Ultrahigh energy storage in multilayer BiFeO3–BaTiO3–NaTaO3 relaxor ferroelectric ceramics†

The rising challenge of high-density electric energy storage has accelerated the research of electric energy-storage capacitors due to their high power density and voltage resistance, excellent temperature stability, and environmental friendliness. However, lead-free ferroelectric capacitors generally have a low discharge energy density. This study used a multilayer ceramic capacitor (MLCC) design with active ceramic layers of relaxor ferroelectric NaTaO₃-modified BiFeO₃–BaTiO₃ co-sintered with 90Ag/10Pd interlayer electrodes. Superb recoverable energy densities of W_rec ∼2.8 J cm⁻³ with an energy efficiency of η ∼73% at 400 kV cm⁻¹ and W_rec ∼4.5 J cm⁻³ with an energy efficiency of η ∼77% at 450 kV cm⁻¹ were attained, respectively, in 9-active-ceramic-layer and 24-active-ceramic-layer MLCCs. Excellent thermal stability and fatigue resistance of energy storage capability were achieved up to 180 °C and exceeding 1 × 10⁴ cycles. The ultrahigh energy-storage properties can be linked to the synergistic effects of multiple local lattice distortions, nanoscale structures, and interfacial E fields at grain boundaries. This report demonstrates an efficient scheme to utilize ternary BiFeO₃–BaTiO₃-based ceramics via the MLCC technology for ultrahigh-energy-density electrostatic energy storage.