▎ 摘　　要

A nanocomposite of needle-like MnO2 nanowires arrays-graphene (NMNAG) is synthesized by in-situ growth of MnO2 nanowires on the surface of graphene nanosheets (GNS), resulting in a sandwich nanoarchitecture hybrid. The preparation is a simple redox reaction between potassium permanganate (KMnO4) and GNS, which is facile to produce in large scale at low cost. The nanocomposite exhibits high-capacitance performance (276 F g(-1) at 0.5 A g(-1)), excellent rate capability (62.7% capacity retention at 60 A g(-1)), stable cycleability (no degradation after 1200 cycles) and a maximum power density of 21.6 kW kg(-1). (C) 2013 Elsevier Ltd and Techna Group S.r.l. All rights reserved.