Preparation method and application of three-dimensional porous composite aerogel electrode material

Abstract

The invention provides a preparation method and application of a three-dimensional porous composite aerogel electrode material, the composite aerogel takes a carboxymethyl polyvinyl alcohol grafted carbon nanotube and a Cu-coated Fe2O3 nanowire as a skeleton, the Cu-coated Fe2O3 nanowire is of a two-dimensional net structure in the composite aerogel, and the Cu-coated Fe2O3 nanowire is of a three-dimensional porous structure. The two-dimensional net structure is obtained by Cu-coated Fe2O3 nanowires under the action of an external magnetic field. Charge transfer and ion diffusion are enhanced by utilizing the interfacial effect between different materials, so that the conductivity and the electrochemical activity are optimized.

Description

Technical Field

[0001] The present invention relates to the field of electrochemistry, and particularly to a preparation method and application of a three-dimensional porous composite aerogel electrode material. Background Art

[0002] With the increasing global demand for renewable energy and efficient energy storage technologies, electrochemical energy storage devices, especially supercapacitors and lithium-ion batteries, have become a research hotspot. Supercapacitors have received extensive attention due to their high power density, fast charge and discharge capabilities, and long cycle life. However, existing electrode materials still have certain limitations in terms of conductivity and energy density, which restricts their application in high-performance electrochemical energy storage devices. In recent years, the introduction of nanomaterials has provided new ideas for the modification of electrode materials. Copper nanowires have become an ideal choice for improving electrode performance due to their excellent conductivity. However, the poor chemical stability of copper nanowires limits their further development. Carbon nanotubes have become a popular electrode material due to their high conductivity, large specific surface area, excellent mechanical properties, and chemical stability. However, they have the limitation of uneven dispersion. Therefore, by appropriately modifying copper nanowires and carbon nanotubes to improve their chemical stability and dispersion, and then using the interfacial effect between the two to enhance charge transfer and ion diffusion, and further optimizing the conductivity and electrochemical activity of the electrode has become a new research direction. Summary of the Invention

[0003] Technical problems to be solved: The present invention provides a preparation method of a three-dimensional porous composite aerogel electrode material. The composite aerogel uses carboxymethyl polyvinyl alcohol-grafted carbon nanotubes and Cu@Fe 2 O 3 nanowires as the skeleton, and the Cu@Fe 2 O 3 nanowires form a network structure inside the aerogel under the action of an external magnetic field. The present invention utilizes the interfacial effect between different materials to enhance charge transfer and ion diffusion, thereby optimizing conductivity and electrochemical activity.

