Lithium insertion into self-organized mesoscopic TiO2 (anatase) electrodes

Self-oganized nanocrystalline anatase films were prepared by a sol-gel tech nique with subsequent hydrothermal growth of crystals in basic solutions. H ydrothermal treatment at 190-230 degreesC leads to the formation of compact films with narrow pore size distribution. Materials prepared at higher tem peratures show more open structure with lower specific surface area. The el ectrochemical activity of the self-organized electrodes decreases with decr easing specific surface area. Ordered electrodes showed higher insertion ca pacity by ca. 15% compared to those of non-ordered electrodes with the same specific surface area. Insertion coefficients, x, exceeding 0.5 were obser ved for very thin (0.2 mg/cm(2)) self-organized films with specific surface area higher than 60 m(2)/g. However, these values were not reproduced for thicker films. The insertion rate depends on the inserted charge with a max imum at x similar to0.1. It indicates that only a part of the total electro de-electrolyte interface is available for charge transfer reaction. The tot al insertion capacity is therefore affected by propagation of the electroch emically active surface within the film. (C) 2000 Elsevier Science B.V. All rights reserved.