Superior Energy Storage Capability and Stability in Lead‐Free Relaxors for Dielectric Capacitors Utilizing Nanoscale Polarization Heterogeneous Regions

The development of high-performance lead-free dielectric ceramic capacitors is essential in the field of advanced electronics and electrical power systems. A huge challenge, however, is how to simultaneously realize large recoverable energy density (W_rec ), ultrahigh efficiency (η), and satisfactory temperature stability to effectuate next-generation high/pulsed power capacitors applications. Here, a strategy of utilizing nanoscale polarization heterogeneous regions is demonstrated for high-performance dielectric capacitors, showing comprehensive properties of large W_rec (≈6.39 J cm^-3 ) and ultrahigh η (≈94.4%) at 700 kV cm^-1 accompanied by excellent thermal endurance (20-160 °C), frequency stability (5-200 Hz), cycling reliability (1-105 cycles) at 500 kV cm^-1 , and superior charging-discharging performance (discharge rate t_0.9 ≈ 28.4 ns, power density PD ≈161.3 MW cm^-3 ). The observations reveal that constructing the polarization heterogeneous regions in a linear dielectric to form novel relaxor ferroelectrics produces favorable microstructural characters, including extremely small polar nanoregions with high dynamics and multiphase coexistence and stable local structure symmetry, which enables large breakdown strength and ultralow polarization switching hysteresis, hence synergistically contributing to high-efficient capacitive energy storage. This study thus opens up a novel strategy to design lead-free dielectrics with comprehensive high-efficient energy storage performance for advanced pulsed power capacitors applications.