The lithium metal whisker diameter increases monotonically with Vapp for all plating experiments. As shown in Figure , the whisker diameter (at the interface with LLZO) grows from ~1 micron to over 10 microns before intrusions are observed. The diameter estimated by this model is somewhat smaller than lithium whisker diameter observed in SEM. However, the electrochemical estimate of the whisker diameter more accurately reflects the lithium-LLZO contact area than the area obtained by SEM imaging because there are a significant number of voids at the lithium-LLZO interface, as observed in focused-ion beam (FIB) cross-sectional SEM images in Figure .