Molecular main-chain and end-group engineering enables high-temperature energy storage in polyetherimide films

As advanced electronic components become more miniaturized and integrated, the performance requirements for polymer dielectric films are becoming increasingly stringent. Although the aromatic polymer polyetherimide (PEI) exhibits excellent thermal stability, the π-π conjugated structures present in its main chain tend to enhance electron delocalization and intermolecular charge transfer, leading to a significant increase in conductance loss under high-temperature conditions, which limits further improvements in its energy storage performance. In contrast to the previously documented trap-modulation strategies, this study proposes an innovative dual-end synergistic modulation strategy that targets both the molecular backbone and terminal groups. The introduction of highly polar sulfone groups into the PEI backbone, in conjunction with 4-phenylacetylene phthalic anhydride (PEPA) into the terminal groups, resulted in the construction of a cross-linked network structure. This process has been shown to enhance the polarization response of the PEI film, whilst concomitantly creating deep-level charge traps. Surprisingly, at an elevated temperature of 150 °C, the characteristic breakdown field strength of SPEI 10%-PEPA was determined to be 575 MV m^-1, representing a 15% increase in comparison with the uncross linked SPEI. Concurrently, an ultra-high energy storage density of 4.64 J cm^-3 was attained, accompanied by a charge-discharge efficiency that surpassed 90%.