A method for preparing a graphene heat-conducting film

Abstract

This invention provides a method for preparing a graphene thermally conductive film, comprising: A) mixing graphene oxide, a solvent, a dispersant, and a binding agent to obtain a slurry; B) coating the slurry onto a substrate, drying it to form a film, and then separating the film from the substrate to obtain a graphene oxide thin film; C) carbonizing the graphene oxide thin film under a protective atmosphere; D) graphitizing the film obtained in step C) under a protective atmosphere; and E) pressing the film obtained in step D) to obtain a graphene thermally conductive film. The preparation method provided by this invention can reduce cracking and surface roughness during the drying process and improve the defects and edge disorder of graphene, thereby increasing the thermal conductivity of the graphene thermally conductive film.

Description

Technical Field

[0001] This invention relates to the field of thermal conductive films, and in particular to a method for preparing a graphene thermal conductive film. Background Technology

[0002] Among existing thermally conductive materials, graphene is a material composed of carbon atoms arranged in sp... 2 Hybridized orbitals form a hexagonal honeycomb lattice, resulting in a planar two-dimensional layered material with excellent physicochemical properties and a theoretical thermal conductivity as high as 5300 W / (m·K). Compared with traditional thermally conductive materials (graphite, aluminum, copper, etc.), it has high thermal conductivity and is lightweight, making it one of the ideal thermally conductive materials.

[0003] Currently, graphene thermal conductive films are mainly prepared using graphene oxide: graphene oxide is dispersed in a solvent to form a graphene oxide slurry, which is then coated onto a substrate using a blade coating method, dried to form a graphene oxide film, and finally the graphene oxide film is chemically or thermally reduced to obtain a graphene thermal conductive film.

[0004] In the process of preparing graphene thermally conductive films using the above method, the viscosity of the graphene oxide slurry increases with the increase of solid content and storage time. Higher viscosity can lead to film cracking and surface roughness during the drying process of the graphene oxide slurry to form the graphene oxide film, thus reducing the thermal conductivity of the resulting graphene thermally conductive film. Simultaneously, the thermal conductivity of graphene is closely related to the size of its sheets, the degree of sheet stacking, and internal structural defects. Because graphene oxide is rich in in-plane and edge oxygen-containing functional groups, the sp(s) of graphene oxide... 2 The hybrid carbon extended network is destroyed, requiring high-temperature reduction of graphene oxide to remove these functional groups in order to restore the graphitized structure. However, this results in defects and disorder at the edges of the graphene, which reduces the thermal conductivity of the graphene. Summary of the Invention

[0005] In view of this, the present invention provides a method for preparing a graphene thermally conductive film. The preparation method provided by the present invention can reduce cracking and surface roughness during the drying and film formation process, improve the defects and edge disorder of graphene, and increase the thermal conductivity of the graphene thermally conductive film.

[0006] This invention provides a method for preparing a graphene thermally conductive film, comprising the following steps:

[0007] A) Graphene oxide, solvent, dispersant, and binding agent are mixed to obtain a slurry;

[0008] B) The slurry is coated onto a substrate, dried to form a film, and then the film is separated from the substrate to obtain a graphene oxide film.

[0009] C) The graphene oxide film is carbonized under a protective atmosphere;

[0010] D) The film obtained in step C) is graphitized under a protective atmosphere;

[0011] E) Press the film obtained in step D) to obtain a graphene thermal conductive film.

[0012] Preferably, in step A), the dispersing agent is at least one of ethanolamine, AMP-95, and silicone resin.

[0013] Preferably, in step A), the connecting agent is boric acid and / or titanium diboride.

[0014] Preferably, in step A), the amount of the dispersing agent is 5% to 50% of the mass of graphene oxide.

[0015] Preferably, in step A), the amount of the connecting agent is 0.1% to 0.5% of the mass of graphene oxide.

[0016] Preferably, in step C), the carbonization treatment is carried out at a temperature of 800–1500°C for 1–5 hours.

[0017] Preferably, in step D), the graphitization treatment is carried out at a temperature of 2600–3100°C for 3–5 hours.

[0018] Preferably, in step E), the pressure of the pressing process is 30-80 MPa, and the holding time is 30-300 min.

[0019] Preferably, in step B):

[0020] The coating thickness is 3-7 mm;

[0021] The drying temperature is 30–80°C.

