During linear sweep voltammetry inside the SEM, we measure two important aspects of Li electroplating: the diameter of plated Li and the critical current density at the onset of Li intrusion. The diameter of plated lithium is controlled by factors including surface Li wetting, defect density, and surface electronic transport. The latter is especially important considering that we deposit metallic silver prior to thermal annealing, a point that we return to later. We note that the lithium plating diameter was directly observed through SEM images rather than being inferred based on the electrochemical constriction models in our previous study. (see discussion in Figure ). Surprisingly, while the Ag + -LLZO shows a slightly improved local critical current density relative to uncoated LLZO (from 200 ± 50 to 280 ± 30 mA/cm 2 ), the plating area at failure is much larger with Ag + surface doping (from 17 ± 1.5 to 73 ± 17 µm). As demonstrated in previous work , local critical current density in microprobe experiments is orders of magnitude greater than in macroscopic cells because the Li intrusion is controlled by the defect density rather than solely by the rate of plating.