Hydration and Amorphization of Active Mass PbO2 Particles and Their Influence on the Electrical Properties of the Lead‐Acid Battery Positive Plate

Abstract

Through TEM observations it was established that PbO2 particles of the positive active mass are heterogeneous in mass distribution. Using electron micro‐micro‐diffraction it was found that PbO2 particles are built up of zones of α‐normaland/normalorβ‐PbO2 crystal structure with various orientation, and of amorphous zones. The latter are more transparent for the electron beam and are assumed to be hydrated. It was determined, through XPS (x‐ray photoelectron spectroscopy), that at least 30% of the PbO2 surface is hydrated. The changes in the crystal part of the active mass particles are followed during charge, discharge, open circuit, and overcharge. It was established that H2SO4 adsorption on the surface of the particles brings about an increase in their amorphous part. When the positive active mass is washed, its crystal part increases. It was also found that O2 causes amorphization of the particles, too. Oxygen atoms are sorbed by the PbO2 particles and increase their zones of disorder. A mechanism of formation of PbO2 particles during battery charge is proposed taking into account the processes of dehydration. OH− ions are assigned a considerable role in the interaction of the particles with the solution or with the neighboring particles.

The stability of hydrous oxide films on platinum

“…The material is probably only poorly crystallized, with the outer regions of the microparticles more dispersed, hydrated -and therefore more accessible to hydroxide ions -in base, than the interior. Strong evidence to support this view of oxide systems was obtained [10] in recent electron microscopy studies of battery grade PbO2. It was suggested earlier [6] that the following type of equilibrium may be involved in the case of platinum, viz.…”

The influence of F− doping on the activity of PbO2 film electrodes in oxygen evolution reaction

“…At the PbO 2 /solution interface, PbO 2 has been shown to consist of a partially hydrated gel layer [16][17][18], generated by the following equilibrium process:…”

Electrocrystallization of lead dioxide: Influence of early stages of nucleation on phase composition

“…Particular attention should be paid to ionic additives in high oxidation states +3, and +4 (compared to places of cation vacancies of lead dioxide, in which Pb 2+ -ions are known to be localized). It is recognized [8][9][10][11], that there are two zones on the lead dioxide surface: crystal (PbO 2 ) and hydrated [PbO(OH) 2 ], that are in equilibrium and are capable to exchange cations and anions with the ions present in the bulk. Lead ions replacement both in hydrated and crystal zone would cause not only the change of amount of oxygen-containing particles in each zone, but their binding energies, that in turn will change the electrocatalytic activity of materials.…”