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

Abstract

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.