Exploring the anchoring effect of surface functionalized 2D electrides Ca2N and Y2C in lithium sulfur battery: First principle study

Although lithium sulfur batteries (LiSBs) have high theoretical capacity and energy density, the shuttle effect seriously hinders its development. In this work, the anchoring properties of single-sided modified Ca2NX and Y2CX and double-sided modified Ca2NX2 and Y2CX2 (X = H, O, F, Cl and S) in LiSBs were systematically studied by first principle calculation. The unmodified sides of Ca2NF, Y2CH, Y2CCl and Y2CS have a strong interaction with S8, but it will promote the decomposition of S8 and cause unnecessary loss of active materials. On the contrary, double-sided modified Ca2NCl2, Y2CF2 and Y2CCl2 have moderate adsorption energies for lithium polysulfides (Li2Sn) and S8. The decomposition barriers of Li2S on the surfaces of Ca2NCl2 and Y2CCl2 are significantly lower than that of natural Li2S, and Li+ has a rapid diffusivity on their surfaces. Therefore, Ca2NCl2 and Y2CCl2 can suppress the shuttle effect and improve the battery performance, which indicates they are ideal anchoring materials for LiSBs.