Preparation method of silicon-carbon negative electrode material for lithium ion battery

Abstract

The application discloses a preparation method of a lithium ion battery silicon-carbon negative electrode material. Phenol, formaldehyde aqueous solution, sodium hydroxide, white oil and a surfactant are mixed and stirred to be dissolved, and the mixed solution is subjected to ultrasonic emulsification to obtain a micron emulsion. The micron emulsion is stirred to react, and then is subjected to filtration and drying to obtain light yellow powder particles. The light yellow powder particles are subjected to high-temperature pyrolysis treatment to obtain carbon aerogel powder. The carbon aerogel powder is immersed in a sodium silicate solution and then is separated, and then is subjected to acid treatment to obtain a carbon aerogel-silicic acid composite. After washing and drying, the carbon aerogel-silicic acid composite is subjected to high-temperature heat treatment at a heat treatment temperature of 1400-1700 DEG C to obtain the lithium ion battery silicon-carbon negative electrode material with a specific capacity of 480-790 mAh / g. The lithium ion battery silicon-carbon negative electrode material is prepared by using phenol, formaldehyde and sodium silicate as main raw materials and by using a pre-pore forming mode to fill silicon into pores of carbon material, and the lithium ion battery silicon-carbon negative electrode material has high performance, low raw material cost, simple process and is beneficial to industrial production.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of ion lithium battery manufacturing, and particularly relates to a preparation method of a silicon-carbon negative electrode material of a lithium ion battery. BACKGROUND

[0002] At present, most of the lithium ion batteries use graphite as a negative electrode material, but the theoretical specific capacity of the graphite negative electrode in the lithium battery is only 372 mAh / g, and the actual specific capacity of the commercial high-end graphite material is 360-365 mAh / g. Based on the graphite negative electrode material, the energy density of the lithium ion battery can only be limitedly improved through thinning the base material, increasing the compaction density, increasing the working voltage, and improving the initial efficiency of the graphite. If the energy density of the lithium ion battery is to be greatly improved, a new type of negative electrode material needs to be developed.

[0003] The silicon-based negative electrode material becomes a breakthrough point for improving the energy density of the lithium ion battery because of its ten times of the graphite negative electrode and a high capacity of up to 4200 mAh / g. However, during the charging and discharging, the silicon material has a huge volume change effect (>300%), and in the cycle process, the silicon material will be pulverized and peeled off from the current collector, thereby causing a sharp decline in the performance of the battery. In recent years, in order to utilize the high specific capacity of silicon and inhibit the volume expansion effect, researchers have conducted a large number of studies, and a relatively optimal technical route is to prepare a silicon / carbon composite material, which simultaneously utilizes the high specific capacity of silicon and the good mechanical properties and conductivity of the carbon material.

[0004] Chinese patent CN109817966A discloses a preparation method of a lithium ion battery negative electrode composite material: first, graphite and silicon monoxide are mixed and then ball milled to obtain a mixed powder A, then the mixed powder A is added into a carboxymethyl chitosan solution, dried, and then added into a phenolic resin solution for mixing and stirring, and finally a battery negative electrode composite material is prepared through calcination. In the preparation of the silicon-carbon negative electrode material by this method, the silicon and the carbon are in a close combination state, and in the charging and discharging process, the volume expansion effect of the silicon is rigidly limited by the carbon skeleton. Long-time charging and discharging are not conducive to the stability of the structure, and the composite material is expensive. SUMMARY

[0005] The present application is aimed at the technical problems of the existing lithium ion battery negative electrode material, such as small specific capacity, large volume change effect in the charging and discharging process, and unstable structure, and provides a preparation method of a lithium ion battery silicon-carbon negative electrode material with low cost, stable structure, excellent cycle performance, and easy industrial production.

