Unlocking the potential of SnS₂: Transition metal catalyzed utilization of reversible conversion and alloying...

The alloying-dealloying reactions of SnS₂ proceeds with the initial conversion reaction of SnS₂ with lithium that produces Li₂S. Unfortunately, due to the electrochemical inactivity of Li₂S, the conversion reaction of SnS₂ is irreversible, which significantly limit its potential applications in lithium-ion batteries. Herein, a systematic understanding of transition metal molybdenum (Mo) as a catalyst in SnS₂ anode is presented. It is found that Mo catalyst is able to efficiently promote the reversible conversion of Sn to SnS₂. This leads to the utilization of both conversion and alloying reactions in SnS₂ that greatly increases lithium storage capability of SnS₂. Mo catalyst is introduced in the form of MoS₂ grown directly onto self-assembled vertical SnS₂ nanosheets that anchors on three-dimensional graphene (3DG) creating a hierarchal nanostructured named as SnS₂/MoS₂/3DG. The catalytic effect results in a significantly enhanced electrochemical properties of SnS₂/MoS₂/3DG; a high initial Coulombic efficiency (81.5%) and high discharge capacities of 960.5 and 495.6 mA h g^-1 at current densities of 50 and 1000 mA g^-1, respectively. Post cycling investigations using ex situ TEM and XPS analysis verifies the successful conversion reaction of SnS₂ mediated by Mo. The successful integration of catalyst on alloying type metal sulfide anode creates a new avenue towards high energy density lithium anodes.