Abstract

The increased usage of EVs will result in rising quantities of end-of-life LIBs. This requires recycling processes capable of recovering valuable metals while minimizing associated environmental impacts. Established metallurgical processes for Li extraction utilize hydro- and pyrometallurgical approaches involving concentrated mineral acids and several separation steps. In addition, emerging deep eutectic solvents (DESs) show promise in tailoring coordination chemistry for effective metal leaching. However, much of the available DES-related literature tends to focus on leaching performances and rarely on downstream process stages aimed at obtaining the desired precursor product. Therefore, the present study aims to fill this knowledge gap by developing an approach towards Mn “leach-to-precursor” via DES leaching, Mn-specific solvent extraction (SX), and MnCO₃ precipitation.
Two related experimental systems were established. Firstly, a choline chloride-D-glucose DES modified by 10 wt.% water was investigated for efficient dissolution of Mn-containing spent cathodes to enhance mass transfer while retaining DES characteristics. Under optimal conditions, nearly 100% dissolution was obtained for lithium and manganese, compared to 71% dissolution of nickel. Secondly, selective Mn extraction from multicomponent Mn-Co-Ni-Li DES extractant solution was achieved using D2EHPA in kerosene. Under optimal conditions, Mn extraction reached 89.7%, with low cobalt and nickel co-extraction and large separation factors (βMn/Co = 143; βMn/Ni = 208). Two-step acid stripping resulted in 94.8% Mn recovery, whereas carbonate precipitation under neutral pH (7-8) yielded rhodochrosite MnCO₃ with 95.3% Mn precipitation recovery and overall recovery of 81.0%.