Preparation And Electrochemical Performance Of Graphene/Nickel-cobalt Oxide

Due to the high power density and excellent cycle performance, graphene-basedcomposite has been a hotspot in the area of electrochemical capacitor.Graphene/nickel-cobalt oxide composite was prepared via hydrothermal andelectrochemical methods respectively in this paper, and their electrochemicalproperties were studied.Graphene/NiCoO2composite was synthesized by a hydrothermal way. The XRD,Raman, XPS, SEM and TEM were used to characterized its morphology and structure.The result indicated that nickel and cobalt existed in the form of NiCoO2, graphenesheets are multilayers, and NiCoO2increased the number of defects in garphenesheets. The surface of composite was wrinked which maintained a layered structure ofgraphene. The electrochemical test results showed that the specific capacitance ofcomposite reached480F/g at a current density of2A/g, and the capacitance remained88%after1000cycles. Electrochemical capacitor assembled by graphene/NiCoO2composite showed a specific capacitance of81.3F/g at a current density of0.5A/g,energy density and power density reached6.34Wh/kg and192.6W/kg respectivelyafter1000cycles, which showed a excellent ability of long time charge and discharge.Graphene/Co2O3-NiO film electrode was prepared by electrochemical method.Morphology and structure characterization results indicate that nickel and cobaltexisted in the form of NiO and Co2O3. NiO and Co2O3distributed between and on thesurface of graphene, formed a sandwich structure. Electrochemical tests presented thatits specific capacitance reached503F/g at a current density of2A/g, and thecapacitance remained91%after500cycles. Electrochemical capacitor assembled bygraphene/Co2O3-NiO film showed a capacitance retention of68.4at a current densityof2A/g, energy density and power density reached8.54Wh/kg and208.7W/kgrespectively after500cycles, which exhibited good high current discharge capacity.