Fabrication NiCo2S4/Co9S8 composites as a promising electrode material for supercapacitors

The series of the nonstoichiometry transition metal sulfides (TMSs) composites were fabricated by hydrothermal route. NiCo2S4/Co9S8-3h shows a superior specific capacity (2532.5 F g−1 at 1 A g−1) and 81.9 % capacitance retention at 10 A g−1. Moreover, the assembled NiCo2S4/Co9S8-3h//active carbon (AC) device exhibits a high energy density of 32.9 Wh kg−1 at 750.6 W kg−1 and outstanding capacitance retention of 94.7 % after 10000 cycles.