Soft and hard carbon-coated nanosilicon-silicon monoxide composite negative electrode material

Abstract

The present application belongs to the technical field of lithium ion battery electrode material, and particularly relates to a soft and hard carbon coated nano silicon-silicon monoxide composite negative electrode material. The present application takes hydrophobic nano silicon monoxide as a silicon source, takes pitch as a main carbon source, carries out temperature control ball milling treatment on the hydrophobic nano silicon monoxide and the pitch, and prepares pitch coated nano silicon monoxide; continues ball milling by adding an emulsifier and a stabilizer, and prepares a suspension system of pitch coated nano silicon monoxide; slowly adds the suspension system into a proper amount of microstructure regulator, stirs to prepare a brown paste precursor, carries out vacuum drying, and carries out heat treatment in an inert atmosphere to prepare a carbon / nano silicon monoxide composite powder; reduces the carbon / nano silicon monoxide powder by an aluminum thermal reduction method to prepare the soft and hard carbon coated nano silicon-silicon monoxide composite negative electrode material. The preparation method of the composite negative electrode material is simple in process, low in cost, friendly to the environment, and easy for scale production, and the prepared composite negative electrode material has excellent electrochemical performance.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of lithium ion battery electrode materials, and particularly relates to a soft and hard carbon coated nano silicon-silicon monoxide composite negative electrode material. BACKGROUND

[0002] Silicon (Si) is a representative negative electrode material for the next generation of lithium ion batteries due to its high theoretical capacity, suitable working potential and high natural abundance. However, due to the inherent volume expansion (up to 300%) during lithium intercalation / deintercalation and poor electrical conductivity and unstable solid electrolyte interface (SEI) film, Si-based negative electrodes have serious stability problems, which greatly hinder practical application. In order to solve these problems, carbon-modified Si negative electrodes are a very promising method, which has been proven to effectively alleviate the inherent volume expansion of Si negative electrodes during lithiation / de-lithiation and improve the electrical conductivity and material plasticity of the negative electrode material.

[0003] Soft and hard carbon composite modified Si negative electrodes have high research value. Soft carbon has good toughness, and the soft carbon film coated on the surface of nano Si is not easy to crack and fall off during charging and discharging. The porous structure of hard carbon can absorb the huge volume expansion of Si and release the stress caused by the volume change of Si, thereby improving the cycle performance of the negative electrode material. In addition, soft carbon has high structural order and good electrical conductivity, while hard carbon has more defects to provide more Li + insertion points. Composite coated Si negative electrodes can effectively improve the electrical conductivity of the whole negative electrode material, ensure smooth conduction of electrons, and thus improve the rate performance of the negative electrode material.

[0004] The common preparation method of the current commercial Si / C composite negative electrode material is to uniformly disperse nano Si in a pitch / tetrachloromethane (CCl4) or pitch / tetrahydrofuran (C4H8O) solution to prepare a pitch / Si precursor, and then heat treat the pitch / Si precursor in an inert atmosphere to obtain a Si / C composite negative electrode material. However, this method for preparing Si / C composite negative electrode material has obvious shortcomings: first, in order to fully dissolve the pitch and uniformly coat it on the surface of nano Si, more CCl4, C4H8O and other organic solvents are used, which results in high cost of the finally prepared Si / C composite negative electrode material; second, the pitch / Si precursor prepared by this method is prone to stick and clump during heat treatment in an inert atmosphere, and the prepared Si / C negative electrode material has a very dense rock-like microstructure, which results in poor rate performance and cycle performance of the prepared negative electrode material. Therefore, this preparation method relies on further ball milling and secondary coating treatment, and the process is complex and the efficiency is low. SUMMARY

[0005] The present application aims at overcoming the above problems existing in the prior art, and provides a soft and hard carbon coated nanometer silicon-silicon monoxide composite negative electrode material. The present application adopts hydrophobic nanometer silicon oxide and pitch as main raw materials, and adopts mechanical ball milling to prepare a suspension system of pitch coated nanometer silicon oxide; the prepared suspension system is slowly added into a microstructure regulator and heated and stirred, and then dried and heat treated in an inert atmosphere to prepare carbon coated nanometer silicon oxide powder, and finally a soft and hard carbon coated nanometer silicon-silicon monoxide composite negative electrode material is prepared through low temperature aluminum thermal reduction.

