Strategic structural design of polyimide dielectrics toward superior high-temperature energy storage performance

All-aromatic polyimide dielectric films will seriously lose their energy storage performance at high temperatures because of high conductive loss caused by the conjugation effect of benzene rings in the backbone and charge transfer effect, especially commercial Kapton film. In order to maintain the low leakage current and energy storage stability of polyimide under high temperature and electric field, a synergistic strategy is employed to synthesize Kapton-based cross-linked dielectric films, involving polyhedral oligomeric silsesquioxane (POSS) cross-linked structure and a partial aliphatic structure. The results show that the energy storage performance of cross-linked ternary polyimides is significantly enhanced at room temperature and high temperature due to the construction of a “peak-shaped barrier” that effectively suppresses charge injection and transport. The discharge energy densities at room temperature and 150 °C are 8.01 J/cm 3 and 5.04 J/cm 3 , respectively, which are much higher than those of pure Kapton. This study provides a valuable strategy and insights for the development of polyimide dielectrics with high capacitive properties over a wide temperature range.