Preparation method and application of material-coated silicon-carbon composite negative electrode material

Abstract

The invention discloses a preparation method and application of a material-coated silicon-carbon composite negative electrode material, and relates to the technical field of lithium ion batteries. The method comprises the following steps: mixing nano silicon powder, cellulose / silk nanofibers or whiskers and graphite powder in a certain proportion in an aqueous solution containing polyvinylpyrrolidone, polyethylene glycol, polyoxyethylene, polyacrylamide, polymaleic anhydride or carboxymethyl cellulose, and carrying out ultrasonic treatment and stirring to form a uniform precursor solution; and granulating by a spray drying method, and carrying out high-temperature calcination carbonization treatment to form a composite carbon coating structure on the surface of the nano silicon, thereby finally preparing the silicon-carbon composite material. The material has a three-dimensional conductive network structure, and can effectively inhibit silicon volume expansion, improve interface stability, improve lithium ion transmission efficiency, and significantly improve first efficiency and cycle life.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery technology, specifically to a method for preparing a silicon-carbon composite anode material with material coating and its application. Background Technology

[0002] With the development of new energy vehicles and portable electronic devices, higher requirements have been placed on the energy density of lithium-ion batteries. Silicon materials have become the most promising anode materials due to their high theoretical specific capacity (4200mAh / g) and abundant reserves. However, they undergo significant volume expansion (>300%) during charge and discharge, leading to the pulverization of active materials and repeated rupture and regeneration of the solid electrolyte interphase (SEI) film, resulting in rapid capacity decay and reduced cycle performance, which seriously restricts practical applications.

[0003] Current strategies for improving the performance of silicon anodes include nanomaterial fabrication, carbon composites, and polymer coatings. However, these strategies still face several challenges: nanomaterials are complex to prepare, costly, and prone to side reactions; carbon-based composites have weak interfacial bonding, making them susceptible to delamination during long-term cycling; and polymer coatings lack sufficient mechanical strength and reduce energy density. Furthermore, existing coating methods often use organic solvents, which is inconsistent with the trend towards green manufacturing.

[0004] Cellulose / silk nanofibers or whiskers have high modulus, high strength, abundant surface functional groups and good biocompatibility, and can be used as reinforcing phases in composite materials. However, there are no reports on their use as functional coating layers for silicon anodes to systematically study their synergistic enhancement of conductivity, inhibition of expansion and stabilization of SEI film.

[0005] Therefore, in order to solve the above problems, this paper proposes a method for preparing silicon-carbon composite anode materials with material coating and its application. Summary of the Invention

[0006] The purpose of this invention is to design a method for preparing a silicon-carbon composite anode material with material coating that can solve the problems of large volume expansion, low initial efficiency and poor cycle stability of silicon anodes during cycling.

[0007] To achieve the above-mentioned technical effects, the present invention is implemented through the following technical solution: 1. A method for preparing a silicon-carbon composite anode material with material coating, characterized by comprising the following steps:

[0008] S1. Weigh out nano-silicon powder, coating material, and graphite powder in a mass ratio of 1~3:0.5~3:1~4. Then add the weighed nano-silicon powder, coating material, and graphite powder to deionized water and disperse by ultrasonication to obtain a mixture.

[0009] S2. After ultrasonic dispersion, add a treatment agent accounting for 5-25% of the total solid mass to the mixture, then treat it with ultrasound at 40-80kHz and perform magnetic stirring for 8-12 hours to obtain a homogeneous precursor solution.

[0010] S3. Spray dry the precursor solution at a feed rate of 500-800 mL / h, an inlet air temperature of 160-200℃, an outlet air temperature of 90-200℃, and collect the granulated powder.

[0011] S4. Then, under an inert atmosphere, the temperature is increased to 500-900℃ at a heating rate of 2-5℃ / min for 1-2 hours for calcination and carbonization. After carbonization, silicon-carbon composite anode material is obtained.

