Preparation method of graphene aerogel composite electrode material for energy storage capacitor

Abstract

The invention provides a preparation method of a graphene aerogel composite electrode material for an energy storage capacitor. The preparation method comprises the following steps: preparing a graphene composite material; and putting the graphene composite material into a coaxial DBD reactor for treatment. Freeze-drying the wet gel, and reserving a pore structure to obtain the GA block material. GA is soaked in a manganous nitrate solution, and a metal oxide nanosheet grows in situ through a hydrothermal method. And cutting the GA block into sheets, directly pressing and attaching the sheets to a foamed nickel current collector, carrying out vacuum drying, and preparing an electrode plate by using a hydraulic machine. According to the method, rapid reduction, precise structure regulation and control and functional compounding of the graphene aerogel are realized, reduction of GO, three-dimensional crosslinking and in-situ loading of a functional material are synchronously completed under a vacuum condition by optimizing plasma energy input and a gas environment, pollution of a chemical reducing agent and energy consumption of high-temperature treatment are avoided, and the method is suitable for large-scale industrial production. And the porosity, the conductivity and the interface bonding strength of the GA can be accurately regulated and controlled.

Description

Technical Field

[0001] The present invention relates to a method for preparing a composite electrode material for a capacitor, and in particular to a method for preparing a graphene aerogel composite electrode material for an energy storage capacitor. Background Art

[0002] As a key component of supercapacitors, electrode materials determine the capacity and energy density of supercapacitors and the energy storage mechanism of the system. They play a vital role in the capacity, cycle performance, rate performance, and safety of supercapacitors.

[0003] Graphene aerogel (GA), a graphene-derived 3D pore-interconnected material, has interconnected pores that effectively alleviate the stacking and agglomeration of graphene sheets while providing 3D channels for the free diffusion of conductive particles in the electrode. The larger specific surface area, higher electrical conductivity, highly interconnected porous structure, good mass transfer efficiency, and self-supporting characteristics enable GA itself and its composite materials to enhance the electrochemical performance of supercapacitors. However, the preparation of GA composites requires ensuring that the heterogeneous interface does not peel or crack during charging, discharging, or mechanical deformation, thereby maintaining the structural integrity and long-cycle stability of the material. This remains a technical challenge that needs to be addressed in this field.

[0004] Currently, the preparation of GA relies primarily on chemical reduction or high-temperature thermal reduction. Chemical reduction requires the use of strong reducing agents (such as hydrazine hydrate and ascorbic acid), resulting in long reaction times (several to dozens of hours) and the production of toxic byproducts that contaminate the material surface and increase post-processing costs. High-temperature thermal reduction requires high-temperature treatment (>800°C) under an inert atmosphere, which consumes extremely high energy and can easily induce structural defects in the graphene sheets. Furthermore, ice crystal growth during freeze-drying can lead to pore collapse, reducing the material's specific surface area and mechanical strength. More critically, existing methods make it difficult to directly introduce functional materials (such as metal oxides and conductive polymers) during GA synthesis. Subsequent loading processes can easily result in uneven distribution of active materials or weak interfacial bonding, leading to active material shedding during cycling and severely compromising the electrode's rate performance and cycling stability.

[0005] In recent years, plasma technology has been used in attempts to reduce and functionalize graphene. For example, hydrogen plasma can be used to rapidly remove oxygen-containing functional groups from the surface of graphene oxide (GO), restoring its conductivity; oxygen plasma can be used to etch the surface of carbon materials to increase active sites. However, the problems of directional synthesis and structural-functional integration of three-dimensional graphene aerogels have not yet been effectively solved. Specifically, the uneven distribution of plasma energy can easily lead to excessive etching or insufficient cross-linking of GO sheets, making it difficult to form a stable three-dimensional porous network; the introduction of functional materials still relies on post-processing steps (such as impregnation and calcination), making in-situ composites impossible and resulting in low interfacial bonding strength; and there is a lack of systematic research on the correlation between plasma parameters (such as power, gas composition, and exposure time) and GA pore structure, conductivity, and functionalization effects. This results in uncontrollable material properties and makes it difficult to meet the dual requirements of supercapacitors for high energy density and high power density. Summary of the Invention

[0006] 1. Technical problems to be solved: How to ensure that the heterogeneous interface does not peel off or crack propagate during charging, discharging or mechanical deformation in the preparation of GA composite materials, thereby maintaining the structural integrity and long-cycle stability of the material.

[0007] 2. Technical solution: In order to solve the above problems, the present invention provides a method for preparing a graphene aerogel composite electrode material for an energy storage capacitor, comprising the following steps: Step S01: preparing a graphene composite material.

