Battery cell, battery, and electric device

Abstract

The present disclosure provides a battery cell, a battery, and an electric device. The battery cell comprises: a casing. The casing comprises a first wall part. The first wall part comprises a first groove. The first wall part is configured to be able to crack along at least a part of the first groove when the battery cell releases pressure. The material of at least the first wall part in the casing comprises an aluminum alloy. The mass fraction of an aluminum element in the aluminum alloy is represented as AD, wherein AD satisfies the following equation: 0.5≤AD≤0.99. The minimum residual thickness of the first groove in the thickness direction of the first wall part is represented as H, wherein H satisfies the following equation: 0.020 mm≤H≤1.000 mm. The battery cell has prolonged service life and can also maintain reliability during thermal runaway.

Description

Battery cells, batteries and electrical equipment Technical Field

[0001] This disclosure relates to the field of battery technology, and more specifically, to a battery cell, a battery, and an electrical device. Background Technology

[0002] With the development of new energy technologies, batteries are being used more and more widely, for example in mobile phones, laptops, electric vehicles, electric cars, electric airplanes, electric ships, electric toy cars, electric toy ships, electric toy airplanes, and power tools.

[0003] For a typical battery cell, a pressure relief component is installed in the battery cell. In the event of thermal runaway, the pressure inside the battery cell is released through the pressure relief component to improve the reliability of the battery cell.

[0004] Pressure relief components can be equipped with pressure relief grooves, allowing the component to crack along these grooves when a battery cell is depressurized, thus releasing the internal pressure of the cell. However, these components are susceptible to corrosion, which can affect the battery's lifespan. Balancing the battery cell's lifespan with reliability requirements during thermal runaway has become a pressing technical challenge. Summary of the Invention

[0005] To address the aforementioned technical problems, this disclosure provides a battery cell, a battery, and an electrical device. The battery cell has an extended service life and maintains its reliability even in the event of thermal runaway.

[0006] This disclosure provides a battery cell, comprising: a casing. The casing includes a first wall portion, the first wall portion including a first groove, the first wall portion being configured to crack along at least a portion of the first groove when the battery cell is depressurized, the material of at least the first wall portion in the casing including an aluminum alloy, the mass fraction of aluminum in the aluminum alloy being expressed as AD, AD satisfying: 0.5≤AD≤0.99, and the minimum residual thickness of the first groove along the thickness direction of the first wall portion being expressed as H, H satisfying: 0.020mm≤H≤1.000mm.

[0007] In this disclosure, the first wall portion includes a first groove, such that the first wall portion can crack along at least a portion of the first groove when the battery cell is depressurized, so as to release the internal pressure of the battery cell.

[0008] Furthermore, by ensuring that 0.020mm ≤ H ≤ 1.000mm, it is beneficial to reduce the risk of reduced corrosion resistance of the first groove due to an excessively small minimum residual thickness H. On the other hand, it is beneficial to reduce the difficulty of opening the first groove during battery thermal runaway due to an excessively large minimum residual thickness H, thereby helping the battery cell maintain its reliability during thermal runaway.

[0009] Furthermore, by controlling AD to be 0.5 ≤ AD ≤ 0.99, it is beneficial to reduce the risk of decreased resistance to electrolyte corrosion on the inner surface (facing the electrolyte) of the first wall due to excessively high AD, and to reduce the risk of decreased resistance to air corrosion on the outer surface (away from the electrolyte) of the first wall due to excessively low AD. This helps to extend the service life of the battery cell.

[0010] In some implementations, AD satisfies the following condition: 0.5 ≤ AD ≤ 0.99. Using aluminum alloys with AD within the above range is beneficial for extending the service life of individual battery cells.

[0011] In some implementations, AD satisfies the following condition: 0.75 ≤ AD ≤ 0.95. Using aluminum alloys with AD within the above range is beneficial for further extending the service life of individual battery cells.

[0012] In some implementations, AD satisfies: 0.75 ≤ AD ≤ 0.90. The corrosion resistance advantage of aluminum alloys with AD within this range is further enhanced, thereby contributing to a further extension of the battery cell's lifespan.

[0013] In some embodiments, the aluminum alloy also includes one or more of the elements selected from zinc, copper, iron, magnesium, manganese, silicon, chromium, titanium, and vanadium. The first wall portion made of this aluminum alloy has higher hardness, greater strength, and stronger corrosion resistance, thereby contributing to a further extension of the battery cell's lifespan.

[0014] In some implementations, H satisfies: 0.04mm ≤ H ≤ 0.6mm. This is beneficial for further extending the service life of the battery cell and improving its reliability in the event of thermal runaway.

[0015] In some implementations, H satisfies: 0.45mm ≤ H ≤ 0.6mm. This helps to further extend the lifespan of the battery cell.

[0016] In some embodiments, the casing has a receiving cavity, and the battery cell also includes an electrolyte contained within the receiving cavity, with the electrolyte in contact with the first wall portion, where c satisfies: 0.5 mol / L ≤ c ≤ 1.4 mol / L. This is beneficial for balancing the battery cell's lifespan and charge / discharge efficiency.

[0017] In some implementations, c satisfies: 0.8mol / L≤c≤1.2mol / L, which helps to further balance the lifespan and charge / discharge efficiency of individual battery cells.

[0018] In some embodiments, the first wall portion further includes a second groove, the first groove and the second groove together defining at least one predetermined pressure relief area, the second groove being able to guide at least a portion of the predetermined pressure relief area to flip over to open at least a portion of the predetermined pressure relief area for pressure relief, the minimum residual thickness of the first groove being less than the minimum residual thickness of the second groove.

[0019] In this implementation, the second groove assists the predetermined pressure relief zone, making it easier to flip and reducing the difficulty of flipping the predetermined pressure relief zone, thereby increasing the opening rate of the predetermined pressure relief zone. This helps the battery cell maintain its reliability during thermal runaway. The minimum residual thickness H of the first groove is smaller than the minimum residual thickness of the second groove, making the first wall portion more prone to cracking in the area where the first groove is located compared to the area where the second groove is located. This improves the pressure relief efficiency, prevents damage or explosion risk to the battery cell due to long-term pressure accumulation, and enhances the reliability of the battery cell during thermal runaway.

[0020] In some embodiments, the first wall portion is provided with a plurality of second grooves. Along the thickness direction of the first wall portion, the projection of the first groove and the projection of the plurality of second grooves together define a plurality of predetermined pressure relief zones, and each predetermined pressure relief zone is provided corresponding to one or more second grooves.

[0021] In this embodiment, the first groove and multiple second grooves together define multiple predetermined pressure relief zones. When a battery cell experiences thermal runaway, the multiple predetermined pressure relief zones start to relieve pressure almost simultaneously, which can improve the opening rate of the predetermined pressure relief zones, achieve pressure relief more quickly, prevent excessive accumulation of internal pressure in the battery cell, and thereby further improve the reliability of the battery cell during thermal runaway.

[0022] In some embodiments, along the thickness direction of the first wall portion, the first wall portion has opposing first and second surfaces, a first groove is disposed on the first surface, and a second groove is disposed on the second surface.

[0023] In this embodiment, the first groove and the second groove are located on both sides of the first wall portion along the thickness direction of the first wall portion, so that the first groove and the second groove can be processed on both sides of the first wall portion respectively. On the one hand, this helps to reduce the mutual influence between the first groove and the second groove during the processing, and on the other hand, it helps to reduce the mutual influence between the first groove and the second groove during pressure relief, thereby improving the reliability of pressure relief.

[0024] In some implementations, the first surface is the outer surface facing the battery cell, and the second surface is the inner surface facing the battery cell.

[0025] In this embodiment, the second groove is disposed on the inner surface of the first wall portion, so that the two sides of the second groove in the width direction are not likely to collide during the outward flipping and opening of the predetermined pressure relief area. This facilitates the rapid and complete unfolding of the predetermined pressure relief area, accelerates the pressure release rate, thereby reducing the internal pressure of the battery and preventing the risk of damage or explosion of the battery cell due to excessive pressure. This further improves the reliability of the battery cell during thermal runaway.

[0026] In some embodiments, the first groove includes multiple levels of grooves arranged sequentially along the direction from the first surface to the second surface. Along the thickness direction of the first wall portion, in two adjacent levels of grooves, the first level groove furthest from the first surface is disposed on the bottom surface of the first level groove closest to the first surface, and the minimum residual thickness of the first level groove furthest from the first surface is taken as the minimum residual thickness of the first groove.

[0027] In this embodiment, by setting the first groove to be arranged in multiple levels along the direction from the first surface to the second surface, each level of groove can be processed one by one along the direction from the first surface to the second surface when forming the first groove, thereby reducing the forming depth of each level of groove, reducing the forming force when forming the first groove, and thus reducing the risk of the first groove being damaged, thereby extending the service life of the battery cell.

[0028] In some embodiments, the first groove includes a first groove segment, a second groove segment, and a third groove segment; the second groove segment and the third groove segment are disposed opposite to each other, and the first groove segment connects the second groove segment and the third groove segment.

[0029] In this embodiment, the first groove has a simple structure. The stress is more concentrated and the area where the first groove segment and the second groove segment are connected is weaker and more prone to cracking. This is beneficial because when the battery cell experiences thermal runaway, it can quickly crack from the first groove segment to the second groove segment after cracking at the connection point, allowing the predetermined pressure relief area to open more quickly and relieve pressure in a timely manner.

[0030] In some embodiments, the connection position between the second groove segment and the first groove segment is offset from both ends of the second groove segment, and the connection position between the third groove segment and the first groove segment is offset from both ends of the third groove segment, so that a predetermined pressure relief zone is formed on both sides of the first groove segment.

[0031] In this embodiment, the first groove segment of the first groove is located between two predetermined pressure relief zones. After the first groove segment splits open, the two predetermined pressure relief zones can open in a split manner to relieve pressure when the battery cell is depressurized, so that the two predetermined pressure relief zones can open quickly, which is beneficial to improving the pressure relief rate of the battery cell.

[0032] In some embodiments, the first groove is stamped onto the first wall portion; and / or, the second groove is stamped onto the first wall portion. If the first groove is stamped onto the first wall portion, the forming method of the first groove is simple, which helps to reduce the production cost of the battery cell. If the second groove is stamped onto the first wall portion, the forming method of the second groove is simple, which helps to reduce the production cost of the battery cell.

[0033] In some embodiments, the housing includes a casing and end caps; the casing has an opening at at least one end; the end caps correspond one-to-one with the openings and close the openings; wherein at least one end cap is a first wall portion; and / or, at least one wall portion in the casing is a first wall portion. If at least one end cap is a first wall portion, enabling at least one end cap to have a pressure relief function, it is easier to form the first and second grooves on the end caps. If at least one wall portion in the casing is a first wall portion, enabling the casing to have a pressure relief function, when the battery cell is depressurized, the emissions discharged from inside the battery cell are less likely to affect external components outside the end caps, reducing the risk of damage to external components from emissions.

[0034] In some embodiments, the housing has an opening at only one end, and the wall portion of the housing opposite the end cap is called the first wall portion. The housing having an opening at one end simplifies the overall structure of the battery cell. The first wall portion, being the wall portion of the housing opposite the end cap, allows for directional pressure relief from the bottom of the housing.

