Molten salt method assisted sulfur-doped porous carbon as well as preparation method and application thereof

Abstract

The invention discloses molten-salt-method-assisted sulfur-doped porous carbon and a preparation method and application thereof, and belongs to the technical field of energy storage.The preparation method of the molten-salt-method-assisted sulfur-doped porous carbon comprises the following steps that 1, lithium chloride and potassium chloride are mixed to be uniform, and molten salt is obtained; (2) carrying out ball milling on bamboo wood, a sulfur source and molten salt, and uniformly mixing to obtain a precursor; and (3) successively carrying out first heat treatment and second heat treatment on the precursor in the presence of inert gas, washing and drying to obtain the molten salt method assisted sulfur-doped porous carbon. The sulfur-doped porous carbon prepared by the invention has excellent energy density, mass specific capacitance and cycle life, and has a good industrial application prospect in the field of supercapacitors.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of energy storage and specifically relates to a molten salt method assisted sulfur-doped porous carbon and a preparation method and application thereof. BACKGROUND

[0002] Electrochemical capacitors, also known as supercapacitors (SCs), have played an important role in energy storage and conversion systems in recent years due to their high strength, durability and environmental friendliness. A wide range of materials have been used as electrodes for SC applications, because the electrochemical efficiency is mainly determined by the electrode material used.

[0003] Carbonaceous materials have unique surface, chemical, electrochemical and electronic properties, and have become a hot spot in energy storage research, but cannot meet the growing demand for high specific energy and specific power. Heteroatom-doped carbon materials have pseudo-capacitive characteristics, and the specific energy, specific power and conductivity are all improved. This makes them more adaptable in SC applications. Among different heteroatom-doped carbons, S-doped carbon has gained considerable attention in SC applications due to its electronic unpaired and easy polarization characteristics. Based on S-doped carbon materials, SCs have enhanced surface wettability, improved conductivity and induced pseudo-capacitive effects, thereby providing better specific energy and specific power. However, traditional sulfur-doping methods usually have problems such as harsh reaction conditions, low sulfur-doping efficiency and difficulty in structure regulation, which limit the further optimization of material performance and the realization of large-scale production.

[0004] As a new material synthesis technology, molten salt assisted method has shown great potential in the field of material preparation due to its unique ionic liquid environment, efficient ion transport capacity and good reaction controllability. At present, there is no report on the method of sulfur-doped bamboo carbon electrode material based on molten salt assistance.

[0005] In view of this, the present application is proposed. SUMMARY

[0006] The purpose of the present application is to overcome the deficiencies in the prior art and provide a molten salt method assisted sulfur-doped porous carbon and a preparation method and application thereof. The sulfur-doped porous carbon prepared has excellent energy density, mass specific capacitance and cycle life, and has good industrial application prospects in the field of supercapacitors.

[0007] To achieve the above purpose, the technical scheme adopted by the present application is as follows: A preparation method of a molten salt method assisted sulfur-doped porous carbon, comprising the following steps: (1) uniformly mixing lithium chloride and potassium chloride to obtain a molten salt; (2) uniformly mixing bamboo, a sulfur source and the molten salt by ball milling to obtain a precursor; (3) The precursor is subjected to first heat treatment and second heat treatment under inert gas, washed, dried, and a sulfur-doped porous carbon prepared by the molten salt method is obtained.

[0008] The application uses lithium chloride and potassium chloride as the molten salt, can significantly reduce the melting temperature, provides a thermodynamic basis for low-temperature reaction, uniformly mixes bamboo, sulfur source and molten salt by ball milling, destroys the layered structure of carbon material to expose defect sites, and improves the reaction activity of sulfur atoms; then two-step heat treatment is carried out in an inert atmosphere, the first heat treatment makes the molten salt melt and flow, and the sulfur source is infiltrated into the carbon skeleton, the second heat treatment cracks the residual sulfide and removes it by volatilization, and a hierarchical porous structure is reconstructed at the same time; finally, the molten salt template is removed by water washing, the mesoporous channels formed by the temporary occupation of the molten salt are exposed, and a self-supporting sulfur-doped bamboo-based porous carbon is obtained.

