Preparation method and application of Si@C@rGO@N@P silicon-carbon composite material

Abstract

The application relates to a preparation method and application of a Si@C@rGO@N@P silicon-carbon composite material, and belongs to the technical field of lithium ion battery negative electrode materials. POSS particles are ball milled in a ball mill to obtain a powder, the obtained powder is added into a GO dispersion solution, an ionic liquid IL-C=N is further added, a mixed solution obtained through ultrasonic dispersion is placed into a high-pressure hydrothermal kettle for reaction, IL-POSS- GO aerogel obtained through the reaction is added with TPP and mixed through ultrasonic treatment, drying, calcination in a tube furnace, washing and drying, and a N / P co-doped porous silicon-carbon composite material Si@C@rGO@N@P is obtained. The silicon-carbon composite material is used for preparing a negative electrode material of a lithium ion battery, the battery is endowed with good cycle performance, a high reversible specific capacity and a first coulomb efficiency, and the overall electrochemical performance is excellent.

Description

Technical Field

[0001] This invention relates to a method for preparing and applying a Si@C@rGO@N@P silicon-carbon composite material, belonging to the technical field of lithium-ion battery anode materials. Background Technology

[0002] The shortcomings of traditional silicon-carbon anodes stem from three major disconnects:

[0003] (1) Silicon source and carbon source are spatially separated during the reaction process. The conventional approach is to first synthesize nano-Si and then coat it with carbon, or to first form porous carbon and then impregnate it with silicon. However, it is always impossible to get rid of the interfacial break caused by the "later combination".

[0004] (2) Separation of high-temperature carbonization and reduction steps. SiO2→Si requires a temperature of over 1800 ℃ or the addition of magnesium / aluminum reducing agent, while the graphitization of carbon skeleton requires inert high temperature. The two-stage process of reduction reaction and high-temperature carbonization causes grain growth and pore structure collapse.

[0005] (3) Separation of volume buffer and electronic conduction network construction. The introduction of graphene into its structure is mostly done by physical mixing. During charging and discharging, the conductive network will be torn ring by ring due to the "slipping interface".

[0006] In existing technologies, some have attempted to use molecular-level POSS as a silicon precursor, but its cage-like Si8O 12 In an inert atmosphere above 1000 °C, the framework only generates SiO2 and free carbon, requiring a secondary carbothermal reduction to produce Si. Direct H2 introduction necessitates temperatures above 1400 °C, resulting in rapid grain growth to the hundred-nanometer scale. In other words, the "one-step carbonization-reduction-confining" process is mutually exclusive, a recognized "temperature-grain-interface" dilemma in the field. Existing technologies often combine silicon with graphene oxide (GO) and introduce a carbon layer to buffer expansion through high-temperature calcination. However, during structure building, traditional physical mixing struggles to achieve nanoscale dispersion of silicon, leading to uneven distribution of dopants (N, P, B, etc.), resulting in limited improvements in rate performance and cycle stability. Summary of the Invention

[0007] To address the aforementioned deficiencies, this invention provides a method for preparing Si@C@rGO@N@P silicon-carbon composite materials. This method not only enables the in-situ self-assembled ionic liquid-POSS-GO layered precursor construction, but also achieves the one-step formation of N / P co-doped porous silicon-carbon anode materials during the subsequent hydrothermal-calcination process.

[0008] Specifically, the technical solution adopted in this application is as follows:

[0009] A method for preparing a Si@C@rGO@N@P silicon-carbon composite material, comprising the following steps:

[0010] S1, graphene oxide (GO) was dispersed in deionized water to form a GO dispersion, and 1-cyanopropyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ionic liquid (IL-C≡N) was added and sonicated at room temperature; then polyhedral oligomeric silsesquioxane (POSS) powder obtained by ball milling was added, and stirring was continued to construct a uniform IL-POSS-GO layered supramolecular sol through self-assembly.

[0011] S2, the above-mentioned IL-POSS-GO layered supramolecular sol is transferred to a hydrothermal reactor to react and obtain IL-POSS-GO aerogel;

[0012] S3, IL-POSS-GO aerogel was impregnated in TPP solution, and after vacuum-assisted impregnation, it was dried to obtain IL-POSS-GO / TPP complex loaded with phosphorus source.

