Positive tubular plates manufacture

Many manufacturers around the world offer tubular-plate gel batteries for heavy-duty RAPS operations. As the name suggests, the batteries have tubes that contain the plate material. This design is employed only for the positive plates, as these are... 

The tubular-plate technology is used in the manufacture of traction and stationary batteries. Figure 2.53 shows die main stages involved in the classical production process of mbular plates. Only the preparation of positive plates will be described briefly, since the other technological stages are identical to those discussed for flat-plate batteries. 

Flat plate and tubular positive plate cells are produced for stationary duty, but where reliability is a prime consideration, Plante cells are used. In a Plants cell, the positive electrodes are manufactured by a quite different process. The oxide is formed by electrochemical oxidation (say, 10 mA cm for 20 h) of a lead baseplate or grid, often shaped to increase its surface area, in an electrolyte which contains sulphuric acid and an anion (perchlorate or nitrate) wliich forms a soluble Pb " salt. This leads to a layer of thick porous oxide the nitrate or perchlorate is present to prevent total passivation of the lead surface. The resulting plate, thickness 6—12 mm, is then reduced to form spongy lead metal, is washed thoroughly, and is recharged when in a fabricated cell. The active material formed in this way adheres to the base lead better than pasted materials and therefore cycles more reUably. Against this, there is less active material on each plate and, inevitably, the energy density of the battery will suffer 7—12 Wh kg is typical. 

Ftat plate and tubular-positive plate cells arc produced for stationary duty, but where reliability is a prime consideration, Plante cells are used. In a Planti cell, the positive electrodes are manufactured by a quite difTerent process. The oxide is formed by clectrochemica] oxidation (say, 10 mA cm for 20 h) of a lead... 

It is characteristic for battery manufacture that lead dioxide (Pb02) as the charged state of the active material is always generated by electrochemical oxidation. Thus, electron-conducting bridges are established between the fine particles, and a matrix is formed of comparatively low electronic resistance. Three general types of positive electrodes are mainly used today Plante, pasted, and tubular plates, which vary not only in their design but also in the way they are manufactured. 

The production of tubular positive plates is in principle similar to that of pasted plates. A number of manufacturers use the same gray oxide as the basic filling substance. Sometimes the share or red lead or minium (Pb304) is increased above 25 or even to 100wt.%. The latter is more economic when the manufacturer runs his own minium plant then the expense of the chemical oxidation of lead oxide (PbO) to minium (Pb304) may be compensated by reduced formation cost. Furthermore, curing is not required, because of the high oxidation state, and the battery starts with full capacity when formed. 

Gravity casting of grids is usually employed for the manufacture of flat positive plates. Flat positive lead-calcium-tin grids are more sensitive and more prone to corrosion than tubular grids. Nevertheless, it must be pointed out that even for batteries with flat positive plates, corrosion has been only one of the limiting factors during standby applications. 

The grids of both flat-plate and tubular batteries should not contain antimony or any other additive that may decrease the hydrogen overpotential of the negative electrode. Indeed, it is recommended that ultra-pure lead be used to manufacture both the grids and the active material in order to avoid the possibility of excessive self-discharge at either the positive or the negative plates. 

Both the positive and negative tubular and pocket current collectors are made of perforated nickel-plated steel. They are very robust and are virtually indestructible. The low energy density, poor charge retention, and poor low temperature performance, along with high cost of manufacture, have led to a decUne in use of the nickel-iron battery system. The negative electrode, or anode, is iron and the positive... 

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