Crosslinked polyetherimide nanocomposites with superior energy storage achieved via trace Al2O3 nanoparticles

Polymer dielectrics which operate under elevated temperatures are widely desirable for advanced electric energy storage systems. However, the currently available polymer dielectrics are limited to relatively low working temperatures. Herein, crosslinked nanocomposites with trace wide-bandgap nanofillers alumina (Al2O3) and heat-resistant polyetherimide (PEI) were prepared by in-situ polymerization and solution casting method. Crosslinked networks in the nanocomposites improve the breakdown strength and suppress dielectric loss. Furthermore, we demonstrate trace Al2O3 nanofillers change the microstructure of polymer matrix and facilitate the dipole rotations in the chain segments by atomic force microscopy-infrared spectroscopy (AFM-IR). The dielectric constant of the nanocomposites is enhanced without sacrificing the breakdown and mechanical properties, which compensates for the dielectric constant reduced by crosslinking. All the composite films maintain excellent dielectric stability over a wide range of frequencies and temperatures. Besides, giant discharged energy density and ultrahigh charge-discharge efficiency are simultaneously achieved at high temperatures. Astoundingly, energy storage performance at high temperatures is superior to most of the reported work. This work demonstrates a viable strategy to prepare high-temperature polymer dielectric films for energy storage applications.