WO2025044227A1 - 负极材料及电池 - Google Patents

负极材料及电池 Download PDF

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Publication number
WO2025044227A1
WO2025044227A1 PCT/CN2024/086922 CN2024086922W WO2025044227A1 WO 2025044227 A1 WO2025044227 A1 WO 2025044227A1 CN 2024086922 W CN2024086922 W CN 2024086922W WO 2025044227 A1 WO2025044227 A1 WO 2025044227A1
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Prior art keywords
negative electrode
electrode material
silicon
primary particles
silicon nano
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PCT/CN2024/086922
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English (en)
French (fr)
Inventor
安威力
何鹏
任建国
贺雪琴
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BTR New Material Group Co Ltd
Dingyuan New Energy Technology Co Ltd
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BTR New Material Group Co Ltd
Dingyuan New Energy Technology Co Ltd
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Priority to JP2025516286A priority Critical patent/JP2025531318A/ja
Priority to KR1020257008782A priority patent/KR20250047397A/ko
Priority to EP24857777.7A priority patent/EP4576255A4/en
Priority to US19/019,087 priority patent/US20250149562A1/en
Publication of WO2025044227A1 publication Critical patent/WO2025044227A1/zh
Anticipated expiration legal-status Critical
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
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    • 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
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    • 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
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    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
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    • H01M4/04—Processes of manufacture in general
    • H01M4/0471—Processes of manufacture in general involving thermal treatment, e.g. firing, sintering, backing particulate active material, thermal decomposition, pyrolysis
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    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/134—Electrodes based on metals, Si or alloys
    • H—ELECTRICITY
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    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • H01M4/1395—Processes of manufacture of electrodes based on metals, Si or alloys
    • H—ELECTRICITY
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    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • H01M4/381—Alkaline or alkaline earth metals elements
    • H01M4/382—Lithium
    • H—ELECTRICITY
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    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
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    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • H01M4/386—Silicon or alloys based on silicon
    • H—ELECTRICITY
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    • 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
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    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/485—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of mixed oxides or hydroxides for inserting or intercalating light metals, e.g. LiTi2O4 or LiTi2OxFy
    • H—ELECTRICITY
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    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H—ELECTRICITY
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    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/621—Binders
    • H01M4/622—Binders being polymers
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    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
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    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/624—Electric conductive fillers
    • H01M4/625—Carbon or graphite
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/60—Particles characterised by their size
    • C01P2004/61—Micrometer sized, i.e. from 1-100 micrometer
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
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    • C01P2004/00—Particle morphology
    • C01P2004/60—Particles characterised by their size
    • C01P2004/62—Submicrometer sized, i.e. from 0.1-1 micrometer
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2006/00—Physical properties of inorganic compounds
    • C01P2006/11—Powder tap density
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2006/00—Physical properties of inorganic compounds
    • C01P2006/12—Surface area
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    • H01M2004/021—Physical characteristics, e.g. porosity, surface area
    • H—ELECTRICITY
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    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/027—Negative electrodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2300/00—Electrolytes
    • H01M2300/0017—Non-aqueous electrolytes
    • H01M2300/0065—Solid electrolytes
    • H01M2300/0068—Solid electrolytes inorganic
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present application relates to the technical field of negative electrode materials, and more specifically, to negative electrode materials and batteries.
  • Lithium-ion batteries are widely used in electric vehicles and consumer electronics due to their advantages such as high energy density, high output power, long cycle life and low environmental pollution.
  • silicon negative electrode materials In order to improve the energy density of batteries, the research and development of silicon negative electrode materials are becoming more and more mature. However, the volume expansion of silicon negative electrode materials is large (>300%) during the process of lithium extraction and insertion. Silicon negative electrode materials will be pulverized and fall from the current collector during the charging and discharging process, causing the active material to lose electrical contact with the current collector, resulting in poor electrochemical performance, capacity attenuation, and decreased cycle stability, making it difficult to obtain commercial applications. In order to improve the conductivity and cycle stability of silicon negative electrode materials, carbon coating can be used. The existing carbon coating preparation method has complicated steps, and simple carbon coating cannot effectively improve the electrochemical performance of silicon-carbon negative electrodes.
  • the present application proposes a negative electrode material and a battery, so that the negative electrode material has excellent cycle stability and good expansion performance.
  • the present application provides a negative electrode material, the negative electrode material comprising secondary particles, the secondary particles comprising silicon nano primary particles;
  • the silicon nano primary particles include at least one silicon crystal grain, the average particle size of the silicon crystal grain is Ds nm, and the average particle size of the silicon nano primary particles is Dn nm;
  • the negative electrode material provided in the present application explores the relationship between the size of silicon nano primary particles and the size of silicon grains.
  • the crystal attitude of silicon nano primary particles is controlled, which can better reduce the stress concentration problem generated by silicon nano primary particles during the lithium extraction process, which is conducive to uniform stress release, ensuring the structural stability of silicon nano primary particles, and reducing particle pulverization.
  • the crystal attitude A of silicon nano primary particles is too large, it means that the size of silicon grains is too small.
  • the grain boundaries between silicon grains will gradually disappear during the lithiation process, and finally form large-sized grains, that is, electrochemical sintering.
  • FIG1 is a schematic diagram of the structure of the negative electrode material provided in this embodiment.
  • FIGS. 2a and 2b are schematic structural diagrams of silicon nano primary particles in the negative electrode material provided in this embodiment
  • 3a and 3b are schematic diagrams of another structure of silicon nano primary particles in the negative electrode material provided in this embodiment.
  • FIG4 is a schematic diagram of a method for preparing a negative electrode material provided in this embodiment.
  • FIG5 is a scanning electron microscope image of the negative electrode material provided in Example 1.
  • the size of the silicon grains 12 is too small, the grain boundaries between the silicon grains will gradually disappear during the lithiation process, and finally form large-sized grains, that is, electrochemical sintering.
  • electrochemical sintering the grain boundaries between the silicon grains disappear, the silicon grains grow, and the local stress of the silicon nano primary particles 11 becomes larger after the negative electrode material is embedded with lithium, and the structural instability of the negative electrode material is enhanced, resulting in a decrease in the cycle performance and capacity of the negative electrode material.
  • Current research has found that when the silicon grain size is less than 10nm, obvious electrochemical sintering will occur.
  • the charging current must be controlled to reduce the degree of sintering, or the silicon grains or silicon particles are isolated with carbon.
  • the value range of A can be 1, 5, 10, 15, 20, 30, 40, 50, 80, 100, 120, 150, 180 or 200, etc., and of course it can also be other values within the above range, which is not limited here.
  • the crystal state A of the silicon nano primary particle 11 is 1, and the silicon nano primary particle is single crystal silicon.
  • the secondary particle 12 includes a plurality of single crystal silicon primary particles 11a.
  • the silicon nano primary particles have a crystalline state 1 ⁇ A ⁇ 200, and the silicon nano primary particles include silicon grains, and the silicon grains include polycrystalline silicon.
  • the average particle size of the secondary particles 12 is Dm nm, 500 ⁇ Dm ⁇ 25000; specifically, it can be 500nm, 1000nm, 1500nm, 2000nm, 3000nm, 5000nm, 8000nm, 10000nm, 15000nm, 20000nm, 23000nm or 25000nm, etc., which is not limited here.
  • the specific value of B can be 5, 10, 20, 50, 80, 100, 150, 200, 300, 350 or 400, etc. Of course, it can also be other values within the above range, which are not limited here. Controlling the stacking degree of the secondary particles 12 can ensure the structural stability of the secondary particles, which is conducive to the formation of a stable SEI film, reducing the expansion rate of the entire negative electrode material, and improving the initial efficiency and cycle performance of the negative electrode material.
  • the size of the silicon nano primary particles 11 is too small, which will cause the specific surface area of the secondary particles 12 to increase, and the negative electrode material
  • the specific surface area of the material also increases.
  • the side reactions increase, and the active lithium ions consumed increase, resulting in a decrease in the first coulombic efficiency of the negative electrode material.
  • the stacking degree of the secondary particles 12 is too small, the size of the silicon nano primary particles is too large under the same secondary particle size, and the expansion stress of the secondary particles 12 is more concentrated, which easily leads to the secondary particles breaking and pulverizing, which is not conducive to improving the structural stability of the negative electrode material, and the cycle stability of the battery prepared by the negative electrode material decreases.
  • the negative electrode material further includes a conductive layer 111 located on at least part of the surface of the silicon nano primary particle 11, and the conductive layer 111 includes at least one of an amorphous carbon material, a graphitized carbon material, and a conductive ceramic material.
  • the conductive layer 111 has a porous structure, and the porous structure is conducive to the transmission of lithium ions and electrons.
  • the conductive layer 111 can improve the conductivity of the silicon nano primary particle 11, and can also effectively alleviate the volume expansion of the silicon nano primary particle 11.
  • the conductive layer 111 includes a graphitized carbon material, the graphitized carbon material is graphene, the number of graphene layers is less than 20, and the number of graphene layers can specifically be 1 layer, 2 layers, 3 layers, 5 layers, 8 layers, 10 layers, 12 layers, 15 layers, 18 layers or 19 layers, etc., and of course it can also be other values within the above range, which is not limited here.
  • the thickness of the conductive layer is 1 nm to 200 nm, and may be specifically 1 nm, 10 nm, 20 nm, 40 nm, 50 nm, 80 nm, 100 nm, 150 nm, 180 nm or 200 nm, etc., which is not limited here.
  • the conductive ceramic material includes at least one of a metal oxide, a transition metal nitride, and a sulfide.
  • the metal oxide includes at least one of V2O5 , TiO2 , Nb2O5 , CdO, CsO , MoO3, WO3 , BaO, SnO2 , Cr2O3 , MnO, Ag2O , CoO , NiO, Cu2O , and SnO.
  • the transition metal nitride includes at least one of VN, TiN, CoN, Fe 3 N, Co 4 N, and WN.
  • the sulfide includes at least one of CdS, Ag2S , Sb2S3 , TiS2 , and Li2S .
  • the negative electrode material further includes a coating layer 121 located on at least a portion of the surface of the secondary particle 12 , and the coating layer 121 includes at least one of an amorphous carbon material, a graphitized carbon material, and a polymer.
  • a coating layer is constructed on the surface of the secondary particles, and the coating layer can further alleviate the volume expansion of the negative electrode material; the negative electrode material is synergistically modified using the conductive layer and the coating layer, and the conductivity of the conductive layer 111 and the alleviation effect on the volume expansion of the silicon nano primary particles are utilized to ensure that the negative electrode material still has excellent electrical contact performance after lithium insertion. Combined with the outermost coating layer 121, the side reactions of the silicon nano primary particles and the electrolyte can be effectively avoided, while enhancing the structural stability of the negative electrode material.
  • the coating layer 121 includes a polymer, and illustratively, the polymer may be at least one of a diblock copolymer, a triblock copolymer, and a multiblock copolymer.
  • the mass content of the polymer in the negative electrode material is 1% to 20%; specifically, it can be 1%, 3%, 4%, 5%, 6%, 7%, 10%, 12%, 15%, 18% or 20%, etc., which is not limited here.
  • the thickness of the coating layer 121 is 5nm to 300nm, which can be 5nm, 50nm, 80nm, 100nm, 150nm, 200nm, 250nm or 300nm, etc., which is not limited here.
  • the polymer includes at least one of polyacrylic acid, polyacrylonitrile, polyimide, polyurethane, polydopamine, xanthan gum, polypyrrole, polythiophene, polyphenylene vinylene, polyaniline, polyacetylene and tannic acid.
  • the polymer is preferably at least one of polypyrrole, polythiophene, polyaniline, polyaniline and polyacetylene.
  • the coating layer 121 includes a graphitized carbon material, and the thickness of the coating layer is 5 nm to 100 nm. Specifically, it can be 5nm, 10nm, 30nm, 50nm, 70nm, 80nm, 90nm or 100nm, etc., which is not limited here.
  • the mass content of carbon in the negative electrode material is 5% to 80%. Specifically, it can be 5%, 8%, 10%, 15%, 20%, 30%, 35%, 40%, 45%, 50%, 60%, 70% or 80%, etc., which is not limited here. It should be noted that the carbon in the negative electrode material comes from the carbon material.
  • the tap density of the negative electrode material powder is 0.3 g/cm 3 to 1.3 g/cm 3 , specifically 0.3 g/cm 3 , 0.5 g/cm 3 , 0.6 g/cm 3 , 0.7 g/cm 3 , 0.8 g/cm 3 , 1.0 g/cm 3 , 1.3 g/cm 3 , etc.
  • it is 0.5 g/cm 3 to 0.8 g/cm 3 .
  • the powder compaction density of the negative electrode material is 1.2 g/cm 3 to 1.8 g/cm 3 , such as 1.2 g/cm 3 , 1.3 g/cm 3 , 1.4 g/cm 3 , 1.5 g/cm 3 , 1.6 g/cm 3 or 1.8 g/cm 3 , and preferably 1.45 g/cm 3 to 1.75 g/cm 3 .
  • the median particle size of the negative electrode material is 0.5 ⁇ m to 25 ⁇ m.
