Fabrication of vanadium sulfide (VS4) wrapped with carbonaceous materials as an enhanced electrode for symmetric supercapacitors.

Exploring electrode materials with excellent electrochemical performance is the key to the development of applications in energy storage and conversion. Herein, three-dimensional (3D) vanadium sulfide/carbon nanotubes/reduced graphene oxide (VS4/CNTs/rGO) composite is synthesized by a simple one-step hydrothermal method. VS4 short nanorods cover the both sides of the rGO sheets, and CNTs distribute at the edge of the composite to form a sandwich-like structure, which effectively prevents the accumulation of rGO. Due to the special 3D hierarchical structure, VS4/CNTs/rGO exhibits a large specific surface area and a rich pore structure, and the addition of CNTs and rGO also improves the electrochemical properties of VS4. At 1 A·g-1, VS4/CNTs/rGO exhibits a capacitance of 497 F·g-1 (1374.0 C·g-1) in the voltage range of -1.4 to 1.4 V, which is much higher than those binary materials including CNTs/rGO, VS4/CNTs and VS4/rGO. The VS4/CNTs/rGO symmetric supercapacitor (SSC) device shows a remarkable electrochemical performance in a large potential window up to 2.2 V. The capacitance of VS4/CNTs/rGO SSC device can reach 1003.5 mF·cm-2 (2207.6 mC·cm-2) at 0.5 mA·cm-2, and it exhibits an energy density of 6.75 Wh·m-2 (72.07 Wh·kg-1) at a power density of 1.38 W·m-2 (14.69 W·kg-1). The high capacitance and energy density of the VS4/CNTs/rGO composite in the high voltage interval make it as the potential energy storage material.