A high-conductivity and high-thermal-conductivity graphite nanosheet-pitch-based carbon fiber modified carbon paper and its preparation method

Abstract

The present invention discloses a highly conductive and thermally conductive graphite nanosheet-asphalt-based carbon fiber modified carbon paper and a preparation method thereof. By introducing graphite nanosheets and asphalt-based carbon fibers, horizontal and longitudinal conductive and thermally conductive channels are formed, effectively improving the electrical conductivity and thermal conductivity of the carbon paper. The main steps include: 1) preparing asphalt-based carbon fibers and short-cut wet-process polyacrylonitrile-based carbon fiber composite felt; 2) preparing a graphite nanosheet dispersion; 3) introducing the graphite nanosheets into the carbon fiber composite felt; 4) introducing a phenolic resin, and drying and curing it; 5) carbonizing and graphitizing the treated carbon paper to obtain graphite nanosheet-asphalt-based carbon fiber modified carbon paper. The method provided by the present invention can prepare a modified carbon paper with high electrical conductivity and high thermal conductivity, which has the characteristics of strong process operability, high yield, low electrical resistance, low thermal resistance and high reliability, can effectively improve the energy conversion efficiency of fuel cells, and is suitable for large-scale batch industrial production.

Description

Technical Field

[0001] The present invention belongs to the field of carbon paper, and in particular relates to a high-electrical and high-thermal-conductivity graphite nanosheet-asphalt-based carbon fiber modified carbon paper and a preparation method thereof. Background Art

[0002] Due to factors such as global warming and the continuous depletion of non-renewable fossil energy, environmental pollution and energy crises are becoming increasingly prominent, and the global energy consumption structure is accelerating its transition towards a low-carbon economy. In this energy revolution, hydrogen energy, due to its clean and pollution-free nature, high energy density per unit mass, storability, renewability, and widespread availability, is considered a disruptive technology for the future energy revolution and has garnered renewed attention in both basic research and industrial applications. Hydrogen fuel cell vehicles, a major downstream application of hydrogen energy, are currently undergoing development. The gas diffusion layer (GDL) is a key component in hydrogen fuel cells, responsible not only for uniform gas distribution but also for current conduction and heat management. While traditional GDL materials, such as carbon paper, offer some electrical conductivity and permeability, their electrical and thermal conductivity still require improvement. This is particularly true in high-power density and fast-response hydrogen fuel cell applications. Due to internal temperature fluctuations and heat generated by chemical reactions, the GDL requires excellent thermal conductivity to ensure efficient heat transfer and distribution, prevent local overheating, and ensure stable fuel cell operation. Furthermore, high electrical conductivity is crucial for reducing the fuel cell's internal resistance and improving energy conversion efficiency.

[0003] Traditional carbon paper uses polyacrylonitrile-based carbon fibers as raw material. Due to the limitations of the raw material itself, its electrical and thermal conductivity is difficult to improve. However, emerging materials such as graphite nanosheets and pitch-based carbon fibers have excellent electrical and thermal conductivity and can be used to modify traditional carbon paper.

[0004] For example, graphite nanosheets, as a two-dimensional material, have excellent electrical and thermal conductivity. Evenly dispersing graphite nanosheets in carbon fiber paper can form a conductive and thermal conductive network, significantly improving the overall electrical and thermal conductivity of the material.

[0005] For example, asphalt-based carbon fiber has excellent properties such as high modulus, high thermal conductivity, good heat resistance and creep resistance. Compared with polyacrylonitrile-based carbon fiber, asphalt-based carbon fiber has a higher degree of graphitization and lower resistivity, which is beneficial to improving the electrical conductivity and thermal conductivity of carbon fiber paper.

[0006] The present invention introduces pitch-based carbon fibers into carbon paper by mixing them with short, wet-process polyacrylonitrile-based carbon fibers to form a felt. The carbon paper is then pre-impregnated with a dispersion of graphite nanosheets to uniformly adhere the graphite nanosheets to the carbon paper. This produces graphite nanosheet-pitch-based carbon fiber-modified carbon paper with high electrical and thermal conductivity. The preparation method offers strong process operability, high yield, low electrical and thermal resistance, and high reliability, making it suitable for large-scale industrial production. Summary of the Invention

[0007] The purpose of the present invention is to provide a highly conductive and thermally conductive graphite nanosheet-asphalt-based carbon fiber modified carbon paper and its preparation method, so as to solve the problems of poor electrical and thermal conductivity of carbon paper in the prior art, large internal resistance of the battery, and large thermal resistance, and effectively improve the energy conversion efficiency of the fuel cell.

