▎ 摘　　要

A manganese dioxide (MnO2)-graphene composite material with a unique structure consisting of MnO2 surrounded by graphene sheets was prepared by a simple hydrothermal and thermal decomposition method. The morphology and structure of the obtained materials were examined by scanning electron microscopy, transition electron microscopy, Raman spectroscopy, X-ray diffraction, and N-2 adsorption-desorption. Electrochemical properties were evaluated by cyclic voltammetry, galvanostatic charge- discharge and electrochemical impedance spectroscopy. The specific surface area increased from 109 to 168 m(2).g(-1) for the composite containing 15% (w) graphene. The specific capacitance also increased from 294 to 454 F.g(-1) at a current density of 0.2 A.g(-1) in an aqueous electrolyte supercapacitor. Moreover, after 2000 cycles of a galvanostatic charge-discharge test, the hybrid electrode still had excellent cycle stability (92% retention rate).