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Summer 2018

Batteries Through the Looking Glass

Reconsidering lithium's interaction with battery materials from spectral fingerprints

Andrea Bruck

To make energy sustainability a reality, batteries are being designed to replace fossil fuels in electric and hybrid-electric vehicles with fast charging, long life, and high capacity in mind. To understand how to effectively create this technology, a team at the Center for Mesoscale Transport Properties (m2M), an Energy Frontier Research Center, looked inside a battery while it was operating to discover how certain materials are able to charge quickly. Studying how certain materials, such as lithium titanate, accommodate fast charging without major degradation has the potential to expedite the use of electric vehicles by allowing batteries to fully charge as fast as it takes to pump a tank of gasoline.

Until recently, when scientists tried to understand why a battery failed, they ripped the battery apart, ground up its components, and tried to figure out what happened. This would be the equivalent of sawing your car in half only to discover you needed an oil change. These types of analysis (referred to as ex situ) are commonplace and prone to error from the deconstruction process. Therefore, scientists at m2M designed a battery with a specialized window that allows X-rays to pass through the battery during its operation (in situ analysis). These high-intensity X-rays interact with the materials inside that battery and provide fingerprints that identify the structural changes that are occurring. The fingerprints for the lithium titanate material are interesting because, unlike current battery materials, lithium titanate can cycle for longer with very little structural changes or degradation over its lifetime.

Lithium titanate contains lithium, titanium, and oxygen atoms that make up its crystal structure, as shown in the image below. This structure is defective because the atoms are not densely packed together. In lithium-ion batteries, moving lithium in a material is very important to obtain the optimal device performance, and this defective structure allows lithium to move freely throughout the material. What eluded scientists for so long was WHY the lithium moved freely in the structure with very little displacement of the titanium and oxygen atoms.


(a) Schematic of the X-ray interacting with the battery and (b) the pathways of how lithium (Li) interacts with the titanium in lithium titanate. Reprinted with permission from American Chemical Society, Copyright 2017

This m2M team found out how lithium traveled by monitoring the subtle movements of titanium. For example, most materials with densely packed atoms need to move atoms around to accommodate lithium; however, the movement of titanium in lithium titanate is very small. This accommodation mechanism is like squeezing a new book on an already filled shelf, you could either move current books off one shelf to another, or you could just squeeze in the additional book by only slightly moving the books closest to the new addition. In batteries, large rearrangements (or reordering from one shelf to another) can cause slow degradation over time and reduce the lifetime of the system. However, an incredible feature of lithium titanate is that lithium tends to surround the titanium and oxygen atoms and restricts large rearrangements, often observed in other materials. This observation shows that lithium stabilizes the titanium atoms during charging and discharging of the battery.

The ability of lithium to move freely in the material and restrict titanium and oxygen reordering allows lithium titanate to provide stable battery operation over many cycles. Without the battery window, the path traveled by lithium during battery operation would still be a mystery. Designing materials where lithium movement stabilizes other atoms in the structure could pave the way for quick charging and long lifetime for the future of electric vehicle battery technology.

Acknowledgments

This work was supported by the Center for Mesoscale Transport Properties, an Energy Frontier Research Center supported by the Department of Energy (DOE), Office of Science, Basic Energy Sciences. Calculations were supported by a Laboratory Directed Research and Development project at Brookhaven National Laboratory. Electron microscopy was supported by the DOE, Office of Science, Basic Energy Sciences, Division of Materials Science and Engineering. The use of the National Synchrotron Light Source was also supported by the DOE, Office of Science, Basic Energy Sciences. This research used resources of the Center for Functional Nanomaterials and the National Energy Research Scientific Computing Center, DOE Office of Science user facilities.

More Information

Zhang W, M Topsakal, C Cama, CJ Pelliccione, H Zhao, S Ehrlich, L Wu, Y Zhu, AI Frenkel, KJ Takeuchi, ES Takeuchi, AC Marschilok, D Lu, and F Wang. 2017. “Multi-Stage Structural Transformations in Zero-Strain Lithium Titanate Unveiled by In Situ X-ray Absorption Fingerprints.” Journal of the American Chemical Society 139(46):16591. DOI: 10.1021/jacs.7b07628

About the author(s):

  • Andrea M. Bruck is currently working toward a Ph.D. at Stony Brook University, Department of Chemistry. She is a young investigator in the Center for Mesoscale Transport Properties (m2M), an Energy Frontier Research Center. Her research focuses on the fundamental processes that occur in a battery during its operation and how synchrotron-based characterization can elucidate the chemical processes that cause battery failure.

Defective Design Could Deliver Longer Lasting Batteries

New technique offers window into innovative electrodes during charging and use

Rather than use techniques that rip apart the battery, researchers built a window into the battery and used X-rays to see what was happening while the battery was working. Image courtesy of Nathan Johnson, Pacific Northwest National Laboratory

Batteries fade and fail. That’s a frustrating fact for electric car owners. New batteries that last longer and charge in about the same amount of time as it takes to fill the car’s gas tank could change the face of transportation. For scientists, the challenge is seeing what happens inside a battery while it charges or powers vehicles. At the Center for Mesoscale Transport Properties (m2M), researchers created lithium titanate batteries with designer windows. X-rays pass through the windows and offer insights as to what’s happening inside. Working with long-lasting lithium titanate batteries, they found that lithium tends to surround other atoms in the electrode and prevents big structural changes during charging and discharging. Designing batteries that feature lithium stabilization could pave the way for faster charging. The m2M center is led by Stony Brook University.

More Information

Zhang W, M Topsakal, C Cama, CJ Pelliccione, H Zhao, S Ehrlich, L Wu, Y Zhu, AI Frenkel, KJ Takeuchi, ES Takeuchi, AC Marschilok, D Lu, and F Wang. 2017. “Multi-Stage Structural Transformations in Zero-Strain Lithium Titanate Unveiled by In Situ X-ray Absorption Fingerprints.” Journal of the American Chemical Society 139(46):16591. DOI: 10.1021/jacs.7b07628

Disclaimer: The opinions in this newsletter are those of the individual authors and do not represent the views or position of the Department of Energy.