A multi-stage buffer boron-doped silicon-carbon composite material and a preparation method thereof

Abstract

The application provides a silicon-carbon composite material and a preparation method thereof. The application has a composite structure, comprising a core and an outer layer, wherein the core is graphite, and the outer layer is a coating layer composed of amorphous carbon and nano-silicon; the nano-silicon has a core-shell structure, comprising a nitrogen-doped carbon coating layer and a boron-doped nano-silicon core. In the application, boron doping of the nano-silicon effectively improves the first-week coulomb efficiency, and a multi-stage carbon buffer structure can effectively relieve the volume change of silicon in the charging and discharging process, and improve the cycle stability of the material. In addition, raw materials of the application are easy to obtain, the preparation process is simple, and the application is easy to produce industrially.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of lithium ion battery negative electrode materials, and particularly relates to a multistage buffer boron-doped silicon-carbon composite material and a preparation method thereof. BACKGROUND

[0002] Since the first commercial lithium ion battery was successfully launched by Sony in 1991, it has successfully replaced nickel-hydrogen batteries and nickel-cadmium batteries in notebook computers, mobile phones, cameras and other 3C products and electric vehicles due to its advantages of high power density, high energy density, high voltage, long cycle life and the like. However, the theoretical specific capacity of the graphite negative electrode is 372 mAhg -1 , and the specific capacity of the current commercial graphite negative electrode exceeds 360 mAhg -1 , which is close to the theoretical limit, limiting the further development of single carbon material negative electrodes. Under this background, silicon material is expected to replace the traditional graphite negative electrode and become the next generation of negative electrode material due to its advantages of high theoretical specific capacity, suitable lithium intercalation and deintercalation potential, and low cost. However, silicon has low electrical conductivity, and severe volume change occurs during the charging and discharging process, which leads to material pulverization and even shedding from the current collector, ultimately resulting in the reduction of cycle stability.

[0003] To solve the above problems, silicon material is usually compounded with carbon material to inhibit the volume expansion of silicon and improve the electrical conductivity of the material, but the surface of nanosilicon lacks a coating layer, the effect of inhibiting the volume change of silicon during the charging and discharging process is poor, and the modification of silicon itself is also lacking, and some methods also have the defects of complex process and difficulty in industrialization. Patent CN 113666354 A discloses a preparation method of a silicon-carbon composite material, which comprises the following steps: uniformly mixing a silicon source and carbon black to obtain a silicon source mixture, then mixing the silicon source mixture and porous carbon powder, ultrasonic dispersion, ball milling, temperature rising, passing in a reducing agent, constant temperature reduction reaction, finally removing impurities with a hydrochloric acid solution, drying to obtain a silicon-carbon composite material, but it does not involve modification of silicon itself. Patent CN 111799460 A discloses a method for preparing a boron-doped nanometal / porous silicon-carbon composite negative electrode based on cutting silicon waste, which comprises the following steps: removing impurities from the cutting silicon waste, then performing metal-assisted etching treatment to obtain a nanometal / porous silicon composite material, mixing the nanometal / porous silicon composite material with a boron source, and then performing high-temperature treatment to form a substitutional doping of boron on silicon, and then compounding with carbon material to obtain a boron-doped nanometal / porous silicon-carbon composite negative electrode. Although the physical combination of metal particles on the surface of the silicon matrix and the chemical doping of boron on the atomic scale on the silicon synergistically improves the intrinsic electrical conductivity of silicon, the constraint on the volume expansion of silicon is insufficient. Patent CN 116072839 A discloses a silicon-carbon negative electrode material, a preparation method and application thereof. The silicon-carbon negative electrode material comprises a core and a coating layer coated on the surface of the core. The material forming the core comprises silicon powder, and the material forming the coating layer is carbon nitride and carbon nanotube, and at least part of one end of the carbon nanotube is embedded in the core. However, the preparation process is complex and difficult to expand production. SUMMARY

[0004] The purpose of the present application is to overcome the problems of poor cycle stability of the battery, complex preparation process of the negative electrode material and other problems existing in the prior art, and to provide a multi-stage buffer boron-doped silicon-carbon composite material and a preparation method thereof.

