Synergistic Interfacial Design of Cation Exchange Membranes via Sequential Electro-Assembly for High-Efficiency Lithium Separation

The industrial application of modified ion-exchange membranes is limited by complex, discontinuous ex-situ processes. This study introduces an in-situ electro-assembly strategy that enables the direct fabrication of a selective layer within an electrodialysis stack without disassembly. By employing a programmed current reversal to orchestrate the sequential deposition of polyethyleneimine (PEI), cross-linking, and polystyrene sulfonate (PSS) adsorption, we achieve precise interfacial engineering. This method culminates in a membrane with an exceptional Li+/Mg2+ selectivity of 107.9 and robust stability, maintaining significant performance over 10 cycles in real salt lake brine. The synergistic combination of operational simplicity, methodological precision, and superior performance demonstrated herein provides a transformative and scalable platform for manufacturing high-performance membranes for selective ion separation.