Synthesis and Characterization of Nanometric Iron and Iron-Titanium Oxides by Mechanical Milling:

Abstract

Nanometric mixed iron-titanium oxides were prepared by mechanical milling with a view to determining their ability to act as anodic materials in lithium cells. At a TiO2∕Fe2O3TiO2∕Fe2O3 mole ratio of 0.4, a solid-state reaction occurs that leads to the formation of Fe5TiO8Fe5TiO8 , which possesses a spinel-like structure; at lower ratios, however, the structure retains the hematite framework. Li∕g-Fe2O3Li∕g-Fe2O3 cells exhibit poor electrochemical reversibility; by contrast, Ti-containing electrodes possess improved cycling properties. Changes in the electrodes upon cycling were examined by X-ray photoelectron spectroscopy (XPS). XPS data confirm the participation of electrolyte in the electrochemical reaction and the different type of electrochemical reversibility exhibited by samples. Both processes were influenced by the presence of titanium. Titanium dioxide, in the presence of iron oxides, seems to be inactive to the electrochemical process. Based on the step potential electrochemical spectroscopy (SPES) curves and photoelectron spectra obtained, the presence of Ti increases the reversibility of the redox reactions undergone by the electrolyte during discharge/charge processes. The increased active-material/electrolyte/inactive-material interaction which is reported here offers new perspectives for the use of well-known transition oxides as anode materials in Li-ion batteries.