Preparation method and application of carbon nanosheet taking anthracite as raw material

Abstract

The application discloses a preparation method and application of carbon nanosheet taking anthracite as raw material, relates to the technical fields of carbon materials and capacitors, and has the following technical points: A1: after being crushed and screened to a particle size less than 0.2 mm, the anthracite is deashed by using a mixed acid of HCl and HF, the mixed acid is in a proportion of 40% HCl, 10% HF and 50% deionized water, 1g of the anthracite is mixed with 15mL of the mixed acid, and then oscillation is carried out under ultrasonic waves for 1h, the ultrasonic frequency is set to 100kHz, then normal-temperature stirring is carried out for 24h, after filtration, multiple deionized water washing is carried out, and then drying is carried out at 60 DEG C for 12h to obtain deashed anthracite; and technical effects: the anthracite is deashed by ultrasonic treatment in the mixed acid, and after hydrothermal acidification in a sulfuric acid solution, acidified carbon with swollen coal organic macromolecules, loose structure, large specific surface area and rich oxygen-containing functional groups is obtained.

Description

Technical Field

[0001] This invention relates to the field of carbon materials and capacitor technology, specifically to a method for preparing carbon nanosheets using anthracite as raw material and their application. Background Technology

[0002] Coal is one of my country's important energy sources, with abundant reserves and low cost, and a high carbon content. Anthracite is a high-rank coal with a high degree of metamorphism, a carbon content of over 90%, low volatile matter content, and high hardness and density, making it a suitable raw material as a precursor for carbon materials. Due to its dense and highly ordered structure, anthracite has high electrical conductivity, making it very suitable as an electrode material for energy storage.

[0003] Supercapacitors have become a hot topic in the application and research of electrochemical energy storage devices due to their advantages such as fast charging and discharging speed, high power density and energy density, and long cycle life. They are widely used in transportation, computers, and power generation, especially in automotive internal combustion engines, where they can provide instantaneous energy for rapid vehicle starting, demonstrating enormous application potential. Using anthracite as a raw material to prepare supercapacitor electrode materials for energy storage is an important way to achieve high-end applications of anthracite and a crucial pathway to promote the transformation of coal resource utilization in my country. This can bring significant economic value and a broad market to the development of non-combustion applications of anthracite.

[0004] Currently, anthracite is mainly used in fuel, metallurgy, and water treatment. Due to its high carbon content, low volatile matter, low cost, and wide availability, anthracite has the potential to be used as a high-end material, such as anode material for lithium-ion batteries. However, electrode materials prepared from anthracite have insufficient specific surface area and poor pore structure. This is because anthracite has a high degree of metamorphism, hardness, and density, making activation and pore formation difficult. The specific surface area of ​​activated anthracite-based materials is generally 300-1000 m² / s. 2 Even with complex activation processes, the specific surface area of ​​materials prepared by g is unlikely to exceed 1500 m² / g. 2 Anthracite-based materials, with their uneven pore size distribution and underdeveloped pore structure, exhibit an excessively high proportion of micropores, hindering electrolyte wetting and rapid ion migration. Current methods for preparing anthracite-based materials as supercapacitor electrode materials suffer from drawbacks such as low specific capacitance and poor rate performance. Therefore, developing carbon materials for supercapacitors using anthracite as a raw material, and achieving a hierarchical pore structure with a large specific surface area and a suitable mix of mesopores and micropores, is a crucial technical challenge that urgently needs to be addressed.

[0005] To address the aforementioned problems, the present invention aims to solve the technical issues of low specific surface area, underdeveloped pores, and low electrical capacity in the preparation of carbon materials using anthracite as raw material, and provides a method for preparing carbon nanosheets using anthracite as raw material and their application. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a method for preparing carbon nanosheets using anthracite as raw material and its application. The porous carbon prepared by the present invention has well-developed pores, a large specific surface area, and a high pore utilization rate. At the same time, capacitors made using the porous carbon prepared by the present invention have a large specific capacitance and a long service life.

