The Role of Glycerol in Modulating Ionic Transport and Electrochemical Performance of PEO:NaCl Solid Polymer Electrolytes

Solid polymer electrolytes (SPEs) are promising alternatives to liquid electrolytes, offering stability and versatility. However, low ionic conductivity remains a challenge, which can be addressed through strategies such as salt incorporation and plasticizer optimization. This study aims to enhance PEO-NaCl-based polymer electrolyte films by adding glycerol to modify crystallinity and improve electrical properties. Characterization included Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and electrochemical impedance spectroscopy (EIS) to analyze structural, spectroscopic, and electrochemical properties as a function of plasticizer content. The study demonstrated significant enhancements in the electrochemical and dielectric properties of PEO-NaCl polymer electrolytes with increasing glycerol content. Electrical Impedance Spectroscopy (EIS) revealed a marked improvement in DC conductivity, increasing from 1.38 × 10 ^− 8 S/cm for the glycerol-free sample to 1.74 × 10 ^− 4 S/cm at 32% glycerol concentration, attributed to reduced bulk resistance and enhanced ion mobility. Glycerol also improves the dielectric properties of PEO-NaCl electrolytes by increasing polarizability, enhancing ion motion, and reducing ion aggregation, which leads to better ionic conductivity and energy dissipation. Additionally, the relaxation dynamics improved, as evidenced by sharper and higher dielectric loss tangent peaks (tanδ) with glycerol addition. The findings confirm that glycerol effectively reduces polymer rigidity, boosts ionic mobility, and improves conductivity, positioning it as a promising plasticizer for solid-state electrolytes.