For example, the negative electrode active material can be any negative electrode active material known in the art for use in battery cells. For example, the negative electrode active material may include at least one of artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate.

[0057] In some embodiments, the electrode assembly further includes a separator provided between the positive and negative electrodes.

[0058] In some embodiments, the separator is a separator membrane. In this application, the type of separator membrane is not particularly limited, and any known porous structure separator membrane having good chemical and mechanical stability can be selected.

[0059] For example, the main material of the separator membrane may be at least one selected from glass fiber, nonwoven fabric, polyethylene, polypropylene, polyvinylidene fluoride, and ceramic.

[0060] In some embodiments, the separator is a solid electrolyte. The solid electrolyte is placed between the positive and negative electrodes and simultaneously performs the roles of ion transport and positive-negative electrode isolation.

[0061] In some embodiments, the battery cell further includes an electrolyte, which plays a role in conducting ions between the positive and negative electrodes. The type of electrolyte is not specifically limited in this application and can be selected as needed. The electrolyte may be liquid, gel-like, or solid.

[0062] 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.

[0063] In some embodiments, the battery cell may include a housing. The housing is for packaging components such as electrode assemblies and electrolytes. The housing may be a steel housing, an aluminum housing, a plastic housing (e.g., polypropylene), a composite metal housing (e.g., copper-aluminum composite housing), or an aluminum-plastic film, etc. The housing includes a case and a lid.

[0064] For example, the battery cell may be a cylindrical battery cell, a prismatic battery cell, a pouch-type battery cell, or a battery cell of other shape. The prismatic battery cell includes prismatic battery cells, blade-type battery cells, and polygonal prismatic batteries, and the polygonal prismatic battery is, for example, a hexagonal prismatic battery, and is not particularly limited in this application.

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

[0066] In some embodiments, the battery may be a battery module, and if there are multiple battery cells, the multiple battery cells are arranged and fixed together to form a single battery module.

[0067] In some embodiments, the battery may be a battery pack, which includes a box and battery cells, and the battery cells or battery modules are housed inside the box.

[0068] In some embodiments, the box may be part of the vehicle's chassis structure. For example, the box may be at least a portion of the vehicle's floor, or at least a portion of the vehicle's cross members and side members.

[0069] In some embodiments, the battery may be located in an energy storage device. The energy storage device includes energy storage containers, energy storage cabinets, and the like.

[0070] The development of battery technology requires the simultaneous consideration of various design factors, such as performance parameters including energy density, cycle life, discharge capacity, and charge / discharge rate. Furthermore, the influence of the case on battery performance must also be considered. For example, the case's space utilization rate, tensile strength, and manufacturability must be taken into account.

[0071] Therefore, the embodiment of this application provides a case. By manufacturing the case from a material whose yield strength Re satisfies 140 MPa ≤ Re ≤ 1000 MPa, the thickness of the case can be reduced without reducing the strength of the case, thereby increasing the space for housing the battery cells. Furthermore, by setting the inner diameter R1 of the first fillet between the two second walls to satisfy 2.5 mm ≤ R1 ≤ 20 mm, the problem of case cracking due to force bearing during the integral molding process of the highest possible strength material is solved, and the difficulty of molding the case is reduced.

[0072] The technical solutions described in the embodiments of this application are all suitable for various electrical devices that use batteries.

[0073] Electrical equipment may include vehicles, mobile phones, portable devices, laptop computers, ships, aircraft, electric toys, and power tools. Vehicles may be fuel-powered vehicles, natural gas vehicles, or new energy vehicles, and new energy vehicles may include battery-powered vehicles, hybrid vehicles, or range-extender vehicles. Aircraft include airplanes, rockets, space shuttles, and spacecraft. Electric toys include stationary or mobile electric toys, such as game consoles, electric vehicle toys, electric boat toys, and electric airplane toys. Power tools include metal cutting power tools, grinding power tools, assembly power tools, and railway power tools, such as electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, electric impact drills, concrete vibrators, and electric planers. The embodiments of this application are not particularly limited to the above-mentioned electrical equipment.

[0074] In the following examples, for the sake of clarity, we will use the vehicle as an example of the electrical equipment.

[0075] For example, as shown in Figure 1, a schematic diagram of the structure of a vehicle 1 according to one embodiment of this application, the vehicle 1 may be a fuel-powered vehicle, a natural gas vehicle, or a new energy vehicle, and the new energy vehicle may be a battery-powered vehicle, a hybrid vehicle, or a range-extender vehicle. A motor 80, a controller 60, and a battery 10 may be provided inside the vehicle 1, and the controller 60 is used to control the power supply of the battery 10 to the motor 80. For example, the battery 10 can be provided at the bottom, front, or rear of the vehicle 1. The battery 10 is used to supply power to the vehicle 1, for example, as the operating power source of the vehicle 1, the battery 10 is used to meet the demands of the vehicle 1's circuit system, such as starting the vehicle 1, navigation, and operating power during driving. In another embodiment of this application, the battery 10 can also provide driving power to the vehicle 1 as a driving power source for the vehicle 1, in place of all or part of gasoline or natural gas, in addition to being the operating power source of the vehicle 1.

[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 box 11, the inside of which is hollow, and the plurality of battery cells 20 are housed inside the box 11. Figure 2 shows a possible embodiment of the box 11 of the embodiment of the present application, and as shown in Figure 2, the box 11 may include two parts, which are hereby called a first part 111 and a second part 112, respectively, and the first part 111 and the second part 112 are integrally engaged. The shapes of the first part 111 and the second part 112 may be determined according to the combined shape of the plurality of battery cells 20, and at least one of the first part 111 and the second part 112 has one opening. For example, as shown in Figure 2, both the first portion 111 and the second portion 112 may be hollow rectangular parallelepipeds, each having an open surface on only one side, with the openings of the first portion 111 and the second portion 112 facing each other, and the first portion 111 and the second portion 112 engaging with each other to form a box 11 having a sealed cavity. This sealed cavity can be used to house a plurality of battery cells 20. The plurality of battery cells 20 are combined by parallel, series, or mixed connections and then placed in the box 11 formed by the engagement of the first portion 111 and the second portion 112.

[0077] Furthermore, unlike the example shown in Figure 2, for example, one of the first part 111 and the second part 112 may be a hollow rectangular parallelepiped with an opening, while the other is plate-shaped and overlaps the opening. For example, if the second part 112 is a hollow rectangular parallelepiped with an opening on only one side, and the first part 111 is plate-shaped, then the first part 111 can be overlapped with the opening of the second part 112 to form a box 11 with a sealed cavity, and the embodiments of this application are not limited to this.

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

[0079] As shown in Figures 3 and 4, the battery cell 20 of the embodiment of this application may include a housing 21 and an electrode assembly 22, the housing 21 having a sealed housing space, and the electrode assembly 22 being arranged in the housing space within the housing 21. The housing 21 may include a case 30 and a cover plate 40, the case 30 being a hollow structure having at least one opening, and the cover plate 40 engaging with the case 30 to form a housing 21 having a sealed housing space.

[0080] In some embodiments, the lid plate 40 is a plate-like structure and is designed to be placed over the opening of the case 30. In some other embodiments, the structure of the lid plate 40 and the case 30 is similar, that is, both the case 30 and the lid plate 40 are hollow structures with one opening, and the two openings are abutted together to form a housing 21 with a sealed storage space.

[0081] It should be understood that if the lid plate 40 is a plate-like structure, the case 30 may be a hollow structure with openings formed at one or more ends. For example, if the case 30 is a hollow structure with an opening at one end, there may be only one lid plate 40. If the case 30 is a hollow structure with openings formed at both opposing ends, there may be two lid plates 40, and the two lid plates 40 are each superimposed on the openings at both ends of the case 30.

[0082] The housing 21 may have various shapes, such as a cylindrical shape, a rectangular parallelepiped, or other polyhedron. Exemplarily, as shown in Figures 3 and 4, the embodiments of this application primarily describe an example in which the housing 21 has a rectangular parallelepiped structure.

[0083] It should be understood that the cover plate 40 in the embodiment of this application is designed to fit together with the case 30 to isolate the internal environment of the battery cell 20 from the external environment. The shape of the cover plate 40 may match the shape of the case 30; as shown in Figures 3 and 4, the case 30 has a rectangular parallelepiped structure, and the cover plate 40 has a rectangular plate structure that matches the case 30.

[0084] It should be understood that the battery cell 20 further includes electrode terminals 214. The electrode terminals 214 in the embodiments of this application are for electrically connecting to an electrode assembly 22 inside the battery cell 20 to output electrical energy from the battery cell 20. As shown in Figures 3 to 4, the battery cell 20 may include at least two electrode terminals 214, which may include at least one first electrode terminal 214a and at least one second electrode terminal 214b, the first electrode terminal 214a for electrically connecting to the positive electrode tab 222a of the electrode assembly 22, and the second electrode terminal 214b for connecting to the negative electrode tab 222b of the electrode assembly 22. The electrode terminals 214 and tabs may be connected directly or indirectly. Exemplarily, an electrode terminal 214 may be electrically connected to one tab via one connecting member 23.

[0085] In the battery cell 20, the electrode assembly 22 is a component that undergoes an electrochemical reaction within the battery cell 20. Depending on practical requirements, there may be one or more electrode assemblies 22 within the case 30. For example, as shown in Figure 4, two electrode assemblies 22 are provided within 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 case 30 may also have a cylindrical structure, and if the electrode assembly 22 has a rectangular parallelepiped structure, the case 30 may also have a rectangular parallelepiped structure.

[0086] It should be understood that, as shown in Figures 3 and 4, the electrode assembly 22 includes tabs 222 and an electrode main body 221, where 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 from a portion of the positive electrode sheet where the positive electrode active material layer is not coated, the negative electrode tab 222b may be formed by laminating from a portion of the negative electrode sheet where the negative electrode active material layer is not coated, and the electrode main body 221 may be formed by laminating the positive electrode sheet and the negative electrode sheet together or by winding them.

[0087] Figure 5 shows a structural diagram of the case 30 provided by an embodiment of the present application. Figure 6 shows a top view of the case 30 shown in Figure 5. Figure 7 shows an enlarged schematic diagram of portion A in Figure 6. It should be noted that the case 30 is applied to a battery cell, for example, the case 30 can be applied to the battery cell 20 shown in Figures 3 and 4. Alternatively, the case 30 may be the case 30 shown in Figures 3 and 4. For example, as shown in Figure 5, the case 30 has an opening 301 and is a integrally molded structure, and the case 30 includes a first wall 31 and at least two second walls 32 provided opposite the opening 301, the first wall 31 and the second walls 32 being provided so as to intersect.

[0088] The case 30 being a one-piece molded structure means that a plate-like structure is stamped into a hollow structure with an opening using a mold, and the case 30 formed by stamping can have openings of various shapes. For example, the opening 301 may be circular, polygonal, or runway-shaped. The polygon may be, for example, a square, pentagon, hexagon, or other irregular shape.

[0089] The first wall 31 of case 30 may be understood as a wall provided opposite the opening 301, and the wall connected to the first wall 31 is the second wall 32, and at least two second walls 32 and the first wall 31 surround each other to form a hollow cavity for housing the electrode assembly. In some embodiments, the first wall 31 and the second wall 32 may be installed vertically.

[0090] In some embodiments, the yield strength under the temperature condition of 25°C in Case 30 is denoted as Re, and Re satisfies the condition 140MPa ≤ Re ≤ 10000MPa. 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, and 1000MPa.

[0091] As shown in the local enlarged view of section A in Figure 5, at least two of the two second walls 32 are connected via a first fillet 331, with the inner diameter of the first fillet 331 being R1, where R1 satisfies 2.5 mm ≤ R1 ≤ 20 mm.

[0092] For example, R1 can be 2.5mm, 5mm, 7.5mm, 10mm, 12.5mm, 15mm, 17.5mm, or 20mm.

[0093] Yield strength may be understood as the critical stress value at which a material yields. Normally, when a material is subjected to stress, as the stress increases, not only does elastic deformation occur, but plastic deformation may also occur. The point at which the material undergoes plastic deformation is called the yield point, and the strength corresponding to the yield point is called the yield strength. The method for measuring the yield strength Re under a temperature of 25°C in Case 30 of the embodiment of this application may be selected according to practical requirements. For example, the yield strength Re may be measured under room temperature conditions of 25°C according to GB / T228.1-2010.

[0094] In some embodiments, two adjacent second walls 32 of at least two second walls 32 can be connected via a first fillet 331. In some other embodiments, two opposing second walls 32 of at least two second walls 32 can be connected via a first fillet 331, for example, the case 30 includes two sets of second walls 32, each set of second walls 32 is installed to be connected in a cross shape in sequence, with one set of second walls 32 being opposite and flat, and the other set of second walls 32 being opposite and arc-shaped.

[0095] Figure 8 shows a schematic diagram of material flow during the integral molding process of case 30. Figure 9 shows a schematic diagram of force bearing during the integral molding process of case 30. As can be seen from Figures 8 and 9, case 30 has high strength, and during molding of case 30, the material of the case tends to accumulate at the position of the first fillet 331, resulting in a large frictional force between case 30 and the mold, making case 30 prone to cracking. In the embodiment of this application, for a case 30 that satisfies 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, so that R is not too small, the difficulty of molding case 30 is reduced, and R is not too large, thus reducing deformation of case 30 due to force bearing.

[0096] In this embodiment, by manufacturing the case 30 with a material whose yield strength Re satisfies 140 MPa ≤ Re ≤ 1000 MPa, the wall thickness of the case 30 can be reduced without reducing the strength of the case 30, thereby increasing the space for housing the battery cells. Furthermore, by setting the inner diameter R1 of the first fillet 331 between the second walls 32 to satisfy 2.5 mm ≤ R1 ≤ 20 mm, the problem of case cracking due to force bearing during the integral molding process of high-strength material is solved as much as possible, and the difficulty of molding the case 30 is reduced.

[0097] In some embodiments, the yield strengths Re and R1 of case 30 can satisfy 150 MPa ≤ Re ≤ 400 MPa and 4 mm ≤ R1 ≤ 15 mm.

[0098] For example, Re = 150MPa, 170MPa, 190MPa, 210MPa, 230MPa, 260MPa, 290MPa, 310MPa, 330MPa, 370MPa, 390MPa, and 400MPa.

[0099] For example, R1 can be 4mm, 6mm, 8mm, 10mm, 12mm, 14mm, or 15mm.

[0100] In this embodiment, limiting the parameters to 150MPa≦Re≦400MPa and 4mm≦R1≦15mm helps to balance the molding difficulty and deformation degree of case 30.

[0101] In some embodiments, the yield strengths Re and R1 of case 30 can satisfy 160 MPa ≤ Re ≤ 300 MPa and 5 mm ≤ R1 ≤ 10 mm.

[0102] For example, Re = 160MPa, 170MPa, 180MPa, 190MPa, 200MPa, 210MPa, 220MPa, 230MPa, 240MPa, 250MPa, 260MPa, 270MPa, 280MPa, 290MPa, 300MPa.

[0103] For example, R1 = 5mm, 6mm, 7mm, 8mm, 9mm, 10mm.

[0104] In this embodiment, by limiting the parameters to 160MPa≦Re≦300MPa and 5mm≦R1≦10mm, deformation of the case 30 due to force bearing during use can be reduced as much as possible without affecting the difficulty of molding the case 30.

[0105] In some embodiments, as shown in Figure 5, the depth of case 30 is H, and H and R1 satisfy the conditions 2.5 mm ≤ R1 ≤ 20 mm and 50 mm ≤ H ≤ 250 mm.

[0106] In the embodiments of this application, depth may be interpreted as the distance from the opening inward to the bottom. For example, the depth H of case 30 may be interpreted as the distance from the opening 201 to the first wall 31.

[0107] In some embodiments, R1 = 2.5 mm, 5 mm, 7.5 mm, 10 mm, 12.5 mm, 15 mm, 17.5 mm, 20 mm. In some other embodiments, H = 50 mm, 100 mm, 150 mm, 200 mm, 250 mm.

[0108] In this embodiment, the depth H of the case 30 and the inner diameter R1 of the first fillet 331 are set to satisfy 2.5 mm ≤ R1 ≤ 20 mm and 50 mm ≤ H ≤ 250 mm, thereby preventing H from being too large or R from being too small, and reducing the risk of the case 30 cracking. Furthermore, preventing H from being too small or R from being too large reduces the impact on the energy density of the battery cell.

[0109] In some embodiments, H and R1 satisfy the conditions 75mm ≤ H ≤ 180mm and 4mm ≤ R1 ≤ 15mm.

[0110] For example, H = 75mm, 100mm, 125mm, 150mm, 175mm, 180mm. For example, R1 = 4mm, 6mm, 8mm, 10mm, 12mm, 14mm, 15mm.

[0111] In this embodiment, by setting H and R1 to satisfy 4mm ≤ R1 ≤ 15mm and 75mm ≤ H ≤ 180mm, the energy density of the battery cell 20 is not reduced due to H being too small or R being too large, while at the same time, the case 30 is not prone to material deposition during the molding process due to H being too large or R being too small, and the case 30 is not subjected to excessive force and crack.

[0112] 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.

[0113] In some embodiments, the tensile strength of case 30 at a temperature of 25°C is denoted as Rm, and Rm and R1 satisfy the conditions 250MPa ≤ Rm ≤ 2000MPa and 2.5mm ≤ R1 ≤ 20mm.

[0114] Tensile strength may be understood as the maximum stress value that a material can withstand while being pulled until it breaks. The method for measuring the tensile strength Rm under a temperature of 25°C in Case 30 of the embodiment of this application can be selected according to practical requirements. For example, tensile strength Rm can be measured under room temperature conditions of 25°C according to ISO 6892-2:2018.

[0115] 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.

[0116] In this embodiment, by setting 250MPa≦Rm≦1000MPa and 2.5mm≦R1≦20mm, the force applied to the mold during the manufacturing process of the case 30 can be reduced as much as possible without affecting the strength of the case 30, and furthermore, the dimensions or surface of the case 30 can be prevented from being affected.

[0117] In some embodiments, Rm and R1 satisfy the conditions 280MPa ≤ Rm ≤ 800MPa and 4mm ≤ R1 ≤ 15mm.

[0118] For example, Rm = 280MPa, 310MPa, 340MPa, 370MPa, 390MPa, 430MPa, 470MPa, 510MPa, 540MPa, 580MPa, 610MPa, 630MPa, 660MPa, 690MPa, 720MPa, 740MPa, 780MPa, 800MPa.

[0119] In some other embodiments, Rm and R1 satisfy 380MPa ≤ Rm ≤ 600MPa and 5mm ≤ R1 ≤ 10mm.

[0120] For example, Rm = 380 MPa, 390 MPa, 410 MPa, 440 MPa, 480 MPa, 520 MPa, 535 MPa, 570 MPa, 596 MPa, and 600 MPa.

[0121] Selectively, as shown in the local enlarged view of portion A in Figure 6, two adjacent second walls 32 are connected via a first fillet 331, where the maximum thickness of the first fillet 331 is T1, and the maximum thickness of the second wall 32 with the greatest thickness among the two adjacent second walls 32 is T0, where T1 is greater than T0.

[0122] As can be seen from Figure 6, the first fillet 331 has two surfaces, an inner surface and an outer surface. The inner and outer surfaces may be arcuate surfaces and are installed coaxially. The maximum thickness T1 of the first fillet 331 may be defined as the length in the first fillet 331 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 one cross section in the axial direction perpendicular to the inner and outer surfaces.

[0123] If the thicknesses of at least two second walls 32 in case 30 are not equal, for example, if they are not equal to the thicknesses of two second walls 32 of one first fillet 331, then in embodiments of this application, T0 is the second wall 32 in case 30 that has the greatest thickness among the two second walls 32 adjacent to the first fillet 331. If the thicknesses of at least two second walls 32 in case 30 are equal, for example, if they are equal to the thicknesses of two second walls 32 of one first fillet 331, then in embodiments of this application, T0 is the thickness of any one of the second walls 32 in case 30.

[0124] It should be explained that if a second wall 32 includes a functional area, the maximum thickness of the second wall 32 actually refers to the maximum thickness of the area of ​​the second wall 32 other than the functional area, and the functional area includes at least one of the following: a pressure release area, an electrode terminal location area, a fluid injection area, and a welding area.

[0125] In this embodiment, by providing a first fillet 331 between two adjacent second walls 32, stress concentration between the two adjacent second walls 32 can be reduced, thereby reducing the risk of structural failure due to stress concentration. Furthermore, by making the maximum thickness T1 of the first fillet 331 greater than the maximum thickness T0 of the second wall with the greatest thickness among the two adjacent second walls, the thickened first fillet 331 can strengthen the structural strength of the case 30, which helps to solve the problem of deformation of the case 30 during the production and installation process of the battery cell 20, and the problem of deformation of the case 30 caused by expansion due to gas generation during the use of the battery cell 20.

[0126] In some embodiments, the maximum thickness T1 of the first fillet 331 and the maximum thickness T0 of the second wall 32 with the greatest thickness among the two adjacent second walls 32 satisfy 1.5 ≤ T1 / T0 ≤ 7.

[0127] In this embodiment, by setting the ratio of the maximum thickness T1 of the first fillet 331 to the maximum thickness T0 of the second wall 32 with the greatest thickness among the two adjacent second walls 32 to [1.5, 7], the strength of the case can be enhanced by the thick first fillet 331, while limiting the manufacturing difficulties of the case 30 due to excessive thickness of the first fillet 331, thereby balancing the strength of the case 30 with the manufacturing difficulty of the case 30.

[0128] In practical applications, the ratio of T1 to T0 is adjustable. For example, the maximum thickness T1 of the first fillet 331 and the maximum thickness T0 of the thickest of the two adjacent second walls 32 may satisfy 2 ≤ T1 / T0 ≤ 4.

[0129] 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.

[0130] In this embodiment, the ratio of the maximum thickness T1 of the first fillet 331 to the maximum thickness T0 of the second wall 32 with the greatest thickness among the two adjacent second walls 32 is set to [2,4], thereby maximizing the balance between the strength of the case 30 and the difficulty of manufacturing the case 30.

[0131] As shown in Figure 7, the inner diameter of the first fillet 331 is R1, and the outer diameter of the first fillet 331 is R2.

[0132] In some embodiments, the first fillet 331 has an inner surface and an outer surface, and both the inner surface and the outer surface are arcuate surfaces. The inner diameter R1 of the first fillet 331 may be interpreted as the radius of the circle on which the inner arc of the first fillet 331 is located, and the outer diameter R2 of the first fillet 331 may be interpreted as the radius of the circle on which the outer arc of the first fillet 331 is located.

[0133] In some 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.

[0134] In this embodiment, by setting the inner diameter of the first fillet 331 between two adjacent second walls 32 to be between [2 mm, 4 mm], the gas generation pressure inside the case 30 will not increase due to the inner diameter occupying too much of the internal space of the case 30, nor will the case 30's strength be insufficient due to the inner diameter being too small. Thus, a balance can be struck between the utilization rate of the internal space of the case 30 and the strength of the case 30.

[0135] In some 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.

[0136] In this embodiment, when the cover plate 40 is fixedly connected to the case 30 by lateral welding, the larger the outer diameter R2 of the first fillet 331 between two adjacent second walls 32, the more difficult it becomes to control the welding quality and the more likely false welds are to occur. However, the smaller the outer diameter R2 of the first fillet 331, the more difficult it becomes to form the case 30. Therefore, by keeping 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 case.

[0137] In another embodiment, the two second walls 32 connected via the first fillet 331 are two opposing second walls 32, and in such a case, increasing the inner diameter R1 of the first fillet is advantageous because it reduces the risk of case cracking due to force bearing during the integral molding process of the high-strength material.

[0138] Figure 10 shows another schematic cross-sectional view of Case 30 of the embodiment of the present application. As shown in the local enlarged view of portion B in Figure 10, the first wall 31 and the second wall 32 are connected via a second fillet 34, as shown in the enlarged schematic view of portion B in Figure 10, the inner diameter of the second fillet 34 is r1, and the minimum thickness of the second wall 32 with the smallest thickness among at least two second walls 32 is T2, where the inner diameter r1 of the second fillet 34 and the minimum thickness T2 of the second wall 32 with the smallest thickness among at least two second walls 32 satisfy 2.0 ≤ r1 / T2 ≤ 30.

[0139] It should be understood that each first wall 31 is connected to at least two second walls 32, and selectively, any one second wall 32 is connected to the first wall 31 via a second fillet 34 shown in Figure 10. Furthermore, the realization of the second fillet 34 here is similar to that of the first fillet 331 in Figure 6; that is, the second fillet 34 has an inner surface and an outer surface, and both the inner and outer surfaces are arcuate surfaces. The inner diameter r1 of the second fillet 34 may be understood as the radius of the circle in which the inner arc is located.

[0140] It should be explained that if each second wall 32 is a wall of uniform thickness, the minimum thickness T2 of the second wall 32 may refer to the thickness of the thinnest of at least two second walls 32. If the thickness of each second wall 32 is non-uniform, the minimum thickness T2 of the second wall 32 may refer to the thickness of the thinnest region of all the second walls 32.