[0007] To achieve the above objectives, the present invention provides the following technical solution: a method for preparing carbon nanosheets using anthracite as raw material, comprising the following steps:

[0008] A1: After the anthracite is crushed and screened to a particle size of less than 0.2 mm, the anthracite powder is deashed with a mixed acid of HCl and HF. The mixed acid ratio is 40% HCl: 10% HF: 50% deionized water. 1 g of anthracite is mixed with 15 mL of the mixed acid and then vibrated under ultrasonic conditions for 1 h. The ultrasonic frequency is set to 100 kHz. Then it is stirred at room temperature for 24 h. After filtration, it is washed with deionized water multiple times and then dried at 60℃ for 12 h to obtain deashed anthracite.

[0009] A2: Mix deashed anthracite with sulfuric acid solution, sonicate for 0.5 h, set the sonic frequency to 100 kHz, place in a reaction vessel, react at 120-200℃ for 8-12 h, cool, filter and wash repeatedly with deionized water until pH is 7, and then dry at 60℃ for 12 h to obtain acidified carbon.

[0010] A3: After mixing the acidified carbon with an activator (one of potassium hydroxide, potassium carbonate or phosphoric acid) and zinc oxide in a certain mass ratio, the mixture is placed in a high-temperature furnace filled with inert gas. The inert gas flow rate is maintained at 300 mL / min, and the mixture is heated from room temperature to 700℃ at a heating rate of 5℃ / min and held for 0.5-2 hours to obtain one-step carbonized activated carbon.

[0011] A4: Immerse the one-step carbonized activated carbon in a 0.1 mol / L dilute hydrochloric acid solution and stir magnetically for 1 hour. Set the magnetic stirrer speed to 600 rpm. After filtration, wash repeatedly with deionized water until the pH value is 7 to obtain carbon nanosheets.

[0012] Furthermore, in step A2, the mixing ratio of deashed anthracite and sulfuric acid solution is 1g deashed anthracite: 30mL sulfuric acid solution with a concentration of 2-6mol / L; in step A3, the mass ratio of acidified carbon, potassium hydroxide and zinc oxide is 1:3:1, the mass ratio of acidified carbon, potassium carbonate and zinc oxide is 1:3:2, and the mass ratio of acidified carbon, phosphoric acid and zinc oxide is 1:2:1.

[0013] A method for preparing carbon nanosheets using anthracite as raw material for use in supercapacitors includes the following steps:

[0014] B1: A mixture of anthracite-based carbon nanosheets, ethylene black, and polytetrafluoroethylene is added to a ball mill and ground for 0.5-1 hours.

[0015] B2: Transfer the mixed slurry to an ultrasonic instrument, ultrasonically treat it at a frequency of 100kHz for 0.5-1h to obtain electrode slurry;

[0016] B3: Coat the electrode slurry onto nickel foam, place it in an oven, set the air speed to 0.3 m / s and the temperature to 80℃ and dry for 15-30 min. Then use a tablet press to press the tablets. After pressing, the electrode sheets are obtained. Place the electrode sheets in an electrolytic cell to obtain a three-electrode supercapacitor. Place a separator between two electrode sheets and assemble them into a symmetrical dual-electrode button cell.

[0017] Furthermore, the carbon nanosheets made from anthracite described in step B1 are observed to be thin-layered nanosheets under a transmission electron microscope, with a specific surface area greater than 2000 m². 2 / g, the ratio of micropore volume to mesopore volume is within the range of 7:1 to 8:1; the mass ratio of carbon nanosheets, ethylene black and polytetrafluoroethylene, which are made from anthracite as raw material, in step B1 is 8:1:1; the slurry mixed in step B2 is transferred to an ultrasonic mill for ultrasonic treatment, the ultrasonic treatment program is set to ultrasonic treatment once every 2 min, ultrasonic treatment for 1.5 min, standing for 30 s, one cycle every 2 min, and a total ultrasonic treatment for 0.5-1 h; the electrode slurry coating thickness on nickel foam in step B3 is 0.2-0.5 mm, the electrolyte is 6 mol / L potassium hydroxide solution, and the diaphragm is a mixed cellulose diaphragm.

