Solid-State Electrolyte for Lithium Extraction from Salt Lake Brines

Abstract

Lithium sources are of great significance for developing the next generation of lithium ion batteries. Most of the world’s lithium sources are found in salt lake brines. The main challenge of lithium extraction from salt lake brine is the separation of lithium ions from other coexisting ions, especially the separation of Li+ and Mg2+. However, the traditional precipitation method for salt lake lithium extraction is cumbersome. In this project, a new electrolytic device with a solid-state electrolyte was developed for high-efficient lithium extraction from salt lake brines. Li1+xAlxTi2−x(PO4)3 (LATP) is a promising NASICON-type solid-state electrolyte, which exhibits high ionic conductivity ( >10-4 S/cm) at room temperature. LATP can be used as a lithium ion conductor, that is only lithium ions can transfer through it, which is ideal for separating lithium ions from other ions in salt lake brines. In this project, high-quality LATP was fabricated at a low cost. An electrolytic device was developed for lithium extraction, in which LATP was used together with a sacrificial anode, molten salts, and an inert cathode. Salt lake brines need to be concentrated by solar and/or wind evaporation before lithium extraction. The electrolytic device was operated above the melting point of the concentrated brine water, at which LATP exhibits a higher ionic conductivity for fast lithium ion transfer. A tiny voltage was applied across the two electrodes to drive the electrochemical reaction. The composition of lithium sources before and after extraction was investigated by inductively coupled plasma-optical emission spectroscopy (ICP-OES). Results show that lithium sources with a higher purity level were successfully extracted with high efficiency. Impurity ions were almost completely blocked by LATP.