Enhanced high-temperature capacitive energy storage in polyetherimide dielectrics through dense crosslinked network structures

Polymer dielectrics that can operate efficiently under harsh environments are desirable in advanced electronic and electrical systems. Whereas, current commercially available polymer dielectrics encounter dramatically declined energy density ( U d ) and charge–discharge efficiency ( η ) at elevated temperatures. In this work, we synthesized a polyetherimide (PEI) dielectric with excellent heat resistance and large bandgap, and introduced crosslinking network structures into PEI chains to further promote high-temperature energy storage performance. Dense crosslinking network within and between molecular chains restricts the polarization movement of chain segments and inhibits the migration of carriers, thereby improving the electrical insulation properties. Consequently, optimum crosslinked PEI film (CPEI-20 %TAC) achieves a high breakdown strength of 660 MV/m, 614 MV/m and 575 MV/m at RT, 150 °C and 200 °C, respectively. Notedly, CPEI-20 %TAC exhibits an ultrahigh η of 95 % at RT and 90 % at 150 °C until breakdown, in which the U d reach 6.3 J/cm 3 and 5.3 J/cm 3 , respectively. Furthermore, even at 200 °C, the U d still can reach 3.0 J/cm 3 with η above 90 %. There exists no degradation in energy storage over 10,000 cycles measurements and CPEI exhibits unique self-healing characteristic. This work provides a paradigm for developing polymer dielectrics applicated in high-temperature capacitive energy storage.