Method for preparing pitch-based carbon material with high specific surface area

Abstract

The invention relates to the technical field of carbon material modification, and discloses a method for preparing an asphalt-based carbon material with high specific surface area, which comprises the following steps in sequence: mixing asphalt powder, potassium carbonate, potassium chloride and sulfur according to a predetermined mass ratio, putting the mixture into grinding equipment, and fully grinding to obtain a mixture A; the grinding time is controlled to be 15-45 minutes, and obtaining a solid powder precursor with uniform particle size distribution after grinding; transferring the precursor into a high-temperature-resistant container, putting the container into a tubular furnace, and heating to a temperature interval of 600-800 DEG C at a heating rate of 3-8 DEG C per minute under the protection of continuous purging of inert gas; sulfur is introduced into a molten salt system to construct a composite modified carrier, and the sulfur and the molten salt generate a synergistic etching effect in a heat treatment process, so that asphalt raw materials are uniformly dispersed and fully contacted in a liquid molten salt environment, and the problem of non-uniform dispersion of asphalt in a traditional process is solved.

Description

Technical Field

[0001] This invention relates to the field of carbon material modification technology, specifically a method for preparing high specific surface area pitch-based carbon materials. Background Technology

[0002] High specific surface area carbon materials, as a key functional material, occupy an important position in modern industry and high-tech fields. With their unique pore structure, excellent electrical conductivity, and good chemical stability, these materials have found wide application in various technological fields, including supercapacitors, lithium-ion batteries, fuel cells, electrocatalytic reactions, gas storage and separation, and water purification. With the rapid development of new energy technologies and the environmental protection industry, the market demand for high-performance carbon materials is showing a continuous upward trend, driving researchers to constantly develop new preparation processes to improve material performance and reduce production costs.

[0003] Currently, the preparation of high specific surface area carbon materials mainly relies on physical activation methods. Physical activation typically uses carbon dioxide, water vapor, or air as activators, which react with the carbon precursor at high temperatures of 800℃ to 1000℃ to form a porous structure within the carbon framework through etching. While this method has a mature process and is relatively simple to operate, it suffers from fundamental drawbacks: the high reaction temperature leads to enormous energy consumption, activation times can be several hours to tens of hours, resulting in low production efficiency; limited mass transfer efficiency in the gas-solid reaction causes uneven pore size distribution, making it difficult to precisely control the ratio of micropores to mesopores; furthermore, carbon materials are prone to excessive ablation under high-temperature conditions, leading to low yields, typically below 30%, significantly increasing raw material costs.

[0004] Chemical activation, another mainstream technical approach, involves mixing carbon precursors with chemical activators such as potassium hydroxide, zinc chloride, phosphoric acid, or sodium carbonate, followed by heat treatment. The chemical reaction between the activator and carbon atoms then etches pores. This method can achieve highly efficient activation at relatively low temperatures, yielding carbon materials with a specific surface area of ​​up to 1000 square meters per gram. However, chemical activation faces more severe challenges: the amount of highly corrosive activators such as potassium hydroxide is typically 2 to 5 times the mass of the carbon precursor, requiring large amounts of acid for neutralization and washing, generating significant amounts of saline wastewater and posing a high risk of environmental pollution; achieving uniform molecular-level dispersion of the activator and carbon material is difficult, leading to localized over-activation or under-activation and poor pore structure consistency; zinc chloride activator generates corrosive vapors at high temperatures, placing stringent requirements on equipment materials and resulting in high equipment investment and maintenance costs; and the carbon materials prepared by chemical activation have a limited range of surface functional groups, primarily oxygen-containing groups, which restricts the material's performance in specific applications.

