Polypyrroles cells

Mohammadi, A., O. Inganas, and 1. Lundstrom. 1986. Properties of polypyrrole-electrolyte-polypyrrole cells. J Electrochem Soc 133 (5) 947. 

Panero et al reported the charge-discharge characteristics of Li/LiC104 in a PC/polypyrrole cell [35]. The maximum doping level at a constant current density (0.4 mA cm" ) was 30% (per monomer unit) for a 1 pm thick film, although the value depended on the polypyrrole film thickness. 

Figure 5.7 Charge-discharge curves of Li/polypyrrole cells. Oxidizing agent for polypyrrole synthesis (a) Fe(C104)3, (b) FeCU, (c) Fe(N03)3, (d) FeNH4(S04)2 (e) Fe2(S04)3. Reprinted from [29] by permission of Elsevier Sequoia S.A.

Figure 5.9 Cycle characteristics of Li-Al/polypyrrole cells. Reprinted from [29] by permission of Elsevier Sequoia S.A.

Polypyrrole cells using Li/LiC104 in PC as electrolyte have been proposed and extensively investigated [410-12]. Commercial application has been achieved two large companies have produced batteries based on litium/polypyrrole [413]. Recently a polypyrrole/Nafion composite was used in a lithium/poly(ethylenoxide) cell with improved characteristics over the simple polypyrrole electrode [414]. 

By setting the ratio of the oxidized and reduced forms of a redox couple in an electrode coating film to unity, the potential of this electrode in an inert electrolyte is poised at the half-wave potential of the couple. This has indeed been shown for platinum wires coated with polyvinylferrocene or ferrocene modified polypyrrole But the long term stability of these electrodes during cell connection... 

In 1983, Yakushi et ai obtained UV-visiblc spectra of polypyrrole at various doping levels via the second approach described above and the results are shown in Figure 3.71. The authors employed a two-electrode cell and hence the potentials quoted are the potentials between the working and counter electrodes prior to removing the film. 

In 1985, Feldman et al. reported in situ conductivity measurements on polypyrrole. These were obtained using a twin electrode, thin-layer cell... 

This means that for a given polypyrrole chain if a unit cell (chosen as 6 monomer units on the basis of the observed maximum doping level of 2 charges per 6 monomer units) already has a polaron on it and a second charge is injected onto the same chain, it is more favourable to form a second polaron on another vacant unit cell than to force spin pairing to give a bipolaron. If, however, all the other unit cells are already occupied, then a bipolaron will be formed in the unit cell, rather than two polarons. 

For example, the p-doping process of a typical heterocyclic polymer, say polypyrrole, can be reversibly driven in an electrochemical cell by polarising the polymer electrode vs a counterelectrode (say Li) in a suitable electrolyte (say LiC104-PC). Under these circumstances the p-doping redox reaction (9.15) can be described by the scheme ... 

Considerable attention is presently devoted to heterocyclic polymers, such as polypyrrole, polythiophene and their derivatives. The kinetics of the electrochemical doping processes of these polymers has been extensively studied in electrochemical cells using non-aqueous electrolytes. 

Cul could be partly in contact with Ti02 directly therefore, the efficiency decreased by the recombination of injected electrons with Cul. In order to increase cell performance, direct contact between the Ti02 film and Cul must be minimized. Solid-state DSSCs have been studied using other organic and inorganic hole conductor materials, such as p-type CuSCN [147,148], polypyrrole [149], and polyacrylonitrile [95]. 

A solid-state solar cell was assembled with an ionic liquid—l-ethyl-3-methylimidazolium bis(trifluoromethanesulfone)amide (EMITFSA) containing 0.2 M lithium bis(trifluoromethanesulfone)amide and 0.2 M 4-tert-butylpyridine—as the electrolyte and Au or Pt sputtered film as the cathode.51,52 The in situ PEP of polypyrrole and PEDOT allows efficient hole transport between the ruthenium dye and the hole conducting polymer, which was facilitated by the improved electronic interaction of the HOMO of the ruthenium dye and the conduction band of the hole transport material. The best photovoltaic result ( 7p=0.62 %, 7SC=104 pA/cm2, FOC=0.716 V, and FF=0.78) was obtained from the ruthenium dye 5 with polypyrrole as the hole transport layer and the carbon-based counterelectrode under 10 mW/cm2 illumination. The use of carbon-based materials has improved the electric connectivity between the hole transport layer and the electrode.51... 

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