A nitrogen-lithium co-doped silicon-carbon composite material, its preparation method and application

Abstract

This invention discloses a method for preparing a lithium nitrogen co-doped silicon-carbon composite material, comprising: etching the surface of nano-silicon using hydrofluoric acid vapor to obtain etched nano-silicon; bonding the etched nano-silicon to nickel foam using an adhesive and hot-pressing; encapsulating polyaniline using electrochemical deposition; performing lithium doping using a hydrothermal reaction; carbonizing; and pulverizing to obtain the lithium nitrogen co-doped silicon-carbon composite material. This invention also discloses the above-mentioned composite material and its applications. This invention uses etched nano-silicon as a raw material, which is chemically bonded to aniline via -Si-COO-N- bonds. The nano-silicon is electrochemically deposited onto the polyaniline-coated nano-silicon composite, and lithium salt is deposited using a hydrothermal method. After final carbonization, the coating layer exhibits low impedance, high rate performance, low irreversible capacity, and high initial efficiency, making it well-suited for use as a material in lithium-ion batteries.

Description

Technical Field

[0001] This invention patent belongs to the field of lithium-ion battery materials, specifically relating to a nitrogen-lithium co-doped silicon-carbon composite material, its preparation method, and its application. Background Technology

[0002] Silicon-carbon materials, with their high specific capacity (theoretical specific capacity 4200 Ah / g), wide availability, and high safety performance (voltage plateau approximately 0.2V higher than graphite), have become a popular choice for anode materials in high-energy-density lithium-ion batteries. However, during the alloying reaction, silicon-carbon anodes undergo phase transitions and experience significant volume expansion (approximately 300%). This drastic volume change introduces a series of problems, such as breakage, pulverization, and electrode coating peeling, ultimately leading to rapid capacity decay and severely hindering their practical application in lithium-ion batteries. Furthermore, silicon itself is a semiconductor material, exhibiting poorer conductivity compared to graphite-based materials, and its ionic conductivity is also biased. The irreversible formation of lithium silicate between silicon and lithium causes an initial efficiency drop, which further hinders the commercial application of silicon-based anodes. Summary of the Invention

[0003] Therefore, the technical problem to be solved by the present invention is the defects of existing silicon-carbon materials such as volume expansion during reaction, poor conductivity, and low initial efficiency, thereby providing a nitrogen-lithium co-doped silicon-carbon composite material, its preparation method and application.

[0004] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0005] This invention provides a method for preparing a nitrogen-lithium co-doped silicon-carbon composite material, comprising the following steps: S1: The surface of the nano-silicon was etched using hydrofluoric acid vapor to obtain etched nano-silicon; S2: Etched nano-silicon is bonded to nickel foam with an adhesive and hot-pressed to form an etched nano-silicon composite. S3: Polyaniline was coated onto the surface of the etched nano-silicon composite using an electrochemical deposition method; S4: The polyaniline-coated etched silicon nanocomposite was mixed with aminosilane coupling agent, ammonium persulfate and organolithium salt in ethyl methyl carbonate and subjected to hydrothermal reaction to obtain lithium-doped polyaniline-coated etched silicon nanocomposite. S5: Carbonize the lithium-doped polyaniline-coated etched nano-silicon composite and pulverize it to obtain the nitrogen-lithium co-doped silicon-carbon composite material.

[0006] Further, in step S1, the etching of the nano-silicon surface using hydrofluoric acid vapor specifically involves heating hydrofluoric acid to 80-90°C to form hydrofluoric acid vapor, etching the nano-silicon surface, and holding at that temperature for 1-2 hours to obtain etched nano-silicon.

[0007] In step S2, the mass ratio of etched nano-silicon, binder, and nickel foam is 100:1 to 10:5-30. The hot pressing is performed at 150°C for 30 minutes at a pressure of 2T.

[0008] In step S3, the electrochemical deposition method involves using an etched nano-silicon composite as the working electrode, a 1-10 wt% aniline hydrochloric acid aqueous solution as the solution, and a saturated calomel as the counter electrode. The method is to scan for 10-100 cycles using cyclic voltammetry under the conditions of a voltage range of -2V to 2V and a scan rate of 0.5-5mV / s. The HCl content in the hydrochloric acid aqueous solution is 1~10 wt%.

