The electrochemical performance of a material is primarily determined by its composition, working mechanism, and electronic conductivity. We derive design recommendations of a simple route for preparing Ni–Co binary metal sulfides (NCS) on reduced graphene oxide (rGO) with outstanding electrochemical properties for all-solid-state supercapacitor fabrication. The combination of the two energy storage mechanisms and the synergistic effect between the redox centers are the main reasons for the excellent electrochemical performance of the rGO/NCS material compare to pristine rGO and NCS materials. Specifically, the rGO/NCS material exhibits a specific capacity 125 % higher than that of NCS material and becomes higher up to 224 % compared to the counterpart of the rGO at a current density of 2 A g−1, retention of up to 95.7% initial specific capacity after 10,000 cycles. In addition, in the power density ranging from 1.6 to 16 kW kg−1 the all-solid-state supercapacitor device based rGO/NCS material exhibited an energy density from 23.6 to 47.2 Wh kg−1. And thus, this work indicates that rGO/NCS is a potential material for manufacturing all-solid-state supercapacitors.
