WO2023124871A1 - 负极材料及其制备方法、锂离子电池 - Google Patents

负极材料及其制备方法、锂离子电池 Download PDF

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WO2023124871A1
WO2023124871A1 PCT/CN2022/137453 CN2022137453W WO2023124871A1 WO 2023124871 A1 WO2023124871 A1 WO 2023124871A1 CN 2022137453 W CN2022137453 W CN 2022137453W WO 2023124871 A1 WO2023124871 A1 WO 2023124871A1
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carbon
buffer layer
negative electrode
electrode material
active material
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PCT/CN2022/137453
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English (en)
French (fr)
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陈曦
庞春雷
梁腾宇
任建国
贺雪琴
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贝特瑞新材料集团股份有限公司
惠州市鼎元新能源科技有限公司
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Priority to KR1020237030187A priority Critical patent/KR20230142582A/ko
Priority to EP22914126.2A priority patent/EP4276949A1/en
Priority to JP2023553449A priority patent/JP2024511939A/ja
Publication of WO2023124871A1 publication Critical patent/WO2023124871A1/zh

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/64—Carriers or collectors
    • H01M4/66—Selection of materials
    • H01M4/665—Composites
    • H01M4/667—Composites in the form of layers, e.g. coatings
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/366—Composites as layered products
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—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
    • H01M4/38—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
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • 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
    • 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
    • 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 application relates to the field of lithium-ion batteries, and relates to negative electrode materials, preparation methods thereof, and lithium-ion batteries.
  • the traditional negative electrode carbon materials have limited their wide application due to their low theoretical specific capacity (372mAh/g).
  • Si-based materials have become more popular research objects for negative electrode materials due to their high specific capacity (4200mAh/g), suitable lithium intercalation potential (0-0.3V) and wide range of sources.
  • the traditional Si-based materials have relatively serious volume expansion when inserting and removing lithium, which may lead to the collapse of the material structure and the peeling off of the electrode material, which in turn makes the cycle capacity retention of the battery poor.
  • the purpose of this application is to provide negative electrode materials and preparation methods thereof, and lithium ion batteries.
  • the negative electrode materials of the present application can effectively buffer the volume expansion of negative electrode materials, improve the stability of the negative electrode material structure, and then The cycle capacity retention rate of the battery can be improved.
  • the present application provides a negative electrode material, which includes an active material, a buffer layer and a carbon layer on the surface of the active material, wherein the buffer layer is formed on the surface of the active material , the carbon layer includes an amorphous carbon material on the surface of the buffer layer and a carbon nanomaterial extending toward and/or away from the buffer layer.
  • the carbon nanomaterial extends to the buffer layer in a direction close to the buffer layer.
  • the carbon nanomaterial extends toward the buffer layer and extends through the buffer layer to the active material.
  • the carbon nanomaterial connects the amorphous carbon material and the buffer layer.
  • the carbon nanomaterial penetrates the buffer layer and connects the amorphous carbon material and the active material.
  • the carbon nanomaterial includes at least one of carbon nanotubes, carbon nanofibers and graphene.
  • the shape of the carbon nanomaterial includes at least one of a wire shape, a tube shape, a sheet shape and a strip shape.
  • the diameter of the carbon nanomaterial is 1 nm to 100 nm.
  • the aspect ratio of the carbon nanomaterial is ⁇ 10.
  • the areal density of the carbon nanomaterial is 20/mm 2 to 10000/mm 2 .
  • the buffer layer includes at least one of alkali metal halides, alkali metal nitrogen compounds, alkali metal oxides, and transition metal oxides.
  • the buffer layer includes at least one of LiF and Li 3 N.
  • the buffer layer includes at least one of Li 2 O, Al 2 O 3 , TiO 2 , ZnO, and ZrO 2 .
  • the buffer layer can catalyze the formation of the carbon nanomaterial from the amorphous carbon material.
  • the buffer layer can catalyze the in-situ growth of the amorphous carbon material to form the carbon nanomaterial.
  • the buffer layer has a thickness of 0.01 ⁇ m ⁇ 2 ⁇ m.
  • the buffer layer includes at least one of LiF, Li 2 O, Li 3 N, Al 2 O 3 , TiO 2 , ZnO, and ZrO 2 .
  • the active material includes SiO x material, 0 ⁇ x ⁇ 2.
  • the active material includes SiO x material, 0.8 ⁇ x ⁇ 1.5.
  • the active material includes SiO x material, and the SiO x material particles are spherical or quasi-spherical.
  • the active material includes a SiO x material, and the SiO x material particles have a sphericity coefficient ⁇ 0.4.
  • the mass percentage of the buffer layer in the negative electrode material is 0.05%-20%.
  • the mass percentage of the carbon layer in the negative electrode material is 0.5%-20%.
  • the thickness of the carbon layer is 10 nm ⁇ 1500 nm.
  • the D 50 of the negative electrode material is 1 ⁇ m ⁇ 20 ⁇ m.
  • the particle size distribution (D 90 -D 50 )/(D 50 -D 10 ) of the negative electrode material is 1.2 ⁇ 1.6.
  • the active material includes Si grains.
  • the active material includes Si grains, and the size of the Si grains is 2 nm ⁇ 10 nm.
  • the negative electrode material has a specific surface area of 1 m 2 /g to 20 m 2 /g.
  • the present application provides a method for preparing an anode material, comprising the steps of:
  • the buffer layer including at least one of alkali metal halides, alkali metal nitrogen compounds, alkali metal oxides and transition metal oxides;
  • the solid composite is subjected to carbon coating treatment in a protective atmosphere to obtain a negative electrode material
  • the negative electrode material includes an active material, a buffer layer and a carbon layer on the surface of the active material
  • the carbon layer includes an amorphous carbon material and a carbon layer.
  • a nanomaterial, the carbon nanomaterial extends from the amorphous carbon material toward and/or away from the buffer layer.
  • the active material includes SiO x material, 0 ⁇ x ⁇ 2.
  • the active material includes SiO x material, 0.8 ⁇ x ⁇ 1.5.
  • the active material includes SiO x material, and the SiO x material particles are spherical or quasi-spherical.
  • the active material includes a SiO x material, and the SiO x material particles have a sphericity coefficient ⁇ 0.4.
  • the active material includes Si grains.
  • the active material includes Si grains, and the size of the Si grains is 2 nm ⁇ 10 nm.
  • the buffer layer can catalyze the formation of the carbon nanomaterial from the amorphous carbon material.
  • the buffer layer can catalyze the in-situ growth of the amorphous carbon material to form the carbon nanomaterial.
  • the buffer layer includes at least one of alkali metal halides, alkali metal nitrogen compounds, alkali metal oxides, and transition metal oxides.
  • the buffer layer includes at least one of LiF, NaF and Li 3 N.
  • the buffer layer includes at least one of Li 2 O, Al 2 O 3 , MgO, TiO 2 , ZnO, CuO, Ag 2 O, and ZrO 2 .
  • the buffer layer has a thickness of 0.01 ⁇ m ⁇ 2 ⁇ m.
  • the buffer layer includes at least one of LiF, Li 2 O, Li 3 N, Al 2 O 3 , TiO 2 , ZnO, and ZrO 2 .
  • the way of forming the buffer layer on the surface of the active material is coating in liquid phase.
  • the step of forming a buffer layer on the surface of the active material to obtain a solid composite includes: mixing the material of the buffer layer with the active material in a solvent to prepare a mixed slurry, and performing a solid-liquid process on the mixed slurry. Separated and processed to obtain a solid complex.
  • the particle size of the buffer layer material in the mixed slurry is 1 nm ⁇ 1 ⁇ m.
  • the solvent includes at least one of water and ethanol.
  • the mass percentage of the buffer layer material in the mixed slurry is 0.05%-0.2%.
  • the mass percentage of the active substance in the mixed slurry is 2%-20%.
  • the solid-liquid separation treatment includes at least one of suction filtration treatment, centrifugation treatment and spray drying treatment.
  • the step of forming a buffer layer on the surface of the active material to obtain a solid composite includes: mixing buffer layer precursor materials in a solvent to prepare a dispersion containing buffer layer materials.
  • the active substance is added to the dispersion liquid, mixed, and solid-liquid separation is carried out to obtain a solid composite.
  • the buffer layer precursor material includes a lithium source and a fluorine source.
  • the buffer layer precursor material includes a lithium source and a fluorine source
  • the lithium source includes at least one of lithium nitrate, lithium acetate, lithium carbonate, and lithium oxalate.
  • the buffer layer precursor material includes a lithium source and a fluorine source
  • the fluorine source includes at least one of ammonium fluoride, sodium fluoride, and calcium fluoride.
  • the buffer layer precursor material includes a lithium source and a fluorine source, the lithium source accounts for 0.01% to 0.5% by mass of the dispersion liquid, and the fluorine source accounts for 0.01% to 0.5% by mass of the dispersion liquid. The percentage is 0.01% to 0.5%.
  • the method further includes: preheating the solid composite, and then performing carbon coating treatment.
  • the method further includes: preheating the solid composite with a preheated protective atmosphere, and then performing carbon coating treatment.
  • the method further includes: preheating the solid composite with a preheated protective atmosphere, and then performing carbon coating treatment, wherein the preheating temperature of the protective atmosphere is 100° C. to 300° C. °C.
  • the method further includes: preheating the solid composite with a preheated protective atmosphere, and then performing carbon coating treatment, wherein the temperature increase rate of the protective atmosphere is 1 °C/min ⁇ 50°C/min.
  • the carbon coating treatment includes at least one of solid phase carbon coating treatment, liquid phase carbon coating treatment and gas phase carbon coating treatment.
  • the carbon coating treatment includes the following steps: mixing the solid composite with a carbon source, and controlling thermal cracking of the carbon source to form a carbon layer on the particle surface of the solid composite.
  • the following step is further included: performing heat treatment on the solid composite after the carbon coating treatment.
  • the protective atmosphere includes at least one of nitrogen, argon, helium, neon, krypton, and xenon.
  • the carbon source comprises a gas phase carbon source.
  • the carbon source includes a gas-phase carbon source
  • the gas-phase carbon source includes a gas-phase hydrocarbon carbon source
  • the carbon source includes a gaseous carbon source
  • the gaseous carbon source includes at least one of methane, ethane, propane, ethylene, propylene, acetylene, propyne, acetone, and benzene.
  • the carbon source comprises a liquid carbon source.
  • the carbon source comprises a liquid-phase carbon source comprising a liquid-phase organic carbon source.
  • the carbon source includes a liquid carbon source
  • the liquid carbon source includes n-hexane, toluene, benzene, xylene, methanol, ethanol, propanol, butanol, pentanol, acetone, butanone , 2-pentanone, methyl acetate, ethyl acetate, propyl acetate, butyl acetate and at least one of amyl acetate.
  • the carbon source comprises a solid phase carbon source.
  • the carbon source comprises a solid phase carbon source comprising a solid phase organic carbon source.
  • the carbon source includes a solid-phase carbon source
  • the solid-phase carbon source includes at least one of citric acid, glucose, pitch, phenolic resin, and furfural resin.
  • the thermal cracking temperature is 600°C to 1200°C.
  • the heating rate of the thermal cracking is 0.1°C/min-10°C/min.
  • the temperature of the heat treatment is 600°C-1200°C.
  • the heating rate of the heat treatment is 1°C/min ⁇ 5°C/min.
  • the time for the heat treatment is 1 h to 48 h.
  • the active material includes SiO x material, 0 ⁇ x ⁇ 2.
  • the method also includes the following steps:
  • the SiOx material is thermally disproportionated.
  • the temperature of the thermal disproportionation treatment is 800°C to 1400°C.
  • the heating rate of the thermal disproportionation treatment is 1°C/min ⁇ 5°C/min.
  • the time of the thermal disproportionation treatment is 2h-50h.
  • the present application provides a lithium ion battery, comprising the above-mentioned negative electrode material or the negative electrode material prepared according to the above-mentioned preparation method of the negative electrode material.
  • the present application provides a rechargeable electrical product, including the above-mentioned lithium-ion battery.
  • the negative electrode material provided by the present application includes an active material, a buffer layer on the surface of the active material, and a carbon layer, wherein the buffer layer is formed on the surface of the active material, and the carbon layer includes amorphous carbon on the surface of the buffer layer materials and carbon nanomaterials extending toward and/or away from the buffer layer.
  • the buffer layer has a certain toughness, which can effectively buffer the volume expansion of the negative electrode material.
  • the extension of the carbon nanomaterial also provides a certain buffer effect, which can further buffer the volume expansion of the negative electrode material.
  • the stress between the negative electrode material particles can improve the stability of the negative electrode material structure, thereby improving the cycle capacity retention rate of the battery.
  • carbon nanomaterials can increase the conductivity of electrons and ions and improve electrical conductivity;
  • the material has high ion conductance and electron conductance, which further improves the cycle capacity retention rate of the battery.
  • a buffer layer is formed on the surface of the active material to obtain a solid composite, and then the solid composite is subjected to carbon coating treatment to obtain the negative electrode material.
  • the carbon coating treatment forms the carbon layer, with the deposition of carbon atoms on the surface of the buffer layer, under the catalysis of the metal compound in the buffer layer, the amorphous carbon material surface of the carbon layer is generated in situ to form carbon nanomaterials. It is beneficial to simplify the preparation process of the negative electrode material.
  • the presence of carbon nanomaterials can not only improve the ionic conductance and electronic conductance of the negative electrode material, improve the cycle capacity retention rate of the battery, but also effectively buffer the volume expansion of the negative electrode material, so that the negative electrode material can maintain a stable structure and performance.
  • the preparation method in this example is simple and easy to implement, and is convenient for large-scale promotion.
  • Fig. 1 is the structural representation of negative electrode material in an embodiment of the present application
  • Fig. 2 is the flow chart of the negative electrode material preparation method in an embodiment of the present application
  • Fig. 3a and Fig. 3b are the electronic mirror image structure diagrams of the anode material prepared in the embodiment 1 of the present application respectively;
  • Fig. 4a and Fig. 4b are the electronic mirror image structure diagrams of the anode material prepared in the embodiment 2 of the present application respectively;
  • Figure 5a is another electron mirror image structure diagram of nanowires in the negative electrode material prepared in Example 2 of the present application.
  • Fig. 5 b is the EDS (Energy Dispersive Spectroscopy, EDS) energy spectrum of the nanowire in the negative electrode material that the embodiment 2 of the present application makes;
  • Fig. 6a and Fig. 6b are the electronic mirror image structure diagrams of the negative electrode material that the application comparative example 1 makes respectively;
  • Fig. 7 is the cyclic expansion test result figure of the lithium-ion battery made of the negative electrode material in Example 1 and Comparative Example 1, wherein the abscissa represents the specific capacity (specific capacity, unit: mAh/g), and the ordinate represents the voltage (Voltage, Unit: V);
  • Fig. 8 is the test result graph of the cycle capacity retention rate of the lithium-ion battery made of negative electrode materials in Example 1 and Comparative Example 1, wherein the abscissa represents the cycle number (cycles, unit: week), and the ordinate represents the cycle capacity retention rate (representative capacity retention, unit: %).
  • the carbon layer 30 includes an amorphous carbon material on the surface of the buffer layer 20 and a carbon nanomaterial 31 extending toward and/or away from the buffer layer.
  • the buffer layer has a certain toughness, which can effectively buffer the volume expansion of the negative electrode material, and at the same time, the extension of the carbon nanomaterial also provides a certain buffer effect, which can further buffer the volume expansion of the negative electrode material. Reducing the stress between the particles of the negative electrode material during the charging and discharging process can improve the stability of the structure of the negative electrode material, thereby improving the cycle capacity retention rate of the battery.
  • carbon nanomaterials can increase the conductivity of electrons and ions and improve electrical conductivity;
  • the material has high ion conductance and electron conductance, which further improves the cycle capacity retention rate of the battery.
  • the carbon layer includes amorphous carbon material on the surface of the buffer layer and carbon nanomaterials extending toward and/or away from the buffer layer.
  • extending toward the buffer layer means that the carbon nanomaterial extends from the amorphous carbon material toward the direction close to the active material
  • extending toward a direction away from the buffer layer means that the carbon nanomaterial extends from the amorphous carbon material toward the direction away from the active material.
  • the carbon nanomaterial extends to the buffer layer in a direction close to the buffer layer.
  • the carbon nanomaterial can connect the amorphous carbon material and the buffer layer, which can increase the 3D conductive network, improve the conductivity, and increase the cycle capacity retention rate of the battery. It can be understood that when the carbon nanomaterials extend to the buffer layer in a direction close to the buffer layer, there may also be other carbon nanomaterials extending in a direction away from the buffer layer.
  • the carbon nanomaterial extends toward the buffer layer and extends through the buffer layer to the active material. At this time, the carbon nanomaterial can penetrate the buffer layer and connect the amorphous carbon material and the active material, that is, the carbon nanomaterial connects the amorphous carbon material, the buffer layer, and the active material to form a double flexible coating layer structure. , to better provide a buffer for the expansion effect of the negative electrode material.
  • the carbon nanomaterial penetrates to the surface of the active material, a certain degree of bonding force is generated between the double flexible coating layer structure, which can make the carbon layer, the buffer layer and the active material have a better binding force, which can further Inhibit the volume expansion of the negative electrode material, so that the negative electrode material maintains a stable structure and performance. It can also be understood that when the carbon nanomaterial extends toward the buffer layer and extends through the buffer layer to the active material, there may also be other carbon nanomaterials extending away from the buffer layer.
  • the buffer layer can catalyze the formation of carbon nanomaterials from carbon materials. Further, the buffer layer can catalyze the in-situ growth of amorphous carbon materials to form carbon nanomaterials.
  • the buffer layer has a thickness of 0.01 ⁇ m ⁇ 2 ⁇ m.
  • the thickness of the buffer layer is 0.01 ⁇ m, 0.015 ⁇ m, 0.03 ⁇ m, 0.05 ⁇ m, 0.08 ⁇ m, 0.1 ⁇ m, 0.2 ⁇ m, 0.3 ⁇ m, 0.4 ⁇ m, 0.5 ⁇ m, 0.6 ⁇ m, 0.7 ⁇ m, 0.8 ⁇ m, 0.9 ⁇ m , 1 ⁇ m, 1.2 ⁇ m, 1.5 ⁇ m, 1.8 ⁇ m or 2 ⁇ m.
  • the active material includes SiO x material, 0 ⁇ x ⁇ 2, x can be 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.2, 1.3, 1.5 , 1.6, 1.8, 1.99, etc., are not limited here.
  • the active material includes SiO x material, 0.8 ⁇ x ⁇ 1.5.
  • the SiOx material is SiO. Still further, the SiO x material is SiO particles.
  • the SiO x material particles are spherical or quasi-spherical.
  • the sphericity coefficient of the SiO x material particles is ⁇ 0.4.
  • the sphericity coefficient of the SiO x core particles is 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95 and so on.
  • the SiO x core particles have a sphericity coefficient ⁇ 0.95.
