Polymer-based nanocomposites employing Bi2S3@SiO2 nanorods for high dielectric performance: Understanding the role of interfacial polarization in semiconductor-insulator core-shell nanostructure

Advanced polymer-based dielectric composites are core materials in the electronics and power systems. Construction of core-shell architectures has been proved as a powerful strategy to dramatically enhance the dielectric and energy storage performances. Herein, core-shell structured amorphous SiO2 encapsulating Bi2S3 nanorods with varying shell thickness were employed as the fillers in poly(vinylidene fluoride) (PVDF) matrix, affording a Bi2S3@SiO2/PVDF nanocomposite. The dielectric behaviors of Bi2S3@SiO2/PVDF composites with varying SiO2 shell thickness as a function of filler loading in comparison with Bi2S3/PVDF were studied. Bi2S3@SiO2 core-shell structure dramatically suppressed the dielectric loss (<0.04) and decrease in conductivity yet maintaining high dielectric constant. Furthermore, adjusting Bi2S3@SiO2-PVDF interface by controlling the SiO2 shell thickness results in changing dielectric behaviors. The effects of SiO2 shell and the arising Bi2S3@SiO2 interface on the dielectric and electric properties were investigated via interfacial charge calculation based on Maxwell-Wagner-Sillars model. The role of semiconductor-insulator interfacial polarization in determining the dielectric behaviors of the composites were understood. Due to the greatly reduced dielectric loss, Bi2S3@SiO2/PVDF nanocomposites can withstand high electric field and the study on energy storage capacity and efficiency was realized in the polymer-based composite with conductive filler. This study demonstrates the robust effect of core-shell architecture in suppressing dielectric loss yet maintaining the high dielectric constant of the polymer-based composites, providing a promising route to achieve high-performance dielectrics.