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 ( T g ) and bandgap ( E g ), 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 (CF 3 ) substituent strategy to develop a heat-resistant aromatic polyimide dielectric (6FDA/TFMB) with a high T g of 329 °C of and a large E g of 3.6 eV. The introduction of the CF 3 group, reducing molecular conjugation and increasing intermolecular spacing, renders the solution-cast 6FDA/TFMB film colorless and transparent. It exhibits remarkable Weibull breakdown strength ( E b ) 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 ( U e ) of 3.21 J/cm 3 with an efficiency ( η ) of 84 % at 150 °C and a U e of 2.42 J/cm 3 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.