Recoverable Energy Storage Density Research Articles

Enhanced energy storage properties and superior thermal stability in SNN-based tungsten bronze ceramics through substitution strategy

Tungsten bronze ceramics of composition Sr2Ag0.2Na0.8Nb5-xTaxO15 were synthesized by solid state methods to investigate the impact of Ta replacement on the structure and energy-storage properties (ESP). The study on the relationship between structure and electric properties revealed three main conclusions: (1) as the Ta5+ concentration increased, the crystal structure transformed from an orthorhombic Im2a phase to a tetragonal paraelectric P4bm phase; (2) a high recoverable energy storage density (1.44 J/cm3) and a moderate efficiency (82%) under low-electric fields was obtained in x = 0.3 sample; (3) both dielectric properties (−9.6 to 232.7 °C) and ESP (30–150 °C) exhibit an excellent thermal stability for x = 0.3 sample. In addition, a high current density (863.69 A/cm2) and a large powder density (70.21 MW/cm3) were achieved simultaneously. The current system could be a promising candidate in temperature-stable dielectric capacitors under low-fields and over a broad temperature range.

Enhanced antiferroelectric-like relaxor ferroelectric characteristic boosting energy storage performance of (Bi0.5Na0.5)TiO3-based ceramics via defect engineering

Lead-free (Bi0.5Na0.5)TiO3 (BNT)-based relaxor ferroelectric (RFE) ceramics have attracted a lot of attention due to their high power density and rapid charge-discharge capabilities, as well as their potential application in pulse power capacitors. However, because of the desire for smaller electronic devices, their energy storage performance (ESP) should be enhanced even further. We describe a defect engineering strategy for enhancing the antiferroelectric-like RFE feature of BNT-based ceramics by unequal substitution of rare-earth La3+ in this paper. The ESP of La3+-doped samples is raised by 25% with the same synthetic procedure and thickness, due to an increase in the critical electric field (E-field) and saturated E-field during polarization response, which is induced by a modification in the energy barrier between the lattice torsion. More impressively, an ultrahigh recoverable energy storage density Wrec of 8.58 J/cm3 and a high energy storage efficiency η of 94.5% are simultaneously attained in 3 at.% La3+-substituted 0.6(Bi0.5Na0.4K0.1)1-1.5xLaxTiO3-0.4[2/3SrTiO3-1/3Bi(Mg2/3Ni1/3)O3] RFE ceramics with good temperature stability (Wrec = 4.6 ± 0.2 J/cm3 and higher η of ≥90% from 30 °C to 120 °C), frequency stability, and fatigue resistance. The significant increase in ESP achieved through defect engineering not only proves the effectiveness of our strategy, but also presents a novel dielectric material with potential applications in pulse power capacitors.

Enhanced energy storage performances of Bi(Ni1/2Sb2/3)O3 added NaNbO3 relaxor ferroelectric ceramics

In the development of dielectric ceramic materials, the requirements of miniaturization and integration are becoming increasingly prominent. How to obtain greater capacitance in a smaller volume is one of the important pursuits. In this paper, lead-free (1-x)NaNbO3-xBi(Ni1/2Sb2/3)O3(xBNS) with high recoverable energy storage density (Wrec) and relatively high energy storage efficiency(η) were prepared by a solid state sintering method. Bi(Ni1/2Sb2/3)O3 was introduced into the Sodium niobate ceramics(NN)-based ceramics to reduce the sintering temperature and increase the maximum breakdown field strength (Eb). Finally, 0.15BNS achieved a high Eb of 460 kV/cm, Wrec of 3.7 J/cm3 and η of 77%. In addition, the sample maintained excellent stability in the frequency range of 1–120 Hz. And the 0.15BNS ceramics also exhibited high power density (PD = 36.4 MW/cm3), large current density (CD = 520.8 A/cm2) and relatively fast charge-discharge rate (t0.9 = 1050 ns). These results demonstrate the potential application value of xBNS ceramics in energy storage capacitors.

