A method for producing supercapacitor activated carbon and product

Abstract

This invention relates to the field of carbon material manufacturing technology, specifically a method for producing activated carbon for supercapacitors. The method involves five steps: raw material pretreatment and deashing, preparation and ultrasonic impregnation of a composite activator, flash Joule heating pre-carbonization, gradient pressure-temperature synergistic activation, and rapid quenching and deep purification. It employs a KHCO3 / H3BO3 composite low-corrosion activation system, adding urea to achieve in-situ nitrogen-boron co-doping. Through rapid flash Joule heating pre-carbonization and gradient pressure-temperature synergistic activation, a hierarchical interconnected pore structure is constructed. This method offers advantages such as being green, efficient, low-cost, and scalable, making it suitable for the industrial production of high-performance activated carbon for supercapacitors.

Description

Technical Field

[0001] This application relates to the field of carbon material manufacturing technology, and in particular to a method and product for producing activated carbon for supercapacitors. Background Technology

[0002] Activated carbon, as the core electrode material of supercapacitors, directly determines the energy storage performance of supercapacitors through its specific surface area, pore structure, conductivity, and cycle stability. Currently, existing production processes for activated carbon in supercapacitors generally suffer from numerous technical challenges, making it difficult to meet the demands for high-performance, green, and large-scale production.

[0003] In conventional production processes, KOH activation is the most widely used method. However, this method has problems such as a high alkali-to-carbon ratio (usually 1:1 to 3:1), highly corrosive activator, large amounts of alkaline wastewater generated during the reaction, and severe equipment wear and tear. Physical activation methods (such as steam and CO2 activation) are environmentally friendly, but they have drawbacks such as low activation efficiency, insufficient product specific surface area (usually below 2000 m² / g), low mesoporous content, and high ion transport resistance. Existing composite activation processes mostly adopt a step-by-step "physical + chemical" activation approach, which is lengthy and difficult to control reaction conditions, resulting in poor batch stability and low yield (usually below 50%). Moreover, most processes do not achieve activator recovery, increasing production costs and environmental burden.

[0004] In addition, the activated carbon for supercapacitors prepared by existing processes is mostly a single-pore structure (mainly micropores) and lacks continuous hierarchical channels, resulting in slow electrolyte ion diffusion rate and poor rate performance. At the same time, most processes do not carry out effective doping modification, and the conductivity and pseudocapacitance of activated carbon are only slightly improved, making it difficult to meet the requirements of high-end energy storage scenarios in terms of cycle stability.

[0005] To address the shortcomings of the existing technologies, this invention provides a green, efficient, precisely controlled pore structure, highly conductive, high specific capacitance, and scalable supercapacitor activated carbon production process, solving many pain points of existing processes and filling a gap in the existing technology. Summary of the Invention

[0006] To address the problems mentioned in the background art, the purpose of this application is to provide a method for producing activated carbon for supercapacitors, comprising the following steps.

[0007] S1. After crushing and screening the biomass raw material to a set particle size, deashing treatment is carried out to obtain preliminary deashed raw material. The deashed raw material is washed until neutral and then dried to obtain deashed raw material.

[0008] S2. Prepare a composite activator solution using KHCO3 and H3BO3, add a nitrogen source to the composite activator solution and stir until homogeneous, then add the deashed raw material to the composite activator solution and place it in an ultrasonic device for ultrasonic impregnation. After impregnation, place it in a drying oven for drying to obtain the pretreated material.

[0009] S3. Place the pretreated material into a flash Joule heating furnace, heat it rapidly to the set peak temperature in a non-oxidizing gas environment using pulse current heating at a set heating rate, maintain the set peak temperature for a set holding time, then stop heating and cool it to room temperature to obtain the pre-carbonized material.

[0010] S4. Transfer the pre-carbonized material into a gradient activation furnace, and introduce CO2-containing gas into the gradient activation furnace for gradient pressure-temperature synergistic activation. The gradient pressure-temperature synergistic activation includes three stages performed sequentially, each stage including the corresponding activation temperature, activation pressure, and activation holding time. After the gradient pressure-temperature synergistic activation is completed, the activated material is obtained.

