WO2024002041A1 - 负极材料及其制备方法、二次电池 - Google Patents

负极材料及其制备方法、二次电池 Download PDF

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Publication number
WO2024002041A1
WO2024002041A1 PCT/CN2023/102585 CN2023102585W WO2024002041A1 WO 2024002041 A1 WO2024002041 A1 WO 2024002041A1 CN 2023102585 W CN2023102585 W CN 2023102585W WO 2024002041 A1 WO2024002041 A1 WO 2024002041A1
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Prior art keywords
hollow carbon
negative electrode
layer
carbon
silicon
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PCT/CN2023/102585
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English (en)
French (fr)
Inventor
安威力
何鹏
任建国
贺雪琴
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BTR New Material Group Co Ltd
Dingyuan New Energy Technology Co Ltd
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BTR New Material Group Co Ltd
Dingyuan New Energy Technology Co Ltd
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Priority to EP23830218.6A priority Critical patent/EP4471897A4/en
Priority to US18/558,525 priority patent/US20240222612A1/en
Publication of WO2024002041A1 publication Critical patent/WO2024002041A1/zh
Anticipated expiration legal-status Critical
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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
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/621—Binders
    • H01M4/622—Binders being polymers
    • 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
    • H01M4/133—Electrodes based on 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
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/134—Electrodes based on metals, Si or alloys
    • 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
    • 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
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • 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
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • H01M4/386—Silicon or alloys based on silicon
    • 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
    • H01M4/624—Electric conductive fillers
    • H01M4/625—Carbon or graphite
    • 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
    • H01M2004/021—Physical characteristics, e.g. porosity, surface area
    • 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
    • H01M2004/027—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, specifically, to a negative electrode material and a preparation method thereof, and a secondary battery.
  • Lithium-ion batteries are widely used in electric vehicles and consumer electronics due to their advantages of high energy density, high output power, long cycle life and low environmental pollution.
  • the research and development of high-capacity anode materials are becoming increasingly mature.
  • the volume of these negative electrode materials expands greatly during the alloying process with lithium.
  • they will pulverize and fall from the current collector, causing the electrical contact between the negative electrode material and the current collector to be lost, resulting in poor electrochemical performance and capacity attenuation.
  • the cycle stability decreases and it is difficult to obtain commercial application.
  • This application proposes negative electrode materials, preparation methods thereof, and secondary batteries, which can reduce volume expansion and improve cycle stability.
  • the present application provides a negative electrode material.
  • the negative electrode material has a core-shell structure.
  • the core includes a silicon-based active material.
  • the outer shell includes a connecting layer, a buffer layer and a protective layer.
  • the connecting layer is coated on the silicon-based active material.
  • the buffer layer is filled between the connection layer and the protective layer, and the connection layer and the buffer layer are connected by covalent bonds.
  • connection layer, buffer layer and protective layer are constructed on the surface of the silicon-based active material, and their synergistic effect is used to effectively alleviate the volume expansion of the silicon-based active material, enhance the structural stability of the silicon-carbon anode material, and improve the cycle Lifespan;
  • connection layer on the surface of the silicon-based active material can greatly improve the conductivity of the material, reduce the occurrence of side reactions, and improve the transmission channels of lithium ions and electrons, thereby improving the conductivity of the negative electrode material and improving the rate performance of the material; filling in the connection layer
  • the buffer layer between the protective layer and the connecting layer is covalently connected, which reduces the volume expansion of the silicon-based active material during the charging and discharging process and causes the buffer layer to fall off, which is beneficial to the negative electrode material to maintain excellent mechanical properties and improve the negative electrode. Structural stability of the material, thereby improving cycle stability.
  • the negative electrode material has a core-shell structure.
  • the core includes a silicon-based active material.
  • the outer shell includes a connecting layer, a buffer layer and a protective layer.
  • the connecting layer is coated on the silicon-based active material.
  • the buffer layer is filled between the connection layer and the protective layer, and the average bonding force between the connection layer and the buffer layer is F>8 ⁇ N.
  • the connecting layer, buffer layer and protective layer are constructed on the surface of the silicon-based active material, and their coordination is used to effectively alleviate the volume expansion of the silicon-based active material and enhance the structural stability of the silicon-carbon anode material.
  • Improve cycle life the connection layer on the surface of the silicon-based active material can greatly improve the conductivity of the material, reduce the occurrence of side reactions, and improve the transmission channels of lithium ions and electrons, thereby improving the conductivity of the anode material and improving the rate performance of the material; filling in The average bonding force between the buffer layer and the protective layer between the connecting layer and the connecting layer is greater than 8 ⁇ N.
  • the buffer layer will not easily fall off from the connecting layer, which will help the negative electrode material maintain excellent mechanical properties and improve the negative electrode. Structural stability of the material, thereby improving cycle stability.
  • the negative electrode material has a core-shell structure.
  • the core includes a silicon-based active material.
  • the outer shell includes a connecting layer and a protective layer.
  • the connecting layer covers the surface of the silicon-based active material.
  • the protective layer includes a conductive base material and hollow carbon material dispersed in the conductive base material, and the average bonding force between the connection layer and the hollow carbon material is F>8 ⁇ N.
  • a connecting layer and a protective layer are constructed on the surface of the silicon-based active material, and their synergistic effect is used to effectively alleviate the volume expansion of the silicon-based active material, enhance the structural stability of the silicon-carbon anode material, and improve the cycle life; silicon
  • the connection layer on the surface of the base active material can greatly improve the conductivity of the material, reduce the occurrence of side reactions, and improve the transmission channels of lithium ions and electrons, thereby improving the conductivity of the negative electrode material and improving the rate performance of the material; the conductive substrate in the protective layer It can improve the conductivity of the material.
  • the hollow carbon material dispersed in the conductive substrate can buffer the volume expansion of the silicon-based active material, and the average binding force between the hollow carbon material and the connection layer is greater than 8 ⁇ N.
  • the hollow carbon material The material is not easy to fall off from the connecting layer, thereby improving the connection stability between the protective layer and the connecting layer, helping the negative electrode material maintain excellent mechanical properties, improving the overall structural stability of the negative electrode material, and thereby improving cycle stability.
  • this application provides a preparation method of anode material, including the following steps:
  • connection layer on the surface of the silicon-based active material, the connection layer having modified functional groups to obtain a first precursor
  • the second precursor is coated to obtain a negative electrode material.
  • a connecting layer with modified functional groups is formed on the surface of the silicon-based active material, and then the buffer layer material with surface functional groups is polymerized with the first precursor, so that the connecting layer and the buffer layer material are covalently bonded Connection can greatly improve the bonding strength between the buffer layer material and the connection layer, effectively tightly connecting the connection layer and the buffer layer material, ensuring excellent electrical contact after volume expansion; finally, coating is performed on the buffer layer to form a protective layer The conductivity and structural integrity of the negative electrode material are further enhanced, which can effectively suppress side reactions caused by contact with the electrolyte.
  • the negative electrode material prepared by the method of the present application relies on the high strength and high toughness of the buffer layer material, combined with the connecting layer, buffer layer and protective layer to synergize the silicon-based active material, which can effectively alleviate the volume expansion of silicon and improve the silicon negative electrode.
  • the electrical conductivity enhances the stability of the silicon-carbon composite structure, thereby improving the cycle life and rate performance of this silicon anode material.
  • the present application provides a secondary battery, including the negative electrode material described in the first aspect or the negative electrode material prepared according to the preparation method of the negative electrode material described in the second aspect.
  • the negative electrode material provided in this application constructs a connecting layer, a buffer layer and a protective layer on the surface of the silicon-based active material, and utilizes their coordination to effectively alleviate the volume expansion of the silicon-based active material and enhance the structural stability of the silicon-carbon negative electrode material.
  • Improve cycle life the connection layer on the surface of the silicon-based active material can greatly improve the conductivity of the material. Reduce the occurrence of side reactions and improve the transmission channels of lithium ions and electrons, thereby improving the conductivity of the negative electrode material and improving the rate performance of the material; filling the buffer layer between the connection layer and the protective layer, and the buffer layer and the connection layer are connected through covalent bonds.
  • the average binding force between the buffer layer and the connecting layer is greater than 8 ⁇ N, which is beneficial to the negative electrode material to maintain excellent mechanical properties, improve the structural stability of the negative electrode material, and thereby improve cycle stability.
  • the negative electrode material provided in this application constructs a connecting layer and a protective layer on the surface of the silicon-based active material, and utilizes their synergistic effect to effectively alleviate the volume expansion of the silicon-based active material, enhance the structural stability of the silicon-carbon negative electrode material, and improve the cycle life.
  • the connection layer on the surface of the silicon-based active material can greatly improve the conductivity of the material, reduce the occurrence of side reactions, and improve the transmission channels of lithium ions and electrons, thereby improving the conductivity of the negative electrode material and improving the rate performance of the material; the conductivity in the protective layer
  • the base material can improve the conductivity of the material.
  • the hollow carbon material dispersed in the conductive base material can buffer the volume expansion of the silicon-based active material, and the average binding force between the hollow carbon material and the connection layer is greater than 8 ⁇ N.
  • the hollow carbon material is not easy to fall off from the connecting layer, which can improve the connection stability between the protective layer and the connecting layer, prevent the buffer layer from falling off due to volume expansion of the silicon-based active material during charging and discharging, and help the negative electrode material maintain excellent mechanical properties. performance, improve the overall structural stability of the anode material, and thereby improve cycle stability.
  • the preparation method provided by this application is to form a connecting layer with modified functional groups on the surface of a silicon-based active material, and then polymerize the buffer layer material with surface functional groups and the first precursor, so that the connecting layer and the buffer layer material pass through
  • the valence bond connection can greatly improve the bonding strength between the buffer layer material and the connection layer, effectively tightly connecting the connection layer and the buffer layer material, ensuring excellent electrical contact after volume expansion; finally, the buffer layer is coated to form
  • the protective layer further enhances the conductivity and structural integrity of the negative electrode material, and can effectively inhibit side reactions from contact with the electrolyte.
  • the negative electrode material prepared by the method of the present application relies on the high strength and high toughness of the hollow carbon material in the buffer layer, and combines the connection layer, buffer layer and protective layer to synergize the silicon-based active material, which can effectively alleviate the volume expansion of silicon. , improve the conductivity of the silicon anode, enhance the stability of the silicon-carbon composite structure, and thereby improve the cycle life and rate performance of this silicon anode material.
  • Figure 1 is a schematic structural diagram of the negative electrode material provided in this embodiment
  • Figure 2 is another structural schematic diagram of the negative electrode material provided in this embodiment.
  • Figure 3 is a schematic flow chart of the preparation method of the negative electrode material provided in this embodiment.
  • Figure 4 is a scanning electron microscope picture of the negative electrode material provided in Example 1;
  • Figure 5 is a Raman diagram of the negative electrode material provided in Example 1;
  • Figure 6 is a cycle performance curve diagram of the negative electrode material provided in Example 1.
  • the anode material is one of the key materials that affects its charge and discharge performance.
  • the research and development of high-capacity anode materials are becoming increasingly mature.
  • the volume of these negative electrode materials expands greatly during the alloying process with lithium.
  • the negative electrode materials will pulverize and fall from the current collector during the charge and discharge process, causing the electrical contact between the negative electrode material and the current collector to be lost, resulting in poor electrochemical performance.
  • Capacity fading and cycle stability decrease, Difficult to obtain commercial application.
  • embodiments of the present application provide a negative electrode material with low expansion and good stability.
  • the negative electrode material has a core-shell structure.
  • the core includes a silicon-based active material 10.
  • the outer shell includes a connecting layer 21, a buffer layer 22 and a protective layer 23.
  • the connecting layer 21 is coated with silicon.
  • the buffer layer 22 is filled between the connection layer 21 and the protective layer 23, and the connection layer 21 and the buffer layer 22 are connected by covalent bonds.
  • connection layer, buffer layer and protective layer are constructed on the surface of the silicon-based active material, and their coordination is used to effectively alleviate the volume expansion of the silicon-based active material, enhance the structural stability of the silicon-carbon anode material, and improve the cycle Lifespan;
  • connection layer on the surface of the silicon-based active material can greatly improve the conductivity of the material, reduce the occurrence of side reactions, and improve the lithium ion and electron transmission channels, thereby improving the conductivity of the negative electrode material and improving the rate performance of the material; filling in the connection layer
  • the buffer layer between the protective layer and the connecting layer is covalently connected, which helps the negative electrode material maintain excellent mechanical properties and improves the structural stability of the negative electrode material.
  • the core is a silicon-based active material
  • the silicon-based active material is a primary particle.
  • the silicon - based active material includes at least one of Si , SiO x and silicon alloy, where 0 ⁇ x ⁇ 2; SiO 0.6 , SiO 0.8 , SiO, SiO 1.2 , SiO 1.5 , SiO 1.8 or SiO 1.9 , etc., are not limited here.
  • the silicon alloy may be ferrosilicon alloy particles, silicon-cobalt alloy particles, silicon-nickel alloy particles, silicon-copper alloy particles, silicon-platinum alloy particles or silicon-gold alloy particles.
  • the median particle diameter of the silicon-based active material is 0.2 ⁇ m to 20 ⁇ m; specifically, it may be 0.2 ⁇ m, 0.5 ⁇ m, 1 ⁇ m, 2 ⁇ m, 5 ⁇ m, 10 ⁇ m, 15 ⁇ m or 20 ⁇ m, which is not limited here.
  • the tie layer includes at least one of a polymer, an amorphous carbon material, and a graphitized carbon material.
  • the buffer layer includes hollow carbon material 221 .
  • this application provides a negative electrode material.
  • the negative electrode material has a core-shell structure.
  • the core includes a silicon-based active material.
  • the outer shell includes a connection layer, a buffer layer and a protective layer.
  • the connection layer covers the surface of the silicon-based active material.
  • the buffer layer The layer is filled between the connection layer and the protective layer, and the average bonding force between the connection layer and the buffer layer is F>8 ⁇ N.
  • the test method for the average bonding force F between the connecting layer and the buffer layer is: measure the minimum pulling force required for five hollow carbon materials to detach from the connecting layer through the nanomechanical testing system and the probe testing system, and the average is the average Binding force.
  • the buffer layer includes at least one of hollow carbon spheres, hollow carbon rods, and hollow carbon tubes.
  • the hollow carbon material includes hollow carbon spheres
  • the diameter of the hollow carbon spheres is 20 nm to 2000 nm
  • the wall thickness of the hollow carbon spheres is 5 nm to 500 nm.
  • the diameter can be 20nm, 50nm, 80nm, 100nm, 200nm, 500nm, 800nm, 1000nm, 1500nm or 2000nm, etc.
  • the wall thickness can be 5nm, 50nm, 80nm, 100nm, 150nm, 200nm, 250nm, 300nm, 450nm or 500nm. nm etc. , no limitation is made here.
  • the hollow carbon material includes a hollow carbon rod
  • the diameter of the hollow carbon rod ranges from 10 nm to 1000 nm
  • the length of the hollow carbon rod ranges from 100 nm to 3000 nm
  • the wall thickness of the hollow carbon rod ranges from 5 nm to 500 nm.
  • the diameter can be 10nm, 50nm, 80nm, 100nm, 200nm, 500nm, 600nm, 700nm, 850nm or 1000nm, etc.
  • the length can be 100nm, 200nm, 400nm, 500nm, 800nm, 1000nm, 2000nm, 2500nm or 3000n.
  • m, etc. wall thickness Specifically, it can be 5nm, 50nm, 80nm, 100nm, 150nm, 200nm, 250nm, 300nm, 450nm or 500nm, etc., which is not limited here.
  • the hollow carbon material includes hollow carbon tubes, the diameter of the hollow carbon tube is 20nm ⁇ 400nm, the length of the hollow carbon tube is 30nm ⁇ 20um, and the wall thickness of the hollow carbon tube is 5nm ⁇ 100nm.
  • the diameter can be 20nm, 50nm, 80nm, 100nm, 200nm, 250nm, 300nm, 350nm, 380nm or 400nm, etc.
  • the length can be 30nm, 50nm, 100nm, 200nm, 400nm, 500nm, 800nm, 1um, 8um, 10um, 15um. Or 20um, etc.
  • the wall thickness can specifically be 5nm, 10nm, 25nm, 30nm, 35nm, 40nm, 45nm or 50nm, etc., which is not limited here.
  • the ratio of the thickness of the buffer layer to the median particle diameter D 50 of the silicon-based active material is 1: (0.5-10); specifically, it can be 1:0.5, 1:0.7, 1:0.8, 1: 0.9, 1:1.0, 1:1.5, 1:2.0, 1:3, 1:5, 1:6, 1:8 or 1:10, etc., are not limited here.
  • the ratio of the thickness of the buffer layer to the median particle diameter D 50 of the silicon-based active material is 1: (1-8).
  • the protective layer covers the surface of the buffer layer.
  • the protective layer covers the surface of the buffer layer, and at least part of the protective layer is filled in the gaps between the hollow carbon materials.
  • the protective layer includes at least one of a polymer, an amorphous carbon material, and a graphitized carbon material.
  • the thickness of the connection layer ranges from 5nm to 200nm, specifically, it can be 5nm, 10nm, 30nm, 50nm, 80nm, 100nm, 150nm, 180nm or 200nm, etc., which is not limited here.
