The objective, then, is to find electrolyte additives that can protect lithium metal like polysulfides do, but without the self-discharge and capacity fading issues. We explore high-sulfur content polymers to accomplish this task. In this study, we specifically experiment with high-sulfur-content polymers based on trichloropropane (TCP).
TCP-based sulfur polymers are synthesized via a facile emulsion method, with CTAB serving a phase transfer catalyst between TCP and lithium/sodium polysulfides. The sulfur content in the polymers can be highly controlled and can be as high as 90 wt%. Upon reacting with lithium, these polymers form both inorganic polysulfides and organic Li-S-C species, which improves the mechanical stability of the SEI. A lithium deposition efficiency of >99% can be achieved for 400 cycles using these high-sulfur-content polymers.
Sulfur cathodes and lithium metal anodes could potentially move battery technology into the 21st century, but challenges still remain to realize their full potential. High-sulfur content polymers mimic the positive effects that lithium polysulfides have on the SEI of lithium metal, while also mitigating self-discharge and capacity fading.