LAUSR

Spinel intercalation compounds are well-known to facilitate high rate and high voltage Li-ion batteries. Little is known, however, about spinel based electrodes for Na- and Mg-ion batteries. Here we systematically study six spinel chemistries with first-principles statistical mechanics approaches to determine how the electrochemical properties of spinel compounds are affected by (i) host ionicity, (ii) guest cation radius, and (iii) guest cation oxidation state. As model systems, we consider spinel CoO2 and TiS2 as hosts and Li, Na, and Mg as guest cations. Electrochemical properties of spinel compounds are strongly dependent on guest cation site preferences. Our study shows that large guest cations prefer octahedral coordination, while the electrostatic interactions in ionic hosts favor tetrahedrally coordinated guest cations. The insights of this study suggest simple design principles with which new spinel intercalation compounds can be developed, with our predictions indicating that transition metal ox...