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

The charging-discharging behavior of lithium/LiCIO₄/polypyrrole 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 Li/LiCIO₄ polypyrrole 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.