Coated lithium-rich metal oxide material, preparation method thereof, method for determining coating layer in coated lithium-rich metal oxide material, positive electrode sheet, battery and electric device

Abstract

The application provides a coated lithium-rich metal oxide material, a preparation method thereof, a method for determining a coating layer in the coated lithium-rich metal oxide material, a positive electrode sheet, a battery, and an electric device. The coated lithium-rich metal oxide material comprises a core and a coating layer. The core comprises Li a MO y ; M comprises one or more elements selected from Ni, Co, Fe, Mn, Zn, Mg, Ca, Cu, Sn, Mo, Ru, Ir, V, Nb, and Cr, 2≤a≤6, and 2≤y≤4. The coating layer comprises one or more of carbon, silicon oxide, and metal oxide. The weight gain rate of the coated lithium-rich metal oxide material is w after being placed at 25°C and a relative humidity of 40% for 144 to 192 hours, and w<0.8%. The coated lithium-rich metal oxide material has a coating layer with high integrity and compactness, reduces lithium elution, improves battery capacity, and reduces material resistance. The method can accurately and quickly determine the integrity and compactness of the coating layer in the coated lithium-rich metal oxide material.

Description

Technical Field

[0001] This application relates to the field of battery technology, and in particular to a coated lithium-rich metal oxide material, a method for preparing the coated lithium-rich metal oxide material, a method for measuring the coating layer in the coated lithium-rich metal oxide material, a positive electrode, a battery, and an electrical device. Background Technology

[0002] In recent years, with the increasingly wide application of secondary batteries, they have been widely used in energy storage power systems such as hydropower, thermal power, wind power, and solar power plants, as well as in power tools, electric bicycles, electric motorcycles, electric cars, military equipment, aerospace, and many other fields. Due to the significant development of secondary batteries, higher requirements have been placed on their energy density, cycle performance, and safety performance.

[0003] Lithium-rich metal oxide materials have a high lithium content, which easily dissolves into the external environment and reacts with carbon dioxide and / or water to form strong alkaline, gel-like byproducts on the material surface. This affects the migration of lithium ions, reduces the battery's charging capacity, and increases the material's resistance. Summary of the Invention

[0004] This application addresses the aforementioned issues and aims to provide a coated lithium-rich metal oxide material, a method for preparing the coated lithium-rich metal oxide material, a method for measuring the coating layer in the coated lithium-rich metal oxide material, a positive electrode, a battery, and an electrical device. The coated lithium-rich metal oxide material of this application possesses a coating layer with high integrity and density, which can reduce the leaching of lithium from the lithium-rich metal oxide core to the external environment and the resulting side reactions, thereby improving battery capacity, reducing material resistance, and increasing the lithium-ion migration rate. The method for measuring the coating layer in the coated lithium-rich metal oxide material of this application can accurately and quickly determine the integrity and density of the coating layer, and is simple to operate.

[0005] To achieve the above objectives, the first aspect of this application provides a coated lithium-rich metal oxide material, including a core and a coating layer covering the core;

[0006] The kernel includes Li a MO y M includes one or more elements selected from Ni, Co, Fe, Mn, Zn, Mg, Ca, Cu, Sn, Mo, Ru, Ir, V, Nb, and Cr, where 2≤a≤6 and 2≤y≤4.

[0007] The coating layer comprises one or more of carbon, silicon oxide, and metal oxide;

[0008] The weight gain rate of the coated lithium-rich metal oxide material after standing for 144 to 192 hours in an environment of 25°C and 40% relative humidity is w, where w < 0.8%.

[0009] Optionally, w ≤ 0.5%.

[0010] Therefore, the coated lithium-rich metal oxide material of this application has a coating layer with high integrity and density, which reduces the dissolution of free lithium in the lithium-rich metal oxide core, thereby reducing the side reactions between the dissolved free lithium and external substances, improving the charging capacity of the battery, increasing the migration rate of lithium ions, and reducing the resistance of the material.

[0011] The second aspect of this application provides a coated lithium-rich metal oxide material, including a core and a coating layer covering the core;

[0012] The kernel includes Li a MO y M includes one or more elements selected from Ni, Co, Fe, Mn, Zn, Mg, Ca, Cu, Sn, Mo, Ru, Ir, V, Nb, and Cr, where 2≤a≤6 and 2≤y≤4.

[0013] The coating layer comprises one or more of carbon, silicon oxide, and metal oxide;

[0014] Furthermore, the d-value of the coated lithium-rich metal oxide material satisfies:

[0015] When 2≤a<3, d≤500ppm;

[0016] When 3 ≤ a < 4, d ≤ 1000 ppm;

[0017] When 4≤a≤6, d≤1500ppm;

[0018] The d-value of the coated lithium-rich metal oxide material is determined through the following steps:

[0019] The coated lithium-rich metal oxide material is mixed with a solvent at a mass ratio of 1:50 to 1:1, wherein the solvent consists of water and ethanol, and the mass content of water in the solvent is b, and b satisfies:

[0020] When 2 ≤ a < 3, b = 100% - a × 10%;

[0021] When 3 ≤ a < 4, b = 100% - a × 20%;

[0022] When 4 ≤ a ≤ 6, b = 0;

[0023] The liquid phase in the resulting mixture is separated, and potentiometric titration is performed on the liquid phase to calculate the free lithium content dissolved in the coated lithium-rich metal oxide material, which is the d-value of the coated lithium-rich metal oxide material.

[0024] Therefore, based on the first aspect, the integrity and density of the coating layer in the coated lithium-rich metal oxide material of this application are further improved, the dissolution of free lithium in the lithium-rich metal oxide core is further reduced, the side reactions between the dissolved free lithium and the external environment are further reduced, thereby further improving the charging capacity of the battery, further improving the migration rate of lithium ions, and further reducing the resistance of the coated lithium-rich metal oxide material.

[0025] In any embodiment, M includes one or more elements selected from Ni, Co, Fe, Mn, Cu, V, and Nb, and optionally includes one or more elements selected from Ni, Co, Fe, Cu, and Nb.

[0026] In any embodiment, the core includes one or more of Li2NiO2, Li2CuO2, Li2MnO3, Li3VO4, Li3NbO4, Li5FeO4 and Li6CoO4, and optionally includes one or more of Li2NiO2, Li2CuO2, Li3NbO4, Li5FeO4 and Li6CoO4.

[0027] In any embodiment, the coating layer includes one or more of carbon, silicon dioxide, aluminum oxide, and titanium oxide.

[0028] Therefore, this application can obtain a coating layer with high integrity and density, thereby reducing the dissolution of free lithium in the lithium-rich core, reducing the side reactions of dissolved free lithium, improving the charging capacity of the battery, reducing the resistance of the material, and improving the migration rate of lithium ions.

[0029] In any embodiment, the coating layer has a mass content of 1.3% to 10% in the coated lithium-rich metal oxide material, optionally 3% to 7%.

[0030] This facilitates the formation of a uniform, complete, and dense coating layer, reduces the dissolution of free lithium in the lithium-rich core, increases battery capacity, reduces material resistance, and exhibits a high lithium-ion migration rate.

[0031] In any embodiment, the particle size D of the coated lithium-rich metal oxide material is... v 50 is 2-10μm, can be selected as 4-10μm, and can be further selected as 4-8μm.

[0032] Therefore, the coated lithium-rich metal oxide material has a suitable specific surface area, which ensures the stability, integrity and density of the coating layer, while also facilitating the migration of lithium ions and improving the charging capacity of the battery.

[0033] In any embodiment, the water content in the coated lithium-rich metal oxide material is ≤1000ppm, optionally ≤500ppm, more preferably ≤300ppm, and even more preferably ≤200ppm.

[0034] This further reduces the dissolution of free lithium in the lithium-rich core, further reduces the side reactions of dissolved lithium, thereby further improving lithium-ion migration, further improving the battery's charging capacity, and further reducing the material's resistance.

[0035] In any embodiment, the powder resistivity of the coated lithium-rich metal oxide material measured at 20 MPa pressure is <4 Ω·cm, and can be optionally ≤3.3 Ω·cm. The reduction in resistivity is beneficial for improving the migration rate of lithium ions, thereby increasing the battery's charging capacity and rate.

[0036] A third aspect of this application also provides a method for preparing coated lithium-rich metal oxide materials, comprising the following steps:

[0037] Provides compound Li z MO y’ Where 0.98≤z≤1.02, 2≤y'≤3;

[0038] Lithium-ionized chemical vapor deposition (CCVD) z MO y’ Perform a coating process;

[0039] The coated product is mixed with a lithium source and sintered to obtain a coated lithium-rich metal oxide material.

[0040] Plasma-enhanced chemical vapor deposition (PECVD) utilizes low-temperature plasma as an energy source. The substrate to be coated is placed on a cathode subjected to glow discharge at low pressure. The substrate is heated to a preset temperature using glow discharge or a heating element. Then, a suitable amount of reactive gas is introduced. Through a series of chemical and plasma reactions, a coating layer is formed on the surface of the substrate. The difference between PECVD and conventional CVD methods lies in the fact that the low-temperature plasma contains a large number of high-energy electrons, which can provide the activation energy required for the process. Collisions between electrons and reactive gas molecules can promote molecular decomposition, combination, excitation, and ionization, generating various highly reactive chemical groups, significantly reducing the temperature required for coating.