[0141] It should be explained that if a second wall 32 includes a functional area, the minimum thickness of the second wall 32 actually refers to the minimum thickness of the area of ​​the second wall 32 other than the functional area, and the functional area includes at least one of the pressure release area, the area where electrode terminals are located, the fluid injection area, and the welding area.

[0142] In this embodiment, the ratio of the inner diameter r1 of the second fillet 34 between the first wall 31 and the second wall 32 to the minimum thickness T2 of the second wall 32, which has the smallest thickness, is set to be between [2.0, 30], which helps to balance the difficulty of machining the case 30 with the spatial capacity and strength of the battery cell 20.

[0143] In some embodiments, the inner diameter r1 of the second fillet 34 and the minimum thickness T2 of the second wall 32 with the smallest thickness among at least two second 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.

[0144] Selectively, the inner diameter r1 of the second fillet 34 may satisfy the condition 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.

[0145] In this embodiment, by setting the inner diameter r1 of the second fillet 34 to within [0.8 mm, 1.5 mm], the manufacturing difficulty of the case 30 is not increased due to r1 being too small, nor is the interference between the electrode assembly 22 and the second fillet 34 reduced due to r1 being too large. In other words, in order to satisfy the mounting of the case 30 and the electrode assembly 22, it is not necessary to sacrifice the capacity of the electrode assembly 22 by reducing the height of the electrode assembly 22, and if r1 is too large, the case 30 is also more prone to deformation.

[0146] Figure 11 shows another localized, enlarged schematic diagram of portion B in Figure 10. As shown in Figure 11, the outer diameter of the second fillet 34 is denoted as 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.

[0147] The definition of the inner diameter r1 of the second fillet 34 is the same, and the outer diameter r2 of the second fillet 34 may be interpreted as the radius of the circle on which the outer arc of the second fillet 34 is located.

[0148] In this embodiment, by setting the outer diameter r2 of the second fillet 34 to within [1.0 mm, 2.5 mm], the insulating film on the outside of the battery cell 20 will not be punctured by sharp points due to r2 being too small, thus preventing insulation failure. On the other hand, the thickness of the second fillet 34 will not become too thin due to r2 being too large, thus not affecting the strength of the case 30.

[0149] In some embodiments, H and T2 satisfy 300 ≤ H / T2 ≤ 800. For example, H / T2 = 300, 350, 400, 450, 500, 550, 600, 650, 700, 750, 800, etc.

[0150] In this embodiment, by setting the ratio of the depth H of the case 30 to the minimum thickness T2 of the second wall 32, which has the smallest thickness, to between [300, 800], it is possible to achieve both volume utilization efficiency and strength of the battery cell 20.

[0151] As shown in Figure 11, the maximum thickness of the second fillet 34 is T3, where the ratio of T3 to T2 satisfies 0.8 ≤ T3 / T2 ≤ 2. For example, T3 / T2 = 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0.

[0152] 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 may be defined as the length in the second fillet 34 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 one cross section in the axial direction perpendicular to the inner and outer surfaces.

[0153] In this embodiment, by setting the ratio of the maximum thickness T3 of the second fillet 34 to the minimum thickness T2 of the second wall 32, which has the smallest thickness, to [0.8,2], a balance can be achieved between the strength and manufacturability of the case 30. That is, the case 30 will not become insufficiently strong due to excessive thinning of the second fillet 34, nor will the case 30 become difficult to manufacture due to insufficient thinning of the second fillet 34.

[0154] In some embodiments, the wall thickness of case 30 is uniform; that is, all walls of case 30 have the same wall thickness.

[0155] In this embodiment, by making the wall thickness of the case 30 uniform, the difficulty of processing the case 30 can be reduced, and furthermore, each wall of the case 30 can be made to the minimum processing thickness, which helps to sufficiently increase the space utilization rate of the case 30.

[0156] As shown in Figures 12 and 13, embodiments of the present application further provide a battery cell 20 comprising an electrode assembly 22 and a case 211, wherein the electrode assembly 22 is housed within the case 211.

[0157] It should be noted that Case 211 may be Case 30 in the various embodiments described above.

[0158] In some embodiments, the battery cell 20 further includes a cover plate 212 that is placed over an opening in the case 211 so as to enclose the electrode assembly 22 within the cavity of the case 211.

[0159] 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 runway-shaped battery cell, where the thickness of the battery cell 20 is D1, and H, R1, and D1 satisfy the condition 0.15 mm ≤ R1 * D1 / H ≤ 36 mm.

[0160] 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.

[0161] In some embodiments, D2 may be the dimension in the expansion direction of the electrode assembly 22 of the battery cell 20.

[0162] In this embodiment, by setting 0.15 mm ≤ R1*D1 / H ≤ 36 mm, material deposition becomes more likely during the molding process of the case 211 due to the value of R1*D1 / H being too small, further reducing the risk of the case 211 cracking due to excessive force, and also mitigating the impact on the energy density of the battery cell 20 due to the value of R1*D1 / H being too large.

[0163] 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.

[0164] In this embodiment, H and R1 satisfy the conditions 50mm ≤ H ≤ 250mm and 2.5mm ≤ R1 ≤ 20mm.

[0165] In some embodiments, H, R1, and D1 satisfy the condition 0.34 mm ≤ R1 * D1 / H ≤ 18 mm.

[0166] In this embodiment, by setting 0.34 mm ≤ R1 * D1 / H ≤ 18 mm, a balance can be struck between the molding difficulty and energy density of case 211.

[0167] For example, R1*D1 / H = 0.34, 0.5, 1, 3, 5, 8, 11, 13, 16, 18.

[0168] Similarly, in this embodiment, D1 satisfies 15mm ≤ D1 ≤ 90mm.

[0169] In this embodiment, H and R1 satisfy the conditions 75mm ≤ H ≤ 180mm and 4mm ≤ R1 ≤ 15mm.

[0170] In some embodiments, H, R1, and D1 satisfy the condition 0.9 mm ≤ R*D / H ≤ 6.6 mm.

[0171] 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.

[0172] 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.

[0173] Furthermore, in this embodiment, H and R1 satisfy the conditions 90mm ≤ H ≤ 140mm and 3mm ≤ R ≤ 10mm.

[0174] It should be explained that the ranges for R1, H, D1, and R1*D1 / H are 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.

[0175] In some embodiments, the thickness of the electrode assembly 22 is D2, and R1 and D2 satisfy 0.125 ≤ R1 / D2 ≤ 0.45.

[0176] 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.

[0177] Selectively, D2 may be the dimension of the electrode assembly 22 in the expansion direction.

[0178] In this embodiment, by setting R1 to 0.125 ≤ R1 / D2 ≤ 0.45, interference with the electrode assembly 22 or insufficient residual space inside the battery cell 20 due to R1 being too large will not occur, nor will the performance of the battery cell 20 be affected. At the same time, molding the case 211 will not become difficult due to R1 being too small.

[0179] In the embodiments of this application, the electrode assembly 22 includes a negative electrode sheet 224, the negative electrode sheet 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, the case 211 houses the electrode assembly 22, and the tensile strength of at least a portion of the case 211 at a temperature of 25°C is Rm, where Rm satisfies 250 MPa ≤ Rm ≤ 2000 MPa.

[0180] It should be understood that, as shown in Figures 12 and 13, the electrode assembly 22 of the embodiment of this application may include tabs 222 and an electrode main body 221, where 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 from portions of the positive electrode sheet 223 that are not coated with positive electrode active material, the negative electrode tab 222b may be formed by laminating from portions of the negative electrode sheet 224 that are not coated with negative electrode active material, and the electrode main body 221 may be formed by laminating the positive electrode sheet 223 and the negative electrode sheet 224 together or by winding them together.

[0181] The negative electrode active material contained in the negative electrode sheet 224 of the embodiment of this application may be flexibly set according to practical requirements. For example, the negative electrode active material may include a silicon-based material. When a silicon-based material is added to the negative electrode sheet 224, the silicon-based material can accommodate more metal ions, effectively increasing the energy density of the battery cell 20, and also increasing the amount of deformation of the electrode assembly 22 in use within the battery cell 20. In particular, during charging of the battery cell 20, the volume of the electrode assembly 22 expands as metal ions are inserted into the silicon-based material of the negative electrode sheet 224, further increasing the pressure of the electrode assembly 22 against the case 211 of the battery cell 20.

[0182] Therefore, by increasing the tensile strength Rm of at least a portion of the case 211 under room temperature conditions of 25°C, the deformation capacity of that portion of the case 211 can be enhanced, thereby making that portion of the case 211 less likely to break during use of the battery cell 20, and further increasing the structural stability and service life of the battery cell 20. However, in order to reduce the difficulty of material selection and processing of the case 211, reduce costs, and facilitate processing, the tensile strength Rm of at least a portion of the case 211 under room temperature conditions should not be excessive. For example, typically, the tensile strength Rm of at least a portion of the case 211 under room temperature conditions may be set to satisfy 250 MPa ≤ Rm ≤ 2000 MPa.

[0183] It should be understood that the range of values ​​for the tensile strength Rm at room temperature conditions of 25°C in at least a portion of the case 211 in the embodiments of this application may be adjusted according to practical requirements. For example, the value of the room temperature tensile strength Rm may satisfy 250MPa ≤ Rm ≤ 2000MPa. Alternatively, for example, the value of the room temperature tensile strength Rm may satisfy 400MPa ≤ Rm ≤ 1200MPa. Increasing the tensile strength Rm at room temperature conditions in at least a portion of the case 211 can enhance the deformation capacity of that portion of the case 211, cope with the expansion of the electrode assembly 22, make that portion of the case 211 less susceptible to breakage, and further increase the structural stability and service life of the battery cell 20. On the other hand, by limiting the tensile strength Rm at room temperature conditions in at least a portion of the case 211 to not be too high, the difficulty of material selection and processing of the case 211 can be reduced, costs can be lowered, and processing can be made easier.

[0184] Furthermore, the tensile strength Rm of at least a portion of the case 211 under room temperature conditions may be set to satisfy 450 MPa ≤ Rm ≤ 800 MPa. The tensile strength Rm of at least a portion of the case 211 under room temperature conditions will not be too large or too small, thereby enhancing the deformation capacity of that portion of the case 211, accommodating the expansion of the electrode assembly 22, and is also easy to implement and cost-effective.

[0185] In some embodiments, the value of the tensile strength Rm under room temperature conditions in at least a portion of the region of Case 211 of the embodiments of this application may be set to a different value. For example, the value of the room-temperature tensile strength Rm may be any one of the following values ​​or any two of the following values: 250MPa, 280MPa, 300MPa, 330MPa, 350MPa, 380MPa, 400MPa, 450MPa, 500MPa, 550MPa, 600MPa, 650MPa, 700MPa, 750MPa, 800MPa, 850MPa, 900MPa, 950MPa, 1000MPa, 1050MPa, 1100MPa, 1150MPa, 1200MPa, 1250MPa, 1300MPa, 1350MPa, 1400MPa, 1450MPa, 1500MPa, 1550MPa, 1600MPa, 1650MPa, 1700MPa, 1750MPa, 1800MPa, 1850MPa, 1900MPa, 1950MPa, and 2000MPa.

[0186] It should be understood that the tensile strength in the embodiments of this application is the maximum stress value that the material experiences before it breaks under tension. The method for measuring the tensile strength Rm under 25°C conditions in at least a portion of Case 211 of the embodiments of this application may be selected according to practical requirements. For example, the tensile strength Rm may be measured under room temperature conditions of 25°C according to the national standard GB / T228.1-2010.

[0187] Figure 14 shows a schematic cross-sectional view of the electrode assembly 22 of an embodiment of the present application. For example, the schematic cross-sectional view shown in Figure 14 may also be the schematic cross-sectional view of the electrode assembly 22 shown in Figure 12, and the cross-section is perpendicular to the height direction Z of the battery cell 20. Figure 15 shows a schematic local cross-sectional view of the positive electrode sheet 223 or negative electrode sheet 224 of an embodiment of the present application. For example, Figure 15 may show a schematic local cross-sectional view of the negative electrode sheet 224 of the electrode assembly 22 shown in Figure 14 along the thickness direction, or it may show a schematic local cross-sectional view of the positive electrode sheet 223 of the electrode assembly 22 shown in Figure 14 along the thickness direction.

[0188] As shown in Figures 12 to 15, the electrode assembly 22 of the embodiment of this application includes a positive electrode sheet 223 and a negative electrode sheet 224, and the electrode assembly 22 may be formed by stacking the positive electrode sheet 223 and the negative electrode sheet 224 on each other or by winding them together. For example, the electrode assembly 22 may include a plurality of positive electrode sheets 223 and a plurality of negative electrode sheets 224, and the plurality of positive electrode sheets 223 and a plurality of negative electrode sheets 224 are arranged alternately in the thickness direction Y of the electrode assembly 22 so as to form a laminated electrode assembly 22. Alternatively, for example, the electrode assembly 22 may include a plurality of positive electrode sheets 223, and the negative electrode sheet 224 includes a plurality of bent portions and a plurality of laminated portions that are connected to each other and arranged alternately, and when the bent portions are bent, the plurality of laminated portions of the plurality of positive electrode sheets 223 and negative electrode sheets 224 are arranged alternately in a manner so as to form a laminated electrode assembly 22. Alternatively, for example, the electrode assembly may be formed as a wound electrode assembly 22 by winding a positive electrode sheet 223 and a negative electrode sheet 224 around each other. For convenience of explanation, the drawings of the embodiments of this application show a wound electrode assembly 22 as an example, but the embodiments of this application are not limited thereto. Furthermore, the electrode assembly 22 may include a separator 225 for separating the positive electrode sheet 223 and the negative electrode sheet 224.

[0189] In the embodiments of this application, the negative electrode sheet 224 includes a negative electrode active material, for example, the negative electrode active material coated on the negative electrode sheet 224 can be used to form a negative electrode active material layer 2241, which may be provided on at least one surface of the negative electrode current collector 2242. For example, the negative electrode active material layer 2241 may be provided on both sides perpendicular to the thickness direction of the negative electrode current collector 2242.

[0190] In some embodiments, the negative electrode current collector 2242 can 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 layer and a metal material layer formed on at least one surface of the polymer material substrate layer. 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 layer may include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0191] It should be understood that the negative electrode active material in the embodiments of this application may be flexibly configured according to practical requirements. Specifically, the negative electrode active material in the embodiments of this application may include a silicon-based material, which can increase the energy density of the battery. For example, the silicon-based material may include at least one of elemental silicon, silicon-oxygen compounds, silicon-carbon composites, silicon-nitrogen composites, silicon-containing alloys, or silicon-oxygen-carbon composite materials.

[0192] In some embodiments, the silicon-based material may contain silicon and one or more alkali metal elements or alkaline earth metal elements. Here, 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 pre-inserted with alkali metals and / or alkaline earth metals, for example, a silicon-based material pre-inserted with Li and / or Mg.

[0193] It should be understood that the mass percentage g of the silicon-based material in the embodiments of this application may be flexibly set according to practical requirements.

[0194] For example, the range of the mass percentage g of the silicon-based material may be set to satisfy 2% ≤ g ≤ 40%. When a silicon-based material is added to the negative electrode active material of the negative electrode sheet 224, the silicon-based material can accommodate more metal ions than other elements. For example, the capacity of the silicon-based material is about 10 times that of graphite, so the energy density of the battery cell 20 can be effectively increased. Furthermore, the mass percentage g of the silicon-based material should not be excessively large, otherwise the difficulty of processing the electrode assembly 22 increases. In addition, the amount of deformation of the electrode assembly 22 during use in the battery cell 20 increases. In particular, during charging of the battery cell 20, metal ions are inserted into the silicon-based material of the negative electrode sheet 224, causing the volume of the electrode assembly 22 to expand. Furthermore, the pressure of the electrode assembly 22 on the case 211 of the battery cell 20 increases, increasing the difficulty of processing the battery cell 20.

[0195] Furthermore, the range of the mass percentage g of the silicon-based material may be set to satisfy 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 charging and discharging of the battery cell 20, i.e., the amount of volume expansion of the electrode assembly 22 can be reduced, and the pressure of the electrode assembly 22 on the case 211 of the battery cell 20 is reduced, the requirements for the structural strength of the case 211 are lowered, processing becomes easier, and costs are reduced.

[0196] Furthermore, the range of the mass percentage g of the silicon-based material may be set to satisfy 10% ≤ g ≤ 30%. By rationally adjusting the mass percentage g of the silicon-based material, the energy density of the battery cell 20 can be effectively increased, the difficulty of processing the electrode assembly 22 can be reduced, the amount of deformation of the electrode assembly 22 during charging and discharging of the battery cell 20 can be effectively reduced, and the requirements for the structural strength of the case 211 can be lowered.

[0197] In some embodiments, the mass percentage g of the silicon-based material in the embodiments of this application may be set to other values. For example, the value of the mass percentage g of the silicon-based material may be any one of 5%, 8%, 10%, 13%, 15%, 18%, 20%, 23%, 25%, 28%, 30%, 33%, 35%, 38%, 40%, 43%, 45%, 48%, and 50%, or any two of these values.

[0198] It should be understood that the mass percentage g of silicon-based material in the negative electrode active material of the embodiments of this application represents the ratio g 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 method for measuring the mass percentage g of silicon-based material may be selected according to practical requirements and can be measured by methods known in the art.

[0199] In the embodiments of this application, the negative electrode active material may include other materials. For example, the negative electrode active material may include a negative electrode binder. For example, the negative electrode binder may include one or more of the following: styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, aqueous acrylic acid resin (e.g., polyacrylate PAA, polymethacrylate PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS), and is not limited to these in the embodiments of this application.

[0200] In some embodiments, the negative electrode active material may include a negative electrode conductive agent. The type of negative electrode conductive agent is not particularly limited in this application, and for 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.

[0201] In some embodiments, the negative electrode active material may contain other additives. For example, the other additives may include thickeners such as sodium carboxymethylcellulose (CMC), PTC thermistor material, etc.

[0202] The negative electrode sheet 224 does not exclude other additional functional layers other than the negative electrode active material layer 2241. For example, in some embodiments, the negative electrode sheet 224 may be sandwiched between the negative electrode current collector 2242 and the negative electrode active material layer 2241 and include a conductive undercoat layer (for example, composed of a conductive agent and a binder) provided on the surface of the negative electrode current collector 2242. In some embodiments, the negative electrode sheet 224 may include a protective layer covering the surface of the negative electrode active material layer 2241.

[0203] In some embodiments, the negative electrode sheet 224 may be manufactured according to the following method. Disperse a negative electrode active material, any negative electrode binder, any negative electrode conductive agent, and any other auxiliary agent in a solvent and stir uniformly to form a negative electrode slurry. Apply the negative electrode slurry to the negative electrode current collector 2242 and form the negative electrode sheet 224 through processes such as drying and cold pressing. The solvent may be N-methylpyrrolidone (NMP) or deionized water, but the embodiments of this application are not limited thereto.

[0204] In the embodiments of this application, the value of the mass ratio g of the silicon-based material and the value of the tensile strength Rm under the condition of the temperature of 25 °C in at least a part of the region of the case 211 may be restricted with each other in order to balance the energy density and the structural strength of the battery cell 20. For example, in the negative electrode active material, the mass ratio of the silicon-based material is g, the material of at least a part of the region of the case 211 contains iron element, and Rm and g satisfy 2% < g < 40% and 300 MPa < Rm < 2000 MPa. When the material of at least a part of the region of the case 211 contains iron element, the structural strength of the material of the part of the case 211 can be increased and the design requirements can be satisfied.

[0205] In some embodiments, the material of at least a part of the region of the case 211 contains carbon steel or stainless steel, and Rm and g satisfy 2.5% ≤ g ≤ 15% and 315 MPa ≤ Rm < 800 MPa. For example, the material of at least a part of the region of the case 211 may contain Q195 carbon steel, thereby facilitating processing and also satisfying the value of the tensile strength Rm under the condition of 25 °C.

[0206] In some embodiments, the material in at least a portion of case 211 includes carbon steel or stainless steel, where Rm and g satisfy 4.5% ≤ g ≤ 40% and 380 MPa ≤ Rm < 2000 MPa. For example, the material in at least a portion of case 211 may include SPCC carbon steel, which facilitates processing and can also satisfy the tensile strength Rm value at 25°C.

[0207] In some embodiments, Rm and g satisfy 8% ≤ g ≤ 40% and 400 MPa ≤ Rm < 2000 MPa. For example, the material in at least a portion of the case 211 may include modified stainless steel, which facilitates processing and can also satisfy the tensile strength Rm value under 25°C conditions.

[0208] In some embodiments, Rm and g satisfy 10% ≤ g ≤ 40% and 480 MPa ≤ Rm < 2000 MPa. For example, the material in at least a portion of the case 211 may include 316 stainless steel, which facilitates processing and can also satisfy the tensile strength Rm value under 25°C conditions.

[0209] In some embodiments, Rm and g satisfy 15% ≤ g ≤ 40% and 520 MPa ≤ Rm < 2000 MPa. For example, the material in at least a portion of the case 211 may include 304 stainless steel, which facilitates processing and can also satisfy the tensile strength Rm value under 25°C conditions.

[0210] In some examples, Rm and g satisfy the conditions 20% ≤ g ≤ 40% and 600 MPa ≤ Rm < 2000 MPa.

[0211] The following will explain by comparing several comparative examples and several embodiments. Specifically, the battery cell 20 in each of the embodiments and comparative examples below will all be the prismatic battery shown in Figures 12 and 13, and the case 211 will have a hollow structure with one end open.

[0212] In the following examples and comparative examples, the manufacturing methods for the positive electrode sheet 223, negative electrode sheet 224, electrolyte, and separator 225 of the battery cell 20 are as follows.

[0213] 1. Manufacturing of the positive electrode sheet 223 LiNi 0.95 Co 0.04 Mn 0.01 O2, the conductive agent Super P, and the binder polyvinylidene fluoride (PVDF) were prepared into a positive electrode slurry in N-methylpyrrolidone (NMP), and the solid content in the positive electrode slurry was set to 50 wt%, with LiNi in the solid component. 0.7 Co 0.1 Mn 0.1 The mass ratio of O2, Super P, and PVDF was set to 8:1:1. The positive electrode slurry was applied to the upper and lower surfaces of the aluminum foil of the current collector, baked at 85°C, then cold-pressed, followed by edge cutting, thinning, and slitting, and finally baked for 4 hours under vacuum conditions at 85°C to produce the positive electrode sheet 223.

[0214] 2. Manufacturing of the negative electrode sheet 224 A negative electrode slurry was prepared by uniformly mixing the negative electrode active material, the conductive agent Super P, the thickener carboxymethylcellulose (CMC), and the binder styrene-butadiene rubber (SBR) with deionized water. The negative electrode active material contained graphite and a silicon-based material, the silicon-based material being a silicon oxygen compound. The solid content in the negative electrode slurry was set to 30 wt%, and the mass ratio of the negative electrode active material, silicon monoxide, Super P, CMC, and the binder styrene-butadiene rubber (SBR) in the solid components was set to 88:7:3:2. The negative electrode slurry was applied to the upper and lower surfaces of the copper foil of the current collector, baked at 85°C, then cold-pressed, edge-cut, thin-cut, and slit, and finally baked for 12 hours under vacuum conditions at 120°C to produce a negative electrode sheet 224.

[0215] 3. Preparation of the electrolyte In an argon gas-atmosphered glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), the electrolyte salt LiPF6, which had been thoroughly dried, was dissolved in a mixed solvent (the mixed solvent contained ethylene carbonate (EC) and diethyl carbonate (DEC), with ethylene carbonate (EC) and diethyl carbonate (DEC) mixed in a mass ratio of 50:50). After homogeneous mixing, an electrolyte solution with a concentration of 1 mol / L was obtained.

[0216] 4. Manufacturing of separator 225 A 16 μm polyethylene film was used as separator 225.

[0217] 5. Manufacturing of lithium-ion battery cells 20 The positive electrode sheet 223, separator 225, and negative electrode sheet 224 were stacked in this order such that the separator 225 served to isolate the positive and negative electrodes between the positive electrode sheet 223 and the negative electrode sheet 224, and the stacked and wound to obtain a bare cell. Tabs were welded, the bare cell was placed in a housing of a different material, the electrolyte prepared above was injected into the dried housing, and packaging, standing, chemical conversion, molding, capacity testing, etc. were performed to complete the manufacture of the lithium-ion battery cell 20.

[0218] In the following examples and comparative examples, Rm is defined as the tensile strength of the case 211 of the battery cell 20 at a temperature of 25°C. Different materials are selected for the case 211 to obtain different tensile strengths Rm. The negative electrode active material of the negative electrode sheet 224 of the electrode assembly 22 of the battery cell 20 contains a silicon-based material, and the mass percentage of the silicon-based material is g. The specific parameter settings are shown in Table 1 below. In addition, the material of all areas of the case 211 is the same in each example and comparative example, and the tensile strength Rm of the case 211 at 25°C is measured by the method specified in GB / T228.1-2010. Furthermore, the battery cell 20 in each example and comparative example is the same except for the parameters shown in Table 1. For example, the wall thickness of each wall of the case 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.

