Method for preparing double-coated graphite composite and lithium ion battery

Abstract

The application provides a preparation method of double-coated graphite composite material and a lithium ion battery, and comprises the following steps: providing carboxylated graphite and a first precursor, wherein the first precursor is prepared by the reaction of pitch, a cross-linking agent and an amino compound; mixing the carboxylated graphite and the first precursor and heating to react, so as to obtain a second precursor; providing an acid-based resin solution, adding the second precursor into the acid-based resin solution to perform hydrothermal reaction, and then drying and carbonizing, so as to obtain the double-coated graphite composite material. Compared with the prior art, the chemical bond connection between the inner core graphite material and the outer shell coating layer can be realized by the chemical method, the rate performance and the tap density are improved, the stable connection between the graphite material and the coating layer is realized, and the fast charging performance of the graphite material is improved.

Description

Technical Field

[0001] This application relates to the field of lithium-ion battery materials, specifically to a method for preparing double-coated graphite composite materials and lithium-ion batteries. Background Technology

[0002] The charging time of lithium-ion batteries increases with capacity, but with the increasingly fast pace of life, longer charging times can delay users' normal use of devices. Therefore, fast charging performance of lithium-ion batteries is an important direction for performance improvement today.

[0003] Currently, the main methods to improve the fast-charging performance of graphite materials in lithium-ion batteries are reducing particle size and coating with amorphous carbon. One common method for coating with amorphous carbon is solid-state melting and carbonization coating, which involves coating the graphite surface with molten resin. However, this coating method suffers from poor adhesion, easy material peeling leading to reduced cycle performance, and also reduces the tap density and compaction density of the graphite material, which is detrimental to the stability of the graphite material and cannot effectively improve the performance of lithium-ion batteries. Summary of the Invention

[0004] This application mainly provides a method for preparing double-coated graphite composite materials and a lithium-ion battery, which can achieve a stable connection between the graphite material and the coating layer, reduce impedance, and improve the fast-charging performance of the material.

[0005] To solve the above-mentioned technical problems, one technical solution adopted in this application is: to provide a method for preparing a double-coated graphite composite material, including providing carboxylated graphite and a first precursor, wherein the first precursor is prepared by reacting asphalt, a crosslinking agent, and an amino compound; mixing carboxylated graphite and the first precursor and heating to react to obtain a second precursor; providing an acid-based resin solution, adding the second precursor to the acid-based resin solution for a hydrothermal reaction, and then drying and carbonizing to obtain the double-coated graphite composite material.

[0006] In one specific embodiment, providing carboxylated graphite and the first precursor includes mixing asphalt, crosslinking agent, pore-forming agent, and amino compound in a ball mill to obtain a first mixture with a mass ratio of asphalt: crosslinking agent: pore-forming agent: amino compound = 100: 10-30: 1-5: 10-50; and heating the first mixture to 300-500°C and reacting for 1-6 hours to obtain the first precursor.

[0007] In one specific embodiment, the crosslinking agent includes at least one selected from maleic anhydride, acetic anhydride, benzoic anhydride, acetic anhydride, and chromic anhydride.

[0008] In one specific embodiment, the pore-forming agent includes at least one of tetraethylammonium hydroxide, tetraethylammonium chloride, tetraethylammonium bromide, tetraethylammonium acetate, and tetraethylammonium bicarbonate.

[0009] In one specific embodiment, the amino compound includes at least one of pyridine, imidazole, quinoline, and pyrimidine.

[0010] In one specific embodiment, the mixing of the carboxylated graphite and the first precursor and the heating reaction includes heating the mixture of the carboxylated graphite and the first precursor to 500-800°C and curing it for 1-6 hours, wherein the mass ratio of the carboxylated graphite to the first precursor is 100:5-20.

[0011] In one specific embodiment, the step of adding the second precursor to the acid-based resin solution for a hydrothermal reaction, followed by drying and carbonization, includes adding the second precursor to the acid-based resin solution, heating it to 100-200°C, and performing a hydrothermal reaction at a pressure of 1-5 MPa for 1-6 hours to obtain a second mixture; drying the second mixture and then carbonizing it at a high temperature of 1000-1500°C for 1-6 hours; wherein the mass ratio of the carboxylated graphite to the acid-based resin solution is 100:50-200.