  • the thickness of the protective layer is 5 nm to 500 nm, specifically 5 nm, 50 nm, 80 nm, 100 nm, 150 nm, 200 nm, 250 nm, 300 nm, 450 nm or 500 nm, etc., which is not limited here.
  • the protective layer includes at least one of an amorphous carbon material and a graphitized carbon material, wherein the mass content of the carbon element in the protective layer in the negative electrode material is 1% to 50%, preferably 5% ⁇ 25%.
  • the protective layer is a carbon layer made of amorphous carbon material
  • the mass content of the carbon layer in the negative electrode material is 2% to 25%
  • the mass content of oxygen in the carbon layer is ⁇ 5%.
  • the protective layer is a carbon layer composed of graphitized carbon material, the mass content of the carbon layer in the negative electrode material is 2% to 15%, and the mass content of oxygen in the carbon layer is ⁇ 3%.
  • the graphitized carbon material is modified graphene containing doping elements; the doping elements include at least one of oxygen, nitrogen, and sulfur.
  • the graphitized carbon material is modified graphene containing doped elements, and the number of layers of modified graphene is less than 10. Too many layers of modified graphene will cause the thickness of the protective layer to be too large, and the carbon If the content is too high, it is not conducive to improving the rate performance of the material.
  • the mass content of the doping element in the graphitized carbon material is 1% to 20%; specifically, it can be 1%, 3%, 4%, 5%, 6%, 7%, 10%, 12% %, 15%, 18% or 20%, etc., are not limited here.
  • electrical conductivity can be significantly enhanced.
  • the protective layer includes a polymer including at least one of a diblock copolymer, a triblock copolymer, and a multiblock copolymer.
  • the mass content of the polymer in the negative electrode material is 1% to 20%, specifically 1%, 3%, 5%, 8%, 10%, 12%, 15% or 20%, etc., No limitation is made here.
  • the polymers include polyacrylic acid, polyacrylonitrile, polyimide, polyurethane, polydopamine, xanthan gum, polypyrrole, polythiophene, polyphenylene vinylene, polyaniline, polyacetylene, and tannic acid. of at least one.
  • the polymer is preferably at least one of polypyrrole, polythiophene, polyaniline, polyaniline and polyacetylene.
  • the present application provides a negative electrode material.
  • the negative electrode material has a core-shell structure.
  • the core includes a silicon-based active material 10.
  • the outer shell includes a connecting layer 21 and a protective layer 23.
  • the connecting layer 21 is coated with silicon.
  • the protective layer 23 includes a conductive base material 231 and hollow carbon materials 221 dispersed in the conductive base material 231 .
  • the average bonding force between the connection layer 21 and the hollow carbon material 221 is F>8 ⁇ N.
  • a connecting layer and a protective layer are constructed on the surface of the silicon-based active material, and their synergistic effect is used to effectively alleviate the volume expansion of the silicon-based active material, enhance the structural stability of the silicon-carbon anode material, and improve the cycle life; silicon
  • the connection layer on the surface of the base active material can greatly improve the conductivity of the material, reduce the occurrence of side reactions, and improve the transmission channels of lithium ions and electrons, thereby improving the conductivity of the negative electrode material and improving the rate performance of the material; the conductive substrate in the protective layer It can improve the conductivity of the material.
  • the hollow carbon material dispersed in the conductive substrate can buffer the volume expansion of the silicon-based active material, and the average binding force between the hollow carbon material and the connection layer is greater than 8 ⁇ N.
  • the hollow carbon material The material is not easy to fall off from the connecting layer, thereby improving the connection stability between the protective layer and the connecting layer, helping the negative electrode material maintain excellent mechanical properties, improving the overall structural stability of the negative electrode material, and thereby improving cycle stability.
  • the conductive substrate includes at least one of a polymer, an amorphous carbon material, and a graphitized carbon material.
  • a polymer an amorphous carbon material
  • a graphitized carbon material the selection of polymer, amorphous carbon material and graphitized carbon material will not be described in detail here, and is the same as the negative electrode material described in the first aspect.
  • the protective layer covers the surface of the connection layer.
  • both the tie layer and the protective layer include a polymer
  • both the connection layer and the protective layer include amorphous carbon material
  • both the tie layer and the protective layer include graphitized carbon material.
  • the bonding force between the connecting layer and the protective layer is stronger, which is more conducive to fixing the hollow carbon material between the connecting layer and the protective layer and reduces the gap between the hollow carbon material and the filling layer. peeled off from the connection layer during discharge.
  • the mass content of carbon element in the negative electrode material is 5% to 80%. Specifically, it can be 5%, 8%, 10%, 15%, 18%, 20%, 30%, 35%, 40%, 45%, 50% or 80%, etc., and is not limited here. It should be noted that the carbon in the negative electrode material comes from the carbon in the connecting layer, buffer layer and protective layer.
  • the mass content of oxygen element in the negative electrode material is less than 20%. Specifically, it can be 5%, 6%, 8%, 10%, 12%, 15%, 18%, 19%, etc., and is not limited here.
  • the powder tap density of the negative electrode material is 0.2g/cm 3 to 1.2g/cm 3 , such as 0.2g/cm 3 , 0.3g/cm 3 , 0.5g/cm 3 , 0.6g/cm 3 , 0.7g/cm 3 , 0.8g/cm 3 , 1.0g/cm 3 , 1.2g/cm 3 , etc.
  • it is 0.5g/ cm3-0.8g / cm3 .
  • the powder compaction density of the negative electrode material is 1.2g/cm 3 to 1.8g/cm 3 , such as 1.2g/cm 3 , 1.3g/cm 3 , 1.4g/cm 3 , 1.5g/cm 3 , 1.6g/ cm3 or 1.8g/ cm3, etc., preferably 1.45g/ cm3 ⁇ 1.75g/cm3 .
  • the median particle size of the negative electrode material is 0.2 ⁇ m to 20 ⁇ m.
  • the median particle size of the negative electrode material may be 0.2 ⁇ m, 0.5 ⁇ m, 1 ⁇ m, 3 ⁇ m, 4 ⁇ m, 5 ⁇ m, 7 ⁇ m, or 10 ⁇ m. , 13 ⁇ m, 15 ⁇ m or 20 ⁇ m, etc., are not limited here.
  • the median particle size of the negative electrode material is preferably 0.5 ⁇ m to 10 ⁇ m, and more preferably 1 ⁇ m to 5 ⁇ m.
  • the specific surface area ratio of the negative electrode material is 1 m 2 /g ⁇ 50 m 2 /g.
  • the specific surface area ratio of the negative electrode material may be 1m 2 /g, 5m 2 /g, 8m 2 /g, 10m 2 /g, 15m 2 /g, 20m 2 /g, 25m 2 /g, 30m 2 / g, 35m 2 /g, 40m 2 /g, 45m 2 /g or 50m 2 /g, etc., there is no limit here; it can be understood that the smaller the specific surface area, the better. Excessive specific surface area can easily lead to the formation of SEI film , consuming too much irreversible lithium salt and reducing the first efficiency of the battery. Considering the cost of the preparation process, the specific surface area is controlled between 2m 2 /g and 15m 2 /g.
  • This application also provides a preparation method of anode material, as shown in Figure 3, including the following steps:
  • connection layer has modified functional groups to obtain the first precursor
  • the negative electrode material prepared by the above method has a core-shell structure.
  • the core includes a silicon-based active material.
  • the outer shell includes a connecting layer, a buffer layer and a protective layer.
  • the connecting layer covers the surface of the silicon-based active material, and the buffer layer is filled in the connecting layer. between the protective layer.
  • a connecting layer with modified functional groups is formed on the surface of the silicon-based active material, and then the buffer layer material with surface functional groups is polymerized with the first precursor, so that the connecting layer and the buffer layer material are covalently bonded.
  • Connection can greatly improve the bonding strength between the buffer layer material and the connection layer, effectively tightly connecting the connection layer and the buffer layer material, ensuring excellent electrical contact after volume expansion; finally, coating is performed on the buffer layer to form a protective layer
  • the conductivity and structural integrity of the negative electrode material are further enhanced, which can effectively suppress side reactions caused by contact with the electrolyte.
  • the negative electrode material prepared by the method of the present application relies on the high strength and high toughness of the buffer layer material, combined with the connecting layer, buffer layer and protective layer to synergize the silicon-based active material, which can effectively alleviate the volume expansion of silicon and improve the silicon negative electrode.
  • the electrical conductivity enhances the stability of the silicon-carbon composite structure, thereby improving the cycle life and rate performance of this silicon anode material.
  • Step S10 Form a connection layer on the surface of the silicon-based active material.
  • the connection layer has modified functional groups to obtain a first precursor.
  • the silicon-based active material is a primary particle.
  • the silicon - based active material includes at least one of Si , SiO x and silicon alloy, where 0 ⁇ x ⁇ 2; SiO 0.6 , SiO 0.8 , SiO, SiO 1.2 , SiO 1.5 , SiO 1.8 or SiO 1.9 , etc., are not limited here.
  • the silicon alloy may be ferrosilicon alloy particles, silicon-cobalt alloy particles, silicon-nickel alloy particles, silicon-copper alloy particles, silicon-platinum alloy particles or silicon-gold alloy particles.
  • the median particle diameter D 50 of the silicon-based active material is 0.2 ⁇ m to 20 ⁇ m; specifically, it may be 0.2 ⁇ m, 0.5 ⁇ m, 1 ⁇ m, 2 ⁇ m, 5 ⁇ m, 10 ⁇ m, 15 ⁇ m or 20 ⁇ m, which is not limited here.
  • connection layer may be modified by gas modification and/or liquid phase modification.
  • step S10 includes: depositing a gas phase carbon source on the surface of the silicon-based active material through vapor deposition under a protective atmosphere to obtain a composite, and using modified gas to make the connection layer on the surface of the composite have modified properties.
  • sexual functional groups include: depositing a gas phase carbon source on the surface of the silicon-based active material through vapor deposition under a protective atmosphere to obtain a composite, and using modified gas to make the connection layer on the surface of the composite have modified properties.
  • Sexual functional groups are examples of a gas phase carbon source on the surface of the silicon-based active material through vapor deposition under a protective atmosphere to obtain a composite, and using modified gas to make the connection layer on the surface of the composite have modified properties.
  • the heating rate of vapor deposition is 1°C/min-20°C/min, for example, it can be 1°C/min, 3°C/min, 5°C/min, 8°C/min, 10°C/min, 15°C/min or 20°C/min, there is no limit here.
  • the temperature of vapor deposition ranges from 600°C to 1000°C, specifically 400°C, 500°C, 600°C, 700°C, 800°C or 1000°C.
  • the gas phase carbon source includes at least one of acetylene, methane, toluene, cyclohexane, ethanol, ethylene, and propylene.
  • the concentration of the gas phase carbon source is 0.1L/min to 10L/min, specifically 0.1L/min, 1L/min, 3L/min, 5L/min, 8L/min or 10L/min. This is not a limitation.
  • the holding time of vapor deposition is 1 h to 48 h, specifically, it may be 1 h, 2 h, 4 h, 6 h, 8 h, 12 h, 18 h, 24 h or 48 h, which is not limited here.
  • the modifying gas includes at least one of oxygen, water vapor, ammonia, hydrogen sulfide, phosphine, hydrogen chloride, hydrogen fluoride, hydrogen bromide, nitric oxide, sulfur dioxide, and chlorine.
  • the flow rate of the modified gas is 0.5L/min ⁇ 5L/min, specifically it can be 0.5L/min, 1L/min, 2L/min, 3L/min, 4L/min or 5L/min, where Not limited.
  • the introduction time of the modified gas is 0.5h to 10h, specifically it can be 0.5h, 2h, 4h, 6h, 8h or 10h, which is not limited here.
  • the modifying functional group is selected from at least one of carboxyl, carbonyl, hydroxyl, epoxy, nitrogen-containing functional groups, sulfur-containing functional groups, halogen element-containing functional groups and derivative functional groups thereof.
  • the protective atmosphere includes at least one of helium, neon, argon, krypton, and xenon.
  • the volume ratio of the protective atmosphere to the gas phase carbon source is 10: (0.5 ⁇ 10), specifically 10:0.5, 10:1, 10:2, 10:3, 10:4, 10:5 , 10:7, 10:8, 10:9 or 10:10, there is no limit here.
  • the volume ratio of the protective atmosphere to the modified gas is 10: (0.1 ⁇ 10), specifically 10:0.1, 10:1, 10:2, 10:3, 10:4, 10:5 , 10:7, 10:8, 10:9 or 10:10, there is no limit here.
  • step S10 includes: depositing a vapor phase carbon source on the surface of the silicon-based active material through vapor deposition under a protective atmosphere to obtain a composite; dispersing the composite in a first layer containing a first modifier.
  • a vapor phase carbon source on the surface of the silicon-based active material through vapor deposition under a protective atmosphere to obtain a composite
  • dispersing the composite in a first layer containing a first modifier.
  • solid-liquid separation, drying, and heat treatment are performed to obtain the first precursor.
  • the first modifier includes an anionic surfactant.
  • the first modifier includes cetyltrimethylammonium bromide, sodium cetyl sulfate, At least one of polyvinylpyrrolidone and sodium polystyrene sulfonate.
  • the mass ratio of the complex to the first modifier in the first modification solution is 1: (0.05 ⁇ 1), specifically it can be 1:0.05, 1:0.1, 1:0.2, 1: 0.4, 1:0.5, 1:0.7, 1:0.8, 1:0.9 or 1:1, there is no limit here.
  • the first modification solution includes a polar solvent.
  • the polar solvent includes at least one of water, absolute ethanol, methanol, and isopropyl alcohol.
  • the dispersion method includes at least one of mechanical stirring and ultrasonic dispersion.
  • solid-liquid separation includes at least one of centrifugation, normal pressure filtration, and negative pressure filtration.
  • the drying temperature is 60°C to 200°C, specifically 60°C, 80°C, 100°C, 120°C, 150°C, 180°C or 200°C, which is not limited here.
  • using the first modifier to form the connecting layer with modified functional groups also includes subjecting the dried product to heat treatment, the heat treatment temperature is 600°C to 900°C, and the heat treatment time is 1h to 6h.
  • step S10 includes spray drying a mixed coating liquid containing a silicon-based active material and a polymer, so that a connecting layer is formed on the surface of the silicon-based active material, and the connecting layer includes the polymer.
  • the solid content of the silicon-based active material in the mixed coating liquid is 5% to 50%
  • the mixed coating fluid includes polar solvents.
  • the polar solvent includes at least one of water, absolute ethanol, methanol, and isopropyl alcohol.
  • the mass ratio of the silicon-based active material to the polymer is 10: (0.1-5), specifically 10:0.1, 10:1, 10:2, 10:3, 10:4 or 10: 5. No limitation is made here.
  • the drying temperature of spray drying is 60°C to 200°C; specifically, it can be 60°C, 80°C, 100°C, 120°C, 150°C, 180°C or 200°C, which is not limited here.
  • the polymer includes at least one of a diblock copolymer, a triblock copolymer, and a multiblock copolymer;
  • the polymers include polyacrylic acid, polyacrylonitrile, polyimide, polyurethane, polydopamine, xanthan gum, polypyrrole, polythiophene, polyphenylene vinylene, polyaniline, polyacetylene, and tannic acid. at least one of;
  • the polymer has modifying functional groups, and the modifying functional groups are selected from at least one of carboxyl groups, carbonyl groups, hydroxyl groups, epoxy groups, nitrogen-containing functional groups, sulfur-containing functional groups, halogen element-containing functional groups and derivative functional groups thereof.
  • the buffer layer material before S20, it also includes: dispersing the buffer layer material in a second modification solution containing a second modifier for modification treatment, solid-liquid separation, and drying to obtain a buffer layer with surface functional groups. Material.
  • the second modifier includes a cationic surfactant.
  • the second modifier includes at least one of polydiallyldimethylammonium chloride, aminopropyltriethoxysilane, and a silane coupling agent;
  • the mass ratio of the buffer layer material to the second modifier in the second modification solution is 1: (0.5-10); specifically, it can be 1:0.5, 1:0.1, 1:2, 1 :3, 1:4, 1:5, 1:6, 1:8 or 1:10 etc.
  • the second modification solution includes a polar solvent.
  • the polar solvent includes at least one of water, absolute ethanol, methanol, and isopropyl alcohol.
  • solid-liquid separation includes at least one of centrifugation, normal pressure filtration, and negative pressure filtration.
  • the drying temperature is 60°C to 200°C, specifically 60°C, 80°C, 100°C, 120°C, 150°C, 180°C or 200°C, which is not limited here.
  • the dispersion method includes at least one of mechanical stirring and ultrasonic dispersion.
  • the buffer layer material can be connected to the connection layer on the surface of the silicon-based active material through self-assembly, electrostatic adsorption or spray granulation coating.
  • the mass ratio of the first precursor to the buffer layer material with surface functional groups is 1: (0.01 ⁇ 2), specifically it can be 1:0.01, 1:0.02, 1:0.05, 1:0.08, 1:0.1, 1:0.2, 1:0.5, 1:0.8, 1:1, 1:1.5 or 1:2 etc.
  • the mass ratio of the first precursor to the buffer layer material having surface functional groups is 1: (0.01-1).
  • the solid content of the first precursor in the mixed slurry is 2% to 50%; specifically, it can be 2%, 5%, 8%, 10%, 15%, 20%, 30%, 40% % or 50%, etc., are not limited here.
