A molecular design strategy to develop all‐organic crosslinked polyetherimide film with high discharged energy density at 150°C

Abstract Miniaturization and lightweight of power systems urgently ask for polymer dielectrics with high discharged energy density at 150°C. Herein, a molecular design strategy is built to prepare new crosslinkable polyetherimide films (PEIDx, x is the molar ratio of dianhydride to amines) through simultaneously improving the polarization degree and reducing the residual polarization. Thermal, mechanical, and dielectric properties of PEIDx improve as x increases. PEID0.92 shows the best integrated performances, especially its discharged energy density (5.46 J cm −3 , at 10 Hz and 454 MV m −1 ) is higher than those of reported polymer dielectrics with discharged energy storage at 150°C, and its charge–discharge efficiency is 80.14%. The outstanding energy storage performance of PEID0.92 is attributed to its unique molecular structure. Specifically, the use of nonplanar and low‐alkaline aliphatic cyclic diamine effectively improves the polarization degree of macromolecules; while the crosslinking of alkynyl groups limits the macromolecular movement, thus ensuring high heat resistance and low residual polarization.