Enhancement of high-temperature capacitive energy storage performance in all-polymer dielectric composites via microphase separation

Polymer dielectric capacitors play a crucial role in modern electronics and power systems owing to their exceptional power density, high breakdown strength, excellent processability, and cost-effectiveness. Nevertheless, their practical deployment in harsh operating environments, particularly in electric vehicles and aerospace power electronics, remains challenging due to the inherent thermal instability of conventional polymer dielectrics. Herein, we report an all-polymer dielectric composite (APDC) material fabricated from partially miscible polyetherimide (PEI)/polyamide-imide (PAI) blends that exhibits significantly improved high-temperature capacitive energy storage properties, including breakdown strength (Eb), discharge energy density (Ud), and charge–discharge efficiency (η). The performance enhancement stems from the self-assembled nanoscale interfacial architectures comprising uniformly dispersed PAI domains within the PEI matrix, coupled with the intrinsic energy band structure mismatch between PEI and PAI (notably in electron affinity). These structural characteristics effectively create deep charge traps, resulting in a substantial reduction of leakage current density by more than one order of magnitude compared to pristine PEI under elevated temperatures and high-electric fields. Notably, the developed APDC materials feature a straightforward, efficient, and cost-effective fabrication process, rendering them highly promising for scalable production of high-performance dielectric films for high-temperature capacitors.