CN108598430B

CN108598430B - Preparation method of silicon-carbon negative electrode material and porous silicon-carbon microsphere negative electrode material

Info

Publication number: CN108598430B
Application number: CN201810396791.2A
Authority: CN
Inventors: 袁雪亚; 王宇航; 白岩; 成信刚; 马书良
Original assignee: Yinlong New Energy Co Ltd; Northern Altair Nanotechnologies Co Ltd
Current assignee: Yinlong New Energy Co Ltd; Northern Altair Nanotechnologies Co Ltd
Priority date: 2018-04-27
Filing date: 2018-04-27
Publication date: 2021-03-09
Anticipated expiration: 2038-04-27
Also published as: CN108598430A

Abstract

The invention discloses a preparation method of a silicon-carbon negative electrode material and a porous silicon-carbon microsphere negative electrode material, and relates to the technical field of battery manufacturing. A preparation method of a silicon-carbon negative electrode material comprises the following steps: and grinding the silicon powder slurry to obtain ground silicon powder slurry. And (3) carrying out graphitization treatment on the carbon micro powder to obtain graphitized carbon micro powder. Stirring the ground silicon powder slurry, continuously adding graphitized carbon micro powder into the ground silicon powder slurry in the stirring process, adding a coating carbon source, performing ultrasonic treatment, stirring simultaneously, and then performing spray drying to obtain the silicon carbon microspheres. And carbonizing the silicon-carbon microspheres to obtain the silicon-carbon microspheres. And etching the silicon carbide carbon microspheres, and then washing and drying the silicon carbide carbon microspheres to obtain the porous silicon carbon microsphere negative electrode material. A porous silicon carbon microsphere negative electrode material is manufactured by the method. The invention can produce the porous silicon carbon microsphere with high gram capacity and high capacity retention rate after multiple cycles.

Description

Preparation method of silicon-carbon negative electrode material and porous silicon-carbon microsphere negative electrode material

Technical Field

The invention relates to the technical field of battery manufacturing, in particular to a preparation method of a silicon-carbon negative electrode material and a porous silicon-carbon microsphere negative electrode material.

Background

With the wide application of electronic products, batteries with high energy density and safe performance become products with great tendency, the theoretical gram capacity of graphite is about 375mAh/g, the theoretical gram capacity of the graphite cannot meet the requirement of the high energy density of the batteries at present, and the research on silicon-based materials with high capacity is paid extensive attention. However, the high expansion rate of the silicon-based material causes the anode powder to be easily pulverized, thereby influencing the high capacity exertion of the silicon-based material.

Disclosure of Invention

The invention aims to provide a preparation method of a silicon-carbon negative electrode material, which can be used for preparing porous silicon-carbon microspheres with high gram capacity, and the porous silicon-carbon microspheres have high capacity retention rate after multiple cycles.

The invention also aims to provide a porous silicon carbon microsphere anode material which is high in gram capacity and capacity retention rate after multiple cycles.

The invention provides a technical scheme that:

a preparation method of a silicon-carbon negative electrode material is used for preparing a porous silicon-carbon microsphere negative electrode material, and comprises the following steps:

and grinding the silicon powder slurry to obtain ground silicon powder slurry.

And (3) carrying out graphitization treatment on the carbon micro powder to obtain graphitized carbon micro powder.

And stirring the ground silicon powder slurry, and continuously adding the graphitized carbon micro powder into the ground silicon powder slurry in the stirring process to obtain a first mixed slurry.

And adding a coating carbon source into the first mixed slurry to obtain a second mixed slurry.

And carrying out ultrasonic treatment on the second mixed slurry, and simultaneously stirring the second mixed slurry to obtain third mixed slurry.

And carrying out spray drying on the third mixed slurry to obtain the silicon-carbon microspheres.

And carbonizing the silicon-carbon microspheres to obtain the silicon-carbon microspheres.

