Photokina 2014 highlights

Add salt to significantly extend the life of lithium-based batteries

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August 18, 2014

Adding certain salts to the anodes of lithium-based batteries has been found to increase t...

Adding certain salts to the anodes of lithium-based batteries has been found to increase their useful life by a very large factor (Photo: Shutterstock)

Salt has long been used to preserve meat, and now researchers at Cornell University have found that adding certain salts to the anodes of lithium-based batteries can also increase their useful life by a very large factor, solving long-standing problems associated with cell degradation. The advance can be adapted to other metal-based chemistries, including the lighter and more energy dense lithium-sulfur cells and, according to the researchers, might see commercial applications in as little as three years.

When a metal-based battery is being built, it is crucial that the anode material be deposited as evenly as possible. This is because, as the battery goes through several charge and discharge cycles, even the tiniest of imperfections will give rise to harmful microscopic crystals known as dendrites. The dendrites can produce internal short circuits on the surface of the electrode that cause the battery to overheat. And if the heating gets out of control, this can lead to potentially dangerous thermal runaway. Moreover, if the heat melts the crystal itself, this creates regions of "orphaned" or electrically disconnected metal that result in a slow but steady decrease in cell capacity over time.

To many researchers, the problem of dendritic growth – a big issue in many metal-based batteries, including lithium-ions – can be somewhat managed, but never completely eradicated. No matter how evenly you try to deposit the anode material, a certain amount of small-scale defects is inevitable and so, in their view, the phenomenon can only be slowed down to a limited extent, by controlling the operating conditions of the battery and designing the electrolyte with care so it doesn't accelerate the growth of defects.

Now, a research team at Cornell led by Prof. Lynden Archer has taken a new approach to the problem that could prevent the growth of these harmful crystals. After examining the chemical stability of the deposition process, the scientists decided to add halide salts to the electrolyte. As expected, this created a nanostructured coating on the anode of the lithium battery which was able to very effectively prevent the formation of dendrites. According to the researchers, this advance produced a very substantial increase in the battery's cycle life.

"Our results show that if untreated, dendritic growth will cause a lithium battery to fail after only 65 hours of continuous charge/discharge cycling," Prof. Archer told Gizmag. "In contrast, addition of the halide salt additives extends the lifetime of the cells from 1,800 hours (i.e. an increase by a factor of around 25) to indefinitely, particularly when the additives are used in conjunction with a nanoporous separator."

The test was performed at room temperature and at substantially higher current densities than those normally used to evaluate polymer or ceramic electrolytes, which makes the result even more impressive.

According to the researchers, the method can also be adapted to other electrode chemistries. For instance, the team has found that a similar approach can be used to create dendrite-free electrodeposition in sodium, and they believe they will soon be able to apply the same technique to other metal electrodes including aluminum, zinc and lead with relative ease, once they have worked out exactly which salt additives to employ in each case.

"Because the halide additives can be used to reinforce existing electrolytes, we do not anticipate any significant hurdles to their optimization and commercial implementation in rechargeable lithium-polymer and lithium ion batteries in current use," says Archer. "We expect these additives to be ready for use in existing battery systems within one year." Archer tells us that the next step for his team will be to demonstrate the technology in full cells that employ thick intercalating cathodes, such as nickel-manganese-cobalt (NMC) and lithium iron phosphate (LFP).

Beyond that, the team will look into applying their advance to so-called "conversion" cathodes, such as sulfur and oxygen, which have the potential for much higher specific capacities (lithium-sulfur batteries being one of the most promising battery chemistries).

"Application of our discovery to enable high-energy lithium-sulfur batteries will require additional research and development," says Archer. "With robust funding, we expect that these systems will require an additional two years of commercial development before becoming suitable for large-scale manufacturing."

The advance was published in a recent edition of the journal Nature Materials.

Source: Cornell University

About the Author
Dario Borghino Dario studied software engineering at the Polytechnic University of Turin. When he isn't writing for Gizmag he is usually traveling the world on a whim, working on an AI-guided automated trading system, or chasing his dream to become the next European thumbwrestling champion.   All articles by Dario Borghino
5 Comments

Ok so, Sand based anode-Lithium-Sulfur-Salt-Air batteries ? (SALSSA)

I combined all the related links below to make this super battery.

No grapheme though.

Brian Mcc
19th August, 2014 @ 09:49 am PDT

After 20 years of reading about major breakthroughs in batteries and photovoltaic cells I read this and say: "I'll believe it when I see it."

Don Duncan
19th August, 2014 @ 12:55 pm PDT

What I found particulary interesting is the possiblility of using this on lead. There is a huge installed base of lead/acid batteries in industrial vehicles. This might not reduce the number of batteries, or increase their capacity, but their useable life could be extended which would increase productivity and reduce energy. It's a little low on the glamour scale and a relatively low tech/cost proposition, so it may not get much attention.

Bruce H. Anderson
19th August, 2014 @ 03:07 pm PDT

Bout time I here more about lithium sulfurs, MIT talked them up with innovations in 2009, gladly things are advancing(finally). Looking forward to their implementaion, big news. Charging speed and weight gains should bring about the stuff the future's made.

BT
19th August, 2014 @ 03:34 pm PDT

@Don

Lithium Polymer batteries using "G8" chemistry have been available for over a year. One of these the size of a banana can deliver over 500 amps at 12 volts with a capacity of around 8 amp-hours and they can be charged in 5 minutes.

Various capacities and voltages are available, I've only used these figures as an example. I have an older G6 version with the above specs that can be charged at 60 amps and it doesn't even get warm.

So the technology IS becoming available.

You can Google "G8 Lithium Polymer" for details.

warren52nz
19th August, 2014 @ 03:50 pm PDT
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