Peanut shell-based porous graphitized carbon, preparation method and supercapacitor electrode

Abstract

The invention discloses peanut shell-based porous graphitized carbon, a preparation method and a supercapacitor electrode, and belongs to the technical field of supercapacitors, and the method comprises the steps: crushing peanut shell carbon, screening, mixing with a Na2CO3 solution, carrying out microwave-assisted immersion treatment, then carrying out centrifugal separation, washing to be neutral, and drying to obtain an activated precursor; then carrying out heat treatment in an inert atmosphere, cooling, washing and drying to obtain peanut shell carbon powder; then carrying out ball-milling mixing with an EDTA-Ni catalyst, and drying to obtain a catalytic graphitization precursor; and finally, performing catalytic graphitization treatment in an inert atmosphere, cooling, performing ultrasonic treatment with an EDTA (Ethylene Diamine Tetraacetic Acid) solution, washing, and drying to obtain the peanut shell-based porous graphitized carbon. Peanut shell-based porous graphitized carbon is used as a core active material, the raw material is green, sustainable and low in cost, the specific capacitance is 276-328F / g, the 5000-time cycle retention rate is 87.9%-92.5%, the method is adaptive to a conventional electrolyte, the process is mature, large-scale production is easy, the mass transfer efficiency is high, and an idea is provided for green and low-cost development of energy storage devices.

Description

Technical Field

[0001] This invention belongs to the field of supercapacitor technology, specifically relating to a peanut shell-based porous graphitized carbon, its preparation method, and a supercapacitor electrode. Background Technology

[0002] Supercapacitors, as novel energy storage devices, are in high demand in fields such as new energy vehicles, smart grids, and portable electronic devices due to their fast charge / discharge rates, long cycle life, and strong environmental adaptability. Their performance hinges on the electrode materials. Carbon-based materials, with their superior conductivity, controllable specific surface area, and good chemical stability, have become the mainstream choice for supercapacitor electrode materials. However, existing carbon-based electrode material preparation technologies have significant limitations: First, the choice of carbon source presents a significant challenge. High-performance carbon sources such as graphene and carbon nanotubes are expensive (tens of thousands of yuan per ton), making large-scale application difficult. Although agricultural waste (such as rice husks and peanut shells) is a low-cost green carbon source, the specific surface area of ​​the products after direct carbonization is low (usually <1200m²). 2 g -1 First, insufficient graphitization results in high electron transport resistance and a specific capacitance generally below 200 F / g, failing to meet high-performance requirements. Second, the applicability of activators is poor. Traditional processes often use strong alkalis such as KOH and NaOH as activators, which can increase the specific surface area, but these strong alkalis are highly corrosive, requiring high-temperature (>800℃) reactions, and post-processing requires multiple acid-base neutralizations, easily generating wastewater pollution. Furthermore, excessive etching leads to uneven pore size distribution in carbon materials, affecting electrolyte ion transport efficiency. Third, there is insufficient process synergy. Activation and graphitization are often carried out in steps: activating before graphitization easily leads to the collapse of the already formed pore structure, while graphitization before activation reduces the utilization rate of catalytic active sites. It is difficult to achieve both simultaneously, resulting in an inability to synergistically achieve high specific surface area and high graphitization degree in carbon materials. Fourth, there is an imbalance between environmental protection and economic efficiency. Some processes rely on toxic catalysts (such as transition metal chlorides) or high-temperature, high-pressure equipment, resulting in high energy consumption (over 50 kWh per batch) and significant pollution, which does not conform to the trend of green manufacturing and hinders industrialization. Therefore, developing a carbon material preparation technology that uses low-cost agricultural waste as a carbon source and green activators as regulators to synergistically achieve high specific surface area and high graphitization degree has become a key direction for solving the contradiction between performance and cost of supercapacitor electrode materials. Summary of the Invention

[0003] In order to overcome the shortcomings of the prior art, the present invention aims to provide a peanut shell-based porous graphitized carbon, its preparation method, and a supercapacitor electrode, so as to solve the technical problems of low specific surface area, insufficient graphitization, complex process and high cost, and poor electrochemical performance stability of traditional carbon-based supercapacitor electrode materials.

[0004] To achieve the above objectives, the present invention employs the following technical solution: This invention discloses a method for preparing peanut shell-based porous graphitized carbon, comprising the following steps: 1) After crushing and sieving the peanut shell charcoal, mix it with Na2CO3 solution and perform microwave-assisted impregnation treatment. Then, centrifuge, wash until neutral, and dry to obtain the activated precursor. 2) The activated precursor obtained in step 1) is heat-treated under an inert atmosphere, cooled, washed and dried to obtain peanut shell char powder. 3) The peanut shell carbon powder obtained in step 2) is ball-milled and mixed with EDTA-Ni catalyst, and then dried to obtain the catalytic graphitization precursor. 4) The catalytic graphitization precursor obtained in step 3) is subjected to catalytic graphitization treatment under an inert atmosphere, cooled and then ultrasonically treated with EDTA solution, washed and dried to obtain peanut shell-based porous graphitized carbon.

[0005] Preferably, in step 1), the mass concentration of the Na2CO3 solution is 8%-12%; the power of the microwave-assisted impregnation is 500-600W, the temperature is 90-95℃, and the time is 2.5-3.0h.

[0006] Preferably, in step 2), the heating rate of the heat treatment is 5-8℃ / min, the target temperature is 680-720℃, and the holding time is 1.5-2.5h.

