Preparation method and application of high-performance composite electrode

Abstract

The invention relates to a preparation method and application of a high-performance composite electrode. Comprising the following steps: firstly, preparing a surface modified carbon nanotube with excellent dispersity through vacuum filtration and a plasma surface modification technology; secondly, preparing nitrogen-doped graphene with high conductivity and high electrochemical activity by utilizing chemical reaction in combination with high-temperature nitrogen treatment; and then uniformly loading the two materials on the carbon nanofiber membrane by adopting an alternate spraying method, and preparing the composite electrode through a liquid nitrogen freeze-drying process. The prepared composite electrode shows excellent electrochemical performance, including high porosity, large specific surface area and excellent specific capacitance. The preparation method is simple and environment-friendly, and the obtained material has good flexibility and high conductivity, is suitable for energy storage devices such as supercapacitors and can be widely applied to the fields of new energy, portable electronic equipment and the like.

Description

Technical Field

[0001] The invention relates to a method for preparing a high-performance composite electrode, and belongs to the fields of composite materials and electrochemistry. Background Art

[0002] With the increasing energy crisis and environmental problems, the research on sustainable energy storage and conversion technology has received extensive attention. Supercapacitors have shown great application potential in the field of energy storage due to their high power density, fast charge and discharge capabilities, and good cycle stability. However, to further improve the performance of supercapacitors, the key lies in the development of electrode materials with high specific capacitance, high conductivity, and high mechanical stability.

[0003] Traditional supercapacitor electrode materials are mainly activated carbon, metal oxides and conductive polymers. Among them, activated carbon is widely used due to its high specific surface area and good stability, but its specific capacitance is relatively low. Metal oxides such as MnO2, NiO and RuO2 have high specific capacitance, but are expensive and have poor cycle stability. Conductive polymers (such as polyaniline and polypyrrole) have high theoretical specific capacitance, but are prone to structural degradation in actual use. Carbon nanomaterials have become a research hotspot for supercapacitor electrode materials in recent years due to their unique physical and chemical properties. Among them, carbon nanotubes (CNTs) and graphene are often used as basic building blocks of electrode materials due to their high conductivity, large specific surface area and excellent mechanical properties. A single carbon nanotube-based electrode material can exhibit a specific capacitance of 150 F / g at a current density of 1 A / g, but its specific surface area is limited and the pore structure is difficult to control. In order to further improve the comprehensive performance of electrode materials, compounding carbon nanotubes with other functional materials is an important research direction. Nitrogen-doped graphene can introduce pseudocapacitive effects due to its nitrogen-containing functional groups, significantly improving the specific capacitance of electrode materials. At the same time, its unique two-dimensional structure can effectively improve the conductivity and porosity of the electrode. The supercapacitor electrode prepared by nitrogen-doped graphene has a specific capacitance of 200F / g at a current density of 1 A / g, but single graphene materials still have certain limitations in mechanical properties and assembly stability (Han H, et al., Chemical Communications, 2015, 51, 8826.) Based on this, it is a very promising strategy to organically combine carbon nanotubes, nitrogen-doped graphene and carbon nanofiber membranes (CNF) to prepare high-performance flexible composite electrodes. As a substrate material, carbon nanofiber membranes not only have good flexibility and mechanical strength, but also provide rich pore structures and effective carrier support for electrodes, thereby improving the overall stability and conductivity of the material. The electrode materials based on the above composite strategy have shown significant improvements in specific capacitance and energy density, but the complex preparation process and high cost of composite materials still need to be further optimized. Summary of the invention The object of the present invention is to provide a method for preparing a high-performance composite electrode and its use, so as to solve the above-mentioned problems existing in the prior art.

