Perovskite lead-free dielectrics for energy storage applications

With the fast development of the power electronics, dielectric materials with high energy-storage density, low loss, and good temperature stability are eagerly desired for the potential application in advanced pulsed capacitors. Based on the physical principals, the materials with higher saturated polarization, smaller remnant polarization, and higher electrical breakdown field are the most promising candidates. According to this rule, so far, four kinds of materials, namely antiferroelectrics, dielectric glass-ceramics, relaxor ferroelectric and polymer-based ferroelectrics are thought to be more likely used in next-generation pulsed capacitors, and have been widely studied. Thus, this review serves to give an overall summary on the state-of-the-art progress on electric energy-storage performance in these materials. Moreover, some general future prospects are also provided from the existed theoretical and experimental results in this work, in order to propel their application in practice.

https://www.worldscientific.com/doi/pdf/10.1142/S2010135X13300016

A review on the dielectric materials for high energy-storage application

Antiferroelectric materials that display double ferroelectric hysteresis loops are receiving increasing attention for their superior energy storage density compared to their ferroelectric counterparts. Despite the good properties obtained in antiferroelectric La-doped Pb(Zr,Ti)O3 -based ceramics, lead-free alternatives are highly desired due to the environmental concerns, and AgNbO3 has been highlighted as a ferrielectric/antiferroelectric perovskite for energy storage applications. Enhanced energy storage performance, with recoverable energy density of 4.2 J cm-3 and high thermal stability of the energy storage density (with minimal variation of ≤±5%) over 20-120 °C, can be achieved in Ta-modified AgNbO3 ceramics. It is revealed that the incorporation of Ta to the Nb site can enhance the antiferroelectricity because of the reduced polarizability of B-site cations, which is confirmed by the polarization hysteresis, dielectric tunability, and selected-area electron diffraction measurements. Additionally, Ta addition in AgNbO3 leads to decreased grain size and increased bulk density, increasing the dielectric breakdown strength, up to 240 kV cm-1 versus 175 kV cm-1 for the pure counterpart, together with the enhanced antiferroelectricity, accounting for the high energy storage density.

Lead-Free Antiferroelectric Silver Niobate Tantalate with High Energy Storage Performance.

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.

Electroceramics for High-Energy Density Capacitors: Current Status and Future Perspectives

This study presents an innovative strategy to improve the energy storage properties of NaNbO3 lead-free ceramics by the addition of Bi2O3. The introduction of Bi2O3 can effectively increase the breakdown strength and decrease the remnant polarization of NaNbO3 ceramics. Meanwhile, hybridization between the O2− 2p and Bi3+ 6p orbitals can enhance the polarization. The novel NaNbO3-based (Na0.7Bi0.1NbO3) ceramics demonstrate ultrahigh energy storage efficiency of 85.4% and remarkably high energy storage density (4.03 J cm−3) at 250 kV cm−1 simultaneously, which are superior to the results of almost all recently reported lead-free alternatives. The outstanding stability of energy storage characteristics in terms of frequency (1–1000 Hz), temperature (20–120 °C) and fatigue (cycle number: 105) is also observed in Na0.7Bi0.1NbO3 ceramics. Furthermore, additional pulsed charge–discharge measurements for Na0.7Bi0.1NbO3 ceramics are also carried out to evaluate actual operation performance. The Na0.7Bi0.1NbO3 ceramics exhibit extremely high power density (62.5 MW cm−3) and current density (1250 A cm−2) and release all stored energy rapidly (∼155 ns) under various electric fields and temperatures. These properties qualify these environment-friendly Na0.7Bi0.1NbO3 ceramics as innovative and most promising alternatives for energy storage applications, especially for high power and pulsed power system applications.

Superior energy storage properties and excellent stability of novel NaNbO3-based lead-free ceramics with A-site vacancy obtained via a Bi2O3 substitution strategy

The energy storage density of a Ba0.4Sr0.6TiO3 ceramic with the addition of 5–20 vol% glass was investigated. The results show that the improvement of the energy density in glass-added Ba0.4Sr0.6TiO3 samples arises due to two factors: one is that the breakdown strength is notably improved due to the decrease of the porosity and the reduction of the grain size and pore size in glass-added samples and the other is that the remnant polarization of glass-added samples is decreased. The energy density of the samples containing 5 vol% glass additive was improved by a factor of 2.4 compared with that of pure Ba0.4Sr0.6TiO3.