[0006] To achieve the above-mentioned purpose of the present application, the preparation method of the lithium ion battery silicon-carbon negative electrode material comprises the following steps:

[0007] (1) Preparation of solution A: Mix and dissolve phenol, formaldehyde aqueous solution, sodium hydroxide and pore-forming agent according to a predetermined molar ratio;

[0008] (2) Preparation of solution B: Take a set amount of white oil, add a set volume ratio of surfactant to it, and stir to dissolve;

[0009] (3) pouring solution A into solution B to obtain a mixed solution, and performing ultrasonic emulsification on the mixed solution to obtain a micron-sized emulsion;

[0010] (4) stirring the micron-sized emulsion at a temperature of 60 to 95° C. to obtain a light yellow suspension;

[0011] (5) filtering the light yellow suspension to obtain a light yellow powder, and drying the light yellow powder to obtain light yellow powder particles;

[0012] (6) subjecting the light yellow powder particles to a high-temperature pyrolysis treatment under an inert atmosphere at a high-temperature pyrolysis temperature of 700 to 1000° C. to obtain carbon aerogel powder;

[0013] (7) immersing the carbon aerogel powder in a sodium silicate solution for a period of time, and then performing solid-liquid separation to obtain a carbon aerogel-sodium silicate complex A;

[0014] (8) immersing the carbon aerogel-sodium silicate complex in an acidic solution for a period of time, and then performing solid-liquid separation to obtain a carbon aerogel-silicic acid complex B;

[0015] (9) After washing and drying the carbon aerogel-silicic acid complex B, a high-temperature heat treatment is performed under an inert atmosphere at a heat treatment temperature of 1400-1700° C. to obtain a lithium-ion battery silicon-carbon negative electrode material with a specific capacity of 480-790 mAh / g.

[0016] Furthermore, in step (1), the molar ratio of phenol to formaldehyde is 1:1-2.2, and the molar ratio of phenol to sodium hydroxide is 10-150:1; the pore-forming agent is polyethylene glycol, and the addition ratio is 1-10% of the mass of solution A.

[0017] Furthermore, in step (2), the volume ratio of white oil to solution A is 1 to 8:1; the surfactant is Span 80, and the addition ratio is 1 to 6% of the mass of solution B.

[0018] Furthermore, in step (1), the molar ratio of phenol to formaldehyde is 1:1.2-2.0, and the molar ratio of phenol to sodium hydroxide is 80-120:1; the addition ratio of the pore-forming agent polyethylene glycol is 2.5-8.0% of the mass of solution A; in step (2), the volume ratio of white oil to solution A is 2-6:1; and the addition ratio of the surfactant Span 80 is 1.5-4.5% of the mass of solution B.

[0019] Furthermore, in step (1), the molar ratio of phenol to formaldehyde is 1:1.5-2.0, the molar ratio of phenol to sodium hydroxide is 90-110:1, and the addition ratio of the pore-forming agent polyethylene glycol is 3.0-8.0% of the mass of solution A; in step (2), the volume ratio of white oil to solution A is 3-5:1; and the addition ratio of the surfactant Span 80 is 1.8-3.5% of the mass of solution B.

[0020] Furthermore, in step (3), the frequency of ultrasonic emulsification is 5 to 20 kHz, and the ultrasonic emulsification time is 10 to 30 minutes.

[0021] Furthermore, the stirring speed in step (4) is 100-300 r / min, and the stirring reaction time is 10-30 h; and the drying temperature in step (5) is 30-150° C.

[0022] As a preferred embodiment of the technical solution of the present invention, the inert atmosphere in step (6) is nitrogen, helium or argon; the solid content of the sodium silicate solution in step (7) is 10-50%, and the immersion time is 1-3 hours; the acidic solution in step (8) is one or more combinations of hydrochloric acid, sulfuric acid, and carbonic acid solution, and the immersion time is 1-3 hours; the inert atmosphere in step (9) is nitrogen, helium or argon, and the high-temperature heat treatment temperature is 1400-1700°C.

[0023] As a preferred embodiment of the technical solution of the present invention, in step (3), the frequency of ultrasonic emulsification is 8 to 18 kHz, and the ultrasonic emulsification time is 10 to 25 min; in step (4), the stirring speed is 100 to 180 r / min, and the stirring reaction time is 15 to 25 h; in step (5), the drying temperature is 35 to 60° C.; in step (6), the pyrolysis temperature is 850 to 950° C.; in step (7), the solid content of the sodium silicate solution is 20 to 40%, and the soaking time is 1.5 to 2.5 h; in step (8), the acidic solution is hydrochloric acid, and the soaking time is 1.5 to 2.5 h; in step (9), the high-temperature heat treatment temperature is 1400-1600° C.

