Enhanced Sulfur Redox and Polysulfide Regulation via Porous VN-Modified Separator for Li-S Batteries.

Lithium-sulfur (Li-S) batteries have now emerged as the next-generation rechargeable energy storage system because of the high energy density and theoretical capacity. However, the notorious "lithium polysulfide (LiPS) shuttle" and sluggish kinetics in sulfur redox have posted great threat to their practical applications. Herein, we develop a VN-modified separator as an effective promoter to regulate the LiPSs and accelerate the electrochemical kinetics of Li-S batteries. Benefiting from the dense packing structure and polar surface of porous VN, the VN-modified separator favorably synergizes bifunctionality of physical confinement and chemical entrapment toward LiPSs while affording smooth lithium-ion migration. In addition, the superb electrical conductivity of VN also propels the LiPS conversion. With these advantages, thus-integrated batteries with VN-modified separator exhibit an average capacity decay of 0.077% per cycle at 1 C for 800 cycles. A reasonable areal capacity of 4.2 mAh cm is achieved even with a high sulfur mass loading of 3.8 mg cm at 0.2 C. The present work offers a rational strategy to regulate the LiPS behavior and guide the sulfur redox kinetics toward effective and long-life Li-S batteries.