“Game-Changing” Batteries for Electric Vehicles and Aviation Unlocked by Oxford Study

Energy, Science and Technology, Technology

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Researchers at Oxford University have found out why lithium metal solid-state batteries (Li-SSBs) fail, which could lead to better batteries for EVs.

The team found that the formation and growth of “dendrites” cause the batteries to short-circuit. This could help solve some of the technical problems that are holding up the development of solid-state batteries.

A new study has found out how lithium metal solid-state batteries break down.
Researchers used a high-resolution image method to see how batteries charged in a level of detail that had never been seen before.
The new information could help solve the technical problems with solid-state batteries and open the door to a technology that could change the way electric cars and airplanes work.

A new study led by University of Oxford researchers and released in Nature on June 7 could be a step toward making electric vehicle (EV) batteries much better. Using new imaging methods, the ways that lithium metal solid-state batteries (Li-SSBs) fail were found. If these problems can be solved, solid-state batteries with lithium metal anodes could make a big difference in the range, safety, and performance of EV batteries and help move electric-powered aircraft forward.

The development of solid-state batteries using lithium metal anodes is one of the most significant difficulties facing the advancement of battery technology, according to Dominic Melvin, one of the study’s co-lead authors and a PhD student in the Department of Materials at the University of Oxford. Research into solid-state batteries has the potential to be highly rewarding and a technology that changes the game, even though lithium-ion batteries of today will continue to get better.

Because Li-SSBs use lithium metal as the anode (negative electrode) instead of the flammable liquid electrolyte found in traditional batteries, they stand out from other batteries. The safety is increased by using a solid electrolyte, and more energy can be stored thanks to the usage of lithium metal. But a significant problem with Li-SSBs is that they are prone to short circuit when charging because of the development of “dendrites”: filaments of lithium metal that break through the ceramic electrolyte. Researchers from the University of Oxford’s Departments of Materials, Chemistry, and Engineering Science have led a number of in-depth investigations as part of the Faraday Institution’s SOLBAT project to learn more about how this short-circuiting occurs.

In this most recent work, the group used an advanced imaging method called X-ray computed tomography at Diamond Light Source to see dendrite failure during the charging process in more detail than ever before. The new imaging study showed that cracks in dendrites start and spread in different ways that are caused by different underlying mechanisms. Dendrite cracks start when lithium builds up in holes below the surface. When the pores are full, charging the battery again raises the pressure, which makes the battery crack. On the other hand, propagation happens when lithium only fills part of the crack. This is done by a wedge-opening device that pushes the crack open from the back.

This new understanding shows how to move forward to solve the problems with Li-SSB technology. Dominic Melvin said, “For example, pressure at the lithium anode can be good to prevent gaps from forming at the interface with the solid electrolyte when the battery is being discharged. However, our results show that too much pressure can be bad, making it more likely that dendrites will grow and the battery will short-circuit when it is being charged.”

Sir Peter Bruce, Wolfson Chair, Professor of Materials at the University of Oxford, Chief Scientist of the Faraday Institution, and corresponding author of the study, said, “It has been hard to figure out how a soft metal like lithium can get through a dense, hard ceramic electrolyte, but many excellent scientists from all over the world have made important contributions.” We hope that the new information we’ve learned will help move studies on solid-state batteries toward a device that can be used in real life.”

A recent report from the Faraday Institution says that by 2040, SSBs could meet 50% of the world demand for batteries in consumer electronics, 30% of the demand in transportation, and more than 10% of the demand in aircraft.

In order to realize high-power batteries with commercially viable performance for automotive applications, Professor Pam Thomas, CEO of the Faraday Institution, said: “SOLBAT researchers continue to develop a mechanistic understanding of solid-state battery failure. The research is providing makers of cells with potential techniques to prevent cell failure for this technology. This research was motivated by an application, which is a perfect illustration of the kind of scientific advancements that the Faraday Institution was created to foster.