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 (Ni₀.₈Co₀.₁Mn₀.₁)O₂‖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.