In recent years, with the rapid growth in the demand for electric vehicles and large-capacity energy storage systems (ESS), the development of secondary batteries with higher energy density is also imperative. Lithium-sulfur batteries have attracted attention as second-generation high-capacity lithium-ion batteries. In theory, energy density is about six times higher than that of lithium-ion batteries. However, the conductivity of sulfur is low, and volume changes also occur during charging and discharging. Lithium polysulfide mesophase is melted and discharged as an electrolyte, which hinders the commercialization of lithium-sulfur batteries.