Three dimensional vanadium pentoxide/graphene foam composite as positive electrode for high performance asymmetric...

The electrochemical performance of hydrothermal synthesized three dimensional (3D) orthorhombic vanadium pentoxide (V₂O₅) nanosheets and vanadium pentoxide/graphene foam (V₂O₅/GF) composites at different mass loading of GF were successfully studied. The optimized V₂O₅/GF-150 mg composite provided a high specific capacity of 73 mA h g^-1, which was much higher than that the pristine V₂O₅ (60 mA h g^-1) nanosheets at a specific current of 1 A g^-1. A hybrid capacitor was also fabricated by adopting a carbon-based negative electrode obtained from the pyrolysis of an iron-PANI polymer (C-Fe/PANI) mixture and the 3D V₂O₅/GF-150 mg composite as the positive electrode in 6 M KOH electrolyte. The hybrid device of V₂O₅/GF-150 mg//C-Fe/PANI demonstrated a high energy density of 39 W h kg^-1 with a corresponding high power density of 947 W kg^-1 at a specific current of 1 A g^-1 in an operating voltage window of 0.0-1.6 V. The hybrid device also exhibited an excellent cycling stability with 74% capacity retention recorded for up to 10,000 constant charging-discharge cycles and an excellent ageing test at a specific current of 10 A g^-1.