A MATHEMATICAL-MODEL OF THE OXYGEN-RECOMBINATION LEAD-ACID CELL

A one-dimensional mathematical model of the oxygen-recombination lead-acid cell is developed. The model is applied to investigate mechanisms associated with oxygen recombination and species transport during charge. The conditions for rapid transport rates of gaseous oxygen through the separator and dissolved oxygen through the liquid film within the Pb electrode are considered, and these rates are rapid for the conditions investigated. Model predictions show that during charge gas volume increases in the Pb electrode and decreases in the PbO2 electrode. At the onset of oxygen recombination during constant-current charge, the polarization of the Pb electrode is reduced, which results in the prediction of a maximum in cell voltage. This voltage behavior is demonstrated experimentally. The prediction of a voltage maximum by the mathematical model occurs when the recombination mechanism is the direct electrochemical reduction of oxygen at the Pb electrode. Model simulation with another recombination mechanism in which oxygen reacts chemically with lead to form lead sulfate does ndt produce a voltage maximum. A decrease in the amount of gas space surrounding the cell results in predictions of increased Pb-electrode depolarization.