Fluoroisatin Mediation Unlocks Durable Lithium–Sulfur Batteries Via Self‐Regulating Solvation Engineering and SEI Reinforcement

ABSTRACT Lithium–sulfur (Li–S) batteries face significant commercialization hurdles, predominantly due to challenges in promoting sulfur conversion reactions and simultaneously stabilizing cathode/electrolyte/anode interfaces. To tackle these issues, Fluoroisatin (FRN), as an electrolyte additive, was introduced in Li–S batteries, which dissolves in the electrolyte, undergoes partial deprotonation, and reacts with LiTFSI/lithium polysulfides. Consequently, it can regulate sulfur conversion pathways, accelerate reaction kinetics, and construct a LiF‐rich solid‐state electrolyte interface. The Li–S battery, with merely 0.5 wt% FRN additive and operating at −20°C, shows a high initial discharge capacity of 912 mAh g −1 at 0.2 C, and it is maintained at 830 mAh g −1 after 120 cycles. The potential of FRN, as a versatile electrolyte modifier, has potential for using in high‐performance Li–S batteries.