  • the carbon nanomaterial is grown in situ on the surface of an amorphous carbon material.
  • the carbon nanomaterials grown in situ can provide better bonding force.
  • the carbon nanomaterials extend to the buffer layer or extend through the buffer layer to the active material, the carbon layer and the buffer layer or the carbon layer, the buffer layer and the SiO x A better binding force is formed between the inner cores, which further inhibits the expansion of the negative electrode material and maintains the structural stability of the negative electrode material.
  • the carbon nanomaterial has a stable extension environment, which can maintain a stable diameter during the extension process.
  • the carbon nanomaterial extends from the amorphous carbon material to the buffer layer in the direction close to the buffer layer, the carbon atoms closest to the buffer layer have dangling bonds, and there is a certain binding force between the buffer layer and the carbon atoms, which can be combined with The self-closing force of the carbon atom dangling bond is balanced, which can make the opening connecting the carbon nanomaterial and the buffer layer exist stably, so that the diameter of the carbon nanomaterial can be kept constant while the length is increased when the carbon nanomaterial is stretched out, forming a relatively large length and diameter. Carbon nanomaterials with uniform diameter.
  • the diameter of the carbon nanomaterial is 1 nm ⁇ 100 nm.
  • the diameter of the carbon nanomaterial is 5nm, 10nm, 15nm, 20nm, 30nm, 40nm, 50nm, 60nm, 70nm, 80nm or 90nm.
  • the aspect ratio of the carbon nanomaterial is ⁇ 10.
  • the long-diameter ratio of carbon nanomaterials is high, which is conducive to extending to the buffer layer or extending through the buffer layer to the SiO x core, and is also conducive to the formation of entanglement between different carbon nanomaterials, which can promote the volume expansion of negative electrode materials. Buffering effect, improve the stability of the negative electrode material structure.
  • the aspect ratio of the carbon nanomaterial may be, but not limited to, 10, 11, 12, 13, 14, 15 and so on.
  • the areal density of the carbon nanomaterial is 20 to 10000/mm 2 .
  • Carbon nanomaterials can provide channels for the movement of electrons.
  • the surface density of carbon nanomaterials is within this range, a large number of electrons and ions can be adsorbed on the surface of carbon nanomaterials and the gap between adjacent carbon nanomaterials, which can Obtain higher discharge capacity and better cycle performance.
  • the areal density of carbon nanomaterials is too low, the movement channels of electrons will be reduced, which is especially unfavorable for high-current charging and discharging.
  • the relative content of active materials When the surface density of carbon nanomaterials is too high, the relative content of active materials will be reduced correspondingly, which will reduce the capacity of the battery; in addition, when the content of carbon nanomaterials is too high, the penetration capacity of electrolyte in the electrode material will be increased , resulting in an increase in the side reactions of the electrolyte, and the thickness of the SEI film may continue to increase, which is not conducive to the improvement of the electrical performance of the battery.
  • the areal density of carbon nanomaterials is 20/mm 2 , 50/mm 2 , 100/mm 2 , 200/mm 2 , 300/mm 2 , 400/ mm 2 , 500/mm 2 mm 2 , 600 pcs/mm 2 , 800 pcs/mm 2 , 1000 pcs/mm 2 , 2000 pcs/mm 2 , 3000 pcs/mm 2 , 4000 pcs/mm 2 , 5000 pcs/ mm 2 , 6000 pcs/mm 2 , 7000/mm 2 , 8000/mm 2 , 9000/mm 2 , 10,000/mm 2 , 12,000/mm 2 , 15,000/mm 2 , 18,000/mm 2
  • the areal density of the carbon nanomaterial is 20 to 2000/mm 2 .
  • the carbon nanomaterial includes at least one of carbon nanowires, carbon nanotubes, carbon nanofibers and graphene.
  • the shape of the carbon nanomaterial includes at least one of a wire shape, a tube shape, a sheet shape and a strip shape.
  • the buffer layer includes at least one of alkali metal halides, alkali metal nitrogen compounds, alkali metal oxides, and transition metal oxides.
  • the alkali metal halide includes at least one of LiF and NaF
  • the alkali metal nitrogen compound includes at least one of Li 3 N and KN 3 ;
  • the alkali metal oxide includes Li 2 O and K 2 O, and the transition metal oxide includes at least one of Al 2 O 3 , MgO, TiO 2 , ZnO, CuO, Ag 2 O and ZrO 2 .
  • the buffer layer can realize ion conduction, but the buffer layer can realize the function similar to the electronic insulating layer, reducing the highly active electrons to pass through the buffer layer and react with the electrolyte.
  • the introduction of the buffer layer can be equivalent to introducing a layer of artificial SEI film (SEI film Represents the solid electrolyte interface film), which reduces the consumption of lithium ions when the SEI film is formed during the discharge process, thereby reducing the irreversible capacity of charge and discharge, and further improving the cycle capacity retention rate of the battery.
  • SEI film represents the solid electrolyte interface film
  • the mass percentage of the buffer layer in the negative electrode material is 0.05%-20%. If the content of the buffer layer is too high, it will make it difficult for the carbon nanomaterials to disperse, and a thicker buffer layer will have a certain negative impact on the electronic conductance and specific capacity. And when the content of the buffer layer is too low, the carbon nanomaterials are difficult to be evenly attached and the amount of the carbon nanomaterials is small, and the degree of improvement of the electrical conductivity is small; and when the buffer layer is too small, it is difficult to form a complete and effective SiO x core surface. The covering layer makes it difficult to fully play the role of the buffer layer.
  • the mass percentage of the buffer layer can be 0.05%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 8%, 9%, 10%, 11%, 12% , 13%, 14%, 15%, 16%, 17%, 18%, 19% or 20%, etc. It can be understood that the mass percentage of the buffer layer in the negative electrode material can also be other values in the range of 0.05% to 20%.
  • the percentage of the mass of the buffer layer to the mass of the negative electrode material can be controlled by the amount of the buffer layer added.
  • the mass percentage of the carbon layer in the negative electrode material is 0.5%-20%.
  • the proportion of the carbon layer is too large, the thickness of the carbon layer will be too large, which will make the transmission distance of lithium ions too long, so that the improvement of electrical properties is not good; at the same time, the carbon layer with too large thickness may bring The problem of reduced tap density and compacted density leads to a decrease in specific capacity.
  • the proportion of the carbon layer is too small, the thickness of the carbon layer will be too small, and it will be difficult to completely and effectively cover the inner buffer layer, which will increase the chance of the active material contacting the electrolyte, which will affect the cycle performance of the battery. The increase will bring adverse effects, and may also make it difficult for the double-flexible cladding layer structure to exert a better effect.
  • the mass percentage of the carbon layer in the negative electrode material can be 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18% , 19% or 20%, etc. It can be understood that the mass percentage of the carbon layer in the negative electrode material can also be other values in the range of 0.5% to 20%. Preferably, the mass percentage of the carbon layer in the negative electrode material is 1%-10%.
  • the mass percentage of the carbon layer in the negative electrode material can be controlled by the deposition amount of the carbon source.
  • the thickness of the carbon layer is 10nm-1500nm; specifically, it can be 10nm, 20nm, 50nm, 80nm, 100nm, 200nm, 500nm, 800nm, 1000nm, 1500nm, etc., which is not limited here.
  • the D 50 of the negative electrode material is 1 ⁇ m ⁇ 20 ⁇ m.
  • the D50 of the negative electrode material is 1 ⁇ m, 2 ⁇ m, 3 ⁇ m, 4 ⁇ m, 5 ⁇ m, 6 ⁇ m, 7 ⁇ m, 8 ⁇ m, 9 ⁇ m, 10 ⁇ m, 11 ⁇ m, 12 ⁇ m, 13 ⁇ m, 14 ⁇ m, 15 ⁇ m, 16 ⁇ m, 17 ⁇ m, 18 ⁇ m, 19 ⁇ m or 20 ⁇ m.
  • the D 50 of the negative electrode material can also be other values in the range of 1 ⁇ m to 20 ⁇ m.
  • the particle size is moderate, and a higher first Coulombic efficiency can be obtained.
  • the particles of the negative electrode material are too small, the more the gap volume between the particles per unit volume, the smaller the volume ratio of the material, which will easily lead to damage to the compacted density.
  • the particles of the negative electrode material are too small, the specific surface area of the negative electrode material in contact with the electrolyte is too large, the SEI film formed during the first charge and discharge consumes more charges, and the irreversible capacity loss is large, which easily leads to a decrease in the first Coulombic efficiency.
  • the particle size distribution (D 90 -D 50 )/(D 50 -D 10 ) of the negative electrode material is 1.2 ⁇ 1.6.
  • the value of (D 90 ⁇ D 50 )/(D 50 ⁇ D 10 ) of the negative electrode material may be, but not limited to, 1.2, 1.3, 1.4, 1.5 or 1.6.
  • the particle size of the negative electrode material can form a better normal distribution, and the particle distribution is wider, so that the small particles in the system The particles can fill the gaps between large particles, which helps to increase the compaction density of the material and increase the energy density of the battery.
  • the particle size distribution is wide, and the viscosity of the slurry is small during coating, which is conducive to increasing the solid content and reducing the difficulty of coating.
  • the active material further includes Si grains, and the size of the Si grains of the negative electrode material is 2nm ⁇ 10nm.
  • the Si grain size of the negative electrode material is 2nm, 3nm, 4nm, 5nm, 6nm, 7nm, 8nm, 9nm or 10nm. It can be understood that the Si grain size of the negative electrode material can also be other values in the range of 2nm-10nm.
  • the specific surface area of the negative electrode material is 1 m 2 /g ⁇ 20 m 2 /g.
  • the specific surface area of the negative electrode material is 1m 2 /g, 2m 2 /g, 3m 2 /g, 4m 2 /g, 5m 2 /g, 6m 2 /g, 7m 2 / g, 8m 2 /g, 9m 2 /g, 10m 2 /g, 11m 2 /g, 12m 2 /g, 13m 2 /g, 14m 2 /g, 15m 2 /g, 16m 2 /g, 17m 2 /g, 18m 2 /g, 19m 2 /g or 20m 2 /g.
  • the specific surface area of the negative electrode material can also be other values in the range of 1 m 2 /g to 20 m 2 /g.
  • FIG. 2 another embodiment of the present application provides a method for preparing an anode material, and the method for preparing an anode material includes the following steps:
  • S101 forming a buffer layer on the surface of the active material to obtain a solid composite, the buffer layer including at least one of alkali metal halides, alkali metal nitrogen compounds, alkali metal oxides, and transition metal oxides;
  • a buffer layer is formed on the surface of the active material to obtain a solid composite, and then the solid composite is subjected to carbon coating treatment to obtain a negative electrode material.
  • the carbon coating treatment forms the carbon layer, with the deposition of carbon atoms on the surface of the buffer layer, under the catalysis of the metal compound in the buffer layer, the amorphous carbon material surface of the carbon layer is generated in situ to form carbon nanomaterials. It is beneficial to simplify the preparation process of the negative electrode material.
  • the presence of carbon nanomaterials can not only improve the ionic conductance and electronic conductance of the negative electrode material, improve the cycle capacity retention rate of the battery, but also effectively buffer the volume expansion of the negative electrode material, so that the negative electrode material maintains a stable structure, thus showing excellent performance. cycle performance.
  • the preparation method in this example is simple and easy to implement, and is convenient for large-scale promotion.
  • this example provides a method for preparing an anode material that does not need to introduce a magnetic material
  • the method for preparing an anode material that does not need to introduce a magnetic material includes the following steps: forming a buffer layer on the surface of SiOx to obtain a solid composite, wherein 0 ⁇ x ⁇ 2; Carry out carbon coating treatment on the solid composite.
  • metals such as iron, nickel and cobalt are used to catalyze the formation of carbon nanomaterials, which not only introduces magnetic substances, but also makes it difficult to control the generation of carbon nanomaterials.
  • demagnetization treatment is not required in the preparation method, which is beneficial to further simplify the preparation process and improve the preparation efficiency.
  • S101 forming a buffer layer on the surface of the active material to obtain a solid composite, where the buffer layer includes at least one of alkali metal halides, alkali metal nitrogen compounds, alkali metal oxides, and transition metal oxides.
  • the alkali metal halide includes at least one of LiF and NaF, and the alkali metal nitrogen compound includes at least one of Li 3 N and KN 3 ;
  • Alkali metal oxides include Li 2 O, K 2 O, Na 2 O, at least one of transition metal oxides Li 2 O, Al 2 O 3 , MgO, TiO 2 , ZnO, CuO, Ag 2 O, and ZrO 2 . It should be noted that the use of magnetic metal oxides such as iron, cobalt, and nickel should be avoided, and the micro-short circuit problem caused by the introduction of magnetic materials should be avoided.
  • the buffer layer may be but not limited to at least one of LiF, Li 2 O, Li 3 N, Al 2 O 3 , TiO 2 , ZnO and ZrO 2 .
  • the buffer layer can be directly coated with buffer layer raw materials in liquid phase.
  • the buffer layer material can be Li 2 O, Li 3 N, Al 2 O 3 , TiO 2 , ZnO and ZrO 2 at least one of .
  • the step of forming a buffer layer on the surface of the active material to obtain a solid composite includes the following steps: mixing the material of the buffer layer and the active material in a solvent to prepare a mixed slurry; Solid-liquid separation treatment to obtain a solid complex.
  • mixing the buffer layer material and the active material in a solvent includes the following steps: preparing a buffer layer material dispersion; mixing the active material with the buffer layer material dispersion.
  • the mixing can be promoted by means of ultrasound and/or stirring.
  • the dispersion can be promoted by means of ultrasound and/or stirring.
  • the dispersion can be promoted by means of ultrasound and/or stirring.
  • the dispersion can be promoted by means of ultrasound and/or stirring.
  • the time for ultrasonication and/or stirring is 20 minutes to 120 minutes.
  • the particle size of the buffer layer material in the mixed slurry is 1 nm ⁇ 1 ⁇ m.
  • the particle size of the buffer layer material in the dispersion liquid is 1 nm to 1 ⁇ m.
  • the particle diameter of the buffer layer material in the mixed slurry or the particle diameter of the buffer layer material in the dispersion can be 1nm, 5nm, 10nm, 15nm, 20nm, 50nm, 60nm, 70nm, 80nm, 90nm, 100nm, 200nm, 300nm, 400nm, 500nm, 600nm, 700nm, 800nm, 900nm, etc.
  • the particle size of the buffer layer material in the mixed slurry or the particle size of the buffer layer in the dispersion liquid may also be other values in the range of 1 nm to 1 ⁇ m.
  • the particle size of the buffer layer material in the mixed slurry or dispersion liquid is too large, it is difficult to disperse to the surface of the active material, and the coating of the buffer layer cannot be achieved.
  • the particle size of the buffer layer material in the mixed slurry or dispersion liquid is too small, the buffer layer particles are prone to agglomeration, resulting in uneven dispersion of the carbon nanomaterials.
  • the solvent includes water.
  • the material of the buffer layer and the active substance can be well dispersed and mixed therein.
  • the buffer layer material accounts for 0.05%-0.2% by mass of the mixed slurry
  • the SiOx accounts for 2%-20% by mass of the mixed slurry.
  • the mass percentage of the buffer layer material in the mixed slurry is 0.05%, 0.08%, 0.1%, 0.12%, 0.15%, 0.18% or 0.2%.
  • the mass percentage of SiOx in the mixed slurry is 2%, 3%, 5%, 8%, 10%, 12%, 15%, 18% or 20%.
  • the solid-liquid separation treatment includes at least one of suction filtration treatment, centrifugation treatment and spray drying treatment.
  • solid-liquid separation treatment includes spray drying treatment.
  • the inlet temperature is 150°C-220°C
  • the outlet temperature is 60°C-110°C.
  • the time for spray drying is 30 minutes to 60 minutes.
  • the inlet temperature is 150°C, 160°C, 170°C, 180°C, 190°C, 200°C, 210°C or 220°C
  • the outlet temperature is 60°C, 70°C, 80°C, 90°C, 100°C or 110°C
  • spray drying time is 30min, 35min, 40min, 45min, 50min, 55min or 60min. It can be understood that, during the spray drying process, the inlet temperature, outlet temperature and spray drying time can be selected independently and correspondingly within the ranges and values listed above.
  • the solid material obtained from solid-liquid separation is dried to obtain a solid composite.
  • the drying temperature is 50°C-100°C
  • the drying time is 10h-30h.
  • the drying temperature is 50°C, 60°C, 70°C, 80°C, 90°C or 100°C
  • the drying time is 10h, 15h, 18h, 20h, 24h, 28h or 30h.
  • the buffer layer can also be prepared by chemical reaction synthesis.
  • the precursor material of the buffer layer can be a lithium source and a fluorine source.
  • the step of forming a buffer layer on the surface of the active material by means of chemical reaction synthesis to obtain a solid composite includes: mixing buffer layer precursor materials in a solvent to prepare a slurry containing buffer layer materials material; adding active substances to the slurry and then performing solid-liquid separation treatment to obtain a solid composite.
  • the material of the buffer layer is LiF.
  • preparing the LiF dispersion includes the following steps: mixing a lithium source and a fluorine source in a solvent to obtain a LiF dispersion.
  • LiF can also be dispersed in a solvent to obtain a LiF dispersion.
  • the lithium source includes at least one of lithium nitrate, lithium acetate, lithium carbonate and lithium oxalate.
  • the fluorine source includes at least one of ammonium fluoride, sodium fluoride and calcium fluoride.
  • the mass percentage of the lithium source in the dispersion is 0.01% to 0.5%
  • the mass percentage of the fluorine source in the dispersion is 0.01% to 0.5%.
  • the mass percentage of the lithium source in the dispersion is 0.01%, 0.02%, 0.05%, 0.08%, 0.1%, 0.12%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45% % or 0.5%.
  • the mass percentage of fluorine source in the dispersion liquid is 0.01%, 0.02%, 0.05%, 0.08%, 0.1%, 0.12%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45% or 0.5% . It can be understood that the mass percentage of the lithium source in the dispersion liquid can also be other values in the range of 0.01% to 0.5%, and the mass percentage of the fluorine source in the dispersion liquid can also be other values in the range of 0.01% to 0.5%.
  • LiF catalyzes carbon atoms to generate carbon nanomaterials in situ
  • the catalytic effect of LiF is weaker than that of metal catalysts. Material generation and growth are controlled.
  • the active material includes SiO x material, 0 ⁇ x ⁇ 2, through heat treatment, the SiO x material can be partially differentiated to form Si and SiO 2 , and its internal buffer matrix can be strengthened, so that the first lithium intercalation platform can gradually become a single substance
  • the proximity of Si improves the electrochemical performance of SiO x .
  • the heat treatment is performed under a protective atmosphere
  • the protective atmosphere includes at least one of nitrogen, argon, helium, neon, krypton and xenon.
  • the heat treatment equipment may be a tube furnace or a box furnace.
  • the protective atmosphere includes at least one of nitrogen, argon, helium, neon, krypton and xenon. Further, during the carbon coating process, the flow rate of the protective atmosphere is 2 mL/min ⁇ 1000 mL/min.
