(a) The ex-situ PDF of silicon extracted from the first discharge process. Dashed lines: the first, second, and third coordination shell Si–Si distances in a Si diamond framework. Two 0 mV samples are included, blue (top): the unwashed sample, teal (bottom): the washed sample. (b) PDF data and the fitting result (R_w = 43%) of the washed 0 mV sample. Characteristic Li₁₅Si₄ correlations are indicated by the dashed lines at 2.85 Å and 4.75 Å, connecting (a) and (b). (c) Schematic illustration of silicon lithiation and delithiation. Crystalline silicon lithiation process (discharged down to 0 mV) corresponds I to IV. Discharge steps are denoted by red arrows, while blue and green arrows denote charge steps. Delithiation of fully lithiated silicon is shown by V to VIII, and VIII to XI correspond to the relithiation of amorphous silicon to form fully lithiated silicon for cycle number x (x > 1).^[46]