[0005] The present invention is achieved through the following technical solutions: A method for preparing a high-performance composite electrode comprises the following steps: preparing carbon nanotubes and nitrogen-doped graphene respectively; The carbon nanotubes are subjected to plasma treatment using oxygen as a working gas to obtain surface-modified carbon nanotubes; The surface modified carbon nanotubes are dispersed in deionized water to obtain a spray liquid A, and the nitrogen-doped graphene is dispersed in deionized water to obtain a spray liquid B. The spray liquid A and the spray liquid B are alternately sprayed on a single side surface of a carbon nanofiber membrane to form repeated alternating superposition of carbon nanotube layers and nitrogen-doped graphene layers. Spraying one carbon nanotube layer and one nitrogen-doped graphene layer is counted as one cycle. The cycle is repeated multiple times, and after each cycle, the carbon nanofiber membrane is frozen with liquid nitrogen and freeze-dried to obtain a high-performance composite electrode.

[0006] As a preferred embodiment, the method for preparing the carbon nanotubes is: Dissolve ferric nitrate and nickel nitrate in distilled water, immerse the porous alumina template, perform vacuum filtration to fill the pores of the porous alumina template with the ferric nitrate and nickel nitrate solutions, and dry at 80-90°C; The dried porous alumina template is reduced with hydrogen at 450-500°C to obtain Fe / Ni nanoparticles loaded on the porous alumina template; The porous alumina template loaded with Fe / Ni nanoparticles is placed in an argon atmosphere, heated to 700-800° C., and then a mixed gas of methane and hydrogen is introduced. After the reaction, the introduction of methane is stopped, and argon is continued to be introduced. After cooling to room temperature, a precursor is obtained; The precursor is immersed in a sodium hydroxide solution, and the porous alumina template is removed at 50-60° C. to obtain carbon nanotubes.

[0007] As a preferred embodiment, the mass ratio of the iron nitrate to the nickel nitrate is (2-5):(1-3).

[0008] As a preferred embodiment, the working conditions of the plasma treatment are as follows: gas pressure is 100-120 mTorr, power is 40-60 W, and treatment time is 15-20 min.

[0009] As a preferred embodiment, the preparation method of the nitrogen-doped graphene is: The graphene is dispersed in concentrated ammonia water and subjected to a hydrothermal reaction at 90-100°C to obtain amino-modified graphene; After uniformly mixing the amino-modified graphene, isopropanol, distilled water, hydrochloric acid and aniline, an aqueous solution of ammonium persulfate is added in an ice-water bath to carry out a polymerization reaction to obtain graphene-grafted polyaniline; The graphene-grafted polyaniline is kept at 200-300° C. for 2-3 hours in a nitrogen atmosphere, and then the temperature is increased to 700-800° C. and kept for 4-6 hours to obtain nitrogen-doped graphene.

[0010] As a preferred embodiment, the mass ratio of the amino-modified graphene to aniline is (1-4): (3-5).

[0011] As a preferred embodiment, in the spray liquid A, the concentration of the surface-modified carbon nanotubes is 1-2 mg / mL, and in the spray liquid B, the concentration of the nitrogen-doped graphene is 1-2 mg / mL.

[0012] A high-performance composite electrode obtained by the aforementioned preparation method is used as a flexible electrode material in a supercapacitor.

[0013] The basic implementation principle of the present invention is: 1. Using porous alumina as a template and Fe / Ni nanoparticles as a catalyst, carbon nanotubes are generated on the template surface by chemical vapor deposition. Finally, active groups such as hydroxyl and carboxyl groups are introduced on the surface of the carbon nanotubes by plasma treatment.

[0014] 2. Graphene is modified by ammonia water to introduce amino groups, and then in situ grafted polymerization with aniline is performed to obtain graphene-grafted polyaniline. Finally, nitrogen-doped graphene is obtained by pre-oxidation, activation and carbonization in a tubular furnace.

[0015] 3. Carbon nanotubes and nitrogen-doped graphene are alternately coated on carbon nanofibers by multi-layer alternating spraying to obtain a high-performance composite electrode material.

[0016] Compared with the prior art, the present invention has the following beneficial effects: 1. Carbon nanotubes provide excellent conductivity, nitrogen-doped graphene improves electrochemical activity, and carbon nanofiber membranes ensure mechanical flexibility. This composite structure effectively improves specific capacitance and conductivity while ensuring structural stability and adaptability.

