CN113224279B - Silica-based composite negative electrode material capable of improving first coulombic efficiency and preparation method thereof - Google Patents

Silica-based composite negative electrode material capable of improving first coulombic efficiency and preparation method thereof Download PDF

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CN113224279B
CN113224279B CN202110767828.XA CN202110767828A CN113224279B CN 113224279 B CN113224279 B CN 113224279B CN 202110767828 A CN202110767828 A CN 202110767828A CN 113224279 B CN113224279 B CN 113224279B
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silica
porous
negative electrode
electrode material
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CN113224279A (en
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李阁
许迪新
李金熠
程晓彦
岳风树
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Beijing One Gold Amperex Technology Ltd
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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
    • 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
    • H01M4/48—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
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    • 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
    • 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
    • H01M4/628—Inhibitors, e.g. gassing inhibitors, corrosion inhibitors
    • 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
    • H01M2004/021—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

Abstract

The invention discloses a silica-based composite negative electrode material for improving the first coulombic efficiency and a preparation method thereof. The composite negative electrode material takes porous silicon monoxide as a substrate, reducing materials are poured into pore channels, and carbon coating layers are optionally covered on the surface. The composite negative electrode material is obtained by pore-forming the silica, pouring a reducing material into the pore channel, heating to 400-900 ℃ and stabilizing. According to the invention, oxygen contained in the porous silicon monoxide is consumed in advance, so that irreversible capacity loss caused in the first charge-discharge process of a battery is reduced, and the first coulombic efficiency of the material is improved; meanwhile, a space for volume expansion required in the lithium embedding process of the silicon-based negative electrode material is provided, so that the crushing and pulverization of porous silicon oxide micron particles can be prevented, and the circulation stability of the material is improved; effectively shortens the transmission path of lithium ions and electrons in the battery and effectively improves the rate capability of the material.

Description

Silica-based composite negative electrode material capable of improving first coulombic efficiency and preparation method thereof
Technical Field
The invention belongs to the technical field of batteries, and particularly relates to a silica-based composite negative electrode material capable of improving the first coulombic efficiency, a preparation method of the silica-based composite negative electrode material, a battery negative electrode containing the silica-based composite negative electrode material and a lithium ion battery.
Background
In recent years, with the rapid consumption of fossil energy, the use of renewable clean energy such as water energy, wind energy, and solar energy has been receiving more and more attention. However, such emerging energy sources as wind and solar energy are generally intermittent and unstable, and energy storage devices with high energy density have become critical to the use of these energy sources. Lithium ion batteries have received much attention due to their high energy conversion efficiency, long cycle life, and high energy and power density, and have been implemented in portable electronic devices, electric vehicles, and large-scale energy storage fields. However, as the demand for energy storage increases, the energy density and cycle life of lithium ion batteries need to be further improved, wherein the negative electrode material plays a crucial role. The most widely used lithium ion battery cathode material at present is graphite, and the theoretical capacity is about 372 mAh/g. In order to improve the energy density of the battery, a silicon-based negative electrode material with ultrahigh capacity is considered as a substitute of a graphite negative electrode, and the theoretical specific capacity of the silicon-based negative electrode material can reach 4200 mAh/g. However, practical application of silicon-based negative electrodes also faces a great challenge, especially for the silica-based materials, since irreversible lithium silicate and lithium oxide are generated during charging and discharging, the first coulombic efficiency is low, and the energy density of the battery is seriously influenced. In addition, the silicon-based negative electrode material can generate huge volume expansion and shrinkage in the lithium intercalation and deintercalation process, thereby causing the crushing and pulverization of particles and reducing the cycling stability of the battery.
Therefore, the problems of low coulombic efficiency and large volume change for the first time have been major obstacles for realizing the application of the silicon oxide negative electrode material. In the aspect of improving the first coulombic efficiency, the current literature and the solutions commonly used in the industry include: 1. pre-consuming components which may consume lithium ions during the first charge and discharge process, including pre-lithiation and pre-doping of metal elements combined therewith; 2. the nano-grade material has extremely large specific surface area, so that more side reactions can be initiated in the battery, and the overall granularity and the specific surface area of the material are controlled; 3. the ion/electron transmission path of the material is reduced, and the electrochemical performance of the material is improved; in terms of reducing the volume change of the material, the currently common methods mainly include: 1. a buffer medium is constructed on the surface or inside of the silicon-based negative electrode material particles to buffer volume expansion and contraction caused by charge and discharge; 2. carrying out structural design on the silicon-based negative electrode material, and manufacturing a porous structure, a linear structure, a core-shell structure and the like; the solution has obvious improvement effect on the problems of low coulombic efficiency of the silicon-based negative electrode material for the first time and volume change in the charging and discharging process.
However, the key to hinder the industrial application of the silicon-based negative electrode material is to solve the problems of low first coulombic efficiency, low cycle stability and poor rate performance while ensuring high energy density. Therefore, it is only possible to popularize the silicon-based anode material into practical applications by combining schemes of improving the first coulombic efficiency and cycle performance of the silicon-based anode material and having industrialization capability.
In the prior art, the doping of reduction metal is uneven in solid phase and gas phase reduction metal doping, and oxygen in the porous silicon oxide material cannot be fully reduced; or if the liquid phase doping reduction is not subjected to proper stabilizing treatment, the matrix material is easily and seriously damaged, the irregular active sites on the particle surface are many, and the material cycle performance is not improved. In addition, the porous silica material has the problems of uneven and incoherent pore channels and the like, and the problems of incomplete reduction and instability of a silicon-based material still exist because the pretreatment is not carried out before the liquid-phase doping reduction or the stabilization treatment is not carried out after the doping, so that the improvement of the performances such as the first coulombic efficiency and the stability is limited to a certain extent.
