WO2021143855A1 - 微米硅碳复合负极材料、制备方法、负极极片以及锂离子电池 - Google Patents

微米硅碳复合负极材料、制备方法、负极极片以及锂离子电池 Download PDF

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WO2021143855A1
WO2021143855A1 PCT/CN2021/072182 CN2021072182W WO2021143855A1 WO 2021143855 A1 WO2021143855 A1 WO 2021143855A1 CN 2021072182 W CN2021072182 W CN 2021072182W WO 2021143855 A1 WO2021143855 A1 WO 2021143855A1
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micron silicon
carbon
negative electrode
electrode material
particles
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PCT/CN2021/072182
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French (fr)
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杨全红
陈凡奇
韩俊伟
肖菁
孔德斌
陶莹
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天津大学
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Priority to KR1020227028212A priority Critical patent/KR20220122772A/ko
Priority to JP2021550276A priority patent/JP7261509B2/ja
Priority to US17/784,238 priority patent/US20230037323A1/en
Priority to EP21740650.3A priority patent/EP4092785A1/en
Publication of WO2021143855A1 publication Critical patent/WO2021143855A1/zh

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
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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
    • 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
    • C01B32/182—Graphene
    • C01B32/198—Graphene oxide
    • 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
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    • 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
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    • H01M4/04—Processes of manufacture in general
    • H01M4/0402—Methods of deposition of the material
    • H01M4/0421—Methods of deposition of the material involving vapour deposition
    • H01M4/0428—Chemical vapour deposition
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    • H01M4/0471—Processes of manufacture in general involving thermal treatment, e.g. firing, sintering, backing particulate active material, thermal decomposition, pyrolysis
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/366—Composites as layered products
    • H—ELECTRICITY
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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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    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • H01M4/386—Silicon or alloys based on silicon
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • 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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    • H01M4/02—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
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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
    • H01M4/624—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
    • C01P2006/00—Physical properties of inorganic compounds
    • C01P2006/10—Solid density
    • 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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    • H01M2004/021—Physical characteristics, e.g. porosity, surface area
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/027—Negative electrodes
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • This application relates to the field of battery technology, and in particular to a micron silicon-carbon composite negative electrode material, a preparation method of the micron silicon-carbon composite negative electrode material, a negative pole piece, and a lithium ion battery.
  • silicon As a new generation of lithium-ion battery anode material, silicon has abundant reserves, and the theoretical lithium storage capacity is the highest among all alloyed lithium storage elements, so it has great potential to replace graphite as a commercial lithium-ion battery anode material. At this stage, significant results have been achieved in related research on silicon anodes. However, a large number of applications of nanotechnology, including the use of nano-silicon as an active material to construct electrode materials and nano-designs of carbon structures, reduce the tap density and electrode density of the material, thereby restricting the improvement of the volumetric performance of silicon anodes.
  • Micron silicon with an average particle size distribution of 3 to 5 ⁇ m has the characteristics of low cost and high tap density, thereby effectively avoiding the inherent defects of nano silicon.
  • the ability of the active particles to effectively buffer internal stress decreases.
  • the traditional surface carbon coating structure cannot effectively guarantee its cycle stability. This is because the silicon material will produce a great volume expansion during the battery cycle.
  • the expansion of silicon is Anisotropy.
  • silicon particles of micrometers and different sizes it is difficult to accurately design a space for buffering volume expansion for each particle; on the other hand, the existence of the above-mentioned space makes it difficult for the silicon material to be maintained during the pole piece compaction process. Its completeness.
  • the present application provides a method for preparing a micron silicon-carbon composite negative electrode material.
  • the micron silicon-carbon composite negative electrode material prepared by the method can not only effectively buffer the expansion of internal micron-scale silicon particles, but also can withstand the external compaction process. pressure.
  • this application also provides a micron silicon-carbon composite negative electrode material prepared by the method.
  • the present application also provides a negative electrode sheet including the micron silicon-carbon composite negative electrode material.
  • the present application also provides a lithium ion battery including the negative pole piece.
  • This application provides a method for preparing a micron silicon-carbon composite negative electrode material, which includes the following steps:
  • micron silicon particles are subjected to a chemical vapor deposition reaction in a carbon-containing gas atmosphere to obtain carbon-coated micron silicon first particles, wherein the mass ratio of the carbon in the carbon-coated micron silicon first particles is 7%-38%;
  • the carbon-coated micron silicon second particles and graphene oxide are dispersed in a second mixed solvent to obtain a mixed solution, and the mixed solution is hydrothermally reacted to obtain reduced graphene oxide-carbon silicon composite water Gel;
  • the hydrogel is heated to remove moisture in the hydrogel, thereby obtaining the micron silicon-carbon composite negative electrode material.
  • This application also provides a micron silicon-carbon composite negative electrode material prepared by the preparation method, and the density of the micron silicon-carbon composite negative electrode material is 0.8-1.2 g/cm 3 .
  • the application also provides a negative pole piece, which includes the micron silicon-carbon composite negative electrode material.
  • the present application also provides a lithium ion battery, which includes a positive pole piece and the negative pole piece.
  • the micron silicon-carbon composite negative electrode material prepared by the method in this application has a multi-level buffer structure, and the micron silicon-carbon composite negative electrode material can effectively buffer the expansion of the internal micron-scale silicon particles, and at the same time can withstand the external compaction process.
  • the pressure makes the negative pole piece and the lithium ion battery prepared by the micron silicon-carbon composite negative electrode material have the characteristics of long cycle life.
  • FIG. 1 is a TEM image and an EDS spectrum of the carbon-coated micron silicon second particles prepared in Example 1 of the application.
