Grain size engineered lead-free ceramics with both large energy storage density and ultrahigh mechanical properties
TL;DR: In this paper, the authors proposed a new strategy, namely, grain size engineering, to develop K0.5Na 0.5NbO3 (KNN)-based ceramics with both an extremely high recoverable energy storage density (Wrec) and large mechanical properties.
About: This article is published in Nano Energy.The article was published on 2019-04-01. It has received 409 citations till now.
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TL;DR: In this article, the fundamental principles of energy storage in dielectric capacitors are introduced and a comprehensive review of the state-of-the-art is presented. But the authors do not consider the use of lead-free materials in high-temperature applications, since their toxicity raises concern over their use in consumer applications.
Abstract: Materials exhibiting high energy/power density are currently needed to meet the growing demand of portable electronics, electric vehicles and large-scale energy storage devices. The highest energy densities are achieved for fuel cells, batteries, and supercapacitors, but conventional dielectric capacitors are receiving increased attention for pulsed power applications due to their high power density and their fast charge-discharge speed. The key to high energy density in dielectric capacitors is a large maximum but small remanent (zero in the case of linear dielectrics) polarization and a high electric breakdown strength. Polymer dielectric capacitors offer high power/energy density for applications at room temperature, but above 100 °C they are unreliable and suffer from dielectric breakdown. For high-temperature applications, therefore, dielectric ceramics are the only feasible alternative. Lead-based ceramics such as La-doped lead zirconate titanate exhibit good energy storage properties, but their toxicity raises concern over their use in consumer applications, where capacitors are exclusively lead free. Lead-free compositions with superior power density are thus required. In this paper, we introduce the fundamental principles of energy storage in dielectrics. We discuss key factors to improve energy storage properties such as the control of local structure, phase assemblage, dielectric layer thickness, microstructure, conductivity, and electrical homogeneity through the choice of base systems, dopants, and alloying additions, followed by a comprehensive review of the state-of-the-art. Finally, we comment on the future requirements for new materials in high power/energy density capacitor applications.
396 citations
TL;DR: In this article, an effective strategy to achieve ultra-high energy storage performance via nano-scale polarization mismatch and reconstruction is proposed, which can be used to design novel high performance dielectric ceramics for future energy storage devices.
284 citations
TL;DR: A strategy to increase the breakdown electric field and thus enhance the energy storage density of polycrystalline ceramics by controlling grain orientation is proposed, which is expected to benefit a wide range of applications of dielectrics for which high breakdown strength is required, such as high-voltage capacitors and electrocaloric solid-state cooling devices.
Abstract: Dielectric ceramics are highly desired for electronic systems owing to their fast discharge speed and excellent fatigue resistance. However, the low energy density resulting from the low breakdown electric field leads to inferior volumetric efficiency, which is the main challenge for practical applications of dielectric ceramics. Here, we propose a strategy to increase the breakdown electric field and thus enhance the energy storage density of polycrystalline ceramics by controlling grain orientation. We fabricated high-quality -textured Na0.5Bi0.5TiO3–Sr0.7Bi0.2TiO3 (NBT-SBT) ceramics, in which the strain induced by the electric field is substantially lowered, leading to a reduced failure probability and improved Weibull breakdown strength, on the order of 103 MV m−1, an ~65% enhancement compared to their randomly oriented counterparts. The recoverable energy density of -textured NBT-SBT multilayer ceramics is up to 21.5 J cm−3, outperforming state-of-the-art dielectric ceramics. The present research offers a route for designing dielectric ceramics with enhanced breakdown strength, which is expected to benefit a wide range of applications of dielectric ceramics for which high breakdown strength is required, such as high-voltage capacitors and electrocaloric solid-state cooling devices. The energy density of dielectric ceramic capacitors is limited by low breakdown fields. Here, by considering the anisotropy of electrostriction in perovskites, it is shown that -textured Na0.5Bi0.5TiO3–Sr0.7Bi0.2TiO3 ceramics can sustain higher electrical fields and achieve an energy density of 21.5 J cm−3.
283 citations
TL;DR: In this article, a series of relaxor ferroelectrics (1−−x)Bi0.5Na0.7La0.2TiO3 ((1− −x)BNT-xSLT) with excellent energy storage performance were successfully fabricated.
238 citations
TL;DR: It is demonstrated that a recoverable energy density and giant energy efficiency can be simultaneously achieved in 0.92BaTiO3-0.09NbO3 ceramics and confirmed by the piezoresponse force microscopy that the appearance of PNRs break the long range order and reduce the stability of microstructure, which explains the excellent energy storage performance of RFE ceramic.
