Battery cell and method for producing the same, battery, electric device

Abstract

A battery cell, its preparation method, battery, and power-consuming device are disclosed. The battery cell includes a positive electrode sheet, which comprises a positive current collector and a positive active material layer and a coating disposed on at least one surface of the positive current collector. The positive active material layer is disposed on the current collector, and the coating is disposed on the positive active material layer. The positive active material layer comprises sulfate ions, and the coating comprises a metal salt. The solubility product K of the inorganic salt formed by the sulfate ions and the metal cation of the metal salt is... sp ≤10 ‑6 The technical solution of this application is beneficial to reducing the sulfate ion content in the electrolyte of battery cells and improving the cycle performance of battery cells.

Description

Technical Field

[0001] This application relates to the field of batteries, and more specifically, to a battery cell and its preparation method, a battery, and an electrical device. Background Technology

[0002] With the rapid development of society and economy, energy and environment have become an increasingly important focus of attention. In recent years, battery technology has been studied and developed in depth and has been widely used in energy storage, electronic products and other fields.

[0003] During the preparation of the positive electrode active material for battery cells, sulfate ions are introduced. After dissolving from the positive electrode active material, these sulfate ions may undergo side reactions with substances in the electrolyte, reducing the cycle performance of the battery cell. Therefore, how to reduce the sulfate ion content in the electrolyte and improve the cycle performance of the battery cell has become an urgent technical problem to be solved. Summary of the Invention

[0004] This application is made in view of the above-mentioned technical problems, and its purpose is to provide a battery cell and its preparation method, battery, and power device, which can reduce the sulfate ion content in the electrolyte of the battery cell and improve the cycle performance of the battery cell.

[0005] In a first aspect, a battery cell is provided, comprising: a positive electrode sheet, the positive electrode sheet including a positive current collector and a positive active material layer and a coating disposed on at least one surface of the positive current collector, the positive active material layer being disposed on the positive current collector, and the coating being disposed on the positive active material layer; wherein the positive active material layer includes sulfate ions, the coating includes a metal salt, and the solubility product K of the inorganic salt formed by the sulfate ions and the metal cation of the metal salt is... sp ≤10 -6 .

[0006] In the embodiments of this application, the coating of the positive electrode sheet includes a metal salt. After sulfate ions dissolve from the positive electrode active material, the metal salt can react with the sulfate ions, and its metal cations can react with the sulfate ions to form an inorganic salt precipitate, reducing the migration of sulfate ions into the electrolyte and preventing side reactions with ions in the electrolyte to generate sulfate byproducts or gases, thereby improving the cycle performance of the battery cell. Therefore, the technical solution of this application is beneficial for reducing the sulfate ion content in the electrolyte and improving the cycle performance of the battery cell.

[0007] In one possible implementation, the metal salt includes at least one of barium salt and calcium salt.

[0008] In this embodiment, barium or calcium salts can react with sulfate ions to form barium sulfate (BaSO4) or calcium sulfate (CaSO4). Barium sulfate (BaSO4) or calcium sulfate (CaSO4) has very low solubility and is unlikely to redissolve, reducing the possibility of sulfate ions redissolving and thus lowering the sulfate ion content in the electrolyte of the battery cell. Furthermore, barium or calcium salts have a low probability of reacting with other ions in the positive electrode active material or electrolyte to form precipitates, reducing the consumption of other ions. The deposition of barium sulfate (BaSO4) or calcium sulfate (CaSO4) as precipitates on the surface and / or coating of the positive electrode active material layer can inhibit lithium dendrite growth, further improving the cycle performance of the battery cell.

[0009] In one possible implementation, the molar ratio n1:n2 of the sulfate ions to the metal cations of the metal salt satisfies: 0.2 ≤ n1:n2 ≤ 2.

[0010] In the embodiments of this application, the above-mentioned molar ratio range is beneficial to improving the reaction efficiency of metal salts and sulfate ions, and reducing the sulfate ion content in the electrolyte of the battery cell. When n1:n2≥0.2, there are sufficient metal cations and sulfate ions in the metal salt to form an inorganic salt with low solubility, so that sulfate ions are deposited on the surface of the positive electrode active material or in the coating, reducing the migration of sulfate ions into the electrolyte; when n1:n2≤2, sulfate ions and metal cations have a suitable molar ratio, avoiding excessive metal anions dissolving in the electrolyte and reducing the migration efficiency of other ions in the electrolyte.

[0011] In one possible implementation, based on the total mass of the active material layer, the mass content 'a' of the metal salt satisfies: 0.08% ≤ a ≤ 0.8%.

[0012] In the embodiments of this application, the metal salt has a suitable mass content, which is beneficial to reducing the sulfate ion concentration in the electrolyte and improving the cycle performance of the battery cell. When the mass content of the metal salt a ≥ 0.08%, the sulfate ions can completely form inorganic salts with the metal cations in the metal salt, reducing the migration of sulfate ions into the electrolyte, lowering the sulfate ion content in the electrolyte, and improving the cycle performance of the battery cell. When the mass content of the metal salt a ≤ 0.8%, it avoids excessively high metal salt content, which would reduce the volume ratio of the positive electrode active material and lower the energy density of the battery cell.

