The behaviour of the lead-aqueous sulfate electrode in relation to the development of electric vehicle batteries

Abstract

The behaviour of smooth lead electrodes in various aqueous sulfate electrolytes has been studied by slow scan (10 mV min^-1) cyclic voltammetry and coulometry and by scanning electron microscopy. The dependence of the amount of charge that can be delivered in discharge of lead to form lead sulfate, as in a lead-acid battery, is found to depend strongly on electrolyte composition, and an acidic ammonium sulfate electrolyte (0.5 mol dm^-3, pH 2.0) was found to yield the highest charge over some 40 charge-discharge cycles when compared with various other sodium sulfate, ammonium sulfate and sulfuric acid electrolytes. The quantity of charge was directly related to the size of the lead sulfate crystals produced. This result is interpreted in terms of the passivating effect of lead sulfate. A tentative mechanism for the anodic formation of lead sulfate is proposed and used to interpret the cyclic voltammograms obtained in concentrated sulfuric acid.