Pseudocapacitive behaviors of mesoporous nickel–cobalt oxide nanoplate electrodes in different electrolyte systems

Abstract

NiCo₂O₄ nanoplates are grown on cellular nickel foam using a facile microwave-assisted method and employed as electrodes for supercapacitors. The mesoporous NiCo₂O₄ electrodes with strong adhesion with the Ni current collector have large electroactive surface areas, allowing fast ion and electron transport. The electrodes exhibit much better supercapacitive performance in a 2 M KOH electrolyte than 2 M NaOH and 2 M LiOH systems due to the smaller radii of hydration spheres, faster mobility and higher ionic conductivity of KOH. The electrodes deliver an excellent specific capacitance of 1188 F g⁻¹ at a current density of 2 A g⁻¹ in KOH solution and a remarkable cyclic stability of 93.1% capacitance retention after 3000 cycles. In addition, the symmetric device exhibits a remarkable specific capacitance of 213.2 F g⁻¹, a high power density of 5 kW kg⁻¹ and an energy density of 29.6 W h kg⁻¹. The facile and cost-effective synthesis process of the mesoporous NiCo₂O₄ electrode material adds to its exceptional pseudocapacitive performance to offer significant potential for practical energy storage applications.