The synergistic contributions of high Pmax, small Pr and large Eb endow the BiFeO3-based ceramics with relaxor ferroelectric characteristics, due to which an ultrahigh Wrec of 13.9 J cm−3 and high η of 89.6% have been achieved synchronously.

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Dielectric capacitors reveal great potential in the application of high power and/or pulsed power electronic devices owing to their ultrafast charge-discharge rate and ultrahigh power density. Among various dielectric capacitors, the environment-friendly lead-free dielectric ceramics have drawn extensive investigations in recent years. Nevertheless, the relatively small recoverable energy storage density (W rec ) is still an obstacle for their application. Herein, the (0.55−x)BiFeO 3 -0.45SrTiO 3 -xBaTiO 3 ternary ceramics with 0.1 wt% MnO 2 were prepared by the solid-state reaction, and achieved enhanced relaxor behavior as well as breakdown strength E b . As a result, the x = 0.12 ceramic exhibited superior comprehensive energy storage performance of large E b (50.4 kV/mm), ultrahigh W rec (7.3 J/cm 3 ), high efficiency η (86.3%), relatively fast charge-discharge speed (t 0.9 = 6.1 μs) and outstanding reliability under different frequency, fatigue, and temperature, indicating that the BiFeO 3 -based relaxor ferroelectric ceramics are prospective alternatives for electrostatic energy storage.