Ultrahigh Capacitive Energy Storage in Lead-Free Relaxors via Localizing Distortion

Abstract

The significant polarization hysteresis under external fields can be stimulated by long-range ordered distortions, including cation displacements and oxygen octahedral tilts, deteriorating the energy storage performance and reliable operation of dielectric capacitors. Here, we propose a strategy of localized distortion to craft a disordered nanostructure landscape, manifested as strongly polar orthorhombic rocks dissociated in the transition region of polymorphic nanoclusters and strong oxygen-tilted blocks embedded in the weak oxygen distortion region, resulting in a smooth polarization response trajectory with large polarization fluctuations, small hysteresis, and delayed polarization saturation. Through localizing distortion, an ultrahigh recoverable energy density of 12.5 J cm^-3 can be realized with an inspiring efficiency of 87%, alongside ultrawide capacitance temperature stability (from -100 to 432 °C) far exceeding X9R criteria, showing breakthrough progress in the overall performance for NaNbO₃-based lead-free bulk ceramics. This work unveils an effective avenue of localized distortion to develop dielectrics with excellent energy storage performance and the potential to be extended to other functionalities.