Reduced graphene oxide film and preparation method thereof

Abstract

The invention provides a preparation method of a reduced graphene oxide film, which comprises the processes of preparation of graphene oxide slurry, coating of a graphene oxide original film, heat treatment and calendaring. The reduced graphene oxide film with the thermal diffusion coefficient larger than or equal to 800 mm < 2 > / s is prepared by adjusting and controlling the particle size of graphene oxide slurry and the coating thickness of the graphene oxide slurry, the relation between the particle size of the graphene oxide slurry and the coating thickness is explored, and the thermal diffusion coefficient of the reduced graphene oxide film can be adjusted and controlled according to the particle size of the graphene oxide slurry. And whether the graphene oxide slurry is adaptive to the high coating thickness or the low coating thickness is preferentially judged, so that raw material selection is provided for preparing the high-thermal-conductivity reduced graphene oxide film, and the production efficiency is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of graphene preparation, in particular to a reduced graphene oxide film and a preparation method thereof. BACKGROUND

[0002] With the progress of electronic and communication technology, intelligent devices become more and more portable and integrated, which puts forward higher requirements for the heat dissipation performance of the devices. The thermal conductivity of single-layer graphene is 5300 W / mK, which is the highest among the known materials. The reduced graphene oxide film and its derivatives are one of the most industrialized graphene thermal management materials so far.

[0003] The reduced graphene oxide film is usually prepared by using graphene oxide as raw material, preparing graphene oxide slurry through slurry preparation, performing film coating self-assembly, and then performing high-temperature or chemical reduction treatment on the graphene oxide film. In the preparation process, the mutual influence and interaction between the processes determine the thermal conductivity of the prepared graphene oxide film. Finding the action mechanism of each process and the law of mutual influence in the research and development process can improve the industrial production efficiency.

[0004] Based on this, the present application is proposed. SUMMARY

[0005] The first object of the present application is to provide a preparation method of a reduced graphene oxide film, which comprises the configuration of graphene oxide slurry, the coating of graphene oxide original film, and the heat treatment process and the calendering process. In the preparation process, by adjusting the particle size of the graphene oxide slurry and the coating thickness of the graphene oxide original film, a reduced graphene oxide film with a thermal diffusivity of ≥800 mm 2 / s is prepared.

[0006] In some embodiments of the first object of the present application, the particle size of the graphene oxide slurry and the coating thickness of the graphene oxide original film are inversely related. Specifically, when the particle size of the graphene oxide slurry is small, the graphene oxide original film should be coated thick; when the particle size of the graphene oxide slurry is large, the graphene oxide original film should be coated thin.

[0007] In some embodiments of the first object of the present application, the D50 of the graphene oxide slurry is 0.3-17 μm.

[0008] In some embodiments of the first object of the present application, the coating thickness of the graphene oxide original film is 2500-6000 μm.

[0009] In some embodiments of the first object of the present application, the particle size of the graphene oxide slurry is adjusted by homogenization, and the coating thickness of the graphene oxide original film is adjusted by the gap size between the doctor blade and the coating substrate.

[0010] In some embodiments of the first object of the present application, the preparation of the graphene oxide slurry comprises: mixing the graphene oxide cake with deionized water and stirring and dispersing, then homogenizing the graphene oxide dispersion slurry using a homogenizer, and defoaming the graphene oxide slurry after homogenization to obtain the graphene oxide slurry.

[0011] In some embodiments of the first object of the present application, the coating of the graphene oxide original film comprises: coating the graphene oxide slurry on a doctor blade coater to form an original film, and then drying the original film and then re-wetting the original film.

[0012] In some embodiments of the first object of the present application, the heat treatment comprises a pretreatment process at 150-380℃, a carbonization process at 900-1400℃, and a graphitization process at 2600-3300℃.

[0013] In some embodiments of the first object of the present application, the pretreatment and / or carbonization and / or graphitization process is carried out under negative pressure.

