Ultrastable lithium–sulfur batteries with outstanding rate capability boosted by NiAs-type vanadium sulfides

Abstract

Vanadium sulfides, such as VS₂, have been often used as sulfur host materials for lithium–sulfur batteries (LSBs), however, their high-symmetry and layered crystalline structure often lead to a poor rate-capability and a limited cycling stability of the resultant LSBs. Thus, in this work, a type of distorted NiAs-type structured V₂S₃ phase was designed and attempted to use it as a sulfur host for LSBs. The results showed that the prepared V₂S₃-nanocrystal decorated carbon nanofiber (CNF@V₂S₃) electrode films are freestanding, highly conductive and flexible. And the resultant CNF@V₂S₃/S cathodes show a high specific capacity (1169 mA h g⁻¹ at 0.1C), an excellent rate capability (retain 78.9% at 2.0C), an ultra-low delay rate per cycle of 0.0071%, and a low self-discharge rate of 3.65% per month. A series of analyses indicate that these high electrochemical performances are mainly due to the high polarity, high conductivity and high catalytic activity of V₂S₃ nanocrystals, as well as the improved diffusivities of Li ions. This research could provide some new insight into the design of sulfur host materials for high-performance LSBs.