Reflux temperature-dependent zinc cobaltite nanostructures for asymmetric supercapacitors

Abstract

Engineering of binary oxide material properties has attracted researchers due to their advance and synergistic application in energy and environment research. Thus, substantial efforts are made for exploring novel synthesis approaches for morphological variations, achieving porous network and high surface area enabling fast ion diffusion and charge transfer, particularly required for supercapacitor applications. With this motivation, the present work demonstrates the temperature-dependent growth of ZnCo₂O₄ nanostructures onto flexible stainless-steel mesh (FSSM) substrate via reflux condensation approach and investigating it as a supercapacitor electrode. The ZnCo₂O₄ nanorods/FSSM prepared at 120 °C exhibit a higher specific capacitance of 315 F g⁻¹ at 2 mA cm⁻² employing 6 M KOH electrolyte. A solid-state ZnCo₂O₄ nanorod (positive electrode)//FeCo₂O₄ nanosheet (negative electrode) asymmetric supercapacitor (ASC) device with PVA-KOH gel as an electrolyte is also fabricated. The ASC device operated at a potential of 1.4 V demonstrates a specific capacitance of 108.4 F g⁻¹ at 6 mA cm⁻². The device delivers a high energy density of 25.45 Wh kg⁻¹ at a power density of 3620 W kg⁻¹ and remarkable cyclic stability with 77% capacitance retention over 3000 cycles.