Original scientific paper
https://doi.org/10.5599/jese.725
The effects of time-variance on impedance measurements: examples of a corroding electrode and a battery cell
Nicolas Murer
orcid.org/0000-0003-3265-9662
; Bio-Logic SAS, 4 Rue de Vaucanson, 38170 Seyssinet-Pariset, France
Jean-Paul Diard
; Bio-Logic SAS, 4 Rue de Vaucanson, 38170 Seyssinet-Pariset, France
Bogdan Petrescu
; Bio-Logic SAS, 4 Rue de Vaucanson, 38170 Seyssinet-Pariset, France
Abstract
When performing electrochemical impedance spectroscopy (EIS) measurements on a system, we must make sure it fulfills certain conditions. One of them is that it should be stationary that is to say, steady-state and time-invariant. Commonly studied systems are
time-variant, for example a corroding electrode or a battery under operation. A corroding electrode sees its polarization resistance decrease with time. A passivating electrode sees its polarization resistance increase with time. These phenomena cause a deformation of
the Nyquist impedance at low frequencies. This result was first simulated and validated by experimental measurements on a corroding steel sample undergoing uniform corrosion. The effect of performing impedance measurements on a discharging battery was also shown. Several methods are available to check and correct time-variance. The nonstationary distortion (NSD) indicator is used to separate valid and invalid data samples and the so called “4D impedance” method can easily produce instantaneous impedance data.
Keywords
EIS; non-stationarity; corrosion; in operando; battery cells; 4D impedance; NSD
Hrčak ID:
235496
URI
Publication date:
10.3.2020.
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