  • the flow rate of the protective atmosphere is 2mL/min, 8mL/min, 10mL/min, 15mL/min, 20mL/min, 30mL/min, 40mL/min, 50mL/min, 80mL/min, 100mL/min , 150mL/min, 200mL/min, 300mL/min, 400mL/min, 500mL/min, 600mL/min, 700mL/min, 800mL/min, 900mL/min or 1000mL/min, etc. It can be understood that the flow rate of the protective atmosphere can also be other values in the range of 2 mL/min to 1000 mL/min.
  • S102 includes: preheating the solid composite, and then performing carbon coating treatment.
  • preheating the solid composite can use a preheated protective atmosphere to preheat the solid composite, which can activate the catalytic activity of the metal compound in the solid composite in advance, which is beneficial to the subsequent carbon coating Catalyze carbon materials to form carbon nanomaterials in coating treatment.
  • the protective atmosphere when using the preheated protective atmosphere to preheat the solid composite, the protective atmosphere is preheated to 100° C. to 300° C.
  • the preheating temperature of the protective atmosphere means the temperature of the protective atmosphere before carbon coating treatment. In this preheating temperature range, the temperature of the protective atmosphere can be effectively used to preheat the solid composite, and the damage to the material structure in the solid composite under vacuum preheating can also be avoided; the metal in the solid composite after preheating Compounds (alkali metal halides, alkali metal nitrogen compounds, alkali metal oxides or transition metal oxides) can fully play a catalytic role and promote the formation of carbon nanomaterials.
  • the protective atmosphere when preheating the protective atmosphere, is preheated to a preset temperature at a heating rate of 1° C./min ⁇ 50° C./min.
  • the preset temperature is 100°C-300°C. Raise the temperature of the protective atmosphere to 100°C to 300°C at a rate of 1°C/min to 50°C/min.
  • controlling the heating rate to the thermal cracking temperature of the carbon source and the thermal cracking temperature of the carbon source can effectively control the disproportionation degree of the SiO x core and maintain the activity of the SiO x core, which is beneficial to the negative electrode.
  • the improvement of the electrochemical performance of the material is not conducive to the improvement of the performance of the negative electrode material, and when the temperature is too high, the energy consumption and cost of carbon coating will also increase accordingly.
  • controlling the heating rate to the thermal cracking temperature of the carbon source and the thermal cracking temperature of the carbon source can effectively control the disproportionation degree of the SiO x core and maintain the activity of the SiO x core, which is beneficial to the negative electrode.
  • the carbon source includes a liquid carbon source and a solid carbon source
  • heat treatment is performed on the solid composite after the carbon coating treatment.
  • the carbon coating treatment includes at least one of solid-phase carbon coating treatment, liquid-phase carbon coating treatment, and gas-phase carbon coating treatment.
  • the carbon coating treatment includes the following steps: under a protective atmosphere, mixing the solid composite with a carbon source, controlling thermal cracking of the carbon source to form a carbon layer on the particle surface of the solid composite.
  • the thermal cracking temperature of the carbon source is 600°C to 1200°C.
  • the thermal cracking temperature of the carbon source is 600°C, 650°C, 700°C, 750°C, 800°C, 850°C, 900°C, 950°C, 1000°C, 1050°C, 1100°C, 1150°C or 1200°C. It can be understood that the thermal cracking temperature of the carbon source can also be other values in the range of 600°C to 1200°C.
  • the heating rate of the thermal cracking of the carbon source is 0.1°C/min-10°C/min, that is, the temperature is raised to the thermal cracking temperature of the carbon source at a heating rate of 0.1°C/min-10°C/min.
  • the temperature increase rate means the temperature increase rate at which the temperature of the solid composite and the carbon source is raised from the initial temperature to the heat treatment temperature.
  • the heating rate is 0.1°C/min, 0.2°C/min, 0.5°C/min, 0.8°C/min, 1°C/min, 1.5°C/min, 2°C/min, 2.5°C/min, 3°C/min, 3.5°C/min, 4°C/min, 4.5°C/min, 5°C/min, 5.5°C/min, 6°C/min, 6.5°C/min, 7°C/min, 7.5°C/min, 8°C/min, 8.5°C/min, 9°C/min, 9.5°C/min or 10°C/min. It can be understood that the heating rate of the thermal cracking of the carbon source can also be other values in the range of 0.1° C./min to 10° C./min.
  • the thermal cracking time of the carbon source is 1 h to 50 h.
  • the thermal cracking time is 1h-10h.
  • the thermal cracking time is 1h, 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h or 10h. It can be understood that the thermal cracking time can also be other values in the range of 1h to 10h.
  • the following step is further included before forming the buffer layer on the surface of the SiO x : performing thermal disproportionation treatment on the SiO x .
  • thermal disproportionation treatment on SiO x first, the Si grain size can be controlled first, and then carbon coating can be carried out, and the first lithium intercalation platform can be gradually approached to simple Si to improve the electrochemical performance of SiO x .
  • the temperature of the thermal disproportionation treatment is 800°C to 1400°C, for example, the temperature of the thermal disproportionation treatment is 800°C, 850°C, 900°C, 950°C, 1000°C, 1050°C, 1100°C, 1150°C, 1200°C, 1250°C °C, 1300 °C, 1350 °C or 1400 °C. It can be understood that the temperature of the thermal disproportionation treatment can also be other values in the range of 800°C to 1400°C. Still further, the heating rate of the thermal disproportionation treatment is 1° C./min ⁇ 5° C./min.
  • the heating rate of thermal disproportionation treatment can be 1°C/min, 1.5°C/min, 2°C/min, 2.5°C/min, 3°C/min, 3.5°C/min, 4°C/min, 4.5°C/min or 5°C °C/min.
  • the temperature of thermal disproportionation is selected to be higher than the temperature of thermal cracking.
  • the equipment for carbon coating treatment may be a rotary kiln, a box furnace, a roller kiln, a tunnel kiln, a pusher kiln, and the like.
  • the solid composite when mixing the solid composite with the carbon source, the solid composite is cooled prior to mixing it with the carbon source.
  • the carbon source includes a gas phase carbon source.
  • the carbon source includes gas phase hydrocarbon carbon source.
  • the carbon source includes at least one of methane, ethane, propane, ethylene, propylene, acetylene, propyne, acetone and benzene.
  • the gaseous carbon source is introduced into the gaseous carbon source under a protective atmosphere to mix the gaseous carbon source with the solid compound.
  • amorphous carbon is deposited on the surface of the solid composite for carbon coating.
  • the carbon coating treatment is performed in a rotary furnace or a box furnace.
  • the carbon source includes a liquid carbon source.
  • the carbon source includes a liquid-phase organic carbon source.
  • the carbon source includes n-hexane, toluene, benzene, xylene, methanol, ethanol, propanol, butanol, pentanol, acetone, butanone, 2-pentanone, methyl acetate, ethyl acetate, propyl acetate At least one of ester, butyl acetate and amyl acetate.
  • the flow rate of the liquid-phase carbon source is 1 mL/min ⁇ 200 mL/min.
  • the flow rate of liquid carbon source is 1mL/min, 5mL/min, 8mL/min, 10mL/min, 15mL/min, 20mL/min, 30mL/min, 40mL/min, 50mL/min, 80mL/min, 100mL /min, 150mL/min, 200mL/min.
  • the carbon source includes at least one of benzene and toluene, or at least one of methanol, ethanol, propanol, butanol and pentanol.
  • the carbon coating treatment is carried out in a rotary kiln, a box furnace, a roller kiln, a tunnel kiln or a pusher kiln.
  • the mixing method of the solid compound and the carbon source can be VC mixing, fusion, ball milling, suction filtration, heating reflux, three-dimensional mixing or fluidized bed mixing, etc.
  • the carbon source includes a solid-phase carbon source.
  • the carbon source includes a solid-phase organic carbon source.
  • the carbon source includes at least one of citric acid, glucose, pitch, phenolic resin and furfural resin.
  • the carbon coating treatment is performed in a rotary kiln, a box furnace, a roller kiln, a tunnel kiln or a pusher kiln.
  • the mixing method of the solid composite and the carbon source can be VC mixing, fusion, ball milling, suction filtration, heating to reflux, three-dimensional mixing or fluidized bed mixing, etc.
  • the following steps are further included: heat-treating the solid composite after the carbon-coating treatment, the temperature of the heat treatment is 600°C-1200°C, and the time of the heat treatment is 1h-48h,
  • the heating rate of the heat treatment is 1° C./min to 5° C./min.
  • the heat treatment temperature may be 600°C, 650°C, 700°C, 750°C, 800°C, 850°C, 900°C, 950°C, 1000°C, 1050°C, 1100°C, 1150°C or 1200°C.
  • the time of heat treatment can be 1h, 1.5h, 2h, 2.5h, 3h, 3.5h or 4h.
  • the heating rate of heat treatment can be 1°C/min, 1.5°C/min, 2°C/min, 2.5°C/min, 3°C/min, 3.5°C/min, 4°C/min, 4.5°C/min or 5°C/min . It can be understood that, during the heat treatment, the temperature of the heat treatment, the time of the heat treatment and the heating rate of the heat treatment can be selected independently and correspondingly within the ranges and values listed above. It can also be understood that the heating rate of the heat treatment means the heating rate of raising the temperature of the heat treatment from the initial temperature to the heat treatment temperature.
  • the negative electrode sheet includes the above-mentioned negative electrode material; or includes the negative electrode material prepared by the above-mentioned preparation method.
  • the negative electrode sheet includes a current collector and the above-mentioned negative electrode material; or includes a current collector and the negative electrode material prepared by the above-mentioned preparation method; the negative electrode material is located on the surface of the current collector.
  • the current collector is a copper current collector or an aluminum current collector.
  • the lithium ion battery includes the above negative electrode material, or the negative electrode material prepared by the above preparation method.
  • the lithium ion battery has a high cycle capacity retention rate.
  • the lithium ion battery includes the above-mentioned negative electrode sheet.
  • the rechargeable electrical product includes the above negative electrode material, or the negative electrode material prepared by the above preparation method.
  • the rechargeable electric product includes the above-mentioned negative electrode sheet.
  • the rechargeable electric product includes the above-mentioned lithium-ion battery.
  • SEM scanning electron microscope
  • EDS X-ray energy spectroscopy
  • the specific surface area was measured by using the American Mike TriStar3000 specific surface area and pore size analyzer.
  • the measurement method of the surface density of carbon nanomaterials first, randomly select three areas with an area of 100mm*75mm for SEM photography, then use ProSEM software to open the pre-saved SEM image, and then select a typical one in this 2D image Features (nanowire structure), click the "Find Similar” button to find similar features, ProSEM automatically finds similar features in the image, so that you can get the number of nanowires in this area, divide the number by the image size of SEM, The areal densities of the carbon nanomaterials can be obtained, and the areal densities of the carbon nanomaterials in the three regions are averaged.
  • the negative electrode material that present embodiment makes comprises SiO core, be positioned at the LiF buffer layer and carbon layer on the surface of SiO core, LiF buffer layer is formed on the surface of SiO core, carbon layer comprises the amorphous carbon material that is positioned at the buffer layer surface and moves toward and away from.
  • the thickness of the LiF buffer layer is 0.5 ⁇ m; the thickness of the carbon layer is 500 nm; wherein, the buffer layer accounts for 5% by mass of the negative electrode material; the carbon layer accounts for 5% by mass of the negative electrode material.
  • Lithium nitrate and sodium fluoride were mixed in deionized water, stirred and sonicated for 120 min to obtain a LiF dispersion.
  • the mass percentage of lithium nitrate in the dispersion liquid is 2%
  • the mass percentage of sodium fluoride in the dispersion liquid is 2%.
  • the low-temperature liquid phase pitch is used as the carbon source
  • nitrogen is used as the protective atmosphere
  • a rotary furnace is used for carbon coating treatment.
  • the granular structure of the negative electrode material that present embodiment makes comprises SiO 1.5 core, is positioned at the LiF buffer layer and carbon layer on the surface of SiO 1.5 core, LiF buffer layer is formed on the surface of SiO 1.5 core, and carbon layer comprises the amorphous carbon that is positioned at the buffer layer surface Material and the carbon nanomaterial extending toward and away from the direction of the buffer layer, the carbon nanomaterial is a carbon nanotube; the diameter of the carbon nanomaterial is 20nm; the aspect ratio of the nanomaterial is 500; the surface density of the carbon nanomaterial is 1000 pieces/mm 2 ;
  • the thickness of the LiF buffer layer is 0.02 ⁇ m; the thickness of the carbon layer is 1000 nm; wherein, the buffer layer accounts for 15% by mass of the negative electrode material; the carbon layer accounts for 8% by mass of the negative electrode material.
  • the negative electrode material prepared in this embodiment includes a SiO 0.8 core, a LiF buffer layer and a carbon layer on the surface of the SiO 0.8 core, the LiF buffer layer is formed on the surface of the SiO 0.8 core, and the carbon layer includes an amorphous carbon material and a carbon layer on the surface of the buffer layer.
  • the carbon nanomaterials extending in the direction close to and away from the buffer layer, the carbon nanomaterials are carbon nanofibers; the diameter of the carbon nanomaterials is 100nm; the aspect ratio of the nanomaterials is 1000; the surface density of the carbon nanomaterials is 5000/ mm2 ;
  • the thickness of the LiF buffer layer is 1.5 ⁇ m; the thickness of the carbon layer is 200 nm; wherein, the mass percentage of the buffer layer in the negative electrode material is 20%; the mass percentage of the carbon layer in the negative electrode material is 2%.
  • Example 1 The difference from Example 1 is that LiF is replaced by Al 2 O 3 .
  • the negative electrode material that present embodiment makes comprises SiO core is positioned at the Al2O3 buffer layer and carbon layer on the surface of SiO core, Al2O3 buffer layer is formed on the surface of SiO core, and carbon layer comprises the amorphous carbon that is positioned at the buffer layer surface Material and the carbon nanomaterial extending toward and away from the buffer layer, the carbon nanomaterial is a carbon nanowire; the diameter of the carbon nanomaterial is 60nm; the aspect ratio of the nanomaterial is 80; the surface density of the carbon nanomaterial is 200 pieces/mm 2 ;
  • the thickness of the Al 2 O 3 buffer layer is 0.5 ⁇ m; the thickness of the carbon layer is 500 nm; wherein, the buffer layer accounts for 5% by mass of the negative electrode material; the carbon layer accounts for 5% by mass of the negative electrode material.
  • Example 1 The difference from Example 1 is that LiF is replaced by Li 2 O.
  • the negative electrode material prepared in this embodiment includes a SiO core, a Li 2 O buffer layer and a carbon layer on the surface of the SiO core, the Li 2 O buffer layer is formed on the surface of the SiO core, and the carbon layer includes an amorphous carbon material on the surface of the buffer layer and
  • the carbon nanomaterials extending toward and away from the buffer layer, the carbon nanomaterials are carbon nanowires; the diameter of the carbon nanomaterials is 40nm; the aspect ratio of the eye nanomaterials is 90; the surface density of the carbon nanomaterials is 250 root/mm 2 ;
  • the thickness of the Li 2 O buffer layer is 0.9 ⁇ m, and the thickness of the carbon layer is 500 nm; wherein, the buffer layer accounts for 5% by mass of the negative electrode material; the carbon layer accounts for 5% by mass of the negative electrode material.
  • Example 1 The difference from Example 1 is that LiF is replaced by TiO 2 .
  • the negative electrode material that the present embodiment makes comprises SiO inner core is positioned at the TiO of SiO inner core surface Buffer layer and carbon layer, TiO Buffer layer is formed on SiO inner core surface, and carbon layer comprises the amorphous carbon material that is positioned at buffer layer surface and close to And the carbon nanomaterial that extends away from the direction of the buffer layer, the carbon nanomaterial is carbon nanowire; the diameter of the carbon nanomaterial is 70nm; the aspect ratio of the eye nanomaterial is 150; the surface density of the carbon nanomaterial is 500/ mm2 ;
  • the thickness of the TiO2 buffer layer is 1 ⁇ m, and the thickness of the carbon layer is 500nm; wherein, the buffer layer accounts for 5% by mass of the negative electrode material; the carbon layer accounts for 5% by mass of the negative electrode material.
  • the difference between this embodiment and the embodiment 1 is that before adding the SiO powder to the dispersion liquid, the SiO powder is also subjected to thermal disproportionation treatment.
  • the temperature of the thermal disproportionation treatment is 900°C.
  • the negative electrode material that present embodiment makes comprises SiO core, be positioned at the LiF buffer layer and carbon layer on the surface of SiO core, LiF buffer layer is formed on the surface of SiO core, carbon layer comprises the amorphous carbon material that is positioned at the buffer layer surface and moves toward and away from.
  • the thickness of the LiF buffer layer is 0.5 ⁇ m, and the thickness of the carbon layer is 500 nm; wherein, the buffer layer accounts for 5% by mass of the negative electrode material; the carbon layer accounts for 5% by mass of the negative electrode material.
  • Example 1 The difference between this example and Example 1 is that the thermal cracking temperature of the carbon source is 600°C.
  • the negative electrode material that present embodiment makes comprises SiO core, be positioned at the LiF buffer layer and carbon layer on the surface of SiO core, LiF buffer layer is formed on the surface of SiO core, carbon layer comprises the amorphous carbon material that is positioned at the buffer layer surface and moves toward and away from.
  • the thickness of the LiF buffer layer is 0.5 ⁇ m, and the thickness of the carbon layer is 500 nm; wherein, the buffer layer accounts for 5% by mass of the negative electrode material; the carbon layer accounts for 5% by mass of the negative electrode material.
  • the difference between this example and Example 1 is that the thermal cracking temperature of the carbon source is 1200°C.
  • the negative electrode material that present embodiment makes comprises SiO core, be positioned at the LiF buffer layer and carbon layer on the surface of SiO core, LiF buffer layer is formed on the surface of SiO core, carbon layer comprises the amorphous carbon material that is positioned at the buffer layer surface and moves toward and away from.
  • the thickness of the LiF buffer layer is 0.4 ⁇ m, and the thickness of the carbon layer is 500 nm; wherein, the buffer layer accounts for 5% by mass of the negative electrode material; the carbon layer accounts for 5% by mass of the negative electrode material.
  • Example 2 The difference between this example and Example 2 is that the heat treatment temperature after the carbon coating treatment is 600°C.
  • the negative electrode material prepared in this embodiment includes a SiO 1.5 core, a LiF buffer layer and a carbon layer positioned on the surface of the SiO 1.5 core, the LiF buffer layer is formed on the surface of the SiO 1.5 core, and the carbon layer includes an amorphous carbon material and a carbon layer positioned on the surface of the buffer layer. carbon nanomaterials extending in a direction close to and away from the buffer layer,
  • the carbon nanomaterial is a carbon nanotube; the diameter of the carbon nanomaterial is 15nm; the aspect ratio of the nanomaterial is 300; the surface density of the carbon nanomaterial is 200/mm 2 ;
  • the thickness of the LiF buffer layer is 0.02 ⁇ m, and the thickness of the carbon layer is 1000 nm; wherein, the buffer layer accounts for 15% by mass of the negative electrode material; the carbon layer accounts for 5% by mass of the negative electrode material.
