Development of positive electrodes with an SnO 2 coating by applying a sputtering technique for lead-acid batteries

Abstract

In order to prevent positive grid corrosion and to obtain a long life for positive electrodes of lead-acid batteries, a conductive and corrosion resistant SnO 2 (tin dioxide) layer was formed on a Ti (titanium) substrate by a conventional dip-coating method. However, it is impossible to apply this method to a Pb (lead) substrate, because the dip-coating method needs a calcination process, at a temperature higher (conventionally from 450 to 600°C) than the melting point of Pb ( T m: 327°C). For this reason, an SnO 2 layer to protect the substrate against passivation and/or corrosion was formed on Ti and/or Pb electrodes by applying sputtering, a method which is often used in the production of semiconductors. This improved electrode, with an SnO 2 layer, was not corroded at all, even though the thickness of the SnO 2 layer was only about 15 μm. The biggest problem of the SnO 2 layer is that it dissolves in sulfuric acid when the positive electrode is polarized below 0.5 V (versus Pb/PbSO 4). This suggests that this electrode should not be subjected to deep discharge.