Deep eutectic solvent‐assisted selective extraction of valuable metals from waste lithium‐ion batteries

Abstract

AbstractA novel synergistic extractant consisting of a deep eutectic solvent (DES) and tri‐n‐butyl phosphate (TBP) is proposed for selective extraction of valuable metals from waste lithium‐ion batteries (LIBs). The extraction efficiencies of Ni2+, Co2+, and Mn2+ were 99.8%, 99.1%, and 95.9%, respectively, and high‐purity Li+ was enriched in the raffinate after the single‐stage extraction. Valuable metal salts, lithium carbonate (92.3 wt%) and cobalt oxalate (94.9 wt%), were obtained. The DES + TBP extractant retained its high extraction performance even after multiple regeneration cycles. The extraction process followed the so‐called “cation exchange mechanism” with thermodynamic properties of ΔH < 0, ΔG < 0, and ΔS < 0. The molecular‐level extraction mechanism demonstrated that the extraction process was dominated by both electrostatic and coordination interactions between the metal ions and DES/TBP, based on quantum chemical calculations. This study aims to provide a new strategy for recycling valuable metals from waste LIBs.