[0005] To achieve the above-mentioned purpose, the technical scheme of the present application is as follows:

[0006] Firstly, a silicon-carbon composite material is provided, characterized in that the silicon-carbon composite material has a composite structure comprising a core and an outer layer, wherein the core of the silicon-carbon composite material is graphite, and the outer layer is a coating layer composed of amorphous carbon and nanosilicon; the nanosilicon has a core-shell structure comprising a nitrogen-doped carbon coating layer and a boron-doped nanosilicon core.

[0007] The nitrogen-doped carbon coating layer and the boron-doping of nanosilicon are both generated by pyrolysis of an organic small molecule. The organic small molecule is 4-aminobenzeneboronic acid.

[0008] The thickness of the nitrogen-doped carbon coating layer is 1-5 nm.

[0009] The median particle size of the graphite is 5-20 μm, and the median particle size of the nano-silicon is 50-150 nm.

[0010] The mass percentage of the nano-silicon is 5-10% based on the total mass of the negative electrode material.

[0011] The carbon of the amorphous carbon layer is composed of pitch pyrolysis carbon and Super P.

[0012] The method comprises the following steps:

[0013] (1) mixing a micron silicon dispersion liquid with 4-aminobenzoic acid, and ball milling to obtain 4-aminobenzoic acid-coated nano-silicon;

[0014] (2) mixing the nano-silicon dispersion liquid obtained in step 1 with pitch and Super P uniformly by ball milling, and then mixing the obtained slurry with graphite by ball milling to obtain a silicon-carbon composite material precursor;

[0015] (3) sintering the precursor obtained in step 2 at 800-1000 o C for 2-4 h under an inert atmosphere to obtain a silicon-carbon composite material.

[0016] Preferably, the mass ratio of the micron silicon to 4-aminobenzoic acid in step (1) is 1:0.1-1:0.5, and the mass ratio of the micron silicon to ethanol is 1:10.

[0017] Preferably, the ball milling condition in step (1) is argon protection, the ball-to-material ratio is 50:1, the ball milling speed is 600 rpm, and the ball milling time is 6-8 h.

[0018] Preferably, the ball milling condition for mixing the nano-silicon dispersion liquid with pitch and Super P in step (2) is argon protection, the mass ratio of the nano-silicon to pitch is 1:1, the mass ratio of the nano-silicon to Super P is 1:0.2, the ball-to-material ratio is 10:1, the ball milling speed is 450 rpm, and the ball milling time is 1 h; the ball milling condition for mixing the slurry with graphite is argon protection, the mass ratio of the nano-silicon to graphite is 1:10-1:5, the ball-to-material ratio is 5:1, the ball milling speed is 200 rpm, and the ball milling time is 1 h.

[0019] Compared with the prior art, the present application has the following beneficial effects:

[0020] (1) The present application selects 4-aminobenzoic acid as an additive in the ball milling process, which can form a coating layer on the surface of the nano-silicon in situ during the ball milling and crushing of the micron silicon, thereby reducing oxidation during the ball milling;

[0021] (2) The 4-aminobenzene boronic acid is selected as the coating layer of the nano silicon, and the silicon can be doped with boron in the subsequent calcination process, the first cycle coulomb efficiency is improved, and the nitrogen-doped carbon coating layer can form a multi-level buffer structure together with graphite and amorphous carbon to improve the cycle stability of the silicon-carbon composite material;

[0022] (3) The multi-level buffer boron-doped silicon-carbon composite material of the application can obtain the precursor by one-step ball milling, and the finished material can be obtained by one-step calcination, so that the process is simple and easy to operate, the process cost is low, and the application is suitable for industrial production. BRIEF DESCRIPTION OF DRAWINGS

[0023] In order to more clearly illustrate the technical solutions of the embodiments of the application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiment or prior art description. Obviously, the drawings in the following description are only embodiments of the application, and those skilled in the art can obtain other drawings according to the provided drawings without creating labor.

