A carbon-based capacitor electrode material and a method for preparing the same

Abstract

This invention discloses a carbon-based capacitor electrode material and its preparation method, relating to the field of supercapacitor technology. In preparing the carbon-based capacitor electrode material, this invention involves ultrasonically mixing sugarcane bagasse biochar and graphene oxide to obtain pre-modified biochar; using urea as a nitrogen source, nitrogen doping is performed on the pre-modified biochar to obtain modified biochar; aniline, 3-aminobenzenesulfonic acid, and o-mercaptoaniline are in-situ copolymerized on the surface of the modified biochar to obtain polyaniline-biochar; N-vinylimidazolium and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide are reacted to obtain a flame retardant precursor; the flame retardant precursor is reacted with 3-chloropropene to obtain a flame retardant monomer; and the flame retardant monomer is grafted onto the surface of the polyaniline-biochar to obtain the carbon-based capacitor electrode material. The carbon-based capacitor electrode material prepared by this invention exhibits excellent flame retardancy, wettability, and electrochemical performance.

Description

Technical Field

[0001] This invention relates to the field of supercapacitor technology, specifically to a carbon-based capacitor electrode material and its preparation method. Background Technology

[0002] Carbon-based capacitors are electrochemical energy storage devices with carbon materials as the core electrodes. They are widely used in electric vehicle start-stop systems, smart grid peak shaving and valley filling, emergency power supply for portable electronic devices, and special energy storage in aerospace. Currently, commercially available and R&D carbon-based electrode materials mainly include activated carbon, carbon nanotubes, graphene, and biomass-derived porous carbon. Among them, biomass-based carbon materials have become a research hotspot in green energy storage technology in recent years due to their renewable raw materials and low cost.

[0003] Guangdong is one of my country's major sugarcane producing areas, with a vast sugarcane planting area and a large-scale sugar industry. Sugarcane bagasse byproducts generated annually by sugar companies in the province alone amount to millions of tons. Traditionally, this bagasse is mostly used for fuel incineration or directly discarded, resulting in a serious waste of biomass resources. Furthermore, the incineration process releases dust and harmful gases, exacerbating regional environmental pressure. Therefore, preparing bagasse as a precursor for high-performance biochar electrodes offers the triple benefits of resource recycling, cost control, and performance optimization.

[0004] Despite the significant advantages of carbon-based capacitors, the performance bottlenecks of core electrode materials still constrain their development towards higher energy density and higher integration. Traditional carbon materials exhibit strong surface chemical inertness, resulting in limited specific capacitance for pure carbon electrodes. Furthermore, under extreme application environments, carbon electrode materials suffer from insufficient thermal stability and flame retardancy, and their interfacial compatibility with electrolytes requires optimization. These issues limit the large-scale application and performance upgrades of carbon-based capacitors. Therefore, developing a carbon-based electrode material that combines high specific surface area, high conductivity, high pseudocapacitance contribution, and excellent stability has become a core research direction for overcoming current technological bottlenecks and propelling carbon-based capacitors towards higher performance and wider application scenarios. Summary of the Invention

[0005] The purpose of this invention is to provide a carbon-based capacitor electrode material and its preparation method to solve the problems existing in the prior art.

[0006] To solve the above-mentioned technical problems, the present invention provides the following solution: A carbon-based capacitor electrode material is disclosed, comprising: preparing pre-modified biochar by ultrasonically mixing sugarcane bagasse biochar and graphene oxide; obtaining modified biochar by nitrogen doping the pre-modified biochar with urea as a nitrogen source; obtaining polyaniline-biochar by in-situ copolymerization of aniline, 3-aminobenzenesulfonic acid, and o-mercaptoaniline on the surface of the modified biochar; obtaining a flame retardant precursor by reacting N-vinylimidazolium and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide; obtaining a flame retardant monomer by reacting the flame retardant precursor with 3-chloropropene; and obtaining the flame retardant monomer by grafting it onto the surface of the polyaniline-biochar. The graphene oxide is prepared by using a modified Hummer process to obtain flake graphite. The sugarcane bagasse biochar is obtained by calcining sugarcane bagasse powder.

[0007] A method for preparing a carbon-based capacitor electrode material, the method comprising the following steps: (1) Mix flake graphite and potassium nitrate at a mass ratio of 1:(1.1~1.3) until homogeneous. Add concentrated sulfuric acid at a mass ratio of 44~48 times that of the flake graphite. Stir at room temperature for 10~20 min. Add potassium permanganate at a mass ratio of 5~7 times that of the flake graphite. Stir and react at 0~4℃ for 1.5~2.5 h. Raise the temperature to 40~50℃ and stir and react for 5~7 h. Add deionized water at a volume ratio of 18~22 times that of the concentrated sulfuric acid. Add 30 vol% hydrogen peroxide aqueous solution at a mass ratio of 0.3~0.5 times that of the potassium permanganate. Let stand for 10~12 h. Filter and wash with deionized water 3~5 times. Freeze-dry at -50~-40℃ for 44~48 h. Place in a muffle furnace and heat at a rate of 4~6℃ / min under a nitrogen atmosphere. Insulation The material was cooled to room temperature, removed, and ground to obtain graphene oxide. (2) Mix the pre-modified biochar, urea, and sodium bicarbonate evenly, place them in a muffle furnace, and heat them at a rate of 4~6℃ / min under a nitrogen atmosphere. Insulation The material was cooled to room temperature, removed, and ground to obtain modified biochar. (3) Mix solution A and solution B evenly, cool to 0~4℃, stir for 20~30min, add solution C at a constant rate within 50~70min, continue stirring and react for 4~6h, filter under vacuum, wash 2~4 times with deionized water and anhydrous ethanol respectively, and dry under vacuum at 45~55℃ for 12~14h to obtain polyaniline-biochar; (4) Polyaniline-biochar, flame retardant monomer, anhydrous ethanol, and 2-hydroxy-2-methyl-1-phenyl-1-propanone are mixed evenly in a mass ratio of 1:(0.01~0.02):(6~8):(0.001~0.003). Under nitrogen protection, the mixture is stirred at room temperature for 30~40 min, irradiated under 365 nm ultraviolet light for 5~7 h, allowed to stand for 2~3 h, filtered, washed 2~4 times with anhydrous ethanol, and vacuum dried at 55~65℃ for 2~4 h to obtain carbon-based capacitor electrode material.

