Local Structure Strategies Promoting Lead-Free Dielectric Energy-Storage Applications.

Dielectric capacitors harvest energy through an electrostatic storage process, which enables an ultrafast charging-discharging rate and ultrahigh power density. However, achieving high energy density (Wrec) and efficiency (η) simultaneously, especially when preserving them across a wide frequency/temperature range or cycling numbers, remains challenging. In this work, by especially introducing NaTaO3 into the representative ferroelectric relaxor of Bi0.5K0.5TiO3-Bi0.5Na0.5TiO3 and leveraging the mismatch between B-site atoms, we proposed a method of enhancing local structural fluctuation to refine the polar configuration and to effectively improve its overall energy-storage performances. As a consequence, the ceramic exhibits an ultrahigh Wrec of 15.0 J/cm3 and high η up to 80 %, along with a very wide frequency stability of 10-200 Hz and extensive cycling number up to 108. In-depth local structure and chemical environment investigations, consisting of atom-scale electron microscopy, neutron total scattering, and solid-state nuclear magnetic resonance, reveal that the randomly distributed A/B-site atom pairs emerge in the system, leading to the evident local structural fluctuations and concomitant polymorphic polar nanodomains. These key ingredients contribute to the large polarization, minimal hysteresis, and high breakdown strength, thereby promoting energy-storage performances. This work opens a new path for designing high-performance dielectric capacitors via manipulating local structural fluctuations.

In the past decades, lead-free ceramics with high polarization, low remnant polarization and high electric breakdown strength have drawn a lot of attention because of their potential applications in dielectric capacitors with excellent energy storage performance. In the current investigation, we develop a novel lead-free Dy doped 0.5Na0.5Bi0.5TiO3–0.5SrTiO3 ceramics, which were fabricated by the conventional electroceramic processing route. By doping Dy2O3 into 0.5Na0.5Bi0.5TiO3–0.5SrTiO3 with various contents from 0.1 at.% to 0.5 at.%, pure perovskite phases and relatively dense structures were obtained. The increase of Dy2O3 concentration not only shifts the Tm toward to lower temperature, but also reduces the permittivity and gain sizes, thus enhancing the temperature stability of dielectric properties. The enhanced dielectric energy storage properties were systematically investigated by testing the polarization–electric field hysteresis loops as a function of the applied electric field, temperature, and loading cycles. The dielectric energy storage density of in 0.1 at.% doped 0.5Na0.5Bi0.5TiO3–0.5SrTiO3 is 1.59 J/cm3, which is nearly twice higher than that of undoped NBT–ST. Hence, the Dy modified 0.5Na0.5Bi0.5TiO3–0.5SrTiO3 ceramics have exhibited potential application as dielectric capacitors with relatively good energy storage performance.

Dielectric capacitors are widely used in pulse power systems, electric vehicles, aerospace, and defense technology as they are crucial for electronic components. Compact, lightweight, and diversified designs of electronic components are prerequisites for dielectric capacitors. Additionally, wide temperature stability and high energy storage density are equally important for dielectric materials. Ferroelectric materials, as special (spontaneously polarized) dielectric materials, show great potential in the field of pulse power capacitors having high dielectric breakdown strength, high polarization, low-temperature dependence and high energy storage density. The first part of this review briefly introduces dielectric materials and their energy storage performance. The second part elaborates performance characteristics of various ferroelectric materials in energy storage and refrigeration based on electrocaloric effect and briefly shed light on advantages and disadvantages of various common ferroelectric materials. Especially, we summarize the polarization effects of underlying substrates (such as GaN and Si) on the performance characteristics of ferroelectric materials. Finally, the review will be concluded with an outlook, discussing current challenges in the field of dielectric materials and prospective opportunities to assess their future progress.

