A trifunctional multi-walled carbon nanotubes/polyethylene glycol (MWCNT/PEG)-coated separator through a layer-by-layer coating strategy for high-energy Li-S batteries

A trifunctional separator fabricated by using a light-weight layer-by-layer multi-walled carbon nanotubes/polyethylene glycol (MWCNT/PEG) coating has been explored in lithium-sulfur (Li-S) batteries. The conductive MWCNT/PEG coating serves as (i) an upper current collector for accelerating the electron transport and benefiting the electrochemical reaction kinetics of the cell, (ii) a net-like filter for blocking and intercepting the migrating polysulfides through a synergistic effect including physical and chemical interactions, and (iii) a layered barrier for inhibiting the continuous diffusion and alleviating the volume change of the trapped active material by introducing a buffer zone in between the coated layers. The multi-layered MWCNT/PEG coating allows the use of the conventional pure sulfur cathode with a high sulfur content (78 wt%) and high sulfur loading (up to 6.5 mg cm(-2)) to achieve a high initial discharge capacity of 1206 mAh g(-1) at C/5 rate, retaining a superior capacity of 630 mA h g(-1) after 300 cycles. The MWCNT/PEG-coated separator optimized by the facile layer-by-layer coating method provides a promising and feasible option for advanced Li-S batteries with high energy density.