Electrical breakdown in ferroelectric polymers for electrical energy storage

High permittivity polymers are attractive materials for electrical energy storage for a wide range of applications such as capacitor dielectrics. Ferroelectric polymers based on vinylidene fluoride (VDF), trifluoroethylene (TrFE), and chlorotrifluoroethylene (CTFE) exhibit some of the highest permittivities and energy densities among polymers. Energy density in a capacitor is exponentially related to the electric field applied to the dielectric, which is limited by the polymer's electrical breakdown strength. Modest increases in a polymer's breakdown strength could easily double or triple its energy density making this a crucial variable for performance. With the goal of identifying the failure mechanism, the influence of chemical composition on the electrical breakdown strength of these ferroelectric polymers is explored. Electromechanical breakdown is identified as the failure mechanism and experimental results are fitted to modeled predictions. Additionally, the breakdown properties are related to the energy densities of the polymers.