[0008] As an optimization, the flake graphite in step (1) is of type KS6, with a particle size of 800 mesh and a purity of 8099, and was purchased from Qingdao Gefit Graphite Carbon Co., Ltd.

[0009] As an optimization, the ratio of pre-modified biochar, urea and sodium bicarbonate in step (2) is: mixed evenly at a mass ratio of 1:(2.5~3.5):(0.4~0.6).

[0010] As an optimization, the preparation process of the pre-modified biochar in step (2) is as follows: sugarcane bagasse biochar, graphene oxide, and deionized water are mixed evenly at a mass ratio of 1:(0.004~0.006):(2.7~2.9), ultrasonically dispersed at room temperature for 1.5~2.5h, and freeze-dried at -50~-40℃ for 44~48h to obtain pre-modified biochar.

[0011] As an optimization, the preparation process of the sugarcane bagasse biochar is as follows: sugarcane bagasse powder is placed in a muffle furnace and heated at a rate of 4~6℃ / min under a nitrogen atmosphere to... Insulation Remove from heat after cooling to room temperature, grind, and strain. The sample was sieved through a fine mesh and washed 3-5 times with deionized water. Sugarcane bagasse biochar was obtained by drying for 12-14 hours.

[0012] As an optimization, the preparation process of solutions A, B, and C in step (3) is as follows: aniline, 3-aminobenzenesulfonic acid, and ammonium persulfate are weighed in a mass ratio of 1:(0.2~0.4):(1.1~1.3); aniline, o-mercaptoaniline, and 1 mol / L hydrogen chloride aqueous solution are mixed evenly in a mass ratio of 1:(0.1~0.3):(8~10) and stirred at room temperature for 10~20 min to obtain solution A; 3-aminobenzenesulfonic acid, octylphenol polyoxyethylene ether, and 1 mol / L hydrogen chloride aqueous solution are mixed evenly in a mass ratio of 1:(0.5~1.5):(10~12) and stirred at room temperature for 10~20 min to obtain solution B; ammonium persulfate, modified biochar, and 1 mol / L hydrogen chloride aqueous solution are mixed evenly in a mass ratio of 1:(0.3~0.5):(6~8) and ultrasonically dispersed at room temperature for 10~20 min to obtain solution C.

[0013] As an optimization, the preparation process of the flame retardant monomer in step (4) is as follows: the flame retardant precursor and 3-chloropropene with a molar ratio of 1:(1.1~1.3) are dissolved in toluene at a mass of 8~10 times that of the flame retardant precursor. Under nitrogen protection, the temperature is raised to 75~85℃, the mixture is stirred and reacted for 11~13h, cooled to room temperature, filtered, washed 2~4 times with anhydrous ethanol, and dried under vacuum at 55~65℃ for 10~14h to obtain the flame retardant monomer.

[0014] As an optimization, the preparation process of the flame retardant precursor is as follows: Equimolar amounts of N-vinylimidazolium and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide are dissolved in toluene at 8-10 times the mass of N-vinylimidazolium. The mixture is heated to 65-75°C and stirred for 5-15 minutes. Then, 0.003-0.005 times the mass of N-vinylimidazolium azobisisobutyronitrile is added, and the reaction is continued with stirring for 7-9 hours. The mixture is then cooled to room temperature, and toluene is removed by rotary evaporation under reduced pressure to obtain the flame retardant precursor.

[0015] Compared with the prior art, the beneficial effects achieved by the present invention are: In preparing carbon-based capacitor electrode materials, this invention employs a modified Hummer method to convert flake graphite into graphene oxide; calcining bagasse powder yields bagasse biochar; ultrasonically mixing bagasse biochar and graphene oxide produces pre-modified biochar; using urea as a nitrogen source, nitrogen doping is performed on the pre-modified biochar to obtain modified biochar; aniline, 3-aminobenzenesulfonic acid, and o-mercaptoaniline are in-situ copolymerized on the surface of the modified biochar to obtain polyaniline-biochar; N-vinylimidazolium and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide are reacted to prepare a flame retardant precursor; the flame retardant precursor is reacted with 3-chloropropene to prepare a flame retardant monomer; and the flame retardant monomer is grafted onto the surface of the polyaniline-biochar to obtain the carbon-based capacitor electrode material.

[0016] First, graphene oxide was prepared from flake graphite using a modified Hummer method. Sugarcane bagasse powder was calcined to obtain sugarcane bagasse biochar. Pre-modified biochar was prepared by ultrasonically mixing sugarcane bagasse biochar and graphene oxide. Sugarcane bagasse mainly consists of a three-dimensional network fiber structure composed of cellulose, hemicellulose, and lignin. The pyrolysis of cellulose and hemicellulose forms numerous micropores and mesopores. After physical or chemical activation, these can be further used to construct hierarchical channels with excellent connectivity, providing pathways for the rapid transport of electrolyte ions. The presence of lignin enhances the skeletal strength of the carbonized product, preventing the collapse of the pore structure during activation. Simultaneously, the oxygen, nitrogen, and other heteroatoms abundant in sugarcane bagasse can be partially retained in the carbon skeleton during carbonization, or can be converted through subsequent doping processes. The process enhances the electrode material by introducing pseudocapacitive active sites. Two-dimensional sheets of graphene oxide interweave and intersect within the porous framework of bagasse biochar, forming continuous conductive pathways, reducing electron transport resistance, and improving material conductivity. Its sheet structure can act as a pore support to inhibit the collapse of biochar micropores, while simultaneously forming new mesopores with biochar particles, constructing a hierarchical pore structure of "micropore energy storage-mesopore mass transfer," thereby improving specific surface area and rate performance. At the same time, the ultra-high mechanical strength of graphene can encapsulate biochar particles to form a rigid protective layer. Combined with the hydrogen-covalent bond interaction between graphene and biochar, it inhibits the pulverization and shedding of active materials during charging and discharging, enhancing structural stability and cycle life, thus endowing carbon-based capacitor electrode materials with excellent electrochemical performance.