[0018] Compared with existing technologies, this invention has the following advantages: Anthracite is deashed by ultrasonic treatment in a mixed acid, and then hydrothermally acidified with sulfuric acid solution to obtain acidified carbon with swollen coal organic macromolecules, loose structure, large specific surface area, and abundant oxygen-containing functional groups. The acidified carbon and the activator work synergistically to promote activation and pore formation, forming a hierarchical porous carbon with well-developed macropores, mesopores, and micropores. The large number of pores provides a wide charge transport channel and charge storage space for subsequent supercapacitor charging and discharging, thereby improving the specific capacitance. In addition, the abundant oxygen-containing functional groups of the porous carbon obtained after acidification modification improve the wettability of aqueous electrolytes, thereby ensuring the improvement of charge transfer rate and increasing the charge and discharge rate under high current. Furthermore, the porous carbon prepared by combining deashing and acidification modification with high-temperature chemical activation has a stable carbon skeleton structure. As an electrode material, it still maintains a stable specific capacitance after multiple charge and discharge cycles, exhibiting excellent cycle stability. Attached Figure Description

[0019] Figure 1This is the nitrogen adsorption / desorption isotherm of Example 1.

[0020] Figure 2 This is the nitrogen adsorption / desorption isotherm of Example 2.

[0021] Figure 3 This is a TEM image of Example 1 (scale bar is 50 nm).

[0022] Figure 4 This is a TEM image of Example 2 (scale bar is 20nm).

[0023] Figure 5 This is a TEM image of Example 3 (scale bar is 20 nm).

[0024] Figure 6 These are XPS diagrams of Examples 1, 2, and 3.

[0025] Figure 7 These are the GCD curves of Example 4 at different scan rates.

[0026] Figure 8 These are the CV curves of Example 4 at different current densities.

[0027] Figure 9 This is the cycle performance graph measured in Example 4. Detailed Implementation

[0028] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. 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 of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0029] Please see Figures 1-9 This invention provides a method for preparing carbon nanosheets using anthracite as raw material and a technical solution for their application. Example 1

[0030] 5g of anthracite was crushed by a ball crusher and screened to a particle size of less than 0.2mm. It was then placed in 15mL of deionized water with a ratio of 40% HCl: 10% HF: 50% and ultrasonically treated for 1h at an ultrasonic frequency of 100kHz. After stirring at room temperature for 24h, it was filtered, washed with deionized water, and dried at 60℃ for 12h to obtain deashed anthracite.

[0031] 2: Place 1g of deashed anthracite in 30mL of 5mol / L sulfuric acid solution, and treat it in an ultrasonic instrument for 0.5h at an ultrasonic frequency of 100kHz. Then place it in a reaction vessel and heat it at 160°C.o The reaction was carried out at C for 10 hours. After cooling, the mixture was filtered and washed with deionized water until the pH was 7. The mixture was then placed in a vacuum drying oven and dried at 60°C for 12 hours to obtain acidified carbon.

[0032] Carbon oxide, potassium hydroxide, and zinc oxide were mixed evenly at a mass ratio of 1:3:1 and placed into a high-temperature furnace filled with N2. The N2 flow rate was maintained at 300 mL / min. -1 , with 5 o Cmin -1 The heating rate is from room temperature to 700. o Keep at C for 1 hour to obtain one-step carbonized activated carbon;

[0033] The obtained one-step carbonized activated carbon was immersed in 20 mL of 0.1 mol / L dilute hydrochloric acid solution and magnetically stirred for 1 h. The magnetic stirrer speed was set to 600 rpm. After filtration, it was repeatedly washed with deionized water until the pH value was 7 to obtain carbon nanosheets.

