Integration of Temperature and Pressure Sensing Functionalities into Li-ion Pouch Cell on an Industry-Relevant Scale

As part of the BATTERY 2030+ research initiative, the project SENSIBAT focuses on developing smart sensing functionalities, novel battery management system strategies, and state determining algorithms considering economic and
nvironmental aspects. With the help of these sensors, integrated in Li-ion pouch cells, it is aimed to gain a better understanding of the battery during its peration.
Profound knowledge about the actual cell conditions (state-of-charge, state-of-health) during cycling can be used for a better prediction of the cell behavior. Indicators for possible degradation processes and failure mechanisms can be determined and enable a more accurate control of the cells in a battery pack, leading to improved BMS state estimation functions. That way, a significant increase in safety, lifetime and quality is targeted. The introduction of sensors into pouch cells is currently not done at industrial scale and therefore several problems can arise. One of them is incompatibilities during integration of the sensors during the pouch cell assembly process. Especially at the sensor feedthrough, it needs to be ensured that no electrolyte leakage appears, and the tightness of the pouch cell is given. Additionally, an interference between sensor and cell components, which can cause side reactions and unwanted by-products, should be avoided, as this can negatively influence the performance of the cell [1, 2, 3]. This work explains how the integration of the developed temperature and pressure sensing functionalities was conducted on an industry-orientated scale. A special focus within the SENSIBAT project is how the implementation influences the overall cell performance compared to equivalent reference cells without
additional sensing elements. A research pilot line was used to fabricate the Li-ion pouch cells with a nominal capacity of 5 Ah per cell. NMC622 cathodes and graphite anodes were stacked by using an automatic single-sheet stacking unit under dryroom conditions. To gain valuable insights and comparable data on how the conducted integration process influences the overall cell, a comparison of cells with and without integrated sensors was conducted. Therefore, a cycling test plan containing symmetric and asymmetric full cycles at different C-rates, pulse test sequences and electrochemical impedance spectroscopy analyses was performed. The SENSIBAT project partners were able to exhibit that the sensor implementation did not negatively influence the electrochemical performance of the cells compared to the reference pouch cells. The absolute discharge deviation of the cells with and without embedded sensors is below 1%. Additionally, no major differences in the calculated pulse resistance values and electrochemical impedance spectra occur. This project has received funding from the European Union’s Horizon 2020 research and innovation programme under Grant greement no. 957273.
REFERENCES
[1] Vincent Dreher, Daniel Joch, Harald Kren, Jannik H. Schwarberg, Michael P.M. Jank, „Ultrathin and flexible sensors for pressure and temperature monitoring inside battery cells”, 2022 IEEE Sensors | 978-1-6654-8464-0/22/
[2] Valentin Sulzer, Peyman Mohtat, Antti Aitio, Suhak Lee, Yen T. Yeh, Frank Steinbacher, Muhammad Umer Khan, Jang Woo Lee, Jason B. Siegel, Anna G. Stefanopoulou, David A. Howey; “The challenge and opportunity of battery lifetime prediction from field data”, 2021 Elsevier Inc. Joule 5, 1934–1955
[3] Lukas Marthaler, Piotr Grudzien, Maarten Buysse, Marcos Ierides, Amy McCready, „KEY TECHNICAL, POLICY AND MARKET DEVELOPMENTS INFLUENCING THE ELECTRIC VEHICLE BATTERY LANDSCAPE”, 2022 Cobra, Grant Agreement 875568, Market Intelligence Report