Nonaqueous Polymer Electrolytes for Electrochromic Devices

Nonaqueous alkali metal salt polyether electrolytes and nonaqueous H3PO4 proton conducting electrolyte gels have been synthesized for application in electrochromic devices. The ionic conductivity of these electrolytes has been optimized to be in the range 10-3 S/cm to 10-6 S/cm at room temperature. The most favourable, stable, polyether electrolytes are blends based upon EO/PO (= 50/50 or 60/40) copolymers with molecular weights in the range of 300-600 and LiCF3SO3 or Li(CF3SO2)2N concentrations of 25:1, PMMA concentrations in the range 8 to 40 vol% and PC < 15 vol%. The most favourable, stable nonaqueous gels were those with H3PO4 dissolved in PC (20 to 50 vol%) entrapped in a PMMA network using a crosslinking agent. These electrolytes are stable from -30° to 100°C.