[0011] S5. Transfer the activated material to a quenching device, introduce inert gas to quench it to the set quenching temperature to obtain quenched material, transfer the quenched material to an acid washing tank for acid washing and water washing in sequence to obtain washed material, transfer the washed material to a drying oven for drying to obtain supercapacitor activated carbon.

[0012] Preferably, in step S1, the biomass raw material is coconut shell, camellia shell, or starch-based biomass. The particle size is set to 100–200 mesh; The deashing process involves transferring biomass raw materials with a set particle size into a reactor, adding a mixed deashing solution of 1.5 mol / L HCl and 10% HF to the reactor with a solid-liquid ratio of 1:3, and stirring at a constant temperature of 85℃ for 4 hours. Wash repeatedly with deionized water until neutral; Drying involves placing the washed raw materials into a forced-air drying oven and drying them at 105℃ for 8 hours.

[0013] Preferably, in step S2, the mass ratio of KHCO3 to H3BO3 in the composite activator solution is 2–4:1; The nitrogen source is urea, and the amount of urea added is 5–12 wt% of the biomass raw material. Ultrasonic impregnation is performed in an ultrasonic device with an ultrasonic power of 400 W, an ultrasonic frequency of 30 kHz, an impregnation time of 30–60 min, and a solid-liquid ratio of 1:2.5. Drying was performed under vacuum conditions of 80℃ and -0.08 MPa for 6 h.

[0014] Preferably, in step S3, the non-oxidizing gas environment is achieved by introducing nitrogen gas into the flash Joule reactor; Set the heating rate to ≥1000 K / s, the peak temperature to 550–650℃, and the holding time to 10–30 s. Preferably, in step S4, the gas containing CO2 is a mixture of N2 and CO2 with a volume ratio of 9:1. The three phases include Phase 1, Phase 2, and Phase 3; The activation temperature for stage 1 is 750℃, the activation pressure is 0.3 MPa, and the activation holding time is 60 s. The activation temperature for stage 2 is 850℃, the activation pressure is 0.15 MPa, and the activation holding time is 90 s. Stage 3 corresponds to an activation temperature of 900℃, an activation pressure of atmospheric pressure, and an activation holding time of 30s.

[0015] Preferably, in step S5, the inert gas is argon, and the quenching temperature is ≤200℃; Pickling was performed using 0.5 mol / L dilute hydrochloric acid, stirred at 60℃ for 2 h. The water washing process involves repeatedly washing with deionized water until the conductivity is ≤5 μs / cm. Drying was performed under vacuum at 120℃ and a vacuum of -0.09 MPa for 6 h.

[0016] Preferably, the method further includes step S6, in which the washing liquid generated during the acid washing and water washing process in step S5 is collected, filtered through a nanofiltration membrane to remove solid impurities in the solution, and concentrated to obtain a concentrated solution rich in KHCO3. The concentrated solution is then transferred to an evaporator crystallizer to evaporate the water at 100°C, cooled and crystallized to obtain KHCO3 crystals. After drying, the KHCO3 crystals are used to prepare the composite activator solution in step S2.

[0017] A supercapacitor activated carbon, prepared by the above method, has a specific surface area of ​​2950-3200 m² / g, a total pore volume of 1.7–2.1 cm³ / g, a mesoporosity of 30-45%, a specific capacitance of 420-490 F / g (1 A / g), a retention rate of 96-98.5% after 5000 cycles, a product yield of 60-72%, a nitrogen doping content of 2.5-4.2 wt%, and a boron doping content of 0.8-1.5 wt%.

