Optimised Molecular Traps and Conjugated Structures for Superior High‐Temperature Capacitive Performance in Polyimide

ABSTRACT In the fields of automotive electronics, power electronics, and aerospace, environmental conditions are often extremely harsh, particularly for materials that must endure high temperatures, high power and require high stability. The degradation of capacitance performance in polymer dielectrics under high electric fields and elevated temperatures is primarily attributed to the decrease in breakdown strength. To address this, a synergistic strategy combining molecular traps with adjustments to the conjugated structure has been developed to enhance the high‐temperature breakdown strength of polymer dielectrics. To address this, we developed a synergistic strategy combining molecular traps with conjugated structure modulation. Experimental and theoretical analyses reveal that polar groups induce deep electron traps via electrostatic interactions, whereas long‐chain flexible groups disrupt the conjugation, which alters charge transport mechanisms. Between aromatic rings in the molecular chain, altering the conductivity mechanism. Furthermore, dihedral angle adjustment regulates trap‐hopping distances, enhancing high‐temperature breakdown strength. As a result, the combined effects of electronic traps and conjugated structure optimisation lead to a discharge energy density of 7.87 J/cm 3 at room temperature and 5.99 J/cm 3 at 200°C, which is 60% higher than that of OD–PM. This performance surpasses most current polymer dielectrics. Our work establishes a molecular design framework to advance high‐temperature capacitive energy storage in polyimides, with direct relevance to harsh‐environment applications.