[0219] Fatigue tests were performed on the battery cells 20 in each of the following embodiments and comparative examples by cyclic charging. Specifically, Figure 16 shows a schematic diagram of the structure of the jig 700 for fatigue testing by cyclic charging according to the embodiment of this application. As shown in Figure 16, the jig 700 includes three 10 mm thick steel plates that completely cover the largest wall area of ​​the battery cell 20. For convenience of explanation, the three jig steel plates are defined here as the first steel plate 710, the second steel plate 720, and the third steel plate 730 in that order. The first steel plate 710 and the third steel plate 730 are located at both ends of the jig 700 and are connected and fixed by bolts. The second steel plate 720 in the middle is restricted by guide rails so that it can only translate in a direction perpendicular to the large surface of the second steel plate 720, a battery cell 20 is sandwiched between the first steel plate 710 and the second steel plate 720, the largest wall of the battery cell 20 is 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, the initial pressing force of the second steel plate 720 on the battery cell 20 can be adjusted.

[0220] Specifically, the battery cell 20 was clamped and fixed in a dedicated jig 700 so that the two largest opposing walls of the battery cell 20 were firmly held, the initial pressure was set to 2000N, and the electrode terminals 214 of the battery cell 20 were connected to a dedicated battery charging and discharging device.

[0221] The jig 700 holding 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.

[0222] 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 cycle cutoff condition for the test was changed to "stop the test when damage occurs to the weld bead 2113 of the battery cell 20."

[0223] For example, the test may be performed according to the following steps: Step a: Discharge at 1I(A) until the discharge termination condition specified by the company is reached. Step b: Leave for 30 minutes or longer or under the conditions 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 under the conditions specified by the company. Step e: Discharge at 1I1(A) until the discharge termination condition specified by the company is reached. Step f: Repeat steps b through e, and stop the test when damage occurs to the weld bead 2113.

[0224] To obtain the condition of case 211 after 1000 cycles as shown in Table 1 below, the weld bead 2113 of the battery cell 20 was continuously observed during the above test process until leakage occurred in the weld bead 2113, and the number of cycles was recorded. Here, in each of the following examples and comparative examples, the weld bead 2113 is the weld bead between case 211 and cover plate 212, that is, the weld bead 2113 surrounds the open end of case 211, and case 211 has an integrally molded structure.

[0225] [Table 1]

[0226] It should be understood that, in Table 1 above, the material for Case 211 may be Q195 carbon steel, and the tensile strength Rm of Q195 carbon steel at room temperature of 25°C is typically at least 315 MPa to 430 MPa. In the above example, only 328 MPa is given as an example, but it is not limited to this. Similarly, the material for case 211 may be SPCC carbon steel, which typically has a tensile strength Rm of at least 380 MPa to 430 MPa under room temperature conditions of 25°C, with only 396 MPa being used as an example in the above example. The material for case 211 may also be modified stainless steel, which typically has a tensile strength Rm of at least 400 MPa to 600 MPa under room temperature conditions of 25°C, with only 421 MPa being used as an example in the above example. The material for case 211 may also be SUS430 stainless steel, which typically has a tensile strength Rm of at least 450 MPa under room temperature conditions of 25°C, with only 459 MPa being used as an example in the above example. The material for case 211 may also be SUS304 stainless steel, which typically has a tensile strength Rm of at least 520 MPa under room temperature conditions of 25°C, with only 533 MPa and 625 MPa being used as examples in the above example.

[0227] As can be seen by comparing the two comparative examples and the twelve examples in Table 1 above, when different materials are used in Case 211, different tensile strengths Rm can be determined accordingly. When 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 sheet 224 of the battery cell 20 is different, the failure fatigue cycles of the battery cell 20 can all reach 1,000 cycles or more, satisfying the design requirements for the battery cell 20. However, when 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 sheet 224 of the battery cell 20 is low, the failure fatigue cycles of the battery cell 20 cannot reach 1,000 cycles, and the design requirements for the battery cell 20 cannot be met.

[0228] It should be understood that the battery cell 20 of the embodiment of this application can also satisfy other design requirements. Specifically, Re is the yield strength of at least a portion of the case 211 under a temperature of 25°C, where Re satisfies 140 MPa ≤ Re ≤ 1000 MPa.

[0229] Increasing the yield strength Re at room temperature in at least a portion of the case 211 can enhance the deformation capability of the case 211, further increasing the structural stability and service life of the battery cell 20. During charging and discharging of the battery cell 20, the electrode assembly 22 undergoes repeated volume expansion and contraction. Increasing the yield strength Re at room temperature in at least a portion of the case 211 increases the maximum compressive force that the case 211 can withstand. As long as the yield strength limit of the case 211 is not exceeded, the case 211 is less likely to break, its deformation can be recovered, and its service life is increased. However, to reduce the difficulty of material selection and processing of the case 211, reduce costs, and facilitate processing, the yield strength Re at room temperature in at least a portion of the case 211 should not be excessive. For example, typically, the yield strength Re at room temperature in at least a portion of the case 211 may be set to satisfy 140 MPa ≤ Re ≤ 1000 MPa.

[0230] It should be understood that the yield strength Re of at least a portion of the case 211 under room temperature conditions at 25°C in the embodiments of this application may be adjusted to suit practical use. For example, the yield strength Re at room temperature may satisfy 140 MPa ≤ Re ≤ 1000 MPa. Alternatively, for example, the yield strength Re at room temperature may satisfy 180 MPa ≤ Re ≤ 600 MPa. By increasing the yield strength Re of at least a portion of the case 211 under room temperature conditions, the deformation capacity of that portion of the case 211 can be strengthened, which can cope with the expansion of the electrode assembly 22 and make that portion of the case 211 less susceptible to failure. If the expansion of the electrode assembly 22 does not exceed the yield strength limit of the case 211, the deformation of the case 211 can also recover as the expansion of the electrode assembly 22 decreases, further increasing the structural stability and service life of the battery cell 20. On the other hand, by limiting the yield strength Re under room temperature conditions in at least a portion of the case 211 so that it does not become too high, the difficulty of selecting the material for the case 211 and the difficulty of processing it can be reduced, costs can be lowered, and processing can be made easier.

[0231] Furthermore, the yield strength Re under room temperature conditions in at least a portion of the case 211 may be set to satisfy 220 MPa ≤ Re ≤ 400 MPa. The yield strength Re under room temperature conditions in at least a portion of the case 211 will not be too large or too small, thereby enhancing the deformation capability of that portion of the case 211, accommodating the expansion of the electrode assembly 22, and is also easy to implement and cost-effective.

[0232] In some embodiments, the yield strength Re value under room temperature conditions for at least a portion of the region of Case 211 of the embodiments of this application may be set to other values. For example, the yield strength Re value at room temperature may be any one or any two of the following values: 140 MPa, 150 MPa, 160 MPa, 180 MPa, 200 MPa, 220 MPa, 250 MPa, 280 MPa, 300 MPa, 330 MPa, 350 MPa, 380 MPa, 400 MPa, 430 MPa, 450 MPa, 480 MPa, 500 MPa, 530 MPa, 550 MPa, 580 MPa, 600 MPa, 630 MPa, 650 MPa, 680 MPa, 700 MPa, 730 MPa, 750 MPa, 780 MPa, 800 MPa, 830 MPa, 850 MPa, 880 MPa, 900 MPa, 930 MPa, 950 MPa, 980 MPa, and 1000 MPa.

[0233] It should be understood that the yield strength in the embodiments of this application may be interpreted as the critical stress value at which the material yields. Normally, when a material is subjected to stress, as the stress increases, in addition to elastic deformation, plastic deformation may also occur. The point at which the material undergoes plastic deformation is called the yield point, and the strength corresponding to the yield point is called the yield strength. Furthermore, the yield strength in the embodiments of this application usually refers to the upper yield strength, that is, the upper yield strength under a temperature of 25°C in at least a portion of the case 211 is denoted as Re.

[0234] The method for measuring the yield strength Re under 25°C temperature conditions in at least a portion of the embodiment of Case 211 of this application may be selected according to practical requirements. For example, the yield strength Re may be measured under normal temperature conditions of 25°C according to the national standard GB / T228.1-2010.

[0235] In the embodiments of this application, the value of the mass percentage g of the silicon-based material and the value of the yield strength Re under a temperature of 25°C in at least a portion of the case 211 may be limited to each other in order to increase the structural strength of the case 211 while increasing the energy density of the battery cell 20, and further increase the structural strength and service life of the battery cell 20.

[0236] For example, in the negative electrode active material, the mass ratio of the silicon-based material is g, and g and Re satisfy 2% < g < 40% and 140 MPa < Re < 600 MPa. When a silicon-based material is added to the negative electrode active material of the negative electrode sheet 224, the silicon-based material can accommodate more metal ions than 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 increased. Also, the mass ratio g of the silicon-based material should not be too large, otherwise the processing difficulty of the electrode assembly 22 increases, and the deformation amount of the electrode assembly 22 during use in the battery cell 20 increases. Especially during charging of the battery cell 20, when metal ions are inserted into the silicon-based material of the negative electrode sheet, the volume of the electrode assembly 22 expands, and further the pressure of the electrode assembly 22 on the case 211 of the battery cell 20 increases, increasing the processing difficulty of the battery cell 20. Therefore, by appropriately increasing the yield strength Re of at least a part of the case 211 under normal temperature conditions, the deformation ability of this part of the case 211 can be strengthened to cope with the expansion amount of the electrode assembly 22, making this part of the case 211 less likely to be damaged. Also, when the limit of the yield strength of the case 211 is not exceeded, when the expansion amount of the electrode assembly 22 decreases, the deformation of the case 211 can also be restored, and further the structural stability and service life of the battery cell 20 can be increased. Also, by controlling the yield strength Re of at least a part of the case 211 under normal temperature conditions so that it does not become too large, the difficulty of material selection and processing of the case 211 can be reduced, the cost can be cut, and the processing can be made easier.

[0237] In some embodiments, the material of at least a part of the case 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 part of the case 211 may include SPCC carbon steel, which facilitates processing and can also satisfy the value of the yield strength Re under the condition of 25°C.

[0238] In some embodiments, g and Re satisfy 8% ≦ g ≦ 40% and 180 MPa ≦ Re < 600 MPa. For example, the material of at least a part of the case 211 may include modified stainless steel, thereby facilitating processing and being able to satisfy the value of the yield strength Re under the condition of 25°C.

[0239] In some embodiments, g and Re satisfy 10% ≦ g ≦ 40% and 190 MPa ≦ Re < 600 MPa. For example, the material of at least a part of the case 211 may include 316 stainless steel, thereby facilitating processing and being able to satisfy the value of the yield strength Re under the condition of 25°C.

[0240] In some embodiments, g and Re satisfy 15% ≦ g ≦ 40% and 200 MPa ≦ Re < 600 MPa. For example, the material of at least a part of the case 211 may include 304 stainless steel, thereby facilitating processing and being able to satisfy the value of the yield strength Re under the condition of 25°C.

[0241] In some embodiments, g and Re satisfy 20% ≦ g ≦ 40% and 210 MPa ≦ Re < 600 MPa.

[0242] Hereinafter, a plurality of comparative examples and a plurality of embodiments will be compared and described. Specifically, the battery cells 20 in the following respective embodiments and comparative examples are all exemplified by the rectangular battery shown in FIGS. 12 and 13, where the case 211 has a hollow structure with one end open.

[0243] In the following respective embodiments and comparative examples, the manufacturing methods of the positive electrode sheet 223, negative electrode sheet 224, electrolytic solution, and separator 225 of the battery cell 20 are as follows.

[0244] 1. Manufacture of the positive electrode sheet 223 LiNi of the positive electrode active material 0.95 Co 0.04 Mn 0.01O2, the conductive agent Super P, and the binder polyvinylidene fluoride (PVDF) were prepared into a positive electrode slurry in N-methylpyrrolidone (NMP), and the solid content in the positive electrode slurry was set to 50 wt%, with LiNi in the solid component. 0.7 Co 0.1 Mn 0.1 The mass ratio of O2, Super P, and PVDF was set to 8:1:1. The positive electrode slurry was applied to the upper and lower surfaces of the aluminum foil of the current collector, baked at 85°C, then cold-pressed, followed by edge cutting, thinning, and slitting, and finally baked for 4 hours under vacuum conditions at 85°C to produce the positive electrode sheet 223.

[0245] 2. Manufacturing of the negative electrode sheet 224 A negative electrode slurry was prepared by uniformly mixing the negative electrode active material, the conductive agent Super P, the thickener carboxymethylcellulose (CMC), and the binder styrene-butadiene rubber (SBR) with deionized water. The negative electrode active material contained graphite and a silicon-based material, the silicon-based material being a silicon oxygen compound. The solid content in the negative electrode slurry was set to 30 wt%, and the mass ratio of the negative electrode active material, silicon monoxide, Super P, CMC, and the binder styrene-butadiene rubber (SBR) in the solid components was set to 88:7:3:2. The negative electrode slurry was applied to the upper and lower surfaces of the copper foil of the current collector, baked at 85°C, then cold-pressed, edge-cut, thin-cut, and slit, and finally baked for 12 hours under vacuum conditions at 120°C to produce a negative electrode sheet 224.

[0246] 3. Preparation of the electrolyte In an argon gas-atmosphered glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), the electrolyte salt LiPF6, which had been thoroughly dried, was dissolved in a mixed solvent (the mixed solvent contained ethylene carbonate (EC) and diethyl carbonate (DEC), with ethylene carbonate (EC) and diethyl carbonate (DEC) mixed in a mass ratio of 50:50). After homogeneous mixing, an electrolyte solution with a concentration of 1 mol / L was obtained.

[0247] 4. Manufacturing of separator 225 A 16 μm polyethylene film was used as separator 225.

[0248] 5. Manufacturing of lithium-ion battery cells 20 The positive electrode sheet 223, separator 225, and negative electrode sheet 224 were stacked in this order such that the separator 225 served to isolate the positive and negative electrodes between the positive electrode sheet 223 and the negative electrode sheet 224, and the stacked and wound to obtain a bare cell. Tabs were welded, the bare cell was placed in a housing of a different material, the electrolyte prepared above was injected into the dried housing, and packaging, standing, chemical conversion, molding, capacity testing, etc. were performed to complete the manufacture of the lithium-ion battery cell 20.

[0249] In the following examples and comparative examples, the yield strength of the case 211 of the battery cell 20 at a temperature of 25°C is denoted as Re. Different materials are selected for the case 211 to obtain different yield strengths Re. The negative electrode active material of the negative electrode sheet 224 of the electrode assembly 22 of the battery cell 20 contains a silicon-based material, and the mass percentage of the silicon-based material is g. The specific parameter settings are shown in Table 1 below. In addition, in each example and comparative example, the material of all areas of the case 211 is the same, and the yield strength Re of the case 211 at 25°C is measured by the method specified in GB / T228.1-2010. Furthermore, in each example and comparative example below, the battery cell 20 has the same settings except for the parameters shown in Table 1. For example, the wall thickness of each wall of the case 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.

[0250] A fatigue test was performed on the battery cells 20 in each of the following examples and comparative examples by cyclic charging. Specifically, the test may be performed using the jig 700 for fatigue testing by cyclic charging shown in the drawing.

[0251] Specifically, the battery cell 20 was clamped and fixed in a dedicated jig 700 so that the two largest opposing walls of the battery cell 20 were firmly held, the initial pressure was set to 2000N, and the electrode terminals 214 of the battery cell 20 were connected to a dedicated battery charging and discharging device.

[0252] The jig 700 holding 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.

[0253] 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 cycle cutoff condition for the test was changed to "stop the test when damage occurs to the weld bead 2113 of the battery cell 20."

[0254] For example, the test may be performed according to the following steps: Step a: Discharge at 1I(A) until the discharge termination condition specified by the company is reached. Step b: Leave for 30 minutes or longer or under the conditions 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 under the conditions specified by the company. Step e: Discharge at 1I1(A) until the discharge termination condition specified by the company is reached. Step f: Repeat steps b through e, and stop the test when damage occurs to the weld bead 2113.

[0255] To obtain the failure fatigue status of case 211 after 1000 cycles as shown in Table 2 below, the weld bead 2113 of the battery cell 20 was continuously observed during the above test process until leakage occurred in the weld bead 2113, and the number of cycles was recorded. Here, in each of the following examples and comparative examples, the weld bead 2113 is the weld bead between case 211 and cover plate 212, that is, the weld bead 2113 surrounds the open end of case 211, and case 211 has an integrally molded structure.

[0256] [Table 2]

[0257] It should be understood that, in Table 2 above, the material for Case 211 may be modified stainless steel, and 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 example only 145 MPa and 173 MPa are given as examples, but it is not limited to these. Similarly, the material for Case 211 may be SUS316 stainless steel, and the yield strength Re of SUS316 stainless steel at room temperature of 25°C is typically at least 177 MPa, and in the above example only 182 MPa and 193 MPa are given as examples. The material for Case 211 may be Q195 carbon steel, and the yield strength Re of Q195 carbon steel at room temperature of 25°C is typically at least 195 MPa, and in the above example only 203 MPa is given as an example. The material for Case 211 may be SUS304 stainless steel, and 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 given as an example.

[0258] As can be seen by comparing the two comparative examples and the twelve examples in Table 2 above, when different materials are used in Case 211, different yield strengths Re can be determined accordingly. 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 sheet 224 of the battery cell 20 is different, the failure fatigue cycles of the battery cell 20 can all reach 1,000 cycles or more, satisfying the design requirements for 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 sheet 224 of the battery cell 20 is low, the failure fatigue cycles of the battery cell 20 cannot reach 1,000 cycles, and the design requirements for the battery cell 20 cannot be met.

[0259] In some embodiments, the electrode assembly 22 further comprises a positive electrode sheet 223, the positive electrode sheet 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 case 211 is p, where p satisfies 1200°C ≤ p ≤ 2000°C.

[0260] The positive electrode sheet 223 of the embodiment of this application is provided with a positive electrode active material that reversibly desorbs and inserts metal ions, and the positive electrode active material may be flexibly set according to practical use. For example, the positive electrode active material may contain a nickel element compound, which can effectively increase the energy density and long cycle life of the battery cell 20, but the temperature and gas generated during use of the battery cell 20 will also increase, and in particular, if thermal runaway occurs during use of the battery cell 20, the internal temperature of the battery cell 20 will rise rapidly and a large amount of gas will be generated.

[0261] Therefore, by moderately increasing the melting point p of at least a portion of the case 211, the case 211 becomes less likely to melt, reducing the possibility of the battery cell 20 exploding, further reducing the risk of thermal runaway in adjacent battery cells 20, and improving the reliability of the battery 10. However, in order to reduce the difficulty of material selection and processing of the case 211, reduce costs, and facilitate processing, the melting point p of at least a portion of the case 211 should not be excessively high. For example, the melting point p of at least a portion of the case 211 may normally be set to satisfy 1200℃ ≤ p ≤ 2000℃.

[0262] It should be understood that the melting point p of at least a part of the region of the case 211 in the embodiments of the present application may be adjusted according to practical applications within the range of its values. For example, the melting point p of at least a part of the region of the case 211 usually satisfies 1200°C ≤ p ≤ 2000°C. Also, for example, the melting point p of at least a part of the region of the case 211 may satisfy 1300°C ≤ p ≤ 1800°C. Appropriately increasing the value of the melting point p can enhance the melting resistance ability of the battery cell 20 in the corresponding part of the case 211 when thermal runaway occurs, thereby making the case 211 less likely to melt, further reducing the risk of thermal runaway occurring in the adjacent battery cell 20, that is, reducing the risk of thermal diffusion and improving the reliability of the battery 10. Also, in order to select appropriate materials, reduce the processing difficulty, further reduce the cost, and facilitate processing, the melting point p should not be set too high.

[0263] Furthermore, the melting point p of at least a part of the region of the case 211 may be set to satisfy 1400°C ≤ p ≤ 1600°C. When thermal runaway occurs in the battery cell 20, it can enhance the structural strength of the case 211, make the case 211 less likely to melt, maintain the structural integrity of the corresponding part of the case 211, and reduce the risk of thermal runaway occurring in the adjacent battery cell 20. Also, the processing difficulty can be reduced and the cost can be cut.

[0264] In some embodiments, the melting point p of at least a part of the region of the case 211 may be set to other values within the range of its values. For example, the value of the melting point p may be any one value or between any two values among 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.

[0265] In an embodiment of the present application, the positive electrode sheet 223 contains a positive electrode active material. For example, the positive electrode active material coated on the positive electrode sheet 223 can be used to form the positive electrode active material layer 2231, and the positive electrode active material layer 2231 may be provided on at least one surface of the positive electrode current collector 2232. For example, the positive electrode active material layers 2231 may be provided on both sides perpendicular to the thickness direction of the positive electrode current collector 2232, but the embodiments of the present application are not limited thereto.

[0266] In some embodiments, as the positive electrode current collector 2232, a metal foil or a composite current collector can be used. As an example of the metal foil, an aluminum foil may be used. The composite current collector may include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. As an example, the metal material may include one or more of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. As an example, the polymer material base layer may include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0267] It should be understood that the positive electrode active material of the embodiment of the present application may be flexibly set according to practical applications. For example, the positive electrode active material may include a nickel element-containing compound. As an example, the nickel element-containing compound includes a layered lithium-containing transition metal oxide, and the molar amount of the nickel element in the layered lithium-containing transition metal oxide accounts for 50% or more of the total molar amount of the transition metal elements in the layered lithium-containing transition metal oxide. By increasing the proportion of the molar amount of the nickel element in the layered lithium-containing transition metal oxide to 50% or more, the energy density and long cycle life of the battery cell 20 can be effectively increased, but the proportion should not be too large, otherwise the processing difficulty of the electrode assembly 22 will increase, and further the processing cost of the battery cell 20 will increase.

[0268] Furthermore, the molar proportion of nickel element in the layered lithium-containing transition metal oxide may be 70% or more, 80% or more, or 90%. In this way, the energy density of the battery cell 20 can be effectively increased while reducing the difficulty of processing the electrode assembly 22 and lowering the processing cost of the battery cell 20.

[0269] In some embodiments, the molar percentage of nickel in the layered lithium-containing transition metal oxide of the embodiments of this application may be set to a different value. 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 any two of these values.

[0270] It should be understood that the methods for measuring the molar amount of nickel and the total molar amount of transition metal elements in the layered lithium-containing transition metal oxides of the embodiments of this application may be selected according to practical requirements and can be measured using apparatus and methods known in the art. For example, a positive electrode active material may be laid and bonded on a conductive adhesive to produce a test sample with dimensions of 6 cm × 1.1 cm, and the particle morphology may be measured using a scanning electron microscope and energy-dispersive spectrometer (e.g., ZEISS Sigma 300). For measurement, refer to JY / T010-1996. To ensure the accuracy of the measurement results, 20 different regions may be randomly selected from the test sample and scanned, and the content of layered lithium-containing transition metal oxides in each region may be statistically calculated at a constant magnification (e.g., 1000x or more). For example, the average value of the measurement results of the 20 measurement regions may be taken as the quantity of layered lithium-containing transition metal oxides in the positive electrode active material, and the molar amount of layered lithium-containing transition metal oxides may be determined. Similarly, the molar amount of nickel element in the layered lithium-containing transition metal oxides may be determined by the same method.

[0271] In some embodiments, the layered lithium-containing transition metal oxide may include lithium cobaltate, one or more of the ternary materials. As an example, the layered lithium-containing transition metal oxide includes LiaNibCocMdOeAf, where 0 < a ≤ 1.2, 0.5 ≤ b < 1, and 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. Here, the molar ratio b of the nickel element in the layered lithium-containing transition metal oxide is set to be 50% or more, that is, the ratio b satisfies 0.5 ≤ b < 1, and further may satisfy 0.8 ≤ b < 1, or 0.9 ≤ b < 1, whereby the energy density of the battery cell 20 can be further increased.

[0272] As an example, the layered lithium-containing transition metal oxide may include one or more of LiNi0.5Co0.2Mn0.3O2 (abbreviated as NCM523), LiNi0.5Co0.25Mn0.25O2 (abbreviated as NCM211), LiNi0.6Co0.2Mn0.2O2 (abbreviated as NCM622), LiNi0.8Co0.1Mn0.1O2 (abbreviated as NCM811), LiNi0.9Co0.06Mn0.04O2, LiNi0.96Co0.02Mn0.02O2, LiNi0.85Co0.15Al0.05O2, but is not limited thereto.

[0273] In some embodiments, the cathode active material may include other materials. For example, the cathode active material may include a cathode conductive agent. In the present application, the type of the cathode conductive agent is not particularly limited. As an example, the cathode conductive agent may include one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0274] In some embodiments, the positive electrode active material may include a positive electrode binder. The type of positive electrode binder is not particularly limited in this application. For example, the positive electrode binder 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 acrylate resin.

[0275] In some embodiments, the positive electrode sheet 223 may be manufactured by the following method. The positive electrode active material layer 2231 is usually obtained by coating a positive electrode slurry onto a 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 binder, 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.

