Lawrence Berkeley National Laboratory

The development of advanced dielectric materials with high breakdown strength, high dischargeable energy densities, and great efficiencies is imperative to meet the ever-increasing demand of modern power systems and electronic devices. Herein, we present the layer-by-layer solution prepared bilayer-structured nanocomposite films with much enhanced capacitive performance via resolving the typical paradox between dielectric constant and breakdown strength in dielectric materials. The bilayered nanocomposite films are composed of Al2O3 dispersed in polystyrene as the interfacial barrier layer to inhibit electrical conduction and the polystyrene layer with TiO2 to enhance dielectric constant. The resulting layered film exhibits a discharged energy density of 4.43 J/cm3 along with ultrahigh charge−discharge efficiencies of >90%, which is among the highest energy densities ever achieved in the polystyrene-based dielectric polymer nanocomposites. In addition, the composite films show outstanding cyclic stability under high electric fields, which would enable the long-term efficient operation of film capacitors. This contribution represents an efficient route to high-energy-density dielectric composite materials by using interfacial barrier architectures.