Method for preparing energy storage material by straw high-pressure hydrothermal and synergic activation

Abstract

The application provides a method for preparing energy storage material by straw high-pressure hydrothermal coupling activation, and relates to the technical field of biochar material.The straw, a nitrogen source and water are mixed to obtain a slurry; the nitrogen source is livestock and poultry manure; the slurry is subjected to high-pressure hydrothermal reaction to obtain hydrothermal carbon; the pressure of the high-pressure hydrothermal reaction is 8-16 MPa, and the temperature is 160-220 DEG C; the hydrothermal carbon is mixed with a chemical activator to be activated and modified to obtain nitrogen-doped active biochar energy storage material.The application adopts straw high-pressure hydrothermal coupling chemical activation to prepare biochar material, the hydrothermal biochar after high-pressure hydrothermal carbonization has uniform carbon sphere structure, which is beneficial to efficient and stable nitrogen doping of the livestock and poultry manure nitrogen source, and can ensure sufficient contact between the chemical activator and the biochar in the activation process, so that the nitrogen-containing functional groups can be retained as much as possible while the rich pore structure is formed.The active biochar material prepared by the application has excellent energy storage performance.

Description

Technical Field

[0001] This invention relates to the field of biochar materials technology, and in particular to a method for preparing energy storage materials by high-pressure hydrothermal synergistic activation of straw. Background Technology

[0002] Hydrothermal treatment is a highly efficient and advanced technology that can directly convert biomass feedstocks with high carbon and moisture content without pre-drying. This endothermic process typically takes place under subcritical or supercritical water conditions, where the feedstock undergoes hydrolysis, depolymerization, and condensation fractionation to extract valuable components. Water is the most environmentally friendly solvent, serving as both a reactant and a suitable medium for acid-catalyzed reactions. The high concentration of hydrogen ions generated by subcritical water decomposes biomass into smaller molecules. Water in the hydrothermal carbonization process provides the medium for a series of complex reactions, typically leading to a reduction in hydrogen and oxygen content, alterations in colloidal structure, removal of hydroxyl groups through dehydration, elimination of carboxyl and carbonyl groups through decarboxylation, and the decomposition of some esters and ether bonds through promoted hydrolysis. The biochar produced by hydrothermal carbonization possesses abundant functional groups, making it an excellent precursor for the preparation of high-performance carbon materials.

[0003] Nitrogen doping is beneficial for improving the energy storage properties of biochar. The pyridine nitrogen and pyrrole nitrogen produced by nitrogen doping are the main functional groups for generating pseudocapacitance during energy storage, and nitrogen oxides and graphitic nitrogen can increase the conductivity of carbon materials. As one of the elements adjacent to carbon in the periodic table, nitrogen has similar chemical properties to carbon and can form stable covalent bonds with it, allowing it to exist stably in the carbon framework and thus largely maintaining the geometric structure of the carbon network. Currently, the nitrogen sources used in the preparation of nitrogen-doped biochar are high-energy-consuming chemical products such as urea and melamine, making it difficult to effectively achieve green production. Furthermore, high-nitrogen-content green nitrogen sources, such as livestock and poultry manure, are difficult to carbonize and dope efficiently during the carbonization process.

[0004] Furthermore, due to the poor pore structure of biochar itself, activation methods are generally used to improve its pore structure. Chemical activation is a commonly used and effective method, producing activated biochar with a rich pore structure, which has attracted widespread attention for this type of carbon material. However, studies have shown that chemical activation easily leads to the loss of nitrogen-containing functional groups. This makes it even more difficult to achieve the combined effect of pores and functional functional groups for green nitrogen sources such as livestock and poultry manure, thus limiting the application of this type of material in energy storage. Summary of the Invention

[0005] In view of this, the purpose of this invention is to provide a method for preparing energy storage materials by high-pressure hydrothermal synergistic activation of straw. The nitrogen-doped activated biochar material prepared by this invention achieves efficient and stable doping using livestock and poultry manure as a nitrogen source, resulting in activated biochar with rich pore structure and functional groups, exhibiting excellent energy storage performance.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0007] This invention provides a method for preparing energy storage materials by high-pressure hydrothermal synergistic activation of straw, comprising the following steps:

[0008] Straw, a nitrogen source, and water are mixed to obtain a slurry; the nitrogen source is livestock and poultry manure.

[0009] The slurry is subjected to a high-pressure hydrothermal reaction to obtain hydrothermal carbon; the pressure of the high-pressure hydrothermal reaction is 8~16MPa and the temperature is 160~220℃.

