Efficient Recovery of Lithium and Cobalt from Spent Lithium-Ion Batteries Using a ChCl-OA-H2O Deep Eutectic Solvent

• • Achieved 99.4% Li leaching efficiency and 97.8% Co recovery as CoC2O4·2H2O under optimal conditions (ChCl:OA:H2O molar ratio 1:1:8, solid-liquid ratio 100 g/L, 90 °C, 6.5 h), demonstrating near-complete metal extraction from spent LiCoO2. • • Lithium recovery via evaporation crystallization as Li2C2O4 reached 88.3%, enabling selective separation without additional precipitants, simplifying the process and reducing chemical consumption. • • The DES solvent exhibited excellent reusability: after six regeneration cycles, Li and Co recoveries remained at 78.1% and 92.8%, respectively, underscoring process sustainability and cost-effectiveness for industrial scale-up. • • The water-regulated strategy allows precise control of metal speciation, providing a mechanistic basis for selective recovery and offering a green alternative to conventional acid leaching methods.