Construction of manganese-cobalt-sulfide anchored onto rGO/Ni foam with a high capacity for hybrid supercapacitors

Ternary metal sulfides such as manganese-cobalt-sulfide (MCS) with the unique physical, chemical properties and high specific capacity can be used as energy storage material for supercapacitor. Herein, we prepared a MCS nanosheet array stick onto reduced graphene oxide (rGO)/Ni foam (MCS/rGO/NF) by a carefully controlled sulfurization time process. As the reaction time increased, the thickness of MCS/rGO/NF nanosheet arrays charged from thin to thick. After 3 h of sulfurization reaction (MCS/rGO/NF-3h), the nanosheets became rough due to the formation of some small sheets, and the composite showed the best electrochemical performance. The MCS/rGO/NF-3h composite exhibited a large specific capacity of 1356 C g−1 at a current density of 1 A g−1, and a long-term cyclic stability of 92.9% at a current density of 10 A g−1 through 3000 cycles. Moreover, a hybrid supercapacitor (HSC) device was assembled using MCS/rGO/NF-3h and rGO as the positive and negative electrodes, respectively. The MCS/rGO/NF-3h//rGO HSC exhibited a high energy density of 45.4 W h kg−1 at a power density of 850.2 W kg−1. The prominent electrochemical performance suggests that MCS/rGO/NF composites are promising electrode materials for energy storage applications.