In a significant advancement for high-temperature energy storage, researchers have developed a novel bilayer nanocomposite material that achieves a record discharged energy density of 12.35 J/cm³ with an efficiency of 90.25% at 150°C. This breakthrough, detailed in a recent study, addresses long-standing challenges associated with the thermal stability and energy density of polymer-based dielectric capacitors, crucial components in high-voltage transmission, electric vehicles, and microelectronic circuits.

Conventional polymer dielectrics, such as biaxially oriented polypropylene (BOPP), typically operate reliably below 105°C, while even high-glass transition temperature polymers like polyimide (PI) suffer from drastic reductions in energy density and efficiency above 150°C due to increased conduction loss. The new bilayer nanocomposite, composed of [0.8(Na0.2Bi0.2Ba0.2Sr0.20Ca0.2)TiO3-0.2NaNbO3]@Al2O3 high-entropy ferroelectric nanoparticles embedded in a polyetherimide (PEI) matrix, alongside an AlN/PEI-triptycene layer, fundamentally redefines performance benchmarks for high-temperature capacitive energy storage.

The innovative design leverages the unique properties of high-entropy ferroelectric fillers, which contribute to a high dielectric constant and minimal hysteresis even at elevated temperatures. The core-shell structure, with an Al2O3 shell, provides a wide bandgap and high thermal conductivity, crucial for mitigating charge injection and transport. Furthermore, the inclusion of AlN nanoparticles significantly enhances thermal dissipation within the composite, while the polyetherimide-triptycene layer improves rigidity and introduces charge carrier traps, inhibiting electromechanical and electrical breakdown. The strategic bilayer configuration also suppresses carrier transport at the film interfaces, further improving breakdown strength and reducing conduction losses.

This multi-component, multi-layered approach allows the material to overcome the inherent trade-offs between energy density and efficiency that plague traditional polymer dielectrics at high temperatures. The high-entropy ferroelectrics exhibit high maximum electric displacement (Dmax), near-zero remnant electric displacement (Dr), and extremely slim electric displacement-electric field (D-E) loops at 150°C, making them ideal for high-temperature applications. The enhanced performance of these nanocomposites, particularly their ability to maintain high efficiency alongside ultra-high energy density, marks a pivotal step toward more compact, reliable, and efficient power electronics for demanding operational environments.