Gas-Phase and Condensed-Phase Synergy in a Nonflammable Electrolyte for Highly Stable Sodium-Ion Batteries

release and interruption of the combustion chain reaction. In contrast, PFPN achieves condensed-phase flame retardancy by forming a dense protective carbon layer at high temperatures, with in-depth X-ray photoelectron spectroscopy (XPS) analysis revealing that P-N/P-F functional groups enable it to act as both a "fire barrier" and an "interfacial stabilizer", thereby preventing continuous decomposition of flammable components. This work provides novel insights for flame-retardant electrolyte design.