[0034] Table 1. Reagent parameters used in Example 1

[0035]

[0036] Example 2

[0037] 5g of anthracite was crushed by a ball crusher and screened to a particle size of less than 0.2mm. It was then placed in 15mL of deionized water with a ratio of 40% HCl: 10% HF: 50% and ultrasonically treated for 1h at an ultrasonic frequency of 100kHz. After stirring at room temperature for 24h, it was filtered, washed with deionized water, and dried at 60℃ for 12h to obtain deashed anthracite.

[0038] 1g of deashed anthracite was placed in 30mL of 3mol / L sulfuric acid solution and treated in an ultrasonic instrument for 0.5h at an ultrasonic frequency of 100kHz. Then it was placed in a reaction vessel and heated at 180°C. o The reaction was carried out at C for 8 hours, cooled and filtered, and washed with deionized water until the pH was 7. The mixture was then placed in a vacuum drying oven and dried at 60°C for 12 hours to obtain acidified carbon.

[0039] Acidified carbon, potassium carbonate, and zinc oxide were mixed evenly at a specific mass ratio of 1:3:2, and then placed into a high-temperature furnace filled with N2. The N2 flow rate was maintained at 300 mL / min. -1 , with 5 o Cmin -1 The heating rate is from room temperature to 700. o Keep at C for 2 hours to obtain one-step carbonized activated carbon;

[0040] The obtained one-step carbonized activated carbon was immersed in 30 mL of 0.1 mol / L dilute hydrochloric acid solution and magnetically stirred for 1 h. The magnetic stirrer speed was set to 600 rpm. After filtration, it was repeatedly washed with deionized water until the pH value was 7 to obtain carbon nanosheets.

[0041] Table 2, Reagent Parameters Used in Example 2

[0042]

[0043] Example 3

[0044] 5g of anthracite was crushed by a ball crusher and screened to a particle size of less than 0.2mm. It was then placed in 15mL of deionized water with a ratio of 40% HCl: 10% HF: 50% and ultrasonically treated for 1h at an ultrasonic frequency of 100kHz. After stirring at room temperature for 24h, it was filtered, washed with deionized water, and dried at 60℃ for 12h to obtain deashed anthracite.

[0045] 1g of deashed anthracite was placed in 30mL of 4mol / L sulfuric acid solution and treated in an ultrasonic instrument for 0.5h at an ultrasonic frequency of 100kHz. Then it was placed in a reaction vessel and heated to 150℃. o The reaction was carried out at C for 12 hours. After cooling, the mixture was filtered and washed with deionized water until the pH was 7. The mixture was then placed in a vacuum drying oven and dried at 60°C for 12 hours to obtain acidified carbon.

[0046] Carbon oxide, phosphoric acid, and zinc oxide were mixed evenly at a mass ratio of 1:2:1 and placed in a high-temperature furnace filled with N2. The N2 flow rate was maintained at 300 mL / min. -1 , with 5 o Cmin -1 The heating rate is from room temperature to 700. o Keep at C for 1.5 hours to obtain one-step carbonization activated carbon;

[0047] The obtained one-step carbonized activated carbon was immersed in 30 mL of 0.1 mol / L dilute hydrochloric acid solution and magnetically stirred for 1 h. The magnetic stirrer speed was set to 600 rpm. After filtration, it was repeatedly washed with deionized water until the pH value was 7 to obtain carbon nanosheets.

[0048] Table 3. Reagent parameters used in Example 3

[0049]

[0050] Example 4

[0051] The carbon nanosheets prepared in Example 1 were added to a ball mill and ground for 1 hour with ethylene black and polytetrafluoroethylene at a mass ratio of 8:1:1.

[0052] The mixed slurry was transferred to an ultrasonic instrument, and the ultrasonic frequency was 100kHz. The ultrasonic treatment was carried out for 1 hour. The ultrasonic treatment program was set to ultrasonicate once every 2 minutes, ultrasonic for 1.5 minutes, stand for 30 seconds, and repeat every 2 minutes for a total of 1 hour to obtain the electrode slurry.