[0005] In recent years, the molten salt method has attracted attention as an emerging technology in the field of carbon material preparation. This method uses a eutectic mixture of alkali metal carbonates and halides to provide a liquid-phase reaction medium for the carbonization and activation of carbon precursors in the molten state. The significant advantages of the molten salt method are: the molten salt forms a highly fluid ionic liquid at the heat treatment temperature, immersing the solid carbon precursor in it to achieve a homogeneous reaction environment and improve reaction uniformity; the molten salt system acts as a liquid template, effectively inhibiting the agglomeration and densification of the carbon precursor during pyrolysis, which is conducive to the formation of open pore structures; the molten salt ions have an etching effect on the carbon framework, promoting the simultaneous development of micropores and mesopores; the reaction temperature of this method is usually lower than that of chemical activation, resulting in relatively lower energy consumption, and the molten salt can be recovered by washing with water, making it more environmentally friendly than traditional chemical activation. Despite the advantages mentioned above, existing technologies still have significant shortcomings: the etching intensity of molten salt systems on carbon precursors is limited, resulting in insufficient improvement in the specific surface area of ​​the prepared carbon materials, typically not exceeding 800 square meters per gram; the pore structure formed by molten salt methods is mainly mesoporous, with a low contribution from micropores, limiting the performance of materials in energy storage devices that rely on micropore filling mechanisms; the molten salt system itself does not provide additional sources of functional groups, resulting in a single surface chemical property of the carbon materials and a lack of polar functional groups, leading to poor surface wettability and high ion transport resistance in electrochemical applications; more critically, pitch-based carbon precursors have poor dispersion in molten salts, easily leading to local aggregation, resulting in uneven spatial distribution of the pore structure and affecting the consistency of material performance.

[0006] Sulfonation, as an important method for surface modification of carbon materials, introduces sulfur-containing functional groups such as CS bonds, C-SO3 groups, or C-SO4 groups into the carbon framework through reaction with sulfur-containing compounds. This treatment technology can significantly improve the surface polarity of carbon materials, enhance their wettability with electrolytes, and promote rapid ion transport. The sulfur-containing functional groups themselves can act as pseudocapacitive active sites, contributing additional specific capacitance. Sulfur atom doping can regulate the electronic structure of carbon materials, optimize charge distribution, and improve electrocatalytic reaction activity. However, traditional sulfonation is usually performed after the carbon material is prepared, requiring additional process steps, increasing production cycle and cost. Subsequent sulfonation is difficult to introduce functional groups into the bulk phase and deep pore surface of carbon materials, with functional group distribution limited to the outer surface, resulting in insufficient modification effect. High-temperature sulfonation processes are prone to thermal decomposition of sulfur-containing groups, resulting in a narrow temperature window and difficult process control. In addition, existing sulfonation technologies have weak ability to regulate pore structure and cannot solve the fundamental problem of uneven pore size distribution.

[0007] Based on the above analysis of existing technologies, there is an urgent need in this field to develop novel preparation methods. These methods should combine the advantages of the uniform reaction environment of the molten salt method with the surface chemical regulation capabilities of sulfonation treatment. While maintaining process simplicity and cost-effectiveness, they should simultaneously optimize the pore structure depth of carbon materials and efficiently introduce surface functional groups, solve the problem of uneven dispersion of pitch precursors, significantly increase the specific surface area of ​​carbon materials and improve the uniformity of pore size distribution, and ultimately obtain high-performance pitch-based carbon materials with excellent physical structural parameters and abundant chemical active sites, meeting the stringent requirements of electrochemical energy storage and electrocatalysis applications for the comprehensive performance of carbon materials. Summary of the Invention

[0008] To address the shortcomings of existing technologies, this invention provides a method for preparing high specific surface area pitch-based carbon materials, thus solving the problems mentioned in the background section.

