Deciphering the catalysis essence of vanadium self-intercalated two-dimensional vanadium sulfides (V5S8) on lithium polysulfide towards high-rate and ultra-stable Li-S batteries

Atom-intercalated transition metal disulfides (TMDs) have attached much attention mainly due to their highly improved conductivity. But it is few reported that the atom intercalation can enable the TMDs have unexpected catalytic properties, caused by the unit-cell deformation in them. In this work, a type of V-0.25-intercalated VS2 (V5S8) nanoflakes was designed via a direct vulcanization method combining Kirkendall heat diffusion effect, and used as the promotor for lithium-sulfur batteries (LSBs). The V5S8 possesses a NiAs crystal structure, in which V atoms occupy the interlayer spacing between VS2 monolayers, which will unavoidably cause the unit cell deformation. As expected, the CNF@V5S8 /S cathodes show a specific capacity of 1260 mAh g(-1) at 0.2 C, and can keep 73.65% of the capacity with charge/discharge rate increasing 10 times; while the CNF@VS2/S ones can only retain 54.0% of the initial capacity. Moreover, the CNF@V5S8/S cathodes show an ultralow decay rate of only 0.0312% per cycle for 1500 cycles at 5 C. Furthermore, the catalysis effect of V5S8 on the conversion of lithium polysulfide (Li2Sn, n = 1, 2, 4, 6 and 8) and S-8 clusters were systematically discusses. Besides, the V5S8 can further enable LSBs achieve a high areal capacity (8.2 mAh cm(-2) with sulfur loading of 7.8 mg cm(-2)) and a high dynamic flexible stability at bending angle between 0 and 180 degrees.

Automated summary

The study focuses on atom-intercalated transition metal disulfides, particularly V-0.25-intercalated VS2 (V5S8), as a promising promoter for lithium-sulfur batteries. The V5S8 nanoflakes display enhanced catalytic properties and improved stability, leading to high specific capacity and low decay rate under various cycling conditions. Furthermore, the V5S8 enables high areal capacity and dynamic flexibility in LSBs, indicating its potential for practical applications.