Poly(vinyl chloride) (PVC)-based polymer electrolytes ﬁlms consisting of lithium triﬂuromethanesulfonate (LiCF3SO3)-ethylene carbonate (EC) were prepared by the solution-casting method. Ionic conductivities of the electrolytes have been determined by an impedance studies in the temperature range of 298–373 K. Complexation of the prepared electrolytes is studied by X-ray diffraction (XRD) analysis. Thermogravimetric analysis (TGA) was used to conﬁrm the thermal stability of the polymer electrolytes. The conductivity–temperature plots were found to follow an Arrhenius nature. All these ﬁlms are found to be thermally stable until 132–167°C.