[0017] Secondly, using urea as a nitrogen source, pre-modified biochar was nitrogen-doped to obtain modified biochar. During the urea nitrogen doping process, nitrogen elements were embedded in the carbon framework in three forms: pyridine N, pyrrole N, and graphitic N. Pyridine N and pyrrole N served as electrochemical active sites, undergoing reversible Faraday redox reactions during charge and discharge to generate additional pseudocapacitance. This compensated for the capacity limitation of pure carbon materials, which relied solely on the double-layer capacitance. The lone pair electrons of the N atom enabled sp... 2 The delocalized π system of the hybrid carbon skeleton carries a negative charge, and its spin density is concentrated on the neighboring C atoms. These activated C atoms become highly active adsorption sites, which can enrich more electrolyte ions through electrostatic interactions, increase the charge concentration of the electric double layer, significantly improve the specific capacitance of the carbon-based capacitor electrode material, and thus further improve the electrochemical performance of the carbon-based capacitor electrode material. The introduction of nitrogen-containing functional groups such as pyridine N and pyrrole N increases the hydrophilic polarization sites on the modified biochar, which increases the contact area between the electrode material and the electrolyte, increases the wettability of the material surface, and reduces the diffusion resistance of electrolyte ions in the pores, thereby further improving the wettability of the carbon-based capacitor electrode material.

[0018] Third, aniline, 3-aminobenzenesulfonic acid, and o-mercaptoaniline were in-situ copolymerized on the surface of modified biochar to prepare polyaniline-biochar. The addition of polyaniline introduces a Faraday pseudocapacitance into the original double-layer capacitance of biochar. The polyaniline molecular chain contains a reversible redox reaction between benzene and quinone rings, resulting in charge transfer during charging and discharging. This redox reaction can rapidly store / release a large amount of charge, contributing to the pseudocapacitance. Simultaneously, the conjugated structure of polyaniline is tightly integrated with the conductive network of the carbon-based material, allowing for rapid electron transport at the two-phase interface. In addition to maintaining the reversibility of the pseudocapacitive reaction, polyaniline can also fill the pores of carbon-based materials to form a multi-level energy storage structure of "micropore-mesopore-polymer chain", thereby further improving the electrochemical performance of carbon-based capacitor electrode materials. The sulfonic acid groups on the polyaniline chain can interact with polar molecules such as water and propylene carbonate in the electrolyte, driving electrolyte molecules to be rapidly adsorbed on the electrode surface, forming a continuous and dense liquid film that replaces the original air layer, significantly reducing the contact angle between the electrolyte and the electrode, thus giving the carbon-based capacitor electrode material excellent wettability.

[0019] Finally, a flame retardant precursor was prepared by reacting N-vinylimidazolium with 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide; the flame retardant precursor was then reacted with 3-chloropropene to prepare a flame retardant monomer, on which a quaternary ammonium salt structure was introduced; the flame retardant monomer was then grafted onto the surface of polyaniline-biochar to prepare a carbon-based capacitor electrode material; the DOPO group in the flame retardant monomer decomposes at high temperatures to produce phosphoric acid substances, which have a strong dehydration catalytic effect, promoting the rapid dehydration and carbonization of polyaniline on the electrode material surface to form a dense glassy carbon layer. This carbon layer can isolate oxygen and heat, prevent flame spread, and inhibit the release of combustible gases. Simultaneously, the imidazole ring in the flame retardant monomer and... The nitrogen doping sites in biochar release inert gases such as nitrogen and ammonia at high temperatures, diluting the concentration of combustible gases around the electrode. Nitrogen can also combine with phosphorus to form phosphorus-nitrogen heterocyclic compounds, further improving the density and thermal stability of the carbon layer, thus endowing carbon-based capacitor materials with excellent flame-retardant properties. Quaternary ammonium salt cations are permanently charged groups that can form ion-dipole interactions with water molecules or polar solvent molecules in the electrolyte. The nitrogen atoms in the imidazole ring have lone pairs of electrons that can form hydrogen bonds with water molecules. These two interactions enable the electrode surface to quickly adsorb electrolyte molecules, forming a continuous liquid film layer, thereby reducing the contact angle between the electrolyte and the electrode and further improving the wettability of the carbon-based capacitor material. Attached Figure Description

[0020] Figure 1 The GCD curves for the examples and comparative examples are shown at a current density of 1 A / g. Detailed Implementation

[0021] 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. Example 1:

[0022] A method for preparing a carbon-based capacitor electrode material, the method comprising the following steps: (1) Mix flake graphite and potassium nitrate at a mass ratio of 1:1.1. Add concentrated sulfuric acid at a mass ratio of 44 times that of flake graphite and stir at room temperature for 20 min. Add potassium permanganate at a mass ratio of 5 times that of flake graphite and stir at 0℃ for 2.5 h. Increase the temperature to 40℃ and stir for 7 h. Add deionized water at a volume ratio of 18 times that of concentrated sulfuric acid and add 30 vol% hydrogen peroxide aqueous solution at a mass ratio of 0.3 times that of potassium permanganate. Let stand for 12 h, filter, wash once with deionized water, freeze dry at -50℃ for 48 h, place in a muffle furnace, heat to 380℃ at a rate of 4℃ / min under a nitrogen atmosphere, keep warm for 2 h, cool to room temperature, grind, and obtain graphene oxide. (2) Sugarcane bagasse powder was placed in a muffle furnace and heated to 380°C at a rate of 4°C / min under a nitrogen atmosphere. The temperature was maintained for 2 hours, cooled to room temperature, ground, passed through a 90-mesh sieve, washed three times with deionized water, and dried at 75°C for 14 hours to obtain sugarcane bagasse biochar. Sugarcane bagasse biochar, graphene oxide, and deionized water were mixed evenly at a mass ratio of 1:0.004:2.7, ultrasonically dispersed at room temperature for 2.5 hours, and freeze-dried at -50°C for 48 hours to obtain pre-modified biochar. Pre-modified biochar, urea, and sodium bicarbonate were mixed evenly at a mass ratio of 1:2.5:0.4, placed in a muffle furnace, heated to 380°C at a rate of 4°C / min under a nitrogen atmosphere, maintained for 2.5 hours, cooled to room temperature, ground, and obtained modified biochar. (3) Weigh aniline, 3-aminobenzenesulfonic acid and ammonium persulfate in a mass ratio of 1:0.2:1.1; mix aniline, o-mercaptoaniline and 1 mol / L hydrogen chloride aqueous solution in a mass ratio of 1:0.1:8 and stir at room temperature for 20 min to obtain solution A; mix 3-aminobenzenesulfonic acid, octylphenol polyoxyethylene ether and 1 mol / L hydrogen chloride aqueous solution in a mass ratio of 1:0.5:10 and stir at room temperature for 20 min to obtain solution B; mix ammonium persulfate, modified biochar and 1 mol / L hydrogen chloride aqueous solution in a mass ratio of 1:0.3:6 and ultrasonically disperse at room temperature for 20 min to obtain solution C; mix solution A and solution B evenly, cool to 0℃, stir for 30 min, add solution C at a uniform rate within 70 min, continue stirring and react for 6 h, vacuum filter, wash twice with deionized water and anhydrous ethanol respectively, and vacuum dry at 45℃ for 14 h to obtain polyaniline-biochar; (4) Equimolar amounts of N-vinylimidazolium and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide were dissolved in toluene at 8 times the mass of N-vinylimidazolium. The mixture was heated to 65°C and stirred for 15 min. Then, 0.003 times the mass of N-vinylimidazolium azobisisobutyronitrile was added, and the mixture was stirred and reacted for another 9 h. The mixture was cooled to room temperature, and toluene was removed by rotary evaporation under reduced pressure to obtain the flame retardant precursor. The flame retardant precursor and 3-chloropropene were dissolved in toluene at a molar ratio of 1:1.1 at 8 times the mass of the flame retardant precursor. The mixture was heated to 75°C under nitrogen protection. The mixture was stirred for 13 hours, cooled to room temperature, filtered, washed twice with anhydrous ethanol, and dried under vacuum at 55°C for 14 hours to obtain the flame-retardant monomer. Polyaniline-biochar, flame-retardant monomer, anhydrous ethanol, and 2-hydroxy-2-methyl-1-phenyl-1-propanone were mixed uniformly at a mass ratio of 1:0.01:6:0.001, stirred at room temperature for 40 minutes under nitrogen protection, irradiated under 365 nm ultraviolet light for 7 hours, allowed to stand for 3 hours, filtered, washed twice with anhydrous ethanol, and dried under vacuum at 55°C for 4 hours to obtain the carbon-based capacitor electrode material. Example 2:

[0023] A method for preparing a carbon-based capacitor electrode material, the method comprising the following steps: (1) Mix flake graphite and potassium nitrate at a mass ratio of 1:1.2. Add concentrated sulfuric acid at a mass ratio of 46 times that of flake graphite and stir at room temperature for 15 min. Add potassium permanganate at a mass ratio of 6 times that of flake graphite and stir at 2℃ for 2 h. Increase the temperature to 45℃ and stir for 6 h. Add deionized water at a volume ratio of 20 times that of concentrated sulfuric acid and add 30 vol% hydrogen peroxide aqueous solution at a mass ratio of 0.4 times that of potassium permanganate. Let stand for 11 h, filter, wash with deionized water 4 times, freeze dry at -45℃ for 46 h, place in a muffle furnace, heat to 400℃ at a rate of 5℃ / min under a nitrogen atmosphere, keep warm for 1.5 h, cool to room temperature, grind, and obtain graphene oxide. (2) Sugarcane bagasse powder was placed in a muffle furnace and heated to 400°C at a rate of 5°C / min under a nitrogen atmosphere. The temperature was maintained for 1.5 h, cooled to room temperature, ground, passed through a 100-mesh sieve, washed 4 times with deionized water, and dried at 80°C for 13 h to obtain sugarcane bagasse biochar. Sugarcane bagasse biochar, graphene oxide, and deionized water were mixed evenly at a mass ratio of 1:0.005:2.8, ultrasonically dispersed at room temperature for 2 h, and freeze-dried at -45°C for 46 h to obtain pre-modified biochar. Pre-modified biochar, urea, and sodium bicarbonate were mixed evenly at a mass ratio of 1:3:0.5, placed in a muffle furnace, heated to 400°C at a rate of 5°C / min under a nitrogen atmosphere, maintained for 2 h, cooled to room temperature, ground, and obtained modified biochar. (3) Weigh aniline, 3-aminobenzenesulfonic acid and ammonium persulfate in a mass ratio of 1:0.3:1.2; mix aniline, o-mercaptoaniline and 1 mol / L hydrogen chloride aqueous solution in a mass ratio of 1:0.2:9 and stir at room temperature for 15 min to obtain solution A; mix 3-aminobenzenesulfonic acid, octylphenol polyoxyethylene ether and 1 mol / L hydrogen chloride aqueous solution in a mass ratio of 1:1:11 and stir at room temperature for 15 min to obtain solution B; mix ammonium persulfate, modified biochar and 1 mol / L hydrogen chloride aqueous solution in a mass ratio of 1:0.4:7 and ultrasonically disperse at room temperature for 15 min to obtain solution C; mix solution A and solution B in a mass ratio of 1:0.4:7, cool to 2℃ and stir for 25 min, add solution C at a uniform rate within 60 min, continue stirring and react for 5 h, vacuum filter, wash 3 times with deionized water and anhydrous ethanol respectively, and vacuum dry at 50℃ for 13 h to obtain polyaniline-biochar; (4) Equimolar amounts of N-vinylimidazolium and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide were dissolved in toluene at 9 times the mass of N-vinylimidazolium. The mixture was heated to 70°C and stirred for 10 min. Azobisisobutyronitrile at 0.004 times the mass of N-vinylimidazolium was added, and the mixture was stirred and reacted for another 8 h. The mixture was cooled to room temperature, and toluene was removed by rotary evaporation under reduced pressure to obtain the flame retardant precursor. The flame retardant precursor and 3-chloropropene were dissolved in toluene at a molar ratio of 1:1.2 at 9 times the mass of the flame retardant precursor. The mixture was heated to 80°C under nitrogen protection. The mixture was stirred for 12 hours, cooled to room temperature, filtered, washed three times with anhydrous ethanol, and dried under vacuum at 60°C for 12 hours to obtain the flame-retardant monomer. Polyaniline-biochar, flame-retardant monomer, anhydrous ethanol, and 2-hydroxy-2-methyl-1-phenyl-1-propanone were mixed uniformly at a mass ratio of 1:0.015:7:0.002, stirred at room temperature for 35 minutes under nitrogen protection, irradiated under 365 nm ultraviolet light for 6 hours, allowed to stand for 2.5 hours, filtered, washed three times with anhydrous ethanol, and dried under vacuum at 60°C for 3 hours to obtain the carbon-based capacitor electrode material. Example 3:

[0024] A method for preparing a carbon-based capacitor electrode material, the method comprising the following steps: (1) Mix flake graphite and potassium nitrate at a mass ratio of 1:1.3. Add concentrated sulfuric acid at a mass ratio of 48 times that of flake graphite and stir at room temperature for 10 min. Add potassium permanganate at a mass ratio of 7 times that of flake graphite and stir at 4℃ for 1.5 h. Increase the temperature to 50℃ and stir for 5 h. Add deionized water at a volume ratio of 22 times that of concentrated sulfuric acid and 30 vol% hydrogen peroxide aqueous solution at a mass ratio of 0.5 times that of potassium permanganate. Let stand for 10 h, filter, wash with deionized water 5 times, freeze dry at -40℃ for 44 h, place in a muffle furnace, heat to 420℃ at a rate of 6℃ / min under a nitrogen atmosphere, keep warm for 1 h, cool to room temperature, grind, and obtain graphene oxide. (2) Sugarcane bagasse powder was placed in a muffle furnace and heated to 420°C at a rate of 6°C / min under a nitrogen atmosphere. The temperature was maintained for 1 hour, cooled to room temperature, ground, passed through a 110-mesh sieve, washed 5 times with deionized water, and dried at 85°C for 12 hours to obtain sugarcane bagasse biochar. Sugarcane bagasse biochar, graphene oxide, and deionized water were mixed evenly at a mass ratio of 1:0.006:2.9, ultrasonically dispersed at room temperature for 1.5 hours, and freeze-dried at -40°C for 44 hours to obtain pre-modified biochar. Pre-modified biochar, urea, and sodium bicarbonate were mixed evenly at a mass ratio of 1:3.5:0.6, placed in a muffle furnace, heated to 420°C at a rate of 6°C / min under a nitrogen atmosphere, maintained for 1.5 hours, cooled to room temperature, ground, and obtained modified biochar. (3) Weigh aniline, 3-aminobenzenesulfonic acid and ammonium persulfate in a mass ratio of 1:0.4:1.3; mix aniline, o-mercaptoaniline and 1 mol / L hydrogen chloride aqueous solution in a mass ratio of 1:0.3:10 and stir at room temperature for 10 min to obtain solution A; mix 3-aminobenzenesulfonic acid, octylphenol polyoxyethylene ether and 1 mol / L hydrogen chloride aqueous solution in a mass ratio of 1:1.5:12 and stir at room temperature for 10 min to obtain solution B; mix ammonium persulfate, modified biochar and 1 mol / L hydrogen chloride aqueous solution in a mass ratio of 1:0.5:8 and ultrasonically disperse at room temperature for 10 min to obtain solution C; mix solution A and solution B evenly, cool to 4℃, stir for 20 min, add solution C at a uniform rate within 50 min, continue stirring and react for 4 h, vacuum filter, wash 4 times with deionized water and anhydrous ethanol respectively, and vacuum dry at 55℃ for 12 h to obtain polyaniline-biochar; (4) Equimolar amounts of N-vinylimidazolium and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide were dissolved in toluene at 10 times the mass of N-vinylimidazolium. The mixture was heated to 75°C and stirred for 5 min. Azobisisobutyronitrile at 0.005 times the mass of N-vinylimidazolium was added, and the mixture was stirred and reacted for 7 h. The mixture was cooled to room temperature, and toluene was removed by rotary evaporation under reduced pressure to obtain the flame retardant precursor. The flame retardant precursor and 3-chloropropene at a molar ratio of 1:1.3 were dissolved in toluene at 10 times the mass of the flame retardant precursor. The mixture was heated to 85°C under nitrogen protection. The mixture was stirred at ℃ for 11 h, cooled to room temperature, filtered, washed four times with anhydrous ethanol, and dried under vacuum at 65℃ for 10 h to obtain the flame-retardant monomer. Polyaniline-biochar, flame-retardant monomer, anhydrous ethanol, and 2-hydroxy-2-methyl-1-phenyl-1-propanone were mixed uniformly at a mass ratio of 1:0.02:8:0.003, stirred at room temperature for 30 min under nitrogen protection, irradiated under 365 nm ultraviolet light for 5 h, allowed to stand for 2 h, filtered, washed four times with anhydrous ethanol, and dried under vacuum at 65℃ for 2 h to obtain the carbon-based capacitor electrode material.

[0025] Comparative Example 1: The difference between the preparation method of the carbon-based capacitor electrode material in Comparative Example 1 and Example 2 is that step (1) is omitted, and step (2) is changed as follows: Sugarcane bagasse powder is placed in a muffle furnace, heated to 400°C at a rate of 5°C / min under a nitrogen atmosphere, held at that temperature for 1.5 h, cooled to room temperature, ground, passed through a 100-mesh sieve, washed four times with deionized water, and dried at 80°C for 13 h to obtain sugarcane bagasse biochar; Sugarcane bagasse biochar, urea, and sodium bicarbonate are mixed evenly in a mass ratio of 1:3:0.5, placed in a muffle furnace, heated to 400°C at a rate of 5°C / min under a nitrogen atmosphere, held at that temperature for 2 h, cooled to room temperature, ground, to obtain modified biochar. The remaining steps are the same as in Example 2.

[0026] Comparative Example 2: The preparation method of the carbon-based capacitor electrode material in Comparative Example 2 differs from that in Example 2 only in that step (2) is changed as follows: sugarcane bagasse powder is placed in a muffle furnace, heated to 400°C at a rate of 5°C / min under a nitrogen atmosphere, held at that temperature for 1.5 h, cooled to room temperature, ground, passed through a 100-mesh sieve, washed four times with deionized water, and dried at 80°C for 13 h to obtain sugarcane bagasse biochar; sugarcane bagasse biochar, graphene oxide, and deionized water are mixed evenly at a mass ratio of 1:0.005:2.8, ultrasonically dispersed at room temperature for 2 h, and freeze-dried at -45°C for 46 h to obtain modified biochar. The remaining steps are the same as in Example 2.

[0027] Comparative Example 3 The preparation method of the carbon-based capacitor electrode material in Comparative Example 3 differs from that in Example 2 in that step (3) is omitted, and step (4) is changed to: dissolving equimolar amounts of N-vinylimidazolium and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide in toluene at 9 times the mass of N-vinylimidazolium, heating to 70°C, stirring for 10 min, adding azobisisobutyronitrile at 0.004 times the mass of N-vinylimidazolium, continuing to stir and react for 8 h, cooling to room temperature, and removing toluene by rotary evaporation under reduced pressure to obtain the electrode material. Flame retardant precursor: A flame retardant precursor and 3-chloropropene in a molar ratio of 1:1.2 were dissolved in toluene at a mass ratio of 9 times that of the flame retardant precursor. Under nitrogen protection, the mixture was heated to 80°C and stirred for 12 hours. After cooling to room temperature, the mixture was filtered, washed three times with anhydrous ethanol, and dried under vacuum at 60°C for 12 hours to obtain a flame retardant monomer. Modified biochar, flame retardant monomer, and anhydrous ethanol were mixed uniformly at a mass ratio of 1:0.015:7, ultrasonically dispersed at room temperature for 1.5 hours, and dried under vacuum at 60°C for 3 hours to obtain a carbon-based capacitor electrode material. The remaining steps were the same as in Example 2.

