Raw materials in battery technology: Iron (Glossary)

Iron is a silvery-white metal, relatively soft, tenacious and ductile in a pure state. It is one of the ferromagnetic metals, i.e. it can be magnetised (below 768°C). Iron is resistant to dry air since it forms a protective oxide film. Iron oxidises to rust in damp air or in water containing oxygen and carbon dioxide. The metal can be attacked by various acids, but is resistant to concentrated nitric and sulphuric acid.

Crude iron is greatly contaminated with carbon and cannot be forged in this state. The material properties of steel, in other words forgeable iron, have been changed through the cleaning of carbon and alloys and heat treatment and is the most important basic material in an industrial economy. Some stainless steels are superior to precious metals in their appearance, hardness or resistance to corrosion. 926 million tons of iron were produced throughout the world in 2001, the most important manufacturing countries are China, Japan, Russia and the USA.

Iron is an essential trace element for humans and must be supplied daily with food.

In battery technology iron is used as a housing material as well as an alloying or matrix or carrier material for electrodes. Although batteries with pure iron electrodes have been built they were not particularly successful, for example the nickel-iron accumulator. In the lithium-iron sulphide system, a high-temperature battery, iron sulphide is reduced to iron at the cathode. Although this type of battery can theoretically produce very high energy densities of up to 650 Wh/kg, the figures in practice so far have been disappointing.

Some key technical data

Chemical symbol: Fe

Atomic number: 26

Relative atomic mass: 55.85

Oxidation numbers: +3, +2

Density: 7.87 g/cm³

Melting point: 1,538°C

Boiling point: 2,860°C

Specific electrical resistance: 10

	See also:
		Glossary overview

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