Sandwich-structured polymer nanocomposites with Ba0·6Sr0·4TiO3 nanofibers networks as mediate layer inducing enhanced energy storage density

Flexible ceramic-polymer nanocomposites have shown tremendous potential in energy storage applications in the electronic and electrical field. Adding high aspect radio nanofibers into the polymers could improve the energy storage properties significantly. However, using the traditional dispersing-blending-casting method is difficult to ensure the interconnection of fibers in the film plane and to avoid the percolation out-of-plane, which results in the early breakdown and limits the energy storage density. In this work, a novel processing method was designed and a unique sandwich film based on completely interconnected Ba0·6Sr0·4TiO3 nanofibers network (BST nfs) and poly-(vinylidene fluoride-co-hexafluoropropylene) was prepared. Compared to the blending films with random BST nanofibers and polymers (random P(VDF-HFP)-BST nfs), the sandwich films P(VDF-HFP)-BST nfs-P(VDF-HFP) (4 vol%) possess higher breakdown strength (2954 kV/cm) and enhanced energy storage density (9.46 J/cm3). This strategy has explored an effective way to solve the contradiction between dielectric constant and breakdown strength and to improve the energy storage density in these composited films.