WO2025065983A1 - 负极材料及其制备方法、锂离子电池 - Google Patents

负极材料及其制备方法、锂离子电池 Download PDF

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WO2025065983A1
WO2025065983A1 PCT/CN2024/073436 CN2024073436W WO2025065983A1 WO 2025065983 A1 WO2025065983 A1 WO 2025065983A1 CN 2024073436 W CN2024073436 W CN 2024073436W WO 2025065983 A1 WO2025065983 A1 WO 2025065983A1
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Prior art keywords
negative electrode
electrode material
graphite
precursor
core
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English (en)
French (fr)
Inventor
董行
周海辉
徐涛
何鹏
任建国
贺雪琴
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BTR New Material Group Co Ltd
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BTR New Material Group Co Ltd
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Priority to EP24869555.3A priority Critical patent/EP4614598A4/en
Priority to KR1020257020491A priority patent/KR20250105468A/ko
Priority to JP2025534620A priority patent/JP2026500286A/ja
Publication of WO2025065983A1 publication Critical patent/WO2025065983A1/zh
Priority to US19/295,982 priority patent/US20250364546A1/en
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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
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00—Carbon; Compounds thereof
    • C01B32/20—Graphite
    • C01B32/21—After-treatment
    • 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
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/364—Composites as mixtures
    • H—ELECTRICITY
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    • 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
    • H—ELECTRICITY
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    • 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
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • 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
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H01M4/587—Carbonaceous material, e.g. graphite-intercalation compounds or CFx for inserting or intercalating light metals
    • 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
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • 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
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/628—Inhibitors, e.g. gassing inhibitors, corrosion inhibitors
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/01—Particle morphology depicted by an image
    • C01P2004/03—Particle morphology depicted by an image obtained by SEM
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/60—Particles characterised by their size
    • C01P2004/61—Micrometer sized, i.e. from 1-100 micrometer
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/60—Particles characterised by their size
    • C01P2004/62—Submicrometer sized, i.e. from 0.1-1 micrometer
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/80—Particles consisting of a mixture of two or more inorganic phases
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2006/00—Physical properties of inorganic compounds
    • C01P2006/12—Surface area
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2006/00—Physical properties of inorganic compounds
    • C01P2006/40—Electric properties
    • H—ELECTRICITY
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    • H01M4/00—Electrodes
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    • H01M2004/021—Physical characteristics, e.g. porosity, surface area
    • H—ELECTRICITY
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    • 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
    • H01M2004/027—Negative 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 present application relates to the technical field of negative electrode materials, and more specifically, to negative electrode materials and preparation methods thereof, and lithium-ion batteries.
  • Lithium-ion batteries have been widely used in portable electronic devices, electric vehicles, drones and other fields due to their advantages such as high energy density, long cycle life, low environmental pollution and no memory effect.
  • the performance indicators of lithium-ion batteries are closely related to the electrode materials, so it is very necessary to further improve the performance of lithium-ion battery negative electrode materials.
  • Graphite materials have been widely used in the field of lithium-ion battery negative electrode materials, but traditional graphite materials still have shortcomings such as poor compatibility with electrolytes and unstable solid electrolyte interface films (SEI), resulting in low initial Coulomb efficiency of the material, poor kinetic transmission and continuous attenuation of cycle capacity.
  • SEI solid electrolyte interface films
  • coating layers are mainly divided into two categories: carbonaceous materials and non-carbonaceous materials.
  • Carbonaceous material coating often uses asphalt or resin as the coating precursor. Through solid or liquid phase mixing and high-temperature carbonization treatment, the precursor is converted into soft carbon or hard carbon material and composited on the graphite particles, which can reduce the specific surface value of the graphite material and improve the compatibility of the electrolyte.
  • the product after carbonization of asphalt or resin is still a carbon material in essence, and it will still undergo irreversible reactions with electrolyte components at low potentials, resulting in continuous decomposition and repair and recombination of the interface layer of the graphite material, causing continuous attenuation of the battery capacity.
  • the purpose of the present application is to provide a negative electrode material and a preparation method thereof, and a lithium-ion battery.
  • the negative electrode material of the present application can reduce the specific surface value of the negative electrode material, enhance the interface stability of the negative electrode material, improve the electrolyte wettability, reduce interfacial side reactions, and improve the lithium ion transmission efficiency, thereby improving the electrochemical performance of the negative electrode material through the synergistic effect of the carbonaceous material and the non-carbonaceous material in the composite layer.
  • the present application provides a negative electrode material, comprising a core and a composite layer located on at least a portion of the surface of the core, wherein the core comprises graphite, and the composite layer comprises a carbonaceous material and a non-carbonaceous material.
  • the non-carbonaceous material is dispersed in the carbonaceous material.
  • the chemical formula of the non-carbonaceous material is AxBy , wherein 1 ⁇ x ⁇ 3 , 1 ⁇ y ⁇ 5, the A element includes at least one of Li, Na, K, Ca, Mg, Al, Zn, Ti, Nb, Zr, Mo, P, Si and B, and the B element includes at least one of B, O, F, Si, P, S, Br and Cl.
  • the graphite includes at least one of natural graphite, artificial graphite and microcrystalline graphite. kind.
  • the median particle size of the inner core is D50, 0.5 ⁇ m ⁇ D50 ⁇ 30 ⁇ m.
  • the mass content of carbon in the graphite is ⁇ 80%.
  • the carbonaceous material includes at least one of amorphous carbon and graphite carbon.
  • the composite layer has a thickness of 1 nm to 200 nm.
  • the non-carbonaceous material includes at least one of LiF, NaF, MgF 2 , MgO, P 2 O 5 , Al 2 O 3 , SiO 2 , and B 2 O 3 .
  • the average particle size of the non-carbonaceous material is G, and G ⁇ 150 nm.
  • a mass ratio of the composite layer to the core is C, and 0.01 ⁇ C ⁇ 0.5.
  • the mass ratio of the carbonaceous material to the non-carbonaceous material is D, and 0.1 ⁇ D ⁇ 80.
  • the powder conductivity of the core is E 1
  • the powder conductivity of the negative electrode material is E 2
  • the ratio of E 2 to E 1 is E, and 1 ⁇ E ⁇ 1000.
  • the inner core has a specific surface area of 6 m 2 /g to 15 m 2 /g.
  • the specific surface area of the negative electrode material is 1 m 2 /g to 5 m 2 /g.
  • the present application provides a method for preparing a negative electrode material, comprising the following steps:
  • the first precursor comprising a core and a polymer layer formed on a surface of the core, wherein the core comprises graphite;
  • the second precursor is carbonized to obtain a negative electrode material.
  • the preparation of the first precursor includes the following steps: subjecting a first mixed solution containing graphite and organic molecular monomers to a polymerization reaction, solid-liquid separation and drying to obtain the first precursor.
  • attaching an inorganic salt on the surface of the first precursor to obtain a second precursor includes the following steps: drying a second mixed solution containing the first precursor and the inorganic salt to obtain a second precursor.
  • the graphite includes at least one of natural graphite, artificial graphite, and microcrystalline graphite.
  • the median particle size of the graphite is 0.5 ⁇ m to 30 ⁇ m.
  • the mass ratio of the graphite to the organic molecular monomer is 1:(0.01-0.4).
  • the organic molecular monomer includes at least one of aniline, styrene, fluorostyrene, hydroxyethyl acrylate, acrylate, pyrrole, vinylidene fluoride, tetrafluoroethylene, and dopamine.
  • the first mixed solution and the second mixed solution both include a solvent
  • the solvent includes at least one of water, methanol, ethanol, acetone, nitrogen methyl pyrrolidone and N,N-dimethylformamide.
  • the first mixed solution further includes an auxiliary agent.
  • the first mixed solution further includes an auxiliary agent, and the mass concentration of the auxiliary agent in the first mixed solution is 0.01 mol/L to 4 mol/L.
  • the first mixed solution further includes an auxiliary agent
  • the auxiliary agent includes an initiator
  • the initiator includes at least one of ammonium persulfate, sodium persulfate, potassium persulfate, aluminum chloride and hydrogen peroxide.
  • the first mixed solution further includes an auxiliary agent, the auxiliary agent includes a catalyst, and the catalyst includes at least one of sodium hydroxide, lithium hydroxide, potassium hydroxide, ammonia water and sodium carbonate.
  • the first mixed solution further includes an auxiliary agent, wherein the auxiliary agent includes a pH adjuster, and the pH adjuster includes at least one of an acidic pH reagent and an alkaline pH reagent.
  • the first mixed solution further includes an auxiliary agent, the auxiliary agent includes a pH adjuster, and the pH of the first mixed solution is 4-10.
  • the first mixed solution further includes an auxiliary agent
  • the auxiliary agent includes a pH adjuster
  • the pH adjuster includes at least one of hydrochloric acid, sulfuric acid, phosphoric acid and nitric acid.
  • the first mixed solution further includes an auxiliary agent, the auxiliary agent includes a pH adjuster, and the pH adjuster includes at least one of lithium hydroxide, sodium hydroxide, potassium hydroxide, sodium carbonate and sodium bicarbonate.
  • the polymerization reaction temperature is 40°C to 100°C.
  • the polymerization reaction time is 3 hours to 48 hours.
  • the polymerization reaction is carried out under stirring.
  • the polymerization reaction is carried out under stirring at a stirring rate of 50 r/min to 1000 r/min.
  • the solid-liquid separation comprises at least one of filtration and centrifugation.
  • the drying comprises at least one of natural volatilization, forced air drying, flash drying, freeze drying, inert atmosphere protection drying, and vacuum drying.
  • the inorganic salt includes at least one of lithium hydroxide, sodium hydroxide, potassium hydroxide, magnesium nitrate, calcium chloride, aluminum nitrate, zinc nitrate, titanium n-propoxide, niobium oxalate, zirconium oxychloride, ammonium molybdate, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, sodium metasilicate, sodium borate, ammonium fluoride, titanium oxysulfide, zinc bromide and zirconium chloride.
  • the mass ratio of the first precursor to the inorganic salt is 1:(0.001-0.1).
  • the drying comprises at least one of natural volatilization, forced air drying, flash drying, freeze drying, inert atmosphere drying and vacuum drying.
  • the drying temperature is 60°C to 600°C.
  • the drying time is 0.5 h to 48 h.
  • the carbonization process is performed under a protective atmosphere.
  • the carbonization treatment is performed under a protective atmosphere
  • the protective atmosphere includes at least one of nitrogen, helium, neon, argon, and air.
  • the heating rate of the carbonization treatment is 1° C./min to 20° C./min.
  • the carbonization treatment is carried out at a holding temperature of 600°C to 2500°C.
  • the carbonization treatment is carried out for a holding time of 0.1 h to 10 h.
  • the present application provides a lithium-ion battery, wherein the lithium-ion battery comprises the negative electrode material described in the first aspect or the negative electrode material prepared by the method for preparing the negative electrode material described in the second aspect.
  • the negative electrode material includes a core and a composite layer located on at least part of the surface of the core, the core includes graphite, and the composite layer includes carbonaceous material and non-carbonaceous material.
  • the specific surface area of the negative electrode material can be reduced, and the high temperature storage performance and electrode processing performance of the negative electrode material can be improved; the interface stability of the negative electrode material can also be improved, the interface side reactions can be reduced, and the electrolyte can be enhanced. Improve wettability, improve lithium ion transmission efficiency, and enhance the reversible capacity, initial efficiency and rate performance of negative electrode materials.
  • a first precursor is obtained by subjecting a first mixed solution containing a graphite material and an organic molecular monomer to a polymerization reaction, so that a polymer formed by the polymerization of the organic molecular monomer is composited on the surface of the graphite particles to form a polymer layer, and the polymer has a highly reactive functional group.
  • a second mixed solution containing the first precursor and an inorganic salt is fully mixed and dried, and the inorganic salt in the second mixed solution is hydrolyzed to form inorganic ions.
  • the inorganic ions are grafted and introduced into the polymer layer on the surface of the graphite particles by utilizing the grafting reaction between the highly reactive functional groups in the polymer and the inorganic ions to obtain a second precursor. Finally, the second precursor is carbonized. After the carbonization treatment, the organic molecules in the polymer layer are in situ cracked into carbonaceous materials, and the inorganic ions are in situ converted into non-carbonaceous materials, so as to form a composite layer containing carbonaceous materials and non-carbonaceous materials on the surface of the graphite particles.
  • the surface of the prepared negative electrode material has a uniformly coated composite layer.
  • the specific surface area of the negative electrode material can be reduced, and the high-temperature storage performance and electrode sheet processing performance of the negative electrode material can be improved; it can also improve the interface stability of the negative electrode material, reduce interface side reactions, enhance electrolyte wettability, improve lithium ion transmission efficiency, and enhance the reversible capacity, initial efficiency and rate performance of the negative electrode material.
