A weakly acidic and reductive deep eutectic solvent used for one-step efficient separation of Li and Co from spent lithium-ion batteries

Abstract

A cleaner recycling process for lithium-ion batteries can effectively relieve the pressure on metal resources to protect the environment. In this work, a weakly acidic and reductive deep eutectic solvent (lactic acid:glycolic acid = 1:1) achieves one-step separation of Li and Co from waste lithium-ion batteries. Mechanism of hydrogen bond formation in DESs by interaction region indicators, molecular dynamics simulations, FT-IR and ¹H NMR. Under the optimal experimental conditions (6 h, 100 °C, L/S = 10, MS = 1:1), the DES can achieve more than 99.5 % leaching efficiency of Li. Combined with the shrinkage core model, the leaching rate of DES to Li mainly depends on the chemical reaction rate at the interface. Without any additional precipitating agent, the Co is converted to a precipitating phase. By using UV–vis, FT-IR, ¹H NMR and XPS to explore the leaching mechanism, it was found that the synergistic effect of reducing molecules and coordinating molecules in DES promoted the formation of Co complex precipitates. Finally, the maximum saturation load of DES to Li reached 5.18 mg/g after the cyclic leaching experiment. Both Li₂CO₃ and Co₃O₄ products are obtained after treatment. This study provides a new strategy for low cost, green and sustainable extraction of LiCoO₂.