[0014] The second object of the present application is to provide a reduced graphene oxide film prepared according to the method of the first object of the present application.

[0015] Compared with the prior art, the technical scheme has the following beneficial effects: 1. By adjusting the particle size parameters of graphene oxide sheets through homogenization, the influence of graphene oxide raw materials with different particle sizes on the thermal conductivity of the macroscopic reduced graphene oxide film is explored, and the graphene oxide sheets with the best particle size range are obtained. The preparation process is simple, low in cost and easy to commercialize.

[0016] 2. The present application explores the relationship between the particle size of the graphene oxide slurry and the coating thickness, and can preferentially determine whether the graphene oxide slurry is suitable for high coating thickness or low coating thickness according to the particle size of the graphene oxide slurry, thereby providing a choice of raw materials for the preparation of high-thermal-conductivity reduced graphene oxide film and improving production efficiency. BRIEF DESCRIPTION OF DRAWINGS

[0017] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are some embodiments of the present application, and those skilled in the art can also obtain other drawings without creative labor on the basis of these drawings.

[0018] Figure 1 Figure for testing the thermal diffusivity of the reduced graphene oxide film in Example 1 Figure 2Particle size-coating thickness-thermal diffusivity relationship graph for reduced graphene oxide films in Examples 1-8 Figure 3 Thermal diffusivity test graph for reduced graphene oxide film in Example 9 Figure 4 Particle size-coating thickness-thermal diffusivity relationship graph for reduced graphene oxide films in Examples 9-16 Figure 5 Particle size-coating thickness-thermal diffusivity relationship graph for reduced graphene oxide films in Examples 17-24 DETAILED DESCRIPTION

[0019] The following detailed description of example embodiments of the application references the drawings, which form a part of the description, and in which are shown by way of example various example embodiments by which the application can be practiced. The various features of the application are described in the specification in connection with the illustrative figures, in which like numerals designate like features. The detailed description of embodiments of the application is not intended to limit the scope of the application as claimed, but to provide examples in which the features of the application are utilized to present the best mode of practicing the application, and to sufficiently enable one skilled in the art to practice the application. However, it is understood that various modifications and changes can be made to the application disclosed without departing from the scope of the application as claimed. The detailed description and accompanying drawings are therefore to be regarded in an illustrative rather than a restrictive sense, and all such modifications are intended to be within the scope of the application described herein. Further, the background is intended to provide context for the present technology and is not intended to be limiting of the present application or the scope of the application and its applications.

[0020] 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 in the description herein is for describing particular embodiments only and is not intended to be limiting of the application; the use herein of the terms "and / or" includes a set of one or more associated listed items.

[0021] In the examples, unless otherwise specified, the operations were performed under ordinary conditions or under the conditions recommended by the manufacturer. In the examples, unless otherwise specified, the reagents and instruments used were commercially available products.

[0022] In order to make the technical problems, technical solutions and advantages of the present application clearer, the following will be described in detail with reference to the accompanying drawings and specific examples.

[0023] In the development of reduced graphene oxide films, the applicant found that the relationship between the size of the graphene oxide slurry particles and the thickness of the graphene oxide film to be coated greatly affects the thermal conductivity of the final product.

[0024] The first aspect of the present application provides a method for preparing a reduced graphene oxide film, comprising the steps of preparing an oxidized graphene oxide slurry, coating an oxidized graphene oxide primary film, and heat treatment and calendering processes. In the preparation process, by controlling the particle size of the oxidized graphene oxide slurry and the coating thickness of the oxidized graphene oxide primary film, a reduced graphene oxide film with a thermal diffusivity ≥ 800 mm 2 / s is prepared.

