The work presented in this thesis describes the development of a mathematical model for the porous lead dioxide electrode. The model follows on from those of previous workers and in particular, the model by Daniel Simonsson which is thought to be one of the most comprehensive to date. It has been convenient to divide the modelling into three aspects: mass transport, kinetics and the effects of structural changes within the porous matrix, and each of these is considered separately. It is concluded that all three aspects should be modelled to the same level of precision. At the level of modelling dictated by current knowledge of the kinetics of the local electrode reactions, mass transport can be adequately described by the equations of dilute solution theory. However, it is shown that the choice of kinetic expression is crucial and that the reverse reaction term (ie. the anodic reaction during cathodic discharge) cannot be neglected. The effects of structural changes are taken into account by developing a model based on the theory of electrocrystallisation. The discharge curves produced show the characteristic initial voltage dip known as the coup de fouet which is commonly observed in actual battery plate discharges and is attributed to nucleation phenomena.