[0012] In one specific embodiment, providing the acid-based resin solution involves dissolving the acid-based resin in an organic solvent to prepare a 5-20 wt% acid-based resin solution, wherein the acid-based resin includes at least one selected from acrylic resin, malic resin, alkyd resin, fumaric resin, and diallyl isophthalate resin.

[0013] In one specific embodiment, providing carboxylated graphite and the first precursor includes pulverizing a coke-based raw material and heating it to 2800–3200 degrees Celsius for graphitization to obtain a graphite material; then reacting the graphite material in an oxidizing solution for 6–24 hours to obtain carboxylated graphite; wherein the oxidizing solution comprises a potassium permanganate solution and concentrated sulfuric acid in a volume ratio of 1:1, and the volume ratio of the graphite material to the oxidizing solution is 1000:200–1000.

[0014] To solve the above-mentioned technical problems, another technical solution adopted in this application is: to provide a lithium-ion battery, the lithium-ion battery including a negative electrode sheet, the negative electrode sheet being a double-coated graphite composite material prepared by the above-mentioned preparation method.

[0015] The beneficial effects of this application are as follows: Unlike the prior art, the embodiments of this application provide a method for preparing a double-coated graphite composite material and a lithium-ion battery. In this method, through the chemical reaction between carboxylated graphite, a first precursor and an acid-based resin, amide groups are used to achieve chemical bonding between the core graphite material and the outer shell coating layer, thereby improving the coating bonding force, reducing the interfacial impedance between the core material and the shell, improving the rate performance and tap density, and obtaining an isotropic amorphous carbon layer and a porous structure through carbonization, reducing expansion and improving the fast charging performance of the material. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0017] Figure 1 This is a SEM image of an embodiment of the double-coated graphite composite material provided in this application;

[0018] Figure 2 This is a schematic flowchart of an embodiment of the preparation method of the double-coated graphite composite material provided in the application. Detailed Implementation

[0019] The present application will now be described in further detail with reference to the accompanying drawings and embodiments. It should be noted that the following embodiments are for illustrative purposes only and do not limit the scope of the application. Similarly, the following embodiments are only some, not all, embodiments of the present application, and all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of this application.

[0020] The terms "first," "second," and "third" in this application are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first," "second," or "third" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified. All directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of this application are only used to explain the relative positional relationships and movements between components in a specific orientation (as shown in the figures). If the specific orientation changes, the directional indications also change accordingly. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion. A process, method, system, product, or device that includes a series of steps or units is not limited to the listed steps or units, but may optionally include steps or units not listed, or may optionally include other steps or units inherent to these processes, methods, products, or devices.

[0021] In this document, the term "implementation" means that a specific feature, structure, or characteristic described in connection with an implementation may be included in at least one implementation of this application. The appearance of this phrase in various places in the specification does not necessarily refer to the same implementation, nor is it a separate or alternative implementation mutually exclusive with other implementations. It will be explicitly and implicitly understood by those skilled in the art that the implementations described herein can be combined with other implementations.

[0022] Please see Figure 2 , Figure 2 This is a schematic flowchart of an embodiment of the preparation method of the double-coated graphite composite material provided in the application. It should be noted that if substantially the same result is obtained, this embodiment is not necessarily identical. Figure 2 The illustrated process sequence is limited. For example... Figure 2 As shown, this embodiment includes:

[0023] S100: Provides carboxylated graphite and a first precursor, the first precursor being prepared by reacting pitch, a crosslinking agent, and an amino compound.

[0024] It provides carboxylated graphite and the first precursor.

[0025] The first precursor can be prepared by reacting asphalt, a crosslinking agent, and an amino compound. The asphalt and the amino compound react under the action of the crosslinking agent to obtain amino-crosslinked asphalt, which is the main component of the first precursor that participates in subsequent reactions.