[0017] 2. The microstructure and interface characteristics of the material are precisely controlled by using processes such as vacuum filtration, liquid nitrogen freeze drying, and plasma treatment. In particular, the process of alternating spraying and freeze drying ensures the close bonding between the composite layers while reducing internal defects.

[0018] 3. Both the materials and methods are environmentally friendly and have the potential for large-scale industrial production, low-temperature nitrogen doping process and the use of economical and efficient alumina templates. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Other features, objects and advantages of the present invention will become more apparent from the detailed description of non-limiting embodiments made with reference to the following drawings: Figure 1 This is a structural diagram of the high-performance composite electrode of the present invention; In the figure: 1, carbon cloth layer, 2, graphene layer, 3, carbon nanotube grafted polyaniline layer. DETAILED DESCRIPTION

[0020] The present invention is described in detail below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those of ordinary skill in the art, several variations and improvements may be made without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

[0021] Unless otherwise specified, all raw materials used in the present invention are commercially available.

[0022] Example 1 This embodiment provides a method for preparing a high-performance composite electrode, which specifically includes the following steps: 1) Preparation of carbon nanotubes Dissolve 0.2 g of ferric nitrate and 0.15 g of nickel nitrate in 50 mL of distilled water, immerse 1 g of porous alumina template in the above solution, fill the solution into the template pores by vacuum filtration, and dry at 80°C for 2 h. Put it in a tube furnace and introduce hydrogen reduction at 500°C for 1 h to obtain Fe / Ni nanoparticles loaded on the porous alumina template. Argon gas is introduced into the tube furnace and the temperature is raised to 750°C. Then methane and hydrogen are introduced, react for 30 min, stop the methane flow, continue to introduce argon (keep hydrogen introduction), cool to room temperature and take out the sample. Immerse the sample in 1 mol / L NaOH solution, stir at 50°C for 1 h to remove the template, and obtain carbon nanotubes. Put the carbon nanotube product into a plasma treatment instrument and use oxygen (O2) as the working gas. Gas pressure: 100mTorr; power: 50 W; treatment time: 15 min, and surface-modified carbon nanotubes are obtained.

[0023] 2) Preparation of nitrogen-doped graphene 0.5 g of graphene was added to the reactor, and then filled with concentrated ammonia water, reacted at 95 ° C for 6 h, filtered, washed and dried to obtain amino-modified graphene. 0.15 g of amino-modified graphene, 4 mL of isopropanol and 15 mL of distilled water, 50 mL of 2 mol / mL hydrochloric acid solution and 0.45 g of aniline were added to a three-necked flask, and the flask was placed in an ice-water bath, and then 15 g of 10% ammonium persulfate aqueous solution was slowly added and stirred for 6 h. Graphene-grafted polyaniline was obtained by filtration, washing and vacuum drying. The graphene-grafted polyaniline was placed in a tubular furnace, heated from 25 ° C to 250 ° C under nitrogen protection, and kept warm for 2.5 h, then heated from 250 ° C to 750 ° C, and kept warm for 5 h, and finally nitrogen-doped graphene was obtained.

[0024] 3) Preparation of carbon nanotube / nitrogen-doped graphene / carbon nanofiber membrane composite electrode 20 mL of surface-modified carbon nanotubes with a concentration of 1 mg / mL was placed in a spray bottle to obtain spray liquid A. 20 mL of nitrogen-doped graphene dispersion with a concentration of 1 mg / mL was placed in another spray bottle to obtain spray liquid B. Spray liquid A and spray liquid B were alternately sprayed on the single-side surface of the carbon nanofiber membrane (size 4 cm × 4 cm) to form repeated alternating superposition of carbon nanotube layers and nitrogen-doped graphene layers. The spraying of one carbon nanotube layer and one nitrogen-doped graphene layer was recorded as one cycle. The cycle was repeated 3 times, and the carbon nanofiber membrane was frozen with liquid nitrogen after each cycle, and freeze-dried to obtain a carbon nanotube / nitrogen-doped graphene / carbon nanofiber membrane composite electrode.