[0035] In some embodiments, openings are formed at both opposite ends of the housing, and at least one wall portion of the housing is a first wall portion. With openings at both opposite ends, the electrode assembly can be assembled into the housing through any one of the openings, reducing the assembly difficulty of the battery cells and improving the assembly quality. This housing structure allows for a greater length (with openings at both ends along the length direction), which is beneficial for increasing the capacity of the battery cells.

[0036] In some embodiments, the wall portion of the casing facing downwards along the direction of gravity is designated as the first wall portion. When a battery cell experiences thermal runaway, the high-pressure gases generated are rapidly expelled with the aid of gravity, thereby improving the reliability of the battery cell under thermal runaway conditions. This is particularly important when the battery cell is used in vehicles, where a large amount of high-temperature gas is generated during thermal runaway. Having the first wall portion located on the gravity-downward wall portion of the casing helps ensure that these high-temperature gases escape from the bottom of the vehicle, preventing them from directly contacting the vehicle's internal structure or passenger compartment, thus ensuring passenger safety.

[0037] A second aspect of this disclosure provides a battery comprising the battery cell provided in the first aspect.

[0038] A third aspect of this disclosure provides an electrical device, including a battery cell provided in the first aspect, the battery cell being used to provide electrical energy to the electrical device. Attached Figure Description

[0039] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of this disclosure. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0040] Figure 1 is a structural schematic diagram of a vehicle provided in one embodiment of this disclosure;

[0041] Figure 2 is an exploded view of a battery provided in one embodiment of this disclosure;

[0042] Figure 3 is an exploded view of a single battery cell provided in one embodiment of this disclosure;

[0043] Figure 4 is an assembly diagram of a battery cell provided according to an embodiment of this disclosure;

[0044] Figure 5 is a partial view of the outer casing shown in Figure 4;

[0045] Figure 6 is an enlarged view of the pressure relief component in the casing shown in Figure 5;

[0046] Figure 7 is an AA cross-sectional view of the outer casing shown in Figure 5;

[0047] Figure 8 is an exploded view of the casing provided in one embodiment of this disclosure;

[0048] Figure 9 is an exploded view of the casing provided in another embodiment of this disclosure;

[0049] Figure 10 is an exploded view of the outer casing provided in another embodiment of this disclosure;

[0050] Figure 11 is an exploded view of the casing provided in another embodiment of the present disclosure;

[0051] Figure 12 is an exploded view of the casing provided in yet another embodiment of this disclosure.

[0052] Explanation of reference numerals in the attached figures

[0053] Icons: 1-Outer shell; 11-Housing shell; 12-End cap; 13-First wall; 131-Pressure relief hole; 132-First wall body; 14-Second wall; 15-Third wall; 2-Electrode assembly; 21-Electrode tab; 3-Electrode terminal; 4-Current collector; 5-Insulator; 6-Pressure relief component; 61-First groove; 611-First groove segment; 612-Second groove segment; 613-Third groove segment; 614-Second stage groove; 615-First stage groove; 62-Second groove; 621 - First groove side; 622 - Second groove side; 63 - Predetermined pressure relief area; 64 - First surface; 65 - Second surface; 10 - Battery cell; 20 - Housing; 201 - First part; 202 - Second part; 100 - Battery; 200 - Controller; 300 - Motor; 1000 - Vehicle; X - Thickness direction of the first wall; Y - Extension direction of the second groove; Z - Width direction of the second groove; H - Minimum residual thickness of the first groove; D - Minimum residual thickness of the second groove. Detailed Implementation

[0054] To make the objectives, technical solutions, and advantages of this disclosure clearer, the technical solutions of this disclosure will be clearly described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this disclosure. Based on the embodiments of this disclosure, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this disclosure.

[0055] Unless otherwise defined, all technical and scientific terms used in this disclosure have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs; the terminology used in the specification of this disclosure and the application is for the purpose of describing particular embodiments only and is not intended to be limiting of this disclosure; the terms "comprising" and "having," and any variations thereof, in the specification, claims, and foregoing drawings of this disclosure are intended to cover non-exclusive inclusion. The terms "first," "second," etc., in the specification, claims, or foregoing drawings of this disclosure are used to distinguish different objects, and not to describe a particular order or hierarchy.

[0056] In this disclosure, the reference to "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this disclosure. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment that is mutually exclusive with other embodiments.

[0057] In the description of this disclosure, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," and "attachment" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection between two components. Those skilled in the art can understand the specific meaning of the above terms in this disclosure according to the specific circumstances.

[0058] In this disclosure, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. Additionally, in this disclosure, the character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0059] In the embodiments of this disclosure, the same reference numerals denote the same components, and for the sake of brevity, detailed descriptions of the same components are omitted in different embodiments. It should be understood that the thickness, length, width, and other dimensions of the various components in this disclosure shown in the accompanying drawings, as well as the overall thickness, length, width, and other dimensions of the integrated device, are merely illustrative and should not constitute any limitation on this disclosure.

[0060] In this disclosure, "multiple" means two or more (including two).

[0061] In this disclosure, the battery cell can be a secondary battery, which refers to a battery cell that can be recharged to activate the active materials and continue to be used after the battery cell has been discharged.

[0062] Battery cells include, but are not limited to, lithium-ion batteries, sodium-ion batteries, sodium-lithium-ion batteries, lithium metal batteries, sodium metal batteries, lithium-sulfur batteries, magnesium-ion batteries, nickel-metal hydride batteries, nickel-cadmium batteries, lead-acid batteries, etc.

[0063] A single battery cell typically includes an electrode assembly. The electrode assembly includes a positive electrode, a negative electrode, and a separator. During the charging and discharging process of a single battery cell, active ions (such as lithium ions) repeatedly insert and extract between the positive and negative electrodes. The separator, positioned between the positive and negative electrodes, reduces the risk of short circuits while allowing active ions to pass through.

[0064] In some embodiments, the positive electrode can be a positive electrode sheet, which may include a positive electrode current collector and a positive electrode active material disposed on at least one surface of the positive electrode current collector.

[0065] As an example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive active material is disposed on either or both of the two opposite surfaces of the positive current collector.

[0066] As an example, the positive electrode current collector can be a metal foil or a composite current collector. For example, as a metal foil, it can be aluminum with a silver-plated surface, stainless steel with a silver-plated surface, stainless steel, copper, aluminum, nickel, carbon electrode, carbon, nickel, or titanium, etc. Composite current collectors can include a polymer material base layer and a metal layer. Composite current collectors can be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.).

[0067] As an example, the positive electrode active material may include at least one of the following materials: lithium phosphate, lithium transition metal oxide, and their respective modified compounds. However, this disclosure is not limited to these materials, and other conventional materials that can be used as battery positive electrode active materials may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium phosphate include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), lithium iron phosphate and carbon composites, lithium manganese phosphate (such as LiMnPO4), lithium manganese phosphate and carbon composites, lithium iron manganese phosphate, and lithium iron manganese phosphate and carbon composites. Examples of lithium transition metal oxides include, but are not limited to, lithium cobalt oxide (such as LiCoO2), lithium nickel oxide (such as LiNiO2), lithium manganese oxide (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, and lithium nickel cobalt manganese oxide (such as LiNi). 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also known as NCM) 333 LiNi 0.5 Co 0.2 Mn 0.3 O2 (also known as NCM) 523 LiNi 0.5 Co 0.25 Mn 0.25 O2 (also known as NCM) 211 LiNi 0.6 Co 0.2 Mn 0.2 O2 (also known as NCM) 622 LiNi 0.8 Co 0.1 Mn 0.1 O2 (also known as NCM) 811 ), lithium nickel cobalt aluminum oxide (such as LiNi) 0.85 Co 0.1 Al 0.05At least one of O2 and its modified compounds. Examples of lithium phosphates with an olivine structure include, but are not limited to, lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), lithium iron phosphate and carbon composites, lithium manganese phosphate (such as LiMnPO4), lithium manganese phosphate and carbon composites, lithium manganese iron phosphate, and lithium manganese iron phosphate and carbon composites.

[0068] In some embodiments, the positive electrode can be a foamed metal. The foamed metal can be foamed nickel, foamed copper, foamed aluminum, foamed alloy, or foamed carbon, etc. When foamed metal is used as the positive electrode, the surface of the foamed metal may or may not contain a positive electrode active material. As an example, lithium source material, potassium metal, or sodium metal can also be filled and / or deposited within the foamed metal, where the lithium source material is lithium metal and / or a lithium-rich material.

[0069] In some implementations, the negative electrode can be a negative electrode sheet, which may include a negative electrode current collector.

[0070] As an example, the negative electrode current collector can be a metal foil, a foamed metal, or a composite current collector. For example, as a metal foil, it can be silver-treated aluminum or stainless steel, stainless steel, copper, aluminum, nickel, carbon electrode, carbon, nickel, or titanium, etc. Foamed metal can be foamed nickel, foamed copper, foamed aluminum, foamed alloy, etc. Composite current collectors can include a polymer material base layer and a metal layer. Composite current collectors can be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.).

[0071] As an example, the negative electrode sheet may include a negative electrode current collector and a negative electrode active material disposed on at least one surface of the negative electrode current collector.

[0072] As an example, the negative electrode current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode active material is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0073] As an example, the negative electrode active material may be a negative electrode active material known in the art for use in battery cells. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate, etc. Silicon-based materials may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Tin-based materials may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. However, this disclosure is not limited to these materials, and other conventional materials that can be used as battery negative electrode active materials may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0074] In some implementations, the positive current collector can be made of aluminum, and the negative current collector can be made of copper.

[0075] In some embodiments, the separator is a separator membrane. The separator membrane can be any known porous structure separator membrane with good chemical and mechanical stability.

[0076] As an example, the material of the separator may include at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may be a single-layer film or a multi-layer composite film. When the separator is a multi-layer composite film, the materials of each layer may be the same or different. The separator may be a separate component located between the positive and negative electrodes, or it may be attached to the surfaces of the positive and negative electrodes.

[0077] In some embodiments, the separator is a solid electrolyte. The solid electrolyte is disposed between the positive and negative electrodes, serving both to transport ions and to isolate the positive and negative electrodes.

[0078] In some embodiments, the battery cell also includes an electrolyte, which acts as a conductor of ions between the positive and negative electrodes. The electrolyte can be liquid, gel-like, or solid. Liquid electrolytes include electrolyte salts and solvents.

[0079] In some embodiments, the electrolyte salt may include at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium dioxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate.

[0080] In some embodiments, the solvent may include at least one selected from ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butyl carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone. The solvent may also be an ether solvent. Ether solvents may include one or more selected from ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, 1,3-dioxolane, tetrahydrofuran, methyl tetrahydrofuran, diphenyl ether, and crown ethers.

[0081] Among them, the gel electrolyte includes a polymer as the electrolyte backbone network, combined with an ionic liquid - lithium salt.

[0082] Solid electrolytes include polymer solid electrolytes, inorganic solid electrolytes, and composite solid electrolytes.