[0007] Preferably, in step 3), 3-5 mmol of EDTA-Ni catalyst is added to every 1g of peanut shell char powder; the ball milling speed is 350-450 rpm and the time is 2.0-3.0h.

[0008] Preferably, in step 4), the conditions for catalytic graphitization treatment include: heating to 600-700℃ at 10-15℃ / min and holding for 1.0-2.0h, then heating to 900-1000℃ at 3-5℃ / min and holding for 1.0-2.0h; the concentration of the EDTA solution is 1.2-1.5M.

[0009] This invention also discloses a peanut shell-based porous graphitized carbon, prepared using the above-described method for preparing peanut shell-based porous graphitized carbon; the specific surface area of ​​the peanut shell-based porous graphitized carbon is 1652-1856 m². 2 ·g -1 The average pore size is 2.6-3.1 nm.

[0010] The present invention also discloses a method for preparing a supercapacitor electrode, wherein the peanut shell-based porous graphitized carbon prepared by the above-mentioned method is used as the active material; the peanut shell-based porous graphitized carbon, conductive agent and binder are mixed and coated on the current collector to obtain a supercapacitor electrode sheet.

[0011] Preferably, the mass ratio of peanut shell-based porous graphitized carbon, conductive agent, and binder is (7-8):(1-1.5):(1-1.5); the conductive agent is acetylene black, the binder is polytetrafluoroethylene, and the current collector is nickel foam.

[0012] The present invention also discloses a supercapacitor electrode, which is prepared by the above-mentioned supercapacitor electrode preparation method. The specific capacitance of the supercapacitor electrode at a current density of 0.5 A / g is 276-328 F / g; and the capacity retention rate after 5000 charge-discharge cycles is 87.9%-92.5%.

[0013] The present invention also discloses a supercapacitor comprising the supercapacitor electrodes described above.

[0014] Compared with the prior art, the present invention has the following beneficial effects: This invention discloses a method for preparing peanut shell-based porous graphitized carbon. The preparation process first involves microwave-assisted impregnation to uniformly penetrate Na2CO3 into the pores of the peanut shell carbon. During subsequent heat treatment, Na2CO3 decomposes to generate alkaline activated species, gently etching the carbon framework to form a porous structure. Simultaneously, an EDTA-Ni catalyst is ball-milled and uniformly loaded onto the carbon surface. At high temperature, Ni particles are released as graphitization active centers, promoting the orderly arrangement of carbon atoms to form a conductive network. The catalytic graphitization treatment employs a segmented heating strategy, first stabilizing the pore structure at a lower temperature, then completing the graphitization transformation at a higher temperature to prevent pore collapse. Finally, residual catalyst is removed by ultrasonic treatment with EDTA solution, preserving the complete porous graphitized structure. This invention achieves process synergy through microwave pretreatment and segmented heat treatment, simultaneously constructing a graphitized network during pore formation. Furthermore, traditional catalysts are difficult to recover, causing pollution. Using an EDTA-complexed nickel catalyst allows for efficient recovery through ultrasonic treatment, reducing environmental burden. This method effectively improves the specific surface area and conductivity of peanut shell carbon, forming a porous graphitized structure with uniform pore size distribution, thereby enhancing electrolyte ion transport efficiency and electronic conductivity. It avoids the use of highly corrosive reagents, simplifies the process, and provides a feasible route for the low-cost preparation of high-performance supercapacitor electrode materials.

[0015] This invention discloses a peanut shell-based porous graphitized carbon. After microwave-assisted impregnation, the active substances generated from the decomposition of sodium carbonate gently etch the carbon framework, forming an initial porous structure. In the subsequent catalytic graphitization process, a nickel catalyst promotes the orderly stacking of carbon layers, while high-temperature treatment further expands the pores and adjusts the pore size distribution. The sequential combination of these two processes avoids the problems of pore structure collapse or catalyst deactivation in traditional stepwise methods. In the final product, the high specific surface area provides abundant charge storage sites, and the predominantly mesoporous pore size distribution optimizes the diffusion path of electrolyte ions. This invention, through the synergistic process of microwave-assisted activation and catalytic graphitization, achieves a concentrated pore size distribution within the 2.6-3.1 nm range while avoiding highly corrosive reagents. This size range can accommodate rapid migration of electrolyte ions while preventing a decrease in the utilization rate of active sites caused by large pores. It solves the problem of balancing specific surface area and conductivity in traditional biomass carbon materials. The prepared material maintains high porosity while possessing good electronic conductivity, making it suitable for energy storage devices requiring rapid charge and discharge. The material's hierarchical porous structure can effectively mitigate volume changes during charge and discharge processes, thereby improving electrode cycle stability.

[0016] This invention discloses a method for preparing a supercapacitor electrode. Microwave-assisted impregnation allows Na2CO3 to uniformly penetrate the interior of peanut shell carbon. Subsequent heat treatment gently etches this Na2CO3 to form a hierarchical mesoporous structure. Simultaneously, an EDTA-Ni catalyst releases active nickel species at high temperatures, promoting carbon atom rearrangement to form a graphitized structure. The porous structure increases the contact area between the electrode and the electrolyte, enhancing the double-layer capacitance, while the graphitized carbon framework reduces resistance, improving charge transport efficiency. The synergistic effect of these two processes enables the electrode to rapidly store and release charge during charging and discharging. This invention uses peanut shell carbon as raw material and employs a synergistic process of microwave activation and catalytic graphitization to achieve graphitization of the carbon structure while maintaining a high specific surface area. This reduces raw material costs and avoids the use of highly corrosive activators. It solves the problems of low capacitance and short cycle life caused by insufficient specific surface area and poor conductivity in traditional carbon-based electrode materials, achieving the preparation of a low-cost, high-specific-capacitance, and cycle-stable supercapacitor electrode.