[0022] Preferably, in step A), the solvent is selected from at least one of water, ethanol, and N,N-dimethylformamide;

[0023] The relationship between the amount of graphene oxide and the solvent is such that the solid content of graphene oxide in the solvent is 2-5 wt%.

[0024] The method for preparing a graphene thermally conductive film provided by this invention involves first mixing graphene oxide, a solvent, a dispersant, and a binding agent to obtain a slurry; then, coating the slurry onto a substrate and drying it to form a film; subsequently, subjecting the film to a series of heat treatments, including carbonization and graphitization; and finally, pressing to obtain the graphene thermally conductive film. Specifically, the introduction of a dispersant and a binding agent during the slurry preparation process reduces the slurry viscosity, resulting in uniform coating and a smooth film; the binding agent links and repairs the graphene sheets. The combined effect of these two agents, coupled with the process parameters of this invention (especially the subsequent heat treatment parameters), effectively improves the thermal conductivity of the final graphene thermally conductive film.

[0025] Experimental results show that the preparation method of the present invention produces a smooth and flat film, and the final graphene thermal conductive film product has a thermal conductivity of over 1476 W / (m·K), exhibiting high thermal conductivity. Attached Figure Description

[0026] 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 embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0027] Figure 1 The effect of dispersant dosage on the viscosity of graphene slurry is shown in the figure.

[0028] Figure 2 The effect of dispersant dosage on the viscosity of graphene slurry is shown in the figure.

[0029] Figure 3 This is a process flow diagram of Example 1;

[0030] Figure 4 This is a comparison chart of the film-forming effect before and after adding the dispersing agent in step B) of Example 1;

[0031] Figure 5 This is a cross-sectional SEM image of the graphene thermally conductive film obtained in Example 1. Detailed Implementation

[0032] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0033] In this article, the technical features described in an open-ended manner include both closed technical solutions composed of the listed features and open technical solutions that include the listed features.

[0034] The term “and / or” as used herein includes any and all combinations of one or more of the related listed items.

[0035] In this document, numerical ranges are referred to as continuous unless otherwise specified, and include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when a range refers to an integer, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are incorporated.

[0036] In this article, when referring to units for data ranges, if the unit is only followed by the right endpoint, it indicates that the units for the left and right endpoints are the same. For example, 30–120 min means that the units for the left endpoint “30” and the right endpoint “120” are both in minutes.

[0037] This document only specifically discloses some numerical ranges. However, any lower limit can be combined with any upper limit to form an unspecified range; and any lower limit can be combined with other lower limits to form an unspecified range, just as any upper limit can be combined with any other upper limit to form an unspecified range. Furthermore, each individually disclosed point or single value can itself serve as a lower or upper limit and be combined with any other point or single value or with other lower or upper limits to form an unspecified range.

[0038] This invention provides a method for preparing a graphene thermally conductive film, comprising the following steps:

[0039] A) Graphene oxide, solvent, dispersant, and binding agent are mixed to obtain a slurry;

[0040] B) The slurry is coated onto a substrate, dried to form a film, and then the film is separated from the substrate to obtain a graphene oxide film.

[0041] C) The graphene oxide film is carbonized under a protective atmosphere;

[0042] D) The film obtained in step C) is graphitized under a protective atmosphere;

[0043] E) Press the film obtained in step D) to obtain a graphene thermal conductive film.

[0044] The preparation method provided by this invention overcomes, on the one hand, the technical problems in the prior art that require graphene oxide slurry with high solid content to prepare graphene thermal conductive films, which lead to cracking and surface roughness during the drying process of graphene oxide films; on the other hand, it solves the problems of graphene sheet defects and edge disorder in graphene thermal conductive films prepared from graphene oxide; by overcoming the above two problems, the thermal conductivity of graphene thermal conductive films is ultimately improved.

[0045] Regarding step A) :

[0046] A) Mix graphene oxide, solvent, dispersant and binding agent to obtain slurry.

[0047] In this invention, the source of the graphene oxide is not particularly limited; it can be any commercially available product.

[0048] In this invention, the solvent is preferably at least one of water, ethanol, and N,N-dimethylformamide. In this invention, the preferred ratio of graphene oxide to solvent is such that the solid content of graphene oxide in the solvent (i.e., the ratio of solid mass to total solid-liquid mass) is 2–5 wt%, specifically 2 wt%, 3 wt%, 4 wt%, or 5 wt%.

