Effect of antimony on premature capacity loss of lead/acid batteries

Lead/acid batteries with antimony-free positive grids have a tendency to lose discharge capacity early indeep-discharge cycling. In this study, the effect of antimony in positive active-material (PAM) on the performance of batteries with Pb-Ca-Snalloy grids is investigated. The corrosion layer of Pb-Ca-Sn positive grids with conventional leady oxide discharges before the PAMdischarges. With Pb-1 wt.%Sb leady oxide, however, the corrosion layer of positive grids of the same composition does not discharge somuch, and antimony is observed in the corrosion layer. These results suggest that the antimony-containing corrosion layerdischarges with difficulty and, thus, the active material discharges more readily than the corrosion layer and a passivation layer does not format the grid/active-material interface. This suggestion is also supported by parallel discharge tests of anodic corrosionlayers on lead and Pb-Sb alloys in dilute sulfuric acid. The corrosion layer of the Pb-Sb alloy has a tendency to discharge after that of pureleads in a parallel circuit.