High-temperature energy storage performance of polyetherimide all-organic composites enhanced by hindering charge hopping and molecular motion

Dielectric capacitors are widely used in aerospace, power systems, and other fields. Working environments with ever-increasing temperatures pose a new challenge to energy storage performance. Polyetherimide (PEI) has gained extensive research for its good high-temperature properties. In order to further improve its energy storage performance at high temperatures, many researchers have worked on PEI all-organic composites doping with molecular semiconductors. Previous studies generally only considered the effect of introduced deep traps on macroscopic properties such as electrical conductivity, electrical breakdown, and energy storage performance. It has been shown that only qualitative analyses can be performed from the perspective of charge trapping, and it is difficult to obtain quantitative results. Therefore, this work proposes to study the macroscopic properties of polymer dielectrics by combining charge trapping with molecular displacement. A comprehensive conduction-breakdown-energy storage model was established to explain the influence mechanism of molecular semiconductors on the improved energy storage performance of PEI composites at high temperatures. The molecular semiconductor fillers increase the coefficient of friction between molecular chains, which restricts the movement of molecular chains and also limits charge hopping. Therefore, the dielectrics have higher breakdown strengths and smaller conduction losses, which synergistically enhance the energy storage performance.