Solar‐Powered Redox Adsorption Method for Round‐the‐Clock Direct Lithium Extraction from Low‐Grade Brines

ABSTRACT Electrochemical lithium (Li) extraction from low‐grade brines is challenged by maintaining high Li selectivity at practically relevant extraction rates while enabling off‐grid, round‐the‐clock operation in remote, infrastructure‐deficient regions. Here we propose a solar‐powered redox adsorption method (SRAM), in which dissolved, regenerable electron carriers (ECs) deliver electrons to dispersed olivine iron phosphate (o‐FePO 4 ) adsorbents. In SRAM, EC‐mediated electron transfer enables electrochemically effective use of dispersed o‐FePO 4 adsorbents, while interfacial charge accumulation and electric double layer (EDL) formation may hinder further access of ECs to the adsorbent surface, thereby moderating local electron flux and suppressing competing‐ion intercalation. As a result, SRAM achieves a high extraction rate of 40 mA mmol −1 o‐FePO 4 while maintaining high selectivity (separation factors of 700 for Li + /Na + and 2400 for Li + /Mg 2+ ) from low‐grade brines (70 ppm Li + ). Meanwhile, ECs function as integrated chemical energy‐storage media that can buffer intermittent photovoltaic input and temporally decouple charging from Li extraction, enabling solar‐buffered day–night operation without an external electrical storage unit. Field demonstrations support stable operation (∼9 mg Li g −1 h −1 ) and provide a lab‐scale validation through 50‐L raw brine processing. Our work establishes EC‐mediated electron transfer as a promising strategy for sustainable Li recovery from previously untapped low‐grade brines.