Manganese oxide films prepared by sol-gel process for supercapacitor application

In this study, manganese oxide electrodes with promising pseudo-capacitive behavior were prepared by sol-gel process using manganese acetate as the precursor. Effects of post-heat treatment on material characteristics and electrochemical properties were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), thermal analysis, synchrotron X-ray absorption spectroscopy (XAS), and cycling voltammetry (CV). Experimental results showed that manganese oxide films prepared by sol-gel technique exhibited Mn2O3 and Mn3O4 phases after heat treating at a temperature higher than 300 degrees C. Meanwhile, a porous manganese oxide coating was observed due to the burnout of organics. The specific capacitance of the manganese oxide electrodes was 53.2, 230.5, 185.6, and 189.9 F/g after heat treating at 250, 300, 350, and 400 degrees C, respectively. After three hundred charging-discharging cycles, the specific capacitance of the manganese oxide electrodes heat treated at 300 degrees C decreased to 78.6% of its maximum. Synchrotron XAS examination revealed that manganese oxide electrodes exhibited the same trend where the trivalent manganese was transited into tetravalent manganese after cyclic voltammetry tests. (C) 2007 Elsevier B.V. All rights reserved.