[0009] In step S4, the mass ratio of the polyaniline-coated etched nano-silicon composite to the aminosilane coupling agent, ammonium persulfate, and organolithium salt is 100:1~5:1~5:5~20. The hydrothermal reaction temperature is 100~200℃, and the reaction time is 1~6h; Ethyl methyl carbonate can be replaced by propylene carbonate or ethylene carbonate.

[0010] In step S5, the carbonization is performed at 800°C for 6 hours.

[0011] Preferably, the aminosilane coupling agent is one of 3-aminopropanetriethoxysilane, 3-aminopropanetrimethoxysilane, and (3-aminopropane)methyldiethoxysilane; The organolithium salt is one of lithium methoxide, lithium ethanol, lithium formate, lithium oxalate, or lithium stearate; The binder is one of asphalt, polyvinyl alcohol, binder CMC-Li, binder LA136D, or β-cyclodextrin.

[0012] The present invention also provides a nitrogen-lithium co-doped silicon-carbon composite material, which is prepared according to the above preparation method.

[0013] Furthermore, in the nitrogen-lithium co-doped silicon-carbon composite material, the mass ratio of nano-silicon, nitrogen-doped amorphous carbon, and lithium salt is 80~95:3.8~18.1:0.5~4.6.

[0014] The present invention also provides the application of the above-mentioned nitrogen-lithium co-doped silicon-carbon composite material in lithium-ion batteries.

[0015] The technical solution of this invention has the following advantages: (1) The present invention uses etched nano-silicon as raw material, which is connected to aniline by chemical bond -Si-COO-N- and coated on the surface by electrochemical deposition. The silicon-carbon material obtained by carbonization has advantages such as strong and tight bonding, low electronic impedance and low expansion, and the core and amorphous carbon are connected by chemical bond. The polyaniline coated nano-silicon obtained by electrochemical deposition has good isotropy and low nitrogen atom impedance after carbonization, which can reduce the impedance of the coating layer and improve the rate performance of the material.

[0016] (2) In this invention, lithium salts are deposited on the surface of polyaniline-coated nano-silicon using a hydrothermal method to reduce the irreversible capacity of the material and improve the initial efficiency. At the same time, the foamed nickel current collector plays a catalytic role in the subsequent carbonization process, improving the reaction progress. Meanwhile, the polyaniline-coated nano-silicon and the aminosilane coupling agent form a three-dimensional network structure through the polymerization of ammonium persulfate, and carbonization yields a three-dimensional porous silicon-carbon composite material.

[0017] (3) In this invention, when lithium salts are deposited using a hydrothermal method, the polyaniline-coated nano-silicon composite material and the aminosilane coupling agent undergo a polymerization reaction under ammonium persulfate conditions to obtain a silane coupling agent-polyaniline composite material, which forms a network structure. At the same time, a nitrogen-lithium co-doped silicon-carbon composite material is prepared by using a hydrothermal method to prepare a solution of polyaniline-coated nano-silicon composite material, aminosilane coupling agent, ammonium persulfate, and organolithium salt in methyl ethyl carbonate. This method can achieve uniform mixing between materials and a more complete reaction.

[0018] (4) In the end, the carbonization of polyaniline, lithium salt and silicon-based material composite can realize the conversion of polyaniline into carbon, and the pre-lithiation of lithium salt can reduce irreversible capacity and improve the first efficiency, and can achieve uniform mixing between materials. It adopts one-step carbonization to obtain nitrogen-lithium co-doped silicon-carbon composite material, avoiding the problems of multiple carbonization processes, slow preparation cycle, etc., and has the advantages of fast reaction speed and good uniformity. Attached Figure Description

[0019] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0020] Figure 1 The image shows a SEM image of the nitrogen-lithium co-doped silicon-carbon composite material obtained in Example 1. Detailed Implementation

[0021] The following embodiments are provided to better understand the present invention and are not limited to the preferred embodiments described. They do not constitute a limitation on the content and scope of protection of the present invention. Any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the protection scope of the present invention.

[0022] Where specific experimental steps or conditions are not specified in the embodiments, they can be performed according to the conventional experimental steps or conditions described in the literature in this field.