[0041] Therefore, this application employs plasma-enhanced chemical vapor deposition to study the compound Li. z MOy’ Coating treatment is performed because the compound Li z MO y’ The lithium content is low, and the reaction gases during the coating process are not easily reacted with the compound Li. z MO y’ The lithium in the coating undergoes side reactions, ensuring the stability and effectiveness of the coating process. Sintering the coated product with lithium yields lithium-rich metal oxide materials with high integrity and density of the coating layer. Furthermore, the method described in this application is simple to operate and easy to industrialize.

[0042] In any embodiment, the coated lithium-rich metal oxide material includes a core and a coating layer covering the core, wherein the core includes Li a MO y The coating layer includes one or more of carbon, silicon oxide, and metal oxide;

[0043] Wherein, a, M and y are as described in the first or second aspect of this application.

[0044] In any embodiment, the coated lithium-rich metal oxide material is the coated lithium-rich metal oxide material of the first or second aspect of this application.

[0045] In any embodiment, the operating parameters for plasma-enhanced chemical vapor deposition include:

[0046] The microwave power is 200–1000W, selectable as 200–800W or 500–1000W; and / or,

[0047] The internal gas pressure of the chemical vapor deposition furnace is -10 to 1000 Pa, and can be selected as 10 to 1000 Pa or -10 to 100 Pa; and / or,

[0048] The furnace temperature of the chemical vapor deposition furnace is 400℃~600℃, optionally 450℃~550℃; and / or,

[0049] The deposition time is 2–10 h, optionally 4–8 h, and more preferably 5–8 h; and / or,

[0050] The gas flow rate at the inlet of the chemical vapor deposition furnace is 10–1000 sccm, optionally 100–700 sccm, and even more preferably 200–500 sccm.

[0051] The microwave power within the above range is beneficial to ensure the ionization deposition rate of the reactive gas, forming a uniform, complete, and dense coating layer on the surface of the coated object, while reducing side reactions between the coated object and the reactive gas.

[0052] The furnace pressure within the aforementioned range can ensure the reaction rate of vapor deposition and the effective coating of the core by the coating layer, thereby forming a uniform, complete, and dense coating layer and reducing the generation of defects.

[0053] The furnace temperature within the aforementioned range can increase the rate of ionization deposition of reactive gases, forming a uniform, complete, and dense coating layer on the surface of the coated material, while reducing the mass loss of the coated material due to side reactions between the coated material and the reactive gases.

[0054] The deposition time within the above range is beneficial to ensuring the appropriate content of the coating material, forming a uniform, complete and dense coating layer, which is conducive to the utilization of battery capacity.

[0055] The inlet gas flow rate within the above range can ensure the appropriate content of coating material, resulting in a uniform, complete, and dense coating layer, and reducing the waste of reactant gas.

[0056] In any embodiment, the raw material used for the coating treatment is selected from one or more of carbon sources, silicon oxide sources, and metal oxide sources.

[0057] Optionally, the raw materials used in the coating treatment are selected from one or more of organic carbon sources, organosilicon sources, inorganic silicon sources, organoaluminum sources, inorganic aluminum sources, organotitanium sources, and inorganic titanium sources, and more preferably from one or more of organic gases, organosilicon sources, organoaluminum sources, and organotitanium sources.

[0058] Optionally, the raw materials used in the coating treatment are selected from one or more of ethylene, acetylene, methane, acetone, ethanol, benzene, tetraethyl orthosilicate, silicon tetrachloride, aluminum isopropoxide, tetrabutyl titanate, and titanium tetrachloride, and more preferably from one or more of ethylene, acetylene, methane, tetraethyl orthosilicate, aluminum isopropoxide, and tetrabutyl titanate.

[0059] The raw materials used in the above coating treatment are conducive to forming a uniform, complete and dense coating layer on the surface of the coated object. At the same time, the raw materials are not prone to side reactions in the coated object, thus ensuring the effectiveness and stability of the coating treatment and reducing the waste of raw materials.

[0060] In any embodiment, the sintering temperature is 500℃~700℃, optionally 550℃~650℃, and more preferably 600℃~650℃; and / or,

[0061] The sintering time is 4h to 10h, optionally 6h to 8h, or even more preferably 6h to 7h; and / or,

[0062] The sintering heating rate is 2℃ / min to 8℃ / min, and can be selected as 4℃ / min to 6℃ / min; and / or,

[0063] Sintering is carried out in an inert atmosphere.

[0064] The sintering temperature, sintering time, and sintering heating rate within the above range are beneficial for obtaining highly crystalline coated lithium-rich metal oxides, reducing the generation of by-products, and saving energy.

[0065] In any implementation, the lithium element in the lithium source reacts with Li z MO y’ The molar ratio is (az):1. This is beneficial for forming a lithium-rich metal oxide core, thereby obtaining a lithium-rich metal oxide material with a complete and dense coating layer.

[0066] In any implementation, before the coating process, Li z MO y’ Crushing. This is beneficial for the uniformity of the coating process and ensures that the coated lithium-rich metal oxide material has a suitable specific surface area, which is conducive to lithium-ion migration and the realization of battery capacity.

[0067] Before the coating process, the raw materials used in the coating process are vaporized, optionally at 300℃ to 500℃. For non-gaseous raw materials, vaporization is required to obtain the reaction gas needed for the coating process, ensuring the plasma-enhanced chemical vapor deposition (PECVD) can proceed.

[0068] The prepared coated lithium-rich metal oxide material is crushed and sieved, optionally in a dry environment, to ensure that the coated lithium-rich metal oxide material has suitable water content and particle size.

[0069] In any implementation, Li z MO y’ Prepared through the following steps:

[0070] The lithium source and the source of element M are mixed and sintered; wherein the molar ratio of lithium element in the lithium source to M element in the source of element M is 0.98:1 to 1.09:1, which can be selected as 0.98:1 to 1.02:1 or 1:1 to 1.09:1, and more preferably 1:1 to 1.05:1.

[0071] Due to the compound Li z MO y’ The lithium content is low, therefore the compound Li is used. z MO y’ The coating process improves stability and enables effective coating.

[0072] In any embodiment, Li is prepared z MO y’ In the steps:

[0073] The sintering temperature is 400℃~600℃, optionally 450℃~550℃; and / or,

[0074] The sintering time is 2 hours to 8 hours, and can be selected as 4 hours to 6 hours; and / or,

[0075] The sintering heating rate is 4℃ / min to 10℃ / min, and can be selected as 6℃ / min to 8℃ / min; and / or,

[0076] Sintering is carried out in an inert atmosphere.

[0077] In any embodiment, the lithium source includes one or more of lithium oxide, lithium carbonate, lithium oxalate, lithium acetate, and lithium hydroxide; and / or,

[0078] The source of element M is selected from one or more of the oxides, hydroxides, halides, sulfates, carbonates, nitrates, oxalates, acetates, sulfides, and nitrides of element M, and may be selected as oxides of element M.

[0079] The fourth aspect of this application provides a method for determining the coating layer in a coated lithium-rich metal oxide material, comprising the following steps:

[0080] We provide a coated lithium-rich metal oxide material, comprising a core and a coating layer covering the core, wherein the core contains Li. a MO y M includes one or more elements selected from Ni, Co, Fe, Mn, Zn, Mg, Ca, Cu, Sn, Mo, Ru, Ir, V, Nb, and Cr, where 2 ≤ a ≤ 6 and 2 ≤ y ≤ 4; the coating layer contains one or more elements selected from carbon, silicon oxide, and metal oxide.

[0081] The coated lithium-rich metal oxide material is mixed with a solvent at a mass ratio of 1:50 to 1:1, or optionally at a mass ratio of 1:50 to 1:10. The solvent consists of water and ethanol, and the mass content of water in the solvent is b, which satisfies the following conditions: when 2 ≤ a < 3, b = 100% - a × 10%; when 3 ≤ a < 4, b = 100% - a × 20%; when 4 ≤ a ≤ 6, b = 0.

[0082] The liquid phase in the resulting mixture is separated, titrated, and the content of free lithium dissolved in the coated lithium-rich metal oxide material (d value) is calculated to confirm whether the d value meets the following requirements:

[0083] When 2≤a<3, d≤500ppm; when 3≤a<4, d≤1000ppm; when 4≤a≤6, d≤1500ppm.

[0084] This application utilizes solvents with varying water content (deionized water, anhydrous ethanol, or a mixture of both) to dissolve free lithium in the material based on the different lithium contents of the lithium-rich metal oxide core. The dissolved free lithium reacts with the dissolved free lithium, and the density and integrity of the coating layer are determined by measuring the content of dissolved free lithium in the material. The measurement results are highly accurate, reliable, and fast. At the same time, the coating layer can be protected from damage during the measurement process.

[0085] In any embodiment, the mixing time is 1 min to 4 min, optionally 1 min to 3 min; and / or,

[0086] Mixing is carried out under stirring conditions of 200 rpm to 800 rpm, or optionally under stirring conditions of 400 rpm to 800 rpm; and / or,

[0087] The determination was performed at 25°C; and / or,

[0088] The titration was a potentiometric titration.

