Impact of Glycerol Content on the Electrochemical and Dielectric Behavior of MC-CS-Sorbitol-TiO ₂ Polymer Electrolytes

This study explores the synergistic role of glycerol in enhancing the ionic conductivity and dielectric properties of a novel methylcellulose (MC)–chitosan (CS) polymer composite doped with sorbitol and TiO2 nanoparticles (NPs), complexed with NaSCN salt. Glycerol was incorporated at varying concentrations (8–40 wt.%) to investigate its influence on polymer flexibility, ion mobility, and charge transport mechanisms. The films were synthesized via solution casting and characterized using FTIR, XRD, and UV-Vis spectroscopy. Electrochemical impedance spectroscopy (EIS) was utilized to analyze ionic conductivity, while dielectric performance was assessed via frequency-dependent dielectric studies. Results indicate that increasing glycerol content significantly reduced bulk resistance (Rb), from 10 kΩ (at 8% glycerol) to 343 Ω (at 40% glycerol), accompanied by an impressive rise in ionic conductivity from 0.414 µS/cm to 16.333 µS/cm a 39.45-fold enhancement. Dielectric relaxation analysis showed a shift in tan δ peaks toward higher frequencies and reduced relaxation times, suggesting enhanced segmental motion and faster ion dynamics. However, excessive glycerol slightly hindered performance due to possible ion clustering and increased viscosity. The optimal glycerol incorporation enhances polymer flexibility, ion dissociation, and charge carrier mobility, establishing the CS:MC:Sorbitol:TiO2–NaSCN–glycerol system as a promising candidate for flexible solid-state batteries and supercapacitors.