WO2021037267A1 - 核壳结构的锂离子电池正极材料及其制备方法和正极片以及锂离子电池及其应用 - Google Patents

核壳结构的锂离子电池正极材料及其制备方法和正极片以及锂离子电池及其应用 Download PDF

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WO2021037267A1
WO2021037267A1 PCT/CN2020/112605 CN2020112605W WO2021037267A1 WO 2021037267 A1 WO2021037267 A1 WO 2021037267A1 CN 2020112605 W CN2020112605 W CN 2020112605W WO 2021037267 A1 WO2021037267 A1 WO 2021037267A1
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positive electrode
lithium
source
shell structure
core
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PCT/CN2020/112605
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English (en)
French (fr)
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熊得军
王大为
张舒
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孚能科技(赣州)股份有限公司
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Publication of WO2021037267A1 publication Critical patent/WO2021037267A1/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
    • H01M4/362—Composites
    • H01M4/366—Composites as layered products
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • 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
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • 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
    • H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
    • H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
    • 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
    • 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
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/028—Positive electrodes
    • 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 invention relates to a lithium ion battery positive electrode material with a core-shell structure, a preparation method thereof, a positive electrode sheet, a lithium ion battery and its application in a new energy automobile.
  • Ternary cathode material is currently the most widely used cathode material in the new energy vehicle pure electric passenger car market. It has excellent performance characteristics such as high energy density, high platform voltage, long cycle life, and high and low temperature performance. It can meet the requirements of new energy passenger vehicles.
  • the car has core requirements for driving range, high energy consumption ratio, and fast charging. Due to the influence of the preparation process of the ternary cathode material, the pH value of the material is relatively high (>10), and alkaline lithium salt substances such as LiCO 3 and LiOH will remain on the surface. With the increase of nickel content, the alkaline lithium salt remains in the ternary cathode material. The content increases exponentially.
  • the residual alkaline lithium salt will react with LiPF 6 in the electrolyte to form a gas, which not only changes the composition of the electrolyte and affects the cycle life of the battery, but also affects the storage life of the battery due to the presence of the gas.
  • the existing cathode material manufacturers mainly use the co-precipitation method to deposit and coat a layer of metal oxide (such as Al 2 O 3 , MgO, ZrO 2, etc.) on the surface of the material to form a core-shell structure.
  • the metal oxide layer on the surface prevents the ternary
  • the material is in direct contact with the electrolyte to improve cycle life and storage life.
  • the problem to be solved by the present invention is to reduce or eliminate the influence of the residual alkaline lithium salt material on the surface of the ternary positive electrode material on the electrolyte, and to improve the cycle life and storage life of the battery.
  • Another problem to be solved by the present invention is to improve the lithium ion battery composite positive electrode material with a core-shell structure, the ion shuttle transmission problem when lithium ions are extracted and inserted through the shell structure, the internal resistance of the positive electrode polarization is improved, the internal resistance of the battery is reduced, and the battery is optimized. Thermal characteristics.
  • the metal oxide coating layer prepared by the co-precipitation method cannot solve the residual lithium salt substance on the surface of the ternary positive electrode material, but is coated in the shell structure. In the process of recycling, once the shell structure is damaged, it can still contact and react with the electrolyte, which affects the cycle life and storage life of the battery.
  • the metal oxide coating layer can prevent direct contact between the electrolyte and the ternary positive electrode material to a certain extent, but the metal oxide coating layer does not have lithium ion shuttle channels, and the extraction and insertion of positive lithium ions need to be oxidized from the metal Shuttle transmission in the gaps of the coating layer.
  • the coating layer is required to be dense, which makes it difficult to shuttle and transport lithium ions, increases the polarization internal resistance of the positive electrode, and macroscopically affects the internal resistance and thermal characteristics of the battery.
  • a core-shell structured lithium ion battery cathode material is provided.
  • the shell structure of the cathode material is a polyanionic lithium salt, and its chemical formula is Li ⁇ RAO 4 ;
  • the core structure of the positive electrode material is a ternary composite positive electrode material, and its structural formula is Li ⁇ Ni x Co y M 1-yx O 2 , wherein R is selected from Mn and/or Fe, A is P and/or Si, M It is Mn and/or Al.
  • the present invention provides a method for preparing the cathode material of the present invention, the method comprising:
  • step (1) stir and disperse the mixture in step (1) under airtight conditions to form a sol
  • step (3) The mixed solution in step (3) is heated to a temperature lower than 100° C., and stirred to saturate and precipitate to form a microgel;
  • step (4) Send the microgel in step (4) into a spray dryer for spray drying to form a core-shell structure with a uniform particle size of the ternary positive electrode material coated with gel on the surface, and the thickness of the coating layer is 50 ⁇ 100nm;
  • the ternary positive electrode material formed in step (5) is coated with the core-shell structure material of the gel, placed in a high-temperature reactor for reduction, and then cooled And sieving.
  • the present invention provides a positive electrode sheet comprising a positive electrode current collector and a positive electrode active material layer coated on the positive electrode current collector, and the positive electrode active material part of the positive electrode active material layer All are derived from the positive electrode material of the present invention.
  • the present invention provides a lithium ion battery
  • the lithium ion battery includes: a positive electrode sheet, a negative electrode sheet, a separator, an electrolyte, a positive electrode tab, a negative electrode tab, and an aluminum plastic film.
  • the sheet is the positive sheet according to the present invention.
  • the present invention has the following technical effects:
  • the residual alkaline lithium salt material on the surface can be consumed as a lithium source reactant. It is speculated that the reason may be that the main component of the alkaline lithium salt material remaining on the surface is lithium carbonate and/or lithium hydroxide, which can be used as a lithium source in the reactant for forming the polyanionic lithium salt.
  • the core-shell structure lithium ion battery composite cathode material provided by the present invention, the shell structure material is a polyanionic lithium salt, its microscopic crystal structure is very stable, and the octahedral and tetrahedral vacancies in the crystal structure provide There are a large number of channels for lithium ions to shuttle, and the material can still ensure the stability of the material at 600°C, and the safety performance of the battery is good during use.
  • the core-shell structure lithium ion battery composite positive electrode material provided by the present invention adopts the specific sol-gel method of the present invention in the preparation process of the shell structure, the surface coating layer is more compact and uniform, and the coating thickness is thinner. It is speculated that the reason may be that the sol solution can be uniformly dispersed on the molecular scale to form a uniform and stable phase. During the evaporation of the solvent to form a gel, the gel is saturated and precipitated to tightly and uniformly coat the surface of the core structure, by controlling the precipitation of the gel The rate and time can control the coating thickness.
  • the polyanionic lithium salt Li ⁇ RAO 4 is used as a positive electrode material and has a stable olivine or spinel structure, lithium ions can be freely deintercalated, safety performance and cycle life are good, and its disadvantage is low energy density; three
  • the composite cathode material Li ⁇ Ni x Co y M 1-yx O 2 has the characteristics of high energy density, especially when x ⁇ 0.7, the energy density can reach 270Wh/kg, but the material’s thermal stability, safety performance, and cycle Poor performance, the combination of the two materials can combine the advantages of the two types of materials and make up for their respective defects.
  • the present invention provides a lithium ion battery cathode material with a core-shell structure.
  • the shell structure of the cathode material is a polyanionic lithium salt, and its chemical formula is Li ⁇ RAO 4 ;
  • the core structure of the cathode material is a ternary composite cathode material, Its structural formula is Li ⁇ Ni x Co y M 1-yx O 2 , wherein R is selected from Mn and/or Fe, A is P and/or Si, and M is Mn and/or Al.
  • the core-shell structure lithium ion battery of the present invention is characterized by a core-shell structure with a ternary positive electrode material as the core and a surface covered with polyanionic lithium salt as the shell.
  • the core-shell structure lithium ion battery composite positive electrode material provided by the present invention is a polyanionic lithium salt, its microscopic crystal structure is very stable, and the octahedral vacancies and tetrahedral vacancies in the crystal structure provide a large amount of supply
  • the material of the lithium ion shuttle channel can still ensure the stability of the material at 600 °C, and the safety performance of the battery is good during the use of the battery.
  • the value range of ⁇ is 0.8-2, for example, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0 .
  • the value of ⁇ ranges from 0.5 to 1.2, for example, it can be 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2.
  • the value range of x and y is 0-1, and x+y ⁇ 1, for example, can be 0.9, 0.8, 0.7, 0.6, 0.5, 0.4, 0.3, 0.2, 0.1.
  • the core-shell structure lithium ion battery composite positive electrode material provided by the present invention has a shell structure that provides a channel for lithium ion shuttle transmission, which is beneficial to reduce the internal resistance of the battery and optimize the thermal characteristics of the battery.
  • the positive electrode material having the above structure and composition can achieve the objective of the present invention.
  • the present invention particularly provides a method for preparing the positive electrode material of the present invention, the method comprising:
  • step (1) stir and disperse the mixture in step (1) under airtight conditions to form a sol
  • step (3) The mixed solution in step (3) is heated to a temperature lower than 100°C, and stirred, and saturated and precipitated to form a microgel;
  • step (4) Send the microgel in step (4) into a spray dryer for spray drying to form a core-shell structure with a uniform particle size of the ternary positive electrode material coated with gel on the surface, and the thickness of the coating layer is 50 ⁇ 100nm;
  • the ternary positive electrode material formed in step (5) is coated with the core-shell structure material of the gel, placed in a high-temperature reactor for reduction, and then cooled And sieving.
  • the method of the present invention includes:
  • step (1) The mixture in step (1) is stirred and dispersed under airtight conditions to form a sol, the dispersion speed is set to 500-1500r/min, and the stirring time is set to 0.5-8hr;
  • step (3) At room temperature, add the ternary cathode material Li ⁇ Ni x Co y M 1-yx O 2 to the sol described in step (2), stir and mix to obtain a mixed solution, and set the stirring speed to 500 -1500r/min, the stirring time is set to 0.5-8hr;
  • step (3) The mixed solution in step (3) is heated to a temperature lower than 100°C, and stirred with solvent volatilization.
