Semi-solid gel electrolytes for electrochromic devices

The di-urethanesil organic-inorganic hybrid bis N-triethoxysilyl propylcarbamoil poly(ethylene oxide) 400 (PEOCS) was used for the preparation of electrolytes appropriate for applications in electrochromic devices. The obtained PEOCS-based sol-gel network was able to accommodate the co-solvent y-butyrolactone up to a molar ratio of PEOCS : y-butyrolactone =I : 20. Lithium bis(trifluoromethanesulfonyl)imide was used as a guest salt. The initial conductivities were of the order 10-4 S/cm to 10-3 S/cm, but diminished during the course of the condensation reactions. This decrease was less obvious when a larger amount of co-solvent was present. The time-dependent stability of the conductivity was achieved with the addition of 3-chloropropylmethyldimethoxysilane. The best response was achieved for electrochromic devices with the electrolyte PEOCS : y-butyrolactone: Li+ salt= 1 : 15 : 0.5, with or without a dialkoxysilane additive.