All-Organic Sandwich-Structured\nDielectric Films Based\non Aramid Nanofibers and Polyimide for High-Temperature Electrical\nEnergy Storage

To meet the urgent requirements of\ncutting-edge power\nelectronics\nand electrical systems at elevated temperatures, all-organic sandwich-structured\ndielectric films were successfully designed and fabricated based on\nthe aramid nanofiber film (ANFm) and polyimide (PI) layer via the\nconvenient “dipping and pulling” technique. On account\nof the flat surface and formed electron traps, the PI-ANFm-PI (P-A-P)\ndielectric films exhibit enhanced breakdown strength (<i>E</i><sub>b</sub>) and reduced leakage current density compared to the\nsingle-layered ANFm at elevated temperatures. The P-A-P dielectric\nfilm shows a maximal discharge energy density (<i>U</i><sub>d</sub>) of 3.68 J/cm<sup>3</sup> with a charge–discharge\nefficiency (η) exceeding 80% at 25 °C and an impressive <i>U</i><sub>d</sub> of 1.76 J/cm<sup>3</sup> with η above\n70% at 150 °C, outstandingly surpassing the performances of single-layered\nANFm and pure PI dielectric film. With the exceptional energy-storage\nproperties, the all-organic sandwich-structured P-A-P films have been\ndemonstrated to be promising candidates for high-temperature electrical\nenergy storage.