Polypropylene (PP)‐based dielectric film capacitors cannot meet the rapid development requirements of electromagnetic energy equipment because of their low energy storage density (Ue). The development of new dielectric materials is hampered by the trade‐off between high energy storage properties and thin film processibility for capacitors. This study proposes a strategy to improve the comprehensive energy storage properties of PP films by reconciling the trade‐offs not only between their polarity and crystallinity but also between their energy storage and processing performance. In this approach, a trifluoroethyl methacrylate (TFEMA) modified PP film is fabricated at the kilogram scale. The TFEMA units regulate PP crystallization in the α‐phase, resulting in improved mechanical, dielectric, and energy storage performance. The optimal PP‐g‐TFEMA film exhibits a remarkable breakdown strength (Eb) of 865 MV m−1 and a record Ue of 8.2 J cm−3 at over 90% discharge efficiency. The promising thin film processibility, excellent self‐healing, and long‐term reliability of PP are finely preserved in the aluminum (Al) coated PP‐g‐TFEMA film. These findings present a novel avenue to significantly increase the Ue of film capacitors for long‐term service not only in academia but also in industry.

Dielectric capacitors are commonly used in in high-power energy storage and pulse power systems. Low energy storage density is currently the bottleneck restricting the development of dielectric capacitors. The dielectric properties, breakdown strength and energy storage performance of oriented P(VDF-HFP)/BNNS nanocomposites are studied. It has been found that the dielectric properties of the oriented P(VDF-HFP)/BNNS nanocomposite have been significantly improved, the breakdown strength can reach 650 MV/m, and the discharged energy density of 16.8 J/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> is finally obtained, which is 2.02 times of P(VDF-HFP). Low loss, high breakdown strength, high discharged energy density and high charge-discharge efficiency make the oriented P(VDF-HFP)/BNNS nanocomposites promising as a dielectric film for high energy density capacitor.

Dielectric capacitors with high energy storage performance are highly desired for advanced power electronic devices and systems. Even though strenuous efforts have been dedicated to closing the gap of energy storage density between the dielectric capacitors and the electrochemical capacitors/batteries, a single-minded pursuit of high energy density without a near-zero energy loss for ultrahigh energy efficiency as the grantee is in vain. Herein, for the purpose of decoupling the inherent conflicts between high polarization and low electric hysteresis (loss), and achieving high energy storage density and efficiency simultaneously in multilayer ceramic capacitors (MLCCs), we propose an interlaminar strain engineering strategy to modulate the domain structure and manipulate the polarization behavior of the dielectric mediums. With a heterogeneous layered structure consisting of different antiferroelectric ceramics [(Pb0.9Ba0.04La0.04)(Zr0.65Sn0.3Ti0.05)O3/(Pb0.95Ba0.02La0.02)(Zr0.6Sn0.4)O3/(Pb0.92Ca0.06La0.02)(Zr0.6Sn0.4)0.995O3], our MLCC exhibits a giant recoverable energy density of 22.0 J cm−3 with an ultrahigh energy efficiency of 96.1%. Combined with the favorable temperature and frequency stabilities and the high antifatigue property, this work provides a strain engineering paradigm for designing MLCCs for high-power energy storage and conversion systems.

Superior comprehensive energy storage in high-entropy Lead-free quasi-linear Relaxor ceramics by local heterogeneous polarization.

Dielectric capacitors have been widely studied because their electrostatic storage capacity is enormous, and they can deliver the stored energy in a very short time. Relaxor ferroelectrics-based dielectric capacitors have gained tremendous importance for the efficient storage of electrical energy. Relaxor ferroelectrics possess low dielectric loss, low remanent polarization, high saturation polarization, and high breakdown strength, which are the main parameters for energy storage. This article focuses on a timely review of the energy storage performance of BiFeO3-based relaxor ferroelectrics in bulk ceramics, multilayers, and thin film forms. The article begins with a general introduction to various energy storage systems and the need for dielectric capacitors as energy storage devices. This is followed by a brief discussion on the mechanism of energy storage in capacitors, ferroelectrics, anti-ferroelectrics, and relaxor ferroelectrics as potential candidates for energy storage. The remainder of this article is devoted to reviewing the energy storage performance of bulk ceramics, multilayers, and thin films of BiFeO3-based relaxor ferroelectrics, along with a discussion of strategies to address some of the issues associated with their application as energy storage systems.

