The behaviour of lead dioxide electrodes in acidic sulfate electrolytes

Abstract

The variation of discharge capacity during charge-discharge cycling of a PbO₂ electrode, prepared by pressing PbO₂ powder onto a smooth lead disc, in sulfuric acid and acidic ammonium sulfate solutions of various concentrations was investigated by the potentiodynamic technique. The discharge capacity was found to increase with cycle number in 0.05-4.3 H₂SO₄; this was explained in terms of the increase in porosity of the electrode with cycling. The rate of increase was highest in a 1 mol dm^-3 solution. The presence of ammonium sulfate decreased the discharge capacity at all concentrations of sulfuric acid except for the 1 mol dm^-3 solution where it caused a small increase in capacity. The morphology of the electrode was studied by scanning electron microscopy and the results are correlated with the discharge capacity.

These results indicated that a solution of composition 0.5 mol dm^-3 ammonium sulfate and 1.0 mol dm^-3 sulfuric acid will produce a greater utilization of positive plate active material (PbO₂) during discharge. This result, taken together with the results of earlier studies on lead in acidic sulfate electrolytes, points to the possibility of a Pb/H₂SO₄,/PbO₂ battery for electric-vehicle propulsion.