In Situ Self-Formed Nanosheet MoS/Reduced Graphene Oxide Material Showing Superior Performance as a Lithium-Ion Battery Cathode.

Although lithium-sulfur (Li-S) batteries have 5-10 times higher theoretical capacity (1675 mAh g) than present commercial lithium-ion batteries, Li-S batteries show a rapid and continuous capacity fading due to the polysulfide dissolution in common electrolytes. Here, we propose the use of a sulfur-based cathode material, amorphous MoS and reduced graphene oxide (r-GO) composite, which can be substituted for the pure sulfur-based cathodes. In order to enhance kinetics and stability of the electrodes, we intentionally pulverize the microsized MoS sheet into nanosheets and form an ultrathin nano-SEI on the surface using in situ electrochemical methods. Then, the pulverized nanosheets are securely anchored by the oxygen functional group of r-GO. As a result, the electrochemically treated MoS/r-GO electrode shows superior performance that surpasses pure sulfur-based electrodes; it exhibits a capacity of about 900 mAh g at a rate of 5C for 2500 cycles without capacity fading. Moreover, a full-cell battery employing the MoS/r-GO cathode with a silicon-carbon composite anode displays a 3-5 times higher energy density (1725 Wh kg/7100 Wh L) than present LIBs.