  • the median particle size of the negative electrode material can be 0.5 ⁇ m, 1 ⁇ m, 3 ⁇ m, 4 ⁇ m, 5 ⁇ m, 7 ⁇ m, 10 ⁇ m, 13 ⁇ m, 15 ⁇ m, 20 ⁇ m or 25 ⁇ m, etc., which are not limited here.
  • the median particle size of the negative electrode material is preferably 0.5 ⁇ m to 10 ⁇ m, and more preferably 1 ⁇ m to 5 ⁇ m.
  • the specific surface area ratio of the negative electrode material is 1m 2 /g to 50m 2 /g.
  • the specific surface area ratio of the negative electrode material can be 1m 2 /g, 5m 2 /g, 8m 2 /g, 10m 2 /g, 15m 2 /g, 20m 2 /g, 25m 2 /g, 30m 2 /g, 35m 2 /g, 40m 2 /g, 45m 2 /g or 50m 2 / g, etc., which are not limited here; it can be understood that the smaller the specific surface area, the better.
  • the specific surface area is controlled to be 2m 2 / g to 15m 2 /g.
  • the mass content of oxygen in the negative electrode material is less than 15%, and may be 5%, 6%, 8%, 10%, 12%, 13%, 14% or 15%, etc., which is not limited here.
  • the present application also provides a method for preparing a negative electrode material, as shown in FIG4 , the method comprising the following steps:
  • the stress concentration generated during the lithiation of silicon nano primary particles can be weakened, the structural stability of silicon nano primary particles during the lithiation process can be improved, and the expansion rate of the negative electrode material can be reduced, which is conducive to the formation of a stable solid electrolyte film on the surface of the negative electrode material, so that the negative electrode material has low expansion, high cycle stability, high rate capability and high first coulombic efficiency.
  • the preparation method of the negative electrode material provided in the present application can not only improve the electrochemical properties of the material, but also be suitable for large-scale production.
  • the prepared negative electrode material can effectively improve the rate performance and cycle stability of the lithium battery.
  • the average particle size of the silicon nano primary particles is Dn nm, 1 ⁇ Dn ⁇ 200; specifically, it can be 1nm, 5nm, 10nm, 15nm, 20nm, 30nm, 40nm, 50nm, 80nm, 100nm, 120nm, 150nm, 180nm, 190nm or 200nm, etc., which is not limited here.
  • the average particle size of the silicon grains is Ds nm, 1 ⁇ Ds ⁇ 100, and can be 1nm, 5nm, 10nm, 15nm, 20nm, 30nm, 40nm, 50nm, 60nm, 70nm, 80nm, 90nm or 100nm, etc., which is not limited here.
  • the value range of A can be 1, 5, 10, 15, 20, 30, 40, 50, 80, 100, 120, 150, 180 or 200, etc., and of course it can also be other values within the above range, which is not limited here.
  • the step of preparing silicon nano primary particles includes performing vapor deposition using a silicon source gas to obtain silicon nano primary particles.
  • the vacuum pressure before vapor deposition is less than 1.0 Torr, and can be specifically 0.9 Torr, 0.8 Torr, 0.7 Torr, 0.6 Torr, 0.5 Torr, 0.4 Torr, 0.3 Torr or 0.1 Torr, etc., which are not limited here. It is understandable that before chemical vapor deposition, the pressure in the furnace can be evacuated to a vacuum state, which is conducive to improving the purity of the silicon nano primary particles. Then heat and introduce an appropriate amount of silicon source gas as the growth raw material of the silicon nano primary particles, and deposit for a period of time to obtain silicon nano primary particles.
  • the heating rate during vapor deposition is 1°C/min to 20°C/min, and may be 1°C/min, 3°C/min, 5°C/min, 8°C/min, 10°C/min, 15°C/min or 20°C/min, which is not limited here.
  • the temperature during vapor deposition is 300°C to 1000°C, and specifically may be 300°C, 400°C, 500°C, 600°C, 700°C, 800°C or 1000°C, etc., which is not limited here.
  • the temperature of vapor deposition is 600°C to 1000°C, and specifically may be 400°C, 500°C, 600°C, 700°C, 800°C or 1000°C.
  • the flow rate of the silicon source gas is 0.05 L/min to 10 L/min, specifically 0.05 L/min, 0.1 L/min, 0.5 L/min, 1 L/min, 2 L/min, 3 L/min, 5 L/min, 7 L/min, 8 L/min or 10 L/min, which is not limited here.
  • the ventilation time of the silicon source gas is 0.1 h to 10 h, and specifically can be 0.1 h, 0.5 h, 1 h, 2 h, 4 h, 6 h, 8 h or 10 h, which is not limited here.
  • the pressure during vapor deposition is 100 Torr to 500 Torr, and specifically may be 100 Torr, 150 Torr, 200 Torr, 250 Torr, 300 Torr, 350 Torr, 400 Torr, 450 Torr or 500 Torr, etc., which is not limited here.
  • the silicon nano primary particles may be prepared by plasma heating method, and the size ratio (crystalline state A) of the silicon nano primary particles to the silicon grains may be controlled within the above range.
  • the method further includes forming a conductive layer on the surface of the silicon nano primary particles, wherein the conductive layer includes at least one of an amorphous carbon material, a graphitized carbon material, and a conductive ceramic material.
  • the step of forming a conductive layer on the surface of the silicon nano primary particles includes: depositing a first gas-phase carbon source on the surface of the silicon nano primary particles by vapor deposition under a protective atmosphere to form a conductive layer.
  • the concentration of the first gas-phase carbon source is 0.1 L/min to 10 L/min, and specifically can be 0.1 L/min, 1 L/min, 3 L/min, 5 L/min, 8 L/min or 10 L/min, which is not limited here.
  • the insulation time of vapor deposition is 1 h to 48 h, and specifically can be 1 h, 2 h, 4 h, 6 h, 8 h, 12 h, 18 h, 24 h or 48 h, which is not limited here.
  • the temperature of vapor deposition is 200°C to 1050°C, and specifically may be 200°C, 300°C, 400°C, 500°C, 600°C, 700°C, 800°C, 950°C or 1050°C, which is not limited here.
  • the heating rate of vapor deposition is 1°C/min to 30°C/min, specifically 1°C/min, 3°C/min, 5°C/min, 8°C/min, 10°C/min, 15°C/min, 20°C/min, 25°C/min or 30°C/min, which is not limited here.
  • the protective atmosphere includes at least one of helium, neon, argon, krypton, and xenon.
  • the volume ratio of the protective atmosphere to the first gaseous carbon source is 10:(0.5-10), specifically 10:0.5, 10:1, 10:2, 10:3, 10:4, 10:5, 10:7, 10:8, 10:9 or 10:10, which is not limited here.
  • the first gas-phase carbon source includes at least one of acetylene, methane, toluene, cyclohexane, ethanol, ethylene, and propylene.
  • the step of forming a conductive layer on the surface of the silicon nano primary particles includes: introducing a conductive material at a preset pulse frequency, and performing atomic layer deposition on the surface of the silicon nano primary particles to form a conductive layer. It can be understood that the formation of a conductive layer by atomic layer deposition on the surface of the silicon nano primary particles is conducive to improving the conductivity of the silicon nano primary particles, thereby improving the conductivity and rate performance of the negative electrode material.
  • silicon nano primary particles can be placed in an atomic layer deposition chamber, evacuated and replaced with inert gas, then heated, and one or more conductive materials as raw materials for the conductive layer are introduced at a certain pulse frequency for a certain period of time, and one or more conductive layers are deposited on the surface of the silicon nano primary particles by controlling the amount of conductive material.
  • the temperature of atomic layer deposition is 200°C to 750°C, specifically 200°C, 300°C, 400°C, 450°C, 500°C, 550°C, 600°C or 750°C, etc.
  • it can also be other values within the above range, which is not limited here.
  • the time of atomic layer deposition is 1 h to 48 h, and specifically can be 1 h, 2 h, 4 h, 6 h, 8 h, 12 h, 18 h, 24 h or 48 h, which is not limited here.
  • the pulse frequency is 40 khz to 500 khz, specifically 40 khz, 60 khz, 80 khz, 100 khz, 150 khz, 200 khz, 250 khz, 300 khz, 400 khz or 500 khz, etc., which is not limited here.
  • the pulse duration of the conductive material is 10 ms to 800 ms, and may specifically be 10 ms, 50 ms, 100 ms, 200 ms, 300 ms, 400 ms, 500 ms, 600 ms, 700 ms or 800 ms, etc., which is not limited here.
  • Silicon nano primary particles with a size ratio within an appropriate range are beneficial to alleviating the stress concentration problem of the silicon nano primary particles.
  • the conductive layer includes a conductive ceramic material, and the conductive ceramic material includes at least one of a metal oxide, a transition metal nitride, and a sulfide.
  • the conductive material includes an oxygen-containing organic compound of a transition metal
  • the oxygen-containing organic compound of a transition metal includes at least one of titanium tetramethoxide, vanadium acetate, tetrabutyl titanate, and niobium oxalate.
  • a metal oxide may be formed on the surface of the silicon nano primary particles by an atomic layer deposition process, and the metal oxide includes at least one of V2O5 , TiO2 , Nb2O5 , CdO, CsO, MoO3 , WO3 , BaO , SnO2 , Cr2O3 , MnO, Ag2O , CoO, NiO, Cu2O , and SnO.
  • the conductive material includes a transition metal nitrogen-containing organic compound
  • the transition metal nitrogen-containing organic compound includes at least one of ammonium metavanadate, ammonium titanate, ammonium cobaltate, ammonium trioxalatoferrate, tetraethylammonium tetrachlorocobaltate, and ammonium tungstate.
  • a transition metal nitride can be formed on the surface of the silicon nano primary particle by an atomic layer deposition process, and the transition metal nitride includes at least one of VN, TiN, CoN, Fe3N , Co4N , and WN.
  • the conductive material includes organic matter of transition metal and sulfur-containing gas
  • the sulfur-containing gas includes at least one of gaseous sulfur vapor, hydrogen sulfide and sulfur dioxide.
  • Sulfide can be formed on the surface of silicon nano primary particles by atomic layer deposition process, the sulfide includes at least one of CdS, Ag2S , Sb2S3 , TiS2 , Li2S .
  • Step S20 assembling silicon nano primary particles into secondary particles to obtain negative electrode materials.
  • the silicon nano primary particles can be assembled into secondary particles by self-assembly, melt assembly, electrostatic adsorption or spray granulation coating, etc., which is not limited here.
  • the step of assembling silicon nano primary particles to form secondary particles comprises: mixing a first solution containing silicon nano primary particles and anionic surfactants with a second solution containing silicon nano primary particles and cationic surfactants, and obtaining secondary particles after solid-liquid separation.
  • the anionic surfactant includes at least one of cetyltrimethylammonium bromide, sodium cetyl sulfate, polyvinylpyrrolidone, and sodium polystyrene sulfonate.
  • the cationic surfactant includes at least one of polydiallyldimethylammonium chloride, aminopropyltriethoxysilane, and a silane coupling agent.
  • the mass ratio of the anionic surfactant to the silicon nano primary particles is (0.05-5):1, specifically 0.05:1, 0.08:1, 1:1, 1.5:1, 2:1, 3:1, 4:1 or 5:1, etc., which is not limited here.
  • the mass ratio of the cationic surfactant to the silicon nano primary particles is (0.05-10):1, specifically 0.05:1, 0.08:1, 1:1, 1.5:1, 2:1, 3:1, 4:1, 5:1, 8:1, 9:1 or 10:1, etc., which is not limited here.
  • the first solution and/or the second solution includes a solvent
  • the solvent may be a polar solvent
  • the solvent includes at least one of water, anhydrous ethanol, methanol, and isopropanol.
  • the mass ratio of silicon nano primary particles in the first solution to silicon nano primary particles in the second solution is 1:(0.5-1.5), specifically 1:0.5, 1:0.8, 1:0.9, 1:1, 1:1.2, 1:1.3 or 1:1.5, which is not limited here.
  • the solid content in the first solution is 2% to 50%, specifically 2%, 5%, 8%, 10%, 15%, 18%, 20%, 25%, 30%, 40%, 45%, 49% or 50%, etc., which is not limited here.
  • the solid content of the second solution is 0.5% to 25%, specifically 0.5%, 0.8%, 1%, 5%, 8%, 9%, 10%, 12%, 13%, 15%, 18%, 20%, 24% or 25%, etc., are not limited here.
  • the solid content of the mixed slurry is 5% to 60%, specifically 5%, 8%, 10%, 15%, 18%, 20%, 25%, 30%, 40%, 45%, 50%, 54%, 59% or 60%, etc., which is not limited here.
  • the step of assembling silicon nano primary particles to form secondary particles comprises: spraying and granulating a mixed slurry containing silicon nano primary particles and anionic surfactants or cationic surfactants to obtain secondary particles.
  • the step of assembling silicon nano primary particles to form secondary particles further includes: dispersing and centrifuging the mixed slurry, wherein the dispersing method includes at least one of mechanical stirring and ultrasonic dispersion.
  • the mixed slurry further includes a solvent, and the solvent is selected from at least one of water, anhydrous ethanol, methanol and isopropanol.
