Abstract
<jats:p>Effective utilization of lithium-bearing oilfield brines could expand domestic critical-mineral supply. Here, we report the first demonstration of electrochemical lithium extraction from a real Canadian oilfield brine in a symmetric flow cell equipped with lithium manganese oxide (LMO) electrodes. Despite a low Li+ concentration of 0.009 M, a Na+/Li+ ratio of approximately 200, and substantial concentrations of K+, Mg2+, and Ca2+, the system extracted approximately 73% of the lithium per cycle and achieved an overall recovery efficiency of 75%. Separation coefficients of 2166, 547, 1615, and 1196 were obtained for Li+ over Na+, K+, Mg2+, and Ca2+, respectively. The system achieved a lithium insertion capacity of 12.04 mg Li g-1 LMO and an energy consumption of 20.91 Wh mol-1 Li. Mechanistic analysis revealed that oxygen evolution, electrolyte acidification, and manganese dissolution limited electrode stability. A Pourbaix-guided constantcurrent/constant-voltage protocol reduced manganese dissolution and improved Faradaic efficiency by restricting the half-cell potentials. Increasing the operating temperature from 20 to 70 °C decreased the Faradaic efficiency from 53% to 41% and intensified electrolyte acidification and manganese dissolution. These results demonstrate the feasibility of selective lithium recovery from Canadian oilfield brines and establish electrode-potential control and temperature management as key requirements for stable operation.</jats:p>