This study aims to investigate the improvement of ionic conductivity and other electrical parameters of a polyethylene oxide/sodium bromide (PEO:NaBr) complex electrolyte with the use of glycerol as a plasticizer. The PEO:NaBr electrolyte was modified by insertion of various concentrations (0, 8, 16, 24, and 32 wt.%) of glycerol to boost the ionic conductivity. The structural and electrical properties of the prepared electrolyte films were examined by x-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and electrochemical impedance spectroscopy (EIS). The results showed that the highest ionic conductivity \(\left(2.3 \times {10}^{-4}\right)\) was attained in the sample containing 24 wt.% glycerol synthesized at room temperature. This increased conductivity may be attributed to the plasticizing effect of glycerol, which made the PEO matrix less crystalline, as evidenced by the broader and less defined XRD peaks. The dielectric constant was enhanced relative to the dielectric loss by increasing the glycerol content in the low-frequency applied electric field. Also, the maximum loss tangent shifted to higher frequencies, indicating that the addition of glycerol shortened the dipole relaxation time. The dissociation of the NaBr in the PEO was confirmed by the FTIR spectra. In addition, a shift in the absorption band showed the interaction between the PEO, NaBr, and glycerol, which contributed to the enhanced amorphous nature and ion transport properties. These findings suggest that glycerol can play a crucial role in modifying the structural and electrical properties of PEO-based electrolytes, paving the way for more efficient solid-state electrolytes for future energy storage applications.
