Positive plate additives

The various types of positive-plate additives and their effect are discussed in detail in Chapter 4. 

POSITIVE-PLATE ADDITIVES TO ENHANCE FORMATION AND BATTERY PERFORMANCE... 

Individual colonies are transferred to matching positions on additional plates. One plate contains tetracycline the other tetracycline and ampicillin. 

The Cracow forensic investigators took hair, presumably cut from inmates, and hair clasps from bags found by the Soviets in Auschwitz. Tested for cyanide residues, both hair and clasps showed positive results. Additionally, a zinc-plated metal cover was tested for cyanide and found to have a positive result as well. The Cracow Institute claims that this metal cover once shielded the exhaust duct of a sup-... 

Zonal processes are slow processes. They are responsible for the long duration of plate formation. Hence, it is important to find methods to by-pass the zonal processes. In order to accelerate the formation of positive plates, some conductive additives have been added to the positive pastes [28]. These additives increase the conductivity of the cured paste and formation proceeds almost uniformly throughout the whole plate volume as the electric current flows along the conductive additive network. The additives should be chemically stable in H2SO4 solution. Data have been reported about successful attempts to reduce the duration of the formation procedure to 8 h. 

This chapter reviews the effects of additives in the positive active-material of the lead acid battery. Common materials found in the oxide and the positive-plate paste, such as lead oxides, basie lead sulfates, and lead earbonate, are not included. Additives and impurities that derive from grid eorrosion or from the reaction of the plate with the electrolyte are also beyond the seope of this chapter. 

Table 4.2. Effect of additives on performance of positive plates in terms of Ah per kg active material [7].

One conductive additive which is relatively stable is barium plumbate (BaPbOs) [11]. This is a ceramic [12] with the perovskite structure and is easily made by standard ceramic-powder technology. Addition of this material to positive plates in a lead-acid battery significantly improves the formation efficiency. The formation mechanism is changed when the conductive particles are dispersed in the plate. Formation not only proceeds from the grid towards the centre of the pellet, but also takes place slowly around the conductive particles in the plate. The conductive paths of Pb02 grow and make connection with each other during formation to establish a network, which further facilitates the formation. 

The effect of loading of BaPb03 in a positive plate on the formation efficiency is summarized in Table 4.4. The data show that significant improvement in formation starts at a loading level as low as 0.5wt.%. This formation enhancement increases with BaPb03 loading and approaches a plateau. Beyond about 7wt.%, additional BaPb03 has no influence on the formation efficiency. 

Once the battery is formed, a stable conductive additive can enhance the current-acceptance of deeply discharged batteries. This has been demonstrated [12] by the addition of lOwt.% BaPbOs to a conventional positive plate made by adding... 

V. When subjected to a current-acceptance test to 2.67 V, the cell with BaPbOs in the positive plate and a control cell without the additive required 2 and 4 min, respectively, to accept 10 A. 

The conductive polymers were also tested at levels of 13 wt.% in a positive plate which contained PbS04, a-Pb02, and p-Pb02 [22]. The optimum concentration was found to be lwt.%. At 2 3 wt.% additive, the discharge capacity was increased by about 30% and the specific surface-area from 3-4 to 5-6m g. Cycle-life declined at additive concentrations above 5wt.% due to mechanical instability of the electrode. Polypyrrole and polythiophene oxidized during overcharge, but polyaniline remained stable. 

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