Separator modification with a high-entropy hydroxyphosphate, Co0.29Ni0.15Fe0.33Cu0.16Ca3.9(PO4)3(OH), for high-performance Li-S batteries.

The shuttle effect of lithium polysulfides (LiPSs) significantly hinders the practical application of lithium-sulfur batteries (LSBs). Herein, a high-entropy hydroxyphosphate (Co_0.29Ni_0.15Fe_0.33Cu_0.16Ca_3.9(PO₄)₃(OH), denoted as HE-CHP), was synthesized by metal cation exchange with calcium hydroxyphosphate (CHP) and then coated on polypropylene (PP) separators to suppress the shuttling of LiPSs. Density functional theory calculations indicated that the various introduced metal cations could effectively modulate the binding strength of soluble polysulfides and enhance the reaction kinetics of LiPSs conversion. As a result, LSBs using the HE-CHP@PP separator exhibited an excellent discharge capacity (1297 mAh g^-1 under 0.2 C) and a slow capacity decay during long-term cycling (0.046 % per cycle at 2 C). At a sulfur loading of up to 6.5 mg cm^-2, the LSB with HE-CHP@PP separator displayed a discharge capacity of 5.8 mAh cm^-2. Notably, the CNT@S||Li Li-S pouch cell with HE-CHP modified separator delivered an initial energy density of 432 Wh kg^-1.