WO2020098088A1 - 一种中空/多孔结构硅基复合材料及其制法 - Google Patents

一种中空/多孔结构硅基复合材料及其制法 Download PDF

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WO2020098088A1
WO2020098088A1 PCT/CN2018/123634 CN2018123634W WO2020098088A1 WO 2020098088 A1 WO2020098088 A1 WO 2020098088A1 CN 2018123634 W CN2018123634 W CN 2018123634W WO 2020098088 A1 WO2020098088 A1 WO 2020098088A1
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silicon
hollow
composite material
carbon
porous structure
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PCT/CN2018/123634
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French (fr)
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晏荦
郑安华
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东莞市凯金新能源科技股份有限公司
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Priority to JP2021508041A priority Critical patent/JP2021520049A/ja
Priority to KR1020207030090A priority patent/KR102388057B1/ko
Publication of WO2020098088A1 publication Critical patent/WO2020098088A1/zh
Priority to US17/316,673 priority patent/US20210273221A1/en

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/366—Composites as layered products
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y30/00—Nanotechnology for materials or surface science, e.g. nanocomposites
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00—Carbon; Compounds thereof
    • C01B32/15—Nano-sized carbon materials
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B33/00—Silicon; Compounds thereof
    • C01B33/02—Silicon
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • H01M4/386—Silicon or alloys based on silicon
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/483—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides for non-aqueous cells
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H01M4/587—Carbonaceous material, e.g. graphite-intercalation compounds or CFx for inserting or intercalating light metals
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/624—Electric conductive fillers
    • H01M4/625—Carbon or graphite
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y40/00—Manufacture or treatment of nanostructures
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/60—Particles characterised by their size
    • C01P2004/61—Micrometer sized, i.e. from 1-100 micrometer
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/60—Particles characterised by their size
    • C01P2004/64—Nanometer sized, i.e. from 1-100 nanometer
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/80—Particles consisting of a mixture of two or more inorganic phases
    • C01P2004/82—Particles consisting of a mixture of two or more inorganic phases two phases having the same anion, e.g. both oxidic phases
    • C01P2004/84—Particles consisting of a mixture of two or more inorganic phases two phases having the same anion, e.g. both oxidic phases one phase coated with the other
    • 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
    • C01P2006/10—Solid 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
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the invention relates to the technical field of new energy materials, in particular to a hollow / porous structure silicon-based composite material and a preparation method thereof.
  • Si has one of the most potential alternative graphite materials due to its high theoretical specific capacity (4200mAh / g), but the Si-based material has a huge volume effect during charge and discharge , Prone to cracking and pulverization, thereby losing contact with the current collector, resulting in a sharp decline in cycle performance. Therefore, reducing the volume expansion effect and improving the cycle performance is of great significance for the application of silicon materials in lithium ion batteries.
  • Chinese patent CN105552323A discloses a silicon / silicon oxide / carbon anode material and its preparation method and application. Ultra-small silicon oxide carbon nanoparticles are uniformly dispersed in a carbon matrix as a buffer matrix, while silicon nanoparticles are It is evenly embedded in the carbon / silicon-carbon buffer matrix. Although this negative electrode active material has high capacity and good cycle performance, its first efficiency is low, which limits its application in lithium ion batteries.
  • Chinese patent CN106374088A is a method for preparing silicon-carbon composite materials by magnesium thermal reduction method. The silicon source (silicon dioxide) and the organic carbon source are dispersed in a solvent and ball milled and dried to obtain a silica-carbon precursor composite material.
  • the aforementioned precursor and magnesium powder are mixed to perform a magnesium thermal reduction reaction, acid washing, water washing, and drying to obtain a silicon-carbon composite material. Since the porous structure of the material is obtained by the environmentally unfriendly method of magnesia reduction and pickling, and the process of magnesia reduction and pickling is difficult to control, many reaction by-products will remain, so that the negative electrode material shows low For the first time.
  • the purpose of the present invention is to provide a hollow / porous structure silicon-based composite material and its preparation method in view of the above-mentioned deficiencies in the prior art, which is a silicon-carbon negative electrode for lithium ion batteries with advantages of high first efficiency, low expansion and long cycle Materials, slowing down the growth of silicon material grains during the heat treatment process, effectively avoiding the powdering of the material during the cycle, alleviating the volume expansion effect of the silicon-based material, improving the cycle performance, and improving the electrical conductivity of the material. Magnification performance.
  • a hollow / porous structure silicon-based composite material includes a hollow / porous structure, a silicon-carbon composite layer and a cladding layer, wherein the silicon-carbon composite layer is uniformly dispersed in a conductive carbon network by nano-silicon / silicon oxide.
  • the particle size D50 of the hollow / porous structure silicon-based composite material is 1-20 ⁇ m, further preferably 2-15 ⁇ m, and particularly preferably 2-10 ⁇ m.
  • the specific surface area of the hollow / porous structure silicon-based composite material is 1-30 m2 / g, further preferably 2-20 m2 / g, and particularly preferably 2-8 m2 / g.
  • the true density of the hollow / porous structure silicon-based composite material is 1-3 g / cm3, further preferably 1.5-2.5 g / cm3, and particularly preferably 2.0-2.5 g / cm3.
  • the center of the hollow / porous structure silicon-based composite material is a hollow structure or a large-diameter composite material composed of a plurality of small particle sizes and a secondary particle structure with an internal hollow / porous structure.
  • the internal hollow / porous structure can effectively relieve the volume effect of the silicon-based material during charge and discharge, thereby effectively avoiding the powdering of the material during the cycle, and the binder can play a good carbon conductive network after high-temperature carbonization , It can improve the conductivity of the material, improve the rate performance of the material, ease the volume expansion effect of the silicon-based material and improve the cycle performance.
  • the cavity inside the hollow / porous structure silicon-based composite material accounts for 10-80% of the total volume of the composite material, further preferably 15-70%, and particularly preferably 20-50%.
  • the cavity in the secondary particles accounts for 10-80% of the total volume of the secondary particles, further preferably 15-70%, particularly preferably 20-50%; the particle size D50 of the secondary particles is 1 -10 ⁇ m, further preferably 2-8 ⁇ m, particularly preferably 2-5 ⁇ m.
