Highly Reversible Diphenyl Trisulfide Catholyte for Rechargeable Lithium Batteries

Organotrisulfide (RSSSR) is a new class of high-capacity cathode materials for rechargeable lithium batteries. The organic R group can tune the structure and property of organotrisulfide as well as electrochemical performance in batteries. Herein, a nominal diphenyl trisulfide (DPTS, C6H5SSSC6H5) catholyte is reported for rechargeable lithium batteries. Three sulfur atoms allow 4e– storage per molecule, affording DPTS with a theoretical capacity of 428 mAh g–1. The DPTS catholyte is synthesized from a coupling reaction of diphenyl disulfide (DPDS) and elemental sulfur in liquid electrolyte at 70 °C. It is found that the DPTS catholyte is a mixture of DPTS, DPDS, and elemental sulfur in the electrolyte. The lithium cell with the DPTS catholyte delivers an initial specific capacity of 330 mAh g–1 DPTS and retains 79% of the initial capacity over 100 cycles at the C/2 rate. The cell delivers an initial discharge specific energy of 751 Wh kg–1 DPTS with a high energy efficiency of over 95% at the C/5 rate. The achievable energy density of the DPTS catholyte (1.0 M) is 158 Wh L–1. This study shows that DPTS is a promising high-capacity cathode material for highly reversible lithium batteries.