[0010] The hydrothermal carbon was mixed with a chemical activator for activation and modification to obtain nitrogen-doped activated biochar energy storage material.

[0011] Preferably, the straw includes one or more of corn straw, wheat straw, rice straw, and cotton straw; the livestock and poultry manure includes one or more of pig manure, cow manure, and chicken manure; and the particle size of the straw and livestock and poultry manure is 0.1~0.3mm.

[0012] Preferably, the mass ratio of straw to livestock and poultry manure is 1:0.5 to 1:2, and the mass ratio of the total mass of straw and livestock and poultry manure to the mass of water is 1:4 to 1:9.

[0013] Preferably, the heating rate to the high-pressure hydrothermal reaction temperature is 10℃ / min; the holding time for the high-pressure hydrothermal reaction is 0.5~1h; and the high-pressure hydrothermal reaction is carried out in a nitrogen atmosphere.

[0014] Preferably, the high-pressure hydrothermal reaction is carried out under stirring conditions, and the stirring speed is 80~100 rpm.

[0015] Preferably, the chemical activator includes one or more of KOH, K2CO3, Na2CO3, NaHCO3 and ZnCl2; the mass ratio of the hydrothermal carbon to the chemical activator is 1:1 to 1:4.

[0016] Preferably, the activation modification temperature is 800~950℃, the time is 1~2h, and the heating rate to the activation modification temperature is 10℃ / min; the activation modification is carried out in a nitrogen atmosphere.

[0017] This invention provides a nitrogen-doped activated biochar energy storage material prepared by the method described above, wherein the nitrogen-doped activated biochar energy storage material has a specific surface area of ​​1800~2000 m². 2 / g, with a microporous content of 50-60% and a nitrogen content of 4.5-5.5wt%, of which the total proportion of pyridine nitrogen and pyrrole nitrogen is 50-60wt%.

[0018] This invention provides the application of the nitrogen-doped activated biochar energy storage material described above in the preparation of supercapacitor electrode materials.

[0019] This invention provides a supercapacitor electrode, wherein the electrode material of the supercapacitor electrode includes an active material, a conductive agent, and a binder, and the active material includes the nitrogen-doped activated biochar energy storage material described in the above technical solutions.

[0020] This invention provides a method for preparing energy storage materials through high-pressure hydrothermal synergistic activation of straw, comprising the following steps: mixing straw, a nitrogen source, and water to obtain a slurry; wherein the nitrogen source is livestock and poultry manure; subjecting the slurry to a high-pressure hydrothermal reaction to obtain hydrothermal carbon; wherein the pressure of the high-pressure hydrothermal reaction is 8~16MPa and the temperature is 160~220℃; and mixing the hydrothermal carbon with a chemical activator for activation modification to obtain nitrogen-doped activated biochar energy storage material. This invention employs high-pressure hydrothermal coupled with chemical activation to prepare activated biochar materials. The hydrothermal biochar after high-pressure hydrothermal carbonization has a uniform carbon spherical structure, which is conducive to efficient nitrogen doping of the livestock and poultry manure nitrogen source. The doped functional groups are more stable, and sufficient contact between the chemical activator and the biochar can be ensured during the activation process. While forming a rich and uniform pore structure, nitrogen-containing functional groups are retained as much as possible. The resulting activated biochar has a more uniform pore size distribution, a higher specific surface area, and a richer variety of nitrogen-containing functional groups (pyridine nitrogen and pyrrole nitrogen), making it a carbon-based material with great potential for energy storage applications and suitable for preparing supercapacitor electrode materials. The method of this invention is a green and efficient nitrogen doping method that solves the problems of poor carbonization and doping effect of livestock and poultry manure.

[0021] The results of the examples show that when the nitrogen-doped activated biochar energy storage material prepared in this invention is used as a supercapacitor electrode material, under three-electrode system conditions (the reference electrode is a saturated calomel electrode, the counter electrode is a platinum foil, and 1 mol / L KOH solution is the electrolyte), the specific capacitance at a current density of 0.02 A / g is 337~340 F / g, and the specific capacitance retention rate is 91~92% after 5000 cycles. Its electrochemical performance is better than that of ordinary commercial activated carbon. Attached Figure Description

[0022] Figure 1 Here is a scanning electron microscope image of the activated biochar material prepared in Example 1;

[0023] Figure 2 This is a scanning electron microscope image of the activated biochar material prepared in Example 2. Detailed Implementation

[0024] This invention provides a method for preparing energy storage materials by high-pressure hydrothermal synergistic activation of straw, comprising the following steps:

[0025] Straw, a nitrogen source, and water are mixed to obtain a slurry; the nitrogen source is livestock and poultry manure.