  • FIG1 is a flow chart of a preparation process of a negative electrode material provided in an embodiment of the present application.
  • FIG2 is a schematic diagram of the structure of the negative electrode material provided in an embodiment of the present application.
  • FIG3a is a scanning electron microscope image of the negative electrode material prepared in Example 1 of the present application.
  • FIG3 b is a scanning electron microscope image of the negative electrode material prepared in Example 1 of the present application at another magnification
  • FIG4 is a scanning electron microscope image of a cross section of the negative electrode material prepared in Example 1 of the present application.
  • the present application provides a negative electrode material, as shown in FIG2 , the negative electrode material comprises a core and a composite layer located on at least a portion of the surface of the core, the core comprises graphite, and the composite layer comprises a carbonaceous material and a non-carbonaceous material.
  • the negative electrode material provided in the present application includes a core and a composite material located on at least a portion of the surface of the core.
  • the inner core includes graphite
  • the composite layer includes carbonaceous material and non-carbonaceous material.
  • the graphite includes at least one of natural graphite, artificial graphite, and microcrystalline graphite.
  • the median particle size of the inner core is D50, 0.5 ⁇ m ⁇ D50 ⁇ 30 ⁇ m, specifically 0.5 ⁇ m, 1 ⁇ m, 3.5 ⁇ m, 5 ⁇ m, 8 ⁇ m, 10 ⁇ m, 12 ⁇ m, 15 ⁇ m, 18 ⁇ m, 19.7 ⁇ m, 21.3 ⁇ m, 24.5 ⁇ m, 26.1 ⁇ m, 28.4 ⁇ m, 29 ⁇ m or 30 ⁇ m, etc., of course, it can also be other values within the above range, which is not limited here.
  • the mass content of carbon element in the graphite is ⁇ 80%, specifically 80%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 98% or 99%, etc., and of course it can also be other values within the above range, which is not limited here.
  • the carbonaceous material includes at least one of amorphous carbon and graphite carbon.
  • the amorphous carbon includes soft carbon and hard carbon.
  • the thickness of the composite layer is 1nm to 200nm.
  • the thickness of the composite layer can be 1nm, 2nm, 5nm, 10nm, 15nm, 30nm, 50nm, 80nm, 100nm, 110nm, 150nm, 180nm or 200nm, etc., which is not limited here.
  • the composite layer is thin, it is difficult for the carbonaceous material and the non-carbonaceous material to form a uniform wrapping effect on the surface of the graphite material, resulting in a higher specific surface area of the negative electrode material.
  • optimizing and controlling the thickness of the composite layer within the range of 1nm to 200nm can reduce the specific surface area of the negative electrode material, improve the high temperature storage performance and pole piece processing performance of the negative electrode material, and at the same time improve the interfacial lithium ion transmission efficiency of the negative electrode material, and improve the first efficiency and rate performance of the negative electrode material.
  • the chemical formula of the non-carbonaceous material is AxBy , wherein 1 ⁇ x ⁇ 3 , 1 ⁇ y ⁇ 5, the A element includes at least one of Li, Na, K, Ca, Mg, Al, Zn, Ti, Nb, Zr, Mo, P, Si and B, and the B element includes at least one of B, O, F, Si, P, S, Br and Cl.
  • the A element includes at least one of Li, Na, Mg, Al, P, Si and B; and the B element is O or F.
  • the non-carbonaceous material is at least one of LiF, NaF, MgF 2 , MgO, P 2 O 5 , Al 2 O 3 , SiO 2 , and B 2 O 3 .
  • the non-carbonaceous material is dispersed in the carbonaceous material. It is understandable that since the carbonaceous material is formed by carbonization of organic matter, before the organic matter is carbonized, the non-carbonaceous material can be attached to the surface or inside of the organic matter in the form of ions to achieve uniform compounding, forming a composite layer composed of cross-linked and interspersed non-carbonaceous materials and carbonaceous materials.
  • the average particle size of the non-carbonaceous material is G, and G ⁇ 150nm, specifically 0.5nm, 1nm, 1.5nm, 3.6nm, 4.8nm, 7nm, 8.9nm, 10nm, 11.2nm, 15nm, 20nm, 30nm, 50nm, 80nm, 100nm, 120nm, 140nm or 150nm, etc., but not limited to the listed values, other unlisted values within the numerical range are also applicable.
  • the non-carbonaceous material in the composite layer When the average particle size of the non-carbonaceous material in the composite layer is too large, the non-carbonaceous material is difficult to be evenly distributed in the carbonaceous material, resulting in a high specific surface area of the negative electrode material and poor interfacial lithium ion transport performance.
  • an S-4800 scanning electron microscope was used to observe the microscopic morphology of the surface of the negative electrode material and the particle size of the non-carbonaceous material.
  • a 1 ⁇ m*1 ⁇ m area was randomly selected on a single negative electrode material particle, the particle size distribution of the non-carbonaceous material in the area was statistically analyzed, and the average particle size of the non-carbonaceous material was calculated as G.
  • the mass ratio of the composite layer to the core is C, and 0.01 ⁇ C ⁇ 0.5.
  • the value of C can specifically be 0.01, 0.03, 0.07, 0.09, 0.1, 0.17, 0.25, 0.3, 0.35, 0.4, 0.42, 0.48 or 0.5, etc., which are not limited here.
  • the C value is low, the content of the composite layer in the negative electrode material is small, and it is difficult to form a complete and uniform coating layer on the surface of the core, resulting in a larger specific surface area of the negative electrode material.
  • the C value is high, the content of the composite layer in the negative electrode material is large, and the coating layer formed on the surface of the core is thick, resulting in poor kinetic performance of the negative electrode material and low capacity.
  • the mass ratio of the carbonaceous material to the non-carbonaceous material is D, and 0.1 ⁇ D ⁇ 80, specifically 0.1, 0.5, 0.8, 1, 5, 10, 18, 24, 30, 35, 40, 50, 62, 74, or 80, etc., of course, it can also be other values within the above range, which are not limited here.
  • the D value is low, the content of non-carbonaceous material in the composite layer is high, resulting in a larger specific surface area of the negative electrode material.
  • the D value is high, the content of carbonaceous material in the composite layer is high, resulting in a decrease in the interfacial lithium ion transmission efficiency of the negative electrode material and a deterioration in the rate performance of the negative electrode material.
  • the powder conductivity of the graphite is E1
  • the powder conductivity of the negative electrode material is E2
  • the ratio of E2 to E1 is E, and 1 ⁇ E ⁇ 1000.
  • the value of E can be 1.01, 5, 10, 50, 100, 150, 200, 300, 400, 500, 600, 700, 800, 900 or 1000, etc., which is not limited here.
  • graphite is the powder conductivity of uncoated graphite raw material
  • the powder conductivity of the negative electrode material refers to the conductivity after the graphite is coated with the composite layer.
  • the value of E can represent the conductivity of the negative electrode material. If the value of E is too small, the conductivity of the negative electrode material is difficult to improve.
  • the specific surface area of the inner core is 6 m 2 /g to 15 m 2 /g, specifically 6 m 2 /g, 6.8 m 2 /g, 7.9 m 2 /g, 8.7 m 2 /g, 9.5 m 2 /g, 10 m 2 /g, 11.3 m 2 /g, 12.4 m 2 /g, 13.5 m 2 /g, 14 m 2 /g or 15 m 2 /g, etc.
  • it can also be other values within the above range, which is not limited here.
  • the specific surface area of the negative electrode material is 1m2 /g to 5m2 /g, specifically 1m2 /g, 1.5m2 /g, 2.3m2 /g, 2.8m2 /g, 3m2 /g, 3.5m2 /g, 4m2 /g, 4.8m2 /g or 5m2 /g, etc.
  • it can also be other values within the above range, which is not limited here.
  • the negative electrode material includes a core and a composite layer located on at least a portion of the surface of the core.
  • the composite layer is completely and evenly coated on the surface of the core, which can reduce the specific surface area of the negative electrode material and control the specific surface area of the negative electrode material within the range of 1m2 /g to 5m2 /g, which is beneficial to improving the high temperature storage performance and electrode processing performance of the negative electrode material, and further beneficial to improving the cycle performance of the lithium ion battery made of the negative electrode material.
  • the present application provides a method for preparing a negative electrode material, as shown in FIG1 , comprising the following steps:
  • Step S100 preparing a first precursor, wherein the first precursor comprises a core and a polymer layer formed on the surface of the core, wherein the core comprises graphite;
  • Step S200 attaching an inorganic salt on the surface of the first precursor to obtain a second precursor
  • Step S300 carbonizing the second precursor to obtain a negative electrode material.
  • a first precursor is obtained by polymerizing a first mixed solution containing a graphite material and an organic molecular monomer, so that a polymer formed by polymerization of the organic molecular monomer is compounded on the surface of graphite particles to form a polymer layer, wherein the polymer layer has a highly reactive functional group, and then ...
  • a precursor and a second mixed solution of an inorganic salt are fully mixed and dried, the inorganic salt in the second mixed solution is hydrolyzed to form inorganic ions, and the inorganic ions are grafted into the polymer layer on the surface of the graphite particles by utilizing the grafting reaction between the highly reactive functional groups in the polymer and the inorganic ions to obtain a second precursor, and finally the second precursor is carbonized.
  • the organic molecules in the polymer layer are in situ cracked into carbonaceous materials, and the inorganic ions are in situ converted into non-carbonaceous materials, forming a composite layer containing carbonaceous materials and non-carbonaceous materials on the surface of the graphite particles.
  • the surface of the prepared negative electrode material has a uniformly coated composite layer, and through the synergistic effect of the carbonaceous materials and non-carbonaceous materials in the composite layer, the specific surface area of the negative electrode material can be reduced, and the high temperature storage performance and pole piece processing performance of the negative electrode material can be improved; the interface stability of the negative electrode material can be improved, the interface side reactions can be reduced, the electrolyte wettability can be enhanced, the lithium ion transmission efficiency can be improved, and the reversible capacity, first efficiency, and rate performance of the negative electrode material can be improved.
  • Step S100 preparing a first precursor, wherein the first precursor comprises a core and a polymer layer formed on a surface of the core, wherein the core comprises graphite.
  • preparing a first precursor includes the following steps: subjecting a first mixed solution containing graphite material and organic molecular monomers to a polymerization reaction, solid-liquid separation and drying to obtain a first precursor, wherein the first precursor includes a core and a polymer layer located on the surface of the core, and the core includes graphite.
  • the graphite material includes at least one of natural graphite, artificial graphite, and microcrystalline graphite.
  • the median particle size of the graphite is 0.5 ⁇ m to 30 ⁇ m, and can be 0.5 ⁇ m, 1 ⁇ m, 3.5 ⁇ m, 5 ⁇ m, 8 ⁇ m, 10 ⁇ m, 12 ⁇ m, 15 ⁇ m, 18 ⁇ m, 19.7 ⁇ m, 21.3 ⁇ m, 24.5 ⁇ m, 26.1 ⁇ m, 28.4 ⁇ m, 29 ⁇ m or 30 ⁇ m, etc., and can also be other values within the above range, which are not limited here.
  • the mass ratio of the graphite material to the organic molecular monomer is 1:(0.01-0.4). Specifically, it can be 1:0.01, 1:0.05, 1:0.1, 1:0.15, 1:0.2, 1:0.25, 1:0.3, 1:0.35 or 1:0.4, etc., but it is not limited to the listed values. Other unlisted values within this numerical range are also applicable.
  • Controlling the mass ratio of graphite material and organic molecular monomer can reduce the situation where the polymer coating is too thick, affecting the capacity; it can also reduce the situation where there is too little polymer and a complete polymer coating cannot be formed, thereby affecting the complete uniformity of the coating of the composite layer, which is not conducive to the decrease in the specific surface area of the negative electrode material.
  • the present application can ensure the formation of a uniform polymer coating on the surface of the graphite particles, thereby improving the coating uniformity of the graphite particles and the composite layer.
  • the organic molecular monomer includes at least one of aniline, styrene, fluorostyrene, hydroxyethyl acrylate, acrylate, pyrrole, vinylidene fluoride, tetrafluoroethylene and dopamine.
  • the first mixed solution and the second mixed solution both include a solvent
  • the solvent includes at least one of water, methanol, ethanol, acetone, nitrogen methyl pyrrolidone and N,N-dimethylformamide.
  • the first mixed solution further includes an auxiliary agent. It can be understood that the addition of the chemical reaction auxiliary agent can promote the polymerization reaction of the organic molecular monomer.
