Technique for Forming a Cathode of a Wet Electrolytic Capacitor

摘要

A technique for forming a cathode of a wet electrolytic capacitor is provided. The cathode contains a metal substrate having a roughened surface and a conductive coating that contains a substituted polythiophene. The degree of surface contact between the conductive coating and the roughened surface is enhanced in the present invention by selectively controlling the manner in which the conductive coating is formed. More particularly, the conductive coating is formed by applying a precursor solution to the roughened surface that includes both a precursor thiophene monomer and an oxidative catalyst. Contrary to techniques in which either the monomer or catalyst is applied separately and initially contacts the metal surface, the presence of the monomer and catalyst within the same solution allows polymer chains to grow immediately adjacent to the surface of the metal substrate and within the pits. This can significantly increase the degree of contact between the conductive coating and metal substrate, thereby resulting in improved mechanical robustness and electrical performance (e.g., reduced equivalent series resistance and leakage current). To minimize the likelihood of premature polymerization, the oxidative catalyst is also employed in an amount less than what is required to fully react all of the reagent assuming 100% yield (i.e., “stoichiometric amount”). This can slow the polymerization of the monomer, creating oligomers that are shorter than if fully polymerized, which can better penetrate into the roughened regions of the metal substrate.