Adjustment of Vulcanization Degree to Prepare High-Performance NiCo2S4 Material for Supercapacitors.

Transition bimetallic sulfides exhibit high capacity and outstanding chemical performance in supercapacitors due to their abundant electrochemical active sites and conductivity. In this paper, NiCo₂S₄ with an obvious core–shell nanosphere structure was prepared by adjusting the amount of thiourea by a one-step hydrothermal method. This special core–shell structure of the NiCo₂S₄ material can provide more active sites to make it exhibit better electrochemical performance. The electrochemical performance test results show that the NiCo₂S₄ material prepared with 16 mmol thiourea can reach 1224.0 F g⁻¹ at the current density of 1 A g⁻¹, and maintain 88.74% capacitance even at 10 A g⁻¹. In addition, with the NiCo₂S₄ as the positive electrode and activated carbon as the negative electrode, the supercapacitor (NiCoS₃//AC) can achieve the specific capacitance of 121.9 F g⁻¹ when the current density is 1 A g⁻¹. At a power density of 614 W kg⁻¹, the energy density reaches 38.1 Wh kg⁻¹. The results show that the microstructure of the material is closely related to the amount of thiourea added, and that only appropriate degree of vulcanization is helpful for the formation of core–shell-like NiCo₂S₄ with excellent performance. NiCo₂S₄ material with its unique core–shell structure makes it exhibit a better energy storage performance. [ABSTRACT FROM AUTHOR]