WO2024098198A1 - 包覆型富锂金属氧化物材料及制备方法、测定包覆型富锂金属氧化物材料中包覆层的方法、正极极片、电池及用电装置 - Google Patents

包覆型富锂金属氧化物材料及制备方法、测定包覆型富锂金属氧化物材料中包覆层的方法、正极极片、电池及用电装置 Download PDF

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WO2024098198A1
WO2024098198A1 PCT/CN2022/130329 CN2022130329W WO2024098198A1 WO 2024098198 A1 WO2024098198 A1 WO 2024098198A1 CN 2022130329 W CN2022130329 W CN 2022130329W WO 2024098198 A1 WO2024098198 A1 WO 2024098198A1
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metal oxide
lithium
oxide material
rich metal
coated lithium
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PCT/CN2022/130329
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English (en)
French (fr)
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王帮润
罗东升
柳娜
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宁德时代新能源科技股份有限公司
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Priority to PCT/CN2022/130329 priority Critical patent/WO2024098198A1/zh
Publication of WO2024098198A1 publication Critical patent/WO2024098198A1/zh

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/485—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of mixed oxides or hydroxides for inserting or intercalating light metals, e.g. LiTi2O4 or LiTi2OxFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
    • H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present 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 a coating layer in a coated lithium-rich metal oxide material, a positive electrode sheet, a battery and an electrical device.
  • secondary batteries are widely used in energy storage power systems such as hydropower, thermal power, wind power and solar power stations, as well as power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace and other fields.
  • energy storage power systems such as hydropower, thermal power, wind power and solar power stations, as well as power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace and other fields.
  • secondary batteries have made great progress, higher requirements have been put forward for their energy density, cycle performance and safety performance.
  • lithium-rich metal oxide materials The lithium content in lithium-rich metal oxide materials is high, and they are easily dissolved into the external environment and react with carbon dioxide and/or water to form highly alkaline, gel-like byproducts on the surface of the materials, which affect the migration of lithium ions, reduce the battery's charging capacity, and increase the material's resistance.
  • the present application is made in view of the above-mentioned problems, and its purpose is 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 plate, a battery and an electrical device.
  • the coated lithium-rich metal oxide material of the present application has a coating layer with high integrity and density, which can reduce the dissolution of lithium in the lithium-rich metal oxide core to the outside to cause side reactions, increase the capacity of the battery, reduce the material resistance, and increase the migration rate of lithium ions; the method for measuring the coating layer in the coated lithium-rich metal oxide material of the present application can accurately and quickly measure the integrity and density of the coating layer, and the operation is simple.
  • the first aspect of the present application provides a coated lithium-rich metal oxide material, including a core and a coating layer coating the core;
  • the inner core comprises Li a MO y ; wherein M comprises one or more elements selected from the group consisting of Ni, Co, Fe, Mn, Zn, Mg, Ca, Cu, Sn, Mo, Ru, Ir, V, Nb and Cr, 2 ⁇ a ⁇ 6, 2 ⁇ y ⁇ 4;
  • the coating layer comprises one or more of carbon, silicon oxide and metal oxide;
  • the weight growth 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, w ⁇ 0.8%;
  • the coated lithium-rich metal oxide material of the present 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 of the dissolved free lithium with external substances, improving the charging capacity of the battery, increasing the migration rate of lithium ions, and reducing the resistance of the material.
  • a second aspect of the present application provides a coated lithium-rich metal oxide material, comprising a core and a coating layer coating the core;
  • the inner core comprises Li a MO y ; wherein M comprises one or more elements selected from the group consisting of Ni, Co, Fe, Mn, Zn, Mg, Ca, Cu, Sn, Mo, Ru, Ir, V, Nb and Cr, 2 ⁇ a ⁇ 6, 2 ⁇ y ⁇ 4;
  • the coating layer comprises one or more of carbon, silicon oxide and metal oxide;
  • the d value of the coated lithium-rich metal oxide material satisfies:
  • the d value of the coated lithium-rich metal oxide material is determined by the following steps:
  • the coated lithium-rich metal oxide material is mixed with a solvent in a mass ratio of 1:50 to 1:1, wherein the solvent consists of water and ethanol, the mass content of water in the solvent is b, and b satisfies:
  • the liquid phase in the obtained mixture is separated and subjected to potentiometric titration to calculate the content of free lithium dissolved in the coated lithium-rich metal oxide material, which is the d value of the coated lithium-rich metal oxide material.
  • the integrity and density of the coating layer in the coated lithium-rich metal oxide material of the present application are further improved, the dissolution of free lithium in the lithium-rich metal oxide core is further reduced, and the side reaction of the dissolved free lithium with the outside world is 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.
  • M includes one or more elements of Ni, Co, Fe, Mn, Cu, V and Nb, and optionally includes one or more elements of Ni, Co, Fe, Cu and Nb.
  • the inner 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 .
  • the coating layer includes one or more of carbon, silica, alumina, and titania.
  • the present 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 dissolving free lithium, increasing the charging capacity of the battery, reducing the resistance of the material, and increasing the migration rate of lithium ions.
  • the mass content of the coating layer in the coated lithium-rich metal oxide material is 1.3% to 10%, and optionally 3% to 7%.
  • the particle size D v 50 of the coated lithium-rich metal oxide material is 2 to 10 ⁇ m, optionally 4 to 10 ⁇ m, and more optionally 4 to 8 ⁇ m.
  • the coated lithium-rich metal oxide material is ensured to have a suitable specific surface area, the stability, integrity and density of the coating layer are guaranteed, and at the same time it is beneficial to the migration of lithium ions and improves the charging capacity of the battery.
  • the mass content of water in the coated lithium-rich metal oxide material is ⁇ 1000 ppm, can be ⁇ 500 ppm, can be ⁇ 300 ppm, and can be ⁇ 200 ppm.
  • the dissolution of free lithium in the lithium-rich core is further reduced, the side reactions of lithium dissolution are further reduced, thereby further improving the migration of lithium ions, further improving the charging capacity of the battery, and further reducing the resistance of the material.
  • the powder resistivity of the coated lithium-rich metal oxide material measured at a pressure of 20 MPa is less than 4 ⁇ cm, and can be ⁇ 3.3 ⁇ cm.
  • the reduction in resistivity is beneficial to increasing the migration rate of lithium ions and improving the charging capacity and rate of the battery.
  • the third aspect of the present application also provides a method for preparing a coated lithium-rich metal oxide material, comprising the following steps:
  • Li z MO y' 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.
  • PECVD Plasma enhanced chemical vapor deposition
  • Low-temperature plasma uses low-temperature plasma as an energy source.
  • the coated object is placed on the cathode of glow discharge under low pressure.
  • the coated object is heated to a preset temperature by glow discharge or heating element.
  • an appropriate amount of reaction gas is introduced.
  • a coating layer is formed on the surface of the coated object.
  • low-temperature plasma contains a large number of high-energy electrons, which can provide the activation energy required for the process.
  • the collision between electrons and reaction gas molecules can promote the decomposition, combination, excitation and ionization of molecules, generate various highly active chemical groups, and significantly reduce the temperature required for coating treatment.
  • the present application adopts plasma enhanced chemical vapor deposition to coat the compound Li z MO y' . Since the lithium content of the compound Li z MO y' is low, the reaction gas in the coating process is not easy to react with the lithium in the compound Li z MO y' , thereby ensuring the stability and effectiveness of the coating operation; the coating product is mixed with lithium and then sintered to obtain a lithium-rich metal oxide material with high integrity and compactness of the coating layer. In addition, the method of the present application is simple to operate and easy to promote industrialization.
  • the coated lithium-rich metal oxide material comprises a core and a coating layer coating the core, the core comprises Li a MO y , and the coating layer comprises one or more of carbon, silicon oxide and metal oxide;
  • a, M and y are as in the first aspect or the second aspect of the present application.
  • the coated lithium-rich metal oxide material is the coated lithium-rich metal oxide material of the first aspect or the second aspect of the present application.
  • the operating parameters of the plasma enhanced chemical vapor deposition include:
  • the microwave power is 200-1000W, and can be 200-800W or 500-1000W; and/or,
  • the gas pressure in the chemical vapor deposition furnace is -10 to 1000 Pa, which may be 10 to 1000 Pa or -10 to 100 Pa; and/or,
  • the temperature inside the chemical vapor deposition furnace is 400° C. to 600° C., optionally 450° C. to 550° C.; and/or,
  • the deposition time is 2 to 10 hours, optionally 4 to 8 hours, more optionally 5 to 8 hours; and/or,
  • the gas flow rate at the gas inlet of the chemical vapor deposition furnace is 10 to 1000 sccm, optionally 100 to 700 sccm, and more optionally 200 to 500 sccm.
  • the microwave power within the above range is conducive to ensuring the ionization deposition rate of the reaction gas, forming a uniform, complete and dense coating layer on the surface of the coated object, and reducing the side reactions between the coated object and the reaction gas.
  • the gas pressure in the furnace within the above range can ensure the reaction rate of vapor deposition and ensure the effective coating of the coating layer on the inner core, thereby forming a uniform, complete and dense coating layer and reducing the generation of defects.
  • the furnace temperature within the above range can increase the rate of ionized deposition of the reaction gas, forming a uniform, complete and dense coating layer on the surface of the coated object, while reducing the mass loss of the coated object caused by side reactions between the coated object and the reaction gas.
  • the deposition time within the above range is beneficial to ensuring the appropriate content of the coating material and forming a uniform, complete and dense coating layer, which is beneficial to the battery capacity.
  • the gas flow rate at the gas inlet within the above range can ensure the appropriate content of the coating layer material, obtain a uniform, complete and dense coating layer, and reduce the waste of reaction gas.
  • the raw material used for coating treatment is selected from one or more of a carbon source, a silicon oxide source, and a metal oxide source;
  • the raw material used for the coating treatment is selected from one or more of an organic carbon source, an organic silicon source, an inorganic silicon source, an organic aluminum source, an inorganic aluminum source, an organic titanium source and an inorganic titanium source, and more optionally selected from one or more of an organic gas, an organic silicon source, an organic aluminum source and an organic titanium source;
  • the raw materials used for 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 optionally selected from one or more of ethylene, acetylene, methane, tetraethyl orthosilicate, aluminum isopropoxide and tetrabutyl titanate.
  • 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 above raw materials are not easy to cause side reactions in the coated object, thereby ensuring the effectiveness and stability of the coating treatment and reducing the waste of raw materials.
  • the sintering temperature is 500° C. to 700° C., optionally 550° C. to 650° C., and more optionally 600° C. to 650° C.; and/or,
  • the sintering time is 4 hours to 10 hours, optionally 6 hours to 8 hours, and more optionally 6 hours to 7 hours; and/or,
  • the heating rate of sintering is 2°C/min to 8°C/min, and can be 4°C/min to 6°C/min; and/or,
  • Sintering is carried out in an inert atmosphere.
  • the sintering temperature, sintering time and sintering heating rate within the above range are conducive to obtaining a coated lithium-rich metal oxide with high crystallinity, reducing the generation of by-products and saving energy consumption.
  • the molar ratio of lithium element in the lithium source to Li z MO y′ is (az): 1. This is conducive to forming a lithium-rich metal oxide core, thereby obtaining a lithium-rich metal oxide material coated with a complete and dense coating layer.
  • the Li z MO y′ is crushed, which is beneficial to the uniformity of the coating process and can ensure that the coated lithium-rich metal oxide material has a suitable specific surface area, thereby facilitating the migration of lithium ions and the utilization of the battery capacity.
  • the raw materials used in the coating process are gasified, and the raw materials used in the coating process are optionally gasified at 300° C. to 500° C.
  • the reaction gas required for the coating process must be obtained by gasification to ensure the plasma enhanced chemical vapor deposition.
  • 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 a suitable water content and particle size.
  • Li z MO y' is prepared by the following steps:
  • a lithium source and a source of an M element are mixed and sintered; wherein the molar ratio of the lithium element in the lithium source to the M element in the source of the M element is 0.98:1 to 1.09:1, optionally 0.98:1 to 1.02:1 or 1:1 to 1.09:1, and more preferably 1:1 to 1.05:1.
  • the compound Li z MO y' Since the compound Li z MO y' has a low lithium content, the compound Li z MO y' has better stability in coating treatment and can achieve effective coating.
  • the sintering temperature is 400°C to 600°C, and can be 450°C to 550°C; and/or,
  • the sintering time is 2h to 8h, and can be 4h to 6h; and/or,
  • the heating rate of sintering is 4°C/min to 10°C/min, and can be 6°C/min to 8°C/min; and/or,
  • Sintering is carried out in an inert atmosphere.
  • the lithium source comprises 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 oxide, hydroxide, halide, sulfate, carbonate, nitrate, oxalate, acetate, sulfide and nitride of element M, and may be the oxide of element M.
  • the fourth aspect of the present application provides a method for measuring a coating layer in a coated lithium-rich metal oxide material, comprising the following steps:
  • a coated lithium-rich metal oxide material comprising a core and a coating layer coating the core, wherein the core comprises Li a MO y ; wherein M comprises one or more elements selected from the group consisting of Ni, Co, Fe, Mn, Zn, Mg, Ca, Cu, Sn, Mo, Ru, Ir, V, Nb and Cr, 2 ⁇ a ⁇ 6, 2 ⁇ y ⁇ 4; and the coating layer comprises one or more selected from the group consisting of carbon, silicon oxide and metal oxide;
  • the liquid phase in the obtained mixture is separated and titrated to calculate the free lithium content d dissolved in the coated lithium-rich metal oxide material to confirm whether the d value satisfies:
  • the present application adopts solvents with different water contents (deionized water, anhydrous ethanol or a mixed solution of the two) to dissolve the free lithium in the material and react with the dissolved free lithium, and determines the density and integrity of the coating layer by measuring the free lithium content dissolved from the material.
  • the measurement result has high accuracy, good reliability and fast detection speed; at the same time, the coating layer can be prevented from being damaged during the measurement process.
  • the mixing time is 1 min to 4 min, optionally 1 min to 3 min; and/or,
  • the mixing is carried out under stirring conditions of 200 rpm to 800 rpm, and can be carried out under stirring conditions of 400 rpm to 800 rpm; and/or,
  • the assay is performed at 25°C; and/or,
  • the titration is potentiometric.
  • the mixing time and stirring speed within the above range can ensure that the dissolved lithium of 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.
  • the free lithium content dissolved in the coated lithium-rich metal oxide material is determined by the following steps:
  • the free lithium content d value dissolved in the coated lithium-rich metal oxide material is calculated according to the following formula:
  • m represents the mass of the coated lithium-rich metal oxide material, in g
  • Va represents the volume of the solvent in mL
  • V b represents the volume of the liquid phase taken, in mL
  • C represents the concentration of hydrochloric acid in the titrant, in mol/L.
