Optimizing high-temperature energy storage capability by regulating interchain spacing with a tailored pendant group in self-crosslinkable polyetherimides

Abstract

High-temperature energy-storage dielectrics are of great significance for the development of advanced electronic devices. Polyetherimides (PEIs), as high-temperature dielectric films, demonstrate an obvious decline in charge–discharge efficiency with increasing temperature due to the β-relaxation effect. In this work, the crosslinking of a PEI is regulated using self-crosslinking phenylacetylene groups, and the β-relaxation effect is restricted by introducing deep traps in the network, thereby reducing conduction loss in the resultant film. The relationship between crosslinking structure, bandgap, and energy-storage performance has been investigated systematically. The optimal film exhibits outstanding energy-storage capability, with an energy density of 14.6 J cm⁻³ and a charge–discharge efficiency of 90.4% under an external field of 600 MV m⁻¹ at 150 °C. The suspension arm disrupts the long-range conjugated architecture of the PEI, and the weakening of bond conjugation hinders electron delocalization, which results in the reliable insulation of the crosslinking polymer with a high bandgap of 3.22 eV. This strategy of inhibiting relaxation while breaking the conjugated structure of PEIs provides fresh insights for the investigation of high-temperature polymer films for dielectric capacitors.