Structural and electrochemical properties of ternary solid polymer electrolytes based on PVA:CS:FSG doped with sodium thiocyanate

Abstract

Biodegradable solid polymer electrolytes (BSPEs) have gained significant attention due to their exceptional processability, safety, and flexibility. This work presents the development of sodium ion (Na +) conducting ternary blended (BSPEs) using a standard solution casting technique. Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) validated the complete salt dissociation and demonstrated the formation of polymer-salt complexes. The deconvoluted XRD spectra revealed the degree of crystallinity () of electrolytes where the sample incorporated 40 wt% of NaSCN salt content (STC4) was found to be the lowest value. The deconvoluted FTIR spectra were used to estimate ionic transport parameters of diffusion coefficient (), ion mobility (), and carrier density (). Ionic conductivity and electrical properties of electrolyte samples were investigated by electrochemical impedance spectroscopy (EIS). The EIS results were fitted with electrical equivalent circuits to understand the electrical behavior of the films. The highest DC conductivity value () of (2.74 × 10−6 S/cm) was achieved for the STC4 sample, attributed to its highest amorphous region and carrier density. The dielectric studies proved beneficial in distinguishing the areas attributed to molecular polarizations and electrodes. The reduction of relaxation time is indicated by shifting loss tangent peaks (tan δ) toward high frequency ranges. According to dielectric relaxation studies, the appearance of peaks confirmed non-Debye type behavior. Distinct areas attributed to the effects of electrode polarization and () are seen in AC conductivity () spectra.