Casings, battery cells, batteries and electrical devices

Abstract

Embodiments of the present application provide a casing, a battery cell, a battery, and an electrical device. The casing has an opening and comprises a first wall facing the opening and at least one second wall, the first and second walls intersecting, and the first and second walls are connected by a first fillet, the relationship between the inner diameter r1 of the first fillet and the minimum thickness T2 of the second wall, which is the minimum thickness of at least one second wall, satisfies 2.0 ≤ r1 / T2 ≤ 30, and the yield strength of the casing at a temperature of 25°C is Re, where Re satisfies 140 MPa ≤ Re ≤ 1000 MPa. The casing, battery cell, battery, and electrical device of embodiments of the present application help to balance the difficulty of processing the casing with the spatial capacity and strength of the battery cell.

Description

[Technical Field]

[0001] [Cross-reference of related applications] This application claims priority to Chinese patent application 202311544543.5, titled "Case, Battery and Electrical Device," filed on 17 November 2023, and the entirety of said application is incorporated into this application by reference.

[0002] This application relates to the battery technology field, and more specifically to casings, battery cells, batteries, and electrical devices. [Background technology]

[0003] Typically, the casing of a battery cell significantly impacts the performance of the battery cell itself. Therefore, how to improve the casing to enhance battery cell performance has been a subject of research. [Overview of the project]

[0004] In view of these, the embodiments of the present application provide a casing, a battery cell, a battery, and an electrical device, which helps to balance the difficulty of processing the casing with the spatial capacity and strength of the battery cell.

[0005] In a first embodiment, a casing is provided having an opening, the casing comprising a first wall facing the opening and at least one second wall, the first wall and the second wall being installed intersecting, the first wall and the second wall being connected by a first fillet, the relationship between the inner diameter r1 of the first fillet and the minimum thickness T2 of the second wall which is the minimum thickness of at least one second wall, satisfies 2.0 ≤ r1 / T2 ≤ 30, the yield strength of the casing at a temperature of 25°C is Re, where Re satisfies 140 MPa ≤ Re ≤ 1000 MPa.

[0006] In this example, by using a material with a yield strength Re satisfying 140MPa≦Re≦1000MPa to manufacture the casing, the strength of the casing can be improved, and by setting the ratio between the inner diameter r1 of the first fillet between the first wall and the second wall and the minimum thickness T2 of the second wall with the smallest thickness within [2.0, 30], it helps balance the processing difficulty of the high-strength casing and the spatial capacity of the battery cell.

[0007] In a possible embodiment, r1 and T2 satisfy 2.5≦r1 / T2≦10.

[0008] In this example, by setting the ratio between the inner diameter r1 of the first fillet and the minimum thickness T2 of the second wall with the smallest thickness within [2.5, 10], on the one hand, the spatial energy density of the battery cell will not be excessively affected, and on the other hand, the deformation resistance capability of the casing can be further maintained.

[0009] In a possible embodiment, the inner diameter r1 of the first fillet satisfies 0.8mm≦r1≦1.5mm.

[0010] In this example, by setting the inner diameter r1 of the first fillet within [0.8mm, 1.5mm], on the one hand, since r1 is not too small, the manufacturing difficulty of the casing will not be increased, and on the other hand, since r1 is not too large, the interference between the electrode assembly and the first fillet will not be increased, that is, there is no need to reduce the height of the electrode assembly to sacrifice the capacity of the electrode assembly to meet the assembly requirements of the casing and the electrode assembly, and when r1 is too large, the casing is prone to deformation.

[0011] In a possible embodiment, the outer diameter r2 of the first fillet satisfies 1.0mm≦r2≦2.5mm.

[0012] In this embodiment, by setting the outer diameter r2 of the first fillet within [1.0 mm, 2.5 mm], on the one hand, if r2 is too small, the insulating film on the outside of the battery cell will not be punctured by the apex and cause an insulation failure, and on the other hand, if r2 is too large, the thickness of the first fillet will not become too thin and will not affect the strength of the casing.

[0013] In one possible embodiment, the relationship between the casing depth H and the minimum thickness T2 of the second wall with the minimum thickness satisfies 300 ≤ H / T2 ≤ 800.

[0014] In this embodiment, by setting the ratio between the casing depth H and the minimum thickness T2 of the second wall, which has the minimum thickness, to [300,800], it is possible to achieve both volume utilization efficiency and strength of the battery cell.

[0015] In one possible embodiment, the relationship between the maximum thickness T3 of the first fillet and the minimum thickness T2 of the second wall, which has the minimum thickness, satisfies 0.8 ≤ T2 / T3 ≤ 2.

[0016] By setting the ratio between the maximum thickness T3 of the first fillet 34 and the minimum thickness T2 of the second wall 32, which has the minimum thickness, to [0.8,2], the strength and manufacturability of the casing 30 can be balanced. That is, the strength of the casing 30 will not be insufficient due to making the first fillet 34 excessively thin, nor will the manufacturing of the casing 30 be difficult due to making the first fillet 34 insufficiently thin.

[0017] In one possible embodiment, there is a transition region between two adjacent second walls in at least one second wall, and the maximum thickness T1 of the transition region and the maximum thickness T0 of the second wall with the maximum thickness in the two second walls satisfy T1 > T0.

[0018] In this embodiment, by providing a transition region between two adjacent second walls, the stress concentration between the two adjacent second walls can be reduced, and the risk of structural failure caused by stress concentration can be lowered. Furthermore, by setting the maximum thickness T1 of the transition region to be greater than the maximum thickness T0 of the second wall with the largest thickness among the two adjacent second walls, the thickened transition region can increase the structural strength of the casing, which is advantageous for solving the problem of casing deformation during the production and assembly processes of the battery cell, as well as the problem of casing deformation caused by gas generation and expansion during the use process of the battery cell.

[0019] In a possible embodiment, the casing is an integrally formed structure, at least one of the gaps between two second walls on the second wall is connected by a second fillet, the inner diameter of the second fillet is R1, and R1 satisfies 2.5mm≦R1≦20mm.

[0020] In this embodiment, when the casing is manufactured using a material whose yield strength Re satisfies 140MPa≦Re≦1000MPa, by setting the inner diameter R1 of the first fillet between adjacent second walls to satisfy 2.5mm≦R1≦20mm, the risk of cracking due to force bearing during the integral forming process of the casing is reduced as much as possible, and the forming difficulty of the casing is lowered.

[0021] In a possible embodiment, the depth H of the casing satisfies 50mm<H≦250mm.

[0022] In this embodiment, by setting the depth H of the casing and the inner diameter R1 of the first fillet to satisfy 2.5mm≦R1≦20mm and 50mm<H≦250mm, without affecting the energy density of the battery cell, the risk of cracking of the casing due to force bearing during the integral forming process is reduced as much as possible, and the forming difficulty of the casing is further reduced.

[0023] In a possible embodiment, the wall thickness of the casing is uniform.

[0024] In this embodiment, by setting the wall thickness of the casing uniformly, the difficulty of processing the casing can be reduced, and on the other hand, each wall of the casing can be set to the minimum processing thickness, which helps to significantly improve the space utilization rate of the casing.

[0025] In one possible embodiment, the material of at least a portion of the casing includes at least one of stainless steel and carbon steel.

[0026] In this embodiment, the strength of the casing can be increased by manufacturing it using stainless steel or carbon steel.

[0027] In one possible embodiment, the mass content of the element chromium in the material of at least a portion of the casing is m, where m satisfies 10% ≤ m ≤ 30%.

[0028] In this embodiment, by increasing the amount of chromium in the material of at least a portion of the casing, the strength of the casing can be improved. Furthermore, since the chromium reacts with oxygen to produce an even denser chromium oxide film, a corrosion-resistant protective film can be formed on the surface of the casing, thereby improving the corrosion resistance of the casing.

[0029] In one possible embodiment, at least a portion of the casing includes all of the walls of the casing.

[0030] In this embodiment, the strength of the casing can be improved by using carbon steel or stainless steel for all walls of the casing, and / or by increasing the amount of chromium in the material of all walls of the casing.

[0031] In a second embodiment, a battery cell is provided comprising an electrode assembly and a casing in the first embodiment and any one of its possible implementations, wherein the electrode assembly is housed within the casing.

[0032] In one possible embodiment, the electrode assembly includes a negative electrode piece, the negative electrode piece 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 casing under conditions of a temperature of 25°C is Rm, where Rm satisfies 250 MPa ≤ Rm ≤ 2000 MPa.

[0033] In this embodiment, by installing a silicon-based material on the negative electrode piece, more metal ions can be accommodated, effectively increasing the energy density of the battery cell. Furthermore, if the negative electrode active material of the negative electrode piece is a silicon-based material, the amount of deformation of the electrode assembly within the battery cell during use can also be increased. In particular, during the charging process of the battery cell, when metal ions are inserted into the silicon-based material of the negative electrode piece, volume expansion occurs in the electrode assembly, further increasing the pressure of the electrode assembly on the casing of the battery cell. Therefore, by increasing the tensile strength Rm at room temperature (25°C) in at least a portion of the casing, the deformation capacity of the casing can be improved, preventing the casing from easily breaking during the use of the battery cell, further improving the structural stability of the battery cell, and further extending the service life of the battery cell. However, in order to reduce the difficulty of selecting and processing the material for the casing, save costs, and facilitate processing, it is undesirable for the tensile strength Rm at room temperature (25°C) in at least a portion of the casing to be too high.

[0034] In one possible embodiment, the electrode assembly includes a negative electrode piece, the negative electrode piece 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 at a temperature of 25°C in at least a portion of the casing is Re, where Re satisfies 140 MPa ≤ Re ≤ 1000 MPa.

[0035] In this embodiment, by installing a silicon-based material on the negative electrode piece, 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 piece is a silicon-based material, the amount of deformation of the electrode assembly within the battery cell during use can also be increased. In particular, during the charging process of the battery cell, when metal ions are inserted into the silicon-based material of the negative electrode piece, volume expansion occurs in the electrode assembly, further increasing the pressure of the electrode assembly on the casing of the battery cell. Therefore, by increasing the yield strength Re at room temperature (25°C) in at least a portion of the casing, the deformation capacity of the casing can be improved, further enhancing the structural stability of the battery cell and extending its service life. During the charging and discharging process of the battery cell, repeated volume expansion and contraction occur in the electrode assembly, increasing the yield strength Re at room temperature in at least a portion of the casing. This increases the maximum compressive force that the casing can withstand. If the limit of the yield strength of the casing is not exceeded, the casing will not easily break, and the deformation of the casing is recoverable, thus improving the service life of the casing. However, in order to reduce the difficulty of selecting and processing the material for the casing, save costs, and facilitate processing, it is also undesirable for the yield strength Re at room temperature in at least some areas of the casing to be too high.

[0036] In one possible embodiment, the electrode assembly includes a positive electrode piece, the positive electrode piece 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 casing is p, where p satisfies 1200°C ≤ p ≤ 2000°C.

[0037] In this embodiment, when the positive electrode active material of the positive electrode piece contains a nickel-containing compound, the energy density of the battery cell can be effectively increased, improving the cycle life. However, the amount of gas generated during the use of the battery cell also increases, and in particular, if thermal runaway occurs in the battery cell, the temperature inside the battery cell rises rapidly and a large amount of gas is generated. Therefore, by appropriately increasing the melting point p of at least a portion of the casing, the casing does not easily melt, reducing the possibility of the battery cell exploding, and further reducing the risk of thermal runaway occurring in adjacent battery cells, thereby improving the reliability of the battery. However, in order to reduce the difficulty of selecting and processing the casing material, save costs, and facilitate processing, it is undesirable for the melting point p of the casing to be too high.

[0038] In one possible embodiment, the electrode assembly includes a positive electrode piece, the positive electrode piece 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 casing at a temperature of 500°C is Rn, where Rn satisfies 100 MPa ≤ Rn ≤ 1200 MPa.

[0039] In this embodiment, when the positive electrode active material of the positive electrode piece contains a nickel-containing compound, the energy density of the battery cell can be effectively increased, improving the cycle life. However, the amount of gas generated during the use of the battery cell also increases, and in particular, when thermal runaway occurs in the battery cell, the temperature inside the battery cell rises rapidly and a large amount of gas is generated. Therefore, by appropriately improving the tensile strength Rn of at least a portion of the casing under high temperature conditions of 500°C, the deformation capacity of that portion of the casing when the battery cell experiences thermal runaway can be improved, preventing the casing from easily and quickly breaking or exploding, further reducing the risk of thermal runaway occurring in adjacent battery cells, thereby improving the reliability of the battery. However, in order to save costs and facilitate processing, it is also undesirable for the tensile strength Rn of at least a portion of the casing under high temperature conditions of 500°C to be too high.

[0040] In a third embodiment, a battery is provided, comprising a plurality of battery cells in the second embodiment and any one of its possible embodiments.

[0041] In a fourth embodiment, an electrical device is provided which includes a battery, the battery comprising a plurality of battery cells in the second embodiment and any one of its possible embodiments. [Brief explanation of the drawing]

[0042] To further clarify the technical concept in the embodiments of the present application, the drawings used in the embodiments of the present application are briefly introduced below. Clearly, the drawings in the following description represent only a few embodiments of the present application, and those skilled in the art can obtain further drawings without any creative effort. [Figure 1] This is a schematic diagram of the structure of a vehicle disclosed in one embodiment of the present application. [Figure 2] This is a schematic diagram of the structure of a battery disclosed in one embodiment of the present application. [Figure 3] This is a schematic diagram of the structure of a battery cell disclosed in one embodiment of the present application. [Figure 4] This is a schematic diagram of an exploded view of a battery cell disclosed in one embodiment of the present application. [Figure 5] This is a cross-sectional view of the casing disclosed in the embodiments of the present application. [Figure 6] This is a schematic diagram showing a localized enlargement of section B in Figure 5. [Figure 7] This is another cross-sectional view of the casing disclosed in the embodiments of the present application. [Figure 8] This is a schematic diagram of a localized enlargement of part A in Figure 7. [Figure 9] This is another close-up schematic view of part A in Figure 7. [Figure 10] This diagram shows a schematic representation of the material flow in the casing during the integral molding process. [Figure 11] This diagram shows a schematic representation of the force bearing of the casing during the integral molding process. [Figure 12] This is a schematic diagram of the structure of another battery cell disclosed in one embodiment of the present application. [Figure 13] This is a schematic diagram of an exploded view of another battery cell disclosed in one embodiment of the present application. [Figure 14] This is a schematic cross-sectional view of an electrode assembly according to one embodiment of the present invention. [Figure 15] This is a schematic cross-sectional view of the negative electrode piece or positive electrode piece of an electrode assembly according to one embodiment of the present application. [Figure 16] This is a schematic diagram of the structure of a clamp for cycle charging fatigue testing according to one embodiment of the present invention. [Figure 17] A schematic side view of the casing of the embodiment of the present application is shown. [Figure 18] This is a schematic top view of the casing of an embodiment of the present application. [Figure 19] This is a magnified view of the local structure of the casing of one embodiment of the present invention. [Figure 20] This is a schematic cross-sectional view of the local structure of a battery according to another embodiment of the present invention. [Figure 21] This is a schematic diagram of the disassembled structure of a battery cell in another embodiment of the present invention. [Figure 22] This is a schematic diagram of the cross-sectional structure of a battery cell according to another embodiment of the present invention. [Figure 23] This is a schematic cross-sectional view of the local structure of a battery according to another embodiment of the present invention. [Figure 24] This is a schematic cross-sectional view of another local structure of a battery according to another embodiment of the present application. [Modes for carrying out the invention]

[0043] To further clarify the purpose, technical proposal, and advantages of the embodiments of this application, the technical proposal of the embodiments of this application will be clearly described below in conjunction with the drawings of the embodiments of this application. However, it should be clear that the embodiments described are only a selection of embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained without creative work by a person skilled in the art fall within the scope of protection of this application.

[0044] Unless otherwise defined, all technical and scientific terms used in this Application have the same meaning as those generally understood by those skilled in the art relating to the Application. Terms used in the Specification of this Application are for illustrative purposes only and are not intended to limit the Application. The terms “includes” and “have,” and any variations thereof, in the description of the Specification, Claims, and the Drawings are intended to cover non-exclusive inclusion. Terms such as “first,” “second,” etc., in the Specification, Claims, or the Drawings are used to distinguish different subjects and are not used to indicate a particular order or priority.

[0045] The “Examples” as used herein mean that certain features, structures, or characteristics described in conjunction with the Examples may be included in at least one Example of this Application. Each occurrence of the “Examples” in the Specification does not necessarily refer to the same Example, nor do they represent mutually exclusive, independent, or substitutable Examples. Those skilled in the art will understand, both explicitly and implicitly, that the Examples described herein may be combined with other Examples.

[0046] In this description, unless otherwise specified or limited, the terms “attachment,” “connection,” “joining,” and “attaching” should be understood broadly to mean, for example, a fixed connection, a removable connection, an integral connection, a direct connection, an indirect connection via an intermediate medium, or internal communication between two elements. A person skilled in the art may understand the specific meaning of these terms in this application depending on the specific circumstances.

[0047] In this application, the term "and / or" simply describes a related relationship that explains the related objects, indicating that three types of relationships are possible. For example, A and / or B can represent three situations: A existing alone, A and B existing simultaneously, and B existing alone. In addition, the symbol " / " in this application generally indicates that the preceding and following related objects are in an "or" relationship.

[0048] In the embodiments of this application, the same drawing symbols represent the same components, and for the sake of brevity, detailed descriptions of the same components are omitted in different embodiments. It should be understood that the dimensions such as thickness, length, and width of various components in the embodiments of this application shown in the attached drawings, as well as the overall thickness, length, and width of the integrated device, are merely illustrative and should not constitute limitations of this application.

[0049] 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).

[0050] In the embodiments of the present invention, the battery cell may be a secondary battery, which refers to a battery cell that can be used continuously by activating the active material through charging after the battery cell has been discharged.

[0051] The battery cell may be a lithium-ion battery, sodium-ion battery, sodium-lithium-ion battery, lithium metal battery, sodium metal battery, lithium-sulfur battery, magnesium-ion battery, nickel-metal hydride battery, nickel-cadmium battery, lead-acid battery, etc., and the embodiments of this application are not limited to these.

[0052] A battery cell generally includes an electrode assembly. The electrode assembly includes a positive electrode, a negative electrode, and a separator. During the charging and discharging process of the battery cell, active ions (e.g., lithium ions) repeatedly insert into and remove from between the positive and negative electrodes. The separator is placed between the positive and negative electrodes and can prevent a short circuit between them while simultaneously allowing the passage of active ions.

[0053] In some embodiments, the positive electrode may be a positive electrode piece that includes a positive electrode current collector and a positive electrode active material placed on at least one surface of the positive electrode current collector.

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

[0055] As an example, the positive electrode current collector can be a metal foil, foamed metal, or a composite current collector. For example, as a metal foil, silver-surface-treated aluminum or stainless steel, stainless steel, copper, aluminum, nickel, carbon electrodes, carbon, nickel, or titanium can be used. The foamed metal may be foamed nickel, foamed copper, foamed aluminum, foamed alloy, or foamed carbon. The composite current collector may include a polymer material base layer and a metal layer. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer material base (a base material such as polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.).

[0056] As an example, the positive electrode active material may include at least one of the following materials: lithium-containing phosphates, lithium transition metal oxides, and modified compounds thereof. However, the present invention is not limited to these materials, and other conventional materials that can be used as positive electrode active materials for batteries may be used. These positive electrode active materials may be used individually or in combination of two or more. Examples of lithium-containing phosphates may include, but are not limited to, at least one of lithium iron phosphate (e.g., LiFePO4 (which may be abbreviated as LFP)), composite materials of lithium iron phosphate and carbon, lithium manganese phosphate (e.g., LiMnPO4), composite materials of lithium manganese phosphate and carbon, lithium iron manganese phosphate, and composite materials of lithium iron manganese phosphate and carbon.

[0057] In some embodiments, the negative electrode may be a negative electrode piece, and the negative electrode piece may include a negative electrode current collector and a negative electrode active material placed on at least one surface of the negative electrode current collector.

[0058] For example, the negative electrode current collector has two opposing surfaces in its thickness direction, and the negative electrode active material is placed on one or both of the two opposing surfaces of the negative electrode current collector.

[0059] As an example, the negative electrode current collector can be a metal foil, foamed metal, or a composite current collector. For example, as the metal foil, aluminum or stainless steel with a silver surface treatment, stainless steel, copper, aluminum, nickel, carbon electrodes, carbon, nickel, or titanium can be used. The composite current collector may include a polymer material base layer and a metal layer. The foamed metal may be foamed nickel, foamed copper, foamed aluminum, foamed alloy, or foamed carbon. The composite current collector is formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer material base (a base material such as polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, or polyethylene).

[0060] As an example, the negative electrode active material can be a negative electrode active material for battery cells known in the art. For example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate.

[0061] In some embodiments, the electrode assembly further includes a separator placed between the positive and negative electrodes.

[0062] In some embodiments, the separator is a separator film. The present application does not impose any particular restrictions on the type of separator film, and any known porous separator film having good chemical and mechanical stability can be selected.

[0063] For example, the main material of the separator film may be at least one selected from glass fiber, nonwoven fabric, polyethylene, polypropylene, polyvinylidene fluoride, and ceramics.

[0064] In some embodiments, the separator is a solid electrolyte. The solid electrolyte is placed between the positive and negative electrodes and serves to transport ions and separate the positive and negative electrodes.

[0065] In some embodiments, the battery cell further includes an electrolyte that plays a role in conducting ions between the positive and negative electrodes. The present application does not specifically limit the type of electrolyte, which can be selected according to the needs. The electrolyte may be in a liquid state, a gel state, or a solid state.

[0066] 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.

[0067] In some embodiments, the battery cell may include an outer casing. The outer casing is used to enclose components such as the electrode assembly and electrolyte. The outer casing may be a steel shell, an aluminum casing, a plastic shell (e.g., polypropylene), a composite metal shell (e.g., copper-aluminum composite outer casing), or an aluminum-plastic film. The outer casing includes a casing and a cover plate.

[0068] For example, the battery cell may be a cylindrical battery cell, a prismatic battery cell, a soft pack battery cell, or a battery cell of another shape. The prismatic battery cell includes rectangular parallelepiped battery cells, blade-shaped battery cells, and polygonal prismatic batteries such as hexagonal prismatic batteries, and the present invention is not particularly limited.

[0069] The batteries referred to in the embodiments of this application may include one or more battery cells to provide a single physical module with higher voltage and capacity. If there are multiple battery cells, the multiple battery cells are connected in series, in parallel, or in series-parallel by a bus component.

[0070] 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 to form a single battery module.

[0071] In some embodiments, the battery may be a battery pack including a case and battery cells, where the battery cells or battery modules are housed within the case.

[0072] In some embodiments, the case may be part of the vehicle's chassis structure. For example, the case portion may be at least part of the vehicle's floor, or it may be at least part of the vehicle's cross members and side members.

[0073] In some embodiments, the battery may be placed within an energy storage device. The energy storage device includes energy storage containers, energy storage electrical cabinets, and the like.

[0074] The development of battery technology requires simultaneous consideration of various design elements, such as performance parameters including energy density, cycle life, discharge capacity, and charge / discharge rate. Furthermore, the impact of the casing on battery performance must also be considered, for example, the casing's space utilization rate, tensile strength, and manufacturability.

[0075] Accordingly, the embodiment of the present application provides a casing that helps balance the difficulty of machining the casing with the spatial capacity and strength of the battery cell by setting the ratio of the inner diameter of the second fillet between the first wall and the second wall to the minimum thickness of the second wall, which is the minimum thickness, between [2.0, 30].

[0076] All of the technical solutions described in the embodiments of this application are applicable to various electrical devices that use batteries.

[0077] Electrical equipment may include vehicles, mobile phones, portable devices, laptop computers, ships, aerospace vehicles, electric toys, and power tools. Vehicles may be fuel-powered vehicles, natural gas vehicles, or new energy vehicles, and new energy vehicles may include pure electric vehicles, hybrid vehicles, or range-extender vehicles. Aerospace vehicles may include airplanes, rockets, space shuttles, and spacecraft. Electric toys include stationary or mobile electric toys such as game consoles, electric car toys, electric boat toys, and electric airplane toys. Power tools include metal cutting power tools such as electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact drills, concrete vibrators, and electric planers, as well as grinding power tools, assembly power tools, and railway power tools. The embodiments of this application do not impose any special limitations on the above-mentioned electrical equipment.

[0078] The following examples illustrate the concept of a vehicle as the electrical equipment, for the sake of clarity.

[0079] As an example, Figure 1 is a schematic diagram of the structure of a vehicle 1 according to one embodiment of the present invention, where the vehicle 1 may be a fuel vehicle, a gas vehicle, or a new energy vehicle, and the new energy vehicle may be a pure electric vehicle, a hybrid vehicle, or a range extender vehicle. A motor 80, a controller 60, and a battery 10 are installed inside the vehicle 1, and the controller 60 is used to control the battery 10 to supply power to the motor 80. For example, the battery 10 may be installed at the bottom of the vehicle 1 or at the front or rear of the vehicle. The battery 10 can be used to power the vehicle 1, for example, as an operating power source for the vehicle 1, it can be used for the operating power needs of the vehicle 1's circuit systems, such as starting the vehicle 1, navigation, and driving the vehicle 1. In another embodiment of the present invention, the battery 10 can not only be an operating power source for the vehicle 1, but can also be a driving power source for the vehicle 1, providing driving force to the vehicle 1 by completely or partially replacing fuel or natural gas.

[0080] Figure 2 shows a schematic diagram of the structure of a battery 10 according to one embodiment of the present application, the battery 10 may include a plurality of battery cells 20. The battery 10 may further include a case 11 having a hollow internal structure, in which the plurality of battery cells 20 are housed. Figure 2 shows a possible embodiment of the case 11 of the embodiment of the present application, the case 11 may include two parts, which are hereby referred to as a first part 111 and a second part 112, respectively, and the first part 111 and the second part 112 are engaged. The shapes of the first part 111 and the second part 112 may be determined according to the shape after the plurality of battery cells 20 have been combined, and at least one of the first part 111 and the second part 112 has one opening. For example, as shown in Figure 2, the first portion 111 and the second portion 112 may both be hollow rectangular parallelepipeds, each with only one open surface, the opening of the first portion 111 and the opening of the second portion 112 facing each other, and the first portion 111 and the second portion 112 engaging with each other to form a case 11 having a sealed cavity. This sealed cavity may be used to house a plurality of battery cells 20. The plurality of battery cells 20 are connected in parallel, in series, or in series-parallel and then combined and placed in the case 11 formed by the engagement of the first portion 111 and the second portion 112.

[0081] Furthermore, unlike what is shown in Figure 2, for example, one of the first portion 111 and the second portion 112 may be a hollow rectangular parallelepiped with an opening, while the other is plate-shaped to cover the opening. For example, if the second portion 112 is a hollow rectangular parallelepiped with only one face being an opening, and the first portion 111 is plate-shaped, then the first portion 111 covers the opening of the second portion 112 to form a case 11 having a sealed cavity, but the embodiments of the present application are not limited to these.

[0082] 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 of the battery 10 shown in Figure 2. Figure 4 shows a schematic diagram of the partially disassembled structure of a battery cell 20 according to one embodiment of the present application. For example, 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 of the battery cell 10 shown in Figure 2.

[0083] As shown in Figures 3 and 4, the battery cell 20 of the embodiment of the present application may include an outer casing 21 and an electrode assembly 22, the outer casing 21 having a sealed housing space, and the electrode assembly 22 being disposed within the housing space of the outer casing 21. The outer casing 21 may include a casing 30 and a cover plate 40, the casing 30 being a hollow structure having at least one opening, and the cover plate 40 engaging with the casing 30 to form an outer casing 21 having a sealed housing space.

[0084] In some embodiments, the cover plate 40 may be a plate-like structure and is used to cover the opening of the casing 30. In some other embodiments, the structures of the cover plate 40 and the casing 30 are similar, that is, both the casing 30 and the cover plate 40 are hollow structures having one opening, and the two openings are joined to form an outer casing 21 having a sealed housing space.

[0085] As can be understood, if the cover plate 40 is a plate-like structure, the casing 30 may be a hollow structure with openings at one or more ends. For example, if the casing 30 is a hollow structure with an opening at one end, one cover plate 40 may be installed. If the casing 30 is a hollow structure with openings at both opposing ends, two cover plates 40 may be installed, each covering the openings at both ends of the casing 30.

[0086] The outer casing 21 may have various shapes, such as a cylinder, a rectangular parallelepiped, or other polyhedron. For illustrative purposes, as shown in Figures 3 and 4, the embodiment of this application will primarily describe the outer casing 21 as having a rectangular parallelepiped structure.

[0087] As can be understood, the cover plate 40 of the embodiment of the present application is used to fit with the casing 30 in order 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 casing 30, and as shown in Figures 3 and 4, the casing 30 has a rectangular parallelepiped structure, and the cover plate 40 has a rectangular plate structure that matches the casing 30.

[0088] As can be understood, the battery cell 20 further includes electrode terminals 214. The electrode terminals 214 in the embodiments of the present application are used to be electrically connected to an electrode assembly 22 inside the battery cell 20 so as to output electrical energy from the battery cell 20. As shown in Figures 3 and 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 being used to be electrically connected to the positive electrode tab 222a of the electrode assembly 22, and the second electrode terminal 214b being used to be electrically connected to the negative electrode tab 222b of the electrode assembly 22. The first electrode terminal 214a may be directly connected to the positive electrode tab 222a or indirectly connected, and the second electrode terminal 214b may be directly connected to the negative electrode tab 222b or indirectly connected. For example, the first electrode terminal 214a may be electrically connected to the positive electrode tab 222a via a connecting component 23, and the second electrode terminal 214b may be electrically connected to the negative electrode tab 222b via a connecting component 23.

