Tailoring Dielectric Performance via Dipole Density and Hydrogen Bonding Interaction Towards High-Temperature Capacitive Energy Storage Polymer

Abstract

In addressing the critical demand for high-performance dielectric materials in advanced energy storage systems under elevated temperatures, this study introduces a molecular engineering strategy integrating copolymerization and polymer blending to optimize dipolar polarization in polyurea-based dielectrics. By systematically modulating the intrinsic molar polarizability through controlled incorporation of small molar volume m-phenylenediamine, here we constructed a novel high dipole density co-polyurea with enhanced dielectric constant. Blending this co-polyurea with polyetherimide disrupted intermolecular hydrogen bond partially, enhancing free volume and dipole mobility and thus increasing orientational polarizability. Experimental characterization revealed that the 1:1 blend exhibited a remarkably increase in dielectric constant (7.13), more than twice that of PEI, alongside low dielectric loss (0.0084), high breakdown strength (550MV/m) and exceptional dielectric thermal stability up to 150℃. In addition, the polymer blend demonstrated a higher breakdown strength and a lower leakage current density compared to PEI. These properties enabled a discharged energy density of 4.6 J/cm3 with over 90% charge-discharge efficiency at 150℃ and 400 MV/m, surpassing conventional high-temperature dielectrics. This work establishes a scalable approach to balance dipolar density and dipolar mobility in polar polymers through copolymerization and blending, offering transformative insights for next-generation dielectric capacitors in high-temperature environments.