[0276] The following will explain by comparing several comparative examples and several embodiments. Specifically, the battery cell 20 in each of the embodiments and comparative examples below will all be the prismatic battery shown in Figures 12 and 13, and the case 211 will have a hollow structure with one end open.

[0277] In the following examples and comparative examples, the manufacturing methods for the positive electrode sheet 223, negative electrode sheet 224, electrolyte, and separator 225 of the battery cell 20 are as follows.

[0278] 1. Manufacturing of the positive electrode sheet 223 LiNi 0.95 Co 0.04 Mn 0.01 O2, the conductive agent Super P, and the binder polyvinylidene fluoride (PVDF) were prepared into a positive electrode slurry in N-methylpyrrolidone (NMP), with the solid content in the positive electrode slurry being set to 50 wt%, and the solid component LiNi 0.7 Co 0.1 Mn 0.1The mass ratio of O2, Super P, and PVDF was set to 8:1:1. The positive electrode slurry was applied to the upper and lower surfaces of the aluminum foil of the current collector, baked at 85°C, then cold-pressed, followed by edge cutting, thinning, and slitting, and finally baked for 4 hours under vacuum conditions at 85°C to produce the positive electrode sheet 223.

[0279] 2. Manufacturing of the negative electrode sheet 224 A negative electrode slurry was prepared by uniformly mixing the negative electrode active material, the conductive agent Super P, the thickener carboxymethylcellulose (CMC), and the binder styrene-butadiene rubber (SBR) with deionized water. The negative electrode active material contained graphite and a silicon-based material, the silicon-based material being a silicon oxygen compound. The solid content in the negative electrode slurry was set to 30 wt%, and the mass ratio of the negative electrode active material, silicon monoxide, Super P, CMC, and the binder styrene-butadiene rubber (SBR) in the solid components was set to 88:7:3:2. The negative electrode slurry was applied to the upper and lower surfaces of the copper foil of the current collector, baked at 85°C, then cold-pressed, edge-cut, thin-cut, and slit, and finally baked for 12 hours under vacuum conditions at 120°C to produce a negative electrode sheet 224.

[0280] 3. Preparation of the electrolyte In an argon gas-atmosphered glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), the electrolyte salt LiPF6, which had been thoroughly dried, was dissolved in a mixed solvent (the mixed solvent contained ethylene carbonate (EC) and diethyl carbonate (DEC), with ethylene carbonate (EC) and diethyl carbonate (DEC) mixed in a mass ratio of 50:50). After homogeneous mixing, an electrolyte solution with a concentration of 1 mol / L was obtained.

[0281] 4. Manufacturing of separator 225 A 16 μm polyethylene film was used as separator 225.

[0282] 5. Manufacturing of lithium-ion battery cells 20 The positive electrode sheet 223, the separator 225, and the negative electrode sheet 224 were laminated in this order such that the separator 225 serves to isolate the positive and negative electrodes between the positive electrode sheet 223 and the negative electrode sheet 224, wound to obtain a bare cell, tabs were welded, the bare cell was placed in a housing made of different materials, the electrolyte prepared above was injected into the dried housing, and packaging, standing, chemical conversion, forming, capacity testing, etc. were performed to complete the manufacture of the lithium-ion battery cell 20.

[0283] In each of the following Examples and Comparative Examples, the melting point of the case 211 of the battery cell 20 is p. In order to obtain different melting points, different materials were correspondingly selected for the case 211. The capacity of the battery cell 20 is C, and the wall thickness of the thickest wall of the battery cell 20 is T. The setting of the above specific parameters is shown in Table 3 below. Also, in each of the Examples and Comparative Examples, the material of all regions of the case 211 is the same. Also, in each of the following Examples and Comparative Examples, except for the parameters shown in Table 3 for the battery cell 20, the remaining setting conditions are the same. For example, the positive electrode active material of the positive electrode sheet 223 of the electrode assembly 22 of the battery cell 20 in each Example contains a nickel element-containing compound. Here, 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 95% of the total molar amount of transition metal elements in the layered lithium-containing transition metal oxide.

[0284] For the battery cell 20 in each of the following Comparative Examples and Examples, referring to the short-circuit test method in Chapter 6.2.4 of "GBT31485-2015 Safety Requirements and Test Methods for Power Batteries for Electric Vehicles", the energy storage cell was tested, and after the test, the integrity of the case 211, that is, whether the case 211 was melted, was observed.

[0285]

Table 3

[0286] As can be seen by comparing the two comparative examples and the six examples in Table 3 above, different melting points p can be determined correspondingly when different materials are used for case 211. If the melting point p satisfies 1200℃ ≤ p ≤ 2000℃, for example, in Examples 1 to 6, if case 211 of the battery cell 20 does not melt, the design requirements for the battery cell 20 can be met. Furthermore, even if other parameters of the battery cell 20 vary in various ways, for example, if the capacity C of the battery cell 20 is different, or if the thickness of the largest wall area of ​​case 211 is different, if the battery cell 20 does not melt, the design requirements for the battery cell 20 can be met. However, if the melting point p does not satisfy 1200℃ ≤ p ≤ 2000℃, for example, in Comparative Examples 1 to 2, if case 211 of the battery cell 20 melts, the design requirements for the battery cell 20 cannot be met.

[0287] In some embodiments, the electrode assembly 22 further includes a positive electrode sheet 223, the positive electrode sheet 223 containing a positive electrode active material capable of reversibly desorbing and inserting metal ions, the positive electrode active material containing a nickel element compound, and the tensile strength of at least a portion of the case 211 under temperature conditions of 500°C is Rn, where Rn satisfies 100 MPa ≤ Rn ≤ 1200 MPa.

[0288] The positive electrode active material may also contain a nickel-containing compound, which can effectively increase the energy density and long cycle life of the battery cell 20. However, this also increases the amount of gas generated during use of the battery cell 20. In particular, if thermal runaway occurs during use of the battery cell 20, the internal temperature of the battery cell 20 rises rapidly, generating a large amount of gas.

[0289] Therefore, moderately increasing the tensile strength Rn of at least a portion of the case 211 under high-temperature conditions of 500°C enhances the deformation capacity of that portion of the case 211 during thermal runaway of the battery cells 20, thereby making rapid fracture and explosion of the case 211 less likely, further reducing the risk of thermal runaway in adjacent battery cells 20, and improving the reliability of the battery 10. However, the tensile strength Rn of at least a portion of the case 211 under high-temperature conditions should not be excessively high; otherwise, the difficulty of processing increases, for example, polishing tools are more easily damaged, and the service life of the polishing tools decreases. Therefore, moderately lowering the tensile strength Rn reduces costs and makes processing easier. For example, the tensile strength Rn may normally be set to satisfy 100 MPa ≤ Rn ≤ 1200 MPa.

[0290] It should be understood that the tensile strength Rn of at least a portion of the case 211 in the embodiment of this application under high-temperature conditions of 500°C may be adjusted to suit practical use. For example, the value of the high-temperature tensile strength Rn may satisfy 100MPa ≤ Rn ≤ 1200MPa. Alternatively, for example, the value of the high-temperature tensile strength Rn may satisfy 112MPa ≤ Rn ≤ 720MPa. Moderately increasing the value of the tensile strength Rn enhances the deformation capacity of that portion of the case 211 during thermal runaway of the battery cells 20, thereby making rapid fracture and explosion of the case 211 less likely, further reducing the risk of thermal runaway in adjacent battery cells 20, and improving the reliability of the battery 10. On the other hand, keeping the tensile strength Rn of at least a portion of the case 211 under high-temperature conditions from becoming too high reduces the difficulty of processing, further reduces costs, and makes processing easier.

[0291] Furthermore, the value of the high-temperature tensile strength Rn may be set to satisfy 152 MPa ≤ Rn ≤ 480 MPa, thereby increasing the deformation capacity of the case 211 in that portion during thermal runaway of the battery cells 20 and increasing the structural strength of the case 211. This makes it less likely for the case 211 to undergo rapid failure and explosion, further reducing the risk of thermal runaway in adjacent battery cells 20, and improving the reliability of the battery 10. It can also reduce the difficulty of processing and lower costs.

[0292] In some embodiments, the value of the high-temperature tensile strength Rn in the embodiments of this application may 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, 60 It may be any one of the following values, or any two of the following values: 0 MPa, 630 MPa, 650 MPa, 680 MPa, 700 MPa, 720 MPa, 750 MPa, 780 MPa, 800 MPa, 830 MPa, 850 MPa, 880 MPa, 900 MPa, 930 MPa, 950 MPa, 980 MPa, 1000 MPa, 1050 MPa, 1100 MPa, 1150 MPa, and 1200 MPa.

[0293] It should be understood that the tensile strength in the embodiments of this application is the maximum stress value that the material experiences before it breaks under tension. The method for measuring the tensile strength Rn under high temperature conditions of 500°C in at least a portion of the region of Case 211 of the embodiments of this application may be selected according to practical requirements. For example, the tensile strength Rn may be measured under high temperature conditions of 500°C according to the national standard GB / T228.1-2010.

[0294] The following will explain by comparing several comparative examples and several embodiments. Specifically, the battery cell 20 in each of the embodiments and comparative examples below will all be the prismatic battery shown in Figures 12 and 13, and the case 211 will have a hollow structure with one end open.

[0295] In the following examples and comparative examples, the manufacturing methods for the positive electrode sheet 223, negative electrode sheet 224, electrolyte, and separator 225 of the battery cell 20 are as follows.

[0296] 1. Manufacturing of the positive electrode sheet 223 LiNi 0.95 Co 0.04 Mn 0.01 O2, the conductive agent Super P, and the binder polyvinylidene fluoride (PVDF) were prepared into a positive electrode slurry in N-methylpyrrolidone (NMP), and the solid content in the positive electrode slurry was set to 50 wt%, with LiNi in the solid component. 0.7 Co 0.1 Mn 0.1 The mass ratio of O2, Super P, and PVDF was set to 8:1:1. The positive electrode slurry was applied to the upper and lower surfaces of the aluminum foil of the current collector, baked at 85°C, then cold-pressed, followed by edge cutting, thinning, and slitting, and finally baked for 4 hours under vacuum conditions at 85°C to produce the positive electrode sheet 223.

[0297] 2. Manufacturing of the negative electrode sheet 224 A negative electrode slurry was prepared by uniformly mixing the negative electrode active material, the conductive agent Super P, the thickener carboxymethylcellulose (CMC), and the binder styrene-butadiene rubber (SBR) with deionized water. The negative electrode active material contained graphite and a silicon-based material, the silicon-based material being a silicon oxygen compound. The solid content in the negative electrode slurry was set to 30 wt%, and the mass ratio of the negative electrode active material, silicon monoxide, Super P, CMC, and the binder styrene-butadiene rubber (SBR) in the solid components was set to 88:7:3:2. The negative electrode slurry was applied to the upper and lower surfaces of the copper foil of the current collector, baked at 85°C, then cold-pressed, edge-cut, thin-cut, and slit, and finally baked for 12 hours under vacuum conditions at 120°C to produce a negative electrode sheet 224.

[0298] 3. Preparation of the electrolyte In an argon gas-atmosphered glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), the electrolyte salt LiPF6, which had been thoroughly dried, was dissolved in a mixed solvent (the mixed solvent contained ethylene carbonate (EC) and diethyl carbonate (DEC), with ethylene carbonate (EC) and diethyl carbonate (DEC) mixed in a mass ratio of 50:50). After homogeneous mixing, an electrolyte solution with a concentration of 1 mol / L was obtained.

[0299] 4. Manufacturing of separator 225 A 16 μm polyethylene film was used as separator 225.

[0300] 5. Manufacturing of lithium-ion battery cells 20 The positive electrode sheet 223, separator 225, and negative electrode sheet 224 were stacked in this order such that the separator 225 served to isolate the positive and negative electrodes between the positive electrode sheet 223 and the negative electrode sheet 224, and the stacked and wound to obtain a bare cell. Tabs were welded, the bare cell was placed in a housing of a different material, the electrolyte prepared above was injected into the dried housing, and packaging, standing, chemical conversion, molding, capacity testing, etc. were performed to complete the manufacture of the lithium-ion battery cell 20.

[0301] In the following examples and comparative examples, Rn is the tensile strength of the case 211 of the battery cell 20 at a temperature of 500°C. Different materials are selected for the case 211 to obtain different tensile strengths Rn. The capacity of the battery cell 20 is C, and the wall thickness of the largest area wall of the battery cell 20 is T. The specific parameter settings are shown in Table 4 below. In addition, in each example and comparative example, the material of all areas of the case 211 is the same, and the tensile strength Rn of the case 211 at 500°C is measured by the method specified in GB / T228.1-2010. Furthermore, in each example and comparative example below, the battery cell 20 has the same settings except for the parameters shown in Table 4. For example, in each embodiment, the positive electrode active material of the positive electrode sheet 223 of the electrode assembly 22 of the battery cell 20 contains a nickel element-containing compound, where the nickel element-containing 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.

[0302] 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 case 211, i.e., whether or not case 211 was cracked, was observed.

[0303] [Table 4]

[0304] As can be seen by comparing the two comparative examples and the six examples in Table 4 above, different tensile strengths Rn can be determined correspondingly when different materials are used for case 211. If the tensile strength Rn satisfies 100MPa ≤ Rn ≤ 1200MPa, for example, in Examples 1 to 6, if the case 211 of the battery cell 20 does not crack, the design requirements for the battery cell 20 can be met. Furthermore, even if other parameters of the battery cell 20 vary in various ways, for example, if the capacity C of the battery cell 20 is different, or if the thickness of the largest wall of case 211 is different, if the battery cell 20 does not crack, the design requirements for the battery cell 20 can be met. However, if the tensile strength Rn does not satisfy 100MPa ≤ Rn ≤ 1200MPa, for example, in Comparative Examples 1 to 2, if the case 211 of the battery cell 20 cracks, the design requirements for the battery cell 20 cannot be met.

[0305] It should be understood that in the embodiments of this application, at least a portion of the region of case 211 may include a local region of case 211 or all of the region of case 211. In some embodiments, the region of case 211 includes a weld bead 2113, and at least a portion of the region of case 211 includes a region of case 211 within a predetermined distance from the weld bead 2113, where the predetermined distance is L, and L = 10 mm. When the negative electrode active material of the negative electrode sheet 224 of 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. This causes the volume of the electrode assembly 22 to expand, and further increases the pressure of the electrode assembly 22 on the case 211 of the battery cell 20. Also, under the same conditions, the structural strength of the region of the case 211 close to the weld bead 2113 is lower than the structural strength of other regions of the case 211. Therefore, the region of the case 211 close to the weld bead 2113 is more susceptible to damage during use of the battery cell 20. Accordingly, by setting the region within a predetermined distance L from the weld bead 2113 to meet the requirements of tensile strength Rm or yield strength Re under room temperature conditions, the deformation capacity of the region of the case 211 close to the weld bead 2113 can be enhanced, thereby making that portion of the case 211 less susceptible to damage, and further increasing the structural stability and service life of the battery cell 20.

[0306] If the positive electrode active material of the positive electrode sheet 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, generating a large amount of gas. Under the same conditions, the structural strength of the region of the case 211 close to the weld bead 2113 is lower than that of other regions of the case 211. Therefore, the region of the case 211 close to the weld bead 2113 is prone to cracking, and furthermore, thermal runaway, i.e., thermal diffusion, can occur in the connected battery cell 20. Thus, by setting the region within a predetermined distance L from the weld bead 2113 to meet the requirements of tensile strength Rn or melting point p under high-temperature conditions, the deformability of that region of the case 211 can be increased, thereby making rapid fracture or complete melting less likely to occur in that region, reducing the risk of thermal diffusion and subsequent explosion between multiple battery cells 20, and improving the reliability of the battery 10.

[0307] It should be understood that the weld bead 2113 included in case 211 of the embodiment of this application may include weld beads 2113 at any position on the case 211. For example, the weld bead 2113 included in case 211 may include the weld bead between the case 211 and the cover plate 212, that is, the region surrounding the open end of the case 211 is a weld bead. For example, the weld bead 2113 of the case 211 may also include weld beads between different parts of the case 211. For example, the case 211 may include at least two parts which are joined by welding to form the case 211, where Figure 13 shows an example in which the case 211 includes two parts along the height Z of the battery cell 20, with the upper half of the case and the lower half having a weld bead 2113, or, contrary to what is shown in Figure 13, weld beads 2113 may also be provided on other parts of the case 211, and the embodiments of this application are not limited thereto.

[0308] In some embodiments, at least a portion of the case 211 includes a peripheral region 2111 of the case 211, the peripheral region 2111 encircling the electrode assembly 22, and the peripheral region 2111 is at least a portion of the side wall of the case 211. Thus, when the negative electrode active material of the negative electrode sheet 224 of the electrode assembly 22 includes a silicon-based material, the silicon-based material can accommodate more metal ions, which increases the amount of deformation of the electrode assembly 22 during use in the battery cell 20, thereby increasing the volume of the electrode assembly 22 and further increasing the pressure of the electrode assembly 22 on the case 211 of the battery cell 20. Therefore, by setting 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 case 211 can be enhanced. Since the surrounding region 2111 is provided around the electrode assembly 22, the radial pressing force of the internal electrode assembly 22 against the case 211 can be limited, thereby making the case 211 less susceptible to damage and further increasing the structural stability and service life of the battery cell 20.

[0309] If the positive electrode active material of the positive electrode sheet 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, generating a large amount of gas. If the surrounding region 2111 meets the requirements for tensile strength Rn or melting point p under high-temperature conditions, the deformation capacity of the surrounding region 2111 of the case 211 can be enhanced, thereby making rapid fracture or complete melting of the surrounding region 2111 less likely. This limits excessive expansion of the electrode assembly 22 inside the case 211 in the thickness direction, reduces the possibility of explosion of the battery cell 20, further reduces the risk of thermal runaway in adjacent battery cells 20, and improves the reliability of the battery 10.

[0310] It should be understood that the position and size of the peripheral region 2111 in the embodiments of this application may be flexibly set according to practical requirements. For example, the height of the peripheral region 2111 in the height direction Z of the battery cell 20 may be less than or equal to the height of the case 211. Specifically, if the height of the peripheral region 2111 in the height direction Z of the battery cell 20 is lower than the height of the case 211, the peripheral region 2111 may be located at any position along the height direction Z of the battery cell 20 in the case 211. For example, the peripheral region 2111 may be located in the middle of the case 211 along the height direction Z of the battery cell 20 so as to limit deformation corresponding to the middle position of the electrode assembly 22.

[0311] If the height of the surrounding region 2111 is equal to the height of the case 211 in the height direction Z of the battery cell 20, the surrounding region 2111 can include all the side walls of the case 211 and enclose the sides of the electrode assembly 22, further increasing the structural strength of the side walls of the case 211, reducing thermal runaway of the battery cell 20 due to the failure of localized weak areas of the side walls of the case 211, and subsequently causing explosions and heat diffusion, thereby further improving the reliability of the battery 10.

[0312] In some embodiments, at least a portion of the case 211 includes all of the walls of the case 211, meaning that at least a portion of the case 211 in the embodiments of this application may refer to all of the case 211. Thus, when the negative electrode active material of the negative electrode sheet 224 of the electrode assembly 22 includes a silicon-based material, the silicon-based material can accommodate more metal ions, thus increasing the amount of deformation of the electrode assembly 22 during use within the battery cell 20, which in turn expands the volume of the electrode assembly 22 and further increases the pressure of the electrode assembly 22 on the case 211 of the battery cell 20. For this reason, setting all of the case 211 to meet the requirements of tensile strength Rm or yield strength Re under room temperature conditions enhances the overall deformation capacity of the case 211 and also limits the pressing force of the internal electrode assembly 22 on the case 211 in each direction, thereby making the strength of each part of the case 211 more uniform, reducing the likelihood of localized weak areas breaking, and further increasing the structural stability and service life of the battery cell 20.

[0313] If the positive electrode active material of the positive electrode sheet 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, generating a large amount of gas. If all areas of the case 211 meet the requirements for tensile strength Rn or melting point p under high-temperature conditions, the deformation capacity of the entire case 211 can be enhanced, thereby making the case 211 less likely to break or melt, limiting the high-temperature, high-pressure gas inside the case 211, reducing the impact on the connected battery cell 20, and further reducing the risk of thermal runaway occurring in adjacent battery cells 20, thereby improving the reliability of the battery 10.

[0314] Furthermore, the cover plate 212 of the embodiments of this application may be made of the same material as at least some areas of case 211 of the embodiments of this application, so that the structural strength of the cover plate 212 similarly meets the design requirements. For example, the cover plate 212 may satisfy at least one of the requirements of tensile strength Rm and yield strength Re under room temperature conditions, tensile strength Rn and melting point p under high temperature conditions, to increase the structural strength of the cover plate 212 and further improve the structural stability of the battery cell 20, but the embodiments of this application are not limited thereto.

[0315] In the embodiment of this application, the case 211 includes at least a portion of a third case wall 2112, the average thickness of the third case wall 2112 being T, where T satisfies 0.05 mm ≤ T ≤ 0.5 mm and 60 mm·MPa ≤ T × Rm ≤ 500 mm·MPa.

[0316] It should be understood that the third case wall 2112 of case 211 in the embodiments of this application may be any one of the walls of case 211. Specifically, the battery cell 20 may be any polyhedral structure, the case 211 may be a hollow structure with at least one end open, the case 211 may include one or more walls, the third case wall 2112 may be any one of the walls of case 211, and the case 211 may include one or more third case walls 2112. For example, if the case 211 is a polygonal prism, the third case wall 2112 may be any one of the walls of the polygonal prism, and the surface of the third case wall 2112 may be any polygon. Also, for example, as shown in Figures 12 and 13, if the case 211 is a rectangular parallelepiped, the third case wall 2112 may be any one of the walls of case 211, and the surface of the third case wall 2112 is rectangular. Furthermore, for example, if the case 211 is cylindrical, the third case wall 2112 may be the bottom surface of the cylinder or a side surface of the cylinder, and the embodiments of this application are not limited thereto. Also, if two adjacent walls of the case 211 are connected by a fillet, when the third case wall 2112 in the embodiments of this application is any one of the walls of the case 211, the third case wall 2112 does not include the connection area of ​​the fillet between that wall and the wall connected to it.

[0317] In the embodiments of this application, at least a portion of the case 211 includes a third case wall 2112, and the tensile strength of the third case wall 2112 at room temperature conditions of 25°C is denoted as Rm. Increasing the tensile strength Rm at room temperature conditions of 25°C in at least a portion of the case 211 can enhance the deformation capacity of the case 211, thereby making the case 211 less susceptible to damage during use of the battery cell 20, and increasing the structural stability and service life of the battery cell 20. However, in order to reduce the difficulty of material selection and processing of the case 211, reduce costs, and facilitate processing, the tensile strength Rm at room temperature in at least a portion of the case 211 should not be excessive.

[0318] If the average thickness T of the third case wall 2112 of case 211 is thin, the structural strength of the third case wall 2112 may be increased by increasing the tensile strength Rm of the third case wall 2112 of case 211 under room temperature conditions of 25°C. In this way, the energy density of the battery cell 20 can be increased, and the structural strength and stability of the battery cell 20 can also be improved. Conversely, if the average thickness T of the third case wall 2112 of case 211 is thick, the structural strength of case 211 can be increased, and the difficulty of material selection for case 211 can be reduced by appropriately lowering the requirement for the tensile strength Rm of the third case wall 2112 of case 211 under room temperature conditions. Furthermore, the difficulty of processing the battery cell 20 and the processing cost can be reduced. T × Rm represents the rigidity of the third case wall, and it is preferable that the rigidity of the third case wall is neither too high nor too low. This strengthens the deformation capacity of the third case wall, reduces the difficulty of processing, and lowers costs.

[0319] It should be understood that the average thickness T of the third case wall 2112 in the embodiments of this application may be flexibly set within a range of values ​​depending on the practical application. For example, the average thickness T of the third case wall 2112 satisfies 0.05 mm ≤ T ≤ 0.5 mm. Furthermore, the average thickness T of the third case wall 2112 satisfies 0.1 mm ≤ T ≤ 0.4 mm. By making the average thickness T of the third case wall 2112 moderately thin, the space occupied by the case 211 inside the battery 10 can be reduced, further increasing the energy density of the battery 10. The structural strength requirements of the case 211 can be met so as to increase the tensile strength Rm of the third case wall 2112 under room temperature conditions, while maintaining the stability of the case 211. By making the average thickness T of the third case wall 2112 moderately thick, the difficulty of processing the third case wall 2112 can be reduced.

[0320] Furthermore, the average thickness T of the third case wall 2112 satisfies the condition 0.1 mm ≤ T ≤ 0.3 mm. The average thickness T of the third case wall 2112 is neither too large nor too small, which improves the structural strength and stability of the case 211, reduces the space occupied by the case 211 inside the battery 10, and further increases the energy density of the battery 10.

