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 °C for 1 h and 800 °C 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 (DLi) were estimated to be 6.8×10−11 cm2 s−1 for Li4/3Ti5/3O4 and 7.1×10−12 cm2 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.