where v i (t 0 ) and v i (t 0 +t) are the velocities of the i-th Li + at times t 0 and t 0 +t, respectively, within the time window ω. The initial time was incrementally shifted by 10 steps to improve the statistical accuracy of G(t). Here, N is the number of Li + in the region of interest. We only used Li + velocity data from the ions remaining within the targeted region during ω.