  • the fifth aspect of the present application provides a positive electrode plate, comprising the coated lithium-rich metal oxide material of the first aspect or the second aspect of the present application or the coated lithium-rich metal oxide material prepared according to the method of the third aspect of the present application.
  • the sixth aspect of the present application provides a battery, comprising the coated lithium-rich metal oxide material of the first aspect or the second aspect of the present application, the coated lithium-rich metal oxide material prepared according to the method of the third aspect of the present application, or the positive electrode plate of the fifth aspect of the present application.
  • the seventh aspect of the present application provides an electrical device, comprising the battery of the sixth aspect of the present application.
  • FIG. 1 is a schematic diagram of a secondary battery according to an embodiment of the present application.
  • FIG. 2 is an exploded view of the secondary battery according to the embodiment of the present application shown in FIG. 1 .
  • FIG. 3 is a schematic diagram of a battery module according to an embodiment of the present application.
  • FIG. 4 is a schematic diagram of a battery pack according to an embodiment of the present application.
  • FIG. 5 is an exploded view of the battery pack shown in FIG. 4 according to an embodiment of the present application.
  • FIG. 6 is a schematic diagram of an electric device using a secondary battery as a power source according to an embodiment of the present application.
  • FIG. 7 is a TEM image of the lithium-rich metal oxide material prepared in Comparative Example 1.
  • FIG8 is a TEM image of the coated lithium-rich metal oxide material prepared in Example 1.
  • FIG9 is a TEM photograph of the coated lithium-rich metal oxide material prepared in Comparative Example 2.
  • the coated lithium-rich metal oxide material and its preparation method, the method for measuring the coating layer in the coated lithium-rich metal oxide material, the positive electrode plate, the battery and the implementation method of the electric device of the present application are specifically disclosed with appropriate reference to the drawings.
  • unnecessary detailed descriptions are omitted.
  • detailed descriptions of well-known matters and repeated descriptions of actually the same structure are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art.
  • the drawings and the following descriptions are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.
  • range disclosed in this application is defined in the form of a lower limit and an upper limit, and a given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of the particular range.
  • the range defined in this way can be inclusive or exclusive of the end values, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form a range. For example, if a range of 60 to 120 and 80 to 110 is listed for a specific parameter, it is understood that the range of 60 to 110 and 80 to 120 is also expected.
  • the numerical range "a to b" represents an abbreviation of any real number combination between a and b, where a and b are both real numbers.
  • the numerical range "0 to 5" means that all real numbers between "0 to 5" have been fully listed in this article, and "0 to 5" is just an abbreviation of these numerical combinations.
  • a parameter is expressed as an integer ⁇ 2, it is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.
  • a method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially.
  • a method may further include step (c), indicating that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.
  • the term "or” is inclusive.
  • the phrase “A or B” means “A, B, or both A and B”. More specifically, any of the following conditions satisfies the condition "A or B”: 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).
  • Secondary batteries also known as rechargeable batteries or storage batteries, refer to batteries that can continue to be used by recharging to activate the active materials after the battery is discharged.
  • a secondary battery includes a positive electrode sheet, a negative electrode sheet, a separator and an electrolyte.
  • active ions such as lithium ions
  • the separator is arranged between the positive electrode sheet and the negative electrode sheet, mainly to prevent the positive and negative electrodes from short-circuiting, while allowing active ions to pass through.
  • the electrolyte is between the positive electrode sheet and the negative electrode sheet, mainly to conduct active ions.
  • One embodiment of the present application provides a coated lithium-rich metal oxide material, including a core and a coating layer coating the core;
  • the inner core comprises Li a MO y ; wherein M comprises one or more elements selected from the group consisting of Ni, Co, Fe, Mn, Zn, Mg, Ca, Cu, Sn, Mo, Ru, Ir, V, Nb and Cr, 2 ⁇ a ⁇ 6, 2 ⁇ y ⁇ 4;
  • the coating layer comprises one or more of carbon, silicon oxide and metal oxide;
  • the weight growth rate of the coated lithium-rich metal oxide material after standing for 144 to 192 hours (e.g., 168 hours) in an environment at 25° C. and a relative humidity of 40% is w, w ⁇ 0.8%;
  • the coated lithium-rich metal oxide material of the present 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 is prone to side reactions with external substances to generate highly alkaline byproducts, the byproducts are prone to cause slurry gel, hindering the migration of lithium ions and battery processing, and increasing the material resistance. Therefore, the coating layer of the coated lithium-rich metal oxide material of the present application reduces the dissolution of free lithium, thereby improving the mobility of lithium ions, reducing the resistance of the material, and is more conducive to the processing of battery products.
  • Another embodiment of the present application provides a coated lithium-rich metal oxide material, including a core and a coating layer coating the core;
  • the inner core comprises Li a MO y ; wherein M comprises one or more elements selected from the group consisting of Ni, Co, Fe, Mn, Zn, Mg, Ca, Cu, Sn, Mo, Ru, Ir, V, Nb and Cr, 2 ⁇ a ⁇ 6, such as 2, 3, 4, 5, 6 and the range formed by any two of the above values, 2 ⁇ y ⁇ 4, such as 2, 3, 4 and the range formed by any two of the above values;
  • the coating layer comprises one or more of carbon, silicon oxide and metal oxide;
  • the d value of the coated lithium-rich metal oxide material satisfies:
  • the d value of the coated lithium-rich metal oxide material is determined by the following steps:
  • the coated lithium-rich metal oxide material and the solvent are mixed in a mass ratio of 1:50 to 1:1 (e.g., 1:1, 1:10, 1:20, 1:40, and a range formed by any two of the above values), wherein the solvent is composed of water and ethanol, the mass content of water in the solvent is b, and b satisfies:
  • the liquid phase in the obtained mixture is separated and subjected to potentiometric titration to calculate the content of free lithium dissolved in the coated lithium-rich metal oxide material, which is the d value of the coated lithium-rich metal oxide material.
  • the integrity and density of the coating layer in the coated lithium-rich metal oxide material of the present application are further improved, the dissolution of free lithium in the lithium-rich metal oxide core is further reduced, and the side reaction of the dissolved free lithium with external substances is further reduced, thereby further improving the capacity of the battery, further improving the migration rate of lithium ions, and further reducing the resistance of the material.
  • M includes one or more elements of Ni, Co, Fe, Mn, Cu, V, and Nb, and optionally includes one or more elements of Ni, Co, Fe, Cu, and Nb.
  • the inner 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 .
  • the coating layer includes one or more of carbon, silica, alumina, and titania.
  • the present 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 dissolving free lithium, increasing the charging capacity of the battery, reducing the resistance of the coated lithium-rich metal oxide material, and increasing the migration rate of lithium ions.
  • the mass content of the coating layer in the coated lithium-rich metal oxide material is 1.3% to 10%, and can be optionally 3% to 7%, for example, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10% and the range formed by any two of the above values.
  • the particle size D v 50 of the coated lithium-rich metal oxide material is 2-10 ⁇ m, optionally 4-10 ⁇ m, and more optionally 4-8 ⁇ m, such as 2 ⁇ m, 3 ⁇ m, 4 ⁇ m, 5 ⁇ m, 6 ⁇ m, 7 ⁇ m, 8 ⁇ m, 9 ⁇ m, 10 ⁇ m, and the range formed by any two of the above values.
  • the coated lithium-rich metal oxide material is ensured to have a suitable specific surface area, the stability, integrity and density of the coating layer are guaranteed, and at the same time it is beneficial to the migration of lithium ions and improves the charging capacity of the battery.
  • the mass content of water in the coated lithium-rich metal oxide material is ⁇ 1000 ppm, optionally ⁇ 500 ppm, more optionally ⁇ 400 ppm or ⁇ 300 ppm, further optionally ⁇ 200 ppm, and further optionally ⁇ 100 ppm.
  • the dissolution of free lithium in the lithium-rich core is further reduced, the side reactions of the dissolved lithium are further reduced, thereby further improving the migration of lithium ions, further improving the charging capacity of the battery, and further reducing the resistance of the material.
  • the powder resistivity of the coated lithium-rich metal oxide material measured at a pressure of 20 MPa is ⁇ 4 ⁇ cm, and may be ⁇ 3.3 ⁇ cm, or may be ⁇ 3 ⁇ cm, ⁇ 2 ⁇ cm, or ⁇ 1 ⁇ cm.
  • the reduction in resistivity is beneficial to increasing the migration rate of lithium ions and improving the charging capacity and rate of the battery.
  • One embodiment of the present application provides a method for preparing a coated lithium-rich metal oxide material, comprising the following steps:
  • Li z MO y' 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.
  • PECVD Plasma enhanced chemical vapor deposition
  • Low-temperature plasma uses low-temperature plasma as an energy source.
  • the coated object is placed on the cathode of glow discharge under low pressure.
  • the coated object is heated to a preset temperature by glow discharge or heating element.
  • an appropriate amount of reaction gas is introduced.
  • a coating layer is formed on the surface of the coated object.
  • low-temperature plasma contains a large number of high-energy electrons, which can provide the activation energy required for the process.
  • the collision between electrons and reaction gas molecules can promote the decomposition, combination, excitation and ionization of molecules, generate various highly active chemical groups, and significantly reduce the temperature required for coating treatment.
  • the present application adopts plasma enhanced chemical vapor deposition to coat the compound Li z MO y' . Since the compound Li z MO y' has a low lithium content, high stability and a low temperature required by the plasma enhanced chemical vapor deposition method, the reaction gas in the coating process is not easy to react with the lithium in the compound Li z MO y' , thereby ensuring the stability and effectiveness of the coating process; the coating product is mixed with lithium and then sintered to obtain a lithium-rich metal oxide material with high integrity and compactness of the coating layer. In addition, the method of the present application is simple to operate and easy to promote industrialization.
  • the coated lithium-rich metal oxide material includes a core and a coating layer coating the core, the core includes Li a MO y , and the coating layer includes one or more of carbon, silicon oxide, and metal oxide;
  • a, M and y are as in the [coated lithium-rich metal oxide material] of the present application;
  • the coated lithium-rich metal oxide material is as described in [Coated lithium-rich metal oxide material] of the present application.
  • operating parameters for plasma enhanced chemical vapor deposition include:
  • the microwave power is 200-1000 W, and can be 200-800 W or 500-1000 W, for example, 200 W, 300 W, 400 W, 500 W, 600 W, 700 W, 800 W, 900 W, 1000 W or a range formed by any two of the above values; and/or,
  • the gas pressure in the chemical vapor deposition furnace is -10 to 1000 Pa, which can be 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 a range formed by any two of the above values; and/or,
  • the temperature in the chemical vapor deposition furnace is 400° C. to 600° C., optionally 450° C. to 550° C., for example, 400° C., 450° C., 500° C., 550° C., 600° C. or a range formed by any two of the above values; and/or,
  • the deposition time is 2 to 10 hours, optionally 4 to 8 hours, more optionally 5 to 8 hours, for example 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours or a range formed by any two of the above values; and/or,
  • the gas flow rate at the inlet of the chemical vapor deposition furnace is 10 to 1000 sccm, optionally 100 to 700 sccm, and more optionally 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 a range formed by any two of the above values.
  • the microwave power within the above range is conducive to ensuring the ionization deposition rate of the reaction gas, forming a uniform, complete and dense coating layer on the surface of the coated object, and reducing the side reactions between the coated object and the reaction gas.
  • the gas pressure in the furnace within the above range can ensure the reaction rate of vapor deposition and ensure the effective coating of the coating layer on the inner core, thereby forming a uniform, complete and dense coating layer and reducing the occurrence of defects.
  • the furnace temperature within the above range can increase the rate of ionized deposition of the reaction gas, forming a uniform, complete and dense coating layer on the surface of the coated object, while reducing the mass loss of the coated object caused by side reactions between the coated object and the reaction gas.
  • the deposition time within the above range is beneficial to ensuring the appropriate content of the coating material and forming a uniform, complete and dense coating layer, which is beneficial to the battery capacity.
  • the gas flow rate at the gas inlet within the above range can ensure the appropriate content of the coating layer material, obtain a uniform, complete and dense coating layer, and reduce the waste of reaction gas.
  • the raw material used for the coating process is selected from one or more of a carbon source, a silicon oxide source, and a metal oxide source;
  • the raw materials used for the coating treatment are selected from one or more of an organic carbon source, an organic silicon source, an inorganic silicon source, an organic aluminum source, an inorganic aluminum source, an organic titanium source and an inorganic titanium source, and more preferably selected from one or more of an organic gas, an organic silicon source, an organic aluminum source and an organic titanium source;
  • the raw materials used for 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 optionally selected from one or more of ethylene, acetylene, methane, tetraethyl orthosilicate, aluminum isopropoxide and tetrabutyl titanate.
  • 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 above raw materials are not easy to cause side reactions in the coated object, thereby ensuring the effectiveness and stability of the coating treatment and reducing the waste of raw materials.
  • the sintering temperature is 500°C to 700°C, optionally 550°C to 650°C, and more optionally 600°C to 650°C, for example, 500°C, 550°C, 600°C, 650°C, 700°C, or a range formed by any two of the above values; and/or,
  • the sintering time is 4 h to 10 h, and may be 6 h to 8 h, and may be 6 h to 7 h, for example, 4 h, 5 h, 6 h, 7 h, 8 h, 9 h, 10 h, or a range formed by any two of the above values; and/or,
  • the heating rate of sintering is 2°C/min to 8°C/min, and can be 4°C/min to 6°C/min, for example, 2°C/min, 3°C/min, 4°C/min, 5°C/min, 6°C/min, 7°C/min, 8°C/min or a range formed by any two of the above values; and/or,
  • Sintering is carried out in an inert atmosphere.
  • the sintering temperature, sintering time and sintering heating rate within the above range are conducive to obtaining a coated lithium-rich metal oxide with high crystallinity, reducing the generation of by-products and saving energy consumption.
  • the molar ratio of lithium element in the lithium source to Li z MO y′ is (az): 1. This is conducive to forming a lithium-rich metal oxide core, thereby obtaining a lithium-rich metal oxide material coated with a complete and dense coating layer.
  • Li z MO y′ is crushed before coating, which is beneficial to the uniformity of coating and can ensure that the coated lithium-rich metal oxide material has a suitable specific surface area, thereby facilitating the migration of lithium ions and the utilization of battery capacity.
  • the raw materials used in the coating process are gasified, and the raw materials used in the coating process are optionally gasified at 300° C. to 500° C.
  • the reaction gas required for the coating process must be obtained by gasification to ensure the plasma enhanced chemical vapor deposition.
  • 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 a suitable water content and particle size.
  • Li z MO y' is prepared by the following steps:
  • a lithium source and a source of an M element are mixed and sintered; wherein the molar ratio of the lithium element in the lithium source to the M element in the source of the M element is 0.98:1 to 1.09:1, optionally 0.98:1 to 1.02:1 or 1:1 to 1.09:1, more optionally 1:1 to 1.05:1, and further optionally 1:1 to 1.02:1.