[0025] In some embodiments of the first aspect of the present application, the control of the particle size of the oxidized graphene oxide slurry and the coating thickness of the oxidized graphene oxide primary film are inversely related. Specifically, when the particle size of the oxidized graphene oxide slurry is controlled smaller, the oxidized graphene oxide primary film should be coated thicker; when the particle size of the oxidized graphene oxide slurry is controlled larger, the oxidized graphene oxide primary film should be coated thinner. The applicant found that small particle size of the oxidized graphene oxide sheet has fewer oxygen-containing functional groups, and a thinner coating thickness will result in too little overlap between the graphene oxide sheet layers, which is not conducive to the self-assembly of the graphene oxide film. With the increase of the coating thickness, the contact between the graphene oxide sheet layers increases during the self-assembly process, enhancing the interaction between the layers and improving the self-assembly ability. At the same time, the small particle size of the graphene oxide has more internal voids after being overlapped into a primary film, and the gaseous substances (CO2, CO, H2O) generated during the heat treatment process to remove the oxygen-containing functional groups can escape through the internal voids. The degree of expansion of the film is low, which does not affect the arrangement of the original graphene oxide sheet layers, so the small particle size of the graphene oxide slurry is more suitable for high coating thickness. While the large particle size of the graphene oxide sheet layer contains more oxygen-containing functional groups, with the increase of the coating thickness, the contact between the graphene oxide sheets during the self-assembly process is large, and the number of stacked layers is large. During the heat treatment process to remove the oxygen-containing functional groups, more gaseous substances (CO2, CO, H2O) are generated. The exhaust efficiency of the thicker graphene oxide primary film is lower, and when the generation rate of the gas is higher than the escape rate, a large amount of gas will accumulate to form large bulges, which will destroy the ordered stacking structure between the original graphene oxide sheet layers. Although most of the gas can be removed by calendering, a large number of wrinkles will be formed in the film, which will seriously affect the thermal conductivity of the reduced graphene oxide film. Therefore, the large particle size of the graphene oxide slurry is more suitable for low coating thickness.

[0026] In some embodiments of the first object of the present application, the D50 of the graphene oxide slurry is 0.3-17 μm. The applicant found that if the graphene oxide particle size is too small, specifically when the D50 < 0.3 μm, it needs to be repeatedly physically cut by a high-pressure homogenizer, has too few oxygen-containing functional groups, has more defects, and will cause the thermal conductivity of the graphene oxide film to be poor; if the graphene oxide particle size is too large, specifically when the D50 > 17 μm, the graphene oxide sheet has too many oxygen-containing functional groups, and in the process of self-assembly into a film, when the sheets are close to each other, they are easy to accumulate into uneven block structures. This accumulation will wrap micropores and wrinkles, which affects the subsequent heat treatment process, and the defects produced cannot be completely repaired in the graphitization stage.

[0027] In some embodiments of the first object of the present application, the coating thickness of the graphene oxide original film is 2500-6000 μm. The applicant found that if the coating thickness of the graphene oxide original film is too thin, specifically if the coating thickness < 2500 μm, it is mainly affected by the film drying speed, and in the process of self-assembly into a film, as the water evaporates, the surface layer dries and shrinks first, causing the internal graphene oxide sheet to be extruded, the sheet orientation to be poor, the phonon transmission scattering to increase, the transmission diffusion path to increase, and the thermal conductivity to decrease; if the coating thickness of the graphene oxide original film is too thick, specifically if the coating thickness > 6000 μm, the film material is difficult to exhaust, and bubbles and delamination phenomena are easy to occur during the heat treatment process.

[0028] In some embodiments of the first object of the present application, the particle size of the graphene oxide slurry is controlled by homogenization, and the coating thickness of the graphene oxide original film is controlled by the gap size of the doctor blade and the coating substrate.

[0029] In some embodiments of the first object of the present application, the configuration of the graphene oxide slurry includes: mixing the graphene oxide cake with deionized water and stirring and dispersing, then using a homogenizer to homogenize the graphene oxide dispersion slurry, and after homogenization, defoaming the graphene oxide slurry to obtain the graphene oxide slurry. Defoaming is also an important means to avoid the generation of a large number of bubbles during the coating of the original film. Typically but not limited to, the defoaming means can be static defoaming or vacuum defoaming.