[0024] As a preferred embodiment of the technical solution of the present invention, in step (1), the molar ratio of phenol to formaldehyde is 1:1.8-2.0, the molar ratio of phenol to sodium hydroxide is 90-110:1, and the addition ratio of the pore-forming agent polyethylene glycol is 7.5-8.0% of the mass of solution A; in step (2), the volume ratio of white oil to solution A is 3.8-4.5:1, and the addition ratio of the surfactant Span 80 is 2.5-3.5% of the mass of solution B; in step (3), the frequency of ultrasonic emulsification is 10-15 kHz, and the ultrasonic emulsification time is 10-13 min; in step (4) The stirring speed is 110-140 r / min, and the stirring reaction time is 16-20 h; the drying temperature in step (5) is 35-50 ° C; the pyrolysis temperature in step (6) is 850-950 ° C; the solid content of the sodium silicate solution in step (7) is 35-40%, and the soaking time is 1.8-2.5 h; the acidic solution in step (8) is hydrochloric acid, and the soaking time is 1.8-2.5 h; in step (9), the high temperature heat treatment temperature is 1450-1520 ° C; the pore volume of the carbon aerogel powder obtained in step (6) is 0.8-1.5 cm 3 / g, average pore size 8-15nm, average particle size 5-8μm; step (9) finally obtains a lithium ion battery silicon-carbon negative electrode material with a specific capacity of 660-790mAh / g.

[0025] Compared with the prior art, the preparation method of a lithium-ion battery silicon-carbon negative electrode material of the present invention has the following beneficial effects:

[0026] (1) The present invention uses phenol, formaldehyde, sodium silicate and the like as main raw materials, and the raw material cost is low and the raw materials are easily available.

[0027] (2) The present invention can be granulated and formed in one step, avoiding the crushing and grinding process and reducing the introduction of impurities; at the same time, during the granulation process, key physical properties such as particle size distribution, pore size distribution, and pore volume can be conveniently controlled by adjusting the formula and process parameters.

[0028] (3) The present invention fills silicon material into the pre-made pores of carbon material. The pores of carbon material reserve a certain space for the volume expansion of silicon, which is beneficial to suppressing the volume expansion effect of silicon and maintaining the stability of silicon-carbon structure, and is beneficial to improving the cycle performance of the battery.

[0029] (4) The present invention adjusts the raw material formula and optimizes the process parameters, and the carbon aerogel powder prepared in step (6) has a pore volume of 0.8 to 1.5 cm 3 / g, with an average pore size of 8-15nm and an average particle size adjustable between 3-9μm. Carbon aerogel powder with this pore volume and pore size, when soaked in a sodium silicate solution, easily forms a silicon-carbon aerogel-silicic acid complex, facilitating the incorporation of silicon into the pores of the carbon material. After high-temperature heat treatment, the resulting silicon-carbon anode material for lithium-ion batteries has a specific capacity of 600-790mAh / g.

[0030] (5) The experiment showed that after optimizing the process parameters of the whole process, a lithium-ion battery silicon-carbon negative electrode material with a specific capacity of 660 to 790 mAh / g can be obtained, which is 180% to 220% of the actual specific capacity of commercial high-end graphite materials, achieving unexpected technical results. DETAILED DESCRIPTION

[0031] To illustrate the present invention, the following further describes in detail a method for preparing a silicon-carbon negative electrode material for a lithium-ion battery in conjunction with examples. However, the present invention is not limited to the examples.

[0032] The upper and lower limits and interval values ​​of the raw materials and process parameters involved in the present invention can all achieve the product of the present invention, and are not listed here one by one.

[0033] Example 1

[0034] A method for preparing a silicon-carbon negative electrode material for a lithium-ion battery comprises the following steps:

[0035] (1) Preparation of solution A: Stir and dissolve phenol, 37% formaldehyde aqueous solution, sodium hydroxide, and a pore-forming agent; the molar ratio of phenol to formaldehyde is 1:1.5; the molar ratio of phenol to sodium hydroxide is 100:1; the pore-forming agent is polyethylene glycol, and the addition ratio is 3% of the mass of solution A.