[0008] 1. A highly conductive and thermally conductive graphite nanosheet-pitch-based carbon fiber modified carbon paper and its preparation method. The paper is characterized by comprising: pitch-based carbon fibers, short-cut wet-process polyacrylonitrile-based carbon fibers, graphite nanosheets, and carbon formed by high-temperature carbonization of phenolic resin; the preparation steps include:

[0009] S01, preparing a composite carbon fiber dispersion: mixing pitch-based carbon fibers of a certain length, short wet-process polyacrylonitrile-based carbon fibers, deionized water, and a modifier in a certain order and a certain proportion to obtain a composite carbon fiber dispersion;

[0010] S02, preparing a composite carbon fiber felt: using a composite carbon fiber dispersion as a raw material, preparing a composite carbon fiber felt through a wet felting and drying process;

[0011] S03, preparing a graphite nanosheet dispersion: mixing graphite nanosheets, a dispersant, and deionized water in a certain proportion, and dispersing the mixture at a certain speed for a certain time using a dispersing device to obtain a graphite nanosheet dispersion;

[0012] S04, introducing graphite nanosheets: introducing a graphite nanosheet dispersion into the composite carbon fiber felt by impregnation or lamination under the action of traction, and then drying at a certain temperature to obtain a graphite nanosheet-composite carbon fiber felt;

[0013] S05, introducing phenolic resin: introducing a high carbonization rate phenolic resin solution of a certain concentration into the graphite nanosheet-composite carbon fiber felt by a dipping or laminating process, and then drying at a certain temperature to obtain an impregnated graphite nanosheet-composite carbon fiber felt;

[0014] S06, hot pressing and curing: hot pressing and curing the impregnated graphite nanosheet composite carbon fiber felt obtained in step S05 at a certain temperature and pressure, and controlling the thickness to obtain a cured graphite nanosheet composite carbon fiber felt;

[0015] S07, high temperature carbonization and graphitization: the solidified graphite nanosheet composite carbon fiber felt obtained in S06 is sequentially carbonized and graphitized to obtain a highly conductive and thermally conductive graphite nanosheet-pitch-based carbon fiber modified carbon paper.

[0016] 2. Further, it is characterized in that the pitch-based carbon fiber in step S01 has a length of 100-600 μm and a thermal conductivity greater than 100 W / (m·K); the short wet-process polyacrylonitrile-based carbon fiber in step S01 has a length of 3-5 mm and is prepared by a wet process, and grooves can be observed on the surface; the mixing order in step S01 is to first add the modifier to deionized water, and then add the pitch-based carbon fiber and the polyacrylonitrile-based carbon fiber in sequence; the modifier in step S01 is one or more of polyethylene oxide (PEO), polyacrylamide (PAM), and sodium dodecylbenzene sulfonate (SDBS), with a mass concentration of 1-3‰, the mass concentration of the pitch-based carbon fiber is 0.1-3‰, and the mass concentration of the polyacrylonitrile-based carbon fiber is 0.3-5‰;

[0017] 3. Further, it is characterized in that the graphite nanosheets in step S03 have a sheet diameter of 2-10 μm and a thickness of 5-50 nm; the dispersant in step S03 is one or more of sodium carboxymethyl cellulose (CMC), hydroxypropyl methylcellulose (HPMC), and hydroxyethyl cellulose (HEC), the mass concentration of the graphite nanosheets is 1-5%, and the mass concentration of the dispersant is 1-5‰; the dispersion speed in step S03 is 300-3000 r / min, and the time is 1-24 hours;

[0018] 4. Furthermore, it is characterized in that the impregnation process in step S04 refers to immersing the composite carbon fiber felt in the graphite nanoplatelet dispersion; the coating process in step S04 refers to spraying the graphite nanoplatelet dispersion onto the composite carbon fiber felt; and the drying temperature in step S04 is 105-150°C;

[0019] 5. Furthermore, it is characterized in that the dipping process in step S05 refers to immersing the graphite nanosheet-composite carbon fiber felt into a certain concentration of high carbonization rate phenolic resin solution; the coating process in step S05 refers to spraying a certain concentration of high carbonization rate phenolic resin solution onto the graphite nanosheet-composite carbon fiber felt; the phenolic resin in step S05 has a residual carbon rate greater than 60%, and its solvent is anhydrous ethanol or deionized water with a mass concentration of 10-50%; the drying temperature in step S05 is 70-165°C;