[0009] To achieve the above objectives, the present invention provides the following technical solution: a method for preparing high specific surface area pitch-based carbon materials using sulfonation-assisted molten salt, the method comprising the following sequential steps: Asphalt powder, potassium carbonate, potassium chloride and sulfur are mixed according to a predetermined mass ratio. The mixture is then placed in a grinding equipment for thorough grinding. The grinding time is controlled between 15 and 45 minutes. After grinding, a solid powder precursor with uniform particle size distribution is obtained. The precursor was transferred to a high-temperature resistant container, which was then placed in a tube furnace. Under continuous inert gas purging protection, the temperature was increased to 600°C to 800°C at a heating rate of 3°C to 8°C per minute. The temperature was then kept constant within this range for 2 hours for annealing. During the annealing process, the molten salt system etched and reconstructed the framework of the pitch matrix. At the same time, sulfur enhanced the molten salt etching effect and introduced sulfur-containing functional groups onto the surface of the carbon material. After annealing, the material is naturally cooled to room temperature under inert gas protection to remove the carbonization products, which are large solids containing carbon materials and molten salt. The carbonized product is soaked in deionized water at a temperature of 20°C to 40°C for 30 to 120 minutes to fully dissolve the molten salt. Then, it is filtered or centrifuged. The separated solid is washed again with deionized water. The washing operation is repeated 6 to 8 times until the conductivity of the filtrate is lower than 10 μS / cm. The washed wet carbon material was subjected to liquid nitrogen freeze-drying, with the liquid nitrogen freeze-drying temperature maintained in the range of -45℃ to -35℃, and the drying time lasting 24 to 36 hours, finally obtaining powdered pitch-based carbon material.

[0010] Preferably, the amount of sulfur added is set to 70% to 90% of the mass of the asphalt powder. This range of addition allows the sulfur to fully sublimate during the annealing process and work with the molten salt in the gas phase to etch the asphalt, while avoiding excessive sulfur from causing excessive etching of carbon materials and structural collapse.

[0011] Preferably, the potassium carbonate and potassium chloride constitute a binary molten salt system. The eutectic point of this binary molten salt system is lower than the melting points of potassium carbonate and potassium chloride. At the annealing temperature, a uniform liquid molten salt environment is formed, which provides a homogeneous reaction medium for the carbonation and activation of asphalt.

[0012] Preferably, the grinding equipment is a ball mill, mortar and pestle or planetary ball mill. During the grinding process, the mixture is rotated and ground in the grinding equipment in a single direction or alternating directions. The grinding speed is set to 100 rpm to 300 rpm. After grinding, the particle size of the precursor is controlled in the range of 50 micrometers to 200 micrometers.

[0013] Preferably, the annealing temperature is precisely controlled within the range of 650°C to 750°C. This temperature range allows potassium carbonate to decompose and generate carbon dioxide gas to physically activate the asphalt, while simultaneously keeping the sulfur in a molten and sublimated state. The molten sulfur and sublimated sulfur vapor work together with molten salt ions to chemically etch and reconstruct the structure of the asphalt matrix.

[0014] Preferably, the inert gas is argon, nitrogen or helium, the purity of the inert gas is higher than 99.99%, the inert gas flow rate is set to 50 mL / min to 200 mL / min, the inert gas is continuously introduced from the gas inlet end of the tube furnace and discharged from the gas outlet end, and the discharged gas is treated by absorption by an alkaline solution.

[0015] Preferably, the mass ratio of the asphalt powder, potassium carbonate, potassium chloride and sulfur is set to 1:3:6:0.8. This ratio is based on the mass of the asphalt powder, with the mass of potassium carbonate being 3 times the mass of the asphalt powder, the mass of potassium chloride being 6 times the mass of the asphalt powder, and the mass of sulfur being 0.8 times the mass of the asphalt powder.

[0016] Preferably, the deionized water washing process is accompanied by ultrasonic-assisted dispersion, with the ultrasonic power set to 100W to 500W, the ultrasonic frequency set to 20kHz to 40kHz, and the ultrasonic treatment time set to 10 minutes to 30 minutes each time. The ultrasonic treatment promotes the detachment of molten salt from the pores of the carbon material.

