Enhancements of Interfacial Properties via Organic Sulfonyl Fluoride Electrolyte Additives for High‐Nickel Lithium Batteries

ABSTRACT High‐nickel lithium nickel cobalt manganese oxide (NCM) cathodes suffer interfacial instability that impairs initial efficiency and long‐term cycling. To overcome those problems, we evaluate a series of five sulfonyl fluoride (–SO 2 F) electrolyte additives—Ethenesulfonyl fluoride (A), 2‐(Benzylthio)‐2‐phenylethane‐1‐sulfonyl fluoride (B), 2‐Chloroethane‐1‐sulfonyl fluoride (C), Methyl 2‐(fluorosulfonyl)acetate (D), Methanesulfonyl fluoride (E) for high‐nickel NCM cells. Additives C and E yielded the highest initial Coulombic efficiencies (ICE) (∼90%), markedly higher than other additives. Additives B and E showed higher specific discharge capacity (∼230 mAh/g). X‐ray photoelectron spectroscopy (XPS) revealed that the effective additives E form F‐rich and S‐containing interfacial layers (e.g., LiF and organosulfur species), in contrast to a negligible S signal without additives. These findings demonstrate that –SO 2 F functional additives can significantly enhance the initial efficiency and interphase stability of Ni‐rich cathodes. The results correlate the molecular structure of additives to their film‐forming behavior: proper small alkyl–SO 2 F (E) effectively form protective interphases. This study qualitatively evaluated the influence of SO 2 F moieties on high‐energy lithium battery performance depending on the surrounding materials and provides material‐function‐performance insights for the design of functional electrolyte additives to enhance battery performance.