[0012] S5. Mix the silicon-carbon material with the conductive agent and binder in a 16-18% ethanol aqueous solution at a mass ratio of 8:1:1. After stirring for 8-12 hours, coat the mixture onto the copper current collector and perform preliminary drying at 55-70℃ for 10-20 minutes. Then, vacuum dry the mixture at 100-200℃ for 12-14 hours to obtain the negative electrode sheet.

[0013] Furthermore, the coating material is cellulose / silk nanofibers / whiskers.

[0014] Furthermore, the cellulose / silk nanofibers / whiskers have a diameter of 4~10nm and a length of 100~500nm.

[0015] Furthermore, the particle size of the nano-silicon powder is 50~150nm.

[0016] Furthermore, the treatment agent is one or more of polyvinylpyrrolidone, polyethylene glycol, polyethylene oxide, polyacrylamide, polymaleic anhydride, or carboxymethyl cellulose.

[0017] Furthermore, the conductive agent is either conductive carbon black or carbon nanotubes.

[0018] Furthermore, the adhesive is one of polyvinylidene fluoride, polyacrylic acid, and sodium alginate.

[0019] Another objective of this invention is to provide the application of a material-coated silicon-carbon composite anode material in lithium-ion batteries.

[0020] The beneficial effects of this invention are:

[0021] This invention utilizes cellulose / silk nanofibers or whiskers to synergistically construct a three-dimensional carbon-coated network with graphite and polymers, which can effectively suppress silicon volume expansion; significantly improve the conductivity of the material and the interfacial lithium-ion transport rate; reduce electrolyte decomposition and improve first-efficiency and cycle stability; the process is simple, environmentally friendly, and suitable for large-scale production. Attached Figure Description

[0022] 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.

[0023] Figure 1 This is a scanning electron microscope image of pure silicon as described in Embodiment 1 of the present invention;

[0024] Figure 2 This is a scanning electron microscope image of the silicon-carbon composite anode material prepared in Example 1 of the present invention;

[0025] Figure 3 These are charge-discharge cycle test diagrams of the silicon-carbon materials prepared in Examples 1-2 and Examples 8-10 of the present invention. Detailed Implementation

[0026] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] Example 1

[0028] A method for preparing a silicon-carbon composite anode material with material coating, comprising the following steps:

[0029] Step 1: Take 6g of nano-silicon (diameter 200nm), 4.5g of cellulose / silk nanofibers / whiskers (diameter 4-10nm, length 100-500nm), and 4.5g of graphite powder and add them to a beaker. Add 400ml of deionized water and sonicate at 60kHz for 2h. Add 2g of polyvinylpyrrolidone / polyethylene glycol / polyoxyethylene / polyacrylamide / polymaleic anhydride / carboxymethyl cellulose and stir at room temperature for 10h to obtain the precursor solution.

[0030] Step 2: Granulate the precursor solution using spray drying. The inlet air temperature is 180℃, the outlet air temperature is 100℃, and the feed rate is 600ml / h. Collect the silicon-carbon precursor powder and place it in a tube furnace for high-temperature calcination at 900℃ for 3h. During calcination, argon gas is introduced as a protective gas, and the heating rate is 5℃ / min. Finally, silicon-carbon composite material is obtained.

[0031] Step 3: Mix 80mg of silicon-carbon composite material, 10mg of conductive carbon black, and 10mg of carboxymethyl cellulose / sodium silk evenly in an agate mortar. Then add the mixture to an ethanol aqueous solution with a mass fraction of 16%-18%. After magnetic stirring for 24 hours, coat the mixture evenly onto the negative electrode current collector copper sheet using a coating machine. The coating thickness is 200μm. After coating, dry the negative electrode current collector copper sheet at 55℃ for 10 minutes and then vacuum dry it at 100℃ for 12 hours to obtain the silicon-based negative electrode material.