[0006] To achieve the above technical purposes and effects, the present application is implemented by the following technical scheme:

[0007] The present application provides a soft and hard carbon coated nanometer silicon-silicon monoxide composite negative electrode material, and the preparation raw materials of the composite negative electrode material include a silicon source and pitch, the silicon source is hydrophobic nanometer silicon oxide with an average particle size of 10-80 nm, and the pitch is pitch with a residual carbon content of 15-25% after 1000℃ heat treatment in an inert atmosphere;

[0008] The preparation method of the composite negative electrode material includes the following steps:

[0009] 1) A certain mass ratio of hydrophobic nanometer silicon oxide and pitch is placed in a stainless steel ball mill tank, the ball mill tank is placed in an adiabatic heat preservation sleeve, and temperature control ball milling is performed at a certain speed for a period of time to prepare pitch coated hydrophobic nanometer silicon oxide;

[0010] 2) A certain mass ratio of the prepared pitch coated hydrophobic nanometer silicon oxide, emulsifier and stabilizer is mixed, and the mixture is ball milled at a certain speed for a period of time at room temperature to prepare a stable pitch coated nanometer silicon oxide suspension system;

[0011] 3) A certain mass ratio of the prepared pitch coated nanometer silicon oxide suspension system is slowly added into a microstructure regulator, and stirring is performed at a certain temperature for a period of time to prepare a brown paste product;

[0012] 4) The obtained brown paste precursor is vacuum dried, and then heat treated in an inert atmosphere at a certain temperature for a period of time to prepare carbon coated nanometer silicon oxide powder, and finally a soft and hard carbon coated nanometer silicon-silicon monoxide is prepared through aluminum thermal reduction.

[0013] Further, in step 1), the mass ratio of hydrophobic nanometer silicon oxide to pitch is 1:1.0-1.5.

[0014] Further, in step 1), the speed of the ball mill is 350-450 rpm, the mass ratio of the material in the tank to the grinding ball is 1:30-40, and the temperature of the ball mill tank is controlled at 90-120℃.

[0015] Further, in step 2), the emulsifier is a solution of sodium dodecyl benzene sulfonate, sodium dodecyl sulfate or sodium stearate with a concentration of 2-5wt%, and the mass ratio of asphalt to the solute in the emulsifier is 1:0.05-0.15.

[0016] Further, in step 2), the stabilizer is a solution of sodium hydroxide with a concentration of 0.2-1.0wt%, and the mass ratio of asphalt to the solute in the stabilizer is 1:0.005-0.020.

[0017] Further, in step 2), the rotation speed of the ball mill is 350-450rpm, and the mass ratio of the material in the tank to the grinding ball is 1:30-40.

[0018] Further, in step 3), the microstructure regulator is a solution of citric acid-ethylene glycol sol, polyvinyl alcohol or citric acid monohydrate, and the mass ratio of hydrophobic nano-silicon oxide to the microstructure regulator is 1:60-90.

[0019] Further, in step 3), the mixing and stirring temperature of the hydrophobic nano-silicon oxide / asphalt suspension and the microstructure regulator is 55-65℃, and the stirring time is 6-10h.

[0020] Further, in step 4), the heat treatment temperature in the inert atmosphere is 900-1100℃, and the heat treatment time is 2-4h.

[0021] The application also provides the use of the soft and hard carbon coated nano-silicon-silicon monoxide composite negative electrode material in the preparation of lithium ion battery electrode materials.

[0022] The present application is mainly based on the following technical principles: (1) The present application can make asphalt and hydrophobic nano-silica uniformly composite without using organic solvents (CCl4, C4H8O, etc.). This is because during the adiabatic heat preservation ball milling process of asphalt and hydrophobic nano-silica, mechanical energy is continuously converted into heat energy, the temperature in the ball milling tank rapidly rises to 80-110℃, the asphalt is converted from solid state to molten state, the molten state asphalt and the used nano-silica both have hydrophobic characteristics, the interface energy between the molten state asphalt and the nano-silica is very small, the molten state asphalt spontaneously coats on the surface of the hydrophobic nano-silica, and in the subsequent ball milling process of mixing with emulsifier and stabilizer, the nano-silica coarse particles coated with asphalt are continuously broken into ultra-fine particles due to the shearing force generated by ball milling, the lipophilic end of the emulsifier molecule is adsorbed on the surface of the nano-silica coated with asphalt, forming a micelle with appropriate density, and finally the nano-silica suspension system uniformly coated with asphalt is obtained. (2) The present application can effectively overcome the problem that the asphalt is adhered and agglomerated during the heat treatment process to form a dense blocky microstructure, resulting in poor electrochemical performance of the final composite electrode material. This is because during the heating and stirring process, the asphalt-coated nano-silica solid-liquid suspension system is added to the microstructure regulator, the asphalt-coated nano-silica ultra-fine particles are wrapped by the microstructure regulator, and the contact between the asphalt-coated nano-silica particles is blocked, so during the subsequent drying and inert atmosphere heat treatment process, the asphalt is prevented from adhering and agglomerating to form a dense blocky microstructure; after the inert atmosphere heat treatment, the soft carbon formed by the pyrolysis of asphalt coats on the surface of nano-silica, and the hard carbon formed by the pyrolysis of the microstructure regulator solute is dispersed between the soft carbon coated on the nano-silica particles (SiO2@C), and finally through low-temperature aluminothermic reduction, the soft and hard carbon coated nano-silicon-silicon monoxide (nano-Si / SiO x @C) is realized.

