Preparation method of reduced graphene oxide film

Abstract

The invention provides a preparation method of a reduced graphene oxide film, which comprises the steps of graphene oxide slurry preparation, graphene oxide original film coating, pretreatment, carbonization treatment and graphitization treatment. The problems of serious expansion and transverse irreparable tearing damage caused by gas production due to the fact that a large number of oxygen-containing groups rapidly fall off in the pretreatment stage of the graphene film are solved, the ordered self-assembly effect of the reduced graphene oxide film is improved, and the time of the pretreatment stage is greatly shortened; meanwhile, the problem of cracking or violent oxidation of the graphene oxide original film in the pretreatment stage is relieved, the safety of the preparation process is improved, and the reduced graphene oxide film with high heat-conducting property is obtained.

Description

Technical Field

[0001] The present application relates to the field of graphene preparation, and specifically, designs a method for preparing a reduced graphene oxide film. Background Art

[0002] Graphene thermal conductive film has excellent thermal conductivity and flexible physical properties, and is gradually replacing traditional thermal conductive materials in the fields of 5G electronic equipment heat dissipation. At present, the mainstream preparation method of graphene thermal conductive film is to use graphene oxide slurry to obtain graphene oxide original film, and then go through a series of pretreatment, carbonization, graphitization and other heat treatment processes to finally obtain graphene thermal conductive film (reduced graphene oxide film).

[0003] The heat treatment stage of reduced graphene oxide film usually requires a lot of time and effort to ensure its performance and yield. This is mainly due to the fact that graphene oxide film is very sensitive to temperature during the heat treatment stage. The large amount of oxygen-containing groups that fall off can easily cause serious bursting, tearing damage, expansion, and even violent oxidation combustion. Therefore, the temperature control during the heat treatment stage needs to be extremely slow and precise to achieve the purpose of controlling the slow shedding of oxygen-containing groups and avoiding serious gas production. Especially in the pretreatment stage, when the heating rate is fast, the oxygen-containing groups in the graphene oxide film fall off rapidly, and the graphene film often has serious expansion, lateral tearing, bulging, etc., which introduces a large number of edge defects, resulting in the attenuation of the performance of the graphene thermal conductive film, and even violent oxidation combustion, which may cause safety hazards in production.

[0004] In the existing process, in order to inhibit the rapid shedding of oxygen-containing groups, the pretreatment stage usually takes more than 60 hours to control the temperature to slowly rise and accurately keep warm. This process step takes too long, affecting industrial production efficiency. Summary of the invention

[0005] In view of the shortcomings of the existing process, the present invention proposes a method for preparing a reduced graphene oxide film, which includes the following steps: graphene oxide slurry preparation, graphene oxide original film coating, pretreatment, carbonization treatment and graphitization treatment, wherein the pretreatment is carried out in a pressurized and humidified environment, and the maximum temperature of the pretreatment is ≤400°C.

[0006] Furthermore, the pretreatment is a staged treatment, and the staged treatment includes a first stage below 200°C and a second stage above 200°C.

[0007] Furthermore, the humidity in the first stage is controlled at 30% to 80%, and the humidity in the second stage is controlled at <30%.

[0008] Furthermore, the heating rate of the first stage is 0.1°C / min to 0.5°C / min, and the heating rate of the second stage is greater than 0.5°C / min.

[0009] Furthermore, the pressurization specifically involves loading the original graphene oxide film with weight during the pretreatment stage.

[0010] Furthermore, the pretreatment time is 5 to 10 hours.

[0011] Furthermore, the original graphene oxide film also includes a rewetting treatment before the pretreatment.

[0012] Furthermore, the rehumidification treatment is to stand at a constant humidity of 40% to 90% for 10 to 60 minutes.

[0013] Furthermore, in the selection of raw materials, through XPS screening, the CO content of graphene oxide in the graphene oxide slurry is ≥35%, and the C=O content is ≤20%.

[0014] Furthermore, the carbonization temperature is 1000-1600°C, and the graphitization temperature is 2800-3200°C, and the temperature is increased in stages during the carbonization and graphitization processes.

