Closed-loop cobalt recycling from spent lithium-ion batteries based on a deep eutectic solvent (DES) with easy solvent recovery

The recycling of LCO is realized in a closed-loop protocol, where the dissolution/extraction of the cobalt element involves no additional precipitates, thus enabling the reusability of the leaching solution. Efficient recycling technology for the rapid growth of spent lithium-ion batteries (LIBs) is essential to tackle the resources and environmental crisis. Hydrometallurgical approach has attracted extensive research due to its potential to reduce the consumption of energy and threat to the environment. However, the simultaneous realization of green, efficient and closed-loop recycling is still challenging. Herein, we report a closed-loop and highly efficient approach to recycle lithium cobalt oxide from spent LIBs based on a choline chloride:oxalic acid (ChCl:OA) type deep eutectic solvent (DES). An ultrafast leaching process is observed at 180 °C for 10 s with no observable residues. The energy barrier during leaching is calculated to be 113.9 kJ/mol. Noteworthy, the solubility of cobalt ions can be reversibly tuned by simply adding/evaporating deionized water, thus avoiding the addition of precipitant and enabling the easy recovery of the leaching solvent for realizing a closed-loop recycling process. The simultaneous realization of high efficiency, green and closed-loop process is expected to push the DES into practical application for recycling the electrodes of LIBs.