To demonstrate the use of ultrasound in battery metrology, we monitored the electrolyte infiltration and wetting in a pouch cell. Electrolyte wetting is a significant time bottleneck in manufacturing, requiring hours or even days before formation cycling can commence. Development of fast, nondestructive methods to measure wetting is an active area of research. Ultrasound has already been shown to be well suited to this task. Electrolyte was added to a commercial pouch cell, which was then vacuum sealed and immediately mounted in a plastic pressure jig and measured by EIS and SAM every 30 minutes for several days. Figure shows SAM images of the pouch cell (optical image in Figure ) at various time points after electrolyte has been added. As expected, when the liquid electrolyte fills pores and displaces the gas inside the cell, the transmission amplitude increases due to the lower reflection coefficient of the solid/liquid versus solid/gas interface. Within an individual scan, amplitude variations at different locations may also arise due to inconsistencies in the contact between the cell and the plastic pressure jig in addition to differences in degree of wetting. As a result, it is more reliable to consider changes over time at a specific pixel or averaged over an area. These spatial variations can be reduced by using rubber pads to hold the cell (or not using any pressure jig when possible), but some spatial variance is unavoidable due to inhomogeneities in the cell itself. This may provide useful information for future studies.