FOUR C BATTERIES CRACK
X-ray computed tomography images showing the progressive growth of a lithium dendrite crack within a solid-state battery during the charging process. Dominic Melvin said: ‘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.’ This new understanding points the way forward to overcoming the technological challenges of Li-SSBs. In contrast, propagation occurs with lithium only partially filling the crack, through a wedge-opening mechanism which drives the crack open from the rear. When the pores become full, further charging of the battery increases the pressure, leading to cracking. Dendrite cracks initiate when lithium accumulates in sub-surface pores. The new imaging study revealed that the initiation and propagation of the dendrite cracks are separate processes, driven by distinct underlying mechanisms.
In this latest study, the group used an advanced imaging technique called X-ray computed tomography at Diamond Light Source to visualise dendrite failure in unprecedented detail during the charging process.
FOUR C BATTERIES SERIES
As part of the Faraday Institution’s SOLBAT project, researchers from the University of Oxford’s Departments of Materials, Chemistry and Engineering Science, have led a series of in-depth investigations to understand more about how this short-circuiting happens. A critical challenge with Li-SSBs, however, is that they are prone to short circuit when charging due to the growth of ‘dendrites’: filaments of lithium metal that crack through the ceramic electrolyte. The use of the solid electrolyte improves the safety, and the use of lithium metal means more energy can be stored. Li-SSBs are distinct from other batteries because they replace the flammable liquid electrolyte in conventional batteries with a solid electrolyte and use lithium metal as the anode (negative electrode). 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.’ Image credit: Faraday Institution / University of Oxford.One of the co-lead authors of the study Dominic Melvin, a PhD student in the University of Oxford’s Department of Materials, said: ‘Progressing solid-state batteries with lithium metal anodes is one of the most important challenges facing the advancement of battery technologies. PhD student Dominic Melvin (left) and Dr Junfu Bu (right) working in the Department of Materials, University of Oxford.
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