Electrochemical impedance spectroscopy for lithium ion batteries has recently gained increasing attention due to its ability of non-invasive evaluation of important electrochemical parameters. Commonly used three-electrode test cells, however, proved unreliable due to asymmetric current line distributions, causing severe distortions of impedance spectra. Finite element method (FEM) simulations can visualize these current lines at different frequencies and simulate impedance spectra at given geometries. By applying FEM simulations to a recently developed coaxial impedance test cell, limiting conditions for reliable impedance measurements could be identified. Using a reference electrode in coaxial position yields sufficiently reliable results as long as the electrode misalignment is small compared to the electrolyte thickness and edge effects are prevented.