A composite material of fast ion complex coated graphite and its preparation method and application

Abstract

This invention discloses a fast-ion composite material coated with graphite, which is a granular material with a three-layer composite structure. The core is etched graphite, the middle layer is a porous composite layer formed by metal oxide, fast-ion conductor, and amorphous carbon, and the outermost layer is an amorphous carbon layer. This invention is prepared by processing the metal oxide to obtain a porous metal oxide, combining it with a fast-ion conductor solution to form the middle layer, coating it with graphite, and finally depositing an amorphous carbon layer on the outer layer in a vapor phase. In this invention, the composite middle layer utilizes the high ionic conductivity of the fast-ion conductor and the high electronic conductivity of the porous metal oxide to improve the power performance of the material. Simultaneously, the porous structure of the metal oxide material in the middle layer gives the material a high specific surface area, increasing the diffusion rate of lithium ions during charging and discharging and reducing the migration path of the material, thus improving power performance. The outermost amorphous carbon layer, due to its high density, prevents the core from directly contacting the electrolyte, reducing side reactions and improving its storage and cycling performance.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery materials, specifically relating to a fast-ion composite material coated with graphite, its preparation method, and its application. Background Technology

[0002] Currently, the main negative electrode material for commercially available lithium-ion batteries is graphite (natural graphite and artificial graphite), which has advantages such as good conductivity and high reversible specific capacity. However, graphite materials also have disadvantages such as poor structural stability, poor compatibility with electrolytes, and slow diffusion rate of lithium ions in its ordered layered structure, which makes the material unable to be charged and discharged at high rates.

[0003] Currently, the above problems are mostly solved by coating the surface of graphite anode materials. However, common soft carbon or hard carbon coating materials have drawbacks such as slow lithium-ion diffusion rate and long lithium intercalation path during charging and discharging. Using fast ion conductor coating materials can provide active sites for lithium / sodium ion exchange during charging and discharging, improving rate performance and diffusion rate. However, the poor electronic conductivity of fast ion conductors will affect the polarization of the material, causing deviations in the power performance of the material. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a fast ion composite material coated with graphite, its preparation method, and its application. By coating the graphite surface with a fast ion conductor with high ionic conductivity and a porous oxide material with high electronic conductivity, the power and fast charging performance are improved.

[0005] To achieve the above technical objectives, the technical solution adopted by the present invention is as follows:

[0006] The technical objective of the first aspect of the present invention is to provide a composite material of graphite coated with fast ion composite, which is a granular material with a three-layer composite structure, wherein the core is etched graphite, the middle layer is a porous composite layer formed by metal oxide, fast ion conductor and amorphous carbon, and the outermost layer is an amorphous carbon layer.

[0007] The metal oxide is selected from at least one of SnO, SnO2, NiO, Co3O4, In2O3, FeO, CuO, MnO2 and MoO; the fast ion conductor is selected from at least one of NaTi2(PO4)3, Na3V2(PO4)3 and Na3Zr2(PO4)3.

[0008] Furthermore, the porosity of the porous composite layer is 10-30%; preferably 20-30%.

[0009] Furthermore, the specific surface area of ​​the etched graphite is 5-10 m². 2 / g, graphite OI value is 1-2;

[0010] Furthermore, based on the total weight of the composite material, the intermediate layer accounts for 1%-10% of the mass percentage, and the outer shell accounts for 1%-10% of the mass percentage; the weight ratio of metal oxide, fast ion conductor, and amorphous carbon in the intermediate layer is 1-4:1-4:2-8.

[0011] The second aspect of the present invention aims to provide a method for preparing a fast ion composite material coated with graphite, comprising the following steps:

[0012] Preparation of etched graphite: Graphite, concentrated sulfuric acid and potassium permanganate are mixed and reacted to obtain graphite oxide, which is then carbonized to obtain the etched graphite.

[0013] Preparation of intermediate layer material: Metal oxide, organic template agent and organic solvent are mixed and subjected to hydrothermal reaction, sintered to obtain porous metal oxide, which is then added to the organic solvent solution of fast ion conductor, dispersed evenly, spray dried and carbonized to obtain composite intermediate layer material.

[0014] Intermediate layer graphite coating: The prepared composite intermediate layer material is formulated into a suspension, etched graphite is added, the mixture is dispersed evenly, filtered to obtain a solid, and the solid is carbonized to obtain a material with intermediate layer graphite coating.

