Fabrication of solid aluminum electrolytic capacitors utilizing conductive polyaniline solutions

To overcome the risk of electrolyte leakage and the shortcoming of higher impedance at high frequencies for the conventional aluminum electrolytic capacitors impregnated with electrolyte solutions, solid aluminum electrolytic capacitors employing conducting polyaniline (PANI) as a counter electrode were developed. The dodecylbenzenesulfonic acid (DBSA) doped PANI/chloroform solution, camphorsulfonic acid (CSA)–DBSA co-doped PANI/chloroform solution and DBSA doped PANI/toluene solution were synthesized by direct and inverse emulsion polymerization pathway. The capacitors using the solution of CSA–DBSA co-doped PANI/chloroform showed the best electrical properties. The performances of the PANI capacitors can be remarkably improved after secondary doping with m-cresol. The as-fabricated solid capacitors have very low impedances at high frequencies and excellent temperature characteristics as well as long shelf-life. The results can be ascribed to high conductivity and superior thermal stability for the CSA–DBSA co-doped PANI. Our strategy of using conductive PANI solution to fabricate the solid capacitors is not only compatible with the existing fabrication procedure for the conventional capacitor but also suitable for commercial mass production of low cost PANI.