Abstract: Intrinsic polysulfide shuttling is the most fatal problem with Li-S batteries but it can be suppressed by functionalizing the separators with strong lithium polysulfide absorbents. Carbon nanotube (CNT)-supported MoSe₂ nanoflakes with a large interlayer spacing were coated on a commercial polypropylene separator to build an efficient barrier (M/C-PP) to polysulfide shuttling for Li-S batteries. The battery with the separator had initial specific capacities of 1 485 and 880 mAh g⁻¹ at 0.1 and 2 C, respectively, and an excellent long-term cycling stability with a low decay rate of 0.093% per cycle at 0.5 C after 300 cycles. This excellent performance was attributed to the strong adsorption of polysulfides by MoSe₂ and the fast charge transport channels provided by the CNTs.