[0032] Figure 1 This is a scanning electron microscope image of the nano-silicon powder used in this embodiment. As can be seen from the image, the nano-silicon has a diameter of approximately 200 nm and consists of spherical particles.

[0033] Figure 2 The image shows a scanning electron microscope (SEM) image of the silicon-carbon composite anode material prepared in this embodiment. As can be seen from the image, the nano-silicon particles are coated with a three-dimensional composite highly conductive carbon material.

[0034] Example 2

[0035] A method for preparing a silicon-carbon composite anode material with material coating, comprising the following steps:

[0036] Step 1: Take 6g of nano-silicon (200nm in diameter), 3g of cellulose / silk nanofibers / whiskers (4-10nm in diameter, 100-500nm in length), and 3g of graphite powder and add them to a beaker. Add 400ml of deionized water and sonicate at 60kHz for 2 hours. Add 1.5g of polyvinylpyrrolidone / polyethylene glycol / polyethylene oxide / polyacrylamide / polymaleic anhydride / carboxymethyl cellulose and stir at room temperature for 10 hours to obtain the precursor solution.

[0037] Step 2: Granulate the precursor solution using spray drying. The inlet air temperature is 180℃, the outlet air temperature is 100℃, and the feed rate is 600ml / h. Collect the silicon-carbon precursor powder and place it in a tube furnace for high-temperature calcination at 900℃ for 3h. During calcination, argon gas is introduced as a protective gas, and the heating rate is 5℃ / min. Finally, silicon-carbon composite material is obtained.

[0038] Step 3: Mix 80mg of silicon-carbon composite material, 10mg of conductive carbon black, and 10mg of carboxymethyl cellulose / sodium silk evenly in an agate mortar. Then add the mixture to an ethanol aqueous solution with a mass fraction of 16%-18%. After magnetic stirring for 24 hours, coat the mixture evenly onto the negative electrode current collector copper sheet using a coating machine. The coating thickness is 200μm. After coating, dry the negative electrode current collector copper sheet at 55℃ for 10 minutes and then vacuum dry it at 100℃ for 12 hours to obtain the silicon-based negative electrode material.

[0039] Example 3

[0040] A method for preparing a silicon-carbon composite anode material with material coating, comprising the following steps:

[0041] Step 1: Take 6g of nano-silicon (diameter 200nm), 7.5g of cellulose / silk nanofibers / whiskers (diameter 4-10nm, length 100-500nm), and 7.5g of graphite powder and add them to a beaker. Add 400ml of deionized water and sonicate at 60kHz for 2h. Add 2.5g of polyvinylpyrrolidone / polyethylene glycol / polyethylene oxide / polyacrylamide / polymaleic anhydride / carboxymethyl cellulose and stir at room temperature for 10h to obtain the precursor solution.

[0042] Step 2: Granulate the precursor solution using spray drying. The inlet air temperature is 180℃, the outlet air temperature is 100℃, and the feed rate is 600ml / h. Collect the silicon-carbon precursor powder and place it in a tube furnace for high-temperature calcination at 900℃ for 3h. During calcination, argon gas is introduced as a protective gas, and the heating rate is 5℃ / min. Finally, silicon-carbon composite material is obtained.

[0043] Step 3: Mix 80mg of silicon-carbon composite material, 10mg of conductive carbon black, and 10mg of carboxymethyl cellulose / sodium silk evenly in an agate mortar. Then add the mixture to an ethanol aqueous solution with a mass fraction of 16%-18%. After magnetic stirring for 24 hours, coat the mixture evenly onto the negative electrode current collector copper sheet using a coating machine. The coating thickness is 200μm. After coating, dry the negative electrode current collector copper sheet at 55℃ for 10 minutes and then vacuum dry it at 100℃ for 12 hours to obtain the silicon-based negative electrode material.