[0089] The mixing time and stirring speed within the above range can ensure that the dissolved lithium in the coated lithium-rich metal oxide material reacts fully and effectively with the solvent, thereby ensuring the accuracy and reliability of the measurement results and avoiding damage to the coating layer.

[0090] In any embodiment, the content of free lithium dissolved in the coated lithium-rich metal oxide material is determined by the following steps:

[0091] The coated lithium-rich metal oxide material is mixed with a solvent at a mass ratio of 1:50 to 1:1, or optionally at a mass ratio of 1:50 to 1:10. The solvent consists of water and ethanol, and the mass content of water in the solvent is b, which satisfies the following conditions: when 2 ≤ a < 3, b = 100% - a × 10%; when 3 ≤ a < 4, b = 100% - a × 20%; when 4 ≤ a ≤ 6, b = 0.

[0092] The liquid phase in the obtained mixture was separated, and the liquid phase was taken and potentiometrically titrated with an ethanol solution of hydrochloric acid as the titrant. The volumes of titrant consumed corresponding to the two potential jump points during the titration process were V1 mL and V2 mL, respectively, and V2 > V1.

[0093] The free lithium content d in the coated lithium-rich metal oxide material is calculated according to the following formula:

[0094] d=C×V a ×(69.4684V2-0.0424V1) / (m×V b )

[0095] in,

[0096] m represents the mass of the coated lithium-rich metal oxide material, in grams;

[0097] V a Indicates the volume of the solvent, in mL;

[0098] V b This indicates the volume of the liquid phase sample taken, in mL.

[0099] C represents the concentration of hydrochloric acid in the titrant, in mol / L.

[0100] The fifth aspect of this application provides a positive electrode sheet, including the coated lithium-rich metal oxide material of the first or second aspect of this application or the coated lithium-rich metal oxide material prepared according to the method of the third aspect of this application.

[0101] The sixth aspect of this application provides a battery comprising a coated lithium-rich metal oxide material according to the first or second aspect of this application, a coated lithium-rich metal oxide material prepared according to the method of the third aspect of this application, or a positive electrode sheet according to the fifth aspect of this application.

[0102] A seventh aspect of this application provides an electrical device including the battery of the sixth aspect of this application. Attached Figure Description

[0103] Figure 1 This is a schematic diagram of a secondary battery according to one embodiment of this application.

[0104] Figure 2 yes Figure 1 An exploded view of a secondary battery according to one embodiment of this application is shown.

[0105] Figure 3 This is a schematic diagram of a battery module according to one embodiment of this application.

[0106] Figure 4 This is a schematic diagram of a battery pack according to one embodiment of this application.

[0107] Figure 5 yes Figure 4 An exploded view of a battery pack according to one embodiment of this application is shown.

[0108] Figure 6 This is a schematic diagram of an electrical device that uses a secondary battery as a power source according to one embodiment of this application.

[0109] Figure 7 A TEM image of the lithium-rich metal oxide material prepared for Comparative Example 1.

[0110] Figure 8 This is a TEM image of the coated lithium-rich metal oxide material prepared in Example 1.

[0111] Figure 9 TEM image of the coated lithium-rich metal oxide material prepared for Comparative Example 2.

[0112] Explanation of reference numerals in the attached figures:

[0113] 1 Battery pack; 2 Upper housing; 3 Lower housing; 4 Battery module; 5 Secondary battery; 51 Housing; 52 Electrode assembly; 53 Top cover assembly. Detailed Implementation

[0114] The following detailed description, with appropriate reference to the accompanying drawings, discloses embodiments of the coated lithium-rich metal oxide material, its preparation method, the method for determining the coating layer in the coated lithium-rich metal oxide material, the positive electrode sheet, the battery, and the power device. 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 to enable those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0115] 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 understood that ranges of 60–110 and 80–120 are also expected. 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 "a–b" 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.

[0116] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0117] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0118] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, if a method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, if it is mentioned that the method may also include step (c), it means 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.

[0119] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0120] Unless otherwise specified, the term "or" is inclusive in this application. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, the condition "A or B" is satisfied by any of the following conditions: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0121] [Rechargeable Battery]

[0122] Secondary batteries, also known as rechargeable batteries or storage batteries, are batteries that can be recharged after being discharged to activate the active materials and continue to be used.

[0123] Typically, a secondary battery consists of a positive electrode, a negative electrode, a separator, and an electrolyte. During charging and discharging, 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, primarily prevents short circuits while allowing active ions to pass through. The electrolyte, also positioned between the positive and negative electrodes, mainly serves to conduct active ions.

[0124] [Coated Lithium-Rich Metal Oxide Materials]

[0125] One embodiment of this application provides a coated lithium-rich metal oxide material, including a core and a coating layer covering the core;

[0126] The kernel includes Li a MO yM includes one or more elements selected from Ni, Co, Fe, Mn, Zn, Mg, Ca, Cu, Sn, Mo, Ru, Ir, V, Nb, and Cr, where 2≤a≤6 and 2≤y≤4.

[0127] The coating layer comprises one or more of carbon, silicon oxide, and metal oxide;

[0128] The weight gain rate w of the coated lithium-rich metal oxide material after standing in an environment of 25°C and 40% relative humidity for 144 to 192 hours (e.g., 168 hours) is w, where w < 0.8%.

[0129] Optionally, w ≤ 0.5%.

[0130] Although the mechanism is not yet clear, the inventors have discovered that the coated lithium-rich metal oxide material of this application has a coating layer with high integrity and density, which blocks and reduces the dissolution of free lithium in the lithium-rich metal oxide core, reduces the loss of active lithium, and improves the charging capacity of the battery. Since the dissolved free lithium easily reacts with external substances to generate strongly alkaline byproducts, these byproducts can easily cause slurry gelation, hindering lithium ion migration and battery processing, and increasing material resistance. Therefore, the coating layer of the coated lithium-rich metal oxide material of this application reduces the dissolution of free lithium, thereby improving lithium ion mobility, reducing material resistance, and making it more conducive to battery product processing.

[0131] Another embodiment of this application provides a coated lithium-rich metal oxide material, including a core and a coating layer covering the core;

[0132] The kernel includes Li a MO y Where M includes one or more elements selected from Ni, Co, Fe, Mn, Zn, Mg, Ca, Cu, Sn, Mo, Ru, Ir, V, Nb and Cr, 2≤a≤6, for example 2, 3, 4, 5, 6 and any two of the above values, and 2≤y≤4, for example 2, 3, 4 and any two of the above values.

[0133] The coating layer comprises one or more of carbon, silicon oxide, and metal oxide;

[0134] Furthermore, the d-value of the coated lithium-rich metal oxide material satisfies:

[0135] When 2≤a<3, d≤500ppm;

[0136] When 3 ≤ a < 4, d ≤ 1000 ppm;

[0137] When 4≤a≤6, d≤1500ppm;

[0138] The d-value of the coated lithium-rich metal oxide material is determined through the following steps:

[0139] The coated lithium-rich metal oxide material is mixed with a solvent at a mass ratio of 1:50 to 1:1 (e.g., 1:1, 1:10, 1:20, 1:40, and any two of the above values), wherein the solvent consists of water and ethanol, and the mass content of water in the solvent is b, and b satisfies:

[0140] When 2 ≤ a < 3, b = 100% - a × 10%;

[0141] When 3 ≤ a < 4, b = 100% - a × 20%;

[0142] When 4 ≤ a ≤ 6, b = 0;

[0143] The liquid phase in the resulting mixture is separated, and potentiometric titration is performed on the liquid phase to calculate the free lithium content dissolved in the coated lithium-rich metal oxide material, which is the d-value of the coated lithium-rich metal oxide material.

[0144] Therefore, based on the first embodiment, the integrity and density of the coating layer in the coated lithium-rich metal oxide material of this application are further improved, the dissolution of free lithium in the lithium-rich metal oxide core is further reduced, the side reactions of dissolved free lithium with external substances are further reduced, thereby further improving the battery capacity, further improving the lithium ion migration rate, and further reducing the material resistance.

[0145] In some embodiments, M includes one or more elements selected from Ni, Co, Fe, Mn, Cu, V, and Nb, and optionally includes one or more elements selected from Ni, Co, Fe, Cu, and Nb.

[0146] In some implementations, the core includes one or more of Li2NiO2, Li2CuO2, Li2MnO3, Li3VO4, Li3NbO4, Li5FeO4 and Li6CoO4, and optionally includes one or more of Li2NiO2, Li2CuO2, Li3NbO4, Li5FeO4 and Li6CoO4.

[0147] In some embodiments, the coating layer includes one or more of carbon, silicon dioxide, aluminum oxide, and titanium oxide.

[0148] Therefore, this application can obtain a coating layer with high integrity and density, thereby reducing the dissolution of free lithium in the lithium-rich core, reducing the side reactions of dissolution of free lithium, improving the charging capacity of the battery, reducing the resistance of the coated lithium-rich metal oxide material, and improving the migration rate of lithium ions.

[0149] In some embodiments, the coating layer has a mass content of 1.3% to 10% in the coated lithium-rich metal oxide material, optionally 3% to 7%, for example 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, and any two of the above values.

