context: To test the cyclability of columnar lithium metal during cell operation, operando GISAXS was used to probe the morphology of lithium metal deposits during cycling. GISAXS, being sensitive to length scales on the order of a few to a few hundred nanometers, exhibits a distinct set of evenly spaced intensity oscillations in the qy direction (Fig. 12) arising from the highly monodispersed columnar microstructure, with column diameters of ∼100–200 nm depending on current density (Fig. S8†); the periodicity Δqy of these oscillations is related to the column diameter d by Δqy = 2π/d. Oscillations in the qz direction arise from interference between X-rays scattered from the lithium–electrolyte and lithium–copper interfaces, complicated by multiple scattering and indicate the top surface of the film is very smooth. At the end of plating 1 mA h cm−2 of lithium, strong intensity oscillations are apparent in the qy direction, indicative of a columnar morphology (Fig. 12c). After stripping half of the plated capacity (0.5 mA h cm−2), the intensity oscillations are still present, though broader and less pronounced, indicating the columnar morphology is maintained but is less monodisperse in size and shape (Fig. 12d). At the end of the second plating half cycle the oscillations are even less pronounced (Fig. 12e), suggesting that cycling a large percentage of the plated 1 mA h cm−2 capacity, in this case 50%, with a columnar morphology leads to a loss of uniformity in the microstructure. This is further evidenced by the fact that if all the columnar lithium is stripped to a 1 V vs. Li/Li+ cutoff voltage, the second plating half cycle does not produce a columnar morphology (Fig. S9†). This is consistent with the report from Zhang et al. which demonstrated using ex situ SEM that lithium is stripped from both the tops and sides of lithium nanorods, enabled by the high lithium-ion diffusivity of the SEI, disrupting uniform re-plating onto the high aspect ratio columns. This limits the cycle life of practical batteries which must uniformly plate and strip high capacities of lithium during each charge/discharge cycle, particularly in “anode-free” configurations. Thus, further understanding the impact of additional conditions, including electrochemical profile and mechanical compression (stack pressure), which could help promote the growth of columns with a lower aspect ratio (disc-like rather than rod-like), will be crucial to maintaining morphology control after hundreds of cycles and enhancing the long term cyclability of lithium metal batteries. The effects of compression, the presence of a separator, and lower volume of electrolyte, in particular, require additional investigation as the behavior observed using the flooded open cell design employed in this study may not be directly transferable to a commercial-type battery.