[0004] Technical solutions: A three-dimensional porous composite aerogel electrode material, characterized in that: the composite aerogel uses carboxymethyl polyvinyl alcohol-grafted carbon nanotubes and Cu@Fe 2 O 3 nanowires as the skeleton, the Cu@Fe 2 O 3 nanowires are in a network structure inside the composite aerogel, and the network structure is obtained by the Cu@Fe 2 O 3 nanowires under the action of an external magnetic field. Preferably, the preparation method comprises the following steps: S1. Disperse carbon nanotubes grafted with carboxymethyl polyvinyl alcohol and Cu@Fe 2 O 3 nanowires in a water / tert-butanol mixed solvent to form a homogeneous dispersion; S2. After pre-cooling the homogeneous dispersion for a certain time, perform freeze-drying and apply an external magnetic field to obtain a three-dimensional porous composite aerogel electrode material. Preferably, in S1, the mass ratio of Cu@Fe 2 O 3 nanowires to carboxymethyl polyvinyl alcohol-grafted carbon nanotubes is 1:4 - 1:6; In S1, the volume ratio of water to tert-butanol is 8 - 10:2 - 3; In S1, the length of Cu@Fe 2 O 3 nanowires is 5 - 15 μm, and the length-to-diameter ratio is 15 - 20; In S1, the mass fraction of the homogeneous dispersion is 10 - 18 wt%. Preferably, the preparation method of the carboxymethyl polyvinyl alcohol-grafted carbon nanotubes in S1 includes the following steps: S11. Disperse carbon nanotubes in an inorganic acid solvent to obtain a suspension, and perform a heating reflux reaction to obtain acidified carbon nanotubes; S12. Disperse the acidified carbon nanotubes obtained in S11 in N,N-dimethylformamide to obtain a uniform suspension, then add 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxysuccinimide and stir to obtain activated acidified carbon nanotubes; S13. Add the activated acidified carbon nanotubes to a carboxymethyl polyvinyl alcohol / N,N-dimethylformamide solution, adjust the pH to 7 - 8, and perform a heating reaction to obtain carboxymethyl polyvinyl alcohol-grafted carbon nanotubes. Preferably, the preparation method of the Cu@Fe 2 O 3 nanowires in S1 includes the following steps: S21. Disperse Cu nanowires in a solvent to form a homogeneous dispersion with a mass fraction of 10 - 20 wt%; S22. Add an iron salt precursor solution and a precipitant to the Cu nanowire dispersion, adjust the pH to 7 - 9, and react at 120 - 200 °C for 5 - 12 h to obtain Cu@Fe 2 O 3 nanowires. Preferably, in S2, the pre-cooling temperature is -30 - -20 °C, and the time is 2 - 4 h; In S2, the temperature of freeze-drying is -60 - -50 °C, and the time is 20 - 40 h; The external magnetic field strength in S2 is 1.0 - 1.8 T. Preferably, the mass fraction of the suspension in S11 is 15 - 25 wt%; The inorganic acid in S11 is any one or more of sulfuric acid, phosphoric acid or sulfuric acid; The temperature of heating and refluxing in S11 is 60 - 100 °C, and the reflux time is 2 - 5 h; Preferably, the mass fraction of the homogeneous suspension in S12 is 10 - 20 wt%; The mass ratio of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride to N-hydroxysuccinimide in S12 is 1:0.5 - 0.7; The total addition amount of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxysuccinimide in S12 is 20 - 35 wt% of the acidified carbon nanotubes. Preferably, the mass fraction of the carboxymethyl polyvinyl alcohol / N,N-dimethylformamide solution in S13 is 4 - 8 wt%; The addition amount of the activated acidified carbon nanotubes in S13 is 35 - 55 wt% of the mass of carboxymethyl polyvinyl alcohol; The temperature of the heating reaction in S13 is 60 °C, and the time is 10 - 15 h. Preferably, the iron salt precursor solution in S22 is one or more of ferric nitrate solution, ferric chloride solution or ferric sulfate solution; The concentration of the iron salt precursor solution in S22 is 0.05 - 1 mol / L; The volume ratio of the iron salt precursor solution to the Cu nanowire dispersion in S22 is 1:3 - 5; The precipitant in S22 is any one or more of urea, hexamethylenetetramine or ammonia water. Beneficial effects: The present invention has the following advantages: 1. In the present invention, Cu@Fe 2 O 3 nanowires construct a three-dimensional interpenetrating network with carboxymethyl polyvinyl alcohol-grafted carbon nanotubes as the conductive skeleton to form a charge transport channel; and Fe 2 O 3 realizes interfacial coupling through hydrogen bonding between the surface hydroxyl group and the carboxyl group on the surface of the carboxymethyl polyvinyl alcohol-grafted carbon nanotubes, thereby significantly reducing the contact resistance; the two-dimensional network structure induced by the magnetic field makes Cu@Fe 2 O 3 arranged in a specific direction to form a relatively ordered electron path; 2. In the present invention, the ice-templating method forms micron-scale macropores through the ice crystal growth exclusion effect, and the magnetic field-regulated two-dimensional network structure generates nano-scale mesopores, providing channels for short-range ion diffusion by constructing "micron-nano" hierarchical pores; moreover, it can avoid the dense packing of raw materials, providing a high specific surface area active interface. This material exhibits high specific capacitance, good cycle stability, and low internal resistance in supercapacitors. 