  • the conductive carbon network in the silicon-carbon composite layer is formed by pyrolysis of a binder at high temperature; the coating layer is a carbon coating layer; the carbon coating layer is at least one layer, and the thickness of a single layer is 0.2- 3 ⁇ m, further preferably 0.2-2 ⁇ m, particularly preferably 0.2-1 ⁇ m.
  • the preparation method of the aforementioned hollow / porous structure silicon-based composite material of the present invention includes the following steps:
  • the solid silicon-based composite material precursor is sintered at a high temperature of 500 to 1200 ° C under a protective atmosphere to carbonize the binder to obtain a silicon-carbon composite layer. After sintering, the salt is washed to remove salt, filtered and dried to obtain a hollow / Porous structure silicon matrix composite precursor;
  • the nano-silicon material is nano-silicon or nano-silicon oxide; the nano-silicon is single-crystal nano-silicon, polycrystalline nano-silicon or amorphous nano-silicon; in the nano-silicon oxide (SiOx) X is 0.8-1.5, preferably 0.8-1.3, particularly preferably 0.8-1.1; the particle size D50 of the silicon material is 5-300nm, further preferably 10-200nm, particularly preferably 10-100nm; the silicon material mesocrystal
  • the single crystal or polycrystal with a particle size of 1-40 nm is further preferably 2-20 nm, and particularly preferably 2-10 nm.
  • the binder is one or more of sucrose, glucose, citric acid, polypyrrolidone and PVDF; the mass ratio of the nano-silicon and the binder is 60: 40 ⁇ 99: 1.
  • the solvent in step S1 is an organic solvent, including one or more of alcohol solvents, ketone solvents, alkane solvents, N-methylpyrrolidone, tetrahydrofuran, toluene, and the alcohol solvents It is one or more of ethanol, methanol, propanol, ethylene glycol, isopropanol, n-octanol, allyl alcohol, octanol, and the ketone solvent is acetone, methyl ethyl ketone, methyl isobutyl One or more of ketone, methyl ethyl ketone, methyl isoacetone, cyclohexanone, methyl ketone, the alkane solvent is cyclohexane, n-hexane, isoheptane, 3,3-dimethylpentane, One or more of 3-methyl hexane; adding a solvent to control the solid content of the slurry is 5
  • the salt in step S1 is a salt soluble in water but insoluble / slightly soluble in an organic solvent, including Na2CO3, Ca (NO2) 2, NaCl, KCl, CuCl2, NiCl2, FeSO4, MgSO4, CuSO4 One or more types; the mass ratio of the nano-silicon material to the salt is 1:99 ⁇ 99: 1.
  • the salt not only reserves space in the material to maintain the hollow / porous structure inside the material, but also forms molten salt during heat treatment to absorb heat, slowing down the growth of silicon material grains during heat treatment.
  • the sintering process in the step S2 is static sintering or dynamic sintering.
  • the equipment used in the static sintering is one of a box furnace, a roller kiln, and a push plate kiln.
  • the dynamic sintering is a rotary sintering furnace; the protection
  • the sex gas is one or more of nitrogen, argon, argon-hydrogen mixed gas; the sintering process is from 1 to 15 °C / min to 500 to 1200 °C under a protective atmosphere, holding for 0.5 to 20 hours, and naturally cooling to room temperature .
  • the carbon coating in the step S3 is a high-temperature cracked carbon coating; the carbon coating adopts one carbon coating or two carbon coatings, the two carbon coatings and the second carbon coating
  • the coating amount of the coating is 0.1 to 10 times the coating amount of the first carbon coating by mass; the carbon is formed by cracking the carbon by organic matter, and the coating layer thickness is 10 to 2000 nm, further preferably 10 to 1500 nm It is particularly preferably 10 to 1000 nm.
  • 2 may be employed two-step carbon coating liquid coated, or vapor coating step 2, the liquid may be first coated with carbon using carbon coated using gas, may be employed before or after the vapor phase coated with carbon using carbon Cladding.
  • the carbon coating in the step S3 adopts liquid-phase carbon coating or gas-phase carbon coating, wherein the liquid-phase carbon coating includes the following process: utilizing the organic carbon source, the material to be coated and the solvent The high-speed disperser mixes and disperses uniformly to form a slurry. The solid content of the slurry is controlled by adjusting the amount of solvent added to 5-50%.
  • the slurry is spray-dried, then heat-treated, and high-purity protection is introduced in the atmosphere furnace
  • the gas is heated to 400-1200 ° C at a heating rate of ⁇ 10 ° C for sintering, kept at 0.5-10h, and naturally cooled to room temperature to obtain a liquid-phase coating product;
  • the amount of the organic carbon source added is the mass of organic matter cracked carbon accounts for the organic matter 1 to 99 wt% of the total mass of the composite material generated by cracking carbon and the material to be coated.
  • the carbon source of the organic substance is sucrose, glucose, citric acid, phenolic resin, epoxy resin, asphalt, polypyrrole, polypyrrolidone, polyaniline, polyacrylonitrile , One or more of polydopamine, polyvinyl alcohol;
  • the solvent is one or more of water, alcohol solvents, ketone solvents, alkane solvents, N-methylpyrrolidone, tetrahydrofuran, toluene,
  • the alcohol solvent is one or more of ethanol, methanol, ethylene glycol, isopropanol, n-octanol, allyl alcohol, and octanol
  • the ketone solvent is acetone, methyl butanone, methyl
  • the alkane solvent is cyclohexanone
  • the carbon coating in the step S3 is liquid-phase carbon coating or gas-phase carbon coating, wherein the gas-phase carbon coating includes the following process: placing the object to be coated in a CVD furnace, Inject protective gas, increase the temperature from 1 to 15 °C / min to 500 to 1200 °C, pass the organic carbon source gas at a flow rate of 0.5 to 20.0L / min, keep the temperature for 0.5 to 20h, and naturally cool to room temperature to obtain the gas phase coating product.
