Improved High‐Temperature Energy Storage Performance of Mass Production‐Polypropylene Capacitive Films by Optimizing the Casting Temperatures

ABSTRACT Polypropylene (PP) are the most widely used dielectric materials for film capacitor due to the ultra‐low dielectric loss and high breakdown strength. However, PP films are not allowed to operate exceed 105°C due to the markedly increase in conduction loss at elevated temperature. This study proposes an efficient strategy to enhance the high‐temperature capacitive properties of PP films by regulating the casting temperatures during the melt‐extrusion‐casting process. The results show that the casting temperature has a deep influence on the surface morphology and crystal structures, which also affects the electrical performance especially the dielectric property at high temperature. The PP films prepared under an extrusion temperature of 210°C and the tape casting temperature of 140°C deliver the optimal energy storage property, a discharge energy density of 1.93 J cm −3 and an energy storage efficiency of 81% at 125°C, accompanying excellent cycle performance.