[0017] This invention discloses a supercapacitor electrode that utilizes the synergistic effect of microwave-assisted activation and catalytic graphitization of peanut shell carbon to construct a carbon framework with a high specific surface area and hierarchical mesoporous structure, while simultaneously forming a continuous graphitized conductive network. During charge and discharge, the mesoporous structure shortens the ion diffusion path, and the graphitized network accelerates electron conduction, enabling the electrode material to achieve high specific capacitance at low current densities. During cycling, the stable pore structure inhibits the pulverization and shedding of active materials, and the graphitized carbon framework resists electrolyte erosion, jointly ensuring capacity retention. This invention, through the synergistic optimization of mild activation and catalytic graphitization processes, forms a stable conductive network while maintaining a high specific surface area, overcoming the bottleneck of synergistic improvement in specific capacitance and cycle life. It effectively solves the technical challenges of rapid capacity decay and short cycle life of supercapacitor electrode materials at high current densities, achieving a balance between high energy storage density and long-cycle stability, and providing a reliable material basis for high-power energy storage devices.

[0018] The supercapacitor disclosed in this invention uses peanut shell char, an agricultural waste, as the core active material, achieving high-value utilization of waste and significantly reducing raw material costs. The peanut shell-based porous graphitized carbon has a high specific surface area and suitable pore size, resulting in electrode performance superior to traditional products and compatibility with conventional electrolytes. The entire process uses conventional equipment, with adjustable process parameters, is green and free of secondary pollution, and is easy to scale up. It also balances high power and practicality, making it widely applicable in civilian, industrial, and new energy fields, offering high cost-effectiveness and great market potential. Detailed Implementation

[0019] The technical solution of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] Unless otherwise specified, all embodiments and preferred embodiments mentioned herein can be combined to form new technical solutions.

[0021] Unless otherwise specified, all the technical features and preferred features mentioned herein can be combined to form new technical solutions.

[0022] In this invention, unless otherwise specified, percentage (%) or parts refer to weight percentage or parts relative to the composition.

[0023] Unless otherwise specified, the components or preferred components involved in this invention can be combined with each other to form new technical solutions.

[0024] In this invention, unless otherwise specified, the numerical range "a~b" represents a shortened representation of any combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "6~22" indicates that all real numbers between "6~22" have been listed in this document, and "6~22" is simply a shortened representation of these numerical combinations.

[0025] The "scope" disclosed in this invention can be in the form of a lower limit and an upper limit, and can be one or more lower limits and one or more upper limits, respectively.

[0026] In this invention, the term "and / or" as used herein refers to any combination of one or more of the associated listed items, as well as all possible combinations, and includes such combinations.

[0027] In this invention, unless otherwise stated, the various reactions or operation steps may be performed sequentially or in a particular order. Preferably, the reaction methods described herein are performed sequentially.

[0028] Unless otherwise stated, the technical and scientific terms used herein have the same meanings as those familiar to those skilled in the art. Furthermore, any methods or materials similar to or equivalent to those described herein may also be used in this invention.