Abstract: Barium titanate-based energy-storage dielectric ceramics have attracted great attention due to their environmental friendliness and outstanding ferroelectric properties. Here, we demonstrate that a recoverable energy density of 2.51 J cm-3 and a giant energy efficiency of 86.89% can be simultaneously achieved in 0.92BaTiO3-0.08K0.73Bi0.09NbO3 ceramics. In addition, excellent thermal stability (25-100 °C) and superior frequency stability (1-100 Hz) have been obtained under 180 kV cm-1. The first-order reversal curve method and transmission electron microscopy measurement show that the introduction of K0.73Bi0.09NbO3 makes ferroelectric domains to transform into highly dynamic polar nanoregions (PNRs), leading to the concurrently enhanced energy-storage properties by the transition from ferroelectric to relaxor ferroelectric (RFE). Furthermore, it is confirmed by piezoresponse force microscopy that the appearance of PNRs breaks the long-range order to some extent and reduces the stability of the microstructure, which explains the excellent energy-storage performance of RFE ceramics. Therefore, this work has promoted the practical application ability of BaTiO3-based energy-storage dielectric ceramics.
221 citations
References
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01 Sep 1951
TL;DR: In this paper, an attempt is made to explain the observed phenomena in the yielding and ageing of mild steel, described in two previous papers, in the general terms of a grain-boundary theory.
Abstract: An attempt is made here to explain the observed phenomena in the yielding and ageing of mild steel, described in two previous papers, in the general terms of a grain-boundary theory. On this hypothesis, a satisfactory explanation of the variation of the lower yield point with grain size may be developed. It is shown that strain-ageing must involve two processes: a healing of the grain-boundary films, coupled with a hardening in the grains themselves. A discussion of the possible nature of the grain-boundary film is also undertaken.
5,893 citations
TL;DR: It is demonstrated that a very high energy density with fast discharge speed and low loss can be obtained in defect-modified poly(vinylidene fluoride) polymers by combining nonpolar and polar molecular structural changes of the polymer with the proper dielectric constants.
Abstract: Dielectric polymers with high dipole density have the potential to achieve very high energy density, which is required in many modern electronics and electric systems. We demonstrate that a very high energy density with fast discharge speed and low loss can be obtained in defect-modified poly(vinylidene fluoride) polymers. This is achieved by combining nonpolar and polar molecular structural changes of the polymer with the proper dielectric constants, to avoid the electric displacement saturation at electric fields well below the breakdown field. The results indicate that a very high dielectric constant may not be desirable to reach a very high energy density.
2,008 citations
TL;DR: In this article, the lattice dynamics and the peculiar dielectric relaxation in relaxors are discussed, and theoretical models for the mechanisms of PNR formation and freezing into nonergodic glassy state are also presented.
Abstract: Relaxor ferroelectrics were discovered almost 50 years ago among the complex oxides with perovskite structure. In recent years this field of research has experienced a revival of interest. In this paper we review the progress achieved. We consider the crystal structure including quenched compositional disorder and polar nanoregions (PNR), the phase transitions including compositional order-disorder transition, transition to nonergodic (probably spherical cluster glass) state and to ferroelectric phase. We discuss the lattice dynamics and the peculiar (especially dielectric) relaxation in relaxors. Modern theoretical models for the mechanisms of PNR formation and freezing into nonergodic glassy state are also presented.
1,784 citations
TL;DR: Crosslinked polymer nanocomposites that contain boron nitride nanosheets have outstanding high-voltage capacitive energy storage capabilities at record temperatures and have been demonstrated to preserve excellent dielectric and capacitive performance after intensive bending cycles, enabling broader applications of organic materials in high-temperature electronics and energy storage devices.
Abstract: Dielectric materials, which store energy electrostatically, are ubiquitous in advanced electronics and electric power systems. Compared to their ceramic counterparts, polymer dielectrics have higher breakdown strengths and greater reliability, are scalable, lightweight and can be shaped into intricate configurations, and are therefore an ideal choice for many power electronics, power conditioning, and pulsed power applications. However, polymer dielectrics are limited to relatively low working temperatures, and thus fail to meet the rising demand for electricity under the extreme conditions present in applications such as hybrid and electric vehicles, aerospace power electronics, and underground oil and gas exploration. Here we describe crosslinked polymer nanocomposites that contain boron nitride nanosheets, the dielectric properties of which are stable over a broad temperature and frequency range. The nanocomposites have outstanding high-voltage capacitive energy storage capabilities at record temperatures (a Weibull breakdown strength of 403 megavolts per metre and a discharged energy density of 1.8 joules per cubic centimetre at 250 degrees Celsius). Their electrical conduction is several orders of magnitude lower than that of existing polymers and their high operating temperatures are attributed to greatly improved thermal conductivity, owing to the presence of the boron nitride nanosheets, which improve heat dissipation compared to pristine polymers (which are inherently susceptible to thermal runaway). Moreover, the polymer nanocomposites are lightweight, photopatternable and mechanically flexible, and have been demonstrated to preserve excellent dielectric and capacitive performance after intensive bending cycles. These findings enable broader applications of organic materials in high-temperature electronics and energy storage devices.
1,324 citations