Raw materials in battery technology: Zinc (Glossary)

Zinc is a bluish, glossy white metal that is rolled and stretched above approx. 100° C. Zinc forms a passivating protective layer of zinc oxide and zinc carbonate in air. It is quite resistant to water, but is easily soluble in acids and lyes.

Zinc does not occur in an elementary form in nature and is generally extracted from its ore, zinc sulphide (e.g. sphalerite or wurtzite). Important deposits can be found in the USA, Canada, the CIS states and Australia. Around half of the world's production (8.3 million tons in 2000) is used in the automotive and construction industry for the galvanic coating of steel products. Furthermore, zinc is an important alloying metal, as a dust it is used as a reducing agent and as dye and also as a base material for many zinc compounds (above all pigments).

Zinc is an essential trace element for the majority of plants and animals.

In battery technology zinc is used as a metal for electrodes and as a container bowl, often alloyed with corrosion-inhibiting additives such as lead. Zinc has proven its worth as an anode material in several primary battery systems. It forms a high voltage potential, is cheap, easily available and environmentally harmless. In secondary batteries, however, problems with the cycle strength of the material have not yet been satisfactorily solved on account of the bad solubility of the zinc oxide that is produced. Nevertheless a rechargeable nickel-zinc cell is granted a good market potential if the existing problems can be solved thanks to its good characteristics.

In the Leclanché battery (zinc-manganese dioxide cell) the zinc container bowl serves as a negative electrode at which zinc is oxidised to zinc oxide. This reaction also occurs, for example, in the zinc-air battery and the nickel-zinc cell. In the zinc-chlorine and zinc-bromine battery the zinc anode is oxidised to zinc chloride and zinc bromide.

Some key technical data

Chemical symbol: Zn

Atomic number: 30

Relative atomic mass: 65.41

Oxidation numbers: +2

Density: 7.14 g/cm³

Melting point: 420°C

Boiling point: 907°C

Specific electrical resistance: 6

	See also:
		Glossary overview

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