Outstanding Energy-Storage Density Together with Efficiency of above 90% via Local Structure Design.

Dielectric ceramic capacitors with high recoverable energy density ( W _rec ) and efficiency (η) are of great significance in advanced electronic devices. However, it remains a challenge to achieve high W _rec and η parameters simultaneously. Herein, based on density functional theory calculations and local structure analysis, the feasibility of developing the aforementioned capacitors is demonstrated by considering Bi _0.25 Na _0.25 Ba _0.5 TiO ₃ (BNT-50BT) as a matrix material with large local polarization and structural distortion. Remarkable W _rec and η of 16.21 J/cm ³ and 90.5% have been achieved in Bi _0.25 Na _0.25 Ba _0.5 Ti _0.92 Hf _0.08 O ₃ via simple chemical modification, which is the highest W _rec value among reported bulk ceramics with η greater than 90%. The examination results of local structures at lattice and atomic scales indicate that the disorderly polarization distribution and small nanoregion (∼3 nm) lead to low hysteresis and high efficiency. In turn, the drastic increase in local polarization activated via the ultrahigh electric field (80 kV/mm) leads to large polarization and superior energy storage density. Therefore, this study emphasizes that chemical design should be established on a clear understanding of the performance-related local structure to enable a targeted regulation of high-performance systems.