[0009] Compared with the unoptimized sulfur-doped process, the application breaks through the technical bottleneck that the surface enrichment and the pore structure are difficult to be synergistically optimized in the traditional sulfur-doped process, mainly benefits from the ion characteristics and high-temperature stability of the molten salt, can effectively improve the uniformity of sulfur doping and the construction of the porous structure, so as to realize the preparation of sulfur-doped bamboo-based porous carbon material with excellent electrochemical performance, and the prepared sulfur-doped porous carbon has excellent energy density, mass specific capacitance and cycle life.

[0010] The preparation method adopted by the application involves few reaction reagents in the preparation process, and the product is pollution-free, meeting the requirements of green chemistry. In addition, the electrode material synthesized by the application has the characteristics of rich porous structure, large specific surface area, good electrochemical performance and the like, and has good industrial application prospect in the field of supercapacitors.

[0011] As a preferred embodiment of the application, the mole percentage content of lithium chloride in the molten salt is 59-60%. Especially when the mole percentage content of lithium chloride in the molten salt is in this range, the molten salt is a eutectic salt system, which significantly reduces the melting temperature, provides a thermodynamic basis for low-temperature reaction, and significantly improves the energy density, mass specific capacitance and cycle life of the sulfur-doped porous carbon.

[0012] As a preferred embodiment of the application, the mole percentage content of lithium chloride in the molten salt is 59.2%.

[0013] As a preferred embodiment of the application, the bamboo material includes at least one of bamboo fiber, bamboo pulp fiber and bamboo-based pulp. The sulfur source includes at least one of sublimed sulfur and sulfur.

[0014] As a preferred embodiment of the application, the mass ratio of the bamboo material, the sulfur source and the molten salt is 2: (1.5-6): (1-6).

[0015] In a preferred embodiment of the present invention, the ball milling speed is 600~1000 rpm and the ball milling time is 2~24h.

[0016] In a preferred embodiment of the present invention, the temperature of the first heat treatment is 353~445℃ and the time is 1~4h.

[0017] In a preferred embodiment of the present invention, the temperature of the first heat treatment is 600~1200℃ and the time is 0.5~2h.

[0018] In a preferred embodiment of the present invention, the inert gas includes at least one of nitrogen and argon.

[0019] In a preferred embodiment of the present invention, the first heat treatment and the second heat treatment are carried out in a tubular furnace.

[0020] In a preferred embodiment of the present invention, the temperatures of the first heat treatment and the second heat treatment are different.

[0021] The present invention also provides a molten salt method-assisted sulfur-doped porous carbon, which is prepared by the preparation method described above.

[0022] This invention also provides an application of molten salt method-assisted sulfur-doped porous carbon as an electrode material in the preparation of supercapacitors.

[0023] The beneficial effects of this invention are as follows: This invention uses lithium chloride and potassium chloride as molten salts, which can significantly reduce the melting temperature and provide a thermodynamic basis for low-temperature reactions. By ball milling and mixing bamboo, sulfur source and molten salt evenly, the layered structure of carbon material is destroyed to expose defect sites and enhance the reactivity of sulfur atoms. Then, a two-step heat treatment is carried out under an inert atmosphere. The first heat treatment makes the molten salt melt and flow, allowing the sulfur source to penetrate into the interior of the carbon skeleton. The second heat treatment cracks the residual sulfides and volatilizes them, while simultaneously reconstructing the hierarchical porous structure. Finally, the molten salt template is removed by water washing, exposing the mesoporous channels formed by the temporary occupancy of the molten salt, thus obtaining self-supporting sulfur-doped bamboo-based porous carbon. Attached Figure Description

[0024] Figure 1 This is a SEM image of the sulfur-doped bamboo-based porous carbon material prepared in Example 1.

[0025] Figure 2 The image shows the XPS spectrum of the sulfur-doped bamboo-based porous carbon material prepared in Example 1.

