Self-limiting Lithiation of Vanadium Diboride Nanosheet as Ultra-stable Mediator 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.