[0083] As an example, polymer solid electrolytes can be polyether (polyoxyethylene), polysiloxane, polycarbonate, polyacrylonitrile, polyvinylidene fluoride, polymethyl methacrylate, monoionic polymers, polyionic liquids-lithium salts, cellulose, etc.

[0084] As an example, inorganic solid electrolytes may include one or more of the following: oxide solid electrolytes (crystalline perovskite, sodium superconducting ion conductor, garnet, amorphous LiPON thin film), sulfide solid electrolytes (crystalline lithium superconducting ion conductor (lithium germanium phosphate sulfide, silver sulfide germanium ore), amorphous sulfides), halide solid electrolytes, nitride solid electrolytes, and hydride solid electrolytes.

[0085] As an example, composite solid electrolytes are formed by adding inorganic solid electrolyte fillers to polymer solid electrolytes.

[0086] In some implementations, the electrode assembly is a wound structure. The positive and negative electrode sheets are wound into a wound structure.

[0087] In some implementations, the electrode assembly is a stacked structure.

[0088] As an example, multiple positive and negative electrodes can be set, and multiple positive and multiple negative electrodes can be stacked alternately.

[0089] As an example, multiple positive electrode plates can be provided, and negative electrode plates can be folded to form multiple stacked folded segments, with a positive electrode plate sandwiched between adjacent folded segments.

[0090] As an example, both the positive and negative electrode plates are folded to form multiple stacked folded segments.

[0091] As an example, multiple separators can be provided, each positioned between any adjacent positive or negative electrode plates.

[0092] As an example, the separators can be continuously arranged, either by folding or rolling between any adjacent positive or negative electrode plates.

[0093] In some embodiments, the electrode assembly can be cylindrical, flat, or polygonal, etc.

[0094] In some embodiments, the electrode assembly is provided with tabs that allow current to be drawn from the electrode assembly. The tabs include a positive tab and a negative tab.

[0095] In some embodiments, the battery cell may include a housing. The housing is used to encapsulate components such as electrode assemblies and electrolytes. The housing may be made of steel, aluminum, plastic (such as polypropylene), composite metal (such as copper-aluminum composite), or aluminum-plastic film, etc.

[0096] As an example, a battery cell can be a cylindrical battery cell, a prismatic battery cell, a pouch battery cell, or a battery cell of other shapes. Prismatic battery cells include prismatic battery cells, blade-shaped battery cells, and multi-prismatic batteries, such as hexagonal prismatic batteries.

[0097] The battery mentioned in the embodiments of this disclosure refers to a single physical module comprising one or more battery cells to provide higher voltage and capacity.

[0098] In some implementations, the battery can be a battery module, and when there are multiple battery cells, the multiple battery cells are arranged and fixed to form a battery module.

[0099] In some implementations, the battery can be a battery pack, which includes a housing and individual battery cells, with the individual battery cells or battery modules housed within the housing.

[0100] In some implementations, the housing may be part of the vehicle's chassis structure. For example, a portion of the housing may be at least a part of the vehicle's floor, or a portion of the housing may be at least a part of the vehicle's crossbeams and longitudinal beams.

[0101] In some implementations, the battery can be an energy storage device. Energy storage devices include energy storage containers, energy storage cabinets, etc.

[0102] The development of battery technology must take into account multiple design factors, such as energy density, cycle life, discharge capacity, charge-discharge rate and other performance parameters. In addition, battery reliability also needs to be considered.

[0103] To improve the reliability of individual battery cells, pressure relief components can generally be installed in the battery cells. These components can be part of the battery cell's casing or components installed on the casing. In the event of thermal runaway of the battery cell, the pressure inside the battery cell can be released through the pressure relief components.

[0104] Currently, aluminum alloy is the most commonly used material. Aluminum, an element in aluminum alloy, is a very reactive metallic element that readily reacts with oxygen at room temperature to form a dense and stable oxide film, thereby protecting the outer shell from corrosion by the external environment.

[0105] The disclosed technology involves welding pressure relief components to an aluminum casing using a welding process. However, the welded area is highly susceptible to corrosion. The reasons for this corrosion are as follows: First, the high temperatures during welding damage the oxide film on the aluminum alloy surface, rendering it ineffective. Second, changes in the microstructure of the welded area may create more active sites, causing reactions and accelerating the corrosion process. Third, the welded area typically has a heat-affected zone and penetration depth, leading to a decrease in its mechanical properties and corrosion resistance. Therefore, the welded area becomes a weak point in the casing, directly impacting battery lifespan.

[0106] To reduce the impact of welded areas on battery life, some technologies create pressure relief components by etching grooves on the casing surface to avoid welded areas. However, this casing still suffers from severe corrosion, which has become a limiting factor for further extending the service life of individual battery cells.

[0107] The applicant discovered that when aluminum elements distributed on the outer surface of the casing are exposed to air, their surface rapidly reacts with oxygen to form a dense and stable oxide film, protecting the casing from corrosion by the external environment. Aluminum elements distributed on the inner surface of the casing come into contact with the electrolyte. During normal battery operation, a stable interface is maintained between the electrolyte and the active materials (positive and / or negative electrode active materials). However, under abnormal conditions (e.g., high temperatures), the electrolyte may decompose, generating corrosive substances (such as HF). These corrosive substances can damage the oxide film on the aluminum casing, thereby corroding the aluminum casing. Particularly in the recessed areas, due to structural weaknesses, they are more susceptible to electrolyte corrosion, which becomes a limiting factor for further extending the service life of individual battery cells.

[0108] Based on the above findings, in order to balance the service life of the battery cell and its reliability during thermal runaway, this disclosure provides a battery cell including a casing. The casing includes a first wall portion, the first wall portion including a first groove, the first wall portion being configured to crack along at least a portion of the first groove when the battery cell is depressurized, the second groove being configured to guide at least a portion of a predetermined depressurization area to flip over, the material of at least the first wall portion in the casing including aluminum alloy, the mass fraction of aluminum element in the aluminum alloy being expressed as AD, AD satisfying: 0.5≤AD≤0.99, and the minimum residual thickness of the first groove along the thickness direction of the first wall portion being expressed as H, H satisfying: 0.020mm≤H≤1.000mm.

[0109] When the alloying degree (AD) of an aluminum alloy is low, the mass fraction of aluminum is low, and the probability of the electrolyte reacting with the aluminum in the alloy is low. This is beneficial to improving the resistance of the pressure relief component to electrolyte corrosion. Conversely, when the alloying degree (AD) is high, it is more conducive to the aluminum coming into contact with oxygen in the air to form a stable and dense oxide film, thereby enhancing the air corrosion resistance of the pressure relief component.

[0110] A higher minimum residual thickness H of the first groove indicates a more robust structure and enhanced corrosion resistance of the first wall, which is beneficial for extending the service life of the battery cell. However, if the minimum residual thickness H of the first groove is too high, it will make it more difficult for the battery cell to crack along at least a portion of the first groove during thermal runaway, and may even fail to meet the reliability requirements of the battery cell during thermal runaway.

[0111] Based on the above findings, this disclosure, by controlling 0.020mm ≤ H ≤ 1.000mm, helps to reduce the risk of decreased corrosion resistance of the first groove due to an excessively small minimum residual thickness H. Conversely, it helps to reduce the difficulty of opening the first groove during battery thermal runaway due to an excessively large minimum residual thickness H, thus helping the battery cell maintain its reliability during thermal runaway. Furthermore, by controlling 0.5 ≤ AD ≤ 0.99, it helps to reduce the risk of decreased electrolyte corrosion resistance of the inner surface (facing the electrolyte) of the first wall due to excessively high AD, and the risk of decreased air corrosion resistance of the outer surface (facing away from the electrolyte) of the first wall due to excessively low AD. This helps to extend the service life of the battery cell.

[0112] The battery cells described in this disclosure are applicable to batteries and electrical devices that use battery cells.

[0113] Electrical equipment can include vehicles, mobile phones, portable devices, laptops, ships, spacecraft, electric toys, and power tools, etc. Vehicles can be gasoline-powered cars, natural gas-powered cars, or new energy vehicles; new energy vehicles can be pure electric vehicles, hybrid electric vehicles, or range-extended electric vehicles, etc. Spacecraft include airplanes, rockets, space shuttles, and spacecraft, etc. Electric toys include stationary or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc. Power tools include metal cutting power tools, grinding power tools, assembly power tools, and railway power tools, such as electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact drills, concrete vibrators, and electric planers, etc. This disclosure does not impose any special limitations on the above-mentioned electrical equipment.

[0114] For ease of explanation, the following embodiments use a vehicle as an example of electrical equipment.

[0115] Please refer to Figure 1, which is a structural schematic diagram of a vehicle 1000 provided in one embodiment of this disclosure. A battery 100 is disposed inside the vehicle 1000, and the battery 100 may be located at the bottom, front, or rear of the vehicle 1000. The battery 100 can be used to power the vehicle 1000; for example, the battery 100 can serve as the operating power source for the vehicle 1000.

[0116] The vehicle 1000 may also include a controller 200 and a motor 300. The controller 200 is used to control the battery 100 to supply power to the motor 300, for example, for the power needs of the vehicle 1000 during startup, navigation and driving.

[0117] In some embodiments of this disclosure, the battery 100 can not only serve as the operating power source for the vehicle 1000, but also as the driving power source for the vehicle 1000, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle 1000.

[0118] Please refer to Figure 2, which is an exploded view of a battery 100 provided in one embodiment of this disclosure. The battery 100 includes a battery cell 10 and a housing 20, with the battery cell 10 housed within the housing 20.

[0119] The housing 20 is a component that houses the battery cell 10, providing a space for the battery cell 10. The housing 20 can adopt various structures. In some embodiments, the housing 20 may include a first part 201 and a second part 202, which overlap each other to define a space for accommodating the battery cell 10. The first part 201 and the second part 202 can have various shapes, such as cuboid or cylindrical. The first part 201 can be a hollow structure open on one side, and the second part 202 can also be a hollow structure open on one side, with the open side of the second part 202 overlapping the open side of the first part 201, thus forming a housing 20 with a accommodating space. Alternatively, the first part 201 can be a hollow structure open on one side, and the second part 202 can be a plate-like structure, with the second part 202 overlapping the open side of the first part 201, thus forming a housing 20 with a accommodating space. The first part 201 and the second part 202 can be sealed by a sealing element, which can be a sealing ring, sealant, etc.

[0120] In battery 100, there can be one or more battery cells 10. If there are multiple battery cells 10, they can be connected in series, parallel, or in a mixed manner. A mixed connection means that multiple battery cells 10 are connected in both series and parallel. Alternatively, multiple battery cells 10 can be first connected in series, parallel, or in a mixed manner to form a battery module, and then multiple battery modules can be connected in series, parallel, or in a mixed manner to form a whole, which is then housed within the housing 20. Another option is that all battery cells 10 can be directly connected in series, parallel, or in a mixed manner, and then the whole consisting of all battery cells 10 is housed within the housing 20.

[0121] Please refer to Figure 3, which is an exploded view of a battery cell 10 provided in one embodiment of this disclosure. The battery cell 10 may include a housing 1 and an electrode assembly 2, the electrode assembly 2 being housed within the housing 1.

[0122] In some embodiments, the housing 1 may include a housing 11 and an end cap 12, the housing 11 having an opening and the end cap 12 closing the opening of the housing 11.

