Enhanced electric displacement induces large energy density in polymer nanocomposites containing core–shell structured BaTiO3@TiO2 nanofibers†
High energy density polymer nanocomposites are quite promising for film capacitors and many other electronic devices. In this study, the promising strategy is to increase the electric displacement in high breakdown strength nanocomposites with low loading nanofillers. The core–shell structured barium titanate@titanium dioxide nanofiber (BTO@TO-nf) reported herein is designed based on interfacial engineering and prepared using coaxial electrospinning. In the PVDF nanocomposites containing the core–shell nanofibers, the dielectric permittivity as well as the electric displacement increase significantly, due to the additional polarization induced by the charge shifting in the interfacial zone between BTO on the inside and TO on the outside, which contributes significantly to the electric displacement. In addition, the breakdown strength of the nanocomposite is maintained through the charge shifting being limited to the interfacial zone so it cannot form a percolation path in the matrix. A large discharged energy density of ca. 10.94 J cm−3 is achieved at a field of 360 kV mm−1 for the nanocomposite film with 3% volume fraction of BTO@TO-nf, which is higher than those of the referenced PVDF nanocomposites under the same electric field. The present study demonstrates the advantages of the core–shell structured nanofibers in improving the dielectric properties and provides a new way to enhance the energy density of polymer nanocomposites.