Electrochemical capacitors (ECs), known as supercapacitors, have attracted great interest as promising energy storage devices due to their high power energy density and long cycle performance than conventional dielectric capacitors. ECs are being considered for different applications such as power sources for camera ash equipment, lasers, pulsed light generators, and as backup power source for computer memory. They also became of interest in hybrid electric vehicles as an auxiliary power source in combination with battery. ECs can provide the peak power in such hybrid systems when accelerating and thus the batteries can be optimized primarily for higher energy density and better cycle-life. Due to its satisfactory electrochemical performance, natural abundance and environmental compatibility, manganese oxide and especially, the composite of manganese oxide with other materials as transition metals, carbon nanotubes or graphene is considered one of the most promising electrode materials for supercapacitor applications.
