Electrochemical intercalation of lithium into the ramsdellite-type structure of Li2Ti3O7

The chemical and electrochemical intercalation of lithium ions into the ramsdellite-type structure of Li2Ti3O7 has been carried out by chemical reduction with n-BuLi or by galvanostatic discharge of an electrochemical cell. A maximum lithium uptake has been found to be of 0.60 and 1 per Li(2)Ti(3)O7 respectively at room temperature. During this intercalation process the ramsdellite network is preserved as shown either by electrochemical galvanostatic discharge or by X-ray powder diffraction analysis. However it is clearly shown by X-ray diffraction analysis and by electrochemical spectroscopy that two intercalation sites of very close energy are involved in this process. The potential difference between the two peaks observed in the voltammogram is 350 +/- 20 mV. The variations of both the charge transfer resistance and the diffusion coefficient observed by a.c. impedance spectroscopy as intercalation proceeds can be explained by the presence of these two different intercalation sites.