Optimized energy storage performances via high-entropy design in KNN-based relaxor ferroelectric ceramics

[Display omitted] •The Wrec of 7.51 J/cm3 with η of 88.4% is obtained in the KNN-0.14VPP ceramic.•The power density (~ 420 MW/cm3) and discharge energy density (~ 4.85 J/cm3) are realized at 160 ℃.•The increased energy gap and improved electrical homogeneity result in the enhanced breakdown strength.•The PNRs and enhanced polarization relaxation lead to the high energy storage density and energy storage efficiency. Dielectric capacitors play an irreplaceable role in complex and integrated electronic systems. However, attaining ultrahigh recoverable energy storage density (Wrec) alongside energy storage efficiency (η) poses a formidable challenge, impeding the advance towards the miniaturization and integration of cutting-edge energy storage devices. In this work, a high-entropy strategy with a viscous polymer process is adopted, bringing about ultrafine grains and polar nanoregions (PNRs) accompanied by enhanced electrical homogeneity and polarization relaxation characteristics. As a result, an ultrahigh Wrec ∼ 7.51 J/cm3 is achieved in a high-entropy KNN-based energy storage ceramic with a high η ∼ 88.4% at 750 kV/cm. Moreover, the ceramic capacitor exhibits a colossal power density reaching approximately 420 MW/cm3 and a discharge energy density of approximately 4.85 J/cm3 at 160 ℃. Impressively, it maintains low variation rates of less than 4% across a broad temperature range from 20 ℃ to 160 ℃. The new approach opens avenues for the design and development of superior dielectric materials used in next-generation high-power pulse devices.