Achieving ultrahigh energy storage density and efficiency above 90% via reducing defect concentrations for AgNbO3-based multilayer capacitors

Dielectric capacitors are exceedingly desired for the next-generation advanced high/pulsed power devices that are demanded for miniaturization and integration because they have the advantages of fast charging and discharging speed and high-power density. Silver niobate (AgNbO3, AN) system has attracted much attention in recent years because of its excellent energy storage performances and environmental friendliness. However, poor efficiency (η) less than 85 % has been major challenges for its practical applications because of its AFE characteristics and large P-E hysteresis. To address this, herein AgNb0.6Ta0.4O3 + x wt% MnO2 (ANT + x wt% MnO2) MLCCs were designed, and an ultrahigh η of ∼91.1 % that has been the highest value for AN system so far as and excellent Urec of ∼10.68 J·cm−3 were achieved in ANT + 0.2 wt% MnO2 MLCCs. This is because the fact that the Mn2+ ions entered the A site in the ANT + x wt% MnO2 MLCCs, made the defect concentrations decreased. Furthermore, ANT + 0.2 wt% MnO2 MLCCs also exhibited a broad operating temperature range of up to 150 °C and excellent frequency stability, with minimal variations of less than 5 % in energy storage density. This work offers a good paradigm for improving the energy storage properties of AN-based MLCCs to meet the demanding requirements of advanced energy storage applications.