[0023] Example 1 This embodiment provides a nitrogen-lithium co-doped silicon-carbon composite material, the specific preparation method of which is as follows: (1) Hydrofluoric acid was heated to 80°C to form hydrofluoric acid vapor, which was then passed into a plastic container containing nano-silicon and kept at the temperature for 1 hour. After washing with deionized water, etched nano-silicon with surface etching was obtained. (2) Mix 100g of etched nano-silicon and 5g of asphalt (softening point: 150℃) evenly and coat it onto 20g of nickel foam. Then use a hot press to hot press for 30min at a pressure of 2T and a temperature of 150℃ to obtain an etched nano-silicon composite. (3) The etched nano-silicon composite was used as the working electrode, 5wt% aniline hydrochloric acid aqueous solution was used as the solvent (HCl in the hydrochloric acid aqueous solution was 5wt%), saturated calomel was used as the counter electrode, and 50 cycles were scanned by cyclic voltammetry under the conditions of voltage range -2V-2V and scan rate of 1mV / s. After filtration and washing with deionized water, polyaniline-coated etched nano-silicon composite material was obtained. (4) 10g of lithium methoxide was added to 100g of methyl ethyl carbonate solution and dispersed evenly. Then, 100g of polyaniline-coated etched nano-silicon composite material, 3g of 3-aminopropanetriethoxysilane and 3g of ammonium persulfate were added and mixed evenly. The mixture was then transferred to a high-pressure reactor and subjected to hydrothermal reaction at 150℃ for 3h. The lithium-doped polyaniline-coated etched nano-silicon composite material was obtained by filtration. (5) The lithium-doped polyaniline-coated etched nano-silicon composite was carbonized at 800°C for 6 hours and then pulverized to obtain the nitrogen-lithium co-doped silicon-carbon composite material.

[0024] Example 2 This embodiment provides a nitrogen-lithium co-doped silicon-carbon composite material, the specific preparation method of which is as follows: (1) Hydrofluoric acid was heated to 90°C to form hydrofluoric acid vapor, which was then passed into a plastic container containing nano-silicon and kept at the temperature for 2 hours. After washing with deionized water, etched nano-silicon with surface etching was obtained. (2) Mix 100g of etched nano-silicon and 1g of polyvinyl alcohol evenly and coat them onto 15g of nickel foam. Then use a hot press to hot press for 30 minutes at a pressure of 2T and a temperature of 150℃ to obtain an etched nano-silicon composite. (3) The etched nano-silicon composite was used as the working electrode, 1 wt% aniline hydrochloric acid aqueous solution was used as the solvent (HCl in the hydrochloric acid aqueous solution was 1 wt%), saturated calomel was used as the counter electrode, and the cyclic voltammetry was used to scan for 10 cycles under the conditions of voltage range -2V to 2V and scan rate of 0.5mV / s. After filtration and washing with deionized water, polyaniline-coated etched nano-silicon composite material was obtained. (4) Add 5g of lithium ethanol to 100g of methyl ethyl carbonate solution and disperse evenly. Then add 100g of polyaniline-coated etched nano-silicon composite material, 1g of 3-aminopropanetrimethoxysilane and 1g of ammonium persulfate and mix evenly. Transfer to a high-pressure reactor and carry out hydrothermal reaction at 100℃ for 6h. Filter to obtain lithium-doped polyaniline-coated etched nano-silicon composite material. (5) The lithium-doped polyaniline-coated etched nano-silicon composite was carbonized at 800°C for 6 hours and then pulverized to obtain the nitrogen-lithium co-doped silicon-carbon composite material.

