Silver-cadmium cells

Silver bromoiodide Silver bronze alloys Silver-cadmium alloys Silver-cadmium cell Silver cell Silver chloride... 

Silver-Cadmium Cells. In satellite applications the nonmagnetic property of the silver-cadmium battery is of utmost importance because magnetometers were used on satellites to measure radiation and the effects of... 

Most silver-cadmium cells contain cadmium electrodes that are manufactured by pressed-power or pasting techniques. Although other methods have been used, such as impregnating nickel plaque with cadrnium salts, as is done for nickel-cadmium cells, the most common method in silver-cadmium cells is to press or paste a mixture of cadmium oxide or cadmium hydroxide with a binder onto a silver or nickel grid. These processes are similar to those used for the pressed and pasted zinc electrodes. 

In general, secondary silver-zinc and silver-cadmium cells require up to three different separators, as shown in Fig. 33.1. The inner separator, or positive interseparator, serves both as an electrolyte reservoir and as a barrier to minimize oxidation of the main separator by the highly oxidative silver electrode. This separator is usually made of an inert fiber such as nylon or polypropylene. 

FIGURE 33.20 Typical charge curve of silver-cadmium cell at 20°C, 10-h charge rate. 

Figure 31.43 Effect of temperature on energy per unit weight of Sllcad YS-18 rechargeable silver-cadmium cells (discharged without heaters) (Courtesyof Yardney)...

Dry cells (batteries) and fuel cells are the main chemical electricity sources. Diy cells consist of two electrodes, made of different metals, placed into a solid electrolyte. The latter facilitates an oxidation process and a flow of electrons between electrodes, directly converting chemical energy into electricity. Various metal combinations in electrodes determine different characteristics of the dry cells. For example, nickel-cadmium cells have low output but can work for several years. On the other hand, silver-zinc cells are more powerful but with a much shorter life span. Therefore, the use of a particular type of dry cell is determined by the spacecraft mission profile. Usually these are the short missions with low electricity consumption. Diy cells are simple and reliable, since they lack moving parts. Their major drawbacks are... 

Although one of the most common storage batteries is called the nickel/cadmium system ( NiCad ), correctly written (-)Cd/KOH/NiO(OH)(+), cadmium is not usually applied as a metal to form a battery anode. The same can be said with regard to the silver/cadmium [(-) Cd / KOH / AgO (+)] and the MerCad battery [(-)Cd/KOH/HgO(+)]. The metallic negative in these cases may be formed starting with cadmium hydroxide, incorporated in the pore system of a sintered nickel plate or pressed upon a nickel-plated steel current collector (pocket plates), which is subsequently converted to cadmium metal by electrochemical reduction inside the cell (type AB2C2). This operation is done by the customers when they start the application of these (storage)... 

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. 

Cadmium (Cd) anode cells are at present manufactured based on nickel-cadmium, silver-cadmium, and mercury-cadmium couples. Thus wastewater streams from cadmium-based battery industries carry toxic metals cadmium, nickel, silver, and mercury, of which Cd is regarded the most hazardous. It is estimated that globally, manufacturing activities add about 3-10 times more Cd to the atmosphere than from natural resources such as forest fire and volcanic emissions. As a matter of fact, some studies have shown that NiCd batteries contribute almost 80% of cadmium to the environment,4,23 while the atmosphere is contaminated when cadmium is smelted and released as vapor into the atmosphere4 Consequently, terrestrial, aquatic, and atmospheric environments become contaminated with cadmium and remain reservoirs for human cadmium poisoning. 

In the preceding example, we found that E for the silver half-cell was 0.781 V and E for the cadmium half-cell was —0.461 V. Place these values on the number line in... 

Method 1 Preparation of flaked highly purified iron, zinc, nickel, gold, chromium, silver, cadmium, titanium, cobalt, or zirconium using an open cell, and dilute hydrochloric acid... 

As well as having electrical conductivity, the transition elements can be used in the production of electrical energy through their chemical reactivity. Perhaps the most immediately familiar example is the dry cell battery. Any of a number of chemical reactions may be exploited in this context. As a consequence, manganese, nickel, zinc, silver, cadmium or mercury may be found in dry cells. 

Fig. 13.11. Clinographic projections of the unit cells of the structures of the phases in the silver-cadmium system.

In the example above, we found that E for the silver half-cell was 0.240 V and E for the cadmium half-cell was -0.461 V. Place these values on the number line in Figure 14-8 and note that electrons flow toward more positive potential. Therefore electrons in the circuit flow from Cd (—0.461 V) to Ag (0.240 V). Electrons always flow from less positive to more positive in Figure 14-8, even if both half-cell potentials are positive or both are negative. 

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