Enhancing High‐Temperature Capacitive Energy Storage Performance via Atom‐Doped Carbon Polymer Dots Engineered Dual‐Barrier

Abstract Advances in high‐temperature‐resistant polymer dielectric present a crucial opportunity for next‐generation electrostatic energy storage in power electronics. However, the practical application of polymer dielectrics at elevated temperatures (above 150 °C) is largely limited due to the exponential increase in conduction loss under the high thermo‐electric field. In this work, N and S atom‐doped carbon polymer dots (NSCPDs) engineered dual‐barrier to address the critical issue of conduction loss is utilized. Specifically, the doping elements of N and S heteroatoms enhance the NSCPDs' electron affinity and facilitate the formation of deeper traps with energy levels of 1.60 eV compared to pristine CPDs (1.07 eV). Furthermore, the Coulomb blocking effect induced by quantum‐sized NSCPDs can capture electrons and tortuous the electron transport path. Therefore, this constructed “Coulomb blockage‐trap barrier” dual energy barrier effectively suppresses carrier migration and lowers leakage current, enabling the 0.5 wt.% NSCPDs/PEI composite to attain a remarkable energy storage density of 3.49 J cm ³ at 200 °C, which represents a 60% enhancement compared to pristine PEI (2.21 J cm ³ ). The composite simultaneously demonstrates excellent efficiency (η > 90%) and robust cycling stability over 10 ⁵ cycles. This study provides a generalizable materials design paradigm for the development of high‐temperature polymer dielectrics.