Layered Double Oxide as a Cl− Selective Anode for High-Performance Electrochemical Lithium Extraction

The widespread application of lithium-ion batteries and the rapid development of electric vehicles have increased the demand for lithium resources. Electrochemical lithium extraction has been proven to be an effective method for Li+ recovery from brine due to its environmental friendliness and excellent selectivity. In a conventional configuration, LiMn2O4 (LMO)||activated carbon (AC)/anion exchange membrane (AEM), AEM is essential to avoid the adsorption of Li+ onto the AC anode during Cl− desorbing. Here, we propose that a layered double oxide (LDO) serves as an anode material with high Cl− selectivity. CoAl-LDO was synthesized by a one-pot hydrothermal method, followed by heat treatment, and used as an anode with LMO as a cathode (LMO||CoAl-LDO). The Li+ intercalation capacity of LMO||CoAl-LDO reached 1.35 mmol g−1 at 1.2 V with a maximum rate of 0.57 mmol g−1 min−1 and a capacity retention of 70.83% after 20 cycles, higher than those of LMO||AC/AEM (1.12 mmol g−1, 0.37 mmol g−1 min−1, 35.48%, respectively). Moreover, the selectivity of Li+ in a Li+/Mg2+ binary solution (1:5) was investigated, showing that the separation factor of Li+/Mg2+ in LMO||CoAl-LDO (2.67) was close to that in LMO||AC/AEM (2.98). In situ Raman characterization was conducted, showing that the high Cl− selectivity and good Cl− capacity were induced by the anion intercalation mechanism of CoAl-LDO. In addition, CoAl-LDO coated with AEM further enhanced the Cl− selectivity and capacity, which assisted the Li+ extraction performance of LMO||CoAl-LDO with 1.80 mmol g−1 Li+ intercalation capacity. We believe that CoAl-LDO is a promising anode material for electrochemical lithium extraction.