[0044] Example 4

[0045] A method for preparing a silicon-carbon composite anode material with material coating, comprising the following steps:

[0046] Step 1: Take 6g of nano-silicon (200nm in diameter), 5g of cellulose / silk nanofibers / whiskers (4-10nm in diameter, 100-500nm in length), and 3g of graphite powder and add them to a beaker. Add 400ml of deionized water and sonicate at 60kHz for 2 hours. Add 1.5g of polyvinylpyrrolidone / polyethylene glycol / polyethylene oxide / polyacrylamide / polymaleic anhydride / carboxymethyl cellulose and stir at room temperature for 10 hours to obtain the precursor solution.

[0047] Step 2: Granulate the precursor solution using spray drying. The inlet air temperature is 180℃, the outlet air temperature is 100℃, and the feed rate is 600ml / h. Collect the silicon-carbon precursor powder and place it in a tube furnace for high-temperature calcination at 900℃ for 3h. During calcination, argon gas is introduced as a protective gas, and the heating rate is 5℃ / min. Finally, silicon-carbon composite material is obtained.

[0048] Step 3: Mix 80mg of silicon-carbon composite material, 10mg of conductive carbon black, and 10mg of carboxymethyl cellulose / sodium silk evenly in an agate mortar. Then add the mixture to an ethanol aqueous solution with a mass fraction of 16%-18%. After magnetic stirring for 24 hours, coat the mixture evenly onto the negative electrode current collector copper sheet using a coating machine. The coating thickness is 200μm. After coating, dry the negative electrode current collector copper sheet at 55℃ for 10 minutes and then vacuum dry it at 100℃ for 12 hours to obtain the silicon-based negative electrode material.

[0049] Example 5

[0050] A method for preparing a silicon-carbon composite anode material with material coating, comprising the following steps:

[0051] Step 1: Take 6g of nano-silicon (200nm in diameter), 3g of cellulose / silk nanofibers / whiskers (4-10nm in diameter, 100-500nm in length), and 5g of graphite powder and add them to a beaker. Add 400ml of deionized water and sonicate at 60kHz for 2 hours. Add 1.5g of polyvinylpyrrolidone / polyethylene glycol / polyethylene oxide / polyacrylamide / polymaleic anhydride / carboxymethyl cellulose and stir at room temperature for 10 hours to obtain the precursor solution.

[0052] Step 2: Granulate the precursor solution using spray drying. The inlet air temperature is 180℃, the outlet air temperature is 100℃, and the feed rate is 600ml / h. Collect the silicon-carbon precursor powder and place it in a tube furnace for high-temperature calcination at 900℃ for 3h. During calcination, argon gas is introduced as a protective gas, and the heating rate is 5℃ / min. Finally, silicon-carbon composite material is obtained.

[0053] Step 3: Mix 80mg of silicon-carbon composite material, 10mg of conductive carbon black, and 10mg of carboxymethyl cellulose / sodium silk evenly in an agate mortar. Then add the mixture to an ethanol aqueous solution with a mass fraction of 16%-18%. After magnetic stirring for 24 hours, coat the mixture evenly onto the negative electrode current collector copper sheet using a coating machine. The coating thickness is 200μm. After coating, dry the negative electrode current collector copper sheet at 55℃ for 10 minutes and then vacuum dry it at 100℃ for 12 hours to obtain the silicon-based negative electrode material.

[0054] Example 6

[0055] A method for preparing a silicon-carbon composite anode material with material coating, comprising the following steps:

[0056] Step 1: Take 6g of nano-silicon (diameter 200nm), 4.5g of cellulose / silk nanofibers / whiskers (diameter 4-10nm, length 100-500nm), and 4.5g of graphite powder and add them to a beaker. Add 400ml of deionized water, sonicate at 60kHz for 2h, add 3g of polyvinylpyrrolidone / polyethylene glycol / polyoxyethylene / polyacrylamide / polymaleic anhydride / carboxymethyl cellulose, and then stir at room temperature for 10h to obtain the precursor solution.

