July 19, 2012
Self-professed "beamline junkie" Johanna Nelson has allowed her fascination for synchrotron radiation to lead her to SLAC from, well, a different "S.L.A.C." Now in her second year as a post-doctoral researcher at the Stanford Synchrotron Radiation Lightsource (SSRL), Nelson's research area is listed as simply "Batteries." That seems like a good place to start….
Tell us what you do with batteries.
JN: I'm working on lithium-ion batteries. We have a multi-pronged approach to looking at them: We use Beam Line 11-3 to get information about the battery's crystal structure and Beam Line 4-3 to look at changes in the battery's chemistry. But the most important feature of our research is that we can use a transmission X-ray microscope on Beam Line 6-2 to examine changes to the battery's morphology, or physical form, in operando – which means while it's actually charging or discharging.
This is an ability that X-rays give us because they're so penetrating: You can see right through the battery.
And SSRL has X-rays.
JN: In fact, the main goal of my postdoc was to start SSRL toward in situ battery research, which is research under lifelike conditions. In operando research is a special case of that.
What does such research show us that other ways of looking at these batteries can't?
JN: For example, we looked at lithium-sulfur batteries. They have about five times the energy-storing capacity of lithium-ion batteries, but the sulfur on the cathode can degrade.
The theory based on previous ex situ scanning electron microscope studies was that polysulfides form during discharge and then diffuse out quickly into the electrolyte.
Which basically means less sulfur where it's supposed to be for the battery to work after recharging, right?
JN: Yes. But what we showed using the microscope was that the polysulfides form, but they aren't lost immediately to the electrolyte. When we present this to battery people, they say: "We don't believe you." But that's what the research shows. It exemplifies why in situ and in operando research are so important.
To change gears a bit – how did you discover your love of synchrotrons?
JN: I'm originally from Gettysburg – I sold ice cream to Civil War fanatics in high school – and studied math and physics at Muhlenberg College, which is a small liberal-arts college.
That's a far cry from synchrotrons!
JN: But it's still imaging. Then I got my Ph.D. at Stony Brook while looking at frozen, hydrated yeast with X-ray microscopes. I commuted to the Advanced Light Source at Berkeley Lab to do the research.
And that's a far cry from stars and galaxies.
JN: The reason I chose that group at Stony Brook wasn't really the yeast, it was the chance to use an X-ray microscope to develop a way to look at biomolecules. I worked on a technique to flash-freeze them so that ice crystals don't form and damage them. The yeast is normally hydrated, so it's a very similar idea to wanting to view something in situ – under life-like conditions. This is an X-ray microscopy technique that can be used by scientists in different fields.
My goal in this is to promote X-ray microscopy. People turn to electron microscopy because they don't understand the penetrating capabilities of X-ray microscopy. But since I've come to SLAC, I use any beamline I can get my hands on – not just the microscopy beamlines. I like the collaborative nature of it. You get a peek at other people's work.
From S.L.A.C. to SLAC. And back?
JN: I do want to teach. I'd like to go back to a small liberal-arts college – I know I really got a good education at one. Ideally I'd stay in the area so I can keep working with SSRL.
Is there anything else that makes you happy beside synchrotrons?
JN: Currently, I'm not very active in any of my hobbies. But I do enjoy contra dancing (a type of folk dancing similar to square dancing). I have also ridden horses on and off since I was small. I love to garden, which means potted plants at the moment since I live in an apartment. And I also enjoy reading and cooking.