Hydrothermal synthesis of VS4/CNTs composite with petal-shape structures performing a high specific capacity in a large potential range for high-performance symmetric supercapacitors.

Vanadium sulfide (VS4) is recognized as a good anode material for energy storage devices because of its chain-like structure and high content of sulfur. Herein, the patronite VS4 anchored on carbon nanocubes (denoted as VS4/CNTs) with a petal-shape structure consisting of nanolayers is successfully prepared through a one-step hydrothermal reaction. The influence of the optimal ratio of VS4 and CNTs on the electrochemical properties of VS4/CNTs composite is studied by cyclic voltammetry (CV), galvanostatic charge-discharge (GCD) and electrochemical impedance spectroscopy (EIS). The addition of CNTs increases the conductivity and relieves the volume expansion/contraction, resulting excellent electrochemical properties of VS4/CNTs. In the potential window of -1.4 V to 1.4 V, the VS4/CNTs composite electrode delivers an outstanding specific capacitance of 330 F g-1 (924 C g-1) at 1 A g-1, which is much higher than that of VS2 with 105 F g-1 (294 C g-1). The VS4/CNTs symmetric supercapacitor (SSC) device exhibits the areal capacitance as high as 676 mF cm-2 (1488 mC cm-2) at 0.5 mA cm-2, and the energy density of 4.55 W h m-2 (51.2 W h kg-1) at the power density of 2.75 W m-2 (30.95 W kg-1) within a large voltage up to 2.2 V. All the results confirm that VS4/CNTs composite with petal-shape structures is a promising material for high-performance energy storage devices.