WO2021134197A1 - 硅基负极材料及其制备方法，锂离子电池 - Google Patents

硅基负极材料及其制备方法，锂离子电池 Download PDF

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WO2021134197A1
WO2021134197A1 PCT/CN2019/129888 CN2019129888W WO2021134197A1 WO 2021134197 A1 WO2021134197 A1 WO 2021134197A1 CN 2019129888 W CN2019129888 W CN 2019129888W WO 2021134197 A1 WO2021134197 A1 WO 2021134197A1
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silicon
coating layer
carbon coating
negative electrode
based negative
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French (fr)
Chinese (zh)
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刘冬冬
马飞
吴玉虎
魏良勤
吴志红
丁晓阳
李凤凤
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Shanghai Shanshan Technology Co Ltd
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Shanghai Shanshan Technology Co Ltd
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Priority to PCT/CN2019/129888 priority Critical patent/WO2021134197A1/zh
Priority to JP2020573437A priority patent/JP7230073B2/ja
Priority to CN202111196137.5A priority patent/CN113964313B/zh
Priority to CN201980003461.5A priority patent/CN111164804B/zh
Publication of WO2021134197A1 publication Critical patent/WO2021134197A1/zh
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • 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
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/027—Negative electrodes
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the invention relates to the field of lithium ion batteries, in particular to a silicon-based negative electrode material and a preparation method thereof, and a lithium ion battery prepared.
  • the liquid-phase coating method has major problems in particle dispersion and coating uniformity, and it is difficult to achieve mass production.
  • the chemical vapor deposition (CVD) method can conveniently prepare composite particles with uniform coating and low particle adhesion. Therefore, the current mainstream technology is CVD preparation. That is, the raw materials are placed in equipment such as rotary kilns, rotary kilns, etc., set at 700 to 1050°C, and directly pass carbon-containing gas or steam. In the same reaction chamber, a continuous carbon layer is formed on the surface of the silicon oxide particles through pyrolysis and polycondensation reactions.
  • the temperature of the conventional CVD coating method is generally lower than 1000 °C, and only a layer of amorphous carbon can be deposited on the surface of the particles.
  • the carbon layer is loose, and the coating layer has relatively small binding capacity to the particles.
  • the volume of the silicon-oxygen particles changes greatly when lithium is released, and the coating layer is very easy to crack, resulting in the formation of a new SEI film. As the SEI film is gradually thickened with cycling, it will cause serious gas production and poor cycling in the lithium battery.
  • the negative electrode active material is easily deactivated after delithiation, that is, because the electrical contact becomes poor and an effective conductive network cannot be formed and the electrochemical activity is lost, the capacity of the lithium battery decays too fast.
  • increasing the amount of coating can alleviate the cracking of the coating layer caused by the volume change of the deintercalation of lithium and the intercalation of lithium, the excessively high content of the coating will also result in lower capacity and first-time coulombic efficiency, which will further lead to the lithium prepared from this material. The energy density of ion batteries is reduced.
  • the technical problem to be solved by the technical solution of the present application is to provide a new silicon-based negative electrode material and its production in view of the defect that the amorphous carbon coating layer structure contained in the prior art silicon-based negative electrode material is easy to crack and affects battery performance.
  • Method and provide a lithium ion battery including the silicon-based negative electrode material.
  • One aspect of the present application provides a method for preparing a silicon-based negative electrode material, which includes: passing a carbon source material through a pre-decomposition zone in a non-oxidizing atmosphere to form a decomposition product, wherein the carbon source material includes a gaseous carbon source material , Vaporized carbon source material or atomized carbon source material; and control the flow velocity V G of the decomposition product into the reaction chamber of the deposition coating zone and the molar flow rate of the decomposition product to the mass ratio of the silicon substrate material Mc/M , Causing the silicon base material and the decomposition product to undergo a deposition coating reaction in the deposition coating zone, forming an amorphous carbon coating layer and a graphitized carbon coating layer on the surface of the silicon base material, and the amorphous carbon coating graphitized carbon layer or the covering layer is directly coated on the surface of the silicon base material, wherein, 0.01 ⁇ V G ⁇ 100,0.001 ⁇ Mc / M ⁇ 1, V G unit is m / min
  • a graphitized carbon coating layer is formed on the surface of the silicon base material; under the second condition: 0.01 ⁇ When V G ⁇ 5 and 0.2 ⁇ Mc/M ⁇ 1, an amorphous carbon coating layer is formed on the surface of the silicon base material.
