In Situ X‐ray Visualization of the Lithiation Process in a Porous Graphite Electrode in an Operating Li‐Ion Cell

An in situ X‐ray radiography technique to observe an operating Li‐ion cell was developed. Transient behaviors of lithiation processes in a porous graphite electrode were visualized in a specifically designed Li‐ion cell consisting of a lithium‐metal electrode and a graphite electrode, using a transmission X‐ray microscope with high spatial and temporal resolution. X‐ray attenuation profiles in both 15 and 30 μm thick graphite electrodes under discharge (lithiation) at the 2 C rate were compared. X‐ray attenuation was pronounced near the separator in the thicker graphite electrode during the lithiation process, whereas less variation was observed near the current collector in the electrode. These X‐ray observations indicate less utilization of the thicker graphite electrode, presumably because of the longer Li‐ion transport path and formation of a solid electrolyte interface layer in the porous electrode, resulting in less discharge capacity of the Li‐ion cell. Feed the porous: An in situ visualization technique is developed that uses low‐energy X‐rays with high spatial and temporal resolution, which is applicable to an operating lithium‐ion half‐cell. This technique is operated by a laboratory‐based instrument and used to examine the lithiation behavior in a graphite electrode in a graphite/lithium‐metal cell.