[0026] The slurry is subjected to a high-pressure hydrothermal reaction to obtain hydrothermal carbon; the pressure of the high-pressure hydrothermal reaction is 8~16MPa and the temperature is 160~220℃.

[0027] The hydrothermal carbon was mixed with a chemical activator for activation and modification to obtain nitrogen-doped activated biochar energy storage material.

[0028] Unless otherwise specified, all raw materials involved in this invention are commercially available products well known to those skilled in the art.

[0029] This invention mixes straw, a nitrogen source, and water to obtain a slurry. In this invention, the biomass preferably includes one or more of corn straw, wheat straw, rice straw, and cotton straw, more preferably corn straw. In this invention, the nitrogen source is livestock and poultry manure, preferably including one or more of pig manure, cow manure, and chicken manure. In this invention, the particle size of the straw and livestock and poultry manure is preferably 0.1~0.3 mm, and this invention preferably obtains the straw and livestock and poultry manure of this particle size through crushing.

[0030] In this invention, the mass ratio of straw to livestock and poultry manure is preferably 1:0.5 to 1:2, more preferably 1:0.5 to 1:1; the mass ratio of the total mass of straw and livestock and poultry manure to the mass of water is preferably 1:4 to 1:9, more preferably 1:5 to 1:9.

[0031] The present invention does not have any special requirements for the mixing method; any mixing method known to those skilled in the art can be used to mix the mixture evenly.

[0032] After obtaining the slurry, the present invention subjectes the slurry to a high-pressure hydrothermal reaction to obtain hydrothermal carbon. In the present invention, the pressure of the high-pressure hydrothermal reaction (or ultra-high-pressure hydrothermal reaction) is 8~16MPa, preferably 8~12MPa, and the temperature is 160~220℃, preferably 180~200℃; the heating rate to the temperature of the high-pressure hydrothermal reaction is preferably 10℃ / min; the holding time of the high-pressure hydrothermal reaction is preferably 0.5~1h. In the present invention, the high-pressure hydrothermal reaction is preferably carried out in a nitrogen atmosphere; the high-pressure hydrothermal reaction is preferably carried out under stirring conditions, and the stirring speed is preferably 80~100rpm, more preferably 80~90rpm.

[0033] Preferably, the slurry is placed in a hydrothermal reactor, and nitrogen gas is introduced into the reactor using a pressure regulating system to bring the internal pressure to 8-16 MPa. The high-pressure hydrothermal reaction is carried out at a temperature of 160-220°C.

[0034] The pressure of the hydrothermal reaction is a crucial factor affecting the physicochemical properties of hydrothermal biochar. High-pressure hydrothermal carbonization facilitates the breaking of carbon-hydrogen bonds and catalytic dehydration during biomass carbonization, promoting the carbonization process and thus improving the carbon skeleton structure of hydrothermal biochar, resulting in a uniform carbon sphere configuration. Conventional hydrothermal carbonization relies on the self-pressurization of the reaction process and is mainly influenced by hydrothermal temperature and the solids content of the raw materials, typically ranging from 4 to 5 MPa. Ultra-high-pressure hydrothermal carbonization requires decoupling pressure from other factors, maintaining the reaction pressure within a high-pressure range through a pressure regulating system. This invention utilizes high-pressure hydrothermal methods to prepare nitrogen-doped biochar, efficiently forming a uniform carbon sphere structure and achieving efficient and stable doping. Furthermore, high-pressure hydrothermal methods lower the carbonization temperature and reduce the carbonization reaction time, improving energy efficiency and reducing the carbon footprint compared to traditional hydrothermal carbonization methods.

[0035] After the high-pressure hydrothermal reaction is completed, the resulting material is preferably washed and dried sequentially to obtain the hydrothermal carbon. In this invention, the washing is preferably repeated with ethanol and deionized water, and the mass fraction of the ethanol is preferably 95%; the drying temperature is preferably 105°C, the drying time is preferably 12 hours, and the drying is preferably carried out in an oven.

[0036] After obtaining hydrothermal carbon, the present invention mixes the hydrothermal carbon with a chemical activator for activation modification to obtain nitrogen-doped activated biochar energy storage material.