  • the stirring speed is set to 200-300r/min, and the stirring time is set to 1-12hr.
  • the sol is saturated and precipitated to form a microgel;
  • step (4) Send the microgel in step (4) into a spray dryer for spray drying to form a core-shell structure with a uniform particle size of the ternary positive electrode material coated with gel on the surface, and the thickness of the coating layer is 50 ⁇ 100nm;
  • the ternary positive electrode material formed in step (5) is coated with the core-shell structure material of the gel and placed in a high-temperature reactor for reduction for 2-12 hours. After that, it is cooled and sieved.
  • the core-shell structure lithium ion battery composite positive electrode material provided by the present invention is prepared by adopting the above-mentioned sol-gel method to obtain a shell structure coating layer, the coating layer formed by the gel is uniform and compact, and the microstructure size reaches the nanometer level. , The surface of the ternary cathode material is completely covered, and the thickness of the coating layer can reach less than 1um.
  • the core-shell structure lithium ion battery composite positive electrode material provided by the present invention the residual alkaline lithium salt material on the surface of the ternary positive electrode material can be used as a lithium source reactant to participate in the shell structure preparation reaction process, and can effectively reduce or remove three components.
  • the residual alkaline lithium salt material on the surface of the positive electrode material reduces or eliminates the impact of this kind of alkaline lithium salt material on the cycle life and storage life of the battery.
  • the core-shell structure lithium ion battery composite positive electrode material provided by the present invention the lithium source used for preparing the sol-gel of the shell structure is preferably lithium carbonate, lithium hydroxide, lithium oxalate, lithium acetate and One or more of lithium citrate.
  • the source of the R compound is preferably one or more of the iron source and the manganese source.
  • the source of compound A is preferably one or more of the phosphorus source and the silicon source.
  • the core-shell structure lithium ion battery composite positive electrode material provided by the present invention the iron source used for preparing the sol-gel of the shell structure is preferably ferrous oxalate, ferrous acetate, iron phosphate and iron oxide One or more of.
  • the core-shell structure lithium ion battery composite positive electrode material provided by the present invention the manganese source used for preparing the sol-gel of the shell structure is preferably one of manganese sulfate, manganese dioxide, and manganese carbonate Or multiple.
  • the core-shell structure lithium ion battery composite positive electrode material provided by the present invention the phosphorus source used for preparing the sol-gel of the shell structure is preferably ammonia dihydrogen phosphate, ammonium hydrogen phosphate, and ammonium phosphate. One or more.
  • the core-shell structure lithium ion battery composite cathode material provided by the present invention the silicon source used for preparing the sol-gel of the shell structure is preferably ethyl orthosilicate and/or methyl orthosilicate .
  • the core-shell structure lithium ion battery composite positive electrode material provided by the present invention the carbon source used for preparing the sol-gel with the shell structure is preferably one or more of glucose, sucrose and carbon black .
  • the core-shell structure lithium ion battery composite positive electrode material provided by the present invention the solvent used for preparing the sol-gel of the shell structure is preferably one or more of acetone, ether and absolute ethanol .
  • the ternary cathode material is LiNi 0.8 Co 0.1 Mn 0.1 O 2 , LiNi 0.83 Co 0.11 Mn 0.06 O 2 , LiNi 0.8 Co 0.1 Al 0.1 O 2 , LiNi 0.6 Co 0.2 Mn 0.2 O 2 and One or more of LiNi 0.5 Co 0.3 Mn 0.2 O 2.
  • the positive electrode material prepared according to the foregoing method of the present invention has the structure and composition of the positive electrode material of the present invention, and the surface coating layer of the positive electrode material of the present invention prepared according to the method of the present invention is more compact and uniform, and the coating thickness is thinner.
  • the molar ratio of Li and C of the lithium source to the carbon source in step (1) is preferably 4-5:1 or 4-10:1, for example, it can be 4:1, 5:1, 6:1 , 7:1, 8:1, 9:1, 10:1.
  • the stirring speed is 900-1100 r/min, and the stirring time is 5-6 hr.
  • the stirring speed is set to 900-1100 r/min, and the stirring time is 2-3 hr.
  • the temperature is 60-100°C, preferably 80-95°C, and the stirring time is set to 2.5-4.5 hr.
  • the spray drying conditions include a feed temperature of 150-350°C, a discharge temperature of 60-120°C, and an atomizer rotation speed of 15000-25000 rpm.
  • the reduction conditions include: a temperature of 600-650° C. and a time of 6-8 hr.
  • the reducing gas is one or more of carbon monoxide, hydrogen, and a mixed gas of nitrogen and hydrogen.
  • the research of the present invention found that the performance of the positive electrode material of the present invention can be improved by reducing according to the following steps.
  • the preferred reduction step includes:
  • the volume ratio of nitrogen to hydrogen is preferably (3:7)-(6:4), and the temperature is raised to 200-300°C at a heating rate of 1-5°C/min for heat preservation, and the holding time is 4 -6h; then continue to be in the presence of a nitrogen-hydrogen mixture, preferably the volume ratio of nitrogen to hydrogen (3:7)-(6:4), and continue to heat up to 400-500°C at a heating rate of 1-5°C/min Keep heat preservation for 2-4hr; finally, in a hydrogen atmosphere, heat up 600-800°C at a heating rate of 1-5°C/min, preferably 600-650°C for heat preservation, and heat preservation time for 2-12hr, preferably 6- 8hr.
  • the preferred cooling conditions include: passing in argon protection, cooling to 150-250°C at 0.1-0.5°C/min, stopping the passing of protective gas argon, and dropping to room temperature at 2-5°C/min.
  • the present invention provides a positive electrode sheet.
  • the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer coated on the positive electrode current collector.
  • the positive electrode active material of the positive electrode active material layer is partially or completely derived from the present invention. Cathode material.
  • the present invention provides a lithium ion battery.
  • the lithium ion battery includes a positive electrode sheet, a negative electrode sheet, a separator, an electrolyte, a positive electrode tab, a negative electrode tab, and an aluminum plastic film.
  • the positive electrode sheet is the positive electrode according to the present invention. sheet.
  • the invention provides the application of the lithium ion battery of the invention in a new energy vehicle.
  • the performance characteristics of the preparation method of the core-shell structure lithium ion battery composite positive electrode material provided by the present invention are that, during the material preparation process, the residual alkaline lithium salt material on the surface of the ternary positive electrode material can be consumed as a reactant, which is effective Eliminate the influence of alkaline lithium salt substances on battery cycle and storage performance.
  • the core-shell structure provided by the present invention can ensure that the structure of the ternary positive electrode material is stable, and at the same time, it can ensure that lithium ions can quickly shuttle through the shell structure, reduce the internal resistance of the battery, and optimize the thermal characteristics of the battery.
  • the core-shell structure lithium ion battery composite positive electrode material provided by the present invention adopts a sol-gel method to form the shell structure, the surface coating layer is more uniform and dense, and the coating thickness is thinner.
  • LiCO 3 LiCO 3
  • FeC 2 O 4 the iron source FeC 2 O 4
  • phosphorus source (NH 4 ) H 2 PO 4 the carbon source glucose into a certain amount of acetone solvent at a certain molar ratio.
  • Li: Fe: P The molar ratio of C is 0.99:1:1:0.2, and the solid-to-liquid ratio is 1:40.
  • step 2 The mixture in step 1 is stirred and dispersed under airtight conditions to form a sol, the dispersion speed is set to 1000r/min, and the stirring time is set to 5.5hr.
  • ternary cathode material LiNi 0.83 Co 0.11 Mn 0.06 O 2 is added to the sol solution described in step 2, fully stirred and mixed, the stirring speed is set to 1000r/min, and the stirring time is set to 2.5hr.
  • step 4 The mixed solution in step 3 is stirred at a temperature of 90°C with solvent volatilization, the stirring speed is set to 250r/min, the stirring time is set to 3.5hr, and the solvent evaporates at high temperature.
  • the sol is saturated and precipitated to form a microgel.
  • step 4 Send the microgel mixture in step 4 into the spray dryer, set the feed temperature to 250°C, the discharge temperature to 90°C, and the atomizer rotation speed to 20000rpm to form a ternary cathode material with uniform particle size
  • the surface is covered with a core-shell structure of gel, and the thickness of the coating layer is 50-100nm.
  • the ternary cathode material formed in step 5 is coated with gel particles and put into a high-temperature reaction kettle. Under the condition of nitrogen and hydrogen mixture, the volume ratio of nitrogen and hydrogen is 5:5, and the heating rate is 3°C/min. Warm up to 250°C for heat preservation, and the heat preservation time is 5h; in the presence of nitrogen-hydrogen mixture, the volume ratio of nitrogen to hydrogen is 5:5, and continue to heat up to 500°C for heat preservation at 2°C/min, and the heat preservation time is 3hr; In a hydrogen atmosphere, the temperature is continuously increased to 650°C at 1°C/min for heat preservation, and the heat preservation time is 8hr.
  • step 6 Put the particles in step 6 into a high-temperature reaction vessel, pass argon protection, cool down to 200°C at 0.1°C/min, stop passing the protective gas argon, and cool down to room temperature at 5°C/min.
  • the core-shell structure of the lithium-ion battery composite cathode material provided by the present invention is obtained (the shell structure of the cathode material is polyanionic lithium salt, and its chemical formula is LiFePO 4 ; the core structure of the cathode material is ternary
  • the composite cathode material has a structural formula of LiNi 0.83 Co 0.11 Mn 0.06 O 2 ).
