Prospect of Ni-related metal oxides for high-performance supercapacitor electrodes

Nowadays, supercapacitors become one of the most promising energy-storage systems owing to their high power density, fast charging–discharging rate, and long cyclic stability. Among many supercapacitor materials, nickel-based oxides are a class of promising candidates with high specific capacities. However, the research on these materials has demonstrated that there are some deficiencies that need to be improved, such as their low conductivity, volume shrinkage/expansion during the working process, and moderate cycle stability. It is of urgent to find a suitable method to solve these issues. In this review, we show that multifunctional structures, such as specific core–shell structures, complex formed with metal–organic frameworks, and three-dimensional micro–nanostructures, as well as multi-valence ion doping are practical techniques to boost the supercapacitor performance of these materials. We summarize some recent work related to this topic and emphasize the importance of the synergic effect and electronic doping on the electrochemical supercapacitance of the metal oxides, hoping to provide constructive significance for the future research and development on these materials.