Enabling electrolyte recycling: Sustainable extraction and separation from black mass using supercritical carbon dioxide

A two-step approach has been developed to enable the recovery of electrolyte from lithium ion battery (LIB) recycling material (black mass), providing a suitable route for extracting and separating electrolyte components. In the first step, the electrolyte is extracted from black mass using supercritical carbon dioxide (ScCO 2 ) in combination with sustainable modifiers such as methanol (MeOH) and isopropanol (IPA). In a second step a supercritical fluid chromatography (SFC) method enables the separation of the electrolyte compounds in five fractions. The electrolyte fractions demonstrate high purity, ensuring their reuse as LIB electrolyte. While IPA exhibits weak solvating capabilities when used as modifier for the ScCO 2 extraction of the conducting salt anion PF 6 − , it was shown that MeOH leads to a high extraction. Total extraction rates of 5.83 wt% and 4.68 wt% of extracted electrolyte compounds could be achieved, respectively corresponding to an extraction yield of 62 to 81% for the main compounds, ethylene carbonate and hexafluorophosphate. The developed SFC method for the separation of the extracted electrolyte compounds yields in total five fractions, the first consists of linear carbonates, the second consists of the bicarbonate aging products, followed by separately eluting ethylene carbonate, water and PF 6 − . • A two-step approach has been developed to enable the recovery of electrolyte. • The recovered electrolyte mixture could be efficiently separated into individual fractions. • Purity was investigated and confirmed.