Enhanced dielectric constant and concurrently suppressed dielectric loss of PVDF composites incorporating BaTiO3@SSCNT@SiO2 core@double-shell structured fillers

Dielectric capacitor is an important component of power systems, but its low dielectric polarization and undesirable dielectric loss have still held back the development of miniaturized microelectronic devices. Hence, we reported core@shell structured fillers with a conducting material@insulating material double-shell to improve the dielectric performance of the poly(vinylidene fluoride) (PVDF) composites. The hybrid fillers introducing ultra-short carbon nanotube (SSCNT) as an inner layer between BaTiO3 (BT) as a core and silica (SiO2) as an outer shell were synthesized. As the thickness of the insulating shell is enough thin, the BT@SSCNT@SiO2/PVDF composites exhibit an enhanced dielectric constant and a concurrently suppressed dielectric loss with the decreasing thickness. The composite incorporating the filler with the thinnest SiO2 shell has the highest dielectric constant of 12.27 and the lowest dielectric loss of 0.023 at 20 wt% filler loading where the breakdown strength is about 15 less than the maximum value of 192.5 kV/mm. Furthermore, the hybrid fillers endow the composites with impressively stable dependence on frequency in a wide range of 102∼105 Hz. The achievement can be ascribed to the conducting property of the SSCNT inner layer and the suitable thickness of the insulating outer layer. They can synergetically provide the composites with an optimized polarization effect at a broad frequency resulting from the improved electrical field. This work reveals that a proper structure of the core@conducting material@insulating material core@double-shell filler can be an approach to optimize the overall dielectric performance of the polymer-based composites with high energy storage density.