Influence of electro-polymerization conditions on the capacitance and dissipation factor of polypyrrole tantalum electrolytic capacitors

The approaches, by which the conducting polypyrrole could be electrodeposited on the surface of tantalun/tantalum pentoxide-based anode (1 microfarad, 16 V), are studied. The galvano-statically polymerized polypyrrole is used for the cathodes of tantalum electrolytic capacitors. Particularly, the influences of electro-polymerization conditions, such as supporting electrolyte solution composition, anodic current and applied mode, on the capacitance and dissipation factor of as-made capacitor are discussed. With over concentration of pyrrole and electrolyte, there is a disadvantageous effect on the properties of the samples. However, it is benefit to keep the ratio of concentration of pyrrole and electrolyte between 3 and 4. The properties would be deteriorated with the increase of anodic current, so the anodic current should be below 1.2 mA. Samples with capacitance almost 98 percent of the rated capacitance and low dissipation factor less than 0.013 were accomplished in supporting electrolyte using mixture of acetonitrile and 1, 2-propanediol carbonate as solvent. During the electro-polymerization process, a larger anodic current first, a smaller one later, must be applied.