Preparation method of carbon nanotube / graphite composite carbon material

Abstract

The invention relates to a preparation method of a carbon nanotube / graphite composite carbon material, which comprises the following steps: S1, carrying out ball milling treatment on calcium hydride in an inert atmosphere, and carrying out ball-material separation to obtain calcium hydride powder; s2, in an inert atmosphere, uniformly mixing the calcium hydride powder obtained in the step S1 and hydroboron in a ball milling tank without milling balls through a ball milling machine, and transferring the mixture into a closed container; and S3, vacuumizing the closed container in the S2, introducing CO2 with preset pressure intensity for reaction, and after the reaction is finished, performing post-treatment to obtain the carbon nanotube / graphite composite carbon material. The carbon nano tube / graphite composite carbon material is synthesized from CO2 as a carbon source, calcium hydride and hydroboron at low temperature, the defect that a nano transition metal catalyst is needed originally is directly overcome, and the method has the advantages that the reaction condition is mild and green, the operation is simple and convenient, and a predetermined carbon material can be efficiently formed.

Description

Technical Field

[0001] The present invention relates to the technical field of composite carbon materials, and particularly to a preparation method of a carbon nanotube / graphite composite carbon material. Background Art

[0002] Carbon nanotubes (CNTs) are a novel nanomaterial with unique structures and excellent properties, showing broad application prospects in many fields. Graphite materials, with their high electrical and thermal conductivity, excellent thermal stability, and chemical stability, have become an ideal choice in the energy field. The composite carbon material formed by the combination of carbon nanotubes and graphite significantly improves the comprehensive performance of the material through synergistic effects. Among them, the one-dimensional conductive channels of carbon nanotubes are combined with the two-dimensional layered structure of graphite to form a three-dimensional interpenetrating network structure, which not only endows the material with more excellent electrical and thermal conductivity, but also ensures its high mechanical strength and structural stability. In addition, this composite carbon material shows great application potential in lightweight aerospace materials, heat sinks for high thermal conductivity electronic devices, and electrocatalytic conversion of CO2. For example, the defect sites on its surface can achieve the directional catalysis of CO2 and convert it into high-value chemical products. At the same time, from the perspectives of environmental protection and economy, combined with CO2 resource utilization technology, this composite carbon material also helps to promote the carbon circular economy and meet the goals of sustainable development. Despite the excellent performance of the carbon nanotube / graphite composite carbon material, its preparation technology still faces significant challenges. Traditional synthesis methods, such as chemical vapor deposition, rely on carbon sources such as methane and ethylene, which leads to high carbon emissions during the production process and requires graphitization treatment at temperatures exceeding 2500 °C, consuming a large amount of energy; in the existing processes, the combination of CNTs and graphite is usually achieved through step-by-step synthesis or mechanical mixing, which results in weak interfacial bonding and uneven structure, seriously affecting the performance consistency; while in-situ growth technology is limited by the efficiency of the catalyst.

[0003] Currently, the main methods for synthesizing carbon nanotube / graphene composites include the following three: (1) Chemical vapor deposition (Chen, X.; Tao, J.; Yi, J.; Liu, Y.; Li, C.; Bao, R., Strengthening behavior of carbon nanotube-graphene hybrids in copper matrix composites. Materials Science and Engineering: A 2018.), which uses copper powder as a catalyst and grows carbon nanotube / graphene composite carbon materials on the surface of copper powder through chemical vapor deposition technology and subsequent annealing sintering process; (2) Microwave radiation method (Odedairo, T.; Ma, J.; Gu, Y.; Chen, J.; Zhao, X. S.; Zhu, Z., One-pot synthesis of carbon nanotube-graphene hybrids via syngas production. Journal of Materials Chemistry A 2013.), which uses high-power microwave to irradiate a mixed gas of hydrogen and carbon monoxide and uses nickel, cadmium, etc. as catalysts to synthesize carbon nanotube / graphene composite carbon materials; (3) Electrophoretic deposition method (Zhou, Y.; Qian, W.; Huang, W.; Liu, B.; Lin, H.; Dong, C., Carbon Nanotube-Graphene Hybrid Electrodes with Enhanced Thermo-Electrochemical Cell Properties. Nanomaterials 2019.), which ultrasonically disperses carbon nanotubes and graphene in specific solutions respectively and finally synthesizes carbon nanotube / graphene composites by using electric current and annealing process. However, these methods generally have the limitations of high energy consumption, complex processes and mostly requiring nano-transition metal catalysts. Therefore, it is particularly important to study a new type of green, efficient and metal-catalyst-free method for preparing carbon nanotube / graphene composite carbon materials. Summary of the Invention

