Engineered Interfacial Electron Barriers for Superior High-Temperature Energy Storage in All-Polymer Dielectrics

The rapid advancement of electric vehicles, renewable energy integration, and next-generation power electronics has intensified the demand for high-performance dielectric capacitors capable of operating reliably under high temperatures and electric fields. In this study, we develop an all-polymer dielectric (APD) system with superior high-temperature capacitive performance achieved through strategically designed heterogeneous interfaces that introduce high electron barriers. These interfaces are constructed via in situ polymerization and cross-linking of a commercial bismaleimide (MIR) monomer within a fluorinated polyimide (FPI) matrix. The pronounced band structure mismatch between FPI and MIR domains generates substantial interfacial electron barriers, which effectively suppress high-temperature leakage currents while concurrently enhancing breakdown strength, charge-discharge efficiency, and energy density. The optimized FPI/MIR APD achieves outstanding discharged energy densities of 5.8 J/cm³ at 150 °C and 3.0 J/cm³ at 200 °C with high efficiency (η > 90%), as well as excellent cycling endurance (>50 000 cycles at 150 °C). Moreover, the material exhibits intrinsic self-healing capability, exceptional scalability, and large-area uniformity. The straightforward and cost-effective fabrication process further underscores its potential for scalable production of high-temperature polymer dielectrics.