Structural and electrical studies of sodium iodide doped poly (vinyl alcohol) polymer electrolyte films for their application in electrochemical cells

Solid polymer electrolyte films based on poly (vinyl alcohol) (PVA) complexed with sodium iodide (NaI) were prepared using solution cast technique. The structural properties of pure and complexed PVA polymer electrolyte films were examined by X-ray diffraction (XRD) studies. The XRD results revealed that the amorphous domains of PVA polymer matrix was increased with the increase in NaI salt concentration. The variation of film morphology was examined by scanning electron microscopy (SEM) studies. Fourier transform infrared spectral studies for pure and complexed PVA films revealed the vibrational changes that occurred due to the effect of dopant salt in the polymer. Direct current conductivity was measured in the temperature range of 303-373 K, and the conductivity was found to increase with the increase in dopant concentration as well as temperature. Measurement of transference number was carried out to investigate the nature of charge transport in these polymer electrolyte films using Wagner's polarization technique. Transport number data showed that the charge transport in these polymer electrolyte systems was predominantly due to ions. Using these polymer electrolytes, solid-state electrochemical cells were fabricated. Various cell parameters like open-circuit voltage, short circuit current, power density, and energy density were deten-nined.