[0026] Optionally, the crosslinking agent may specifically include at least one of maleic anhydride, acetic anhydride, benzoic anhydride, acetic anhydride, and chromic anhydride. This type of anhydride-based crosslinking agent can undergo a dehydration reaction, thereby forming pores on the asphalt surface. This facilitates the subsequent formation of a porous structure of an amorphous carbon layer, thereby reducing material expansion and improving liquid retention performance.

[0027] Optionally, a pore-forming agent can be added during the preparation of the first precursor. The asphalt, crosslinking agent, pore-forming agent and amino compound are reacted and carbonized to give the amino-crosslinked asphalt a porous structure. In subsequent processes, porous and isotropic amorphous carbon can be coated on the graphite material, reducing the expansion of the coating material and improving the liquid retention performance of the material.

[0028] Specifically, the process for preparing the first precursor can be as follows: Asphalt, crosslinking agent, pore-forming agent, and amino compound are added to a ball mill and mixed evenly to obtain a first mixture. The first mixture is then transferred to a carbonization furnace and heated to 300–500°C for 1–6 hours to obtain the first precursor. The mass ratio of asphalt, crosslinking agent, pore-forming agent, and amino compound can be asphalt:crosslinking agent:pore-forming agent:amino compound = 100:10–30:1–5:10–50.

[0029] Specifically, the pore-forming agent may include at least one of tetraethylammonium hydroxide, tetraethylammonium chloride, tetraethylammonium bromide, tetraethylammonium acetate, and tetraethylammonium bicarbonate. This type of pore-forming agent contains nitrogen; when heated, it decomposes to release gas used for pore formation. Simultaneously, it can dope nitrogen into the amino-crosslinked pitch, thereby improving the material's electronic conductivity. Furthermore, this type of pore-forming agent is alkaline, which can neutralize anhydride-type crosslinking agents to a certain extent, creating an alkaline environment that is beneficial for subsequent reactions between carboxylated graphite, amino-crosslinked pitch, and acid-based resins.

[0030] Optionally, the amino compound may specifically include at least one of pyridine, imidazole, quinoline, and pyrimidine. The amino compound may be an organic basic amino compound as described above. Such compounds are adaptable to alkaline environments, exhibit a certain pore-forming effect during decomposition, and, compared to inorganic amino compounds, do not leave excess impurities in the first precursor, which is beneficial for subsequent reactions between carboxylated graphite, amino-crosslinked pitch, and acid-based resins.

[0031] Alternatively, carboxylated graphite can be prepared using coke-based raw materials and an oxidizing agent. The specific process for preparing carboxylated graphite involves first graphitizing the coke-based raw material, and then treating it with an oxidizing agent to oxidize the graphite and obtain carboxylated graphite. For example, the coke-based raw material can be pulverized and heated to 2800–3200℃ for graphitization for 48–60 hours to obtain graphite material. This graphite material is then placed in an oxidizing solution and reacted for 6–24 hours to obtain carboxylated graphite.

[0032] Specifically, the oxidizing solution can include a potassium permanganate solution and concentrated sulfuric acid in a 1:1 volume ratio. The volume ratio of graphite material to the oxidizing solution is 100:200 to 1000. Concentrated sulfuric acid can react with potassium permanganate to form manganese heptaoxide, a highly oxidizing substance. When calculating the volume ratio of graphite material to the oxidizing solution, the required volume of the oxidizing solution can be determined by calculating the molar amounts of manganese heptaoxide and concentrated sulfuric acid in the oxidizing solution and their oxidizing power.

[0033] Optionally, the concentration of potassium permanganate solution can be 0.05 mol / L, and the concentration of concentrated sulfuric acid can be 16 mol / L.

[0034] Optionally, the particle size of the coke raw material can be pulverized to 6-15 μm to facilitate full graphitization and to facilitate the subsequent coating process.

[0035] Furthermore, after oxidizing the graphite material with an oxidizing solution, it can be washed with deionized water and then vacuum dried to obtain carboxylate graphite with a low impurity content.