  • the CVD furnace is a rotary furnace with a rotation speed of 0.2 to 5.0 rpm;
  • the protective gas is one or more of nitrogen, helium, neon, argon, krypton, and xenon;
  • the organic carbon source gases are methane, ethane, propane, isopropane, butane, isobutane, ethylene, propylene, acetylene, butene, vinyl chloride, vinyl fluoride, vinyl fluoride, ethyl chloride, ethyl fluoride, One or more of difluoroethane, chloromethane, fluoromethane, difluoromethane, trifluoromethane, methylamine, formaldehyde, benzene, toluene, xylene, styrene, phenol.
  • the hollow / porous structure silicon-based composite material of the present invention comprises a hollow / porous structure, a silicon-carbon composite layer and a cladding layer, wherein the silicon-carbon composite layer is uniformly dispersed in a conductive carbon network by nano-silicon / silicon oxide,
  • the internal hollow / porous structure can effectively alleviate the volume effect of the silicon-based material during charging and discharging, thereby effectively avoiding the powdering of the material during the cycle and improving the cycle performance of the material.
  • the binder can start after high-temperature carbonization To a good carbon conductive network, it can improve the conductivity of the material, improve the rate performance of the material, alleviate the volume expansion effect of the silicon-based material and improve the cycle performance.
  • the salt not only reserves space in the material so that the material remains hollow / porous Structure, and the formation of molten salt during heat treatment absorbs heat, slowing down the growth of silicon material grains during heat treatment.
  • the hollow / porous structure silicon-based composite material of the present invention first binds nano-silicon / silicon oxide uniformly on the salt, uses high-temperature sintering to carbonize the binder to obtain a silicon-carbon composite layer, and then uses water washing to remove the salt to obtain hollow / The porous structure is finally coated to obtain a hollow / porous structure silicon-based composite material.
  • the lithium ion battery prepared by using this material can exhibit good cycle performance and rate performance.
  • FIG. 1 is an electron micrograph of a silicon-based composite material in Example 4 of the present invention.
  • Example 2 is an XRD picture of a silicon-based composite material in Example 4 of the present invention.
  • Example 3 is the first charge-discharge curve of the silicon-based composite material in Example 4 of the present invention.
  • FIG. 4 is the cycle performance curve of the silicon-based composite material in Example 4 of the present invention.
  • FIG. 5 is the rate performance curve of the silicon-based composite material in Example 4 of the present invention.
  • 30% (calculated as the percentage of the mass of organic matter cracked carbon in the total mass of the silicon-based composite material) asphalt, 70% solid silicon-based composite material precursor and alcohol are mixed and dispersed by a high-speed disperser to form a slurry uniformly, by adjusting Add the amount of alcohol to control the solid content of the slurry to 20%, spray-dry the slurry, heat-treat the dried product, pass a high-purity protective gas nitrogen in an atmosphere furnace, and increase the temperature to 1 °C / min to Keep it at 1050 °C for 5h, and cool it to room temperature naturally to obtain a silicon-based composite material.
  • the solid silicon-based composite material precursor was placed in a rotary furnace, the rotation speed was adjusted to 1.5 rpm, protective gas nitrogen was introduced, the temperature was raised to 900 ° C at 5 °C / min, and methane gas was introduced at a rate of 1.5 L / min for 20 min , Insulation for 3h, natural cooling to room temperature, to obtain a primary carbon-coated product; first, 15% (calculated as a percentage of the mass of organic matter cracked carbon in the total mass of the silicon-based composite material) asphalt, 85% primary carbon-coated product and Alcohol is mixed and dispersed uniformly by a high-speed dispersing machine to form a mixture. The solid content of the mixture is controlled to 20% by adjusting the amount of alcohol added.
  • the mixture is spray-dried and the sprayed material is heat-treated and passed into the atmosphere furnace.
  • the high-purity protective gas, nitrogen was heated to 900 ° C at 1 ° C / min, held for 3 hours, and naturally cooled to room temperature to obtain a silicon-based composite material.
  • the slurry is uniformly formed by mixing and dispersing with a high-speed dispersing machine, and the slurry is spray-dried to obtain a solid silicon-based composite material precursor.
  • the solid silicon-based composite material precursor was heat-treated, and a high-purity protective gas nitrogen was introduced into the atmosphere furnace, and the temperature was raised to 1050 ° C at 1 ° C / min, held for 5 hours, and naturally cooled to room temperature, and then the sintered material was washed with water , Filtration and drying treatment to obtain a hollow / porous structure silicon matrix composite precursor.
  • 20g of nanosilicon material with D50 particle size 150nm, 6g of Na2CO3, and 4g of sucrose were added to 150g of propanol.
  • the slurry is uniformly formed by mixing and dispersing with a high-speed dispersing machine, and the slurry is spray-dried to obtain a solid silicon-based composite material precursor.
  • the solid silicon-based composite material precursor was heat-treated, a high-purity protective gas nitrogen was introduced into the atmosphere furnace, the temperature was raised to 900 ° C at 1 ° C / min, the temperature was kept for 3 hours, and the temperature was naturally cooled to room temperature. , Filtration and drying treatment to obtain a hollow / porous structure silicon matrix composite precursor.
  • the mixture is spray-dried and the sprayed material is heat-treated in an atmosphere furnace Pass high-purity protective gas nitrogen, heat to 900 ° C at 1 ° C / min, hold for 3 hours, and naturally cool to room temperature to obtain a silicon-based composite material.
  • the slurry is uniformly formed by mixing and dispersing with a high-speed dispersing machine, and the slurry is spray-dried to obtain a solid silicon-based composite material precursor.
  • the solid silicon-based composite material precursor was heat-treated, a high-purity protective gas nitrogen was introduced into the atmosphere furnace, the temperature was raised to 900 ° C at 1 ° C / min, the temperature was kept for 3 hours, and the temperature was naturally cooled to room temperature, and then the sintered material was washed with water , Filtration and drying treatment to obtain a hollow / porous structure silicon matrix composite precursor.
  • expansion ratio (thickness of pole piece after 50 cycles-thickness of pole piece before cycle) / (thickness of pole piece before cycle-thickness of copper foil) * 100%.
