Investigating the lithium ion battery electrolyte additive tris (2,2,2-trifluoroethyl) phosphite by gas chromatography with a flame ionization detector (GC-FID)

Abstract

The quantification of lithium ion battery electrolyte additives provides challenges in terms of methods and instrumentation. In this work, the detectability of the flame retardant additive tris(2,2,2-trifluoroethyl) phosphite (TTFPi) differs unusually when added to a standard electrolyte (1 M LiPF6 in ethylene carbonate (EC):dimethyl carbonate (DMC) 1:1 wt%) using gas chromatography with a flame ionization detector (GC-FID). In this work, nuclear magnetic resonance (NMR), ion trap time of flight mass spectrometry (IT-TOF™ MS) and gas chromatography-mass spectrometry (GC-MS) are used to investigate a pure TTFPi solution and a standard battery electrolyte with TTFPi as an additive with regard to parasitic TTFPi consuming reactions and different TTFPi concentrations, respectively. NMR and IT-TOF™ MS measurements confirm the chemical stability of the TTFPi/standard electrolyte mixture and concentration dependent GC-MS and GC-FID experiments indicate a premature FID saturation limit for TTFPi in presence of standard electrolyte. The findings explain the counterintuitive absence of TTFPi for higher concentrations and provide important information for future sample preparation.