[0089] In the battery cell 20, the electrode assembly 22 is a component that causes an electrochemical reaction within the battery cell 20. Depending on the needs of actual use, one electrode assembly 22 may be installed in the casing 30, or multiple electrode assemblies may be installed. For example, as shown in Figure 4, two electrode assemblies 22 are installed in the battery cell 20. The electrode assembly 22 may be cylindrical, a rectangular parallelepiped, or the like. If the electrode assembly 22 has a cylindrical structure, the casing 30 may also have a cylindrical structure. If the electrode assembly 22 has a rectangular parallelepiped structure, the casing 30 may also have a rectangular parallelepiped structure.

[0090] As can be understood, as shown in Figures 3 and 4, the electrode assembly 22 includes tabs 222 and an electrode body 221, of which the tabs 222 of the electrode assembly 22 may include a positive electrode tab 222a and a negative electrode tab 222b, the positive electrode tab 222a being formed by laminating from portions of the positive electrode piece that are not coated with the positive electrode active material layer, the negative electrode tab 222b being formed by laminating from portions of the negative electrode piece that are not coated with the negative electrode active material layer, and the electrode body 221 may be formed by laminating the positive electrode piece and the negative electrode piece together or by winding them together.

[0091] Figure 5 shows another exemplary cross-sectional view of the casing 30 according to an embodiment of the present application. For the purposes of explanation, the casing 30 is applied to a battery cell, for example, the battery cell 20 shown in Figures 3 and 4, and the casing 30 may be the casing 30 shown in Figures 3 and 4. The yield strength of the casing 30 at a temperature of 25°C is Re, where Re satisfies 140 MPa ≤ Re ≤ 1000 MPa.

[0092] Yield strength can be understood as the critical stress value at which a material yields. Normally, after a material is subjected to stress, in addition to elastic deformation, plastic deformation may also occur as the stress increases. The point at which plastic deformation occurs in a material may be called the yield point, and the strength corresponding to the yield point is called the yield strength. The test method for the yield strength Re of the casing 30 at a temperature of 25°C according to the embodiment of this application can be selected according to the actual application. For example, GB / T 228.1-2010 can be used to measure the yield strength Re at room temperature conditions of 25°C. The tested yield strengths Re = 140 MPa, 180 MPa, 200 MPa, 230 MPa, 250 MPa, 280 MPa, 300 MPa, 320 MPa, 350 MPa, 380 MPa, 400 MPa, 430 MPa, 450 MPa, 480 MPa, 500 MPa, 550 MPa, 600 MPa, 650 MPa, 700 MPa, 750 MPa, 800 MPa, 850 MPa, 900 MPa, 950 MPa, and 1000 MPa.

[0093] As shown in Figure 4, the casing 30 has an opening 301 and includes a first wall 31 installed opposite the opening 301 and at least one second wall 32, the first wall 31 and the second wall 32 being installed intersecting each other.

[0094] In some embodiments, the second wall 32 and the first wall 31 may be perpendicular to each other.

[0095] In some embodiments, at least one second wall 32 can be connected end to end to form a hollow structure that is enclosed and open at both ends, of which the first wall 31 covers the opening at one end of the hollow structure.

[0096] In some embodiments, the casing 30 may be cylindrical or rectangular. If the casing 30 is cylindrical, it may include one second wall 32. If the casing 30 is rectangular, it may include four second walls 32. In other embodiments, the casing 30 may further include a different number of second walls 32, and the shape of the casing 30 may be determined based on the shape of the electrode assembly.

[0097] In some embodiments, the arrangement of the casing 30 is as shown in Figure 4, where the first wall 31 may be the bottom wall of the casing 30 for supporting the electrode assembly 22, and in this case, the second wall 32 is the side wall of the casing 30 installed surrounding the electrode assembly 22.

[0098] In some embodiments, the first wall 31 and the second wall 32 may be integrally molded, that is, the casing 30 may be an integrally molded structure. For example, a plate-like structure may be stamped into a hollow structure with an opening using a mold, and the stamped casing 30 may have openings of various shapes, for example, the opening 301 may be circular, polygonal, or racetrack-shaped. The polygon may be, for example, a square, pentagon, hexagon, or other irregular shape.

[0099] As shown in the localized enlarged view of portion B in Figure 5, the first wall 31 and the second wall 32 are connected by a first fillet 34, the inner diameter of the first fillet 34 is r1, and the minimum thickness of at least one of the second walls 32 is T2, and the relationship between the inner diameter r1 of the first fillet 34 and the minimum thickness T2 of at least one of the second walls 32 satisfies 2.0 ≤ r1 / T2 ≤ 30.

[0100] In some embodiments, the first fillet 34 has an inner surface and an outer surface, both of which are arcuate surfaces. The inner diameter r1 of the first fillet 34 can be understood as the radius of the circle in which the inner arc of the first fillet 34 is located.

[0101] As can be understood, if the casing 30 includes a plurality of second walls 32, the first wall 31 and the plurality of second walls 32 are all connected, and any one of the second walls 32 and the first wall 31 may be connected by a first fillet 34 as shown in Figure 5.

[0102] For the purposes to be explained, 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 second wall 32 among the multiple 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 among all the second walls 32.

[0103] Furthermore, 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 a pressure release area, an area where electrode terminals are located, a fluid injection area, and a welding area.

[0104] In this embodiment, by manufacturing the casing 30 using a material that satisfies a yield strength Re of 140 MPa ≤ Re ≤ 1000 MPa, the strength of the casing 30 can be improved. Furthermore, by setting the ratio of the inner diameter r1 of the first 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 minimum thickness, between [2.0, 30], it is possible to balance the difficulty of processing the high-strength casing 30 with the spatial capacity of the battery cell 20.

[0105] In several embodiments, the inner diameter r1 of the first fillet 34 and the minimum thickness T2 of the second wall 32, which has the minimum thickness, satisfy the condition 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.

[0106] In this embodiment, by aligning the inner diameter r1 of the first fillet 34 with the minimum thickness T2 of the second wall 32, which has the minimum thickness, between [2.5,10], it is possible to further maintain the deformation resistance capability of the casing 30 without excessively affecting the spatial energy density of the battery cell 20.

[0107] Selectively, the inner diameter r1 of the first 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.

[0108] In this embodiment, by setting the inner diameter r1 of the first fillet 34 within [0.8 mm, 1.5 mm], on the one hand, if r1 is too small, the difficulty of manufacturing the casing 30 is not increased, and on the other hand, if r1 is too large, the interference between the electrode assembly 22 and the first fillet 34 is not reduced, that is, by lowering the height of the electrode assembly 22, it is not necessary to sacrifice the capacity of the electrode assembly 22 to satisfy the assembly of the casing 30 and the electrode assembly 22, and on the other hand, if r1 is too large, the casing 30 is more prone to deformation.

[0109] Figure 6 shows another localized schematic view of section B in Figure 5. As shown in Figure 6, the outer diameter of the first fillet 34 is r2, where r2 satisfies the condition 1 mm ≤ r2 ≤ 2.5 mm. For example, r2 = 1.0 mm, 1.1 mm, 1.2 mm, 1.3 mm, 1.4 mm, 1.5 mm, 1.6 mm, 1.7 mm, 1.8 mm, 1.9 mm, 2.0 mm, 2.1 mm, 2.2 mm, 2.3 mm, 2.4 mm, 2.5 mm.

[0110] Similar to the definition of the inner diameter r1 of the first fillet 34, the outer diameter r2 of the first fillet 34 can be understood as the radius of the circle on which the outer arc of the first fillet 34 is located.

[0111] In this embodiment, by setting the outer diameter r2 of the first fillet 34 within [1.0 mm, 2.5 mm], on the one hand, r2 is not too small, so the insulating film on the outside of the battery cell 20 is not punctured at the sharp point and causes an insulation failure. On the other hand, r2 is not too large, so the thickness of the first fillet 34 is not too thin and affects the strength of the casing 30.

[0112] Selectively, as shown in Figure 4, the depth of the casing 30 is H.

[0113] In the embodiments of the present application, depth can be understood as the distance from the opening to the bottom inward. For example, the depth H of the casing 30 can be understood as the distance from the opening 301 to the first wall 31.

[0114] In some embodiments, the relationship between H and T2 satisfies 300 ≤ H / T2 ≤ 800. For example, H / T2 = 300, 350, 400, 450, 500, 550, 600, 650, 700, 750, 800, etc.

[0115] In this embodiment, by setting the ratio between the depth H of the casing 30 and the minimum thickness T2 of the second wall 32, which has the minimum thickness, to be between [300, 800], it is possible to achieve both volume utilization efficiency and strength of the battery cell 20.

[0116] As shown in Figure 6, the maximum thickness of the first fillet 34 is T3, and the ratio of T3 to T2 satisfies 0.8 ≤ T3 / T2 ≤ 2. For example, T3 / T2 = 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, and 2.0.

[0117] The thickness of the first fillet 34 may be uniform or non-uniform. Hereinafter, the maximum thickness T3 of the first fillet 34 is defined as an example where the thickness of the first fillet 34 is uniform. In some embodiments, the maximum thickness T3 of the first fillet 34 can be defined as the length of the extension of the connecting line between the center of the circle on which the inner arc of the first fillet 34 is located and the center of the circle on which the outer arc is located, in any one cross section along a direction perpendicular to the axes of the inner and outer surfaces.

[0118] In this embodiment, by setting the ratio between the maximum thickness T3 of the first fillet 34 and the minimum thickness T2 of the second wall 32, which has the minimum thickness, to [0.8,2], the strength and manufacturability of the casing 30 can be balanced. That is, the strength of the casing 30 is not compromised by making the first fillet 34 excessively thin, nor is the manufacturing of the casing 30 difficult by making the first fillet 34 insufficiently thin.

[0119] Selectively, in embodiments of the present application, the casing 30 includes a plurality of second walls 32, the thickness of the plurality of second walls 32 being uniform and equal.

[0120] In this embodiment, by setting the thickness of the multiple second walls 32 of the casing 30 to be uniform and equal, on the one hand, the difficulty of processing the casing 30 can be reduced, and on the other hand, all of the multiple second walls 32 can be set to the minimum processing thickness, which helps to significantly improve the space utilization rate of the casing 30.

[0121] Selectively, in the embodiments of the present application, the thickness of the casing 30 is uniform, that is, the thickness of all walls of the casing 30 is uniform and equal.

[0122] In this embodiment, by setting the wall thickness of all walls of the casing 30 to be uniform and equal, on the one hand, the difficulty of processing the casing 30 can be reduced, and on the other hand, each wall of the casing 30 can be set to the minimum processing thickness, which helps to significantly improve the space utilization rate of the casing 30.

[0123] Figure 7 shows another exemplary cross-sectional view of a casing 30 according to an embodiment of the present application. As shown in the local enlargement view of portion A of Figure 7, the casing 30 includes at least two second walls 32, with a transition region 33 having a maximum thickness T1 between two adjacent second walls 32, where the maximum thickness of the second wall 32 is T0, of which T1 is greater than T0.

[0124] Typically, the second wall 32 is not manufactured independently; that is, the at least two second walls 32 may be integrally molded.

[0125] In some embodiments, the thickness of the transition region 33 may be uniform or non-uniform. Hereinafter, we define the maximum thickness T1 of the transition region 33, taking the case where the thickness of the transition region 33 is uniform as an example.

[0126] As can be seen from Figure 7, the transition region 33 has two surfaces, namely an inner surface and an outer surface. In some embodiments, the inner and outer surfaces may be arcuate surfaces, and they are coaxially positioned. The maximum thickness T1 of the transition region 33 can be defined as the length of the extension of the connecting line between the center of the circle on which the inner arc is located and the center of the circle on which the outer arc is located, in any cross section along a direction perpendicular to the axes of the inner and outer surfaces. In some other embodiments, the inner and outer surfaces may be planar, and they are parallel to each other, and the maximum thickness T1 of the transition region 33 can be defined as the perpendicular distance between the inner and outer surfaces. Similarly, the second wall 32 also has two surfaces, namely an inner surface and an outer surface, of which the maximum perpendicular distance between the inner and outer surfaces is the maximum thickness of a given second wall 32.

[0127] If the thicknesses of at least two second walls 32 of the casing 30 are not equal, for example, if they are not equal to the thicknesses of two second walls 32 adjacent to one transition region 33, then in embodiments of the present application, T0 is the second wall 32 with the maximum thickness of the two second walls 32 adjacent to the transition region 33 in the casing 30. On the other hand, if the thicknesses of at least two second walls 32 of the casing 30 are equal, for example, if they are equal to the thicknesses of two second walls 32 of one transition region 33, then in embodiments of the present application, T0 is the thickness of any one of the second walls 32 of the casing 30.

[0128] 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 a pressure release area, an area where electrode terminals are located, a fluid injection area, and a welding area.

[0129] In this embodiment, by installing a transition region 33 between two adjacent second walls 32, stress concentration between the two adjacent second walls 32 can be reduced, thereby lowering the risk of structural failure due to stress concentration. Furthermore, by setting the maximum thickness T1 of the transition region 33 to be greater than the maximum thickness T0 of the second wall with the maximum thickness between the two adjacent second walls, the thicker transition region 33 can increase the structural strength of the casing 30, which is advantageous in solving the problems of deformation of the casing 30 during the production and assembly process of the battery cell 20, as well as the problems of deformation of the casing 30 due to gas generation and expansion during the use of the battery cell 20.

[0130] In some embodiments, the maximum thickness T1 of the transition region 33 and the maximum thickness T0 of the second wall 32, which is the maximum thickness among the two adjacent second walls 32, satisfy 1.5 ≤ T1 / T0 ≤ 7.

[0131] In this embodiment, by setting the ratio of the maximum thickness T1 of the transition region 33 to the maximum thickness T0 of the second wall 32, which is the thickest of the two adjacent second walls 32, between [1.5, 7], the strength of the casing can be increased by the relatively thick transition region 33, and the difficulty in manufacturing the casing 30 due to the transition region 33 being too thick can be limited, thereby balancing the strength of the casing 30 with the difficulty of manufacturing the casing 30.

[0132] In practical applications, the ratio of T1 to T0 can be adjusted. For example, the maximum thickness T1 of the transition region 33 and the maximum thickness T0 of the second wall 32, which is the maximum thickness of the two adjacent second walls 32, can satisfy 2 ≤ T1 / T0 ≤ 4.

[0133] 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.

[0134] In this embodiment, by setting the ratio of the maximum thickness T1 of the transition region 33 to the maximum thickness T0 of the second wall 32, which is the maximum thickness of the two adjacent second walls 32, between [2,4], the strength of the casing 30 and the difficulty of manufacturing the casing 30 can be balanced to the greatest extent possible.

[0135] Selectively, as shown in Figures 7 and 8, the space between two adjacent second walls 32 is connected by a second fillet 331, and the transition region 33 includes the second fillet 331. That is, the transition region 33 is realized by a fillet.

[0136] In this embodiment, by creating a transition region 33 between two adjacent second walls 32 using fillets, the casing 30 can be formed more easily, has better surface smoothness, and at the same time reduces the risk of cracking of the casing 30 due to stress concentration at the cusp when affected by internal gas generation in the battery cell 20.

[0137] As shown in Figure 8, the inner diameter of the second fillet 331 is R1, and the outer diameter of the second fillet 331 is R2.

[0138] In some embodiments, the second fillet 331 has an inner surface and an outer surface, both of which are arcuate surfaces. The inner diameter R1 of the second fillet 331 can be understood as the radius of the circle in which the inner arc of the second fillet 331 is located, while the outer diameter R2 of the second fillet 331 can be understood as the radius of the circle in which the outer arc of the second fillet 331 is located.

[0139] In several embodiments, the inner diameter R1 of the second 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.

[0140] In this embodiment, by setting the inner diameter of the second fillet 331 between two adjacent second walls 32 within the range of [2mm, 4mm], on the one hand, the situation that the inner diameter is too large to occupy the internal space of the casing 30 and thus increase the pressure of gas generation inside the casing 30 is avoided, and on the other hand, the situation that the inner diameter is too small to result in insufficient increase in the wall thickness of the second fillet 331 and further insufficient strength of the casing 30 is also avoided, so that the utilization efficiency of the internal space of the casing 30 and the strength of the casing 30 can be balanced.

[0141] In some embodiments, the outer diameter R2 of the second fillet 331 satisfies 1.5mm≦R2≦3.5mm. For example, R2 is 1.5mm, 2mm, 2.5mm, 3.0mm, 3.5mm and the like.

[0142] In this embodiment, when the side welding method is adopted to fixedly connect the cover plate 40 and the casing 30, the larger the outer diameter R2 of the second fillet 331 between two adjacent second walls 32 is, the more difficult it is to control the welding quality, and cold solder joints are more likely to occur; on the other hand, the smaller the outer diameter R2 of the second fillet 331 is, the more difficult it is to form the casing 30. Therefore, by controlling the outer diameter R2 of the second fillet 331 within the range of [1.5mm, 3.5mm], the welding quality and the forming difficulty of the casing can be balanced.

[0143] In some other embodiments, as shown in Figure 9, two adjacent second walls 32 are connected by a chamfer, for example, the angles between the chamfer and the two adjacent second walls 32 are both 45°.

[0144] In one embodiment, the casing 30 may be an integrally formed structure. As shown in Figure 4, the depth of the casing 30 is H, wherein the depth H of the casing 30 and the inner diameter R1 of the second fillet 331 satisfy 2.5mm≦R1≦20mm and 50mm<H≦250mm.

[0145] In the embodiments of the present application, the depth can be understood as the distance from the opening inward to the bottom. For example, the depth H of the casing 30 can be understood as the distance from the opening 301 to the first wall 31.

[0146] Figure 10 shows a schematic diagram of material flow during the integral molding process of the casing 30. Figure 11 shows a schematic diagram of force bearing during the integral molding process of the casing 30. As can be seen from Figure 10 and Figure 11, when the casing 30 is molded, the material of the casing 30 tends to accumulate at the position of the second fillet 331, which increases the frictional force between the casing 30 and the mold, making the casing 30 prone to cracking. Therefore, in this embodiment, by setting the depth H of the casing 30 and the inner diameter R1 of the second fillet 331 to satisfy 2.5mm≦R1≦20mm and 50mm<H≦250mm, without affecting the energy density of the battery cell 20, the risk of cracking caused by force bearing during the integral molding process of the casing 30 can be reduced as much as possible, and the molding difficulty of the casing 30 is further reduced.

[0147] By way of example, R1 is 2.5mm, 5mm, 7.5mm, 10mm, 12.5mm, 15mm, 17.5mm, 20mm, and / or H is 50mm, 100mm, 150mm, 200mm, 250mm.

[0148] In some embodiments, H and R1 satisfy 75mm≦H≦180mm and 4mm≦R1≦15mm.

[0149] For example, H is 75mm, 100mm, 125mm, 150mm, 175mm, 180mm. For example, R1 is 4mm, 6mm, 8mm, 10mm, 12mm, 14mm, 15mm.

[0150] In this embodiment, by setting H and R1 to satisfy 4mm ≤ R1 ≤ 15mm and 75mm ≤ H ≤ 180mm, on the one hand, the energy density of the battery cell 20 is not reduced due to H being too small or R being too large, and on the other hand, the casing 30 is not prone to deposition during the molding process due to H being too large or R being too small, and furthermore, the casing 30 does not crack due to excessive force bearing.

[0151] 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.

[0152] In some other embodiments, the casing 30 is a single-piece molded structure, and the yield strength of the casing 30 at a temperature of 25°C is Re, where the interval between the yield strength Re and the inner diameter R1 of the second fillet 331 satisfies 140 MPa ≤ Re ≤ 1000 MPa and 2.5 mm ≤ R1 ≤ 20 mm.

[0153] For example, Re = 140MPa, 180MPa, 200MPa, 230MPa, 250MPa, 280MPa, 300MPa, 320MPa, 350MPa, 380MPa, 400MPa, 430MPa, 450MPa, 480MPa, 500MPa, 550MPa, 600MPa, 650MPa, 700MPa, 750MPa, 800MPa, 850MPa, 900MPa, 950MPa, 1000MPa.

[0154] For example, R1 can be 2.5mm, 5mm, 7.5mm, 10mm, 12.5mm, 15mm, 17.5mm, or 20mm.

[0155] Yield strength can be understood as the critical stress value at which a material yields. Normally, after a material is subjected to stress, in addition to elastic deformation, plastic deformation may also occur as the stress increases. The point at which plastic deformation occurs in a material may be called the yield point, and the strength corresponding to the yield point is called the yield strength. The test method for the yield strength Re of the casing 30 at a temperature of 25°C according to the embodiment of this application can be selected according to the actual application. For example, GB / T 228.1-2010 can be used to measure the yield strength Re at room temperature conditions of 25°C.

[0156] When integrally molding the casing 30, the material accumulates on the second fillet 331, increasing the frictional force between the casing 30 and the mold, which makes the casing 30 prone to cracking. To address this problem, the embodiment of the present application further provides another solution: for a casing 30 satisfying a yield strength Re of 140 MPa ≤ Re ≤ 1000 MPa, the inner diameter R1 of the second fillet 331 is set to 2.5 mm ≤ R1 ≤ 20 mm. This reduces the difficulty of molding the casing 30 without R1 being too small, and reduces deformation of the casing 30 due to force bearing without R1 being too large.

[0157] In this embodiment, by using a material with a yield strength Re satisfying 140MPa ≤ Re ≤ 1000MPa to manufacture the casing 30, the wall thickness of the casing can be reduced without reducing the strength of the casing 30, thereby increasing the capacity space of the battery cell 20. Furthermore, by setting the inner diameter R1 of the second fillet 331 between adjacent second walls 32 to satisfy 2.5mm ≤ R1 ≤ 20mm, the risk of cracking due to force bearing during the integral molding process of the casing 30 is reduced as much as possible, thereby reducing the difficulty of molding the casing 30.

[0158] In some embodiments, the yield strengths Re and R1 of the casing 30 can satisfy 150 MPa ≤ Re ≤ 400 MPa and 4 mm ≤ R1 ≤ 15 mm.

[0159] For example, Re = 150MPa, 170MPa, 190MPa, 210MPa, 230MPa, 260MPa, 290MPa, 310MPa, 330MPa, 370MPa, 390MPa, 400MPa.

[0160] For example, R1 can be 4mm, 6mm, 8mm, 10mm, 12mm, 14mm, or 15mm.

[0161] In this embodiment, limiting the ranges to 150MPa ≤ Re ≤ 400MPa and 4mm ≤ R1 ≤ 15mm helps to balance the difficulty of molding the casing 30 with the degree of deformation.

[0162] In some embodiments, the yield strengths Re and R1 of the casing 30 can satisfy 160MPa ≤ Re ≤ 300MPa and 5mm ≤ R1 ≤ 10mm.

[0163] For example, Re = 160MPa, 170MPa, 180MPa, 190MPa, 200MPa, 210MPa, 220MPa, 230MPa, 240MPa, 250MPa, 260MPa, 270MPa, 280MPa, 290MPa, 300MPa.

[0164] For example, R1 = 5mm, 6mm, 7mm, 8mm, 9mm, 10mm.

[0165] In this embodiment, by limiting the ranges to 160MPa≦Re≦300MPa and 5mm≦R1≦10mm, deformation due to force bearing during use of the casing 30 can be reduced as much as possible, provided that it does not affect the difficulty of molding the casing 30.

[0166] In several examples, the tensile strength of the casing 30 at a temperature of 25°C is Rm, and Rm and R1 satisfy the conditions 250 MPa ≤ Rm ≤ 2000 MPa and 2.5 mm ≤ R1 ≤ 20 mm.

[0167] Tensile strength can be understood as the maximum stress value experienced by a material during fracture. The test method for the tensile strength Rm of the casing 30 at a temperature of 25°C according to the embodiment of this application can be selected according to the actual application. For example, the tensile strength Rm can be measured at room temperature conditions of 25°C by adopting ISO 6892-2:2018.

[0168] 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.

[0169] In this embodiment, by setting 250MPa≦Rm≦1000MPa and 2.5mm≦R1≦20mm, if the strength of the casing 30 is not affected, the force bearing of the mold during the manufacturing process of the casing 30 can be reduced as much as possible, and furthermore, the dimensions or surface of the casing 30 can not be affected.

[0170] In some embodiments, Rm and R1 satisfy the conditions 280 MPa ≤ Rm ≤ 800 MPa and 4 mm ≤ R1 ≤ 15 mm.

[0171] For example, Rm = 280MPa, 310MPa, 340MPa, 370MPa, 390MPa, 430MPa, 470MPa, 510MPa, 540MPa, 580MPa, 610MPa, 630MPa, 660MPa, 690MPa, 720MPa, 740MPa, 780MPa, 800MPa.

[0172] In several other embodiments, Rm and R1 satisfy the conditions 380 MPa ≤ Rm ≤ 600 MPa and 5 mm ≤ R1 ≤ 10 mm.

[0173] For example, Rm = 380 MPa, 390 MPa, 410 MPa, 440 MPa, 480 MPa, 520 MPa, 535 MPa, 570 MPa, 596 MPa, 600 MPa.

[0174] As shown in Figures 12 and 13, embodiments of the present invention further provide a battery cell 20 comprising an electrode assembly 22 and a casing 211, wherein the electrode assembly 22 is housed within the casing 211.

[0175] It should be noted that the casing 211 may be the casing 30 in the various embodiments described above.

[0176] In some embodiments, the battery cell 20 further includes a cover plate 212 to cover an opening in the casing 211 in order to seal the electrode assembly 22 within the cavity of the casing 211.

[0177] In some embodiments, the shape of the battery cell 20 is approximately a rectangular parallelepiped; for example, the battery cell 20 is a rectangular parallelepiped battery cell. Alternatively, for example, the battery cell 20 is a racetrack-shaped battery cell, and the thickness of the battery cell 20 is D1, where H, R1, and D1 satisfy the condition 0.15 mm ≤ R1 * D1 / H ≤ 36 mm.

[0178] 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.

[0179] In some embodiments, D2 may be the dimension in the expansion direction of the electrode assembly 22 of the battery cell 20.

[0180] In this embodiment, by setting 0.15 mm ≤ R1*D1 / H ≤ 36 mm, the risk of the casing 211 easily accumulating during the molding process due to the R1*D1 / H value being too small, and the risk of the casing 211 cracking due to excessive force bearing, can be reduced. Furthermore, the impact on the energy density of the battery cell 20 can be reduced because the R1*D1 / H value is not too large.

[0181] 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.

[0182] In this embodiment, H and R1 satisfy the conditions 50 mm ≤ H ≤ 250 mm and 2.5 mm ≤ R1 ≤ 20 mm.

[0183] In some embodiments, H, R1, and D1 satisfy the condition 0.34 mm ≤ R1 * D1 / H ≤ 18 mm.

[0184] In this embodiment, by setting 0.34 mm ≤ R1 * D1 / H ≤ 18 mm, the difficulty of molding the casing 211 and its energy density can be balanced.

[0185] For example, R1*D1 / H = 0.34, 0.5, 1, 3, 5, 8, 11, 13, 16, 18.

[0186] Similarly, in this embodiment, D1 satisfies the condition 15 mm ≤ D1 ≤ 90 mm.

[0187] In this embodiment, H and R1 satisfy the conditions 75mm ≤ H ≤ 180mm and 4mm ≤ R1 ≤ 15mm.

[0188] In some embodiments, H, R1, and D1 satisfy the condition 0.9 mm ≤ R*D / H ≤ 6.6 mm.

[0189] 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.

[0190] 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.

[0191] Furthermore, in this embodiment, H and R1 satisfy the conditions 90mm ≤ H ≤ 140mm and 3mm ≤ R ≤ 10mm.

[0192] It should be explained that the ranges of values ​​for R1, H, D1, and R1*D1 / H can be related to each other. For example, if 15mm≦D1≦90mm, 50mm≦H≦250mm, and 2.5mm≦R1≦20mm, then 0.15mm≦R1*D1 / H≦36mm. Also, for example, if 15mm≦D1≦90mm, 75mm≦H≦180mm, and 4mm≦R1≦15mm, then 0.34mm≦R*D / H≦18mm. Furthermore, for example, if 25mm≦D1≦60mm, 90mm≦H≦140mm, and 3mm≦R1≦10mm, then 0.9mm≦R1*D1 / H≦6.6mm.

[0193] In some embodiments, the thickness of the electrode assembly 22 is D2, and R1 and D2 satisfy 0.125 ≤ R1 / D2 ≤ 0.45.

[0194] 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.

[0195] Selectively, D2 may be a dimension in the expansion direction of the electrode assembly 22.

[0196] In this embodiment, by setting 0.125≦R1 / D2≦0.45, on the one hand, R1 is not too large, which would interfere with the electrode assembly 22 or leave insufficient space inside the battery cell 20, thus not affecting the performance of the battery cell 20. On the other hand, R1 is not too small, which would not make it difficult to mold the casing 211.

[0197] In embodiments of the present invention, the electrode assembly 22 includes a negative electrode piece 224, the negative electrode piece 224 includes a negative electrode active material capable of reversibly desorbing and inserting metal ions, the negative electrode active material includes a silicon-based material, and the tensile strength at a temperature of 25°C in at least a portion of the casing 211 used to house the electrode assembly 22 is Rm, where Rm satisfies 250 MPa ≤ Rm ≤ 2000 MPa.