[0026] Figure 3 The image shows the CV curve of the sulfur-doped bamboo-based porous carbon material electrode prepared in Example 1. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0028] In this application, the technical features described in an open-ended manner include both closed technical solutions consisting of the listed features and open technical solutions that include the listed features.

[0029] In this application, numerical ranges are referred to as continuous unless otherwise specified, and include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to integers, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be merged. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are incorporated.

[0030] In this application, there are no particular restrictions on the specific dispersion and mixing methods.

[0031] Unless otherwise specified, all components, raw materials, or instruments used in the embodiments and comparative examples of this invention are commercially available, and the same type of components and raw materials are used in each parallel experiment.

[0032] The following embodiments are provided to facilitate understanding of the invention. These embodiments are not intended to limit the scope of the claims.

[0033] Example 1 A method for preparing sulfur-doped bamboo-based porous carbon materials using a molten salt method includes the following steps: (1) Weigh 22.60 g of LiCl and 27.40 g of KCl according to the molar ratio of LiCl / (KCl+LiCl)=0.592, grind and mix them evenly to obtain 50 g of molten salt.

[0034] (2) Weigh 100 g of bamboo fiber and 75 g of sublimed sulfur. Put the bamboo, sulfur source and molten salt into a planetary ball mill in a mass ratio of 2:1.5:1. Add 38 g of zirconia grinding beads and grind them thoroughly at 800 r / min for 2 h to obtain a mixture of carbon source / sulfur source / molten salt.

[0035] (3) The mixture of bamboo / sulfur source / molten salt was placed in a ceramic boat and heated in a tubular furnace. Under a nitrogen atmosphere, it was reacted with the bamboo charcoal material at 353 °C for 2 hours to allow the molten salt to melt and flow, guiding the sulfur source to fully penetrate into the bamboo charcoal material. Then, the temperature was increased to 445 °C and held for 1 hour to allow the unreacted sulfur source to volatilize and be transported to the tail gas cylinder for collection via carrier gas.

[0036] (4) After the furnace has cooled to room temperature, the mixture in the ceramic boat is thoroughly washed with deionized water and dried to obtain sulfur-doped bamboo-based porous carbon material.

[0037] The scanning electron microscope (SEM) image of the sulfur-doped bamboo-based porous carbon material prepared is as follows: Figure 1 As shown, the overall particle size of the product is approximately 0.5-2 μm, exhibiting a porous, honeycomb morphology. Figure 2 XPS spectra analysis reveals that sulfur was successfully doped into the carbon material after ball milling, and the material surface contains abundant oxygen-, nitrogen-, and sulfur-containing functional groups. These functional groups and the dopant elements work synergistically to significantly alter the material's electronic structure, surface properties, and chemical activity, providing diverse performance regulation pathways for applications in energy storage (such as supercapacitors and batteries), catalysis, and adsorption separation. Figure 3 The CV curves of the electrode material at three different scan rates (10 mV / s, 50 mV / s, and 100 mV / s) demonstrate the significant electrochemical performance of sulfur-doped porous carbon materials, namely, higher specific capacitance, good electrochemical reversibility, and excellent rate performance. These properties make sulfur-doped porous carbon materials highly valuable for applications in energy storage devices such as supercapacitors.

[0038] Example 2 A method for preparing sulfur-doped bamboo-based porous carbon materials using a molten salt method includes the following steps: (1) Weigh 135.63 g of LiCl and 164.37 g of KCl according to the molar ratio of LiCl / (KCl+LiCl)=0.592, grind and mix them evenly to obtain 300 g of molten salt.

[0039] (2) Weigh 100 g of bamboo pulp fiber and 300 g of sulfur. Put the bamboo, sulfur source and molten salt into a planetary ball mill in a mass ratio of 2:6:6. Then add 180 g of zirconia ball milling beads and grind them thoroughly at 800 r / min for 24 h to obtain a mixture of carbon source / sulfur source / molten salt.

