X-Ray-Based Diagnostics for Battery Modeling and Testing

Ann Nguyen:
Hello. This is Ann Nguyen, Senior Associate Conference Producer with Cambridge EnerTech. We're here for a podcast for the Battery Safety conference, which runs this November 3-4 in Bethesda, Maryland. Right now, we have one of our featured speakers, Dr. Michael F. Toney, Synchotron Materials Sciences Division Head and Professor in Photon Sciences and Stanford Synchotron Radiation Light Source with the SLAC National Accelerator Center at Stanford University.

Mike, thank you for joining us.

Michael Toney:
Sure. I'm glad to talk to you and the audience.

Ann Nguyen

You are a globally recognized expert in developing and using X-ray techniques for determining structure and morphology in energy materials, including energy storage, metal oxides, and so forth. What led you down that path, and how did you come to see such applications?

Michael Toney:
Well, I started as a graduate student doing fundamental surface science, and actually, this is what the 2016 Nobel Prize in Physics was for, and in fact, I was fortunate enough to have one of the Nobel laureates be my professor for solid-state physics. This is fundamental physics, and that led me into using X-rays, so using X-rays to probe the fundamental science, serve the science, of two-dimensional materials.

I did that for my graduate work and as a postdoc in Denmark. Subsequent to that, I went to IBM and started to use the X-ray approaches to look at aspects of aqueous electro-chemistry, so that is solids that are in contact with water or aqueous electrolytes. And we pretty much pioneered this field and continued to make progress in that for probably 5 or 10 years until, basically, IBM became less interested in that kind of science as it changed more into a software company.

About that same time, the importance of energy became, I think, more widely accepted, at least within the scientific community, and importance of developing materials to solve some of the, say, CO2-neutral energy challenges that we now face. And because of the realization of the importance of that to society and in fact, all of humanity, I started to apply these same kinds of approaches now towards what you might call energy materials.

Those were solar cells largely at that point in time, and also increasingly towards battery, towards energy storage materials. Over the last about 10 years, we've been using these approaches to watch energy storage materials for safety aspects as well as our operational aspects, and so that's pretty much the path that led me to where I am now.

Ann Nguyen:
What challenges might be encountered with the use of such non-invasive technology for battery modeling and testing, and what can be done to manage them?

Michael Toney:
Non-invasive may be a bit of a stretch. It's probably true that nothing is truly non-invasive. The X-rays are perhaps less invasive than other probes. The advantage they have is that we can use them in a more realistic environment, but they still do create problems. The primary one that we notice is actually what we call beam damage. So the X-rays are very intense. They will change the material just by interacting with it.

X-rays are ionized using radiation, so they create ions, which can do chemistry, and so the beam damage is actually the primary problem that we have. It tends to cause the most problem with the electrolyte than non-aqueous electrolytes that are used in batteries. And so as a mitigation strategy, it's not very sophisticated. We basically take data for as long as we can before we create problems with the battery cell, and that's pretty much just a workaround. Most of the time that works pretty well. That's one of the primary challenges.

The other one is more fundamental to battery materials, and that's the situation where these are basically hierarchical, so the aspects of the electrode materials that matter span a range of length or range of length scales from atomistic, so a few nanometers or less, up to the size of the electrode, which will be 100 microns or so. And so being able to observe or watch that whole range of length scales at once is, I won't say impossible, but extremely challenging.

What we've done is take the approach of using different tools or different X-ray techniques or other techniques to be able to observe the different length scales in different sets of experiments. And that's really been the workaround for that. And then we take the various bits or various pieces of data that we get and merge them together into a holistic picture to understand actually what's happening within the battery.

Ann Nguyen:
When you talk about “Operando Diagnostics of Lithium-Ion Batteries” during your presentation on November 3, and how using X-ray diagnostics can be applied to the battery safety testing concerns of the audience, what's the main theme you'd like to convey to this community?

Michael Toney:
Well, I think that the main theme is that the community has developed over the past 5 to 10 years, probably reaching beyond past that, a suite of tools that allow us now to rapidly advance energy storage technologies. So I'll be talking about one specific case of those, and that's the X-ray-based diagnostics. But there are other approaches that provide valuable information as well. Electron microscopies have made tremendous progress over the last 5 or 10 years to be able to image in a highly…system battery electrodes, as well. There is a suite of optical probes and all of these complements to the classic electro-chemistry, which has been done in the past and is extremely valuable.

This has allowed us now to be able to observe battery electrodes while they're operating and then get a much better understanding of the failure mechanisms and the operational mechanisms. And that I think is poising us now to be able to rapidly advance energy storage. Where I see a need, then, is to make these tools, and again, that goes beyond X-ray-based diagnostics, but other ones as well, more broadly available to the entire community. The academic community has been pretty successful in using these, but to make these kind of tools more available to companies, startups or established companies, to be able to actually probe the materials they're making I think is a challenge that we're still trying to address.

I think the key take home is that we're now at a state that we can start to more rapidly advance energy storage technologies to address some of the global energy challenges that the planet has, and the challenge then that we have is to make these more broadly and easily accessible.

Ann Nguyen

That was Michael Toney of Stanford. He'll be speaking during the Battery Safety conference, happening November 3-4 in Bethesda, Maryland. To learn more from him, visit www.knowledgefoundation.com/battery-safety for registration info and enter the keycode “Podcast”.

This is Ann Nguyen. Thanks for listening.

Speaker Proposals