  • FIG. 3 is an SEM image of the micron silicon-carbon composite negative electrode material prepared in Example 1 of the application.
  • Example 4 is a TEM image of the micron silicon-carbon composite negative electrode material prepared in Example 1 of the application.
  • FIG. 5 is a graph showing the cycle performance of a lithium ion battery negative electrode constructed with micron silicon particles, carbon-coated micron silicon second particles, and a micron silicon-carbon composite negative electrode material prepared in different steps in Example 1 of the application.
  • Some embodiments of the present application provide a method for preparing a micron silicon-carbon composite negative electrode material, which includes the following steps:
  • Step S11 the micron silicon particles are subjected to a chemical vapor deposition reaction in a carbon-containing gas atmosphere to obtain carbon-coated micron silicon first particles, wherein the carbon is in the carbon-coated micron silicon first particles
  • the mass ratio is 7% to 18%.
  • micron silicon particles with a particle size distribution range of 3 ⁇ m to 5 ⁇ m are placed in a loading container, and the loading container in which the micron silicon particles are placed is placed in a reaction container, and the process is carried out in a carbon-containing gas atmosphere. Chemical vapor deposition reaction to obtain carbon-coated micron silicon first particles.
  • the carbon-containing gas is methane.
  • the loading container is a crucible.
  • the reaction vessel is a tube furnace.
  • the chemical vapor deposition reaction includes:
  • the heating stage is carried out under an argon atmosphere, the flow rate of the argon gas is 30-50 mL/min, and the heating rate is 5-10°C/min;
  • the constant temperature stage is carried out under a mixed atmosphere of methane and argon, the flow rate of the methane is 30-50mL/min, the flow rate of the argon gas is 30-50mL/min, the constant temperature temperature is 900 ⁇ 1000°C, and the constant temperature time 40 ⁇ 60min; and
  • the cooling stage is carried out under an argon atmosphere, the flow rate of the argon gas is 30-50 mL/min, the cooling rate is 5-10° C./min, and the temperature is cooled down naturally. Wherein, in the cooling stage, the temperature may be lowered to 400° C. and then naturally cooled.
  • the carbon coating layer obtained by chemical vapor deposition (that is, the carbon in the carbon-coated micron silicon first particles) has a higher degree of graphitization, Therefore, the electrical conductivity and mechanical properties are better.
  • Step S12 dispersing the carbon-coated micron silicon first particles in a first mixed solvent to obtain a dispersion.
  • the carbon-coated micron silicon first particles are dispersed in the first mixed solvent by ultrasound to obtain a uniform dispersion.
  • the first mixed solvent is a mixed solvent of water and ethanol.
  • the volume ratio of water and ethanol may be 0.8:1 to 1:1.
  • the ethanol in the first mixed solvent is beneficial to disperse the carbon-coated micron silicon first particles, and the water in the first mixed solvent is beneficial to dissolve the alkali added later.
  • the concentration of the carbon-coated micron silicon first particles is 1 to 3 mg/mL.
  • Step S13 adding an alkali to the dispersion liquid and heating, so that the alkali etches part of the micron silicon particles to obtain carbon-coated second micron silicon particles.
  • an alkali is added to the dispersion liquid, and the dispersion liquid is heated so that the alkali etches the micron silicon particles, and the hydrogen generated by the etching escapes from the dispersion liquid.
  • the micron silicon particles can be etched to different degrees, and then the dispersion is sequentially sonicated and filtered, and the filter residue obtained after filtering is washed and dried to obtain carbon-coated micron silicon second particles.
  • the etching can generate a gap between the carbon coating layer and the second micron silicon particles, that is, there is a suitable space between the carbon coating layer and the second micron silicon particles.
  • the space can buffer the expansion of the volume of the micron silicon particles.
  • the base includes at least one of sodium hydroxide and potassium hydroxide.
  • the concentration of the alkali is 0.5-1 mol/L.
  • the heating temperature of the dispersion is 70-80°C.
  • the ultrasound time is 4-10 minutes.
  • the washing may be alternately washed with water and ethanol.
  • the drying temperature is 70-80°C.
  • Step S14 Disperse the carbon-coated micron silicon second particles and graphene oxide in a second mixed solvent to obtain a mixed solution, and perform a hydrothermal reaction on the mixed solution to obtain reduced graphene oxide-carbon silicon Composite hydrogel.
  • the carbon-coated micron silicon second particles and graphene oxide are ultrasonically dispersed in a second mixed solvent to obtain a mixed solution, and then the mixed solution is added to a hydrothermal reaction kettle for hydrothermal reaction , So as to reduce the graphene oxide to obtain a reduced graphene oxide-carbon silicon composite hydrogel.
  • the mass ratio of the carbon-coated micron silicon second particles to the graphene oxide is 2:1 to 3:1.
  • the concentration of the graphene oxide is 1.5-2 mol/L.
  • the second mixed solvent is a mixed solvent of water and ethanol.
  • the volume ratio of water and ethanol may be 0.8:1 to 1:1.
  • the temperature of the hydrothermal reaction is 180-200° C.
  • the time of the hydrothermal reaction is 6-10 h.
  • Step S15 heating the hydrogel to remove moisture in the hydrogel, thereby obtaining the micron silicon-carbon composite negative electrode material.
  • the reduced graphene oxide in the hydrogel shrinks to form a dense three-dimensional network, and the carbon-coated micron silicon second particles are dispersed in the three-dimensional reduced graphene oxide. Network.
  • the temperature for removing water is 60-80°C, and the time for removing water is 24 to 48 hours.
