Does anyone know why I get this weird EIS spectra (pic attached) at high temperature on Li-ion full cell? I use high power A123 26650 cyclindrical LFP cell (2.5 Ah). My EIS device is BRS Messtechnik, uses 4 wire connection set up (galvanostatic) and is directly soldered to the cell. Is soldering a good idea to do Impedance measurements ? Any other way or suggestions will be useful.
Thanks in advance
Dear Praveen Kumar Kuppusamy[1-3],
1) what is the parameter of the VDC (=0.0 ?) polarization, during your "weird" EIS spectra ?
2) What is the model of your EIS device (version of a BRS Messtechnik comm. device) ?
3) Do you include a Battery Multiplexer, during your "weird" EIS spectra ?
1. As Aparna Sathya Murthy. Always avoid soldering, since transient temperatures might be exceeding a safety value for Li-batteries; it is, nearly, never[2] implemented in the (industrial) batteries labs. Instead of soldering (or even worse the reflow soldering) they implement an electro-welding (or laser-welding, TIG-welding, etc.) technique.
2. Do not allow the soldering iron to make direct contact with the bodies of the batteries. Proceed with the soldering quickly within 5 seconds. Chapter 4: Batteries with Terminals and Soldering Lithium Batteries https://industrial.panasonic.com/cdbs/www-data/pdf/AAA4000/AAA4000COL21.pdf
3. As Artur Braun, advice, also.
@Mr. Ioannis
1. The device is galvanostatic, so Ac current is 100 mA and dc current is 50 mA.
2. Model is BIM 2 (range 1 mΩ to 1 Ω ), please find in the picture
3. These results doesn't include multiplexer. But results are even more worse if I include them.
Regarding soldering, the battery has a special laser welded strip which helps to solder on them. There is no direct contact on them. Any other way to implement EIS other than soldering ? Reference links will be useful
Thank you so much for your suggestions
@Ms. Aparna,
Thanks, I also thought that the soldering might be the issue.
Dear Praveen Kumar Kuppusamy,
the dc current[1] should be (near) zero (mA).
1. Your quote : @Mr. Ioannis 1. The device is galvanostatic, so Ac current is 100 mA and dc current is 50 mA.
Dear Prof. Ioannis,
The device current is standard. I am not able to change is to 0 mA, it is 50 mA for range 30 mΩ. Could you recommend any way of connecting EIS to the cell instead of soldering ?
Dear Praveen Kumar Kuppusamy,
if the devices' minimum DC current is "standard" (but not zero mA), then try EIS using both (DC parametric) polarities of the iDC=(+,) - iminimum polarizations.
I recommend the 4-electrode "Round Cell Adapter RZA"[1] or an electro-welding[2] (under Ar), instead of soldering.
1. Round Cell Adapter RZA https://www.brs-messtechnik.de/english/aktuelles.html
2. Since a laser welding is extravagant, very special and expensive for a common, academic, research lab.
Dear Prof. Ioannis,
Thank you so much. You always help me with perfect suggestions and solutions.
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