Simultaneously Enhanced Permittivity and Electric Breakdown Strength of Polyacrylonitrile Composites by Introducing Ultralow Content BaSrTiO3 Nanofibers

Introducing nanoparticles in a polymer matrix to simultaneously enhance permittivity and electric breakdown strength is a challenge for the polymer‐based dielectric films to obtain improved energy‐storage density and efficiency. Herein, it is demonstrated that both of the aforementioned properties are enhanced by using an ultralow content of BaSrTiO 3 nanofibers (BST NFs) with high aspect ratios (9–18) in the polyacrylonitrile (PAN) matrix. As the filler loading is 0.1–0.9 wt%, the permittivities of the composites are increased from 6.3 of the pure PAN to 6.93–7.92 at 1 kHz. The maximum electrical breakdown strength achieved at 0.3 wt% is 3865 kV cm −1 , which is much higher than that of the pure PAN of ≈2987 kV cm −1 . Significantly enhanced discharged energy density of 8.25 J cm −3 at a high charge–discharge efficiency of 83% is achieved. The electrical breakdown mechanism at ultralow filler content is investigated based on the simulation of space charges distribution.