A bifunctional N-doped carbon nanosheet embedded with VN/Mo2C heterointerfaces electrocatalyst for expediting sulfur redox and lithium regulation toward advanced Li-S battery

•VN/Mo2C heterointerfaces nanoparticles are monodispersed on N-doped carbon nanosheets.•Mo2C and VN synergistically promote the diffusion and conversion of polysulfides.•The functional separator also has excellent protective effect on the lithium anode.•The modified separator exhibits superb electrochemical performance in Li-S batteries. Lithium-sulfur (Li-S) battery is deemed as one of the optimal next-generation energy storage devices due to its low cost and high energy density. However, the shuttle effect of lithium polysulfide (LiPS), sluggish reaction kinetics, and fatal Li-dendrite growth hinder its practical applications. In this work, a bifunctional nitrogen-doped carbon nanosheet conductive framework embedded with VN-Mo2C heterointerfaces (VN/Mo2C@CNS) is reported as a separator modifier for both sulfur cathode and lithium anode. The VN/Mo2C@CNS can offer a synergistic effect of strong surface affinity, good catalytic activity, and small diffusion barrier to accelerate the conversion of polysulfides, which was confirmed by in-situ Raman and theoretical calculation. Moreover, the composite has good lithiophilicity, thus inhibiting the formation of dendrites and achieving uniform lithium deposition. Benefiting from the above merits, the Li-S cells with VN/Mo2C@CNS separator obtain desirable rate performance (687 mAh g−1 at 4 C), long cycle life of 1000 cycles (0.042 % capacity attenuation per cycle at 1 C), high areal capacity of 4.2 mAh cm−2 (under a high sulfur loading of 5.6 mg cm−2), and stable performance in protecting the Li anode (at 5 mA cm−2 for 1000 h). This work highlights a novel strategy for facilely designing heterostructures, offering valuable insights to tackle sulfur cathode and lithium anode challenges simultaneously for longevous Li-S batteries.