Simultaneous Realization of Significantly Enhanced Breakdown Strength and Moderately Enhanced Permittivity in Layered PMMA/P(VDF–HFP) Nanocomposites via Inserting an Al2O3/P(VDF–HFP) Layer

Paraelectric/ferroelectric bilayer composites are promising candidates for high-performance dielectric capacitors. However, the energy densities of these composites need to be further improved to satisfy the miniaturization of electronic devices. Herein, an Al2O3/P(VDF–HFP) buffer layer is inserted between a paraelectric PMMA layer and a ferroelectric P(VDF–HFP) layer, forming a novel trilayer structure. It is interesting to find that the buffer layer effectively alleviates the huge electric field gap between the P(VDF–HFP) layer and PMMA layer, yielding substantially improved breakdown strengths (>600 kV/mm), which are over 140% that of the bilayer P(VDF–HFP)/PMMA composite (∼425 kV/mm). In addition, the introduction of the buffer layer also results in improved interfacial polarization, hence, the moderately elevated permittivity. Consequently, a high energy density of 10.03 J/cm3, which is about 260% that of the bilayer P(VDF–HFP)/PMMA composite (∼3.9 J/cm3), is achieved at 600 kV/mm. This work offers a facile strategy to achieve dielectric composites with high breakdown strengths, which is illuminating for the design of high-voltage energy-storage capacitors.