Achieving high capacitive energy storage, high-temperature stability and fatigue endurance synchronously at moderate fields in BNT-based ceramics

In response to the urgent need for efficient and reliable energy storage solutions, this study investigates the synergistic integration of high-entropy and superparaelectric engineering in Bi 0.5 Na 0.5 TiO 3 -K 0.5 Na 0.5 NbO 3 (BNT-KNN) ceramics, thereby achieving superior comprehensive energy storage performance in moderate electric fields. With the incorporation of Sr(Sc 0.5 Ta 0.5 )O 3 (SST), the BNT-0.2KNN-0.2SST demonstrates a high recoverable energy density ( W rec  > 7 J/cm 3 ) and efficiency ( η  > 95 %) at 420 kV/cm and the BNT-0.3KNN-0.15SST achieves W rec  ~ 8 J/ cm 3 and η  > 91 % at 500 kV/cm. The optimized ceramics achieve excellent comprehensive energy storage performance, exceptional high-temperature stability (20–240 °C) and fatigue resistance (≥10 6  cycles) under moderate electric fields (300–500 kV/cm) synchronously. The synergistic combination of high-entropy design and superparaelectric state regulation can effectively suppress the drastic fluctuations of the permittivity and the thermally induced phase transitions, thereby maintaining excellent performance across a broader temperature range and significantly enhancing the cyclic life of BNT-based ceramics through the reduction of defect generation and aggregation. The synergistic combination of these properties suggests promising applicability in next-generation capacitor devices, especially for energy storage applications requiring reliable performance in extreme operational environments.