Fluorinated aromatic polyimide with large bandgap exhibiting superior capacitive performance at elevated temperatures

High-temperature energy storage performance of traditional polymer dielectrics is insufficient due to the mutual constraints of glass transition temperature (Tg) and bandgap (Eg), making them challenging to meet the demands of harsh environmental applications. In this work, in conjunction with density functional calculations (DFT), we employed the trifluoromethyl (CF3) substituent strategy to develop a heat-resistant aromatic polyimide dielectric (6FDA/TFMB) with a high Tg of 329 °C of and a large Eg of 3.6 eV. The introduction of the CF3 group, reducing molecular conjugation and increasing intermolecular spacing, renders the solution-cast 6FDA/TFMB film colorless and transparent. It exhibits remarkable Weibull breakdown strength (Eb) values of 578 MV m−1 and 452 MV m−1 at 150 °C and 200 °C, respectively. Moreover, 6FDA/TFMB achieves an energy density (Ue) of 3.21 J/cm3 with an efficiency (η) of 84 % at 150 °C and a Ue of 2.42 J/cm3 with an η of 82 % at 200 °C, which outperforms most existing heat-resistant polymer dielectrics. Additionally, 6FDA/TFMB demonstrates excellent fatigue resistance and self-healing ability. This study provides a promising and cost-effective approach for developing high-performance flexible dielectrics capable of withstanding extreme thermal and electric field conditions.