Bifunctional N, S Dual-Doped Carbon Enabling Fast Polysulfide Redox and Stable Lithium Deposition

Lithium-sulfur (Li-S) batteries, despite their high theoretical capacity (1675 mAh g^-1) and low-cost sulfur, suffer from poor cycling stability, and rate performance. This is mainly due to sluggish redox kinetics at the sulfur cathode-particularly during the Li₂S₂ to Li₂S conversion. In addition, uneven lithium-ion distribution and random diffusion lead to unsafe issues due to unstable lithium deposition and dendrite growth. In this study, an interlayer composed of N, S dual-doped carbon is designed to reinforcing sulfur redox electrochemistry and promoting uniform Li deposition. The NSC interlayer enhances the electrochemical performances via the formation of N^…Li and S_B ⁰ active sites, which accelerate polysulfides conversion and regulate Li deposition. As a result, the Li-S batteries with the NSC interlayer achieve an ultrahigh discharge specific capacity of 1215 mAh g^-1 at 0.2C and 617 mAh g^-1 at a high current of 5C. In addition, the NSC interlayer enables uniform Li deposition for over 1000 h. The work provides a facile method for designing functional interlayers and opens a new avenue for realizing Li-S batteries with high energy efficiency.