Unifying and suppressing conduction losses of polymer dielectrics for superior high-temperature capacitive energy storage.

Superior high-temperature capacitive performance of polymer dielectrics is extremely critical for the modern film capacitor demanded in the harsh-environment electronic and electrical systems. Unfortunately, the energy storage capabilities of polymer dielectrics degrade rapidly at elevated temperatures and electric fields owing to the exponential increase of conduction loss. The conduction loss at high temperatures and electric fields is mainly composed of electrode-limited conduction and bulk-limited conduction. Herein, we depart from prior work by unifying the contribution of the above two factors to conduction loss and fundamentally suppress the conduction and energy losses of polymer dielectrics at elevated temperatures. The experimental results demonstrate that the polar oxygen-containing groups, generated on the surface of polymer dielectrics during the exposure to an ultraviolet (UV) source, can act as the charges trap site to immobilize the injected charges from metal electrodes and these trapped charges can in turn establish a built-in field to weaken the external electric field, consequently augmenting the injection barrier height and suppressing the electrode-limited conduction loss. Wide bandgap aluminium oxide (Al 2 O 3 ) nanoparticles fillers can not only act as a physical block center to dissipate the kinetic energy of injected or thermally activated charges but also serve as deep traps to constrain the charges transport in dielectrics, accordingly contributing to the inhibition of bulk-limited conduction loss. From this, at 150°C, the discharged energy density (U e ) with a discharge-charge efficiency (η) of 90% increases by 324.63% from 1.34 J/cm 3 for pristine PEI to 5.69 J/cm 3 for UV-Al 2 O 3 /polyetherimide (PEI) film. Moreover, the pristine PEI could merely deliver a U e of 0.31 J/cm 3 with a η of around 90% up to 200°C while the UV-Al 2 O 3 /PEI exhibits an increase of 1058.06% with a U e of 3.59 J/cm 3 at 500 MV/m, which outperforms most of the state-of-the-art high-temperature polymer dielectrics. The principle of simultaneously inhibiting the electrode-limited and bulk-limited conduction loss could be easily extended to other polymer dielectrics for high-temperature capacitive performance. This article is protected by copyright. All rights reserved.