Graphene heat-conducting film and preparation method thereof
By introducing cellulose nanocrystals mixed with graphene oxide into a graphene thermal conductive film, and utilizing its hydroxyl electrostatic repulsion and rigid structure, combined with secondary graphitization treatment, a graphene thermal conductive film with high thermal conductivity was prepared, solving the problem of low thermal conductivity in the existing technology and achieving a significant performance improvement.
Patent Information
- Application Number
- CN202511721227.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-21
- Publication Date
- 2026-01-23
AI Technical Summary
Existing graphene thermal conductive films have low thermal conductivity, which is difficult to improve effectively using conventional methods, and traditional repair strategies are prone to performance degradation.
A high thermal conductivity graphene film was prepared by mixing cellulose nanocrystals with graphene oxide, enhancing dispersion through electrostatic repulsion of hydroxyl groups, improving assembly order and flatness through a one-dimensional rigid rod structure, and combining welding and defect repair strategies with secondary graphitization treatment.
The thermal conductivity of graphene thermal conductive film has been significantly improved, achieving a thermal diffusivity of up to 975.419 mm²/s, solving the problem of improving thermal conductivity while avoiding performance degradation.
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Figure CN121376986A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of thermal management, and more particularly to a graphene thermally conductive film, its preparation method, and its application. Background Technology
[0002] With the rapid development of modern electronic information technology, the integration and power density of electronic components have also increased. This leads to a rapid accumulation of heat in a short period of time. How to quickly and effectively dissipate this heat to ensure the safe and reliable operation of devices and equipment is a challenging problem. Compared to traditional metal heat dissipation materials and composite materials, graphene, with its carbon atoms in sp... 2 Two-dimensional materials composed of single-layer carbon atoms bonded by hybridization are preferred as next-generation heat dissipation materials due to their intrinsic thermal conductivity of up to 5300 W / (mk).
[0003] Among them, graphene thermal conductive film, as a representative of graphene materials in the field of heat dissipation, has become the preferred product for mid-to-high-end heat dissipation due to its thermal conductivity, which is several times higher than that of traditional heat dissipation materials, as well as its flexibility, lightness, and plasticity. However, the thermal conductivity of graphene thermal conductive film is generally around 1300-1700 W / (mk). How to further improve the thermal conductivity of thermal conductive film on the current level is a challenge facing countless researchers. Conventional methods include catalytic graphitization strategy and defect repair strategy. The catalytic graphitization strategy aims to repair defects by introducing iron, cobalt, and nickel catalysts to catalytically decompose carbon active substances at high temperatures, while accelerating the graphitization process and converting non-graphitized carbon structures into highly crystalline graphitized structures. However, the improvement effect of catalytic graphitization is far less than expected, which is related to the formation of carbides. The defect repair strategy involves introducing defect repair agents to repair single-atom vacancies and diatomic vacancies within the graphene framework. However, this strategy is mostly used in research on the microscopic repair mechanism of CVD monolayer graphene, and its application in macroscopic thermal conductive films is relatively limited. Although some studies have mentioned using substances such as glucose, benzene, and lignin to provide active carbon materials for repair at high temperatures, the parameters for the effective decomposition and release of active carbon materials from such carbon sources are quite complex. It is not as simple as changing the heating process, and it can easily lead to the formation and aggregation of amorphous carbon structures, thereby deteriorating the thermal conductivity of the graphene film. Summary of the Invention
[0004] To address the aforementioned strategies and existing problems, we propose a method for preparing high thermal conductivity graphene films by focusing on four aspects: assembly flatness, orderliness, defect control, and defect repair. Specifically, this method involves introducing cellulose nanocrystals into graphene oxide slurry. By utilizing the hydroxyl-rich surface and one-dimensional rigid rod-like structure of cellulose nanocrystals, we can improve the orderliness and flatness of the assembly, while simultaneously inhibiting film expansion, reducing and repairing defects, thereby obtaining a high thermal conductivity graphene film. The order of introduction, amount, and type of surface groups of the cellulose nanocrystals are crucial.
[0005] The first aspect of this application provides a method for preparing a graphene thermal conductive film, comprising the following steps: mixing cellulose nanocrystals with graphene oxide cake, ammonia and deionized water to form a slurry and coating it into a graphene oxide film; then subjecting the graphene oxide film to pretreatment, carbonization, graphitization, and calendering to obtain the graphene thermal conductive film.
