Achieving high discharge energy density and efficiency with NBT-based ceramics for application in capacitors

High-performance capacitors, which have high energy storage density as well as high discharge efficiency, are desired. In this study, we have designed and prepared novel and high quality (1 − x )(0.65Bi 0.5 Na 0.5 TiO 3 -0.35Bi 0.1 Sr 0.85 TiO 3 )- x (K 0.5 Na 0.5 NbO 3 ) [(1 − x )(BNT-BST)- x KNN, x = 0, 0.04, 0.06, 0.08, and 0.10] ceramics that demonstrated a remarkable energy storage capability, high efficiency, and ultrafast discharge speed. Particularly, the 0.94(BNT-BST)-0.06KNN ceramic possessed an excellent stored energy storage density ( W s = ∼3.13 J cm −3 ) and recoverable energy storage density ( W r = ∼2.65 J cm −3 ), and maintained a relatively high efficiency ( η = ∼84.6%) at a relatively low electric field of 180 MV m −1 , which is superior to those of the lead-free BNT-based energy-storage materials. Moreover, excellent temperature (20-120 °C) and frequency (1-100 Hz) stabilities of the 0.94(BNT-BST)-0.06KNN ceramic were also achieved. More importantly, the 0.94(BNT-BST)-0.06KNN ceramic exhibited an ultrafast discharge rate ( τ 0.9 = ∼1.01 μs), a high level of discharge energy density ( W d −1.21 J cm −3 ), and excellent reliability in energy storage performance by consecutive cycling. Moreover, this study also provides an effective approach to attain large energy-storage capability along with high efficiency in BNT-based ceramics for application in pulsed power capacitors. The 0.94(BNT-BST)-0.06KNN ceramic possesses an excellent stored energy storage density ( W s = ∼3.13 J cm −3 ), a recoverable energy storage density ( W r = ∼2.65 J cm −3 ), and maintains a relatively high efficiency ( η ∼ 84.6%).