[0015] The present application improves the process of reducing graphene oxide film, and performs pressurized humidification treatment in the pretreatment stage of the original graphene oxide film. The oxygen-containing group shedding reaction of the original graphene oxide film in the pretreatment stage is a quasi-reversible reaction, and the reaction products are water, carbon dioxide, carbon monoxide, etc. Setting a higher humidity in the pretreatment stage can inhibit the violent shedding reaction of the oxygen-containing groups of the graphene oxide film, thereby making the reaction proceed slowly. This process improvement solves the serious expansion and lateral irreparable tearing damage of the graphene film caused by the rapid shedding of a large number of oxygen-containing groups and gas production in the pretreatment stage, improves the orderly self-assembly effect of the reduced graphene oxide film, greatly reduces the pretreatment stage time, and at the same time alleviates the cracking or violent oxidation problem of the original graphene oxide film in the pretreatment stage, improves the safety of the preparation process, and obtains a reduced graphene oxide film with high thermal conductivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0017] Figure 1 This is the XPS graph of the graphene oxide cake used in Example 1 of the present application; Figure 2 This is a SEM image of the reduced graphene oxide film provided in Example 1 of the present application; Figure 3This is a test graph of the thermal diffusion coefficient of the reduced graphene oxide film provided in Example 1 of the present application; Figure 4 This is a SEM image of the reduced graphene oxide film provided in Comparative Example 1 of the present application. DETAILED DESCRIPTION

[0018] The following detailed description of the exemplary embodiments of the present application refers to the accompanying drawings, which form a part of the description, and in which the exemplary embodiments that can be implemented by the present application are shown as examples, wherein the features of the present application are identified by the figure numerals. The following more detailed description of the embodiments of the present application is not intended to limit the scope of the present application as required, but is only for the purpose of illustrating and not limiting the description of the characteristics and features of the present application, so as to propose the best way to perform the present application, and is sufficient to enable those skilled in the art to implement the present application. However, it should be understood that various modifications and variations can be made without departing from the scope of the present application as defined by the appended claims. The detailed description and the accompanying drawings should be considered only as illustrative, not restrictive, and if there are any such modifications and variations, they will all fall within the scope of the present application described herein. In addition, the background technology is intended to illustrate the current status and significance of the research and development of the present technology, and is not intended to limit the present application or the application field of the present application and the present application.

[0019] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by technicians in the technical field to which this application belongs; the terms used in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application; the term "and / or" used herein includes any and all combinations of one or more related listed items.

[0020] If the specific conditions are not specified in the examples, the experiments were carried out under conventional conditions or conditions recommended by the manufacturer. If the manufacturers of the reagents or instruments are not specified, they are all conventional products that can be purchased commercially.

[0021] In order to make the technical problems, technical solutions and advantages to be solved by the present application clearer, a detailed description will be given below with reference to the accompanying drawings and specific embodiments.

[0022] The applicant found that during the heat treatment process of reducing graphene oxide film, it is very sensitive to temperature, especially in the pretreatment stage. When the heating rate is fast, some oxygen-containing groups in the graphene oxide film fall off quickly, resulting in expansion, lateral tearing, bulging and other phenomena of the graphene film. A large number of edge defects are introduced, resulting in the thermal performance of the graphene thermal conductive film attenuation, and even violent oxidation combustion may occur, causing safety hazards in production. In order to suppress the excessive gas production during the pretreatment process, the existing process usually uses temperature control with an accuracy of 0.1°C to slowly heat up and accurately keep warm, but this method usually takes more than 60 hours in this section, affecting industrial production efficiency.

[0023] Based on the above, the applicant improved the existing process and proposed a method for preparing a reduced graphene oxide film.

[0024] A method for preparing a reduced graphene oxide film comprises the following steps: graphene oxide slurry configuration, graphene oxide original film coating, pretreatment, carbonization treatment and graphitization treatment, wherein the pretreatment is carried out in a pressurized and humidified environment, and the maximum temperature of the pretreatment is ≤400°C.

[0025] During the pretreatment of graphene oxide, CO type oxygen-containing groups are mainly removed. This process is a quasi-reversible reaction, and the reaction products are water, carbon dioxide, carbon monoxide, etc. The generation of gaseous products will cause the graphene oxide film to expand at this stage. During the pretreatment process, the graphene oxide film is pressurized to initially inhibit its expansion, thereby controlling the thickness of the pretreated film; the graphene oxide film is humidified, that is, the concentration of the product of the forward reaction in this type of reversible reaction is increased, which can further inhibit the forward reaction and reduce the gas production rate; and according to the thermogravimetric curve of the graphene oxide film, CO type oxygen-containing groups can be completely removed below 400°C. Therefore, based on the consideration of controlling production energy consumption, the maximum temperature of the pretreatment is controlled at ≤400°C.

