Interfacial Polarization Restriction for Ultrahigh Energy‐Storage Density in Lead‐Free Ceramics

Abstract Dielectric capacitors with high power densities are crucial for pulsed electronic devices and clean energy technologies. However, their breakdown strengths ( E b ) strongly limit their power densities. Herein, by modifying the interfacial polarization by adjusting the difference in activation energies (Δϕ) between the grain and grain boundary phases, the significant enhancement of E b in the (1‐ x )(0.94Na 0.5 Bi 0.5 TiO 3 ‐0.06BaTiO 3 )‐ x Ca 0.7 La 0.2 TiO 3 (NBT‐BT‐ x CLT, x = 0, 0.18, 0.23, 0.28, 0.33, 0.38, and 0.43) ceramics is achieved. The results indicate that adding CLT introduces a super‐paraelectric state, refines grain size, and, most importantly, decreases the Δϕ value. When Δϕ is tuned close to zero in the specific NBT‐BT‐0.38CLT sample, a significant boost in E b value of 64 kV mm −1 is obtained. As a result, the recoverable energy storage density of the ceramics reaches an unprecedented giant value of 15.1 J cm −3 together with a high efficiency of 82.4%, as well as ultrafast discharge rate of 32 ns, and high thermal and frequency stability. The results demonstrate that interfacial polarization engineering holds huge promise for the development of dielectrics with high‐energy‐storage performance.