Sandwich‐Structured hBN/BT‐VTS/PVDF‐HFP Nanocomposites with Solid and Interconnected Porous Central Layers as Flexible Piezoelectric Energy Harvesters for Self‐Powered Wearable Electronics: Enhanced Breakdown Strength and Power Density by Tailoring S

Sandwich‐structured poly(vinylidene fluoride)‐co‐hexafluoropropylene (PVDF‐HFP) matrix nanocomposites with solid and interconnected porous central layers are prepared by hot pressing to investigate the structural design's role on their dielectric properties, energy storage, and energy harvesting performances. Solid monolayered nanocomposites reinforced with 4 wt% hexagonal boron nitride (hBN) nanoparticles (NPs) and solid and porous monolayered nanocomposites incorporated with 25 wt% silane‐modified BaTiO 3 NPs (BT‐VTS) are located in outer and central layers, respectively, to achieve the BN‐BT‐BN configuration. Despite the low energy storage performances (discharged energy densities) of sandwich structures, the charge‐blocking hBN/PVDF‐HFP nanocomposites at the outer layers of the solid sandwiches enhance the breakdown strength of solid monolayered BT‐VTS/PVDF‐HFP nanocomposites ( E b : 271 MV m −1 ) by 23%. On the other hand, piezoelectric output voltages of the porous monolayer and sandwich structures (1.7 and 1.1 V) are 6 and 3 times those of their solid counterparts, respectively, under finger bending at 1 Hz. This indicates a significant impact of structural design on the energy harvesting performance, which is considerably improved by a 3D pore network. Therefore, porous sandwich‐structured 4% hBN/25% BT‐VTS/PVDF‐HFP nanocomposites with an enhanced power density of 22.11 μW cm −3 have the capability to be used as flexible piezoelectric nanogenerators in self‐powered wearable devices.