CN115557505B - Pre-lithiated silicon-based negative electrode material and preparation method thereof - Google Patents

Pre-lithiated silicon-based negative electrode material and preparation method thereof Download PDF

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CN115557505B
CN115557505B CN202211163707.5A CN202211163707A CN115557505B CN 115557505 B CN115557505 B CN 115557505B CN 202211163707 A CN202211163707 A CN 202211163707A CN 115557505 B CN115557505 B CN 115557505B
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silicon
lithium
mass
negative electrode
compound
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CN115557505A (en
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王辉
王庆莉
林少雄
万文文
丁男
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Hefei Gotion High Tech Power Energy Co Ltd
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Hefei Guoxuan High Tech Power Energy Co Ltd
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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B33/00—Silicon; Compounds thereof
    • C01B33/06—Metal silicides
    • 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
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/134—Electrodes based on metals, Si or alloys
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • H01M4/386—Silicon or alloys based on silicon
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    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
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    • C01P2004/00—Particle morphology
    • C01P2004/01—Particle morphology depicted by an image
    • C01P2004/03—Particle morphology depicted by an image obtained by SEM
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    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/60—Particles characterised by their size
    • C01P2004/61—Micrometer sized, i.e. from 1-100 micrometer
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
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    • 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
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    • 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 pre-lithiated silicon-based negative electrode material and a preparation method thereof, wherein the preparation method comprises the following steps: s1, under inert atmosphere, dissolving a compound I in an organic solvent, then adding triethylamine, uniformly mixing, and then adding a lithium source for reaction to obtain a mixed solution A; s2, mixing the silicon oxide with the mixed solution A, performing reaction, performing solid-liquid separation after the reaction is finished, and drying the obtained solid substance to obtain powder B; and S3, sintering the powder B in an inert atmosphere, cooling, and washing the obtained product with isopropanol vapor to obtain the pre-lithiated silicon-based anode material. The pre-lithiated silicon-based negative electrode material is used for a lithium ion battery, and can obviously improve the specific capacity, initial effect and cycle stability of the lithium ion battery.

Description

Pre-lithiated silicon-based negative electrode material and preparation method thereof
Technical Field
The invention relates to the technical field of lithium ion batteries, in particular to a pre-lithiated silicon-based negative electrode material and a preparation method thereof.
Background
With the development of electric vehicles and portable electric appliances, the demand for high energy density lithium ion batteries is also increasing. The theoretical specific capacity of the traditional graphite anode material is only 372mAh/g, and the market demand is hardly met. The first gram capacity of the silicon material is 4200mAh/g, the lithium intercalation platform is higher, the crust is rich in storage, the silicon material is environment-friendly, and the like, so that the silicon material gradually attracts wide attention of researchers.
However, the volume expansion of silicon is as high as 300%, which can cause not only separation of silicon from the surrounding conductive carbon network during cycling, forming "dead silicon", but also stripping of silicon from the current collector. And secondly, the larger volume expansion can also cause continuous recombination and damage of the SEI film on the surface, so that the SEI film is thicker and thicker, li+ of the positive electrode is continuously consumed, and the coulomb efficiency is reduced. Finally, the larger volume expansion leads to pulverization of the silicon material at the later stage of the cycle, and these problems eventually lead to a drastic deterioration of the cycle performance.
Due to the above problems, the academia and industry have partly been focusing on silica. Compared with nano silicon, the silicon oxide has relatively small expansion (100 percent) although the partial capacity is sacrificed, and byproducts such as lithium oxide, lithium silicate, lithium metasilicate and the like generated in the charge and discharge process can provide a buffer effect, so that the cycle performance of the material is greatly improved. However, conventional silica materials are relatively poor in conductivity and have a low initial efficiency. In addition, the silicon oxide after partial lithiation not only further reduces the intrinsic electronic conductivity of the material due to the generation of byproducts such as lithium metasilicate, but also has negative effects such as slurry gas production caused by higher residual alkali on the surface and reduced adhesive performance caused by side reaction with the adhesive. Lee D J [ Lee D J, ryou M H, lee J N, et al Nitrogen-doped carbon coating for a high-performance SiO anode in lithium-ion batteries [ J ]. Electrochemistry Communications,2013,34:98-101 ] and the like prepare nitrogen-doped carbon-coated SiO materials by means of liquid phase mixing and high temperature carbonization, the materials circulate relatively well, but the first coulombic efficiency of the materials is lower, and the intrinsic electronic conductivity of the materials is not improved. Jee Hoyom et al [ Yom J H, sun W H, cho S M, et al, improvement of irreversible behavior of SiO anodes for lithium ion batteries by a solid state reaction at high temperature [ J ]. Journal of Power Sources,2016,311:159-166 ] prepare high first efficiency silicon-based anode materials by solid phase reaction of SiO with lithium metal, and carbon coating, the method improves the first coulombic efficiency of the materials, but the recycling performance of the materials is relatively poor, and the synthesis conditions are relatively harsh due to the use of lithium metal as a reactant, which presents a safety risk, and the risk of gas production during the battery slurry mixing process. In addition, the electron conductivity of the material is further lower due to the formation of lithium silicate and other by-products during the reaction.
Disclosure of Invention
Based on the technical problems in the background technology, the invention provides a pre-lithiated silicon-based anode material with high specific capacity, high initial efficiency and good cycling stability and a preparation method thereof.
The invention provides a preparation method of a pre-lithiated silicon-based negative electrode material, which comprises the following steps:
s1, under inert atmosphere, dissolving a compound I in an organic solvent, then adding triethylamine, uniformly mixing, and then adding a lithium source for reaction to obtain a mixed solution A;
the structural formula of the compound I is shown as a formula (1):
s2, mixing the silicon oxide with the mixed solution A, performing reaction, performing solid-liquid separation after the reaction is finished, and drying the obtained solid substance to obtain powder B;
and S3, sintering the powder B in an inert atmosphere, cooling, and washing the obtained product with isopropanol vapor to obtain the pre-lithiated silicon-based anode material.
