Increasing the stability of LiMn2O4 against harsh conditions during lithium recovery from real brine solutions

Brines are abundant waste products from desalination plants having higher lithium contents than sea water (0.17 ppm). Here, we report on electrochemical lithium recovery from real brine solutions using Li-selective LiMn2O4. Free-standing electrodes were prepared completely solvent-free. At low current densities, the complete theoretical capacity of 148 mAh g‒1 can be utilized. The process is highly rate dependent due to the lithium concentration in the mM range. The high salt content of the brine depicts a challenging environment for electrodes and reactor materials. Competing earth-alkali metals lead to scale formation blocking the electrode surface and reducing the electrode capacity for lithium uptake. The high chloride concentration enables the formation of chlorine Cl2 at potentials <1 V vs. Ag/AgCl competing with the deintercalation of lithium. A combination of commercial antiscalants was used to supress the formation of CaCO3 at the electrode prolonging cycle life. It was shown that an cation exchange membrane effectively blocks chloride ions from the electrode but also decreases the Li-diffusion. Finally, the selectivity of the process was proven in a real brine with a low lithium content (0.7 mM) and an actual recovery experiment was performed in a flow setup.