Intercalation strategy induced superior energy storage performance in Aurivillius Bi₆Ti₃FeAlO₁₈ film under low and medium electric fields

A new type of lead-free dielectric film capacitor with high energy density and rapid charge-discharge performance under a low and medium applied electric field is essential for electrical and electronic systems. Herein, we propose an efficient and straightforward approach to enhance the energy storage performance of the Aurivillius Bi₅Ti₃FeO₁₅ film through intercalation strategy. The insertion of BiAlO₃ units, which have a weak domain-forming potential, into the Bi₅Ti₃FeO₁₅ matrix establishes an ergodic relaxor. This modification further increases the difference between the maximum polarization and the remanent polarization. Under 1500 kV/cm, the Bi₆Ti₃FeAlO₁₈ film exhibits an excellent energy storage density of 67.5 J/cm³, along with a high energy storage efficiency of 75.5%. This leads to an exceptionally high energy storage response coefficient, which surpasses those of most dielectric films. Furthermore, the Bi₆Ti₃FeAlO₁₈ film exhibits outstanding thermal stability within a temperature range of −30 ℃–150 ℃, commendable frequency stability from 0.05 kHz to 20.00 kHz, and remarkable fatigue resistance after 1 × 10⁸ cycles. This study investigates a potential lead-free material suitable for low-electric-field-driven capacitors and also lays a foundation for developing Aurivillius-type lead-free high-energy-storage applications at low and medium electric fields through intercalation strategy.