  • step 2 The mixture in step 1 is stirred and dispersed under airtight conditions to form a sol, the dispersion speed is set to 1000r/min, and the stirring time is set to 5.5hr.
  • ternary cathode material LiNi 0.83 Co 0.11 Mn 0.06 O 2 is added to the sol solution described in step 2, fully stirred and mixed, the stirring speed is set to 1000r/min, and the stirring time is set to 2.5hr.
  • step 4 The mixed solution in step 3 is stirred at a temperature of 90°C with solvent volatilization, the stirring speed is set to 250r/min, the stirring time is set to 3.5hr, and the solvent evaporates at high temperature.
  • the sol is saturated and precipitated to form a microgel.
  • step 4 Send the microgel mixture in step 4 into the spray dryer, set the feed temperature to 250°C, the discharge temperature to 90°C, and the atomizer rotation speed to 20000rpm to form a ternary cathode material with uniform particle size
  • the surface is covered with a core-shell structure of gel, and the thickness of the coating layer is 50-100nm.
  • the ternary cathode material formed in step 5 is coated with gel particles and placed in a high-temperature reactor. Under the condition of a mixture of nitrogen and hydrogen, the volume ratio of nitrogen to hydrogen is 5:5, and the heating rate is 3°C/min. Warm up to 250°C for heat preservation, and the heat preservation time is 5h; in the presence of nitrogen-hydrogen mixture, the volume ratio of nitrogen to hydrogen is 5:5, and continue to heat up to 500°C for heat preservation at 2°C/min, and the heat preservation time is 3hr; In a hydrogen atmosphere, the temperature is continuously increased to 650°C at 1°C/min for heat preservation, and the heat preservation time is 8hr.
  • the core-shell structure of the lithium-ion battery composite cathode material provided by the present invention is obtained (the shell structure of the cathode material is a polyanionic lithium salt, and its chemical formula is Li 2 FeSiO 4 ; the core structure of the cathode material is Ternary composite cathode material, its structural formula is LiNi 0.83 Co 0.11 Mn 0.06 O 2 ).
  • step 2 The mixture in step 1 is stirred and dispersed under airtight conditions to form a sol, the dispersion speed is set to 1000r/min, and the stirring time is set to 5.5hr.
  • ternary cathode material LiNi 0.83 Co 0.11 Mn 0.06 O 2 is added to the sol solution described in step 2, fully stirred and mixed, the stirring speed is set to 1000r/min, and the stirring time is set to 2.5hr.
  • step 4 The mixed solution in step 3 is stirred at a temperature of 90°C with solvent volatilization, the stirring speed is set to 250r/min, the stirring time is set to 3.5hr, and the solvent evaporates at high temperature.
  • the sol is saturated and precipitated to form a microgel.
  • step 4 Send the microgel mixture in step 4 into the spray dryer, set the feed temperature to 250°C, the discharge temperature to 90°C, and the atomizer rotation speed to 20000rpm to form a ternary cathode material with uniform particle size
  • the surface is covered with a core-shell structure of gel, and the thickness of the coating layer is 50-100nm.
  • the ternary cathode material formed in step 5 is coated with gel particles and put into a high-temperature reaction kettle. Under the condition of nitrogen and hydrogen mixture, the volume ratio of nitrogen and hydrogen is 5:5, and the heating rate is 3°C/min. Warm up to 250°C for heat preservation, and the heat preservation time is 5h; in the presence of nitrogen-hydrogen mixture, the volume ratio of nitrogen to hydrogen is 5:5, and continue to heat up to 500°C for heat preservation at 2°C/min, and the heat preservation time is 3hr; In a hydrogen atmosphere, the temperature is continuously increased to 650°C at 1°C/min for heat preservation, and the heat preservation time is 8hr.
  • step 6 Put the particles in step 6 into a high-temperature reaction vessel, pass argon protection, and cool down to 150°C at 0.2°C/min, stop passing the protective gas argon, and cool down to room temperature at 3°C/min.
  • the core-shell structure of the lithium-ion battery composite cathode material provided by the present invention is obtained (the shell structure of the cathode material is polyanionic lithium salt, and its chemical formula is LiMnPO 4 ; the core structure of the cathode material is ternary
  • the composite cathode material has a structural formula of LiNi 0.83 Co 0.11 Mn 0.06 O 2 ).
  • step 2 The mixture in step 1 is stirred and dispersed under airtight conditions to form a sol, the dispersion speed is set to 1000r/min, and the stirring time is set to 5.5hr.
  • ternary cathode material LiNi 0.83 Co 0.11 Mn 0.06 O 2 is added to the sol solution described in step 2, fully stirred and mixed, the stirring speed is set to 1000r/min, and the stirring time is set to 2.5hr.
  • step 4 The mixed solution in step 3 is stirred at a temperature of 90°C with solvent volatilization, the stirring speed is set to 250r/min, the stirring time is set to 3.5hr, and the solvent evaporates at high temperature.
  • the sol is saturated and precipitated to form a microgel.
  • step 4 Send the microgel mixture in step 4 into the spray dryer, set the feed temperature to 250°C, the discharge temperature to 90°C, and the atomizer rotation speed to 20000rpm to form a ternary positive electrode with uniform particle size
  • the surface of the material is coated with a core-shell structure of gel, and the thickness of the coating layer is 50-100nm.
  • step 6 Put the ternary cathode material coated gel particles formed in step 5 into a high-temperature reaction kettle, and heat up to 250°C at a heating rate of 3°C/min under nitrogen conditions, and the holding time is 5h; Under nitrogen conditions, the temperature is continuously increased to 500°C at 2°C/min for insulation, and the holding time is 3hr; in a nitrogen atmosphere, the temperature is continuously increased to 650°C at 1°C/min for insulation, and the holding time is 8hr.
  • step 6 Put the particles in step 6 into a high-temperature reaction vessel, pass argon protection, and cool down to 250°C at 0.1°C/min, stop passing the protective gas argon, and cool down to room temperature at 2°C/min.
  • the core-shell structure of the lithium-ion battery composite cathode material provided by the present invention is obtained (the shell structure of the cathode material is polyanionic lithium salt, and its chemical formula is LiFePO 4 ; the core structure of the cathode material is ternary
  • the composite cathode material has a structural formula of LiNi 0.83 Co 0.11 Mn 0.06 O 2 ).
  • step 2 The mixture in step 1 is stirred and dispersed under airtight conditions to form a sol, the dispersion speed is set to 1000r/min, and the stirring time is set to 5.5hr.
  • ternary cathode material LiNi 0.83 Co 0.11 Mn 0.06 O 2 is added to the sol solution described in step 2, fully stirred and mixed, the stirring speed is set to 1000r/min, and the stirring time is set to 2.5hr.
  • step 4 The mixed solution in step 3 is stirred at a temperature of 90°C with solvent volatilization, the stirring speed is set to 250r/min, the stirring time is set to 3.5hr, and the solvent evaporates at high temperature.
  • the sol is saturated and precipitated to form a microgel.
  • step 4 Send the microgel mixture in step 4 into the spray dryer, set the feed temperature to 250°C, the discharge temperature to 90°C, and the atomizer rotation speed to 20000rpm to form a ternary cathode material with uniform particle size
  • the surface is covered with a core-shell structure of gel, and the thickness of the coating layer is 50-100nm.
  • the ternary cathode material formed in step 5 is coated with gel particles and put into a high-temperature reaction kettle. Under the condition of nitrogen and hydrogen mixture, the volume ratio of nitrogen and hydrogen is 5:5, and the heating rate is 3°C/min. Warm up to 250°C for heat preservation, and the heat preservation time is 5h; in the presence of nitrogen-hydrogen mixture, the volume ratio of nitrogen to hydrogen is 5:5, and continue to heat up to 500°C for heat preservation at 2°C/min, and the heat preservation time is 3hr; In a hydrogen atmosphere, the temperature is continuously increased to 650°C at 1°C/min for heat preservation, and the heat preservation time is 8hr.
  • step 6 Put the particles in step 6 into a high-temperature reaction vessel, pass argon protection, and cool down to 150°C at 0.2°C/min, stop passing the protective gas argon, and cool down to room temperature at 3°C/min.
  • the core-shell structure of the lithium-ion battery composite cathode material provided by the present invention is obtained (the shell structure of the cathode material is a polyanionic lithium salt, and its chemical formula is Li 2 MnSiO 4 ; the core structure of the cathode material is Ternary composite cathode material, its structural formula is LiNi 0.83 Co 0.11 Mn 0.06 O 2 ).
  • step 2 The mixture in step 1 is stirred and dispersed under airtight conditions to form a sol, the dispersion speed is set to 1000r/min, and the stirring time is set to 5.5hr.
  • ternary cathode material LiNi 0.83 Co 0.11 Mn 0.06 O 2 is added to the sol solution described in step 2, fully stirred and mixed, the stirring speed is set to 1000r/min, and the stirring time is set to 2.5hr.
  • step 4 The mixed solution in step 3 is stirred at a temperature of 90°C with solvent volatilization, the stirring speed is set to 250r/min, the stirring time is set to 3.5hr, and the solvent evaporates at high temperature.
  • the sol is saturated and precipitated to form a microgel.
  • step 4 Send the microgel mixture in step 4 into the spray dryer, set the feed temperature to 250°C, the discharge temperature to 90°C, and the atomizer rotation speed to 20000rpm to form a ternary cathode material with uniform particle size
  • the surface is covered with a core-shell structure of gel, and the thickness of the coating layer is 50-100nm.
  • step 6 Put the ternary cathode material coated gel particles formed in step 5 into a high-temperature reaction kettle, and heat up to 250°C at a heating rate of 3°C/min under nitrogen conditions, and the holding time is 5h; Under nitrogen conditions, the temperature is continuously increased to 500°C at 2°C/min for insulation, and the holding time is 3hr; in a nitrogen atmosphere, the temperature is continuously increased to 650°C at 1°C/min for insulation, and the holding time is 8hr.
