Uncovering the Residual Electrolyte Quantity in Recycled Battery Black Mass via Liquid Chromatography Tandem Mass Spectrometry and Ion Chromatography‐Conductivity Detection

A workflow for the quantification of electrolyte residues, including linear and cyclic carbonates, conducting salt and selected degradation products from shredded lithium ion battery material black mass, is developed. Therefore, a liquid chromatography method hyphenated to a tandem mass spectrometer is set up which is capable of separating and reliably quantifying standard organic electrolyte compounds showing low limits of quantification and detection. For the quantification of ionic species, ion chromatography with a conductivity detector is used. The combination of data sets shows that up to 5.5 wt% of organic compounds and 2.46 wt% of ionic species are extracted from the black mass with ethylene carbonate and hexafluorophosphate (PF₆ ^-) being the most prominent species. The use of protic solvents, such as water and methanol, results in degradation reactions forming ethylene glycol and fluoride (F^-) respectively. Three different extraction methods are evaluated for their applicability in a quantitative analysis setup. The results demonstrate that shake extraction using the aprotic acetonitrile is the most suitable sample preparation technique with over 90% extraction after a single cycle without introducing solvolysis nor thermal degradation.