Phase Stability and Electronic Structure of Tin Sulfide Compounds for Li-Ion Batteries

Tin is an important component of a variety of promising anode and solid electrolyte chemistries for Li and Na ion batteries. Here we report on a first-principles investigation of phase stability and electronic structure in the Li-Sn-S ternary composition space, which hosts several compounds that can either serve as an anode or as a solid electrolyte in Li-ion batteries. Calculations based on density functional theory predict a tendency for charge-disproportionation into localized Sn2+ and Sn4+ oxidation states upon addition of Li to SnS2. Furthermore, the preferred sulfur coordination environment of Sn is found to depend strongly on the Sn oxidation state. As a result, the thermodynamically preferred path of Li insertion into SnS2 proceeds according to a conversion reaction involving signficant crystallographic rearrangements to accommodate the changes in coordination preferences with Sn oxidation state. Li insertion according to a metastable topotactic intercalation path is also found to involve charge d...