Conductivity Study on PEO Based Polymer Electrolytes Containing Hexafluorophosphate Anion: Effect of Plasticizer

Abstract

AbstractPEO based polymer electrolytes containing ammonium hexafluorophosphate (NH4PF6) and hexafluorophosphoric acid (HPF6), both with PF anion have been studied. The effect of the addition of propylene carbonate (PC) to PEO‐NH4PF6 and PEO‐HPF6 has been observed to increase in ionic conductivity which is attributed to an increase in free ion concentration due to the dissociation of ion aggregates present at higher acid/salt concentrations. The plasticized polymer electrolytes containing HPF6 show relatively higher conductivity (σmax = 1.02 × 10−4 S/cm at 10 wt% HPF6) as compared to electrolytes containing NH4PF6 (σmax = 1.09 × 10−5 S/cm at 10 wt% NH4PF6). Presence of free ions, ion aggregates and their dissociation with the addition of PC has been studied by Fourier Transform Infrared Spectroscopy (FTIR). The change in amorphous phase with PC content was also studied by X‐Ray Diffraction (XRD). The variation of conductivity with temperature shows Vogel–Tammen–Fulcher (VTF) behavior, which is associated with the highly amorphous nature of electrolytes. 1H Nuclear magnetic Resonance (NMR) spectra at different temperatures shows line narrowing and suggests the onset of long range ion diffusional motion. Change in surface morphology of polymer electrolytes with the addition of PC is also checked by Scanning Electron Microscopic (SEM) studies.