"How do we produce batteries at the cost that is suitable for mass adoption globally, and how do you do this to electrify the planet?" Clare Grey asked an audience of over 450 combined in-person and virtual attendees at the sixth annual Dresselhaus Lecture, organized by MIT.nano on Nov. 18. "The biggest challenge is, how do you make batteries to allow more renewables on the grid."
These questions emphasized one of Grey's key messages in her presentation: The future of batteries aligns with global climate efforts. She addressed sustainability issues with lithium mining and stressed the importance of increasing the variety of minerals that can be used in batteries. But the talk primarily focused on advanced imaging techniques to produce insights into the behaviors of materials that will guide the development of new technology. "We need to come up with new chemistries and new materials that are both more sustainable and safer," she said, as well as think about other issues like secondhand use, which requires batteries to be made to last longer.
Video: MIT.nano
Better understanding will produce better batteries
"Batteries have really transformed the way we live," Grey said. "In order to improve batteries, we need to understand how they work, we need to understand how they operate, and we need to understand how they degrade."
Grey, a Royal Society Research Professor and the Geoffrey Moorhouse-Gibson Professor of Chemistry at Cambridge University, introduced new optical methods for studying batteries while they are operating, visualizing reactions down to the nanoscale. "It is much easier to study an operating device in-situ," she said. "When you take batteries apart, sometimes there are processes that don't survive disassembling."
Grey presented work coming out of her research group that uses in-situ metrologies to better understand different dynamics and transformational phenomena of various materials. For example, in-situ nuclear magnetic resonance can identify issues with wrapping lithium with silicon (it does not form a passivating layer) and demonstrate why anodes cannot be replaced with sodium (it is the wrong size molecule). Grey discussed the value of being able to use in-situ metrology to look at higher energy density materials that are more sustainable such as lithium sulfur or lithium air batteries.
The lecture connected local structure to mechanisms and how materials intercalate. Grey spoke about using interferometric scattering (iSCAT) microscopy, typically used by biologists, to follow how ions are pulled in and out of materials. Sharing iSCAT images of graphite, she gave a shout out to the late Institute Professor and lecture namesake Mildred Dresselhaus when discussing nucleation, the process by which atoms come together to form new structures that is important for considering new, more sustainable materials for batteries.
"Millie, in her solid-state physics class for undergrads, nicely explained what's going on here," Grey explained. "There is a dramatic change in the conductivity as you go from diluted state to the dense state. The conductivity goes up. With this information, you can explore nucleation."
Designing for the future
"How do we design for fast charging?" Grey asked, discussing gradient spectroscopy to visualize different materials. "We need to find a material that operates at a high enough voltage to avoid lithium plating and has high lithium mobility."
"To return to the theme of graphite and Millie Dresselhaus," said Grey, "I've been trying to really understand what is the nature of the passivating layer that grows on both graphite and lithium metal. Can we enhance this layer?" In the question-and-answer session that followed, Grey spoke about the pros and cons of incorporating nitrogen in the anode.
After the lecture, Grey was joined by Yet-Ming Chiang, the Kyocera Professor of Ceramics in the MIT Department of Materials Science and Engineering, for a fireside chat. The conversation touched on political and academic attitudes toward climate change in the United Kingdom, and audience members applauded Grey's development of imaging methods that allow researchers to look at the temperature dependent response of battery materials.
This was the sixth Dresselhaus Lecture, named in honor of MIT Institute Professor Mildred Dresselhaus, known to many as the "Queen of Carbon Science." "It's truly wonderful to be here to celebrate the life and the science of Millie Dresselhaus," said Grey. "She was a very strong advocate for women in science. I'm honored to be here to give a lecture in honor of her."
