Manipulating Li2 S Redox Kinetics and Lithium Dendrites by Core-Shell Catalysts under High Sulfur Loading and Lean-Electrolyte Conditions.

ABSTRACT

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 Li2 S and lithium dendrite growth. Herein, the tiny Co nanoparticles embedded N-doped carbon@Co9 S8 core-shell material (CoNC@Co9 S8 NC) is designed to address these challenges. The Co9 S8 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 Li2 S deposition/decomposition. Consequently, the cell with CoNC@Co9 S8 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@Co9 S8 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.