[0321] In some embodiments, the average thickness T of the third case wall 2112 in the embodiments of this application may be set to a different value. For example, the average thickness T of the third case wall 2112 may be one of the following values ​​or any two of the following values: 0.05 mm, 0.075 mm, 0.1 mm, 0.125 mm, 0.15 mm, 0.175 mm, 0.2 mm, 0.225 mm, 0.25 mm, 0.275 mm, 0.3 mm, 0.325 mm, 0.35 mm, 0.375 mm, 0.4 mm, 0.425 mm, 0.45 mm, 0.475 mm, and 0.5 mm.

[0322] In some embodiments, the range of the value of T×Rm may be adjusted according to practical requirements. For example, Rm and T may satisfy 60 mm·MPa ≤ T×Rm ≤ 500 mm·MPa, and furthermore, Rm and T may satisfy 100 mm·MPa ≤ T×Rm ≤ 500 mm·MPa. By selecting an appropriate material, the tensile strength Rm of the third case wall 2112 under room temperature conditions can be increased, and the average thickness T of the third case wall 2112 can be reduced, thereby bringing the stiffness value of the third case wall 2112 to match the design requirements, improving the structural strength and structural stability of the third case wall 2112 of case 211, and also increasing the energy density of the battery cell 20 and battery 10.

[0323] Furthermore, the range of the T×Rm value may be set such that Rm and T satisfy 100 mm·MPa ≤ T×Rm ≤ 300 mm·MPa, thereby making the rigidity value of the third case wall 2112 more appropriate, strengthening the deformation capacity of the third case wall 2112, increasing the service life of the battery cell 20, reducing the difficulty of material selection, and further reducing the difficulty and cost of processing.

[0324] In some embodiments, the value of T×Rm in the embodiments of the present application may be set to other values. For example, the value of T×Rm may be any one value or between any two values among 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.

[0325] In the embodiments of the present application, in order to balance the energy density and structural strength of the battery cell 20, the value of the mass ratio g of the silicon-based material may be restricted with the value of the average thickness T of the third case wall 2112, and may also be restricted with the value of the tensile strength Rm under the condition of the temperature of 25°C in at least a part of the region of the case 211. 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 0.15 mm ≤ T ≤ 0.4 mm. When the mass ratio g of the silicon-based material is small, the average thickness T of the third case wall 2112 may be appropriately reduced to increase the space utilization rate of the case 211, and while increasing the energy density of the battery cell 20, the balance with the structural strength of the case 211 can also be achieved.

[0326] In some embodiments, the mass ratio of the silicon-based material in the negative electrode active material is g, and g, T, and Rm satisfy 15% < g < 40%, 0.2 mm ≤ T ≤ 0.4 mm, and 100 mm·MPa ≤ T×Rm ≤ 500 mm·MPa. By increasing the mass g of the silicon-based material, the energy density of the battery cell 20 can be effectively increased, and by improving the thickness and rigidity T×Rm of the third case wall 2112, the structural strength and stability of the battery cell 20 can be improved.

[0327] It should be understood that the average thickness T of the third case wall 2112 in the embodiments of this application may refer to the average thickness of at least a portion of the third case wall 2112. For example, the average thickness T of the third case wall 2112 may refer to the average thickness T of all areas of the third case wall 2112, and in particular, if the third case wall 2112 is flat, that is, if the thickness of most of the third case wall 2112 is approximately equal or does not differ significantly, or if the thickness of all areas of the third case wall 2112 is approximately equal or does not differ significantly, then the average thickness of all areas of the third case wall 2112 can be determined as T.

[0328] For example, the average thickness T of the third case wall 2112 may refer to the average thickness T of a local region of the third case wall 2112, that is, the average thickness T of the remaining region after excluding a portion of the third case wall 2112. For example, if there is a special region in the third case wall 2112, and the thickness of that special region differs significantly from that of other regions, for example, if the thickness of that special region is greater or smaller than that of other regions due to the presence of a protruding structure or a recessed region in that special region, then the average thickness T of the remaining region of the third case wall 2112 may be calculated after excluding that special region.

[0329] In some embodiments, the third case wall 2112 includes a functional region, and the average thickness T of the third case wall 2112 is the average thickness of the region of the third case wall 2112 excluding 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 thickness of the functional region is usually significantly different from the thickness of other regions of the third case wall 2112, and therefore, calculating the average thickness T of the third case wall 2112 without including the functional region can make the design of the third case wall 2112 better meet strength requirements and improve the structural strength and stability of the battery cell 20.

[0330] Specifically, the functional region of the embodiment of this application may include a region in the third case wall 2112 that is provided with a specific structure or has a specific purpose. For example, the functional region may include a pressure release region, which is for providing a pressure release mechanism, and the pressure release mechanism is an element or component that operates to release the internal pressure or temperature of the battery cell 20 when the internal pressure or temperature reaches a predetermined threshold. The predetermined threshold may be adjusted according to design requirements. For example, the predetermined threshold may be determined by one or more materials in the battery cell 20, including the positive electrode sheet, negative electrode sheet, electrolyte, and separator film.

[0331] As used in this application, "operation" refers to the operation or activation of the pressure release mechanism, thereby releasing the internal pressure and temperature of the battery cell 20. The operation performed by the pressure release mechanism includes, but is not limited to, rupture, shattering, tearing, or opening of at least a portion of the pressure release mechanism. When the pressure release mechanism is activated, the high-temperature, high-pressure material inside the battery cell 20 is discharged as waste from the operating part. In this way, pressure and temperature release of the battery cell 20 can be performed while the pressure or temperature is controllable, and the occurrence of more serious potential accidents can be avoided.

[0332] The emissions from the battery cell 20 as referred to in this application include, but are not limited to, electrolyte, dissolved or torn positive and negative electrode sheets, fragments of the separator film, high-temperature and high-pressure gases from the reaction, and flames.

[0333] The pressure relief mechanism in the embodiment of this application may be provided on any one wall of the battery cell 20, for example, in the pressure relief region of the third case wall 2112 of the battery cell 20. The pressure relief mechanism may be part of the third case wall 2112, or it may be a separate structure fixed to the third case wall 2112, for example by welding. For example, if the pressure relief mechanism is part of the third case wall 2112, the pressure relief mechanism may be formed by providing a notch in the third case wall 2112, i.e., a notch is provided in the pressure relief region of the third case wall 2112, and the thickness of the notch is significantly smaller than the thickness of other areas of the third case wall 2112, so that the thickness of the notch does not need to be included in the average thickness T of the third case wall 2112. The notch is the most vulnerable part of the pressure relief mechanism. When the amount of gas generated by the battery cell 20 becomes too large and the internal pressure rises to a threshold, or when the internal temperature of the battery cell 20 rises to a threshold due to the heat generated by the reaction inside the battery cell 20, the pressure release mechanism can rupture 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 through the rupture of the pressure release mechanism, and the explosion of the battery cell 20 is prevented.

[0334] For example, the pressure relief mechanism may be a structure separate from the third case wall 2112, and the pressure relief mechanism may take the form of an explosion-proof valve, gas valve, pressure relief valve, or safety valve, and specifically a pressure-sensitive or temperature-sensitive element or structure may be employed. For example, a through hole is provided in the pressure relief region of the third case wall 2112, and the pressure relief mechanism is attached and fixed to the third case wall 2112 through the through hole, and after attachment, the pressure relief mechanism may protrude or recede from other areas of the third case wall 2112, and therefore the pressure relief region in which the pressure relief mechanism exists does not need to be included in the calculation of the average thickness T of the third case wall 2112.

[0335] In some embodiments, the functional region may include the region where the electrode terminals 214 are located. Specifically, the electrode terminals 214 in the embodiments of this application are electrically connected to the electrode assembly 22 inside the battery cell 20 to output electrical energy from the battery cell 20. The battery cell 20 may also include at least two electrode terminals 214, and these at least two electrode terminals 214 may include at least one first electrode terminal 214a and at least one second electrode terminal 214b, where the first electrode terminal 214a and the second electrode terminal 214b are of opposite polarity. For example, the first electrode terminal 214a may be a positive electrode terminal, in which case the second electrode terminal 214b is a negative electrode terminal, or the first electrode terminal 214a may be a negative electrode terminal, in which case the second electrode terminal 214b is a positive electrode terminal. Here, the positive electrode terminal is for electrically connecting to the positive electrode tab 222a of the electrode assembly 22, and the negative electrode terminal is for connecting to the negative electrode tab 222b of the electrode assembly 22. The positive electrode terminal and the positive electrode tab 222a may be connected directly or indirectly, and the negative electrode terminal and the negative electrode tab 222b may be connected directly or indirectly. Exemplarily, the positive electrode terminal may be electrically connected to the positive electrode tab 222a via one connecting member 23, and the negative electrode terminal may be electrically connected to the negative electrode tab 222b via one connecting member 23.

[0336] It should be understood that each electrode terminal 214 in the embodiments of this application may be provided on any one wall, and multiple electrode terminals 214 may be provided on the same wall or different walls of the battery cell 20. For example, as shown in Figures 12 and 13, each battery cell 20 includes two electrode terminals 214, and the two electrode terminals 214 are located on the same wall, and for example, both electrode terminals 214 may be located on the cover plate 212.

[0337] For example, taking the case where each battery cell 20 similarly includes two electrode terminals 214 and the two electrode terminals 214 are located on the same wall, unlike in Figures 12 and 13, the two electrode terminals 214 may be located on the case 211, for example, both electrode terminals 214 may be located on the third case wall 2112 of the case 211. When the electrode terminals 214 are located on the third case wall 2112, they usually protrude from other areas of the third case wall 2112, i.e., the thickness of the area where the electrode terminals 214 are located is far greater than the thickness of other areas of the third case wall 2112. Therefore, the area where the electrode terminals 214 are located does not need to be included in the calculation of the average thickness T of the third case wall 2112.

[0338] In some embodiments, the functional region may include an electrolyte injection region. For example, an electrolyte injection hole may be provided in the electrolyte injection region of the third case wall 2112, and electrolyte is injected into the case 211 through the injection hole. After the electrolyte injection is complete, the injection hole may be sealed with a sealing member. Since 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 case wall 2112, the electrolyte injection region may not be included in the calculation of the average thickness T of the third case wall 2112.

[0339] In some embodiments, the functional area may include a welded area. For example, the third case wall 2112 may be fixed to other walls by welding, or the third case wall 2112 itself may need to be fabricated by welding, in which case the third case wall 2112 may include a welded area. For example, as shown in Figure 13, the case 211 may be welded in a jointing manner, in which case the case 211 may have a weld bead 2113. Specifically, the case 211 may include at least two parts, which are joined by welding to form the case 211, where Figure 13 shows an example in which the case 211 includes two parts along the height Z direction of the battery cell 20, and the upper half of the case and the lower half of the case have a weld bead 2113, or, contrary to what is shown in Figure 13, other parts of the case 211 may also have a weld bead 2113, and the embodiments of this application are not limited thereto. The welded area of ​​the functional region in the embodiment of this application may include the weld bead 2113. Due to the manufacturing process, the thickness of the welded area is usually greater than the thickness of other areas of the third case wall 2112, so the welded area does not need to be included in the calculation of the average thickness T of the third case wall 2112.

[0340] In the embodiment of this application, the third case wall 2112 of case 211 may be any one of the walls of case 211. For example, the third case wall 2112 is the wall with the smallest thickness of case 211. That is, by limiting the thickness T of the wall with the smallest thickness of case 211, the thickness of the other walls of case 211 can be limited, so that any of the walls of case 211 can meet the structural strength requirements, and furthermore, the structural strength and stability of the battery cell 20 are improved.

[0341] In some embodiments, the third case wall 2112 is the largest wall in the case 211. When multiple battery cells 20 are arranged within the battery 10, the multiple battery cells 20 typically come into contact with each other through the largest wall in the case 211. Therefore, this largest wall typically receives the greatest pressure from the electrode assembly 22. By limiting the average thickness T and room-temperature tensile strength Rm of the third case wall 2112, the deformation capacity of the case 211 can be effectively enhanced, further improving the structural strength and stability of the battery cells 20.

[0342] It should be understood that the location of the largest wall in case 211 of the embodiments of this application may be set according to practical requirements. 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 largest wall of case 211, and the embodiments of this application are not limited thereto.

[0343] In some embodiments, the case 211 includes intersecting bottom and side walls, where the bottom wall is for supporting the electrode assembly housed within the case 211. Specifically, the case 211 may be a hollow structure with at least one end open, and the bottom and side walls of the case 211 do not necessarily refer to the wall opposite the opening and the adjacent wall, respectively. The electrode assembly 22 is housed inside the case 211, and considering that in practical use, the orientation in which the electrode assembly 22 is installed may differ depending on the application, the case 211 may include walls for supporting the electrode assembly 22. Therefore, the bottom wall of the case 211 in the embodiments of this application is a wall for supporting the electrode assembly 22, that is, the bottom wall of the case 211 is for receiving the gravitational force of the electrode assembly 22, while the wall of the case 211 that directly intersects with the bottom wall is the side wall of the case 211.

[0344] In some embodiments, the third case wall 2112 is a side wall of the case 211. Considering the different uses of the bottom wall and side walls of the case 211, the design requirements for the bottom wall and side walls may also differ. For example, the side walls of the case 211 typically have higher requirements for deformation capacity, and if the third case wall 2112 is a side wall of the case 211, limiting the tensile strength Rm and average thickness T of the side wall of the case 211 under room temperature conditions can effectively enhance the deformation capacity of the side wall of the case 211 and further improve the structural stability of the battery cell 20.

[0345] In some embodiments, the case 211 includes a plurality of side walls, the thickness of which is equal to facilitate processing.

[0346] In some embodiments, the thickness of the bottom wall of the case 211 and the thickness of the side walls of the case 211 are equal to facilitate processing and optimize the space occupied by the case 211.

[0347] In some embodiments, the third case wall 2112 is perpendicular to the stacking direction of the electrode sheets of the electrode assembly 22. The stacking direction of the electrode sheets of the electrode assembly 22 is usually the thickness direction of the electrode assembly 22, and considering that the electrode assembly 22 is prone to expansion in the thickness direction during the cyclic charge-discharge use of the battery cell 20, the requirements for deformation of the corresponding case wall 211 are high. Therefore, by making the third case wall 2112 a wall perpendicular to the stacking direction of the electrode sheets of the electrode assembly 22, or by aligning the third case wall 2112 with the electrode assembly 22 in the stacking direction of the electrode sheets of the electrode assembly 22, and limiting the tensile strength Rm and average thickness T of the third case wall 2112 under room temperature conditions, the energy density of the battery cell 20 is increased, the deformation capacity of the third case wall 2112 is also effectively enhanced, and the structural stability of the battery cell 20 is further improved.

[0348] It should be understood that the cover plate 212 in the embodiments of this application may employ the same or a different design as the third case wall 2112. For example, the cover plate 212 may employ the same design as the third case wall 2112, i.e., the average thickness of the cover plate 212 may be T, and the room temperature tensile strength of the cover plate 212 may be b, satisfying the design requirements of b and T, thereby increasing the deformation capacity of the cover plate 212 and further improving the structural strength and stability of the battery cell 20.

[0349] In some embodiments, the ratio of the internal volume of the case 211 to the external volume of the case 211 is 93% or more. That is, the case 211 is thin, which reduces the space occupied by the case 211 itself, and further increases the space utilization rate and energy density of the battery 10.

[0350] It should be understood that the specific calculation methods for the internal volume of case 211 and the external volume of case 211 in the embodiments of this application are related to the shape of case 211. For example, consider the case 211 to be a rectangular parallelepiped. Figure 17 shows a schematic side view of case 211 in the embodiments of this application, and Figure 18 shows a schematic top view of case 211 in the embodiments of this application. For example, the case 211 shown in Figures 17 and 18 may be the case 211 of the battery cell 20 shown in Figures 12 and 13.

[0351] As shown in Figures 17 and 18, a rectangular parallelepiped case 211 is used as an example, and this case 211 is a hollow rectangular parallelepiped with one end open. When calculating the internal volume of the case 211 and the external volume of the case 211, fillet connections between adjacent walls of the case 211 may be ignored. As shown in Figures 17 and 18, each wall of the case 211 has a constant thickness, and in the length direction Y, the internal length of the case 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 case 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 case 211 is Z1 and the external height is Z2, where Z2 is greater than Z1. Therefore, the volume of the internal space of the case 211 is V1 = X1 × Y1 × Z1, and the volume of the external space of the case 211 is V2 = X2 × Y2 × Z2, and V1 / V2 is 93% or more, thereby reducing the space occupied by the case 211 itself, and further increasing the space utilization rate and energy density of the battery 10.

[0352] The following will explain by comparing several comparative examples and several embodiments. Specifically, the battery cell 20 in each of the embodiments and comparative examples below will all be the prismatic battery shown in Figures 12 and 13, and the case 211 will have a hollow structure with one end open.

[0353] In the following examples and comparative examples, the manufacturing methods for the positive electrode sheet 223, negative electrode sheet 224, electrolyte, and separator 225 of the battery cell 20 are as follows.

[0354] 1. Manufacturing of the positive electrode sheet 223 LiNi 0.95 Co 0.04 Mn 0.01 O2, the conductive agent Super P, and the binder polyvinylidene fluoride (PVDF) were prepared into a positive electrode slurry in N-methylpyrrolidone (NMP), and the solid content in the positive electrode slurry was set to 50 wt%, with LiNi in the solid component. 0.7 Co 0.1 Mn 0.1The mass ratio of O2, Super P, and PVDF was set to 8:1:1. The positive electrode slurry was applied to the upper and lower surfaces of the aluminum foil of the current collector, baked at 85°C, then cold-pressed, followed by edge cutting, thinning, and slitting, and finally baked for 4 hours under vacuum conditions at 85°C to produce the positive electrode sheet 223.

[0355] 2. Manufacturing of the negative electrode sheet 224 A negative electrode slurry was prepared by uniformly mixing the negative electrode active material, the conductive agent Super P, the thickener carboxymethylcellulose (CMC), and the binder styrene-butadiene rubber (SBR) with deionized water. The negative electrode active material contained graphite and a silicon-based material, the silicon-based material being a silicon oxygen compound. The solid content in the negative electrode slurry was set to 30 wt%, and the mass ratio of the negative electrode active material, silicon monoxide, Super P, CMC, and the binder styrene-butadiene rubber (SBR) in the solid components was set to 88:7:3:2. The negative electrode slurry was applied to the upper and lower surfaces of the copper foil of the current collector, baked at 85°C, then cold-pressed, edge-cut, thin-cut, and slit, and finally baked for 12 hours under vacuum conditions at 120°C to produce a negative electrode sheet 224.

[0356] 3. Preparation of the electrolyte In an argon gas-atmosphered glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), the electrolyte salt LiPF6, which had been thoroughly dried, was dissolved in a mixed solvent (the mixed solvent contained ethylene carbonate (EC) and diethyl carbonate (DEC), with ethylene carbonate (EC) and diethyl carbonate (DEC) mixed in a mass ratio of 50:50). After homogeneous mixing, an electrolyte solution with a concentration of 1 mol / L was obtained.

[0357] 4. Manufacturing of separator 225 A 16 μm polyethylene film was used as separator 225.

[0358] 5. Manufacturing of lithium-ion battery cells 20 The positive electrode sheet 223, separator 225, and negative electrode sheet 224 were stacked in this order such that the separator 225 served to isolate the positive and negative electrodes between the positive electrode sheet 223 and the negative electrode sheet 224, and the stacked and wound to obtain a bare cell. Tabs were welded, the bare cell was placed in a housing of a different material, the electrolyte prepared above was injected into the dried housing, and packaging, standing, chemical conversion, molding, capacity testing, etc. were performed to complete the manufacture of the lithium-ion battery cell 20.

[0359] In the following examples and comparative examples, the tensile strength of the case 211 of the battery cell 20 at a temperature of 25°C is denoted as Rm. Different materials are selected for the case 211 to obtain different tensile strengths Rm, and the average thickness of the third case wall 2112 of the case 211 is denoted as T. The specific parameter settings are shown in Table 5 below. In addition, in each example and comparative example, the material of all areas of the case 211 is the same, and the tensile strength Rm of the case 211 at 25°C is measured by the method specified in GB / T228.1-2010. Furthermore, in each example and comparative example below, the battery cell 20 has the same settings except for the parameters shown in Table 5. For example, the capacity of the battery cell 20 in each example is 350Ah.

[0360] A fatigue test was performed on the battery cells 20 in each of the following examples and comparative examples by cyclic charging. Specifically, the test may be performed using the jig 700 for fatigue testing by cyclic charging shown in Figure 16.

[0361] Specifically, the battery cell 20 was clamped and fixed in a dedicated jig 700 so that the two largest opposing walls of the battery cell 20 were firmly held, the initial pressure was set to 2000N, and the electrode terminals 214 of the battery cell 20 were connected to a dedicated battery charging and discharging device.

[0362] The jig 700 holding 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.

[0363] 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 cycle cutoff condition for the test was changed to "stop the test when damage occurs to the weld bead 2113 of the battery cell 20."

[0364] For example, the test may be performed according to the following steps: Step a: Discharge at 1I(A) until the discharge termination condition specified by the company is reached. Step b: Leave for 30 minutes or longer or under the conditions 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 under the conditions specified by the company. Step e: Discharge at 1I1(A) until the discharge termination condition specified by the company is reached. Step f: Repeat steps b through e, and stop the test when damage occurs to the weld bead 2113.

[0365] To obtain the condition of case 211 after 1000 cycles as shown in Table 5 below, the weld bead 2113 of the battery cell 20 was continuously observed during the above test process until leakage occurred in the weld bead 2113, and the number of cycles was recorded. Here, in each of the following examples and comparative examples, the weld bead 2113 is the weld bead between case 211 and cover plate 212, that is, the weld bead 2113 surrounds the open end of case 211, and case 211 has an integrally molded structure.

[0366] [Table 5]

[0367] It should be understood that, in Table 5 above, the material for Case 211 may be Q195 carbon steel, and 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 given as an example, but it is not limited to this. Similarly, the material for Case 211 may be SPCC carbon steel, and 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 given as an example. The material for Case 211 may be SUS430 stainless steel, and the tensile strength Rm of SUS430 stainless steel at room temperature of 25°C is typically at least 450 MPa, and in the above example only 459 MPa is given as an example. The material for Case 211 may be SUS304 stainless steel, and the tensile strength Rm of SUS304 stainless steel at room temperature of 25°C is typically at least 520 MPa, and in the above example only 533 MPa, 625 MPa and 763 MPa are given as examples.

[0368] As can be seen from Table 5 above, in Examples 1 to 12 above, the Rm and T of the third case wall 2112 of case 211 satisfy 250MPa≦Rm≦2000MPa, 0.05mm≦T≦0.5mm, and 60mm·MPa≦T×Rm≦500mm·MPa, and the number of failure fatigue cycles of the battery cell 20 can reach 1,000 cycles or more, satisfying the design requirements of the battery cell 20. Furthermore, even if the average thickness T of the third case wall 2112 is set small, the number of failure fatigue cycles of the battery cell 20 can reach 1,000 cycles or more, and setting the average thickness T of the third case wall 2112 small can also increase the energy density of the battery 10. However, in the two comparative examples, the structural strength of the third case wall 2112 is insufficient, and neither Rm nor T×Rm satisfies the above values. Even if the average thickness T of the third case wall 2112 is increased, the number of failure fatigue cycles of the battery cell 20 cannot reach 1,000 cycles, and the design requirements of the battery cell 20 cannot be met.

[0369] In some embodiments, the capacity of the battery cell is C, where C satisfies 25Ah ≤ C ≤ 550Ah. Increasing the capacity C of the battery cell 20 can increase the capacity density of the battery 10 containing multiple battery cells 20, or, if the total capacity of the battery 10 is constant, increasing the capacity C of a single battery cell 20 can reduce the number of battery cells 20 installed, and accordingly reduce the number of electrical connections between multiple battery cells 20, thereby lowering the probability of electrical connection failure and contributing to improved battery reliability. Furthermore, if the capacity C of the battery cell 20 is large, the requirements for the structural strength of the case 211 for the high-capacity battery cell 20 can be met by increasing the tensile strength Rm of at least a portion of the case 211 under normal temperature conditions of 25°C, further increasing the reliability and service life of the battery cell 20. On the other hand, when the battery cell 20 has a large capacity, the internal reaction becomes more intense, further increasing the requirements for the structural strength of the case 211. Therefore, the capacity C of the battery cell 20 should not be excessively large so as to limit the design requirements for the structural strength of the case 211, thereby reducing the difficulty of material selection and processing of the battery cell 20, lowering costs, and increasing processing efficiency.

[0370] It should be understood that the capacity C of the battery cell 20 in the embodiments of this application may be adjusted within a range of practical application. For example, the capacity C of the battery cell 20 may be reasonably selected according to the actual requirements 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 moderately increasing the capacity C of the battery cell 20, the energy density of the battery 10 can be increased, and the capacity C of the battery cell 20 should not be excessive in order to balance the capacity C of the battery cell 20 with the structural strength of the case 211 and to increase the reliability and service life of the battery cell 20.

