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A team of researchers from the University of Oxford, UK, assessed how lithium batteries for electric vehicles fail, according to a study published in Nature. The researchers suggested that, if these problems can be overcome, better batteries using metal anodes could significantly improve car range, safety, and performance.
“Progressing solid-state batteries with lithium metal anodes is one of the most important challenges facing the advancement of battery technologies. While lithium-ion batteries of today will continue to improve, research into solid-state batteries has the potential to be high-reward and a gamechanger technology,” said co-author of the study Dominic Melvin, a Ph.D. student in the University of Oxford’s Department of Materials.
Lithium metal solid-state batteries (Li-SSBs) are not like other batteries. Instead of a flammable liquid electrolyte (present in conventional batteries), Li-SSBs have lithium metal as the negative electrode. Using solid electrodes improves safety, and lithium means more energy can be stored in the battery. However, there are some downsides to Li-SSBs: they are prone to short-circuit when charging caused by a growth of filaments of lithium metal that crack through the ceramic electrode. As part of the SOLBAT project, a team from Oxford run a series of tests to understand more about how this short-circuiting happens and how it can be avoided.
The team used advanced imaging techniques to assess the failures during the charging process to conduct these tests. The results showed that the start and propagation of the cracks occur separately, driven by different mechanisms. Cracks start when lithium accumulates in pores just below the surface. When the pores are full, charging increases the pressure and causes cracking. Then, propagation occurs when lithium only partially fills the crack, operating like a wedge to cause further opening from the back.
The authors hope this knowledge will help create better batteries in the future. Estimates show that SSBs will cover 50% of global demand for batteries in consumer electronics, 30% in transportation, and over 10% in aircraft by 2040. “For instance, while pressure at the lithium anode can be good to avoid gaps developing at the interface with the solid electrolyte on discharge, our results demonstrate that too much pressure can be detrimental, making dendrite propagation and short-circuit on charging more likely,” said Melvin.
“The process by which a soft metal such as lithium can penetrate a highly dense hard ceramic electrolyte has proved challenging to understand with many important contributions by excellent scientists around the world. We hope the additional insights we have gained will help the progress of solid-state battery research towards a practical device,” added Sir Peter Bruce, Wolfson Chair, Professor of Materials at the University of Oxford, and Chief Scientist of the Faraday Institution.
Ning, Z., Li, G., Melvin, D.L.R. et al. Dendrite initiation and propagation in lithium metal solid-state batteries. Nature 618, 287–293 (2023). https://doi.org/10.1038/s41586-023-05970-4