The standard deviation of the fitted parameters was calculated using the bootstrapping scheme (see Methods) . In this model, the parameters k and d0 provide quantitative metrics to compare the failure probabilities between different sample conditions, where a larger d0 implies a lower failure probability for a constant lithium whisker diameter, and a larger k value implies a tighter distribution of failure diameters. In addition, we emphasize that the exponent, k in this model is not the Weibull modulus typically reported in fracture mechanics literature. This is because the Weibull modulus quantifies the variability in failure strength under constant sample geometry.