[0040] (3) The mixture of bamboo / sulfur source / molten salt was placed in a ceramic boat and heated in a tubular furnace. Under an argon atmosphere, it was reacted with the bamboo charcoal material at 445°C for 2 hours to allow the molten salt to melt and flow, guiding the sulfur source to fully penetrate into the bamboo charcoal material. Then, the temperature was increased to 1200°C and held for 1 hour to allow the unreacted sulfur source to volatilize and be transported to the tail gas cylinder for collection via a carrier gas.

[0041] (4) After the furnace has cooled to room temperature, the mixture in the ceramic boat is thoroughly washed with deionized water and dried to obtain sulfur-doped bamboo-based porous carbon material.

[0042] The morphology of the product obtained in this embodiment is similar to that of Example 1. The particle size of the product is approximately 0.5-2 μm, exhibiting a porous, honeycomb morphology. The product also has a loose microstructure, and the surface of the material contains abundant oxygen-, nitrogen-, and sulfur-containing functional groups. The synergistic effect of these functional groups and doping elements gives the sulfur-doped porous carbon material significant electrochemical performance, namely higher specific capacitance, good electrochemical reversibility, and excellent rate performance, making it of great application value in energy storage devices such as supercapacitors.

[0043] Example 3 A method for preparing sulfur-doped bamboo-based porous carbon materials using a molten salt method includes the following steps: (1) Weigh 67.82 g of LiCl and 82.18 g of KCl according to the molar ratio of LiCl / (KCl+LiCl)=0.592, grind and mix them evenly to obtain 150 g of molten salt.

[0044] (2) Weigh 100 g of bamboo-based pulp and 175 g of sublimed sulfur. Put the bamboo, sulfur source and molten salt into a planetary ball mill in a mass ratio of 2:3.5:3. Add 76 g of zirconia ball milling beads and grind them thoroughly at 800 r / min for 12 h to obtain a mixture of carbon source / sulfur source / molten salt.

[0045] (3) The mixture of bamboo / sulfur source / molten salt was placed in a ceramic boat and heated in a tubular furnace. Under a nitrogen atmosphere, it was reacted with the bamboo charcoal material at 400 °C for 2 hours to allow the molten salt to melt and flow, guiding the sulfur source to fully penetrate into the bamboo charcoal material. Then, the temperature was increased to 800 °C and held for 1 hour to allow the unreacted sulfur source to volatilize and be transported to the tail gas cylinder for collection via carrier gas.

[0046] (4) After the furnace has cooled to room temperature, the mixture in the ceramic boat is thoroughly washed with deionized water and dried to obtain sulfur-doped bamboo-based porous carbon material.

[0047] The morphology of the product obtained in this embodiment is similar to that of Example 1. The particle size of the product is approximately 0.5-2 μm, exhibiting a porous, honeycomb morphology. The product also has a loose microstructure, and the surface of the material contains abundant oxygen-, nitrogen-, and sulfur-containing functional groups. The synergistic effect of these functional groups and doping elements gives the sulfur-doped porous carbon material significant electrochemical performance, namely higher specific capacitance, good electrochemical reversibility, and excellent rate performance, making it of great application value in energy storage devices such as supercapacitors.

[0048] Example 4 A method for preparing sulfur-doped bamboo-based porous carbon materials using a molten salt method includes the following steps: (1) Weigh 45.21 g of LiCl and 54.79 g of KCl according to the molar ratio of LiCl / (KCl+LiCl)=0.592, grind and mix them evenly to obtain 100 g of molten salt.

[0049] (2) Weigh 100 g of bamboo fiber and 150 g of sulfur. Put the bamboo, sulfur source and molten salt into a planetary ball mill in a mass ratio of 2:3:2. Then add 90 g of zirconia grinding beads and grind them thoroughly at 800 r / min for 8 h to obtain a mixture of carbon source / sulfur source / molten salt.

[0050] (3) The mixture of bamboo / sulfur source / molten salt was placed in a ceramic boat and heated in a tubular furnace. Under an argon atmosphere, it was reacted with the bamboo charcoal material at 380 °C for 2 hours to allow the molten salt to melt and flow, guiding the sulfur source to fully penetrate into the bamboo charcoal material. Then, the temperature was increased to 600 °C and held for 1 hour to allow the unreacted sulfur source to volatilize and be transported to the tail gas cylinder for collection via a carrier gas.

