Achieving High Energy Density and Low Loss in PVDF/BST Nanodielectrics with Enhanced Structural Homogeneity

Abstract

Poor compatibility of polymer/ceramic composites used as high-pulse capacitors with high permittivity suffers from the reduced breakdown strength (E_b) and lowered energy density (U_e). Herein, mussel-inspired poly(dopamine) (PDA)-modified BaSrTiO₃ (mBST) nanoparticle and poly(vinylidene fluoride) (PVDF) matrix are bonded together to fabricate nanocomposites with a cross-linked network and enhanced compatibility. The significantly improved E_b of 466 MV/m and the highest U_e of 11.0 J/cm³ for PVDF-based polymer/BST composites have been obtained. By comparing the properties of the three series of composites with different structures, the contribution of ferroelectric relaxation, interface polarization, and leakage conduction to the dielectric loss has been well addressed. Notably, the surface modification of BST with PDA could remarkably enhance the compatibility of the two components and the structural homogeneity of the composite. The improved bonding between the polymer matrix and the filler chemically or physically is responsible for the reduced dielectric loss from both conduction loss and interfacial polarization, which is the key to improve the E_b, U_e, and η of the composite. It has been revealed that enhancing the homogeneity of the composites by modifying ceramics and constructing cross-linked networks between the polymer matrix and the filler might be a facile strategy to achieve high energy storage performance in polymer composites.