Preferably, in the structural formula of the compound I, R1 is selected from substituted or unsubstituted C 1-6 Alkyl, C 2-6 Alkenyl, C 2-6 Alkynyl, C 6-12 At least one of aryl groups, R2 and R3 are respectively selected from at least one of butyl (Bu), naphthyl (Np), trimethylsilyl (TMS) and diisopropylphenyl (Dipp).
The synthesis method of the compound I comprises the following steps:
isopropanol and water were mixed according to 2:1, and then mixing uniformly according to a mole ratio of 2:1 adding amine compound (R2-NH 2 or R3-NH 2) and 40% aldehyde compound, stirring at 40-60 ℃ for reaction for 0.5h, adding a proper amount of water, filtering, and drying to obtain an intermediate product A. Intermediate A and lithium are mixed according to a mole ratio of 2 at-20 ℃ to 0 ℃:1 is added into tetrahydrofuran solution, stirred for 4 to 8 hours at room temperature, the solvent is pumped down, a small amount of unreacted intermediate product A is removed by washing with n-hexane, and the intermediate product B is obtained by drying. The intermediate product B and silicon tetrachloride are mixed according to a mole ratio of 1 at-100 ℃ to-80 ℃:2 is added into tetrahydrofuran solution, stirred at room temperature for reaction for 6 hours, and then n-hexane is added for extraction after pumping, thus obtaining an intermediate product C. Intermediate C and potassium carbide are mixed according to a mole ratio of 1 at-100 ℃ to-80 ℃): 2, adding the mixture into tetrahydrofuran solution, maintaining the temperature between minus 30 ℃ and minus 70 ℃ for reaction for 48 hours, pumping the solvent, adding n-hexane for extraction, and concentrating to obtain a compound I;
in the synthesis method of the compound I, the amine compound is at least one of butylamine (n-butylamine and tert-butylamine), naphthylamine, trimethylsilyl amine and diisopropylaniline, and the aldehyde compound is glyoxal and homologs thereof, butenedialdehyde and homologs thereof, phthaldialdehyde and homologs thereof, butynediol and homologs thereof. Wherein the amine compound is used for forming an R2-N-structure and an R3-N-structure in the compound I; the aldehyde compound is used for forming a-R1-structure in the compound I; silicon tetrachloride is added in the synthesis step in order to introduce Si into the compound I and to finally form a-Si-structure by reduction with potassium carbide.
Preferably, the weight of the triethylamine is 2-8% of the sum of the weight of the compound I and the weight of the triethylamine, and the weight of the lithium source is 4-50% of the sum of the weight of the compound I, the weight of the triethylamine and the weight of the lithium source; the lithium source is lithium, liH or LiBH 4 、Li 3 At least one of N and lithium ethynyl; the organic solvent is at least one of tetrahydrofuran, normal hexane and toluene.
Preferably, in S1, the reaction temperature is between-20 ℃ and 30 ℃ and the reaction time is between 0.5h and 6h.
In S1, the compound I is an organic compound containing nitrogen and silicon, and forms a lithium-containing polymer under the action of a lithium source, wherein the saturated compound I and the lithium source further react to generate a dilithium dimer, the unsaturated compound I can further react with the lithium source to generate a dilithium trimer or even a tetramer, and the lithium content in the liquid phase reaction can be improved under the same ligand, so that the pre-lithium effect of the silicon oxide material is improved. By introducing triethylamine, the compound I can be prevented from being reduced, the reaction temperature is too high, a single lithium dimer is formed, and the lithium content in the material is influenced, so that the control of process parameters is important. The general reaction equation is as follows:
in which, taking specific saturated compound I (R1 is ethyl (-C2H 4-), R2 and R3 are butyl) as an example, the reaction equation is as follows:
taking a specific unsaturated compound I (taking R1 as phenyl (-C6H 4-), R2 and R3 as naphthyl) as an example, the reaction equation is as follows:
different from the saturated compound I, because of unsaturated groups, double lithium trimers and even tetramers can be formed on the premise of controlling the proportion of the compound I and a lithium source, the pre-lithium depth and the pre-lithium uniformity are effectively controlled, and a foundation is laid for controlling silicon grains in the material.
Preferably, the ratio of the mass of the silicon oxide to the mass of the lithium element in the mixture a is (9 to 24): 1, a step of; the Silica (SiO) has a hierarchical particle size of: dmin is more than or equal to 1.5 mu m, D10 is more than or equal to 3 mu m, D50 is more than or equal to 5 and less than or equal to 7 mu m, and Dmax is less than or equal to 10 mu m. The silica having the above-mentioned classified particle size can be obtained by a conventional pulverizing and classifying treatment. By controlling the SiO particle size distribution, the negative influence of the pre-lithium process can be effectively reduced, too small Dmin or too large Dmax can cause the problems of excessive pre-lithium of small particles and insufficient pre-lithium of large particles, and finally the first effect of the material, the grain size of monocrystalline silicon and the cycle performance are influenced.
Preferably, in S2, the mass of the silicon oxide is 5-20% of the sum of the mass of the silicon oxide and the mass of the mixed solution A; the reaction temperature is 20-80 ℃ and the reaction time is 1-12 h; in S2, the drying method is vacuum drying, the vacuum degree is 10-100 Pa, the drying temperature is 60-100 ℃, and the drying time is 3-12 h.
In S2, silicon oxide reacts with the mixture A containing lithium, lithium ions can enter the silicon oxide material to form byproducts such as lithium metasilicate, lithium silicate, lithium oxide and the like, so that the first coulombic efficiency of the material is improved, and the volume expansion is reduced. In order to improve the pre-lithium effect of the material and the final cycle performance of the material, the proportion of the silicon oxide to the mixed solution A needs to be limited, so that the content of the silicon oxide in a reaction system is strictly controlled, the content of the silicon oxide in the reaction system is low, the pre-lithium rate is too high, silicon grains in the silicon oxide material grow too fast, the grain size is large, and the cycle performance of the material is poor; the content of the silicon oxide in the reaction system is too high, the pre-lithium rate is too slow, the required reaction time is too long, and the industrialized amplification is not facilitated. And because the concentration difference of lithium ions is small (the surface and the inside of the silicon oxide), the expansion rate is too slow, the surface of the silicon oxide is extremely easy to be reduced to generate silicon, and the cycle performance is fast attenuated.