  • the drying temperature of the spray granulation is 100°C to 200°C, and can be specifically 100°C, 120°C, 130°C, 140°C, 150°C, 160°C, 180°C or 200°C, which is not limited herein.
  • the feed rate of spray granulation is 100 mL/min to 1000 mL/min, specifically 100 mL/min, 200 mL/min, 300 mL/min, 400 mL/min, 600 mL/min, 800 mL/min or 1000 mL/min, etc., which is not limited here.
  • the average particle size of the secondary particles is Dm nm, 500 ⁇ Dm ⁇ 25000; specifically, it can be 500nm, 1000nm, 1500nm, 2000nm, 3000nm, 5000nm, 8000nm, 10000nm, 15000nm, 20000nm, 23000nm or 25000nm, etc., which is not limited here.
  • the specific value of B can be 5, 10, 20, 50, 80, 100, 150, 200, 300, 350 or 400, etc. Of course, it can also be other values within the above range, which are not limited here. Controlling the stacking degree of the secondary particles can ensure the structural stability of the secondary particles, which is conducive to the formation of a stable SEI film, reducing the expansion rate of the negative electrode material, and improving the first efficiency and cycle performance of the negative electrode material.
  • the size of the silicon nano primary particles is too small, which will lead to an increase in the specific surface area of the secondary particles, and the specific surface area of the negative electrode material is also increased.
  • the side reactions increase, and the consumption of active lithium ions increases, resulting in a decrease in the first coulombic efficiency of the negative electrode material.
  • the stacking degree of the secondary particles is too small, under the same secondary particle size, the size of the silicon nano primary particles is too large, and the expansion stress of the secondary particles is more concentrated, which is easy to cause the secondary particles to crack and pulverize, which is not conducive to improving the negative electrode material
  • the structural stability of the negative electrode material decreases, and the cycle stability of the battery prepared by the negative electrode material decreases.
  • the method further includes: forming a coating layer on the surface of the secondary particles, wherein the coating layer includes at least one of an amorphous carbon material, a graphitized carbon material, and a polymer.
  • the step of forming a coating layer on the surface of the secondary particles comprises: spray-drying a mixed coating liquid comprising the secondary particles and a polymer, so that a coating layer is formed on the surface of the secondary particles, wherein the coating layer comprises a polymer.
  • the solid content of the secondary particles in the mixed coating liquid is 5% to 50%, specifically 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45% or 50%, etc., which is not limited here.
  • the mixed coating fluid includes a polar solvent.
  • the polar solvent includes at least one of water, anhydrous ethanol, methanol, and isopropanol.
  • the mass ratio of the secondary particles to the polymer is 10:(0.1-5), specifically 10:0.1, 10:1, 10:2, 10:3, 10:4 or 10:5, which is not limited here.
  • the drying temperature of spray drying is 60°C to 200°C, specifically 60°C, 80°C, 100°C, 120°C, 150°C, 180°C or 200°C.
  • the polymer includes at least one of a diblock copolymer, a triblock copolymer, and a multiblock copolymer.
  • the polymer includes at least one of polyacrylic acid, polyacrylonitrile, polyimide, polyurethane, polydopamine, xanthan gum, polypyrrole, polythiophene, polyphenylene vinylene, polyaniline, polyacetylene, and tannic acid.
  • the step of forming a coating layer on the surface of the secondary particles includes: introducing a second gas-phase carbon source into the secondary particles, heating the second gas-phase carbon source until a thermal cracking reaction occurs, so that the surface of the secondary particles is deposited to form a coating layer, and the coating layer includes at least one of an amorphous carbon material and a graphitized carbon material.
  • the second gas-phase carbon source includes at least one of acetylene, methane, toluene, cyclohexane, ethanol, ethylene, and propylene.
  • the heating rate of the thermal cracking reaction is 1°C/min to 20°C/min, for example, 1°C/min, 3°C/min, 5°C/min, 8°C/min, 10°C/min, 15°C/min or 20°C/min, without limitation herein.
  • the temperature of the thermal cracking reaction is 600°C to 1000°C, specifically, the reaction temperature can be 600°C, 650°C, 700°C, 750°C, 800°C, 890°C, 900°C, 960°C or 1000°C.
  • the reaction temperature is 700°C to 900°C.
  • the insulation time of the thermal cracking reaction is 1 h to 48 h; specifically, it can be 1 h, 4 h, 8 h, 12 h, 16 h, 24 h, 28 h, 32 h, 38 h or 48 h, which is not limited here.
  • the concentration of the second gas-phase carbon source is 0.1 L/min to 10 L/min; specifically, it can be 0.1 L/min, 0.4 L/min, 0.6 L/min, 0.8 L/min, 1.0 L/min, 2 L/min, 5 L/min, 6 L/min, 8 L/min, 9 L/min or 10 L/min, etc., which is not limited here.
  • the protective atmosphere includes at least one of helium, neon, argon, krypton, and xenon.
  • the present application also provides a battery using the negative electrode material provided in the above embodiment of the present application or using The negative electrode material is prepared by the preparation method of the negative electrode material provided in the above embodiment of the present application.
  • the battery provided in the embodiment of the present application has the advantages of high capacity, high initial efficiency, long cycle life, excellent rate performance and low expansion.
  • the battery can be a lithium ion battery, a sodium ion battery, a solid electrolyte battery, etc., which is not limited here.
  • the chemical vapor deposition furnace is pumped down to 0.5 Torr, it is heated to 600°C at a heating rate of 3°C/min, and silane gas is introduced at a rate of 0.5 L/min.
  • the vapor deposition pressure of the entire deposition furnace is controlled at 300 Torr, the deposition duration is 2 h, and silicon nano primary particles are collected after cooling.
  • the silicon nano primary particles are placed in a rotary atmosphere furnace, and under the protection of an argon atmosphere, heated to 950°C at a heating rate of 3°C/min, and then 0.5 L/min of acetylene gas is introduced so that the volume ratio of argon to acetylene in the rotary atmosphere furnace is 9:1.
  • the precursor is obtained by cooling, wherein the precursor includes the silicon nano primary particles and a carbon layer located on the surface thereof.
  • the negative electrode material prepared in this embodiment includes secondary particles and a coating layer located on at least part of the surface of the secondary particles, and the coating layer is a polymer layer; the secondary particles include silicon nano primary particles and a conductive layer located on at least part of the surface of the silicon nano primary particles, and the conductive layer is an amorphous carbon layer, and the silicon nano primary particles include multiple silicon grains.
  • FIG5 is a scanning electron microscope image of the negative electrode material prepared in this embodiment 1;
  • FIG6 is an XRD diagram of the negative electrode material prepared in this embodiment 1;
  • FIG7 is a cycle performance curve of the negative electrode material prepared in this embodiment 1, with a charge and discharge current of 1000 mA/g.
  • the surface of the prepared negative electrode material has a spherical structure and is wrapped with a dense coating layer on the surface.
  • the material has excellent cycle performance. After 100 cycles at a current of 0.25C, the capacity still remains at 1255 mAh/g, with a capacity retention rate of 75%.
  • the negative electrode material prepared in this embodiment includes secondary particles and a coating layer located on at least part of the surface of the secondary particles, and the coating layer is an amorphous carbon layer; the secondary particles include silicon nano primary particles and a conductive layer located on at least part of the surface of the silicon nano primary particles, and the conductive layer is an amorphous carbon layer, and the silicon nano primary particles include multiple silicon grains.
  • Embodiment 3 is a diagrammatic representation of Embodiment 3
  • the negative electrode material prepared in this embodiment includes secondary particles and a coating layer located on at least part of the surface of the secondary particles, wherein the coating layer is an amorphous carbon layer; the secondary particles include silicon nano primary particles and a conductive layer located on at least part of the surface of the silicon nano primary particles, wherein the conductive layer is a titanium oxide layer; the silicon nano primary particles include a plurality of silicon crystals. grain.
  • a silicon substrate coated with a thin layer of metal copper was placed in a chemical vapor deposition furnace chamber. After the chemical vapor deposition furnace was evacuated to 0.5 Torr, it was heated to 1000°C at a heating rate of 20°C/min, and silane gas was introduced at 0.5 L/min. The pressure of the entire deposition furnace was controlled at 100 Torr for 2 hours. After cooling, silicon nanoparticles were collected.
  • the negative electrode material prepared in this embodiment includes secondary particles and a coating layer located on at least part of the surface of the secondary particles, and the coating layer is an amorphous carbon layer; the secondary particles include silicon nano primary particles and a conductive layer located on at least part of the surface of the silicon nano primary particles, and the conductive layer is a titanium oxide layer, and the silicon nano primary particles are single crystal silicon particles.
  • a silicon substrate coated with a thin layer of metal copper was placed in a chemical vapor deposition furnace chamber. After the chemical vapor deposition furnace was evacuated to 0.5 Torr, it was heated to 1000°C at a heating rate of 20°C/min, and silane gas was introduced at 0.5 L/min. The pressure of the entire deposition furnace was controlled at 100 Torr for 2 hours. After cooling, silicon nanoparticles were collected.
  • the negative electrode material prepared in this embodiment includes secondary particles and a coating layer located on at least a portion of the surface of the secondary particles, and the coating layer is an amorphous carbon layer; the secondary particles include silicon nano primary particles and a conductive layer located on at least a portion of the surface of the silicon nano primary particles, and the conductive layer is a graphitized carbon layer, and the silicon nano primary particles are single crystal silicon particles.
  • the silicon nano primary particles are placed in a rotary atmosphere furnace, and under the protection of an argon atmosphere, heated to 1050° C. at a heating rate of 3° C./min, and then 0.1 L/min of methane gas is introduced so that the volume ratio of argon to methane in the rotary atmosphere furnace is 9:1.
  • the precursor is cooled to obtain the precursor, which includes the silicon nano primary particles and a graphene carbon layer located on the surface thereof, and the number of graphene layers is 5.
  • the chemical vapor deposition furnace is pumped down to 0.5 Torr, it is heated to 600°C at a heating rate of 3°C/min, and silane gas is introduced at a rate of 0.5 L/min.
  • the vapor deposition pressure of the entire deposition furnace is controlled at 300 Torr, the deposition duration is 2 h, and silicon nano primary particles are collected after cooling.
  • the negative electrode material prepared in this embodiment includes secondary particles, wherein the secondary particles include silicon nano primary particles, and the silicon nano primary particles include a plurality of silicon crystal grains.
  • the negative electrode material prepared in this embodiment includes secondary particles and a coating layer located on at least part of the surface of the secondary particles, and the coating layer is an amorphous carbon layer; the secondary particles include silicon nano primary particles and a conductive layer located on at least part of the surface of the silicon nano primary particles, and the conductive layer is a titanium oxide layer, and the silicon nano primary particles include multiple silicon grains.
  • the negative electrode material prepared in this embodiment includes secondary particles and a coating layer located on at least part of the surface of the secondary particles, and the coating layer is an amorphous carbon layer; the secondary particles include silicon nano primary particles and a conductive layer located on at least part of the surface of the silicon nano primary particles, and the conductive layer is a titanium oxide layer, and the silicon nano primary particles include multiple silicon grains.
  • reaction product was dissolved in a 1 mol/L dilute hydrochloric acid solution and stirred for 3 h, then filtered and dried to obtain micron silicon secondary particles.
  • the negative electrode material prepared in this embodiment includes secondary particles and a coating layer located on at least a portion of the surface of the secondary particles, wherein the coating layer is an amorphous carbon layer; the secondary particles include silicon nano primary particles.
  • the equipment used is the TriStar3000&3020 fully automatic specific surface area and pore size analyzer from Micromeritics Inc. of the United States, which complies with the national standard GB/T 19587-2017. Under constant temperature and low temperature, the adsorption amount of gas on the solid surface at different relative pressures is measured, and then the monolayer adsorption amount of the sample is obtained based on the Brownauer-Etter-Taylor adsorption theory and its formula (BET formula), thereby calculating the specific surface area of the material.
  • BET formula Brownauer-Etter-Taylor adsorption theory and its formula
  • the tap density of powders was tested using the DAT-6-220 powder tap density instrument produced by Quantachrome Inc. of the United States. According to the national standard GB/T 5162-2006/ISO 3953:1993, a certain amount of sample was weighed and the tap density was tested at a rate of 300 times/min and 3000 vibrations.
  • the oxygen content was measured by Nicolet Is10 Fourier infrared spectrometer from Thermo Fisher Company of the United States, and the carbon layer content was tested by thermogravimetric analysis.
  • the scanning electron microscopy characterization was carried out on a S4800 field emission electron microscope of Hitachi Company, Japan, with an operating voltage of 200 kV, to observe the structure of the negative electrode material and to scale the thickness of the coating layer.
  • the average particle size was measured using an E3500 ion mill and an S4800 field emission electron microscope from Hitachi, Japan.
  • the XRD spectrum of the sample was measured by TD-3600 X-ray diffractometer of Tongda Company in Dandong, China.
  • the half-maximum width of the diffraction peak of the sample and the corresponding Bragg angle were obtained by jade software.
  • the materials were processed using an E3500 ion mill and an S4800 field emission electron microscope from Hitachi, Japan.
  • the cross-sections were processed and the layer thickness of the particle modification layer and the protective layer were measured in SEM.
