Equimolar high-entropy for excellent energy storage performance in Bi0.5Na0.5TiO3-based ceramics

High-entropy ceramics hold tremendous promise for energy-storage applications. However, it is still a great challenge to achieve an ultrahigh recoverable energy density (Wrec > 10 J/cm3) with high efficiency (η > 80%) in equimolar high-entropy materials. Herein, the Bi1/5Na1/5Ba1/5Nd1/5K1/5TiO3, Bi1/6Na1/6Ba1/6Nd1/6K1/6Sr1/6TiO3, and Bi1/7Na1/7Ba1/7Nd1/7K1/7Sr1/7Ca1/7TiO3 high-entropy ceramics were designed based on the Bi0.5Na0.5TiO3 matrix by compositing highly insulative equimolar components at A-site in order to reduce mismatch of the resistance between grain and grain boundary. Our results reveal that the high-entropy design significantly suppresses the interfacial polarization, leading to a remarkable increase in breakdown strength, relaxor diffuse factor, band gap, and decreases in grain size. As a result, an unprecedented Wrec of 11.8 J/cm3 with a large η 86.4% was achieved in BNBNKSCT. The energy-storage performance of the sample also exhibits excellent discharge performance and good thermal/frequency stability. This work indicates that the Bi1/7Na1/7Ba1/7Nd1/7K1/7Sr1/7Ca1/7TiO3 high-entropy ceramic is a promising material with great potential for energy-storage capacitors, confirming that suppressing interfacial polarization via high-entropy design is an efficient strategy for exploring high energy-storage performance dielectric materials.