<p>In this study, poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP)-based composite polymer electrolytes containing ionic liquid (IL) and TiSiO₄ nanofiller are developed to determine the coupled effects of filler content, temperature and frequency on dielectric characteristics and ion transport. Membranes are prepared by the conventional solution-casting method and characterized by Fourier transform infrared spectroscopy, X-ray diffraction, thermogravimetric analysis and scanning electron microscopy tests. The characterizations confirm strong IL-polymer interactions, reduced crystallinity, effective filler dispersion and sufficient thermal stability. AC conductivity (<i>σ</i>_ac) measurements show that IL incorporation improves conductivity, while TiSiO₄ further enhances the physical film properties. The TiSiO₄ filler maintained ionic conductivity at comparable levels while modifying interfacial polarization behavior and the dielectric response of the composite electrolyte. At 430&#xa0;K, the highest DC conductivities (<i>σ</i>_dc) are observed for the PVDF-HFP/IL and PVDF-HFP/IL/TiSiO₄(1.5) composite membranes, reaching 8.03 × 10⁻⁴ and 6.86 × 10⁻⁴ S/m, respectively, which are nearly three orders of magnitude higher than that of pure PVDF-HFP (3.58 × 10⁻⁷ S/m). Dielectric analyses reveal pronounced low-frequency permittivity amplification, with the dielectric constant (<i>ε</i>′) reaching 1.51 × 10⁴ at 20&#xa0;Hz and 430&#xa0;K for PVDF-HFP/IL/TiSiO₄(2.0). Loss tangent (tan <i>δ</i>) profiles exhibit composition- and temperature-dependent relaxation behavior and indicate thermally-activated dipolar reorientation. Unlike conventional oxide fillers, TiSiO₄ acts as an active interfacial component that modulates coupling between polarization dynamics and ion transport. The IL–TiSiO₄ interaction optimizes conductivity and dielectric behavior, demonstrating promising potential for high-performance composite electrolytes.</p>