[0030] In some embodiments of the first object of the present application, the coating of the graphene oxide raw film comprises: coating the graphene oxide slurry into a raw film on a knife coater, and then performing a drying and rewetting treatment on the raw film. This is because in the process of industrial mass production of reduced graphene oxide films, the coating substrate used is usually a polymer material similar to PP, and the surface of the substrate has tiny pores. When the graphene oxide slurry is coated in a wet state, part of the slurry penetrates into the pores, causing the graphene oxide raw film after complete drying to be difficult to peel off the substrate, and the graphene oxide raw film after complete drying is brittle and prone to breakage during the peeling and rolling process. The above problems can be solved by performing a slight rewetting treatment on the graphene oxide raw film after drying. Specifically, the rewetting is to place the dried graphene oxide raw film in an environment with a temperature of 20-50°C and a relative humidity of 60%-90%.

[0031] In some embodiments of the first object of the present application, the heat treatment comprises a pretreatment process at 150-380°C, a carbonization process at 900-1400°C, and a graphitization process at 2600-3300°C. The segmented heat treatment can avoid excessive gas production during rapid thermal reduction of the film, and the rapid gas production of the graphene oxide film to the cross-sectional process is easy to tear the internal structure of the graphene film, which is not conducive to heat conduction, and more directly leads to the explosion of the furnace and the scrap. The segmented heat treatment mainly removes water and a small amount of oxygen-containing functional groups in the pretreatment stage, removes most of the oxygen-containing functional groups in the carbonization stage, and basically removes the oxygen-containing functional groups in the graphitization stage, while various defects are repaired, and the intrinsic thermal conductivity of the reduced graphene oxide film is improved.

[0032] In some embodiments of the first object of the present application, the film to be treated is subjected to negative pressure during the pretreatment and / or carbonization and / or graphitization process. During the heat treatment of the graphene oxide film, the gas discharge will cause the film material to expand violently, and without pressure, the expansion coefficient is uncontrollable, resulting in uncontrollable thickness.

[0033] The second object of the present application is to provide a reduced graphene oxide film prepared according to the method of the first object of the present application. The reduced graphene oxide film prepared according to the method of the first object has a thermal diffusivity ≥800 mm 2 / s.

[0034] In specific embodiments of the present application, the detection methods of various parameters involved are as follows: Particle size: tested using a laser particle size analyzer; Thermal diffusivity test method: the method described in standard Q / GDMR 04-2023 "Laser Flash Method for Testing Thermal Conductivity". Example 1

[0035] S1, preparation of graphene oxide slurry: The A52 model graphene oxide cake purchased by Yuntian Mo Rui was mixed with deionized water and put into a planetary stirring device for stirring and dispersion treatment. The stirring rate was set to 800 r / min, the dispersion rate was set to 3000 r / min, and the working time was set to 3 h. A graphene oxide slurry with a solid content of 5% was obtained. A homogenizer was used to control the particle size of the graphene oxide dispersion slurry, and the particle size D50 control value was 0.503 μm. After homogenization, the graphene oxide slurry was subjected to vacuum degassing treatment to obtain the target graphene oxide slurry.

[0036] S2, preparation of reduced graphene oxide film: PP was used as the coating substrate, and a doctor blade coater was used to coat the target graphene oxide slurry with a thickness of 4000 mm. After drying, the coated film was placed in an environment with a temperature of 25°C and a relative humidity of 70% for re-humidification treatment. A graphene oxide film was obtained. The graphene oxide film was pretreated under a load at 220°C for 1 h, carbonized in a nitrogen atmosphere at 1200°C for 1 h, and graphitized in an argon atmosphere at 2800°C for 1 h. Finally, the target reduced graphene oxide film was obtained by flat pressing.

