Nanostructured ZnCo₂O₄@NiMn-LDH Electrodes for Supercapacitor and Zinc-Air Battery Application

Herein, we have developed a two-step hydrothermal reaction to fabricate core–shell nanostructured ZnCo2O4@NiMn-LDH on nickel foam. The electrode material composition is optimized by different feed ratios of Ni in the shell structure, which is composed of NiMn-LDH. In three-electrode electrochemical analysis, ZnCo2O4@NiMn-LDH (2:1) exhibited a specific capacitance of 5165 F/g at a current density of 1 A/g in 6 M KOH electrolyte. Moreover, the rate capability of retention of ZnCo2O4@NiMn-LDH (2:1) reached 80% at a current density of 4 A/g. Finally, a solid-state asymmetric supercapacitor is assembled by using ZnCo2O4@NiMn-LDH as the positive electrode and α-Fe2O3 as the negative electrode placed inside the Swagelok cell device with a separator. The fabricated supercapacitor ZnCo2O4@NiMn-LDH (2:1)||α-Fe2O3 exhibits an energy density of 64.6 Wh/kg at a power density of 748 W/kg and a cyclic stability of 97.9% after 3000 cycles. For the zinc–air battery (ZAB) application, ZnCo2O4@NiMn-LDH (2:1) delivered a lower overpotential of 390 mV at a 50 mA/cm2 current density with good stability in an alkaline medium. It exhibited a power density of 43 mW/cm2 with stability throughout the 200 h. Both applications suggest that ZnCo2O4@NiMn-LDH is considered an efficient nanostructured electrode for energy applications.