  • Table 1 shows the performance test evaluation results of Comparative Examples 1 to 2 and Examples 1 to 6.

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Abstract

本发明公开了一种中空/多孔结构硅基复合材料包括中空/多孔结构、硅碳复合层和包覆层，硅碳复合层是纳米硅或氧化硅均匀的分散在导电碳网中而形成，硅碳复合层中导电碳网络由粘结剂高温裂解形成，包覆层为碳包覆层，碳包覆层至少为一层。本发明的复合材料采用纳米硅/氧化硅、粘结剂和盐均匀混合后进行喷雾造粒、高温烧结、水洗除盐以及包覆处理的方法制备。本发明是具有高首效、低膨胀和长循环等优点的锂离子电池硅碳负极材料，减缓热了处理过程中硅材料晶粒长大，有效的避免了材料在循环过程中的粉化，缓解了硅基材料的体积膨胀效应、提升了循环性能，能提高材料的导电性和倍率性能。

Description

一种中空/多孔结构硅基复合材料及其制法 技术领域
本发明涉及新能源材料技术领域，特别涉及一种中空/多孔结构硅基复合材料及其制法。
背景技术
二次电池已广泛应用于便携式电子产品中，但是随着便携式电子产品小型化发展及二次电池在航空、军事及汽车产业中的需求日益增大，电池的容量和能量密度均亟待大幅度提高。目前商业化负极材料主要为石墨类材料，但因其理论容量较低(372mAh/g)，无法满足于市场的需求。近年来，人们的目光瞄准新型高比容量负极材料：储锂金属及其氧化物(如Sn，Si)和锂过渡金属磷化物。在众多新型高比容量负极材料中，Si因具有高的理论比容量(4200mAh/g)而成为最具潜力的可替代石墨类材料之一，但是Si基在充放电过程中存在巨大的体积效应，易发生破裂和粉化，从而丧失与集流体的接触，造成循环性能急剧下降。因此降低体积膨胀效应和提升循环性能对硅材料在锂离子电池中的应用有重大意义。
现有技术中，中国专利CN105552323A公开一种硅/碳氧化硅/碳负极材料及其制备方法和应用，采用超小硅氧碳纳米粒子均匀分散在碳基质中作为缓冲基质，而硅纳米粒子则被均匀镶嵌在碳/硅氧碳缓冲基质中。虽然该负极活性材料具有容量高和循环性能较好，但是其的首次效率偏低，限制了它在锂离子电池中的应用。中国专利CN106374088A一种利用镁热还原法制备硅碳复合材料的方法，将硅源(二氧化硅)与有机碳源分散在溶剂中球磨、烘干得 到二氧化硅-碳前驱体复合材料，随后将上述前驱体与镁粉混合进行镁热还原反应、酸洗、水洗、干燥得到硅碳复合材料。由于该材料的多孔结构采用镁热还原和酸洗这种环境不友好的方法得到，且镁热还原反应和酸洗过程很难控制，会残留许多反应副产物，从而使该负极材料表现出低的首次效率。
为此，确有必要开发一种中空/多孔结构硅基复合材料可以用于锂离子电池，具有高首效、低膨胀和长循环等优点的锂离子电池硅碳负极材料及其制备方法，来克服现有技术领域Si基材料在充放电过程中存在巨大的体积效应，易发生破裂和粉化，从而丧失与集流体的接触，造成循环性能急剧下降，以及硅基负极活性材料体积效应大和电导率低导致其循环性能差以及倍率性能差等技术难题。
发明内容
本发明的目的在于，针对现有技术的上述不足，提供一种中空/多孔结构硅基复合材料及其制法，是具有高首效、低膨胀和长循环等优点的锂离子电池硅碳负极材料，减缓热了处理过程中硅材料晶粒长大，有效的避免了材料在循环过程中的粉化，缓解了硅基材料的体积膨胀效应、提升了循环性能，能提高材料的导电性和倍率性能。
本发明为达到上述目的所采用的技术方案是：
一种中空/多孔结构硅基复合材料，包括中空/多孔结构、硅碳复合层和包覆层组成，其中硅碳复合层是由纳米硅/氧化硅均匀的分散在导电碳网中。
优选地，所述中空/多孔结构硅基复合材料的粒度D50为1-20μm，进一步优选为2-15μm，特别优选为2-10μm。
优选地，所述中空/多孔结构硅基复合材料的比表面积为1-30m2/g，进一步优选为2-20m2/g，特别优选为2-8m2/g。
优选地，所述中空/多孔结构硅基复合材料的真密度为1-3g/cm3，进一步优选为1.5-2.5g/cm3，特别优选为2.0-2.5g/cm3。
优选地，所述中空/多孔结构硅基复合材料中心为空心结构或者由多个小粒径、内部空心/多孔结构的二次粒子结构构成的一个大粒径复合材料。内部中空/多孔结构能有效的缓解硅基材料在充放电过程中的体积效应，从而有效的避免了材料在循环过程中的粉化，粘结剂在高温碳化后可以起到良好的碳导电网络，能提高材料的导电性，改善材料的倍率性能，缓解了硅基材料的体积膨胀效应和提升了循环性能。
优选地，所述中空/多孔结构硅基复合材料内部的空腔占复合材料总体积的10-80％，进一步优选为15-70％，特别优选为20-50％。
优选地，所述二次粒子中的空腔占二次粒子总体积的10-80％，进一步优选为15-70％，特别优选为20-50％；所述二次粒子的粒度D50为1-10μm，进一步优选为2-8μm，特别优选为2-5μm。
优选地，所述硅碳复合层中导电碳网络由粘结剂高温裂解形成；所述包覆层为碳包覆层；所述碳包覆层至少为一层，其单层厚度为0.2-3μm，进一步优选为0.2-2μm，特别优选为0.2-1μm。
