Cadmium-nickel oxide cells

The manufacture of secondary batteries based on aqueous electrolytes forms a major part of the world electrochemical industry. Of this sector, the lead-acid system (and in particular SLI power sources), as described in the last chapter, is by far the most important component, but secondary alkaline cells form a significant and distinct commercial market. They are more expensive, but are particularly suited for consumer products which have relatively low capacity requirements. They are also used where good low temperature characteristics, robustness and low maintenance are important, such as in aircraft applications. Until recently the secondary alkaline industry has been dominated by the cadmium-nickel oxide ( nickel-cadmium ) cell, but two new systems are making major inroads, and may eventually displace the cadmium-nickel oxide cell - at least in the sealed cell market. These are the so-called nickel-metal hydride cell and the rechargeable zinc-manganese dioxide cell. There are also a group of important but more specialized alkaline cell systems which are in use or are under further development for traction, submarine and other applications. 

The first patent on an alkaline secondary battery was taken out by Walde-mar Jungner of Sweden, who in 1899 proposed a system based on nickel hydroxide as the positive electroactive material, a mixture of cadmium and iron as the negative electrode, and an aqueous solution of potassium 

Cell construction is mainly confined to two types, using either pocket plate electrodes (vented cells) or sintered , bonded or fibre plate electrodes (vented and sealed cells). In the former, the active materials are retained within pockets of finely perforated nickel-plated sheet steel which are interlocked to form a plate. Positive and negative plates are then interleaved with insulating spacers placed between them. In sintered plate electrodes, a porous sintered nickel mass is formed and the active materials are distributed within the pores. In sintered plate vented cells, cellulose or other membrane materials are used in combination with a woven nylon separator. In sealed or recombining cells, special nylon separators are used which permit rapid oxygen diffusion through the electrolyte layer. 

The electrochemical reactions at the negative electrode are the comparatively straightforward processes  

However, it is recognized that slightly soluble intermediates such as CdO(OH) and Cd(OH)3 are involved. Cadmium does not corrode since its equilibrium potential is more positive than that of hydrogen in the same solution. The active material in pocket plate cells consists of metallic cadmium, with up to 25% of iron and small quantities of nickel and graphite to prevent agglomeration. Two methods of preparation are used. One involves the electrochemical co-reduction of a solution of cadmium and iron sulphate in the other, dry mixtures of cadmium oxide or hydroxide and Fe304 or iron powder are used. In some methods of pocket plate manufacture, the electrode material is pressed into pellets or briquettes before being inserted into the pockets, and various waxes or oils may be used to facilitate this process. 

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Cadmium-Nickel Oxide (Ni-Cd) Secondary Cells Besides lead-acid batteries, cadmium-nickel oxide cells represent the most popular type of rechargeable batteries [344]. The scheme of the cell is ... 

The sealed nickel-metal hydride cell (more consistently metal hydride-nickel oxide cell) has a similar chemistry to the longer-established hydro-gen-nickel oxide cell considered in Chapter 9. In most respects (including OCV and performance characteristics), it is very similar to the sealed nickel-cadmium cell, but with hydrogen absorbed in a metal alloy as the active negative material in place of cadmium. The replacement of cadmium not only increases the energy density, but also produces a more environmentally friendly power source with less severe disposal problems. The nickel-metal hydride cell, however, has lower rate capability, poorer charge retention and is less tolerant of overcharge than the nickel-cadmium cell. 

In cadmium-nickel oxide secondary cells ( + ) 2Ni00H + 2e- + 2H+ anode 2Ni(OH>2... 

With the exception of the anode contact (where slight modification of the top/anode interface is necessary), materials for the cadmium/mercuric oxide cell are generally the same as for the zinc/mercuric oxide cell. However, because of the wide range of storage and operating conditions of most applications, cellulose and its derivatives are not used, and low-melting-point polymers are also avoided. Nickel is usually used on the anode side of the cell and also, conveniently, at the cathode. 

Oxygen evolution occurs on nickel oxide electrodes throughout charge, on overcharge, and on standby. It is the anodic process in the self-discharge reaction of the positive electrode in nickel-cadmium cells. Early work in the field has been reviewed [9], No significant new work has been reported in recent years. 

Nickel(lll) oxide, prepared from a nickel(ii) salt and sodium hypochlorite, is used for the oxidation of alkanols in aqueous alkali [46]. Residual nickel(Ii) oxide can be re-activated by reaction with sodium hypochlorite. Nickel oxides have also long been used in the manufacture of the positive pole in the Edison nickel-iron rechargeable battery, now largely superseded by die lead-acid accumulator, and in the Jungner nickel-cadmium batteries used as button cells for calculators [47]. Here, prepared nickel oxide is pressed into a holding plate of perforated nickel. Such prepared plates of nickel(lli) oxide have been proposed as reagent for the oxidation, in alkaline solution, of secondary alcohols to ketones and primary alcohols to carboxylic acids [48]. Used plates can be regenerated by anodic oxidation. 

Beryllium connections and contacts are employed for switchgear and relays. Beryllium oxide is used as substrata for electronic circuits. Cadmium is used in television and fluorescent light phosphors. Cadmium, nickel and mercury are employed in batteries such as "nicad" cells and mercury cells. Mercury is used in fluorescent lamps, electrical switches, and outdoor lamps, as well as instruments for measuring pressure, temperature, and density. Selenium is employed as a photoreceptor in copying machines, and as a semiconductor in rectifiers. Lead applications include lead add storage batteries, a component in color television glass, and, in its oxide form, use as a dielectric material. 

Schmid, M., Zimmerman, S., Krug, H.E., Sures, B. Influence of platinum, palladium and rhodium as compared with cadmium, nickel and chromium on cell viability and oxidative stress in human bronchial epithelial cells. Environ. InL 33, 385-390 (2007)... 

New, high-density nickel oxide electrode materials, coupled with nonwoven nickel-fiber current collectors, have significantly improved the performance of the nickel electrode even in the nickel-cadmium cells [5j. The alloys used to form hydride, which capture and release hydrogen in volumes up to nearly a thousand times their own, include rare-earth/nickel alloys (generally based on LaNis and called AB5)... 

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