Thermally self-crosslinkable polyetherimide dielectrics with superior hightemperature energy storage efficiency

Abstract

The growing demand for high-temperature dielectric capacitor in aerospace and energy exploration has driven the development of polymer films capable of operating under extreme conditions. Here, a series of thermally self-crosslinkable polyetherimide (PEI) film has been developed as polymer candidate with outstanding energy density and charge-discharge efficiency under high-temperature external field. The resultant PEI film demonstrates dense networks through controlled thermal treatment without releasing volatile compounds, and also the reduced interchain spacing contributes to the effectively restricting dipole rotation and chain segment mobility. Meanwhile, the crosslinking network serves as deep charge trapping site that suppresses the carrier migration through the shortened hopping distance. The optimized crosslinking PEI film delivers exceptional high-temperature energy storage performance, achieving energy density of 12.6 J cm -3 with efficiency of 91.1% at 150 °C and 575 MV m -1 , along with outstanding stability over 100000 cycles. This work provides fundamental insights into the relationship between molecular aggregation and dielectric displacement, offering a promising strategy for developing high-performance polymer dielectrics for extreme-condition energy storage application.