Effect on cathodic reduction of β-PbO 2 in sulfuric acid solution of surface concentration of Pb 2+ ions formed on β-PbO 2

Abstract

The discharge reaction of positive electrode of lead-acid battery was investigated with the rotating ring-disc electrode. The large supersaturation of Pb 2+ ion on the electrode surface was obtained during discharge of initial period and the PbSO 4 nuclei was formed. The precipitation of PbSO 4 proceeded smoothly in the presence of PbSO 4 nuclei. In the steady state, the colloidal PbSO 4 film on the electrode surface of which stability depended on the concentrations of sulfuric acids was formed from the dissolving Pb 2+ ions. Especially its stability in 1.0 M H 2SO 4 was so low that the concentration of Pb 2+ ions during discharge was the largest of those in any other sulfuric acids, so that the effect of the film on the overpotential during galvanostatic discharge is the smallest, as discussed in a following paper[1]. The particle sizes of PbSO 4 precipitated during discharge were related to the concentration of Pb 2+ ions on the electrode. These sizes increased with increasing concentration of Pb 2+ ions. If the discharge capacity is limited by the passivation with PbSO 4 crystal, the use of 1.0 M H 2SO 4 as the electrolyte of lead-acid battery may be favoured.