[0123] The housing 11 is a component used to house the electrode assembly 2. The housing 11 can be a hollow structure with an opening at one end, or a hollow structure with openings at both opposite ends. The housing 11 can be in various shapes, such as cylindrical or cuboid.

[0124] End cap 12 is a component that closes the opening of housing 11 to isolate the internal environment of battery cell 10 from the external environment. End cap 12 and housing 11 together define a storage space for accommodating electrode assembly 2, electrolyte, and other components. End cap 12 can be connected to housing 11 by welding or roll sealing to close the opening of housing 11. The shape of end cap 12 can be adapted to the shape of housing 1. For example, if housing 11 is a cuboid structure, end cap 12 can be a rectangular plate structure adapted to housing 1; or if housing 11 is a cylindrical structure, end cap 12 can be a circular plate structure adapted to housing 11. The material of end cap 12 can also be various, such as copper, iron, aluminum, steel, aluminum alloy, plastic, etc. The materials of end cap 12 and housing 11 can be the same or different.

[0125] In an embodiment where the housing 11 has an opening at one end, one end cap 12 may be provided accordingly. In an embodiment where the housing 11 has openings at both opposite ends, two end caps 12 may be provided accordingly. The two end caps 12 respectively close the two openings of the housing 11, and the two end caps 12 and the housing 11 together define the receiving space.

[0126] In some embodiments, the battery cell 10 may further include electrode terminals 3, which are disposed on the housing 1 and are used for electrical connection with the tabs 21 of the electrode assembly 2 to input or output electrical energy of the battery cell 10. The electrode terminals 3 may be disposed on the housing 11 of the housing 1 or on the end cap 12 of the housing 1. The electrode terminals 3 and the tabs 21 may be directly connected, for example, by direct welding. Alternatively, the electrode terminals 3 and the tabs 21 may be indirectly connected, for example, through a current collector 4. The current collector 4 may be a metallic conductor, such as copper, iron, aluminum, steel, or aluminum alloy.

[0127] As an example, as shown in Figure 3, one end of the housing 11 has an opening, and there is one end cap 12 in the housing 1, which closes one opening of the housing 11. Two electrode terminals 3 are provided on the end cap 12, which are a positive electrode terminal and a negative electrode terminal, respectively. The end of the electrode assembly 2 facing the end cap 12 has a positive electrode tab and a negative electrode tab. The positive electrode terminal is connected to the positive electrode tab through a current collector 4, and the negative electrode terminal is connected to the negative electrode tab through another current collector 4.

[0128] In some embodiments, referring to Figure 3, the battery cell 10 may further include an insulating member 5. The insulating member 5 is a component that separates the housing 11 from the electrode assembly 2, thereby achieving insulation isolation between the housing 11 and the electrode assembly 2. The insulating member 5 is made of an insulating material, which includes, but is not limited to, plastic, rubber, etc.

[0129] As an example, the insulating member 5 covers the outer side of the electrode assembly 2 along the circumferential direction of the opening of the housing 11. The electrode assembly 2 inside the housing 1 can be one or more. If there is one electrode assembly 2, the insulating member 5 covers the periphery of the electrode assembly 2; if there are multiple electrode assemblies 2, one insulating member 5 can be provided for each electrode assembly 2, with each insulating member 5 covering the periphery of one electrode assembly 2, or multiple electrode assemblies 2 can be treated as a single unit, with the insulating member 5 covering the periphery of this single unit.

[0130] Please refer to Figures 4-7. Figure 4 is an assembly diagram of a battery cell provided according to an embodiment of the present disclosure; Figure 5 is a partial view of the housing shown in Figure 4; Figure 6 is an enlarged view of the pressure relief component in the housing shown in Figure 5; and Figure 7 is a cross-sectional view (AA) of the housing shown in Figure 5.

[0131] This disclosure provides a battery cell 10, the housing 1 including a first wall portion 13, the first wall portion 13 including a first groove 61, the first wall portion 13 being configured to crack along at least a portion of the first groove 61 when the battery cell 10 is depressurized, the material of at least the first wall portion 13 in the housing 1 including aluminum alloy, the mass fraction of aluminum element in the aluminum alloy being expressed as AD, AD satisfying: 0.5≤AD≤0.99; the minimum residual thickness of the first groove 61 along the thickness direction X of the first wall portion is expressed as H.

[0132] In this disclosure, the first wall portion 13 includes a first groove 61, which allows the first wall portion 13 to crack along at least a portion of the first groove 61 when the battery cell 10 is depressurized, thereby releasing the internal pressure of the battery cell. Furthermore, by controlling the thickness of the groove to be 0.020mm ≤ H ≤ 1.000mm, it is beneficial to reduce the risk of reduced corrosion resistance of the first groove 61 due to an excessively small minimum residual thickness H. On the other hand, it is beneficial to reduce the increased difficulty in opening the first groove 61 during battery thermal runaway due to an excessively large minimum residual thickness H, thereby helping the battery cell 10 maintain its reliability during thermal runaway.

[0133] Furthermore, by controlling AD to be 0.5 ≤ AD ≤ 0.99, it is beneficial to reduce the risk of reduced resistance to electrolyte corrosion on the inner surface (facing the electrolyte) of the first groove 61 due to excessively high AD, and to reduce the risk of reduced resistance to air corrosion on the outer surface (away from the electrolyte) of the first groove 61 due to excessively low AD. This helps to extend the service life of the battery cell 10.

[0134] In this disclosure, the housing 1 includes multiple walls that collectively define an internal receiving space for accommodating the electrode assembly 2, electrolyte, and other components, such as current collectors 4 and insulating components 5. In the housing 1, at least one end cap 12 may serve as the first wall 13, or at least one wall within the housing 11 may serve as the first wall 13.

[0135] In some embodiments, the pressure relief component 6 is disposed on the first wall portion 13, and the pressure relief component 6 includes a first groove 61 and a second groove 62.

[0136] In this application, the pressure relief component 6 is a component in the battery cell 10 used to release the internal pressure of the battery cell 10. The pressure relief component 6 can be integrally formed with the outer casing 1 (first wall portion 13). In some embodiments, the pressure relief component 6 can also be separately provided from the outer casing 1, with the pressure relief component 6 and the outer casing 1 being two separately manufactured components, and the pressure relief component 6 being installed on the first wall portion.

[0137] In this disclosure, the pressure relief component 6 is a component used to release the pressure inside the battery cell 10. When the battery cell 10 experiences thermal runaway, the pressure inside the battery cell can be released through the pressure relief component 6.

[0138] In this disclosure, the first wall portion 13 / pressure relief component 6 is made of aluminum alloy. In this disclosure, the aluminum alloy is an alloy formed by adding one or more other elements to aluminum. Compared to other metal materials, such as steel or iron, aluminum alloy can reduce the overall weight of the battery cell 10, which is very important for mobile applications such as vehicles and electronic devices because it can reduce the energy consumption of the entire system. Furthermore, aluminum alloy has good electrical and thermal conductivity, making it beneficial for heat dissipation of the battery cell 10 during operation when used as the casing material.

[0139] In some embodiments, the aluminum alloy also includes one or more of zinc, copper, iron, magnesium, manganese, silicon, chromium, titanium, and vanadium. The first wall portion 13 pressure relief component 6 made of this aluminum alloy has higher hardness, greater strength, and stronger corrosion resistance, thereby contributing to a further extension of the service life of the battery cell 10.

[0140] In this disclosure, alloying degree (AD) refers to the mass fraction of aluminum in an aluminum alloy. For the pressure relief component 6 made of aluminum alloy, the following pattern exists: when the alloying degree (AD) is low, the mass fraction of aluminum is low, and the probability of reaction between the electrolyte and the aluminum in the aluminum alloy is low. This is beneficial to improving the electrolyte corrosion resistance of the pressure relief component 6. Conversely, when the alloying degree (AD) is high, the mass fraction of aluminum in the aluminum alloy is high, which is conducive to the formation of a stable and dense oxide film by the aluminum in contact with oxygen in the air, thereby enhancing the air corrosion resistance of the pressure relief component 6.

[0141] In this disclosure, AD satisfies: 0.5 ≤ AD ≤ 0.99. For example, AD is 0.5, 0.6, 0.7, 0.8, 0.9, 0.99, or any value between two values.

[0142] In some embodiments, AD satisfies: 0.75 ≤ AD ≤ 0.95. The pressure relief component 6 / first wall portion 13 is made of an aluminum alloy with AD within the above range, which can optimize the balance between the electrolyte corrosion resistance and air corrosion resistance of the pressure relief component 6 / first wall portion 13, thereby helping to further extend the service life of the battery cell 10.

[0143] In some implementations, AD satisfies the condition: 0.75 ≤ AD ≤ 0.90. AD within this range is beneficial for further extending the service life of the battery cell 10.

[0144] In this disclosure, the alloying degree can be determined in the following manner. The sample to be tested (e.g., the first wall portion 13) can be a prepared sample or a sample obtained by disassembling the battery cell 10. The latter will be used as an example to illustrate the testing process below. Specifically, the first wall portion 13 is obtained by disassembling the battery cell 10, and the first wall portion 13 is digested with a digestion solution to obtain a sample. Energy dispersive spectroscopy (EDS) is used to detect the content of aluminum (Al) and other alloying elements (such as zinc, copper, iron, magnesium, manganese, silicon, chromium, titanium, vanadium, etc.) in the sample, and the alloying degree of the aluminum alloy is calculated based on the detection results.

[0145] In this disclosure, the first groove 61 is a pressure relief groove. When the pressure inside the battery cell 10 reaches the burst pressure of the first wall portion 13 (pressure relief component 6), the first wall portion 13 (pressure relief component 6) can crack along at least a portion of the first groove 61 to open the first wall portion 13 (pressure relief component 6). It is understood that when the battery cell 10 is depressurized, the first wall portion 13 (pressure relief component 6) can crack along the entire first groove 61 or crack along a portion of the first groove 61.

[0146] In this disclosure, the minimum residual thickness of the first groove 61 is the minimum thickness of the residual portion after the first wall portion 13 (pressure relief component 6) has the first groove 61, and this residual portion can be the bottom wall of the first groove 61. The thickness of the bottom wall of the first groove 61 can be uniform or non-uniform. If the thickness of the bottom wall of the first groove 61 is uniform, the thickness of the bottom wall of the first groove 61 is the minimum residual thickness H of the first groove 61. If the thickness of the bottom wall of the first groove 61 is non-uniform, the thickness of the thinnest part of the bottom wall of the first groove 61 is the minimum residual thickness H of the first groove 61.

[0147] In this disclosure, the minimum residual thickness H of the first groove 61 satisfies: 0.020mm ≤ H ≤ 1.000mm. For example, the minimum residual thickness H of the first groove 61 is 0.020mm, 0.040mm, 0.060mm, 0.080mm, 0.100mm, 0.200mm, 0.300mm, 0.400mm, 0.500mm, 0.600mm, 0.700mm, 0.800mm, 0.900mm, 1.000mm, or any value between two such values.

