Multiple-design and synergism toward superhigh capacitive energy storage with (Bi0.5K0.5)TiO3-based lead-free superparaelectrics

Abstract

The relentless drive toward miniaturization and integration in electronic devices has sparked an urgent demand for dielectric ceramics that provide large recoverable energy density (W_rec), high efficiency (η), wide thermal stability, and outstanding mechanical quality. Lead-free dielectric ceramics possessing these multiple attributes are highly sought after for advanced pulsed power capacitors, but realizing such a combination is still a formidable challenge. Herein, through a synergistically devised domain and microstructure design, an unprecedented η of 91.2% and a remarkably high W_rec of 6.03 J cm⁻³ under the action of 500 kV cm⁻¹ are first achieved in (Bi_0.5K_0.5)TiO₃ (BKT)-based superparaelectrics with an impressive Vickers hardness (H_v) of ≈7.61 GPa. The exceptional comprehensive characteristics are mainly associated with the simultaneous multiple-design of ultrasmall-size polar nanoregions with high dynamics and strong local heterogeneity, high electrical homogeneity, extremely small grain size, and compact microstructure, yielding significantly delayed polarization saturation, reduced hysteresis, and substantially reinforced polarization, breakdown strength, and H_v. Furthermore, excellent stabilities under various temperatures/frequencies/cycles and high charge–discharge performance are also simultaneously realized. This study unveils immense advances in the overall capacitive energy storage in BKT-based ceramics and stimulates further attempts to develop high-performance energy storage dielectrics.