Preferably, in S3, sintering is carried out until the half-peak width of silicon grains of the silicon oxide in the obtained product is more than or equal to 0.8; s3, sintering is sectional type heating sintering, and the specific steps are as follows: the first stage sintering is carried out at 200-400 ℃ for 1-6 h, and then the second stage sintering is carried out at 600-1200 ℃ for 2-12 h.
In the sintering process, at the first stage temperature, the double lithium polymer of the compound I is melted and is uniformly mixed with the silicon oxide under the continuous rotation of the rotary furnace, so that a foundation is provided for the subsequent carbonization uniformity. At the second stage temperature, in the double lithium polymer of the compound I, nitrogen continuously diffuses into the silicon-based material to replace part of silicon atoms, so that substitution doping is formed, the electron concentration in the silicon oxide is improved, and the intrinsic electron conductivity of the silicon material is improved. At high temperature, lithium ions which are not completely reacted in the liquid phase react with the silicon oxide to further form byproducts such as lithium metasilicate, lithium silicate, lithium oxide and the like, thereby improving the first coulombic efficiency of the material. In addition, the double lithium polymer of the compound I is carbonized at high temperature to form a conductive carbon and silicon nitride composite coating layer with high conductivity and mechanical property, and the conductive carbon and silicon nitride composite coating layer is uniformly coated on the surface of the silicon oxide material, so that the electronic conductivity of the silicon-based material is improved, the volume expansion of the material is buffered, and the cycle performance of the material is improved. The half-width is mainly used for controlling the grain size of silicon in SiO and improving the first effect and the cycle performance of the material.
Preferably, in S3, the obtained product is washed by isopropanol steam until the residual lithium on the surface is less than or equal to 500ppm and the PH is less than or equal to 11.5; in S3, the flow rate of the isopropanol steam is 1 mL/min-10 mL/min, the washing time is 0.5 h-6 h, and the washing temperature is 120-180 ℃.
The product obtained after sintering in S3 is washed by isopropanol vapor, so that residual alkali and residual lithium on the surface of the material are reduced, the risk of gas production of the material in slurry combination in the process of manufacturing the battery cell can be reduced, side reaction between the residual alkali and a binder is reduced, the bonding performance is improved, and the cycle stability is improved. The isopropanol has smaller polarity, is relatively mild in reaction with active lithium, can effectively avoid the damage of water washing and other processes to the material, and further improves the cycle performance of the material. In addition, the isopropanol vapor can continuously carry away the lithium carbonate and the lithium hydroxide remained on the surface after contacting with the material in a flowing gaseous state, and can effectively prevent the dissolution of lithium silicate phase in the material relative to the treatment of the material in a liquid solvent, thereby further reducing the residual alkali on the surface, stabilizing the material structure and improving the cycle performance.
Preferably, in S3, a post-treatment may be further included after washing, and the post-treatment may include deagglomeration, and the deagglomeration may be performed by a conventional method, for example, a grinding treatment in a mechanical mill.
Preferably, the particle size D50 of the pre-lithiated silicon-based negative electrode material after deagglomeration is 5 μm to 8 μm.
Preferably, the inert atmosphere is at least one of helium, neon, argon, krypton, and xenon.
The invention also provides a pre-lithiated silicon-based negative electrode material prepared by the preparation method.
The invention also provides application of the pre-lithiated silicon-based negative electrode material as a negative electrode material of a lithium ion battery.
According to the actual demand, the invention further provides a lithium ion battery anode material which consists of a carbon material and the pre-lithiated silicon-based anode material; wherein the mass of the carbon material accounts for 1-95% of the total mass of the lithium ion battery anode material. The carbon material has higher electronic conductivity and soft quality, so that the volume expansion of the silicon-based material can be further buffered, and according to the actual application requirement, the carbon material and the pre-lithiated silicon-based negative electrode material can be mixed in a proper proportion in order to obtain the negative electrode material of the lithium ion battery with lower volume expansion.
Preferably, the granularity D50 of the carbon material is 8-20 mu m, and the granularity D50 of the pre-lithiated silicon-based negative electrode material is 5-8 mu m; the carbon material is at least one of natural graphite, artificial graphite, mesophase carbon microsphere, hard carbon and soft carbon.
Silicon oxide (SiO) has low initial efficiency and large expansion due to poor conductivity, so that the wide application of the silicon oxide (SiO) in the field of lithium ion batteries is limited. According to the invention, the liquid phase reaction is used for pre-lithium SiO, so that the reaction is more uniform, the first-effect coulomb efficiency of the material is improved, the reaction intensity can be controlled, the grain size of monocrystalline silicon in SiO is effectively reduced, the expansion of the material is reduced, and the cycling stability of the material is improved. And secondly, cracking the compound I loaded with lithium ions in a liquid phase at high temperature, diffusing nitrogen element into the silicon-based material to form substitutional doping, and improving the electron concentration in the silicon oxide so as to improve the intrinsic electron conductivity of the silicon material. And the compound I is cracked to form a carbon-coated and silicon nitride-coated composite coating layer, so that not only is the electronic conductivity of the material improved, but also the cycling stability of the material is improved due to the volume expansion of the buffer material with strong mechanical properties of silicon nitride. In addition, residual alkali and residual lithium on the surface of the material are reduced through isopropanol steam washing, the stability of the material in the process of the cell manufacturing process is improved, meanwhile, the damage of conventional treatment modes such as water washing to the surface of the material is reduced, and the cycle performance of the material is further improved. Therefore, the silicon-based anode material prepared by the invention overcomes the defects of the traditional SiO material, improves the intrinsic electronic conductivity, the first coulomb efficiency and the cycling stability of the material and the stability of the material in the process of the cell manufacturing process, and simultaneously reduces the volume expansion of the material.
The beneficial effects of the invention are as follows:
according to the invention, the liquid phase reaction is used for pre-lithium SiO, so that the reaction is more uniform, the first-effect coulomb efficiency of the material is improved, the reaction intensity can be controlled, the reaction is carried out under relatively mild conditions, the grain size of monocrystalline silicon in SiO is effectively reduced, the expansion of the material is reduced, and the cycling stability of the material is improved.