[0036] (2) Preparation of solution B: Take an appropriate amount of white oil, with the volume ratio of white oil to solution A being 4:1, add 3 wt% of the total mass of solution B, surfactant Span 80, to the white oil, and stir to dissolve.

[0037] (3) Solution A was poured into solution B to obtain a mixed solution, and the mixed solution was subjected to ultrasonic emulsification at an ultrasonic frequency of 15 kHz and an ultrasonic emulsification time of 20 min to obtain a micron-sized emulsion.

[0038] (4) The micron-sized emulsion was stirred at 80° C. and a stirring speed of 150 r / min for 18 h.

[0039] (5) The light yellow suspension was filtered to obtain a light yellow powder, which was then dried at 40° C. to obtain light yellow powder particles.

[0040] (6) The obtained light yellow powder particles were subjected to high temperature pyrolysis treatment in an argon atmosphere at a temperature of 900°C to obtain carbon aerogel powder. The pore volume of the carbon aerogel powder was 0.5 cm 3 / g, the average pore diameter is 8nm, and the average particle size is 2-5μm.

[0041] (7) The obtained carbon aerogel powder was immersed in a sodium silicate solution with a solid content of 20 wt% for 2 h, and then solid-liquid separation was performed to obtain a carbon aerogel-sodium silicate complex A.

[0042] (8) The obtained carbon aerogel-sodium silicate complex A was immersed in a dilute hydrochloric acid solution for 2 hours, and then solid-liquid separation was performed to obtain a carbon aerogel-silicic acid complex B.

[0043] (9) The obtained carbon aerogel-silicic acid composite B was washed and dried, and then subjected to high-temperature heat treatment at 1500°C in an argon atmosphere to obtain a lithium-ion battery silicon-carbon negative electrode material with a specific capacity of 482.2 mAh / g.

[0044] Example 2

[0045] The solid content of the sodium silicate solution in step (7) of Example 2 is 30 wt %, and the rest is the same as in Example 1. The specific capacity of the obtained lithium ion battery silicon-carbon negative electrode material is 523.6 mAh / g.

[0046] Example 3

[0047] A method for preparing a silicon-carbon negative electrode material for a lithium-ion battery comprises the following steps:

[0048] (1) Preparation of solution A: Stir and dissolve phenol, 37% formaldehyde aqueous solution, sodium hydroxide, and a pore-forming agent; the molar ratio of phenol to formaldehyde is 1:1.8; the molar ratio of phenol to sodium hydroxide is 100:1; the pore-forming agent is polyethylene glycol, and the addition ratio is 6.5% of the mass of solution A.

[0049] (2) Preparation of solution B: Take an appropriate amount of white oil, with the volume ratio of white oil to solution A being 4:1, add 2 wt% of the total mass of solution B, surfactant Span 80, to the white oil, and stir to dissolve.

[0050] (3) Solution A was poured into solution B to obtain a mixed solution, and the mixed solution was subjected to ultrasonic emulsification at an ultrasonic frequency of 10 kHz and an ultrasonic emulsification time of 10 min to obtain a micron-sized emulsion.

[0051] (4) The micron-sized emulsion was stirred at 80° C. and a stirring speed of 100 r / min for 18 h.

[0052] (5) Filter the light yellow suspension to obtain a light yellow powder, which is then dried at 40° C. to obtain light yellow powder particles.

[0053] (6) The obtained light yellow powder particles were subjected to high temperature pyrolysis treatment in an argon atmosphere at a temperature of 900°C to obtain carbon aerogel powder. The pore volume of the carbon aerogel powder was 0.8 cm 3 / g, the average pore diameter is 13nm, and the average particle size is 6-9μm.

[0054] (7) The obtained carbon aerogel powder was immersed in a sodium silicate solution with a solid content of 20 wt% for 2 h, and then solid-liquid separation was performed to obtain a carbon aerogel-sodium silicate complex A.

[0055] (8) The obtained carbon aerogel-sodium silicate complex A was immersed in a dilute hydrochloric acid solution for 2 hours, and then solid-liquid separation was performed to obtain a carbon aerogel-silicic acid complex B.