[0006] Furthermore, the selected cellulose nanocrystals have a diameter of 5-30 nm and a length of 50-300 nm.
[0007] Generally, the more ordered the assembly of a graphene thermal conductive film, the better its thermal conductivity. Furthermore, cellulose nanocrystals possess modifying functional groups, specifically hydroxyl groups. Adding hydroxyl-rich cellulose nanocrystals to graphene oxide slurry increases the number of hydroxyl groups in the entire mixture, leading to enhanced electrostatic repulsion between hydroxyl groups and between hydroxyl groups and other oxygen-containing functional groups. This improves the dispersibility of the slurry, promotes better assembly order, and ultimately enhances the thermal conductivity of the final graphene thermal conductive film. Although carboxyl and sulfonic acid-modified cellulose nanocrystals also improve the dispersibility of the slurry, they are not suitable for this mixture. The specific reasons are as follows: after the introduction of the carboxyl-COOH group, its hydrolysis transforms the group into a negatively charged COO group. - While electrostatic repulsion between like charges improves the dispersion of the slurry, the introduction of carboxyl groups also increases the carbon loss rate during high-temperature heat treatment. That is, the carboxyl groups decompose into CO2 at high temperatures, which carries away carbon atoms from the edges of graphene oxide, thereby introducing atomic vacancy defects, increasing defect density, and deteriorating thermal conductivity. Sulfonic acid groups are negatively charged, and their addition also improves the dispersion of the slurry. However, the addition of sulfonic acid groups introduces additional sulfur impurities, affecting the crystallization quality of the film material and leading to performance degradation.
[0008] Furthermore, CNC is added after the ammonia, deionized water and graphene oxide cake are mixed and dispersed evenly. This is because the surface of cellulose nanocrystals is rich in hydroxyl groups. When added first, the hydroxyl groups on the surface will be removed in the alkaline environment of the ammonia solution, resulting in poor dispersibility and the formation of clusters. Moreover, after the functional groups are removed, they cannot effectively participate in the self-assembly process of the film material, thus affecting the orderly and flat self-assembly of graphene oxide layer by layer, and the improvement effect on thermal conductivity is not obvious.
[0009] Furthermore, the solid content of cellulose nanocrystals is 0.2~5wt%. In this application, the solid content of cellulose nanocrystals refers to the mass percentage of cellulose nanocrystals in the graphene oxide slurry. With an appropriate amount of cellulose nanocrystals, they play a positive role in promoting orderly assembly and flatness, assisting in the construction of the structure, repairing gaps and overlaps, and repairing defects. However, when the amount added is excessive, the cellulose nanocrystals will form a large number of random and disorderly arrangements and aggregates within and between the sheets, affecting the orderly splicing and assembly of the graphene oxide sheets, thereby leading to performance degradation.
[0010] Preferably, the solid content of the cellulose nanocrystals is 0.6~5wt%.
[0011] Furthermore, the pretreatment temperature is 240~360℃, and / or the carbonization temperature is 900~1400℃, and / or the primary graphitization temperature is 2200~3150℃. Pretreatment aims to remove most of the physically bound water and easily detachable hydroxyl groups; carbonization aims to remove most of the carboxyl groups, carbonyl groups, and some ketones; and graphitization aims to repair defects, promote grain growth, and rearrange the carbon atom structure.
[0012] Furthermore, the density after a single calendering cycle ranges from 1.2 to 2.2 g / cm³. 3 The purpose of calendering is twofold: firstly, to artificially orient the arrangement of the sheets through calendering, thereby eliminating some wrinkles; secondly, since the thermal conductivity of graphene thermal conductive film = specific heat capacity * density * thermal expansion coefficient, calendering is also used to obtain a graphene thermal conductive film of a target thickness with high thermal conductivity.
[0013] Furthermore, after the first calendering, a second graphitization process is also included. The temperature of the second graphitization is 2600~3150℃, which is greater than or equal to the temperature of the first graphitization, in order to achieve better secondary crystallization growth, repair defects, and improve the thermal conductivity of the graphene thermal conductive film.