[0004] The problem to be solved by the present invention is to provide a preparation method of a carbon nanotube / graphite composite carbon material in view of the above deficiencies in the prior art. The method uses CO2 as a carbon source and synthesizes the carbon nanotube / graphite composite carbon material at low temperature with calcium hydride and borohydride, directly overcoming the defect of the original need for a nano-transition metal catalyst, and having the advantages of mild and green reaction conditions, simple operation, and being able to efficiently form a predetermined carbon material.

[0005] The above object of the present invention is achieved by the following technical solutions: A preparation method of a carbon nanotube / graphite composite carbon material includes the following steps: S1 Under an inert atmosphere, calcium hydride is subjected to ball milling treatment, and after separating the balls from the material, calcium hydride powder is obtained; S2 Under an inert atmosphere, the calcium hydride powder obtained in S1 and borohydride are mechanically mixed in a ball milling jar without milling balls, and then transferred to a closed container; S3 After evacuating the closed container in S2, CO2 at a predetermined pressure is introduced for reaction, and after post-treatment after the reaction, a carbon nanotube / graphite composite carbon material is obtained.

[0006] Further, in S1 and S2, the inert gas of the inert atmosphere is argon, nitrogen, and / or helium.

[0007] Further, in S1, the material of the milling balls for the ball milling treatment is stainless steel, agate, or zirconia.

[0008] Further, in S1, the ball-to-material ratio of the ball milling treatment is controlled to be 20-80:1.

[0009] Further, in S1, the ball milling speed of the ball milling treatment is controlled to be 300-500 rpm, and the ball milling time is 3-24 h.

[0010] Further, in S2, the borohydride is crystalline lithium borohydride and / or sodium borohydride powder, and the particle size range of the borohydride is 50-300 μm.

[0011] Still further, in S2, the dosage ratio of calcium hydride to borohydride is controlled to be 2-5 mol:1 mol.

[0012] Further, in S3, it is controlled that the maximum pressure of CO2 during the reaction needs to exceed 150 bar, and CO2 is in excess relative to calcium hydride and borohydride.

[0013] Further, in S3, the heating rate of the reaction is controlled to be 0.1-10 °C / min, and the target reaction temperature is 50-200 °C.

[0014] Further, in the step S3, after the reaction is completed, pickling, solid-liquid separation, and solid drying treatments are carried out in sequence.

[0015] Still further, in the step S3, the pickling acid solution is hydrochloric acid with a concentration of 0.5 - 2.0 mol / L, the pickling time is controlled to be 12 - 36 h, and the pickling temperature is 150 - 200 °C.

[0016] Still further, in the step S3, the drying temperature for solid drying is controlled to be 60 - 120 °C, and the drying time is 6 - 24 h.

[0017] In summary, the beneficial technical effects of the present invention are as follows: 1. The preparation method of the present invention can obtain graphite materials under low-temperature conditions without going through the traditional high-temperature graphitization process at 3000 °C, which is beneficial for saving energy, reducing potential environmental risks, and has great potential for industrial and commercial applications; 2. The preparation method of the present invention does not require the traditional method of step-by-step synthesis or mechanical mixing to synthesize composite carbon materials. It can in-situ synthesize the predetermined carbon nanotube / graphite composite carbon materials through a one-step method. This method not only simplifies the operation process, has a simple process, but also improves production efficiency, reduces production costs, and makes the preparation process of composite carbon materials more efficient and economical; 3. The preparation method of the present invention prepares composite carbon materials by consuming the greenhouse gas CO2, which not only reduces greenhouse gas emissions but also realizes the recycling of resources, meeting the current requirements for green and low-carbon development; 4. The raw materials of the present invention are simple and easy to obtain. It uses CO2 as a carbon source and synthesizes carbon nanotube / graphite composite carbon materials at low temperature with calcium hydride and borohydride, directly overcoming the limitations of the original need for nano-transition metal catalysts, which is of great significance for breaking through the field barriers. Description of the Drawings

[0018] Figure 1 is the temperature-pressure curve of the S3 reaction process in Example 1 of the present invention.

