DISCHARGE BEHAVIOR OF TUBULAR LEAD DIOXIDE ELECTRODES .2. 2-DIMENSIONAL CURRENT-DENSITY DISTRIBUTION

The initial current density distribution in lead acid batteries with t ubular lead dioxide electrodes and flat lead electrodes has been studi ed by means of a two-dimensional model and experimental verification b y polarization curves and potential transients during galvanostatic di scharge. The cell geometry was modelled with and without separators an d a tubular electrode envelope. The governing equations were solved wi th a finite element method. It was found that the tube envelope has a large impact on the current density distribution and had to be incorpo rated into the model to fit the experimental results. Although the env elope increases the ohmic losses, it has the positive effect of giving a more uniform current distribution around the electrode tube, A lead acid cell with tubular positive electrodes and flat negative electrod es can therefore be approximated by a one-dimensional model consisting of a positive electrode tube placed concentrically in a cylindrical l ead electrode, The two-dimensional model was further used to study the effects of different design factors, for example, cell width and kine tic parameters of the lead dioxide electrode.