Enabling High Dielectric Response in PVDF/V2C MXene–TiO2 Composites Based on Nontypical V–F–Ti Bonding and Fermi-Level Overlapping Mechanisms

High dielectric constant and breakdown strength are crucial for high-energy-density polymer/ceramic composites. Anatase-TiO 2 with low dielectric constant and V 2 C MXene with high work function are not satisfactory fillers. In the present work, V 2 C–TiO 2 hybrid filler was in situ synthesized, followed by fabricating poly(vinylidene fluoride) (PVDF)/V 2 C–TiO 2 composites via solution cast. Compared with PVDF/TiO 2 and PVDF/V 2 C composites, PVDF/V 2 C–TiO 2 composites have an improved high dielectric constant, depressed low dielectric loss, and maintained high breakdown strength. High overall electric traits are ascribed to the synergy of conductive V 2 C and semiconductive TiO 2 . Outer and inner surfaces of V 2 C were ornament-combined by anatase-TiO 2 particles having surface point defects as electron traps, contributing to low interface leakage conduction. Through density functional theory (DFT) calculations, nontypical V–F–Ti-bonding-induced dipole enhancement and Fermi-level ( E F ) overlapping-induced high electron localization mechanisms improve the dielectric response. Ternary composite with 10 wt % hybrid filler exhibits a dielectric constant of ∼99, a dielectric loss of ∼0.24 at 1 kHz, and a breakdown strength of ∼189 MV/m. This work might enable large-scale preparation of promising polymer/MXene composite dielectrics.