  • Some embodiments of the present application also provide a micron silicon-carbon composite negative electrode material prepared by the method, and the density of the micron silicon-carbon composite negative electrode material is 0.8-1.2 g/cm 3 .
  • micron-scale silicon-carbon composite negative electrode material Select a micron-scale area on the micron-scale silicon-carbon composite negative electrode material, and test the mechanical properties of the micron-scale silicon-carbon composite negative electrode material in the micron-scale area.
  • the test results show that the micron-scale area is Inside, the micron silicon-carbon composite negative electrode material exhibits a high yield strength greater than 150 MPa and a yield strain of 8.6%.
  • the micron silicon-carbon composite negative electrode material exhibits a strength as high as 1.7 GPa and a high plasticity of 15%.
  • Some embodiments of the present application also provide a negative pole piece, which includes the micron silicon-carbon composite negative electrode material.
  • Some embodiments of the present application also provide a lithium ion battery, which includes a positive pole piece and the negative pole piece.
  • the tube furnace was heated to 1000° C. at a temperature increase rate of 10° C./min, and then methane gas was introduced at this temperature with a flow rate of 50 mL/min and a reaction time of 60 min. After the reaction, the methane gas was turned off, the argon gas flow rate remained unchanged, and the temperature was lowered to 400° C. at a rate of 10° C./min and then naturally cooled to room temperature to obtain carbon-coated micron silicon first particles.
  • 500 mg of the carbon-coated micron silicon first particles are ultrasonically dispersed in a mixed solvent of 100 mL of water and 100 mL of ethanol to obtain a uniform dispersion.
  • the third step 6 g of sodium hydroxide was added to the dispersion, and the temperature of the dispersion was heated to 80° C. and maintained for 15 minutes. When bubbles are generated in the dispersion liquid, it is ultrasonicated for 5 minutes, then filtered, washed alternately with water and ethanol, and dried at 70° C. to obtain SiMP@C coated micron silicon second particles.
  • the fourth step 300 mg of the SiMP@C and 150 mg of graphene oxide were dispersed in a mixed solvent of 50 mL of water and 50 mL of ethanol by ultrasound to obtain a mixed solution, and then the mixed solution was added to the hydrothermal reaction kettle at 180 The hydrothermal reaction was carried out at °C for 6h to obtain the reduced graphene oxide-carbon silicon composite hydrogel.
  • the obtained hydrogel was dried at 70° C. for 24 hours to obtain SiMP@C-GN, a micron silicon-carbon composite negative electrode material.
  • Example 2 The difference between Example 2 and Example 1 is that the flow rate of the methane gas introduced in the first step is 30 mL/min.
  • Example 3 The difference between Example 3 and Example 1 is that in the first step, the tube furnace is heated to 950°C at a heating rate of 7°C/min under an argon flow rate of 40 mL/min, and then at this temperature Methane gas was introduced, the flow rate was 50 mL/min, and the reaction time was 40 min. After the reaction, the methane gas was turned off, the argon gas flow rate remained unchanged, and the temperature was lowered to 400°C at a rate of 7°C/min and then naturally cooled to room temperature.
  • Example 4 The difference between Example 4 and Example 1 is that in the fourth step, the amount of SiMP@C is 400 mg, the amount of water is 40 mL, and the amount of ethanol is 60 mL.
  • Example 5 The difference between Example 5 and Example 1 is that the amount of sodium hydroxide used in the third step is 4 g.
  • Example 6 The difference between Example 6 and Example 1 is that in the third step, the sodium hydroxide is changed to potassium hydroxide.
  • Example 7 The difference between Example 7 and Example 1 is that when bubbles are generated in the dispersion liquid, it is ultrasonicated for 8 minutes.
  • Example 8 The difference between Example 8 and Example 1 is that in the fourth step, the amount of SiMP@C is 250 mg, the amount of water is 60 mL, and the amount of ethanol is 40 mL.
  • Example 9 The difference between Example 9 and Example 1 is that the amount of graphene oxide used in the fourth step is 170 mg.
  • Example 10 The difference between Example 10 and Example 1 is that the drying temperature in the fifth step is 80°C.
  • the carbon-coated micron silicon first particles obtained in the first step of Example 1 were directly used as the micron silicon-carbon composite negative electrode material.
  • the carbon-coated micron silicon second particles SiMP@C obtained in the third step of Example 1 were directly used as the micron silicon-carbon composite negative electrode material.
  • the first step place 1.0g of micron silicon particles with a particle size distribution ranging from 3 ⁇ m to 5 ⁇ m in the crucible, and transfer the crucible with the micron silicon particles to the tube furnace, under an argon flow rate of 50 mL/min ,
  • the tube furnace was heated to 1000°C at a temperature increase rate of 10°C/min, and then methane gas was introduced at this temperature with a flow rate of 50 mL/min and a reaction time of 60 minutes.
  • the methane gas was turned off, the argon gas flow rate remained unchanged, and the temperature was lowered to 400° C. at a rate of 10° C./min and then naturally cooled to room temperature to obtain carbon-coated micron silicon first particles.
  • the obtained hydrogel was dried at 70° C. for 24 hours to obtain SiMP@C-GN, a micron silicon-carbon composite negative electrode material.
  • Comparative Example 4 The difference between Comparative Example 4 and Example 1 is that in the first step, silicon particles with a particle size distribution ranging from 3 ⁇ m to 5 ⁇ m are changed to nano-silicon particles.
  • the first to third steps in Comparative Example 5 are the same as the first to third steps in Example 1. Please refer to Example 1 for details.
