Excellent high-temperature breakdown and energy storage performances of polyetherimide dielectric film with silver/alumina nanosheets derived from sequential bimetallic ion exchange.

Polymer dielectrics have attracted substantial attention for their extensive applications in advanced electronic power systems. However, their practical implementation is substantially hindered by the drastic deterioration in breakdown strength and energy storage capabilities at elevated temperatures. Herein, corrugated alumina (Al₂O₃) nanosheets anchored with uniformly dispersed silver nanoparticles (AgNPs) are fabricated via a sequential bimetallic ion exchange method using polyimide (PI) film as the sacrificing template. The AgNPs and Al₂O₃ nanosheets (AONSs) are in-situ formed on the molecular chain of PI in one step, which not only avoids the aggregation of AgNPs but also ensures the high purity of the AgNPs@AONSs. Benefiting from the excellent high-temperature insulating properties of Al₂O₃ and the Coulomb blockade effect of AgNPs, when the AgNPs@AONSs are incorporated into polymer dielectrics, they can act as powerful charge transport buffer strips and improve the breakdown strength. The polyetherimide film filled with merely 0.1 wt% AgNPs@AONSs shows ultra-high energy densities of 10.22 J cm^-3 at 150 °C with 90 % efficiency and 7.49 J cm^-3 at 200 °C with 80 % efficiency, which are 542 % and 226 % that of the pristine polyetherimide, respectively. The excellent high-temperature performances of the composite films make them promising candidates for high-temperature pulsed power systems.