Intermolecular Cyclic Polysulfide as Cathode Material for Rechargeable Lithium Batteries
An intermolecular cyclic polysulfide (ICPS), i.e., 2,3,4,6,7,8-hexathia-1,5(1,3)-dibenzenacyclooctaphane (HDBCO), is designed, synthesized, and applied as a cathode material in rechargeable lithium battery for the first time. With the aid of chromatographic and spectroscopic analysis, it is confirmed that HDBCO is successfully synthesized along with two larger ICPS molecules. A HDBCO molecule possesses six active sulfur atoms, affording a theoretical specific capacity of 623.4 mAh g-1. In the discharge of a lithium half-cell, these ICPS are converted to lithium 1,3-benzenedithiolate and lithium sulfide. In the recharge, the starting materials are recovered and HDBCO is the predominant product. The cell delivers an initial capacity of 625.0 mAh g-1 and retains 72.9% of the initial capacity over 100 cycles at C/10 rate. Even at 1C rate, it also can deliver an initial capacity of 596.1 mAh g-1 and retains 63.4% of the initial capacity over 500 cycles. This work adds a new member to the organopolysulfide cathode family.