Intercalation Performance and Degradation of LiMn₂O₄ Supported on Vitreous Carbon Foam to Recover Lithium from Highly Concentrated Brines

The use of lithium intercalation electrodes (LIE) for recovering lithium from geothermal sources (containing ≤ 400 ppm of lithium) has the potential to revolutionize the lithium mining industry. This work proposes a conceptual scaled-up process for LIE, utilizing concentrated brine of 15 m 3 h −1 (384.32 mM or 2,666 ppm of lithium) obtained from a reverse osmosis unit. Given the high lithium concentration in the concentrated brine, testing LIE performance under high lithium content conditions (1 M LiCl) is essential. In this study, LiMn 2 O 4 supported on vitreous carbon foam is evaluated as the positive electrode. Degradation of the intercalation-active material, LiMn 2 O 4 , was observed in acidic media, with significant manganese dissolution. In contrast, at near neutral pH, dissolution rate is considered lower. Faradaic efficiency in acid media showed 98% efficiency only during the first potentiostatic deintercalation run. Subsequent runs exhibited non-faradaic behavior, which was also attributed to manganese dissolution. To develop strategies for mitigating LiMn 2 O 4 degradation, equilibrium diagrams for the Li-Mn-H 2 O system (Poubaix Diagram) was constructed. In addition to propose a scaled-up process for lithium recovery from geothermal sources, this work investigates the performance of lithium intercalation under conditions relevant to large-scale operations.