  • the first mixed solution also includes an auxiliary agent
  • the mass concentration of the auxiliary agent in the first mixed solution is 0.01mol/L to 4mol/L, specifically 0.01mol/L, 0.05molL, 0.08mol/L, 0.1mol/L, 0.5mol/L, 1mol/L, 1.5mol/L, 1.8mol/L, 2mol/L, 2.5mol/L, 3mol/L, 3.5mol/L or 4mol/L, etc., of course, it can also be other values within the above range, which is not limited here.
  • the first mixed solution further includes an auxiliary agent
  • the auxiliary agent includes an initiator
  • the initiator includes at least one of ammonium persulfate, sodium persulfate, potassium persulfate, aluminum chloride and hydrogen peroxide.
  • the first mixed solution further includes an auxiliary agent, the auxiliary agent includes a catalyst, and the catalyst includes at least one of sodium hydroxide, lithium hydroxide, potassium hydroxide, ammonia water and sodium carbonate.
  • the first mixed solution also includes an auxiliary agent, the auxiliary agent includes a pH adjusting agent, and the pH adjusting agent includes at least one of an acidic pH reagent and an alkaline pH reagent.
  • the acidic pH adjusting agent used can be at least one of hydrochloric acid, sulfuric acid, phosphoric acid, and nitric acid
  • the alkaline pH adjusting agent used can be at least one of lithium hydroxide, sodium hydroxide, potassium hydroxide, sodium carbonate, and sodium bicarbonate. It should be noted that the pH value of the first mixed solution here is adjusted according to the required polymerization reaction environment of different organic molecular monomers.
  • the first mixed solution also includes an auxiliary agent, and the auxiliary agent includes a pH adjuster.
  • the pH of the first mixed solution is 4 to 10, and can be specifically 4, 5, 6, 7, 8, 9 or 10, etc., but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.
  • the polymerization reaction temperature is 40° C. to 100° C.
  • the polymerization reaction temperature can be 40° C., 45° C., 50° C., 55° C., 60° C., 70° C., 80° C., 90° C. or 100° C., etc., which is not limited here.
  • the polymerization reaction time is 3 h to 48 h, specifically 3 h, 5 h, 8 h, 12 h, 15 h, 18 h, 20 h, 24 h, 30 h, 36 h, 40 h, 45 h or 48 h, etc., and of course, it can also be other values within the above range, which is not limited here.
  • the polymerization reaction is carried out under stirring, and the polymer formed by the polymerization of the organic molecular monomers is entangled on the surface of the graphite to form a polymer layer.
  • the present application can promote the full polymerization reaction of organic monomer molecules by controlling the temperature, time and amount of chemical reaction aid added in the polymerization reaction. Under stirring, the polymer formed by polymerization can be more evenly wrapped around the surface of graphite.
  • the polymerization reaction is carried out under stirring, and the stirring rate is 50 r/min to 1000 r/min, specifically 50 r/min, 100 r/min, 200 r/min, 300 r/min, 400 r/min, 500 r/min, 800 r/min or 1000 r/min, etc., and of course, other values within the above range are also possible, which are not limited here. Controlling the stirring rate within the above range is conducive to the polymer generated by the polymerization reaction being more evenly wrapped around the surface of the graphite.
  • the polymerization reaction is carried out under ultraviolet light irradiation. It can be understood that ultraviolet light irradiation can promote the polymerization reaction of organic molecular monomers.
  • the solid-liquid separation comprises at least one of filtration and centrifugation.
  • Step S200 attaching an inorganic salt on the surface of the first precursor to obtain a second precursor.
  • attaching an inorganic salt on the surface of the first precursor to obtain a second precursor includes the following steps: drying a second mixed solution containing the first precursor and the inorganic salt to obtain the second precursor.
  • the inorganic salt includes at least one of lithium hydroxide, sodium hydroxide, potassium hydroxide, magnesium nitrate, calcium chloride, aluminum nitrate, zinc nitrate, titanium n-propoxide, niobium oxalate, zirconium oxychloride, ammonium molybdate, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, sodium metasilicate, sodium borate, ammonium fluoride, titanium oxysulfide, zinc bromide, and zirconium chloride.
  • the mass ratio of the first precursor to the inorganic salt is 1:(0.001-0.1), specifically 1:0.001, 1:0.003, 1:0.005, 1:0.01, 1:0.02, 1:0.05, 1:06, 1:0.09 or 1:0.1, etc., but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.
  • Controlling the mass ratio of the first precursor and the inorganic salt can control the mass ratio of the carbonaceous material and the non-carbonaceous material in the composite layer, thereby reducing the situation where the content of the carbonaceous material in the composite layer is too high, resulting in a large specific surface area of the negative electrode material; it can also reduce the situation where the content of the non-carbonaceous material in the composite layer is too high, resulting in a decrease in the interfacial lithium ion transmission efficiency of the negative electrode material, causing the rate performance of the negative electrode material to deteriorate.
  • the present application can ensure that the negative electrode material has a lower specific surface area, and can also improve the interfacial lithium ion transmission efficiency of the negative electrode material and improve the rate performance of the negative electrode material.
  • the drying method includes at least one of natural volatilization, forced air drying, flash drying, freeze drying, inert atmosphere protection drying and vacuum drying.
  • the drying temperature is 60°C to 600°C, specifically 60°C, 100°C, 200°C, 300°C, 400°C, 500°C or 600°C, etc.
  • it can also be other values within the above range, which is not limited here.
  • the drying time is 0.5h to 48h, specifically 0.5h, 1h, 5h, 10h, 12h, 15h, 18h, 24h, 36h, 45h or 48h, etc.
  • it can also be other values within the above range, which is not limited here.
  • Step S300 carbonizing the second precursor to obtain a negative electrode material.
  • the carbonization treatment is carried out under a protective atmosphere
  • the protective atmosphere includes at least one of nitrogen, helium, neon, argon, and air. It is understandable that the introduction of nitrogen, helium, neon, argon, etc. as a protective atmosphere during the carbonization treatment can effectively inhibit the oxidation reaction of the graphite material, reduce the burning of the graphite material at high temperatures, and ensure the stability and uniformity of the carbonization process.
  • the introduction of air can promote the beneficial phase change transformation of the surface state of the graphite material, can access oxygen-containing functional groups on the surface of the graphite material, improve the electrolyte wettability and interface stability of the composite graphite negative electrode material, and enhance the electrochemical performance of the composite graphite negative electrode material. Therefore, according to different actual application requirements and carbonization treatment conditions, selecting a suitable atmosphere protection method can effectively control the chemical composition and surface state of the graphite material, thereby adjusting its performance and application effect.
  • the heating rate of the carbonization treatment is 1°C/min to 20°C/min, specifically 1°C/min, 2°C/min, 3°C/min, 4°C/min, 5°C/min, 6°C/min, 7°C/min, 8°C/min, 9°C/min, 10°C/min, 12°C/min, 15°C/min, 18°C/min or 20°C/min, etc.
  • it can also be other values within the above range, which is not limited here.
  • the insulation temperature of the carbonization treatment is 600°C to 2500°C, specifically 600°C, 800°C, 900°C, 1000°C, 1200°C, 1500°C, 1800°C, 2000°C, 2200°C, 2300°C or 2500°C, etc.
  • 600°C to 2500°C specifically 600°C, 800°C, 900°C, 1000°C, 1200°C, 1500°C, 1800°C, 2000°C, 2200°C, 2300°C or 2500°C, etc.
  • it can also be other values within the above range, which is not limited here.
  • the insulation time of the carbonization treatment is 0.1h to 10h, specifically 0.1h, 0.5h, 1h, 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h or 10h, etc., and of course, it can also be other values within the above range, which is not limited here.
  • the present application provides a lithium-ion battery, wherein the lithium-ion battery comprises the negative electrode material described in the first aspect or the negative electrode material prepared by the method for preparing the negative electrode material described in the second aspect.
  • the first mixed solution was stirred at 45° C. and the stirring rate was controlled to be 300 r/min. At the same time, 15 ml (concentration of 2 mol/L) of ammonium persulfate aqueous solution was added dropwise thereto. After completion, the mixture was stirred for 120 min to carry out polymerization reaction. The mixture was filtered and dried to obtain a first precursor.
  • the first precursor included a core and polyaniline located on the surface of the core, and the core included natural graphite.
  • the second precursor was heated to 1250° C. and then carbonized for 4 hours to obtain a negative electrode material.
  • the negative electrode material prepared in this embodiment includes a core and a composite layer located on at least a portion of the surface of the core, the composite layer includes hard carbon and lithium oxide (Li 2 O), and the core includes natural graphite.
  • Figure 3a is a scanning electron microscope image of the negative electrode material prepared in Example 1
  • Figure 3b is a scanning electron microscope image of the negative electrode material prepared in Example 1 at another magnification.
  • the surface of the negative electrode material particles prepared in Example 1 contains carbonaceous material-non-carbonaceous material nanoparticles co-composite and is smooth overall.
  • FIG4 is a scanning electron microscope image of a cross section of the negative electrode material prepared in Example 1. As shown in FIG4 , the composite layer thickness of the negative electrode material prepared in Example 1 is about 60 nm.
  • the first mixed solution was stirred at 45° C. and the stirring rate was controlled to be 300 r/min. At the same time, 15 ml (concentration of 2 mol/L) of ammonium persulfate aqueous solution was added dropwise thereto. After completion, the mixture was stirred for 120 min to carry out polymerization reaction. The mixture was filtered and dried to obtain a first precursor.
  • the first precursor included a core and polyaniline located on the surface of the core, and the core included natural graphite.
  • the second precursor was heated to 1250° C. and then carbonized for 4 hours to obtain a negative electrode material.
  • the negative electrode material prepared in this embodiment includes a core and a composite layer located on at least a portion of the surface of the core, the composite layer includes hard carbon and phosphorus pentoxide (P 2 O 5 ), the core includes natural graphite, and the thickness of the composite layer is about 55 nm.
  • the first mixed solution was stirred at 45° C. and the stirring rate was controlled to be 300 r/min. At the same time, 15 ml (concentration of 2 mol/L) of ammonium persulfate aqueous solution was added dropwise thereto. After completion, the mixture was stirred for 120 min to carry out polymerization reaction. The mixture was filtered and dried to obtain a first precursor.
  • the first precursor included a core and polyaniline located on the surface of the core, and the core included natural graphite.
  • the second precursor was heated to 1250° C. and then carbonized for 4 hours to obtain a negative electrode material.
  • the negative electrode material prepared in this embodiment includes a core and a composite layer located on at least a portion of the surface of the core, the composite layer includes hard carbon and carbon fluoride (CF 4 ), the core includes natural graphite, and the thickness of the composite layer is 65 nm.
  • the composite layer includes hard carbon and carbon fluoride (CF 4 )
  • the core includes natural graphite
  • the thickness of the composite layer is 65 nm.
  • the carbon fluoride (CF 4 ) in the composite layer of this embodiment is a fluorine-doped carbon material, that is, the carbon fluoride (CF 4 ) in the composite layer includes carbonaceous materials and non-carbonaceous materials.
  • first mixed solution placing the first mixed solution at 65° C. and stirring for 120 min to perform a polymerization reaction, controlling the stirring rate to 400 r/min, filtering and drying to obtain a first precursor, wherein the first precursor comprises a core and polystyrene located on the surface of the core, and the core comprises natural graphite.
  • the second precursor was heated to 1250° C. and then carbonized for 4 hours to obtain a negative electrode material.
  • the negative electrode material prepared in this embodiment includes a core and a composite layer located on at least a portion of the surface of the core, the composite layer includes hard carbon and lithium oxide (Li 2 O), the core includes natural graphite, and the thickness of the composite layer is 55 nm.
  • first mixed solution placing at 65° C. and stirring for 120 min to perform a polymerization reaction, controlling the stirring rate to 500 r/min, filtering and drying to obtain a first precursor, wherein the first precursor comprises a core and polyfluorostyrene located on the surface of the core, and the core comprises natural graphite.
  • the second precursor was heated to 1250° C. and then carbonized for 4 hours to obtain a negative electrode material.
  • the negative electrode material prepared in this embodiment includes a core and a composite layer located on at least a portion of the surface of the core, the composite layer includes hard carbon, lithium fluoride (LiF) and lithium oxide (Li 2 O), the core includes natural graphite, and the thickness of the composite layer is 55 nm.
  • first precursor comprises a core and polyfluorostyrene located on the surface of the core, and the core comprises natural graphite.
  • the second precursor was heated to 1250° C. and then carbonized for 4 hours to obtain a negative electrode material.
  • the negative electrode material prepared in this embodiment includes a core and a composite layer located on at least a portion of the surface of the core, the composite layer includes soft carbon and lithium oxide (Li 2 O), the core includes graphite, and the thickness of the composite layer is 60 nm.
