Date of Award
2025
Document Type
Dissertation
Degree Name
Doctor of Philosophy (PhD)
Department
Mechanical Engineering
Committee Chair
Guangsheng Zhang
Committee Member
James Baird
Committee Member
Keith Hollingsworth
Committee Member
Yu Lei
Committee Member
George Nelson
Research Advisor
Guangsheng Zhang
Subject(s)
Lithium ion batteries--Performance--Simulation methods, Lithium ion batteries--Thermal properties, Lithium ion batteries--Safety measures.
Abstract
Internal short circuit (ISC) caused thermal runaway is a critical challenge for Li-ion batteries that are widely used in various applications. However, currently, there is still a lack of understanding on how exactly an ISC triggers thermal runaway. ISC is a highly localized and transient phenomenon, hence, in situ diagnosis is important in understanding the development of ISC. In this work, experimental methods were developed for simultaneous in situ measurement of ISC temperature, ISC current, and ISC resistance during slow nail penetration of small single-layer Li-ion cells and large-format multiple-layer Li-ion cells. Furthermore, the experimental results of multiple-layer Li-ion cells were used for the development and validation of a thermal-electrochemical coupled model. Then the model was used to enhance the understanding of the experimental results. The investigation with single-layer cells revealed that the dynamic change of the ISC temperature during nail penetration was due to the ISC current change, which was further attributed to the ISC resistance change. In particular, the change of the contact resistance between the nail and the Al foil current collector associated with mechanical rupture or melting of the Al foil plays a critical role in the dynamic behaviors of ISC during nail penetration. The investigation with segmented multi-layer cells not only confirmed the relationship between the ISC temperature, the ISC current, and the ISC resistance, but also revealed an interesting phenomenon. Thermal runaway can be confined to a small segment that is nail penetrated and does not propagate to the rest of the cell. This phenomenon was further investigated using the thermal-electrochemical coupled model. It was found that conductive heat transfer between the segments played an important role in determining if thermal runaway propagates from the small segment to the entire cell. These results demonstrate that integration of in situ diagnosis and numerical modeling can enhance the understanding of how an ISC evolves to trigger thermal runaway. In addition, the observations of the dramatic change in ISC resistance and the confinement of thermal runaway imply potential strategies to mitigate the risk of ISC-caused thermal runaway.
Recommended Citation
Liu, Siyi, "Understanding the behaviors of internal short circuit and thermal runaway of Li-ion batteries through in situ diagnosis and modeling" (2025). Dissertations. 451.
https://louis.uah.edu/uah-dissertations/451