[0057] Step 2: Granulate the precursor solution using spray drying. The inlet air temperature is 180℃, the outlet air temperature is 100℃, and the feed rate is 600ml / h. Collect the silicon-carbon precursor powder and place it in a tube furnace for high-temperature calcination at 900℃ for 3h. During calcination, argon gas is introduced as a protective gas, and the heating rate is 5℃ / min. Finally, silicon-carbon composite material is obtained.

[0058] Step 3: Mix 80mg of silicon-carbon composite material, 10mg of conductive carbon black, and 10mg of carboxymethyl cellulose / sodium silk evenly in an agate mortar. Then add the mixture to an ethanol aqueous solution with a mass fraction of 16%-18%. After magnetic stirring for 24 hours, coat the mixture evenly onto the negative electrode current collector copper sheet using a coating machine. The coating thickness is 200μm. After coating, dry the negative electrode current collector copper sheet at 55℃ for 10 minutes and then vacuum dry it at 100℃ for 12 hours to obtain the silicon-based negative electrode material.

[0059] Example 7

[0060] A method for preparing a silicon-carbon composite anode material with material coating, comprising the following steps:

[0061] Step 1: Take 6g of nano-silicon (200nm in diameter), 3g of cellulose / silk nanofibers / whiskers (4-10nm in diameter, 100-500nm in length), and 3g of graphite powder and add them to a beaker. Add 400ml of deionized water and sonicate at 60kHz for 2 hours. Add 3g of polyvinylpyrrolidone / polyethylene glycol / polyethylene oxide / polyacrylamide / polymaleic anhydride / carboxymethyl cellulose and stir at room temperature for 10 hours to obtain the precursor solution.

[0062] Step 2: Granulate the precursor solution using spray drying. The inlet air temperature is 180℃, the outlet air temperature is 100℃, and the feed rate is 600ml / h. Collect the silicon-carbon precursor powder and place it in a tube furnace for high-temperature calcination at 900℃ for 3h. During calcination, argon gas is introduced as a protective gas, and the heating rate is 5℃ / min. Finally, silicon-carbon composite material is obtained.

[0063] Step 3: Mix 80mg of silicon-carbon composite material, 10mg of conductive carbon black, and 10mg of carboxymethyl cellulose / sodium silk evenly in an agate mortar, then add it to an ethanol aqueous solution with a mass fraction of 16%-18%, stir magnetically for 24 hours, and then coat it evenly on the negative electrode current collector copper sheet using a coating machine. The coating thickness is 200μm. After coating, the negative electrode current collector copper sheet is initially dried at 55℃ for 10 minutes and then vacuum dried at 100℃ for 12 hours to obtain the silicon-based negative electrode material.

[0064] Example 8

[0065] This embodiment is Comparative Example 1; the preparation method of the silicon-carbon composite anode material in this embodiment is as follows:

[0066] Step 1: Take 6g of nano-silicon (diameter 200nm), 4.5g of cellulose / silk nanofibers / whiskers (diameter 4-10nm, length 100-500nm), add 400ml of deionized water, sonicate at 60kHz for 2h, add 1.5g of polyvinylpyrrolidone / polyethylene glycol / polyoxyethylene / polyacrylamide / polymaleic anhydride / carboxymethyl cellulose, and then stir at room temperature for 10h to obtain the precursor solution.

[0067] Step 2: Granulate the precursor solution using spray drying. The inlet air temperature is 180℃, the outlet air temperature is 100℃, and the feed rate is 600ml / h. Collect the silicon-carbon precursor powder and place it in a tube furnace for high-temperature calcination at 900℃ for 3h. During calcination, argon gas is introduced as a protective gas, and the heating rate is 5℃ / min. Finally, silicon-carbon composite material is obtained.

