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The future of batteries: Mg-ion and Li-air

18sep13StAndrewsResearchers are looking beyond lithium ion to take batteries into the future.

Two of the most promising are magnesium ion and lithium-air.

To find out how research into these two is going, Electronics Weekly asked Professor Peter Bruce of the University of St Andrews’ school of chemistry, renowned for its work on battery science.

Li-ion has proved to be a great battery technology, powering just about every phone, laptop and electric car made today.

However, lithium is not a common metal, making it so expensive that the price of an electric car battery often has to be subsidised.

And, although it is improving by a few per cent a year, Li-ion capacity is not increasing fast enough for some – particularly the electric vehicle people.

Silicon anodes by companies including Panasonic, Amprius and the UK’s Nexeon promise comparatively large increases in Li-ion capacity. Is there a limit?

“Silicon instead of graphite anodes will step things up,” said Bruce. However, with any spin on lithium ion chemistry, “the best you can do is probably double capacity.”

Magnesium ion is being proposed as an alternative to lithium ion because magnesium is more abundant and cheaper than lithium.

“It’s a potentially attractive new-kid-on-the-block. Magnesium works in a similar way to Li-ion, it is fairly abundant, reasonably low cost, and easier to handle,” said Bruce. But, “it comes with quite a lot of challenges.” For example: “Lithium is difficult to plate and strip with high efficiency; magnesium is even more difficult to plate and strip.”

If it can be made into cells, there is a chance that magnesium could also help increase capacity: “You get two electrons for every ion so, in principle, you might be able to store more charge”, said Bruce.


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