3. In the present invention, a certain amount of Fe is coated on the surface of Cu nanowires 2 O 3 , which inhibits the oxidation reaction of Cu and maintains the chemical stability of Cu. At the same time, it can also inhibit the fracture caused by the volume expansion of Cu during the charge and discharge process, improving the stability of the material; grafting carboxymethyl polyvinyl alcohol on the surface of carbon nanotubes improves their dispersibility in aqueous solution; in addition, carboxymethyl polyvinyl alcohol is a long-chain polymer with steric hindrance effect, making the Cu@Fe 2 O 3 nanowires disperse uniformly in the solution, improving the uniformity of the three-dimensional composite material. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 It is the pore size distribution diagram of the material prepared in Example 8; Figure 2 It is the CV curves of the materials obtained in Example 8, Comparative Example 1, Comparative Example 2, Comparative Example 3, and Comparative Example 4 under the three-electrode system and the test condition of 50 mV / s. DETAILED DESCRIPTION OF THE INVENTION The present invention will be further described below in conjunction with embodiments. The following embodiments are explanations of the present invention and the present invention is not limited to the following embodiments: Example 1 A three-dimensional porous composite aerogel electrode material, the composite aerogel uses carboxymethyl polyvinyl alcohol-grafted carbon nanotubes and Cu@Fe 2 O 3 nanowires as the framework. The Cu@Fe 2 O 3 nanowires form a network structure inside the composite aerogel, and the network structure is obtained by the Cu@Fe 2 O 3 nanowires under the action of an external magnetic field. Among them, the preparation method includes the following steps: S1. Disperse carboxymethyl polyvinyl alcohol-grafted carbon nanotubes with a mass ratio of 1:1 and Cu@Fe 2 O 3 nanowires with a length of 5 μm and a length-to-diameter ratio of 15 in a water / tert-butanol mixed solvent with a volume ratio of 8:2 to form a homogeneous dispersion with a mass fraction of 10 wt%; S2. Pre-cool the homogeneous dispersion at -30 °C for 2 h, then freeze-dry it at -60 °C for 20 h, and apply an external magnetic field of 1.0 T to obtain a three-dimensional porous composite aerogel electrode material. Among them, the preparation method of the carbon nanotubes grafted with carboxymethyl polyvinyl alcohol in S1 includes the following steps: S11. Disperse carbon nanotubes in sulfuric acid to obtain a suspension with a mass fraction of 15 wt%, and heat it under reflux at 60 °C for 2 h to obtain acidified carbon nanotubes; S12. Disperse the acidified carbon nanotubes obtained in S11 in N,N-dimethylformamide to obtain a homogeneous suspension with a mass fraction of 10 wt%. Subsequently, add 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxysuccinimide with a mass ratio of 1:0.5 and stir. The total addition amount of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxysuccinimide is 20 wt% of the acidified carbon nanotubes to obtain activated acidified carbon nanotubes; S13. Add the activated acidified carbon nanotubes to a 4 wt% carboxymethyl polyvinyl alcohol / N,N-dimethylformamide solution. The addition amount of the activated acidified carbon nanotubes is 35 wt% of the mass of carboxymethyl polyvinyl alcohol. Adjust the pH to 7 and react at 60 °C for 10 h to obtain carbon nanotubes grafted with carboxymethyl polyvinyl alcohol. Among them, the Cu@Fe 2 O 3 The preparation method of the nanowires includes the following steps: S21. Disperse Cu nanowires in a solvent to form a homogeneous dispersion with a mass fraction of 10 wt%; S22. Add a ferric nitrate solution with a concentration of 0.05 mol / L and urea to the Cu nanowire dispersion, adjust the pH to 8, and react at 120 °C for 5 h to obtain Cu@Fe 2 O 3 Nanowires. Example 2 A three-dimensional porous composite aerogel electrode material, the composite aerogel uses carbon nanotubes grafted with carboxymethyl polyvinyl alcohol and Cu@Fe 2 O 3 Nanowires as the framework. The Cu@Fe 2 O 3 Nanowires are in a network structure inside the composite aerogel. The network structure is obtained by the Cu@Fe 2 O 3 Nanowires under the action of an external magnetic field. Among them, the preparation method includes the following steps: S1. Disperse carbon nanotubes grafted with carboxymethyl polyvinyl alcohol with a mass ratio of 3:2 and Cu@Fe nanowires with a length of 15 μm and an aspect ratio of 18 in a water / tert-butanol mixed solvent with a volume ratio of 9:2 to form a homogeneous dispersion with a mass fraction of 12 wt%. 