  • D50 was measured using a laser particle size analyzer, and it had a symmetrical distribution similar to a normal distribution. In its volume reference distribution, the cumulative 50% diameter is D50, and by analogy, the cumulative 90% diameter is D90, and the cumulative 10% diameter is D10.
  • the negative electrode materials prepared in Examples 1 to 13 have sample numbers corresponding to S1 to S13; the performance parameters of the negative electrode materials are shown in Table 1:
  • the negative electrode material was mixed with sodium carboxymethyl cellulose, styrene-butadiene rubber, conductive graphite (KS-6) and carbon black (SP) in a ratio of 92:2:2:2:2 to prepare a slurry, which was evenly coated on copper foil and dried to form a negative electrode sheet.
  • the button cell was assembled in the kit, the diaphragm used was a polypropylene microporous membrane, the electrolyte used was 1 mol/L lithium hexafluorophosphate (the solvent was a mixture of ethylene carbonate, ethyl methyl carbonate and dimethyl carbonate), and the counter electrode used was a metal lithium sheet.
  • the above 13 groups of batteries were tested for discharge specific capacity on a Blue Power CT2001A battery testing system.
  • the ratio of the amount of electricity discharged in one hour to the battery capacity is the discharge specific capacity.
  • the above 13 groups of batteries were subjected to the first coulombic efficiency test on the Blue Power CT2001A battery testing system, with the charge and discharge current being 0.05C, and the first coulombic efficiency was measured.
  • the above 13 groups of batteries were cycled for 100 cycles on a Blue Power CT2001A battery testing system with a charge and discharge current of 0.2C. After 100 cycles, the battery capacity and capacity retention rate after the cycle were calculated.
  • the negative electrode materials prepared in Examples 1 to 9 can reduce the stress concentration generated during the lithiation process of the silicon nano primary particles and improve the structural stability of the silicon nano primary particles by controlling the size relationship between the silicon nano primary particles and the silicon grains. Controlling the size relationship between the secondary particles and the silicon nano primary particles can improve the structural stability of the negative electrode material during the lithiation process, reduce the expansion rate of the material, and facilitate the formation of a stable solid electrolyte film on the surface of the negative electrode material.
  • the negative electrode material is synergistically modified using the conductive layer and the coating layer, and the conductivity of the conductive layer is utilized to
  • the mitigating effect on the volume expansion of silicon nano primary particles ensures that the negative electrode material still has excellent electrical contact performance after lithium insertion.
  • it can effectively reduce the side reactions between silicon nano primary particles and the electrolyte, while enhancing the structural stability of the negative electrode material, so that the battery prepared with the negative electrode material has low expansion, high cycle stability, high rate capability and first coulombic efficiency.
  • Example 10 since there is no conductive layer on the surface of the primary particles of the negative electrode material and no coating layer on the surface of the secondary particles, although the first coulombic efficiency of the negative electrode material is comparable to that of Example 1, its cycle capacity retention rate and the capacity after 200 cycles are lower than those of Example 1. This is because the lack of protection of the coating layer increases the side reactions between the electrolyte and the negative electrode material, aggravates the volume expansion of the negative electrode material, and significantly reduces the electrochemical performance.
  • the stacking degree B of the secondary particles is too large, indicating that the size of the silicon nano primary particles is relatively small, which will lead to an increase in the specific surface area of the secondary particles and the specific surface area of the negative electrode material.
  • the side reactions between the negative electrode material and the electrolyte increase, and the consumption of active lithium ions increases, resulting in a decrease in the first coulombic efficiency of the battery prepared with the negative electrode material.
  • the crystal attitude A of the silicon nano primary particles is too large, indicating that the size of the silicon grains is too small. Electrochemical sintering is easily caused on the surface of the silicon nano primary particles. After sintering, the silicon grains grow. After the negative electrode material is embedded with lithium, the local stress of the silicon nano primary particles becomes larger, and the instability of the entire structure is enhanced, resulting in a decrease in the cycle performance and capacity of the negative electrode material, and a deterioration in the electrochemical performance of the negative electrode material.
  • the stacking degree B of the secondary particles is too small, the size of the silicon nano primary particles is too large, and the expansion stress of the secondary particles is more concentrated, which easily leads to the cracking and pulverization of the secondary particles, which is not conducive to improving the structural stability of the negative electrode material and reduces the cycle stability of the battery prepared with the negative electrode material.
  • the present application uses the above-mentioned embodiments to illustrate the detailed process equipment and process flow of the present application, but the present application is not limited to the above-mentioned detailed process equipment and process flow, that is, it does not mean that the present application must rely on the above-mentioned detailed process equipment and process flow to be implemented.
