Selective recovery of cobalt from mixed lithium ion battery wastes using deep eutectic solvent

Despite the efforts devoted to the development of new cathodic materials, cobalt-based lithium-ion batteries (LIBs) remain the first choice for many applications, turning cobalt into a critical raw material. Here, we report a method for the selective recovery of cobalt from mixed LIBs electrode materials. The method relies on the application of a green deep eutectic solvent (DES) and yields an extraction of 90% for cobalt and only 10% for nickel. A solvent extraction procedure was optimized to recover cobalt as cobalt oxalate, which was employed to produce lithium cobalt oxide cathode material. This produced cathode material delivered a discharge capacity of 150 mAh g−1 and a capacity retention between 10 and 100 galvanostatic cycles of 83%. Remarkably, the residual DES solution was reused delivering the same cobalt extraction attained using the fresh DES. Cobalt separation constitutes one of the major bottleneck during LIBs recycling, requiring costly and complex hydrometallurgical operations. The demonstrated selectivity of the implemented leaching method, along with the possibility to reuse the residual DES solution, paves the way to a green recycling alternative allowing for the reintroduction of strategic materials into the LIBs production chain.