[0056] (9) The obtained carbon aerogel-silicic acid composite B was washed and dried, and then subjected to high-temperature heat treatment in an argon atmosphere at a temperature of 1500°C to obtain a lithium-ion battery silicon-carbon negative electrode material with a specific capacity of 532.4 mAh / g.

[0057] Example 4

[0058] The solid content of the sodium silicate solution in step (7) of Example 4 is 30 wt %, and the rest is the same as in Example 3. The specific capacity of the obtained lithium ion battery silicon-carbon negative electrode material is 586.5 mAh / g.

[0059] Example 5

[0060] A method for preparing a silicon-carbon negative electrode material for a lithium-ion battery comprises the following steps:

[0061] (1) Preparation of solution A: Stir and dissolve phenol, 37% formaldehyde aqueous solution, sodium hydroxide, and a pore-forming agent; the molar ratio of phenol to formaldehyde is 1:2; the molar ratio of phenol to sodium hydroxide is 100:1; the pore-forming agent is polyethylene glycol, and the addition ratio is 8% of the mass of solution A.

[0062] (2) Preparation of solution B: Take an appropriate amount of white oil, with the volume ratio of white oil to solution A being 4:1, add 3 wt% of the total mass of solution B, surfactant Span 80, to the white oil, and stir to dissolve.

[0063] (3) Solution A was poured into solution B to obtain a mixed solution, and the mixed solution was subjected to ultrasonic emulsification at an ultrasonic frequency of 12 kHz and an ultrasonic emulsification time of 10 min to obtain a micron-sized emulsion.

[0064] (4) The micron-sized emulsion was stirred at 80° C. and a stirring speed of 120 r / min for 18 h.

[0065] (5) The light yellow suspension was filtered to obtain a light yellow powder, which was then dried at 40° C. to obtain light yellow powder particles.

[0066] (6) The obtained light yellow powder particles were subjected to high temperature pyrolysis treatment in an argon atmosphere at a temperature of 900°C to obtain carbon aerogel powder. The pore volume of the carbon aerogel powder was 1.5 cm 3 / g, the average pore diameter is 15nm, and the average particle size is 5-8μm.

[0067] (7) The obtained carbon aerogel powder was immersed in a sodium silicate solution with a solid content of 40 wt% for 2 h, and then solid-liquid separation was performed to obtain a carbon aerogel-sodium silicate complex A.

[0068] (8) The obtained carbon aerogel-sodium silicate complex A is immersed in a dilute hydrochloric acid solution for 2 hours, and then separated to obtain a carbon aerogel-silicic acid complex.

[0069] (9) After washing and drying the carbon aerogel-silicic acid composite, a high-temperature heat treatment at 1500° C. was performed under an argon atmosphere to obtain a lithium-ion battery silicon-carbon negative electrode material with a specific capacity of 716.2 mAh / g.

[0070] Example 7

[0071] In step (1), the molar ratio of phenol to formaldehyde is 1:2.0, the molar ratio of phenol to sodium hydroxide is 110:1, and the addition ratio of the pore-forming agent polyethylene glycol is 8.0% of the mass of solution A; in step (2), the volume ratio of white oil to solution A is 3.9:1, and the addition ratio of the surfactant Span 80 is 2.9% of the mass of solution B; in step (3), the frequency of ultrasonic emulsification is 10-15 kHz, and the ultrasonic emulsification time is 13 min; in step (4), the stirring speed is 120 r / min, and the stirring reaction time is 20 h; in step (5), the drying temperature is 50° C.; in step (6), the pyrolysis temperature is 890° C.; in step (7), the solid content of the sodium silicate solution is 37%, and the immersion time is 2.1 h; in step (8), the acidic solution is hydrochloric acid, and the immersion time is 2.1 h; in step (9), the high-temperature heat treatment temperature is 1480° C.; the carbon aerogel powder obtained in step (6) has a pore volume of 1.3 cm 3 / g, average pore size 8-13nm, average particle size 4-8μm; step (9) finally obtains a lithium ion battery silicon-carbon negative electrode material with a specific capacity of 660.7mAh / g.

