Nickel-iron cells

Because the nickel—iron cell system has a low cell voltage and high cost compared to those of the lead—acid battery, lead—acid became the dorninant automotive and industrial battery system except for heavy-duty appHcations. Renewed interest in the nickel—iron and nickel—cadmium systems, for electric vehicles started in the mid-1980s using other cell geometries. 

Fig. 10. Power and voltage characteristics of the nickel—iron cell where the internal resistance of the cell, R, is 0.70 mQ, at various states of discharge ( )...

Iron—Air Cells. The iron—air system is a potentially low cost, high energy system being considered mainly for mobile appHcations. The iron electrode, similar to that employed in the nickel—iron cell, exhibits long life and therefore this system could be more cost effective than the ziac-air cell. Reactions iaclude ... 

The Edison dry cell nickel/cadmium battery and the Jungers nickel/iron cell are developed work on these endeavors lasts until 1905. 

The electrochemical equivalent of iron (if only the first step is taken into account) is 960 Ah/kg and the open-circuit voltage of the nickel/iron cell is 1.4 V. 

Nickel hydroxides, 17 111 Nickel—iron alloys, 17 101 Nickel—iron—aluminum catalyst, 17 121 Nickel—iron cells, 3 491—493 Nickel—iron—chromium alloy 825 in galvanic series, 7 805t Nickel—iron—chromium alloys, 17 102—103 Nickel—iron plating, 9 821 Nickel itch, 12 691, 701 Nickel—matrix composites, 17 104 Nickel metal, forms of, 17 95—99 Nickel metal hydride cells, 3 431, 471, 509-512... 

Some versions of the cell are manufactured in which the active materials are supported in tubular elements made from spirally wound perforated steel ribbon. Such a design is more common for alkaline nickel-iron cells, and will therefore be described for the latter system. 

Nickel-Iron Cells. There has been renewed interest in the system for electric vehicles (EV). The EV design is based on a high rate, usually sintered, iron electrode as well as high rate nickel electrodes. 

Sintered nickel electrodes used in nickel iron cells are usually thicker than those used in Ni-Cd cells. These result in high energy density cells, because very high discharge rates are usually not required. 

The constraction of a tubular or pocket plate nickel-iron cell is shown in Fig. 25.2. The active materials are filled in nickel-plate perforated steel tubes or pockets. The tubes are fastened into plates of desired dimensions and assembled into cells by interleaving the positive and negative plates. The container is fabricated from nickel-plated sheet steel. The cells may be assembled into batteries in molded nylon cases or mounted into wooden traps. The steel cases may be coated with plastic or mbber for insulation or spaced by insulating buttons. 

FIGURE 25.5 Effect of decreasing rate on battery voltage of nickel-iron cell. 

A further example of a rechargeable battery is the nickel-iron cell. In the discharged state the negative plate of this cell is iron with hydrated ferrous oxide, and the positive plate is nickel with hydrated nickel oxide. When charged, the ferrous oxide is reduced to iron, and the nickel oxide is oxidized to a hydrated peroxide. The cell reaction may thus be represented by... 

Eagle Kcher s experience with the nickel-iron system has been equally encouraging. They have 40Ah nickel-iron cells on cycle test with energy densities between 40 and 50Wh/kg. 

Figure 4.12 shows the voltage profile for a single nickel-iron cell tested to the constant current modes as indicated. 

Figure4.12 Nickel-iron cell charge/discharge profile (Courtesy of Eagle Picher)...

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