[0023] The present application has the following advantages:

[0024] 1. The present application realizes the uniform coating of asphalt on hydrophobic nano-silica by ball milling the asphalt / hydrophobic nano-silica at 80-110℃, and uses mechanical ball milling technology to convert the asphalt-coated nano-silica into a stable solid-liquid suspension system with the help of inexpensive emulsifiers and stabilizers, avoiding the problem of high cost of the final negative electrode material caused by the use of more CCl4, C4H8O and other organic solvents in the current asphalt-coated nano-Si Si / C negative electrode material.

[0025] 2. The present application drops the asphalt-coated nano-silica suspension system into the microstructure regulator, and through heating and stirring, the microstructure regulator solute is coated on the surface of the suspension ultra-fine particles, effectively preventing the re-agglomeration of nano-particles caused by the adhesion and agglomeration of asphalt, and avoiding the problem of poor rate performance and cycle performance of the prepared negative electrode material caused by the adhesion and agglomeration of asphalt to form a dense blocky microstructure.

[0026] 3. This invention achieves the processing of nano-Si / SiO x The soft and hard carbon composite coating, with the soft carbon from asphalt pyrolysis exhibiting good strength and toughness, is coated with nano-Si / SiO. x The surface is not easily cracked or peeled off during charging and discharging, while the hard carbon from the pyrolysis of the microstructure regulator solute has a porous structure, which is coated on the pitch carbon-coated nano-Si / SiO. x The surface can absorb nano-Si / SiO x The volume expansion releases the stress caused by the volume change, improving the cycle performance of the negative electrode material. Moreover, the soft and hard carbon composite coating can effectively improve the conductivity of the entire material, ensuring that electrons can be smoothly conducted, thereby improving the rate performance of the electrode material.

[0027] 4. The preparation method of this invention has the advantages of simple process, simple equipment, low cost and environmental friendliness, and is easy to achieve mass production. The obtained silicon-carbon anode material can be produced at a current density of 0.05 A g. -1 At that time, the discharge / charge capacity during the first cycle was 2713.8 / 1670.6 mAh g, respectively. -1 The initial coulombic efficiency was 61.6%; when the current density was increased to 2.0 A g... -1 At that time, the measured reversible capacity was 748.7 mAh g. -1 The capacity retention rate is as high as 46.9%; at 0.50A g -1 After 200 cycles, the electrode material capacity still reached 561.0 mAh g. -1 The capacity retention rate was 79.6%.

[0028] Of course, any product implementing this invention does not necessarily need to achieve all of the above advantages at the same time. Attached Figure Description

[0029] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 The nano-Si / SiO prepared in Example 1 x XRD pattern of C anode material;

[0031] Figure 2 The nano-Si / SiO prepared in Example 1 x XPS plot of @C anode material;

[0032] Figure 3 nano-Si / SiO x FESEM image of the C anode material of Example 1;

[0033] Figure 4 nano-Si / SiO x TEM image of the C anode material of Example 1;

[0034] Figure 5 nano-Si / SiO x galvanostatic charge-discharge curve of the assembled battery sample of the C anode material of Example 1 at a current density of 0.05 A g -1

[0035] Figure 6 nano-Si / SiO x rate curve of the assembled battery sample of the C anode material of Example 1 at different current densities;

[0036] Figure 7 nano-Si / SiO x cycle performance curve of the assembled battery sample of the C anode material of Example 1 at a current density of 0.5 A g -1 DETAILED DESCRIPTION

[0037] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative effort belong to the scope of protection of the present application.