[0013] In one possible implementation, 0.12% ≤ a ≤ 0.6%.

[0014] In the embodiments of this application, the metal salt has a suitable mass content, which is beneficial to reduce the concentration of sulfate ions in the electrolyte and improve the cycle performance of the battery cell.

[0015] In one possible implementation, the anion of the metal salt includes at least one element selected from nitrogen and chlorine.

[0016] In the embodiments of this application, the metal salt in the coating may partially dissolve in the electrolyte, which also includes free metal anions. By selecting anions containing the aforementioned elements, it is beneficial to improve the ionic conductivity in the electrolyte, increase the ion migration efficiency, and thereby improve the cycle performance of the battery cell.

[0017] In a second aspect, a method for preparing a battery cell is provided, comprising: providing a positive electrode sheet to prepare a battery cell; wherein providing the positive electrode sheet comprises: coating a positive active material onto at least one side surface of a positive current collector to form a positive active material layer, wherein the positive active material layer comprises sulfate ions; spraying a metal salt onto the surface of the active material layer to form a coating to obtain the positive electrode sheet, wherein the solubility product K of the inorganic salt formed by the sulfate ions and the metal cation of the metal salt is... sp ≤10 -6 .

[0018] The battery cell obtained by the above preparation method has a coating of metal salt in the positive electrode sheet. After the sulfate ions in the positive electrode active material dissolve, the metal salt can react with the sulfate ions. Its metal cations can react with the sulfate ions to form inorganic salt precipitates, reducing the migration of sulfate ions into the electrolyte and the side reactions with ions in the electrolyte to generate sulfate by-products or gases, thereby improving the cycle performance of the battery cell.

[0019] In one possible implementation, the thickness d of the coating satisfies: 1μm≤d≤10μm.

[0020] In the embodiments of this application, the coating has a suitable thickness, which can maintain good ionic conductivity and reduce the sulfate ion content in the electrolyte. When d ≥ 1 μm, it can avoid the phenomenon that the coating thickness is too low, resulting in uneven distribution of metal salts and migration of some sulfate ions into the electrolyte. When d ≤ 10 μm, the coating has a suitable thickness, which maintains good ionic conductivity when the cations in the metal salt and the sulfate ions dissolved in the positive electrode active material form inorganic salts, avoiding excessive dissolution of metal salts in the electrolyte or increasing the ion transport path, thereby improving the cycle performance of the battery cell.

[0021] In one possible implementation, 2μm≤d≤7μm.

[0022] In the embodiments of this application, the coating has a suitable thickness, which can maintain good ionic conductivity and reduce the sulfate ion content in the electrolyte.

[0023] Thirdly, a battery is provided, the battery comprising a battery cell as in the first aspect and any possible implementation thereof, and / or a battery cell as in the second aspect and any possible implementation thereof.

[0024] Fourthly, an electrical device is provided, the electrical device comprising a battery as described in the third aspect and any possible implementation thereof. Attached Figure Description

[0025] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments of this application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on the drawings without creative effort.

[0026] Figure 1 This is a schematic diagram of the positive electrode sheet according to an embodiment of this application;

[0027] Figure 2 This is a schematic diagram of a method for preparing a battery cell according to an embodiment of this application;

[0028] Figure 3 This is a schematic diagram of a battery cell according to an embodiment of this application;

[0029] Figure 4 This is a schematic diagram of a battery according to an embodiment of this application;

[0030] Figure 5 This is a schematic diagram of an electrical device according to an embodiment of this application;

[0031] Figure 6 This is a schematic diagram of an electrical device in another embodiment of this application. Detailed Implementation

[0032] The following detailed description, with appropriate reference to the accompanying drawings, discloses embodiments of the positive electrode material, positive electrode sheet, sodium-ion battery, and power application device of this application. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided for the purpose of enabling those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0033] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0034] In the description of this application, it should be noted that, unless otherwise stated, "a plurality of" means two or more; the terms "upper," "lower," "left," "right," "inner," "outer," etc., indicating orientation or positional relationships are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on this application. Furthermore, the terms "first," "second," "third," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0035] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0036] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0037] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0038] Unless otherwise specified, the following terms have the following meanings. Any undefined terms have their technically accepted meanings.

[0039] If mentioned, "metal salt" refers to an inorganic compound composed of a metal cation and an acid radical anion. Examples include alkali metal salts and transition metal salts.

[0040] As mentioned, the "solubility product" refers to the product of the ion concentrations of the solute when a sparingly soluble (or slightly soluble) salt dissolves in a saturated solution. The solubility product is a constant that depends only on temperature; typically, K0... sp Smaller substances are more difficult to dissolve. For example, the solubility product (K product) of calcium sulfate (CaSO4) at 25°C is... sp The value is 2.4 × 10^ -5 The solubility product (K) of barium sulfate (BaSO4) at 25°C sp The value is 1.1 × 10^ -10 .

[0041] Typically, a battery cell includes a positive electrode, a negative electrode, an electrolyte, and a separator. During the charging and discharging process, active ions move back and forth between the positive and negative electrodes, inserting and extracting. The electrolyte acts as a conductor between the positive and negative electrodes. The separator, located between the positive and negative electrodes, primarily prevents short circuits while allowing active ions to pass through.

