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Abstract:：

  The high-temperature and high-field energy storage performances of film capacitors are a key bottleneck restricting their applications in new energy, aerospace and other fields. Traditional dielectric biaxially oriented polypropylene (BOPP) has insufficient high-temperature resistance, while high-temperature resistant polymers such as polyimide (PI) exhibit excellent thermal stability but suffer from narrow bandgap and poor insulation performance. They cannot meet current demands under the common operating conditions of 200 °C and 100~400 MV/m. Existing composite modification and intrinsic modification strategies have problems such as poor filler dispersion and high time cost, respectively. To address these issues, this study modifies Kapton through molecular design using commercial monomers as raw materials: high bandgap monomers are introduced to disrupt the conjugated structure, widen the material''s bandgap, and thereby enhance high-temperature insulation; high polarity monomers are introduced to improve permittivity by virtue of their high dipole moment, strengthening polarization and energy storage capacity under unit electric field. Through the synergistic regulation of dual monomers, a PI material with both high bandgap and high polarity was successfully prepared. Under the high-temperature and high-field conditions of 200 °C and 400 MV/m, it maintains a charge-discharge efficiency of over 90% and achieves a discharge energy density of 2.68 J/cm3, which is significantly superior to BOPP and traditional PI. This work provides a feasible polymer design path for the development of high-performance high-temperature energy storage dielectrics.