An industrial collaboration between Hummingbird Scientific and a team of researchers from the ALS, SLAC, Berkeley Lab, Stanford University, and other institutions has resulted in a new x-ray microscopy platform that gives scientists the ability to image nanoscale changes inside lithium-ion battery particles in real time as they charge and discharge. Data obtained from the imaging platform have already provided surprising new insights and could help researchers improve batteries for electric vehicles as well as smart phones, laptops, and other devices.
Using liquid cell technology from Hummingbird Scientific, lead researcher Will Chueh, a faculty scientist at SLAC, and his team built a battery inside the liquid cell that consists of two silicon nitride transparent windows with a very small gap between the microfabricated chips. Liquid electrolyte flowed between the chips to deliver the lithium ions to the nanoparticles. Hummingbird Scientific created a customized correlative liquid-cell sample holder that worked with the scanning transmission x-ray microscopy (STXM) beamlines at the ALS.
“We are really proud of the team. It’s a really good example of where two universities (Stanford/MIT), a national lab (Berkeley Lab), and a private company (Hummingbird) came together to achieve a result that couldn’t have happened without all parties,” says Daan Hein Alsem, Director of Research at Hummingbird Scientific.
Hummingbird Scientific first developed and commercialized the liquid-cell microscopy technology for transmission electron microscopes (TEMs) as part of a DOE Basic Energy Science–funded Small Business Innovation Research (SBIR) project. Recently, with follow-up funding from the DOE SBIR program, Hummingbird developed their liquid-cell technology for x-ray beamlines as a correlative microscopy platform. This ALS research project is the first high-impact study that has been published using this new platform.
Working at ALS Beamlines 11.0.2 and 126.96.36.199, scientists were able to image the battery nanoparticles in operando, as the lithium ions migrated in and out. The specially designed “liquid electrochemical STXM nanoimaging platform” can image about thirty particles at a time.
In a real battery, thousands of these particles form an electrode, and positively charged lithium ions embed in the electrode as the battery charges. Ideally, the ions are inserted uniformly across the electrode’s surface. But this rarely happens, especially as a battery ages, which negatively affects performance. Using the new platform at the ALS, scientists discovered that the battery charging process doesn’t play out uniformly on the surface of a particle, a phenomenon that likely curbs battery performance over time. Understanding more about this phenomenon could help researchers counteract it and develop batteries that charge faster and last longer.
The team also found that slow charging actually resulted in more irregular distribution than fast charging. This was surprising, considering that fast charging is usually considered more harmful to the battery. Charging the battery caused more uneven distribution than discharging, or using the battery, does. Results of the research were published in a recent issue of Science.
“We were able to see for the first time how electrochemical behavior changes with charging rate,” says ALS Staff Scientist David Shapiro, who helped Chueh develop the platform. “The faster you charge, the more uniform current density is; when you have a very heterogeneous current density you get hot spots, which is important to know.”
“When we looked at batteries using STXM at the ALS before, we’d have to take them apart to image them at each stage, which meant a lot of missed information,” says Shapiro. “Now that we’re able to look at operando systems, there’s nothing missed—we can see the changes over time, the asymmetry.”
Hummingbird’s platform, which right now is exclusively available at the ALS, but could also be used more broadly at other light source facilities, can help advance battery design, but is also appealing to other scientific disciplines. Shapiro says he recently received a beam time request from a research group that wants to use it to study chromium deposition.
“Soft x-rays, and particularly scanning microscopy, are very useful for looking at spatially resolved maps of electron states,” says Shapiro. “And being able to look at operando systems means that there’s nothing missed.”