The preparation of MnO2-doped NaNbO3-based lead-free ceramics with enhanced energy storage performance and attractive electrocaloric effect

MnO2-doped 0.955NaNbO3-0.045La(Nb1/3Mg2/3)O3 ceramics were prepared through a conventional method. The effects of MnO2 amount on the dielectric property, and the phase transition behavior and energy storage performance were studied. The introduction of MnO2 can obviously improve sintering performance and effectively stabilize anti-ferroelectric phase, accompanied with the variation of phase transition temperature. An enhanced recoverable energy storage density of 2.63 J·cm−3 with efficiency of 66.8% was obtained at RT when 1.5% MnO2 was applied. This sample also demonstrated attractive thermal stability in energy storage from 30 °C–90 °C. In addition, the coexistence of positive and negative electrocaloric effect was observed due to the emergence of anti-ferroelectric phase. A further advantage of the thermal hysteresis phenomenon possesses abilities to enhance dielectric and energy storage properties. This will contribute to the promotion of NaNbO3-based lead-free dielectric capacitors.

Dependence of Phase Structure and Discharge Performance on the Temperature of Perovskite Composited Ceramics

0.8Sr0.875Pb0.125TiO3–0.2Bi(Mg0.5Zr0.5)O3–x(K0.5Na0.5)NbO3 (0.8SPT–0.2BMZ–xKNN, x = 0.015–0.035) ceramics are calcined by solid-state methods. The phase structures, energy storage, and discharge performance, as well as their temperature stability, are systematically investigated. All samples are verified as a single perovskite structure by X-ray diffraction (XRD) results. The x = 0.03 ceramic possesses excellent temperature stability, meeting the X7R standard for pulsed power capacitors. According to P–E loops calculation, the recoverable energy storage density (W rec) and efficiency (η) are 1.27 J cm−3 and 90% at 240 kV cm−1, respectively. Moreover, W rec and η also have good temperature insensitivity over a wide temperature range from 30 to 150 °C. The x = 0.03 ceramic has a high discharge energy density of ≈2.05 J cm−3 and a large power density of ≈143 MW cm−3 at 300 kV cm−1. The excellent temperature insensitivity and large discharge energy density exhibit that the x = 0.03 sample is a potential candidate material for pulsed power capacitors with a wide temperature range.

Synergic Enhancement of Energy Storage Density and Efficiency in MnO2-Doped AgNbO3@SiO2 Ceramics via A/B-Site Substitutions

Dielectric energy storage devices with high power density show great potential in applications of smart grids, electrical vehicles, pulsed power weapons, and so on. However, their limited recoverable energy density badly restricts their utilization and harms the miniaturization, portability, and integration of electronics. Herein, equivalent amounts of Bi2O3 and Sc2O3 were introduced to improve the energy storage property of 0.10 wt % MnO2-doped AgNbO3@SiO2 ceramics by simultaneously enhancing the maximum polarization, breakdown strength, and relaxation feature. It is particularly interesting that the AgNbO3-based ceramics with 4 mol % Bi2O3 and Sc2O3 demonstrate the recoverable energy storage density of 5.9 J/cm3 with the energy storage efficiency of 71%, exhibiting 1.9 and 1.4 times enhancement compared to 0.10 wt % MnO2-doped AgNbO3@SiO2 ceramics. In addition, the benign energy storage performance can be maintained at elevated temperatures and frequencies and up to 105 cycling, indicating great potential in advanced high-power applications.

Remarkably enhanced dielectric stability and energy storage properties in BNT\u2014BST relaxor ceramics by A-site defect engineering for pulsed power applications

