Macro–Micro Synergistic Design Driven by Interlayer Electric Field Load Regulation: All-Organic Sandwich Dielectrics for High-Temperature Energy Storage Applications of PMMA

To address the severe performance degradation of polymer dielectric capacitors under extreme high-temperature and high-field conditions, this study proposes a layered dielectric electric-field reconstruction strategy. An all-organic PC/PMMA/PC (CMC) sandwich-structured composite film was fabricated via layer-by-layer solution casting, utilizing polycarbonate (PC) as the outer buffer layer and poly(methyl methacrylate) (PMMA) as the functional core. The dielectric mismatch between layers induces intrinsic electric-field redistribution, allowing the low-dielectric PC outer layers to sustain higher local fields and dissipate stress, thereby reducing the electric-field load on the high-dielectric, wide-bandgap PMMA core. This architecture circumvents the high-temperature breakdown of PMMA while fully exploiting its polarization capability, synergistically optimizing polarization and breakdown strength. Additionally, deep traps at heterogeneous interfaces effectively suppress carrier transport and reduce conduction loss. At 100 °C, the CMC film achieves a breakdown strength of 630 MV/m, a discharged energy density of 8.50 J/cm3, and an efficiency of 88%, significantly outperforming single-component polymers. By integrating macroscopic electric-field modulation with microscopic band-structure engineering, this study elucidates the regulatory mechanisms of the layered stacking structure on electric-field distribution and carrier behavior. It effectively resolves the limitations of PMMA in high-temperature applications, providing technical insights and theoretical support for the structural design and performance optimization of high-performance all-organic high-temperature energy-storage dielectric materials.