  • the solid content of the buffer layer material with surface functional groups in the mixed slurry is 0.5% to 25%; specifically, it can be 0.5%, 2%, 5%, 8%, 10%, 15%, 18% %, 20% or 25%, etc., are not limited here.
  • the buffer layer material includes hollow carbon material
  • the hollow carbon material includes at least one of hollow carbon spheres, hollow carbon rods, and hollow carbon tubes.
  • the solid content in the mixed slurry is 5% to 60%, specifically 5%, 2%, 6%, 10%, 20%, 30%, 40%, 50% or 60%, etc. , no limitation is made here.
  • the mass ratio of the first precursor to the active agent in the mixed slurry is 1: (0.1-0.5); specifically, it can be 1:0.1, 1:0.2, 1:0.3, 1:0.4 or 1 :0.5 etc.
  • the mixed slurry is further subjected to dispersion and centrifugation, and the dispersion method includes at least one of mechanical stirring and ultrasonic dispersion.
  • the mixed slurry further includes an active agent selected from the group consisting of polydiallyldimethylammonium chloride, aminopropyltriethoxysilane, silane coupling agent, cetyltrimethyl At least one of ammonium bromide, sodium cetyl sulfate, polyvinylpyrrolidone and sodium polystyrene sulfonate.
  • an active agent selected from the group consisting of polydiallyldimethylammonium chloride, aminopropyltriethoxysilane, silane coupling agent, cetyltrimethyl At least one of ammonium bromide, sodium cetyl sulfate, polyvinylpyrrolidone and sodium polystyrene sulfonate.
  • the mixed slurry further includes a solvent, and the solvent is selected from at least one of water, absolute ethanol, methanol, and isopropyl alcohol.
  • the drying method is spray drying.
  • the temperature of spray drying is 100°C to 200°C; specifically it can be 100°C, 110°C, 120°C, 150°C, 170°C, 180°C or 200°C, which is not limited here.
  • the feed rate of spray drying is 100mL/min-1000mL/min, specifically it can be 100mL/min, 200mL/min, 300mL/min, 400mL/min, 600mL/min, 800mL/min or 1000mL/min. min, etc., are not limited here.
  • the coating process includes carbon coating and/or polymer coating.
  • coating treatment can be performed by vapor deposition, liquid phase coating, organic matter pyrolysis, etc.
  • the step of carbon coating the second precursor includes: introducing a gas phase carbon source into the second precursor, and heating the gas phase carbon source until a thermal cracking reaction occurs, so that the surface of the second precursor
  • the deposition forms a protective layer, and the protective layer includes at least one of an amorphous carbon material and a graphitized carbon material.
  • the gas phase carbon source includes at least one of acetylene, methane, toluene, cyclohexane, ethanol, ethylene, and propylene.
  • the heating rate is 1°C/min to 20°C/min, specifically 1°C/min, 2°C/min, 3°C/min, 4°C/min, 5°C/min, or 8°C/min. °C/min, 10°C/min, 12°C/min, 15°C/min, 18°C/min, 20°C/min.
  • the heating rate is 3°C/min to 5°C/min. The applicant found through multiple experiments that controlling the heating rate at 3°C/min to 5°C/min can effectively ensure the progress of the carbonization reaction and shorten the time for heating to the preset temperature range.
  • the temperature of the thermal cracking reaction is 600°C to 1000°C.
  • the reaction temperature can be 600°C, 650°C, 700°C, 750°C, 800°C, 890°C, 900°C, 960°C or 1000°C. °C.
  • the applicant found through many experiments that controlling the reaction temperature within 600°C to 1000°C can improve the reaction efficiency and form a uniform carbon layer on the surface of the second precursor.
  • the carbon layer can be amorphous carbon.
  • the reaction temperature is 700°C to 900°C.
  • the holding time of the thermal cracking reaction is 1h to 48h; specifically, it can be 1h, 4h, 8h, 12h, 16h, 24h, 28h, 32h, 38h or 48h, which is not limited here.
  • the concentration of the gas phase carbon source is 0.1L/min ⁇ 10L/min; specifically, it can be 0.1L/min, 0.4L/min, 0.6L/min, 0.8L/min, 1.0L/min, 2L /min, 5L/min, 6L/min, 8L/min, 9L/min or 10L/min, etc., are not limited here.
  • the thermal cracking reaction is performed under a protective atmosphere.
  • the protective atmosphere includes at least one of helium, neon, argon, krypton, and xenon.
  • the volume ratio of the protective atmosphere to the gas phase carbon source is 10: (0.5 ⁇ 10), specifically 10:0.5, 10:1, 10:2, 10:3, 10:5, 10:6.5 , 10:7.5, 10:8.5, 10:9 or 10:10, etc., there is no limit here.
  • the step of subjecting the second precursor to polymer coating includes spray drying a mixed coating liquid containing the second precursor and the polymer, so that a protective layer is formed on the surface of the second precursor.
  • the protective layer includes polymer.
  • the solid content of the second precursor in the mixed coating liquid is 5% to 50%, specifically 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45% or 50%, etc., are not limited here.
  • the mixed coating fluid includes polar solvents.
  • the polar solvent includes at least one of water, absolute ethanol, methanol, and isopropyl alcohol.
  • the mass ratio of the second precursor to the polymer is 10: (0.1-5), specifically 10:0.1, 10:1, 10:2, 10:3, 10:4 or 10: 5. No limitation is made here.
  • the drying temperature of spray drying is 60°C to 200°C, specifically 60°C, 80°C, 100°C, 120°C, 150°C, 180°C or 200°C.
  • the polymer includes at least one of a diblock copolymer, a triblock copolymer, and a multiblock copolymer.
  • the polymers include polyacrylic acid, polyacrylonitrile, polyimide, polyurethane, polydopamine, xanthan gum, polypyrrole, polythiophene, polyphenylene vinylene, polyaniline, polyacetylene, and tannic acid. of at least one.
  • Embodiments of the present application also provide a secondary battery, using the negative electrode material provided in the above embodiments of the present application or the negative electrode material prepared by using the preparation method of the negative electrode material provided in the above embodiments of the present application.
  • the secondary battery may be a lithium-ion battery, a sodium-ion battery, etc.
  • the lithium-ion battery provided in the embodiment of the present application has the advantages of high capacity, high first efficiency, long cycle life, excellent rate performance, and low expansion.
  • a preparation method of negative electrode material including the following steps:
  • the negative electrode material prepared in this embodiment has a core-shell structure.
  • the core includes silicon.
  • the outer shell includes a connecting layer, a buffer layer and a protective layer.
  • the connecting layer is an amorphous carbon material layer, and the amorphous carbon material layer is coated on the silicon particles.
  • the buffer layer includes hollow carbon balls
  • the protective layer is a polymer layer (polyacrylic acid)
  • the buffer layer is filled between the connection layer and the protective layer
  • the amorphous carbon material layer and the buffer layer The hollow carbon spheres are connected by covalent bonds (carbon-nitrogen bonds).
  • the median particle size of the negative electrode material is 2.5 ⁇ m, the specific surface area is 5m 2 /g, the powder tap density is 0.9g/cm 3 , and the powder compaction density is 1.65g/cm 3 .
  • the oxygen element in the negative electrode material is The mass content is 5%, the mass content of carbon element in the negative electrode material is 25%, the thickness of the connecting layer is 50nm, the thickness of the buffer layer is 500nm, the thickness of the protective layer is 30nm, and the mass content of the protective layer in the negative electrode material is 5%.
  • Figure 4 is a scanning electron microscope picture of the negative electrode material in this embodiment; the surface of the negative electrode material has a spherical carbon structure and is wrapped with a dense carbon layer on the surface.
  • Figure 5 is the XRD pattern of the anode material of this embodiment. As shown in Figure 5, it can be seen from the XRD pattern of the anode material that three strong peaks at 28.4°, 47.3° and 56.1° are related to silicon (JCPDS No. 27-1402 ) correspond to the three strong peaks, and there is basically no impurity phase.
  • Figure 6 is the cycle performance curve of the anode material of this embodiment. As shown in Figure 6, the material has excellent cycle performance.
  • the charge and discharge current is 1000mA/g. It has a capacity of 1068mAh/g after 500 cycles at 0.25C current. The capacity retention rate reaches 81%.
  • a preparation method of negative electrode material including the following steps:
  • the negative electrode material prepared in this embodiment has a core-shell structure.
  • the core includes silicon.
  • the outer shell includes a connecting layer, a buffer layer and a protective layer.
  • the connecting layer is an amorphous carbon material layer, and the amorphous carbon material layer is coated on the silicon particles.
  • the buffer layer includes hollow carbon balls
  • the protective layer is a polymer layer (polyacrylonitrile)
  • the buffer layer is filled between the connection layer and the protective layer
  • the amorphous carbon material layer and the buffer layer The hollow carbon spheres in the layers are connected by covalent bonds (carbon-sulfur bonds).
  • the median particle size of the obtained silicon carbon negative electrode material is 2.8 ⁇ m, the specific surface area is 2 m 2 /g, the powder tap density is 1.0 g/cm 3 , and the powder compaction density is 1.5 g/cm 3 .
  • the mass content of oxygen element in the negative electrode material is 4%, the mass content of carbon element in the negative electrode material is 30%, the thickness of the connecting layer is 60nm, the thickness of the buffer layer is 800nm, the thickness of the protective layer is 20nm, the mass of the protective layer in the negative electrode material Content is 8%.
  • the negative electrode material prepared in this embodiment has a core-shell structure.
  • the core includes silicon.
  • the outer shell includes a connecting layer, a buffer layer and a protective layer.
  • the connecting layer is an amorphous carbon material layer, and the amorphous carbon material layer is coated on the silicon particles. surface, buffer layer It includes a hollow carbon tube, the protective layer is a polymer layer (polytannic acid), the buffer layer is filled between the connection layer and the protective layer, and the amorphous carbon material layer and the hollow of the buffer layer
  • the carbon spheres are connected by covalent bonds (carbon-chlorine bonds).
  • the negative electrode material prepared in this embodiment has a core-shell structure.
  • the core includes silicon.
  • the outer shell includes a connecting layer and a protective layer.
  • the connecting layer is an amorphous carbon material layer.
  • the protective layer includes polytannic acid and polytannic acid dispersed in the polytannic acid. Hollow carbon tube.
  • the median particle size of the negative electrode material is 4.5 ⁇ m, the specific surface area is 8m 2 /g, the powder tap density is 1.1g/cm 3 , and the powder compacted density is 1.7g/cm 3 .
  • the mass content of oxygen element is 7%
  • the mass content of carbon element in the negative electrode material is 35%
  • the thickness of the connecting layer is 60nm
  • the thickness of the buffer layer is 700nm
  • the thickness of the protective layer is 45nm
  • the mass content of the protective layer in the negative electrode material is 15% .
  • (1) Put silicon with a median particle size of 2 ⁇ m into a rotating atmosphere furnace, and under the protection of an argon atmosphere, heat it to 900°C at a heating rate of 3°C/min, and then pass in 0.5L/min acetylene gas. Make the volume ratio of argon to acetylene in the rotating atmosphere furnace 9:1. After 3 hours of heat preservation, turn off the acetylene gas and introduce 1.5L/min ammonia, so that the volume ratio of argon to ammonia in the rotating atmosphere furnace is 4:1, turn off the ammonia gas after 3 hours of heat preservation, and cool to obtain the first precursor.
  • the negative electrode material prepared in this embodiment has a core-shell structure.
  • the core includes silicon.
  • the outer shell includes a connecting layer, a buffer layer and a protective layer.
  • the connecting layer is an amorphous carbon material layer, and the amorphous carbon material layer is coated on the silicon particles.
  • the buffer layer includes hollow carbon tubes
  • the protective layer is a polymer layer (polyacrylic acid)
  • the buffer layer is filled between the connection layer and the protective layer
  • the amorphous carbon material layer and the buffer layer The hollow carbon spheres are connected by covalent bonds (carbon-nitrogen bonds).
  • the negative electrode material prepared in this embodiment has a core-shell structure.
  • the core includes silicon.
  • the outer shell includes a connecting layer and a protective layer.
  • the connecting layer is an amorphous carbon material layer.
  • the protective layer includes polyacrylic acid and hollow carbon tubes dispersed in the polyacrylic acid.
  • the median particle size of the negative electrode material is 3.5 ⁇ m, the specific surface area is 15m 2 /g, the powder tap density is 0.88g/cm 3 , and the powder compaction density is 1.36g/cm 3 .
  • the oxygen element in the negative electrode material is The mass content is 11%, the mass content of carbon element in the negative electrode material is 21%, the thickness of the connecting layer is 50nm, the thickness of the buffer layer is 300nm, the thickness of the protective layer is 33nm, and the mass content of the protective layer in the negative electrode material is 5%.
  • (1) Put silicon with a median particle size of 3 ⁇ m into a rotating atmosphere furnace, and under the protection of an argon atmosphere, heat it to 800°C at a heating rate of 5°C/min, and then pass in 0.5L/min acetylene gas. Make the volume ratio of argon to acetylene in the rotating atmosphere furnace 9:1. After 3 hours of heat preservation, turn off the acetylene gas and introduce 2.5L/min ammonia, so that the volume ratio of argon to ammonia in the rotating atmosphere furnace is 6:1, after 3 hours of heat preservation, turn off the ammonia gas and cool to obtain the first precursor;
  • the negative electrode material prepared in this embodiment has a core-shell structure.
  • the core includes silicon.
  • the outer shell includes a connecting layer, a buffer layer and a protective layer.
  • the connecting layer is an amorphous carbon material layer, and the amorphous carbon material layer is coated on the silicon particles.
  • the buffer layer includes hollow carbon tubes
  • the protective layer is a polymer layer (polyacrylonitrile)
  • the buffer layer is filled between the connection layer and the protective layer
  • the amorphous carbon material layer is in contact with the buffer layer.
  • the hollow carbon spheres in the layers are connected by covalent bonds (carbon-nitrogen bonds).
  • the negative electrode material prepared in this embodiment has a core-shell structure.
  • the core includes silicon.
  • the outer shell includes a connecting layer and a protective layer.
  • the connecting layer is an amorphous carbon material layer.
  • the protective layer includes polyacrylonitrile and hollow carbon dispersed in the polyacrylonitrile. Tube.
  • the obtained silicon carbon anode material has a median particle size of 5 ⁇ m, a specific surface area of 19 m 2 /g, a powder tap density of 0.98 g/cm 3 and a powder compaction density of 1.4 g/cm 3.
  • the negative electrode The mass content of oxygen element in the material is 23%, the mass content of carbon element in the negative electrode material is 29%, the thickness of the connecting layer is 66nm, the thickness of the buffer layer is 200nm, the thickness of the protective layer is 25nm, the mass content of the protective layer in the negative electrode material is 5%.
  • (1) Put silicon with a median particle size of 6 ⁇ m into a rotating atmosphere furnace, and under the protection of an argon atmosphere, heat it to 900°C at a heating rate of 3°C/min, and then pass in 0.5L/min acetylene gas. Make the volume ratio of argon to acetylene in the rotating atmosphere furnace 9:1. After 3 hours of heat preservation, turn off the acetylene gas and introduce 3.5L/min of hydrogen fluoride so that the volume ratio of argon to hydrogen fluoride in the rotating atmosphere furnace is 2: 1. After keeping the temperature for 8 hours, turn off the hydrogen fluoride and cool it to obtain the first precursor.
  • the negative electrode material prepared in this embodiment has a core-shell structure.
  • the core includes silicon.
  • the outer shell includes a connecting layer and a protective layer.
  • the connecting layer is an amorphous carbon material layer.
  • the connecting layer covers the surface of the silicon particles.
  • the protective layer includes a non-crystalline carbon material layer. Crystalline carbon materials and hollow carbon tubes dispersed in amorphous carbon materials. The amorphous carbon material layer and the hollow carbon tubes are connected by covalent bonds (carbon-fluorine bonds).
  • the median particle size of the negative electrode material is 8 ⁇ m, the specific surface area is 11m 2 /g, the powder tap density is 0.98g/cm 3 , the powder compaction density is 1.3g/cm 3 , and the mass of oxygen element in the negative electrode material
  • the content is 8%, the mass content of carbon element in the negative electrode material is 32%, the thickness of the connecting layer is 50nm, the thickness of the protective layer is 350nm, and the mass content of the protective layer in the negative electrode material is 14%.
  • step (1) is not modified with ammonia gas.
  • step (1) is not modified with ammonia gas.
  • the negative electrode material prepared in this embodiment has a core-shell structure.
  • the core includes silicon.
  • the outer shell includes a connecting layer, a buffer layer and a protective layer.
  • the connecting layer is an amorphous carbon material layer, and the amorphous carbon material layer is coated on the silicon particles.
  • the buffer layer includes hollow carbon balls
  • the protective layer is a polymer layer (polyacrylic acid)
  • the buffer layer is filled between the connection layer and the protective layer
  • the amorphous carbon material layer and the buffer layer The hollow carbon spheres are connected by covalent bonds (carbon-nitrogen bonds).
  • the median particle size of the negative electrode material is 2.2 ⁇ m, the specific surface area is 4.8m 2 /g, the powder tap density is 0.92g/cm 3 , the powder compacted density is 1.59g/cm 3 , and the oxygen element in the negative electrode material
  • the mass content of the carbon element in the negative electrode material is 7%, the mass content of the carbon element in the negative electrode material is 23%, the thickness of the connecting layer is 60nm, the thickness of the buffer layer is 550nm, the thickness of the protective layer is 50nm, and the mass content of the protective layer in the negative electrode material is 5.2%.