[0068] Step 3: Mix 80mg of silicon-carbon composite material, 10mg of conductive carbon black, and 10mg of carboxymethyl cellulose / sodium silk evenly in an agate mortar. Then add the mixture to an ethanol aqueous solution with a mass fraction of 16%-18%. After magnetic stirring for 24 hours, coat the mixture evenly onto the negative electrode current collector copper sheet using a coating machine. The coating thickness is 200μm. After coating, dry the negative electrode current collector copper sheet at 55℃ for 10 minutes and then vacuum dry it at 100℃ for 12 hours to obtain the silicon-based negative electrode material.

[0069] Example 9

[0070] This embodiment is Comparative Example 2; the preparation method of the silicon-carbon composite anode material in this embodiment is as follows:

[0071] Step 1: Take 6g of nano-silicon (200nm in diameter) and 4.5g of graphite powder and add them to a beaker. Add 400ml of deionized water and sonicate at 60kHz for 2 hours. Add 1.5g of polyvinylpyrrolidone / polyethylene glycol / polyoxyethylene / polyacrylamide / polymaleic anhydride / carboxymethyl cellulose and stir at room temperature for 10 hours to obtain the precursor solution.

[0072] Step 2: Granulate the precursor solution using spray drying. The inlet air temperature is 180℃, the outlet air temperature is 100℃, and the feed rate is 600ml / h. Collect the silicon-carbon precursor powder and place it in a tube furnace for high-temperature calcination at 900℃ for 3h. During calcination, argon gas is introduced as a protective gas, and the heating rate is 5℃ / min. Finally, silicon-carbon composite material is obtained.

[0073] Step 3: Mix 80mg of silicon-carbon composite material, 10mg of conductive carbon black, and 10mg of carboxymethyl cellulose / sodium silk evenly in an agate mortar. Then add the mixture to an ethanol aqueous solution with a mass fraction of 16%-18%. After magnetic stirring for 24 hours, coat the mixture evenly onto the negative electrode current collector copper sheet using a coating machine. The coating thickness is 200μm. After coating, dry the negative electrode current collector copper sheet at 55℃ for 10 minutes and then vacuum dry it at 100℃ for 12 hours to obtain the silicon-based negative electrode material.

[0074] Example 10

[0075] This embodiment is Comparative Example 3; the preparation method of the silicon-carbon composite anode material in this embodiment is as follows:

[0076] Take 80 mg of pure silicon powder, 10 mg of conductive carbon black, and 10 mg of carboxymethyl cellulose / sodium silk and mix them evenly in an agate mortar. Then add them to an ethanol aqueous solution with a mass fraction of 16%-18%. After magnetic stirring for 24 hours, coat the mixture evenly onto the negative electrode current collector copper sheet using a coating machine. The coating thickness is 200 μm. After coating, dry the negative electrode current collector copper sheet at 55℃ for 10 minutes and then vacuum dry it at 100℃ for 12 hours to obtain the silicon-based negative electrode material.

[0077] Example 11

[0078] Performance testing:

[0079] The silicon-based anode material prepared in Examples 1-10 above was sliced ​​into circular electrode sheets with a diameter of 14 mm using a slicing machine. After weighing and recording the mass of the electrode sheets, a 14 mm diameter lithium metal sheet was used as the counter electrode and reference electrode. The electrolyte was 1 mol / L LiPF6 / EC-DEC (1:1), and the separator was selected as Celgard2500. The cells were assembled into button cells in a vacuum glove box with water and oxygen content below 0.1 ppm. After standing for 24 hours, constant current charge-discharge tests were performed in the Xinwei charge-discharge test system. The test voltage range was 0.01-2.5V. The first three cycles were activated at a current density of 200 mA / g, and then the cycle test was performed at a current density of 500 mA / g.

