Enhancement in Electrochemical Performance of Lithium‐Sulfur Cells through Sulfur Encapsulation in Hollow Carbon Nanospheres Coated with Ultra‐Thin Aluminum Fluoride Layer

The current status of cathode materials for lithium‐sulfur (Li−S) battery is not satisfactory for full‐scale commercial production. This mainly stems from the unsolved problems associated with the polysulfide shuttle, which leads to lower sulfur utilization and significant capacity decay after a few hundred cycles. To better confine sulfur and its associated polysulfides, a core/double‐shelled nanocomposite was synthesized. The inner shell was composed of a carbon nanosphere with high conductivity, while the outer shell was an ultra‐thin aluminum fluoride (AlF 3 ) layer to better retain polysulfides in the cathode structure. The AlF 3 coating increased the initial discharge capacity to 1191 mA h g −1 with capacity retention of 76.3% and Coulombic efficiency > 99% over 100 cycles. Taking advantage of this tailored design, a reversible capacity of 702 mA h g −1 over 500 cycles at 1 C was achieved with only 0.052% capacity decay per cycle. This impressive electrochemical performance was ascribed to the enhanced conductivity and effective entrapment of polysulfides.