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

Abstract

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_0.5Na_0.5TiO₃–0.35Bi_0.1Sr_0.85TiO₃)–x(K_0.5Na_0.5NbO₃) [(1 − x)(BNT–BST)–xKNN, 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.