Fluorinated Polyimide/<scp>CaCu₃Ti₄O₁₂</scp> Composite Films With High Energy Density for High‐Temperature Dielectric Capacitor

ABSTRACT The demand for dielectric capacitor materials has significantly increased, owing to the need for highly efficient operation at elevated temperatures amidst the rapid advancements in modern electronics. In this contest, fluorinated polyimide (FPI)/CaCu 3 Ti 4 O 12 (CCTO) composite films have been successfully fabricated through a straightforward blending approach. The modified CCTO (mCCTO) is prepared by first hydroxylation CCTO and subsequently by grafting KH550 onto its surface, a strategy aimed at enhancing the interfacial compatibility with FPI. The synergistic effect of the high dielectric constant and good dispersibility of CCTO inorganic fillers underscores the significant role of filler dispersibility in enhancing the high‐temperature capacitive performance of polymer composite materials. The dielectric constant of FPI‐mCCTO composite films containing 9 wt.% mCCTO reached 8.5 at 150°C, more than double that of pure FPI (3.0). Furthermore, the FPI‐0.09‐mCCTO composite films exhibited the highest discharge energy density of 4.92 J·cm −3 at 355 MV·m −1 . This facile approach provided a viable strategy for fabricating high‐temperature dielectric materials for electrical energy storage.