[0042] The positive electrode active material is one of the key factors affecting battery development. During the preparation of the positive electrode active material for battery cells, sulfate ions are introduced. These ions can form stable compounds with metal ions in the positive electrode active material, which helps enhance the structural stability of the material. However, after dissolving from the positive electrode active material, sulfate ions may migrate into the electrolyte, reacting with substances in the electrolyte and reducing the cycle performance of the battery cell. For example, sulfate ions dissolved in the electrolyte may combine with other ions to form sulfate byproducts, such as sodium sulfate (Na₂SO₄), thereby reducing the ionic conductivity of the electrolyte. Furthermore, the generated sulfate byproducts may migrate between the positive and negative electrodes, reacting chemically with the active materials to generate gases, leading to capacity decay and reduced cycle performance of the battery cell.

[0043] In some processing methods, to reduce the sulfate ion content in the positive electrode active material, the material can be continuously washed with water during preparation to remove any sulfate impurities that may be present. However, washing consumes water resources, and the wastewater after washing requires proper treatment, leading to increased production costs. Furthermore, the material surface may be corroded during washing, especially for certain metal oxide materials, potentially damaging their surface passivation layer and reducing the performance of the positive electrode active material. For example, a protective cobalt oxide layer may form on the surface of lithium cobalt oxide (LiCoO2) positive electrode active material, but under continuous washing conditions, this oxide layer may be damaged, reducing battery performance.

[0044] In other treatment methods, the solubility of certain sulfates can be controlled by adjusting the pH of the washing solution, but strict pH control is required. For example, for some layered ternary materials, changes in pH may cause them to transform from a layered structure to a spinel structure or other unstable structures, reducing the electrochemical performance of the battery cells.

[0045] In view of this, this application provides a battery cell, its preparation method, a battery, and an electrical device. The battery cell includes a positive electrode sheet, which includes a positive current collector and a positive active material layer and a coating disposed on at least one side of the positive current collector. The positive active material layer is disposed on the positive current collector, and the coating is disposed on the positive active material layer. The positive active material layer includes sulfate ions, and the coating includes a metal salt. After the sulfate ions in the positive active material dissolve, the metal salt can react with the sulfate ions, and its metal cation can react with the sulfate ions to form an inorganic salt precipitate, reducing the migration of sulfate ions into the electrolyte and avoiding side reactions between sulfate ions and ions in the electrolyte to generate sulfate byproducts or gases, thereby reducing the sulfate ion content in the electrolyte and improving the cycle performance of the battery cell. The technical solution of this application is beneficial for reducing the sulfate ion content in the electrolyte and improving the cycle performance of the battery cell.

[0046] [Positive electrode plate]

[0047] Figure 1 This is a schematic diagram of a positive electrode sheet according to an embodiment of this application. For example, in conjunction with... Figure 1 As shown, the positive electrode 1 includes a positive current collector and a positive active material layer and a coating disposed on at least one side surface of the current collector. The positive active material layer is disposed on the positive current collector, and the coating is disposed on the positive active material layer. The positive active material layer includes sulfate ions, and the coating includes a metal salt. The solubility product K of the inorganic salt formed by the sulfate ions and the metal cation of the metal salt is... sp ≤10 -6 .

[0048] The positive electrode current collector 50 has two opposing sides along its own thickness direction. The positive electrode active material layer 51 is disposed on one or both of the two opposing surfaces of the positive electrode current collector 50. The coating 52 is disposed on the surface of the positive electrode active material layer 51 away from the positive electrode current collector 50.

[0049] As one example, the positive electrode active material layer 51 is disposed on one side surface of the positive electrode current collector 50. As another example, the positive electrode active material layer 51 is disposed on both sides surface of the positive electrode current collector 50.

[0050] In the above embodiments, the coating of the positive electrode sheet includes a metal salt. After the sulfate ions in the positive electrode active material dissolve, the metal salt can react with the sulfate ions. Its metal cations can react with the sulfate ions to form inorganic salt precipitates, reducing the migration of sulfate ions into the electrolyte and causing side reactions with ions in the electrolyte to generate sulfate by-products or gases, thereby improving the cycle performance of the battery cell.

[0051] Optionally, the positive current collector can be a metal foil or a composite current collector. For example, aluminum foil can be used as the metal foil. The composite current collector may include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector can be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0052] In some embodiments, the metal salt includes at least one of barium salt and calcium salt.

[0053] In the above embodiments, barium or calcium salts can react with sulfate ions to form barium sulfate (BaSO4) or calcium sulfate (CaSO4). Barium sulfate (BaSO4) or calcium sulfate (CaSO4) has very low solubility and almost never dissolves again, reducing the possibility of sulfate ions redissolving and thus lowering the sulfate ion content in the electrolyte of the battery cell. Furthermore, barium or calcium salts have a low probability of reacting with other ions in the positive electrode active material or electrolyte to form precipitates, reducing the consumption of other ions. The deposition of barium sulfate (BaSO4) or calcium sulfate (CaSO4) in the form of precipitates on the surface and / or coating of the positive electrode active material layer can inhibit the growth of lithium dendrites, further improving the cycle performance of the battery cell.