[0029] The method for preparing peanut shell-based porous graphitized carbon disclosed in this invention includes: Step 1: Preparation of activated precursor Raw material pretreatment: After crushing the peanut shell charcoal, it is sieved using a 120-mesh standard sieve, and the sieve-passing material is collected (to ensure that the raw material has a uniform particle size and to provide a stable contact area for the subsequent impregnation reaction). Impregnation system preparation: Prepare a Na2CO3 solution with a mass concentration of 8%-12% (10% is preferred in the example), mix it at a solid-liquid ratio of 1g:15mL (such as 18.5g of sieved peanut shell char and 277.5mL of Na2CO3 solution in the example), and transfer the mixture into a 500mL microwave reactor. Microwave-assisted impregnation: Set the microwave power to 500-600W (600W is preferred in this example) and the impregnation temperature to 90-95℃ (95℃ is preferred in this example). Impregnate at a constant temperature for 2.5-3.0h (2.8h is preferred in this example). Stir at 200rpm every 30min during the impregnation process to promote the full reaction of Na2CO3 with the peanut shell carbon surface and form a preliminary porous structure. Solid-liquid separation and drying: After impregnation, the mixture was transferred to a centrifuge tube and centrifuged at 4000 rpm for 15 min to separate the solid product; the solid was repeatedly washed with deionized water until the pH of the filtrate was 7 (to remove residual Na2CO3); the washed solid was transferred to a vacuum drying oven and dried at 90℃ and -0.09MPa for 8 h to obtain the activated precursor. Step 2: Preparation of peanut shell charcoal powder Inert atmosphere preparation: Take the activated precursor (12.8g in the example) and put it into a 50mL covered corundum crucible. Place it in a tube furnace and purge it with high-purity nitrogen gas (flow rate 60mL / min) with a purity of 99.999% for 30 minutes to remove air from the furnace and prevent oxidation of the raw material during heat treatment. Heat treatment process: Set a heating program and raise the temperature from room temperature (25°C) to 680-720°C (700°C) at a rate of 5-8°C / min (7°C / min is preferred in this example). After reaching the target temperature, keep it at a constant temperature for 1.5-2.5 hours (2.0 hours is preferred in this example). The high-temperature heat treatment further constructs a porous structure and removes impurities. Post-processing and sieving: After the heat preservation is completed, nitrogen gas is introduced until the tube furnace cools naturally to room temperature, and the solid product is taken out; the solid is washed with deionized water 4 times, vacuum dried at 90℃ for 8 hours, and then sieved through a 200-mesh standard sieve to obtain peanut shell charcoal (PHC) powder. Step 3: Preparation of catalytic graphitization precursor Material mixing: Weigh 1.0g of PHC powder, add 3-5mmol (5mmol preferred in this example) of EDTA-Ni catalyst, put them together into a 50mL polytetrafluoroethylene ball mill jar, and add 6g of agate balls with a diameter of 5mm (ball-to-material mass ratio 6:1). Ball milling dispersion: Set the ball mill speed to 350-450 rpm (400 rpm is preferred in this example), and ball mill the mixture for 2.0-3.0 h (3.0 h is preferred in this example) to ensure that the EDTA-Ni catalyst is uniformly loaded on the surface of the PHC powder; Pre-activation and drying: The ball-milled mixture is transferred to a vacuum drying oven and pre-activated for 1.5 hours at a temperature of 130℃ and a vacuum of -0.09MPa to remove residual moisture from the mixture and avoid the generation of impurity gases during the subsequent graphitization process, thus obtaining a catalytic graphitization precursor. Step 4: Catalytic graphitization and product purification Two-stage catalytic graphitization: The catalytic graphitization precursor (1.02 g in the example) was placed into a 20 mL corundum crucible, placed in a tube furnace again, and high-purity nitrogen gas (flow rate 60 mL / min) was introduced. First stage: Increase the temperature to 600-700℃ (preferably 650℃ in the example) at a rate of 10-15℃ / min (13℃ / min in the example), and react at a constant temperature for 1.0-2.0h (1.5h in the example) to initially activate the catalyst activity; Second stage: Adjust the heating rate to 3-5℃ / min (4℃ / min is preferred in the example), raise it to 900-1000℃ (1000℃ is preferred in the example), and keep it at a constant temperature for 1.0-2.0h (1.5h is preferred in the example). Promote the graphitization of carbon materials through the action of catalysts, while retaining the porous structure. Catalyst removal: After cooling to room temperature, the product was removed and mixed with a 1.2-1.5M (preferably 1.5M) EDTA solution at a solid-liquid ratio of 1g:147mL (e.g., 1.02g product to 150mL EDTA solution in the example). The mixture was then transferred to an ultrasonic cleaner; the temperature was set to 50℃, the ultrasonic power to 300W, and the ultrasonic treatment lasted for 3.0h. The catalyst was removed by reacting EDTA with Ni... 2+ Complexation removes residual catalyst; Product drying: After ultrasonic treatment, the product was allowed to stand for 8 hours, filtered to separate the solid product, washed 4 times with 30% ethanol aqueous solution (to further purify the product), and dried under vacuum at 90℃ for 8 hours to obtain peanut shell-based porous graphitized carbon (denoted as PGPC). The performance indicators of peanut shell-based porous graphitized carbon disclosed in this invention Specific surface area: 1652-1856 m² 2 ·g -1 (High specific surface area provides sufficient sites for ion adsorption). Average pore size: 2.6-3.1 nm (suitable pore size facilitates rapid ion transport in electrolyte). The method for preparing a supercapacitor electrode disclosed in this invention includes the following steps: Electrode slurry preparation: Peanut shell-based porous graphitized carbon (PGPC) is used as the active material and mixed with conductive agent (acetylene black) and binder (polytetrafluoroethylene, PTFE) at a mass ratio of (7-8):(1-1.5):(1-1.5) (preferably 8:1:1 in the example), and then thoroughly ground to form an electrode slurry; Electrode forming: The electrode slurry is coated onto the current collector (nickel foam) to form an electrode sheet with an area of ​​1 cm² and a thickness of 0.1 mm, which is the supercapacitor electrode. The supercapacitor electrode performance indicators disclosed in this invention Specific capacitance: At a current density of 0.5 A / g, the specific capacitance is 276-328 F / g (demonstrating excellent charge storage capability). Cyclic stability: After 5000 charge-discharge cycles, the capacity retention rate is 87.9%-92.5% (indicating good electrode structure stability and long service life). Electrolyte compatibility: Compatible with 6M KOH alkaline electrolyte (a commonly used electrolyte system for conventional energy storage devices, with strong compatibility). Supercapacitor Assembly Disclosed in This Invention Using the supercapacitor electrode prepared in this invention as the core component, and combined with components such as 6MKOH electrolyte and polypropylene membrane, the supercapacitor is assembled according to the structure of positive electrode-membrane-negative electrode. Its energy storage performance depends on the high specific capacitance and cycle stability of the electrode, and it can be applied to portable electronic devices, auxiliary power supplies for new energy vehicles and other scenarios.

[0030] This invention utilizes peanut shell char, an agricultural waste, as a green carbon source, EDTA-Ni as a catalytic graphitizing agent, and Na2CO3 as an activator to prepare peanut shell-based porous graphitized carbon (PGPC) through a two-step core process of microwave-assisted activation and catalytic graphitization. Results show that Comparative Example 2 (peanut shell char without catalytic graphitization) has a specific surface area of ​​only 1089 m². 2 g -1 The specific capacitance is 186 F / g, while the specific surface area of ​​PGPC-1 prepared in Example 1 reaches 1856 m². 2 g -1 With a specific capacitance of 328 F / g and a capacity retention of 92.5% after 5000 cycles, its rate performance (capacity retention of 78.3% when current density increases from 0.5 A / g to 5 A / g) is significantly better than that of traditional carbon materials, providing a new green and large-scale preparation path for high-performance supercapacitor electrode materials.

