Manipulating Li 2 S Redox Kinetics and Lithium Dendrites by Core-Shell Catalysts under High Sulfur Loading and Lean-Electrolyte Conditions.

For practical lithium-sulfur batteries (LSBs), the high sulfur loading and lean-electrolyte are necessary conditions to achieve the high energy density. However, such extreme conditions will cause serious battery performance fading, due to the uncontrolled deposition of Li 2 S and lithium dendrite growth. Herein, the tiny Co nanoparticles embedded N-doped carbon@Co 9 S 8 core-shell material (CoNC@Co 9 S 8 NC) is designed to address these challenges. The Co 9 S 8 NC-shell effectively captures lithium polysulfides (LiPSs) and electrolyte, and suppresses the lithium dendrite growth. The CoNC-core not only improves electronic conductivity, but also promotes Li + diffusion as well as accelerates Li 2 S deposition/decomposition. Consequently, the cell with CoNC@Co 9 S 8 NC modified separator delivers a high specific capacity of 700 mAh g -1 with a low-capacity decay rate of 0.035% per cycle at 1.0 C after 750 cycles under a sulfur loading of 3.2 mg cm -2 and a E/S ratio of 12 µL mg -1 , and a high initial areal capacity of 9.6 mAh cm -2 under a high sulfur loading of 8.8 mg cm -2 and a low E/S ratio of 4.5 µL mg -1 . Besides, the CoNC@Co 9 S 8 NC exhibits an ultralow overpotential fluctuation of 11 mV at a current density of 0.5 mA cm -2 after 1000 h during a continuous Li plating/striping process.