Vertically Aligned MoS2/MXene Heterojunction as a Bifunctional Separator Coating for Suppressing Shuttle Effect and Enhancing Li+ Transport in Li-S Batteries.

Lithium-sulfur batteries are considered one of the most promising next-generation energy storage systems owing to their high theoretical energy density and natural abundance of sulfur. However, their practical application is severely hampered by the polysulfide shuttle effect and sluggish conversion kinetics. Herein, a two-dimensional MoS2/MXene heterojunction composite (MMS) is rationally designed via one-step hydrothermal growth of vertically aligned MoS2 nanoflowers on conductive Ti3C2Tx MXene substrates. This unique architecture integrates the high conductivity of MXene with abundant catalytic edge sites of MoS2, forming a tightly coupled heterointerface with 1T/2H mixed-phase MoS2 that synergistically enables physical confinement, chemical adsorption, and electrocatalytic conversion of polysulfides. When employed as a functional coating on polypropylene separators, MMS@PP exhibits enhanced electrolyte wettability, high ionic conductivity (1.476 mS cm-1), and a lithium-ion transference number of 0.49. Consequently, Li-S batteries incorporating MMS@PP deliver a high specific capacity of 1294.1 mAh g-1 at 0.1 C with low polarization (161 mV), excellent rate capability (5 C), and outstanding cycling stability with 89.1% capacity retention after 100 cycles at 0.2 C. This work provides a rational heterojunction design strategy for developing multifunctional separators toward high-performance Li-S batteries.