[0031] Compared with the prior art, the present invention has the following advantages: Firstly, this invention achieves synergistic regulation of activation and catalytic graphitization, breaking the technical barrier of stepwise activation and graphitization in traditional carbon material preparation. In traditional processes, activation followed by graphitization easily leads to pore structure collapse, while graphitization followed by activation reduces catalytic efficiency. In this invention, Na2CO3 (activator) and EDTA-Ni (catalyst) are uniformly mixed through microwave-assisted pretreatment. In the subsequent tubular furnace heat treatment, the decomposition products of Na2CO3 first gently etch and create pores in the peanut shell carbon skeleton, while EDTA-Ni simultaneously releases Ni active sites to promote carbon structure graphitization. The timing of their actions is matched and their mechanisms are complementary, fundamentally ensuring the synergistic achievement of high specific surface area and excellent graphitization degree.

[0032] Secondly, the process mechanism is better suited to the structural and performance requirements of supercapacitor electrode materials. Traditional activators (such as KOH) have excessively strong etching activity, which can easily lead to uneven pore size distribution and partial pore blockage in carbon materials, affecting electrolyte transport. In contrast, the activating species generated by the decomposition of Na2CO3 have mild reactivity, and the etching rate is highly compatible with the carbonization rate of peanut shell carbon, which can construct a multi-level mesoporous structure of 2.6-3.1 nm, significantly improving the electrolyte ion migration efficiency. At the same time, the graphitized structure generated by EDTA-Ni catalysis can reduce electron transport resistance. Combined with the porous structure formed by activation, it achieves synergistic enhancement of double-layer capacitance and Faraday pseudocapacitance, resulting in electrochemical performance superior to traditional single-pore structures or low-graphitized carbon materials.

[0033] Thirdly, the economic and environmental benefits are significantly improved through process optimization. Existing technologies often rely on high-cost carbon sources (such as graphene and carbon nanotubes) or toxic reagents (such as strong acid and alkali post-treatment), which not only increases costs but also easily causes environmental pollution. This invention uses waste peanut shell char as a carbon source to realize the resource utilization of agricultural waste, reducing raw material costs by more than 40%. The EDTA-Ni catalyst can be gently eluted and recovered through EDTA solution, and the Na2CO3 decomposition products are easily soluble in water, eliminating the need for complex acid and alkali neutralization treatment. The process energy consumption is reduced by 25% compared to traditional high-temperature and high-pressure preparation methods. From a technical mechanism perspective, this reduces pollution emissions and energy consumption, making it more suitable for the needs of large-scale industrial production.

[0034] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. The components of the embodiments of the present invention shown herein can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0035] Example 1 A method for preparing a supercapacitor electrode includes the following steps: Step 1: The crushed peanut shell charcoal was sieved through a 120-mesh standard sieve, and the undersize material was collected. A 10% Na2CO3 solution was prepared, and 18.5g of the sieved peanut shell charcoal was mixed with 277.5mL of Na2CO3 solution and transferred to a 500mL microwave reactor. The microwave power was set to 600W and the temperature to 95℃, and the mixture was soaked at a constant temperature for 2.8h, with stirring once every 30min (200rpm). After soaking, the mixture was transferred to a centrifuge tube and centrifuged at 4000rpm for 15min to separate the solid product. The solid was washed repeatedly with deionized water until the pH of the filtrate was 7, and the washed solid was collected. The solid was transferred to a vacuum drying oven and dried for 8h at a temperature of 90℃ and a vacuum of -0.09MPa to obtain the activated precursor.

[0036] Step 2: Take 12.8g of activated precursor, put it into a 50mL covered corundum crucible, place it in a tube furnace, and purge the furnace with high-purity nitrogen (99.999% purity, flow rate 60mL / min, time 30min) to remove air from the furnace; set the heating program: raise the temperature from room temperature (25℃) to 700℃ at a rate of 7℃ / min, and hold the temperature at the target temperature for 2.0h; after the holding time is completed, keep the nitrogen gas flowing in, let it cool naturally to room temperature, and take out the solid; wash the solid 4 times with deionized water, dry it under vacuum at 90℃ for 8h, and sieve it through a 200-mesh standard sieve to obtain peanut shell charcoal (PHC) powder.

[0037] Step 3: Weigh 1.0g of PHC powder, add 5mmol of EDTA-Ni catalyst, and place them together in a 50mL polytetrafluoroethylene ball mill jar. Add 6g of agate balls (5mm in diameter, mass ratio 6:1). Set the ball mill speed to 400rpm and ball mill for 3.0h. Transfer the ball-milled mixture to a vacuum drying oven and pre-activate at 130℃ and -0.09MPa for 1.5h to remove residual moisture and obtain the catalytic graphitization precursor.

[0038] Step 4: 1.02 g of precursor was placed into a 20 mL corundum crucible and placed in a tube furnace again. High-purity nitrogen gas was introduced (flow rate 60 mL / min), and the temperature was raised to 650 °C at a rate of 13 °C / min and held for 1.5 h. The heating rate was then adjusted to 4 °C / min, and the temperature was raised to 1000 °C and held for 1.5 h. After cooling to room temperature, the product was removed and mixed with 150 mL of 1.5 M EDTA solution. The mixture was then transferred to an ultrasonic cleaner. The temperature was set to 50 °C and the ultrasonic power to 300 W, and the ultrasonic treatment was carried out for 3.0 h. After ultrasonic treatment, the mixture was allowed to stand for 8 h. The solid was separated by filtration, washed four times with 30% ethanol aqueous solution, and vacuum dried at 90 °C for 8 h to obtain peanut shell-based porous graphitized carbon, denoted as PGPC-1.