Dielectric capacitors harvest energy through an electrostatic storage process, which enables an ultrafast charging‐discharging rate and ultrahigh power density. However, achieving high energy density ( W rec ) and efficiency ( η ) simultaneously, especially when preserving them across a wide frequency/temperature range or cycling numbers, remains challenging. In this work, by especially introducing NaTaO 3 into the representative ferroelectric relaxor of Bi 0.5 K 0.5 TiO 3 ‐Bi 0.5 Na 0.5 TiO 3 and leveraging the mismatch between B‐site atoms, we proposed a method of enhancing local structural fluctuation to refine the polar configuration and to effectively improve its overall energy‐storage performances. As a consequence, the ceramic exhibits an ultrahigh W rec of 15.0 J/cm 3 and high η up to 80 %, along with a very wide frequency stability of 10–200 Hz and extensive cycling number up to 10 8 . In‐depth local structure and chemical environment investigations, consisting of atom‐scale electron microscopy, neutron total scattering, and solid‐state nuclear magnetic resonance, reveal that the randomly distributed A/B‐site atom pairs emerge in the system, leading to the evident local structural fluctuations and concomitant polymorphic polar nanodomains. These key ingredients contribute to the large polarization, minimal hysteresis, and high breakdown strength, thereby promoting energy‐storage performances. This work opens a new path for designing high‐performance dielectric capacitors via manipulating local structural fluctuations.

Stepwise-design activated high capacitive energy storage in lead-free NaNbO3-based relaxor antiferroelectric ceramics

Energy storage performances of La doped SrBi5Ti4FeO18 films

Local chemical inhomogeneities in TiZrNb-based refractory high-entropy alloys

Excellent energy storage performance in BSFCZ/AGO/BNTN double-heterojunction capacitors via the synergistic effect of interface and dead-layer engineering

High-performance dielectric capacitors featuring large recoverable energy storage density (Wrec) and high discharge efficiency (η) are beneficial to realize the device miniaturization, lightweight property, and sustainability of advanced pulse power systems. The obtainment of a high electric breakdown strength (Eb) is crucial for improving the energy storage performance of dielectric materials. However, as for Bi0.5Na0.5TiO3 (BNT) lead-free relaxor ferroelectric ceramics, the relatively lower Eb directly limits their electrical performance improvement and practical applications. Herein, a popular high entropy strategy was employed to rationally design and prepare the (Bi0.5Na0.5)x(Sr0.25Ba0.25La0.25K0.25)(1-x)TiO3 (BNSLBKT-x) lead-free relaxor ferroelectric ceramics based on the BNT matrix. Encouragingly, the BNSLBKT-0.2 high-entropy ceramic exhibits a high Eb of 510 kV/cm, and this can be ascribed to the refined grains and enhanced activation energy. Moreover, it is confirmed that the polar nanoregions (PNRs) exist in the BNSLBKT-0.2 ceramic by the piezoresponse force microscopy (PFM) and transmission electron microscopy (TEM) characteristics, further strengthening relaxation behaviors and decreasing remanent polarization (Pr). It is anticipated that a high Wrec of 4.6 J/cm3 and a good η of 86% are obtained in this BNSLBKT-0.2 high-entropy ceramic. More importantly, the BNSLBKT-0.2 ceramic displays excellent frequency stability of capacitive energy storage at 10-1000 Hz and good temperature stability at 20-140 °C. The fast discharge rate (τ0.9 = 0.26 μs) and the high PD of 49.2 MW/cm are also achieved in this BNSLBKT-0.2 ceramic. The findings demonstrate that this high entropy design is an effective strategy for developing dielectrics with excellent energy storage capability to meet the requirements of modern dielectric capacitor applications.

Improved energy storage performance achieved in (Bi0.5Na0.5)TiO3-based relaxor ferroelectrics via composition engineering