As a critical research direction in dielectric energy storage applications, achieving a synergistic balance between a high breakdown strength (E_b) and high polarization remains a significant challenge for lead-free relaxor ferroelectrics. In this work, we proposed a rational chemical design strategy by simultaneously doping A- and B-site ions into classical BaTiO₃ (BT) ferroelectrics, breaking the long-range ordered polarization, increasing the maximum polarization (P_m), reducing the remnant polarization (P_r), and improving the E_b. An ultrahigh recoverable energy storage density (W_rec) of 15.3 J/cm³, accompanied by a high energy storage efficiency (η) of 82.4%, was finally achieved at 1150 kV/cm. Impedance spectroscopy and microstructure analyses reveal enhanced activation energies for both grains and grain boundaries, as well as multiphase coexistence and formation of polar nanoregions (PNRs). This collectively contributes to an elevated breakdown strength while maintaining robust polarization. This study presents a promising pathway to achieve advanced energy storage performance in lead-free dielectric systems.

Dielectric capacitors exhibiting high energy-storage properties and excellent pulse performance are critical components in advanced pulsed power systems. Multilayer ceramic capacitors (MLCCs) are the most widely used capacitors due to their high integration and excellent high-temperature endurance. Nevertheless, achieving high energy density and reliable performance over a wide temperature range and prolonged cycling remains the major challenge for existing commercial MLCCs based on linear dielectrics or Pb-based antiferroelectrics. Herein, we developed BaTiO₃-based relaxor ferroelectric MLCCs with X9S characteristics for high-voltage applications. The BaTiO₃-based MLCCs exhibit a good energy density of 6.09 J cm⁻³ and an ultrahigh efficiency of 98.2%, with superior stability in temperature (< 10%, 24–250 °C) and fatigue (after 10⁶ cycles, < 4% at 200 °C). The pulse properties of MLCCs show minimal variation (< 4.5%, 22–200 °C). Moreover, 6878-size MLCCs with 300 nF can release a peak current of 3600 A at a rated voltage of 3000 V, which exhibits higher peak currents than linear MLCCs and better stability than Pb-based MLCCs. The excellent performance and superior stability demonstrate that relaxor ferroelectric MLCCs have great potential for advanced energy storage and pulsed power applications.

Dielectric pulse capacitors are of great concerns due to the fast charge/discharge rate and high-power density over traditional counterparts. However, energy-storage capacitor in power converters typically works at a large DC-biased voltage, where the energy-storge density (W_dis) and efficiency (η) will dramatically decay, thus fatally blocks its further applications. Herein, we proposed a synergistic strategy to achieve a comprehensively improved energy storage property in Bi_1-xNa_xTiO₃-NaNbO₃ based ceramics. Configuration of chemical composition optimization, A-site vacancy engineering, grain size refinement, and sample thickness reduction were designed in the ceramics. Finally, an optimum W_dis of 8.04 J/cm³ and an ultrahigh η of 85% was achieved for the 0.50 (0.95Bi_0.52Na_0.44TiO₃-0.05SrZrO₃)-0.50NaNbO₃ composite under a breakdown strength of 630 kV/cm, along with a stable DC-biased capacitance retention. Additionally, a superior performance stability was affirmed in a wide temperature/frequency range (25–150 ℃ and 1–100 Hz, respectively). It also exhibits an impressive ability in fatigue resistance after being subjected to up to 10⁶ cycles, which enable it to be a suitable candidate for high energy density storage devices.