  • the values of V G and Mc/M are adjusted to alternately switch between the first condition and the second condition to form an alternately coated amorphous carbon coating on the surface of the silicon base material Layer and graphitized carbon coating.
  • the gaseous carbon source material includes methane, ethane, ethylene, acetylene, propane, and propylene
  • the vaporized carbon source material includes n-hexane, ethanol, and benzene
  • the atomized carbon source Substances include polyethylene and polypropylene.
  • N-containing substances in the process of the deposition coating reaction, N-containing substances may also be passed in, and the N-containing substances include one or more of NH 3 , acetonitrile, aniline or butylamine .
  • the non-oxidizing atmosphere refers to a reaction environment including any one or more of hydrogen, nitrogen, or inert gas.
  • the temperature range of the pre-decomposed carbon source material is 500°C to 1500°C.
  • the temperature at which the deposition and coating reaction occurs is 500°C to 1100°C.
  • the temperature range for the pre-decomposition of the carbon source material is 700°C to 1300°C, and the temperature at which the deposition coating reaction occurs is 650°C to 1000°C.
  • the silicon base material includes metallurgical silicon, silicon oxide SiOx (0 ⁇ x ⁇ 1.5), one or more mixtures of porous silicon, and particles of the silicon base material
  • the median diameter range is 1 ⁇ m-20 ⁇ m.
  • the silicon base material further includes a compound with the general formula MSiOy, where 0.85 ⁇ y ⁇ 3.5; M is any one of Li, Na, Mg, Al, Fe, and Ca, or Many kinds.
  • the present application also provides a silicon-based negative electrode material, including: a silicon base material; an amorphous carbon coating layer; and a graphitized carbon coating layer, wherein the amorphous carbon coating layer or the graphitized carbon coating layer The coating layer directly covers the surface of the silicon base material.
  • the Raman spectrum of the amorphous carbon coating layer is Id/Ig>0.7, and the Raman spectrum of the graphitized carbon coating layer is Id/Ig ⁇ 0.5.
  • the oxidation starting temperature of the amorphous carbon coating layer is ⁇ 400°C, and the starting oxidation temperature of the graphitized carbon coating layer is ⁇ 450°C.
  • the amorphous carbon coating layer is doped with nitrogen atoms
  • the graphitized carbon coating layer is doped with nitrogen atoms
  • the surface of the silicon base material includes more than one layer of the amorphous carbon coating layer and more than one layer of the graphitized carbon coating layer, The amorphous carbon coating layer and more than one layer of the graphitized carbon coating layer are alternately arranged.
  • the thickness of each layer of amorphous carbon coating layer is in the range of 1 nm to 20 nm, and the thickness of each layer of graphitized carbon coating layer is in the range of 1 nm to 20 nm.
  • the total thickness of the amorphous carbon coating layer and the graphitized carbon coating layer on the surface of the silicon base material is 1 nm to 1000 nm.
  • the mass percentage content of the amorphous carbon coating layer in the silicon-based negative electrode material is 1-10%, and the graphitized carbon coating layer is on the silicon-based negative electrode material.
  • the silicon base material includes metallurgical silicon, silicon oxide SiOx (0 ⁇ x ⁇ 1.5), one or more mixtures of porous silicon, and particles of the silicon base material
  • the median diameter range is 1 ⁇ m-20 ⁇ m.
  • the silicon base material further includes a compound with the general formula MSiOy, where 0.85 ⁇ y ⁇ 3.5; M is any one of Li, Na, Mg, Al, Fe, and Ca, or Many kinds.
  • the present application also provides a lithium ion battery, the negative electrode of the lithium ion battery includes the above-mentioned silicon-based negative electrode material.
  • the amorphous carbon coating layer and the graphitized carbon coating layer are formed on the surface of the silicon substrate material, thereby improving the charge-discharge cycle capability of the silicon-based anode material and further improving The service life of the secondary battery.