[0072] Example 8

[0073] In step (1), the molar ratio of phenol to formaldehyde is 1:1.9, the molar ratio of phenol to sodium hydroxide is 100:1, and the addition ratio of the pore-forming agent polyethylene glycol is 7.6% of the mass of solution A; in step (2), the volume ratio of white oil to solution A is 4.2:1, and the addition ratio of the surfactant Span 80 is 3.1% of the mass of solution B; in step (3), the frequency of ultrasonic emulsification is 13kHz, and the ultrasonic emulsification time is 12min; in step (4), the stirring speed is 130r / min, and the stirring reaction time is 19h; in step (5), the drying temperature is 45°C; in step (6), the pyrolysis temperature is 890°C; in step (7), the solid content of the sodium silicate solution is 35%, and the immersion time is 2.2h; in step (8), the acidic solution is hydrochloric acid, and the immersion time is 2.2h; in step (9), the high-temperature heat treatment temperature is 1500°C; the carbon aerogel powder obtained in step (6) has a pore volume of 1.5cm 3 / g, average pore size 9-12nm, average particle size 5-8μm; step (9) finally obtains a lithium ion battery silicon-carbon negative electrode material with a specific capacity of 790.2mAh / g.

[0074] A method for preparing a silicon-carbon negative electrode material for lithium-ion batteries has successfully completed laboratory and pilot tests. The prepared product was delivered to two domestic lithium-ion battery manufacturers for verification. The results demonstrate that the method utilizes phenol, formaldehyde, and sodium silicate as primary raw materials, and utilizes a pre-formed pore-forming method to fill silicon into the pores of the carbon material, resulting in a high-performance silicon-carbon negative electrode material for lithium-ion batteries with a specific capacity 180% to 220% higher than commercial high-end graphite materials.

Claims

1. A method for preparing a silicon-carbon negative electrode material for a lithium ion battery, characterized in that The following steps are involved: (1) Preparation of solution A: Mix and dissolve phenol, formaldehyde aqueous solution, sodium hydroxide and pore-forming agent according to a predetermined molar ratio; (2) Preparation of solution B: Take a set amount of white oil, add a set volume ratio of surfactant to it, and stir to dissolve; (3) pouring solution A into solution B to obtain a mixed solution, and performing ultrasonic emulsification on the mixed solution to obtain a micron-sized emulsion; (4) stirring the micron-sized emulsion at a temperature of 60 to 95° C. to obtain a light yellow suspension; (5) filtering the light yellow suspension to obtain a light yellow powder, and drying the light yellow powder to obtain light yellow powder particles; (6) subjecting the light yellow powder particles to a high-temperature pyrolysis treatment in an inert atmosphere at a high-temperature pyrolysis temperature of 700 to 1000° C. to obtain carbon aerogel powder; (7) immersing the carbon aerogel powder in a sodium silicate solution for a period of time, and then performing solid-liquid separation to obtain a carbon aerogel-sodium silicate complex A; (8) immersing the carbon aerogel-sodium silicate complex A in an acidic solution for a period of time, and then performing solid-liquid separation to obtain a carbon aerogel-silicic acid complex B; (9) After washing and drying the carbon aerogel-silicic acid complex B, a high-temperature heat treatment is performed under an inert atmosphere at a heat treatment temperature of 1400-1700° C. to obtain a lithium-ion battery silicon-carbon negative electrode material with a specific capacity of 480-790 mAh / g.

2. The method for preparing a silicon-carbon negative electrode material for a lithium-ion battery according to claim 1, wherein: In step (1), the molar ratio of phenol to formaldehyde is 1:1-2.2, and the molar ratio of phenol to sodium hydroxide is 10-150:1; the pore-forming agent is polyethylene glycol, and the addition ratio is 1-10% of the mass of solution A.

3. The method for preparing a silicon-carbon negative electrode material for a lithium-ion battery according to claim 1, wherein: In step (2), the volume ratio of white oil to solution A is 1 to 8:1; the surfactant is Span 80, and the addition ratio is 1 to 6% of the mass of solution B.

