On the thermodynamics of the agglomerate-of-spheres' model for the PbO2 electrode

The agglomerate-of-spheres' model concerns the structure of particulate battery electrodes, in particular the positive lead/acid battery electrode. This model consists of an agglomerate-of-spheres of the active material electrically connected by vase-shaped 'necks'. It has been claimed that for electrodes made from non-stoichiometric compounds - in particular PbO2 electrodes - there exists a certain combination of neck-and-sphere dimensions which, by the way of the non-stoichiometry, is thermodynamically stable. In the present paper this situation is discussed from a rigorous thermodynamic point of view. It is found that no sphere-neck configuration exists, representing an equilibrium state.