[0054] In some embodiments, the molar ratio n1:n2 of sulfate ions to the metal cations of the metal salt satisfies: 0.2 ≤ n1:n2 ≤ 2.

[0055] Specifically, n1:n2 can be 0.2, 0.4, 0.6, 0.8, 1.0, 1.2, 1.4, 1.6, 1.8, 2.0, or any value within the range obtained by any combination of the above two values.

[0056] The aforementioned molar ratio range is beneficial for improving the reaction efficiency between metal salts and sulfate ions, and reducing the sulfate ion content in the electrolyte of the battery cell. When n1:n2≥0.2, there are enough metal cations in the metal salt to react with sulfate ions, causing sulfate ions to be deposited on the surface of the positive electrode active material or in the coating, reducing the migration of sulfate ions into the electrolyte. When n1:n2≤2, the sulfate ions and metal cations have a suitable molar ratio, avoiding excessive metal anions dissolving in the electrolyte and reducing the migration efficiency of other ions in the electrolyte.

[0057] In some embodiments, based on the total mass of the active material layer, the mass content 'a' of the metal salt satisfies: 0.08% ≤ a ≤ 0.8%.

[0058] Specifically, 'a' can be 0.08%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, or any value within the range obtained by combining any two of the above values.

[0059] In the above embodiments, the metal salt has a suitable mass content, which is beneficial for reducing the sulfate ion concentration in the electrolyte and improving the cycle performance of the battery cell. When the mass content of the metal salt a ≥ 0.08%, the sulfate ions can react completely with the metal salt, reducing the migration of sulfate ions into the electrolyte, lowering the sulfate ion content in the electrolyte, and improving the cycle performance of the battery cell. When the mass content of the metal salt a ≤ 0.8%, it avoids excessively high metal salt content, which would reduce the volume ratio of the positive electrode active material and lower the energy density of the battery cell.

[0060] In some embodiments, 0.1% ≤ a ≤ 0.6%.

[0061] In the above embodiments, the metal salt has a suitable mass content, which is beneficial to reduce the concentration of sulfate ions in the electrolyte and improve the cycle performance of the battery cell.

[0062] In some embodiments, the anion of the metal salt includes at least one element selected from nitrogen and chlorine.

[0063] The metal salts in the coating may partially dissolve in the electrolyte, which also contains free metal anions. By selecting anions containing the aforementioned elements, it is beneficial to improve the ionic conductivity of the electrolyte, increase ion migration efficiency, and inhibit the formation or growth of lithium dendrites, thereby improving the cycle performance of the battery cell.

[0064] In some embodiments, the positive electrode active material layer includes a positive electrode active material. Optionally, the positive electrode active material may include positive electrode active materials known in the art for use in batteries. As an example, the positive electrode active material may include at least one of the following materials: lithium phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds. However, this application is not limited to these materials, and other conventional materials that can be used as positive electrode active materials for batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides may include, but are not limited to, lithium cobalt oxides (such as LiCoO2), lithium nickel oxides (such as LiNiO2), lithium manganese oxides (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, and lithium nickel cobalt manganese oxides (such as LiNi). 1 / 3Co 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 0.15 Al 0.05 At 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.

[0065] In some embodiments, the positive electrode active material layer may optionally include a binder. As an example, the binder may include at least one selected from polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0066] In some embodiments, the positive electrode active material layer may optionally include a conductive agent. As an example, the conductive agent may include at least one selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0067] In some embodiments, the positive electrode sheet can be prepared by dispersing the components used to prepare the positive electrode sheet, such as the positive active material, conductive agent, binder, and any other components, in a solvent (e.g., NMP) to form a positive electrode slurry 1; dispersing a metal salt in a solvent (e.g., NMP) to form a positive electrode slurry 2; coating the positive electrode slurry 1 onto a positive current collector, and after drying, cold pressing, and other processes, forming a positive active material layer on the positive current collector; then spraying the positive electrode slurry 2 onto the positive active material layer; and finally drying to obtain the positive electrode sheet. It should be understood that the cold pressing process can also be performed after spraying the positive electrode slurry 2 and drying.

[0068] In some embodiments, the dispersion method may include at least one of mechanical stirring, ultrasonic dispersion, and ball milling, which is beneficial to obtaining a uniformly distributed metal salt dispersion.

[0069] In some embodiments, the spraying method may include at least one of air spraying, ultrasonic spraying, atomized spraying, and electrostatic spraying, which is beneficial to obtaining a uniform coating, so that the metal salt reacts as much as possible with the sulfate ions dissolved from various positions of the positive electrode active material layer, thereby reducing the sulfate ion content in the electrolyte.

[0070] [Negative electrode plate]

[0071] In some embodiments, the negative electrode sheet may include a negative current collector and a negative electrode film layer disposed on at least one surface of the negative current collector, the negative electrode film layer including a negative electrode active material.