[0150] This facilitates the formation of a uniform, complete, and dense coating layer, reduces the dissolution of free lithium in the lithium-rich core, increases battery capacity, reduces material resistance, and exhibits a high lithium-ion migration rate.

[0151] In some embodiments, the particle size D of the coated lithium-rich metal oxide material v 50 is 2 to 10 μm, can be selected as 4 to 10 μm, or more preferably 4 to 8 μm, such as 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm and any two of the above values.

[0152] Therefore, the coated lithium-rich metal oxide material has a suitable specific surface area, which ensures the stability, integrity and density of the coating layer, while also facilitating the migration of lithium ions and improving the charging capacity of the battery.

[0153] In some embodiments, the water content in the coated lithium-rich metal oxide material is ≤1000ppm by mass, optionally ≤500ppm, more preferably ≤400ppm or ≤300ppm, further preferably ≤200ppm, and even more preferably ≤100ppm.

[0154] This further reduces the dissolution of free lithium in the lithium-rich core, further reduces the side reactions of dissolved lithium, thereby further improving lithium-ion migration, further improving the battery's charging capacity, and further reducing the material's resistance.

[0155] In some embodiments, the resistivity of the coated lithium-rich metal oxide material measured at 20 MPa pressure is <4 Ω·cm, optionally ≤3.3 Ω·cm, and more preferably ≤3 Ω·cm, ≤2 Ω·cm, or ≤1 Ω·cm. The reduction in resistivity is beneficial for improving the migration rate of lithium ions, thereby increasing the battery's charging capacity and rate.

[0156] [Preparation Method of Coated Lithium-Rich Metal Oxide Materials]

[0157] One embodiment of this application provides a method for preparing coated lithium-rich metal oxide materials, comprising the following steps:

[0158] Provides compound Li z MO y’ Where 0.98≤z≤1.02, 2≤y'≤3;

[0159] Lithium-ionized chemical vapor deposition (CCVD) z MO y’ Perform a coating process;

[0160] The coated product is mixed with a lithium source and sintered to obtain a coated lithium-rich metal oxide material.

[0161] Plasma-enhanced chemical vapor deposition (PECVD) utilizes low-temperature plasma as an energy source. The substrate to be coated is placed on a cathode subjected to glow discharge at low pressure. The substrate is heated to a preset temperature using glow discharge or a heating element. Then, a suitable amount of reactive gas is introduced. Through a series of chemical and plasma reactions, a coating layer is formed on the surface of the substrate. The difference between PECVD and conventional CVD methods lies in the fact that the low-temperature plasma contains a large number of high-energy electrons, which can provide the activation energy required for the process. Collisions between electrons and reactive gas molecules can promote molecular decomposition, combination, excitation, and ionization, generating various highly reactive chemical groups, significantly reducing the temperature required for coating.

[0162] Therefore, this application employs plasma-enhanced chemical vapor deposition to study the compound Li. z MO y’ Coating treatment is performed because the compound Li z MO y’ The low lithium content, high stability, and low temperature required for plasma-enhanced chemical vapor deposition (PECVD) mean that the reactant gases during the coating process do not readily react with the Li compound. z MO y’ The lithium in the coating undergoes side reactions, ensuring the stability and effectiveness of the coating process. Sintering the coated product after mixing it with lithium yields a lithium-rich metal oxide material with high integrity and density of the coating layer. Furthermore, the method described in this application is simple to operate and easy to industrialize.

[0163] In some embodiments, the coated lithium-rich metal oxide material includes a core and a coating layer covering the core, wherein the core includes Li a MO y The coating layer includes one or more of carbon, silicon oxide, and metal oxide;

[0164] Wherein, a, M and y are as described in this application [coated lithium-rich metal oxide materials];

[0165] In some embodiments, coated lithium-rich metal oxide materials are as described in this application [coated lithium-rich metal oxide materials].

[0166] In some implementations, the operating parameters for plasma-enhanced chemical vapor deposition include:

[0167] The microwave power is 200–1000W, selectable from 200–800W or 500–1000W, for example 200W, 300W, 400W, 500W, 600W, 700W, 800W, 900W, 1000W, or any range formed by two of the above values; and / or,

[0168] The internal gas pressure of the chemical vapor deposition furnace is -10 to 1000 Pa, and can be selected as 10 to 1000 Pa or -10 to 100 Pa, for example -10 Pa, 0 Pa, 10 Pa, 20 Pa, 50 Pa, 100 Pa, 150 Pa, 200 Pa, 300 Pa, 400 Pa, 500 Pa, 600 Pa, 700 Pa, 800 Pa, 900 Pa, 1000 Pa, or any range formed by two of the above values; and / or,

[0169] The furnace temperature of the chemical vapor deposition furnace is 400℃~600℃, optionally 450℃~550℃, for example 400℃, 450℃, 500℃, 550℃, 600℃ or any range formed by two of the above values; and / or,

[0170] The deposition time is 2–10 h, optionally 4–8 h, more preferably 5–8 h, for example 2 h, 3 h, 4 h, 5 h, 6 h, 7 h, 8 h, 9 h, 10 h, or any range formed by any two of the above values; and / or,

[0171] The inlet gas flow rate of the chemical vapor deposition furnace is 10 to 1000 sccm, optionally 100 to 700 sccm, and more preferably 200 to 500 sccm, for example 20 sccm, 50 sccm, 100 sccm, 200 sccm, 300 sccm, 400 sccm, 500 sccm, 600 sccm, 700 sccm, 800 sccm, 900 sccm, 1000 sccm, or any range formed by two of the above values.

[0172] The “sccm” above represents the flow rate unit at standard atmospheric pressure—milliliters per minute.

[0173] The microwave power within the above range is beneficial to ensure the ionization deposition rate of the reactive gas, forming a uniform, complete, and dense coating layer on the surface of the coated object, while reducing side reactions between the coated object and the reactive gas.

[0174] The furnace pressure within the aforementioned range can ensure the reaction rate of vapor deposition and the effective coating of the core by the coating layer, thereby forming a uniform, complete, and dense coating layer and reducing the generation of defects.

[0175] The furnace temperature within the aforementioned range can increase the rate of ionization deposition of reactive gases, forming a uniform, complete, and dense coating layer on the surface of the coated material, while reducing the mass loss of the coated material due to side reactions between the coated material and the reactive gases.

[0176] The deposition time within the above range is beneficial to ensuring the appropriate content of the coating material, forming a uniform, complete and dense coating layer, which is conducive to the utilization of battery capacity.

[0177] The inlet gas flow rate within the above range can ensure the appropriate content of coating material, resulting in a uniform, complete, and dense coating layer, and reducing the waste of reactant gas.

[0178] In some embodiments, the raw materials used in the coating process are selected from one or more of carbon sources, silicon oxide sources, and metal oxide sources.

[0179] Optionally, the raw materials used in the coating treatment are selected from one or more of organic carbon sources, organosilicon sources, inorganic silicon sources, organoaluminum sources, inorganic aluminum sources, organotitanium sources, and inorganic titanium sources, and may be selected from one or more of organic gases, organosilicon sources, organoaluminum sources, and organotitanium sources.

[0180] Optionally, the raw materials used in the coating treatment are selected from one or more of ethylene, acetylene, methane, acetone, ethanol, benzene, tetraethyl orthosilicate, silicon tetrachloride, aluminum isopropoxide, tetrabutyl titanate, and titanium tetrachloride, and more preferably from one or more of ethylene, acetylene, methane, tetraethyl orthosilicate, aluminum isopropoxide, and tetrabutyl titanate.

[0181] The raw materials used in the above coating treatment are conducive to forming a uniform, complete and dense coating layer on the surface of the coated object. At the same time, the raw materials are not prone to side reactions in the coated object, thus ensuring the effectiveness and stability of the coating treatment and reducing the waste of raw materials.

[0182] In some embodiments, the sintering temperature is 500°C to 700°C, optionally 550°C to 650°C, and more preferably 600°C to 650°C, for example, 500°C, 550°C, 600°C, 650°C, 700°C, or any range formed by two of the above values; and / or,

[0183] The sintering time is 4h to 10h, optionally 6h to 8h, or more preferably 6h to 7h, for example 4h, 5h, 6h, 7h, 8h, 9h, 10h, or any range formed by two of the above values; and / or,

[0184] The sintering heating rate is 2℃ / min to 8℃ / min, and can be selected from 4℃ / min to 6℃ / min, for example, 2℃ / min, 3℃ / min, 4℃ / min, 5℃ / min, 6℃ / min, 7℃ / min, 8℃ / min, or any range formed by any two of the above values; and / or,

[0185] Sintering is carried out in an inert atmosphere.

[0186] The sintering temperature, sintering time, and sintering heating rate within the above range are beneficial for obtaining highly crystalline coated lithium-rich metal oxides, reducing the generation of by-products, and saving energy.

[0187] In some implementations, the lithium element in the lithium source reacts with Li z MO y’ The molar ratio is (az):1. This is beneficial for forming a lithium-rich metal oxide core, thereby obtaining a lithium-rich metal oxide material with a complete and dense coating layer.

[0188] In some implementations, Li is subjected to coating treatment prior to the coating process. z MO y’ Crushing. This is beneficial for the uniformity of the coating process and ensures that the coated lithium-rich metal oxide material has a suitable specific surface area, which is conducive to lithium-ion migration and the realization of battery capacity.

