Realizing Excellent Energy Storage Performance in Nb-Doped (Bi_0.5Na_0.5)_0.94Ba_0.06TiO₃-Based High-Entropy Ceramics

As a more sustainable and environmentally friendly alternative, lead-free dielectric ceramics have huge potential in energy storage applications. However, achieving excellent recoverable energy storage density ( W rec ) and efficiency (η) in ceramic capacitors is still a major challenge. To realize superior comprehensive energy storage characteristics, this study developed Nb-modified lead-free (Bi 0.5 Na 0.5 ) 0.94 Ba 0.06 TiO 3 -based high-entropy ceramics. The findings revealed that Nb doping can promote the increase of entropy, grain refinement, improvement of dielectric relaxation, and broadening of the band gap, gaining greatly enhanced electric breakdown strength ( E b ). Eventually, an outstanding W rec of 6.64 J/cm 3 and η of 82% are attained at a great E b (641 kV/cm) in 0.06 mol % Nb high-entropy ceramic, along with good thermal and frequency stability as well as excellent charge–discharge characteristics. All of the above results confirm that high-entropy engineering based on Nb doping is a feasible approach to obtain high-performance energy storage materials, and the optimal ceramic can serve as a candidate material for advanced energy storage devices.