  • the difference between this example and Example 2 is that the heat treatment temperature after the carbon coating treatment is 1200°C.
  • the negative electrode material prepared in this embodiment includes a SiO 1.5 core, a LiF buffer layer and a carbon layer positioned on the surface of the SiO 1.5 core, the LiF buffer layer is formed on the surface of the SiO 1.5 core, and the carbon layer includes an amorphous carbon material and a carbon layer positioned on the surface of the buffer layer.
  • the carbon nanomaterials extending in the direction close to and away from the buffer layer, the carbon nanomaterials are carbon nanotubes; the diameter of the carbon nanomaterials is 50nm; the aspect ratio of the nanomaterials is 600; the surface density of the carbon nanomaterials is 4000/ mm2 ;
  • the thickness of the LiF buffer layer is 0.015 ⁇ m, and the thickness of the carbon layer is 1000 nm; wherein, the buffer layer accounts for 15% by mass of the negative electrode material; the carbon layer accounts for 5% by mass of the negative electrode material.
  • the negative electrode material that present embodiment makes comprises SiO core, be positioned at the LiF buffer layer and carbon layer on the surface of SiO core, LiF buffer layer is formed on the surface of SiO core, carbon layer comprises the amorphous carbon material that is positioned at the buffer layer surface and moves toward and away from.
  • the thickness of the LiF buffer layer is 5 ⁇ m, and the thickness of the carbon layer is 800 nm; wherein, the buffer layer accounts for 50% by mass of the negative electrode material; the carbon layer accounts for 5% by mass of the negative electrode material.
  • Example 2 The difference from Example 1 is that SiO with a sphericity coefficient of 0.96 is selected as the raw material.
  • the negative electrode material that present embodiment makes comprises SiO core, be positioned at the LiF buffer layer and carbon layer on the surface of SiO core, LiF buffer layer is formed on the surface of SiO core, carbon layer comprises the amorphous carbon material that is positioned at the buffer layer surface and moves toward and away from.
  • the thickness of the LiF buffer layer is 0.5 ⁇ m, and the thickness of the carbon layer is 500 nm; wherein, the buffer layer accounts for 5% by mass of the negative electrode material; the carbon layer accounts for 5% by mass of the negative electrode material.
  • this embodiment does not use the preheated protective atmosphere to preheat the solid composite when performing carbon coating treatment on the solid composite in step (4).
  • the negative electrode material that this comparative example makes comprises SiO 1.5 core, is positioned at the LiF buffer layer and carbon layer on the surface of SiO 1.5 core, LiF buffer layer is formed on the surface of SiO1.5 core, and carbon layer includes being positioned at the amorphous carbon material on the surface of buffer layer And the carbon nanomaterial that extends to the direction close to and away from the buffer layer;
  • the carbon nanomaterial is a carbon nanotube;
  • the diameter of the carbon nanomaterial is 20nm;
  • the aspect ratio of the carbon nanomaterial is 500;
  • the surface density of the carbon nanomaterial is 15 pieces/mm 2 ;
  • the thickness of the LiF buffer layer is 0.02 ⁇ m; the thickness of the carbon layer is 1000 nm; wherein, the buffer layer accounts for 15% by mass of the negative electrode material; the carbon layer accounts for 8% by mass of the negative electrode material.
  • the preparation method of negative electrode material in this comparative example is:
  • SiO sinode-coated carbon-coated carbon-coated.
  • methane is used as the carbon source
  • nitrogen is used as the protective atmosphere
  • a rotary furnace is used for carbon coating treatment.
  • the negative electrode material prepared in this comparative example includes a SiO core and an amorphous carbon layer on the surface of the SiO core without nanostructures.
  • the thickness of the carbon layer is 500nm; the mass percentage of the carbon layer in the negative electrode material is 5%.
  • the negative electrode material prepared in this comparative example includes a SiO core, a carbon layer on the surface of the SiO core, and the carbon layer includes an amorphous carbon material and a carbon nanomaterial on the surface of the SiO core.
  • the carbon nanomaterial is carbon nanowire; the diameter of the carbon nanomaterial is 100nm; the aspect ratio of the nanomaterial is 10,000; the surface density of the carbon nanomaterial is 100,000 pieces/mm 2 ; the thickness of the carbon layer is 500nm; the carbon layer occupies the negative electrode
  • the mass percentage of the material is 5%.
  • the negative electrode material also includes a ferromagnetic material, the existence of the ferromagnetic material may cause a micro-short circuit problem of the battery, and further demagnetization treatment is required for the negative electrode material.
  • the preparation method of negative electrode material in this comparative example is:
  • the negative electrode material prepared in this comparative example includes a SiO core, a carbon layer located on the surface of the SiO core, and the carbon layer includes an amorphous carbon material located on the surface of the SiO core and a carbon nanomaterial attached to the carbon layer ex-situ.
  • the carbon nanomaterial is a carbon nanotube; the diameter of the carbon nanomaterial is 1.8nm; the aspect ratio of the nanomaterial is 2500; the surface density of the carbon nanomaterial is 500/mm 2 ; the thickness of the carbon layer is 500nm;
  • the mass percentage of negative electrode material is 5%.
  • the preparation method of negative electrode material in this comparative example is:
  • the negative electrode material prepared in this comparative example includes a SiO core, a carbon layer on the surface of the SiO core, and a LiF layer.
  • the carbon layer is formed on the surface of the SiO core, and the LiF layer is located on the surface of the carbon layer. There is no carbon nanostructure.
  • the thickness of the carbon layer is 500nm; the mass percentage of the carbon layer in the negative electrode material is 5%.
  • the test method for the reversible specific capacity and the first Coulombic efficiency is: according to the negative electrode material, conductive carbon black, polyacrylic acid glue (PAA glue) according to the mass ratio of 75:15:10 to prepare the negative electrode slurry, on the copper foil coated, dried and made into a negative electrode sheet.
  • a lithium metal sheet was used as a counter electrode and assembled into a button cell in an argon-filled glove box. Under the current density of 0.1C, the charge and discharge test is carried out according to the charge and discharge interval of 0.01-1.5V. The first reversible specific capacity and the first coulombic efficiency of the battery were tested.
  • FIG. 3a The structure of the negative electrode material in Example 1 is shown in Figure 3a and Figure 3b, wherein Figure 3a is a surface structure diagram of the negative electrode material prepared in Example 1, and Figure 3b is a cross-sectional view of the negative electrode material produced in Example 1. It can be seen from Figure 3a and Figure 3b that there is a nanowire structure on the surface of the negative electrode material, and the particle size is below 100nm. And according to Fig. 3b, it can be seen that part of the nanowires extend toward the interior of the negative electrode material.
  • FIG. 4a is the surface structure figure of the nanowire in the negative electrode material in embodiment 2
  • Fig. 5 b is the EDS energy spectrum of the nanowire in the negative electrode material in embodiment 2
  • the nanowire mainly contains carbon element composition, indicating that carbon nanomaterials were formed on the surface of the anode material.
  • the structure of the negative electrode material in Comparative Example 1 is shown in Figure 6a and Figure 6b. It can be seen from Figure 6a and Figure 6b that there is no nanowire structure in the negative electrode material of Comparative Example 1, and except that there is no nanowire structure.
  • the surface morphology is similar to Example 1 and Example 2.
  • the lithium-ion batteries made of negative electrode materials in Example 1 and Comparative Example 1 have similar cycle retention rates in the early stage, but after 25 cycles, the lithium ion batteries made of negative electrode materials in Example 1
  • the cycle retention rate of the ion battery is significantly higher than that of Comparative Example 1.
  • the reason may be that the volume expansion of the double-layer flexible structure buffer material in the negative electrode material reduces the formation of the SEI film.
  • the presence of carbon nanomaterials improves the electronic conductivity. Performance, which promotes the improvement of battery cycle performance.
