CoS2 impregnated in mesoporous carbon hollow spheres as polysulfide trapper for highly stable Li-S batteries

Abstract

Li-S batteries with high theoretical energy density are considered as promising energy storage devices. However, the reduction reaction of element sulfur converts to the long-chain lithium polysulfide, which could soluble into the liquid electrolyte. As a result, the utilization of active sulfur materials is low, leading to a rapid capacity deceasing. Herein, the strategy of separator modification were used to introduce the mesoporous carbon hollow spheres impregnated with CoS2 into Li-S batteries. The CoS2 with polar groups provide chemical bonding sites for polysulfides. Meanwhile, the mesoporous carbon hollow spheres with large specific surface area served as the polysulfide trappers through strong physical affinity. Owing to the synergetic effects of physical and chemical interaction, the prepared composite could efficiently hinder the shuttle effect, which is the soluble polysulfides shuttling between the anode and cathode. Therefore, Li-S batteries with modified separators exhibit highly reversible capacity of 651 mA h g−1 after 500 cycles at 1.0 C and superior rate capability.