  • the embodiment of the present application also provides a method for manufacturing the silicon-based negative electrode material.
  • the entire preparation process of the method is simple to operate and is very suitable for industrial production.
  • FIG. 1 is an SEM image of a silicon-based anode material provided by an embodiment of the present application
  • FIG. 2 is a Raman spectrum diagram of an amorphous carbon coating layer and a graphitized carbon coating layer in a silicon-based negative electrode material provided by an embodiment of the present application.
  • the silicon-based negative electrode material includes: a silicon base material; an amorphous carbon coating layer; and a graphitized carbon coating layer, wherein the amorphous carbon coating layer or the graphitized carbon coating layer is directly coated on The surface of the silicon base material.
  • an amorphous carbon coating layer and a graphitized carbon coating layer are formed on the surface of the silicon base material.
  • the amorphous carbon coating layer is directly coated on the surface of the silicon base material, and the graphitized carbon coating layer is then coated on the amorphous carbon coating layer surface.
  • the graphitized carbon coating layer is directly coated on the surface of the silicon base material, and the amorphous carbon coating layer is then coated on the graphitized carbon coating ⁇ Layer surface.
  • the "coating" described in the examples of this application can be partial coating or full coating. The degree of coating of the "coating" is also different depending on the manufacturing process of the silicon-based negative electrode material. .
  • the total coating thickness of the amorphous carbon coating layer and the graphitized carbon coating layer on the surface of the silicon substrate material is 500 nm, and the amorphous carbon coating layer with a total thickness of 400 nm is coated on the silicon substrate
  • the surface of the material (the amorphous carbon coating layer with a total thickness of 400 nm may include several single-layer amorphous carbon coating layers with a thickness of 1 nm to 20 nm), and the graphitized carbon coating layer with a total thickness of 100 nm is coated on
  • the surface of the amorphous carbon coating layer (the graphitized carbon coating layer with a total thickness of 100 nm may include several single graphitized carbon coating layers with a thickness of 1 nm to 20 nm), the amorphous carbon coating
  • the coating degree of the coating layer or the graphitized carbon coating layer is relatively high, which is close to full coating. In the embodiment of the present application, if the thickness of the amorphous carbon coating layer or the graphitized carbon coating
  • the total coating thickness of the amorphous carbon coating layer and the graphitized carbon coating layer on the surface of the silicon base material is 30 nm, wherein the surface of the silicon base material is sequentially coated with a 5 nm graphitized carbon coating layer , 3nm amorphous carbon coating layer, 4nm graphitized carbon coating layer, 2nm amorphous carbon coating layer, 10nm graphitized carbon coating layer, 6nm amorphous carbon coating layer.
  • the surface of the silicon base material includes more than one layer of the amorphous carbon coating layer and more than one layer of the graphitized carbon coating layer, and the one or more layers of the amorphous carbon coating layer The carbon coating layer and more than one layer of the graphitized carbon coating layer are alternately arranged.
  • the amorphous carbon coating layer or the graphitized carbon coating layer can be directly coated on the silicon The surface of the base material.
  • the amorphous carbon coating layer is a loose amorphous carbon structure, it plays a buffer role in the lithium-intercalation expansion of the silicon base material, and the graphitized carbon coating layer is a crystalline carbon structure with a high degree of graphitization. It has a certain restraint effect on the lithium insertion expansion of the silicon base material, and prevents the cracking of the coating layer and the inactivation of the active material in the silicon base material during the lithium removal process. Therefore, the alternately arranged amorphous carbon structure and The graphitized carbon coating structure can better adjust the charge and discharge performance of the silicon-based negative electrode material, and improve the cycle life of the battery.
  • the thickness of each layer of amorphous carbon coating layer is in the range of 1 nm to 20 nm, and the thickness of each layer of graphitized carbon coating layer is in the range of 1 nm to 20 nm.
  • the total thickness of the amorphous carbon coating layer and the graphitized carbon coating layer on the surface of the silicon base material is 2 nm to 1000 nm.
  • the surface of the silicon base material includes an amorphous carbon coating layer with a thickness of 10 nm and Graphitized carbon coating layers with a thickness of 10 nm are alternately arranged 15 times.