For example, CN109768246 discloses a silicon composite anode material: taking solid particles containing a porous silica phase and metal/nonmetal or alloy thereof as raw materials, sublimating the metal/nonmetal or alloy thereof in a saturated vapor pressure mode at a specific temperature under vacuum or continuous argon gas flow, carrying out gas-solid reaction on the surface of solid particle powder containing the porous silica phase, carrying out solid-phase mass transfer, and further carrying out heat treatment and coating treatment to prepare the bulk phase doped nano silicon composite anode material. However, in this document, only the reducing metal is mixed with the solid particles of the porous silica phase and then coated, and therefore the first coulombic efficiency and the cycle stability are still not effectively improved.
Disclosure of Invention
The invention aims to solve the problems of low energy density, poor cycle stability and low power density of the conventional lithium ion battery. The specific method starts from the negative electrode material of the lithium ion battery, uses the silicon-based negative electrode material with higher specific capacity, and simultaneously solves the problems of low initial coulombic efficiency and volume expansion of the silicon-based negative electrode material in the charge and discharge process. The first coulombic efficiency of the silicon-based negative electrode material is improved, so that the specific capacity of the lithium ion battery can be effectively exerted in the actual charging and discharging process, the loss of irreversible capacity is reduced, and the energy density of the battery is improved; the problem of volume expansion of the silicon-based negative electrode material in the charging and discharging processes can be solved, so that the problems of particle breakage and pulverization of the silicon-based negative electrode material in the charging and discharging processes can be effectively avoided, and the cycling stability of the silicon-based negative electrode material is improved; meanwhile, through the structural design of the porous silicon-based anode material and the metal element, the metal element is filled into the pore channel of the porous silicon-based anode material, so that the transmission path of lithium ions and electrons in the battery is reduced, the multiplying power performance of the silicon-based anode material is improved, the power density of the battery is ensured, a certain volume expansion space is provided, the integrity of particles is maintained, and the service life of the battery is prolonged.
The first purpose of the invention is to provide a silica-based composite negative electrode material for improving the first coulombic efficiency, wherein the negative electrode material is a silica composite material, porous silica is used as a substrate, reducing materials are poured into pore channels, and optionally, a carbon coating layer is covered on the surface; the reducing material is selected from at least one metal or compound thereof that is more reducing than hydrogen.
The composite negative electrode material is obtained by carrying out porous treatment (namely pore-forming) on the silicon monoxide, then pouring a reducing material into a pore channel, heating to 400-900 ℃ and carrying out stabilization treatment.
The aperture of the silica-based composite negative electrode material is 10-100nm, preferably 20-80nm, and the inside of the pore channel is uniform and communicated.
The median particle diameter of the silica-based composite negative electrode material is 1-30. If the median diameter is larger than 30, the transmission distance of electrons and lithium ions is obviously increased when the battery material consisting of the silicon monoxide particles is used as a negative electrode, and the polarization of the battery is increased, so that the rate performance and the capacity exertion of the battery are influenced; if the median diameter is less than 1, the specific surface area of the silica particles is too large, which affects the battery preparation process and causes too many side reactions inside the battery, and thus reduces the cycle life and effective capacity of the battery.
The specific surface area of the porous silicon oxide composite negative electrode material is 1-50m2(ii) in terms of/g. If the specific surface area is more than 50m2The volume energy density of the material is obviously reduced due to excessive pore channels of the material, and excessive side reactions are caused on the surface of the material due to excessive specific surface area, so that the coulomb efficiency of the material is reduced; if the specific surface area is less than 1m2And g, the pore channel of the material is insufficient, the purposes of expanding the buffer body and reducing the transmission distance of electrons and ions cannot be effectively realized, and the circulation stability and the rate capability of the material cannot be improved.
The porous silica may be of the formula SiOxWherein x is more than or equal to 0.5 and less than or equal to 1.5.
The reducibility of metal contained in the pore channel of the porous silicon oxide is required to be stronger than that of hydrogen, the further requirement is easy to combine with oxygen in the silicon oxide or combine with the oxygen in the silicon oxide in a heating mode, the oxygen in the porous silicon oxide material is reduced by the reducibility metal, so that the generation of irreversible capacity during the first charge and discharge of silicon oxide particles is effectively reduced, and the first coulombic efficiency and the cycle stability of the material are improved.
The metal contained in the pore channels of the porous silica can be lithium, potassium, barium, calcium, sodium, magnesium, aluminum, titanium, zinc, cobalt, nickel, iron, tin, antimony and the like, preferably one or more of lithium, potassium, calcium, sodium, magnesium, aluminum, zinc and antimony, and more preferably one or more of alkali metals lithium, sodium and potassium; or a compound of the corresponding metal element or a product of oxidation-reduction reaction of the metal with porous silica, such as silicate.
The proportion of the metal or the compound accounts for 5-20 percent of the mass of the porous silica, preferably 5-15 percent; if the mass ratio of the metal exceeds 20%, the amount of silicon which can be alloyed with lithium in the material is obviously reduced, and the metal element can fix part of silicon and oxygen in the silicon monoxide, so that the specific capacity of the material is obviously reduced; if the mass ratio of the metal elements is lower than 1%, the doped metal elements in the material are too few to effectively combine with oxygen in the silicon monoxide, so that the first coulomb efficiency of the battery cannot be effectively improved, and meanwhile, the doped metal elements are too few to effectively improve the conductivity of the material, which is not beneficial to improving the power density of the battery.
The liquid phase perfusion method has the advantages that metal can be fully compounded with the silicon monoxide, so that the proportion of metal elements can be controlled by the adding amount of raw materials, the loss in the pore-forming process is little, and the proportion is basically the same as that of the raw materials.
Meanwhile, the surface of the porous silicon oxide can be covered with a carbon material coating layer as an electron transmission layer, so that the electron conductivity and the rate capability of the material are ensured; the carbon material can be graphene, carbon nanotubes and amorphous carbon;
as the carbon coating layer, the carbon material on the surface of the oxidized silica accounts for 1-10% of the mass of the composite negative electrode material. If the proportion of the carbon material is more than 10%, the specific capacity of the material is greatly reduced, and the migration of lithium ions from the electrolyte to the interior of the material is influenced, so that the rate performance of the battery is deteriorated; if the proportion of the carbon material is less than 1%, the carbon layer cannot be completely and effectively coated on the surface of the oxidized sub-silicon, so that partial surface of the particles is not conductive, the capacity exertion of the battery is influenced, and the rate capability of the battery is reduced.