[0051] (4) After the furnace has cooled to room temperature, the mixture in the ceramic boat is thoroughly washed with deionized water and dried to obtain sulfur-doped bamboo-based porous carbon material.

[0052] The morphology of the product obtained in this embodiment is similar to that of Example 1. The particle size of the product is approximately 0.5-2 μm, exhibiting a porous, honeycomb morphology. The product also has a loose microstructure, and the surface of the material contains abundant oxygen-, nitrogen-, and sulfur-containing functional groups. The synergistic effect of these functional groups and doping elements gives the sulfur-doped porous carbon material significant electrochemical performance, namely higher specific capacitance, good electrochemical reversibility, and excellent rate performance, making it of great application value in energy storage devices such as supercapacitors.

[0053] Example 5 A method for preparing sulfur-doped bamboo-based porous carbon materials using a molten salt method includes the following steps: (1) Weigh 90.42 g of LiCl and 109.58 g of KCl according to the molar ratio of LiCl / (KCl+LiCl)=0.592, grind and mix them evenly to obtain 200 g of molten salt.

[0054] (2) Weigh 100 g of bamboo pulp fiber and 200 g of sublimed sulfur. Put the bamboo, sulfur source and molten salt into a planetary ball mill in a mass ratio of 2:4:4. Then add 75 g of zirconia grinding beads and grind them thoroughly at 800 r / min for 16 h to obtain a mixture of carbon source / sulfur source / molten salt.

[0055] (3) The mixture of bamboo / sulfur source / molten salt was placed in a ceramic boat and heated in a tubular furnace. Under a nitrogen atmosphere, it was reacted with the bamboo charcoal material at 420 °C for 2 hours to allow the molten salt to melt and flow, guiding the sulfur source to fully penetrate into the bamboo charcoal material. Then, the temperature was increased to 1000 °C and held for 1 hour to allow the unreacted sulfur source to volatilize and be transported to the tail gas cylinder for collection via a carrier gas.

[0056] (4) After the furnace has cooled to room temperature, the mixture in the ceramic boat is thoroughly washed with deionized water and dried to obtain sulfur-doped bamboo-based porous carbon material.

[0057] The morphology of the product obtained in this embodiment is similar to that of Example 1. The particle size of the product is approximately 0.5-2 μm, exhibiting a porous, honeycomb morphology. The product also has a loose microstructure, and the surface of the material contains abundant oxygen-, nitrogen-, and sulfur-containing functional groups. The synergistic effect of these functional groups and doping elements gives the sulfur-doped porous carbon material significant electrochemical performance, namely higher specific capacitance, good electrochemical reversibility, and excellent rate performance, making it of great application value in energy storage devices such as supercapacitors.

[0058] Comparative Example 1 A method for preparing sulfur-doped bamboo-based porous carbon materials using a molten salt method includes the following steps: (1) Weigh 50 g of LiCl as molten salt.

[0059] (2) Weigh 100 g of bamboo pulp fiber and 75 g of sulfur. Put the bamboo, sulfur source and LiCl into a planetary ball mill in a mass ratio of 2:1.5:1. Add 38 g of zirconia grinding beads and grind thoroughly at 800 r / min for 2 h to obtain a mixture of carbon source / sulfur source / LiCl.

[0060] (3) The mixture of bamboo / sulfur source / / LiCl was placed in a ceramic boat and placed in the heating center of a tube furnace. It was then reacted with the bamboo charcoal material at 353 °C for 2 h in an argon atmosphere. Then, the temperature was increased to 445 °C and held for 1 h to allow the unreacted sulfur source to volatilize. The volatilized sulfur source was then transported to the tail gas bottle for collection via a carrier gas.

[0061] (4) After the furnace has cooled to room temperature, the mixture in the ceramic boat is thoroughly washed with deionized water and dried to obtain sulfur-doped bamboo-based porous carbon material.