And etching the silicon carbide carbon microspheres, and then washing and drying the silicon carbide carbon microspheres to obtain the porous silicon carbon microsphere negative electrode material.

Further, before the step of grinding the silicon powder slurry to obtain ground silicon powder slurry, the preparation method of the silicon-carbon anode material further comprises the following steps: and adding an organic solvent into the silicon powder to obtain the silicon powder slurry.

Further, the solid content of the silicon powder slurry is 15%.

Further, the step of grinding the silicon powder slurry to obtain ground silicon powder slurry includes: and carrying out wet ball milling on the silicon powder slurry in a circulating closed ball mill, and grinding for 4 hours to obtain the ground silicon powder slurry, wherein the ground silicon powder slurry comprises nano silicon powder, and the particle size of the nano silicon powder is less than or equal to 20 nm.

Further, the step of graphitizing the carbon micro powder to obtain graphitized carbon micro powder includes:

and putting the carbon micro powder into a graphite furnace, and filling protective gas into the graphite furnace.

The temperature in the graphite furnace was raised to 1000 ℃ over 180 minutes and held for 150 minutes.

It took 100 minutes to raise the temperature in the graphite oven from 1000 ℃ to 1800 ℃.

And (3) raising the temperature in the graphite furnace from 1800 ℃ to 2500 ℃ in 80 minutes, and preserving the heat for 180 minutes to obtain the graphitized carbon micro powder.

Further, the solid content of the third mixed slurry was 18%.

Further, the spray drying the third mixed slurry to obtain the silicon carbon microspheres comprises: and filling the third mixed slurry into a closed spray drying device in a spray form, filling protective gas into the closed spray drying device, controlling the inlet temperature of the closed spray drying device to be 85 ℃ and the outlet temperature to be 60 ℃, and controlling the flow rate of spray formed by the third mixed slurry to be 5.2 mL/min.

Further, the step of carbonizing the silicon carbon microspheres to obtain silicon carbide carbon microspheres comprises:

and putting the silicon-carbon microspheres into a tubular furnace, and filling protective gas into the tubular furnace.

The temperature in the tube furnace was raised to 200 ℃ over 60 minutes and held for 180 minutes.

It took 100 minutes to raise the temperature in the tube furnace from 200 ℃ to 400 ℃.

The temperature in the tubular furnace is increased from 400 ℃ to 900 ℃ within 150 minutes, the temperature is kept for 150 minutes, and in the heat preservation process, air is filled into the tubular furnace at intervals of 30 minutes at a rate of 80mL/min for a preset time to obtain the silicon carbide carbon microspheres.

Further, the step of etching the silicon carbide carbon microspheres, and then washing and drying the silicon carbide carbon microspheres to obtain the porous silicon carbon microsphere negative electrode material comprises:

adding the silicon carbide carbon microspheres into a 5% hydrofluoric acid solution, and standing for 10 minutes.

And taking out the silicon carbide carbon microspheres, and washing the silicon carbide carbon microspheres by using deionized water.

And drying the silicon carbide carbon microspheres in a vacuum environment at 80 ℃ to obtain the porous silicon carbon microsphere negative electrode material.

A porous silicon carbon microsphere negative electrode material is prepared by a preparation method of a silicon carbon negative electrode material. The preparation method of the silicon-carbon negative electrode material comprises the following steps:

and grinding the silicon powder slurry to obtain ground silicon powder slurry.

Compared with the prior art, the preparation method of the silicon-carbon anode material provided by the invention has the beneficial effects that:

according to the preparation method of the silicon-carbon negative electrode material, the porous silicon-carbon microspheres can be prepared by a processing method of etching after spray drying, the gram capacity of the porous silicon-carbon microspheres can reach 600mAh/g, the first charge-discharge rate can reach 92%, and the capacity retention rate is over 90% after multiple cycles.