Preferably, the surface carbon coating layer is generated in situ, and more preferably graphene, carbon nanotubes and amorphous carbon grown in situ on the particle surface by a Chemical Vapor Deposition (CVD) method.
In the silicon oxide composite negative electrode material, oxygen in the porous silicon oxide is further reduced by the reducing metal material filled in the pore channel of the porous silicon oxide so as to reduce lithium ions consumed in the first charge-discharge process, so that the composite negative electrode material has high first coulombic efficiency.
The surface of the silicon oxide composite negative electrode material is covered with the carbon coating layer, and the material is in a porous structure, so that the composite negative electrode material has good rate performance and excellent cycling stability.
The second purpose of the invention is to provide a preparation method of the porous silicon monoxide composite negative electrode material, which comprises the following steps:
1) pore-forming of porous silica:
enabling the silicon monoxide to have a pore channel structure by a ball milling spraying method, a disproportionation etching method or an evaporation deposition method to obtain porous silicon monoxide; the concrete description is as follows:
the ball milling spraying method in the pore forming method mainly comprises the following steps: firstly, crushing a silicon monoxide block into small particles by a liquid phase ball milling crushing method, and adding a binder and a pore-forming agent in the ball milling process to obtain mixed slurry; secondly, spray drying the slurry mixed with the small silicon monoxide particles, the binder and the pore-forming agent to obtain powdery microspheres; thirdly, carrying out post-treatment according to different types of pore-forming agents to obtain porous silica micro-particles with a porous channel structure;
after the pore-forming step, the aperture of the porous silica is 10-100 nm. If the pore diameter is larger than 100nm, the density of the silicon monoxide particles can be greatly reduced, namely the volume energy density of the material is greatly reduced, which is not beneficial to improving the energy density of the battery; if the aperture is smaller than 10nm, the filling of subsequent metal is not facilitated, the effect of buffering volume expansion is not obvious when the efficiency of doping reducing metal is reduced, the transmission paths of electrons and ions cannot be effectively reduced, and the first coulomb efficiency of the material is not facilitated to be improved.
Wherein, the binder is preferably one or more of asphalt, sucrose, chitosan and resin polymers;
the pore-forming agent is selected from one or more of water-soluble salt, phenolic resin and polyvinyl alcohol;
for example, when water-soluble salts are used as the pore-forming agent, the micron particles obtained by spray drying are carbonized and washed, and the original water-soluble salts in the carbonized micron particles are washed away to obtain the porous silica micron particles; and (3) calcining the micron particles obtained by spray drying in an inert atmosphere by using high-molecular materials with low residual carbon after high-temperature calcination, such as phenolic resin, polyvinyl alcohol and the like, as pore-forming agents to obtain the silica micron particles with the pore channel structure.
The binder is used in an amount of 1 to 15wt% based on the weight of the silica block.
The pore-forming agent accounts for 5-25wt% of the silicon monoxide block, and preferably 10-20 wt%.
The pore size of the prepared material can be regulated and controlled by regulating the dosage of the pore-forming agent and the type of the pore-forming agent.
If the dosage of the pore-forming agent is too low, the pore-forming effect is not enough, and the pore channel of the porous silica material is not completely formed, which is not beneficial to the perfusion of the reducing agent metal; if the pore-forming agent is used in an excessive amount, the pore channel is too large, collapse is easy to occur, and the uniformity of the pore channel is not good, so that the proportion of the pore-forming agent is suitable to be 5-25wt%, the pore diameter range of the porous silicon oxide is suitable at the moment, and the sufficiency and effectiveness of pouring metal can be ensured.
The disproportionation etching method in the pore-forming method mainly comprises the following steps: firstly, crushing a silicon monoxide block body to a micron level through an airflow crushing process; secondly, carrying out high-temperature treatment on the crushed silicon monoxide micron particles to cause the silicon monoxide micron particles to be disproportionated, thereby forming a nano-scale uniformly dispersed structure of silicon dioxide and silicon crystal regions; etching the disproportionated porous silicon oxide by using hydrofluoric acid, and obtaining porous silicon oxide particles with porous structures due to different reaction degrees of each component of the disproportionated porous silicon oxide and the hydrofluoric acid; wherein the high-temperature treatment temperature of the porous silicon oxide micron particles obtained by crushing is 1000-1200 ℃, if the treatment temperature is too high, the disproportionation is too serious, the holes obtained after etching are too large, and if the treatment temperature is too low, obvious holes are not easily formed after etching; meanwhile, the size of the formed pore channel can be adjusted by adjusting the etching time and the concentration of hydrofluoric acid.
The evaporation deposition method in the pore-forming method mainly comprises the following steps: uniformly mixing a silicon monoxide block body and a pore-forming agent, drying, and heating and evaporating a material mixed with the silicon monoxide and the pore-forming agent under a high-temperature negative-pressure condition; preparing porous silica blocks with different deposition forms by adjusting the ratio of evaporation temperature to deposition temperature; thirdly, the obtained porous silicon oxide block is crushed into micron particles, and the pore-forming agent is removed by heat treatment to obtain the porous silicon oxide micron particles with the pore channel structure.
Wherein the temperature under the high-temperature negative pressure condition is 1200-1500 ℃, and the vacuum degree is 1-10 Pa; the pore-forming agent is used in an amount of 15 to 40wt%, preferably 20 to 35wt%, based on the silica block. The heating temperature for removing the pore-forming agent by the heat treatment is 500-800 ℃.
The pore-forming agent is silicate, preferably magnesium silicate.
