<p>This study investigates the influence of titanium oxide (TiO₂) nanofiller concentration (0, 1, 3, 5, and 7 wt%) on the structural, dielectric, and electrochemical behavior of glycerol-plasticized chitosan-sorbitol-NaNO₃ polymer electrolytes. Comprehensive characterizations, including X-ray diffraction (XRD) with peak deconvolution, Fourier-transform infrared spectroscopy (FTIR), and electrochemical impedance spectroscopy (EIS), were employed to evaluate the electrolyte performance. The experimental results reveal that the sample incorporated with 5 wt% TiO₂ (CST-5) delivers the optimum performance. At room temperature, CST-5 exhibits the highest DC ionic conductivity of 1.67 × 10^− 6 S cm^− 1 and the lowest bulk resistance of 3858 Ω, accompanied by an enhanced AC conductivity response and a well-defined ionic relaxation. Structural analysis via XRD deconvolution using a Gaussian function confirms that CST-5 possesses the lowest degree of crystallinity (12.6%). This structural amorphization arises from the effective dispersion of TiO₂ nanoparticles, which disrupts the polymer chain ordering and promotes amorphous domains, thereby enhancing local chain flexibility. FTIR analysis confirmed the complexation and molecular interactions within the electrolyte matrix, evidenced by noticeable shifts and intensity variations in the bands corresponding to O-H, N-H, and C = O functional groups, indicating successful coordination between Na⁺ ions, the polymer backbone, and TiO₂ nanoparticles. Consequently, ion transport parameters (diffusivity, mobility, and relaxation time) are significantly optimized, facilitating efficient Na⁺ ion migration. Beyond 5 wt% TiO₂, a decline in electrochemical properties is observed due to nanofiller agglomeration. These findings demonstrate that the fabricated flexible nanocomposite films hold strong potential for next-generation solid-state batteries, supercapacitors, and advanced energy storage applications.</p> Graphical abstract <p></p>