[0024] Figure 1 The scanning electron microscope image of the silicon-carbon composite material provided for the embodiment 1 of the application.

[0025] Figure 2 The high-resolution transmission electron microscope image of the 4-aminobenzene boronic acid pyrolytic carbon-coated nano silicon in the silicon-carbon composite material provided for the embodiment 1 of the application.

[0026] Figure 3 The X-ray photoelectron spectrogram of the 4-aminobenzene boronic acid pyrolytic carbon-coated nano silicon in the silicon-carbon composite material provided for the embodiment 1 of the application.

[0027] Figure 4 The first cycle charge-discharge curve diagram of the lithium ion battery assembled by using the silicon-carbon composite material provided for the embodiment 1 of the application.

[0028] Figure 5 The cycle curve diagram of the lithium ion battery assembled by using the silicon-carbon composite material provided for the embodiment 1 of the application. DETAILED DESCRIPTION

[0029] The specific embodiments of the application will be further described in combination with the embodiments below, and it should be pointed out that the specific embodiments described here are only for illustrating and explaining the application, and are not limited to the application.

[0030] Example 1: 0.5 g micron silicon, 0.15 g 4-aminobenzoic acid were weighed into a ball mill jar, zirconia beads and anhydrous ethanol were added, and ball milling was carried out under argon protection. The mass ratio of ethanol to micron silicon was 10:1, the mass ratio of zirconia beads to micron silicon was 50:1, the ball milling speed was 600 rpm, and the ball milling time was 6 h. After 0.5 g pitch and 0.1 g Super P were added to the slurry and the slurry was again placed in a ball mill jar, zirconia beads were added, and ball milling was carried out under argon protection. The mass ratio of zirconia beads to solid substances in the slurry was 10:1, the ball milling speed was 450 rpm, and the ball milling time was 1 h. After 5 g graphite was added to the slurry and the slurry was again placed in a ball mill jar, zirconia beads were added, and ball milling was carried out under argon protection. The mass ratio of zirconia beads to solid substances in the slurry was 5:1, the ball milling speed was 450 rpm, and the ball milling time was 1 h. After the ball milling was completed, the slurry was centrifuged to obtain a silicon-carbon composite precursor. The precursor was transferred to a tube furnace, and calcined at 900 o C for 3 h under argon atmosphere, and then naturally cooled to room temperature. The product was ground through a 400 mesh screen to obtain a boron-doped silicon-carbon composite material with multi-stage buffering.

[0031] Further explanation of Example 1: As can be seen from the scanning electron microscope image of Figure 1 , the particle size of the boron-doped silicon-carbon composite material with multi-stage buffering is between 5-20 μm; as can be seen from the high-resolution transmission electron microscope image of Figure 2 , there is an amorphous carbon coating layer with a thickness of about 2-3 nm on the surface of the 4-aminobenzoic acid pyrolysis carbon-coated nanosilicon in the boron-doped silicon-carbon composite material with multi-stage buffering; as can be seen from the X-ray photoelectron spectroscopy image of Figure 3 , there are Si, C, N, O, B element peaks in Figure 3 (1), indicating that the material provided in Example 1 contains the above elements, Figure 3 (2) there is a B-Si bond peak, indicating that boron forms a substitutional doping with silicon, Figure 3 (3) there is a pyridine nitrogen peak, indicating that the carbon coating layer on the surface of the 4-aminobenzoic acid pyrolysis carbon-coated nanosilicon forms nitrogen doping; as can be seen from the first cycle charge-discharge curve of Example 1 Figure 4 , the first cycle discharge specific capacity of the material provided in Example 1 is 605.7 mAhg -1 , the first cycle charge specific capacity is 544.3 mAhg -1 , and the first cycle coulombic efficiency is 89.9%; as can be seen from the cycle curve of Example 1 Figure 5 , the 100th cycle capacity retention rate of the material provided in Example 1 is 89.7%.