[0198] As can be understood, as shown in Figures 12 and 13, the electrode assembly 22 according to the embodiment of the present application may include tabs 222 and an electrode main body 221, of which the tabs 222 of the electrode assembly 22 may include a positive electrode tab 222a and a negative electrode tab 222b. The positive electrode tab 222a may be formed by laminating portions of a positive electrode piece 223 that are not coated with the positive electrode active material, the negative electrode tab 222b may be formed by laminating portions of a negative electrode piece 224 that are not coated with the negative electrode active material, and the electrode main body 221 may be formed by laminating the positive electrode piece 223 and the negative electrode piece 224 together or by winding them together.

[0199] The negative electrode active material contained in the negative electrode piece 224 according to the embodiment of the present invention can be flexibly configured according to the actual application. For example, the negative electrode active material may include a silicon-based material. When a silicon-based material is added to the negative electrode piece 224, the silicon-based material can accommodate more metal ions, effectively increasing the energy density of the battery cell 20, and increasing the amount of deformation of the electrode assembly 22 during use within the battery cell 20. In particular, during the charging process of the battery cell 20, metal ions are inserted into the silicon-based material of the negative electrode piece 224, causing volume expansion of the electrode assembly 22 and further increasing the pressure of the electrode assembly 22 on the casing 211 of the battery cell 20.

[0200] Therefore, by increasing the tensile strength Rm of at least a portion of the casing 211 under room temperature conditions of 25°C, the deformation capacity of that portion of the casing 211 can be improved, and that portion of the casing 211 will not easily break during the use of the battery cell 20, further improving the structural stability and service life of the battery cell 20. However, in order to reduce the difficulty of selecting and processing the material for the casing 211, save costs, and facilitate processing, it is also undesirable for the tensile strength Rm of at least a portion of the casing 211 under room temperature conditions to be too high. For example, the tensile strength Rm of at least a portion of the casing 211 under room temperature conditions may normally be set to satisfy 250 MPa ≤ Rm ≤ 2000 MPa.

[0201] As can be understood, the range of values ​​for the tensile strength Rm at room temperature conditions of 25°C in at least a portion of the casing 211 according to the embodiment of the present application can be adjusted according to the actual application. For example, the value of the tensile strength Rm at room temperature can satisfy 250 MPa ≤ Rm ≤ 2000 MPa. For example, the value of the tensile strength Rm at room temperature can further satisfy 400 MPa ≤ Rm ≤ 1200 MPa. On the one hand, by increasing the tensile strength Rm at room temperature conditions in at least a portion of the casing 211, the deformation capacity of that portion of the casing 211 can be improved to resist the expansion of the electrode assembly 22, and the portion of the casing 211 can not be easily broken, further improving the structural stability and service life of the battery cell 20. On the other hand, by controlling the tensile strength Rm at room temperature conditions in at least a portion of the casing 211 so that it is not too high, the difficulty of selecting and processing the material for the casing 211 can be reduced, saving costs and making processing easier.

[0202] Furthermore, the casing 211 may be configured such that the tensile strength Rm of at least a portion of the casing 211 at room temperature satisfies 450 MPa ≤ Rm ≤ 800 MPa. By ensuring that the tensile strength Rm of at least a portion of the casing 211 at room temperature is neither too high nor too low, the deformation capacity of that portion of the casing 211 can be improved to resist the expansion of the electrode assembly 22, and this can be easily implemented and cost-effective.

[0203] In some embodiments, the tensile strength Rm value at room temperature for at least a portion of the casing 211 according to the embodiments of the present application may also be set to other values. For example, the values ​​of the tensile strength Rm at room temperature may be 250 MPa, 280 MPa, 300 MPa, 330 MPa, 350 MPa, 380 MPa, 400 MPa, 450 MPa, 500 MPa, 550 MPa, 600 MPa, 650 MPa, 700 MPa, 750 MPa, 800 MPa, 850 MPa, 900 MPa, 950 MPa, 1000 MPa, 1050 MPa, 1100 MPa, and 1150 MPa. The value may be any one of the following values: Pa, 1200 MPa, 1250 MPa, 1300 MPa, 1350 MPa, 1400 MPa, 1450 MPa, 1500 MPa, 1550 MPa, 1600 MPa, 1650 MPa, 1700 MPa, 1750 MPa, 1800 MPa, 1850 MPa, 1900 MPa, 1950 MPa, and 2000 MPa, or it may be any two of these values.

[0204] As is to be understood, the tensile strength in the embodiments of this application refers to the maximum stress value that the material experiences before fracture. The test method for the tensile strength Rm at a temperature of 25°C in at least a portion of the casing 211 in the embodiments of this application can be selected according to the actual application. For example, the tensile strength Rm can be measured at room temperature conditions of 25°C by adopting the national standard GB / T 228.1-2010.

[0205] Figure 14 shows a schematic cross-sectional view of an electrode assembly 22 according to an embodiment of the present application. For example, the schematic cross-sectional view shown in Figure 14 may be a 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 a positive electrode piece 223 or a negative electrode piece 224 according to an embodiment of the present application. For example, Figure 15 may show a schematic local cross-sectional view of the negative electrode piece 224 of the electrode assembly 22 shown in Figure 14 along its thickness direction, or it may show a schematic local cross-sectional view of the positive electrode piece 223 of the electrode assembly 22 shown in Figure 14 along its thickness direction.

[0206] As shown in Figures 12 to 15, the electrode assembly 22 according to the embodiment of the present application includes positive electrode pieces 223 and negative electrode pieces 224, and the electrode assembly 22 can be formed by stacking the positive electrode pieces 223 and negative electrode pieces 224 on each other or by winding them together. For example, the electrode assembly 22 may include a plurality of positive electrode pieces 223 and a plurality of negative electrode pieces 224. Along the thickness direction Y of the electrode assembly 22, the plurality of positive electrode pieces 223 and a plurality of negative electrode pieces 224 are stacked alternately on each other to form a laminated electrode assembly 22. Alternatively, for example, the electrode assembly 22 may include a plurality of positive electrode pieces 223, and the negative electrode pieces 224 include a plurality of bent sections and a plurality of stacked sections that are connected to each other and arranged alternately, and after the bent sections are bent, the plurality of stacked sections of the plurality of positive electrode pieces 223 and negative electrode pieces 224 are stacked alternately on each other to form a laminated electrode assembly 22. Alternatively, for example, the electrode assembly may be wound around each other by the positive electrode piece 223 and the negative electrode piece 224 to form a wound electrode assembly 22. For convenience of explanation, the drawings of the embodiments of the present application show a wound electrode assembly 22 as an example, but the embodiments of the present application are not limited to these. Furthermore, the electrode assembly 22 may further include a separator 225 used to separate the positive electrode piece 223 and the negative electrode piece 224.

[0207] In the embodiments of the present invention, the negative electrode piece 224 includes a negative electrode active material, and for example, the negative electrode active material coated on the negative electrode piece 224 may be used to form a negative electrode active material layer 2241, which may be installed on at least one surface of the negative electrode current collector 2242. For example, the negative electrode active material layer 2241 may be installed on both sides of the negative electrode current collector 2242 that are perpendicular to its thickness direction.

[0208] In some embodiments, the negative electrode current collector 2242 may be a metal foil or a composite current collector. Examples of metal foils include copper foil, copper alloy foil, aluminum foil, and aluminum alloy foil. The composite current collector may include a polymer material substrate and a metal material layer formed on at least one surface of the polymer material substrate. For example, the metal material may include one or more of copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. For example, the polymer material substrate may include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0209] As can be understood, the negative electrode active material according to the embodiments of the present application can be flexibly configured according to the actual application. Specifically, the negative electrode active material according to the embodiments of the present application can improve the energy density of the battery by including a silicon-based material. For example, the silicon-based material may include at least one of elemental silicon, silicon-oxygen compounds, silicon-carbon composites, silicon-nitrogen composites, silicon-containing alloys, or silicon-oxygen-carbon composite materials.

[0210] In some embodiments, the silicon-based material may contain silicon and one or more alkali metal elements and alkaline earth metal elements. For example, the alkali metal element may include Li. For example, the alkaline earth metal element may include Mg. For example, the silicon-based material may be a silicon-based material in which alkali metals and / or alkaline earth metals are pre-embedded, for example, a silicon-based material in which Li and / or Mg are pre-embedded.

[0211] As can be understood, the mass percentage g of the silicon-based material in the embodiment of the present application can be flexibly set according to the actual application.

[0212] For example, the silicon-based material may be set so that the range of the mass percentage g satisfies 2% ≤ g ≤ 40%. By adding a silicon-based material to the negative electrode active material of the negative electrode piece 224, the silicon-based material can accommodate more metal ions compared to other elements, for example, the capacity of the silicon-based material is about 10 times that of graphite, which can effectively improve the energy density of the battery cell 20. At the same time, it is undesirable to set the mass percentage g of the silicon-based material to be too large, otherwise it will increase the difficulty of processing the electrode assembly 22 and increase the amount of deformation of the electrode assembly 22 during use in the battery cell 20. In particular, during the charging process of the battery cell 20, metal ions are inserted into the silicon-based material of the negative electrode piece 224, causing volume expansion of the electrode assembly 22, further increasing the pressure of the electrode assembly 22 on the casing 211 of the battery cell 20, and further increasing the difficulty of processing the battery cell 20.

[0213] Furthermore, the mass percentage g of the silicon-based material may be set to satisfy the range of 8% ≤ g ≤ 40%. By appropriately reducing the mass percentage g of the silicon-based material, the difficulty of processing the electrode assembly 22 can be reduced, the amount of deformation of the electrode assembly 22 during the charging and discharging process of the battery cell 20 can be reduced, i.e., the amount of volume expansion of the electrode assembly 22 can be reduced, the pressure of the electrode assembly 22 on the casing 211 of the battery cell 20 can be further reduced, the requirements for the structural strength of the casing 211 can be reduced, processing can be made easier and costs can be reduced.

[0214] Furthermore, the mass percentage g of the silicon-based material may be set to satisfy the range of 10% ≤ g ≤ 30%. By rationally adjusting the mass percentage g of the silicon-based material, not only can the energy density of the battery cell 20 be effectively increased, but the difficulty of processing the electrode assembly 22 can also be reduced, and the amount of deformation of the electrode assembly 22 during the charging and discharging process of the battery cell 20 can also be effectively reduced, further reducing the requirements for the structural strength of the casing 211.

[0215] In some embodiments, the mass percentage g of the silicon-based material in the embodiments of the present application may also be set to other values. For example, the mass percentage g of the silicon-based material may be any one of the following values: 5%, 8%, 10%, 13%, 15%, 18%, 20%, 23%, 25%, 28%, 30%, 33%, 35%, 38%, 40%, 43%, 45%, 48%, and 50%, or it may be between any two of these values.

[0216] As can be understood, the mass percentage g of silicon-based material in the negative electrode active material according to the embodiment of the present application means that g is the ratio of the mass of silicon-based material in the negative electrode active material to the total mass of the negative electrode active material, and the test method for the mass percentage g of silicon-based material can be selected according to the actual application and can be measured by employing methods known in the art.

[0217] In the embodiments of the present application, the negative electrode active material may further contain other materials. For example, the negative electrode active material may further contain a negative electrode adhesive. For example, the negative electrode adhesive may contain one or more of the following: styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, aqueous acrylic resin (e.g., polyacrylate PAA, polymethacrylate PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS), but the embodiments of the present application are not limited to these.

[0218] In some embodiments, the negative electrode active material may further contain a negative electrode conductive agent. The present application is not particularly limited to the type of negative electrode conductive agent, and as an example, the negative electrode conductive agent may include one or more of the following: superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0219] In some embodiments, the negative electrode active material may further comprise other auxiliaries. As an example, the other auxiliaries may include thickeners such as sodium carboxymethyl cellulose (CMC) and PTC thermistor materials.

[0220] 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 further comprise a conductive primer layer (e.g., consisting of a conductive agent and an adhesive) sandwiched between the negative electrode current collector 2242 and the negative electrode active material layer 2241 and disposed on the surface of the negative electrode current collector 2242. In some embodiments, the negative electrode sheet 224 may further comprise a protective layer covering the surface of the negative electrode active material layer 2241.

[0221] In some embodiments, the negative electrode sheet 224 can be manufactured by the following method: dispersing a negative electrode active material, an optional negative electrode adhesive, an optional negative electrode conductive agent, and optional other auxiliaries in a solvent, stirring uniformly to form a negative electrode slurry, coating the negative electrode slurry on the negative electrode current collector 2242, performing processes such as drying and cold pressing, and then forming the negative electrode sheet 224. The solvent may be N-methylpyrrolidone (NMP) or deionized water, but the embodiments of the present application are not limited thereto.

[0222] In the embodiments of the present application, the value of the mass proportion g of the silicon-based material and the value of the tensile strength Rm of at least a partial region of the casing 211 under the condition of 25°C can mutually restrict each other to balance the relationship between the energy density and the structural strength of the battery cell 20. For example, in the negative electrode active material, the mass proportion of the silicon-based material is g, the material of at least a partial region of the casing 211 contains an iron element, and Rm and g satisfy 2%<g<40% and 300MPa<Rm<2000MPa. The material of at least a partial region of the casing 211 contains the iron element, which can increase the structural strength of the material in the corresponding partial region of the casing 211, thereby meeting design requirements.

[0223] In some embodiments, the material of at least a portion of the casing 211 includes 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 portion of the casing 211 may include Q195 carbon steel, which not only facilitates processing but also satisfies the tensile strength Rm value at 25°C.

[0224] In some embodiments, the material of at least a portion of the casing 211 includes carbon steel or stainless steel, and Rm and g satisfy 4.5% ≤ g ≤ 40% and 380 MPa ≤ Rm < 2000 MPa. For example, the material of at least a portion of the casing 211 may include SPCC carbon steel, which not only facilitates processing but also satisfies the tensile strength Rm value at 25°C.

[0225] In some embodiments, Rm and g satisfy 8% ≤ g ≤ 40% and 400 MPa ≤ Rm < 2000 MPa. For example, the material of at least a portion of the casing 211 may include modified stainless steel, which not only facilitates processing but also satisfies the tensile strength Rm value at 25°C.

[0226] In some embodiments, Rm and g satisfy 10% ≤ g ≤ 40% and 480 MPa ≤ Rm < 2000 MPa. For example, the material of at least a portion of the casing 211 may include 316 stainless steel, which not only facilitates processing but also satisfies the tensile strength Rm value at 25°C.

[0227] In some embodiments, Rm and g satisfy the conditions 15% ≤ g ≤ 40% and 520 MPa ≤ Rm < 2000 MPa. For example, the material of at least a portion of the casing 211 may include 304 stainless steel, which not only facilitates processing but also satisfies the tensile strength Rm value at 25°C.

[0228] In several examples, Rm and g satisfy the conditions 20% ≤ g ≤ 40% and 600 MPa ≤ Rm < 2000 MPa.

[0229] The following will be explained by comparing multiple comparative examples and multiple examples. Specifically, the battery cell 20 in each of the following examples and comparative examples is a rectangular parallelepiped type battery cell as shown in Figures 12 and 13, and among them, a hollow structure is adopted in which the casing 211 opens at one end.

[0230] In the following examples and comparative examples, the manufacturing methods for the positive electrode piece 223, negative electrode piece 224, electrolyte, and separator 225 of the battery cell 20 are as follows.

[0231] 1. Manufacturing of positive electrode piece 223 Positive electrode active material LiNi 0.95 Co 0.04 Mn 0.01 O2, the conductive agent Super P, and the adhesive polyvinylidene fluoride (PVDF) were prepared as a positive electrode slurry in N-methylpyrrolidone (NMP), with a solid content of 50 wt% in the positive electrode slurry, and LiNi 0.7 Co 0.1 Mn 0.1 The mass ratio of O2, Super P, and PVDF was 8:1:1. The positive electrode slurry was applied to the upper and lower surfaces of the aluminum foil current collector, dried at 85°C, then cold-pressurized, edge-trimmed, cut, and slit, and finally dried under vacuum conditions at 85°C for 4 hours to produce the positive electrode piece 223.

[0232] 2. Manufacturing of the negative electrode piece 224 A negative electrode slurry was prepared by uniformly mixing a negative electrode active material, a conductive agent Super P, a thickener carboxymethylcellulose (CMC), and an adhesive styrene-butadiene rubber (SBR) in deionized water. The negative electrode active material contained graphite and a silicon-based material, and the silicon-based material was a silicon-oxygen compound. The solid content in the negative electrode slurry was 30 wt%, and the mass ratio of the negative electrode active material, silicon monoxide, Super P, CMC, and adhesive styrene-butadiene rubber (SBR) in the solid content was 88:7:3:2. The negative electrode slurry was applied to the upper and lower surfaces of a copper foil current collector and dried at 85°C. Then it was cold-pressed, edge-trimmed, cut, and slit, and then dried under vacuum conditions at 120°C for 12 hours to produce a negative electrode piece 224.

[0233] 3. Manufacturing of electrolyte In a glove box under an argon atmosphere (H2O < 0.1 ppm, O2 < 0.1 ppm), a thoroughly dried electrolyte salt, LiPF6, was dissolved in a mixed solvent (the mixed solvent contained ethylene carbonate (EC) and diethyl carbonate (DEC), and the ethylene carbonate (EC) and diethyl carbonate (DEC) were mixed in a 50:50 mass ratio). After homogeneous mixing, an electrolyte solution with a concentration of 1 mol / L was obtained.

[0234] 4. Manufacturing of separator 225 A 16 μm polyethylene film was used as separator 225.

[0235] 5. Manufacturing of lithium-ion battery cells 20 The positive electrode piece 223, separator 225, and negative electrode piece 224 are stacked in order, with the separator 225 positioned between the positive electrode piece 223 and the negative electrode piece 224 to isolate the positive and negative electrodes. The cells are then wound to obtain a bare cell, tabs are welded, the bare cell is placed in an outer casing made of a different material, the manufactured electrolyte is injected into the dried outer casing, and sealing, standing, chemical conversion, shaping, and capacity testing are performed to complete the manufacturing of the lithium-ion battery cell 20.

[0236] In each of the following examples and comparative examples, the tensile strength of the casing 211 of the battery cell 20 at a temperature of 25°C is Rm, and in order to obtain different tensile strengths Rm, different materials were correspondingly selected for the casing 211. The negative electrode active material of the negative electrode piece 224 of the electrode assembly 22 of the battery cell 20 contains a silicon-based material with a mass percentage of g, and the specific parameter settings are shown in Table 1 below. Furthermore, in each example and comparative example, the material of all areas of the casing 211 is the same, and the tensile strength Rm of the casing 211 at 25°C was measured using the method specified in GB / T 228.1-2010. In addition, the battery cell 20 in each of the following examples and comparative examples is the same in all other conditions except for the differences in the parameter settings shown in Table 1. For example, the wall thickness of each wall of the casing 211 of the battery cell 20 in each embodiment is 0.25 mm, and for example, the capacity of the battery cell 20 in each embodiment is 350 Ah.

[0237] A cycle charge fatigue test was performed on the battery cells 20 in each of the embodiments and comparative examples described below. Specifically, Figure 16 shows a schematic diagram of the structure of the clamp 700 for cycle charge fatigue testing according to the embodiment of the present application. As shown in Figure 16, the clamp 700 includes three 10 mm steel plates, which completely cover the walls of the battery cell 20 over the largest area. For convenience of explanation, the three clamp steel plates are defined here as the first steel plate 710, the second steel plate 720, and the third steel plate 730, respectively. The first steel plate 710 and the third steel plate 730 are located at both ends of the clamp 700 and are connected and fixed by bolts. The central second steel plate 720 is constrained by guide rails so that it can translate only in a direction perpendicular to the large surface of the second steel plate 720, the space between the first steel plate 710 and the second steel plate 720 is used to clamp the battery cell 20, and the walls of the battery cell 20 with the largest surface area are bonded to the first steel plate 710 and the second steel plate 720, and a pressure sensor 740 is provided between the second steel plate 720 and the third steel plate 730. By adjusting the position of the second steel plate 720, it is possible to adjust the initial pressing force of the battery cell 20 on the second steel plate 720.

[0238] Specifically, the battery cell 20 is clamped and fixed within a dedicated clamp 700, ensuring that the two opposing walls of the maximum surface area of ​​the battery cell 20 are firmly held in place, and the initial pressure is set to 2000N. The electrode terminals 214 of the battery cell 20 are then connected to a dedicated battery charging and discharging device.

[0239] The clamp 700, which held the battery cell 20, was placed in a constant temperature environment of 25±2℃, and the test was started after the battery cell 20 reached temperature equilibrium.

[0240] The specific test steps were carried out by referring to Chapter 6.4, "Standard Cycle Life," of "GBT31484-2015 Cycle Life Requirements and Test Methods for Power Storage Batteries for Electric Vehicles," and the test cycle cutoff condition was changed to "Stop the test until the welded seam 2113 of the battery cell 20 is damaged."

[0241] For example, the test can be performed according to the following steps: step a, discharge at 1I(A) until the discharge stop condition specified by the company; step b, leave for 30 minutes or longer or until the leave condition specified by the company; step c, charge according to the method in 6.1.1.3; step d, leave for 30 minutes or longer or until the leave condition specified by the company; step e, discharge at 1I1(A) until the discharge stop condition specified by the company; and step f, cycle through steps b to e until the weld joint 2113 is damaged and the test is stopped.

[0242] During the above test process, the welded seam 2113 of the battery cell 20 was continuously observed and the number of cycles recorded until leakage occurred at the welded seam 2113, thereby obtaining the state of the casing 211 after 1000 cycles, as shown in Table 1 below. In each of the following examples and comparative examples, the welded seam 2113 refers to the welded seam between the casing 211 and the cover plate 212, that is, the welded seam 2113 surrounds the open end of the casing 211, while the casing 211 employs an integrally molded structure.

[0243] [Table 1]

[0244] As can be understood, in Table 1 above, the material of the casing 211 may be Q195 carbon steel, but the tensile strength Rm of Q195 carbon steel at room temperature of 25°C is typically at least 315 MPa to 430 MPa, and in the above example only 328 MPa is taken as an example, but it is not limited to this. Similarly, the material of the casing 211 may be SPCC carbon steel, but the tensile strength Rm of SPCC carbon steel at room temperature of 25°C is typically at least 380 MPa to 430 MPa, and in the above example only 396 MPa is taken as an example. The material of the casing 211 may also be modified stainless steel, but the tensile strength Rm of modified stainless steel at room temperature of 25°C is typically at least 400 MPa to 600 MPa, and in the above example only 421 MPa is taken as an example. The material of the casing 211 may be SUS430 stainless steel, but the tensile strength Rm of SUS430 stainless steel at room temperature of 25°C is usually at least 450 MPa, and in the above example only 459 MPa is taken as an example. The material of the casing 211 may also be SUS304 stainless steel, but the tensile strength Rm of SUS304 stainless steel at room temperature of 25°C is usually at least 520 MPa, and in the above example only 533 MPa and 625 MPa are taken as examples.

[0245] As can be seen by comparing the two comparative examples and the twelve examples in Table 1 above, when different materials are used for the casing 211, correspondingly different tensile strengths Rm can be determined. If the tensile strength Rm satisfies 250MPa ≤ Rm ≤ 2000MPa, for example, in Examples 1 to 12, even if the mass percentage g of silicon-based material in the negative electrode piece 224 of the battery cell 20 is different, the failure fatigue cycles of the battery cell 20 can reach more than 1,000, thereby meeting the design needs of the battery cell 20. However, if the tensile strength Rm does not satisfy 250MPa ≤ Rm ≤ 2000MPa, for example, in Comparative Examples 1 to 2, even if the mass percentage g of silicon-based material in the negative electrode piece 224 of the battery cell 20 is relatively low, the failure fatigue cycles of the battery cell 20 do not reach 1,000, and the design needs of the battery cell 20 cannot be met.

[0246] As can be understood, the battery cell 20 according to the embodiment of the present application can further satisfy other design needs. Specifically, the yield strength at a temperature of 25°C in at least a portion of the casing 211 is Re, where Re satisfies 140 MPa ≤ Re ≤ 1000 MPa.

[0247] By increasing the yield strength Re at room temperature in at least a portion of the casing 211, the deformation capacity of the casing 211 can be improved, further enhancing the structural stability and service life of the battery cell 20. During the charging and discharging process of the battery cell 20, the electrode assembly 22 undergoes repeated volume expansion and contraction. By increasing the yield strength Re at room temperature in at least a portion of the casing 211, the maximum compressive force that the casing 211 can withstand can be increased. If this does not exceed the limit of the yield strength of the casing 211, the casing 211 will not easily break, and the deformation of the casing 211 is recoverable, thus improving the service life of the casing 211. However, in order to reduce the difficulty of selecting and processing the material for the casing 211, save costs, and facilitate processing, it is undesirable for the yield strength Re at room temperature in at least a portion of the casing 211 to be too high. For example, the casing 211 may typically be installed such that the yield strength Re in at least a portion of the casing 211 under ambient temperature conditions satisfies 140 MPa ≤ Re ≤ 1000 MPa.

[0248] As can be understood, the range of yield strength Re values ​​at room temperature conditions of 25°C in at least a portion of the casing 211 according to the embodiment of the present application can be adjusted according to the actual application. For example, the yield strength Re value at room temperature can satisfy 140 MPa ≤ Re ≤ 1000 MPa. Alternatively, for example, the yield strength Re value at room temperature can satisfy 180 MPa ≤ Re ≤ 600 MPa. On the one hand, by increasing the yield strength Re at room temperature in at least a portion of the casing 211, the deformation capacity of that portion of the casing 211 can be improved to resist the expansion of the electrode assembly 22, and if that portion of the casing 211 is not easily broken and does not exceed the limit of the yield strength of the casing 211, then when the expansion of the electrode assembly 22 is reduced, the deformation of the casing 211 can also be recovered, further improving the structural stability and service life of the battery cell 20. On the other hand, by controlling the yield strength Re of at least a portion of the casing 211 at room temperature so that it is not too high, the difficulty of selecting and processing the material for the casing 211 can be reduced, costs can be saved, and processing can be made easier.

[0249] Furthermore, the casing 211 may be installed such that the yield strength Re in at least a portion of the casing 211 at room temperature satisfies 220 MPa ≤ Re ≤ 400 MPa. By ensuring that the yield strength Re in at least a portion of the casing 211 at room temperature is neither too high nor too low, the deformation capacity of that portion of the casing 211 can be improved to resist the expansion of the electrode assembly 22, and this can be easily implemented and cost-effective.

[0250] In some embodiments, the yield strength Re value at room temperature for at least a portion of the casing 211 according to the embodiment of the present application may also be set to other values. For example, the yield strength Re value at room temperature may be any one of the following values: 140MPa, 150MPa, 160MPa, 180MPa, 200MPa, 220MPa, 250MPa, 280MPa, 300MPa, 330MPa, 350MPa, 380MPa, 400MPa, 430MPa, 450MPa, 480MPa, 500MPa, 530MPa, 550MPa, 580MPa, 600MPa, 630MPa, 650MPa, 680MPa, 700MPa, 730MPa, 750MPa, 780MPa, 800MPa, 830MPa, 850MPa, 880MPa, 900MPa, 930MPa, 950MPa, 980MPa, and 1000MPa, or it may be between any two of these values.

[0251] As can be understood, the yield strength in the embodiments of the present application can be understood as the critical stress value for material yielding. Normally, after a material is subjected to stress, in addition to elastic deformation, plastic deformation may also occur as the stress increases. The point at which plastic deformation of the material occurs may be called the yield point, and the strength corresponding to the yield point is called the yield strength. Furthermore, the yield strength in the embodiments of the present application usually refers to the upper yield strength, that is, the upper yield strength under the condition of a temperature of 25°C in at least a portion of the casing 211 is Re.

[0252] The test method for the yield strength Re of at least a portion of the casing 211 under a temperature of 25°C according to the embodiment of this application can be selected according to the actual application. For example, the yield strength Re can be measured under room temperature conditions of 25°C by adopting the national standard GB / T 228.1-2010.

[0253] In the embodiments of the present application, the value of the mass ratio g of the silicon-based material and the value of the yield strength Re of at least a partial region of the casing 211 under the condition of 25°C can be mutually restricted, so as to improve the energy density of the battery cell 20, enhance the structural strength of the casing 211, and further improve the structural strength and service life of the battery cell 20.

[0254] 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 140MPa<Re<600MPa. By adding the silicon-based material to the negative electrode active material of the negative electrode piece 224, the silicon-based material can accommodate more metal ions compared with other elements. For example, 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 improved. At the same time, it is not desirable to set the mass ratio g of the silicon-based material to an excessively large value, otherwise the processing difficulty of the electrode assembly 22 will be increased, and the deformation amount of the electrode assembly 22 in the battery cell 20 during the use process will also be increased. Especially during the charging process of the battery cell 20, metal ions are inserted into the silicon-based material of the negative electrode piece, which causes volume expansion of the electrode assembly 22, further increases the pressure of the electrode assembly 22 on the casing 211 of the battery cell 20, and further increases the processing difficulty of the battery cell 20. Therefore, by appropriately increasing the yield strength Re of at least a partial region of the casing 211 under normal temperature conditions, the deformability of the corresponding part of the casing 211 can be improved to resist the expansion amount of the electrode assembly 22. The corresponding part of the casing 211 will not be easily damaged, and when the yield strength limit of the casing 211 is not exceeded, if the expansion amount of the electrode assembly 22 decreases, the deformation of the casing 211 can also be recovered, which can further improve the structural stability and service life of the battery cell 20. In addition, by controlling the yield strength Re of at least a partial region of the casing 211 under normal temperature conditions not to be excessively large, the difficulty of material selection and processing for the casing 211 can be reduced, costs can be saved, and processing can be facilitated.

