Development of positive electrodes with an SnO2 coating by applying a sputtering technique for lead-acid batteries

In order to prevent positive grid corrosion and to obtain a long life for p ositive electrodes of lead-acid batteries, a conductive and corrosion resis tant SnO2 (tin dioxide) layer was formed on a Ti (titanium) substrate by a conventional dip-coating method. However, it is impossible to apply this me thod to a Pb (lead) substrate, because the dip-coating method needs a calci nation process, at a temperature higher (conventionally from 450 to 600 deg reesC) than the melting point of Pb (T-m: 327 degreesC). For this reason, an SnO2 layer to protect the substrate against passivation and/or corrosion was formed on Ti and/or Pb electrodes by applying sputter ing, a method which is often used in the production of semiconductors. This improved electrode, with an SnO2 layer, was not corroded at all, even though the thickness of the SnO2 layer was only about 15 mum. The biggest problem of the SnO2 layer is that it dissolves in sulfuric acid when the positive electrode is polarized below 0.5 V (versus Pb/ PbSO4). T his suggests that this electrode should not be subjected to deep discharge. (C) 2001 Elsevier Science B.V. All rights reserved.