[0019] Figure 2 is the XRD pattern of the carbon nanotube / graphite composite carbon material obtained in Example 1 of the present invention.

[0020] Figure 3 is the scanning electron microscope image of the carbon nanotube / graphite composite carbon material obtained in Example 1 of the present invention.

[0021] Figure 4 is the transmission electron microscope image and selected area electron diffraction pattern of the carbon nanotube / graphite composite carbon material obtained in Example 1 of the present invention.

[0022] Figure 5It is the scanning electron microscope image and XRD pattern of the carbon material obtained in Comparative Example 1 of the present invention.

[0023] Figure 6 It is the scanning electron microscope image and XRD pattern of the carbon material obtained in Comparative Example 2 of the present invention.

[0024] Figure 7 It is the scanning electron microscope image and XRD pattern of the carbon material obtained in Comparative Example 3 of the present invention.

[0025] Figure 8 It is the scanning electron microscope image and XRD pattern of the carbon material obtained in Comparative Example 4 of the present invention. Detailed implementation manners

[0026] In order to make the technical means, creative features, achieved purposes and functions of the present invention clearer and easier to understand, the present invention will be further described below with reference to the accompanying drawings and specific implementation manners. Examples

[0027] Example 1: A preparation method of a carbon nanotube / graphite composite carbon material disclosed in the present invention, comprising the following steps. S1 Under an argon atmosphere, 2 g of calcium hydride and zirconia grinding balls are loaded into a stainless steel ball mill jar for ball milling, and the ball-to-material ratio is controlled at 40:1. After sealing, it is ball milled at a speed of 500 rpm on a planetary ball mill for 24 h to obtain calcium hydride powder. S2 Under an argon atmosphere, 0.04 mol of the calcium hydride powder obtained in S1 and 0.01 mol of borohydride are mechanically mixed in a ball mill jar without grinding balls. The borohydride is lithium borohydride, and it is transferred to a sealed container. S3 After evacuating the sealed container of S2, 38 g of CO2 is introduced, and it is heated to a reaction temperature of about 60 °C at a heating rate of 5 °C / min. The reaction is carried out at a maximum reaction pressure greater than 150 bar. Observe the temperature-pressure curve (refer to Figure 1 ), and when the temperature-pressure suddenly rises and then falls, the reaction ends. Then, it is successively treated with 1.0 mol / L hydrochloric acid at 200 °C for 24 h, solid-liquid separation, and drying of the solid at 80 °C for 6 h to obtain the carbon nanotube / graphite composite carbon material.

[0028] Example 2: A preparation method of a carbon nanotube / graphite composite carbon material disclosed in the present invention, comprising the following steps. S1 Under an argon atmosphere, 2 g of calcium hydride and zirconia grinding balls are loaded into a stainless steel ball mill jar for ball milling, and the ball-to-material ratio is controlled at 40:1. After sealing, it is ball milled at a speed of 500 rpm on a planetary ball mill for 24 h to obtain calcium hydride powder. S2 Under an argon atmosphere, 0.03 mol of the calcium hydride powder obtained in S1 and 0.01 mol of borohydride were mechanically mixed in a ball milling jar without milling balls. The borohydride was lithium borohydride, and then transferred to a sealed container; S3 After evacuating the sealed container of S2, 38 g of CO2 was introduced, and it was heated to a reaction temperature of about 60 °C at a heating rate of 5 °C / min. The reaction was carried out at a maximum reaction pressure greater than 150 bar. The temperature-pressure curve was observed. When the temperature-pressure suddenly increased and then decreased, the reaction ended. Then, it was successively treated with 1.0 mol / L hydrochloric acid at 150 °C for 24 h, solid-liquid separation, and drying of the solid at 80 °C for 6 h to obtain the carbon nanotube / graphite composite carbon material.