[0018] In summary, this application includes the following beneficial technical effects: 1. Employing ultrasonic-coupled flash Joule heating rapid activation technology, high-temperature pre-carbonization can be completed in just 20–60 seconds, breaking the limitation of traditional processes that require "long-term high-temperature heating", significantly shortening the reaction time and reducing energy consumption; 2. A pioneering KHCO3 / H3BO3 composite low-corrosion activation system replaces the traditional high-corrosion KOH activator, reducing corrosion intensity by more than 80%. At the same time, H3BO3 has both doping and pore-forming auxiliary functions, achieving "activation + doping" in one step. 3. By introducing urea as a nitrogen source and combining it with boron in the composite activator, in-situ nitrogen-boron co-doping is achieved, solving the problem of "step-by-step and uneven doping" in traditional doping processes, and simultaneously improving conductivity and pseudocapacitance. 4. Design a gradient pressure-temperature synergistic activation process. Through three-stage pressure-temperature precise control, controllable construction of hierarchical channels can be achieved. The ratio of micropores to mesopores can be adjusted according to needs to adapt to different energy storage scenarios. 5. Construct a closed-loop activator recovery system. Through nanofiltration, evaporation, and crystallization processes, the KHCO3 activator recovery rate is ≥92%, which can be directly reused, significantly reducing production costs and achieving green circular production.

[0019] Other advantages, objectives and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination or study, or may be learned from the practice of the invention. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the production method of the present invention. Detailed Implementation

[0021] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] The following is in conjunction with the appendix Figure 1 This application will be further described in detail below. The present invention provides a method for producing activated carbon for supercapacitors, comprising the following steps.

[0023] S1. After crushing and screening the biomass raw material to a set particle size, deashing treatment is carried out to obtain preliminary deashed raw material. The deashed raw material is washed until neutral and then dried to obtain deashed raw material. The biomass raw materials can be coconut shells, camellia shells, or starch-based biomass, which can be flexibly selected according to the availability of the raw materials. Starch-based biomass can increase the specific volume of the product, while coconut shell-based raw materials can improve electrical conductivity. The particle size is set at 100–200 mesh. The biomass raw materials are crushed in a crusher and then sieved to the set particle size through a vibrating screen to ensure uniform particle size and increase the contact area with the activator.

[0024] The deashing process involves placing biomass raw materials of a set particle size into a reactor, adding a mixed deashing solution of 1.5 mol / L HCl and 10% HF to the reactor with a solid-liquid ratio of 1:3, and stirring at a constant temperature of 85℃ for 4 hours to remove ash (mainly impurities such as Ca, Mg, and Si) from the biomass raw materials of the set particle size, thus obtaining preliminarily deashed raw materials.

[0025] The washing process involves repeatedly washing the preliminarily deashed raw materials with deionized water until the washing liquid reaches neutrality, i.e., pH = 7. Drying involves placing the washed raw materials into a forced-air drying oven and drying them at 105℃ for 8 hours to remove free moisture, yielding deashed raw materials. The ash content of the deashed raw materials is ≤0.5% to ensure the uniformity of subsequent activation reactions and the stability of product performance.

[0026] S2. Prepare a composite activator solution with KHCO3 and H3BO3, add a nitrogen source to the composite activator solution and stir evenly, then add the deashed raw material to the composite activator solution and place it in an ultrasonic device for ultrasonic impregnation. After impregnation, place it in a drying oven for drying to obtain the pretreated material. In this composite activator solution, the mass ratio of KHCO3 to H3BO3 is 2–4:1. Deionized water is then added and stirred until completely dissolved to prepare the composite activator solution.

[0027] The nitrogen source is urea, and the amount of urea added is 5–12 wt% of the biomass raw material. Stir evenly to ensure uniform dispersion of the nitrogen source.

[0028] Ultrasonic impregnation is performed in an ultrasonic device with an ultrasonic power of 400 W, an ultrasonic frequency of 30 kHz, and an impregnation time of 30–60 min. The solid-liquid ratio of the initial deashed raw material to the composite activator solution is 1:2.5, which allows the activator and nitrogen source to fully penetrate into the raw material.

[0029] Drying was performed in a drying oven at a temperature of 80℃ and a vacuum degree of -0.08 MPa for 6 hours to remove free water from the material and obtain pretreated material.

