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.

Dielectric capacitors have become an important component in current pulsed power devices and thus have attracted great research interest in recent years. Among all kinds of dielectric materials, the bismuth ferrite (BiFeO 3 )-based ceramic capacitors show possible applications in dielectric energy storage because of their large polarization. However, the relatively high conductivity badly limits the improvement of electric breakdown strength, thus leading to low energy density. Herein, the perovskite end-member La(Mg 2/3 Nb 1/3 )O 3 and sintering aid MnO 2 were simultaneously introduced into BiFeO 3 −SrTiO 3 solid solutions to improve the relaxation features and electric breakdown strength. Accordingly, a high recoverable energy density of 6.3 J/cm 3 and an acceptable efficiency of 74.3% were realized under 450 kV/cm. In addition, the good frequency/thermal stability and superior charge−discharge performances were also realized. This work provides feasible approaches to modify the capacitive energy storage of BiFeO 3 -based relaxor ferroelectric ceramics.

Antiferroelectric ceramics are recently, a research hotspot for electrostatic energy storage because of their large electric‐field induced polarization. Lead‐free sodium niobate (NaNbO3)‐based ceramics are one of the emerging antiferroelectric counterparts. However, the unstable antiferroelectric phase seriously restricts the further improvement of energy density and efficiency. In this work, by introducing binary perovskite end‐member BiFeO3–BaTiO3 with lower tolerance factor and average electronegativity into NaNbO3 ceramics, the stablized antiferroelectric phase with improved relaxation characteristic is identified by slim double‐like polarization‐electric field (P–E) loops and four‐peak current–electric field (I–E) curves. Meanwhile, the antiferroelectric P to R phase transition is verified through Raman spectra, X‐ray diffraction (XRD) patterns, and dielectric performance. In particular, the enhanced electric breakdown strength Eb is achieved by synergic contributions from ultralow dielectric loss, reduced grain size, and so on. Consequently, the sample with optimized composition displays ultrahigh recoverable energy storage density (Wrec) of 14.5 J cm−3 and satisfied efficiency (η) of 83.9%, which shows the superiority in the state‐of‐the‐art dielectric ceramics. These results provide a feasible route by regulating the relationship between antiferroelectric structure and properties to explore high‐performance dielectrics for electrostatic energy storage applications.