[0080] The results of the electrochemical performance tests are shown in Table 1 below;

[0081] Table 1

[0082] Group First discharge specific capacity mAh / g First-time effect% 50-cycle capacity retention % Example 1 2055.8 85.1 80.2 Example 2 2196.4 83.4 75.0 Example 3 1833.5 82.2 78.6 Example 4 2117.3 83.7 77.3 Example 5 2204.2 82.1 79.6 Example 6 2197.5 83.8 80.1 Example 7 1939.8 82.3 78.2 Example 8 2226.7 77.2 25.5 Example 9 2026.7 84.1 17.1 Example 10 3195.9 77.3 0.5

[0083] A comparison of the experimental data from Examples 1-7 in Table 1 reveals that the silicon-carbon anode material prepared by this invention exhibits excellent electrochemical performance and maintains good performance even after multiple uses. The silicon-carbon material in Example 1 demonstrates the best performance. In Example 8 (Comparative Example 1), without the addition of graphite powder, the silicon-carbon material exhibits a low initial efficiency and poor capacity retention. In Example 9 (Comparative Example 2), without the addition of cellulose / silk nanofibers / whiskers, a tight connection is not formed between the graphite and silicon particles, resulting in low capacity retention. In Example 10 (Comparative Example 3), it can be seen that pure silicon has a high initial specific capacity, but its capacity retention is very poor. As shown in Table 1, the material prepared using the process of this invention exhibits excellent electrochemical performance. Specifically, the capacity can reach over 2000 mAh / g, with an initial efficiency ≥80%, and after 50 cycles, the capacity retention (starting from the fourth cycle) can reach 75-80%, far exceeding the 0.5% of pure silicon.

[0084] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a silicon-carbon composite anode material with material coating, characterized in that, Includes the following steps: S1. Weigh out nano-silicon powder, coating material, and graphite powder in a mass ratio of nano-silicon powder: coating material: graphite powder = 1~3:0.5~3:1~4. Then add the weighed nano-silicon powder, coating material, and graphite powder to deionized water and disperse them by ultrasonication. A mixture is obtained; S2. After ultrasonic dispersion, add a treatment agent accounting for 5-25% of the total solid mass to the mixture, then treat it with ultrasound at 40-80kHz and perform magnetic stirring for 8-12 hours to obtain a homogeneous precursor solution. S3. Spray dry the precursor solution at a feed rate of 500-800 mL / h, an inlet air temperature of 160-200℃, an outlet air temperature of 90-200℃, and collect the granulated powder. S4. Then, under an inert atmosphere, the temperature is increased to 500-900℃ at a heating rate of 2-5℃ / min for 1-2 hours for calcination and carbonization. After carbonization, silicon-carbon composite anode material is obtained. S5. Mix the silicon-carbon material with the conductive agent and binder in a 16-18% ethanol aqueous solution at a mass ratio of 8:1:

1. After stirring for 8-12 hours, coat the mixture onto the copper current collector and perform preliminary drying at 55-70℃ for 10-20 minutes. Then, vacuum dry at 100-200℃ for 12-14 hours to obtain the negative electrode sheet.

2. The method for preparing a silicon-carbon composite anode material with material coating according to claim 1, characterized in that, The coating material is cellulose / silk nanofibers / whiskers.

3. The method for preparing a silicon-carbon composite anode material with material coating according to claim 2, characterized in that, The cellulose / silk nanofibers / whiskers have a diameter of 4~10nm and a length of 100~500nm.

4. The method for preparing a silicon-carbon composite anode material with material coating according to claim 1, characterized in that, The particle size of the nano-silicon powder is 50~150nm.

5. The method for preparing a silicon-carbon composite anode material with material coating according to claim 1, characterized in that, The treatment agent is one or more of polyvinylpyrrolidone, polyethylene glycol, polyethylene oxide, polyacrylamide, polymaleic anhydride, or carboxymethyl cellulose.

6. The method for preparing a silicon-carbon composite anode material with material coating according to claim 1, characterized in that, The conductive agent is either conductive carbon black or carbon nanotubes.

7. The method for preparing a silicon-carbon composite anode material with material coating according to claim 1, characterized in that, The adhesive is one of polyvinylidene fluoride, polyacrylic acid, and sodium alginate.

8. The application of the silicon-carbon composite anode material with material coating according to claim 1 in lithium-ion batteries.

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