Bilayer structured PVDF-based composites via integrating BaTiO3 nanowire arrays and BN nanosheets for high energy density capacitors

Abstract

Polymer based dielectric nanocomposites with high energy density are highly desirable to satisfy the lightweight and integration of electrostatic capacitors in electronic and electrical equipment. Recently, it is proved that polymer incorporated with aligned nanowire array represents an effective strategy for significantly improving the permittivity due to largely enhanced space charge and orientation polarization. Nevertheless, it is still a great challenge to overcome the contradictory relationship between permittivity and electric breakdown strength. In this work, a unique spatial design in bilayer structured PVDF based nanocomposites are proposed by incorporating BaTiO3 nanowire array with high-permittivity and BN nanosheets with wide-band gap, respectively. The bottom BaTiO3/PVDF layer and upper BN/PVDF layer are constructed for the synergy ascension of permittivity and breakdown strength by the optimization of BN nanosheet content. As a consequence, the dielectric permittivity of BaTiO3/BN-PVDF nanocomposite reaches 35.3 at 1 kHz, which is higher than that of 33.9 for BaTiO3/PVDF nanocomposite and 9.1 for pristine PVDF film, respectively. Also, the significantly increased electric displacement, e.g., 12.1 μC cm−2, enhanced Eb, e.g., 500.3 kV mm−1 and suppressed leakage current density are obtained in BaTiO3/BN-PVDF nanocomposites. The highest discharged energy density reaches 16.1 J cm−3, which shows a great improvement comparing to that of commercial biaxially oriented polypropylene (BOPP) film. This work demonstrates a unique design of spatial structure integrating various anisotropic nanofillers in polymer-based nanocomposite, whose outstanding energy storage performance makes it as a promising candidate for high-performance electrostatic capacitors application.