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

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.