Direct growth of MnO2 on carbon fiber cloth for electrochemical capacitor

Self-standing MnO2 electrodes have been fabricated through the redox reaction between carbon fiber and potassium permanganate. The porous film of birnessite-type MnO2 deposited tightly onto surfaces of the carbon fibers to form manganese dioxide/carbon fiber cloth electrode. The electrodes have not only excellent capacitive performances, but also superior electrochemical stability. Owing to the formation of thin-film morphology, porous structure and the intimate contact between the electroactive material and the current collector, the MnO2 film provides an enhancement of the kinetics by short transport/diffusion path lengths, timely accompanying of electrolyte and large specific surface areas, thus both high energy density and high power density are achieved. In addition to the effective release of stress resulting from charge/discharge, the porous structure also facilitates accompanying electrolyte at high rate operation and avoiding dramatic capacitance fade in cycling. The specific capacitance still retains at least about 84% after continuous 5000 charge/discharge cycles.