Spinel NiCo2O4 nanowires synthesized on Ni foam as innovative binder-free supercapacitor electrodes

Abstract

Well-organized, independent nanoscale binary metal oxides exhibit high electrical conductivity and good ion transportability. In this study, a nickel-cobalt oxide (NiCo2O4) nanoparticle electrode was synthesized on Ni foam with a large surface area. Such a composite material is valuable as a binder-free and excellent current-carrying electrode material. Hence, it is particularly attractive for high-performance energy storage systems. NiCo2O4 nanowires were fabricated via a simple chemical bath deposition process. Consequently, the NiCo2O4 electrodes exhibited a remarkable specific capacity of 342.5 mA h g−1 at the current density of 3 A g−1 and cycling stability of 80.7%, which was maintained following 10,000 long-cycles at 5 A g−1. In addition, an asymmetric supercapacitor (NiCo2O4//graphite) device comprising of NiCo2O4 as a positive electrode and graphite as a negative electrode was fabricated. The NiCo2O4//graphite asymmetric supercapacitor has the highest energy density of 45.8 W h kg−1, and an excellent power density of approximately 5689 W h kg−1. Furthermore, NiCo2O4//graphite device delivered sufficient capacitive power to enlighten a red LED indicator. The excellent electrochemical performance of the asymmetric supercapacitor device can be attributed to the high specific surface area of the cathode electrode material and its enriched redox kinetics. This paper presents an easy and environmentally-friendly procedure for fabricating a compound electrode material for an asymmetric supercapacitor. It is expected that this novel high-performance electrode can stimulate new directions in the development of efficient energy storage.