[0371] Furthermore, the capacity C of the battery cell 20 may satisfy 150Ah ≤ C ≤ 250Ah. Further limiting the capacity C of the battery cell 20 can increase the energy density of the battery 10, increase the structural strength of the case 211, and further increase the reliability and service life of the battery cell 20 and the battery 10.

[0372] In some embodiments, the value of the capacity C of the battery cell 20 in the embodiments of this application may be set to a different value. For example, the value of the capacity C of the battery cell 20 may be any one of the following values ​​or any two of the following values: 25Ah, 30Ah, 35Ah, 40Ah, 45Ah, 50Ah, 55Ah, 60Ah, 65Ah, 70Ah, 75Ah, 80Ah, 85Ah, 90Ah, 95Ah, 100Ah, 130Ah, 150Ah, 180Ah, 200Ah, 230Ah, 250Ah, 280Ah, 300Ah, 330Ah, 350Ah, 380Ah, 400Ah, 430Ah, 450Ah, 480Ah, 500Ah, 530Ah, and 550Ah.

[0373] It should be understood that the capacity C of the battery cell 20 in the embodiments of this application represents the amount of electricity output when the battery cell 20 is fully charged and discharged under specified discharge conditions until it reaches the termination voltage. The method for measuring the capacity C of the battery cell 20 may be selected according to practical requirements. For example, the capacity C of the battery cell 20 may be determined by performing a discharge measurement according to GB / T31467.1, but the embodiments of this application are not limited to this.

[0374] The following will explain by comparing several comparative examples and several embodiments. Specifically, the battery cell 20 in each of the embodiments and comparative examples below will all be the prismatic battery shown in Figures 12 and 13, and the case 211 will have a hollow structure with one end open.

[0375] In the following examples and comparative examples, the manufacturing methods for the positive electrode sheet 223, negative electrode sheet 224, electrolyte, and separator 225 of the battery cell 20 are as follows.

[0376] 1. Manufacturing of the positive electrode sheet 223 LiNi0.95 Co 0.04 Mn 0.01 O2, the conductive agent Super P, and the binder polyvinylidene fluoride (PVDF) were prepared into a positive electrode slurry in N-methylpyrrolidone (NMP), and the solid content in the positive electrode slurry was set to 50 wt%, with LiNi in the solid component. 0.7 Co 0.1 Mn 0.1 The mass ratio of O2, Super P, and PVDF was set to 8:1:1. The positive electrode slurry was applied to the upper and lower surfaces of the aluminum foil of the current collector, baked at 85°C, then cold-pressed, followed by edge cutting, thinning, and slitting, and finally baked for 4 hours under vacuum conditions at 85°C to produce the positive electrode sheet 223.

[0377] 2. Manufacturing of the negative electrode sheet 224 A negative electrode slurry was prepared by uniformly mixing the negative electrode active material, the conductive agent Super P, the thickener carboxymethylcellulose (CMC), and the binder styrene-butadiene rubber (SBR) with deionized water. The negative electrode active material contained graphite and a silicon-based material, the silicon-based material being a silicon oxygen compound. The solid content in the negative electrode slurry was set to 30 wt%, and the mass ratio of the negative electrode active material, silicon monoxide, Super P, CMC, and the binder styrene-butadiene rubber (SBR) in the solid components was set to 88:7:3:2. The negative electrode slurry was applied to the upper and lower surfaces of the copper foil of the current collector, baked at 85°C, then cold-pressed, edge-cut, thin-cut, and slit, and finally baked for 12 hours under vacuum conditions at 120°C to produce a negative electrode sheet 224.

[0378] 3. Preparation of the electrolyte In an argon gas-atmosphered glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), the electrolyte salt LiPF6, which had been thoroughly dried, was dissolved in a mixed solvent (the mixed solvent contained ethylene carbonate (EC) and diethyl carbonate (DEC), with ethylene carbonate (EC) and diethyl carbonate (DEC) mixed in a mass ratio of 50:50). After homogeneous mixing, an electrolyte solution with a concentration of 1 mol / L was obtained.

[0379] 4. Manufacturing of separator 225 A 16 μm polyethylene film was used as separator 225.

[0380] 5. Manufacturing of lithium-ion battery cells 20 The positive electrode sheet 223, separator 225, and negative electrode sheet 224 were stacked in this order such that the separator 225 served to isolate the positive and negative electrodes between the positive electrode sheet 223 and the negative electrode sheet 224, and the stacked and wound to obtain a bare cell. Tabs were welded, the bare cell was placed in a housing of a different material, the electrolyte prepared above was injected into the dried housing, and packaging, standing, chemical conversion, molding, capacity testing, etc. were performed to complete the manufacture of the lithium-ion battery cell 20.

[0381] In the following examples and comparative examples, the tensile strength of the case 211 of the battery cell 20 at a temperature of 25°C is denoted as Rm. Different materials are selected for the case 211 to obtain different tensile strengths Rm, the capacity of the battery cell 20 is denoted as 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 case 211 is the same, and the tensile strength Rm of the case 211 at 25°C is measured by the method specified in GB / T228.1-2010. Furthermore, in each example and comparative example below, the battery cell 20 has the same settings except for the parameters shown in Table 6. For example, the wall thickness of the largest area wall of the battery cell 20 in each example is 0.15 mm, and the chemical system of the battery cell 20 in each example is nickel-cobalt-manganese ternary.

[0382] [Table 6]

[0383] As can be seen by comparing the two comparative examples and the six examples in Table 6 above, different tensile strengths Rm can be determined correspondingly when different materials are used for case 211. 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 the case 211 of the battery cell 20 does not crack, then the structural strength of the case 211 can be used for a large-capacity battery cell 20, and the design requirements 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 case 211 of the battery cell 20 cracks, then the design requirements of the battery cell 20 cannot be met.

[0384] It should be understood that, in order to satisfy the above design requirements, the materials of at least some areas of Case 211 of the embodiment of this application may be flexibly selected according to practical requirements.

[0385] In some embodiments, the material of at least a portion of the case 211 includes at least one of steel, copper alloy, titanium alloy, and nickel alloy. These materials have high strength, can meet the strength requirements of the case 211, are easy to process, and are low in cost.

[0386] In some embodiments, the material of at least a portion of the case 211 includes at least one of stainless steel, carbon steel, and high-strength alloy steel. For example, when stainless steel is used for the case 211, its structural strength is high and it can usually satisfy 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 stainless steel is usually between 1400°C and 1500°C. Furthermore, using stainless steel for the case 211 makes it less susceptible to rust, which can increase the service life of the case 211 compared to other materials.

[0387] When carbon steel material is used for case 211, its structural strength is high, and it can easily satisfy 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. Also, considering that carbon steel material is susceptible to corrosion during use, nickel may be plated on the outer surface of the carbon steel case 211. For example, the thickness of the nickel plating layer is usually between 1 μm and 10 μm to protect the surface of case 211 from corrosion due to oxidation and to increase the service life of case 211.

[0388] In case 211, other high-strength alloy steel materials may be used to effectively increase the structural strength of case 211. For example, if the structural strength requirements for case 211 are high, a high-strength alloy steel material may be selected, which can easily satisfy 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.

[0389] In some embodiments, when steel is used in at least a portion of the area of ​​Case 211, the steel grade 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 requirements, and they are low in cost. For example, Table 7 below shows approximate values ​​for 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).

[0390] [Table 7]

[0391] It should be understood that, in at least some areas of the embodiment of Case 211 of this application, other materials may be selected. For example, different materials may be rationally selected depending on the mass content of different elements in the material and the function that the elements perform.

[0392] In some embodiments, the mass content of chromium in the material of at least a portion of the case 211 is m, where m satisfies 10% ≤ m ≤ 30%. By adding an appropriate amount of chromium to the material of at least a portion of the case 211, the melting point and strength of the material can be increased, thereby allowing the material to easily 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 in the embodiments of this application. Furthermore, since chromium can react with oxygen gas to form a dense chromium oxide film, it is also possible to form a corrosion-resistant protective film on the surface of the case 211, thereby improving the corrosion resistance of the case 211.

[0393] In some embodiments, the mass content of nickel element in the material of at least a portion of the case 211 is n, where n satisfies 8% ≤ n ≤ 25%. By adding an appropriate amount of nickel element to the material of at least a portion of the case 211, the structural strength and plasticity of the case 211 can be increased, 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 increased, and the corrosion resistance of the material can also be provided.

[0394] In some embodiments, using Case 211 as an example, steel is used, and the mass content of different elements in different types of steel varies. For example, in stainless steel material, the mass content of 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, where the values ​​in Table 8 are the maximum percentage of mass of each element in that material, meaning that the mass percentage of each element in its corresponding application is usually less than or equal to the values ​​shown in Table 8.

[0395] [Table 8]

[0396] It should be understood that, when steel is used in at least a portion of Case 211, increasing the mass content of carbon in the steel can increase its strength and hardness. For example, generally, the higher the carbon content, the higher the hardness and strength of the steel, but the lower its corrosion resistance may be.

[0397] Increasing the mass content of chromium in steel allows the chromium to react with oxygen gas to form a dense chromium oxide film, creating a corrosion-resistant protective layer on the surface of the steel, thereby improving the corrosion resistance of the steel.

[0398] Increasing the mass content of nickel in steel can improve the corrosion resistance, strength, and plasticity of the steel.

[0399] Increasing the mass content of molybdenum in steel can improve its corrosion resistance and strength, which is particularly noticeable in corrosive media such as acids and salts.

[0400] Increasing the mass content of manganese in steel can improve its flexibility and fatigue resistance.

[0401] Increasing the mass content of silicon in steel can improve the corrosion resistance and strength of stainless steel.

[0402] Reducing the mass content of phosphorus and sulfur in steel can mitigate the adverse effects of these two elements on the corrosion resistance, plasticity, and flexibility of the steel.

[0403] Furthermore, steel materials may contain other elements. For example, steel materials may contain copper, and the mass content of copper in Q195, Q215, and Q235 is generally 0.3% or less, while in modified stainless steel it is generally 2% to 3.5% or less. Also, for example, steel materials may contain nitrogen, and the mass content of nitrogen in Q195, Q215, and Q235 is generally 0.12% or less.

[0404] It should be understood that the method for measuring the mass content of each element in the steel material described in the embodiments of this application may be set according to practical requirements. For example, it may be measured by inductively coupled plasma atomic emission spectroscopy, i.e., inductively coupled plasma (ICP) technology, but the embodiments of this application are not limited to this.

[0405] Figure 19 shows a schematic local structure of case 211 of the embodiment of the present application, which may be, for example, a local enlargement of region A' shown in Figure 18. As shown in Figure 19, case 211 of the embodiment of the present application has a multilayer structure, and the material of the outermost layer case 2117 of case 211 includes at least one of aluminum, aluminum alloy, copper, copper alloy, and chromium.

[0406] It should be understood that the case 211 in the embodiment of this application has a multilayer structure, that is, multiple layers of structure are stacked in the thickness direction of any one wall of the case 211, thereby making the case 211 a multilayer structure. Furthermore, the method of attaching the multilayer structures of the case 211 may be flexibly set according to practical use. For example, one could first process multiple single-layer case structures of different sizes but substantially the same shape to obtain a case, for example, each single-layer case structure being a hollow structure with an opening, and then fitting the larger case structure to the outside of the smaller case structure in this order, thereby making the multiple single-layer case structures combinable as a multilayer case 211. Alternatively, one could first process a substantially plate-like structure having a multilayer structure, and then assemble multiple such plate-like structures by connecting them to each other, similarly forming a multilayer case 211, but the embodiment of this application is not limited to this.

[0407] It should be understood that the outermost case 2117 of case 211 in the embodiment of this application includes the outermost layer structure of each wall of case 211, that is, the outermost case 2117 is a single-layer case structure that includes the outer surface of case 211.

[0408] In embodiments of this application, the material of the outermost case 2117 of the case 211 may include at least one of aluminum, aluminum alloy, copper, copper alloy, and chromium. Here, if the material of the outermost case 2117 contains aluminum, the aluminum can be oxidized to dense aluminum oxide, thus preventing corrosion; if the material of the outermost case 2117 contains copper, the copper can be oxidized to copper oxide, i.e., verdigris, thus preventing corrosion; and if the material of the outermost case 2117 contains chromium, the chromium can be oxidized to chromium oxide, thus preventing corrosion. Therefore, if the material of the outermost case 2117 is one of the above corrosion-resistant materials, the outermost case 2117 can protect other case layers located inside it, improve the structural stability of the case 211, and increase the service life of the case 211.

[0409] It should be understood that the specific thickness of the outermost case 2117 in the embodiments of this application may be flexibly set according to practical requirements. For example, the thickness of the outermost case 2117 may be set at a constant ratio to the thickness of case 211.

[0410] In some embodiments, the average thickness of the outermost case 2117 is set to T11, and the average thickness of case 211 is set to T10, such that T11 and T10 satisfy 0.15 ≤ T11 / T10 ≤ 0.5. If the ratio of T11 / T10 is set too small, the average thickness T10 of case 211 is limited, so the average thickness T11 of the outermost case 2117 becomes small, increasing the difficulty of processing, while at the same time the corrosion resistance of the outermost case 2117 decreases and the structural reliability of case 211 is affected. Conversely, if the ratio of T11 / T10 is set too large, the average thickness T11 of the outermost case 2117 becomes large, and the thickness of the other layers of case 211 excluding the outermost case 2117 becomes small. However, the structural strength of the outermost case 2117 may be insufficient, especially after oxidation, when its deformation capacity is weak and its average thickness T11 is large, which affects the overall structural strength of case 211 and further reduces the stability of case 211.

[0411] Furthermore, T11 and T10 satisfy 0.15 ≤ T11 / T10 ≤ 0.4. By moderately reducing the maximum value of the T11 / T10 ratio and moderately increasing the minimum value of the T11 / T10 ratio, the average thickness T11 of the outermost case 2117 can be kept from becoming too large or too small, thereby improving the corrosion resistance and also improving the structural strength and stability of the case 211.

[0412] Furthermore, T11 and T10 satisfy 0.2 ≤ T11 / T10 ≤ 0.3 to better improve the anti-corrosion effect and enhance the stability and reliability of case 211.

[0413] In some embodiments, the value of T11 / T10, which is the ratio of the average thickness T11 of the outermost case 2117 to the average thickness T10 of case 211 in the embodiments of this application, may be set to other values. For example, the value of the T11 / T10 ratio may be any one or any two of the following values: 0.15, 0.18, 0.2, 0.23, 0.25, 0.28, 0.3, 0.33, 0.35, 0.38, 0.4, 0.43, 0.45, 0.48, and 0.5.

[0414] It should be understood that the average thickness T10 of case 211 in the embodiment of this application may be set flexibly within a range that is appropriate for practical use. For example, the average thickness T10 of case 211 satisfies 0.05 mm ≤ T10 ≤ 0.5 mm. The value of the average thickness T10 of case 211 should not be too small, in order to reduce the difficulty of processing the multi-layer case 211, increase the structural strength of the case 211, for example, make the case 211 less prone to cracking, and further increase the service life of the case 211. Conversely, the value of the average thickness T10 of case 211 should not be too large, in order to save the space occupied by the case 211, increase the space utilization rate of the battery cells 20, and further increase the energy density of the battery 10 provided with multiple battery cells 20.

[0415] Furthermore, the average thickness T10 of the case 211 satisfies the condition 0.075 mm ≤ T10 ≤ 0.4 mm. By making the average thickness T10 of the case 211 moderately thin, the space occupied by the case 211 inside the battery 10 can be reduced, and the energy density of the battery 10 can be increased. By making the average thickness T10 of the case 211 moderately thick, the difficulty of processing the case 211 can be reduced.

[0416] Furthermore, the average thickness T10 of the case 211 satisfies the condition 0.1 mm ≤ T10 ≤ 0.3 mm. The average thickness T10 of the case 211 is neither too large nor too small, improving the structural strength and stability of the case 211, reducing the space occupied by the case 211 inside the battery 10, and further increasing the energy density of the battery 10.

[0417] In some embodiments, the average thickness T10 of case 211 in the embodiments of this application may be set to other values. For example, the average thickness T10 of case 211 may be one of the following values ​​or any two of the following values: 0.05 mm, 0.075 mm, 0.1 mm, 0.125 mm, 0.15 mm, 0.175 mm, 0.2 mm, 0.225 mm, 0.25 mm, 0.275 mm, 0.3 mm, 0.325 mm, 0.35 mm, 0.375 mm, 0.4 mm, 0.425 mm, 0.45 mm, 0.475 mm, and 0.5 mm.

[0418] It should be understood that the average thickness T11 of the outermost case 2117 in the embodiments of this application may be set flexibly within a range that is appropriate for practical use, for example, T11 satisfying 0.015 mm ≤ T11 ≤ 0.25 mm. The average thickness T11 of the outermost case 2117 should not be too small in order to reduce the difficulty of processing, improve the corrosion resistance of the outermost case 2117, and further improve the structural reliability of the case 211. Conversely, the average thickness T11 of the outermost case 2117 should not be too large, considering that when the outermost case 2117 is oxidized, its deformation capacity is weak, and if the average thickness T11 becomes too large, it will affect the deformation capacity of the entire structure of the case 211, further reducing the reliability and stability of the case 211.

[0419] Furthermore, the average thickness T11 of the outermost case 2117 may satisfy the condition 0.05 mm ≤ T11 ≤ 0.2 mm. By moderately increasing the minimum value of the average thickness T11 of the outermost case 2117, the corrosion protection effect of the outermost case 2117 can be improved, and by moderately decreasing the maximum value of the average thickness T11 of the outermost case 2117, the deformation capacity of the entire structure of the case 211 can be enhanced, further improving the reliability and stability of the case 211.

[0420] Furthermore, the average thickness T11 of the outermost case 2117 may satisfy the condition 0.075 mm ≤ T11 ≤ 0.15 mm. This can improve the corrosion resistance of the outermost case 2117, enhance the overall deformation capacity of the case 211 structure, and thereby improve the reliability and stability of the case 211.

[0421] In some embodiments, the average thickness T11 of the outermost case 2117 in the embodiments of this application may be set to a different value. For example, the average thickness T11 of the outermost case 2117 may be one of the following values ​​or any two of the following values: 0.015mm, 0.02mm, 0.025mm, 0.03mm, 0.035mm, 0.04mm, 0.045mm, 0.05mm, 0.055mm, 0.06mm, 0.065mm, 0.07mm, 0.075mm, 0.08mm, 0.085mm, 0.09mm, 0.095mm, 0.1mm, 0.11mm, 0.12mm, 0.13mm, 0.14mm, 0.15mm, 0.16mm, 0.17mm, 0.18mm, 0.19mm, 0.2mm, 0.21mm, 0.22mm, 0.23mm, 0.24mm, and 0.25mm.

[0422] It should be understood that the thickness of the inner layer case 2118 of case 211 in the embodiments of this application may be flexibly set according to practical needs, where the inner layer case 2118 is any one of the layers of case 211 other than the outermost layer case 2117. Furthermore, case 211 may include one or more inner layer cases 2118, and if case 211 includes multiple inner layer cases 2118, the thicknesses of the multiple inner layer cases 2118 may be the same to facilitate processing, or they may be different to flexibly adjust the thickness of the inner layer cases 2118 at different positions according to practical needs. For example, as shown in Figure 19, here is an example in which case 211 includes a three-layer case structure, which includes the outermost layer case 2117 located on the outermost side and two inner layer cases 2118 located inside, and the two inner layer cases 2118 include the innermost layer case 2118b and the intermediate layer case 2118a. The average thickness of the innermost case 2118b and the average thickness of the intermediate case 2118a may be the same or different. For example, both the average thickness of the innermost case 2118b and the average thickness of the intermediate case 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, equal to, or less than T11, and the embodiments of this application are not limited thereto.

[0423] It should be understood that the average thickness T10 of case 211 in the embodiments of this application may refer to the average thickness of at least a portion of the case 211. The average thickness T11 of the outermost layer case 2117 of case 211 may refer to the average thickness of at least a portion of the outermost layer case 2117. The average thickness T12 of the inner layer case 2118 of case 211 may refer to the average thickness of at least a portion of the inner layer case 2118. Furthermore, the calculation area for the average thickness T10 of case 211 usually coincides with the calculation area for the average thickness T11 of the outermost layer case 2117 and also coincides with the calculation area for the average thickness T12 of the inner layer case 2118. For example, if a portion of the case is excluded from the calculation of the average thickness T10 of case 211, then similar portions must be excluded from the calculation of the average thickness T11 of the outermost layer case 2117, and similar portions must be excluded from the calculation of the average thickness T12 of the inner layer case 2118. For the sake of explanation, an example of calculating the average thickness T10 of case 211 will be described below. However, the same explanation applies to determining the average thickness T11 of the outermost case 2117 and the average thickness T12 of the inner case 2118, so the explanation will be omitted here.

[0424] For example, the average thickness T10 of case 211 may refer to the average thickness T10 of all areas of case 211, and in particular, if the entire surface of case 211 is flat, that is, if the thickness of most areas of case 211 is approximately equal or does not differ significantly, or if the thickness of all areas of case 211 is approximately equal or does not differ significantly, then the average thickness of all areas of case 211 can be determined to be T10.

[0425] For example, the average thickness T10 of case 211 may refer to the average thickness T10 of a local region of case 211, that is, the average thickness T10 of the remaining region after excluding a portion of case 211. For example, if a special region exists in case 211, and the thickness of that special region differs significantly from that of other regions, for example, if a protruding structure or recessed region exists in that special region along the thickness direction, causing the thickness of that special region to be greater or smaller than that of other regions, then the special region may be excluded, and the average thickness T10 of the remaining region of case 211 may be calculated.

[0426] In some embodiments, the case 211 may include a functional region, and the average thickness T10 of the case 211 is the average thickness of the region of the case 211 excluding the functional region, for example, 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 thickness of the functional region is usually significantly different from the thickness of other regions of the case 211, and therefore, calculating the average thickness T10 of the case 211 without including the functional region can make the design of the case 211 better meet strength requirements and improve the structural strength and stability of the battery cell 20.

[0427] It should be understood that the functional area of ​​the embodiment of this application may include an area in the case 211 where a specific structure is provided or has a specific use, and this falls under the "functional area" described above, and for the sake of brevity, the explanation is omitted here. For example, the functional area may include a pressure release area for providing a pressure release mechanism. The pressure release mechanism of the embodiment of this application may be provided on any one wall of the battery cell 20, for example, the pressure release mechanism may be provided in the pressure release area of ​​the case 211 of the battery cell 20. The pressure release mechanism may be part of the case 211, or it may be a separate structure from the case 211, fixed to the case 211, for example by welding. For example, if the pressure release mechanism is part of the case 211, the pressure release mechanism may be formed by making a notch in the case 211, i.e., a notch is made in the pressure release region of the case 211, and the thickness of the notch is significantly smaller than the thickness of other areas of the case 211, so the thickness of the notch does not need to be included in the average thickness T10 of the case 211. The notch is the most vulnerable part of the pressure release mechanism. When the amount of gas generated by the battery cell 20 is too much and the internal pressure rises to a threshold, or when the internal temperature of the battery cell 20 rises to a threshold due to the heat generated by the reaction inside the battery cell 20, the pressure release mechanism can rupture at the notch, connecting 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.

[0428] For example, the pressure relief mechanism may be a separate structure from the case 211, and may take the form of an explosion-proof valve, gas valve, pressure relief valve, or safety valve, and specifically can employ pressure-sensitive or temperature-sensitive elements or structures. For example, a through hole may be provided in the pressure relief region of the case 211, and the pressure relief mechanism may be attached and fixed to the case 211 through the through hole, and after attachment, the pressure relief mechanism may protrude or recede from other areas of the case 211, and therefore the pressure relief region in which the pressure relief mechanism exists may not be included in the calculation of the average thickness T10 of the case 211. When the internal pressure or temperature of the battery cell 20 reaches a predetermined threshold, the pressure relief mechanism will operate or a vulnerable structure provided within the pressure relief mechanism will be destroyed, thereby forming an opening or passage that can release the internal pressure or temperature.

[0429] In some embodiments, the functional region may include the region where the electrode terminals 214 are located. Each electrode terminal 214 in the embodiments of this application may be provided on any one wall, and multiple electrode terminals 214 may be provided on the same wall or on different walls of the battery cell 20. For example, as shown in Figures 3 to 4, each battery cell 20 includes two electrode terminals 214, and the two electrode terminals 214 are located on the same wall, and for example, both electrode terminals 214 may be located on the cover plate 212.

[0430] For example, taking the case where each battery cell 20 similarly includes two electrode terminals 214 and the two electrode terminals 214 are located on the same wall, unlike in Figures 3 and 4, the two electrode terminals 214 may be located on any one wall of the case 211, for example, both electrode terminals 214 may be located on the smallest wall of the case 211. When one or more electrode terminals 214 are located on the case 211, each electrode terminal 214 usually protrudes from other areas of the case 211, i.e., the thickness of the area where the electrode terminal 214 is located is far greater than the thickness of other areas of the case 211. Therefore, the calculation of the average thickness T10 of the case 211 does not need to include the area where all electrode terminals 214 are located.