  • Example 1 and Example 14 Comparing Example 1 and Example 14 in the table, it can be seen that if the solid composite is not preheated, the metal compound in the solid mixture is put into the reaction furnace at normal temperature, and its catalytic activity is low, and the raw materials cannot be completely reacted, affecting the carbon nanotubes. As a result, the surface density of the obtained carbon nanowires is small, and the side reactions of the material during the cycle are reduced, thereby improving the specific capacity and the first effect. However, due to the low content of carbon nanotubes, it will affect its Cycle capacity retention and cycle volume expansion.
  • the Coulombic efficiency for the first time and the capacity retention rate after 50 cycles are higher, and the volume expansion rate after 50 cycles is smaller.
  • the reason is that the improvement of capacity retention and expansion rate is derived from the improvement of coating toughness brought about by the LiF artificial SEI film structure and the suppression of the formation of natural SEI film, which is conducive to maintaining the structural integrity of SiOx particles.
  • the improvement of the first Coulombic efficiency is due to its high electrical insulation and wide bandwidth. This characteristic prevents the electrolyte from decomposing, thus limiting the additional SEI generation, which reduces the irreversible capacity and leads to the first Coulombic efficiency improvement.
  • Example 1 Comparing Example 1 and Comparative Example 3 in the table, since the subsequent addition of CNT is not generated in situ and cannot penetrate the carbon coating to form a "cage" structure, it is more effective in maintaining the interface during the cycle than in Example 1.
  • the effect of stability is weak, so that the particles are more likely to be broken and collapsed than in Example 1, so the continuous penetration of the electrolyte makes the new SEI film continue to be generated, resulting in an increase in the irreversible specific capacity during the cycle, which is reflected as slightly Decreased capacity retention and slightly increased expansion.
  • the preparation method in Example 1 has better cycle performance than adding CNT later.
  • Example 1 and Comparative Example 4 in the comparison table if the C layer is coated with the SiO core, and the buffer layer is coated with the C layer, forming a structure that is SiO core-C layer-buffer layer from the inside to the outside, although this structure can be To a certain extent, the first Coulombic efficiency is improved, but because it coats the highly electrically insulating LiF on the outermost layer, it will affect the cycle performance of the material, and the improvement of electronic conductance brought by the coating of the C layer cannot be brought into play.

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Abstract

本申请涉及一种负极材料及其制备方法和应用。所述负极材料包括活性物质、位于活性物质表面的缓冲层和碳层，其中，所述缓冲层形成于所述活性物质表面，所述碳层包括位于所述缓冲层表面的无定型碳材料及向靠近及/或远离所述缓冲层的方向延伸的碳纳米材料。在上述负极材料的颗粒结构中，缓冲层具有一定的韧性，能够有效缓冲负极材料的体积膨胀，同时碳纳米材料的延伸也提供了一定的缓冲效果，可以进一步缓冲负极材料的体积膨胀，减少充放电过程中负极材料颗粒间的应力，从而可以提高负极材料结构的稳定性，进而可以提高电池的循环容量保持率。

Description

负极材料及其制备方法、锂离子电池
本申请要求于2021年12月31日提交中国专利局，申请号为202111673916X、申请名称为“负极材料及其制备方法和应用”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
本申请涉及锂离子电池领域，涉及负极材料及其制备方法、锂离子电池。
背景技术
随着新能源技术的不断发展，锂离子电池的使用范围越来越大，传统的负极碳材料由于具有较低的理论比容量(372mAh/g)而限制了其广泛使用。在非碳材料中，Si基材料由于具有较高的比容量(4200mAh/g)和较合适的嵌锂电位(0～0.3V)且来源广泛而成为较为热门的负极材料的研究对象。但是，传统的Si基材料在嵌脱锂是存在较为严重的体积膨胀，从而可能导致材料的结构崩塌和电极材料的剥落，进而使得电池的循环容量保持率表现欠佳。
申请内容
针对现有技术中存在的上述问题，本申请的目的在于提供负极材料及其制备方法、锂离子电池，本申请的负极材料能够有效缓冲负极材料的体积膨胀，提高负极材料结构的稳定性，进而可以提高电池的循环容量保持率。
为实现上述申请目的，第一方面，本申请提供一种负极材料，所述负极材料包括活性物质、位于活性物质表面的缓冲层和碳层，其中，所述缓冲层形成于所述活性物质表面，所述碳层包括位于所述缓冲层表面的无定型碳材料及向靠近和/或远离所述缓冲层的方向延伸的碳纳米材料。
在一些实施方式中，所述碳纳米材料向靠近所述缓冲层的方向延伸至所述缓冲层。
在一些实施方式中，所述碳纳米材料向靠近所述缓冲层的方向延伸并贯穿所述缓冲层延伸至所述活性物质。
在一些实施方式中，所述碳纳米材料连接所述无定型碳材料以及所述缓冲层。
在一些实施方式中，所述碳纳米材料贯穿所述缓冲层并连接所述无定型碳材料以及所述活性物质。
在一些实施方式中，所述碳纳米材料包括碳纳米管、碳纳米纤维以及石墨烯中的至少一种。
在一些实施方式中，所述碳纳米材料的形状包括线状、管状、片状以及长条状中的至少一种。
在一些实施方式中，所述碳纳米材料的直径为1nm～100nm。
在一些实施方式中，所述碳纳米材料的长径比≥10。
在一些实施方式中，所述负极材料中，所述碳纳米材料的面密度为20根 /mm 2～10000根/mm 2。
在一些实施方式中，所述缓冲层包括碱金属卤化物、碱金属氮化合物、碱金属氧化物和过渡金属氧化物中的至少一种。
在一些实施方式中，所述缓冲层包括LiF及Li 3N中的至少一种。
在一些实施方式中，所述缓冲层包括Li 2O、Al 2O 3、TiO 2、ZnO以及ZrO 2中的至少一种。
在一些实施方式中，所述缓冲层能催化所述无定型碳材料形成所述碳纳米材料。
在一些实施方式中，所述缓冲层能催化所述无定型碳材料原位生长形成所述碳纳米材料。
在一些实施方式中，所述缓冲层的厚度为0.01μm～2μm。
在一些实施方式中，所述缓冲层包括LiF、Li 2O、Li 3N、Al 2O 3、TiO 2、ZnO以及ZrO 2中的至少一种。
在一些实施方式中，所述活性物质包括SiO x材料，0＜x＜2。
在一些实施方式中，所述活性物质包括SiO x材料，0.8≤x≤1.5。
在一些实施方式中，所述活性物质包括SiO x材料，SiO x材料颗粒呈球形或类球形。
在一些实施方式中，所述活性物质包括SiO x材料，所述SiO x材料颗粒的球形度系数≥0.4。
在一些实施方式中，所述缓冲层占所述负极材料的质量百分数为0.05％～20％。
在一些实施方式中，所述碳层占所述负极材料的质量百分数为0.5％～20％。
在一些实施方式中，所述碳层的厚度为10nm～1500nm。
在一些实施方式中，所述负极材料的D 50为1μm～20μm。
在一些实施方式中，所述负极材料的粒径分布(D 90-D 50)/(D 50-D 10)为1.2～1.6。
在一些实施方式中，所述活性物质包括Si晶粒。
在一些实施方式中，所述活性物质包括Si晶粒，所述Si晶粒尺寸为2nm～10nm。
在一些实施方式中，所述负极材料的比表面积为1m 2/g～20m 2/g。
第二方面，本申请提供一种负极材料的制备方法，包括如下步骤：
在活性物质表面形成缓冲层，得到固体复合物，所述缓冲层包括碱金属卤化物、碱金属氮化合物、碱金属氧化物和过渡金属氧化物中的至少一种；
在保护气氛中对所述固体复合物进行碳包覆处理，得到负极材料，所述负极材料包括活性物质、位于活性物质表面的缓冲层和碳层，所述碳层包括无定型碳材料以及碳纳米材料，所述碳纳米材料自所述无定型碳材料向靠近和/或远离所述缓冲层的方向延伸。
在一些实施方式中，所述活性物质包括SiO x材料，0＜x＜2。
在一些实施方式中，所述活性物质包括SiO x材料，0.8≤x≤1.5。
在一些实施方式中，所述活性物质包括SiO x材料，SiO x材料颗粒呈球形或类球形。
在一些实施方式中，所述活性物质包括SiO x材料，所述SiO x材料颗粒的球形度系数≥0.4。
在一些实施方式中，所述活性物质包括Si晶粒。
在一些实施方式中，所述活性物质包括Si晶粒，所述Si晶粒尺寸为2nm～10nm。
在一些实施方式中，所述缓冲层能催化所述无定型碳材料形成所述碳纳米材料。
在一些实施方式中，所述缓冲层能催化所述无定型碳材料原位生长形成所述碳纳米材料。
在一些实施方式中，所述缓冲层包括碱金属卤化物、碱金属氮化合物、碱金属氧化物和过渡金属氧化物中的至少一种。
在一些实施方式中，所述缓冲层包括LiF、NaF及Li 3N中的至少一种。
在一些实施方式中，所述缓冲层包括Li 2O、Al 2O 3、MgO、TiO 2、ZnO、CuO、Ag 2O以及ZrO 2中的至少一种。
在一些实施方式中，所述缓冲层的厚度为0.01μm～2μm。
在一些实施方式中，所述缓冲层包括LiF、Li 2O、Li 3N、Al 2O 3、TiO 2、ZnO以及ZrO 2中的至少一种。
在一些实施方式中，所述在活性物质表面形成缓冲层的方式为液相包覆。
在一些实施方式中，所述在活性物质表面形成缓冲层，得到固体复合物的步骤，包括：将缓冲层材料与活性物质在溶剂中混合，制备混合浆料，并对混合浆料进行固液分离处理，得到固体复合物。
在一些实施方式中，所述混合浆料中缓冲层材料的粒径为1nm～1μm。
在一些实施方式中，所述溶剂包括水、乙醇中的至少一种。
在一些实施方式中，所述缓冲层材料占所述混合浆料的质量百分数为0.05％～0.2％。
在一些实施方式中，所述活性物质占所述混合浆料的质量百分数为2％～20％。
在一些实施方式中，所述固液分离处理包括抽滤处理、离心处理以及喷雾干燥处理中的至少一种。
在一些实施方式中，所述在活性物质表面形成缓冲层，得到固体复合物的步骤，包括：将缓冲层前驱体材料在溶剂中混合，制备含缓冲层材料的分散液。往分散液中加入活性物质混合后进行固液分离处理，得到固体复合物。
在一些实施方式中，所述缓冲层前驱体材料包括锂源及氟源。
在一些实施方式中，所述缓冲层前驱体材料包括锂源及氟源，所述锂源包括硝酸锂、醋酸锂、碳酸锂以及草酸锂中的至少一种。
在一些实施方式中，所述缓冲层前驱体材料包括锂源及氟源，所述氟源包括氟化铵、氟化钠以及氟化钙中的至少一种。
在一些实施方式中，所述缓冲层前驱体材料包括锂源及氟源，所述锂源占所述分散液的质量百分数为0.01％～0.5％，所述氟源占所述分散液的质量百分数为0.01％～0.5％。
在一些实施方式中，所述方法还包括：对所述固体复合物进行预热，再进行碳包覆处理。
在一些实施方式中，所述方法还包括：采用预热的保护气氛对所述固体复合物进 行预热，再进行碳包覆处理。
在一些实施方式中，所述方法还包括：采用预热的保护气氛对所述固体复合物进行预热，再进行碳包覆处理，其中，所述保护气氛的预热温度为100℃～300℃。
在一些实施方式中，所述方法还包括：采用预热的保护气氛对所述固体复合物进行预热，再进行碳包覆处理，其中，所述保护气氛的升温速率为1℃/min～50℃/min。
在一些实施方式中，所述碳包覆处理包括固相碳包覆处理、液相碳包覆处理以及气相碳包覆处理中的至少一种。
在一些实施方式中，所述碳包覆处理包括如下步骤：将所述固体复合物与碳源混合，控制所述碳源热裂解以在所述固体复合物的颗粒表面形成碳层。
在一些实施方式中，对所述固体复合物进行碳包覆处理之后还包括如下步骤：对进行碳包覆处理之后的固体复合物进行热处理。
在一些实施方式中，所述保护气氛包括氮气、氩气、氦气、氖气、氪气以及氙气中的至少一种。
在一些实施方式中，所述碳源包括气相碳源。
在一些实施方式中，所述碳源包括气相碳源，所述气相碳源包括气相烃类碳源。
在一些实施方式中，所述碳源包括气相碳源，所述气相碳源包括甲烷、乙烷、丙烷、乙烯、丙烯、乙炔、丙炔、丙酮以及苯中的至少一种。
在一些实施方式中，所述碳源包括液相碳源。
在一些实施方式中，所述碳源包括液相碳源，所述液相碳源包括液相有机碳源。
在一些实施方式中，所述碳源包括液相碳源，所述液相碳源包括正己烷、甲苯、苯、二甲苯、甲醇、乙醇、丙醇、丁醇、戊醇、丙酮、丁酮、2-戊酮、乙酸甲酯、乙酸乙酯、乙酸丙酯、乙酸丁酯以及乙酸戊酯中的至少一种。
在一些实施方式中，所述碳源包括固相碳源。
在一些实施方式中，所述碳源包括固相碳源，所述固相碳源包括固相有机碳源。
在一些实施方式中，所述碳源包括固相碳源，所述固相碳源包括柠檬酸、葡萄糖、沥青、酚醛树脂以及糠醛树脂中的至少一种。
在一些实施方式中，所述热裂解的温度为600℃～1200℃。
在一些实施方式中，所述热裂解的升温速率为0.1℃/min～10℃/min。
在一些实施方式中，所述热处理的温度为600℃～1200℃。
在一些实施方式中，所述热处理的升温速率为1℃/min～5℃/min。
在一些实施方式中，所述热处理的时间为1h～48h。
在一些实施方式中，所述活性物质包括SiO x材料，0＜x＜2。在活性物质表面形成缓冲层之前，所述方法还包括如下步骤：
对所述SiO x材料进行热歧化处理。
在一些实施方式中，所述热歧化处理的温度为800℃～1400℃。
在一些实施方式中，所述热歧化处理的升温速率为1℃/min～5℃/min。
在一些实施方式中，所述热歧化处理的时间为2h～50h。
第三方面，本申请提供一种锂离子电池，包括如上述的负极材料或根据上述的负极材料的制备方法制得的负极材料。
第四方面，本申请提供一种可充电用电产品，包括如上述的锂离子电池。
与现有技术相比，本申请具有以下有益效果：
本申请提供的负极材料包括活性物质、位于活性物质表面的缓冲层和碳层，其中，所述缓冲层形成于所述活性物质表面，所述碳层包括位于所述缓冲层表面的无定型碳材料及向靠近及/或远离所述缓冲层的方向延伸的碳纳米材料。
在上述负极材料的颗粒结构中，缓冲层具有一定的韧性，能够有效缓冲负极材料的体积膨胀，同时碳纳米材料的延伸也提供了一定的缓冲效果，可以进一步缓冲负极材料的体积膨胀，减少充放电过程中负极材料颗粒间的应力，从而可以提高负极材料结构的稳定性，进而可以提高电池的循环容量保持率。
另外，碳纳米材料一方面能够提高电子和离子的导通率，改善导电性能，另一方面还可以有效规避和弱化缓冲层的电绝缘性所带来的对电子电导的不利影响，进而使负极材料具有较高的离子电导和电子电导，进一步提高电池的循环容量保持率。
上述负极材料的制备方法中，在活性物质表面形成缓冲层，得到固体复合物，再将固体复合物进行碳包覆处理，制得负极材料。在碳包覆处理形成碳层时，随着碳原子在缓冲层表面的沉积，在缓冲层中的金属化合物的催化作用下，碳层的无定型碳材料表面原位生成形成碳纳米材料，有利于简化负极材料的制备工序。其中，碳纳米材料的存在不仅能够提高负极材料的离子电导和电子电导，提高电池的循环容量保持率，还能够有效缓冲负极材料的体积膨胀，使负极材料保持稳定的结构和性能。本实施例中的制备方法简单易行，便于大规模推广。
附图说明
图1为本申请一实施例中负极材料的结构示意图；
图2为本申请一实施例中负极材料制备方法的流程图；
图3a及图3b分别为本申请实施例1制得的负极材料的电子镜像结构图；
图4a及图4b分别为本申请实施例2制得的负极材料的电子镜像结构图；
图5a为本申请实施例2制得的负极材料中纳米线的另一电子镜像结构图；
图5b为本申请实施例2制得的负极材料中纳米线的EDS(Energy Dispersive Spectroscopy，EDS)能谱图；
图6a及图6b分别为本申请对比例1制得的负极材料的电子镜像结构图；
图7为实施例1、对比例1中的负极材料制成锂离子电池的循环膨胀测试结果图，其中横坐标表示比容量(specific capacity，单位：mAh/g)，纵坐标表示电压(Voltage，单位：V)；
图8为实施例1、对比例1中的负极材料制成锂离子电池的循环容量保持率测试结果图，其中横坐标表示循环周数(cycles，单位：周)，纵坐标表示循环容 量保持率(representative capacity retention，单位：％)。
具体实施方式
为使本申请的上述目的、特征和优点能够更加明显易懂，下面对本申请的具体实施方式做详细的说明。在下面的描述中阐述了很多具体细节以便于充分理解本申请。但是本申请能够以很多不同于在此描述的其它方式来实施，本领域技术人员可以在不违背本申请内涵的情况下做类似改进，因此本申请不受下面公开的具体实施例的限制。
除非另有定义，本文所使用的所有的技术和科学术语与属于本申请的技术领域的技术人员通常理解的含义相同。本文中在本申请的说明书中所使用的术语只是为了描述具体的实施例的目的，不是旨在于限制本申请。本文所使用的术语“和/或”包括一个或多个相关的所列项目的任意的和所有的组合。
本申请一实施例提供了一种负极材料，如图1所示，负极材料包括活性物质10、位于活性物质10表面的缓冲层20和碳层30，其中，所述缓冲层20形成于所述活性物质表面，所述碳层30包括位于所述缓冲层20表面的无定型碳材料及向靠近和/或远离所述缓冲层的方向延伸的碳纳米材料31。
