Nickel/cadmium batteries are also used for standby as well as other applications. They are available with pocket-plate or sintered electrodes in steel or plastic containers. A full range of applications is served and nickel/cadmium is especially suited to electrically or mechanically arduous applications.
Nickel/cadmium batteries have a positive electrode of nickel hydroxide and a negative electrode of cadmium.
On discharge the nickel hydroxide is reduced to a different form of nickel hydroxide with a lower oxidation state and the cadmium is oxidised to cadmium hydroxide. The reverse reactions take place on recharge. The electrolyte is a potassium hydroxide solution. The construction of the battery differs for particular applications but there are two basic types; either a pocket-plate type or types using a sintered or bonded electrode structure. For pocket-plate types, a perforated nickel-plated steel pocket is used to contain the active material. For sintered or bonded types, a porous partially sintered nickel substrate may be used but various plastic bonded structures and fibrous constructions are also offered. The pocket-plate construction is highly reliable and offers moderate performance but the other types offer higher levels of electrical performance. Nickel/cadmium batteries may also be constructed in a fully sealed form similar to VRLA batteries.
Nickel/cadmium batteries offer good resistance to electrical use as they can be left in a discharged condition for long periods without permanent damage and also offer good performance in higher ambient temperatures.
bron: www.eurobat.org