A novel flow battery: a lead acid battery based on an electrolyte with soluble lead(II): Part VII. Further studies of the lead dioxide positive electrode

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Description/Abstract

Extensive cycling of the soluble lead flow battery has revealed unexpected problems with the reduction
of lead dioxide at the positive electrode during discharge. This has led to a more detailed study of the
PbO2/Pb2+ couple in methanesulfonic acid. The variation of the phase composition (XRD) and deposit
structure (SEM) have been defined as a function of current density, Pb2+ andH+ concentrations, deposition
charge and temperature aswell as the consequences of charge cycling. Pure-PbO2, pure-PbO2 and their
mixtures can be deposited from methanesulfonic acid media. The -phase deposits as a more compact,
smoother layer, which iswell suited to charge cycling. While the anodic deposition of thick layers of PbO2
is straightforward, their reduction is not; the complexities are explained by an increase in pH within the
pores of the deposit. The results suggest that operating the battery at lead(II) concentrations <0.3M and
elevated temperatures should be avoided.