[0014] Furthermore, after secondary graphitization, a secondary calendering process is also included. The density of the graphene thermally conductive film obtained after secondary calendering is 1.8~2.2 g / cm³. 3 To obtain a graphene thermally conductive film of a target thickness with high thermal conductivity.
[0015] The second aspect of this application provides a graphene thermally conductive film prepared according to the preparation method described in the first aspect of this application.
[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. Assists assembly and enhances the orderliness of membrane assembly. Cellulose nanocrystals are rich in hydroxyl groups on their surface. When added to graphene oxide slurry, they increase the number of hydroxyl groups in the entire mixture, leading to enhanced electrostatic repulsion between hydroxyl groups and between hydroxyl groups and other oxygen-containing functional groups. This improves the dispersibility of the slurry and is beneficial to enhancing the orderliness of assembly.
[0017] 2. Assisting assembly and improving membrane assembly flatness. On one hand, cellulose nanocrystals, with their one-dimensional rod-shaped, highly crystalline, and rigid structure, can effectively act as reinforcing ribs when combined with two-dimensional planar graphene oxide sheets. This reduces the collapse and wrinkling problems caused by the low out-of-plane bending stiffness of the graphene oxide sheets, thus improving sheet flatness. On the other hand, the introduction of hydroxyl groups can also increase the out-of-plane stiffness of graphene oxide, further reducing wrinkle formation and improving sheet assembly flatness.
[0018] 3. Welding and overlapping to suppress membrane expansion and reduce defects. Cellulose nanocrystals are assembled with graphene oxide sheets through abundant surface groups, including in-plane horizontal overlapping, which bridges two graphene oxide sheets together to fill and repair gaps and reduce defects. Interlayer welding also exists, where surface hydroxyl groups bond the upper and lower graphene oxide layers together through hydrogen and chemical bonds. This can suppress thickness expansion during heat treatment and prevent sheet tearing caused by expansion.
[0019] 4. Defect Repair: In-situ repair of defects using activated carbon. During high-temperature graphitization, some outer shell layers of the cellulose nanocrystal structure decompose. The resulting carbon-active materials and atoms participate in defect repair, thereby reducing the defect density of single-atom vacancies and diatomic vacancies.
[0020] 5. Two graphitization processes are performed, with the second graphitization enabling better secondary crystallization and growth of carbon atoms, repairing defects, and improving the thermal conductivity of the graphene thermal conductive film. Attached Figure Description
[0021] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0022] Figure 1The thermal conductivity test results are as shown in Example 1. Figure 2 The thermal conductivity test results are as shown in Example 3. Figure 3 The thermal conductivity test results are for Example 4. Figure 4 The thermal conductivity test results are for Example 5. Figure 5 The thermal conductivity test results are as shown in Example 6. Figure 6 The thermal conductivity test results are for Comparative Example 1. Figure 7 The thermal conductivity test results are for Comparative Example 2. Figure 8 The thermal conductivity test results are for Comparative Example 3. Figure 9 The thermal conductivity test results are for Comparative Example 4. Detailed Implementation
[0023] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described below are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.
[0024] The testing methods involved in this application are as follows: Thermal diffusivity: The test method described in the standard "Q / GDMR 04-2023 Thermal conductivity test by laser flash method" is used, and the test is conducted using the in-plane test method. Example 1
[0025] A method for preparing a graphene thermally conductive film includes the following steps: S1. Weigh a certain amount of deionized water, ammonia water and graphene oxide cake and stir and disperse them. After dispersion, add hydroxycellulose nanocrystal solution with a graphene oxide addition mass ratio of 1wt% and continue stirring and dispersing. After uniform dispersion, coat it into a film in any way and dry it. S2. The coated film is pretreated at 240℃, carbonized at 1200℃, and graphitized at 2800℃ in the order of processing. S3. The sample after primary graphitization is calendered, and the calendering density is controlled at 1.516 g / cm³. 3 ; S4. The calendered sample after the first graphitization is subjected to a second graphitization treatment at 3150℃. After natural cooling, the sample is removed and its performance is tested. The test results are as follows: Figure 1 As shown in the results, at this addition amount, the thermal diffusivity of the resulting membrane material is as high as 975.419 mm. 2 / s.
