Gel polymer electrolyte films comprised of 50% epoxidised natural rubber polymer host, lithium triflate salt (LiCF3SO3), and ethylene carbonate (EC) or propylene carbonate (PC) plasticizer are prepared using the solution-casting technique. AC impedance studies show that the electrical conductivity of the electrolytes is dependent on both the salt and plasticizer concentrations. The highest room temperature conductivity of 4.92×10−4 Scm−1 is achieved when 10wt.% propylene carbonate is introduced into the system containing 1.0g 50% epoxidised natural rubber polymer doped with 35wt.% LiCF3SO3. Conductivity studies of these polymer electrolytes are carried out at various temperatures and are found to obey the Vogel–Tamman–Fulcher (VTF) rule. The highest conducting plasticized sample is used as a gelled electrolyte for lithium–air cells.