Lead-free bulk ceramics for advanced pulsed power capacitors show relatively low recoverable energy storage density (Wrec) especially at low electric field condition. To address this challenge, we propose an A-site defect engineering to optimize the electric polarization behavior by disrupting the orderly arrangement of A-site ions, in which {rm{B}}{{rm{a}}_{0.105}}{rm{N}}{{rm{a}}_{0.325}}{rm{S}}{{rm{r}}_{0.245 - 1.5x}}{_{0.5x}}{rm{B}}{{rm{i}}_{0.325 + x}}{rm{Ti}}{{rm{O}}_3} ({rm{BN}}{{rm{S}}_{0.245 - 1.5x}}{_{0.5x}}{{rm{B}}_{0.325 + x}}{rm{T}}, x = 0, 0.02, 0.04, 0.06, and 0.08) lead-free ceramics are selected as the representative. The {rm{BN}}{{rm{S}}_{0.245 - 1.5x}}{_{0.5x}}{{rm{B}}_{0.325 + x}}{rm{T}} ceramics are prepared by using pressureless solid-state sintering and achieve large Wrec (1.8 J/cm3) at a low electric field (@110 kV/cm) when x = 0.06. The value of 1.8 J/cm3 is super high as compared to all other Wrec in lead-free bulk ceramics under a relatively low electric field (< 160 kV/cm). Furthermore, a high dielectric constant of 2930 within 15% fluctuation in a wide temperature range of 40–350 °C is also obtained in {rm{BN}}{{rm{S}}_{0.245 - 1.5x}}{_{0.5x}}{{rm{B}}_{0.325 + x}}{rm{T}} (x = 0.06) ceramics. The excellent performances can be attributed to the A-site defect engineering, which can reduce remnant polarization (Pr) and improve the thermal evolution of polar nanoregions (PNRs). This work confirms that the {rm{BN}}{{rm{S}}_{0.245 - 1.5x}}{_{0.5x}}{{rm{B}}_{0.325 + x}}{rm{T}} (x = 0.06) ceramics are desirable for advanced pulsed power capacitors, and will push the development of a series of Bi0.5Na0.5TiO3 (BNT)-based ceramics with high Wrec and high-temperature stability.

Ultra-high energy storage density of transparent capacitors based on linear dielectric ZrO2 thin films with the thickness scaled up to hundreds nanometers

In this work, a high energy storage density in transparent capacitors, based on linear dielectric ZrO2 thin films, with thickness scaled up to hundreds of nanometers, is reported. Linear dielectric ZrO2 films with a thickness of several hundred nanometers are grown on Sn-doped In2O3 (ITO) electrode layers grown on transparent glass substrates at room temperature. The fabricated ITO/ZrO2/ITO capacitors show excellent dielectric energy storage performance, including a large dielectric constant, low loss and leakage current, and large breakdown strength. Consequently, these capacitors present high energy density and efficiency, as well as robust device endurance. In particular, ultra-high recoverable energy storage density (Wrec ∼ 75.4 J/cm3) and efficiency (η ∼ 88%) are achieved simultaneously in ZrO2 film-based (470 nm thick) capacitors, rivaling those of other lead-free ferroelectric-like and other linear dielectric film capacitors. Moreover, the capacitors show good transparency in the visible range, indicating the potential energy-storage applications in transparent electronics.

Structural, dielectric and energy storage properties of BaO–Na2O–Nb2O5–P2O5 glass-ceramics

A series of (1−x)[(2BaO–0·5Na2O)–1P2O5] –xNb2O5 (BNPN, x=0·41, 0·43, 0·45, 0·48) glass-ceramics based on phosphate glasses have been prepared via a controlled-crystallisation route. The structure, dielectric properties, interfacial polarisation and energy storage properties were systematically investigated. The x-ray diffraction results showed the simultaneous presence of Ba2NaNb5O15 tungsten bronze structure (TTB) and the NaNbO3 perovskite. A stable dielectric constant over a temperature range from 25–200°C, low dielectric losses less than 0·03 and excellent frequency stability at room temperature were obtained. The decrease of niobium content promoted the TTB crystallisation with improvement of the high dielectric properties of the system. The optimum of the dielectric constant and recoverable energy storage density were obtained for BNP41 crystallised at 1000°C. Analyses of the complex impedance indicated that the niobium content and crystallisation temperature affect the interfacial polarisation.

Dielectric property and energy storage performance enhancement for iron niobium based tungsten bronze ceramic.

Ceramic dielectric capacitors have attracted increasing interest due to their wide applications in pulsed power electronic systems. Nevertheless, synchronously achieving the high energy storage density, high energy storage efficiency and good thermal stability in dielectric ceramics is still a great challenge. Herein, lead free Sr3SmNa2Fe0.5Nb9.5O30 (SSNFN) ceramic with tetragonal tungsten bronze structure was synthesized and characterized, high total energy storage density (2.1 J cm-3), recoverable energy storage density (1.7 J cm-3), energy storage efficiency (80%) and good thermal stability are obtained simultaneously in the compound, due to the contribution of high maximum polarization (P max), low remanent polarization (P r) and large breakdown strength (E b). The high P max is related with the intrinsic characteristic of Sr4Na2Nb10O30 (SNN) based system, while the small P r and good thermal stability stem from the significantly enhanced relaxor behavior. In addition, the large E b originates from the improved microstructure with fewer defects and decreased average grain size, and the reduction of electrical heterogeneity compared with SNN. The capacitive performance obtained in this work points out the great potential of tungsten bronze ceramic designed for energy storage applications and pave a feasible way to develop novel lead-free dielectric capacitors.

