Ion conduction in solid polymer electrolytes composed of graft copolymer-lithium salt

Ion conduction in the solid polymer electrolytes of polyoxyethylene graft copolymers were investigated. The ion conducting polymer films were prepared via photo cross-linking reactions of methoxy polyethylene glycol-mono methacrylate with tri(propylene glycol) diacrylate in the presence of a photo initiator and lithium salt. The optimum [EO]/[Li] ratio in the photopolymerizable mixture for high ion conductivity was found to be 10, at which the conductivity of the film at room temperature approached to 10⁵S/cm. The effect of salt content on conductivity could be explained by the increased charge carriers and T_k with high salt concentration. The temperature dependence of the polymer electrolyte films showed VTF behaviour throughout the available thermal range (25∼ 130 °C), indicating that ion transport in the film can be much affected by the thermal motion of the polymer segments. The VTF parameters calculated from the temperature dependence of conductivity, the effect of POE chain length, and the effect of salt content on the ion conductivity of the film confirmed the influence of polymer segmental motion on ion conductivity.