[0013] S4. The IL-POSS-GO / TPP composite was calcined and kept at a constant temperature under hydrogen and inert atmosphere to allow POSS to be reduced in situ by carbothermal reduction to generate Si@C nanocrystals, thus obtaining the crude product Si@C@rGO@N@P.

[0014] S5. The crude product is acid-washed, water-washed, and dried to obtain N / P co-doped purified Si@C@rGO@N@P silicon-carbon composite material.

[0015] In the above scheme, GO is a three-in-one carrier of "conductive framework + buffer cushion + chemical anchor point", and has a "triple identity" in the preparation system of this application: (1) Flexible "framework": Two-dimensional sheets are pre-built into a three-dimensional conductive network, which becomes rGO after high temperature graphitization, providing a continuous electronic channel for the entire electrode, eliminating the need for external conductive agent in the later stage. (2) Buffer "cushion": The interlayer spacing is expanded to 0.37~0.40 nm by Si@C nano islands, forming a reversible "spring cavity", and the volume expansion during silicon lithium intercalation reduces the cycle expansion rate from the traditional 60% to less than 20%. (3) Reaction "anchor point": The surface epoxy / carboxyl groups condense with the POSS active sites to generate Si–O–C covalent bonds, realizing molecular-level interface welding and completely eliminating the "slip-peeling" phenomenon during the charging and discharging process. Polyhedral oligomeric silsesquioxane (POSS) provides a highly dispersed nano silicon source and is a three-in-one precursor of "silicon + reducing agent + nano nail": molecular-level Si8O 12The cage provides ultra-high purity and precisely measured active silicon, avoiding the runaway reaction caused by the uneven particle size of traditional SiO2 particles, which is the function of POSS as a silicon source storage unit. After the cage is opened, the Si–H / Si–OH active sites formed are like "nails" driven into the GO layers, firmly locking the subsequently generated Si@C grains in the 5~50 nm range, preventing high-temperature rampant growth, and playing the function of POSS as a confined "template nanonail". Ionic liquid (IL) has the characteristics of strong designability. It works in conjunction with the π-π / electrostatic self-assembly characteristics of GO to realize the alternating arrangement of POSS silicon cage and GO layers at the molecular level, constructing a layered supramolecular precursor and inhibiting silicon agglomeration. By using ionic liquid decomposition to simultaneously introduce N and F doping, and adding an organophosphorus source to introduce P doping, an N / P co-doped porous carbon framework is formed. The three complete the "molecular rivet-confined carbonization" integrated reaction under a low-temperature hydrogen atmosphere, and finally jointly derive a high-capacity, long-lifetime, low-expansion Si@C@rGO@N@P silicon-carbon composite material.

[0016] Furthermore, as a preferred option:

[0017] In S1,

[0018] The concentration of the graphene oxide dispersion is 0.5~5 mg / ml, preferably 0.5~2 mg / ml.

[0019] The duration of the room temperature ultrasound is 10-120 min, preferably 10-60 min.

[0020] The POSS is at least one of octaphenyl-POSS, octamethyl-POSS, octavinyl-POSS, or octaamino-POSS.

[0021] In the IL-POSS-GO layered supramolecular sol, the mass ratio of POSS to GO is 1:10 to 10:1, preferably 1:3 to 3:1, and 1:1 is optimal.

[0022] The ball milling speed of the POSS is 300~800 r / min, preferably 400~600 r / min.

[0023] The ball milling time is 2 to 12 hours, preferably 2 to 6 hours.

[0024] The POSS powder is in the micron and / or nanometer scale, with a particle size ≤500 nm.

[0025] In S2,

[0026] The reaction temperature in the hydrothermal reactor is 180–240°C, and the reaction time is 2–48 h, preferably 6–24 h.

[0027] In S3

[0028] The TPP solution is an ethanol solution of TPP with a TPP concentration of 0.1 to 1 g / L, preferably 0.6 g / L (e.g., 30 mg of TPP in 60 mL TPP solution).

[0029] The vacuum impregnation time is 1 to 6 hours.

[0030] The drying temperature is 70-80℃, and the drying time is 1-12 hours.

[0031] In S4,

[0032] The heating rate for calcination is 2~10 ℃ / min, preferably 2~5 ℃ / min.

[0033] The temperature of the heat preservation reaction is 800~1500 ℃.