[0255] In some embodiments, the material of at least a partial region of the casing 211 includes carbon steel or stainless steel, and g and Re satisfy 4.5%≦g≦40% and 170MPa≦Re<600MPa. For example, the material of at least a partial region of the casing 211 may include SPCC carbon steel, which not only facilitates processing, but also can satisfy the value of the yield strength Re under the condition of 25°C.

[0256] In some embodiments, g and Re satisfy 8%≦g≦40% and 180MPa≦Re<600MPa. For example, the material of at least a partial region of the casing 211 may include modified stainless steel, which not only facilitates processing, but also can satisfy the value of the yield strength Re under the condition of 25°C.

[0257] In some embodiments, g and Re satisfy 10%≦g≦40% and 190MPa≦Re<600MPa. For example, the material of at least a partial region of the casing 211 may include 316 stainless steel, which not only facilitates processing, but also can satisfy the value of the yield strength Re under the condition of 25°C.

[0258] In some embodiments, g and Re satisfy 15%≦g≦40% and 200MPa≦Re<600MPa. For example, the material of at least a partial region of the casing 211 may include 304 stainless steel, which not only facilitates processing, but also can satisfy the value of the yield strength Re under the condition of 25°C.

[0259] In some embodiments, g and Re satisfy 20%≦g≦40% and 210MPa≦Re<600MPa.

[0260] Hereinafter, description will be made by comparison with a plurality of comparative examples and a plurality of examples. Specifically, each of the battery cells 20 in the following examples and comparative examples takes a rectangular parallelepiped type battery cell as shown in FIG. 12 and FIG. 13 as an example, and the casing 211 adopts a hollow structure with an opening at one end.

[0261] In each of the following Examples and Comparative Examples, the manufacturing methods of the positive electrode piece 223, the negative electrode piece 224, the electrolytic solution and the separator 225 of the battery cell 20 are as follows.

[0262] 1. Production of positive electrode piece 223 Positive electrode active material LiNi 0.95 Co 0.04 Mn 0.01 O2, conductive agent Super P, and binder polyvinylidene fluoride (PVDF) are prepared into a positive electrode slurry in N-methylpyrrolidone (NMP), wherein the solid content in the positive electrode slurry is 50 wt%, and in the solid components, LiNi 0.7 Co 0.1 Mn 0.1 The mass ratio of O2, Super P and PVDF is 8:1:1. The positive electrode slurry is applied to the upper and lower surfaces of aluminum foil as the current collector, dried at 85°C, then cold-pressed, then edge-trimmed, cut, and slit, and then dried for 4 h under a vacuum condition of 85°C to produce the positive electrode piece 223.

[0263] 2. Production of negative electrode piece 224 A negative electrode active material, conductive agent Super P, thickener carboxymethyl cellulose (CMC), and binder styrene-butadiene rubber (SBR) are uniformly mixed in deionized water to prepare a negative electrode slurry. The negative electrode active material includes graphite and a silicon-based material, and the silicon-based material is a silicon-oxygen compound. The solid content in the negative electrode slurry is 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 content is 88:7:3:2. The negative electrode slurry is applied to the upper and lower surfaces of copper foil as the current collector, dried at 85°C, then cold-pressed, edge-trimmed, cut, and slit, and then dried for 12 h under a vacuum condition of 120°C to produce the negative electrode piece 224.

[0264] 3. Production of electrolytic solution In a glove box under an argon atmosphere (H2O < 0.1 ppm, O2 < 0.1 ppm), a thoroughly dried electrolyte salt, LiPF6, was dissolved in a mixed solvent (the mixed solvent contained ethylene carbonate (EC) and diethyl carbonate (DEC), and the ethylene carbonate (EC) and diethyl carbonate (DEC) were mixed in a 50:50 mass ratio). After homogeneous mixing, an electrolyte solution with a concentration of 1 mol / L was obtained.

[0265] 4. Manufacturing of separator 225 A 16 μm polyethylene film was used as separator 225.

[0266] 5. Manufacturing of lithium-ion battery cells 20 The positive electrode piece 223, separator 225, and negative electrode piece 224 are stacked in order, with the separator 225 positioned between the positive electrode piece 223 and the negative electrode piece 224 to isolate the positive and negative electrodes. The cells are then wound to obtain a bare cell, tabs are welded, the bare cell is placed in an outer casing made of a different material, the manufactured electrolyte is injected into the dried outer casing, and sealing, standing, chemical conversion, shaping, and capacity testing are performed to complete the manufacturing of the lithium-ion battery cell 20.

[0267] In each of the following examples and comparative examples, the yield strength of the casing 211 of the battery cell 20 at a temperature of 25°C is Re, and to obtain different yield strengths Re, different materials are correspondingly selected for the casing 211. The negative electrode active material of the negative electrode piece 224 of the electrode assembly 22 of the battery cell 20 includes a silicon-based material with a mass percentage of g, and the specific parameter settings are shown in Table 1 below. In addition, in each example and comparative example, the material is the same for all areas of the casing 211, and the yield strength Re of the casing 211 at 25°C was measured using the method specified in GB / T 228.1-2010. Furthermore, in each of the following examples and comparative examples, the battery cell 20 is the same in all other conditions except for the parameter settings shown in Table 1. For example, the wall thickness of each wall of the casing 211 of the battery cell 20 in each example is 0.25 mm, and the capacity of the battery cell 20 in each example is 350 Ah.

[0268] A cycle charge fatigue test was performed on the battery cells 20 in each of the following examples and comparative examples. Specifically, the test can be performed using the cycle charge fatigue test clamp 700 shown in the figure.

[0269] Specifically, the battery cell 20 is clamped and fixed within a dedicated clamp 700, ensuring that the two opposing walls of the maximum surface area of ​​the battery cell 20 are firmly held in place, and the initial pressure is set to 2000N. The electrode terminals 214 of the battery cell 20 are then connected to a dedicated battery charging and discharging device.

[0270] The clamp 700, which held the battery cell 20, was placed in a constant temperature environment of 25±2℃, and the test was started after the battery cell 20 reached temperature equilibrium.

[0271] The specific test steps were carried out by referring to Chapter 6.4, "Standard Cycle Life," of "GBT31484-2015 Cycle Life Requirements and Test Methods for Power Storage Batteries for Electric Vehicles," and the test cycle cutoff condition was changed to "Stop the test until the welded seam 2113 of the battery cell 20 is damaged."

[0272] For example, the test can be performed according to the following steps: step a, discharge at 1I(A) until the discharge stop condition specified by the company; step b, leave for 30 minutes or longer or until the leave condition specified by the company; step c, charge according to the method in 6.1.1.3; step d, leave for 30 minutes or longer or until the leave condition specified by the company; step e, discharge at 1I1(A) until the discharge stop condition specified by the company; and step f, cycle through steps b to e until the weld joint 2113 is damaged and the test is stopped.

[0273] During the above test process, the welded seams 2113 of the battery cell 20 were continuously observed and the number of cycles recorded until leakage occurred at the welded seams 2113, thereby obtaining the failure fatigue state of the casing 211 after 1000 cycles, as shown in Table 2 below. In each of the following examples and comparative examples, the welded seam 2113 refers to the welded seam between the casing 211 and the cover plate 212, that is, the welded seam 2113 surrounds the open end of the casing 211, while the casing 211 employs an integrally molded structure.

[0274] [Table 2]

[0275] As can be understood, in the above Table 2, the material of the casing 211 may be modified stainless steel, and the yield strength Re of the modified stainless steel at a normal temperature of 25°C is usually at least 140 MPa to 180 MPa. In the above examples, only 145 MPa and 173 MPa are taken as examples, but the present disclosure is not limited thereto. Similarly, the material of the casing 211 may be SUS316 stainless steel, and the yield strength Re of SUS316 stainless steel at a normal temperature of 25°C is usually at least 177 MPa. In the above examples, only 182 MPa and 193 MPa are taken as examples. The material of the casing 211 may be Q195 carbon steel, and the yield strength Re of Q195 carbon steel at a normal temperature of 25°C is usually at least 195 MPa. In the above examples, only 203 MPa is taken as an example. The material of the casing 211 may be SUS304 stainless steel, and the yield strength Re of SUS304 stainless steel at a normal temperature of 25°C is usually at least 205 MPa. In the above examples, only 212 MPa is taken as an example.

[0276] As can be seen by comparing the two comparative examples and the 12 examples in the above Table 2, when the casing 211 adopts different materials, the corresponding different yield strength Re can be determined. When the yield strength Re satisfies 140MPa≦Re≦1000MPa, for example, in Examples 1 to 12, even if the mass ratio g of the silicon-based material in the material of the negative electrode piece 224 of the battery cell 20 is different, the number of failure fatigue cycles of the battery cell 20 can reach more than one thousand, thereby meeting the design requirements of the battery cell 20. However, when the yield strength Re does not satisfy 140MPa≦Re≦1000MPa, for example, in Comparative Examples 1 to 2, even if the mass ratio g of the silicon-based material in the material of the negative electrode piece 224 of the battery cell 20 is relatively low, the number of failure fatigue cycles of the battery cell 20 cannot reach one thousand, and the design requirements of the battery cell 20 cannot be met.

[0277] In some embodiments, the electrode assembly 22 further comprises a positive electrode piece 223, the positive electrode piece 223 comprising a positive electrode active material capable of reversibly desorbing and inserting metal ions, the positive electrode active material comprising a nickel-containing compound, and the melting point of at least a portion of the casing 211 is p, where p satisfies 1200°C ≤ p ≤ 2000°C.

[0278] The positive electrode piece 223 in the embodiment of the present invention is equipped with a positive electrode active material that can reversibly desorb and insert metal ions, and the positive electrode active material can be flexibly installed according to the actual application. For example, the positive electrode active material may contain a nickel element compound, which can effectively increase the energy density of the battery cell 20 and improve the cycle life, but at the same time, it also increases the temperature and gas generated during the use of the battery cell 20, and in particular, if thermal runaway occurs during the use of the battery cell 20, the internal temperature of the battery cell 20 rises rapidly and a large amount of gas is generated.

[0279] Therefore, by appropriately improving the melting point p of at least a portion of the casing 211, the casing 211 will not easily melt, reducing the possibility of the battery cell 20 exploding, and further reducing the risk of thermal runaway in adjacent battery cells 20, thereby improving the reliability of the battery 10. However, in order to reduce the difficulty of selecting and processing the material for the casing 211, save costs, and facilitate processing, it is also undesirable for the melting point p of at least a portion of the casing 211 to be too high. For example, the melting point p of at least a portion of the casing 211 may normally be set to satisfy 1200°C ≤ p ≤ 2000°C.

[0280] As can be understood, the range of the melting point p value for at least a portion of the casing 211 in the embodiment of the present application can be adjusted according to the actual application. For example, the melting point p of at least a portion of the casing 211 usually satisfies 1200°C ≤ p ≤ 2000°C. Alternatively, for example, the melting point p of at least a portion of the casing 211 may satisfy 1300°C ≤ p ≤ 1800°C. On the one hand, by appropriately increasing the value of the melting point p, the resistance of the casing 211 in that portion to melting when thermal runaway occurs in the battery cell 20 can be improved, the casing 211 will not melt easily, further reducing the risk of thermal runaway occurring in adjacent battery cells 20, i.e., reducing the risk of thermal diffusion, thereby improving the reliability of the battery 10. At the same time, the melting point p should not be too high in order to easily select a suitable material, reduce the difficulty of processing, save costs, and facilitate processing.

[0281] Furthermore, the melting point p of at least a portion of the casing 211 may be set to satisfy 1400°C ≤ p ≤ 1600°C. This improves the structural strength of the casing 211 when thermal runaway occurs in the battery cell 20, preventing the casing 211 from easily melting, maintaining the structural integrity of that portion of the casing 211, and reducing the risk of thermal runaway occurring in adjacent battery cells 20. At the same time, it can reduce the difficulty of processing and save costs.

[0282] In some embodiments, the range of the melting point p value for at least a portion of the casing 211 may be set to other values. For example, the melting point p value may be one of the following values: 1200°C, 1250°C, 1300°C, 1350°C, 1400°C, 1450°C, 1500°C, 1550°C, 1600°C, 1650°C, 1700°C, 1750°C, 1800°C, 1850°C, 1900°C, 1950°C, and 2000°C, or it may be between any two of these values.

[0283] In the embodiments of the present application, the positive electrode piece 223 includes a positive electrode active material, and for example, the positive electrode active material coated on the positive electrode piece 223 may be used to form a positive electrode active material layer 2231, which may be installed on at least one surface of the positive electrode current collector 2232. For example, a positive electrode active material layer 2241 may be installed on both sides of the positive electrode current collector 2232 perpendicular to its thickness direction, but the embodiments of the present application are not limited to these.

[0284] In some embodiments, the positive electrode current collector 2232 may be a metal foil or a composite current collector. As an example of a metal foil, aluminum foil may be used. The composite current collector may include a polymer material substrate and a metal material layer formed on at least one surface of the polymer material substrate. As an example, the metal material may include one or more of aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. As an example, the polymer material substrate may include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0285] As can be understood, the cathode active material according to the embodiment of the present invention can be flexibly configured according to the actual application. For example, the cathode active material may contain a nickel element-containing compound. As an example, the nickel element-containing compound contains a layered lithium-containing transition metal oxide, and the molar amount of nickel element in the layered lithium-containing transition metal oxide accounts for 50% or more of the total molar amount of transition metal elements in the layered lithium-containing transition metal oxide. By increasing the proportion of nickel element in the layered lithium-containing transition metal oxide to 50% or more, the energy density of the battery cell 20 can be effectively improved and the cycle life can be improved. However, it is not desirable to set this proportion to be excessively large, otherwise it will increase the difficulty of processing the electrode assembly 22 and further increase the processing cost of the battery cell 20.

[0286] Furthermore, the molar proportion of nickel in the layered lithium-containing transition metal oxide may be 70% or more, 80% or more, or 90%. In this way, if the energy density of the battery cell 20 can be effectively improved, the difficulty of processing the electrode assembly 22 can be controlled, thereby reducing the processing cost of the battery cell 20.

[0287] In some embodiments, the molar percentage of nickel in the layered lithium-containing transition metal oxide according to the embodiments of the present application may also be set to other values. For example, the molar percentage of nickel in the layered lithium-containing transition metal oxide may be any one of 50%, 53%, 55%, 58%, 60%, 63%, 65%, 68%, 70%, 73%, 75%, 78%, 80%, 83%, 85%, 88%, 90%, 92%, 94%, 96%, and 98%, or it may be between any two of these values.

[0288] As can be understood, the test methods for the molar amount of nickel and the total molar amount of transition metal elements in layered lithium-containing transition metal oxides according to the embodiments of this application can be selected according to the actual application and can be measured using instruments and methods known in the art. For example, a cathode active material can be laid and bonded to a conductive adhesive to prepare a sample for measurement with dimensions of 6 cm × 1.1 cm, and the particle morphology can be tested using a scanning electron microscope and energy-dispersive X-ray spectrometer (e.g., ZEISS Sigma 300). The test can be referred to in JY / T010-1996. To ensure the accuracy of the test results, 20 different regions are randomly selected from the sample awaiting measurement and scanned. The content of layered lithium-containing transition metal oxides in each region can be statistically calculated at a constant magnification (e.g., 1000x or more). For example, the average value of the test results from the 20 test regions can be taken as the number of layered lithium-containing transition metal oxides in the cathode active material, and the molar amount of layered lithium-containing transition metal oxides can be determined. Similarly, the molar amount of nickel element in the layered lithium-containing transition metal oxides can also be determined using this method.

[0289] In some embodiments, the layered lithium-containing transition metal oxide may contain one or more of lithium cobalt oxide and ternary materials. For example, the layered lithium-containing transition metal oxide may contain Li a Ni b Co c M d O e A f, where 0<a≦1.2, 0.5≦b<1, optionally 0.9≦b<1, 0<c<1, 0<d<1, 1≦e≦2, 0≦f≦1, M includes, but is not limited to, one or more of Mn, Al, Zr, Zn, Cu, Cr, Mg, Fe, V, Ti and B, and A includes, but is not limited to, one or more of N, F, S and Cl. Wherein, the molar ratio b of the nickel element in the layered lithium-containing transition metal oxide is set to 50% or more, that is, the ratio b satisfies 0.5≦b<1, and may further satisfy 0.8≦b<1, or 0.9≦b<1, which can further improve the energy density of the battery cell 20.

[0290] As an example, the layered lithium-containing transition metal oxide may be LiNi 0.5 Co 0.2 Mn 0.3 O2 (abbreviated as NCM523), LiNi 0.5 Co 0.25 Mn 0.25 O2 (abbreviated as NCM211), LiNi 0.6 Co 0.2 Mn 0.2 O2 (abbreviated as NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O2 (abbreviated as NCM811), LiNi 0.9 Co 0.06 Mn 0.04 O2, LiNi 0.96 Co 0.02 Mn 0.02 O2, LiNi 0.85 Co 0.15 Al 0.05 O2, but is not limited to one or more of the above.

[0291] In some embodiments, the positive electrode active material may further contain other materials. For example, the positive electrode active material may further contain a positive electrode conductive agent. The present application is not particularly limited to the type of positive electrode conductive agent. As an example, the positive electrode conductive agent may contain one or more of the following: superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0292] In some embodiments, the positive electrode active material may further include a positive electrode adhesive. The present application is not particularly limited to the type of positive electrode adhesive. For example, the positive electrode adhesive may include one or more of the following: polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylic resin.

[0293] In some embodiments, the positive electrode piece 223 can be manufactured by the following method: The positive electrode active material layer 2231 is usually formed by applying a positive electrode slurry to the positive electrode current collector 2232, drying, and cold pressing. The positive electrode slurry is usually formed by dispersing a positive electrode active material, a positive electrode adhesive, a positive electrode conductive agent, etc., in a solvent and stirring uniformly. The solvent may be N-methylpyrrolidone (NMP) or deionized water, but the embodiments of this application are not limited to these.

[0294] The following will be explained by comparing multiple comparative examples and multiple examples. Specifically, the battery cell 20 in each of the following examples and comparative examples is a rectangular parallelepiped type battery cell as shown in Figures 12 and 13, and among them, a hollow structure is adopted in which the casing 211 opens at one end.

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

[0296] 1. Manufacturing of positive electrode piece 223 Positive electrode active material LiNi 0.95 Co 0.04 Mn 0.01 O2, the conductive agent Super P, and the adhesive polyvinylidene fluoride (PVDF) were prepared as a positive electrode slurry in N-methylpyrrolidone (NMP), with a solid content of 50 wt% in the positive electrode slurry, and LiNi 0.7 Co 0.1 Mn 0.1 The mass ratio of O2, Super P, and PVDF was 8:1:1. The positive electrode slurry was applied to the upper and lower surfaces of the aluminum foil current collector, dried at 85°C, then cold-pressurized, edge-trimmed, cut, and slit, and finally dried under vacuum conditions at 85°C for 4 hours to produce the positive electrode piece 223.

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

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

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

[0301] In each of the following examples and comparative examples, the melting point of the casing 211 of the battery cell 20 is p, and different materials are selected correspondingly for the casing 211 to obtain different melting points. The capacity of the battery cell 20 is C, and the wall thickness of the maximum area of ​​the battery cell 20 is T. The specific parameter settings are shown in Table 3 below. In addition, the material of all areas of the casing 211 is the same in each of the examples and comparative examples below. Furthermore, the battery cell 20 in each of the following examples and comparative examples is the same in all other conditions except for the parameter settings shown in Table 3. For example, in each example, the positive electrode active material of the positive electrode piece 223 of the electrode assembly 22 of the battery cell 20 contains a nickel element compound, of which the nickel element compound contains a layered lithium-containing transition metal oxide, and the molar amount of nickel in the layered lithium-containing transition metal oxide accounts for 95% of the total molar amount of transition metal elements in the layered lithium-containing transition metal oxide.

[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 the casing 211 was observed, i.e., whether or not the casing 211 had melted.

[0303] [Table 3]

[0304] As can be seen by comparing the two comparative examples and the six examples in Table 3 above, when different materials are used for the casing 211, correspondingly different melting points p can be determined. When the melting point p satisfies 1200℃ ≤ p ≤ 2000℃, for example in Examples 1 to 6, the design needs of the battery cell 20 can be met without melting of the casing 211 of the battery cell 20. Furthermore, when other parameters of the battery cell 20 have different variations, such as different capacities C of the battery cell 20 or different wall thicknesses of the maximum area of ​​the casing 211, the design requirements of the battery cell 20 can be met without melting of any of the battery cells 20. However, when the melting point p does not satisfy 1200℃ ≤ p ≤ 2000℃, for example in Comparative Examples 1 to 2, if the casing 211 of the battery cell 20 melts, the design needs of the battery cell 20 will no longer be met.

[0305] In some embodiments, the electrode assembly 22 further comprises a positive electrode piece 223, the positive electrode piece 223 comprising a positive electrode active material capable of reversibly desorbing and inserting metal ions, the positive electrode active material comprising a nickel-containing compound, and the tensile strength of at least a portion of the casing 211 at a temperature of 500°C is Rn, where Rn satisfies 100 MPa ≤ Rn ≤ 1200 MPa.

[0306] The positive electrode active material, by containing a nickel-containing compound, can effectively increase the energy density of the battery cell 20 and improve its cycle life, but it also increases the amount of gas generated during the use of the battery cell 20. In particular, if thermal runaway occurs during the use of the battery cell 20, the internal temperature of the battery cell 20 rises rapidly and a large amount of gas is generated.

[0307] Therefore, by appropriately improving the tensile strength Rn of at least a portion of the casing 211 under high-temperature conditions of 500°C, the deformation capacity of that portion of the casing 211 when thermal runaway occurs in the battery cell 20 can be improved, further reducing the risk of thermal runaway occurring in adjacent battery cells 20 without the casing 211 easily and quickly breaking or exploding, thereby improving the reliability of the battery 10. However, it is also undesirable for at least a portion of the casing 211 to have a tensile strength Rn that is too high under high-temperature conditions, otherwise it will be more prone to scratching of grinding tools, shortening the service life of the grinding tools and increasing the difficulty of processing. Therefore, by appropriately reducing the tensile strength Rn, costs can be saved and processing can be made easier. For example, the tensile strength Rn may normally be set to satisfy 100 MPa ≤ Rn ≤ 1200 MPa.

[0308] As can be understood, the range of values ​​for the tensile strength Rn at high temperature conditions of 500°C in at least a portion of the casing 211 according to the embodiment of the present application can be adjusted according to the actual application. For example, the value of the tensile strength Rn at high temperature can satisfy 100MPa ≤ Rn ≤ 1200MPa. Alternatively, for example, the value of the tensile strength Rn at high temperature can satisfy 112MPa ≤ Rn ≤ 720MPa. On the one hand, by appropriately increasing the value of the tensile strength Rn, the deformation capacity of the casing 211 in that portion when thermal runaway occurs in the battery cell 20 can be improved, further reducing the risk of thermal runaway occurring in adjacent battery cells 20 without the casing 211 easily and quickly breaking or exploding, thereby improving the reliability of the battery 10. At the same time, in order to reduce the difficulty of processing, further save costs, and facilitate processing, the tensile strength Rn at high temperature conditions in at least a portion of the casing 211 is controlled so as not to be too high.

[0309] Furthermore, the casing may be installed such that the tensile strength Rn value at high temperatures satisfies 152 MPa ≤ Rn ≤ 480 MPa, improving the deformation capacity of the casing 211 in that portion when thermal runaway occurs in the battery cell 20, thereby improving the structural strength of the casing 211. This further reduces the risk of thermal runaway occurring in adjacent battery cells 20 without the casing 211 easily and quickly breaking or exploding, thereby improving the reliability of the battery 10. At the same time, it is possible to reduce the difficulty of processing and save costs.

[0310] In some embodiments, the value of the high-temperature tensile strength Rn in the embodiments of the present application may also be set to other values. For example, the values ​​of the high-temperature tensile strength Rn may be 100MPa, 112MPa, 130MPa, 150MPa, 152MPa, 168MPa, 180MPa, 200MPa, 228MPa, 250MPa, 280MPa, 300MPa, 320MPa, 350MPa, 380MPa, 400MPa, 430MPa, 450MPa, 480MPa, 500MPa, 530MPa, 550MPa, 580MPa, and 600MPa. The value may be any one of the following values: Pa, 630MPa, 650MPa, 680MPa, 700MPa, 720MPa, 750MPa, 780MPa, 800MPa, 830MPa, 850MPa, 880MPa, 900MPa, 930MPa, 950MPa, 980MPa, 1000MPa, 1050MPa, 1100MPa, 1150MPa, and 1200MPa, or it may be any one of the two values.

[0311] To be understood, the tensile strength in the embodiments of this application refers to the maximum stress value that the material experiences before fracture. The test method for the tensile strength Rn at a high temperature of 500°C in at least a portion of the casing 211 in the embodiments of this application can be selected according to the actual application. For example, the tensile strength Rn at a high temperature of 500°C can be measured by adopting the national standard GB / T 228.1-2010.

[0312] The following will be explained by comparing multiple comparative examples and multiple examples. Specifically, the battery cell 20 in each of the following examples and comparative examples is a rectangular parallelepiped type battery cell as shown in Figures 12 and 13, and among them, a hollow structure is adopted in which the casing 211 opens at one end.

[0313] In the following examples and comparative examples, the manufacturing methods for the positive electrode piece 223, negative electrode piece 224, electrolyte, and separator 225 of the battery cell 20 are as follows.

[0314] 1. Manufacturing of positive electrode piece 223 Positive electrode active material LiNi 0.95 Co0.04 Mn 0.01 O2, the conductive agent Super P, and the adhesive polyvinylidene fluoride (PVDF) were prepared as a positive electrode slurry in N-methylpyrrolidone (NMP), with a solid content of 50 wt% in the positive electrode slurry, and LiNi 0.7 Co 0.1 Mn 0.1 The mass ratio of O2, Super P, and PVDF was 8:1:1. The positive electrode slurry was applied to the upper and lower surfaces of the aluminum foil current collector, dried at 85°C, then cold-pressurized, edge-trimmed, cut, and slit, and finally dried under vacuum conditions at 85°C for 4 hours to produce the positive electrode piece 223.

[0315] 2. Manufacturing of the negative electrode piece 224 A negative electrode slurry was prepared by uniformly mixing a negative electrode active material, a conductive agent Super P, a thickener carboxymethylcellulose (CMC), and an adhesive styrene-butadiene rubber (SBR) in deionized water. The negative electrode active material contained graphite and a silicon-based material, and the silicon-based material was a silicon-oxygen compound. The solid content in the negative electrode slurry was 30 wt%, and the mass ratio of the negative electrode active material, silicon monoxide, Super P, CMC, and adhesive styrene-butadiene rubber (SBR) in the solid content was 88:7:3:2. The negative electrode slurry was applied to the upper and lower surfaces of a copper foil current collector and dried at 85°C. Then it was cold-pressed, edge-trimmed, cut, and slit, and then dried under vacuum conditions at 120°C for 12 hours to produce a negative electrode piece 224.

[0316] 3. Manufacturing of electrolyte In a glove box under an argon atmosphere (H2O < 0.1 ppm, O2 < 0.1 ppm), a thoroughly dried electrolyte salt, LiPF6, was dissolved in a mixed solvent (the mixed solvent contained ethylene carbonate (EC) and diethyl carbonate (DEC), and the ethylene carbonate (EC) and diethyl carbonate (DEC) were mixed in a 50:50 mass ratio). After homogeneous mixing, an electrolyte solution with a concentration of 1 mol / L was obtained.

[0317] 4. Manufacturing of separator 225 A 16 μm polyethylene film was used as separator 225.

[0318] 5. Manufacturing of lithium-ion battery cells 20 The positive electrode piece 223, separator 225, and negative electrode piece 224 are stacked in order, with the separator 225 positioned between the positive electrode piece 223 and the negative electrode piece 224 to isolate the positive and negative electrodes. The cells are then wound to obtain a bare cell, tabs are welded, the bare cell is placed in an outer casing made of a different material, the manufactured electrolyte is injected into the dried outer casing, and sealing, standing, chemical conversion, shaping, and capacity testing are performed to complete the manufacturing of the lithium-ion battery cell 20.

[0319] In each of the following examples and comparative examples, the tensile strength of the casing 211 of the battery cell 20 at a temperature of 500°C is Rn, and different materials are selected correspondingly for the casing 211 to obtain different tensile strengths Rn. The capacity of the battery cell 20 is C, and the wall thickness of the maximum area of ​​the battery cell 20 is T. The specific parameter settings are shown in Table 4 below. In each example and comparative example, the material of all areas of the casing 211 is the same, and the tensile strength Rn of the casing 211 at 500°C is measured using the method specified in GB / T 228.1-2010. Furthermore, in each of the following examples and comparative examples, the battery cell 20 is the same in all other conditions except for the parameter settings shown in Table 4. For example, in each embodiment, the positive electrode active material of the positive electrode piece 223 of the electrode assembly 22 of the battery cell 20 contains a nickel element compound, of which the nickel element compound contains a layered lithium-containing transition metal oxide, and the molar amount of nickel in the layered lithium-containing transition metal oxide accounts for 95% of the total molar amount of transition metal elements in the layered lithium-containing transition metal oxide.

[0320] For each of the comparative examples and examples below, the battery cell 20 was tested by referring to the short-circuit test method in Chapter 6.2.4 of "GBT31485-2015 Safety Requirements and Test Methods for Power Storage Batteries for Electric Vehicles," and after the test, the integrity of the casing 211 was observed, i.e., whether or not the casing 211 had ruptured.