[0026] In some embodiments of the present application, the pretreatment is a staged treatment, which includes a first stage below 200° C. and a second stage above 200° C. From the thermogravimetric curve of the graphene oxide film, it can be seen that at around 200° C., CO-type oxygen-containing groups can be almost removed.

[0027] Based on the above, further, in some embodiments of the present application, the humidity in the first stage is controlled at 30% to 80%, and the humidity in the second stage is controlled to be less than 30%. In the first stage, the shedding reaction of CO-type oxygen-containing groups can be basically completed. The humidity in the first stage is controlled to be relatively high, thereby reducing the reaction gas production rate of the graphene oxide film and preventing the graphene oxide film from serious expansion and lateral irreparable tearing damage; the humidity in the second stage is controlled to be relatively low, on the one hand, the degree of forward reaction can be improved, and the CO-type oxygen-containing groups that have not been completely removed by the reaction in the previous stage can be supplemented with reaction, and secondly, it can ensure that the film material obtained after the pretreatment stage is dry, which is convenient for subsequent carbonization and graphitization treatment.

[0028] In some embodiments of the present application, the heating rate of the first stage is 0.1°C / min~0.5°C / min, and the heating rate of the second stage is greater than 0.5°C / min. The heating rate of the first stage is controlled to be relatively low, and the reaction gas production rate is further controlled. Since the reaction is basically complete in the second stage, the heating rate can be appropriately increased to save industrial production time.

[0029] In some embodiments of the present application, the pressurization is specifically to load the original graphene oxide film during the pretreatment stage. Specifically, a plate material such as a metal plate or a graphite plate capable of withstanding a temperature of 400° C. can be used to press the original graphene oxide film.

[0030] In some embodiments of the present application, the pretreatment time is 5 to 10 hours. In the existing process, the gas production rate is usually controlled by precise heating rate and insulation time. This method of temperature control needs to be accurate to 0.1°C and is too time-consuming, usually requiring a treatment time of more than 60 hours. The pretreatment method provided in this application only takes 5 to 10 hours in the pretreatment stage.

[0031] In some embodiments of the present application, the graphene oxide original film also includes a rewetting treatment before the pretreatment. The rewetting treatment can make the graphene oxide film fully absorb water, and prevent the uneven wetting of the film material caused by direct pretreatment.

[0032] In some embodiments of the present application, the rehumidification treatment is to stand at a constant humidity of 40% to 90% for 10 to 60 minutes.

[0033] In some embodiments of the present application, in the selection of raw materials, the CO content of the graphene oxide in the graphene oxide slurry is ≥35%, and the C=O content is ≤20% by screening by XPS. The applicant found that for CO, the increase of CO functional groups helps to improve the thermal conductivity of the reduced graphene oxide film, mainly because the CO functional group is located on the surface of the graphene oxide sheet and is removed through the subsequent heat treatment process to restore the original conjugated structure, which not only retains the complete structure of graphite but also increases the stripping rate. The CO-type oxygen-containing group has a low bond energy and is preferentially detached during the low-temperature pretreatment stage. As for C=O, the applicant found that a high C=O content is not conducive to thermal conductivity. C=O is generally considered to be located at the defect holes or edges within the GO surface. When preparing graphene oxide, C=O is formed by the cleavage of CC bonds through strong oxidation, which is usually accompanied by the formation of permanent structural defects. It is removed in the form of CO2 during the heat treatment process to form carbon etching, which is not conducive to the repair of defects. In addition, the C=O type oxygen-containing group has a high bond energy and is mainly detached during the carbonization stage at medium temperature. Controlling the proportion of CO functional groups to be higher, higher than 35%, is more conducive to improving the thermal conductivity of the reduced graphene oxide film; while controlling the proportion of C=O functional groups to be lower, lower than 20%, to reduce the negative effects on the reduced graphene oxide film. At the same time, in this part of the embodiment, since a large proportion of CO functional groups can be removed in the pretreatment stage, the process in the pretreatment stage is more critical.

[0034] In some embodiments of the present application, the carbonization temperature is 1000-1600° C., the graphitization temperature is 2800-3200° C., and the temperature is increased in stages during the carbonization and graphitization processes.

