Nickel-metal-hydride batteries use neodymium, cerium, lanthanum and praseodymium, none of which are used in more efficient lithium-ion batteries.

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But there is no spot market: you cannot go to Toyota with your lanthanum and say, well, you use lanthanum in your batteries, buy mine!

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Exactly what is a rare earth metal is very slightly arguable, some would say it is only the lanthanides, lanthanum, cerium through to lutetium in that little box at the bottom of the periodic table.

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