| Summary: | 碩士 === 東海大學 === 化學系 === 106 === In this study, the composites consisting of vanadium metal oxide and three dimensional graphene (VOx-3DG) were synthesized using the hydrothermal method and the as-synthesized composites were used as the electrode materials for supercapacitors. VOx-3DG can be used as a cathode material for supercapacitors and shows the specific capacitance of 400 mF/cm2 at 1 mA/cm2 current density in 0.5M KCl electrolyte, with a poor cycling stability. Therefore, electrochemical properties have been examined by using redox additive VOSO4 (0.5 g) in 0.5M KCl at a controlled pH (2.60) using Glycine buffer (0.25M) to maintain the stability of electrode with electrodeposition. Thus, redox additive VOSO4 has improved the overall performance of the capacitor by controlling the effective electrode weight and ion conduction more quickly. In that way, the overall resistance has been reduced and the overall performance of the electrode increased as compared to pure KCl solution. To examine the capacitive performance of the composite electrode in a full-cell configuration, an asymmetric supercapacitor device is fabricated by using the VOx-3DG composite as the cathode and reduce graphene oxide as the anode. The asymmetric supercapacitor device has been operated reversibly from 0 to 1.6V, and a high specific capacitance of 44.8 F/g at 0.25 A/g has been observed. It delivers a maximum energy density of 22.17 Wh/kg at a power density of 952.68 W/kg. Furthermore, the asymmetric supercapacitor retains 95.8% of its initial capacitance after a consecutive 4000 cycles of galvanostatic charge-discharge at a current density of 1 A/g.
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