Hexagonal WO3 Nanorods as Ambipolar Electrode Material in Asymmetric WO3//WO3/MnO2 Supercapacitor

Abstract

Unique efficacy of hexagonal WO3 (h-WO3) nanorods (NRs) both as anode and cathode materials realized via a core-shell design for constructing an asymmetric supercapacitor (ASC) with compelling performances is demonstrated. The WO3/MnO2 core-shell NR cathode designed by combining ultra-thin MnO2 nano-flake shell with h-WO3 NR core shows ameliorated electrochemical performance in terms of areal capacitance and rate capability in relation to pristine MnO2 electrodes. The study also elucidates the high charge storage capacity of h-WO3 NRs anode with contributions arising both from redox pseudocapacitance and intercalation capacitance due to proton intercalation/deintercalation inside the intracrystalline tunnels in h-WO3. Accordingly, the WO3//WO3/MnO2 ASC exhibits stable capacitance within a potential window of 1.8 V in an aqueous electrolyte with a volumetric capacitance of 7.22 F/cm3 and an energy density of 3.25 mWh/cm3, characterizing it as one of the state-of-the-art ASCs in the present scenario. The use of versatile h-WO3 NRs in designing both the negative and positive electrodes could be critical in realizing next-generation high-performance supercapacitors.