[0148] In some embodiments, 0.04mm ≤ H ≤ 0.6mm. By controlling the minimum residual thickness H of the first groove 61 within the above range, it is beneficial to further improve the corrosion resistance (resistance to electrolyte corrosion and air corrosion) of the first groove 61 and increase the pressure relief rate of the first groove 61. This is beneficial to further extend the service life of the battery cell 10 and improve the reliability of the battery cell 10 in the event of thermal runaway.

[0149] In some implementations, 0.45mm ≤ H ≤ 0.6mm. This is beneficial for further extending the service life of the battery cell 10.

[0150] In this disclosure, the minimum residual thickness H of the first groove 61 can be determined in the following manner. The sample to be tested (e.g., the first wall portion 13) can be a prepared sample or a sample obtained by disassembling the battery. The latter is used as an example to illustrate the testing process. Specifically: 1) Disassemble the battery cell 10 to obtain the first wall portion 13, which has the first groove 61. 2) If the bottom wall of the first groove 61 is uniform, take four test points on the bottom wall of the first groove 61 and measure the thickness value of the four test points in the thickness direction X of the first wall portion. Take the minimum value of the four thickness values ​​as the minimum residual thickness H of the first groove 61. If the bottom wall of the first groove 61 is not uniform, divide the bottom wall of the first groove 61 into N (N≥2) regions, and take four test points on the bottom wall of each region. Measure the thickness of each test point, select the minimum thickness as the minimum residual thickness of that region, and obtain the minimum residual thickness of N regions. Select the minimum value among the minimum residual thicknesses of the N regions as the minimum residual thickness H of the first groove 61.

[0151] In this disclosure, the electrolyte comprises at least an electrolyte salt. Exemplarily, the electrolyte salt may be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium dioxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate.

[0152] In some embodiments, the molar concentration c of the electrolyte salt satisfies: 0.5 mol / L ≤ c ≤ 1.4 mol / L. A molar concentration c within this range indicates a suitable concentration, which helps reduce the risk of decreased charge / discharge efficiency of the battery cell 10 due to excessively low concentrations. Conversely, it helps reduce corrosion of the first groove 61 in the first wall portion 13 due to excessively high concentrations. Therefore, a molar concentration c within this range allows the battery cell 10 to achieve both low corrosion performance (i.e., extended lifespan) and high charge / discharge efficiency. For example, the molar concentration c of the electrolyte salt is 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L, 1 mol / L, 1.1 mol / L, 1.2 mol / L, 1.3 mol / L, 1.4 mol / L, or any value between two of these.

[0153] In this disclosure, the molar concentration of the electrolyte salt can be tested using the following method: the sample to be tested (e.g., electrolyte) can be a prepared sample or a sample obtained by disassembling the battery. The latter is used as an example to illustrate the testing process. Specifically: the electrolyte is obtained by disassembling the battery cell 10, and the volume of the electrolyte is measured. Then, the solvent is evaporated to obtain the electrolyte salt, and the mass of the electrolyte salt is weighed. Finally, based on the mass of the electrolyte salt and the type of electrolyte salt (relative molar mass), the molar amount of the electrolyte salt can be determined. Finally, based on the molar amount of the electrolyte salt and the volume of the electrolyte, the molar concentration of the electrolyte salt can be calculated.

[0154] In some embodiments, the molar concentration c of the electrolyte salt satisfies: 0.8 mol / L ≤ c ≤ 1.2 mol / L. Having the molar concentration c of the electrolyte salt within this range helps to further reduce the risk of decreased charge / discharge efficiency of the battery cell 10 due to excessively low molar concentration of the electrolyte salt, and also helps to further reduce the corrosion effect on the first wall portion 13 (pressure relief component 6) due to excessively high molar concentration of the electrolyte salt. This helps to further balance the service life and charge / discharge efficiency of the battery cell 10.

[0155] In some embodiments, c, AD, and H satisfy the following condition: 0.25 mol / (L*mm) ≤ (c*AD) / H ≤ 69.3 mol / (L*mm). When c, AD, and H satisfy the above condition, the balance between the corrosivity (c) of the electrolyte to the first wall portion 13 (pressure relief component 6) and the corrosion resistance (AD, H) of the first wall portion 13 (pressure relief component 6) can be optimized. That is, when the above condition is met, it is beneficial to control the corrosivity of the electrolyte to the first wall portion 13 (pressure relief component 6) and enhance the corrosion resistance of the first wall portion 13 (pressure relief component 6). Through this balance control, the service life of the battery cell 10 can be extended.

[0156] For example, (c*AD) / H is 0.25mol / (L*mm), 0.3mol / (L*mm), 0.375mol / (L*mm), 0.4mol / (L*mm), 0.5mol / (L*mm), 0.6mol / (L*mm), 0.7mol / (L*mm), 0.8mol / (L*mm), 0.9mol / (L*mm), 1mol / (L*mm), 10mol / (L*mm), 20mol / (L*mm), 30mol / (L*mm), 40mol / (L*mm), 50mol / (L*mm), 60mol / (L*mm), 63.0mol / (L*mm), 66.5mol / (L*mm), 69.3mol / (L*mm), or a value between any two values. This helps to further extend the service life of the battery cell 10 and improve the pressure relief rate of the first wall portion 13 (pressure relief component 6). Further optionally, 0.375mol / (L*mm)≤(c*AD) / H≤66.5mol / (L*mm), and even more optionally, 0.375mol / (L*mm)≤(c*AD) / H≤63.0mol / (L*mm).

[0157] In some embodiments, the electrolyte further includes a solvent. Exemplarily, the solvent may be selected from at least one of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butyl carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0158] In some embodiments, the electrolyte may optionally include additives. For example, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.

[0159] In some embodiments, the first wall portion 13 further includes a second groove 62, the projection of the first groove 61 and the projection of at least one second groove 62 together defining at least one predetermined pressure relief region 63 along the thickness direction of the first wall portion 13, the second groove 62 being configured to guide at least a portion of the predetermined pressure relief region 63 to flip to open at least a portion of the predetermined pressure relief region 63, the minimum residual thickness H of the first groove 61 being less than the minimum residual thickness D of the second groove 62.

[0160] In this disclosure, the second groove 62 guides at least a portion of the predetermined pressure relief zone 63 to flip, thereby opening at least a portion of the predetermined pressure relief zone 63 for pressure relief. The second groove 62 assists the predetermined pressure relief zone 63, making it easier to flip, reducing the difficulty of flipping the predetermined pressure relief zone 63, and increasing the opening rate of the predetermined pressure relief zone 63. This rapidly reduces the internal pressure of the casing, preventing the battery cell 10 from exploding or being damaged due to excessive pressure, thereby improving the reliability of the battery cell 10 during thermal runaway. The minimum residual thickness H of the first groove 61 is less than the minimum residual thickness D of the second groove 62, making the first wall portion 13 more prone to cracking in the area where the first groove 61 is located compared to the area where the second groove 62 is located. This improves the efficiency of pressure relief, prevents the risk of damage or explosion of the battery cell 10 due to long-term pressure accumulation, and improves the reliability of the battery cell 10 during thermal runaway.

[0161] In some embodiments, along the width direction Z of the second groove, the second groove 62 includes a first groove side surface 621 and a second groove side surface 622 that are disposed opposite to each other and connected to the surface of the first wall portion 13.

[0162] In some embodiments, please continue to refer to FIG6. The first wall portion 13 (pressure relief component 6) is provided with a plurality of second grooves 62. Along the thickness direction X of the first wall portion, the projection of the first groove 61 and the projection of the plurality of second grooves 62 together define a plurality of predetermined pressure relief areas 63. Each predetermined pressure relief area 63 is provided corresponding to one or more second grooves 62.

[0163] In this embodiment, the first groove 61 and the plurality of second grooves 62 together define a plurality of predetermined pressure relief zones 63. When the battery cell 10 thermally runs away, the plurality of predetermined pressure relief zones 63 start to relieve pressure almost simultaneously, which can improve the opening rate of the predetermined pressure relief zones 63, achieve pressure relief more quickly, prevent excessive accumulation of internal pressure in the battery cell 10, and thereby further improve the reliability of the battery cell 10 during thermal runaway.

[0164] In this disclosure, along the thickness direction X of the first wall portion, the projection of the first groove 61 and the projections of the plurality of second grooves 62 together define a predetermined pressure relief area 63, which can be two, three, four, five, or more. Each predetermined pressure relief area 63 can be corresponding to at least one second groove 62, that is, each predetermined pressure relief area 63 can be corresponding to one second groove 62 or to multiple second grooves 62.

[0165] In some embodiments, along the thickness direction X of the first wall portion 13 (pressure relief component 6), the first wall portion 13 has a first surface 64 and a second surface 65 disposed opposite to each other. One of the first surface 64 and the second surface 65 is the outer surface of the first wall portion 13 (pressure relief component 6), and the other is the inner surface of the first wall portion 13 (pressure relief component 6). The outer surface of the first wall portion 13 (pressure relief component 6) faces the outside of the battery cell 10, and the inner surface of the first wall portion 13 (pressure relief component 6) faces the inside of the battery cell 10.

[0166] In some embodiments, the first groove 61 and the second groove 62 are both disposed on the same side surface of the first wall portion 13. For example, the first groove 61 and the second groove 62 are both disposed on the first surface 64, and the groove openings of the first groove 61 and the second groove 62 are both formed on the first surface 64. As another example, the first groove 61 and the second groove 62 are both disposed on the second surface 65, and the groove openings of the first groove 61 and the second groove 62 are both formed on the second surface 65.

[0167] In some embodiments, a first groove 61 is disposed on a first surface 64, and a second groove 62 is disposed on a second surface 65. The first groove 61 and the second groove 62 are respectively located on both sides of the first wall portion 13 along the thickness direction X of the first wall portion 13, so that the first groove 61 and the second groove 62 can be processed on both sides of the first wall portion 13 respectively. On the one hand, this helps to reduce the mutual influence between the first groove 61 and the second groove 62 during the processing, and on the other hand, it helps to reduce the mutual influence between the first groove 61 and the second groove 62 during pressure relief, thereby improving the reliability of pressure relief.

[0168] In some embodiments, the first surface 64 is the outer surface facing the battery cell 10, and the second surface 65 is the inner surface facing the battery cell. In this embodiment, the second groove 62 is disposed on the second surface (inner surface) of the first wall portion 13, so that when the predetermined pressure relief area 63 is flipped open outward, the two groove sides (first groove side 621 and second groove side 622) in the width direction of the second groove 62 are less likely to abut against each other, which is conducive to the rapid and complete unfolding of the predetermined pressure relief area 63, accelerating the pressure release rate, thereby reducing the internal pressure of the battery, preventing the risk of damage or explosion of the battery cell 10 due to excessive pressure, and thus further improving the reliability of the battery cell 10 in the event of thermal runaway.

[0169] In some embodiments, the first groove 61 includes multiple levels of grooves arranged sequentially along the direction from the first surface 64 to the second surface 65. Along the thickness direction X of the first wall portion, in adjacent grooves, the first-level groove furthest from the first surface 64 is located on the bottom surface of the first-level groove closest to the first surface 64. The minimum residual thickness of the first-level groove furthest from the first surface 64 is taken as the minimum residual thickness H of the first groove. In this embodiment, by setting the first groove 61 to have multiple levels of grooves arranged along the thickness direction X of the first wall portion (the direction from the first surface 64 to the second surface 65), when forming the first groove 61, each level of groove can be processed sequentially along the direction from the first surface 64 to the second surface 65, reducing the forming depth of each level of groove, reducing the forming force experienced when forming the first groove 61, reducing the risk of the first groove 61 being damaged during forming, thereby extending the service life of the battery cell 10.

