Scalable crosslinking-regulated membranes with ultra-high Li+/Mg2+ selectivity for lithium recovery from brines

Membrane-based separation has emerged as a competitive technology for lithium extraction from salt-lake brines. However, its industrial implementation remains limited by the low Li + /Mg 2+ selectivity of conventional membranes. In this work, we demonstrate that regulation of the crosslinking degree during membrane formation enables subnanometer pore size control within the narrow window required for Li + /Mg 2+ separation. Under electrodialysis conditions, the membrane achieved a Li + /Mg 2+ separation factor of up to 6454 at an Mg/Li mass ratio of 140, outperforming previously reported membranes for Li + /Mg 2+ separation. Importantly, the membrane maintained a Li + /Mg 2+ separation factor above 1200 in untreated natural salt-lake brine, despite the high Mg/Li mass ratio (Mg/Li = 87) and the presence of multiple competing ions. Fabrication of a 25 cm × 35 cm membrane and stable performance over 15 days of repeated operation further supported the practical viability of this approach. The practical membrane design strategy reported in this work can inspire the development of ion-selective membranes with precisely regulated subnanometer pores for a wide range of sustainable separation processes.