[0037] The obtained reduced graphene oxide film was tested, and the thermal diffusivity in the horizontal direction was as shown in Figure 1 , which was 1022.429 mm 2 / s. Example 2-8

[0038] Different from Example 1, in step S2, a doctor blade coater was used to coat the target graphene oxide slurry with a thickness of 2500 mm, 3000 mm, 3500 mm, 4500 mm, 5000 mm, 5500 mm, and 6000 mm, respectively. The other processes in steps S1 and S2 were consistent with Example 1.

[0039] The obtained reduced graphene oxide film was tested, and the thermal diffusivity in the horizontal direction was as shown in Figure 2 . It can be seen from Figure 2 that when the D50 of the graphene oxide slurry is about 0.5 μm, the coating thickness of the graphene oxide film is controlled to be about 4000 mm, and the thermal performance of the reduced graphene oxide obtained is the best. Example 9

[0040] The difference between this example and Example 1 is that in step S1, the particle size of the graphene oxide dispersion slurry is controlled, and the particle size D50 control value is 0.353 μm. The other steps and process parameters are the same as those of Example 1. The purpose is to explore the influence of graphene oxide slurry with different median particle sizes on the thermal conductivity of graphene thermal conductivity film.

[0041] The test results show that the horizontal thermal diffusivity of the reduced graphene oxide film is as follows: Figure 3 As shown, it is 833.995mm. 2 / s. Examples 10-16

[0042] Unlike Example 9, in step S2, a doctor blade coater is used to coat the target graphene oxide slurry with thicknesses of 2500 mm, 3000 mm, 3500 mm, 4500 mm, 5000 mm, 5500 mm, and 6000 mm, respectively. The other processes in steps S1 and S2 are the same as in Example 1.

[0043] The obtained reduced graphene oxide film was tested, and its horizontal thermal diffusivity was obtained as follows: Figure 4 As shown. From Figure 4 It can be seen that when the D50 of the graphene oxide slurry is about 0.3 μm, the thermal properties of the reduced graphene oxide are best when the coating thickness of the original graphene oxide film is controlled at about 5000 mm. Examples 17-24

[0044] Unlike Example 1, in step S1, the particle size of the graphene oxide dispersion slurry was controlled, with a D50 value of 16.571 μm. In step S2, the target graphene oxide slurry was coated with a doctor blade coater at thicknesses of 2500 mm, 3000 mm, 3500 mm, 4500 mm, 5000 mm, 5500 mm, and 6000 mm, respectively. All other processes in steps S1 and S2 were the same as in Example 1.

[0045] The obtained reduced graphene oxide film was tested, and its horizontal thermal diffusivity was obtained as follows: Figure 5 As shown. From Figure 5 It can be seen that when the D50 of the graphene oxide slurry is about 17 μm, the thermal properties of the reduced graphene oxide are best when the coating thickness of the original graphene oxide film is controlled at about 3000 mm.

[0046] contrast Figure 2 , Figure 4 , Figure 5It can be known that the particle size of the graphene oxide slurry and the coating thickness of the graphene oxide original film should be inversely related, that is, when the particle size of the graphene oxide slurry is small, the graphene oxide original film should be coated thick; when the particle size of the graphene oxide slurry is large, the graphene oxide original film should be coated thin, so that the reduced graphene oxide obtained has better thermal performance; by controlling the D50 of the graphene oxide slurry in the range of 0.3-17 μm, controlling the coating thickness of the graphene oxide original film in the range of 2500-6000 mm, and following the rule that the particle size and the coating thickness are inversely related to match the corresponding process parameters, a reduced graphene oxide film with a thermal diffusivity ≥800 mm 2 / s can be obtained. Example 25

[0047] S1, preparation of graphene oxide slurry: The A52 type graphene oxide cake purchased by Yuntian Mo Rui was mixed with deionized water and put into a planetary stirring device for stirring and dispersion treatment, the stirring rate was set to 800 r / min, the dispersion rate was set to 3000 r / min, and the working time was set to 3 h, to obtain a graphene oxide slurry with a solid content of 5%. The graphene oxide dispersion slurry was subjected to particle size regulation using a homogenizer, and the particle size D50 regulation value was 0.503 μm; the graphene oxide slurry was subjected to vacuum degassing treatment after homogenization, to obtain the target graphene oxide slurry.

