Electrochemical lithium recovery from brine with high Mg2+/Li+ ratio using mesoporous λ-MnO2/LiMn2O4 modified 3D graphite felt electrodes

Developing effective technologies for the extraction of lithium from seawater and salt-lake brines is paramount for sustainable lithium reuse in battery industries. Conventional adsorption technology for extracting lithium from brines has been limited due to the low adsorption rate and dissolution of adsorbents. Here, we report a novel flow-type electrochemical lithium recovery system based on mesoporous λ-MnO2/LiMn2O4 modified three-dimensional flow-through graphite felt electrodes. The mesoporous LiMn2O4 has a specific surface area of 183 m2/g, which provides a large solid-liquid interface for Li+ intercalation and deintercalation of LiMn2O4 phases. The three-dimensional graphite felt conductor could support abundant electroactive LiMn2O4 adsorbents and enhance the important diffusion and migration effects. In operation, a constant potential was applied on the cells to absorb Li+ by mesoporous λ-MnO2 from brine and desorb Li+ from mesoporous LiMn2O4 into recovery solution simultaneously. This system is successful to extract lithium of 75 mg/h per gram LiMn2O4, with a Li/Mg separation coefficient of 46 and energy consumption of 23.4 Wh/mol. This study highlights the remarkably electrochemical activity, quick mass-transfer kinetics, and excellent stability of the mesoporous LiMn2O4@GF electrode, and provides an energy-efficient method for the recovery of Li+ from brines with high Mg2+/Li+ ratios.