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 (Ga³⁺) with gallic acid (GA). This structure constructs deep-level traps via Ga³⁺ 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.