Poly(tetrafluoroethylene-hexafluoropropylene) films with high energy density and low loss for high-temperature pulse capacitors

As the most important material of metalized capacitors, dielectric polymers with large energy density (U_e), promising discharging efficiency (η), and elevated breakdown strength (E_b) are dreadfully requested for energy storage purpose. During the charging and discharging circles, the Joule heat could cause significant temperature rising and undesirable early failure in the capacitors. Few of the known polymeric dielectrics are able to work functionally at temperature over 100 °C, especially under high electric field. In present contribution, poly(tetrafluoroethylene-hexafluoropropylene) (P(TFE-HFP)) is fabricated into thin films via hot-pressing followed by uniaxially stretching. At ambient temperature, P(TFE-HFP) films exhibit linear dielectric behaviour like biaxially orientated polypropylene (BOPP). The high T_m and Young's modulus allow P(TFE-HFP) films to work functionally at temperature up to 110 °C, whose E_b is over 500 MV/m, U_e is more than 6 J/cm³ and η is larger than 80%, respectively. The excellent performance suggests that P(TFE-HFP) films may substitute BOPP films to work as dielectric materials at elevated temperature.