Improvement of High-Temperature Energy Storage Performance of PI with Non-planar Structures

Polyimide (PI) is kind of a commonly used high temperature resistant polymer materials, whose high thermal stability depends on its rigid heterocyclic structures. However, the charge transfer between the diamine and the dianhydride unit is not conducive to dielectric and capacitive properties at high temperatures. In order to destroy the planar conjugated system to a certain extent, three-dimensional structures is introduced into the molecular chain of three different kinds of dianhydride units during the synthesis of PI film materials in this paper, aiming to hinder the carrier movement process, increase the electric and thermal resistance, and finally achieve the improvement of comprehensive capacitive performances. Results show that a proper number of non-planar multi-chain or spiral structures can effectively improve the DC breakdown strength of the films by up to 65.2%. At the same time, due to the improvement of efficiency, the maximum energy storage density of the composite films is approximately doubled at 200 ℃, showing a huge potential in the field of high-temperature energy storage.