Effective SEI Formation via Phosphazene‐Based Electrolyte Additives for Stabilizing Silicon‐Based Lithium‐Ion Batteries

Abstract Silicon, as potential next‐generation anode material for high‐energy lithium‐ion batteries (LIBs), suffers from substantial volume changes during (dis)charging, resulting in continuous breakage and (re‐)formation of the solid electrolyte interphase (SEI), well consumption active lithium, which negatively impacts long‐term performance prevents silicon‐rich anodes practical application. In this work, fluorinated phosphazene compounds are investigated additives concerning their SEI‐forming ability boosting silicon oxide (SiO x )‐based LIB cells. detail, electrochemical NCM523 || SiO /C pouch cells is studied, combination with analyses regarding gas evolution properties, post‐mortem morphological electrode SEI, possible degradation. Introducing dual‐additive approach state‐of‐the‐art electrolytes leads to synergistic effects between fluoroethylene carbonate hexafluorocyclotriphosphazene‐derivatives (HFPN), enhanced performance. The formation a more effective SEI increased stabilization improves lifetime results an overall lower cell impedance. Furthermore, chromatography‐mass spectrometry measurements aged HFPN‐derivatives additive compound show suppressed ethylene ethyl methyl decomposition, reduced trans‐ esterification oligomerization products electrolyte.