[0170] For example, the first groove 61 can be a two-level groove, a three-level groove, a four-level groove, a five-level groove, etc. It can be understood that the first groove 61 is a stepped groove. Along the direction from the first surface 64 to the second surface 65, the width of each level of groove gradually decreases. As shown in Figure 7, taking a two-level groove 61 as an example, the two levels are a first-level groove 615 and a second-level groove 614. During processing, the wider first-level groove 615 can be machined first on the first surface 64, and then the narrower second-level groove 614 can be machined on the bottom surface of the first-level groove 615.

[0171] In this disclosure, the first groove 61 may include at least one groove segment, and the cross-sectional shape of the groove segment may be various, such as rectangular, trapezoidal, etc. The cross-section of the groove segment is perpendicular to the extension direction of the groove segment. The shape of the first groove 61 may be various, for example, the first groove 61 is a groove extending along an arc trajectory, or the first groove 61 includes multiple groove segments, and the multiple groove segments may form U-shaped, H-shaped, V-shaped, Y-shaped, X-shaped, T-shaped, etc.

[0172] In embodiments where the first groove 61 includes multiple groove segments, the minimum residual thickness of all groove segments can be equal, and the minimum residual thickness of any one groove segment is the minimum residual thickness H of the first groove 61; if the minimum residual thickness of at least two groove segments is not equal, the minimum residual thickness of the groove segment with the smallest minimum residual thickness is the minimum residual thickness H of the first groove 61.

[0173] In this disclosure, when the first groove 61 comprises multiple groove segments, the minimum residual thickness H of the first groove 61 can be determined in the following manner. The sample to be tested (e.g., the first wall portion 13) can be a prepared sample or a sample obtained by disassembling the battery. The latter will be used as an example to illustrate the testing process below. Specifically:

[0174] 1) Disassemble the battery cell 10 to obtain the first wall portion 13. The first wall portion 13 is provided with a first groove 61, which includes M (M>1) groove segments. Take four experimental points on the bottom wall of each groove segment.

[0175] 2) For the four experimental points of each groove segment, the following processing is performed: the thickness of each experimental point is measured, and the minimum thickness is selected as the minimum residual thickness of the groove segment. The minimum residual thickness of M groove segments is obtained, and the minimum value among the minimum residual thicknesses of M groove segments is selected as the minimum residual thickness H of the first groove 61.

[0176] In some embodiments, the first groove 61 includes a first groove segment 611, a second groove segment 612, and a third groove segment 613, with the second groove segment 612 and the third groove segment 613 arranged opposite to each other, and the first groove segment 611 connecting the second groove segment 612 and the third groove segment 613. In this embodiment, the first groove 61 has a simple structure, and the stress is more concentrated and the area is weaker at the connection between the first groove segment 611 and the second groove segment 612, making it easier to crack. This is beneficial because if the battery cell 10 cracks at the connection between the first groove segment 611 and the second groove segment 612 during thermal runaway, it can quickly crack from the first groove segment 611 and the second groove segment 612, allowing the predetermined pressure relief zone 63 to open more quickly and relieve pressure in a timely manner.

[0177] In this disclosure, the first slot segment 611 connects the second slot segment 612 and the third slot segment 613. The connection point between the second slot segment 612 and the first slot segment 611 can be located at one end of the second slot segment 612 or between its two ends. Similarly, the connection point between the third slot segment 613 and the first slot segment 611 can be located at one end of the third slot segment 613 or between its two ends. The first slot segment 611, the second slot segment 612, and the third slot segment 613 can form a U-shaped, H-shaped, or other similar structure.

[0178] In some embodiments, the connection position between the second groove segment 612 and the first groove segment 611 is offset from both ends of the second groove segment 612, and the connection position between the third groove segment 613 and the first groove segment 611 is offset from both ends of the third groove segment 613, so that a predetermined pressure relief zone 63 is formed on both sides of the first groove segment 611.

[0179] In this embodiment, the connection position between the second groove segment 612 and the first groove segment 611 is offset from both ends of the second groove segment 612. During the pressure relief process, after the first wall portion 13 (pressure relief component 6) cracks at the connection position between the second groove segment 612 and the first groove segment 611, the crack can propagate along the second groove segment 612 towards both ends, shortening the time for the first wall portion 13 (pressure relief component 6) to crack along the second groove segment 612. Similarly, the connection position between the third groove segment 613 and the first groove segment 611 is offset from both ends of the third groove segment 613. During the pressure relief process, after the first wall portion 13 (pressure relief component 6) cracks at the connection position between the third groove segment 613 and the first groove segment 611, the crack can propagate along the third groove segment 613 towards both ends, shortening the time for the first wall portion 13 (pressure relief component 6) to crack along the third groove segment 613. In this structure, the first groove segment 611 of the first groove 61 is located between two predetermined pressure relief zones 63. After the first wall portion 13 (pressure relief component 6) splits along the first groove segment 611, the two predetermined pressure relief zones 63 can open in a split manner to relieve pressure when the battery cell 10 is depressurized, so that the two predetermined pressure relief zones 63 can open quickly, which is beneficial to improving the pressure relief rate of the battery cell 10.

[0180] In some embodiments, the first groove 61 and the second groove 62 can be directly formed into the first wall portion 13, forming an integral first wall portion 13 with higher reliability, eliminating the need for the installation process of the pressure relief component 6, and thus having better economic efficiency. Furthermore, avoiding welded areas helps improve the corrosion resistance of the first wall portion 13.

[0181] In some embodiments, a first groove 61 is stamped onto the first wall portion 13; and / or, a second groove 62 is stamped onto the first wall portion 13. In this embodiment, if the first groove 61 is stamped onto the first wall portion 13, on the one hand, the forming method of the first groove 61 is simple, which helps to reduce the production cost of the battery cell 10; on the other hand, it avoids the appearance of welding areas, thereby improving the corrosion resistance of the first wall portion 13 (pressure relief component 6). If the second groove 62 is stamped onto the first wall portion 13, the forming method of the second groove 62 is simple, which helps to reduce the production cost of the battery cell 10; on the other hand, it avoids the appearance of welding areas, thereby improving the corrosion resistance of the first wall portion 13 (pressure relief component 6).

[0182] In some embodiments, referring to Figures 8-12, the housing 11 has an opening at at least one end. End caps 12 correspond one-to-one with the openings, and the end caps 12 close the openings. At least one end cap 12 is a first wall portion 13; and / or, at least one wall portion in the housing 11 is a first wall portion 13.

[0183] In this disclosure, the housing 11 may have only one opening, for example, the housing 11 may have an opening at only one end; the housing 11 may also have multiple openings, for example, the housing 11 may have openings at both opposite ends. The number of end caps 12 is the same as the number of openings in the housing 11. It is understood that if the housing 11 has only one opening, there is one end cap 12; if the housing 11 has two openings, there are two end caps 12. One or more end caps 12 may be the first wall portion 13, or one or more walls in the housing 11 may be the first wall portion 13. In the embodiment where the housing 11 has an opening at one end, the positive electrode terminal and the negative electrode terminal may be disposed on the end cap 12, and the positive electrode tab and the negative electrode tab may be formed on the end of the electrode assembly 2 facing the end cap 12, so as to facilitate electrical connection with the positive electrode terminal and the negative electrode terminal, respectively. In an embodiment where openings are formed at both opposite ends of the housing 11, the positive electrode terminal can be disposed on one end cap 12, and the negative electrode terminal can be disposed on the other end cap 12. The positive and negative tabs can be formed at opposite ends of the electrode assembly 2, so as to facilitate electrical connection between the positive tab and the positive electrode terminal and between the negative tab and the negative electrode terminal.

[0184] In some embodiments, please refer to FIG8, which is an exploded view of the housing 1 provided in one embodiment of the present disclosure. The housing 11 has an opening at one end and includes a first wall portion 13. The first wall portion 13 (pressure relief component 6) is integrally formed with the first wall portion 13. The first wall portion 13 can be entirely used as the pressure relief component 6, or a portion of the first wall portion 13 can be used as the pressure relief component 6, thus achieving integral forming of the pressure relief component 6 with the first wall portion 13. A first groove 61 and a second groove 62 are both provided on the first wall portion 13.

[0185] In some embodiments, please refer to FIG9, which is an exploded view of the housing 1 provided in another embodiment of the present disclosure. The housing 11 has an opening at one end and includes a first wall portion 13. The first wall portion 13 includes a first wall portion body 132 and a pressure relief component 6. The first wall portion body 132 is provided with a pressure relief hole 131. The pressure relief component 6 can be installed in the pressure relief hole 131 by welding, riveting, bonding or other means, and the pressure relief component 6 covers the pressure relief hole 131.

[0186] In the embodiments shown in Figures 8 and 9, at least one wall portion of the housing 11 is a first wall portion 13, which enables the housing 11 to have a pressure relief function. When the battery cell 10 is depressurized, the emissions discharged from inside the battery cell 10 are less likely to affect the external components outside the end cover 12, reducing the risk of damage to the external components by the emissions. The external components may be busbars connected to the electrode terminals 3, temperature detection components, voltage detection components, etc. The emissions include, but are not limited to: electrolyte, dissolved or split positive and negative electrode plates, fragments of separators, high-temperature and high-pressure gases generated by the reaction, flames, etc.

[0187] In some embodiments, referring to FIG10, FIG10 is an exploded view of the housing 1 provided in another embodiment of the present disclosure. The end cap 12 is a first wall portion 13, and the pressure relief component 6 is integrally formed with the first wall portion 13.

[0188] In some embodiments, referring to FIG11, FIG11 is an exploded view of the housing 1 provided in another embodiment of the present disclosure. The end cap 12 is a first wall portion 13, and the pressure relief component 6 is installed in the pressure relief hole 131 and covers the pressure relief hole 131.

[0189] In the embodiments of Figures 10 and 11, at least one end cap 12 is a first wall portion 13, and it is easy to form the first groove 61 and the second groove 62 on the end cap 12.

[0190] In some embodiments, referring to Figures 8 and 9, the housing 11 has an opening at only one end, and the wall portion of the housing 11 opposite to the end cap 12 is a first wall portion 13. As an example, the housing 11 is cuboid in shape and also includes four side walls surrounding the first wall portion 13. These four side walls, together with the first wall portion 13, define the internal space of the housing 11. In this embodiment, the housing 11 has an opening at one end, simplifying the overall structure of the battery cell 10. The first wall portion 13, being the wall portion of the housing 11 opposite to the end cap 12, allows for directional pressure relief from the bottom of the housing 11.

