Lead Sulfate Crystals Research Articles

Modeling the Recharge Kinetics of the Positive Electrode Active Mass of a Lead‐Acid Battery

A mathematical model has been developed and compared with experimental data from the literature. A characteristic fourfold increase in the Tafel slope with increasing current density found in the experimental polarization curves is predicted by the model. The model is based on the assumption that the positive active mass has a structure with microporous agglomerates forming a macroporous skeleton. During charging, lead ions dissolve from the surface of the lead sulfate crystals, diffuse through the skeleton and into the agglomerates, and finally react on the . The fourfold increase of the Tafel slope is attributed to the combined effect of strong pore diffusion resistance in both macro‐ and micropores. In other respects as well, the model is consistent with published kinetic data.

Discharge behaviour of electrodeposited PbO 2 and Pb electrodes

The discharge behaviour of electrodeposited lead dioxide and lead electrodes was investigated under various conditions; the surfaces of the discharged electrodes were observed with a scanning electron microscope. Both the positive and negative electrodes were passivated by a covering of deposited lead sulphate crystals. The amount of lead sulphate required for passivation depended on the size of the crystals.

Recharge Kinetics of the Porous Lead Dioxide Electrode: II . The Effect of Sulfuric Acid Concentration

Anodic polarization curves for partially recharged porous lead dioxide electrodes have been recorded at different sulfuric acid concentrations. These curves can be fitted by the rate equation for two consecutive single‐electron transfer reactions. The dependence of the two exchange current densities on the sulfuric acid concentration is strongly negative. The apparent electrochemical reaction order for the first transfer step approaches −3 as the sulfuric acid concentration approaches 7M. The polarization curves also depend on the acid concentration during the previous discharge. At the same current density, the overvoltage at recharge in was much higher when the electrode had been discharged in compared to a discharge in . This effect can probably be attributed to the larger lead sulfate crystals formed at lower sulfuric acid concentrations.

The surface morphology of ion-selective membrane electrodes: Part 3. Studies on the Lead Ion-selective Membrane

Studies of the changes in the surface state of the ion-selective membrane and in the performance of the silver sulphide-lead sulphide (2:1) precipitate-based electrode are described. A scanning electron microscope was used to examine the surface of the electrode membrane. The results indicate that passivation of the lead-selective electrode caused by chemical and electrochemical oxidation is due to transformation of the lead sulphide at the membrane surface. The electrode surface becomes depleted in lead sulphide; lead sulphate crystals are formed during chemical oxidation with hydrogen peroxide, and lead oxide crystals during anodic oxidation.

Electrochemical cycling of pasted antimonial lead electrodes (positives)

The behaviour of Pb-5% Sb positives during electrochemical cycling experiments is followed using a combination of linear sweep voltammetry and potentiostatic pulse experiments. The poor charge acceptance of antimonial lead is discussed in terms of the morphology of the lead sulphate crystals. A comparison is made between unpasted and pasted Pb-Sb electrodes.

Discharge behaviour of electrodeposited PbO 2 and Pb electrodes

The discharge behaviour of electrodeposited lead dioxide and lead electrodes was investigated under various conditions; the surfaces of the discharged electrodes were observed with a scanning electron microscope. Both the positive and negative electrodes were passivated by a covering of deposited lead sulphate crystals. The amount of lead sulphate required for passivation depended on the size of the crystals.

The behaviour of the lead-aqueous sulfate electrode in relation to the development of electric vehicle batteries

The behaviour of smooth lead electrodes in various aqueous sulfate electrolytes has been studied by slow scan (10 mV min-1) cyclic voltammetry and coulometry and by scanning electron microscopy. The dependence of the amount of charge that can be delivered in discharge of lead to form lead sulfate, as in a lead-acid battery, is found to depend strongly on electrolyte composition, and an acidic ammonium sulfate electrolyte (0.5 mol dm-3, pH 2.0) was found to yield the highest charge over some 40 charge-discharge cycles when compared with various other sodium sulfate, ammonium sulfate and sulfuric acid electrolytes. The quantity of charge was directly related to the size of the lead sulfate crystals produced. This result is interpreted in terms of the passivating effect of lead sulfate. A tentative mechanism for the anodic formation of lead sulfate is proposed and used to interpret the cyclic voltammograms obtained in concentrated sulfuric acid.

A method of growing large lead sulfate crystals

Single crystals of lead sulfate (anglesite) up to 1 cm × 3 mm × 3 mm have been grown from 1 molar perchloric acid in a period of four months.

A mathematical model for the porous lead dioxide electrode. II. The pseudo-steady state approach for low rates of discharge

A theoretical analysis of the discharge behaviour of the porous lead dioxide electrode at low current densities is made on the basis of a previously proposed model. The pseudo-steady state approach proves to be useful for low rates of discharge, while it fails for rapid discharges. The current distribution at low rates of discharge becomes non-uniform during discharge because of concentration changes and decreasing porosity. The maximum of the current distribution moves inwards into the electrode during discharge, as a result of the gradual insulation of the electrode surface by lead sulphate crystals. At the end of a slow discharge the electrode material has been uniformly utilized along the depth of the electrode, provided that the porosity is sufficiently high. If, however, the initial porosity is less than about 50% the inner parts of the electrode may not always be fully utilized because of the extensive plugging of the pores by lead sulphate crystals.

A mathematical model for the porous lead dioxide electrode

A theoretical model for the porous lead dioxide electrode is proposed on the basis of the macrohomogeneous model for porous electrodes. The structural changes during discharge, due to precipitation of lead sulphate, are considered. The two main structural effects, plugging of the pores and gradual insulation of the active electrode surface by the reaction product, lead sulphate, are both considered by relating them to the local degree of discharge. The numerical results show that, at high current densities, the discharge capacity is limited by both structural and transport restrictions. At the end of discharge a layer of lead sulphate crystals blocks the electrode surface in the outer layers of the electrode. The current can then neither be transferred across this insulated surface nor reach remaining active material in the inner parts of the electrode because of acid depletion, which is furthermore accelerated by the decreasing porosity.

The Mechanism of the Aging of Freshly Prepared Lead Sulfate Crystals

The Mechanism of the Aging of Freshly Prepared Lead Sulfate Crystals