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

Abstract Pb‐free dielectric energy storage capacitors are core components in advanced pulse‐power electronic systems and devices. However, the relatively low energy density ( W rec ) for the industrial pillar BaTiO 3 (BT)‐based capacitors remains a significant obstacle for their cutting‐edge applications, due to their low intrinsic polarization and breakdown strength ( E B ). Herein, through chemical composition and local structure design, a giant W rec 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 (Bi 0.5 Na 0.5 ) 2+ ions in combination with B ‐site fastest relaxation alternative (Zn 1/3 Nb 2/3 ) 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 (Δ P ) of 49 µC cm −2 and a high E B 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 W rec bottleneck of ≈10 J cm −3 in BT‐based bulk ceramics, presenting an approach to optimize the energy storage performance of Pb‐free relaxors.