  • the content of the amorphous carbon coating layer in the silicon-based negative electrode material is 1-10% by mass
  • the graphitized carbon coating layer is in the silicon-based negative electrode material.
  • the content of the mass percentage in 1-10%.
  • the amorphous carbon coating layer and the graphitized carbon coating layer account for 2-20% of the total mass percentage of the silicon-based negative electrode material.
  • the specific surface area of the silicon-based negative electrode material is generally higher (1-20m 2 /g).
  • the specific surface area of the silicon-based negative electrode material is generally low (0.1-15 m 2 /g).
  • the mass percentage content of the amorphous carbon coating layer in the silicon-based negative electrode material may be 5%, 3%, 8%, and the graphitized carbon coating layer is in the silicon-based negative electrode material.
  • the mass percentage content in the silicon-based negative electrode material can be 4%, 6%, 9%, or 5%, 3%, or 8%. That is to say, in the silicon-based negative electrode material, the mass percentage content of the amorphous carbon coating layer and the graphitized carbon coating layer may be the same or different.
  • the Raman spectrum of the amorphous carbon coating layer is Id/Ig>0.7, and the Raman spectrum of the graphitized carbon coating layer is Id/Ig ⁇ 0.5.
  • the initial oxidation temperature of the amorphous carbon coating layer is less than or equal to 400°C, and the initial oxidation temperature of the graphitized carbon coating layer is greater than or equal to 450°C. Since the structure of the silicon-based negative electrode material plays a decisive role in the oxidation initiation temperature, the oxidation initiation temperature of the amorphous carbon coating layer and the graphitized carbon coating layer reflects the coating of the silicon-based negative electrode material. The nature of the cladding.
  • the strength of the D peak in the Raman spectrum represents the degree of disorder of the carbon layer
  • the strength of the G peak represents the degree of order of the material, that is, Id/Ig can effectively characterize the degree of graphitization of the carbon layer.
  • the oxidation initiation temperature of amorphous carbon is lower, and the oxidation initiation temperature of graphitized carbon is higher.
  • the amorphous carbon coating layer may also be doped with nitrogen atoms.
  • the graphitized carbon coating layer may also be doped with nitrogen atoms.
  • the nitrogen atom can be from one or more of N-containing substances such as NH 3 , acetonitrile, aniline or butylamine. Adding nitrogen atoms to the amorphous carbon coating layer and the graphitized carbon coating layer can further improve the charge and discharge capacity of the silicon-based negative electrode material, because nitrogen doping can further improve the conductivity of the material. Thereby reducing the internal resistance of the battery, thereby ensuring the battery's high-current charge and discharge capability.
  • the silicon base material includes metallurgical silicon, silicon oxide SiOx (0 ⁇ x ⁇ 1.5), one or more mixtures of porous silicon, and particles of the silicon base material The median diameter ranges from 1 ⁇ m to 20 ⁇ m.
  • the silicon base material further includes a compound with the general formula MSiOy, where 0.85 ⁇ y ⁇ 3.5; M is any one of Li, Na, Mg, Al, Fe, and Ca, or Many kinds.
  • the amorphous carbon coating layer and the graphitized carbon coating layer are formed on the surface of the silicon substrate material, thereby improving the charge-discharge cycle capability of the silicon-based anode material and further improving The service life of the secondary battery.
  • the embodiment of the present application also provides a method for manufacturing the silicon-based negative electrode material.
  • the entire preparation process of the method is simple to operate and is very suitable for industrial production.
  • the embodiment of the present application provides a method for preparing a silicon-based negative electrode material, including: in a non-oxidizing atmosphere, a carbon source material is passed through a pre-decomposition zone to form a decomposition product, wherein the carbon source material includes a gaseous carbon source material, One or more of vaporized carbon source materials or atomized carbon source materials; regulating the flow velocity V G of the decomposition products into the reaction chamber of the deposition coating zone and the molar flow rate of the decomposition products to the base material mass ratio Mc/M, so that the silicon The substrate material and the decomposition product undergo a deposition coating reaction in the deposition coating zone, and an amorphous carbon coating layer and a graphitized carbon coating layer are formed on the surface of the silicon substrate material.
