Blend polymer electrolyte films based on poly(ethyl methacrylate)/poly(vinylidenefluoride-co-hexafluoropropylene) incorporated with 1-butyl-3-methyl imidazolium iodide ionic liquid

• Competition between Li+ and BMI+ ions affect number density and free ion mobility
• Interactions between BMI+ ions of BMII and PEMA/PVdF-HFP blend was confirmed
• BMII-based films which are thermally stable up to 200 °C have been developed

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 × 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 °C.