  • the composite material is heat-treated at 800° C. for 2 h at an argon flow rate of 50 mL/min at a temperature increase rate of 5° C./min to obtain a micron silicon-carbon composite negative electrode material.
  • the carbon coating layer in the carbon-coated micron silicon second particles SiMP@C achieves good coating of internal silicon particles, and A suitable space is reserved between the two.
  • the carbon coating layer in the carbon-coated micron silicon first particles has poor coverage of the internal silicon particles, and the two The distance between them is quite different.
  • the continuous and dense reduced graphene oxide network closely connects the dispersed micron silicon-carbon active particles and firmly defines the micron inside. Silicon carbon active particles.
  • micron silicon particle SiMP prepared in different steps in Example 1 the carbon-coated micron silicon second particle SiMP@C, and the micron silicon-carbon composite anode material SiMP@C-GN were used to construct lithium-ion battery anodes, and their cycles were tested. performance.
  • the electrode constructed by SiMP@C-GN can maintain a specific capacity of 750mAh/g even after 1,000 cycles.
  • the specific capacity of the electrode constructed by SiMP@C after 1000 cycles is only 300 mAh/g, while the specific capacity of the electrode constructed by SiMP after 20 cycles is less than 400 mAh/g.
  • the multi-layer buffer structure of the micron silicon-carbon composite negative electrode material in the present application has good effectiveness, and at the same time highlights the role of the continuous dense redox graphene of the outer layer as a conductive network and a buffer network.
  • Electrolyte Ethylene carbonate/diethyl carbonate (EC/DEC, 1:1, v/v) containing 10vol% fluoroethylene carbonate (FEC) and 1vol% vinylene carbonate (VC) additives, in 1A
  • FEC fluoroethylene carbonate
  • VC vinylene carbonate
  • Example 1 by comparing Example 1 with Examples 2 and 3, it can be seen that when the content of the carbon coating layer of the chemical vapor deposition is reduced, the silicon active particles inside cannot be effectively protected, and the cycle stability of the material is reduced.
  • Example 1 and Examples 4, 8 and 9, and Example 1 and Comparative Examples 1 and 2 it can be seen that as the relative content of graphene in the outer layer of the composite material decreases until it disappears, the stress buffering effect is weakened, and the cycle of the material is stable sexual decline.
  • Example 1 Third, by comparing Example 1 with Example 7, and Comparative Example 3, it can be seen that as the etching degree increases, the overall cycle stability of the material is improved, but due to the decrease of active material, the capacity that can be exerted is correspondingly reduced.
  • Example 1 Fourth, by comparing Example 1 with Comparative Example 4, it can be seen that when nano-silicon is used as a raw material, although the cycle performance of the material is slightly improved, its density is much lower than that of a composite material prepared with micro-silicon as a raw material.
  • the application of multi-layer buffer structure to micron silicon anode can obtain higher volume performance.
  • micron silicon-carbon composite negative electrode material prepared by the method in this application is a strong and tough multi-stage buffer structure, which can stabilize the micron silicon particles crushed during the circulation process internally, and can resist externally the pressure during the compaction of the pole piece. huge stress.
  • the inner layer of highly graphitized carbon shell and suitable space have excellent mechanical flexibility, which can effectively stabilize the inner micron silicon particles and protect the fresh surface exposed by rupture, while the outer layer is densely contracted and reduced graphene oxide network
  • the internal silicon-carbon active particles SiMP@C
  • the electrode structure is strengthened and toughened, so as to achieve effective mechanical buffering and continuous and rapid electron transfer in the process of deintercalating lithium.
  • the dense network of redox graphene with high strength and high modulus that is assembled and overlapped between the layers can maintain the structural integrity of the internal silicon-carbon active particles during the compaction process to the greatest extent.
  • micron silicon-carbon composite negative electrode material prepared in this application is used as a lithium-ion battery negative electrode (compact density 1.0g/cm 3 ), which can achieve an ultra-long cycle life of 1000 cycles and maintain a high capacity (750mAh/cm3). g) It is of great significance for the practical application of micron silicon anode.