在本实施例负极材料的颗粒结构中，缓冲层具有一定的韧性，能够有效缓冲负极材料的体积膨胀，同时碳纳米材料的延伸也提供了一定的缓冲效果，可以进一步缓冲负极材料的体积膨胀，减少充放电过程中负极材料颗粒间的应力，从而可以提高负极材料结构的稳定性，进而可以提高电池的循环容量保持率。
另外，碳纳米材料一方面能够提高电子和离子的导通率，改善导电性能，另一方面还可以有效规避和弱化缓冲层的电绝缘性所带来的对电子电导的不利影响，进而使负极材料具有较高的离子电导和电子电导，进一步提高电池的循环容量保持率。
可以理解的是，碳层包括位于缓冲层表面的无定型碳材料及向靠近和/或远离缓冲层的方向延伸的碳纳米材料。其中，向靠近缓冲层的方向延伸表示碳纳米材料自无定型碳材料朝向靠近活性物质方向延伸，向远离缓冲层的方向延伸表示碳纳米材料自无定型碳材料朝向远离活性物质方向延伸。
在一个具体的示例中，碳纳米材料向靠近缓冲层的方向延伸至缓冲层。此时，碳纳米材料可以将无定型碳材料和缓冲层进行连接，可以增加3D导电网络，可以改善导电性能，提高电池的循环容量保持率。可以理解的是，碳纳米材料向靠近缓冲层的方向延伸至缓冲层时，也可以存在其他的碳纳米材料向远离缓冲层的方向延伸。
在另一个具体的示例中，碳纳米材料向靠近缓冲层的方向延伸并穿过缓冲层延伸至活性物质。此时，碳纳米材料能够贯穿所述缓冲层并连接所述无定型碳材料以及所述活性物质，即碳纳米材料连接无定型碳材料、缓冲层以及活性物质，可以 形成双柔性包覆层结构，更好地为负极材料的膨胀效应提供缓冲。同时，由于碳纳米材料贯穿到活性物质的表面，使得双柔性包覆层结构之间产生了一定的粘结力，可以使碳层、缓冲层和活性物质具有更好的结合力，这样可以进一步抑制负极材料的体积膨胀，使负极材料保持稳定的结构和性能。同样可以理解的是，碳纳米材料向靠近缓冲层的方向延伸并穿过缓冲层延伸至活性物质时，也可以存在其他的碳纳米材料向远离缓冲层的方向延伸。
在一个具体的示例中，缓冲层能催化碳材料形成碳纳米材料。进一步地，缓冲层能催化无定型碳材料原位生长形成碳纳米材料。
在一个具体的示例中，缓冲层的厚度为0.01μm～2μm。可选地，缓冲层的厚度为0.01μm、0.015μm、0.03μm、0.05μm、0.08μm、0.1μm、0.2μm、0.3μm、0.4μm、0.5μm、0.6μm、0.7μm、0.8μm、0.9μm、1μm、1.2μm、1.5μm、1.8μm或2μm。
在一个具体的示例中，所述活性物质包括SiO x材料，0＜x＜2，x可以是0.1、0.2、0.3、0.4、0.5、0.6、0.7、0.8、0.9、1、1.2、1.3、1.5、1.6、1.8、1.99等等，在此不做限定。
在一个具体的示例中，所述活性物质包括SiO x材料，0.8≤x≤1.5。可选地，x为0.8、0.9、1、1.1、1.2、1.3、1.4或1.5等。进一步地，x＝1。优选地，SiO x材料为SiO。再进一步地，SiO x材料为SiO颗粒。
在一个具体的示例中，SiO x材料颗粒呈球形或类球形。
在一个具体的示例中，所述SiO x材料颗粒的球形度系数≥0.4。可选地，SiO x内核颗粒的球形度系数为0.4、0.45、0.5、0.55、0.6、0.65、0.7、0.75、0.8、0.85、0.9、0.95等。优选地，SiO x内核颗粒的球形度系数≥0.95。
在一个具体的示例中，碳纳米材料是无定型碳材料的表面原位生长出来的。原位生长的碳纳米材料可以提供更好的结合力，当碳纳米材料延伸至缓冲层或者穿过缓冲层延伸至活性物质时，可以使碳层与缓冲层或者碳层、缓冲层以及SiO x内核之间形成更好的结合力，进一步抑制负极材料的膨胀，保持负极材料的结构稳定性。
在本实施例负极材料的颗粒结构中，碳纳米材料具有稳定的延伸环境，可以使其在延伸过程中保持稳定的直径。当碳纳米材料自无定型碳材料向靠近缓冲层的方向延伸至缓冲层时，最靠近缓冲层的碳原子存在悬挂键，缓冲层与碳原子之间存在一定的结合力，该结合力能够与碳原子悬挂键自动闭合的作用力相平衡，可以使得碳纳米材料与缓冲层相连的开口稳定的存在，这样可以使碳纳米材料伸出时保持直径不变而长度增加，形成长径比较大且直径均一的碳纳米材料。
在一个具体的示例中，碳纳米材料的直径为1nm～100nm。可选地，碳纳米材料的直径为5nm、10nm、15nm、20nm、30nm、40nm、50nm、60nm、70nm、80nm或90nm。进一步地，碳纳米材料的长径比≥10。碳纳米材料的长径比较高，有利于其延伸至缓冲层或穿过缓冲层延伸至SiO x内核，还有利于使不同的碳纳米材料之间形成缠绕，这样可以促进对负极材料体积膨胀的缓冲作用，提高负极材料结构 的稳定性。作为碳纳米材料的长径比的一些举例，碳纳米材料的长径比可以是但不限定为10、11、12、13、14、15等。
在一个具体的示例中，负极材料中，碳纳米材料的面密度为20根/mm 2～10000根/mm 2。碳纳米材料可以为电子的移动提供通道，当碳纳米材料的面密度在该范围内时，可以使大量的电子和离子吸附在碳纳米材料的表面以及相邻的碳纳米材料的间隙，这样能够获得较高的放电容量和较好的循环性能。碳纳米材料的面密度过低时，会导致电子的移动通道减少，尤其是不利于大电流充放电。当碳纳米材料的面密度过高时，相应地会降低活性物质的相对含量，使得电池的容量降低；另外，当碳纳米材料含量过高时，会加大电解液在电极材料中的渗透能力，导致电解液的副反应增多，SEI膜的厚度可能会持续增大，不利于电池电性能的提升。
可选地，碳纳米材料的面密度为20根/mm 2、50根/mm 2、100根/mm 2、200根/mm 2、300根/mm 2、400根/mm 2、500根/mm 2、600根/mm 2、800根/mm 2、1000根/mm 2、2000根/mm 2、3000根/mm 2、4000根/mm 2、5000根/mm 2、6000根/mm 2、7000根/mm 2、8000根/mm 2、9000根/mm 2、10000根/mm 2、12000根/mm 2、15000根/mm 2、18000根/mm 2等。优选地，碳纳米材料的面密度为20根/mm 2～2000根/mm 2。
在一个具体的示例中，碳纳米材料包括碳纳米线、碳纳米管、碳纳米纤维以及石墨烯中的至少一种。
在一个具体的示例中，碳纳米材料的形状包括线状、管状、片状以及长条状中的至少一种。
在一个具体的示例中，缓冲层包括碱金属卤化物、碱金属氮化合物、碱金属氧化物和过渡金属氧化物中的至少一种。
具体地，碱金属卤化物包括LiF、NaF中的至少一种，碱金属氮化合物包括Li 3N、KN 3中的至少一种；
碱金属氧化物包括Li 2O、K 2O，过渡金属氧化物包括Al 2O 3、MgO、TiO 2、ZnO、CuO、Ag 2O以及ZrO 2中的至少一种。
此时，缓冲层能够实现离子传导，但是缓冲层能够实现类似电子绝缘层的功能，减少高活性电子穿越缓冲层与电解质反应，缓冲层的引入能够等效于引入一层人工SEI膜(SEI膜表示固体电解质界面膜)，减少放电过程中SEI膜形成时的锂离子消耗，从而降低充放电的不可逆容量，进一步改善电池的循环容量保持率。
在一个具体的示例中，缓冲层占负极材料的质量百分数为0.05％～20％。缓冲层的含量过高，会导致碳纳米材料难以分散，且较厚的缓冲层对电子电导和比容量会产生一定的负面影响。而当缓冲层的含量过低时，碳纳米材料难以均匀附着且碳纳米材料的量较少，对于导电性能的改善程度较小；并且当缓冲层过少时，难以在SiO x内核表面形成完整有效的包覆层，导致缓冲层的作用难以充分发挥。可选地，缓冲层的质量占负极材料的质量的百分数可以是0.05％、0.1％、0.2％、0.3％、0.4％、0.5％、0.6％、0.7％、0.8％、0.9％、1％、1.5％、2％、2.5％、3％、3.5％、4％、4.5％、 5％、5.5％、6％、6.5％、7％、8％、9％、10％、11％、12％、13％、14％、15％、16％、17％、18％、19％或20％等。可以理解的是，缓冲层占负极材料的质量百分数还可以是0.05％～20％中的其他值。可选地，在制备过程中，可以通过缓冲层的加入量控制缓冲层的质量占负极材料的质量的百分数。
在一个具体的示例中，碳层的质量占负极材料的质量百分数为0.5％～20％。当碳层的占比过大时，会导致碳层的厚度过大，这样会使得锂离子的传输距离过长，使得电性能的改善欠佳；同时，厚度过大的碳层可能会带来振实密度和压实密度降低的问题，使得比容量有所下降。当碳层的占比过小时，会导致碳层的厚度过小，难以对其内层的缓冲层进行完整有效的包覆，会增加活性材料与电解液接触的机会，这样对电池的循环性能的提升会带来不利影响，还可能会使得双柔性包覆层结构难以发挥较佳的效果。
可选地，碳层占负极材料的质量百分数可以是0.5％、0.6％、0.7％、0.8％、0.9％、1％、1.5％、2％、2.5％、3％、3.5％、4％、4.5％、5％、5.5％、6％、6.5％、7％、8％、9％、10％、11％、12％、13％、14％、15％、16％、17％、18％、19％或20％等。可以理解的是，碳层占负极材料的质量百分数还可以是0.5％～20％中的其他值。优选地，碳层占负极材料的质量百分数为1％～10％。可选地，在制备过程中，可以通过碳源的沉积量控制碳层占负极材料的质量百分数。
在一个具体的示例中，碳层的厚度为10nm～1500nm；具体可以是10nm、20nm、50nm、80nm、100nm、200nm、500nm、800nm、1000nm、1500nm等等，在此不做限定。
在一个具体的示例中，负极材料的D 50为1μm～20μm。可选地，负极材料的D50为1μm、2μm、3μm、4μm、5μm、6μm、7μm、8μm、9μm、10μm、11μm、12μm、13μm、14μm、15μm、16μm、17μm、18μm、19μm或20μm。可以理解的是，负极材料的D 50还可以是1μm～20μm中的其他值。负极材料的D 50在该范围时，颗粒粒径适中，能够获得较高的首次库伦效率。当负极材料的颗粒过小时，单位体积下，颗粒之间的缝隙体积越多，材料体积占比减少，容易导致压实密度受损。另外，负极材料的颗粒过小，负极材料与电解液接触的比表面积过大，首次充放电过程中形成的SEI膜所消耗的电荷多，不可逆容量损失大，容易导致首次库伦效率降低。当负极材料的颗粒过大时，会导致锂离子的扩散路径变大，锂离子嵌入和脱出的通道数量变少，并且嵌入时需要克服的范德华力大，使得锂离子嵌入困难，不利于形成嵌锂的状态，会造成首次放电比容量的降低。
可选地，负极材料的粒径分布(D 90-D 50)/(D 50-D 10)为1.2～1.6。比如，负极材料的(D 90-D 50)/(D 50-D 10)的值可以是但不限定为1.2、1.3、1.4、1.5或1.6等。当负极材料满足(D 90-D 50)/(D 50-D 10)为1.2～1.6时，负极材料的粒径能够形成较好的正态分布，并且颗粒分布较宽，这样体系中的小颗粒能够填充到大颗粒之间的空隙中，有助于提高材料的压实密度，提高电池的能量密度。另外，粒径分布较宽，在进行涂布时浆料的粘度较小，有利于提高固含量，降低涂布难度。
在一个具体的示例中，活性物质还包括Si晶粒，负极材料的Si晶粒尺寸为2nm～10nm。可选地，负极材料的Si晶粒尺寸为2nm、3nm、4nm、5nm、6nm、7nm、8nm、9nm或10nm。可以理解的是，负极材料的Si晶粒尺寸还可以是2nm～10nm中的其他值。
在一个具体的示例中，负极材料的比表面积为1m 2/g～20m 2/g。可选地，负极材料的比表面积为1m 2/g、2m 2/g、3m 2/g、4m 2/g、5m 2/g、6m 2/g、7m 2/g、8m 2/g、9m 2/g、10m 2/g、11m 2/g、12m 2/g、13m 2/g、14m 2/g、15m 2/g、16m 2/g、17m 2/g、18m 2/g、19m 2/g或20m 2/g。可以理解的是，负极材料的比表面积还可以是1m 2/g～20m 2/g中的其他值。
请参阅图2，本申请还有一实施例提供了一种负极材料的制备方法，该负极材料的制备方法包括如下步骤：
S101：在活性物质表面形成缓冲层，得到固体复合物，所述缓冲层包括碱金属卤化物、碱金属氮化合物、碱金属氧化物和过渡金属氧化物中的至少一种；
S102：在保护气氛中对所述固体复合物进行碳包覆处理，得到负极材料。
在本实施例的制备方法中，在活性物质表面形成缓冲层，得到固体复合物，再将固体复合物进行碳包覆处理，制得负极材料。在碳包覆处理形成碳层时，随着碳原子在缓冲层表面的沉积，在缓冲层中的金属化合物的催化作用下，碳层的无定型碳材料表面原位生成形成碳纳米材料，有利于简化负极材料的制备工序。其中，碳纳米材料的存在不仅能够提高负极材料的离子电导和电子电导，提高电池的循环容量保持率，还能够有效缓冲负极材料的体积膨胀，使负极材料保持稳定的结构，从而表现出优异的循环性能。本实施例中的制备方法简单易行，便于大规模推广。
在一个具体的示例中，制备方法中不需要引入磁性材料。即本示例提供了一种不需要引入磁性材料的负极材料的制备方法，该不需要引入磁性材料的负极材料的制备方法包括如下步骤：在SiOx表面形成缓冲层，得到固体复合物，其中，0＜x＜2；对固体复合物进行碳包覆处理。传统的方法中，会使用铁镍钴等金属来催化形成碳纳米材料，这样不仅引入了磁性物质，同时，不易控制碳纳米材料的生成，而在本示例的制备方法中，不需要引入磁性材料，能够有效避免磁性材料的引入带来的微短路问题，有效提高电池的安全性能和使用寿命。另外，在制备负极材料之后，不需要进行额外的除磁操作来除去制备过程中引入的磁性材料，有效简化了加工工艺。
在一个具体的示例中，制备方法中不需要进行除磁处理，有利于进一步简化制备流程，提高制备效率。
S101：在活性物质表面形成缓冲层，得到固体复合物，所述缓冲层包括碱金属卤化物、碱金属氮化合物、碱金属氧化物和过渡金属氧化物中的至少一种。
在一个具体的示例中，碱金属卤化物包括LiF、NaF中的至少一种，碱金属氮化合物包括Li 3N、KN 3中的至少一种；
碱金属氧化物包括Li 2O、K 2O、Na 2O，过渡金属氧化物Li 2O、Al 2O 3、MgO、 TiO 2、ZnO、CuO、Ag 2O以及ZrO 2中的至少一种。需要说明的是，应该避免铁、钴及镍等磁性金属氧化物的使用，避免磁性材料的引入带来的微短路问题。
进一步优选地，缓冲层可以是但不限定为LiF、Li 2O、Li 3N、Al 2O 3、TiO 2、ZnO以及ZrO 2中的至少一种。
在一些实施方式中，缓冲层可以直接采用缓冲层原料进行液相包覆，示例性地，缓冲层材料可以是Li 2O、Li 3N、Al 2O 3、TiO 2、ZnO以及ZrO 2中的至少一种。
在一个具体的示例中，所述在活性物质表面形成缓冲层，得到固体复合物的步骤，包括如下步骤：将缓冲层材料与活性物质在溶剂中混合，制备混合浆料；对混合浆料进行固液分离处理，得到固体复合物。
在一个具体的示例中，将缓冲层材料与活性物质在溶剂中混合包括如下步骤：制备缓冲层材料分散液；将活性物质与缓冲层材料分散液混合。
在一个具体的示例中，将缓冲层材料和活性物质在溶剂中混合的过程中，可以通过超声和/或搅拌的方式来促进混合。制备缓冲层材料分散液的过程中，可以通过超声和/或搅拌的方式来促进分散。将缓冲层材料分散于溶剂的过程中，可以通过超声和/或搅拌的方式来促进分散。将活性物质与缓冲层材料分散液混合的过程中，可以通过超声和/或搅拌的方式来促进分散。
可选地，超声和/或搅拌的时间为20min～120min。
在一个具体的示例中，混合浆料中缓冲层材料的粒径为1nm～1μm。当先将缓冲层材料分散于溶剂中时，分散液中缓冲层材料的粒径为1nm～1μm。可选地，混合浆料中缓冲层材料的粒径或者分散液中缓冲层材料的粒径可以是1nm、5nm、10nm、15nm、20nm、50nm、60nm、70nm、80nm、90nm、100nm、200nm、300nm、400nm、500nm、600nm、700nm、800nm、900nm等。可以理解的是，混合浆料中缓冲层材料的粒径或者分散液中缓冲层的粒径还可以是1nm～1μm中的其他值。当缓冲层材料在混合浆料或者分散液中的粒径过大时，较难分散到活性物质的表面，而不能实现缓冲层的包覆。当缓冲层材料在混合浆料或者分散液中的粒径过小时，缓冲层颗粒容易出现团聚问题，导致碳纳米材料分散不均匀。
在一个具体的示例中，溶剂包括水。在选择溶剂时，可以使缓冲层材料和活性物质在其中进行良好的分散和混合。
在一个具体的示例中，缓冲层材料占混合浆料的质量百分数为0.05％～0.2％，SiOx占混合浆料的质量百分数为2％～20％。可选地，缓冲层材料占混合浆料的质量百分数为为0.05％、0.08％、0.1％、0.12％、0.15％、0.18％或0.2％。SiOx占混合浆料的质量百分数为2％、3％、5％、8％、10％、12％、15％、18％或20％。
作为固液分离处理的一些类型举例，固液分离处理包括抽滤处理、离心处理以及喷雾干燥处理中的至少一种。
作为固液分离处理的一些类型举例，固液分离处理包括喷雾干燥处理，喷雾干燥处理中，进口温度为150℃～220℃，出口温度为60℃～110℃。可选地，喷雾干燥的时间为30min～60min。具体地，喷雾干燥处理中，进口温度为150℃、160℃、170℃、 180℃、190℃、200℃、210℃或220℃；出口温度为60℃、70℃、80℃、90℃、100℃或110℃；喷雾干燥的时间为30min、35min、40min、45min、50min、55min或60min。可以理解的是，在喷雾干燥处理时，进口温度、出口温度以及喷雾干燥时间可以在以上所列范围和数值中独立地对应选择。
作为固液分离处理的一些类型举例，当采用抽滤处理、离心处理进行固液分离处理之后，对固液分离得到的固体物料进行干燥处理，进而得到固体复合物。可选地，干燥温度为50℃～100℃，干燥时间为10h～30h。比如，干燥温度为50℃、60℃、70℃、80℃、90℃或100℃，干燥时间为10h、15h、18h、20h、24h、28h或30h。
在另一些实施方式中，也可以采用化学反应合成的方式制得缓冲层，示例性地，缓冲层前驱体材料可以是锂源和氟源。
在一个具体的示例中，所述采用化学反应合成的方式在活性物质表面形成缓冲层，得到固体复合物的步骤，包括：将缓冲层前驱体材料在溶剂中混合，制备含缓冲层材料的浆料；往浆料中加入活性物质混合后进行固液分离处理，得到固体复合物。
在一个具体的示例中，缓冲层材料为LiF。其中，制备LiF分散液包括如下步骤：将锂源和氟源在溶剂中混合，得到LiF分散液。在直接采用缓冲层原料进行包覆时，也可以将LiF分散于溶剂中，得到LiF分散液。
可选地，锂源包括硝酸锂、醋酸锂、碳酸锂以及草酸锂中的至少一种。氟源包括氟化铵、氟化钠以及氟化钙中的至少一种。
更进一步地，将锂源和氟源在溶剂中混合，得到LiF分散液时，锂源占分散液的质量百分数为0.01％～0.5％，氟源占分散液的质量百分数为0.01％～0.5％。可选地，锂源占分散液的质量百分数为0.01％、0.02％、0.05％、0.08％、0.1％、0.12％、0.15％、0.2％、0.25％、0.3％、0.35％、0.4％、0.45％或0.5％。氟源占分散液的质量百分数为0.01％、0.02％、0.05％、0.08％、0.1％、0.12％、0.15％、0.2％、0.25％、0.3％、0.35％、0.4％、0.45％或0.5％。可以理解的是，锂源占分散液的质量百分数还可以是0.01％～0.5％中的其他值，氟源占分散液的质量百分数还可以是0.01％～0.5％中的其他值。
进一步地，当LiF催化碳原子原位生成碳纳米材料时，LiF的催化作用相对金属催化剂较弱，比如LiF的催化作用相对铁、钴、镍等金属催化剂较弱，可以更加方便地对碳纳米材料的生成和生长进行控制。
在一个具体的示例中，活性物质包括SiO x材料，0＜x＜2，通过热处理可以使得SiO x材料部分歧化生成Si和SiO 2，增强其内部缓冲基质，可以使首次嵌锂平台逐渐向单质Si靠近，提升SiO x的电化学性能。
在一个具体的示例中，热处理在保护气氛下进行，保护气氛包括氮气、氩气、氦气、氖气、氪气以及氙气中的至少一种。可以理解的是，热处理的设备可以是管式炉或箱式炉等。
S102：在保护气氛下对固体复合物进行碳包覆处理，得到负极材料。
具体地，保护气氛包括氮气、氩气、氦气、氖气、氪气以及氙气中的至少一种。进一步地，在碳包覆处理过程中，通入保护气氛的流量为2mL/min～1000mL/min。示例性 地，通入保护气氛的流量为2mL/min、8mL/min、10mL/min、15mL/min、20mL/min、30mL/min、40mL/min、50mL/min、80mL/min、100mL/min、150mL/min、200mL/min、300mL/min、400mL/min、500mL/min、600mL/min、700mL/min、800mL/min、900mL/min或1000mL/min等。可以理解的是，通入保护气氛的流量还可以是2mL/min～1000mL/min中的其他值。
