STABILITY STUDY OF POLYPYRROLE AND APPLICATION TO HIGHLY THERMOSTABLE ALUMINUM SOLID ELECTROLYTIC CAPACITOR

This paper describes the stability of electropolymerized polypyrrole and a highly thermostable aluminum solid electrolytic capacitor in which polypyrrole is applied as an electrolyte. We found that polypyrrole doped with tri-i-propylnaphthalenesulfonate (PPy/TIPNS) shows excellent thermostability and its conductivity decay stems from the addition reaction of oxygen followed by thermal decomposition in which oxygen participates. On the basis of these results, we developed a highly thermostable aluminum solid electrolytic capacitor which is composed of an etched and anodized aluminum foil anode covered with electropolymerized PPy/TIPNS and is hermetically sealed. The capacitor continuously functioned for more than 3600 h at 150 degrees C without any deterioration. Moreover, the capacitor also showed ideal impedance-frequency characteristics comparable to those of the multilayer ceramic capacitor and flat temperature characteristics in the wide range of -50 to 150 degrees C.