A dual-functional CoF₂@C-coated separator toward synergistic suppression of polysulfide shuttle and Lithium dendrite...

Lithium‑sulfur (LiS) batteries are regarded as promising next-generation energy storage systems, owing to their high theoretical specific capacity (1675 mAh g^-1) and energy density (2600 Wh kg^-1). However, their commercialization is impeded by the shuttle effect of soluble lithium polysulfides (LiPSs) and uncontrolled lithium dendrite growth. Herein, a functional separator coated with cobalt fluoride embedded in carbon (CoF₂@C) is developed. The fluoride-induced strong polar bonds and modulated electronic structures synergistically enhance LiPSs adsorption and facilitate their conversion kinetics. Simultaneously, in-situ formed lithium fluoride (LiF) regulates Li⁺ deposition behavior and suppresses dendrite formation. The CoF₂@C-based cell delivers an initial discharge capacity of 1072.1 mAh g^-1 at 0.2C and maintains 790.3 mAh g^-1 after 500 cycles. Moreover, the Li||Li symmetric cell exhibits an ultralow overpotential of 5 mV over 1000 h at 0.5 mA cm^-2. This work demonstrates a dual-functional separator coating that concurrently mitigates the LiPSs shuttle effect and suppresses lithium dendrite growth, providing an effective strategy for developing high-performance LiS batteries.