Dielectric polymer capacitors are extensively applied in advanced electronics by virtue of their extremely high power density. However, it remains a challenge to concurrently realize high energy density and high discharge efficiency. In order to solve this conundrum, we herein design a novel all-polymer trilayer structure, where the paraelectric poly­(methyl methacrylate) (PMMA) is used as the top layer to obtain a high discharge efficiency, and ferroelectric P­(VDF-HFP) is employed as the bottom layer to obtain a high energy density. Particularly, the PMMA/poly­(vinylidene fluoride-hexafluoropropylene) (P­(VDF-HFP)) blend composite is used as the middle layer to homogenize the electric field inside the trilayer composites, turning out an obviously boosted breakdown strength and elevated energy density. Consequently, an efficiency as high as 85% and an energy density up to 7.5 J/cm3 along with excellent cycling stability are simultaneously realized at an ultrahigh electric field of 490 kV/mm. These attractive characteristics of the all-polymer trilayer structure suggest that the feasible pathway presented herein is significant to realize concurrently a high energy density and discharge efficiency.

Dielectric film capacitors have aroused considerable attention on account of the fast development of pulsed power systems. However, enhanced energy density is always acquired at the cost of deteriorated charge/discharge efficiency. Herein, well balanced energy density and efficiency are achieved in a series of reasonably designed bilayer composites consisting of a ferroelectric layer and a paraelectric layer at the meantime. It is interesting to find that, when merely 1.6 wt% Zr(HPO4)2 nanosheets are introduced into the ferroelectric layer, a substantially improved energy density of 11.22 J cm−3, which is about 165% that of the bilayer composite without Zr(HPO4)2 nanosheets, is achieved at 650 kV mm−1. Meanwhile, a high charge/discharge efficiency of 89.8% and a low loss tangent of 0.024@10 kHz which is much lower than the pristine ferroelectric polymer layer (0.058@10 kHz) is maintained. Furthermore, finite element simulation reveals that the electric breakdown paths will develop along the macroscopical‐interfaces between adjoining layers and the microcosmic‐interfaces between the Zr(HPO4)2 nanosheets and polymer matrix, which can effectively increase the length of breakdown paths and contribute to improved breakdown strength. This work demonstrates that the Zr(HPO4)2 nanosheets can be promising fillers for other high‐performance dielectric composites.

No abstract

No abstract

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.