[0029] Example 3: A method for preparing a carbon nanotube / graphite composite carbon material disclosed in the present invention, comprising the following steps, S1 Under an argon atmosphere, 2 g of calcium hydride and zirconia grinding balls were loaded into a stainless steel ball milling jar for ball milling, and the ball-to-material ratio was controlled to be 40:1. After sealing, it was ball milled at a speed of 500 rpm on a planetary ball mill for 24 h to obtain calcium hydride powder; S2 Under an argon atmosphere, 0.03 mol of the calcium hydride powder obtained in S1 and 0.01 mol of borohydride were mechanically mixed in a ball milling jar without milling balls. After that, the borohydride was sodium borohydride, and then transferred to a sealed container; S3 After evacuating the sealed container of S2, 38 g of CO2 was introduced, and it was heated to a reaction temperature of about 70 °C at a heating rate of 5 °C / min. The reaction was carried out at a maximum reaction pressure greater than 150 bar. The temperature-pressure curve was observed. When the temperature-pressure suddenly increased and then decreased, the reaction ended. Then, it was successively treated with 1.0 mol / L hydrochloric acid at 150 °C for 24 h, solid-liquid separation, and drying of the solid at 80 °C for 6 h to obtain the carbon nanotube / graphite composite carbon material.

[0030] Example 4: A method for preparing a carbon nanotube / graphite composite carbon material disclosed in the present invention, comprising the following steps, S1 Under an argon atmosphere, 2 g of calcium hydride and zirconia grinding balls were loaded into a stainless steel ball milling jar for ball milling, and the ball-to-material ratio was controlled to be 40:1. After sealing, it was ball milled at a speed of 500 rpm on a planetary ball mill for 24 h to obtain calcium hydride powder; S2 Under an argon atmosphere, 0.04 mol of the calcium hydride powder obtained in S1 and 0.01 mol of borohydride were mechanically mixed in a ball milling jar without milling balls. The borohydride was sodium borohydride, and then transferred to a sealed container; After evacuating the closed container of S2 to a vacuum, 38 g of CO2 was introduced, and it was heated to a reaction temperature of about 70 °C at a heating rate of 5 °C / min for the reaction. The maximum reaction pressure was greater than 150 bar. The temperature-pressure curve was observed. When a sudden increase and then a drop in temperature and pressure occurred, the reaction ended. Then, it was successively treated with 1.0 mol / L hydrochloric acid at 150 °C for 24 h, solid-liquid separation, and drying of the solid at 80 °C for 6 h to obtain the carbon nanotube / graphite composite carbon material.

[0031] Example 5: A method for preparing a carbon nanotube / graphite composite carbon material disclosed in the present invention includes the following steps. S1: Under an argon atmosphere, 2 g of calcium hydride and stainless steel grinding balls were loaded into a stainless steel ball mill jar for ball milling, and the ball-to-material ratio was controlled to be 20:1. After sealing, it was ball milled at a speed of 300 rpm on a planetary ball mill for 3 h to obtain calcium hydride powder. S2: Under an argon atmosphere, 0.02 mol of the calcium hydride powder obtained in S1 and 0.01 mol of borohydride were mechanically mixed in a ball mill jar without grinding balls. The borohydride was lithium borohydride, and then it was transferred to a closed container. S3: After evacuating the closed container of S2 to a vacuum, 38 g of CO2 was introduced, and it was heated to a reaction temperature of about 70 °C at a heating rate of 0.1 °C / min. The reaction was carried out with a maximum reaction pressure greater than 150 bar. The temperature-pressure curve was observed. When a sudden increase and then a drop in temperature and pressure occurred, the reaction ended. Then, it was successively treated with 0.5 mol / L hydrochloric acid at 120 °C for 12 h, solid-liquid separation, and drying of the solid at 60 °C for 2 h to obtain the carbon nanotube / graphite composite carbon material.

[0032] Example 6: A method for preparing a carbon nanotube / graphite composite carbon material disclosed in the present invention includes the following steps. S1: Under a helium atmosphere, 2 g of calcium hydride and agate grinding balls were loaded into a stainless steel ball mill jar for ball milling, and the ball-to-material ratio was controlled to be 80:1. After sealing, it was ball milled at a speed of 500 rpm on a planetary ball mill for 24 h to obtain calcium hydride powder. S2: Under a helium atmosphere, 0.05 mol of the calcium hydride powder obtained in S1 and 0.01 mol of borohydride were mechanically mixed in a ball mill jar without grinding balls. The borohydride was sodium borohydride, and then it was transferred to a closed container. After evacuating the closed container of S2 to vacuum by S3, 48 g of CO2 was introduced, and it was heated to a reaction temperature of about 70 °C at a heating rate of 10 °C / min. The reaction was carried out with the maximum reaction pressure greater than 150 bar. The temperature-pressure curve was observed. When the temperature and pressure suddenly increased and then decreased, the reaction ended. Then, it was successively treated with 2.0 mol / L hydrochloric acid at 200 °C for 60 h, solid-liquid separation, and drying of the solid at 120 °C for 12 h to obtain a carbon nanotube / graphite composite carbon material. Comparative Example

