Optimizing sandwich-structured composites based on the structure of the filler and the polymer matrix: toward high...

Polymer-based energy storage materials have been widely applied in the energy storage industry, such as in the hybrid electric vehicle and power-conditioning equipment, due to their moderate energy density and ultrafast charging/discharging speed. Accordingly, the improvement of the energy storage density of polymer matrix composites has become the focus of current research. In this study, different fillers (e.g., 0.5Ba(Zr_0.2Ti_0.8)O₃-0.5(Ba_0.7Ca_0.3)TiO₃ nanofibers (BCZT NFs), BCZT + Ag NFs and BCZT + Ag@Al₂O₃ NFs) were synthesized via electrospinning and were added to the poly(vinylidene fluoride) (PVDF) matrix as a middle layer in sandwich-structure composites. The PVDF polymer-containing PMMA was prepared as the outer layer in the sandwich structure composites. These sandwich-structured composites have low loss, low current density, better breakdown strength and higher efficiency. In particular, 40% PMMA/PVDF/3 vol% BCZT + Ag@Al₂O₃/PVDF/40% PMMA/PVDF composites have an energy density of 7.23 J cm^-3 and efficiency above 75.8% at 370 kV mm^-1. This article could open up a convenient and effective means for the practical application of power-pulsed capacitors by tuning the filler nanostructure and polymer nanocomposites.