Anion Intercalation of VS4 Triggers Atomic Sulfur Transfer to Organic Disulfide in Rechargeable Lithium Battery

Abstract Transition metal polysulfides MS x ( x > 2) have attracted much attention because of their high theoretical capacities as electrode materials for lithium batteries. Among them, VS 4 has a linear chain structure in which van der Walls forces exist between chains. Previous reports found lithium ions can be intercalated into VS 4 in the discharge, and elemental V and Li 2 S are formed when discharged to low voltage (e.g., <1.0 V vs Li/Li + ). In this study is found that bis(trifluoromethanesulfonyl)imide (TFSI − ) anions can be intercalated into VS 4 when charged to 3.0 V or above after discharged to 1.8 V in rechargeable lithium battery, triggering sulfur evolution. To improve its cycling reversibility diphenyl disulfide (DPDS) is used as a sulfur receptor in the composite electrode consisting of nanoscaled VS 4 particles and carbon nanotubes (CNTs). In the charge, sulfur atoms are transferred from VS 4 to DPDS forming diphenyl trisulfide (DPTS). This strategy enables improved capacity retention and material utilization. The electrode shows a reversible capacity of 130.7 mAh g −1 after 300 cycles at the current density of 240 mA g −1 .