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 similar to 10(-12) cm(2) s(-1) and exhibit a W type varying with the lithium concentration in silicon. Two minimum regions of DLi+ (at Li2.1+0.2 Si 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. (C) 2008 Elsevier B.V. All rights reserved.