Oxford Research Could Lead to Revolutionary Batteries for Electric Transportation and Aviation

A study published in Nature reveals that advanced imaging techniques have been used to understand the reasons for failure in lithium metal solid-state batteries (Li-SSBs). Li-SSBs replace the flammable liquid electrolyte in conventional batteries with a solid one and use lithium metal as the anode. This increases safety and energy storage possibilities, leading to potential revolutionizing of the electric vehicle (EV) and aviation sectors.

Oxford University researchers have identified the causes resulting in the failure of lithium metal solid-state batteries (Li-SSBs). The team discovered that the development and growth of “dendrites” cause the batteries to short-circuit, a revelation that helps to address technological issues in solid-state battery development, and potentially improve EV batteries.

A new study led by researchers at the University of Oxford predicts the possibility of significantly improving EV batteries. Published on June 7, the advanced imaging techniques used in this research led to the discovery of mechanisms that result in the failure of lithium metal solid-state batteries (Li-SSBs). If the techniques to overcome these mechanisms can be developed, solid-state batteries that use lithium metal anodes could vastly improve EV battery range and performance, leading the way to advancement of electrically powered aviation.

Li-SSBs differ from conventional batteries in that they have a solid electrolyte instead of a flammable liquid one, and use lithium metal as the anode (negative electrode). The use of the solid electrolyte means that Li-SSBs manifest better safety profiles and the use of lithium metal enables a higher amount of stored energy. A root issue with Li-SSBs is that they are prone to short circuit when charged, due to "dendrites,” filaments of lithium metal that crack the ceramic electrolyte. Researchers at the University of Oxford’s Departments of Materials, Chemistry, and Engineering Science, during the Faraday Institution’s SOLBAT project, have carried out a series of thorough investigations to understand the process in detail.

This latest study demonstrates how X-ray computed tomography, an advanced imaging technique, was used to capture the dendrite failure in detail during the charging process and led to identifying two separate processes: initiation and propagation of the dendrite cracks driven by two distinct underlying mechanisms. Generally, dendrite cracks initiate when lithium accumulates in sub-surface pores. When these pores become full, charging increases pressure and cause cracking. On the other hand, propagation occurs with lithium only partially filling the crack, and this drives the crack from the rear, using a wedge-opening mechanism.

This new insight could pave the way forward in overcoming technological challenges with Li-SSBs, such as understanding the effect of pressure in the anode can avoid gaps, but too much pressure can lead to short circuits and dendrite propagation. Sir Peter Bruce, Wolfson Chair, Professor of Materials at the University of Oxford and Chief Scientist of the Faraday Institution said that the research will help in making progress of solid-state battery research towards a practical device.

The Faraday Institution recently reported that SSBs might satisfy 50% of global demand for batteries in consumer electronics, 30% in transportation and over 10% in aircraft by 2040.

Professor Pam Thomas, CEO, Faraday Institution, said: “SOLBAT researchers continue to develop a mechanistic understanding of solid-state battery failure – one hurdle that needs to be overcome before high-power batteries with commercially relevant performance could be realized for automotive applications. The project is informing strategies that cell manufacturers might use to avoid cell failure for this technology. This application-inspired research is a prime example of the type of scientific advances that the Faraday Institution was set up to drive.”