Double Core–Shell BaTiO3@Al2O3@PDA-Based Nanocomposites for Energy Storage Applications

With their ultrahigh power density and excellent reliability, polymer-based dielectric capacitors are highly attractive for use in critical applications, such as DC-link capacitors in electric vehicles and power conditioning systems for renewable energy integration. Incorporating high-dielectric-constant inorganic fillers into polymers is the most common and direct strategy for enhancing energy storage. However, conventional composites suffer from poor compatibility and a large dielectric mismatch between the inorganic phase and the polymer matrix, which hinders simultaneous improvement of discharge energy density and energy storage efficiency. Herein, we report a BaTiO 3 @Al 2 O 3 @PDA double core–shell nanoparticle that significantly enhances the energy storage performance of PVDF-based composites at an ultralow filler loading. In this system, the Al 2 O 3 interlayer acts as a wide-bandgap-insulating barrier, mitigating local electric field concentration and suppressing leakage current, while the outer polydopamine (PDA) shell enhances both the dispersion of the fillers and their compatibility with the PVDF matrix. In this study, the 0.5 wt % BaTiO 3 @Al 2 O 3 @PDA/PVDF composite film exhibited significantly enhanced breakdown strength (437.02 kV/mm), a discharge energy density of up to 13.8 J/cm 3 , and an energy storage efficiency of 76.8%. These results indicate that this nanocomposite holds great potential for use in next-generation, high-performance film capacitors for electric vehicles and renewable energy systems.