Influence of TiO\(_2\) Nanoparticles in Enhancing the Structural, Thermal and Electrochemical Properties of PVdF-HFP: NaI based Polymer Electrolyte Systems

Abstract

This study investigates the influence of TiO₂ nanoparticles on the structural, thermal, and electrochemical properties of PVdF-HFP: NaI based polymer electrolyte films prepared by solution casting. The films were characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), and electrochemical impedance spectroscopy (EIS). XRD analysis showed that incorporation of NaI and subsequent TiO₂ addition altered the crystalline–amorphous balance of the polymer matrix, with the 6 wt.% TiO₂ composition exhibiting enhanced amorphous character relative to the other filler concentrations. FTIR spectra indicated polymer–salt–filler interactions through shifts and changes in characteristic vibrational bands, supporting complex formation within the electrolyte system. DSC measurements further showed a pronounced reduction in melting temperature to 77.11 °C at 6 wt.% TiO₂, consistent with increased chain flexibility and reduced crystalline ordering. Impedance analysis demonstrated that ionic conductivity increased by approximately one order of magnitude compared with the unfilled electrolyte. The optimally filled 6 wt.% TiO₂ sample reached a room-temperature ionic conductivity of 2.24 × 10⁻² S cm⁻¹, whereas further filler addition reduced conductivity. The combined results indicate that TiO₂ concentration strongly influences polymer structure, thermal transitions, and ion transport. Within the investigated compositions, 6 wt.% TiO₂ provided the most favorable balance between amorphous character and ionic conductivity, supporting the suitability of this nanocomposite polymer electrolyte system for electrochemical applications.