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

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.