Ultrahigh energy storage performance in (Bi,Na)TiO3-based relaxor ferroelectrics via multi-scale high-entropy design

Abstract

Due to their exceptional power density and fast charge–discharge performance, dielectric ceramic capacitors have emerged as vital components in advanced pulsed power systems. However, concurrently achieving excellent recoverable energy density (W_rec) and high efficiency (η) in lead-free systems remains challenging. Herein, a multi-scale high-entropy design strategy is proposed for (Bi_0.5Na_0.5)_0.94Ba_0.06TiO₃-based relaxor ferroelectrics. The approach involves sequentially introducing (Sr_0.7Bi_0.2)TiO₃ and (Bi_0.5La_0.5)(Nb_1/3Mg_2/3)O₃ to construct a high-entropy system that simultaneously regulates material behavior across lattice, microstructural, and electronic structure scales. This coordinated approach induces strong lattice distortion and local random fields to disrupt ferroelectric order and stabilize polar nanoregions, while sluggish diffusion kinetics refine grain morphology and wide-bandgap ions enhance breakdown strength. Consequently, an ultrahigh energy storage performance with W_rec ∼10.72 J cm⁻³ and η ∼86.9% is achieved at 698 kV cm⁻¹, accompanied by excellent energy storage stability and high hardness (∼8.58 GPa). This work demonstrates that multi-scale high-entropy design is an effective paradigm for developing advanced lead-free energy storage ceramics.