Preparation Of Three-Dimensional Graphene&Polymer Hydrogel Composite Material And Its Application In Supercapacitors

Flexible solid-state supercapacitors have important application value as mobile power sources for flexible electronic devices in the future.However,flexibility and stability are the key to determining whether supercapacitors can be used in flexible electronic devices.The traditional electrolyte will damage it when it is impacted by an external force,leading to dangers such as electrolyte leakage and explosion in the device.The gel electrolyte can withstand pressure and impact.it is essentially a gel-like solid with an ideal microstructure and has highly stable electrochemical performance at room temperature.In this paper,the three-dimensional nitrogen-doped graphene with high conductivity is incorporated into the hydrogel with three-dimensional network structure,and a gel electrolyte with strong flexibility,self-healing and high conductivity is prepared by different methods.A series of studies have been carried out on the assembly of supercapacitor devices with a sandwich structure.The specific research content of the paper is as follows:（1）By incorporating three-dimensional nitrogen-doped graphene into poly-N,N-dimethyl acrylamide hydrogel,a three-dimensional nitrogen-doped graphene nanostructure（3DNG-PDM A）for assembling high-performance flexible solid-state supercapacitors was prepared.The influence of the mass ratio of three-dimensional nitrogen-doped graphene and N,N-dimethyl acrylamide monomer（DMA）on the flexible mechanical properties,swelling balanceand electro chemical properties of the gel electrolyte was explored.Studies have found that 3DNG can significantly improve the flexible mechanical properties and electrochemical properties of3DNG-PDMA nanohydrogels.When the mass ratio is 10 wt%,the tensile fracture rate of the material reaches 1803%,and the electrical conductivity is 0.063 S·cm^-1.At a current density of 1A·g^-1,the supercapacitor device assembled by 3DNG-PDMA has a specific capacitance value of187.5 F·g^-1.When the power density is 5 Kw·kg^-1,it still has an energy density of 38.0 Wh·kg^-1.（2）Using N,N-dimethylacrylamide and acrylic acid as monomers,N,N’-methylene bisacrylamide and Fe Cl₃as crosslinking agents,a supercapacitor gel electrolyte(Fe³⁺/P（AA-co-DMA）)with strong flexibility and excellent self-healing properties was prepared.After incorporating 3DNG with high electrochemical properties into Fe³⁺/P（AA-co-DMA）hydrogel,a3DNG-Fe³⁺/P（AA-co-DMA）gel electrolyte with high conductivity is obtained.The study found that when the Fe Cl₃content is 6 mol%,the tensile fracture rate of Fe³⁺/P（AA-co-DMA）hydrogel reaches 1149%,and the tensile strength reaches 689 Kpa.At the same time,the Fe³⁺/P（AA-co-DMA）hydrogel can be healed after being cut in contact for 24 hours.The 3DNG-Fe³⁺/P（AA-co-DMA）gel electrolyte assembled supercapacitors doped with 3DNG have a specific capacitance value of up to 231.8 F·g^-1at a current density of 1 A·g^-1,and conductivity It is 0.053S·cm^-1.When the power density is 5 Kw·kg^-1,the energy density of the device is 38.7 Wh·Kg^-1.（3）Using N,N-dimethylacrylamide and acrylic acid as monomers,N,N’-methylene bisacrylamide and Co Cl₂·H₂O as crosslinking agents,a polymer hydrogel electrolyte(Co²⁺/P（AA-co-DMA）)with strong flexibility was prepared.After incorporating 3DNG with high electrochemical properties into Co²⁺/P（AA-co-DMA）hydrogel,a 3DNG-Co²⁺/P（AA-co-DMA）gel electrolyte with high conductivity is obtained.The study found that the tensile fracture rate of Co²⁺/P（AA-co-DMA）hydrogel with divalent Co²⁺as the crosslinking agent reached 1925%,and the tensile strength reached 1696.0 Kpa.It is significantly higher than the tensile fracture rate（1149%）and tensile strength（689 Kpa）of Fe³⁺/P（AA-co-DMA）hydrogel with trivalent Fe³⁺as the crosslinking agent.However,there is no significant difference in electrochemical performance between the two.At the current density of 1 A·g^-1,the specific capacitance value of3DNG-CO²⁺/P（AA-co-DMA）supercapacitor is 234.4 F·g^-1,and the conductivity is 0.084 S·cm^-1.At a power density of 5 k W·kg^-1,the energy density of the device is 34.2 Wh·kg^-1.