Giant Capacitive Energy-Storage in BaTiO-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 (W) for the industrial pillar BaTiO (BT)-based capacitors remains a significant obstacle for their cutting-edge applications, due to their low intrinsic polarization and breakdown strength (E). Herein, through chemical composition and local structure design, a giant W of 15.1 J cm 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 (BiNa) ions in combination with B-site fastest relaxation alternative (ZnNb) 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 and a high E of 90 kV mm. Moreover, a giant power density (677 MW cm), high discharge energy density (3.9 J cm), and excellent stability are achieved. This study overcomes the current W bottleneck of ≈10 J cm in BT-based bulk ceramics, presenting an approach to optimize the energy storage performance of Pb-free relaxors.