Simultaneously achieving large energy density and high efficiency in NaNbO3–(Sr,Bi)TiO3–Bi(Mg,Zr)O3 relaxor ferroelectric ceramics for dielectric capacitor applications

A large recoverable energy storage density of 7.59 J cm−3 and high energy storage efficiency of 81.3% are simultaneously achieved in NaNbO3–(Sr,Bi)TiO3–Bi(Mg,Zr)O3 relaxor ferroelectric ceramics.

High energy-storage performance of lead-free Ba0.4Sr0.6TiO3–Sr0.7Bi0.2TiO3 relaxor-ferroelectric ceramics with ultrafine grain size

Relaxor-ferroelectric (RFE) ceramics possess slender ferroelectric hysteresis loop and low remnant polarization ( P r ). They have great potential to provide excellent energy-storage performance as dielectric energy-storage materials. Herein, a lead-free 0.8Ba 0.4 Sr 0.6 TiO 3 –0.2Sr 0.7 Bi 0.2 TiO 3 (0.8BST–0.2SBT) RFE ceramic with high energy-storage performance has been realized successfully. The addition of Bi 3+ and increase in Sr 2+ content at the A site of the BST can effectively inhibit the growth of grains for high breakdown strength ( E b ). As a result, an ultrafine average grain size of 0.7 μm was obtained in 0.8BST–0.2SBT RFE ceramic, affording a high E b of 300 kV/cm. Further investigation revealed that the mutual conversion of short-range polar nanoregions and long-range-ordered ferroelectric domains upon application and withdrawal of a 300 kV/cm applied electric field resulted in a high maximum polarization ( P max ) of 31 μC/cm 2 and a low P r of 2.5 μC/cm 2 . Hence, the 0.8BST–0.2SBT RFE ceramic simultaneously exhibited a high recoverable energy-storage density of 3.3 J/cm 3 and a high energy-storage efficiency of 85% at 300 kV/cm. Additionally, a good energy-storage performance was reported over a temperature range of 50°C-120 °C and frequency from 10 to 1000 Hz, making the 0.8BST-0.2SBT RFE ceramic a potential lead-free dielectric energy-storage material.

Ultrahigh electric breakdown strength, excellent dielectric energy storage density, and improved electrocaloric effect in Pb-free (1-x)Ba(Zr0.15Ti0.85)O3-xNaNbO3 ceramics

In this study, NaNbO3 (NN) was introduced into Ba(Zr0.15Ti0.85)O3 (BZT) to form a solid solution with relaxor ferroelectric characteristics. The dielectric breakdown strength (BDS) of the specimen with 6 mol.% NN reached 680 kV/cm, the corresponding recoverable energy storage density (Wrec) was 5.15 J/cm3, and the energy storage efficiency (η) was 77%. The dissolution of Na + ions at the A position and Nb5+ ions at the B position of the perovskite structure reduced the concentration of oxygen vacancies in the lattice and compensated for defects. The doped ceramics exhibited lower dielectric loss and better thermal stability: the Wrec value was 2 ± 1% J/cm3 at 30–120 °C. In particular, in the 0.02NN ceramics, a ΔT of 1.81 K was achieved at 130 kV/cm, and the operating temperature zone expanded with the increase in doping concentration. The introduction of NN resulted in BZT ceramics that possess excellent energy storage performance and electrocaloric effect properties.

