First-principles Study on the Catalytic Effect of Co, P co-Doped MoS2 in Lithium-sulfur Batteries

In lithium-sulfur batteries, metal compound catalytic materials enhance the electrochemical redox reaction kinetics, fundamentally prevent the shuttle effect of polysulfides, and improve the electrochemical performance. MoS2 material has received widespread attention due to the affinity for polysulfides and catalytic ability. However, the base surface that occupies most of the reaction interface exhibits weaker catalytic activity than the few edge sites. The Co, P co-doping strategy was used for the first time to modify MoS2 material as cathode material in lithium-sulfur battery. Compared with undoped and Co single-doped materials, it achieves excellent discharge capacity, rate performance and cycling stability. To explore the origin of Co, P co-doping MoS2 to improve the electrochemical performance of lithium-sulfur batteries, the first-principles research was carried out, clarifying the adsorption and conversion of polysulfides on the surface of undoped, Co single doped, Co, P co-doped MoS2. The calculation results indicate that the adsorption energy shows the trend of undoped <Co single doped <Co, P co-doped MoS2. The Li-S and S-P double bonding between the co-doped surface and polysulfides make Co, P co-doped MoS2 have the greatest adsorption capacity. Additionally, the significant stabilizing effect for discharge product Li2S reduces the energy requirement of the dissociation step and increases the overall. energy release during the conversion process, providing driving forces for the polysulfide conversion. These two factors jointly enhance the catalytic activity of MoS2, effectively inhibit the shuttle effect, and improve the electrochemical performance of the battery. It is hoped that the conclusion could promote the application of surface modified metal sulfide catalytic materials in lithium-sulfur batteries.