The compound I loaded with lithium ions in the liquid phase is cracked at high temperature, nitrogen diffuses into the silicon-based material to form substitutional doping, and the electron concentration in the silicon oxide is improved, so that the intrinsic electron conductivity of the silicon material is improved. And secondly, the compound I is cracked to form a carbon-coated and silicon nitride-coated composite coating layer, so that the carbon-coated and silicon nitride-coated composite coating layer has good electronic conductivity and high mechanical strength, not only improves the conductivity of the material, but also improves the cycling stability of the material due to the volume expansion of the buffer material with strong mechanical property of silicon nitride.
The reaction product is washed by the isopropanol vapor, so that residual alkali and residual lithium on the surface of the material are effectively reduced, the risk of gas production of the material during slurry mixing in the process of the battery cell can be reduced, the side reaction between the residual alkali and the binder is reduced, the bonding performance is improved, and the cycle stability is improved. The isopropanol has smaller polarity, is relatively mild in reaction with active lithium, can effectively avoid the damage of water washing and other processes to the material, and further improves the cycle performance of the material.
The method comprises the working procedures of liquid-phase pre-lithium reaction, sintering, isopropanol steam washing and the like, and is relatively simple in process, easy to amplify and suitable for industrial mass production.
The silicon-based anode material prepared by the invention overcomes the defects of the traditional SiO material, improves the intrinsic electronic conductivity, the first coulomb efficiency and the cycling stability of the material and the stability of the material in the process of manufacturing the battery cell, reduces the volume expansion of the material, and can obviously improve the specific capacity, the first effect and the cycling stability of the lithium ion battery when being used for the lithium ion battery.
Drawings
Fig. 1 is an SEM image of the silicon-based anode material prepared in example 1.
Fig. 2 is an SEM image of a commercial pre-lithium silicon anode material of comparative example 1.
Fig. 3 is an XRD pattern of the silicon-based negative electrode material prepared in example 1.
Fig. 4 is a first charge-discharge curve of example 1 and comparative example 1 at a current density of 0.1C.
Fig. 5 is a first charge-discharge curve of example 5 at a current density of 0.1C.
FIG. 6 is a graph of the cycling performance of the full cell at a current density of 1C/1C for example 5 and comparative example 6, comparative example 7.
Detailed Description
The technical scheme of the invention is described in detail through specific embodiments.
Example 1
Preparing a pre-lithiated silicon-based negative electrode material:
s1, introducing argon atmosphere into a liquid phase reaction kettle for protection, then adding 1L of tetrahydrofuran and 92g of a compound I, stirring and dissolving completely, then adding 8g of triethylamine, mechanically stirring and mixing uniformly, then adding 10g of lithium metal, and reacting for 0.5h at the temperature of minus 20 ℃ to obtain a mixed solution A, wherein the structural formula of the compound I is as follows:
s2, mixing 90g of silicon oxide with the mixed solution A (the mass of the silicon oxide is 7.5% of the sum of the masses of the silicon oxide and the mixed solution A), reacting at 20 ℃ for 12 hours, then carrying out solid-liquid separation, and vacuum drying the obtained solid substance at 60 ℃ for 12 hours to obtain powder B, wherein the silicon oxide is prepared through conventional crushing and grading treatment, and the particle size distribution is as follows: dmin=1.5 μm, d10=3 μm, d50=5 μm, dmax=10 μm;
s3, placing the powder B into a kiln, and sintering under an argon atmosphere, wherein the sintering process is as follows: firstly preserving heat for 1h at 400 ℃, then raising the temperature to 700 ℃ and preserving heat for 3h, controlling the half-width of silicon grains in SiO to be 1 at 28.4 ℃, cooling to room temperature, introducing 10mL/min of isopropanol steam, washing the obtained product at 120 ℃ for 6h until the surface residual lithium is less than or equal to 500ppm and the PH is less than or equal to 11.5, and then placing the product in a mechanical mill for grinding and deagglomerating until D50=6mu.m to obtain the pre-lithiated silicon-based negative electrode material.
Example 2
Preparing a pre-lithiated silicon-based negative electrode material:
s1, introducing helium atmosphere into a liquid phase reaction kettle for protection, then adding 0.5L of tetrahydrofuran solvent and 98g of compound I, adding 2g of triethylamine after stirring and dissolving completely, mechanically stirring and mixing uniformly, then adding 5g of lithium metal, and reacting for 6 hours at 30 ℃ to obtain a mixed solution A, wherein the structural formula of the compound I is as follows:
s2, mixing 95g of silicon oxide with the mixed solution A (the mass of the silicon oxide is 14 percent of the sum of the masses of the silicon oxide and the mixed solution A), reacting for 1h at 80 ℃, then carrying out solid-liquid separation, and vacuum drying the obtained solid substance at 100 ℃ for 3h to obtain powder B, wherein the silicon oxide is prepared through conventional crushing and grading treatment, and the particle size distribution is as follows: dmin=2 m, d10=3 μm, d50=7 μm, dmax=9 μm;
s3, placing the powder B into a kiln, and sintering in a helium atmosphere, wherein the sintering process is as follows: firstly preserving heat for 6 hours at 200 ℃, then raising the temperature to 1200 ℃ and preserving heat for 2 hours, controlling the half-width of silicon grains in SiO to be 0.8 at 28.4 ℃, cooling to room temperature, introducing 1mL/min of isopropanol steam, washing the obtained product at 180 ℃ for 0.5 hours until the residual lithium on the surface is less than or equal to 500ppm and the PH is less than or equal to 11.5, and then placing the product in a mechanical mill for grinding and deagglomerating until D50=8 mu m is obtained.