[0030] S3. Place the pretreated material into a flash Joule heating furnace, heat it rapidly to the set peak temperature in a non-oxidizing gas environment using pulse current heating at a set heating rate, hold the set peak temperature for a set holding time, then stop heating and cool it to room temperature to obtain the pre-carbonized material. The non-oxidizing gas environment is achieved by introducing nitrogen into the flash Joule reactor to purge air from the furnace and prevent material oxidation. The nitrogen purity is ≥99.99%, and the nitrogen flow rate is controlled at 50 mL / min.

[0031] Set the heating rate to ≥1000 K / s, the peak temperature to 550–650℃, and the holding time to 10–30 s. After the holding time is reached, pre-carbonization is complete. Heating is then stopped, and the material is rapidly cooled to room temperature under nitrogen atmosphere to obtain pre-carbonized material. Flash Joule heating is fast, quickly removing volatile components from the material and forming a preliminary porous structure, while avoiding material agglomeration and performance degradation caused by prolonged heating.

[0032] S4. Transfer the pre-carbonized material into a gradient activation furnace, and introduce CO2-containing gas into the gradient activation furnace for gradient pressure-temperature co-activation. The gradient pressure-temperature co-activation includes three stages performed sequentially. The three stages include the corresponding activation temperature, activation pressure, and activation holding time, respectively. After the gradient pressure-temperature co-activation is completed, the activated material is obtained. The gas containing CO2 is a mixture of N2 and CO2 with a volume ratio of 9:1. The flow rate of the mixed gas is controlled at 80 mL / min to maintain a stable atmosphere inside the activation furnace.

[0033] The three phases are Phase 1, Phase 2, and Phase 3.

[0034] The activation temperature of stage 1 is 750℃, the activation pressure is 0.3 MPa, and the activation holding time is 60 s, which mainly forms a microporous structure. The activation temperature for stage 2 is 850℃, the activation pressure is 0.15 MPa, and the activation holding time is 90 s, which mainly expands the mesoporous structure. Stage 3 corresponds to an activation temperature of 900℃, an activation pressure of atmospheric pressure, and an activation holding time of 30s, thereby improving the connectivity of the hierarchical channels.

[0035] The total activation time is 3 min, which is 20–80 times higher than the traditional process (60–240 min). Under the synergistic effect of gradient pressure and temperature, KHCO3 decomposes to produce CO2 and K2CO3, and H3BO3 decomposes to produce B2O3. The two work together to create pores, while the boron element and the nitrogen element produced by the decomposition of urea are in situ doped into the activated carbon framework.

[0036] S5. Transfer the activated material to the quenching device, introduce inert gas to quench to the set quenching temperature to obtain quenched material, transfer the quenched material to the pickling tank for pickling and water washing in sequence to obtain washed material, transfer the washed material to the drying oven for drying, and obtain supercapacitor activated carbon after drying.

[0037] The inert gas is argon with a purity of ≥99.99%. The quenching temperature is ≤200℃ to prevent the pore structure from collapsing and to fix the nitrogen-boron doping sites.

[0038] Pickling was performed using 0.5 mol / L dilute hydrochloric acid, stirred at 60°C for 2 h, to remove residual activators and impurities from the material.

[0039] The water washing process involves repeatedly washing with deionized water until the conductivity is ≤5 μs / cm, to ensure that impurities are completely removed.

[0040] Drying was performed under vacuum at 120℃ and a vacuum of -0.09 MPa for 6 h.

[0041] Furthermore, to facilitate material reuse, step S6 is included. Step S6 involves collecting the washing liquid generated during the acid washing and water washing processes in step S5 and transferring it to a solution processing tank. The washing liquid is then filtered through a nanofiltration membrane to remove solid impurities and concentrated to obtain a KHCO3-rich concentrate. This concentrate is then transferred to an evaporator crystallizer, where water is evaporated at 100°C, followed by cooling and crystallization to obtain KHCO3 crystals. After drying, the KHCO3 crystals are directly used in step S2 to prepare the composite activator solution, achieving a closed-loop activator cycle with a KHCO3 recovery rate ≥92%.

