Characterization and Long-Term Performance of Polyaniline-Based Electrochemical Capacitors

The performance of polyaniline‐based electrochemical capacitors was evaluated under various experimental conditions. The capacitor consisted of two platinized tantalum foils coated with polyaniline as the active material, a separator, and an appropriate aqueous electrolyte solution. The polyaniline coatings were formed galvanostafically from a 0.1 M aniline +1.0 M HCl aqueous solution. With a polyaniline loading formed by a deposition charge of on each electrode and with a aqueous solution as the electrolyte for an optimized capacitor, energy and power densities of and (of active polymer) were achieved, respectively. Cyclic voltammograms for both positive and negative polyaniline electrodes of the capacitor before and after 20,000 cycles showed only a 5% loss of polyaniline electroactivity, which was smaller than the observed 33% decrease in the discharge capacity of the capacitor. Cyclic voltammetry and electrochemical impedance spectroscopy were used to characterize the capacitors and to understand their initial performance loss upon constant‐current cycling. © 2000 The Electrochemical Society. All rights reserved.