Superior Energy Storage Performance in a Self‐Organized Trirelaxor‐Antiferroelectric Nanocomposite Over a Wide Temperature Range

Abstract A fundamental paradox in energy storage dielectrics lies in the challenge of achieving superior performance consistently across both room and elevated temperatures. This is addressed by designing a self‐organized nanocomposite (1−x)(Ba,Sr)(Ti,Sn)O 3 ‐xBi 1.5 ZnNb 1.5 O 7 composed of nano‐sized antiferroelectric(AFE) particles embedded into a trirelaxor(TRE) matrix through nanoscale phase separation process. The optimal composition at x = 0.11 exhibits outstanding energy storage performance from room temperature (energy density = 8.5 J cm −3 , efficiency = 94.8%, and figure of merit of 167 J cm −3 ) up to 200 °C (energy density = 4.85 J cm −3 , efficiency >90% and figure of merit of 49 J cm −3 ), outperforming existing Pb‐free dielectrics. High‐resolution transmission electron microscopy and synchrotron x‐ray diffractometry reveal that the coexisting nanometric antiferroelectric particles and the trirelaxor nanodomains sustain over a wide temperature range. Piezoresponse force microscopy and phase‐field simulation show that hysteresis‐free switching of trirelaxor nanodomains enables enhanced polarization and low hysteretic loss. Resistivity shows a 2–3 order of magnitude increases accompanying significant increase in breakdown strength up to high temperatures, attributable to deep charge trapping effect at high‐density TRE/AFE interfaces as evidenced by thermally stimulated depolarization current. These favorable effects in the nano‐composite are responsible for its high energy storage performance up to high temperatures.