[0053] Electrode slurry was coated onto nickel foam to a thickness of 0.2 mm. The foam was dried at 80°C for 15 min with an air velocity of 0.3 m / s. The foam was then pressed into tablets using a tablet press. Electrode sheets were obtained after pressing. The electrode sheets were placed in an electrolytic cell with a 6 mol / L potassium hydroxide solution as the electrolyte to obtain a three-electrode supercapacitor. A hybrid cellulose membrane was placed between two electrode sheets coated with electrode slurry to assemble a symmetrical dual-electrode button cell.

[0054] Table 4. Reagent parameters used in Example 4

[0055]

[0056] Example 5

[0057] The carbon nanosheets prepared in Example 2 were added to a ball mill at a mass ratio of 8:1:1 and ground for 0.5 h.

[0058] The mixed slurry was transferred to an ultrasonic instrument, and the ultrasonic frequency was 100kHz. The ultrasonic treatment was carried out for 0.5h. The ultrasonic treatment program was set to ultrasonic once every 2min, ultrasonic for 1.5min, stand for 30s, and cycle every 2min for a total of 0.5h to obtain electrode slurry.

[0059] Electrode slurry was coated onto nickel foam to a thickness of 0.4 mm. The foam was dried at 80°C for 30 min with an air velocity of 0.3 m / s. The foam was then pressed into tablets using a tablet press. Electrode sheets were obtained after pressing and placed in an electrolytic cell with a 6 mol / L potassium hydroxide solution as the electrolyte to obtain a three-electrode supercapacitor. A hybrid cellulose membrane was placed between two electrode sheets coated with electrode slurry to assemble a symmetrical dual-electrode button cell.

[0060] Table 5. Reagent parameters used in Example 5

[0061]

[0062] Example 6

[0063] The carbon nanosheets prepared in Example 3 were added to a ball mill and ground for 1 hour with ethylene black and polytetrafluoroethylene at a mass ratio of 8:1:1.

[0064] The mixed slurry was transferred to an ultrasonic instrument, and the ultrasonic frequency was 100kHz. The ultrasonic treatment was carried out for 45 minutes. The ultrasonic treatment program was set to ultrasonic once every 2 minutes, ultrasonic for 1.5 minutes, stand for 30 seconds, and repeat every 2 minutes for a total of 1 hour of ultrasonic treatment to obtain electrode slurry.

[0065] Electrode slurry was coated onto nickel foam with a thickness of 0.3 mm. The foam was dried at 80°C for 20 min with an air velocity of 0.3 m / s. Then, the foam was pressed into tablets using a tablet press. After pressing, electrode sheets were obtained. The electrode sheets were placed in an electrolytic cell with a 6 mol / L potassium hydroxide solution as the electrolyte to obtain a three-electrode supercapacitor. A hybrid cellulose membrane was placed between two electrode sheets coated with electrode slurry to assemble a symmetrical dual-electrode button cell.

[0066] Table 6. Reagent parameters used in Example 6

[0067]

[0068] Comparative Example 1

[0069] This comparative example is basically the same as Example 1, except that it is not acidified with sulfuric acid.

[0070] Comparative Example 2

[0071] This comparative example is basically the same as Example 1, except that zinc oxide is not added during the one-step carbonization and activation of carbon.

[0072] Comparative Example 3

[0073] The material prepared in Comparative Example 1 was added to a ball mill along with ethylene black and polytetrafluoroethylene at a mass ratio of 8:1:1 and ground for 1 hour.

[0074] The mixed slurry was transferred to an ultrasonic instrument, and the ultrasonic frequency was 100kHz. The ultrasonic treatment was carried out for 45 minutes. The ultrasonic treatment program was set to ultrasonic once every 2 minutes, ultrasonic for 1.5 minutes, stand for 30 seconds, and repeat every 2 minutes for a total of 1 hour of ultrasonic treatment to obtain electrode slurry.

