LATP-incorporated Cellulose Membrane for Direct Lithium Extraction from Salt Lake Brine under an Electrochemical System

Abstract

Lithium (Li) is a critical raw material for lithium-ion batteries (LIBs) and energy storage systems (ESS). With the ongoing clean energy transition, the demand for lithium is expected to rise continuously. However, conventional lithium extraction methods from salt lake brines, which rely on solar evaporation, face significant limitations in meeting this increasing demand and present environmental issues. Solar evaporation based lithium extraction typically requires 10–24 months and consumes substantial amounts of water, particularly in dry regions like the lithium triangle of South America. Due to these limitations, Direct Lithium Extraction (DLE), a method capable of selectively extracting lithium with high efficiency in a short time, has recently emerged as a promising alternative to evaporation-based methods. In this study, we developed an electrically driven lithium-selective membrane as a DLE technology due to its low energy consumption, high extraction efficiency, and environmental advantages, including its compatibility with renewable energy sources. The lithium-selective membrane, referred to as the LATP/CA membrane, incorporates the NASICON-type lithium ionic conductor LATP (Li1.3Al0.3Ti1.7(PO4)3) for high lithium selectivity. Additionally, cellulose acetate (CA) was used to maintain the mechanical strength of the membrane. Lithium separation tests were conducted under both binary systems and simulated brine solutions, along with a multi-step process, to examine the effects of applied current and multi-ion systems on membrane performance. Under an applied current of 200 µA in a simulated brine solution, the LATP/CA membrane achieved lithium selectivity ratios of Li/Mg: 467.3, Li/Na: 44.8, and Li/K: 22. This lithium selectivity could be attributed to the crystal structural characteristics of LATP. Consequently, the application of the LATP/CA membrane shows the potential to address supply challenges associated with conventional evaporation methods while mitigating environmental concerns for lithium extraction.