MODELING OF CYLINDRICAL ALKALINE CELLS .5. HIGH DISCHARGE RATES

A one-dimensional mathematical model of a AA size Zn-MnO2 alkaline cell is presented to describe nonisothermal, high constant current discharge conditions. The model accounts for the variation of the overpotential, current density, porosity, volume, average velocity, hydroxyl ion concentration, and zincate ion concentration throughout a complete cell, including the anode, cathode, and separator regions. This model is the first to examine the importance of the zincate ion concentration. Three variations of the model are presented: (i) the zincate ion is restricted to the anode region, (ii) the zincate ion is unconfined in the cell, but can precipitate as ZnO in the anode, and (iii) the zincate ion is unconfined in the cell but can precipitate in both the anode and separator. Experimental data are best represented by model (iii). Pore plugging, particularly in the separator, has been found to be an important factor limiting cell performance. Additionally, the sensitivity of several parameters on the cell performance is evaluated.