Investigation Of Graphene And Metal Oxides Electrode Materials And Their Asymmetric Structure Supercapacitors

Attention is paid to supercapacitor in the fields of novel energy storage, however, thelow energy density has limited its further application. Thus lots of research mainly focusedon increasing the energy density. In this thesis, the high energy density of supercapacitorwith high power density was put forward by way of extending the voltage (V) andincreasing the specific capacitance (C). Therefore, the negative electrode materials withlarge voltage range and positive electrode materials with high specific capacitance werefabricated, respectively. And the asymmetric supercapacitor is assembled based on thesematerials.The main achieved results is as follows:We prepared graphene by reducing graphene oxides with a chemical method. Thevoltage of graphene is-1.1-0V, which can be used as negative material of asymmetricsupercapacitor. To increase the specific capacitance of graphene, the Fe3O4/rGOcomposites is prepared by a simple hydrolysis and annealing method. The specificcapacitance of Fe3O4/rGO composite can be improved due to the positive synergisticeffect of Fe3O4and rGO. We also find that the electrochemical performance of Fe3O4/rGOcan be effected by the mass ratio of Fe3O4and rGO in the composites.The NiCo2O4nanomaterial was fabricated through a solvothermal and annealingprocess. NiCo2O4is very suitable for the positive material of asymmetric supercapacitordue to its high specific capacitance. NiCo2O4has a very high specific capacitance as aresult of its unique nanostructure. The specific capacitance is1274.3F g-1at1A g-1and1010.9F g-1at20A g-1, indicating good rate characteristics.We assembled Graphene//NiCo2O4asymmetric supercapacitor with graphene asnegative material and NiCo2O4as positive material, respectively. The asymmetricsupercapacitor combined the large voltage range of graphene (power sources) with highspecific capacitance of NiCo2O4(energy sources). It can be found that the cell voltage is 1.6V, and the specific capacitance is69.5F g-1at0.5A g-1. The retention of specificcapacitance is80%after1000cycles, indicating good cycle performance. An energydensity24.7Wh kg-1is obtained with the power density of400W kg-1, which shows agood application potential.