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Dielectric capacitors based on antiferroelectric ceramics are promising for applications in advanced high-power electric and electronic devices, for which more efforts should be devoted to enhancing the recoverable energy storage density and energy efficiency. In this work, a record-high recoverable energy storage density Wrec up to 9.0 J cm−3 and energy efficiency η of 90% are achieved in lead-free AgNbO3-based ceramics composed of antiferroelectric and paraelectric phases, which were realized by phase engineering via Bi-doping. Compared with pristine AgNbO3, the enhancement in recoverable energy storage density and energy efficiency reaches 621% and 241%, respectively. In addition, the breakdown strength Eb exceeds 650 kV cm−1 in 12 mol% Bi-doped 0.10 wt% MnO2–AgNbO3 ceramics, which greatly contributes to the exceptionally enhanced energy storage performance. The excellent performance could be retained at elevated temperatures, and various frequencies and cycles. Moreover, the discharge energy density Wd in direct-current charge–discharge performance reaches 8.0 J cm−3, which is also superior to those reported in other lead-free dielectric energy storage ceramics. The strategy can provide an applicable method to optimize energy storage performance and other functionalities of dielectric materials. [ABSTRACT FROM AUTHOR]

High-performance energy storage dielectrics have been the key to solve energy problems in the context of energy crisis. Designing multilayered structures is an effective approach to break the paradox between high dielectric constant and high breakdown strength existing in polymer-based composite films to enhance energy storage performance. Herein, a designed sandwich-structured poly(vinylidene fluoride) (PVDF)-based composite film, with a characteristic of the inner PVDF layer filled with Na0.5Bi0.5TiO3 (NBT) whiskers and the outer layers of pure PVDF, is proposed. An ultrahigh discharged energy density of 30.55 J cm−3 and an outstanding discharged efficiency of 80.26% can be obtained in the optimized composition with the inner layer containing 6 vol% NBT whiskers, which outperforms all the previously reported PVDF-based composite films. Furthermore, it reveals that such a sandwich structure with NBT whiskers is able to adjust dielectric properties and reform electric field distribution, as evidenced by dielectric and insulation properties as well as the dielectric breakdown model by finite element analysis, which prompts the enhancement of polarization and breakdown strength synergistically, and thus, contributes to excellent energy storage performance. This work provides a strategy for developing high-end dielectrics for electrostatic energy storage applications. [ABSTRACT FROM AUTHOR]

Negative environmental consequences of non-renewable energy resources and limited reserves of fossil fuel supplies have spurred the development of renewable and environmentally friendly energies as well as advanced energy conversion and storage technologies. Among the currently available electrical energy storage devices, electrostatic capacitors possess highest power density because of their fast charge–discharge capability. However, their low energy densities limit their applications. Herein, we demonstrated a remarkable improvement in the breakdown strength and energy density of a group of three-tiered ferroelectric polyvinylidene fluoride (PVDF) films with the content of barium titanate (BT) nanoparticle fillers gradually increasing layer by layer. It was found that a weak electric field region could be formed as an efficient insulating barrier to hamper the development of electrical trees via tailoring of the gradient of filler contents. Optimization of the composite compositions guided by simulation studies resulted in a greatly enhanced breakdown strength of 390 MV m−1 with an ultrahigh maximum polarization of 12.5 μC cm−2, and thus, an impressive discharged energy density of 16.5 J cm−3 was achieved. This successful structural design provides a new paradigm to explore polymer nanocomposites having excellent dielectric and capacitive properties, which can also be applied to other materials in electric and electrical applications. [ABSTRACT FROM AUTHOR]