  • the technicians in the relevant technical field should understand that any improvement to the present application, the equivalent replacement of the raw materials of the product of the present application, the addition of auxiliary components, the selection of specific methods, etc., all fall within the scope of protection and disclosure of the present application.

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Abstract

一种负极材料及电池，负极材料包括二次颗粒，二次颗粒包括硅纳米一次颗粒；硅纳米一次颗粒包括至少一个硅晶粒，硅晶粒的平均粒径为D s nm，硅纳米一次颗粒的平均粒径为D n nm；硅纳米一次颗粒的晶态度为A，A＝D n/D s，且1≤A≤200。通过探索硅纳米一次颗粒的尺寸与硅晶粒的尺寸关系，可以减弱硅纳米一次颗粒脱嵌锂产生的应力集中问题，进而提高负极材料的结构稳定性，降低负极材料的膨胀率，从而提升负极材料的电化学性能及循环性能。

Description

负极材料及电池
本申请要求于2023年8月31日提交中国国家知识产权局，申请号为202311125354.4、发明名称为“负极材料及其制备方法、电池”的中国专利申请的优先权，其全部内容通过引用结合在本申请中。
技术领域
本申请涉及负极材料技术领域，具体地讲，尤其涉及负极材料及电池。
背景技术
锂离子电池由于具备能量密度大、输出功率高、循环寿命长和环境污染小等优点而被广泛应用于电动汽车以及消费类电子产品中。
为了提高电池能量密度，硅负极材料的研究和开发日趋成熟。但是硅负极材料脱嵌锂过程中体积膨胀较大(>300％)，硅负极材料在充放电过程中会粉化从集流体上掉落，使得活性物质与集流体之间失掉电触摸，导致电化学性能变差，容量衰减、循环稳定性下降，难以得到商业应用。为了提高硅负极材料的导电性和循环稳定性，可以采用碳包覆，现有的碳包覆制备方法步骤复杂，且单纯的碳包覆无法有效提升硅碳负极的电化学性能。
基于此，亟需开发一种具有长循环、低膨胀性能的硅碳负极材料。
申请内容
本申请提出了一种负极材料及电池，使得负极材料具有优异的循环稳定性及较好的膨胀性能。
第一方面，本申请提供一种负极材料，所述负极材料包括二次颗粒，所述二次颗粒包括硅纳米一次颗粒；
所述硅纳米一次颗粒包括至少一个硅晶粒，所述硅晶粒的平均粒径为Ds nm，硅纳米一次颗粒的平均粒径为Dn nm；
所述硅纳米一次颗粒的晶态度为A，A＝Dn/Ds，且1≤A≤200。
本申请的技术方案至少具有以下有益的效果：
本申请提供的负极材料，通过探索硅纳米一次颗粒的尺寸与硅晶粒的尺寸关系，相同硅纳米一次颗粒尺寸下，控制硅纳米一次颗粒的晶态度，可以更好地减弱硅纳米一次颗粒在脱嵌锂过程中产生的应力集中问题，有利于应力均匀释放，保障硅纳米一次颗粒的结构稳定性，减少颗粒粉化。相同一次颗粒尺寸下，当硅纳米一次颗粒的晶态度A过大时，说明硅晶粒的尺寸过小。硅晶粒的尺寸过小在锂化过程硅晶粒之间的晶界会逐渐消失，最后形成大尺寸晶粒，即电化学烧结。电化学烧结后的硅晶粒之间的晶界消失，硅晶粒长大，负极材料嵌锂后会导致硅纳米一次颗粒的局部应力变大，负极材料的结构不稳定性增强，导致负极材料的循环性能下降以及容量降低。
附图说明
图1为本实施例提供的负极材料的结构示意图；
图2a及图2b分别为本实施例提供的负极材料中的硅纳米一次颗粒的结构示意图；
图3a及图3b分别为本实施例提供的负极材料中的硅纳米一次颗粒的另一结构示意图；
图4为本实施例提供的负极材料的制备方法的示意图；
图5为实施例1提供的负极材料的扫描电镜图片；
图6为实施例1提供的负极材料的XRD图；
图7为实施例1提供的负极材料的循环性能曲线图。
具体实施方式
为了更好的理解本申请的技术方案，下面结合附图对本申请实施例进行详细描述。
应当明确，所描述的实施例仅仅是本申请一部分实施例，而不是全部的实施例。基于本申请中的实施例，本领域普通技术人员在没有作出创造性劳动前提下所获得的所有其它实施例，都属于本申请保护的范围。
在本申请实施例中使用的术语是仅仅出于描述特定实施例的目的，而非旨在限制本申请。在本申请实施例和所附权利要求书中所使用的单数形式的“一种”、“所述”和“该”也旨在包括多数形式，除非上下文清楚地表示其它含义。
应当理解，本文中使用的术语“和/或”仅仅是一种描述关联对象的关联关系，表示可以存在三种关系，例如，A和/或B，可以表示：单独存在A，同时存在A和B，单独存在B这三种情况。另外，本文中字符“/”，一般表示前后关联对象是一种“或”的关系。
目前，在锂离子电池中，负极材料是影响其充放电性能的关键材料之一，为了提高电池能量密度，高容量的负极材料的研究和开发日趋成熟。然而这些负极材料与锂合金化过程体积膨胀较大，负极材料在充放电过程中会粉化从集流体上掉落，使得负极材料与集流体之间失去电触摸，导致负极材料制备的电池的电化学性能变差，容量衰减、循环稳定性下降，难以得到商业应用。
硅材料在脱嵌锂过程中会出现宏观结构的变化，这些转变与硅材料的晶粒尺寸、硅颗粒大小以及构建的二次颗粒尺寸的大小都有着密切的关联。目前硅晶粒、硅一次颗粒以及二次颗粒的尺寸比例没有合适的平衡点，导致含硅负极材料在脱嵌锂过程中，应力集中，容易出现负极材料颗粒的破裂，负极材料的结构稳定性差。
第一方面，本申请提供了一种负极材料，如图1所示，负极材料包括二次颗粒12，二次颗粒12包括硅纳米一次颗粒11。
如图2a及图2b所示，硅纳米一次颗粒11包括至少一个硅晶粒112，硅晶粒112的平均粒径为Ds nm，硅纳米一次颗粒11的平均粒径为Dn nm；硅纳米一次颗粒11的晶态度为A，A＝Dn/Ds，且1≤A≤200。
在上述方案中，通过探索硅纳米一次颗粒11的尺寸与硅晶粒12的尺寸关系，相同硅纳米一次颗粒尺寸下，控制硅纳米一次颗粒11的晶态度A，可以更好地减弱 硅纳米一次颗粒11在脱嵌锂过程中产生的应力集中问题，有利于纳米一次颗粒的应力均匀释放，保障硅纳米一次颗粒11的结构稳定性，减少颗粒粉化。相同硅纳米一次颗粒尺寸下，当硅纳米一次颗粒11的晶态度A过大时，说明硅晶粒12的尺寸过小。硅晶粒12的尺寸过小在锂化过程硅晶粒之间的晶界会逐渐消失，最后形成大尺寸晶粒，即电化学烧结。电化学烧结后的硅晶粒之间的晶界消失，硅晶粒长大，负极材料嵌锂后会导致硅纳米一次颗粒11的局部应力变大，负极材料的结构不稳定性增强，导致负极材料的循环性能以及容量降低。目前研究发现，硅晶粒尺寸小于10nm，会出现明显电化学烧结，必须控制充电电流才可以减弱烧结程度，或者硅晶粒或者硅颗粒用碳隔离开。
在一些实施方式中，硅纳米一次颗粒11的平均粒径为Dn nm，1≤Dn≤200；具体可以是1nm、5nm、10nm、15nm、20nm、30nm、40nm、50nm、80nm、100nm、120nm、150nm、180nm、190nm或200nm等，在此不做限定。
在一些实施方式中，硅晶粒112的平均粒径为Ds nm，1≤Ds≤100，具体可以是1nm、5nm、10nm、15nm、20nm、30nm、40nm、50nm、60nm、70nm、80nm、90nm或100nm等，在此不做限定。
在一些实施方式中，硅纳米一次颗粒11的晶态度为A，A＝Dn/Ds，且1≤A≤200，A的取值范围具体可以是1、5、10、15、20、30、40、50、80、100、120、150、180或200等，当然也可以是上述范围内的其他值，在此不做限定。
在一些实施方式中，如图3a及图3b所示，硅纳米一次颗粒11的晶态度A＝1，硅纳米一次颗粒为单晶硅。二次颗粒12包括多个单晶硅一次颗粒11a。
在一些实施方式中，硅纳米一次颗粒的晶态度1＜A≤200，硅纳米一次颗粒包括硅晶粒，硅晶粒包括多晶硅。
在一些实施方式中，如图1所示，负极材料包括二次颗粒12，二次颗粒12包括硅纳米一次颗粒11；硅纳米一次颗粒11的平均粒径为Dn nm，二次颗粒12的平均粒径为Dm nm；二次颗粒12的堆积度为B，B＝Dm/Dn，且5≤B≤400。
在上述方案中，通过探究二次颗粒与硅纳米一次颗粒的尺寸之间关系，相同硅一次颗粒尺寸下，降低堆积度B的值，可以降低负极材料的膨胀率，因为二次颗粒锂化后受到的压应力和拉应力是累计应力，堆积度越低，一次颗粒越少，累计应力越低，因此负极材料的膨胀率越小，这有利于负极材料表面形成稳定的固态电解质膜，从而提升负极材料的倍率性能以及循环稳定性。
在一些实施方式中，二次颗粒12的平均粒径为Dm nm，500≤Dm≤25000；具体可以是500nm、1000nm、1500nm、2000nm、3000nm、5000nm、8000nm、10000nm、15000nm、20000nm、23000nm或25000nm等，在此不做限定。
在一些实施方式中，二次颗粒12的堆积度为B，B＝Dm/Dn，且5≤B≤400，B的具体取值可以是5、10、20、50、80、100、150、200、300、350或400等，当然也可以是上述范围内的其他值，在此不做限定。控制二次颗粒12的堆积度，可以保证二次颗粒的结构稳定性，有利于形成稳定的SEI膜，降低整个负极材料的膨胀率，提高负极材料的首效和循环性能。当二次颗粒12的堆积度过大时，相同二次颗粒尺寸下，硅纳米一次颗粒11尺寸偏小，会导致二次颗粒12的比表面积增大，负极材 料的比表面积也增大，在脱嵌锂过程中，副反应增多，消耗的活性锂离子增多，导致负极材料的首次库伦效率下降。当二次颗粒12的堆积度过小时，相同二次颗粒尺寸下，硅纳米一次颗粒尺寸偏大，二次颗粒12的膨胀应力更加集中，容易导致二次颗粒崩裂、粉化，不利于提高负极材料的结构稳定性，负极材料制备的电池的循环稳定性下降。
在一些实施方式中，负极材料还包括位于硅纳米一次颗粒11至少部分表面的导电层111，导电层111包括非晶碳材料、石墨化碳材料和导电陶瓷材料中的至少一种。导电层111具有多孔结构，多孔结构有利于锂离子及电子的传输。并且，通过在硅纳米一次颗粒表面构建导电层111，导电层111可以提升硅纳米一次颗粒11的导电性，还能够有效缓解硅纳米一次颗粒11的体积膨胀。
在一些实施方式中，导电层111包括石墨化碳材料，石墨化碳材料为石墨烯，石墨烯的层数＜20，石墨烯的层数具体可以是1层、2层、3层、5层、8层、10层、12层、15层、18层或19层等，当然也可以是上述范围内的其他值，在此不做限定。
在一些实施方式中，导电层的厚度为1nm～200nm，具体可以是1nm、10nm、20nm、40nm、50nm、80nm、100nm、150nm、180nm或200nm等，在此不做限定。
在一些实施方式中，导电陶瓷材料包括金属氧化物、过渡金属氮化物、硫化物中的至少一种。
在一些实施方式中，金属氧化物包括V2O5、TiO2、Nb2O5、CdO、CsO、MoO3、WO3、BaO、SnO2、Cr2O3、MnO、Ag2O、CoO、NiO、Cu2O和SnO中的至少一种。
在一些实施方式中，过渡金属氮化物包括VN、TiN、CoN、Fe3N、Co4N和WN中的至少一种。
在一些实施方式中，硫化物包括CdS、Ag2S、Sb2S3、TiS2、Li2S中的至少一种。
在一些实施方式中，负极材料还包括位于二次颗粒12的至少部分表面的包覆层121，包覆层121包括非晶碳材料、石墨化碳材料、聚合物中的至少一种。
可以理解地，在二次颗粒的表面构建包覆层，包覆层可以进一步缓解负极材料的体积膨胀；采用导电层和包覆层对负极材料进行协同修饰，利用导电层111的导电性、对硅纳米一次颗粒的体积膨胀的缓解作用保证负极材料在嵌锂后仍具有优异的电接触性能，结合最外层的包覆层121可有效避免硅纳米一次颗粒与电解液的副反应，同时增强负极材料的结构稳定性。
在一些实施方式中，包覆层121包括聚合物，示例性地，聚合物可以是双嵌段共聚物、三嵌段共聚物和多嵌段共聚物中的至少一种。
在一些实施方式中，聚合物在负极材料中的质量含量为1％～20％；具体可以是1％、3％、4％、5％、6％、7％、10％、12％、15％、18％或20％等，在此不做限定。包覆层121的厚度为5nm～300nm，具体可以是5nm、50nm、80nm、100nm、150nm、200nm、250nm或300nm等，在此不做限定。
在一些实施方式中，聚合物包括聚丙烯酸、聚丙烯腈、聚酰亚胺、聚氨酯、聚多巴胺、黄原胶、聚吡咯、聚噻吩、聚苯乙炔、聚苯胺、聚乙炔和单宁酸中的至少一种。聚合物优选为聚吡咯、聚噻吩、聚苯胺、聚苯胺和聚乙炔中的至少一种。
在一些实施方式中，包覆层121包括石墨化碳材料，包覆层的厚度为5nm～100nm， 具体可以是5nm、10nm、30nm、50nm、70nm、80nm、90nm或100nm等，在此不做限定。
在一些实施方式中，包覆层121包括非晶碳材料，包覆层的厚度为10nm～500nm；具体可以是10nm、50nm、80nm、100nm、150nm、200nm、250nm、300nm、450nm或500nm等，在此不做限定。
