Ionic conductivity and transport properties of poly(vinylidene fluoride-co-hexafluoropropylene)-based solid polymer electrolytes

Highlights: • Free-standing (PVdF-HFP) – LiTf films were successfully prepared and characterized. • XRD, FTIR, SEM and DSC analyses confirm complexation between polymer and salt. • Ionic conductivity depends on salt content as well as temperature. • Charge transport is mainly due to ionic motion. Polymer electrolytes containing poly(vinylidene fluoride-co-hexafluoropropylene) (PVdF-HFP) and various concentrations of lithium triflate were prepared to determine the optimal polymer-salt composition for maximum ionic conductivity. Complex formation was ascertained from X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and differential scanning calorimetry (DSC) studies. The conductivity measurements reveal that the ionic conductivity of the polymer electrolytes containing various salt concentrations increases with temperature and obeys the Arrhenius rule. It is found that the electrolyte containing 25 wt.% of lithium triflate exhibits the highest room temperature conductivity. Moreover, Ionic transference measurements show predominance of ionic motion.