Thermally stable polyimide nanocomposite films from electrospun BaTiO3 fibers for high-density energy storage capacitors

Abstract

Barium titanate (BaTiO₃, BT) fibers were prepared via electrospinning with a sol–gel precursor, followed by a calcination process. Polyimide (PI) nanocomposite films with the electrospun BT fibers were fabricated using an in situ dispersion polymerization method. The morphology and crystal structure of the BT fibers were analyzed through scanning electron microscopy and X-ray diffraction. It was found that their diameter and length were greatly dependent on the calcination temperature. Compared to the spherical BT nanoparticles, the introduction of one-dimensional BT fibers into the PI matrix gave rise to improved thermal stability. Besides, the dielectric behaviors of the PI/BT-fiber composite films were investigated over the frequency range from 10² Hz to 10⁶ Hz and within a temperature range of 20–150 °C. The results demonstrated that the dielectric permittivity at 10² Hz of the PI nanocomposite films with 30 vol% BT fibers was improved up to ∼27, and the corresponding dielectric loss is relatively low (∼0.015). The dielectric permittivity of the PI/BT-fiber composite films exhibited a slight dependence on temperature, while it is highly dependent on the calcination temperature of the electrospun BT fibers. This work opens a new path to optimize the dielectric properties of thermosetting polymer composite films with high energy storage density.