  • the compound Li z MO y' Since the compound Li z MO y' has a low lithium content, the compound Li z MO y' has better stability in coating treatment and can achieve effective coating.
  • the sintering temperature is 400°C to 600°C, and may be 450°C to 550°C, such as 400°C, 450°C, 500°C, 550°C, 600°C or a range formed by any two of the above values; and/or,
  • the sintering time is 2 h to 8 h, and can be 4 h to 6 h, for example, 2 h, 3 h, 4 h, 5 h, 6 h, 7 h, 8 h or a range formed by any two of the above values; and/or,
  • the heating rate of sintering is 4°C/min to 10°C/min, and can be 6°C/min to 8°C/min, for example, 4°C/min, 5°C/min, 6°C/min, 7°C/min, 8°C/min, 9°C/min, 10°C/min or a range formed by any two of the above values; and/or,
  • Sintering is carried out in an inert atmosphere.
  • 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 oxide, hydroxide, halide, sulfate, carbonate, nitrate, oxalate, acetate, sulfide and nitride of element M, and may be the oxide of element M.
  • One embodiment of the present application provides a method for determining a coating layer in a coated lithium-rich metal oxide material, comprising the following steps:
  • a coated lithium-rich metal oxide material comprising a core and a coating layer coating the core, wherein the core comprises Li a MO y ; wherein M comprises one or more elements selected from the group consisting of Ni, Co, Fe, Mn, Zn, Mg, Ca, Cu, Sn, Mo, Ru, Ir, V, Nb and Cr, 2 ⁇ a ⁇ 6, 2 ⁇ y ⁇ 4; and the coating layer comprises one or more selected from the group consisting of carbon, silicon oxide and metal oxide;
  • the liquid phase in the obtained mixture is separated and titrated to calculate the free lithium content d value dissolved in the coated lithium-rich metal oxide material to confirm whether the d value satisfies:
  • the integrity and density of the coating layer of the coated lithium-rich metal oxide material are good, otherwise the integrity and density of the coating layer of the coated lithium-rich metal oxide material are poor.
  • the present application adopts solvents with different water contents (deionized water, anhydrous ethanol or a solution of the two mixed in a specific ratio) to dissolve the free lithium in the coated lithium-rich metal oxide material and react with the dissolved free lithium.
  • the density and integrity of the coating layer are determined by measuring the free lithium content dissolved from the coated lithium-rich metal oxide material. The measurement result has high accuracy, good reliability and fast detection speed. At the same time, the coating layer can be prevented from being damaged during the measurement process.
  • the titration can be performed by any common titration method in the art, and can be potentiometric titration.
  • 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 a range formed by any two of the above values; and/or,
  • the mixing is carried out under stirring conditions of 200 rpm to 800 rpm, and can be carried out under stirring conditions of 400 rpm to 800 rpm, for example, 200 rpm, 300 rpm, 400 rpm, 500 rpm, 600 rpm, 700 rpm, 800 rpm or a range formed by any two of the above values; and/or,
  • the mixing time and stirring speed within the above range can ensure that the dissolved lithium of 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.
  • the free lithium content dissolved in the coated lithium-rich metal oxide material is determined by the following steps:
  • the free lithium content d value dissolved in the coated lithium-rich metal oxide material is calculated according to the following formula:
  • m represents the mass of the coated lithium-rich metal oxide material, in g
  • Va represents the volume of the solvent in mL
  • V b represents the volume of the liquid phase taken, in mL
  • C represents the concentration of hydrochloric acid in the titrant, in mol/L.
  • a graph is drawn with the pH value during the titration as the ordinate and the volume of titrant consumed as the abscissa, V1 and V2 refer to the titrant consumption volumes corresponding to the two potential jump points in the graph, and V2 > V1 .
  • the positive electrode plate generally includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector, and 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.
  • the positive electrode current collector has two surfaces opposite to each other in its thickness direction, and the positive electrode film layer is disposed on any one or both of the two opposite surfaces of the positive electrode current collector.
  • the positive electrode current collector may be a metal foil or a composite current collector.
  • aluminum foil may be used as the metal foil.
  • the composite current collector may include a polymer material base and a metal layer formed on at least one surface of the polymer material base.
  • the composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
  • PP polypropylene
  • PET polyethylene terephthalate
  • PBT polybutylene terephthalate
  • PS polystyrene
  • PE polyethylene
  • the positive electrode film layer may further include a binder.
  • the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylate resin.
  • PVDF polyvinylidene fluoride
  • PTFE polytetrafluoroethylene
  • PTFE polytetrafluoroethylene
  • vinylidene fluoride-tetrafluoroethylene-propylene terpolymer vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer
  • the positive electrode film layer may further include a conductive agent, for example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.
  • the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.
  • the positive electrode sheet can be prepared by the following method: dispersing the above components for preparing the positive electrode sheet in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry on the positive electrode collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.
  • a solvent such as N-methylpyrrolidone
  • the negative electrode sheet includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector, wherein the negative electrode film layer includes a negative electrode active material.
  • the negative electrode current collector has two surfaces opposite to each other in its thickness direction, and the negative electrode film layer is disposed on any one or both of the two opposite surfaces of the negative electrode current collector.
  • the negative electrode current collector may be a metal foil or a composite current collector.
  • the metal foil copper foil may be used.
  • the composite current collector may include a polymer material base layer 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.).
  • PP polypropylene
  • PET polyethylene terephthalate
  • PBT polybutylene terephthalate
  • PS polystyrene
  • PE polyethylene
  • the negative electrode active material may adopt the negative electrode active material for the battery known in the art.
  • 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, lithium titanate, etc.
  • the silicon-based material may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys.
  • the tin-based material may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys.
  • the present application is not limited to these materials, and other traditional 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.
  • the negative electrode film layer may further include a binder.
  • 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).
  • the negative electrode film layer may further include a conductive agent.
  • the conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.
  • the negative electrode film layer may also optionally include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).
  • a thickener eg, sodium carboxymethyl cellulose (CMC-Na)
  • the negative electrode sheet can be prepared in the following manner: the components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder and any other components are dispersed in a solvent (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained.
  • a solvent such as deionized water
  • the electrolyte plays the role of conducting ions between the positive electrode and the negative electrode.
  • the present application has no specific restrictions on the type of electrolyte, which can be selected according to needs.
  • the electrolyte can be liquid, gel or all-solid.
  • the electrolyte is liquid and includes an electrolyte salt and a solvent.
  • the electrolyte salt can 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 difluorooxalatoborate, lithium dioxalatoborate, lithium difluorodioxalatophosphate, and lithium tetrafluorooxalatophosphate.
  • the solvent can be selected from at least one of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclopentane sulfone, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.
  • the electrolyte may further include additives.
  • the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, additives that improve battery high or low temperature performance, etc.
  • the secondary battery further includes a separator.
  • the present application has no particular limitation on the type of separator, and any known porous separator with good chemical stability and mechanical stability can be selected.
  • the material of the isolation membrane can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride.
  • the isolation membrane can be a single-layer film or a multi-layer composite film, without particular limitation.
  • the materials of each layer can be the same or different, without particular limitation.
  • the positive electrode sheet, the negative electrode sheet, and the separator may be formed into an electrode assembly by a winding process or a lamination process.
  • the secondary battery may include an outer package, which may be used to encapsulate the electrode assembly and the electrolyte.
  • the outer packaging of the secondary battery may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc.
  • the outer packaging of the secondary battery may also be a soft package, such as a bag-type soft package.
  • the material of the soft package may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, and polybutylene succinate.
  • FIG1 is a secondary battery 5 of a square structure as an example.
  • the outer package may include a shell 51 and a cover plate 53.
  • the shell 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity.
  • the shell 51 has an opening connected to the receiving cavity, and the cover plate 53 can be covered on the opening to close the receiving cavity.
  • the positive electrode sheet, the negative electrode sheet and the isolation film can form an electrode assembly 52 through a winding process or a lamination process.
  • the electrode assembly 52 is encapsulated in the receiving cavity.
  • the electrolyte is infiltrated in the electrode assembly 52.
  • the number of electrode assemblies 52 contained in the secondary battery 5 can be one or more, and those skilled in the art can select according to specific actual needs.
  • secondary batteries may be assembled into a battery module.
  • the number of secondary batteries contained in the battery module may be one or more, and the specific number may be selected by those skilled in the art according to the application and capacity of the battery module.
  • FIG3 is a battery module 4 as an example.
  • a plurality of secondary batteries 5 may be arranged in sequence along the length direction of the battery module 4. Of course, they may also be arranged in any other manner. Further, the plurality of secondary batteries 5 may be fixed by fasteners.
  • the battery module 4 may further include a housing having a housing space, and the plurality of secondary batteries 5 are housed in the housing space.
  • the battery modules described above may also be assembled into a battery pack.
  • the battery pack may contain one or more battery modules, and the specific number may be selected by those skilled in the art according to the application and capacity of the battery pack.
  • FIG4 and FIG5 are battery packs 1 as an example.
  • the battery pack 1 may include a battery box and a plurality of battery modules 4 disposed in the battery box.
  • the battery box includes an upper box body 2 and a lower box body 3, and the upper box body 2 can be covered on the lower box body 3 to form a closed space for accommodating the battery modules 4.
  • the plurality of battery modules 4 can be arranged in the battery box in any manner.
  • the present application also provides an electrical device, which includes at least one of the secondary battery, battery module, or battery pack provided in the present application.
  • the secondary battery, battery module, or battery pack can be used as a power source for the electrical device, or as an energy storage unit for the electrical device.
  • the electrical device may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as 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., but are not limited thereto.
  • a secondary battery, a battery module or a battery pack can be selected according to its usage requirements.
  • Fig. 6 is an example of an electric device.
  • the electric device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc.
  • a battery pack or a battery module may be used.
  • the intermediate product LiFeO2 is gas-broken and then placed in a plasma enhanced chemical vapor deposition furnace for coating treatment.
  • the raw material gas-ethylene is introduced into the furnace with a gas flow rate of 400 sccm (standard milliliter/minute), a furnace temperature of 500°C, a furnace pressure of 10Pa, a deposition time of 6 hours, and a microwave power of 500W.
  • the organic gas is decomposed in the furnace and then deposited on the surface of the intermediate product LiFeO2 to obtain carbon-coated LiFeO2 ;
  • the carbon-coated LiFeO 2 was mixed with a lithium source (the lithium source was the same as the above), the molar ratio of lithium element in the lithium source to LiFeO 2 was 4:1, the temperature was raised to 600°C for secondary sintering, the heating rate was 5°C/min, the sintering time was 7h, and after sintering, it was crushed and sieved in a dry environment to obtain carbon-coated Li 5 FeO 4 .
  • negative electrode sheets Dissolve the negative electrode active material artificial graphite, conductive agent acetylene black, binder styrene butadiene rubber (SBR), and thickener sodium carboxymethyl cellulose (CMC-Na) in deionized water at a mass ratio of 96:1.5:1.5:1.0, stir and mix well to prepare negative electrode slurry; coat the negative electrode slurry on the negative electrode collector copper foil, and then dry, cold press, and cut to obtain negative electrode sheets.
  • SBR binder styrene butadiene rubber
  • CMC-Na thickener sodium carboxymethyl cellulose
  • Isolation film polypropylene film.
  • Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a volume ratio of 1:1:1, and then LiPF6 was uniformly dissolved in the above solution to obtain an electrolyte.
  • the concentration of LiPF6 in the electrolyte was 1 mol/L.
  • Preparation of secondary batteries stack and wind the above-mentioned positive electrode sheets, separators, and negative electrode sheets in order to obtain an electrode assembly; place the electrode assembly in an outer package, add the above-prepared electrolyte, and obtain a secondary battery after packaging, standing, formation, aging and other processes.
  • a high-frequency infrared carbon-sulfur analyzer (C content analyzer, model HCS-140, Shanghai Dekai Instrument Co., Ltd.) is used to test the coating content in the coated lithium-rich metal oxide material in accordance with GBT20123-2006 "Determination of total carbon and sulfur content of steel using infrared absorption method after combustion in a high-frequency induction furnace (conventional method)".
  • the coating layer content is determined by ICP (inductively coupled plasma) atomic emission spectrometry using an inductively coupled plasma atomic emission spectrometer (model ICAP7400, Thermo Fisher Scientific, USA), specifically:
  • the coated lithium-rich metal oxide material was added to aqua regia and digested under mechanical stirring for 30 minutes; the digested solution was added to the ICAP7400 spectrometer to quantitatively analyze the chemical composition elements in the coated lithium-rich metal oxide material, and the mass fraction p of the M element was tested, and the content of the coating layer was calculated according to the following formula:
  • Coating content 100% ⁇ (n ⁇ p) / m
  • n represents the relative molecular mass of MxOy
  • m represents the relative atomic mass of M.
  • the particle size distribution was determined using a laser particle size analyzer (Malvern Panalytical Mastersizer 2000E).
  • Dv50 can be adjusted by controlling the degree of crushing and screening of the coated lithium-rich metal oxide material.
  • the water content can be adjusted by crushing and screening the coated lithium-rich metal oxide material under different humidity environments.
  • the assembled secondary battery was charged at a constant current of 0.1C to 4.25V, left to stand for 5 minutes, and the first-cycle charging capacity of the secondary battery was recorded.
  • the first-cycle charging capacity of the secondary battery was obtained by dividing the first-cycle charging capacity of the battery by the mass of the coated lithium-rich metal oxide material used.
  • the powder of the coated lithium-rich metal oxide material was dried, and an appropriate amount of powder was weighed. Then, a powder resistivity tester (ST2722 digital four-probe tester, Suzhou Jingge Electronics Co., Ltd.) was used to measure the powder resistivity of the sample according to GB/T 30835-2014 "Carbon composite lithium iron phosphate positive electrode material for lithium-ion batteries" at a test pressure of 20 MPa.
  • Weight increase rate w 100% ⁇ (t-s)/t
  • w ⁇ 0.5% indicating that the integrity and density of the coating layer are excellent
  • 0.5% ⁇ w ⁇ 0.8% indicating that the integrity and density of the coating layer are good
  • w ⁇ 0.8% indicating that the integrity and density of the coating layer are poor.
  • m (g) of coated lithium-rich metal oxide material is placed in a beaker, and Va (mL) of a mixed solvent of deionized water and anhydrous ethanol is added, wherein the mass proportion of deionized water in the mixed solvent is b, and b satisfies:
  • the mixed system was stirred at a speed of 600 rpm for 3 min, and then filtered using a vacuum filtration device after standing.
  • V b (mL) of the filtrate was taken, and the filtrate was titrated with an ethanol solution of hydrochloric acid (hydrochloric acid concentration was C mol/L) as a titrant.
