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

Abstract

High dielectric constant and breakdown strength are crucial for high-energy-density polymer/ceramic composites. Anatase-TiO2 with low dielectric constant and V2C MXene with high work function are not satisfactory fillers. In the present work, V2C–TiO2 hybrid filler was in situ synthesized, followed by fabricating poly(vinylidene fluoride) (PVDF)/V2C–TiO2 composites via solution cast. Compared with PVDF/TiO2 and PVDF/V2C composites, PVDF/V2C–TiO2 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 V2C and semiconductive TiO2. Outer and inner surfaces of V2C were ornament-combined by anatase-TiO2 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 (EF) 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.