Natural Lepidolite Enables Fast Polysulfide Redox for High-Rate Lithium Sulfur Batteries

Lithium sulfur (Li–S) batteries possess energy capacities well beyond those of current Li-ion technologies, but are plagued by severe diffusion loss of sulfur intermediates and sluggish sulfur reduction kinetics. Here, the design is reported of a lepidolite-modified polypropylene (C-Lepidolite@PP) separator to suppress polysulfide shuttling and accelerate the transformation of polysulfides. Because the electrons of S atoms transfer to the 3p antibonding orbits of Si atoms, lepidolite effectively confines polysulfides by forming strong Si–S bonds to weaken the S–S bonds of polysulfides. The ultralow lithium-ion diffusion barrier (0.081 eV) of lepidolite allows for free lithium-ion migration and thus significantly facilitates polysulfide conversion from liquid Li₂S₈ to solid Li₂S to enable fast polysulfide redox for high-rate current operation. With the C-Lepidolite@PP design, Li–S batteries deliver an ultrahigh rate capability of 703 mAh g⁻¹ at 7 C and a high areal capacity of 7.53 mAh cm⁻² with a sulfur loading of 6.5 mg cm⁻². Moreover, the 15-d self-discharge rate is reduced by ≈85% with the C-Lepidolite@PP separator, which provides promise for the practical use of Li–S batteries.