[0048] S2, preparation of reduced graphene oxide film: PP was used as the coating substrate, and the target graphene oxide slurry was coated on the substrate using a knife coating machine at a thickness of 4000 mm, and the coated film was dried and then subjected to humidity recovery treatment in an environment with a temperature of 45°C and a relative humidity of 85%, to obtain a graphene oxide film. The graphene oxide film was subjected to 340°C pretreatment for 1 h under a load, carbonization treatment for 1 h in a nitrogen atmosphere, and graphitization treatment for 1 h in an argon atmosphere, and finally a target reduced graphene oxide film was obtained by flat pressing.

[0049] The obtained reduced graphene oxide film was tested, and the horizontal thermal diffusivity of the film was 1047.505 mm 2 / s. Comparative Example 1

[0050] S1, preparation of graphene oxide slurry: The A52 type graphene oxide material cake purchased by Yuntian Mo Rui was mixed with deionized water and put into a planetary stirring equipment for stirring and dispersing treatment, the stirring rate was set to 800 r / min, the dispersing rate was set to 3000 r / min, and the working time was 3 h, and a graphene oxide slurry with a solid content of 5% was obtained. The particle size D50 of the graphene oxide dispersion slurry was controlled to 0.249 μm by using a homogenizer; and the graphene oxide slurry was subjected to vacuum degassing treatment after homogenization treatment, and the target graphene oxide slurry was obtained.

[0051] S2, preparation of reduced graphene oxide film: PP was used as the coating substrate, and the target graphene oxide slurry was coated by using a knife coating machine at a thickness of 5500 mm, and the coated film was dried and then placed in an environment with a temperature of 25°C and a relative humidity of 70% for re-humidification treatment, and a graphene oxide film was obtained. The graphene oxide film was pretreated under a load at 220°C for 1 h, carbonized at 1200°C in a nitrogen atmosphere for 1 h, and graphitized at 2800°C in an argon atmosphere for 1 h, and finally the target reduced graphene oxide film was obtained by flat pressing.

[0052] The obtained reduced graphene oxide film was tested, and the horizontal thermal diffusivity coefficient of the film was 652.953 mm 2 / s.

[0053] According to the data of Comparative Example 1, even if the particle size and coating thickness meet the rule that the graphene oxide original film should be coated thicker when the particle size of the graphene oxide slurry is controlled to be smaller, the graphene oxide film still cannot achieve a better thermal diffusivity coefficient due to the too small particle size of the graphene oxide slurry. The applicant speculates that the poor thermal conductivity of the graphene oxide film is caused by the too few oxygen-containing functional groups and too many defects. Comparative Example 2

[0054] S1, preparation of graphene oxide slurry: The A52 type graphene oxide material cake purchased by Yuntian Mo Rui was mixed with deionized water and put into a planetary stirring equipment for stirring and dispersing treatment, the stirring rate was set to 800 r / min, the dispersing rate was set to 3000 r / min, and the working time was 3 h, and a graphene oxide slurry with a solid content of 5% was obtained. The particle size D50 of the graphene oxide dispersion slurry was controlled to 0.249 μm by using a homogenizer; and the graphene oxide slurry was subjected to vacuum degassing treatment after homogenization treatment, and the target graphene oxide slurry was obtained.

[0055] S2, preparation of reduced graphene oxide film: PP is used as the coating substrate, the target graphene oxide slurry is coated by using a doctor blade coater at a thickness of 2000 mm, and the coated film is dried and then placed in an environment at 25°C and a relative humidity of 70% for re-humidification treatment to obtain a graphene oxide film. The graphene oxide film is pre-treated at 220°C for 1h under a load, carbonized at 1200°C for 1h in a nitrogen atmosphere, and graphitized at 2800°C for 1h in an argon atmosphere, and finally a target reduced graphene oxide film is obtained by flat pressing.

