Interfacial fluorine migration-induced low leakage conduction in PVA based high-k composites with V2C MXene-SWCNT switchboard-like ceramic via ab initio MD simulations

Abstract

A high dielectric constant and electric breakdown strength are desired in high-energy-density polymer/ceramic composites. Ultrahigh interface leakage conduction between polymer and carbon nanotubes (CNTs) hinders the development of CNT-filled composite dielectrics. In this work, composite dielectrics bearing V₂C MXene-CNT hybrid-particles were fabricated. Environment-friendly polyvinyl alcohol (PVA) was employed as the matrix. Interface polarization between PVA and ceramics improved the dielectric constant of composites. A switchboard micro-structure was obtained in the hybrid-ceramic consisting of layered V₂C and thread-like single-walled carbon nanotubes (SWCNTs). This micro-structure led to adsorption-migration of fluorine from V₂C to CNTs, triggering Coulomb-blockade zones at CNT surfaces supported by first-principles molecular-dynamics calculations. Interface leakage conduction between CNTs and PVA was depressed by quick-slow-quick (QSQ) electron transmission of CNTs. Compared to PVA/CNT composites, PVA/V₂C–CNT composites exhibited a favorable high dielectric constant, strongly depressed low dielectric loss and conductivity, and elevated high breakdown strength. The ternary composite with 5 wt% hybrid-ceramic showed a dielectric constant of ∼232 (122 times that of PVA) and a dielectric loss of ∼0.2 (1.4 times that of PVA) at 100 Hz, as well as a breakdown strength of ∼35 MV m⁻¹ (60% of that of PVA). A balance of high dielectric constant and breakdown strength was achieved in the ternary system. This work might enable large-scale preparation of high-performance composite dielectrics.