[0042] The supercapacitor activated carbon prepared by the process of this invention, as characterized by a third-party testing institution, exhibits significantly superior performance compared to products prepared by traditional processes. Specific comparisons and parameters are as follows:

[0043]

[0044] Example 1 (Coconut shell base, optimal example) S1. Raw material pretreatment and deashing: Coconut shells were selected as raw materials, crushed and sieved to 150 mesh, and a deashing solution of 1.5 mol / L HCl and 10% HF was added. The mixture was stirred at 85℃ for 4 h, washed with water until neutral, and dried at 105℃. The ash content after deashing was 0.45%. S2. Preparation of composite activator and ultrasonic impregnation: Weigh KHCO3 and H3BO3 at a mass ratio of 3:1, dissolve them in deionized water, add urea (8 wt% of the coconut shell raw material), solid-liquid ratio of 1:2.5, ultrasonically impregnate at 400 W and 30 kHz for 45 min, and vacuum dry at 80℃ for 6 h. S3. Flash Joule heating pre-carbonization: Nitrogen atmosphere (50 mL / min), pulsed current heating, heating rate 1200 K / s, peak temperature 600℃, hold for 20 s, and then rapidly cool to room temperature; S4. Gradient pressure-temperature synergistic activation: N2+CO2 mixed gas (volume ratio 9:1, 80 mL / min), stage 1: 750℃, 0.3 MPa, 60 s; stage 2: 850℃, 0.15 MPa, 90 s; stage 3: 900℃, atmospheric pressure, 30 s, total activation time 3 min; S5. Rapid quenching and deep purification: Argon quenching to 180℃, stirring with 0.5 mol / L dilute hydrochloric acid at 60℃ for 2 h, washing with water until conductivity is 4.2 μs / cm, and vacuum drying at 120℃ for 6 h; S6. Activator recovery: Collect the washing liquid, concentrate it by nanofiltration, evaporate and crystallize it, with a KHCO3 recovery rate of 93.5%, and reuse it directly; Product performance: Specific surface area 3120 m² / g, total pore volume 1.95 cm³ / g, mesoporosity 42%, specific capacitance 468 F / g (1A / g), retention rate after 5000 cycles 97.6%, product yield 70%, nitrogen doping 3.8 wt%, boron doping 1.2 wt%.

[0045] Example 2 (Starch-based) S1. Raw material pretreatment and deashing: Starch was selected as the raw material, cross-linked and pre-carbonized, then crushed to 120 mesh, and a deashing solution of 1.5 mol / L HCl and 10% HF was added. The mixture was stirred at 85℃ for 4 h, washed with water until neutral, and dried at 105℃. The ash content after deashing was 0.38%. S2. Preparation of composite activator and ultrasonic impregnation: Weigh KHCO3 and H3BO3 at a mass ratio of 4:1, dissolve them in deionized water, add urea (10 wt% of starch raw material mass), solid-liquid ratio of 1:2.5, ultrasonically impregnate at 400 W and 30 kHz for 60 min, and vacuum dry at 80℃ for 6 h. S3. Flash Joule heating pre-carbonization: Nitrogen atmosphere (50 mL / min), pulsed current heating, heating rate 1000 K / s, peak temperature 650℃, hold for 30 s, and then rapidly cool to room temperature; S4. Gradient pressure-temperature synergistic activation: N2+CO2 mixed gas (volume ratio 9:1, 80 mL / min), stage 1: 750℃, 0.3 MPa, 60 s; stage 2: 870℃, 0.15 MPa, 90 s; stage 3: 900℃, atmospheric pressure, 30 s, total activation time 3 min; S5. Rapid quenching and deep purification: Argon quenching to 190℃, stirring with 0.5 mol / L dilute hydrochloric acid at 60℃ for 2 h, washing with water until conductivity is 4.8 μs / cm, and vacuum drying at 120℃ for 6 h; S6 activator recovery: KHCO3 recovery rate 92.3%, directly reused; Product performance: Specific surface area 2980 m² / g, total pore volume 1.82 cm³ / g, mesoporosity 38%, specific capacitance 442 F / g (1A / g), retention rate after 5000 cycles 96.8%, product yield 68%, nitrogen doping 4.2 wt%, boron doping 1.5 wt%.

