Ultrahigh energy-storage dielectric ceramics via synergistic polymorphic nanodomain and defect design

Dielectric capacitors are critical for advanced energy storage due to their ultrahigh power density and rapid charge-discharge rates. However, their application is limited by the low energy density. Here, we design a BaTiO₃-(K_0.5Na_0.5)NbO₃-(Bi_0.5Na_0.5)Ti_0.9Zr_0.1O₃ solid-solution system through synergistic polymorphic nanodomain engineering and defect optimization. By engineering polymorphic nanodomains with coexisting rhombohedral, orthorhombic, tetragonal, cubic nanodomain in 1.0-2.0 nm size and defect design with reduces oxygen vacancy concentration and forms defect complexes, we achieve an ultrahigh energy density of 18.7 J cm⁻³ with remarkable efficiency of 92.1% in multilayer ceramic capacitors, along with excellent cycling stability (>10⁷ cycles) and thermal stability (<±5% from 25 to 150 °C). In this work, we provide a paradigm for designing high-performance dielectric capacitors through the synergistic manipulation of domain structures and defect engineering.