Poly(vinylidene fluoride) nanocomposite capacitors with a significantly enhanced dielectric constant and energy density by filling with surface-fluorinated Ba0.6Sr0.4TiO3 nanofibers

Abstract

We report nanocomposites with an increased dielectric constant, enhanced electric breakdown strength and high-energy density based on a surface-modified Ba_0.6Sr_0.4TiO₃ nanofiber (BST NF) filled poly(vinylidene fluoride) polymer. To improve the dispersion stability of the fillers in the polymer matrices, surface modification of the dielectric fillers was obtained through functionalization of the BST NF by hydroxylation using H₂O₂ treatment and subsequent fluorination. The surface-fluorinated BST NF (F-BST NF) exhibit excellent dispersion in the PVDF polymer matrix and strong interfacial adhesion with the matrix, leading to excellent flexibility for the composites. The composites exhibit the optimum dielectric performance (i.e. high dielectric constant and high breakdown strength). With 2.5 vol% of F-BST NF, the extractable energy density of the F-BST NF/PVDF composites is 7.5 J cm⁻³, which is three times as high as that of a pure PVDF matrix, showing good potential for energy storage applications. Our strategy provides a simple but effective way to prepare high performance flexible dielectric composite capacitors with high storage density.