Enhanced Energy Storage Performance of High‐Temperature Dielectric Films by Internally Constructing Oriented Microfibril Structure

Abstract

ABSTRACT High‐temperature dielectric films are essential components for capacitive energy storage in severe environments, ranging from hybrid electric vehicles to power systems. However, the surge in leakage current at elevated temperatures leads to a dramatic decrease in discharge energy efficiency, falling well short of the requirements for the next‐generation high‐temperature polymer dielectrics. Herein, a novel technology of “melting extrusion‐hot stretching‐quenching” was utilized to generate high‐temperature polycarbonate (HTPC)‐based dielectric films, where the compatible blends of polymethyl methacrylate/polyvinylidene fluoride (PMMA/PVDF) were in situ formed into highly aligned microfibrils. The well‐designed microfibrils enhanced the interfacial polarization and efficiently served as carrier traps, thereby synergistically improving the discharge energy density and discharge energy efficiency at high temperature. Consequently, the as‐prepared all‐organic dielectric film exhibited an appreciable discharge energy density as high as 6.54 J/cm 3 with a discharge energy efficiency of 87.5% at 600 MV/m and 120°C. After being continuously charged and discharged at 300 MV/m and 120°C for 10 5 times, a negligible attenuation was observed in energy storage properties. This work provides a feasible way to tailor the comprehensive performance of HTPC by internally constructing oriented microfibril structure, thereby advancing the design and scalable fabrication of HTPC‐engineered dielectric films for high‐temperature energy storage.