Abstract

一种微米硅碳复合负极材料的制备方法，包括以下步骤：将微米硅颗粒进行化学气相沉积反应，得到碳包覆的微米硅第一颗粒；将所述碳包覆的微米硅第一颗粒分散于第一混合溶剂中，得到分散液；将碱加入到所述分散液中后加热，得到碳包覆的微米硅第二颗粒；将所述碳包覆的微米硅第二颗粒和氧化石墨烯分散于第二混合溶剂中，并进行水热反应，得到水凝胶；以及加热所述水凝胶后得到所述微米硅碳复合负极材料。所述方法制备的微米硅碳复合负极材料既能有效缓冲内部微米级硅颗粒的膨胀，同时又能承受外部压实过程的压力。一种由所述方法制备的微米硅碳复合负极材料以及负极极片和锂离子电池。

Description

微米硅碳复合负极材料、制备方法、负极极片以及锂离子电池 技术领域
本申请涉及电池技术领域，尤其涉及一种微米硅碳复合负极材料、所述微米硅碳复合负极材料的制备方法、负极极片以及锂离子电池。
背景技术
硅作为新一代锂离子电池负极材料，储量丰富，且理论储锂比容量在所有合金化储锂元素中最高，因而具备取代石墨成为商用锂离子电池负极材料的巨大潜力。现阶段，对于硅负极的相关研究已取得显著的成果。但是，纳米化技术的大量应用，包括采用纳米硅作为活性物质来构筑电极材料和碳结构的纳米设计，降低了材料的振实密度和电极密度，从而制约了硅负极体积性能的提升。
平均粒径分布在3～5μm的微米硅具有成本低廉、振实密度高等特点，从而有效规避了纳米硅的固有缺陷。然而，随着尺寸增加，活性颗粒有效缓冲内应力的能力降低。有研究表明，当硅活性颗粒的尺寸超过150nm时，其在充放电过程中就会在内应力作用下破碎成更小的纳米颗粒，不仅导致部分活性物质失去电接触，同时造成材料比表面积增加，暴露出新鲜的硅表面，使得SEI膜在颗粒表面持续重复生长，严重制约了其循环稳定性。
进一步地，对于微米硅负极，传统的表面碳包覆结构无法有效地保证其循环稳定性，这是因为，硅材料在电池循环过程中会产生极大的体积膨胀，一方面，硅的膨胀为各向异性，对于微米级且尺寸不一的硅颗粒，难以针对每个颗粒精确设计用于缓冲体积膨胀的空间；另一方面，上述空间的存在使得硅材料难以在极片压实过程中保持其完整性。
发明内容
有鉴于此，本申请提供一种微米硅碳复合负极材料的制备方法，所述方法制备的微米硅碳复合负极材料既能有效缓冲内部微米级硅颗粒的膨胀，同时又能承受外部压实过程的压力。
另，本申请还提供一种所述方法制备的微米硅碳复合负极材料。
另，本申请还提供一种包括所述微米硅碳复合负极材料的负极极片。
另，本申请还提供一种包括所述负极极片的锂离子电池。
本申请提供一种微米硅碳复合负极材料的制备方法，包括以下步骤：
将微米硅颗粒在含碳的气体氛围中进行化学气相沉积反应，得到碳包覆的微米硅第一颗粒，其中，所述碳在所述碳包覆的微米硅第一颗粒中的质量比为7％-38％；
将所述碳包覆的微米硅第一颗粒分散于第一混合溶剂中，得到分散液；
将碱加入到所述分散液中后加热，使所述碱对部分所述微米硅颗粒进行刻蚀，得到碳包覆的微米硅第二颗粒；
将所述碳包覆的微米硅第二颗粒和氧化石墨烯分散于第二混合溶剂中，得到混合液，并对所述混合液进行水热反应，得到还原氧化石墨烯-碳硅复合的水凝胶；以及
加热所述水凝胶以脱除所述水凝胶中的水分，从而得到所述微米硅碳复合负极材料。
本申请还提供一种所述制备方法制备的微米硅碳复合负极材料，所述微米硅碳复合负极材料的密度为0.8～1.2g/cm 3。
本申请还提供一种负极极片，所述负极极片包括所述微米硅碳复合负极材料。
本申请还提供一种锂离子电池，所述锂离子电池包括正极极片以及所述负极极片。
本申请中的所述方法制备的微米硅碳复合负极材料具有多级缓冲结构， 所述微米硅碳复合负极材料既能有效缓冲内部微米级硅颗粒的膨胀，同时又能承受外部压实过程的压力，从而使得所述微米硅碳复合负极材料制备的负极极片和锂离子电池具有长循环寿命的特点。
附图说明
图1为本申请实施例1制备的碳包覆的微米硅第二颗粒的TEM图以及EDS谱图。
图2为本申请对比例3制备碳包覆的微米硅第一颗粒的TEM图以及EDS谱图。
图3为本申请实施例1制备的微米硅碳复合负极材料的SEM图。
图4为本申请实施例1制备的微米硅碳复合负极材料的TEM图。
图5为本申请实施例1不同步骤制备的微米硅颗粒、碳包覆的微米硅第二颗粒、以及微米硅碳复合负极材料分别构建的锂离子电池负极的循环性能图。
具体实施方式
下面将结合本申请实施例中的附图，对本申请实施例中的技术方案进行清楚、完整地描述，显然，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他实施例，都属于本申请保护的范围。
除非另有定义，本文所使用的所有的技术和科学术语与属于本申请的技术领域的技术人员通常理解的含义相同。本文中在本申请的说明书中所使用的术语只是为了描述具体的实施例的目的，不是旨在于限制本申请。
为能进一步阐述本申请达成预定目的所采取的技术手段及功效，以下结合附图及较佳实施方式，对本申请作出如下详细说明。
请参阅图1，本申请一些实施例提供一种微米硅碳复合负极材料的制备方法，包括以下步骤：
步骤S11，将微米硅颗粒在含碳的气体氛围中进行化学气相沉积反应，得到碳包覆的微米硅第一颗粒，其中，所述碳在所述碳包覆的微米硅第一颗粒中的质量比为7％～18％。
