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posted by Fnord666 on Wednesday May 03 2017, @09:08AM   Printer-friendly
from the more-flammable-metals dept.

Arndt Remhof's team has developed a solid electrolyte that facilitates good mobility of sodium ions at 20 degrees. This last point is crucial: ions require a source of heat in order to move, and inducing a reaction at room temperature poses a technical challenge. The electrolyte is also non-flammable and is chemically stable up to 300 degrees, which addresses the various safety concerns associated with lithium-ion batteries. Hans Hagemann's team at the University of Geneva has been working in parallel to develop cheaper technology for the production of this new solid electrolyte.

Unlike lithium, there are huge reserves of sodium: it's one of the two components of table salt. "Availability is our key argument", says Léo Duchêne of Empa and first author of the research paper. "However, it stores less energy than the equivalent mass of lithium and thus could prove to be a good solution if the size of the battery isn't a factor for its application."

Magnesium: the perfect but complex material

The same team has also developed a solid magnesium-based electrolyte. Until now, very little research had been done in this field. The fact that it is much more difficult to set this element in motion doesn't mean that it is any less attractive: it's available in abundance, it's light, and there's no risk of it exploding. But more importantly, a magnesium ion has two positive charges, whereas lithium only has one. Essentially, this means that it stores almost twice as much energy in the same volume.

Some experimental electrolytes have already been used to stimulate magnesium ions to move, but at temperatures in excess of 400 degrees. The electrolytes used by the Swiss scientists have already recorded similar conductivities at 70 degrees. "This is pioneering research and a proof of concept," says Elsa Roedern of Empa, who led the experiments. "We are still a long way from having a complete and functional prototype, but we have taken the first important step towards achieving our goal."

The energy density of a magnesium electrolyte would solve the EV range problem, if it is double lithium's.


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  • (Score: 1) by pTamok on Thursday May 04 2017, @06:50AM

    by pTamok (3042) on Thursday May 04 2017, @06:50AM (#504227)

    Well, it is used commercially. One further issue, pointed out in the Wikipedia article, is the formation of polysulfides, which are highly corrosive. As a battery, it works best at scale, so you are unlikely to get a sodium-sulfur battery powering your laptop, and even cars are probably marginal. Grid-scale storage of power generated earlier that can be released at times of peak demand (shaving the peak) is what it is good for, and what such batteries are currently used for, until something better comes along.