  • the automatic potentiometric titrator was turned on, and the titration was performed with the pH value as the ordinate and the volume of the titrant consumed as the abscissa.
  • the jump points EP 1 and EP 2 of the electrode potential were recorded, and the volumes of the titrant consumed corresponding to the two jump points were V 1 (mL) and V 2 (mL), respectively (V 2 >V 1 ); wherein,
  • the integrity and density of the coating are good, otherwise the integrity and density of the coating are poor:
  • the integrity and density of the coating layer in the coated lithium-rich metal oxide material of the present application are higher; among them, the integrity and density of the coating layer in the coated lithium-rich metal oxide material of Examples 1-29 of the present application are further improved.
  • the coating layer material content in the coated lithium-rich metal oxide material of the present application is higher.
  • the powder resistivity of the coated lithium-rich metal oxide materials of Examples 1-5 and 13-15 of the present application is lower, and the first-cycle charging gram capacity of the secondary battery is higher.
  • the powder resistivity of the coated lithium-rich metal oxide materials in Examples 24-26 of the present application is lower, and the first-cycle charging gram capacity of the secondary battery is higher.
  • the powder resistivity of the coated lithium-rich metal oxide material prepared by Examples 1-2, 5, 15, 30 and 33 of the present application using a microwave power of 200 to 1000 W and a furnace pressure of -10 to 1000 Pa is lower, and the first-cycle charging gram capacity of the secondary battery is higher.
  • the coating layer in the coated lithium-rich metal oxide material of the present application has better integrity and density, lower powder resistivity, better conductivity, higher coating layer material content, and higher first-cycle charging gram capacity of the secondary battery.
  • the stability test is an existing method, the results of the method for determining the integrity and density of the coating layer in the coated lithium-rich metal oxide material in the present application are consistent with the results of the stability test, indicating that the determination method of the present application has high accuracy.

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Abstract

本申请提供了包覆型富锂金属氧化物材料及其制备方法、测定包覆型富锂金属氧化物材料中包覆层的方法、正极极片、电池及用电装置。本申请包覆型富锂金属氧化物材料包括内核及包覆层；内核包含Li aMO y；M包括Ni、Co、Fe、Mn、Zn、Mg、Ca、Cu、Sn、Mo、Ru、Ir、V、Nb和Cr中一种或多种元素，2≤a≤6，2≤y≤4；包覆层包含碳、硅氧化物和金属氧化物中一种或多种；包覆型富锂金属氧化物材料在25℃及相对湿度40％中静置144至192小时后重量增长率为w，w<0.8％。本申请包覆型富锂金属氧化物材料具有完整性和致密性高的包覆层，减少了锂溶出，提高了电池容量，降低了材料电阻。本申请方法能准确、快速测定包覆型富锂金属氧化物材料中包覆层的完整性和致密性。

Description

包覆型富锂金属氧化物材料及制备方法、测定包覆型富锂金属氧化物材料中包覆层的方法、正极极片、电池及用电装置 技术领域
本申请涉及电池技术领域，尤其涉及一种包覆型富锂金属氧化物材料、该包覆型富锂金属氧化物材料的制备方法、测定包覆型富锂金属氧化物材料中包覆层的方法、正极极片、电池和用电装置。
背景技术
近年来，随着二次电池的应用范围越来越广泛，二次电池广泛应用于水力、火力、风力和太阳能电站等储能电源系统，以及电动工具、电动自行车、电动摩托车、电动汽车、军事装备、航空航天等多个领域。由于二次电池取得了极大的发展，因此对其能量密度、循环性能和安全性能等也提出了更高的要求。
富锂金属氧化物材料中的锂含量较高，容易溶出至外界环境中与二氧化碳和/或水反应副反应，在材料表面生成碱性较强、呈凝胶状的副产物，影响了锂离子的迁移，降低了电池的充电容量，提高了材料的电阻。
发明内容
本申请是鉴于上述课题而进行的，其目的在于，提供一种包覆型富锂金属氧化物材料、该包覆型富锂金属氧化物材料的制备方法、测定包覆型富锂金属氧化物材料中包覆层的方法、正极极片、电池和用电装置。本申请的包覆型富锂金属氧化物材料具有完整性和致密性高的包覆层，能够减少富锂金属氧化物内核中的锂溶出至外界发生副反应，提高了电池的容量，降低了材料电阻，提高了锂离子的迁移速率；本申请测定包覆型富锂金属氧化物材料中包覆层的方法能够准确、快速地测定包覆层的完整性和致密性，操作简单。
为了达到上述目的，本申请第一方面提供了一种包覆型富锂金属氧化物材料，包括内核及包覆内核的包覆层；
内核包含Li aMO y；其中，M包括Ni、Co、Fe、Mn、Zn、Mg、Ca、Cu、Sn、Mo、Ru、Ir、V、Nb和Cr中的一种或多种元素，2≤a≤6，2≤y≤4；
包覆层包含碳、硅氧化物和金属氧化物中的一种或多种；
包覆型富锂金属氧化物材料在25℃及相对湿度40％的环境中静置144至192小时后的重量增长率为w，w<0.8％；
可选地，w≤0.5％。
由此，本申请包覆型富锂金属氧化物材料具有完整性和致密性较高的包覆层，减少了富锂金属氧化物内核中游离锂的溶出，从而减少了溶出游离锂与外界物质的副反应，提高了电池的充电容量，提高了锂离子的迁移速率，降低了材料的电阻。
本申请的第二方面提供了一种包覆型富锂金属氧化物材料，包括内核及包覆内核的包覆层；
内核包含Li aMO y；其中，M包括Ni、Co、Fe、Mn、Zn、Mg、Ca、Cu、Sn、Mo、Ru、Ir、V、Nb和Cr中的一种或多种元素，2≤a≤6，2≤y≤4；
包覆层包含碳、硅氧化物和金属氧化物中的一种或多种；
并且，包覆型富锂金属氧化物材料的d值满足：
当2≤a<3时，d≤500ppm；
当3≤a<4时，d≤1000ppm；
当4≤a≤6时，d≤1500ppm；
其中，包覆型富锂金属氧化物材料的d值通过如下的步骤测定：
将包覆型富锂金属氧化物材料与溶剂以1:50至1:1的质量比混合，其中，溶剂由水和乙醇组成，水在溶剂中的质量含量为b，且b满足：
当2≤a<3时，b＝100％-a×10％；
当3≤a<4时，b＝100％-a×20％；
当4≤a≤6时，b＝0；
分离出所得的混合物中的液相物，对液相物进行电位滴定，计算出包覆型富锂金属氧化物材料中溶出的游离锂含量，即为包覆型富锂金属氧化物材料的d值。
由此，在第一方面的基础上，本申请包覆型富锂金属氧化物材料中包覆层的完整性和致密性进一步提高，进一步减少了富锂金属氧化物内核中的游离锂的溶出，进一步降低了溶出游离锂与外界的副反应，从而进一步提高了电池的充电容量，进一步提高了锂离子的迁移速率，进一步降低了包覆型富锂金属氧化物材料的电阻。
在任意实施方式中，M包括Ni、Co、Fe、Mn、Cu、V和Nb中的一种或多种元素，可选地包括Ni、Co、Fe、Cu和Nb中的一种或多种元素。
在任意实施方式中，内核包括Li 2NiO 2、Li 2CuO 2、Li 2MnO 3、Li 3VO 4、Li 3NbO 4、Li 5FeO 4和Li 6CoO 4中的一种或多种，可选地包括Li 2NiO 2、Li 2CuO 2、Li 3NbO 4、Li 5FeO 4和Li 6CoO 4中的一种或多种。
在任意实施方式中，包覆层包括碳、二氧化硅、氧化铝和氧化钛中的一种或多种。
由此，本申请能够获得完整性和致密性较高的包覆层，从而减少了富锂内核中的游离锂溶出，减少溶出游离锂的副反应，提高电池的充电容量，降低材料的电阻，提高锂离子的迁移速率。
在任意实施方式中，包覆层在包覆型富锂金属氧化物材料中的质量含量为1.3％至10％，可选为3％至7％。
由此，有利于形成均匀、完整、致密的包覆层，减少富锂内核中的游离锂溶出，提高电池容量，降低材料电阻，且具有较高的锂离子迁移速率。
在任意实施方式中，包覆型富锂金属氧化物材料的粒径D v50为2～10μm，可选为4～10μm，更可选为4～8μm。
由此，保证包覆型富锂金属氧化物材料具有合适的比表面积，保障了包覆层的稳定性、完整性和致密性，同时有利于锂离子的迁移，提高了电池的充电容量。
在任意实施方式中，包覆型富锂金属氧化物材料中的水的质量含量≤1000ppm，可选为≤500ppm，更可选为≤300ppm，进一步可选为≤200ppm。
由此，进一步减少了富锂内核中的游离锂溶出，进一步减少了溶 出锂的副反应，从而进一步提高了锂离子的迁移，进一步提高了电池的充电容量，进一步降低了材料的电阻。
在任意实施方式中，包覆型富锂金属氧化物材料在20MPa压强下测得的粉末电阻率<4Ω·cm，可选为≤3.3Ω·cm。电阻率的降低有利于提高锂离子的迁移速率，提高电池的充电容量和速率。
本申请的第三方面还提供一种制备包覆型富锂金属氧化物材料的方法，包括如下步骤：
提供化合物Li zMO y’，其中，0.98≤z≤1.02，2≤y’≤3；
通过等离子体增强化学气相沉积对Li zMO y’进行包覆处理；
将包覆处理的产物与锂源混合，烧结，得到包覆型富锂金属氧化物材料。
等离子体增强化学气相沉积法(PECVD)是利用低温等离子体作为能量源，将被包覆物置于低气压下辉光放电的阴极上，利用辉光放电或加发热体使被包覆物升温到预设的温度，然后通入适量的反应气体，经一系列化学反应和等离子体反应，在被包覆物表面形成包覆层。PECVD与普通CVD方法的区别在于低温等离子体中含有大量高能量的电子，可以提供过程所需的激活能，电子与反应气体分子的碰撞可以促进分子的分解、化合、激发和电离，生成高活性的各种化学基团，显著降低包覆处理所需的温度。
由此，本申请采用等离子体增强化学气相沉积法对化合物Li zMO y’进行包覆处理，由于化合物Li zMO y’的锂含量较低，包覆处理过程中的反应气体不易与化合物Li zMO y’中的锂发生副反应，确保了包覆处理操作的稳定性和有效性；将包覆处理的产物混锂之后进行烧结，能够得到包覆层的完整性和致密性较高的富锂金属氧化物材料。并且，本申请方法操作简单，易于工业化推广。
在任意实施方式中，包覆型富锂金属氧化物材料包括内核及包覆内核的包覆层，内核包括Li aMO y，包覆层包括碳、硅氧化物和金属氧化物中的一种或多种；
其中，a、M和y如本申请第一方面或第二方面中。
在任意实施方式中，包覆型富锂金属氧化物材料为本申请第一方 面或第二方面的包覆型富锂金属氧化物材料。
在任意实施方式中，等离子体增强化学气相沉积的操作参数包括：
微波功率为200～1000W，可选为200～800W或500～1000W；和/或，
化学气相沉积炉的炉内气压为-10～1000Pa，可选为10～1000Pa或-10～100Pa；和/或，
化学气相沉积炉的炉内温度为400℃～600℃，可选地为450℃～550℃；和/或，
沉积时间为2～10h，可选地为4～8h，更可选为5～8h；和/或，
化学气相沉积炉的进气口气体流量为10～1000sccm，可选地为100～700sccm，更可选为200～500sccm。
