Long-Term selective electrodialysis experiments for Li separation in LFP battery recycling

Selective electrodialysis (SED) is a promising technique for Li + separation; however, its application in Li-ion batteries (LIBs) recycling requires further studies to assess its feasibility under long-term operation and to develop maintenance protocols that enable continuous operation as a step toward scaling up the process. This work proposed a long-term SED process comprising three sequential stages for Li + separation from LiFePO 4 (LFP) battery leachate. First, the effect of pH (1.0–2.4), Li + concentration (3.2–6 g/L) and coexisting ions (Fe 2+ and Al 3+ ) were evaluated to elucidate system behavior and to define operating conditions for long-term experiment. Li + separation was performed in the first two stages using fresh LFP leached solution, followed by a final purification stage. System limitations were observed (e.g., ion leakage, membrane scaling, maintenance operation and recovery-purity trade-off). Final solution in the process contains 3 g/L Li + (7.8 × 10 −5 to 8.6 × 10 −5 mol/(cm 2 ·h) and 91% purity) with residual 0.3 g/L Fe 2+ and 0.003 g/L Al 3+ reaching Li + separation over 74%, with selectivity values of 5.3–18.8 (Li + /Fe 2+ ) and 18.3–279.9 (Li + /Al 3+ ). Ion-exchange membranes changes were further evaluated revealing degradation of both cationic and anionic membranes, while the monovalent ion-exchange membrane structure and morphology remained unchanged demonstrating its chemical stability after 160 h of operation. Overall, this work advances the understanding of SED for LIB recycling and provides insights for process optimization prior to scaling up.