Positive active mass structure

An important result of these studies was the discovery that a lack of antimony has not only an effect on the grid/positive-material interface, but also on the whole crystalline structure of the positive active mass [43] and on the so-called mass softening process. Nowadays deleterious effects that are promoted by using grids without antimony are collectively termed premature capacity loss (PCL). There has been much research effort worldwide to overcome the PCL problem [47]. 

The above-described structure of the lead dioxide particles is likely to exert an influence on the electrochemical and chemical processes that proceed in the positive active mass on charge and discharge, as well as on the behaviour of the positive plates in sulfuric acid solution. 

Employing scanning electron microscopy and porometry we have examined the strueture of the positive active mass after formation and during cycling of the plates and have proposed a model for this structure [22—25]. Figure 10.16 presents SEM pictures of PAM at high magnifications. 

Shedding positives I active mass structure, battery design O number of cycles, depth of discharge, charge factor... 

FORMATION OF LEAD-ACID BATTERIES AND STRUCTURE OF POSITIVE AND NEGATIVE ACTIVE MASSES... 

In this Chapter, the discussion is confined to the processes that occur during soaking and formation of the positive and negative plates, as well as to the structures of the two types of active mass obtained as a result of the formation procedure. These steps are identified in the dashed-line frame in Fig. 3.1. 

The delivery of too much overcharge can also result in damage to the positive active-material [24]. It has been suggested that the vigorous evolution and movement of gas as a result of this process can disrupt the internal structure of the active material. The related decrease in performance has been explained in terms of a loss of electrical conductivity within the positive plate due to progressive expansion of the active mass. 

The manufacture of positive battery plates is essentially a process of oxidation of 3Pb0 PbS04 H20 or 4Pb0 PbS04 and PbO to a-PbOi and P-Pb02. This technological process is called formation. Now let us discuss the structure of the Pb02 active mass obtained as a result of formation. 

How would electrolyte stratification affect the structure and composition of the active masses The data in Figs 3.16 and 3.17 indicate that the electrolyte in the bottom part of the cells reaches a concentration of 1.35 g cm . As evident from Fig. 3.11, the positive plates get progressively passivated at acid concentrations higher than 1.28 g cm. Furthermore,... 

The lead dioxide active mass has a fairly complex structure, sensitive to foreign substances, which may degrade or get passivated under the action of even small amounts of additives to the positive paste, respectively to PAM. That is why the number of additives to the positive paste is limited and their effect is not always unambiguous. 

Active mass utilization coefficient, (rj). This coefficient gives the share (by weight) of the energetic structure in the total amount of positive or negative active mass per cell ... 

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