  • the first mixed solution is stirred at 40° C. and the stirring rate is controlled to be 300 r/min. At the same time, 15 ml (concentration of 4 mol/L) of ammonia water is added dropwise thereto as a polymerization catalyst. After the polymerization reaction is completed, stirring is continued for 120 min. The polymerization reaction is filtered and dried to obtain a first precursor.
  • the first precursor includes a core and polydopamine located on the surface of the core, and the core includes natural graphite.
  • the second precursor was heated to 1250° C. and then carbonized for 4 hours to obtain a negative electrode material.
  • the negative electrode material prepared in this embodiment includes a core and a composite layer located on at least a portion of the surface of the core, the composite layer includes hard carbon and lithium oxide (Li 2 O), the core includes artificial graphite, and the thickness of the composite layer is 50 nm.
  • Example 2 Different from Example 1, (3) 100 g of the first precursor was mixed evenly with 200 ml of deionized water, and then 24.5 g of Al(NO 3 ) 3 ⁇ 9H 2 O was added and stirred evenly to form a second mixed solution, and the second mixed solution was stirred at 90° C. to evaporate the solvent and then dried to obtain a second precursor.
  • the negative electrode material prepared in this embodiment includes a core and a composite layer located on at least a portion of the surface of the core, the composite layer includes hard carbon and aluminum oxide (Al 2 O 3 ), the core includes graphite, and the thickness of the composite layer is 100 nm.
  • Example 1 The difference from Example 1 is that natural graphite is replaced by artificial graphite with the same particle size distribution, and the other process parameters are exactly the same as those in Example 1.
  • the negative electrode material prepared in this embodiment includes a core and a composite layer located on at least a portion of the surface of the core, the composite layer includes hard carbon and lithium oxide (Li 2 O), the core includes artificial graphite, and the thickness of the composite layer is 70 nm.
  • the second precursor is heated to 2000° C. and then carbonized for 4 hours to obtain a negative electrode material.
  • the negative electrode material prepared in this embodiment includes a core and a composite layer located on at least a portion of the surface of the core, the composite layer includes hard carbon and lithium oxide (Li 2 O), the core includes natural graphite, and the thickness of the composite layer is 150 nm.
  • the second precursor is heated to 1600° C. and then carbonized for 4 hours to obtain a negative electrode material.
  • the negative electrode material prepared in this embodiment includes a core and a composite layer located on at least a portion of the surface of the core, the composite layer includes hard carbon and lithium oxide (Li 2 O), the core includes natural graphite, and the thickness of the composite layer is 120 ⁇ m.
  • Example 1 The difference from Example 1 is that (1) 100 g of natural graphite is dispersed in 200 ml of deionized water, 5 g of aniline monomer is added and stirred to form a first mixed solution, and phosphoric acid solution is added to adjust the pH of the first mixed solution to 4.5.
  • the negative electrode material prepared in this embodiment includes a core and a composite layer located on at least a portion of the surface of the core, the composite layer includes hard carbon and lithium oxide (Li 2 O), and the core includes natural graphite.
  • Example 1 The difference from Example 1 is that (1) 100 g of natural graphite is dispersed in 200 ml of deionized water, 5 g of aniline monomer is added and stirred to form a first mixed solution, and sodium hydroxide solution is added to adjust the pH of the first mixed solution to 8.5.
  • the negative electrode material prepared in this embodiment includes a core and a composite layer located on at least a portion of the surface of the core, the composite layer includes hard carbon and lithium oxide (Li 2 O), and the core includes natural graphite.
  • the precursor was heated to 1250°C and then carbonized for 4 hours to obtain a negative electrode material.
  • the negative electrode material prepared in this comparative example includes a core and a carbon coating layer located on at least a portion of the surface of the core, and the core includes natural graphite.
  • the precursor was heated to 1250°C and then carbonized for 4 hours to obtain a negative electrode material.
  • the negative electrode material prepared in this comparative example includes a core and a lithium oxide coating layer located on at least a portion of the surface of the core, and the core includes graphite.
  • the precursor was heated to 1250°C and then carbonized for 4 hours to obtain a negative electrode material.
  • the negative electrode material prepared in this comparative example includes a core and a carbon coating layer located on at least a portion of the surface of the core, and the core includes artificial graphite.
  • the particle size distribution range of the negative electrode material was tested by Malvern laser particle size analyzer.
  • the monolayer adsorption amount of the sample is obtained based on the Brownauer-Etter-Taylor adsorption theory and its formula (BET formula), thereby calculating the specific surface area of the material.
  • the microstructure of the surface of the negative electrode material was observed using a S-4800 scanning electron microscope.
  • the microscopic morphology of the surface of the negative electrode material and the particle size of the non-carbonaceous material were observed using an S-4800 scanning electron microscope.
  • a 1 ⁇ m*1 ⁇ m area was randomly selected on a single negative electrode material particle, the particle size distribution of the non-carbonaceous material in the area was statistically analyzed, and the average particle size of the non-carbonaceous material was calculated as G.
  • the graphite particles were cut open using a focused ion beam to obtain a cross section, and the S-4800 scanning electron microscope was used to observe the microscopic morphology of the cross section of the negative electrode material and the thickness of the composite layer.
  • the powder resistivity test system was used to test the powder conductivity of the negative electrode material.
  • the negative electrode materials prepared in Examples 1 to 13 and Comparative Examples 1 to 3 were dissolved in deionized water according to a mass ratio of 96.5:1.5:1 for the negative electrode material, carboxymethyl cellulose and styrene-butadiene rubber, respectively, and the solid content was controlled to be 50%.
  • the negative electrode was coated on a copper foil current collector, and vacuum dried to obtain a negative electrode plate.
  • a metal lithium sheet was used as a counter electrode and assembled into a button cell in an argon-filled glove box.
  • the charge and discharge test was carried out in a charge and discharge range of 0.01-1.5V. Cyclic charge and discharge were performed to obtain the first reversible specific capacity, the first cycle charge capacity and the first cycle discharge capacity.
  • the first coulomb efficiency the first cycle discharge capacity/the first cycle charge capacity. Cyclic charge and discharge at different rates to obtain the rate performance.
  • a first precursor is obtained by subjecting a first mixed solution containing a graphite material and an organic molecule monomer to a polymerization reaction.
  • the polymer formed by the polymerization of the organic molecule monomer is composited on the surface of the graphite particles to form a polymer layer.
  • the polymer has a highly reactive functional group.
  • a second mixed solution containing the first precursor and an inorganic salt is fully mixed and then dried. During the drying process, the inorganic salt in the second mixed solution is hydrolyzed to form inorganic ions.
  • the inorganic ions are grafted and introduced into the polymer layer on the surface of the graphite particles by utilizing the grafting reaction between the highly reactive functional groups in the polymer and the inorganic ions to obtain a second precursor. Finally, the second precursor is carbonized. After the carbonization treatment, the organic molecules in the polymer layer are in situ cracked into carbonaceous materials, and the inorganic ions are in situ converted into non-carbonaceous materials, forming a composite layer containing carbonaceous materials and non-carbonaceous materials on the surface of the graphite particles.
  • the surface of the prepared negative electrode material has a uniformly coated composite layer.
  • the specific surface value of the negative electrode material can be reduced, and the high-temperature storage performance and electrode sheet processing performance of the negative electrode material can be improved; it can also improve the interface stability of the negative electrode material, reduce interface side reactions, enhance electrolyte wettability, improve lithium ion transmission efficiency, increase the reversible capacity and initial efficiency of the negative electrode material, and improve the rate performance of the negative electrode material.
  • the negative electrode material of Comparative Example 1 directly carbonizes the first precursor during the preparation process, and the coating layer in the prepared negative electrode material is a single carbon coating layer, which is easy to undergo irreversible reaction with the electrolyte components at low potential, resulting in continuous repair and generation of the SEI film, reduced surface and interfacial stability of the negative electrode material, intensified side reactions with the electrolyte, reduced lithium ion transmission efficiency, reduced powder conductivity of the negative electrode material, and reduced reversible capacity, initial efficiency, and rate performance of the material.
  • Example 2 Compared with Example 1, during the preparation process of the negative electrode material of Comparative Example 2, the natural graphite material and the non-carbonaceous material are directly compounded.
  • the coating layer in the prepared negative electrode material is a single non-carbonaceous material coating layer.
  • the negative electrode material has a larger specific surface area, and the contact between the material and the electrolyte is increased. The interfacial side reaction is intensified, the surface stability of the material is reduced, and the lithium ion transmission efficiency is reduced, resulting in a decrease in the powder conductivity of the negative electrode material, a decrease in its reversible capacity and rate performance, and a significant decrease in the first efficiency.
  • Example 9 and Comparative Example 3 use artificial graphite as raw material.
  • the negative electrode of Comparative Example 3 is During the preparation of the material, the first precursor is directly carbonized, and the coating layer in the prepared negative electrode material is a single carbon coating layer.
  • the surface stability of the negative electrode material is low, and the side reaction with the electrolyte is more intense at low potential. Its performance indicators such as the first coulombic efficiency, powder conductivity and rate performance have all deteriorated to varying degrees.
  • the present application uses the above-mentioned embodiments to illustrate the detailed process equipment and process flow of the present application, but the present application is not limited to the above-mentioned detailed process equipment and process flow, that is, it does not mean that the present application must rely on the above-mentioned detailed process equipment and process flow to be implemented.
  • the technicians in the relevant technical field should understand that any improvement to the present application, the equivalent replacement of the raw materials of the present application product, the addition of auxiliary components, the selection of specific methods, etc., all fall within the scope of protection and disclosure of the present application.

