Significantly Enhanced Energy Density of Polyvinylidene Fluoride/Polyimide-Based Nanocomposites by Core–Shell BaTiO3@SiO2

Improving the limited energy storage capacity of dielectric materials has long been an attractive challenge. In this work, a four-phase hybridized nanocomposite was designed. The linear polymer polyimide (PI) was added to the ferroelectric polymer polyvinylidene fluoride (PVDF) and compounded with a nanoceramic BT@SiO₂ with a core–shell structure. The results show that PVDF–PI/BT@SiO₂ nanocomposites prepared by a straightforward spin-coating method have a significantly increased discharge energy density. The polymer blends obtain a tightly extended conformation in the amorphous region. Also, this provides an excellent matrix environment for the homogeneous dispersion of fillers. The core–shell structure, as a physical barrier, not only hinders the expansion of the breakdown path but also extends multiple polarization surfaces with gradient variations at the microscopic level. Therefore, the synergistic effect generated by polymer blending and core–shell structure effectively enhances the dielectric and stored energy characteristics of nanocomposites. The dielectric constant is stable at 11.39–18.7, and the dielectric loss is always lower than 0.136. The discharge energy density is 2.5 J/cm³, almost 110% higher than that of the BOPP films (about 1.2 J/cm³). These experimental results suggest that the composite system using core–shell structure and polymer blending is a new way to improve the energy density of dielectric materials.