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

[0073] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0074] In some embodiments, the negative electrode active material may be a negative electrode active material known in the art for use in batteries. 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. The silicon-based material may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. However, this application is not limited to these materials, and other conventional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0075] In some embodiments, the negative electrode film layer may optionally include an adhesive. The adhesive may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0076] In some embodiments, the negative electrode film may optionally include a conductive agent. The conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0077] In some embodiments, the negative electrode film may optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0078] In some embodiments, the negative electrode sheet can be prepared by dispersing the above-mentioned components for preparing the negative electrode sheet, such as negative electrode active material, conductive agent, binder and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry onto the negative electrode current collector, and then obtaining the negative electrode sheet after drying, cold pressing and other processes.

[0079] [Electrolytes]

[0080] The electrolyte acts as a conductor of ions between the positive and negative electrodes. This application does not impose specific restrictions on the type of electrolyte; it can be selected according to requirements. For example, the electrolyte can be liquid, gel, or entirely solid.

[0081] In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0082] For lithium-ion battery cells or lithium metal battery cells, the electrolyte salt may include one or more 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.

[0083] For lithium-ion battery cells or lithium metal battery cells, the solvent may include one or more of the following: 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.

[0084] For sodium-ion battery cells or sodium metal battery cells, the electrolyte salt may include at least one of NaPF6, NaBF4, NaN(SO2F)2, NaClO4, NaAsF6, NaB(C2O4)2, NaBF2(C2O4), NaN(SO2RF)2, and NaN(SO2F)(SO2RF), where RF includes C b F 2b+1 b is an integer from 1 to 10; optionally, the electrolyte salt includes at least one of NaPF6, NaN(SO2F)2, and NaBF2(C2O4); optionally, b is an integer from 1 to 3; optionally, RF includes at least one of CF3, C2F5, and CF2CF2CF3.

[0085] For sodium-ion battery cells or sodium metal battery cells, the solvent may include 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, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, diethyl sulfone, 1,3-dioxolane, tetrahydrofuran, ethylene glycol dimethyl ether, and acetonitrile; optionally, the solvent may include at least one of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, and butyl carbonate.

[0086] 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.

[0087] [Preparation methods for battery cells]

[0088] Figure 2 This is a schematic diagram illustrating a method for preparing a single battery cell according to an embodiment of this application. Figure 2 As shown, the method 200 for preparing a single battery cell includes the following steps.

[0089] Step 210: Provide a positive electrode sheet to prepare a battery cell.

[0090] Providing a positive electrode sheet includes: coating a positive electrode active material onto at least one side surface of a positive electrode current collector to form a positive electrode active material layer, wherein the positive electrode active material layer includes sulfate ions; spraying a metal salt onto the surface of the positive electrode active material layer to form a coating, thereby obtaining a positive electrode sheet 1, wherein the solubility product K of the inorganic salt formed by the sulfate ions and the metal cations of the metal salt is... sp ≤10 -6 .

[0091] In the process of preparing the positive electrode sheet, binders, conductive agents and solvents can be added separately, and the positive electrode active material can be obtained after mixing.

[0092] In some embodiments, after step 210, the positive electrode sheet, negative electrode sheet, and separator can be prepared into an electrode assembly by winding or stacking, and then the electrode assembly is placed into a housing to prepare a battery cell.

[0093] In some embodiments, the coating thickness d satisfies: 1μm≤d≤10μm.

[0094] Specifically, d can be 1μm, 2μm, 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, or any value within the range obtained by any combination of the above two values.

[0095] In the above embodiments, the coating has a suitable thickness, which can maintain good ionic conductivity and reduce the sulfate ion content in the electrolyte. When d ≥ 1 μm, it can avoid the phenomenon that the coating thickness is too low, resulting in uneven distribution of metal salts and migration of some sulfate ions into the electrolyte. When d ≤ 10 μm, the coating has a suitable thickness, which maintains good ionic conductivity when the metal salt reacts with the sulfate ions dissolved in the positive electrode active material, avoiding excessive dissolution of metal salts in the electrolyte or increasing the ion transport path, thereby improving the cycle performance of the battery cell.

[0096] In some embodiments, 2μm≤d≤7μm.

[0097] In the above embodiments, the coating has a suitable thickness, which can maintain good ionic conductivity and reduce the sulfate ion content in the electrolyte.

[0098] In the battery cell preparation method of this application embodiment, the coating of the positive electrode sheet includes a metal salt. After sulfate ions dissolve from the positive electrode active material, the metal salt can react with the sulfate ions, and its metal cations can react with the sulfate ions to form an inorganic salt precipitate, reducing the migration of sulfate ions into the electrolyte and preventing side reactions with ions in the electrolyte to generate sulfate byproducts or gases, thereby improving the cycle performance of the battery cell. Therefore, the technical solution of this application is beneficial for reducing the sulfate ion content in the electrolyte and improving the cycle performance of the battery cell.

[0099] [Battery cell]

[0100] Figure 3 This is a schematic diagram of a battery cell according to an embodiment of this application. For example, such as... Figure 3 As shown, the battery cell 3 is a square battery cell. The battery cell 3 includes a housing 31, an end cap assembly 32, and an electrode assembly 33 disposed in the housing 31.

