α-Al2O3 Networks on MLG Membranes for Continuous Lithium Ion Extraction from Artificial Sea Water with Enhanced Selectivity and Durability

Abstract

The escalating demand for lithium-ion batteries highlights the critical need for alternative lithium sources beyond limited terrestrial reserves. Seawater offers a promising yet challenging lithium resource due to its sub-ppm level Li+ concentration and the presence of competing cations (Na+, K+, Mg2+, and Ca2+). Here, we present a multilayer graphene membrane decorated with alpha-phase Al2O3 networks (alpha-Al2O3/MLG) as a selective and durable platform for lithium extraction from seawater. This membrane leverages van der Waals gaps at Al2O3-MLG heterointerfaces and vertical channels formed at MLG grain boundary defects to achieve high Li+ selectivity. By integrating the membrane into an electrodialysis system, a stable Li+ flux of 0.084 mol h m-2 was maintained over 100 h, which resulted in lithium purity and recovery rates of 88.9% and 88.6% from artificial seawater over three extraction cycles. These findings demonstrate the membrane's potential for selective lithium extraction from seawater while minimizing competing ion transport.