Electrochemical lithium insertion in sol-gel deposited LiNbO3 films

Inorganic LiNbO₃ ion conducting films were prepared by sol-gel process involving two alkoxides, lithium ethoxide and niobium ethoxide. The films were analyzed by ellipsometry, X-ray diffractometry, scanning electron microscopy and impedance spectroscopy. Impedance spectroscopy indicated that the Li⁺ conductivity values were in the range of 6–8 × 10⁻⁷ S cm⁻¹. The morphology and thickness of these films played an important role in the insertion of lithium ions. Spectrophotometric investigation showed that LiNbO₃ films exhibit very weak cathodic coloration from 350 to 900 nm spectral region. The electrochemical and optical properties clearly indicate that sol-gel deposited LiNbO₃ films can be used as lithium ion conducting layers for electrochromic device application.