Jones Investigates Lithium-Ion Batteries in Microscopy Suite

Elizabeth Jones uses the scanning electron microscope (SEM) to characterize the homogeneity of electrodes used in high-capacity lithium-ion batteries. During charge and discharge cycles of the batteries, the electrodes expand and contract; if they expand too much, they crack and diminish the integrity of the battery. Jones is perfecting an electrode that delivers high-capacity energy without cracking.

Beckman's Microscopy Suite offers a wide variety of tools for researchers to use. Elizabeth Jones, a graduate student in the Autonomous Materials Systems Group, utilizes the scanning electron microscopy to help her improve high-capacity lithium-ion batteries. 

Researchers come to the Microscopy Suite for a variety of reasons, but they all have a common purpose: to use some of most powerful and state-of-the-art microscopes available. Each instrument housed in the lab in the basement of the Beckman Institute is managed by a knowledgeable staff member who has expertise working with biological samples, biomaterials, and various other materials. The staff are there specifically to aid users in attaining research goals. The four main modes of imaging include light/laser microscopy/spectroscopy, scanned probe microscopy, electron microscopy/ energy-dispersive spectroscopy, and x-ray micro- and nano-computed tomography (CT). 

The scanning electron microscope (SEM) is one of the workhorses of the Microscopy Suite, providing high-resolution images at an ultimate resolution of two nanometers (two billionths of a meter). A beam of electrons scans repeatedly across the sample and produces stunningly crisp images of its surface topography and (depending on which detector is used) composition. 

Elizabeth Jones, a graduate student working in the Autonomous Materials Systems Group, uses the SEM for her work to improve high-capacity lithium-ion batteries.

 Lithium-ion batteries, which power devices like laptops and cell phones, utilize internal electrodes that permit them to charge and discharge. During these cycles the electrodes expand and contract, but—especially with high-capacity lithium-ion batteries— the electrodes may expand too much and then crack, degrading the capacity and lifetime of the battery. Researchers are working to create longer-lasting high-capacity batteries by reducing the strain upon/expansion of the electrodes to prevent cracking. 

“People are looking at using high-capacity materials in batteries for electric vehicles to extend the range of electric vehicles,” said Jones. “If you have a high-capacity electrode material, you can make the battery smaller and it will last just as long as current batteries. Or, if the high-capacity battery is the same size, it’ll last a lot longer.” 

Electrodes are the conductors through which electricity enters and leaves lithium-ion batteries; thus they are the driving force behind the batteries’ power. They have three main components: active material particles, a conductive additive to fill in the interstitial regions between the active material particles, and a polymer that binds the first two materials together. 

Jones’ work focuses on designing an electrode for which expansion and contraction are minimized, and cracking is thus minimized as well. In order to find the most effective combination, she creates new electrodes with different ratios of the three main components. That’s where the SEM comes in. 

“I use the SEM to see what the electrodes look like after I create a new one. They’re only around 90 microns thick (a micron is a millionth of a meter), so I need to use the SEM to characterize the dispersion of the different materials in the electrodes,” Jones said. “I’ve worked with several different ratios of materials, and also tried different active materials. It’s a continual process of trial and error, and the SEM is fundamental in understanding how the materials mix together.” 

This is just one project of hundreds, at any given time, that benefit from the capabilities of the Microscopy Suite, which has been a Beckman Institute core facility since the late 1990s. In the last year, the Microscopy Suite has undergone significant expansion in terms of both physical space and capabilities. The fluorescence microscope has been completely updated with a new instrument, software, and computer; many of the instruments have had control computers upgraded; and two of the microCT systems have been given new computers, new RAID arrays, 360-degree capability, and load-cell capability, among other improvements. A new ultramicrotome has been delivered and set up in completely remodeled space that also houses several other instruments and microscopes. 

Additionally, biosafety level 2 (BL-2) space is being created to facilitate live-cell imaging. Because some live cells may only be imaged under BL-2 conditions, this new space will house the cell and tissue culture facility that incorporates two new systems: a FRET (fluorescence resonance energy transfer) microscope and BioSLIM (biological spatial light interference microscopy) with TIRF (total internal reflectance fluorescence) imaging capability in opposition, permitting a novel form of correlative microscopy. 

“We keep updating and growing to meet the needs of our users,” said lab manager Scott Robinson, who has been a member of the staff since 1998. “The caliber of work that researchers perform, and that we are able to support, continues to amaze me.”