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_0.25Na_0.25Ba_0.5TiO₃ (BNT-50BT) as a matrix material with large local polarization and structural distortion. Remarkable W_rec and η of 16.21 J/cm³ and 90.5% have been achieved in Bi_0.25Na_0.25Ba_0.5Ti_0.92Hf_0.08O₃ 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.