A mathematical model which describes the transient behavior of porous zinc electrodes has been developed on the basis of concentrated ternary electrolyte theory. The model predicts the current distribution, potentials in the solution, concentrations of hydroxide ion and zincate ion, porosity, and volume fractions of zinc and zinc oxide as a function of time and position perpendicular to the surface of the electrode. Numerical techniques were used to predict zinc electrode behavior during galvanostatic operation of the cell with and without a membrane. During discharge of the cell without a membrane, much of the discharge product, zincate ions, are lost into the counter‐electrode compartment. For the cell with a membrane, this zincate loss is effectively restricted, but the utilization of zinc is severely limited by depletion of hydroxide ions within the zinc electrode compartment. In both cases, the reaction profiles are highly nonuniform and the reaction zone, located near the electrode surface, is very thin. This highly nonuniform reaction distribution accentuates the failure due to electrolyte depletion in the interior of the porous electrode, resulting in the low discharge capacity. On repeated cycling, the difference in anodic and cathodic reaction distribution causes the redistribution of solid zinc and zinc oxide species.

Experiments were conducted to characterize behavior and failure mechanisms of porous zinc electrodes, prepared by pressing amalgamated zinc powder of particle size ranging from 250 to 325 mesh. The zinc test electrodes were disks with a cross‐sectional area of 1 cm2 and a thickness of 0.1 cm. Distribution of zinc and normalZnO , and electrode overpotentials were measured during galvanostatic discharge in 40 normalw/normaloKOH solution saturated with normalZnO . The observed reaction profiles were highly nonuniform and the reaction zone, located near the electrode surface, was very thin, typically 0.2 mm. The utilization of the present electrodes was very sensitive to the applied current density, initial porosity, amount of electrolyte, and the type of membrane. The measured reaction profiles and overpotentials were compared with the theoretical predictions of a recently developed mathmatical model. The agreement between observations and predictions provides a good interpretation of the discharge failure modes of negative zinc electrodes.

The potential distribution in thin electrodes of the automotive battery type was determined experimentally and predicted from a model. Potentials at various locations on the plates were measured in cells at various discharge rates and for different plate widths. A model, based on the application of Kirchoff's law to each intersection of grid members, was solved numerically to predict potential distribution. The measured and calculated potential distributions were in excellent agreement. The implications of the model are discussed with emphasis on the interaction between grid design, grid weight, and plate performance. Performance is measured in terms of the maximum (i.e., the tab‐to‐corner) ohmic potential loss.

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Current density and electrolyte distributions were investigated in a lead‐acid cell of the industrial motive power type. The current density distribution was calculated from the measured potential distribution using a treatment based on the terminal effect. Results show that the current density is strongly nonuniform and dependent on plate height. The acid density distribution was measured directly under both stationary and circulating electrolyte conditions over a range of discharge rates. Analysis of the data confirms that, under stationary conditions, stratification develops due to natural convection and shows that the electrode capacity is limited by the availability of electrolyte within the electrode pores.