Strongly polarizable nanodomains enable excellent energy storage performance at moderate electric fields in lead-free Bi_0.5Na_0.5TiO₃-based ceramics

The simultaneous achievement of high recoverable energy storage density (W_rec) and high efficiency (η) under moderate electric fields remains a critical challenge for dielectric ceramic capacitors in modern electronic systems, despite their ultrahigh power density and rapid charge-discharge capabilities. Here, we propose a strategy to construct strongly polarizable nanodomains, enabling excellent energy storage performance (ESP) under moderate electric fields in Bi_0.5Na_0.5TiO₃ (BNT)-based ceramics. Compositional modulation by multiple cations, together with a regulative proportion of rhombohedral (R) and tetragonal (T) phases, enhances random fields, weakens interdomain interactions, forms strongly polarizable nanodomains, and elevates the breakdown strength (E_b) without sacrificing the intrinsic high polarity of the matrix. Consequently, the optimized 0.98(BNSB)_0.985S_0.01T–0.02CMN ceramic exhibits an ultrahigh maximum polarization (P_max) of 65.8 μC/cm², with slim polarization–electric (P–E) field loops. Owing to these features, the optimized bulk ceramic achieves a record W_rec of 6.11 J/cm³ and an impressive η of 86% at an E_b of 330 kV/cm. Moreover, this sample also presents outstanding temperature/frequency stability and charging–discharging performance. These findings suggest that the (BNSB)_1–1.5yS_yT–0.02CMN component has immense potential for advanced pulse power capacitors under a moderate applied electric field and further offers a valid avenue for exploring high-performance lead-free dielectric materials.