  • Example 1 The preparation steps are the same as those in Example 1. The only difference from Example 1 is that SiO is used as the silicon-based active material.
  • the negative electrode material prepared in this embodiment has a core-shell structure.
  • the core includes SiO.
  • the outer shell includes a connecting layer, a buffer layer and a protective layer.
  • the connecting layer is an amorphous carbon material layer, and the amorphous carbon material layer is coated on the silicon particles.
  • the buffer layer includes hollow carbon balls
  • the protective layer is a polymer layer (polyacrylic acid)
  • the buffer layer is filled between the connection layer and the protective layer
  • the amorphous carbon material layer and the buffer layer The hollow carbon spheres are connected by covalent bonds (carbon-nitrogen bonds).
  • the median particle size of the negative electrode material is 2.6 ⁇ m, the specific surface area is 5.3m 2 /g, the powder tap density is 0.97g/cm 3 , and the powder compaction density is 1.64g/cm 3 .
  • the oxygen element in the negative electrode material The mass content of the carbon element in the negative electrode material is 19%, the mass content of the carbon element in the negative electrode material is 22%, the thickness of the connecting layer is 54nm, the thickness of the buffer layer is 500nm, the thickness of the protective layer is 40nm, and the mass content of the protective layer in the negative electrode material is 8%.
  • Example 1 The preparation steps are the same as those in Example 1. The only difference from Example 1 is that lithium-silicon alloy is used as the silicon-based active material.
  • the negative electrode material prepared in this embodiment has a core-shell structure.
  • the core includes a lithium-silicon alloy.
  • the outer shell includes a connecting layer, a buffer layer and a protective layer.
  • the connecting layer is an amorphous carbon material layer, and the amorphous carbon material layer is coated on the silicon.
  • the buffer layer includes hollow carbon spheres
  • the protective layer is a polymer layer (polyacrylic acid)
  • the buffer layer is filled between the connection layer and the protective layer
  • the amorphous carbon material layer and the The hollow carbon spheres in the buffer layer are connected by covalent bonds (carbon-nitrogen bonds).
  • the median particle size of the negative electrode material is 3.1 ⁇ m, the specific surface area is 6.1m 2 /g, the powder tap density is 1.01g/cm 3 , the powder compacted density is 1.72g/cm 3 , and the oxygen element in the negative electrode material
  • the mass content of the negative electrode material is 12%, the mass content of the carbon element in the negative electrode material is 28%, the thickness of the connecting layer is 50nm, the thickness of the buffer layer is 600nm, the thickness of the protective layer is 60nm, and the mass content of the protective layer in the negative electrode material is 8.5%.
  • the negative electrode material prepared in this embodiment has a core-shell structure.
  • the core includes silicon.
  • the outer shell includes a connecting layer, a buffer layer and a protective layer.
  • the connecting layer is a graphitized carbon material layer, where the graphitized carbon material includes graphene.
  • Graphitized carbon The material layer covers the surface of the silicon particles, the buffer layer includes hollow carbon spheres, the protective layer is a polymer layer (polyacrylic acid), and the buffer layer is filled between the connection layer and the protective layer, The graphitized carbon material layer and the hollow carbon spheres of the buffer layer are connected through covalent bonds (carbon-nitrogen bonds).
  • the median particle size of the negative electrode material is 2.4 ⁇ m, the specific surface area is 5.6m 2 /g, the powder tap density is 0.88g/cm 3 , and the powder compaction density is 1.63g/cm 3 .
  • the oxygen element in the negative electrode material The mass content of the carbon element in the negative electrode material is 4.6%, the mass content of the carbon element in the negative electrode material is 22%, the thickness of the connecting layer is 5nm, the thickness of the buffer layer is 500nm, the thickness of the protective layer is 30nm, and the mass content of the protective layer in the negative electrode material is 5%.
  • (1) Put silicon with a median particle size of 6 ⁇ m into a solution of 0.1 mol/L triblock copolymer P123 (polyethylene oxide-polypropylene oxide-polyethylene oxide), and the silicon and polymerization
  • the mass ratio of substance P123 is 10:1.
  • the solid content in the mixed coating liquid is 40%.
  • the slurry is dried by spray drying at 100°C to obtain the first precursor.
  • a precursor includes silicon and a polymer connection layer covering the silicon surface.
  • the polyethylene oxide-polypropylene oxide-polyethylene oxide used in this step itself has phenolic hydroxyl, carboxyl and carbonyl modified functional groups.
  • the negative electrode material prepared in this embodiment has a core-shell structure.
  • the core includes silicon.
  • the outer shell includes a connecting layer, a buffer layer and a protective layer.
  • the connecting layer is a polymer layer.
  • the polymer layer covers the surface of the silicon particles.
  • the buffer layer It includes hollow carbon balls, the protective layer is a polymer layer (polyacrylic acid), the buffer layer is filled between the connection layer and the protective layer, and the hollow carbon balls between the polymer layer and the buffer layer Connected by covalent bonds (carbon-oxygen bonds).
  • the negative electrode material prepared in this embodiment has a core-shell structure, the core includes silicon, and the outer shell includes a connecting layer and a protective layer.
  • the connecting layer is a polymer layer, and the protective layer includes polyacrylic acid and hollow carbon spheres dispersed in polyacrylic acid.
  • the median particle size of the negative electrode material is 2.6 ⁇ m, the specific surface area is 5.7m 2 /g, the powder tap density is 0.89g/cm 3 , and the powder compaction density is 1.61g/cm 3 .
  • the oxygen element in the negative electrode material The mass content of the carbon element in the negative electrode material is 4.9%, the mass content of the carbon element in the negative electrode material is 27%, the thickness of the connecting layer is 20nm, the thickness of the buffer layer is 500nm, the thickness of the protective layer is 30nm, and the mass content of the protective layer in the negative electrode material is 5%.
  • the negative electrode material prepared in this comparative example includes silicon element, a buffer layer and a protective layer covering the surface of the silicon element.
  • the buffer layer is hollow carbon spheres
  • the protective layer is polypropylene, and there is no connecting layer on the surface of the silicon element.
  • the median particle size of the negative electrode material is 2.2 ⁇ m, the specific surface area is 8.5m 2 /g, the powder tap density is 0.8g/cm 3 , and the powder compaction density is 1.1g/cm 3 .
  • the mass content of oxygen element is 25%, the mass content of carbon element in the negative electrode material is 15%, the thickness of the buffer layer is 500nm, and the mass content of the protective layer in the negative electrode material is 3%.
  • the negative electrode material prepared in this embodiment has a core-shell structure.
  • the core includes silicon.
  • the outer shell includes a connecting layer, a buffer layer and a protective layer.
  • the connecting layer is an amorphous carbon material layer, and the amorphous carbon material layer is coated on the silicon particles.
  • the buffer layer includes hollow carbon balls
  • the protective layer is a polymer layer (polyacrylic acid), and the buffer layer is filled between the connection layer and the protective layer.
  • the median particle size of the negative electrode material is 2.9 ⁇ m, the specific surface area is 9m 2 /g, the powder tap density is 0.8g/cm 3 , and the powder compaction density is 1.5g/cm 3 .
