Effect of Mg(CF3SO3)2 concentration on structural and electrochemical properties of ionic liquid incorporated polymer electrolyte membranes

In the present study, a magnesium ion conducting polymer electrolyte membrane system based on polyethylene oxide (PEO) containing magnesium triflate Mg(CF3SO3)2 salt and 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIM-BF4) ionic liquid is prepared using standard solution casting technique. X-ray diffraction and differential scanning calorimetry studies reveal change in crystalline character with variation in Mg(CF3SO3)2 concentration within PEMs. Fourier transform infrared spectroscopy technique reflects ion-polymer interactions within the prepared polymer electrolyte system. Dielectric and modulus properties of prepared electrolyte membranes show significant changes in dielectric constant and relaxation behavior respectively on varying Mg(CF3SO3)2 concentration. The optimized polymer electrolyte membrane with 6 wt% of magnesium triflate salt shows maximum ionic conductivity of ~ 9.4 × 10−5 S cm−1 at room temperature. The ionic conductivity variation with temperature shows Arrhenius behavior for PEMs. The Mg2+ conduction within the PEMs is established using CV study and electrochemical stability window of ~ 4.0 V is determined using linear sweep voltammetry. The PEMs are dominantly ionic conducting with Mg2+ transport number ~ 0.22 for the optimized PEM.