High‐Entropy Chemical Composition Design for Ultrahigh Capacitive Energy Storage

Superior energy-storage performance is imperative for next-generation electronics and pulsed power systems. However, in lead-free dielectric ceramics, achieving synergistic optimization of energy storage performance remains a critical challenge. The central obstacle lies in the simultaneous enhancement of both energy density (W_rec) and efficiency (η). Herein, a high-entropy lead-free Bi_0.32Na_0.32Ba_0.32La_0.04TiO₃-NaNbO₃ ceramics system is designed, guided by phase-field simulations and a strategic chemical composition approach. The synergistic effect of La-donor doping and NaNbO₃ addition induces local random fields and local random stresses, stabilizing multiphase ultrasmall polar nanoregions. Benefiting from these features, an ultrahigh energy storage performance of W_rec ≈ 12.4 J cm^{- 3} and η ≈ 82.6% is realized under the applied field 790 kV cm^-1. Furthermore, a large W_rec of ≈6.2 J cm^-3 and a high η ≈ 85.8% with less than 5% variation across a broad temperature (30-150 °C) range are highly promising results for lead-free ceramics. This study marks a significant advancement in the energy storage performance and also provides a paradigm for the development of new lead-free ceramics for the next generation of pulsed power applications.