  • step 6 Put the particles in step 6 into a high-temperature reaction vessel, pass argon protection, and cool down to 250°C at 0.1°C/min, stop passing the protective gas argon, and cool down to room temperature at 2°C/min.
  • the core-shell structure of the lithium-ion battery composite cathode material provided by the present invention is obtained (the shell structure of the cathode material is a polyanionic lithium salt, and its chemical formula is Li 2 FeSiO 4 ; the core structure of the cathode material is Ternary composite cathode material, its structural formula is LiNi 0.83 Co 0.11 Mn 0.06 O 2 ).
  • step 1 Adjust the pH of the mixed solution in step 1 to around 9, and adjust the temperature in the reactor to 60°C.
  • step 3 Add 2% aluminum acetate solution and the mixed solution in step 1 to the mixed solution in step 2 in a mass ratio of 1:10, and at the same time add ammonia water dropwise to adjust the pH to between 9.
  • step 4 Filter the mixed solution in step 3, and repeatedly wash the filter residue with deionized water and dry it.
  • step 4 Put the filter residue in step 4 in a high-temperature reaction kettle, heat up to 500°C, and keep it for 3 hours.
  • step 6 The high-temperature reaction kettle in step 5 is cooled down to room temperature and sieved to obtain a lithium ion composite ternary cathode material with a core-shell structure.
  • Lithium-ion battery preparation
  • the positive electrode active material Using the positive electrode materials prepared in the above examples and comparative examples as the positive electrode active material, the positive electrode active material, conductive agent carbon nanotubes, conductive agent carbon black (Super Li), binder polyvinylidene fluoride (PVDF) and solvent N -Methylpyrrolidone is made into a positive electrode slurry in a certain proportion.
  • the proportion of the positive electrode active material is 96%, the conductive agent carbon nanotubes 0.5%, and the conductive agent carbon black 1.5%.
  • Binder 2% evenly coat the prepared positive electrode slurry on both sides of the aluminum foil, the coating surface density is controlled at 3.6g/100cm 2 , dry (condition 125 °C) to obtain a roll, roll once, The sheet was punched to obtain a positive electrode sheet, and the compaction of the roll pressing was controlled at 3.4 g/cc.
  • the negative electrode active material artificial graphite (brand CP5M, D50 is 16 ⁇ m), conductive agent carbon nanotubes, binder styrene butadiene rubber, thickener sodium carboxymethyl cellulose and solvent deionized water are made into negative electrode slurry in a certain proportion .
  • the proportion of negative electrode active material is 95.5%, conductive agent 1%, binder 2%, thickener 1.5% by mass percentage; the prepared negative electrode slurry is evenly coated Coated on both sides of the copper foil, the coating surface density is controlled at 2.0g/100cm 2 , dried (at 70°C) to obtain a coil, rolled twice, punched to obtain a negative sheet, and the compaction of the roll is controlled at 1.5g/cc.
  • Cell preparation After drying the obtained positive and negative sheets, stack them with the separator in the order of separator-negative sheet-diaphragm-positive sheet-diaphragm-negative sheet, and use an ultrasonic welding machine to connect the positive electrode aluminum tab with the separator.
  • the copper and nickel-plated tabs of the negative electrode are welded on the battery core, and the welded battery core is placed in a punched aluminum plastic film for packaging, and the diaphragm adopts a PP-PE-PP film.
  • Cell injection Bake the packaged cells and inject the electrolyte. Before the injection, the moisture of the cell should be controlled below 200ppm. After the injection, the cell is sealed and the cell is statically activated, so that the electrolyte can dissolve the positive and negative plates. Fully infiltrate the diaphragm.
  • the conditions for baking the battery cell are: temperature 82°C, time 25h, the electrolyte is a mixed solution of lithium salt, additives and organic solvent, the concentration of lithium salt in the mixed solution is 1 mol/L, and the lithium salt is A mixture of lithium hexafluorophosphate and lithium bis(fluorosulfonyl)imide (8:2), the organic solvent is ethylene carbonate, diethyl carbonate and ethyl methyl carbonate (volume ratio 3:3:4);
  • the additives are vinylene carbonate, propyl sulfite, vinyl sulfate, lithium difluorophosphate and 1-propylene-1,3-sultone.
  • the volume percentage of the additives in the electrolyte is 3% (vinylene carbonate).
  • the weight ratios of five esters, propyl sulfite, vinyl sulfate, lithium difluorophosphate and 1-propylene-1,3-sultone are 0.5%, 1%, 0.5%, 0.5% and 0.5% respectively.
  • the conditions for the battery cell to stand still are: a temperature of 25° C., and a time of 45 hours.
