Yang Liu, Weichen Zhao, Zhenjun Shao, Zhaobo Liu, Diming Xu, Zhentao Wang, Jian Bao, Tiezhu Guo, Xin Wang, Xiangkun Li, Zenghui Liu, Wenyuan Liu, Yao Zhou, Wenfeng Liu, Jinzhan Su, Houbing Huang, Jordi Jacas, Joan Ramon Morante Lleonart, Andreu Cabot, Kar Ban Tan, Pengjian Wang, Qin Guo, Di Zhou
Polymer dielectrics are vital for high-power electronics, yet their high-temperature application is fundamentally constrained by the inherent trade-offs among thermal stability, polarization retention, and conduction loss. Here, we mitigate these limitations by integrating high-entropy nanofillers with a preferentially oriented, wide-bandgap inorganic nanocoating to construct a multiscale heterointerfacial architecture. Within this design, entropy-driven compositional disorder enhances the structural stability and polarization response of the nanofillers, while the conformal inorganic network synergistically suppresses carrier injection and modulates bulk trap-mediated transport. Consequently, the engineered composites deliver a discharged energy density of 10.44 J cm-3 with 95% efficiency and a breakdown strength of 650 MV m-1 at room temperature. Notably, at 150 °C, the composites retain 8.35 J cm-3, 80% efficiency, and a breakdown strength of 610 MV m-1. First-principles calculations and phase-field simulations suggest multiscale field confinement that weakens electrothermal coupling and enhances high-temperature stability. This work establishes a comprehensive, multiscale design paradigm for next-generation polymer dielectric capacitors operating in extreme thermal environments.