上述范围的微波功率有利于保证反应气体的电离沉积速率，在被包覆物表面形成均匀、完整、致密的包覆层，同时减少被包覆物与反应气体之间的副反应。
上述范围的炉内气压能够保证气相沉积的反应速率，保证包覆层对内核的有效包覆，从而形成均匀、完整、致密的包覆层，减少缺陷的产生。
上述范围的炉内温度能够提高反应气体电离沉积的速率，在被包覆物表面形成均匀、完整、致密的包覆层，同时减少被包覆物与反应气体之间发生副反应而导致被包覆物的质量损失。
上述范围的沉积时间有利于保证包覆层物质的合适含量，形成均匀、完整和致密的包覆层，从而有利于电池容量的发挥。
上述范围的进气口气体流量能够保证包覆层物质的合适含量，得到均匀、完整、致密的包覆层，并且减少反应气体的浪费。
在任意实施方式中，包覆处理采用的原料选自碳源、硅氧化物的源以及金属氧化物的源中的一种或多种；
可选地，包覆处理采用的原料选自有机碳源、有机硅源、无机硅源、有机铝源、无机铝源、有机钛源和无机钛源中的一种或多种，更可选地选自有机气体、有机硅源、有机铝源和有机钛源中的一种或多种；
可选地，包覆处理采用的原料选自乙烯、乙炔、甲烷、丙酮、乙醇、苯、正硅酸乙酯、四氯化硅、异丙醇铝、钛酸四丁酯和四氯化钛中的一种或多种，更可选地选自乙烯、乙炔、甲烷、正硅酸乙酯、异丙醇铝和钛酸四丁酯中的一种或多种。
上述包覆处理采用的原料有利于在被包覆物表面形成均匀、完整、致密的包覆层，同时上述原料不易于被包覆物发生副反应，从而保证了包覆处理的有效性和稳定性，也减少了原料的浪费。
在任意实施方式中，烧结的温度为500℃～700℃，可选为550℃～650℃，更可选为600℃～650℃；和/或，
烧结的时间为4h～10h，可选为6h～8h，更可选为6h～7h；和/或，
烧结的升温速率为2℃/min～8℃/min，可选为4℃/min～6℃/min；和/或，
烧结在惰性气氛中进行。
上述范围的烧结温度、烧结时间和烧结升温速率有利于获得结晶度高的包覆型富锂金属氧化物，减少副产物的产生，并且能够节约能耗。
在任意实施方式中，锂源中的锂元素与Li zMO y’的摩尔比为(a-z):1。有利于形成富锂金属氧化物内核，从而获得包覆有完整和致密的包覆层的富锂金属氧化物材料。
在任意实施方式中，在包覆处理之前，将Li zMO y’破碎。有利于包覆处理的均匀性，并且能够保证包覆型富锂金属氧化物材料具有合适的比表面积，从而有利于锂离子的迁移，电池容量的发挥。
在包覆处理之前，将包覆处理采用的原料气化，可选地将包覆处理采用的原料在300℃～500℃下气化。对于非气态的原料需通过气化来获得包覆处理所需的反应气体，以保证等离子体增强化学气相沉积的进行。
将制得的包覆型富锂金属氧化物材料破碎及筛分，可选地在干燥环境中破碎及筛分。以保证包覆型富锂金属氧化物材料具有合适的水含量和粒径。
在任意实施方式中，Li zMO y’通过如下的步骤制备：
将锂源与M元素的源混合，烧结；其中，锂源中的锂元素与M元素的源中的M元素的摩尔比为0.98:1～1.09:1，可选为0.98:1～1.02:1或者1:1～1.09:1，更可选为1:1～1.05:1。
由于化合物Li zMO y’的锂含量较低，因此采用化合物Li zMO y’进行包覆处理的稳定性更好，能实现有效地包覆。
在任意实施方式中，制备Li zMO y’的步骤中：
烧结的温度为400℃～600℃，可选为450℃～550℃；和/或，
烧结的时间为2h～8h，可选为4h～6h；和/或，
烧结的升温速率为4℃/min～10℃/min，可选为6℃/min～8℃/min；和/或，
烧结在惰性气氛中进行。
在任意实施方式中，锂源包括氧化锂、碳酸锂、草酸锂、醋酸锂和氢氧化锂中的一种或多种；和/或，
M元素的源选自M元素的氧化物、氢氧化物、卤化物、硫酸盐、碳酸盐、硝酸盐、草酸盐、醋酸盐、硫化物及氮化物中的一种或多种，可选为M元素的氧化物。
本申请第四方面提供一种测定包覆型富锂金属氧化物材料中包覆层的方法，包括如下步骤：
提供包覆型富锂金属氧化物材料，包覆型富锂金属氧化物材料包括内核及包覆内核的包覆层，内核包含Li aMO y；其中，M包括Ni、Co、Fe、Mn、Zn、Mg、Ca、Cu、Sn、Mo、Ru、Ir、V、Nb和Cr中的一种或多种元素，2≤a≤6，2≤y≤4；包覆层包含碳、硅氧化物和金属氧化物中的一种或多种；
将包覆型富锂金属氧化物材料与溶剂以1:50至1:1的质量比混合，可选为以1:50至1:10的质量比混合，其中，溶剂由水和乙醇组成，水在溶剂中的质量含量为b，并且b满足：当2≤a＜3时，b＝100％-a×10％；当3≤a＜4时，b＝100％-a×20％；当4≤a≤6时，b＝0；
分离出所得的混合物中的液相物，对液相物进行滴定，计算出包覆型富锂金属氧化物材料中溶出的游离锂含量d值，确认d值是否满 足：
当2≤a＜3时，d≤500ppm；当3≤a＜4时，d≤1000ppm；当4≤a≤6时，d≤1500ppm。
本申请根据富锂金属氧化物内核的不同锂含量，采用不同含水量的溶剂(去离子水、无水乙醇或二者的混合溶液)溶出材料中的游离锂并与溶出的游离锂发生反应，通过测定材料溶出的游离锂含量来判定包覆层的致密性和完整性，测定结果准确度高、可靠性好，检测速度快；同时，在测定过程中能够避免包覆层被破坏。
在任意的实施方式中，混合的时间为1min～4min，可选为1min～3min；和/或，
混合在200rpm～800rpm转速的搅拌条件下进行，可选为在400rpm～800rpm转速的搅拌条件下进行；和/或，
测定在25℃下进行；和/或，
滴定为电位滴定。
上述范围的混合时间和搅拌转速能够保证包覆型富锂金属氧化物材料的溶出锂与溶剂充分、有效地反应，从而保证测定结果的准确性和可靠性，并且能够避免破坏包覆层。
在任意的实施方式中，通过如下的步骤测定包覆型富锂金属氧化物材料中溶出的游离锂含量：
将包覆型富锂金属氧化物材料与溶剂以1:50至1:1的质量比混合，可选为以1:50至1:10的质量比混合，其中，溶剂由水和乙醇组成，水在溶剂中的质量含量为b，并且b满足：当2≤a＜3时，b＝100％-a×10％；当3≤a＜4时，b＝100％-a×20％；当4≤a≤6时，b＝0；
分离出所得的混合物中的液相物，取液相物，以盐酸的乙醇溶液为滴定剂进行电位滴定，滴定过程中的两个电位突跃点所对应的滴定剂消耗体积分别为V 1mL和V 2mL，且V 2>V 1；
按照下式计算包覆型富锂金属氧化物材料中溶出的游离锂含量d值；
d＝C×V a×(69.4684V 2-0.0424V 1)/(m×V b)
其中，
m表示包覆型富锂金属氧化物材料的质量，单位为g；
V a表示溶剂的体积，单位为mL；
V b表示所取的液相物的体积，单位为mL；
C表示滴定剂中的盐酸浓度，单位为mol/L。
本申请的第五方面提供一种正极极片，包括本申请第一方面或第二方面的包覆型富锂金属氧化物材料或者根据本申请第三方面的方法制得的包覆型富锂金属氧化物材料。
本申请的第六方面提供一种电池，包括本申请第一方面或第二方面的包覆型富锂金属氧化物材料、根据本申请第三方面的方法制备的包覆型富锂金属氧化物材料或者本申请第五方面的正极极片。
本申请的第七方面提供一种用电装置，包括本申请的第六方面的电池。
附图说明
图1是本申请一实施方式的二次电池的示意图。
图2是图1所示的本申请一实施方式的二次电池的分解图。
图3是本申请一实施方式的电池模块的示意图。
图4是本申请一实施方式的电池包的示意图。
图5是图4所示的本申请一实施方式的电池包的分解图。
图6是本申请一实施方式的二次电池用作电源的用电装置的示意图。
图7为对比例1制备的富锂金属氧化物材料的TEM照片。
图8为实施例1制备的包覆型富锂金属氧化物材料的TEM照片。
图9为对比例2制备的包覆型富锂金属氧化物材料的TEM照片。
附图标记说明：
1电池包；2上箱体；3下箱体；4电池模块；5二次电池；51壳体；52电极组件；53顶盖组件。
具体实施方式
以下，适当地参照附图详细说明具体公开了本申请的包覆型富锂 金属氧化物材料及其制备方法、测定包覆型富锂金属氧化物材料中的包覆层的方法、正极极片、电池和用电装置的实施方式。但是会有省略不必要的详细说明的情况。例如，有省略对已众所周知的事项的详细说明、实际相同结构的重复说明的情况。这是为了避免以下的说明不必要地变得冗长，便于本领域技术人员的理解。此外，附图及以下说明是为了本领域技术人员充分理解本申请而提供的，并不旨在限定权利要求书所记载的主题。
本申请所公开的“范围”以下限和上限的形式来限定，给定范围是通过选定一个下限和一个上限进行限定的，选定的下限和上限限定了特别范围的边界。这种方式进行限定的范围可以是包括端值或不包括端值的，并且可以进行任意地组合，即任何下限可以与任何上限组合形成一个范围。例如，如果针对特定参数列出了60～120和80～110的范围，理解为60～110和80～120的范围也是预料到的。此外，如果列出的最小范围值1和2，和如果列出了最大范围值3，4和5，则下面的范围可全部预料到：1～3、1～4、1～5、2～3、2～4和2～5。在本申请中，除非有其他说明，数值范围“a～b”表示a到b之间的任意实数组合的缩略表示，其中a和b都是实数。例如数值范围“0～5”表示本文中已经全部列出了“0～5”之间的全部实数，“0～5”只是这些数值组合的缩略表示。另外，当表述某个参数为≥2的整数，则相当于公开了该参数为例如整数2、3、4、5、6、7、8、9、10、11、12等。
如果没有特别的说明，本申请的所有实施方式以及可选实施方式可以相互组合形成新的技术方案。
如果没有特别的说明，本申请的所有技术特征以及可选技术特征可以相互组合形成新的技术方案。
如果没有特别的说明，本申请的所有步骤可以顺序进行，也可以随机进行，优选是顺序进行的。例如，方法包括步骤(a)和(b)，表示方法可包括顺序进行的步骤(a)和(b)，也可以包括顺序进行的步骤(b)和(a)。例如，提到方法还可包括步骤(c)，表示步骤(c)可以任意顺序加入到方法，例如，方法可以包括步骤(a)、(b)和(c)，也可包括步骤 (a)、(c)和(b)，也可以包括步骤(c)、(a)和(b)等。
如果没有特别的说明，本申请所提到的“包括”和“包含”表示开放式，也可以是封闭式。例如，“包括”和“包含”可以表示还可以包括或包含没有列出的其他组分，也可以仅包括或包含列出的组分。
如果没有特别的说明，在本申请中，术语“或”是包括性的。举例来说，短语“A或B”表示“A，B，或A和B两者”。更具体地，以下任一条件均满足条件“A或B”：A为真(或存在)并且B为假(或不存在)；A为假(或不存在)而B为真(或存在)；或A和B都为真(或存在)。
[二次电池]
二次电池又称为充电电池或蓄电池，是指在电池放电后可通过充电的方式使活性材料激活而继续使用的电池。
通常情况下，二次电池包括正极极片、负极极片、隔离膜及电解液。在电池充放电过程中，活性离子(例如锂离子)在正极极片和负极极片之间往返嵌入和脱出。隔离膜设置在正极极片和负极极片之间，主要起到防止正负极短路的作用，同时可以使活性离子通过。电解液在正极极片和负极极片之间，主要起到传导活性离子的作用。
[包覆型富锂金属氧化物材料]
本申请的一个实施方式提供一种包覆型富锂金属氧化物材料，包括内核及包覆内核的包覆层；
内核包含Li aMO y；其中，M包括Ni、Co、Fe、Mn、Zn、Mg、Ca、Cu、Sn、Mo、Ru、Ir、V、Nb和Cr中的一种或多种元素，2≤a≤6，2≤y≤4；
包覆层包含碳、硅氧化物和金属氧化物中的一种或多种；
包覆型富锂金属氧化物材料在25℃及相对湿度40％的环境中静置144至192小时(例如168小时)后的重量增长率为w，w<0.8％；
可选地，w≤0.5％。
虽然机理尚不明确，但发明人发现：本申请包覆型富锂金属氧化 物材料具有完整性和致密性高的包覆层，其阻挡并减少了富锂金属氧化物内核中游离锂的溶出，减少了活性锂的损失，提高了电池的充电容量。由于溶出的游离锂易与外界物质发生副反应而生成的碱性较强的副产物，副产物易造成浆料凝胶，阻碍锂离子的迁移和电池加工，同时会增加材料电阻，因此，本申请包覆型富锂金属氧化物材料的包覆层减少了游离锂的溶出，从而提高了锂离子的迁移率，降低了材料的电阻，更有利于电池产品的加工。
本申请的另一实施方式提供一种包覆型富锂金属氧化物材料，包括内核及包覆内核的包覆层；
内核包含Li aMO y；其中，M包括Ni、Co、Fe、Mn、Zn、Mg、Ca、Cu、Sn、Mo、Ru、Ir、V、Nb和Cr中的一种或多种元素，2≤a≤6、例如2、3、4、5、6及上述任意两个数值形成的范围，2≤y≤4、例如2、3、4及上述任意两个数值形成的范围；
包覆层包含碳、硅氧化物和金属氧化物中的一种或多种；
并且，包覆型富锂金属氧化物材料的d值满足：
当2≤a<3时，d≤500ppm；
当3≤a<4时，d≤1000ppm；
当4≤a≤6时，d≤1500ppm；
其中，包覆型富锂金属氧化物材料的d值通过如下的步骤测定：
将包覆型富锂金属氧化物材料与溶剂以1:50至1:1(例如1:1、1:10、1:20、1:40及上述任意两个数值形成的范围)的质量比混合，其中，溶剂由水和乙醇组成，水在溶剂中的质量含量为b，且b满足：
当2≤a<3时，b＝100％-a×10％；
当3≤a<4时，b＝100％-a×20％；
当4≤a≤6时，b＝0；
分离出所得的混合物中的液相物，对液相物进行电位滴定，计算出包覆型富锂金属氧化物材料中溶出的游离锂含量，即为包覆型富锂金属氧化物材料的d值。
由此，在第一实施方式的基础上，本申请包覆型富锂金属氧化物材料中包覆层的完整性和致密性进一步提高，进一步减少了富锂金属 氧化物内核中的游离锂的溶出，进一步降低了溶出游离锂与外界物质的副反应，从而进一步提高了电池的容量，进一步提高了锂离子的迁移速率，进一步降低了材料的电阻。
在一些实施方式中，M包括Ni、Co、Fe、Mn、Cu、V和Nb中的一种或多种元素，可选地包括Ni、Co、Fe、Cu和Nb中的一种或多种元素。
在一些实施方式中，内核包括Li 2NiO 2、Li 2CuO 2、Li 2MnO 3、Li 3VO 4、Li 3NbO 4、Li 5FeO 4和Li 6CoO 4中的一种或多种，可选地包括Li 2NiO 2、Li 2CuO 2、Li 3NbO 4、Li 5FeO 4和Li 6CoO 4中的一种或多种。
