A new type of plasticizer, a modified carbonate (MC3) made by attaching three ethylene oxide units to the 4-position of ethylene carbonate, has been synthesized. The ionic conductivity of a polymer electrolyte using this type of plasticizer in a poly(ethylene oxide) (PEO)-LiCF3SO3 complex has been studied. Adding 50% of this plasticizer by weight of PEO to the PEO-LiCF3SO3 complex, yielded an ionic conductivity of 5 x 10(-5) S/cm at 25-degrees-C, which is two orders of magnitude higher than that found f or a PEO-LiCF3SO3 electrolyte without a plasticizer, and one order of magnitude higher than that found when using propylene carbonate (PC) as a plasticizer. The temperature dependence of the conductivity and thermal analysis results indicate that this new plasticizer increases the ionic conductivity throughout the entire complex system, whereas conventional plasticizers, like PC, simply create a high conductivity pathway through the plasticizer itself. The new plasticizer also enhances the ion pair dissociation which in turn improves the ionic conductivity
