All-organic sandwich structured polymer dielectrics with polyimide and PVDF for high temperature capacitor application

Polyimide (PI) dielectrics is limited to become an essential part of electrostatic capacitors in extreme conditions due to low dielectric constant and discharge energy density (Ud). Most of PIs are neither dissolved nor fused and have extremely high reaction temperature of thermal imidization, which impedes the construction of PI-based all-organic multilayered dielectric films with ferroelectric polymers based on solution casting method. Herein, in this work, PI based on chemical imidization and ferroelectric polymers poly(vinylidene fluoride) (PVDF) with high dielectric constant were selected to prepare high performance all-organic sandwich structured dielectrics at low temperature. The formation of the sandwich structured films can promote the redistribution of the electric field. Meanwhile, PI outer layer with excellent insulating properties can effectively suppress charge injection. Consequently, a maximum Ud of 6.25 J cm-3 is obtained at room temperature with elevated breakdown strength of 510.9 MV m- 1. Moreover, a superior Ud of 2.58 J cm-3 is achieved at 150 degrees C, which is 2.46 times that of PI. This research contributes to broadening the application of PI in flexible dielectrics, and provides great inspiration for the development of polymer dielectric films with high capacitive performance over a wide temperature range.