Enhanced capacitive energy storage of polyetherimide at high temperatures by integration of electrical insulation and thermal conductivity

Polymer dielectrics possessing excellent electrical insulation and high thermal conductivity are pivotal for dielectric capacitors at elevated temperatures. However, the integration of electrical insulation and thermal conductivity in polymers remains a challenge. In this work, we present a feasible strategy to integrate high electrical insulation and high thermal conductivity by bonding carbon quantum dots (CQDs) with the diamine monomer of polyetherimide (PEI). The CQDs with Coulomb blockade effect serve as traps for the migrating of electrons in the dielectrics, while the bonding networks formed by CQDs and PEI further deepen the traps and augment trap density. As a result, the hybrid dielectrics (PEI-NH₂-CQDs) exhibit nearly an order of magnitude higher electrical resistivity than that of pure PEI, leading to an 80% increase in discharge energy density with an energy efficiency of 90% at 200 ​°C compared to pure counterpart. Additionally, this all-organic dielectric achieves a significantly increased thermal conductivity of 0.65 ​W ​m⁻¹ ​K⁻¹ compared to 0.26 ​W ​m⁻¹ ​K⁻¹ of PEI, which supports its cyclic stability at elevated temperatures. We also demonstrate the kilogram-scale production of CQDs, synthesizing over 8 ​kg in a single batch, paving the way for large-scale production of reliable PEI-NH₂-CQDs dielectrics.