Solid-state batteries using lithium metal anodes are seen as being able to deliver a step-change improvement in EV battery range, safety and performance. They could also have a role in the development of electrically powered aviation.
Li-SSBs replace the flammable liquid electrolyte in conventional batteries with a solid electrolyte and use lithium metal as the anode. The use of the solid electrolyte improves safety, and the use of lithium metal means more energy can be stored.
Li-SSBs are, however, prone to short circuit when charging due to the growth of dendrites, which are filaments of lithium metal that crack through the ceramic electrolyte.
Now, as part of the Faraday Institution’s SOLBAT project, researchers from Oxford University’s Departments of Materials, Chemistry and Engineering Science, have led a series of investigations to understand more about how this short-circuiting happens. Their findings are detailed in Nature.
In a statement, co-lead author Dominic Melvin, a PhD student in Oxford University’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. While today's lithium-ion batteries will continue to improve, research into solid-state batteries has the potential to be high-reward and a game-changer technology.”
In this latest study, the group used X-ray computed tomography at Diamond Light Source to visualise dendrite failure in exceptional detail during the charging process.
The new imaging study revealed that the initiation and propagation of the dendrite cracks are separate processes, driven by distinct underlying mechanisms.
Dendrite cracks initiate when lithium accumulates in sub-surface pores. When the pores become full, further charging of the battery increases the pressure, leading to cracking. In contrast, propagation occurs with lithium only partially filling the crack, through a wedge-opening mechanism which drives the crack open from the rear.
This new understanding points the way forward to overcoming the technological challenges of Li-SSBs.
Melvin said: “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.”
According to a recent report by the Faraday Institution, SSBs could satisfy 50 per cent of global demand for batteries in consumer electronics, 30 per cent in transportation, and over 10 per cent in aircraft by 2040.
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