Optimizing the High-Temperature Energy Storage Performance of Polyimide Films Using Double-Layer Interfacial Barrier Layers

Abstract Advanced electronic and electrical systems increasingly require polymer dielectric materials capable of delivering efficient energy storage even when subjected to elevated temperatures and intense electric fields. However, conventional polyimide (PI) films suffer from limited energy density and severe performance degradation due to intensified charge transport and leakage conduction at high temperature. In this work, a double-layer inorganic barrier heterostructure is constructed on PI films via a high-vacuum magnetron sputtering technique to address these challenges. The introduced inorganic functional layers form well-defined multilayer architectures with dense interfaces and tailored energy band alignment. Mechanistically, the incorporation of wide-bandgap insulating layers enhances carrier-blocking capability and induces built-in electric fields at the interfaces, which effectively suppress Schottky emission and reduce leakage current while promoting interfacial polarization. Consequently, the optimized Al2O3-BN-PI-BN-Al2O3 (A-B-P-B-A) structured composite film demonstrates a remarkable breakdown strength of up to 540 MV/m, along with enhanced discharge energy densities of 2.49 J/cm3 at 150 °C. In addition, the composites demonstrate excellent charge-discharge efficiency, fast energy release (95% within 1.5 μs), and outstanding cycling stability over 50,000 cycles at 150 °C. This study proposes a practical, scalable approach for fabricating high-performance polymer dielectrics suited to energy storage under elevated-temperature conditions.