[0032] Example 2: 0.5 g of micron silicon and 0.05 g of 4-aminobenzoic acid were weighed into a ball mill jar, zirconia beads and anhydrous ethanol were added, and ball milling was carried out under argon protection. The mass ratio of ethanol to micron silicon was 10:1, the mass ratio of zirconia beads to micron silicon was 50:1, the ball milling speed was 600 rpm, and the ball milling time was 7 h. After 0.5 g of pitch and 0.1 g of Super P were added to the slurry, the slurry was again placed in a ball mill jar, zirconia beads were added, and ball milling was carried out under argon protection. The mass ratio of zirconia beads to solid substances in the slurry was 10:1, the ball milling speed was 450 rpm, and the ball milling time was 1 h. After 5 g of graphite was added to the slurry, the slurry was again placed in a ball mill jar, zirconia beads were added, and ball milling was carried out under argon protection. The mass ratio of zirconia beads to solid substances in the slurry was 5:1, the ball milling speed was 450 rpm, and the ball milling time was 1 h. After the ball milling was completed, the slurry was centrifuged to obtain a silicon-carbon composite precursor. The precursor was transferred to a tube furnace, calcined at 800 o C for 4 h, and after natural cooling to room temperature, the product was ground through a 400-mesh screen to obtain a multi-stage buffer boron-doped silicon-carbon composite material.

[0033] Example 3: 0.5 g of micron silicon and 0.25 g of 4-aminobenzoic acid were weighed into a ball mill jar, zirconia beads and anhydrous ethanol were added, and ball milling was carried out under argon protection. The mass ratio of ethanol to micron silicon was 10:1, the mass ratio of zirconia beads to micron silicon was 50:1, the ball milling speed was 600 rpm, and the ball milling time was 6 h. After 0.5 g of pitch and 0.1 g of Super P were added to the slurry, the slurry was again placed in a ball mill jar, zirconia beads were added, and ball milling was carried out under argon protection. The mass ratio of zirconia beads to solid substances in the slurry was 10:1, the ball milling speed was 450 rpm, and the ball milling time was 1 h. After 5 g of graphite was added to the slurry, the slurry was again placed in a ball mill jar, zirconia beads were added, and ball milling was carried out under argon protection. The mass ratio of zirconia beads to solid substances in the slurry was 5:1, the ball milling speed was 450 rpm, and the ball milling time was 1 h. After the ball milling was completed, the slurry was centrifuged to obtain a silicon-carbon composite precursor. The precursor was transferred to a tube furnace, calcined at 1000 o C for 3 h, and after natural cooling to room temperature, the product was ground through a 400-mesh screen to obtain a multi-stage buffer boron-doped silicon-carbon composite material.

[0034] Example 4: 0.5 g of micron silicon and 0.15 g of 4-aminobenzoic acid were weighed into a ball milling jar, zirconia beads and anhydrous ethanol were added, and ball milling was carried out under argon protection. The mass ratio of ethanol to micron silicon was 10:1, the mass ratio of zirconia beads to micron silicon was 50:1, the ball milling speed was 600 rpm, and the ball milling time was 6 h. After 0.5 g of pitch and 0.1 g of Super P were added to the slurry, the slurry was again placed in a ball milling jar, zirconia beads were added, and ball milling was carried out under argon protection. The mass ratio of zirconia beads to solid substances in the slurry was 10:1, the ball milling speed was 450 rpm, and the ball milling time was 1 h. After 5 g of graphite was added to the slurry, the slurry was again placed in a ball milling jar, zirconia beads were added, and ball milling was carried out under argon protection. The mass ratio of zirconia beads to solid substances in the slurry was 5:1, the ball milling speed was 450 rpm, and the ball milling time was 1 h. After the ball milling was completed, the slurry was centrifuged to obtain a silicon-carbon composite precursor. The precursor was transferred to a tube furnace, calcined at 1000 o C for 2 h, and after natural cooling to room temperature, the product was ground through a 400-mesh screen to obtain a multi-stage buffer boron-doped silicon-carbon composite material.