[0189] Before the coating process, the raw materials used in the coating process are vaporized, optionally at 300℃ to 500℃. For non-gaseous raw materials, vaporization is required to obtain the reaction gas needed for the coating process, ensuring the plasma-enhanced chemical vapor deposition (PECVD) can proceed.

[0190] The prepared coated lithium-rich metal oxide material is crushed and sieved, optionally in a dry environment, to ensure that the coated lithium-rich metal oxide material has suitable water content and particle size.

[0191] In some implementations, Li z MO y’ Prepared through the following steps:

[0192] The lithium source and the source of element M are mixed and sintered; wherein the molar ratio of lithium element in the lithium source to M element in the source of element M is 0.98:1 to 1.09:1, which can be selected as 0.98:1 to 1.02:1 or 1:1 to 1.09:1, more preferably 1:1 to 1.05:1, and even more preferably 1:1 to 1.02:1.

[0193] Due to the compound Li z MO y’ The lithium content is low, therefore the compound Li is used.z MO y’ The coating process improves stability and enables effective coating.

[0194] In some embodiments, Li is prepared z MO y’ In the steps:

[0195] The sintering temperature is 400℃~600℃, and can be selected from 450℃~550℃, for example 400℃, 450℃, 500℃, 550℃, 600℃, or any range formed by two of the above values; and / or,

[0196] The sintering time is 2h to 8h, and can be selected from 4h to 6h, for example, 2h, 3h, 4h, 5h, 6h, 7h, 8h, or any range formed by any two of the above values; and / or,

[0197] The sintering heating rate is 4℃ / min to 10℃ / min, and can be selected as 6℃ / min to 8℃ / min, for example, 4℃ / min, 5℃ / min, 6℃ / min, 7℃ / min, 8℃ / min, 9℃ / min, 10℃ / min, or any range formed by any two of the above values; and / or,

[0198] Sintering is carried out in an inert atmosphere.

[0199] In some embodiments, the lithium source includes one or more of lithium oxide, lithium carbonate, lithium oxalate, lithium acetate, and lithium hydroxide; and / or,

[0200] The source of element M is selected from one or more of the oxides, hydroxides, halides, sulfates, carbonates, nitrates, oxalates, acetates, sulfides, and nitrides of element M, and may be selected as oxides of element M.

[0201] [Method for determining the coating layer in coated lithium-rich metal oxide materials]

[0202] One embodiment of this application provides a method for determining the coating layer in a coated lithium-rich metal oxide material, comprising the following steps:

[0203] A coated lithium-rich metal oxide material is provided, the coated lithium-rich metal oxide material comprising a core and a coating layer covering the core, the core comprising Li a MO y M includes one or more elements selected from Ni, Co, Fe, Mn, Zn, Mg, Ca, Cu, Sn, Mo, Ru, Ir, V, Nb, and Cr, where 2 ≤ a ≤ 6 and 2 ≤ y ≤ 4; the coating layer contains one or more elements selected from carbon, silicon oxide, and metal oxide.

[0204] The coated lithium-rich metal oxide material is mixed with a solvent at a mass ratio of 1:50 to 1:1 (selectable as a mass ratio of 1:50 to 1:10, such as 1:1, 1:10, 1:20, 1:40, and any two of the above values). The solvent consists of water and ethanol, and the mass content of water in the solvent is b, which satisfies the following conditions: when 2 ≤ a < 3, b = 100% - a × 10%; when 3 ≤ a < 4, b = 100% - a × 20%; when 4 ≤ a ≤ 6, b = 0.

[0205] The liquid phase in the resulting mixture is separated, titrated, and the content of free lithium dissolved in the coated lithium-rich metal oxide material (d value) is calculated to confirm whether the d value meets the following requirements:

[0206] When 2≤a<3, d≤500ppm; when 3≤a<4, d≤1000ppm; when 4≤a≤6, d≤1500ppm.

[0207] Optionally, if the d value meets the above conditions, the coating layer of the coated lithium-rich metal oxide material has good integrity and density; otherwise, the coating layer of the coated lithium-rich metal oxide material has poor integrity and density.

[0208] This application utilizes solvents with varying water content (deionized water, anhydrous ethanol, or a mixture of both in a specific ratio) to dissolve free lithium in coated lithium-rich metal oxide materials based on the different lithium contents of the core. The dissolved free lithium reacts with the dissolved free lithium, and the density and integrity of the coating layer are determined by measuring the content of dissolved free lithium in the coated lithium-rich metal oxide material. The measurement results are highly accurate, reliable, and fast; at the same time, the coating layer can be protected from damage during the measurement process.

[0209] In some implementations, the titration can be any commonly used titration method within the relevant technical field, such as potentiometric titration.

[0210] In some embodiments, the mixing time is 1 min to 4 min, optionally 1 min to 3 min, for example 1 min, 2 min, 3 min, 4 min, or any range formed by any two of the above values; and / or,

[0211] Mixing is carried out under stirring conditions of 200 rpm to 800 rpm, or optionally 400 rpm to 800 rpm, for example, 200 rpm, 300 rpm, 400 rpm, 500 rpm, 600 rpm, 700 rpm, 800 rpm, or any range of two of the above values; and / or,

[0212] The measurements were performed at 25°C.

[0213] The mixing time and stirring speed within the above range can ensure that the dissolved lithium in the coated lithium-rich metal oxide material reacts fully and effectively with the solvent, thereby ensuring the accuracy and reliability of the measurement results and avoiding damage to the coating layer.

[0214] In some embodiments, the content of free lithium dissolved in the coated lithium-rich metal oxide material is determined by the following steps:

[0215] The coated lithium-rich metal oxide material is mixed with a solvent at a mass ratio of 1:50 to 1:1 (optionally 1:50 to 1:10), wherein the solvent consists of water and ethanol, the mass content of water in the solvent is b, and b satisfies: when 2≤a<3, b=100%-a×10%; when 3≤a<4, b=100%-a×20%; when 4≤a≤6, b=0;

[0216] The liquid phase in the obtained mixture was separated, and the liquid phase was taken and potentiometrically titrated with an ethanol solution of hydrochloric acid as the titrant. The volumes of titrant consumed corresponding to the two potential jump points during the titration process were V1 mL and V2 mL, respectively, and V2 > V1.

[0217] The free lithium content d in the coated lithium-rich metal oxide material is calculated according to the following formula:

[0218] d=C×V a ×(69.4684V2-0.0424V1) / (m×V b )

[0219] in,

[0220] m represents the mass of the coated lithium-rich metal oxide material, in grams;

[0221] V a Indicates the volume of the solvent, in mL;

[0222] V b This indicates the volume of the liquid phase sample taken, in mL.

[0223] C represents the concentration of hydrochloric acid in the titrant, in mol / L.

[0224] In some embodiments, during potentiometric titration, a graph is plotted with the pH value during the titration process on the ordinate and the volume of titrant consumed on the abscissa. V1 and V2 refer to the volumes of titrant consumed corresponding to the two potential jump points in the graph, where V2 > V1.

[0225] [Positive electrode plate]

[0226] The positive electrode typically includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector. The positive electrode film layer includes the aforementioned coated lithium-rich metal oxide material or the coated lithium-rich metal oxide material prepared by the aforementioned method.

[0227] As an example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0228] In some embodiments, the positive current collector may be a metal foil or a composite current collector. For example, aluminum 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 (aluminum, aluminum 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.).

[0229] In some embodiments, the positive electrode film layer may optionally include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0230] In some embodiments, the positive electrode film 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.

[0231] In some embodiments, the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry onto a positive electrode current collector, and then obtaining the positive electrode sheet after drying, cold pressing and other processes.

[0232] [Negative electrode plate]

[0233] The negative electrode sheet includes 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.

[0234] 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.

[0235] 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 material substrate and a metal layer formed on at least one surface of the polymer material 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 material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0236] 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. 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 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.

[0237] In some embodiments, the negative electrode film layer may optionally include a binder. As an example, the binder 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).

[0238] In some embodiments, the negative electrode film may optionally include a conductive agent. As an example, 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.

[0239] In some embodiments, the negative electrode film may optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0240] In some embodiments, the negative electrode sheet can be prepared by dispersing the components used to prepare the negative electrode sheet, such as the 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.

[0241] [Electrolytes]

[0242] 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.

[0243] In some embodiments, the electrolyte is liquid and includes an electrolyte salt and a solvent.

[0244] In some embodiments, 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.

[0245] In some embodiments, 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.

[0246] In some embodiments, the electrolyte may optionally include additives. As examples, 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.

[0247] [Isolation membrane]

[0248] In some embodiments, the secondary battery also includes a separator. This application does not impose any particular limitation on the type of separator; any known porous separator with good chemical and mechanical stability can be selected.

[0249] In some embodiments, the material of the separator can be selected from at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0250] In some implementations, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly using a winding or stacking process.

[0251] In some embodiments, the secondary battery may include an outer packaging. This outer packaging may be used to encapsulate the electrode assembly and electrolyte described above.

