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

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 4C), long cycle life of 1000 cycles (0.042 % capacity attenuation per cycle at 1C), high areal capacity of 4.2 mAh cm−2 (under a high sulfur loading of 5.6 mg cm−1), 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.