A synopsis of recent attempts toward construction of rechargeable batteries utilizing conducting polymer cathodes and anodes

This paper reports on our recent attempts in the characterization of n-doping of polythiophene (PTh) and p-doping of polypyrrole (PPy) for their use as the anode and cathode, respectively, for rechargeable batteries. N-doping of PTh with large (TEA) cations was studied by combined application of cyclic voltammetry, in situ conductometry and ex situ atomic force microcopy (AFM). The average potential for n-doping of PTh was close to 1.2 V (versus Li/Li⁺). Substantial trapping of negatively charged polarons was observed during consecutive n-doping. Addition of Li-salt to the background electrolyte, even in a small concentration, resulted in the almost complete deactivation of the film with respect to n-doping. We suggest that the above drawback can be overcome by using the more robust fluorosubstituted polyphenyl(thiophene), P3FPhTh. On the other hand, when addressing polymer cathodes, specially prepared PPy films showed highly reversible behavior and a large capacity of up to one electron per ring (or 420 mAh per gram of neutral polymer) when cycled up to 4.6-4.7 V (versus Li/Li⁺). Only above 5 V (versus Li/Li⁺) did an irreversible over-oxidation of PPy occur. Electrochemical characteristics of p-doped PPy cathode are compared with that of lithiated V₂O₅ film. Two possible alternative ways for changing the dopants in p-doped PPy, from anions to cations, are discussed.