Pulsed electric field controlled lithium extraction process by LMO/MXene composite electrode from brines

Low-cost and highly efficient extraction of lithium from brine is the key to solving energy and environmental problems for sustainable development. The electrochemical lithium extraction method is of high selectivity, low energy consumption and environmental friendly. In this work, two innovations were proposed for electrochemical lithium extraction technology. Firstly, the layered Ti3C2-MXene was combined with a LiMn2O4 (LMO) electrode to reduce the damage to the LMO crystal structure caused by manganese dissolution and the Jahn-Teller effect, and to greatly improve the lithium-ion transport rate and the cyclic stability of the electrode material. The good cyclic stability and high capacity were verified by XRD, SEM, and electrochemical tests before and after cycling. Secondly, the influence of four electric field controlling modes, namely constant current (CC) mode, pulse-rest(P10r2 and P10r10), pulse-rest-reverse pulse(P12r2R2), on the selectivity of lithium extraction was studied in simulated brine with an initial lithium/sodium ratio as low as 0.01. The results show that the Pulse Electric Field controlling method can effectively improve the lithium/sodium separation coefficient. Finally, an actual lithium extraction test was carried out in Atacama salt Lake brine with an initial Li/Na ratio of about 0.06. The Li/Na separation coefficient reached 1020 under the optimized electrode material structure and electric field mode. In conclusion, the application of LMO/MXene electrode under the pulse electric field mode is a highly selective method for lithium extraction with low initial lithium/sodium ratios.