[0075] Electrode slurry was coated onto nickel foam with a thickness of 0.3 mm. The foam was dried at 80°C for 20 min with an air velocity of 0.3 m / s. Then, the foam was pressed into tablets using a tablet press. After pressing, electrode sheets were obtained. The electrode sheets were placed in an electrolytic cell with a 6 mol / L potassium hydroxide solution as the electrolyte to obtain a three-electrode supercapacitor. A hybrid cellulose membrane was placed between two electrode sheets coated with electrode slurry to assemble a symmetrical dual-electrode button cell.

[0076] Comparative Example 4

[0077] The material prepared in Comparative Example 2 was added to a ball mill along with ethylene black and polytetrafluoroethylene at a mass ratio of 8:1:1 and ground for 1 hour.

[0078] The mixed slurry was transferred to an ultrasonic instrument, and the ultrasonic frequency was 100kHz. The ultrasonic treatment was carried out for 45 minutes. The ultrasonic treatment program was set to ultrasonic once every 2 minutes, ultrasonic for 1.5 minutes, stand for 30 seconds, and repeat every 2 minutes for a total of 1 hour of ultrasonic treatment to obtain electrode slurry.

[0079] Electrode slurry was coated onto nickel foam with a thickness of 0.3 mm. The foam was dried at 80°C for 20 min with an air velocity of 0.3 m / s. Then, the foam was pressed into tablets using a tablet press. After pressing, electrode sheets were obtained. The electrode sheets were placed in an electrolytic cell with a 6 mol / L potassium hydroxide solution as the electrolyte to obtain a three-electrode supercapacitor. A hybrid cellulose membrane was placed between two electrode sheets coated with electrode slurry to assemble a symmetrical dual-electrode button cell.

[0080] Comparative Example 5

[0081] Example 1 with publication number CN202310419264.X was selected as Comparative Example 3.

[0082] To more intuitively demonstrate the performance of the materials prepared in this application, the table below lists the materials prepared in Examples 1, 2, Comparative Example 1 and Comparative Example 2, as well as the main parameters of the electrode materials prepared by each material.

[0083] Table 7 shows the materials prepared in each embodiment and the main parameters of the electrode materials prepared by each material.

[0084]

[0085] Table 7 shows the parameters for Examples 1, 2, 3, Comparative Example 1, and Comparative Example 2, measured using an Autosorb-1-MP surface area and pore size analyzer manufactured by Quantachrome, USA. These parameters included nitrogen adsorption-desorption isotherms, pore size distribution of activated carbon, and pore structure. Before testing, the samples were ground to 80 mesh and then... o The activated carbon was dried in a vacuum drying oven at a temperature of C for 5 hours. The instrument testing conditions were as follows: liquid nitrogen temperature 77K, vacuum degree 10⁻⁷ mmHg, and high-purity nitrogen gas as the adsorbate. The pore size distribution of the activated carbon was calculated using the QSDFT model, and the specific surface area of ​​the activated carbon sample was calculated using the BET method.

[0086] As can be seen from the analysis of Table 7, the carbon nanosheets prepared by the present invention have better physical properties. Among them, the carbon nanosheets prepared in Examples 1, 2 and 3 have well-developed pores and larger specific surface areas. In particular, the carbon nanosheets prepared in Example 1 have a very high specific surface area, well-developed microporous structure, and a large number of mesoporous structures, which can store a large amount of charge and are suitable as electrode materials for supercapacitors.

[0087] Electrochemical testing:

[0088] Electrochemical tests were performed on the supercapacitors prepared in Examples 4, 5, 6, and Comparative Examples 3, 4, and 5, with a current density of 0.5 A / g.

[0089] Table 8. Electrochemical test results

[0090]

[0091] The cyclic voltammetry test instrument for Comparative Examples 3 and 4 was the CHI604E electrochemical workstation from Shanghai Chenhua Instrument Co., Ltd., with a test range of 0-1V for button cells.

