Enhanced Dielectric and Energy Storage Capacity of Polymer Dielectrics via Reverse Infiltration of Poly(vinylidene fluoride)–Boron Nitride into a Three-Dimensional Barium Titanate Network

A large dielectric constant and high breakdown strength in a flexible energy storage capacitor would allow for increased energy storage capacity and higher durability, making it a more efficient and reliable option for various electronic devices. This work presented a continuous three-dimensional barium titanate (3DBT) skeleton, which was facilely synthesized by the sol–gel method and subsequent high-temperature calcination process using a cleanroom wiper as a template. Flexible 3DBT/PVDF-BNNS dielectric materials were then prepared by reversely infiltrating poly(vinylidene fluoride)–boron nitride nanosheet (PVDF-BNNS) solutions into the above 3DBT network. The obtained 3DBT/PVDF-BNNS composites were dense with a saturated 3DBT concentration of ∼18 wt % (6.1 vol %). The 3DBT enabled successive polarization, while the BNNS inhibited charge carrier transition, thereby enhancing the dielectric constant, breakdown strength, and energy storage density of 3DBT/PVDF-BNNS composites simultaneously. The 3DBT/PVDF-0.75BNNS composite reached a comprehensive large dielectric constant of 18.2@1 kHz, high breakdown strength of 120.9 kV·mm–1, and accordingly an enhanced energy density of 1.16 J·cm–3, overperforming that of neat PVDF and 3DBT/EP systems. The synergistic effect of 3DBT and wide bandgap BNNS is distinct, indicating potential applications in embedded capacitor related applications.