Lithiation of Tin Oxide: A Computational Study

TL;DR

This computational study proposes a new layered lithiation model for SnO, explaining experimental observations and volume expansion phases, and introduces a 'zipper' nucleation mechanism for the transformation.

Contribution

The paper introduces a novel layered lithiation model for SnO that differs from previous assumptions, providing insights into volume changes and nucleation mechanisms.

Findings

The lithiation of SnO forms layered Li_xO with surface tin agglomerates.

Three distinct volume expansion phases are identified during lithiation.

A 'zipper' nucleation mechanism for transformation is proposed.

Abstract

We suggest that the lithiation of pristine SnO forms a layered Li$_\text{X}$O structure while the expelled tin atoms agglomerate into 'surface' planes separating the Li$_\text{X}$O layers. The proposed lithiation model widely differs from the common assumption that tin segregates into nano-clusters 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; (iii) finally, as the Li concentration further increases a saturation of the lithia takes place until a layered Li$_2$O 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.