Bilayer functional interlayer coupling defect and Li-ion channel for high-performance Li-S batteries

Lithium-sulfur (Li-S) batteries have been demonstrated as one of the promising candidates for next-generation energy-storage devices. However, low utilization of active materials, detrimental shuttle effect of lithium pol-ysulfides, and sluggish redox kinetics hamper the commercial applications of Li-S batteries. Herein, we design a bilayer functional interlayer composed of reduced graphene oxide/Se-doped MoS2 (rGO/MoSSe) layer and carbon nanofiber (CNF) layer (rGO/MoSSe@CNF) for high-performance Li-S batteries. The defective structure of Se-doped MoS2 significantly improves the polysulfide adsorption-catalytic ability due to the exposure of more active sites and the adjustment of local electronic structure. Accordingly, the rGO/MoSSe functional layer effectively improves the electrochemical reaction kinetics and cyclic stability. In addition, the CNF layer effec-tively reduces the transport resistance of Li+, and improves the reversible capacity at high current densities. The Li-S coin cell with rGO/MoSSe@CNF interlayer delivers a remarkable reversible specific capacity of 922.4 mAh g- 1 after 140 cycles at 0.2 C and a slow capacity decay rate of 0.057% per cycle over 1000 cycles at 1 C. Moreover, the Li-S pouch cell with rGO/MoSSe@CNF interlayer at sulfur loading of 3 mg cm-2 can maintain a reversible specific capacity of 706.2 mAh g- 1 after the rate test and 175 cycles at 0.2 C.