Increasing the Energy Storage Density of PVDF/BT Nanocomposite Films by the Synergy of Linear Polymer Intercalation in PVDF and Core‐Shell Structure on BT Surface

ABSTRACT This study aims to enhance the energy storage density of polymer dielectric thin films. A linear polymer, polyimide (PI), was blended with polyvinylidene fluoride (PVDF). Subsequently, BaTiO 3 @SiO 2 (BT@SiO 2 ) nanoparticles with high dielectric constant (ε r ) were prepared and incorporated into the blend. PVDF/PI‐BT@SiO 2 nanocomposite films were prepared by the spin‐coating method, and the relationship between composition and properties was systematically investigated. The charge energy density of the nanocomposite films initially increases and then decreases with increasing BaTiO 3 mass fraction. The maximum energy density reaches 3.78 J/cm 3 in the film containing 30 wt.% BT@SiO 2 , representing improvements of 633% and 540% compared to films with 10 wt.% BT@SiO 2 and 30 wt.% BT, respectively. The breakdown strength reaches 2274 kV/cm. The rigid structure of the PI molecular chains hinders the cooperative switching of PVDF ferroelectric domains and reduces coherent coupling between them. This effect alleviates energy loss during polarization reversal and modulates amorphous polarizability. Additionally, the core‐shell structure of the nanoparticles enhances interfacial compatibility. The synergistic effect of PI and BT@SiO 2 enhances the polarization response and dielectric properties of PVDF, resulting in nanocomposite films with excellent energy density and breakdown strength.