[0321] [Table 4]

[0322] As can be seen by comparing the two comparative examples and the six examples in Table 4 above, when different materials are used for the casing 211, correspondingly different tensile strengths Rn can be determined. When the tensile strength Rn satisfies 100MPa ≤ Rn ≤ 1200MPa, for example in Examples 1 to 6, the design requirements of the battery cell 20 can be met without cracking of the casing 211 of the battery cell 20. Furthermore, when other parameters of the battery cell 20 have different variations, such as different capacities C of the battery cell 20 or different wall thicknesses of the maximum area of ​​the casing 211, the design needs of the battery cell 20 can be met without cracking of any of the battery cells 20. However, when the tensile strength Rn does not satisfy 100MPa ≤ Rn ≤ 1200MPa, for example in Comparative Examples 1 to 2, if the casing 211 of the battery cell 20 cracks, the design needs of the battery cell 20 will no longer be met.

[0323] To be understood, at least a portion of the casing 211 in the embodiments of the present application may include a local area of ​​the casing 211, or it may include all of the casing 211. In some embodiments, the casing 211 includes a welded seam 2113, and at least a portion of the casing 211 includes an area of ​​the casing 211 within a predetermined distance from the welded seam 2113, where the predetermined distance is L, and L = 10 mm. If the negative electrode active material of the negative electrode piece 224 in the electrode assembly 22 contains a silicon-based material, the silicon-based material can accommodate more metal ions, which increases the amount of deformation of the electrode assembly 22 during use in the battery cell 20, causing volume expansion of the electrode assembly 22. Furthermore, this increases the pressure of the electrode assembly 22 on the casing 211 of the battery cell 20. Under the same conditions, the structural strength of the region of the casing 211 adjacent to the welded seam 2113 is relatively low compared to the structural strength of other regions of the casing 211, making the region of the casing 211 adjacent to the welded seam 2113 more easily damaged during use in the battery cell 20. Therefore, by setting the region within a predetermined distance L from the welded seam 2113 to meet the requirements of tensile strength Rm or yield strength Re at room temperature, the deformation capacity of the region of the casing 211 adjacent to the welded seam 2113 can be improved, further improving the structural stability and service life of the battery cell 20 without that portion of the casing 211 being easily damaged.

[0324] If the positive electrode active material of the positive electrode piece 223 of the electrode assembly 22 contains a nickel-containing compound, when thermal runaway occurs in the battery cell 20, the temperature inside the battery cell 20 rises rapidly and a large amount of gas is generated. On the other hand, under the same conditions, the structural strength of the region of the casing 211 adjacent to the welded seam 2113 is relatively low compared to the structural strength of other regions of the casing 211. Therefore, the casing 211 is prone to rupture in the region adjacent to the welded seam 2113, and furthermore, thermal runaway, i.e., thermal diffusion, can occur in the connected battery cells 20. Accordingly, by setting the region within a predetermined distance L from the welded seam 2113 to meet the requirements of tensile strength Rn or melting point p under high-temperature conditions, the deformability of that region of the casing 211 can be improved. This reduces the risk of thermal diffusion or explosion between multiple battery cells 20 without that region easily and rapidly breaking or completely melting, thereby improving the reliability of the battery 10.

[0325] As can be understood, the welded seams 2113 included in the casing 211 according to the embodiment of the present application may include welded seams 2113 at any position on the casing 211. For example, the welded seams 2113 included in the casing 211 may include the welded seam between the casing 211 and the cover plate 212, i.e., the region surrounding the open end of the casing 211 is a welded seam. Furthermore, for example, the welded seams 2113 of the casing 211 may further include welded seams between different parts of the casing 211, for example, the casing 211 may include at least two parts, the at least two parts being joined by welding to form the casing 211, of which Figure 13 shows an example in which the casing 211 includes two parts along the height Z direction of the battery cell 20, with a welded seam 2113 between the upper half casing and the lower half casing, or, contrary to what is shown in Figure 13, the welded seams 2113 may be located on other parts of the casing 211, and the embodiments of the present application are not limited thereto.

[0326] In some embodiments, at least a portion of the casing 211 includes a surrounding region 2111 of the casing 211, the surrounding region 2111 encloses the electrode assembly 22, and the surrounding region 2111 is at least a portion of the side wall of the casing 211. In this way, if the negative electrode active material of the negative electrode piece 224 of the electrode assembly 22 includes a silicon-based material, the silicon-based material can accommodate more metal ions, thereby increasing the amount of deformation of the electrode assembly 22 during use in the battery cell 20, causing volume expansion of the electrode assembly 22, and further increasing the pressure of the electrode assembly 22 on the casing 211 of the battery cell 20. Therefore, by positioning the surrounding region 2111 to satisfy the requirements of tensile strength Rm or yield strength Re under room temperature conditions, the deformation capacity of the casing 211 can be improved, and by positioning the surrounding region 2111 to surround the electrode assembly 22, the radial pressing force of the internal electrode assembly 22 on the casing 211 can be limited, thereby further improving the structural stability and service life of the battery cell 20 without the casing 211 being easily damaged.

[0327] If the positive electrode active material of the positive electrode piece 223 of the electrode assembly 22 contains a nickel-containing compound, when thermal runaway occurs in the battery cell 20, the internal temperature of the battery cell 20 rises rapidly and a large amount of gas is generated. On the other hand, if the surrounding region 2111 meets the requirements of tensile strength Rn or melting point p under high-temperature conditions, the deformation capacity of the surrounding region 2111 of the casing 211 can be improved, thereby limiting excessive expansion of the electrode assembly 22 inside the casing 211 along its thickness direction without the surrounding region 2111 easily and rapidly breaking or completely melting, reducing the possibility of the battery cell 20 exploding, further reducing the risk of thermal runaway occurring in adjacent battery cells 20, and thereby improving the reliability of the battery 10.

[0328] As can be understood, the position and dimensions of the surrounding region 2111 in the embodiments of the present application can be flexibly set according to the actual application. For example, the height of the surrounding region 2111 along the height direction Z of the battery cell 20 may be less than or equal to the height of the casing 211. Specifically, if the height of the surrounding region 2111 along the height direction Z of the battery cell 20 is less than the height of the casing 211, the surrounding region 2111 may be located at any position in the casing 211 along the height direction Z of the battery cell 20. For example, in order to limit deformation of the central position corresponding to the electrode assembly 22, the surrounding region 2111 may be located in the center of the casing 211 along the height direction Z of the battery cell 20.

[0329] If the height of the surrounding region 2111 is equal to the height of the casing 211 along the height direction Z of the battery cell 20, the surrounding region 2111 may include all the side walls of the casing 211 and may also wrap around the sides of the electrode assembly 22, further improving the structural strength of the side walls of the casing 211, thereby suppressing the explosion and thermal diffusive reaction of the battery cell 20 after thermal runaway due to the failure of a localized weak area of ​​the side wall of the casing 211, and further improving the reliability of the battery 10.

[0330] In some embodiments, at least a portion of the casing 211 includes all of its walls, i.e., at least a portion of the casing 211 in the embodiments of this application may refer to all of the casing 211. In this way, if the negative electrode active material of the negative electrode piece 224 of the electrode assembly 22 includes a silicon-based material, the silicon-based material can accommodate more metal ions, thereby increasing the amount of deformation of the electrode assembly 22 during use within the battery cell 20, causing volume expansion of the electrode assembly 22, and further increasing the pressure of the electrode assembly 22 on the casing 211 of the battery cell 20. Therefore, by positioning all of the casing 211 so that each satisfies the requirements of tensile strength Rm or yield strength Re at room temperature, the overall deformation capacity of the casing 211 can be improved, the pressing force of the internal electrode assembly 22 on the casing 211 along each direction can be limited, the strength of each part of the casing 211 can be balanced, and the structural stability and service life of the battery cell 20 can be further improved without easy breakage in localized weak areas.

[0331] If the positive electrode active material of the positive electrode piece 223 of the electrode assembly 22 contains a nickel-containing compound, when thermal runaway occurs in the battery cell 20, the temperature inside the battery cell 20 rises rapidly and a large amount of gas is generated. On the other hand, if all areas of the casing 211 meet the requirements of tensile strength Rn or melting point p under high-temperature conditions, the deformation capacity of the entire casing 211 can be improved, thereby limiting the high-temperature, high-pressure gas inside the casing 211 without the casing 211 easily breaking or melting, reducing the impact on the connected cell 20, further reducing the risk of thermal runaway occurring in adjacent battery cells 20, and thereby improving the reliability of the battery 10.

[0332] Furthermore, the cover plate 212 according to the embodiment of the present application may employ the same material as at least a portion of the casing 211 according to the embodiment of the present application, so that the structural strength of the cover plate 212 similarly meets the design needs. For example, the cover plate 212 may also satisfy at least one of the requirements of tensile strength Rm and yield strength Re at room temperature, tensile strength Rn and melting point p at high temperature, in order to improve the structural strength of the cover plate 212 and further improve the structural stability of the battery cell 20, but the embodiment of the present application is not limited to these.

[0333] In the embodiment of the present application, the casing 211 includes at least a portion of a third casing wall 2112, the average thickness of the third casing wall 2112 being T, where T satisfies 0.05 mm ≤ T ≤ 0.5 mm and 60 mm MPa ≤ T × Rm ≤ 500 mm MPa.

[0334] To be understood, the third casing wall 2112 of the casing 211 in the embodiment of the present application may be any one wall of the casing 211. Specifically, the battery cell 20 may be any polyhedral structure, the casing 211 may be a hollow structure with an opening at at least one end, the casing 211 may include one or more walls, the third casing wall 2112 may be any one wall of the casing 211, and the casing 211 may include one or more third casing walls 2112. For example, if the casing 211 is a polygonal prism, the third casing wall 2112 may be any one wall of the polygonal prism, and the surface of the third casing wall 2112 may be any polygon. Furthermore, for example, as shown in Figures 12 and 13, if the casing 211 is a rectangular parallelepiped, the third casing wall 2112 may be any one of the walls of the casing 211, and the surface of the third casing wall 2112 is rectangular. Also, for example, if the casing 211 is a cylindrical body, the third casing wall 2112 may be the bottom surface of the cylinder or a side surface of the cylinder, but the embodiments of the present application are not limited thereto. Furthermore, if two adjacent walls of the casing 211 are connected by a fillet, and the third casing wall 2112 in the embodiments of the present application is any one of the walls of the casing 211, the third casing wall 2112 does not include the connection area of ​​the fillet between the wall and the connecting wall.

[0335] In the embodiments of the present application, if at least a portion of the casing 211 includes a third casing wall 2112, the tensile strength of the third casing wall 2112 at room temperature conditions of 25°C is Rm. By increasing the tensile strength Rm at room temperature conditions of 25°C in at least a portion of the casing 211, the deformation capacity of the casing 211 can be improved, and the casing 211 will not easily break during the use of the battery cell 20, further improving the structural stability and service life of the battery cell 20. However, in order to reduce the difficulty of selecting and processing the material for the casing 211, save costs, and facilitate processing, it is also undesirable for the tensile strength Rm at room temperature in at least a portion of the casing 211 to be too large.

[0336] On the other hand, if the average thickness T of the third casing wall 2112 of the casing 211 is relatively thin, the structural strength of the third casing wall 2112 can be increased by increasing the tensile strength Rm of the third casing wall 2112 of the casing 211 at room temperature of 25°C. In this way, not only can the energy density of the battery cell 20 be improved, but the structural strength and stability of the battery cell 20 can also be improved. Conversely, if the average thickness T of the third casing wall 2112 of the casing 211 is relatively thick, the structural strength of the casing 211 can be improved, and the requirement for the tensile strength Rm of the third casing wall 2112 of the casing 211 at room temperature can be appropriately reduced, thereby reducing the difficulty of selecting the material for the casing 211 and further reducing the difficulty and cost of processing the battery cell 20. Furthermore, T×Rm indicates the rigidity of the third casing wall, and by limiting the rigidity of the third casing wall so that it is neither too low nor too high, the third casing wall not only has relatively good deformation capability, but the difficulty of processing can also be reduced and costs can be lowered.

[0337] As can be understood, the range of the average thickness T of the third casing wall 2112 in the embodiment of the present application can also be flexibly set according to the actual application. For example, the average thickness T of the third casing wall 2112 satisfies 0.05 mm ≤ T ≤ 0.5 mm. Furthermore, the average thickness T of the third casing wall 2112 satisfies 0.1 mm ≤ T ≤ 0.4 mm. By appropriately reducing the average thickness T of the third casing wall 2112, the space occupied by the casing 211 inside the battery 10 can be reduced, further improving the energy density of the battery 10. To maintain the stability of the casing 211, the tensile strength Rm of the third casing wall 2112 at room temperature can be improved to meet the structural strength requirements of the casing 211. On the other hand, by appropriately increasing the average thickness T of the third casing wall 2112, the difficulty of processing the third casing wall 2112 can also be reduced.

[0338] Furthermore, the average thickness T of the third casing wall 2112 satisfies the condition 0.1 mm ≤ T ≤ 0.3 mm. By ensuring that the average thickness T of the third casing wall 2112 is neither too large nor too small, it is possible to improve the structural strength and structural stability of the casing 211, as well as reduce the space occupied by the casing 211 inside the battery 10, thereby further improving the energy density of the battery 10.

[0339] In some embodiments, the average thickness T of the third casing wall 2112 according to the embodiments of the present application may also be set to other values. For example, the average thickness T of the third casing wall 2112 may be any one of the following values: 0.05 mm, 0.075 mm, 0.1 mm, 0.125 mm, 0.15 mm, 0.175 mm, 0.2 mm, 0.225 mm, 0.25 mm, 0.275 mm, 0.3 mm, 0.325 mm, 0.35 mm, 0.375 mm, 0.4 mm, 0.425 mm, 0.45 mm, 0.475 mm, and 0.5 mm, or it may be between any two of these values.

[0340] In some embodiments, the range of the T×Rm value can be adjusted according to the actual application. For example, Rm and T satisfy 60 mm MPa ≤ T×Rm ≤ 500 mm MPa. Furthermore, Rm and T can also satisfy 100 mm MPa ≤ T×Rm ≤ 500 mm MPa. By selecting an appropriate material, the tensile strength Rm of the third casing wall 2112 at room temperature can be improved, and the average thickness T of the third casing wall 2112 can be reduced, thereby meeting the design requirements for the stiffness value of the third casing wall 2112. This not only improves the structural strength and structural stability of the third casing wall 2112 of the casing 211, but also improves the energy density of the battery cell 20 and the battery 10.

[0341] Furthermore, the range of the T×Rm value may also be set such that Rm and T satisfy 100 mm MPa ≤ T×Rm ≤ 300 mm MPa. By making the rigidity value of the third casing wall 2112 more appropriate, the third casing wall 2112 can have good deformation capability to improve the service life of the battery cell 20, as well as reduce the difficulty of material selection, and further reduce the difficulty and cost of processing.

[0342] In some embodiments, the T×Rm value in the embodiments of the present application may also be set to other values. For example, the T×Rm value may be any one of the following values: 60 mm MPa, 65 mm MPa, 70 mm MPa, 75 mm MPa, 80 mm MPa, 85 mm MPa, 90 mm MPa, 95 mm MPa, 100 mm MPa, 130 mm MPa, 150 mm MPa, 180 mm MPa, 200 mm MPa, 230 mm MPa, 250 mm MPa, 280 mm MPa, 300 mm MPa, 330 mm MPa, 350 mm MPa, 380 mm MPa, 400 mm MPa, 430 mm MPa, 450 mm MPa, 480 mm MPa, and 500 mm MPa, or it may be between any two of these values.

[0343] In the embodiments of the present application, the value of the mass proportion g of the silicon-based material may mutually restrict with the value of the average thickness T of the third casing wall 2112, and may also mutually restrict with the value of the tensile strength Rm of at least a partial region of the casing 211 under the condition of 25°C, so as to balance the relationship between the energy density and the structural strength of the battery cell 20. For example, in the negative electrode active material, the mass proportion of the silicon-based material is g, and g and T satisfy 2%<g<20% and 0.15mm≦T≦0.4mm. When the mass proportion g of the silicon-based material is relatively small, by appropriately reducing the average thickness T of the third casing wall 2112, the space utilization rate of the casing 211 can be improved, the energy density of the battery cell 20 can be increased, and the structural strength of the casing 211 can also be balanced.

[0344] In some embodiments, the mass proportion of the silicon-based material in the negative electrode active material is g, and g, T and Rm satisfy 15%<g<40%, 0.2mm≦T≦0.4mm, and 100mm MPa≦T×Rm≦500mm MPa. By increasing the mass proportion g of the silicon-based material, the energy density of the battery cell 20 can be effectively increased, and at the same time, by improving the thickness and rigidity T×Rm of the third casing wall 2112, the structural strength and stability of the battery cell 20 can be enhanced.

[0345] As can be understood, the average thickness T of the third casing wall 2112 according to the embodiments of the present application may refer to the average thickness of at least a partial region of the third casing wall 2112. For example, the average thickness T of the third casing wall 2112 may refer to the average thickness T of all regions of the third casing wall 2112, especially when the third casing wall 2112 is relatively flat, that is, when the thickness of most regions of the third casing wall 2112 is basically equal or the difference is relatively small, or when the thickness of all regions of the third casing wall 2112 is basically equal or the difference is relatively small, the average thickness of all regions of the third casing wall 2112 can be determined as T.

[0346] For example, the average thickness T of the third casing wall 2112 may also refer to the average thickness T of a local region of the third casing wall 2112, that is, the average thickness T of the remaining region after excluding a portion of the third casing wall 2112. For example, if a specific region exists in the third casing wall 2112, and the thickness of that specific region differs relatively significantly from that of other regions, for example, if a protruding structure or recessed region exists in that specific region, making the thickness of that specific region greater or smaller than that of other regions, then the average thickness T of the remaining region of the third casing wall 2112 can be calculated by excluding that specific region.

[0347] In some embodiments, the third casing wall 2112 includes a functional region, and the average thickness T of the third casing wall 2112 is the average thickness of the region of the third casing wall 2112 other than the functional region, the functional region including at least one of a pressure release region, a region where electrode terminals 214 are located, a fluid injection region, and a welding region. The difference between the thickness of the functional region and the thickness of the other regions of the third casing wall 2112 is usually relatively large, and therefore, if the average thickness T of the third casing wall 2112 is calculated so as not to include the functional region, the design of the third casing wall 2112 can better meet the strength needs, thereby improving the structural strength and stability of the battery cell 20.

[0348] Specifically, the functional region according to the embodiment of the present application may include a region having a specific structure or purpose installed on the third casing wall 2112. For example, the functional region may include a pressure relief region for installing a pressure relief mechanism used for an element or component that operates to release internal pressure or temperature when the internal pressure or temperature of the battery cell 20 reaches a predetermined threshold. The predetermined threshold may be adjusted according to design needs. For example, the predetermined threshold may depend on one or more materials among the positive electrode piece, negative electrode piece, electrolyte, and separator film in the battery cell 20.

[0349] As used in this application, "operation" refers to the release of pressure and temperature inside the battery cell 20 due to the pressure release mechanism acting or being activated to a certain state. The operation caused by the pressure release mechanism includes, but is not limited to, the rupture, shattering, tearing, or opening of at least a part of the pressure release mechanism. When the pressure release mechanism is operated, high-temperature, high-pressure material inside the battery cell 20 is discharged as waste from the point of operation to the outside. In this way, the pressure and temperature release of the battery cell 20 is made possible at a controllable pressure or temperature, thereby avoiding the occurrence of potentially more serious accidents.

[0350] The waste products from the battery cell 20 relating to this application include, but are not limited to, electrolyte, dissolved or fragmented positive and negative electrode pieces, fragments of separator film, high-temperature and high-pressure gases from the reaction, and flames.

[0351] The pressure relief mechanism according to the embodiment of the present application may be installed on any one wall of the battery cell 20. For example, the pressure relief mechanism may be installed in the pressure relief region of the third casing wall 2112 of the battery cell 20. The pressure relief mechanism may be part of the third casing wall 2112, or it may be a separate structure and fixed to the third casing wall 2112, for example, by welding. For example, if the pressure relief mechanism is part of the third casing wall 2112, the pressure relief mechanism may be formed by installing a notch in the third casing wall 2112, i.e., the third casing wall 2112 has a notch installed in the pressure relief region, and the thickness of the notched area is clearly smaller than the thickness of other areas of the third casing wall 2112. Therefore, the average thickness T of the third casing wall 2112 does not need to be calculated based on the thickness of the notched area. The notched area is the most vulnerable location of the pressure relief mechanism. When the internal pressure of the battery cell 20 rises to a threshold due to excessive gas generation, or when the internal temperature of the battery cell 20 rises to a threshold due to heat generated by the internal reaction of the battery cell 20, the pressure release mechanism ruptures at the notch, creating communication between the inside and outside of the battery elevator 20. The gas pressure and temperature are released to the outside by the rupture of the pressure release mechanism, further preventing the explosion of the battery cell 20.

[0352] For example, the pressure relief mechanism may also be a separate structure from the third casing wall 2112, and the pressure relief mechanism may take the form of an explosion-proof valve, a gas valve, a pressure relief valve, or a safety valve, and more specifically, it may take the form of a pressure-sensitive element or pressure-sensitive structure or a temperature-sensing element or temperature-sensing structure. For example, the third casing wall 2112 may have a communication hole in the pressure relief region, and the pressure relief mechanism may be attached and fixed to the third casing wall 2112 through the communication hole, and after attachment, the pressure relief mechanism may protrude or recess relative to other areas of the third casing wall 2112, and therefore the calculation of the average thickness T of the third casing wall 2112 may not include the pressure relief region in which the pressure relief mechanism is located. When the internal pressure or temperature of the battery cell 20 reaches a predetermined threshold, the pressure relief mechanism is activated, or a vulnerable structure provided within the pressure relief mechanism is destroyed, thereby forming an opening or passage for releasing the internal pressure or temperature.

[0353] In some embodiments, the functional region may further include the region in which the electrode terminals 214 are located. Specifically, the electrode terminals 214 in the embodiments of the present application are used to be electrically connected to an electrode assembly 22 inside the battery cell 20 so as to output electrical energy from the battery cell 20. Furthermore, the battery cell 20 may include at least two electrode terminals 214, each including at least one first electrode terminal 214a and at least one second electrode terminal 214b, wherein the polarity of the first electrode terminal 214a and the second electrode terminal 214b are opposite. For example, if the first electrode terminal 214a is a positive electrode terminal, the second electrode terminal 214b may be a negative electrode terminal, or if the first electrode terminal 214a is a negative electrode terminal, the second electrode terminal 214b may be a positive electrode terminal. Of these, the positive electrode terminal is used to be electrically connected to the positive electrode tab 222a of the electrode assembly 22, and the negative electrode terminal is used to be connected to the negative electrode tab 222b of the electrode assembly 22. The positive electrode terminal and the positive electrode tab 222a may be directly connected or indirectly connected, and the negative electrode terminal and the negative electrode tab 222b may be directly connected or indirectly connected. Exemplaryly, the positive electrode terminal may be electrically connected to the positive electrode tab 222a via one connecting component 23, and the negative electrode terminal may be electrically connected to the negative electrode tab 222b via one connecting component 23.

[0354] As can be understood, each electrode terminal 214 in the embodiments of the present application may be installed on any one wall, and multiple electrode terminals 214 may be installed on the same wall or different walls of the battery cell 20. For example, taking as shown in Figures 12 and 13, if each battery cell 20 includes two electrode terminals 214 located on the same wall, then, for example, both electrode terminals 214 may be located on the cover plate 212.

[0355] For example, if each battery cell 20 includes two electrode terminals 214 located on the same wall, then, unlike what is shown in Figures 12 and 13, the two electrode terminals 214 may also be located on the casing 211, for example, both electrode terminals 214 may be located on a third casing wall 2112 of the casing 211. If the electrode terminals 214 are located on the third casing wall 2112, they usually protrude into other areas of the third casing wall 2112, i.e., the thickness of the area where the electrode terminals 214 are located is much greater than the thickness of other areas of the third casing wall 2112. Therefore, the calculation of the average thickness T of the third casing wall 2112 does not need to include the area where the electrode terminals 214 are located.

[0356] In some embodiments, the functional region may further include an electrolyte injection region. For example, an electrolyte injection hole may be provided in the electrolyte injection region of the third casing wall 2112, and the electrolyte is injected into the interior of the casing 211 through the electrolyte injection hole. After the electrolyte injection is complete, the electrolyte injection hole may be sealed with a sealing member. Considering that the thickness of the electrolyte injection region where the sealing member is located is usually much greater than the thickness of other regions of the third casing wall 2112, the calculation of the average thickness T of the third casing wall 2112 does not need to include the electrolyte injection region.

[0357] In some embodiments, the functional area may further include a welded area. For example, the third casing wall 2112 may be fixed to another wall by welding, or if the third casing wall 2112 itself needs to be fabricated by welding, the third casing wall 2112 may include a welded area. For example, as shown in Figure 13, the casing 211 may be welded by splicing, and the casing 211 may have a welded seam 2113. Specifically, the casing 211 may include at least two parts, which are joined by welding to form the casing 211, and taking Figure 13 as an example, the casing 211 includes two parts along the height direction Z of the battery cell 20, with a welded seam 2113 between the upper half casing and the lower half casing, or, contrary to what is shown in Figure 13, the welded seam 2113 may be located in other parts of the casing 211, and the embodiments of the present application are not limited to these. The welded area of ​​the functional region according to the embodiments of the present application may further include the welded seam 2113. Due to the manufacturing process, the thickness of the welded area is usually greater than the thickness of other areas of the third casing wall 2112, and therefore the calculation of the average thickness T of the third casing wall 2112 does not need to include the welded area.

[0358] In the embodiment of the present invention, the third casing wall 2112 of the casing 211 may be any one of the walls of the casing 211. For example, the third casing wall 2112 is the wall with the minimum thickness in the casing 211. That is, by limiting the thickness T of the wall with the minimum thickness in the casing 211, the thickness of the other walls of the casing 211 is limited, thereby ensuring that each wall of the casing 211 meets the structural strength requirements, further improving the structural strength and stability of the battery cell 20.

[0359] In some embodiments, the third casing wall 2112 is the wall with the largest surface area of ​​the casing 211. When multiple battery cells 20 are arranged within the battery 10, the multiple battery cells 20 are usually in contact with each other by the wall with the largest surface area of ​​the casing 211, and therefore, this wall with the largest surface area is usually subjected to the greatest pressing force from the electrode assembly 22. By limiting the average thickness T and tensile strength Rm at room temperature of the third casing wall 2112, the deformation capacity of the casing 211 can be effectively improved, further enhancing the structural strength and stability of the battery cells 20.

[0360] As can be understood, the location of the wall with the largest area of ​​the casing 211 in the embodiments of the present application can be set according to the actual application. For example, the battery 10 may include a plurality of battery cells 20, and the arrangement direction of the plurality of battery cells 20 may be perpendicular or parallel to the wall with the largest area of ​​the casing 211, and the embodiments of the present application are not limited to these.

[0361] In some embodiments, the casing 211 includes intersecting bottom and side walls, the bottom wall of which is used to support the electrode assembly housed within the casing 211. Specifically, the casing 211 may be a hollow structure with at least one end open, and the bottom and side walls of the casing 211 do not necessarily refer to walls opposite or adjacent to the opening, respectively. The electrode assembly 22 is housed inside the casing 211, and in actual applications, considering different application scenarios, the orientation of the electrode assembly 22 may differ, and the casing 211 may include walls to support the electrode assembly 22. Therefore, the bottom wall of the casing 211 in the embodiments of the present application is a wall for supporting the electrode assembly 22, that is, the bottom wall of the casing 211 is used to withstand the gravitational force of the electrode assembly 22, while the wall of the casing 211 that directly intersects the bottom wall is a side wall of the casing 211.

[0362] In some embodiments, the third casing wall 2112 is a side wall of the casing 211. Considering the different uses of the bottom wall and side walls of the casing 211, the design needs for the bottom wall and side walls may also differ. For example, the side walls of the casing 211 typically have higher requirements for deformation capacity, and if the third casing wall 2112 is a side wall of the casing 211, the deformation capacity of the side wall of the casing 211 can be effectively improved by limiting the tensile strength Rm of the side wall of the casing 211 at room temperature and the average thickness T of the side wall, thereby further improving the structural stability of the battery cell 20.

[0363] In some embodiments, the casing 211 includes a plurality of side walls of equal thickness to facilitate processing.

[0364] In some embodiments, in order to facilitate processing and optimize the space occupied by the casing 211, the thickness of the bottom wall of the casing 211 is equal to the thickness of the side walls of the casing 211.

[0365] In some embodiments, the third casing wall 2112 is perpendicular to the stacking direction of the electrode pieces of the electrode assembly 22. The stacking direction of the electrode pieces of the electrode assembly 22 is usually the thickness direction of the electrode assembly 22, and considering that the electrode assembly 22 easily expands in the thickness direction during the charge-discharge cycle of the battery cell 20, the deformation requirements of the corresponding casing wall 211 are relatively high. Therefore, by installing the third casing wall 2112 as a wall perpendicular to the stacking direction of the electrode pieces of the electrode assembly 22, or by aligning the third casing wall 2112 and the electrode assembly 22 along the stacking direction of the electrode pieces of the electrode assembly 22, and limiting the tensile strength Rm and average thickness T of the third casing wall 2112 at room temperature, it is possible not only to improve the energy density of the battery cell 20 but also to effectively improve the deformation capacity of the third casing wall 2112 and further improve the structural stability of the battery cell 20.

[0366] As can be understood, the cover plate 212 according to the embodiment of the present application may employ the same or a different design as the third casing wall 2112. For example, the cover plate 212 may employ the same design as the third casing wall 2112, that is, the average thickness of the cover plate 212 may be T, the tensile strength of the cover plate 212 at room temperature may be b, and the design requirements of b and T are met, thereby improving the deformation capacity of the cover plate 212 and further improving the structural strength and stability of the battery cell 20.

