A. Stacy, M. Gilaki, E. Sahraei and D. Soudbakhsh, “Investigating the Effects of Mechanical Damage on Electrical Response of Li-Ion Pouch Cells,” 2020 American Control Conference (ACC), 2020, pp. 242-247, doi: 10.23919/ACC45564.2020.9147883.

https://ieeexplore.ieee.org/document/9147883

Li-ion batteries (LIB) are used in many applications because of their high-power/energy density, long life cycle, and low self-discharge rate. Li-ion batteries are susceptible to mechanical damages which may lead to an electrical short, thermal runaway, and possibly explosions or fires. However, in some situations such as in a mild car accident, battery packs can get moderate deformations without an electrical short or immediate thermal runaway. Currently, there is no reliable battery characterization method to determine the safety of the batteries for future use after sustaining mechanical damage. In this study, we investigated the connection between the mechanical indentation of Li-ion cells to their impedance spectra. After the initial characterization of four Li-ion pouch cells, the first part of the study included indenting a cell and monitoring their Electrochemical Impedance Spectroscopy (EIS) and charge/discharge cycling data and comparing them to the ones from the control (intact) samples. The second part of the study included incremental indentation of the cell and collecting EIS measurements at specific times after each increment. The control group went through the same EIS measurements and the time series data were compared to the indented cell. Our results showed that while some properties of batteries such as ohmic resistance remain relatively constant when the battery is subjected to incremental mechanical damage, changes in low-frequency impedance were observed with the mechanical loading, suggesting a criterion to measure the safety of pouch cells.