α-Fe₂O₃-Based Core-Shell-Nanorod–Structured Positiveand Negative Electrodes for a High-Performance α-Fe₂O₃/C//α-Fe₂O₃/MnO<i>_x</i>Asymmetric Supercapacitor

Abstract

A α-Fe2O3/MnOx core-shell nanorod (NR)-based positive electrode is designed combining the traits of α-Fe2O3 and MnOx with an ultrathin MnOx shell serving as active site for surface or near-surface based fast and reversible faradaic-reactions and α-Fe2O3 NR core facilitating electron transfer toward the current collector. The α-Fe2O3/MnOx core-shell NR electrode shows ameliorated electrochemical performance in terms of capacitance and rate capability within the potential window of 0–1 V in relation to both pristine α-Fe2O3 NR electrode and pristine MnOx thin film electrode. Similarly, α-Fe2O3/C core-shell NR negative electrode is also realized. The assembled α-Fe2O3/C//α-Fe2O3/MnOx core-shell NR asymmetric supercapacitor (ASC) exhibits a volumetric capacitance of ∼ 1.28 F/cm3 at a scan rate of 10 mV/s with nearly 78% capacitance retention at the scan rate of 400 mV/s within a potential window of 0–2 V in aqueous electrolyte medium. Interestingly, the ASC delivers a maximum energy-density of ∼ 0.64 mWh/cm3 and a maximum power-density of 155 mW/cm3, which are higher than the values obtained for α-Fe2O3 //α-Fe2O3/MnOx core-shell NR ASC. Thus the study clearly exhibits the potency of core-shell nano-architechtured electrode design in realizing high-performance, cost-effective and environment-friendly ASCs.