  • Cell formation The activated cell is formed under the conditions of a temperature of 25°C and a pressure torque of 8 Nm.
  • the process step of the formation is: first charge to 3.6V with a constant current of 0.05C, and then use 0.1C Constant current charge to 3.8V, and finally 0.2C constant current and constant voltage charge to 3.9V, cut-off current 0.01C.
  • the cells after the formation are allowed to stand at 45 ⁇ 2°C for 45h and then degas, and the cells after the end of the gas extraction and sealing are charged and discharged at 0.33C.
  • Residual lithium content test refer to GB/T 11064.1-2013
  • the residual amount of lithium hydroxide is: 0.05*V1*23.94*2/50/30*1000000; the residual amount of lithium carbonate is: 0.05*(V2-V1)*36.94*2/50/30*1000000.
  • High temperature storage performance test refer to GB/T 31486-2015
  • the charge retention rate is Q2/Q1
  • the capacity recovery rate is Q3/Q1.
  • the composite ternary cathode material with core-shell structure has a significant reduction in residual lithium content compared with the ternary cathode material without shell structure.
  • the battery prepared has obvious cycle life and storage performance. Improvement.
  • using the composite ternary positive electrode materials of Examples 1, 2, 3, 4, 5, and 6 with the polyanionic lithium salt as the shell structure of the present invention compared with Comparative Example 1 with the metal oxide as the shell structure, the remaining The lithium content is further reduced, showing that the residual lithium can be consumed as a reactant in the process of forming the shell.
  • the lithium ion battery prepared by the composite ternary cathode material described in Examples 1, 2, 3, 4, 5, and 6 has better cycle life and storage performance.

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Abstract

本发明涉及锂电池领域，提供一种核壳结构的锂离子电池正极材料及其制备方法，该正极材料的壳结构组成为聚阴离子锂盐，其化学式为Li βRAO 4；该正极材料的核结构组成为三元复合正极材料，其结构式为Li αNi xCo yM 1-y-xO 2，R选自Mn和/或Fe，A为P和/或Si，M为Mn和/或Al。本发明提供一种正极片和锂离子电池及其应用。本发明提供的核壳结构的锂离子电池复合正极材料，其壳结构材料为一种铁基聚阴离子锂盐，其微观晶体结构非常稳定、其晶体结构中的八面体空位和四面体空位提供了大量供锂离子穿梭的通道，其材料在600℃仍能保证材料稳定，电池使用过程中安全性能好。

Description

核壳结构的锂离子电池正极材料及其制备方法和正极片以及锂离子电池及其应用 技术领域
本发明涉及核壳结构的锂离子电池正极材料及其制备方法和正极片以及锂离子电池及其在新能源汽车中的应用。
背景技术
三元正极材料是目前新能源汽车纯电动乘用车市场应用最广泛的正极材料，具有能量密度高、平台电压高、循环寿命长、高低温性能兼顾等优良性能特点，能够满足新能源乘用车对于续驶里程、高能耗比、快速充电等核心要求。三元正极材料因制备工艺影响，材料PH值较高(＞10)，表面会残留有LiCO 3和LiOH等碱性锂盐物质，三元正极材料随着镍含量的提高，残留碱性锂盐含量成倍提高。
在电池循环过程中，残留碱性锂盐会与电解液中的LiPF 6发生反应形成气体,既改变电解液的成分影响电池的循环寿命，又因气体的存在影响了电池的存储寿命。现有正极材料厂家主要采用共沉淀法在材料表面沉淀包覆一层金属氧化物(如Al 2O 3、MgO、ZrO 2等)，形成核壳结构，通过表面的金属氧化物层阻止三元材料与电解液直接接触，改善循环寿命和存储寿命。
发明内容
本发明所要解决的问题是降低或杜绝三元正极材料表面残留碱性锂盐物质对电解液的影响，提高电池循环寿命和存储寿命。
本发明需要解决的另一个问题是改善核壳结构的锂离子电池复合正极材料，锂离子脱出和嵌入通过壳结构时的离子穿梭传输问题，改善正极极化 内阻，降低电池内阻，优化电池热特性。
研究认为，现有技术中采用的共沉淀法在材料表面包覆一层金属氧化物，能在一定程度上改善三元正极材料的性能，但是存在的一些问题仍然会对电池的性能造成影响：
1.共沉淀法制备的金属氧化物包覆层，无法解决三元正极材料表面的残留锂盐物质，只是被包覆在壳结构内。在循环使用过程中，一旦壳结构出现破损，仍然能够与电解液接触并反应，影响电池的循环寿命和存储寿命。
2.金属氧化物包覆层能在一定程度上阻止电解液与三元正极材料直接接触，但是金属氧化物包覆层不具有锂离子穿梭的通道，正极锂离子的脱出和嵌入需从金属氧化物包覆层的空隙中穿梭传输。而包覆层为阻止电解液渗入，要求包覆层致密，导致锂离子穿梭传输困难，增加了正极的极化内阻，宏观影响了电池的内阻和热特性。
为改善技术现状，实现前述目的，根据本发明的一方面，提供一种核壳结构的锂离子电池正极材料，该正极材料的壳结构组成为聚阴离子锂盐，其化学式为Li βRAO 4；该正极材料的核结构组成为三元复合正极材料，其结构式为Li αNi xCo yM 1-y-xO 2，其中，R选自Mn和/或Fe，A为P和/或Si，M为Mn和/或Al。
根据本发明的第二方面，本发明提供一种制备本发明所述的正极材料的方法，该方法包括：
(1)按计量摩尔比称量锂源、R化合物源、A化合物源、碳源加入到溶剂中；
(2)将步骤(1)中的混合物在密闭条件下搅拌分散，形成溶胶；
(3)在常温下，将所述三元正极材料Li αNi xCo yM 1-y-xO 2加入到步骤(2)所述的溶胶中，搅拌混合得混合液；
(4)将步骤(3)中的混合液，升温至低于100℃的温度下，进行搅拌， 饱和析出形成微凝胶；
(5)将步骤(4)中的微凝胶送入喷雾干燥器中进行喷雾干燥，形成颗粒尺寸均匀的三元正极材料表面包覆有凝胶的核壳结构，包覆层厚度为50～100nm；
(6)在还原气氛下，在温度为500-800℃下，将步骤(5)形成的三元正极材料包覆凝胶的核壳结构材料，放入高温反应釜中进行还原，之后进行冷却和筛分。
根据本发明的第三方面，本发明提供一种正极片，所述正极片包括正极集流体和涂覆在正极集流体上的正极活性物质层，所述正极活性物质层的正极活性物质部分或全部来源于本发明所述的正极材料。
根据本发明的第四方面，本发明提供一种锂离子电池，所述锂离子电池包括：正极片、负极片、隔膜、电解液、正极极耳、负极极耳和铝塑膜，所述正极片为本发明所述的正极片。
通过上述技术方案，本发明具有如下技术效果：
1.本发明提供的核壳结构的锂离子电池复合正极材料，其壳结构形成的过程，表面残留的碱性锂盐物质可以作为锂源反应物消耗。推测原因可能是表面残留的碱性锂盐物质主要成分为碳酸锂和/或氢氧化锂，可以作为形成聚阴离子锂盐的反应物中的锂源。
2.本发明提供的核壳结构的锂离子电池复合正极材料，其壳结构材料为一种聚阴离子锂盐，其微观晶体结构非常稳定、其晶体结构中的八面体空位和四面体空位提供了大量供锂离子穿梭的通道，其材料在600℃仍能保证材料稳定，电池使用过程中安全性能好。
3.本发明提供的核壳结构的锂离子电池复合正极材料，其壳结构制备过程采用本发明的特定溶胶-凝胶方法，表面包覆层更紧密均匀，涂层厚度更薄。推测原因可能是，溶胶液中能够在分子尺度上分散均匀，形成均一稳 定的相，在蒸发溶剂形成凝胶过程中，凝胶饱和析出紧密均匀包覆在核结构表面，通过控制凝胶的析出速率和时间，能够控制涂层厚度。
本发明中，聚阴离子锂盐Li βRAO 4作为正极材料，具有结构稳定的橄榄石或尖晶石结构，锂离子可以自由脱嵌，安全性能和循环寿命好，其缺点是能量密度低；三元复合正极材料Li αNi xCo yM 1-y-xO 2具有能量密度高的特点，尤其是当x≥0.7时，能量密度能够达到270Wh/kg，但是材料的热稳定性能、安全性能、循环性能差，两种材料复合可以融合两类材料的优点，弥补各自的缺陷。
具体实施方式
在本文中所披露的范围的端点和任何值都不限于该精确的范围或值，这些范围或值应当理解为包含接近这些范围或值的值。对于数值范围来说，各个范围的端点值之间、各个范围的端点值和单独的点值之间，以及单独的点值之间可以彼此组合而得到一个或多个新的数值范围，这些数值范围应被视为在本文中具体公开。
本发明提供一种核壳结构的锂离子电池正极材料，该正极材料的壳结构组成为聚阴离子锂盐，其化学式为Li βRAO 4；该正极材料的核结构组成为三元复合正极材料，其结构式为Li αNi xCo yM 1-y-xO 2，其中，R选自Mn和/或Fe，A为P和/或Si，M为Mn和/或Al。
本发明的核壳结构的锂离子电池，其材料特点是以三元正极材料为核，表面包覆聚阴离子锂盐为壳的核壳结构。
本发明提供的核壳结构的锂离子电池复合正极材料，其壳结构材料为一种聚阴离子锂盐，其微观晶体结构非常稳定、其晶体结构中的八面体空位和四面体空位提供了大量供锂离子穿梭的通道，其材料在600℃仍能保证材料稳定，电池使用过程中安全性能好。
根据本发明的一种优选的实施方式，其中，β取值范围为0.8-2，例如可以为0.8、0.9、1.0、1.1、1.2、1.3、1.4、1.5、1.6、1.7、1.8、1.9、2.0。
