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 MoS₂nanosheets. The MoS₂with relatively rich sulfur vacancies (MoS_2-x-500°C) delivers significantly enhanced immobilization and accelerated conversion of polysulfides. Due to these beneficial effects, the Li-S battery with the MoS_2-x-500°C-modified separator delivers a superb initial specific capacity of 961 mA h g^-1at 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^-2at 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.