[0020] 6. Furthermore, it is characterized in that the temperature of the hot pressing curing in step S06 is 180-210°C, the pressure is 0.1-5MPa, and the thickness is 50-500μm;

[0021] 7. Furthermore, it is characterized in that the carbonization temperature of step S07 is 1100-1500°C and the graphitization temperature is 2300-2800°C;

[0022] 8. A highly conductive and thermally conductive graphite nanosheet-pitch-based carbon fiber modified carbon paper, characterized in that the carbon paper is prepared by the method of any one of claims 1 to 7, has the characteristics of high conductivity and high thermal conductivity, and its horizontal thermal conductivity is greater than 15 W / (m·K), the longitudinal thermal conductivity is greater than 1 W / (m·K), and the resistivity is less than 6 mΩ·cm.

[0023] Compared with the prior art, the present invention has the following advantages.

[0024] (1) The present invention provides a method for preparing highly conductive and thermally conductive graphite nanosheet-pitch-based carbon fiber modified carbon paper, which obtains modified carbon paper with excellent electrical and thermal conductivity, greatly reduces the internal resistance and thermal resistance of the battery, and effectively improves the energy conversion efficiency of the fuel cell;

[0025] (2) The present invention adopts a method of mixing and dispersing asphalt-based carbon fibers and short-cut wet-process polyacrylonitrile-based carbon fibers into a felt, which allows some asphalt-based carbon fibers to be vertically inserted between the layers of carbon paper, significantly enhancing the longitudinal heat conduction capacity of the carbon paper, effectively reducing the longitudinal thermal resistance of the battery, and improving the heat dissipation efficiency of the battery;

[0026] (3) The present invention introduces graphite nanosheets by an impregnation or lamination process, which effectively solves the problem of difficult dispersion of nanomaterials such as graphite nanosheets, increases the introduction content of graphite nanosheets, and thus improves the electrical and thermal conductivity of carbon paper;

[0027] (4) The entire preparation process has few steps and is relatively simple to operate, making it suitable for industrial mass production. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a schematic diagram of the process flow of the present invention;

[0029] Figure 2 (a) is a plane scanning electron microscope image of a pitch-based carbon fiber-polyacrylonitrile-based carbon fiber composite carbon fiber felt;

[0030] Figure 2 (b) is a vertical scanning electron microscope image of a pitch-based carbon fiber-polyacrylonitrile-based carbon fiber composite carbon fiber felt;

[0031] Figure 3 (a) is a high-magnification scanning electron microscope image of traditional polyacrylonitrile-based carbon fiber paper;

[0032] Figure 3(b) is a high-magnification scanning electron microscope image of graphite nanosheet-pitch-based carbon fiber modified carbon paper;

[0033] Figure 3 (c) is a high-magnification scanning electron microscope image of the vertical surface of traditional polyacrylonitrile-based carbon fiber paper;

[0034] Figure 3 (d) is a high-magnification scanning electron microscope image of the vertical surface of the graphene nanosheet-pitch-based carbon fiber modified carbon paper;

[0035] Figure 4 (a) is a planar scanning electron micrograph of conventional polyacrylonitrile-based carbon fiber paper;

[0036] Figure 4 (b) is a planar scanning electron micrograph of graphite nanosheet-pitch-based carbon fiber modified carbon paper; Specific implementation methods

[0037] The highly conductive and thermally conductive graphite nanosheet-pitch-based carbon fiber modified carbon paper and its preparation method of the present invention are further described in conjunction with the accompanying drawings. The present invention is further described in detail below in conjunction with implementation cases.

[0038] Example 1

[0039] A method for preparing high electrical and thermal conductivity graphite nanosheet-pitch-based carbon fiber modified carbon paper, such as Figure 1 As shown, the following steps are included:

[0040] S01, preparing a composite carbon fiber dispersion: adding pitch-based carbon fibers with a length of 200 μm and a thermal conductivity of 1000 W / (m·K) and short-cut polyacrylonitrile-based carbon fibers with a length of 3 mm and a grooved surface structure prepared by a wet process to a mixed polyethylene oxide (PEO) aqueous solution, wherein the mass concentration of polyethylene oxide (PEO) is 2‰, the mass concentration of the pitch-based carbon fibers is 0.3‰, and the mass concentration of the polyacrylonitrile-based carbon fibers is 0.5‰, to obtain a composite carbon fiber dispersion;

[0041] S02, preparing a composite carbon fiber felt: using a composite carbon fiber dispersion as a raw material, preparing a composite carbon fiber felt through a wet felting and drying process;