[0036] S200: Mix carboxylate graphite and the first precursor and heat to react, yielding the second precursor.

[0037] Carboxylated graphite and a first precursor are mixed and heated to react, yielding a second precursor. During this process, the amino-crosslinked pitch in the first precursor coats the surface of the carboxylated graphite. The amidation reaction between amino and carboxyl groups enhances the bonding strength of the coating, thereby improving the performance of the graphite material.

[0038] In step S200, the mixture of carboxylated graphite and the first precursor can be heated to 500–800°C for 1–6 hours for a curing reaction. The mass ratio of carboxylated graphite to the first precursor can be 100:5–20. This curing reaction allows the amino-crosslinked pitch to coat the carboxylated graphite, forming a soft carbon layer of suitable thickness, increasing the tap density of the material, and reducing impedance.

[0039] S300: Provides an acid-based resin solution, adds the second precursor to the acid-based resin solution for a hydrothermal reaction, then dries and carbonizes to obtain a double-coated graphite composite material.

[0040] The second precursor obtained in step S200 is added to an acid-based resin solution for a hydrothermal reaction. The mixture after the hydrothermal reaction is dried and carbonized to obtain a double-coated graphite composite material. After the reaction in step S200, the surface of the carboxylated graphite is coated with a soft carbon layer formed by amino-crosslinked pitch. After adding the second precursor containing this graphite material to the acid-based resin solution for a hydrothermal reaction, the amino groups in the soft carbon layer can form chemical bonds with the acid-based resin, thereby stably coating the acid-based resin in the soft carbon layer. During the drying and carbonization process, the acid-based resin can form a hard carbon layer, resulting in a double-coated graphite composite material with a double-layer coating structure.

[0041] Specifically, a second precursor can be added to an acid-based resin solution, heated to 100–200°C, and pressurized to 1–5 MPa for a hydrothermal reaction for 1–6 hours, causing the acid-based resin to coat the soft carbon layer. The second mixture obtained from the hydrothermal reaction is dried, and then heated to 1000–1500°C for carbonization for 1–6 hours, thereby carbonizing the outer layer of acid-based resin to form a hard carbon layer, resulting in a double-coated graphite composite material with a double-layer coating structure. By utilizing the chemical reactions between the functional groups of carboxylated graphite, amino-crosslinked pitch, and acid-based resin, chemical bonds are used to connect the graphite core, soft carbon layer, and hard carbon layer, forming a relatively stable double-coated structure, which can improve the material's fast-charging performance.

[0042] Optionally, the mass ratio of carboxylated graphite to acid-based resin solution can be 100:50 to 200 to ensure that the thickness of the coated hard carbon layer is uniform and meets the material performance requirements.

[0043] Optionally, an acid-based resin solution can be prepared by dissolving the acid-based resin in an organic solvent. The mass concentration of the acid-based resin solution can be 5–20 wt%. The acid-based resin may include at least one of acrylic resin, malic resin, alkyd resin, fumaric resin, and diallyl isophthalate resin. These acid-based resins are relatively common and readily available, which can reduce the cost of the preparation process. The organic solvent may be butanol, acetone, carbon tetrachloride, or other solvents capable of dissolving acid-based resins. The mass concentration of the solution can be determined based on the solvent's ability to dissolve the acid-based resin, as well as the efficiency and progress of the reaction.

[0044] This application also provides a lithium-ion battery. The lithium-ion battery includes a negative electrode, which may include a double-coated graphite composite material prepared using the above-described preparation method. This double-coated graphite composite material utilizes chemical bonds to connect the core and the coating layer, thereby forming a stable coating effect. The coating layer can reduce material expansion and impedance, thus improving the fast-charging performance of the lithium-ion battery.

[0045] The double-coated graphite composite materials prepared in Examples 1 to 3 below can be applied to lithium-ion batteries.

