ELECTROCHEMICAL INTERCALATION OF LITHIUM INTO THE RAMSDELLITE-TYPE STRUCTURE OF LI2TI3O7

The chemical and electrochemical intercalation of lithium ions into th e ramsdellite-type structure of Li2Ti3O7 has been carried out by chemi cal reduction with n-BuLi or by galvanostatic discharge of an electroc hemical cell. A maximum lithium uptake has been found to be of 0.60 an d 1 per Li(2)Ti(3)O7 respectively at room temperature. During this int ercalation process the ramsdellite network is preserved as shown eithe r by electrochemical galvanostatic discharge or by X-ray powder diffra ction analysis. However it is clearly shown by X-ray diffraction analy sis and by electrochemical spectroscopy that two intercalation sites o f very close energy are involved in this process. The potential differ ence between the two peaks observed in the voltammogram is 350 +/- 20 mV. The variations of both the charge transfer resistance and the diff usion coefficient observed by a.c. impedance spectroscopy as intercala tion proceeds can be explained by the presence of these two different intercalation sites.