Abstract
A symmetrical hybrid capacitor consisting of interdigitated, horizontal nanowires is described. Each of the 750 nanowires within the capacitor is 2.5 mm in length, consisting of a gold nanowire core (40 X approximate to 200 nm) encapsulated within a hemicylindrical shell of delta-phase MnO2 (thickness = 60-220 nm). These Au@delta-MnO2 nanowires are patterned onto a planar glass surface using lithographically patterned nanowire electrodeposition (LPNE). A power density of 165 kW/kg and energy density of 24 Wh/kg were obtained for a typical nanowire array in which the MnO2 shell thickness was 68 +/- 8 nm. Capacitors incorporating these ultralong nanowires lost approximate to 10% of their capacity rapidly, during the first 20 discharge cycles, and then retained 90% of their maximum capacity for the ensuing 6000 cycles. The ability of capacitors consisting of ultralong Au@delta-MnO2 nanowires to simultaneously deliver high power and high capacity with acceptable cycle life is demonstrated.