Separation and Quantification of Organic Electrolyte Components in Lithium-Ion Batteries via a Developed HPLC Method

The development of a High Performance Liquid Chromatography (HPLC) method with an ultraviolet/visible light (UV/VIS) detector for the separation and quantification of organic carbonates, which are used in common organic carbonate-based electrolyte systems in lithium-ion batteries, is explored. The limit of detection, the limit of quantification as well as the linear range of the developed HPLC-UV/VIS method are reported. Furthermore, the HPLC was coupled to an electrospray ionization mass spectrometer (ESI-MS), also using the atmospheric pressure chemical ionization (APCI)-MS mode, for clear identification of analytes. Object of investigation are pure organic carbonates and thermally aged electrolytes. For the purpose of thermal aging, different electrolyte samples are stored at least one week at selected different temperatures. In addition, the HPLC method is compared to an established gas chromatography with flame ionization detector (GC-FID) and mass spectrometer (GC-MS) method that is also used for the separation, identification and quantification of organic carbonates. For comparison of the GC and HPLC method, an extracted fresh electrolyte out of an EV lithium ion cell was analyzed with both techniques. The developed HPLC method is more sensitive toward electrolyte additives and impurities e.g. vinylene carbonate (VC), Tetrabromobisphenol A (TBBA) and N-Methyl-2-pyrrolidone (NMP) compared to the existing GC method, and is therefore an important and complementary method for the analysis for electrolytes, especially for electrolyte additives.