Significantly increased energy density and discharge efficiency at high temperature in polyetherimide nanocomposites by a small amount of Al2O3 nanoparticles

Abstract

Polymer dielectrics with available energy storage performance at high temperatures are critical to meet the demands of emerging applications such as hybrid electric vehicles (HEVs), wind turbine generators, and oil and gas exploration. But the dielectric properties of most engineering polymers with thermotolerance rapidly deteriorate with temperature rising. Here, polyetherimide (PEI) nanocomposite films containing Al₂O₃ nanoparticles (AO-nps) were fabricated by a solution casting method. The dielectric properties, breakdown strength, and energy storage performances of PEI/AO-nps nanocomposites were investigated from 25 °C to 150 °C. With the introduction of AO-nps, the breakdown strength of the nanocomposites was greatly improved at high temperatures because AO-nps significantly inhibit the injected charges. The 1 vol% PEI/AO-nps nanocomposite exhibits excellent capacitive performance, e.g., a discharge energy density of 3.70 J cm⁻³ with a charge–discharge efficiency of 90.1% evaluated at 500 MV m⁻¹ and 150 °C, which is the maximal value compared with the state-of-the-art counterparts. The high-temperature applicability of the present nanocomposite film makes it promising in manufacturing dielectric energy storage devices for harsh environments.