[0035] Example 5: 1 g of micron silicon and 0.3 g of 4-aminobenzoic acid were weighed into a ball milling jar, zirconia beads and anhydrous ethanol were added, and ball milling was carried out under argon protection. The mass ratio of ethanol to micron silicon was 10:1, the mass ratio of zirconia beads to micron silicon was 50:1, the ball milling speed was 600 rpm, and the ball milling time was 6 h. After 1 g of pitch and 0.2 g of Super P were added to the slurry, the slurry was again placed in a ball milling jar, zirconia beads were added, and ball milling was carried out under argon protection. The mass ratio of zirconia beads to solid substances in the slurry was 10:1, the ball milling speed was 450 rpm, and the ball milling time was 1 h. After 5 g of graphite was added to the slurry, the slurry was again placed in a ball milling jar, zirconia beads were added, and ball milling was carried out under argon protection. The mass ratio of zirconia beads to solid substances in the slurry was 5:1, the ball milling speed was 450 rpm, and the ball milling time was 1 h. After the ball milling was completed, the slurry was centrifuged to obtain a silicon-carbon composite precursor. The precursor was transferred to a tube furnace, calcined at 900 o C for 4 h, and after natural cooling to room temperature, the product was ground through a 400-mesh screen to obtain a multi-stage buffer boron-doped silicon-carbon composite material.

[0036] Comparative Example 1: 0.5 g of micron silicon was weighed into a ball mill jar, zirconium oxide beads and anhydrous ethanol were added, and ball milling was performed under argon protection. The mass ratio of ethanol to micron silicon was 10:1, the mass ratio of zirconium oxide beads to micron silicon was 50:1, the ball milling speed was 600 rpm, and the ball milling time was 6 h. After 0.5 g of pitch and 0.1 g of Super P were added to the slurry and the slurry was again placed into a ball mill jar, zirconium oxide beads were added, and ball milling was performed under argon protection. The mass ratio of zirconium oxide beads to solid substances in the slurry was 10:1, the ball milling speed was 450 rpm, and the ball milling time was 1 h. After 5 g of graphite was added to the slurry and the slurry was again placed into a ball mill jar, zirconium oxide beads were added, and ball milling was performed under argon protection. The mass ratio of zirconium oxide beads to solid substances in the slurry was 5:1, the ball milling speed was 450 rpm, and the ball milling time was 1 h. After the ball milling was completed, the slurry was centrifuged to obtain a silicon-carbon composite precursor. The precursor was transferred into a tube furnace, calcined at 900 o C for 3 h under an argon atmosphere, and after natural cooling to room temperature, the product was ground through a 400-mesh screen to obtain a boron-doped silicon-carbon composite material with multi-stage buffering.

[0037] Comparative Example 2: 0.5 g of micron silicon and 0.25 g of boric acid were weighed into a ball mill jar, zirconium oxide beads and anhydrous ethanol were added, and ball milling was performed under argon protection. The mass ratio of ethanol to micron silicon was 10:1, the mass ratio of zirconium oxide beads to micron silicon was 50:1, the ball milling speed was 600 rpm, and the ball milling time was 6 h. After 0.5 g of pitch and 0.1 g of Super P were added to the slurry and the slurry was again placed into a ball mill jar, zirconium oxide beads were added, and ball milling was performed under argon protection. The mass ratio of zirconium oxide beads to solid substances in the slurry was 10:1, the ball milling speed was 450 rpm, and the ball milling time was 1 h. After 5 g of graphite was added to the slurry and the slurry was again placed into a ball mill jar, zirconium oxide beads were added, and ball milling was performed under argon protection. The mass ratio of zirconium oxide beads to solid substances in the slurry was 5:1, the ball milling speed was 450 rpm, and the ball milling time was 1 h. After the ball milling was completed, the slurry was centrifuged to obtain a silicon-carbon composite precursor. The precursor was transferred into a tube furnace, calcined at 900 o C for 3 h under an argon atmosphere, and after natural cooling to room temperature, the product was ground through a 400-mesh screen to obtain a boron-doped silicon-carbon composite material with multi-stage buffering.