根据本发明的一种优选的实施方式，其中，α取值范围为0.5-1.2，例如可以为0.5、0.6、0.7、0.8、0.9、1.0、1.1、1.2。
根据本发明的一种优选的实施方式，其中，x，y取值范围为0-1，且x+y＜1，例如可以为0.9、0.8、0.7、0.6、0.5、0.4、0.3、0.2、0.1。
本发明提供的这种核壳结构的锂离子电池复合正极材料，其壳结构提供锂离子穿梭传输的通道，有利于降低电池内阻，优化电池热特性。
具有上述结构和组成的正极材料均可实现本发明的目的，本发明特别提供一种制备本发明所述的正极材料的方法，该方法包括：
(1)按计量摩尔比称量锂源、R化合物源、A化合物源、碳源加入到溶剂中；
(2)将步骤(1)中的混合物在密闭条件下搅拌分散，形成溶胶；
(3)在常温下，将所述三元正极材料Li αNi xCo yM 1-y-xO 2加入到步骤(2)所述的溶胶中，搅拌混合得混合液；
(4)将步骤(3)中的混合液，升温至低于100℃的温度下，进行搅拌，饱和析出形成微凝胶；
(5)将步骤(4)中的微凝胶送入喷雾干燥器中进行喷雾干燥，形成颗粒尺寸均匀的三元正极材料表面包覆有凝胶的核壳结构，包覆层厚度为50～100nm；
(6)在还原气氛下，在温度为500-800℃下，将步骤(5)形成的三元正极材料包覆凝胶的核壳结构材料，放入高温反应釜中进行还原，之后进行冷却和筛分。
优选本发明的方法包括：
(1)按计量摩尔比称量锂源、R化合物源、A化合物源、碳源加入到 溶剂中；
(2)将步骤(1)中的混合物在密闭条件下搅拌分散，形成溶胶，分散转速设定为500-1500r/min，搅拌时间设定为0.5-8hr；
(3)在常温下，将所述三元正极材料Li αNi xCo yM 1-y-xO 2加入到步骤(2)所述的溶胶中，搅拌混合得混合液，搅拌转速设定为500-1500r/min，搅拌时间设定为0.5-8hr；
(4)将步骤(3)中的混合液，升温至低于100℃的温度下，进行搅拌并伴有溶剂挥发，搅拌转速设定为200-300r/min，搅拌时间设定为1-12hr，溶胶饱和析出形成微凝胶；
(5)将步骤(4)中的微凝胶送入喷雾干燥器中进行喷雾干燥，形成颗粒尺寸均匀的三元正极材料表面包覆有凝胶的核壳结构，包覆层厚度为50～100nm；
(6)在还原气氛下，在温度为500-800℃下，将步骤(5)形成的三元正极材料包覆凝胶的核壳结构材料，放入高温反应釜中进行还原2-12hr，之后进行冷却和筛分。
本发明提供的这种核壳结构的锂离子电池复合正极材料，其制备方式采用上述溶胶-凝胶方法得到壳结构包覆层，凝胶形成的包覆层均匀致密，微观结构尺寸达到纳米级，三元正极材料表面包覆完整，包覆层厚度可以达到1um以下。
本发明提供的这种核壳结构的锂离子电池复合正极材料，其三元正极材料表面残留的碱性锂盐物质可以作为锂源反应物参与壳结构制备反应过程中，能够有效降低或祛除三元正极材料表面残留的碱性锂盐物质，减轻或杜绝这类碱性锂盐物质对电池循环寿命和存储寿命的影响。
根据本发明的方法，本发明提供的这种核壳结构的锂离子电池复合正极材料，其壳结构制备溶胶-凝胶所用的锂源优选为碳酸锂、氢氧化锂、草酸 锂、乙酸锂和柠檬酸锂中的一种或多种。
根据本发明的方法，优选R化合物源为所述铁源和所述锰源中的一种或多种。
根据本发明的方法，优选A化合物源为所述磷源和所述硅源中的一种或多种。
根据本发明的方法，本发明提供的这种核壳结构的锂离子电池复合正极材料，其壳结构制备溶胶-凝胶所用的铁源优选为草酸亚铁、醋酸亚铁、磷酸铁和氧化铁中的一种或多种。
根据本发明的方法，本发明提供的这种核壳结构的锂离子电池复合正极材料，其壳结构制备溶胶-凝胶所用的锰源优选为硫酸锰、二氧化锰、碳酸锰中的一种或多种。
根据本发明的方法，本发明提供的这种核壳结构的锂离子电池复合正极材料，其壳结构制备溶胶-凝胶所用的磷源优选为磷酸二氢氨、磷酸氢氨、磷酸氨中的一种或多种。
根据本发明的方法，本发明提供的这种核壳结构的锂离子电池复合正极材料，其壳结构制备溶胶-凝胶所用的硅源优选为正硅酸乙酯和/或正硅酸甲酯。
根据本发明的方法，本发明提供的这种核壳结构的锂离子电池复合正极材料，其壳结构制备溶胶-凝胶所用的碳源优选为葡萄糖、蔗糖和碳黑中的一种或多种。
根据本发明的方法，本发明提供的这种核壳结构的锂离子电池复合正极材料，其壳结构制备溶胶-凝胶所用的溶剂优选为丙酮、乙醚和无水乙醇中的一种或多种。
根据本发明的方法，优选所述三元正极材料为LiNi 0.8Co 0.1Mn 0.1O 2、LiNi 0.83Co 0.11Mn 0.06O 2、LiNi 0.8Co 0.1Al 0.1O 2、LiNi 0.6Co 0.2Mn 0.2O 2和LiNi 0.5Co 0.3Mn 0.2O 2 中的一种或多种。
按照本发明前述方法制备的正极材料具有本发明正极材料的结构和组成，且按照本发明的方法制备的本发明的正极材料表面包覆层更紧密均匀，涂层厚度更薄。
根据本发明的方法，优选步骤(1)中锂源与碳源的Li和C摩尔比为4-5:1或4-10:1，例如可以为4:1、5:1、6:1、7:1、8:1、9:1、10:1。
根据本发明的方法，优选步骤(2)中，搅拌转速为900-1100r/min，搅拌时间为5-6hr。
根据本发明的方法，优选步骤(3)中，搅拌转速设定为900-1100r/min，搅拌时间为2-3hr。
根据本发明的方法，优选步骤(4)中，温度为60-100℃，优选80-95℃，搅拌时间设定为2.5-4.5hr。
根据本发明的方法，优选步骤(5)中，喷雾干燥的条件包括进料温度为150-350℃，出料温度为60-120℃，雾化器转速为15000-25000rpm。
根据本发明的方法，优选步骤(6)中，还原的条件包括：温度为600-650℃，时间为6-8hr。
根据本发明的方法，优选所述还原性气体为一氧化碳、氢气和氮氢混合气中的一种或多种。
根据本发明的方法，本发明研究发现，按照下述步骤还原，能够提高本发明的正极材料的性能，针对本发明，优选还原的步骤包括：
在氮氢混合气条件下，优选氮气与氢气的体积比(3:7)-(6:4)，以1-5℃/min的升温速率升温至200-300℃进行保温，保温时间为4-6h；然后继续在氮氢混合气存在下，优选氮气与氢气的体积比(3:7)-(6:4)，以1-5℃/min的升温速率进行持续升温至400-500℃进行保温，保温时间为2-4hr；最后在氢气气氛下，以1-5℃/min的升温速率升温600-800℃，优选600-650℃ 进行保温，保温时间为2-12hr，优选6-8hr。
根据本发明，优选冷却的条件包括：通入氩气保护，以0.1-0.5℃/min降温至150-250℃，停止通入保护气氩气，以2-5℃/min降至室温。
本发明提供一种正极片，所述正极片包括正极集流体和涂覆在正极集流体上的正极活性物质层，所述正极活性物质层的正极活性物质部分或全部来源于本发明所述的正极材料。
本发明提供一种锂离子电池，所述锂离子电池包括：正极片、负极片、隔膜和电解液、正极极耳、负极极耳和铝塑膜，所述正极片为本发明所述的正极片。
本发明提供了本发明所述的锂离子电池在新能源汽车中的应用。
本发明提供的这种核壳结构的锂离子电池复合正极材料的制备方法的性能特点是，在材料制备过程中，三元正极材料表面残留的碱性锂盐物质可以作为反应物被消耗，有效杜绝碱性锂盐物质对电池循环和存储性能的影响。
本发明提供的这种核壳结构能够保证三元正极材料结构稳定，同时能够保证锂离子能够快速穿梭通过壳结构，降低电池内阻，优化电池热特性。
本发明提供的这种核壳结构的锂离子电池复合正极材料，其壳结构形成采用溶胶-凝胶方法，表面包覆层更均匀致密，涂层厚度更薄。
实施例1
1.以一定计量摩尔比称量锂源LiCO 3、铁源FeC 2O 4、磷源(NH 4)H 2PO 4、碳源葡萄糖加入到一定量丙酮溶剂中，其中，Li：Fe：P：C摩尔比为0.99:1:1：0.2，固液比为1:40。
2.将步骤1中的混合物在密闭条件下搅拌分散，形成溶胶，分散转速设定为1000r/min，搅拌时间设定为5.5hr。
3.将一定量的三元正极材料LiNi 0.83Co 0.11Mn 0.06O 2加入到步骤2所述的 溶胶溶液中，充分搅拌混合，搅拌转速设定为1000r/min，搅拌时间设定为2.5hr。
4.将步骤3中的混合液，在设定90℃的温度下，进行搅拌并伴有溶剂挥发，搅拌转速设定为250r/min，搅拌时间设定为3.5hr，溶剂在高温下蒸发，溶胶饱和析出形成微凝胶。
5.将步骤4中微凝胶混合液送入喷雾干燥器中，设定进料温度为250℃，出料温度为90℃，雾化器转速为20000rpm，形成颗粒尺寸均匀的三元正极材料表面包覆有凝胶的核壳结构，包覆层厚度为50～100nm。
6.将步骤5形成的三元正极材料包覆凝胶颗粒，放入高温反应釜中，在氮氢混合气条件下，氮气与氢气的体积比5：5，以3℃/min的升温速率升温至250℃进行保温，保温时间为5h；在氮氢混合气存在下，氮气与氢气的体积比5:5，以2℃/min进行持续升温至500℃进行保温，保温时间为3hr；在氢气气氛下，以1℃/min进行持续升温至650℃进行保温，保温时间为8hr。
7.将步骤6中的颗粒在高温反应釜中，通入氩气保护，以0.1℃/min降温至200℃，停止通入保护气氩气，以5℃/min降至室温，冷却、筛分，即得到本发明提供的这种核壳结构的锂离子电池复合正极材料(该正极材料的壳结构组成为聚阴离子锂盐，其化学式为LiFePO 4；该正极材料的核结构组成为三元复合正极材料，其结构式为LiNi 0.83Co 0.11Mn 0.06O 2)。
实施例2
1.以一定计量摩尔比称量锂源LiOH、铁源Fe(COOCH 3) 2、硅源TEOS、碳源蔗糖加入到一定量丙酮溶剂中，其中，Li：Fe：Si：C摩尔比为1.98:1:1：0.25，固液比为1:40。
2.将步骤1中的混合物在密闭条件下搅拌分散，形成溶胶，分散转速设定为1000r/min，搅拌时间设定为5.5hr。
3.将一定量的三元正极材料LiNi 0.83Co 0.11Mn 0.06O 2加入到步骤2所述的溶胶溶液中，充分搅拌混合，搅拌转速设定为1000r/min，搅拌时间设定为2.5hr。
4.将步骤3中的混合液，在设定90℃的温度下，进行搅拌并伴有溶剂挥发，搅拌转速设定为250r/min，搅拌时间设定为3.5hr，溶剂在高温下蒸发，溶胶饱和析出形成微凝胶。
5.将步骤4中微凝胶混合液送入喷雾干燥器中，设定进料温度为250℃，出料温度为90℃，雾化器转速为20000rpm，形成颗粒尺寸均匀的三元正极材料表面包覆有凝胶的核壳结构，包覆层厚度为50～100nm。
6.将步骤5形成的三元正极材料包覆凝胶颗粒，放入高温反应釜中，在氮氢混合气条件下，氮气与氢气的体积比5:5，以3℃/min的升温速率升温至250℃进行保温，保温时间为5h；在氮氢混合气存在下，氮气与氢气的体积比5:5，以2℃/min进行持续升温至500℃进行保温，保温时间为3hr；在氢气气氛下，以1℃/min进行持续升温至650℃进行保温，保温时间为8hr。
7.将步骤6中的颗粒在高温反应釜中，通入氩气保护，以0.3℃/min降温至150℃，停止通入保护气氩气，以2℃/min降至室温，冷却、筛分，即得到本发明提供的这种核壳结构的锂离子电池复合正极材料(该正极材料的壳结构组成为聚阴离子锂盐，其化学式为Li 2FeSiO 4；该正极材料的核结构组成为三元复合正极材料，其结构式为LiNi 0.83Co 0.11Mn 0.06O 2)。
实施例3
1.以一定计量摩尔比称量锂源LiCOOCH 3、锰源MnSO 4、磷源(NH 4) 3PO 4、碳源碳黑加入到一定量丙酮溶剂中，其中，Li：Mn：P：C摩尔比为0.99:1:1:0.225，固液比为1:40。