Compared with the prior art, the porous silicon carbon microsphere negative electrode material provided by the invention has the beneficial effects that:

the porous silicon-carbon microsphere negative electrode material provided by the invention is prepared by the preparation method of the silicon-carbon negative electrode material, the gram capacity of the porous silicon-carbon microsphere negative electrode material can reach 600mAh/g, the first charge-discharge rate can reach 92%, and the capacity retention rate is over 90% after multiple cycles.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required to be used in the embodiments will be briefly described below. It is appreciated that the following drawings depict only certain embodiments of the invention and are therefore not to be considered limiting of its scope. For a person skilled in the art, it is possible to derive other relevant figures from these figures without inventive effort.

Fig. 1 is a schematic flow chart of a method for preparing a silicon carbon microsphere anode material according to a first embodiment of the present invention;

FIG. 2 is a partial schematic flow chart diagram provided in accordance with a first embodiment of the present invention;

fig. 3 is a schematic flowchart of step S102 according to the first embodiment of the present invention;

fig. 4 is a schematic flowchart of step S107 provided in the first embodiment of the present invention;

fig. 5 is a flowchart of step S108 according to the first embodiment of the present invention;

fig. 6 is a schematic flow chart of a method for preparing a silicon carbon microsphere anode material according to a second embodiment of the present invention;

fig. 7 is a flowchart of step S204 according to a second embodiment of the present invention;

fig. 8 is a gram capacity cycle diagram of a porous silicon carbon microsphere anode material provided by a third embodiment of the invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention. It is to be understood that the embodiments described are only a few embodiments of the present invention, and not all embodiments. The components of embodiments of the present invention generally described and illustrated in the figures herein may be arranged and designed in a wide variety of different configurations.

Thus, the following detailed description of the embodiments of the present invention, presented in the figures, is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

It should be noted that: like reference numbers and letters refer to like items in the following figures, and thus, once an item is defined in one figure, it need not be further defined and explained in subsequent figures.

In the description of the present invention, it is to be understood that the terms "upper", "lower", "inside", "outside", "left", "right", and the like, indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, or the orientations or positional relationships that the products of the present invention are conventionally placed in use, or the orientations or positional relationships that are conventionally understood by those skilled in the art, and are used for convenience of describing the present invention and simplifying the description, but do not indicate or imply that the devices or elements referred to must have a specific orientation, be constructed in a specific orientation, and be operated, and thus, should not be construed as limiting the present invention.

Furthermore, the terms "first," "second," and the like are used merely to distinguish one description from another, and are not to be construed as indicating or implying relative importance.

In the description of the present invention, it is also to be noted that, unless otherwise explicitly stated or limited, the terms "disposed" and "connected" are to be interpreted broadly, and for example, "connected" may be a fixed connection, a detachable connection, or an integral connection; can be mechanically or electrically connected; the connection may be direct or indirect via an intermediate medium, and may be a communication between the two elements. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.

The following detailed description of embodiments of the invention refers to the accompanying drawings.

First embodiment

Referring to fig. 1, the present embodiment provides a method for preparing a silicon carbon microsphere negative electrode material, which is used for preparing a porous silicon carbon microsphere negative electrode material. The method can prepare the porous silicon-carbon microspheres with high gram capacity, and the porous silicon-carbon microspheres have high capacity retention rate after multiple cycles.

In this embodiment, the preparation method of the silicon-carbon negative electrode material comprises the following steps:

and S101, grinding the silicon powder slurry to obtain ground silicon powder slurry.

Wherein, step S101 includes: and carrying out wet ball milling on the silicon powder slurry in a circulating closed ball mill for 4 hours to obtain the milled silicon powder slurry. And the ground silicon powder slurry obtained by wet ball milling comprises nano silicon powder, and the particle size of the nano silicon powder is less than or equal to 20 nm. That is, in this embodiment, the micron silicon powder can be ground into the nano silicon powder by wet ball milling, and the particle size of the nano silicon powder can be less than 20 nm.

In other embodiments, the grinding time and the particle size of the nano silicon powder obtained by grinding may be different, and only the silicon powder is ground to the nano silicon powder.

