• • The PA-TAG membrane achieves a pure water permeance of 15.5 L m−2 h−1 bar−1 and a separation factor of ~30, breaking the selectivity-permeability trade-off in lithium extraction.
• • Divalent ion rejection exceeds 98%, enabling a Li+/M2+ mass ratio increase from 0.12 in the feed to 53.35 after two-stage nanofiltration, a 445-fold enrichment.
• • The relative volumetric lithium recovery rate reaches 48.2% after two-stage nanofiltration, with LiCl purity of 99.3%, demonstrating industrial viability.
• • The membrane exhibits robust chemical stability in acidic conditions (pH=2) for at least 20 days, ensuring durability in real battery leachate environments.