本发明前述的中空/多孔结构硅基复合材料的制备方法，包括以下步骤：
S1：将纳米硅材料、粘结剂和盐加入溶剂中，利用高速分散机混合分散均匀形成浆料，对所述浆料进行喷雾干燥，得到实心硅基复合材料前驱体；
S2：将所述实心硅基复合材料前驱体在保护气氛下以及500～1200℃进行高温烧结使得粘结剂碳化得到硅碳复合层，在烧结后经水洗去除盐、过滤和干燥处理，得到中空/多孔结构硅基复合材料前驱体；
S3：将所述中空/多孔结构硅基复合材料前驱体进行碳包覆，即得中空/多孔结构硅基复合材料。
优选地，所述步骤S1中所述纳米硅材料为纳米硅或纳米氧化亚硅；纳米硅为单晶纳米硅、多晶纳米硅或非晶纳米硅；所述纳米氧化亚硅(SiOx)中X为0.8-1.5，优选为0.8-1.3，特别优选为0.8-1.1；所述硅材料粒度D50为5-300nm，进一步优选为10-200nm，特别优选为10-100nm；所述硅材料中晶粒大小为1-40nm的单晶或多晶，进一步优选为2-20nm，特别优选为2-10nm。
优选地，所述步骤S1中所述粘结剂为蔗糖、葡萄糖、柠檬酸、聚吡咯烷酮和PVDF中的一种或几种；所述纳米硅和所述粘结剂质量比为60:40～99:1。
优选地，所述步骤S1中所述溶剂为有机溶剂，包含醇类溶剂、酮类溶剂、烷类溶剂、N-甲基吡咯烷酮、四氢呋喃、甲苯中的一种或几种，所述醇类溶剂为乙醇、甲醇、丙醇、乙二醇、异丙醇、正辛醇、丙烯醇、辛醇中的一种或几种，所述酮类溶剂为丙酮、甲基丁酮、甲基异丁酮、甲乙酮、甲异丙酮、环已酮、甲已酮中的一种或几种，所述烷类溶剂为环己烷、正己烷、异庚烷、3,3-二甲基戊烷、3-甲基己烷中的一种或几种；添加溶剂控制浆料的固含量为5～50％。
优选地，所述步骤S1中所述的盐为溶于水而不溶/微溶于有机溶剂的盐，包含Na2CO3、Ca(NO2)2、NaCl、KCl、CuCl2、NiCl2、FeSO4、MgSO4、CuSO4中的一种或几种；所述纳米硅材料与所述盐的质量比为1:99～99:1。利用盐溶于水而不溶于有机溶剂来构筑中空/多孔结构，通过控制盐的粒径和添加量来有效的控制复合材料内部的中空/多孔结构的大小和占体积比，且后续除盐过程中采用水洗和过滤，这种方法环境友好无污染。盐不仅在材料中预留空 间使得材料内部维持中空/多孔结构，而且在热处理过程中形成融盐吸收热量，减缓热处理过程中硅材料晶粒长大。
优选地，所述步骤S2中烧结处理为静态烧结或动态烧结，静态烧结时用的设备为箱式炉、辊道窑、推板窑中的一种，动态烧结为转动烧结炉；所述保护性气体为氮气、氩气、氩氢混合气体中的一种或几种；烧结过程为在保护气氛下以1～15℃/min升温至500～1200℃，保温0.5～20h，自然冷却至室温。
优选地，所述步骤S3中所述碳包覆为高温裂解碳包覆；所述碳包覆采用一次碳包覆或者两次碳包覆，采用所述两次碳包覆，第二次碳包覆的包覆量按质量计为第一次碳包覆包覆量的0.1～10倍；经有机物裂解碳形成包覆层，包覆层厚度为10～2000nm，进一步优选为10～1500nm，特别优选为10～1000nm。两次碳包覆可以 采用2步液相包覆或者2步气相包覆，也可以先采用液相碳包覆后采用气相碳包覆，也可以 或者先采用气相碳包覆后采用液相碳包覆。
优选地，所述步骤S3中所述碳包覆采用液相碳包覆或者气相碳包覆，其中，所述液相碳包覆包括如下过程：将有机物碳源、待包覆物与溶剂利用高速分散机混合分散均匀，形成浆料，通过调节溶剂的添加量来控制浆料的固含量5～50％，对浆料进行喷雾干燥，再进行热处理，在气氛炉中通入高纯保护性气体，以≦10℃的升温速率升温至400～1200℃进行烧结，保温0.5～10h，自然冷却至室温，得到液相包覆产物；所述有机物碳源加入量为有机物裂解碳的质量占有机物裂解碳与待包覆物生成的复合材料的总质量的1～99wt％。
进一步优选地，碳包覆采用液相碳包覆时，其中所述有机物碳源为蔗糖、葡萄糖、柠檬酸、酚醛树脂、环氧树脂、沥青、聚吡咯、聚吡咯烷酮、聚苯胺、聚丙烯腈、聚多巴胺、聚乙烯醇中的一种或几种；所述溶剂为水、醇类 溶剂、酮类溶剂、烷类溶剂、N-甲基吡咯烷酮、四氢呋喃、甲苯中的一种或几种，所述醇类溶剂为乙醇、甲醇、乙二醇、异丙醇、正辛醇、丙烯醇、辛醇中的一种或几种，所述酮类溶剂为丙酮、甲基丁酮、甲基异丁酮、甲乙酮、甲异丙酮、环已酮、甲已酮中的一种或几种，所述烷类溶剂为环己烷、正己烷、异庚烷、3,3-二甲基戊烷、3-甲基己烷中的一种或几种；所述保护性气体为氮气、氩气、氩氢混合气体中的一种或几种；
优选地，所述步骤S3中所述碳包覆采用液相碳包覆或者气相碳包覆，其中，所述气相碳包覆是，包括如下过程：将待包覆物置于CVD炉中，通入保护性气体，以1～15℃/min升温至500～1200℃，以0.5～20.0L/min通入速率通入有机碳源气体，保温0.5～20h，自然冷却至室温，得到气相包覆产物。
进一步优选地，所述CVD炉为回转炉，回转速度为0.2～5.0rpm；所述保护性气体为氮气、氦气、氖气、氩气、氪气、氙气中的一种或几种；所述有机碳源气体为甲烷、乙烷、丙烷、异丙烷，丁烷，异丁烷、乙烯、丙烯、乙炔、丁烯、氯乙烯，氟乙烯，二氟乙烯、氯乙烷，氟乙烷，二氟乙烷、氯甲烷，氟甲烷，二氟甲烷，三氟甲烷，甲胺，甲醛、苯、甲苯、二甲苯、苯乙烯、苯酚中的一种或几种。