[0025] The structure of the carbon nanotube / nitrogen-doped graphene / carbon nanofiber membrane composite electrode material prepared in Example 1 is as follows: Figure 1The porosity of the composite electrode is 91.12% and the specific surface area is 57.2 m 2 / g, the conductivity is 1.99 S / m. The prepared composite electrode material has a specific capacitance of 201 F / g at a current density of 1 A / g.

[0026] Example 2 This embodiment provides a method for preparing a high-performance composite electrode, which specifically includes the following steps: 1) Preparation of carbon nanotubes Dissolve 0.15 g of ferric nitrate and 0.12 g of nickel nitrate in 50 mL of distilled water, immerse 1 g of porous alumina template in the above solution, fill the solution into the template pores by vacuum filtration, and dry at 80°C for 2 h. Put it in a tube furnace and introduce hydrogen reduction at 450°C for 1 h to obtain Fe / Ni nanoparticles loaded on the porous alumina template. Argon gas is introduced into the tube furnace and the temperature is raised to 700°C. Then methane and hydrogen are introduced, react for 30 min, stop the methane flow, continue to introduce argon gas (keep the introduction of hydrogen), cool to room temperature and take out the sample. Immerse the sample in 1 mol / L NaOH solution, stir at 50°C for 1 h to remove the template, and obtain carbon nanotubes. Put the carbon nanotube product into a plasma treatment instrument and use oxygen (O2) as the working gas. Gas pressure: 120mTorr; power: 40 W; treatment time: 20 min, and surface-modified carbon nanotubes are obtained.

[0027] 2) Preparation of nitrogen-doped graphene 0.5 g of graphene was added to the reactor, and then filled with concentrated ammonia water, reacted at 95 ° C for 6 h, filtered, washed and dried to obtain amino-modified graphene. 0.12 g of amino-modified graphene, 4 mL of isopropanol and 15 mL of distilled water, 50 mL of 2 mol / mL hydrochloric acid solution and 0.4 g of aniline were added to a three-necked flask, and the flask was placed in an ice-water bath, and then 15 g of 10% ammonium persulfate aqueous solution was slowly added and stirred for 6 h. Graphene-grafted polyaniline was obtained by filtration, washing and vacuum drying. The graphene-grafted polyaniline was placed in a tubular furnace, heated from 25 ° C to 280 ° C under nitrogen protection, and kept warm for 2.5 h, then heated from 280 ° C to 780 ° C, and kept warm for 5 h, and finally nitrogen-doped graphene was obtained.

[0028] 3) Preparation of carbon nanotube / nitrogen-doped graphene / carbon nanofiber membrane composite electrode 20 mL of surface-modified carbon nanotubes with a concentration of 1.5 mg / mL was placed in a spray bottle to obtain spray liquid A. 20 mL of nitrogen-doped graphene dispersion with a concentration of 1.5 mg / mL was placed in another spray bottle to obtain spray liquid B. Spray liquid A and spray liquid B were alternately sprayed on the single-side surface of the carbon nanofiber membrane (size 4 cm × 4 cm) to form repeated alternating superposition of carbon nanotube layers and nitrogen-doped graphene layers. Spraying one carbon nanotube layer and one nitrogen-doped graphene layer was recorded as one cycle. The cycle was repeated 4 times, and the carbon nanofiber membrane was frozen with liquid nitrogen after each cycle, and freeze-dried to obtain a carbon nanotube / nitrogen-doped graphene / carbon nanofiber membrane composite electrode.

[0029] The porosity of the composite electrode prepared in Example 2 is 90.88% and the specific surface area is 60.12 m 2 / g, the conductivity is 2.01 S / m. The prepared composite electrode material has a specific capacitance of 211 F / g at a current density of 1 A / g.