As shown in fig. 2, in addition, before step S101, the method for preparing a silicon-carbon anode material further includes:

and S111, adding an organic solvent into the silicon powder to obtain silicon powder slurry.

That is, in the present embodiment, by adding an organic solvent to the silicon powder, when the grinding is performed in step S101, the silicon powder can be prevented from being oxidized during the grinding. In this embodiment, the organic solvent is absolute ethanol. It should be understood that in other embodiments, other organic solvents, such as ethylene glycol, may be used, as long as the silicon powder is prevented from being oxidized during the grinding process.

It should be noted that, in this embodiment, the silicon powder is micron silicon powder, that is, micron silicon powder can be ground into nanometer silicon powder, oxidation of nanometer silicon powder in the grinding process can be avoided through an organic solvent, and the cost for purchasing nanometer silicon powder can be saved.

Further, in the present embodiment, the solid content of the silicon powder slurry is configured to be 15%, so that the oxidation preventing effect of the organic solvent on the silicon powder is ensured under the condition that sufficient grinding is ensured. It should be understood that in other embodiments, the solid content of the silicon powder slurry can be prepared in other proportions under the condition of ensuring sufficient grinding and the oxidation prevention effect of the organic solvent on the silicon powder.

And S102, carrying out graphitization treatment on the carbon micro powder to obtain graphitized carbon micro powder.

As shown in fig. 3, step S102 includes:

and S1021, putting the carbon micro powder into a graphite furnace, and filling protective gas into the graphite furnace.

The carbon micro powder adopted in the embodiment is the recycled waste carbon micro powder, so that a large amount of cost can be saved, and the waste resources are recycled through recycling.

In addition, in the present embodiment, Ar gas is used as the shielding gas, and it should be understood that in other embodiments, other shielding gases, such as nitrogen, may also be used.

S1022, the temperature in the graphite furnace is raised to 1000 ℃ in 180 minutes, and the temperature is maintained for 150 minutes.

S1023, the temperature in the graphite furnace is increased from 1000 ℃ to 1800 ℃ in 100 minutes.

And S1024, taking 80 minutes, raising the temperature in the graphite furnace from 1800 ℃ to 2500 ℃, and preserving the temperature for 180 minutes to obtain the graphitized carbon micro powder.

In other embodiments, before the waste carbon micro powder is graphitized, the waste carbon micro powder may be purified; the graphitization procedure of the carbon micro powder can also be improved, so that the graphitized carbon micro powder with better graphitization degree and performance can be obtained after the carbon micro powder is graphitized.

In addition, in other embodiments, the order of step S101 and step S102 may be interchanged.

S103, stirring the ground silicon powder slurry, and continuously adding graphitized carbon micro powder into the ground silicon powder slurry in the stirring process to obtain first mixed slurry.

In this embodiment, 200g of ground silicon powder slurry is taken, and an appropriate amount of graphitized carbon micro powder is continuously added to the ground silicon powder slurry while stirring the ground silicon powder slurry, wherein the amount of the graphitized carbon micro powder continuously added in this embodiment is 300 g. In addition, it should be understood that, in other embodiments, the usage amount of the ground silicon powder slurry and the graphitized carbon micro powder can be changed, so that the mass ratio of the ground silicon powder slurry to the graphitized carbon micro powder is only 2:3, and the mass ratio of the ground silicon powder to the graphitized carbon micro powder is only 1: 10-1: 4.

And S104, adding a coated carbon source into the first mixed slurry to obtain a second mixed slurry.

In this example, 300g of phenolic resin was used as the carbon source. It should be understood that in other embodiments, the amount of phenolic resin may also be adjusted according to the amount of ground silicon powder slurry and graphitized carbon micro powder. For example, when 400g of the ground silicon powder slurry and 600g of the graphitized carbon fine powder are taken, 600g of the phenolic resin is used. In addition, the mass ratio of the added phenolic resin to the ground silicon powder can be 1:1.5, namely the mass of the added phenolic resin is 600g when 400g of ground silicon powder is taken. In addition, other coated carbon sources besides phenolic resin, such as glucose, sucrose, carboxymethyl cellulose, citric acid and the like, can be used, wherein the adding mass of different coated carbon sources is different according to the carbon residue rate, and the ratio of the silicon powder to the carbonized amorphous carbon is 1: 0.5-1: 1.