[0015] Preparation of three-layer composite material: Carbon source gas vapor deposition was performed on the material with graphite in the middle layer to obtain a fast ion composite material with graphite.

[0016] Furthermore, in preparing etched graphite, the weight ratio of graphite, concentrated sulfuric acid, and potassium permanganate is 100:100-500:10-30; the temperature of the mixture reaction is 50-150℃, and the time is 1-24h.

[0017] Furthermore, when preparing etched graphite, the carbonization temperature is 600-900℃ and the time is 1-6h; the carbonization reaction atmosphere is a mixture of ammonia and argon, and the volume ratio of ammonia and argon in the mixture is 1:10.

[0018] Furthermore, when preparing the intermediate layer material, the hydrothermal reaction temperature is 50-120℃, and the sintering temperature is 200-500℃.

[0019] Furthermore, when preparing the intermediate layer material, the concentration of the fast ion conductor in the organic solvent solution of the fast ion conductor is 1wt%-10wt%.

[0020] Furthermore, the organic template agent is selected from at least one of tetrapropylammonium hydroxide and tetraethylammonium hydroxide; wherein the organic solvents involved are all selected from at least one of carbon tetrachloride, N-methylpyrrolidone, cyclohexane and tetrahydrofuran.

[0021] Furthermore, the mass ratio of the metal oxide, organic template agent, organic solvent, and fast ion conductor is 10-50:1-5:100-500:10-50.

[0022] Furthermore, when preparing the intermediate layer material, the carbonization is carried out in an inert atmosphere at a temperature of 700-1000℃ for 1-6 hours.

[0023] Furthermore, the particle size D50 of the prepared composite intermediate layer material is 15-20 μm, and the particle size D50 of the prepared etched graphite is 5-10 μm.

[0024] Furthermore, when the intermediate layer is coated with graphite, the solid concentration in the suspension of the composite intermediate layer material is 1wt%-10wt%. The solvent used is selected from at least one of carbon tetrachloride, N-methylpyrrolidone, and cyclohexane.

[0025] Furthermore, when the intermediate layer is coated with graphite, the mass ratio of the composite intermediate layer material to the etched graphite is 5-10:100.

[0026] Furthermore, when the intermediate layer is coated with graphite, the carbonization is carried out in an inert atmosphere at a temperature of 700-1000℃ for 1-6 hours.

[0027] Furthermore, the carbon source gas is selected from at least one of methane, acetylene, and ethane. The vapor deposition temperature is 700-1000℃, and the reaction time is 1-6 hours. An amorphous carbon layer is formed on the outer surface of the material through vapor deposition.

[0028] The technical objective of the third aspect of this invention is to provide the application of the fast ion composite coated graphite composite material as a negative electrode material for rechargeable batteries.

[0029] The technical solution of this invention has the following beneficial effects:

[0030] (1) By coating the graphite surface with a composite intermediate layer including a fast ion conductor, the high ionic conductivity of the fast ion conductor and the high electronic conductivity of the porous metal oxide are utilized to improve the power performance of the material. At the same time, the metal oxide material of the intermediate layer has a porous structure, which gives the material a high specific surface area, increases the diffusion rate of lithium ions during charging and discharging and reduces the migration path of the material, thereby improving the power performance. The amorphous carbon layer set on the outermost layer has high density, which can prevent the core from directly contacting the electrolyte, reduce the occurrence of side reactions, and improve its storage and cycle performance.

[0031] (2) In the preparation method of the present invention, a hydrothermal reaction is carried out by mixing metal oxide, organic template agent and organic solvent. General organic template agents such as tetrapropylammonium hydroxide are alkaline, while metal oxides are mostly acidic oxides. During the reaction, the metal oxide and the organic template agent undergo a chemical reaction rather than physical adsorption, which improves the structural stability of the composite material. After sintering at 200-500℃, the metal compound is doped between the porous amorphous carbon. In the preferred technical solution, the specific organic template agent contains nitrogen atoms to form nitrogen doping, which improves the electronic conductivity of the metal oxide.

