Innovative Sulfur-Carbon Nanotube Cathodes for High-Performance Li/S Batteries

Li/S batteries suffer from major problems including low active material utilization, poor cycling performance and low Coulombic efficiency due to high solubility of intermediate polysulfides and low conductivity of sulfur. Here, we report modified carbon nanotubes (MCNT)-S comprising the key features of elemental sulfur (S₈) and sulfurized carbon (SC) when used as cathode materials. The use of a mixed solvent of MCNT in hydrogen peroxide and sulfur in carbon disulfide followed by 300°C heat treatment in vacuum oven leads to extremely uniform and dense sulfur layers on CNT surfaces via physical and chemical deposition, and enables the fabrication of remarkably improved Li/S cathodes with a reversible capacity of 1180 mAhg^-1 without obvious capacity decay over 300 cycles at 0.25 C, and 67.5% of capacity retention from 1182 to 799 mAhg^-1 over 600 cycles at 0.75 C with an average Coulombic efficiency of 95.5%. The results provide important progress towards the understanding of the role of MCNT on the realization of high efficiency and long cycle performances for Li/S batteries.