CDC-wrapped S/Se/SeS2 cathode preparation

The selenium sulfide (SeS₂) melted at 120 °C and was absorbed into the CDC pores based on capillary action. Both inner and outer surfaces of the carbon were coated during the infiltration process. Any extra SeS₂ that coated the outside of the pores, which could easily dissolve and lower the sulfur utilization/the active mass during cycling, was evaporated at 200 °C. From the gas sorption (Supplementary Fig. 11) and thermo-gravimetric analysis (Supplementary Fig. 12) analyses, it was confirmed that most of pores were successfully filled with SeS₂ and stronger bonding between SeS₂ and CDC was formed within nano-pores of the SeS₂/CDC, respectively. The SeS₂/CDC powders and PAA (Sigma Aldrich) binder were mixed in ethanol/water solution to prepare the slurry for casting the electrode. Pure black (Superior Graphite) and purified exfoliated graphite (Superior Graphite) were used as conductive additives, and the mass ratio was 75:15:5:5, respectively, SeS₂/CDC, PAA binder, pure black and purified exfoliated graphite. The slurry was stirred at room temperature for 12 h and cast on aluminum foil. After drying overnight at room temperature under vacuum, the electrodes were used.