[0008] Step S02: placing the graphene composite material obtained in step S01 into a coaxial DBD reactor for treatment for 25-35 minutes.

[0009] Step S03: freeze-drying the wet gel to retain the pore structure and obtain a GA block material.

[0010] Step S04: soaking GA in a manganese nitrate solution and in-situ growing metal oxide nanosheets by a hydrothermal method.

[0011] Step S05: Cut the GA block into sheets, directly press them onto the nickel foam current collector, vacuum dry them and use a hydraulic press to form electrode sheets.

[0012] In step S01, the specific method is: Step S11: Oxidation treatment of natural graphite powder is performed using a modified Hummers method: graphite powder is mixed with concentrated sulfuric acid, sodium nitrate, and potassium permanganate in a ratio of 1:0.5:23:3, 2-4 g of potassium permanganate is slowly added under ice bath conditions, the reaction temperature is controlled below 20°C, and then the temperature is raised to 35-40°C and stirred continuously for 2-4 hours to embed oxygen-containing groups between graphite layers to form graphite oxide.

[0013] Step S12: adding deionized water to dilute and dropping hydrogen peroxide to terminate the reaction, washing by centrifugation until neutral, and removing residual acid and metal ions.

[0014] Step S13: The graphite oxide obtained above is dispersed in water and subjected to ultrasonic exfoliation to obtain a uniform GO dispersion. After further purification by dialysis, the concentration is adjusted to 2-10 mg / mL. At this stage, metal salts or conductive polymer monomers are introduced, and uniform mixing and drying are achieved by stirring or ultrasonication to obtain a graphene composite material.

[0015] In step S02, the coaxial DBD reactor includes an inner electrode, an outer electrode and a dielectric barrier layer. The quartz glass tube is used as the dielectric barrier layer. The stainless steel mesh outer electrode is wound on the quartz tube. The stainless steel rod inner electrode is coaxially arranged with the quartz glass tube.

[0016] The inner electrode is connected to a nanosecond pulse power supply, the nanosecond pulse power supply voltage output peak is 15 kV, the frequency peak is 15 kHz; the pulse width adjustment range is 0 ns-1 ms; the rising edge and falling edge time adjustment range is 50ns-250 ns.

[0017] The coaxial DBD reactor is provided with an air inlet, through which the working gas enters the quartz tube. A working gas control system is provided, which includes a mass flow controller and a gas flow regulating needle valve. The gas flow regulating needle valve is used to assist the mass flow controller in accurately controlling the flow rate of the working gas.

[0018] The working gas is argon, and the gas flow rate adjustment range is 0-10 L / min. When the composite material is placed in the quartz tube, both ends of the quartz tube are blocked to prevent the mixed material from being blown out of the reaction zone by the airflow. The airflow is flowed into the glass tube at a constant flow rate through a mass flow controller.

[0019] In step S03 , freeze drying is performed at a temperature of -45-55° C. for 20-28 hours.

[0020] In step S04, the hydrothermal method is to soak at 110-130° C. for 4-8 hours.

[0021] In step S05, the vacuum drying is performed at a temperature of 55-65°C for 1.5-2.5 hours.

[0022] 3.Beneficial effects: The present invention realizes the rapid reduction, precise structural control and functional composite of graphene aerogel. By optimizing the plasma energy input and gas environment, the reduction, three-dimensional cross-linking and in-situ loading of GO and functional materials are simultaneously completed under vacuum conditions. This not only avoids the pollution of chemical reducing agents and the energy consumption of high-temperature treatment, but also can precisely control the porosity, conductivity and interface bonding strength of GA. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a flow chart of the preparation method. DETAILED DESCRIPTION

[0024] The present invention is described in detail below with reference to the accompanying drawings and embodiments.

[0025] Example 1 like Figure 1 As shown, a method for preparing a graphene aerogel composite electrode material for an energy storage capacitor comprises the following steps: Step S01: Natural graphite powder is oxidized, exfoliated, and purified by the Hummers method to obtain a GO dispersion and prepare a composite material.

[0026] Step S02: placing the composite material obtained in step S01 into a coaxial DBD reactor for a treatment time of 25-35 minutes, preferably 30 minutes.

[0027] Step S03: freeze-drying the wet gel to retain the pore structure and obtain a GA block material. The freeze-drying step is performed at a temperature of -45-55°C for 20-28 h, preferably 50°C for 24 h.

[0028] Step S04: soaking GA in a manganese nitrate solution, and in-situ growing metal oxide nanosheets by a hydrothermal method. The hydrothermal method is soaking at 110-130° C. for 4-8 h, preferably 120° C. for 6 h.

