Nickel iron oxide

The discharge-charge reaction of this electrode will be done in two steps but only the first step (Fe <-> Fe2+ + 2e ) is of practical use. For the iron/nickel oxide-hydroxide system these steps (or voltage plateaus) may be written as ... 

The iron-nickel oxide alkaline battery system has many features in common with the nickel-cadmium system discussed above. It was first developed by Edison in the USA at the turn of the century and was patented in the same year as Jungner s first nickel-cadmium US patent, 1901. Iron can be regarded as a favourable active battery material because of its low cost, high theoretical specific capacity (twice that of cadmium) and non-toxic, pollution-free characteristics. However, because its reduction potential is below that of hydrogen, and since hydrogen overvoltage is low on iron, charge retention is poor and efficiency is low. 

Manufacture of iron-nickel oxide batteries commenced in 1908, but the system did not have the commercial success of nickel-cadmium. Until comparatively recently, there was only a very limited production of stationary batteries in the USA, Germany and Russia. Developments of improved iron electrodes have altered the situation, and the iron-nickel oxide system is now being actively considered for EV propulsion and other applications. 

Iron-nickel oxide cells are always vented. Tubular/pocket plate electrodes are constructed as described above and are generally housed in nickel-plated steel cases. Cells with sintered plate electrodes have smaller inter-electrode spacings. They use synthetic fibre fabrics as separators, and plastic containers. 

Iron-nickel oxide batteries have been used for many years in railway lighting applications, and for motive power in industrial trucks, tractors and mine locomotives. There is some utilization of the system in emergency lighting and alarm circuits. 

Batteries based on the iron-nickel oxide system are now being developed for electric vehicle applications. These use fibre-plaque electrodes, as described above for the nickel-cadmium system, and incorporate electrolyte circulation systems to permit removal of gases evolved during charge... 

Fig, 6.20 Discharge (a) and charge (b) characteristics of a typical iron-nickel oxide cell ai C/3, as a function of percentage capacity... 

Voltage. A typical discharge-charge curve of a coimnercial iron/nickel oxide battery is shown in Fig. 25.3. The battery s open-circuit voltage is 1.4 V its nominal voltage is 1.2 V. On charge, at rates most commonly used, the maximum voltage is 1.7 to 1.8 V. 

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