[0026] In other embodiments, the pretreatment temperature can be any temperature between 240 and 360°C, the carbonization temperature can be any temperature between 900 and 1400°C, the primary graphitization temperature can be any temperature between 2200 and 3150°C, and the secondary graphitization temperature can be any temperature between 2600 and 3150°C, and the secondary graphitization temperature is greater than or equal to the primary graphitization temperature. Example 2
[0027] This embodiment differs from Embodiment 1 in that it further includes step S5: after the sample has undergone secondary graphitization and has cooled naturally, it is subjected to a secondary calendering process. The density of the graphene thermally conductive film obtained after the secondary calendering process is 2.095 g / cm³. 3 . Example 3
[0028] A method for preparing a graphene thermally conductive film includes the following steps: S1. Weigh a certain amount of deionized water, ammonia water and graphene oxide cake and stir and disperse them. After dispersion, add 3wt% of hydroxycellulose nanocrystals of graphene oxide and continue stirring and dispersing. After dispersion, coat it into a film in any way and dry it. S2. The coated film is pretreated at 240℃, carbonized at 1200℃, and graphitized at 2800℃ in the order of processing. S3. The sample after primary graphitization is calendered, and the calendering density is controlled at 1.509 g / cm³. 3 ; S4. The calendered sample after the first graphitization is subjected to a second graphitization treatment at 3150℃. After natural cooling, the sample is removed and its performance is tested. The test results are as follows: Figure 2 As shown in the results, the thermal diffusivity of the resulting membrane at this addition amount is 930.078 mm. 2 / s. Example 4
[0029] A method for preparing a graphene thermally conductive film includes the following steps: S1. Weigh a certain amount of deionized water, ammonia water and graphene oxide cake and stir and disperse them. After dispersion, add 5 wt% of hydroxycellulose nanocrystals to the graphene oxide and continue stirring and dispersing. After dispersion, coat it into a film in any way and dry it. S2. The coated film is pretreated at 240℃, carbonized at 1200℃, and graphitized at 2800℃ in the order of processing. S3. The sample after primary graphitization is calendered, and the calendering density is controlled at 1.504 g / cm³. 3 ; S4. The calendered sample after the first graphitization is subjected to a second graphitization treatment at 3150℃. After natural cooling, the sample is removed and its performance is tested. The test results are as follows: Figure 3 As shown in the results, the thermal diffusivity of the resulting membrane material at this addition amount is 914.951 mm. 2 / s. Example 5
[0030] A method for preparing a graphene thermally conductive film includes the following steps: S1. Weigh a certain amount of deionized water, ammonia water and graphene oxide cake and stir and disperse them. After dispersion, add 0.8wt% of hydroxycellulose nanocrystals of graphene oxide and continue stirring and dispersing. After dispersion, coat it into a film in any way and dry it. S2. The coated film is pretreated at 240℃, carbonized at 1200℃, and graphitized at 2800℃ in the order of processing. S3. The sample after primary graphitization is calendered, and the calendering density is controlled at 1.510 g / cm³. 3 ; S4. The calendered sample after the first graphitization is subjected to a second graphitization treatment at 3150℃. After natural cooling, the sample is removed and its performance is tested. The test results are as follows: Figure 4 As shown in the results, the thermal diffusivity of the resulting membrane material at this addition amount is 940.102 mm. 2 / s. Example 6
[0031] A method for preparing a graphene thermally conductive film, except for changing the order of adding cellulose nanocrystals in step S1 and the single-calendering density, is identical to that in Example 1. Specifically, cellulose nanocrystals are added first. The steps involve weighing cellulose nanocrystals (1% wt of graphene oxide) into a mixed solution of deionized water and ammonia, then stirring and dispersing them. After dispersion, graphene oxide cake is added and dispersed. The density of the graphene thermally conductive film after single-calendering is controlled at 1.508 g / cm³.3 The test results of the sample are as follows: Figure 5 As shown in the results, the thermal diffusivity of the resulting membrane material at this addition amount is 912.930 mm. 2 / s. Comparative Example 1
[0032] A method for preparing a graphene thermally conductive film, wherein cellulose nanocrystals are not added in step S1, and the primary calendering density is controlled at 1.538 g / cm³. 3 Except for the steps, the rest are the same as in Example 1. The test results for the samples are as follows: Figure 6 As shown in the results, the thermal diffusivity of the resulting membrane material without the addition of cellulose nanocrystals is 897.629 mm. 2 / s. Comparative Example 2
