Recent Achievements on Nonflammable Electrolytes with Ethoxy(pentafluoro)cyclotriphosphazene for Stable and Safe Lithium-Ion Batteries

Abstract

The increasing demand for high-energy-density lithium-ion batteries (LIBs) has intensified concerns regarding electrolyte flammability, interfacial degradation, and thermal runaway. Phosphazene-based compounds, particularly ethoxy(pentafluoro)cyclotriphosphazene (PFPN), have emerged as promising multifunctional electrolyte compounds that synergistically address these challenges. This review systematically summarizes the molecular design strategies and dual functional mechanisms of phosphazene-based compounds. Their flame-retardant capability operates through gas‑phase radical scavenging and condensed‑phase barrier effects. P- and N-containing fragments capture H· and OH· radicals to interrupt combustion chain reactions. Simultaneously, these compounds participate in constructing robust, inorganic-rich solid electrolyte interphase and cathode electrolyte interphase films, suppressing electrolyte decomposition and enhancing interfacial stability. The effectiveness of PFPN-based compounds is evaluated across diverse battery systems, including LiFePO₄, LiNi_xCo_yMn_zO₂, lithium metal, and SiO_x/C anodes, demonstrating significant improvements in cycling stability, overcharge resistance, and thermal safety. Synergistic effects of PFPN with other functional components in composite additive systems are also discussed. Finally, future perspectives are outlined, encompassing advanced in situ characterization, machine learning-assisted electrolyte screening, and validation in large-format cells to accelerate commercial deployment.