[0017] A high specific surface area pitch-based carbon material is disclosed. The specific surface area of ​​the carbon material, as determined by nitrogen adsorption-desorption testing, is greater than 1400 m² / g and less than 2500 m² / g. The pore structure comprises a composite hierarchical pore structure of micropores, mesopores, and macropores, with a pore volume greater than 0.6 cm³ / g and an average pore size distribution in the range of 2 nm to 10 nm. The material surface is rich in defect sites, and the defect site concentration, as determined by Raman spectroscopy, has an I_D / I_G ratio greater than 0.9. The surface chemical structure of the material includes CS bonds, C-SO3 groups, and C-SO4 groups. The sulfur content, as determined by X-ray photoelectron spectroscopy, is 0.5 at% to 3 at%.

[0018] This invention provides a method for preparing high specific surface area pitch-based carbon materials. It has the following beneficial effects: 1. This invention introduces sulfur into a molten salt system to construct a composite modified carrier. During heat treatment, sulfur and molten salt produce a synergistic etching effect, promoting uniform dispersion and full contact of the asphalt raw material in the liquid molten salt environment. This solves the problem of uneven asphalt dispersion in traditional processes and simultaneously enhances the etching effect of molten salt on the asphalt matrix, inducing the formation of richer pore structures and surface defects. This method achieves carbonization, activation, and surface functionalization simultaneously through a one-step annealing process, avoiding the complexity of multi-step processing. It has the advantages of simple operation process, mild reaction conditions, and easy control of process parameters. The raw material used is widely available and inexpensive asphalt, combined with conventional inorganic salts and sulfur, effectively reducing production costs and providing technical support for the large-scale production of high specific surface area asphalt-based carbon materials.

[0019] 2. The pitch-based carbon material prepared by this invention possesses high specific surface area and a pore structure exhibiting a composite distribution of micropores and mesopores. Its surface is rich in defective active sites and sulfur-containing functional groups, with sulfur in situ doped into the carbon framework in various chemical states. This structural feature significantly optimizes the material's electron transport performance, enhances ion accessibility and reactive site density, enabling the material to exhibit excellent charge storage capacity when used as an electrode material in electrochemical energy storage devices, effectively promote catalytic reaction kinetics when used as an electrocatalyst support, and demonstrate strong adsorption efficiency for target pollutants when used as an adsorbent. It is applicable to multiple technical fields, including supercapacitors, lithium-ion batteries, electrocatalysis, and environmental remediation. Attached Figure Description

[0020] Figure 1 Scanning electron microscope image of high specific surface area pitch-based carbon material prepared by sulfonation-assisted molten salt in Example 2 of this invention; Figure 2 Scanning electron microscope image of the high specific surface area pitch-based carbon material prepared by sulfonation-assisted molten salt in Comparative Example 2 of this invention; Figure 3Scanning electron microscope image of the high specific surface area pitch-based carbon material prepared by sulfonation-assisted molten salt in Comparative Example 1 of this invention; Figure 4 The adsorption-desorption curve of the high specific surface area pitch-based carbon material prepared by sulfonated molten salt in Example 2 of this invention; Figure 5 Adsorption-desorption curves of high specific surface area pitch-based carbon materials prepared by sulfonated assisted molten salt in Comparative Example 2 of this invention. Figure 6 Adsorption-desorption curves of high specific surface area pitch-based carbon materials prepared by sulfonated assisted molten salt in Comparative Example 1 of this invention. Figure 7 The X-ray diffraction patterns of Embodiment 2, Comparative Example 1, and Comparative Example 2 of the present invention; Figure 8 The S2pXPS spectra of Embodiment 2, Comparative Example 1, and Comparative Example 2 of the present invention are shown. Detailed Implementation

[0021] 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 described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] Please see the appendix Figure 1 - Appendix Figure 8 This invention provides a method for preparing high specific surface area pitch-based carbon materials.

