Polymer Blends of Polyetherimide and Poly(ether ester urethane): Controlling Dielectric Properties for Ultrahigh Energy Storage

Polymer dielectrics offer outstanding advantages for high-power energy storage applications, such as high breakdown strength (<i>E_b</i>) and efficiency (<i>η</i>), while both decrease rapidly at elevated temperature (>150 °C). Although several strategies including nanocomposites and crosslinking have been evaluated to enhance <i>E_b</i> and heat resistance, the discharged energy density (<i>U_d</i>) of polymer dielectrics is still limited by the low dielectric constant (<i>K</i>). Herein, we have implemented a blending strategy by utilizing hydrogen bonding interactions between molecular chains for polyetherimide (PEI) and poly(ester ether urethane) (PEEU). Both the experimental and computational simulation results reveal that the blending can contribute to the increased molecular chain spacing and control the charge transport by destroying the conjugated structure to broaden bandgap and induce deep traps, improving the <i>K</i> and <i>E_b</i> simultaneously. As a result, the blend film achieves an unprecedented <i>U_d</i> of 5.50 with the <i>η</i> above 90% at 200 °C. Furthermore, it exhibits stable performances during ultralong 10⁵ charge-discharge cycles in harsh environments (250 MV/m and 200 °C). This work opens a new avenue to scalable high Ud all-polymer dielectric for high-temperature applications and promotes the understanding of the dielectric behavior of polymer blend films.