The Multi-Functional Effects of CuS as Modifier to Fabricate Efficient Interlayer for Li-S Batteries.

The shuttle effect of lithium polysulfides in lithium-sulfur batteries (LSBs) has a detrimental impact on their electrochemical performance. To effectively mitigate the shuttle effect, in this study, the coral-like CuS is introduced to modify the carbon nanotube (CNTs), which is coated on commercial separator and served as the S cathode interlayer (PE@CuS/CNTs). The CuS/CNTs interlayer possesses efficient physical impediment and chemisorption to polysulfide anions. When achieving maximum adsorption to polysulfide anions, a "polysulfide-phobic" surface would be formed as a shield to restrain the polysulfide anions in the cathode region. Simultaneously, the CuS/CNTs interlayer can improve the lithium ion diffusion and guarantee desirable electrochemical reaction kinetics. Consequently, the LSBs with PE@CuS/CNTs show an initial discharge capacity of 1242.4 mAh g -1 at 0.5 C (1 C = 1675 mA g -1 ) and retain a long-term cycling stability (568.5 mAh g -1 after 1000 cycles, 2 C), corresponding to an ultra-low capacity fading rate of only 0.05% per cycle. Also, the LSBs with PE@CuS/CNTs exhibit high resistance to self-discharge and favorable performance under high S loading (4.5 mg cm -2 ) and lean electrolyte (9.4 mL Electrolyte  g  S -1 ).