在一些实施方式中，包覆层包括碳、二氧化硅、氧化铝和氧化钛中的一种或多种。
由此，本申请能够获得完整性和致密性较高的包覆层，从而减少了富锂内核中的游离锂溶出，减少溶出游离锂的副反应，提高电池的充电容量，降低包覆型富锂金属氧化物材料的电阻，提高锂离子的迁移速率。
在一些实施方式中，包覆层在所述的包覆型富锂金属氧化物材料中的质量含量为1.3％至10％，可选为3％至7％，例如2％、3％、4％、5％、6％、7％、8％、9％、10％及上述任意两个数值形成的范围。
由此，有利于形成均匀、完整、致密的包覆层，减少富锂内核中的游离锂溶出，提高电池容量，降低材料电阻，且具有较高的锂离子迁移速率。
在一些实施方式中，包覆型富锂金属氧化物材料的粒径D v50为2～10μm，可选为4～10μm，更可选为4～8μm，例如2μm、3μm、4μm、5μm、6μm、7μm、8μm、9μm、10μm及上述任意两个数值形成的范围。
由此，保证包覆型富锂金属氧化物材料具有合适的比表面积，保障了包覆层的稳定性、完整性和致密性，同时有利于锂离子的迁移，提高了电池的充电容量。
在一些实施方式中，包覆型富锂金属氧化物材料中的水的质量含量≤1000ppm，可选为≤500ppm，更可选为≤400ppm或≤300ppm， 进一步可选为≤200ppm，更进一步可选为≤100ppm。
由此，进一步减少了富锂内核中的游离锂溶出，进一步减少了溶出锂的副反应，从而进一步提高了锂离子的迁移，进一步提高了电池的充电容量，进一步降低了材料的电阻。
在一些实施方式中，包覆型富锂金属氧化物材料在20MPa压强下测得的粉末电阻率<4Ω·cm，可选为≤3.3Ω·cm，更可选为≤3Ω·cm、≤2Ω·cm、≤1Ω·cm。电阻率的降低有利于提高锂离子的迁移速率，提高电池的充电容量和速率。
[包覆型富锂金属氧化物材料的制备方法]
本申请的一个实施方式提供一种制备包覆型富锂金属氧化物材料的方法，包括如下步骤：
提供化合物Li zMO y’，其中，0.98≤z≤1.02，2≤y’≤3；
通过等离子体增强化学气相沉积对Li zMO y’进行包覆处理；
将包覆处理的产物与锂源混合，烧结，得到包覆型富锂金属氧化物材料。
等离子体增强化学气相沉积法(PECVD)是利用低温等离子体作为能量源，将被包覆物置于低气压下辉光放电的阴极上，利用辉光放电或加发热体使被包覆物升温到预设的温度，然后通入适量的反应气体，经一系列化学反应和等离子体反应，在被包覆物表面形成包覆层。PECVD与普通CVD方法的区别在于低温等离子体中含有大量高能量的电子，可以提供过程所需的激活能，电子与反应气体分子的碰撞可以促进分子的分解、化合、激发和电离，生成高活性的各种化学基团，显著降低包覆处理所需的温度。
由此，本申请采用等离子体增强化学气相沉积法对化合物Li zMO y’进行包覆处理，由于化合物Li zMO y’的锂含量较低、稳定性高以及等离子体增强化学气相沉积法所需的温度较低，包覆处理过程中的反应气体不易与化合物Li zMO y’中的锂发生副反应，确保了包覆处理的稳定性和有效性；将包覆处理的产物混锂之后进行烧结，能够得到包覆层的完整性和致密性高的富锂金属氧化物材料。并且，本申请方法操作简单，易于工业化推广。
在一些实施方式中，包覆型富锂金属氧化物材料包括内核及包覆内核的包覆层，内核包括Li aMO y，包覆层包括碳、硅氧化物和金属氧化物中的一种或多种；
其中，a、M和y如本申请[包覆型富锂金属氧化物材料]中；
在一些实施方式中，包覆型富锂金属氧化物材料如本申请[包覆型富锂金属氧化物材料]中。
在一些实施方式中，等离子体增强化学气相沉积的操作参数包括：
微波功率为200～1000W，可选为200～800W或500～1000W，例如200W、300W、400W、500W、600W、700W、800W、900W、1000W或上述任意两个数值形成的范围；和/或，
化学气相沉积炉的炉内气压为-10～1000Pa，可选为10～1000Pa或-10～100Pa，例如-10Pa、0Pa、10Pa、20Pa、50Pa、100Pa、150Pa、200Pa、300Pa、400Pa、500Pa、600Pa、700Pa、800Pa、900Pa、1000Pa或上述任意两个数值形成的范围；和/或，
化学气相沉积炉的炉内温度为400℃～600℃，可选地为450℃～550℃，例如400℃、450℃、500℃、550℃、600℃或上述任意两个数值形成的范围；和/或，
沉积时间为2～10h，可选地为4～8h，更可选为5～8h，例如2h、3h、4h、5h、6h、7h、8h、9h、10h或上述任意两个数值形成的范围；和/或，
化学气相沉积炉的进气口气体流量为10～1000sccm，可选地为100～700sccm，更可选为200～500sccm，例如20sccm、50sccm、100sccm、200sccm、300sccm、400sccm、500sccm、600sccm、700sccm、800sccm、900sccm、1000sccm或上述任意两个数值形成的范围。
上述“sccm”表示标准大气压下的流量单位—毫升/分钟。
上述范围的微波功率有利于保证反应气体的电离沉积速率，在被包覆物表面形成均匀、完整、致密的包覆层，同时减少被包覆物与反应气体之间的副反应。
上述范围的炉内气压能够保证气相沉积的反应速率，保证包覆层对内核的有效包覆，从而形成均匀、完整、致密的包覆层，减少缺陷 的产生。
上述范围的炉内温度能够提高反应气体电离沉积的速率，在被包覆物表面形成均匀、完整、致密的包覆层，同时减少被包覆物与反应气体之间发生副反应而导致被包覆物的质量损失。
上述范围的沉积时间有利于保证包覆层物质的合适含量，形成均匀、完整和致密的包覆层，从而有利于电池容量的发挥。
上述范围的进气口气体流量能够保证包覆层物质的合适含量，得到均匀、完整、致密的包覆层，并且减少反应气体的浪费。
在一些实施方式中，包覆处理采用的原料选自碳源、硅氧化物的源以及金属氧化物的源中的一种或多种；
可选地，包覆处理采用的原料选自有机碳源、有机硅源、无机硅源、有机铝源、无机铝源、有机钛源和无机钛源中的一种或多种，更可选为选自有机气体、有机硅源、有机铝源和有机钛源中的一种或多种；
可选地，包覆处理采用的原料选自乙烯、乙炔、甲烷、丙酮、乙醇、苯、正硅酸乙酯、四氯化硅、异丙醇铝、钛酸四丁酯和四氯化钛中的一种或多种，更可选地选自乙烯、乙炔、甲烷、正硅酸乙酯、异丙醇铝和钛酸四丁酯中的一种或多种。
上述包覆处理采用的原料有利于在被包覆物表面形成均匀、完整、致密的包覆层，同时上述原料不易于被包覆物发生副反应，从而保证了包覆处理的有效性和稳定性，也减少了原料的浪费。
在一些实施方式中，烧结的温度为500℃～700℃，可选为550℃～650℃，更可选为600℃～650℃，例如500℃、550℃、600℃、650℃、700℃或上述任意两个数值形成的范围；和/或，
烧结的时间为4h～10h，可选为6h～8h，更可选为6h～7h，例如4h、5h、6h、7h、8h、9h、10h或上述任意两个数值形成的范围；和/或，
烧结的升温速率为2℃/min～8℃/min，可选为4℃/min～6℃/min，例如2℃/min、3℃/min、4℃/min、5℃/min、6℃/min、7℃/min、8℃/min或上述任意两个数值形成的范围；和/或，
烧结在惰性气氛中进行。
上述范围的烧结温度、烧结时间和烧结升温速率有利于获得结晶度高的包覆型富锂金属氧化物，减少副产物的产生，并且能够节约能耗。
在一些实施方式中，锂源中的锂元素与Li zMO y’的摩尔比为(a-z):1。有利于形成富锂金属氧化物内核，从而获得包覆有完整和致密的包覆层的富锂金属氧化物材料。
在一些实施方式中，在包覆处理之前，将Li zMO y’破碎。有利于包覆处理的均匀性，并且能够保证包覆型富锂金属氧化物材料具有合适的比表面积，从而有利于锂离子的迁移，电池容量的发挥。
在包覆处理之前，将包覆处理采用的原料气化，可选地将包覆处理采用的原料在300℃～500℃下气化。对于非气态的原料需通过气化来获得包覆处理所需的反应气体，以保证等离子体增强化学气相沉积的进行。
将制得的包覆型富锂金属氧化物材料破碎及筛分，可选地在干燥环境中破碎及筛分。以保证包覆型富锂金属氧化物材料具有合适的水含量和粒径。
在一些实施方式中，Li zMO y’通过如下的步骤制备：
将锂源与M元素的源混合，烧结；其中，锂源中的锂元素与M元素的源中的M元素的摩尔比为0.98:1～1.09:1，可选为0.98:1～1.02:1或者1:1～1.09:1，更可选为1:1～1.05:1，进一步可选为1:1～1.02:1。
由于化合物Li zMO y’的锂含量较低，因此采用化合物Li zMO y’进行包覆处理的稳定性更好，能实现有效地包覆。
在一些实施方式中，制备Li zMO y’的步骤中：
烧结的温度为400℃～600℃，可选为450℃～550℃，例如400℃、450℃、500℃、550℃、600℃或上述任意两个数值形成的范围；和/或，
烧结的时间为2h～8h，可选为4h～6h，例如2h、3h、4h、5h、6h、7h、8h或上述任意两个数值形成的范围；和/或，
烧结的升温速率为4℃/min～10℃/min，可选为6℃/min～8℃ /min，例如4℃/min、5℃/min、6℃/min、7℃/min、8℃/min、9℃/min、10℃/min或上述任意两个数值形成的范围；和/或，
烧结在惰性气氛中进行。
在一些实施方式中，锂源包括氧化锂、碳酸锂、草酸锂、醋酸锂和氢氧化锂中的一种或多种；和/或，
M元素的源选自M元素的氧化物、氢氧化物、卤化物、硫酸盐、碳酸盐、硝酸盐、草酸盐、醋酸盐、硫化物及氮化物中的一种或多种，可选为M元素的氧化物。
[测定包覆型富锂金属氧化物材料中包覆层的方法]
本申请的一个实施方式提供一种测定包覆型富锂金属氧化物材料中包覆层的方法，包括如下步骤：
提供包覆型富锂金属氧化物材料，所述的包覆型富锂金属氧化物材料包括内核及包覆内核的包覆层，内核包含Li aMO y；其中，M包括Ni、Co、Fe、Mn、Zn、Mg、Ca、Cu、Sn、Mo、Ru、Ir、V、Nb和Cr中的一种或多种元素，2≤a≤6，2≤y≤4；包覆层包含碳、硅氧化物和金属氧化物中的一种或多种；
将包覆型富锂金属氧化物材料与溶剂以1:50至1:1的质量比(可选为1:50至1:10的质量比，例如1:1、1:10、1:20、1:40及上述任意两个数值形成的范围)混合，其中，溶剂由水和乙醇组成，水在溶剂中的质量含量为b，并且b满足：当2≤a＜3时，b＝100％-a×10％；当3≤a＜4时，b＝100％-a×20％；当4≤a≤6时，b＝0；
分离出所得的混合物中的液相物，对液相物进行滴定，计算出包覆型富锂金属氧化物材料中溶出的游离锂含量d值，确认d值是否满足：
当2≤a＜3时，d≤500ppm；当3≤a＜4时，d≤1000ppm；当4≤a≤6时，d≤1500ppm。
可选地，如果d值满足上述的条件，则包覆型富锂金属氧化物材料的包覆层的完整性和致密性好，否则包覆型富锂金属氧化物材料的包覆层的完整性和致密性差。
本申请根据富锂金属氧化物内核的不同锂含量，采用不同含水量 的溶剂(去离子水、无水乙醇或二者以特定比例混合的溶液)溶出包覆型富锂金属氧化物材料中的游离锂并与溶出的游离锂发生反应，通过测定包覆型富锂金属氧化物材料溶出的游离锂含量来判定包覆层的致密性和完整性，测定结果准确度高、可靠性好，检测速度快；同时，在测定过程中能够避免包覆层被破坏。
在一些实施方式中，滴定可以选择所属技术领域内任意的常用滴定方式，可选为电位滴定。
在一些实施方式中，混合的时间为1min～4min，可选为1min～3min，例如1min、2min、3min、4min或上述任意两个数值形成的范围；和/或，
混合在200rpm～800rpm转速的搅拌条件下进行，可选为在400rpm～800rpm转速的搅拌条件下进行，例如200rpm、300rpm、400rpm、500rpm、600rpm、700rpm、800rpm或上述任意两个数值形成的范围；和/或，
测定在25℃下进行。
上述范围的混合时间和搅拌转速能够保证包覆型富锂金属氧化物材料的溶出锂与溶剂充分、有效地反应，从而保证测定结果的准确性和可靠性，并且能够避免破坏包覆层。
在一些实施方式中，通过如下的步骤测定包覆型富锂金属氧化物材料中溶出的游离锂含量：
将包覆型富锂金属氧化物材料与溶剂以1:50至1:1的质量比(可选为1:50至1:10的质量比)混合，其中，溶剂由水和乙醇组成，水在溶剂中的质量含量为b，并且b满足：当2≤a＜3时，b＝100％-a×10％；当3≤a＜4时，b＝100％-a×20％；当4≤a≤6时，b＝0；
分离出所得的混合物中的液相物，取液相物，以盐酸的乙醇溶液为滴定剂进行电位滴定，滴定过程中的两个电位突跃点所对应的滴定剂消耗体积分别为V 1mL和V 2mL，且V 2>V 1；
按照下式计算包覆型富锂金属氧化物材料中溶出的游离锂含量d值；
d＝C×V a×(69.4684V 2-0.0424V 1)/(m×V b)
其中，
m表示包覆型富锂金属氧化物材料的质量，单位为g；
V a表示溶剂的体积，单位为mL；
V b表示所取的液相物的体积，单位为mL；
C表示滴定剂中的盐酸浓度，单位为mol/L。
在一些实施方式中，电位滴定过程中，以滴定过程中的pH值为纵坐标、滴定剂消耗的体积量为横坐标做图，V 1和V 2是指图中的两个电位突跃点所对应的滴定剂消耗体积，V 2>V 1。
[正极极片]
正极极片通常包括正极集流体以及设置在正极集流体至少一个表面的正极膜层，正极膜层包括前述的包覆型富锂金属氧化物材料或者前述的方法制得的包覆型富锂金属氧化物材料。
作为示例，正极集流体具有在其自身厚度方向相对的两个表面，正极膜层设置在正极集流体相对的两个表面的其中任意一者或两者上。
在一些实施方式中，正极集流体可采用金属箔片或复合集流体。例如，作为金属箔片，可采用铝箔。复合集流体可包括高分子材料基层和形成于高分子材料基层至少一个表面上的金属层。复合集流体可通过将金属材料(铝、铝合金、镍、镍合金、钛、钛合金、银及银合金等)形成在高分子材料基材(如聚丙烯(PP)、聚对苯二甲酸乙二醇酯(PET)、聚对苯二甲酸丁二醇酯(PBT)、聚苯乙烯(PS)、聚乙烯(PE)等的基材)上而形成。
