An ion-selective Li1.3Al0.3Ti1.7(PO4)3 membrane for electrolytic lithium extraction from brine

Abstract

The rapid increase in the commercialization of electric vehicles and portable electronics has markedly raised the demand for lithium resources. Extracting lithium from brine has become a critical pathway to address future lithium production challenges. However, the lithium extraction efficiency of conventional technologies is limited by the low levels of Li⁺ and the high Mg²⁺/Li⁺ ratio present in brine. A method involving one-step electrolysis with a solid-state electrolyte has been introduced for the direct and efficient extraction of metallic lithium. Li_1.3Al_0.3Ti_1.7(PO₄)₃ (LATP) is considered a highly promising selective membrane for large-scale lithium extraction from brine sources due to its low cost, excellent stability, and high ionic conductivity. Herein, LATP electrolytes were synthesized through the optimization of solid-state reaction conditions. The resulting LATP pellets exhibited a high relative density of 98.29 % and an impressive ionic conductivity of 3.88 × 10⁻⁴ S cm⁻¹. The lithium extraction device utilizing LATP as a selective membrane achieved a remarkable current efficiency of 97.4 % and a high lithium production rate of 40.4 μg h⁻¹ cm⁻². After lithium extraction process, the LATP pellets retained the ionic conductivity of 2.69 × 10⁻⁴ S cm⁻¹ and preserved the sodium super ion conductors (NASICON) crystal structure. This study presents an efficient Li⁺ selective membrane for extracting lithium directly from natural brine.