And S105, carrying out ultrasonic treatment on the second mixed slurry, and simultaneously stirring the second mixed slurry to obtain third mixed slurry.

In the present embodiment, the solid content of the third mixed slurry was configured to be 18%.

It should be noted that, while the second mixed slurry is subjected to ultrasonic treatment and stirring, an appropriate organic solvent may be added to the second mixed slurry, so that the solid content of the resulting third mixed slurry can be configured to be 18%. The organic solvent may be ethanol or ethylene glycol.

In this example, the ultrasonic treatment and the stirring treatment were performed on the second mixed slurry for 4 hours.

And S106, carrying out spray drying on the third mixed slurry to obtain the silicon-carbon microspheres.

Wherein, step S106 includes:

and filling the third mixed slurry into the closed spray drying device in a spray form, and filling protective gas into the closed spray drying device, wherein the protective gas is Ar protective gas, and in other embodiments, the protective gas can also be inert gas such as nitrogen. In addition, the inlet temperature of the closed spray drying device is controlled to be 85 ℃ and the outlet temperature is controlled to be 60 ℃. And simultaneously controlling the air flow of the spray formed by the third mixed slurry to be 5.2 mL/min.

It should be understood that in other embodiments, the inlet temperature and the outlet temperature of the closed spray drying device may be adjusted according to actual needs, and similarly, the air flow rate of the spray formed by the third mixed slurry may also be adjusted.

In the embodiment, since the second mixed slurry is subjected to ultrasonic treatment and stirred while adding a suitable organic solvent, the organic solvent can prevent the third mixed slurry from being oxidized during spraying.

Wherein, the problem of limited carbon source selection is solved by adopting solvent type spray drying to replace the spray drying of a common water system in the prior art. That is, the range of carbon sources that can be selected by solvent-based spray drying is expanded, and the method is closer to the industrial production process.

S107, carbonizing the silicon-carbon microspheres to obtain the silicon-carbon microspheres.

As shown in fig. 4, wherein step S107 includes:

s1071, putting the silicon-carbon microspheres into a tubular furnace, and filling protective gas into the tubular furnace.

The protective gas is Ar protective gas, and in addition, inert gases such as nitrogen and the like can also be used in other embodiments.

S1072, the temperature in the tube furnace is raised to 200 ℃ in 60 minutes, and the temperature is kept for 180 minutes.

S1073, the temperature in the tube furnace is increased from 200 ℃ to 400 ℃ in 100 minutes.

S1074, raising the temperature in the tubular furnace from 400 ℃ to 900 ℃ in 150 minutes, preserving the heat for 150 minutes, and filling air into the tubular furnace at intervals of 30 minutes for a preset time at 80mL/min during the heat preservation process to obtain the silicon carbide carbon microspheres.

In this example, air was introduced into the tube furnace at an air flow rate of 80mL/min for 15 minutes at intervals of 30 minutes. In addition, in other embodiments, the duration of the air charging can be adjusted according to the difference of the coated carbon source so as to prepare silicon carbon materials with different oxidation degrees.

And S108, etching the silicon carbide carbon microspheres, and then washing and drying the silicon carbide carbon microspheres to obtain the porous silicon carbon microsphere negative electrode material.

As shown in fig. 5, step S108 includes:

s1081, adding the silicon carbide carbon microspheres into a 5% hydrofluoric acid solution, and standing for 10 minutes.

Namely, the prepared porous silicon carbon microsphere negative electrode material can relieve the problem of volume expansion of silicon powder under the etching action of hydrofluoric acid solution.