[0049] In this invention, the dispersing agent is at least one of ethanolamine, AMP-95, and organosilicon resin, more preferably two of ethanolamine, AMP-95, and organosilicon resin, and most preferably ethanolamine and organosilicon resin. The organosilicon resin is preferably an amine-functionalized siloxane resin (i.e., an amine-functionalized siloxane resin); specifically, the amine-functionalized siloxane resin is preferably at least one of 3-aminopropylmethyldimethylsiloxane and (3-aminopropyl)dimethylmethoxysilane. The introduction of the above-mentioned dispersing agent in this invention can reduce the viscosity of the slurry and prevent cracking and surface roughness during the film formation process of the graphene oxide slurry. Specifically, the introduction of the above-mentioned dispersing agent introduces hydroxyl groups, which can form hydrogen bonds with the solvent water during the slurry dispersion process, reducing the viscosity of the slurry; and during the drying and heat treatment of the graphene oxide slurry, it can interact with the interlayer hydrogen bonds and van der Waals forces of the graphene oxide sheets, self-assembling into an oriented arrangement to make the film smooth and flat. Moreover, the present invention can only achieve the desired effect by introducing the above-mentioned specific dispersing agent. If other dispersing agents such as hydroxypropyl methylcellulose are used, the product effect will not be improved.

[0050] In this invention, the amount of the dispersing agent is preferably 5% to 50% of the mass of graphene oxide, specifically 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, and 50%. When the dispersing agent is ethanolamine and silicone resin, the amount of ethanolamine is preferably 20% of the mass of graphene oxide, and the amount of silicone resin is preferably 30% of the mass of graphene oxide.

[0051] The applicant conducted a study on the dosage of dispersing agents, using graphene oxide and water as the base slurry (solid content 5 wt%), and added different amounts of ethanolamine dispersing agent. The effect of the dispersing agent dosage on the slurry viscosity is shown in [reference needed]. Figure 1 The vertical axis represents the percentage decrease in slurry viscosity, and the horizontal axis represents the amount of ethanolamine used (expressed as a percentage of the mass of graphene oxide). It can be seen that as the amount of dispersant ethanolamine increases, the slurry viscosity gradually decreases. When the amount of ethanolamine reaches approximately 15% of the mass of graphene oxide, the slurry viscosity remains essentially unchanged, with the percentage decrease maintained at around 0.4 (based on a base slurry viscosity of 1). Furthermore, when the two dispersants are used in combination, specifically with a base slurry of graphene oxide and water (solid content 5 wt%), after adding 20% ​​ethanolamine to reduce viscosity, different amounts of organosilicon resin (3-aminopropylmethyldimethylsiloxane) are added to further reduce viscosity. The results are as follows. Figure 2 As shown in the figure, the vertical axis represents the percentage decrease in slurry viscosity, and the horizontal axis represents the amount of silicone resin used (expressed as a percentage of the mass of graphene oxide). It can be seen that as the amount of silicone resin increases, the slurry viscosity gradually decreases. When the amount of silicone resin added reaches approximately 30% of the mass of graphene oxide, the slurry viscosity remains essentially unchanged, with the percentage decrease maintained at around 0.3. Overall, after mixing and adding the two dispersing agents (20% ethanolamine + 30% silicone resin), the viscosity reduction percentage of the graphene slurry is approximately 0.12.

[0052] In this invention, the connecting agent is boric acid and / or titanium diboride. The introduction of these connecting agents enables the repair of graphene defects and the connection of graphene sheets. Specifically, heteroatomic doping can effectively regulate the band structure and other properties of graphene, thereby improving product performance by changing the size or structure of graphene and connecting and repairing graphene sheets. In this invention, the preferred amount of the connecting agent is 0.1% to 0.5% of the mass of graphene oxide, specifically 0.1%, 0.2%, 0.3%, 0.4%, or 0.5%.

[0053] In this invention, the preferred method for mixing graphene oxide, solvent, dispersant, and binding agent is ultrasonic dispersion. The preferred power for ultrasonic dispersion is 720W; the preferred ultrasonic dispersion time is 30–120 min, specifically 30 min, 60 min, 90 min, or 120 min. The materials are then uniformly mixed through ultrasonic dispersion.

