Quantification of ionic organo(fluoro)phosphates in decomposed lithium battery electrolytes

Abstract

A method for the separation, identification and quantification of the ionic decomposition products of LiPF₆ based organic electrolytes was developed. It employed the simultaneous coupling of two-dimensional ion chromatography (2D IC) with electrospray-ionization mass spectrometry (ESI-MS) and with inductively coupled plasma-mass spectrometry (ICP-MS). The electrolyte under investigation was a commercially available electrolyte by BASF, consisting of 1 mol L⁻¹ LiPF₆ in a mixture of one linear and one cyclic organic carbonate (50 : 50 wt%). The quantification was based on the use of a structurally similar compound as calibration standard for the ICP-MS measurement, while the identification was carried out with ESI-MS. Several organo(fluoro)phosphate species were successfully separated and quantified. Since these species show a high structural similarity to the warfare agent sarin, their investigation is of special interest with regard to their potential toxicity. Additionally, a quantification study of an electrolyte extracted from a cycled lithium metal cell was carried out.