Multilayer Structured Poly(vinylidene fluoride)-Based Composite Film with Ultrahigh Breakdown Strength and Discharged Energy Density

Poly(vinylidene fluoride)-based (PVDF) composites with high discharged energy density (U_e) have been considered as advanced dielectric materials for pulsed power systems and electrical weapon systems. However, further improvement of the U_e of PVDF-based composites with higher breakdown strength (E_b) is of utmost importance. Based on the principle of voltage distribution in the multilayer structure, the multilayer structure (five-layer structure) ceramic/polymer composite films consisting of pristine PVDF layers with high breakdown strength and PVDF layers doped with one-dimensional 0.15SrTiO₃-0.85Na_0.5Bi_0.5TiO₃ (1D SNBT) fibers where the two kinds of layers stacked alternately has been designed and fabricated. Accordingly, a series of analyses of the dielectric properties and energy storage performances are presented, and the related results are tentatively explained by finite element simulation. The energy storage characteristics of the composite films are greatly improved due to the newly designed structure. An excellent U_e of 20.82 J cm^-3 is achieved at an ultrahigh electric field of 640 MV m^-1 with the PVDF layers containing 6 vol % SNBT fibers. Therefore, this work provides a new strategy to design and fabricate advanced polymer-based energy storage materials.