Influence of the Si particle size on the mechanical stability of Si-based electrodes evaluated by in-operando dilatometry and acoustic emission

The influence of the Si particle size (85 nm versus 230 nm) on the mechanical stability of composite Si/C/carboxymethyl cellulose (CMC) electrodes is evaluated from in-operando dilatometry and acoustic emission measurements. A lower, more progressive and more reversible expansion/contraction of the electrode is observed with the Si 230 nm powder, with a maximum expansion of similar to 140% and a residual irreversible expansion of similar to 25% measured during the first cycle compared to similar to 350% and similar to 90% for the Si 85 nm based electrode. Moreover, during the 2nd cycle, an abrupt and very large expansion/contraction (up to similar to 400%) is observed for the Si 85 nm based electrode, which results in the irreversible cracking and exfoliation of the electrode as confirmed by post-mortem scanning electron microscopy observations. This is also in accordance with the more intensive acoustic activity measured during the Si 85 nm electrode cycling. The lower mechanical strength of the Si 85 nm electrode is interpreted as the consequence of an insufficient amount of CMC binder relative to the larger specific surface area of the Si 85 nm powder. This tends to be confirmed by the significant improvement of its electrochemical cycling performance as its CMC content is increased. (C) 2016 Elsevier B.V. All rights reserved.