Synergistic S n S e 2 @Ti 3 C 2 T x MX ene Heterostructured Separator for Highly Efficient Polysulfide Adsorption, Catalytic Redox Acceleration, and Enhanced Electrochemical Stability in Advanced Lithium–Sulfur Batteries

Lithium–sulfur (Li–S) batteries hold tremendous promise for next‐generation energy storage due to their high theoretical energy density and low cost. However, commercialization is hindered by severe polysulfide shuttling, sluggish redox kinetics, and rapid capacity decay under practical loading conditions. Herein, we report a rationally engineered SnSe 2 @Ti 3 C 2 T x MXene heterostructure as a multifunctional separator coating that synergistically combines strong Lewis acidic adsorption sites with catalytic interfaces and a highly conductive, polar‐terminated MXene matrix. The SnSe 2 nanosheets provide abundant catalytic centers to accelerate the redox conversion of soluble Li 2 S x species, while Ti 3 C 2 T x ensures rapid electron transport and robust chemical immobilization of polysulfide intermediates. This interfacial synergy effectively suppresses the shuttle effect, lowers electrochemical polarization, and promotes rapid charge transfer. Electrochemical evaluations reveal an initial discharge capacity of 1626 mAh g −1 at 0.2 C with nearly 100% Coulombic efficiency. Under high sulfur loading (5 mg cm −2 ) and lean‐electrolyte conditions (E/S = 6 μL mg −1 ), cells with the SnSe 2 @MXene‐coated separator deliver 751 mAh g −1 after 120 cycles, retaining 70.9% of their initial capacity. Remarkably, long‐term cycling at 1 C exceeds 1000 cycles with 44.4% capacity retention and minimal structural degradation. This work demonstrates a scalable, effective separator‐engineering strategy, establishing SnSe 2 @MXene as a promising platform for practical, high‐energy‐density Li–S batteries.