Polyimide dielectrics sandwiched by large-bandgap Al2O3 for high-temperature energy storage

High-temperature polymer dielectric capacitors are urgently needed in the new-generation electronic and electrical systems. Whereas, current commercial polymer represented by polyimide (PI) suffer from exponentially growing conduction loss at high temperatures and high electric fields, and hence extremely low discharged energy density and sharply declined charge-discharge efficiency. In this work, we developed superior Al₂O₃/PI/Al₂O₃ sandwich films with drastically improved capacitive energy storage performance via atomic layer deposition (ALD) technology. Notably, resultant PI hybrid dielectrics deposited by 130 nm-thickness Al₂O₃ (Al₂O₃/PI/Al₂O₃-130nm) exhibits the highest breakdown strength and the lowest leakage current density compared to pristine PI. Consequently, Al₂O₃/PI/Al₂O₃-130nm delivers a discharged energy density of 4.9 J/cm³ at 25 °C and 3.3 J/cm³ at 150 °C, as high as 2.7 times and 3.3 times respectively that of near PI film. Moreover, PI hybrid dielectrics can operate steadily under 200 MV/m and 150 °C during 10,000 cycle measurements. The excellent performance is mainly attributed to the improved barrier height of the electrode/PI interface endowed by deposited large-bandgap Al₂O₃.This work provides a scalable approach to enable excellent high-temperature energy storage performance of polymer dielectrics and promising to promote the application of PI for capacitive energy storage under harsh conditions.