Electrophoretically deposited manganese oxide coatings for supercapacitor application

In the present study, manganese oxide electrodes with promising pseudo-capacitive properties were prepared by electrophoretic deposition (EPD) using needle-like manganese dioxide powders. As-deposited coating exhibited a porous microstructure where the size and shape of the starting powders can be observed. The electrochemical performance of the as-deposited coating was then evaluated by cyclic voltammetry (CV) up to 300 times. The initial specific capacitance was 236 F/g which dropped to 200 F/g after 25 CV tests, and decreased gradually to 190 F/g thereafter. The electrochemical behaviors during EPD and CV were examined by synchrotron X-ray absorption spectroscopy techniques from which it was deciphered that a reduction reaction from Mn4+ to Mn3+ occurred during EPD concomitant with re-oxidization during repetitive CV cycles.