Since the deposition temperature determines the state of deposition, the pore size of porous silica is affected to some extent. The ratio of evaporation to deposition temperature is therefore 1: 0.4-0.8. If the ratio is lower than 1: 0.4, pores with overlarge pore diameters are easy to form, and the pore distribution is not uniform; if the ratio is higher than 1: 0.8, the pore diameter of the formed pore canal is too small, which influences the perfusion of the reducing material.
The pore-forming method is preferably an evaporation deposition method, and the evaporation deposition method is characterized in that the pore-forming agent is introduced in the preparation process of the porous silicon oxide, so that the nano-grade uniform doping of the pore-forming agent can be realized, the pore channel distribution of the porous structure formed by the evaporation deposition method is more uniform, the perfusion of the reductive metal elements into the particles is facilitated, and the first coulomb efficiency of the material can be more effectively improved; in addition, the more uniform nanoscale internal pore channels can more effectively buffer the volume expansion of the porous silicon oxide in the charging and discharging processes, reduce the internal stress of particles and improve the cycling stability of the material.
Similarly, in the evaporation deposition pore-forming process, if the usage amount of the pore-forming agent is less than 15%, the pore-forming effect is insufficient, and the pore channels of the porous silica material are not completely formed, which is not beneficial to the perfusion of the reducing agent metal; if the pore-forming agent is used in an amount exceeding 40%, the pores are too large to easily collapse and the uniformity of the pores is not good, so that the pore-forming agent proportion is suitably 15 to 40% by weight, preferably 20 to 35% by weight. At the moment, the pore diameter of the porous silica is suitable, and the sufficiency and effectiveness of the poured metal can be ensured.
Alternatively, the crushing in the above step may be performed by conventional crushing means such as ball milling, sand milling, mechanical crushing, air flow crushing, and the like, preferably air flow crushing.
2) The porous silica micron particle is infused with metal or compound thereof with reducibility stronger than hydrogen:
impregnating the porous silica micron particles obtained in the step 1) in steam or solution of a material to be impregnated to realize impregnation. Preferably a liquid phase infusion method in which the porous silica microparticles are immersed in a solution of the material to be infused or a precursor thereof.
Dissolving or dispersing the material to be infused in an organic solvent, then soaking the porous silica micron particles in the organic solvent, and carrying out vacuum drying to remove the organic solvent.
In at least one embodiment, when the metal (such as lithium, sodium, and potassium) is infused, the metal is dissolved in an ether solvent in which an aromatic ring solute is dissolved in advance to prepare an aromatic ring-metal organic solution, then the porous silica microparticles are immersed in the organic solution, and vacuum drying is performed to remove the organic solvent, so as to obtain the aromatic ring-metal infused porous silica microparticles;
among them, the aromatic ring solvent has a good complexing effect on lithium, and is preferably polycyclic aromatic hydrocarbons such as biphenyl, terphenyl, dimethylbiphenyl, naphthalene, anthracene, and the like, and the ether solvent is preferably tetrahydrofuran, ethylene glycol dimethyl ether.
In at least one embodiment, when lithium nitride is used as the material to be poured, the lithium nitride is dispersed in an N, N-dimethylformamide solvent, then the porous silica microparticles are dipped in a dispersion liquid, and the porous silica microparticles poured with the lithium nitride are obtained after drying and removing the solvent.
Further, the concentration of the metal/metal compound in the solution is in the range of 0.1 to 2M, preferably 0.1 to 1M;
the concentration range of aromatic ring solute is 0.1-1M, preferably 0.1-0.5M, the aromatic hydrocarbon can effectively dissolve lithium, only a small amount of cracking carbon is left after volatilization and pyrolysis, and excessive lithium silicate is coated with carbon.
When the concentration of the aromatic ring solute is lower than 0.1M, metal lithium cannot be effectively dissolved, so that the metal lithium cannot be effectively embedded into the material, and when the concentration of the aromatic ring solute is higher than 1M, the aromatic ring solute cannot be completely removed, so that the effective utilization rate is too low, and the post-treatment difficulty is increased.
Preferably, the molar concentration ratio of metal to aromatic ring solute is in the range of 4-6: 1, the solubility is better.
The solute and the solvent are subjected to water removal and oxygen removal, so that the influence of the environment such as water, oxygen and the like on the material is reduced.
The aromatic ring solute is preferably one or more of biphenyl, terphenyl, dimethyl biphenyl, naphthalene and anthracene, and the solvent ether is preferably tetrahydrofuran or ethylene glycol dimethyl ether;
the impregnation process can also adopt a negative pressure mode (the pressure range is-0.08 to-0.1 MPa), so that the air in the porous material is discharged, and the liquid can enter the porous material more conveniently.
3) And (3) stabilizing the porous silica after pouring:
the porous silica microparticles impregnated with reducing material are stabilized by heat treatment under an inert atmosphere, followed by washing to remove excess impregnated material.
Wherein the temperature of the heat treatment is the temperature at which the perfusion material and the porous silicon oxide micron particles are subjected to reduction reaction.
The poured metal reacts with the silicon monoxide in the inert atmosphere to generate silicate, and oxygen in the silicon monoxide is captured, so that the first coulombic efficiency is improved.
Specifically, the heat treatment is carried out on the infused porous silica micro-particles in an inert atmosphere to stabilize the infused material, wherein the heat treatment temperature is 400-900 ℃, and preferably 500-800 ℃.
For example, the aromatic ring-lithium is subjected to 600-800 ℃ heat treatment in an argon atmosphere, so that the aromatic ring organic matter is carbonized in a pore channel, the metal lithium and the silicon oxide are combined to form lithium silicate, and then the cooled porous silicon oxide micron particles are washed to remove the lithium silicate excessively formed and then are subjected to carbon coating, so that the lithium-infused silicon oxide composite negative electrode material capable of improving the initial coulombic efficiency is obtained.
