Structural Parameters of β ‐ PbO2 and Their Relationship to the Hydrogen‐Loss Concept of Lead‐Acid Battery Failure

Publisher Website
Google Scholar
Abstract
Full‐profile, Rietveld‐type, x‐ray powder diffraction studies have been performed on samples either prepared chemically or obtained from batteries operated under simulated electric vehicle service at 25° and 50°C. After a sharp initial decrease, the unit cell volume and cell edge ratio of battery assume relatively stable values which are both independent of the battery capacity and indistinguishable from those of chemically prepared material. A comparison of the observed unit cell volumes with values calculated for given levels of O2−/(OH)−, Pb4+/Pb2+ coupled substitution in the structure indicates that the maximum amount of this substitution is about 0.01 atoms of hydrogen per formula unit. These results suggest that the decline in battery capacity is not a function of the loss of a hydrogen species from the crystal structure of electrochemically active . Estimates of the changes in crystallite size as a function of battery cycling history show that batteries began service with crystallite sizes of around 250Å, irrespective of the temperature of operation, but increased to values of about 700 and 900Å at 25° and 50°C, respectively. Since this increase in crystallite size occurred well before battery failure, the loss in battery capacity with cycling cannot be correlated with the changes in crystallite size and, therefore, with changes in the degree of structural order of the active material.

This publication has 0 references indexed in Scilit: