Dual‐Mode Strategy Based on Metal‐Phenolic Networks for Charge Modulation of High‐Temperature Polymer Dielectrics

Polymer dielectrics are attractive for high‐temperature capacitors owing to their lightweight and flexibility, yet their low energy density ( U e ) and high conduction losses at elevated temperatures severely constrain practical applications. Here, a dual‐mode intrinsic charge regulation strategy is proposed based on a self‐assembled meatal‐polyphenol network (MPN‐GA), formed by coordinating of gallium ions (Ga 3 ⁺) with gallic acid (GA). This structure constructs deep‐level traps via Ga 3 ⁺ centers for carrier capture, while accumulated charges induces a reverse electric field to effectively shield further injection. This dual mechanism markedlyenhances the breakdown strength of PEI ( E b , >700 MV m −1 at 25 °C and >580 MV m −1 at 150 °C). To further suppress bulk‐limited conduction loss, boron nitride nanosheets (BNNS) with a wide bandgap and high thermal stability are employed as nanocarriers for MPN‐GA. The hybrid filler enables multiscale carrier modulation, achieving a discharged energy density of 7.13 J cm − 3 and 90% efficiency at 150 °C, representing 3.4‐fold and 9% improvements over pristine PEI. Even at 200 °C, the efficiency remains ≈90% with 4.26 J cm − 3 output. This work demonstrates the potential of MPN‐based intrinsic structure design for dielectric regulation and offers a scalable approach toward high‐performance polymer dielectrics for next‐generation energy storage.