Influence of NaF salt doping on electrical and optical properties of PVA/PVP polymer blend electrolyte films for battery application

Solid polymer electrolyte films of poly(vinyl alcohol) (PVA)/polyvinylpyrrolidone (PVP) doped with sodium fluoride (NaF) of different weight ratios (2, 4, 6, 8, and 10 wt%) have been prepared by using solution casting method. These films are characterized by XRD, FTIR, and SEM analysis. The X-ray diffraction (XRD) spectra show a characteristic PVA peak signifying its semi-crystalline nature. As NaF salt is incorporated into the polymer blend, the peak intensity decreases gradually, implying a decrease in the degree of crystallinity of the samples. The FTIR study confirmed the complexation, functional group occurred, and interaction between the different components in the polymer blend electrolyte, which suggests the micro-structural variations, takes place in polymer blended films by addition of NaF salt. The a.c. conductivity was measured at room temperature as well as in the temperature between the range 300 and 343 K. The conductivity was found to depend on NaF concentration which increases with increase in frequency and rise in temperature. The dielectric constant was found to decrease with increase in frequency and increased with temperature increase. The dielectric loss tangent peak was observed to increase in lower frequency range and its intensity is found to decrease with increasing frequency. Optical constants such as absorption coefficient (α), bandgap (E_g), extinction coefficient (k), refractive index (n), and real & imaginary part of optical dielectric constant were calculated. It was found that these optical constants found to depend on the concentration of NaF in PVA/PVP blend system. Transference number measurement (TNM) was carried out in order to investigate the nature of charge transport mechanism which showed that charge transport in the as-prepared polymer blend films is predominantly due to ions. Electrochemical cells were fabricated for the as-prepared samples and various cell parameters were determined.