Composite Electrodes Made from Carbon Cloth as Supercapacitor Material and Manganese and Cobalt Oxide as Battery One

Abstract

Mn oxide and/or Co oxide are deposited on flexible carbon cloth by a cathodic potentiodynamic procedure from their respective sulfates. In KOH electrolyte, the charge stored from reversible redox reactions of the two oxides (battery response) overlaps with the charge stored from the double layer of the carbon cloth (supercapacitor response). These charges or capacities are compared. For the electrodes having one oxide only, either Mn or Co oxide, the highest capacity is obtained for 8 wt% oxide load. To overcome this limitation, both Mn and Co oxide are simultaneously or sequentially electrodeposited on carbon cloth over a broad compositional range. The electrode capacity can reach 71 mA·h·g-1 or 0.9 mA · h · cm-2, which are higher than the values found for the bare carbon cloth. The electrode capacity depends on the relative content of the carbon cloth and the two deposited oxides according to the rule of mixtures. The decrease of the specific surface area of the carbon cloth is discussed in relation to the deposited oxide. The high capacity retention vs current is due to the contribution of the carbon cloth substrate. The electrode cycle life is discussed on the basis of the supercapacitor response and battery one.