[0035] Specifically, the staged heating during the carbonization process can adjust different heating rates according to the thermogravimetric curve of the graphene oxide film.

[0036] Specifically, the segmented heating process of carbonization is: heating to 500-600 degrees Celsius at a heating rate of 1.5°C / min-4°C / min. Basically, no oxygen-containing group shedding reaction occurs in this temperature range. The heating rate can be appropriately increased. After heating to 500-600 degrees Celsius, the temperature is kept for 0.5-2h to allow the C=O type oxygen-containing group to shedding reaction. Subsequently, the temperature is raised to a carbonization treatment temperature of 1000-1600°C at a heating rate of <1.5°C / min, and the temperature is kept for 30min-3h to complete the carbonization treatment.

[0037] Specifically, the stepwise heating process of graphitization is as follows: heating to 800°C~1200°C at a heating rate of 3°C / min~10°C / min, and then heating to the target temperature at a heating rate of 0.1°C / min~3°C / min. The closer to the target temperature, the slower the heating rate, to ensure that at the graphitization temperature, the carbon atoms can fully crystallize and rearrange to produce a high thermal conductivity reduced graphene oxide film. Example 1

[0038] This embodiment provides a method for preparing a reduced graphene oxide film: S1. Graphene oxide film slurry configuration: Select graphene oxide raw materials with high oxidation degree, high CO ratio, and low C=O ratio, specifically graphene oxide cake with a solid content of 47%, and its XPS characterization is as follows: Figure 1 As shown, the CO ratio is 65.72%, and the C=O ratio is 4.87%; deionized water, 47% solid graphene oxide cake, and ammonia water are used to prepare graphene oxide slurry, wherein the solid content of graphene oxide in the slurry is 11%, and the ratio of ammonia water is 10% of the mass of the input graphene oxide cake. After the graphene oxide cake is stirred and dispersed with a double planetary mixer, an ATS homogenizer is used to homogenize it at a pressure of 700 bar for 2 hours, and then the homogenized graphene oxide water slurry is degassed to obtain graphene oxide slurry.

[0039] S2. Coating of graphene oxide original film: Use a coating machine to coat the degassed graphene oxide slurry on a breathable substrate by blade coating, with a coating thickness of 3500 μm. After drying, a graphene oxide original film is obtained.

[0040] S3, pretreatment: the obtained graphene oxide original film is cut and then laminated, and the lamination order is: stainless steel plate, graphite paper, graphene oxide original film, graphite paper stainless steel plate... stacked in sequence, and after lamination, it is transferred to a programmable constant temperature and humidity tester, and a weight of 10kg is placed on the outermost surface of the laminated sample; the temperature and humidity program is set, firstly, the rehumidification treatment is carried out at a constant temperature of 50℃ and a constant humidity of 80% for 20 minutes, and then the temperature is increased from 50℃ to 200℃ at a heating rate of 0.5℃ / min, and the humidity is always controlled within the range of 70%±5% in this interval, and the graphene oxide film basically completes the CO-type oxygen-containing group shedding reaction in this temperature range; the temperature is increased from 200℃ to 240℃ at a heating rate of 0.8℃ / min, and the humidity is controlled within the range of 20%±5% in this high temperature pretreatment stage, and finally, it is kept at 240℃ for 60 minutes; after the pretreatment is completed, a high-density graphene pretreatment film is obtained; S4, carbonization: The carbonization temperature is 1400°C. The temperature is raised from 25°C to 530°C at a heating rate of 2°C / min, and kept at 530°C for 1.5h, and then the temperature is raised from 530°C to 1400°C at a heating rate of 0.5°C / min, and kept at 1400°C for 60min. After the carbonization treatment is completed, a graphene carbonized film can be obtained.

[0041] S5. Graphitization: The graphitization temperature is 3100°C. Specifically, the temperature is raised to 1000°C at a heating rate of 5°C / min; the temperature is raised from 1000°C to the middle temperature of 2600°C at a heating rate of 2°C / min, and kept warm for 30 minutes; the temperature is raised from 2600°C to 2900°C at a heating rate of 0.5°C / min, and kept warm for 30 minutes; finally, the temperature is raised from 2900°C to the graphitization temperature at a heating rate of 0.1°C / min-0.5°C / min, and kept warm for 1 hour. The entire graphitization process of this step uses high-purity argon gas for atmosphere protection. After the graphitization is completed, the reduced graphene oxide film is rolled to obtain the SEM image of the reduced graphene oxide film as shown in Figure 2 As shown, no large number of pores and tear marks were found in the cross section.