  • the oxygen element in the negative electrode material is The mass content is 12%, the mass content of carbon element in the negative electrode material is 20%, the thickness of the connecting layer is 10nm, the thickness of the buffer layer is 400nm, the thickness of the protective layer is 40nm, and the mass content of the protective layer in the negative electrode material is 22%.
  • the median particle size test method refers to GB/T 19077-2016. It can be easily measured with a laser particle size analyzer, such as the Mastersizer 3000 laser particle size analyzer of Malvern Instruments Co., Ltd. in the UK.
  • the sample monolayer adsorption amount is calculated based on the Brownauer-Etter-Taylor adsorption theory and its formula (BET formula), and then calculated The specific surface area of the material.
  • thermogravimetric analysis was used to test carbon content.
  • the dimensions of the hollow carbon materials were measured using atomic force microscopy (AFM) and high-power transmission microscopy (HRTEM).
  • connection layer and protective layer was measured in the SEM.
  • the maximum pulling force (F) required for a single hollow carbon material to detach from the connection layer is measured through the nanomechanical testing system and the probe testing system.
  • the bonding strength at 5 positions is tested, and the average value is calculated. .
  • the sample numbers of the negative electrode materials prepared in Examples 1 to 11 and Comparative Examples 1 to 2 correspond to S1 to S11 and R1 to R2; the performance parameters of the negative electrode materials are as described in Table 1:
  • the negative electrode sheet is made by drying on the top, and is assembled into a button battery in an argon atmosphere glove box.
  • the separator used is a polypropylene microporous membrane, and the electrolyte used is 1 mol/L lithium hexafluorophosphate (the solvent is a volume ratio of 1:1:1
  • the counter electrode used is a metal lithium sheet.
  • the above 13 groups of batteries were tested on the discharge specific capacity on the Blue Power CT2001A battery testing system.
  • the battery was discharged from the open circuit voltage to a voltage of 0.01V at 0.01C, and the specific capacity it had was the discharge specific capacity.
  • the above 13 sets of batteries were tested for the first time on the Blue Power CT2001A battery test system.
  • the charge and discharge current was 0.05C, and the first Coulomb efficiency was measured.
  • the above 13 groups of batteries were tested for 100 cycles on the Blue Power CT2001A battery testing system.
  • the charge and discharge current was 0.2C.
  • the battery capacity and the capacity retention rate after the cycle were calculated.
  • the negative electrode material of the present application has the advantages of low expansion and excellent cycle stability.
  • the negative electrode materials prepared in Examples 1 to 11 are formed by forming a connecting layer with modified functional groups on the surface of the silicon-based active material, and then polymerizing the hollow carbon material with surface functional groups and the first precursor. , so that the connection layer and the hollow carbon material are connected through covalent bonds, which can greatly improve the bonding strength between the hollow carbon material and the connection layer, effectively tightly connect the connection layer and the hollow carbon material, and ensure excellent electrical contact after volume expansion; the formed
  • the protective layer further enhances the conductivity and structural integrity of the negative electrode material, and can effectively inhibit side reactions caused by contact with the electrolyte. It helps the negative electrode material maintain excellent mechanical properties, improves the structural stability of the negative electrode material, and thereby improves cycle stability.
  • connection layer was not modified.
  • the hollow carbon material could not be connected to the connection layer through covalent bonds.
  • the two were connected through intermolecular forces, and the connection stability decreased during the cycle.
  • the expansion stress of silicon particles easily causes the hollow carbon balls to disconnect from the silicon, the electrical contact decreases, the capacity retention rate of the material decreases, and the expansion rate increases significantly.

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Abstract

本申请涉及负极材料领域，提供负极材料及其制备方法、二次电池，其中，负极材料具有核壳结构，内核包括硅基活性物质，外壳包括连接层、缓冲层及保护层，所述连接层包覆于所述硅基活性物质的表面，所述缓冲层填充于所述连接层与所述保护层之间，所述连接层与所述缓冲层之间通过共价键连接。本申请的负极材料及其制备方法，低成本、可规模化生产，能降低负极材料的体积膨胀，提高负极材料的结构稳定性和循环稳定性。

Description

负极材料及其制备方法、二次电池
本申请要求于2022年6月27日提交中国专利局，申请号为2022107453416、申请名称为“复合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，涉及一种负极材料及其制备方法、二次电池。
背景技术
锂离子电池由于具备能量密度大、输出功率高、循环寿命长和环境污染小等优点而被广泛应用于电动汽车以及消费类电子产品中。为了提高电池能量密度，高容量的负极材料的研究和开发日趋成熟。然而这些负极材料与锂合金化过程体积膨胀较大，在充放电过程中会粉化从集流体上掉落，使得负极材料与集流体之间失掉电触摸，导致电化学性能变差，容量衰减、循环稳定性下降，难以得到商业应用。
申请内容
本申请提出了负极材料及其制备方法、二次电池，能降低体积膨胀、提高循环稳定性。
第一方面，本申请提供一种负极材料，所述负极材料具有核壳结构，内核包括硅基活性物质，外壳包括连接层、缓冲层及保护层，所述连接层包覆于所述硅基活性物质的表面，所述缓冲层填充于所述连接层与所述保护层之间，所述连接层与所述缓冲层之间通过共价键连接。
在上述方案中，通过在硅基活性物质的表面构建连接层、缓冲层及保护层，利用其协同作用，有效缓解硅基活性物质的体积膨胀，增强硅碳负极材料的结构稳定性，提升循环寿命；硅基活性物质表面的连接层，可以极大地提高材料的导电性，减少副反应发生，提升锂离子、电子传输通道，从而改善负极材料的导电性，提升材料倍率性能；填充在连接层与保护层之间的缓冲层，其与连接层通过共价键连接，减少在进行充放电过程因硅基活性物质发生体积膨胀导致缓冲层脱落，有利于负极材料保持优异的机械性能，提升负极材料的结构稳定性，进而提升循环稳定性。
本申请还提供一种负极材料，所述负极材料具有核壳结构，内核包括硅基活性物质，外壳包括连接层、缓冲层及保护层，所述连接层包覆于所述硅基活性物质的表面，所述缓冲层填充于所述连接层与所述保护层之间，所述连接层与所述缓冲层之间的平均结合力F＞8μN。
在上述方案中，通过在硅基活性物质的表面构建连接层、缓冲层及保护层，利用其协调作用，有效缓解硅基活性物质的体积膨胀，增强硅碳负极材料的结构稳定性， 提升循环寿命；硅基活性物质表面的连接层，可以极大地提高材料的导电性，减少副反应发生，提升锂离子、电子传输通道，从而改善负极材料的导电性，提升材料倍率性能；填充在连接层与保护层之间的缓冲层，其与连接层之间的平均结合力大于8μN，在循环过程中，缓冲层不容易与连接层脱落，有利于负极材料保持优异的机械性能，提升负极材料的结构稳定性，进而提升循环稳定性。
本申请还提供一种负极材料，所述负极材料具有核壳结构，内核包括硅基活性物质，外壳包括连接层及保护层，所述连接层包覆于所述硅基活性物质的表面，所述保护层包括导电基材及分散于所述导电基材中的空心碳材料，所述连接层与所述空心碳材料之间的平均结合力F＞8μN。
在上述方案中，通过在硅基活性物质的表面构建连接层及保护层，利用其协同作用，有效缓解硅基活性物质的体积膨胀，增强硅碳负极材料的结构稳定性，提升循环寿命；硅基活性物质表面的连接层，可以极大地提高材料的导电性，减少副反应发生，提升锂离子、电子传输通道，从而改善负极材料的导电性，提升材料倍率性能；保护层中的导电基材能够提高材料的导电性，分散于导电基材中的空心碳材料能够缓冲硅基活性物质的体积膨胀，并且空心碳材料与连接层之间的平均结合力大于8μN，在循环过程中，空心碳材料不容易与连接层脱落，从而能够提高保护层与连接层的连接稳定性，有利于负极材料保持优异的机械性能，提升负极材料的整体结构稳定性，进而提升循环稳定性。
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：
在硅基活性物质的表面形成连接层，所述连接层具有改性官能团，得到第一前驱体；
将包含所述第一前驱体与具有表面官能团的缓冲层材料的混合浆料进行聚合反应，干燥得到第二前驱体；及
对所述第二前驱体进行包覆处理，得到负极材料。
在上述方案中，通过在硅基活性物质表面形成具有改性官能团的连接层，然后将具有表面官能团的缓冲层材料与第一前驱体进行聚合反应，使得连接层与缓冲层材料通过共价键连接，可以大幅提高缓冲层材料与连接层的结合强度，有效把连接层与缓冲层材料紧密连接，确保体积膨胀后能保证优异电接触；最后在缓冲层上进行包覆处理，形成的保护层进一步加强了负极材料的导电性和结构完整性，可以有效抑制与电解液接触发生副反应。通过本申请方法制得的负极材料，依靠缓冲层材料的高强度以及高韧性，结合连接层、缓冲层和保护层对硅基活性物质进行协同作用，可以有效缓解硅的体积膨胀，改善硅负极的导电性，增强硅碳复合结构稳定性，进而提升这个硅负极材料的循环寿命和倍率性能。
第三方面，本申请提供一种二次电池，包括如第一方面所述的负极材料或根据第二方面所述负极材料的制备方法制备的负极材料。
相比于现有技术，本申请的技术方案至少具有以下技术效果：
本申请提供的负极材料，通过在硅基活性物质的表面构建连接层、缓冲层及保护层，利用其协调作用，有效缓解硅基活性物质的体积膨胀，增强硅碳负极材料的结构稳定性，提升循环寿命；硅基活性物质表面的连接层，可以极大地提高材料的导电性， 减少副反应发生，提升锂离子、电子传输通道，从而改善负极材料的导电性，提升材料倍率性能；填充在连接层与保护层之间的缓冲层，缓冲层与连接层通过共价键连接，或者缓冲层与连接层的平均结合力大于8μN，有利于负极材料保持优异的机械性能，提升负极材料的结构稳定性，进而提升循环稳定性。
本申请提供的负极材料，通过在硅基活性物质的表面构建连接层及保护层，利用其协同作用，有效缓解硅基活性物质的体积膨胀，增强硅碳负极材料的结构稳定性，提升循环寿命；硅基活性物质表面的连接层，可以极大地提高材料的导电性，减少副反应发生，提升锂离子、电子传输通道，从而改善负极材料的导电性，提升材料倍率性能；保护层中的导电基材能够提高材料的导电性，分散于导电基材中的空心碳材料能够缓冲硅基活性物质的体积膨胀，并且空心碳材料与连接层之间的平均结合力大于8μN，在循环过程中，空心碳材料不容易与连接层脱落，从而能够提高保护层与连接层的连接稳定性，防止在进行充放电过程因硅基活性物质发生体积膨胀导致缓冲层脱落，有利于负极材料保持优异的机械性能，提升负极材料的整体结构稳定性，进而提升循环稳定性。本申请提供的制备方法，通过在硅基活性物质表面形成具有改性官能团的连接层，然后将具有表面官能团的缓冲层材料与第一前驱体进行聚合反应，使得连接层与缓冲层材料通过共价键连接，可以大幅提高缓冲层材料与连接层的结合强度，有效把连接层与缓冲层材料紧密连接，确保体积膨胀后能保证优异电接触；最后在缓冲层上进行包覆处理，形成的保护层进一步加强了负极材料的导电性和结构完整性，可以有效抑制与电解液接触发生副反应。通过本申请方法制得的负极材料，依靠缓冲层中的空心碳材料的高强度以及高韧性，结合连接层、缓冲层和保护层对硅基活性物质进行协同作用，可以有效缓解硅的体积膨胀，改善硅负极的导电性，增强硅碳复合结构稳定性，进而提升这个硅负极材料的循环寿命和倍率性能。
附图说明
图1为本实施例提供的负极材料的结构示意图；
图2为本实施例提供的负极材料的另一结构示意图；
图3为本实施例提供的负极材料的制备方法的流程示意图；
图4为实施例1提供的负极材料的扫描电镜图片；
图5为实施例1提供的负极材料的拉曼图；
图6为实施例1提供的负极材料的循环性能曲线图。
具体实施方式
以下所述是本申请实施例的优选实施方式，应当指出，对于本技术领域的普通技术人员来说，在不脱离本申请实施例原理的前提下，还可以做出若干改进和润饰，这些改进和润饰也视为本申请实施例的保护范围。
目前，在锂离子电池中，负极材料是影响其充放电性能的关键材料之一，为了提高电池能量密度，高容量的负极材料的研究和开发日趋成熟。然而这些负极材料与锂合金化过程体积膨胀较大，负极材料在充放电过程中会粉化从集流体上掉落，使得负极材料与集流体之间失去电接触，导致电化学性能变差，容量衰减、循环稳定性下降， 难以得到商业应用。为了提高锂离子电池的循环稳定性，本申请实施例提供了一种膨胀低、稳定性好的负极材料。
本申请提供一种负极材料，如图1所示，负极材料具有核壳结构，内核包括硅基活性物质10，外壳包括连接层21、缓冲层22及保护层23，连接层21包覆于硅基活性物质10的表面，缓冲层22填充于连接层21与保护层23之间，连接层21与缓冲层22之间通过共价键连接。
在上述方案中，通过在硅基活性物质的表面构建连接层、缓冲层及保护层，利用其协调作用，有效缓解硅基活性物质的体积膨胀，增强硅碳负极材料的结构稳定性，提升循环寿命；硅基活性物质表面的连接层，可以极大地提高材料的导电性，减少副反应发生，提升锂离子、电子传输通道，从而改善负极材料的导电性，提升材料倍率性能；填充在连接层与保护层之间的缓冲层，其与连接层通过共价键连接，有利于负极材料保持优异的机械性能，提升负极材料的结构稳定性。
在一些实施方式中，共价键包括碳碳键(C-C、C＝C)、碳氧键(C-O、C＝O)、碳氮键(C-N)、碳硫键(C-S)、碳氯键(C-Cl)、氟碳键(C-F)、氮氧键(O-N)、氧硫键(O-S)、氧氯键(O-Cl)和氮硫键(N-S)中的至少一种。