4. The method for preparing a silicon-carbon negative electrode material for a lithium-ion battery according to claim 1, wherein: In step (1), the molar ratio of phenol to formaldehyde is 1:1.2-2.0, the molar ratio of phenol to sodium hydroxide is 80-120:1, and the addition ratio of the pore-forming agent polyethylene glycol is 2.5-8.0% of the mass of solution A; in step (2), the volume ratio of white oil to solution A is 2-6:1; and the addition ratio of the surfactant Span 80 is 1.5-4.5% of the mass of solution B.

5. The method for preparing a silicon-carbon negative electrode material for a lithium-ion battery according to claim 4, wherein: In step (1), the molar ratio of phenol to formaldehyde is 1:1.5-2.0, the molar ratio of phenol to sodium hydroxide is 90-110:1, and the addition ratio of the pore-forming agent polyethylene glycol is 3.0-8.0% by mass of solution A; in step (2), the volume ratio of white oil to solution A is 3-5:1; and the addition ratio of the surfactant Span 80 is 1.8-3.5% by mass of solution B.

6. The method for preparing a silicon-carbon negative electrode material for a lithium ion battery according to claim 1, 2, 3, 4 or 5, wherein: In the step (3), the frequency of ultrasonic emulsification is 5 to 20 kHz, and the ultrasonic emulsification time is 10 to 30 minutes.

7. The method for preparing a silicon-carbon negative electrode material for a lithium-ion battery according to claim 6, wherein: The stirring speed in step (4) is 100-300 r / min, and the stirring reaction time is 10-30 h; the drying temperature in step (5) is 30-150° C.

8. The method for preparing a silicon-carbon negative electrode material for a lithium-ion battery according to claim 7, wherein: The inert atmosphere in step (6) is nitrogen, helium or argon; the solid content of the sodium silicate solution in step (7) is 10-50%, and the immersion time is 1-3 hours; the acidic solution in step (8) is one or more combinations of hydrochloric acid, sulfuric acid, and carbonic acid solution, and the immersion time is 1-3 hours; the inert atmosphere in step (9) is nitrogen, helium or argon, and the high-temperature heat treatment temperature is 1400-1700°C.

9. The method for preparing a silicon-carbon negative electrode material for a lithium-ion battery according to claim 8, wherein: In step (3), the frequency of ultrasonic emulsification is 8 to 18 kHz, and the ultrasonic emulsification time is 10 to 25 minutes; in step (4), the stirring speed is 100 to 180 r / min, and the stirring reaction time is 15 to 25 hours; in step (5), the drying temperature is 35 to 60° C.; in step (6), the pyrolysis temperature is 850 to 950° C.; in step (7), the solid content of the sodium silicate solution is 20 to 40%, and the soaking time is 1.5 to 2.5 hours; in step (8), the acidic solution is hydrochloric acid, and the soaking time is 1.5 to 2.5 hours; in step (9), the high-temperature heat treatment temperature is 1400-1600° C.

10. The method for preparing a silicon-carbon negative electrode material for a lithium-ion battery according to claim 9, wherein: In step (1), the molar ratio of phenol to formaldehyde is 1:1.8-2.0, the molar ratio of phenol to sodium hydroxide is 90-110:1, and the addition ratio of the pore-forming agent polyethylene glycol is 7.5-8.0% of the mass of solution A; in step (2), the volume ratio of white oil to solution A is 3.8-4.5:1, and the addition ratio of the surfactant Span 80 is 2.5-3.5% of the mass of solution B; in step (3), the frequency of ultrasonic emulsification is 10-15 kHz, and the ultrasonic emulsification time is 10-13 min; the stirring speed in step (4) is 100-150 kHz, and the stirring time is 10-13 min. The drying temperature in step (5) is 35-50°C; the pyrolysis temperature in step (6) is 850-950°C; the solid content of the sodium silicate solution in step (7) is 35-40%, and the soaking time is 1.8-2.5h; the acidic solution in step (8) is hydrochloric acid, and the soaking time is 1.8-2.5h; in step (9), the high-temperature heat treatment temperature is 1450-1520°C; the pore volume of the carbon aerogel powder obtained in step (6) is 0.8-1.5cm 3 / g, average pore size 8-15nm, average particle size 5-8μm; step (9) finally obtains a lithium ion battery silicon-carbon negative electrode material with a specific capacity of 660-790mAh / g.