Designing Green Deep Eutectic Solvents for Selective Lithium Recovery: From Thermodynamic Screening to Electronic Structure Insights

Abstract Sustainable and selective recovery of lithium ions is essential for environmentally responsible lithium-ion battery recycling. In this work, we established a multiscale theoretical framework to elucidate the mechanisms underlying lithium-ion recognition and complexation in low-melting-point green solvents, with a particular focus on deep eutectic solvents (DESs). Guided by the COSMO-RS framework and complemented by thermophysical property databases and QSPR methods, 111 potential hydrogen bond donors were screened, resulting in 28 compounds capable of forming stable DESs with choline chloride. Their eutectic behavior was validated through solid–liquid equilibrium calculations. Lithium-ion solvation in these DESs was evaluated using the infinite dilution activity coefficient model, revealing clear structure–activity relationships between hydrogen bond donor molecular structures and lithium-ion affinity. Representative systems were further investigated using density functional theory and electron localization function analysis, confirming the presence of directional lithium-bond interactions with partial covalent characteristics. The coordination strength was found to be governed by the number and spatial arrangement of oxygen atoms in the donor molecules. This study provides molecular-level insights and a rational design strategy for developing DES-based green solvents for lithium recovery and related separation applications.