Measurement of Ionic Conductivity of Intact Battery Electrodes Using a Four-Line Probe
In order to optimize Li-ion battery performance, an accurate understanding of ionic and electronic conductivity within the porous electrode is needed. Measuring effective ionic conductivity for an electronically conductive battery electrode is a challenge, since for commonly used techniques electronic conductivity contributes to the measured conductivity. To remedy this problem, our research group has previously measured ionic conductivity using a polarization-interrupt method; however, the prior work required a destructive test, namely that the electrode film was delaminated from its current collector. The goal of this work is to measure local effective ionic conductivity for an intact battery electrode. To do this we are using a micro-four-line-probe technique which is related to the commonly used four-point-probe method. Effective conductivity of the thin-film electrode at multiple locations can be calculated using an apparent resistance determined by the probe combined with a shape factor determined by a mathematical model. To test the method, the ionic conductivities of representative cathode and anode films as well as separators were determined. To validate the new method, results are compared to those of previous methods.