Li Recovery from Brines using Recyclable Intercalation-Based Redox Membranes

The accelerated push towards renewable energy is leading to an exponential consumption of battery materials. Today, the United States net import reliance on battery materials varies widely from 25 to 80% (USGS Reports). If nothing is done, this import reliance is only expected to grow as electric vehicle and energy grid storage demands surge. Therefore, securing novel, domestic sources of critical lithium-ion battery components is of paramount importance and necessary to shield the U.S. from future global trade volatility and unforeseeable supply chain disruptions. The United States currently sources all its domestically produced lithium from one mine in Nevada where lithium carbonate is produced from evaporation ponds. Geothermal brines have been identified as a domestic lithium source candidate with the capacity to fulfill the entire Li consumption needs of the U.S., but this resource is currently unexploited. Isolating a pure Li product from these hot brines poses a major challenge due to their corrosivity, elevated temperatures, high levels of dissolved solids, and numerous cationic species.<br/>To address this challenge, we use a novel redox membrane concept for Direct Lithium Extraction (DLE). Our team’s proprietary molten salt platform is capable of manufacturing fully dense layered, spinel, and olivine transition metal oxide battery cathode materials. We demonstrate that dense cathode materials could function as membranes between the input (lithium brine source) and output (enriched lithium product) streams while permitting Li-flux via an electrochemically driven redox reaction. Unlike traditional membranes, which utilize concentration gradients to drive ion migration between solutions, an electrochemical driving force is envisioned to selectively mobilize lithium cations through a dense, electroplated transition metal oxide membrane. Extracted lithium will be directly converted to a highly valuable LiOH product. Transition metal oxides are ideal candidates for lithium brine extraction due to their capability to selectively uptake lithium ions, high degree of chemical stability at elevated temperatures, and high corrosion resistance. We show that such intercalation based membranes are highly selective for lithium ions over other competing ions such as sodium as well as multivalent cations including calcium and magnesium. Selectivity factors of over 100 has been achieved in our benchtop testing. Continuous operation of this novel redox membrane concept in a flow cell format will also be presented. Combined electrochemical and characterization data confirm the applicability of such concept in several lithium brine streams from geothermal to salar brine compositions. Summary of techno-economics of Li extraction using these membranes, that are recyclable, will also be presented.