Roll-to-Roll Manufactured Polyetherimide Nanocomposite With Different Diameters of SiO2 Nanoparticles Exhibiting Improved High-Temperature Dielectric Energy Storage Performance.

To enhance the high-temperature energy storage performance of the polymer-based dielectric film, inorganic nanofillers with large band gaps are much more effective and have been widely adopted. However, the impact of nanoparticle diameters on the dielectric properties of polymer nanocomposites has been less studied. Herein, silicon dioxide nanoparticles (SiO2-NPs) with varying diameters (20, 60, 120, 200 nm) prepared by the sol-gel method are incorporated in the PEI matrix to form PEI/SiO2 nanocomposites. The characterization results reveal a distinct correlation between the dielectric properties of polyetherimide (PEI) composites and the diameters of SiO2-NPs. Leakage current density analysis and breakdown strength simulations indicate that SiO2-NPs with smaller diameters generate more deep traps that impede the transport of charge carriers, especially under high temperatures. Notably, PEI/20 nm-SiO2 exhibits a high discharged energy density of 4.4 J cm-3 with an efficiency of 90% at 150 °C. Furthermore, PEI/SiO2 films with 10 µm in thickness are manufactured by a large-scale solution casting process. The continuously prepared PEI/20 nm-SiO2 film exhibits a discharged energy density of 3.2 J cm-3 with an efficiency of 90% at 150 °C. This study not only provides a strategy for the design of high-performance dielectric polymer composites but also offers a large-scale high-temperature dielectric film for practical use.

Excellent Stability in Polyetherimide/SiO2 Nanocomposites with Ultrahigh Energy Density and Discharge Efficiency at High Temperature.

Polymer dielectrics with excellent thermal stability are the essential core material for thin film capacitors applied in a harsh-environment. However, the dielectric and mechanical properties of polymers are commonly deteriorated with temperature rising. Herein, polyetherimide (PEI)-based nanocomposites contained with SiO2 nanoparticles (SiO2 -NPs) are fabricated by a solution casting method. It is found that the introduction of SiO2 -NPs decreases the electric conductivity and significantly enhances the breakdown strength of the nanocomposites, especially under high temperatures. As a result, the 5 vol% PEI/SiO2 -NPs nanocomposite film displays a superior dielectric energy storage performance, e.g., a discharged energy density of 6.30 J cm-3 and a charge-discharge efficiency of 90.5% measured at 620 MV m-1 and 150 °C. In situ scanning Kelvin probe microscopy characterization indicates that the charge carriers can be trapped in the interfacial regions between the polymer matrix and the SiO2 -NPs till the temperature reaches as high as 150 °C. This work demonstrates an effective strategy to fabricate high-temperature dielectric polymer nanocomposites by embedding inorganic nanoparticles and provides a method for directly detecting charge behavior at the nanoscale inside the matrix.