[0033] A method for preparing a graphene thermally conductive film includes the following steps: S1. Weigh a certain amount of deionized water, ammonia water and graphene oxide cake and stir and disperse them. After dispersion, add 10wt% of hydroxycellulose nanocrystals of graphene oxide and continue stirring and dispersing. After dispersion, coat it into a film in any way and dry it. S2. The coated film is pretreated at 240℃, carbonized at 1200℃, and graphitized at 2800℃ in the order of processing. S3. The sample after primary graphitization is calendered, and the calendering density is controlled at 1.585 g / cm³. 3 ; S4. The calendered sample after the first graphitization is subjected to a second graphitization treatment at 3150℃. After natural cooling, the sample is removed and its performance is tested. The test results are as follows: Figure 7 As shown in the results, the thermal diffusivity of the resulting membrane material at this addition amount is 837.264 mm. 2 / s. Comparative Example 3
[0034] A method for preparing a graphene thermally conductive film, which, except that the hydroxyl cellulose nanocrystals in step S1 are replaced with carboxylated cellulose nanocrystals, and the primary calendering density is controlled at 1.524 g / cm³. 3 Except for the steps, the rest are the same as in Example 1. The test results for the samples are as follows: Figure 8 As shown in the results, the thermal diffusivity of the resulting membrane material at this addition amount is 895.137 mm. 2 / s. Comparative Example 4
[0035] A method for preparing a graphene thermally conductive film, wherein the hydroxyl cellulose nanocrystals in step S1 are replaced with sulfonated cellulose nanocrystals, and the primary calendering density is controlled at 1.512 g / cm³. 3 Except for the steps, the rest are the same as in Example 1. The test results for the samples are as follows: Figure 9 As shown in the results, the thermal diffusivity of the resulting membrane material at this addition amount is 895.165 mm. 2 / s.
[0036] By comparing Examples 1 to 5 and Comparative Examples 1 and 2, it can be found that the thermal diffusivity of the membrane material obtained without the addition of cellulose nanocrystals is 897.625 mm² / s. When 0.8% wt of cellulose nanocrystals is introduced, the thermal diffusivity of the membrane material can be significantly improved to 940.102 mm² / s. 2 The performance is significantly improved. Further increases in the amount of cellulose nanocrystals lead to an optimal addition point of 1%wt, where the thermal diffusion performance gains are maximized to 975.419 mm² / s. Before this point, the thermal diffusion value increases with increasing cellulose nanocrystal addition. Beyond this point, the thermal diffusion decreases with further increases in addition. When the addition reaches 10%wt, the thermal diffusion drops below the performance of normal membrane materials, actually deteriorating performance. This is because, at appropriate addition levels, cellulose nanocrystals play a positive role in promoting assembly order and flatness, repairing gaps and overlaps, and repairing defects. However, when the addition is excessive, cellulose nanocrystals undergo a large amount of random and disordered arrangement and aggregation within and between the sheets, affecting the orderly assembly of graphene oxide sheets. Simultaneously, the release of large amounts of carbon-containing materials during the high-temperature graphitization heat treatment cannot be consumed or diffused in time, resulting in the accumulation of amorphous carbon deposition regions, which become phonon scattering centers, leading to performance degradation.
[0037] By comparing Example 1, Comparative Example 3, and Comparative Example 4, it can be concluded that under the same amount of cellulose nanocrystals added, different modifying groups have a significant impact on the final thermal diffusivity of the membrane material. Hydroxylation has the best effect, while carboxylation and sulfonic acid groups have virtually no improvement effect. Hydroxylated cellulose nanocrystals are rich in hydroxyl groups on their surface. Adding them to the graphene oxide slurry increases the number of hydroxyl groups in the entire mixture, leading to enhanced electrostatic repulsion between hydroxyl groups and between hydroxyl groups and other oxygen-containing functional groups. This improves the dispersibility of the slurry and is beneficial for improving assembly order. Furthermore, the surface hydroxyl groups weld the upper and lower layers of graphene oxide together through hydrogen and chemical bonds, which can suppress the thickness expansion and sheet tearing problems caused by expansion during heat treatment. For carboxylated cellulose nanocrystals (CNC), the introduction of carboxyl-COOH groups results in hydrolysis, turning the groups into negatively charged COO groups. - While electrostatic repulsion between like charges improves the dispersion of the slurry, the introduction of carboxyl groups also increases the carbon loss rate during high-temperature heat treatment. That is, the carboxyl groups decompose into CO2 at high temperatures, carrying away carbon atoms from the edges of graphene oxide, thereby introducing atomic vacancy defects, increasing defect density, and failing to improve thermal conductivity. Sulfonic acid groups are negatively charged, and their addition also improves the dispersion of the slurry. However, the addition of sulfonic acid groups introduces additional sulfur impurities, affecting the crystallization quality of the film material, resulting in no performance improvement.
