Investigation of thermal aging and hydrolysis mechanisms in commercial lithium ion battery electrolyte

Novel methods based on hyphenated analytical techniques for the analysis of LiPF6 commercially available battery electrolytes are presented. PF6− and the formed main decomposition products F−, PO2F2− and HPO3F− were separated by ion chromatography (IC) and detected by electrospray ionization mass spectrometry (ESI-MS). Inductively coupled plasma optical emission spectroscopy (ICP-OES) on the phosphorous trace supported the results obtained by ESI-MS. Samples, which were stored at room temperature and at 5 °C, were analyzed several times over a period of two weeks to demonstrate the progress of the hydrolysis of LiPF6 in aqueous solution and commercially available electrolyte (EC/DEC (3:7 w/w) 1 M LiPF6). Subsequently, the same commercially available electrolyte system was analyzed to prove the usefulness of the proposed method to investigate the influence of the thermal aging in lithium-ion batteries.