High-entropy strategy for enhanced energy storage performance in BNT-ST-KNN relaxor ferroelectrics under moderate electric fields

Advanced lead-free energy storage ceramics play a critical role in the development of next-generation pulse power capacitors. However, it remains challenging to attain high recoverable energy density ( W rec ) and efficiency ( η ) within a moderate electric field environment. In this study, the evolution of energy storage performance with increasing configurational entropy change Δ S config (Δ S config  = 1.09R, 1.56R, 1.78R, 1.84R) was systematically investigated in Bi 0.5 Na 0.5 TiO 3 -SrTiO 3 -K 0.5 Na 0.5 NbO 3 (BNT-ST-KNN) ceramics. The resulting high-entropy lead-free relaxor ferroelectrics achieved a W rec of 5.3 J/cm 3 and an η of 83%, representing a nearly 76% increase in energy storage density compared to low-entropy ones in BNT-ST-KNN system. The superior energy storage performance is attributed to strong multiple local distortions and an enhanced breakdown field. Furthermore, the ceramics exhibit excellent frequency and temperature stability, as well as robust charging/discharging performance with thermal stability. These results indicate that increasing Δ S config is a practical strategy for designing high-performance dielectrics, promoting the development of capacitor technologies.