[0042] The obtained graphitized graphene thermal conductive film sample was characterized and tested. The test results showed that the density of the pre-treated film obtained in step S3 was 1.203 g / cm 3 The thermal diffusion coefficient of the graphene thermal conductive film obtained in step S6 is as follows: Figure 3 As shown, up to 1024.190mm 2 / s; This is mainly attributed to the fact that the shedding reaction of oxygen-containing groups in the original graphene oxide film during the pretreatment stage is a quasi-reversible reaction, and the reaction products are water, carbon dioxide, carbon monoxide, etc. Setting a higher humidity during the pretreatment stage can inhibit the violent shedding reaction of oxygen-containing groups in the graphene oxide film, thereby making the reaction proceed slowly. This process improvement solves the serious expansion and lateral irreparable tearing damage of the graphene film caused by the rapid shedding of a large number of oxygen-containing groups during the pretreatment stage, improves the orderly self-assembly effect of the reduced graphene oxide film, greatly reduces the pretreatment stage time, and at the same time alleviates the cracking or violent oxidation problem of the original graphene oxide film during the pretreatment stage, improves the safety of the preparation process, and obtains a reduced graphene oxide film with high thermal conductivity. Example 2

[0043] Different from Example 1, in the selection of raw materials, the CO ratio of the selected graphene oxide cake is 39.30%, and the C=O content is 19.67%. The remaining steps of this example are consistent with those of Example 1.

[0044] The obtained graphite thermal conductive graphene film sample was characterized and tested. The test results showed that the density of the pre-treated film obtained in step S3 was 1.193 g / cm 3 The thermal diffusion coefficient of the reduced graphene oxide film obtained in step S5 is as high as 996.756 mm 2 / s. Example 3

[0045] Different from Example 1, when the original graphene oxide film is pretreated in step S3, the temperature and humidity program in the constant temperature and humidity test machine is designed as follows: first, rehumidify for 50 minutes at a constant temperature of 50°C and a constant humidity of 40%, then increase the temperature from 50°C to 200°C at a heating rate of 0.2°C / min, and control the humidity in this interval within the range of 40%±5%. In this temperature range, the graphene oxide film basically completes the CO-type oxygen-containing group shedding reaction; increase the temperature from 200°C to 360°C at a heating rate of 1.0°C / min, and control the humidity in the high-temperature pretreatment stage within the range of 20%±5%, and finally keep the temperature at 360°C for 60 minutes; after completing the pretreatment, a high-density graphene pretreatment film is obtained. The remaining steps of this embodiment are consistent with those of Example 1.

[0046] The obtained graphite thermal conductive graphene film sample was characterized and tested. The test results showed that the density of the pre-treated film obtained in step S3 was 1.210 g / cm 3 The thermal diffusion coefficient of the reduced graphene oxide film obtained in step S5 is as high as 1008.674 mm 2 / s. Example 4

[0047] The difference between this embodiment and embodiment 1 is that in the pretreatment process of step S3, there is no rewetting treatment at 50°C constant temperature and 80% constant humidity for 20 minutes, and the other steps are consistent with embodiment 1. The purpose is to explore whether the rewetting treatment in the pretreatment stage has an effect on the performance of the graphene thermal conductive film. The results show that the density of the pretreated film obtained in step S3 is 0.957g / cm 3 The thermal diffusion coefficient of the reduced graphene oxide film obtained in step S6 is 955.817 mm 2 / s, both parameters are slightly decreased compared with Example 1. This is mainly due to the fact that there is no rewetting treatment, the graphene oxide film absorbs moisture unevenly, some areas of the graphene oxide film are relatively dry, and the shedding reaction of the oxygen-containing groups of the graphene oxide cannot be perfectly suppressed in the pretreatment stage. The oxygen-containing groups shed and produce gas and are excluded from the cross section, causing certain damage to the graphene thermal conductive film and introducing defects. Comparative Example 1

[0048] The difference between this comparative example and Example 1 is that in the pretreatment process of step S3, the pretreatment is carried out by the conventional pretreatment process, that is, the temperature is raised from room temperature to 70°C within 60 minutes, and kept at 70°C for 480 minutes, thereafter, the temperature is raised from 70°C to 125°C with a gradient of 2°C and a heating rate of 0.2°C / min-0.4°C / min, and the insulation treatment is carried out for 90min-240min at each gradient temperature, and finally the temperature is raised to 240°C at a heating rate of 1°C / min, and kept at 240°C for 180min, the total pretreatment stage takes 69h35min, and the other steps are consistent with Example 1. The purpose is to explore whether there is a difference in performance of the reduced graphene oxide film obtained by the conventional pretreatment means compared with the treatment means of step S3 of Example 1.

