Combined Thermodynamic‐Electrochemical Understandings of Non‐Flammable Electrolyte for High‐Nickel Lithium Batteries

The high flammability of high‐energy‐density lithium batteries remains a critical safety challenge, while the low reduction potential and high cost of conventional flame‐retardant materials limit their practical use. Here, we report a synergistic design strategy for non‐flammable and fluorine electrolyte additive combinations that stabilize high‐nickel layered cathodes and enable both high energy density and safety. Through a systematic additive screening and thermodynamic analysis based on Gibbs free energy–derived reduction potentials of P2PFS (4,4'‐(propane‐2,2‐diyl) bis (4,1‐phenylene) disulfo‐ fluoridate) and related species, we identified additive interactions that suppress exothermic decomposition of carbonate electrolytes. The optimized electrolyte exhibited near non‐flammability, significantly improved cycle retention (83% after 200 cycles at 0.3 C), and enhanced interfacial robustness, as confirmed by XPS and TEM analyses. Moreover, 1 Ah‐level Li (Ni 0 . 8 Co 0 . 1 Mn 0 . 1 )O 2 ‖graphite full cells demonstrated excellent long‐term stability (>700 cycles) and no thermal propagation under nail penetration, validating the intrinsic safety of our formulation. The combined thermodynamic–electrochemical approach provides new insights into designing next‐generation electrolytes that harmonize non‐flammability, cost‐effectiveness, and high‐voltage stability for advanced lithium‐ion batteries.