Lithium selective electrodes for direct lithium extraction from complex brine: A comprehensive review

As premium lithium resources are dwindling, research endeavors in lithium recovery have gradually shifted toward unconventional resources, such as saline brines and seawater, which contain ultralow Li + concentrations and abundant competing ions (e.g., Na + , Mg 2+ ). Consequently, lithium-selective electrodes (LSEs) that possess both high selectivity and rapid response have become the research focus of electrochemical direct lithium extraction (DLE). This review systematically elucidates the two fundamental selectivity mechanisms of LSEs: size sieving and ion-electrode interaction (thermodynamic/kinetic). It then systematically assesses the design principles, modification strategies, and inherent limitations of representative LSEs, namely LiMn 2 O 4 , LiFePO 4 , MXenes and porous framework materials. It also discusses innovative separation concepts such as “reverse lithium extraction”. Furthermore, it critically highlights the key challenges currently faced in LSE research and proposes promising avenues for further work. This work seeks to deliver theoretical guidance and technical references that support the design, preparation, and industrial application of advanced lithium-selective electrodes.