[0023] Example 1 A method for preparing high specific surface area pitch-based carbon materials using sulfonation-assisted molten salt includes the following steps: 0.25g of asphalt powder was ground into powder, and then 0.75g of K2CO3, 1.25g of KCl and 0.1g of S were added. The mixture was ground and mixed evenly, and placed in a boat. The mixture was kept at 700℃ for 2 hours under an argon atmosphere. After the sample was taken out, it was washed 7 times with deionized water and then freeze-dried with liquid nitrogen to obtain the sample powder. The asphalt-based carbon material annealed by sulfonation-molten salt method was obtained and denoted as 0.1S-PC (MSS).

[0024] Example 2 A method for preparing high specific surface area pitch-based carbon materials using sulfonation-assisted molten salt includes the following steps: 0.25g of asphalt powder was ground into powder, and then 0.75g of K2CO3, 1.25g of KCl and 0.2g of S were added. The mixture was ground and mixed evenly, and placed in a boat. The mixture was kept at 700℃ for 2 hours under an argon atmosphere. After the sample was removed, it was washed 7 times with deionized water and then freeze-dried with liquid nitrogen to obtain the sample powder. The asphalt-based carbon material annealed by sulfonation-molten salt method was obtained and denoted as 0.2S-PC (MSS).

[0025] Example 3 A method for preparing high specific surface area pitch-based carbon materials using sulfonation-assisted molten salt includes the following steps: 0.25g of asphalt powder was ground into powder, and then 0.75g of K2CO3, 1.25g of KCl, and 0.3g of S were added. The mixture was ground and mixed evenly, and placed in a boat. The mixture was kept at 700℃ for 2 hours under an argon atmosphere. After the sample was removed, it was washed 7 times with deionized water and then freeze-dried with liquid nitrogen to obtain the sample powder. The resulting asphalt-based carbon material, annealed by sulfonation-molten salt method, was designated as 0.3S-PC (MSS). To further illustrate the technical effects of the present invention, comparative examples are also provided, as follows: Comparative Example 1 0.25g of asphalt powder was ground into powder and placed in a boat. The mixture was kept at 700℃ for 2 hours under an argon atmosphere. The sample was then removed and ground into powder to obtain a simple annealed asphalt-based carbon material, denoted as PC. Comparative Example 2 0.25g of asphalt powder was ground into powder, and then 0.75g of K2CO3 and 1.25g of KCl were added. The mixture was ground and mixed evenly, and placed in a boat. The mixture was kept at 700℃ for 2 hours under an argon atmosphere. After the sample was removed, it was washed 7 times with deionized water and then freeze-dried with liquid nitrogen to obtain the sample powder. The resulting asphalt-based carbon material annealed by molten salt method was denoted as PC(MSS). I. A comparison of scanning electron microscope (SEM) images of the 0.2S-PC (MSS) prepared in this invention, the PC (MSS) of Comparative Example 1, and the PC of Comparative Example 2 is made, such as... Figure 1 , 2 As shown in Figure 3.

[0026] Depend on Figure 1 , 2 As can be seen from Figures 3 and 4, PC exhibits a blocky morphology, while PC(MSS) exhibits a porous morphology. S-PC(MSS) treated with S tends to have a more lamellar morphology, with a surface rich in wrinkles and nanopores.

[0027] II. The adsorption-desorption curves and BET values ​​of the 0.2S-PC (MSS) prepared in this invention, the PC (MSS) of Comparative Example 1, and the PC of Comparative Example 2 are compared. Figure 4 , 5 As shown in Figure 6.