[0049] The results show that the density of the pretreated membrane obtained in step S3 is 0.182 g / cm 3 The thermal diffusion coefficient of the reduced graphene oxide film obtained in step S5 is 893.645 mm 2 / s. The obtained reduced graphene oxide film is as follows Figure 4 As shown in the figure, it can be clearly seen that tear marks appear on the cross section due to the shedding of oxygen-containing groups and gas generation.

[0050] This is mainly attributed to the pretreatment of the graphene oxide film in a dry forced air oven. Although the heating rate is very slow and gentle, due to the excessively high CO content in the graphene oxide cake, it is difficult to suppress the shedding reaction rate of oxygen-containing groups in the highly oxidized graphene film. The large-scale shedding of oxygen-containing groups causes a large amount of gas production. The process of gas production being eliminated from the cross section inevitably causes irreversible tearing damage to the graphene sheet and introduces a large number of edge defects, causing the performance of the reduced graphene oxide film to decay. Comparative Example 2

[0051] The difference between this comparative example and Example 1 is that the pretreatment in step S3 is carried out in a dry programmable blast oven, and the humidity in the blast oven is not controlled during the entire pretreatment process. The remaining steps are consistent with Example 1. The purpose is to explore the effect of humidity control in the pretreatment stage on the pretreatment film. It was found that the graphene oxide film had a violent oxidation reaction at a temperature of 80°C, and most of the graphene oxide film was burned. This is mainly attributed to the high degree of oxidation of the selected graphene oxide cake, the high proportion of CO-type oxygen-containing groups with bond energy, and the violent oxygen-containing group shedding reaction during the pretreatment stage under dry environmental conditions. The violent oxygen-containing group shedding reaction caused a strong oxidation reaction of the graphene oxide film, resulting in the burning of the graphene oxide film during the pretreatment stage.

[0052] In the above embodiments, the description of each embodiment has its own emphasis. For parts that are not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0053] The above is a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any technician familiar with the technical field 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 included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A method for preparing a reduced graphene oxide film, comprising graphene oxide slurry preparation, graphene oxide original film coating, pretreatment, carbonization treatment and graphitization treatment, characterized in that: The pretreatment is performed in a pressurized and humidified environment, and the maximum temperature of the pretreatment is ≤400°C.

2. The method for preparing a reduced graphene oxide film according to claim 1, wherein: The pretreatment is a staged treatment, and the staged treatment includes a first stage below 200° C. and a second stage above 200° C.

3. The method for preparing a reduced graphene oxide film according to claim 2, characterized in that: The humidity in the first stage is controlled at 30% to 80%, and the humidity in the second stage is controlled at less than 30%.

4. The method for preparing a reduced graphene oxide film according to claim 2, characterized in that: The heating rate of the first stage is 0.1°C / min to 0.5°C / min, and the heating rate of the second stage is greater than 0.5°C / min.

5. The method for preparing a reduced graphene oxide film according to claim 1, characterized in that: The pressurization specifically involves applying a weight on the original graphene oxide film.

6. The method for preparing a reduced graphene oxide film according to claim 1, characterized in that: The pretreatment time is 5 to 10 hours.

7. The method for preparing a reduced graphene oxide film according to claim 1, characterized in that: The graphene oxide original film also includes a rewetting treatment before the pretreatment.

8. The method for preparing a reduced graphene oxide film according to claim 7, characterized in that: The rehumidification treatment is to stand for 10 to 60 minutes under a constant humidity condition of 40% to 90%.

9. The method for preparing a reduced graphene oxide film according to claim 1, characterized in that: The CO content of the graphene oxide in the graphene oxide slurry is ≥35%, and the C=O content is ≤20%.

10. The method for preparing a reduced graphene oxide film according to claim 1, characterized in that: The carbonization temperature is 1000-1600° C., the graphitization temperature is 2800-3200° C., and the carbonization and graphitization processes are both performed by step-by-step temperature increase.

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