Cadmium-mercuric oxide system

Zinc-mercuric oxide, cadmium-mercuric oxide, zinc-silver oxide and related systems... 

Replacing zinc with cadmium produces a cell with an OCV of 0.90 V, with characteristics very similar to those of the zinc-mercuric oxide system described above, but which is able to be stored and operated at extreme temperatures (—55 to 80°C) due to the low solubility of cadmium oxide even in concentrated KOH. Cells have been successfully operated at 180°C. Note that hydrogen generation does not occur at a cadmium anode. Because of cost and disposal problems, such cells are used only for applications where their special properties can be exploited, e.g. telemetry from internal combustion, jet or rocket engines. 

Cadmium/Mercuric Oxide Battery. The substitution of cadmium for the zinc anode (the cadmium/mercuric oxide cell) results in a lower-voltage but very stable system, with a shelf life of up to 10 years as well as performance at high and low temperatures. Because of the lower voltage, the watthour capacity of this battery is about 60% of the zinc/mercuric oxide battery capacity. Again, because of the hazardous characteristics of mercury and cadmium, the use of this battery is limited. 

This system utilizes two toxic materials, mercuric oxide and cadmium metal. Because of its low voltage, however, it is thermodynamically stable, and if it is well sealed, it has a very long lifetime. It also has a very stable voltage and can be used as a voltage reference in electronic circuits. It is seeing less and less usage because of disposal issues and the availability of stable lithium cells with equivalent lifetime and voltage stability. 

Crompton-Parkinson supply mereurie oxide-indium-bismuth and mercuric oxidc-cadmium batteries. These arc alkaline systems recommended for applications in which high reliability in particularly onerous longterm storage and use eonditions is a prime requirement. 

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