[0029] During the plasma treatment process, metal salts or polymer monomers are simultaneously introduced, and high-energy particles are used to activate the reaction to achieve in-situ uniform loading of functional materials (such as MnO2 and polyaniline), strengthen interface bonding, and improve electrode cycle stability.

[0030] Step S05: Cut the GA block into sheets, directly press them onto the nickel foam current collector, vacuum dry them and use a hydraulic press to form electrode sheets. The vacuum drying is performed at a temperature of 55-65° C. for 1.5-2.5 h, preferably 60° C. for 2 h.

[0031] The present invention uses high-energy plasma to dynamically regulate the formation of multi-level pores and the in-situ anchoring of functional materials on the surface of the graphene skeleton: active particles (such as electrons and ions) in the plasma selectively etch the edges of the graphene sheets to form a micro / mesoporous composite structure, while stimulating the decomposition and directionally depositing of functional material precursors on the pore surface. The instantaneous high temperature and high pressure environment promotes the dual action mechanism of covalent bonds (COM) and π-π stacking between functional particles and graphene through defect sites, while real-time feedback control of plasma parameters (such as electron density gradient and ion bombardment energy) can suppress the collapse of the carbon skeleton caused by local overheating, and induce topological matching between the functional material lattice and the graphene corrugated structure through pulsed energy input, thereby achieving synergistic optimization of porosity, conductivity and interface strength at the atomic scale, and ultimately constructing a composite electrode system with fast ion diffusion channels, high active site density and stress adaptive release capability.

[0032] Example 2 Step S01 specifically includes: Step S11: oxidizing the natural graphite powder using a modified Hummers method: mixing the graphite powder with concentrated sulfuric acid and sodium nitrate in a ratio of 1:0.5:23:3, slowly adding 3 g of potassium permanganate in an ice bath, and controlling the reaction temperature below 20°C to avoid excessive oxidation; then heating to 35-40°C and stirring continuously for 2-4 hours to embed oxygen-containing groups (such as carboxyl groups and epoxy groups) between the graphite layers to form graphite oxide; Step S12: adding deionized water to dilute and dropping hydrogen peroxide (30% concentration) to terminate the reaction, washing to neutrality by centrifugation to remove residual acid and metal ions.

[0033] In step S13, the graphite oxide obtained above is dispersed in water and subjected to ultrasonic exfoliation (power 300-500 W, time 1-3 hours) to obtain a uniform GO dispersion. After further purification by dialysis, the concentration is adjusted to 2-10 mg / mL. At this stage, metal salts or conductive polymer monomers (accounting for 20% of the graphite oxide) are introduced and uniformly mixed and dried by stirring or ultrasonication, providing a foundation for subsequent three-dimensional aerogel construction and plasma in situ reduction.

[0034] Example 3 This innovation proposes a plasma-based method for preparing graphene aerogel composite electrode materials. Plasma is used to generate high-energy particles and free radicals to treat the precursors, thereby improving the porosity and electrochemical performance of the composite material. The reactor consists of a coaxial dielectric barrier discharge reactor, a nanosecond pulse power supply, an electro-optical measurement system, and an airflow control system. The reactor consists of an inner electrode, an outer electrode, and a dielectric barrier. A 200 mm long, 1 mm thick quartz glass tube serves as the dielectric barrier. A 40 mm long stainless steel mesh outer electrode is wrapped around the quartz tube, and a 4 mm diameter stainless steel rod inner electrode is coaxially placed with the quartz glass tube. Plasma high-energy particles (such as electrons and free radicals) can efficiently reduce graphene oxide (GO) within tens of minutes, avoiding the problem of traditional chemical reduction methods taking hours to days. At the same time, it induces rapid self-assembly of three-dimensional porous networks, significantly shortening the preparation cycle.

[0035] Example 4 The nanosecond pulse power supply has a peak voltage output of 15 kV and a peak frequency of 15 kHz. The pulse width is adjustable from 0 ns to 1 ms, preferably 1 µs. The rise and fall times are adjustable from 50 ns to 250 ns, preferably 50 ns. Relatively uniform powder treatment is achieved within a voltage amplitude range of 3.0-10.0 kV and a power supply frequency range of 1.0-10.0 kHz. The preferred voltage in this experiment was 10.0 kV and a frequency of 5.0 kHz.

