The Electrochemical Performance Of Supercapacitors Based On Manganese Oxides And Graphene Materials

As we enter the21st Century, the increasing environmental pollution and depletion of fossil fuels are serious. There is a very urgent need for clean, efficient and sustainable sources of energy, such as the electric vehicles, wind energy and solar energy. The development new technologies associated with energy conversion and storage have gradually caused extensive concern. Supercapacitors have attracted significant attention, owing to their high power density, long lifecycle, and the ability of charge/discharge. Supercapacitor can combine the advantages of batteries/fuel cells and traditional dielectric capacitors (which provide high power output).However, the disadvantages of Supercapacitor, especially the high production cost and low energy density, have been identified as major challenges for the application of supercapacitor technologies. Now, the development of new materials for supercapacitor electrodes is the main approach to overcome the obstacle of its low energy density. We have prepared graphene and graphene-based composite material.The prepared materials were characterized using scanning electron microscopy and powder X-ray diffraction, achieved the following results:(1) In our work, we synthesized graphene/Mn3O4nanocomposites in a very simple method. From SEM and TEM images, we can see the Mn3O4distributed on graphene layers. It can be inferred that the pseudocapacitance of Mn3O4could be effectively utilized, meanwhile, graphene could improve the electrical conductivity of Mn3O4.The G/Mn3O4nanocomposites exhibits a specific capacitance of140F/g with good rate property and good cycle stability.(2) In our work, a simple method for fabricating MnO2/graphene/CNTs composite electrodes was presented to further improve the electrochemical performance. MnO2was synthesized by a simple precipitation method using ethanol and KMnO4in neutral environment. The maximum CMnO2in the ternary composites electrode is240F/g at a scan rate of5mV/s.(3) To further explore the electrochemical property of MnO2/GNS/CNTs composite, we use the GNS/CNTs with different weight ratios. From these results, we can see that using GNS and CNTs as the backbone to support the MnO2nanoparticles could signally improve the performance of pure nano-MnO2. A maximum energy density of11.94Wh/kg is obtained for our symmetric supercapacitors with a power density of100W/kg.