Glycerol-enhanced ion transport and electrical properties in chitosan–methyl cellulose–NH4CF3SO3–TiO2 nanocomposite electrolytes

Abstract

Polymer electrolytes are increasingly recognized for their potential in energy storage applications such as batteries and supercapacitors, owing to their mechanical flexibility, thermal stability, and safety advantages over liquid counterparts. This study explores a nanocomposite polymer electrolyte system based on chitosan (CS), methyl cellulose (MC), sorbitol, TiO₂ nanoparticles, and ammonium trifluoromethanesulfonate (NH₄CF₃SO₃), with glycerol added at varying concentrations (9–45 wt.%) to enhance ion mobility. Five samples (EX1–EX5) were fabricated via solution casting and systematically analyzed. XRD revealed a semicrystalline structure with crystallinity decreasing from 31.84% to 23.38% as glycerol content increased, indicating enhanced amorphous character. FTIR spectra confirmed strong hydrogen bonding and polymer–plasticizer interactions, while EIS measurements showed a sharp reduction in bulk resistance from 16.55 kΩ (EX1) to 182 Ω (EX5), resulting in a conductivity increase from 0.209 µS cm⁻¹ to 27.11 µS cm⁻¹, an over 129-fold improvement. AC conductivity and dielectric analyses demonstrated increased permittivity and reduced relaxation times, reflecting faster ion dynamics and improved segmental mobility. Electrical modulus studies further supported enhanced local ionic transport and reduced dielectric relaxation time. These results underscore the effectiveness of glycerol as a plasticizer in promoting ion transport and optimizing electrochemical performance in CS–MC-based polymer electrolytes for advanced energy storage technologies.