[0034] The duration of the heat preservation reaction is 1 to 6 hours, preferably 1 to 4 hours.

[0035] The inert atmosphere is argon, nitrogen, or an argon / hydrogen mixture, wherein the hydrogen gas fraction is 0-10%, and when the fraction is 0, the inert atmosphere is pure argon.

[0036] In S5,

[0037] The pickling process uses 5-20 wt% hydrofluoric acid, hydrochloric acid, or nitric acid, and the pickling time is 5-30 min.

[0038] The silicon-carbon composite material prepared by the above method has a self-supporting three-dimensional skeleton structure, which is beneficial to structural stability and prevents structural collapse and deformation.

[0039] Applying the silicon-carbon composite material prepared by the above method to the preparation of lithium-ion battery anode materials can endow the corresponding anode materials with high reversible capacity, excellent rate capability and long cycle life, so as to achieve excellent electrochemical performance, good cycle performance and high reversible specific capacity and first coulombic efficiency of the corresponding lithium-ion battery.

[0040] The beneficial effects of this invention are as follows:

[0041] Molecular rivet-type interface bonding.

[0042] By utilizing the condensation reaction between the epoxy / hydroxyl groups on the rGO surface and the active sites generated by POSS pre-reduction to form Si–O–C covalent bonds, Si@C nanocrystals and rGO are anchored at the molecular scale, solving the interfacial slippage problem caused by physical mixing.

[0043] Confined carbonization grain locking technology.

[0044] By using the nanoscale confinement space between rGO layers, POSS fragments are separated into islands of <5 nm, and 5~50 nm Si@C grains are generated in situ at high temperature. The grain size is reduced by an order of magnitude compared with the traditional method, and the distribution uniformity is improved by 300%.

[0045] Self-supporting three-in-one skeleton.

[0046] Si@C nano islands act as "pillars" to expand the interlayer spacing of rGO, forming a natural buffer cavity. This simultaneously achieves the integration of three functions: conductive network (rGO), volume buffer (interlayer cavity), and active center (Si@C). The cycle expansion rate is <20%, while the cycle expansion rate of traditional silicon-carbon exceeds 60%.

[0047] The reduction-carbonization-graphitization process is completed simultaneously in one step.

[0048] By using the π-π self-assembly of IL-C≡N and GO, the POSS silicon cage is dispersed at the molecular level in the layered carbon framework, with an average silicon particle size of 3~8 nm, which significantly reduces the volume expansion stress.

[0049] The decomposition of ionic liquids simultaneously introduces N and F doping, while TPP provides P doping, forming ternary co-doped porous carbon to improve electronic / ionic conductivity.

[0050] Abandoning the traditional multi-stage process of "reducing SiO2 first and then coating it with carbon", the Si@C crystal transformation and rGO graphitization can be completed simultaneously in a single calcination at 1300℃ and atmospheric pressure in H2 / Ar, reducing energy consumption by 40% and yielding a yield of >80%, making it suitable for large-scale production. Attached Figure Description

[0051] Figure 1 This is a schematic diagram of the POSS and Si molecule rivet-type interface bonding process of the present invention.

[0052] Figure 2 X-ray photoelectron spectroscopy data analysis of the product prepared in Example 1 of this invention.

[0053] Figure 3 This is a scanning electron microscope (SEM) image of the product prepared in Example 1 of the present invention.

[0054] Figure 4 This is a scanning electron microscope (SEM) image of the product prepared in Example 2 of the present invention.

[0055] Figure 5 The first cycle diagram of specific capacity-voltage of the product prepared in Example 1 of this invention at a current density of 200 mA / g is shown.

[0056] Figure 6The image shows the cycling curves of the products prepared in Examples 1, 2, 1, and 2 of this invention at a current density of 200 mA / g for 100 cycles.

[0057] Figure 7 The graphs show the rate performance test results of the products prepared in Examples 1, 2, Comparative Examples 1 and 2 of this invention at different current densities (current densities are 0.1 C, 0.2 C, 0.5 C, 1 C, 2 C, 5 C, 10 C, 20 C and 0.1 C, respectively). Detailed Implementation

[0058] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. 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.

[0059] To facilitate the explanation of the preparation method and the silicon-carbon anode material prepared by the present invention, the following specific embodiments are provided. It should be noted that the present invention is not limited to the following embodiments. The following embodiments do not exhaustively describe the technical solutions of the present invention.

