Observation of lithiation-induced structural variations in TiO2 nanotube arrays by X-ray absorption fine structure

Abstract

We report here a study of self-organized TiO₂ nanotube arrays both in the amorphous and anatase phases with superior electrochemical performance upon lithiation and delithiation. X-ray absorption fine structure (XAFS) study at the Ti K and L, O K and Li K edges has been conducted to track the behavior. Characteristic features for amorphous and anatase TiO₂ are identified. After lithiation, it is found that although no obvious variation of chemical states is apparent at the Ti K and L edges, charge transfer from Ti 3d to O 2p and also partial amorphization of anatase TiO₂ are evident from spectral intensities. The Li and O K edge XAFS show the successful intercalation of lithium and reveal the existence of a nearly linear “O–Li–O” arrangement in the lithiated TiO₂ nanotube. This study helps in understanding of the lithiation process in nanostructured TiO₂ anodes from a spectroscopic viewpoint.