Molecular engineering of polyamide-imide copolymers for high-temperature energy storage

Abstract

Advanced electronics and power systems critically require polymer-based dielectric materials capable of operating efficiently at high temperatures while maintaining high discharged energy density and efficiency. However, conventional polymer dielectrics often suffer from significant capacitive performance degradation when subjected to elevated temperatures, limiting their practical application in advanced energy storage systems. Herein, we report a molecularly engineered series of polyamide-imide (PAI) copolymers designed for significantly improved high-temperature capacitive energy storage. The rigid fluorene-based diamine comonomer enhances dipole polarization through steric hindrance and asymmetric electron distribution. Furthermore, a higher density of amide groups enables the formation of a robust hydrogen-bond network, which reinforces intermolecular interactions and effectively suppresses conduction losses at elevated temperatures. Consequently, the optimized PAI-C film exhibits an outstanding discharged energy density (U_d) of 5.9 J cm⁻³ with a charge–discharge efficiency of 90.1% at 150 °C. This work offers a compelling molecular-level design pathway toward high-performance polymer dielectrics integrating mechanical robustness, thermal stability, and superior energy storage capability.