Enhanced energy density and electric cycling reliability via MnO₂modification in sodium niobate-based relaxor dielectric capacitors

Sodium niobate (NaNbO₃)-based dielectrics have received much attention for energy storage applications due to their low-cost, lightweight, and nontoxic nature. The field-induced metastable ferroelectric phase in NaNbO₃-based dielectrics, however, leads to a large hysteresis of the polarization-electric field (P-E) loops and hence deteriorate the energy storage performance. In this study, the hysteresis was successfully reduced by introducing Bi³⁺and Ti⁴⁺into A-site and B-site of NaNbO₃, respectively. MnO₂addition was added to further increase the ceramic density and enhance the cycling reliability. As a result, a high recoverable energy density of 4.3 J/cm³and a high energy efficiency of 90% were simultaneously achieved in the ceramic capacitor at an applied electric field of 360 kV/cm. Of particular importance is that the ceramic capacitor exhibits a stable energy storage properties over a wide temperature range of -70 to 170 °C, with much improved electric cycling reliability up to 10⁵cycles.