[0046] Example 3 (Camellia oleifera shell base) S1. Raw material pretreatment and deashing: Camellia oleifera shells were selected as raw material, crushed and sieved to 200 mesh, and a mixed deashing solution of 1.5 mol / L HCl and 10% HF was added. The mixture was stirred at 85℃ for 4 h, washed with water until neutral, and dried at 105℃. The ash content after deashing was 0.42%. S2. Preparation of composite activator and ultrasonic impregnation: Weigh KHCO3 and H3BO3 at a mass ratio of 2:1, dissolve them in deionized water, add urea (6 wt% of the weight of camellia shell raw material), solid-liquid ratio of 1:2.5, ultrasonically impregnate at 400 W and 30 kHz for 30 min, and vacuum dry at 80℃ for 6 h. S3. Flash Joule heating pre-carbonization: Nitrogen atmosphere (50 mL / min), pulsed current heating, heating rate 1100 K / s, peak temperature 550℃, hold for 15 s, and then rapidly cool to room temperature; S4. Gradient pressure-temperature synergistic activation: N2+CO2 mixed gas (volume ratio 9:1, 80 mL / min), stage 1: 750℃, 0.3 MPa, 60 s; stage 2: 830℃, 0.15 MPa, 90 s; stage 3: 900℃, atmospheric pressure, 30 s, total activation time 3 min; S5. Rapid quenching and deep purification: Argon quenching to 170℃, stirring with 0.5 mol / L dilute hydrochloric acid at 60℃ for 2 h, washing with water until conductivity is 4.5 μs / cm, and vacuum drying at 120℃ for 6 h; S6. Activator recovery: KHCO3 recovery rate 92.8%, directly reused; Product performance: Specific surface area 3050 m² / g, total pore volume 1.88 cm³ / g, mesoporosity 40%, specific capacitance 455 F / g (1A / g), retention rate after 5000 cycles 97.2%, product yield 72%, nitrogen doping 3.2 wt%, boron doping 1.0 wt%.

[0047] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and not restrictive. It is understood that those skilled in the art can make equivalent substitutions or changes based on the technical solution and concept of this application, and all such substitutions or changes should fall within the protection scope of the appended claims.

Claims

1. A method for producing supercapacitor activated carbon, characterized by, Includes the following steps: S1. After crushing and screening the biomass raw material to a set particle size, deashing treatment is carried out to obtain preliminary deashed raw material. The deashed raw material is washed until neutral and then dried to obtain deashed raw material. S2. Prepare a composite activator solution with KHCO3 and H3BO3, add a nitrogen source to the composite activator solution and stir evenly, then add the deashing raw material to the composite activator solution and place it in an ultrasonic device for ultrasonic impregnation. After impregnation, place it in a drying oven for drying to obtain pretreated material. S3. The pretreated material is placed in a flash Joule heating furnace and heated rapidly to a set peak temperature in a non-oxidizing gas environment using pulse current heating at a set heating rate. After holding at the set peak temperature for a set holding time, the heating is stopped, and then the material is cooled to room temperature to obtain the pre-carbonized material. S4. The pre-carbonized material is transferred into a gradient activation furnace, and a gas containing CO2 is introduced into the gradient activation furnace for gradient pressure-temperature co-activation. The gradient pressure-temperature co-activation includes three stages performed sequentially. The three stages include corresponding activation temperature, activation pressure and activation holding time, respectively. After the gradient pressure-temperature co-activation is completed, the activated material is obtained. S5. The activated material is transferred to a quenching device, and inert gas is introduced to quench it to a set quenching temperature to obtain quenched material. The quenched material is then transferred to an acid washing tank for acid washing and water washing to obtain washed material. The washed material is then transferred to a drying oven for drying to obtain supercapacitor activated carbon.

