DISCHARGE BEHAVIOR OF TUBULAR PBO2 ELECTRODES .1. EXPERIMENTAL INVESTIGATIONS

The discharge behavior of tubular lead dioxide electrodes has been experimentally studied by means of electrochemical measurements, scanning electron microscopy, and electron probe microanalysis in order to investigate how the utilization of these electrodes is affected by the geometry, current load, and the tube envelope. Structural and kinetic parameters have been evaluated from polarization measurements at different concentrations. The one-dimensional initial current density distribution could be satisfactorily described by a macrohomogeneous model with a cathodic transfer coefficient equal to two and an initial volumetric exchange current density, S(o)j(o) [Am-3], that varied with the concentration according to the equation log(S(o)j(o) = 5.12-0.37c for 1 < c < 5.1M. It was found that the cell geometry only has a minor effect on electrode performance at high and medium current loads iri comparison to the effects of the tube envelope. Current constriction in the pores of the fabric causes three-dimensional growth of dendritic lead sulfate crystals and severe hindrance to both migration and diffusion. The initial local current density as well as the utilization of the lead dioxide were found to be higher in the exterior parts of the electrode in the same way as that for flat, pasted electrodes.