[0101] The housing 31 may include a base plate and side plates connected to the base plate, the base plate and side plates forming a receiving cavity. The housing 31 has an opening communicating with the receiving cavity, and an end cap assembly 32 can be placed over the opening to close the receiving cavity. A positive electrode sheet, a negative electrode sheet, and a separator can be formed into an electrode assembly 33 by a winding process or a stacking process. The electrode assembly 33 is encapsulated within the receiving cavity. Electrolyte is immersed in the electrode assembly 33. The number of electrode assemblies 33 contained in a single battery cell 3 can be one or more, which can be selected by those skilled in the art according to specific practical needs.

[0102] The electrode assembly 33 can be made from a positive electrode, a negative electrode, and a separator through a winding process or a stacking process.

[0103] End cap assembly 32 includes electrode terminals 322, such as Figure 2 As shown, the end cap assembly 32 includes two electrode terminals 322, one of which is a positive electrode terminal and the other is a negative electrode terminal.

[0104] The battery cell 3 also includes a current collector 34, which is used to connect the tab 331 of the electrode assembly 33 and the electrode terminal 322. For example, in the case where the electrode 1 in this embodiment is a positive electrode, one current collector 34 is used to connect the tab of the positive electrode and the positive electrode terminal, and another current collector 34 is used to connect the tab of the negative electrode and the negative electrode terminal.

[0105] In some embodiments, the battery cell 3 includes an electrode assembly 33, which includes an electrode assembly body 330 and a tab 331 extending from the electrode assembly body 330.

[0106] In some embodiments, the battery cell 3 can be assembled into a battery module, and the number of battery cells 3 contained in the battery module can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery module.

[0107] [Battery]

[0108] In some embodiments, the battery may include an outer packaging. This outer packaging may be used to encapsulate the electrode assembly and electrolyte described above.

[0109] In some implementations, the battery's outer packaging can be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The battery's outer packaging can also be a soft pack, such as a pouch. The soft pack can be made of plastic, such as polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0110] In some embodiments, the batteries can be assembled into a battery module, and the number of batteries contained in the battery module can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery module.

[0111] Figure 4 Battery 4 is used as an example. (See reference...) Figure 4 In battery 4, multiple battery cells 3 can be arranged sequentially along the length of battery 4. Of course, they can also be arranged in any other manner. Furthermore, these multiple battery cells 3 can be fixed in place using fasteners.

[0112] Optionally, the battery 4 may also include a housing with a receiving space in which multiple battery cells 3 are housed.

[0113] Battery cells 3 can be directly assembled into battery 4, or they can be first assembled into battery modules, and then multiple battery modules can be assembled into battery 4.

[0114] In some embodiments, the batteries described above can also be assembled into battery modules / battery packs. The number of battery modules contained in a battery pack can be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0115] [Electrical appliances]

[0116] This application also provides an electrical device, which includes at least one of the battery, battery module, or battery pack provided in this application. The battery, battery module, or battery pack can be used as a power source for the electrical device or as an energy storage unit of the electrical device. The electrical device may include, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0117] As an electrical device, a secondary battery, battery module, or battery pack can be selected according to its usage requirements.

[0118] Figure 5 Here is an example of an electrical device 5. This electrical device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. To meet the high power and high energy density requirements of this electrical device, a battery pack or battery module can be used.

[0119] Another example device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can be powered by a battery.

[0120] Figure 6 This is a schematic diagram of an electrical device according to another embodiment of this application. Figure 6 As shown, this application provides an electrical device, which is an energy storage device 7, and the energy storage device 7 may include multiple batteries 4. The energy storage device 7 can be applied to a power storage station to store and release electrical energy.

[0121] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0122] [Examples and Comparative Examples]

[0123] Example 1

[0124] (1) Preparation of positive electrode sheet

[0125] Lithium iron phosphate (LiFePO4), carbon black (COP), and polyvinylidene fluoride (PVDF) (PVDF) (co-active material) were mixed in a mass ratio of 97:1:2 and then added to N-methylpyrrolidone (NMP) solvent. The mixture was stirred thoroughly to form LiFePO4 slurry 1. LiFePO4 slurry 1 was coated onto aluminum foil (current collector), and after drying and cold pressing, a LiFePO4 active material layer was obtained. Based on the mass of the LiFePO4 active layer, 0.4% barium nitrate (BaNO3) was added to N-methyl-2-pyrrolidone (NMP) solvent and dissolved by stirring to obtain a uniformly distributed dispersion, which is LiFePO4 slurry 2. LiFePO4 slurry 2 was sprayed onto the surface of the LiFePO4 active material layer by air spraying, and after drying and rolling, a LiFePO4 electrode sheet was obtained. The molar ratio of barium ions to sulfate ions, n1:n2, was 1:1.

[0126] (2) Preparation of negative electrode sheet

[0127] Artificial graphite (anode active material), carbon black (conductive agent), and styrene-butadiene rubber (SBR) (binder) are dissolved in deionized water at a mass ratio of 97:1:1.1. After thorough mixing, a negative electrode slurry is prepared. The negative electrode slurry is coated onto copper foil (anode current collector), and then dried, cold-pressed, and slit to obtain the negative electrode sheet.