[0028] Depend on Figure 4 , 5 As shown in section 6, the specific surface area of ​​simply annealed pure carbon material (PC) is only 13.8033 m² / g. The specific surface area of ​​PC (MSS) treated by the molten salt method increases to 711.5729 m² / g due to the molten salt inhibiting agglomeration, constructing a porous structure, and promoting the expansion of the carbon skeleton. The specific surface area of ​​sulfonated S-PC (MSS) is further increased to 1435.4182 m² / g (approximately twice that of PC (MSS)) because the S species further etches the carbon surface and generates more pores during annealing. III. A comparison was made of the X-ray diffraction patterns of the 0.2S-PC (MSS) prepared in this invention, the PC (MSS) of Comparative Example 1, and the PC of Comparative Example 2. Figure 7 As shown.

[0029] Depend on Figure 7 As shown, PC exhibits diffraction peaks at 25° and 44°. The diffraction peak at 25° corresponds to the characteristic peak of the (002) crystal plane of the graphite layered structure of the carbon material, while the diffraction peak at 44° is related to the six-membered ring structure within the graphite layer. The appearance of these two peaks indicates that the pitch powder undergoes partial graphitization after simple annealing, but the degree of graphitization is low. The intensity of the above two diffraction peaks of PC(MSS) is significantly reduced. This is because the molten salt treatment has both etching and reconstruction effects, which destroys the original ordered crystal structure of the carbon material, resulting in a decrease in its degree of graphitization and a reduction in the ordered region, thereby weakening the intensity of the diffraction peaks or even causing some diffraction peaks to disappear. The intensity of the above two diffraction peaks of 0.2S-PC(MSS) is slightly increased because the introduction of S deepens the graphitization degree of the pitch carbon material and improves the order of the carbon material.

[0030] IV. A comparison was made of the S2pXPS spectra of the 0.2S-PC (MSS) prepared in this invention, the PC (MSS) of Comparative Example 1, and the PC of Comparative Example 2. Figure 8 As shown.

[0031] Depend on Figure 8As shown, only the characteristic signal of CS bonds was detected in PC, while in PC(MSS), not only were the CS bond signals present, but also the characteristic signals of C-SO3 and C-SO4 groups were detected. This difference indicates that simple annealing under an inert gas atmosphere can isolate oxygen and inhibit oxidation reactions, causing the sulfur element in PC to exist only in the form of CS bonds. However, after adding molten salt, the K2CO3 in the molten salt can provide an oxidizing environment, promoting the oxidation of some sulfur elements and forming sulfur-containing functional groups with higher oxidation states. The same signal was also detected in S-PC(MSS). The signals of CS bonds, C-SO3 and C-SO4 groups are observed, and compared with PC (MSS), the signal of CS bonds is stronger. The signal peaks corresponding to C-SO3 and C-SO4 groups are also shifted towards lower binding energies. This indicates that after the addition of S, S in the molten salt is more likely to combine with C in a low valence state, thereby promoting the formation of CS bonds. At the same time, the introduced S will change the local charge density of C-SO3 and C-SO4 functional groups, and the increase in the number of CS bonds and the increase in the electron density of C-SO3 and C-SO4 groups on the surface of S-PC (MSS) are also observed.

[0032] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing high surface area pitch-based carbon material using sulfonated assisted molten salt, characterized by, The method comprises the following steps performed: Mixing asphalt powder, potassium carbonate, potassium chloride and sulfur according to predetermined mass ratio, placing the mixture in a grinding device for sufficient grinding, controlling the grinding time at 15-45 minutes, and obtaining a solid powder precursor with uniform particle size distribution after grinding; Transferring the precursor to a high-temperature-resistant container, placing the container in a tube furnace, heating to a temperature range of 600-800°C at a heating rate of 3°C / min-8°C / min under continuous inert gas blowing protection, and keeping the temperature constant for 2 hours for annealing treatment, during which the molten salt system etches and reconstructs the asphalt matrix, and sulfur strengthens the etching effect of molten salt and introduces sulfur-containing functional groups on the surface of carbon materials; After the annealing treatment is completed, the carbonization product is obtained by natural cooling to room temperature under inert gas protection, which is a bulk solid containing carbon materials and molten salt; Soaking the carbonization product in deionized water with a temperature of 20-40°C for 30-120 minutes to fully dissolve the molten salt, followed by filtration or centrifugal separation, and washing the separated solid with deionized water again, repeating the washing operation 6-8 times until the conductivity of the filtrate is less than 10 μS / cm; The wet carbon material after washing is subjected to liquid nitrogen freeze-drying treatment, the liquid nitrogen freeze-drying temperature is maintained in the range of-45°C to-35°C, and the drying time is 24-36 hours, and finally a powder-like asphalt-based carbon material is obtained.