[0056] The obtained reduced graphene oxide film is tested, and the thermal diffusivity coefficient in the horizontal direction is 600.137 mm 2 / s.

[0057] In the above embodiments, the description of each embodiment has its own focus, and the parts not described in detail in a certain embodiment can be referred to the relevant description of other embodiments.

[0058] The above is a specific embodiment of the present application, but the protection scope of the present application is not limited to this. Any person skilled in the art can easily think of various equivalent modifications or replacements within the technical scope disclosed in the present application, and these modifications or replacements should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A method for producing a reduced graphene oxide film, comprising a configuration of a graphene oxide slurry, a coating of a graphene oxide original film, a heat treatment, and a calendering process, characterized by, By controlling the particle size of graphene oxide slurry and the coating thickness of graphene oxide slurry, a reduced graphene oxide film with a thermal diffusivity ≥ 800 mm 2 / s is prepared.

2. The method of claim 1, wherein the reduced graphene oxide film is prepared by the steps of: The particle size of the graphene oxide slurry and the coating thickness of the graphene oxide original film are inversely related.

3. The method of claim 2, wherein the reduced graphene oxide film is prepared by the steps of: (a) preparing a graphene oxide film; (b) immersing the graphene oxide film in a solution of a reducing agent; and (c) drying the graphene oxide film. The D50 of the graphene oxide slurry is 0.3-17 μm.

4. The method of claim 2, wherein the reduced graphene oxide film is prepared by the steps of: (a) preparing a graphene oxide film; (b) immersing the graphene oxide film in a solution of a reducing agent; and (c) drying the graphene oxide film. The coating thickness of the graphene oxide original film is 2500-6000 μm.

5. The method of claim 1, wherein the reduced graphene oxide film is prepared by the steps of: (a) preparing a graphene oxide film; (b) immersing the graphene oxide film in a solution of a reducing agent; and (c) drying the graphene oxide film. The particle size of the graphene oxide slurry is regulated by homogenization, and the coating thickness of the graphene oxide original film is regulated by the gap size between the doctor blade and the coating substrate.

6. The method of claim 1, wherein the reduced graphene oxide film is prepared by the steps of: The preparation of the graphene oxide slurry comprises mixing the graphene oxide cake with deionized water, stirring and dispersing, then homogenizing the graphene oxide dispersion slurry, and defoaming the graphene oxide slurry to obtain the graphene oxide slurry.

7. The method of claim 1, wherein the reduced graphene oxide film is prepared by the steps of: (a) preparing a graphene oxide film; (b) immersing the graphene oxide film in a solution of a reducing agent; and (c) drying the graphene oxide film. The coating of the graphene oxide original film comprises coating the graphene oxide slurry on a doctor blade coater to form an original film, and then drying and rewetting the original film.

8. The method of claim 1, wherein the reduced graphene oxide film is prepared by the steps of: (a) preparing a graphene oxide film; (b) immersing the graphene oxide film in a solution of a reducing agent; and (c) drying the graphene oxide film. The heat treatment comprises a pretreatment process at 150-380℃, a carbonization process at 900-1400℃, and a graphitization process at 2600-3300℃.

9. The method of claim 7, wherein the reduced graphene oxide is prepared by the steps of: preparing a graphene oxide solution by dispersing graphene oxide in water; and reducing the graphene oxide in the graphene oxide solution by adding a reducing agent to the graphene oxide solution. During the pretreatment and / or carbonization and / or graphitization process, the film to be treated is subjected to negative pressure.

10. A reduced graphene oxide film, characterized by, The reduced graphene oxide film is prepared according to the preparation method of any one of claims 1-9.

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