Synthesis and characterization of nanostructured manganese dioxide used as positive electrode material for electrochemical capacitor with lithium hydroxide electrolyte

A nanostructured manganese dioxide electrode material was prepared using a solid-reaction route starting with MnCl2 center dot 4H(2)O and NH4HCO3, and its electrochemical performance as a positive electrode for MnO2/activated carbon hybrid supercapacitor with I mol center dot L-1 LiOH electrolyte was reported. The material was proved to be a mixture of nanostructured gamma-MnO2 and alpha-MnO2 containing some bound water in the structure, which was characterized by X-ray diffraction analysis, infrared spectrum analysis, and transmission electron microscope observation. Electrochemical properties of the MnO2 electrode and the MnO2/AC capacitor were investigated by cyclic voltammetry, ac impedance and galvanostatic charge/discharge methods. Experimental results showed that the MnO2 electrode exhibited faradaic pseudocapacitance behavior and higher specific capacitance in I mol center dot L-1 LiOH electrolyte. The MnO2/AC hybrid capacitor with I mol center dot L-1 LiOH electrolyte presented excellent rate charge/discharge ability and cyclic stability.