Manufacture of the Active Material

The production of the active material for positive and negative electrodes starts with the same substance, a mixture of lead oxide (PbO) and metallic lead called gray oxide or lead dust. It is a fine powder that contains 20-30 wt.% of lead (Pb). The size of the primary particles is in the range of 1-10 /an. Larger agglomerates are usually formed. 

Gray oxide can be produced by a milling process, which, strictly speaking, does not mill the material. A rotating drum is filled with solid balls or ingots of lead. 

Flakes are shared, crushed, and at the same time partly oxidized by an airstream that flows through the drum. Temperature and airflow rate are used to control the process to achieve the desired powder. At the end the oxidized material is carried away by an airstream and classified. Particles that are too coarse are fed back into mill. 

Another process, the Barton process, is based on molten lead. The core of such a device is the Barton reactor , a heated pot that is partly filled with molten lead. It is continuously refilled by a fine stream of molten lead. Fine droplets of lead are produced by a fast rotating paddle that is partly immersed under the surface of the molten lead within the Barton reactor . The surface of each droplet is transformed by oxidation into a shell of PbO by an airstream that simultaneously carries away the oxidized particles if they are small enough otherwise, they fall back into the melt and the process is repeated. Thus the airstream acts as a classifier for particle size. 

A short description of both processes is given in Ref. [16]. Nowadays, the Barton process is preferred for a number of reasons it can more easily be installed in small units and it can be controlled faster [17]. (In a mill it takes a number of hours for the material to run through the drum, so controlling actions are slow). 

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Lead oxide (PbO) (also called litharge) is formed when the lead surface is exposed to oxygen. Furthermore, it is important as a primary product in the manufacturing process of the active material for the positive and negative electrodes. It is not stable in acidic solution but it is formed as an intermediate layer between lead and lead dioxide at the surface of the corroding grid in the positive electrode. It is also observed underneath lead sulfate layers at the surface of the positive active material. 

Basic sulfates are important intermediates during the manufacturing process, since they determine the structure of the active material in the positive electrode, which again is decisive with respect to the... 

It is characteristic for battery manufacture is that lead dioxide (Pb02) as the charged state of the active material is al-... 

Depending on the composition of the active materials and on the manganese dioxide type employed, the OCV of freshly manufactured zinc-carbon cells with salt electrolyte varies between 1.55 and 1.85 V. It decreases during discharge and formation of the variable-composition mass. Upon prolonged storage of undischarged batteries, their OCV also decreases. 

Cylinders have the advantage that they are cheap to manufacture. In addition to varying the shape, the distribution of the active material within the pellets can be varied, as illustrated in Figure 6.7. For packed-bed reactors, the size and shape of the pellets and the distribution of active material within the pellets can be varied through the length of the reactor to control the rate of heat release (for exothermic reactions) or heat input (for endothermic reactions). This involves creating different zones in the reactor, each with its own catalyst designs. 

Battery price is calculated on the basis of the material and manufacturing costs. The cost of the active materials is directly related to their availability. With the exception of Na-S, Fe-air, and a few other exploratory systems, all EV battery candidates are based on materials whch are either not too abundant worldwide, reside in diluted ores, or can be extracted viably only from ores located geographically in a few areas. The Imports may be subject to politically Induced shortages or stoppages, in analogy to the gasoline situation. In some cases, even the domestic resource utilization may become prohibitive because of the environmental impact. 

It is expected that the principles of GMP be observed throughout all stages of the manufacture of the active pharmaceutical ingredients. However, full evidence of GMP compliance should be given from the step from which the process or the raw materials used, have an influence on the quality of the active pharmaceutical ingredient. This step should be determined in each individual case in agreement between the competent authority and the manufacturer. 

The capacity and cycle life of the battery depend greatly on the structure of the active materials. Hence, it was important to examine the structure of the two types of active masses and to elucidate how it was formed during the technological process of plate manufacture. 

Batteries of this type have been developed with film, tablet, and cylindrical designs. In the first type, the electrolyte film is applied onto the metal anode or cathodic current collector by sputtering or vaporization. The tablet and cylindrical batteries designed for comparatively high drain rates employ porous electrodes manufactured by pressing a mixture of the powders of the active materials (silver or polyiodide), electrolyte, and conductive additive (carbon black, etc.). 

One of the battery prototypes for electric vehicles had a volume of 3201 and mass of 820 kg. The positive electrode is manufactured from FeS with the addition of C0S2. A few layers of the active material alternating with graphitized fabric are placed into a basket of molybdenum mesh welded to the central molybdenum current collector. The positive electrode is wrapped into a two-layer separator. The inner layer consists of Zr02 fabric and the outer layer of BN fabric. The negative electrode consists of a lithium-silicon alloy in the porous nickel matrix. The container and the cover are manufactured from stainless steel and electrically connected to the negative electrode. The prototype was drained with current up to 50 A, and the specific power was as high as 53 W/kg (Martino FJ et al, 1978). 

The cell chemistry is the driving factor for battery cost once the power and energy requirements have been specified. The relative cost of the active materials for specific cell chemistries clearly affects the end price of a battery. Perhaps more importantly, the performance of the cell chemistry directly impacts the material requirements, both active and inactive, that in turn determine the size of the manufacturing process. This subsection will explore the cormection between performance and cost to illustrate that high cell voltage and specific capacity with specific low impedance drives down costs in a multitude of ways. In other words, this section demonstrates that factors that increase energy and power density lower battery cost. 

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