在一个具体的示例中，S102，包括：对所述固体复合物进行预热，再进行碳包覆处理。
在一个具体的示例中，对固体复合物进行预热可以采用预热的保护气氛对固体复合物进行预热，这样可以提前激活固体复合物中的金属化合物的催化活性，有利于后续的碳包覆处理中催化碳材料形成碳纳米材料。
具体地，采用预热后的保护气氛对固体复合物进行预热处理时，将保护气氛预热至100℃～300℃。保护气氛的预热温度表示在进行碳包覆处理前保护气氛的温度。在该预热温度范围内，可以有效利用保护气氛的温度来预热固体复合物，还能够避免真空预热等情况下对固体复合物中物质结构的破坏；预热后固体复合物中的金属化合物(碱金属卤化物、碱金属氮化合物、碱金属氧化物或过渡金属氧化物)能够充分发挥催化作用，促进碳纳米材料的生成。
进一步地，对保护气氛预热处理时，将保护气氛以1℃/min～50℃/min的升温速率预热至预设温度。可选地，预设温度为100℃～300℃。以1℃/min～50℃/min将保护气氛升温至100℃～300℃。比如，以1℃/min、2℃/min、3℃/min、4℃/min、5℃/min、6℃/min、7℃/min、8℃/min、9℃/min、10℃/min、15℃/min、20℃/min、25℃/min、30℃/min、35℃/min、40℃/min、45℃/min或、50℃/min将保护气氛升温至100℃～300℃。
在进行碳包覆处理时，先以1℃/min～50℃/min将保护气氛升温至预热温度100℃～300℃，然后将固体复合物与碳源混合，再以0.1℃/min～10℃/min升温至所述碳源的热裂解温度600℃～1200℃。在碳包覆处理时，碳源的热解温度过低时，难以完全裂解得到碳层；碳源的热解温度过高时，SiO x内核会发生严重的歧化，影响SiO x内核的活性，不利于负极材料性能的提高，且温度过高时，碳包覆的能耗和成本也会随之增加。在碳包覆处理时，控制升温至碳源热裂解温度的升温速率以及碳源热裂解的温度，可以对SiO x内核的歧化程度进行有效地控制，保持SiO x内核的活性，进而有利于负极材料电化学性能的提高。
在一个具体的示例中，当碳源包括液相碳源和固相碳源时，对进行碳包覆处理之后的固体复合物进行热处理。
作为碳包覆处理的一些类型举例，碳包覆处理包括固相碳包覆处理、液相碳包覆处理以及气相碳包覆中的至少一种。
在一个具体的示例中，碳包覆处理包括如下步骤：在保护气氛下，将固体复合物与碳源混合，控制碳源热裂解以在固体复合物的颗粒表面形成碳层。
具体地，碳源热裂解的温度为600℃～1200℃。比如，碳源热裂解的温度为600℃、650℃、700℃、750℃、800℃、850℃、900℃、950℃、1000℃、1050℃、1100℃、1150℃ 或1200℃。可以理解的是，碳源热裂解的温度还可以是600℃～1200℃中的其他值。
具体地，碳源热裂解的升温速率为0.1℃/min～10℃/min，即以0.1℃/min～10℃/min的升温速率升温至碳源的热裂解温度。此时，升温速率表示将固体复合物与碳源所处的温度由初始温度升高到热处理温度的升温速率。比如，升温速率为0.1℃/min、0.2℃/min、0.5℃/min、0.8℃/min、1℃/min、1.5℃/min、2℃/min、2.5℃/min、3℃/min、3.5℃/min、4℃/min、4.5℃/min、5℃/min、5.5℃/min、6℃/min、6.5℃/min、7℃/min、7.5℃/min、8℃/min、8.5℃/min、9℃/min、9.5℃/min或10℃/min。可以理解的是，碳源热裂解的升温速率还可以是0.1℃/min～10℃/min中的其他值。
具体地，碳源热裂解的时间为1h～50h。优选地，热裂解的时间为1h～10h。在一些可选的示例中，热裂解的时间为1h、2h、3h、4h、5h、6h、7h、8h、9h或10h。可以理解的是，热裂解的时间还可以是1h～10h中的其他值。
在一个具体的示例中，在SiO x表面形成缓冲层之前还包括如下步骤：对SiO x进行热歧化处理。通过先对SiO x进行热歧化处理，可以先控制Si晶粒尺寸，然后再进行碳包覆，也可以使首次嵌锂平台逐渐向单质Si靠近，提升SiO x的电化学性能。进一步地，热歧化处理的温度为800℃～1400℃，比如热歧化处理的温度为800℃、850℃、900℃、950℃、1000℃、1050℃、1100℃、1150℃、1200℃、1250℃、1300℃、1350℃或1400℃。可以理解的是，热歧化处理的温度还可以是800℃～1400℃中的其他值。再进一步地，热歧化处理的升温速率为1℃/min～5℃/min。比如热歧化处理的升温速率可以为1℃/min、1.5℃/min、2℃/min、2.5℃/min、3℃/min、3.5℃/min、4℃/min、4.5℃/min或5℃/min。可选地，热歧化处理的温度选择高于热裂解的温度。
可以理解的是，在进行碳包覆处理时，碳包覆处理的设备可以是回转炉、箱式炉、辊道窑、隧道窑、推板窑等。
还可以理解的是，将固体复合物与碳源混合时，先将固体复合物冷却，然后再将其与碳源混合。
在一个具体示例中，碳源包括气相碳源。进一步地，碳源包括气相烃类碳源。再进一步地，碳源包括甲烷、乙烷、丙烷、乙烯、丙烯、乙炔、丙炔、丙酮以及苯中的至少一种。此时，在进行碳包覆处理时，在保护气氛下通入气相碳源使气相碳源与固体复合物混合。在碳源热裂解时，无定型碳沉积在固体复合物的表面进行碳包覆。可选地，当碳源包括气相碳源时，碳包覆处理在回转炉或箱式炉中进行。
在另一个具体示例中，碳源包括液相碳源。进一步地，碳源包括液相有机碳源。再进一步地，碳源包括正己烷、甲苯、苯、二甲苯、甲醇、乙醇、丙醇、丁醇、戊醇、丙酮、丁酮、2-戊酮、乙酸甲酯、乙酸乙酯、乙酸丙酯、乙酸丁酯以及乙酸戊酯中的至少一种。可选地，当采用液相碳源时，液相碳源的流量为1mL/min～200mL/min。比如，液相碳源的流量为1mL/min、5mL/min、8mL/min、10mL/min、15mL/min、20mL/min、30mL/min、40mL/min、50mL/min、80mL/min、100mL/min、150mL/min、200mL/min。可选地，碳源包括苯和甲苯中的至少一种，或者甲醇、乙醇、丙醇、丁醇以及戊醇中的至少一种。可选地，当碳源包括液相碳源时，碳包覆处理在回转炉、箱式炉、辊道 窑、隧道窑或推板窑中进行。当碳源包括液相碳源时，固体复合物与碳源的混合方式可以采用VC混合、融合、球磨、抽滤、加热回流、三维混合或流化床混合等。
在另一个具体示例中，碳源包括固相碳源。进一步地，碳源包括固相有机碳源。再进一步地，碳源包括柠檬酸、葡萄糖、沥青、酚醛树脂以及糠醛树脂中的至少一种。可选地，当碳源包括固相碳源时，碳包覆处理在回转炉、箱式炉、辊道窑、隧道窑或推板窑中进行。当碳源包括固相碳源时，固体复合物与碳源的混合方式可以采用VC混合、融合、球磨、抽滤、加热回流、三维混合或流化床混合等。
进一步地，对固体复合物进行碳包覆处理之后还包括如下步骤：对进行碳包覆处理之后的固体复合物进行热处理，热处理的温度为600℃～1200℃，热处理的时间为1h～48h，热处理的升温速率为1℃/min～5℃/min。具体地，热处理的温度可以为600℃、650℃、700℃、750℃、800℃、850℃、900℃、950℃、1000℃、1050℃、1100℃、1150℃或1200℃。热处理的时间可以为1h、1.5h、2h、2.5h、3h、3.5h或4h。热处理的升温速率可以为1℃/min、1.5℃/min、2℃/min、2.5℃/min、3℃/min、3.5℃/min、4℃/min、4.5℃/min或5℃/min。可以理解的是，在热处理时，热处理的温度、热处理的时间以及热处理的升温速率可以在以上所列范围和数值中独立地对应选择。还可以理解的是，热处理的升温速率表示将热处理的温度由初始温度升高到热处理温度的升温速率。
除了上述负极材料和负极材料的制备方法，本申请还有一实施例提供了一种负极极片。该负极极片包括上述负极材料；或者包括上述制备方法制得的负极材料。
进一步地，负极极片包括集流体以及上述负极材料；或者包括集流体以及上述制备方法制得的负极材料；负极材料位于集流体的表面。可选地，集流体为铜集流体或铝集流体等。
本申请还有一实施例提供了一种锂离子电池。该锂离子电池包括上述负极材料，或包括上述制备方法制得的负极材料。该锂离子电池具有较高的循环容量保持率。
本申请还有一实施例提供了一种锂离子电池。该锂离子电池包括上述负极极片。
本申请还有一实施例提供了一种可充电用电产品。该可充电用电产品包括上述负极材料，或包括上述制备方法制得的负极材料。
本申请还有一实施例提供了一种可充电用电产品。该可充电用电产品包括上述负极极片。
本申请还有一实施例提供了一种可充电用电产品。该可充电用电产品包括上述锂离子电池。
作为本申请中的参数测定，可选地，采用以下设备和方法进行测定：
(1)使用扫描电子显微镜(SEM)来确认材料中颗粒结构，同时结合X射线能谱分析(EDS)对于材料中Si、O、C等元素分布的均匀性进行表征。
(2)使用激光粒度仪测得D 50，D 90和D 10，再计算得到(D 90-D 10)/D 50的值，同时其存在类正态分布的对称分布。其体积基准分布中，累积10％直径为D10，累积50％直径为D 50，累积90％直径为D 90。(D 90-D 50)/(D 50-D 10)的范围为1.2～1.6。
(3)使用美国麦克TriStar3000比表面积与孔径分析仪设备测得比表面积。
(4)使用帕那科X’pert Pro X射线衍射仪测得XRD峰，接着使用Jade 6.5软件对于XRD中的Si峰进行拟合，从而得到Si微晶尺寸。
(5)碳纳米材料面密度的测定方法：首先随机选择三个面积为100mm*75mm的区域进行SEM拍照，然后运用ProSEM软件将预先保存的SEM图像打开，然后在此2D图像中选定一个典型特征(纳米线结构)，单击“Find Similar”键查找相似特征，ProSEM自动在图像中查找相似特征，这样就可以得到在该区域内的纳米线数量，用该数量除以SEM的图像尺寸，就可以得到碳纳米材料的面密度，对三个区域的碳纳米材料面密度进行取平均值。
以下为具体实施例。
实施例1
本实施例中负极材料的制备方法为：
(1)将10g LiF分散在10L去离子水中，搅拌并超声处理60min，得到分散液。
(2)将200g SiO粉末(球形度系数为0.5)加入分散液中，搅拌2h，得到混合浆料。
(3)将混合浆料离心处理，并在85℃下干燥24h，得到固体复合物。
(4)对固体复合物进行碳包覆处理；其中以甲烷作为碳源，氮气为保护气氛，采用回转炉进行碳包覆处理。先以25℃/min将保护气氛以流速5L/min升温至预热温度200℃，保温30min，利用预热后的保护气氛对固体复合物进行预热。然后将预热后的固体复合物与碳源混合，再以5℃/min升温至所述碳源的热裂解温度900℃，热裂解的时间为25h，得到负极材料。
本实施例制得的负极材料包括SiO内核、位于SiO内核表面的LiF缓冲层和碳层，LiF缓冲层形成于SiO内核表面，碳层包括位于缓冲层表面的无定型碳材料及向靠近及远离缓冲层的方向延伸的碳纳米材料，碳纳米材料为碳纳米线；碳纳米材料的直径为50nm；纳米材料的长径比为100；所述碳纳米材料的面密度为300根/mm 2；
LiF缓冲层的厚度为0.5μm；碳层厚度为500nm；其中，缓冲层占负极材料的质量百分数为5％；碳层占负极材料的质量百分数为5％。
实施例2
本实施例中负极材料的制备方法为：
(1)将硝酸锂和氟化钠在去离子水中混合，搅拌并超声120min，得到LiF分散液。其中，硝酸锂占分散液的质量百分比为2％，氟化钠占分散液的质量百分比为2％。
(2)将80gSiO 1.5粉末(球形度系数为0.45)加入LiF分散液中，搅拌2h，得到混合浆料。
(3)将混合浆料抽滤处理，并在90℃下干燥18h，得到固体复合物。
(4)对固体复合物进行碳包覆处理。其中以低温液相沥青作为碳源，氮气为保护气氛，采用回转炉进行碳包覆处理。先以50℃/min将保护气氛以流速0.5L/min升温至预热温度300℃，保温30min，利用预热后的保护气氛对固体复合物进行预热。然后将预热后的固体复合物与碳源混合，再以0.1℃/min升温至所述碳源的热裂解温度800℃，热裂解的时间为1h。
(5)将碳包覆处理之后的复合物放入窑炉中，在980℃下热处理24h，得到负极材料。
本实施例制得的负极材料的颗粒结构包括SiO 1.5内核、位于SiO 1.5内核表面的LiF缓冲层和碳层，LiF缓冲层形成于SiO 1.5内核表面，碳层包括位于缓冲层表面的无定型碳材料及向靠近及远离缓冲层的方向延伸的碳纳米材料，碳纳米材料为碳纳米管；碳纳米材料的直径为20nm；纳米材料的长径比为500；所述碳纳米材料的面密度为1000根/mm 2；
LiF缓冲层的厚度为0.02μm；碳层厚度为1000nm；其中，缓冲层占负极材料的质量百分数为15％；碳层占负极材料的质量百分数为8％。
实施例3
本实施例中负极材料的制备方法为：
(1)将10gLiF分散在6L去离子水中，搅拌并超声处理90min，得到分散液。
(2)将50gSiO 0.8(球形度系数为0.55)粉末加入分散液中，搅拌2h，得到混合浆料。
(3)将混合浆料喷雾干燥处理，喷雾干燥的进口温度180℃，出口温度90℃，得到固体复合物。
(4)对固体复合物进行碳包覆处理。其中以葡萄糖作为碳源，氮气为保护气氛，采用辊道窑进行碳包覆处理。先以1℃/min将保护气氛升温至预热温度100℃，保温20min，利用预热后的保护气氛对固体复合物进行预热。然后将预热后的固体复合物与碳源VC混合，再以10℃/min升温至所述碳源的热裂解温度600℃，热裂解的时间为50h。
(5)将碳包覆处理之后的复合物放入窑炉中，在1000℃下热处理18h，得到负极材料。
本实施例制得的负极材料包括SiO 0.8内核、位于SiO 0.8内核表面的LiF缓冲层和碳层，LiF缓冲层形成于SiO 0.8内核表面，碳层包括位于缓冲层表面的无定型碳材料及向靠近及远离缓冲层的方向延伸的碳纳米材料，碳纳米材料为碳纳米纤维；碳纳米材料的直径为100nm；纳米材料的长径比为1000；所述碳纳米材料的面密度为5000根/mm 2；
LiF缓冲层的厚度为1.5μm；碳层厚度为200nm；其中，缓冲层占负极材料的质量百分数为20％；碳层占负极材料的质量百分数为2％。
实施例4
与实施例1不同的是，将LiF替换为Al 2O 3。
本实施例制得的负极材料包括SiO内核、位于SiO内核表面的Al 2O 3缓冲层和碳层，Al 2O 3缓冲层形成于SiO内核表面，碳层包括位于缓冲层表面的无定型碳材料及向靠近及远离缓冲层的方向延伸的碳纳米材料，碳纳米材料为碳纳米线；碳纳米材料的直径为60nm；纳米材料的长径比为80；所述碳纳米材料的面密度为200根/mm 2；
Al 2O 3缓冲层的厚度为0.5μm；碳层厚度为500nm；其中，缓冲层占负极材料的质量百分数为5％；碳层占负极材料的质量百分数为5％。
实施例5
与实施例1不同的是，将LiF替换为Li 2O。
本实施例制得的负极材料包括SiO内核、位于SiO内核表面的Li 2O缓冲层和碳层，Li 2O缓冲层形成于SiO内核表面，碳层包括位于缓冲层表面的无定型碳材料及向靠近及远离缓冲层的方向延伸的碳纳米材料，碳纳米材料为碳纳米线；碳纳米材料的直径为40nm；眼纳米材料的长径比为90；所述碳纳米材料的面密度为250根/mm 2；
Li 2O缓冲层的厚度为0.9μm，碳层厚度为500nm；其中，缓冲层占负极材料的质量百分数为5％；碳层占负极材料的质量百分数为5％。
实施例6
与实施例1不同的是，将LiF替换为TiO 2。
本实施例制得的负极材料包括SiO内核、位于SiO内核表面的TiO 2缓冲层和碳层，TiO 2缓冲层形成于SiO内核表面，碳层包括位于缓冲层表面的无定型碳材料及向靠近及远离缓冲层的方向延伸的碳纳米材料，碳纳米材料为碳纳米线；碳纳米材料的直径为70nm；眼纳米材料的长径比为150；所述碳纳米材料的面密度为500根/mm 2；
TiO 2缓冲层的厚度为1μm，碳层厚度为500nm；其中，缓冲层占负极材料的质量百分数为5％；碳层占负极材料的质量百分数为5％。
实施例7
本实施例与实施例1不同的是，将SiO粉末加入分散液之前，还包括对SiO粉末进行热歧化处理。热歧化处理的温度为900℃。
本实施例制得的负极材料包括SiO内核、位于SiO内核表面的LiF缓冲层和碳层，LiF缓冲层形成于SiO内核表面，碳层包括位于缓冲层表面的无定型碳材料 及向靠近及远离缓冲层的方向延伸的碳纳米材料，碳纳米材料为碳纳米线；碳纳米材料的直径为50nm；碳纳米材料的长径比为100；所述碳纳米材料的面密度为300根/mm 2；
LiF缓冲层的厚度为0.5μm，碳层厚度为500nm；其中，缓冲层占负极材料的质量百分数为5％；碳层占负极材料的质量百分数为5％。
实施例8
本实施例与实施例1不同的是，碳源的热裂解温度为600℃。
本实施例制得的负极材料包括SiO内核、位于SiO内核表面的LiF缓冲层和碳层，LiF缓冲层形成于SiO内核表面，碳层包括位于缓冲层表面的无定型碳材料及向靠近及远离缓冲层的方向延伸的碳纳米材料，碳纳米材料为碳纳米线；碳纳米材料的直径为50nm；纳米材料的长径比为160；所述碳纳米材料的面密度为200根/mm 2；
LiF缓冲层的厚度为0.5μm，碳层厚度为500nm；其中，缓冲层占负极材料的质量百分数为5％；碳层占负极材料的质量百分数为5％。
实施例9
本实施例与实施例1不同的是，碳源的热裂解温度为1200℃。
本实施例制得的负极材料包括SiO内核、位于SiO内核表面的LiF缓冲层和碳层，LiF缓冲层形成于SiO内核表面，碳层包括位于缓冲层表面的无定型碳材料及向靠近及远离缓冲层的方向延伸的碳纳米材料，碳纳米材料为碳纳米线；碳纳米材料的直径为80nm；纳米材料的长径比为260；所述碳纳米材料的面密度为2000根/mm 2；
LiF缓冲层的厚度为0.4μm，碳层厚度为500nm；其中，缓冲层占负极材料的质量百分数为5％；碳层占负极材料的质量百分数为5％。
实施例10
本实施例与实施例2不同的是，碳包覆处理之后的热处理温度为600℃。
本实施例制得的负极材料包括SiO 1.5内核、位于SiO 1.5内核表面的LiF缓冲层和碳层，LiF缓冲层形成于SiO 1.5内核表面，碳层包括位于缓冲层表面的无定型碳材料及向靠近及远离缓冲层的方向延伸的碳纳米材料，
碳纳米材料为碳纳米管；碳纳米材料的直径为15nm；纳米材料的长径比为300；所述碳纳米材料的面密度为200根/mm 2；
LiF缓冲层的厚度为0.02μm，碳层厚度为1000nm；其中，缓冲层占负极材料的质量百分数为15％；碳层占负极材料的质量百分数为5％。
实施例11
本实施例与实施例2不同的是，碳包覆处理之后的热处理温度为1200℃。
本实施例制得的负极材料包括SiO 1.5内核、位于SiO 1.5内核表面的LiF缓冲层和碳层，LiF缓冲层形成于SiO 1.5内核表面，碳层包括位于缓冲层表面的无定型碳材料及向靠近及远离缓冲层的方向延伸的碳纳米材料，碳纳米材料为碳纳米管；碳纳米材料的直径为50nm；纳米材料的长径比为600；所述碳纳米材料的面密度为4000根/mm 2；
LiF缓冲层的厚度为0.015μm，碳层厚度为1000nm；其中，缓冲层占负极材料的质量百分数为15％；碳层占负极材料的质量百分数为5％。
实施例12
(1)将10g LiF分散在10L去离子水中，搅拌并超声处理60min，得到分散液。
(2)将20g SiO(球形度系数为0.5)粉末加入分散液中，搅拌2h，得到混合浆料。
(3)将混合浆料离心处理，并在85℃下干燥24h，得到固体复合物。
(4)对固体复合物进行碳包覆处理。其中以甲烷作为碳源，氮气为保护气氛，采用回转炉进行碳包覆处理。先以25℃/min将保护气氛气氛以流速1L/min升温至预热温度200℃，保温20min，利用预热后的保护气氛对固体复合物进行预热。然后将预热后的固体复合物与碳源混合，再以5℃/min升温至所述碳源的热裂解温度900℃，热裂解的时间为25h。
本实施例制得的负极材料包括SiO内核、位于SiO内核表面的LiF缓冲层和碳层，LiF缓冲层形成于SiO内核表面，碳层包括位于缓冲层表面的无定型碳材料及向靠近及远离缓冲层的方向延伸的碳纳米材料，碳纳米材料为石墨烯；碳纳米材料的直径为100nm；纳米材料的长径比为10000；所述碳纳米材料的面密度为40000根/mm 2；
LiF缓冲层的厚度为5μm，碳层厚度为800nm；其中，缓冲层占负极材料的质量百分数为50％；碳层占负极材料的质量百分数为5％。
实施例13
和实施例1不同的是，选取球形度系数为0.96的SiO作为原料。
本实施例制得的负极材料包括SiO内核、位于SiO内核表面的LiF缓冲层和碳层，LiF缓冲层形成于SiO内核表面，碳层包括位于缓冲层表面的无定型碳材料及向靠近及远离缓冲层的方向延伸的碳纳米材料，碳纳米材料为碳纳米线；碳纳米材料的直径为50nm；纳米材料的长径比为100；所述碳纳米材料的面密度为300根/mm 2；
LiF缓冲层的厚度为0.5μm，碳层厚度为500nm；其中，缓冲层占负极材料的质量百分数为5％；碳层占负极材料的质量百分数为5％。