[0252] In some embodiments, the outer packaging of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The outer packaging of the secondary battery can also be a soft pack, such as a pouch. The material of the soft pack can be plastic; examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0253] This application does not impose any particular limitation on the shape of the secondary battery; it can be cylindrical, square, or any other arbitrary shape. For example, Figure 1 This is an example of a square-structured secondary battery 5.

[0254] In some implementations, refer to Figure 2 The outer packaging may include a housing 51 and a cover 53. The housing 51 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 51 has an opening communicating with the receiving cavity, and the cover 53 can be placed over the opening to close the receiving cavity. The positive electrode, negative electrode, and separator may be formed into an electrode assembly 52 by a winding process or a stacking process. The electrode assembly 52 is encapsulated within the receiving cavity. Electrolyte is immersed in the electrode assembly 52. ​​The secondary battery 5 may contain one or more electrode assemblies 52, which can be selected by those skilled in the art according to specific practical needs.

[0255] In some implementations, the secondary batteries can be assembled into a battery module, and the number of secondary 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.

[0256] Figure 3 This is battery module 4, used as an example. (See reference...) Figure 3 In battery module 4, multiple secondary batteries 5 can be arranged sequentially along the length of battery module 4. Of course, they can also be arranged in any other manner. Furthermore, these multiple secondary batteries 5 can be fixed in place using fasteners.

[0257] Optionally, the battery module 4 may also include a housing with a receiving space in which a plurality of secondary batteries 5 are received.

[0258] In some embodiments, the battery modules described above can also be assembled into a battery pack, and the number of battery modules contained in the battery pack 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 pack.

[0259] Figure 4 and Figure 5 This is battery pack 1 as an example. (See reference...) Figure 4 and Figure 5The battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box includes an upper body 2 and a lower body 3, with the upper body 2 covering the lower body 3 to form a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0260] In addition, this application also provides an electrical device, which includes at least one of the secondary battery, battery module, or battery pack provided in this application. The secondary battery, battery module, or battery pack can be used as the power source of the electrical device or as the 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.

[0261] As an electrical device, a secondary battery, battery module, or battery pack can be selected according to its usage requirements.

[0262] Figure 6 This is an example of an electrical device. The device could be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of the secondary battery for this device, a battery pack or battery module can be used.

[0263] [Example]

[0264] 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.

[0265] Example 1

[0266] 1. Preparation of coated lithium-rich metal oxide materials:

[0267] Lithium hydroxide and ferric oxide were mixed, wherein the molar ratio of lithium in lithium hydroxide to iron in ferric oxide was 1.05:1. The mixture was sintered once in nitrogen at 500°C with a heating rate of 7°C / min for 5 hours to obtain the intermediate product LiFeO2.

[0268] The intermediate product LiFeO2 was subjected to airflow crushing and then placed in a plasma-enhanced chemical vapor deposition furnace for coating treatment. The raw material gas—ethylene—was introduced into the furnace at a flow rate of 400 sccm (standard milliliters / minute), a furnace temperature of 500℃, a furnace pressure of 10 Pa, a deposition time of 6 h, and a microwave power of 500 W. After the organic gas decomposed in the furnace, it was deposited on the surface of the intermediate product LiFeO2 to obtain carbon-coated LiFeO2.

[0269] Carbon-coated LiFeO2 was mixed with a lithium source (the same as described above), with a lithium element to LiFeO2 molar ratio of 4:1. The mixture was heated to 600℃ for secondary sintering at a heating rate of 5℃ / min for 7 hours. After sintering, the mixture was crushed and sieved in a dry environment to obtain carbon-coated Li5FeO4.

[0270] 2. Preparation of positive electrode sheet: The above-mentioned coated lithium-rich metal oxide material, binder polyvinylidene fluoride (PVDF), and conductive agent acetylene black are dissolved in solvent N-methylpyrrolidone (NMP) at a mass ratio of 97:2:1. After thorough stirring and mixing, a positive electrode slurry is prepared. The positive electrode slurry is uniformly coated on the positive electrode current collector aluminum foil, and then dried, cold-pressed, and slit to obtain the positive electrode sheet.

[0271] 3. Preparation of negative electrode sheet: The negative electrode active material artificial graphite, conductive agent acetylene black, binder styrene-butadiene rubber (SBR), and thickener sodium carboxymethyl cellulose (CMC-Na) are dissolved in deionized water at a mass ratio of 96:1.5:1.5:1.0 and thoroughly stirred and mixed to prepare a negative electrode slurry; the negative electrode slurry is coated on the negative electrode current collector copper foil, and then dried, cold-pressed, and slit to obtain the negative electrode sheet.

[0272] 4. Separation membrane: Polypropylene membrane is used.

[0273] 5. Preparation of electrolyte: Ethyl carbonate (EC), methyl ethyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a volume ratio of 1:1:1. LiPF6 was then uniformly dissolved in the mixture to obtain the electrolyte. The concentration of LiPF6 in this electrolyte was 1 mol / L.

[0274] 6. Preparation of secondary battery: The above positive electrode sheet, separator and negative electrode sheet are stacked and wound in sequence to obtain electrode assembly; the electrode assembly is placed in outer packaging, the electrolyte prepared above is added, and after processes such as encapsulation, standing, formation and aging, a secondary battery is obtained.

[0275] Examples 2-33 and Comparative Examples 1-19 are similar to the secondary battery preparation method in Example 1, but the parameters and composition have been adjusted. The different parameters are detailed in Table 1.

[0276]

[0277]

[0278] Performance testing

[0279] (1) Determination of coating content in coated lithium-rich metal oxide materials:

[0280] If the coating is carbon, a high-frequency infrared carbon-sulfur analyzer (model HCS-140, Shanghai Dekai Instruments Co., Ltd.) is used to test the coating content in coated lithium-rich metal oxide materials according to GBT20123-2006 "Determination of total carbon and sulfur content of steel by infrared absorption method after combustion in a high-frequency induction furnace (conventional method)".

[0281] If the coating layer is an oxide M x O y The coating content was determined using an inductively coupled plasma atomic emission spectrometer (model ICAP7400, Thermo Fisher Scientific, USA) according to the ICP (inductively coupled plasma) atomic emission spectrometry method. Specifically:

[0282] The coated lithium-rich metal oxide material was added to aqua regia and digested under mechanical stirring for 30 minutes. The digested solution was then added to an ICAP7400 spectrometer to quantitatively analyze the chemical composition of the coated lithium-rich metal oxide material. The mass fraction p of element M was determined, and the content of the coating layer was calculated according to the following formula:

[0283] Coating content = 100% × (n × p) / m

[0284] Where n represents M x O y The relative molecular mass of M is given by m, where m represents the relative atomic mass of M.

[0285] (2) Determination of particle size Dv50 of coated lithium-rich metal oxide materials:

[0286] Particle size distribution was determined using a laser particle size analyzer (Malvin Panaco Mastersizer 2000E) in accordance with GB / T 19077-2016 Laser Diffraction Method.

[0287] Dv50 can be adjusted by controlling the degree of crushing and screening of coated lithium-rich metal oxide materials.

[0288] (3) Determination of water content in coated lithium-rich metal oxide materials:

[0289] A Karl Fischer moisture analyzer (model 831, Metrohm, Switzerland) was used. 10g of coated lithium-rich metal oxide material was heated at 170℃ in the fully automatic Karl Fischer sample heater (model 874, Metrohm, Switzerland) that comes with the analyzer. Dry nitrogen was purged at a flow rate of 40mL / min and the titration time was 400s.

[0290] The water content can be adjusted by crushing and screening coated lithium-rich metal oxide materials under different humidity conditions.

[0291] (4) TEM images of the lithium-rich metal oxide material of Comparative Example 1, and the coated lithium-rich metal oxide materials of Example 1 and Comparative Example 2 are shown below. Figures 7-9 As shown.

[0292] (5) Determination of the initial charge capacity of a secondary battery:

[0293] The assembled secondary battery was charged to 4.25V at a constant current rate of 0.1C and left to stand for 5 minutes. The first charge capacity of the secondary battery was recorded at this time. The first charge capacity of the secondary battery was obtained by dividing the first charge capacity of the battery by the mass of the coated lithium-rich metal oxide material.

[0294] (6) Measurement of resistivity of coated lithium-rich metal oxide powder:

[0295] The powder of the coated lithium-rich metal oxide material was dried, an appropriate amount of powder was weighed, and then the powder resistivity of the sample was determined by a powder resistivity tester (ST2722 digital four-probe instrument, Suzhou Jingge Electronics Co., Ltd.) according to GB / T 30835-2014 "Carbon composite lithium iron phosphate cathode material for lithium-ion batteries" at a test pressure of 20 MPa.

[0296] (7) Stability testing of coated lithium-rich metal oxide materials:

[0297] Take s(g) coated lithium-rich metal oxide material and place it in a constant temperature (25℃) and constant humidity (40% relative humidity) environment for 7 days. Then weigh the sample to obtain the mass t(g). Calculate the weight growth rate w according to the following formula.

[0298] Weight growth rate w = 100% × (ts) / t

[0299] w≤0.5% indicates excellent integrity and density of the coating layer; 0.5%<w<0.8% indicates good integrity and density of the coating layer; w≥0.8% indicates poor integrity and density of the coating layer.