[0046] Example 1

[0047] Step S1: 100g of petroleum coke was pulverized to 10μm and graphitized at 3000℃ for 54h. After cooling to room temperature, the resulting graphite material was placed in 500g of oxidizing acid solution (volume ratio of potassium permanganate to concentrated sulfuric acid = 1:1, concentration of concentrated sulfuric acid 16mol / L, molar concentration of potassium permanganate 0.05mol / L) and reacted for 12h. After washing with deionized water, it was vacuum dried at 80℃ for 24h to obtain carboxylate graphite.

[0048] Step S2: Add 100g asphalt, 20g maleic anhydride, 3g tetraethylammonium hydroxide and 30g pyridine to a ball mill and mix evenly. Then transfer the mixture to a carbonization furnace and heat it to 400℃ for 3h under an inert argon atmosphere to obtain amino-crosslinked asphalt as the first precursor.

[0049] Step S3: Dissolve 10g of acrylic resin in 100g of butanol organic solvent to prepare a 10wt% solution as an acid-based resin solution;

[0050] Step S4: Mix 100g of carboxylated graphite with 10g of the first precursor and heat to 600℃ for 3h to obtain the second precursor; then add the second precursor to 100g of acid-based resin solution and react hydrothermally at 150℃ and 3MPa for 3h, then vacuum dry at 80℃ for 24h and carbonize at 1250℃ for 3h to obtain the double-coated graphite composite material.

[0051] Example 2

[0052] Step S1: 100g of needle coke was pulverized to 6μm and graphitized at 2800℃ for 60h. After cooling to room temperature, the resulting graphite material was placed in 200g of oxidizing acid solution (volume ratio of potassium permanganate to concentrated sulfuric acid = 1:1, concentration of concentrated sulfuric acid 16mol / L, molar concentration of potassium permanganate 0.05mol / L) and reacted for 24h. After washing with deionized water, it was vacuum dried at 80℃ for 24h to obtain carboxylate graphite.

[0053] Step S2: Add 100g asphalt, 10g acetic anhydride, 1g tetraethylammonium chloride and 10g imidazole to a ball mill and mix evenly. Then transfer the mixture to a carbonization furnace and heat it to 300℃ under an inert argon atmosphere to cure for 6 hours to obtain amino-crosslinked asphalt as the first precursor.

[0054] Step S3: Dissolve 5g of malic acid resin in 100g of butanol organic solvent to prepare a 5wt% solution as the acid-based resin solution;

[0055] Step S4: Mix 100g of carboxylated graphite with 5g of the first precursor and heat to 500℃ for 6h to obtain the second precursor; then add the second precursor to 50g of acid-based resin solution and react hydrothermally at 100℃ and 5MPa for 6h, then vacuum dry at 80℃ for 24h and carbonize at 1000℃ for 6h to obtain the double-coated graphite composite material.

[0056] Example 3

[0057] Step S1: 100g of pitch coke was pulverized to 15μm and graphitized at 3200℃ for 48h. After cooling to room temperature, the resulting graphite material was placed in 1000g of oxidizing acid solution (volume ratio: potassium permanganate: concentrated sulfuric acid = 1:1, concentrated sulfuric acid concentration 16mol / L, potassium permanganate molar concentration 0.05mol / L) and reacted for 6h. After washing with deionized water, it was vacuum dried at 80℃ for 24h to obtain carboxylate graphite.

[0058] Step S2: Add 100g asphalt, 30g benzoic anhydride, 5g tetraethylammonium bromide and 50g quinoline to a ball mill and mix evenly. Then transfer the mixture to a carbonization furnace and heat it to 500℃ for 1h under an inert argon atmosphere to obtain amino-crosslinked asphalt as the first precursor.

[0059] Step S3: Dissolve 20g of fumaric acid resin in 100g of butanol organic solvent to prepare a 20wt% solution as the acid-based resin solution;

[0060] Step S4: Mix 100g of carboxylated graphite with 20g of the first precursor and heat to 800℃ for 1h to obtain the second precursor; then add the second precursor to 200g of acid-based resin solution and react hydrothermally at 200℃ and 1MPa for 1h, then vacuum dry at 80℃ for 24h and carbonize at 1500℃ for 1h to obtain the double-coated graphite composite material.

