Self-limiting lithiation of vanadium diboride nanosheets as ultra-stable mediators towards high-sulfur loading and long-cycle lithium sulfur batteries

The high performance of lithium-sulfur (Li-S) batteries generally suffers from the sluggish reaction kinetics and notorious shuttle effect, resulting from the multi-phase/interface evolution and multistep electron-transfer/non-transfer processes. In this article, the novel vanadium diboride (VB2) nanosheet shows the self-limiting lithiation property in the 1.5-2.8 V polysulfide reaction range, which can afford better electron/ion transport under the stable reaction interface of the catalytic mediator in the Li-S cell cycling. Moreover, electrochemical measurements and density-functional theory calculations reveal that the boron sites of VB2 have a strong surface interaction with Li2S4, which can further improve the conversion rate between Li2S4 and Li2S2/Li2S. Thereinto, these VB2-based Li-S cells possess high sulfur loading (4 mg cm-2), impressive current rate (2C), excellent cycling stability (1000 cycles), and great rate capability (1013 mA h g-1 at 5 mA cm-2). This work provides insight into the stable structure to support the advancement of electrocatalysis technology.