Poly(ether\nimide) Film Doped with Protonated Tetra(aniline)\nMolecules for Efficiently Enhancing the Capacitive Energy Storage\nPerformance

The polymer dielectric spacer plays\na key role in the performance\nof film capacitors. However, currently, commercial polymer dielectric\nfilms generally have low relative dielectric constants (<4) and\nlow capacitive energy storage densities (<3 J cm<sup>–3</sup>). Here, we report the use of protonated tetra(aniline) (TANI) molecules\nwith a length of 1.3 nm to improve the energy storage performance\nof poly(ether imide) (PEI) films. With only a small content of TANI\ndoping, i.e., 0.7 wt %, both the dielectric constant and energy storage\ndensity of PEI film can be significantly improved, while the dielectric\nloss remains as low as that of pure PEI. A maximum energy density\nof 9.4 J cm<sup>–3</sup> is achieved. To manifest the efficacy\nof protonated TANI, polyaniline and deprotonated TANI are also prepared\nand used as dopants in PEI. The PANI filler can also increase the\ndielectric constant, while the dielectric loss is increased as well.\nThe deprotonated TANI doped in PEI has no influence on both the dielectric\nconstant and energy density, implying that the protonated amino groups\nof TANI molecules are responsible for the enhanced dielectric constant\nof the PEI/TANI composite. The correlation between protonation of\nTANI dopants and dielectric properties is discussed in detail.