Cycle test and degradation analysis of WO3/PC+LiClO4/CeO2·TiO2 electrochromic device

We fabricated an electrochromic full cell device adopting WO3 as a working electrode, and 1 M LiClO4 in PC with 3% water addition as an electrolyte and CeO2·TiO2 with various thicknesses as an ion storage layer. CeO2·TiO2 with less than 100 nm shows large charge density but the long-term cyclability is not good due to lithium ion diffusion into ITO thin film. Therefore, the thickness of CeO2·TiO2 ion storage layer should be coated at more than 200 mm/min. Long-term cycle test results show that CeO2·TiO2 ion storage layer with more than 150 nm thickness and two time coating enhance the long-term stability. SIMS analysis results show that the degradation is due to the remaining lithium ion in the working electrode, WO3.