Local Atomic Disorder‐Driven Deep Relaxor State for Ultrahigh Dielectric Energy Storage With High Thermal Stability

ABSTRACT Lead‐free dielectric ceramic capacitors are indispensable for advanced high‐power electronic pulse systems owing to their exceptional power density and rapid charge‐discharge kinetics. However, the simultaneous realization of ultrahigh recoverable energy density ( W rec ) and high efficiency ( η ), especially with robust thermal stability, remains challenging. Here, we propose a local structural design strategy focused on implementing atomic‐scale disorder within relaxor ferroelectrics to achieve a deep relaxor state across a wide temperature window. Atomic‐scale structure characterizations reveal that this local chemical/structural disorder induces ultrafine, highly active polar nanoregions, fostering an optimized polarization response while remaining resilient against thermal fluctuations. Consequently, the designed ceramics exhibit superior energy‐storage performance, characterized by a large W rec of 13.1 J cm −3 and ultrahigh η of 93%, leading to a high figure of merit up to 187.1. Notably, exceptional performance stability across diverse operating conditions is bestowed, with η remaining above 90% at temperatures up to 200°C. This study thus provides a robust paradigm for designing dielectric capacitors that deliver both high energy‐storage performance and reliability in harsh working environments.