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 m³/h (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, LiMn₂O₄ supported on vitreous carbon foam is evaluated as the positive electrode. Degradation of the intercalation-active material, LiMn₂O₄, 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 LiMn₂O₄ degradation, equilibrium diagrams for the Li-Mn-H2O 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.