Vapor deposition of aluminium oxide into N-rich mesoporous carbon framework as a reversible sulfur host for lithium-sulfur battery cathode

Restraining the shuttle effects of lithium polysulfides is the key to improve the cycling reversibility and stability of lithium-sulfur (Li-S) batteries for which design of robust sulfur hosts has been regarded as the most effective strategy. In this work, we report a new type of hybrid sulfur host which is composed of Al₂O₃ homogenously decorated in nitrogen-rich mesoporous carbon framework (NMC-Al₂O₃). The NMC-Al₂O₃ hybrid host features a poly-dispersed spherical morphology and a mesoporous configuration with high surface area and large pore volume that can accommodate a high sulfur content up to 73.5 wt.%. As a result, the fabricated NMC-Al₂O₃-S cathode exhibits all-round improvements in electrochemical properties in term of capacities (1,212 mAh·g⁻¹ at 0.2 C; 755 mAh·g⁻¹ at 2 C), cycling charge-discharge reversibility (sustainably 100% efficiencies) and stability (1,000 cycles with only 0.023% capacity decay per cycle at 0.5 C). By contrast, the Al₂O₃-free NMC-S cathode shows both decreased capacities and rapidly descending Coulombic efficiencies during cycling. Density functional theory (DFT) calculations further reveal that the implanted Al₂O₃ can greatly enhance the chemical adsorption and catalytic conversion for various lithium polysulfides and thereby effectively prevent the polysulfide shuttling and significantly improve the utilizability, reversibility and stability of sulfur cathode. [Figure not available: see fulltext.].