Example 3
Preparing a pre-lithiated silicon-based negative electrode material:
s1, introducing neon atmosphere into a liquid phase reaction kettle for protection, then adding 0.26L of tetrahydrofuran solvent and 95g of compound I, stirring and dissolving completely, then adding 5g of triethylamine, mechanically stirring and mixing uniformly, adding 95g of compound I and 5g of triethylamine into the liquid phase reaction kettle under the neon atmosphere, mechanically stirring and mixing uniformly, then adding 8g of lithium metal, and reacting for 3 hours at 0 ℃ to obtain a mixed solution A, wherein the structural formula of the compound I is as follows:
s2, mixing 92g of silicon oxide with the mixed solution A (the mass of the silicon oxide is 20% of the sum of the masses of the silicon oxide and the mixed solution A), reacting for 3 hours at 40 ℃, then carrying out solid-liquid separation, and vacuum drying the obtained solid substance at 80 ℃ for 6 hours to obtain powder B, wherein the silicon oxide is prepared through conventional crushing and classification treatment, and the particle size distribution is as follows: dmin=2 μm, d10=3 μm, d50=6 μm, dmax=9 μm;
s3, placing the powder B into a kiln, and sintering in a neon atmosphere, wherein the sintering process is as follows: firstly, preserving heat for 2 hours at 300 ℃, then raising the temperature to 800 ℃, preserving heat for 6 hours, controlling the half-width of silicon grains in SiO to be 0.9 at 28.4 ℃, cooling to room temperature, introducing 5mL/min of isopropanol steam, washing the obtained product at 160 ℃ for 2 hours until the surface residual lithium is less than or equal to 500ppm and the PH is less than or equal to 11.5, and then grinding and deagglomerating in a mechanical mill until D50=7μm is obtained.
Example 4
Preparing a pre-lithiated silicon-based negative electrode material:
s1, introducing helium atmosphere into a liquid phase reaction kettle for protection, then adding 0.8L of tetrahydrofuran solvent and 96g of compound I, adding 4g of triethylamine after stirring and dissolving completely, mechanically stirring and mixing uniformly, then adding 6g of lithium metal, and reacting for 6 hours at 30 ℃ to obtain a mixed solution A, wherein the structural formula of the compound I is as follows:
s2, mixing 94g of silicon oxide with the mixed solution A (the mass of the silicon oxide is 5% of the sum of the masses of the silicon oxide and the mixed solution A), reacting for 4 hours at 80 ℃, then carrying out solid-liquid separation, and vacuum drying the obtained solid substance at 60 ℃ for 6 hours to obtain powder B, wherein the silicon oxide is prepared through conventional crushing and classification treatment, and the particle size distribution is as follows: dmin=2 μm, d10=4 μm, d50=5 μm, dmax=9 μm;
s3, placing the powder B into a kiln, and sintering in a helium atmosphere, wherein the sintering process is as follows: firstly preserving heat for 4 hours at 200 ℃, then raising the temperature to 600 ℃ and preserving heat for 12 hours, controlling the half-width of silicon grains in SiO to be 1.2 at 28.4 ℃, cooling to room temperature, introducing 8mL/min of isopropanol steam, washing the obtained product at 140 ℃ for 3 hours until the surface residual lithium is less than or equal to 500ppm and the PH is less than or equal to 11.5, and then placing the product in a mechanical mill for grinding and deagglomerating until D50=6mu.m is obtained.
Comparative example 1
Comparative example 1 is a commercially available pre-lithiated silica material.
Comparative example 2
Comparative example 2 differs from example 1 only in that: s1, lithium is not added, and the specific steps are as follows:
preparing a silicon-based anode material:
s1, introducing argon atmosphere into a liquid phase reaction kettle for protection, then adding 1L of tetrahydrofuran and 92g of a compound I, adding 8g of triethylamine after stirring and dissolving completely, mechanically stirring and mixing uniformly, and then reacting at the temperature of minus 20 ℃ for 0.5h to obtain a mixed solution A, wherein the structural formula of the compound I is as follows:
s2, mixing 90g of silicon oxide with the mixed solution A, reacting for 12 hours at 20 ℃, then carrying out solid-liquid separation, and vacuum drying the obtained solid substance at 60 ℃ for 12 hours to obtain powder B, wherein the silicon oxide is prepared by conventional crushing and grading treatment, and the particle size distribution is as follows: dmin=1.5 μm, d10=3 μm, d50=5 μm, dmax=10 μm;
s3, placing the powder B into a kiln, and sintering under an argon atmosphere, wherein the sintering process is as follows: firstly preserving heat for 1h at 400 ℃, then raising the temperature to 700 ℃, preserving heat for 3h, cooling to room temperature, introducing 10mL/min of isopropanol steam, washing the obtained product at 120 ℃ for 6h until the residual lithium on the surface is less than or equal to 500ppm and the PH is less than or equal to 11.5, and then placing the product in a mechanical mill for grinding and deagglomerating until D50=6μm is obtained.
Comparative example 3
Comparative example 3 differs from example 1 only in that: s1, no compound I is added, and CVD carbon coating is carried out through acetylene, and the method is concretely as follows:
s1, introducing argon atmosphere into a liquid phase reaction kettle for protection, then adding 1L of tetrahydrofuran, adding 8g of triethylamine after stirring and dissolving completely, mechanically stirring and mixing uniformly, then adding 10g of lithium metal, and reacting for 0.5h at the temperature of minus 20 ℃ to obtain a mixed solution A;
s2, mixing 90g of silicon oxide with the mixed solution A, reacting for 12 hours at 20 ℃, then carrying out solid-liquid separation, and vacuum drying the obtained solid substance at 60 ℃ for 12 hours to obtain powder B, wherein the silicon oxide is prepared by conventional crushing and grading treatment, and the particle size distribution is as follows: dmin=1.5 μm, d10=3 μm, d50=5 μm, dmax=10 μm;
s3, placing 50g of powder B into a kiln, and sintering under an argon atmosphere, wherein the sintering process is as follows: firstly, preserving heat for 1h at 400 ℃, then heating to 700 ℃, introducing nitrogen and acetylene, preserving heat for 3h, wherein the flow rate of the nitrogen is 60mL/min, the flow rate of the acetylene is 60mL/min, cooling to room temperature, introducing 10mL/min of isopropanol steam, washing the obtained product at 120 ℃ for 6h until the residual lithium on the surface is less than or equal to 500ppm and the PH is less than or equal to 11.5, and then, grinding and deagglomerating in a mechanical mill until D50=6μm is obtained.
