Research advance of NiCoP-based materials for high-performance supercapacitors

Transition metal phosphides exhibit a high electrical conductivity and electrochemical activity, which have been widely used in the field of energy storage and conversion, such as, electrocatalysis, LiS batteries and supercapacitors. Compared with single metal phosphides, bimetallic phosphides show a higher electrochemical activity for the synergistic effect between different phosphide phases. Herein, we highlight the recent advance of NiCoP-based electrode materials for constructing high-performance supercapacitors. According to the synthesis procedure, the synthetic method of NiCoP is classified into one-step, two-step and multi-step method, and the relationship between microstructure, performance and preparation method is disclosed. Subsequently, the heteroatom doping of NiCoP is introduced, including the type of dopant and the influence of mono-doping, dual-doping and multi-doping. Based on the characteristic of introduced materials, NiCoP-based composites are classified into NiCoP/carbon or metal framework and NiCoP/active materials. The design principle, electrochemical performance and synergistic effect of different components are highlighted. Finally, the existing problems, possible solutions and future research trends are put forward. We expect that this review will provide practical guidelines for developing metal phosphides-based electrode materials.