The “confined-capture-induced blocking” interference mechanism of Mg2+ in lithium extraction via spinel λ-MnO2 under ultra-high Mg/Li ratio and strategy for its suppression

Electrically Switched Ion Exchange (ESIX) technology boasts advantages of high selectivity, low energy consumption, and environmental friendliness, and its core material, LiMn 2 O 4 , can efficiently separate lithium through unique lattice sieving and charge matching effect, yet it suffers from severe performance degradation in brine environments with ultra-high Mg/Li ratio. Currently, the microscopic mechanism responsible for this degradation remains unclear. In this study, we propose a “confined-capture-induced blocking” mechanism using experimental investigations, characterization techniques, and density functional theory (DFT) calculations. Specifically, the strong Coulomb interaction between high-charge-density Mg 2+ and the O atoms at the entrances of the [111] channels (the Li + migration channels) of LiMn 2 O 4 results in blockage of the channel entrances, thereby blocking the intercalation of Li + . Based on this mechanism, we propose a targeted solution: adopting a dynamic adsorption mode with solution flow. This approach effectively mitigates the adverse effects of Li + concentration polarization and Mg 2+ enrichment near the electrode, which lead to an abnormally high Mg/Li ratio in static adsorption, thereby enhancing the adsorption capacity from 1.437 mg/g in static adsorption to 5.124 mg/g at a flow rate of 2 l/min. Subsequently, pilot-scale experiments further validate the effectiveness of this strategy. This research provides theoretical support, engineering evidence, and practical guidance for the development of lithium extraction technology from salt lakes with ultra-high Mg/Li ratio.