Nb2O5/reduced Graphene Oxide Nanocomposite Anode for High Power Hybrid Supercapacitor Applications

Hybridizing faradaic and non-faradaic charge storage mechanisms permits hybrid supercapacitors to achieve desirable high energy-power characteristics. Although the hybridization approach increases the energy density, discrepancies in the reaction kinetics, especially sluggish charge-transfer reactions in Faradaic battery-type electrodes, curtails the power density. To increase the power density of battery-type electrodes, an orthorhombic phase of niobium pentoxide (Nb2O5) is one of the most prominent contenders because the orthorhombic crystal structure provides two-dimensional transport channels for fast Li-ion diffusion. However, such ultrafast Li-ion diffusion cannot be realized due to its electrical-insulating nature. Herein, we synthesized a composite of the orthorhombic phase of niobium pentoxide (Nb2O5) interconnected with reduced graphene oxide nanosheets via facile microwave assisted methods. Such a dual-conductive composite anode exhibits excellent rate performance to match that of the cathode which operates conventional adsorption-desorption charge storage mechanism. By combining the composite anode with a nitrogen doped reduced graphene oxide (N-rGO) cathode, the device delivers maximum energy density of 89 Wh kg(-1) (at 125 W kg(-1)), and the energy density of 20 Wh kg(-1) is retained even at 3500 W kg(-1), which is one of the highest energy density reported for Nb2O5 based HSC to the best of our knowledge.