Enhancing Breakdown Field Strength and Energy Density in Sandwich-Structured P(VDF-HFP)/BT Films with BN Coating

With the rapid development of communication, electronics, medical, and energy industries in modern society, film capacitors have garnered widespread attention and undergone significant growth. However, the low energy density (Ue) resulting from low breakdown strength (Eb) significantly limits the application of thin-film capacitors. In this work, we use a low-cost and effective dip-coating method to apply boron nitride (BN) layers onto the outer layers of poly(vinylidene fluoride-co-hexafluoropropylene)/barium titanate (P(VDF-HFP)/BT) composite films to prepare boron nitride-poly(vinylidene fluoride-co-hexafluoropropylene/barium titanate-boron nitride (BN-P(VDF-HFP)/BT-BN) composite films with a sandwich structure that exhibits extremely high Eb and Ue. The experimental results show that the sandwich-structured BN-P(VDF-HFP)/BT-BN films containing 7.5 wt% BT nanoparticles obtained 530 MV/m Eb and 18.12 J/cm3 Ue, both of which are much higher than those of the corresponding monolayer films. In addition, the finite element simulation results show that the designed sandwich-structured films can reduce local field strength distortion, decrease leakage current, and suppress the development of breakdown channels, thereby significantly improving Eb and Ue. In summary, this study presents a low-cost and effective method for enhancing the breakdown strength and energy density of thin-film capacitors.