High-energy density dielectric film capacitors enabled by grain boundary engineering

Lead-free dielectric film capacitors are widely used in electronic devices and power systems. However, the relatively low energy density and poor stability have become the bottlenecks restricting their further application. In this work, we demonstrate that the high-energy storage density (114.49 J cm⁻³) can be achieved in 0.85BaTiO₃-0.15Bi(Mg_0.5Zr_0.5)O₃ (BT-BMZ) films by optimized grain boundary characteristics. The enhancement of the energy storage performance originates from strengthening the breakdown strength and polarization switching behavior. In addition, the film capacitors exhibit good thermal stability over the temperature range of −100 to 225 °C and fatigue properties (10⁶ cycles). Importantly, the energy storage density reaches 62.3 J cm⁻³ at 225 °C, and the energy storage efficiency is as high as ∼81%. Our results show that the optimal BT-BMZ film achieved by tuning growth pressure can significantly improve the breakdown strength and polarization switching behavior of dielectric films, which results in excellent energy-storage performance over a wider temperature range and opens up a promising and practical avenue for designing high-performance dielectric film capacitors.