在一些实施方式中，负极材料中碳元素的质量含量为5％～80％。具体可以是5％、8％、10％、15％、20％、30％、35％、40％、45％、50％、60％、70％或80％等，在此不做限定。需要说明的是，负极材料中的碳来源于碳材料。
在一些实施方式中，负极材料的粉体振实密度为0.3g/cm3～1.3g/cm3，具体可以是0.3g/cm3、0.5g/cm3、0.6g/cm3、0.7g/cm3、0.8g/cm3、1.0g/cm3、1.3g/cm3等。优选为0.5g/cm3～0.8g/cm3。
在一些实施方式中，负极材料的粉体压实密度为1.2g/cm3～1.8g/cm3，例如1.2g/cm3、1.3g/cm3、1.4g/cm3、1.5g/cm3、1.6g/cm3或1.8g/cm3等，优选为1.45g/cm3～1.75g/cm3。
在一些实施方式中，负极材料的中值粒径为0.5μm～25μm，可选地，负极材料的中值粒径具体可以是0.5μm、1μm、3μm、4μm、5μm、7μm、10μm、13μm、15μm、20μm或25μm等，在此不做限定。负极材料的中值粒径优选为0.5μm～10μm，更优选为1μm～5μm。
在一些实施方式中，负极材料的比表面积比为1m2/g～50m2/g。可选地，负极材料的比表面积比可以是1m2/g、5m2/g、8m2/g、10m2/g、15m2/g、20m2/g、25m2/g、30m2/g、35m2/g、40m2/g、45m2/g或50m2/g等，在此不做限定；可以理解地，比表面积越小越好，过大的比表面积容易导致SEI膜形成，消耗不可逆锂盐过多，降低电池的首次效率低，综合考虑制备工艺的成本，将比表面积控制在2m2/g～15m2/g。
在一些实施方式中，负极材料中氧元素的质量含量小于15％。具体可以是5％、6％、8％、10％、12％、13％、14％或15％等，在此不做限定。
本申请还提供一种负极材料的制备方法，如图4所示，所述方法包括以下步骤：
S10，制备硅纳米一次颗粒，硅纳米一次颗粒包括至少一个硅晶粒；硅晶粒的平均粒径为Ds nm，1≤Ds≤100，硅纳米一次颗粒的平均粒径为Dn nm，1≤Dn≤200；硅纳米一次颗粒的晶态度为A，A＝Dn/Ds，且1≤A≤200；
S20，将硅纳米一次颗粒组装形成二次颗粒，得到负极材料。
在本方案中，通过探索硅纳米一次颗粒的尺寸与硅晶粒的尺寸关系以及二次颗粒与硅纳米一次颗粒的尺寸之间的平衡关系，可以减弱硅纳米一次颗粒锂化过程中产生的应力集中，提高硅纳米一次颗粒在锂化过程中的结构稳定性，降低负极材料的膨胀率，有利于在负极材料表面形成稳定的固态电解质膜，使得负极材料兼具低膨胀、高循环稳定性、高倍率性以及高首次库伦效率。
本申请提供的负极材料的制备方法，不仅能改善材料的电化学性能，适合大规模生产，制备得到负极材料，能够有效提高锂电池的倍率性能及循环稳定性。
以下结合实施例具体介绍本申请的制备方法：
步骤S10，制备硅纳米一次颗粒，硅纳米一次颗粒包括至少一个硅晶粒；硅晶粒的平均粒径为Ds nm，1≤Ds≤100，硅纳米一次颗粒的平均粒径为Dn nm，1≤Dn≤200；硅纳米一次颗粒的晶态度为A，A＝Dn/Ds，且1≤A≤200。
在一些实施方式中，硅纳米一次颗粒的平均粒径为Dn nm，1≤Dn≤200；具体可以是1nm、5nm、10nm、15nm、20nm、30nm、40nm、50nm、80nm、100nm、120nm、150nm、180nm、190nm或200nm等，在此不做限定。
在一些实施方式中，硅晶粒的平均粒径为Ds nm，1≤Ds≤100，具体可以是1nm、5nm、10nm、15nm、20nm、30nm、40nm、50nm、60nm、70nm、80nm、90nm或100nm等，在此不做限定。
在一些实施方式中，硅纳米一次颗粒的晶态度为A，A＝Dn/Ds，且1≤A≤200，A的取值范围具体可以是1、5、10、15、20、30、40、50、80、100、120、150、180或200等，当然也可以是上述范围内的其他值，在此不做限定。
在一些实施方式中，制备硅纳米一次颗粒的步骤包括利用硅源气体进行气相沉积，得到硅纳米一次颗粒。
在一些实施方式中，硅源气体包括硅烷、乙硅烷、三氯硅烷、二氯硅烷、四氯化硅中的至少一种。
在一些实施方式中，气相沉积前的真空压力小于1.0Torr，具体可以是0.9Torr、0.8Torr、0.7Torr、0.6Torr、0.5Torr、0.4Torr、0.3Torr或0.1Torr等，在此不做限定。可以理解地，在进行化学气相沉积之前，可以将炉内的压力抽至真空状态，这样有利于提高硅纳米一次颗粒的纯净度。然后加热并通入适量的硅源气体作为硅纳米一次颗粒的生长原料，沉积一段时间，即可得到硅纳米一次颗粒。
在一些实施方式中，气相沉积时的加热速率为1℃/min～20℃/min。具体可以是1℃/min、3℃/min、5℃/min、8℃/min、10℃/min、15℃/min或20℃/min，在此不做限定。
在一些实施方式中，气相沉积时的温度为300℃～1000℃，具体可以是300℃、400℃、500℃、600℃、700℃、800℃或1000℃等，在此不做限定。
在一些实施方式中，气相沉积的温度为600℃～1000℃，具体可以是400℃、500℃、600℃、700℃、800℃或1000℃。
在一些实施方式中，硅源气体的流量为0.05L/min～10L/min，具体可以是0.05L/min、0.1L/min、0.5L/min、1L/min、2L/min、3L/min、5L/min、7L/min、8L/min或10L/min，在此不做限定。
在一些实施方式中，硅源气体的通气时间(即气相沉积的时间)为0.1h～10h，具体可以是0.1h、0.5h、1h、2h、4h、6h、8h或10h，在此不做限定。
在一些实施方式中，气相沉积时的压力为100Torr～500Torr，具体可以是100Torr、150Torr、200Torr、250Torr、300Torr、350Torr、400Torr、450Torr或500Torr等，在此不做限定。
在其他实施方式中，可以采用等离子体加热法制备硅纳米一次颗粒，并控制硅纳米一次颗粒与硅晶粒的尺寸比(晶态度A)在上述范围内即可。
进一步地，在步骤S20之前，方法还包括在硅纳米一次颗粒的表面形成导电层，导电层包括非晶碳材料、石墨化碳材料、导电陶瓷材料中的至少一种。
在一些实施方式中，在硅纳米一次颗粒的表面形成导电层的步骤包括：在保护气氛下，将第一气相碳源通过气相沉积方式沉积在硅纳米一次颗粒的表面形成导电层。
在一些实施方式中，第一气相碳源的浓度为0.1L/min～10L/min，具体可以是0.1L/min、1L/min、3L/min、5L/min、8L/min或10L/min，在此不作限定。
在一些实施方式中，气相沉积的保温时间为1h～48h，具体可以是1h、2h、4h、6h、8h、12h、18h、24h或48h，在此不做限定。
在一些实施方式中，气相沉积的温度为200℃～1050℃，具体可以是200℃、300℃、400℃、500℃、600℃、700℃、800℃、950℃或1050℃，在此不做限定。
在一些实施方式中，气相沉积的加热速率为1℃/min～30℃/min，具体可以是1℃/min、3℃/min、5℃/min、8℃/min、10℃/min、15℃/min、20℃/min、25℃/min或30℃/min，在此不作限定。
在一些实施方式中，保护气氛包括氦气、氖气、氩气、氪气及氙气中的至少一种。
在一些实施方式中，保护气氛与第一气相碳源的体积比为10：(0.5～10)，具体可以是10:0.5、10:1、10:2、10:3、10:4、10:5、10:7、10:8、10:9或10:10，在此不作限定。
在一些实施方式中，第一气相碳源包括乙炔、甲烷、甲苯、环已烷、乙醇、乙烯和丙烯中的至少一种。
在一些实施方式中，在硅纳米一次颗粒的表面形成导电层的步骤包括：以预设的脉冲频率通入导电材料，在硅纳米一次颗粒表面进行原子层沉积形成导电层。可以理解地，通过原子层沉积技术在硅纳米一次颗粒表面沉积形成导电层，有利于提高硅纳米一次颗粒的导电性，进而提升负极材料的导电性及倍率性能。
具体地，可以将硅纳米一次颗粒放入原子层沉积室中，抽真空后采用惰性气体置换，然后进行加热，并以一定的脉冲频率持续一定时间通入一种或多种的导电材料作为导电层的原料，通过控制导电材料的量在硅纳米一次颗粒的表面沉积出一层或者多层导电层。
在一些实施方式中，原子层沉积的温度为200℃～750℃，具体可以是200℃、300℃、400℃、450℃、500℃、550℃、600℃或750℃等，当然也可以是上述范围内的其他值，在此不做限定。
在一些实施方式中，原子层沉积的时间为1h～48h，具体可以是1h、2h、4h、6h、8h、12h、18h、24h或48h，在此不做限定。
在一些实施方式中，脉冲频率为40khz～500khz，具体可以是40khz、60khz、80khz、100khz、150khz、200khz、250khz、300khz、400khz或500khz等，在此不做限定。
在一些实施方式中，导电材料的脉冲时长为10ms～800ms，具体可以是10ms、50ms、100ms、200ms、300ms、400ms、500ms、600ms、700ms或800ms等，在此不做限定。
通过控制原子层沉积的各项参数，有利于形成硅纳米一次颗粒尺寸以及硅晶粒 尺寸的比值在合适范围内的硅纳米一次颗粒，有利于缓解硅纳米一次颗粒的应力集中问题。
在一些实施方式中，导电层包括导电陶瓷材料，导电陶瓷材料包括金属氧化物、过渡金属氮化物、硫化物中的至少一种。
在一些实施方式中，导电材料包括过渡金属的含氧有机物，过渡金属的含氧有机物包括四甲醇钛、醋酸钒、钛酸四丁酯和草酸铌中的至少一种。通过原子层沉积工艺可以在硅纳米一次颗粒表面形成金属氧化物，金属氧化物包括V2O5、TiO2、Nb2O5、CdO、CsO、MoO3、WO3、BaO、SnO2、Cr2O3、MnO、Ag2O、CoO、NiO、Cu2O和SnO中的至少一种。
在一些实施方式中，导电材料包括过渡金属的含氮有机物，过渡金属的含氮有机物包括偏钒酸铵、钛酸铵、钴酸铵、三草酸合铁酸铵、四氯钴酸四乙基铵和钨酸铵中的至少一种。通过原子层沉积工艺可以在硅纳米一次颗粒表面形成过渡金属氮化物，过渡金属氮化物包括VN、TiN、CoN、Fe3N、Co4N和WN中的至少一种。
在一些实施方式中，导电材料包括过渡金属的有机物与含硫气体，含硫气体包括气态硫蒸气，硫化氢和二氧化硫中的至少一种。通过原子层沉积工艺可以在硅纳米一次颗粒表面形成硫化物，硫化物包括CdS、Ag2S、Sb2S3、TiS2、Li2S中的至少一种。
步骤S20，将硅纳米一次颗粒组装形成二次颗粒，得到负极材料。
需要说明的是，硅纳米一次颗粒能够通过自组装、熔融组装、静电吸附或者喷雾造粒包覆等方式组装形成二次颗粒，在此不做限定。
在一些实施方式中，将硅纳米一次颗粒组装形成二次颗粒的步骤包括：将包含硅纳米一次颗粒与阴离子表面活性剂的第一溶液与包含硅纳米一次颗粒与阳离子表面活性剂的第二溶液进行混合，固液分离后得到二次颗粒。
在一些实施方式中，阴离子表面活性剂包括十六烷基三甲基溴化铵、十六烷基硫酸钠、聚乙烯吡咯烷酮和聚苯乙烯磺酸钠中的至少一种。
在一些实施方式中，阳离子表面活性剂包括聚二烯丙基二甲基氯化铵、氨丙基三乙氧基硅烷和硅烷偶联剂中的至少一种。
在一些实施方式中，阴离子表面活性剂与硅纳米一次颗粒的质量比为(0.05～5)：1，具体可以是0.05:1、0.08:1、1:1、1.5:1、2:1、3:1、4:1或5:1等，在此不作限定。
在一些实施方式中，阳离子表面活性剂与硅纳米一次颗粒的质量比为(0.05～10)：1，具体可以是0.05:1、0.08:1、1:1、1.5:1、2:1、3:1、4:1、5:1、8:1、9:1或10:1等，在此不做限定。
在一些实施方式中，第一溶液和/或第二溶液包括溶剂，溶剂可以是极性溶剂。具体地，溶剂包括水、无水乙醇、甲醇和异丙醇中的至少一种。
在一些实施方式中，第一溶液中的硅纳米一次颗粒与第二溶液中的硅纳米一次颗粒的质量比为1：(0.5～1.5)，具体可以是1:0.5、1:0.8、1:0.9、1:1、1:1.2、1:1.3或1:1.5，在此不做限定。
在一些实施方式中，第一溶液中的固含量为2％～50％，具体可以是2％、5％、8％、10％、15％、18％、20％、25％、30％、40％、45％、49％或50％等，在此不做限定。
在一些实施方式中，第二溶液中的固含量为0.5％～25％，具体可以是0.5％、0.8％、 1％、5％、8％、9％、10％、12％、13％、15％、18％、20％、24％或25％等，在此不做限定。
在一些实施方式中，混合浆料的固含量为5％～60％，具体可以是5％、8％、10％、15％、18％、20％、25％、30％、40％、45％、50％、54％、59％或60％等，在此不做限定。
在一些实施方式中，将硅纳米一次颗粒组装形成二次颗粒的步骤包括：将包含硅纳米一次颗粒、阴离子表面活性剂或阳离子表面活性剂的混合浆料进行喷雾造粒，得到二次颗粒。
需要说明的是，阳离子表面活性剂、阴离子表面活性剂的类型及含量如前述所示，在此不再赘述。
在一些实施方式中，将硅纳米一次颗粒组装形成二次颗粒的步骤还包括：对混合浆料进行分散、离心处理，分散的方式包括机械搅拌和超声分散中的至少一种。
在一些实施方式中，混合浆料还包括溶剂，溶剂选自水、无水乙醇、甲醇和异丙醇中的至少一种。
在一些实施方式中，喷雾造粒的干燥温度为100℃～200℃，具体可以是100℃、120℃、130℃、140℃、150℃、160℃、180℃或200℃，在此不作限定。
在一些实施方式中，喷雾造粒的进料速度为100mL/min～1000mL/min，具体可以是100mL/min、200mL/min、300mL/min、400mL/min、600mL/min、800mL/min或1000mL/min等，在此不做限定。