[0054] In this invention, after the above mixing, homogenization and degassing are preferably further performed. There are no special limitations on the homogenization and degassing operation in this invention; it can be performed according to conventional procedures in the art. After the above treatment, a slurry is obtained.

[0055] Regarding step B) :

[0056] B) The slurry is coated onto a substrate, dried to form a film, and then the film is separated from the substrate to obtain a graphene oxide film.

[0057] In this invention, the substrate is preferably a PP (polypropylene) substrate, a PI (polyimide) substrate, or a PET (polyethylene terephthalate) substrate. The coating method for applying the slurry to the substrate is not particularly limited in this invention; any conventional coating method in the art, such as blade coating, is acceptable. The coating thickness is preferably 3–7 mm, specifically 3 mm, 4 mm, 5 mm, 6 mm, or 7 mm.

[0058] In this invention, after coating, the material is dried to form a film. The drying temperature is preferably 30–80°C, specifically 30°C, 40°C, 50°C, 60°C, 70°C, or 80°C. After the above drying process, the formed film is separated from the substrate to obtain a graphene oxide film.

[0059] Regarding step C) :

[0060] C) The graphene oxide film is carbonized under a protective atmosphere.

[0061] In this invention, there are no special restrictions on the type of gas used to provide the protective atmosphere; any conventional protective gas in the field, such as nitrogen or argon, is acceptable.

[0062] In this invention, the preferred heating rate for the carbonization treatment is 5–50℃ / min, specifically 5℃ / min, 10℃ / min, 15℃ / min, 20℃ / min, 25℃ / min, 30℃ / min, 35℃ / min, 40℃ / min, 45℃ / min, or 50℃ / min. The preferred carbonization temperature is 800–1500℃, specifically 800℃, 850℃, 900℃, 950℃, 1000℃, 1050℃, 1100℃, 1150℃, 1200℃, 1250℃, 1300℃, 1350℃, 1400℃, 1450℃, or 1500℃. The preferred holding time for the carbonization treatment is 1–5 hours, specifically 1 hour, 2 hours, 3 hours, 4 hours, or 5 hours.

[0063] Regarding step D) :

[0064] D) The film obtained in step C) is graphitized under a protective atmosphere.

[0065] In this invention, there are no special restrictions on the type of gas used to provide the protective atmosphere; any conventional protective gas in the field, such as nitrogen or argon, is acceptable.

[0066] In this invention, the heating rate of the graphitization treatment is preferably 5–10 °C / min, specifically 5 °C / min, 6 °C / min, 7 °C / min, 8 °C / min, 9 °C / min, or 10 °C / min. The temperature of the graphitization treatment is preferably 2600–3100 °C, specifically 2600 °C, 2700 °C, 2800 °C, 2900 °C, 3000 °C, or 3100 °C. In this invention, the holding time of the graphitization treatment is preferably 3–5 h, specifically 3 h, 4 h, or 5 h.

[0067] Regarding step E) :

[0068] E) Press the film obtained in step D) to obtain a graphene thermal conductive film.

[0069] In this invention, the pressing process can be performed using a hydraulic press. The pressing pressure is preferably 30–80 MPa, specifically 30 MPa, 40 MPa, 50 MPa, 60 MPa, 70 MPa, or 80 MPa. The holding time for the pressing process is preferably 30–300 min, specifically 30 min, 60 min, 90 min, 120 min, 150 min, 180 min, 210 min, 240 min, 270 min, or 300 min. After the above pressing process, a graphene thermally conductive film product is obtained.

[0070] The method for preparing a graphene thermally conductive film provided by this invention involves first mixing graphene oxide, a solvent, a dispersant, and a binding agent to obtain a slurry; then, coating the slurry onto a substrate and drying it to form a film; subsequently, subjecting the film to a series of heat treatments, including carbonization and graphitization; and finally, pressing to obtain the graphene thermally conductive film. Specifically, the introduction of a dispersant and a binding agent during the slurry preparation process reduces the slurry viscosity, resulting in uniform coating and a smooth film; the binding agent links and repairs the graphene sheets. The combined effect of these two agents, coupled with the process parameters of this invention (especially the subsequent heat treatment parameters), effectively improves the thermal conductivity of the final graphene thermally conductive film.

