Hexagonal WO 3 Nanorods as Ambipolar Electrode Material in Asymmetric WO 3 //WO 3 /MnO 2 Supercapacitor

Unique efficacy of hexagonal WO 3 ( h -WO 3 ) 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 WO 3 /MnO 2 core-shell NR cathode designed by combining ultra-thin MnO 2 nano-flake shell with h -WO 3 NR core shows ameliorated electrochemical performance in terms of areal capacitance and rate capability in relation to pristine MnO 2 electrodes. The study also elucidates the high charge storage capacity of h -WO 3 NRs anode with contributions arising both from redox pseudocapacitance and intercalation capacitance due to proton intercalation/deintercalation inside the intracrystalline tunnels in h -WO 3 . Accordingly, the WO 3 //WO 3 /MnO 2 ASC exhibits stable capacitance within a potential window of 1.8 V in an aqueous electrolyte with a volumetric capacitance of 7.22 F/cm 3 and an energy density of 3.25 mWh/cm 3 , characterizing it as one of the state-of-the-art ASCs in the present scenario. The use of versatile h -WO 3 NRs in designing both the negative and positive electrodes could be critical in realizing next-generation high-performance supercapacitors.