Batteries nickel-cadmium cell

Mercury button cell (primary battery) Silver button cell (primary battery) Nickel-cadmium cell (NiCd) (secondary battery)... 

The aimual production value of small, sealed nickel—cadmium cells is over 1.2 biUion. However, environmental considerations relating to cadmium are necessitating changes in the fabrication techniques, as well as recovery of failed cells. Battery system designers are switching to nickel —metal hydride (MH) cells for some appHcations, typically in "AA"-si2e cells, to increase capacity in the same volume and avoid the use of cadmium. 

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... 

Battery types are either lead-acid or nickel-cadmium cells. Lead-acid types have been used for a long time and, when correctly maintained, have a working life of 25 years. Nickel-cadmium batteries offer the same working life as lead-acid but are smaller in weight and volume, generally with a higher initial capital cost. Loads applied to D.C. systems can be categorized into three types ... 

Apart from the improvement and scaling up of known systems such as the lead accumulator or the nickel/cadmium cell, new types of cells have also been developed. Here, rechargeable lithium batteries and nickel-systems seem to be the most promising the reason for this will be apparent from the following sections [3]. 

Many types of rechargeable batteries are much more portable than a car battery. For example, there is now a rechargeable version of the alkaline battery. Another example, shown in Figure 11.20, is the rechargeable nickel-cadmium (nicad) battery. Figure 11.21 shows a nickel-cadmium cell, which has a potential of about 1.4 V. A typical nicad battery contains three cells in series to produce a suitable voltage for electronic devices. When the cells in a nicad battery operate as galvanic cells, the half-reactions and the overall cell reaction are as follows. 

Secondary cells are voltaic cells that can be recharged repeatedly. The lead storage battery and nickel-cadmium cell are examples of secondary cells. The lead storage battery consists of six voltaic cells. Its electrodes are lead alloy plates, which take the form of a grill, filled with spongy lead metal. The cathode consists of another group of plates filled with lead (IV) oxide, P6O2. Dilute sulfuric acid is the electrolyte of the cell. When the battery delivers a current, the lead is oxidized to lead ions, which combine with sulfate fS0 7 ions of the electrolyte to cover the lead electrode. 

Although more expensive, the nickel-cadmium cell is superior to the Leclanche cell in almost all respects, except that the toxicity of cadmium places some restrictions on the disposal of defunct nicad cells. Even the rechargeable Ni/Cd cell has a limited life, due to a memory effect after discharge (i.e., it is not quite fully rechargeable), and consideration must be given to proper disposal or, better, recycling. Peugeot s entry in the ZEV field, the Model 106 electric car, uses 20 liquid-cooled 6 V Ni/Cd cells to deliver 120 V, and the supplier undertakes to recycle the battery at the end of its useful life. 

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. 

Fig. 6.10 Battery for Viking Mars orbiting spacecraft, comprising 26 sealed 30 Ah nickel-cadmium cells, which was placed in Mars orbit in 1976. (By courtesy of Jet Propulsion Laboratory,)...

Button, cylindrical and prismatic sealed cells are similar in design to the starved-electrolyte configuration of nickel-cadmium cells. A schematic diagram of a six-cell battery is shown in Fig. 6.11. Because of the slightly... 

Despite the fact that cadmium is very toxic and that the number of batteries based on this metal (i.e. nickel-cadmium cells) is very significant, there are very few recycling plants in operation. One very effective recycling process has been designed and developed by SAFT NIFE AB in Sweden to treat both industrial and consumer nickel-cadmium batteries. The flow... 

Ni-Cd cells — The nickel-cadmium cell is a secondary - battery that has a nominal cell potential of 1.20-1.25 V. The negative electrode comprises nickel hydroxide-nickel oxyhydroxide, the positive electrode is cadmium, and the electrolyte solution is based on aqueous potassium hydroxide (KOH, 32% in water). At the anode, the discharge reaction is the oxidation of cadmium metal to cadmium hydroxide with the release of two electrons [i] ... 

Developed in the 1960s, it makes use of different technologies for its electrodes NiO(OH) is from nickel cadmium and H2 from fuel-cell systems. Because of its longer cycle life the main use of the nickel-hydrogen battery is in aerospace applications to replace the nickel cadmium cells. For example, the Hubble Space Telescope launched in 1990 was equipped with nickel-hydrogen cells [12]. 

A major goal of the research on conducting polymers has been the development of a rechargeable plastic battery. Cells based on polypyrrole and lithium electrodes have been developed in which the energy per unit mass and discharge characteristics are comparable to nickel-cadmium cells. Current interest appears to center around stable, processable polymers, such as polythiophene and its derivatives, and polyaniline. 

Primary cells are cells like the ordinary dry cell that cannot be recharged. Storage cells are cells like the nickel-cadmium cell or the lead-storage battery that can be recharged. Is the Zn-Cu + cell shown above a primary cell or a storage cell ... 

Batteries vary in size and chemistry. Shown here are an automobile lead-storage battery, rechargeable nickel-cadmium cells, alkaline cells, and zinc-carbon dry cells. 

The nickel-cadmium cell (or nicad battery Fig. 17.8) is used in handheld electronic calculators and other cordless electric implements such as portable shavers. Its half-cell reactions during discharge are... 

Rechargeable batteries have become an essential part of our environmentally conscientious society. The nickel-cadmium cell battery is a rechargeable battery used in small electronic devices. The half reactions that take place in the nickel-cadmium battery during discharge are ... 

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