2. The method of claim 1, wherein, The addition amount of sulfur is set to 70%-90% of the mass of the asphalt powder, which makes the sulfur fully sublimate during the annealing process and etch the asphalt in the gas phase in cooperation with the molten salt, while avoiding excessive sulfur leading to excessive etching of the carbon material and structural collapse.

3. The method of claim 1, wherein, The potassium carbonate and potassium chloride form a binary molten salt system, and the eutectic point of the binary molten salt system is lower than the melting point of potassium carbonate and the melting point of potassium chloride, forming a uniform liquid molten salt environment at the annealing temperature, which provides a homogeneous reaction medium for the carbonization and activation of asphalt.

4. The method of claim 1, wherein, The grinding device is selected from a ball mill, a mortar or a planetary ball mill, and the mixture is rotated in the grinding device in a single direction or alternating directions during the grinding process, and the rotation speed is set to 100-300 rpm, and the particle size of the precursor after grinding is controlled in the range of 50-200 microns.

5. The method of claim 1, wherein, The annealing temperature is accurately controlled in the range of 650-750°C, which makes the carbon dioxide gas generated by the decomposition of potassium carbonate physically activate the asphalt, and at the same time makes the sulfur in a molten and sublimated state, and the molten sulfur and sublimated sulfur vapor cooperate with the molten salt ions to chemically etch and structurally reconstruct the asphalt matrix.

6. The method of claim 1, wherein, The inert gas is selected from argon, nitrogen or helium, the purity of the inert gas is higher than 99.99%, the flow rate of the inert gas is set to 50-200 mL / min, the inert gas is continuously introduced from the gas inlet end of the tube furnace and discharged from the gas outlet end, and the discharged gas is absorbed by a basic solution.

7. The method of claim 1, wherein, The mass ratio of the asphalt powder, potassium carbonate, potassium chloride and sulfur is set to 1:3:6:0.8, wherein the mass of the asphalt powder is taken as the basis, the mass of the potassium carbonate is 3 times the mass of the asphalt powder, the mass of the potassium chloride is 6 times the mass of the asphalt powder, and the mass of the sulfur is 0.8 times the mass of the asphalt powder.

8. The method of claim 1, wherein, The deionized water washing process is accompanied by ultrasonic auxiliary dispersion, the ultrasonic power is set to 100 W to 500 W, the ultrasonic frequency is set to 20 kHz to 40 kHz, and the ultrasonic treatment time is set to 10 minutes to 30 minutes each time, and the ultrasonic treatment promotes the separation of the molten salt from the pores of the carbon material.

9. A high surface area pitch-based carbon material characterized in that, The carbon material is prepared by the method of any one of claims 1 to 8, the specific surface area of the carbon material is greater than 1400 m² / g and less than 2500 m² / g as determined by nitrogen adsorption and desorption testing, the pore structure comprises a composite multi-level pore structure of micropores, mesopores and macropores, the pore volume is greater than 0.6 cm³ / g, the average pore size distribution is in the range of 2 nanometers to 10 nanometers, the material surface is rich in defect sites, the defect site concentration is greater than 0.9 as determined by the Raman spectrum test I_D / I_G ratio, and the material surface chemical structure comprises C-S bonds, C-SO3 groups and C-SO4 groups, and the sulfur element content is 0.5 at% to 3 at% as determined by X-ray photoelectron spectroscopy.

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