Novel P(VDF-HFP)/BST nanocomposite films with enhanced dielectric properties and optimized energy storage performance

Abstract

Nanocomposites using poly (vinylidene fluoride-co-hexafluoropropylene), P(VDF-HFP), as the matrix, and barium strontium titanium oxide (BST) nanoparticles as the filler were systematically studied. P(VDF-HFP)/BST composite films containing different amounts of BST were prepared using the solution-casting method. The dielectric constant (εr), dielectric loss (tan δ), and their frequency and temperature dependence, were characterised for the films under weak electric fields. The behaviour of the films under high electric fields was explored using polarisation-electric field (P-E) loops. The εr was found to increase from 14.1 to 42.1 as the BST content increased from 0 vol% to 40 vol%, and the Maxwell-Wagner model showed a good fit with the measured εr values, indicating that the microstructure of the fabricated nanocomposites is uniform, which can also be observed in SEM images of all P(VDF-HFP)/BST nanocomposite films. In determining the temperature (T) dependence of the εr and tan δ of the composites, P(VDF-HFP) plays a decisive role, while BST plays an influential role. As the BST content increases, the charge/discharge energy density (Ucharge/Udischarge) increases, while the breakdown strength (Eb) and charge-discharge efficiency (η) decrease. Notably, the maximal Udischarge 3.79 J/cm3 was obtained when the BST content was 20 vol% at 2100 kV/cm. In addition, from the perspective of practical application, when the applied electric field intensity is lower than 900 kV/cm or between 900 kV/cm and 2100 kV/cm, in order to obtain the maximal Udischarge, the P(VDF-HFP)/BST composite with BST content of 30 vol% or 20 vol% should be selected respectively.