Design of Single Ionic Conduction in Polymeric Solid Electrolytes

Oligo(oxyethylene) methacrylate, MEO, has been synthesized as a basic material to design a polymeric solid electrolyte. The homopolymer P(MEO) has a glass transition temperature of -78°C. P(MEO) solubilizes inorganic salts without solvent, and the dissociated ions migrate fast to give very high ionic conductivity, above 10^?5 S/cm for ac. Although the ac conductivity is high, the current decreases gradually under dc conditions. This is improved by the design of an ionic conductor using only cations. Polyoligo(oxyethylene) methacrylate-co-alkali metal methacrylate], P(MEO-MAM), is prepared as an organic solid electrolytes which allows cationic single-ion conduction. The ionic conductivity of the films depends on the electrolyte content, the dissociation energy of the comonomeric electrolytes, and the degree of segmental motion surrounding the ions in the polymer matrix. The ionic conductivity of Li or K is around 10^?6 S/cm in these polymeric systems at 80°C. The plot of logarithmic conducticity vs reciprocal absolute temperature is a curved line. The Williams-Landel-Ferry parameters, calculated from the temperature dependence of the conductivity, coincided with theoretical values within a certain range. The single-ion conduction in these films is concluded to be affected considerably by the segmental motion of the matrix polymer. This is also confirmed by the Vogel-Tammann-Fulcher plot.