Comparative study of the properties of plasticized (PVDF-HFP)-MG49-LiBF4 blend polymer electrolytes

Abstract

Poly(vinylidene fluoride-hexafluoro propylene) (PVDF-HFP) blended with poly (methyl methacrylate) grafted natural rubber (MG49) and lithium tetrafluoroborate (LiBF4) as charge carriers based polymer electrolyte was prepared by solution casting technique. The effect of propylene carbonate (PC) and ethylene carbonate (EC) plasticizers on the properties of the polymer electrolyte films was investigated. Electrochemical impedance spectroscopy (EIS) showed that ionic conductivity increases as the concentration of plasticizer increases and the highest room temperature conductivities obtained are 1.51 × 10−3 S cm−1 and 7.39 × 10−4 S cm−1 at 80 wt % PC and 40 wt % EC, respectively. The addition of PC resulted in ionic conductivity enhancement in contrast with EC plasticizer. The temperature dependence conductivity for 80 wt % PC reached 6.52 × 10−2 S cm−1 at 373 K. Scanning electron microscopy (SEM) indicated the compatibility of PC with (PVDF-HFP)-MG49-LiBF4 whereas EC shows immiscibility with (PVDF-HFP)-MG49-LiBF4 complex. X-Ray Diffraction (XRD) studies show high degree of amorphous nature of the plasticized polymer electrolytes as indicated by reduction in the intensity of crystalline peaks. Thermogravimetric analysis (TGA) illustrates that the addition of plasticizer decreases the thermal stability of polymer electrolyte. However, linear sweep voltammetry (LSV) shows the electrochemical stability is up to 4 V.