S1082, taking out the silicon carbide carbon microspheres, and washing the silicon carbide carbon microspheres by using deionized water.

And washing the silicon carbide carbon microspheres by using deionized water so as to wash away the hydrofluoric acid solution attached to the etched silicon carbide carbon microspheres.

S1083, drying the silicon carbide carbon microspheres in a vacuum environment at 80 ℃ to obtain the porous silicon carbon microsphere negative electrode material.

According to the preparation method of the silicon-carbon negative electrode material, the porous silicon-carbon microspheres are prepared through a processing method of spray drying and etching, the gram capacity of the porous silicon-carbon microspheres can reach 600mAh/g, the first charge-discharge rate can reach 92%, and the capacity retention rate is over 90% after multiple cycles. The silicon-carbon microspheres with good silicon dispersibility can be prepared by high-energy ball milling combined with spray drying, so that the cycling stability of the half-cell is improved. And the porous silicon carbon microspheres are prepared by micro-oxidation and etching, so that the problem of volume expansion of the silicon powder is solved. In addition, the solvent-type closed ball milling device can be used for grinding micron silicon into nano silicon powder, so that the oxidation of the silicon powder in the ball milling process can be inhibited, and the cost for purchasing the nano silicon powder is saved. The cost can be further saved by recycling waste materials to prepare the porous carbon microspheres from the recycled waste carbon powder through purification and graphitization.

Second embodiment

Referring to fig. 6, in the present embodiment, a method for preparing a silicon carbon negative electrode material is provided, and is used for preparing a porous silicon carbon microsphere negative electrode material, and the porous silicon carbon microsphere negative electrode material prepared by the method for preparing a silicon carbon negative electrode material provided in the present embodiment has a high gram capacity and a high capacity retention rate after multiple charge and discharge cycles.

The preparation method of the silicon-carbon anode material provided by the embodiment comprises the following steps:

s201, putting the nano silicon powder and the artificial graphite into a 10% sucrose aqueous solution to obtain a first mixed solution.

In the embodiment, the nano silicon powder is directly purchased, and the using amount of the nano silicon powder is 30 g. The amount of the artificial graphite is 300 g. It should be understood that in other embodiments, the amounts of the nano silicon powder and the artificial graphite may be 60g, 600g, or 90g, 900g, respectively, that is, the amounts of the nano silicon powder and the artificial graphite satisfy the ratio of 1: 10.

S202, stirring and carrying out ultrasonic treatment on the first mixed solution for 4 hours to obtain a second mixed solution.

And S203, spray drying the second mixed solution.

In this example, the second mixed solution was also charged into a closed spray drying apparatus and spray-dried. The inlet temperature of the closed spray drying device is controlled to be 230 ℃, and the outlet temperature is controlled to be 120 ℃. And simultaneously controlling the air flow of the spray formed by the second mixed solution to be 5.6 mL/min.

And S204, carbonizing the sample obtained by spray drying to obtain the silicon-carbon negative electrode material.

The carbonization process is likewise carried out in a tube furnace. And Ar protective gas was also charged in the tube furnace. Further, as shown in fig. 7, the carbonization step includes:

s2041, taking 60 minutes, raising the temperature in the tube furnace to 200 ℃, and keeping the temperature for 60 minutes.

S2042, taking 80 minutes, and increasing the temperature in the tube furnace from 200 ℃ to 400 ℃.

And S2043, raising the temperature in the tubular furnace from 400 ℃ to 900 ℃ in 100 minutes, and preserving the temperature for 120 minutes to obtain the silicon-carbon negative electrode material.

The first gram capacity of the silicon-carbon negative electrode material is 550mAh/g, the first charge-discharge efficiency is about 80%, and the capacity retention rate is 60% after 50 cycles.

Third embodiment

The embodiment provides a porous silicon carbon microsphere anode material which is high in gram capacity and high in capacity retention rate after multiple cycles.