2 O 3 S2. Pre-cool the homogeneous dispersion at -30 °C for 3 h and then freeze-dry it at -60 °C for 25 h, and apply an external magnetic field of 1.3 T to obtain a three-dimensional porous composite aerogel electrode material. Among them, the preparation method of the carbon nanotubes grafted with carboxymethyl polyvinyl alcohol in S1 includes the following steps: S11. Disperse carbon nanotubes in sulfuric acid to obtain a suspension with a mass fraction of 22 wt%, and heat it under reflux at 70 °C for 2 h to obtain acidified carbon nanotubes; S12. Disperse the acidified carbon nanotubes obtained in S11 in N,N-dimethylformamide to obtain a uniform suspension with a mass fraction of 15 wt%, then add 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxysuccinimide with a mass ratio of 1:0.7 and stir. The total addition amount of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxysuccinimide is 28 wt% of the acidified carbon nanotubes to obtain activated acidified carbon nanotubes; S13. Add the activated acidified carbon nanotubes to a 5 wt% carboxymethyl polyvinyl alcohol / N,N-dimethylformamide solution. The addition amount of the activated acidified carbon nanotubes is 40 wt% of the mass of carboxymethyl polyvinyl alcohol, adjust the pH to 8, and react at 60 °C for 11 h to obtain carbon nanotubes grafted with carboxymethyl polyvinyl alcohol. Among them, the preparation method of the Cu@Fe nanowires in S1 includes the following steps: S21. Disperse Cu nanowires in a solvent to form a uniform dispersion with a mass fraction of 12 wt%; 2 O 3 S22. Add a ferric chloride solution with a concentration of 0.08 mol / L and hexamethylenetetramine to the Cu nanowire dispersion, adjust the pH to 8, and react at 150 °C for 8 h to obtain Cu@Fe nanowires. S22. Add a ferric chloride solution with a concentration of 0.08 mol / L and hexamethylenetetramine to the Cu nanowire dispersion, adjust the pH to 8, and react at 150 °C for 8 h to obtain Cu@Fe S22. Add a ferric chloride solution with a concentration of 0.08 mol / L and hexamethylenetetramine to the Cu nanowire dispersion, adjust the pH to 8, and react at 150 °C for 8 h to obtain Cu@Fe 2 O 3 nanowires. Example 3 A three-dimensional porous composite aerogel electrode material, the composite aerogel uses carbon nanotubes grafted with carboxymethyl polyvinyl alcohol and Cu@Fe 2 O 3 nanowires as the framework, and the Cu@Fe 2 O 3The nanowires are in a network structure inside the composite aerogel, and the network structure is obtained from Cu@Fe 2 O 3 nanowires under the action of an external magnetic field. Among them, the preparation method includes the following steps: S1. Graft carboxymethyl polyvinyl alcohol onto carbon nanotubes with a mass ratio of 3:5 and Cu@Fe 2 O 3 nanowires with a length of 12 μm and an aspect ratio of 18 are dispersed in a water / tert-butanol mixed solvent with a volume ratio of 10:3 to form a homogeneous dispersion with a mass fraction of 12 wt%; S2. The homogeneous dispersion is pre-cooled at -30 °C for 3 h and then freeze-dried at -55 °C for 24 h, and an external magnetic field of 1.5 T is applied to obtain a three-dimensional porous composite aerogel electrode material. Among them, the preparation method of the carboxymethyl polyvinyl alcohol-grafted carbon nanotubes in S1 includes the following steps: S11. Carbon nanotubes are dispersed in sulfuric acid to obtain a suspension with a mass fraction of 20 wt%, and refluxed at 80 °C for 4 h to obtain acidified carbon nanotubes; S12. The acidified carbon nanotubes obtained in S11 are dispersed in N,N-dimethylformamide to obtain a homogeneous suspension with a mass fraction of 15 wt%. Subsequently, 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxysuccinimide with a mass ratio of 1:0.6 are added and stirred. The total addition amount of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxysuccinimide is 32 wt% of the acidified carbon nanotubes to obtain activated acidified carbon nanotubes; S13. The activated acidified carbon nanotubes are added to a 5 wt% carboxymethyl polyvinyl alcohol / N,N-dimethylformamide solution, and the addition amount of the activated acidified carbon nanotubes is 40 wt% of the mass of carboxymethyl polyvinyl alcohol. The pH is adjusted to 8, and the reaction is carried out at 60 °C for 12 h to obtain carboxymethyl polyvinyl alcohol-grafted carbon nanotubes. Among them, the preparation method of the Cu@Fe 2 O 3 nanowires in S1 includes the following steps: S21. Cu nanowires are dispersed in a solvent to form a homogeneous dispersion with a