Boffins dump the fluids to build solid state lithium battery

No fires, more power, and better lifespan from new tech

The structure of a solid battery
The structure of the new substance could mean much better batteries

Researchers at MIT and Samsung have built a battery that eschews the use of liquid electrolytes in favor of a solid state substance that offers some serious benefits.

Most commercial lithium-ion batteries use a liquid electrolyte to transport charged particles and provide power. But there are problems with this – the liquid degrades over time, and if the battery leaks there are serious safety issues.

"All of the fires you've seen, with Boeing, Tesla, and others, they are all electrolyte fires," said Gerbrand Ceder, visiting professor of materials science and engineering at MIT.

"The lithium itself is not flammable in the state it's in in these batteries. [With a solid electrolyte] there's no safety problem — you could throw it against the wall, drive a nail through it — there's nothing there to burn."

The research, published in Nature Materials, details how the team investigated new types of solid materials dubbed superionic lithium-ion conductors, which could replace liquid. In this case they used a compound of lithium, germanium, phosphorus, and sulfur, but they think that with more research, even better materials can be found.

Leaving aside the safety aspect on the new material, the relative density of a solid substance means the new battery design can hold 20–30 per cent more charge. The solid material also lasts through "hundreds of thousands" of recharges, Ceder said, rather than the few hundred common in liquid lithium-ion batteries.

NASA might also be interested in the technology. Liquid batteries need to be kept warm to operate properly, to a minimum of about –20 degrees Fahrenheit, but solid-state batteries can work at much lower temperatures.

The technology isn't remotely ready for commercial manufacture, although that's what Samsung and the MIT team are aiming for. But the research does prove the viability of the solid-state technology.

"There was a view that solids cannot conduct fast enough," Ceder said. "That paradigm has been overthrown." ®




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