[0191] In some embodiments, please refer to FIG12, which is an exploded view of the housing 1 provided in some further embodiments of the present disclosure. Openings are formed at both opposite ends of the housing 11, and at least one wall portion of the housing 11 is a first wall portion 13. In this embodiment, the housing 11 has a structure with openings at both opposite ends, allowing the electrode assembly 2 to be assembled into the housing 11 through any one of the openings. This reduces the assembly difficulty of the battery cell 10 and improves the assembly quality of the battery cell 10. This structure allows the housing 11 to be made longer (with openings at both ends in the length direction), which is beneficial for increasing the capacity of the battery cell 10.

[0192] In some embodiments, the downward-facing wall of the outer casing 1 along the direction of gravity is designated as the first wall 12. The first wall 12 is the downward-facing wall of the outer casing 1 along the direction of gravity, which is the thickness direction of the first wall. Because the first wall 12 is the downward-facing wall of the outer casing 1 along the direction of gravity, the high-pressure gas generated when the battery cell 10 experiences thermal runaway will be rapidly discharged with the aid of gravity, thereby improving the reliability of the battery cell 10 under thermal runaway conditions. This is particularly important when the battery cell is used in a vehicle, as the battery cell 10 generates a large amount of high-temperature gas during thermal runaway. The pressure relief component 6 is located on the downward-facing wall of the outer casing 1, which helps ensure that this high-temperature gas is discharged from the bottom of the vehicle, thus preventing it from directly contacting the vehicle's internal structure or passenger compartment and ensuring passenger safety.

[0193] In this disclosure, "gravity direction downward" refers to the direction in which gravity points, and specifically in the context of vehicles, it refers to the direction from the top of the vehicle to the chassis.

[0194] This disclosure also provides a battery cell 10, which includes a housing 1 and an electrode assembly 2. The electrode assembly 2 has a positive electrode tab and a negative electrode tab, and is housed within the housing 1. The housing 1 is rectangular and includes a shell 11 and an end cap 12. One end of the shell 11 forms an opening, and the end cap 12 closes the opening. The end cap 12 is provided with a positive electrode terminal and a negative electrode terminal. The positive electrode terminal is electrically connected to the positive electrode tab through a current collector 4, and the negative electrode terminal is electrically connected to the negative electrode tab through another current collector 4.

[0195] The housing 11 is made of aluminum alloy. The wall of the housing 11 opposite to the end cap 12 is a pressure relief component 6. The pressure relief component 6 is a rectangular wall. The outer surface of the pressure relief component 6 is provided with a first groove 61, and the inner surface of the pressure relief component 6 is provided with two second grooves 62. Along the width direction of the pressure relief component 6, the first groove 61 is located between the two second grooves 62, and the second grooves 62 are spaced apart from the first groove 61. The minimum residual thickness H of the first groove 61 is less than the minimum residual thickness D of the second groove 62. The first groove 61 has an H-shaped structure. The first groove 61 is a stepped groove, including two levels of grooves. Along the thickness direction X of the first wall portion, the projections of the first groove segment 611, the second groove segment 612, the extension line of the second groove segment 612, the third groove segment 613, the extension line of the third groove segment 613, and the two second grooves 62 together enclose two predetermined pressure relief zones 63. The two predetermined pressure relief zones 63 are located on both sides of the first groove segment 611. The pressure relief component 6 is configured to be able to crack along at least a portion of the first groove 61 when the battery cell 10 is depressurized. The second groove 62 is configured to be able to guide at least a portion of the predetermined pressure relief zone 63 to flip over, so as to open at least a portion of the predetermined pressure relief zone 63. The minimum residual thickness of the first groove is denoted as H, and 0.020mm≤H≤1.000mm. The mass fraction of aluminum in the aluminum alloy is denoted as AD, and 0.5≤AD≤0.99. The molar concentration of the electrolyte salt is denoted as c, and 0.5mol / L≤c≤1.4mol / L. Among them, AD, c and H satisfy: 0.25mol / (L*mm)≤(c*AD) / H≤69.3mol / (L*mm).

[0196] Example

[0197] Example 1

[0198] I. Preparation of battery cells

[0199] 1. Preparation of positive electrode sheet

[0200] LiNi, the positive electrode active material 0.7 Co 0.1 Mn 0.1 A positive electrode slurry is prepared in N-methylpyrrolidone (NMP) using O2, conductive agent Super P, and binder polyvinylidene fluoride (PVDF). The solid content of the positive electrode slurry is 50 wt%, and the solid component is LiNi. 0.7 Co 0.1 Mn 0.1 The mass ratio of O2, Super P, and PVDF is 8:1:1. The positive electrode slurry is coated on the upper and lower surfaces of the current collector aluminum foil and dried at 85°C. After cold pressing, the foil is trimmed, cut into sheets, and slit. Then, it is dried under vacuum at 85°C for 4 hours to produce the positive electrode sheet.

[0201] 2. Preparation of negative electrode sheet

[0202] Graphite, conductive agent Super P, thickener carboxymethyl cellulose (CMC), and binder styrene-butadiene rubber (SBR) are mixed evenly in deionized water to prepare a negative electrode slurry. The solid content of the negative electrode slurry is 30 wt%, and the mass ratio of graphite, Super P, CMC, and binder styrene-butadiene rubber (SBR) in the solid components is 88:7:3:2. The negative electrode slurry is coated on the upper and lower surfaces of the current collector copper foil and dried at 85°C. Then, it is cold-pressed, trimmed, cut into sheets, and slit. Finally, it is dried under vacuum at 120°C for 12 hours to prepare the negative electrode sheet.

[0203] 3. Preparation of electrolyte

[0204] In an argon atmosphere glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), thoroughly dried electrolyte salt LiPF6 was dissolved in a mixed solvent (the mixed solvent included ethylene carbonate (EC) and diethyl carbonate (DEC), and ethylene carbonate (EC) and diethyl carbonate (DEC) were mixed in a mass ratio of 50:50) and mixed evenly to obtain an electrolyte with a LiPF6 concentration of 1 mol / L.

[0205] 4. Isolation components

[0206] A 16μm polyethylene film was used as the separator.

[0207] 5. Preparation of battery cells

[0208] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator positioned between the positive and negative electrodes to isolate them. The electrode assembly is then wound up and placed inside the casing. The electrolyte prepared above is injected into the dried casing, followed by encapsulation, settling, formation, shaping, and capacity testing to complete the preparation of the battery cell.

[0209] Referring to Figure 5, the outer shell has a cuboid structure. The shell 11 of the outer shell 1 has an opening at only one end. Both the shell 11 and the end cap 12 are made of aluminum alloy. The end cap 12 is the first wall portion 13. The pressure relief component 6 is integrally formed with the first wall portion 13. The first wall portion 13 is a rectangular wall portion. The first groove 61 has an H-shaped structure (including a first groove segment 611, a second groove segment 612, and a third groove segment 613), and it is a two-stage groove (a first-stage groove 615 and a second-stage groove 614, where the first-stage groove 615 is located on the outer surface of the first wall portion 13, and the second-stage groove 614 is located on the bottom surface of the first-stage groove 615). The second groove 62 is located on the inner surface of the first wall portion 13. Along the width direction of the first wall portion 13, the first groove 61 is located between the two second grooves 62.

[0210] II. Performance Parameter Testing

[0211] 1. Method for measuring the number of cycle fatigue cycles of a single battery cell (10)

[0212] 1) Prepare a special test fixture. Specifically, the fixture includes three 10mm steel plates (first steel plate, second steel plate, and third steel plate). Each steel plate can completely cover the large surface of the battery cell 10 (the outer surface of the housing 11 perpendicular to the width direction of the first wall 13). The first steel plate and the third steel plate are located at both ends of the fixture and are fixed by bolts. The second steel plate is located between the first steel plate and the third steel plate, and the second steel plate is constrained by the guide rail. The second steel plate can only move along the thickness direction of the second steel plate.

[0213] 2) Install the battery cell 10 between the first steel plate and the second steel plate. Place a support structure between the large surface of one side of the battery cell 10 and the first steel plate, and between the large surface of the other side and the second steel plate. The support structure can be a heat insulation pad or a water cooling plate (consistent with the material / structure between two adjacent battery cells 10 in the actual battery 100). The support structure can be compressed to provide expansion space for the battery cell 10 during charge-discharge cycle aging. The large surface of the battery cell 10 is in contact with the support structure, the first steel plate is in contact with the corresponding support structure, the second steel plate is in contact with the corresponding support structure, and a pressure sensor is provided between the second steel plate and the third steel plate.

[0214] 3) Adjust the position of the second steel plate by adjusting the preload of the bolts, observe the pressure sensor, so that the initial compressive force on the battery cell 10 is 2000N, and connect the positive electrode terminal and positive electrode terminal of the battery cell 10 to the charging and discharging equipment.

[0215] 4) Place the battery cell 10 and the fixture in a constant temperature environment of 25±2℃, and start the test after the battery cell 10 reaches temperature equilibrium.

[0216] 5) The test procedure shall be performed in accordance with the "Standard Cycle Life" section 6.4 of "GBT31484-2015 Requirements and Test Methods for Cycle Life of Power Batteries for Electric Vehicles", and the test cycle cutoff condition shall be changed to "the test shall be stopped when the first groove 61 is provided on the first wall 13 and the damage occurs".

[0217] Specifically, test according to the following steps:

[0218] a) Charge at a current of 0.33C to the charging cutoff voltage, then charge at a constant voltage of 4.25V until the current is 0.04C;

[0219] b) Let it sit for 30 minutes;

[0220] c) Discharge at a current of 0.33C until the discharge cutoff voltage;

[0221] d) Repeat steps a) to c) until the first groove 61 of the first wall 13 is damaged and the test is stopped.

[0222] The test process involves continuously observing the area where the first groove 61 is located on the first wall 13 of the battery cell 10 until that area breaks and leaks liquid. The number of cycles is recorded as the cycle fatigue number of the battery cell 10. The more cycle fatigue numbers the battery cell 10 has, the lower the probability of leakage due to gas generation during long-term use, and the longer its service life.

[0223] 2. Test method for thermal runaway of a single battery cell

[0224] 1. Select a heating plate according to the size of the battery cell 10. The size of the heating plate should cover the largest surface of the battery cell 10 as much as possible (coverage area ≥ 60%).

[0225] 2. Before testing, charge the battery cell 10 to 100% SOC and place the battery cell 10 in a constant temperature environment of 25±2℃.

[0226] 3. Sensor arrangement:

[0227] 1) Arrangement of temperature sensing wires: Apply a layer of Teflon to the center area of ​​each of the two large surfaces of the battery cell 10, arrange the temperature sensing wires on top of the Teflon, and then apply another layer of Teflon.

[0228] 2) Voltage sampling line arrangement: Apply a layer of Teflon to the positive electrode terminal of the battery cell 10, the positive electrode terminal and the outer casing 1, arrange the voltage sampling line on top of the Teflon, and then apply another layer of Teflon.

[0229] 3) Air tube arrangement: Drill a hole in the first wall portion 13 of the battery cell 10. Along the length direction of the first wall portion 13, the drilling position is located at the midpoint between the first groove 61 and the side of the housing 11 (the outer surface of the wall portion of the housing 11 adjacent to the first wall portion 13 along the length direction of the first wall portion 13). Insert the air tube into the hole and seal it. Connect the air tube to the air pressure sensor.