[0030] Example 3 This embodiment provides a method for preparing a high-performance composite electrode, which specifically includes the following steps: 1) Preparation of carbon nanotubes Dissolve 0.18 g of ferric nitrate and 0.18 g of nickel nitrate in 50 mL of distilled water, immerse 1 g of porous alumina template in the above solution, fill the solution into the template pores by vacuum filtration, and dry at 80°C for 2 h. Put it in a tube furnace and introduce hydrogen reduction at 500°C for 1 h to obtain Fe / Ni nanoparticles loaded on the porous alumina template. Argon gas is introduced into the tube furnace and the temperature is raised to 750°C. Then methane and hydrogen are introduced, react for 30 min, stop the methane flow, continue to introduce argon (keep hydrogen introduction), cool to room temperature and take out the sample. Immerse the sample in 1 mol / L NaOH solution, stir at 50°C for 1 h to remove the template, and obtain carbon nanotubes. Put the carbon nanotube product into a plasma treatment instrument and use oxygen (O2) as the working gas. Gas pressure: 100mTorr; power: 45 W; treatment time: 20 min, and surface-modified carbon nanotubes are obtained.

[0031] 2) Preparation of nitrogen-doped graphene 0.5 g of graphene was added to the reactor, and then filled with concentrated ammonia water, reacted at 95 ° C for 6 h, filtered, washed and dried to obtain amino-modified graphene. 0.18 g of amino-modified graphene, 4 mL of isopropanol and 15 mL of distilled water, 50 mL of 2 mol / mL hydrochloric acid solution and 0.5 g of aniline were added to a three-necked flask, and the flask was placed in an ice-water bath, and then 15 g of 10% ammonium persulfate aqueous solution was slowly added and stirred for 6 h. Graphene-grafted polyaniline was obtained by filtration, washing and vacuum drying. The graphene-grafted polyaniline was placed in a tubular furnace, heated from 25 ° C to 260 ° C under nitrogen protection, and kept warm for 2.5 h, then heated from 260 ° C to 760 ° C, and kept warm for 5 h, and finally nitrogen-doped graphene was obtained.

[0032] 3) Preparation of carbon nanotube / nitrogen-doped graphene / carbon nanofiber membrane composite electrode 20 mL of surface-modified carbon nanotubes with a concentration of 1.3 mg / mL was placed in a spray bottle to obtain spray liquid A. 20 mL of nitrogen-doped graphene dispersion with a concentration of 1.8 mg / mL was placed in another spray bottle to obtain spray liquid B. Spray liquid A and spray liquid B were alternately sprayed on the single-side surface of the carbon nanofiber membrane (size 4 cm × 4 cm) to form repeated alternating superposition of carbon nanotube layers and nitrogen-doped graphene layers. Spraying one carbon nanotube layer and one nitrogen-doped graphene layer was recorded as one cycle. The cycle was repeated 4 times, and the carbon nanofiber membrane was frozen with liquid nitrogen after each cycle, and freeze-dried to obtain a carbon nanotube / nitrogen-doped graphene / carbon nanofiber membrane composite electrode.

[0033] The structure of the carbon nanotube / nitrogen-doped graphene / carbon nanofiber membrane composite electrode material prepared in Example 1 is as follows: Figure 1 The porosity of the composite electrode is 89.09% and the specific surface area is 58.8 m 2 / g, the conductivity is 2.09 S / m. The prepared composite electrode material has a specific capacitance of 198 F / g at a current density of 1 A / g.

[0034] Comparative Example 1 The difference from Example 1 is that the carbon nanotubes obtained in step 1) are not subjected to plasma treatment, and the carbon nanotubes are directly used in step 3). The porosity of the high-performance composite electrode finally obtained is 90.47, and the specific surface area is 60.98 m 2 / g, the conductivity is 1.79 S / m. The high-performance composite electrode material prepared has a specific capacitance of 185 F / g at a current density of 1 A / g.

[0035] Comparative Example 2 The difference from Example 1 is that step 2) is omitted and graphene is directly used in step 3). Finally, a carbon nanotube / graphene / carbon nanofiber membrane composite electrode is obtained. The porosity of the composite electrode is 81.22% and the specific surface area is 49.01 m 2 / g, the conductivity is 1.76 S / m. The prepared high-performance composite electrode material has a specific capacitance of 167F / g under the condition of current density of 1 A / g.

