Insights into Li+, Na+, and K+ Intercalation in Lepidocrocite-Type Layered TiO2 Structures

Abstract

A lamellar lepidocrocite-type titanate structure with ∼25% Ti4+ vacancies was recently synthesized, and it showed potential for use as an electrode in rechargeable lithium-ion batteries. In addition to lithium, we explore this material’s ability to accommodate other monovalent ions with greater natural abundance (e.g., sodium and potassium) in order to develop lower-cost alternatives to lithium-ion batteries constructed from more widely available elements. Galvanostatic discharge/charge curves for the lepidocrocite material indicate that increasing the ionic radius of the monovalent ion results in a deteriorating performance of the electrode. Using first-principles electronic structure calculations, we identify the relaxed geometries of the structure while varying the placement of the ion in the structure. We then use these geometries to compute the energy of formations. Additionally, we determine that all ions are favorable in the structure, but interlayer positions are preferred compared to vacancy posi...