One-step hydrothermal synthesis of sandwich-type NiCo2S4@reduced graphene oxide composite as active electrode material for supercapacitors

A facile one step hydrothermal process is developed for the synthesis of NiCo2S4@reduced graphene oxide (NiCo2S4@RGO) composite as electrode for electrochemical supercapacitors. This NiCo2S4@RGO electrode exhibits an ultrahigh specific capacitance of 2003 F g−1 at 1 A g−1 and 1726 F g−1 at 20 A g−1 (86.0% capacitance retention from 1 A g−1 to 20 A g−1), excellent cycling stabilities (86.0% retention after 3500 cycles). Moreover, an asymmetric supercapacitor is successfully assembled by using NiCo2S4@RGO nanoparticle as the positive electrode and active carbon(AC) as the negative electrode in 2 M KOH electrolyte. The fabricated NiCo2S4@RGO//AC asymmetric supercapacitor exhibits a high energy density of 21.9 Wh kg−1 at a power density of 417.1 W kg−1 and still remains an impressive energy density of 13.5 Wh kg−1 at a large power density of 2700 W kg−1. The results demonstrate that the NiCo2S4@RGO composite is a promising electrode material as supercapacitors in energy storage.