[0037] In this invention, the chemical activator preferably includes one or more of KOH, K2CO3, Na2CO3, NaHCO3 and ZnCl2, more preferably KOH or NaHCO3; the mass ratio of the hydrothermal carbon to the chemical activator is preferably 1:1 to 1:4, more preferably 1:1 to 1:2.

[0038] In this invention, the preferred method for mixing the hydrothermal carbon and the chemical activator is grinding and mixing.

[0039] In this invention, the activation and modification temperature is preferably 800~950℃, more preferably 800~850℃, and the time is preferably 1~2h, more preferably 1.5~2h; the heating rate to the activation and modification temperature is preferably 10℃ / min; the activation and modification is preferably carried out in a nitrogen atmosphere.

[0040] In this invention, the activation modification is preferably carried out in a tubular furnace, and the tubular furnace is purged with nitrogen before the activation modification.

[0041] After the activation modification is completed, the obtained material is preferably cooled to room temperature under a nitrogen gas flow, and then washed and dried sequentially to obtain the nitrogen-doped activated biochar energy storage material. In this invention, the washing is preferably performed by repeatedly rinsing with dilute hydrochloric acid and deionized water until neutral, wherein the concentration of the dilute hydrochloric acid is 0.05 mol / L. This method removes metal ions from the activator adhering to the surface of the biochar using the dilute hydrochloric acid. In this invention, the drying temperature is preferably 105°C, the drying time is preferably 12 hours, and the drying is preferably carried out in an oven.

[0042] Based on the synergistic properties of high-pressure hydrothermal carbonization, nitrogen doping, and chemical activation, this invention uses straw as raw material and livestock and poultry manure as nitrogen source to prepare activated biochar with a porous structure (high specific surface area, high proportion of micropores, and uniform pore size distribution) and abundant functional groups.

[0043] This invention provides a nitrogen-doped activated biochar energy storage material prepared by the method described above, wherein the nitrogen-doped activated biochar energy storage material has a specific surface area of ​​1800~2000 m². 2 The nitrogen-doped activated biochar energy storage material provided by this invention has a high specific surface area, a relatively uniform pore size distribution, is mainly composed of micropores and mesopores, and is rich in nitrogen-containing functional groups. The micropores account for 50-60% of the total pore size, while the nitrogen content is 4.5-5.5 wt%, of which pyridine nitrogen and pyrrole nitrogen account for 50-60 wt%.

[0044] This invention provides the application of the nitrogen-doped activated biochar energy storage material described above in the preparation of supercapacitor electrode materials. The nitrogen-doped activated biochar energy storage material provided by this invention possesses a rich and uniform pore structure while retaining nitrogen-containing functional groups as much as possible. It exhibits a more uniform pore size distribution, a higher specific surface area, and abundant nitrogen-containing functional groups, giving it significant potential for energy storage applications and making it suitable for preparing supercapacitor electrode materials.

[0045] This invention provides a supercapacitor electrode. The electrode material of the supercapacitor electrode includes an active material, a conductive agent, and a binder. The active material includes the nitrogen-doped activated biochar energy storage material described in the above technical solutions. This invention does not have special requirements for the conductive agent and binder; any conductive agent and binder well-known to those skilled in the art can be used, such as acetylene black as the conductive agent and polyvinylidene fluoride as the binder. In this invention, the preferred mass ratio of the active material, conductive agent, and binder is 8:1:1. This invention does not have special requirements for the preparation method of the supercapacitor electrode; any preparation method well-known to those skilled in the art can be used. In an embodiment of this invention, the active material, conductive agent, and binder are ground, and an organic solvent is added to the ground material to form a thick slurry. The thick slurry is then dropped onto highly conductive graphite paper and dried to obtain the supercapacitor electrode. The organic solvent is preferably N-methylpyrrolidone.

[0046] To further illustrate the present invention, the method for preparing energy storage materials by high-pressure hydrothermal synergistic activation of straw provided by the present invention will be described in detail below with reference to examples, but these should not be construed as limiting the scope of protection of the present invention.

[0047] Example 1

[0048] The method for preparing nitrogen-doped activated biochar energy storage materials by high-pressure hydrothermal synergistic activation of straw is as follows:

[0049] (1) The straw raw material, livestock and poultry manure nitrogen source and deionized water are mixed evenly to obtain a slurry; the straw raw material is corn straw powder with a particle size of 0.3 mm and a mass of 4.5 g; the livestock and poultry manure nitrogen source is cow manure powder with a particle size of 0.3 mm and a mass of 4.5 g; and the deionized water is 51 mL.

