Suppressing interfacial polarization via entropy increase strategy for superior energy-storage performance of Na_0.5Bi_0.5TiO₃-based ceramics

High entropy engineering has emerged as a new strategy to improve the energy storage density and efficiency of dielectric capacitors due to its unique design concept. However, the recyclable energy storage density (W_rec) reported so far has never exceeded 2 J/cm³ for the type of high-entropy ceramics with equimolar elements occupying A or B site. In order to improve this type high-entropy ceramics. Na_0.5Bi_0.5TiO₃ (NBT) was used as the matrix, equimolar Sr²⁺, La³⁺, K⁺ and Ba²⁺ were gradually introduced into at the A-site of the matrix lattice to increase configurational entropy. The results show that the relaxor degree, band gap width, interfacial polarization, and breakdown field strength are effectively improved with increasing entropy. Among them, suppressing interfacial polarization is an important factor to increase the breakdown field strength and thus enhance the energy storage performance. The (Na_1/6Bi_1/6Sr_1/6La_1/6K_1/6Ba_1/6)TiO₃ (NBSLKBT) sample with the highest configurational entropy shows an ultra-high W_rec of 9.8 J/cm³ and the energy storage efficiency (η = 86.5%). This work demonstrates that entropy strategy for superior energy-storage performance still works on the above type high-entropy ceramics and opens up a new way of modulating interface polarization by entropy increase strategy.