[0039] Step 5: Mix PGPC-1 with acetylene black and PTFE in a mass ratio of 8:1:1, and coat the mixture onto the nickel foam current collector (1 cm² area). 2The working electrode (with a thickness of 0.1 mm) was fabricated, and its capacitance performance was tested in 6M KOH electrolyte.

[0040] Example 2 A method for preparing a supercapacitor electrode includes the following steps: The preparation process of Example 2 is exactly the same as that of Example 1, except that the amount of EDTA-Ni catalyst in step 3 is changed to 3 mmol. The other steps and parameters are exactly the same as those of Example 1. The final product is denoted as PGPC-2.

[0041] Example 3 A method for preparing a supercapacitor electrode includes the following steps: The preparation process of Example 3 is exactly the same as that of Example 1, except that the graphitization temperature in step four is changed to 900℃ (instead of 1000℃). The other steps and parameters are exactly the same as those in Example 1. The final product is denoted as PGPC-3.

[0042] Example 4 A method for preparing a supercapacitor electrode includes the following steps: The preparation process of Example 4 is exactly the same as that of Example 1, except that the ball milling time in step 3 is changed to 2.0h (instead of 3.0h). The other steps and parameters are exactly the same as those of Example 1. The final product is denoted as PGPC-4.

[0043] Example 5 A method for preparing a supercapacitor electrode includes the following steps: The preparation process of Example 5 is exactly the same as that of Example 1, except that the microwave power in step one is changed to 500W (instead of 600W). The other steps and parameters are exactly the same as those of Example 1. The final product is denoted as PGPC-5.

[0044] Example 6 A method for preparing a supercapacitor electrode includes the following steps: The preparation process of Example 6 is exactly the same as that of Example 1, except that the concentration of EDTA solution in step four is changed to 1.2M (instead of 1.5M). The other steps and parameters are exactly the same as those in Example 1. The final product is denoted as PGPC-6.

[0045] Example 7 A method for preparing a supercapacitor electrode includes the following steps: Step 1: The crushed peanut shell charcoal was sieved through a 120-mesh standard sieve, and the undersize material was collected. An 8% Na2CO3 solution was prepared, and 18.5g of the sieved peanut shell charcoal was mixed with 277.5mL of Na2CO3 solution. The mixture was then transferred to a 500mL microwave reactor. The microwave power was set to 550W and the temperature to 90℃, and the mixture was soaked at a constant temperature for 2.5h, with stirring every 30min (200rpm). After soaking, the mixture was transferred to a centrifuge tube and centrifuged at 4000rpm for 15min to separate the solid product. The solid was washed repeatedly with deionized water until the pH of the filtrate was 7, and the washed solid was collected. The solid was then transferred to a vacuum drying oven and dried at 90℃ and -0.09MPa for 8h to obtain the activated precursor.

[0046] Step 2: Take 12.8g of activated precursor, put it into a 50mL covered corundum crucible, place it in a tube furnace, and purge the furnace with high-purity nitrogen (99.999% purity, flow rate 60mL / min, time 30min) to remove air from the furnace; set the heating program: raise the temperature from room temperature (25℃) to 680℃ at a rate of 5℃ / min, and hold the temperature for 1.5h after reaching the target temperature; after the holding time is completed, keep the nitrogen gas flowing in, let it cool naturally to room temperature, and take out the solid; wash the solid 4 times with deionized water, dry it under vacuum at 90℃ for 8h, and sieve it through a 200-mesh standard sieve to obtain peanut shell charcoal (PHC) powder.

[0047] Step 3: Weigh 3.0g of PHC powder, add 5mmol of EDTA-Ni catalyst, and place them together in a 50mL polytetrafluoroethylene ball mill jar. Add 6g of agate balls (5mm in diameter, mass ratio 6:1). Set the ball mill speed to 350rpm and ball mill for 2.5h. Transfer the ball-milled mixture to a vacuum drying oven and pre-activate at 130℃ and -0.09MPa for 1.5h to remove residual moisture and obtain the catalytic graphitization precursor.

[0048] Step 4: 1.02 g of precursor was placed into a 20 mL corundum crucible and placed in a tube furnace again. High-purity nitrogen gas was introduced (flow rate 60 mL / min), and the temperature was raised to 600 °C at a rate of 10 °C / min and held for 2 h. The heating rate was then adjusted to 3 °C / min, and the temperature was raised to 950 °C and held for 2 h. After cooling to room temperature, the product was removed and mixed with 150 mL of 1.2 M EDTA solution. The mixture was then transferred to an ultrasonic cleaner. The temperature was set to 50 °C and the ultrasonic power to 300 W, and the ultrasonic treatment was carried out for 3.0 h. After ultrasonic treatment, the mixture was allowed to stand for 8 h. The solid was separated by filtration, washed 4 times with 30% ethanol aqueous solution, and dried under vacuum at 90 °C for 8 h to obtain peanut shell-based porous graphitized carbon, denoted as PGPC-7.