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Abstract

一种负极材料及其制备方法、锂离子电池，负极材料包括内核及位于内核至少部分表面的复合层，内核包括石墨，复合层包括碳质材料和非碳质材料。负极材料通过复合层中碳质材料与非碳质材料的协同作用，能够降低负极材料的比表值，增强负极材料的界面稳定性，改善电解液浸润性，减少界面副反应，提升锂离子传输效率，进而提升负极材料的电化学性能。

Description

负极材料及其制备方法、锂离子电池
本申请要求于2023年9月27日提交国家知识产权局，申请号为202311279012.8、发明名称为“负极材料及其制备方法、锂离子电池”的中国专利申请的优先权，其全部内容通过引用结合在本申请中。
技术领域
本申请涉及负极材料技术领域，具体地讲，尤其涉及负极材料及其制备方法、锂离子电池。
背景技术
锂离子电池凭借较高的能量密度、循环寿命长、环境污染小和无记忆效应等优点，已在可携带电子设备、电动汽车、无人机等领域取得了广泛的应用。近年来，随着锂离子电池应用场景的进一步丰富，对其性能的需求也日益升高。锂离子电池的性能指标与电极材料密切相关，因此非常有必要进一步提升锂离子电池负极材料的性能。石墨材料已在锂离子电池负极材料领域取得广泛的商业应用，但传统石墨材料依然存在如与电解液相容性差、固体电解质界面膜(SEI)不稳定等缺点，造成材料初始库仑效率偏低、动力学传输变差和循环容量持续衰减。研究发现，通过使用各种改性剂对石墨进行表面包覆复合可以提升石墨材料的电化学性能。
目前，包覆层主要分为碳质材料和非碳质材料两类。碳质材料包覆往往采用沥青或树脂为包覆前驱体，通过固相或液相混合并高温碳化处理，前驱体转化为软炭或硬碳材料复合在石墨颗粒上，能够实现石墨材料比表值降低、电解液相容性改善。但沥青或树脂碳化后的产物本质仍为碳材料，低电位下依然会与电解质组分发生不可逆反应，导致石墨材料界面层不断分解并修复重组，造成电池容量持续衰减。
因此，如何增强负极材料的界面稳定性，减少界面副反应，是目前仍需解决的技术问题之一。
申请内容
本申请的目的在于提供负极材料及其制备方法、锂离子电池，本申请的负极材料通过复合层中碳质材料与非碳质材料的协同作用，能够降低负极材料的比表值，增强负极材料的界面稳定性，改善电解液浸润性，减少界面副反应，提升锂离子传输效率，进而提升负极材料的电化学性能。
第一方面，本申请提供一种负极材料，所述负极材料包括内核及位于所述内核至少部分表面的复合层，所述内核包括石墨，所述复合层包括碳质材料和非碳质材料。
在一些实施方式中，所述非碳质材料分散于所述碳质材料中。
在一些实施方式中，所述非碳质材料的化学通式为AxBy，其中，1≤x≤3，1≤y≤5，A元素包括Li、Na、K、Ca、Mg、Al、Zn、Ti、Nb、Zr、Mo、P、Si和B中的至少一种，B元素包括B、O、F、Si、P、S、Br和Cl中的至少一种。
在一些实施方式中，所述石墨包括天然石墨、人造石墨和微晶石墨中的至少一 种。
在一些实施方式中，所述内核的中值粒径为D50，0.5μm≤D50≤30μm。
在一些实施方式中，所述石墨中碳元素的质量含量≥80％。
在一些实施方式中，所述碳质材料包括无定形碳和石墨碳中的至少一种。
在一些实施方式中，所述复合层的厚度为1nm～200nm。
在一些实施方式中，所述非碳质材料包括LiF、NaF、MgF2、MgO、P2O5、Al2O3、SiO2、B2O3中的至少一种。
在一些实施方式中，所述非碳质材料的平均粒径为G，且G≤150nm。
在一些实施方式中，所述复合层与所述内核的质量比为C，且0.01≤C≤0.5。
在一些实施方式中，所述碳质材料与所述非碳质材料的质量比为D，且0.1≤D≤80。
在一些实施方式中，所述内核的粉末电导率为E1，所述负极材料的粉末电导率为E2，E2与E1的比值为E，且1＜E＜1000。
在一些实施方式中，所述内核的比表面积为6m2/g～15m2/g。
在一些实施方式中，所述负极材料的比表面积为1m2/g～5m2/g。
第二方面，本申请提供一种负极材料的制备方法，包括以下步骤：
制备第一前驱体，所述第一前驱体包括内核和在所述内核表面形成的聚合物层，其中，所述内核包括石墨；
在所述第一前驱体表面附着无机盐得到第二前驱体；及
将所述第二前驱体进行碳化处理，得到负极材料。
在一些实施方式中，所述制备第一前驱体包括以下步骤：将含有石墨和有机分子单体的第一混合溶液进行聚合反应，固液分离并干燥，得到所述第一前驱体。
在一些实施方式中，所述在所述第一前驱体表面附着无机盐得到第二前驱体包括以下步骤：将含有所述第一前驱体和无机盐的第二混合溶液进行干燥，得到第二前驱体。
在一些实施方式中，所述石墨包括天然石墨、人造石墨和微晶石墨中的至少一种。
在一些实施方式中，所述石墨的中值粒径为0.5μm～30μm。
在一些实施方式中，所述石墨和所述有机分子单体的质量比为1：(0.01～0.4)。
在一些实施方式中，所述有机分子单体包括苯胺、苯乙烯、氟苯乙烯、丙烯酸羟乙酯、丙烯酸酯、吡咯、偏氟乙烯、四氟乙烯和多巴胺中的至少一种。
在一些实施方式中，所述第一混合溶液和所述第二混合溶液均包括溶剂，所述溶剂包括水、甲醇、乙醇、丙酮、氮甲基吡咯烷酮和N，N二甲基甲酰胺中的至少一种。
在一些实施方式中，所述第一混合溶液中还包括助剂。
在一些实施方式中，所述第一混合溶液中还包括助剂，所述助剂在所述第一混合溶液中的质量浓度为0.01mol/L～4mol/L。
在一些实施方式中，所述第一混合溶液中还包括助剂，所述助剂包括引发剂，所述引发剂包括过硫酸铵、过硫酸钠、过硫酸钾、氯化铝及过氧化氢中的至少一种。
在一些实施方式中，所述第一混合溶液中还包括助剂，所述助剂包括催化剂，所述催化剂包括氢氧化钠、氢氧化锂、氢氧化钾、氨水及碳酸钠中的至少一种。
在一些实施方式中，所述第一混合溶液中还包括助剂，所述助剂包括pH调节剂，所述pH调节剂包括酸性pH试剂和碱性pH试剂中的至少一种。
在一些实施方式中，所述第一混合溶液中还包括助剂，所述助剂包括pH调节剂，所述第一混合溶液的pH为4～10。
在一些实施方式中，所述第一混合溶液中还包括助剂，所述助剂包括pH调节剂，所述pH调节剂包括盐酸、硫酸、磷酸和硝酸中的至少一种。
在一些实施方式中，所述第一混合溶液中还包括助剂，所述助剂包括pH调节剂，所述pH调节剂包括氢氧化锂、氢氧化钠、氢氧化钾、碳酸钠和碳酸氢钠中的至少一种。
在一些实施方式中，所述聚合反应的温度为40℃～100℃。
在一些实施方式中，所述聚合反应的时间为3h～48h。
在一些实施方式中，所述聚合反应在搅拌下进行。
在一些实施方式中，所述聚合反应在搅拌状态下进行，搅拌速率为50r/min～1000r/min。
在一些实施方式中，所述固液分离包括过滤、离心中的至少一种。
在一些实施方式中，所述干燥包括自然挥发、鼓风干燥、闪蒸干燥、冷冻干燥、惰性气氛保护干燥、真空干燥中的至少一种。
在一些实施方式中，所述无机盐包括氢氧化锂、氢氧化钠、氢氧化钾、硝酸镁、氯化钙、硝酸铝、硝酸锌、正丙醇钛、草酸铌、氯氧化锆、钼酸铵、磷酸二氢铵、磷酸氢二铵、偏硅酸钠、硼酸钠、氟化铵、氧硫化钛、溴化锌及氯化锆中的至少一种。
在一些实施方式中，所述第一前驱体与所述无机盐的质量比为1：(0.001～0.1)。
在一些实施方式中，所述干燥包括自然挥发、鼓风干燥、闪蒸干燥、冷冻干燥、惰性气氛保护干燥及真空干燥中的至少一种。
在一些实施方式中，在一些实施方式中，所述干燥的温度为60℃～600℃。
在一些实施方式中，所述干燥的时间为0.5h～48h。
在一些实施方式中，所述碳化处理在保护性气氛下进行。
在一些实施方式中，所述碳化处理在保护性气氛下进行，所述保护性气氛包括氮气、氦气、氖气、氩气、空气中的至少一种。
在一些实施方式中，所述碳化处理的升温速率为1℃/min～20℃/min。
在一些实施方式中，所述碳化处理的保温温度为600℃～2500℃。
在一些实施方式中，所述碳化处理的保温时间0.1h～10h。
第三方面，本申请提供一种锂离子电池，所述锂离子电池包括第一方面所述的负极材料或第二方面所述的负极材料的制备方法制备得到的负极材料。
与现有技术相比，本申请的技术方案至少具有以下有益效果：
本申请提供的负极材料中，负极材料包括内核及位于内核至少部分表面的复合层，内核包括石墨，复合层包括碳质材料和非碳质材料，通过复合层中碳质材料与非碳质材料的协同作用，能够降低负极材料的比表面积，改善负极材料的高温存储性能和极片加工性能；还可以提高负极材料的界面稳定性，减少界面副反应，增强电解液 浸润性，改善锂离子传输效率，提升负极材料的可逆容量、首次效率和倍率性能。
本申请提供的负极材料的制备方法中，通过将含有石墨材料和有机分子单体的第一混合溶液进行聚合反应得到第一前驱体，使得有机分子单体聚合形成的聚合物复合在石墨颗粒表面形成聚合物层，聚合物中具有高反应活性官能团，再将含有第一前驱体和无机盐的第二混合溶液充分混合后进行干燥，第二混合溶液中的无机盐水解形成无机离子，利用聚合物中的高反应活性官能团与无机离子之间的嫁接反应，将无机离子嫁接引入到石墨颗粒表面的聚合物层中，得到第二前驱体，最后将第二前驱体进行碳化处理，经过碳化处理，聚合物层中的有机分子原位裂解为碳质材料，同时无机离子原位转化为非碳质材料，在石墨颗粒表面形成包含碳质材料和非碳质材料的复合层。制备得到的负极材料表面具有均匀包覆的复合层，通过复合层中碳质材料和非碳质材料的协同作用，能够降低负极材料的比表面积，改善负极材料的高温存储性能和极片加工性能；还可以提高负极材料的界面稳定性，减少界面副反应，增强电解液浸润性，改善锂离子传输效率，提升负极材料的可逆容量、首次效率和倍率性能。
附图说明
下面结合附图和实施例对本申请进一步说明。
图1为本申请实施例提供的负极材料的制备工艺流程图；
图2为本申请实施例提供的负极材料的结构示意图；
图3a为本申请实施例1制备的负极材料的扫描电镜图；
图3b为本申请实施例1制备的负极材料在另一放大倍数下的扫描电镜图；
图4为本申请实施例1制备的负极材料的切面扫描电镜图。
具体实施方式
为了更好的理解本申请的技术方案，下面结合附图对本申请实施例进行详细描述。
应当明确，所描述的实施例仅仅是本申请一部分实施例，而不是全部的实施例。基于本申请中的实施例，本领域普通技术人员在没有作出创造性劳动前提下所获得的所有其它实施例，都属于本申请保护的范围。
在本申请实施例中使用的术语是仅仅出于描述特定实施例的目的，而非旨在限制本申请。在本申请实施例和所附权利要求书中所使用的单数形式的“一种”、“所述”和“该”也旨在包括多数形式，除非上下文清楚地表示其它含义。
应当理解，本文中使用的术语“和/或”仅仅是一种描述关联对象的关联关系，表示可以存在三种关系，例如，A和/或B，可以表示：单独存在A，同时存在A和B，单独存在B这三种情况。另外，本文中字符“/”，一般表示前后关联对象是一种“或”的关系。
第一方面，本申请提供一种负极材料，如图2所示，所述负极材料包括内核及位于所述内核至少部分表面的复合层，所述内核包括石墨，所述复合层包括碳质材料和非碳质材料。
本申请提供的负极材料中，负极材料包括内核及位于内核至少部分表面的复合 层，内核包括石墨，复合层包括碳质材料和非碳质材料，通过复合层中碳质材料与非碳质材料的协同作用，能够降低负极材料的比表面积，改善负极材料的高温存储性能和极片加工性能；还可以提高负极材料的界面稳定性，减少界面副反应，增强电解液浸润性，改善锂离子传输效率，提升负极材料的可逆容量、首次效率和倍率性能。
在一些实施方式中，所述石墨包括天然石墨、人造石墨和微晶石墨中的至少一种。
在一些实施方式中，所述内核的中值粒径为D50，0.5μm≤D50≤30μm，具体可以是0.5μm、1μm、3.5μm、5μm、8μm、10μm、12μm、15μm、18μm、19.7μm、21.3μm、24.5μm、26.1μm、28.4μm、29μm或30μm等，当然也还可以是上述范围内其他数值，在此不做限定。
在一些实施方式中，所述石墨中碳元素的质量含量≥80％，具体可以是80％、85％、86％、87％、88％、89％、90％、91％、92％、93％、94％、95％、96％、98％或99％等，当然也还可以是上述范围内其他数值，在此不做限定。