[0033] Comparative Example 1: A method for preparing a carbon nanotube / graphite composite carbon material disclosed in the present invention. The difference from Example 1 is that only lithium borohydride was used as the solid reactant, and other experimental conditions were ensured to be the same. The reaction occurred when heated to a reaction temperature of about 60 °C, but no carbon material could be obtained. It was continuously heated to about 270 °C, and a secondary reaction occurred. It was successively treated with 1.0 mol / L hydrochloric acid at 150 °C for 24 h, solid-liquid separation, and drying of the solid at 80 °C for 6 h to obtain an amorphous carbon material without graphite and carbon nanotubes.

[0034] Comparative Example 2: A method for preparing a carbon nanotube / graphite composite carbon material disclosed in the present invention. The difference from Example 1 is that only calcium hydride was used as the solid reactant, and other experimental conditions were ensured to be the same. The reaction occurred when heated to a reaction temperature of about 240 °C, and then it was successively treated with 1.0 mol / L hydrochloric acid at 150 °C for 24 h, solid-liquid separation, and drying of the solid at 80 °C for 6 h to obtain a graphite material.

[0035] Comparative Example 3: A method for preparing a carbon nanotube / graphite composite carbon material disclosed in the present invention. The difference from Example 1 is that the maximum pressure during the reaction process was controlled to be 100 bar by reducing the mass of CO2 introduced, and then it was successively treated with 1.0 mol / L hydrochloric acid at 150 °C for 24 h, solid-liquid separation, and drying of the solid at 80 °C for 6 h to obtain a carbon material without carbon nanotubes and with a low degree of graphitization.

[0036] Comparative Example 4: A method for preparing a carbon nanotube / graphite composite carbon material disclosed in the present invention. The difference from Example 1 is that the reaction was carried out according to the reaction conditions of Example 5 of CN105271178B, including the following steps: S1 Under an argon atmosphere, 2 g of calcium hydride and zirconia grinding balls were loaded into a stainless steel ball milling tank for ball milling treatment, and the ball-to-material ratio was controlled to be 40:1. After sealing, it was ball milled at a speed of 500 rpm on a planetary ball mill for 24 h to obtain calcium hydride powder. S2 Under an argon atmosphere, 0.04 mol of calcium hydride powder and 0.01 mol of borohydride were mechanically mixed in a ball milling jar without grinding balls. The borohydride was lithium borohydride, and then it was transferred to a ventable ball milling jar. S3 After slowly introducing 5 g of CO2 into the ball milling jar, 0.5 mL of ethanol was injected into the reactor through the pressure difference. The heat released by the reaction of ethanol with calcium hydride / lithium borohydride could trigger the reaction of calcium hydride / lithium borohydride and CO2 gas. (During the reaction process, the pressure in the reactor increased from 15 bar to 25 bar) After the reaction ended and cooled, the gas in the reactor was collected first, and then the solid product in the reactor was taken out and soaked in 5 wt% dilute hydrochloric acid for 12 h, and then it was filtered, washed with water, and dried to obtain an amorphous carbon material without graphite and carbon nanotubes. Performance detection test

[0037] The reaction temperature and pressure during the S3 reaction process of Example 1 were tested, and the reaction temperature and pressure curve was plotted. From Figure 1 It can be seen that the addition of lithium borohydride and the reaction with CO2 further reduced the reaction temperature of calcium hydride and CO2, realizing a more low-temperature and green conversion of greenhouse gases into carbon materials.

[0038] The composite carbon material prepared in Example 1 was verified by XRD, and the results were as Figure 2 shown. It can be seen that the preparation method of the present invention can in-situ synthesize the predetermined carbon nanotube / graphite composite carbon material by a one-step method.