[0060] Example 1

[0061] The preparation process of the Si@C@rGO@N@P silicon-carbon composite material in this embodiment is as follows: Figure 1 As shown:

[0062] (1) Ball milling activation: 2.0 g of commercially available POSS (molecular formula: Si8O) was added. 12 (C6H5)8 (average particle size 50 μm) was placed together with 60g of zirconia grinding balls (5 mm in diameter) into a 100 mL zirconia ball milling jar and ball-milled at 400 rpm for 6 h on a planetary ball mill to obtain POSS powder with an average particle size of 200 nm.

[0063] (2) Ultrasonic dispersion: 200 mg of POSS powder obtained in step (1) was added to 200 mL of 1 mg / mL graphene oxide aqueous dispersion (GO content was 0.2 g, POSS:GO = 1:1), and then 150 mg of IL-C≡N was added and ultrasonically treated (power 300 W, frequency 40 kHz) for 30 min to obtain a uniformly dispersed POSS / GO mixture.

[0064] (3) Hydrothermal reduction: The above POSS / GO mixture was transferred to a 300 mL polytetrafluoroethylene-lined pressure-resistant bottle, sealed and placed in a forced-air drying oven, heated to 220 °C and kept at that temperature for 12 h, and then naturally cooled to room temperature. During the reaction, GO was reduced to rGO, and POSS was chemically bonded to the surface of rGO through Si–O–C bonds.

[0065] (4) Filtration and drying: The hydrogel obtained in step (3) was filtered through a 0.22 μm polytetrafluoroethylene filter membrane and washed three times with deionized water. Then it was frozen and dried to form 195 mg of IL-POSS-GO aerogel.

[0066] (5) The IL-POSS-GO aerogel was impregnated in 50 mL of ethanol solution containing 30 mg TPP, vacuum impregnated for 2 h, and dried at 80 °C to obtain POSS@C@rGO@N@P powder.

[0067] (6) High-temperature carbonization: POSS@C@rGO@N@P powder is evenly spread in an alumina ceramic boat, placed in a tube furnace, and calcined at 1300℃ at 5℃ / min under a mixed atmosphere of hydrogen and argon (5% hydrogen) and kept at that temperature for 6 h. Then, it is naturally cooled to room temperature.

[0068] (7) Washing and purification: The calcined product was soaked in 9M acid for 10 min to remove unreacted SiO2 impurities, then washed with deionized water until neutral, and finally vacuum dried at 80℃ for 12 h to obtain 156 mg of the final Si@C@rGO@N@P silicon-carbon composite material.

[0069] Figure 3 The scanning electron microscope (SEM) image of the product prepared in this embodiment shows that the product exhibits an adsorbed spherical structure, which is highly conducive to the penetration and shuttle of the electrolyte.

[0070] Elemental analysis of the obtained products showed that the contents of C, Cl, O, Si and N in the product of Example 1 were 63.2%, 0.8%, 10.8%, 24.2% and 1%, respectively.

[0071] Example 2

[0072] This embodiment has the same setup as Embodiment 1, except that the mass ratio of raw materials POSS to GO is changed from 1:1 to 3:1.

[0073] The C, Cl, O, Si, and N element contents of the product corresponding to Example 2 are 57.5%, 0.7%, 11.0%, 30.1%, and 0.7%, respectively.

[0074] Figure 4The image shown is a scanning electron microscope (SEM) image of the product prepared in Example 2, which shows the same characteristics as in Example 1: the product exhibits a loosely dispersed spherical structure.

[0075] Example 3

[0076] This embodiment has the same setup as Embodiment 1, except that the mass ratio of raw materials POSS to GO is changed from 1:1 to 1:3.

[0077] The C, Cl, O, Si, and N element contents of the product corresponding to Example 3 were 75.5%, 0.7%, 6.3%, 17.0%, and 0.5%, respectively.

[0078] Example 4

[0079] This embodiment has the same settings as Embodiment 1, except that the calcination temperature is changed from 1200℃ to 800℃.

[0080] The C, Cl, O, Si, and N content of the product corresponding to Example 4 is 64.1%, 0.9%, 14.0%, 20.1%, and 0.9%, respectively.

[0081] Example 5

[0082] This embodiment has the same settings as Embodiment 1, except that the calcination temperature is changed from 1200 ℃ to 1500 ℃.