Comparative example 4
Comparative example 4 differs from example 1 only in that: s3, adopting water washing to replace isopropanol steam washing, wherein the method comprises the following steps:
preparing a pre-lithiated silicon-based negative electrode material:
s1, introducing argon atmosphere into a liquid phase reaction kettle for protection, then adding 1L of tetrahydrofuran and 92g of a compound I, stirring and dissolving completely, then adding 8g of triethylamine, mechanically stirring and mixing uniformly, then adding 10g of lithium metal, and reacting for 0.5h at the temperature of minus 20 ℃ to obtain a mixed solution A, wherein the structural formula of the compound I is as follows:
s2, mixing 90g of silicon oxide with the mixed solution A, reacting for 12 hours at 20 ℃, then carrying out solid-liquid separation, and vacuum drying the obtained solid substance at 60 ℃ for 12 hours to obtain powder B, wherein the silicon oxide is prepared by conventional crushing and grading treatment, and the particle size distribution is as follows: dmin=1.5 μm, d10=3 μm, d50=5 μm, dmax=10 μm;
s3, placing the powder B into a kiln, and sintering under an argon atmosphere, wherein the sintering process is as follows: firstly preserving heat for 1h at 400 ℃, then raising the temperature to 600 ℃ and preserving heat for 12h, cooling to room temperature, washing the obtained product with water for 6h, and after drying, putting the product into a mechanical mill to grind and deagglomerate until D50=6μm to obtain the pre-lithiated silicon-based negative electrode material.
Comparative example 5
Comparative example 5 differs from example 1 only in that: s3, washing is not carried out, and the specific steps are as follows:
preparing a pre-lithiated silicon-based negative electrode material:
s1, introducing argon atmosphere into a liquid phase reaction kettle for protection, then adding 1L of tetrahydrofuran and 92g of a compound I, stirring and dissolving completely, then adding 8g of triethylamine, mechanically stirring and mixing uniformly, then adding 10g of lithium metal, and reacting for 0.5h at the temperature of minus 20 ℃ to obtain a mixed solution A, wherein the structural formula of the compound I is as follows:
s2, mixing 90g of silicon oxide with the mixed solution A, reacting for 12 hours at 20 ℃, then carrying out solid-liquid separation, and vacuum drying the obtained solid substance at 60 ℃ for 12 hours to obtain powder B, wherein the silicon oxide is prepared by conventional crushing and grading treatment, and the particle size distribution is as follows: dmin=1.5 μm, d10=3 μm, d50=5 μm, dmax=10 μm;
s3, placing the powder B into a kiln, and sintering under an argon atmosphere, wherein the sintering process is as follows: firstly, preserving heat for 1h at 400 ℃, then, heating to 600 ℃, preserving heat for 12h, cooling to room temperature, and then, placing in a mechanical mill for grinding and deagglomeration until D50=6μm to obtain the pre-lithiated silicon-based negative electrode material.
Fig. 1 is an SEM image of the silicon-based anode material prepared in example 1, and it can be found that the particle size is relatively uniform, the particle size is about 6 μm, and the surface of the material is relatively flat. Fig. 2 is an SEM image of comparative example 1, which shows that more punctiform particles appear on the surface of the material, because the surface is insufficiently washed, and a large amount of lithium carbonate and lithium hydroxide exist on the surface of the material, so that the PH of the material is improved, the process stability of the material in the battery cell is affected, and the cycle stability of the material is reduced.
FIG. 3 is an XRD pattern of example 1, showing the presence of lithium metasilicate (Li 2 SiO 3 ) The characteristic diffraction peak of (2) shows that lithium ions react with part of silicon/oxygen elements in silicon oxide in the synthesis process of the material, so that the consumption of positive lithium ions can be reduced in the subsequent battery cycle process, the first coulombic efficiency of the material and the battery is improved, and the elastic modulus (elastic modulus: 80 GPa) compared to silica (modulus of elasticity: 29 GPa) is high, so the volume expansion energy of the antibody is stronger and the circulation stability is better.
The silicon-based anode materials prepared in example 1 and comparative examples 1 to 5 were prepared as silicon-based anode materials: SP: slurry mixing and coating were performed at a ratio of LA 133=8:1:1, a CR2016 button cell was assembled, and 1mol/LLiPF was used as an electrolyte solution 6 Ec+dmc solution of (c), and performing electrochemical performance tests. The results are shown in FIG. 4 and Table 1.
TABLE 1
The results showed that the material prepared in example 1 had a first discharge specific capacity of 1466.6mAh/g, a specific charge capacity of 1352.2mAh/g and a first coulomb efficiency of 92.2% at a current density of 0.1C. Specific capacity 1245.1mAh/g after 50 weeks circulation, capacity retention rate 92.1%; the material prepared in comparative example 1 has a first discharge specific capacity of 1495.1mAh/g, a charge specific capacity of 1332.1mAh/g and a first coulomb efficiency of 89.1%. After 50 weeks circulation, the specific capacity is 1142.7mAh/g, and the capacity retention rate is 85.8%.
As can be seen from the comparison of the example 1 and the comparative example 1, the material prepared by the invention has better specific capacity, first effect and cycle capacity retention rate than commercial materials, and has lower residual alkali and PH and less gas generation in water for 24 hours. The invention is characterized in that the liquid phase reaction is used for pre-lithium SiO, so that the reaction is more uniform, the first-effect coulomb efficiency of the material is improved, the reaction intensity is controlled, the grain size of monocrystalline silicon in SiO is effectively reduced, the material expansion is reduced, and the cycling stability of the material is improved. And secondly, cracking the C6H4N2Si (Np) 2 material loaded with lithium ions in a liquid phase at high temperature, diffusing nitrogen element into the silicon-based material to form substitutional doping, and improving the electron concentration in the silicon oxide so as to improve the intrinsic electron conductivity of the silicon material. Again, C6H4N2Si (Np) 2 cracking also forms a homogeneous composite coating of carbon and silicon nitride coating, which not only improves the electronic conductivity of the material, but also improves the cycling stability of the material due to the volumetric expansion of the buffer material with strong mechanical properties of silicon nitride. In addition, residual alkali and residual lithium on the surface of the material are reduced through isopropanol steam circulation washing, the stability of the material in the process of the cell manufacturing process is improved, meanwhile, the damage to the surface of the material caused by conventional treatment modes such as water washing is reduced, and the circulation performance of the material is further improved.
