High-Performance Supercapacitor with a Hybrid Nanostructure of Sputter-Decorated AgxO over Co–Mn–Cu Ternary Metal Oxide

Recent studies have indicated that ternary and quaternary metal oxides are efficient electrode materials for supercapacitors, owing to synergism between multiple metal ions. Herein, we report quaternary composite (QC) electrodes with hybrid nanostructures, consisting of AgxO nanostructures sputter deposited over flower-like copper–manganese–cobalt oxide (CMC) nanostructures. AgxO nanostructures were deposited using a DC magnetron sputtering system at different plasma powers. The morphology of the QC electrodes and the relative abundance of different oxidation states of Ag vary with plasma power, which affects the electrochemical performance of the electrodes. QC electrodes fabricated at 45 W plasma power had well-defined AgxO nanodots on partially exposed CMC nanoflowers, which outperformed the QC electrodes with other morphologies, as well as ternary metal oxide and AgxO-based electrodes. A specific capacitance of 2136 F/g at a scan rate of 1 mV/s was obtained with the outperformed electrode. The solid-state symmetric supercapacitor assembled with the best-performed electrodes delivered an energy density of 98.16 W h kg–1 at a power density of 3000 W kg–1.