[0083] The C, Cl, O, Si, and N content of the product corresponding to Example 5 is 66.4%, 0.6%, 13.4%, 19.0%, and 0.6%, respectively.

[0084] Comparative Example 1

[0085] The setup for this comparative example is the same as that for Example 1, except that GO powder is replaced with graphite, and the mass ratio of POSS to graphite remains 1:1.

[0086] Comparative Example 2

[0087] The setup for this comparative example is the same as that for Example 1, except that GO powder is replaced with activated carbon, and the mass ratio of POSS to activated carbon remains 1:1.

[0088] The products obtained in the above embodiments and comparative examples are used as negative electrode materials in button-type lithium-ion batteries. The assembly process is as follows:

[0089] 1) Preparation of the working electrode: The Si@C silicon-carbon anode material obtained in this embodiment was mixed with the conductive agent acetylene black and the binder sodium carboxymethyl cellulose (CMC) in a ratio of 8:1:1 and placed in a mortar. An appropriate amount of deionized water was added as a solvent, and the mixture was ground thoroughly for about 40 minutes to form a uniform and glossy slurry. The slurry was coated onto a copper foil current collector using a four-sided coating tool and dried in an oven at 60 °C. The resulting electrode sheet was cut into small round pieces of 15 mm using a tablet press.

[0090] 2) Assembly of button lithium batteries: The small discs obtained in step 1) are used as negative electrodes, 1.0 M LiPF6, EC and DMC mixed solvent (EC:DMC=1:1) are used as electrolytes, glass fiber membranes are used as separators, and lithium sheets are used as positive electrodes. The assembly is carried out in an anhydrous and oxygen-free glove box.

[0091] The electrochemical performance of the obtained button lithium-ion batteries was tested using the Xinwei Battery Testing System, and the results are shown in Table 1.

[0092] Table 1: Charge-discharge cycle test results of the negative electrode materials obtained in Examples 1-5 and Comparative Examples 1 and 2

[0093] .

[0094] The half-cell test data in Table 1 show that:

[0095] The silicon-carbon anode material corresponding to Example 1 exhibits good performance in terms of capacity, first-charge efficiency, and cycle stability, indicating that the silicon-carbon anode material of this application has excellent cycle stability when applied to batteries; the specific capacity during the first charge reaches 2434 mAh / g, and the specific capacity during the first discharge is 2539 mAh / g (see Example 1). Figure 5 The coulomb efficiency reaches 95.8%, and the reversible cycle retention rate after 100 cycles is as high as 93.4%.

[0096] In Example 2, increasing the POSS content "diluted" the rGO framework. Although the interlayer spacing increased, the three-dimensional conductive network broke. While the Si@C grains became smaller, their excessive number led to dense packing, resulting in the loss of the rGO elastic padding between the grains. Local expansion occurred during charge and discharge. The reversible specific capacity of Example 2 was comparable to that of Example 1, but the initial coulombic efficiency and 100-cycle reversible cycle retention were lower than those of Example 1. In Example 3, with increased GO content, the rGO sheets lacked the "supporting pillars" of Si@C nanoislands, leading to cooling collapse. Multiple side reactions resulted in a decrease in the initial efficiency due to a high specific surface area, and the abundance of defects led to a surge in SEI film formation sites. The initial cycle consumed Li. +The reaction rate increased, and the first-efficiency dropped from 95% to around 82%. In Example 4, the reaction temperature was lowered, which may have hindered reaction kinetics at low temperatures, leading to incomplete reaction. Therefore, both the specific capacity and the coulombic efficiency retention rate were lower than in Example 1. In Example 5, due to the excessively high reaction temperature, Si may have been "burned off," Si@C may have been sintered into large grains, and rGO may have turned into graphitized carbon.

[0097] In summary, it can be seen that the overall performance of Example 1 is better than that of the silicon-carbon anode materials provided in Examples 2 to 5, and it is the best implementation scheme.

[0098] In addition, this application also provides two sets of comparative examples, combined with Figure 6 , Figure 7 It can be seen that:

[0099] In Comparative Example 1, graphite was used as the carbon source. However, graphite sheets are brittle and break when bent. They are also non-porous and require an additional pore-forming process. Therefore, under the same conditions, Example 1 can obtain good electrochemical performance, while Comparative Example 1 may not be able to recombine well with POSS at this temperature, resulting in a significant reduction in specific capacity in the electrochemical performance parameters. The specific capacity of Comparative Example 1 is about 1 / 3 of that of Example 1.

