Researchers develop methods to study battery chemistry in action

February 4, 2014
Liquid battery electrolytes makes this view of an uncharged electrode (top) and a charged electrode (bottom) a bit fuzzy.Credit: Gu, et al., Nano Letters 2013

Researchers at a host of national laboratories and universities have developed a way to microscopically view battery electrodes while they are bathed in wet electrolytes, mimicking realistic conditions inside actual batteries. While life sciences researchers regularly use transmission electron microscopy to study wet environments, this time scientists have applied it successfully to rechargeable battery research.

The results, reported in December 11's issue of Nano Letters, are good news for scientists studying materials under dry conditions. The work showed that many aspects can be studied under dry conditions, which are much easier to use. However, wet conditions are needed to study the hard-to-find solid electrolyte interphase layer, a coating that accumulates on the electrode's surface and dramatically influences .

"The liquid cell gave us global information about how the electrodes behave in a battery environment," said materials scientist Chongmin Wang of Pacific Northwest National Laboratory. "And it will help us find the solid electrolyte layer. It has been hard to directly visualize in sufficient detail."

Wang and colleagues have used high-powered microscopes to watch how the ebbing and flowing of positively charged ions deform electrodes in batteries. Metal ions squeezing into the electrode's pores makes the electrodes swell, and repeated use can wear them down. For example, recent work funded through the Joint Center for Energy Storage Research—a DOE Energy Innovation Hub established to speed battery development—showed that sodium ions leave bubbles behind, potentially interfering with battery function.

But up to this point, the transmission electron microscopes have only been able to accommodate dry battery cells, which researchers refer to as open cells. In a real battery, electrodes are bathed in liquid electrolytes that provide an environment ions can easily move through.

So, working with JCESR colleagues, Wang led development of a wet battery cell in a transmission electron microscope at EMSL, the DOE's Environmental Molecular Sciences Laboratory on the PNNL campus, giving scientists a more realistic view of what's happening.

It began with the team building a battery so small that several could fit on a dime. The battery had one silicon electrode and one lithium metal electrode, both contained in a bath of electrolyte. When the team charged the battery, they saw the silicon electrode swell, as expected. However, under dry conditions, the electrode is attached at one end to the lithium source—and swelling starts at just one end as the ions push their way in, creating a leading edge. In this study's liquid cell, lithium could enter the silicon anywhere along the electrode's length. The team watched as the electrode swelled all along its length at the same time.

"The electrode got fatter and fatter uniformly. This is how it would happen inside a battery," said Wang.

The total amount the electrode swelled was about the same, though, whether the researchers set up a dry or wet . That suggests researchers can use either condition to study certain aspects of .

"We have been studying battery materials with the dry, open cell for the last five years," said Wang. "We are glad to discover that the open cell provides accurate information with respect to how behave chemically. It is much easier to do, so we will continue to use them."

As far as the elusive solid electrolyte interphase layer goes, Wang said they couldn't see it in this initial experiment. In future experiments, they will try to reduce the thickness of the wet layer by at least half to increase the resolution, which might provide enough detail to observe the solid electrolyte interphase layer.

"The layer is perceived to have peculiar properties and to influence the charging and discharging performance of the battery," said Wang. "However, researchers don't have a concise understanding or knowledge of how it forms, its structure, or its chemistry. Also, how it changes with repeated charging and discharging remains unclear. It's very mysterious stuff. We expect the liquid cell will help us to uncover this mystery layer."

Explore further: Composite battery boost

More information: Gu M, LR Parent, BL Mehdi, RR Unocic, MT McDowell, RL Sacci, W Xu, JG Connell, P Xu, P Abellan, X Chen, Y Zhang, DE Perea, JE Evans, LJ Lauhon, JG Zhang, J Liu, ND Browning, Y Cui, I Arslan, and CM Wang. 2013. "Demonstration of an Electrochemical Liquid Cell for Operando Transmission Electron Microscopy Observation of the Lithiation/Delithiation Behavior of Si Nanowire Battery Anodes." Nano Letters 13(12):6106-6112. DOI: 10.1021/nl403402q.

Related Stories

Composite battery boost

December 4, 2013

(Phys.org) —New composite materials based on selenium (Se) sulfides that act as the positive electrode in a rechargeable lithium-ion (Li-ion) battery could boost the range of electric vehicles by up to five times, according ...

Better batteries possible with new spectroscopic technique

December 5, 2013

(Phys.org) —A new technique developed at Berkeley Lab's Advanced Light Source could help scientists better understand and improve the materials required for high-performance lithium-ion batteries that power EVs and other ...

Batteries as they are meant to be seen

December 26, 2013

Researchers have developed a way to microscopically view battery electrodes while they are bathed in wet electrolytes, mimicking realistic conditions inside actual batteries. While life sciences researchers regularly use ...

Battery development may extend range of electric cars

January 9, 2014

It's known that electric vehicles could travel longer distances before needing to charge and more renewable energy could be saved for a rainy day if lithium-sulfur batteries can just overcome a few technical hurdles. Now, ...

Recommended for you

New nanomaterial maintains conductivity in 3-D

September 4, 2015

An international team of scientists has developed what may be the first one-step process for making seamless carbon-based nanomaterials that possess superior thermal, electrical and mechanical properties in three dimensions.

Graphene made superconductive by doping with lithium atoms

September 2, 2015

(Phys.org)—A team of researchers from Germany and Canada has found a way to make graphene superconductive—by doping it with lithium atoms. In their paper they have uploaded to the preprint server arXiv, the team describes ...

Making nanowires from protein and DNA

September 3, 2015

The ability to custom design biological materials such as protein and DNA opens up technological possibilities that were unimaginable just a few decades ago. For example, synthetic structures made of DNA could one day be ...

For 2-D boron, it's all about that base

September 2, 2015

Rice University scientists have theoretically determined that the properties of atom-thick sheets of boron depend on where those atoms land.

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.