We present a new design for an asymmetric supercapacitor combining a vertically aligned Ni/Ni(OH) 2 nanowire array electrode and a graphite-based electrode. The arrangement of these two electrodes in a sandwiched fashion allows the device to function at a high operating voltage window of 2.0 V in an aqueous electrolyte. A thin layer of Ni(OH) 2 can be readily formed on Ni nanowires (NiNWs) to yield a Ni/Ni(OH) 2 structure. The redox reaction of Ni(OH) 2 formed on the surface of NiNWs was crucial in achieving improved capacitance over this wide voltage window. The modification of the graphite electrode using graphene flakes was found to provide a more stable response at high current densities. The shape of the voltammogram can be retained up to high values and thus the device can operate at very rapid charge/discharge rates at an enhanced voltage window. Furthermore, the capacitance was found to be unchanged after 10000 continuous potential cycles.[a] Dr.