[0367] In some embodiments, the ratio of the internal volume of the casing 211 to the external volume of the casing 211 is 93% or more. That is, by making the thickness of the casing 211 relatively thin in order to relatively reduce the space occupied by the casing 211 itself, the space utilization rate and energy density of the battery 10 are further improved.

[0368] To ensure understanding, the specific calculation methods for the internal volume of the casing 211 and the external volume of the casing 211 according to the embodiment of the present application are related to the shape of the casing 211. For example, let's take the case where the casing 211 is a rectangular parallelepiped. Figure 17 shows a schematic side view of the casing 211 according to the embodiment of the present application, and Figure 18 shows a schematic top view of the casing 211 according to the embodiment of the present application. For example, the casing 211 shown in Figures 17 and 18 may be the casing 211 of the battery cell 20 shown in Figures 12 and 13.

[0369] As shown in Figures 17 and 18, taking a rectangular casing 211 as an example, the casing 211 is a hollow rectangular casing with an opening at one end. When calculating the internal volume of the casing 211 and the external volume of the casing 211, fillet connections between adjacent walls of the casing 211 can be ignored. As shown in Figures 17 and 18, each wall of the casing 211 has a constant thickness, so in the length direction Y, the internal length of the casing 211 is Y1 and the external length is Y2, where Y2 is greater than Y1. Similarly, in the width direction X, the internal width of the casing 211 is X1 and the external width is X2, where X2 is greater than X1. In the height direction Z, the internal height of the casing 211 is Z1 and the external height is Z2, where Z2 is greater than Z1. Therefore, the volume of the internal space of the casing 211 is V1 = X1 × Y1 × Z1, the volume of the external space of the casing 211 is V2 = X2 × Y2 × Z2, and V1 / V2 is 93% or more, thereby reducing the space occupied by the casing 211 itself and further improving the space utilization rate and energy density of the battery 10.

[0370] The following will be explained by comparing multiple comparative examples and multiple examples. Specifically, the battery cell 20 in each of the following examples and comparative examples is a rectangular parallelepiped type battery cell as shown in Figures 12 and 13, and among them, a hollow structure is adopted in which the casing 211 opens at one end.

[0371] In the following examples and comparative examples, the manufacturing methods for the positive electrode piece 223, negative electrode piece 224, electrolyte, and separator 225 of the battery cell 20 are as follows.

[0372] 1. Manufacturing of positive electrode piece 223 Positive electrode active material LiNi 0.95 Co 0.04 Mn 0.01 O2, the conductive agent Super P, and the adhesive polyvinylidene fluoride (PVDF) were prepared as a positive electrode slurry in N-methylpyrrolidone (NMP), with a solid content of 50 wt% in the positive electrode slurry, and LiNi 0.7 Co0.1 Mn 0.1 The mass ratio of O2, Super P, and PVDF was 8:1:1. The positive electrode slurry was applied to the upper and lower surfaces of the aluminum foil current collector, dried at 85°C, then cold-pressurized, edge-trimmed, cut, and slit, and finally dried under vacuum conditions at 85°C for 4 hours to produce the positive electrode piece 223.

[0373] 2. Manufacturing of the negative electrode piece 224 A negative electrode slurry was prepared by uniformly mixing a negative electrode active material, a conductive agent Super P, a thickener carboxymethylcellulose (CMC), and an adhesive styrene-butadiene rubber (SBR) in deionized water. The negative electrode active material contained graphite and a silicon-based material, and the silicon-based material was a silicon-oxygen compound. The solid content in the negative electrode slurry was 30 wt%, and the mass ratio of the negative electrode active material, silicon monoxide, Super P, CMC, and adhesive styrene-butadiene rubber (SBR) in the solid content was 88:7:3:2. The negative electrode slurry was applied to the upper and lower surfaces of a copper foil current collector and dried at 85°C. Then it was cold-pressed, edge-trimmed, cut, and slit, and then dried under vacuum conditions at 120°C for 12 hours to produce a negative electrode piece 224.

[0374] 3. Manufacturing of electrolyte In a glove box under an argon atmosphere (H2O < 0.1 ppm, O2 < 0.1 ppm), a thoroughly dried electrolyte salt, LiPF6, was dissolved in a mixed solvent (the mixed solvent contained ethylene carbonate (EC) and diethyl carbonate (DEC), and the ethylene carbonate (EC) and diethyl carbonate (DEC) were mixed in a 50:50 mass ratio). After homogeneous mixing, an electrolyte solution with a concentration of 1 mol / L was obtained.

[0375] 4. Manufacturing of separator 225 A 16 μm polyethylene film was used as separator 225.

[0376] 5. Manufacturing of lithium-ion battery cells 20 The positive electrode piece 223, separator 225, and negative electrode piece 224 are stacked in order, with the separator 225 positioned between the positive electrode piece 223 and the negative electrode piece 224 to isolate the positive and negative electrodes. The cells are then wound to obtain a bare cell, tabs are welded, the bare cell is placed in an outer casing made of a different material, the manufactured electrolyte is injected into the dried outer casing, and sealing, standing, chemical conversion, shaping, and capacity testing are performed to complete the manufacturing of the lithium-ion battery cell 20.

[0377] In each of the following examples and comparative examples, the tensile strength of the casing 211 of the battery cell 20 at a temperature of 25°C is Rm, and different materials are selected correspondingly for the casing 211 to obtain different tensile strengths Rm, the average thickness of the third casing wall 2112 of the casing 211 is T, and the specific parameter settings are shown in Table 5 below. In addition, in each example and comparative example, the material is the same for all areas of the casing 211, and the tensile strength Rm of the casing 211 at 25°C was measured using the method specified in GB / T 228.1-2010. Furthermore, in each of the following examples and comparative examples, the battery cell 20 is the same in all other installation conditions except for the differences in the parameter settings shown in Table 5. For example, the capacity of the battery cell 20 in each example is 350Ah.

[0378] A cycle charge fatigue test was performed on the battery cells 20 in each of the following examples and comparative examples. Specifically, the test can be performed using the cycle charge fatigue test clamp 700 shown in Figure 16.

[0379] Specifically, the battery cell 20 is clamped and fixed within a dedicated clamp 700, ensuring that the two opposing walls of the maximum surface area of ​​the battery cell 20 are firmly held in place, and the initial pressure is set to 2000N. The electrode terminals 214 of the battery cell 20 are then connected to a dedicated battery charging and discharging device.

[0380] The clamp 700, which held the battery cell 20, was placed in a constant temperature environment of 25±2℃, and the test was started after the battery cell 20 reached temperature equilibrium.

[0381] The specific test steps were carried out by referring to Chapter 6.4, "Standard Cycle Life," of "GBT31484-2015 Cycle Life Requirements and Test Methods for Power Storage Batteries for Electric Vehicles," and the test cycle cutoff condition was changed to "Stop the test until the welded seam 2113 of the battery cell 20 is damaged."

[0382] For example, the test can be performed according to the following steps: step a, discharge at 1I(A) until the discharge stop condition specified by the company; step b, leave for 30 minutes or longer or until the leave condition specified by the company; step c, charge according to the method in 6.1.1.3; step d, leave for 30 minutes or longer or until the leave condition specified by the company; step e, discharge at 1I1(A) until the discharge stop condition specified by the company; and step f, cycle through steps b to e until the weld joint 2113 is damaged and the test is stopped.

[0383] During the above test process, the welded seam 2113 of the battery cell 20 was continuously observed and the number of cycles recorded until leakage occurred at the welded seam 2113, thereby obtaining the state of the casing 211 after 1000 cycles, as shown in Table 5 below. In each of the following examples and comparative examples, the welded seam 2113 refers to the welded seam between the casing 211 and the cover plate 212, that is, the welded seam 2113 surrounds the open end of the casing 211, while the casing 211 employs an integrally molded structure.

[0384] [Table 5]

[0385] As can be understood, in Table 5 above, the material of the casing 211 may be Q195 carbon steel, but the tensile strength Rm of Q195 carbon steel at room temperature of 25°C is typically at least 315 MPa to 430 MPa, and in the above example only 328 MPa is taken as an example, but it is not limited to this. Similarly, the material of the casing 211 may be SPCC carbon steel, but the tensile strength Rm of SPCC carbon steel at room temperature of 25°C is typically at least 380 MPa to 430 MPa, and in the above example only 396 MPa is taken as an example. The material of the casing 211 may also be SUS430 stainless steel, but 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 taken as an example. The material of the casing 211 may be SUS304 stainless steel, but the tensile strength Rm of SUS304 stainless steel at room temperature of 25°C is typically at least 520 MPa, and in the above examples only 533 MPa, 625 MPa, and 763 MPa are given as examples.

[0386] As can be seen from Table 5 above, in Examples 1 to 12 above, the Rm and T of the third casing wall 2112 of the casing 211 satisfy 250MPa≦Rm≦2000MPa, 0.05mm≦T≦0.5mm, and 60mm MPa≦T×Rm≦500mm MPa, and in order to meet the design needs of the battery cell 20, the number of failure fatigue cycles of the battery cell 20 can reach more than 1,000. Furthermore, even if the average thickness T of the third casing wall 2112 is set to be relatively small, the number of failure fatigue cycles of the battery cell 20 can reach more than 1,000, and by setting the average thickness T of the third casing wall 2112 to be relatively small, the energy density of the battery 10 can also be increased. However, in the two comparative examples, the structural strength of the third casing wall 2112 was insufficient, and neither Rm nor T×Rm met the above values. Even with a relatively large average thickness T of the third casing wall 2112, the number of failure fatigue cycles of the battery cell 20 could not reach 1,000, thus failing to meet the design needs of the battery cell 20.

[0387] In some embodiments, the capacity of the battery cell is C, where C satisfies 25Ah ≤ C ≤ 550Ah. On the one hand, increasing the capacity C of a battery cell 20 can improve the capacity density of a battery 10 containing multiple such battery cells 20. Alternatively, if the total capacity of the battery 10 does not change, increasing the capacity C of a single battery cell 20 can reduce the number of battery cells 20 installed, correspondingly reducing the number of electrical connections between multiple battery cells 20 and lowering the probability of electrical connection failures, thereby improving the reliability of the battery. Furthermore, when the capacity C of a battery cell 20 is relatively large, increasing the tensile strength Rm of at least a portion of the casing 211 under normal temperature conditions of 25°C can satisfy the structural strength requirements of the casing 211 for high-capacity battery cells 20, further improving the reliability and service life of the battery cell 20. On the other hand, when a battery cell 20 has a relatively large capacity, the internal reaction becomes more vigorous, further increasing the structural strength requirements of the casing 211. Therefore, in order to limit the design requirements for the structural strength of the casing 211, it is undesirable for the capacity C of the battery cell 20 to be too large, thereby reducing the difficulty of selecting and processing the battery cell 20, reducing costs, and improving processing efficiency.

[0388] As can be understood, the range of the capacity C value of the battery cell 20 in the embodiments of the present application can be adjusted according to the actual application. For example, the capacity C of the battery cell 20 can be reasonably selected according to the actual needs of the battery 10. In some embodiments, the capacity C of the battery cell 20 may be set to further satisfy 100Ah ≤ C ≤ 300Ah. By appropriately increasing the capacity C of the battery cell 20, the energy density of the battery 10 can be improved. At the same time, it is undesirable for the capacity C of the battery cell 20 to be too large in order to balance the relationship between the capacity C of the battery cell 20 and the structural strength of the casing 211 and to improve the reliability and service life of the battery cell 20.

[0389] Furthermore, the capacity C of the battery cell 20 can further satisfy the condition 150Ah ≤ C ≤ 250Ah. By further limiting the capacity C of the battery cell 20, not only can the energy density of the battery 10 be improved, but the structural strength of the casing 211 can also be improved, further enhancing the reliability and service life of the battery cell 20 and the battery 10.

[0390] In some embodiments, the value of the capacity C of the battery cell 20 according to the embodiment of the present application may also be set to other values. For example, the capacity C of the battery cell 20 may be any one of the following values: 25Ah, 30Ah, 35Ah, 40Ah, 45Ah, 50Ah, 55Ah, 60Ah, 65Ah, 70Ah, 75Ah, 80Ah, 85Ah, 90Ah, 95Ah, 100Ah, 130Ah, 150Ah, 180Ah, 200Ah, 230Ah, 250Ah, 280Ah, 300Ah, 330Ah, 350Ah, 380Ah, 400Ah, 430Ah, 450Ah, 480Ah, 500Ah, 530Ah, and 550Ah, or it may be between any two of these values.

[0391] To ensure understanding, the capacity C of the battery cell 20 in the embodiment of the present application represents the amount of electricity output when the battery cell 20 is fully charged and discharged to the cutoff voltage under predetermined discharge conditions. The test method for the capacity C of the battery cell 20 can be selected according to the actual application. For example, the capacity C of the battery cell 20 may be determined by performing a discharge test using GB / T 31467.1, but the embodiments of the present application are not limited to these.

[0392] The following will be explained by comparing multiple comparative examples and multiple examples. Specifically, the battery cell 20 in each of the following examples and comparative examples is a rectangular parallelepiped type battery cell as shown in Figures 12 and 13, and among them, a hollow structure is adopted in which the casing 211 opens at one end.

[0393] In the following examples and comparative examples, the manufacturing methods for the positive electrode piece 223, negative electrode piece 224, electrolyte, and separator 225 of the battery cell 20 are as follows.

[0394] 1. Manufacturing of positive electrode piece 223 Positive electrode active material LiNi 0.95 Co 0.04 Mn 0.01 O2, the conductive agent Super P, and the adhesive polyvinylidene fluoride (PVDF) were prepared as a positive electrode slurry in N-methylpyrrolidone (NMP), with a solid content of 50 wt% in the positive electrode slurry, and LiNi 0.7 Co 0.1 Mn 0.1 The mass ratio of O2, Super P, and PVDF was 8:1:1. The positive electrode slurry was applied to the upper and lower surfaces of the aluminum foil current collector, dried at 85°C, then cold-pressurized, edge-trimmed, cut, and slit, and finally dried under vacuum conditions at 85°C for 4 hours to produce the positive electrode piece 223.

[0395] 2. Manufacturing of the negative electrode piece 224 A negative electrode slurry was prepared by uniformly mixing a negative electrode active material, a conductive agent Super P, a thickener carboxymethylcellulose (CMC), and an adhesive styrene-butadiene rubber (SBR) in deionized water. The negative electrode active material contained graphite and a silicon-based material, and the silicon-based material was a silicon-oxygen compound. The solid content in the negative electrode slurry was 30 wt%, and the mass ratio of the negative electrode active material, silicon monoxide, Super P, CMC, and adhesive styrene-butadiene rubber (SBR) in the solid content was 88:7:3:2. The negative electrode slurry was applied to the upper and lower surfaces of a copper foil current collector and dried at 85°C. Then it was cold-pressed, edge-trimmed, cut, and slit, and then dried under vacuum conditions at 120°C for 12 hours to produce a negative electrode piece 224.

[0396] 3. Manufacturing of electrolyte In a glove box under an argon atmosphere (H2O < 0.1 ppm, O2 < 0.1 ppm), a thoroughly dried electrolyte salt, LiPF6, was dissolved in a mixed solvent (the mixed solvent contained ethylene carbonate (EC) and diethyl carbonate (DEC), and the ethylene carbonate (EC) and diethyl carbonate (DEC) were mixed in a 50:50 mass ratio). After homogeneous mixing, an electrolyte solution with a concentration of 1 mol / L was obtained.

[0397] 4. Manufacturing of separator 225 A 16 μm polyethylene film was used as separator 225.

[0398] 5. Manufacturing of lithium-ion battery cells 20 The positive electrode piece 223, separator 225, and negative electrode piece 224 are stacked in order, with the separator 225 positioned between the positive electrode piece 223 and the negative electrode piece 224 to isolate the positive and negative electrodes. The cells are then wound to obtain a bare cell, tabs are welded, the bare cell is placed in an outer casing made of a different material, the manufactured electrolyte is injected into the dried outer casing, and sealing, standing, chemical conversion, shaping, and capacity testing are performed to complete the manufacturing of the lithium-ion battery cell 20.

[0399] In each of the following examples and comparative examples, the tensile strength of the casing 211 of the battery cell 20 at a temperature of 25°C is Rm, and different materials are selected correspondingly for the casing 211 to obtain different tensile strengths Rm, the capacity of the battery cell 20 is C, and the specific parameter settings are shown in Table 6 below. In addition, in each example and comparative example, the material of all areas of the casing 211 is the same, and the tensile strength Rm of the casing 211 at 25°C was measured using the method specified in GB / T 228.1-2010. Furthermore, in each of the following examples and comparative examples, the battery cell 20 is the same in all other installation conditions except for the parameter settings shown in Table 6. For example, the wall thickness of the maximum area of ​​the battery cell 20 in each example is 0.15 mm, and for example, the chemical system of the battery cell 20 in each example is nickel-cobalt-manganese ternary.

[0400] [Table 6]

[0401] As can be seen by comparing the two comparative examples and the six examples in Table 6 above, when different materials are used for the casing 211, correspondingly different tensile strengths Rm can be determined. If the tensile strength Rm satisfies 250MPa ≤ Rm ≤ 2000MPa and the capacity C of the battery cell 20 satisfies 25Ah ≤ C ≤ 550Ah, for example, in Examples 1 to 6, if no cracks occur in the casing 211 of the battery cell 20, the structural strength of the casing 211 can be used for battery cells 20 with relatively large capacities and can meet the design needs of the battery cell 20. However, if the tensile strength Rm does not satisfy 250MPa ≤ Rm ≤ 2000MPa, for example, in Comparative Examples 1 to 2, if the casing 211 of the battery cell 20 cracks, the design needs of the battery cell 20 cannot be met.

[0402] As can be understood, in order to meet the above design needs, the material of at least a portion of the casing 211 in the embodiment of the present application can be flexibly selected according to the actual application.

[0403] In some embodiments, the material of at least a portion of the casing 211 includes at least one of steel, copper alloy, titanium alloy, and nickel alloy. These materials have relatively high strength, so they can meet the strength requirements of the casing 211, and are easy to process and relatively inexpensive.

[0404] In some embodiments, the material of at least a portion of the casing 211 includes at least one of stainless steel, carbon steel, and high-strength alloy steel. For example, when the casing 211 is made of stainless steel, its structural strength is relatively high and can usually satisfy the requirements of tensile strength Rm at room temperature, yield strength Re at room temperature, tensile strength Rn at high temperature, and melting point p. For example, the melting point of stainless steel is usually between 1400°C and 1500°C. Furthermore, when the casing 211 is made of stainless steel, it becomes less susceptible to rust, which can improve the service life of the casing 211 compared to other materials.

[0405] When carbon steel is used for the casing 211, its structural strength is high, and it easily meets the requirements for tensile strength Rm at room temperature, yield strength Re at room temperature, tensile strength Rn at high temperature, and melting point p. For example, the melting point of carbon steel is usually between 1425°C and 1525°C. Furthermore, considering that carbon steel is susceptible to corrosion during use, nickel plating can be applied to the outer surface of the carbon steel casing 211. For example, the thickness of the nickel plating layer is usually between 1 μm and 10 μm to protect the surface of the casing 211 from corrosion due to oxidation and to improve the service life of the casing 211.

[0406] To effectively improve the structural strength of the casing 211, other high-strength alloy steel materials may be used. For example, if the requirements for the structural strength of the casing 211 are relatively high, a high-strength alloy steel material can be selected, which easily satisfies the above-mentioned requirements for tensile strength Rm at room temperature, yield strength Re at room temperature, tensile strength Rn at high temperature, and melting point p.

[0407] In some embodiments, when at least a portion of the casing 211 is made of steel, the steel type may include at least one of SPCC, Q195, Q215, Q235, SUS304, SUS316, and other modified stainless steels. These steels are readily available, their strength can meet design needs, and their cost is relatively low. For example, approximate values ​​of the tensile strength Rm, yield strength Re, tensile strength Rn, and melting point p of different steels at room temperature (25°C), room temperature (25°C), and high temperature (500°C) can be found in Table 7 below.

[0408] [Table 7]

[0409] As can be understood, the material of at least a portion of the casing 211 according to the embodiment of the present application may also be made of other materials. For example, different materials can be reasonably selected based on the mass content of different elements in the material and the function that those elements perform.

[0410] In some embodiments, the mass content of chromium in the material of at least a portion of the casing 211 is m, where m satisfies 10% ≤ m ≤ 30%. By increasing the amount of chromium in the material of at least a portion of the casing 211, the melting point and strength of the material can be improved, easily satisfying the requirements of tensile strength Rm at room temperature, yield strength Re at room temperature, tensile strength Rn at high temperature, and melting point p in the embodiments of this application. Furthermore, since chromium reacts with oxygen to form an even denser chromium oxide film, a corrosion-resistant protective film can be formed on the surface of the casing 211, improving the corrosion resistance of the casing 211.

[0411] In some embodiments, the mass content of nickel in the material of at least a portion of the casing 211 is n, where n satisfies 8% ≤ n ≤ 25%. By increasing the nickel content in the material of at least a portion of the casing 211 by an appropriate amount, the structural strength and plasticity of the casing 211 can be improved, for example, the tensile strength Rm at room temperature, the yield strength Re at room temperature, and the tensile strength Rn at high temperature can be improved, and the corrosion resistance of the material can also be provided.

[0412] In some embodiments, taking steel as an example, the mass content of different elements in different types of steel varies. For example, in the case of stainless steel, iron is one of the basic elements of stainless steel, and its mass content is usually 60% to 70%. For example, Table 8 shows the mass content of different elements in several types of steel, and the values ​​in Table 8 are the maximum mass percentages of each element in that material; that is, the mass percentages of each element in the corresponding applications are usually less than or equal to the values ​​shown in Table 8.

[0413] [Table 8]

[0414] As can be understood, if at least a portion of the casing 211 is made of steel, increasing the mass content of carbon in the steel can improve the strength and hardness of the steel. For example, generally, the higher the carbon content, the higher the hardness and strength of the steel, but the lower the corrosion resistance may be.

[0415] Increasing the mass content of chromium in steel allows the chromium to react with oxygen to form a denser chromium oxide film, creating a corrosion-resistant protective film on the surface of the steel, thereby improving the corrosion resistance of the steel.

[0416] Increasing the mass content of nickel in steel materials can improve the corrosion resistance, strength, and plasticity of the steel.

[0417] Increasing the molybdenum content in steel materials can improve their corrosion resistance and strength, which is particularly noticeable in corrosive media such as acids and salts.

[0418] Increasing the mass content of manganese in steel materials can increase the toughness and fatigue resistance of the steel.

[0419] Increasing the mass content of silicon in steel materials can increase the corrosion resistance and strength of stainless steel.

[0420] Reducing the mass content of phosphorus and sulfur in steel materials can mitigate the adverse effects of these two elements on the corrosion resistance, plasticity, and toughness of the steel.

[0421] Furthermore, other elements may be incorporated into the steel material. For example, the steel material may further contain copper, and in Q195, Q215, and Q235, for example, the mass content of copper is generally 0.3% or less, while in modified stainless steel it is generally 2% to 3.5% or less. Also, for example, the steel material may further contain nitrogen, and in Q195, Q215, and Q235, for example, the mass content of nitrogen is generally 0.12% or less.

[0422] As can be understood, in the embodiments of this application, the test method for determining the mass content of each element in the steel material can be adapted to the actual application. For example, the test can be performed using inductively coupled plasma atomic emission spectroscopy, i.e., inductively coupled plasma (ICP) technology, but the embodiments of this application are not limited thereto.

[0423] Figure 19 shows a schematic diagram of the local structure of the casing 211 according to an embodiment of the present application, which may be, for example, a magnified view of region A' shown in Figure 18. As shown in Figure 19, the casing 211 according to an embodiment of the present application has a multilayer structure, and the material of the outermost casing 2117 of the casing 211 includes at least one of aluminum, aluminum alloy, copper, copper alloy, and chromium.

[0424] As can be understood, the casing 211 according to the embodiment of the present application has a multilayer structure, that is, for any one wall of the casing 211, the multilayer structure is stacked along the thickness direction of the wall in order to make the casing 211 a multilayer structure. Furthermore, the method of mounting between the multilayer structures of the casing 211 can be flexibly installed according to the actual application. For example, first, multiple single-layer casing structures that have different dimensions but are basically the same shape can be obtained by processing, for example, hollow structures in which each single-layer casing structure has an opening, and then the casing structures with relatively larger dimensions among the multiple single-layer casing structures can be fitted sequentially onto the outside of the casing structures with relatively smaller dimensions to combine the multiple single-layer casing structures into a multilayer casing 211. Alternatively, for example, a substantially plate-like structure having a multilayer structure can be obtained by processing, and then multiple such plate-like structures can be spliced ​​together to form a multilayer casing 211 in the same way, but the embodiment of the present application is not limited to these.

[0425] As can be understood, the outermost casing 2117 of the casing 211 according to the embodiment of the present application includes the outermost structure of each wall of the casing 211, that is, the outermost casing 2117 is a single casing structure including the outer surface of the casing 211.

[0426] In the embodiments of the present invention, the material of the outermost casing 2117 of the casing 211 may include at least one of aluminum, aluminum alloy, copper, copper alloy, and chromium. Of these, if the material of the outermost casing 2117 includes aluminum, the aluminum is oxidized to dense aluminum oxide, making corrosion protection possible. If the material of the outermost casing 2117 includes copper, the copper is oxidized to copper oxide, i.e., verdigris, making corrosion protection possible. If the material of the outermost casing 2117 includes chromium, the chromium is oxidized to chromium oxide, also making corrosion protection possible. Therefore, if the material of the outermost casing 2117 is one of the above corrosion-resistant materials, the outermost casing 2117 can protect other casing layers located inside it, improving the structural stability of the casing 211 and extending the service life of the casing 211.

[0427] As can be understood, the specific thickness of the outermost casing 2117 in the embodiments of the present application can be flexibly set according to the actual application. For example, the thickness of the outermost casing 2117 can be set according to a certain ratio depending on the thickness of the casing 211.

[0428] In some embodiments, the average thickness of the outermost casing 2117 is T11, and the average thickness of the casing 211 is T10, where T11 and T10 satisfy 0.15 ≤ T11 / T10 ≤ 0.5. If the ratio T11 / T10 is set too small, the average thickness T10 of the casing 211 is limited, resulting in a very small average thickness T11 of the outermost casing 2117. On the one hand, this increases the difficulty of processing, on the other hand, it reduces the corrosion protection effect of the outermost casing 2117 and further affects the structural reliability of the casing 211. Conversely, if the ratio T11 / T10 is set too large, the average thickness T11 of the outermost casing 2117 becomes very large, while the thickness of the other layers of the casing 211 other than the outermost casing 2117 becomes very small. However, the structural strength of the outermost casing 2117 may be insufficient, and especially after oxidation, if its deformation capacity is relatively low and its average thickness T11 is relatively large, it will affect the overall structural strength of the casing 211 and further reduce the stability of the casing 211.

[0429] Furthermore, T11 and T10 satisfy the condition 0.15 ≤ T11 / T10 ≤ 0.4. By appropriately reducing the maximum value of the ratio T11 / T10 and increasing the minimum value of the ratio T11 / T10, the average thickness T11 of the outermost casing 2117 can be limited to not being too large or too small, thereby improving the corrosion protection effect, as well as improving the structural strength and structural stability of the casing 211.

[0430] Furthermore, in order to further improve the corrosion protection effect and enhance the stability and reliability of the casing 211, T11 and T10 satisfy the condition 0.2 ≤ T11 / T10 ≤ 0.3.

[0431] In some embodiments, the ratio T11 / T10 of the average thickness T11 of the outermost casing 2117 to the average thickness T10 of the casing 211 according to the embodiments of the present application may also be set to other values. For example, the value of the ratio T11 / T10 may be any one of 0.15, 0.18, 0.2, 0.23, 0.25, 0.28, 0.3, 0.33, 0.35, 0.38, 0.4, 0.43, 0.45, 0.48, and 0.5, or it may be between any two of these values.

[0432] As can be understood, the range of the average thickness T10 of the casing 211 in the embodiment of the present application can be flexibly set according to the actual application, for example, the average thickness T10 of the casing 211 satisfies 0.05 mm ≤ T10 ≤ 0.5 mm. In order to reduce the difficulty of processing the multilayer casing 211 and improve the structural strength of the casing 211, for example, in order to further improve the service life of the casing 211 without the casing 211 easily rupturing, it is undesirable for the average thickness T10 of the casing 211 to be too small. Conversely, in order to relatively reduce the space occupied by the casing 211, improve the space utilization rate of the battery cells 20, and further improve the energy density of the battery 10 in which multiple battery cells 20 are installed, it is also undesirable for the average thickness T10 of the casing 211 to be too large.

[0433] Furthermore, the average thickness T10 of the casing 211 satisfies the condition 0.075 mm ≤ T10 ≤ 0.4 mm. By appropriately reducing the average thickness T10 of the casing 211, the space occupied by the casing 211 inside the battery 10 can be reduced, thereby further improving the energy density of the battery 10. On the other hand, by appropriately increasing the average thickness T10 of the casing 211, the difficulty of processing the casing 211 can also be reduced.

[0434] Furthermore, the average thickness T10 of the casing 211 satisfies the condition 0.1 mm ≤ T10 ≤ 0.3 mm. By ensuring that the average thickness T10 of the casing 211 is neither too large nor too small, not only can the structural strength and structural stability of the casing 211 be improved, but the space occupied by the casing 211 inside the battery 10 can also be reduced, further improving the energy density of the battery 10.

