Deep eutectic solvents for high-efficiency recovery of valuable metals from spent lithium-ion batteries: Rational design and mechanistic insights

The recovery of valuable metals in cathode materials from spent lithium-ion batteries (LIBs) is crucial for reducing environmental pollution and addressing resource scarcity. In this work, a systematic framework is presented to explore deep eutectic solvents (DESs) as leaching solvents for achieving green and efficient recovery of spent cathodes. Guided by empirical leaching mechanisms suggested in literature, the quantum chemical calculation of coordination ability and reducibility as well as the data-driven estimation of acidity and key physical properties are first integrated for the rational design of promising DESs. The leaching performance and kinetics of as-designed DESs are thoroughly investigated by leaching experiments with spent LiNi0.6Co0.2Mn0.2O2 cathode. The leaching mechanisms of valuable metals in the as-designed DES are deeply elucidated by combining experimental characterization and theoretical calculations. Valuable metals are precipitated from the DES leachate and the cycling performance of the DESs is thoroughly evaluated. Finally, the economic and environmental analysis of the DES-based recycling process is investigated and compared with benchmark processes. This work provides a high-efficiency strategy for valuable metal recovery from spent LIB cathodes, showcasing the mechanism-guided rational design of task-specific DESs.