[0061] Two comparative examples are provided below for comparison with the preparation method of the double-coated graphite composite material described in this application.

[0062] Comparative Example 1: Unlike Example 1, in step S1, carboxylated graphite was replaced with artificial graphite, and in step S2, amino-crosslinked pitch was replaced with pitch. Other conditions and operations were the same as in Example 1.

[0063] Comparative Example 2: Unlike Example 1, no acidic resin solution was added. The detailed preparation process was as follows: 100g of carboxylated graphite was mixed with 10g of the first precursor and heated to 600℃ for 3h to obtain the second precursor; then carbonized at 1250℃ for 3h to obtain the double-coated graphite composite material.

[0064] The materials prepared in the above embodiments and comparative examples were subjected to the following performance tests.

[0065] The tests include:

[0066] (1) SEM (Scanning Electron Microscopy) test

[0067] The double-coated graphite 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, the double-coated graphite composite material exhibits a spherical structure with a uniform size distribution and a particle size between (10-15) μm.

[0068] (2) Physical and chemical properties and button cell testing

[0069] The interlayer spacing (D002), specific surface area, tap density, and powder compaction density (2T) of the double-coated graphite composite materials prepared in Examples 1-3 and the graphite composite materials prepared in Comparative Examples 1 and 2 were measured according to the methods in the national standard GB / T-24533-2019 "Graphite Anode Materials for Lithium-ion Batteries". Simultaneously, a four-probe tester was used to measure the powder resistivity of the materials. The test results are shown in Table 1.

[0070] The double-coated graphite composite materials from Examples 1-3 and the graphite composite materials from Comparative Examples 1 and 2 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 mixture of hard carbon composite material, CMC, SBR, SP, and H2O in a mass ratio of 94:2.5:1.5:2:150 was used to obtain the negative electrode sheet; a lithium sheet was used as the counter electrode; the electrolyte was LiPF6 (solvent: EC:DEC:PC:propylene glycol polyoxypropylene ether = 1:2:1:0.05, concentration 1.3 mol / L); the separator was a composite membrane of polyethylene (PE), polypropylene (PP), and polyethylene propylene (PEP). The coin cells were assembled in an argon-filled glove box. Electrochemical performance was tested on a Wuhan Landian CT2001A battery tester. The charge / discharge voltage range was 0.00V to 2.0V, and the charge / discharge rate was 0.1C. The initial discharge capacity and initial efficiency of the coin cells were tested, and the rate performance (1C / 0.1C) was also tested. The test results are shown in Table 1.

[0071] Table 1

[0072]

[0073] As can be seen from Table 1, the double-coated graphite composite material prepared in the examples is superior to the comparative example in terms of tap density and powder resistivity. This is because the double-coated graphite composite material prepared by acid-base reaction has chemical bond connection, low impedance, strong activity, reduced polarization, and can reduce powder resistivity.

[0074] (3) Pouch battery test:

[0075] The double-coated graphite composite materials of Examples 1-3 and the graphite composite materials of Comparative Examples 1 and 2 were slurried and coated to prepare negative electrode sheets. Lithium iron phosphate was used as the positive electrode and LiPF6 (solvent: EC:DEC:PC:=1:1:1, concentration 1.3mol / L) was used as the electrolyte to prepare a 5Ah soft pack battery.

[0076] Cyclic performance test: charge / discharge current 1.0C / 1.0C, voltage range 2.5-3.65V, number of cycles 500.

[0077] Rate performance testing: Testing the initial cycle DCR and constant current ratio under 2C charging conditions of the pouch battery.

[0078] The test results are shown in Table 2.

[0079] Table 2

[0080] Example 1 95.7 15.4 94.7 Example 2 96.3 16.4 93.8 Example 3 95.3 14.7 95.5 Comparative Example 1 92.4 22.1 90.4 Comparative Example 2 93.1 19.5 91.8

[0081] As shown in Table 2, compared with the comparative example, the cycling performance and constant current ratio of the double-coated graphite composite materials in Examples 1 to 3 are significantly better than those in the comparative example. The reason for this is that the double-coated graphite composite materials in the examples have a high specific surface area, which improves the liquid retention performance of the material and enhances the cycling performance; at the same time, the powder material has a low powder resistance, which can improve the constant current ratio.

