Significantly Enhanced Energy Density by Tailoring the Interface in Hierarchically Structured TiO2–BaTiO3–TiO2 Nanofillers in PVDF-Based Thin-Film Polymer Nanocomposites

Dielectric polymer nanocomposites with a high breakdown field and high dielectric constant have drawn significant attention in modern electrical and electronic industries due to their potential applications in dielectric and energy storage systems. The interfaces of the nanomaterials play a significant role in improving the dielectric performance of polymer nanocomposites. In this work, polydopamine (dopa)-functionalized TiO2–BaTiO3–TiO2 (TiO2–BT–TiO2@dopa) core@double-shell nanoparticles have been developed as novel nanofillers for high-energy-density capacitor applications. The hierarchically designed nanofillers help in tailoring the interfaces surrounding the polymer matrix as well as act as individual capacitors in which the core and outer TiO2 shell function as a capacitor plate because of their high electrical conductivity while the middle BT layer functions as a dielectric medium due to high dielectric constant. Detailed electrical characterizations have revealed that TiO2–BT–TiO2@dopa/poly(vinylidene fluoride) (PVDF) possesses a higher relative dielectric permittivity (εr), breakdown strength (Eb), and energy density as compared to those of PVDF, TiO2/PVDF, TiO2@dopa/PVDF, and TiO2–BT@dopa/PVDF polymer nanocomposites. The εr and energy density of TiO2–BT–TiO2@dopa/PVDF were 12.6 at 1 kHz and 4.4 J cm–3 at 3128 kV cm–1, respectively, which were comparatively much higher than those of commercially available biaxially oriented polypropylene having εr of 2.2 and the energy density of 1.2 J cm–3 at a much higher electric field of 6400 kV cm–1. It is expected that these results will further open new avenues for the design of novel architecture for high-performance polymer nanocomposite-based capacitors having core@multishell nanofillers with tailored interfaces.