Study on High Electric Field Electron Transfer Characteristics and High‐Temperature Energy Storage Performance of Polyimide Modified with Polar Group

Abstract The strong conjugation effect in homogeneous phenylene polyimide exhibits remarkable electron transfer characteristics, leading to significant leakage currents, which severely constrain the energy storage performance of polyimide. However, the electron transfer mechanism of polyimide under high electric fields remains unclear, and the influence mechanisms of polar group modifications at different positions on the intrinsic electron transfer properties of polyimide still require further investigation. To address the aforementioned key issues, this study systematically investigates the regulatory mechanisms of polar groups and their positions on the electron transfer properties of polyimide by combining theoretical calculations with experimental validation. DFT computational results indicate that introducing highly polar groups into the donor structure of polyimide can effectively reduce the electrostatic potential difference induced by conjugation and enhance the localization characteristics of electron transfer. Moreover, experimental test results are highly consistent with theoretical predictions. The polyimide incorporating sulfonyl groups into its donor structure with leakage current density significantly reduce to 1.66 × 10 −10 A cm −2 , and demonstrate outstanding high‐temperature energy storage performance. At 150 °C, the discharge energy density substantially increases to 4.70 J cm −3 , representing an impressive 310.5% improvement over conventional PI. This study provides crucial theoretical foundations and practical guidance for developing high‐performance polyimide energy storage materials.