DMSO-assisted copolymerization of acetone and sulfur and its application as a Li-S battery cathode

Abstract

There is an ongoing pursuit of new chemistries to advance lithium-sulfur (Li-S) battery technologies. Among these, electroactive sulfur-containing polymers have attracted significant interest. Here, we report a simple and novel synthesis route for producing a sulfur-rich polymer, acetone polysulfide (AcPS), using acetone, elemental sulfur, and dimethyl sulfoxide (DMSO) as starting materials. The reaction is performed in sealed vials at a moderate temperature of 130 degrees C, yielding organosulfur polymers containing carbonyl groups, condensation-derived conjugated carbon structures, and sulfur bridges between organic segments, with polymerized sulfur contents as high as similar to 59 wt%. Structural analyses confirm the formation of amorphous sulfur-carbonyl polymer networks without detectable crystalline sulfur domains. Electrochemical evaluation demonstrates that AcPS is active as a Li-S cathode material. In an optimized configuration employing a conductive carbon-coated separator, slurry-coated AcPS cathodes deliver a sulfur-specific discharge capacity of similar to 615 mAh g(-1) at 0.2 C. Coulombic efficiency remains modest, stabilizing at approximately 90%, which is attributed to the dissolution of electroactive polymer-derived fragments and their transient interfacial accumulation on the Li anode, as supported by shuttle-current analysis and GITT-EIS. DOL/DME extraction further supports this interpretation, as removal of some soluble sulfur-containing polymer fractions suppresses the pronounced charge/discharge imbalance, causing the Coulombic efficiency to approach unity. Beyond materials development, this work also introduces a practical diagnostic rationale to distinguish conventional polysulfide shuttling from the migration of soluble polymer-derived redox-active species in Li-S cells.