Determination of the diffusion coefficient of lithium ions in nano-Si

The diffusion coefficients of lithium ions (DLi+) in nano-Si were determined by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and galvanostatic intermittent titration technique (GITT). DLi+ values are estimated to be ~ 10− 12 cm2 s− 1 and exhibit a “W” type varying with the lithium concentration in silicon. Two minimum regions of DLi+ (at Li2.1 ± 0.2Si and Li3.2 ± 0.2Si) are found, which probably result from two amorphous compositions (a-Li7Si3 and a-Li13Si4). Besides the two minimum regions, one maximum DLi+ is observed at Li15Si4, corresponding to the crystallization of highly lithiated amorphous LixSi.