在一些实施方式中，所述碳质材料包括无定形碳和石墨碳中的至少一种。具体地，所述无定形碳包括软碳和硬碳。在一些实施方式中，所述复合层的厚度为1nm～200nm。具体地，复合层的厚度可以是1nm、2nm、5nm、10nm、15nm、30nm、50nm、80nm、100nm、110nm、150nm、180nm或200nm等，在此不做限定。复合层较薄时，碳质材料和非碳质材料难以在石墨材料表面形成均匀包裹的效果，导致负极材料比表面积偏高。复合层太厚时，负极材料的界面锂离子传输效率降低，导致负极材料的倍率性能恶化。因此优化控制复合层厚度在1nm～200nm范围内，能够降低负极材料的比表面积，改善负极材料的高温存储性能和极片加工性能，同时还能提升负极材料的界面锂离子传输效率，提升负极材料的首次效率和倍率性能。
在一些实施方式中，所述非碳质材料的化学通式为AxBy，其中，1≤x≤3，1≤y≤5，A元素包括Li、Na、K、Ca、Mg、Al、Zn、Ti、Nb、Zr、Mo、P、Si和B中的至少一种，B元素包括B、O、F、Si、P、S、Br和Cl中的至少一种。
在一些实施方式中，A元素包括Li、Na、Mg、Al、P、Si和B中的至少一种；B元素为O或F。
在一些实施方式中，所述非碳质材料为LiF、NaF、MgF2、MgO、P2O5、Al2O3、SiO2、B2O3中的至少一种。
在一些实施方式中，非碳质材料分散在碳质材料中。可以理解地，由于碳质材料由有机物碳化形成，在有机物碳化之前，非碳质材料可以以离子形态附着在有机物的表面或内部，实现均匀复合，形成交联穿插分布的非碳质材料与碳质材料构成的复合层。
在一些实施方式中，所述非碳质材料的平均粒径为G，且G≤150nm，具体可以是0.5nm、1nm、1.5nm、3.6nm、4.8nm、7nm、8.9nm、10nm、11.2nm、15nm、20nm、30nm、50nm、80nm、100nm、120nm、140nm或150nm等，但并仅限于所列举的数值，该数值范围内其他未列举的数值同样适用。当复合层中非碳质材料平均粒径过大时，非碳质材料难以在碳质材料中均匀分布，导致负极材料的比表高和界面锂离子传输性能变差。
本申请中，使用S-4800扫描电子显微镜观察负极材料表面的微观形貌和非碳质材料的粒径，在单个负极材料颗粒上随机取1μm*1μm区域，统计区域内非碳质材料的粒径分布，并计算非碳质材料的平均粒径为G。
在一些实施方式中，所述复合层与所述内核的质量比为C，且0.01≤C≤0.5。C的值具体可以是0.01、0.03、0.07、0.09、0.1、0.17、0.25、0.3、0.35、0.4、0.42、0.48或0.5等，在此不做限定。当C值偏低时，负极材料中复合层含量较少，难以在内核表面形成完整均匀的包覆层，导致负极材料的比表面积偏大。当C值偏高时，负极材料中复合层含量较多，内核表面形成的包覆层较厚，导致负极材料动力学性能较差，容量较低。
在一些实施方式中，所述碳质材料与所述非碳质材料的质量比为D，且0.1≤D≤80，具体可以是0.1、0.5、0.8、1、5、10、18、24、30、35、40、50、62、74、或80等，当然也还可以是上述范围内其他值，在此不做限定。当D值偏低时，复合层中非碳质材料的含量较高，导致负极材料的比表面积偏大。当D值偏高时，复合层中碳质材料的含量较高，导致负极材料的界面锂离子传输效率降低，负极材料的倍率性能恶化。
在一些实施方式中，所述石墨的粉末电导率为E1，所述负极材料的粉末电导率为E2，E2与E1的比值为E，且1＜E＜1000。E的值具体可以是1.01、5、10、50、100、150、200、300、400、500、600、700、800、900或1000等，在此不做限定。需要说明的是，石墨即为未包覆的石墨原料的粉末电导率，负极材料的粉末电导率是指石墨包覆复合层后的电导率。E的值可以表示负极材料的电导率，E的值过小，负极材料的电导率难以得到提升。
在一些实施方式中，所述内核的比表面积为6m2/g～15m2/g，具体可以是6m2/g、6.8m2/g、7.9m2/g、8.7m2/g、9.5m2/g、10m2/g、11.3m2/g、12.4m2/g、13.5m2/g、14m2/g或15m2/g等，当然也还可以是上述范围内其他值，在此不做限定。
在一些实施方式中，所述负极材料的比表面积为1m2/g～5m2/g，具体可以是1m2/g、1.5m2/g、2.3m2/g、2.8m2/g、3m2/g、3.5m2/g、4m2/g、4.8m2/g或5m2/g等，当然也还可以是上述范围内其他值，在此不做限定。
本申请中，负极材料包括内核及位于内核至少部分表面的复合层，复合层完整均匀地包覆在内核表面，可以降低负极材料的比表面积，将负极材料的比表面积控制在1m2/g～5m2/g范围内，有利于提升负极材料的高温存储性能与极片加工性能，进而有利于提高由该负极材料制成的锂离子电池的循环性能。
第二方面，本申请提供一种负极材料的制备方法，如图1所示，包括以下步骤：
步骤S100，制备第一前驱体，所述第一前驱体包括内核和在所述内核表面形成的聚合物层，其中，所述内核包括石墨；
步骤S200，在所述第一前驱体表面附着无机盐得到第二前驱体；
步骤S300，将所述第二前驱体进行碳化处理，得到负极材料。
本申请提供的负极材料的制备方法中，通过将含有石墨材料和有机分子单体的第一混合溶液进行聚合反应得到第一前驱体，使得有机分子单体聚合形成的聚合物复合在石墨颗粒表面形成聚合物层，聚合物层中具有高反应活性官能团，再将含有第 一前驱体和无机盐的第二混合溶液充分混合后进行干燥，第二混合溶液中的无机盐水解形成无机离子，利用聚合物中的高反应活性官能团与无机离子之间的嫁接反应，将无机离子嫁接引入到石墨颗粒表面的聚合物层中，得到第二前驱体，最后将第二前驱体进行碳化处理，经过碳化处理，聚合物层中的有机分子原位裂解为碳质材料，同时无机离子原位转化为非碳质材料，在石墨颗粒表面形成包含碳质材料和非碳质材料的复合层。制备得到的负极材料表面具有均匀包覆的复合层，通过复合层中碳质材料和非碳质材料的协同作用，能够降低负极材料的比表面积，改善负极材料的高温存储性能和极片加工性能；还可以提高负极材料的界面稳定性，减少界面副反应，增强电解液浸润性，改善锂离子传输效率，提升负极材料的可逆容量、首次效率，和倍率性能。
步骤S100，制备第一前驱体，所述第一前驱体包括内核和在所述内核表面形成的聚合物层，其中，所述内核包括石墨。
在一些实施方式中，制备第一前驱体包括以下步骤：将含有石墨材料和有机分子单体的第一混合溶液进行聚合反应，固液分离并干燥，得到第一前驱体，其中，所述第一前驱体包括内核及位于所述内核表面的聚合物层，所述内核包括石墨。
在一些实施方式中，所述石墨材料包括天然石墨、人造石墨和微晶石墨中的至少一种。
在一些实施方式中，所述石墨的中值粒径为0.5μm～30μm。具体可以是0.5μm、1μm、3.5μm、5μm、8μm、10μm、12μm、15μm、18μm、19.7μm、21.3μm、24.5μm、26.1μm、28.4μm、29μm或30μm等，当然也还可以是上述范围内其他数值，在此不做限定。
在一些实施方式中，所述石墨材料和所述有机分子单体的质量比为1：(0.01～0.4)。具体可以是1：0.01、1：0.05、1：0.1、1：0.15、1：0.2、1：0.25、1：0.3、1：0.35或1：0.4等，但并不仅限于所列举的数值，该数值范围内其他未列举的数值同样适用。控制石墨材料和有机分子单体的质量比可以减少聚合物包覆层太厚，影响容量的情况；也可以减少聚合物太少，则无法形成完整的聚合物包覆层，进而影响复合层的包覆完整均匀性，不利于负极材料比表面积的下降的情况。本申请通过控制石墨材料与有机分子单体的质量比，可以保障石墨颗粒表面形成均匀的聚合物包覆层，进而提高石墨颗粒与复合层的包覆均匀性。
在一些实施方式中，所述有机分子单体包括苯胺、苯乙烯、氟苯乙烯、丙烯酸羟乙酯、丙烯酸酯、吡咯、偏氟乙烯、四氟乙烯和多巴胺至少一种。
在一些实施方式中，所述第一混合溶液和所述第二混合溶液均包括溶剂，所述溶剂包括水、甲醇、乙醇、丙酮、氮甲基吡咯烷酮和N，N二甲基甲酰胺中的至少一种。
在一些实施方式中，所述第一混合溶液中还包括助剂。可以理解地，化学反应助剂的加入，可以促进有机分子单体的聚合反应的进行。
在一些实施方式中，所述第一混合溶液中还包括助剂，所述助剂在所述第一混合溶液中的质量浓度为0.01mol/L～4mol/L，具体可以是0.01mol/L、0.05molL、0.08mol/L、0.1mol/L、0.5mol/L、1mol/L、1.5mol/L、1.8mol/L、2mol/L、2.5mol/L、3mol/L、3.5mol/L或4mol/L等，当然也还可以是上述范围内其他值，在此不做限定。
在一些实施方式中，所述第一混合溶液中还包括助剂，所述助剂包括引发剂，所述引发剂包括过硫酸铵、过硫酸钠、过硫酸钾、氯化铝及过氧化氢中的至少一种。
在一些实施方式中，所述第一混合溶液中还包括助剂，所述助剂包括催化剂，所述催化剂包括氢氧化钠、氢氧化锂、氢氧化钾、氨水及碳酸钠中的至少一种。
在一些实施方式中，所述第一混合溶液中还包括助剂，所述助剂包括pH调节剂，所述pH调节剂包括酸性pH试剂和碱性pH试剂中的至少一种。具体地，使用的酸性pH调节剂可以为盐酸、硫酸、磷酸、硝酸中的至少一种，使用的碱性pH调节剂可以为氢氧化锂、氢氧化钠、氢氧化钾、碳酸钠、碳酸氢钠中的至少一种。需要说明的是，这里的第一混合溶液的pH值根据不同的有机分子单体的所需要的聚合反应环境来进行调节。
在一些实施方式中，所述第一混合溶液中还包括助剂，所述助剂包括pH调节剂，所述第一混合溶液的pH为4～10，具体可以是4、5、6、7、8、9或10等，但并不仅限于所列举的数值，该数值范围内其他未列举的数值同样适用。
在一些实施方式中，所述聚合反应的温度为40℃～100℃。聚合反应的温度具体可以是40℃、45℃、50℃、55℃、60℃、70℃、80℃、90℃或100℃等，在此不做限定。
在一些实施方式中，所述聚合反应的时间为3h～48h，具体可以是3h、5h、8h、12h、15h、18h、20h、24h、30h、36h、40h、45h或48h等，当然也还可以是上述范围内其他值，在此不做限定。
在一些实施方式中，所述聚合反应在搅拌下进行，有机分子单体聚合形成的聚合物缠绕在所述石墨的表面形成聚合物层。
本申请通过控制聚合反应的温度、时间及化学反应助剂的加入量等，能够促进有机单体分子进行充分的聚合反应，在搅拌状态下，聚合形成的聚合物能够更加均匀地缠绕在石墨的表面。
在一些实施方式中，所述聚合反应在搅拌状态下进行，搅拌速率为50r/min～1000r/min，具体可以是50r/min、100r/min、200r/min、300r/min、400r/min、500r/min、800r/min或1000r/min等，当然也还可以是上述范围内其他值，在此不做限定。控制搅拌速率在上述范围内，有利于聚合反应生成的聚合物更加均匀地缠绕在石墨的表面。
在一些实施方式中，所述聚合反应在紫外光照射下进行。可以理解地，紫外光照射下，可以促进有机分子单体的聚合反应的进行。
在一些实施方式中，所述固液分离包括过滤、离心中的至少一种。
步骤S200，在所述第一前驱体表面附着无机盐得到第二前驱体。
在一些实施方式中，在所述第一前驱体表面附着无机盐得到第二前驱体包括以下步骤：将含有所述第一前驱体和无机盐的第二混合溶液进行干燥，得到第二前驱体。
在一些实施方式中，所述无机盐包括氢氧化锂、氢氧化钠、氢氧化钾、硝酸镁、氯化钙、硝酸铝、硝酸锌、正丙醇钛、草酸铌、氯氧化锆、钼酸铵、磷酸二氢铵、磷酸氢二铵、偏硅酸钠、硼酸钠、氟化铵、氧硫化钛、溴化锌、氯化锆中的至少一种。