[0300] (8) Testing of the integrity and density of the coating layer of coated lithium-rich metal oxide materials:

[0301] At 25°C, take m(g) of coated lithium-rich metal oxide material into a beaker, and add V a A mixed solvent of (mL) deionized water and anhydrous ethanol, wherein the mass percentage of deionized water in the mixed solvent is b, and b satisfies:

[0302] When 2 ≤ a < 3, b = 100% - a × 10%;

[0303] When 3 ≤ a < 4, b = 100% - a × 20%;

[0304] When 4 ≤ a ≤ 6, b = 0;

[0305] After sealing with sealing film, stir the above mixture at 600 rpm for 3 minutes, let it stand, and then filter it using a vacuum filtration device. Take V b (mL) of filtrate was titrated with an ethanolic solution of hydrochloric acid (hydrochloric acid concentration of C mol / L). An automatic potentiometric titrator was used, and the titration was performed with pH value on the ordinate and the volume of titrant consumed on the abscissa. The abrupt change points EP1 and EP2 of the electrode potential were recorded. The titrant consumption volumes corresponding to the two abrupt change points were V1 (mL) and V2 (mL), respectively (V2>V1).

[0306] When the titration reaction proceeds to the electrode potential jump point EP1, the following chemical reaction occurs:

[0307] LiOH + HCl → LiCl + H₂O

[0308] Li₂CO₃ + HCl → LiCl + LiHCO₃

[0309] When the titration reaction proceeds to the electrode potential jump point EP2, the following chemical reaction occurs:

[0310] LiHCO3 + HCl → LiCl + H2O + CO2

[0311] The free lithium content d (ppm) dissolved in the m(g) coated lithium-rich metal oxide material is calculated using the following formula:

[0312] d=C×V a ×(69.4684V2-0.0424V1) / (m×V b )

[0313] The integrity and density of the coating layer are good if the d value meets the following conditions; otherwise, the integrity and density of the coating layer are poor:

[0314] When 2≤a<3, d≤500ppm;

[0315] When 3 ≤ a < 4, d ≤ 1000ppm;

[0316] When 4≤a≤6, d≤1500ppm.

[0317] The results are shown in Table 2.

[0318]

[0319]

[0320] As shown in Table 1-2:

[0321] Compared with Comparative Examples 1-8, the coating layer in the lithium-rich metal oxide coating materials of this application exhibits higher integrity and density; among them, the integrity and density of the coating layer in the lithium-rich metal oxide coating materials of Examples 1-29 of this application are further improved. Compared with Comparative Examples 6-8, the coating layer material content in the lithium-rich metal oxide coating materials of this application is higher.

[0322] Compared with Comparative Examples 1-2, the powder resistivity of the coated lithium-rich metal oxide materials in Examples 1-5 and 13-15 of this application is lower, and the first charge capacity of the secondary battery is higher.

[0323] Compared with Comparative Examples 3-5, the coated lithium-rich metal oxide materials of Examples 24-26 of this application have lower powder resistivity and higher first-charge capacity of the secondary battery.

[0324] Compared with Comparative Examples 6-8, the coated lithium-rich metal oxide materials prepared by Examples 1-2, 5, 15, 30 and 33 of this application using microwave power of 200-1000W and furnace pressure of -10-1000Pa have lower powder resistivity and higher first-charge capacity of secondary batteries.

[0325] The results of the determination of coating integrity and density using deionized water as solvent (b=100%) in Comparative Examples 9-14 showed a large deviation from the stability test results. In contrast, the results of the determination of coating integrity and density using appropriate solvents in Comparative Examples 1-2, Examples 1 and 37-39 of this application were consistent with the stability test results.

[0326] The results of coating integrity and density determination in Comparative Examples 15-19, which used an excessively low ratio of coated lithium-rich metal oxide material and solvent, deviated significantly from the stability test results. In contrast, the results of coating integrity and density determination in Examples 1 and 13-14, which used a suitable ratio of coated lithium-rich metal oxide material and solvent, were consistent with the stability test results.

[0327] The above demonstrates that the coating layer in the lithium-rich metal oxide material of this application has better integrity and density, lower powder resistivity, better conductivity, higher coating layer material content, and higher first-charge capacity of the secondary battery.

[0328] Since stability testing is an existing method, the results of the method used in this application to determine the integrity and density of the coating layer in coated lithium-rich metal oxide materials are consistent with the stability test results, indicating that the method used in this application has high accuracy.

[0329] 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 coated lithium-rich metal oxide material, comprising a core and a coating layer covering the core; The kernel contains LiaMOy; where... The M includes one or more elements selected from Ni, Co, Fe, Mn, Zn, Mg, Ca, Cu, Sn, Mo, Ru, Ir, V, Nb and Cr, where 2≤a≤6 and 2≤y≤4. The coating layer is carbon or silicon oxide; The weight gain rate w of the coated lithium-rich metal oxide material after standing for 144 to 192 hours in an environment of 25°C and 40% relative humidity is w < 0.8%; the particle size Dv50 of the coated lithium-rich metal oxide material is 4~10 μm.

2. The coated lithium-rich metal oxide material according to claim 1, wherein, The w ≤ 0.5%.

3. A coated lithium-rich metal oxide material, comprising a core and a coating layer covering the core; The kernel contains LiaMOy; where... The M includes one or more elements selected from Ni, Co, Fe, Mn, Zn, Mg, Ca, Cu, Sn, Mo, Ru, Ir, V, Nb and Cr, where 2≤a≤6 and 2≤y≤4. The coating layer is carbon or silicon oxide; Furthermore, the d-value of the coated lithium-rich metal oxide material satisfies: When 2 ≤ a < 3, d ≤ 500 ppm; When 3 ≤ a < 4, d ≤ 1000 ppm; When 4≤a≤6, d≤1500 ppm; The d-value of the coated lithium-rich metal oxide material is determined through the following steps: The coated lithium-rich metal oxide material is mixed with a solvent at a mass ratio of 1:50 to 1:1, wherein the solvent is composed of water and ethanol, and the mass content of water in the solvent is b, and b satisfies: When 2 ≤ a < 3, b = 100% - a × 10%; When 3 ≤ a < 4, b = 100% - a × 20%; When 4 ≤ a ≤ 6, b = 0; The liquid phase in the resulting mixture is separated, and the liquid phase is subjected to potentiometric titration to calculate the free lithium content dissolved in the coated lithium-rich metal oxide material, which is the d-value of the coated lithium-rich metal oxide material. The particle size Dv50 of the coated lithium-rich metal oxide material is 4~10μm.

4. The coated lithium-rich metal oxide material according to any one of claims 1 to 3, wherein, The M includes one or more elements selected from Ni, Co, Fe, Mn, Cu, V, and Nb.

5. The coated lithium-rich metal oxide material according to claim 4, wherein, The M includes one or more elements selected from Ni, Co, Fe, Cu, and Nb.

6. The coated lithium-rich metal oxide material according to any one of claims 1 to 3, wherein, The core includes one or more of Li2NiO2, Li2CuO2, Li2MnO3, Li3VO4, Li3NbO4, Li5FeO4, and Li6CoO4.

7. The coated lithium-rich metal oxide material according to claim 6, wherein, The core includes one or more of Li2NiO2, Li2CuO2, Li3NbO4, Li5FeO4, and Li6CoO4.

8. The coated lithium-rich metal oxide material according to any one of claims 1 to 3, wherein, The coating layer is carbon or silicon dioxide.

9. The coated lithium-rich metal oxide material according to any one of claims 1 to 3, wherein, The coating layer has a mass content of 1.3% to 10% in the coated lithium-rich metal oxide material.

10. The coated lithium-rich metal oxide material according to claim 9, wherein, The coating layer has a mass content of 3% to 7% in the coated lithium-rich metal oxide material.

11. The coated lithium-rich metal oxide material according to any one of claims 1 to 3, wherein, The particle size Dv50 of the coated lithium-rich metal oxide material is 4~8 μm.

12. The coated lithium-rich metal oxide material according to any one of claims 1 to 3, wherein, The water content in the coated lithium-rich metal oxide material is ≤ 1000 ppm by mass.

13. The coated lithium-rich metal oxide material according to claim 12, wherein, The water content in the coated lithium-rich metal oxide material is ≤ 500 ppm by mass.

14. The coated lithium-rich metal oxide material according to claim 12, wherein, The water content in the coated lithium-rich metal oxide material is ≤ 300 ppm by mass.

15. The coated lithium-rich metal oxide material according to claim 12, wherein, The water content in the coated lithium-rich metal oxide material is ≤ 200 ppm by mass.

16. The coated lithium-rich metal oxide material according to any one of claims 1 to 3, wherein, The resistivity of the coated lithium-rich metal oxide material measured at 20 MPa pressure is <4 Ω·cm.

17. The coated lithium-rich metal oxide material according to claim 16, wherein, The powder resistivity of the coated lithium-rich metal oxide material measured at 20 MPa pressure is ≤3.3 Ω·cm.