[0025] Example 3 This embodiment provides a nitrogen-lithium co-doped silicon-carbon composite material, the specific preparation method of which is as follows: (1) Hydrofluoric acid was heated to 85°C to form hydrofluoric acid vapor, which was then passed into a plastic container containing nano-silicon and kept at the temperature for 1 hour. After washing with deionized water, etched nano-silicon with surface etching was obtained. (2) Mix 100g of etched nano-silicon and 10g of CMC-Li evenly and coat them onto 30g of nickel foam. Then use a hot press to hot press for 30min at a pressure of 2T and a temperature of 150℃ to obtain an etched nano-silicon composite. (3) The etched nano-silicon composite was used as the working electrode, 10wt% aniline hydrochloric acid aqueous solution was used as the solvent (HCl in the hydrochloric acid aqueous solution was 10wt%), saturated calomel was used as the counter electrode, and cyclic voltammetry was used to scan for 100 cycles under the conditions of voltage range -2V-2V and scan rate of 5mV / s. After filtration and washing with deionized water, polyaniline-coated etched nano-silicon composite material was obtained. (4) 20g of lithium oxalate was added to 100g of methyl ethyl carbonate solution and dispersed evenly. Then, 100g of polyaniline-coated etched nano-silicon composite material, 5g of (3-aminopropane)methyldiethoxysilane and 5g of ammonium persulfate were added and mixed evenly. The mixture was then transferred to a high-pressure reactor and subjected to hydrothermal reaction at 200℃ for 1h. The lithium-doped polyaniline-coated etched nano-silicon composite material was obtained by filtration. (5) The lithium-doped polyaniline-coated etched nano-silicon composite was carbonized at 800°C for 6 hours and then pulverized to obtain the nitrogen-lithium co-doped silicon-carbon composite material.

[0026] Comparative Example 1 This comparative example provides a lithium-doped silicon-carbon composite material, the specific preparation method of which is as follows: Take 100g of nano-silicon, 3g of 3-aminopropane-methyldiethoxysilane, 10g of lithium methoxide and 100g of methyl ethyl carbonate, mix them evenly, transfer them to a high-pressure reactor, carry out hydrothermal reaction at 150℃ for 3h, filter, carbonize at 800℃ for 6h, and pulverize to obtain the lithium-doped silicon-carbon composite material.

[0027] Comparative Example 2 This comparative example provides a nitrogen-doped silicon-carbon composite material. The difference between this example and Example 1 is that the polyaniline-coated etched nano-silicon composite material obtained in step (3) is directly carbonized at 800°C for 6 hours and then pulverized to obtain the nitrogen-doped silicon-carbon composite material.

[0028] Comparative Example 3 This comparative example provides a lithium-doped silicon-carbon composite material. The difference from Example 1 is that polyaniline is not used to coat the etched nano-silicon composite material. After obtaining the etched nano-silicon composite material in step (2), the hydrothermal reaction in step (4) is carried out directly.

[0029] Comparative Example 4 This comparative example provides a nitrogen-lithium co-doped silicon-carbon composite material, which differs from Example 1 in that the nano-silicon surface is not etched.

[0030] Comparative Example 5 This comparative example provides a nitrogen-lithium co-doped silicon-carbon composite material. The difference from Example 1 is that a liquid-phase method is used to coat and etch the nano-silicon composite material with polyaniline. The specific preparation method is as follows: (1) Hydrofluoric acid was heated to 80°C to form hydrofluoric acid vapor, which was then passed into a plastic container containing nano-silicon and kept at the temperature for 1 hour. After washing with deionized water, etched nano-silicon with surface etching was obtained. (2) Mix 100g of etched nano-silicon and 5g of asphalt (softening point: 150℃) evenly and coat it onto 20g of nickel foam. Then use a hot press to hot press for 30min at a pressure of 2T and a temperature of 150℃ to obtain an etched nano-silicon composite. (3) Add 10g of polyaniline to 100g of N-methylpyrrolidone and disperse evenly. Then add 100g of etched nano-silicon composite, disperse evenly by ultrasonication, filter, and vacuum dry to obtain polyaniline-coated etched nano-silicon composite material. (4) 10g of lithium methoxide was added to 100g of methyl ethyl carbonate solution and dispersed evenly. Then, 100g of polyaniline-coated etched nano-silicon composite material, 3g of 3-aminopropanetriethoxysilane and 3g of ammonium persulfate were added and mixed evenly. The mixture was then transferred to a high-pressure reactor and subjected to hydrothermal reaction at 150℃ for 3h. The lithium-doped polyaniline-coated etched nano-silicon composite material was obtained by filtration. (5) The lithium-doped polyaniline-coated etched nano-silicon composite was carbonized at 800°C for 6 hours and then pulverized to obtain the nitrogen-lithium co-doped silicon-carbon composite material.

[0031] Experimental Example 1 The nitrogen-lithium co-doped silicon-carbon composite material prepared in Example 1 was subjected to SEM testing, and the test results are as follows: Figure 1 As shown. By Figure 1 As can be seen from the results, the composite material prepared in Example 1 exhibits a concave granular structure with a relatively uniform size distribution and a particle size between 2 and 10 µm.

