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 α-phase Al2O3 networks (α-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.