[0435] In some embodiments, the average thickness T10 of the casing 211 according to the embodiments of the present application may also be set to other values. For example, the average thickness T10 of the casing 211 may be any one of the following values: 0.05 mm, 0.075 mm, 0.1 mm, 0.125 mm, 0.15 mm, 0.175 mm, 0.2 mm, 0.225 mm, 0.25 mm, 0.275 mm, 0.3 mm, 0.325 mm, 0.35 mm, 0.375 mm, 0.4 mm, 0.425 mm, 0.45 mm, 0.475 mm, and 0.5 mm, or it may be between any two of these values.

[0436] As can be understood, the range of the average thickness T11 of the outermost casing 2117 in the embodiments of this application can be flexibly set according to the actual application, for example, T11 satisfies 0.015 mm ≤ T11 ≤ 0.25 mm. It is undesirable for the average thickness T11 of the outermost casing 2117 to be too small in order to reduce the difficulty of processing, improve the corrosion protection effect of the outermost casing 2117, and further improve the structural reliability of the casing 211. Conversely, it is also undesirable for the average thickness T11 of the outermost casing 2117 to be too large, considering that if the deformation capacity of the outermost casing 2117 is relatively low after oxidation and its average thickness T11 is too large, it will affect the deformation capacity of the overall structure of the casing 211 and further reduce the reliability and stability of the casing 211.

[0437] Furthermore, the average thickness T11 of the outermost casing 2117 can further satisfy the condition 0.05 mm ≤ T11 ≤ 0.2 mm. By appropriately improving the minimum value of the average thickness T11 of the outermost casing 2117, the corrosion protection effect of the outermost casing 2117 can be improved. By appropriately decreasing the maximum value of the average thickness T11 of the outermost casing 2117, the deformation capacity of the overall structure of the casing 211 can be improved, further enhancing the reliability and stability of the casing 211.

[0438] Furthermore, the average thickness T11 of the outermost casing 2117 can further satisfy the condition 0.075 mm ≤ T11 ≤ 0.15 mm. This not only improves the corrosion protection effect of the outermost casing 2117, but also improves the deformation capacity of the overall structure of the casing 211, thereby improving the reliability and stability of the casing 211.

[0439] In some embodiments, the average thickness T11 of the outermost casing 2117 according to the embodiments of the present application may also be set to other values. For example, the average thickness T11 of the outermost casing 2117 may be any one of the following values: 0.015mm, 0.02mm, 0.025mm, 0.03mm, 0.035mm, 0.04mm, 0.045mm, 0.05mm, 0.055mm, 0.06mm, 0.065mm, 0.07mm, 0.075mm, 0.08mm, 0.085mm, 0.09mm, 0.095mm, 0.1mm, 0.11mm, 0.12mm, 0.13mm, 0.14mm, 0.15mm, 0.16mm, 0.17mm, 0.18mm, 0.19mm, 0.2mm, 0.21mm, 0.22mm, 0.23mm, 0.24mm, and 0.25mm, or it may be between any two of these values.

[0440] As can be understood, the thickness of the inner casing 2118 of the casing 211 according to the embodiment of the present application can be flexibly set according to the actual application, and the inner casing 2118 is any single layer of casing other than the outermost casing 2117 of the casing 211. Furthermore, the casing 211 may include one or more layers of inner casing 2118, and if the casing 211 includes multiple layers of inner casing 2118, the thicknesses of the multiple layers of inner casing 2118 may be the same to facilitate processing, or they may be different to flexibly adjust the thickness of the inner casing 2118 at different positions according to the actual application. For example, as shown in Figure 19, taking the example that the casing 211 includes a three-layer casing structure, the three-layer casing structure includes the outermost outermost casing 2117 and two inner layers casing 2118 located inside, the two inner layers casing 2118 including the innermost casing 2118b and the intermediate casing 2118a. The average thickness of the innermost casing 2118b and the average thickness of the intermediate casing 2118a may be the same or different. For example, both the average thickness of the innermost casing 2118b and the average thickness of the intermediate casing 2118a may be set to T12, and the value of T12 may be set according to the application, for example, T12 may be greater than, less than, or equal to T11, but the embodiments of the present application are not limited to these.

[0441] As can be understood, the average thickness T10 of the casing 211 in the embodiments of the present application may refer to the average thickness of at least a portion of the casing 211. The average thickness T11 of the outermost casing 2117 of the casing 211 may also refer to the average thickness of at least a portion of the outermost casing 2117. The average thickness T12 of the inner casing 2118 of the casing 211 may also refer to the average thickness of at least a portion of the inner casing 2118. Furthermore, the calculation domain for the average thickness T10 of the casing 211 usually coincides with the calculation domain for the average thickness T11 of the outermost casing 2117 and also coincides with the calculation domain for the average thickness T12 of the inner casing 2118. For example, when calculating the average thickness T10 of the casing 211, if a certain area is excluded from the calculation, then correspondingly, the calculation of the average thickness T11 of the outermost casing 2117 must also exclude the same area, and the calculation of the average thickness T12 of the inner casing 2118 must also exclude the same area. For the sake of explanation, the calculation of the average thickness T10 of the casing 211 will be used as an example below, but the relevant explanations apply similarly to determining the average thickness T11 of the outermost casing 2117 and the average thickness T12 of the inner casing 2118, and those explanations will be omitted here.

[0442] For example, the average thickness T10 of the casing 211 may refer to the average thickness T10 of all areas of the casing 211, and in particular, if the entire surface of the casing 211 is relatively flat, that is, if the thickness of most areas of the casing 211 is basically equal or the difference is relatively small, or if the thickness of all areas of the casing 211 is basically equal or the difference is relatively small, then the average thickness of all areas of the casing 211 can be determined as T10.

[0443] Furthermore, for example, the average thickness T10 of the casing 211 may also refer to the average thickness T10 of a localized area of ​​the casing 211, that is, the average thickness T10 of the remaining area after excluding a portion of the casing 211. For example, if a specific area exists in the casing 211, and the thickness of that specific area differs relatively significantly from that of other areas, for example, if a protruding structure or recessed area exists in that specific area along the thickness direction, and the thickness of that specific area is greater or smaller than that of other areas, then the average thickness of the remaining area of ​​the casing 211 can be calculated as T10 by excluding that specific area.

[0444] In some embodiments, the casing 211 may include a functional region, and the average thickness T10 of the casing 211 is the average thickness of the region of the casing 211 other than the functional region, for example, the functional region includes at least one of a pressure release region, a region where electrode terminals 214 are located, a fluid injection region, and a welding region. The difference between the thickness of the functional region and the thickness of the other regions of the casing 211 is usually relatively large, and therefore, if the average thickness T10 of the casing 211 is calculated so as not to include the functional region, the design of the casing 211 can better meet the strength needs, thereby improving the structural strength and stability of the battery cell 20.

[0445] To ensure clarity, the functional area in the embodiment of the present application may include an area in the casing 211 where a specific structure is installed or which has a specific purpose, and is applicable to the “functional area” described above, and for brevity, its description is omitted here. For example, the functional area may include a pressure relief area for installing a pressure relief mechanism. The pressure relief mechanism in the embodiment of the present application may be installed on any one wall of the battery cell 20, for example, the pressure relief mechanism may be installed in the pressure relief area of ​​the casing 211 of the battery cell 20. The pressure relief mechanism may be part of the casing 211, or it may be a separate structure from the casing 211, and may be fixed to the casing 211, for example, by welding. For example, if the pressure release mechanism is part of the casing 211, the pressure release mechanism may be formed by installing a notch in the casing 211, i.e., the casing 211 has a notch installed in the pressure release region, and the thickness of the notched area is clearly smaller than the thickness of other areas of the casing 211, so the average thickness T10 of the casing 211 does not need to be calculated from the thickness of the notched area. The notched area is the most vulnerable location of the pressure release mechanism. When the internal pressure rises to a threshold due to too much gas generated from the battery cell 20, or when the internal temperature of the battery cell 20 rises to a threshold due to heat generated in the internal reaction of the battery cell 20, the pressure release mechanism ruptures at the notch, creating communication between the inside and outside of the battery elevator 20, releasing the gas pressure and temperature to the outside through the rupture of the pressure release mechanism, and further preventing the explosion of the battery cell 20.

[0446] For example, the pressure relief mechanism may be a separate structure from the casing 211, and the pressure relief mechanism can take the form of an explosion-proof valve, a gas valve, a pressure relief valve, or a safety valve, and may specifically employ a pressure-sensitive or temperature-sensitive element or structure. For example, the casing 211 may have a communication hole in the pressure relief region, and the pressure relief mechanism may be attached and fixed to the casing 211 via the communication hole, and the attached pressure relief mechanism may protrude or recess relative to other areas of the casing 211, so that the calculation of the average thickness T10 of the casing 211 does not have to include the pressure relief region where the pressure relief mechanism is located. When the internal pressure or temperature of the battery cell 20 reaches a predetermined threshold, the pressure relief mechanism is activated, or a vulnerable structure provided within the pressure relief mechanism is destroyed, thereby forming an opening or passage for releasing the internal pressure or temperature.

[0447] In some embodiments, the functional region may further include the region in which the electrode terminals 214 are located. Each electrode terminal 214 in the embodiments of the present application may be installed on any one wall, and multiple electrode terminals 214 may be installed on the same wall or different walls of the battery cell 20. For example, as shown in Figures 3 and 4, if each battery cell 20 includes two electrode terminals 214 located on the same wall, then, for example, both electrode terminals 214 may be located on the cover plate 212.

[0448] For example, if each battery cell 20 includes two electrode terminals 214 located on the same wall, then, unlike what is shown in Figures 3 and 4, the two electrode terminals 214 may be located on any one wall of the casing 211, for example, both electrode terminals 214 may be located on the wall with the smallest area of ​​the casing 211. When one or more electrode terminals 214 are located on the casing 211, each electrode terminal 214 usually protrudes into other areas of the casing 211, i.e., the thickness of the area where the electrode terminal 214 is located is much greater than the thickness of other areas of the casing 211. Therefore, the calculation of the average thickness T10 of the casing 211 does not need to include the area where all electrode terminals 214 are located.

[0449] In some embodiments, the functional region may further include an electrolyte injection region. For example, an electrolyte injection hole may be provided in the electrolyte injection region of the casing 211, and the electrolyte is injected into the interior of the casing 211 through the electrolyte injection hole. After the electrolyte injection is complete, the electrolyte injection hole may be sealed with a sealing member. Considering that the thickness of the electrolyte injection region where the sealing member is located is usually much greater than the thickness of other regions of the casing 211, the calculation of the average thickness T10 of the casing 211 does not need to include the electrolyte injection region.

[0450] In some embodiments, the functional area may further include a welded area. For example, the casing 211 and the cover plate 212 may be fixed together by welding, or the casing 211 itself may include a welded area if it is necessary to process and form the casing 211 by welding, for example, if any two walls of the casing 211 are welded together, or if the casing 211 is formed by splicing at least two parts together. For example, the casing 211 may be welded by splicing, and the casing 211 may have a welded seam 2113. Specifically, the casing 211 may include at least two parts, which are joined by welding to form the casing 211, and in the embodiments of the present application, taking as an example that the casing 211 mainly includes two parts along the height direction Z of the battery cell 20, there is a welded seam 2113 between the upper half casing and the lower half casing, or, contrary to what is shown in Figure 4, the welded seam 2113 may be located in other parts of the casing 211, and the embodiments of the present application are not limited to these. The welded area of ​​the functional area according to the embodiments of the present application may further include the welded seam 2113. Due to the manufacturing process, the thickness of the welded area is usually greater than the thickness of other areas of the casing 211, and therefore the calculation of the average thickness T10 of the casing 211 does not need to include the welded area.

[0451] As can be understood, in order to further improve the structural strength and reliability of the casing 211, the inner casing 2118 of the casing 211 can be installed according to the actual application. In some embodiments, the tensile strength of the inner casing 2118 of the casing 211 at 25°C is Rm1, and Rm1 satisfies 250MPa ≤ Rm1 ≤ 2000MPa. Increasing the tensile strength Rm1 of the inner casing 2118 of the casing 211 at room temperature (25°C) improves the overall structural strength and stability of the casing 211. However, it is also undesirable for the tensile strength Rm1 of the inner casing 2118 at room temperature to be too high in order to reduce the difficulty of selecting the material for the inner casing 2118 and to reduce the difficulty and cost of processing the battery cell 20.

[0452] As can be understood, the range of values ​​for the tensile strength Rm1 of the inner casing 2118 at room temperature conditions of 25°C according to the embodiment of the present application can be adjusted according to the actual application. For example, the value of the tensile strength Rm1 at room temperature can further satisfy 400 MPa ≤ Rm1 ≤ 1200 MPa. On the one hand, by increasing the tensile strength Rm1 of the inner casing 2118 at room temperature conditions, the deformation capacity of the inner casing 2118 can be improved to resist the expansion of the electrode assembly 22, and the inner casing 2118 will not easily break, further improving the structural stability and service life of the casing 211 and the battery cell 20. On the other hand, by controlling the tensile strength Rm1 of the inner casing 2118 at room temperature conditions so that it is not too large, the difficulty of material selection and processing of the inner casing 2118 can be reduced, costs can be saved, and processing can be made easier.

[0453] Furthermore, the inner casing 2118 may be installed such that its tensile strength Rm1 at room temperature satisfies 450 MPa ≤ Rm1 ≤ 800 MPa. By ensuring that the tensile strength Rm1 of the inner casing 2118 at room temperature is neither too high nor too low, the deformation capacity of the inner casing 2118 can be improved to resist the expansion of the electrode assembly 22, and this can be easily implemented while saving costs.

[0454] In some embodiments, the value of the tensile strength Rm1 of the inner casing 2118 according to the embodiments of the present application at room temperature may also be set to other values. For example, the values ​​of the tensile strength Rm1 at room temperature may be 250 MPa, 280 MPa, 300 MPa, 330 MPa, 350 MPa, 380 MPa, 400 MPa, 450 MPa, 500 MPa, 550 MPa, 600 MPa, 650 MPa, 700 MPa, 750 MPa, 800 MPa, 850 MPa, 900 MPa, 950 MPa, 1000 MPa, 1050 MPa, 1100 MPa, 1150 MPa The value may be any one of the following numbers: MPa, 1200MPa, 1250MPa, 1300MPa, 1350MPa, 1400MPa, 1450MPa, 1500MPa, 1550MPa, 1600MPa, 1650MPa, 1700MPa, 1750MPa, 1800MPa, 1850MPa, 1900MPa, 1950MPa, and 2000MPa, or it may be any two of these numbers.

[0455] To be understood, the tensile strength in the embodiments of this application refers to the maximum stress value that the material experiences before fracture. The test method for the tensile strength Rm1 of the inner casing 2118 at a temperature of 25°C in the embodiments of this application can be selected according to the actual application. For example, the tensile strength Rm1 can be measured at room temperature conditions of 25°C by adopting the national standard GB / T 228.1-2010.

[0456] The above explanation mainly uses a rectangular battery cell 20 as an example. Below, the explanation will use a cylindrical battery cell 20 as an example, as shown in the drawings. The cylindrical battery cell 20 according to the embodiment of this application and the rectangular battery cell 20 described above are mutually applicable except for their shapes, and the explanation of these differences will be omitted here.

[0457] 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 a partially 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 partially disassembled structure of the battery cell 20 shown in Figure 20. Figure 22 shows a schematic cross-sectional view of the casing 211 of a battery cell 20 according to one embodiment of the present application. For example, Figure 22 may be a cross-sectional view of the casing 211 of the battery cell 20 shown in Figures 20 and 21, and the cross-section is a cross-section of the casing 211.

[0458] In the embodiment of the present application, as shown in Figures 20 to 22, the battery cell 20 includes an electrode assembly 22 including a first tab 2221, a first electrode terminal 214a, and a casing 211 including a cylindrical body 211b and a cover 211a connected to the cylindrical body 211b, wherein the cylindrical body 211b is installed surrounding the outer circumference of the electrode assembly 22, the cover 211a includes the first electrode terminal 214a, the first tab 2221 is electrically connected to the first electrode terminal 214a by the cylindrical body 211b, and the casing 211 has a multilayer structure with different resistivity.

[0459] The casing 211 may have various shapes, such as a cylinder, a rectangular parallelepiped, or other polyhedron. For illustrative purposes, as shown in Figures 20 to 22, the casing 211 is described here as a hollow cylindrical structure. Furthermore, in the embodiments of this application, if the casing 211 is a hollow structure with an opening at one end, the cover plate 212 is a corresponding circular plate structure that matches the casing 211. In the case of a cylindrical casing 211, the cylindrical body 211b is a cylinder, and the lid 211a is a circular plate structure.

[0460] The electrode assembly 22 according to the embodiment of the present application may include a first tab 2221, which may be electrically connected to the first electrode terminal 214a by the cylindrical body 211b of the casing 211, thereby simplifying the structure of the battery cell 20. By arranging the casing 211 in a multilayer structure with different resistivity, the current passability of the battery cell 20 can be improved by a single layer structure having a relatively low resistivity, while the structural strength of the casing 211 can be improved by a single layer structure having a relatively high resistivity. This not only improves the performance of the battery cell 20 but also improves the structural strength of the battery cell 20, further extending its service life.

[0461] In the embodiment of the present application, the electrode assembly 22 further includes a second tab 2222, the polarity of the second tab 2222 and the first tab 2221 being opposite. Specifically, in terms of external appearance, the electrode assembly 22 includes a main body 221 and a tab 222 protruding from the main body 221, the tab 2221 including the first tab 2221 and the second tab 2222. The first tab 2221 is the portion of the first electrode piece that is not coated with the active material layer, and the second tab 2222 is the portion of the second electrode piece that is not coated with the active material layer. The first tab 2221 and the second tab 2222 are used to draw current from within the main body 221.

[0462] The first tab 2221 and the second tab 2222 may extend from the same side of the main body 221, i.e., the first tab 2221 and the second tab may be located on the same end face of the electrode assembly 22. Alternatively, the first tab 2221 and the second tab 2222 may extend from different sides of the main body 221, i.e., the first tab 2221 and the second tab may be located on different end faces of the electrode assembly 22. For example, to facilitate machining, the first tab 2221 and the second tab 2222 may extend from opposite sides, i.e., the first tab 2221 and the second tab 2222 may be located on opposing end faces of the electrode assembly 22. As shown in Figures 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. Of these, the first direction Z may be the height direction Z of the electrode assembly 22.

[0463] As can be understood, the electrode assembly 22 includes a first electrode piece, a second electrode piece, and a separator for separating the first electrode piece and the second electrode piece. The polarities of the first and second electrode pieces are opposite; in other words, one of the first and second electrode pieces is the positive electrode piece 223, and the other of the first and second electrode pieces is the negative electrode piece 224.

[0464] The first pole piece, the second pole piece, and the separator are all strip-shaped structures, and the first pole piece, the second pole piece, and the separator are wound together to form a wound structure. The wound structure may be cylindrical, flattened, or of other shapes.

[0465] Selectively, the first tab 2221 is wound multiple times around the central axis of the electrode assembly 22, and the first tab 2221 includes multiple tab layers. After winding is complete, the first tab 2221 is substantially columnar, with slits remaining between two adjacent tab layers. Embodiments of the present application can reduce the slits between the tab layers by processing the first tab 2221, which facilitates connection between the first tab 2221 and other conductive structures. For example, embodiments of the present application can perform a kneading treatment on the first tab 2221, thereby converging and gathering the end region of the first tab 2221 away from the main body 221. The kneading treatment forms a dense end face at one end of the first tab 2221 away from the main body 221, reducing the slits between the tab layers and facilitating connection between the first tab 2221 and other conductive structures. Alternatively, embodiments of the present invention may fill the space between two adjacent tab layers with conductive material to reduce the slits between the tab layers.

[0466] Selectively, the second tab 2222 is wound multiple times around the central axis of the electrode assembly 22, and the second tab 2222 includes multiple tab layers. Exemplarily, the second tab 2222 is also kneaded to reduce the slits between the tab layers of the second tab 2222.

[0467] In the embodiment of the present application, the battery cell 20 further includes a second electrode terminal 214b electrically connected to the second tab 2222, and the first electrode terminal 214a and the second electrode terminal 214b are located on the same wall of the battery cell 20, thereby improving the integration density of the battery cell 20, improving the space utilization rate of the battery cell 20 within the battery 10, and facilitating processing and assembly.

[0468] As can be understood, the cover 211a in the embodiment of the present application includes a first electrode terminal 214a, for example, the first electrode terminal 214a may be installed on the cover 211a, or the cover 211a may be the first electrode terminal 214a directly.

[0469] In some embodiments, the cover 211a is the first electrode terminal 214a, the cover 211a is provided with an electrode lead-out hole 211c, and the second electrode terminal 214b is installed insulated from the cover 211a and attached to the electrode lead-out hole 211c, with one of the cover 211a and the second electrode terminal 214b being the positive output electrode of the battery cell and the other being the negative output electrode of the battery cell. By making at least a portion of the casing 211 itself one output electrode of the battery cell 20, one conventional electrode terminal can be omitted, and the structure of the battery cell 20 can be simplified. When assembling multiple battery cells 20 into a set, the casing 211 can be electrically connected to a bus member, which not only increases the current passage area but also allows for greater flexibility in the structural design of the bus member.

[0470] For the sake of explanation, the following examples will mainly use the cover 211a as the first electrode terminal 214a, but the embodiments of this application are not limited to this.

[0471] Figure 23 is a schematic local cross-sectional view of a battery 10 provided in some embodiments of the present application, which may include a plurality of battery cells 20. Figure 24 is another schematic local cross-sectional view of a battery 10 provided in some embodiments of the present application, which may be, for example, an enlarged schematic view of region B' of the battery 10 shown in Figure 23.

[0472] 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 used to electrically connect to the first connecting component 81 and the first tab 2221 of the battery 10, and the second electrode terminal 214b is used to electrically connect to the second connecting component 82 and the second tab 2222 of the battery 10, and the second electrode terminal 214b is installed insulated from the cover 211a and attached to the electrode lead-out hole 211c, and one of the cover 211a and the second electrode terminal 214b is the positive output electrode of the battery cell 20 and the other is the negative output electrode of the battery cell 20.

[0473] The lid 211a is electrically connected to the cylinder 211b, and the lid 211a and the cylinder 211b may have the same polarity.

[0474] As can be understood, the lid 211a and the cylinder 211b in the embodiments of the present application may be integrally molded, that is, the casing 211 is an integrally molded part. In this way, the process of connecting the lid 211a and the cylinder 211b can be omitted. For example, the casing 211 may be formed by a tensile process. Of course, the lid 211a and the cylinder 211b may be two separate parts that are then connected by welding, riveting, bonding, etc. The embodiments of the present application mainly take the example of the lid 211a and the cylinder 211b being integrally molded.

[0475] The casing 211 according to the embodiment of the present application may be a hollow structure with an opening at one end. Specifically, it has an opening 211d at one end of the cylindrical body 211b that is separated from the lid 211a. The battery cell 20 further includes a cover plate 212 that covers the opening 211d of the cylindrical body 211b in order to seal the opening 211d of the cylindrical body 211b. The cover plate 212 may have various structures; for example, the cover plate 212 may have a plate-like structure.

[0476] In some embodiments, an electrode extraction hole 211c is provided in the lid 211a, and the area of ​​the lid 211a other than the electrode extraction hole 211c includes an area for welding to the first connecting component 81, that is, the lid 211a may be welded to the first connecting component 81 to form a first welded portion W1. Exemplarily, during welding, the laser acts on the surface of the first connecting component 81 that is separated from the lid 211a, and the laser melts and connects a part of the first connecting component 81 and a part of the lid 211a, forming a first welded portion W1.

[0477] The electrode extraction holes 211c penetrate the cover 211a, facilitating the discharge of electrical energy within the electrode assembly 22 to the outside of the casing 211. Exemplarily, the electrode extraction holes 211c penetrate the cover 211a along a first direction Z.

[0478] The electrode lead-out holes 211c in the embodiment of the present application are manufactured after the casing 211 has been tensile-formed. For example, in this embodiment, the positive and negative output electrodes are positioned at one end of the battery cell 20 away from the opening of the casing 211 by forming the electrode lead-out holes 211c in the lid 211a using a perforation process for attaching the second electrode terminal 214b. The lid 211a is formed during the molding process of the casing 211 and ensures flatness even after the electrode lead-out holes 211c are opened, thereby ensuring the connection strength between the lid 211a and the first connecting component 81. At the same time, since the flatness of the lid 211a is not limited by its own dimensions, the lid 211a can have relatively large dimensions, thereby improving the current passability of the battery cell 20.

[0479] In some embodiments, the cylindrical body 211b is cylindrical, the electrode extraction hole 211c is a circular hole, and the central axis of the cylindrical body 211b and the central axis of the electrode extraction hole 211c are set to overlap. "Set to overlap" does not require that the central axis of the cylindrical body 211b and the central axis of the electrode extraction hole 211c absolutely and perfectly overlap, and there may be a process-acceptable deviation.

[0480] The electrode extraction hole 211c may be used to limit the position of the second electrode terminal 214b. In this embodiment, by aligning the central axis of the electrode extraction hole 211c with the central axis of the cylindrical body 211b, at least a portion of the second electrode terminal 214b can be positioned at the center of the cover 211a. In this way, when assembling multiple battery cells 20 into a set, the requirements for positional accuracy of the second electrode terminal 214b can be reduced, the assembly process can be simplified, and assembly efficiency can be improved.

[0481] The central axis of the electrode assembly 22 is a virtual straight line parallel to the first direction Z. The central axis of the electrode assembly 22 may pass through the electrode extraction hole 211c, or it may be offset from the electrode extraction hole 211c, and this embodiment is not limited to these.

[0482] The first tab 2221 is electrically connected to the lid 211a. The first tab 2221 may be directly electrically connected to the lid 211a, or it may be indirectly electrically connected to the lid 211a by another conductive structure. For example, the first tab 2221 may be electrically connected to the lid 211a by the cylinder 211b.

[0483] The second tab 2222 is electrically connected to the second electrode terminal 214b. The second tab 2222 may be directly electrically connected to the second electrode terminal 214b, or it may be indirectly electrically connected to the second electrode terminal 214b by other conductive structures. For example, the second tab 2222 may be electrically connected to the second electrode terminal 214b by the current collector component 23.

[0484] The second electrode terminal 214b is installed insulated from the cover 211a, and therefore the second electrode terminal 214b and the cover 211a may have different polarities, and the second electrode terminal 214b and the cover 211a may be different output poles.

[0485] The second electrode terminal 214b is fixed to the cover 211a. The second electrode terminal 214b may be fixed entirely to the outside of the cover 211a, or it may extend into the interior of the casing 211 through the electrode lead-out hole 211c.

[0486] When the first tab 2221 is the negative electrode tab and the second tab 2222 is the positive electrode tab, the cover 211a is the negative output electrode of the battery cell 20, while the second electrode terminal 214b is the positive output electrode of the battery cell 20. When the first tab 2221 is the positive electrode tab and the second tab 2222 is the negative electrode tab, the cover 211a is the positive output electrode of the battery cell 20, while the second electrode terminal 214b is the negative output electrode of the battery cell 20.

[0487] In the battery 10, a plurality of battery cells 20 are electrically connected by a bus member. The bus member includes a first connecting component 81 for connecting to the cover 211a of the battery cell 20 and a second connecting component 82 for connecting to the second electrode terminal 214b of the battery cell 20.

[0488] The first connecting component 81 can be connected to the cover 211a by welding, bonding, or other means to achieve an electrical connection between the first connecting component 81 and the cover 211a. The second connecting component 82 can be connected to the second electrode terminal 214b by welding, bonding, riveting, or other means to achieve an electrical connection between the second connecting component 82 and the second electrode terminal 214b.

[0489] For example, the first connecting component 81 connects the cover 211a of one battery cell 20 to the second electrode terminal 214b of another battery cell 20, while the second connecting component 82 connects the second electrode terminal 214b of the first battery cell 20 to the cover 211a of the other battery cell 20, so that the first connecting component 81 and the second connecting component 82 connect the three battery cells 20 in series.

[0490] In this embodiment, by using the cover 211a and the second electrode terminal 214b as output electrodes, the structure of the battery cell 20 can be simplified while ensuring the current passing capability of the battery cell 20. The cover 211a and the second electrode terminal 214b are located at the same end of the battery cell 20, and in this way the first connecting component 81 and the second connecting component 82 are assembled on the same side of the battery cell 20, thus simplifying the assembly process and improving the efficiency of assembling multiple battery cells 20 into sets.

[0491] As can be understood, as shown in Figures 20 to 24, the second electrode terminal 214b according to the embodiment of the present application includes a terminal body 2141. Furthermore, the terminal body 2141 may be fixed to the cover 211a by riveting. For example, at least a portion of the terminal body 2141 is located within the electrode lead hole 211c, and both ends of the terminal body 2141 are riveted to the electrode lead hole 211c.

[0492] In some embodiments, the terminal body 2141 may be provided with a recess extending in the direction toward the electrode assembly 22 from the outer surface of the terminal body 2141. The bottom of the recess is used for welding to the current collector component 23.

[0493] The electrode assembly 22 and the current collector component 23 are mounted inside the casing 211 through the opening 211d of the cylindrical body 211b, and after the current collector component 23 is brought into contact with the cover 211a, an external welding device can weld the bottom of the recess to the current collector component 23 from the side away from the current collector component 23 at the bottom of the recess.

[0494] In this embodiment, the thickness of the terminal body 2141 is reduced by providing a recess, thereby reducing the welding power required to weld the bottom of the recess to the current collector component 23, reducing the heat generated, and thus reducing the risk of other components (for example, the first insulating component 61 and the second insulating component 60) being burned.

