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.