2. The method for producing supercapacitor activated carbon according to claim 1, characterized in that, In step S1, the biomass raw material is coconut shell, camellia shell, or starch-based biomass; The set particle size is 100–200 mesh; The deashing process involves transferring the biomass raw material with the set particle size into a reactor, adding a mixed deashing solution of 1.5 mol / L HCl and 10% HF to the reactor, with a solid-liquid ratio of 1:3, and stirring at a constant temperature of 85°C for 4 hours. The washing process involves repeatedly washing with deionized water until the solution is neutral. The drying process involves placing the washed raw materials into a forced-air drying oven and drying them at 105°C for 8 hours.

3. The method for producing supercapacitor activated carbon according to claim 1, characterized in that, In step S2, the mass ratio of KHCO3 to H3BO3 in the composite activator solution is 2–4:1; The nitrogen source is urea, and the amount of urea added is 5–12 wt% of the biomass raw material. The ultrasonic impregnation is performed in an ultrasonic device with the ultrasonic power set to 400 W, the ultrasonic frequency to 30 kHz, the impregnation time to 30–60 min, and the solid-liquid ratio to 1:2.

5. The drying process involved vacuum drying at 80°C and a vacuum degree of -0.08 MPa for 6 hours.

4. The method for producing supercapacitor activated carbon according to claim 1, characterized in that, In step S3, the non-oxidizing gas environment is achieved by introducing nitrogen gas into the flash Joule reactor. The set heating rate is ≥1000 K / s, the set peak temperature is 550–650℃, and the set holding time is 10–30 s.

5. The method for producing supercapacitor activated carbon according to claim 1, characterized in that, In step S4, The gas containing CO2 is a mixture of N2 and CO2 in a volume ratio of 9:

1. The three phases include Phase 1, Phase 2, and Phase 3; The activation temperature for stage 1 is 750℃, the activation pressure is 0.3 MPa, and the activation holding time is 60 s. The activation temperature for stage 2 is 850℃, the activation pressure is 0.15 MPa, and the activation holding time is 90 s. The activation temperature corresponding to stage 3 is 900℃, the activation pressure is atmospheric pressure, and the activation holding time is 30s.

6. The method for producing supercapacitor activated carbon according to claim 1, characterized in that, In step S5, the inert gas is argon, and the quenching temperature is ≤200℃; The pickling was performed using 0.5 mol / L dilute hydrochloric acid, stirred at 60°C for 2 h. The water washing involves repeatedly washing with deionized water until the conductivity is ≤5 μs / cm; The drying process involved vacuum drying at 120°C and a vacuum degree of -0.09 MPa for 6 hours.

7. The method for producing supercapacitor activated carbon according to claim 1, characterized in that, The method also includes step S6, in which the washing liquid generated during the acid washing and water washing processes in step S5 is collected, filtered through a nanofiltration membrane to remove solid impurities from the solution, and concentrated to obtain a concentrated solution rich in KHCO3. The concentrated solution is then transferred to an evaporator crystallizer to evaporate water at 100°C, cooled and crystallized to obtain KHCO3 crystals. The KHCO3 crystals are then dried and used in step S2 to prepare the composite activator solution.

8. A supercapacitor activated carbon, made by the method according to any one of claims 1-7, characterized in that, The supercapacitor activated carbon has a specific surface area of ​​2950-3200 m² / g, a total pore volume of 1.7-2.1 cm³ / g, a mesoporosity of 30-45%, a specific capacitance of 420-490 F / g (1 A / g), a retention rate of 96-98.5% after 5000 cycles, a product yield of 60-72%, a nitrogen doping content of 2.5-4.2 wt%, and a boron doping content of 0.8-1.5 wt%.

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