[0092] Analysis of Table 8 shows that the supercapacitors prepared using carbon nanosheets prepared in Examples 1, 2 and 3 have larger specific capacitance and a capacitance retention rate of over 100% after cyclic charging. Among them, the supercapacitor prepared in Example 3 has the best specific capacitance because it uses carbon nanosheets prepared in Example 1.

[0093] It should be noted that the above tests were all conducted in a manner known to those skilled in the art, and will not be described in detail in this application.

[0094] The above are merely specific embodiments of the present invention, but the technical features of the present invention are not limited thereto. Any simple changes, equivalent substitutions, or modifications made based on the present invention to solve essentially the same technical problems and achieve essentially the same technical effects are all covered within the protection scope of the present invention.

Claims

1. A method for preparing carbon nanosheets using anthracite as a raw material, characterized by comprising the steps of: Specifically comprising the following steps: ​ A1: after the anthracite is crushed and sieved to a particle size of less than 0.2 mm, the anthracite powder is subjected to a deashing treatment with a mixed acid of HCl and HF, to obtain deashed anthracite; A2: the deashed anthracite and a sulfuric acid solution are mixed, ultrasonic treatment is performed for 0.5 h at an ultrasonic frequency of 100 kHz, and then the mixture is placed in a reaction kettle, and reacted at 120-200 ℃ for 8-12 h, and then filtered and repeatedly washed with deionized water until the pH is 7, and then dried at 60 ℃ for 12 h, to obtain acidified carbon; A3: the acidified carbon, an activating agent and zinc oxide are uniformly mixed, and then placed in a high-temperature furnace filled with an inert gas, the inert gas flow rate is maintained at 300 mL / min, and the temperature is raised from room temperature to 700 ℃ at a rate of 5 ℃ / min, and maintained for 0.5-2 h, to obtain one-step carbonized activated carbon; A4: the one-step carbonized activated carbon is immersed in a 0.1 mol / L dilute hydrochloric acid solution, and magnetically stirred at a speed of 600 rpm for 1 h, and then filtered and repeatedly washed with deionized water until the pH is 7, to obtain carbon nanosheets.

2. The method according to claim 1, wherein the method is characterized by: The mixed acid is mixed by HCl, HF and deionized water in a volume ratio of 4:1:

5.

3. The method according to claim 2, wherein the method is characterized by: The deashing treatment specifically comprises the following steps: A11: 1 g of anthracite is mixed with 15 mL of the mixed acid; A12: after mixing, ultrasonic oscillation is performed for 1 h at an ultrasonic frequency of 100 kHz; A13: then stirred at room temperature for 24 h, and then filtered and repeatedly washed with deionized water; A14: then dried at 60 ℃ for 12 h, to obtain deashed anthracite.

4. The method according to claim 1, wherein the method is characterized by: The ratio of the deashed anthracite to the sulfuric acid solution in step A2 is 1 g of deashed anthracite to 30 mL of a sulfuric acid solution with a concentration of 2-6 mol / L.

5. The method according to claim 1, wherein the method is characterized by: The activating agent is one of potassium hydroxide, potassium carbonate or phosphoric acid.

6. The method according to claim 5, wherein the method is characterized by: The activating agent is potassium hydroxide, and the mass ratio of the acidified carbon, the potassium hydroxide and the zinc oxide is 1:3:

1.

7. The method according to claim 5, wherein the method is characterized by: The activating agent is potassium carbonate, and the mass ratio of the acidified carbon, the potassium carbonate and the zinc oxide is 1:3:

2.

8. The method according to claim 5, wherein the method is characterized by: The activating agent is phosphoric acid, and the mass ratio of the acidified carbon, the phosphoric acid and the zinc oxide is 1:2:

1.

9. Use of the carbon nanosheets according to any one of claims 1-8 for the preparation of supercapacitors, characterized by, The carbon nanosheets have a specific surface area greater than 2000 m 2 / g, the ratio of micropore volume to mesopore volume is 7:1 to 8:1.

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