mass fraction of 15 wt%; S22. A ferric sulfate solution with a concentration of 0.08 mol / L and ammonia water are added to the Cu nanowire dispersion, and the pH is adjusted to 9, and then the reaction is carried out at 180 °C for 8 h to obtain Cu@Fe 2 O 3 nanowires. Example 4 A three-dimensional porous composite aerogel electrode material, wherein the composite aerogel is composed of carbon nanotubes grafted with carboxymethyl polyvinyl alcohol and Cu@Fe 2 O 3 nanowires as the skeleton, and the Cu@Fe 2 O 3 nanowires form a network structure inside the composite aerogel, and the network structure is obtained by the Cu@Fe 2 O 3 nanowires under the action of an external magnetic field. Among them, the preparation method includes the following steps: S1. Carbon nanotubes grafted with carboxymethyl polyvinyl alcohol with a mass ratio of 3:5 and Cu@Fe 2 O 3 nanowires with a length of 12 μm and a length-to-diameter ratio of 18 are dispersed in a water / tert-butanol mixed solvent with a volume ratio of 9:2 to form a homogeneous dispersion with a mass fraction of 15 wt%. S2. The homogeneous dispersion is pre-cooled at -25°C for 3 h and then freeze-dried at -55°C for 25 h, and an external magnetic field of 1.5 T is applied to obtain the three-dimensional porous composite aerogel electrode material. Among them, the preparation method of the carbon nanotubes grafted with carboxymethyl polyvinyl alcohol in S1 includes the following steps: S11. Carbon nanotubes are dispersed in sulfuric acid to obtain a suspension with a mass fraction of 18 wt%, and are heated under reflux at 90°C for 3 h to obtain acidified carbon nanotubes. S12. The acidified carbon nanotubes obtained in S11 are dispersed in N,N-dimethylformamide to obtain a homogeneous suspension with a mass fraction of 15 wt%. Subsequently, 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxysuccinimide with a mass ratio of 1:0.6 are added and stirred. The total addition amount of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxysuccinimide is 22 wt% of the acidified carbon nanotubes to obtain activated acidified carbon nanotubes. S13. The activated acidified carbon nanotubes are added to a 5 wt% carboxymethyl polyvinyl alcohol / N,N-dimethylformamide solution, and the addition amount of the activated acidified carbon nanotubes is 40 wt% of the mass of the carboxymethyl polyvinyl alcohol. The pH is adjusted to 8, and the reaction is carried out by heating at 60°C for 12 h to obtain carbon nanotubes grafted with carboxymethyl polyvinyl alcohol. Among them, the preparation method of the Cu@Fe 2 O 3 nanowires includes the following steps: S21. Cu nanowires are dispersed in a solvent to form a homogeneous dispersion with a mass fraction of 15 wt%. S22. Add the precipitant urea, an iron nitrate solution with a concentration of 0.09 mol / L, to the Cu nanowire dispersion. After adjusting the pH to 8, react at 180 °C for 10 h to obtain Cu@Fe 2 O 3 nanowires. Example 5 A three-dimensional porous composite aerogel electrode material, wherein the composite aerogel uses carbon nanotubes grafted with carboxymethyl polyvinyl alcohol and Cu@Fe 2 O 3 nanowires as the framework. The Cu@Fe 2 O 3 nanowires form a network structure inside the composite aerogel, and the network structure is obtained by the Cu@Fe 2 O 3 nanowires under the action of an external magnetic field. Among them, the preparation method includes the following steps: S1. Disperse carbon nanotubes grafted with carboxymethyl polyvinyl alcohol and Cu@Fe 2 O 3 nanowires with a length of 12 μm and a length-to-diameter ratio of 18 in a water / tert-butanol mixed solvent with a volume ratio of 9:2 to form a homogeneous dispersion with a mass fraction of 12 wt%; S2. Pre-cool the homogeneous dispersion at -25 °C for 3 h, then freeze-dry at -50 °C for 25 h, and apply an external magnetic field of 1.5 T to obtain the three-dimensional porous composite aerogel electrode material. Among them, the preparation method of the carbon nanotubes grafted with carboxymethyl polyvinyl alcohol in S1 includes the following steps: S11. Disperse the carbon nanotubes in sulfuric acid to obtain a suspension with a mass fraction of 18 wt%, and heat and reflux at 95 °C for 3 h to obtain acidified carbon nanotubes; S12. Disperse the acidified carbon nanotubes obtained in S11 in N,N-dimethylformamide to obtain a uniform suspension with a mass fraction of 18 wt%. Subsequently, add 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxysuccinimide with a mass ratio of 1:0.5 and stir. The total addition amount of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxysuccinimide is 20 wt% of the acidified carbon nanotubes to obtain activated acidified carbon nanotubes; S13. Add the activated acidified carbon nanotubes to a 5 wt% carboxymethyl polyvinyl alcohol / N,N-dimethylformamide solution. The addition amount