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 Bi 2 O 3 and Sc 2 O 3 were introduced to improve the energy storage property of 0.10 wt % MnO 2 -doped AgNbO 3 @SiO 2 ceramics by simultaneously enhancing the maximum polarization, breakdown strength, and relaxation feature. It is particularly interesting that the AgNbO 3 -based ceramics with 4 mol % Bi 2 O 3 and Sc 2 O 3 demonstrate the recoverable energy storage density of 5.9 J/cm 3 with the energy storage efficiency of 71%, exhibiting 1.9 and 1.4 times enhancement compared to 0.10 wt % MnO 2 -doped AgNbO 3 @SiO 2 ceramics. In addition, the benign energy storage performance can be maintained at elevated temperatures and frequencies and up to 10 5 cycling, indicating great potential in advanced high-power applications.

Owing to the merits of giant power density and ultrafast charge–discharge time, dielectric capacitors including ceramics and films have inspired increasing interest lately. Nevertheless, the energy storage density of dielectric ceramics should be further optimized to cater to the boosting demand for the compact and portable electronic devices. Herein, an ultrahigh recoverable energy storage density W rec of 13.44 J/cm3 and a high efficiency η of 90.14% are simultaneously realized in BiFeO3–BaTiO3–NaTaO3 relaxor ferroelectric ceramics with high polarization P max, reduced remanent polarization P r, and optimized electric breakdown strength E b. High P max originates from the genes of BiFeO3-based ceramics, and reduced P r is induced by enhanced relaxor behavior. Particularly, a large E b is achieved by the synergic contributions from complicated internal and external factors, such as decreased grain size and improved resistivity and electrical homogeneity. Furthermore, the ceramics also exhibit satisfactory frequency, cycling and thermal reliability, and decent charge–discharge property. This work not only indicates that the BiFeO3-based relaxor ferroelectric materials are promising choices for the next-generation electrostatic capacitors but also paves a potential approach to exploit novel high-performance dielectric ceramics.

Lead-free antiferroelectric ceramics have drawn widespread interest recently on account of their environmentally friendly components and potential applications in high-power systems. However, their relatively low recoverable energy storage density (W rec < 10 J/cm 3 ), limited by the electric breakdown strength (E b < 60 kV/mm), and low efficiency (η < 80%), generated by large hysteresis during the antiferroelectric−ferroelectric phase transition, have seriously restricted their application in portable and compact electronic devices. In this study, the relaxor antiferroelectric (1− x)NaNbO 3−x (0.55BiFeO 3 -0.45SrTiO 3 ) ceramics were elaborately designed and systematically explored. With the help of composition regulation, the ceramics not only exhibited a stable antiferroelectric phase but also underwent a structural transformation from an antiferroelectric P (Pbma) phase to R (Pnma) phase, as confirmed by the temperature-dependent dielectric constants, Raman spectra, X-ray diffraction (XRD) refinement, pinched polarization-electric field (P−E) curves, and four-peak current-electric field (I−E) curves. In addition, the relaxor characteristic was demonstrated by the diffuse dielectric peaks, slim P−E curves, flattened Raman peaks, and I−E curves. Consequently, novel relaxor antiferroelectric ceramics were successfully obtained, which simultaneously revealed the features of relaxor and antiferroelectricity. Specifically, the E b was significantly improved because of the reduced grain size, small sample thickness, exceptionally low dielectric loss, and a moderate dielectric constant. Finally, the sample with x = 0.12 showed an ultrahigh W rec value of 16.2 J/cm 3 and satisfactory η of 82.3% at 97 kV/mm, outperforming most state-of-the-art counterparts. Furthermore, the ceramic also exhibited a large current density (C D ) of 1268.4 A/cm 2 and power density (P D ) of 177.6 MW/cm 3 at 28 kV/mm, offering prospective applications in high-power capacitors. This work not only achieved outstanding comprehensive energy storage performance in sodium niobate-based ceramics by modulating the antiferroelectric structure but also provided a feasible route to developing high-performance dielectric capacitors from the viewpoint of structure−property relationship.

BNT-based ceramics with polymorphic PNRs display an ultrahigh Wrec of 7.4 J cm−3 and a high η of 89% at 400 kV cm−1, as well as excellent thermal reliability.

Dielectric capacitors have attracted growing attention because of their important applications in advanced high power and/or pulsed power electronic devices. Nevertheless, the synergistic enhancement of recoverable energy storage density (W rec > 10 J/cm3) and efficiency (η > 80%) is still a great challenge for lead-free dielectric bulk ceramics. Herein, by introducing complex perovskite compound (Bi0.9Na0.1)­(Fe0.8Ti0.2)­O3 with a smaller tolerance factor into an NaNbO3 matrix (NN-BNFT), we have achieved and explored stable relaxor antiferroelectric ceramics with enhanced relaxor behavior. Of particular importance is the composition of 0.88NN-0.12BNFT, which exhibits a large electric breakdown strength E b of 87.3 kV/mm, an ultrahigh W rec of 12.7 J/cm3, and a high efficiency η of 82.5%, as well as excellent thermal reliability and an ultrafast discharge speed, resulting from the dense microstructure, the moderate dielectric constant, the reduced grain size, the dielectric loss, and the sample thickness. The outstanding energy storage properties of NN-BNFT display great promise in advanced dielectric capacitors for energy storage applications.