The material prepared in comparative example 2 has a first charge specific capacity of 1610.9mAh/g, a first coulombic efficiency of 75.8%, a specific capacity of 1457.3mAh/g after 50 weeks of cycling, and a capacity retention of 90.5%. As can be seen from comparison of example 1 and comparative example 2, the silicon-based anode material after liquid-phase prelithiation has greatly improved initial coulombic efficiency despite reduced capacity, and better cycle performance, because the material synthesized by the invention consumes part of oxygen element in silicon oxide in advance, and the formed lithium silicate has higher elastic modulus, and the energy of the material for inhibiting expansion is stronger, so that initial efficiency and cycle performance are improved. The material prepared in comparative example 3 has a first charge specific capacity of 1290.6mAh/g, a first coulomb efficiency of 88.3%, a specific capacity of 1053.4mAh/g after 50 weeks of cycling, and a capacity retention of 81.6%. As can be seen from the comparison of example 1 and comparative example 3, the carbon coating by CVD is carried out instead of adding the compound I during the synthesis, and the material performance is rather deteriorated, because the compound I can not only carry out nitrogen doping on SiO during the sintering process, but also decompose to form a homogeneous composite coating of silicon nitride and carbon material, thereby not only improving the material conductivity, but also being caused by nitridingThe good mechanical property of the silicon improves the capacity of the coating layer for inhibiting the volume expansion of the silicon and improves the circulation stability of the material. Comparative example 4 the specific surface area of the prepared material was 3.7m 2 Per gram, the first charge specific capacity is 1358.8mAh/g, the first coulomb efficiency is 91.3%, the specific capacity after 50 weeks circulation is 1012.4mAh/g, and the capacity retention rate is 75.4%. As can be seen from the comparison of example 1 with comparative example 4, the performance of example 1 is better because the surface of the material is damaged to some extent after washing, so that the specific surface area is increased, and the pre-lithium material is sensitive to water, and internal lithium may be eluted after washing, resulting in a decrease in the initial effect and cycle stability of the material. The pH of the material prepared in comparative example 5 was 12.2, the residual alkali was 1265ppm, the first charge specific capacity was 1296.9mAh/g, the first coulomb efficiency was 90%, the specific capacity after 50 weeks of circulation was 547.8mAh/g, and the capacity retention rate was 42.2%. As can be seen from the comparison of the example 1 and the comparative example 5, the residual alkali on the surface of the material is higher without the treatment of isopropanol vapor, the gas production of the homogenate is more obvious, and the residual alkali and the binder undergo side reaction, so that the binding performance is reduced, and the cycle performance is greatly reduced. Based on the above, the performance of the prepared material is better through the steps and the raw materials and the proportions used in the example 1.
Example 5
Preparing a lithium ion battery anode material:
mixing the pre-lithiated silicon-based negative electrode material prepared in the embodiment 1 with artificial graphite according to the mass ratio of 25:75 to obtain a lithium ion battery negative electrode material; wherein the particle size D50 of the artificial graphite is 15 μm.
Example 6
Preparing a lithium ion battery anode material:
mixing the pre-lithiated silicon-based negative electrode material prepared in the example 2 with artificial graphite according to a mass ratio of 5:95 to obtain a lithium ion battery negative electrode material; wherein the particle size D50 of the artificial graphite is 8 μm.
Example 7
Mixing the pre-lithiated silicon-based negative electrode material prepared in the embodiment 3 with hard carbon according to the mass ratio of 10:90 to obtain a lithium ion battery negative electrode material; wherein the hard carbon has a particle size D50 of 20 μm.
Example 8
Mixing the pre-lithiated silicon-based negative electrode material prepared in the example 4 with soft carbon according to a mass ratio of 42:58 to obtain a lithium ion battery negative electrode material; wherein the soft carbon has a particle size D50 of 10 μm.
Comparative example 6
Mixing the commercial pre-lithium silicon oxide material of the comparative example 1 with artificial graphite according to the mass ratio of 25:75 to obtain a lithium ion battery anode material; wherein the particle size D50 of the artificial graphite is 15 μm.
Comparative example 7
Mixing the pre-lithiated silicon-based negative electrode material prepared in the comparative example 3 with artificial graphite according to the mass ratio of 25:75 to obtain a lithium ion battery negative electrode material; wherein the particle size D50 of the artificial graphite is 15 μm.
The lithium ion battery anode materials prepared in examples 5 to 8 and comparative examples 6 to 7 were prepared according to the following lithium ion battery anode materials: SP: slurry mixing and coating were performed at a ratio of LA 133=8:1:1, a CR2016 button cell was assembled, and 1mol/L LiPF was used as an electrolyte solution 6 Ec+dmc solution of (c), and performing electrochemical performance tests. The results are shown in Table 2.
TABLE 2
As can be seen from fig. 5 and table 2, the material prepared in example 5 has a specific capacity of 604.3mAh/g for initial charge at a current density of 0.1C, and a first effect of 92.98%. The results show that the material prepared in comparative example 6 has a first discharge specific capacity of 657.01mAh/g, a specific charge capacity of 599.28mAh/g and a first coulomb efficiency of 91.21% at a current density of 0.1C. The material prepared in comparative example 7 has a first discharge specific capacity of 648.65mAh/g, a charge specific capacity of 588.90mAh/g and a first coulomb efficiency of 90.79%. As can be seen by comparing the example 5 with the comparative example 6 in the table 2, the gram capacity and the initial effect of the pre-lithium silicon anode material prepared by the invention are higher than those of the commercial pre-lithium material, and the initial effect is improved by 1.8% after the pre-lithium silicon anode material is compounded to 600 mAh/g. As can be seen by comparing example 5 with comparative example 7, the gram capacity and the initial effect of the prepared material are lower than those of example 5 by carrying out carbon coating by CVD without using the compound I in the synthesis step, and the initial effect of example 5 is improved by-2% after the compound I is compounded to 600 mAh/g.