[0032] (3) In the preparation method of the present invention, a fast ion conductor is dissolved in an organic solvent to coat a porous metal oxide. On the one hand, after filtration, residual organic solvent will remain on the surface or in the pores of the fast ion conductor. After carbonization, the organic solvent forms amorphous carbon, which coats or dops into the fast ion conductor, thereby improving the electronic conductivity of the material. On the other hand, the organic solution of the fast ion conductor is mixed with the porous oxide. Relying on the high capacity of the oxide, the ionic conductivity of the fast ion conductor and the amorphous carbon doped in between, the electronic conductivity of the composite material is improved and the expansion is reduced.

[0033] (4) In the preparation method of the present invention, by performing secondary carbon source treatment on the composite material, an amorphous carbon layer is formed on the outer surface of the material by vapor deposition, which can reduce the contact between the fast ion conductor and the electrolyte and improve the electronic conductivity of the material. At the same time, the vapor deposition obtains an amorphous carbon layer with high density and high uniformity, which can improve its rate, cycle and storage characteristics when used in batteries. Attached Figure Description

[0034] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art 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.

[0035] in:

[0036] Figure 1 The image shows a SEM image of the composite material prepared in Example 1. Detailed Implementation

[0037] 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.

[0038] In Examples 1-3, composite materials of graphite coated with fast ion complexes were prepared:

[0039] Example 1

[0040] S1, 100g of artificial graphite, 300g of concentrated sulfuric acid, and 20g of potassium permanganate were weighed and mixed, and chemically oxidized at 100℃ for 6 hours to obtain graphite oxide. This oxide was then transferred to a tube furnace, and a mixture of ammonia and argon (volume ratio NH3:Ar = 1:10) was introduced. The furnace was then heated to 800℃ for carbonization for 3 hours to obtain etched graphite A, with a particle size D50 of 6.0μm and a specific surface area of ​​9.2m². 2 / g, graphite OI value is 1.5;

[0041] The method for testing the graphite OI value is: OI = C004 / C110, where C004 is the peak area of ​​the 004 characteristic diffraction peak in the X-ray diffraction pattern of the negative electrode active material powder, and C110 is the peak area of ​​the 110 characteristic diffraction peak in the X-ray diffraction pattern of the negative electrode active material powder.

[0042] S2, 30g SnO, 3g tetrapropylammonium hydroxide and 300g carbon tetrachloride were mixed evenly and subjected to hydrothermal reaction at 120℃ for 3h. After filtration, vacuum drying at 80℃ for 24h and sintering at 250℃ for 3h, a porous metal oxide was obtained. Then it was added to 600mL of 5wt% NaTi2(PO4)3 in carbon tetrachloride organic solution, dispersed evenly, spray dried, and then carbonized at 800℃ for 3h under an argon inert atmosphere to obtain SnO / NaTi2(PO4)3 composite intermediate layer material B, with a particle size D50 of 17.8μm and a porosity of 20%.

[0043] S3, 8g of SnO / NaTi2(PO4)3 composite intermediate layer material was added to 160mL of carbon tetrachloride to prepare a suspension with a mass concentration of 5%, then 100g of etched graphite A was added, dispersed evenly, filtered, and then carbonized at 800℃ for 3h under an argon inert atmosphere to obtain SnO / NaTi2(PO4)3 coated graphite composite material C.

[0044] S4. The composite material C was transferred to a tube furnace and vapor-deposited at 850°C for 3 hours using methane as the carbon source to obtain amorphous carbon / SnO / NaTi2(PO4)3 coated graphite composite material D.

[0045] Example 2

[0046] S1, 100g of artificial graphite, 100g of concentrated sulfuric acid, and 10g of potassium permanganate were weighed and mixed. The mixture was chemically oxidized at 50℃ for 24h to obtain graphite oxide. This oxide was then transferred to a tube furnace, and a mixture of ammonia and argon (volume ratio NH3:Ar = 1:10) was introduced. The temperature was raised to 600℃ for carbonization for 6h to obtain etched graphite A, with a particle size D50 of 8.2μm and a specific surface area of ​​7.8m². 2 / g, graphite OI value is 1.0;

[0047] The graphite OI value test method is: OI = C004 / C110, where C004 is the peak area of ​​the 004 characteristic diffraction peak in the X-ray diffraction pattern of the negative electrode active material powder, and C110 is the peak area of ​​the 110 characteristic diffraction peak in the X-ray diffraction pattern of the negative electrode active material powder.