[0028] Comparative Example 4: The preparation method of the carbon-based capacitor electrode material in Comparative Example 4 differs from that in Example 2 in that step (4) is omitted, and step (3) is changed to: weighing aniline, 3-aminobenzenesulfonic acid and ammonium persulfate in a mass ratio of 1:0.3:1.2; mixing aniline and 1 mol / L hydrogen chloride aqueous solution in a mass ratio of 1:9, stirring at room temperature for 15 min to obtain solution A; mixing 3-aminobenzenesulfonic acid, octylphenol polyoxyethylene ether and 1 mol / L hydrogen chloride aqueous solution in a mass ratio of 1:1:11, stirring at room temperature for 15 min to obtain solution A. Solution B was prepared by stirring at room temperature for 15 min. Ammonium persulfate, modified biochar, and a 1 mol / L aqueous solution of hydrogen chloride were mixed uniformly at a mass ratio of 1:0.4:7 and ultrasonically dispersed at room temperature for 15 min to prepare solution C. Solutions A and B were mixed uniformly, cooled to 2°C, and stirred for 25 min. Solution C was added uniformly over 60 min, and the reaction was continued with stirring for 5 h. The mixture was then vacuum filtered, washed three times with deionized water and anhydrous ethanol, and vacuum dried at 50°C for 13 h to obtain the carbon-based capacitor electrode material. The remaining steps were the same as in Example 2.

[0029] Test Example 1 Electrochemical performance testing Test Method: The carbon-based capacitor electrode materials of the PSS-doped examples and comparative examples were directly coated onto indium tin oxide conductive glass using a wet film preparation device to obtain the working electrodes. A silver / silver chloride electrode was used as the reference electrode, and a platinum electrode as the counter electrode, forming a three-electrode system with the working electrodes. A 0.2 mol / L TBAP / PC solution was used as the electrolyte. Constant current charge-discharge tests were performed using a CS2350H electrochemical workstation, and the specific capacity C at 1 A / g was calculated. Where I is the current density, m is the mass of the electrode material, and ∆V is the voltage window. The results are shown in Table 1.

[0030] Table 1 A comparison of the experimental data from Examples 1-3 and Comparative Examples 1-4 in Table 1 reveals that the carbon-based capacitor electrode material prepared by this invention exhibits excellent electrochemical performance.

[0031] By comparison, the specific capacity of Examples 1-3 is greater than that of Comparative Example 1, indicating that the modified Hummer method is used to convert flake graphite into graphene oxide; sugarcane bagasse powder is calcined to obtain sugarcane bagasse biochar; and sugarcane bagasse biochar and graphene oxide are ultrasonically mixed to obtain pre-modified biochar. The two-dimensional sheets of graphene oxide overlap and interweave in the porous framework of sugarcane bagasse biochar to form continuous conductive pathways, reduce electron transport resistance, and improve the conductivity of the material. Its sheet structure can act as a pore support to inhibit the collapse of biochar micropores, and at the same time form new mesopores with biochar particles to construct a hierarchical pore structure of "micropore energy storage-mesopore mass transfer", which improves the specific surface area and rate performance. Meanwhile, the ultra-high mechanical strength of graphene can wrap biochar particles to form a rigid protective layer. Combined with the hydrogen-covalent bond interaction between graphene and biochar, it inhibits the pulverization and shedding of active materials during charging and discharging, enhances structural stability and cycle life, and thus endows the carbon-based capacitor electrode material with excellent electrochemical performance.

[0032] By comparison, the specific capacity of Examples 1-3 is greater than that of Comparative Example 2, indicating that using urea as a nitrogen source to dope pre-modified biochar with nitrogen can produce modified biochar. During the urea nitrogen doping process, nitrogen elements are embedded in the carbon framework in three forms: pyridine N, pyrrole N, and graphitic N. Pyridine N and pyrrole N serve as electrochemical active sites, undergoing reversible Faraday redox reactions during charge and discharge to generate additional pseudocapacitance. This compensates for the capacity limitation of pure carbon materials, which rely solely on double-layer capacitance. The lone pair electrons of the N atom enable sp... 2 The delocalized π system of the hybrid carbon framework carries a negative charge, and the spin density is concentrated on the neighboring C atoms. These activated C atoms become highly active adsorption sites, which can enrich more electrolyte ions through electrostatic interactions, increase the charge concentration of the electric double layer, significantly improve the specific capacitance of the carbon-based capacitor electrode material, and thus further improve the electrochemical performance of the carbon-based capacitor electrode material.

[0033] By comparison, the specific capacity of Examples 1-3 is greater than that of Comparative Example 3, indicating that polyaniline-biochar is prepared by in-situ copolymerization of aniline, 3-aminobenzenesulfonic acid, and o-mercaptoaniline on the surface of modified biochar. The addition of polyaniline introduces a Faraday pseudocapacitance on the basis of the original biochar double-layer capacitance. The polyaniline molecular chain has a reversible redox reaction of benzene ring-quinone ring, and charge transfer occurs during charging and discharging. This redox reaction can quickly store / release a large amount of charge, contributing to the pseudocapacitance. At the same time, the conjugated structure of polyaniline is tightly combined with the conductive network of carbon-based materials, and electrons can be quickly transferred at the interface between the two phases, ensuring the reversibility of the pseudocapacitance reaction. Polyaniline can also fill the pores of carbon-based materials to form a multi-level energy storage structure of "micropore-mesopore-polymer chain", thereby further improving the electrochemical performance of carbon-based capacitor electrode materials.

[0034] Test Example 2 Wetting performance test Test method: Cut nickel foam into 2×1cm rectangles. Mix the carbon-based capacitor electrode material, acetylene black, and polytetrafluoroethylene emulsion from the examples and comparative examples at a mass ratio of 8:1:1. Add anhydrous ethanol and stir until a paste is formed. Take 0.02g and evenly apply it to a 1×1cm area of ​​the nickel foam. Dry at 60℃ for 10 hours and allow to cool naturally to room temperature. Overlap the nickel foam coated with the active material with another piece of nickel foam without the active material. Press the pieces into thin sheets using an infrared tablet press at 10MPa pressure. A 0.2 mol / L TBAP / PC electrolyte was dropped onto the material surface, and the contact angle was measured using an optical contact angle meter. The results are shown in Table 2.

