Designing Polysulfide-Resistant Solid Electrolyte Interphase for Long-Cycling Lithium–Sulfur Batteries

Lithium–sulfur (Li–S) batteries are promising next-generation energy storage systems due to their ultrahigh theoretical energy density. However, their practical application is critically hindered by severe lithium polysulfide (LiPS) corrosion at the Li metal anode, resulting in irreversible Li consumption and rapid cell failure. Herein, a lithium fluoride (LiF)-rich solid electrolyte interphase (SEI) is rationally designed and systematically validated to resist aggressive LiPS corrosion and to enable long-cycle Li–S batteries. Model SEI with LiF reduces the LiPS shuttle current by over 50% and increases the average Coulombic efficiency from 95.6% to 98.0% compared with the SEI without LiF. Building on this mechanistic insight, a robust LiF-rich SEI is prepared via a simple and scalable immersion method. As a result, the cycling lifespan of Li–S coin cells is extended from 54 to 105 cycles, and 3 Ah-level pouch cells exhibit a 28% improvement in cycling lifespan. Furthermore, a 9 Ah-level pouch cell achieves an actual energy density of 493 Wh kg⁻¹ and maintains stable operation for 28 cycles. This work elucidates the critical protective role of LiF in mitigating LiPS corrosion and provides a viable pathway toward long-cycling Li–S batteries.