在一些实施方式中，正极膜层还可选地包括粘结剂。作为示例，粘结剂可以包括聚偏氟乙烯(PVDF)、聚四氟乙烯(PTFE)、偏氟乙烯～四氟乙烯～丙烯三元共聚物、偏氟乙烯～六氟丙烯～四氟乙烯三元共聚物、四氟乙烯～六氟丙烯共聚物及含氟丙烯酸酯树脂中的至少一种。
在一些实施方式中，正极膜层还可选地包括导电剂。作为示例，导电剂可以包括超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯及碳纳米纤维中的至少一种。
在一些实施方式中，可以通过以下方式制备正极极片：将上述用 于制备正极极片的组分分散于溶剂(例如N～甲基吡咯烷酮)中，形成正极浆料；将正极浆料涂覆在正极集流体上，经烘干、冷压等工序后，即可得到正极极片。
[负极极片]
负极极片包括负极集流体以及设置在负极集流体至少一个表面上的负极膜层，负极膜层包括负极活性材料。
作为示例，负极集流体具有在其自身厚度方向相对的两个表面，负极膜层设置在负极集流体相对的两个表面中的任意一者或两者上。
在一些实施方式中，负极集流体可采用金属箔片或复合集流体。例如，作为金属箔片，可以采用铜箔。复合集流体可包括高分子材料基层和形成于高分子材料基材至少一个表面上的金属层。复合集流体可通过将金属材料(铜、铜合金、镍、镍合金、钛、钛合金、银及银合金等)形成在高分子材料基材(如聚丙烯(PP)、聚对苯二甲酸乙二醇酯(PET)、聚对苯二甲酸丁二醇酯(PBT)、聚苯乙烯(PS)、聚乙烯(PE)等的基材)上而形成。
在一些实施方式中，负极活性材料可采用本领域公知的用于电池的负极活性材料。作为示例，负极活性材料可包括以下材料中的至少一种：人造石墨、天然石墨、软炭、硬炭、硅基材料、锡基材料和钛酸锂等。硅基材料可选自单质硅、硅氧化合物、硅碳复合物、硅氮复合物以及硅合金中的至少一种。锡基材料可选自单质锡、锡氧化合物以及锡合金中的至少一种。但本申请并不限定于这些材料，还可以使用其他可被用作电池负极活性材料的传统材料。这些负极活性材料可以仅单独使用一种，也可以将两种以上组合使用。
在一些实施方式中，负极膜层还可选地包括粘结剂。作为示例，粘结剂可选自丁苯橡胶(SBR)、聚丙烯酸(PAA)、聚丙烯酸钠(PAAS)、聚丙烯酰胺(PAM)、聚乙烯醇(PVA)、海藻酸钠(SA)、聚甲基丙烯酸(PMAA)及羧甲基壳聚糖(CMCS)中的至少一种。
在一些实施方式中，负极膜层还可选地包括导电剂。作为示例，导电剂可选自超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯及碳纳米纤维中的至少一种。
在一些实施方式中，负极膜层还可选地包括其他助剂，例如增稠剂(如羧甲基纤维素钠(CMC～Na))等。
在一些实施方式中，可以通过以下方式制备负极极片：将上述用于制备负极极片的组分，例如负极活性材料、导电剂、粘结剂和任意其他组分分散于溶剂(例如去离子水)中，形成负极浆料；将负极浆料涂覆在负极集流体上，经烘干、冷压等工序后，即可得到负极极片。
[电解质]
电解质在正极极片和负极极片之间起到传导离子的作用。本申请对电解质的种类没有具体的限制，可根据需求进行选择。例如，电解质可以是液态的、凝胶态的或全固态的。
在一些实施方式中，电解质为液态的，且包括电解质盐和溶剂。
在一些实施方式中，电解质盐可选自六氟磷酸锂、四氟硼酸锂、高氯酸锂、六氟砷酸锂、双氟磺酰亚胺锂、双三氟甲磺酰亚胺锂、三氟甲磺酸锂、二氟磷酸锂、二氟草酸硼酸锂、二草酸硼酸锂、二氟二草酸磷酸锂及四氟草酸磷酸锂中的至少一种。
在一些实施方式中，溶剂可选自碳酸亚乙酯、碳酸亚丙酯、碳酸甲乙酯、碳酸二乙酯、碳酸二甲酯、碳酸二丙酯、碳酸甲丙酯、碳酸乙丙酯、碳酸亚丁酯、氟代碳酸亚乙酯、甲酸甲酯、乙酸甲酯、乙酸乙酯、乙酸丙酯、丙酸甲酯、丙酸乙酯、丙酸丙酯、丁酸甲酯、丁酸乙酯、1,4～丁内酯、环丁砜、二甲砜、甲乙砜及二乙砜中的至少一种。
在一些实施方式中，电解液还可选地包括添加剂。作为示例，添加剂可以包括负极成膜添加剂、正极成膜添加剂，还可以包括能够改善电池某些性能的添加剂，例如改善电池过充性能的添加剂、改善电池高温或低温性能的添加剂等。
[隔离膜]
在一些实施方式中，二次电池中还包括隔离膜。本申请对隔离膜的种类没有特别的限制，可以选用任意公知的具有良好的化学稳定性和机械稳定性的多孔结构隔离膜。
在一些实施方式中，隔离膜的材质可选自玻璃纤维、无纺布、聚乙烯、聚丙烯及聚偏二氟乙烯中的至少一种。隔离膜可以是单层薄膜， 也可以是多层复合薄膜，没有特别限制。在隔离膜为多层复合薄膜时，各层的材料可以相同或不同，没有特别限制。
在一些实施方式中，正极极片、负极极片和隔离膜可通过卷绕工艺或叠片工艺制成电极组件。
在一些实施方式中，二次电池可包括外包装。该外包装可用于封装上述电极组件及电解质。
在一些实施方式中，二次电池的外包装可以是硬壳，例如硬塑料壳、铝壳、钢壳等。二次电池的外包装也可以是软包，例如袋式软包。软包的材质可以是塑料，作为塑料，可列举出聚丙烯、聚对苯二甲酸丁二醇酯以及聚丁二酸丁二醇酯等。
本申请对二次电池的形状没有特别的限制，其可以是圆柱形、方形或其他任意的形状。例如，图1是作为一个示例的方形结构的二次电池5。
在一些实施方式中，参照图2，外包装可包括壳体51和盖板53。其中，壳体51可包括底板和连接于底板上的侧板，底板和侧板围合形成容纳腔。壳体51具有与容纳腔连通的开口，盖板53能够盖设于开口，以封闭容纳腔。正极极片、负极极片和隔离膜可经卷绕工艺或叠片工艺形成电极组件52。电极组件52封装于容纳腔内。电解液浸润于电极组件52中。二次电池5所含电极组件52的数量可以为一个或多个，本领域技术人员可根据具体实际需求进行选择。
在一些实施方式中，二次电池可以组装成电池模块，电池模块所含二次电池的数量可以为一个或多个，具体数量本领域技术人员可根据电池模块的应用和容量进行选择。
图3是作为一个示例的电池模块4。参照图3，在电池模块4中，多个二次电池5可以是沿电池模块4的长度方向依次排列设置。当然，也可以按照其他任意的方式进行排布。进一步可以通过紧固件将该多个二次电池5进行固定。
可选地，电池模块4还可以包括具有容纳空间的外壳，多个二次电池5容纳于该容纳空间。
在一些实施方式中，上述电池模块还可以组装成电池包，电池包 所含电池模块的数量可以为一个或多个，具体数量本领域技术人员可根据电池包的应用和容量进行选择。
图4和图5是作为一个示例的电池包1。参照图4和图5，在电池包1中可以包括电池箱和设置于电池箱中的多个电池模块4。电池箱包括上箱体2和下箱体3，上箱体2能够盖设于下箱体3，并形成用于容纳电池模块4的封闭空间。多个电池模块4可以按照任意的方式排布于电池箱中。
另外，本申请还提供一种用电装置，用电装置包括本申请提供的二次电池、电池模块、或电池包中的至少一种。二次电池、电池模块、或电池包可以用作用电装置的电源，也可以用作用电装置的能量存储单元。用电装置可以包括移动设备(例如手机、笔记本电脑等)、电动车辆(例如纯电动车、混合动力电动车、插电式混合动力电动车、电动自行车、电动踏板车、电动高尔夫球车、电动卡车等)、电气列车、船舶及卫星、储能系统等，但不限于此。
作为用电装置，可以根据其使用需求来选择二次电池、电池模块或电池包。
图6是作为一个示例的用电装置。该用电装置为纯电动车、混合动力电动车、或插电式混合动力电动车等。为了满足该用电装置对二次电池的高功率和高能量密度的需求，可以采用电池包或电池模块。
[实施例]
以下，说明本申请的实施例。下面描述的实施例是示例性的，仅用于解释本申请，而不能理解为对本申请的限制。实施例中未注明具体技术或条件的，按照本领域内的文献所描述的技术或条件或者按照产品说明书进行。所用试剂或仪器未注明生产厂商者，均为可以通过市购获得的常规产品。
实施例1
1、包覆型富锂金属氧化物材料的制备：
将氢氧化锂与三氧化二铁混合，其中，氢氧化锂中的锂元素与三 氧化二铁中的铁元素的摩尔比为1.05:1，在氮气中升温至500℃进行一次烧结，升温速率为7℃/min，烧结时间为5h，得到中间产物LiFeO 2；
将中间产物LiFeO 2进行气流破碎，之后放入等离子体增强化学气相沉积炉中进行包覆处理，向炉中通入原料气—乙烯，气体流量为400sccm(标准毫升/分钟)，炉内温度为500℃，炉内气压为10Pa，沉积时间为6h，微波功率为500W，有机气体在炉中分解后沉积到中间产物LiFeO 2表面，得到碳包覆的LiFeO 2；
将碳包覆的LiFeO 2与锂源(锂源与前述的相同)混合，锂源中的锂元素与LiFeO 2的摩尔比为4:1，升温至600℃进行二次烧结，升温速率为5℃/min，烧结时间为7h，烧结后在干燥环境中破碎并过筛，得到碳包覆的Li 5FeO 4。
2、正极极片的制备：将上述包覆型富锂金属氧化物材料、粘结剂聚偏氟乙烯(PVDF)、导电剂乙炔黑按照质量比为97:2:1溶于溶剂N～甲基吡咯烷酮(NMP)中，充分搅拌混合均匀后制备成正极浆料；将正极浆料均匀涂覆在正极集流体铝箔上，之后经过烘干、冷压、分切，得到正极极片。
3、负极极片的制备：将负极活性材料人造石墨、导电剂乙炔黑、粘结剂丁苯橡胶(SBR)、增稠剂羧甲基纤维素钠(CMC～Na)按照质量比为96:1.5:1.5:1.0溶于去离子水中，充分搅拌混合均匀后制备成负极浆料；将负极浆料涂覆在负极集流体铜箔上，之后经过烘干、冷压、分切，得到负极极片。
4、隔离膜：采用聚丙烯膜。
5、电解液的制备：将碳酸亚乙酯(EC)、碳酸甲乙酯(EMC)、碳酸二乙酯(DEC)按体积比1:1:1混合，然后将LiPF6均匀溶解在上述溶液中，得到电解液。该电解液中，LiPF 6的浓度为1mol/L。
6、二次电池的制备：将上述正极极片、隔离膜、负极极片按顺序堆叠并卷绕，得到电极组件；将电极组件放入外包装中，加入上述制备的电解液，经封装、静置、化成、老化等工序后，得到二次电池。
实施例2～33和对比例1～19与实施例1的二次电池制备方法相似， 但是调整了参数和组成，不同的参数详见表1。
Figure PCTCN2022130329-appb-000001
Figure PCTCN2022130329-appb-000002
性能测试
(1)包覆型富锂金属氧化物材料中包覆层含量的测定：
如果包覆层是碳，采用高频红外碳硫分析仪(C content analyzer，型号HCS-140，上海德凯仪器有限公司)，依据GBT20123-2006“钢铁总碳硫含量的测定使用高频感应炉燃烧后红外吸收法(常规方法)”测试包覆型富锂金属氧化物材料中的包覆层含量。
如果包覆层是氧化物M xO y，采用电感耦合等离子体原子发射光谱仪(型号ICAP7400，美国Thermo Fisher Scientific公司)按照ICP(电感耦合等离子体)原子发射光谱法确定包覆层含量，具体为：
取包覆型富锂金属氧化物材料加入王水中在机械搅拌下消解，消解时间为30min；将消解后的溶液加入ICAP7400光谱仪中，定量分析包覆型富锂金属氧化物材料中的化学组成元素，测试出M元素的质量分数p，按照如下公式计算包覆层的含量：
包覆层含量＝100％×(n×p)/m，
其中，n表示M xO y的相对分子质量，m表示M的相对原子质量。
(2)包覆型富锂金属氧化物材料的粒径Dv50的测定：
参照GB/T 19077-2016粒度分布激光衍射法，采用激光粒度分析仪(马尔文帕纳科Mastersizer 2000E)测定。
通过控制包覆型富锂金属氧化物材料破碎和筛分的程度可以调整Dv50。
(3)包覆型富锂金属氧化物材料中的水质量含量的测定：
采用卡尔费休水分测定仪(831型，瑞士万通)，取10g包覆型富锂金属氧化物材料在上述测定仪自带的全自动卡氏样品加热器(874型，瑞士万通)中于170℃加热，采用40mL/min流速的干燥氮气吹扫，滴定时间为400s。
通过在不同湿度的环境下对包覆型富锂金属氧化物材料破碎和筛分可以调整水质量含量。
(4)对比例1的富锂金属氧化物材料、实施例1及对比例2的包覆型富锂金属氧化物材料的TEM照片分别如图7～9所示。
(5)二次电池的首圈充电克容量的测定：
将组装后的二次电池以0.1C倍率恒流充电至4.25V，静置5min，记录此时二次电池的首圈充电容量；以电池的首圈充电容量除以采用的包覆型富锂金属氧化物材料的质量得到二次电池的首圈充电克容量。
(6)包覆型富锂金属氧化物材料的粉末电阻率测定：
将包覆型富锂金属氧化物材料的粉末干燥，称取适量粉末，然后采用粉末电阻率测试仪(ST2722型数字式四探针仪，苏州晶格电子有限公司)，依据GB/T 30835-2014“锂离子电池用炭复合磷酸铁锂正极材料”测定样品的粉末电阻率，测试压强为20MPa。
(7)包覆型富锂金属氧化物材料的稳定性测试：
取s(g)包覆型富锂金属氧化物材料置于恒温(25℃)和恒湿(相对湿度为40％)环境下静置7天，然后对样品进行称重得到质量t(g)，按照下式计算重量增长率w；
重量增长率w＝100％×(t-s)/t
w≤0.5％，说明包覆层的完整性和致密性优秀；0.5％＜w＜0.8％，说明包覆层的完整性和致密性良好；w≥0.8％，说明包覆层的完整性和致密性较差。
(8)包覆型富锂金属氧化物材料的包覆层完整性和致密性测试：
在25℃下，取m(g)包覆型富锂金属氧化物材料于烧杯中，加入V a(mL)去离子水和无水乙醇的混合溶剂，其中，去离子水在混合溶剂中的质量占比为b，并且b满足：
当2≤a＜3时，b＝100％-a×10％；
当3≤a＜4时，b＝100％-a×20％；
当4≤a≤6时，b＝0；
使用封口膜封口后，将上述混合体系以转速600转/min搅拌3min，静置后采用真空抽滤装置抽滤，取V b(mL)滤液，以盐酸的乙醇溶液(盐酸浓度为C mol/L)为滴定剂滴定滤液，开启自动电位滴定仪，以pH值为纵坐标，滴定剂消耗体积为横坐标进行滴定，记录电极电位的突跃点EP 1和EP 2，两个突跃点对应的滴定剂消耗体积分别为V 1(mL)和V 2(mL)(V 2>V 1)；其中，
滴定反应进行至电极电位突跃点EP 1时，发生如下化学反应：
LiOH+HCl→LiCl+H 2O
Li 2CO 3+HCl→LiCl+LiHCO 3
滴定反应进行至电极电位突跃点EP 2时，发生如下化学反应：