[0049] Step 5: Mix PGPC-7 with acetylene black and PTFE in a mass ratio of 7.5:1.5:1.5, and coat the mixture onto the nickel foam current collector (1 cm² area). 2The working electrode (with a thickness of 0.1 mm) was fabricated and its capacitance performance was tested in 6 MKOH electrolyte.

[0050] Example 8 A method for preparing a supercapacitor electrode includes the following steps: Step 1: The crushed peanut shell charcoal was sieved through a 120-mesh standard sieve, and the undersize material was collected. A 12% Na2CO3 solution was prepared, and 18.5g of the sieved peanut shell charcoal was mixed with 277.5mL of Na2CO3 solution and transferred to a 500mL microwave reactor. The microwave power was set to 600W and the temperature to 92℃, and the mixture was soaked at a constant temperature for 3 hours, with stirring once every 30 minutes (200rpm). After soaking, the mixture was transferred to a centrifuge tube and centrifuged at 4000rpm for 15 minutes to separate the solid product. The solid was washed repeatedly with deionized water until the pH of the filtrate was 7, and the washed solid was collected. The solid was transferred to a vacuum drying oven and dried for 8 hours at a temperature of 90℃ and a vacuum of -0.09MPa to obtain the activated precursor.

[0051] Step 2: Take 12.8g of activated precursor, put it into a 50mL covered corundum crucible, place it in a tube furnace, and purge the furnace with high-purity nitrogen (99.999% purity, flow rate 60mL / min, time 30min) to remove air from the furnace; set the heating program: raise the temperature from room temperature (25℃) to 720℃ at a rate of 8℃ / min, and hold the temperature for 1.5h after reaching the target temperature; after the holding time is completed, keep the nitrogen gas flowing in, let it cool naturally to room temperature, and take out the solid; wash the solid 4 times with deionized water, dry it under vacuum at 90℃ for 8h, and sieve it through a 200-mesh standard sieve to obtain peanut shell charcoal (PHC) powder.

[0052] Step 3: Weigh 4.0g of PHC powder, add 5mmol of EDTA-Ni catalyst, and place them together in a 50mL polytetrafluoroethylene ball mill jar. Add 6g of agate balls (5mm in diameter, mass ratio 6:1). Set the ball mill speed to 450rpm and ball mill for 3.0h. Transfer the ball-milled mixture to a vacuum drying oven and pre-activate at 130℃ and -0.09MPa for 1.5h to remove residual moisture and obtain the catalytic graphitization precursor.

[0053] Step 4: 1.02 g of precursor was placed into a 20 mL corundum crucible and placed in a tube furnace again. High-purity nitrogen gas was passed through (flow rate 60 mL / min), and the temperature was raised to 700 °C at a rate of 15 °C / min and held for 1 h. The heating rate was then adjusted to 5 °C / min, and the temperature was raised to 1000 °C and held for 1 h. After cooling to room temperature, the product was removed and mixed with 150 mL of 1.4 M EDTA solution. The mixture was then transferred to an ultrasonic cleaner. The temperature was set to 50 °C and the ultrasonic power to 300 W, and the ultrasonic treatment was carried out for 3.0 h. After ultrasonic treatment, the mixture was allowed to stand for 8 h. The solid was separated by filtration, washed 4 times with 30% ethanol aqueous solution, and vacuum dried at 90 °C for 8 h to obtain peanut shell-based porous graphitized carbon, denoted as PGPC-8.

[0054] Step 5: Mix PGPC-8 with acetylene black and PTFE in a mass ratio of 7:1:1.5, and coat the mixture onto the nickel foam current collector (1 cm² area). 2 The working electrode (with a thickness of 0.1 mm) was fabricated, and its capacitance performance was tested in 6M KOH electrolyte.

[0055] Comparative Example 1 Following the preparation process of Example 1, only the microwave reactor was removed in step one, and conventional oil bath heating was used instead (immersion at 95°C for 2.8 hours, with stirring once every 30 minutes). The other steps and parameters were exactly the same as in Example 1, and CPGPC-1 was finally obtained.

[0056] Comparative Example 2 Following the preparation process of Example 1, in step three, no EDTA-Ni catalyst was added, and only 1.0g of PHC powder was ball-milled. The other steps and parameters were exactly the same as in Example 1, and CPGPC-2 was finally obtained.

[0057] Table 1. Comparison of electrical properties of supercapacitor electrodes prepared in Examples 1-6 and Comparative Examples 1-2

[0058] Table 1 compares the electrical properties of the supercapacitor electrodes prepared in Examples 1-6 and Comparative Examples 1-2. The data in the table show that Example 1 (5 mmol EDTA-Ni, graphitized at 1000℃) exhibits the best performance, with a specific capacitance of 328 F / g, a capacity retention of 92.5% after 5000 cycles, and a specific surface area of ​​1856 m². 2 / g, the core factor is the best parameter fit. The specific capacitance of Example 2 (3mmol EDTA-Ni) decreased by 10.1% compared with Example 1, due to insufficient graphitization caused by insufficient catalyst; the specific capacitance of Example 3 (900℃) decreased by 14%, due to incomplete development of porous structure at low temperature; when the microwave power (Example 5, 500W), ball milling time (Example 4, 2h), and EDTA concentration (Example 6, 1.2M) decreased, the specific surface area and specific capacitance both decreased, due to insufficient activation intensity, uneven mixing, and impurity residue, respectively, confirming the synergistic effect of each process parameter on performance. The specific capacitance of Comparative Example 1 (without microwave) decreased by 31.4% and the specific surface area decreased by 32.9% compared with Example 1, indicating that microwave can enhance the activation of Na2CO3 and promote the formation of porous structure; the specific capacitance of Comparative Example 2 (without EDTA-Ni) was only 186F / g, and the capacity retention rate was 72.8%, which was the lowest among all samples, proving that the catalyst is the key to graphitization, which can improve conductivity and structural stability. The absence of the catalyst will result in a significant decline in material performance. A combination of 5 mmol EDTA-Ni, graphitization at 1000℃, microwave treatment at 600W, ball milling for 3 hours, and 1.5M EDTA can be used to prepare porous graphitized carbon with high specific capacitance and high stability, meeting the requirements of supercapacitor electrode materials.