[0036] By adjusting the plasma power, gas composition, and treatment time, the aerogel's porosity (80-99%), pore size distribution (1-50 μm), and conductivity (100-1000 S / m) can be precisely controlled to meet the customized requirements of electrode materials for different application scenarios. Example 5 The working gas control system mainly includes a mass flow controller (Sevenstar D08-4F), a gas flow regulating needle valve and other devices. The gas flow regulating needle valve is used to assist the mass flow controller to accurately control the flow rate of the working gas. Argon is used as the working gas, and the gas flow rate adjustment range is 0-10 L / min. The above-mentioned composite material is placed in a glass tube, and both ends are blocked with quartz wool to prevent the mixed material from being blown out of the reaction zone by the airflow. During the experiment, the airflow was flowed into the glass tube at a constant flow rate of 0.5L / min through the mass flow controller, and the processing time was 30 minutes.

Claims

1. A method for preparing a graphene aerogel composite electrode material for an energy storage capacitor, comprising the following steps: Step S01: preparing a graphene composite material; Step S02: placing the graphene composite material obtained in step S01 into a coaxial DBD reactor for treatment for 25-35 minutes; Step S03: freeze-drying the wet gel to retain the pore structure and obtain a GA block material; Step S04: soaking GA in a manganese nitrate solution to in-situ grow metal oxide nanosheets by a hydrothermal method; Step S05: Cut the GA block into sheets, directly press them onto the nickel foam current collector, vacuum dry them and use a hydraulic press to form electrode sheets.

2. The method for preparing a graphene aerogel composite electrode material for an energy storage capacitor according to claim 1, wherein: In step S01, the specific method is: Step S11: Oxidation treatment of natural graphite powder using a modified Hummers method: Graphite powder is mixed with concentrated sulfuric acid, sodium nitrate, and potassium permanganate in a ratio of 1:0.5:23:3, and 3 g of potassium permanganate is slowly added in an ice bath. The reaction temperature is controlled below 20°C, and then the temperature is raised to 35-40°C and stirred for 2-4 hours to embed oxygen-containing groups between graphite layers to form graphite oxide. Step S12: adding deionized water to dilute and dropping hydrogen peroxide to terminate the reaction, washing by centrifugation until neutral to remove residual acid and metal ions; Step S13: The graphite oxide obtained above is dispersed in water and subjected to ultrasonic exfoliation to obtain a uniform GO dispersion. After further purification by dialysis, the concentration is adjusted to 2-10 mg / mL. At this stage, metal salts or conductive polymer monomers are introduced, and uniform mixing and drying are achieved by stirring or ultrasonication to obtain a graphene composite material.

3. The method for preparing a graphene aerogel composite electrode material for an energy storage capacitor according to claim 1, wherein: In step S02, the coaxial DBD reactor includes an inner electrode, an outer electrode and a dielectric barrier layer. The quartz glass tube is used as the dielectric barrier layer. The stainless steel mesh outer electrode is wound on the quartz tube. The stainless steel rod inner electrode is coaxially arranged with the quartz glass tube.

4. The method for preparing a graphene aerogel composite electrode material for an energy storage capacitor according to claim 3, wherein: The inner electrode is connected to a nanosecond pulse power supply, the nanosecond pulse power supply voltage output peak is 15 kV, the frequency peak is 15 kHz; the pulse width adjustment range is 0 ns-1 ms; the rising edge and falling edge time adjustment range is 50 ns-250 ns.

5. The method for preparing a graphene aerogel composite electrode material for an energy storage capacitor according to claim 1, wherein: The coaxial DBD reactor is provided with an air inlet, through which the working gas enters the quartz tube. A working gas control system is provided, which includes a mass flow controller and a gas flow regulating needle valve. The gas flow regulating needle valve is used to assist the mass flow controller in accurately controlling the flow rate of the working gas.

6. The method for preparing a graphene aerogel composite electrode material for an energy storage capacitor according to claim 6, wherein: The working gas is argon, and the gas flow rate adjustment range is 0-10 L / min. When the composite material is placed in the quartz tube, both ends of the quartz tube are blocked to prevent the mixed material from being blown out of the reaction zone by the airflow. The airflow is flowed into the glass tube at a constant flow rate through a mass flow controller.

7. The method for preparing a graphene aerogel composite electrode material for an energy storage capacitor according to any one of claims 1 to 6, wherein: In step S03 , freeze drying is performed at a temperature of -45-55° C. for 20-28 hours.

8. The method for preparing a graphene aerogel composite electrode material for an energy storage capacitor according to any one of claims 1 to 6, wherein: In step S04, the hydrothermal method is to soak at 110-130° C. for 4-8 hours.

9. The method for preparing a graphene aerogel composite electrode material for an energy storage capacitor according to any one of claims 1 to 6, wherein: In step S05, the vacuum drying is performed at a temperature of 55-65°C for 1.5-2.5 hours.

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