Enhanced Energy Storage Performance in Mn-Doped SrBi5Ti4FeO18 Thin Films via Defect Engineering

Dielectric capacitors are essential in advanced electronics and power systems due to their high power density and fast charge–discharge rates. However, their application is limited by their low energy storage density and efficiency. Aurivillius-phase ferroelectrics have shown promise as energy storage materials, but their low polarization and significant hysteresis remain critical challenges. In this study, we present a simple and cost-effective defect-engineering strategy to enhance the energy storage performance of SrBi5Ti4FeO18 thin film through Mn doping. Mn incorporation suppresses oxygen vacancy formation and induces tensile chemical stress in the lattice, which simultaneously enhances maximum polarization and reduces the hysteresis. Additionally, the reduction in oxygen vacancies promotes grain refinement, reduces leakage current, and significantly enhances the breakdown strength. The optimized SrBi5Ti3.91Mn0.09FeO18 thin film achieves an ultrahigh energy storage density of 105 J/cm3 with improved efficiency of 70% at 3569 kV/cm. Moreover, it demonstrates good frequency stability (100 Hz to 10 kHz), thermal stability (20–160 °C), and fatigue endurance over 105 cycles. This work provides a feasible method for developing advanced dielectric capacitors with high energy storage performance by the rational design and precise control of defects.