在一些实施方式中，二次颗粒包括硅纳米一次颗粒；硅纳米一次颗粒的平均粒径为Dn nm，二次颗粒的平均粒径为Dm nm；二次颗粒的堆积度为B，B＝Dm/Dn，且5≤B≤400。
在上述方案中，通过探究二次颗粒与硅纳米一次颗粒的尺寸之间关系，相同硅一次颗粒尺寸下，降低堆积度B的值，可以降低负极材料的膨胀率，因为二次颗粒锂化后收到的压应力和拉应力是累计应力，堆积度越低，一次颗粒越少，累计应力越低，因此负极材料的膨胀率越小，这有利于在负极材料的表面形成稳定的固态电解质膜，从而提升负极材料的倍率性能以及首次库伦效率。
在一些实施方式中，二次颗粒的平均粒径为Dm nm，500≤Dm≤25000；具体可以是500nm、1000nm、1500nm、2000nm、3000nm、5000nm、8000nm、10000nm、15000nm、20000nm、23000nm或25000nm等，在此不做限定。
在一些实施方式中，二次颗粒的堆积度为B，B＝Dm/Dn，且5≤B≤400，B的具体取值可以是5、10、20、50、80、100、150、200、300、350或400等，当然也可以是上述范围内的其他值，在此不做限定。控制二次颗粒的堆积度，可以保证二次颗粒的结构稳定性，有利于形成稳定的SEI膜，降低负极材料的膨胀率，提高负极材料的首效和循环性能。当二次颗粒的堆积度过大时，相同二次颗粒尺寸下，硅纳米一次颗粒尺寸偏小，会导致二次颗粒的比表面积增大，负极材料的比表面积也增大，在脱嵌锂过程中，副反应增多，消耗的活性锂离子增多，导致负极材料的首次库伦效率下降。当二次颗粒的堆积度过小时，相同二次颗粒尺寸下，硅纳米一次颗粒尺寸偏大，二次颗粒的膨胀应力更加集中，容易导致二次颗粒崩裂、粉化，不利于提高负极材料 的结构稳定性，负极材料制备的电池的循环稳定性下降。
在步骤S20之后，方法还包括：在二次颗粒的表面形成包覆层，包覆层包括非晶碳材料、石墨化碳材料、聚合物中的至少一种。
在一些实施方式中，在二次颗粒的表面形成包覆层的步骤包括：将包含二次颗粒与聚合物的混合包覆液进行喷雾干燥，使得二次颗粒的表面形成包覆层，包覆层包括聚合物。
在一些实施方式中，二次颗粒在混合包覆液中的固含量为5％～50％，具体可以是5％、10％、15％、20％、25％、30％、35％、40％、45％或50％等，在此不做限定。
在一些实施方式中，混合包覆液包括极性溶剂。
在一些实施方式中，极性溶剂包括水、无水乙醇、甲醇和异丙醇中的至少一种。
在一些实施方式中，二次颗粒与聚合物的质量比为10：(0.1～5)，具体可以是10:0.1、10:1、10:2、10:3、10:4或10:5，在此不做限定。
在一些实施方式中，喷雾干燥的干燥温度为60℃～200℃，具体可以是60℃、80℃、100℃、120℃、150℃、180℃或200℃。
在一些实施方式中，聚合物包括双嵌段共聚物、三嵌段共聚物和多嵌段共聚物中的至少一种。
在一些实施方式中，聚合物包括聚丙烯酸、聚丙烯腈、聚酰亚胺、聚氨酯、聚多巴胺、黄原胶、聚吡咯、聚噻吩、聚苯乙炔、聚苯胺、聚乙炔和单宁酸中的至少一种。
在一些实施方式中，在二次颗粒的表面形成包覆层的步骤包括：往二次颗粒中通入第二气相碳源，加热至第二气相碳源发生热裂解反应，使得二次颗粒的表面沉积形成包覆层，包覆层包括非晶碳材料和石墨化碳材料中的至少一种。
在一些实施方式中，第二气相碳源包括乙炔、甲烷、甲苯、环已烷、乙醇、乙烯和丙烯中的至少一种。
在一些实施方式中，热裂解反应的加热速率为1℃/min～20℃/min，例如可以是1℃/min、3℃/min、5℃/min、8℃/min、10℃/min、15℃/min或20℃/min，在此不作限定。
在一些实施方式中，热裂解反应的温度为600℃～1000℃，具体地，反应温度可以是600℃、650℃、700℃、750℃、800℃、890℃、900℃、960℃或1000℃。申请人通过多次试验发现，将反应温度控制在600℃～1000℃内，可以提高反应效率，使得二次颗粒表面形成均匀的碳层，碳层可以是无定型碳。优选地，反应温度为700℃～900℃。
在一些实施方式中，热裂解反应的保温时间为1h～48h；具体可以是1h、4h、8h、12h、16h、24h、28h、32h、38h或48h，在此不做限定。
在一些实施方式中，第二气相碳源的浓度为0.1L/min～10L/min；具体可以是0.1L/min、0.4L/min、0.6L/min、0.8L/min、1.0L/min、2L/min、5L/min、6L/min、8L/min、9L/min或10L/min等，在此不做限定。
在一些实施方式中，热裂解反应在保护气氛下进行。
在一些实施方式中，保护气氛包括氦气、氖气、氩气、氪气及氙气中的至少一种。
本申请实施例还提供了一种电池，采用本申请上述实施例提供的负极材料或采 用本申请上述实施例提供的负极材料的制备方法制得的负极材料。本申请实施例提供的电池具有高容量、高首效、长循环寿命、优异倍率性能以及低膨胀的优点。电池可以是锂离子电池、钠离子电池、固态电解质电池等等，在此不做限定。
下面分多个实施例对本申请实施例进行进一步的说明。其中，本申请实施例不限定于以下的具体实施例。在不变主权利的范围内，可以适当的进行变更实施。
实施例1
(1)将化学气相沉积炉抽到0.5Torr后，以3℃/min的升温速率加热到600℃后，通入0.5L/min的硅烷气体，控制整个沉积炉的气相沉积压力在300Torr，沉积持续时间为2h，冷却后收集硅纳米一次颗粒。
(2)将硅纳米一次颗粒放入旋转气氛炉中，在氩气气氛保护下，以3℃/min的升温速率加热到950℃后，通入0.5L/min的乙炔气体，使得旋转气氛炉中的氩气与乙炔的体积比为9:1，保温4h后冷却得到前驱体，所述前驱体包括硅纳米一次颗粒及位于其表面的碳层。
(3)将10g前驱体与十六烷基三甲基溴化铵按质量比10:2分散于200ml去离子水中后搅拌30分钟后超声10分钟，离心干燥后得到修饰后的前驱体A1。将10g前驱体与1g聚二烯丙基二甲基氯化铵溶于100ml去离子水中搅拌30分钟后超声20分钟，离心干燥后得到修饰后的前驱体B2。将10g修饰后的前驱体A1溶于100ml去离子水中搅拌10分钟得到溶液E，将10g修饰后的前驱体B2分散在100ml的去离子水中搅拌10分钟得到溶液F。将溶液E缓慢滴入溶液F中，并持续快速搅拌40分钟后，离心干燥得到复合物。
(4)取10g复合物溶于100g无水乙醇中，加入1g聚丙烯酸后，机械搅拌30分钟，通过喷雾干燥方式，控制干燥温度在100℃，使得复合材料表面包覆上聚合物，得到负极材料。
本实施例制得到的负极材料包括二次颗粒及位于所述二次颗粒至少部分表面的包覆层，包覆层为聚合物层；所述二次颗粒包括硅纳米一次颗粒及位于所述硅纳米一次颗粒至少部分表面的导电层，导电层为非晶碳层，硅纳米一次颗粒包括多个硅晶粒。
图5为本实施例1制得的负极材料的扫描电镜图片；图6为本实施例1制得的负极材料的XRD图；图7本实施例1制得的负极材料的循环性能曲线，充放电电流为1000mA/g。
从图5中的扫描电镜图片可以看出，制得的负极材料表面具有球状结构并在表面包裹一层致密的包覆层。
从图6的XRD图谱中可以看出在28.4°、47.3°和56.1°的三强峰与硅(JCPDSNo.27-1402)的三强峰相对应，基本无杂相，根据谢乐公式计算得出硅晶粒尺寸为5nm；
图7中可以看出材料具有优异的循环性能，在0.25C电流下循环100周还有1255mAh/g的容量，容量保持率75％。
本实施例中负极材料的参数详见表1。
实施例2
(1)将化学气相沉积炉抽到0.5Torr后，以3℃/min的升温速率加热到700℃后，通入1.5L/min的硅烷气体，控制整个沉积炉的压力在200Torr，沉积持续时间为2h，冷却后收集硅纳米一次颗粒。
(2)将硅纳米一次颗粒放入旋转气氛炉中，在氩气气氛保护下，以3℃/min的升温速率加热到950℃后，通入1.5L/min的乙炔气体，使得旋转气氛炉中的氩气与乙炔的体积比为9:1，保温3h后冷却得到前驱体，所述前驱体包括硅纳米一次颗粒及位于其表面的碳层。
(3)将10g前驱体溶于200ml无水乙醇中，加入2g聚乙烯吡咯烷酮后搅拌30分钟后超声10分钟得到混合浆料，将混合浆料采用喷雾造粒的方式在130℃的干燥条件下进行球形化得到复合物H。
(4)取100g复合物置于旋转气氛炉中，在氩气气氛保护下，以3℃/min的升温速率加热到900℃后，通入0.5L/min的甲烷气体，使得旋转气氛炉中的氩气与乙炔的体积比为9:1，保温6h后关闭乙炔气体，冷却得到负极材料。
本实施例制得到的负极材料包括二次颗粒及位于所述二次颗粒至少部分表面的包覆层，包覆层为非晶碳层；所述二次颗粒包括硅纳米一次颗粒及位于所述硅纳米一次颗粒至少部分表面的导电层，导电层为非晶碳层，硅纳米一次颗粒包括多个硅晶粒。
本实施例中负极材料的参数详见表1。
实施例3：
(1)将化学气相沉积炉抽到0.5Torr后，以3℃/min的升温速率加热到600℃后，通入0.5L/min的硅烷气体，控制整个沉积炉的压力在300Torr，持续时间为2h，冷却后收集硅纳米一次颗粒。
(2)将100g硅纳米一次颗粒放入原子层沉积设备处理腔室内，抽真空至0.5mbar后，加热温度到250℃，然后通过脉冲器以500Hz的频率将反应气态四甲醇钛作为导电材料打入处理腔室中，脉冲时间200ms，气态四甲醇钛流量为200sccm。最后关闭气态四甲醇钛，采用氩气置换仓内残余反应气体，冷却后得到前驱体，前驱体包括硅纳米一次颗粒及位于其表面的氧化钛层。
(3)将10g前驱体溶于300ml无水乙醇中，加入2g聚乙烯吡咯烷酮后搅拌30min后超声10min得到混合浆料，将混合浆料采用喷雾造粒的方式(进料速度为500mL/min)在150℃的干燥条件下进行球形化得到复合物。
(4)取100g复合物旋转气氛炉中，在氩气气氛保护下，以5℃/min的升温速率加热到950℃后，通入2.5L/min的乙炔气体，使得旋转气氛炉中的氩气与乙炔的体积比为8:2，保温6h后关闭乙炔气体，冷却得到负极材料。
本实施例制得到的负极材料包括二次颗粒及位于所述二次颗粒至少部分表面的包覆层，包覆层为非晶碳层；所述二次颗粒包括硅纳米一次颗粒及位于所述硅纳米一次颗粒至少部分表面的导电层，导电层为氧化钛层，硅纳米一次颗粒包括多个硅晶 粒。
本实施例中负极材料的参数详见表1。
实施例4
(1)将镀有金属铜薄层的硅衬底放入化学气相沉积炉腔体内，化学气相沉积炉抽到0.5Torr后，以20℃/min的升温速率加热到1000℃后，通入0.5L/min的硅烷气体，控制整个沉积炉的压力在100Torr，持续时间为2h，冷却后收集硅纳米一次颗粒。
(2)将100g硅纳米一次颗粒放入原子层沉积设备处理腔室内，抽真空至0.5mbar后，加热温度到250℃，然后通过脉冲器以500Hz的频率将气态四甲醇钛作为导电材料打入处理腔室中，脉冲时间200ms，气态四甲醇钛流量为200sccm。最后关闭气态四甲醇钛，采用氩气置换仓内残余反应气体，冷却后得到前驱体，前驱体包括硅纳米一次颗粒及位于其表面的氧化钛层。
(3)将10g前驱体溶于300ml无水乙醇中，加入2g聚乙烯吡咯烷酮后搅拌30min后超声10min得到混合浆料，将混合浆料采用喷雾造粒的方式(进料速度为300mL/min)在150℃的干燥条件下进行球形化得到复合物。
(4)取100g复合物旋转气氛炉中，在氩气气氛保护下，以5℃/min的升温速率加热到950℃后，通入2.5L/min的乙炔气体，使得旋转气氛炉中的氩气与乙炔的体积比为8:2，保温6h后关闭乙炔气体，冷却得到负极材料。
本实施例制得到的负极材料包括二次颗粒及位于所述二次颗粒至少部分表面的包覆层，包覆层为非晶碳层；所述二次颗粒包括硅纳米一次颗粒及位于所述硅纳米一次颗粒至少部分表面的导电层，导电层为氧化钛层，硅纳米一次颗粒为单晶硅颗粒。
本实施例中负极材料的参数详见表1。
实施例5
(1)将镀有金属铜薄层的硅衬底放入化学气相沉积炉腔体内，化学气相沉积炉抽到0.5Torr后，以20℃/min的升温速率加热到1000℃后，通入0.5L/min的硅烷气体，控制整个沉积炉的压力在100Torr，持续时间为2h，冷却后收集硅纳米一次颗粒。
(2)将100g硅纳米一次颗粒放入旋转气氛炉内，在氩气气氛保护下，以3℃/min的升温速率加热到1050℃后，通入0.5L/min的甲烷气体，使得旋转气氛炉中的氩气与乙炔的体积比为9:1，保温3h后冷却得到前驱体，前驱体包括硅纳米一次颗粒及位于其表面的石墨化碳层。
(3)将10g前驱体溶于300ml无水乙醇中，加入2g聚乙烯吡咯烷酮后搅拌30min后超声10min得到混合浆料，将混合浆料采用喷雾造粒的方式(进料速度为800mL/min)在150℃的干燥条件下进行球形化得到复合物。
(4)取100g复合物旋转气氛炉中，在氩气气氛保护下，以5℃/min的升温速率加热到950℃后，通入2.5L/min的乙炔气体，使得旋转气氛炉中的氩气与乙炔的体积比为8:2，保温6h后关闭乙炔气体，冷却得到负极材料。
本实施例制得到的负极材料包括二次颗粒及位于所述二次颗粒至少部分表面的包覆层，包覆层为非晶碳层；所述二次颗粒包括硅纳米一次颗粒及位于所述硅纳米一次颗粒至少部分表面的导电层，导电层为石墨化碳层，硅纳米一次颗粒为单晶硅颗粒。
本实施例中负极材料的参数详见表1。
实施例6
与实施例3不同的是：
(2)将100g硅纳米一次颗粒放入原子层沉积设备处理腔室内，抽真空至0.5mbar后，加热温度到250℃，然后通过脉冲器以500KHz的频率将偏钒酸铵作为导电材料打入处理腔室中，脉冲时间200ms，偏钒酸铵流量为200sccm。最后关闭偏钒酸铵，采用氩气置换仓内残余反应气体，冷却后得到前驱体，前驱体包括硅纳米一次颗粒及位于其表面的氮化钒(VN)层。
本实施例中负极材料的参数详见表1。
实施例7
与实施例3不同的是：
