Thermally self-crosslinkable polyetherimide dielectrics with superior high-temperature energy storage efficiency

Abstract

The growing demand for high-temperature dielectric capacitors 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) films have been developed as polymer candidates with outstanding energy density and charge–discharge efficiency under a high-temperature external field. The resultant PEI film demonstrates a dense network through controlled thermal treatment without releasing volatile compounds, and also the reduced interchain spacing contributes to effectively restricting dipole rotation and chain segment mobility. Meanwhile, the crosslinking network serves as a deep charge trapping site that suppresses carrier migration through a shortened hopping distance. The optimized crosslinking PEI film delivers exceptional high-temperature energy storage performance, achieving an energy density of 12.6 J cm⁻³ with an efficiency of 91.1% at 150 °C and 575 MV m⁻¹, along with outstanding stability over 10⁵ 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 applications.