在一些实施方式中，所述第一前驱体与所述无机盐的质量比为1：(0.001～0.1)，具体可以是是1：0.001、1：0.003、1：0.005、1：0.01、1：0.02、1：0.05、1：06、1：0.09或1：0.1等，但并不仅限于所列举的数值，该数值范围内其他未列举的数值同样适用。控制第一前驱体和无机盐的质量比可以控制复合层中碳质材料和非碳质材料的质量比，进而可以减少复合层碳质材料的含量过高，导致负极材料的比表面积偏大的情况；也可以减少复合层中非碳质材料的含量过高，导致负极材料的界面锂离子传输效率降低，引起负极材料倍率性能的恶化的情况。本申请通过控制第一前驱体和无机盐的质量比，可以保障负极材料具有较低的比表面积，还可以提升负极材料的界面锂离子传输效率，提升负极材料的倍率性能。
在一些实施方式中，所述干燥的方式包括所述干燥包括自然挥发、鼓风干燥、闪蒸干燥、冷冻干燥、惰性气氛保护干燥和真空干燥中的至少一种。
在一些实施方式中，所述干燥的温度为60℃～600℃，具体可以是60℃、100℃、200℃、300℃、400℃、500℃或600℃等，当然也还可以是上述范围内其他值，在此不做限定。
在一些实施方式中，所述干燥的时间为0.5h～48h，具体可以是0.5h、1h、5h、10h、12h、15h、18h、24h、36h、45h或48h等，当然也还可以是上述范围内其他值，在此不做限定。
步骤S300，将所述第二前驱体进行碳化处理，得到负极材料。
在一些实施方式中，所述碳化处理在保护性气氛下进行，所述保护性气氛包括氮气、氦气、氖气、氩气、空气中的至少一种。可以理解地，在碳化处理过程中通入氮气、氦气、氖气、氩气等作为保护性气氛，可以有效地抑制石墨材料的氧化反应，减少石墨材料在高温下被烧损的情况，保证碳化过程的稳定性和均匀性。需要说明的是，在低温热处理时，例如热处理温度在700℃以下时，通入空气可以促进石墨材料表面状态的有益相变转化，能够在石墨材料表面接入含氧官能团，改善复合石墨负极材料的电解质浸润性和界面稳定性，提升复合石墨负极材料的电化学性能。因此，根据不同的实际应用需求和碳化处理条件，选择合适的气氛保护方式可以有效地控制石墨材料的化学成分和表面状态，进而调节其性能和应用效果。
在一些实施方式中，所述碳化处理的升温速率为1℃/min～20℃/min，具体可以是1℃/min、2℃/min、3℃/min、4℃/min、5℃/min、6℃/min、7℃/min、8℃/min、9℃/min、10℃/min、12℃/min、15℃/min、18℃/min或20℃/min等，当然也还可以是上述范围内其他值，在此不做限定。
在一些实施方式中，所述碳化处理的保温温度为600℃～2500℃，具体可以是600℃、800℃、900℃、1000℃、1200℃、1500℃、1800℃、2000℃、2200℃、2300℃或2500℃等，当然也还可以是上述范围内其他值，在此不做限定。
在一些实施方式中，所述碳化处理的保温时间0.1h～10h，具体可以是0.1h、0.5h、1h、2h、3h、4h、5h、6h、7h、8h、9h或10h等，当然也还可以是上述范围内其他值，在此不做限定。
第三方面，本申请提供一种锂离子电池，所述锂离子电池包括第一方面所述的负极材料或第二方面所述的负极材料的制备方法制备得到的负极材料。
实施例
实施例1
(1)取100g天然石墨分散于200ml的去离子水中，加入5g苯胺单体后充分搅拌均匀形成第一混合溶液。
(2)将上述第一混合溶液置于45℃条件下搅拌，控制搅拌速率为300r/min，同时向其中逐滴加入15ml(浓度为2mol/L)的过硫酸铵水溶液，结束后持续搅拌120min进行聚合反应，过滤烘干得到第一前驱体，所述第一前驱体包括内核及位于所述内核表面的聚苯胺，所述内核包括天然石墨。
(3)取100g第一前驱体与200ml去离子水均匀混合，再加入2.5g的LiOH.H2O搅拌均匀形成第二混合溶液，在90℃下将第二混合溶液进行搅拌使溶剂挥发后干燥处理，得到第二前驱体。
(4)在氮气氛围下，将第二前驱体升温到1250℃后碳化处理4小时，得到负极材料。
本实施例制得的负极材料包括内核及位于内核至少部分表面的复合层，复合层包括硬碳和氧化锂(Li2O)，内核包括天然石墨。
图3a为实施例1制备的负极材料的扫描电镜图，图3b为实施例1制备的负极材料在另一放大倍数下的扫描电镜图，如图3a及图3b所示，实施例1制备得到的负极材料颗粒表面存在碳质材料-非碳质材料纳米颗粒共复合且整体平滑。
图4为实施例1制备的负极材料的切面扫描电镜图，如图4所示，实施例1制备得到的负极材料的复合层厚度约为60nm。
实施例2
(1)取100g天然石墨分散于200ml的去离子水中，加入5g苯胺单体后充分搅拌均匀形成第一混合溶液。
(2)将上述第一混合溶液置于45℃条件下搅拌，控制搅拌速率为300r/min，同时向其中逐滴加入15ml(浓度为2mol/L)的过硫酸铵水溶液，结束后持续搅拌120min进行聚合反应，过滤烘干得到第一前驱体，所述第一前驱体包括内核及位于所述内核表面的聚苯胺，所述内核包括天然石墨。
(3)取100g第一前驱体与200ml去离子水均匀混合，再加入7.5g的(NH4)2HPO4搅拌均匀形成第二混合溶液，在90℃下将第二混合溶液搅拌使溶剂挥发后干燥处理，得到第二前驱体。
(4)在氮气氛围下，将第二前驱体升温到1250℃后碳化处理4小时，得到负极材料。
本实施例制得的负极材料包括内核及位于内核至少部分表面的复合层，复合层包括硬碳和五氧化二磷(P2O5)，内核包括天然石墨，复合层的厚度约为55nm。
实施例3
(1)取100g天然石墨分散于200ml的去离子水中，加入5g苯胺单体后充分搅拌均匀形成第一混合溶液。
(2)将上述第一混合溶液置于45℃条件下搅拌，控制搅拌速率为300r/min，同时向其中逐滴加入15ml(浓度为2mol/L)的过硫酸铵水溶液，结束后持续搅拌120min进行聚合反应，过滤烘干得到第一前驱体，所述第一前驱体包括内核及位于所述内核表面的聚苯胺，所述内核包括天然石墨。
(3)取100g第一前驱体与200ml去离子水均匀混合，再加入7.5g的NH4F搅拌均匀形成第二混合溶液，在90℃下将第二混合溶液进行搅拌使溶剂挥发后干燥处理，得到第二前驱体。
(4)在氮气氛围下，将第二前驱体升温到1250℃后碳化处理4小时，得到负极材料。
本实施例制得的负极材料包括内核及位于内核至少部分表面的复合层，复合层包括硬碳和氟化碳(CF4)，内核包括天然石墨，复合层的厚度为65nm。
需要说明的是，本实施例复合层中氟化碳(CF4)是氟掺杂的碳材料，即复合层中的氟化碳(CF4)包括碳质材料和非碳质材料。
实施例4
(1)取100g天然石墨分散于200ml的乙醇中，加入10g苯乙烯单体后充分搅拌均匀形成第一混合溶液。
(2)将上述第一混合溶液置于65℃条件下持续搅拌120min进行聚合反应，控制搅拌速率为400r/min，过滤烘干得到第一前驱体，所述第一前驱体包括内核及位于所述内核表面的聚苯乙烯，所述内核包括天然石墨。
(3)取100g第一前驱体与200ml去离子水均匀混合，再加入2.5g的LiOH.H2O搅拌均匀形成第二混合溶液，在90℃下将第二混合溶液进行搅拌使溶剂挥发后干燥处理，得到第二前驱体。
(4)在氮气氛围下，将第二前驱体升温到1250℃后碳化处理4小时，得到负极材料。
本实施例制得的负极材料包括内核及位于内核至少部分表面的复合层，复合层包括硬碳和氧化锂(Li2O)，内核包括天然石墨，复合层的厚度为55nm。
实施例5
(1)取100g天然石墨分散于200ml的乙醇中，加入10g氟苯乙烯单体后充分搅拌均匀形成第一混合溶液。
(2)将上述第一混合溶液置于65℃条件下持续搅拌120min进行聚合反应，控制搅拌速率为500r/min，过滤烘干得到第一前驱体，所述第一前驱体包括内核及位于所述内核表面的聚氟苯乙烯，所述内核包括天然石墨。
(3)取100g第一前驱体与200ml去离子水均匀混合，再加入2.5g的LiOH.H2O搅拌均匀形成第二混合溶液，在90℃下将第二混合溶液进行搅拌使溶剂挥发后干燥处理，得到第二前驱体。
(4)在氮气氛围下，将第二前驱体升温到1250℃后碳化处理4小时，得到负极材料。
本实施例制得的负极材料包括内核及位于内核至少部分表面的复合层，复合层包括硬碳、氟化锂(LiF)和氧化锂(Li2O)，内核包括天然石墨，复合层的厚度为55nm。
实施例6
(1)取100g天然石墨分散于200ml的乙醇中，加入10g多巴胺单体后充分搅拌均匀形成第一混合溶液。
(2)将上述第一混合溶液置于65℃条件下持续搅拌180min进行聚合反应，控制搅拌速率为500r/min，过滤烘干得到第一前驱体，所述第一前驱体包括内核及位于所述内核表面的聚氟苯乙烯，所述内核包括天然石墨。
(3)取100g第一前驱体与200ml去离子水均匀混合，再加入2.5g的LiOH.H2O搅拌均匀形成第二混合溶液，在90℃下将第二混合溶液进行搅拌使溶剂挥发后干燥处理，得到第二前驱体。
(4)在氮气氛围下，将第二前驱体升温到1250℃后碳化处理4小时，得到负极材料。
本实施例制得的负极材料包括内核及位于内核至少部分表面的复合层，复合层包括软碳和氧化锂(Li2O)，内核包括石墨，复合层的厚度为60nm。
实施例7
(1)取100g天然石墨分散于200ml的去离子水中，加入5g多巴胺后充分搅拌均匀形成第一混合溶液。
(2)将上述第一混合溶液置于40℃条件下搅拌，控制搅拌速率为300r/min，同时向其中逐滴加入15ml(浓度为4mol/L)的氨水作为聚合催化剂，结束后持续搅拌120min进行聚合反应，过滤烘干得到第一前驱体，所述第一前驱体包括内核及位于所述内核表面的聚多巴胺，所述内核包括天然石墨。
(3)取100g第一前驱体与200ml去离子水均匀混合，再加入2.5g的LiOH.H2O搅拌均匀形成第二混合溶液，在90℃下将第二混合溶液进行搅拌使溶剂挥发后干燥处理，得到第二前驱体。
(4)在氮气氛围下，将第二前驱体升温到1250℃后碳化处理4小时，得到负极材料。
本实施例制得的负极材料包括内核及位于内核至少部分表面的复合层，复合层包括硬碳和氧化锂(Li2O)，内核包括人造石墨，复合层的厚度为50nm。
实施例8
与实施例1不同的是，(3)取100g第一前驱体与200ml去离子水均匀混合，再加入24.5g的Al(NO3)3·9H2O搅拌均匀形成第二混合溶液，在90℃下将第二混合溶液进行搅拌使溶剂挥发后干燥处理，得到第二前驱体。
本实施例制得的负极材料包括内核及位于内核至少部分表面的复合层，复合层包括硬碳和氧化铝(Al2O3)，内核包括石墨，复合层的厚度为100nm。
实施例9
与实施例1不同的是，将天然石墨换成同粒径分布的人造石墨，其他工艺参数与实施例1完全相同。
本实施例制得的负极材料包括内核及位于内核至少部分表面的复合层，复合层包括硬碳和氧化锂(Li2O)，内核包括人造石墨，复合层的厚度为70nm。
实施例10
与实施例1不同的是，(4)在氩气氛围下，将第二前驱体升温到2000℃后碳化处理4小时，得到负极材料。
本实施例制得的负极材料包括内核及位于内核至少部分表面的复合层，复合层包括硬碳和氧化锂(Li2O)，内核包括天然石墨，复合层的厚度为150nm。
实施例11
与实施例1不同的是，(4)在氩气氛围下，将第二前驱体升温到1600℃后碳化处理4小时，得到负极材料。
本实施例制得的负极材料包括内核及位于内核至少部分表面的复合层，复合层包括硬碳和氧化锂(Li2O)，内核包括天然石墨，复合层的厚度为120m。
实施例12
与实施例1不同的是，(1)取100g天然石墨分散于200ml的去离子水中，加入5g苯胺单体后充分搅拌均匀形成第一混合溶液，加入磷酸溶液调节第一混合溶液pH为4.5。
本实施例制得的负极材料包括内核及位于内核至少部分表面的复合层，复合层包括硬碳和氧化锂(Li2O)，内核包括天然石墨。
实施例13
与实施例1不同的是，(1)取100g天然石墨分散于200ml的去离子水中，加入5g苯胺单体后充分搅拌均匀形成第一混合溶液，加入氢氧化钠溶液调节第一混合溶液pH为8.5。
本实施例制得的负极材料包括内核及位于内核至少部分表面的复合层，复合层包括硬碳和氧化锂(Li2O)，内核包括天然石墨。
对比例1
(1)取100g天然石墨分散于200ml的去离子水中，加入5g苯胺单体后充分搅拌均匀形成混合溶液。
