Superior Capacitive Energy Storage in Relaxor Ferroelectric Perovskites Engineered by Atomic‐Scale Lattice Distortion and Strain

Abstract Dielectric capacitors exhibit exceptional potential for pulse power applications, while addressing the inherent trade‐off between energy density ( W rec ) and efficiency ( η ) is essential for advancing miniaturization and integration. Herein, we implement an atomic‐scale regulation strategy involving lattice distortion and strain engineering in relaxor ferroelectrics (FEs) to optimize polarization‐field response for desirable energy storage. By incorporating large ions with different valence states and polarizabilities (Ba 2+ , Mg 2+ , and Nb 5+ ) into both A and B sites of (Bi 0.5 Na 0.5 )TiO 3 , we successfully create polar nanoclusters exhibiting strong tetragonal FE distortions, with dimensions of only several unit cells, embedded within a rhombohedral relaxor matrix. The resulting significant local lattice strain enables these heterogeneous nanoclusters, comprising various FE symmetries, to display a strong and linear‐like polarization‐field response with outstanding thermal stability. Consequently, the optimized composition delivers remarkable energy storage performances of W rec of 15.8 J cm −3 and η of 97.8% under a moderate field of 84 kV mm −1 in multilayer ceramic capacitors (MLCCs) configurations. Furthermore, the MLCCs maintains broad temperature operational capabilities ( W rec > 10 J cm −3 and η > 96% at 60 kV mm −1 across 20–170°C). These findings highlight an effective strategy of lattice distortion and strain engineering for realizing superior energy storage in dielectrics.