[0038] The present application realizes uniform coating of hydrophobic nano-silica by ball milling at 80-110℃, and converts the asphalt-coated nano-silica (asphalt / SiO2) into a stable solid-liquid suspension system by mechanical ball milling with the aid of inexpensive emulsifiers and stabilizers. The asphalt-coated nano-silica suspension system is dropped into a microstructure regulator, and the asphalt / SiO2 particles are coated and isolated by the microstructure regulator, which prevents the adhesion between the asphalt / SiO2 particles and the formation of dense block structure in the subsequent heat treatment process. The soft and hard carbon-coated nano-Si / SiO x is prepared by inert atmosphere heat treatment and low-temperature aluminum reduction. x ​​The preparation method of the composite negative electrode material is simple in process, high in efficiency, low in cost, environment-friendly, easy to realize large-scale production, and the prepared lithium ion battery negative electrode material has excellent comprehensive electrochemical performance.

[0039] The present application realizes uniform coating of hydrophobic nano-silicon oxide by ball milling of asphalt and the hydrophobic nano-silicon oxide under the condition of 80-110 DEG C, and converts the nano-silicon oxide coated with asphalt into a stable solid-liquid suspension system by mechanical ball milling with the aid of cheap emulsifiers and stabilizers, overcomes the defects of current Si / C negative electrode material prepared by using asphalt as carbon source, i.e., dependence on a large amount of organic solvents (CCl4, C4H8O, etc.), and solves the problem of high cost of the prepared Si / C composite negative electrode material.

[0040] The specific embodiments of the present application are as follows:

[0041] Example 1

[0042] 1) 3.0002g of nano-silicon oxide and 3.5001g of asphalt are weighed according to the weight ratio of hydrophobic nano-silicon oxide to asphalt of 1:1.1667, and are placed in a stainless steel ball mill tank, the ball mill tank is placed in an adiabatic insulation jacket, and ball milling is carried out at 400 rpm for 8h, the temperature of the ball mill tank is controlled at 110 DEG C, and the weight ratio of the material in the tank to the grinding ball is 1:40, and asphalt-coated hydrophobic nano-silicon oxide is prepared;

[0043] 2) 17.5005g of 2wt% sodium dodecylbenzenesulfonate solution and 7.0002g of 0.5wt% NaOH solution are weighed according to the weight ratio of the solute in asphalt to the solute in the emulsifier of 1:0.1 and the weight ratio of the solute in asphalt to the solute in the stabilizer of 1:0.01, and ball milling is carried out at 400 rpm at room temperature for 6h, and a stable asphalt-coated nano-silicon oxide suspension system is prepared;

[0044] 3) 0.8602g of monohydrated citric acid and 0.1693g of ethylene glycol are dissolved in 50ml of deionized water according to the molar ratio of monohydrated citric acid to ethylene glycol of 1:0.6667, and mixed and stirred at 70 DEG C and pH 4 for 5h, and a citric acid-ethylene glycol sol is prepared, 20.0012g of the asphalt-coated nano-silicon oxide suspension system is dropped into the prepared citric acid-ethylene glycol sol according to the weight ratio of hydrophobic nano-silicon oxide to microstructure regulator of 1:79.0910, and stirring is continued at 60 DEG C for 8h, and a brown paste product is prepared;

[0045] 4) The brown paste product is placed in a vacuum drying oven at 60°C for 6h, and the dried product is heat treated at 1000°C for 3h in an argon atmosphere to obtain hydrophobic nano-silicon oxide coated with soft and hard carbon, which is subjected to low-temperature aluminothermic reduction to obtain nano-silicon-silicon monoxide composite negative electrode material coated with soft and hard carbon (referred to as Si / SiO x @C);

[0046] The negative electrode material prepared according to the above steps is assembled into a half-cell, and the electrochemical performance is measured as follows: when the current density is 0.05A g -1 , the first cycle discharge / charge capacity is 2713.8 / 1670.6mAh g -1 , and the first coulombic efficiency is 61.6%; when the current is increased to 2.0A g -1 , the measured reversible capacity is 748.7mAh g -1 , and the capacity retention rate is as high as 46.9%; after 200 cycles at 0.50A g -1 , the electrode material capacity is still as high as 561.0mAh g -1 , and the capacity retention rate is 79.6%.