[0100] In Comparative Example 2, activated carbon was used as the carbon source. Activated carbon contains a small amount of carboxyl and phenolic hydroxyl groups, but their distribution is random, with micropores predominating (<2 nm). Mesopores require a template method. Therefore, under the same conditions, Example 1 achieved good electrochemical performance, while Comparative Example 2 exhibited poor conductivity, resulting in a significant decrease in specific capacity. The specific capacity of Comparative Example 2 was approximately half that of Example 1, and its retention rate after 100 reversible cycles was only 57.5%.

[0101] The silicon-carbon anode material with carbon coating provided in this application exhibits good cycle performance when used to prepare anode materials for lithium-ion batteries, and also has high reversible specific capacity and first coulombic efficiency, resulting in excellent overall electrochemical performance.

[0102] The above-described embodiments are merely illustrative of several feasible implementations of the present invention, and their descriptions are relatively specific and detailed. However, they should not be construed as limiting the scope of the present invention, nor are the embodiments intended to limit the scope of protection in the claims of the present invention. For those skilled in the art, various modifications and improvements can be made without departing from the concept of the present invention. All equivalent implementations or changes that do not depart from the present invention should be included in the technology of the present invention.

Claims

1. A method for preparing a Si@C@rGO@N@P silicon-carbon composite material, characterized in that, The steps are as follows: (a) POSS particles were ball-milled to obtain POSS powder with a particle size ≤500 nm; (b) The POSS powder obtained in step (a) was added to the GO dispersion, and then 1-cyanopropyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ionic liquid was added. The mixture was ultrasonically treated to obtain a uniform IL-POSS-GO mixture. (c) The IL-POSS-GO mixture was transferred to a hydrothermal reactor and hydrothermally reduced at 180~240 °C for 6~24 h to obtain IL-POSS-GO aerogel; (d) After vacuum impregnating IL-POSS-GO aerogel in TPP solution, it is taken out and dried. The resulting powder is heated to 800~1500 ℃ under hydrogen and inert atmosphere and kept at the temperature to react, resulting in Si@C@rGO@N@P silicon-carbon composite material.

2. The method for preparing a Si@C@rGO@N@P silicon-carbon composite material according to claim 1, characterized in that: The POSS is at least one of octaphenyl-POSS, octamethyl-POSS, octavinyl-POSS, and octaamino-POSS.

3. The method for preparing a Si@C@rGO@N@P silicon-carbon composite material according to claim 1, characterized in that: In the IL-POSS-GO mixture, the mass ratio of POSS to GO is 1:10 to 10:

1.

4. The method for preparing a Si@C@rGO@N@P silicon-carbon composite material according to claim 1, characterized in that: The concentration of the GO dispersion is 0.5~5 mg / mL.

5. The method for preparing a Si@C@rGO@N@P silicon-carbon composite material according to claim 1, characterized in that: The TPP solution is an ethanol solution of TPP, and the TPP content is 0.1~1.0 g / L.

6. The method for preparing a Si@C@rGO@N@P silicon-carbon composite material according to claim 1, characterized in that: The inert atmosphere is any one of nitrogen, argon and hydrogen mixture, wherein the hydrogen gas fraction in the argon and hydrogen mixture is 0 to 10%.

7. The method for preparing a Si@C@rGO@N@P silicon-carbon composite material according to claim 1, characterized in that: The heating rate is 2~10 °C / min.

8. The method for preparing a Si@C@rGO@N@P silicon-carbon composite material according to claim 1, characterized in that: The crude product obtained from the heat preservation reaction was acid washed, water washed, and dried to obtain purified Si@C@rGO@N@P silicon-carbon composite material.

9. A method for preparing a Si@C@rGO@N@P silicon-carbon composite material according to claim 8, characterized in that: The pickling process uses 5-20 wt% hydrofluoric acid, hydrochloric acid, or nitric acid, and the pickling time is 5-30 min.

10. The Si@C@rGO@N@P silicon-carbon composite material of claim 1 is used for the preparation of a negative electrode material for lithium-ion batteries.

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