Layered TiS2 Positive Electrode for Mg Batteries

Magnesium batteries are a good candidate for high energy storage systems, but the limited discovery of functional positive electrode materials beyond the seminal Chevrel phase (Mo6S8) has slowed their development. Herein, we report on layered TiS2 as a promising positive electrode intercalation material, providing 115 mAh g–1 stabilized capacity in a Mg full cell. Reversible Mg2+ intercalation into the structure is proven by elemental analysis combined with X-ray diffraction studies that elucidate the phase behavior upon cycling. The voltage profiles reveal distinct Mg2+ cation ordering, unlike the solid solution behavior exhibited by Li+. Our findings not only point to the important role of “soft” lattices to facilitate divalent solid-state cation mobility but also now provide an alternative sulfide to serve as a platform for the fundamental understanding of Mg2+ intercalation in lattices.