Origin of High Power Performance of Mesoporous Carbon-TiO2(B) Nanocomposite Electrodes: An In Situ Synchrotron X-ray Diffraction Study of TiO2(B) Electrode upon Lithium Insertion

摘要

Mesoporous carbon-titanium dioxide (TiO2) nanocomposites (MCTs), which have two types of TiO2 phases (anatase and TiO2(B)), were synthesized by sol-gel method. Structural characterization of the MCT samples was performed using thermo-gravimetric analysis (TGA), transmission electron microscope (TEM) observations, N2 adsorption-desorption isotherm measurements at 77 K, and powder X-ray diffraction (XRD) analysis. Lithium storage properties of the MCT samples were evaluated by galvanostatic charge-discharge measurements. The obtained electrochemical data indicated that TiO2(B) nanocrystals in MCTs play a crucial role in exhibiting their superior electrode properties. In order to discuss the detailed lithium storage mechanism of the TiO2(B) phase in MCT electrodes, in situ synchrotron XRD investigation during a galvanostatic charge-discharge test was performed using a single-phase TiO2(B) electrode. It was shown by this experiment that a unique lithium storage behavior enabled stable and high rate of lithium storage.