Dependence of Film Thickness on Electrochemical Kinetics of Polypyrrole and on Properties of Lithium/Polypyrrole Battery

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Abstract
The charging‐discharging behavior of battery was found to show a different dependence on the thickness of a polypyrrole film cathode prepared at various polymerization potentials. Lithium batteries constructed with a polypyrrole cathode formed at a higher potential show better charging‐discharging performance characteristics than those with a film prepared at a lower potential. The electrode kinetics of electrochemically prepared polypyrrole were investigated in an attempt to clarify the interesting dependence of the behavior of Li/polypyrrole battery on the thickness of polypyrrole cathode as a function of formation potential. A potential step chronoamperometry, together with an ac impedance measurement, has evidenced that there is a strong relationship between the doping charges and the apparent diffusion coefficients of polypyrrole electrodes. In practice, the battery performance of cells was examined by varying the current density. The upper limit of the current density at which the coulombic yield in the charging‐discharging curves remains at 100% was found for both thin and thick films of 1 and 5 C cm−2 film formation charges.