Nickel-cadmium battery separator

One version of the microporous, filled polyethylene separator ( PowerSep ) [113], which is so successful in the lead-acid battery, is also being tested in nickel-cadmium batteries. This separator is manu-... 

Jahn-Teller distortions 309 ff Japanese separators 264, 267 Joule effect, heat losses 13 jump frequency, solid electrolytes 532 Jungner nickel cadmium batteries 22... 

Subcategory A encompasses the manufacture of all batteries in which cadmium is the reactive anode material. Cadmium anode batteries currently manufactured are based on nickel-cadmium, silver-cadmium, and mercury-cadmium couples (Table 32.1). The manufacture of cadmium anode batteries uses various raw materials, which comprises cadmium or cadmium salts (mainly nitrates and oxides) to produce cell cathodes nickel powder and either nickel or nickel-plated steel screen to make the electrode support structures nylon and polypropylene, for use in manufacturing the cell separators and either sodium or potassium hydroxide, for use as process chemicals and as the cell electrolyte. Cobalt salts may be added to some electrodes. Batteries of this subcategory are predominantly rechargeable and find application in calculators, cell phones, laptops, and other portable electronic devices, in addition to a variety of industrial applications.1-4 A typical example is the nickel-cadmium battery described below. 

Starved electrolyte battery — A -> battery with minimum amount of -> electrolyte. The electrolyte in starved electrolyte cells or batteries exists in the porous structure of the - electrodes and absorbed in the separator, so it contains little or no free fluid electrolytic solution. This type of batteries is used in certain constructions of sealed - lead-acid and -> nickel-cadmium batteries that rely on gas diffusion and recombination on the electrodes during charging or overcharging in order to maintain maintenance-free conditions, and to suppress pressure buildup. Starved electrolyte batteries benefit from larger - energy density due to the reduced amount of electrolyte. This design may suffer from poor heat dissipation compared with -> flooded batteries, thus for high power applications this point has to be taken into account. 

Figure 10.14 The construction of a cylindrical nickel/ cadmium battery. Key A, seal By positive terminal C, cell lid D, connection to positive plate E, cell case Fy positive plate G, separator H, sintered metal foil Iy negative paste Jy connection to negative plate. Diagram supplied by Berec Ltd.

Zirconia fiber cloths, such as those made by the relic process (see Chapter 8), are used as separators in aerospace nickel-hydrogen and nickel-cadmium batteries [9j. These fibers display a high resistance to many corrosive media, including hot potassium hydroxide. Zirconia fiber felts are also present in aerospace solid oxide fuel cells. 

The origins of this book go back to two-day seminars on batteries taught at the Technical Academy of Esslingen. In 1980, Expert Verlag published the hrst edition of Batteries. By 1983, a revised second edition was necessary. The chapters dealing with primary batteries and small rechargeable batteries (lead-acid and nickel-cadmium batteries) were published at the same time as a separate book. Portable Batteries, which now constitutes the second half of this volume. 

Application of absorbent-glass-mat separators (AGM) that are soaked by the acid so that liquid acid is not left within the cell. In alkaline electrolyte, polyamide or polypropylene fibers form corresponding mats that are used, for example, in sealed nickel/cadmium batteries (Section 1.8.2.2). 

With use over time, a nickel-cadmium battery gradually loses eapacity, resulting in a gradual increase in internal resistance. This is caused by gradual deterioration of the separator and electrodes and by loss of liquid through the seals, which changes the electrolyte concentration and level. The net effect is an increase in internal impedance. 

An aqueous solution of potassium hydroxide is the major component of the electrolyte. A minimum amount of electrolyte is used in this sealed cell design, with most of the Uquid absorbed by the separator and the electrodes. This starved-electrolyte design, similar to the one in sealed nickel-cadmium batteries, facilitates the diffusion of oxygen to the negative electrode at the end of the charge for the oxygen-recombination reaction. This is essentially a dry-cell construction, and the cell is capable of operating in any position. 

One version of the microporous, filled polyethylene separator ( PowerSep ) [113], which is so successful in the lead-acid battery, is also being tested in nickel-cadmium batteries. This separator is manufactured largely in the same way and also has similar properties to those described in Section 11.2.2.1. Of course, silica cannot be used as a filler, but has to be replaced by an alkali-resistant substance, for example, titanium dioxide. The resulting separator membrane excels, with very small pore sizes and low electrical resistance as well as outstanding mechanical properties. A comprehensive presentation of the different separation materials follows in Section 11.3.5. 

Comparison cf vented lend-aeid and nickel-cadmium batteries for standby and motive power applications A niekel-eadmium battery eontains plenty of electrolyte. Positive and negative electrodes are kept apart by separators whose only purpose is to keep the electrodes electrically insulated from... 

Aluminium-air cells were first developed for portable applications such as mooring lights, and for recharging nickel-cadmium and lead-acid storage batteries. They have been fabricated in many unusual designs, e.g. the concentric rope battery which has an aluminium core surrounded by a separator and then the oxygen cathode. The rope may be several hundred metres long and can provide 0.03 W/m for a period of 6 months on immersion in the sea. 

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