Atomic-Scale High-Entropy Design for Superior Capacitive Energy Storage Performance in Lead-Free Ceramics

Abstract

Dielectric ceramics with high energy storage performance are crucial for the development of advanced high-power capacitors. However, achieving ultrahigh recoverable energy storage density and efficiency remains challenging, limiting the progress of leading-edge energy storage applications. In this study, (Bi_1/2Na_1/2)TiO₃ (BNT) is selected as the matrix, and the effects of different A-site elements on domain morphology, lattice polarization, and dielectric and ferroelectric properties are systematically investigated. Mg, La, Ca, and Sr are shown to enhance relaxation behavior by different magnitudes; hence, a high-entropy strategy for designing local polymorphic distortions is proposed. Based on atomic-scale investigations, a series of BNT-based high-entropy compositions are designed by introducing trace amounts of Mg and La to improve the electric breakdown strength and further disrupt the polar nanoscale regions (PNRs). A disordered polarization distribution and ultrasmall PNRs with a minimum size of ≈1 nm are detected in the high-entropy ceramics. Ultimately, a high recoverable energy density of 10.1 J cm⁻³ and an efficiency of 90% are achieved for (Ca_0.2Sr_0.2Ba_0.2Mg_0.05La_0.05Bi_0.15Na_0.15)TiO₃. Furthermore, it displays a high-power density of 584 MW cm⁻³ and an ultrashort discharge time of 27 ns. This work presents an effective approach for designing dielectric energy storage materials with superior comprehensive performance via a high-entropy strategy.