Attaining a high energy density of 106 Wh kg−1 for aqueous supercapacitor based on VS4/rGO/CoS2@Co electrode.

Graphical abstract An aqueous ASC assembled by a potential-widened positive electrode (VS 4 /RGO/CoS 2 @Co) and a new-developed negative electrode (RGO/Co 9 S 8 @Co), exhibited an ultrahigh energy density up to 106 Wh kg−1. Highlights • Introduction of VS 4 expanded the potential window of CoS 2 from 0.5 to 0.75 V. • VS 4 /RGO/CoS 2 @Co cathode showed a 89.6% retention after 20,000 cycles. • The nanosheet arrays-constructed RGO/Co 9 S 8 @Co was innovatively used as anode. • An ASC device performed an ultrahigh energy density up to 106 Wh kg−1. Abstract Improving the energy density has been being a challenge for supercapacitors, and the efficient approach is to choose active materials (composites) based on the potential window (chemical stability) and theoretical specific capacitance of both matched electrodes, which usually own unique nano-sized and porous (hierarchical) structure. Herein, hierarchical VS 4 /rGO/CoS 2 @Co (VRCS@Co) nanocomposite cathode and rGO/Co 9 S 8 @Co (RCS@Co) anode with nanosheet arrays were both in-situ synthesized on Co foam through a simple one-step hydrothermal process in the presence of graphene oxide (GO). VRCS@Co cathode exhibited a high capacitance of 274.3 mAh g−1 (1353 F g−1) at 0.625 A g−1 and an excellent cyclic life of 89.6% retention at 20,000th cycles, while RCS@Co anode delivered a superior capacitance of 619.5 mAh g−1 (2230 F g−1) at 0.714 A g−1 and a good cyclability of 93.3% retention at 2000th cycles. An asymmetric supercapacitor (ASC) assembled by using VRCS@Co cathode and RCS@Co anode revealed an ultrahigh energy density of 106 Wh kg−1 along with a power density of 2.67 kW kg−1. [ABSTRACT FROM AUTHOR]