Significantly Enhanced High‐Temperature Energy Storage Performance of Polyetherimide via Deep Trap Construction and Carrier Transport Regulation

ABSTRACT Polymer dielectrics are core components of advanced energy storage materials, and studies have confirmed that incorporating inorganic fillers is an effective strategy to enhance their energy storage performance. However, the application of polymer/inorganic filler composite dielectrics in high‐temperature energy storage is limited by the leakage current and dielectric breakdown strength. In this work, we propose a synergistic mechanism based on deep trap construction and carrier transport regulation by introducing hydrothermally synthesized ZrO ₂ quantum dots (QDs, 4.68 nm in diameter) into a polyetherimide (PEI) matrix to establish deep traps. The electronegativity difference between Zr and O induces a strong positive surface electrostatic potential at the QDs, acting as carrier attraction centers. Upon capturing electrons, the QDs serve as Coulomb scattering centers, significantly suppressing carrier transport at elevated temperatures. The composite achieves outstanding high‐temperature energy storage performance: discharge energy density U _d = 6.84 J cm ⁻³ , discharge efficiency η > 90%, at 150°C; U _d = 6.68 J cm ⁻³ , η > 85%, at 200°C, outperforming most existing polymer/inorganic filler composites. This strategy of synergizing deep trap construction with carrier transport regulation provides a cost‐effective and highly efficient approach for the design of high‐temperature energy storage dielectrics.