Electrodialysis in osmosis tube with ionic liquid membrane for recovery of cathode materials from spent Li-ion battery

An electrochemically assisted bulk liquid membrane (BLM) system was developed for selective lithium recovery from complex spent cathode leachates. The study systematically elucidates the influence of ionic liquid alkyl-chain length, carrier chemistry, and applied electric field on lithium flux, selectivity, and energy consumption. Imidazolium-based ionic liquids ([C n mim][PF 6 ], n = 4, 6, 8) were combined with carriers (TBP, TBPO, HTTA) to form the membrane phase and evaluated in a U-shaped electro-membrane cell. Simulated and authentic leachates were subjected to pH-neutralization pretreatment to remove major impurities while retaining lithium. Linear sweep voltammetry and electrochemical impedance spectroscopy demonstrated enhanced interfacial kinetics and membrane stability under optimized compositions. Response surface methodology revealed applied voltage as the dominant factor governing lithium transport. Optimal conditions were identified at 2.21 V, 47.73% ionic liquid fraction, 600 rpm stirring rate, and [C 8 MIM][PF 6 ] as the membrane solvent. Additional analysis established TBP as the most effective carrier, [C 8 mim][PF 6 ] as the preferred ionic liquid, and a 50/50 ionic liquid/carrier ratio as the optimal balance between permeability and selectivity. A coupled extraction-diffusion-electromigration mechanism is proposed to describe lithium transport, providing valuable mechanistic insight for the design of next-generation electro-membrane systems for sustainable lithium recycling.