Current Distributions in Soluble Battery Electrodes: I . Theoretical

A mathematical model is developed concerning the reaction profile in soluble porous electrodes, and the reaction profiles in a zinc-zincate electrode are calculated for a set of typical electrode parameters. The results show that considerable differences in current distribution exist during charge and discharge processes. The physical origin for the differences could be traced to a resistivity change in pore electrolyte and to a change in interfacial reaction resistance at the electrolyte and pore matrix surface. The electrolyte resistivity change is caused by a chemical reaction between the pore electrolyte and the product species of the electrochemical reaction on the pore wall. The calculation suggests that the pore strcture of an alkaline zinc electrode will change during charge and discharge cycles even in a relatively small current region where no passivation film is formed.