Communication—A Phosphorus Pentafluoride Scavenger to Suppress Solid Electrolyte Interphase Damage at Moderately Elevated Temperature

Abstract

We demonstrate that lithium/silicon monoxide (SiO) cell failure can be hindered by utilizing a Lewis-basic tris(2,2,2-trifluoroethyl) phosphite (TTFP), as an electrolyte additive. In the absence of TTFP, the solid electrolyte interphase (SEI) on the SiO electrode is attacked by Lewis-acidic phosphorus pentafluoride (PF5) generated by thermal decomposition of lithium hexafluorophosphate (LiPF6) at moderately elevated temperature. The SEI damage is followed by electrolyte decomposition/film deposition on the damaged electrode surface causing film growth, which leads to severe cell polarization and eventual failure. Conversely, effective PF5 scavenging by TTFP through Lewis acid-base adduct formation decreases SEI damage and thus hinders cell failure.