Facile synthesis of yolk-shelled NiO/Ni composites as cathode material for high-performance hybrid supercapacitors

Electrochemical energy storage (EES) devices that combine high-performance are essential to resolve the extreme shortage of non-renewable energy sources and environmental issues. Nickel oxide (NiO) is considered to be a promising EES cathode material because of its ultra-high theoretical specific capacitance, whereas the practical applications are greatly limited with poor rate and cycle performance. Herein, we report the yolk-shelled NiO/Ni composites (YS NiO/Ni) that exhibit good charge storage capability in the aqueous electrolyte with high specific capacitance (2207.3 F g(-1) at 1 A g(-1)), exceptional rate capability, and ultra-high cycling stability (95.8% retention after 10,000 cycles). The superior property can be ascribed to the special yolk-shelled structure that exposes more redox reaction active sites, and the associate Ni nanoparticles with flower-like NiO which can improve electron transfer as current collectors.