[0431] In some embodiments, the functional region may include an electrolyte injection region. For example, the electrolyte injection region of the case 211 may be provided with an injection hole, through which electrolyte is injected into the interior of the case 211. After the electrolyte injection is complete, the injection hole may be sealed with a sealing member. Since 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 case 211, the electrolyte injection region may not be included in the calculation of the average thickness T10 of the case 211.

[0432] In some embodiments, the functional area may include a welded area. For example, the case 211 may be fixed to the cover plate 212 by welding, or the case 211 itself may be fabricated by welding, for example, any two walls of the case 211 may be welded together, or the case 211 may be formed by joining at least two parts together, in which case the case 211 may include a welded area. For example, the case 211 may be welded in a jointing manner, in which case the case 211 may have a weld bead 2113. Specifically, the case 211 may include at least two parts, which are joined by welding to form the case 211, where the embodiments of this application mainly include two parts along the height direction Z of the battery cell 20, with the upper and lower halves of the case having a weld bead 2113, or, as shown in Figure 4, other parts of the case 211 may also have a weld bead 2113, and the embodiments of this application are not limited thereto. The welded area of ​​the functional area in the embodiments of this application may include the weld bead 2113. Due to the manufacturing process, the thickness of the welded area is usually greater than the thickness of other areas of the case 211, so the welded area may not be included in the calculation of the average thickness T10 of the case 211.

[0433] It should be understood that, in order to further improve the structural strength and reliability of case 211, the inner layer case 2118 of case 211 may be set according to practical requirements. In some embodiments, the tensile strength Rm1 of the inner layer case 2118 of case 211 at 25°C is denoted as Rm1, and Rm1 satisfies 250MPa ≤ Rm1 ≤ 2000MPa. Increasing the tensile strength Rm1 of the inner layer case 2118 of the raised case 211 at room temperature and 25°C improves the overall structural strength and stability of case 211. However, the tensile strength Rm1 of the inner layer case 2118 at room temperature should not be excessive in order to reduce the difficulty of material selection for the inner layer case 2118 and further reduce the difficulty and cost of processing the battery cell 20.

[0434] It should be understood that the tensile strength Rm1 of the inner layer case 2118 under room temperature conditions of 25°C in the embodiments of this application may be adjusted within a range that is appropriate for practical use. For example, the value of the room temperature tensile strength Rm1 may satisfy 400 MPa ≤ Rm1 ≤ 1200 MPa. Increasing the tensile strength Rm1 of the inner layer case 2118 under room temperature conditions can enhance its deformation capacity, cope with the expansion of the electrode assembly 22, make the inner layer case 2118 less susceptible to breakage, and further increase the structural stability and service life of the case 211 and battery cell 20. On the other hand, by keeping the tensile strength Rm1 of the inner layer case 2118 under room temperature conditions from becoming too high, the difficulty of material selection and processing of the inner layer case 2118 can be reduced, costs can be lowered, and processing can be made easier.

[0435] Furthermore, the tensile strength Rm1 of the inner case 2118 under room temperature conditions may be set to satisfy 450 MPa ≤ Rm1 ≤ 800 MPa. The tensile strength Rm1 of the inner case 2118 under room temperature conditions will not be too large or too small, which will enhance the deformation capacity of the inner case 2118, accommodate the expansion of the electrode assembly 22, and will also be easy to implement and cost-effective.

[0436] In some embodiments, the value of the tensile strength Rm1 of the inner case 2118 of the embodiments of this application under room temperature conditions may be set to a different value. For example, the value of the room-temperature tensile strength Rm1 may be one of the following values ​​or any two of the following values: 250MPa, 280MPa, 300MPa, 330MPa, 350MPa, 380MPa, 400MPa, 450MPa, 500MPa, 550MPa, 600MPa, 650MPa, 700MPa, 750MPa, 800MPa, 850MPa, 900MPa, 950MPa, 1000MPa, 1050MPa, 1100MPa, 1150MPa, 1200MPa, 1250MPa, 1300MPa, 1350MPa, 1400MPa, 1450MPa, 1500MPa, 1550MPa, 1600MPa, 1650MPa, 1700MPa, 1750MPa, 1800MPa, 1850MPa, 1900MPa, 1950MPa, and 2000MPa.

[0437] It should be understood that the tensile strength in the embodiments of this application is the maximum stress value that the material experiences before it breaks under tension. The method for measuring the tensile strength Rm1 of the inner layer case 2118 in the embodiments of this application under a temperature of 25°C may be selected according to practical requirements. For example, the tensile strength Rm1 may be measured under room temperature conditions of 25°C according to the national standard GB / T228.1-2010.

[0438] The above explanation mainly used a rectangular battery cell 20 as an example. Below, with reference to the drawings, a cylindrical battery cell 20 will be explained as an example. The cylindrical battery cell 20 of the embodiment of this application differs from the rectangular battery cell 20 described above in shape, but all other descriptions apply to each other, so the explanation will be omitted here.

[0439] Figure 20 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 21 shows a schematic diagram of the locally disassembled structure of a battery cell 20 according to one embodiment of the present application. For example, Figure 21 may be a schematic diagram of the locally disassembled structure of the battery cell 20 shown in Figure 20. Figure 22 shows a schematic cross-sectional view of the case 211 of the battery cell 20 according to one embodiment of the present application. For example, Figure 22 may be a cross-sectional view of the case 211 of the battery cell 20 shown in Figures 20 and 21, and the cross-section is a cross-section of the case 211.

[0440] In the embodiments of this application, as shown in Figures 18 to 22, the battery cell 20 includes an electrode assembly 22 including a first tab 2221, a first electrode terminal 214a, and a case 211 including a cylinder 211b and a cover 211a connected to the cylinder 211b, wherein the cylinder 211b is provided around 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 via the cylinder 211b, and the case 211 has a multilayer structure with different resistivity of the multilayer structure.

[0441] The case 211 may have various shapes, such as a cylinder, a rectangular parallelepiped, or other polyhedron. Exemplarily, an example where the case 211 is a hollow cylindrical structure is described here, as shown in Figures 20 to 22. Furthermore, in the embodiments of this application, an example is given where the case 211 is a hollow structure with an opening at one end, and the corresponding cover plate 212 is a circular plate structure matching the case 211. For a cylindrical case 211, correspondingly, the cylinder 211b is cylindrical, and the cover 211a is a circular plate structure.

[0442] The electrode assembly 22 of the embodiment of this application may include a first tab 2221 which can be electrically connected to the first electrode terminal 214a via the cylinder 211b of the case 211, thereby simplifying the structure of the battery cell 20. By making the case 211 a multilayer structure, the resistivity of the multilayer structure differs, so the current passability of the battery cell 20 can be enhanced by the structure of the low resistivity layer, and the structural strength of the case 211 can be increased by the structure of the high resistivity layer, thereby improving the performance of the battery cell 20, increasing the structural strength of the battery cell 20, and further increasing the service life of the battery cell 20.

[0443] In the embodiments of this application, the electrode assembly 22 further includes a second tab 2222, the second tab 2222 and the first tab 2221 having opposite polarities. Specifically, from an external view, the electrode assembly 22 includes a main body 221 and tabs 222, the tabs 222 include a first tab 2221 and a second tab 2222, the first tab 2221 and the second tab 2222 protruding from the main body 221. The first tab 2221 is the portion of the first electrode sheet that is not coated with the active material layer, and the second tab 2222 is the portion of the second electrode sheet that is not coated with the active material layer. The first tab 2221 and the second tab 2222 are for drawing current from within the main body 221.

[0444] 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, the first tab 2221 and the second tab 2222 may each extend from opposite sides, i.e., the first tab 2221 and the second tab 2222 may each be located on opposing end faces of the electrode assembly 22 to facilitate processing. As shown in Figures 20 to 22, 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. Here, the first direction Z may be the height direction Z of the electrode assembly 22.

[0445] It should be understood that the electrode assembly 22 includes a first electrode sheet, a second electrode sheet, and a separator, the separator being used to separate the first electrode sheet and the second electrode sheet. The first electrode sheet and the second electrode sheet have opposite polarities; in other words, one of the first and second electrode sheets is the positive electrode sheet 223, and the other is the negative electrode sheet 224.

[0446] The first electrode sheet, the second electrode sheet, and the separator are all strip-shaped structures, and the first electrode sheet, the second electrode sheet, and the separator are wound together to form a wound structure. The wound structure may be cylindrical, flat, or of other shapes.

[0447] Selectively, the first tab 2221 is wound several times around the central axis of the electrode assembly 22, and the first tab 2221 includes several tab layers. After winding is complete, the first tab 2221 is substantially columnar, with a gap remaining between two adjacent tab layers. In embodiments of the present application, the first tab 2221 may be treated to reduce the gap between the tab layers and to facilitate connection between the first tab 2221 and other conductive structures. For example, in embodiments of the present application, the first tab 2221 may be flattened with a roll to converge and bring together the end region of the first tab 2221 away from the main body 221, thereby forming a dense end face at the end of the first tab 2221 away from the main body 221, reducing the gap between the tab layers and facilitating connection between the first tab 2221 and other conductive structures. Alternatively, in embodiments of the present application, conductive material may be filled between two adjacent tab layers to reduce the gap between the tab layers.

[0448] Selectively, the second tab 2222 is wound several times around the central axis of the electrode assembly 22, and the second tab 2222 contains several layers of tabs. Exemplarily, the second tab 2222 is also flattened by rolling to reduce the gaps between the tab layers of the second tab 2222.

[0449] In the embodiment of this application, the battery cell 20 further includes a second electrode terminal 214b which is electrically connected to the second tab 2222, and the first electrode terminal 214a and the second electrode terminal 214b are located on the same wall of the battery cell 20, 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.

[0450] It should be understood that the cover 211a of the embodiment of this application includes a first electrode terminal 214a, for example, the first electrode terminal 214a may be provided on the cover 211a, or the cover 211a may be the first electrode terminal 214a directly.

[0451] In some embodiments, the cover 211a is the first electrode terminal 214a, the cover 211a is provided with an electrode lead-out hole 211c, the second electrode terminal 214b is provided insulated from the cover 211a and attached to the electrode lead-out hole 211c, one of the cover 211a and the second electrode terminal 214b is the positive output electrode of the battery cell, and the other is the negative output electrode of the battery cell. At least a portion of the case 211 itself may also serve as one output electrode of the battery cell 20, thereby omitting one conventional electrode terminal and simplifying the structure of the battery cell 20. When multiple battery cells 20 are assembled into a set, the case 211 may be electrically connected to a bus member, thereby increasing the current passage area and allowing for greater flexibility in the structural design of the bus member.

[0452] For the sake of explanation, the following will mainly describe an example in which the cover 211a is the first electrode terminal 214a, but the embodiments of this application are not limited to this.

[0453] Figure 23 is a schematic local cross-sectional view of a battery 10 provided in some embodiments of this application, which may include a plurality of battery cells 20. Figure 24 is another schematic local cross-sectional view of a battery 10 provided in some embodiments of this application, which may be, for example, an enlarged schematic view of region B' of the battery 10 shown in Figure 23.

[0454] As shown in Figures 20 to 24, the cover 211a is provided with an electrode lead-out hole 211c, and at least a portion of the cover 211a is for electrically connecting the first connecting member 81 and the first tab 2221 of the battery 10, and the second electrode terminal 214b is for electrically connecting the second connecting member 82 and the second tab 2222 of the battery 10, and the second electrode terminal 214b is provided 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.

[0455] The cover 211a is electrically connected to the cylinder 211b, and the cover 211a and the cylinder 211b may have the same polarity.

[0456] It should be understood that the cover 211a and cylinder 211b in the embodiments of this application may be integrally formed, i.e., the case 211 is an integrally molded member. In this way, the process of connecting the cover 211a and cylinder 211b can be omitted. For example, the case 211 may be formed by a tensioning process. Of course, the cover 211a and cylinder 211b may be connected as two separately provided members by methods such as welding, riveting, or bonding. The embodiments of this application mainly describe an example in which the cover 211a and cylinder 211b are integrally formed.

[0457] The case 211 in the embodiment of this application may be a hollow structure with one end open. Specifically, the cylinder 211b has an opening 211d at the end opposite to the cover 211a. The battery cell 20 further includes a cover plate 212, which is placed over the opening 211d of the cylinder 211b to seal the opening 211d of the cylinder 211b. The cover plate 212 may have various structures; for example, the cover plate 212 may be a plate-like structure.

[0458] In some embodiments, the cover 211a is provided with an electrode extraction hole 211c, and the area of ​​the cover 211a other than the electrode extraction hole 211c includes an area for welding to the first connecting member 81, i.e., the cover 211a may be welded to the first connecting member 81 to form a first weld W1. Exemplarily, during welding, a laser is applied to the surface of the first connecting member 81 opposite to the cover 211a, and the laser melts and connects a part of the first connecting member 81 and a part of the cover 211a to form a first weld W1.

[0459] The electrode lead-out hole 211c penetrates the cover 211a to allow electrical energy in the electrode assembly 22 to be easily drawn out of the case 211. Exemplarily, the electrode lead-out hole 211c penetrates the cover 211a in the first direction Z.

[0460] In the embodiment of this application, the electrode lead-out holes 211c are manufactured after the case 211 is tensile-formed. For example, in this embodiment, the electrode lead-out holes 211c for attaching the second electrode terminal 214b are formed in the cover 211a by a drilling process, and the positive and negative output electrodes are provided at one end of the battery cell 20 opposite to the opening in the case 211. The cover 211a is formed during the molding of the case 211, ensuring flatness even after the electrode lead-out holes 211c are opened, and ensuring the connection strength between the cover 211a and the first connecting member 81. Furthermore, since the flatness of the cover 211a is not limited by its own size, the cover 211a may have a large size, thereby increasing the current pass-through capability of the battery cell 20.

[0461] In some embodiments, the cylinder 211b is cylindrical, the electrode extraction hole 211c is circular, and the central axes of the cylinder 211b and the electrode extraction hole 211c are aligned. "Aligned" does not require that the central axes of the cylinder 211b and the electrode extraction hole 211c be absolutely perfectly aligned, and there may be process-acceptable deviations.

[0462] The electrode lead-out hole 211c can be used to limit the position of the second electrode terminal 214b. In this embodiment, by aligning the central axis of the electrode lead-out hole 211c with the central axis of the cylinder 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 lowered, simplifying the assembly process and increasing assembly efficiency.

[0463] The central axis of the electrode assembly 22 is a virtual straight line and is 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; in this embodiment, this is not limited.

[0464] The first tab 2221 is electrically connected to the cover 211a. The first tab 2221 may be electrically connected directly to the cover 211a, or it may be electrically connected indirectly to the cover 211a via another conductive structure, for example, the first tab 2221 may be electrically connected to the cover 211a via the cylinder 211b.

[0465] 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 via another conductive structure. For example, the second tab 2222 may be electrically connected to the second electrode terminal 214b via the current collector member 23.

[0466] Since the second electrode terminal 214b is provided insulated from the cover 211a, 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.

[0467] The second electrode terminal 214b is fixed to the cover 211a. The second electrode terminal 214b may be fixed as a whole to the outside of the cover 211a, or it may extend into the inside of the case 211 through the electrode lead-out hole 211c.

[0468] If 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 terminal of the battery cell 20 and the second electrode terminal 214b is the positive output terminal of the battery cell 20. If 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 terminal of the battery cell 20 and the second electrode terminal 214b is the negative output terminal of the battery cell 20.

[0469] In the battery 10, multiple battery cells 20 are electrically connected via a bus member. The bus member includes a first connecting member 81 and a second connecting member 82. The first connecting member 81 is for connecting to the cover 211a of the battery cell 20, and the second connecting member 82 is for connecting to the second electrode terminal 214b of the battery cell 20.

[0470] The first connecting member 81 may be connected to the cover 211a by welding, bonding, or other means to achieve an electrical connection between the first connecting member 81 and the cover 211a. The second connecting member 82 may be connected to the second electrode terminal 214b by welding, bonding, riveting, or other means to achieve an electrical connection between the second connecting member 82 and the second electrode terminal 214b.

[0471] For example, the first connecting member 81 connects the cover 211a of one battery cell 20 to the second electrode terminal 214b of another battery cell 20, and the second connecting member 82 connects the second electrode terminal 214b of the first battery cell 20 to the cover 211a of yet another battery cell 20, so that the first connecting member 81 and the second connecting member 82 connect three battery cells 20 in series.

[0472] 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 and the current pass capability of the battery cell 20 can be ensured. The cover 211a and the second electrode terminal 214b are located at the same end of the battery cell 20, and in this way the first connecting member 81 and the second connecting member 82 can be assembled to the same side of the battery cell 20, thereby simplifying the assembly process and increasing the efficiency of assembling multiple battery cells 20 into a set.

[0473] It should be understood that, as shown in Figures 20 to 24, the second electrode terminal 214b in the embodiment of this application includes a terminal body 2141. Furthermore, the terminal body 2141 can be fixed to the cover 211a by riveting. For example, at least a portion of the terminal body 2141 is located within the electrode lead hole 211c, and both ends of the terminal body 2141 are riveted to the electrode lead hole 211c.

[0474] In some embodiments, the terminal body 2141 may be provided with a recess, which is recessed in a direction toward the electrode assembly 22 from the outer surface of the terminal body 2141. The bottom of the recess is for connection to the current collector member 23.

[0475] The electrode assembly 22 and the current collector member 23 are mounted inside the case 211 through the opening 211d of the cylinder 211b. When the current collector member 23 abuts against the cover 211a, the external welding device can weld the bottom of the recess to the current collector member 23 from the opposite side of the bottom of the recess from the current collector member 23.

[0476] In this embodiment, by providing a recess, the thickness of the terminal body 2141 is reduced, thereby reducing the welding power required to weld the bottom of the recess to the current collector 23, reducing the heat generated, and thus reducing the risk of burnout of other components (for example, the first insulating member 61 and the second insulating member 60).

[0477] In some embodiments, the second electrode terminal 214b further includes a sealing plate 2142 for sealing the opening of the recess. The sealing plate 2142 may be located entirely outside the recess or partially housed within the recess, as long as the sealing plate 2142 can seal the opening of the recess. The sealing plate 2142 can protect the recess from the outside, reduce external foreign matter entering the recess, reduce the risk of the bottom of the recess being damaged by external foreign matter, and improve the sealing performance of the battery cell 20.

[0478] In some embodiments, the sealing plate 2142 is welded to the second connecting member 82 to form a second weld W2. The second weld W2 can reduce the contact resistance between the sealing plate 2142 and the second connecting member 82 and enhance the current flow capability.

[0479] In some embodiments, at least a portion of the sealing plate 2142 protrudes from the outer surface of the terminal body 2141. When it is necessary to weld the second connecting member 82 and the sealing plate 2142, first the second connecting member 82 is bonded to the surface of the sealing plate 2142 (i.e., the surface opposite to the recess of the sealing plate 2142), and then the second connecting member 82 and the sealing plate 2142 are welded together. At least a portion of the sealing plate 2142 protrudes from the outer surface of the terminal body 2141 to avoid interference from the outer surface of the terminal body 2141 with the bonding of the sealing plate 2142 and the second connecting member 82, and to ensure a close bonding between the second connecting member 82 and the sealing plate 2142.

[0480] In embodiments of the present application, the battery cell 20 further includes a first insulating member 61 for insulatingly isolating at least a portion of the second electrode terminal 214b from the cover 211a. Exemplarily, at least a portion of the first insulating member 61 is sandwiched between the cover 211a and the second electrode terminal 214b to insulatingly isolate the cover 211a from the second electrode terminal 214b and reduce the risk of short circuits.

[0481] In the embodiment of this application, the battery cell 20 further includes a second insulating member 60 located between the cover 211a and the electrode assembly 22. Specifically, the second insulating member 60 isolates the electrode assembly 22 from the cover 211a, reducing the risk of contact and conductivity between the electrode assembly 22 and the cover 211a when the battery cell 20 vibrates, thereby improving safety.

[0482] In some embodiments, at least one of the first insulating member 61 and the second insulating member 60 can be used to seal the electrode lead hole 211c. In some other embodiments, the battery cell 20 further includes a seal ring 62 that is fitted onto the second electrode terminal 214b to seal the electrode lead hole 211c. Selectively, a portion of the seal ring 62 extends into the electrode lead hole 211c to isolate the hole wall of the electrode lead hole 211c from the second electrode terminal 214b.

[0483] 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 opposite to the cover 211a. The cylinder 211b connects the first tab 2221 to the cover 211a, thereby electrically connecting the first tab 2221 to the cover 211a.

[0484] The cylinder 211b may be electrically connected directly to the first tab 2221, or it may be electrically connected to the first tab 2221 via other components. For example, the first tab 2221 may be electrically connected to the cylinder 211b via the cover plate 212.

[0485] In the embodiment of this application, by providing the first tab 2221 and the second tab 2222 at both ends of the electrode assembly 22, the risk of conductivity between the first tab 2221 and the second tab 2222 can be reduced, and the current-passing area of ​​the first tab 2221 and the current-passing area of ​​the second tab 2222 can be increased.

[0486] In some embodiments, the first tab 2221 is the negative electrode tab, and the base material of the case 211 is steel. The case 211 is electrically connected to the negative electrode tab, i.e., the case 211 is in a low potential state. The steel case 211 is less susceptible to corrosion by the electrolyte in the low potential state, thus reducing safety risks.

[0487] In some embodiments, the battery cell 20 further includes a current collector 23 for connecting a second tab 2222 and a second electrode terminal 214b. The current collector 23 may be connected to the second tab 2222 by means of welding, abutting, or bonding, and may also be connected to the second electrode terminal 214b by means of welding, abutting, bonding, riveting, etc., thereby achieving an electrical connection between the second tab 2222 and the second electrode terminal 214b.

[0488] In the first direction Z, the second electrode terminal 214b is positioned opposite the central region of the second tab 2222. Directly connecting the second electrode terminal 214b to the second tab 2222 would lengthen the conductive path between the edge region of the second tab 2222 and the second electrode terminal 214b, resulting in uneven current density in the second electrode sheet of the electrode assembly 22, increased internal resistance, and affecting the current flow capability and charging efficiency of the battery cell 20.

[0489] The current collector 23 and the second tab 2222 in the embodiment of this application may have a large connection area, and the current from the second tab 2222 can flow into the second electrode terminal 214b via the current collector 23. In this way, the current collector 23 can reduce the difference in conductive paths between different regions of the second tab 2222 and the second electrode terminal 214b, improve the uniformity of the current density of the second electrode sheet, reduce internal resistance, and improve the current passage capability and charging efficiency of the battery cell 20.

[0490] It should be understood that case 211 in the embodiment of this application has a multilayer structure, meaning that the cylinder 211b and cover 211a of case 211 are all multilayer structures. For the sake of explanation, all cases 211 below include the cylinder 211b and cover 211a.

[0491] In the embodiments of this application, the case 211 includes a first case layer 2115, the resistivity of the first case layer 2115 being K1, and K1 satisfying 1 × 10⁻⁸ Ω·m ≤ K1 ≤ 6 × 10⁻⁸ Ω·m. Here, the first case layer 2115 is any one of the multiple layers of case 211. For example, Figure 22 shows an example where the innermost case is the first case layer 2115, but the embodiments of this application are not limited to this. By reducing the resistivity K1 of the first case layer 2115 included in case 211, the current passing capability of case 211 can be enhanced, and the performance of the battery cell 20 can be further improved.

[0492] In some embodiments, the resistivity K1 of the first case layer 2115 may satisfy 1 × 10⁻⁸ Ω·m ≤ K1 ≤ 2.8 × 10⁻⁸ Ω·m. This can improve the current pass capability and performance of case 211 and is easy to implement. In some embodiments, the value of the resistivity K1 of the first case layer 2115 may be set to other values. For example, the values ​​of the resistivity K1 of the first case layer 2115 may be 1 × 10⁻⁸ Ω·m, 1.3 × 10⁻⁸ Ω·m, 1.5 × 10⁻⁸ Ω·m, 1.8 × 10⁻⁸ Ω·m, 2 × 10⁻⁸ Ω·m, 2.3 × 10⁻⁸ Ω·m, 2.5 × 10⁻⁸ Ω·m, 2.8 × 10⁻⁸ Ω·m, 3 × 10⁻⁸ Ω·m, 3.3 × 10⁻⁸ Ω·m, 3.5 × It may be any one of the following values ​​or any two of the following values: 10⁻⁸Ω·m, 3.8×10⁻⁸Ω·m, 4×10⁻⁸Ω·m, 4.3×10⁻⁸Ω·m, 4.5×10⁻⁸Ω·m, 4.8×10⁻⁸Ω·m, 5×10⁻⁸Ω·m, 5.3×10⁻⁸Ω·m, 5.5×10⁻⁸Ω·m, 5.8, and 6×10⁻⁸Ω·m.

[0493] It should be understood that the specific thickness of the first case layer 2115 in the embodiments of this application may be flexibly set according to practical requirements. For example, the thickness of the first case layer 2115 may be set at a constant ratio depending on the thickness of the case 211.

