Separator modification by MoxC/N-doped graphene enabling polysulfide catalytic conversion for high-performance Li–S batteries

The shuttle effect and sluggish electrochemical conversion of polysulfides have been believed to strongly influence the performances of lithium-sulfur (Li–S) batteries. Herein, we propose the synthesis of nanosized Mo x C electrocatalysts embedded on N-doped graphene and develop its application for separator modification of Li–S batteries. The N-doped graphene provides a two-dimension conductive barrier layer to chemically adsorb polysulfides and inhibit polysulfides diffusion, while Mo x C nanoparticles could serve as the functional electrocatalyst to facilitate the redox kinetics of the multiphase conversion. The Li–S coin cells with Mo x C@N-rGO-modified separator can exhibit good long-term cycling stability with a capacity decay of 0.069% per cycle after 400 cycles at 0.5C and excellent rate performance with a discharge capacity of 653 mAh/g at 4C. An area capacity of 4.5 mAh/cm 2 is also achieved with a high sulfur loading of 5.2 mg/cm 2 and a low electrolyte/sulfur ratio of ∼5 μL/mg.