[0082] The above description is only a partial embodiment of this application and does not limit the scope of protection of this application. Any equivalent device or equivalent process transformation made based on the content of this application specification and drawings, or directly or indirectly applied to other related technical fields, are similarly included within the scope of patent protection of this application.

Claims

1. A method for preparing a double-coated graphite composite material, characterized in that, include: Carboxylated graphite and a first precursor are provided, wherein the first precursor is prepared by reacting pitch, a crosslinking agent, and an amino compound; The carboxylated graphite and the first precursor are mixed and heated to react, yielding the second precursor; An acid-based resin solution is provided, and the second precursor is added to the acid-based resin solution for a hydrothermal reaction, followed by drying and carbonization to obtain the double-coated graphite composite material. The provision of carboxylated graphite and the first precursor includes: Asphalt, crosslinking agent, pore-forming agent, and amino compound are added to a ball mill and mixed evenly to obtain a first mixture with a mass ratio of asphalt: crosslinking agent: pore-forming agent: amino compound = 100: 10~30: 1~5: 10~50; The first mixture is heated to 300-500℃ and reacted for 1-6 hours to obtain the first precursor. The asphalt and amino compound react under the action of a crosslinking agent to obtain amino-crosslinked asphalt, which is the main component of the first precursor that participates in subsequent reactions.

2. The method for preparing the double-coated graphite composite material according to claim 1, characterized in that, The crosslinking agent includes at least one of maleic anhydride, acetic anhydride, benzoic anhydride, and chromic anhydride.

3. The method for preparing the double-coated graphite composite material according to claim 1, characterized in that, The pore-forming agent includes at least one of tetraethylammonium hydroxide, tetraethylammonium chloride, tetraethylammonium bromide, tetraethylammonium acetate, and tetraethylammonium bicarbonate.

4. The method for preparing the double-coated graphite composite material according to claim 1, characterized in that, The amino compound includes at least one of pyridine, imidazole, quinoline, and pyrimidine.

5. The method for preparing the double-coated graphite composite material according to claim 1, characterized in that, The mixing of the carboxylated graphite and the first precursor, followed by heating and reaction, comprises: The mixture of the carboxylated graphite and the first precursor is heated to 500-800°C and cured for 1-6 hours, wherein the mass ratio of the carboxylated graphite to the first precursor is 100:5-20.

6. The method for preparing the double-coated graphite composite material according to claim 1, characterized in that, The step of adding the second precursor to an acidic resin solution for a hydrothermal reaction, followed by drying and carbonization, includes: The second precursor is added to the acidic resin solution, heated to 100-200°C, and subjected to a hydrothermal reaction at a pressure of 1-5 MPa for 1-6 hours to obtain the second mixture. After drying the second mixture, heat it to 1000~1500℃ and carbonize it for 1~6 hours; The mass ratio of the carboxylated graphite to the acid-based resin solution is 100:50~200.

7. The method for preparing the double-coated graphite composite material according to claim 6, characterized in that, The provided acid-based resin solution includes: An acid-based resin is dissolved in an organic solvent to prepare a 5-20 wt% solution of the acid-based resin, wherein the acid-based resin includes at least one of acrylic resin, malic resin, alkyd resin, fumaric resin, and diallyl isophthalate resin.

8. The method for preparing the double-coated graphite composite material according to claim 1, characterized in that, The provision of carboxylated graphite and the first precursor includes: Coke-based raw materials are crushed and heated to 2800~3200℃ for graphitization to obtain graphite materials; The graphite material is placed in an oxidizing solution and reacted for 6-24 hours to obtain carboxylated graphite; The oxidation solution comprises a potassium permanganate solution and concentrated sulfuric acid in a volume ratio of 1:1, and the volume ratio of the graphite material to the oxidation solution is 100:200~1000.

Images