[0494] In some embodiments, the average thickness of the first case layer 2115 is set to T13, and the average thickness of the case 211 is set to T10, such that T13 and T10 satisfy 0.15 ≤ T13 / T10 ≤ 0.85. If T13 / T10 is set too small, T13 becomes too small when the average thickness T10 of the case 211 is constant, increasing the difficulty of processing, generating too much heat due to current flow, and making thermal runaway more likely. Conversely, if T13 / T10 is set too large, T13 becomes too large when the average thickness T10 of the case 211 is constant, in which case the thickness of the other structural layers becomes too small, affecting the structural strength of the case 211.

[0495] Furthermore, T13 and T10 satisfy 0.2 ≤ T13 / T10 ≤ 0.6. This enhances the current-passing capability of case 211 and also increases the structural strength of case 211. In some embodiments, the value of the T13 / T10 ratio may be set to other values. For example, the value of the T13 / T10 ratio may be any one or any two of the following values: 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, and 0.85.

[0496] It should be understood that the average thickness T10 of case 211 in the embodiment of this application may be set flexibly within a range that is appropriate for practical use. For example, the average thickness T10 of case 211 satisfies 0.05 mm ≤ T10 ≤ 0.5 mm. The value of the average thickness T10 of case 211 should not be too small, in order to reduce the difficulty of processing the multi-layer case 211, increase the structural strength of the case 211, for example, make the case 211 less prone to cracking, and further increase the service life of the case 211. Conversely, the value of the average thickness T10 of case 211 should not be too large, in order to save the space occupied by the case 211, increase the space utilization rate of the battery cells 20, and further increase the energy density of the battery 10 provided with multiple battery cells 20.

[0497] Furthermore, the average thickness T10 of the case 211 satisfies the condition 0.075 mm ≤ T10 ≤ 0.4 mm. By making the average thickness T10 of the case 211 moderately thin, the space occupied by the case 211 inside the battery 10 can be reduced, and the energy density of the battery 10 can be increased. By making the average thickness T10 of the case 211 moderately thick, the difficulty of processing the case 211 can be reduced.

[0498] Furthermore, the average thickness T10 of the case 211 satisfies the condition 0.1 mm ≤ T10 ≤ 0.3 mm. The average thickness T10 of the case 211 is neither too large nor too small, improving the structural strength and stability of the case 211, reducing the space occupied by the case 211 inside the battery 10, and further increasing the energy density of the battery 10.

[0499] In some embodiments, the average thickness T10 of case 211 in the embodiments of this application may be set to other values. For example, the average thickness T10 of case 211 may be one of the following values ​​or any two of the following values: 0.05 mm, 0.075 mm, 0.1 mm, 0.125 mm, 0.15 mm, 0.175 mm, 0.2 mm, 0.225 mm, 0.25 mm, 0.275 mm, 0.3 mm, 0.325 mm, 0.35 mm, 0.375 mm, 0.4 mm, 0.425 mm, 0.45 mm, 0.475 mm, and 0.5 mm.

[0500] In the embodiments of this application, the material of the first case layer 2115 may be flexibly set according to practical requirements. For example, the material of the first case layer 2115 includes at least one of silver, copper, aluminum, magnesium, and brass to satisfy the design requirement for the resistivity K1 of the first case layer 2115.

[0501] In the embodiments of this application, the case 211 includes a second case layer 2116, the tensile strength of the second case layer 2116 at a temperature of 25°C is Rm2, and Rm2 satisfies 250MPa ≤ Rm2 ≤ 2000MPa. Here, the second case layer 2116 is any one of the multiple layers of case 211; for example, Figure 22 shows an example where the outermost case is the second case layer 2116, but the embodiments of this application are not limited to this. By increasing the tensile strength Rm2 of the second case layer 2116 included in case 211 at a temperature of 25°C, the structural strength and deformation capacity of case 211 can be improved, thereby making case 211 less susceptible to damage during use of the battery cell 20, and further increasing the structural stability and service life of the battery cell 20. However, the tensile strength Rm2 of the second case layer 2116 under room temperature conditions of 25°C should not be excessive in order to reduce the difficulty of material selection and processing for the case 211, thereby reducing costs and facilitating processing.

[0502] It should be understood that the tensile strength Rm2 of the second case layer 2116 of case 211 in the embodiments of this application at room temperature conditions of 25°C may be adjusted within a range that is appropriate for practical use. For example, the value of the room temperature tensile strength Rm2 may satisfy 400 MPa ≤ Rm2 ≤ 1200 MPa. Increasing the tensile strength Rm2 of the second case layer 2116 at room temperature conditions strengthens the deformation capacity of that portion of the second case layer 2116, copes the expansion of the electrode assembly 22, makes the second case layer 2116 less susceptible to breakage, and further increases the structural stability and service life of the battery cell 20. On the other hand, by keeping the tensile strength Rm2 of the second case layer 2116 at room temperature conditions from becoming too high, the difficulty of material selection and processing of the second case layer 2116 can be reduced, costs can be lowered, and processing can be made easier.

[0503] Furthermore, the tensile strength Rm2 of the second case layer 2116 under room temperature conditions may be set to satisfy 450 MPa ≤ Rm2 ≤ 800 MPa. The tensile strength Rm2 of the second case layer 2116 under room temperature conditions will not be too large or too small, thereby enhancing the deformation capacity of the case 211 in that portion, accommodating the expansion of the electrode assembly 22, and is also easy to implement and reduces costs.

[0504] In some embodiments, the value of the tensile strength Rm2 of the second case layer 2116 of case 211 in the embodiments of this application under room temperature conditions may be set to a different value. For example, the value of the room-temperature tensile strength Rm2 may be any one of the following values ​​or any two of the following values: 250MPa, 280MPa, 300MPa, 330MPa, 350MPa, 380MPa, 400MPa, 450MPa, 500MPa, 550MPa, 600MPa, 650MPa, 700MPa, 750MPa, 800MPa, 850MPa, 900MPa, 950MPa, 1000MPa, 1050MPa, 1100MPa, 1150MPa, 1200MPa, 1250MPa, 1300MPa, 1350MPa, 1400MPa, 1450MPa, 1500MPa, 1550MPa, 1600MPa, 1650MPa, 1700MPa, 1750MPa, 1800MPa, 1850MPa, 1900MPa, 1950MPa, and 2000MPa.

[0505] It should be understood that the tensile strength in the embodiments of this application is the maximum stress value that the material experiences before it breaks under tension. The measurement of the tensile strength Rm2 of the second case layer 2116 of Case 211 of the embodiments of this application under a temperature of 25°C may be selected according to practical requirements. For example, the tensile strength Rm2 may be measured under room temperature conditions of 25°C according to the national standard GB / T228.1-2010.

[0506] In the embodiment of this application, the average thickness of the second case layer 2116 is T14, and the average thickness of the case 211 is T10, such that T14 and T10 satisfy 0.15 ≤ T14 / T10 ≤ 0.85. If T14 / T10 is set too small, T14 becomes too small when the average thickness T10 of case 211 is constant, affecting the structural strength of case 211. Conversely, if T14 / T10 is set too large, T14 becomes too large when the average thickness T10 of case 211 is constant. In this case, the thickness of other structural layers becomes too small; for example, the thickness T13 of the first case layer 2115 becomes too small. Furthermore, the difficulty of processing increases, the heat generated by current flow becomes too great, and thermal runaway is likely to occur.

[0507] Furthermore, T14 and T10 satisfy 0.2 ≤ T14 / T10 ≤ 0.6. This enhances the current-passing capability of case 211 and also increases the structural strength of case 211. In some embodiments, the value of the T14 / T10 ratio may be set to other values. For example, the value of the T14 / T10 ratio may be any one or any two of the following values: 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, and 0.85.

[0508] Furthermore, the average thickness T14 of the second case layer 2116 and the average thickness T13 of the first case layer 2115 in the embodiments of this application may be the same or different in order to satisfy different design requirements.

[0509] It should be understood that the average thickness T10 of case 211 in the embodiments of this application may refer to the average thickness of at least a portion of the case 211. The average thickness T13 of the first case layer 2115 of case 211 may refer to the average thickness of at least a portion of the first case layer 2115. The average thickness T14 of the second case layer 2116 of case 211 may refer to the average thickness of at least a portion of the second case layer 2116. Furthermore, the calculation area for the average thickness T10 of case 211 usually coincides with the calculation area for the average thickness T13 of the first case layer 2111 and also coincides with the calculation area for the average thickness T14 of the second case layer 2116. For example, if a portion of the case is excluded from the calculation of the average thickness T10 of case 211, then similar portions must be excluded from the calculation of the average thickness T13 of the first case layer 2115 and similar portions must be excluded from the calculation of the average thickness T14 of the second case layer 2116. For the sake of explanation, an example of calculating the average thickness T10 of case 211 will be described below. However, the same explanation applies to determining the average thickness T13 of the first case layer 2115 and the average thickness T14 of the second case layer 2116, so the explanation will be omitted here.

[0510] For example, the average thickness T10 of case 211 may refer to the average thickness T10 of all areas of case 211, and in particular, if the entire surface of case 211 is flat, that is, if the thickness of most areas of case 211 is approximately equal or does not differ significantly, or if the thickness of all areas of case 211 is approximately equal or does not differ significantly, then the average thickness of all areas of case 211 can be determined to be T10.

[0511] For example, the average thickness T10 of case 211 may refer to the average thickness T10 of a local region of case 211, that is, the average thickness T10 of the remaining region after excluding a portion of case 211. For example, if a special region exists in case 211, and the thickness of that special region differs significantly from that of other regions, for example, if a protruding structure or recessed region exists in that special region along the thickness direction, causing the thickness of that special region to be greater or smaller than that of other regions, then the special region may be excluded, and the average thickness T10 of the remaining region of case 211 may be calculated.

[0512] In some embodiments, the case 211 may include a functional region, and the average thickness T10 of the case 211 is the average thickness of the region of the case 211 excluding the functional region, for example, 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 thickness of the functional region is usually significantly different from the thickness of other regions of the case 211, and therefore, calculating the average thickness T10 of the case 211 without including the functional region can make the design of the case 211 better meet strength requirements and improve the structural strength and stability of the battery cell 20.

[0513] Specifically, the functional region of the embodiment of this application may include a region in case 211 that is provided with a particular structure or has a particular use. For example, the functional region may include a pressure release region, which is for providing a pressure release mechanism, and the pressure release mechanism is an element or component that operates to release the internal pressure or temperature of the battery cell 20 when the internal pressure or temperature reaches a predetermined threshold. The predetermined threshold may be adjusted according to design requirements. For example, the predetermined threshold may be determined by one or more materials among the positive electrode sheet, negative electrode sheet, electrolyte, and separator film in the battery cell 20.

[0514] As used in this application, "operation" refers to the operation or activation of the pressure release mechanism, thereby releasing the internal pressure and temperature of the battery cell 20. The operation performed by the pressure release mechanism includes, but is not limited to, rupture, shattering, tearing, or opening of at least a portion of the pressure release mechanism. When the pressure release mechanism is activated, the high-temperature, high-pressure material inside the battery cell 20 is discharged as waste from the operating part. In this way, pressure and temperature release of the battery cell 20 can be performed while the pressure or temperature is controllable, and the occurrence of more serious potential accidents can be avoided.

[0515] The emissions from the battery cell 20 as referred to in this application include, but are not limited to, electrolyte, dissolved or torn positive and negative electrode sheets, fragments of the separator film, high-temperature and high-pressure gases from the reaction, and flames.

[0516] The pressure relief mechanism in the embodiment of this application may be provided on any one wall of the battery cell 20, for example, in the pressure relief region of the case 211 of the battery cell 20. The pressure relief mechanism may be part of the case 211, or it may be a separate structure fixed to the case 211, for example by welding. For example, if the pressure relief mechanism is part of the case 211, the pressure relief mechanism may be formed by providing a notch in the case 211, i.e., a notch is provided in the pressure relief region of the case 211, and the thickness of the notch is significantly smaller than the thickness of other areas of the case 211, so that the thickness of the notch does not need to be included in the average thickness T10 of the case 211. The notch is the most vulnerable part of the pressure relief mechanism. When the amount of gas generated by the battery cell 20 becomes too large and the internal pressure rises to a threshold, or when the internal temperature of the battery cell 20 rises to a threshold due to the heat generated by the reaction inside the battery cell 20, the pressure release mechanism can rupture 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 through the rupture of the pressure release mechanism, and the explosion of the battery cell 20 is prevented.

[0517] For example, the pressure relief mechanism may be a separate structure from the case 211, and may take the form of an explosion-proof valve, gas valve, pressure relief valve, or safety valve, and specifically can employ pressure-sensitive or temperature-sensitive elements or structures. For example, a through hole may be provided in the pressure relief region of the case 211, and the pressure relief mechanism may be attached and fixed to the case 211 through the through hole, and after attachment, the pressure relief mechanism may protrude or recede from other areas of the case 211, and therefore the pressure relief region in which the pressure relief mechanism exists may not be included in the calculation of the average thickness T10 of the case 211. When the internal pressure or temperature of the battery cell 20 reaches a predetermined threshold, the pressure relief mechanism will operate or a vulnerable structure provided within the pressure relief mechanism will be destroyed, thereby forming an opening or passage that can release the internal pressure or temperature.

[0518] In some embodiments, the functional region may include the region where the electrode terminals 214 are located. Specifically, the electrode terminals 214 in the embodiments of this application are electrically connected to the electrode assembly 22 inside the battery cell 20 to output electrical energy from the battery cell 20. The battery cell 20 may also include at least two electrode terminals 214, each including at least one positive electrode terminal and at least one negative electrode terminal, the positive electrode terminal being for electrical connection to the positive electrode tab of the electrode assembly 22, and the negative electrode terminal being for electrical connection to the negative electrode tab of the electrode assembly 22. The positive electrode terminal and the positive electrode tab may be directly connected or indirectly connected, and the negative electrode terminal and the negative electrode tab may be directly connected or indirectly connected. Exemplary, in the embodiments of this application, the positive electrode terminal may be the first electrode terminal 214a, in which case the negative electrode terminal is the second electrode terminal 214b, or the positive electrode terminal may be the second electrode terminal 214b, in which case the negative electrode terminal is the first electrode terminal 214a.

[0519] It should be understood that each electrode terminal 214 in the embodiments of this application may be provided on any one wall, and multiple electrode terminals 214 may be provided on the same wall or different walls of the battery cell 20. For example, as shown in Figures 20 to 24, each battery cell 20 includes two electrode terminals 214, and these two electrode terminals 214 are located on the same wall. For example, both electrode terminals 214 may be located on the cover 211a. However, in the embodiments of this application, the cover 211a is the first electrode terminal 214a, and in this case, one of the two electrode terminals 214 included in the battery cell 20 protrudes from the rest of the cover 211a of the case 211, i.e., the thickness of the region where the second electrode terminal 214b is located is far greater than the thickness of the rest of the case 211. Therefore, the calculation of the average thickness T10 of the case 211 does not need to include the region where all of the second electrode terminals 214b are located.

[0520] In some embodiments, the functional region may include an electrolyte injection region. For example, the electrolyte injection region of the case 211 may be provided with an injection hole, through which electrolyte is injected into the interior of the case 211. After the electrolyte injection is complete, the injection hole may be sealed with a sealing member. Since 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 case 211, the electrolyte injection region may not be included in the calculation of the average thickness T10 of the case 211.

[0521] In some embodiments, the functional area may include a welded area. For example, the case 211 may be fixed to the cover plate 212 by welding, or the case 211 itself may be fabricated by welding, for example, any two walls of the case 211 may be welded together, or the case 211 may be formed by joining at least two parts together, in which case the case 211 may include a welded area. For example, the case 211 may be welded in a jointing manner, in which case the case 211 may have a weld bead 2113. Specifically, the case 211 may include at least two parts, which are joined by welding to form the case 211, where the embodiments of this application mainly include two parts along the height direction Z of the battery cell 20, with the upper and lower halves of the case having a weld bead 2113, or, as shown in Figure 21, other parts of the case 211 may also have a weld bead 2113, and the embodiments of this application are not limited thereto. The welded area of ​​the functional area in the embodiments of this application may include the weld bead 2113. Due to the manufacturing process, the thickness of the welded area is usually greater than the thickness of other areas of the case 211, so the welded area may not be included in the calculation of the average thickness T10 of the case 211.

[0522] In some embodiments, the resistivity of the second case layer 2116 is set to K2, and K2 and K1 satisfy 2 ≤ K2 / K1 ≤ 40, and may also satisfy 2 ≤ K2 / K1 ≤ 20, thereby limiting the resistivity K1 of the first case layer 2115 and further enhancing the current passability of case 211.

[0523] In the embodiments of this application, the material of the second case layer 2116 may be flexibly set according to practical requirements. For example, the material of the second case layer 2116 includes at least one of titanium, steel, silicon steel, and stainless steel, so as to satisfy the design requirements of the second case layer 2116.

[0524] In some embodiments, the materials for the first case layer 2115 and the second case layer 2116 may be selected from the materials shown in Table 9 to satisfy the design requirements.

[0525] [Table 9]

[0526] It should be understood that case 211 of the embodiment of this application has a multilayer structure, and the number of layers of case 211 may be set according to practical requirements. For example, case 211 includes a plurality of first case layers 2115 and / or a plurality of second case layers 2116, and the positions of the different first case layers 2115 and second case layers 2116 may be flexibly set according to practical requirements, thereby satisfying different application scenarios.

[0527] In some embodiments, the case 211 may include a plurality of first case layers 2115 and one second case layer 2116, the second case layer 2116 may be located in the middle of or on one side of the plurality of first case layers 2115. Similarly, the case 211 may include one first case layer 2115 and a plurality of second case layers 2116, the first case layer 2115 may be located in the middle of or on one side of the plurality of second case layers 2116. For example, the case 211 may include a plurality of first case layers 2115 and a plurality of second case layers 2116, the plurality of first case layers 2115 and the plurality of second case layers 2116 may be spaced apart, or the plurality of first case layers 2115 may be located on one side of the plurality of second case layers 2116, and the embodiments of this application are not limited thereto.

[0528] In some embodiments, if the case 211 includes a plurality of first case layers 2115 that satisfy the above design requirements, the materials of the plurality of first case layers 2115 may be the same or different, the resistivity K1 may be the same or different, and the thickness T13 may be the same or different, thereby increasing the design flexibility. Similarly, if the case 211 includes a plurality of second case layers 2116 that satisfy the above design requirements, the materials of the plurality of second case layers 2116 may be the same or different, the tensile strength Rm2 at room temperature may be the same or different, and the thickness T14 may be the same or different, thereby increasing the design flexibility.

[0529] The embodiments of this application further provide a battery including the battery cell 20 described in the various embodiments described above.

[0530] Embodiments of this application further provide an electrical device that includes a battery containing the battery cell 20 of the above-described embodiments, wherein the battery is for supplying electrical energy to the electrical device.

[0531] The electrical device may be the vehicle shown in Figure 1, or it may be a device that uses any battery.

[0532] Although this application has been described with reference to preferred embodiments, various improvements can be made without departing from the scope of this application, and components therein can be replaced with equivalents. In particular, any of the technical features described in each embodiment can be arbitrarily combined, provided that there is no structural inconsistency. This application is not limited to the specific embodiments disclosed herein, but includes all technical solutions that fall within the claims. [Explanation of Symbols]

[0533] 1 vehicle 11 boxes 20 battery cells 21 Housing 22 Electrode assembly 30 cases 31 1st wall 32 Second wall 34. Second fillet 40 Lid plate 60 Second insulating member 61 First insulating member 62 Seal rings 80 motor 81 First connecting member 82 Second connecting member 111 Part 1 112 Part 2 201 Aperture 211 cases 211a Cover 211b Cylinder 211c Electrode extraction hole 211d aperture 212 Lid plate 214 Electrode terminal 214a 1st electrode terminal 214b 2nd electrode terminal 221 Electrode main part 222 tabs 222a Positive Tab 222b Negative Tab 223 Positive electrode sheet 224 Negative Electrode Sheet 225 Separator 301 Aperture 331 First fillet 700 jigs 710 1st steel plate 720 2nd steel plate 730 Third steel plate 740 Pressure Sensor 2111 First Case Layer 2112 Third Case Wall 2113 Weld bead 2115 Case Layer 1 2116 Second Case Layer 2117 Outermost case 2118 Inner Case 2118a Intermediate layer case 2118b Innermost case 2141 Terminal main body 2142 Sealing plate 2221 Tab 1 2222 Second Tab 2231 Cathode active material layer 2232 Positive electrode current collector 2241 Negative electrode active material layer 2242 Negative electrode current collector

Claims

1. A case having an opening, having an integrally molded structure, including a first wall and at least two second walls provided opposite the opening, wherein the first wall and the second walls are provided so as to intersect, A case characterized in that two of the at least two second walls are connected by a first fillet, the inner diameter of the first fillet is R1, the yield strength of the case at a temperature of 25°C is Re, and Re and R1 satisfy 140 MPa ≤ Re ≤ 1000 MPa and 2.5 mm ≤ R1 ≤ 20 mm.

2. The case according to claim 1, characterized in that Re and R1 satisfy 150 MPa ≤ Re ≤ 400 MPa and 4 mm ≤ R1 ≤ 15 mm.

3. The case according to claim 1 or 2, characterized in that the depth of the case is H, and H satisfies the condition 50 mm < H ≤ 250 mm.

4. The case according to any one of claims 1 to 3, characterized in that Rm is the tensile strength of the case under the condition of a temperature of 25°C, and Rm satisfies the condition 250 MPa ≤ Rm ≤ 2000 MPa.

5. The case according to any one of claims 1 to 4, characterized in that the two second walls are two adjacent second walls, and the maximum thickness T1 of the first fillet and the maximum thickness T0 of the second wall with the greatest thickness among the two second walls satisfy T1 > T0.

6. The case according to any one of claims 1 to 4, characterized in that the two second walls are two second walls provided opposite to each other.

7. The case according to any one of claims 1 to 6, characterized in that the first wall and the second wall are connected by a second fillet, and the inner diameter r1 of the second fillet and the minimum thickness T2 of the second wall with the smallest thickness among the at least two second walls satisfy 2.0 ≤ r1 / T2 ≤ 30.

8. The case according to any one of claims 1 to 7, characterized in that the thickness of the case is uniform.

9. The case according to any one of claims 1 to 8, characterized in that the material of at least a portion of the case comprises at least one of stainless steel and carbon steel.

10. The case according to any one of claims 1 to 9, characterized in that m is the mass content of the element chromium in the material in at least a portion of the case, and m satisfies the condition 10% ≤ m ≤ 30%.

11. The case according to claim 9 or 10, characterized in that at least a portion of the case includes all the walls of the case.

12. A battery cell comprising an electrode assembly and a case according to any one of claims 1 to 11, wherein the electrode assembly is housed in the case.

13. The battery cell according to claim 12, characterized in that the thickness of the battery cell is D1, and H, R1, and D1 satisfy 0.15 mm ≤ R1 * D1 / H ≤ 36 mm.

14. The battery cell according to claim 13, characterized in that H, R1, and D1 satisfy 0.34 mm ≤ R1 * D1 / H ≤ 18 mm.

15. The battery cell according to any one of claims 12 to 14, characterized in that the thickness of the electrode assembly is D2, and R1 and D2 satisfy 0.125 ≤ R1 / D2 ≤ 0.

45.

16. The electrode assembly includes a negative electrode sheet, the negative electrode sheet includes a negative electrode active material capable of reversibly desorbing and inserting metal ions, and the negative electrode active material includes a silicon-based material. A battery cell according to any one of claims 12 to 15, characterized in that Rm is the tensile strength of at least a portion of the case under a temperature of 25°C, and Rm satisfies the condition 250 MPa ≤ Rm ≤ 2000 MPa.

17. The electrode assembly includes a negative electrode sheet, the negative electrode sheet includes a negative electrode active material capable of reversibly desorbing and inserting metal ions, and the negative electrode active material includes a silicon-based material. The battery cell according to any one of claims 12 to 16, characterized in that Re is the yield strength under a temperature of 25°C in at least a portion of the case, and Re satisfies the condition 140 MPa ≤ Re ≤ 1000 MPa.

18. The electrode assembly includes a positive electrode sheet, the positive electrode sheet includes a positive electrode active material capable of reversibly desorbing and inserting metal ions, and the positive electrode active material includes a nickel element-containing compound. The battery cell according to any one of claims 12 to 17, characterized in that the melting point of at least a portion of the case is p, and p satisfies the condition 1200°C ≤ p ≤ 2000°C.

19. The electrode assembly includes a positive electrode sheet, the positive electrode sheet includes a positive electrode active material capable of reversibly desorbing and inserting metal ions, and the positive electrode active material includes a nickel element-containing compound. A battery cell according to any one of claims 12 to 18, characterized in that Rn is the tensile strength of at least a portion of the case under a temperature of 500°C, and Rn satisfies the condition 100 MPa ≤ Rn ≤ 1200 MPa.

20. Includes a plurality of battery cells according to any one of claims 12 to 19 A battery characterized by the following features.

21. An electrical device comprising a battery including a battery cell according to any one of claims 12 to 19, wherein the battery is for supplying power to the electrical device. An electrical device characterized by the following features.

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