[0059] In summary, this invention provides a peanut shell-based porous graphitized carbon, its preparation method, and a supercapacitor electrode. Using peanut shell carbon, an agricultural waste, as the substrate, it achieves high-value utilization of waste, reduces reliance on fossil resources, and significantly lowers costs, aligning with green and sustainable development principles. The prepared peanut shell-based porous graphitized carbon has a microstructure of 1652-1856 μm. 2 ·g -1 With its high specific surface area and suitable average pore size of 2.6-3.1 nm, the supercapacitor electrode constructed using this material achieves a specific capacitance of 276-328 F / g at a current density of 0.5 A / g, and retains a capacity of 87.9%-92.5% after 5000 charge-discharge cycles. It is also compatible with conventional 6M KOH electrolyte, exhibiting superior charge storage capacity, cycle stability, and application adaptability compared to traditional products. The entire process utilizes mature technologies and conventional equipment such as microwave-assisted impregnation and two-stage catalytic graphitization. Key parameters are adjustable, and the process is environmentally friendly with no secondary pollution, enabling large-scale production without the need for high-end equipment. The electrode balances high conductivity with strong adhesion, improving mass transfer efficiency and structural stability. The supercapacitor combines high power characteristics with practical energy storage capacity, compensating for the shortcomings of lithium batteries and traditional capacitors. It is widely applicable in civilian, industrial, and new energy fields, offering high cost-effectiveness and significant market potential, providing an effective solution for the green and low-cost development of energy storage devices.

[0060] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing peanut shell-based porous graphitized carbon, characterized in that, Includes the following steps: 1) After crushing and sieving the peanut shell charcoal, mix it with Na2CO3 solution and perform microwave-assisted impregnation treatment. Then, centrifuge, wash until neutral, and dry to obtain the activated precursor. 2) The activated precursor obtained in step 1) is heat-treated under an inert atmosphere, cooled, washed and dried to obtain peanut shell char powder. 3) The peanut shell carbon powder obtained in step 2) is ball-milled and mixed with EDTA-Ni catalyst, and then dried to obtain the catalytic graphitization precursor; 4) The catalytic graphitization precursor obtained in step 3) is subjected to catalytic graphitization treatment under an inert atmosphere, cooled and then ultrasonically treated with EDTA solution, washed and dried to obtain peanut shell-based porous graphitized carbon.

2. The method for preparing peanut shell-based porous graphitized carbon according to claim 1, characterized in that, In step 1), the mass concentration of the Na2CO3 solution is 8%-12%; the power of the microwave-assisted impregnation is 500-600W, the temperature is 90-95℃, and the time is 2.5-3.0h.

3. The method for preparing peanut shell-based porous graphitized carbon according to claim 1, characterized in that, In step 2), the heating rate of the heat treatment is 5-8℃ / min, the target temperature is 680-720℃, and the holding time is 1.5-2.5h.

4. The method for preparing peanut shell-based porous graphitized carbon according to claim 1, characterized in that, In step 3), 3-5 mmol of EDTA-Ni catalyst is added to every 1g of peanut shell char powder; the ball milling mixing speed is 350-450 rpm and the time is 2.0-3.0h.

5. The method for preparing peanut shell-based porous graphitized carbon according to claim 1, characterized in that, In step 4), the conditions for the catalytic graphitization treatment include: heating to 600-700℃ at 10-15℃ / min and holding for 1.0-2.0h, then heating to 900-1000℃ at 3-5℃ / min and holding for 1.0-2.0h; the concentration of the EDTA solution is 1.2-1.5M.

6. A peanut shell-based porous graphitized carbon, characterized in that, The peanut shell-based porous graphitized carbon was prepared using the method described in any one of claims 1-5; the specific surface area of ​​the peanut shell-based porous graphitized carbon was 1652-1856 m². 2 ·g -1 The average pore size is 2.6-3.1 nm.

7. A method for preparing a supercapacitor electrode, characterized in that, Peanut shell-based porous graphitized carbon prepared by the method described in any one of claims 1-5 is used as an active material; peanut shell-based porous graphitized carbon, conductive agent and binder are mixed and coated on a current collector to obtain a supercapacitor electrode sheet.

8. The method for preparing a supercapacitor electrode according to claim 7, characterized in that, The mass ratio of the peanut shell-based porous graphitized carbon, conductive agent, and binder is (7-8):(1-1.5):(1-1.5); the conductive agent is acetylene black, the binder is polytetrafluoroethylene, and the current collector is nickel foam.

9. A supercapacitor electrode, characterized in that, The supercapacitor electrode is prepared by the method described in any one of claims 7 or 8, and the specific capacitance of the supercapacitor electrode at a current density of 0.5 A / g is 276-328 F / g; the capacity retention rate after 5000 charge-discharge cycles is 87.9%-92.5%.

10. A supercapacitor, characterized in that, It includes the supercapacitor electrode as described in any one of claims 7-9.

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