[0495] In some embodiments, the second electrode terminal 214b further includes a seal plate 2142 for sealing the opening of the recess. The seal plate 2142 may be located entirely outside the recess, or a portion thereof may be housed inside the recess, as long as it can seal the opening of the recess. The seal plate 2142 can protect the recess from the outside, reduce external impurities entering the recess, reduce the risk of the bottom of the recess being damaged by external impurities, and improve the sealing performance of the battery cell 20.

[0496] In some embodiments, the seal plate 2142 is used to weld to the second connecting component 82 to form a second weld W2. The second weld W2 can reduce the contact resistance between the seal plate 2142 and the second connecting component 82 and improve the current transmission capability.

[0497] In some embodiments, at least a portion of the seal plate 2142 protrudes from the outer surface of the terminal body 2141. When it is necessary to weld the second connector 82 to the seal plate 2142, the second connector 82 is first bonded to the upper surface of the seal plate 2142 (i.e., the surface away from the recess of the seal plate 2142), and then the second connector 82 and the seal plate 2142 are welded together. At least a portion of the seal plate 2142 protrudes from the outer surface of the terminal body 2141, thereby preventing the outer surface of the terminal body 2141 from interfering with the bonding of the seal plate 2142 to the second connector 82, and ensuring a tight bond between the second connector 82 and the seal plate 2142.

[0498] In embodiments of the present invention, the battery cell 20 further includes a first insulating component 61 for insulating at least a portion of the second electrode terminal 214b from the cover 211a. Exemplarily, at least a portion of the first insulating component 61 is sandwiched between the cover 211a and the second electrode terminal 214b, thereby insulating the cover 211a from the second electrode terminal 214b and reducing the risk of short circuits.

[0499] In the embodiment of the present invention, the battery cell 20 further includes a second insulating component 60 located between the cover 211a and the electrode assembly 22. Specifically, the second insulating component 60 separates the electrode assembly 22 from the cover 211a, reducing the risk of the electrode assembly 22 coming into contact with the cover 211a and becoming electrically conductive during vibration of the battery cell 20, thereby improving safety performance.

[0500] In some embodiments, at least one of the first insulating component 61 and the second insulating component 60 may be used to seal the electrode lead hole 211c. In some other embodiments, the battery cell 20 further includes a seal ring 62 which is fitted onto the second electrode terminal 214b and used to seal the electrode lead hole 211c. Selectively, a portion of the seal ring 62 extends into the electrode lead hole 211c to separate the hole wall of the electrode lead hole 211c from the second electrode terminal 214b.

[0501] In some embodiments, the second tab 2222 is provided at one end of the electrode assembly 22 facing the cover 211a, and the first tab 2221 is provided at the other end of the electrode assembly 22 away from the cover 211a. The cylindrical body 211b is used to connect the first tab 2221 to the cover 211a so that the first tab 2221 is electrically connected to the cover 211a.

[0502] The cylindrical body 211b may be electrically connected directly to the first tab 2221, or it may be electrically connected to the first tab 2221 by other components. For example, the first tab 2221 may be electrically connected to the cylindrical body 211b by the cover plate 212.

[0503] In the embodiment of the present application, by providing the first tab 2221 and the second tab 2222 at both ends of the electrode assembly 22, the risk of electrical 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.

[0504] In some embodiments, the first tab 2221 is a negative electrode tab, and the substrate material of the casing 211 is steel. The casing 211 is electrically connected to the negative electrode tab, i.e., the casing 211 is in a low potential state. The steel casing 211 is not easily corroded by the electrolyte in a low potential state, thereby reducing safety risks.

[0505] 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 can be connected to the second tab 2222 by welding, abutment, or adhesive, and to the second electrode terminal 214b by welding, abutment, adhesive, riveting, or the like, thereby achieving an electrical connection between the second tab 2222 and the second electrode terminal 214b.

[0506] In the first direction Z, the second electrode terminal 214b is positioned opposite the central region of the second tab 2222. If the second electrode terminal 214b and the second tab 2222 were directly connected, the conductive path between the edge region of the second tab 2222 and the second electrode terminal 214b would be too long, resulting in uneven current density in the second electrode piece of the electrode assembly 22, increasing internal resistance and affecting the current passability and charging efficiency of the battery cell 20.

[0507] A relatively large connection area can be provided between the current collector 23 and the second tab 2222 according to the embodiment of the present application, 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 piece, reduce internal resistance, and improve the current passability and charging efficiency of the battery cell 20.

[0508] As can be understood, the casing 211 in the embodiment of the present application has a multilayer structure, that is, both the cylindrical body 211b and the lid 211a of the casing 211 have a multilayer structure. For the sake of explanation, the casing 211 described later will all include the cylindrical body 211b and the lid 211a.

[0509] In the embodiments of the present application, the casing 211 includes a first casing layer 2115, the resistivity of the first casing layer 2115 is K1, and K1 satisfies 1 × 10⁻⁸ Ω·m ≤ K1 ≤ 6 × 10⁻⁸ Ω·m. The first casing layer 2115 is one of any of the multiple layers of the casing 211. For example, in Figure 22, the innermost casing is the first casing layer 2115, but the embodiments of the present application are not limited thereto. By setting the resistivity K1 of the first casing layer 2115 included in the casing 211 to be relatively small, the current passing capability of the casing 211 can be improved, further improving the performance of the battery cell 20.

[0510] In some embodiments, the resistivity K1 of the first casing layer 2115 can further satisfy 1 × 10⁻⁸ Ω·m ≤ K1 ≤ 2.8 × 10⁻⁸ Ω·m. This not only improves the current passability and performance of the casing 211, but is also easy to implement. In some embodiments, the value of the resistivity K1 of the first casing layer 2115 may also be set to other values. For example, the resistivity K1 values ​​of the first casing layer 2115 are 1 × 10⁻⁸ Ω·m, 1.3 × 10⁻⁸ Ω·m, 1.5 × 10⁻⁸ Ω·m, 1.8 × 10⁻⁸ Ω·m, 2 × 10⁻⁸ Ω·m, 2.3 × 10⁻⁸ Ω·m, 2.5 × 10⁻⁸ Ω·m, 2.8 × 10⁻⁸ Ω·m, 3 × 10⁻⁸ Ω·m, 3.3 × 10⁻⁸ Ω·m, 3.5 × 10 It may be any one of the following values: ^-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, or it may be between any two of these values.

[0511] As can be understood, the specific thickness of the first casing layer 2115 in the embodiments of the present application can be flexibly set according to the actual application. For example, the thickness of the first casing layer 2115 can be set according to a certain ratio depending on the thickness of the casing 211.

[0512] In some embodiments, the average thickness of the first casing layer 2115 is T13, and the average thickness of the casing 211 is T10, such that T13 and T10 satisfy 0.15 ≤ T13 / T10 ≤ 0.85. If T13 / T10 is set to be too small, and the average thickness T10 of the casing 211 is constant, T13 will be too small, increasing the difficulty of processing and making thermal runaway more likely due to excessive heat generated by current flow. Conversely, if T13 / T10 is set to be too large, and the average thickness T10 of the casing 211 is constant, T13 will be too large, causing the thickness of other structural layers to be too small and affecting the structural strength of the casing 211.

[0513] Furthermore, T13 and T10 satisfy 0.2 ≤ T13 / T10 ≤ 0.6. This not only improves the current-passing capability of the casing 211 but also improves the structural strength of the casing 211. In some embodiments, the value of the ratio T13 / T10 may also be set to other values. For example, the value of the ratio T13 / T10 may be any one of 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, or it may be between any two of these values.

[0514] As can be understood, the range of the average thickness T10 of the casing 211 in the embodiment of the present application can be flexibly set according to the actual application, for example, the average thickness T10 of the casing 211 satisfies 0.05 mm ≤ T10 ≤ 0.5 mm. In order to reduce the difficulty of processing the multilayer casing 211 and improve the structural strength of the casing 211, for example, in order to further improve the service life of the casing 211 without the casing 211 easily rupturing, it is undesirable for the average thickness T10 of the casing 211 to be too small. Conversely, in order to relatively reduce the space occupied by the casing 211, improve the space utilization rate of the battery cells 20, and further improve the energy density of the battery 10 in which multiple battery cells 20 are installed, it is also undesirable for the average thickness T10 of the casing 211 to be too large.

[0515] Furthermore, the average thickness T10 of the casing 211 satisfies the condition 0.075 mm ≤ T10 ≤ 0.4 mm. By appropriately reducing the average thickness T10 of the casing 211, the space occupied by the casing 211 inside the battery 10 can be reduced, thereby further improving the energy density of the battery 10. On the other hand, by appropriately increasing the average thickness T10 of the casing 211, the difficulty of processing the casing 211 can also be reduced.

[0516] Furthermore, the average thickness T10 of the casing 211 satisfies the condition 0.1 mm ≤ T10 ≤ 0.3 mm. By ensuring that the average thickness T10 of the casing 211 is neither too large nor too small, not only can the structural strength and structural stability of the casing 211 be improved, but the space occupied by the casing 211 inside the battery 10 can also be reduced, further improving the energy density of the battery 10.

[0517] In some embodiments, the average thickness T10 of the casing 211 according to the embodiments of the present application may also be set to other values. For example, the average thickness T10 of the casing 211 may be any one of the following values: 0.05 mm, 0.075 mm, 0.1 mm, 0.125 mm, 0.15 mm, 0.175 mm, 0.2 mm, 0.225 mm, 0.25 mm, 0.275 mm, 0.3 mm, 0.325 mm, 0.35 mm, 0.375 mm, 0.4 mm, 0.425 mm, 0.45 mm, 0.475 mm, and 0.5 mm, or it may be between any two of these values.

[0518] In the embodiments of the present invention, the material of the first casing layer 2115 can be flexibly configured according to the actual application. For example, to meet the design needs of the resistivity K1 of the first casing layer 2115, the material of the first casing layer 2115 includes at least one of silver, copper, aluminum, magnesium, and brass.

[0519] In the embodiments of the present application, the casing 211 includes a second casing layer 2116, the tensile strength of the second casing layer 2116 at a temperature of 25°C is Rm2, and Rm2 satisfies 250MPa ≤ Rm2 ≤ 2000MPa. The second casing layer 2116 is one of any of the multiple layers of the casing 211. For example, in Figure 22, the outermost casing is the second casing layer 2116, but the embodiments of the present application are not limited to these examples. By setting the tensile strength Rm2 of the second casing layer 2116 included in the casing 211 at a temperature of 25°C to be relatively high, the structural strength and deformation capacity of the casing 211 can be improved, and the casing 211 will not easily break during the use of the battery cell 20, further improving the structural stability and service life of the battery cell 20. However, in order to reduce the difficulty of selecting and processing the material for the casing 211, save costs, and facilitate processing, it is also undesirable for the tensile strength Rm2 of the second casing layer 2116 at room temperature of 25°C to be too high.

[0520] As can be understood, the range of values ​​for the tensile strength Rm2 of the second casing layer 2116 of the casing 211 in the embodiment of the present application at room temperature conditions of 25°C can be adjusted according to the actual application. For example, the value of the tensile strength Rm2 at room temperature can further satisfy 400 MPa ≤ Rm2 ≤ 1200 MPa. On the one hand, by increasing the tensile strength Rm2 of the second casing layer 2116 at room temperature conditions, the deformation capacity of that portion of the second casing layer 2116 can be improved to resist the expansion of the electrode assembly 22, and the second casing layer 2116 will not easily break, further improving the structural stability and service life of the battery cell 20. On the other hand, by controlling the tensile strength Rm2 of the second casing layer 2116 at room temperature conditions so that it is not too high, the difficulty of selecting the material and processing the second casing layer 2116 can be reduced, saving costs and making processing easier.

[0521] Furthermore, the second casing layer 2116 may be installed such that its tensile strength Rm2 at room temperature satisfies 450 MPa ≤ Rm2 ≤ 800 MPa. By ensuring that the tensile strength Rm2 of the second casing layer 2116 at room temperature is neither too high nor too low, the deformation capacity of the casing 211 in that portion can be improved to resist the expansion of the electrode assembly 22, and this can be easily implemented and cost-effective.

[0522] In some embodiments, the value of the tensile strength Rm2 of the second casing layer 2116 of the casing 211 according to the embodiment of the present application at room temperature may also be set to other values. For example, the values ​​of the tensile strength Rm2 at room temperature may be 250 MPa, 280 MPa, 300 MPa, 330 MPa, 350 MPa, 380 MPa, 400 MPa, 450 MPa, 500 MPa, 550 MPa, 600 MPa, 650 MPa, 700 MPa, 750 MPa, 800 MPa, 850 MPa, 900 MPa, 950 MPa, 1000 MPa, 1050 MPa, 1100 MPa, 1150 MPa The value may be any one of the following numbers: MPa, 1200MPa, 1250MPa, 1300MPa, 1350MPa, 1400MPa, 1450MPa, 1500MPa, 1550MPa, 1600MPa, 1650MPa, 1700MPa, 1750MPa, 1800MPa, 1850MPa, 1900MPa, 1950MPa, and 2000MPa, or it may be any two of these numbers.

[0523] As can be understood, the tensile strength in the embodiments of this application refers to the maximum stress value that the material experiences before fracture. The test method for the tensile strength Rm2 of the second casing layer 2116 of the casing 211 at a temperature of 25°C in the embodiments of this application can be selected according to the actual application. For example, the tensile strength Rm2 can be measured at room temperature conditions of 25°C by adopting the national standard GB / T 228.1-2010.

[0524] In the embodiment of the present application, the average thickness of the second casing layer 2116 is T14, and the average thickness of the casing 211 is T10, where T14 and T10 satisfy 0.15 ≤ T14 / T10 ≤ 0.85. If T14 / T10 is set to be too small, and the average thickness T10 of the casing 211 is constant, T14 will be too small, affecting the structural strength of the casing 211. Conversely, if T14 / T10 is set to be too large, and the average thickness T10 of the casing 211 is constant, T14 will be too large, causing the thickness of other structural layers to be too small. For example, the thickness T13 of the first casing layer 2115 will be too small, further increasing the difficulty of processing, and the heat generated by current flow will be too great, making thermal runaway more likely.

[0525] Furthermore, T14 and T10 satisfy 0.2 ≤ T14 / T10 ≤ 0.6. This not only improves the current-passing capability of the casing 211 but also improves the structural strength of the casing 211. In some embodiments, the value of the ratio T14 / T10 may also be set to other values. For example, the value of the ratio T14 / T10 may be any one of 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, or it may be between any two of these values.

[0526] Furthermore, in order to meet different design needs, the average thickness T14 of the second casing layer 2116 and the average thickness T13 of the first casing layer 2115 in the embodiment of the present application may be the same or different.

[0527] As can be understood, the average thickness T10 of the casing 211 in the embodiment of the present application may refer to the average thickness of at least a portion of the casing 211. The average thickness T13 of the first casing layer 2115 of the casing 211 may also refer to the average thickness of at least a portion of the first casing layer 2115. The average thickness T14 of the second casing layer 2116 of the casing 211 may also refer to the average thickness of at least a portion of the second casing layer 2116. Furthermore, the calculation domain for the average thickness T10 of the casing 211 typically coincides with the calculation domain for the average thickness T13 of the first casing layer 2111 and also coincides with the calculation domain for the average thickness T14 of the second casing layer 2116. For example, when calculating the average thickness T10 of the casing 211, if a certain area is excluded from the calculation, then correspondingly, the calculation of the average thickness T13 of the first casing layer 2115 must also exclude the same area, and the calculation of the average thickness T14 of the second casing layer 2116 must also exclude the same area. For the sake of explanation, the calculation of the average thickness T10 of the casing 211 will be used as an example below, but the relevant explanations apply similarly to determining the average thickness T13 of the first casing layer 2115 and the average thickness T14 of the second casing layer 2116, and those explanations will be omitted here.

[0528] For example, the average thickness T10 of the casing 211 may refer to the average thickness T10 of all areas of the casing 211, and in particular, if the entire surface of the casing 211 is relatively flat, that is, if the thickness of most areas of the casing 211 is basically equal or the difference is relatively small, or if the thickness of all areas of the casing 211 is basically equal or the difference is relatively small, then the average thickness of all areas of the casing 211 can be determined as T10.

[0529] Furthermore, for example, the average thickness T10 of the casing 211 may also refer to the average thickness T10 of a localized area of ​​the casing 211, that is, the average thickness T10 of the remaining area after excluding a portion of the casing 211. For example, if a specific area exists in the casing 211, and the thickness of that specific area differs relatively significantly from that of other areas, for example, if a protruding structure or recessed area exists in that specific area along the thickness direction, and the thickness of that specific area is greater or smaller than that of other areas, then the average thickness of the remaining area of ​​the casing 211 can be calculated as T10 by excluding that specific area.

[0530] In some embodiments, the casing 211 may include a functional region, and the average thickness T10 of the casing 211 is the average thickness of the region of the casing 211 other than the functional region, for example, the functional region includes at least one of a pressure release region, a region where electrode terminals 214 are located, a fluid injection region, and a welding region. The difference between the thickness of the functional region and the thickness of the other regions of the casing 211 is usually relatively large, and therefore, if the average thickness T10 of the casing 211 is calculated so as not to include the functional region, the design of the casing 211 can better meet the strength needs, thereby improving the structural strength and stability of the battery cell 20.

[0531] Specifically, the functional region according to the embodiment of the present application may include a region having a specific structure or purpose installed in the casing 211. For example, the functional region may include a pressure release region for installing a pressure release mechanism used in an element or component that operates to release internal pressure or temperature when the internal pressure or temperature of the battery cell 20 reaches a predetermined threshold. The predetermined threshold may be adjusted according to design needs. For example, the predetermined threshold may depend on one or more materials among the positive electrode piece, negative electrode piece, electrolyte, and separator film in the battery cell 20.

[0532] As used in this application, "operation" refers to the release of pressure and temperature inside the battery cell 20 due to the pressure release mechanism acting or being activated to a certain state. The operation caused by the pressure release mechanism includes, but is not limited to, the rupture, shattering, tearing, or opening of at least a part of the pressure release mechanism. When the pressure release mechanism is operated, high-temperature, high-pressure material inside the battery cell 20 is discharged as waste from the point of operation to the outside. In this way, the pressure and temperature release of the battery cell 20 is made possible at a controllable pressure or temperature, thereby avoiding the occurrence of potentially more serious accidents.

[0533] The waste products from the battery cell 20 relating to this application include, but are not limited to, electrolyte, dissolved or fragmented positive and negative electrode pieces, fragments of separator film, high-temperature and high-pressure gases from the reaction, and flames.

[0534] The pressure relief mechanism according to the embodiment of the present application may be installed on any one wall of the battery cell 20. For example, the pressure relief mechanism may be installed in the pressure relief region of the casing 211 of the battery cell 20. The pressure relief mechanism may be part of the casing 211, or it may be a separate structure, fixed to the casing 211, for example, by welding. For example, if the pressure relief mechanism is part of the casing 211, it may be formed by installing a notch in the casing 211, i.e., the casing 211 has a notch installed in the pressure relief region, and the thickness of the notched area is clearly smaller than the thickness of other areas of the casing 211. Therefore, the average thickness T10 of the casing 211 does not need to be calculated from the thickness of the notched area. The notched area is the most vulnerable location of the pressure relief mechanism. When the internal pressure of the battery cell 20 rises to a threshold due to excessive gas generation, or when the internal temperature of the battery cell 20 rises to a threshold due to heat generated by the internal reaction of the battery cell 20, the pressure release mechanism ruptures at the notch, creating communication between the inside and outside of the battery elevator 20. The gas pressure and temperature are released to the outside by the rupture of the pressure release mechanism, further preventing the explosion of the battery cell 20.

[0535] For example, the pressure relief mechanism may be a separate structure from the casing 211, and the pressure relief mechanism can take the form of an explosion-proof valve, a gas valve, a pressure relief valve, or a safety valve, and may specifically employ a pressure-sensitive or temperature-sensitive element or structure. For example, the casing 211 may have a communication hole in the pressure relief region, and the pressure relief mechanism may be attached and fixed to the casing 211 via the communication hole, and the attached pressure relief mechanism may protrude or recess relative to other areas of the casing 211, so that the calculation of the average thickness T10 of the casing 211 does not have to include the pressure relief region where the pressure relief mechanism is located. When the internal pressure or temperature of the battery cell 20 reaches a predetermined threshold, the pressure relief mechanism is activated, or a vulnerable structure provided within the pressure relief mechanism is destroyed, thereby forming an opening or passage for releasing the internal pressure or temperature.

[0536] In some embodiments, the functional region may further include the region in which the electrode terminals 214 are located. Specifically, the electrode terminals 214 in embodiments of the present application are used to be electrically connected to an electrode assembly 22 inside the battery cell 20 so as to output electrical energy from the battery cell 20. 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 used to be electrically connected to the positive tab of the electrode assembly 22, and the negative electrode terminal being used to be electrically connected to the negative tab of the electrode assembly 22. The positive electrode terminal and the positive tab may be directly connected or indirectly connected, and the negative electrode terminal and the negative tab may be directly connected or indirectly connected. For example, in the embodiment of the present application, if the positive electrode terminal is the first electrode terminal 214a, the negative electrode terminal may be the second electrode terminal 214b, or if the positive electrode terminal is the second electrode terminal 214b, the negative electrode terminal may be the first electrode terminal 214a.

[0537] As can be understood, each electrode terminal 214 in the embodiment of the present application may be installed on any one wall, and multiple electrode terminals 214 may be installed on the same wall or different walls of the battery cell 20. For example, as shown in Figures 20 to 24, if each battery cell 20 includes two electrode terminals 214 located on the same wall, then, for example, both electrode terminals 214 may be located on the cover 211a. However, in the embodiment of the present application, if the cover 23 is the first electrode terminal 214a, then the two electrode terminals 214 included in the battery cell 20 further have electrode terminals 214 that protrude into other areas of the cover 211a of the casing 211, i.e., the thickness of the area where the second electrode terminal 214b is located is much greater than the thickness of other areas of the casing 211. Therefore, the calculation of the average thickness T10 of the casing 211 does not need to include the area where the second electrode terminal 214b is located.

[0538] In some embodiments, the functional region may further include an electrolyte injection region. For example, an electrolyte injection hole may be provided in the electrolyte injection region of the casing 211, and the electrolyte is injected into the interior of the casing 211 through the electrolyte injection hole. After the electrolyte injection is complete, the electrolyte injection hole may be sealed with a sealing member. Considering that the thickness of the electrolyte injection region where the sealing member is located is usually much greater than the thickness of other regions of the casing 211, the calculation of the average thickness T10 of the casing 211 does not need to include the electrolyte injection region.

[0539] In some embodiments, the functional area may further include a welded area. For example, the casing 211 and the cover plate 212 may be fixed together by welding, or the casing 211 itself may include a welded area if it is necessary to process and form the casing 211 by welding, for example, if any two walls of the casing 211 are welded together, or if the casing 211 is formed by splicing at least two parts together. For example, the casing 211 may be welded by splicing, and the casing 211 may have a welded seam 2113. Specifically, the casing 211 may include at least two parts, which are joined by welding to form the casing 211, and in the embodiments of the present application, taking as an example that the casing 211 mainly includes two parts along the height direction Z of the battery cell 20, there is a welded seam 2113 between the upper half casing and the lower half casing, or, contrary to what is shown in Figure 21, the welded seam 2113 may be located in other parts of the casing 211, and the embodiments of the present application are not limited to these. The welded area of ​​the functional area according to the embodiments of the present application may further include the welded seam 2113. Due to the manufacturing process, the thickness of the welded area is usually greater than the thickness of other areas of the casing 211, and therefore the calculation of the average thickness T10 of the casing 211 does not need to include the welded area.

[0540] In some embodiments, the resistivity of the second casing layer 2116 is K2, and K2 and K1 satisfy 2 ≤ K2 / K1 ≤ 40. Furthermore, in order to limit the resistivity K1 of the first casing layer 2115, 2 ≤ K2 / K1 ≤ 20 can be further satisfied, thereby further improving the current passing capability of the casing 211.

[0541] In embodiments of the present invention, the material of the second casing layer 2116 can be flexibly specified according to the actual application. For example, to meet the design needs of the second casing layer 2116, the material of the second casing layer 2116 includes at least one of titanium, steel, silicon steel, and stainless steel.

[0542] In some embodiments, to meet design needs, the materials for the first casing layer 2115 and the second casing layer 2116 can be selected from the materials shown in Table 9.

[0543] [Table 9]

[0544] As can be understood, the casing 211 according to the embodiment of the present application has a multilayer structure, and the number of layers of the casing 211 can be set according to the actual application. For example, the casing 211 includes a plurality of first casing layers 2115 and / or a plurality of second casing layers 2116, and the positions of the different first casing layers 2115 and second casing layers 2116 can be flexibly set according to the actual application to meet different application scenes.

[0545] In some embodiments, the casing 211 may include a plurality of first casing layers 2115 and a single second casing layer 2116, wherein the second casing layer 2116 may be located in the middle of or on one side of the plurality of first casing layers 2115. Similarly, the casing 211 may include a single first casing layer 2115 and a plurality of second casing layers 2116, wherein the first casing layer 2115 may be located in the middle of or on one side of the plurality of second casing layers 2116. For example, the casing 211 may include a plurality of first casing layers 2115 and a plurality of second casing layers 2116, and the plurality of first casing layers 2115 and the plurality of second casing layers 2116 may be installed with gaps between them, or the plurality of first casing layers 2115 may be installed on one side of the plurality of second casing layers 2116, and the embodiments of the present application are not limited to these.

[0546] In some embodiments, if the casing 211 includes a plurality of first casing layers 2115 that satisfy the abov...

Claims

1. A casing having an opening, comprising a first wall and at least one second wall facing the opening, wherein the first wall and the second wall are installed intersecting each other. The first wall and the second wall are connected by a first fillet, and the distance between the inner diameter r1 of the first fillet and the minimum thickness T2 of the second wall, which is the minimum thickness of at least one of the second walls, satisfies 2.0 ≤ r1 / T2 ≤ 30. The yield strength of the casing at a temperature of 25°C is Re, and Re satisfies the condition 140 MPa ≤ Re ≤ 1000 MPa. Casing.

2. r1 and T2 are characterized in that 2.5 ≤ r1 / T2 ≤ 10. The casing according to claim 1.

3. The inner diameter r1 of the first fillet is characterized in that it satisfies the condition 0.8 mm ≤ r1 ≤ 1.5 mm. The casing according to claim 1 or 2.

4. The outer diameter r2 of the first fillet is characterized in that it satisfies the condition 1.0 mm ≤ r2 ≤ 2.5 mm. A casing according to any one of claims 1 to 3.

5. The relationship between the depth H of the casing and the minimum thickness T2 of the second wall, which has the minimum thickness, is characterized in that 300 ≤ H / T2 ≤ 800. A casing according to any one of claims 1 to 4.

6. The relationship between the maximum thickness T3 of the first fillet and the minimum thickness T2 of the second wall, which has the minimum thickness, is characterized in that 0.8 ≤ T2 / T3 ≤ 2. A casing according to any one of claims 1 to 5.

7. The at least one second wall has a transition region between two adjacent second walls, and the maximum thickness T1 of the transition region and the maximum thickness T0 of the second wall with the maximum thickness among the two second walls satisfy T1 > T0. A casing according to any one of claims 1 to 6.

8. The casing is a one-piece molded structure, and the two second walls in at least one second wall are connected by a second fillet, the inner diameter of the second fillet is R1, and R1 satisfies 2.5 mm ≤ R1 ≤ 20 mm. A casing according to any one of claims 1 to 7.

9. The depth H of the casing is characterized in that 50 mm < H ≤ 250 mm. The casing according to claim 8.

10. The casing is characterized by having a uniform wall thickness. A casing according to any one of claims 1 to 9.

11. The material of at least a portion of the casing is characterized by including at least one of stainless steel and carbon steel. A casing according to any one of claims 1 to 10.

12. The mass content of chromium element in the material of at least a portion of the casing is m, and m is characterized in that 10% ≤ m ≤ 30%. A casing according to any one of claims 1 to 11.

13. At least a portion of the casing is characterized in that it includes all of the walls of the casing. The casing according to claim 11 or 12.

14. A battery cell comprising an electrode assembly and a casing according to any one of claims 1 to 13, wherein the electrode assembly is housed within the casing. Battery cell.

15. The electrode assembly includes a negative electrode piece, the negative electrode piece 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 tensile strength of at least a portion of the casing at a temperature of 25°C is Rm, and Rm is characterized in that 250 MPa ≤ Rm ≤ 2000 MPa. The battery cell according to claim 14.

16. The electrode assembly includes a negative electrode piece, the negative electrode piece 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 yield strength of at least a portion of the casing at a temperature of 25°C is Re, and Re satisfies the condition 140 MPa ≤ Re ≤ 1000 MPa. The battery cell according to claim 14 or 15.

17. The electrode assembly includes a positive electrode piece, the positive electrode piece 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 melting point of at least a portion of the casing is p, and p satisfies the condition 1200°C ≤ p ≤ 2000°C. A battery cell according to any one of claims 14 to 16.

18. The electrode assembly includes a positive electrode piece, the positive electrode piece 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 tensile strength of at least a portion of the casing at a temperature of 500°C is Rn, and Rn is characterized in that 100 MPa ≤ Rn ≤ 1200 MPa. A battery cell according to any one of claims 14 to 17.

19. It is a battery, The invention comprises a plurality of battery cells, wherein each battery cell is a battery cell according to any one of claims 14 to 18. battery.

20. An electrical device, The present invention is characterized by including a battery, which includes a battery cell according to any one of claims 14 to 18, used to supply power to the aforementioned electrical device. Electrical device.

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