High energy density capacitor using coal tar pitch derived nanoporous carbon/MnO2 electrodes in aqueous electrolytes

Asymmetric aqueous electrochemical capacitors with energy densities as high as 22 Wh kg(-1) power densities of 11 kW kg(-1) and a cell voltage of 2 V were fabricated using cost effective high surface carbon derived from coal tar pitch and manganese dioxide The narrow pore size distribution of the activated carbon (mean pore size similar to 0 8 nm) resulted in strong electroadsorption of protons making them suitable for use as negative electrodes Amorphous manganese dioxide anodes were synthesized by chemical precipitation method with high specific capacitance (300 Fg(-1)) in aqueous electrolytes containing bivalent cations The fabricated capacitors demonstrated excellent cyclability with no signs of capacitance fading even after 1000 cycles (C) 2010 Elsevier B V All rights reserved