NiCo2S4-based nanocomposites for energy storage in supercapacitors and batteries

Abstract NiCo2S4 has received wide attention as a promising electrode material for supercapacitors (SCs), Li-ion batteries (LIBs), and Na-ion batteries (SIBs) in the past few years because of its excellent mechanical property, low cost, and rich redox chemistry. In addition, NiCo2S4 has higher electronic conductivity than the corresponding nickel cobaltite oxide (NiCo2O4) and higher redox ability than the corresponding single-phase sulfide. Nevertheless, the actual applications of pristine NiCo2S4 without unique morphology have been restrained on account of the small specific surface area, agglomeration, and big volume change during cycling, resulting in low reversible specific capacity (capacitance) and poor cycle stability at high rates. Constructing NiCo2S4 with novel nanostructures and heterogeneous core-shell structures have been considered as one of the most promising strategy to solve these problems. In the present review, the recent research developments in the electrochemical reaction mechanisms, preparation methods, morphology control, and electrochemical property of NiCo2S4-based composites as electrode materials for SCs and secondary batteries are summarized. The main focus is to discuss the dominant factors affecting the electrochemical properties of NiCo2S4-based materials, and then highlight hopeful strategies to improve specific capacitances/capacities and cycling stability, especially at high current densities. Finally, several insights into the future developments, challenges, and prospects of NiCo2S4-based composites for SCs, LIBs, and SIBs are proposed.