具体地，将粒径分布范围为3μm～5μm的微米硅颗粒放置在装载容器中，并将放置有所述微米硅颗粒的所述装载容器置于反应容器中，在含碳的气体氛围中进行化学气相沉积反应，得到碳包覆的微米硅第一颗粒。
在一些实施例中，所述含碳的气体为甲烷。
在一些实施例中，所述装载容器为坩埚。
在一些实施例中，所述反应容器为管式炉。
在一些实施例中，所述化学气相沉积反应包括：
升温阶段，在氩气气氛下进行，所述氩气的流量为30～50mL/min，升温的速率为5～10℃/min；
恒温阶段，在甲烷和氩气混合气氛下进行，所述甲烷的流量为30～50mL/min，所述氩气的流量为30～50mL/min，恒温的温度为900～1000℃，恒温的时间为40～60min；以及
降温阶段，在氩气气氛下进行，所述氩气的流量为30～50mL/min，降温的速率为5～10℃/min，降温后自然冷却。其中，在所述降温阶段，可降温至400℃后自然冷却。
相比于聚合物热解得到的碳包覆层，化学气相沉积得到的碳包覆层(即所述碳包覆的微米硅第一颗粒中的所述碳)具有较高的石墨化程度，因而电导率和机械性能更优。
步骤S12，将所述碳包覆的微米硅第一颗粒分散于第一混合溶剂中，得到分散液。
具体地，将所述碳包覆的微米硅第一颗粒通过超声分散于第一混合溶剂中，得到均匀的分散液。
在一些实施例中，所述第一混合溶剂为水和乙醇的混合溶剂。其中，在所述第一混合溶剂中，水和乙醇的体积比可为0.8:1～1:1。其中，所述第一混合溶剂中的乙醇有利于分散所述碳包覆的微米硅第一颗粒，所述第一混合溶剂中的水有利于溶解后续加入的碱。
在所述分散液中，所述碳包覆的微米硅第一颗粒的浓度为1～3mg/mL。
步骤S13，将碱加入到所述分散液中后加热，使所述碱对部分所述微米硅颗粒进行刻蚀，得到碳包覆的微米硅第二颗粒。
具体地，将碱加入到所述分散液中，并加热所述分散液使所述碱刻蚀所述微米硅颗粒，刻蚀产生的氢气从所述分散液中逸出，通过控制反应的时间可以使所述微米硅颗粒达到不同的刻蚀程度，随后对该所述分散液依次进行超声和过滤，并对过滤后得到的滤渣进行洗涤和干燥，得到碳包覆的微米硅第二颗粒。
其中，所述刻蚀可使所述碳包覆层与所述微米硅第二颗粒之间产生间隙，即在所述碳包覆层与所述微米硅第二颗粒之间具有合适的空间。所述空间可缓冲所述微米硅颗粒体积的膨胀。
在一些实施例中，所述碱包括氢氧化钠以及氢氧化钾中的至少一种。在所述分散液中，所述碱的浓度为0.5～1mol/L。
在一些实施例中，所述分散液的加热温度为70～80℃。
在一些实施例中，所述超声的时间为4～10min。
在一些实施例中，所述洗涤可采用水和乙醇交替洗涤。
在一些实施例中，所述干燥的温度为70～80℃。
步骤S14，将所述碳包覆的微米硅第二颗粒和氧化石墨烯分散于第二混合溶剂中，得到混合液，并对所述混合液进行水热反应，得到还原氧化石墨烯-碳硅复合的水凝胶。
具体地，将所述碳包覆的微米硅第二颗粒和氧化石墨烯通过超声分散于第二混合溶剂中，得到混合液，随后将所述混合液加入到水热反应釜中进行水热反应，以使所述氧化石墨烯还原，从而得到还原氧化石墨烯-碳硅复合的水凝胶。
在一些实施例中，所述碳包覆的微米硅第二颗粒与所述氧化石墨烯的质量比为2:1～3:1。
在所述混合液中，所述氧化石墨烯的浓度为1.5～2mol/L。
在一些实施例中，所述第二混合溶剂为水和乙醇的混合溶剂。其中，在所述第二混合溶剂中，水和乙醇的体积比可为0.8:1～1:1。
在一些实施例中，所述水热反应的温度为180～200℃，所述水热反应的时间为6～10h。
步骤S15，加热所述水凝胶以脱除所述水凝胶中的水分，从而得到所述微米硅碳复合负极材料。
在所述水分脱除过程中，所述水凝胶中的所述还原氧化石墨烯收缩形成致密的三维网络，所述碳包覆的微米硅第二颗粒分散于所述还原氧化石墨烯的三维网络中。
在一些实施例中，所述水分脱除的温度为60～80℃，所述水分脱除的时间为24～48h。
本申请一些实施例还提供一种所述方法制备的微米硅碳复合负极材料，所述微米硅碳复合负极材料的密度为0.8～1.2g/cm 3。
在所述微米硅碳复合负极材料上选取一个微米尺度的区域，并测试所述微米尺度的区域内的所述微米硅碳复合负极材料的机械性能，测试结果显示，在所述微米尺度的区域内，所述微米硅碳复合负极材料表现出大于150MPa的高屈服强度和8.6％的屈服应变。同理，在所述纳米尺度的区域内，所述微米硅碳复合负极材料表现出高达1.7GPa的强度和15％的高塑性。
本申请一些实施例还提供一种负极极片，所述负极极片包括所述微米硅碳复合负极材料。
本申请一些实施例还提供一种锂离子电池，所述锂离子电池包括正极极片以及所述负极极片。
下面通过实施例和对比例对本申请进行具体说明。
实施例1
第一步，在坩埚中放置1.0g粒径分布范围为3μm～5μm的微米硅颗粒SiMP，并将放置有所述微米硅颗粒的坩埚转移至管式炉内，在50mL/min的氩气流量下，以10℃/min的升温速率将所述管式炉加热至1000℃，随后在此温度下通入甲烷气体，流量50mL/min，反应时间为60min。反应结束后，关闭甲烷气体，氩气流量保持不变，以10℃/min的速率降温至400℃后自然冷却至室温，得到碳包覆的微米硅第一颗粒。