LiHCO 3+HCl→LiCl+H 2O+CO 2
按照如下公式计算得到m(g)包覆型富锂金属氧化物材料中溶出的游离锂含量d(ppm)：
d＝C×V a×(69.4684V 2-0.0424V 1)/(m×V b)
如果d值满足如下的条件，则包覆层的完整性和致密性好，否则包覆层的完整性和致密性差：
当2≤a＜3时，d≤500ppm；
当3≤a＜4时，d≤1000ppm；
当4≤a≤6时，d≤1500ppm。
以上的结果见表2。
Figure PCTCN2022130329-appb-000003
Figure PCTCN2022130329-appb-000004
由表1-2可知：
与对比例1-8相比，本申请包覆型富锂金属氧化物材料中包覆层的完整性和致密性更高；其中，本申请实施例1-29包覆型富锂金属氧化物材料中包覆层的完整性和致密性进一步提高。与对比例6-8相比，本申请包覆型富锂金属氧化物材料中的包覆层物质含量更高。
与对比例1-2相比，本申请实施例1-5、13-15包覆型富锂金属氧化物材料的粉末电阻率更低，二次电池的首圈充电克容量更高。
与对比例3-5相比，本申请实施例24-26包覆型富锂金属氧化物材料的粉末电阻率更低，二次电池的首圈充电克容量更高。
与对比例6-8相比，本申请实施例1-2、5、15、30和33采用200～1000W的微波功率和-10～1000Pa的炉内气压所制备的包覆型富锂金属氧化物材料的粉末电阻率更低，二次电池的首圈充电克容量更高。
对比例9-14采用去离子水作为溶剂(b＝100％)测定包覆层完整性和致密性的结果与稳定性测试结果有较大偏差，与之相较，对比例1-2、本申请实施例1、37-39采用合适的溶剂测定包覆层完整性和致密性的结果与稳定性测试结果相符。
对比例15-19采用过低的包覆型富锂金属氧化物材料和溶剂的比例测定的包覆层完整性和致密性结果与稳定性测试结果的偏差较大，与之相较，实施例1、13-14采用合适的包覆型富锂金属氧化物材料和溶剂的比例测定包覆层完整性和致密性的结果与稳定性测试结果相符。
以上说明，本申请包覆型富锂金属氧化物材料中包覆层的完整性和致密性更好，粉末电阻率更低，导电性更好，包覆层物质含量更高，二次电池的首圈充电克容量更高。
由于稳定性测试为现有方法，本申请测定包覆型富锂金属氧化物材料中包覆层完整性和致密性的方法的结果与稳定性测试结果相符，说明本申请测定方法的准确度高。
需要说明的是，本申请不限定于上述实施方式。上述实施方式仅为示例，在本申请的技术方案范围内具有与技术思想实质相同的构成、发挥相同作用效果的实施方式均包含在本申请的技术范围内。此外，在不脱离本申请主旨的范围内，对实施方式施加本领域技术人员能够想到的各种变形、将实施方式中的一部分构成要素加以组合而构筑的其它方式也包含在本申请的范围内。

Claims (26)

  1. 一种包覆型富锂金属氧化物材料，包括内核及包覆所述内核的包覆层；
    所述内核包含Li aMO y；其中，所述M包括Ni、Co、Fe、Mn、Zn、Mg、Ca、Cu、Sn、Mo、Ru、Ir、V、Nb和Cr中的一种或多种元素，2≤a≤6，2≤y≤4；
    所述包覆层包含碳、硅氧化物和金属氧化物中的一种或多种；
    所述包覆型富锂金属氧化物材料在25℃及相对湿度40％的环境中静置144至192小时后的重量增长率为w，所述w<0.8％；
    可选地，所述w≤0.5％。
  2. 一种包覆型富锂金属氧化物材料，包括内核及包覆所述内核的包覆层；
    所述内核包含Li aMO y；其中，所述M包括Ni、Co、Fe、Mn、Zn、Mg、Ca、Cu、Sn、Mo、Ru、Ir、V、Nb和Cr中的一种或多种元素，2≤a≤6，2≤y≤4；
    所述包覆层包含碳、硅氧化物和金属氧化物中的一种或多种；
    并且，所述包覆型富锂金属氧化物材料的d值满足：
    当2≤a<3时，d≤500ppm；
    当3≤a<4时，d≤1000ppm；
    当4≤a≤6时，d≤1500ppm；
    其中，所述包覆型富锂金属氧化物材料的d值通过如下的步骤测定：
    将所述包覆型富锂金属氧化物材料与溶剂以1:50至1:1的质量比混合，其中，所述溶剂由水和乙醇组成，所述水在所述溶剂中的质量含量为b，且b满足：
    当2≤a<3时，b＝100％-a×10％；
    当3≤a<4时，b＝100％-a×20％；
    当4≤a≤6时，b＝0；
    分离出所得的混合物中的液相物，对所述液相物进行电位滴定，计算出所述包覆型富锂金属氧化物材料中溶出的游离锂含量，即为所述包覆型富锂金属氧化物材料的d值。
  3. 根据权利要求1或2所述的包覆型富锂金属氧化物材料，其中，所述M包括Ni、Co、Fe、Mn、Cu、V和Nb中的一种或多种元素，可选地包括Ni、Co、Fe、Cu和Nb中的一种或多种元素。
  4. 根据权利要求1至3中任一项所述的包覆型富锂金属氧化物材料，其中，所述内核包括Li 2NiO 2、Li 2CuO 2、Li 2MnO 3、Li 3VO 4、Li 3NbO 4、Li 5FeO 4和Li 6CoO 4中的一种或多种，可选地包括Li 2NiO 2、Li 2CuO 2、Li 3NbO 4、Li 5FeO 4和Li 6CoO 4中的一种或多种。
  5. 根据权利要求1至4中任一项所述的包覆型富锂金属氧化物材料，其中，所述包覆层包括碳、二氧化硅、氧化铝和氧化钛中的一种或多种。
  6. 根据权利要求1至5中任一项所述的包覆型富锂金属氧化物材料，其中，所述包覆层在所述包覆型富锂金属氧化物材料中的质量含量为1.3％至10％，可选为3％至7％。
  7. 根据权利要求1至6中任一项所述的包覆型富锂金属氧化物材料，其中，所述包覆型富锂金属氧化物材料的粒径D v50为2～10μm，可选为4～10μm，更可选为4～8μm。
  8. 根据权利要求1至7中任一项所述的包覆型富锂金属氧化物材料，其中，所述包覆型富锂金属氧化物材料中的水的质量含量≤1000ppm，可选为≤500ppm，更可选为≤300ppm，进一步可选为≤200ppm。
  9. 根据权利要求1至8中任一项所述的包覆型富锂金属氧化物材料，其中，所述包覆型富锂金属氧化物材料在20MPa压强下测得的粉末电阻率<4Ω·cm，可选为≤3.3Ω·cm。
  10. 一种制备包覆型富锂金属氧化物材料的方法，包括如下步骤：
    提供化合物Li zMO y’，其中，0.98≤z≤1.02，2≤y’≤3；
    通过等离子体增强化学气相沉积对所述Li zMO y’进行包覆处理；
    将包覆处理的产物与锂源混合，烧结，得到包覆型富锂金属氧化物材料。
  11. 根据权利要求10所述的方法，其中，所述包覆型富锂金属氧化物材料包括内核及包覆所述内核的包覆层，所述内核包括Li aMO y，所述包覆层包括碳、硅氧化物和金属氧化物中的一种或多种；
    其中，所述a、M和y如权利要求1至9任一项中所述。
  12. 根据权利要求10或11所述的方法，其中，所述包覆型富锂金属氧化物材料为权利要求1至9中任一项所述的包覆型富锂金属氧化物材料。
  13. 根据权利要求10至12中任一项所述的方法，其中，所述等离子体增强化学气相沉积的操作参数包括：
    微波功率为200～1000W，可选为200～800W或500～1000W；和/或，
    化学气相沉积炉的炉内气压为-10～1000Pa，可选为10～1000Pa或-10～100Pa；和/或，
    化学气相沉积炉的炉内温度为400℃～600℃，可选地为450℃～550℃；和/或，
    沉积时间为2～10h，可选地为4～8h，更可选为5～8h；和/或，
    化学气相沉积炉的进气口的气体流量为10～1000sccm，可选地为100～700sccm，更可选为200～500sccm。
  14. 根据权利要求10至13中任一项所述的方法，其中，所述包覆处理采用的原料选自碳源、硅氧化物的源以及金属氧化物的源中的一种或多种；
    可选地，所述包覆处理采用的原料选自有机碳源、有机硅源、无机硅源、有机铝源、无机铝源、有机钛源和无机钛源中的一种或多种；
    可选地，所述包覆处理采用的原料选自乙烯、乙炔、甲烷、丙酮、乙醇、苯、正硅酸乙酯、四氯化硅、异丙醇铝、钛酸四丁酯和四氯化钛中的一种或多种，更可选地选自乙烯、乙炔、甲烷、正硅酸乙酯、异丙醇铝和钛酸四丁酯中的一种或多种。
  15. 根据权利要求10至14中任一项所述的方法，其中，所述烧结的温度为500℃～700℃，可选为550℃～650℃，更可选为600℃～650℃；和/或，
    所述烧结的时间为4h～10h，可选为6h～8h，更可选为6h～7h；和/或，
    所述烧结的升温速率为2℃/min～8℃/min，可选为4℃/min～6℃/min；和/或，
    所述烧结在惰性气氛中进行。
  16. 根据权利要求10至15中任一项所述的方法，其中，所述锂源中的锂元素与所述Li zMO y’的摩尔比为(a-z):1。
  17. 根据权利要求10至16中任一项所述的方法，其中，
    在所述包覆处理之前，将所述Li zMO y’破碎；和/或，
    在所述包覆处理之前，将所述包覆处理采用的原料气化，可选地将所述包覆处理采用的原料在300℃～500℃下气化；和/或，
    将制得的包覆型富锂金属氧化物材料破碎及筛分，可选地在干燥环境中破碎及筛分。
  18. 根据权利要求10至17中任一项所述的方法，其中，所述Li zMO y’通过如下的步骤制备：
    将锂源与M元素的源混合，烧结；其中，所述锂源中的锂元素与所述M元素的源中的M元素的摩尔比为0.98:1～1.09:1，可选为0.98:1～1.02:1或者1:1～1.09:1，更可选为1:1～1.05:1。
  19. 根据权利要求18所述的方法，其中，制备所述Li zMO y’的步骤中：
    所述烧结的温度为400℃～600℃，可选为450℃～550℃；和/或，
    所述烧结的时间为2h～8h，可选为4h～6h；和/或，
    所述烧结的升温速率为4℃/min～10℃/min，可选为6℃/min～8℃/min；和/或，
    所述烧结在惰性气氛中进行。
  20. 根据权利要求18或19所述的方法，其中，
    所述锂源包括氧化锂、碳酸锂、草酸锂、醋酸锂和氢氧化锂中的一种或多种；和/或，
    所述M元素的源选自M元素的氧化物、氢氧化物、卤化物、硫酸盐、碳酸盐、硝酸盐、草酸盐、醋酸盐、硫化物及氮化物中的一种或多种，可选为M元素的氧化物。
  21. 一种测定包覆型富锂金属氧化物材料中包覆层的方法，包括如下步骤：
    提供包覆型富锂金属氧化物材料，所述包覆型富锂金属氧化物材料包括内核及包覆所述内核的包覆层，所述内核包含Li aMO y；其中，所述M包括Ni、Co、Fe、Mn、Zn、Mg、Ca、Cu、Sn、Mo、Ru、Ir、V、Nb和Cr中的一种或多种元素，2≤a≤6，2≤y≤4；所述包覆层包含碳、硅氧化物和金属氧化物中的一种或多种；
    将所述包覆型富锂金属氧化物材料与溶剂以1:50至1:1的质量比 混合，可选为以1:50至1:10的质量比混合，其中，所述溶剂由水和乙醇组成，所述水在所述溶剂中的质量含量为b，并且b满足：当2≤a＜3时，b＝100％-a×10％；当3≤a＜4时，b＝100％-a×20％；当4≤a≤6时，b＝0；
    分离出所得的混合物中的液相物，对所述液相物进行滴定，计算出所述包覆型富锂金属氧化物材料中溶出的游离锂含量d值，确认d值是否满足：
    当2≤a＜3时，d≤500ppm；当3≤a＜4时，d≤1000ppm；当4≤a≤6时，d≤1500ppm。
  22. 根据权利要求2所述的包覆型富锂金属氧化物材料或者权利要求21所述的方法，其中，
    所述混合的时间为1min～4min，可选为1min～3min；和/或，
    所述混合在200rpm～800rpm转速的搅拌条件下进行，可选为在400rpm～800rpm转速的搅拌条件下进行；和/或，
    所述测定在25℃下进行；和/或，
    所述滴定为电位滴定。
  23. 根据权利要求2所述的包覆型富锂金属氧化物材料或者权利要求21所述的方法，其中，通过如下的步骤测定所述包覆型富锂金属氧化物材料中溶出的游离锂含量：
    将包覆型富锂金属氧化物材料与溶剂以1:50至1:1的质量比混合，可选为以1:50至1:10的质量比混合，其中，所述溶剂由水和乙醇组成，所述水在所述溶剂中的质量含量为b，并且b满足：当2≤a＜3时，b＝100％-a×10％；当3≤a＜4时，b＝100％-a×20％；当4≤a≤6时，b＝0；
    分离出所得的混合物中的液相物，取液相物，以盐酸的乙醇溶液为滴定剂进行电位滴定，滴定过程中的两个电位突跃点所对应的滴定剂消耗体积分别为V 1mL和V 2mL，且V 2>V 1；
    按照下式计算所述包覆型富锂金属氧化物材料中溶出的游离锂 含量d值；
    d＝C×V a×(69.4684V 2-0.0424V 1)/(m×V b)
    其中，
    m表示包覆型富锂金属氧化物材料的质量，单位为g；
    V a表示溶剂的体积，单位为mL；
    V b表示所取的液相物的体积，单位为mL；
    C表示滴定剂中的盐酸浓度，单位为mol/L。
  24. 一种正极极片，包括权利要求1至9中任一项或权利要求22至23中任一项所述的包覆型富锂金属氧化物材料或者通过权利要求10至20中任一项所述的方法制得的包覆型富锂金属氧化物材料。
  25. 一种电池，包括权利要求1至9中任一项或权利要求22至23中任一项所述的包覆型富锂金属氧化物材料、通过权利要求10至20中任一项所述的方法制得的包覆型富锂金属氧化物材料或者权利要求24所述的正极极片。
  26. 一种用电装置，包括权利要求25所述的电池。
PCT/CN2022/130329 2022-11-07 2022-11-07 包覆型富锂金属氧化物材料及制备方法、测定包覆型富锂金属氧化物材料中包覆层的方法、正极极片、电池及用电装置 WO2024098198A1 (zh)

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