Structural study of carbon-coated TiO2 anatase nanoparticles as high-performance anode materials for Na-ion batteries

In this work, we study the electronic and atomic structural modifications occurring in TiO2 anatase nanoparticles as anode materials in Na-ion batteries upon sodiation and desodiation. The structural investigation is performed over both long- and short-range order by combining a comprehensive extended X-ray absorption fine structure (EXAFS) characterization with X-ray diffraction (XRD). The evolution of the electronic structure upon cycling is qualitatively investigated by X-ray absorption near-edge structure (XANES) analysis. The goal of this work is to correlate the outstanding electrochemical performance of carbon-coated TiO2 anatase nanoparticles in sodium batteries with the electronic and structural modifications induced during the sodiation and desodiation processes upon cycling. This work also demonstrates for the first time a coherent explanation of the structural changes observed, where an electrochemically induced short-range ordering is revealed upon cycling.