Lithium–sulfur (Li–S) batteries are among the most promising next-generation energy storage systems, offering a high theoretical energy density and cost advantages over conventional chemistries. Yet, their practical deployment is limited by polysulfide shuttling, sluggish reaction kinetics, and poor long-term stability. In this work, we introduce a SnSe2@Ti3C2Tx MXene heterostructure as a multifunctional separator coating that addresses these challenges through a combination of strong polysulfide adsorption, catalytic activity, and rapid electron transport. The SnSe2 nanosheets act as abundant catalytic centers to accelerate the conversion of soluble Li2Sx intermediates, while the Ti3C2Tx MXene matrix provides a highly conductive, polar-terminated scaffold for robust chemical confinement. This cooperative interface suppresses shuttle effects, lowers polarization, and enhances charge transfer kinetics. As a result, cells achieve an initial capacity of 1626 mAh g-1 at 0.2 C with nearly 100% Coulombic efficiency. Even under realistic high-loading (5 mg cm-2) and lean-electrolyte (E/S = 6 μL mg-1) conditions, the system maintains 751 mAh g-1 after 120 cycles with ~71% retention. Long-term cycling at 1 C extends beyond 1000 cycles with stable performance. These results highlight separator engineering as a powerful strategy for advancing Li–S technology and establish SnSe2@MXene heterostructures as a scalable, high-impact platform for practical energy storage applications.
