Enhanced energy-storage in lead-free multilayer capacitors via entropy-assisted polymorphic domain engineering

Lead-free multilayer ceramic capacitors with high energy storage performance are essential components in environmentally sustainable and miniaturized pulsed power systems. However, their practical application is limited by inherently low energy density and suboptimal energy efficiency. In this study, a stepwise dual-site entropy increase strategy is introduced to simultaneously modulate relaxor behavior and enhance the breakdown strength of Bi_0.5Na_0.5TiO₃-based capacitors. Atomic-scale structural analyses reveal that the coexistence of rhombohedral, tetragonal, and cubic polymorphic domains effectively prevents premature polarization saturation while maintaining high maximum polarization. Additionally, the high configurational entropy induces non-periodic lattice distortions, promoting grain refinement and improving electrical resistance, which collectively enhance breakdown endurance. Consequently, an enhanced energy density of 17.8 J cm^-3 with a high efficiency of 97.6% is achieved in the high-entropy capacitors. Furthermore, the high-entropy capacitors exhibit excellent thermal and fatigue stability, along with superior charge-discharge performance. This study provides a viable structural design approach for developing high-performance relaxor ferroelectric materials and devices with optimized energy storage characteristics.