与现有技术相比，本发明的有益效果是：
1.本发明的中空/多孔结构硅基复合材料包括中空/多孔结构、硅碳复合层和包覆层组成，其中硅碳复合层是由纳米硅/氧化硅均匀的分散在导电碳网中，内部中空/多孔结构能有效的缓解硅基材料在充放电过程中的体积效应，从而有效的避免了材料在循环过程中的粉化，改善材料的循环性能，粘结剂在高温碳化后可以起到良好的碳导电网络，能提高材料的导电性，改善材料 的倍率性能，缓解了硅基材料的体积膨胀效应和提升了循环性能，盐不仅在材料中预留空间使得材料内部维持中空/多孔结构，而且在热处理过程中形成融盐吸收热量，减缓热处理过程中硅材料晶粒长大。
2.本发明的中空/多孔结构硅基复合材料先将纳米硅/氧化硅均匀的粘结在盐上，利用高温烧结使得粘结剂碳化得到硅碳复合层，再利用水洗去除盐得到中空/多孔结构，最后进行包覆处理，得到中空/多孔结构硅基复合材料，采用该材料制备锂离子电池可以表现出良好的循环性能和倍率性能。
上述是发明技术方案的概述，以下结合附图与具体实施方式，对本发明做进一步说明。
附图说明
图1为本发明实施例4中硅基复合材料电镜图片；
图2为本发明实施例4中硅基复合材料XRD图片；
图3为本发明实施例4中硅基复合材料首次充放电曲线；
图4为本发明实施例4中硅基复合材料循环性能曲线；
图5为本发明实施例4中硅基复合材料倍率性能曲线。
具体实施方式：
为了使本发明的目的和技术方案及优点更加清楚明白，以下结合实施例和附图作详细说明。应当理解，此处所描述的具体实施例仅仅用以解释本发明，并不用于限定本发明的范围，本领域的技术人员参照本发明实施例作出一些非本质的改动或调整，仍属于本发明的保护范围。
比较例1
将20gD50粒径＝50nm的纳米硅材料，4g蔗糖，添加到150g酒精中。利用高速分散机混合分散均匀形成浆料，对浆料进行喷雾干燥，得到实心硅基复合材料前驱体。将得到实心硅基复合材料前驱体进行热处理，在气氛炉中通入高纯保护性气体氮气，以1℃/min升温至1050℃，保温5h，自然冷却至室温。再将30％(按有机物裂解碳的质量占所述硅基复合材料总质量的百分 比计算)沥青、70％实心硅基复合材料前驱体和酒精利用高速分散机混合分散均匀形成浆料，通过调节酒精的添加量来控制浆料的固含量为20％，对浆料进行喷雾干燥，将干燥后的产物进行热处理，在气氛炉中通入高纯保护性气体氮气，以1℃/min升温至1050℃，保温5h，自然冷却至室温，得到硅基复合材料。
比较例2
将20gD50粒径＝150nm的纳米硅材料，4g柠檬酸，添加到100g酒精中。利用高速分散机混合分散均匀形成浆料，对浆料进行喷雾干燥，得到实心硅基复合材料前驱体。将得到实心硅基复合材料前驱体进行热处理，在气氛炉中通入高纯保护性气体氮气，以1℃/min升温至900℃，保温3h，自然冷却至室温。将得到实心硅基复合材料前驱体置于回转炉中，调节回转速度为1.5rpm，通入保护性气体氮气，以5℃/min升温至900℃，以1.5L/min速率通入甲烷气体20min，保温3h，自然冷却至室温，得到一次碳包覆产物；先将15％(按有机物裂解碳的质量占所述硅基复合材料总质量的百分比计算)沥青、85％一次碳包覆产物和酒精利用高速分散机混合分散均匀形成混合料，通过调节酒精的添加量来控制混合料的固含量为20％，对混合料进行喷雾干燥，对喷雾后的物料进行热处理，在气氛炉中通入高纯保护性气体氮气，以1℃/min升温至900℃，保温3h，自然冷却至室温，得到硅基复合材料。
实施例1
将20gD50粒径＝50nm的纳米硅材料，4gNaCl，4g蔗糖，添加到150g酒精中。利用高速分散机混合分散均匀形成浆料，对浆料进行喷雾干燥，得到实心硅基复合材料前驱体。将得到实心硅基复合材料前驱体进行热处理，在气氛炉中通入高纯保护性气体氮气，以1℃/min升温至1050℃，保温5h，自然冷却至室温，再将烧结后的材料水洗、过滤和干燥处理，得到中空/多孔结构硅基复合材料前驱体。再将30％(按有机物裂解碳的质量占所述硅基复合材料总质量的百分比计算)沥青、70％中空/多孔结构硅基复合材料前驱体和酒精利用高速分散机混合分散均匀形成浆料，通过调节酒精的添加量来控制浆料的固含量为20％，对浆料进行喷雾干燥，将干燥后的产物进行热处理， 在气氛炉中通入高纯保护性气体氮气，以1℃/min升温至1050℃，保温5h，自然冷却至室温，得到硅基复合材料。
实施例2
将20gD50粒径＝100nm的纳米硅材料，4gNaCl，4g蔗糖，添加到150g酒精中。利用高速分散机混合分散均匀形成浆料，对浆料进行喷雾干燥，得到实心硅基复合材料前驱体。将得到实心硅基复合材料前驱体进行热处理，在气氛炉中通入高纯保护性气体氮气，以1℃/min升温至900℃，保温3h，自然冷却至室温，再将烧结后的材料水洗、过滤和干燥处理，得到中空/多孔结构硅基复合材料前驱体。再将30％(按有机物裂解碳的质量占所述硅基复合材料总质量的百分比计算)沥青、70％中空/多孔结构硅基复合材料前驱体和酒精利用高速分散机混合分散均匀形成浆料，通过调节酒精的添加量来控制浆料的固含量为20％，对浆料进行喷雾干燥，将干燥后的产物进行热处理，在气氛炉中通入高纯保护性气体氮气，以1℃/min升温至900℃，保温5h，自然冷却至室温，得到硅基复合材料。