of the activated acidified carbon nanotubes is 40 wt% of the mass of carboxymethyl polyvinyl alcohol. Adjust the pH to 8 and react at 60 °C for 14 h to obtain carbon nanotubes grafted with carboxymethyl polyvinyl alcohol. Among them, the Cu@Fe in S1 2 O3 The preparation method of the nanowires comprises the following steps: S21. Disperse the Cu nanowires in a solvent to form a homogeneous dispersion with a mass fraction of 14 wt%. S22. Add a ferric nitrate solution with a concentration of 0.08 mol / L and urea to the Cu nanowire dispersion, adjust the pH to 8, and react at 190 °C for 8 h to obtain Cu@Fe 2 O 3 nanowires. Example 6 A three-dimensional porous composite aerogel electrode material, wherein the composite aerogel uses carbon nanotubes grafted with carboxymethyl polyvinyl alcohol and Cu@Fe 2 O 3 nanowires as the framework, and the Cu@Fe 2 O 3 nanowires are in a network structure inside the composite aerogel, and the network structure is obtained by the Cu@Fe 2 O 3 nanowires under the action of an external magnetic field. Among them, the preparation method comprises the following steps: S1. Disperse carbon nanotubes grafted with carboxymethyl polyvinyl alcohol with a mass ratio of 1:5 and Cu@Fe 2 O 3 nanowires with a length of 12 μm and an aspect ratio of 18 in a water / tert-butanol mixed solvent with a volume ratio of 9:2 to form a homogeneous dispersion with a mass fraction of 15 wt%. S2. Pre-cool the homogeneous dispersion at -25 °C for 3 h, then freeze-dry at -55 °C for 30 h, and apply an external magnetic field of 1.6 T to obtain the three-dimensional porous composite aerogel electrode material. Among them, the preparation method of the carbon nanotubes grafted with carboxymethyl polyvinyl alcohol in S1 comprises the following steps: S11. Disperse the carbon nanotubes in sulfuric acid to obtain a suspension with a mass fraction of 18 wt%, and heat and reflux at 85 °C for 3 h to obtain acidified carbon nanotubes. S12. Disperse the acidified carbon nanotubes obtained in S11 in N,N-dimethylformamide to obtain a homogeneous suspension with a mass fraction of 15 wt%, then add 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxysuccinimide with a mass ratio of 1:0.5 and stir. The total addition amount of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxysuccinimide is 25 wt% of the acidified carbon nanotubes to obtain activated acidified carbon nanotubes. S13. Add the activated acidified carbon nanotubes to a 5 wt% carboxymethyl polyvinyl alcohol / N,N-dimethylformamide solution. The addition amount of the activated acidified carbon nanotubes is 45 wt% of the mass of the carboxymethyl polyvinyl alcohol. Adjust the pH to 8 and react at 60 °C for 11 h to obtain carbon nanotubes grafted with carboxymethyl polyvinyl alcohol. Among them, the Cu@Fe in S1 2 O 3 The preparation method of the nanowires includes the following steps: S21. Disperse the Cu nanowires in a solvent to form a homogeneous dispersion with a mass fraction of 12 wt%. S22. Add a 0.08 mol / L iron chloride solution and urea to the Cu nanowire dispersion, adjust the pH to 9, and react at 160 °C for 8 h to obtain Cu@Fe 2 O 3 nanowires. Example 7 A three-dimensional porous composite aerogel electrode material, the composite aerogel uses carbon nanotubes grafted with carboxymethyl polyvinyl alcohol and Cu@Fe 2 O 3 nanowires as the framework. The Cu@Fe 2 O 3 nanowires are in a network structure inside the composite aerogel. The network structure is obtained by the Cu@Fe 2 O 3 nanowires under the action of an external magnetic field. Among them, the preparation method includes the following steps: S1. Disperse carbon nanotubes grafted with carboxymethyl polyvinyl alcohol with a mass ratio of 1:6 and Cu@Fe with a length of 12 μm and an aspect ratio of 18 2 O 3 nanowires in a water / tert-butanol mixed solvent with a volume ratio of 9:3 to form a homogeneous dispersion with a mass fraction of 15 wt%. S2. Pre-cool the homogeneous dispersion at -25 °C for 3 h and then freeze-dry it at -55 °C for 35 h, and apply an external magnetic field of 1.2 T to obtain the three-dimensional porous composite aerogel electrode material. Among them, the preparation method of the carbon nanotubes grafted with carboxymethyl polyvinyl alcohol in S1 includes the following steps: S11. Disperse the carbon nanotubes in sulfuric acid to obtain a suspension with a mass fraction of 18 wt%, and heat and reflux at 70 °C for 3 h to obtain acidified carbon nanotubes. S12. Disperse the acidified carbon nanotubes obtained in S11 in N,N-dimethylformamide to obtain a homogeneous suspension with a mass fraction of 15 wt%, then add 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxysuccinimide with a mass ratio of 1:0.6 and stir. The total addition amount of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxysuccinimide is 24 wt% of the