The all-organic polyimide with excellent capacitive performance at high temperatures by molecular isolation strategy

The commercial high-temperature dielectric aromatic polyetherimide (PEI), due to the electron conjugation between aromatic rings in molecular chains, causing an exponential increase in conduction loss, which results in a sharp decline in capacitive performance at elevated temperatures and electric fields. Here, an all-organic dielectric based on molecular isolation strategy is proposed, attempting to suppress the conduction loss and improve the high-temperature capacitive performance of PEI by introducing the cyclodextrin (CD) with large ring-like structure and amounts of hydroxyl groups. The addition of CD expands the interchain spacing of PEI, interrupts the electron conjugation of aromatic rings and hinders the formation of electronic channels between molecular chains. As results, CD/PEI composites show enhanced breakdown strength ( E b ) (increased by 24 %) and suppressed leakage current (reduced by 220 %), with much lower energy loss than that of pure PEI. The 1.5 wt% CD/PEI all-organic composite achieves an energy storage density ( U e ) of 5.12 J cm −3 with charge-discharge efficiencies ( η ) > 90 %. It achieves stable cyclability over 100,000 cycles at 150 °C compared with 4217 cycles of pure PEI. This work offers an innovative strategy for the fabrication of all-organic composite dielectrics with high U e and η simultaneously at harsh environment.