Rationally\nDesigned High-Sulfur-Content Polymeric Cathode Material for Lithium–Sulfur\nBatteries

Abstract

Polyethylene\nhexasulfide (PEHS) is investigated as a cathode material in lithium\nbatteries. By utilizing a condensation reaction, ethylene groups are\ninserted between six linear sulfurs in a chain to obtain PEHS while\nsimultaneously exercising control over the polysulfur chain length.\nAdditionally, by selecting a low-molecular-weight organic group, PEHS\ncontains 87 wt % sulfur, thus maximizing the material-level specific\ncapacity to 1217 mA h g^–1. Furthermore, this synthesis\nmethod is validated using a host of materials characterization techniques.\nIn a battery, PEHS prevents the formation of soluble long-chain intermediates\nthat plague traditional sulfur cathodes. This enables a high material-level\ncapacity of 774 mA h g^–1 at 1C-rate alongside a\nstable performance over 350 cycles with a capacity fade rate of only\n0.083% per cycle. We also elucidate the unique reaction pathway of\nour short-chain polysulfur material and provide a useful foundation\nfor further development of sulfur-containing polymer-based cathode\nmaterials.