实施例3
将20gD50粒径＝150nm的纳米硅材料，6gNa2CO3，4g蔗糖，添加到150g丙醇中。利用高速分散机混合分散均匀形成浆料，对浆料进行喷雾干燥，得到实心硅基复合材料前驱体。将得到实心硅基复合材料前驱体进行热处理，在气氛炉中通入高纯保护性气体氮气，以1℃/min升温至900℃，保温3h，自然冷却至室温，再将烧结后的材料水洗、过滤和干燥处理，得到中空/多孔结构硅基复合材料前驱体。再将30％(按有机物裂解碳的质量占所述硅基复合材料总质量的百分比计算)沥青、70％中空/多孔结构硅基复合材料前驱体和酒精利用高速分散机混合分散均匀形成浆料，通过调节酒精的添加量来控制浆料的固含量为20％，对浆料进行喷雾干燥，将干燥后的产物进行热处理，在气氛炉中通入高纯保护性气体氮气，以1℃/min升温至900℃，保温5h，自然冷却至室温，得到硅基复合材料。
实施例4
将20gD50粒径＝50nm的纳米硅材料，4gNaCl，4g柠檬酸，添加到100g 酒精中。利用高速分散机混合分散均匀形成浆料，对浆料进行喷雾干燥，得到实心硅基复合材料前驱体。将得到实心硅基复合材料前驱体进行热处理，在气氛炉中通入高纯保护性气体氮气，以1℃/min升温至900℃，保温3h，自然冷却至室温，再将烧结后的材料水洗、过滤和干燥处理，得到中空/多孔结构硅基复合材料前驱体。将得到中空/多孔结构硅基复合材料前驱体置于回转炉中，调节回转速度为1.5rpm，通入保护性气体氮气，以5℃/min升温至900℃，以1.5L/min速率通入甲烷气体20min，保温3h，自然冷却至室温，得到一次碳包覆产物；先将15％(按有机物裂解碳的质量占所述硅基复合材料总质量的百分比计算)沥青、85％一次碳包覆产物和酒精利用高速分散机混合分散均匀形成混合料，通过调节酒精的添加量来控制混合料的固含量为20％，对混合料进行喷雾干燥，对喷雾后的物料进行热处理，在气氛炉中通入高纯保护性气体氮气，以1℃/min升温至900℃，保温3h，自然冷却至室温，得到硅基复合材料。
实施例5
将20gD50粒径＝50nm的纳米硅材料，4gNaCl，4g柠檬酸，添加到100g酒精中。利用高速分散机混合分散均匀形成浆料，对浆料进行喷雾干燥，得到实心硅基复合材料前驱体。将得到实心硅基复合材料前驱体进行热处理，在气氛炉中通入高纯保护性气体氮气，以1℃/min升温至900℃，保温3h，自然冷却至室温，再将烧结后的材料水洗、过滤和干燥处理，得到中空/多孔结构硅基复合材料前驱体。先将15％(按有机物裂解碳的质量占所述硅基复合材料总质量的百分比计算)沥青、85％中空/多孔结构硅基复合材料前驱体和酒精利用高速分散机混合分散均匀形成混合料，通过调节酒精的添加量来控制混合料的固含量为20％，对混合料进行喷雾干燥，对喷雾后的物料进行热处理，在气氛炉中通入高纯保护性气体氮气，以1℃/min升温至900℃，保温3h，自然冷却至室温，得到一次碳包覆产物；将得到一次碳包覆产物置于回转炉中，调节回转速度为1.5rpm，通入保护性气体氮气，以5℃/min升温至900℃，以1.5L/min速率通入甲烷气体20min，保温2h，自然冷却至室温，得到硅基复合材料。
实施例6
将20gD50粒径＝50nm的纳米硅材料，6gNa2CO3，4g柠檬酸，添加到100g丙醇中。利用高速分散机混合分散均匀形成浆料，对浆料进行喷雾干燥，得到实心硅基复合材料前驱体。将得到实心硅基复合材料前驱体进行热处理，在气氛炉中通入高纯保护性气体氮气，以1℃/min升温至900℃，保温3h，自然冷却至室温，再将烧结后的材料水洗、过滤和干燥处理，得到中空/多孔结构硅基复合材料前驱体。先将15％(按有机物裂解碳的质量占所述硅基复合材料总质量的百分比计算)沥青、85％中空/多孔结构硅基复合材料前驱体和酒精利用高速分散机混合分散均匀形成混合料，通过调节酒精的添加量来控制混合料的固含量为20％，对混合料进行喷雾干燥，对喷雾后的物料进行热处理，在气氛炉中通入高纯保护性气体氮气，以1℃/min升温至900℃，保温3h，自然冷却至室温，得到一次碳包覆产物；将得到一次碳包覆产物置于回转炉中，调节回转速度为1.5rpm，通入保护性气体氮气，以5℃/min升温至900℃，以1.5L/min速率通入甲烷气体20min，保温2h，自然冷却至室温，得到硅基复合材料。
采用以下方法对比较例1～2及实施例1～6进行测试：
取比较例1～2及实施例1～6制备的材料作为负极材料，与粘结剂聚偏二氟乙烯(PVDF)、导电剂(Super-P)按照70:15:15的质量比混合，加入适量的N-甲基吡咯烷酮(NMP)作为溶剂调成浆料，涂覆在铜箔上，并经真空干燥、辊压，制备成负极片；采用金属锂片作为对电极，使用1mol/L的LiPF6三组分混合溶剂按EC:DMC:EMC＝1:1:1(v/v)混合的电解液，采用聚丙烯微孔膜为隔膜，在充满惰性气体手套箱中组装成CR2032型扣式电池。扣式电池的充放电测试在武汉市蓝电电子股份有限公司LANHE电池测试系统上，在常温条件，0.1C恒流充放电，充放电电压限制在0.005～1.5V。