The porous silicon carbon microsphere negative electrode material provided in the embodiment is prepared by the preparation method of the silicon carbon negative electrode material provided in the first embodiment.

Referring to fig. 8, the gram capacity of the porous silicon carbon microsphere negative electrode material provided in the present embodiment can reach 600mAh/g, the first charge-discharge rate can reach 92%, and the capacity retention rate after multiple cycles is over 90%.

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A preparation method of a silicon-carbon negative electrode material is used for preparing a porous silicon-carbon microsphere negative electrode material, and is characterized by comprising the following steps:

adding an organic solvent into the silicon powder to obtain silicon powder slurry;

performing wet ball milling on the silicon powder slurry in a circulating closed ball mill, and grinding for 4 hours to obtain ground silicon powder slurry, wherein the ground silicon powder slurry comprises nano silicon powder, and the particle size of the nano silicon powder is less than or equal to 20 nm;

graphitizing the carbon micro powder to obtain graphitized carbon micro powder;

stirring the ground silicon powder slurry, and continuously adding the graphitized carbon micro powder into the ground silicon powder slurry in the stirring process to obtain a first mixed slurry;

adding a coating carbon source into the first mixed slurry to obtain a second mixed slurry;

carrying out ultrasonic treatment on the second mixed slurry, and simultaneously stirring the second mixed slurry to obtain third mixed slurry;

adding an organic solvent into the second mixed slurry while performing ultrasonic treatment and stirring on the second mixed slurry;

spray drying the third mixed slurry to obtain silicon-carbon microspheres;

carbonizing the silicon-carbon microspheres to obtain silicon-carbon microspheres;

2. The method for preparing a silicon-carbon negative electrode material according to claim 1, wherein the solid content of the silicon powder slurry is 15%.

3. The method for preparing the silicon-carbon negative electrode material according to claim 1, wherein the step of graphitizing the carbon micro powder to obtain graphitized carbon micro powder comprises the following steps:

putting the carbon micro powder into a graphite furnace, and filling protective gas into the graphite furnace;

the temperature in the graphite furnace is raised to 1000 ℃ within 180 minutes, and the temperature is kept for 150 minutes;

the temperature in the graphite furnace is raised from 1000 ℃ to 1800 ℃ within 100 minutes;

4. The method for preparing a silicon-carbon anode material according to claim 1, wherein the solid content of the third mixed slurry is 18%.

5. The preparation method of the silicon-carbon negative electrode material, according to claim 1, wherein the spray drying the third mixed slurry to obtain the silicon-carbon microspheres comprises: and filling the third mixed slurry into a closed spray drying device in a spray form, filling protective gas into the closed spray drying device, controlling the inlet temperature of the closed spray drying device to be 85 ℃ and the outlet temperature to be 60 ℃, and controlling the flow rate of spray formed by the third mixed slurry to be 5.2 mL/min.

6. The preparation method of the silicon-carbon anode material according to claim 1, wherein the step of carbonizing the silicon-carbon microspheres to obtain silicon-carbon microspheres comprises:

putting the silicon-carbon microspheres into a tubular furnace, and filling protective gas into the tubular furnace;

the temperature in the tube furnace is raised to 200 ℃ within 60 minutes, and the temperature is kept for 180 minutes;

increasing the temperature in the tube furnace from 200 ℃ to 400 ℃ in 100 minutes;

7. The preparation method of the silicon-carbon anode material according to claim 1, wherein the step of etching the silicon carbide carbon microspheres, and then washing and drying the silicon carbide carbon microspheres to obtain the porous silicon-carbon microsphere anode material comprises the following steps:

adding the silicon carbide carbon microspheres into a 5% hydrofluoric acid solution, and standing for 10 minutes;

taking out the silicon carbide carbon microspheres, and washing the silicon carbide carbon microspheres by using deionized water;

8. A porous silicon carbon microsphere negative electrode material, which is characterized by being prepared by the preparation method of the silicon carbon negative electrode material as claimed in any one of claims 1 to 7.