Achieving high dielectric permittivity, high breakdown strength and high efficiency by cross-linking of poly(vinylidene fluoride)/BaTiO3 nanocomposites

Polymer nanocomposite dielectrics have drawn increasing attention recent years. However, dispersion of high-ε nanoparticles causes decreased breakdown strength and increased loss tangent. High dielectric permittivity, high breakdown strength, low dielectric loss and high charging-discharging energy efficiency are hard to achieve at the same time. In this research, in order to achieve all these goals, a combination method consists of cross-linking and dispersion of high-ε nanoparticles was carried out. The cross-linking points limit polymer chain mobility in the amorphous phase, providing lower dielectric loss and lower conductivity. Therefore, breakdown strength increased from 402.8 MV/m of PVDF to 517.2 MV/m of cross-linked PVDF. By dispersing coated BaTiO3 nanoparticles, followed by cross-linking, cross-linked nanocomposites with higher ε, higher breakdown strength and higher efficiency compared with the polymer matrix were prepared. The maximum discharging energy density reached up to 14.1 J/cm3, about 70% higher than 8.02 J/cm3 for pristine PVDF. This research provides us a novel approach to achieve all these goals by a combination of cross-linking and dispersion of coated BT nanoparticles.