2.将步骤1中的混合物在密闭条件下搅拌分散，形成溶胶，分散转速 设定为1000r/min，搅拌时间设定为5.5hr。
3.将一定量的三元正极材料LiNi 0.83Co 0.11Mn 0.06O 2加入到步骤2所述的溶胶溶液中，充分搅拌混合，搅拌转速设定为1000r/min，搅拌时间设定为2.5hr。
4.将步骤3中的混合液，在设定90℃的温度下，进行搅拌并伴有溶剂挥发，搅拌转速设定为250r/min，搅拌时间设定为3.5hr，溶剂在高温下蒸发，溶胶饱和析出形成微凝胶。
5.将步骤4中微凝胶混合液送入喷雾干燥器中，设定进料温度为250℃，出料温度为90℃，雾化器转速为20000rpm，形成颗粒尺寸均匀的三元正极材料表面包覆有凝胶的核壳结构，包覆层厚度为50～100nm。
6.将步骤5形成的三元正极材料包覆凝胶颗粒，放入高温反应釜中，在氮氢混合气条件下，氮气与氢气的体积比5：5，以3℃/min的升温速率升温至250℃进行保温，保温时间为5h；在氮氢混合气存在下，氮气与氢气的体积比5:5，以2℃/min进行持续升温至500℃进行保温，保温时间为3hr；在氢气气氛下，以1℃/min进行持续升温至650℃进行保温，保温时间为8hr。
7.将步骤6中的颗粒在高温反应釜中，通入氩气保护，以0.2℃/min降温至150℃，停止通入保护气氩气，以3℃/min降至室温，冷却、筛分，即得到本发明提供的这种核壳结构的锂离子电池复合正极材料(该正极材料的壳结构组成为聚阴离子锂盐，其化学式为LiMnPO 4；该正极材料的核结构组成为三元复合正极材料，其结构式为LiNi 0.83Co 0.11Mn 0.06O 2)。
实施例4
1.以一定计量摩尔比称量锂源Li 2CO 3、铁源FeC 2O 4、磷源(NH 4)H 2PO 4、碳源葡萄糖加入到一定量丙酮溶剂中，其中，Li：Fe：P：C摩尔比为0.99:1:1：0.2，固液比为1:40。
2.将步骤1中的混合物在密闭条件下搅拌分散，形成溶胶，分散转速设定为1000r/min，搅拌时间设定为5.5hr。
3.将一定量的三元正极材料LiNi 0.83Co 0.11Mn 0.06O 2加入到步骤2所述的溶胶溶液中，充分搅拌混合，搅拌转速设定为1000r/min，搅拌时间设定为2.5hr。
4.将步骤3中的混合液，在设定90℃的温度下，进行搅拌并伴有溶剂挥发，搅拌转速设定为250r/min，搅拌时间设定为3.5hr，溶剂在高温下蒸发，溶胶饱和析出形成微凝胶。
5.将步骤4中个微凝胶混合液送入喷雾干燥器中，设定进料温度为250℃，出料温度为90℃，雾化器转速为20000rpm，形成颗粒尺寸均匀的三元正极材料表面包覆有凝胶的核壳结构，包覆层厚度为50～100nm。
6.将步骤5形成的三元正极材料包覆凝胶颗粒，放入高温反应釜中，在氮气条件下，以3℃/min的升温速率升温至250℃进行保温，保温时间为5h；在氮气条件下，以2℃/min进行持续升温至500℃进行保温，保温时间为3hr；在氮气气氛下，以1℃/min进行持续升温至650℃进行保温，保温时间为8hr。
7.将步骤6中的颗粒在高温反应釜中，通入氩气保护，以0.1℃/min降温至250℃，停止通入保护气氩气，以2℃/min降至室温，冷却、筛分，即得到本发明提供的这种核壳结构的锂离子电池复合正极材料(该正极材料的壳结构组成为聚阴离子锂盐，其化学式为LiFePO 4；该正极材料的核结构组成为三元复合正极材料，其结构式为LiNi 0.83Co 0.11Mn 0.06O 2)。
实施例5
1.以一定计量摩尔比称量锂源LiCOOCH 3、锰源MnSO 4、硅源正硅酸甲酯、碳源葡萄糖加入到一定量丙酮溶剂中，其中，Li：Mn：Si：C摩尔比为1.98:1:1:0.4，固液比为1:40。
2.将步骤1中的混合物在密闭条件下搅拌分散，形成溶胶，分散转速设定为1000r/min，搅拌时间设定为5.5hr。
3.将一定量的三元正极材料LiNi 0.83Co 0.11Mn 0.06O 2加入到步骤2所述的溶胶溶液中，充分搅拌混合，搅拌转速设定为1000r/min，搅拌时间设定为2.5hr。
4.将步骤3中的混合液，在设定90℃的温度下，进行搅拌并伴有溶剂挥发，搅拌转速设定为250r/min，搅拌时间设定为3.5hr，溶剂在高温下蒸发，溶胶饱和析出形成微凝胶。
5.将步骤4中微凝胶混合液送入喷雾干燥器中，设定进料温度为250℃，出料温度为90℃，雾化器转速为20000rpm，形成颗粒尺寸均匀的三元正极材料表面包覆有凝胶的核壳结构，包覆层厚度为50～100nm。
6.将步骤5形成的三元正极材料包覆凝胶颗粒，放入高温反应釜中，在氮氢混合气条件下，氮气与氢气的体积比5：5，以3℃/min的升温速率升温至250℃进行保温，保温时间为5h；在氮氢混合气存在下，氮气与氢气的体积比5:5，以2℃/min进行持续升温至500℃进行保温，保温时间为3hr；在氢气气氛下，以1℃/min进行持续升温至650℃进行保温，保温时间为8hr。
7.将步骤6中的颗粒在高温反应釜中，通入氩气保护，以0.2℃/min降温至150℃，停止通入保护气氩气，以3℃/min降至室温，冷却、筛分，即得到本发明提供的这种核壳结构的锂离子电池复合正极材料(该正极材料的壳结构组成为聚阴离子锂盐，其化学式为Li 2MnSiO 4；该正极材料的核结构组成为三元复合正极材料，其结构式为LiNi 0.83Co 0.11Mn 0.06O 2)。
实施例6
1.以一定计量摩尔比称量锂源LiOH、铁源Fe(COOCH 3) 2、硅源TEOS、碳源蔗糖加入到一定量丙酮溶剂中，其中，Li：Fe：Si：C摩尔比为1.98:1:1：0.25，固液比为1:40。
2.将步骤1中的混合物在密闭条件下搅拌分散，形成溶胶，分散转速设定为1000r/min，搅拌时间设定为5.5hr。
3.将一定量的三元正极材料LiNi 0.83Co 0.11Mn 0.06O 2加入到步骤2所述的溶胶溶液中，充分搅拌混合，搅拌转速设定为1000r/min，搅拌时间设定为2.5hr。
4.将步骤3中的混合液，在设定90℃的温度下，进行搅拌并伴有溶剂挥发，搅拌转速设定为250r/min，搅拌时间设定为3.5hr，溶剂在高温下蒸发，溶胶饱和析出形成微凝胶。
5.将步骤4中微凝胶混合液送入喷雾干燥器中，设定进料温度为250℃，出料温度为90℃，雾化器转速为20000rpm，形成颗粒尺寸均匀的三元正极材料表面包覆有凝胶的核壳结构，包覆层厚度为50～100nm。
6.将步骤5形成的三元正极材料包覆凝胶颗粒，放入高温反应釜中，在氮气条件下，以3℃/min的升温速率升温至250℃进行保温，保温时间为5h；在氮气条件下，以2℃/min进行持续升温至500℃进行保温，保温时间为3hr；在氮气气氛下，以1℃/min进行持续升温至650℃进行保温，保温时间为8hr。
7.将步骤6中的颗粒在高温反应釜中，通入氩气保护，以0.1℃/min降温至250℃，停止通入保护气氩气，以2℃/min降至室温，冷却、筛分，即得到本发明提供的这种核壳结构的锂离子电池复合正极材料(该正极材料的壳结构组成为聚阴离子锂盐，其化学式为Li 2FeSiO 4；该正极材料的核结构组成为三元复合正极材料，其结构式为LiNi 0.83Co 0.11Mn 0.06O 2)。
对比例1
1、将1:50的三元正极材料LiNi 0.83Co 0.11Mn 0.06O 2与水加入到反应釜中，充分搅拌混合，搅拌转速设定为1000r/min，搅拌时间设定为2.5hr。
2、将步骤1中的混合溶液，调节pH控制在9左右，调节反应釜内温度 控制在60℃。
3、将2％浓度的醋酸铝溶液，与步骤1中的混合液按照1:10的质量比，加入到步骤2中的混合溶液中，同时滴加氨水调节pH控制在9之间。
4、将步骤3中的混合溶液过滤，并用去离子水反复清洗滤渣，烘干。
5、将步骤4中的滤渣置于高温反应釜中，升温至500℃，保温3h。
6、将步骤5中的高温反应釜冷却降至室温，筛分，得到一种核壳结构的锂离子复合三元正极材料。
锂离子电池制备：
正极片制备：
使用上述实施例和对比例制备得到的正极材料作为正极活性物质，将正极活性物质、导电剂碳纳米管、导电剂碳黑(Super Li)、粘接剂聚偏氟乙烯(PVDF)和溶剂N-甲基吡咯烷酮按一定比例制成正极浆料，所述正极浆料干粉中，按质量百分比计，正极活性物质比例为：96％，导电剂碳纳米管0.5％，导电剂碳黑1.5％，粘结剂2％；将制得的正极浆料均匀地涂覆在铝箔的两侧，涂布面密度控制在3.6g/100cm 2，干燥(条件125℃)得卷料，辊压1次，冲片得到正极片，所述辊压的压实控制在3.4g/cc。
负极片制备：
将负极活性物质人造石墨(牌号CP5M，D50为16μm)、导电剂碳纳米管、粘结剂丁苯橡胶、增稠剂羧甲基纤维素钠与溶剂去离子水按一定比例制成负极浆料，所述负极浆料干粉中，按质量百分比计，负极活性物质比例为：95.5％，导电剂1％，粘结剂2％，增稠剂1.5％；将制得的负极浆料均匀地涂覆在铜箔的两侧，涂布面密度控制在2.0g/100cm 2，干燥(条件70℃)得卷料，辊压2次，冲片得到负极片，所述辊压的压实控制在1.5g/cc。
电芯制备：将所得的正、负极片经过干燥后，与隔膜按照隔膜-负极片- 隔膜-正极片-隔膜-负极片的顺序依次叠成电芯，利用超声波焊接机将正极铝极耳与负极铜镀镍极耳焊接在电芯上，并将焊接完成的电芯放入已冲坑好的铝塑膜内进行封装，所述隔膜采用PP-PE-PP膜。
电芯注液：将封装好的电芯烘烤后注入电解液，注液前电芯水分控制200ppm以下，注液后封口并将电芯静置活化，使电解液能将正极片、负极片与隔膜充分浸润。所述电芯烘烤的条件为：温度82℃，时间25h，所述电解液为锂盐、添加剂和有机溶剂的混合溶液，所述混合溶液中锂盐的浓度为1mol/L，锂盐为六氟磷酸锂和双(氟磺酰)亚胺锂的混合物(8:2)，所述有机溶剂为碳酸乙烯酯、碳酸二乙酯和碳酸甲乙酯(体积比为3:3:4)；所述添加剂为碳酸亚乙烯酯、亚硫酸丙酯、硫酸乙烯酯和二氟磷酸锂和1-丙烯-1,3-磺酸内酯，电解液中添加剂的体积百分含量为3％(碳酸亚乙烯酯、亚硫酸丙酯、硫酸乙烯酯和二氟磷酸锂和1-丙烯-1,3-磺酸内酯五者的重量比分别为0.5％，1％，0.5％，0.5％和0.5％)，所述电芯静置的条件为：温度25℃，时间45h。
1、电芯化成：将活化结束的电芯在温度为25℃，压力扭矩8牛米的条件下化成，所述化成工步为：先用0.05C恒流充至3.6V，后用0.1C恒流充至3.8V，最后0.2C恒流恒压充至3.9V，截止电流0.01C。
2、化成结束的电芯在45±2℃的环境下静置45h后进行Degas抽气，抽气封边结束后的电芯进行0.33C充放电分容。
表1
Figure PCTCN2020112605-appb-000001
Figure PCTCN2020112605-appb-000002
残余锂含量测试：参考GB/T 11064.1-2013
1.称取30g待测试料于150mL烧杯中，加入磁力搅拌子及100mL纯水，盖上表面皿，置于磁力搅拌器上搅拌30min后过滤。
2.用量筒量取50mL滤液置于锥形瓶中，加入0.1-0.2mL酚酞指示剂。
3.用0.05mol/L的HCl标准滴定液滴定至红色刚好消失，记下用去的HCl的体积V1。
4.向滤液中加入0.1-0.2mL甲基红-溴甲酚绿指示剂，继续用HCl滴定至滤液由绿色变为红色，煮沸2min祛除CO2，冷却。
5.继续滴定至滤液突跃为酒红色即为终点，记下用去HCl的体积V2.
