The importance of cell geometry for electrochemical impedance spectroscopy in three-electrode lithium ion battery test cells

The influence of geometric and electrochemical asymmetries on the impedance spectra recorded in three-electrode test cells for lithium ion batteries was investigated. These asymmetries lead to distortions such as e.g. scaling effects which appear in common Swagelok cells. Moving the reference electrode to a coaxial position in combination with a precise alignment of the electrode stack optimized the geometry of current lines, leading to reliable impedance spectra up to frequencies of 50 kHz regardless of the electrode configuration.

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► EIS is a powerful tool for the analysis of lithium ion batteries.
► Impedance spectra of full cells are a sum of the impedance of each electrode.
► A reference electrode separates the working and counter electrode impedance.
► Geometric or electrical asymmetries cause distortions in impedance spectra.
► A new Swagelok-type cell was developed which prevents these distortions.