Giant Capacitive Energy‐Storage in BaTiO3‐Based Fine‐Grained Relaxors via Local Polarization Enhancement

Pb-free dielectric energy storage capacitors are core components in advanced pulse-power electronic systems and devices. However, the relatively low energy density (Wrec) for the industrial pillar BaTiO3 (BT)-based capacitors remains a significant obstacle for their cutting-edge applications, due to their low intrinsic polarization and breakdown strength (EB). Herein, through chemical composition and local structure design, a giant Wrec of 15.1 J cm-3 along with a high efficiency (η) of 85% is demonstrated in a BT-based relaxor bulk ceramic. This is achieved by introducing rare A-site polarization enhancement substitution (Bi0.5Na0.5)2+ ions in combination with B-site fastest relaxation alternative (Zn1/3Nb2/3)4+ ions to enhance local polarization and refine grain structure. Atomic-level local structure analysis has revealed that the diversified atomic polar displacement vectors, characterized by largely extended magnitude and heterogeneous directions, assemble into highly polarizable clusters at several unit-cells scale. Consequently, it exerts a large polarization difference (ΔP) of 49 µC cm-2 and a high EB of 90 kV mm-1. Moreover, a giant power density (677 MW cm-3), high discharge energy density (3.9 J cm-3), and excellent stability are achieved. This study overcomes the current Wrec bottleneck of ≈10 J cm-3 in BT-based bulk ceramics, presenting an approach to optimize the energy storage performance of Pb-free relaxors.