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New electrolyte could mean an end to spontaneously combusting lithium batteries

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February 11, 2014

The Boeing 787 Dreamliner aircraft initially suffered from problems with its lithium-ion b...

The Boeing 787 Dreamliner aircraft initially suffered from problems with its lithium-ion batteries overheating, on two occasions resulting in fires

Last year, lithium-ion battery fires became a hot topic, pardon the inescapable pun, with both a Tesla automobile and the Boeing 787 Dreamliner succumbing to fires. In cross-disciplinary research at the University of North Carolina (UNC), a compound being studied to prevent marine life from sticking to ships may also be the solvent (and the solution) to keep lithium ion batteries from catching alight when they overheat.

The surprising chemical in question is a lubricant called perfluoropolyether (PFPE), which is traditionally used to a heavy-duty lubricant for plasma etching equipment or aircraft fuel systems. Generally polymers don’t mix with electrolytes, yet not only does PFPE combine with lithium salts, but it retains its nonflammability and is thermally stable beyond 200º C (392º F). In contrast, the common solvent in commercial lithium batteries begins to degrade at 34º C (93º F) and has a low flashpoint. The team confirmed the stability of these compounds with every lab assistant’s dream experiment, setting things on fire.

Furthermore, the PFPE-lithium combination exhibits characteristics pointing to it not just being a safe battery, but an excellent battery. Scientists commonly refer to the transference number and electrochemical polarization of batteries, both of which relate to battery life and performance.

In measuring the transference number, the team came to the surprising discovery that PFPE carries most of its current in the cation (the positive ion), resulting in a transference value higher than most other solvents. Though the conductivity of the PFPE mixture is relatively low, previous research suggests that high transference can make up for low conductivity.

Finally, all of this doesn’t matter if an electrolyte can’t operate well with a cathode and anode. The researchers charged and discharged the PFPE lithium battery with high-voltage cathodes and established that the compound did so stably and was promising for use in grid batteries that need to cycle within eight hours.

While the team acknowledges the necessity of further research into increasing the conductivity and cyclability of the battery, the finding is promising for large batteries used in aircraft and automobiles where overheating becomes an issue, and even in the reverse, in cold environments where conventional batteries fail.

Earlier this month we saw research that solved the flammable battery problem by using a wax as an electrolyte that melted when it became too hot, severing the connection with the cathode and anode.

The research team at UNC, led by Joseph DeSimone, first published their research in the Proceedings of the National Academy of Sciences.

Source: University of North Carolina at Chapel Hill

About the Author
Heidi Hoopes Heidi measures her life with the motley things she's done in the name of scientific exploration. While formally educated in biology and chemistry, informally she learns from adventures and hobbies with her family. Her simple pleasures in life are finding turtles while jogging and obsessively winnowing through her genetic data.   All articles by Heidi Hoopes
5 Comments

Very interesting. What appeared to be a serious problem might be pointing the way not only to a solution, but another improvement in the better battery world.

Little by little, we are moving toward practical, safe electric vehicles and tools for life.

James Smith
12th February, 2014 @ 08:52 am PST

It would be great if this chemical could prevent Li-ion batteries in cell phones from catching fire. But, at 392 F it could still cause burns and melt phones.

Bassmandan
12th February, 2014 @ 09:49 am PST

Heidi it is high time that you and others at Gizmag do a meta article summing up the current state of play in battery development. Guesstimate how long until the various bits of incremental research is combined to create a new plateau of battery performance, cost, durability, safety, recycleability, etc. Thanks In Advance!

StWils
12th February, 2014 @ 11:10 am PST

The batteries are not the problem the proper use of them is lithium batteries cannot be over charged like lead acid cells can. If you over charge them the grow dentrites through their electrolyte which internally short circuts the cell. Placing another cell in series keeps this from happening, for no single cell reaches the point of being over charged. Lead acid batteries have the ability to release hydrogen as they over charge this is taken advantage of by industry to balance the cells at the top of their voltage. With lithium cells you can balance them at the bottom of their charge and since they dont have the mechanisim lead acid cells do they stay balanced.

Nathan Knappenburger
12th February, 2014 @ 06:35 pm PST

Why all the Tesla- bashing on Gizmag? The battery fire in the Tesla roadster was started by a piece of metal debris that pierced the bottom of the car and (luckily) got stuck on the battery pack (instead of a passenger). It did NOT happen because the battery overheated. Gasoline car fires happen all the time but rarely make the news anymore.

Skipjack
14th February, 2014 @ 10:25 am PST
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