Ionic conductivity of polymer gel electrolytes based on poly(polyethylene glycol dimethacrylate)

Abstract

Gel electrolytes have been prepared by thermal polymerization of poly(polyethylene glycol dimethacrylate) (P(PEGD)) in the presence of propylene carbonate (PC) and alkali metal salts, such as LiClO 4, LiCF 3SO 3 and LiBF 4. The conductivity was studied by means of impedance spectroscopy, and it is found that the temperature dependence of conductivities follow a Arrhenius relationship when the molar percentage of PC is higher than 75% or LiClO 4 concentration is lower than 0.9 mol/l. However, when LiCF 3SO 3 or LiBF 4 is used instead of LiClO 4 as the salt, the situation is different. For LiCF 3SO 3, the Arrhenius relationship almost holds true for all the salt concentrations studied; while for LiBF 4, the Arrhenius equation hardly fits for any salt concentration. The dependence of activation energy on salt concentration is also examined, both for LiClO 4 and LiCF 3SO 3, the values of E a tend to reach a minimum value with increasing salt concentration.