Improved energy storage property in polyvinylidene fluoride-based multilayered composite regulated by oriented carbon nanotube@SiO2 nanowires

High-performance dielectric capacitors are essential components of advanced electronic and pulsed power systems for energy storage. Because of their high breakdown strength and excellent flexibility, polymer-based capacitors are regarded as auspicious energy storage material. However, the energy storage capacity of polymer-based capacitors is severely limited due to their low polarisation and low dielectric permittivity. The modified Stöber method was used to construct two types of CNT@SiO₂ (CS) one-dimensional core-shell structured nanowires with different shell thicknesses. By integrating the procedures of solution mixing, melt blending, hot-stretching orientation and hot pressing, sandwich-structured poly (vinylidene fluoride) (PVDF)-based composites were fabricated. The CS core-shell nanowires dispersed in the inter-layer serve as electron donors, leading to a high permittivity, while two PVDF outer layers provide the favourable overall breakdown strength. The insulating SiO₂ shell can effectively limit the migration of carriers and keep the dielectric loss at a relatively low level in the composites. The CS/PVDF composite exhibited an enhanced discharged density (~6.1 J/cm³) and breakdown strength (~241 kV/mm) when the interlayer filled with as small as 1 wt% CS nanowires with the SiO₂ shell thickness of 8 nm, which is 203% and 18.7 % higher than pure PVDF (~2.01 J/cm³ at 203 kV/mm), respectively. This research presents a practical strategy for designing and fabricating advanced polymer film capacitor energy storage devices.