[0036] Comparative Example 3 The difference from Example 1 is that in step 3), ordinary commercial carbon cloth is used instead of carbon nanofiber membrane, and finally a carbon nanofiber / graphene / carbon cloth composite electrode is obtained. The porosity of the composite electrode is 81.12%, and the specific surface area is 50.98 m 2 / g, the conductivity is 1.55 S / m. The high-performance composite electrode material prepared has a specific capacitance of 147 F / g at a current density of 1 A / g.

[0037] The above describes the specific embodiments of the present invention. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art may make various modifications or variations within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A method for preparing a high-performance composite electrode, characterized in that: The steps include: preparing carbon nanotubes and nitrogen-doped graphene respectively; The carbon nanotubes are subjected to plasma treatment using oxygen as a working gas to obtain surface-modified carbon nanotubes; The surface modified carbon nanotubes are dispersed in deionized water to obtain a spray liquid A, and the nitrogen-doped graphene is dispersed in deionized water to obtain a spray liquid B. The spray liquid A and the spray liquid B are alternately sprayed on a single side surface of a carbon nanofiber membrane to form repeatedly alternately stacked carbon nanotube layers and nitrogen-doped graphene layers. Spraying one carbon nanotube layer and one nitrogen-doped graphene layer is counted as one cycle. The cycle is repeated multiple times, and after each cycle, the carbon nanofiber membrane is frozen with liquid nitrogen and freeze-dried at -50°C to obtain a high-performance composite electrode.

2. The method for preparing a high-performance composite electrode according to claim 1, characterized in that: The preparation method of the carbon nanotubes is: Dissolve ferric nitrate and nickel nitrate in distilled water, immerse the porous alumina template, perform vacuum filtration to fill the pores of the porous alumina template with the ferric nitrate and nickel nitrate solutions, and dry at 80-90°C; The dried porous alumina template is reduced with hydrogen at 450-500°C to obtain Fe / Ni nanoparticles loaded on the porous alumina template; The porous alumina template loaded with Fe / Ni nanoparticles is placed in an argon atmosphere, heated to 700-800° C., and then a mixed gas of methane and hydrogen is introduced. After the reaction, the introduction of methane is stopped, and argon is continued to be introduced. After cooling to room temperature, a precursor is obtained; The precursor is immersed in a sodium hydroxide solution, and the porous alumina template is removed at 50-60° C. to obtain carbon nanotubes.

3. The method for preparing a high-performance composite electrode according to claim 2, characterized in that: The mass ratio of the iron nitrate to the nickel nitrate is (2-5):(1-3).

4. The method for preparing a high-performance composite electrode according to claim 1, characterized in that: The working conditions of the plasma treatment are as follows: gas pressure is 100-120 mTorr, power is 40-60 W, and treatment time is 15-20 min.

5. The method for preparing a high-performance composite electrode according to claim 1, characterized in that: The preparation method of the nitrogen-doped graphene is: The graphene is dispersed in concentrated ammonia water and subjected to a hydrothermal reaction at 90-100°C to obtain amino-modified graphene; After uniformly mixing the amino-modified graphene, isopropanol, distilled water, hydrochloric acid and aniline, adding an aqueous solution of ammonium persulfate in an ice-water bath to carry out a polymerization reaction to obtain graphene-grafted polyaniline; The graphene-grafted polyaniline is kept at 200-300° C. for 2-3 hours in a nitrogen atmosphere, and then the temperature is increased to 700-800° C. and kept for 4-6 hours to obtain nitrogen-doped graphene.

6. The method for preparing a high-performance composite electrode according to claim 5, characterized in that: The mass ratio of the amino-modified graphene to aniline is (1-4):(3-5).

7. The method for preparing a high-performance composite electrode according to claim 1, characterized in that: In the spray liquid A, the concentration of the surface-modified carbon nanotubes is 1-2 mg / mL, and in the spray liquid B, the concentration of the nitrogen-doped graphene is 1-2 mg / mL.

8. Use of the high-performance composite electrode obtained by the preparation method according to claim 1 as a flexible electrode material in a supercapacitor.

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