[0050] (2) Add the slurry into the hydrothermal reactor, introduce nitrogen to adjust the reaction pressure inside the reactor to 8 MPa, the reaction temperature inside the hydrothermal reactor to 200℃, the reaction time to 0.5 h, and the stirring speed to 80 rpm; the material obtained by ultra-high pressure hydrothermal carbonization is repeatedly washed with 95 wt% ethanol and deionized water, the washed solid is filtered and placed in an oven to dry, the oven temperature to 105℃, the drying time to 12 h, to obtain ultra-high pressure hydrothermal carbon;

[0051] (3) The ultra-high pressure hydrothermal carbon and the activator were ground and mixed and placed in a tube furnace for activation modification. The activator was KOH, and the mass ratio of ultra-high pressure hydrothermal carbon to KOH was 1:1. The temperature was raised to 850℃ at a rate of 10℃ / min and the activation time was 1.5h. The activation process was carried out under a nitrogen atmosphere. After the reaction was completed, the obtained material was cooled to room temperature under a nitrogen flow and repeatedly washed with dilute hydrochloric acid and deionized water until neutral. The concentration of dilute hydrochloric acid was 0.05mol / L. The cleaned solid was filtered and dried (the oven temperature was 105℃ and the drying time was 12h) to obtain activated biochar material.

[0052] Figure 1 This is a scanning electron microscope (SEM) image of the activated biochar material prepared in Example 1. Figure 1 It can be seen that the obtained biochar material has a relatively rich pore structure, mainly consisting of micropores and mesopores.

[0053] The specific surface area of ​​the activated biochar material prepared in Example 1 was 1834 m². 2 / g, with a microporous content of 57.2% and a nitrogen content of 4.79wt%, of which pyridine nitrogen and pyrrole nitrogen account for a total of 51.23wt%.

[0054] The prepared activated biochar material, polyvinylidene fluoride, and acetylene black were ground in a mass ratio of 8:1:1. An organic solvent, N-methylpyrrolidone, was added to form a thick slurry. This slurry was then dropped onto highly conductive graphite paper and placed in a 60 °C oven for 12 h to obtain the working electrode. The energy storage capacity of the activated biochar was tested using a three-electrode system.

[0055] The reference electrode was a saturated calomel electrode, the counter electrode was a platinum foil, and the electrolyte was 1 mol / L KOH solution. The specific capacitance at a current density of 0.02 A / g was 337 F / g, and the specific capacitance retention rate was 91% after 5000 cycles.

[0056] Example 2

[0057] The method for preparing nitrogen-doped activated biochar materials by high-pressure hydrothermal synergistic activation of straw is as follows:

[0058] (1) The straw raw material, livestock and poultry manure nitrogen source and deionized water are mixed evenly to obtain a slurry; the straw raw material is corn straw powder with a particle size of 0.3 mm and a mass of 4 g; the livestock and poultry manure nitrogen source is chicken manure powder with a particle size of 0.3 mm and a mass of 2 g; and the deionized water is 54 mL.

[0059] (2) Add the slurry into the hydrothermal reactor, introduce nitrogen to adjust the reaction pressure inside the reactor to 12MPa, the reaction temperature inside the hydrothermal reactor to 180℃, the reaction time to 1h, and the stirring speed to 80rpm; repeatedly wash the material obtained by ultra-high pressure hydrothermal carbonization with 95wt% ethanol and deionized water, filter the washed solid and place it in an oven to dry, the oven temperature to 105℃, the drying time to 12h, to obtain ultra-high pressure hydrothermal carbon;

[0060] (3) The ultra-high pressure hydrothermal carbon and the activator were ground and mixed and placed in a tube furnace for activation modification. The activator was NaHCO3, and the mass ratio of ultra-high pressure hydrothermal carbon to NaHCO3 was 1:2. The temperature was raised to 800℃ at a rate of 10℃ / min and the activation time was 2h. The activation process was carried out under a nitrogen atmosphere. After the reaction was completed, the carbon was cooled to room temperature under a nitrogen flow and repeatedly washed with dilute hydrochloric acid and deionized water until neutral. The concentration of dilute hydrochloric acid was 0.05mol / L. The cleaned solid was filtered and dried (the oven temperature was 105℃ and the drying time was 12h) to obtain activated biochar material.

[0061] Figure 2 This is a scanning electron microscope (SEM) image of the activated biochar material prepared in Example 2. Figure 2 It can be seen that the obtained biochar material has a relatively rich pore structure, mainly consisting of micropores and mesopores.

