Exploring the influence of hydrogen bond donors in deep eutectic solvents on the extraction of metals during the recycling process of lithium-ion batteries

Abstract

This report introduces an innovative and environmentally friendly approach to recycling lithium-ion batteries (LIBs) utilizing deep eutectic solvents (DESs) as an alternative to mineral acids, commonly employed in traditional hydrometallurgical processes. The focus of this study is on the extraction of valuable metals from LIB cathodes through the application of DESs, emphasizing the critical role of hydrogen bond donors (HBDs) in enhancing the leaching process. We conducted a comprehensive assessment of various complexing agents within the DES framework to evaluate their effectiveness in dissolving metal oxides. Previous reports demonstrated the potential of DESs as green solvents for LIB recycling. However, the activity of various HBDs and the leaching mechanism involved in structurally different molecules that act as HBDs in DESs have not been investigated in detail. Herein, we address this gap by exploring the influence of various HBDs on the dissolution of metal oxides. The results indicate that aromatic acidic HBDs and more effective complexing agents significantly enhance leaching efficiency, achieving up to 96% and 94% extraction of cobalt and lithium respectively from used LIB materials. This finding underscores the importance of selecting appropriate HBDs to optimize metal recovery. Overall, this comprehensive analysis of leaching mechanisms not only contributes to a deeper understanding of the interactions within DES systems but also provides valuable insights for the future design of sustainable solvent systems. © 2025 The Royal Society of Chemistry.