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

Energy storage materials and their applications have attracted attention among both academic and industrial communities. Over the past few decades, extensive efforts have been put on the development of lead-free high-performance dielectric capacitors. In this review, we comprehensively summarize the research progress of lead-free dielectric ceramics for energy storage, including ferroelectric ceramics, composite ceramics, and multilayer capacitors. The results indicate that dielectric capacitors with both high energy density and high efficiency are feasible using the materials providing high breakdown electric field and a slim hysteresis loop. This article also lists the factors affecting the fabrication cost of dielectric capacitors, such as sintering temperature, raw material costs, and types of internal electrodes, to promote the industrial application of ceramic energy storage capacitors.

A review on the development of lead-free ferroelectric energy-storage ceramics and multilayer capacitors

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

Energy storage performance of Na0.5Bi0.5TiO3-SrTiO3 lead-free relaxors modified by AgNb0.85Ta0.15O3

Phase structure and properties of sodium bismuth titanate lead-free piezoelectric ceramics

Lead-free (1 − x)Bi0.5Na0.5TiO3–xSrTiO3 + ywt%Nb2O5 electroceramics were synthesized using the conventional method to investigate the influences of SrTiO3 content and Nb2O5 doping on the material’s phase structure, microstructure, and energy storage properties. All the investigated compositions possessed a single perovskite phase structure of pseudocubic symmetry. The introduction of SrTiO3 and Nb2O5 led to a weakened relaxor characteristic and a decrease of Tm. The microstructure was refined by Nb2O5 doping, and the average grain size of the 0.6Bi0.5Na0.5TiO3–0.4SrTiO3 sample decreased drastically from ~ 10 to ~ 1 µm when 2.5 wt% Nb2O5 was added. Enhanced electrical breakdown and polarization were achieved for the samples with the refined microstructure. Among the various Bi0.5Na0.5TiO3-based ceramics, 0.6Bi0.5Na0.5TiO3–0.4SrTiO3 + 2.5 wt%Nb2O5 ceramic exhibited excellent energy-storage properties with thermal stability, in which large recoverable energy-storage density Wrec ~ 1.82 J/cc and efficiency η ~ 81% were both achieved. Our results indicate that this ceramic is a promising material for lead-free energy storage applications.

Enhanced energy storage properties in Nb-modified Bi 0.5 Na 0.5 TiO 3 –SrTiO 3 lead-free electroceramics

Giant electrostrain under low driving field in Bi1/2Na1/2TiO3-SrTiO3 ceramics for actuator applications

Lead-free Bi0.5Na0.5TiO3-SrTiO3 incipient piezoceramics with Li2CO3 and MnO2 additives were successfully fabricated at low firing temperature for applications in co-fired multilayer piezoactuators. The addition of Li2CO3 effectively shifted the sintering temperature from 1230 °C down to 1075 °C, where the ceramics were co-fired with a Ag/Pd (75/25) inner electrode. The prototype actuators were prepared by tape-casting method using ceramics with the composition of 0.74Bi0.5Na0.5TiO3-0.26 SrTiO3 + 0.15 wt%MnO2 + 0.45 wt%Li2CO3. The total number of active layers was 13, and each ceramic layer had a thickness of 60 μm. The actuator output a large strain up to ∼0.20% at a driving field of 4 kV/mm, due to the field-induced phase transition between the ergodic relaxor and ferroelectric phases. The excellent voltage-displacement performance of the prototype actuator demonstrates the potential for industrial applications.

Low-temperature sintered Bi0.5Na0.5TiO3-SrTiO3 incipient piezoceramics and the co-fired multilayer piezoactuator thereof

Energy-storage properties of low-temperature Co-fired BNT-ST/AgPd multilayer lead-free ceramic capacitors

A series of (1-x)Bi1/2Na1/2TiO3-xSrTiO3+0.05 wt% MnO2 lead-free multilayer piezoactuators was prepared using a tape casting method, and the field-induced strain performance, temperature stability, electric fatigue and load characteristics were evaluated to assess potential practical applications. In contrast to traditional PZT ceramics, the fabrication of BNT bulk ceramics into multilayer piezoactuators provides significantly decreased strain (S)-electric field (E) characteristics as a result of internal compressive residual stress. The inactive edge distance, sintering temperature and layer thickness were all found to affect the compressive residual stress of the actuator. Through reconstructing the material composition and structure of BNT-ST actuators, active strain (0.168 %, 2 kV/mm), total strain (>0.15 %, E ≤ 2.5 kV/mm) and blocking stress (42.6 MPa) were realized in BNT-based cofired multilayer actuators, displaying a better performance than commercial PZT actuators. These results indicate that environmental-friendly BNT-based lead-free multilayer piezoactuators are promising candidates with regard to practical applications. 

Effect of stress on the phase transition and optimizing electric-induced strain behavior of Bi0.5Na0.5TiO3-SrTiO3 lead-free co-fired multilayer piezoactuators

Xing-Ye Tong

Papers

Enhanced energy storage properties in Nb-modified Bi 0.5 Na 0.5 TiO 3 –SrTiO 3 lead-free electroceramics

Giant electrostrain under low driving field in Bi1/2Na1/2TiO3-SrTiO3 ceramics for actuator applications

Low-temperature sintered Bi0.5Na0.5TiO3-SrTiO3 incipient piezoceramics and the co-fired multilayer piezoactuator thereof

Energy-storage properties of low-temperature Co-fired BNT-ST/AgPd multilayer lead-free ceramic capacitors

Effect of stress on the phase transition and optimizing electric-induced strain behavior of Bi0.5Na0.5TiO3-SrTiO3 lead-free co-fired multilayer piezoactuators