Preparation And Energy Storage Properties Of Self-supporting Electrode Based On Two-dimensional Materials

In recent years,the issue of energy shortage and environmental pollution have become more and more serious.The development of environmentally friendly new energy sources and the development of new and efficient energy storage equipment are extremely urgent.The research and development of high-efficiency energy storage appliances focuses on the selection of electrode materials and the design of electrode structures.The existing main method for preparing the electrode is to uniformly mix the binder and the active substance,and then scrape the mixture on the surface of the current collector.For the electrode prepared by this method,the mass of the inactive substance of the electrode is increased,thus reducing the specific capacity of the electrode as a whole.In the development of independent self-supporting electrodes,self-supporting electrodes based on two-dimensional materials have become a hot research topic in recent years.Graphene has become the research focus of researchers due to its good conductivity and large specific surface area.In recent years,the new two-dimensional material MXene has also become the research object of self-supporting electrodes for energy storage devices due to its many advantages.This paper integrates the advantages of the two,and uses graphene oxide?GO?and Ti₃C₂T_X MXene as raw materials to prepare reduced graphene oxide?r GO?/MXene self-supporting membrane electrode,and applies it to high energy density supercapacitors.The r GO/MXene-S three-dimensional composite self-supporting foam electrode with high sulfur loading was further designed and prepared,and the lithium-sulfur battery was assembled with this electrode to investigate the effect of self-supporting electrode structure on the electrochemical performance of the battery.The specific contents and research results of electrode preparation,capacitor and battery assembly and their performance are as follows:1. r GO/MXene-H₂SO₄ laminated composite membrane electrode:Constructing compact self-supporting electrode is one of the effective methods to improve the volume energy density of supercapacitor.In this paper,the r GO/MXene laminated composite the membrane was prepared by metal reduction of mixed dispersion of MXene and graphene oxide.Furthermore,sulfuric acid electrolyte was introduced into the dense structure layer of the electrode by replacing electrolyte?H₂SO₄?to obtain dense structure r GO/MXene-H₂SO₄composite membrane electrode.Sulfuric acid electrolyte existing between the electrode dense structure layers realizes full contact between the electrode material and the electrolyte.Therefore,the volume energy density of the supercapacitor based on the composite film reaches 115 F cm^-3.2. Three-dimensional core-shell structure r GO/MXene-S@r GO/MXene composite foam electrode:In order to obtain energy storage devices with higher energy density,the electrode structure is improved on the basis of the materials used in the first part of the work to construct the electrode.The composite foam electrode with three-dimensional core-shell structure is prepared by two-step hydrothermal reaction and in-situ loading of nano-sulfur.The internal r GO/MXene-S,as the active material of lithium-sulfur battery,acts as the"core"part of the core-shell structure,while the network structure formed by crossing r GO/MXene sheets improves the conductivity of the electrode.The r GO/MXene coated on the outer layer is the"shell"part of the core-shell structure,and has both physical confinement and chemical adsorption to inhibit the shuttle effect of polysulfide.The composite foam?r GO/MXene-S@r GO/MXene?self-supporting electrode with the structure achieves a high sulfur load of more than 70%.Based on the current density of the battery with the electrode at 0.1 C,the discharge capacity in the first cycle is 1400 m Ah g^-1,and the discharge capacity remains1200 m Ah g^-1 after 300 cycles of battery cycling.