在一些实施方式中，内核为硅基活性物质，硅基活性物质为一次颗粒。
在一些实施方式中，硅基活性物质包括Si、SiOx和硅合金中的至少一种，其中，0<x＜2；SiOx具体可以是SiO0.1、SiO0.2、SiO0.3、SiO0.4、SiO0.6、SiO0.8、SiO、SiO1.2、SiO1.5、SiO1.8或SiO1.9等，在此不做限定。硅合金可以是硅铁合金颗粒、硅钴合金颗粒、硅镍合金颗粒、硅铜合金颗粒、硅铂合金颗粒或硅金合金颗粒。
在一些实施方式中，硅基活性物质的中值粒径为0.2μm～20μm；具体可以是0.2μm、0.5μm、1μm、2μm、5μm、10μm、15μm或20μm，在此不做限定。
在一些实施方式中，连接层包括聚合物、非晶碳材料和石墨化碳材料中的至少一种。
在一些实施方式中，如图1所示，缓冲层包括空心碳材料221。
在一些实施方式中，通过聚焦离子束显微镜(FIB-SEM)、X射线光电子能谱、电子能量损失谱或者红外吸收光谱仪进行检测，连接层与缓冲层中的空心碳材料连接处，存在多种共价键，包括碳碳键(C-C、C＝C)、碳氧键(C-O、C＝O)、碳氮键(C-N)、碳硫键(C-S)、碳氯键(C-Cl)、氟碳键(C-F)、氮氧键(O-N)、氧硫键(O-S)、氧氯键(O-Cl)和氮硫键(N-S)中的至少一种。
第二方面，本申请提供一种负极材料，负极材料具有核壳结构，内核包括硅基活性物质，外壳包括连接层、缓冲层及保护层，连接层包覆于硅基活性物质的表面，缓冲层填充于连接层与保护层之间，连接层与缓冲层之间的平均结合力F＞8μN。
连接层与缓冲层之间的平均结合力F的测试方法为：通过纳米力学测试系统以及探针测试系统测量5个空心碳材料从连接层上脱离所需要的最小拉力，取平均值即为平均结合力。
可以理解地，平均结合力越大，可以保证缓冲层与连接层牢固接触，减少由于硅基活性物质嵌锂后产生的巨大应力而导致缓冲层与连接层脱离，增强电子传导，缓冲层中的空心碳材料可以有效缓解硅的体积膨胀，缓冲层与连接层紧密结合也可以减少 材料极化，降低接触电阻，加快锂离子传输，带来高容量和高倍率性能。
在一些实施方式中，缓冲层包括空心碳球、空心碳棒和空心碳管中的至少一种。
在一些实施方式中，空心碳材料包括空心碳球，空心碳球的直径20nm～2000nm，空心碳球的壁厚5nm～500nm。直径具体可以是20nm、50nm、80nm、100nm、200nm、500nm、800nm、1000nm、1500nm或2000nm等，壁厚具体可以是5nm、50nm、80nm、100nm、150nm、200nm、250nm、300nm、450nm或500nm等，在此不做限定。
在一些实施方式中，空心碳材料包括空心碳棒，空心碳棒的直径10nm～1000nm，空心碳棒的长度100nm～3000nm，空心碳棒的壁厚5nm～500nm。直径具体可以是10nm、50nm、80nm、100nm、200nm、500nm、600nm、700nm、850nm或1000nm等，长度具体可以是100nm、200nm、400nm、500nm、800nm、1000nm、2000nm、2500nm或3000nm等，壁厚具体可以是5nm、50nm、80nm、100nm、150nm、200nm、250nm、300nm、450nm或500nm等，在此不做限定。
在一些实施方式中，空心碳材料包括空心碳管，空心碳管的直径为20nm～400nm，空心碳管的长度在30nm～20um；空心碳管的壁厚为5nm～100nm。直径具体可以是20nm、50nm、80nm、100nm、200nm、250nm、300nm、350nm、380nm或400nm等，长度具体可以是30nm、50nm、100nm、200nm、400nm、500nm、800nm、1um、8um、10um、15um或20um等，壁厚具体可以是5nm、10nm、25nm、30nm、35nm、40nm、45nm或50nm等，在此不做限定。
在一些实施方式中，缓冲层的厚度与硅基活性物质的中值粒径D50的比值为1：(0.5-10)；具体可以是1:0.5、1:0.7、1:0.8、1:0.9、1:1.0、1:1.5、1:2.0、1:3、1:5、1:6、1:8或1:10等，在此不做限定。优选地，缓冲层的厚度与硅基活性物质中值粒径D50的比值为1：(1～8)。
在一些实施方式中，保护层包覆于缓冲层的表面。
在一些实施方式中，保护层包覆于缓冲层的表面，且至少部分的保护层填充于空心碳材料之间的空隙中。
在一些实施方式中，保护层包括聚合物、非晶碳材料和石墨化碳材料中的至少一种。
在一些实施方式中，连接层的厚度为5nm～200nm，具体可以是5nm、10nm、30nm、50nm、80nm、100nm、150nm、180nm或200nm等，在此不做限定。
在一些实施方式中，保护层的厚度为5nm～500nm，具体可以是5nm、50nm、80nm、100nm、150nm、200nm、250nm、300nm、450nm或500nm等，在此不做限定。
在一些实施方式中，保护层包括非晶碳材料和石墨化碳材料中的至少一种，其中，保护层中的碳元素在负极材料中的质量含量为1％～50％，优选为5％～25％。
在一些实施方式中，保护层为非晶碳材料构成的碳层，碳层在负极材料中的质量含量2％～25％，碳层中的氧元素的质量含量＜5％。
在一些实施方式中，保护层为石墨化碳材料构成的碳层，碳层在负极材料中的质量含量2％～15％，碳层中的氧元素的质量含量＜3％。
在一些实施方式中，石墨化碳材料为含掺杂元素的改性石墨烯；掺杂元素包括氧、氮和硫中的至少一种。
在一些实施方式中，石墨化碳材料为含掺杂元素的改性石墨烯，改性石墨烯的层数＜10，改性石墨烯的层数过多会导致保护层的厚度过大，碳含量过高，不利于提高材料的倍率性能。
在一些实施方式中，掺杂元素在石墨化碳材料中的质量含量为1％～20％；具体可以是1％、3％、4％、5％、6％、7％、10％、12％、15％、18％或20％等，在此不做限定。具有掺杂元素的石墨化碳材料，导电性可以得到显著增强。
在一些实施方式中，保护层包括聚合物，聚合物包括双嵌段共聚物、三嵌段共聚物和多嵌段共聚物中的至少一种。
在一些实施方式中，聚合物在负极材料中的质量含量为1％～20％，具体可以是1％、3％、5％、8％、10％、12％、15％或20％等，在此不做限定。
在一些实施方式中，聚合物包括聚丙烯酸、聚丙烯腈、聚酰亚胺、聚氨酯、聚多巴胺、黄原胶、聚吡咯、聚噻吩、聚苯乙炔、聚苯胺、聚乙炔和单宁酸中的至少一种。聚合物优选为聚吡咯、聚噻吩、聚苯胺、聚苯胺和聚乙炔中的至少一种。
第三方面，本申请提供一种负极材料，如图2所示，负极材料具有核壳结构，内核包括硅基活性物质10，外壳包括连接层21及保护层23，连接层21包覆于硅基活性物质10的表面，保护层23包括导电基材231及分散于所述导电基材231中的空心碳材料221，连接层21与空心碳材料221之间的平均结合力F＞8μN。
在上述方案中，通过在硅基活性物质的表面构建连接层及保护层，利用其协同作用，有效缓解硅基活性物质的体积膨胀，增强硅碳负极材料的结构稳定性，提升循环寿命；硅基活性物质表面的连接层，可以极大地提高材料的导电性，减少副反应发生，提升锂离子、电子传输通道，从而改善负极材料的导电性，提升材料倍率性能；保护层中的导电基材能够提高材料的导电性，分散于导电基材中的空心碳材料能够缓冲硅基活性物质的体积膨胀，并且空心碳材料与连接层之间的平均结合力大于8μN，在循环过程中，空心碳材料不容易与连接层脱落，从而能够提高保护层与连接层的连接稳定性，有利于负极材料保持优异的机械性能，提升负极材料的整体结构稳定性，进而提升循环稳定性。
在一些实施方式中，导电基材包括聚合物、非晶碳材料和石墨化碳材料中的至少一种。其中，聚合物、非晶碳材料和石墨化碳材料的选择在此不再赘述，与第一方面所述的负极材料相同。
在一些实施方式中，保护层包覆于连接层的表面。
在一些实施方式中，连接层和保护层均包括聚合物；
在一些实施方式中，连接层和保护层均包括非晶碳材料；
在一些实施方式中，连接层和保护层均包括石墨化碳材料。
可以理解地，连接层和保护层的材质相同时，连接层和保护层之间的结合力更强，更有利于把空心碳材料固定在连接层和保护层之间，减少空心碳材料在充放电过程中从连接层脱落。
在一些实施方式中，负极材料中的碳元素的质量含量为5％～80％。具体可以是5％、8％、10％、15％、18％、20％、30％、35％、40％、45％、50％或80％等，在此不做限定。需要说明的是，负极材料中的碳来源于连接层、缓冲层以及保护层中的碳。
在一些实施方式中，负极材料中的氧元素的质量含量为小于20％。具体可以是5％、6％、8％、10％、12％、15％、18％、19％等，在此不做限定。
在一些实施方式中，负极材料的粉体振实密度为0.2g/cm3～1.2g/cm3，例如0.2g/cm3、0.3g/cm3、0.5g/cm3、0.6g/cm3、0.7g/cm3、0.8g/cm3、1.0g/cm3、1.2g/cm3等。优选为0.5g/cm3～0.8g/cm3。
在一些实施方式中，负极材料的粉体压实密度为1.2g/cm3～1.8g/cm3，例如1.2g/cm3、1.3g/cm3、1.4g/cm3、1.5g/cm3、1.6g/cm3或1.8g/cm3等，优选为1.45g/cm3～1.75g/cm3。
在一些实施方式中，负极材料的中值粒径为0.2μm～20μm，可选地，负极材料的中值粒径具体可以是0.2μm、0.5μm、1μm、3μm、4μm、5μm、7μm、10μm、13μm、15μm或20μm等，在此不做限定。负极材料的中值粒径优选为0.5μm～10μm，更优选为1μm～5μm。
负极材料的比表面积比为1m2/g～50m2/g。可选地，负极材料的比表面积比可以是1m2/g、5m2/g、8m2/g、10m2/g、15m2/g、20m2/g、25m2/g、30m2/g、35m2/g、40m2/g、45m2/g或50m2/g等，在此不做限定；可以理解地，比表面积越小越好，过大的比表面积容易导致SEI膜形成，消耗不可逆锂盐过多，降低电池的首次效率低，综合考虑制备工艺的成本，将比表面积控制在2m2/g～15m2/g。
本申请还提供一种负极材料的制备方法，如图3所示，包括以下步骤：
S10，在硅基活性物质的表面形成连接层，连接层具有改性官能团，得到第一前驱体；
S20，将包含第一前驱体与具有表面官能团的缓冲层材料的混合浆料进行聚合反应，干燥得到第二前驱体；及
S30，对第二前驱体进行包覆处理，得到负极材料。
通过上述方法制得的负极材料，具有核壳结构，内核包括硅基活性物质，外壳包括连接层、缓冲层及保护层，连接层包覆于硅基活性物质的表面，缓冲层填充于连接层与保护层之间。
在本方案中，通过在硅基活性物质表面形成具有改性官能团的连接层，然后将具有表面官能团的缓冲层材料与第一前驱体进行聚合反应，使得连接层与缓冲层材料通过共价键连接，可以大幅提高缓冲层材料与连接层的结合强度，有效把连接层与缓冲层材料紧密连接，确保体积膨胀后能保证优异电接触；最后在缓冲层上进行包覆处理，形成的保护层进一步加强了负极材料的导电性和结构完整性，可以有效抑制与电解液接触发生副反应。通过本申请方法制得的负极材料，依靠缓冲层材料的高强度以及高韧性，结合连接层、缓冲层和保护层对硅基活性物质进行协同作用，可以有效缓解硅的体积膨胀，改善硅负极的导电性，增强硅碳复合结构稳定性，进而提升这个硅负极材料的循环寿命和倍率性能。
以下结合实施例具体介绍本申请的制备方法：
步骤S10，在硅基活性物质的表面形成连接层，连接层具有改性官能团，得到第一前驱体。
在一些实施方式中，硅基活性物质为一次颗粒。
在一些实施方式中，硅基活性物质包括Si、SiOx和硅合金中的至少一种，其中，0<x＜2；SiOx具体可以是SiO0.1、SiO0.2、SiO0.3、SiO0.4、SiO0.6、SiO0.8、SiO、SiO1.2、SiO1.5、SiO1.8或SiO1.9等，在此不做限定。硅合金可以是硅铁合金颗粒、硅钴合金颗粒、硅镍合金颗粒、硅铜合金颗粒、硅铂合金颗粒或硅金合金颗粒。
在一些实施方式中，硅基活性物质的中值粒径D50为0.2μm～20μm；具体可以是0.2μm、0.5μm、1μm、2μm、5μm、10μm、15μm或20μm，在此不做限定。
在一些实施方式中，连接层的改性处理方式可以气体改性和/或液相改性。
在一些实施方式中，步骤S10包括：在保护气氛下，将气相碳源通过气相沉积方式沉积在硅基活性物质的表面，得到复合物，并利用改性气体使得复合物表面的连接层具有改性官能团。
在一些实施方式中，气相沉积的加热速率为1℃/min-20℃/min，例如可以是1℃/min、3℃/min、5℃/min、8℃/min、10℃/min、15℃/min或20℃/min，在此不作限定。
在一些实施方式中，气相沉积的温度为600℃～1000℃，具体可以是400℃、500℃、600℃、700℃、800℃或1000℃。
在一些实施方式中，气相碳源包括乙炔、甲烷、甲苯、环已烷、乙醇、乙烯和丙烯中的至少一种。
在一些实施方式中，气相碳源的浓度为0.1L/min～10L/min，具体可以是0.1L/min、1L/min、3L/min、5L/min、8L/min或10L/min，在此不作限定。
在一些实施方式中，气相沉积的保温时间为1h～48h，具体可以是1h、2h、4h、6h、8h、12h、18h、24h或48h，在此不做限定。
在一些实施方式中，改性气体包括氧气、水蒸气、氨气、硫化氢、磷化氢、氯化氢、氟化氢、溴化氢、一氧化氮、二氧化硫和氯气中的至少一种。
在一些实施方式中改性气体的流量为0.5L/min～5L/min，具体可以是0.5L/min、1L/min、2L/min、3L/min、4L/min或5L/min，在此不作限定。
在一些实施方式中，改性气体的通入时间为0.5h～10h，具体可以是0.5h、2h、4h、6h、8h或10h，在此不做限定。
在一些实施方式中，改性官能团选自羧基、羰基、羟基、环氧基、含氮官能团、含硫官能团、含卤素元素官能团及其衍生官能团中的至少一种。
在一些实施方式中，保护气氛包括氦气、氖气、氩气、氪气及氙气中的至少一种。
在一些实施方式中，保护气氛与气相碳源的体积比为10：(0.5～10)，具体可以是10:0.5、10:1、10:2、10:3、10:4、10:5、10:7、10:8、10:9或10:10，在此不作限定。
在一些实施方式中，保护气氛与改性气体的体积比为10：(0.1～10)，具体可以是10:0.1、10:1、10:2、10:3、10:4、10:5、10:7、10:8、10:9或10:10，在此不作限定。
在一些实施方式中，步骤S10包括：在保护气氛下，将气相碳源通过气相沉积方式沉积在硅基活性物质的表面，得到复合物；将复合物分散于含第一改性剂的第一改性溶液中，固液分离、干燥、热处理，得到第一前驱体。
其中，制备复合物的方式参见上文所述，在此不再赘述。
在一些实施方式中，第一改性剂包括阴离子表面活性剂。
在一些实施方式中，第一改性剂包括十六烷基三甲基溴化铵、十六烷基硫酸钠、 聚乙烯吡咯烷酮和聚苯乙烯磺酸钠中的至少一种。
在一些实施方式中，第一改性溶液中的复合物与第一改性剂的质量比为1：(0.05～1)，具体可以是1:0.05、1:0.1、1:0.2、1:0.4、1:0.5、1:0.7、1:0.8、1:0.9或1:1，在此不作限定。
在一些实施方式中，第一改性溶液包括极性溶剂。
在一些实施方式中，极性溶剂包括水、无水乙醇、甲醇和异丙醇中的至少一种。
在一些实施方式中，分散的方式包括机械搅拌和超声分散中的至少一种。
在一些实施方式中，固液分离包括离心、常压过滤和负压过滤中的至少一种。
在一些实施方式中，干燥的温度为60℃～200℃，具体可以是60℃、80℃、100℃、120℃、150℃、180℃或200℃，在此不作限定。
在一些实施方式中，利用第一改性剂形成具有改性官能团的连接层时还包括将干燥产物进行热处理，热处理的温度为600℃～900℃，所述热处理的时间为1h～6h。
在一些实施方式中，热处理的温度具体可以是600℃、650℃、700℃、720℃、750℃、800℃、850℃或900℃，热处理的时间具体可以是1h、2h、3h、4h、5h或6h，在此不做限定。在一些实施方式中，步骤S10包括：将包含硅基活性物质与聚合物的混合包覆液进行喷雾干燥，使得硅基活性物质的表面形成连接层，连接层包括聚合物。
在一些实施方式中，硅基活性物质在混合包覆液中的固含量为5％～50％，
在一些实施方式中，混合包覆液包括极性溶剂。
在一些实施方式中，极性溶剂包括水、无水乙醇、甲醇和异丙醇中的至少一种。
在一些实施方式中，硅基活性物质与聚合物的质量比为10：(0.1～5)，具体可以是10:0.1、10:1、10:2、10:3、10:4或10:5，在此不作限定。
在一些实施方式中，喷雾干燥的干燥温度为60℃～200℃；具体可以是60℃、80℃、100℃、120℃、150℃、180℃或200℃，在此不作限定。
在一些实施方式中，聚合物包括双嵌段共聚物、三嵌段共聚物和多嵌段共聚物中的至少一种；
在一些实施方式中，聚合物包括聚丙烯酸、聚丙烯腈、聚酰亚胺、聚氨酯、聚多巴胺、黄原胶、聚吡咯、聚噻吩、聚苯乙炔、聚苯胺、聚乙炔和单宁酸中的至少一种；
在一些实施方式中，聚合物具有改性官能团，改性官能团选自羧基、羰基、羟基、环氧基、含氮官能团、含硫官能团、含卤素元素官能团及其衍生官能团中的至少一种。
在一些实施方式中，在S20之前，还包括：将缓冲层材料分散于含第二改性剂的第二改性溶液中进行改性处理，固液分离、干燥，得到具有表面官能团的缓冲层材料。
在一些实施方式中，第二改性剂包括阳离子表面活性剂。
在一些实施方式中，第二改性剂包括聚二烯丙基二甲基氯化铵、氨丙基三乙氧基硅烷和硅烷偶联剂中的至少一种；
在一些实施方式中，第二改性溶液中的缓冲层材料与第二改性剂的质量比为1：(0.5～10)；具体可以是1:0.5、1:0.1、1:2、1:3、1:4、1:5、1:6、1:8或1:10等。
在一些实施方式中，第二改性溶液包括极性溶剂。
在一些实施方式中，极性溶剂包括水、无水乙醇、甲醇和异丙醇中的至少一种。
在一些实施方式中，固液分离包括离心、常压过滤和负压过滤中的至少一种。
在一些实施方式中，干燥的温度为60℃～200℃，具体可以是60℃、80℃、100℃、120℃、150℃、180℃或200℃，在此不作限定。
在一些实施方式中，分散的方式包括机械搅拌和超声分散中的至少一种。
S20，将包含第一前驱体与具有表面官能团的缓冲层材料的混合浆料进行聚合反应，使得缓冲层材料的表面官能团与所述连接层的改性官能团通过共价键连接，干燥得到第二前驱体。
需要说明的是，缓冲层材料能够通过自组装、静电吸附或者喷雾造粒包覆等方式连接于硅基活性物质表面的连接层上。
在一些实施方式中，混合浆料中，第一前驱体与具有表面官能团的缓冲层材料的质量比为1：(0.01～2)，具体可以是1:0.01、1:0.02、1:0.05、1:0.08、1:0.1、1:0.2、1:0.5、1:0.8、1:1、1:1.5或1:2等。优选地，第一前驱体与具有表面官能团的缓冲层材料的质量比为1：(0.01～1)。
在一些实施方式中，混合浆料中的第一前驱体的固含量为2％～50％；具体可以是2％、5％、8％、10％、15％、20％、30％、40％或50％等，在此不做限定。
在一些实施方式中，混合浆料中的具有表面官能团的缓冲层材料的固含量为0.5％～25％；具体可以是0.5％、2％、5％、8％、10％、15％、18％、20％或25％等，在此不做限定。
在一些实施方式中，所述缓冲层材料包括空心碳材料，所述空心碳材料包括空心碳球、空心碳棒、空心碳管中的至少一种。
