Enhancing energy density of poly(vinylidene fluoride) composite film via addition of N-doped carbon modified boron nitride and sandwich-structural engineering

It is a challenge to simultaneously enhance dielectric constant and breakdown strength of dielectrics and achieve a greatly elevated energy density. Herein, polyaniline was first coated onto the surface of boron nitride nanosheets (BN), and then nitrogen-doped carbon (NC) was formed through a carburization process, resulting in BN@NC composite, which was subsequently added to poly(vinylidene fluoride) (PVDF) to prepare a composite film with high dielectric performance. The characterization showed that BN@NC effectively preserved the nanosheet structure of BN and formed strong hydrogen bonding interactions with the PVDF matrix, promoting the β-PVDF formation. This not only improved the compatibility but also enhanced the interfacial polarization between conductive NC and the polymer, leading to a high dielectric constant. Moreover, the electrically insulating BN prevented the formation of leakage current, resulting in a high breakdown strength. Finally, a sandwich-structured film was constructed, and exhibited a dielectric constant of 10.2 (at 1 kHz), a breakdown strength of 380 MV m−1, and an energy density of 6.1 J cm−3, which were 20%, 36%, and 74% higher, respectively, than those of pure PVDF film (8.5, 280 MV m−1, and 3.5 J cm−3). This work highlights significant potential for applications in low-cost and high-energy density dielectric composites.