Introduction to Electrochemical Impedance Spectroscopy as a Measurement Method for the Wetting Degree of Lithium-Ion Cells

In the production process chain of lithium-ion battery cells, the filling, consisting of dosing and wetting steps, of the cell and its components with electrolyte liquid is eminent for the final product quality and costs. To reduce the unnecessary wetting duration between filling and formation, and thereby the production costs, a measurement method for the wetting progress is necessary. In this paper, electrochemical impedance spectroscopy (EIS) as a well-established technique is used for the first time to quantify the wetting degree of batteries during cell production. The experimental data of the EIS acquired during the dosing and subsequent wetting process is correlated to images recorded by in situ neutron radiography. Results show that the impedance of the battery cells strongly depends on the wetting degree of the cell assembly and can thus be used to determine the fully wetted state enabling faster processing.