Ultrahigh energy storage density and efficiency in a novel BiFeO₃-BaTiO₃-based ceramics via high entropy design

Lead-free relaxor ferroelectric ceramics have attracted considerable attention due to their environmental friendliness and potential applications in energy storage. Dielectric capacitors are extensively used in high-power environments due to their ultrahigh power density, rapid charge–discharge capability, long cycle life, excellent thermal stability, and compatibility with miniaturized electronic systems. Despite these advantages, the widespread deployment of dielectric capacitors in advanced energy systems remains constrained by their relatively low recoverable energy density and low energy efficiency. To address these challenges, high-entropy-designed (1-x)(0.4BiFeO₃-0.6BaTiO₃)-x(Bi_0.5Sm_0.5)(Mg_2/3Ta_1/3)O₃ lead-free relaxor ferroelectric ceramics were systematically investigated in this work. In ceramics with x = 0.17, an ultrahigh W_rec of 9.2 J/cm3 and a high η of 87% at 550 kV/cm was achieved. The high-entropy design strategy based on enhanced configurational entropy has significantly improved the energy storage performance of (Bi_0.5Sm_0.5)(Mg_2/3Ta_1/3)O₃-modified BiFeO₃-BaTiO₃-based relaxor ferroelectrics. The increased entropy strengthens random fields and relaxor behavior and reduces grain size. As a result, excellent thermal stability and fatigue reliability are achieved, leading to a substantial enhancement in comprehensive energy-storage performance. These results highlight high-entropy engineering as an effective and practical approach for dielectric materials for high-performance capacitor applications.