Enhanced Energy Storage Performance with High-Temperature Stability of Polyetherimide Nanocomposites

Polyetherimide (PEI) nanocomposite doped with hafnium oxide (HfO
2
) nanoparticles have been prepared by conventional solution cast method to investigate the effect of nanofillers with moderate dielectric constant on dielectric and capacitive properties of the polymer nanocomposite. The microstructure characteristic, insulation properties and energy storage performance of PEI/HfO
2
nanocomposites were studied by scanning electronic microscopy (SEM), high-field leakage current and displacement-electric field (D-E) loops. It was found that incorporating HfO
2
not only enhances dielectric constant and resistivity of the nanocomposites but also improves capacitive performance such as increased electric displacement, discharged energy density and charge-discharge efficiency. The 3 vol% HfO
2
-filled PEI nanocomposite delivers an energy density of 2.20 J/cm
³
at 150 °C, which manifests the feasibility of improving high-temperature energy storage properties of polymer nanocomposites through incorporation of the nanofillers with medium dielectric constants.