Facile Growth of Caterpillar-like NiCo₂S₄ Nanocrystal Arrays on Nickle Foam for High-Performance Supercapacitors

Ternary cobalt nickel sulfide as a novel and efficient electrode material in supercapacitors has recently gained extensive interests. Herein, we first report a highly conductive caterpillar-like NiCo₂S₄, composed of NiCo₂S₄ nanosheet core and nanowire shell grown on Ni foam via a facile and cost-effective chemical liquid process. Growth mechanism of the NiCo₂S₄ nanosheets@nanowires (NSNWs) structure was also investigated in detail by analyzing time-dependent experimental as well as the amount of additive ammonium fluoride in solution. Furthermore, the electrochemical measurements were performed among three different morphologies of NiCo₂S₄ including nanosheets, nanosheets@nanoparticles, and NSNWs structure, which were obtained from different reaction stages. Because the NSNWs structure has relatively high electroactive surface area, conductivity, and effective electron transport pathways, the as-prepared NiCo₂S₄ NSNWs structure comparing with two other morphologies exhibits the maximum specific capacity of 1777 F/g at 1 A/g and the highest capacitance retention (83% after 3000 cycles) at a high scan rate of 10 A/g with a mass loading density of 4.0 mg/cm². These results indicate that the NiCo₂S₄ NSNWs structure has great potential in supercapacitors.