[0128] (3) Preparation of the separating membrane

[0129] A polyethylene film with a thickness of 10 μm was used as the separator.

[0130] (4) Preparation of electrolyte

[0131] At 25°C, ethylene carbonate (EC), diethyl carbonate (DEC), and dimethyl carbonate (DMC) were mixed in a volume ratio of 1:1:1 to obtain a mixed solvent. Then, fully dried lithium salt (LiPF6) was dissolved in the above mixed solvent at a ratio of 1 mol / L to obtain an electrolyte.

[0132] (5) Preparation of battery cells

[0133] The positive electrode sheet, separator, and negative electrode sheet are stacked, wound, and hot-pressed in sequence to obtain an electrode assembly. The electrode assembly is placed in an outer packaging, and the electrolyte prepared above is added. After encapsulation, standing, formation, aging and other processes, a battery cell is obtained.

[0134] Example 2

[0135] Compared with Example 1, in Example 2, the metal salt is barium chloride and the metal anion is chloride ion.

[0136] Example 3

[0137] Compared with Example 1, in Example 3, the metal salt is calcium nitrate and the metal cation is calcium ion.

[0138] Example 4

[0139] Compared with Example 3, in Example 4, the metal salt is calcium chloride and the metal anion is chloride ion.

[0140] Examples 5-9

[0141] Compared with Example 1, in Examples 5-9, n1:n2 are 0.2, 0.3, 0.8, 1.5, and 2, respectively.

[0142] Example 10

[0143] Compared to Example 1, in Example 16, the positive electrode active material is LiNi. 0.5 Co 0.2 Mn 0.3 O2.

[0144] Comparative Example 1

[0145] Compared to Example 1, the positive electrode sheet of Comparative Example 1 has no coating.

[0146] Table 1. Product parameters and performance parameters of the examples and comparative examples.

[0147]

[0148]

[0149] In Table 1, “K” sp “n1:n2” represents the solubility product constant of the inorganic salt, “n1:n2” represents the molar ratio of sulfate ions in the positive electrode active material layer to metal cations in the coating, “a” represents the mass content of the metal salt, and “d” represents the thickness of the coating in the positive electrode sheet.

[0150] Examples 1-10 and Comparative Example 1 and their test results are explained below:

[0151] In conjunction with Examples 1-10 and Comparative Example 1, the K of inorganic salts sp Satisfy 3.2×10 -7 ~1.1×10 -10 In Comparative Example 1, the retention rate after 600 cycles was 90.2%. In Examples 1-10, the retention rate after 600 cycles ranged from a maximum of 92.4% to a minimum of 91%. This was achieved by providing a coating containing metal salt in the positive electrode sheet. The solubility product K of the inorganic salt formed by the sulfate ions in the positive electrode active material layer and the metal cations of the metal salt increased. sp ≤10 -6 This helps reduce the migration of sulfate ions into the electrolyte, which can lead to side reactions with ions in the electrolyte, generating sulfate byproducts or gases, thus improving the cycle performance of the battery cells.

[0152] In conjunction with Examples 1-4 and Comparative Example 1, by setting the metal salt to barium or calcium salt, the 600-cycle retention rate of the battery cell increased from 90.2% in Comparative Example 1 to 92.1%, 91.6%, 91.5%, and 91.4%, respectively. This is because barium or calcium salt can form barium sulfate (BaSO4) or calcium sulfate (CaSO4) with sulfate ions, which have very low solubility, thereby reducing the sulfate ion content in the electrolyte of the battery cell and improving the cycle performance of the battery cell.

[0153] By setting the anion element of the metal salt to nitrogen or chloride, the metal salt exists in the form of nitrate ions or chloride ions. The metal salt may partially dissolve in the electrolyte, which may contain free nitrate ions or chloride ions. This is beneficial to improving the ionic conductivity of the electrolyte and improving the cycle performance of the battery cell.

[0154] Referring to Examples 1, 5-9, and Comparative Example 1, by setting the molar ratio of sulfate ions to metal cations in the positive electrode active material layer (n1:n2) to be 0.2–2, the mass content of the metal salt (a) to be 0.08%–0.8%, and the coating thickness to be 1 μm–10 μm, the cycle retention rates of the battery cells after 600 cycles were 92.1%, 91%, 91%, 91.5%, 92.4%, and 94%, respectively. This ensures that the metal salt contains sufficient metal cations and sulfate ions to form an inorganic salt with extremely low solubility, which is deposited on the surface of the positive electrode active material or in the coating. This reduces the migration of sulfate ions into the electrolyte and avoids excessive metal anions dissolving in the electrolyte, thus reducing the migration efficiency of other ions in the electrolyte and improving the cycle performance of the battery cells.

[0155] Increasing the molar ratio n1:n2 of sulfate ions to metal cations in the positive electrode active material layer, with a metal salt mass content a of 0.12–0.6 in the positive electrode sheet and a coating thickness of 2–7 μm, allows sulfate ions to completely form inorganic salts with the metal cations in the metal salt. The coating's appropriate thickness maintains good ionic conductivity when the cations in the metal salt form inorganic salts with the sulfate ions dissolved from the positive electrode active material, preventing excessive dissolution of the metal salt in the electrolyte or increasing the ion transport path, thus improving the cycle performance of the battery cell.

