Experiments were conducted to characterize critical processes which determine performance of totally immersed, porous, secondary electrodes having sparingly soluble reactants. Particulate beds comprised of silver spheres, 37.7 -+-4.2 ~m in diameter, were used as Ag/AgC1 electrodes in 1N KC1. Silver chloride product distribution and facial potential as functions of time during galvanostatic charging are compared to predictions of a recently developed mathematical model. Good accord is shown over the tested time range, 1-19 rain, and exterior current density 50 mA cm-~. Time for onset of pore blockage with failure to accumulate charge, about 18 rain, and the reaction penetration, mostly less than 0.03 era, are predicted with reasonable accuracy. A characteristic minimum in polarization occurs during galvanostatic discharge due to reduction in pore blockage at the beginning of discharge, increase in KC1 concentration in the depth of the electrode, and increase in effective matrix electronic conductivity with silver deposition. A final rise in polarization occurs when silver chloride is depleted. Theory is used to show how governing rate processes are shifted by the occurrence of blockages of the first and second kinds.) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 128.6.218.72 Downloaded on 2015-06-06 to IP Vol. 123, No. 9 ANALYSIS OF POROUS ELECTRODES Basis of parameter selection Measured Approximate measured value Measured Measured Estimated from photomicrographs Approximate, measured value, Ref. (13)Calculated from porosity and sphere diameter, Ref. (15) Calculated from porosity and sphere diameter, Ref. (15) Calculated from estimated diffusion coefficient, Ref. (12), and diffusion path, Ref. (13) Best value fitting data From Ref. (12) where A is specific surface area in era-1 and from assumption of 0.9 coverage factor, Fig. 8 Assumed functional dependence and mode change at 0.9, Fig. 8 Geometrical reasoning, e.g., Ref. (21)9 A parabolic decrease with distance is a~sumed for the porosity change at depths from 0 to 0.45 mm as an approximation based o• photomicrographs. 9 * Surface is calculated according to ReL (15) from the porosity and sphere radius for depths from 0 to 0.45 ram.) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 128.6.218.72 Downloaded on 2015-06-06 to IP