Abstract
Lithium-sulfur (Li-S) batteries are receiving increasing attention due to their extraordinary performances. However, the insulating nature of sulfur and the “shuttling mechanism” caused by the dissolution of polysulfide in organic electrolytes have limited their practical applications. Herein, we used cobalt disulfide (CoS2) as an additive to improve cycling performance owning to its high electric conductivity and chemical binding of the polysulfide. Hydrothermally synthesized CoS2 was introduced to sulfur-carbon composite and pure sulfur cells through slurry mixing process. The results showed that with a certain amount of CoS2 in cathode slurry could prolong cycle life of the cells and increase their stability without sacrificing capacity performances. Furthermore, incorporating CoS2 with smaller particle sizes, which was successfully decreased from 1.5 μm to 450 nm by also a hydrothermal process, could provide more surface areas for depositing polysulfide, thus reducing charge transfer resistance and therefore enhance capacity and cycle life.