High-Entropy Design Toward Ultrahigh Energy Storage Density Under Moderate Electric Field in Bulk Lead-Free Ceramics

Electrostatic capacitors with ultrahigh energy-storage density are crucial for the miniaturization of pulsed power devices. A long-standing challenge is developing dielectric materials that achieve ultrahigh recoverable energy density Wrec ≥ 10 J cm−3 under moderate electric fields (30 ≤ E ≤ 50 kV mm−1). Herein, a specific high-entropy strategy is proposed to modulate the phase structure and interfacial polarization of medium-entropy base materials using linear dielectrics. This strategy ensures a sufficient polar phase and a high enough electric field for complete polarization, thereby achieving ultrahigh Wrec by enhancing polarization strength. The validity of this strategy is demonstrated in the (Na0.282Bi0.282Ba0.036Sr0.28Nd0.08)TiO3-xCa0.7Bi0.2TiO3 (NBBSNT-xCBT) (x = 0–0.15) system. The CBT-modulated samples exhibit a polyphase structure of R3c, P4bm, and Pm-3m with reduced remnant polarization (Pr). Additionally, the addition of CBT effectively suppresses interfacial polarization, enhancing the maximum polarization (Pmax). These factors significantly improve the value of ∆P = Pmax − Pr. As a result, an ultrahigh Wrec of 10.5 J cm−3 with a high-efficiency η of 80.3% is obtained in the x = 0.1 sample under a moderate electric field of 45 kV mm−1 for the first time. This work paves the way for achieving superior energy-storage performance under moderate electric fields.