High-Performance Energy Storage in Ba(Al_0.5Nb_0.5)O₃-Modified (Bi_0.5Na_0.5)TiO₃-Based Lead-Free Ceramics via High-Entropy Strategy

Lead-free dielectric capacitors are widely utilized in high-power pulse devices due to their outstanding power density, rapid charging–discharging speed, and environmental friendliness. However, there are still challenges in further improving their energy storage performance. Recently, a high-entropy strategy has received widespread attention to obtain high-performance dielectric capacitors. In this work, Ba(Al 0.5 Nb 0.5 )O 3 (BAN) was introduced into lead-free (Bi 0.5 Na 0.5 )TiO 3 -based ceramics to increase configuration entropy and chemical disorder, exploiting a synergistic high-entropy strategy to optimize the energy storage characteristics. Remarkably, superior energy storage density ( W rec ∼7.40 J/cm 3 ) and efficiency (η ∼85.5%) at a great electric breakdown strength ( E b ∼547 kV/cm) are achieved in 0.85(0.6(Bi 0.5 Na 0.5 )TiO 3 –0.4(Sr 0.7 Bi 0.2 )TiO 3 )–0.15BAN high-entropy ceramic. The integration of BAN boosts the increase of entropy and induces grain refinement, strengthened relaxation behavior, formation of polar nanoregions, and a widened band gap, leading to reduced P r and improved E b as well as excellent energy storage performance. Moreover, good thermal stability, frequency stability, and charge–discharge performance are also realized. This study confirms that high-entropy engineering is a feasible route to realize high-performance energy storage, providing prospective lead-free dielectric materials for practical applications.