[0048] S2, 10g NiO, 1g tetraethylammonium hydroxide and 100g N-methylpyrrolidone were mixed evenly and subjected to hydrothermal reaction at 120℃ for 3h. After filtration, the mixture was vacuum dried at 80℃ for 24h and sintered at 200℃ for 3h to obtain a porous metal oxide. Then, it was added to 100mL of a 1wt% Na3V2(PO4)3 organic solution in carbon tetrachloride, dispersed evenly, spray dried, and then carbonized at 700℃ for 6h under an argon inert atmosphere to obtain NiO / Na3V2(PO4)3 composite intermediate layer material B, with a particle size D50 of 15.2μm and a porosity of 27%.

[0049] S3, 5g of NiO / Na3V2(PO4)3 composite intermediate layer material B was added to 500ml of N-methylpyrrolidone to prepare a suspension with a mass concentration of 1%, then 100g of etched graphite A was added, dispersed evenly, filtered, and then carbonized at 700℃ for 6h under an argon inert atmosphere to obtain NiO / Na3V2(PO4)3 coated graphite composite material C;

[0050] S4. The composite material C was transferred to a tube furnace and vapor-deposited at 700℃ for 6 hours using acetylene as the carbon source to obtain amorphous carbon / NiO / Na3V2(PO4)3 coated graphite composite material D.

[0051] Example 3

[0052] S1, 100g of artificial graphite, 500g of concentrated sulfuric acid, and 30g of potassium permanganate were weighed and chemically oxidized at 150℃ for 1 hour to obtain graphite oxide. This oxide was then transferred to a tube furnace, through which a mixture of ammonia and argon (volume ratio NH3:Ar = 1:10) was introduced, and the temperature was raised to 900℃ for carbonization for 1 hour to obtain etched graphite A, with a particle size D50 of 7.3μm and a specific surface area of ​​8.4m². 2 / g, graphite OI value is 2;

[0053] The graphite OI value test method is: OI = C004 / C110, where C004 is the peak area of ​​the 004 characteristic diffraction peak in the X-ray diffraction pattern of the negative electrode active material powder, and C110 is the peak area of ​​the 110 characteristic diffraction peak in the X-ray diffraction pattern of the negative electrode active material powder.

[0054] S2, 50g Co3O4, 5g tetrapropylammonium hydroxide and 500mL cyclohexane were mixed evenly and subjected to hydrothermal reaction at 120℃ for 3h. After filtration, vacuum drying at 80℃ for 24h and sintering at 500℃ for 3h were obtained to obtain a porous metal oxide. Then, 500mL of Na3V2(PO4)3 cyclohexane organic solution with a concentration of 10wt% was added and dispersed evenly. After spray drying, carbonization was carried out at 1000℃ for 1h under an argon inert atmosphere to obtain Co3O4 / Na3V2(PO4)3 composite intermediate layer material B with a particle size D50 of 20.0μm and a porosity of 18%.

[0055] S3, 10g of Co3O4 / Na3V2(PO4)3 composite intermediate layer material B was added to 100mL of cyclohexane solution to prepare a suspension with a mass concentration of 10%, then 100g of etched graphite A was added, dispersed evenly, filtered, and then carbonized at 1000℃ for 1h under an argon inert atmosphere to obtain Co3O4 / Na3V2(PO4)3 coated graphite composite material C;

[0056] S4, the composite material C was transferred to a tube furnace and vapor-deposited at 1000℃ for 1 hour using ethane as the carbon source to obtain amorphous carbon / Co3O4 / Na3V2(PO4)3 coated graphite composite material D.

[0057] Comparative Example 1:

[0058] 100g of artificial graphite and 10g of asphalt were mixed evenly in a ball mill. Then, the mixture was heated to 250℃ and held for 1 hour in an inert argon atmosphere. After that, the mixture was heated to 800℃ and carbonized for 3 hours. Finally, the mixture was allowed to cool naturally to room temperature in an inert atmosphere and then pulverized to obtain the artificial graphite material.

[0059] Comparative Example 2

[0060] The etched graphite A prepared in S1 of Example 1 was transferred to a tube furnace and deposited at 850°C for 3 hours using methane as the carbon source to obtain an amorphous carbon-coated graphite composite material.

