Lithium Intercalation in Anatase Titanium Vacancies and the Role of Local Anionic Environment

Abstract

The structure of bulk and nondefective compounds is generally described with crystal models built from well mastered techniques such the analysis of an X-ray diffractogram. The presence of defects, such as cationic vacancies, locally disrupt the long-range order, with the appearance of local structures with order extending only a few nanometers. To probe and describe the electrochemical properties of cation-deficient anatase, we investigated a series of materials having different concentrations of vacancies, i.e., Ti1–x–y□x+yO2–4(x+y)F4x(OH)4y, and compared their properties with respect to defect-free stoichiometric anatase TiO2. At first, we characterized the series of materials Ti1–x–y□x+yO2–4(x+y)F4x(OH)4y by means of pair distribution function (PDF), 19F nuclear magnetic resonance (NMR), Raman and X-ray photoelectron spectroscopies, to probe the compositional and structural features. Second, we characterized the insertion electrochemical properties vs metallic lithium where we emphasized the beneficia...