[0047] Example 2

[0048] 1) According to the weight ratio of hydrophobic nano-silicon oxide to pitch of 1:1.1667, 3.0002g of nano-silicon oxide and 3.5001g of pitch are weighed and placed in a stainless steel ball mill jar, the jar is placed in an adiabatic insulation sleeve, and ball milling is carried out at 400rpm for 8h, the jar temperature is controlled at 110°C, and the weight ratio of the material in the jar to the milling ball is 1:40, to obtain pitch-coated hydrophobic nano-silicon oxide;

[0049] 2) According to the weight ratio of pitch to solute in the emulsifier of 1:0.1, and the weight ratio of pitch to solute in the stabilizer of 1:0.01, 17.5005g of 2wt% sodium dodecyl sulfate solution and 7.0002g of 0.5wt% NaOH solution are weighed and ball milled at 400rpm for 6h at room temperature to obtain a stable pitch-coated nano-silicon oxide suspension system;

[0050] 3) According to the molar ratio of monohydrated citric acid to ethylene glycol of 1:0.6667, 0.8602g of monohydrated citric acid and 0.1693g of ethylene glycol are dissolved in 50ml of deionized water, and mixed and stirred at 60-80°C and pH 4 for 5h to obtain a citric acid-ethylene glycol sol, according to the weight ratio of hydrophobic nano-silicon oxide to microstructure regulator of 1:79.0910, 20.0012g of the pitch-coated nano-silicon oxide suspension system is added dropwise into the prepared citric acid-ethylene glycol sol, and stirring is continued at 60°C for 8h to obtain a brown paste product;

[0051] 4) The brown paste product is placed in a vacuum drying oven at 60°C for 6h, and the dried product is placed in an argon atmosphere and heat treated at 1000°C for 3h to obtain hydrophobic nano-silicon oxide coated with soft and hard carbon, which is subjected to low-temperature aluminothermic reduction to obtain nano-silicon-silicon monoxide composite negative electrode material coated with soft and hard carbon (referred to as Si / SiO x @C);

[0052] The negative electrode material prepared according to the above steps is assembled into a half-cell, and the electrochemical performance is measured as follows: when the current density is 0.05A g -1 , the first cycle discharge / charge capacity is 2675.3 / 1626.6mAh g -1 , and the first coulombic efficiency is 60.9%; when the current is increased to 2.0A g -1 , the measured reversible capacity is 702.3mAh g -1 , and the capacity retention rate is as high as 43.5%; after 200 cycles at 0.50A g -1 , the electrode material capacity is still as high as 523.4mAh g -1 , and the capacity retention rate is 75.8%.

[0053] Example 3

[0054] 1) According to the weight ratio of hydrophobic nano-silicon oxide to pitch of 1:1.1667, 3.0002g of nano-silicon oxide and 3.5001g of pitch are weighed and placed in a stainless steel ball mill jar, the jar is placed in an adiabatic insulation sleeve, and ball milling is carried out at 400rpm for 8h, the jar temperature is controlled at 110°C, and the weight ratio of material in the jar to grinding balls is 1:40, to obtain pitch-coated hydrophobic nano-silicon oxide;

[0055] 2) According to the weight ratio of pitch to solute in emulsifier of 1:0.1, and the weight ratio of pitch to stabilizer of 1:0.01, 17.5005g of 2wt% sodium dodecylbenzenesulfonate solution and 7.0002g of 0.5wt% NaOH solution are weighed and ball milled at 400rpm for 6h at room temperature to obtain a stable pitch-coated nano-silicon oxide suspension system;

[0056] 3) 1.0295g of PVA is dissolved in 50ml of deionized water, heated to reflux at 80°C for 8h with stirring to obtain a PVA solution, and according to the weight ratio of hydrophobic nano-silicon oxide to microstructure regulator of 1:79.0910, 20.0012g of pitch-coated nano-silicon oxide suspension system is added dropwise into the prepared citric acid-ethylene glycol sol, and stirring is continued at 60°C for 8h to obtain a brown paste product;

[0057] 4) The brown paste product is dried in a vacuum drying oven at 60°C for 6h, and the dried product is heat treated in an argon atmosphere at 1000°C for 3h to obtain hydrophobic nano-silicon oxide coated with soft and hard carbon, which is subjected to low-temperature aluminothermic reduction to obtain nano-silicon-silicon monoxide composite negative electrode material coated with soft and hard carbon (referred to as Si / SiO x @C);

[0058] The negative electrode material prepared according to the above steps is assembled into a half-cell, and the electrochemical performance is measured as follows: when the current density is 0.05A g -1 , the first cycle discharge / charge capacity is 2589.7 / 1566.8mAh g -1 , and the first coulombic efficiency is 60.5%; when the current is increased to 2.0A g -1 , the measured reversible capacity is 723.4mAh g -1 , and the capacity retention rate is as high as 41.9%; after 200 cycles at 0.50A g -1 , the electrode material capacity is still as high as 501.8mAh g -1 , and the capacity retention rate is 75.5%.

