Manganese oxide/graphene oxide composites for high-energyaqueous asymmetric electrochemical capacitors

Abstract

A high-energy aqueous asymmetric electrochemical capacitor was developed using manganese diox-ide ( -MnO2)/graphene oxide (GO) nanocomposites. The nanostructured -MnO2was prepared frommicron-sized commercial electrolytic manganese dioxide (EMD) via a hydrothermal reaction in the pres-ence and absence of sodium dodecylsulphate (SDS), -MnO2(SDS)and -MnO2, respectively. Unlike theas-prepared -MnO2, the presence of SDS during the hydrothermal reaction conferred different mor-phologies on the intermediate precursors for the -MnO2(SDS). Also, the XRD patterns showed that the -MnO2(SDS)are more crystalline than the as-prepared -MnO2. The superior electrochemical perfor-mance of the -MnO2(SDS)/GO composite (280 F g−1, 35 Wh kg−1, and 7.5 kW kg−1at 0.5 A g−1) coupledwith excellent long cycle life clearly indicates that this electrode system has the potential of beingdeveloped as an efficient aqueous asymmetric electrochemical capacitor. The high performance of the -MnO2(SDS)/GO composite was interpreted in terms of the enhanced crystallinity of the -MnO2(SDS).Interestingly, the electrochemical performance is comparable to or even better than those reported for the more conductive graphene/MnO2composites.