Fabrication of thin film electrodes for all solid state rechargeable lithium batteries

Thin film electrodes for rechargeable lithium batteries were prepared by a sol-gel method with poly(vinylpyrrolidone) (PVP). The Li-Ti-O and Li-Mn-O sols were successfully prepared by using PVP. The sol deposited on Au substrate by a spin coater was converted to a gel film through the spin coating process. The Li-Ti-O and Li-Mn-O gel films were heated at 600 degreesC for 1 h and 800 degreesC for 1 h, respectively. The prepared thin films were characterized by X-ray diffraction and scanning electron microscopy. From these results, it was found that the prepared electrode films were Li4/3Ti5/3O4 and LiMn2O4, respectively. The electrochemical properties of the prepared electrode films were evaluated by using charge and discharge measurements and cyclic voltammetry in a mixed solvent of ethylene carbonate and diethyl carbonate (1:1 v/v) with 1.0 M LiClO4. From cyclic voltammograms, the apparent chemical diffusion coefficients for Li+ ions in the oxide films (D-Li) were estimated to be 6.8 x 10(-11) cm(2) s(-1) for Li4/3Ti5/3O4 and 7.1 x 10(-12) cm(2) s(-1) for LiMn2O4, respectively. Excellent electrochemical properties were observed in discharge and charge tests. From these results, it can be said that the PVP sol-gel method is very useful to prepare thin film electrodes. (C) 2002 Elsevier Science B.V. All rights reserved.