Computational Discovery of Li-M-O Ion Exchange Materials for Lithium Extraction from Brines

Lithium is an essential element for today's high-performance batteries. Brine resources contain most of the world's lithium reserves, but conventional processes for extracting lithium from brines are limited by low lithium recovery and large evaporation ponds. Lithium ion exchange is an alternative extraction method with potential to access lower-quality resources and decrease costs. Ion exchange materials absorb lithium from brine resources and then release the lithium in acid while absorbing hydrogen. New ion exchange materials are sought to facilitate this transformative approach. We use high-throughput density functional theory and specific ion interaction theory to predict promising new lithium metal oxide compounds suitable for lithium extraction. Starting from the Open Quantum Materials Database (OQMD) of ∼400,000 compounds, we consider 77 candidate lithium metal oxide compounds that are stable or nearly stable in their lithiated states. We interrogate this list for compounds that thermodynamically release lithium while binding hydrogen in acid and that also release hydrogen while binding lithium in brine. We further screen for selective binding of lithium relative to sodium in brine. We find that most candidate compounds either bind lithium in both acid and brine solutions or bind hydrogen in both acid and brine solutions. Such compounds are not suitable for lithium ion exchange. However, we identify nine compounds that are most promising for lithium extraction from brines: LiAlO₂, LiCuO₂, Li₂MnO₃, Li₄Mn₅O₁₂, Li₂SnO₃, Li₄TiO₄, Li₄Ti₅O₁₂, Li₇Ti₁₁O₂₄, and Li₃VO₄. Four additional compounds are promising when the pH of the brine is adjusted to 10 to help drive hydrogen release: Li₂TiO₃, LiTiO₂, Li₂FeO₃, and Li₂Si₃O₇. Four of the previously mentioned compounds are also promising for Li extraction from seawater: Li₂MnO₃, Li₄Mn₅O₁₂, Li₇Ti₁₁O₂₄, and Li₃VO₄.