[0042] S03, preparing a graphite nanosheet dispersion: mixing graphite nanosheets, hydroxyethyl cellulose (HEC), and deionized water, wherein the graphite nanosheets have a diameter of 2-10 μm, a thickness of 5-50 nm, a mass concentration of 2%, and a mass concentration of hydroxyethyl cellulose (HEC) of 2‰, and dispersing the mixture at 800 rpm for 2 h using a dispersing device to obtain a graphite nanosheet dispersion;

[0043] S04, introducing graphite nanosheets: introducing a graphite nanosheet dispersion into the composite carbon fiber felt through an impregnation process under the action of traction, and then drying at 105° C. to obtain a graphite nanosheet-composite carbon fiber felt;

[0044] S05, introducing phenolic resin: introducing a 10 wt.% high carbonization rate phenolic resin solution into the graphite nanosheet-composite carbon fiber felt through a dipping process, wherein the residual carbon rate of the phenolic resin is 68%, and the solvent is anhydrous ethanol; then drying at 75° C. to obtain the dipping graphite nanosheet-composite carbon fiber felt;

[0045] S06, hot pressing and curing: hot pressing and curing the impregnated graphite nanosheet composite carbon fiber felt obtained in step S05 at a temperature of 180° C. and a pressure of 0.2 MPa, and controlling the thickness to be 180 μm to obtain a cured graphite nanosheet composite carbon fiber felt;

[0046] S07, high temperature carbonization and graphitization: the solidified graphite nanosheet composite carbon fiber felt obtained in S06 is carbonized at 1300°C and graphitized at 2300°C in sequence to obtain highly conductive and thermally conductive graphite nanosheet-asphalt-based carbon fiber modified carbon paper.

[0047] Mixing pitch-based carbon fiber and short-cut wet-process polyacrylonitrile-based carbon fiber into felt can make the pitch-based carbon fiber distributed in the carbon felt in an orderly manner. The length of the pitch-based carbon fiber is 200μm, and the length of the short-cut polyacrylonitrile-based carbon fiber is 3mm, so Figure 2 In the figure, the short fibers marked with red dotted circles are pitch-based carbon fibers. Figure 2 As shown, a part of the asphalt-based carbon fibers are horizontally overlapped between the carbon fibers, which enhances the horizontal connection between the carbon fibers and enriches the thermal and electrical conductive paths in the horizontal direction of the carbon paper; another part of the asphalt-based carbon fibers are vertically inserted between the layers of the carbon felt to form a three-dimensional interlocking structure, forming an additional thermal conductive path in the vertical direction, thereby enhancing the thermal conduction efficiency of the modified carbon paper in the vertical direction.

[0048] After the introduction of graphite nanosheets, the conventional polyacrylonitrile-based carbon fiber carbon paper and the prepared graphite nanosheet-pitch-based carbon fiber modified carbon paper were characterized by scanning electron microscopy. Figure 3 As shown in the figure, graphite nanosheets adhere to and wrap the entire carbon fiber. The graphite nanosheets contact each other, adding more fine branches to the skeleton formed by the interwoven arrangement of carbon fibers. These fine branches bring complexity to the thermal and electrical conductive network, making the entire network more developed, thereby improving the thermal and electrical conductivity of the modified carbon paper.

[0049] Figure 4Scanning images of a conventional polyacrylonitrile-based carbon fiber paper and a carbon paper modified with graphite nanosheets and pitch-based carbon fibers. Compared to conventional polyacrylonitrile-based carbon fiber paper, the modified carbon paper has fewer pores on its surface, but the stacking structure of the carbon paper is still visible.

[0050] Example 2

[0051] The preparation process is basically the same as that in Example 1, except that the mass concentration of the asphalt-based carbon fiber is 0.15‰, and other process and material parameters are the same.

[0052] Example 3

[0053] The preparation process is basically the same as that of Example 1, except that the pitch-based carbon fiber used in the preparation process has a length of 500 μm and a thermal conductivity of 600 W / (m·K). Other process and material parameters are the same.

[0054] Example 4

[0055] The preparation process is basically the same as that of Example 1, except that pitch-based carbon fiber is not introduced, and other process and material parameters are the same.

[0056] Comparative Example

[0057] The preparation process is basically the same as that of Example 1, except that pitch-based carbon fibers and graphite nanosheets are not introduced, and other process and material parameters are the same.

