Oxidation of electrodeposited lead-tin alloys in 5 M H2SO4

By electroplating lead-tin alloys on a lightweight substrate material, such as glassy carbon, it is possible to obtain less dense electrodes with good contact between the active material and the substrate. The former is espec ially important for the lead-acid battery since it has relatively low energ y density compared to many other battery systems. In order to obtain higher power densities for applications in, for example, electric or hybrid vehic les, the weight of the battery needs to be minimised. In the present investigation, the oxidation of electrodeposited lead-tin al loys in 5 M H2SO4 was studied as a function of tin concentration. The alloy s were prepared by electrodeposition and the oxidation behaviour was studie d by the means of cyclic voltammetry. Microstructural information on the de posited layer was obtained by scanning electron microscopy (SEM). The experimental results show that electrodeposited lead-tin alloys contain a supersaturated solid solution phase with up to 12 at.% Sn. Oxidation of this phase in 5 M H2SO4 leads to the formation of a PbO phase with increase d conductivity compared to pure PbO. In addition, the amounts of PbO and Pb O2 decrease with increasing amounts of tin in the alloy and for high tin al loys, where a bulk tin phase is present, no PbO phase is observed. (C) 2000 Elsevier Science S.A. All rights reserved.