  • said graphitized carbon coating layer coated directly on the surface of the silicon base material, wherein, 0.01 ⁇ V G ⁇ 100,0.001 ⁇ Mc / M ⁇ 1, V G unit is m / min, m C in units of mol / min , In terms of carbon atoms, M is the mass of the silicon base material, in kg.
  • the preparation of the silicon-based negative electrode material can use coating equipment such as a rotary furnace and a rotary furnace to achieve the purpose of uniform coating.
  • the coating equipment may be configured to include a pre-decomposition zone and a deposition coating zone, and both the pre-decomposition zone and the deposition coating zone include a reaction chamber.
  • the pre-decomposition zone is used to pre-decompose carbon source materials.
  • the carbon source material is passed into the pre-decomposition zone of the coating device, and in a non-oxidizing atmosphere, the carbon source material undergoes pyrolysis, cracking, polycondensation and other reactions to become a gaseous material.
  • the low molecular weight substance in the carbon source material undergoes pyrolysis, polycondensation, addition and other reactions into medium and large molecular weight substances; the cracking of high molecular weight substances into medium and small molecular weight substances is also accompanied by pyrolysis, polycondensation, addition and other reactions.
  • the gas that provides the non-oxidizing atmosphere includes, for example, any one or more of hydrogen, nitrogen, or inert gas, and is used as a protective gas, carrier gas, and diluent gas for the reaction in the pre-decomposition zone.
  • the gaseous carbon source materials include hydrocarbons that are gaseous at room temperature and aldehydes that are gaseous at room temperature, and the gaseous carbon source materials include methane, ethane, ethylene, acetylene, propane, and propylene.
  • the vaporized carbon source material is a liquid at room temperature and a gaseous carbonaceous material above room temperature but below the temperature of the pre-decomposition zone.
  • the vaporized carbon source material includes n-hexane, ethanol, and benzene.
  • the atomized carbon source material is a material that is difficult to evaporate by heating, and can be made into small droplets through an atomization device, for example, a material that is liquid when the temperature is lower than the pre-decomposition zone.
  • the atomized carbon source material includes polyethylene and polypropylene.
  • the flow rate V G of the decomposition product entering the reaction chamber of the deposition coating zone and the value of the molar flow rate of the decomposition product to the mass ratio Mc/M of the substrate material are adjusted to make the silicon substrate material and the substrate material mass ratio Mc/M.
  • the decomposition product undergoes a deposition coating reaction in the deposition coating zone, thereby forming an amorphous carbon coating layer and a graphitized carbon coating layer on the surface of the silicon base material.
  • V G unit is m / min, M C in units of mol / min, to a carbon atom, M being the quality of the silicon base material, the unit kg.
  • a graphitized carbon coating layer is formed on the surface of the silicon base material; under the second condition: 0.01 ⁇ V G ⁇ 5, 0.2 ⁇ Mc/ When M ⁇ 1, an amorphous carbon coating layer is formed on the surface of the silicon base material. That is to say, the manufacturing process of the silicon-based negative electrode material described in the embodiments of the present application can adjust the formed amorphous carbon coating layer and graphitized carbon coating layer only by adjusting the flow rate and quality of the reactants, and the reaction time. The thickness and alternate cladding.
  • the flow rate and quality of the reactant can be adjusted quickly, and then the coating layer can be switched to another coating layer.
  • setting the flow rate and quality adjustment speed of the reactant is relatively slow, and there may be a composite coating layer that includes both an amorphous carbon coating layer and a graphitized carbon coating layer.
  • the crystal structure of the coating layer can be controlled by adjusting V G (m/min) and Mc/M (M C unit mol/min, in terms of carbon atoms, M is the mass of the silicon base material, unit kg), so as to obtain Amorphous carbon coating layer and graphitized carbon coating layer.
  • the reaction time is combined to adjust the mass percentage content of the carbon coating layer.
  • Adjusting the operating speed of the silicon base material and the flow speed of the decomposition products entering the reaction chamber can ensure that a uniform and continuous amorphous carbon coating layer and graphitized carbon coating layer are obtained during the reaction process, while minimizing material loss.