第二步，将500mg的所述碳包覆的微米硅第一颗粒通过超声分散于100mL水和100mL乙醇的混合溶剂中，得到均匀的分散液。
第三步，将6g的氢氧化钠加入到所述分散液中，并加热所述分散液的温度至80℃，并维持15min。当所述分散液中有气泡产生后，超声5min，随后进行过滤、用水和乙醇交替洗涤，在70℃下干燥得到碳包覆的微米硅第二颗粒SiMP@C。
第四步，将300mg的所述SiMP@C和150mg的氧化石墨烯通过超声分散于50mL水和50mL乙醇的混合溶剂中，得到混合液，随后将所述混合液加入水热反应釜中在180℃下进行水热反应6h，得到还原氧化石墨烯-碳硅复合的水凝胶。
第五步，将所得水凝胶在70℃下干燥24h，得到微米硅碳复合负极材料SiMP@C-GN。
实施例2
实施例2与实施例1的区别在于：在第一步中通入所述甲烷气体的流量为30mL/min。
实施例3
实施例3与实施例1的区别在于：在第一步中在40mL/min的氩气流量下，以7℃/min的升温速率将所述管式炉加热至950℃，随后在此温度下通入甲烷气体，流量50mL/min，反应时间为40min。反应结束后，关闭甲烷气体，氩气流量保持不变，以7℃/min的速率降温至400℃后自然冷却至室温。
实施例4
实施例4与实施例1的区别在于：在第四步中所述SiMP@C用量为400mg，所述水的用量为40mL，所述乙醇的用量为60mL。
实施例5
实施例5与实施例1的区别在于：在第三步中所述氢氧化钠的用量为4g。
实施例6
实施例6与实施例1的区别在于：在第三步中将所述氢氧化钠变更为氢氧化钾。
实施例7
实施例7与实施例1的区别在于：当所述分散液中有气泡产生后，超声8min。
实施例8
实施例8与实施例1的区别在于：在第四步中所述SiMP@C用量为250mg，所述水的用量为60mL，所述乙醇的用量为40mL。
实施例9
实施例9与实施例1的区别在于：在第四步中所述氧化石墨烯的用量为170mg。
实施例10
实施例10与实施例1的区别在于：在第五步中所述干燥的温度为80℃。
对比例1
将实施例1第一步中得到的所述碳包覆的微米硅第一颗粒直接作为微米硅碳复合负极材料。
对比例2
将实施例1第三步中得到的所述碳包覆的微米硅第二颗粒SiMP@C直接作为微米硅碳复合负极材料。
对比例3
第一步，在坩埚中放置1.0g粒径分布范围为3μm～5μm的微米硅颗粒，并将放置有所述微米硅颗粒的坩埚转移至管式炉内，在50mL/min的氩气流量下，以10℃/min的升温速率将所述管式炉加热至1000℃，随后在此温度下通入甲烷气体，流量50mL/min，反应时间为60min。反应结束后，关闭甲烷气体，氩气流量保持不变，以10℃/min的速率降温至400℃后自然冷却至室温，得到碳包覆的微米硅第一颗粒。
第二步，将300mg的所述碳包覆的微米硅第一颗粒和150mg的氧化石墨烯通过超声分散于50mL水和50mL乙醇的混合溶剂中，得到混合液，随后将所述混合液加入水热反应釜中在180℃下进行水热反应6h，得到还原氧化石墨烯-碳硅复合的水凝胶。
第三步，将所得水凝胶在70℃下干燥24h，得到微米硅碳复合负极材料SiMP@C-GN。
对比例4
对比例4与实施例1的区别在于：在第一步中将粒径分布范围为3μm～5μm的硅颗粒变更为纳米硅颗粒。
对比例5
对比例5中的第一步至第三步与实施例1中的第一步至第三步相同，具体请参见实施例1。
第四步，将300mg的所述SiMP@C和150mg的氧化石墨烯通过超声分散于50mL水和50mL乙醇的混合溶剂中，随后进行真空抽滤，70℃下干燥得到复合材料。
第五步，将所述复合材料在50mL/min的氩气流量下，800℃热处理2h，升温速率为5℃/min，得到微米硅碳复合负极材料。
请参阅图1，实施例1制备的微米硅碳复合负极材料中，所述碳包覆的微米硅第二颗粒SiMP@C中的碳包覆层对内部硅颗粒实现了良好的包覆，且二者之间预留有合适的空间。
请参阅图2，对比例3制备的微米硅碳复合负极材料中，所述碳包覆的微米硅第一颗粒中的碳包覆层对内部硅颗粒的包覆性较差，且二者之间的间距相差较大。
请参阅图3和图4，实施例1制备的微米硅碳复合负极材料中，连续致密的还原氧化石墨烯网络将内部分散的微米硅碳活性颗粒紧密连接起来，并牢牢限定其内部的微米硅碳活性颗粒。
将实施例1中不同步骤制备的微米硅颗粒SiMP、碳包覆的微米硅第二颗粒SiMP@C以及微米硅碳复合负极材料SiMP@C-GN分别构建锂离子电池负极，并分别测试其循环性能。
请参阅图5，在1A/g的电流密度下，由SiMP@C-GN构建的电极在循环1000圈后仍能保持750mAh/g的比容量。作为对比，由SiMP@C构建的电极在循环1000圈后的比容量仅剩300mAh/g，而由SiMP构建的电极在循环20圈后比容量就已不足400mAh/g。由此可知，本申请中的所述微米硅碳复合负极材料的多层缓冲结构具有良好的有效性，同时也凸显出外层连续致密氧化还原石墨烯作为导电网络和缓冲网络的作用。
将实施例1–10以及对比例1–4的制备的材料分别与导电碳、粘结剂SBR按照质量比96：2：2制备电极片，以锂片为对电极组装半电池，并采用如下电解液：含有10vol％氟代碳酸乙烯酯(FEC)和1vol％碳酸亚乙烯酯(VC) 添加剂的碳酸乙烯酯/碳酸二乙酯(EC/DEC,1:1,v/v)，在1A/g的电流密度下其性能测试结果如下表所示。
