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Lithium-ion without the rare earth metals

Thu, 07/19/2012 - 18:02 -- Ruth Williams

A Tohoku University researcher last month announced the development of a lithium-ion battery whose positive electrode does not use any rare earth metals.

Conventional lithium-ion batteries do use rare metals, such as cobalt and nickel, in the positive electrode. Due to their geochemical properties rare earth elements can be dispersed and often not found in concentrated or economically exploitable forms.  This makes these metals costly, and supplies not always stable. Eliminating them will likely make the batteries cheaper to manufacture.

China announced plans in 2009 to reduce its export quota of rare earth minerals to around 350,000 tons per year to conserve scarce resources and protect the environment.  This has led to other countries stock-piling their reserves.  The EU, US and Japan have brought a complaint to the World Trade Organisation alleging China is restricting the exports to maximize domestic use and thus distort the global economy.

Professor Itaru Honma of Tohoku University's Institute of Multidisciplinary Research for Advanced Materials has succeeded in replacing these metals with organic substances. As a result, costs of materials for the positive electrode have been slashed to less than one-fifth what they were before.

Professor Honma made a button-sized lithium-ion battery for testing. This prototype achieved an energy density of 200 watt-hours per kilogram -- roughly double that of current lithium-ion batteries. Tests confirmed that the button-sized battery could withstand at least 100 charge-discharge cycles.

The next step will be to look further for organic materials that more efficiently store power and boost the battery's capacity, with a goal of developing a secondary battery for electric vehicles.

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