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

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.