Synthesis and Characterization of KNN Modified BNT-ST Ceramics for Energy Storage Applications

Lead-free [(0.76-x)Bi0.5Na0.5TiO3–0.24SrTiO3–x(K0.5Na0.5)NbO3; BNT-ST-KNN] ceramics with x = 0, 0.03, 0.05, 0.07, 0.10, 0.15 wt.% were synthesized by using a solid-state reaction method. The effect of x content on phase, microstructure electrical and energy density properties was investigated. The samples were analyzed by X-ray diffraction (XRD) and the XRD patterns were fitted using the Rietveld refinement. The grain growth is obviously inhibited and smaller grains are formed in the ceramic samples at a high concentration of x. Dielectric study confirmed relax or nature with a drastic decrease of T max with the increase of x content in BNT-ST-KNN system. The maximum density (ρ = 5.420.13 g/cm3), highest dielectric constant (εr =3300) with tanδ∼0.05, high recoverable energy storage density (W rec=0.16 J/cm3) with energy storage efficiency of (η = 64) were obtained in x = 0.03 wt.% ceramic samples, which suggested its usefulness for energy-storage capacitor applications.

Scaling behavior of different shapes of hysteresis loops and recoverable energy storage density in Na0.5Bi0.5TiO3, K0.5Bi0.5TiO3, and Na0.25K0.25Bi0.5TiO3 ferroelectrics

In this work, the dependency of the polarization (P) - electric field (E) loop area A of lead free ferroelectrics Na0.5Bi0.5TiO3 (NBT), K0.5Bi0.5TiO3 (KBT), and Na0.25K0.25Bi0.5TiO3 (NKBT) on the amplitude (E0) of the electric field is studied. Based on the nature of the hysteresis loop with increasing E0, the lnA versus lnE0 graph is divided into three stages and the scaling exponents of each stage are estimated. In the third stage, NBT, KBT, and NKBT show different shapes of P-E loops (square, slanted and pinched, respectively). Although, almost similar slopes in the third stage are obtained from the lnA versus lnE0 graphs of KBT and NKBT, the formation of pinched P-E loop of NKBT is discussed based on the current-time curve under a complete cycle of the applied electric field. The shape of the P-E loop also affects the recoverable energy storage density (Wrec) of the material. Similar to the scaling of A, the variation of lnWrec with lnE0 of NBT, KBT and NKBT are examined. Interestingly, three stages are only noticed in the lnWrec−lnE0 curve of pinched P-E loop (NKBT), whereas lnWrec linearly increases with lnE0 for square and slanted P-E loop. Such type of behavior of Wrec of NKBT is explained based on the reversible domain switching mechanism of the pinched P-E loop.

Significant increase in comprehensive energy storage performance of potassium sodium niobate-based ceramics via synergistic optimization strategy

K0.5Na0.5NbO3 (KNN)-based ceramics are considered as one of the most promising lead-free dielectric ceramics owing to relatively high dielectric breakdown strength (DBS) resulted from their unique submicron grains. Unfortunately, it has been difficult to increase recoverable energy-storage density (Wrec) and energy-storage efficiency (η) simultaneously at present. Herein, we propose a synergistic optimization strategy, namely, simultaneously enhancing DBS by tailoring grain size to submicron scale and inducing the temperature range between the maximum dielectric permittivity temperature (Tmax) and the Burns temperature (TB) to room temperature, for solving the bottleneck. (1-x)K0.5Na0.5NbO3-xBi(Ni0.5Zr0.5)O3 (KNN-BNZ) ceramics were chosen as an example to illustrate the validity of this strategy. An ultrahigh Wrec of 8.09 J·cm−3 was obtained at the optimum composition of x = 0.15 under the electric field of 870 kV·cm−1, which is much higher than those of other reported KNN-based ceramics. Most importantly, this high Wrec was accompanied by a high η of 88.46%, which is superior to those of other KNN-based ceramics and very important for practical applications. The excellent comprehensive energy storage performance was resulted from the polar nanoregions, which is confirmed by high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM), piezo-force microscopy (PFM) and first-order reversal curve (FORC) distributions. The work not only finds out novel KNN-based ceramics with excellent comprehensive energy storage properties, but also provides a remarkable designing strategy for exploring a series of novel lead-free dielectric ceramics with high energy storage properties for practical applications in the future.

