DFT-Based investigation of Amic-Acid extractants and their application to the recovery of Ni and Co from spent automotive Lithium-Ion batteries

To establish more efficient and environmentally friendly lithium-ion battery (LiB) recycling processes, novel extractants derived from amino acids that enable better separation of Ni and Co were explored using density functional theory (DFT) calculations. DFT calculations and experimental validation indicated that of the three coordination sites-namely amine, amide, and carboxyl groups in the amic-acid ligands-the bond strength of the central amine group to the metal determines the Ni and Co separation performance. Based on the findings, the glycine-derived amic-acid extractant N-[N,N-di(2-ethylhexyl)aminocarbonylmethyl]glycine (D2EHAG) was applied for the recovery of Ni and Co from a spent automotive LiB leachate. Preferential and mutual recovery of Ni and Co from manganese by the D2EHAG-based recycling process was demonstrated. This study provides insights into the design of extractants that enable the mutual separation of Ni, Co, and Mn, and indicates the suitability of amic-acid extractants for LiB recycling processes.