At the Faraday Institution, scientists working in the SOLBAT project have made an important step in comprehending the reasons as to how and why solid-state batteries (SSBs) tend to fail.
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In a paper published in the journal Nature Materials on April 22nd, 2021, researchers offer answers to a crucial piece of this scientific puzzle.
New battery chemistries “beyond lithium ion” should be designed to make stepwise changes in electric vehicle (EV) battery range and safety at a reduced cost. SSBs fall under one such potential technology. However, large-scale adoption of SSBs has been hampered by various critical technical challenges that result in the failure of the battery while being charged and discharged.
Moreover, SSBs can short circuit following the repetition of charging and discharging. One well-identified reason for battery failure is the development of dendrites—branching lithium networks that grow via the solid electrolyte when a battery is charged. Finding solutions to these two challenges could possibly open the door for a new period of SSB-powered electric vehicles.
Scientists in the Materials, Chemistry and Engineering Science Departments at the University of Oxford worked with the Diamond Light Source and the Paul Scherrer Institute in Switzerland to produce powerful evidence that supports one of two competing theories with respect to the mechanism by which lithium metal dendrites grow via ceramic electrolytes, resulting in short circuits at high rates of charge.
The team used an imaging method quite similar to the one utilized in medical CAT scanners—X-ray computed tomography—together with spatially mapped X-ray diffraction, to envision and characterize the development of dendrites and cracks deep inside an operating solid-state battery.
Initially, conical pothole-like cracks develop in the electrolyte close to the plated lithium anode. The crack propagates along the path where the porosity is more than the ceramic’s average value.
Then, metallic lithium is deposited along the crack, and this ingress induces the propagation of the cracks by broadening the crack from the rear. The crack front propagates before lithium deposition, and lithium does not exist at the crack tip. The cell eventually short circuits only when lithium plates along the complete crack.
Ning, Z., et al. (2021) Visualizing plating-induced cracking in lithium-anode solid-electrolyte cells. Nature Materials. doi.org/10.1038/s41563-021-00967-8.