Solvent effect on gel electrolytes containing lithium salts

Gel electrolytes of polymer–solvent–salt type are suitable for electrochromic window applications due to their high value of ionic conductivity, good electrode–electrolyte interfacial contacts, good adhesive properties etc. In the present paper, we report the results on polymeric gel electrolytes with polymethylmethacrylate (PMMA) as the polymer, γ-butyrolactone, propylene carbonate, ethylene carbonate as the solvent, and lithium triflate as the salt. The effect of different solvents (single and mixed) on the properties of gel electrolytes has been studied. The variation of conductivity with salt concentration and temperature has also been studied. The addition of polymers has been found to result in an increase in the viscosity of gel electrolytes accompanied by a small decrease in conductivity value. The room-temperature conductivity of these polymeric gel electrolytes is of the order of 1–10 mS cm−1 and they also have high transmission in the visible region. The small variation in conductivity over the operational temperature range has been found to be advantageous for electrochromic device applications.