Abstract
Due to physical effects that happen during fabrication of lithium-ion battery electrodes, the microstructure of the porous electrodes is not uniform. Such heterogeneity has been associated with several battery application issues. For example, variability in transport of ions can lead to a tendency for localized plating of lithium on anodes during fast charging and can contribute to other failure modes [1].
There are several approaches to represent heterogeneity. Our research focuses on heterogeneity on a millimeter scale in terms of ionic transport. In a previous presentation, we introduced a technique to measure the local ionic impedance of electrodes [2]. In this report, we provide an update on the development of this technique and display several MacMullin number maps (e.g. Figure 1) to illustrate the heterogeneity of both anodes and cathodes. MacMullin number is a dimensionless ionic resistance related to the tortuosity.
On average, the ionic resistivity and the electronic resistivity show different correlations with the porosity [3-4]. MacMullin number maps will be compared to electronic resistivity maps for the same electrodes to evaluate a local correlation between the ionic resistivity and the electronic resistivity. Further, we will evaluate the effect of these heterogeneities on cell performance.
[1] Forouzan et al., Journal of The Electrochemical Society 165.10 (2018): A2127.
[2] Liu et al., 2019 Meet. Abstr. MA 2019-02 255.
[3] Landesfeind et al., Journal of The Electrochemical Society 163.7 (2016).
[4] Peterson et al., Journal of The Electrochemical Society 161.14 (2014): A2175.
Figure 1