[0156] It should be understood that when the molar ratio of sulfate ions to metal cations of the metal salt in the positive electrode active material layer changes, the mass content of the metal salt will change, and the thickness of the coating will also change accordingly. For example, when the molar ratio increases, the mass content of the metal salt increases, and the coating thickness increases accordingly.

[0157] The following is a brief description of the testing methods for the physicochemical and performance parameters involved in the embodiments of this application. It should be understood that the following testing methods are only examples, and other testing methods known in the art can also be used for testing.

[0158] 1. Component testing of the positive electrode active material layer and coating

[0159] The components of the positive electrode active material layer and coating can be detected by any means possible in the art. For example, the components in the positive electrode active material layer and coating can be detected by methods such as XRD, AES, and XPS.

[0160] The following explanation uses XRD as an example: Place an appropriate amount of the sample to be tested in the sample slot of a glass slide and press it into a pellet. Then place the sample on the sample holder of the XRD diffractometer and close the sample chamber door. Set the detection parameters on the computer software, such as the scanning angle range (5°~90°) and scanning rate (0.02° / min~10° / min). Then start the test. After the test is completed, the measured data can be compared with the standard cards in Jade. Based on the position, intensity, and elemental characteristics of the three strongest peaks, determine the substances present in the sample. Test the types of inorganic salts in the coating; based on the types of inorganic salts, determine the K of the inorganic salts. sp (Solubility product constant).

[0161] 2. Detection of sulfate ions in the positive electrode active material layer

[0162] The mass of sulfate ions in the active material layer can be detected by measuring the sulfur content in the positive electrode active material layer.

[0163] The sulfur (S) content in the active material layer was tested according to the national standards EPA6010D-2018 and JY / T0567-2020, using inductively coupled plasma atomic emission spectrometry (ICP-AES). As an example, 0.5g of the prepared positive electrode active layer material was scraped into a test tube, 10mL of aqua regia was added, and the mixture was microwave-digested for 20min. Then, 1mL of the sample was diluted to 100mL for testing. Based on the collected spectral data, qualitative analysis of S was performed to determine the presence of S in the sample; quantitative analysis was also performed to determine the S content based on the intensity of the characteristic spectral lines of S.

[0164] 3. Capacity retention test

[0165] At 45℃, the prepared battery cell is charged to 3.8V with a constant current of 1C, then charged to 0.05C with a constant voltage of 3.8V, rested for 5 minutes, and then discharged to 2.0V with 1C. The resulting discharge capacity is recorded as the initial capacity C0. The above steps are repeated for the same battery, and the discharge capacity Cn of the battery after the nth cycle is recorded. The battery capacity retention rate after the nth cycle is: Pn=(Cn / C0)×100%. The difference in cycle performance can be reflected by the battery capacity retention rate after 600 cycles.

[0166] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A battery cell, characterized in that, include: A positive electrode sheet, comprising a positive current collector and a positive active material layer and a coating disposed on at least one surface of the positive current collector, wherein the positive active material layer is disposed on the positive current collector, and the coating is disposed on the positive active material layer; wherein the positive active material layer comprises sulfate ions, the coating comprises a metal salt, and the solubility product Ksp of the inorganic salt formed by the sulfate ions and the metal cation of the metal salt is ≤10. -6 .

2. The battery cell according to claim 1, characterized in that, The metal salt includes at least one of barium salt and calcium salt.

3. The battery cell according to claim 1 or 2, characterized in that, The molar ratio n1:n2 of the sulfate ion to the metal cation of the metal salt satisfies: 0.2≤n1:n2≤2.

4. The battery cell according to any one of claims 1-3, characterized in that, Based on the total mass of the positive electrode active material layer, the mass content 'a' of the metal salt satisfies: 0.08% ≤ a ≤ 0.8%.

5. The battery cell according to claim 4, characterized in that, 0.1％≤a≤0.6％。 6. The battery cell according to any one of claims 1-5, characterized in that, The anion of the metal salt includes at least one element selected from nitrogen and chlorine.

7. A method for preparing a single battery cell, characterized in that, include: Provide positive electrode sheets to prepare battery cells; The positive electrode sheet provided includes: A positive electrode active material is coated on at least one side surface of a positive electrode current collector to form a positive electrode active material layer, wherein the positive electrode active material layer includes sulfate ions; A metal salt is sprayed onto the surface of the positive electrode active material layer to form a coating, thereby obtaining the positive electrode sheet. The solubility product K of the inorganic salt formed by the sulfate ions and the metal cations of the metal salt is... sp ≤10 -6 .

8. The preparation method according to claim 7, characterized in that, The thickness d of the coating satisfies: 1μm≤d≤10μm.

9. The preparation method according to claim 8, characterized in that, 2μm≤d≤7μm.

10. A battery, characterized in that, The battery comprises a battery cell as described in any one of claims 1-6, and / or a battery cell obtained by the preparation method as described in any one of claims 7-9.

11. An electrical appliance, characterized in that, Includes the battery as described in claim 10, the battery being used to provide electrical energy to the electrical device.

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