Abstract: Transition metal sulfides are considered promising electrocatalysts for anchoring and catalyzing the soluble lithium polysufides (LiPSs) in lithium-sulfur batteries (LSBs). However, it is still confused whether transition metal sulfides can work as a Li-ion host or provide additional sulfur to contribute extra specific capacities for LSBs. In this work, VS₄ with a high sulfur content and a linear chain structure is designed into the interlayer for LSBs to address these issues. VS₄ nanoworms grown on reduced graphene oxide nanosheets (VS₄@rGO) are coated on carbon fiber paper (CFP) to achieve an advanced multifunctional VS₄@rGO/CFP interlayer for LSBs, which is demonstrated to effectively suppress the shuttle effect of LiPSs, promote the redox reactions and provide extra capacities. Consequently, ultra-high specific capacities of 2079, 1803, and 1161 mAh g^-1 are achieved at 0.2 C, 0.5 C, and 6 C, respectively. The specific capacities at 0.2 C and 0.5 C exceed the theoretical value (1675 mAh g^-1) of the sulfur cathode. The mechanism investigation reveals that VS₄ can accommodate Li-ions in the first discharge process and release extra sulfur along with bis(trifluoromethanesulfonyl) imide (TFSI^-) anions insertion in the first charge process. The in-situ generated sulfur from VS₄ participates in S₈-Li₂S_n-Li₂S reactions in the subsequent cycles to provide extra capacities beyond the sulfur cathode, thus resulting in ultra-high specific capacities over the theoretical value. This work offers a new choice to design advanced cathodes/interlayers of high-performance LSBs.

Key words: VS₄, Multifunctional interlayers, Anion intercalation, Lithium-sulfur batteries