Gel-electrolyte supercapacitors with thermally annealed electrodeposited Zn-Mn composite electrodes

Abstract Zn–Mn hydroxide was electrodeposited onto carbon cloth via cathodic electrodeposition and then thermally annealed at 300 °C to convert the hydroxide into mixed Zn–Mn oxides. Different annealing durations were explored to determine the optimal conditions. The Zn–Mn composite electrodes were then assembled into supercapacitors by sandwiching a PVA–KOH gel electrolyte between two electrodes. These supercapacitors demonstrated a maximum areal capacitance of 94.91 mF cm −2 and an energy density of 7.85 μWh cm −2 . The capacitance retention remained at 92.3% after 10,000 cycles of cyclic voltammetry (CV) testing and 99% after bending tests (with curvature varying from 0.5 to 1.25 cm −1 ).