[0039] The composite carbon material prepared in Example 1 and the carbon materials prepared in Comparative Examples 1-3 were tested by scanning electron microscopy, and the composite carbon material prepared in Example 1 was tested by transmission electron microscopy. The results were as Figures 3 - 7 shown. From Figure 3 It can be seen that the composite carbon material prepared in Example 1 contains a large amount of carbon materials in the morphology of carbon nanotubes. From Figure 4It can be seen that the interplanar spacing of the graphite (002) crystal plane is approximately 0.335 nm, which is consistent with the graphite card PDF#41-1487 corresponding to the XRD results and the literature reports (Peng J, Chen N, He R, et al. Electrochemically Driven Transformation of Amorphous Carbons to Crystalline Graphite Nanoflakes: A Facile and Mild Graphitization Method[J]. Angewandte Chemie, 2017, 56(7): 1751-1755. DOI: 10.1002 / anie.201609565.).

[0040] However, from Figures 5 - 6 it can be seen that under the same reaction conditions, when borohydride or calcium hydride is used as a single solid reactant for the gas-solid reaction with CO2 respectively, the formation of carbon nanotube / graphite composite carbon materials is not detected in the resulting carbon materials. At the same time, from Figure 7 it can be seen that when borohydride and calcium hydride are used as composite solid reactants, the maximum reaction pressure is 100 bar, and the formation of carbon nanotube / graphite composite carbon materials is also not detected in the resulting carbon materials.

[0041] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the spirit and scope of the technical solutions of the present invention, and they should all be covered by the scope of the claims of the present invention.

Claims

1. A preparation method of a carbon nanotube / graphite composite carbon material, characterized in that: comprising the following steps, S1 Under an inert atmosphere, calcium hydride is subjected to ball milling treatment, and after separating the balls from the material, calcium hydride powder is obtained; S2 Under an inert atmosphere, the calcium hydride powder obtained in S1 and a borohydride are mechanically mixed in a ball milling jar without milling balls, and then transferred to a closed container; S3 After evacuating the closed container in S2, CO2 at a predetermined pressure is introduced for reaction, and after post-treatment after the reaction, a carbon nanotube / graphite composite carbon material is obtained.

2. The preparation method of a carbon nanotube / graphite composite carbon material according to claim 1, characterized in that: In S1 and S2, the inert gas of the inert atmosphere is argon, nitrogen, and / or helium.

3. The preparation method of a carbon nanotube / graphite composite carbon material according to claim 1, characterized in that: In S1, the material of the milling balls for the ball milling treatment is stainless steel, agate, or zirconia, and the ball-to-material ratio of the ball milling treatment is controlled to be 20 - 80:1, the ball milling speed is 300 - 500 rpm, and the ball milling time is 3 - 24 h.

4. The preparation method of a carbon nanotube / graphite composite carbon material according to claim 1, characterized in that: In S2, the borohydride is crystalline lithium borohydride and / or sodium borohydride powder, and the particle size range of the borohydride is 50 - 300 μm.

5. The preparation method of a carbon nanotube / graphite composite carbon material according to claim 4, characterized in that: In S2, the dosage ratio of calcium hydride to the borohydride is controlled to be 2 - 5 mol:1 mol.

6. The preparation method of a carbon nanotube / graphite composite carbon material according to claim 1, characterized in that: In S3, it is controlled that the maximum pressure of CO2 during the reaction needs to exceed 150 bar, and CO2 is in excess relative to calcium hydride and the borohydride.

7. The preparation method of a carbon nanotube / graphite composite carbon material according to claim 1, characterized in that: In S3, the heating rate of the reaction is controlled to be 0.1 - 10 °C / min, and the target reaction temperature is 50 - 200 °C.

8. The preparation method of a carbon nanotube / graphite composite carbon material according to claim 1, characterized in that: In S3, after the reaction is completed, it is successively subjected to pickling, solid-liquid separation, and solid drying treatment.

9. The preparation method of a carbon nanotube / graphite composite carbon material according to claim 8, characterized in that: In S3, the pickling acid solution is 0.5 - 2.0 mol / L hydrochloric acid, and the pickling time is controlled to be 12 - 36 h, and the pickling temperature is 150 - 200 °C.

10. The preparation method of a carbon nanotube / graphite composite carbon material according to claim 8, characterized in that: In S3, the drying temperature of the solid drying is controlled to be 60 - 120 °C, and the drying time is 6 - 24 h.

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