Transparent storage layers for H+ and Li+ ions prepared by sol-gel technique

Abstract

Thin layers of mixed oxides CeO2-TiO2 and CeO2-ZrO2 with molar ratio 1:1 have been prepared by sol-gel process using the dip-coating technique. The precursor sols consist of a mixture of nitrate ammonium cerium salt (Ce(NH4)2(NO3)6), zirconium propoxide or tetraisopropyl orthotitanate and ethanol. The thickness of the multilayer films is typically 300nm after densification at 450°C. Their use as transparent H+ and Li+ ions storage electrode (counter electrode) for electrochromic devices is studied by electrochemical voltammetry, impedance and optical spectroscopies. They have typically an optical transmission of 80% in the visible range, do not color after ions insertion and show good electrochemical stability. These layers have been also tested in complete all solid state cell having the configuration /glass/ITO/EC/electrolyte/CeO2-TiO2/ITO/glass/. The electrochromic layer (EC) was either WO3 or polytoluidine. The protonic electrolyte was a cellulose-polyacetate polymer and the lithium electrolyte was PEO-LiN(SO2CF3)2. Their electrochemical, optical and lifetime performance are reported.