[0032] Experimental Example 2 Physical and chemical properties: The particle size, compacted density, specific surface area, and trace element nitrogen content of the silicon-carbon composite materials prepared in Examples 1-3 and Comparative Examples 1-5 were measured according to the methods in the national standard GB / T-38823-2020 "Silicon-Carbon". The test results are shown in Table 1.

[0033] Table 1 Physicochemical properties of silicon-carbon composite materials

[0034] Experimental Example 3 Button cell battery testing: The silicon-carbon composite materials from Examples 1-3 and Comparative Examples 1-5 were used as negative electrode materials for lithium-ion batteries to assemble coin cells. The specific preparation method for the negative electrode material was as follows: a binder, conductive agent, and solvent were added to the composite material, stirred to form a slurry, coated onto copper foil, and then dried and rolled. The binder used was LA132, the conductive agent was SP, and the solvent was double-distilled water. The negative electrode sheet was prepared according to the ratio of composite material: SP:LA132:double-distilled water = 90g:4g:6g:220mL. A lithium metal sheet was used as the positive electrode. The electrolyte was LiPF6 / EC+DEC, where LiPF6 was the electrolyte, and a 1:1 volume ratio mixture of EC and DEC was used as the solvent, with an electrolyte concentration of 1.3 mol / L. The separator was a composite membrane of polyethylene (PE), polypropylene (PP), or polyethylene propylene (PEP). The coin cells were assembled in an argon-filled glove box. Electrochemical performance was performed using a Wuhan Landian CT2001A battery tester. The charge / discharge voltage range was 0.005V to 2.0V, and the charge / discharge rate was 0.1C. The initial discharge capacity and initial efficiency of the coin cells were tested, along with rate performance (5C, 0.1C) and cycle performance (0.5C / 0.5C, 200 cycles). The negative electrode expansion rate was also tested by dissecting the coin cells at 100% SOC after full charge. The test results are shown in Table 2.

[0035] Table 2. Button Cell Performance

[0036] As can be seen from Tables 1 and 2, the materials prepared in the embodiments of the present invention have high specific capacity and initial efficiency. This is because the doping of lithium compounds in the material improves the initial efficiency, and nitrogen reduces impedance, thereby lowering the battery plateau and improving the rate and initial efficiency. Furthermore, the electrochemical deposition method has the characteristic of high deposition density, thus increasing the compaction density of the material. Electrochemical deposition of polyaniline on its surface improves rate performance and cycle performance. Comparative Examples 1-3 lack specific steps from the embodiments, and the performance of the materials obtained is significantly lower than that of the embodiments. In Comparative Example 4, nano-silicon is used directly instead of etched nano-silicon, resulting in poor density of aniline deposition on the nano-silicon surface and higher impedance. In Comparative Example 5, polyaniline is deposited using a liquid phase method. Due to the small particle size of silicon, it is prone to agglomeration, resulting in poor coating uniformity and higher impedance and expansion.

[0037] Test Example 4 Soft-pack battery test: (1) The silicon-carbon composite materials in Examples 1-3 and Comparative Examples 1-5 were mixed with 90% artificial graphite as negative electrodes, and the negative electrode sheets were prepared by slurry mixing and coating, using ternary materials (LiNi) 1 / 3 Co 1 / 3 Mn 1 / 3A 2Ah pouch cell was prepared using O2 as the positive electrode, LiPF6 (solvent EC+DEC, volume ratio 1:1, electrolyte concentration 1.3mol / L) as the electrolyte, and Celgard 2400 membrane as the separator.

[0038] (2) Ratio performance test: The rate performance of the pouch battery was tested under a charge / discharge voltage range of 2.5–4.2V and a temperature of 25±3.0℃. Charging was performed at 1.0C, 3.0C, 5.0C, and 10.0C, and discharging was performed at 1.0C. The results are shown in Table 3.

[0039] Table 3 Performance Test of Pouch Batteries

[0040] As shown in Table 3, the rate charging performance of the soft-pack batteries prepared by the materials in Examples 1-3 is significantly better than that of Comparative Examples 1-5, that is, the charging time is shorter. The reason for this is that lithium ions need to migrate during the battery charging process. The materials in each example are coated with lithium salts and have high deposition density and low impedance, which improves the rate performance.

