Selective Electrochemical Lithium-Ion Extraction from Low-Grade Lithium Sources with Optimized Pulsed Operation

Abstract

Abstract Lithium recovery from brines, particularly low-grade resources, remains a major challenge. Here, we develop an electrochemical lithium-ion extraction system based on carbon-coated LiFePO4 as the working electrode and systematically elucidate how the carbon coating governs electrochemical behavior and lithium-ion extraction performance. The system is optimized and evaluated in binary Li+/Na+ electrolytes over a wide range of competing-ion concentrations and subsequently extended to low-grade brine conditions featuring ultralow lithium-ion levels in a high sodium-ion environment. To further enhance lithium-ion selectivity and cycling stability, we implement a pulsed-operation protocol with tailored rest times and validate its effectiveness using representative low-grade brines from a salt lake and seawater. The dynamic regulation and refreshment of the ion arrangement at the electrode interface were realized by rationally designing the discharge/rest interval, and a scaled-up prototype reactor was operated for lithium-ion recovery practice from simulated low-grade brine. By combining operational optimization and advanced characterization, we further establish the mechanistic basis for the observed improvements in lithium-ion selectivity and long-term stability.