[0038] Comparative Example 3: 0.5 g of micron silicon and 0.25 g of citric acid were weighed into a ball mill jar, and zirconium oxide beads and anhydrous ethanol were added. Ball milling was performed under argon protection. The mass ratio of ethanol to micron silicon was 10:1, the mass ratio of zirconium oxide beads to micron silicon was 50:1, the ball milling speed was 600 rpm, and the ball milling time was 6 h. After 0.5 g of pitch and 0.1 g of Super P were added to the slurry, the slurry was again placed into a ball mill jar, and zirconium oxide beads were added. Ball milling was performed under argon protection. The mass ratio of zirconium oxide beads to solid substances in the slurry was 10:1, the ball milling speed was 450 rpm, and the ball milling time was 1 h. After 5 g of graphite was added to the slurry, the slurry was again placed into a ball mill jar, and zirconium oxide beads were added. Ball milling was performed under argon protection. The mass ratio of zirconium oxide beads to solid substances in the slurry was 5:1, the ball milling speed was 450 rpm, and the ball milling time was 1 h. After the ball milling was completed, the slurry was centrifuged to obtain a silicon-carbon composite precursor. The precursor was transferred into a tube furnace, and calcination was performed under an argon atmosphere at 800 o C for 2 h. After natural cooling to room temperature, the product was ground through a 400-mesh screen to obtain a multi-stage buffer boron-doped silicon-carbon composite material.

[0039] The silicon-carbon composite negative electrode materials prepared in Examples 1-6 and Comparative Examples 1-3 were made into negative electrode sheets and batteries as follows:

[0040] Graphite, silicon-carbon negative electrode material, conductive agent, and binder were prepared into a uniform slurry in a mass ratio of 80:10:10 and coated on a copper foil. The conductive agent used was Super P, and the binder was prepared by stirring carboxymethyl cellulose (CMC), 50% styrene-butadiene rubber (SBR), and deionized water in a mass ratio of 1:1:48 for 24 h. After vacuum drying, rolling, and punching, a negative electrode sheet was prepared. A lithium metal sheet was used as the negative electrode, and 1 mol / L LiPF6 (solvent: a mixture of ethylene carbonate, diethyl carbonate, methyl ethyl carbonate, and fluoroethylene carbonate) was used as the electrolyte to assemble a coin cell battery in a glove box.

[0041] The charge-discharge test of the coin cell battery was performed on a Wuhan LAND battery test system. The test voltage range was 0.01-1.5 V, and the test current density was 0.5 C (1 C = 500 mA / g).

[0042] The test results are shown in Table 1.

[0043] Table 1. Test results of coin cell batteries of Examples 1-5 and Comparative Examples 1-3

[0044]

[0045] It can be known from the examples and test results that the multi-stage buffer boron-doped silicon-carbon composite material has higher first cycle reversible capacity, higher first cycle coulomb efficiency and better cycle stability. It can be known from the comparison between example 1 and comparative example 1 that, due to the lack of 4-aminobenzoic acid in the ball milling process, the oxidation degree of nanosilicon is deepened in the ball milling process, and the boron doping and surface carbon coating are also lacking, so the electrochemical properties such as the first cycle reversible capacity, the first cycle coulomb efficiency and the cycle stability of the silicon-carbon composite material provided by comparative example 1 are all reduced; it can be known from the comparison between example 1 and comparative example 2 that, the 4-aminobenzoic acid is replaced by boric acid, and the surface carbon coating is lacking, so the cycle stability of the silicon-carbon composite material provided by comparative example 2 is reduced; it can be known from the comparison between example 1 and comparative example 3 that, the 4-aminobenzoic acid is replaced by citric acid, and since the citric acid cannot form in-situ coating in the ball milling process, so the first cycle coulomb efficiency and the cycle stability of the silicon-carbon composite material provided by comparative example 3 are both reduced.