[0035] Table 2 A comparison of the experimental data from Examples 1-3 and Comparative Examples 1-4 in Table 2 reveals that the carbon-based capacitor electrode material prepared by this invention has good wetting properties.

[0036] By comparison, the contact angles of Examples 1-3 are smaller than those of Comparative Example 1, indicating that the modified Hummer method was used to prepare graphene oxide from flake graphite; sugarcane bagasse powder was calcined to obtain sugarcane bagasse biochar; sugarcane bagasse biochar and graphene oxide were ultrasonically mixed to obtain pre-modified biochar; the two-dimensional sheets of graphene oxide overlapped and interspersed in the porous framework of sugarcane bagasse biochar, forming new mesopores with biochar particles, constructing a hierarchical pore structure of "micropore energy storage-mesopore mass transfer", increasing the specific surface area, maximizing the exposure of hydrophilic groups, and thus improving the wettability of carbon-based capacitor electrode materials.

[0037] By comparison, the contact angles of Examples 1-3 are smaller than those of Comparative Example 2, indicating that using urea as a nitrogen source to dope pre-modified biochar with nitrogen can produce modified biochar. During the urea nitrogen doping process, nitrogen elements are embedded in the carbon skeleton in three forms: pyridine N, pyrrole N, and graphite N. The introduction of nitrogen-containing functional groups such as pyridine N and pyrrole N increases the hydrophilic polarization sites on the modified biochar, thereby increasing the contact area between the electrode material and the electrolyte, increasing the wettability of the material surface, reducing the diffusion resistance of electrolyte ions in the pores, and further improving the wettability of the carbon-based capacitor electrode material.

[0038] By comparison, the contact angles of Examples 1-3 are smaller than those of Comparative Example 3, indicating that polyaniline-biochar is prepared by in-situ copolymerization of aniline, 3-aminobenzenesulfonic acid, and o-mercaptoaniline on the surface of modified biochar. The sulfonic acid groups on the polyaniline chain can interact with polar molecules such as water and propylene carbonate in the electrolyte, driving electrolyte molecules to be rapidly adsorbed on the electrode surface, forming a continuous and dense liquid film that replaces the original air layer, significantly reducing the contact angle between the electrolyte and the electrode, thereby giving the carbon-based capacitor electrode material excellent wettability.

[0039] By comparison, the contact angles of Examples 1-3 are smaller than those of Comparative Example 4, indicating that the flame retardant precursor is prepared by reacting N-vinylimidazolium with 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide; the flame retardant precursor is reacted with 3-chloropropene to prepare a flame retardant monomer, and a quaternary ammonium salt structure is introduced onto the flame retardant monomer; the flame retardant monomer is grafted onto the surface of polyaniline-biochar to prepare a carbon-based capacitor electrode material; the quaternary ammonium salt positive ion is a permanently charged group that can form ion-dipole interactions with water molecules or polar solvent molecules in the electrolyte, and the nitrogen atom in the imidazolium ring has a lone pair of electrons that can form hydrogen bonds with water molecules. These two interactions enable the electrode surface to quickly adsorb electrolyte molecules, forming a continuous liquid film layer, thereby reducing the contact angle between the electrolyte and the electrode and further improving the wettability of the carbon-based capacitor electrode material.

[0040] Test Example 3 Flame retardant performance test Test method: The carbon-based capacitor electrode material, acetylene black, and polytetrafluoroethylene emulsion of the examples and comparative examples were mixed evenly at a mass ratio of 8:1:1. Anhydrous ethanol was added and stirred until a paste was formed. This paste was then coated onto nickel foam and dried at 60°C for 10 hours. After naturally cooling to room temperature, the nickel foam coated with the active material was stacked on top of another piece of nickel foam without the active material. The mixture was then pressed into a thin sheet using an infrared tablet press at a pressure of 10 MPa. The sheet was cut into standard strips with dimensions of 100 mm × 6.5 mm, and the limiting oxygen index was tested using an HC-2 oxygen index meter. The results are shown in Table 3.

[0041] Table 3 A comparison of the experimental data from Examples 1-3 and Comparative Examples 1-4 in Table 3 reveals that the carbon-based capacitor electrode material prepared by this invention has good flame-retardant properties.

[0042] By comparison, the limiting oxygen index of Examples 1-3 is greater than that of Comparative Example 2, indicating that using urea as a nitrogen source to dope pre-modified biochar with nitrogen yields modified biochar. During the urea nitrogen doping process, nitrogen is embedded in the carbon skeleton in three forms: pyridine N, pyrrole N, and graphite N. At high temperatures, this releases inert gases such as nitrogen and ammonia, diluting the concentration of combustible gases around the electrodes. Nitrogen can also combine with phosphorus to form phosphorus-nitrogen heterocyclic compounds, further improving the density and thermal stability of the carbon layer, thereby further enhancing the flame retardant performance of the carbon-based capacitor material. By comparison, the limiting oxygen index of Examples 1-3 is greater than that of Comparative Example 4, indicating that the flame retardant precursor is prepared by reacting N-vinylimidazolium with 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide; the flame retardant precursor is reacted with 3-chloropropene to prepare a flame retardant monomer, and a quaternary ammonium salt structure is introduced onto the flame retardant monomer; the flame retardant monomer is grafted onto the surface of polyaniline-biochar to prepare a carbon-based capacitor electrode material; the DOPO group in the flame retardant monomer decomposes at high temperature to produce phosphoric acid substances, which have a strong dehydration catalytic effect, which can promote the rapid dehydration and carbonization of polyaniline on the surface of the electrode material to form a dense glassy carbon layer. This carbon layer can isolate oxygen and heat, prevent the spread of flame, and inhibit the release of combustible gases, thereby giving the carbon-based capacitor material excellent flame retardant properties.

[0043] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A carbon-based capacitor electrode material, characterized in that, The carbon-based capacitor electrode material is a pre-modified biochar prepared by ultrasonically mixing sugarcane bagasse biochar and graphene oxide. Using urea as a nitrogen source, pre-modified biochar was nitrogen-doped to obtain modified biochar; aniline, 3-aminobenzenesulfonic acid, and o-mercaptoaniline were in-situ copolymerized on the surface of the modified biochar to obtain polyaniline-biochar; N-vinylimidazolium and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide were reacted to obtain a flame retardant precursor; the flame retardant precursor was reacted with 3-chloropropene to obtain a flame retardant monomer; the flame retardant monomer was grafted onto the surface of polyaniline-biochar to obtain the final product. The graphene oxide is prepared by using a modified Hummer process to obtain flake graphite. The sugarcane bagasse biochar is obtained by calcining sugarcane bagasse powder.

