Study On Preparation And Electrochemical Performance Of Electrode Mmaterials In Supercapacitors

Electrochemical capacitor which is a power-type energy storage device that can providea very high power density and a long cycle-life, has been received enormous attention inrecent years. The capacitance and stability of electrode materials are key factors for highperformance super-capacitors. Generally, the most widely used active electrode materialsof super-capacitors are carbon, conducting polymers, and transition-metal oxides. Of thevarious materials, MnO2and grapheme attracts intense interests. MnO2for its low cost,environmental friendliness, natural abundance and high security during fabrication andoperations which is ideal capacitor material. But the crystal types of manganese dioxideis numerous and complicated structure, therefore need to be further studied to find out thesuitable one for the super capacitor. Similarly，graphene benefit of its special layeredstructure and large specific surface area， can also be used as electrode material forsupercapacitor. But the average reduction of GO by chemical methods can not get the highperformance grapheme， therefore we need to find out a better method for the preparationof graphene.we describe a simple controlled preparation of MnO2microspheres throughself-assembly with an intermediate crystal-template process. Such a mild condition routefor controlled synthesis of MnO2microspheres without the need for any template hadrarely been reported previously. The structure and electrochemical performance of theMnO2microspheres were characterized in this work. Electrochemical characterization wasperformed using CV, charge–discharge tests and EIS. The as-prepared MnO2exhibited ahigh specific capacitance of525F g-1in Na2SO4aqueous solution at a scan rate of5mV s-1,and an excellent cycling performance.The Hummers method is the most widely used method to prepare Graphite oxide (GO),using strong oxidants in the presence of strong acid, and many methods have beendeveloped to reduct of Graphite oxide (rGO), such as chemically reduced with hydrazinemonohydrate. It has been found that the specific capacitance of the rGO is much lower than the calculated value due to the stacking of the graphene nanosheets, which leads to thelimited supercapacitor behaviors. In this work, a surface functionalized reduced grapheneoxide (SF-rGO) which has a higher specific surface area (531m2g-1) was successfullyachieve. It is inferred that our SF-rGO could have better properties while as the electrodematerials of supercapacitors. The supercapacitive characteristics were evaluated by cyclicvoltammetry (CV) and galvanostatic charge–discharge tests with3mol L1KOH as theelectrolyte.