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

Significantly Improvement of Comprehensive Energy Storage Performances with Lead-free Relaxor Ferroelectric Ceramics for High-temperature Capacitors Applications

Giant energy density and high efficiency achieved in silver niobate-based lead-free antiferroelectric ceramic capacitors via domain engineering

Ultrahigh energy density in short-range tilted NBT-based lead-free multilayer ceramic capacitors by nanodomain percolation

The development of lead-free bulk ceramics with high recoverable energy density (Wrec) and high efficiency plays a major role in meeting the requirements for miniaturization and integration of advanced pulsed power capacitors. In this study, composition-dependent phase structures and ferroelectric properties of lead-free relaxor ferroelectric ceramics (1 − x)(0.84Bi0.5Na0.5TiO3–0.16K0.5Bi0.5TiO3)–x(Bi0.2Sr0.7TiO3) [(1 − x)(BNT–KBT)–xSBT, x = 0–0.45] are investigated. The introduction of SBT into the morphotropic phase boundary (MPB) BNT–BKT system constructs the relaxor ferroelectrics according to the order–disorder theory, leading to an improved energy storage performance. Results show that an ultrahigh recoverable energy density of 4.06 J cm−3 and a high energy-storage efficiency of 87.3% under an electric field of 350 kV cm−1 are achieved concomitantly, together with a superior high temperature stability (30–160 °C) and strong fatigue endurance (104 cycles). In particular, the corresponding ceramic exhibits an ultrafast discharge rate (τ0.9 = 127 ns) and a high level of discharge energy density (Udis = 1.29 J cm−3). Our study provides the groundwork for an effective way to design high-performance ceramics for application in next generation energy storage capacitors.

Xiang Zhang

Papers

Greatly enhanced discharge energy density and efficiency of novel relaxation ferroelectric BNT–BKT-based ceramics

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

Optimization the energy density and efficiency of BaTiO3-based ceramics for capacitor applications

Significantly improved recoverable energy density and ultrafast discharge rate of Na0.5Bi0.5TiO3-based ceramics

Effective improved energy storage performances of Na0.5Bi0.5TiO3-based relaxor ferroelectrics ceramics by A/B-sites co-doping