[0041] (3) Cyclic performance test: The obtained soft-pack batteries were subjected to cycle performance testing under the following conditions: charge / discharge current 2C / 2C, voltage range 2.5-4.2V, and 1000 cycles. The test results are shown in Table 4.

[0042] Table 4 Cyclic Performance Test

[0043] As shown in Table 4, the lithium-ion batteries prepared using the composite materials obtained in Examples 1-3 exhibit significantly better cycle performance than the comparative examples at all stages. Experimental results demonstrate that the present invention, by depositing polyaniline on the surface of nano-silicon using electrochemical deposition and then doping with lithium salt using a hydrothermal method, can increase the lithium-ion content during charging and discharging, thereby improving cycle performance.

[0044] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for preparing a nitrogen-lithium co-doped silicon-carbon composite material, characterized in that, Includes the following steps: S1: The surface of the nano-silicon was etched using hydrofluoric acid vapor to obtain etched nano-silicon; S2: Etched nano-silicon is bonded to nickel foam with an adhesive and hot-pressed to form an etched nano-silicon composite. S3: Polyaniline was coated onto the surface of the etched nano-silicon composite by electrochemical deposition to obtain a polyaniline-coated etched nano-silicon composite. S4: The polyaniline-coated etched silicon nanocomposite was mixed with aminosilane coupling agent, ammonium persulfate and organolithium salt in ethyl methyl carbonate and subjected to hydrothermal reaction to obtain lithium-doped polyaniline-coated etched silicon nanocomposite. S5: Carbonize the lithium-doped polyaniline-coated etched nano-silicon composite and pulverize it to obtain the nitrogen-lithium co-doped silicon-carbon composite material.

2. The preparation method according to claim 1, characterized in that, In step S1, the etching of the nano-silicon surface using hydrofluoric acid vapor specifically involves heating hydrofluoric acid to 80-90℃ to form hydrofluoric acid vapor, etching the nano-silicon surface, and holding the temperature for 1-2 hours to obtain etched nano-silicon.

3. The preparation method according to claim 2, characterized in that, In step S2, the mass ratio of etched nano-silicon, binder, and nickel foam is 100:1~10:5~30; The hot pressing is performed at 150°C for 30 minutes at a pressure of 2T.

4. The preparation method according to claim 3, characterized in that, In step S3, the electrochemical deposition method involves using an etched nano-silicon composite as the working electrode, a 1-10 wt% aniline hydrochloric acid aqueous solution as the solution, and a saturated calomel as the counter electrode. The method is to scan for 10-100 cycles using cyclic voltammetry under the conditions of a voltage range of -2V to 2V and a scan rate of 0.5-5mV / s. The HCl content in the hydrochloric acid aqueous solution is 1~10 wt%.

5. The preparation method according to claim 4, characterized in that, In step S4, the mass ratio of the polyaniline-coated etched nano-silicon composite to the aminosilane coupling agent, ammonium persulfate, and organolithium salt is 100:1~5:1~5:5~20. The hydrothermal reaction temperature is 100~200℃, and the reaction time is 1~6h.

6. The preparation method according to claim 5, characterized in that, In step S5, the carbonization is performed at 800°C for 6 hours.

7. The preparation method according to claim 6, characterized in that, The aminosilane coupling agent is one of 3-aminopropanetriethoxysilane, 3-aminopropanetrimethoxysilane, and (3-aminopropane)methyldiethoxysilane. The organolithium salt is one of lithium methoxide, lithium ethanol, lithium formate, lithium oxalate, or lithium stearate; The binder is one of asphalt, polyvinyl alcohol, binder CMC-Li, binder LA136D, or β-cyclodextrin.

8. A nitrogen-lithium co-doped silicon-carbon composite material, characterized in that, Prepared by the preparation method according to any one of claims 1 to 7.

9. The nitrogen-lithium co-doped silicon-carbon composite material according to claim 8, characterized in that, In the nitrogen-lithium co-doped silicon-carbon composite material, the mass ratio of nano-silicon, nitrogen-doped amorphous carbon, and lithium salt is 80~95:3.8~18.1:0.5~4.

6.

10. The application of the nitrogen-lithium co-doped silicon-carbon composite material according to claim 8 or 9, characterized in that, Used in lithium-ion batteries.

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