  • the values of V G and Mc/M are adjusted to alternately switch between the first condition and the second condition to form alternately coated amorphous carbon on the surface of the silicon base material.
  • Coating layer and graphitized carbon coating layer Since the amorphous carbon coating layer is a loose amorphous carbon structure, it plays a buffer role in the lithium-intercalation expansion of the silicon base material, and the graphitized carbon coating layer is a crystalline carbon structure with a high degree of graphitization. It has a certain restraint effect on the lithium insertion expansion of the silicon base material, and prevents the cracking of the coating layer and the inactivation of the active material in the silicon base material during the lithium removal process. Therefore, the alternately arranged amorphous carbon structure and The graphitized carbon coating structure can better adjust the charge and discharge performance of the silicon-based negative electrode material, and improve the cycle life of the battery.
  • the atomized carbon source is thermally decomposed in the pre-decomposition zone to calculate the molar flow rate M C of the pyrolysis products, which can be determined by the method of measuring the CO 2 content after oxidation and combustion.
  • the gaseous and vaporous carbon sources directly determine the molar flow rate of pyrolysis products M C according to the molecular structure of the inlet gas.
  • N-containing substances in the process of the deposition coating reaction, N-containing substances may also be passed in, and the N-containing substances include one or more of NH 3 , acetonitrile, aniline or butylamine .
  • the temperature range of the pre-decomposed carbon source material is set to 500°C to 1500°C, preferably 700°C to 1300°C, so that the carbon source material can be changed into It is gaseous and rapidly undergoes pyrolysis or polycondensation reaction to form a product in the pre-decomposition zone that can rapidly undergo subsequent coating reactions.
  • conventional heating methods or microwave or radio frequency can be used to reach the desired temperature.
  • microwave heating can ionize C-containing substances, which can significantly reduce the pre-decomposition temperature and improve the pre-decomposition efficiency compared with other heating methods.
  • reactions such as dehydrogenation, free radical addition, etc. occur, and become those with larger relative molecular mass and lower Gibbs free energy.
  • Linear or aromatic compounds After the vaporized carbon source material passes through the pre-decomposition zone, it undergoes dehydrogenation (cracking), free radical addition and other reactions to become linear or aromatic compounds.
  • dehydrogenation Cracking
  • the mixed gas passing through the pre-decomposition zone is the decomposition product, and the decomposition product includes the non-oxidizing gas passed in the reaction atmosphere and the pre-decomposed carbon source substance.
  • the pre-decomposed carbon source material (gaseous state) accounts for 1 to 70% of the volume of the decomposition product, and the pre-decomposition reaction step can make the silicon-based negative electrode material manufacturing method
  • the medium reaction temperature control is more flexible, which is beneficial to control the reaction progress such as decomposition and addition of carbon source substances, and has little interference with the temperature of the coating zone.
  • the decomposition product is passed into the deposition coating area of the coating device, so that the silicon base material and the pre-decomposed carbon source material undergo a deposition and coating reaction, and an amorphous shape is formed on the surface of the silicon base material.
  • the temperature at which the deposition and coating reaction occurs is 500°C to 1100°C, preferably, the temperature at which the deposition and coating reaction occurs is 650°C to 1000°C.
  • the temperature at which the deposition and coating reaction occurs is 500°C to 1100°C, preferably, the temperature at which the deposition and coating reaction occurs is 650°C to 1000°C.
  • the silicon base material includes metallurgical silicon, silicon oxide SiOx (0 ⁇ x ⁇ 1.5), one or more mixtures of porous silicon, and the median particle size of the silicon base material ranges from 1 ⁇ m to 20 ⁇ m.
  • the silicon base material also includes a compound with the general formula MSiOy, where (0.85 ⁇ y ⁇ 3.5; M is any one of Li, Na, Mg, Al, Fe, and Ca Or multiple.
  • N-containing substances may also be passed in, and the N-containing substances include one or more of NH 3 , acetonitrile, aniline or butylamine.
  • the N-containing substances include one or more of NH 3 , acetonitrile, aniline or butylamine.
