Interfacial‐Polarization Engineering in BNT‐Based Bulk Ceramics for Ultrahigh Energy‐Storage Density

Abstract Ceramic capacitors, known for their exceptional energy‐storage performance (ESP), are crucial components in high‐pulsed power systems. However, their ESP is significantly constrained by breakdown strength ( E b ), which is influenced by interfacial polarization. This study delves into the physics, characterization, and application of interfacial polarization. The findings indicate that key factors affecting ESP, such as grain size, relaxor factor, and bandgap, are intrinsically linked to interfacial polarization, establishing it as the most critical determinant of ESP. To demonstrate the practical applications of interfacial polarization engineering, lead‐free ceramics of (1‐x)(0.94Bi 0.5 Na 0.5 TiO 3 ‐0.06BaTiO 3 )‐ x Ca 0.7 Bi 0.2 (Sn 0.5 Ti 0.5 )O 3 (abbreviated as (BNT‐BT)‐ x CBST is designed, where x = 0, 0.1, 0.15, 0.2, and 0.25). The (BNT‐BT)‐0.25CBST sample, with a thickness of 120 µm, achieved an ultrahigh recoverable energy‐storage density ( W rec ) of 12.2 J cm −3 and a high efficient (η) of 88.8%, along with excellent temperature/frequency stability and outstanding charge/discharge performance. The remarkable ESP is attributed to the suppression of interfacial polarization, which significantly enhances E b . This work highlights the pivotal role of interfacial polarization engineering in the development of energy‐storage ceramics with superior comprehensive performance.