Rationally Designed High-Sulfur-Content Polymeric Cathode Material for Lithium-Sulfur Batteries.

Polyethylene hexasulfide (PEHS) is investigated as a cathode material in lithium batteries. By utilizing a condensation reaction, ethylene groups are inserted between six linear sulfurs in a chain to obtain PEHS while simultaneously exercising control over the polysulfur chain length. Additionally, by selecting a low-molecular-weight organic group, PEHS contains 87 wt % sulfur, thus maximizing the material-level specific capacity to 1217 mA h g-1. Furthermore, this synthesis method is validated using a host of materials characterization techniques. In a battery, PEHS prevents the formation of soluble long-chain intermediates that plague traditional sulfur cathodes. This enables a high material-level capacity of 774 mA h g-1 at 1C-rate alongside a stable performance over 350 cycles with a capacity fade rate of only 0.083% per cycle. We also elucidate the unique reaction pathway of our short-chain polysulfur material and provide a useful foundation for further development of sulfur-containing polymer-based cathode materials.