Background: Solid polymer electrolyte (SPEs) films based on poly (vinylidene
fluoride-co-hexafluoropropylene) P(VDF–HFP) and sodium thiocyanate (NaSCN) are prepared
using the solution casting technique.
Methods: Ionic liquid (IL; 1-ethyl-3-methyl-imidazolium tricyanomethanide ([EMIM]
[TCM]) is incorporated into the prepared polymer-salt complex matrix to enhance its ionic
conductivity further. Polarized optical microscopy (POM) shows a change in the surface
morphology of IL doped polymer electrolyte films. The composite nature of polymer electrolyte
films is confirmed using Fourier transform infrared (FT-IR) spectroscopy via studying
ion-ion and ion-polymer interactions. The structural morphology of ionic liquid doped
polymer electrolyte films (ILDPE) confirms the complexation between the ionic liquid
([EMIM][TCM]), salt (NaSCN) and polymer P(VDF-HFP). This is further confirmed using
DSC and XRD measurements. The XRD structural analysis confirms that the intensity of
crystalline peaks present in IL doped solid polymer electrolyte films decreases as compared
to that of the pure polymer as well as polymer salt complex system. XRD clearly indicates
the enhancement in its amorphous nature, which is necessary to increase the conductivity.
Results: The incorporation of IL into polymer salt-complex matrix leads to changes in the
melting of polymer electrolytes, confirmed by DSC thermograms. Polymer electrolyte films
are also characterized using impedance spectroscopy (IS) to check their electrical properties.
The highest ionic conductivity is found to be 7.80×10-4 S cm-1 for 6 wt% IL doped polymer
Conclusion: The Linear sweep voltammetry (LSV) analysis shows that the optimized polymer
gel electrolyte is electrochemically stable up to 1.5 V. The calculated value of ionic
transference number (tion) is found to be 0.985. A laboratory scale electrical double layer capacitor
(EDLC) has been fabricated using this highly conducting polymer electrolyte film.
The specific capacitance value is found to be 1.31 F g-1.
Keywords: Polymer electrolyte, electrical double layer capacitor, ionic transference number (tion), charge
carriers, mobility, ionic conductivity.
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