实施例14
本实施例与实施例2相比，在步骤(4)对固体复合物进行碳包覆处理时，不采用预热后的保护气氛对固体复合物进行预热处理。
本对比例制得的负极材料，包括SiO 1.5内核、位于SiO 1.5内核表面的LiF缓冲层和碳层，LiF缓冲层形成于SiO1.5内核表面，碳层包括位于缓冲层表面的无定型碳材料及向靠近及远离缓冲层的方向延伸的碳纳米材料；碳纳米材料为碳纳米管；碳纳米材料的直径为20nm；碳纳米材料的长径比为500；所述碳纳米材料的面密度为15根/mm 2；
LiF缓冲层的厚度为0.02μm；碳层厚度为1000nm；其中，缓冲层占负极材料的质量百分数为15％；碳层占负极材料的质量百分数为8％。
对比例1
本对比例中负极材料的制备方法为：
对200g SiO(球形度系数为0.50)进行碳包覆处理。其中以甲烷作为碳源，氮气为保护气氛，采用回转炉进行碳包覆处理。先以25℃/min将保护气氛以流速8L/min升温至预热温度200℃，然后将SiO与碳源混合，再以5℃/min升温至所述碳源的热裂解温度900℃，热裂解的时间为25h。
本对比例制得的负极材料，包括SiO内核、位于SiO内核表面的无定型碳层，无纳米结构。碳层厚度为500nm；碳层占负极材料的质量百分数为5％。
对比例2
本实施例中负极材料的制备方法为：
(1)将71.7g二茂铁分散在10L去离子水中，搅拌并超声处理60min，得到分散液。
(2)将200g SiO(球形度系数为0.50)粉末加入分散液中，搅拌2h，得到混合浆料。
(3)将混合浆料离心处理，并在85℃下干燥24h，得到固体复合物。
(4)对固体复合物进行碳包覆处理，得到负极材料。其中以甲烷作为碳源，氮气为保护气氛，采用回转炉进行碳包覆处理。先以25℃/min将保护气氛以流速10L/min升温至预热温度200℃，然后将固体复合物与碳源混合，再以5℃/min升温至所述碳源的热裂解温度900℃，热裂解的时间为25h。
本对比例制得的负极材料，包括SiO内核、位于SiO内核表面的碳层，碳层包括位于SiO内核表面的无定型碳材料及碳纳米材料。碳纳米材料为碳纳米线；碳纳米材料的直径为100nm；纳米材料的长径比为10000；所述碳纳米材料的面密度为100000根/mm 2；碳层厚度为500nm；碳层占负极材料的质量百分数为5％。
在本对比例中，负极材料中还包括铁磁性材料，铁磁性材料的存在会可能带来电池的微短路问题，需要对负极材料进行进一步的除磁处理。
对比例3
本对比例中负极材料的制备方法为：
(1)称取碳纳米管加入去离子水中，搅拌45min，加入200g(球形度系数为0.50)SiO粉末，搅拌3h，加入酒精，搅拌30min，抽滤，干燥，得到碳纳米管复合SiO材料，其中，碳纳米管的质量含量为0.10％。
(2)对碳纳米管复合SiO材料进行碳包覆处理。其中以甲烷作为碳源，氮气为保护气氛，采用回转炉进行碳包覆处理。先以25℃/min将保护气氛以流速0.5L/min升温至预热温度220℃，保温30min。然后将碳纳米管复合SiO材料与碳源混合，再以5℃/min升温至所述碳源的热裂解温度920℃，热裂解的时间为25h，得到碳纳米管复合碳包覆SiO材料。
本对比例制得的负极材料，包括SiO内核、位于SiO内核表面的碳层，碳层包括位于SiO内核表面的无定型碳材料及非原位附着在碳层上的碳纳米材料。碳纳米材料为碳纳米管；碳纳米材料的直径为1.8nm；纳米材料的长径比为2500；所述碳纳米材料的面密度为500根/mm 2；碳层厚度为500nm；碳层占负极材料的质量百分数为5％。
对比例4
本对比例中负极材料的制备方法为：
(1)对200g SiO(球形度为0.50)进行碳包覆处理。其中以甲烷作为碳源，氮气为保护气氛，采用回转炉进行碳包覆处理。先以25℃/min将保护气氛以流速7L/min升温至预热温度200℃，然后将固体复合物与碳源混合，再以5℃/min升温至所述碳源的热裂解温度900℃，热裂解的时间为25h。
(2)将碳包覆处理之后的复合物放入窑炉中，在980℃下热处理24h。
(3)将10gLiF分散在10L去离子水中，搅拌并超声处理60min，得到分散液。
(4)将(2)中得到的粉末加入分散液中，搅拌2h，得到混合浆料。
(5)将混合浆料离心处理，并在85℃下干燥24h，得到固体复合物。
本对比例制得的负极材料，包括SiO内核、位于SiO内核表面的碳层和LiF层，碳层形成于SiO内核表面，LiF层位于碳层表面，不存在碳纳米结构。碳层厚度为500nm；碳层占负极材料的质量百分数为5％。
测试方法
以实施例1～14(S1～S14)、对比例1～4(D1～D4)中负极材料制成锂离子电池测试可逆比容量、首次库伦效率、循环50圈后的体积膨胀率以及容量保持率。
(1)可逆比容量和首次库伦效率的测试方法为：按照负极材料、导电炭黑、聚丙烯酸胶(PAA胶)按质量比为75:15:10的比例调制成负极浆料，在铜箔上涂 布，干燥后制成负极极片。以金属锂片作为对电极，在充满氩气的手套箱中组装成扣式电池完成。在0.1C的电流密度下，按充放电区间为0.01-1.5V进行充放电测试。测试得到电池的首次可逆比容量和首次库伦效率。
(2)循环50圈后的体积膨胀率和容量保持率的测试方法为：按照负极材料：导电炭黑(Super-P)：导电石墨(KS-6)：羧甲基纤维素(CMC)：丁苯橡胶(SBR)＝92：2：2：2：2调制成负极浆料，在铜箔上涂布，干燥后制成负极极片。以金属锂片作为对电极，在充满氩气的手套箱中组装成扣式电池完成。在1C的电流密度下，按充放电区间为0.01V-1.5V进行充放电测试。测试得到电池的循环50圈后的体积膨胀率和容量保持率。
实施例1～14、对比例1～4中负极材料的性能参数如下表所示。
Figure PCTCN2022137453-appb-000001
Figure PCTCN2022137453-appb-000002
性能参数 对比例1 对比例2 对比例3 对比例4
D 10(μm) 1.7 1.7 1.7 1.7
D 50(μm) 5.0 5.3 5.3 5.3
(D 90-D 50)/(D 50-D 10) 1.4 1.5 1.4 1.4
比表面积(m 2/g) 3.0 9.6 2.2 2.0
Si微晶尺寸(nm) 4.9 5.1 5.2 5.9
首次可逆比容量(mAh/g) 1575.6 1213.7 1506.3 1519.4
首次库伦效率(％) 77.03 69.41 77.21 77.30
循环50圈后容量保持率(％) 80.0 82.6 79.0 79.9
循环50圈后体积膨胀率(％) 39.7 39.4 38.4 40.0
碳纳米材料面密度(根/mm 2) / 100000 500 /
SiO x球形度 0.5 0.5 0.5 0.5
缓冲层厚度(μm) / / / /
实施例1中负极材料的结构如图3a及图3b所示，其中图3a为实施例1制得的负极材料的表面结构图，图3b为实施例1制得的负极材料的切面图。从图3a及图3b中能够看出，在负极材料表面有纳米线结构，且粒径在100nm以下。并且根据图3b可以看出部分纳米线朝向负极材料的内部延伸。
实施例2中负极材料的结构如图4a及图4b所示，由图4a及图4b可以看出，负极材料表面存在纳米线，且纳米线相互缠绕。图5a为实施例2中负极材料中纳米线的表面结构图，图5b为实施例2中负极材料中纳米线的EDS能谱，由图5a及图5b可以看出，纳米线主要有碳元素组成，表明在负极材料表面形成了碳纳米材料。
对比例1中负极材料的结构如图6a及图6b所示，由图6a及图6b可以看出，在对比例1的负极材料中没有纳米线结构产生，并且除了没有纳米线结构产生，其表面形貌与实施例1和实施例2相似。
实施例1、对比例1中的负极材料制成锂离子电池的循环膨胀测试结果如图7所示，循环容量保持率如图8所示。
由图7可以看出，实施例1和对比例1中的负极材料制成的锂离子电池的充放电平台接近，表明缓冲层的引入能够使材料保持较好的电化学性能。
由图8可以看出，实施例1和对比例1中的负极材料制成的锂离子电池在前期的循环保持率接近，但是从25周循环之后，实施例1中的负极材料制成的锂离子电池的循环保持率明显高于对比例1，其原因可能是负极材料中的双层柔性结构缓冲材料的体积膨胀，且减少了SEI膜的生成，另外，碳纳米材料的存在改善了电子电导性能，促进了电池循环性能的提升。
比较表中实施例1和实施例14可知，固体复合物不预热的话，固体混合物中的金属化合物是常温下投入到反应炉中，其催化活性低，不能使原料彻底反应，影响碳纳米管的生成，从而使得得到的碳纳米线的面密度较小，材料在循环时的副反应减少，从而使得比容量和首效有所提升，但是由于碳纳米管生成的含量较少，会影响其循环容量保持率及循环体积膨胀率。
比较表中实施例1和对比例1，首次库伦效率和循环50圈后容量保持率较高，且循环50圈后体积膨胀率较小。原因在于，容量保持率和膨胀率的改善源自于LiF人造SEI膜结构带来的包覆韧性提升及抑制天然SEI膜的生成，有利于保持SiOx颗粒的结构完整性。而首次库伦效率的提升则得益于其高度电绝缘性及宽带宽，这种特性阻止了电解液分解，从而限制了额外的SEI生成，这样减少不可逆容量，导致了首次库伦效率提升。
比较表中实施例1和对比例2，使用二茂铁作为催化剂的主要劣势从工艺上来说需要经过后续除磁过程，因此会更加繁琐。此外，使用二茂铁作为催化剂时，相同摩尔浓度时得到表面的碳纳米材料的面密度更大，过量的碳纳米材料导致材料的比表面积增加，从而使得材料在首次充放电过程中与电解液反应生成SEI的厚度(数量)增加，使得反应得到的比容量和首次库伦效率降低，电池的体积膨胀率和循环性能也略有劣化。
比较表中实施例1和对比例3，后续加入CNT由于不是原位生成，且不能穿入碳包覆层形成“笼状”结构，因而其相比较实施例1在循环过程中对于维持界面的稳定性的作用较弱，从而使得颗粒相比较实施例1更易出现破碎和坍塌，因而电解液的持续渗透使得新的SEI膜不断生成，导致了循环过程中不可逆比容量的增加，从而反映为略微下降的容量保持率和略微上升的膨胀率。另外，也表明了实施例1中的制备方法相比较后期加入CNT具有更优的循环性能。
比较表中实施例1和对比例4，如果将C层包覆SiOx内核，缓冲层包覆C层，形成由内到外为SiOx内核-C层-缓冲层的结构，该结构虽然可以在一定程度上提升首次库伦效率，但因为其将高度电绝缘的LiF包覆在最外层，因而会影响材料的循环性能，且包覆C层所带来的对于电子电导的改善作用无法发挥出来。
以上所述实施例的各技术特征可以进行任意的组合，为使描述简洁，未对上述实施例中的各个技术特征所有可能的组合都进行描述，然而，只要这些技术特征的组合不存在矛盾，都应当认为是本说明书记载的范围。
以上所述实施例仅表达了本申请的几种实施方式，其描述较为具体和详细，但并不能因此而理解为对申请专利范围的限制。应当指出的是，对于本领域的普通 技术人员来说，在不脱离本申请构思的前提下，还可以做出若干变形和改进，这些都属于本申请的保护范围。因此，本申请专利的保护范围应以所附权利要求为准，说明书及附图可以用于解释权利要求的内容。

Claims (15)

  1. 一种负极材料，其特征在于，所述负极材料包括活性物质、位于活性物质表面的缓冲层和碳层，其中，所述缓冲层形成于所述活性物质表面，所述碳层包括位于所述缓冲层表面的无定型碳材料及向靠近和/或远离所述缓冲层的方向延伸的碳纳米材料。
  2. 如权利要求1所述的负极材料，其特征在于，包括以下特征(1)至(16)中至少一种：
    (1)所述碳纳米材料向靠近所述缓冲层的方向延伸至所述缓冲层；
    (2)所述碳纳米材料向靠近所述缓冲层的方向延伸并贯穿所述缓冲层延伸至所述活性物质；
    (3)所述碳纳米材料连接所述无定型碳材料以及所述缓冲层；
    (4)所述碳纳米材料贯穿所述缓冲层并连接所述无定型碳材料以及所述活性物质；
    (5)所述碳纳米材料包括碳纳米管、碳纳米纤维以及石墨烯中的至少一种；
    (6)所述碳纳米材料的形状包括线状、管状、片状以及长条状中的至少一种；
    (7)所述碳纳米材料的直径为1nm～100nm；
    (8)所述碳纳米材料的长径比≥10；
    (9)所述负极材料中，所述碳纳米材料的面密度为20根/mm 2～10000根/mm 2；
    (10)所述缓冲层包括碱金属卤化物、碱金属氮化合物、碱金属氧化物和过渡金属氧化物中的至少一种；
    (11)所述缓冲层包括LiF、NaF及Li 3N中的至少一种；
    (12)所述缓冲层包括Li 2O、Al 2O 3、MgO、TiO 2、ZnO、CuO、Ag 2O以及ZrO 2中的至少一种；
    (13)所述缓冲层能催化所述无定型碳材料形成所述碳纳米材料；
    (14)所述缓冲层能催化所述无定型碳材料原位生长形成所述碳纳米材料；
    (15)所述缓冲层的厚度为0.01μm～2μm；
    (16)所述缓冲层包括LiF、Li 2O、Li 3N、Al 2O 3、TiO 2、ZnO以及ZrO 2中的至少一种。
  3. 如权利要求1～2中任一项所述的负极材料，其特征在于，包括以下特征(1)至(12)中至少一种：
    (1)所述活性物质包括SiO x材料，0＜x＜2；
    (2)所述活性物质包括SiO x材料，0.8≤x≤1.5；
    (3)所述活性物质包括SiO x材料，SiO x材料颗粒呈球形或类球形；
    (4)所述活性物质包括SiO x材料，所述SiO x材料颗粒的球形度系数≥0.4；
    (5)所述缓冲层占所述负极材料的质量百分数为0.05％～20％；
    (6)所述碳层占所述负极材料的质量百分数为0.5％～20％；
    (7)所述碳层的厚度为10nm～1500nm；
    (8)所述负极材料的D 50为1μm～20μm；
    (9)所述负极材料的粒径分布(D 90-D 50)/(D 50-D 10)为1.2～1.6；
    (10)所述活性物质包括Si晶粒；
    (11)所述活性物质包括Si晶粒，所述Si晶粒尺寸为2nm～10nm；
    (12)所述负极材料的比表面积为1m 2/g～20m 2/g。
  4. 一种负极材料的制备方法，其特征在于，包括如下步骤：
    在活性物质表面形成缓冲层，得到固体复合物，所述缓冲层包括碱金属卤化物、碱金属氮化合物、碱金属氧化物和过渡金属氧化物中的至少一种；
    在保护气氛中对所述固体复合物进行碳包覆处理，得到负极材料，所述负极材料包括活性物质、位于活性物质表面的缓冲层和碳层，所述碳层包括无定型碳材料以及碳纳米材料，所述碳纳米材料自所述无定型碳材料向靠近和/或远离所述缓冲层的方向延伸。
  5. 如权利要求4所述的制备方法，其特征在于，包括以下特征(1)至(6)中至少一种：
    (1)所述活性物质包括SiO x材料，0＜x＜2；
    (2)所述活性物质包括SiO x材料，0.8≤x≤1.5；
    (3)所述活性物质包括SiO x材料，SiO x材料颗粒呈球形或类球形；
    (4)所述活性物质包括SiO x材料，所述SiO x材料颗粒的球形度系数≥0.4；
    (5)所述活性物质包括Si晶粒；
    (6)所述活性物质包括Si晶粒，所述Si晶粒尺寸为2nm～10nm。
  6. 如权利要求4所述的制备方法，其特征在于，包括以下特征(1)至(7)中至少一种：
    (1)所述缓冲层能催化所述无定型碳材料形成所述碳纳米材料；
    (2)所述缓冲层能催化所述无定型碳材料原位生长形成所述碳纳米材料；
    (3)所述缓冲层包括LiF、NaF及Li 3N中的至少一种；
    (4)所述缓冲层包括Li 2O、Al 2O 3、MgO、TiO 2、ZnO、CuO、Ag 2O以及ZrO 2中的至少一种；
    (5)所述缓冲层的厚度为0.01μm～2μm；
    (6)所述缓冲层包括LiF、Li 2O、Li 3N、Al 2O 3、TiO 2、ZnO以及ZrO 2中的至少一种；
    (7)所述在活性物质表面形成缓冲层的方式为液相包覆。
  7. 如权利要求6所述的制备方法，其特征在于，包括以下特征(1)至(6)中至少一种：
    (1)所述在活性物质表面形成缓冲层，得到固体复合物的步骤，包括：将缓冲层材料与活性物质在溶剂中混合，制备混合浆料，并对混合浆料进行固液分离处理，得到固体复合物；
    (2)所述混合浆料中缓冲层材料的粒径为1nm～1μm；
    (3)所述溶剂包括水、乙醇中的至少一种；
    (4)所述缓冲层材料占所述混合浆料的质量百分数为0.05％～0.2％；
    (5)所述活性物质占所述混合浆料的质量百分数为2％～20％；
    (6)所述固液分离处理包括抽滤处理、离心处理以及喷雾干燥处理中的至少一种。
  8. 如权利要求6所述的制备方法，其特征在于，包括以下特征(1)至(5)中至少一 种：
    (1)所述在活性物质表面形成缓冲层，得到固体复合物的步骤，包括：将缓冲层前驱体材料在溶剂中混合，制备含缓冲层材料的分散液；往分散液中加入活性物质混合后进行固液分离处理，得到固体复合物；
    (2)所述缓冲层前驱体材料包括锂源及氟源；
    (3)所述缓冲层前驱体材料包括锂源及氟源，所述锂源包括硝酸锂、醋酸锂、碳酸锂以及草酸锂中的至少一种；
    (4)所述缓冲层前驱体材料包括锂源及氟源，所述氟源包括氟化铵、氟化钠以及氟化钙中的至少一种；
    (5)所述缓冲层前驱体材料包括锂源及氟源，所述锂源占所述分散液的质量百分数为0.01％～0.5％，所述氟源占所述分散液的质量百分数为0.01％～0.5％。
  9. 如权利要求4所述的制备方法，其特征在于，包括以下特征(1)至(4)中至少一种：
    (1)所述方法还包括：对所述固体复合物进行预热，再进行碳包覆处理；
    (2)所述方法还包括：采用预热的保护气氛对所述固体复合物进行预热，再进行碳包覆处理；
    (3)所述方法还包括：采用预热的保护气氛对所述固体复合物进行预热，再进行碳包覆处理，其中，所述保护气氛的预热温度为100℃～300℃；
    (4)所述方法还包括：采用预热的保护气氛对所述固体复合物进行预热，再进行碳包覆处理，其中，所述保护气氛的升温速率为1℃/min～50℃/min。
  10. 如权利要求4～9任一项所述的制备方法，其特征在于，包括以下特征(1)至(4)中至少一种：
    (1)所述碳包覆处理包括固相碳包覆处理、液相碳包覆处理以及气相碳包覆处理中的至少一种；
    (2)所述碳包覆处理包括如下步骤：将所述固体复合物与碳源混合，控制所述碳源热裂解以在所述固体复合物的颗粒表面形成碳层；
    (3)对所述固体复合物进行碳包覆处理之后还包括如下步骤：对进行碳包覆处理之后的固体复合物进行热处理；
    (4)所述保护气氛包括氮气、氩气、氦气、氖气、氪气以及氙气中的至少一种。
  11. 如权利要求10所述的制备方法，其特征在于，包括以下特征(1)至(14)中至少一种：
    (1)所述碳源包括气相碳源；
    (2)所述碳源包括气相碳源，所述气相碳源包括气相烃类碳源；
    (3)所述碳源包括气相碳源，所述气相碳源包括甲烷、乙烷、丙烷、乙烯、丙烯、乙炔、丙炔、丙酮以及苯中的至少一种；
    (4)所述碳源包括液相碳源；
    (5)所述碳源包括液相碳源，所述液相碳源包括液相有机碳源；
    (6)所述碳源包括液相碳源，所述液相碳源包括正己烷、甲苯、苯、二甲苯、甲醇、乙醇、丙醇、丁醇、戊醇、丙酮、丁酮、2-戊酮、乙酸甲酯、乙酸乙酯、乙酸丙 酯、乙酸丁酯以及乙酸戊酯中的至少一种；
    (7)所述碳源包括固相碳源；
    (8)所述碳源包括固相碳源，所述固相碳源包括固相有机碳源；
    (9)所述碳源包括固相碳源，所述固相碳源包括柠檬酸、葡萄糖、沥青、酚醛树脂以及糠醛树脂中的至少一种；
    (10)所述热裂解的温度为600℃～1200℃；
    (11)所述热裂解的升温速率为0.1℃/min～10℃/min；
    (12)所述热处理的温度为600℃～1200℃；
    (13)所述热处理的升温速率为1℃/min～5℃/min；
    (14)所述热处理的时间为1h～48h。
  12. 如权利要求4～9中任一项所述的制备方法，其特征在于，所述活性物质包括SiO x材料，0＜x＜2；在活性物质表面形成缓冲层之前，所述方法还包括如下步骤：
    对所述SiO x材料进行热歧化处理。
  13. 如权利要求12所述的制备方法，其特征在于，包括以下特征(1)至(3)中至少一种：
    (1)所述热歧化处理的温度为800℃～1400℃；
    (2)所述热歧化处理的升温速率为1℃/min～5℃/min；
    (3)所述热歧化处理的时间为2h～50h。
  14. 一种锂离子电池，其特征在于，包括如权利要求1～3任一项所述的负极材料或根据权利要求4～13任一项所述的负极材料的制备方法制得的负极材料。
  15. 一种可充电用电产品，其特征在于，包括如权利要求14所述的锂离子电池。
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