Critically damaged Li-ion cell in the setup for synchrotron X-ray tomography experiments at the BAMline.
Source: BAM
The transition to a zero-emission energy economy depends on the integration of efficient electrical energy storage systems, of which lithium-ion batteries (LIBs) are a key technology. Although they are generally safe, deviations from their operating specifications due to manufacturing errors or improper use can lead to critical safety risks, and in particular thermal runaway (TR). Internal short circuits (ISCs) are the main cause of TRs in LIBs. In tests, among other things, ISCs are triggered by the penetration of nails. The study presented here was published in the Journal of Power Sources by researchers from divisions 3.1 and 8.5. It investigates the structural changes and mechanisms underlying ISC-induced TR in LIBs using synchrotron X-ray computed tomography (SXCT) at low temperatures.
For this purpose, test cells were deep-frozen at the BAM main site in the cell test center, punctured with a nail and then transported cooled to the large-scale research facility BESSY II. The cryogenic set-up developed makes it possible to achieve a gradual rise in temperature of the frozen, damaged battery. Electrical parameters such as voltage and current are monitored and high-resolution SXCT images are recorded at the same time. The results show that the damage at -80 °C not only prevents immediate TR, but that the first structural and electrical processes only become apparent during controlled thawing. Thus, the onset of TR processes could be observed at damaged areas, as evidenced by voltage fluctuations and structural changes such as cracking and decomposition of the cathode material.
These results illustrate the importance of using low temperatures to analyze and model fast processes such as TR using imaging techniques. The low-temperature SXCT setup developed here provides a powerful tool for non-destructive, high-resolution investigation of battery defects and thus contributes to improving the safety of LIBs. The results of this study provide important findings that can be incorporated into the further development of regulations regarding the transport conditions of critically defective battery cells.
Visualization of stepwise electrode decomposition in a nail penetrated commercial lithium-ion cell using low-temperature synchrotron X-ray computed tomography
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Nils Böttcher, Shahabeddin Dayani, Henning Markötter, Anita Schmidt, Julia Kowal, Yan Lu, Jonas Krug von Nidda, Giovanni Bruno
Journal of Power Sources, Volume 623, 15 December 2024