Giant energy storage efficiency and high recoverable energy storage density achieved in K0.5Na0.5NbO3-Bi(Zn0.5Zr0.5)O3 ceramics

Abstract

K_0.5Na_0.5NbO₃ (KNN)-based ceramics, as promising candidate materials that could replace lead-based ceramics, exhibit outstanding potential in pulsed power systems due to their large dielectric constant, high Curie temperature and environmental friendliness. Although a large amount of KNN-based ceramics with high recoverable energy storage density (W_rec) have been designed for energy storage applications, the relatively low energy storage efficiency (η) limits their further development. In this work, a record high for η (86.8%) and a giant W_rec (3.50 J cm⁻³) were simultaneously obtained in the 0.85K_0.5Na_0.5NbO₃-0.15Bi(Zn_0.5Zr_0.5)O₃ (0.85KNN-0.15BZZ) ceramic, thanks to the introduction of Bi(Zn_0.5Zr_0.5)O₃ (BZZ), which increased the relaxation behavior and enhanced the breakdown strength (BDS). Furthermore, desirable W_rec and η with a variation of less than 10% can be accordingly obtained in the temperature range of 20–120 °C. More importantly, it can be confirmed by the first-order reversal curve (FORC) distribution that the outstanding energy storage performances of the 0.85KNN-0.15BZZ ceramic should be ascribed to its desirable relaxor ferroelectric performances. In addition, the 0.85KNN-0.15BZZ ceramic displays excellent pulsed charging–discharging performances with an outstanding power density of 33.76 MW cm⁻³, a current density of 562.63 A cm⁻² and a fast discharge speed (t_0.9 = 114.6 ns). The results reveal that the 0.85KNN-0.15BZZ ceramic is an attractive candidate material for next-generation dielectric capacitors.