Tailoring dielectric performance via dipole density and hydrogen bonding interaction towards high-temperature capacitive energy storage polymers

Abstract

In addressing the critical demand for high-performance dielectric materials in advanced energy storage systems at 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 an enhanced dielectric constant. Blending this co-polyurea with polyetherimide disrupted intermolecular hydrogen bonding 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 the dielectric constant (7.13), more than twice that of PEI, alongside low dielectric loss (0.0084), high breakdown strength (550 MV m⁻¹) and exceptional dielectric thermal stability up to 150 °C. 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 cm⁻³ with over 90% charge–discharge efficiency at 150 °C and 400 MV m⁻¹, 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.