Enhanced High‐Temperature Energy Storage Performance of All‐Organic Composite Dielectric via Constructing Fiber‐Reinforced Structure

Optimizing the high‐temperature energy storage characteristics of energy storage dielectrics is of great significance for the development of pulsed power devices and power control systems. Selecting a polymer with a higher glass transition temperature ( T g ) as the matrix is one of the effective ways to increase the upper limit of the polymer operating temperature. However, current high‐ T g polymers have limitations, and it is difficult to meet the demand for high‐temperature energy storage dielectrics with only one polymer. For example, polyetherimide has high‐energy storage efficiency, but low breakdown strength at high temperatures. Polyimide has high corona resistance, but low high‐temperature energy storage efficiency. In this work, combining the advantages of two polymer, a novel high‐ T g polymer fiber‐reinforced microstructure is designed. Polyimide is designed as extremely fine fibers distributed in the composite dielectric, which will facilitate the reduction of high‐temperature conductivity loss for polyimide. At the same time, due to the high‐temperature resistance and corona resistance of polyimide, the high‐temperature breakdown strength of the composite dielectric is enhanced. After the polyimide content with the best high‐temperature energy storage characteristics is determined, molecular semiconductors (ITIC) are blended into the polyimide fibers to further improve the high‐temperature efficiency. Ultimately, excellent high‐temperature energy storage properties are obtained. The 0.25 vol% ITIC‐polyimide/polyetherimide composite exhibits high‐energy density and high discharge efficiency at 150 °C (2.9 J cm −3 , 90%) and 180 °C (2.16 J cm −3 , 90%). This work provides a scalable design idea for high‐performance all‐organic high‐temperature energy storage dielectrics.