High‐Entropy Chemical Composition Design for Ultrahigh Capacitive Energy Storage

Abstract 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 _0.32 Na _0.32 Ba _0.32 La _0.04 TiO ₃ ‐NaNbO ₃ ceramics system is designed, guided by phase‐field simulations and a strategic chemical composition approach. The synergistic effect of La‐donor doping and NaNbO ₃ 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.