Derakhshan, Mohsen, Mehdi Gilaki, Andrew Stacy, Elham Sahraei, and Damoon Soudbakhsh. “Bending Detection of Li-Ion Pouch Cells Using Impedance Spectra.” ASME L in Dynamic Systems and Control 1, no. 3 (2021): 031005.

Abstract

Li-ion batteries are the preferred choice of energy storage in many applications. However, the potential for fire and explosion due to mechanical damage remains a safety concern. Currently, there are no criteria for the extent of the mechanical damage under which the batteries are safe to use. Here, we investigate the effects of bending damage to Li-ion cells on their impedance spectra. After the initial characterization of four Li-ion pouch cells, one of the cells underwent a three-point bending load. We measured the impedance spectra of this cell after each increment of loading. The impedance data of the control group cells were collected at the same intervals as the damaged cell. A distributed equivalent circuit model (dECM) was developed using the data from the electrochemical impedance spectroscopy (EIS) procedure. We observed that several model parameters such as the magnitude of constant phase elements had similar trends in the control cells and the bent cell. However, some model parameters such as resistances in parallel with constant phase elements, and the inductor showed dependency on the extent of the damage. These results suggest the potential for use of such parameters as an indicator of mechanical damage when visual inspection of cells is not possible in a battery pack setup. Future steps include investigation of similar trends for other commercial batteries and chemistries and form factors to verify the applicability of the current findings in a broader context.

https://asmedigitalcollection.asme.org/lettersdynsys/article/1/3/031005/1094059/Bending-Detection-of-Li-Ion-Pouch-Cells-Using

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.

The autonomous car project ranked as one of the top senior design teams. Due to the pandemic, the top teams were not ranked. Katie Martin, Stefanie Beard, Austin Cook, Nick Mecca, and Alex Wroblewski developed this autonomous car-like robot for research.

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 the pouch cells.

Read More:

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