Preparation And Properties Of Two Dimensional Material Based Composite Electrode For Supercapacitor

Supercapacitors have a great development potential and been successfully applied in many areas such as smart grid,rail traffic,heavy machinery and defense industry,due to huge instantaneous output power density,fast charge-discharge,long cycle life and high reliability.Electrode materials are important for the performance and cost of supercapacitor.Novel two-dimensional materials have a unique structure and advanced physical properties.Hence,it is a significant and worthwhile work to explore the prepare and preparation of two-dimensional materials and its application in supercapacitors.In this dissertation,reduced graphene oxide?rGO?prepared by the modified Hummers method and solvothermal method was used as the research object.Binary and ternary composite materials with amorphous hydrous ruthenium oxide?RuO₂?,multi-walled carbon nanotube?MWNTs?,reduced graphene oxide were synthesized by hydrothermal method.Electrodes were made by the acquired composites via different processes.The morphology and structure of composite materials were characterized by X-ray diffraction,scanning electron microscope,thermogravimetric analysis.Electrochemical properties of composite electrodes were investigated by cyclic voltammetry,galvanostatic charge-discharge tests and electrochemical impedance spectroscopy,the following conclusions were drawn.1.rGO/RuO₂ composites synthesized by hydrothermal method,can prevent the aggregation of rGO,improve the utilization of specific surface and dispersity of RuO₂ exhibit a good electrochemical performance.When mass ratio of rGO/RuO₂ composites is 1:3,mass fraction of acetylene black?AB?is 10 percent,mass fraction of polyvinylidene fluoride?PVDF?is 10 percent,under the pressures of 15 MPa,composite electrode exhibits a high specific capacitance of 403 F/g,resistance is 0.562 ?.At a current density of 20 mA/cm2 and 50 mA/cm2,the average power density is 2.02 kW/kg and 12.17 kW/kg respectively.After 800 cycles,the specific capacitance maintains 89 percent,and the resistance variation is less than 20 percent.2.MWNTs/RuO₂ composites synthesized by hydrothermal method.When MWNTs were treated by mixed acid solution for 1 h,mass ratio of MWNTs/Ru O₂ composites is 4:3,under the pressures of 10 MPa,composite electrode exhibits a high specific capacitance of 441 F/g,resistance is 1.052 ?.At a current density of 20 mA/cm2,the average power density is 2.21 kW/kg.After 800 cycles,the specific capacitance maintains 86 percent,and the resistance variation is less than 30 percent.The specific capacitance of MWNTs/RuO₂ electrode is higher than rGO/RuO₂ electrode,when the consumption of RuO₂ is less than rGO/RuO₂ electrode,because MWNTs have high surface area efficiency.But the performance of impedance,discharge rate and life-cycle is lower than rGO/RuO₂ electrode.3.rGO-MWNTs/Ru O₂ ternary composite electrodes were synthesized by hydrothermal method and layer-by-layer assembly respectively.One of electrodes exhibits a specific capacitance of 633 F/g,resistance is 0.233 ?.At a current density of 20 mA/cm2,the average power density is 3.17 kW/kg.After 800 cycles,the specific capacitance maintains 85 percent,and the resistance variation is less than 20 percent.The other electrode exhibits a higher specific capacitance of 978 F/g,resistance is 0.351 ?.At a current density of 20 mA/cm2,the average power density is 4.9 kW/kg.After 800 cycles,the specific capacitance maintains 81 percent,and the resistance variation is less than 30 percent.Ternary composite electrodes based on RuO₂-coated and three-dimensional rGO-MWNTs carbon structure,can improve the dispersity of RuO₂ and electrochemical performance of composite electrodes further,compared with binary composites.The ternary composite electrode via layer-by-layer assembly takes full advantage of rGO and MWNTs structures,to enhance the utilization of three-dimensional space,with excellent electrochemical performance.