Polymorphic relaxor phase and defect dipole polarization co-reinforced capacitor energy storage in temperature-monitorable high-entropy ferroelectrics

Energy storage high-entropy ceramics are famous for their ultrahigh power density and ultrafast discharge rate. However, achieving a synchronous combination of high energy density and efficiency along with intelligent temperature-monitorable function remains a significant challenge. Here, based on high-entropy strategy and phase field simulation, the polarization response of domains in Bi_0.5Na_0.5TiO₃-based ceramics is optimized by constructing a concomitant nanostructure of defect dipole polarization and a polymorphic relaxor phase. The optimal ceramic possesses a high recyclable energy storage density (11.23 J cm^-3) and a high energy storage efficiency (90.87%) at 670 kV cm^-¹. Furthermore, real-time temperature sensing is explored based on abnormal fluorescent negative thermal expansion, highlighting the application of intelligent cardiac defibrillation pulse capacitors. This study develops an effective strategy for enhancing the overall energy storage performance of ferroelectric ceramics to overcome the problems of insufficient energy supply and thermal runaway in traditional counterparts.