[0038] By comparing Examples 1 and 6, it can be found that the order of addition of cellulose nanocrystals is also an important factor affecting the improvement of the thermal conductivity of the membrane material. This is because the surface of cellulose nanocrystals is rich in hydroxyl groups. When added first, the hydroxyl groups on the surface will be removed in the alkaline environment of ammonia solution, which will lead to poor dispersibility and the formation of clusters. Furthermore, after the functional groups are removed, they cannot effectively participate in the self-assembly process of the membrane material, thus affecting the orderly and flat self-assembly of graphene oxide layer by layer, and the final performance improvement is not significant.
[0039] In summary, this invention provides a method for preparing high thermal conductivity graphene films that combines assembly assistance, defect repair, and gap control. By introducing cellulose nanocrystals into graphene oxide slurry, the functional groups and rigid rod-like structure of cellulose nanocrystals enhance the assembly order and flatness of the graphene oxide. Secondly, welding inhibits film expansion and reduces the introduction of tearing defects. Finally, in-situ defect repair repairs single-atom and two-atom vacancies, and secondary graphitization achieves better secondary crystallization growth of carbon atoms, resulting in a high-performance, high thermal conductivity graphene thermal conductive film. This is a simple, efficient, economical, and easily scalable feasible production solution for large-scale mass production.
[0040] In the above embodiments, the descriptions of each embodiment have different focuses. For parts that are not described in detail in a certain embodiment, please refer to the relevant descriptions in other embodiments.
[0041] The above description describes specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and these modifications or substitutions should all be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.
Claims
1. A method for preparing a graphene thermally conductive film, characterized in that, Includes the following steps: Cellulose nanocrystals are mixed with graphene oxide cake, ammonia and deionized water to form a slurry, which is then coated onto a graphene oxide film. The graphene oxide film is then pretreated, carbonized, graphitized once, and calendered once to obtain a graphene thermal conductive film.
2. The method for preparing a graphene thermally conductive film according to claim 1, characterized in that, The functional group modifying the cellulose nanocrystals is hydroxyl.
3. The method for preparing a graphene thermally conductive film according to claim 2, characterized in that, The cellulose nanocrystals were added after the ammonia water, deionized water and graphene oxide cake were mixed and dispersed evenly.
4. The method for preparing a graphene thermally conductive film according to claim 1, characterized in that, The solid content of the cellulose nanocrystals is 0.2~5wt%.
5. The method for preparing a graphene thermally conductive film according to claim 4, characterized in that, The solid content of the cellulose nanocrystals is 0.6~5wt%.
6. The method for preparing a graphene thermally conductive film according to claim 1, characterized in that, The pretreatment temperature is 240~360℃, and / or the carbonization temperature is 900~1400℃, and / or the primary graphitization temperature is 2200~3150℃.
7. The method for preparing a graphene thermally conductive film according to claim 1, characterized in that, The density of the graphene thermally conductive film obtained after the first rolling process is 1.2~2.2 g / cm³. 3 .
8. The method for preparing a graphene thermally conductive film according to claim 1, characterized in that, After the first rolling, a second graphitization process is also included, with the temperature of the second graphitization being 2600~3150℃.
9. The method for preparing a graphene thermally conductive film according to claim 8, characterized in that, Following the secondary graphitization, a secondary calendering process is also included, resulting in a graphene thermally conductive film with a density of 1.8~2.2 g / cm³. 3 .
10. A graphene thermally conductive film, characterized in that, The graphene thermal conductive film is prepared by the preparation method according to any one of claims 1 to 9.