A nanocomposite of needle-like MnO2 nanowires arrays sandwiched between graphene nanosheets for supercapacitors

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.