Nanostructured MnO2/exfoliated graphite composite electrode as supercapacitors

Nanostructured manganese oxides/exfoliated graphite composite (MnO2/EG) were synthesized via a new sol-gel route. Scanning electron microscope (SEM) was employed for surface morphology and X-ray diffraction (XRD) was used for structure characterization. Cyclic voltammetry (CV), galvanostatic charge/discharge, and the electrochemical impedance measurements were applied to investigate the electrochemical performance of the MnO2/EG composite electrodes. When used for electrodes of supercapacitors, the as-prepared MnO2/EG and the pure MnO2 exhibited excellent capacitance characteristics in 6 mol L-1 KOH electrolyte and showed high specific capacitance values of 398 F g(-1) and 326 F g(-1), respectively, at a scan rate of 10 mV s(-1). The galvanostatic charge-discharge measurements showed approximately 0.5% loss of capacitance after 500 cycles, and charge-discharge efficiency above 99%. In addition, the synthesized nanomaterial showed a good reversibility and cycling stability. (C) 2009 Elsevier B.V. All rights reserved.