[0230] 4) Connect the temperature sensing wire, voltage sampling wire, and barometric pressure sensor to the data acquisition instrument to collect and analyze data in real time. The data acquisition frequency of the data acquisition instrument is ≤0.1s.

[0231] 4. Assembly fixture: The fixture completely covers the large surface of the battery cell 10 (the outer surface of the housing 11 in the width direction perpendicular to the first wall 13), with a clamping force of 3000N. The arrangement sequence of the fixture, heating plate and battery cell 10 is: fixture + heating plate + battery cell 10 + fixture.

[0232] 5. Test: Turn on the data acquisition device to collect temperature, voltage and air pressure data, and then turn on the heating plate at 500W to heat the battery cell 10 until the battery cell 10 thermally runs away.

[0233] 6. Obtain the pressure holding time of battery cell 10: Determine the thermal runaway time and valve opening time based on the temperature, voltage and air pressure data collected by the data acquisition instrument, and obtain the pressure holding time of battery cell 10 according to the formula: pressure holding time = valve opening time - thermal runaway time.

[0234] Thermal runaway determination criteria: a) The triggering object generates a voltage drop, and the voltage drops to more than 25% of the initial voltage;

[0235] b) The temperature at the detection point reaches the maximum operating temperature specified by the manufacturer;

[0236] c) The temperature rise rate at the detection point, dT / dt, is ≥1℃ / s and lasts for more than 3s.

[0237] When a) and c) or b) and c) occur, thermal runaway is determined, and the moment of thermal runaway is identified.

[0238] Valve opening time determination: When the air pressure drops by more than 25%, it can be determined that the valve has opened (at least part of the first wall 13 cracks along the first groove 61), and the moment when the air pressure begins to drop is the valve opening time. Both the valve opening time and the thermal runaway time can be obtained from the data acquisition unit.

[0239] 3. Testing the minimum residual thickness H of the first groove 61;

[0240] 1) Using the end cap 12 (first wall portion 13) as the sample to be tested, take four measurement points on the bottom surface of the second-level groove 614 of the first groove section 611;

[0241] 2) Test the thickness of each measurement point along the thickness direction X of the first wall to obtain 4 thickness values;

[0242] 3) Take the minimum value among the four thickness values ​​as the minimum residual thickness of the first groove segment 611.

[0243] 4) Then measure the minimum residual thickness of the second groove segment 612 and the minimum residual thickness of the third groove segment 613 in sequence.

[0244] The minimum residual thickness among the minimum residual thicknesses of the first groove segment 611, the second groove segment 612, and the third groove segment 613 is selected as the minimum residual thickness H of the first groove. The test results are recorded in Table 1.

[0245] Examples 2 to 13

[0246] Examples 2 to 13 were prepared using the same method as Example 1 to prepare battery cells 10. The only difference was that the alloy strength AD of the aluminum alloy used in the pressure relief component 6 (end cap 12), the molar concentration c of the electrolyte salt, and the minimum residual thickness H of the first groove were as shown in Table 1.

[0247] The performance parameters were tested in the same manner as in Example 1, and the test results are recorded in Table 1.

[0248] The performance parameters were tested in the same manner as in Example 1, and the test results are recorded in Table 1.

[0249] Comparative Examples 1 to 4

[0250] Comparative Examples 1 to 4 were prepared using the same method as Example 1, with the only difference being that the alloy strength AD of the aluminum alloy used in the pressure relief component 6 (end cap 12), the molar concentration c of the electrolyte salt, and the minimum residual thickness H of the first groove are shown in Table 1.

[0251] The performance parameters were tested in the same manner as in Example 1, and the test results are recorded in Table 1.

[0252] Table 1

[0253] Compared to Comparative Examples 1 and 2, when the aluminum alloy used for the pressure relief component 6 in Examples 1 to 13 has an AD of 0.5 to 0.99 and the minimum residual thickness of the first groove is 0.020 mm to 1.000 mm, the cycle fatigue number of the battery cells 10 in Examples 1 to 13 is significantly increased, and the air-holding time of the battery cells in Examples 1 to 13 is all within 5 seconds. The battery cells 10 in Examples 1 to 13 can also maintain their reliability during thermal runaway.

[0254] Although the battery cells of Comparative Examples 2 and 4 can also maintain a high number of cycle fatigue cycles, the air-holding time of the battery cells of Comparative Examples 2 and 4 is greater than 5 seconds. In the event of thermal runaway, the battery cells cannot release pressure in time, and the battery cells 10 of Comparative Examples 2 and 4 cannot maintain their reliability in the event of thermal runaway.

[0255] A comparison of Examples 1 and 2 with Examples 3 to 13 shows that when the AD of the aluminum alloy used in the pressure relief component 6 is between 0.75 and 0.95, it is beneficial to further improve the reliability and service life of the battery cell 10 or improve the reliability during thermal runaway.

[0256] A comparison of Examples 3 and 4 to 13 shows that when the AD of the aluminum alloy used in the pressure relief component 6 is between 0.75 and 0.9, it is beneficial to further improve the reliability and service life of the battery cell 10.

[0257] A comparison of Examples 5 and Examples 6 to 8 shows that when the minimum residual thickness of the first groove is between 0.04 mm and 0.6 mm, it is beneficial to further improve the reliability and service life of the battery cell 10.

[0258] A comparison of Examples 6 with Examples 7 and 8 shows that when the minimum residual thickness of the first groove is between 0.45 mm and 0.6 mm, it is beneficial to further improve the reliability and service life of the battery cell 10.

[0259] Compared with Example 12, the battery cells of Examples 8 to 11 contain more electrolyte salt, which helps to reduce the risk of decreased charge and discharge efficiency of battery cell 10 due to excessively low molar concentration of electrolyte salt.

[0260] Compared with Example 13, the battery cells of Examples 8 to 11 contain more electrolyte salt. When the concentration c of the electrolyte salt is between 0.5 mol / L and 1.4 mol / L, it is beneficial to further improve the reliability and service life of the battery cell 10. In particular, when c is between 0.8 mol / L and 1.2 mol / L, it is beneficial to further balance the reliability, service life and charge / discharge efficiency of the battery cell 10.

[0261] It should be noted that the above embodiments are only used to illustrate the technical solutions of this disclosure, and not to limit them. Although this disclosure has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this disclosure, and they should all be covered within the scope of the claims and specification of this disclosure. In particular, as long as there is no structural conflict, the various technical features mentioned in the various embodiments can be combined in any way. This disclosure is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A battery cell, wherein, include: The housing includes a first wall portion, the first wall portion including a first groove, the first wall portion being configured to crack along at least a portion of the first groove when the battery cell is depressurized, the material of at least the first wall portion in the housing including aluminum alloy, the mass fraction of aluminum element in the aluminum alloy being expressed as AD, the AD satisfying: 0.5≤AD≤0.99, and the minimum residual thickness of the first groove along the thickness direction of the first wall portion being expressed as H, the H satisfying: 0.020mm≤H≤1.000mm.

2. The battery cell according to claim 1, wherein, The AD satisfies: 0.75≤AD≤0.

95.

3. The battery cell according to claim 1 or 2, wherein, The AD satisfies: 0.75≤AD≤0.

90.

4. The battery cell according to any one of claims 1 to 3, wherein, The aluminum alloy also includes one or more of the following elements: zinc, copper, iron, magnesium, manganese, silicon, chromium, titanium, and vanadium.

5. The battery cell according to any one of claims 1 to 4, wherein, The value of H satisfies: 0.04mm ≤ H ≤ 0.6mm.

6. The battery cell according to any one of claims 1 to 5, wherein, The value of H satisfies: 0.45mm≤H≤0.6mm.

7. The battery cell according to any one of claims 1 to 6, wherein, The outer casing has a receiving cavity, and the battery cell further includes an electrolyte. The electrolyte is contained within the receiving cavity and is in contact with the first wall. The electrolyte includes at least an electrolyte salt, and the molar concentration of the electrolyte salt relative to the electrolyte is expressed as c, where c satisfies: 0.5 mol / L ≤ c ≤ 1.4 mol / L.

8. The battery cell according to claim 7, wherein, The c satisfies: 0.8 mol / L ≤ c ≤ 1.2 mol / L.

9. The battery cell according to any one of claims 1 to 8, wherein, The first wall portion further includes a second groove, and along the thickness direction of the first wall portion, the projection of the first groove and the projection of at least one second groove together define at least one predetermined pressure relief area, the second groove being configured to guide at least a portion of the predetermined pressure relief area to flip, and the minimum residual thickness of the first groove being less than the minimum residual thickness of the second groove.

10. The battery cell according to claim 9, wherein, The first wall portion is provided with a plurality of second grooves. Along the thickness direction of the first wall portion, the projection of the first groove and the projection of the plurality of second grooves together define a plurality of predetermined pressure relief zones. Each predetermined pressure relief zone is provided corresponding to one or more second grooves.

11. The battery cell according to claim 9 or 10, wherein, Along the thickness direction of the first wall portion, the first wall portion has a first surface and a second surface opposite to each other, the first groove is disposed on the first surface, and the second groove is disposed on the second surface.

12. The battery cell according to claim 11, wherein, The first surface is the outer surface facing the battery cell, and the second surface is the inner surface facing the battery cell.

13. The battery cell according to claim 11 or 12, wherein, The first groove includes multiple levels of grooves arranged sequentially along the direction from the first surface to the second surface. Along the thickness direction of the first wall portion, in two adjacent levels of grooves, the first level groove furthest from the first surface is disposed on the bottom surface of the first level groove closest to the first surface. The minimum residual thickness of the first level groove furthest from the first surface in the multiple levels of grooves is the minimum residual thickness of the first groove.

14. The battery cell according to any one of claims 1 to 13, wherein, The first groove includes a first groove segment, a second groove segment, and a third groove segment; The second slot segment and the third slot segment are arranged opposite to each other, and the first slot segment connects the second slot segment and the third slot segment.

15. The battery cell according to claim 14, wherein, The connection position of the second groove segment to the first groove segment is offset from both ends of the second groove segment, and the connection position of the third groove segment to the first groove segment is offset from both ends of the third groove segment, so that the predetermined pressure relief zone is formed on both sides of the first groove segment.

16. The battery cell according to any one of claims 1 to 15, wherein, The first groove is formed by stamping on the first wall portion.

17. The battery cell according to any one of claims 1 to 16, wherein, The outer casing includes: The shell has an opening at at least one end; End caps, each corresponding to one of the openings, close the openings; Wherein, at least one of the end caps is the first wall portion, and / or, at least one wall portion of the housing is the first wall portion.

18. The battery cell according to claim 17, wherein, The opening is formed at only one end of the housing, and the wall portion of the housing opposite to the end cap is the first wall portion.

19. The battery cell according to claim 17, wherein, The openings are formed at both opposite ends of the housing, and at least one wall portion of the housing is the first wall portion.

20. The battery cell according to any one of claims 1 to 19, wherein, The wall portion of the outer shell that points downwards along the direction of gravity is the first wall portion.

21. A battery, wherein, Includes the battery cell according to any one of claims 1 to 20.

22. An electrical appliance, wherein, The battery cell includes any one of claims 1 to 21, the battery cell being used to provide electrical energy to the electrical equipment.

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