Achieving High Energy\nStorage Capability of Polypropylene\nFilms through Clean Electron Beam Irradiation Induced Grafting Strategy

In order to develop polypropylene (PP) based dielectric\nmaterials\nwith high dielectric and energy storage properties, PP grafted polystyrene\nfilms (PP-<i>g</i>-PS) with different grafting content have\nbeen prepared by electron beam irradiation grafting method. Free radicals\nwere generated in the PP chains during irradiation and also enhanced\nthe polarity of PP due to the oxidation reaction. The results have\nshown that the presence of grafted PS introduced smaller spherical\ncrystals, which led to more interfacial regions and increased the\ninterfacial polarization. DFT simulations and TSDC proved that the\ngrafted PS introduced deeper traps, which could effectively trap carriers\nat high speeds and reduce the carrier mobility. When the content of\nPS was 8 wt %, the PP-<i>g</i>-PS film achieved 600 MV/m\nbreakdown strength, 5.43 J/cm<sup>3</sup> discharge energy density,\nand more than 96% charge–discharge efficiency. What’s\nmore, the grafting of PS significantly improved the high-temperature\nenergy storage properties of PP. At 110 °C, the discharge energy\ndensity of the PP-<i>g</i>-PS (8%) film is 3.44 J/cm<sup>3</sup>, which is 93% higher than that of the PP film (1.78 J/cm<sup>3</sup>). And at the electric field strength of 440 MV/m, the efficiency\nstill exceeds 96%. This study provides a simple and feasible strategy\nfor the development of high-performance PP-based dielectric films.