Active Materials for Lead—Acid Cells

Calculation of the Active Materials for Lead—Acid Cells 609... 

SEM micrographs for micro-structured and nanostructured Pb02, the cathode active material of lead-acid cell. (Reprinted with permission from /. Power Sources, 158, J. Morales et al.. Synthesis and characterization of lead dioxide activematerial for lead-acid batteries, 831-836, Copyright 2006, Elsevier.)... 

Fig. 5.6 (a) Tubular plates for lead-acid cells, (b) Cross-section showing central lead current collector, active material and porous separators... 

Most battery systems employ carbon materials in one form or another, as noted in Table 10.1. The use of carbon materials in batteries stretches across a wide spectrum of battery technologies. The variety of carbon runs the gamut from bituminous materials, used to seal carbon-zinc and carbon black powders in lead acid batteries, to high performance synthetic graphites, used as active materials in lithium-ion cells. The largest use is as a conductive diluent to enhance the performance of cathode materials. In many instances, it is used as a conductive diluent for poorly conducting cathode materials where carbon blacks, such as acetylene black, are preferred. It is essential that... 

There are three active materials in the lead—acid battery Pb, Pb02 and H2SO4 electrol de. One, or rarely two, of these active materials limit the cell capacity on discharge. Most often, the capacity-limiting active material is the one with the highest utilization coefficient. Let us assume that this rule holds for the three active materials in the lead—acid cell. 

This is, in brief, the basic knowledge to be used for calculating the amounts of active materials needed for the production of a lead—acid cell. 

For many years, cells with electrolyte gelled by the addition of sodium siUcate or sulphuric acid adsorbed onto a felted glass fibre mat or thick paper have been manufactured such cells avoid the hazards of acid spillage and were sold mainly for aircraft or motorbikes. Now cylindrical lead/acid cells, typical capacity 2 A h and without free electrolyte, are produced to compete with small Ni/Cd and primary cells for the consumer market. These cells are spirally wound (as a Swiss roll) with electrodes of thin, pure lead sheet perforated to increase the amount of pasted active material adhering to the metal and an adsorbent glass fibre paper separator, packed into a metal can. 

Figure 1.19 represents the theoretical maximum amount of energy that a lead-acid cell can deliver. For 1 kWh to be delivered by a theoretical lead-acid battery cell, 6.15 kg of active materials are needed for the reaction. To transform this theoretical cell into a practical power source, however, a number of technical components are necessary such as grids, separators, battery container, valve, H2SO4 diluted with water in excess amount, etc. 

The starved system, porous separator and oxygen recombination allow efficient space utilization for active material in the spiral-wound sealed lead-acid cell, resulting in a 15-50% increase in volumetric energy density over gelled-electrolyte systems. 

Another study [40] examined the effect of adding lOg of natural graphite with a grain size of 520 pm to positive plates in 4.5-Ah VRLA cells. The active material was prepared by mixing 2kg of leady oxide and 0.8 g of polyester fibre with 150 ml of water and then 271ml of 1.200 rel. dens, sulfuric acid. The pastes were applied to lead-caldum tin grids, cured at 80°C for 72 h, and dried in air. The test cells, composed of one positive and two negative plates, were formed and then floated at a... 

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