LAUSR

Pb‐free relaxor ferroelectric (RFE)‐based dielectric capacitors have great potential in cutting‐edge pulsed‐power/high‐power systems. Particularly, a high energy density (Wrec) under a moderate electric‐field (E) is urgent for electric vehicles and advanced electronic devices. However, achieving this, such as overcoming the bottleneck of Wrec > 10 J cm−3 under E ≤ 60 kV mm−1, remains challenging owing to trade‐off between critical parameters. Herein, an adaptive local‐global structure tactic is presented to obtain large and high‐reversible polarizability, and realizing a record‐high Wrec of 12 J cm−3 and a high efficiency (η) of 89% among Pb‐free bulk ceramics under moderate E. This is implemented by combining the strong distorted (Bi0.5Na0.25K0.25)TiO3 ferroelectric and paraelectric BaZrO3 to form global tolerance factor optimized solid‐solutions. Locally, such RFE state exhibits fluctuating atomic displacement vectors, featured by a broad range of magnitudes and orientations, and forming strongly polarizable and small‐sized clusters. It results in a record‐high reversible polarizability and large polarization difference of 56.3 µC cm−2 under 56 kV mm−1. Furthermore, the excellent reliability, high discharge energy density (4.5 J cm−3), and large power density (504.5 MW cm−3) are obtained. These results demonstrate the feasibility of adaptive local‐global structure in enhancing the energy‐storage capabilities under moderate E.