[0061] Comparative Example 3

[0062] S1, weigh 100g of artificial graphite, 300g of concentrated sulfuric acid and 20g of potassium permanganate and mix them. Then, chemically oxidize them at 100℃ for 6h to obtain graphite oxide. Then, transfer it to a tube furnace and introduce a mixture of ammonia and argon (volume ratio NH3:Ar = 1:10). Then, heat it to 800℃ for carbonization for 3h to obtain etched graphite A.

[0063] S2, 30g SnO was added to 600mL of a 5wt% NaTi2(PO4)3 carbon tetrachloride organic solution, dispersed evenly, spray-dried, and then carbonized at 800℃ for 3h under an argon inert atmosphere to obtain SnO / NaTi2(PO4)3 composite intermediate layer material B.

[0064] S3, 8g of SnO / NaTi2(PO4)3 composite intermediate layer material was added to 160mL of carbon tetrachloride to prepare a suspension with a mass concentration of 5%, then 100g of etched graphite A was added, dispersed evenly, filtered, and then carbonized at 800℃ for 3h under an argon inert atmosphere to obtain SnO / NaTi2(PO4)3 coated graphite composite material C.

[0065] S4. The composite material C was transferred to a tube furnace and vapor-deposited at 850°C for 3 hours using methane as the carbon source to obtain amorphous carbon / SnO / NaTi2(PO4)3 coated graphite composite material D.

[0066] Comparative Example 4

[0067] Compared to Example 1, step S1 was omitted, and step S3 used graphite (specific surface area 1.2 m²) that had been carbonized at 800°C for 3 hours. 2 / g, OI value 3.0) replaces etched graphite A, otherwise the same as in Example 1.

[0068] Performance testing of the materials prepared in the above embodiments and comparative examples:

[0069] (1) SEM testing

[0070] The amorphous carbon / SnO / NaTi2(PO4)3-coated graphite composite material D prepared in Example 1 was subjected to SEM testing, and the test results are as follows. Figure 1 As shown.

[0071] Depend on Figure 1As can be seen from the results, the composite material prepared in Example 1 is granular with a uniform size distribution and a particle size between 8 and 15 μm.

[0072] (2) Physical and chemical performance testing

[0073] The composite materials prepared in the examples and comparative examples were tested for powder electrical conductivity, powder compaction density, specific surface area, particle size, degree of graphitization, and metal element content.

[0074] Testing of powder conductivity: The composite materials prepared in the examples and comparative examples were pressed into block structures, and then the conductivity of the powder was tested using a four-probe tester.

[0075] Test of powder compaction density: Weigh a certain mass of the composite material powder prepared in the example and comparative example and place it in the mold. Press it with a pressure of 2T (using a powder compaction density meter, place 1g of powder in a fixed container and press it with a pressure of 2T, let it stand for 10s, then calculate the volume under pressure and calculate the compaction density). Calculate the powder compaction density.

[0076] Specific surface area, particle size, and degree of graphitization were determined according to the methods in the national standard GB / T-24533-2019 "Graphite Anode Materials for Lithium-ion Batteries".

[0077] The content of metallic elements was determined by the EDS method.

[0078] The results are shown in Table 1.

[0079] Table 1

[0080]

[0081] As can be seen from Table 1, the resistivity of the graphite composite material obtained by the present invention is significantly lower than that of the comparative example. This is because the surface of the negative electrode material is doped with metal oxides with high electronic conductivity, which reduces its electronic resistivity. In addition, the oxides have the characteristic of high tap density, which increases the compaction density of the powder. At the same time, the metal oxides have a catalytic effect, which increases the graphitization degree of the material during the carbonization process.

[0082] (3) Button cell battery test

[0083] The composite materials used in the examples and comparative examples were assembled into coin cells as negative electrode materials for lithium-ion batteries. 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 = 95g:1g:4g:220mL. A lithium metal sheet was used as the counter 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 1.2mol / L. The separator was a polyethylene (PE), polypropylene (PP), or polypropylene (PEP) composite membrane. The coin cell assembly was carried out 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, initial efficiency, and liquid absorption capacity of the coin cells were tested. The test results are shown in Table 2.

