Enhanced energy storage and cycling stability of (Sr_0.7La_0.2)(Mg_1/3Nb_2/3)O₃-modified K_0.5Na_0.5NbO₃ ceramics via multiple synergistic strategies

Ceramic capacitors are widely used devices due to their excellent characteristics, such as rapid charge and discharge rates and high power density. However, simultaneously attaining exceptional energy storage performance and outstanding cycling stability in ceramic-based energy storage capacitors remains a considerable challenge. In this work, a multi-scale synergistic optimization strategy was proposed to enhance the energy storage performance and cycling stability of K_0.5Na_0.5NbO₃ ceramics, accomplished through grain refinement, introducing polar nanoregions (PNRs), and inducing weakly polar pseudo-cubic phases. As a result, ultrafine grains (∼110 nm), excellent energy storage performance [energy storage density (W_rec) ∼ 3.16 J/cm³, energy storage efficiency (η) ∼ 65%], and incredible cycling stability (W_rec variation: ∼0.09%, η variation: ∼0.28%) are concurrently realized in the 0.93K_0.5Na_0.5NbO₃-0.07(Sr_0.7La_0.2)(Mg_1/3Nb_2/3)O₃ relaxation ferroelectric ceramic. This work investigates the microscopic origins of the improved energy storage performance of KNN-based ceramics and presents a synergistic optimization strategy to achieve exceptional energy storage performance and incredible cycling stability.