GREEN SOLVENTS FOR DIRECT CATHODE RECOVERY FROM ELECTRODE SCRAPS

Direct recycling of cathode materials from spent Li-ion batteries (LIBs) or electrode scraps necessitates efficiently recovering valuable active materials from the aluminum foil. The variability in electrode types and recovery processes across previous studies complicates the comparative assessment of the recovery performance of green solvents. Furthermore, constant requirements of high temperature during recovery and impurities retained on the active material surface inhibit the progress to full-scale commercialization. In this study, we evaluated the performance of three green solvents—triethyl phosphate (TEP), dihydrolevoglucosenone (Cyrene), and propylene carbonate (PC)—in recovering valuable active materials from industrial-grade cathode scraps. Using ultrasonication, we developed a standardized, energy-efficient recovery process that eliminated the need for conventional stirring and achieved complete cathode delamination from the aluminum foil. Additionally, solvent washing was implemented on recovered active materials for impurity removal to achieve competitive electrochemical performance. Furthermore, we successfully recovered the used green solvents after the process, ensuring their reuse and supporting a circular economy. The recovered materials retained their original morphology, chemical composition, and crystalline structure; however, the presence of surface impurities varied significantly depending on the choice of green solvent. These impurities considerably impacted the electrochemical performance of the recovered materials. TEP and PC yielded high-purity active materials and aluminum foils suitable for reuse or direct recycling, while Cyrene resulted in substantial residues of PVDF/solvent, requiring washing with stronger solutions such as reagent alcohol. Additionally, the recyclability of these green solvents was influenced by their solubility power for PVDF. This study provides valuable insights into the green solvent-based recycling process and the importance of post-recovery washing steps laying the groundwork for future sustainable practices in LIB recycling.