Three‐Phase Multiscale Modeling of a LiCoO₂ Cathode: Combining the Advantages of FIB–SEM Imaging and X‐Ray Tomography

Abstract

LiCoO2 electrodes contain three phases, or domains, each having specific‐intended functions: ion‐conducting pore space, lithium‐ion‐reacting active material, and electron conducting carbon‐binder domain (CBD). Transport processes take place in all domains on different characteristic length scales: from the micrometer scale in the active material grains through to the nanopores in the carbon‐binder phase. Consequently, more than one imaging approach must be utilized to obtain a hierarchical geometric representation of the electrode. An approach incorporating information from the micro‐ and nanoscale to calculate 3D transport‐relevant properties in a large‐reconstructed active domain is presented. Advantages of focused ion beam/scanning electron microscopy imaging and X‐ray tomography combined by a spatial stochastic model, validated with an artificially produced reference structure are used. This novel approach leads to significantly different transport relevant properties compared with previous tomographic approaches: nanoporosity of the CBD leads to up to 42% additional contact area between active material and pore space and increases ionic conduction by a factor of up to 3.6. The results show that nanoporosity within the CBD cannot be neglected.

Micro-Four-Line Probe to Measure Electronic Conductivity and Contact Resistance of Thin-Film Battery Electrodes

“…Moreover, the spatial variability of electrodes could be correlated with microstructural determination and mesoscale models of electrode performance. [16][17][18] Such efforts are planned by our group.…”

Influence of Electrode Density on the Performance of Li-Ion Batteries: Experimental and Simulation Results

“…In this regard, tortuosity can also be influenced badly. The extent of these effects can be investigated with advanced electrode imaging techniques such as those presented by Hutzenlaub et al [24,25]: using a combination of X-ray tomography to image the AM domain, and Focused Ion Beam Scanning Electron Microscope (FTB/SEM) images to obtain a phase distribution of AM, CBD and pore space, they are able to establish a full digital 3D image of the electrode.…”

Three-Dimensional Visualization of Gas Evolution and Channel Formation inside a Lithium-Ion Battery

“…25 Due to the high fluxes generated by synchrotron sources, synchrotron X-ray imaging has evolved into a powerful characterization tool in the field of materials science. [26][27][28][29][30][31][32][33][34][35][36] Especially synchrotron X-ray tomography has enabled researchers to obtain unprecedented insights into LIBs from the level of individual particles to the scale of entire electrodes. [37][38][39][40] Most recently, Ebner et al, have directly observed and quantified electrochemical and mechanical degradation in a SnO anode.…”