[0059] The preferred embodiments disclosed above are only used to help explain the present application. The preferred embodiments do not describe all the details, nor limit the present application to only the specific embodiments. Obviously, many modifications and variations can be made according to the content of the present specification. The present specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present application, so that those skilled in the art can well understand and utilize the present application. The present application is limited only by the claims and their full scope and equivalents.

Claims

1. Soft-hard carbon-coated nanosilicon-silicon monoxide composite negative electrode material, characterized in that, The preparation raw material of the composite negative electrode material comprises a silicon source and pitch, wherein the silicon source is hydrophobic nano silicon oxide with an average particle size of 10-80 nm, and the pitch is pitch with a residual carbon content of 15-25% after heat treatment at 1000 ℃ in an inert atmosphere; The preparation method of the composite negative electrode material comprises the following steps: 1) A certain amount of hydrophobic nano silicon oxide and pitch are placed in a stainless steel ball mill jar, the jar is placed in an adiabatic heat preservation sleeve, and temperature-controlled ball milling is performed at a certain speed for a period of time to obtain pitch-coated hydrophobic nano silicon oxide; 2) A certain amount of emulsifier and stabilizer are mixed with the obtained pitch-coated hydrophobic nano silicon oxide at a certain mass ratio, and the mixture is ball milled at a certain speed for a period of time at room temperature to obtain a stable pitch-coated nano silicon oxide suspension system; 3) The obtained pitch-coated nano silicon oxide suspension system is slowly added into a microstructure regulator at a certain mass ratio, and stirring is performed at a certain temperature for a period of time to obtain a brown paste product; 4) The obtained brown paste precursor is vacuum dried, and then heat treated at a certain temperature in an inert atmosphere for a period of time to obtain carbon-coated nano silicon oxide powder, and soft and hard carbon-coated nano silicon-silicon suboxide is obtained after aluminum thermal reduction. 2.The soft-hard carbon-coated nanosilicon-silicon monoxide composite anode material of claim 1, characterized in that, In step 1), the mass ratio of hydrophobic nano silicon oxide to pitch is 1:1.0-1.

5. 3.The soft-hard carbon-coated nanosilicon-silicon monoxide composite anode material of claim 1, wherein, In step 1), the speed of the ball mill is 350-450 rpm, the mass ratio of the material in the jar to the grinding ball is 1:30-40, and the temperature of the jar is controlled at 90-120 ℃. 4.The soft-hard carbon-coated nanosilicon-silicon monoxide composite anode material of claim 1, wherein, In step 2), the emulsifier is a 2-5 wt% sodium dodecyl benzene sulfonate, sodium dodecyl sulfate or sodium stearate solution, and the mass ratio of pitch to the solute in the emulsifier is 1:0.05-0.

15. 5.The soft-hard carbon-coated nanosilicon-silicon monoxide composite anode material of claim 1, wherein, In step 2), the stabilizer is a 0.2-1.0 wt% sodium hydroxide solution, and the mass ratio of pitch to the solute in the stabilizer is 1:0.005-0.

020. 6.The soft-hard carbon-coated nanosilicon-silicon monoxide composite anode material of claim 1, wherein, In step 2), the speed of the ball mill is 350-450 rpm, and the mass ratio of the material in the jar to the grinding ball is 1:30-40. 7.The soft-hard carbon-coated nanosilicon-silicon monoxide composite anode material of claim 1, wherein, In step 3), the microstructure regulator is a citric acid-ethylene glycol sol, a polyvinyl alcohol solution or a citric acid monohydrate solution, and the mass ratio of hydrophobic nano silicon oxide to the microstructure regulator is 1:60-90. 8.The soft-hard carbon-coated nanosilicon-silicon monoxide composite anode material of claim 1, wherein, In step 3), the mixing and stirring temperature of the hydrophobic nano silicon oxide / pitch suspension and the microstructure regulator is 55-65 ℃, and the stirring time is 6-10 h. 9.The soft-hard carbon-coated nanosilicon-silicon monoxide composite anode material of claim 1, characterized in that, In step 4), the heat treatment temperature in the inert atmosphere is 900-1100 ℃, and the heat treatment time is 2-4 h.

10. Use of the soft and hard carbon-coated nano silicon-silicon suboxide composite negative electrode material according to any one of claims 1-9 in the preparation of lithium ion battery electrode materials.

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