Efficient Lithium-Ion Separation Using AI₂O₃-Based Lithium Aluminium Titanium Phosphate (LATP) Composite Membranes via Electrodialysis Process

Introduction. The rising global demand for lithium, especially for electric vehicles and renewable energy storage, necessitates efficient extraction methods. This study presents a novel, dense composite ceramic membrane integrated with electrodialysis technology for selective lithium extraction from salt lakes. Featuring a ~20 μm-thick NASICON-type Li₁.₃Al₀.₃Ti₁.₇(PO₄)₃ (LATP) layer on porous alumina, the 3D LATP structure enhances Li⁺ ion transport and selectivity. This membrane exhibits high mechanical strength and superior lithium conductivity, making it cost-effective and scalable for industrial applications.

Experimental/methodology. LATP powder was synthesised with precise control over aluminum doping, sintering temperature, and duration. The LATP-Al₂O₃ composite membrane preparation involved systematic optimisation of dip-coating parameters and sintering conditions. Comprehensive characterisation using XRD, SEM, EDS, TEM, and EIS provided insights into the membrane's structure and performance. A custom-designed three-stage electrodialysis system was developed to test the efficacy of membrane in separating lithium from magnesium-rich solutions, simulating real-world salt lake.

Results and discussion. The optimal LATP synthesis (Al doping content 0.3, sintered at 900°C for 2h) yielded high crystallinity without impurities. LATP powder showed globular morphology with 200—1300 nm particle sizes. EIS analysis revealed 4.17×10-4 S/cm ionic conductivity for the LATP. Optimal dip-coating conditions produced a composite membrane with a 20 μm-thick LATP layer on alumina substrate, exhibiting 34.2 MPa flexural strength. In three-stage electrodialysis, the membrane reduced Mg/Li ratio of simulated salt-lake solution from 40 to 2.1, achieving 77.15% Li⁺recovery with 47.6 kWh/kg-Li₂CO₃ energy consumption. The obtained Li₂SO₄ solution reacted with Na₂CO₃, producing 99% pure Li₂CO₃. The membrane maintained performance after long-term operation, demonstrating industrial application potential.