Closed-loop lithium recovery via antisolvent crystallization and the critical role of fluorine impurity control in regenerated LiNi_0.6Co_0.2Mn_0.2O₂ cathodes

This study presents a sustainable hydrometallurgical process for the selective recovery of lithium (Li) from spent lithium-ion batteries (LIBs), followed by cathode regeneration and electrochemical performance evaluation. Water leaching at 90 °C for 1 h enables highly selective Li leaching over transition metals, achieving over 80 % efficiency. Lithium recovery proceeds via optimized antisolvent crystallization using isopropanol, which achieves greater than 99 % precipitation efficiency across a broad concentration range and maintaining robust performance over eight solvent reuse cycles, thereby improving process sustainability. The recovered Li, however, contains fluorine (F) impurities, which originate from thermal decomposition of fluorinated battery components such as polyvinylidene fluoride and lithium hexafluorophosphate in the spent LIBs. Electrochemical testing of regenerated LiNi_0.6Co_0.2Mn_0.2O₂ (NCM622) cathodes indicates that F impurities negatively impact battery performance. Specifically, high F content (3.5 %) results in more than 85 % reduction in discharge capacity compared to commercial NCM622, whereas reducing the F content to 0.1 % restores performance to near-commercial levels. These findings highlight that while controlled F doping offers benefits in synthetic cathode materials, uncontrolled F impurity during recycling severely compromises battery performance. Overall, the results underscore the necessity of effective impurity control for closed-loop on LIB recycling to achieve regenerated battery with commercially competitive performance.