A trade-off-free fluorosulfate-based flame-retardant electrolyte additive for high-energy lithium batteries

The flammability of organic electrolytes raises increasing safety concerns about the high-capacity batteries of next-generation electric vehicles and smart grid systems. Herein, we report a synthetic dual-functional electrolyte additive bearing two-fold fluorosulfate moieties, which allows flame retardancy without sacrificing battery performance. Electrochemical performance is measured using a high-capacity cell built with a Ni-rich LiNi_0.9Co_0.05Mn_0.05O₂ cathode and lithium metal anode. Compared with triphenyl phosphate as a known representative flame-retardant, the fluorosulfate-based electrolyte additive shows remarkable capacity retention, reduced interfacial resistance, and enhanced rate capability via the formation of a stable cathode solid electrolyte interfacial layer due to the inflammable sulfite-to-sulfate conversion mechanism.