Ionization potential-based design of deep eutectic solvent for recycling of spent lithium ion batteries

Deep eutectic solvent (DES) is becoming an important alternative for green and high efficient recycling of spent lithium ion batteries (LIBs). In this study, we proposed a simple and universal approach by applying ionization potential (IP) calculation assisted with cyclic voltammetry test to assist selection of organic acid as efficient reductant in the DES for battery recycling. The reducibility of organic acid was found to have a close relationship with the IP, with organic acids of lower IP being a more preferred reductant. Based on this approach, the hydrous choline chloride-L-ascorbic acid DES was identified and verified to be efficient for metals leaching from LiNi1/3Co1/3Mn1/3O2 cathode in multiple cycles, exhibiting leaching efficiencies over 96% for Li, Mn, Co and Ni under a mild leaching condition (50℃, 1 h). The IP calculation is effective for screening reductive acids, and is also feasible for predicting reaction mechanism. Metals were effectively recovered through sequential precipitation. The deep eutectic solvent designed from IP calculation is versatile for treating various kinds of spent battery cathodes and recyclable for multiple uses, decreasing the production of secondary chemical waste and pollution.