[0046] The above embodiments are only example embodiments for illustrating the principles of the present application, and the present application is not limited thereto. Any modification, equivalent, replacement and improvement of the present application all fall within the protection scope of the present application.

Claims

1. A multi-stage buffered boron-doped silicon-carbon composite material, characterized by, The silicon-carbon composite material has a composite structure, including an inner core and an outer layer, wherein the inner core of the silicon-carbon composite material is graphite, and the outer layer is a coating layer composed of amorphous carbon and nano-silicon; the nano-silicon has a core-shell structure, including a nitrogen-doped carbon coating layer and a boron-doped nano-silicon inner core.

2. The multi-stage buffered boron-doped silicon-carbon composite material of claim 1, wherein, The nitrogen-doped carbon coating layer and the boron-doping of the nano-silicon are both generated by pyrolysis of an organic small molecule; wherein the organic small molecule is 4-aminobenzoic acid.

3. The multi-stage buffered boron-doped silicon-carbon composite material of claim 1, wherein, The thickness of the nitrogen-doped carbon coating layer is 1-5 nm.

4. The multi-stage buffered boron-doped silicon-carbon composite material of claim 1, wherein, The median particle size of the graphite is 5-20 μm, and the median particle size of the nano-silicon is 50-150 nm.

5. The multi-stage buffered boron-doped silicon-carbon composite material of claim 1, wherein, The mass percentage content of the nano-silicon is 5-10% based on the total mass of the negative electrode material.

6. The multi-stage buffered boron-doped silicon-carbon composite material of claim 1, wherein, The carbon of the amorphous carbon layer is composed of bitumen pyrolysis carbon and Super P.

7. A method of making a multistage buffered boron-doped silicon- carbon composite material according to any one of claims 1 to 6, characterized in that The method comprises the following steps: (1) mixing an ethanol dispersion of micro-silicon with 4-aminobenzoic acid, and ball milling to obtain 4-aminobenzoic acid-coated nano-silicon; (2) dispersing the nano-silicon dispersion obtained in step 1 with bitumen and Super P by ball milling, then mixing the obtained slurry with graphite by ball milling to obtain a silicon-carbon composite material precursor; (3) sintering the precursor obtained in step 2 at 800-1000°C for 2-4 h under an inert atmosphere to obtain a silicon-carbon composite material.

8. The method of claim 7, wherein, The mass ratio of micro-silicon to 4-aminobenzoic acid in step (1) is 1:0.1-1:0.5, and the mass ratio of micro-silicon to ethanol is 1:

10.

9. The preparation method according to claim 7, characterized in that, The ball milling conditions in step (1) are as follows: argon protection, ball-to-material ratio of 50:1, ball milling speed of 600 rpm, and ball milling time of 6-8 h.

10. The method of claim 7, wherein, The ball milling conditions for mixing the nano-silicon dispersion with bitumen and Super P in step (2) are as follows: argon protection, mass ratio of nano-silicon to bitumen of 1:1, mass ratio of nano-silicon to Super P of 1:0.2, ball-to-material ratio of 10:1, ball milling speed of 450 rpm, and ball milling time of 1 h; the ball milling conditions for mixing the slurry with graphite are as follows: argon protection, mass ratio of nano-silicon to graphite of 1:10-1:5, ball-to-material ratio of 5:1, ball milling speed of 200 rpm, and ball milling time of 1 h.

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