| Electronically conducting polymers can be doped (ionic absorption into polymer matrix) and dedoped at high-power rates and to high energy densities. With lower cost predictions than for high power batteries or noble metal oxide pseudocapacitors, yet with similar energy densities, these are potential active materials for use in electrochemical supercapacitors. Paramount to the use of these materials in deep charge and discharge duty cycles is their achievement of high cycle life with very little loss in capacitance or charge/discharge efficiency. This dissertation explores several aspects of the poly-[3-(4-fluorophenyl)thiophene] (PFPT) conducting polymer with a modifying additive, 3,3 bithiophene (BT). Electrochemical investigation is combined with material science characterization to provide new insights and information on this material in a manner that could not be achieved if only one of these approaches were applied.; Specifically, implications of cycling this material with delays or rest periods inserted in the deep cycling routines are explored. Significant reductions in capacitance are observed after only a couple dozen cycles, compared to the same cycle routines with no rest periods. This reduced capacitance effect may have other causes unrelated to the lag cycling however and represents an area for further research.; Electrochemical Cycling is shown to induce structural changes such as ‘melting’ or smoothing which modify the surface area of the copolymer. These results are discussed in relation to some more general theoretical findings for polyampholytes and high surface area polymers which suggest that the ionic cycling may contribute to the smoothing behavior.; Atomic force microscopy (AFM) studies reveal greater numbers of nucleation sites during growth of the new high surface structure of the additive modified PFPT/BT (copolymer). Additionally, such films are smoother at first (as previously reported elsewhere), but undergo a transition to the high surface area structure at larger growth levels. The new copolymer also shows improved penetration into the carbon fiber electrode substrate during electrochemical polymerization. Finally, X-ray diffraction shows that the level of crystallinity in this material is low, although not insignificant, at roughly 10% in the PFPT/BT and 20% in the pure PFPT, which may influence electrochemical performance in supercapacitor applications. |
