ABSTRACT Extracting lithium from seawater offers an additional Li source but is hindered by corrosion of Li 1.5 Al 0.5 Ge 1.5 (PO 4 ) 3 (LAGP) and weak adhesion of conventional coating layers. Here we propose a permeation growth strategy to construct an intergrowth TiO 2 protection layer on a LAGP membrane (LAGP membrane with intergrowth layer) for long‐term stable lithium extraction from seawater. An acidic TiO 2 sol is spin‐coated onto a polished LAGP membrane and sintered, during which acid etching and Ti 4+ /Ge 4+ ion exchange generate a lattice‐matched Li 1+x Al x Ti 2‐x (PO 4 ) 3 /LAGP interfacial phase beneath a dense TiO 2 intergrowth layer. This intergrowth‐structure eliminates interfacial gaps, enhances peel strength and hardness, and provides continuous Li + transport pathways, delivering an ionic conductivity of 2.40 × 10 −4 S cm −1 at room temperature and excellent chemical stability in seawater. Applied in a lithium extraction device using natural seawater as anolyte and an organic electrolyte as catholyte, the LAGP membrane with intergrowth layer maintains integrity, Li + /Na + selectivity, and stable operation for 650 h, achieving a Coulombic efficiency of 97.4% and an energy consumption of 17.4 kWh kg −1 Li . This permeation growth strategy offers a general route to construct intergrowth‐structure Li ion‐sieve membranes with chemical stability and Li + transport for seawater lithium extraction.
Wang et al. (Mon,) studied this question.