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Popular topics · Measurement quality and accuracy

How can an EIS measurement be split into sequences to save time without compromising quality?

In EC-Lab and BT-Lab an EIS technique can be split into several sequences; choosing point density, averaging and amplitude separately for each frequency region shortens the measurement. A comparison on a battery and a dummy cell.

Key points

  • Reliable EIS requires the system to remain linear and stationary throughout the measurement; for time-variant systems such as batteries, corrosion and supercapacitors, shortening the measurement directly improves quality.
  • Sequences are added with the '+' button at the top left of the technique window; points per decade, wait (Pw), frequency range and amplitude can differ in each sequence.
  • On a LIR2032 cell, from 1 MHz to 10 mHz with Ia = 2 mA, 10 points per decade, Pw = 0.10 and Na = 2, the single-sequence measurement took 34.05 minutes while the split measurement took 21.68 minutes (about 12 minutes saved). This matters for EIS during charge/discharge.
  • Because battery repeatability is limited, a like-for-like comparison was made on the time-invariant DC-BCS dummy cell. With an R1 + C2/R2 + C3/R3 + M4 circuit the fit parameters are practically identical (e.g. R2 = 10.33 and 10.37 Ω); since the point counts differ, the compared χ/√N changes from 0.1302 to 0.1287.
  • GEIS-AA: selecting Va instead of Ia in the amplitude menu of the GEIS technique adapts the current amplitude to deliver the target voltage amplitude across the whole frequency range. The amplitude must be large enough to stand out from noise and small enough to stay within the linear range.

Figures

A new sequence is added to an EC-Lab/BT-Lab technique with the "+" button.
Figure 1. A new sequence is added to an EC-Lab/BT-Lab technique with the "+" button.
The 1 MHz - 10 mHz scan split into three sequences; points per decade and averaging are chosen separately for each.
Figure 2. The 1 MHz - 10 mHz scan split into three sequences; points per decade and averaging are chosen separately for each.
Single-sequence and multi-sequence GEIS (2 mA) results and fits on a LIR2032 cell; duration falls from 34 to 22 minutes.
Figure 3. Single-sequence and multi-sequence GEIS (2 mA) results and fits on a LIR2032 cell; duration falls from 34 to 22 minutes.
On the time-invariant DC-BCS dummy cell the two methods overlap; fit parameters and χ/√N are practically identical.
Figure 4. On the time-invariant DC-BCS dummy cell the two methods overlap; fit parameters and χ/√N are practically identical.
GEIS-AA: selecting Va instead of Ia in the amplitude menu adapts the current amplitude to the target voltage amplitude.
Figure 5. GEIS-AA: selecting Va instead of Ia in the amplitude menu adapts the current amplitude to the target voltage amplitude.

Images: Bio-Logic Science Instruments; taken from the source article.

Videos

Splitting EIS into sequences (Bio-Logic video)Watch on YouTube

Related application notes

Related curriculum module: Electrochemical Impedance Spectroscopy (EIS)

Related products:BCS-900 Series (BCS-905 / 910 / 915)MPG-200 Series (MPG-2 / MPG-205)SP-300BT-Lab® Suite
Source: Bio-Logic Learning Center, “Split electrochemical impedance spectroscopy (EIS) experiments into multiple sequences: save time without compromising quality” · Source updated: November 18, 2024
Copyright of the images and the original text belongs to Bio-Logic SAS.

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