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 MoxC 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 MoxC nanoparticles could serve as the functional electrocatalyst to facilitate the redox kinetics of the multiphase conversion. The Li–S coin cells with MoxC@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/cm2 is also achieved with a high sulfur loading of 5.2 mg/cm2 and a low electrolyte/sulfur ratio of ∼5 μL/mg.