Effect of Glycerol Content on Crystallinity, Dielectric Behavior and Ionic Transport of CS–Dextran–LiClO ₄ –Al ₂ O ₃ Films

This study systematically examines the influence of glycerol (9–45 wt%) as a plasticizer on the structural, physicochemical, and electrochemical properties of chitosan–dextran–LiClO 4 –Al 2 O 3 nanocomposite polymer electrolytes prepared by solution casting. Electrochemical impedance spectroscopy revealed a pronounced reduction in bulk resistance from 64,310 Ω to 160 Ω and an increase in ionic conductivity from 0.04 to 18.10 μS cm −1 (over 450‐fold). The relaxation time ( τ ) decreased from 1441.49 to 4.18 μs, indicating accelerated ion reorientation and enhanced charge‐carrier mobility at higher glycerol content. FTIR analysis evidences strong hydrogen‐bonding interactions among polymer hydroxyl/amine groups, Li + ions, and Al 2 O 3 nanoparticles, which promote salt dissociation and complex formation. Increasing glycerol content also elevated the dielectric constant ( ε ′) and dielectric loss ( ε ″), reflecting intensified dipolar and interfacial polarization and a higher mobile charge density. Glycerol augmented the amorphous fraction and segmental mobility, thereby facilitating ion transport. The optimized CS–Dextran–LiClO 4 –Al 2 O 3 –glycerol film demonstrates significantly improved ionic and dielectric performance, making it a promising solid polymer electrolyte for advanced electrochemical and energy‐storage applications.