Catalyst for polysulfide conversion by Mo2C/MoO3 hybrids modified separator in lithium-sulfur batteries

The lithium-sulfur (Li-S) batteries have achieved important developments, but still suffer from some main intrinsic disadvantages, such as the dissolution and diffusion of the lithium polysulfides (LiPSs). In response, here we develop a Mo2C/MoO3 heterostructure as the interlayer to restrain the leakage and migration of LiPSs. Owing to its good conductivity and excellent electronic transport, this heterostructure can perform excellently as an ideal carrier for providing reduction reaction sites of LiPSs conversion, thus greatly improving the electrochemical properties of Mo2C/MoO3 for Li-S batteries. The resultant Mo2C/MoO3 electrodes can deliver a high specific capacity of 1346 mAh g- 1 at 0.1C and long-term cycling stability (660 mAh g- 1 after 800 cycles at 2C) with a low capacity decay rate of 0.05% per cycle, indicating high sulfur utilization and fast kinetic conversion of LiPSs and Li2S. When the sulfur loading is increased to 4.34 mg cm-2, the initial discharge capacity and areal capacity of the Mo2C/MoO3 electrode at 0.1C is still up to 1405 mAh g- 1 and 6.1 mAh cm-2 with a coulombic efficiency of 99% in the first cycle, indicating faster LiPSs conversion. First-principle calculations reveal that the as-synthesized LiPSs species are selectively adsorbed on the MoO3 (001) and Mo2C (001) surface. This work provides an alternative strategy toward high-performance Li-S battery with high sulfur loading.