The effect of SnS04 on the deep-discharge capacity of lead/acid batteries is investigated when It is added to the sulfuric acid electrolyte.
The electrochemical behaviour of Sn'+ ions in sulfuric acid is studied by using chemical-analysis and cyclicvoltammetry methods. In the battery system, Sn '+ ions will be reduced to tin on the negative plates or will be oxidized to tin(IV) species on the positive plates. Tin metal formed on the negative plates will improve the charge/discharge properties. Tin(W) species formed on the positive plates may be incorporated as Sn02 in the positive active material (PAM) as well as in the anodic film that is produced at the grid/active-material interface.
The effect of Sn02 on the properties of the PAM are explained in terms of the gel-crystal model. The SnO, is stable during the discharge process. The compound increases the electronic conductivity of the gel zones, thereby, enhances the capacity of the PAM. The SnO, species may also act as nuclei for the formation of /3-Pb02 in the crystal zones. The corrosion of positive grids is inhibited by the presence of SnOZ. By virtue of these effects, the addition of SnSO, is beneficial to the operation of lead/acid batteries.