Bimetallic Chalcogenides Enable Highly Efficient Polysulfide Capture and Conversion in Lean-Electrolyte Li-S Batteries

Abstract

The commercialization of Li-S batteries is obstructed by the sluggish redox kinetics and serious shuttling behaviors of polysulfides. Herein, we report a rationally structured sulfur host material to tackle these issues, i.e. (Co, Ni)₉S₈ nanoparticles uniformly decorated on electrospun carbon nanofibers. The (Co, Ni)₉S₈ nanoparticles are demonstrated to effectively capture polysulfides and catalytically promote their redox conversions. Moreover, the interlinked porous architecture of (Co, Ni)₉S₈@CNFs also contributes to alleviate volume expansion of sulfur cathode and provide the rapid electron transfer paths and Li-ion diffusion channels. Benefiting from these attributes, the (Co, Ni)₉S₈@CNFs cathode delivers an excellent rate capability and long cycling stability (capacity decay of 0.142% per cycle over 300 cycles). Additionally, the (Co, Ni)₉S₈@CNFs with high sulfur content (83.3%) and lean electrolyte (5 μL mg^-1) shows high capacity of 556 mAh g^-1 at 0.5 C and 590 mAh g^-1 after 180 cycles at 0.2 C, demonstrating highly efficient utilization of sulfur and extraordinary potential for practical application of Li-S batteries.