Batteries

Published on April 18th, 2017 | by Tina Casey

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Creepy Herbicide Repurposed To Solve Creepy EV Battery Problem

April 18th, 2017 by  

Paraquat became a household word for all the wrong reasons during the Vietnam War, but this indiscriminate herbicide is helping to solve an EV battery “dendrite” problem that has stumped researchers for 40 years. If all goes according to plan, the result will be a new generation of lithium-based EV batteries that beats the range of today’s mobile energy storage devices by five to 10 times.

Whoa!

Dendrites Vs. EV Batteries

Dendrite sounds like the name of a pesky alien race populating a random Star Trek planet from the cheap season, and they really are pesky.

Dendrites are miniature fibers that form on the anodes (the negative side) of lithium-metal batteries when they are recharging. They inhibit performance and can cause short circuits and fires.

That’s why one reason why you don’t see lithium-metal EV batteries tooling around the streets, even though they have the potential to outperform conventional batteries on range.

Today’s gold standard for energy storage is lithium-ion, which typically uses a carbon-based material like graphite for the anode.

Researchers have tried “glass” batteries, a honeycomb-style structure based on carbon nanotubes, and various other approaches to solving the dendrite problem, but so far nothing has stuck.

The Paraquat Solution

The latest energy storage breakthrough is an interesting one. A research team from the University of California – Riverside coated a test battery with methyl viologen and here’s what happened next:

The team discovered that by coating the battery with an organic compound called methyl viologen they are able to stabilize battery performance, eliminate dendrite growth and increase the lifetime of the battery by more than three times compared to the current standard electrolyte used with lithium metal anodes.

That’s pretty good for an initial attempt, right? It makes you wonder why nobody ever thought of this before, but the catch is getting the recipe right.

The researchers used a specific methyl viologen molecule that dissolves in the electrolyte when the battery is charged, and self-applies to the electrode. Here’s a snippet from the research:

Using this approach, a lifetime of 300 cycles with Columbic efficiency of 99.1% and 400 cycles with Columbic efficiency of 98.2% at a current density of 1 mA cm–2 in ether-based electrolyte can be obtained.

Here’s the plain language version from UC -Riverside:

By adding only .5 percent of viologen into the electrolyte, the cycling lifetime can already be enhanced by three times. In addition, methyl viologen is very low in cost and can easily be scaled up.

Of course, there’s a catch. The research team solved the dendrite problem, but safety issues still need to be addressed before lithium-metal batteries come to an EV near you.

On the plus side, the research is so promising that UC-Riverside’s Office of Technology Commercialization has already applied for a patent.

If you want all the details, look for the paper titled “In Situ Formation of Stable Interfacial Coating for High Performance Lithium Metal Anodes” in the journal Chemistry Materials.

The March for Science is coming up this Saturday, April 22, so here’s a shoutout to the authors of the paper (all of UC-Riverside): Haiping Wu, Yue Cao, Linxiao Geng, and Chao Wang.

Science!

Speaking of the March for Science, interest in the event has been overlapping with pushback against President Trump’s Muslim ban and other anti-immigrant policies of the Trump Administration.

A good deal of that energy is coming from private sector stakeholders in science and technology fields, but you ain’t seen nothing yet.

The summer tourism season hasn’t even heated up yet and the US tourism industry is already beginning to feel the squeeze.

Media reports of a “Trump slump” in US tourism began circulating soon after Trump signed his first travel order on January 29, and earlier this month the UK’s Independent summed it up:

The drop-off in tourism is predicted to result in 4.3 million fewer visitors this year, which adds up to a staggering loss of $7.4 billion in revenue for the US.

Last week the Washington Post ran the numbers:

Next year, the fallout is expected to be even larger, with 6.3 million fewer tourists and $10.8 billion in losses.

Don’t be surprised to see the travel and hospitality industries represented at your local March for Science.

Image (cropped): via UC – Riverside. Lower level shows dendrite-free results with methyl viologen coating.


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About the Author

specializes in military and corporate sustainability, advanced technology, emerging materials, biofuels, and water and wastewater issues. Tina’s articles are reposted frequently on Reuters, Scientific American, and many other sites. Views expressed are her own. Follow her on Twitter @TinaMCasey and Google+.



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