  • the amorphous carbon coating layer and the graphitized carbon coating layer doped with N atoms can further improve the charge and discharge capacity of the silicon-based negative electrode material, because the amorphous carbon coating layer and the graphitized carbon coating layer After the coating layer is doped with nitrogen, the conductivity of the material can be further improved, thereby reducing the internal resistance of the battery, and thereby ensuring the high-current charging and discharging capacity of the battery.
  • the mass percentage of the amorphous carbon coating layer and the graphitized carbon coating layer in the silicon-based negative electrode material is, for example, 0.01 to 99:1.
  • the The proportion of the amorphous carbon coating layer is 10% to 90%, such as 20%, 30%, 40%, 50%, 60%, 70%, 80%, etc.
  • the surface of the silicon base material in the silicon-based negative electrode material has more than one layer of the amorphous carbon coating layer and/or more than one layer of the graphitized carbon coating layer, Furthermore, the one or more layers of the amorphous carbon coating layer and the one or more layers of the graphitized carbon coating layer are alternately arranged.
  • methane with a flow rate of 10m/min is first introduced, nitrogen is used as a protective gas, and the reaction temperature is 1000 degrees Celsius. After being introduced for 180 minutes, it is stopped. In the pre-decomposition zone, the flow rate is 1m/min. Alkane, continue to use nitrogen as the protective gas, and stop after 120 minutes.
  • the process of introducing methane and n-hexane can be performed alternately.
  • propylene with a flow rate of 5m/min is first introduced into the pre-decomposition zone, Ar is used as the protective gas, and the reaction temperature is 1000 degrees Celsius, and the flow is stopped after 300 minutes.
  • the flow rate is 0.1 m/min polypropylene melt, continue to use Ar as the protective gas, and stop after 240 minutes.
  • the process of introducing propylene and polypropylene can be performed alternately.
  • hydrogen is used as the protective gas, and a mixed gas of ethane and ethanol is introduced into the pre-decomposition zone.
  • the flow rate of ethane and ethanol is 50m/min, and the reaction temperature is 1200 degrees Celsius for 100 minutes. After stopping.
  • a rotary furnace including a pre-decomposition zone and a deposition coating zone
  • the temperature of the deposition coating zone is 900° C.
  • the total reaction time is 20 min to form the silicon-based negative electrode material S1-1.
  • Table 1 shows the process conditions of each step of the silicon-based negative electrode material preparation method in Example 1 to Example 6, and Comparative Example 1 and Comparative Example 2. For the specific process description, refer to Example 1 and Example 2 and Comparative Example 1 and The text part of Comparative Example 2.
  • Table 2 shows the amorphous carbon coating layer (AC) and the graphitized carbon coating in the silicon-based negative electrode material formed by the preparation method of the silicon-based negative electrode material in the foregoing Examples 1 to 6 and Comparative Example 1 and Comparative Example 2
  • the silicon-based negative electrode material is used as the negative electrode material of the lithium battery, and the electrochemical performance of the negative electrode material is also shown in Figure 2 (capacity mAh/g, efficiency% and 30-week cycle capacity retention rate %, where The efficiency% mentioned refers to the first Coulomb efficiency %).
  • the silicon-based anode material formed by the method for preparing the silicon-based anode material described in the examples of this application is used as the anode material of a lithium battery.
  • the capacity mAh/g per unit mass, the first coulombic efficiency and the 30-week cycle capacity retention rate are all much higher than the silicon-based anode materials in the comparative test.
  • Figures 1 and 2 of the present application also provide SEM images of the silicon-based anode material described in the embodiments of the present application and the amorphous carbon coating layer and the graphitized carbon coating layer in the silicon-based anode material provided in the embodiments of the present application Raman spectrum. It can be seen from FIG. 1 that the silicon-based negative electrode material particles with an amorphous carbon-carbon coating layer and a graphitized carbon coating layer on the surface described in the embodiments of the present application are uniformly dispersed. It can be seen from FIG.
  • the line 1 is a graphitized carbon coating layer
  • the line 2 is an amorphous carbon coating layer.
  • the Raman spectrum Id/Ig of the amorphous carbon coating layer is 0.92
  • the Raman spectrum Id/Ig of the graphitized carbon coating layer is 0.43.

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