[0071] Experimental results show that the preparation method of the present invention produces a smooth and flat film, and the final graphene thermal conductive film product has a thermal conductivity of over 1476 W / (m·K), exhibiting high thermal conductivity.

[0072] To further understand the present invention, preferred embodiments are described below with reference to examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention and are not intended to limit the scope of the claims. Unless otherwise stated, the raw materials and reagents used in the following examples are commercially available or can be prepared by known methods. All instruments are conventionally selected in the art.

[0073] Example 1

[0074] A) Graphene oxide, water solvent, dispersant (ethanolamine), and binding agent (titanium diboride) were ultrasonically dispersed at 720W for 60 min, followed by homogenization and degassing to obtain a slurry. The solid content of graphene oxide in the solvent was 2 wt%, the amount of dispersant was 23% of the mass of graphene oxide, and the amount of binding agent was 0.1% of the mass of graphene oxide.

[0075] B) The slurry is coated onto PP fiber cloth to a thickness of 7 mm. The cloth is then placed in an oven and dried at 60°C for 10 hours. The film is then separated from the PP fiber cloth substrate to obtain a graphene oxide film.

[0076] C) Under a nitrogen atmosphere, graphene oxide was placed in a vacuum furnace and heated from room temperature to 1500℃ at a rate of 25℃ / min for 1 hour.

[0077] D) Under an argon atmosphere, the film obtained in step C) is graphitized at a rate of 8°C / min from room temperature to 2700°C for 4 hours.

[0078] E) Press the graphene oxide film obtained in step D) using a hydraulic press at 50 MPa for 30 min to obtain a graphene thermal conductive film.

[0079] The above process flow is as follows Figure 3 As shown.

[0080] Characterization:

[0081] (1) The film-forming effect of the slurry after being coated in step B) was observed. Simultaneously, based on Example 1, without adding a dispersant, the film-forming effect of the slurry without a dispersant was observed. The results are as follows: Figure 4 As shown, Figure 4 This image shows a comparison of film-forming effects before and after adding a dispersant. The sample on the left is the one before adding the dispersant, and the sample on the right is the one after adding the dispersant. It can be seen that adding the dispersant significantly improves the film-forming effect, resulting in a smooth and even film.

[0082] (2) The cross-sectional structure of the graphene thermally conductive film obtained in Example 1 was characterized using scanning electron microscopy, and the results are as follows: Figure 5 As shown, the graphene sheets are evenly distributed and arranged in an orderly manner.

[0083] Example 2

[0084] A) Graphene oxide, water solvent, dispersant (AMP-95), and linker (boric acid) were ultrasonically dispersed at 720W for 120 min, followed by homogenization and degassing to obtain a slurry. The solid content of graphene oxide in the solvent was 5 wt%, the amount of dispersant was 6% of the mass of graphene oxide, and the amount of linker was 0.2% of the mass of graphene oxide.

[0085] B) The slurry is coated onto PP fiber cloth to a thickness of 3 mm. The cloth is then placed in an oven and dried at 30°C for 10 hours. The film is then separated from the PP fiber cloth substrate to obtain a graphene oxide film.

[0086] C) Under a nitrogen atmosphere, graphene oxide was placed in a vacuum furnace and heated from room temperature to 1500℃ at a rate of 30℃ / min for 3 hours for carbonization.

[0087] D) Under an argon atmosphere, the film obtained in step C) is graphitized at a rate of 10°C / min from room temperature to 3100°C for 3 hours.

[0088] E) Press the graphene oxide film obtained in step D) using a hydraulic press at 70 MPa for 180 min to obtain a graphene thermal conductive film.

[0089] Example 3

[0090] A) Graphene oxide, water solvent, dispersing agent (ethanolamine and silicone resin in a 1:1 mass ratio), and binding agent (boric acid) were ultrasonically dispersed at 720W for 90 min, followed by homogenization and degassing to obtain a slurry. The solid content of graphene oxide in the solvent was 5 wt%, the amount of dispersing agent was 50% of the mass of graphene oxide, and the amount of binding agent was 0.5% of the mass of graphene oxide.

[0091] B) The slurry is coated onto PP fiber cloth to a thickness of 5 mm. The cloth is then placed in an oven and dried at 80°C for 10 hours. The film is then separated from the PP fiber cloth substrate to obtain a graphene oxide film.

