US Patent 8493713 Conductive coating for use in electrolytic capacitors

A dispersion that contains an intrinsically conductive polythiophene formed via poly(ionic liquid)-mediated polymerization is provided. Without intending to be limited by theory, it is believed that a thiophene monomer can polymerize along the chains of a poly(ionic liquid). In this manner, the poly(ionic liquid) may act as a template for polymerization to provide a particle dispersion that is substantially homogeneous and stable. Such dispersions may be employed in an electrolytic capacitor as a solid electrolyte and/or as a conductive coating that is electrical communication with the electrolyte. Regardless, the dispersion may be more easily and cost effectively formed and incorporated into the structure of the capacitor. Moreover, due to the presence of the ionic liquid, the dispersion is conductive and does not require the addition of conventional dopants, such as polystyrene sulfonic acid. For example, the dispersion may have a specific conductivity, in the dry state, of about 1 Siemen per centimeter (“S/cm”) or more, in some embodiments about 10 S/cm or more, in some embodiments about 20 S/cm or more, and in some embodiments, from about 50 to about 500 S/cm.