Molybdenum Disulfide and Reduced Graphene Oxide Hybrids as Anodes for Low-Temperature Lithium- and Sodium-Ion Batteries

Lithium- and sodium-ion batteries (LIBs and SIBs) suffer from the significant degradation of electrochemical performance at low temperatures. This work presents promising hybrid anodes synthesized by the rapid thermolysis of ammonium tetrathiomolybdate and graphene oxide (GO) at 600 and 700 degrees C. Transmission electron microscopy revealed the formation of MoS2 crystallites oriented along or perpendicular to the surface of reduced GO (rGO) layers. X-ray photoelectron spectroscopy found the covalent C-S bonds connecting components in the MoS2/rGO hybrids. The MoS2/rGO_600 hybrid showed higher specific capacities in LIBs of 1370 mAh/g, 835 mAh/g, and 711 mAh/g at a current density of 0.1 A/g and temperatures of 25 degrees C, 0 degrees C, and -20 degrees C, respectively, due to the presence of excess sulfur in the sample. Increasing the current density to 2 A/g retained 78 and 34% of the capacity at 25 degrees C and -20 degrees C. In SIBs, the MoS2/rGO_700 hybrid showed more promising results, achieving 550 mAh/g at 0.1 A/g and 400 mAh/g at 2 A/g, while lowering the temperature to -20 degrees C retained 48 and 17% of the capacity. Such good SIB performance is attributed to the enrichment of the sample with vertically oriented MoS2 layers covalently bonded to the rGO surface.