[0062] Comparative Example 2 A method for preparing sulfur-doped bamboo-based porous carbon materials using a molten salt method includes the following steps: (1) Weigh 50 g of KCl as molten salt.

[0063] (2) Weigh 100 g of bamboo-based pulp and 75 g of sulfur. Put the bamboo, sulfur source and KCl into a planetary ball mill in a mass ratio of 2:1.5:1. Add 38 g of zirconia ball milling beads and grind thoroughly at 800 r / min for 2 h to obtain a mixture of carbon source / sulfur source / KCl.

[0064] (3) The mixture of bamboo / sulfur source / KCl was placed in a ceramic boat and placed in the heating center of a tube furnace. It was then reacted with the bamboo charcoal material at 353 °C for 2 h in an argon atmosphere. Then, the temperature was increased to 445 °C and held for 1 h to allow the unreacted sulfur source to volatilize. The volatilized sulfur source was then transported to the tail gas bottle for collection via a carrier gas.

[0065] (4) After the furnace has cooled to room temperature, the mixture in the ceramic boat is thoroughly washed with deionized water and dried to obtain sulfur-doped bamboo-based porous carbon material.

[0066] Comparative Example 3 A method for preparing sulfur-doped bamboo-based porous carbon materials using a molten salt method includes the following steps: (1) Weigh 22.60 g of LiCl and 27.40 g of KCl according to the molar ratio of LiCl / (KCl+LiCl)=0.592, grind and mix them evenly to obtain 50 g of molten salt.

[0067] (2) Weigh 100 g of bamboo-based pulp and 50 g of molten salt into a planetary ball mill, add 38 g of zirconia grinding beads, and grind thoroughly at 800 r / min for 2 h to obtain a mixture of carbon source / molten salt.

[0068] (3) The bamboo / molten salt mixture was loaded into a ceramic boat and placed in the heating center of a tube furnace. Under a nitrogen atmosphere, it was fully reacted with the bamboo charcoal material at 353 °C for 2 h. Then, the temperature was increased to 445 °C and held for 1 h.

[0069] (4) After the furnace has cooled to room temperature, the mixture in the ceramic boat is thoroughly washed with deionized water and dried to obtain bamboo-based porous carbon material.

[0070] Comparative Example 4 A method for preparing sulfur-doped bamboo-based porous carbon materials using a molten salt method includes the following steps: (1) Weigh 11.30 g of LiCl and 13.70 g of KCl according to the molar ratio of LiCl / (KCl+LiCl)=0.592, grind and mix them evenly to obtain 25 g of molten salt.

[0071] (2) Weigh 100 g of bamboo fiber and 25 g of sublimed sulfur. Put the bamboo, sulfur source and molten salt into a planetary ball mill in a mass ratio of 2:0.5:0.5. Then add 38 g of zirconia grinding beads and grind them thoroughly at 800 r / min for 2 h to obtain a mixture of carbon source / sulfur source / molten salt.

[0072] (3) The mixture of bamboo / sulfur source / molten salt was placed in a ceramic boat and heated in a tubular furnace. Under a nitrogen atmosphere, it was reacted with the bamboo charcoal material at 353 °C for 2 hours to allow the molten salt to melt and flow, guiding the sulfur source to fully penetrate into the bamboo charcoal material. Then, the temperature was increased to 445 °C and held for 1 hour to allow the unreacted sulfur source to volatilize and be transported to the tail gas cylinder for collection via carrier gas.

[0073] (4) After the furnace has cooled to room temperature, the mixture in the ceramic boat is thoroughly washed with deionized water and dried to obtain sulfur-doped bamboo-based porous carbon material.

[0074] Comparative Example 5 A method for preparing sulfur-doped bamboo-based porous carbon materials using a molten salt method includes the following steps: (1) Weigh 22.60 g of LiCl and 27.40 g of KCl according to the molar ratio of LiCl / (KCl+LiCl)=0.592, grind and mix them evenly to obtain 50 g of molten salt.

