Gordon Adams of Waihola asks :-

Electric cars using lithium ion batteries may be the new transport to avoid future oil shocks. What is lithium, where is it mined, is there enough to prevent future lithium shocks, is it toxic and can it be recycled?

Barrie Peake, an environmental chemist at the University of Otago, responded.

Lithium is a soft, silver-white metal which is the lightest and least dense solid element. The chemical and physical properties of lithium have lead to it to be increasingly used as an anode in batteries in conjunction with electrolytes containing dissolved lithium salts. The very high current density of the resulting electrical output makes this type of battery increasingly popular as power sources in many electronic devices such as in laptop computers, digital cameras and to power electric cars where power output to weight ratio is critical to their performance.

Although the average global concentration of lithium is very low, high concentrations of lithium-containing minerals do occur in specific deposits and, in particular, the Salay de Uyuni salt flat area of Bolivia which is reputed to contain up to 5.4 million tons, half of the world’s known accessible reserves of lithium.

Whether these reserves are enough to satisfy the likely future demand for the metal particularly if battery-powered cars become predominant, is the subject of much current geo-political, economic and scientific debate (try Googling ‘world supplies of lithium’). One recent report (http:ergobalance.blogspot.com/2008/05/world-lithium-supplies.html) suggests that there are enough known reserves to manufacture batteries to power 600 million new cars.

Lithium compounds are moderately toxic to humans and so it is important to carefully dispose of any lithium-ion batteries. There are a number of commercial processes already used in North America and Europe for this purpose and these typically involve cooling the spent battery to – 200 C which renders the metallic lithium relatively inert. The batteries are then safely shredded, the metal components separated and the lithium converted to lithium carbonate for resale. However in this form it cannot be directly electrolysed to reform metallic lithium but can be chemically converted into appropriate lithium salts to act as electrolytes in new lithium-ion batteries.