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

Compared with fuel cells and electrochemical capacitors, dielectric capacitors are regarded as promising devices to store electrical energy for pulsed power systems due to their fast charge/discharge rates and ultrahigh power density. Dielectric materials are core components of dielectric capacitors and directly determine their performance. Over the past decade, extensive efforts have been devoted to develop high-performance dielectric materials for electrical energy storage applications and great progress has been achieved. Here, we present an overview on the current state-of-the-art lead-free bulk ceramics for electrical energy storage applications, including SrTiO3, CaTiO3, BaTiO3, (Bi0.5Na0.5)TiO3, (K0.5Na0.5)NbO3, BiFeO3, AgNbO3 and NaNbO3-based ceramics. This review starts with a brief introduction of the research background, the development history and the basic fundamentals of dielectric materials for energy storage applications as well as the universal strategies to optimize their energy storage performance. Emphases are placed on the design strategies for each type of dielectric ceramic based on their special physical properties with a summary of their respective advantages and disadvantages. Challenges along with future prospects are presented at the end of this review. This review will not only accelerate the exploration of higher performance lead-free dielectric materials, but also provides a deeper understanding of the relationship among chemical composition, physical properties and energy storage performance.

High-performance lead-free bulk ceramics for electrical energy storage applications: design strategies and challenges

Relaxor ferroelectric (FE) ceramic capacitors have attracted increasing attention for their excellent energy-storage performance. However, it is extremely difficult to achieve desirable comprehensive energy-storage features required for industrial applications. In this work, very high recoverable energy density W-rec approximate to 8.73 J cm(-3), high efficiency eta approximate to 80.1%, ultrafast discharge rate of

NaNbO3-(Bi0.5Li0.5)TiO3 Lead-Free Relaxor Ferroelectric Capacitors with Superior Energy-Storage Performances via Multiple Synergistic Design

Enhancement of recoverable energy density and efficiency of lead-free relaxor-ferroelectric BNT-based ceramics

Optimization of polarization and electric field of bismuth ferrite-based ceramics for capacitor applications

Lead-free (0.70-x)BiFeO3-0.30BaTiO3-xAgNbO3+5‰mol CuO (abbreviated as BF-BT-xAN) ceramics were fabricated using a modified thermal quenching technique. BF-BT-xAN ceramics are of a perovskite structure with morphotropic phase boundary (MPB) and show strong relaxor properties. Remarkably, the high recoverable energy storage density of 2.11 J/cm3 is obtained for BF-BT-xAN with x = 0.14. For the x = 0.14 ceramics, its energy storage efficiency is as high as 84 % at relative low field of 195 kV/cm, together with an outstanding thermal stability in a broad temperature range from 25 °C to 150 °C. In addition, this ceramic maintains superior energy storage performance even after 8 × 104 electrical cycles due to its high densification after doping Ag2O and Nb2O5. The result suggests that lead-free BF-BT-xAN ceramics may be promising candidate for dielectric energy storage application.

Large energy storage density in BiFeO3-BaTiO3-AgNbO3 lead-free relaxor ceramics

Dielectric energy storage materials are becoming increasingly popular due to their potential superiority, for example, excellent pulse performance as well as good fatigue resistance. Although numerous studies have focused on lead-free dielectric materials which possess outstanding energy storage characteristics, the results are still not satisfying in terms of achieving both large discharging energy density (Wd) and high discharging efficiency (η) under low electric fields, which is crucial to be conducted in miniatured electronic components. Here, we adopt the strategy of domain engineering to develop sodium bismuth titanate (Bi0.5Na0.5TiO3)-based ceramics employed in the low-field situation. Remarkably, a large Wd of 2.86 J/cm3 and an ultrahigh η of 90.3% are concurrently obtained in 0.94(Bi0.5Na0.5)0.65(Ba0.3Sr0.7)0.35TiO3-0.06 Bi(Zn2/3Nb1/3)O3 system when the electric field is as low as 180 kV/cm. Additionally, the ceramic shows brilliant thermal endurance (20-160 °C) and frequency stability (0.1-100 Hz) with high Wd (>1.48 J/cm3) together with an ultra-high η (>90%). What's more, the ceramic displays a fast charge-discharge time (t0.9 = 109.2 ns). The piezoresponse force microscopy (PFM) results reveal that the introduced Bi(Zn2/3Nb1/3)O3 disrupts the microdomains of (Bi0.5Na0.5)0.65(Ba0.3Sr0.7)0.35TiO3 ceramics and promotes the formation of nanodomains, leading to enhanced energy storage properties. The current work may arouse interest in developing low-field high-performing dielectric capacitors for energy storage application.

Domain Engineered Lead-Free Ceramics with Large Energy Storage Density and Ultra-High Efficiency under Low Electric Fields.

Enhanced energy storage density of Sr0.7BixTiO3 lead-free relaxor ceramics via A-site defect and grain size tuning

Dielectric capacitors with high energy storage and dielectric properties at high temperatures have significantly practical application in many fields. Lead-free ceramics of (1-x)(0.65Bi0.5Na0.5TiO3-0.35Bi0.2Sr0.7TiO3)-xBaSnO3 were prepared by a solid-state reaction method. It was found that the 0.8(0.65Bi0.5Na0.5TiO3-0.35Bi0.2Sr0.7TiO3)-0.2BaSnO3 ceramic shows a large recoverable energy storage density (Wr) of 3.75 J/cm3 and efficiency (η) of 84.8% under 380 kV/cm along with outstanding power density of 38.73 MW/cm3 under 130 kV/cm at room temperature. Additionally, a high Wr of 3.21 J/cm3 and η of 77% are achieved under a high electric field of 300 kV/cm at 100 °C. When the temperature reaches 140 °C, it still has a high Wr of 3.1 J/cm3 and η of 72%. The outstanding energy storage performance at high temperatures can be explained by the enhancement of breakdown strength and the constructing of polar phase stability caused by the introduction of BaSnO3.

Bi0.5Na0.5TiO3-based lead-free ceramics with superior energy storage properties at high temperatures

Large electric-field-induced strain and energy storage properties in Bi0.5Na0.5TiO3-(0.5Ba0.7Ca0.3TiO3-0.5BaTi0.8Zr0.2O3) lead-free relaxor ferroelectric ceramics

Xiaoxiao Zhang

Papers

Large energy storage density in BiFeO3-BaTiO3-AgNbO3 lead-free relaxor ceramics

Domain Engineered Lead-Free Ceramics with Large Energy Storage Density and Ultra-High Efficiency under Low Electric Fields.

Enhanced energy storage density of Sr0.7BixTiO3 lead-free relaxor ceramics via A-site defect and grain size tuning

Bi0.5Na0.5TiO3-based lead-free ceramics with superior energy storage properties at high temperatures

Large electric-field-induced strain and energy storage properties in Bi0.5Na0.5TiO3-(0.5Ba0.7Ca0.3TiO3-0.5BaTi0.8Zr0.2O3) lead-free relaxor ferroelectric ceramics