2. A method for preparing a carbon-based capacitor electrode material, characterized in that, The preparation method of the carbon-based capacitor electrode material includes the following preparation steps: (1) Mix flake graphite and potassium nitrate at a mass ratio of 1:(1.1~1.3) until homogeneous. Add concentrated sulfuric acid at a mass ratio of 44~48 times that of the flake graphite. Stir at room temperature for 10~20 min. Add potassium permanganate at a mass ratio of 5~7 times that of the flake graphite. Stir and react at 0~4℃ for 1.5~2.5 h. Raise the temperature to 40~50℃ and stir and react for 5~7 h. Add deionized water at a volume ratio of 18~22 times that of the concentrated sulfuric acid. Add 30 vol% hydrogen peroxide aqueous solution at a mass ratio of 0.3~0.5 times that of the potassium permanganate. Let stand for 10~12 h. Filter and wash with deionized water 3~5 times. Freeze-dry at -50~-40℃ for 44~48 h. Place in a muffle furnace and heat at a rate of 4~6℃ / min under a nitrogen atmosphere. Insulation The material was cooled to room temperature, removed, and ground to obtain graphene oxide. (2) Mix the pre-modified biochar, urea, and sodium bicarbonate evenly, place them in a muffle furnace, and heat them at a rate of 4~6℃ / min under a nitrogen atmosphere. Insulation The material was cooled to room temperature, removed, and ground to obtain modified biochar. (3) Mix solution A and solution B evenly, cool to 0~4℃, stir for 20~30min, add solution C at a constant rate within 50~70min, continue stirring and react for 4~6h, filter under vacuum, wash 2~4 times with deionized water and anhydrous ethanol respectively, and dry under vacuum at 45~55℃ for 12~14h to obtain polyaniline-biochar; (4) Polyaniline-biochar, flame retardant monomer, anhydrous ethanol, and 2-hydroxy-2-methyl-1-phenyl-1-propanone are mixed evenly in a mass ratio of 1:(0.01~0.02):(6~8):(0.001~0.003). Under nitrogen protection, the mixture is stirred at room temperature for 30~40 min, irradiated under 365 nm ultraviolet light for 5~7 h, allowed to stand for 2~3 h, filtered, washed 2~4 times with anhydrous ethanol, and vacuum dried at 55~65℃ for 2~4 h to obtain carbon-based capacitor electrode material.

3. The method for preparing the carbon-based capacitor electrode material according to claim 2, characterized in that, The flake graphite in step (1) is of type KS6, with a particle size of 800 mesh and a purity of 8099.

4. The method for preparing the carbon-based capacitor electrode material according to claim 2, characterized in that, The ratio of the pre-modified biochar, urea and sodium bicarbonate in step (2) is: 1:(2.5~3.5):(0.4~0.6) by mass and mixed evenly.

5. The method for preparing the carbon-based capacitor electrode material according to claim 2, characterized in that, The preparation process of the pre-modified biochar in step (2) is as follows: sugarcane bagasse biochar, graphene oxide and deionized water are mixed evenly at a mass ratio of 1:(0.004~0.006):(2.7~2.9), ultrasonically dispersed at room temperature for 1.5~2.5h, and freeze-dried at -50~-40℃ for 44~48h to obtain pre-modified biochar.

6. The method for preparing the carbon-based capacitor electrode material according to claim 5, characterized in that, The preparation process of the sugarcane bagasse biochar is as follows: sugarcane bagasse powder is placed in a muffle furnace and heated at a rate of 4~6℃ / min under a nitrogen atmosphere. Insulation Remove from heat after cooling to room temperature, grind, and strain. The sample was sieved through a fine mesh and washed 3-5 times with deionized water. Sugarcane bagasse biochar was obtained by drying for 12-14 hours.

7. The method for preparing the carbon-based capacitor electrode material according to claim 2, characterized in that, The preparation process of solutions A, B, and C in step (3) is as follows: aniline, 3-aminobenzenesulfonic acid, and ammonium persulfate are weighed in a mass ratio of 1:(0.2~0.4):(1.1~1.3); aniline, o-mercaptoaniline, and 1 mol / L hydrogen chloride aqueous solution are mixed evenly in a mass ratio of 1:(0.1~0.3):(8~10) and stirred at room temperature for 10~20 min to obtain solution A; 3-aminobenzenesulfonic acid, octylphenol polyoxyethylene ether, and 1 mol / L hydrogen chloride aqueous solution are mixed evenly in a mass ratio of 1:(0.5~1.5):(10~12) and stirred at room temperature for 10~20 min to obtain solution B; ammonium persulfate, modified biochar, and 1 mol / L hydrogen chloride aqueous solution are mixed evenly in a mass ratio of 1:(0.3~0.5):(6~8) and ultrasonically dispersed at room temperature for 10~20 min to obtain solution C.

8. The method for preparing the carbon-based capacitor electrode material according to claim 2, characterized in that, The preparation process of the flame retardant monomer in step (4) is as follows: the flame retardant precursor and 3-chloropropene in a molar ratio of 1:(1.1~1.3) are dissolved in toluene at a mass of 8~10 times that of the flame retardant precursor. Under nitrogen protection, the temperature is raised to 75~85℃, and the mixture is stirred for 11~13h. After cooling to room temperature, the mixture is filtered, washed 2~4 times with anhydrous ethanol, and dried under vacuum at 55~65℃ for 10~14h to obtain the flame retardant monomer.

9. The method for preparing the carbon-based capacitor electrode material according to claim 8, characterized in that, The preparation process of the flame retardant precursor is as follows: Equimolar amounts of N-vinylimidazolium and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide are dissolved in toluene at 8-10 times the mass of N-vinylimidazolium. The mixture is heated to 65-75°C and stirred for 5-15 minutes. Then, 0.003-0.005 times the mass of N-vinylimidazolium azobisisobutyronitrile is added, and the mixture is stirred and reacted for 7-9 hours. The mixture is then cooled to room temperature, and toluene is removed by rotary evaporation under reduced pressure to obtain the flame retardant precursor.

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