Hi,

This may not be just waiting time . Several other causes may contribute to the noise. You may need to increase the stimulation amplitude. Be sure that drift of the mean voltage and current during the EIS measurement are negligible. What kind of instrument do you use, what is the frequency range, the amplitude, do you conduct the EIS in voltage or current control, the length of the cables? Are the units of the real and imaginary axis Ohm or mili-Ohm? If the unit is Ohm then I am surprised to see such high values for a LFP 26650 battery. Do you use 4 point connection to your cell?

Hi,

I am BRS Messtechnik battery impedance meters, range is from 1000 Hz to 0.1 Hz, EIS in galvanostatic or current control mode, cables are about 1m long and the units are in milli-ohm. The device uses 4 point connection

Dear Praveen Kumar Kuppusamy,

(pre)set, please, a much higher number Nb[1] (Nb>>10) of measurements per frequency band[1], at least in the high freq. part of your spectra. What is the amplitude of your AC[2]-current ?

1. The term-label Nb is named as the "frequency grid", in the BRS Messtechnik battery impedance meter (Manual BIM-BTC-SW17.pdf).

2. Apply iDC = i(DC-current) = 0.

Dear colleague Praveen Kumar Kuppusamy

Have a nice time and good day,

Peace be up on you, your question's readers and all RG members.

This may be some kinds of aging. Aging has two types short and long aging. So short aging may be an affect your samples.

The attached file my help you.

I wish this is useful and help you.

Yours

A. El-Denglawey

Praveen, I would suggest to use a minimum of 200 mA amplitude. However there is something strange in your results. The measurement issues you have looks to be more systematic than random errors. Noise would bring more erratic results from one measure to another...

Hi, I was using 10 mA and now I changed to 200 mA. The results are reasonable

Dear Bogdan, (about Praveen, he is) using,

1) iAC=10 mA, Praveen received systematic and high random errors (%);

and now using, a much higher amplitude, e.g. using,

2) iAC=200 mA, he is receiving, mainly, high systematic, but much low(er) random errors (%); a high systematic errors' source is, chiefly, the contact impedance Zc[1], using, only, 2-electrodes.

So[1,2], dear Praveen, please, try to use 4-electrodes (2+up + 2-down) for this Lithium cell (LFP 26650).

1. The contact impedance Zc(f, T) depends on the frequency f, and the Temperature T (of the contact, also), during, even, a single measurement scan; so, Zc is an important source of high (and variable level[2] of, chiefly,) systematic errors.

2. Also, waiting time affects Impedance Spectroscopy of your sample, both a)after setting a SOC, whenever is strong(er), at the start, and the end of SOC, mainly, due to Li-diffusion, as well as b)the effect of the Temperature T (of the contact impedance Zc), always present, mainly, for the short(er) waiting time.

Thank you so much everyone for your help. I am using 4 electrode.