Promoting Energy Storage Performance of Sr0.7Ba0.3Nb2O6 Tetragonal Tungsten Bronze Ceramic by a Two-Step Sintering Technique

Dielectric ceramic capacitors have attracted immense interest because of their remarkable power density and excellent charging–discharging performance. Tetragonal tungsten bronze (TTB)-based ferroelectrics are the second large category of ferroelectric materials. However, they have not received enough appreciation in the dielectric capacitor field because of their poor energy storage properties. In this study, a two-step sintering technique was employed to prepare TTB relaxor ferroelectric ceramic Sr0.7Ba0.3Nb2O6 (SBN70), aiming to promote its energy storage performance. Remarkable recoverable energy storage density (Wrec ∼ 3.2 J/cm3) and excellent efficiency (η ∼ 90%) were realized simultaneously, which profited from the reduction of the average grain size and the enhancement of the breakdown strength. Moreover, the ceramic also exhibited an ultrashort discharge time (<65 ns), great discharge current density (789.8 A/cm2), and large power density (79 MW/cm3). The obtained results indicate the immense potential of TTB structure relaxor ferroelectric ceramics for energy storage applications.

Realizing excellent energy storage properties in Na0.5Bi0.5TiO3-based lead-free relaxor ferroelectrics

Development of lead-free dielectric capacitors with high recoverable energy storage density (Wrec), large energy storage efficiency (η), and wide usage temperature range are in high demanded for pulse power systems. Herein, we realized the enhancement of energy storage properties [high Wrec = 3.76 J/cm3, large η = 78.80 %, and broad operating temperature range (20−180 °C)] in lead-free Na0.5Bi0.5TiO3 (BNT)-based relaxor ferroelectrics via component regulation. Excellent energy storage properties mainly originate from suppressing early polarization saturation and improving dielectric breakdown strength (Eb). Domain evolution on the nanoscale offers robust support to suppression of early polarization saturation. The enhancement of Eb can be derived from the contribution of the Mg-rich phase, which is also corroborative via first-principles calculation on basis of density functional theory (DFT). We believe that these findings in this work may provide a practicable guideline to build new lead-free ceramics for electrical energy storage applications.

Achieving ultrahigh energy storage performance over a broad temperature range in (Bi0.5Na0.5)TiO3-based eco-friendly relaxor ferroelectric ceramics via multiple engineering processes

The development of ABO3 perovskite-structured dielectric materials with high recoverable energy storage density (Wrec) and power density (PD) is crucial for the downsizing of pulsed power devices. Despite several research efforts, achieving a high Wrec over a wide working temperature range in an environmentally benign system remains a difficulty. A synergistic design strategy is given here, which includes concurrently doping at the A- and B-site to achieve a spread and depressed dielectric response, adding sintering aids, and employing advanced viscous polymer rolling technology for dense and ultra-thin ceramic samples, respectively. Finally, at a relatively low electric field of 380 kV/cm, an ultrahigh Wrec of 6.57 J/cm3 is realized in (Bi0.5Na0.5)0.93Ca0.07Ti0.85Zr0.15O3-0.5 wt% Li2CO3 component, which benefits from gentle polarization saturating and improved breakdown strength. The Wrec can be maintained above 6 J/cm3 while maintaining strong thermal stability (variation ≤ ± 3%) over a temperature range of 30–150 °C. Because BNT-based materials have such high energy storage performance and temperature stability, they are not only a promising candidate for replacing lead-based dielectrics, but also a valuable guide for developing new high-performance ferroelectric materials for future energy storage devices in the pulsed power system.

Investigation on high energy storage properties in La3+-doped 0.88PMN-0.12PT relaxor ferroelectric films

Relaxor ferroelectric Pb1-xLax(Mg1/3Nb2/3)0.88Ti0.12O3 (P1-xLxMNT, x = 0.00, 0.01, 0.02, 0.03) films with pure perovskite structure are successfully deposited onto Pt(111)/Ti/SiO2/Si substrate by sol-gel process. Note that donor doping for P1-xLxMNT (x = 0.01∼0.03) allows the change of P-E loop from the slanted feature to the square characteristic. Under the condition of the identical electric field and larger Pmax-Pr value, relatively lower recoverable energy storage density (Wrec) is obtained with the loss (η) of small difference resulting from slim P-E loop. While, the largest Wrec of 25.2 J/cm3 and η of 63.2% are obtained in the relaxor P0.98L0.02MNT film, which are strongly dependent on the raised breakdown strength (EBD= 2947.2 kV/cm), larger difference between the maximum and remnant polarization (ΔP = 29.6 μC/cm2). This study provides a newfangled guidance for tailoring the energy storage performance of the materials by doping effect.