Ultrahigh energy density and thermal stability in sandwich-structured nanocomposites with dopamine@Ag@BaTiO3

Abstract The progress in advanced dielectrics by tremendously enhancing the discharge energy densities is of great importance for the current electronic power systems. Herein, we report heterogeneous sandwich-structured nanocomposites with low nanofillers content, which offered the ultrahigh discharge energy density (Ue) of 21.03 ​J/cm3 at 592.1 ​MV/m. This energy density is the highest reported until now, with similar nanoparticle content and equivalent electric field. We used linear-type polyetherimide as the outer two layers, which offered insulation of charge injection from electrodes, reduced polymer free-volume, improved breakdown strength, and enhanced the overall thermo-mechanical stability. Besides, dopamine@Ag@BaTiO3 nanoparticles (DA@Ag@BT NPs)-modified ferroelectric-type polyvinylidene fluoride is employed as the middle layer for rendering higher polarizability and additionally increased breakdown strength due to well-known Coulomb blockade effect. Finite element simulations showed reduced local electric field in the outer, as well as middle layer matrixes, indicating higher breakdown strength and consequently higher energy storage prospects of heterogeneous sandwich-structured nanocomposites. The energy storage results at high temperatures demonstrated its significant thermal stability until 170 ​°C. Overall, this contribution not only paves the new way for developing industrially viable low nanofillers-concentrated flexible dielectric films but also provides the insight of polarization mechanism and electric breakdown in heterogeneous sandwich-structured dielectric materials.