[0062] The specific surface area of ​​the activated biochar material prepared in Example 2 was 1923 m². 2 / g, with a microporous content of 54.3% and a nitrogen content of 5.43wt%, of which pyridine nitrogen and pyrrole nitrogen account for a total of 57.36wt%.

[0063] The prepared activated biochar material, polyvinylidene fluoride, and acetylene black were ground in a mass ratio of 8:1:1. An organic solvent, N-methylpyrrolidone, was added to form a thick slurry. This slurry was then dropped onto highly conductive graphite paper and placed in a 60°C oven for 12 hours to obtain the working electrode. A three-electrode system was assembled, and the energy storage capacity of the activated biochar was tested.

[0064] The reference electrode was a saturated calomel electrode, the counter electrode was a platinum foil, and the electrolyte was 1 mol / L KOH solution. The specific capacitance at a current density of 0.02 A / g was 340 F / g, and the specific capacitance retention rate was 92% after 5000 cycles.

[0065] The specific surface area of ​​ordinary commercial activated carbon is generally 700~1500 m². 2 The specific capacitance is typically 200-250 F / g, and the capacitance retention rate is approximately 91% after 5000 cycles. Therefore, the activated biochar prepared in this embodiment of the invention exhibits superior electrochemical performance compared to ordinary commercial activated carbon when used as a supercapacitor electrode material.

[0066] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing energy storage material by straw high-pressure hydrothermal and activation, characterized in that, The method comprises the following steps: Mixing straw, a nitrogen source and water to obtain a slurry; the nitrogen source is livestock and poultry manure; Performing high-pressure hydrothermal reaction on the slurry to obtain hydrothermal carbon; the high-pressure hydrothermal reaction is performed at a pressure of 8-16 MPa and a temperature of 160-220 ℃. The water heat carbon is mixed with a chemical activation agent for activation modification, to obtain a nitrogen-doped active biochar energy storage material; the specific surface area of the nitrogen-doped active biochar energy storage material is 1800-2000 m 2 / g, the micropore ratio is 50-60%, the nitrogen content is 4.5-5.5 wt%, and the total ratio of pyridine nitrogen and pyrrole nitrogen is 50-60 wt%.

2. The method of claim 1, wherein, The straw includes one or more of corn straw, wheat straw, rice straw and cotton stalk; the livestock and poultry manure includes one or more of pig manure, cow manure and chicken manure; the particle size of the straw and the livestock and poultry manure is 0.1-0.3 mm.

3. The method according to claim 1 or 2, characterized in that, The mass ratio of the straw to the livestock and poultry manure is 1:0.5-1:2, and the total mass of the straw and the livestock and poultry manure to the mass of water is 1:4-1:

9.

4. The method of claim 1, wherein, The heating rate for heating to the temperature of the high-pressure hydrothermal reaction is 10 ℃ / min; the holding time of the high-pressure hydrothermal reaction is 0.5-1 h; the high-pressure hydrothermal reaction is performed in a nitrogen atmosphere.

5. The method of claim 4, wherein, The high-pressure hydrothermal reaction is performed under stirring, and the stirring speed is 80-100 rpm.

6. The method of claim 1, wherein, The chemical activator includes one or more of KOH, K2CO3, Na2CO3, NaHCO3 and ZnCl2; the mass ratio of the hydrothermal carbon to the chemical activator is 1:1-1:

4.

7. The method according to claim 1 or 6, characterized in that, The activation modification is performed at a temperature of 800-950 ℃ for 1-2 h, and the heating rate for heating to the temperature of the activation modification is 10 ℃ / min; the activation modification is performed in a nitrogen atmosphere.

8. The nitrogen-doped activated biochar energy storage material prepared by the method of any one of claims 1-7, wherein the nitrogen-doped activated biochar energy storage material has a specific surface area of 1800-2000 m2 / g, a micropore ratio of 50-60%, a nitrogen content of 4.5-5.5 wt%, and a total pyridine nitrogen and pyrrole nitrogen content of 50-60 wt%. 2 / g, a micropore ratio of 50-60%, a nitrogen content of 4.5-5.5 wt%, and a total pyridine nitrogen and pyrrole nitrogen content of 50-60 wt%.

9. Use of the nitrogen-doped active biochar energy storage material of claim 8 in the preparation of a supercapacitor electrode material.

10. A supercapacitor electrode, characterized by, The electrode material of the supercapacitor electrode includes an active material, a conductive agent and a binder, and the active material includes the nitrogen-doped active biochar energy storage material of claim 8.

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