A flexible carbon/sulfur-cellulose core-shell structure for advanced lithium-sulfur batteries

Lithium sulfur (Li-S) batteries are viewed as a promising candidate for next-generation energy storage systems due to their high energy density, low cost and ease of manufacturing. However, rapid capacity decay caused by lithium polysulfide shuttle during charging/discharging processes hinder its practical application. In this work, we demonstrate a cellulose encapsulated carbon/sulfur core-shell structure for advanced Li-S batteries based on electrostatic spinning with coaxial spinnerets. Cellulose serves as an excellent shell due to its good ion conductivity, flexible structure to accommodate volumetric expansion of sulfur, and strong capability to prevent sulfur and its intermediate reaction products from dissolving into the electrolyte. CMK-3 mesoporous carbon in the core is helpful to confine sulfur in the pores, and improve the electrical conductivity of the fiber electrode together with the carbon black particles on the outside of the fiber. As a result, the obtained cellulose based flexible sulfur electrode delivers a high initial discharge capacity (> 1200 mA h g(-1)), good electrochemical performance with Coulombic efficiency above 99%, and a low capacity decay rate of similar to 0.12% per cycle over 300 charging/discharging cycles.