(2)将上述混合溶液置于45℃条件下搅拌，控制搅拌速率为500r/min，同时向其中逐滴加入15ml(浓度为2mol/L)的过硫酸铵水溶液，结束后持续搅拌120min进行聚合反应，过滤烘干得到前驱体，所述前驱体包括内核及位于所述内核表面的聚苯 胺，所述内核包括天然石墨。
(3)在氮气氛围下，将前驱体升温到1250℃后碳化处理4小时，得到负极材料。
本对比例制得的负极材料包括内核及位于内核至少部分表面的碳包覆层，内核包括天然石墨。
对比例2
(1)取100g天然石墨材料与200ml去离子水均匀混合，再加入2.5g的LiOH.H2O搅拌均匀形成混合溶液，在90℃下将混合溶液进行搅拌挥发并干燥，得到前驱体。
(3)在氮气氛围下，将前驱体升温到1250℃后碳化处理4小时，得到负极材料。
本对比例制得的负极材料包括内核及位于内核至少部分表面的氧化锂包覆层，内核包括石墨。
对比例3
(1)与实施例9相似，取100g人造石墨分散于200ml的去离子水中，加入5g苯胺单体后充分搅拌均匀形成混合溶液。
(2)将上述混合溶液置于45℃条件下搅拌，控制搅拌速率为300r/min，同时向其中逐滴加入15ml(浓度为2mol/L)的过硫酸铵水溶液，结束后持续搅拌120min进行聚合反应，过滤烘干得到前驱体，所述前驱体包括内核及位于所述内核表面的聚苯胺，所述内核包括人造石墨。
(3)在氮气氛围下，将前驱体升温到1250℃后碳化处理4小时，得到负极材料。
本对比例制得的负极材料包括内核及位于内核至少部分表面的碳包覆层，内核包括人造石墨。
测试方法
(1)负极材料的平均粒径的测试方法：
通过马尔文激光粒度仪测试负极材料的粒径分布范围。
(2)负极材料的比表面积的测试方法：
在恒温低温下，测定不同相对压力时的气体在固体表面的吸附量后，基于布朗诺尔-埃特-泰勒吸附理论及其公式(BET公式)求得试样单分子层吸附量，从而计算出材料的比表面积。
(3)负极材料颗粒表面平滑度的观察：
使用S-4800扫描电子显微镜观察负极材料表面的微观形貌。
(4)非碳质材料的平均粒径的测试方法：
使用S-4800扫描电子显微镜观察负极材料表面的微观形貌和非碳质材料的粒径，在单个负极材料颗粒上随机取1μm*1μm区域，统计区域内非碳质材料的粒径分布，并计算非碳质材料的平均粒径为G。
(5)复合层的厚度的测试方法：
使用聚焦离子束将石墨颗粒切开获取切面，使用S-4800扫描电子显微镜观察负极材料切面的微观形貌和复合层厚度。
(6)粉末电导率测试：
使用粉末电阻率测试系统测试负极材料的粉末电导率。
(7)电化学性能测试
将实施例1～13与对比例1～3制备得到的负极材料，分别按照质量比为96.5:1.5:1的负极材料、羧甲基纤维素和丁苯橡胶溶解在去离子水中，控制固含量为50％，涂覆于铜箔集流体上，真空烘干、制得负极极片；以金属锂片作为对电极，在充满氩气的手套箱中组装成扣式电池完成。在0.1C的电流密度下，按充放电区间为0.01-1.5V进行充放电测试。循环充放电，得到首次可逆比容量、首圈充电容量和首圈放电容量。首次库伦效率＝首圈放电容量/首圈充电容量。不同倍率下循环充放电，得到倍率性能。
上述性能测试结果详见表1。
表1.各实施例和对比例制备得到的负极材料及其电池的性能参数

如表1所示，实施例1～13通过将含有石墨材料和有机分子单体的第一混合溶液进行聚合反应得到第一前驱体，有机分子单体聚合形成的聚合物复合在石墨颗粒表面形成聚合物层，聚合物中的具有高反应活性官能团，再将含有第一前驱体和无机盐的第二混合溶液充分混合后进行干燥，干燥过程中，第二混合溶液中的无机盐水解形成无机离子，利用聚合物中的高反应活性官能团与无机离子之间的嫁接反应，将无机离子嫁接引入到石墨颗粒表面的聚合物层中，得到第二前驱体，最后将第二前驱体进行碳化处理，经过碳化处理，聚合物层中的有机分子原位裂解为碳质材料，同时无机离子原位转化为非碳质材料，在石墨颗粒表面形成包含碳质材料和非碳质材料的复合层。制备得到的负极材料表面具有均匀包覆的复合层，通过复合层中碳质材料和非碳质材料的协同作用，能够降低负极材料的比表值，改善负极材料的高温存储性能和极片加工性能；还可以提高负极材料的界面稳定性，减少界面副反应，增强电解液浸润性，改善锂离子传输效率，提升负极材料的可逆容量和首次效率，提升负极材料的倍率性能。
与实施例1相比，对比例1的负极材料在制备过程中直接将第一前驱体进行碳化处理，制备得到的负极材料中包覆层为单一的碳包覆层，在低电位下容易与电解质组分发生不可逆反应，导致SEI膜不断修复与生成，负极材料的表界面稳定性下降，与电解液间的副反应加剧，锂离子传输效率降低，负极材料的粉末电导率下降，材料的可逆容量、首次效率、倍率性能降低。
与实施例1相比，对比例2的负极材料在制备过程中，直接将天然石墨材料与非碳质材料进行复合，制备得到的负极材料中包覆层为单一的非碳质材料包覆层，负极材料的比表面积较大，材料与电解液之间的接触增加，界面副反应加剧，材料的表界面稳定性下降，锂离子传输效率降低，导致负极材料的粉末电导率下降，其可逆容量与倍率性能下降，首次效率也明显降低。
实施例9和对比例3采用人造石墨为原料，与实施例9相比，对比例3的负极 材料在制备过程中直接将第一前驱体进行碳化处理，制备得到的负极材料中包覆层为单一的碳包覆层，负极材料表面稳定性较低，低电位下与电解液的副反应更剧烈，其首次库伦效率、粉末电导率和倍率性能等性能指标均出现不同程度的恶化。
申请人声明，本申请通过上述实施例来说明本申请的详细工艺设备和工艺流程，但本申请并不局限于上述详细工艺设备和工艺流程，即不意味着本申请必须依赖上述详细工艺设备和工艺流程才能实施。所属技术领域的技术人员应该明了，对本申请的任何改进，对本申请产品各原料的等效替换及辅助成分的添加、具体方式的选择等，均落在本申请的保护范围和公开范围之内。

Claims (13)

  1. 一种负极材料，其特征在于，所述负极材料包括内核及位于所述内核至少部分表面的复合层，所述内核包括石墨，所述复合层包括碳质材料和非碳质材料。
  2. 根据权利要求1所述的负极材料，其特征在于，所述非碳质材料分散于所述碳质材料中。
  3. 根据权利要求1所述的负极材料，其特征在于，所述非碳质材料的化学通式为AxBy，其中，1≤x≤3，1≤y≤5，A元素包括Li、Na、K、Ca、Mg、Al、Zn、Ti、Nb、Zr、Mo、P、Si和B中的至少一种，B元素包括B、O、F、Si、P、S、Br和Cl中的至少一种。
  4. 根据权利要求1所述的负极材料，其特征在于，其满足以下技术特征中的至少一种：
    (1)所述石墨包括天然石墨、人造石墨和微晶石墨中的至少一种；
    (2)所述内核的中值粒径为D50，0.5μm≤D50≤30μm；
    (3)所述石墨中碳元素的质量含量≥80％；
    (4)所述碳质材料包括无定形碳和石墨碳中的至少一种；
    (5)所述复合层的厚度为1nm～200nm；
    (6)所述非碳质材料包括LiF、NaF、MgF2、MgO、P2O5、Al2O3、SiO2、B2O3中的至少一种；
    (7)所述非碳质材料的平均粒径为G，且G≤150nm。
  5. 根据权利要求1～3任一项所述的负极材料，其特征在于，其满足以下技术特征中的至少一种：
    (1)所述复合层与所述内核的质量比为C，且0.01≤C≤0.5；
    (2)所述碳质材料与所述非碳质材料的质量比为D，且0.1≤D≤80；
    (3)所述内核的粉末电导率为E1，所述负极材料的粉末电导率为E2，E2与E1的比值为E，且1＜E＜1000；
    (4)所述内核的比表面积为6m2/g～15m2/g；
    (5)所述负极材料的比表面积为1m2/g～5m2/g。
  6. 一种负极材料的制备方法，其特征在于，包括以下步骤：
    制备第一前驱体，所述第一前驱体包括内核和在所述内核表面形成的聚合物层，其中，所述内核包括石墨；
    在所述第一前驱体表面附着无机盐得到第二前驱体；及
    将所述第二前驱体进行碳化处理，得到负极材料。
  7. 根据权利要求6所述的制备方法，其特征在于，所述制备第一前驱体包括以下步骤：
    将含有石墨和有机分子单体的第一混合溶液进行聚合反应，固液分离并干燥，得到所述第一前驱体。
  8. 根据权利要求6所述的制备方法，其特征在于，所述在所述第一前驱体表面附着无机盐得到第二前驱体包括以下步骤：将含有所述第一前驱体和无机盐的第二混 合溶液进行干燥，得到第二前驱体。
  9. 根据权利要求7所述的制备方法，其特征在于，其满足以下技术特征中的至少一种：
    (1)所述石墨包括天然石墨、人造石墨和微晶石墨中的至少一种；
    (2)所述石墨的中值粒径为0.5μm～30μm；
    (3)所述石墨和所述有机分子单体的质量比为1：(0.01～0.4)；
    (4)所述有机分子单体包括苯胺、苯乙烯、氟苯乙烯、丙烯酸羟乙酯、丙烯酸酯、吡咯、偏氟乙烯、四氟乙烯和多巴胺中的至少一种；
    (5)所述第一混合溶液和所述第二混合溶液均包括溶剂，所述溶剂包括水、甲醇、乙醇、丙酮、氮甲基吡咯烷酮和N，N二甲基甲酰胺中的至少一种。
  10. 根据权利要求7所述的制备方法，其特征在于，其满足以下技术特征中的至少一种：
    (1)所述第一混合溶液中还包括助剂；
    (2)所述第一混合溶液中还包括助剂，所述助剂在所述第一混合溶液中的质量浓度为0.01mol/L～4mol/L；
    (3)所述第一混合溶液中还包括助剂，所述助剂包括引发剂，所述引发剂包括过硫酸铵、过硫酸钠、过硫酸钾、氯化铝及过氧化氢中的至少一种；
    (4)所述第一混合溶液中还包括助剂，所述助剂包括催化剂，所述催化剂包括氢氧化钠、氢氧化锂、氢氧化钾、氨水及碳酸钠中的至少一种；
    (5)所述第一混合溶液中还包括助剂，所述助剂包括pH调节剂，所述pH调节剂包括酸性pH试剂和碱性pH试剂中的至少一种；
    (6)所述第一混合溶液中还包括助剂，所述助剂包括pH调节剂，所述第一混合溶液的pH为4～10；
    (7)所述第一混合溶液中还包括助剂，所述助剂包括pH调节剂，所述pH调节剂包括盐酸、硫酸、磷酸和硝酸中的至少一种；
    (8)所述第一混合溶液中还包括助剂，所述助剂包括pH调节剂，所述pH调节剂包括氢氧化锂、氢氧化钠、氢氧化钾、碳酸钠和碳酸氢钠中的至少一种。
  11. 根据权利要求7所述的制备方法，其特征在于，其满足以下技术特征中的至少一种：
    (1)所述聚合反应的温度为40℃～100℃；
    (2)所述聚合反应的时间为3h～48h；
    (3)所述聚合反应在搅拌下进行；
    (4)所述聚合反应在搅拌状态下进行，搅拌速率为50r/min～1000r/min；
    (5)所述固液分离包括过滤、离心中的至少一种。
  12. 根据权利要求8所述的制备方法，其特征在于，其满足以下技术特征中的至少一种：
    (1)所述无机盐包括氢氧化锂、氢氧化钠、氢氧化钾、硝酸镁、氯化钙、硝酸铝、硝酸锌、正丙醇钛、草酸铌、氯氧化锆、钼酸铵、磷酸二氢铵、磷酸氢二铵、偏硅酸钠、硼酸钠、氟化铵、氧硫化钛、溴化锌及氯化锆中的至少一种；
    (2)所述第一前驱体与所述无机盐的质量比为1：(0.001～0.1)；
    (3)所述干燥包括自然挥发、鼓风干燥、闪蒸干燥、冷冻干燥、惰性气氛保护干燥及真空干燥中的至少一种；
    (4)所述干燥的温度为60℃～600℃；
    (5)所述干燥的时间为0.5h～48h；
    (6)所述碳化处理在保护性气氛下进行；
    (7)所述碳化处理在保护性气氛下进行，所述保护性气氛包括氮气、氦气、氖气、氩气、空气中的至少一种；
    (8)所述碳化处理的升温速率为1℃/min～20℃/min；
    (9)所述碳化处理的保温温度为600℃～2500℃；
    (10)所述碳化处理的保温时间0.1h～10h。
  13. 一种锂离子电池，其特征在于，所述锂离子电池包括权利要求1～5任一项所述的负极材料或权利要求6～12任一项所述的负极材料的制备方法制备得到的负极材料。
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