Improved Energy Storage Density in Barium Strontium Titanate by Addition of BaO-SiO2-B2O3 Glass

(100−x) wt% Ba04Sr06TiO3−x wt% MgO composites (10≤x≤30) were prepared using Ba04Sr06TiO3 powder and nanosized MgO powder (∼60 nm) by a solid-state reaction The energy storage density and dielectric loss were investigated for the purpose of a potential application in solid-state pulse-forming line The results show that Ba04Sr06TiO3/MgO composites exhibit a notably enhanced energy density and low dielectric loss, compared with pure Ba04Sr06TiO3 The enhancement of the energy density is attributed to the notable increase in breakdown strength of the composites and the improvement of dielectric constant stability with regard to electric field In the case of x=30, the samples exhibited a breakdown strength of 331 kV/mm, an energy density of 114 J/cm3, a moderate dielectric constant of 270, and a low dielectric loss of 4 × 10−4

Ba0.4Sr0.6TiO3/MgO Composites with Enhanced Energy Storage Density and Low Dielectric Loss for Solid‐State Pulse‐Forming Line

Na2O-PbO-Nb2O5- SiO2 glass-ceramic dielectrics and internal electrode structures were investigated to improve the general energy storage density of capacitors. This work was brought out by the motivation of elimination of structural flaws and pores remaining in dielectrics and at electrode/dielectric interfaces, which are the main causes of low dielectric strength and low energy storage density of the traditional sintered dielectric capacitors. The combination of pore-free glass-ceramic dielectrics and series internal electrodes was adapted in the design of high energy storage density capacitors (HESDCs). The results show that the dielectric properties and the breakdown strength of glass-ceramics could be optimized through appropriate crystallization profiles, which could lead to an energy storage density of up to 17 J/cm3 for glass-ceramics crystallized at 850degC for 3 h. The series multilayer capacitors could bear a rather higher electric field compared with the traditional ones without internal electrodes, and the dielectric strength could be further improved when the internal electrodes are made of sputtered gold films and printed paste. As a result, an overall energy storage density of about 8 J/cm3 has been achieved for the capacitor with internal electrodes made of gold film and screen-printed paste when the 850degC-crystallized glass-ceramic dielectric was used.

Lead Sodium Niobate Glass-Ceramic Dielectrics and Internal Electrode Structure for High Energy Storage Density Capacitors

Structural and dielectric characterization of Gd2O3-added BaO–Na2O–Nb2O5–SiO2 glass–ceramic composites

The structural and dielectric properties were investigated in the La2O3 added glass-ceramics based on complex niobates. With the addition of La2O3, the optimization of microstructure was observed which resulted in the improvement of breakdown strength for the glass-ceramics. Besides, the dielectric constant was drastically enhanced because of the doping effect of La3+ in the A-sites of both crystallographic structures. Due to the combined effects of both high breakdown strength and polarization difference, the maximum discharged energy density of 1.2 J/cm3 was achieved in the niobate glass-ceramics with 2 mol% La2O3, suggesting dielectric glass-ceramics of this composition could be the most attractive candidate for high-energy density capacitors.

Jun Luo

Papers

Improved Energy Storage Density in Barium Strontium Titanate by Addition of BaO-SiO2-B2O3 Glass

Ba0.4Sr0.6TiO3/MgO Composites with Enhanced Energy Storage Density and Low Dielectric Loss for Solid‐State Pulse‐Forming Line

Lead Sodium Niobate Glass-Ceramic Dielectrics and Internal Electrode Structure for High Energy Storage Density Capacitors

Structural and dielectric characterization of Gd2O3-added BaO–Na2O–Nb2O5–SiO2 glass–ceramic composites

Structural Optimization and Improved Discharged Energy Density for Niobate Glass-Ceramics by La2O3 Addition