[0075] (2) Weigh 5g of bamboo fiber and 50g of sublimed sulfur. Put the bamboo, sulfur source and molten salt into a planetary ball mill in a mass ratio of 2:10:10. Then add 38g of zirconia grinding beads and grind them thoroughly at 800 r / min for 2 h to obtain a mixture of carbon source / sulfur source / molten salt.

[0076] (3) The mixture of bamboo / sulfur source / molten salt was placed in a ceramic boat and heated in a tubular furnace. Under a nitrogen atmosphere, it was reacted with the bamboo charcoal material at 353 °C for 2 hours to allow the molten salt to melt and flow, guiding the sulfur source to fully penetrate into the bamboo charcoal material. Then, the temperature was increased to 445 °C and held for 1 hour to allow the unreacted sulfur source to volatilize and be transported to the tail gas cylinder for collection via carrier gas.

[0077] (4) After the furnace has cooled to room temperature, the mixture in the ceramic boat is thoroughly washed with deionized water and dried to obtain sulfur-doped bamboo-based porous carbon material.

[0078] Test case The obtained product, collotype (conductive agent), and polytetrafluoroethylene emulsion (binder) were mixed in a 7:2:1 ratio to prepare an electrode slurry, which was then uniformly drop-coated onto a nickel mesh. After drying, the slurry was immersed in a 6 mol / L potassium hydroxide electrolyte for 24 h to prepare a sulfur-doped bamboo-based porous carbon material electrode. Subsequently, a three-electrode system was constructed using a DC-EC 1200 electrochemical workstation, and electrochemical tests were performed using 6 mol / L potassium hydroxide as the electrolyte. The energy density, specific capacitance, and capacity retention after 100 cycles of the battery are shown in Table 1.

[0079] Table 1 As can be seen from Table 1, the sulfur-doped porous carbon prepared by this invention has excellent energy density, specific capacitance and cycle life, and has good prospects for industrial application in the field of supercapacitors.

[0080] 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 the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for preparing sulfur-doped porous carbon using a molten salt method, characterized in that, Includes the following steps: (1) Mix lithium chloride and potassium chloride evenly to obtain molten salt; (2) The bamboo material, sulfur source and molten salt are ball-milled and mixed evenly to obtain the precursor; (3) The precursor was subjected to a first heat treatment and a second heat treatment under an inert gas, washed and dried to obtain sulfur-doped porous carbon assisted by molten salt method.

2. The method for preparing sulfur-doped porous carbon using the molten salt method according to claim 1, characterized in that, The lithium chloride has a molar percentage of 59-60% in the molten salt.

3. The method for preparing sulfur-doped porous carbon using the molten salt method according to claim 1, characterized in that, The lithium chloride has a molar percentage of 59.2% in the molten salt.

4. The method for preparing sulfur-doped porous carbon using the molten salt method according to claim 1, characterized in that, The bamboo material includes at least one of bamboo raw fiber, bamboo pulp fiber, and bamboo-based pulp. The sulfur source includes at least one of sublimed sulfur and sulfur.

5. The method for preparing sulfur-doped porous carbon using the molten salt method according to claim 1, characterized in that, The mass ratio of bamboo, sulfur source, and molten salt is 2:(1.5~6):(1~6).

6. The method for preparing sulfur-doped porous carbon using the molten salt method according to claim 1, characterized in that, The ball mill rotates at 600-1000 rpm for 2-24 hours.

7. The method for preparing sulfur-doped porous carbon using the molten salt method according to claim 1, characterized in that, The temperature of the first heat treatment is 353~445℃, and the time is 1~4h.

8. The method for preparing sulfur-doped porous carbon using the molten salt method according to claim 1, characterized in that, The temperature of the first heat treatment is 445~1200℃, and the time is 0.5~2h.

9. A molten salt method-assisted sulfur-doped porous carbon, characterized in that, It is prepared by any of the preparation methods described in claims 1 to 8.

10. The application of the molten salt method-assisted sulfur-doped porous carbon as an electrode material in the preparation of supercapacitors as described in claim 9.

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