The mixed materials in example 5, comparative example 6 and comparative example 7 are taken as the anode, and the working procedures of slurry mixing, coating, rolling, slitting, die cutting, lamination, electrode lug welding, top side sealing, baking, liquid injection and the like are respectively carried out to assemble the 7Ah soft package battery, after the battery is formed into the capacity, the normal temperature cycle test is carried out under the current density of 1C/1C, and the result is that as shown in figure 6, the current comparative example 6 is carried out for 1200 weeks, and the capacity retention rate is 81.6%. Comparative example 7 was cycled for 1200 weeks with a capacity retention of 83.8%. By comparing example 5 with comparative example 6 in fig. 6, it can be found that the 1200 cycle performance of the material in the full cell is improved by-5%, because the material synthesized by the present invention consumes part of oxygen element in the silica in advance, and thus the initial coulombic efficiency of the material and the cell is improved. Through the mode of organic reaction and liquid-phase pre-lithium, the pre-lithium is more uniform, the crystal grains of silicon in the material are smaller, and the residual alkali is lower, so that the first effect, capacity and circulation are improved to a certain extent. Example 5 compared with comparative example 7 can find that the 1200 cycle performance of the material in a full cell is improved by 2.8 percent, and the cycle performance of comparative example 6 is combined, because the compound I is used in the material synthesis process, and C6H4N2Si (Np) 2 not only can carry out nitrogen doping on SiO in the sintering process, but also can be decomposed to form a homogeneous composite coating layer of silicon nitride and carbon material, thereby not only improving the conductivity of the material, but also improving the capacity of the coating layer for inhibiting the volume expansion of silicon due to the good mechanical property of the silicon nitride, and improving the cycle stability of the material.
The foregoing is only a preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art, who is within the scope of the present invention, should make equivalent substitutions or modifications according to the technical scheme of the present invention and the inventive concept thereof, and should be covered by the scope of the present invention.

Claims (9)

1. The preparation method of the pre-lithiated silicon-based negative electrode material is characterized by comprising the following steps of:
s1, under inert atmosphere, dissolving a compound I in an organic solvent, then adding triethylamine, uniformly mixing, and then adding a lithium source for reaction to obtain a mixed solution A;
the structural formula of the compound I is shown as a formula (1):
in the structural formula of the compound I, R1 is selected from substituted or unsubstituted C 1-6 Alkyl, C 2-6 Alkenyl, C 2-6 Alkynyl, C 6-12 At least one of aryl groups, R2 and R3 are respectively and independently selected from at least one of butyl, naphthyl, trimethylsilyl and diisopropylphenyl;
s2, mixing the silicon oxide with the mixed solution A, performing reaction, performing solid-liquid separation after the reaction is finished, and drying the obtained solid substance to obtain powder B; the mass of the silicon oxide is 5-20% of the sum of the mass of the silicon oxide and the mass of the mixed solution A;
and S3, sintering the powder B in an inert atmosphere, cooling, and washing the obtained product with isopropanol vapor to obtain the pre-lithiated silicon-based anode material.
2. The preparation method of the pre-lithiated silicon-based negative electrode material according to claim 1, wherein the mass of triethylamine is 2% -8% of the sum of the mass of the compound i and the mass of triethylamine, and the mass of the lithium source is 4% -50% of the sum of the mass of the compound i, the mass of triethylamine and the mass of the lithium source; the lithium source is lithium, liH or LiBH 4 、Li 3 At least one of N and lithium ethynyl; the organic solvent is at least one of tetrahydrofuran, normal hexane and toluene.
3. The method for preparing a pre-lithiated silicon-based negative electrode material of claim 1, wherein in S1, the reaction temperature is-20 ℃ to 30 ℃ and the reaction time is 0.5h to 6h.
4. The method for producing a prelithiated silicon-based anode material according to claim 1, wherein the ratio of the mass of the silicon oxide to the mass of the lithium element in the mixture a is (9 to 24): 1, a step of; the grading particle size of the silicon oxide is as follows: dmin is more than or equal to 1.5 mu m, D10 is more than or equal to 3 mu m, D50 is more than or equal to 5 and less than or equal to 7 mu m, and Dmax is less than or equal to 10 mu m.
5. The method for preparing the pre-lithiated silicon-based negative electrode material of claim 1, wherein in S2, the reaction temperature is 20-80 ℃ and the reaction time is 1-12 h; in S2, the drying method is vacuum drying, the vacuum degree is 10-100 Pa, the drying temperature is 60-100 ℃, and the drying time is 3-12 h.
6. The method for preparing a pre-lithiated silicon-based negative electrode material of claim 1, wherein in S3, the silicon grains of the silicon oxide sintered to the obtained product are at least 0.8 at 28.4 ° half-width; s3, sintering is sectional type heating sintering, and the specific steps are as follows: the first stage sintering is carried out at 200-400 ℃ for 1-6 h, and then the second stage sintering is carried out at 600-1200 ℃ for 2-12 h;
s3, washing the obtained product with isopropanol vapor until the residual lithium on the surface is less than or equal to 500ppm and the PH is less than or equal to 11.5; in S3, the flow rate of the isopropanol steam is 1 mL/min-10 mL/min, the washing time is 0.5 h-6 h, and the washing temperature is 120-180 ℃.
7. A pre-lithiated silicon-based negative electrode material prepared by the preparation method of any one of claims 1-6.
8. A lithium ion battery anode material, which is characterized by comprising a carbon material and the pre-lithiated silicon-based anode material according to claim 7; wherein the mass of the carbon material accounts for 1-95% of the total mass of the lithium ion battery anode material.
9. The lithium ion battery anode material according to claim 8, wherein the carbon material has a particle size D50 of 8 μm to 20 μm, and the pre-lithiated silicon-based anode material has a particle size D50 of 5 μm to 8 μm; the carbon material is at least one of natural graphite, artificial graphite, mesophase carbon microsphere, hard carbon and soft carbon.
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