The poured reducing metal material has higher activity, and the stabilization treatment is adopted in the invention, so that the poured porous silicon oxide micron particles are subjected to heat treatment in an inert atmosphere, and the condition that the capacity exertion of the battery material is influenced by the fact that the reducing metal material is directly oxidized when being contacted with air or the reducing metal material is reacted with air and moisture to generate a compound in the post-treatment process can be avoided, thereby obviously reducing the reversible specific capacity and the first coulombic efficiency of the material.
Preferably, a pretreatment step is also required before the stabilization treatment: dissolving the porous silicon oxide impregnated with lithium in eutectic solvent, and then in inert atmosphere or inert atmosphere/H2The treatment temperature is 50-80 ℃, preferably 55-70 ℃, and the treatment time is 1-5 h.
The inert atmosphere is selected from one or more of helium, argon and nitrogen, and the ratio of hydrogen: volume ratio of inert atmosphere = 1: 3-5.
The eutectic solvent is a hydrogen bond acceptor choline chloride and a hydrogen bond donor: urea, carboxylic acid or polyol in a molar ratio of 1:1 to 3, preferably in a molar ratio of 1: 2 choline chloride-urea or choline chloride-ethylene glycol.
The eutectic solvent is a two-component or three-component eutectic mixture formed by combining a hydrogen bond acceptor (such as quaternary ammonium salt) and a hydrogen bond donor (such as amide, carboxylic acid, polyalcohol and other compounds) in a certain stoichiometric ratio, is used as a novel green solvent, and has the advantages of low price, no toxicity, low vapor pressure, biodegradation and the like.
Through the heating pretreatment of the eutectic solvent, impurities such as volatile solvent can be removed, oxygen in the porous silicon oxide can be further reduced, the poured reduced metal can fully enter the pore channel structure, the requirements of the stabilization treatment process on the environment can be reduced, the effect of side reactions such as oxidation and the like of the poured reduced metal can be prevented, the porous silicon oxide after lithium pouring tends to be stabilized, the volume expansion of the negative electrode material can be reduced, and the stability of the negative electrode material can be improved.
4) Carbon coating step: the carbon coating is preferably realized by a chemical vapor deposition method, the carbon source of the chemical vapor deposition method is preferably one or a combination of acetylene, methane, propane and propylene, the coating temperature of the carbon coating is 600-1000 ℃, preferably 700-1000 ℃, and the time of the carbon coating is 1-2.5 h.
The third purpose of the invention is to provide the application of the silicon monoxide composite negative electrode material for improving the first coulombic efficiency in the negative electrode material of the lithium ion battery.
The principle of the invention is that the raw material of the silicon monoxide block body is subjected to porous treatment, then the reducing material is poured into a pore channel, and the oxygen contained in the silicon monoxide is consumed in advance, so that the irreversible capacity caused in the first charge-discharge process in the battery is reduced, and the first coulombic efficiency of the material is improved; meanwhile, the porous material provides a space for volume expansion required in the lithium embedding process of the silicon-based negative electrode material, so that the porous silicon oxide micron particles can be prevented from being crushed and pulverized, and the circulation stability of the material is further improved; in addition, the porous structure can effectively shorten the transmission path of lithium ions and electrons in the battery, and simultaneously, through a proper stabilizing treatment process, the rate capability and the cycling stability of the material are effectively improved.
The preparation method is simple and convenient, is beneficial to industrial implementation, and enables the composite material to have very wide application prospect.
Drawings
Fig. 1 is a scanning electron microscope photograph of the porous silica composite negative electrode material with improved first coulombic efficiency prepared in example 1.
Fig. 2 is an X-ray diffraction spectrum of the porous silica composite anode material with improved first coulombic efficiency prepared in example 1.
Fig. 3 is an electron micrograph of the porous silica composite anode material with improved first coulombic efficiency obtained in example 1 and an element distribution diagram of silicon, oxygen and doped elements.
Fig. 4 is a charge-discharge curve of the porous silica composite anode material for improving the first coulombic efficiency prepared in example 1.
Fig. 5 is a cycle performance curve of the porous silica composite anode material for improving the first coulombic efficiency prepared in example 1.
Fig. 6 is a cross-sectional scanning electron microscope image of the porous silica composite anode material with improved first coulombic efficiency prepared in example 1.
Detailed Description
The present invention will be further described with reference to the following examples, but the present invention is not limited to the following examples.
The experimental methods described in the following examples are all conventional methods unless otherwise specified; the reagents and materials are commercially available, unless otherwise specified.
The Scanning Electron Microscope (SEM) is electron scanning electron microscope JEOL-6701F, and the Transmission Electron Microscope (TEM) adopts JEM-2100F.
Example 1
1) Pore-forming of the silica by a ball-milling spray method: adding certain mass of a silica block, high-temperature asphalt and phenolic resin into a high-energy ball mill for high-energy ball milling, wherein the high-temperature asphalt is used as a binder and accounts for 5% of the silica block by mass, and the phenolic resin is used as a pore-forming agent and accounts for 10% of the silica block by mass; then adding a proper amount of water into the high-energy ball mill, and adjusting the solid content of the materials to be 20%; after the materials are mixed, high-speed ball milling is carried out for 6 hours at the rotating speed of 1000 r/min, thus obtaining the silica composite material slurry with the solid content of 20 percent, and then the slurry is treated by spray drying to form raw material powder microspheres with uniformly distributed components; thirdly, heating the raw material microspheres containing the silicon monoxide, the binder asphalt and the phenolic resin to 800 ℃ under the protection of argon, and preserving heat for 1 h to fully carbonize the binder asphalt and the phenolic resin to obtain porous silicon monoxide micron particles (amorphous carbon formed by carbonizing a small amount of layer of binder and pore-forming agent coated on the surface) with pore channel structures;
2) and (2) infusing the reducing metal material into the porous silica micro-particles with the pore channel structure by using a liquid phase infusion method: firstly, preparing an organic solution dissolved with metal lithium, adding a certain mass of metal lithium block into an ethylene glycol dimethyl ether solution dissolved with dimethyl biphenyl, wherein the concentrations of the metal lithium and the dimethyl biphenyl are respectively 0.5M and 0.1M; then adding the porous silica micro-particles with the pore channel structure obtained in the step (1) into the solution, and violently stirring for 10 hours, wherein the using amount of the metal lithium is 10wt% of the porous silica micro-particles; heating the mixed solution to evaporate glycol dimethyl ether to obtain porous silica micron particles infused with dimethyl biphenyl-metal lithium;
3) carrying out stabilization treatment: heating the porous silicon oxide micron particles filled with the dimethyl biphenyl-metal lithium obtained in the step 2) to 680 ℃ under the protection of argon, and preserving heat for 5 hours, so that the dimethyl biphenyl is carbonized, the metal lithium and the porous silicon oxide are combined to form lithium silicate, and the porous silicon oxide composite negative electrode material with the improved first coulombic efficiency is obtained.