在一些实施方式中，混合浆料中的固含量为5％～60％，具体可以是5％、2％、6％、10％、20％、30％、40％、50％或60％等，在此不做限定。
在一些实施方式中，混合浆料中的第一前驱体与活性剂的质量比为1：(0.1～0.5)；具体可以是1:0.1、1:0.2、1:0.3、1:0.4或1:0.5等。
在一些实施方式中，混合浆料还进行分散、离心处理，分散的方式包括机械搅拌和超声分散中的至少一种。
在一些实施方式中，混合浆料还包括活性剂，活性剂选自聚二烯丙基二甲基氯化铵、氨丙基三乙氧基硅烷、硅烷偶联剂、十六烷基三甲基溴化铵、十六烷基硫酸钠、聚乙烯吡咯烷酮和聚苯乙烯磺酸钠中的至少一种。
在一些实施方式中，混合浆料还包括溶剂，溶剂选自水、无水乙醇、甲醇和异丙醇中的至少一种。
在一些实施方式中，干燥的方式为喷雾干燥。喷雾干燥的温度为100℃～200℃；具体可以是100℃、110℃、120℃、150℃、170℃、180℃或200℃，在此不作限定。
在一些实施方式中，喷雾干燥的进料速度为100mL/min-1000mL/min，具体可以是100mL/min、200mL/min、300mL/min、400mL/min、600mL/min、800mL/min或1000mL/min等，在此不做限定。
S30，对第二前驱体进行包覆处理，得到负极材料。
在一些实施方式中，包覆处理包括碳包覆处理和/或聚合物包覆处理。
在一些实施方式中，可以采用通过气相沉积、液相包覆、有机物裂解等方式进行包覆处理。
在一些实施方式中，对第二前驱体进行碳包覆处理的步骤，包括：往第二前驱体中通入气相碳源，加热至气相碳源发生热裂解反应，使得第二前驱体的表面沉积形成保护层，保护层包括非晶碳材料和石墨化碳材料中的至少一种。
在一些实施方式中，气相碳源包括乙炔、甲烷、甲苯、环已烷、乙醇、乙烯和丙烯中的至少一种。
在一些实施方式中，加热的升温速率为1℃/min～20℃/min，具体可以是1℃/min、2℃/min、3℃/min、4℃/min、5℃/min、8℃/min、10℃/min、12℃/min、15℃/min、18℃/min、20℃/min。优选地，升温速率为3℃/min～5℃/min。申请人通过多次试验发现，将升温速率控制在3℃/min～5℃/min时，能够有效保障碳化反应的进行，也能够缩短升温至预设温度范围的时间。
在一些实施方式中，热裂解反应的温度为600℃～1000℃，具体地，反应温度可以是600℃、650℃、700℃、750℃、800℃、890℃、900℃、960℃或1000℃。申请人通过多次试验发现，将反应温度控制在600℃～1000℃内，可以提高反应效率，使得第二前驱体表面形成均匀的碳层，碳层可以是无定型碳。优选地，反应温度为700℃～900℃。
在一些实施方式中，热裂解反应的保温时间为1h～48h；具体可以是1h、4h、8h、12h、16h、24h、28h、32h、38h或48h，在此不做限定。
在一些实施方式中，气相碳源的浓度为0.1L/min～10L/min；具体可以是0.1L/min、0.4L/min、0.6L/min、0.8L/min、1.0L/min、2L/min、5L/min、6L/min、8L/min、9L/min或10L/min等，在此不做限定。
在一些实施方式中，热裂解反应在保护气氛下进行。
在一些实施方式中，保护气氛包括氦气、氖气、氩气、氪气及氙气中的至少一种。
在一些实施方式中，保护气氛与气相碳源的体积比为10：(0.5～10)，具体可以是10:0.5、10:1、10:2、10:3、10:5、10:6.5、10:7.5、10:8.5、10:9或10:10等，在此不做限定。
在一些实施方式中，对第二前驱体进行聚合物包覆处理的步骤，包括：将包含第二前驱体与聚合物的混合包覆液进行喷雾干燥，使得第二前驱体的表面形成保护层，保护层包括聚合物。
在一些实施方式中，第二前驱体在混合包覆液中的固含量为5％～50％，具体可以是5％、10％、15％、20％、25％、30％、35％、40％、45％或50％等，在此不做限定。
在一些实施方式中，混合包覆液包括极性溶剂。
在一些实施方式中，极性溶剂包括水、无水乙醇、甲醇和异丙醇中的至少一种。
在一些实施方式中，第二前驱体与聚合物的质量比为10：(0.1～5)，具体可以是10:0.1、10:1、10:2、10:3、10:4或10:5，在此不作限定。
在一些实施方式中，喷雾干燥的干燥温度为60℃～200℃，具体可以是60℃、80℃、100℃、120℃、150℃、180℃或200℃。
在一些实施方式中，聚合物包括双嵌段共聚物、三嵌段共聚物和多嵌段共聚物中的至少一种。
在一些实施方式中，聚合物包括聚丙烯酸、聚丙烯腈、聚酰亚胺、聚氨酯、聚多巴胺、黄原胶、聚吡咯、聚噻吩、聚苯乙炔、聚苯胺、聚乙炔和单宁酸中的至少一种。
本申请实施例还提供了一种二次电池，采用本申请上述实施例提供的负极材料或采用本申请上述实施例提供的负极材料的制备方法制得的负极材料。二次电池可以是锂离子电池、钠离子电池等，本申请实施例提供的锂离子电池具有高容量、高首效、长循环寿命、优异倍率性能以及低膨胀的优点。
下面分多个实施例对本申请实施例进行进一步的说明。其中，本申请实施例不限定于以下的具体实施例。在不变主权利的范围内，可以适当的进行变更实施。
实施例1
一种负极材料的制备方法，包括以下步骤：
(1)将中值粒径为2μm的硅放入旋转气氛炉中，在氩气气氛保护下，以3℃/min的升温速率加热到900℃后，通入0.5L/min的乙炔气体，使得旋转气氛炉中的氩气与乙炔的体积比为9:1，保温3h后关闭乙炔气体，通入1.5L/min的氨气，使得旋转气氛炉中的氩气与氨气的体积比为10:1，保温3h后关闭氨气，冷却得到复合物；将10g复合物与十六烷基三甲基溴化铵按质量比10:2分散于200ml去离子水中后搅拌30分钟后超声10分钟，离心干燥后得到第一前驱体。
(2)将1g直径100nm的空心碳球与1g聚二烯丙基二甲基氯化铵溶于100ml去离子水中搅拌30分钟后超声20分钟，离心干燥后得到表面羟基化的空心碳球材料。将10g第一前驱体溶于100ml去离子水中搅拌10分钟得到溶液E，将1g修饰后的空心碳球分散在100ml的去离子水中，搅拌10分钟得到溶液F。将溶液E缓慢滴入溶液F中，并持续快速搅拌40分钟后，离心干燥得到第二前驱体。
(3)取10g第二前驱体溶于100g无水乙醇中，加入1g聚丙烯酸后，机械搅拌30分钟，通过喷雾干燥方式，控制干燥温度在100℃，得到负极材料。
本实施例制得的负极材料具有核壳结构，内核包括硅，外壳包括连接层、缓冲层及保护层，连接层为非晶碳材料层，非晶碳材料层包覆于所述硅颗粒的表面，缓冲层包括空心碳球，所述保护层为聚合物层(聚丙烯酸)，所述缓冲层填充于所述连接层与所述保护层之间，非晶碳材料层与所述缓冲层的空心碳球之间通过共价键(碳氮键)连接。
负极材料的中值粒径为2.5μm，比表面积为5m2/g，粉体振实密度为0.9g/cm3，粉体压实密度为1.65g/cm3，负极材料中的氧元素的质量含量为5％，负极材料中的碳元素的质量含量为25％，连接层厚度为50nm，缓冲层厚度500nm，保护层厚度30nm，保护层在负极材料中的质量含量为5％。
图4为本实施例的负极材料的扫描电镜图片；负极材料表面具有球状碳结构并在表面包裹一层致密的碳层。
图5为本实施例的负极材料的XRD图，如图5所示，负极材料的XRD图谱中可以看出在28.4°、47.3°和56.1°的三强峰与硅(JCPDS No.27-1402)的三强峰相对应，基本无杂相。
图6本实施例的负极材料的循环性能曲线，如图6所示，材料具有优异的循环性能，充放电电流为1000mA/g，在0.25C电流下循环500周还有1068mAh/g的容量，容量保持率达到81％。
实施例2
一种负极材料的制备方法，包括以下步骤：
(1)将中值粒径为2.5μm的硅放入旋转气氛炉中，在氩气气氛保护下，以3℃/min的升温速率加热到950℃后，通入0.5L/min的乙炔气体，使得旋转气氛炉中的氩气与乙炔的体积比为9:1，保温4h后关闭乙炔气体，通入1.5L/min的硫化氢，使得旋转气氛炉中的氩气与硫化氢的体积比为5:1，保温3h后，冷却得到复合物；将10g复合物与十六烷基三甲基溴化铵按质量比10:1分散于200ml去离子水中后搅拌30分钟后超声10分钟，离心干燥后得到第二前驱体。
(2)将1g直径200nm的空心碳球与2g聚二烯丙基二甲基氯化铵溶于100ml去离子水中搅拌30分钟后超声20分钟，离心干燥后得到表面羧基化的空心碳球材料。将10g第一前驱体溶于100ml去离子水中搅拌10分钟得到溶液E，将2g修饰后的空心碳球分散在100ml的去离子水中，搅拌10分钟得到溶液F。将溶液E缓慢滴入溶液F中，并持续快速搅拌40分钟后，离心干燥得到第二前驱体。
(3)取10g第二前驱体溶于100g去离子水中，加入1g聚丙烯腈后，机械搅拌30分钟，通过喷雾干燥方式，控制干燥温度在120℃，得到负极材料。
本实施例制得的负极材料具有核壳结构，内核包括硅，外壳包括连接层、缓冲层及保护层，连接层为非晶碳材料层，非晶碳材料层包覆于所述硅颗粒的表面，缓冲层包括空心碳球，所述保护层为聚合物层(聚丙烯晴)，所述缓冲层填充于所述连接层与所述保护层之间，非晶碳材料层与所述缓冲层的空心碳球之间通过共价键(碳硫键)连接。
经过测试，所得的硅碳负极材料的中值粒径为2.8μm，比表面积为2m2/g，粉体振实密度为1.0g/cm3，粉体压实密度为1.5g/cm3，负极材料中的氧元素的质量含量为4％，负极材料中的碳元素的质量含量为30％，连接层厚度为60nm，缓冲层厚度800nm，保护层厚度20nm，保护层在负极材料中的质量含量为8％。
实施例3
(1)将中值粒径为2.5μm的硅放入旋转气氛炉中，在氩气气氛保护下，以3℃/min的升温速率加热到950℃后，通入0.5L/min的乙炔气体，使得旋转气氛炉中的氩气与乙炔的体积比为9:1，保温4h后关闭乙炔气体，通入2.5L/min的氯化氢，使得旋转气氛炉中的氩气与氯化氢的体积比为8:1，保温4h后，冷却得到复合物；将10g复合物与聚乙烯吡咯烷酮按质量比10:3分散于200ml无水乙醇中后搅拌30分钟后超声10分钟，离心干燥后得到第一前驱体。
(2)将1g直径50nm长度1000nm空心碳管与2g氨丙基三乙氧基硅烷溶于100ml去离子水中搅拌30分钟后超声20分钟，离心干燥后得到的具有氨基的空心碳管材料。将10g第一前驱体溶于100ml去离子水中搅拌10分钟得到溶液E，将2g修饰后的空心碳管分散在100ml的去离子水中，搅拌10分钟得到溶液F。将溶液E缓慢滴入溶液F中，并持续快速搅拌40分钟后，离心干燥得到第二前驱体。
(3)取10g第二前驱体溶于100g去无水乙醇中，加入3g单宁酸后，机械搅拌30分钟，通过喷雾干燥方式，控制干燥温度在120℃，得到负极材料。
本实施例制得的负极材料具有核壳结构，内核包括硅，外壳包括连接层、缓冲层及保护层，连接层为非晶碳材料层，非晶碳材料层包覆于所述硅颗粒的表面，缓冲层 包括空心碳管，所述保护层为聚合物层(聚单宁酸)，所述缓冲层填充于所述连接层与所述保护层之间，非晶碳材料层与所述缓冲层的空心碳球之间通过共价键(碳氯键)连接。
本实施例制得的负极材料具有核壳结构，内核包括硅，外壳包括连接层及保护层，连接层为非晶碳材料层，保护层包括聚单宁酸及分散于聚单宁酸中的空心碳管。
经过测试，负极材料的中值粒径为4.5μm，比表面积为8m2/g，粉体振实密度为1.1g/cm3，粉体压实密度为1.7g/cm3，负极材料中的氧元素的质量含量为7％，负极材料中的碳元素的质量含量为35％，连接层厚度为60nm，缓冲层厚度700nm，保护层厚度45nm，保护层在负极材料中的质量含量为15％。
实施例4
(1)将中值粒径为2μm的硅放入旋转气氛炉中，在氩气气氛保护下，以3℃/min的升温速率加热到900℃后，通入0.5L/min的乙炔气体，使得旋转气氛炉中的氩气与乙炔的体积比为9:1，保温3h后关闭乙炔气体，通入1.5L/min的氨气，使得旋转气氛炉中的氩气与氨气的体积比为4:1，保温3h后关闭氨气，冷却得到第一前驱体。
(2)将10g第一前驱体与0.5g(直径50nm、长度1000nm)的空心碳管溶于200ml无水乙醇中，加入2g聚乙烯吡咯烷酮后搅拌30分钟后超声10分钟得到混合浆料，将混合浆料采用喷雾造粒的方式在130℃的干燥条件下进行球形化得到第二前驱体。
(3)取10g第二前驱体溶于100g无水乙醇中，加入1g聚丙烯酸后，机械搅拌30分钟，通过喷雾干燥方式，控制干燥温度在100℃，得到负极材料。
本实施例制得的负极材料具有核壳结构，内核包括硅，外壳包括连接层、缓冲层及保护层，连接层为非晶碳材料层，非晶碳材料层包覆于所述硅颗粒的表面，缓冲层包括空心碳管，所述保护层为聚合物层(聚丙烯酸)，所述缓冲层填充于所述连接层与所述保护层之间，非晶碳材料层与所述缓冲层的空心碳球之间通过共价键(碳氮键)连接。
本实施例制得的负极材料具有核壳结构，内核包括硅，外壳包括连接层及保护层，连接层为非晶碳材料层，保护层包括聚丙烯酸及分散于聚丙烯酸中的空心碳管。
负极材料的中值粒径为3.5μm，比表面积为15m2/g，粉体振实密度为0.88g/cm3，粉体压实密度为1.36g/cm3，负极材料中的氧元素的质量含量为11％，负极材料中的碳元素的质量含量为21％，连接层厚度为50nm，缓冲层厚度300nm，保护层厚度33nm，保护层在负极材料中的质量含量为5％。
实施例5
(1)将中值粒径为3μm的硅放入旋转气氛炉中，在氩气气氛保护下，以5℃/min的升温速率加热到800℃后，通入0.5L/min的乙炔气体，使得旋转气氛炉中的氩气与乙炔的体积比为9:1，保温3h后关闭乙炔气体，通入2.5L/min的氨气，使得旋转气氛炉中的氩气与氨气的体积比为6:1，保温3h后关闭氨气，冷却得到第一前驱体；
(2)将10g第一前驱体与0.5g(直径80nm、长度1100nm)的空心碳管溶于200ml无水乙醇中，加入2g聚乙烯吡咯烷酮后搅拌30分钟后超声10分钟得到混合浆料，将混合浆料采用喷雾造粒的方式在130℃的干燥条件下进行球形化得到第二前驱体。
(3)取10g第二前驱体溶于100g无水乙醇中，加入1g聚丙烯腈后，机械搅拌30 分钟，通过喷雾干燥方式，控制干燥温度在100℃，得到负极材料。
本实施例制得的负极材料具有核壳结构，内核包括硅，外壳包括连接层、缓冲层及保护层，连接层为非晶碳材料层，非晶碳材料层包覆于所述硅颗粒的表面，缓冲层包括空心碳管，所述保护层为聚合物层(聚丙烯腈)，所述缓冲层填充于所述连接层与所述保护层之间，非晶碳材料层与所述缓冲层的空心碳球之间通过共价键(碳氮键)连接。
本实施例制得的负极材料具有核壳结构，内核包括硅，外壳包括连接层及保护层，连接层为非晶碳材料层，保护层包括聚丙烯腈及分散于聚丙烯腈中的空心碳管。
经过测试，所得的硅碳负极材料的中值粒径为5μm，比表面积为19m2/g，粉体振实密度为0.98g/cm3，粉体压实密度为1.4g/cm3，负极材料中的氧元素的质量含量为23％，负极材料中的碳元素的质量含量为29％，连接层厚度为66nm，缓冲层厚度200nm，保护层厚度25nm，保护层在负极材料中的质量含量为5％。
实施例6
(1)将中值粒径为6μm的硅放入旋转气氛炉中，在氩气气氛保护下，以3℃/min的升温速率加热到900℃后，通入0.5L/min的乙炔气体，使得旋转气氛炉中的氩气与乙炔的体积比为9:1，保温3h后关闭乙炔气体，通入3.5L/min的氟化氢，使得旋转气氛炉中的氩气与氟化氢的体积比为2:1，保温8h后关闭氟化氢，冷却得到第一前驱体。
(2)将10g第一前驱体与0.5g(直径50nm、长度1000nm)的羟基化的空心碳管溶于200ml无水乙醇中，加入2g聚乙烯吡咯烷酮后搅拌30分钟后超声10分钟得到混合浆料，将混合浆料采用喷雾造粒的方式在130℃的干燥条件下进行球形化，得到第二前驱体。
(3)取100g第二前驱体旋转气氛炉中，在氩气气氛保护下，以3℃/min的升温速率加热到900℃后，通入0.5L/min的甲烷气体，使得旋转气氛炉中的氩气与乙炔的体积比为9:1，保温6h后关闭乙炔气体，冷却得到负极材料。
本实施例制得的负极材料具有核壳结构，内核包括硅，外壳包括连接层及保护层，连接层为非晶碳材料层，连接层包覆于所述硅颗粒的表面；保护层包括非晶碳材料及分散于非晶碳材料中的空心碳管，非晶碳材料层与空心碳管之间通过共价键(碳氟键)连接。
负极材料的中值粒径为8μm，比表面积为11m2/g，粉体振实密度为0.98g/cm3，粉体压实密度为1.3g/cm3，负极材料中的氧元素的质量含量为8％，负极材料中的碳元素的质量含量为32％，连接层厚度为50nm，保护层厚度350nm，保护层在负极材料中的质量含量为14％。
实施例7
其制备步骤与实施例1相同，与实施例1不同的仅是步骤(1)没有用氨气进行改性，本实施例步骤(1)的具体操作为：
将中值粒径为6μm的硅放入旋转气氛炉中，在氩气气氛保护下，以3℃/min的升温速率加热到900℃后，通入0.5L/min的乙炔气体，使得旋转气氛炉中的氩气与乙炔的体积比为9:1，保温3h后关闭乙炔气体，冷却得到复合物；将10g复合物与十六烷基三甲基溴化铵按质量比10:2分散于200ml去离子水中后搅拌30分钟后超声10分 钟，离心干燥后得到的产物置于真空反应器中，加热至700℃后保温3h，得到表面氨基化修饰后的第一前驱体。
本实施例制得的负极材料具有核壳结构，内核包括硅，外壳包括连接层、缓冲层及保护层，连接层为非晶碳材料层，非晶碳材料层包覆于所述硅颗粒的表面，缓冲层包括空心碳球，所述保护层为聚合物层(聚丙烯酸)，所述缓冲层填充于所述连接层与所述保护层之间，非晶碳材料层与所述缓冲层的空心碳球之间通过共价键(碳氮键)连接。
负极材料的中值粒径为2.2μm，比表面积为4.8m2/g，粉体振实密度为0.92g/cm3，粉体压实密度为1.59g/cm3，负极材料中的氧元素的质量含量为7％，负极材料中的碳元素的质量含量为23％，连接层厚度为60nm，缓冲层厚度550nm，保护层厚度50nm，保护层在负极材料中的质量含量为5.2％。
实施例8
其制备步骤与实施例相同，与实施例1不同的仅是：采用SiO作为硅基活性物质。
本实施例制得的负极材料具有核壳结构，内核包括SiO，外壳包括连接层、缓冲层及保护层，连接层为非晶碳材料层，非晶碳材料层包覆于所述硅颗粒的表面，缓冲层包括空心碳球，所述保护层为聚合物层(聚丙烯酸)，所述缓冲层填充于所述连接层与所述保护层之间，非晶碳材料层与所述缓冲层的空心碳球之间通过共价键(碳氮键)连接。
负极材料的中值粒径为2.6μm，比表面积为5.3m2/g，粉体振实密度为0.97g/cm3，粉体压实密度为1.64g/cm3，负极材料中的氧元素的质量含量为19％，负极材料中的碳元素的质量含量为22％，连接层厚度为54nm，缓冲层厚度500nm，保护层厚度40nm，保护层在负极材料中的质量含量为8％。
实施例9
其制备步骤与实施例相同，与实施例1不同的仅是：采用锂硅合金作为硅基活性物质。
本实施例制得的负极材料具有核壳结构，内核包括锂硅合金，外壳包括连接层、缓冲层及保护层，连接层为非晶碳材料层，非晶碳材料层包覆于所述硅颗粒的表面，缓冲层包括空心碳球，所述保护层为聚合物层(聚丙烯酸)，所述缓冲层填充于所述连接层与所述保护层之间，非晶碳材料层与所述缓冲层的空心碳球之间通过共价键(碳氮键)连接。
负极材料的中值粒径为3.1μm，比表面积为6.1m2/g，粉体振实密度为1.01g/cm3，粉体压实密度为1.72g/cm3，负极材料中的氧元素的质量含量为12％，负极材料中的碳元素的质量含量为28％，连接层厚度为50nm，缓冲层厚度600nm，保护层厚度60nm，保护层在负极材料中的质量含量为8.5％。
实施例10
