Poly(ethyl methacrylate) (PEMA) and poly(vinylidenefluoride-co-hexafluoropropylene) (PVdF-HFP) in the weight ratio of 70:30 are chosen as hosts for the development of a polymer blend electrolyte system containing lithium trifluoromethanesulfonate (LiTf) salt as ion provider and 1-butyl-3-methyl imidazolium iodide (BMII) as ionic liquid. The best ambient conductivity is achieved at 4.86 x 10(-5) S CM-1 in the polymer blend-salt sample incorporated with 12.5 wt.% BMII. The imidazolium (BMI+) cations of BMII have interacted with the oxygen atoms in the ethoxy (O-C2H5) groups of PEMA as well as the fluorine atoms in the CF2 groups of PVdF-HFP. Competition between the Li+ ions and BMI+ ions for the coordination sites at the polar atoms of the polymer blend host exists and plays a role in determining the number density and mobility of the free ions. Thermal gravimetric analysis (TGA) has shown that the BMII-based polymer electrolytes are thermally stable up to about 200 degrees C. (C) 2016 Elsevier B.V. All rights reserved.