Sulfur-Deficient TiS2-x for Promoted Polysulfide Redox Conversion in Lithium-Sulfur Batteries

Sulfur-deficient TiS2-x is prepared through high temperature vacuum annealing. Electron spin resonance (ESR) and X-ray photoelectron spectroscopy (XPS) data confirm the presence of sulfur vacancies in TiS2-x. Effective polysulfide adsorption and promotion to polysulfide redox conversion was proven by adsorption simulation experiments and electrochemical measurements. Thus, TiS2-x is used as cathode promoter for Li-S half-cells to improve the overall electrochemical performance. As expected, the TiS2-x/S electrode shows a high and stable capacity of 751 mAhg(-1) even after 500 cycles and a fade rate as low as 0.04% per cycle at 1 C. Besides, the high sulfur loading of the electrode of 4 mgcm(-2) also displays an admirable cycling performance of 963 mAhg(-1) with a capacity retention up to 91.7% over 50 cycles at 0.2 C.