(1)将中值粒径为6μm的硅放入1mol/L的醋酸镍溶液中，超声30min得到分散液，通过喷雾干燥对浆料进行干燥，得到醋酸镍修饰表面的硅前驱体。将前驱体放入旋转气氛炉中，在氩气气氛保护下，以3℃/min的升温速率加热到900℃后，通入 0.5L/min的甲苯蒸汽，通入1.5L/min的氨气，使得旋转气氛炉中的氩气与甲苯的体积比为9:1，保温3h后关闭氨气，冷却得到复合物；将10g复合物与十六烷基三甲基溴化铵按质量比10:2分散于200ml去离子水中后搅拌30分钟后超声10分钟，离心干燥后得到第一前驱体。
(2)将1g直径100nm的空心碳球与1g聚二烯丙基二甲基氯化铵溶于100ml去离子水中搅拌30分钟后超声20分钟，离心干燥后得到表面具有羟基的空心碳球材料。将10g第一前驱体溶于100ml去离子水中搅拌10分钟得到溶液E，将1g修饰后的空心碳球分散在100ml的去离子水中，搅拌10分钟得到溶液F。将溶液E缓慢滴入溶液F中，并持续快速搅拌40分钟后，离心干燥得到第二前驱体。
(3)取10g第二前驱体溶于100g无水乙醇中，加入1g聚丙烯酸后，机械搅拌30分钟，通过喷雾干燥方式，控制干燥温度在100℃，得到负极材料。
本实施例制得的负极材料具有核壳结构，内核包括硅，外壳包括连接层、缓冲层及保护层，连接层为石墨化碳材料层，其中，石墨化碳材料包括石墨烯，石墨化碳材料层包覆于所述硅颗粒的表面，缓冲层包括空心碳球，所述保护层为聚合物层(聚丙烯酸)，所述缓冲层填充于所述连接层与所述保护层之间，石墨化碳材料层与所述缓冲层的空心碳球之间通过共价键(碳氮键)连接。
负极材料的中值粒径为2.4μm，比表面积为5.6m2/g，粉体振实密度为0.88g/cm3，粉体压实密度为1.63g/cm3，负极材料中的氧元素的质量含量为4.6％，负极材料中的碳元素的质量含量为22％，连接层厚度为5nm，缓冲层厚度500nm，保护层厚度30nm，保护层在负极材料中的质量含量为5％。
实施例11
(1)将中值粒径为6μm的硅放入0.1mol/L的三嵌段共聚物P123(聚环氧乙烷-聚环氧丙烷-聚环氧乙烷)的溶液中，硅与聚合物P123的质量比为10：1，超声60min得到混合包覆液，混合包覆液中的固含量为40％，在100℃下通过喷雾干燥对浆料进行干燥，得到第一前驱体，第一前驱体包括硅及包覆于硅表面的聚合物连接层，该步骤所用聚环氧乙烷-聚环氧丙烷-聚环氧乙烷自身带有酚羟基、羧基和羰基改性官能团。
(2)将1g直径100nm的空心碳球与1g聚二烯丙基二甲基氯化铵溶于100ml去离子水中搅拌30分钟后超声20分钟，离心干燥后得到表面羟基化修饰后的空心碳球材料。将10g第一前驱体溶于100ml去离子水中搅拌10分钟得到溶液E，将1g修饰后的空心碳球分散在100ml的去离子水中，搅拌10分钟得到溶液F。将溶液E缓慢滴入溶液F中，并持续快速搅拌40分钟后，离心干燥得到第二前驱体。
(3)取10g第二前驱体溶于100g无水乙醇中，加入1g聚丙烯酸后，机械搅拌30分钟，通过喷雾干燥方式，控制干燥温度在100℃，得到负极材料。
本实施例制得的负极材料具有核壳结构，内核包括硅，外壳包括连接层、缓冲层及保护层，连接层为聚合物层，聚合物层包覆于所述硅颗粒的表面，缓冲层包括空心碳球，所述保护层为聚合物层(聚丙烯酸)，所述缓冲层填充于所述连接层与所述保护层之间，聚合物层与所述缓冲层的空心碳球之间通过共价键(碳氧键)连接。
本实施例制得的负极材料具有核壳结构，内核包括硅，外壳包括连接层及保护层， 连接层为聚合物层，保护层包括聚丙烯酸及分散于聚丙烯酸中的空心碳球。
负极材料的中值粒径为2.6μm，比表面积为5.7m2/g，粉体振实密度为0.89g/cm3，粉体压实密度为1.61g/cm3，负极材料中的氧元素的质量含量为4.9％，负极材料中的碳元素的质量含量为27％，连接层厚度为20nm，缓冲层厚度500nm，保护层厚度30nm，保护层在负极材料中的质量含量为5％。
对比例1
(1)将10g中值粒径为2μm的硅材料与十六烷基三甲基溴化铵按质量比10:2分散于200ml去离子水中后搅拌30分钟后超声10分钟，离心干燥后得到修饰后的硅材料。将1g直径100nm的空心碳球与1g聚二烯丙基二甲基氯化铵溶于100ml去离子水中搅拌30分钟后超声20分钟，离心干燥后得到修饰后的空心碳球材料。将10g修饰后的硅材料溶于100ml去离子水中搅拌10分钟得到溶液E1，将1g修饰后的空心碳球分散在100ml的去离子水中，搅拌10分钟得到溶液F1。将溶液E1缓慢滴入溶液F中，并持续快速搅拌40分钟后，离心干燥得到复合产物H1。
(2)取10g复合物H1溶于100g无水乙醇中，加入1g聚丙烯酸后，机械搅拌30分钟，通过喷雾干燥方式，控制干燥温度在100℃，得到负极材料。
本对比例制得的负极材料包括硅单质、包覆于硅单质表面的缓冲层及保护层，缓冲层为空心碳球，保护层为聚丙乙烯，硅单质表面无连接层。
经过测试，负极材料的中值粒径为2.2μm，比表面积为8.5m2/g，粉体振实密度为0.8g/cm3，粉体压实密度为1.1g/cm3，负极材料中的氧元素的质量含量为25％，负极材料中的碳元素的质量含量为15％，缓冲层厚度500nm，保护层在负极材料中的质量含量为3％。
对比例2
(1)将中值粒径为2μm的硅放入旋转气氛炉中，在氩气气氛保护下，以3℃/min的升温速率加热到900℃后，通入0.5L/min的乙炔气体，使得旋转气氛炉中的氩气与乙炔的体积比为9:1，保温3h后关闭乙炔气体，得到第一前驱体。
(2)将10g第一前驱体溶于100ml去离子水中搅拌10分钟得到溶液E，将1g空心碳球分散在100ml的去离子水中，搅拌10分钟得到溶液F。将溶液E缓慢滴入溶液F中，并持续快速搅拌40分钟后，离心干燥得到第二前驱体。
(3)取10g第二前驱体溶于100g无水乙醇中，加入1g聚丙烯酸后，机械搅拌30分钟，通过喷雾干燥方式，控制干燥温度在100℃，得到负极材料。
本实施例制得的负极材料具有核壳结构，内核包括硅，外壳包括连接层、缓冲层及保护层，连接层为非晶碳材料层，非晶碳材料层包覆于所述硅颗粒的表面，缓冲层包括空心碳球，所述保护层为聚合物层(聚丙烯酸)，所述缓冲层填充于所述连接层与所述保护层之间。
负极材料的中值粒径为2.9μm，比表面积为9m2/g，粉体振实密度为0.8g/cm3，粉体压实密度为1.5g/cm3，负极材料中的氧元素的质量含量为12％，负极材料中的碳元素的质量含量为20％，连接层厚度为10nm，缓冲层厚度400nm，保护层厚度40nm，保护层在负极材料中的质量含量为22％。
测试方法：
1)负极材料的中值粒径：
中值粒径测试方法参照GB/T 19077-2016。可以用激光粒度分析仪方便地测定，如英国马尔文仪器有限公司的Mastersizer 3000型激光粒度分析仪。
2)负极材料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)振实密度的测试方法：
采用百特振实，称取一定量样品，以300times/min，振动3000次测试振实密度。
4)氧含量及碳含量的测试方法：
采用傅里叶红外光谱测量仪测量氧含量，热重分析法测试碳含量。
5)空心碳材料的尺寸的测试方法：
通过原子力显微镜(AFM)以及高倍投射显微镜(HRTEM)测量空心碳材料的尺寸。
6)连接层、保护层厚度的测试方法：
通过FIB-SEM设备对材料进行切面处理，在SEM中测量得到连接层、保护层的平均厚度。
7)空心碳材料与连接层的结合强度的测试方法：
通过纳米力学测试系统以及探针测试系统测量单个空心碳材料从连接层上脱离所需要的最大拉力(F)，在本实施例和对比例中，测试5个位置的结合强度，并计算平均值。
经过上述测试，实施例1～11与对比例1～2制得的负极材料，样本编号对应为S1～S11及R1～R2；负极材料的性能参数如表1所述：
表1.负极材料的性能参数

9)电化学测试：
将负极材料分别与羧甲基纤维素钠、丁苯橡胶以及导电石墨(KS-6)和碳黑(SP)按照比例92:2:2:2:2配置浆料，均匀涂覆与铜箔上烘干制成负极极片，在氩气气氛手套箱中组装成扣式电池，所用隔膜为聚丙烯微孔膜，所用电解液为1mol/L的六氟磷酸锂(溶剂为体积比1:1:1的碳酸乙烯酯、碳酸甲乙酯和碳酸二甲酯的混合浆料)，所用对电极为金属锂片。
对上述13组电池在蓝电CT2001A电池测试系统上进行放电比容量测试，电池0.01C下从开路电压放电至电压为0.01V，具有的比容量为放电比容量。
对上述13组电池在蓝电CT2001A电池测试系统上进行首次库伦效率测试，充放电电流为0.05C，测得首次库伦效率。
对上述13组电池在蓝电CT2001A电池测试系统上进行循环100周测试，充放电电流为0.2C，循环100圈后测试计算圈后电池容量及圈后容量保持率。
其中，0.2C循环100圈后容量保持率＝第100圈循环放电容量/第三周放电容量*100％，
0.2C循环100圈后电极膜膨胀率＝(第100圈循环后电极膜的厚度-电极膜初始厚度)/电极膜初始厚度*100％，结果如表2所示。
表2各电池的参数性能比对表

本申请的负极材料具有低膨胀、循环稳定佳优点。
如表2所示，实施例1至11制得的负极材料，通过在硅基活性物质表面形成具有改性官能团的连接层，然后将具有表面官能团的空心碳材料与第一前驱体进行聚合反应，使得连接层与空心碳材料通过共价键连接，可以大幅提高空心碳材料与连接层的结合强度，有效把连接层与空心碳材料紧密连接，确保体积膨胀后能保证优异电接触；形成的保护层进一步加强了负极材料的导电性和结构完整性，可以有效抑制与电解液接触发生副反应；有利于负极材料保持优异的机械性能，提升负极材料的结构稳定性，进而提升循环稳定性。
对比例1的负极材料在制备过程中，未在硅单质表面形成连接层，空心碳球附着在硅单质颗粒的表面，连接稳定性下降，在循环过程中，硅颗粒的膨胀应力导致空心碳球与硅断开连接，电接触下降，材料的容量保持率下降，膨胀率大幅上升。
对比例2的负极材料在制备过程中，没有对连接层进行改性处理，空心碳材料无法通过共价键与连接层连接，两者通过分子间作用力连接，连接稳定性下降，在循环过程中，硅颗粒的膨胀应力容易使得空心碳球与硅断开连接，电接触下降，材料的容量保持率下降，膨胀率大幅上升。
本申请虽然以较佳实施例公开如上，但并不是用来限定权利要求，任何本领域技术人员在不脱离本申请构思的前提下，都可以做出若干可能的变动和修改，因此本申请的保护范围应当以本申请权利要求所界定的范围为准。

Claims (13)

  1. 一种负极材料，其特征在于，所述负极材料具有核壳结构，内核包括硅基活性物质，外壳包括连接层、缓冲层及保护层，所述连接层包覆于所述硅基活性物质的表面，所述缓冲层填充于所述连接层与所述保护层之间，所述连接层与所述缓冲层之间通过共价键连接。
  2. 根据权利要求1所述的负极材料，其特征在于，所述共价键包括碳碳键、碳氧键、碳氮键、碳硫键、碳氯键、氟碳键、氮氧键、氧硫键、氧氯键和氮硫键中的至少一种。
  3. 一种负极材料，其特征在于，所述负极材料具有核壳结构，内核包括硅基活性物质，外壳包括连接层、缓冲层及保护层，所述连接层包覆于所述硅基活性物质的表面，所述缓冲层填充于所述连接层与所述保护层之间，所述连接层与所述缓冲层之间的平均结合力F＞8μN。
  4. 根据权利要求1或3所述的负极材料，其特征在于，包含以下特征(1)至(24)中的至少一种：
    (1)所述连接层包括聚合物、非晶碳材料和石墨化碳材料中的至少一种；
    (2)所述缓冲层包括空心碳材料；
    (3)所述缓冲层包括空心碳材料，所述空心碳材料包括空心碳球、空心碳棒和空心碳管中的至少一种；
    (4)所述缓冲层包括空心碳材料，所述空心碳材料包括空心碳球，所述空心碳球的直径20nm～2000nm；
    (5)所述缓冲层包括空心碳材料，所述空心碳材料包括空心碳球，所述空心碳球的壁厚5nm～500nm；
    (6)所述缓冲层包括空心碳材料，所述空心碳材料包括空心碳棒，所述空心碳棒的直径10nm～1000nm；
    (7)所述缓冲层包括空心碳材料，所述空心碳材料包括空心碳棒，所述空心碳棒的长度100nm～3000nm；
    (8)所述缓冲层包括空心碳材料，所述空心碳材料包括空心碳棒，所述空心碳棒的壁厚5nm～500nm；
    (9)所述缓冲层包括空心碳材料，所述空心碳材料包括空心碳管，所述空心碳管的长度在30nm-20um；
    (10)所述缓冲层包括空心碳材料，所述空心碳材料包括空心碳管，所述空心碳管的壁厚为5nm～100nm；
    (11)所述缓冲层包括空心碳材料，所述空心碳材料包括空心碳管，所述空心碳管的直径为20nm～400nm；
    (12)所述缓冲层的厚度与所述硅基活性物质的中值粒径D50的比值为1：(0.5-10)；
    (13)所述保护层包覆于所述缓冲层的表面；
    (14)所述缓冲层包括空心碳材料，至少部分的所述保护层填充于所述空心碳材 料之间的空隙中；
    (15)所述保护层包括聚合物、非晶碳材料和石墨化碳材料中的至少一种；
    (16)所述连接层的厚度为5nm～200nm；
    (17)所述保护层的厚度为5nm～500nm；
    (18)所述保护层包括石墨化碳材料，所述石墨化碳材料为含掺杂元素的改性石墨烯；
    (19)所述保护层包括石墨化碳材料，所述石墨化碳材料为含掺杂元素的改性石墨烯，改性石墨烯的层数＜10；
    (20)所述保护层包括石墨化碳材料，所述石墨化碳材料为含掺杂元素的改性石墨烯，所述掺杂元素包括氧、氮和硫中的至少一种；
    (21)所述保护层包括石墨化碳材料，所述石墨化碳材料为含掺杂元素的改性石墨烯，所述掺杂元素在所述石墨化碳材料中的质量含量为1％～20％；
    (22)所述保护层包括聚合物，所述聚合物包括双嵌段共聚物、三嵌段共聚物和多嵌段共聚物中的至少一种；
    (23)所述保护层包括聚合物，所述聚合物在所述负极材料中的质量含量为1％～20％；
    (24)所述保护层包括聚合物，所述聚合物包括聚丙烯酸、聚丙烯腈、聚酰亚胺、聚氨酯、聚多巴胺、黄原胶、聚吡咯、聚噻吩、聚苯乙炔、聚苯胺、聚乙炔和单宁酸中的至少一种。
  5. 一种负极材料，其特征在于，所述负极材料具有核壳结构，内核包括硅基活性物质，外壳包括连接层及保护层，所述连接层包覆于所述硅基活性物质的表面，所述保护层包括导电基材及分散于所述导电基材中的空心碳材料，所述连接层与所述空心碳材料之间的平均结合力F＞8μN。
  6. 根据权利要求5所述的负极材料，其特征在于，包含以下特征(1)至(21)中的至少一种：
    (1)所述连接层包括聚合物、非晶碳材料和石墨化碳材料中的至少一种；
    (2)所述空心碳材料包括空心碳球、空心碳棒、空心碳管中的至少一种；
    (3)所述空心碳材料包括空心碳球，所述空心碳球的直径20nm～2000nm；
    (4)所述空心碳材料包括空心碳球，所述空心碳球的壁厚5nm～500nm；
    (5)所述空心碳材料包括空心碳棒，所述空心碳棒的直径10nm～1000nm；
    (6)所述空心碳材料包括空心碳棒，所述空心碳棒的长度100nm～3000nm；
    (7)所述空心碳材料包括空心碳棒，所述空心碳棒的壁厚5nm～500nm；
    (8)所述空心碳材料包括空心碳管，所述空心碳管的长度在30nm-20um；
    (9)所述空心碳材料包括空心碳管，所述空心碳管的壁厚为5nm～100nm；
    (10)所述空心碳材料包括空心碳管，所述空心碳管的直径为20nm～400nm；
    (11)所述保护层包覆于所述连接层的表面；
    (12)所述导电基材包括聚合物、非晶碳材料和石墨化碳材料中的至少一种；
    (13)所述连接层的厚度为5nm～200nm；
    (14)所述保护层的厚度为5nm～500nm；
    (15)所述连接层包括石墨化碳材料，所述石墨化碳材料为含掺杂元素的改性石墨烯；
    (16)所述连接层包括石墨化碳材料，所述石墨化碳材料为含掺杂元素的改性石墨烯，改性石墨烯的层数＜10；
    (17)所述连接层包括石墨化碳材料，所述石墨化碳材料为含掺杂元素的改性石墨烯，所述掺杂元素包括氧、氮和硫中的至少一种；
    (18)所述连接层包括石墨化碳材料，所述石墨化碳材料为含掺杂元素的改性石墨烯，所述掺杂元素在所述石墨化碳材料中的质量含量为1％～20％；
    (19)所述连接层包括聚合物，所述聚合物包括双嵌段共聚物、三嵌段共聚物和多嵌段共聚物中的至少一种；
    (20)所述连接层包括聚合物，所述聚合物在所述负极材料中的质量含量为1％～20％；
    (21)所述连接层包括聚合物，所述聚合物包括聚丙烯酸、聚丙烯腈、聚酰亚胺、聚氨酯、聚多巴胺、黄原胶、聚吡咯、聚噻吩、聚苯乙炔、聚苯胺、聚乙炔和单宁酸中的至少一种。
  7. 根据权利要求1～6任一项所述的负极材料，其特征在于，包含以下特征(1)至(12)中的至少一种：
    (1)所述硅基活性物质为一次颗粒；
    (2)所述硅基活性物质包括Si、SiOx和硅合金中的至少一种，其中，0<x＜2；
    (3)所述硅基活性物质的中值粒径为0.2μm～20μm；
    (4)所述负极材料中的碳元素的质量含量为5％～80％；
    (5)所述负极材料中的氧元素的质量含量＜20％；
    (6)所述负极材料的粉体振实密度为0.2g/cm3～1.2g/cm3；
    (7)所述负极材料的粉体压实密度为1.2g/cm3～1.8g/cm3；
    (8)所述负极材料的中值粒径为0.2μm～20μm；
    (9)所述负极材料的比表面积为1.0m2/g～50m2/g；
    (10)所述连接层和所述保护层均包括聚合物；
    (11)所述连接层和所述保护层均包括非晶碳材料；
    (12)所述连接层和所述保护层均包括石墨化碳材料。
  8. 一种负极材料的制备方法，其特征在于，包括以下步骤：
    在硅基活性物质的表面形成连接层，所述连接层具有改性官能团，得到第一前驱体；
    将包含所述第一前驱体与具有表面官能团的缓冲层材料的混合浆料进行聚合反应，干燥得到第二前驱体；及
    对所述第二前驱体进行包覆处理，得到负极材料。
  9. 根据权利要求8所述的负极材料的制备方法，其特征在于，所述制备方法包含以下特征(1)至(3)中的至少一种：
    (1)所述硅基活性物质为一次颗粒；
    (2)所述硅基活性物质包括Si、SiOx和硅合金中的至少一种，其中，0<x＜2；
    (3)所述硅基活性物质的中值粒径为0.2μm～20μm。
  10. 根据权利要求8所述的负极材料的制备方法，其特征在于，所述在硅基活性物质的表面形成连接层的步骤，包括：在保护气氛下，将气相碳源通过气相沉积方式沉积在硅基活性物质的表面，得到复合物，并利用改性气体使得所述复合物表面的连接层具有改性官能团。
  11. 根据权利要求8所述的负极材料的制备方法，其特征在于，所述在硅基活性物质的表面形成连接层的步骤，包括：在保护气氛下，将气相碳源通过气相沉积方式沉积在硅基活性物质的表面，得到复合物；将复合物分散于含第一改性剂的第一改性溶液中，固液分离、干燥，得到第一前驱体。
  12. 根据权利要求8所述的负极材料的制备方法，其特征在于，所述在硅基活性物质的表面形成连接层的步骤，包括：将包含所述硅基活性物质与聚合物的混合包覆液进行喷雾干燥，使得所述硅基活性物质的表面形成连接层，所述连接层包括聚合物。
  13. 一种二次电池，其特征在于，包括如权利要求1～7任一项所述的负极材料或根据权利要求8～12任一项所述负极材料的制备方法制备的负极材料。
PCT/CN2023/102585 2022-06-27 2023-06-27 负极材料及其制备方法、二次电池 Ceased WO2024002041A1 (zh)

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