PEIS, GEIS or GEIS-AA? Which control mode should be chosen and when?

Key points

• Without prior knowledge, a potential amplitude of 5 - 20 mV is considered small; this is why PEIS is generally used.
• Low-impedance systems (e.g. a Li-ion cell with a high-frequency impedance of a few mΩ): a small potential change produces a large current and the regulation loop struggles. Under current control a large current amplitude gives a small voltage response and the measurement is stable.
• Time-variant systems: as the corrosion potential drifts, PEIS stays at the initial potential and the measurement ends up at an anodic point. GEIS (I = 0) keeps the measurement at the actual corrosion potential at all times.
• In-situ EIS during charge or discharge can only be performed under galvanostatic control around a non-zero DC current.
• GEIS-AA: current is controlled while the amplitude is set in volts; the instrument adapts the current amplitude to meet the target voltage amplitude. The result is the same as a potential-controlled measurement, while keeping the current control required for time-variant systems.
• In the battery example the mean DC current during PEIS reached 166 mA but stayed at about 2 mA with GEIS: controlling zero current stresses the cell far less than controlling the initial OCP.

Figures

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

Related application notes

• Potentio-EIS or galvano-EIS? Which one should be chosen in which case? Battery AN49
• How are EC-Lab® parameters set for EIS on a Li-ion cell? Battery AN23
• White paper: Studying batteries with EIS WP Battery EIS
• Why is EIS misinterpreted on time-varying systems? Corrosion AN55