Fast lithium ionic conductivity observed in LiI-MoS₂ composite

The enhancement of lithium ion conductivity is observed in the composite solid electrolyte LiI-MoS₂, which was synthesized by ball milling of the mixture of LiI and MoS₂. The composite electrolyte shows an ionic conductivity as high as 7.1 × 10⁻⁵ S cm⁻¹ at room temperature which is nearly three orders of magnitude higher than the pristine LiI and can be ascribed to the formation of the amorphous interface between the two phases. In addition, the composite electrolyte LiI-MoS₂ exhibits a wide apparent electrochemical stability window of −1 to 5 V. X-ray diffraction measurements on the composite inform that original phases are well maintained after ball milling process. Transmission electron microscopy (TEM) and field emission scanning electron microscopy (FE-SEM) reveal the homogeneous distribution of LiI over the surface of MoS₂ and the favorable interface for Li-ion migration between the two phases. Our work proposes a novel strategy to design solid electrolytes with high Li-ion conductive, and also provides some possibility for two-dimensional materials to be applied in superior solid electrolytes.