18. A method for preparing coated lithium-rich metal oxide materials, comprising the following steps: Provide compound LizMOy', wherein, The M includes one or more elements selected from Ni, Co, Fe, Mn, Zn, Mg, Ca, Cu, Sn, Mo, Ru, Ir, V, Nb, and Cr, with 0.98 ≤ z ≤ 1.02 and 2 ≤ y' ≤ 3; The LizMOy' was coated by plasma-enhanced chemical vapor deposition; The coated product is mixed with a lithium source and sintered to obtain a coated lithium-rich metal oxide material.

19. The method according to claim 18, wherein, The coated lithium-rich metal oxide material includes a core and a coating layer covering the core. The core includes LiaMOy, and the coating layer includes one or more of carbon, silicon oxide, and metal oxide. Wherein, a, M and y are as described in any one of claims 1 to 17.

20. The method according to claim 18 or 19, wherein, The coated lithium-rich metal oxide material is the coated lithium-rich metal oxide material according to any one of claims 1 to 17.

21. The method according to claim 18 or 19, wherein, The operating parameters for the plasma-enhanced chemical vapor deposition include: Microwave power is 200~1000W; and / or, The internal gas pressure of the chemical vapor deposition furnace is -10 to 1000 Pa; and / or, The furnace temperature of the chemical vapor deposition furnace is 400 ℃~600 ℃; and / or, The deposition time is 2 to 10 hours; and / or, The gas flow rate at the inlet of the chemical vapor deposition furnace is 10~1000 sccm.

22. The method of claim 21, wherein, The operating parameters for the plasma-enhanced chemical vapor deposition include: Microwave power is 200~800W or 500~1000W; and / or The internal gas pressure of the chemical vapor deposition furnace is 10~1000 Pa or -10~100 Pa; and / or The furnace temperature of the chemical vapor deposition furnace is 450 ℃~550 ℃; and / or, The deposition time is 4-8 h or 5-8 h; and / or, The gas flow rate at the inlet of the chemical vapor deposition furnace is 100~700 sccm or 200~500 sccm.

23. The method according to claim 18 or 19, wherein, The raw materials used in the coating process are selected from one or more of carbon sources, silicon oxide sources, and metal oxide sources.

24. The method according to claim 23, wherein, The coating process uses raw materials selected from one or more of the following: organic carbon source, organic silicon source, inorganic silicon source, organic aluminum source, inorganic aluminum source, organic titanium source, and inorganic titanium source.

25. The method according to claim 23, wherein, The raw materials used in the coating process are selected from one or more of ethylene, acetylene, methane, acetone, ethanol, benzene, tetraethyl orthosilicate, silicon tetrachloride, aluminum isopropoxide, tetrabutyl titanate, and titanium tetrachloride.

26. The method according to claim 23, wherein, The raw materials used in the coating process are selected from one or more of ethylene, acetylene, methane, tetraethyl orthosilicate, aluminum isopropoxide, and tetrabutyl titanate.

27. The method according to claim 18 or 19, wherein, The sintering temperature is 500 ℃~700 ℃; and / or, The sintering time is 4 h to 10 h; and / or, The sintering heating rate is 2 °C / min to 8 °C / min; and / or, The sintering is carried out in an inert atmosphere.

28. The method of claim 27, wherein, The sintering temperature is 550 ℃~650 ℃; and / or, The sintering time is 6 h to 8 h; and / or, The heating rate for sintering is 4 ℃ / min to 6 ℃ / min.

29. The method of claim 27, wherein, The sintering temperature is 600 ℃~650 ℃; and / or, The sintering time is 6 h to 7 h.

30. The method according to claim 18 or 19, wherein, The molar ratio of lithium in the lithium source to LizMOy' is (az):

1.

31. The method according to claim 18 or 19, wherein, Prior to the coating process, the LizMOy' is crushed; and / or, Prior to the coating process, the raw materials used in the coating process are gasified; and / or, The prepared coated lithium-rich metal oxide material is crushed and screened.

32. The method according to claim 31, wherein, The raw materials used in the coating process are vaporized at 300 ℃ to 500 ℃.

33. The method according to claim 31, wherein, The prepared coated lithium-rich metal oxide material was crushed and sieved in a dry environment.

34. The method according to claim 18 or 19, wherein, The LizMOy' is prepared through the following steps: The lithium source and the source of element M are mixed and sintered; wherein the molar ratio of lithium element in the lithium source to element M element in the source of element M is 0.98:1 to 1.09:

1.

35. The method according to claim 34, wherein, The molar ratio of lithium in the lithium source to M in the source of M is 0.98:1 to 1.02:1 or 1:1 to 1.09:

1.

36. The method according to claim 34, wherein, The molar ratio of lithium in the lithium source to M in the source of M is 1:1 to 1.05:

1.

37. The method of claim 34, wherein, In the steps of preparing LizMOy': The sintering temperature is 400 ℃~600 ℃; and / or, The sintering time is 2 h to 8 h; and / or, The sintering heating rate is 4 °C / min to 10 °C / min; and / or, The sintering is carried out in an inert atmosphere.

38. The method according to claim 37, wherein, In the steps of preparing LizMOy': The sintering temperature is 450 ℃~550 ℃; and / or, The sintering time is 4 h to 6 h; and / or, The heating rate for sintering is 6 ℃ / min to 8 ℃ / min.

39. The method according to claim 34, wherein, The lithium source includes one or more of lithium oxide, lithium carbonate, lithium oxalate, lithium acetate, and lithium hydroxide; and / or, The source of element M is selected from one or more of the oxides, hydroxides, halides, sulfates, carbonates, nitrates, oxalates, acetates, sulfides, and nitrides of element M.

40. The method according to claim 39, wherein, The source of element M is an oxide of element M.

41. A method for determining the coating layer in a coated lithium-rich metal oxide material, comprising the following steps: A coated lithium-rich metal oxide material is provided, the coated lithium-rich metal oxide material comprising a core and a coating layer covering the core, wherein the core comprises LiaMOy; wherein, The M includes one or more elements selected from Ni, Co, Fe, Mn, Zn, Mg, Ca, Cu, Sn, Mo, Ru, Ir, V, Nb, and Cr, where 2≤a≤6 and 2≤y≤4; the coating layer contains carbon or silicon oxide, and the particle size Dv50 of the coated lithium-rich metal oxide material is 4~10μm. The coated lithium-rich metal oxide material is mixed with a solvent at a mass ratio of 1:50 to 1:1, wherein the solvent is composed of water and ethanol, and the mass content of water in the solvent is b, and b satisfies: when 2≤a<3, b=100%-a×10%; when 3≤a<4, b=100%-a×20%; when 4≤a≤6, b=0. The liquid phase in the resulting mixture is separated, and the liquid phase is titrated to calculate the free lithium content d value dissolved in the coated lithium-rich metal oxide material. It is then confirmed whether the d value meets the following requirements: When 2≤a<3, d≤500 ppm; when 3≤a<4, d≤1000 ppm; when 4≤a≤6, d≤1500 ppm.

42. The method according to claim 41, wherein, The coated lithium-rich metal oxide material is mixed with a solvent at a mass ratio of 1:50 to 1:

10.

43. The coated lithium-rich metal oxide material according to claim 3 or the method according to claim 41, wherein, The mixing time is 1 min to 4 min; and / or, The mixing is carried out under stirring conditions at a speed of 200 rpm to 800 rpm; and / or, The determination was performed at 25°C; and / or, The titration is a potentiometric titration.

44. The method according to claim 43, wherein, The mixing time is 1 min to 3 min; and / or, The mixing is carried out under stirring conditions at a speed of 400 rpm to 800 rpm.

45. The coated lithium-rich metal oxide material according to claim 3 or the method according to claim 41, wherein, The content of free lithium dissolved in the coated lithium-rich metal oxide material was determined by the following steps: The coated lithium-rich metal oxide material is mixed with a solvent at a mass ratio of 1:50 to 1:1, wherein the solvent is composed of water and ethanol, and the mass content of water in the solvent is b, and b satisfies: when 2≤a<3, b=100% - a×10%; when 3≤a<4, b=100% - a×20%; when 4≤a≤6, b=0. The liquid phase in the resulting mixture was separated, and the liquid phase was taken and potentiometrically titrated with an ethanol solution of hydrochloric acid as the titrant. The volumes of titrant consumed corresponding to the two potential jump points during the titration process were V1 mL and V2 mL, respectively, and V2 > V1. The content of free lithium dissolved in the coated lithium-rich metal oxide material, d, is calculated according to the following formula: d=C×Va×(69.4684V2-0.0424V1) / (m×Vb) in, m represents the mass of the coated lithium-rich metal oxide material, in grams; Va represents the volume of the solvent, in mL; Vb represents the volume of the liquid sample taken, in mL; C represents the concentration of hydrochloric acid in the titrant, in mol / L.

46. ​​The method according to claim 45, wherein, The coated lithium-rich metal oxide material is mixed with a solvent at a mass ratio of 1:50 to 1:

10.

47. A positive electrode, comprising the coated lithium-rich metal oxide material according to any one of claims 1 to 17 or the coated lithium-rich metal oxide material prepared by any one of claims 18 to 40.

48. A battery comprising a coated lithium-rich metal oxide material according to any one of claims 1 to 17, a coated lithium-rich metal oxide material prepared by any one of claims 18 to 40, or a positive electrode sheet according to claim 47.

49. An electrical device comprising the battery of claim 48.

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