Hierarchical porous NiCo2S4-rGO composites for high-performance supercapacitors.

Transition metal sulfides hold great potential for achieving high-performance supercapacitors. Herein, we have rationally fabricated NiCo 2 S 4 nanosheets within three-dimensional (3D) reduced graphene oxide (rGO) via a facile approach. In this unique hierarchical architecture, the 3D rGO serve as interconnected porous matrices that are highly conductive, thus allowing the hybrid electrode to realize fast ionic and electronic transportation. Benefiting from the synergistic effect between NiCo 2 S 4 and rGO, the hybrid electrode delivers substantially improved energy storage capability in a three-electrode system, with high cycling stability of 90% capacitance retention (5000 cycles, 5 A g −1 ). An asymmetric supercapacitor was fabricated with the NiCo 2 S 4 -rGO composites as positive electrode and porous carbon framework-rGO as negative electrode. The asymmetric supercapacitor exhibits a high energy density of 36 Wh kg −1 along with an excellent cycling performance of 95% capacitance retention over 8000 cycles. This presents a promising way to engineer advanced hybrid materials of transition metal sulfides for high energy density supercapacitors. [ABSTRACT FROM AUTHOR]