Advanced Separator Enabled by Sulfur Defect Engineering for High-Performance Lithium–Sulfur Batteries

A rechargeable lithium–sulfur (Li–S) battery is being pursued as a promising candidate for future energy storage and conversion because of its theoretical high energy density and low cost. However, commercial application of Li–S batteries is critically impeded by their notorious shuttle effect and the sluggish conversion kinetics. In this work, we proposed a strategy to enhance the surface adsorption and the conversion of lithium polysulfides with the construction and concentration regulation of sulfur defects in MoS2 nanosheets. The MoS2 with relatively rich sulfur vacancies (MoS2–x-500°C) delivers significantly enhanced immobilization and accelerated conversion of polysulfides. Due to these beneficial effects, the Li–S battery with the MoS2–x-500°C-modified separator delivers a superb initial specific capacity of 961 mA h g–1 at 1 C and the cycling stability with only 0.088% decay per cycle during 300 cycles. Even at the relatively high sulfur loading of 7 mg cm–2, the cell still displays a satisfactory areal capacity of 5.18 mA h cm–2 at 0.2 C. The strategy of sulfur defect engineering proposed in this work has been proven to be a simple but efficient way for constructing high-performance Li–S batteries.