Ultrathin TA‐MXene Modification Layer with Sub‐Nanometer Interlayer Channels Suppresses Polysulfide Shuttling and Accelerates Li + Desolvation

Abstract Lithium–sulfur (Li–S) batteries are prominent candidates for next‐generation energy storage systems owing to their exceptional theoretical energy density (2600 Wh kg −1 ). Nevertheless, their practical application is hindered by the polysulfide shuttle effect, sluggish sulfur redox kinetics, and lithium dendrite growth. To mitigate these issues, an ultrathin (≈530 nm) tannic acid‐Ti 3 C 2 T x (TA‐MXene) layer is designed. Density functional theory calculations demonstrate that both TA and MXene exhibit excellent anchoring capability for lithium polysulfides. Experiments reveal that TA‐MXene's sub‐nanometer interlayer channels simultaneously suppress polysulfide migration and accelerate lithium‐ion desolvation. The resultant anion‐rich solvation structure fosters an inorganic‐rich solid electrolyte interphase formation, mitigating lithium dendrite growth. Consequently, a Li–S cell with TA‐MXene‐modified separator achieves a high specific capacity of 603.1 mAh g −1 at 4.0 C and retain 90.3% capacity after 100 cycles at 0.2 C. Notably, under high sulfur loading (3.5 mg cm −2 ) and lean electrolyte (10 µL mg S −1 ), the cells demonstrate exceptional cycling stability over 300 cycles at 0.2 C while delivering a remarkable mass/areal specific capacity of 1158.0 mAh g −1 /4.0 mAh cm −2 at 0.1 C. This work establishes a new design principle for separator modifications, demonstrating how ultrathin, lightweight architectures can integrate multifunctionality to overcome the intrinsic limitations of Li–S batteries.