Microwave rapid synthesis of nickel cobalt sulfides/CNTs composites as superior cycling ability electrode materials for supercapacitors

Nickel cobalt sulfides (NCS) have been regarded as potential candidate electrode materials for high-performance supercapacitors owing to the attractive theoretical capacitance. However, traditional synthesis (i.e., hydrothermal) of NCS is both time-consuming and energy demanding, which restricts NCS large-scale practical applications. Herein, a green and effective microwave liquid synthesis followed by a simple post-annealing process was employed to anchor NCS nanoparticles on multiwall carbon nanotubes (CNTs) forming NCS/CNTs-H composites. The NCS/CNTs-H composites hold significantly enhanced electrochemical performance is due to the combination of high redox activity of NCS anchored on superior conductivity of CNTs, which can serve as an effective carrier for NCS and decrease the aggregation of NCS nanoparticles. The optimized NCS/CNTs-H composites display high capacitance of 1261 F g−1 (175 mA h g−1) at 1 A g−1, with a remarkable rate capability, i.e., 84.4% retention from 1 to 50 A g−1. Besides, the assembled hybrid supercapacitor of NCS/CNTs-H//AC could deliver a high energy density (58.4 Wh kg−1 at the power density of 400 W kg−1) and remarkable long-term cycling stability (85.4% capacitance retention after 50 000 charge/discharge cycles). Such impressive electrochemical results indicate NCS/CNTs-H composites could be promising electrode materials for practical supercapacitor applications.