Fig. 1 is a scanning electron microscope photograph of the porous silicon oxide composite negative electrode material with the first coulombic efficiency improving effect, which is prepared in example 1, wherein the particle size is about 20 μm, and the porous silicon oxide composite negative electrode material is in a porous structure with the pore size of about 50 nm.
FIG. 2 is an XRD diffraction pattern of the porous silica composite negative electrode material obtained in example 1 analyzed by an X-ray diffraction analyzer (XRD, Rigaku D/max 2500, Cu K α). Significant lithium silicate such as Li appears in the diffractogram2Si2O5And Li2SiO3Also, since lithium metal reacts with porous silicon oxide to form lithium silicate and part of silicon is reduced, a diffraction peak of Si occurs.
FIG. 3 is an electron micrograph of the porous silica composite anode material prepared in example 1 and an element distribution diagram of silicon, oxygen and carbon, wherein element signals are uniform and do not agglomerate.
Fig. 6 is a cross-sectional scanning electron microscope photograph of the porous silica composite anode material obtained in example 1, which shows the distribution of the pores inside the particles, except for the pores visible outside the particles, the pores inside the particles are also uniformly distributed, the pores are uniformly distributed inside the whole material, and the interiors of the pores are communicated. Therefore, the method firstly carries out a proper pore-forming step, fills the reducing metal by means of a proper pore channel structure, and is favorable for fully reducing the metal.
Example 2
The other operation steps are the same as the example 1, except that the step 1) adopts the evaporation deposition method to carry out the pore-forming of the silicon monoxide, and the steps are as follows: firstly, uniformly mixing silica and a pore-forming agent magnesium silicate, and then drying to prepare mixed powder in which the silica and the magnesium silicate are uniformly dispersed, wherein the using amount of the magnesium silicate is 25 percent of that of massive silica; then heating the mixed powder to 1350 ℃ under the pressure of 1 Pa of vacuum degree, so that the silicon monoxide and the magnesium silicate are uniformly evaporated; secondly, reducing the temperature to 800 ℃, and obtaining a block body with a porous structure and uniformly distributed porous silica and magnesium silicate after condensation and deposition; and thirdly, crushing the blocks into powder with the particle size of 5 mu m in an air flow crushing mode. The pore diameter of the porous silicon oxide composite negative electrode material is about 25 nm.
Example 3
The other operation steps are the same as example 1, except that the metallic lithium in step 2) is changed into metallic sodium.
Example 4
The other operation steps are the same as example 1 except that in the step 1) of pore-forming porous silica by the ball-milling spray method, the amount of the pore-forming agent phenolic resin is 15wt% of the silica bulk. The pore diameter of the porous silicon oxide composite negative electrode material is about 80 nm.
Example 5
The other operation steps are the same as example 1 except that in the step 1) of pore-forming porous silica by the ball-milling spray method, the amount of the pore-forming agent phenolic resin is 20wt% of the silica bulk. The pore diameter of the porous silicon oxide composite negative electrode material is about 90 nm.
Example 6
The other operation steps are the same as the example 2, except that in the step 1), the pore-forming of the silica is carried out by adopting an evaporation deposition method, and the usage of the pore-forming agent magnesium silicate is 20wt% of the silica block. The pore diameter of the porous silicon oxide composite negative electrode material is about 20 nm.
Example 7
The other procedure was the same as in example 1 except that the amount of lithium metal used was 5wt% of the porous silica micro-particles by adjusting the amount of silica micro-particles to maintain the concentrations of lithium metal and dimethylbiphenyl constant in step 2).
Example 8
The other operation steps are the same as example 2, except that the metallic lithium in step 2) is changed into metallic potassium.
Example 9
The other operation steps are the same as example 2 except that in step 1), the pore-forming step of silica was performed by vapor deposition, and the amount of magnesium silicate was adjusted to 35%. The pore diameter of the porous silicon oxide composite negative electrode material is about 100 nm.
Example 10
The other steps are the same as the operation of the example 2, except that the step 3) is carried out for stabilizing the porous silicon oxide micron particles filled with the dimethyl biphenyl-metal lithium, and then the step 4) is carried out for chemical vapor deposition carbon coating, wherein the specific method is as follows: and heating the stabilized material to 950 ℃ for 2 h, introducing methane gas while keeping the high temperature, and coating the stabilized porous silicon oxide micron particles with a vertical carbon layer.
Example 11
The other operation was the same as in example 1 except that the amount of lithium metal used in step 2) was 15wt% based on the porous silica micro-particles.
Example 12
The other operation steps are the same as the example 1, except that the reducing metal material is poured into the silica micron particles with the pore channel structure by using a liquid phase pouring method in the step 2): dispersing lithium nitride in N, N-dimethylformamide, wherein the concentration of the lithium nitride is 0.5M; then adding the porous silicon oxide micron particles with the pore channel structure obtained in the step 1) into the solution, and violently stirring for 10 hours, wherein the using amount of lithium nitride is 10% of that of the silicon oxide micron particles; and heating the mixed solution to evaporate N, N-dimethylformamide to obtain the porous micron particles infused with the lithium nitride.
