Gradient Defect Architecture for Ultrahigh Energy Storage in Lead‐Free Relaxor Ferroelectrics

ABSTRACT Next‐generation pulsed power electronics demand miniaturized dielectric capacitors with exceptional energy density. However, achieving this remains challenged by the intrinsic trade‐off between polarization capability and dielectric breakdown strength in lead‐free perovskites. Here, we overcome this fundamental limit via a “gradient defect architecture” strategy that constructs a heterogeneous architecture comprising a highly polarization disordered surface layer and a relatively ordered polarization interior within a 0.88Bi 0.48 Na 0.48 Ba 0.04 TiO 3– 0.12Sm 1/3 NbO 3 ceramic. Crucially, by geometrically modulating the volume fraction of these functional layers, the optimized ceramic achieves an ultrahigh recoverable energy density of 22.3 J cm −3 under an ultrahigh electric field of 1840 kV cm −1 . The disordered surface layer acts as a robust charge‐blocking barrier to elevate breakdown strength, while the highly polarizable relaxor interior layer sustains a strong polarization response to secure high energy capacity. These findings establish a generic design paradigm for utilizing intrinsic manufacturing gradients to transcend geometric scaling limits, offering a viable pathway for developing high‐performance energy storage materials.