Ultrafast Microwave Synthesis of Nickel-Cobalt Sulfide/Graphene Hybrid Electrodes for High-Performance Asymmetrical Supercapacitors

Abstract

Nickel-cobalt sulfides (NCSs) with rich redox-active sites and remarkable theoretical capacitance have been regarded as promising electrode materials for supercapacitors. Various approaches have been developed for the synthesis of NCSs-based electrode materials. However, most of these methods require complex steps, high energy consumption, and time-consuming processes, which result in high cost, chemical contamination, and safety problems. Herein, we demonstrated a one-step ultrafast microwave approach for the successful preparation of NCS/graphene composite in 1 min. The prepared NCS/graphene composite can be used as a high-performance supercapacitor electrode with a high specific capacitance of 710 F g–1 at a current density of 0.5 A g–1 and a prominent cycling stability of 75% capacitance retention after 10 000 cycles. In addition, a high-performance asymmetric supercapacitor (ASC) was assembled using NCS/graphene composite as a positive electrode and activated carbon as a negative electrode. The fabricated ASC can deliver a high energy density of 30.29 Wh kg–1 at a power density of 400 W kg–1 and exhibit excellent cycling stability with a capacitance retention of 112% after 10 000 cycles. These impressive results demonstrated that microwave synthesis can be used as a highly efficient and ultrafast approach for the preparation of high-performance NCSs-based electrode materials.