(2)将100g硅纳米一次颗粒放入原子层沉积设备处理腔室内，抽真空至0.5mbar后，加热温度到250℃，然后通过脉冲器以500Hz的频率将气态四甲醇钛和气态硫蒸气作为导电材料打入处理腔室中，脉冲时间220ms，气态四甲醇钛流量为200sccm，气态硫蒸气流量为100sccm。最后关闭气态四甲醇钛和气态硫蒸气，采用氩气置换仓内残余反应气体，冷却后得到前驱体，前驱体包括硅纳米一次颗粒及位于其表面的Li2S层。
本实施例中负极材料的参数详见表1。
实施例8
与实施例3不同的是：
(2)将硅纳米一次颗粒放入旋转气氛炉中，在氩气气氛保护下，以3℃/min的升温速率加热到1050℃后，通入0.1L/min的甲烷气体，使得旋转气氛炉中的氩气与甲烷的体积比为9:1，保温2h后冷却得到前驱体，所述前驱体包括硅纳米一次颗粒及位于其表面的石墨烯碳层，石墨烯的层数为5层。
本实施例中负极材料的参数详见表1。
实施例9
与实施例3不同的是：
(4)取100g复合物旋转气氛炉中，在氩气气氛保护下，以10℃/min的升温速率加热到1050℃后，通入2.5L/min的乙炔气体，使得旋转气氛炉中的氩气与乙炔的体积比为8:2，保温6h后关闭乙炔气体，冷却得到负极材料，包覆层包括石墨化碳及非晶碳。
本实施例中负极材料的参数详见表1。
实施例10
(1)将化学气相沉积炉抽到0.5Torr后，以3℃/min的升温速率加热到600℃后，通入0.5L/min的硅烷气体，控制整个沉积炉的气相沉积压力在300Torr，沉积持续时间为2h，冷却后收集硅纳米一次颗粒。
(2)将10g硅纳米一次颗粒与十六烷基三甲基溴化铵按质量比10:2分散于200ml去离子水中后搅拌30分钟后超声10分钟，离心干燥后得到修饰后的硅纳米一次颗粒A1。将10g硅纳米一次颗粒与1g聚二烯丙基二甲基氯化铵溶于100ml去离子水中搅拌30分钟后超声20分钟，离心干燥后得到修饰后的硅纳米一次颗粒B2。将10g修饰后的硅纳米一次颗粒A1溶于100ml去离子水中搅拌10分钟得到溶液E，将10g修饰后的硅纳米一次颗粒B2分散在100ml的去离子水中搅拌10分钟得到溶液F。将溶液E缓慢滴入溶液F中，并持续快速搅拌40分钟后，离心干燥得到二次颗粒，即得到负极材料。
本实施例制得到的负极材料包括二次颗粒，所述二次颗粒包括硅纳米一次颗粒，硅纳米一次颗粒包括多个硅晶粒。
本实施例中负极材料的参数详见表1。
实施例11
与实施例3不同的是：
(1)将化学气相沉积炉抽到0.5Torr后，以3℃/min的升温速率加热到500℃后，通入0.5L/min的硅烷气体，控制整个沉积炉的压力在500Torr，持续时间为2h，冷却后收集硅纳米一次颗粒。
本实施例制得到的负极材料包括二次颗粒及位于所述二次颗粒至少部分表面的包覆层，包覆层为非晶碳层；所述二次颗粒包括硅纳米一次颗粒及位于所述硅纳米一次颗粒至少部分表面的导电层，导电层为氧化钛层，硅纳米一次颗粒包括多个硅晶粒。
本实施例中负极材料的参数详见表1。
实施例12
与实施例3不同的是：
(1)将化学气相沉积炉抽到0.5Torr后，以3℃/min的升温速率加热到500℃后，通入3.5L/min的硅烷气体，控制整个沉积炉的压力在100Torr，持续时间为5h，冷却后收集硅纳米一次颗粒。
本实施例制得到的负极材料包括二次颗粒及位于所述二次颗粒至少部分表面的包覆层，包覆层为非晶碳层；所述二次颗粒包括硅纳米一次颗粒及位于所述硅纳米一次颗粒至少部分表面的导电层，导电层为氧化钛层，硅纳米一次颗粒包括多个硅晶粒。
本实施例中负极材料的参数详见表1。
实施例13
(1)取100g平均粒径为8um的二氧化硅与100g镁粉混合均匀后，通过镁热还原二氧化硅工艺，放入充满保护气氛的气氛炉中，以3℃/min的升温速率，升温到650℃，保温3h后待冷却至室温后，得到由纳米硅组成的微米硅二次颗粒。
(2)将反应产物溶于1mol/L稀盐酸溶液中搅拌3h后，抽滤干燥得到微米硅二次颗粒。
(3)取100g酸洗后的微米硅二次颗粒放入旋转气氛炉中，在氩气气氛保护下，以5℃/min的升温速率加热到950℃后，通入2.5L/min的乙炔气体，使得旋转气氛炉中的氩气与乙炔的体积比为8:2，保温6h后关闭乙炔气体，冷却得到负极材料。
本实施例制得到的负极材料包括二次颗粒及位于所述二次颗粒至少部分表面的包覆层，包覆层为非晶碳层；所述二次颗粒包括硅纳米一次颗粒。
本实施例中负极材料的参数详见表1。
性能测试
1)负极材料比表面积的测试方法：
采用的设备是美国麦克有限公司的TriStar3000&3020全自动比表面与孔径分析仪，执行国标GB/T 19587-2017，在恒温低温下，测定不同相对压力时的气体在固体表面的吸附量后，基于布朗诺尔-埃特-泰勒吸附理论及其公式(BET公式)求得试样单分子层吸附量，从而计算出材料的比表面积。
2)振实密度的测试方法：
采用美国康塔公司的DAT-6-220粉末振实密度仪器测试粉末的振实密度百特振实，根据国标GB/T 5162-2006/ISO 3953:1993，称取一定量样品，以300times/min，振动3000次测试振实密度。
3)氧含量和碳含量的测试方法：
采用美国Thermo Fisher公司的Nicolet Is10傅里叶红外光谱测量仪测量氧含量，热重分析法测试碳层含量。
4)SEM测试：
扫描电镜表征在日本Hitachi公司S4800场发射电子显微镜上进行，操作电压为200kV，观察负极材料的结构以及对包覆层的厚度进行标尺。
5)一次颗粒、二次颗粒平均尺寸的测试方法：
采用日本Hitachi公司E3500离子研磨机和S4800场发射电子显微镜对颗粒平均尺寸测量。
6)硅晶粒平均大小的测试方法：
通过中国丹东通达公司的TD-3600X射线衍射仪测量出样品的XRD图谱，通过jade软件得到样品衍射峰半峰高宽度以及对应的布拉格角，通过谢乐公式D＝Kγ/Bcosθ计算得出纳米硅的平均晶粒尺寸。
7)导电层和包覆层的厚度的测试方法：
采用日本Hitachi公司E3500离子研磨机和S4800场发射电子显微镜对材料进行 切面处理，在SEM中对颗粒修饰层和保护层的层厚度进行测量。
8)负极材料的粒径的测试方法：
使用激光粒度仪测得D50，其存在类正态分布的对称分布。其体积基准分布中，累积50％直径为D50，依次类推，累计90％直径为D90，累计10％直径为D10。
经过上述测试，实施例1～13制得的负极材料，样本编号对应为S1～S13；负极材料的性能参数如表1所述：
表1
10)电化学测试：
将负极材料分别与羧甲基纤维素钠、丁苯橡胶以及导电石墨(KS-6)和碳黑(SP)按照比例92:2:2:2:2配置浆料，均匀涂覆与铜箔上烘干制成负极极片，在氩气气氛手 套箱中组装成扣式电池，所用隔膜为聚丙烯微孔膜，所用电解液为1mol/L的六氟磷酸锂(溶剂为碳酸乙烯酯、碳酸甲乙酯和碳酸二甲酯的混合液)，所用对电极为金属锂片。
对上述13组电池在蓝电CT2001A电池测试系统上进行放电比容量测试，1小时放电的电量与电池容量的比为放电比容量。
对上述13组电池在蓝电CT2001A电池测试系统上进行首次库伦效率测试，充放电电流为0.05C，测得首次库伦效率。
对上述13组电池在蓝电CT2001A电池测试系统上进行循环100周测试，充放电电流为0.2C，循环100圈后测试计算圈后电池容量及圈后容量保持率。
其中，0.2C循环100圈后容量保持率＝第100圈循环放电容量/第一周放电容量*100％，结果如表2所示。
表2各电池的参数性能比对表
如表2所示，实施例1至9制得的负极材料，通过控制硅纳米一次颗粒的尺寸与硅晶粒的尺寸关系，可以减弱硅纳米一次颗粒锂化过程中产生的应力集中，提高硅纳米一次颗粒的结构稳定性。控制二次颗粒与硅纳米一次颗粒的尺寸关系，可以提高负极材料在锂化过程中的结构稳定性，降低材料的膨胀率，有利于在负极材料表面形成稳定的固态电解质膜。通过在硅纳米一次颗粒表面构建导电层，在二次颗粒的表面构建包覆层，采用导电层和包覆层对负极材料进行协同修饰，利用导电层的导电性以 及对硅纳米一次颗粒的体积膨胀的缓解作用保证负极材料在嵌锂后仍具有优异的电接触性能，结合最外层的包覆层可有效减少硅纳米一次颗粒与电解液的副反应，同时增强负极材料的结构稳定性，使得负极材料制备的电池兼具低膨胀、高循环稳定性、高倍率性以及首次库伦效率。
实施例10由于负极材料的一次颗粒表面不存在导电层，二次颗粒表面也不存在包覆层，虽然负极材料的首次库伦效率与实施例1不相上下，但是其循环容量保持率以及循环200圈后容量相比于实施例1有所下降，这是因为缺少包覆层的保护，电解液与负极材料的副反应增加，负极材料体积膨胀加剧，电化学性能下降明显。
实施例11的负极材料在制备过程中，二次颗粒的堆积度B过大，说明硅纳米一次颗粒尺寸偏小，会导致二次颗粒的比表面积增大，负极材料的比表面积也增大，在负极材料脱嵌锂过程中，负极材料与电解液的副反应增多，消耗的活性锂离子增多，导致负极材料制备的电池的首次库伦效率下降。
实施例12的负极材料在制备过程中，硅纳米一次颗粒的晶态度A过大，说明硅晶粒的尺寸过小，硅纳米一次颗粒表面容易发生电化学烧结，烧结后硅晶粒长大，负极材料嵌锂后导致硅纳米一次颗粒的局部应力变大，整个结构不稳定性增强，导致负极材料的循环性能以及容量降低，负极材料的电化学性能恶化。
实施例13的负极材料在制备过程中，二次颗粒的堆积度B过小，硅纳米一次颗粒尺寸偏大，二次颗粒的膨胀应力更加集中，容易导致二次颗粒崩裂、粉化，不利于提高负极材料的结构稳定性，使得负极材料制备的电池的循环稳定性下降。
申请人声明，本申请通过上述实施例来说明本申请的详细工艺设备和工艺流程，但本申请并不局限于上述详细工艺设备和工艺流程，即不意味着本申请必须依赖上述详细工艺设备和工艺流程才能实施。所属技术领域的技术人员应该明了，对本申请的任何改进，对本申请产品各原料的等效替换及辅助成分的添加、具体方式的选择等，均落在本申请的保护范围和公开范围之内。

Claims (15)

  1. 一种负极材料，其特征在于，包括二次颗粒，所述二次颗粒包括硅纳米一次颗粒；
    所述硅纳米一次颗粒包括至少一个硅晶粒，所述硅晶粒的平均粒径为Ds nm，所述硅纳米一次颗粒的平均粒径为Dn nm；
    所述硅纳米一次颗粒的晶态度为A，A＝Dn/Ds，且1≤A≤200。
  2. 根据权利要求1所述的负极材料，其特征在于，所述硅纳米一次颗粒的晶态度A＝1，所述硅纳米一次颗粒为单晶硅。
  3. 根据权利要求1所述的负极材料，其特征在于，所述硅纳米一次颗粒的晶态度1＜A≤200，所述硅纳米一次颗粒包括多晶硅。
  4. 根据权利要求1所述的负极材料，其特征在于，包含以下特征中的至少一种：
    (1)所述硅晶粒的平均粒径为Ds nm，1≤Ds≤100；
    (2)所述硅纳米一次颗粒的平均粒径为Dn nm，1≤Dn≤200。
  5. 根据权利要求1～4任一项所述的负极材料，其特征在于，所述二次颗粒的平均粒径为Dm nm；所述二次颗粒的堆积度为B，B＝Dm/Dn，且5≤B≤400。
  6. 根据权利要求5所述的负极材料，其特征在于，所述二次颗粒的平均粒径为Dm nm，500≤Dm≤25000。
  7. 根据权利要求1所述的负极材料，其特征在于，所述负极材料还包括位于所述硅纳米一次颗粒至少部分表面的导电层。
  8. 根据权利要求7所述的负极材料，其特征在于，所述负极材料满足以下特征中的至少一种：
    (1)所述导电层包括非晶碳材料、石墨化碳材料和导电陶瓷材料中的至少一种；
    (2)所述导电层包括石墨化碳材料，所述石墨化碳材料为石墨烯，石墨烯的层数＜20；
    (3)所述导电层的厚度为1nm～200nm；
    (4)所述导电层包括导电陶瓷材料，所述导电陶瓷材料包括金属氧化物、过渡金属氮化物、硫化物中的至少一种；
    (5)所述导电层包括导电陶瓷材料，所述导电陶瓷材料包括金属氧化物，所述金属氧化物包括V2O5、TiO2、Nb2O5、CdO、CsO、MoO3、WO3、BaO、SnO2、Cr2O3、MnO、Ag2O、CoO、NiO、Cu2O和SnO中的至少一种；
    (6)所述导电层包括导电陶瓷材料，所述导电陶瓷材料包括过渡金属氮化物，所述过渡金属氮化物包括VN、TiN、CoN、Fe3N、Co4N和WN中的至少一种。
  9. 根据权利要求1所述的负极材料，其特征在于，所述负极材料还包括位于所述二次颗粒的至少部分表面的包覆层，所述包覆层包括非晶碳材料、石墨化碳材料、聚合物中的至少一种；所述负极材料满足以下特征中的至少一种：
    (1)所述负极材料中的碳元素的质量含量为5％～80％；
    (2)所述包覆层包括聚合物，所述聚合物包括聚丙烯酸、聚丙烯腈、聚酰亚胺、聚氨酯、聚多巴胺、黄原胶、聚吡咯、聚噻吩、聚苯乙炔、聚苯胺、聚乙炔、单宁酸中的至少一种；
    (3)所述包覆层包括聚合物，所述聚合物在所述负极材料中的质量含量为1％～20％；
    (4)所述包覆层包括石墨化碳材料，所述包覆层的厚度为5nm～100nm；
    (5)所述包覆层包括非晶碳材料，所述包覆层的厚度为10nm～500nm；
    (6)所述包覆层包括聚合物，所述包覆层的厚度为5nm～300nm。
  10. 根据权利要求1所述的负极材料，其特征在于，所述负极材料的粉体振实密度为0.3g/cm3～1.3g/cm3。
  11. 根据权利要求1所述的负极材料，其特征在于，所述负极材料的粉体压实密度为1.2g/cm3～1.8g/cm3。
  12. 根据权利要求1所述的负极材料，其特征在于，所述负极材料的中值粒径为0.5μm～25μm。
  13. 根据权利要求1所述的负极材料，其特征在于，所述负极材料的比表面积为1.0m2/g～50m2/g。
  14. 根据权利要求1所述的负极材料，其特征在于，所述负极材料中氧元素的质量含量＜15％。
  15. 一种电池，其特征在于，包括如权利要求1～14任一项所述的负极材料。
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