[0092] C) Under a nitrogen atmosphere, graphene oxide was placed in a vacuum furnace and heated from room temperature to 800°C at a rate of 20°C / min for 5 hours.

[0093] D) Under an argon atmosphere, the film obtained in step C) is graphitized at a rate of 8°C / min from room temperature to 3000°C for 5 hours.

[0094] E) Press the graphene oxide film obtained in step D) using a hydraulic press at 30 MPa for 300 min to obtain a graphene thermal conductive film.

[0095] Comparative Example 1

[0096] The procedure was carried out in accordance with Example 1, except that the dispersing agent in step A) was replaced with hydroxypropyl methylcellulose.

[0097] Comparative Example 2

[0098] The procedure was carried out according to Example 1, except that the linking agent in step A) was replaced with potassium 4-hydroxyphenylboronic acid.

[0099] Performance testing:

[0100] The thermal conductivity of the graphene thermal conductive film products obtained in each embodiment and comparative example was tested, and the results are shown in Table 1.

[0101] Table 1: Thermal conductivity of graphene thermal conductive films obtained in each embodiment and comparative example

[0102] Thermal conductivity, W / (m·K) Example 1 1509 Example 2 1482 Example 3 1476 Comparative Example 1 1246 Comparative Example 2 1273

[0103] As can be seen from the test results in Table 1, the thermal conductivity of the graphene thermal conductive films obtained in Examples 1-3 of this invention is above 1476 W / (m·K), exhibiting high thermal conductivity. In contrast, the thermal conductivity of Comparative Examples 1-2 is significantly lower than that of the Examples, demonstrating that the use of certain dispersing and binding agents in this invention is beneficial for improving the thermal conductivity of the graphene thermal conductive film.

[0104] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of these embodiments are merely to aid in understanding the method and core ideas of the present invention, including the best mode, and to enable any person skilled in the art to practice the present invention, including manufacturing and using any device or system, and implementing any combined method. It should be noted that those skilled in the art can make various improvements and modifications to the present invention without departing from its principles, and these improvements and modifications also fall within the scope of protection of the claims. The scope of protection of this patent is defined by the claims and may include other embodiments that can be conceived by those skilled in the art. If these other embodiments have structural elements similar to those expressed in the claims, or if they include equivalent structural elements that are not substantially different from those expressed in the claims, then these other embodiments should also be included within the scope of the claims.

Claims

1. A method for preparing a graphene thermally conductive film, characterized in that, Includes the following steps: A) Mix graphene oxide, solvent, dispersant and binding agent, homogenize and degas to obtain slurry; The dispersing agent is at least one of ethanolamine and organosilicon resin; wherein the organosilicon resin is an amine-functionalized siloxane resin; and the amine-functionalized siloxane resin is at least one of 3-aminopropylmethyldimethylsiloxane and (3-aminopropyl)dimethylmethoxysilane. The amount of the dispersing agent is 5% to 50% of the mass of graphene oxide; The amount of the connecting agent is 0.1% to 0.5% of the mass of graphene oxide; The relationship between the amount of graphene oxide and the solvent is such that the solid content of graphene oxide in the solvent is 2-5 wt%. B) The slurry is coated onto a substrate, dried to form a film, and then the film is separated from the substrate to obtain a graphene oxide film. C) The graphene oxide film is carbonized under a protective atmosphere; The heating rate of the carbonization treatment is 5~50℃ / min, and the holding time is 1~5h; D) The film obtained in step C) is graphitized under a protective atmosphere; The heating rate of the graphitization treatment is 5~10℃ / min, and the holding time is 3~5h; E) Press the film obtained in step D) to obtain a graphene thermally conductive film; The pressing process is performed at a pressure of 30-80 MPa for a holding time of 30-300 min.

2. The preparation method according to claim 1, characterized in that, In step A), the connecting agent is boric acid and / or titanium diboride.

3. The preparation method according to claim 1, characterized in that, In step C), the carbonization temperature is 800~1500℃.

4. The preparation method according to claim 1, characterized in that, In step D), the temperature of the graphitization treatment is 2600~3100℃.

5. The preparation method according to claim 1, characterized in that, In step B): The coating thickness is 3~7 mm; The drying temperature is 30~80℃.

6. The preparation method according to claim 1, characterized in that, In step A), the solvent is selected from at least one of water, ethanol, and N,N-dimethylformamide.

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