Enhanced energy density in sandwich-structured P(VDF-HFP) nanocomposites containing Hf0.5Zr0.5O2 nanofibers.

• Ferroelectric HZO-NFs was fabricated via electrospinning technique. • Continuous interface was built between HZO-NFs with low ɛ r and P(VDF-HFP). • Ultrahigh E b of 706.71 kV/mm was obtained due to the existence of multi-interfaces. • Enhanced U d of 21.63 J/cm3 was achieved in P-3 wt% HZO/P-P sandwich structures. Ceramic/polymer composites with high energy density attract great interest due to their application in micro-electric power systems. However, the large permittivity mismatch between ceramic fillers and polymer matrix will largely decrease the breakdown strength and energy density of nanocomposites. Herein, one-dimensional Hf 0.5 Zr 0.5 O 2 nanofibers (HZO-NFs) with very low permittivity were proposed as the loading fillers in poly (vinylidene fluoride - hexafluoro propylene) (P(VDF-HFP)) copolymer for energy-storage applications for the first time via a simple scalable method of electrospinning technique. P(VDF-HFP) nanocomposites with 3 wt% HZO-NFs (3 wt% HZO/P) showed a high discharged energy density (U d) of 13.68 J/cm3 with a high breakdown strength (E b) of 508.66 kV/mm. Sandwich-structured P-3 wt% HZO/P-P nanocomposite achieved an excellent U d of 21.63 J/cm3 and a high η of ∼ 65.68% at ultrahigh E b of 706.71 kV/mm, which are much higher than those of the commercial BOPP, i.e. 2 J/cm3 at 640 kV/mm. Moreover, the COMSOL simulations revealed that the introduction of 1D nanofibers and charge traps could effectively improve the local distribution of electric field, and finally increased the breakdown strength. The major contribution to the improved U d originates from the large breakdown strength (4 ∼ 8 MV/cm), because of the large band width of HZO and the existence of multi-interfaces. This work can provide a new perspective for promoting the performance of polymer nanocomposites. [ABSTRACT FROM AUTHOR]