Lithium extraction from brine through a decoupled and membrane-free electrochemical cell design

Efficient lithium extraction from natural seawater would greatly enhance the sustainability of renewable energy technologies such as batteries. Herein, we present a decoupled and membrane-free electrochemical cell design that cycles lithium ions between iron phosphate electrodes. The cathode in the brine is physically isolated from the anode in freshwater, but they are electrochemically interconnected through a pair of silver/silver halide redox electrodes. This design was compatible with harsh brines featuring Mg/Li molar ratios of up to 3258 and low lithium concentrations down to 0.15 mM to produce battery-grade lithium carbonate with purity > 99.95%. Furthermore, the process could efficiently harness the osmotic energy of the brines, leading to up to ca. 21.5% of total energy savings. A pilot-scale cell with an electrode surface of 33.75 m2 realized lithium extraction from Dead Sea brine at a recovery rate of 84.0%.