Synergistic Effect of Al₂O₃@BaTiO₃–BNNSs Hybrid Fillers for Improved Energy Storage and Thermal Conductivity Properties of PVDF-Based Composites

Motivated by growing energy demands, dielectric materials with improved energy storage density and thermal conductivity are highly desirable. In this paper, hybrid fillers composed of BaTiO 3 nanofibers, Al 2 O 3 nanoparticles, and hexagonal boron nitride nanosheets (BNNSs) were utilized to prepare different poly(vinylidene fluoride) (PVDF)-based composite films. The effects of hybrid filler nanostructures on the comprehensive properties of composite films are investigated systematically. The designed Al 2 O 3 @BaTiO 3 nanofibers (AO@BT NFs) and BNNSs are constructed for the synergistic enhancement of breakdown strength and thermal conductivity. Consequently, PVDF composite films with 1.5 vol % AO@BT NFs and 4.0 vol % BNNSs exhibit the highest energy storage density of 8.3 J/cm 3 at 353.9 kV/mm, along with a thermal conductivity of 0.508 W/(m·K), which are 2.86 and 2.85 times those of the pristine PVDF, respectively. This work provides a convenient and effective strategy for flexible energy storage materials with designed hybrid fillers, which show potential applications in high-performance dielectric capacitors.