[0084] Table 2

[0085]

[0086] As shown in Table 2, the lithium-ion battery using the artificial graphite composite material obtained in the examples as the negative electrode material exhibits significantly higher initial discharge specific capacity and initial charge-discharge efficiency than the graphite composite material prepared in the comparative examples. This is because the fast-ion conductor, which consumes fewer lithium ions and its metal oxides during overcharging and over-charging, possesses high specific capacity and electronic conductivity, reducing irreversible capacity during charge-discharge processes and improving the overall specific capacity and initial efficiency of the composite material. Furthermore, the material prepared in the examples has a high specific surface area, enhancing its liquid absorption capacity.

[0087] (4) Pouch battery test:

[0088] The composite materials used in the examples and comparative examples were slurryed and coated to prepare negative electrode sheets, using ternary materials (LiNi). 1 / 3 Co 1 / 3 Mn 1 / 3 A 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.

[0089] Testing the cycle performance and rate performance of pouch cells:

[0090] Rate performance test conditions: charging rate: 1C / 2C / 3C / 5C, discharging rate: 1C; voltage range: 2.8-4.2V; temperature: 25±3℃; constant current ratio of the test battery.

[0091] The cycle test conditions are: charge / discharge rate 2C / 2C, voltage range: 2.8-4.2V; temperature: 25±3℃, number of cycles: 500.

[0092] The results are shown in Table 3.

[0093] Table 3

[0094]

[0095] As can be seen from Table 3, the pouch battery prepared from the composite material of the present invention has a better constant current ratio. The reason is that the graphite composite material prepared in Examples 1-3 is coated with a fast ion conductor, which has high lithium-ion conductivity, improving the fast charging performance of the material, that is, improving the constant current ratio of the material, and improving the cycle performance.

[0096] The above description discloses only preferred embodiments of the present invention and should not be construed as limiting the scope of the present invention. Therefore, equivalent variations made in accordance with the claims of the present invention are still within the scope of the present invention.

Claims

1. A method for preparing a fast-ion composite material coated with graphite, comprising the following steps: Preparation of etched graphite: Graphite, concentrated sulfuric acid and potassium permanganate are mixed and reacted to obtain graphite oxide, which is then carbonized to obtain the etched graphite. Preparation of intermediate layer material: Metal oxide, organic template agent and organic solvent are mixed and subjected to hydrothermal reaction, sintered to obtain porous metal oxide, which is then added to the organic solvent solution of fast ion conductor, dispersed evenly, spray dried and carbonized to obtain composite intermediate layer material. Intermediate layer graphite coating: The prepared composite intermediate layer material is formulated into a suspension, etched graphite is added, the mixture is dispersed evenly, filtered to obtain a solid, and the solid is carbonized to obtain a material with intermediate layer graphite coating. Preparation of three-layer composite material: Carbon source gas vapor deposition was performed on the material with graphite in the middle layer to obtain a fast ion composite material with graphite.

2. The production method according to claim 1, characterized by, When preparing etched graphite, the weight ratio of graphite, concentrated sulfuric acid, and potassium permanganate is 100:100-500:10-30; the temperature of the mixture reaction is 50-150℃, and the time is 1-24h.

3. The preparation method according to claim 1, characterized in that, When preparing the intermediate layer material, the hydrothermal reaction temperature is 50-120℃, and the sintering temperature is 200-500℃.

4. The preparation method according to claim 1, characterized in that, When preparing the intermediate layer material, the concentration of the fast ion conductor in the organic solvent solution of the fast ion conductor is 1wt%-10wt%.

5. The preparation method according to claim 1, characterized in that, When preparing the intermediate layer material, the organic template agent is selected from at least one of tetrapropylammonium hydroxide and tetraethylammonium hydroxide; the organic solvents involved are all selected from at least one of carbon tetrachloride, N-methylpyrrolidone, cyclohexane and tetrahydrofuran.

6. The preparation method according to claim 1, characterized in that, When the intermediate layer is coated with graphite, the solid concentration in the suspension of the composite intermediate layer material is 1wt%-10wt%; the solvent used is selected from at least one of carbon tetrachloride, N-methylpyrrolidone and cyclohexane.

7. The application of the composite material prepared by the preparation method according to claim 1 as a battery negative electrode material.

8. A composite material of graphite coated with a fast ion composite, characterized in that, It is prepared by any one of the preparation methods according to claims 1 to 6.

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