Epitaxial growth and electrochemical properties of Li4Ti5O12 thin-film lithium battery anodes

Abstract

Epitaxial Li₄Ti₅O₁₂ thin-films were successfully synthesized on SrTiO₃ single-crystal substrates with (111), (110), and (100) lattice plane orientations using pulsed laser deposition (PLD). Thin-film X-ray diffraction (XRD) revealed that the Li₄Ti₅O₁₂ films had the same orientation as the SrTiO₃ substrates: Li₄Ti₅O₁₂ (111) on SrTiO₃ (111), Li₄Ti₅O₁₂ (110) on SrTiO₃ (110), and Li₄Ti₅O₁₂ (100) on SrTiO₃ (100). These epitaxial films contained island structures, and the morphology of the (111), (110), and (100) films, observed by field emission scanning electron microscopy (FE-SEM), exhibited angular, needle-like, and circular shapes, respectively. The electrochemical properties of 20 nm thick Li₄Ti₅O₁₂ (111) and (110) films were investigated by cyclic voltammetry. Reversible intercalation proceeded through both lattice planes due to the three-dimensional diffusion pathway of lithium in the spinel framework. Reduction peaks in the first cathodic scan appeared at different positions from those in subsequent scans, suggesting a surface reconstruction at the Li₄Ti₅O₁₂ surface due to interfacial reactions.