acidified carbon nanotubes to obtain activated acidified carbon nanotubes; S13. Add the activated acidified carbon nanotubes to a 6 wt% carboxymethyl polyvinyl alcohol / N,N-dimethylformamide solution. The addition amount of the activated acidified carbon nanotubes is 40 wt% of the mass of the carboxymethyl polyvinyl alcohol. Adjust the pH to 8 and react at 60 °C for 14 h to obtain carbon nanotubes grafted with carboxymethyl polyvinyl alcohol. Among them, in S1, the preparation method of the Cu@Fe 2 O 3 nanowires includes the following steps: S21. Disperse the Cu nanowires in a solvent to form a homogeneous dispersion with a mass fraction of 10 - 20 wt%; S22. Add a ferric nitrate solution with a concentration of 0.05 mol / L and urea to the Cu nanowire dispersion, adjust the pH to 8, and react at 160 °C for 8 h to obtain Cu@Fe 2 O 3 nanowires. Example 8 A three-dimensional porous composite aerogel electrode material, the composite aerogel uses carbon nanotubes grafted with carboxymethyl polyvinyl alcohol and Cu@Fe 2 O 3 nanowires as the framework. The Cu@Fe 2 O 3 nanowires are in a network structure inside the composite aerogel. The network structure is obtained by the Cu@Fe 2 O 3 nanowires under the action of an external magnetic field. Among them, the preparation method includes the following steps: S1. Disperse carbon nanotubes grafted with carboxymethyl polyvinyl alcohol and Cu@Fe 2 O 3 nanowires with a length of 12 μm and an aspect ratio of 18 in a water / tert-butanol mixed solvent with a volume ratio of 8:3 to form a homogeneous dispersion with a mass fraction of 15 wt%; S2. Pre-cool the homogeneous dispersion at -28 °C for 3 h and then freeze-dry it at -55 °C for 25 h, and apply an external magnetic field of 1.5 T to obtain a three-dimensional porous composite aerogel electrode material. Among them, the preparation method of the carboxymethyl polyvinyl alcohol grafted carbon nanotubes in S1 includes the following steps: S11. Disperse the carbon nanotubes in sulfuric acid to obtain a suspension with a mass fraction of 20 wt%, and heat and reflux at 80 °C for 3 h to obtain acidified carbon nanotubes; S12. Disperse the acidified carbon nanotubes obtained in S11 in N,N-dimethylformamide to obtain a homogeneous suspension with a mass fraction of 15 wt%. Subsequently, add 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxysuccinimide with a mass ratio of 1:0.6 and stir. The total addition amount of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxysuccinimide is 30 wt% of the acidified carbon nanotubes to obtain activated acidified carbon nanotubes; S13. Add the activated acidified carbon nanotubes to a 7 wt% carboxymethyl polyvinyl alcohol / N,N-dimethylformamide solution. The addition amount of the activated acidified carbon nanotubes is 45 wt% of the mass of the carboxymethyl polyvinyl alcohol. Adjust the pH to 8 and react at 60 °C for 12 h to obtain carboxymethyl polyvinyl alcohol grafted carbon nanotubes. Among them, the Cu@Fe 2 O 3 The preparation method of the nanowires includes the following steps: S21. Disperse the Cu nanowires in a solvent to form a homogeneous dispersion with a mass fraction of 18 wt%; S22. Add a 0.08 mol / L iron nitrate solution and urea to the Cu nanowire dispersion, adjust the pH to 8, and react at 150 °C for 10 h to obtain Cu@Fe 2 O 3 Nanowires. Comparative Example 1 The difference between this comparative example and Example 8 is that carboxymethyl polyvinyl alcohol is not grafted on the surface of the carbon nanotubes. Comparative Example 2 The difference between this comparative example and Example 8 is that Fe 2 O 3 is not coated on the surface of the Cu nanowires. Comparative Example 3 The difference between this comparative example and Example 8 is that the direct freeze-drying method is used instead of the ice template method when preparing the aerogel. Comparative Example 4 The difference between this comparative example and Example 8 is that carboxymethyl polyvinyl alcohol is not grafted on the surface of the carbon nanotubes and Fe 2 O 3 is not coated on the surface of the Cu nanowires. Performance Test For the materials prepared in Examples 1-8 and Comparative Examples 1-4, a three-electrode system was used to test their specific capacitance values and the specific capacitance retention rate after 300 cycles of cyclic testing at a current density of 1 A·g -1 . The results are shown in Table 1: Table 1 Test of specific capacitance value and specific capacitance retention rate Obviously, the above examples are merely illustrations for clear explanation and are not limitations on the implementation manners. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to enumerate all implementation manners here. And the obvious changes or modifications derived therefrom are still within the protection scope of the present invention.

