Ultrahigh Energy\nStorage Performance in BiFeO<sub>3</sub>‑Based Lead-Free Ceramics\nvia Tuning Structural Homogeneity\nand Domain Engineering Strategies

Lead-free ceramic-based dielectric capacitors are critical\nin electronics\nand environmental safety. Nevertheless, developing ideal lead-free\nceramics with excellent energy storage properties remains a challenging\ntask for practical applications. Herein, the enhanced relaxation behavior\nand increased breakdown electric field are utilized to realize the\nhigh energy storage behavior of (0.7-<i>x</i>)BiFeO<sub>3</sub>-0.3BaTiO<sub>3</sub>-<i>x</i>(Na<sub>0.7</sub>Sm<sub>0.1</sub>)NbO<sub>3</sub>(BF-BT-<i>x</i>NSN) ceramics.\nThe introduction of complex perovskite compound NSN facilitates the\ntransition of domains to nanodomains and improves the homogeneity\nof the microstructure, which results in the enhancement of the relaxation\nproperties and breakdown electric field. Hence, the BF-BT-0.2NSN ceramic\ncan achieve an ultrahigh energy storage density of 13.1 J/cm<sup>3</sup> under an electric field of 650 kV/cm. Moreover, the designed BF-BT-0.2NSN\nceramic achieves remarkable thermal stability (20–100 °C),\nfrequency stability (1–100 Hz), and excellent charge/discharge\nperformance. This study develops an idea of dielectric capacitor design\nand reveals the remarkable potential of BiFeO<sub>3</sub>-based dielectric\nceramics within the realm of energy storage applications.