Flexible LATP composite membrane for lithium extraction from seawater via an electrochemical route

The lithium resources in seawater are more abundant than that on land, which is expected to meet the growing demand for the energy storage device like the lithium batteries. The electrochemical method is regarded as the most potential application. However, this method relies on membranes with advanced lithium-ion selectivity, and the emergence of super ionic conductor is expected to solve this problem. Herein, we employed polymer poly (vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) as the flexible framework and Li1.3Al0.3Ti1.7(PO4)3 (LATP) as the lithium ion conductor to prepare a flexible LATP/PVDF-HFP composite membrane (FLCM). Optimized FLCM has high lithium-ion selectivity and can be enriched up to 5.525 ppm Li+ in diluted seawater (lithium extraction rate: 4.777 x 10-3 mol/(m2 h)), which is 48.465 times that of commercial cation-exchange membrane (CEM). In addition, the FLCM exhibits excellent equilibrium selectivity for Li + over Ca2+and Mg2+. The selectivity of Li+/Ca2+ and Li+/Mg2+ is up to 8424.706, 853.395, respectively. In an electrocatalytic-driven Li-ion extraction device with four recycle chambers at 2 V voltage, the concentration of Mg2+and Ca2+ in the catholyte can be reduced to 0.744% and 1.249% of the seawater concentration, respectively. The work will be significant to solve the challenges of lithium extraction from seawater.