Enhanced High-Temperature Capacitive Performance of PEI Dielectrics by an Adjustable Al₂O₃ Interlayer

With the escalating dielectric capacitor application in miniaturization and integration, high energy density is urgently needed for polymer dielectrics. Due to the polymer dielectrics being prone to breakdown as the temperature increases, it is challenging to break the adverse coupling between the breakdown resistance and heat resistance of polymer dielectrics at high temperatures. Herein, poly(ether imide) (PEI)-based dielectrics with an adjustable Al2O3 interlayer by atomic layer deposition are proposed. The inorganic interlayer Al2O3 with a wide bandgap (8.6 eV) not only can improve the dielectric constant but also can reduce leakage current by its block effects capture free electrons, leading to enhanced capacitive performance at high temperatures. The results show that the energy density of the multilayer composite with an optimal 50 nm thickness of Al2O3 layers reaches 7.02 J/cm3 under the 550 kV/mm electric field with an energy efficiency of 94.94%, which is about 49% higher than that of pure PEI. Even at 150 °C, the energy density maintains 4.84 J/cm3 under 540 kV/mm, which is 1.5 times that of pure PEI. This work provides a feasible route for polymer dielectrics for energy storage applications at high temperatures.