As the continuous development of technology and power system, film capacitors are increasingly used as energy storage devices due to excellent safety, but they have poor energy storage. Therefore, it is imperative to improve the discharged energy density (Ue) and the charge-discharge efficiency (η) composite dielectric for high temperature applications. In recent years, Polyetherimide（PEI）and polyimide (PI) have been extensively studied due to their excellent Ue and η. In this work, it is proposed to blend PEI and PI to enhance the high temperature Ue and η by adjusting their blending ratio. In addition, the microstructure, electrical properties and energy storage properties of PEI/PI allorganic dielectric blend films are studied in detail. The results show that the breakdown strength (Eb) and energy storage performance of PEI/PI composite dielectric inhance with the increase of PI content. When the content of PI is 75vol%, the Ue of the composite dielectric achieves an improved of 5.91 J/cm3 . The results indicate that the strategy of blending PEI with PI can not only increase the Eb of the composite dielectric, but also enhance the Ue . This work shows that it has a valuable potential to increase the Ue and η of all-organic composite films by blending process.

polyetherimide, polyimide, high temperature energy storage, breakdown strength