Influence of antimony on the properties of the anodic oxide layer formed on Pb-Sb alloys

Electric and dielectric properties, changes in structure and kinetics of formation and reduction of anodic phase layers on Pb and Pb-Sb electrodes in H2SO4 have been studied by means of electrochemical and structure characterizing impedance spectroscopy methods. The results obtained were discussed with respect to the effectiveness of Sb on the solid-state PbO → PbOn and PbOn → PbO2 transformations. It is found that Sb facilitates the appearance of a potential region in which non-stoichiometric mixed oxides are formed; it has a catalytic effect on the PbO into the PbOn transformation. The formation of the mixed oxide leads to a shift in the potential of the oxidation of PbSO4 to PbO2 of about 200 mV in comparison with the pure-Pb electrode. It seems that the observed effects could explain why Sb prolongs the positive plate cycle life. It was shown that the electrochemical impedance spectroscopy is a very sensitive and suitable method for in situ investigation of solid-state processes in the positive lead/acid battery plate.