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

Abstract 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 Li 2 S 8 to solid Li 2 S 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.