A comparative study of M2CS2 and M2CO2 MXenes as anode materials for lithium ion batteries

Oxygen functionalized MXenes are promising candidates for anode materials of Li ion batteries (LIBs), however, have intrinsic drawbacks. Sulfur functionalized MXenes are new potential anode materials for LIBs. A comparative study on O-terminated and S-terminated M2C MXenes was performed to evaluate their performance as anode for LIBs by first-principles calculations. The formation energy, stability, electrical conductivity, Li-ion adsorption, Li-ion diffusion, and capacity have been compared. All the studied M2CT2 (T = O, S) MXenes are stable. When metal elements of MXenes in Group IVB, the S-terminated M2C MXenes exhibit enhanced electrical conductivity than corresponding O-terminated MXenes. Some S-terminated MXenes have lower OCV than corresponding O-terminated ones. The O-terminated M2C (M = Mo) and S-terminated M2C MXenes (M = Cr, Mo) present high capacities. The diffusion barriers of Li ion on the S-terminated M2C MXenes (M = Ti, Zr, Hf, Nb, Ta) are lower than those of O-terminated MXenes. Cr2CS2 and Mo2CS2 exhibit high overall electrochemical performance for LIBs anode materials.