Optimizing high-temperature capacitive energy storage performance by constructing crosslinked structure in self-crosslinkable polyetherimides

Crosslinking is a proven method for effectively improving the high-temperature energy storage performance of polymer dielectrics. In this work, the relationship between crosslinked structure and energy storage performance was demonstrated by crosslinked polyetherimide films with various degree of crosslinking. Specifically, the maximum weight average molecular weight (Mw) of soluble parts and proper gel content favors the formation of an optimal crosslinked structure with an optimal energy density (∼3.6 J/cm3) and charge–discharge efficiency (≥ 95%) at 150 °C. Furthermore, the energy storage performance of the crosslinked films obtained by the longtime treatment under relatively low temperatures is equivalent to that obtained by the short-time treatment under relatively high temperatures. This work provides a reference model for designing high-temperature crosslinked polymer dielectrics.