Enhanced Energy Storage Characteristics in PVDF-Based Nanodielectrics with Core-Shell Structured and Optimized Shape Fillers

Introducing high-permittivity nano-fillers into a dielectric polymer is a practical way to enhance the permittivity of nanocomposite dielectrics. However, this normally leads to a decrease in the breakdown strength, which has limited the development of electrostatic capacitors. In this work, silica (SiO₂) coating and polydopamine (PDA) surface modification methods were combined for enhancement of the breakdown strength; we prepared poly(vinylidene fluoride) (PVDF) based composite dielectrics doped using double core-shell structure BaTiO₃ nano-particles (BT NPs) and nano-fibers (NFs) (PDA-SiO₂@BT NPs/PVDF or PDA-SiO₂@BT NFs/PVDF). Then, the contributions of the double-layer core-shell structure and filler shape to improving the energy storage performance of the dielectrics were systematically discussed. The results show that the synergy between the silica and PDA effectively increased the breakdown strength. Furthermore, the dielectric properties and energy storage properties of the PVDF-based dielectrics with various double core-shell filler (PDA-SiO₂@BT NPs or PDA-SiO₂@BT NFs) contents were also investigated. Compared with the particles, appropriate introduction of the PDA-SiO₂@BT NFs could more preferentially improve the energy storage characteristics. It was found that 1.0 vol.% PDA-SiO₂@BT NFs/PVDF exhibited a high energy storage density of 14.7 J/cm³ with an efficiency of 68%. This research provides a promising avenue for enhancing the energy storage capability of PVDF-based nanocomposite dielectrics.