Example 13
The other steps are the same as example 4, except that the porous silica microparticles impregnated with dimethyl biphenyl-metal lithium obtained in step 2) are placed in a 1: 2, then introducing hydrogen/nitrogen (3: 1) mixed atmosphere, pretreating for 3h at 60 ℃, taking out, and carrying out stabilization treatment.
Example 14
The other steps are the same as the operation of the example 2, except that the porous silica micron particles impregnated with the dimethyl biphenyl-metal lithium obtained in the step 2) are placed in a reaction chamber of 1: 2, then introducing hydrogen/nitrogen (3: 1) mixed atmosphere, pretreating for 3h at 60 ℃, taking out, and carrying out stabilization treatment.
Example 15
The evaporation temperature in step 2) was 1350 deg.c and the deposition temperature was 540 deg.c, and the other steps were the same as in example 2.
Example 16
The evaporation temperature in step 2) was 1350 deg.C and the deposition temperature was 1000 deg.C, and the other steps were the same as in example 2.
Example 17
The impregnation is carried out under negative pressure of-0.95 MPa in the step 2), and the other steps are the same as those in the example 1.
Comparative example 1
The other steps were carried out as in example 1, except that step 2) was omitted, and the amount of lithium metal used was 0.
Comparative example 2
The other steps were performed as in example 1, except that the amount of metallic lithium used in step 2) was 3%.
Comparative example 3
The other steps were performed as in example 1, except that the amount of metallic lithium used in step 2) was 22%.
Comparative example 4
The other steps were the same as those of example 2 except that the amount of magnesium silicate used in the pore-forming step of porous silica by vapor deposition in step 1) was adjusted to 10% and the pore diameter was about 5 nm.
Comparative example 5
The other steps were the same as those of example 2 except that the amount of magnesium silicate used in the pore-forming step of porous silica by vapor deposition in step 1) was adjusted to 45% and the pore diameter was about 200 nm.
Comparative example 6
The other steps were the same as those in example 2 except that the stabilization treatment in step 3) was not performed.
Application example
The electrochemical properties of the silicon-based anode materials prepared in the examples and the comparative examples are tested according to the following methods: mixing the prepared porous silica composite negative electrode material with the improved first coulombic efficiency, carbon black, carboxymethyl cellulose (CMC) and Styrene Butadiene Rubber (SBR) composite binder in a mass ratio of 80:10:10 to prepare slurry (wherein the mass ratio of the CMC to the SBR is 1: 1), uniformly coating the slurry on a copper foil current collector, and performing vacuum drying for 12 hours to prepare a working electrode; lithium foil as counter electrode, glass fiber membrane (from Whatman, UK) as separator, 1 mol/L LiPF6(the solvent is a mixed solution of ethylene carbonate and dimethyl carbonate with the volume ratio of 1: 1) is used as electrolyte, VC with the volume fraction of 1% and FEC with the volume fraction of 5% are added into the electrolyte, and the button cell is assembled in a German Braun inert gas glove box in an argon atmosphere.
Electrochemical analysis tests were performed on the porous silica composite anode material with improved first coulombic efficiency prepared in example 1, and the results are shown in fig. 4. The charging and discharging interval is 0-1.5V, the material capacity can reach 1418 mAh/g when charging and discharging are carried out under the condition that the current density is 0.2C, the coulombic efficiency of the first circle is 89.7 percent, the figure 5 is a capacity retention rate curve of a battery circulating for 100 circles, the capacity retention is as high as 97.3 percent, and the modified silicon monoxide material obtained by the invention is proved to have higher capacity and excellent circulating performance.
The charge and discharge tests were performed on the negative electrode materials of examples and comparative examples according to the above-described methods, and the results are shown in table 1 below:
TABLE 1 negative electrode materials test Performance
Figure DEST_PATH_IMAGE001
The embodiment data show that a proper porous structure of the silicon monoxide is provided for reducing metal, the amount of the pore-forming agent is controlled to be 10-20% in the process of spray pore-forming, and the amount of the pore-forming agent is controlled to be 20-35% in the process of evaporation pore-forming, so that the prepared negative electrode material has good first reversible specific volume, first effect and capacity retention rate of 100 circles. When the consumption of the reducing metal is 5-15%, the first efficiency of the negative electrode material is higher than 89%, and the retention rate of 100 circles is higher than 96.8%.
After the reduced metal material is filled into the pore channel, the channel is not subjected to stabilization treatment, and the filled reduced metal material is likely to be directly oxidized when contacting with air in the post-treatment process due to high activity, so that the improvement of the coulombic efficiency for the first time is limited; in addition, compounds generated by reaction of the reductive metal material which is not subjected to stabilization treatment with air and moisture exert adverse effects on the capacity of the battery material, and the reversible specific capacity of the material can be remarkably reduced, so that the negative electrode material prepared through stabilization treatment has obvious advantages in the first specific capacity, the first coulombic efficiency and the retention rate of 100 circles.
After the pretreatment of the eutectic solvent, the method is favorable for preventing the injected reductive metal from generating side reactions such as oxidation and the like, and ensures the thoroughness of the injected reductive metal on oxygen, thereby being favorable for the stability of lithium silicate. Moreover, the pretreatment temperature does not need to be very high, the environment before stabilization can be adjusted to a better state, side reactions are reduced while oxygen is further consumed, and the first effect and the cycling stability are further improved.
According to the invention, the porous silica obtained through porous treatment has more uniform pore channel distribution, so that the porous silica is beneficial to pouring the reducing metal element into the particles, effectively buffers the volume expansion of the porous silica in the charge and discharge processes, and reduces the internal stress of the particles, therefore, the first coulombic efficiency and the cycle stability of the material are more advantageous. In conclusion, the preparation method is simple and efficient, and when the obtained porous silicon monoxide composite negative electrode material is used as a negative electrode material of a lithium ion battery, the first coulombic efficiency (up to 90 percent) is improved, the rate performance and the cycle performance (up to 98 percent) are good, and the electrochemical performance is more excellent.
