Improved dielectric and energy storage properties of three-dimensional BaTiO3/polyvinyl alcohol-boron nitride flexible dielectric composite via template infiltration strategy

Continuous three-dimensional BaTiO₃ (3DBT) ceramic network was prepared by the sol-gel method using cleanroom wipers as the template. Subsequently, flexible 3DBT/polyvinyl alcohol-boron nitride nanosheets (PVA-BNNS) composite dielectric films were facilely fabricated by inversely introducing different BNNS concentrations of PVA-BNNS solution into the 3DBT network. The results demonstrated that PVA solution effectively embedded into the 3DBT framework through an inverse infiltration process, thereby endowing the material with excellent flexibility. The content of 3DBT in the saturated 3DBT/PVA-BNNS composite was ∼27 wt% (6.9 vol%). In addition, the 3DBT/PVA-1.0%BNNS system exhibited an excellent dielectric constant of 17.4 (at 1 kHz), a high breakdown strength of 114.5 kV·mm⁻¹ and an energy density of 2.51 J·cm⁻³ (at 110 kV·mm⁻¹), being 1.67, 1.58 and 7.17 times higher than those of traditional fabricated 27 wt% nano-BT/PVA (at 70 kV·mm⁻¹) composite, respectively. What's more, the obtained 3DBT/PVA-BNNS dielectric film exhibited superior thermal and mechanical stability, indicating potential applications in harsh environments.