Theoretical insights into the anchoring and catalytic effect of bilayer C3N3 for lithium‑selenium batteries

Polymeric carbon nitride (PCN) materials have been identified as promising host materials for lithium‑selenium (LiSe) batteries due to the capability of suppressing the shuttle effect of high-order polyselenides. In the present work, the viability of bilayer C3N3 (AA-/AB-stacking bilayer C3N3) as host material for LiSe batteries was conducted utilizing first-principles calculations. The computational results show that the AA-stacking bilayer C3N3 demonstrates enhanced anchoring interactions for the high-order polyselenides due to the synergistic effect of physical confinement and strong LiN bonds. Compared with the conventional electrolytes, the polyselenides prefer to anchor within the AA- and AB-stacking bilayer C3N3 instead of interacting with electrolytes, which in turn demonstrates the ability of the bilayer C3N3 in suppressing shuttle effect of high-order polyselenides. The anchored structures of Se8 or Li2Sen (n = 1, 2, 4, 6, 8) molecules within the bilayer C3N3 exhibit high electrical conductivities, which contributes to the improved electrochemical performance of LiSe batteries. In addition, the catalytic effect of AA- and AB-stacking bilayer C3N3 was investigated in terms of the reduction of Se8 and the energy barrier associated with the decomposition of Li2Se. The results indicate that the AA-stacking bilayer C3N3 structure is more advantageous in improving the utilization of selenium active material and promoting the conversion of solid phase Li2Se. Our present work not only unveils a theoretical basis for the study of bilayer C3N3 but also provides some ideas for the design of host materials for high-performance LiSe batteries.