Several strategies are investigated for 'activating' polypyrrole electrodes for use in electrochemical supercapacitors. These include: the development of columnar morphologies by micellar deposition, self-doping by attachment of anions' and the use of aryl sulfonates to promote cross-linking and hydrophilicity. The key to improved performance, especially in this last example, is the apparent coupling of doping processes to structural relaxations that encourage solvent uptake by the polymer and ready access for dopant ions to all available sites. Thick (15-20 mum) films of polypyrrole activated in this way can be charged and discharged reversibly at scan rates up to 300 mV s(-1), indicating a possible use in high-power supercapacitors. (C) 2004 Elsevier B.V. All rights reserved.
Bibliographical noteWe thank EPSRC and DERA (UK) for financial support, and Amanda Pappin (University of Aberdeen), Roger Latham (De Montfort University), and Kevin Green (DERA) for helpful discussions and practical help. MDI thanks the Alexander von Humboldt Foundation for a Research Award, which enabled him to spend a research sabbatical at the Institute of Physical Chemistry in the University of Münster, where this paper was written.
- electrochemical supercapacitors
- doping mechanisms
- high power devices