Claims

1. A three-dimensional porous composite aerogel electrode material, characterized in that: The composite aerogel uses carbon nanotubes grafted with carboxymethyl polyvinyl alcohol and Cu@Fe2O3 nanowires as skeletons. The Cu@Fe2O3 nanowires are in a mesh structure inside the composite aerogel, and the mesh structure is obtained by the Cu@Fe2O3 nanowires under the action of an external magnetic field.

2. The method for preparing the three-dimensional porous composite aerogel electrode material according to claim 1, characterized in that: The preparation method comprises the following steps: S1. dispersing the carbon nanotubes grafted with carboxymethyl polyvinyl alcohol and Cu@Fe2O3 nanowires in a water / tert-butyl alcohol mixed solvent to form a homogeneous dispersion; S2. The homogeneous dispersion is precooled for a certain period of time and then freeze-dried, and an external magnetic field is applied to obtain a three-dimensional porous composite aerogel electrode material.

3. The method for preparing the three-dimensional porous composite aerogel electrode material according to claim 2, characterized in that: The mass ratio of Cu@Fe2O3 nanowires to carboxymethyl polyvinyl alcohol grafted carbon nanotubes in S1 is 1:4 to 1:6; And / or, the volume ratio of water to tert-butyl alcohol in S1 is 8-10:2-3; and or, the length of the Cu@Fe2O3 nanowires in S1 is 5 to 15 μm, and the aspect ratio is 15 to 20; And / or, the mass fraction of the homogeneous dispersion in S1 is 10-18wt%.

4. The method for preparing the three-dimensional porous composite aerogel electrode material according to claim 2, characterized in that: The method for preparing carbon nanotubes grafted with carboxymethyl polyvinyl alcohol in S1 comprises the following steps: S11. dispersing the carbon nanotubes in an inorganic acid solvent to obtain a suspension, and heating the suspension under reflux to obtain acidified carbon nanotubes; S12. The acidified carbon nanotubes obtained in S11 are dispersed in N,N-dimethylformamide to obtain a uniform suspension, and then 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxysuccinimide are added and stirred to obtain activated acidified carbon nanotubes; S13. Add the activated acidified carbon nanotubes into the carboxymethyl polyvinyl alcohol / N,N-dimethylformamide solution, adjust the pH to 7-8, and obtain the carboxymethyl polyvinyl alcohol-grafted carbon nanotubes by heating reaction.

5. The method for preparing the three-dimensional porous composite aerogel electrode material according to claim 2, characterized in that: The preparation method of Cu@Fe2O3 nanowires in S1 comprises the following steps: S21. Dispersing the Cu nanowires in a solvent to form a uniform dispersion having a mass fraction of 10 to 20 wt %; S22. Add an iron salt precursor solution and a precipitant to the Cu nanowire dispersion, adjust the pH to 7-9, and react at 120-200° C. for 5-12 hours to obtain Cu@Fe2O3 nanowires.

6. The method for preparing the three-dimensional porous composite aerogel electrode material according to claim 4, characterized in that: The precooling temperature in S2 is -30 to -20°C and the time is 2 to 4 hours; And / or, the freeze drying temperature in S2 is -60 to -50°C and the time is 20 to 40 hours; And / or, the strength of the external magnetic field in S2 is 1.0-1.8T.

7. The method for preparing the three-dimensional porous composite aerogel electrode material according to claim 4, characterized in that: The mass fraction of the suspension in S11 is 15-25wt%; And / or, the inorganic acid in S11 is any one or more of sulfuric acid, phosphoric acid or sulfuric acid; And / or, the heating reflux temperature in S11 is 60-100° C., and the reflux time is 2-5 h.

8. The method for preparing the three-dimensional porous composite aerogel electrode material according to claim 4, characterized in that: The mass fraction of the uniform suspension in S12 is 10-20wt%; And / or, the mass ratio of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride to N-hydroxysuccinimide in S12 is 1:0.5-0.7; And / or, the total amount of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxysuccinimide added in S12 is 20-35wt% of the acidified carbon nanotubes.

9. The method for preparing the three-dimensional porous composite aerogel electrode material according to claim 4, characterized in that: The mass fraction of the carboxymethyl polyvinyl alcohol / N,N-dimethylformamide solution in S13 is 4-8wt%; And / or, the amount of activated acidified carbon nanotubes added in S13 is 35-55wt% of the mass of carboxymethyl polyvinyl alcohol; And / or, the temperature of the heating reaction in S13 is 60° C. and the time is 10 to 15 hours.

10. The method for preparing the three-dimensional porous composite aerogel electrode material according to claim 5, characterized in that: The iron salt precursor solution in S22 is one or more of ferric nitrate solution, ferric chloride solution or ferric sulfate solution; and / or, the concentration of the iron salt precursor solution in S22 is 0.05 to 1 mol / L; and / or, the volume ratio of the iron salt precursor solution to the Cu nanowire dispersion in S22 is 1:3-5; And / or, the precipitant in S22 is any one or more of urea, hexamethylenetetramine or ammonia water.

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