Lithiation of Tin Oxide: A Computational Study

We suggest that the lithiation of pristine SnO forms a layered LiXO structure, while the expelled tin atoms agglomerate into "surface" planes separating the LiXO layers. The proposed lithiation model widely differs from the common assumption that tin segregates into nanoclusters embedded in the lithia matrix. With this model, we are able to account for the various tin bonds that are seen experimentally and explain the three volume expansion phases that occur when SnO undergoes lithiation: (i) at low concentrations Li behaves as an intercalated species inducing small volume increases; (ii) for intermediate concentrations SnO transforms into lithia causing a large expansion; and (iii) finally, as the Li concentration further increases a saturation of the lithia takes place until a layered Li2O is formed. A moderate volume expansion results from this last process. We also report a "zipper" nucleation mechanism that could provide the seed for the transformation from tin oxide to lithium oxide.