Lithiation of $Li_{2}SnO_{3}$ and $Li_{2}SnS_{3}$ in context of Li-ion battery materials*

The closed pack layered crystal material (space group 15 ($C2/c$)) $Li_{2}SnO_{3}$ has been studied as a possible anode material since the late 1990’s.\footnote{Courtney \& Dahn, JES {\bf{144}}, 2045(1997)}$^,$\footnote{Zhang et al., J. Alloy compd. {\bf{415}}, 229(2006)}$^,$\footnote{Wang et al., Surf. Interface Anal. {\bf{45}}, 1297(2013)} The material undergoes an irreversible decomposition to $Li_{2}O$ and $Li_{X}Sn$ alloys during the first lithiation cycle. The crystal material $Li_{2}SnS_{3}$ of the same structure was recently proposed as an electrolyte material.\footnote{Brant et al., Chem.Mater. {\bf{27}},189 (2015)} The question is posed whether $Li_{2}SnS_{3}$ would be a good electrolyte or whether it could function as an anode material similar to $Li_{2}SnO_{3}$. In this research a model is proposed for the lithiation process of $Li_{2}SnO_{3}$ and $Li_{2}SnS_{3}$; $Li$ -- $Li_{2}SnS_{3}$ interfaces are also examined. The results show $Li_{2}SnO_{3}$ begins to decompose at approximately $Li_{2 + 0.5}SnO_{3}$. In $Li_{2}SnS_{3}$ the lithiation process shows it can lithiate to $Li_{2+1}SnS_{3}$ without significant lattice distortion, volume expansion, or decomposition. $Li$ -- $Li_{2}SnS_{3}$ interfaces are shown to be unstable, showing the formation of $Li_{2}S.