The applicant states that the present invention is illustrated by the above examples to show the detailed process equipment and process flow of the present invention, but the present invention is not limited to the above detailed process equipment and process flow, i.e. it does not mean that the present invention must rely on the above detailed process equipment and process flow to be implemented. It should be understood by those skilled in the art that any modification of the present invention, equivalent substitutions of the raw materials of the product of the present invention, addition of auxiliary components, selection of specific modes, etc., are within the scope and disclosure of the present invention.

Claims (7)

1. The silica-based composite negative electrode material for improving the first coulombic efficiency is characterized in that the negative electrode material takes porous silica as a substrate, and a reducing material is poured into a pore channel; the aperture of the silica-based composite negative electrode material is 10-100nm, and the inside of a pore channel is uniform and communicated; the reducing material is selected from at least one metal or compound thereof with the reducibility higher than that of hydrogen, wherein the metal with the reducibility higher than that of hydrogen is selected from one or more of lithium, potassium, barium, calcium, sodium, magnesium, aluminum, titanium, zinc, cobalt, nickel, iron, tin and antimony; the metal or the compound thereof accounts for 5-20wt% of the porous silica, and the silica-based composite anode material is obtained by forming pores in the silica, pouring a reducing material into the pore channels, heating to 400-900 ℃ and carrying out stabilization treatment;
the median particle diameter of the silica-based composite negative electrode material is 1-30 mu m, and the specific surface area of the silica-based composite negative electrode material is 1-50m2/g。
2. The silica-based composite anode material of claim 1, wherein the pore-forming is to obtain porous silica by a ball-milling spray method, a disproportionation etching method or an evaporation deposition method; the reduction material is poured by placing porous silica in steam or precursor solution of the material to be poured.
3. A method for preparing a silica-based composite anode material according to claim 1 or 2, which mainly comprises the following steps:
1) pore-forming: enabling the silicon monoxide to have a pore channel structure by a ball milling spraying method, a disproportionation etching method or an evaporation deposition method to obtain porous silicon monoxide;
2) pouring: dipping the porous silicon monoxide obtained in the step 1) in a material to be poured or a precursor solution thereof;
step 2) the perfusion is to dissolve metal in an ether solvent containing aromatic ring solute in advance to prepare an aromatic ring-metal organic solution, then to dip the porous silicon oxide micron particles obtained in the step 1) into the organic solution, and to obtain the porous silicon oxide micron particles perfused with aromatic ring-metal by vacuum drying;
the aromatic ring solute is selected from one or more of biphenyl, terphenyl, dimethyl biphenyl, naphthalene and anthracene, and the ether solvent is tetrahydrofuran or ethylene glycol dimethyl ether;
or step 2) the perfusion is to disperse a metal compound in an organic solvent, then to dip the porous silica micron particles obtained in step 1), and to dry the porous silica micron particles to obtain the porous silica micron particles;
3) and (3) stabilizing treatment: the porous silica impregnated with the reducing material is stabilized by heat treatment at 900 ℃ under an inert atmosphere.
4. The method of claim 3, wherein the ball milling spray method of step 1) comprises: firstly, crushing a silicon monoxide block into small particles by a liquid phase ball milling crushing method, and adding a binder and a pore-forming agent in the ball milling process to obtain mixed slurry; secondly, spray drying the slurry mixed with the small silicon monoxide particles, the binder and the pore-forming agent to obtain powdery microspheres; removing the pore-forming agent to obtain porous silica microparticles with a porous structure; wherein the pore-forming agent is selected from one or more of water-soluble inorganic ammonium salt, phenolic resin and polyvinyl alcohol; the amount of the pore-forming agent accounts for 5-25wt% of the silicon monoxide block;
the evaporation deposition method comprises the following steps: uniformly mixing a silicon monoxide block body and a pore-forming agent, drying, and heating and evaporating a material mixed with the silicon monoxide and the pore-forming agent under a high-temperature negative-pressure condition; preparing porous silica blocks with different deposition forms by adjusting the ratio of the evaporation temperature to the deposition temperature; thirdly, crushing the obtained porous silicon oxide block into micron particles, and removing the pore-forming agent through heat treatment to obtain porous silicon oxide micron particles with a pore channel structure; wherein the temperature under the high-temperature negative pressure condition is 1200-1500 ℃, and the vacuum degree is 1-10 Pa; the pore-forming agent is silicate and accounts for 15-40wt% of the silicon monoxide block; the ratio of the evaporation temperature to the deposition temperature is 1: 0.4-0.8; the temperature for removing the pore-forming agent is 500-800 ℃;
the disproportionation etching method comprises the following steps: firstly, crushing a silicon monoxide block body to a micron level through an airflow crushing process; secondly, carrying out high-temperature treatment on the crushed silicon monoxide micron particles to cause the silicon monoxide micron particles to be disproportionated, thereby forming a nano-scale uniformly dispersed structure of silicon dioxide and silicon crystal regions; etching the disproportionated porous silicon oxide by using hydrofluoric acid, and obtaining porous silicon oxide micron particles with porous structures due to different reaction degrees of each component of the disproportionated porous silicon oxide and the hydrofluoric acid; wherein the high-temperature treatment temperature of the porous silica micron particles obtained by crushing is 1000-1200 ℃.
5. The method as claimed in claim 3, wherein the temperature of the stabilizing treatment in step 3) is 500-800 ℃ and the time is 2-10 h.
6. The method of claim 5, wherein the stabilization treatment of step 3) is preceded by a pretreatment step: dissolving the porous silicon oxide infused with lithium in eutectic solvent, and then reacting the mixture with H in inert atmosphere or inert atmosphere2The treatment temperature is 50-80 ℃, and the treatment time is 1-5 h;
the eutectic solvent is formed by choline chloride and one of urea, carboxylic acid or polyalcohol according to the molar ratio of 1: 1-3.
7. Use of the silica-based composite anode material according to claim 1 or 2 or the porous silica-based composite anode material prepared by the preparation method according to any one of claims 3 to 6 in an anode material of a lithium ion battery.
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