Cobalt-doped molybdenum sulfide as an interlayer facilitates polysulfide conversion to obtain high-performance lithium-sulfur batteries

Lithium-sulfur (Li-S) batteries are considered to be a promising energy storage system due to their theoretical specific capacity. However, the "shuttle effect" of polysulfides (LiPSs) and the slow redox kinetics of LiPSs in the conversion reaction have hindered their large-scale application. In this study, the Co-MoS2 is prepared and coated on the polypropylene (PP) separator of Li-S batteries. The Co elements are successful addition and uniform distribution in the Co-MoS2. This coating is designed to provide chemical adsorption and catalysis for LiPSs. Consequently, Li-S batteries with a Co-MoS2 interlayer exhibit outstanding long-cycle and high-rate performance. After 500 cycles at 0.5C, the reversible capacity is found to be 561 mAh g(-1), with only a lowcapacity reduction of 0.097 % per cycle. Furthermore, 602 mAh g(-1) is delivered even at 4C. The results of electrochemical measurements and first principles calculations demonstrate that the high performance of Li-S batteries is attributed to the chemical adsorption and electrocatalysis roles of the Co-MoS2 interlayer, which inhibit the "shuttle effect" and enable fast redox reaction kinetics. In addition, the introduction of cobalt doping results in the formation of the 1T phase of MoS2, which enhances the conductivity of the Co-MoS2. The presence of plentiful cobalt-doped MoS2 defects provides abundant catalytic sites for the electrochemical reaction of LiPSs.