Characterization of sulfur/carbon copolymer cathodes for Li-S batteries: a combined experimental and ab initio Raman spectroscopy study

Optimization of lithium-sulfur batteries highly depends on exploring and characterizing new cathode materials. Sulfur/carbon copolymers have recently attracted much attention as an alternative class of cathodes to replace crystalline sulfur. In particular, poly(sulfur-n-1,3-diisopropenylbenzene) (S/DIB) has been under considerable experimental and theoretical investigations, promising a good performance in mitigating the so-called shuttle effect. Here, combining ab initio Raman spectroscopy simulations with experimental measurements, we show that S/DIB copolymers containing short and long sulfur chains are distinguishable based on their Raman activity in 400-500 1/cm. This frequency range corresponds to S--S stretching vibrations and is only observed in the Raman spectra of those copolymers with longer sulfur chains. The results reported in this study have direct applications in identification and characterization of general sulfur/carbon copolymers with different sulfur contents.