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Here we report a novel and simple method for triggering internal short circuit (ISC) in Li-ion cells on demand and measuring critical ISC parameters in situ. The method works by inserting a pair of metal pads into a Li-ion cell and connecting the pads outside the cell through a switch and a current sensor. Different types of ISC that are common in field failures can be simulated by this method. ISC current and ISC resistance can be measured. The measurement further enables determination of local ISC heat generation rate. By attaching a micro temperature sensor between the metal pads, the ISC temperature can be also measured. The method was applied to both lab-made single-layer cells and commercially available multiple-layer cells in this work. The results generally verified previous modeling predictions about the effects of ISC types and ISC resistance on behaviors of Li-ion cells. It suggested that the proposed method can be used to validate models and enhance understanding of highly localized and transient behaviors of ISC. It was also demonstrated that the method has minimal effects on Li-ion cell performance and has good repeatability in triggering ISC.
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Understanding internal short circuit and thermal runaway of large-format Li-ion cells triggered by slow nail penetration through in situ diagnosis
Here we report a method of simultaneously measuring internal short circuit (ISC) current, ISC resistance, and ISC temperature in large-format Li-ion cells to understand the behaviors of ISC-caused thermal runaway (TR). It is enabled by dividing electrodes and current collectors into a small segment and a large segment and triggering ISC in the small segment through slow nail penetration. ISC temperature and ISC current showed multiple peaks before TR, which was attributed to the change in ISC resistance as the nail went through different layers of cell components. TR occurred when the ISC resistance suddenly dropped by an order of magnitude. More interestingly, it was found that TR was confined to the small segment and did not propagate to the large segment. It was hypothesized that reduced heat transfer in the gap between the segments contributed to the confinement of TR. A comparison between a fully segmented cell and a cathode-segmented cell, with different effective thermal conductivity in the gap region, supported this hypothesis.
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- Award ID(s):
- 2240029
- PAR ID:
- 10660879
- Publisher / Repository:
- Elsevier
- Date Published:
- Journal Name:
- Journal of Power Sources
- Volume:
- 647
- Issue:
- C
- ISSN:
- 0378-7753
- Page Range / eLocation ID:
- 237344
- Subject(s) / Keyword(s):
- internal short circuit, thermal runaway, large-format Li-ion cells, slow nail penetration, in situ diagnosis
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript
- Journal Article:
- https://doi.org/10.1016/j.jpowsour.2025.237344
