Improving the energy-storage performance of KNN-based energy-storage ceramics through multiple regulation

K_0.5Na_0.5NbO₃ (KNN)-based energy-storage ceramics have been widely concerned because of their excellent energy-storage performance. In this work, Ta₂O₅ (4 eV) and ZnO (3.37 eV) with wide band gap were added to KNN ceramics to improve the insulation and the breakdown field strength E_b. Linear dielectric SrTiO₃ was selected to reduce the hysteresis of the hysteresis loop and, thus, increase the energy-storage efficiency η. Meanwhile, the introduction of Ta⁵⁺, Sr²⁺, Zn²⁺, and Ti⁴⁺ ions with different ionic radii and valence states can produce charge imbalance in the lattice and induce the generation of relaxation phase. Through the multiple regulation of grain size, relaxation, and insulation properties, we obtain dielectric energy-storage ceramics with excellent performance, when x = 0.09, the (1 − 2x)(K_0.5Na_0.5)(Nb_0.97Ta_0.03)O₃-xSrTiO₃-xZnO sample has a submicron level grain size, a large resistivity, and strong relaxation ferroelectricity. The energy-storage density W_rec and efficiency η are 2.47 J/cm³ and 79%, respectively, at E_b = 340 kV/cm. At the same time, the x = 0.09 sample has a large current density, excellent power density, good temperature, and frequency stability.