A comparative study of reaction mechanism of MoS2 negative electrode materials for sodium-ion batteries

Sodium-ion batteries (SIBs) are becoming increasingly popular because of their low cost and the relative abundance of sodium compared to lithium. However, the energy density of SIBs is low and needs to be improved. In this study, the reaction mechanism of MoS2 as a high-capacity negative electrode for SIBs is studied through the electrochemical and spectroscopic analyses. MoS2 undergoes an insertion reaction with sodium, which is followed by a conversion reaction. A comparative study of MoS2 with MoO2 reveals that MoS2 can store sodium through the insertion reaction because it has a larger interlayer distance than that of MoO2. In addition, the bonds of MoS2 are weaker than those of MoO2, which favors the conversion reaction of MoS2 with sodium.