6.氢氧化锂残余量为：0.05*V1*23.94*2/50/30*1000000；碳酸锂残余量为：0.05*(V2-V1)*36.94*2/50/30*1000000。
循环寿命测试：参考GB/T 31484-2015
1.在25℃±2℃环境下，以1C恒流充电至4.2V转恒压充电，至电流降至0.05C截止；
2.在25℃±2℃环境下静置1h；
3.在25℃±2℃环境下，以1C恒流放电至2.75V；
4.在25℃±2℃环境下静置1h；
5.重复1-4步骤，直至放电容量低于初始放电容量的80％时，终止。
高温存储性能测试：参考GB/T 31486-2015
1.在25℃±2℃环境下，以1C恒流充电至4.2V转恒压充电，至电流降至0.05C截止，静置1h，以1C恒流放低至2.75V，记录初始放电容量为Q1；
2.在25℃±2℃环境下，以1C恒流充电至4.2V转恒压充电，至电流降至0.05C截止；
3.放置于55℃±2℃环境下，静置28d，后取出在室温静置12h；
4.在25℃±2℃环境下，以1C恒流放低至2.75V，放电容量记为Q2；
5.在25℃±2℃环境下，以1C恒流充电至4.2V转恒压充电，至电流降至0.05C截止，静置1h，以1C恒流放低至2.75V，记录放电容量为Q3；
6.荷电保持率为Q2/Q1，容量恢复率为Q3/Q1。
通过表1的结果可以看出，具备核壳结构的复合三元正极材料对比无壳结构的三元正极材料在残留锂含量有明显的降低，所制备的电池，在循环寿命和存储性能有明显的改善。同时，采用本发明所述的以聚阴离子锂盐为壳结构的实施例1、2、3、4、5、6复合三元正极材料，对比以金属氧化物为壳结构的对比例1，残留锂含量进一步降低，显示出形成壳过程中，能够以残留锂为反应物被消耗。实施例1、2、3、4、5、6中所述复合三元正极材料制备的锂离子电池，循环寿命和存储性能更佳。
以上详细描述了本发明的优选实施方式，但是，本发明并不限于此。在本发明的技术构思范围内，可以对本发明的技术方案进行多种简单变型，包括各个技术特征以任何其它的合适方式进行组合，这些简单变型和组合同样应当视为本发明所公开的内容，均属于本发明的保护范围。

Claims (10)

  1. 一种核壳结构的锂离子电池正极材料，其特征在于，该正极材料的壳结构组成为聚阴离子锂盐，其化学式为Li βRAO 4；该正极材料的核结构组成为三元复合正极材料，其结构式为Li αNi xCo yM 1-y-xO 2，其中，R选自Mn和/或Fe，A为P和/或Si，M为Mn和/或Al。
  2. 根据权利要求1所述的正极材料，其中，β取值范围为0.8-2，α取值范围为0.5-1.2，x，y取值范围为0-1，且x+y＜1。
  3. 一种制备权利要求1或2所述的正极材料的方法，其特征在于，该方法包括：
    (1)按计量摩尔比称量锂源、R化合物源、A化合物源、碳源加入到溶剂中；
    (2)将步骤(1)中的混合物在密闭条件下搅拌分散，形成溶胶；
    (3)在常温下，将所述三元正极材料Li αNi xCo yM 1-y-xO 2加入到步骤(2)所述的溶胶中，搅拌混合得混合液；
    (4)将步骤(3)中的混合液，升温至低于100℃的温度下，进行搅拌，饱和析出形成微凝胶；
    (5)将步骤(4)中的微凝胶送入喷雾干燥器中进行喷雾干燥，形成颗粒尺寸均匀的三元正极材料表面包覆有凝胶的核壳结构，包覆层厚度为50～100nm；
    (6)在还原气氛下，在温度为500-800℃下，将步骤(5)形成的三元正极材料包覆凝胶的核壳结构材料，放入高温反应釜中进行反应，之后进行冷却和筛分。
  4. 根据权利要求3所述的方法，其中，
    步骤(1)中锂源与碳源的Li和C的摩尔比为4-10:1；
    步骤(2)中，搅拌转速设定为500-1500r/min，搅拌时间设定为0.5-8hr；优选搅拌转速设定为900-1100r/min，搅拌时间为5-6hr；
    步骤(3)中，搅拌转速设定为500-1500r/min，搅拌时间设定为0.5-8hr；优选搅拌转速设定为900-1100r/min，搅拌时间为2-3hr；
    步骤(4)中，搅拌转速设定为200-300r/min，搅拌时间设定为1-12hr；优选温度为60-100℃，优选80-95℃，搅拌时间为2.5-4.5hr；
    步骤(5)中，喷雾干燥的条件包括进料温度为150-350℃，出料温度为60-120℃，雾化器转速为15000-25000rpm；
    步骤(6)中，还原的条件包括：温度为600-650℃，时间为2-12hr，优选为6-8hr；
    所述还原性气体为一氧化碳、氢气和氮氢混合气中的一种或多种。
  5. 根据权利要求3或4所述的方法，其中，步骤(6)中，还原的步骤包括：在氮氢混合气条件下，优选氮气与氢气的体积比(3:7)-(6:4)，以1-5℃/min的升温速率升温至200-300℃进行保温，保温时间为4-6h；然后继续在氮氢混合气存在下，优选氮气与氢气的体积比(3:7)-(6:4)，以1-5℃/min的升温速率进行持续升温至400-500℃进行保温，保温时间为2-4hr；最后在氢气气氛下，以1-5℃/min的升温速率升温至600-800℃，优选600-650℃进行保温，保温时间为2-12hr，优选6-8hr。
  6. 根据权利要求3或4所述的方法，其中，冷却的条件包括：通入氩气保护，以0.1-0.5℃/min降温至150-250℃，停止通入保护气氩气，以2-5℃/min降至室温。
  7. 根据权利要求3或4所述的方法，其中，
    所述锂源为碳酸锂、氢氧化锂、草酸锂、乙酸锂和柠檬酸锂中的一种或多种；
    所述R化合物源为铁源和/或锰源，所述铁源为草酸亚铁、醋酸亚铁、磷酸铁和氧化铁中的一种或多种，所述锰源为硫酸锰、二氧化锰、碳酸锰中的一种或多种；
    所述A化合物源为磷源和/或硅源，所述磷源为磷酸二氢氨、磷酸氢氨和磷酸氨中的一种或多种，所述硅源为正硅酸乙酯和/或正硅酸甲酯；
    所述碳源为葡萄糖、蔗糖和碳黑中的一种或多种；
    所述溶剂为丙酮、乙醚和无水乙醇中的一种或多种；
    所述三元正极材料为LiNi 0.8Co 0.1Mn 0.1O 2、LiNi 0.83Co 0.11Mn 0.06O 2、LiNi 0.8Co 0.1Al 0.1O 2、LiNi 0.6Co 0.2Mn 0.2O 2和LiNi 0.5Co 0.3Mn 0.2O 2中的一种或多种。
  8. 一种正极片，其特征在于，所述正极片包括正极集流体和涂覆在正极集流体上的正极活性物质层，所述正极活性物质层的正极活性物质部分或全部来源于权利要求1或2所述的正极材料或权利要求3-7中任意一项所述的制备方法制备得到的正极材料。
  9. 一种锂离子电池，所述锂离子电池包括：正极片、负极片、隔膜、电解液、正极极耳、负极极耳和铝塑膜，其特征在于，所述正极片为权利要求8所述的正极片。
  10. 权利要求9所述的锂离子电池在新能源汽车中的应用。
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