▎ 摘　　要

Innovative materials with excellent cyclic performance become the mantra for energy storage. Graphene encapsulated NiS/Ni3S4 (NSG) nanostructure is synthesized via polyethylene glycol assisted one-step hydrothermal method. The encapsulated nanostructure is examined for supercapacitor applications. The NSG nanostructure offers a large specific capacity of 827 C g(-1) at 5 A g(-1) (pristine PEG assisted nickel sulphide yields 574 C g(-1)) and shows good cyclic stability (88%) and Coulombic efficiency (95%) after 5000 cycles at a high and practically useful specific current of 70 A g(-1). The superior electrochemical performance of NSG is due to its high conductivity, high surface area, a synergistic effect between the graphene and nickel sulphide and their mesoporous graphene encapsulated nanostructure. The NSG and reduced graphene oxide based asymmetric supercapacitor device achieves a maximum energy density of 86.3 W h kg(-1) at 2 A g(-1) with excellent device stability (98%) over 5000 cycles. The superior electrochemical features of NSG makes it a potential electroactive material for supercapacitor applications. (C) 2020 Elsevier Ltd. All rights reserved.