Superior Moderate‐Field Energy Storage via Phase Structure Engineering and Polar Nanoregion Design

Abstract

Increasing the breakdown field strength as a valid way for energy storage improvement is always in the spotlight. However, in contrast to improvement in recoverable energy density (Wrec) by pursuing high electric fields, the achievement in high energy storage coefficient (Wrec/Eb) and efficiency (η) at a decent electric field is more pivotal for practical applications. Herein, we induce the phase and domain structure evolution through precise compositional modification aimed at minimizing interfacial polarization. For the (0.67 − x)BiFeO3–0.33BaTiO3–xK0.5Na0.5(Nb0.85Ta0.15)O3 ceramics, the microstructural and local defect characteristics also ameliorated, enabling a moderate electric field with pronounced polarization. The ability of polarization fully exerted, providing an exceptional Wrec of 7.4 J/cm3 and a remarkable η of 90% in the optimal composition at 418 kV/cm. Moreover, a superior Wrec/Eb of 0.0176 µC/cm2 along with extraordinary charge‐discharge performances, including high discharge density (Wd ∼ 5.0 J/cm3), short discharge time (t0.9 ∼ 50 ns) were obtained. This work provides beneficial insights for adjusting the energy storage performances of lead‐free relaxor ferroelectric ceramics.