表1 实施例1–10以及对比例1–4制备的电池的测试结果
Figure PCTCN2021072182-appb-000001
由表1可知：
一，通过比较实施例1与实施例2、3可知，当化学气相沉积的碳包覆层含量降低时，内部的硅活性颗粒无法得到有效保护，材料的循环稳定性下降。
二，由实施例1与实施例4、8和9，实施例1与对比例1、2可知，随着复合材料中外层石墨烯相对含量的减少直至消失，应力缓冲效果减弱，材料的循环稳定性下降。
三，通过比较实施例1与实施例7、对比例3可知，随着刻蚀程度的增加，材料整体的循环稳定性有所改善，但由于活性物质减少，所能发挥的容量相应降低。
四，通过比较实施例1与对比例4可知，以纳米硅为原料时，虽然材料的循环性能有些许提高，但其密度远低于以微米硅为原料制备的复合材料，因此本申请中的多层缓冲结构应用于微米硅负极可以获得较高的体积性能。
本申请中的所述方法制备的所述微米硅碳复合负极材料为一种强韧性多级缓冲结构，对内能够稳定循环过程中粉碎的微米硅颗粒，对外能够抵抗极片压实过程中的巨大压力。
具体来说，内层高度石墨化的碳壳以及合适的空间具有优异的机械柔性，可以有效稳定内部的微米硅颗粒，并保护破裂暴露的新鲜表面，而外层致密收缩的还原氧化石墨烯网络不仅将内部的硅碳活性颗粒(SiMP@C)紧密联结成一个力学和电学整体，实现电极结构的增强增韧，从而在脱嵌锂的过程中实现有效的机械缓冲和连续快速的电子传递，同时经过组装、片层之间相互搭接的高强度和高模量的氧化还原石墨烯致密网络能够最大程度地保持内部硅碳活性颗粒在压实过程中结构的完整性。
此外，本申请制备出的所述微米硅碳复合负极材料作为锂离子电池负极(压实密度1.0g/cm 3)，可实现1000圈循环的超长循环寿命并保持较高的容量(750mAh/g)，对于微米硅负极的实用化具有重要意义。
以上说明仅仅是对本申请一种优化的具体实施方式，但在实际的应用过程中不能仅仅局限于这种实施方式。对本领域的普通技术人员来说，根据本申请的技术构思做出的其他变形和改变，都应该属于本申请的保护范围。

Claims (10)

  1. 一种微米硅碳复合负极材料的制备方法，其特征在于，包括以下步骤：
    将微米硅颗粒在含碳的气体氛围中进行化学气相沉积反应，得到碳包覆的微米硅第一颗粒，其中，所述碳在所述碳包覆的微米硅第一颗粒中的质量比为7％～18％；
    将所述碳包覆的微米硅第一颗粒分散于第一混合溶剂中，得到分散液；
    将碱加入到所述分散液中后加热，使所述碱对部分所述微米硅颗粒进行刻蚀，得到碳包覆的微米硅第二颗粒；
    将所述碳包覆的微米硅第二颗粒和氧化石墨烯分散于第二混合溶剂中，得到混合液，并对所述混合液进行水热反应，得到还原氧化石墨烯-碳硅复合的水凝胶；以及
    加热所述水凝胶以脱除所述水凝胶中的水分，从而得到所述微米硅碳复合负极材料。
  2. 如权利要求1所述的微米硅碳复合负极材料的制备方法，其特征在于，所述化学气相沉积反应包括：
    升温阶段，在氩气气氛下进行，所述氩气的流量为30～50mL/min，升温的速率为5～10℃/min；
    恒温阶段，在甲烷和氩气混合气氛下进行，所述甲烷的流量为30～50mL/min，所述氩气的流量为30～50mL/min，恒温的温度为900～1000℃，恒温的时间为40～60min；以及
    降温阶段，在氩气气氛下进行，所述氩气的流量为30～50mL/min，降温的速率为5～10℃/min，降温后自然冷却。
  3. 如权利要求1所述的微米硅碳复合负极材料的制备方法，其特征在于，所述第一混合溶剂为水和乙醇的混合溶剂，在所述第一混合溶剂中，水和乙醇的体积比为0.8:1～1:1，所述第二混合溶剂为水和乙醇的混合溶剂，在所述 第二混合溶剂中，水和乙醇的体积比为0.8:1～1:1。
  4. 如权利要求1所述的微米硅碳复合负极材料的制备方法，其特征在于，在所述分散液中，所述碳包覆的微米硅第一颗粒的浓度为1～3mg/mL。
  5. 如权利要求1所述的微米硅碳复合负极材料的制备方法，其特征在于，在所述分散液中，所述碱的浓度为0.5～1mol/L，所述分散液的加热温度为70～80℃。
  6. 如权利要求1所述的微米硅碳复合负极材料的制备方法，其特征在于，所述碳包覆的微米硅第二颗粒与所述氧化石墨烯的质量比为2:1～3:1，在所述混合液中，所述氧化石墨烯的浓度为1.5～2mol/L。
  7. 如权利要求1所述的微米硅碳复合负极材料的制备方法，其特征在于，所述水热反应的温度为180～200℃，所述水热反应的时间为6～10h。
  8. 一种如权利要求1至7中任一项所述的制备方法制备的微米硅碳复合负极材料，所述微米硅碳复合负极材料的密度为0.8～1.2g/cm 3。
  9. 一种负极极片，其特征在于，所述负极极片包括如权利要求8所述的微米硅碳复合负极材料。
  10. 一种锂离子电池，包括正极极片，其特征在于，所述锂离子电池还包括如权利要求9所述的负极极片。
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