Concurrently Improved Breakdown Strength and Storage Energy Capacitance in the Core–Shell-Structured Aromatic Polythiourea@BaTiO₃ Polymer Nanocomposites Induced by the Nature of Interfacial Polarization and Crystallization

Interfacial architecture of the nanofillers is the critical factor to achieve desirable dielectric properties in the polymer nanocomposites. However, a basic understanding of the role of interfacial polarization and crystallization on energy storage is very seldom. Herein, we synthesized the core–shell aromatic polythiourea@BaTiO3 nanoparticles (ArPTU@BT NPs) as nanofillers to prepare ferroelectric polymer nanocomposites. Remarkably, direct detections of interfacial morphology, polarization, and interfacial crystallization mechanism in ferroelectric nanocomposites were revealed by a combination of atomic force microscopy (AFM) and flash differential scanning calorimetry sites (Flash DSC), which were experimentally detected by AFM, can suppress the local electric field and the migration of charges, leading to a high breakdown strength (Eb). Second, the addition of ArPTU@BT NPs, which were served as heterogeneous nucleators, can promote the crystallization rate (t0.5) and form a tiny spherulite, which is beneficial for reducing the energy barrier of dipole switching and enhancing the interfacial polarization to achieve a high dielectric constant (ε) as well as an ultrahigh energy density (U). Our systematic studies provide the possibilities in understanding interfacial behaviors to design ferroelectric polymer nanocomposites for high-capacitance capacitor applications.