Superior energy storage performance in Bi0.5Na0.5TiO3 based ceramics via synergistic design of high-entropy and superparaelectric-relaxor strategy

Abstract

Lead-free dielectric ceramics have attracted considerable attention for use in pulsed power systems owing to their ultrafast discharge rates and exceptionally high power density. However, achieving both ultra-high recoverable energy density (W_rec > 10 J cm⁻³) and high energy efficiency (η > 80%) simultaneously remains a significant challenge. In this study, an entropy engineering strategy is employed to disrupt long-range ferroelectric order, thereby stabilizing ultra-small polar nanodomains characterized by diverse BO₆ octahedral tilts and locally distinct polarization states. This structural modulation effectively reduces the transition barrier, inducing a superparaelectric-relaxor behavior. Moreover, it enables a high polarization response, low remanent polarization (P_r), delayed polarization saturation, and a substantially enhanced breakdown electric field (E_b). As a result, an outstanding W_rec of 12.2 J cm⁻³ and a high η of 81% are achieved under an E_b of up to 980 kV cm⁻¹. The material also exhibits excellent discharge performance, along with robust thermal and frequency stability. This work not only presents a promising candidate material for high-power pulse capacitors but also provides valuable insights for enhancing energy storage performance in BNT-based and related lead-free dielectric ceramics.