[0058] The above examples 1-3 and the comparative example were tested, and the specific results are as follows:

[0059]

[0060]

[0061] Comparing Example 4 with the comparative example, the carbon paper prepared in Example 4, which incorporated a 2 wt.% dispersion of graphite nanoplatelets, increased the carbon paper's in-plane thermal conductivity from 10.89 W / (m·K) to 23.90 W / (m·K), its longitudinal thermal conductivity from 0.09 W / (m·K) to 1.34 W / (m·K), and its in-plane resistivity from 10.2 mΩ·cm to 5.61 mΩ·cm. The addition of graphite nanoplatelets provides more fine branches within the carbon paper's electrical and thermal conductivity network, significantly improving both its electrical and thermal conductivity.

[0062] Comparing Example 2 and Example 4, when preparing the carbon paper of Example 2, a graphite nanosheet dispersion with a content of 2wt.% was introduced, and a pitch-based carbon fiber with a content of 0.15wt.‰ was also introduced into the mixed carbon fiber dispersion; when preparing the carbon paper of Example 4, only a graphite nanosheet dispersion with a content of 2wt.% was introduced. The in-plane thermal conductivity of the carbon paper increased from 23.90W / (m·K) to 28.67W / (m·K), the longitudinal thermal conductivity increased from 1.34W / (m·K) to 2.61W / (m·K), and the in-plane resistivity decreased from 5.61mΩ·cm to 5.27mΩ·cm. The addition of pitch-based carbon fibers formed additional thermal and electrical conductive pathways in the carbon paper, further improving the thermal conductivity of the carbon paper and reducing the resistivity of the carbon paper.

[0063] Comparing Example 1 and Example 2, when preparing the carbon paper of Example 1, a graphite nanosheet dispersion with a content of 2wt.% was introduced, and a pitch-based carbon fiber with a content of 0.3wt.‰ was introduced into the mixed carbon fiber dispersion; when preparing the carbon paper of Example 2, a graphite nanosheet dispersion with a content of 2wt.% was introduced, and a pitch-based carbon fiber with a content of 0.15wt.‰ was introduced into the mixed carbon fiber dispersion. The in-plane thermal conductivity of the carbon paper increased from 28.67W / (m·K) to 32.37W / (m·K), the longitudinal thermal conductivity increased from 2.61W / (m·K) to 4.05W / (m·K), and the in-plane resistivity decreased from 5.27mΩ·cm to 4.77mΩ·cm. The electrical and thermal conductivity of the carbon paper increased with the increase of the content of the pitch-based carbon fiber in the carbon paper.

[0064] Comparing Example 3 with Example 1, the pitch-based carbon fiber length of the carbon paper in Example 3 is 500 μm and the thermal conductivity is 600 W / (m·K); the pitch-based carbon fiber length of the carbon paper in Example 1 is 200 μm and the thermal conductivity is 1000 W / (m·K). The planar thermal conductivity of the carbon paper decreased from 32.37 W / (m·K) to 31.62 W / (m·K), the longitudinal thermal conductivity decreased from 4.05 W / (m·K) to 1.82 W / (m·K), and the planar resistivity increased from 4.77 mΩ·cm to 5.14 mΩ·cm. It can be seen from the data that the length and thermal conductivity of the pitch-based carbon fiber have an impact on the electrical and thermal conductivity of the carbon paper finally prepared.

[0065] In summary, the present invention introduces asphalt-based carbon fibers and graphite nanosheets into carbon paper. The thermal conductivity of asphalt-based carbon fibers is better than that of traditional polyacrylonitrile-based carbon fibers, providing an additional conductive and thermal conductive pathway for carbon paper. At the same time, the addition of graphite nanosheet fillers further improves the conductive and thermal conductive network of carbon paper, making the graphite nanosheet-asphalt-based carbon fiber modified carbon paper have superior conductive and thermal conductive capabilities.