采用如下方法测试和计算材料体积膨胀率：膨胀率＝(50周循环后极片厚度-循环前极片厚度)/(循环前极片厚度-铜箔厚度)*100％。
测试结果如表1所示：
表1为比较例1～2及实施例1～6性能测试评价结果
Figure PCTCN2018123634-appb-000001
根据上述说明书的揭示和教导，本发明所属领域的技术人员还可以对上述实施方式进行变更和修改。因此，上述说明并非对发明的限制，本发明并不局限于上面揭示和描述的具体实施方式，对发明的一些修改和变更如本技术领域的普通技术人员在实施例的实质范围内对各原料的等效替换及辅助成分的添加、具体方式的选择等做出的变化、改型、添加或替换等变型，也应当落入本发明的权利要求的保护范围内。

Claims (10)

  1. 一种中空/多孔结构硅基复合材料，其特征在于，该中空/多孔结构硅基复合材料包括中空/多孔结构、硅碳复合层和包覆层；所述硅碳复合层是纳米硅或氧化硅均匀的分散在导电碳网中而形成。
  2. 如权利要求1所述的中空/多孔结构硅基复合材料，其特征在于，所述的硅碳复合层中导电碳网络由粘结剂高温裂解形成；所述包覆层为碳包覆层，碳包覆层至少为一层，单层厚度为0.2-3μm。
  3. 如权利要求1所述的中空/多孔结构硅基复合材料，其特征在于，该中空/多孔结构硅基复合材料中心为空心结构或是由多个小粒径、内部空心/多孔结构的二次粒子形成的复合结构；该中空/多孔结构硅基复合材料内部的空腔占复合材料总体积的10-80％；所述二次粒子中的空腔占二次粒子总体积的10-80％，二次粒子的粒度D50为1-10μm。
  4. 如权利要求1所述的中空/多孔结构硅基复合材料，其特征在于，该中空/多孔结构硅基复合材料的粒度D50为1-20μm，比表面积为1-30m2/g，真密度为1-3g/cm3。
  5. 一种权利要求1-4任一所述中空/多孔结构硅基复合材料的制法，其特征在于，包括下列步骤：
    S1：将纳米硅材料、粘结剂和盐加入溶剂中，利用高速分散机混合分散均匀形成浆料，对所述浆料进行喷雾干燥，得到实心硅基复合材料前驱体；
    S2：将所述实心硅基复合材料前驱体在保护气氛下以及500～1200℃进行高温烧结使得粘结剂碳化得到硅碳复合层，在烧结后经水洗去除盐、过滤和干燥处理，得到中空/多孔结构硅基复合材料前驱体；
    S3：将所述中空/多孔结构硅基复合材料前驱体进行碳包覆，即得中空/多孔结构硅基复合材料。
  6. 如权利要求5所述的中空/多孔结构硅基复合材料的制法，其特征在于，所述的纳米硅材料为纳米硅或纳米氧化亚硅，纳米硅为单晶纳米硅、多晶纳米硅或非晶纳米硅中任一种或多种；纳米硅材料中晶粒大小为1-40nm的单晶或多晶，硅材料粒度D50为5-300nm，纳米氧化亚硅(SiOx)中X为 0.8-1.5。
  7. 如权利要求5所述的中空/多孔结构硅基复合材料的制法，其特征在于，所述的粘结剂为蔗糖、葡萄糖、柠檬酸、聚吡咯烷酮和PVDF中的任一种或几种；所述的纳米硅材料和粘结剂的添加质量比为60:40～99:1；所述的溶剂为有机溶剂，为醇类溶剂、酮类溶剂、烷类溶剂、N-甲基吡咯烷酮、四氢呋喃、甲苯中的一种或几种，其中醇类溶剂为乙醇、甲醇、丙醇、乙二醇、异丙醇、正辛醇、丙烯醇、辛醇中的一种或几种，酮类溶剂为丙酮、甲基丁酮、甲基异丁酮、甲乙酮、甲异丙酮、环已酮、甲已酮中的一种或几种，烷类溶剂为环己烷、正己烷、异庚烷、3,3-二甲基戊烷、3-甲基己烷中的一种或几种；添加溶剂量控制浆料的固含量为5～50％；所述的盐为溶于水而不溶或微溶于有机溶剂的盐类，为Na2CO3、Ca(NO2)2、NaCl、KCl、CuCl2、NiCl2、FeSO4、MgSO4、CuSO4中的一种或几种；所述纳米硅材料与所述盐的质量比为1:99～99:1。
  8. 如权利要求5所述的中空/多孔结构硅基复合材料的制法，其特征在于，所述的碳包覆为高温裂解包覆，采用一次碳包覆或者二次碳包覆；采用二次碳包覆时，第二次碳包覆的包覆量按质量计为第一次碳包覆包覆量的0.1～10倍，所述碳包覆形成的包覆层厚度为10～2000nm。
  9. 如权利要求5所述的中空/多孔结构硅基复合材料的制法，其特征在于，所述的碳包覆为液相碳包覆，包括如下过程：将有机物碳源、待包覆物与溶剂利用高速分散机混合分散均匀，形成浆料，对浆料进行喷雾干燥，再进行热处理，在气氛炉中通入高纯保护性气体，以≦10℃的升温速率升温至400～1200℃进行烧结，保温0.5～10h，自然冷却至室温，得到液相包覆产物；所述有机物碳源加入量为有机物裂解碳的质量占有机物裂解碳与待包覆物生成的复合材料的总质量的1～99wt％；所述溶剂的添加量为控制浆料的固含量为5～50％。
  10. 如权利要求5所述的中空/多孔结构硅基复合材料的制法，其特征在于，所述的碳包覆为气相碳包覆，包括如下过程：将待包覆物置于CVD炉中，通入保护性气体，以1～15℃/min升温至500～1200℃，以0.5～20.0L/min通入 速率通入有机碳源气体，保温0.5～20h，自然冷却至室温，得到气相包覆产物。
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