[0066] Obviously, the above embodiments of the present invention are merely examples for the purpose of clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. Those skilled in the art will appreciate that other variations or modifications can be made based on the above description. It is not necessary and impossible to enumerate all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing high electrical and thermal conductivity graphite nanosheet-pitch-based carbon fiber modified carbon paper, characterized in that: The main components include: pitch-based carbon fiber, short wet-process polyacrylonitrile-based carbon fiber, graphite nanosheets and carbon formed by high-temperature carbonization of phenolic resin; its production steps include: S01, preparing a composite carbon fiber dispersion: mixing pitch-based carbon fibers of a certain length, short wet-process polyacrylonitrile-based carbon fibers, deionized water, and a modifier in a certain order and a certain proportion to obtain a composite carbon fiber dispersion; S02, preparing a composite carbon fiber felt: using a composite carbon fiber dispersion as a raw material, preparing a composite carbon fiber felt through a wet felting and drying process; S03, preparing a graphite nanosheet dispersion: mixing graphite nanosheets, a dispersant, and deionized water in a certain proportion, and dispersing the mixture at a certain speed for a certain time using a dispersing device to obtain a graphite nanosheet dispersion; S04, introducing graphite nanosheets: introducing a graphite nanosheet dispersion into the composite carbon fiber felt by impregnation or lamination under the action of traction, and then drying at a certain temperature to obtain a graphite nanosheet-composite carbon fiber felt; S05, introducing phenolic resin: introducing a high carbonization rate phenolic resin solution of a certain concentration into the graphite nanosheet-composite carbon fiber felt by a dipping or laminating process, and then drying at a certain temperature to obtain an impregnated graphite nanosheet-composite carbon fiber felt; S06, hot pressing and curing: hot pressing and curing the impregnated graphite nanosheet composite carbon fiber felt obtained in step S05 at a certain temperature and pressure, and controlling the thickness to obtain a cured graphite nanosheet composite carbon fiber felt; S07, high temperature carbonization and graphitization: the solidified graphite nanosheet composite carbon fiber felt obtained in S06 is sequentially carbonized and graphitized to obtain a highly conductive and thermally conductive graphite nanosheet-pitch-based carbon fiber modified carbon paper.

2. The preparation method according to claim 1, characterized in that The pitch-based carbon fiber of step S01 has a length of 100-600 μm and a thermal conductivity greater than 100 W / (m·K); the short wet-process polyacrylonitrile-based carbon fiber of step S01 has a length of 3-5 mm and is prepared by a wet process, and grooves can be observed on the surface; the mixing order of step S01 is to first add the modifier to deionized water, and then add the pitch-based carbon fiber and the polyacrylonitrile-based carbon fiber in sequence; the modifier of step S01 is one or more of polyethylene oxide, polyacrylamide, and sodium dodecylbenzene sulfonate, with a mass concentration of 1-3‰, the mass concentration of the pitch-based carbon fiber is 0.1-3‰, and the mass concentration of the polyacrylonitrile-based carbon fiber is 0.3-5‰.

3. The preparation method according to claim 1, characterized in that The graphite nanosheets in step S03 have a sheet diameter of 2-10 μm and a thickness of 5-50 nm; the dispersant in step S03 is one or more of sodium carboxymethyl cellulose, hydroxypropyl methylcellulose, and hydroxyethyl cellulose, the mass concentration of the graphite nanosheets is 1-5%, and the mass concentration of the dispersant is 1-5‰; the dispersion speed in step S03 is 300-3000 r / min, and the time is 1-24 h.

4. The preparation method according to claim 1, characterized in that The impregnation process in step S04 refers to immersing the composite carbon fiber felt in the graphite nanosheet dispersion; the coating process in step S04 refers to spraying the graphite nanosheet dispersion onto the composite carbon fiber felt; the drying temperature in step S04 is 105-150°C.

5. The preparation method according to claim 1, characterized in that The dipping process in step S05 refers to immersing the graphite nanosheet-composite carbon fiber felt into a high carbonization rate phenolic resin solution of a certain concentration; the laminating process in step S05 refers to spraying a high carbonization rate phenolic resin solution of a certain concentration onto the graphite nanosheet-composite carbon fiber felt; the phenolic resin in step S05 has a residual carbon rate greater than 60%, and its solvent is anhydrous ethanol or deionized water with a mass concentration of 10-50%; the drying temperature in step S05 is 70-165°C.

6. The preparation method according to claim 1, characterized in that The temperature of the hot pressing curing in step S06 is 180-210° C., the pressure is 0.1-5 MPa, and the thickness is 50-500 μm.

7. The preparation method according to claim 1, characterized in that The carbonization temperature of step S07 is 1100-1500°C, and the graphitization temperature is 2300-2800°C.

8. A high electrical and thermal conductivity graphite nanosheet-pitch-based carbon fiber modified carbon paper, characterized in that: The carbon paper is prepared by the method of any one of claims 1 to 7 and has the characteristics of high electrical conductivity and high thermal conductivity. Its horizontal thermal conductivity is greater than 15 W / (m·K), its longitudinal thermal conductivity is greater than 1 W / (m·K), and its resistivity is less than 6 mΩ·cm.

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